研究者データベース

松井 佳彦(マツイ ヨシヒコ)
工学研究院 環境工学部門 環境工学
教授

基本情報

所属

  • 工学研究院 環境工学部門 環境工学

職名

  • 教授

学位

  • 博士(工学)(北海道大学)

J-Global ID

研究キーワード

  • 吸着   浄水   膜分離   農薬   活性炭   MF膜   フミン質   凝集剤   PAC   硫酸バンド   ウイルス   不活化   ジェオスミン   2-メチルイソボルネオール   凝集材   アワヒバリガイ   脱離力   アルミニウム   防汚塗料   付着防止   淡水性二枚貝   Limonoperna fortunei   クロラミン   上下水道   シミュレーション   地理情報   

研究分野

  • 社会基盤(土木・建築・防災) / 土木環境システム
  • 環境・農学 / 環境動態解析

職歴

  • 2005年05月 - 現在 北海道大学大学院工学研院 教授
  • 1998年10月 - 2005年04月 岐阜大学工学部 教授
  • 1995年04月 - 1998年09月 岐阜大学工学部 助教授
  • 1984年04月 - 1995年03月 北海道大学工学部 助手

学歴

  • 1982年04月 - 1984年03月   北海道大学大学院工学研究科博士後期課程
  • 1980年04月 - 1982年03月   北海道大学大学院工学研究科修士課程
  • 1976年04月 - 1980年03月   北海道大学教養部+工学部

所属学協会

  • 米国水道協会   国際水協会   日本水道協会   土木学会   日本水環境学会   

研究活動情報

論文

  • Shun Saito, Yoshihiko Matsui, Nobutaka Shirasaki, Taku Matsushita
    Journal of Water Process Engineering 49 2022年10月 
    Catalytic oxidation of dissolved divalent Mn ion (Mn2+) by free chlorine and superfine powdered activated carbon (SPAC) before microfiltration has been emerged as a new technology to remove Mn from natural water for drinking water production. However, Mn was not sufficiently removed in pilot-plant experiments yet. The present study clarified underlaying removal mechanisms. In natural water, soluble Mn exists as colloidal Mn with a molecular weight ≥ 10,000 Da in the oxidized form in addition to Mn2+. Mn2+ was removed by SPAC‑chlorine, but Ca2+, Mg2+, and NOM decreased the Mn2+ removal rate as a result of competitive adsorption. The colloidal Mn was not removed by SPAC‑chlorine, but could be removed by coagulation and microfiltration or ultrafiltration alone. With the addition of coagulant (poly‑aluminum chloride), the soluble Mn concentration increased because of redissolution of precipitated-oxidized Mn due an increase in local acidity, in particular at low temperature, and coagulation reduced soluble Mn removal rate due to hindrance of mass transfer. These negative impacts may be partially attenuated by using high-intensity mixing or waiting to add the coagulant after the oxidation of Mn2+ has progressed sufficiently. Mn removal rate changed with temperature and mixing intensity in the same trend as predicted by the mass-transfer model, but it was smaller than the prediction. Together with the effects of Ca2+, Mg2+, and NOM, it appears that not only mass transfer but also the process of adsorption is a factor affecting the overall Mn removal rate.
  • Yuanjun Zhao, Yoshihiko Matsui, Shun Saito, Nobutaka Shirasaki, Taku Matsushita
    Separation and Purification Technology 296 2022年09月01日 
    Membrane fouling is still a major problem in water treatment that uses membrane separation. In this study, submicron-sized super-fine powdered activated carbon (SSPAC) was applied in a pulse/continuous dose to ceramic-membrane microfiltrations of two very different types: a submerged tubular membrane system that enabled vacuum-driven, outside-in filtration and a monolithic membrane system that enabled pressure-driven, inside-out filtration. Constant-flux filtration with repeated hydraulic backwashing was performed using diluted secondary-treated municipal wastewater and natural river water, and the effect and mechanism of membrane fouling mitigation were investigated. Pulse dosing with SSPAC alleviated a rise of transmembrane pressure (TMP) more than continuous dosing in the submerged tubular membrane system because of the effects, inter alia, associated with precoating the SSPAC layer as well as adsorption, by which soluble membrane foulants were effectively removed. Moreover, pulse-dosed SSPAC combined with a coagulant formed a precoat layer on the membrane that was easy to peel off with hydraulic backwashing. Continuous dosing of SSPAC was inferior to pulse dosing of SSPAC in terms of water quality, and some SSPAC was left on the membrane surface after hydraulic backwashing. In the monolithic membrane system, however, the superiority of pulse dosing of SSPAC was not observed: pulse and continuous dosing of SSPAC led to similar reductions of TMP rise. The SSPAC layer was unevenly distributed along the length of a channel and between channels in the monolithic membrane.
  • Shun Saito, Yoshihiko Matsui, Nobutaka Shirasaki, Taku Matsushita
    Water Research X 16 2022年08月01日 
    Catalytic oxidative removal of Mn2+ on activated-carbon surfaces by free chlorine was recently discovered and found to be potentially practicable for water treatment when using micrometer-sized activated carbon. Herein, we newly derived a kinetic model for trace-substance removal by catalytic reaction and applied it to the Mn2+ removal. External-film mass transfer, adsorption, and oxidation/desorption contributed similarly to the Mn2+ removal rate under actual practical conditions. The low removal rate in natural water was attributed to decreases in available adsorption sites: e.g., a 50% decrease in available sites in water with 0.26 mmol-Ca2+/L caused a 15% reduction in removal rate. Low temperature greatly reduced the removal rate by both enhancing the decrease in available sites and hindering mass transfer through increased viscosity. While adsorption sites differed 8-fold between different carbon particles, causing a 2.2-fold difference in removal rates, carbon particle size was more influential, with a >10-fold difference between 2- and 30-μm sizes.
  • Long Pan, Akiko Nakayama, Yoshihiko Matsui, Taku Matsushita, Nobutaka Shirasaki
    Water Research 208 2022年01月01日 
    Submerged-membrane hybrid systems (SMHSs) that combine membrane filtration with powdered activated carbon (PAC) take advantage of PAC's ability to adsorb and remove contaminants dissolved in water. However, the risk of contaminant desorption due to temporal changes in the influent concentration of the contaminant has not been thoroughly explored. In this study, we used a SMHS with conventionally-sized PAC or superfine PAC (SPAC) to remove 2-methylisoborneol (MIB), a representative micropollutant, from water containing natural organic matter (NOM), with the goal of elucidating adsorption–desorption phenomena in the SMHS. We found that 20–40% of the MIB that adsorbed on PAC and SPAC while the influent was contaminated with MIB (6 h, contamination period) desorbed to the liquid phase within 6 h from the time that the MIB-containing influent was replaced by MIB-free influent (no-contamination period). The percentage of desorption during the no-contamination period increased with increasing MIB breakthrough concentration during the contamination period. These findings indicate that the PAC/SPAC in the SMHS should be replaced while the breakthrough concentration is low, not only to keep a high removal rate but also to decrease the desorption risk. SPAC is fast in removal by adsorption, but it is also fast in release by desorption. SPAC (median diameter: 0.94 µm) showed almost the same adsorption-desorption kinetics as PAC (12.1 µm) of a double dose. A two-component branched-pore diffusion model combined with an IAST (ideal adsorbed solution theory)–Freundlich isotherm was used to describe and analyze the adsorption–desorption of MIB. The diffusivity of MIB molecules in the pores of the activated carbon particles decreased markedly in a short period of time. This decrease, which was attributed to fouling of the activated carbon in the SMHS by coagulant-treated water containing NOM, not only reduced the rate of MIB removal during the contamination period but also hindered the rate of MIB desorption during the no-contamination period and thus prevented the effluent MIB concentration from becoming high. On the other hand, coagulation did not change the concentration of NOM that competes with MIB for adsorption sites.
  • Taku Matsushita, Yuji Kikkawa, Kei Omori, Yoshihiko Matsui, Nobutaka Shirasaki
    CHEMICAL RESEARCH IN TOXICOLOGY 34 9 2070 - 2078 2021年09月 [査読有り]
     
    Drinking water quality guideline values for toxic compounds are determined based on their acceptable daily intake. The toxicological end point for determining the acceptable daily intake of most organophosphorus insecticides is inhibition of acetylcholinesterase (AChE). Although insecticides ingested with drinking water are partly metabolized by the liver before transport to the rest of the body, no current cell-independent AChE activity assay takes the effects of metabolism into account. Here, we incorporated metabolism into a cell-independent AChE activity assay and then evaluated the change in anti-AChE activity during chlorination of a solution containing the organophosphorus insecticide diazinon. The anti-AChE activities of solutions of diazinon or diazinon-oxon, the major transformation product of diazinon during chlorination, were dramatically changed by metabolism: the activity of diazinon solution was markedly increased, whereas that of diazinon-oxon solution was slightly decreased, clearly indicating the importance of incorporating metabolism into assays examining toxicity after oral ingestion. Upon chlorination, diazinon was completely transformed, in part to diazinon-oxon. Although diazinon solution without metabolism did not show antiAChE activity before chlorination, it did after chlorination. In contrast, with metabolism, diazinon solution did show anti-AChE activity before chlorination, but chlorination gradually decreased this activity over time. The observed anti-AChE activities were attributable solely to diazinon and diazinon-oxon having been contained in the samples before metabolism, clearly suggesting that the presence not only of diazinon but also of diazinon-oxon should be monitored in drinking water. Further examination using a combination of tandem mass spectrometry and in silico site-of-metabolism analyses revealed the structure of a single metabolite that was responsible for the observed anti-AChE activity after metabolism. However, because this compound is produced via metabolism in the human body after oral ingestion of diazinon, its presence in drinking water need not be monitored and regulated.
  • Yoshifumi Nakazawa, Taketo Abe, Yoshihiko Matsui, Koki Shinno, Sakiko Kobayashi, Nobutaka Shirasaki, Taku Matsushita
    WATER RESEARCH 203 2021年09月 [査読有り]
     
    One of the main purposes of drinking water treatment is to reduce turbidity originating from clay particles. Relatively little is known about the removal of other types of particles, including conventionally sized powdered activated carbon (PAC) and superfine PAC (SPAC), which are intentionally added during the treatment process; microplastic particles; and viruses. To address this knowledge gap, we conducted a preliminary investigation in full-scale water treatment plants and then studied the removal of these particles during coagulation-flocculation, sedimentation, and rapid sand filtration (CSF) in bench-scale experiments in which these particles were present together. Numbers of all target particles were greatly decreased by coagulation-flocculation and sedimentation (CS). Subsequent rapid sand filtration greatly reduced the concentrations of PAC and SPAC but not the concentrations of viruses, microplastic particles, and clay particles. Overall removal rates by CSF were 4.6 logs for PAC and SPAC, 3.5 logs for viruses, 2.9 logs for microplastics, and 2.8 logs for clay. The differences in removals were not explained by particle sizes or zeta potentials. However, for clays, PAC and SPAC, for which the particle size distributions were wide, smaller particles were less efficiently removed. The ratios of both clay to PAC and clay to SPAC particles increased greatly after rapid sand filtration because removal rates of PAC and SPAC particles were about 2 logs higher than removal rates of clay particles. The trend of greater reduction of PAC concentrations than turbidity was confirmed by measurements made in 14 full-scale water purification plants in which residual concentrations of PAC in treated water were very low, 40-200 particles/mL. Clay particles therefore accounted for most of the turbidity in sand filtrate, even though PAC was employed. The removal rate of microplastic particles was comparable to that of clays. Sufficient turbidity removal would therefore provide comparable removal of microplastics. We investigated the effect of mechanical/photochemical weathering on the removal of microplastics via CSF. Photochemical weathering caused a small increment in the removal rate of microplastics during CS but a small reduction in the removal rate of microplastics during rapid sand filtration; mechanical weathering decreased the removal rate via CS but increased the removal rate via rapid sand filtration. The changes of removal of microplastics might have been caused by changes of their zeta potential.
  • Shun Saito, Yoshihiko Matsui, Yasuhiko Yamamoto, Shuhei Matsushita, Satoru Mima, Nobutaka Shirasaki, Taku Matsushita
    WATER RESEARCH 202 2021年09月 [査読有り]
  • Mari Asami, Yoshikazu Furuhashi, Yuji Nakamura, Yuki Sasaki, Yoshio Adachi, Nobuko Maeda, Yoshihiko Matsui
    The Science of the total environment 771 144979 - 144979 2021年06月01日 
    The elution of lead, and nickel from water supply devices into water is a potential health concern. This study was performed to examine the actual concentrations of nickel and lead in the water from taps in homes and offices, focusing on the differences between first flush and fully flushed water. The water quality management target value and water quality standard in Japan specify nickel and lead concentrations in drinking water <20 and <10 μg/L, respectively. Nickel concentration in the first flush water (100 mL) from 110 household taps revealed 22 cases (20%) > 20 μg/L, while the fully flushed water satisfied the standard after running 5000 mL of water. The nickel concentration decreased gradually in sequential sampling of each 100 mL from the taps. Lead concentration in the first flush water exceeded the standard in 32 cases (29%), while the fully flushed water was below the target value. The concentration in the first flush water tended to decrease with time since the tap installation, and this was significant after 10 years for nickel but not significant for lead. It is important to flush retained water out of the tap after several hours without use. No significant correlation was found with the volume of the test faucet in the market, but bronze-based products showed higher nickel concentrations than brass and plastic products.
  • Gang Shi, Shota Nishizawa, Taku Matsushita, Yuna Kato, Takahiro Kozumi, Yoshihiko Matsui, Nobutaka Shirasaki
    WATER RESEARCH 197 2021年06月 [査読有り]
     
    1,4-Dioxane is one of the most persistent organic micropollutants in conventional drinking-water treatment processes. Vacuum ultraviolet (VUV) treatment is a promising means of removing micropollutants such as 1,4-dioxane from source water, but this approach has not yet been implemented in a fullscale water treatment plant, partly because the operating parameters for pilot and full-scale VUV photoreactors have not been optimized. Here, we developed a computational fluid dynamics-based method for optimizing VUV photoreactor performance through energy-based analyses that take into account the effects of two important operating parameters-flow rate and radiant exitance. First, we constructed a computational fluid dynamics model and determined the sole parameter required for the model, the pseudo-first-order rate constant for the reaction of 1,4-dioxane, by simple batch experiment. Then, we validated the model by using a pilot-scale flow-through annular photoreactor. Finally, we used the validated model to examine the effects of flow rate and radiant exitance on the efficiency of 1,4-dioxane degradation in a virtual annular photoreactor. Radiation efficiency, which was defined as the ratio of the logarithmic residual ratio of 1,4-dioxane to the theoretical minimum logarithmic residual ratio (best possible performance) under the given operating conditions, was calculated as an energy-based index of cost-effectiveness. Radiation efficiency was found to increase with increasing flow rate but decreasing radiant exitance. An electrical energy per order (EEO) analysis suggested that VUV treatment under laminar flow was most economical when low-power lamps and a high flow rate were used. In contrast, VUV treatment under turbulent flow was suggested to be most economical when high-power lamps were used at a high flow rate.(c) 2021 Elsevier Ltd. All rights reserved.
  • Yoshifumi Nakazawa, Taketo Abe, Yoshihiko Matsui, Nobutaka Shirasaki, Taku Matsushita
    WATER RESEARCH 190 2021年02月 [査読有り]
     
    Although superfine powdered activated carbon has excellent adsorption properties, it is not used in conventional water treatment processes comprising coagulation-flocculation, sedimentation, and sand filtration (CSF) due to concerns about its residual in treated water. Here, we examined the production and fate of very fine carbon particles with lacking in charge neutralization as a source of the residual in sand filtrate after CSF treatment. Almost all of the carbon particles in the water were charge-neutralized by coagulation treatment with rapid mixing, but a very small amount (<= 0.4% of the initial concentration) of very fine carbon particles with a lesser degree of charge neutralization were left behind in coagulation process. Such carbon particles, defined as stray carbon particles, were hardly removed by subsequent flocculation and sedimentation processes, and some of them remained in the sand filtrate. The concentration of residual carbon particles in the sand filtrate varied similarly with that of the stray carbon particles. The stray and residual carbon particles were similarly smaller than the particles before coagulation treatment, but the residual carbon particles had less charge neutralization than the stray carbon particles. The turbidity of water samples collected after sedimentation was not correlated with the residual carbon concentration in the sand filtrate, even though it is often used as an indicator of treatment performance with respect to the removal of suspended matter. Based on these findings, we suggest that reduction of the amount of stray particles should be a performance goal of the CSF treatment. Examining this concept further, we confirmed that the residence time distributions in the coagulation and flocculation reactors influenced the concentration of stray carbon particles and then the residual carbon particle concentration in sand filtrate, but found that the effect was dependent on coagulant type. A multi-chamberedreactor configuration lowered both the stray carbon particle concentration after coagulation treatment and the residual carbon particle concentration in sand filtrate compared with a single-chambered reactor configuration. When a normal basicity PACl that consisted mainly of monomeric Al species was used, the stray carbon particle concentration was decreased during coagulation process and then gradually decreased during subsequent flocculation process because the monomeric Al species were transformed to colloidal Al species via polymeric Al species. In contrast, when a high-basicity PACl that consisted mostly of colloidal Al species was used, coagulation treatment largely decreased the stray carbon particle concentration, which did not decrease further during subsequent flocculation process. These findings will be valuable for controlling residual carbon particles after the CSF treatment. (c) 2020 Elsevier Ltd. All rights reserved.
  • Kentaro Narita, Yoshihiko Matsui, Taku Matsushita, Nobutaka Shirasaki
    SCIENCE OF THE TOTAL ENVIRONMENT 751 2021年01月 [査読有り]
     
    Several risk scoring and ranking methods have been applied for the prioritization of micropollutants, including pesticides, and in the selection of pesticides to be regulated regionally and nationally. However, the effectiveness of these methods has not been evaluated in Japan. We developed a risk prediction method to select pesticides that have a high probability of being detected in drinking water sources where no monitoring data is available. The risk prediction method was used to select new pesticides for the 2013 Primary List in the Japanese Drinking Water Quality Guidelines. Here, we examined the effectiveness of the method on the basis of the results of water quality examinations conducted by water supply authorities across Japan, and studied ways to improve the risk prediction method. Of the 120 pesticides in the 2013 Primary List, 80 were detected in drinking water sources (raw water entering water treatment plants). The rates of detection of the newly selected pesticides and previously listed pesticides were not significantly different: 64% and 68%, respectively. When the risk predictor was revised to incorporate degradability of dry-field pesticides and current pesticide sales data, the rate of detection of pesticides selected as having a high risk of detection improved from 72% to 88%. We prepared regional versions of the Primary List using the revised risk predictors and verified their utility. The number of listed pesticides varied greatly by region, ranging from 32 to 73; all regional lists were much shorter than the national Primary List. In addition, 55% to 100% of the pesticides detected in each region were included in a Regional Primary List. This work verifies the ability of the risk prediction method to screen pesticides and select those with a high risk of detection. (C) 2020 Elsevier B.V. All rights reserved.
  • Taku Matsushita, Yuki Fujita, Kei Omori, Yuxiang Huang, Yoshihiko Matsui, Nobutaka Shirasaki
    CHEMOSPHERE 261 2020年12月 [査読有り]
     
    Organophosphorus insecticides are known to be partly transformed to their respective oxons during the chlorination step of drinking water treatment. For most organophosphorus insecticides, the toxicological endpoint for determining acceptable daily intake levels is inhibition of acetylcholinesterase (AChE). Like the parent insecticides, oxons also inhibit AChE, so the presence of oxons in drinking water is also evaluated. However, no attention is paid to the possible presence of transformation products (TPs) other than oxons. In the present study, we determined whether the anti-AChE activity observed for chlorinated solutions of the organophosphorus insecticides malathion and methidathion could be solely attributed to the parent compounds and their oxons. Upon chlorination, both malathion and methidathion were immediately transformed to their oxons; the maximum transformation ratios were 60% and 30%, respectively, indicating that at least 40% and 70% of these compounds were transformed into other TPs. Before chlorination, malathion- and methidathion-containing solutions exhibited little to no anti-AChE activity, but the solutions showed strong activity after chlorination. The contributions of the parent insecticides and their oxons to the activities of the chlorinated samples were calculated from the concentrations of the compounds in the samples and dose-response curves for chemical standards of the compounds. For both the malathion-containing solution and the methidathion-containing solution, the calculated anti-AChE activities were almost the same as the observed activities at every chlorination time. This suggests that the observed activities could be attributed solely to the parent insecticides and their oxons, indicating that other TPs need not be considered. (C) 2020 Elsevier Ltd. All rights reserved.
  • Shun Saito, Yoshihiko Matsui, Yasuhiko Yamamoto, Shuhei Matsushita, Satoru Mima, Nobutaka Shirasaki, Taku Matsushita
    WATER RESEARCH 187 2020年12月 [査読有り]
     
    Here, we examined the removal of soluble divalent manganese (Mn(II)) by combination treatment with superfine powdered activated carbon (SPAC) and free chlorine in a membrane filtration pilot plant and batch experiments. Removal rates > 95% were obtained with 3 mg/L SPAC, 1 mg/L chlorine, and a contact time of 4 min, meeting practical performance standards. Mn(II) was found to be oxidized and precipitated on the surface of the activated carbon particles by chlorine. The Mn(II) removal rate was fitted to pseudo -first-order reaction kinetics, and the rate coefficient changed in inverse proportion to as-is particle size, but not to true particle size. The rate coefficient was independent of both Mn(II) concentration, except at high Mn(II) concentration, and the chlorine concentrations tested. The rate-determining step of Mn(II) removal was confirmed to be external-film mass transfer, not chemical oxidation. Activated carbon was found to have a catalytic effect on the oxidation of Mn(II), but the effect was minimal for conventionally sized activated carbon. However, Mn(II) removal at feasible rates for practical application can be expected when the activated carbon particle diameter is reduced to several micrometers. Activated carbon with a particle size of around 1-2 mu m may be the most appropriate for Mn(II) removal because particles below this size were aggregated, resulting in reduced removal efficiency. (c) 2020 Elsevier Ltd. All rights reserved.
  • N. Shirasaki, T. Matsushita, Y. Matsui, S. Koriki
    Water Research 186 2020年11月01日 
    © 2020 Elsevier Ltd Evaluating the efficacy of disinfection processes to inactivate human enteric viruses is important for the prevention and control of waterborne diseases caused by exposure to those viruses via drinking water. Here, we evaluated the inactivation of two representative human enteric viruses (adenovirus type 40 [AdV] and coxsackievirus B5 [CV]) by thermal or free-chlorine disinfection. In addition, we compared the infectivity reduction ratio of a plant virus (pepper mild mottle virus [PMMoV], a recently proposed novel surrogate for human enteric viruses for the assessment of virus removal by coagulation‒rapid sand filtration and membrane filtration) with that of the two human enteric viruses to assess the suitability of PMMoV as a human enteric virus surrogate for use in thermal and free-chlorine disinfection processes. Finally, we examined whether conventional or enhanced viability polymerase chain reaction (PCR) analysis using propidium monoazide (PMA) or improved PMA (PMAxx) with or without an enhancer could be used as alternatives to infectivity assays (i.e., plaque-forming unit method for AdV and CV; local lesion count assay for PMMoV) for evaluating virus inactivation by disinfection processes. We found that PMMoV was more resistant to heat treatment than AdV and CV, suggesting that PMMoV is a potential surrogate for these two enteric viruses with regard to thermal disinfection processes. However, PMMoV was much more resistant to chlorine treatment compared with AdV and CV (which is chlorine-resistant) (CT value for 4-log10 inactivation: PMMoV, 84.5 mg-Cl2·min/L; CV, 1.15–1.19 mg-Cl2·min/L), suggesting that PMMoV is not useful as a surrogate for these enteric viruses with regard to free-chlorine disinfection processes. For thermal disinfection, the magnitude of the signal reduction observed with PMAxx-Enhancer-PCR was comparable with the magnitude of reduction in infectivity, indicating that PMAxx-Enhancer-PCR is a potential alternative to infectivity assay. However, for free-chlorine disinfection, the magnitude of the signal reduction observed with PMAxx-Enhancer-PCR was smaller than the magnitude of the reduction in infectivity, indicating that PMAxx-Enhancer-PCR underestimated the efficacy of virus inactivation (i.e., overestimated the infectious virus concentration) by chlorine treatment. Nevertheless, among the PCR approaches examined in the present study (PCR alone, PMA-PCR or PMAxx-PCR either with or without enhancer), PMAxx-Enhancer-PCR provided the most accurate assessment of the efficacy of virus inactivation by thermal or free chlorine disinfection processes.
  • Motoyuki Kamata, Yoshihiko Matsui, Mari Asami
    SCIENCE OF THE TOTAL ENVIRONMENT 744 2020年11月 [査読有り]
     
    Although agricultural activities-especially paddy rice cultivation-are prominent in watersheds in Asian countries, few comprehensive studies have examined pesticide concentrations in water in these areas. Here, we report the concentrations of 162 pesticides in treated drinking water and source water (14,076 samples) in Japan, where rice cultivation is common, along with trends in sales of herbicides, fungicides, and insecticides from 1963 to 2016. Herbicides and fungicides-especially those used in rice farming were frequently detected in drinking water sources.The herbicide bromobutide, which is not listed in drinking water quality standards or guidelines except in Japan, as well as the widely used-and-detected bentazone, were frequently detected in source water (bromobutide and bentazone were detected at concentrations >0.1 mu g/L in 31.1% and 33.8% of samples, respectively). Dymron and tefuryltrione were also detected in over 10% of samples at concentrations >0.1 mu g/L. The highest observed concentration of bromobutide was 10 mu g/L, and 7.5% of samples had concentrations >1 mu g/L. High concentrations were also observed for halosulfuron methyl (7.9 mu g/L), pyroquilon (7.0). molinate (6.8), and metominostrobin (4.6). Some of the pesticides frequently detected in source water were not detected at all in drinking water, but the main cause of the non-detection appeared to be degradation by chlorine. From the 1970s onward, sales of herbicides and fungicides with higher acceptable daily intakes (ADIs; i.e., with lower toxicity) have increased. However, the percentage of herbicides with very low ADIs (<10(-2)(.5) mg kg(-1) d(-1)) being shipped has also increased. Tefuryltrione, which was detected at normalized concentrations >0.1 in 8% of samples, is an example of this type of herbicide. The average log-Kow of herbicides has decreased from the 1970s to the present, due to the strong trend towards the application of hydrophilic herbicides, such glyphosate. The need for increased monitoring of pesticides used in rice paddy farming is highlighted. (C) 2020 Elsevier B.V. All rights reserved.
  • Shota Nishizawa, Taku Matsushita, Yoshihiko Matsui, Nobutaka Shirasaki
    SCIENCE OF THE TOTAL ENVIRONMENT 737 2020年10月 [査読有り]
     
    Vacuum ultraviolet (VUV) treatment is a promising advanced oxidation process for the removal of organic contaminants during water treatment. Here, we investigated the formation of disinfection by-products from coexisting organic matter during VUV or ultraviolet (UV) treatment following pre-chlorination, and their fates after post-chlorination, in a standard Suwannee River humic acid water and a natural lake water. VUV treatment after pre-chlorination decreased the total trihalomethane (THM) concentration but increased total aldehyde and chloral hydrate concentrations; total haloacetic acid (HAA) and haloacetonitrile (HAN) concentrations did not change. UV treatment after pre-chlorination produced similar changes in the by-products as those observed for VUV treatment, with the exception that the total THM concentration was not changed, and the total HAN concentration was increased. The final concentrations of by-products after post-chlorination were increased by VUV or UV treatment, except for the total HAA concentration, which remained unchanged after UV treatment. The increases were greater after VUV treatment than after UV treatment, probably because the larger amount of hydroxyl radicals generated during VUV treatment compared with during UV treatment transformed coexisting organic matter into precursors of by-products that were then converted to by-products during post-chlorination. (C) 2020 Elsevier B.V. All rights reserved.
  • Yize Chen, Yoshifumi Nakazawa, Yoshihiko Matsui, Nobutaka Shirasaki, Taku Matsushita
    WATER RESEARCH 183 2020年09月 [査読有り]
     
    Many PACT (poly-aluminum chloride) coagulants with different characteristics have been trial-produced in laboratories and commercially produced, but the selection of a proper PACT still requires empirical information and field testing. Even PACls with the same property sometimes show different coagulation performances. In this study, we compared PACls produced by AICl(3)-titration and Al(OH)(3)-dissolution on their performance during coagulation-flocculation, sedimentation, and sand filtration (CSF) processes. The removal targets were particles of superfine powdered activated carbon (SPAC), which are used for efficient adsorptive removal of micropollutants, but strict removal of SPAC is required because of the high risk of their leakage after CSF. PACIs of high-basicity produced by AICl(3) -titration and Al(OH)(3)-dissolution were the same in terms of the ferron assay and colloid charge, but their performance in CSF were completely different. High-basicity Al(OH)(3) -dissolution PACls formed large floc particles and yielded very few remaining SPAC particles in the filtrate, whereas high-basicity AICl(3)-titration PACls did not form large floc particles. High-basicity PACls produced by Al(OH)(3)-dissolution were superior to low-basicity PACT in lowering remaining SPAC particles by the same method because of their high charge neutralization capacity, although their floc formation ability was similar or slightly inferior. However, highbasicity Al(OH)(3)-dissolution PACT was inferior when the sulfate ion concentration in the raw water was low. Sulfate ions were required in the raw water for high-basicity PACls to be effective in floc formation. In particular, very high sulfate concentrations were required for high-basicity AICl(3)-titration PACls. The rate of hydrolysis, which is related to the polymerization of aluminum species, is a key property, besides charge neutralization capacity, for proper coagulation, including formation of large floc particles. The aluminum species in the high-basicity PACls, in particular that produced by AICl(3)-titration, was resistant to hydrolysis, but sulfate ions in raw water accelerated the rate of hydrolysis and thereby facilitated floc formation. Normal-basicity Al(OH)(3)-dissolution PACT was hydrolysis-prone, even without sulfate ions. Aluminum species in the high-basicity AICl(3)-titration PACT were mostly those with a molecular weight (MW) of 1-10 kDa, whereas those of high-basicity Al(OH)(3)-dissolution PACls were mostly characterized by a MW > 10 kDa. Normal-basicity Al(OH)(3)-dissolution PACT was the least polymerized and contained monomeric species. (C) 2020 Elsevier Ltd. All rights reserved.
  • Akiko Nakayama, Asuka Sakamoto, Taku Matsushita, Yoshihiko Matsui, Nobutaka Shirasaki
    WATER RESEARCH 182 2020年09月 [査読有り]
     
    Three different natural organic matter (NOM)-loading methods were compared for the adsorptive removal of 2-methylisoborneol (MIB) by superfine powdered activated carbon (SPAC) and conventionally-sized powdered activated carbon (PAC). The three NOM-loading methods were: NOM adsorption followed by MIB (MIB adsorption on NOM-preloaded carbon), MIB adsorption followed by NOM (MIB adsorption on NOM post-loaded carbon), and simultaneous NOM and MIB loading (MIB adsorption on NOM-simultaneously loaded carbon). MIB removals were similar for the smaller-sized carbon (SPAC) at higher AC dosages and at lower initial NOM concentrations. The similar MIB removals indicate direct site competition between MIB and NOM with MIB adsorption reversibility (complete desorption of MIB by NOM). At lower AC doses, especially for PACs, and at higher initial NOM concentrations, the adsorption of MlBs depended on the sequence of MIB or NOM adsorption. MIB removal was lowest for the NOM-preloaded carbon, followed by NOM-simultaneously loaded carbon. The highest MIB removal was achieved by post-loading of NOM, indicating that the adsorption is irreversible. MIB adsorption on SPAC was more reversible than on PAC, although the pore size distributions of the two carbons were similar. The high degree of adsorption irreversibility for PAC compared with SPAC indicated that pore blocking occurs due to NOM loading at the PAC particle surface. Images of the external adsorption were obtained using isotope mapping and 15 N-labeled effluent organic matter. (C) 2020 Elsevier Ltd. All rights reserved.
  • Yuanjun Zhao, Ryosuke Kitajima, Nobutaka Shirasaki, Yoshihiko Matsui, Taku Matsushita
    WATER RESEARCH 177 2020年06月 
    Commercially available powdered activated carbon (PAC) with a median diameter of 12-42 mu m was ground into 1 mu m sized superfine PAC (SPAC) and 200 nm sized submicron SPAC (SSPAC) and investigated as a pretreatment material for the prevention of hydraulically irreversible membrane fouling during a submerged microfiltration (MF) process. Compared with PAC and SPAC, SSPAC has a high capacity for selective biopolymer adsorption, which is a characteristic found in natural organic matter and is commonly considered to be a major contributor to membrane fouling. Precoating the membrane surface with SSPAC during batch filtration further removes the biopolymers by straining them out. In lab-scale membrane filtration experiments, an increase in the transmembrane pressure (TMP) was almost completely prevented through a precoating with SSPAC based on its pulse dose after coagulation pretreatment. The precoated SSPAC formed a dense layer on the membrane preventing biopolymers from attaching to the membrane. Coagulation pretreatment enabled the precoated activated carbon to be rinsed off during hydraulic backwashing. The functionality of the membrane was thereby retained for a long-term operation. Precoating the membranes with SSPAC after coagulation is a promising way to control membrane fouling, and efficiently prevents an increase in the TMP because of the straining effect of the SSPAC and the high capacity of the SSPAC to adsorb any existing biopolymers. (C) 2020 Elsevier Ltd. All rights reserved.
  • 松井佳彦
    Water Research 164 2019年11月 [査読有り][通常論文]
     
    1,4-Dioxane is one of the most persistent organic micropollutants and is quite difficult to remove via conventional drinking water treatment consisting of coagulation, sedimentation, and sand filtration. Vacuum ultraviolet (VUV) treatment has recently been found to show promise as a treatment method for 1,4-dioxane removal, but the associated decomposition rate of 1,4-dioxane is known to be very sensitive to water quality characteristics. Some computational models have been proposed to predict the decomposition rate of micropollutants during VUV treatment, but the effects of only bicarbonate and natural organic matter have been considered in the models. In the present study, we attempted to develop a versatile computational model for predicting the behavior of 1,4-dioxane during VUV treatment that took into account the effects of other coexisting inorganic ions commonly found in natural waters. We first conducted 1,4-dioxane decomposition experiments with low-pressure mercury lamps and test waters that had been prepared by adding various inorganic ions to an aqueous phosphate buffer. The apparent decomposition rate of 1,4-dioxane was suppressed when bicarbonate, chloride, and nitrate were added to the test waters. Whereas bicarbonate and chloride directly suppressed the apparent decomposition rate by consuming HO center dot, nitrate became influential only after being transformed into nitrite by concomitant UV light (lambda= 254 nm) irradiation. Cl-related radicals (Cl center dot and Cl-2 center dot(-)) did not react with 1,4-dioxane directly. A computational model consisting of 31 ordinary differential equations with respect to time that had been translated from 84 reactions (10 photochemical and 74 chemical reactions) among 31 chemical species was then developed for predicting the behavior of 1,4-dioxane during VUV treatment. Nine of the parameters in the ordinary differential equations were determined by least squares fitting to an experimental dataset that included different concentrations of bicarbonate, chloride, nitrate, and nitrite. Without further parameter adjustments, the model successfully predicted the behavior of 1,4-dioxane during VUV treatment of three groundwaters naturally contaminated with 1,4-dioxane as well as one dechlorinated tap water sample supplemented with 1,4-dioxane. (C) 2019 Elsevier Ltd. All rights reserved.
  • 松井佳彦
    Regulatory Toxicology and Pharmacology 106 43 - 49 2019年08月 [査読有り][通常論文]
     
    Volatilization volumes and health risks associated with indirect inhalation exposure to formaldehyde evaporated from water have not been investigated quantitatively. We experimentally investigated formaldehyde volatility, compared with chloroform volatility, predicted formaldehyde inhalation exposure concentrations in Japanese bathrooms, and then re-evaluated drinking water quality standards. Although the Henry's law constant of formaldehyde is 1/10(4) that of chloroform, with a 30-min exposure period, the formaldehyde non-equilibrium partition coefficient (K'(d)) was 1/500th the chloroform value because of formaldehyde's faster volatilization rate. We used this ratio to estimate the cumulative probability distribution of formaldehyde concentrations in bathroom air. For a formaldehyde concentration in water of <= 2.6 mg/L-water (WHO tolerable concentration), the probability that the incremental formaldehyde concentration due to volatilization would exceed 100 mu g/m(3)-air (WHO indoor air quality guideline) was low. However, major sources of formaldehyde in indoor air are building materials and furniture. We therefore calculated the allowable concentration in water by allocating a small percentage of the indoor air guideline value to indirect inhalation exposure via volatilization from tap water. With an allocation factor of 20% (10%), the allowable concentration was 0.52 (0.26) mg/L-water. These concentrations are similar to the Health Canada guideline concentration but they are 3-6 times the Japanese water quality standard.
  • 松井佳彦
    Water Research 155 66 - 75 2019年05月 [査読有り][通常論文]
     
    Superfine powdered activated carbon (SPAC) of micron to submicron particle size is produced by micro-milling of conventionally sized powdered activated carbon. SPAC has attracted attention because of its high adsorption capacity; however, milling to the submicron particle size range lowers its adsorption capacity. Here, we found that this decrease of adsorption capacity was due to the introduction of oxygen/hydrogen-containing functional groups into the graphene structure of the carbon from water during the milling, causing it to become less hydrophobic. This finding was supported by three analyses of SPAC particles before and after milling: 1) elemental analysis revealed increased oxygen and hydrogen content, 2) Boehm titration analysis revealed increased amounts of acidic functional groups, including carboxylic and phenolic hydroxyl groups, and 3) Fourier-transform infrared spectroscopy showed increased peaks at 1200, 1580, and 3400 cm(-1), confirming the presence of those groups. Dissolved oxygen concentration did not strongly affect the increase of oxygen content in SPAC, and no evidence was found for hydroxyl radical production during micro-milling, suggesting that a mechanochemical reaction underlies the increase in oxygen/hydrogen-containing functional groups. An increase in O-18 content in the SPAC particles after milling in water-O-18 indicated that the oxygen in the functional groups originated from the surrounding water. (C) 2019 Elsevier Ltd. All rights reserved.
  • Yoshifumi Nakazawa, Yoshihiko Matsui, Yusuke Hanamura, Koki Shinno, Nobutaka Shirasaki, Taku Matsushita
    WATER RESEARCH 147 311 - 320 2018年12月 [査読有り][通常論文]
     
    Because of the eminent adsorptive capacity and rate for dissolved organic molecules compared to conventionally-sized powdered activated carbon (PAC), super-fine powdered activated carbon (SPAC) is gathering momentum for use in not only the pretreatment for membrane filtration for drinking water purification but also the conventional water purification process consisting of coagulation-flocculation, sedimentation, and rapid sand-filtration (CSF). However, the probability of SPAC particles to leak through a sand bed is higher than that of PAC, and their strict leakage control is an issue to be challenged when applying SPAC to CSF. However, study focusing on very high particle removal, which yield residual concentrations down to around 100 particles/mL, has been very limited. A previous study mentioned that the tendency of SPAC leakage is related to its low destabilization. In response to this, the present study focused on the two key components of coagulation (mixing intensity and coagulants) and investigated how to effectively reduce the residual SPAC after CSF.Astonishingly, the flash mixing (the first process of CSF), especially its G (velocity gradient) value, played the most important role in determining the residual SPAC in the filtrate of sand filter (the fourth process). Even if the slow mixing time was short, a sufficiently large G value but short T (mixing time) value in flash mixing effectively reduced the residual SPAC. When the total GT value of flash and slow mixing was fixed at a constant, priority should be given to flash mixing to reduce the residual SPAC.Among 23 PACI (poly-aluminum chloride) coagulants, PACI with a high-basicity (basicity 70%) and with sulfate ion (0.14 of sulfate/aluminum in molar ratio), produced by Al(OH)(3)-dissolution, were the most effective to reduce the residual SPAC after CSF. PACIs produced by base-titration, which have been intensively investigated in previous researches, were not effective due to lack of floc-formation ability. However, their Al species composition determined by the ferron method were almost the same as those of PACT by Al(OH)(3)-dissolution, and their charge-neutralization capacities were higher. PACIs produced by Al(OH)(3)-dissolution possessed both charge-neutralization and floc-formation abilities, but the former ability was more important to minimize the residual of SPAC. (C) 2018 Elsevier Ltd. All rights reserved.
  • Ohno, K, Asami, M, Matsui, Y
    Journal of Water and Health 16 4 562 - 573 2018年08月 [査読有り][通常論文]
     
    Two liters per day is generally applied as the default drinking water intake rate for risk assessments, although evidence supporting this value is insufficient. This study aimed to reveal actual water intakes from tap water and other types of drinks, and to explore the relationships between these intakes. For this purpose, we conducted a nationwide Internet questionnaire survey. Tap water intake negatively correlated with bottled water and soft drink intakes, suggesting a mutually complementary relationship. We propose an index, potential Tap Water Intake (pTWI), calculated by adding soft drinks and bottled water to tap water intake. Mean per-capita tap water intake across the entire Japanese population was estimated at 1.28 L/d, whereas mean pTWI was estimated at 1.65 L/d. Two liters per day corresponds to the 88th percentile of tap water intake and to the 76th percentile of pTWI, and covers the intake of the majority of the population in Japan. This rate should continue being used as the default in the Japanese population, but the rate to cover the tap water intake of almost the entire population would be higher: it was >2.5 L/d.
  • Yoshifumi Nakazawa, Yoshihiko Matsui, Yusuke Hanamura, Koki Shinno, Nobutaka Shirasaki, Taku Matsushita
    WATER RESEARCH 138 160 - 168 2018年07月 [査読有り][通常論文]
     
    Superfine powdered activated carbon (SPAC; particle diameter similar to 1 mu m) has greater adsorptivity for organic molecules than conventionally sized powdered activated carbon (PAC). Although SPAC is currently used in the pretreatment to membrane filtration at drinking water purification plants, it is not used in conventional water treatment consisting of coagulation-flocculation, sedimentation, and rapid sand filtration (CSF), because it is unclear whether CSF can adequately remove SPAC from the water. In this study, we therefore investigated the residual SPAC particles in water after CSF treatment. First, we developed a method to detect and quantify trace concentration of carbon particles in the sand filtrate. This method consisted of 1) sampling particles with a membrane filter and then 2) using image analysis software to manipulate a photomicrograph of the filter so that black spots with a diameter >0.2 mu m (considered to be carbon particles) could be visualized. Use of this method revealed that CSF removed a very high percentage of SPAC: approximately 5-log in terms of particle number concentrations and approximately 6-log in terms of particle volume concentrations. When waters containing 7.5-mg/L SPAC and 30-mg/L PAC, concentrations that achieved the same adsorption performance, were treated, the removal rate of SPAC was somewhat superior to that of PAC, and the residual particle number concentrations for SPAC and PAC were at the same low level (100-200 partides/mL). Together, these results suggest that SPAC can be used in place of PAC in CSF treatment without compromising the quality of the filtered water in terms of particulate matter contamination. However, it should be noted that the activated carbon particles after sand filtration were smaller in terms of particle size and were chargeneutralized to a lesser extent than the activated carbon particles before sand filtration. Therefore, the tendency of small particles to escape in the filtrate would appear to be related to the fact that their small size leads to a low destabilization rate during the coagulation process and a low collision rate during the flocculation and filtration processes. (C) 2018 Elsevier Ltd. All rights reserved.
  • Taku Matsushita, Ayako Morimoto, Taisuke Kuriyama, Eisuke Matsumoto, Yoshihiko Matsui, Nobutaka Shirasaki, Takashi Kondo, Hirokazu Takanashi, Takashi Kameya
    Water Research 138 67 - 76 2018年07月01日 [査読有り][通常論文]
     
    Removal efficiencies of 28 pesticide transformation products (TPs) and 15 parent pesticides during steps in drinking water treatment (coagulation–sedimentation, activated carbon adsorption, and ozonation) were estimated via laboratory-scale batch experiments, and the mechanisms underlying the removal at each step were elucidated via regression analyses. The removal via powdered activated carbon (PAC) treatment was correlated positively with the log Kow at pH 7. The adjusted coefficient of determination (r2) increased when the energy level of the highest occupied molecular orbital (HOMO) was added as an explanatory variable, the suggestion being that adsorption onto PAC particles was largely governed by hydrophobic interactions. The residual error could be partly explained by π-π electron donor–acceptor interactions between the graphene surface of the PAC particles and the adsorbates. The removal via ozonation correlated positively with the energy level of the HOMO, probably because compounds with relatively high energy level HOMOs could more easily transfer an electron to the lowest unoccupied molecular orbital of ozone. Overall, the TPs tended to be more difficult to remove via PAC adsorption and ozonation than their parent pesticides. However, the TPs that were difficult to remove via PAC adsorption did not induce strong mutagenicity after chlorination, and the TPs that were associated with strong mutagenicity after chlorination could be removed via PAC adsorption. Therefore, PAC adsorption is hypothesized to be an effective method of treating drinking water to reduce the possibility of post-chlorination mutagenicity associated with both TPs and their parent pesticides.
  • Megumi Akiyama, Yoshihiko Matsui, Junki Kido, Taku Matsushita, Nobutaka Shirasaki
    Regulatory Toxicology and Pharmacology 95 161 - 174 2018年06月01日 [査読有り][通常論文]
     
    The probability distributions of total potential doses of disinfection byproducts and volatile organic compounds via ingestion, inhalation, and dermal exposure were estimated with Monte Carlo simulations, after conducting physiologically based pharmacokinetic model simulations to takes into account the differences in availability between the three exposures. If the criterion that the 95th percentile estimate equals the TDI (tolerable daily intake) is regarded as protecting the majority of a population, the drinking water criteria would be 140 (trichloromethane), 66 (bromodichloromethane), 157 (dibromochloromethane), 203 (tribromomethane), 140 (dichloroacetic acid), 78 (trichloroacetic acid), 6.55 (trichloroethylene, TCE), and 22 μg/L (perchloroethylene). The TCE criterion was lower than the Japanese Drinking Water Quality Standard (10 μg/L). The latter would allow the intake of 20% of the population to exceed the TDI. Indirect inhalation via evaporation from water, especially in bathrooms, was the major route of exposure to compounds other than haloacetic acids (HAAs) and accounted for 1.2–9 liter-equivalents/day for the median-exposure subpopulation. The ingestion of food was a major indirect route of exposure to HAAs. Contributions of direct water intake were not very different for trihalomethanes (30–45% of TDIs) and HAAs (45–52% of TDIs).
  • N. Shirasaki, T. Matsushita, Y. Matsui, R. Yamashita
    Water Research 129 460 - 469 2018年02月01日 [査読有り][通常論文]
     
    Here, we evaluated the removal of three representative human enteric viruses — adenovirus (AdV) type 40, coxsackievirus (CV) B5, and hepatitis A virus (HAV) IB — and one surrogate of human caliciviruses — murine norovirus (MNV) type 1 — by coagulation–rapid sand filtration, using water samples from eight water sources for drinking water treatment plants in Japan. The removal ratios of a plant virus (pepper mild mottle virus PMMoV) and two bacteriophages (MS2 and φX174) were compared with the removal ratios of human enteric viruses to assess the suitability of PMMoV, MS2, and φX174 as surrogates for human enteric viruses. The removal ratios of AdV, CV, HAV, and MNV, evaluated via the real-time polymerase chain reaction (PCR) method, were 0.8–2.5-log10 when commercially available polyaluminum chloride (PACl, basicity 1.5) and virgin silica sand were used as the coagulant and filter medium, respectively. The type of coagulant affected the virus removal efficiency, but the age of silica sand used in the rapid sand filtration did not. Coagulation–rapid sand filtration with non-sulfated, high-basicity PACls (basicity 2.1 or 2.5) removed viruses more efficiently than the other aluminum-based coagulants. The removal ratios of MS2 were sometimes higher than those of the three human enteric viruses and MNV, whereas the removal ratios of φX174 tended to be smaller than those of the three human enteric viruses and MNV. In contrast, the removal ratios of PMMoV were similar to and strongly correlated with those of the three human enteric viruses and MNV. Thus, PMMoV appears to be a suitable surrogate for human enteric viruses for the assessment of the efficacy of coagulation–rapid sand filtration to remove viruses.
  • Taku Matsushita, Shiho Honda, Taisuke Kuriyama, Yuki Fujita, Takashi Kondo, Yoshihiko Matsui, Nobutaka Shirasaki, Hirokazu Takanashi, Takashi Kameya
    Water Research 129 347 - 356 2018年02月01日 [査読有り][通常論文]
     
    We used Ames assays to investigate the effects of ozonation (designated O3), ozonation followed by chlorination (O3/Cl), an advanced oxidation process (AOP, UV/H2O2), and AOP followed by chlorination (AOP/Cl) on the mutagenicity of solutions of 3-methyl-4-nitrophenol (3M4NP), a major environmental degradation product of the organophosphorus insecticide fenitrothion. Whereas O3 did not induce mutagenicity, O3/Cl, AOP, and AOP/Cl converted 3M4NP into mutagenic transformation products (TPs). Using liquid chromatography–mass spectrometry, we detected a total of 138 peaks in the solutions subjected to O3/Cl, AOP, and AOP/Cl. To elucidate the TPs responsible for the observed mutagenicity, we performed simple regression analyses of the relationship between the area of each peak and the observed mutagenicity of samples withdrawn periodically during each oxidation process. The area of each of 10 peaks was found to be positively correlated (r2 ≥ 0.8) with the observed mutagenicity, suggesting that the TPs corresponding to these peaks contributed to the mutagenicity. After taking into account the consistency of mutagenicity induction by the oxidation processes and analyzing the peaks by tandem mass spectrometry, we identified 3 TPs, corresponding to 6 peaks, as candidate mutagens. These TPs were assessed by means of 4 quantitative structure–activity relationship (QSAR) models, and all 3 were predicted to be mutagenic by at least one model. This result was consistent with our assumption that these TPs were mutagens. Ames assays of an authentic sample of one of the 3 TPs revealed that it did not contribute to the mutagenicity. This left 3-methoxy-4-nitrophenol and 2-[(E)-[(2,5-dihydroxyphenyl) methylidene]amino]-5-dihydroxybenzaldehyde on the list of mutagens suspected of contributing to the mutagenicity induced by AOP. No TPs were identified as candidate mutagens responsible for the mutagenicity induced by O3/Cl and AOP/Cl.
  • Taku Matsushita, Miki Sakuma, Shiori Tazawa, Taiki Hatase, Nobutaka Shirasaki, Yoshihiko Matsui
    WATER RESEARCH 125 332 - 340 2017年11月 [査読有り][通常論文]
     
    Off-flavor in drinking water can be caused by transformation products (TPs) generated from organic compounds, such as amino acids, present during chlorination. However, the contributions of many of these TPs to overall off-flavor have not been quantified, mainly because the lack of appropriate chemical standards prevents sensory evaluation by means of a conventional flask test. In the present study, we used gas chromatography mass spectrometry olfactometry (GC-MS-O) to identify compounds responsible for the off-flavor generated by chlorination of an aqueous solution of the amino acid phenylalanine, and we propose a sensory evaluation procedure for quantification of the contributions of the identified TPs to the overall off-flavor, regardless of the availability of chemical standards of the TPs. GC-MS-O revealed that two TPs, N-chlorophenylacetaldimine and 2-chloro-2-phenylacetaldehyde, for which chemical standards are not commercially available, were the main components responsible for the off-flavor of the chlorinated solution. By using a sensory evaluation procedure involving a combination of GC-MS-0 and a conventional flask test, we quantified the contributions of TPs to the overall off-flavor of the chlorinated solution. Approximately 60% of the off-flavor was attributable to free chlorine (13%), 2-chloro-2-phenylacetaldehyde (13%), trichloramine (12%) phenylacetaldehyde (11%) phenylacetonitrile (8%), and N-chlorophenylacetaldimine (2%). Treatment with powdered activated carbon (PAC) removed the off-flavor. Experiments with chlorination of N-15-labeled phenylalanine suggested that PAC reductively decomposed trichloramine into N-2 gas and adsorbed all of the other identified TPs. Superfine PAC (median diameter, 0.7 mu m) removed the off-flavor more rapidly than normal-size PAC (median diameter, 8.0 mu m). (C) 2017 Elsevier Ltd. All rights reserved.
  • Long Pan, Yuki Nishimura, Hideki Takaesu, Yoshihiko Matsui, Taku Matsushita, Nobutaka Shirasaki
    WATER RESEARCH 124 425 - 434 2017年11月 [査読有り][通常論文]
     
    The capacity of activated carbon particles with median diameters (D50s) of >similar to 1 mu m for adsorption of hydrophobic micropollutants such as 2-methylisolborneol (MIB) increases with decreasing particle size because the pollutants are adsorbed mostly on the exterior (shell) of the particles owing to the limited diffusion penetration depth. However, particles with D50s of <1 mu m have not been thoroughly investigated. Here, we prepared particles with D50s of similar to 30 mu m-similar to 140 nm and evaluated their adsorption capacities for MIB and several other environmentally relevant adsorbates. The adsorption capacities for low-molecular-weight adsorbates, including MIB, deceased with decreasing particle size for D50s of less than a few micrometers, whereas adsorption capacities increased with decreasing particle size for larger particles. The oxygen content of the particles increased substantially with decreasing particle size for D50s of less than a few micrometers, and oxygen content was negatively correlated with adsorption capacity. The decrease in adsorption capacity with decreasing particle size for the smaller particles was due to particle oxidation during the micromilling procedure used to decrease D50 to similar to 140 nm. When oxidation was partially inhibited, the MIB adsorption capacity decrease was attenuated. For high molecular-weight adsorbates, adsorption capacity increased with decreasing particle size over the entire range of tested particle sizes, even though particle oxygen content increased with decreasing particle size. (C) 2017 Elsevier Ltd. All rights reserved.
  • Yoshihiko Matsui, Nobutaka Shirasaki, Takuro Yamaguchi, Kenta Kondo, Kaori Machida, Taiga Fukuura, Taku Matsushita
    WATER RESEARCH 118 177 - 186 2017年07月 [査読有り][通常論文]
     
    We evaluated 51 poly-aluminum chloride (PACl) coagulants to determine the coagulant characteristics that were responsible for effective arsenate removal from contaminated river water by means of experiments involving coagulation, settling, and microfiltration. Some of the high-basicity PACls exhibited high arsenate removal percentages, particularly under alkaline conditions, and we investigated various relevant properties and characteristics of these high-basicity PACls. Effective arsenate removal was correlated with the content of polymeric and colloidal aluminum species (Alb and Alc) in the PACls but was not well correlated with colloid charge or zeta potential. Multiple regression analysis revealed that a portion of Alb and Alc, which reacted with the ferron reagent during the period from 30 min to 3 h, that is, the (Al30min-3h) fraction, had the highest arsenate sorption capacity, followed by a colloidal aluminum fraction (Al->3h, which reacted with ferron at a time of >3 h). The Al30min-3h fraction was stable, and its arsenate sorption capacity did not decrease markedly with increasing pH. The Al30min-3h fraction did not correspond to the Keggin-type e-Al-13 polycation or the delta-Al-30 polycation; it is likely to be an aluminum polymer that is unobservable by Al-27 NMR spectroscopy. Our results suggest that PACls with a high proportion of the Al30min-3h fraction should be used for enhanced arsenate removal by coagulation. A high content of the e-Al-13 polycation or the delta-Al-30 polycation was not indispensable for effective arsenate removal. (C) 2017 Elsevier Ltd. All rights reserved.
  • Kamata, M, Asami, M, Matsui, Y
    Chemosphere 178 333 - 339 2017年07月 [査読有り][通常論文]
     
    Triketone herbicides are becoming popular because of their herbicidal activity against sulfonylurea-resistant weeds. Among these herbicides, tefuryltrione (TFT) is the first registered herbicide for rice farming, and recently its distribution has grown dramatically. In this study, we developed analytical methods for TFT and its degradation product 2-chloro-4-methylsulfonyl-3-[(tetrahydrofuran-2-ylmethoxy) methyl] benzoic acid (CMTBA). TFT was found frequently in surface waters in rice production areas at concentrations as high as 1.9 a. The maximum observed concentration was lower than but close to 2 mu g/L, which is the Japanese reference concentration of ambient water quality for pesticides. However, TFT was not found in any drinking waters even though the source waters were purified by conventional coagulation and filtration processes; this was due to chlorination, which transforms TFT to CMTBA. The conversion rate of TFT to CMBA on chlorination was almost 100%, and CMTBA was stable in the presence of chlorine. Moreover, CMTBA was found in drinking waters sampled from household water taps at a similar concentration to that of TFT in the source water of the water purification plant. Although the acceptable daily intake and the reference concentration of CMTBA are unknown, the highest concentration in drinking water exceeded 0.1 mu g/L, which is the maximum allowable concentration for any individual pesticide and its relevant metabolites in the European Union Drinking Directive. (C) 2017 Elsevier Ltd. All rights reserved.
  • Long Pan, Yuichi Takagi, Yoshihiko Matsui, Taku Matsushita, Nobutaka Shirasaki
    WATER RESEARCH 114 50 - 58 2017年05月 [査読有り][通常論文]
     
    We milled granular activated carbons (GACs) that had been used for 0-9 years in water treatment plants and produced carbon particles with different sizes and ages: powdered activated carbons (PAC, median diameter 12-42 mu m), superfine PAC (SPAC, 0.9-3.5 mu m), and submicron-sized SPAC (SSPAC, 220 290 nm). The fact that SPAC produced from 1-year-old GAC and SSPAC from 2-year-old GAC removed 2-methylisoborneol (MIB) from water with an efficiency similar to that of virgin PAC after a carbon contact time of 30 min suggests that spent GAC could be reused for water treatment after being milled. This potential for reuse was created by increasing the equilibrium adsorption capacity via reduction of the carbon particle size and improving the adsorption kinetics. During long-term (>1 year) use in GAC beds, the volume of pores in the carbon, particularly pores with widths of 0.6-0.9 nm, was greatly reduced. The equilibrium adsorption capacities of the carbon for compounds with molecular sizes in this range could therefore decrease with increasing carbon age. Among these compound's, the decreases of capacities were prominent for hydrophobic compounds, including MIB. For hydrophobic compounds, however, the equilibrium adsorption capacities could be increased with decreasing carbon particle size. The iodine number, among other indices, was best correlated with the equilibrium adsorption capacity of the MIB and would be a good index to assess the remaining MIB adsorption capacity of spent carbon. Spent GAC can possibly be reused as SPAC or SSPAC if its iodine number is >= 600 mg/g. (C) 2017 Elsevier Ltd. All rights reserved.
  • N. Shirasaki, T. Matsushita, Y. Matsui, K. Murai
    WATER RESEARCH 115 29 - 39 2017年05月 [査読有り][通常論文]
     
    Here, we evaluated the efficacy of direct microfiltration (MF) and ultrafiltration (UF) to remove three representative human enteric viruses (i.e., adenovirus [AdV] type 40, coxsackievirus [CV] B5, and hepatitis A virus [HAV] IB), and one surrogate of human caliciviruses (i.e., murine norovirus [MNV] type 1). Eight different MF membranes and three different UF membranes were used. We also examined the ability of coagulation pretreatment with high-basicity polyaluminum chloride (PACl) to enhance virus removal by MF. The removal ratios of two bacteriophages (MS2 and phi X174) and a plant virus (pepper mild mottle virus; PMMoV) were compared with the removal ratios of the human enteric viruses to assess the suitability of these viruses to be used as surrogates for human enteric viruses. The virus removal ratios obtained with direct MF with membranes with nominal pore sizes of 0.1-0.22 mu m differed, depending on the membrane used; adsorptive interactions, particularly hydrophobic interactions between virus particles and the membrane surface, were dominant factors for virus removal. In contrast, direct UF with membranes with nominal molecular weight cutoffs of 1-100 kDa effectively removed viruses through size exclusion, and >4-log(10) removal was achieved when a membrane with a nominal molecular weight cutoff of 1 kDa was used. At pH 7 and 8, in-line coagulation-MF with non-sulfated high-basicity PACls containing Al-30 species had generally a better virus removal (i.e., >4-log(10) virus removal) than the other aluminum-based coagulants, except for phi X174. For all of the filtration processes, the removal ratios of AdV, CV, HAV, and MNV were comparable and strongly correlated with each other. The removal ratios of MS2 and PMMoV were comparable or smaller than those of the three human enteric viruses and MNV, and were strongly correlated with those of the three human enteric viruses and MNV. The removal ratios obtained with coagulation-MF for phi X174 were markedly smaller than those obtained for the three human enteric viruses and MNV. However, because MS2 was inactivated after contact with PACI during coagulation pretreatment, unlike AdV, CV, MNV, and PMMoV, the removal ratios of infectious MS2 were probably an overestimation of the ability of coagulation-MF to remove infectious AdV, CV, and caliciviruses. Thus, PMMoV appears to be a suitable surrogate for human enteric viruses, whereas MS2 and phi X174 do not, for the assessment of the efficacy of membrane filtration processes to remove viruses. (C) 2017 Elsevier Ltd. All rights reserved.
  • Taku Matsushita, Yoshihiko Matsui, Shohei Ikekame, Miki Sakuma, Nobutaka Shirasaki
    ENVIRONMENTAL SCIENCE & TECHNOLOGY 51 8 4541 - 4548 2017年04月 [査読有り][通常論文]
     
    Mechanisms underlying trichloramine removal with activated carbon treatment were proven by batch experiments and theoretical analysis with diffusion-reaction models. The observed values of trichloramine and free chlorine were explained only by the model in which (1) both trichloramine and free chlorine were involved as reactants, (2) the removals of reactants were affected both by the intraparticle diffusion and by the reaction with activated carbon, and (3) trichloramine decomposition was governed by two distinct reductive reactions. One reductive reaction was expressed as a first-order reaction: the reductive reaction of trichloramine with the basal plane of PAC, which consists of graphene sheets. The other reaction was expressed as a second-order reaction: the reductive reaction of trichloramine with active functional groups located on the edge of the basal plane. Free chlorine competitively reacted with-both the basal plane and the active functional groups. The fact that the model prediction succeeded even in experiments with different activated carbon doses, with different initial trichloramine concentrations, and with different sizes of activated carbon particles clearly proved that the mechanisms described in the model were reasonable for explaining trichloramine removal with activated carbon treatment.
  • N. Shirasaki, T. Matsushita, Y. Matsui, K. Murai, A. Aochi
    JOURNAL OF HAZARDOUS MATERIALS 326 110 - 119 2017年03月 [査読有り][通常論文]
     
    We examined the removal of representative contaminant candidate list (CCL) viruses (coxsackievirus [CV] B5, echovirus type [EV] 11, and hepatitis A virus [HAV] IB), recombinant norovirus virus-like particles (rNV-VLPs), and murine norovirus (MNV) type 1 by coagulation. Water samples were subjected to coagulation with polyaluminum chloride (PACT, basicity 1.5) followed by either settling or settling and filtration. Together with our previously published results, the removal ratio order, as evaluated by a plaque-forming-unit method or an enzyme-linked immunosorbent assay after settling, was HAV > EV = rNV-VLPs >= CV = poliovirus type 1 = MNV> adenovirus type 40 (range, 0.1-2.7-log(10)). Infectious HAV was likely inactivated by the PACl and therefore was removed to a greater extent than the other viruses. A nonsulfated high-basicity PACl (basicity 2.1), removed the CCL viruses more efficiently than did two other sulfated PACls (basicity 1.5 or 2.1), alum, or ferric chloride. We also examined the removal ratio of two bacteriophages. The removal ratios for MS2 tended to be larger than those of the CCL viruses, whereas those for phi X174 were comparable with or smaller than those of the CCL viruses. Therefore, phi X174 may be a useful conservative surrogate for CCL viruses during coagulation. (C) 2016 Elsevier B.V. All rights reserved.
  • 小坂浩司, 浅見真理, 佐々木万紀子, 松井佳彦, 秋葉道宏
    水環境学会誌 40(3) 3 125 - 133 公益社団法人 日本水環境学会 2017年 [査読有り][通常論文]
     
    全国の水道事業を対象に2009~2011年度の原水での農薬の測定計画と検出状況の関連性を水道統計のデータを基に解析した。農薬を測定した水道事業は約650, その約20%で農薬が検出された。農薬を測定した水道事業を水道水源, 農薬の測定回数と測定種類数で分類したとき, 地表水を水源とし農薬の測定回数と測定種類数が多い水道事業のグループは農薬を検出した水道事業の割合 (検出率) や検出された農薬の種類数が多かった。農薬の測定回数が1回のグループは農薬が検出された水道事業の割合は少なく, その多くは1種の農薬を単年度のみで検出していた。地下水を水道水源に使用している水道事業は総じて検出率は低かった。検出された個別農薬は77種, 比較的多くの水道事業 (10以上) で検出されたのは10種程度であった。検出される可能性がある農薬には地域多様性があるが, いくつかは全国の多くの水道事業から検出される可能性が示された。
  • Long Pan, Yoshihiko Matsui, Taku Matsushita, Nobutaka Shirasaki
    WATER RESEARCH 102 516 - 523 2016年10月 [査読有り][通常論文]
     
    Superfine powdered activated carbon (SPAC), which is produced from conventionally sized powdered activated carbon (PAC) by wet milling in a bead mill, has attracted attention for its high adsorptive removal ability in both research and practice. In this study, the performance of dry-milled SPAC was investigated. 2-Methylisoborneol (MIB), an earthy-musty compound commonly targeted by water treatment systems, was used as the target adsorbate. Dry-milled SPAC exhibited lower adsorptive removal of MIB than wet-milled SPAC, even when both SPACs were produced from the same PAC and were composed of particles of the same size. One reason for the lower removal of MIB by the dry-milled SPAC was a higher degree of aggregation in the dry-milled SPAC after production; as a result the apparent particle size of dry-milled SPAC was larger than that of wet-milled SPAC. The dry-milled SPAC was also more negatively charged than the wet-milled SPAC, and, owing to its higher repulsion, it was more amenable to dispersion by ultrasonication. However, even after the dry-milled SPAC was ultrasonicated so that its apparent particle size was similar to or less than that of the wet-milled SPAC, the dry-milled SPAC was still inferior in adsorptive removal to the wet-milled SPAC. Therefore, another reason for the lower adsorptive removal of dry-milled SPAC was its lower equilibrium adsorption capacity, due to the oxidation during the milling. The adsorption kinetics by SPACs with different degrees of particle aggregation were successfully simulated by a pore diffusion model and a fractal aggregation model. (C) 2016 Elsevier Ltd. All rights reserved.
  • Shirasaki, N, Matsushita, T, Matsui, Y, Marubayashi, T, Murai, K
    Science of the Total Environment 563 29 - 39 2016年09月 [査読有り][通常論文]
     
    We evaluated the removal of enteric adenovirus (AdV) type 40 and poliovirus (PV) type 1 by coagulation, using water samples from 13 water sources for drinking water treatment plants in Japan. The behaviors of two widely accepted enteric virus surrogates, bacteriophages MS2 and phi X174, were compared with the behaviors of AdV and PV. Coagulation with polyaluminum chloride (PACl, basicity 1.5) removed AdV and PV from virus-spiked source waters: the infectious AdV and PV removal ratios evaluated by means of a plaque-forming-unit method were 0.1-1.4-log(10) and 0.5-2.4-log(10), respectively. A nonsulfated high-basicity PACl (basicity 2.1) removed infectious AdV and PV more efficiently than did other commercially available PACls (basicity 1.5-2.1), alum, and ferric chloride. The MS2 removal ratios tended to be larger than those of AdV and PV, partly because of differences in the hydrophobicities of the virus particles and the sensitivity of the virus to the virucidal activity of PACl; the differences in removal ratios were not due to differences in the surface charges of the virus particles. MS2, which was more hydrophobic than the other viruses, was inactivated during coagulation with PACl. Therefore, MS2 does not appear to be an appropriate surrogate for AdV and PV during coagulation. In contrast, because phi X174, like AdV and PV, was not inactivated during coagulation, and because the hydrophobicity of phi X174 was similar to or somewhat lower than the hydrophobicities of AdV and PV, the phi X174 removal ratios tended to be similar to or somewhat smaller than those of the enteric viruses. Therefore, phi X174 is a potential conservative surrogate for AdV and PV during coagulation. In summary, the surface hydrophobicity of virus particles and the sensitivity of the virus to the virucidal activity of the coagulant are probably important determinants of the efficiency of virus removal during coagulation. (c) 2016 Elsevier B.V. All rights reserved.
  • N. Shirasaki, T. Matsushita, Y. Matsui, K. Ohno
    WATER SCIENCE AND TECHNOLOGY-WATER SUPPLY 16 3 737 - 745 2016年06月 [査読有り][通常論文]
     
    Noroviruses (NVs) are one of the leading causes of epidemic gastroenteritis around the world. Water treatment technologies using membrane filtration for virus removal are becoming increasingly important. However, experiments to test removal of NVs from water have been hampered because NVs do not grow in cell culture or in small-animal models and therefore cannot be easily artificially propagated. Expression of the NV genome in a baculovirus-silkworm expression system has produced recombinant NV virus-like particles (rNV-VLPs) that aremorphologically and antigenically similar to native NV. Here, we characterized these rNV-VLPs and evaluated their potential use in assessing NV removal. Electron microscopic analysis and peptide mass fingerprinting showed that the rNV-VLPs were morphologically identical to native NV. In addition, surface charge and particle size distribution, which are important factors for explaining virus particle behavior during membrane filtration, were successfully evaluated by using rNV-VLPs. The rNV-VLPs were easy to quantify with a commercially available enzyme-linked immunosorbent assay kit, they remained stable for several days at 4 degrees C after dilution in river water, and they were easy to concentrate with the ultrafiltration entrapment method used. Thus, rNV-VLPs can be used to facilitate our understanding of the behavior of NVs during membrane filtration processes.
  • Nobutaka Shirasaki, Taku Matsushita, Yoshihiko Matsui, Takuya Marubayashi
    JOURNAL OF WATER SUPPLY RESEARCH AND TECHNOLOGY-AQUA 65 4 322 - 329 2016年06月 [査読有り][通常論文]
     
    We investigated the effect of coagulant basicity on bacteriophage removal from river water by polyferric chloride (PFC). PFC at three basicities (basicity 0.9-2.1) was prepared by means of base titration (NaOH was added to ferric chloride (FeCl3) solution) and the virus removal efficiencies of those PFCs were compared with that of FeCl3 (basicity 0). The virus removal efficiencies of the PFCs were equal to or less than that of FeCl3 at both pH 6 and pH 8. This suggests that, unlike aluminum-based coagulants, increasing the basicity of iron-based coagulants does not improve virus removal efficiency. Furthermore, the relative abundance of monomeric iron(III) species in the PFCs decreased, whereas that of precipitated iron(III) species increased with increasing basicity, as assessed with a ferron method. Colloid charge density also decreased with increasing basicity. Therefore, it is likely that the reduction in the abundance of monomeric iron(III) species led to the reduction in colloid charge density, which then reduced virus removal efficiency. Thus, the development of novel iron-based coagulants with increased virus removal efficiency may not be possible by simply increasing the basicity of the coagulant.
  • Matsushita, T, Hashizuka, M, Kuriyama, T, Matsui, Y, Shirasaki, N
    Chemosphere 148 233 - 240 2016年04月 [査読有り][通常論文]
     
    The effects of two water purification processes (ozonation, and chlorination after ozonation) on the mutagenicity of a solution containing iopamidol (X-ray contrast medium) were investigated by using the Ames assay. No mutagenicity was observed during ozonation. In contrast, mutagenicity was induced by the ozone-treated iopamidol-containing solution after subsequent chlorination, indicating that mutagenic transformation-products (TPs) were generated. Ten of 70 peaks detected on the LC/MS total ion chromatogram (TIC) of the ozone-treated iopamidol-containing solution after chlorination had a positive correlation (r(2) > 0.6) between their peak areas and the observed mutagenicity, suggesting that TPs detected as these peaks may induce mutagenicity. To narrow down the possible contributors to the observed mutagenicity, we compared the areas of the peaks on the TIC-charts with and without chlorination. Of the ten peaks, six were also detected in the ozone-treated iopamidol-containing solution without chlorination, which did not induce mutagenicity, indicating that these peaks were not related to the observed mutagenicity. Accurate m/z values and MS/MS analysis with an orbitrap MS of the remaining four peaks revealed that two of them represented the same TP in the negative and positive ion modes. The three remaining TPs were assessed in four quantitative structure activity relationship models for predicting Ames mutagenicity. At least one model predicted that two of the three TPs were mutagenic, whereas none of the models predicted that the other TP was a mutagen, suggesting that the former TPs, estimated as N1-acetyl-5-amino-6-chloro-2-iodobenzene-1,3-dicarboxamide and 3-hydroxy-243-[(2-hydroxyethoxy)carbony1]-2,4,6-triiodo-5-nitrobenzoyl}amino)propanoic acid, could be the candidate compounds that contributed to the observed mutagenicity. (C) 2016 Elsevier Ltd. All rights reserved.
  • N. Shirasaki, T. Matsushita, Y. Matsui, T. Marubayashi
    CHEMICAL ENGINEERING JOURNAL 284 786 - 793 2016年01月 [査読有り][通常論文]
     
    We prepared different types of aluminum-based coagulants, consisting of mainly monomeric aluminum species, polymeric aluminum species, or colloidal aluminum species, to investigate the effect of aluminum hydrolyte species on the removal of two types of human enteroviruses, poliovirus (PV) type 1 and the free-chlorine-resistant virus coxsackievirus (CV) B5, from lake and river water samples during the coagulation process. We found that differences in the distribution of the aluminum hydrolyte species in the coagulant affected the removal of these enteroviruses during coagulation: the removal ratios of PV and CV observed with polyaluminum chloride (PACl) with a high colloidal aluminum content and a basicity of 2.1 (i.e., PACl-2.1c) were larger than those observed with high monomeric aluminum content coagulant (i.e., AlCl3 solution) and with high polymeric aluminum content coagulant PACl (PACl-2.1b). Unlike AlCl3 or PACl-2.1b, PACl-2.1c contains Al-30 species, indicating that Al-30 species probably play a major role in the removal of enteroviruses. The PV and CV removal ratios were almost identical, regardless of the coagulant type or viral quantification method used (plaque-forming unit method or real-time polymerase chain reaction method), suggesting that PV and CV behaved similarly during the coagulation process. We also experimentally confirmed that the main mechanism for virus removal was coprecipitation into growing aluminum hydroxide during charge neutralization; virus adsorption onto formed aluminum hydroxide flocs also contributed to virus removal, but played a limited role. (C) 2015 Elsevier B.V. All rights reserved.
  • Yoshihiko Matsui, Soichi Nakao, Asuka Sakamoto, Takuma Taniguchi, Long Pan, Taku Matsushita, Nobutaka Shirasaki
    WATER RESEARCH 85 95 - 102 2015年11月 [査読有り][通常論文]
     
    The adsorption capacities of nine activated carbons for geosmin and 2-methylisoborneol (MIB) were evaluated. For some carbons, adsorption capacity substantially increased when carbon particle diameter was decreased from a few tens of micrometers to a few micrometers, whereas for other carbons, the increase of adsorption capacity was small for MIB and moderate for geosmin. An increase of adsorption capacity was observed for other hydrophobic adsorbates besides geosmin and MIB, but not for hydrophilic adsorbates. The parameter values of a shell adsorption model describing the increase of adsorption capacity were negatively correlated with the oxygen content of the carbon among other characteristics. Low oxygen content indicated low hydrophilicity. The increase of adsorption capacity was related to the hydrophobic properties of both adsorbates and activated carbons. For adsorptive removal of hydrophobic micropollutants such as geosmin, it is therefore recommended that less-hydrophilic activated carbons, such as coconut-shell-based carbons, be microground to a particle diameter of a few micrometers to enhance their equilibrium adsorption capacity. In contrast, adsorption by hydrophilic carbons or adsorption of hydrophilic adsorbates occur in the inner pores, and therefore adsorption capacity is unchanged by particle size reduction. (C) 2015 Elsevier Ltd. All rights reserved.
  • Taku Matsushita, Nozomi Kobayashi, Masahiro Hashizuka, Haruki Sakuma, Takashi Kondo, Yoshihiko Matsui, Nobutaka Shirasaki
    CHEMOSPHERE 135 101 - 107 2015年09月 [査読有り][通常論文]
     
    In the present study, the effects of chlorination on the mutagenicity (assessed via the Ames assay) and acute toxicity (assessed via a bioluminescence inhibition assay) of solutions containing one of five commonly used iodinated X-ray contrast media (ICM) (iopamidol, iohexol, iopromide, iomeprol, and diatrizoate) were investigated. Of the five ICM tested, only iopamidol was degraded by chlorine. Chlorination of the iopamidol-containing solution induced both mutagenicity and acute toxicity, which increased with chlorination time (up to 96 h). The areas of five out of 54 peaks detected on the LC/MS total ion chromatogram had good correlation (r(2) > 0.90) between peak area and observed mutagenicity. To identify possible contributors to the observed mutagenicity, the Ames assay and LC/MS analysis were conducted on samples collected at 48-h chlorination time and extracted under different pH conditions. Of the five peaks, one peak was detected in the sample extracted at pH 7, but this sample was not mutagenic, indicating that the peak was not related to the observed mutagenicity. MS/MS analysis with an orbitrap mass spectrometer of the remaining four peaks revealed that two of the peaks represented the same TP (detected in negative and positive ion modes). Finally, three TPs were identified as suspected contributors to the mutagenicity induced by the iopamidol-containing solution after chlorination: 5-[(1,3-dihydroxypropan-2-yl)carbamoyl]-3-[(3-hydroxypropanoyl)oxy]-2,4-diiodobenzoic acid; N-(1,3-dihydroxypropan-2-yl)-3-(2,3-dioxopropyl)-2,4,6-triiodobenzamide; and 3-[(1,3-dihydroxypropan-2-yl)carbamoyl]-5-[(3-hydroxybutanoyl)oxy]-2,4,6-triiodobenzoic acid. Prediction of the mutagenicity potential of these three TPs with a battery of four quantitative structure-activity relationship models did not contradict our conclusion that these TPs contributed to the observed mutagenicity. (C) 2015 Elsevier Ltd. All rights reserved.
  • Taku Matsushita, Keisuke Nakamura, Yoshihiko Matsui, Nobutaka Shirasaki
    MEMBRANE WATER TREATMENT 6 3 225 - 235 2015年05月 [査読有り][通常論文]
     
    During low-pressure membrane treatments of cyanobacterial cells, including microfiltration (MF) and ultrafiltration (UF), there have reportedly been releases of intracellular compounds including cyanotoxins and compounds with an earthy-musty odor into the water, probably owing to cyanobacterial cell breakage retained on the membrane. However, to our knowledge, no information was reported regarding the effect of growth phase of cyanobacterial cells on the release of the intracellular compounds. In the present study, we used a geosmin-producing cyanobacterium, Anabaena smithii, to investigate the effect of the growth phase of the cyanobacterium on the release of intracellular geosmin during laboratory-scale MF experiments with the cells in either the logarithmic growth or stationary phase. Separate detection of damaged and intact cells revealed that the extent of cell breakage on the MF membrane was almost the same for logarithmic growth and stationary phase cells. However, whereas the geosmin concentration in the MF permeate increased after 3 h of filtration with cells in the logarithmic growth phase, it did not increase during filtration with cells in the stationary phase: the trend in the geosmin concentration in the MF permeate with time was much different between the logarithmic growth and stationary phases. Adsorption of geosmin to algogenic organic matter (AOM) retained on the MF membrane and/or pore blocking with the AOM were greater when the cells were in the stationary phase versus the logarithmic growth phase, the result being a decrease in the apparent release of intracellular geosmin from the stationary phase cells. In actual drinking water treatment plants employing membrane processes, more attention should be paid to the cyanobacterial cells in logarithmic growth phase than in stationary phase from a viewpoint of preventing the leakage of intracellular earthy-musty odor compounds to finished water.
  • T. Matsushita, S. Hirai, T. Ishikawa, Y. Matsui, N. Shirasaki
    PROCESS SAFETY AND ENVIRONMENTAL PROTECTION 94 528 - 541 2015年03月 [査読有り][通常論文]
     
    We report the first use of vacuum ultraviolet (VUV) treatment to decompose 1,4-dioxane, a persistent organic contaminant that is difficult to remove by conventional drinking water treatment processes. The efficiency of VUV treatment was compared to that of VUV- and UV-based advanced oxidation processes (AOPs) (VUV/TiO2, VUV/H2O2, UV/TiO2, and UV/H2O2), and by-product formation was investigated. VUV treatment decomposed 1,4-dioxane more rapidly than did UV and UV/TiO2 treatments. The decomposition rate was enhanced when VUV irradiation was combined with TiO2 or H2O2. VUV/H2O2 decomposed 1,4-dioxane more rapidly than UV/H2O2 at a low H2O2 dose (1 mg/L), but the rate difference became small at a high H2O2 dose (5 mg/L). Electrical energy per order analysis revealed that VUV treatment, and the VUV- and UV-based AOPs, were economically feasible for 1,4-dioxane decomposition. Using raw water samples, we investigated by-product formation during VUV treatment and the effect of VUV irradiation on chlorinated disinfection by-product formation potential. Although the samples contained high concentrations of bromide, no bromate was produced by VUV treatment. VUV treatment slightly decreased trihalomethane formation potential (THMFP), whereas haloacetic acid formation potential (HAAFP) was unchanged, and total aldehyde concentration increased. The trend in HAAFP agreed with that had been reported for the VUV irradiation with much higher dose (Buchanan et al., 2006), whereas the trend in THMFP was different from that with much higher dose. THMFP, HAAFP, and aldehyde concentration were reduced by subsequent treatment with granular activated carbon (GAG) or biological activated carbon (BAG). Nitrite was produced by VUV treatment but disappeared after subsequent BAG treatment. These results suggest that VUV treatment should be combined with GAG or BAG treatment to suppress by-product formation. (C) 2014 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.
  • Masaoki Kimura, Yoshihiko Matsui, Shun Saito, Tomoya Takahashi, Midori Nakagawa, Nobutaka Shirasaki, Taku Matsushita
    JOURNAL OF MEMBRANE SCIENCE 477 115 - 122 2015年03月 [査読有り][通常論文]
     
    The extent of hydraulically irreversible membrane fouling in a coagulation-filtration system depends on several factors, including properties of the coagulant. Effects of polyaluminum chloride (PACI) coagulant properties, specifically basicity and sulfation, were investigated by conducting long-term direct filtration experiments. Elemental analysis determined Al and Si to be the major foulants, though the Si/Al ratios of the foulants differed from those of coagulated floc particles. While floc particle size depended on the concentrations of sulfate ions and polymeric species in the PACIs, floc-size changes did not affect transmembrane pressure (TMP) buildup and thus did not affect irreversible fouling. Differences in PACI basicity, which affected the distribution of aluminum species, resulted in changes to the degree of irreversible fouling. Pretreatment with high-basicity (71%) PACI was superior to pretreatment with normal-basicity (51%) PACI in reducing irreversible fouling and attenuating TMP buildup during filtration. Higher basicities resulted in less Al breakthrough and a decrease in the Si/Al ratio of the foulants. However, IMP buildup was the same for PACIs with basicities of 71% and 90%; therefore, TMP buildup is not simply related to Al breakthrough and deposition. Increasing the basicity of PACIs would be an effective way to reduce the amount of foulant deposited on the membrane by decreasing the amount of aluminum that passes through the membrane. (C) 2014 Elsevier B.V. All rights reserved,
  • Miki Sakuma, Taku Matsushita, Yoshihiko Matsui, Tomoko Aki, Masahito Isaka, Nobutaka Shirasaki
    WATER RESEARCH 68 839 - 848 2015年01月 [査読有り][通常論文]
     
    This study investigated the mechanism by which activated carbon removes trichloramine, a byproduct of water treatment that has a strongly offensive chlorinous odor. A stoichiometrical mass balance for 15N before and after activated carbon treatment of laboratory-prepared N-15-labeled trichloramine solutions clearly revealed that the mechanism of trichloramine removal with activated carbon was not adsorption but rather reductive decomposition to nitrogen gas. There was a weak positive correlation between the surface decomposition rate constant of trichloramine and the concentration of basic functional groups on the surface of the carbon particles, the suggestion being that the trichloramine may have been reduced by sulfhydryl groups (SH) on the activated carbon surface. Efficient decomposition of trichloramine was achieved with super powdered activated carbon (SPAC), which was prepared by pulverization of commercially available PAC into very fine particles less than 1 mu m in diameter. SPAC could decompose trichloramine selectively, even when trichloramine and free chlorine were present simultaneously in water, the indication being that the strong disinfection capability of residual free chlorine could be retained even after trichloramine was effectively decomposed. The residual ratio of trichloramine after carbon contact increased somewhat at low water temperatures of 1-5 degrees C. At these low temperatures, biological treatment, the traditional method for control of a major trichloramine precursor (ammonium nitrogen), is inefficient. Even at these low temperatures, SPAC could reduce the trichloramine concentration to an acceptable level. A theoretical analysis with a diffusion-reaction model developed in the present study revealed that the increase in the trichloramine residual with decreasing water temperature was attributable to the temperature dependence of the rate of the reductive reaction rather than to the temperature dependence of the diffusive mass transfer rate. (C) 2014 Elsevier Ltd. All rights reserved.
  • Mariya Ikari, Yoshihiko Matsui, Yuta Suzuki, Taku Matsushita, Nobutaka Shirasaki
    WATER RESEARCH 68 227 - 237 2015年01月 [査読有り][通常論文]
     
    Chlorine oxidation followed by treatment with activated carbon was studied as a possible method for removing radioactive iodine from water. Chlorination time, chlorine dose, the presence of natural organic matter (NOM), the presence of bromide ion (Br-), and carbon particle size strongly affected iodine removal. Treatment with superfine powdered activated carbon (SPAC) after 10-min oxidation with chlorine (1 mg-Cl-2/L) removed 90% of the iodine in NOM-containing water (dissolved organic carbon concentration, 1.5 mg-C/L). Iodine removal in NOM-containing water increased with increasing chlorine dose up to >0.1 mg-Cl-2/L but decreased at chlorine doses of >1.0 mg-Cl-2/L. At a low chlorine dose, nonadsorbable iodide ion (I-) was oxidized to adsorbable hypoiodous acid (HOI). When the chlorine dose was increased, some of the HOI reacted with NOM to form adsorbable organic iodine (organic-I). Increasing the chlorine dose further did not enhance iodine removal, owing to the formation of nonadsorbable iodate ion (IO3-). Co-existing Br- depressed iodine removal, particularly in NOM-free water, because hypobromous acid (HOBr) formed and catalyzed the oxidation of HOI to However, the effect of Br- was small in the NOM-containing water because organic-I formed instead of SPAC (median particle diameter, 0.62 gm) had a higher equilibrium adsorption capacity for organic-I than did conventional PAC (median diameter, 18.9 mu m), but the capacities of PAC and SPAC for HOI were similar. The reason for the higher equilibrium adsorption capacity for organic-I was that organic-I was adsorbed principally on the exterior of the PAC particles and not inside the PAC particles, as indicated by direct visualization of the solid-phase iodine concentration profiles in PAC particles by field emission electron probe microanalysis. In contrast, HOI was adsorbed evenly throughout the entire PAC particle. (C) 2014 Elsevier Ltd. All rights reserved.
  • Yoshihiko Matsui, Asuka Sakamoto, Soichi Nakao, Takuma Taniguchi, Taku Matsushita, Nobutaka Shirasaki, Naoya Sakamoto, Hisayoshi Yurimoto
    Environmental science & technology 48 18 10897 - 903 2014年09月16日 [査読有り][通常論文]
     
    Decreasing the particle size of powdered activated carbon may enhance its equilibrium adsorption capacity for small molecules and micropollutants, such as 2-methylisoborneol (MIB) and geosmin, as well as for macromolecules and natural organic matter. Shell adsorption, in which adsorbates do not completely penetrate the adsorbent but instead preferentially adsorb near the outer surface of the adsorbent, may explain this enhancement in equilibrium adsorption capacity. Here, we used isotope microscopy and deuterium-doped MIB and geosmin to directly visualize the solid-phase adsorbate concentration profiles of MIB and geosmin in carbon particles. The deuterium/hydrogen ratio, which we used as an index of the solid-phase concentration of MIB and geosmin, was higher in the shell region than in the inner region of carbon particles. Solid-phase concentrations of MIB and geosmin obtained from the deuterium/hydrogen ratio roughly agreed with those predicted by shell adsorption model analyses of isotherm data. The direct visualization of the localization of micropollutant adsorbates in activated carbon particles provided direct evidence of shell adsorption.
  • Kentaro Narita, Yoshihiko Matsui, Kensuke Iwao, Motoyuki Kamata, Taku Matsushita, Nobutaka Shirasaki
    ENVIRONMENT INTERNATIONAL 63 114 - 120 2014年02月 [査読無し][通常論文]
     
    Pesticides released into the environment may pose both ecological and human health risks. Governments set the regulations and guidelines for the allowable levels of active components of pesticides in various exposure sources, including drinking water. Several pesticide risk indicators have been developed using various methodologies, but such indicators are seldom used for the selection of pesticides to be included in national regulations and guidelines. The aim of the current study was to use risk indicators for the selection of pesticides to be included in regulations and guidelines. Twenty-four risk indicators were created, and a detection rate was defined to judge which indicators were the best for selection. The combination of two indicators (local sales of a pesticide for the purposes of either rice farming or other farming, divided by the guideline value and annual precipitation, and amended with the scores from the physical and chemical properties of the pesticide) gave the highest detection rates. In this case study, this procedure was used to evaluate 134 pesticides that are currently unregulated in the Japanese Drinking Water Quality Guidelines, from which 44 were selected as pesticides to be added to the primary group in the guidelines. The detection probability of the 44 pesticides was more than 72%. Among the 102 pesticides currently in the primary group, 17 were selected for withdrawal from the group. (C) 2013 The Authors. Published by Elsevier Ltd. All rights reserved.
  • N. Shirasaki, T. Matsushita, Y. Matsui, A. Oshiba, T. Marubayashi, S. Sato
    WATER RESEARCH 48 375 - 386 2014年01月 [査読無し][通常論文]
     
    We investigated the effects of basicity, sulfate content, and aluminum hydrolyte species on the ability of polyaluminum chloride (PACl) coagulants to remove F-specific RNA bacteriophages from river water at a pH range of 6-8. An increase in PACl basicity from 1.5 to 2.1 and the absence of sulfate led to a reduction of the amount of monomeric aluminum species (i.e., an increase of the total amount of polymeric aluminum and colloidal aluminum species) in the PACl, to an increase in the colloid charge density of the PACl, or to both and, as a result, to high virus removal efficiency. The efficiency of virus removal at around pH 8 observed with PACl-2.1c, a nonsulfated high-basicity PACl (basicity 2.1-2.2) with a high colloidal aluminum content, was larger than that observed with PACl-2.1b, a nonsulfated high-basicity PACl (basicity 2.1-2.2) with a high polymeric aluminum content. In contrast, although extremely high basicity PACls (e.g., PACl-2.7ns, basicity 2.7) effectively removed turbidity and UV260-absorbing natural organic matter and resulted in a very low residual aluminum concentration, the virus removal ratio with PACl-2.7ns was smaller than the ratio with PACl-2.1c at around pH 8, possibly as a result of a reduction of the colloid charge density of the PACl as the basicity was increased from 2.1 to 2.7. Liquid Al-27 NMR analysis revealed that PACl-2.1c contained Al-30 species, which was not the case for PACl-2.1b or PACl-2.7ns. This result suggests that Al-30 species probably played a major role in virus removal during the coagulation process. In summary, PACl-2.1c, which has high colloidal aluminum content, contains Al-30 species, and has a high colloid charge density, removed viruses more efficiently (>4 log(10) for infectious viruses) than the other aluminum-based coagulants-including commercially available PACls (basicity 1.5-1.8), alum, and PACl-2.7ns-over the entire tested pH (6-8) and coagulant dosage (0.54-5.4 mg-Al/L) ranges. (C) 2013 Elsevier Ltd. All rights reserved.
  • 松林良典, 福原勝, 渡部譲, 天野重己, 松井佳彦
    土木学会論文集G(環境) 70(7) 7 III_119 - III_130 Japan Society of Civil Engineers 2014年 [査読有り][通常論文]
     
    本研究は,日本の水道が抱える種々の課題への対応策として広域的事業統合に着目し,石狩川流域全体(面積約15,000km2,人口約310万人,46市町村,73水道事業)という広大な圏域を対象として,約40年後の平成62年度における給水人口,水需要動向などの将来の予測を行い,更新時のダウンサイジングや施設形態の再構築を考慮したうえで,同流域の事業形態が現状どおり推移した場合と全事業体が統合した場合について,年間支出額や給水原価などを定量化したものである.その結果,流域内の給水原価は一律249円/m3となり,統合しない場合の200~600円/m3と比較して格差を是正できるものの,統合による流域内の年間平均総支出額の削減率は3.3%にとどまる結果となった.しかしながら,大都市の札幌市を除くと削減率は8.8%となり,水道事業の持続確保に大きく寄与することが示された.
  • N. Shirasaki, T. Matsushita, Y. Matsui, T. Urasaki, M. Kimura, K. Ohno
    WATER SCIENCE AND TECHNOLOGY-WATER SUPPLY 14 3 429 - 437 2014年 [査読有り][通常論文]
     
    The ability of in-line coagulation pretreatment with high-basicity polyaluminum chloride (PACl) coagulants to enhance virus removal by ceramic microfiltration (MF) was examined by comparing virus removal efficiencies from water pretreated with PACl-2.2 (basicity 2.2) and PACl-2.5 (basicity 2.5) versus alum, a synthetic aluminum chloride (AlCl3) solution, and two commercially available PACls, PACl-1.5 and PACl-1.8. The virus removal ratios for AlCl3, alum, PACl-1.5, and PACl-1.8 decreased markedly when the pH of the treated water shifted from 6.8 to 7.8, but was high at both pHs for PACl-2.2 and PACl-2.5. PACl-2.5 contains Al-13 species and possibly Al-30 species, and has a high colloid charge density. It removed viruses more efficiently than the other aluminum-based coagulants, not only at neutral pH, but also under weakly alkaline conditions. Moreover, the in-line coagulation-ceramic MF process with PACl-2.5 pretreatment removed not only viruses but also dissolved organic carbon and UV260-absorbing natural organic matter more efficiently and resulted in a lower residual aluminum concentration than did commercially available PACls, especially under weakly alkaline conditions. A combination of coagulation pretreatment with a high-basicity PACl and ceramic MF can provide effective treatment of drinking water over a broader pH range than is possible with commercially available aluminum-based coagulants.
  • Yoshihiko Matsui, Tairyo B. Ishikawa, Masaoki Kimura, Kaori Machida, Nobutaka Shirasaki, Taku Matsushita
    SEPARATION AND PURIFICATION TECHNOLOGY 119 58 - 65 2013年11月 [査読無し][通常論文]
     
    The residual aluminum concentration in treated water after aluminum coagulation and solid-liquid separation is one of the key factors in evaluating the effectiveness of water treatments. Polymeric membrane filters have been widely used to operationally define dissolved substances from particulate matter, and have sometimes been employed in laboratories and pilot studies to approximately simulate media filtration. A comparison between media and membrane filters, however, has not yet been fully investigated. This study compared aluminum concentrations in the filtrate after sand bed and membrane filtrations. The aluminum concentration after sand bed filtration was lower than that after filtration using a membrane with a pore size of 0.1 mu m, irrespective of the membrane material, with one exception. A PVDF membrane with a pore size of 0.1 mu m produced a similar residual aluminum concentration to that obtained using a sand bed. When the natural organic matter concentration was very low, the aluminum concentration in the PVDF membrane (pore size 0.1 mu m) and sand bed filtrates was lower than that obtained using other membranes with the same pore size. It is believed that adsorption of dissolved aluminum may enhance aluminum removal by the sand bed and the PVDF membrane when the aluminum exists in an uncomplexed form with natural organic matter. (C) 2013 Elsevier B.V. All rights reserved.
  • Mari Asami, Nobue Yoshida, Koji Kosaka, Koichi Ohno, Yoshihiko Matsui
    SCIENCE OF THE TOTAL ENVIRONMENT 463 199 - 208 2013年10月 [査読無し][通常論文]
     
    The contributions of water to total levels of chlorate and perchlorate intake were determined using food and water samples from a market basket study from 10 locations in Japan between 2008 and 2009. Foods were categorized into 13 groups and analyzed along with tap water. The average total chlorate intake was 333 (min. 193-max. 486) mu g/day for samples cooked with tap water. The contribution of tap water to total chlorate intake was as high as 47%-58%, although total chlorate intake was less than 32% of the tolerable daily intake, 1500 mu g/day for body weight of 50 kg. For perchlorate, daily intake from water was 0.7 (0.1-4.4) mu g/day, which is not high compared to the average total intake of 14 (2.5-84) mu g/day, while the reference dose (RfD) is 35 mu g/day and the provisional maximum tolerable daily intake (PMTDI) is 500 mu g/day for body weight of 50 kg. The highest intake of perchlorate was 84 mu g/day, where concentrations in foods were high, but not in water. The contribution of water to total perchlorate intake ranged from 0.5% to 22%, while the ratio of highest daily intake to RfD was 240% and that to PMTDI was 17%. Eight baby formulas were also tested - total chlorate and perchlorate intakes were 147 (42-332) mu g/day and 1.11 (0.05-4.5) mu g/day, respectively, for an ingestion volume of 1 L/day if prepared with tap water. (C) 2013 The Authors. Published by Elsevier B.V. All rights reserved.
  • Taku Matsushita, Nobutaka Shirasaki, Yuichi Tatsuki, Yoshihiko Matsui
    WATER RESEARCH 47 15 5819 - 5827 2013年10月 [査読無し][通常論文]
     
    The removal of microorganisms by drinking water treatment processes has been widely investigated in laboratory-scale experiments using artificially propagated microorganisms. However, this approach cannot be applied to norovirus removal, because this virus does not grow in cell or organ culture, and this fact has hampered our ability to investigate its behavior during drinking water treatment. To overcome this difficulty, our research group previously used recombinant norovirus virus-like particles (rNV-VLPs), which consist of an artificially expressed norovirus capsid protein, in laboratory-scale drinking water treatment experiments. However, the enzyme-linked immunosorbent assay (ELISA) method generally used to detect rNV-VLPs is not sensitive enough to evaluate high removal ratios such as those obtained by ultrafiltration (UF). We therefore developed and applied a real-time immuno-polymerase chain reaction (iPCR) assay for rNV-VLP quantification to investigate norovirus removal by microfiltration (MF), UF, and hybrid precoagulation-MF processes. The rNV-VLP detection limit with the developed iPCR assay was improved at least 1000-fold compared with ELISA. Whereas MF with a nominal pore size of 0.1 gm could not eliminate NV-VLPs, a 4-log reduction was achieved by UF with a molecular weight cutoff of 1 kDa. When MF was combined with precoagulation (>= 10 mu mol-Fe/L for ferric chloride; >= 20 mu mol-Al/L for polyaluminum chloride; >= 40 mu mol-Al/L for alum), the performance of the hybrid process in eliminating rNV-VLPs was greater than that achieved by the 1 kDa UF. For all processes, the removal ratios of the bacteriophages MS2 and Q beta were greater than the rNV-VLP removal ratios by 1-2 logs, so neither bacteriophage can be recommended as a possible conservative surrogate for predicting the behavior of native NV during these processes. (C) 2013 Elsevier Ltd. All rights reserved.
  • Shun Niizuma, Yoshihiko Matsui, Koichi Ohno, Sadahiko Itoh, Taku Matsushita, Nobutaka Shirasaki
    REGULATORY TOXICOLOGY AND PHARMACOLOGY 67 1 98 - 107 2013年10月 [査読無し][通常論文]
     
    Drinking water quality standard (DWQS) criteria for chemicals for which there is a threshold for toxicity are derived by allocating a fraction of tolerable daily intake (TDI) to exposure from drinking water. We conducted physiologically based pharmacokinetic model simulations for chloroform and have proposed an equation for total oral-equivalent potential intake via three routes (oral ingestion, inhalation, and dermal exposures), the biologically effective doses of which were converted to oral-equivalent potential intakes. The probability distributions of total oral-equivalent potential intake in Japanese people were estimated by Monte Carlo simulations. Even when the chloroform concentration in drinking water equaled the current DWQS criterion, there was sufficient margin between the intake and the TDI: the probability that the intake exceeded TDI was below 0.1%. If a criterion that the 95th percentile estimate equals the TDI is regarded as both providing protection to highly exposed persons and leaving a reasonable margin of exposure relative to the TDI, then the chloroform drinking water criterion could be a concentration of 0.11 mg/L. This implies a daily intake equal to 34% of the TDI allocated to the oral intake (2 L/d) of drinking water for typical adults. For the highly exposed persons, inhalation exposure via evaporation from water contributed 53% of the total intake, whereas dermal absorption contributed only 3%. (C) 2013 Elsevier Inc. All rights reserved.
  • Yoshihiko Matsui, Soichi Nakao, Tomoaki Yoshida, Takuma Taniguchi, Taku Matsushita
    SEPARATION AND PURIFICATION TECHNOLOGY 113 75 - 82 2013年07月 [査読無し][通常論文]
     
    The adverse effect of natural organic matter (NOM) on the capacity of activated carbon to adsorb 2-methylisoborneol (MIB), a compound with an earthy/musty odor, is less severe for submicron-sized powdered activated carbon (SPAC) than for conventionally sized powdered activated carbon (PAC) [11]. In this study the NOM effect was confirmed, and the mechanism responsible for the effect was investigated by studies with another malodorous compound, geosmin. The mechanism was investigated with respect to the properties of NOM by simplified equivalent background compound (EBC) estimation and penetration index. Correlations between penetration index values and fractional areas of size-exclusion chromatogram indicated that higher NOM loading on SPAC were associated mainly with a fraction of NOM having a molecular weight (MW) >2 kDa and a chromophoric moiety, which did not diffuse into the inner region of adsorbent particles and instead adsorbed only onto their external surfaces. Therefore SPAC, which has a larger specific surface area per unit mass of adsorbent, adsorbs such high-MW chromophoric NOM to a greater extent than does PAC. However, such NOM does not compete for adsorption sites with geosmin because geosmin adsorbs onto the interior surfaces of adsorbent particles. Contrariwise, NOM with a MW of <2 kDa and with an nonchromophoric moiety penetrates adsorbent particles and adsorbs onto interior surfaces. The estimated EBC concentration and its correlations with both size-exclusion chromatogram fractions and penetration index values indicated the characteristics of the NOM that competes with geosmin to be similar to those of MIB. Chromophoric NOM with a MW of <230 Da competes for adsorption sites with both geosmin and MIB. Beside the nonchromophoric, low-MW (<2 kDa) NOM, such chromophoric, very-low-MW NOM also penetrates adsorbent particles and adsorbs onto interior surfaces. The loading of such NOM is therefore independent of the size of the carbon particles (SPAC or PAC). The NOM effects on geosmin adsorption capacity were therefore found to be similar for SPAC and PAC, despite the fact that more NOM was loaded onto SPAC than PAC. The very-low-MW chromophoric NOM accounted for <2% of the entire NOM. (C) 2013 Elsevier B.V. All rights reserved.
  • Yoshihiko Matsui, Soichi Nakao, Takuma Taniguchi, Taku Matsushita
    WATER RESEARCH 47 8 2873 - 2880 2013年05月 [査読無し][通常論文]
     
    2-Methylisoborneol (MIB) and geosmin are naturally occurring compounds responsible for musty-earthy taste and odor in public drinking-water supplies, a severe problem faced by many utilities throughout the world. In this study, we investigated adsorptive removal of these compounds by superfine powdered activation carbon (SPAC, particle size <1 mu m) produced by novel micro-grinding of powdered activated carbon; we also discuss the optimization of carbon particle size to efficiently enhance the adsorptive removal. After grinding, the absorptive capacity remained unchanged for a 2007 carbon sample and was increased for a 2010 carbon sample; the capacity increase was quantitatively described by the shell adsorption model, in which MIB and geosmin adsorbed more in the exterior of a carbon particle than in the center. The extremely high uptake rates of MIB and geosmin by SPAC were simulated well by a combination of the branched-pore kinetic model and the shell adsorption model, in which intraparticle diffusion through macropores was followed by diffusion from macropore to micropore. Simulations suggested that D-40 was on the whole the best characteristic diameter to represent a size-disperse group of adsorbent particles; D-40 is the diameter through which 40% of the particles by volume pass. Therefore, D-40 can be used as an index for evaluating the improvement of adsorptive removal that resulted from pulverization. The dose required for a certain percentage removal of MIB or geosmin decreased linearly with carbon particle size (D-40), but the dose reduction became less effective as the activated carbon was ground down to smaller sizes around a critical value of D-40. For a 60-min contact time, critical D-40 was 2-2.5 mu m for MIB and 0.4-0.5 mu m for geosmin. The smaller critical D40 was when the shorter the carbon-water contact time was or the slower the intraparticle mass transfer rate of an adsorbate was. (C) 2013 Elsevier Ltd. All rights reserved.
  • Masaoki Kimura, Yoshihiko Matsui, Kenta Kondo, Tairyo B. Ishikawa, Taku Matsushita, Nobutaka Shirasaki
    Water Research 47 6 2075 - 2084 2013年04月15日 [査読無し][通常論文]
     
    Aluminum coagulants are widely used in water treatment plants to remove turbidity and dissolved substances. However, because high aluminum concentrations in treated water are associated with increased turbidity and because aluminum exerts undeniable human health effects, its concentration should be controlled in water treatment plants, especially in plants that use aluminum coagulants. In this study, the effect of polyaluminum chloride (PACl) coagulant characteristics on dissolved residual aluminum concentrations after coagulation and filtration was investigated. The dissolved residual aluminum concentrations at a given coagulation pH differed among the PACls tested. Very-high-basicity PACl yielded low dissolved residual aluminum concentrations and higher natural organic matter (NOM) removal. The low residual aluminum concentrations were related to the low content of monomeric aluminum (Ala) in the PACl. Polymeric (Alb)/colloidal (Alc) ratio in PACl did not greatly influence residual aluminum concentration. The presence of sulfate in PACl contributed to lower residual aluminum concentration only when coagulation was performed at around pH 6.5 or lower. At a wide pH range (6.5-8.5), residual aluminum concentrations < 0.02 mg/L were attained by tailoring PACl properties (Ala percentage ≤0.5%, basicity ≥85%). The dissolved residual aluminum concentrations did not increase with increasing the dosage of high-basicity PACl, but did increase with increasing the dosage of normal-basicity PACl. We inferred that increasing the basicity of PACl afforded lower dissolved residual aluminum concentrations partly because the high-basicity PACls could have a small percentage of Ala, which tends to form soluble aluminum-NOM complexes with molecular weights of 100 kDa-0.45 μm. © 2013 Elsevier Ltd.
  • Taku Matsushita, Hideaki Suzuki, Nobutaka Shirasaki, Yoshihiko Matsui, Koichi Ohno
    Separation and Purification Technology 107 79 - 84 2013年 [査読無し][通常論文]
     
    We investigated the removal of bacteriophages by adsorption on commercially available powdered activated carbon (N-PAC, median diameter > 10 μm) and super-powdered activated carbon (S-PAC, median diameter 0.7-2.8 μm). N-PACs failed to remove the virus in Milli-Q water buffered with 100 μM Ca 2+, but some S-PACs successfully removed it under the same condition. Three factors contributed substantially to virus removal: a smaller electrophoretic repulsive force between the virus and the PAC particles, a large proportion of pores 20-50 nm in diameter, and a greater hydrophobicity of the virus surface. © 2013 Published by Elsevier B.V.
  • 小坂浩司, 浅見真理, 佐々木万紀子, 松井佳彦, 秋葉道宏
    土木学会論文集 G(環境) 69 7 III_363 - III_374 Japan Society of Civil Engineers 2013年 [査読無し][通常論文]
     
    水道統計を基にして, 国内1554全水道事業等(以下, 水道事業)を対象に農薬類の測定実態を解析した. 農薬類の年間測定回数が多い水道事業ほど測定農薬類数が多い傾向や, 測定が年1回であっても, 農薬類が検出される傾向が高い春期~夏期に測定を行っているなど適切な水質管理の側面が見受けられた. 一方, 約50%の水道事業は農薬頬測定を行っておらず, 測定していた割合は, 規模が大きい水道事業の方が高かった. 農薬類測定を行っている水道事業の多くは年間測定回数が4回以下で, 特に1回の水道事業が最も多かった. 水質管理目標設定項目でリストされている第1候補群全102種を測定していた水道事業の割合は, 原水, 浄水でそれぞれ34%, 38%で, それ以外では測定する農薬類の選定を行っていた.
  • Y. Kobayashi, M. Itoh, T. Yamada, M. Akiba, Y. Matsui
    Water Science and Technology: Water Supply 13 1 139 - 146 2013年 [査読有り][通常論文]
     
    One effect of climate change on the water supply systems in Japan may be a sharp increase in the raw-water turbidity following heavy rain. The objective of this study was to evaluate water treatment performance with a sharp increase in raw-water turbidity. This evaluation was carried out from the perspective of turbidity response by a pilot-scale plant using sand filtration and membrane filtration with coagulation-sedimentation pretreatment. Two coagulants were used namely, polyaluminum chloride with a basicity of either 72% (PACl-72%) or 51% (PACl-51%). Raw-water turbidity was increased from 5 to 300 TU by adding kaolin suspension. In the case of sand filtration, the filteredwater turbidity increased during the filter stabilization period. An increase in the coagulant dosage produced a more rapid decrease in the filtered-water turbidity and shortened the filter stabilizing period. Filtered-water turbidity decreased more rapidly for PACl-72% than for PACl-51%. In the case of membrane filtration, an increase in raw-water turbidity caused no significant increase in filteredwater turbidity or transmembrane pressure. These results demonstrated that, although neither filtration technique completely failed, membrane filtration was more robust than sand filtration against a sharp increase in raw-water turbidity. Copyright © IWA Publishing 2013.
  • Yoshihiko Matsui, Tomoaki Yoshida, Soichi Nakao, Detlef R. U. Knappe, Taku Matsushita
    WATER RESEARCH 46 15 4741 - 4749 2012年10月 [査読無し][通常論文]
     
    When treating water with activated carbon, natural organic matter (NOM) is not only a target for adsorptive removal but also an inhibitory substance that reduces the removal efficiency of trace compounds, such as 2-methylisoborneol (MIB), through adsorption competition. Recently, superfine (submicron-sized) activated carbon (SPAC) was developed by wet-milling commercially available powdered activated carbon (PAC) to a smaller particle size. It was reported that SPAC has a larger NOM adsorption capacity than PAC because NOM mainly adsorbs close to the external adsorbent particle surface (shell adsorption mechanism). Thus, SPAC with its larger specific external surface area can adsorb more NOM than PAC. The effect of higher NOM uptake on the adsorptive removal of MIB has, however, not been investigated. Results of this study show that adsorption competition between NOM and MIB did not increase when NOM uptake increased due to carbon size reduction; i.e., the increased NOM uptake by SPAC did not result in a decrease in MIB adsorption capacity beyond that obtained as a result of NOM adsorption by PAC. A simple estimation method for determining the adsorbed amount of competing NOM (NOM that reduces MIB adsorption) is presented based on the simplified equivalent background compound (EBC) method. Furthermore, the mechanism of adsorption competition is discussed based on results obtained with the simplified EBC method and the shell adsorption mechanism. Competing NOM, which likely comprises a small portion of NOM, adsorbs in internal pores of activated carbon particles as MIB does, thereby reducing the MIB adsorption capacity to a similar extent regardless of adsorbent particle size. SPAC application can be advantageous because enhanced NOM removal does not translate into less effective removal of MIB. Molecular size distribution data of NOM suggest that the competing NOM has a molecular weight similar to that of the target compound. (C) 2012 Elsevier Ltd. All rights reserved.
  • Koji Tani, Yoshihiko Matsui, Kensuke Iwao, Motoyuki Kamata, Taku Matsushita
    WATER RESEARCH 46 3 741 - 749 2012年03月 [査読無し][通常論文]
     
    Measuring river water concentrations of all pesticides applied in a catchment area is a daunting task. This study aims to develop new score tables for selecting analytical target pesticides. Sensitivity analyses were conducted using a diffuse pollution hydrologic model to quantitatively evaluate the influence of pesticide properties (e.g., log K-OC, degradability [half-life]) on concentrations of rice-farming pesticides in river water. Using the results of the analyses, score tables were systematically designed for the pesticide properties such that the sum of the scores for a particular pesticide, designated as the contamination index, was proportional to the expected/predicted concentration of that pesticide in river water. The contamination indexes for pesticides applied in three river basins were calculated and compared with the corresponding observed pesticide concentrations. Correlations between contamination indexes and observed concentrations were fairly good. Pesticides were ranked according to the quotients obtained by dividing the pesticide concentrations predicted from the contamination indexes by the corresponding drinking-water quality guideline values, and pesticide candidates to be monitored were successfully selected on the basis of a threshold quotient. (C) 2011 Elsevier Ltd. All rights reserved.
  • N. Shirasaki, T. Matsushita, Y. Matsui, T. Urasaki, K. Ohno
    WATER SCIENCE AND TECHNOLOGY-WATER SUPPLY 12 5 666 - 673 2012年 [査読無し][通常論文]
     
    Difference in behaviors of F-specific DNA and RNA bacteriophages during coagulation-rapid sand filtration and coagulation-microfiltration (MF) processes were investigated by using river water spiked with F-specific DNA bacteriophage f1 and RNA bacteriophage f2. Because the particle characteristics of f1 (filamentous) and f2 (spherical) are quite different and the surface charge of f1 in the river water was slightly more negative than that of f2, the removal ratios of f1 were approximately 1-log lower than the removal ratio of f2 after any treatment process used in the present study. This result indicates that the behaviors of the two bacteriophages during the treatment processes were different, and that the removal of f1 by the combination of coagulation and filtration processes was more difficult than that of f2. The removal ratios for f1 and f2 were approximately 3-log and 4-log, respectively, in the coagulation-rapid sand filtration process, and 6-log and 7-log, respectively, in the coagulation-MF filtration process. Therefore, as expected, the coagulation-MF process appears to be more effective than the coagulation-rapid sand filtration process for the removal of not only spherical viruses but also filamentous viruses.
  • 白崎伸隆, 松下拓, 松井佳彦, 大芝淳
    土木学会論文集G(環境) 68 7 III_41 - III_50 Japan Society of Civil Engineers 2012年 [査読無し][通常論文]
     
    本研究では,凝集剤の塩基度,凝集剤中の硫酸およびアルミニウム形態がウイルスの処理性に与える影響を詳細に評価し,ウイルス処理に有効な新規アルミニウム系凝集剤を開発した.開発した新規凝集剤を凝集沈澱処理に用いた場合,弱酸性および中性のpH領域のみならず,弱アルカリ性のpH領域においても,約6 logの高い除去率が得られ,従来のアルミニウム系凝集剤を用いた場合に比べ,除去率が飛躍的に向上した.また,ESI-FT-MS法および27Al-NMR法による分析の結果,新規凝集剤には,アルミニウム13量体や30量体が含まれていることが明らかとなったことから,これらのアルミニウム種がウイルスの処理性の向上に大きく影響している可能性が示唆された.
  • Taku Matsushita, Nobutaka Shirasaki, Yoshihiko Matsui, Koichi Ohno
    CHEMOSPHERE 85 4 571 - 576 2011年10月 [査読無し][通常論文]
     
    We used the bacteriophages Q beta and MS2 to determine whether viruses are inactivated by aluminum coagulants during the coagulation process. We performed batch coagulation and filtration experiments with virus-containing solutions. After filtering the supernatant of the coagulated solution through a membrane with a pore size of 50 nm, we measured the virus concentration by both the plaque forming unit (PFU) and polymerase chain reaction (PCR) methods. The virus concentration determined by the PFU method, which determines the infectious virus concentration, was always lower than that determined by the PCR-based method, which determines total virus concentration, regardless of infectivity. This discrepancy can be explained by the formation of aggregates consisting of several virus particles or by the inactivation of viruses in the coagulation process. The former possibility can be discounted because (i) aggregates of several virus particles would not pass through the 50-nm pores of the filtration membrane, and (ii) our particle size measurements revealed that the virus particles in the membrane filtrate were monodispersed. These observations clearly showed that non-infectious Q beta particles were present in the membrane filtrate after the coagulation process with aluminum coagulants. We subsequently revealed that the viruses lost their infectivity after being mixed with hydrolyzing aluminum species during the coagulation process. (C) 2011 Elsevier Ltd. All rights reserved.
  • Yoshihiko Matsui, Naoya Ando, Tomoaki Yoshida, Ryuji Kurotobi, Taku Matsushita, Koichi Ohno
    WATER RESEARCH 45 4 1720 - 1728 2011年02月 [査読無し][通常論文]
     
    The capacity to adsorb natural organic matter (NOM) and polystyrene sulfonates (PSSs) on small particle-size activated carbon (super-powdered activated carbon, SPAC) is higher than that on larger particle-size activated carbon (powdered-activated carbon, PAC). Increased adsorption capacity is likely attributable to the larger external surface area because the NOM and PSS molecules do not completely penetrate the adsorbent particle; they preferentially adsorb near the outer surface of the particle. In this study, we propose a new isotherm equation, the Shell Adsorption Model (SAM), to explain the higher adsorption capacity on smaller adsorbent particles and to describe quantitatively adsorption isotherms of activated carbons of different particle sizes: PAC and SPAC. The SAM was verified with the experimental data of PSS adsorption kinetics as well as equilibrium. SAM successfully characterized PSS adsorption isotherm data for SPACs and PAC simultaneously with the same model parameters. When SAM was incorporated into an adsorption kinetic model, kinetic decay curves for PSSs adsorbing onto activated carbons of different particle sizes could be simultaneously described with a single kinetics parameter value. On the other hand, when SAM was not incorporated into such an adsorption kinetic model and instead isotherms were described by the Freundlich model, the kinetic decay curves were not well described. The success of the SAM further supports the adsorption mechanism of PSSs preferentially adsorbing near the outer surface of activated carbon particles. (C) 2010 Elsevier Ltd. All rights reserved.
  • パイロットプラントを用いた高塩基度PACの濁度の除去性及びアルミニウムの残留性に関する評価
    古林祐正, 伊藤雅喜, 山田俊郎, 松井佳彦
    水道協会雑誌 80 3 2 - 11 2011年 [査読無し][通常論文]
  • Naoya Ando, Yoshihiko Matsui, Taku Matsushita, Koichi Ohno
    WATER RESEARCH 45 2 761 - 767 2011年01月 [査読無し][通常論文]
     
    Decreasing the particle size of powdered activated carbon (PAC) by pulverization increases its adsorption capacities for natural organic matter (NOM) and polystyrene sulfonate (PSS, which is used as a model adsorbate). A shell adsorption mechanism in which NOM and PSS molecules do not completely penetrate the adsorbent particle and instead preferentially adsorb near the outer surface of the particle has been proposed as an explanation for this adsorption capacity increase. In this report, we present direct evidence to support the shell adsorption mechanism. PAC particles containing adsorbed PSS were sectioned with a focused ion beam, and the solid-phase PSS concentration profiles of the particle cross-sections were directly observed by means of field emission scanning electron microscopy/energy-dispersive X-ray spectrometry (FE-SEM/EDXS). X-ray emission from sulfur, an index of PSS concentration, was higher in the shell region than in the inner region of the particles. The X-ray emission profile observed by EDXS did not agree completely with the solid-phase PSS concentration profile predicted by shell adsorption model analysis of the PSS isotherm data, but the observed and predicted profiles were not inconsistent when the analytical errors were considered. These EDXS results provide the first direct evidence that PSS is adsorbed mainly in the vicinity of the external surface of the PAC particles, and thus the results support the proposition that the increase in NOM and PSS adsorption capacity with decreasing particle size is due to the increase in external surface area on which the molecules can be adsorbed. (C) 2010 Elsevier Ltd. All rights reserved.
  • Naoya Ando, Yoshihiko Matsui, Ryuji Kurotobi, Yu Nakano, Taku Matsushita, Koichi Ohno
    WATER RESEARCH 44 14 4127 - 4136 2010年07月 [査読無し][通常論文]
     
    We examined the natural organic matter (NOM) adsorption characteristics of super-powdered activated carbon (S-PAC) produced by pulverizing commercially available, normal PAC to a submicron particle size range. The adsorption capacities of S-PAC for NOM and polystyrene sulfonates (PSS) with molecular weights (MWs) of 1.1, 1.8, and 4.6 kDa, which we used as model compounds, were considerably higher than those of PAC. The adsorption capacity increases were observed for all five types of carbon tested (two wood-based, two coconut-based, and one coal-based carbon). The adsorption capacities of S-PAC and PAC for polyethylene glycols (PEGs) with MWs of 0.3 and 1.0 were the same. The adsorption capacities of S-PAC for PEGs with MWs of 3.0 and 8.0 kDa were slightly higher than the adsorption capacities of PAC, but the difference in adsorption capacity was not as large as that observed for NOM and the PSSs, even though the MW ranges of the adsorbates were similar. We concluded that the adsorption capacity differences between S-PAC and PAC observed for NOM and PSSs were due to the difference in particle size between the two carbons, rather than to differences in internal pore size or structure, to differences in activation, or to non-attainment of equilibrium that resulted from the change in particle size. The difference in adsorption capacity between S-PAC and PAC was larger for NOM with a high specific UV absorbance (SUVA) value than for low-SUVA NOM. The larger adsorption capacities of S-PAC compared with PAC were explained by the larger specific external surface area per unit mass. We hypothesize that a larger fraction of the internal pore volume is accessible with carbon of smaller particle size because the NOM and PSS molecules preferentially adsorb near the outer surface of the particle and therefore do not completely penetrate the adsorbent particle. (C) 2010 Elsevier Ltd. All rights reserved.
  • Koichi Ohno, Yoshihiko Matsui, Masaki Itoh, Yoshifumi Oguchi, Takuya Kondo, Yosuke Konno, Taku Matsushita, Yasumoto Magara
    DESALINATION 254 1-3 17 - 22 2010年05月 [査読無し][通常論文]
     
    The effects of coagulant residuals on fouling of a nanofiltration (NF) membrane were investigated. Experiments were carried out with a laboratory-scale microfiltration (MF)-NF setup and a pilot MF-NF plant. In the laboratory-scale experiments, NF feed water was pretreated with poly-aluminum chloride (PACl) or alum followed by MF. NF membrane permeability declined when the feed water contained residual aluminum at 18 mu g/L or more, but not when it was lower than 9 mu g/L. When pretreated with ferric chloride, no substantial decline of NE membrane permeability was observed: residual iron did not affect the permeability. When SiO(2) was added to the water before the pretreatment with PACl, the NF membrane permeability declined at about double the speed. Thermodynamic calculations and elemental analysis of foulants recovered from the membranes indicated that the majority of inorganic foulants were compounds composed of aluminum, silicate, and possibly potassium. In the pilot plant, NF feed was pretreated by PACl. Transmembrane pressure for NF doubled over 4.5 months of operation. Although the aluminum concentration in the NE feed was not high (30 mu g/L), analysis of membrane foulants revealed excessive accumulation of aluminum and silicate, also suggesting that aluminum residuals caused the membrane fouling by alumino-silicates or aluminum hydroxide. (C) 2010 Elsevier B.V. All rights reserved.
  • Koichi Ohno, Yoshihiko Matsui, Masaki Itoh, Yoshifumi Oguchi, Takuya Kondo, Yosuke Konno, Taku Matsushita, Yasumoto Magara
    DESALINATION 254 1-3 17 - 22 2010年05月 [査読無し][通常論文]
     
    The effects of coagulant residuals on fouling of a nanofiltration (NF) membrane were investigated. Experiments were carried out with a laboratory-scale microfiltration (MF)-NF setup and a pilot MF-NF plant. In the laboratory-scale experiments, NF feed water was pretreated with poly-aluminum chloride (PACl) or alum followed by MF. NF membrane permeability declined when the feed water contained residual aluminum at 18 mu g/L or more, but not when it was lower than 9 mu g/L. When pretreated with ferric chloride, no substantial decline of NE membrane permeability was observed: residual iron did not affect the permeability. When SiO(2) was added to the water before the pretreatment with PACl, the NF membrane permeability declined at about double the speed. Thermodynamic calculations and elemental analysis of foulants recovered from the membranes indicated that the majority of inorganic foulants were compounds composed of aluminum, silicate, and possibly potassium. In the pilot plant, NF feed was pretreated by PACl. Transmembrane pressure for NF doubled over 4.5 months of operation. Although the aluminum concentration in the NE feed was not high (30 mu g/L), analysis of membrane foulants revealed excessive accumulation of aluminum and silicate, also suggesting that aluminum residuals caused the membrane fouling by alumino-silicates or aluminum hydroxide. (C) 2010 Elsevier B.V. All rights reserved.
  • Koichi Ohno, Yoshihiko Matsui, Masaki Itoh, Yoshifumi Oguchi, Takuya Kondo, Yosuke Konno, Taku Matsushita, Yasumoto Magara
    DESALINATION 254 1-3 17 - 22 2010年05月 [査読無し][通常論文]
     
    The effects of coagulant residuals on fouling of a nanofiltration (NF) membrane were investigated. Experiments were carried out with a laboratory-scale microfiltration (MF)-NF setup and a pilot MF-NF plant. In the laboratory-scale experiments, NF feed water was pretreated with poly-aluminum chloride (PACl) or alum followed by MF. NF membrane permeability declined when the feed water contained residual aluminum at 18 mu g/L or more, but not when it was lower than 9 mu g/L. When pretreated with ferric chloride, no substantial decline of NE membrane permeability was observed: residual iron did not affect the permeability. When SiO(2) was added to the water before the pretreatment with PACl, the NF membrane permeability declined at about double the speed. Thermodynamic calculations and elemental analysis of foulants recovered from the membranes indicated that the majority of inorganic foulants were compounds composed of aluminum, silicate, and possibly potassium. In the pilot plant, NF feed was pretreated by PACl. Transmembrane pressure for NF doubled over 4.5 months of operation. Although the aluminum concentration in the NE feed was not high (30 mu g/L), analysis of membrane foulants revealed excessive accumulation of aluminum and silicate, also suggesting that aluminum residuals caused the membrane fouling by alumino-silicates or aluminum hydroxide. (C) 2010 Elsevier B.V. All rights reserved.
  • N. Shirasaki, T. Matsushita, Y. Matsui, A. Oshiba, K. Ohno
    WATER RESEARCH 44 5 1307 - 1316 2010年03月 [査読無し][通常論文]
     
    Norovirus (NV) is an important human pathogen that causes epidemic acute nonbacterial gastroenteritis worldwide. Because of the lack of a cell culture system or an animal model for this virus, studies of drinking water treatment such as separation and disinfection processes are still hampered. We successfully estimated NV removal performance during a coagulation-rapid sand filtration process by using recombinant NV virus-like particles (rNV-VLPs) morphologically and antigenically similar to native NV. The behaviors of two widely accepted surrogates for pathogenic waterborne viruses, bacteriophages Q beta and MS2, were also investigated for comparison with that of rNV-VLPs. Approximately 3-log(10) removals were observed for rNV-VLPs with a dose of 40 mu M-Al or -Fe, as polyaluminum chloride at pH 6.8 or ferric chloride at pH 5.8, respectively. Smaller removal ratios were obtained with alum and ferric chloride at pH 6.8. The removal performance for MS2 was somewhat larger than that for rNV-VLPs, meaning that MS2 is not recommended as an appropriate surrogate for native NV. By comparison, the removal performance for Q beta was similar to, or smaller than, that for rNV-VLPs. However, the removal performances for rNV-VLPs and Q beta differed between the coagulation process and the following rapid sand filtration process. Therefore, Q beta also is not recommended as an appropriate surrogate for native NV. (C) 2009 Elsevier Ltd. All rights reserved.
  • N. Shirasaki, T. Matsushita, Y. Matsui, A. Oshiba, K. Ohno
    WATER RESEARCH 44 5 1307 - 1316 2010年03月 [査読無し][通常論文]
     
    Norovirus (NV) is an important human pathogen that causes epidemic acute nonbacterial gastroenteritis worldwide. Because of the lack of a cell culture system or an animal model for this virus, studies of drinking water treatment such as separation and disinfection processes are still hampered. We successfully estimated NV removal performance during a coagulation-rapid sand filtration process by using recombinant NV virus-like particles (rNV-VLPs) morphologically and antigenically similar to native NV. The behaviors of two widely accepted surrogates for pathogenic waterborne viruses, bacteriophages Q beta and MS2, were also investigated for comparison with that of rNV-VLPs. Approximately 3-log(10) removals were observed for rNV-VLPs with a dose of 40 mu M-Al or -Fe, as polyaluminum chloride at pH 6.8 or ferric chloride at pH 5.8, respectively. Smaller removal ratios were obtained with alum and ferric chloride at pH 6.8. The removal performance for MS2 was somewhat larger than that for rNV-VLPs, meaning that MS2 is not recommended as an appropriate surrogate for native NV. By comparison, the removal performance for Q beta was similar to, or smaller than, that for rNV-VLPs. However, the removal performances for rNV-VLPs and Q beta differed between the coagulation process and the following rapid sand filtration process. Therefore, Q beta also is not recommended as an appropriate surrogate for native NV. (C) 2009 Elsevier Ltd. All rights reserved.
  • N. Shirasaki, T. Matsushita, Y. Matsui, A. Oshiba, K. Ohno
    WATER RESEARCH 44 5 1307 - 1316 2010年03月 [査読無し][通常論文]
     
    Norovirus (NV) is an important human pathogen that causes epidemic acute nonbacterial gastroenteritis worldwide. Because of the lack of a cell culture system or an animal model for this virus, studies of drinking water treatment such as separation and disinfection processes are still hampered. We successfully estimated NV removal performance during a coagulation-rapid sand filtration process by using recombinant NV virus-like particles (rNV-VLPs) morphologically and antigenically similar to native NV. The behaviors of two widely accepted surrogates for pathogenic waterborne viruses, bacteriophages Q beta and MS2, were also investigated for comparison with that of rNV-VLPs. Approximately 3-log(10) removals were observed for rNV-VLPs with a dose of 40 mu M-Al or -Fe, as polyaluminum chloride at pH 6.8 or ferric chloride at pH 5.8, respectively. Smaller removal ratios were obtained with alum and ferric chloride at pH 6.8. The removal performance for MS2 was somewhat larger than that for rNV-VLPs, meaning that MS2 is not recommended as an appropriate surrogate for native NV. By comparison, the removal performance for Q beta was similar to, or smaller than, that for rNV-VLPs. However, the removal performances for rNV-VLPs and Q beta differed between the coagulation process and the following rapid sand filtration process. Therefore, Q beta also is not recommended as an appropriate surrogate for native NV. (C) 2009 Elsevier Ltd. All rights reserved.
  • N. Shirasaki, T. Matsushita, Y. Matsui, T. Urasaki, A. Oshiba, K. Ohno
    WATER SCIENCE AND TECHNOLOGY 61 8 2027 - 2034 2010年 [査読無し][通常論文]
     
    Norovirus (NV) is a prototype strain of a group of human caliciviruses responsible for epidemic outbreaks of acute gastroenteritis worldwide. Because of the lack of a cell culture system or an animal model for this virus, studies on drinking water treatment such as separation and disinfection processes are still hampered. In the present study, we investigated NV removal performance as particles during a coagulation-ceramic microfiltration (MF) process by using recombinant NV virus-like particles (rNV-VLPs), which are morphologically and antigenically similar to native NV. We also experimentally investigated the behaviors of two widely accepted surrogates for pathogenic waterborne viruses, bacteriophages Q beta and MS2, for comparison with the behavior of rNV-VLPs. More than 4-log removal was observed for rNV-VLPs with a 1.08 mg-Al/L dose of polyaluminium chloride in the coagulation-ceramic MF process. This high removal ratio of rNV-VLPs satisfies the U. S. Environmental Protection Agency requirement of 4-log removal or inactivation. In addition, the removal ratios of Q beta and MS2 were approximately 2-log and 1-log, smaller than the ratio of rNV-VLPs. Accordingly, both bacteriophages have the potential to become appropriate surrogates for native NV in the coagulation-ceramic MF process, and, of the two, Q beta is the more conservative surrogate.
  • Nobutaka Shirasaki, Taku Matsushita, Yoshihiko Matsui, Makoto Kobuke, Koichi Ohno
    JOURNAL OF WATER SUPPLY RESEARCH AND TECHNOLOGY-AQUA 59 8 501 - 511 2010年 [査読無し][通常論文]
     
    The feasibility of in-line coagulation as a pretreatment for ceramic microfiltration (MF) was verified by comparing its efficiency in the removal of viruses with that of the traditional mechanical mixing approach for coagulation, and by examining the effect of coagulant dose and coagulation time on virus removal. The in-line coagulation-ceramic MF system efficiently removed bacteriophage Q beta and MS2: removal ratios were > 8.2 log for infectious viruses and > 5.4 log for total (infectious + inactivated) virus particles. These values were similar to those of the mechanical coagulation-ceramic MF system. The in-line coagulation system has potential as a useful pretreatment for the removal of viruses as an alternative to the mechanical mixing system, because the former efficiently removes viruses and has a smaller footprint in treatment plants. For the in-line coagulation-ceramic MF system, a coagulant dose of 1.08 mg-Al/L and a coagulation time of 1 min were required to achieve a high level of virus removal. Infectious Q beta and MS2 were removed to similar levels by the two precoagulation methods tested, but the removal of total MS2 particles was higher than that of Q beta particles, possibly because of the selective interaction with the cake layer.
  • Y. Matsui, Y. Nakano, H. Hiroshi, N. Ando, T. Matsushita, K. Ohno
    WATER SCIENCE AND TECHNOLOGY 62 11 2664 - 2668 2010年 [査読無し][通常論文]
     
    Geosmin and 2-methylisoborneol (2-MIB) are naturally occurring compounds responsible for musty-earthy-odors in surface water supplies. They are a severe problem confronting utilities worldwide. Adsorption by powdered activated carbon (PAC) is a widely used process to control this problem, but it has low efficiency, which engenders large budget spending for utilities services. Super-powdered activated carbon (S-PAC) is activated carbon with much finer particles than those of PAC. Experiments on geosmin and 2-MIB adsorptions on S-PAC and PAC were conducted. Geosmin and 2-MIB adsorption capacities on S-PAC were not smaller than those on PAC although natural organic matter, which adversely impacted the adsorption capacity of geosmin and 2-MIB, was more adsorbed on S-PAC than on PAC, meaning that the adsorption competition is less severe for S-PAC than for PAC.
  • Koji Tani, Yoshihiko Matsui, Kentaro Narita, Koichi Ohno, Taku Matsushita
    WATER SCIENCE AND TECHNOLOGY 62 11 2579 - 2589 2010年 [査読無し][通常論文]
     
    We quantitatively evaluated the factors that affect the concentrations of rice-farming pesticides (an herbicide and a fungicide) in river water by a sensitivity analysis using a diffuse pollution hydrologic model. Pesticide degradation and adsorption in paddy soil affected concentrations of the herbicide pretilachlor but did not affect concentrations of the fungicide isoprothiolane. We attributed this difference to the timing of pesticide application in relation to irrigation and drainage of the rice paddy fields. The herbicide was applied more than a month before water drainage of the fields and runoff was gradual over a long period of time, whereas the fungicide was applied shortly before drainage and runoff was rapid. However, the effects of degradability-in- water on the herbicide and fungicide concentrations were similar, with concentrations decreasing only when the rate constant of degradation in water was large. We also evaluated the effects of intermittent irrigation methods (irrigation/artificial drainage or irrigation/percolation) on pesticide concentrations in river water. The runoff of the fungicide, which is applied near or in the period of intermittent irrigation, notably decreased when the method of irrigation/artificial drainage was changed to irrigation/percolation. In a sensitivity analysis evaluating the synergy effect of degradation and adsorbability in soil, the degradation rate constant in soil greatly affected pesticide concentration when the adsorption coefficient was small but did not affect pesticide concentration when the adsorption coefficient was large. The pesticide concentration in the river water substantially decreased when either or both the degradation rate constant in soil and adsorption coefficient was large.
  • Koichi Ohno, Kohei Ishikawa, Yuki Kurosawa, Yoshihiko Matsui, Taku Matsushita, Yasumoto Magara
    WATER SCIENCE AND TECHNOLOGY 62 11 2694 - 2701 2010年 [査読無し][通常論文]
     
    Daily intakes of 17 metals (boron, aluminium, chromium, manganese, nickel, copper, zinc, arsenic, selenium, molybdenum, cadmium, antimony, lead, uranium, magnesium, calcium, and iron) via drinking water and total diet were investigated in six cities in Japan. The daily metal intakes were estimated and compared with tolerable daily intake (TDI) values proposed by the WHO or Joint FAO/WHO Expert Committee on Food Additives for toxic metals and with recommended dietary allowances (RDAs) or adequate intake (AI) values proposed for essential metals by the Japanese Ministry of Health, Labour and Welfare. Among the 13 toxic metals, mean dietary intakes of 10 (except arsenic, selenium, and molybdenum) were less than 50% of TDI, suggesting that for these 10 metals the allocation of intake to drinking water in establishing guidelines or standards could possibly be increased from the normal allocation of 10-20% of TDI. For the 13 toxic metals, the contribution of drinking water to TDI was 2% or less in all six cities. Mean dietary intakes of the essential elements magnesium, calcium, and iron were less than the RDA or AI values. Drinking water did not contribute much to essential metal intake, accounting for less than 10% of RDA or AI.
  • Matsushita, T, Kobayashi, Y, Nakamura, K, Matsui, Y, Ohno, K
    Water Practice and Technology 5 3 2010年 [査読無し][通常論文]
     
    The mechanisms of increase in geosmin concentration in MF permeate with filtration time were investigated when inflow to the MF contained cyanobacteria incorporating geosmin inside and outside their cells. Whereas the geosmin concentration in the MF permeate was almost the same as the extracellular geosmin concentration in the MF inflow at the beginning of filtration, it increased and exceeded the extracellular geosmin concentration in MF inflow after 2 h of filtration. A cell viability test using a double-staining method revealed that a portion of the intracellular geosmin, which was incorporated in the cyanobacterial cells and therefore retained on the MF membrane, was released from the cells. This occurred probably because increased transmembrane pressure (TMP) with filtration time forced the cells to compress. However, geosmin release was not explained simply by cell breakage: other possible factors were implied.
  • Yoshihiko Matsui, Hiroki Hasegawa, Koich Ohno, Taku Matsushita, Satoru Mima, Yuji Kawase, Takako Aizawa
    WATER RESEARCH 43 20 5160 - 5170 2009年12月 [査読無し][通常論文]
     
    As a pretreatment for membrane microfiltration (MF), the use of powdered activated carbon (PAC) with a particle size much smaller than that of conventional PAC (super-powdered PAC, or S-PAC) has been proposed to enhance the removal of dissolved substances. In this paper, another advantage of S-PAC as a pretreatment for MF is described: the use of S-PAC attenuates trans-membrane pressure increases during the filtration operation. The floc particles that formed during coagulation preceded by S-PAC pretreatment were larger and more porous than the floc particles formed during coagulation preceded by PAC pretreatment and those formed during coagulation without pretreatment. This result was due to increased particle-particle collision frequency and better removal of natural organic matter, which inhibits coagulation by consuming coagulant, before the coagulation reaction. The caked fouling layer that built up on the membrane surface was thus more permeable with S-PAC than with normal PAC. Both physically reversible and irreversible membrane foulings were reduced, and more stable filtration was accomplished with S-PAC pretreatment. (C) 2009 Elsevier Ltd. All rights reserved.
  • Yoshihiko Matsui, Hiroki Hasegawa, Koich Ohno, Taku Matsushita, Satoru Mima, Yuji Kawase, Takako Aizawa
    WATER RESEARCH 43 20 5160 - 5170 2009年12月 [査読無し][通常論文]
     
    As a pretreatment for membrane microfiltration (MF), the use of powdered activated carbon (PAC) with a particle size much smaller than that of conventional PAC (super-powdered PAC, or S-PAC) has been proposed to enhance the removal of dissolved substances. In this paper, another advantage of S-PAC as a pretreatment for MF is described: the use of S-PAC attenuates trans-membrane pressure increases during the filtration operation. The floc particles that formed during coagulation preceded by S-PAC pretreatment were larger and more porous than the floc particles formed during coagulation preceded by PAC pretreatment and those formed during coagulation without pretreatment. This result was due to increased particle-particle collision frequency and better removal of natural organic matter, which inhibits coagulation by consuming coagulant, before the coagulation reaction. The caked fouling layer that built up on the membrane surface was thus more permeable with S-PAC than with normal PAC. Both physically reversible and irreversible membrane foulings were reduced, and more stable filtration was accomplished with S-PAC pretreatment. (C) 2009 Elsevier Ltd. All rights reserved.
  • Yoshihiko Matsui, Hiroki Hasegawa, Koich Ohno, Taku Matsushita, Satoru Mima, Yuji Kawase, Takako Aizawa
    WATER RESEARCH 43 20 5160 - 5170 2009年12月 [査読無し][通常論文]
     
    As a pretreatment for membrane microfiltration (MF), the use of powdered activated carbon (PAC) with a particle size much smaller than that of conventional PAC (super-powdered PAC, or S-PAC) has been proposed to enhance the removal of dissolved substances. In this paper, another advantage of S-PAC as a pretreatment for MF is described: the use of S-PAC attenuates trans-membrane pressure increases during the filtration operation. The floc particles that formed during coagulation preceded by S-PAC pretreatment were larger and more porous than the floc particles formed during coagulation preceded by PAC pretreatment and those formed during coagulation without pretreatment. This result was due to increased particle-particle collision frequency and better removal of natural organic matter, which inhibits coagulation by consuming coagulant, before the coagulation reaction. The caked fouling layer that built up on the membrane surface was thus more permeable with S-PAC than with normal PAC. Both physically reversible and irreversible membrane foulings were reduced, and more stable filtration was accomplished with S-PAC pretreatment. (C) 2009 Elsevier Ltd. All rights reserved.
  • Koichi Ohno, Emi Kadota, Yoshihiko Matsui, Yoshimi Kondo, Taku Matsushita, Yasumoto Magara
    JOURNAL OF WATER SUPPLY RESEARCH AND TECHNOLOGY-AQUA 58 7 476 - 487 2009年11月 [査読無し][通常論文]
     
    The quality of treated water produced by a drinking water treatment plant (DWTP) is affected by many factors. Relative impacts of various factors that affect the following treated water quality indices-turbidity, color, aluminum concentration and aggregate organic constituents-were investigated. Multivariate statistical analysis based on Hayashi's Quantification Theory Type 1 was performed on a dataset comprised of statistics on raw and treated water quality collected from thousands of DWTPs throughout Japan. Explanatory factors were the source of the raw water, water treatment process employed, plant capacity, total plant capacity of the water supplier (TCWS), raw water quality and pH of treated water. The statistical analyses mainly revealed that not only did obvious factors such as raw water quality affect treated water quality, but also more obscure factors such as plant capacity and TCWS. The results also imply that the larger the water supplier a DWTP of a given size belongs to, the higher the quality of treated water will be.
  • Yoshihiko Matsui, Naoya Ando, Hiroshi Sasaki, Taku Matsushita, Koichi Ohno
    WATER RESEARCH 43 12 3095 - 3103 2009年07月 [査読無し][通常論文]
     
    Super-powdered activated carbon (S-PAC) is activated carbon of much finer particle size than powdered activated carbon (PAC). Geosmin is a naturally occurring taste and odor compound that impairs aesthetic quality in drinking water. Experiments on geosmin adsorption on S-PAC and PAC were conducted, and the results using adsorption kinetic models were analyzed. PAC pulverization, which produced the S-PAC, did not change geosmin adsorption capacity, and geosmin adsorption capacities did not differ between SPAC and PAC. Geosmin adsorption kinetics, however, were much higher oil S-PAC than on PAC. A solution to the branched pore kinetic model (BPKM) was developed, and experimental adsorption kinetic data were analyzed by BPKM and by a homogeneous surface diffusion model (HSDM). The HSDM describing the adsorption behavior of geosmin required different surface diffusivity values for S-PAC and PAC, which indicated a decrease in surface diffusivity apparently associated with activated carbon particle size. The BPKM, consisting of macropore diffusion followed by mass transfer from macropore to micropore, successfully described the batch adsorption kinetics on S-PAC and PAC with the same set of model parameter values, including surface diffusivity. The BPKM simulation clearly showed geosmin removal was improved as activated carbon particle size decreased. The simulation also implied that the rate-determining step in overall mass transfer shifted from intraparticle radial diffusion in macropores to local mass transfer from macropore to micropore. Sensitivity analysis showed that adsorptive removal of geosmin improved with decrease in activated carbon particle size down to I pm, but further particle size reduction produced little improvement. (C) 2009 Elsevier Ltd. All rights reserved.
  • Shirasaki, N, Matsushita, T, Matsui, Y, Urasaki, T, Ohno, K
    Water Research 43 3 605 - 612 2009年02月 [査読無し][通常論文]
     
    Differences in the behaviors of two surrogates for pathogenic waterborne viruses, F-specific RNA bacteriophages Q beta and MS2, were investigated during the coagulation process by using river water spiked with these bacteriophages. The particle size and electrophoretic mobility of Q beta and MS2 were similar, but the removal performances of infectious Q beta and MS2, as measured by a plaque forming unit (PFU) method, differed markedly during the coagulation process. The. removal ratio of the infectious Q beta concentration was approximately 2 log higher than that of the infectious MS2 concentration at all coagulant doses tested. The total Q beta and MS2 bacteriophage concentrations, which were measured by a real-time reverse transcription-polymerase chain reaction (RT-PCR) method and represented the total number of bacteriophages regardless of their infectivity, were similar after the coagulation process, suggesting that the behaviors of Q beta and MS2 as particles were similar during the coagulation process. The difference between total concentration and infectious concentration indicated that some of the bacteriophages were probably inactivated during the coagulation process. This differ Price was larger for Q beta than MS2, meaning that Q beta was more sensitive to the virucidal activity of the aluminum coagulant. Analysis of the PFU and real-time RT-PCR findings together suggested that the difference in removal performances of Q beta and MS2 during the coagulation process was probably caused by differences not in the extent of bacteriophage entrapment in the aluminum floc particles but in the sensitivity to virucidal activity of the aluminum coagulant. (C) 2008 Elsevier Ltd. All rights reserved.
  • 遺伝子組換えノロウイルス外套タンパク粒子(rNV-VLPs)を用いたヒトノロウイルスの浄水処理性評価
    白崎伸隆, 松下拓, 松井佳彦, 大芝淳, 浦崎稔史, 大野浩一
    環境工学研究論文集 46 415 - 422 2009年 [査読無し][通常論文]
  • Shirasaki, N, Matsushita, T, Matsui, Y, Kobuke, M, Ohno, K
    Journal of Membrane Science 326 2 564 - 571 2009年01月 [査読無し][通常論文]
     
    The removal performance of two surrogates for pathogenic waterborne viruses, F-specific RNA bacteriophages Q beta and MS2, was evaluated during the coagulation-ceramic microfiltration process. River water spiked with these bacteriophages was used to investigate differences in their behaviors. Infectious and total (infectious + inactivated) bacteriophage concentrations were measured by plaque forming unit and real-time reverse transcription-polymerase chain reaction methods, respectively. Removal of infectious Q beta and MS2 was similar under each coagulation condition. Approximately 6-log reduction was achieved for both bacteriophages at 1.08 mg-Al/L of coagulant dose and 5-min coagulation time. At least 4-log reduction occurred even when coagulant dose and coagulation time were reduced to 0.54 mg-Al/L and 1.8 s, respectively. In contrast, removal of total Q beta and MS2 differed markedly. Removal of total MS2 was approximately 2-log larger than that of total Q beta, possibly owing to selective interaction with the cake layer, although the particle diameters and electrophoretic mobilities of Q beta and MS2 were similar. The total number of bacteriophages retained in the microfiltration compartment after 4-h filtration was similar for Q beta and MS2, but there were approximately 3 log fewer infectious Q beta than infectious MS2, probably owing to the difference in sensitivity to the virucidal activity of aluminum coagulant. (C) 2008 Elsevier B.V. All rights reserved.
  • K. Ohno, Y. Matsuo, T. Kimura, T. Yanase, M. H. Rahman, Y. Magara, T. Matsushita, Y. Matsui
    WATER SCIENCE AND TECHNOLOGY 59 2 195 - 201 2009年 [査読無し][通常論文]
     
    The effect of rice-cooking water to the daily arsenic intake of Bangladeshi people was investigated. At the first field survey, uncooked rice and cooked rice of 29 families were collected. Their arsenic concentrations were 0.22 +/- 0.11 and 0.26 +/- 0.15 mg/kg dry wt, respectively. In 15 families, arsenic concentration in rice increased after cooking. Good correlation (R(2) = 0.89) was observed between arsenic in rice-cooking water and the difference of arsenic concentration in rice by cooking. In the second survey, we collected one-day duplicated food of 18 families. As a result, we estimated that six of 18 families likely used the arsenic contaminated water for cooking rice even they drank less arsenic-contaminated water for drinking purpose. We also conducted rice-cooking experiments in the laboratory, changing arsenic concentration in rice-cooking water. Clear linear relationships were obtained between the arsenic in rice-cooking water and the difference of arsenic concentration in rice by cooking. Factors that affect arsenic concentration in cooked rice are suggested as follows: (1) arsenic concentration in uncooked rice, (2) that in rice-cooking water, (3) difference in water content of rice before and after cooking, and (4) types of rice, especially, the difference between parboiled and non-parboiled rice.
  • Yoshihiko Matsui, Kenji Murai, Hiroshi Sasaki, Koichi Ohno, Taku Matsushita
    JOURNAL OF WATER SUPPLY RESEARCH AND TECHNOLOGY-AQUA 57 8 577 - 583 2008年12月 [査読無し][通常論文]
     
    Submicron-sized powdered activated carbon (PAC) was produced from a commercially available normal PAC by a bead mill. The submicron PAC decomposed dichloramine and nitrogen trichloride, impairing aesthetic quality with chlorinous odor, at a much faster rate than did normal PAC. Moreover, decomposition rates were faster for dichloramine and nitrogen trichloride than for monochloramine and free chlorine. Selective removal of chlorinous odors among chlorine compounds in a short time was thereby possible. The earthy-musty compound geosmin was also much more rapidly removed by adsorption on submicron PAC than on normal PAC. The increased removal rate was partly due to the adsorption capacity increase owing to the particle size reduction of PAC to submicron range, which accounted for 40% of the improvement of geosmin removal at a PAC contact time of 10 min.
  • Yoshihiko Matsui, Takahiro Ozu, Takanobu Inoue, Taku Matsushita
    DESALINATION 226 1-3 215 - 221 2008年06月 [査読無し][通常論文]
     
    The release of pharmaceuticals into the aquatic environment and their occurrence in surface waters has become an increasing concern in recent years. In this study we investigated the occurrence of oxytetracycline (OTC), one of the most widely used veterinary antibiotics, in stream waters in a small catchment area with many livestock farms. OTC was detected in the concentration range of 2 ng/L to 68 mu g/L. Increasing trends in OTC concentrations and daily loads during winter were observed, which correspond to the common veterinary practice of using higher dosages of antibiotics as prophylaxis against disease in winter. High concentrations of OTC in stream water were observed in the vicinity of a livestock farm. There, the daily OTC load rate was in a reasonable range when the number of animals, the additive rate of antibiotics to fodder, and the OTC removal efficiency in activated sludge processes were estimated.
  • Koichi Ohno, Takehiro Minami, Yoshihiko Matsui, Yasumoto Magara
    WATER RESEARCH 42 6-7 1753 - 1759 2008年03月 [査読無し][通常論文]
     
    We investigated effects of chlorination on four organophosphorus pesticides (diazinon, isoxathion, malathion, and tolclofos-methyl) adsorbed on powdered activated carbon (PAC). Following adsorption of each pesticide on 10mg/L of PAC in water, chlorine was added. After 30min of chlorination, the corresponding oxons were detected in the water, but the parent compounds were not detected. Molar ratios of the oxon concentration in solution after 30min of chlorine addition to the initial pesticide concentration before the adsorption process were 4.1% and 7.9% for diazinon, 3.9% and 5.8% for isoxathion, 1.2% and 1.7% for malathion, and 1.4% and 1.4% for tolchlofos-methyl, in the case of 2 and 5 mg/L of chlorine addition. The results suggested that the oxons were desorbed from the PAC by chlorination. The concentrations of the desorbed oxons gradually decreased with time, apparently owing to their readsorption by the PAC. Results from additional experiments suggest the following sequence of events: (i) adsorbed pesticides are oxidized by chlorine on the surface of the PAC and transformed into corresponding oxons; (ii) the oxons are released from the PAC; (iii) the released oxons are gradually readsorbed by the PAC, decreasing their concentrations in the water phase. (c) 2007 Elsevier Ltd. All rights reserved.
  • 安藤直哉, 松井佳彦, 松下拓, 大野浩一, 佐々木洋志, 中野優
    環境工学研究論文集 45 309 - 315 Japan Society of Civil Engineers 2008年 [査読無し][通常論文]
     
    天然有機物質 (NOM) の除去方法の一つとして活性炭による吸着がある. 本研究では, 粉末活性炭とそれをさらに粉砕した微粉化活性炭を用い, NOM, そのモデル物質であるポリスチレンサルフォネート (PSS) 及びポリエチレングリコール (PEG) を対象とした活性炭吸着実験を行った. その結果, 活性炭の微粉化により, NOMの平衡吸着容量が増加することが分かった. さらに, 平衡吸着容量の増加は, 高分子量になるほど増加率は大きくなるが, 物質によりその増加率に違いがあることが示唆された. モデルシミュレーションにより, 微粉化に伴う吸着除去性の増加に寄与する因子は物質により異なることが示され, PSSのように平衡吸着容量の増加の寄与を大きく受ける物質や, PEGのように活性炭比表面積の増加の寄与を大きく受ける物質があることが分かった.
  • T. Matsushita, Y. Matsui, D. Sawaoka, K. Ohno
    JOURNAL OF WATER SUPPLY RESEARCH AND TECHNOLOGY-AQUA 57 7 481 - 487 2008年 [査読無し][通常論文]
     
    Engineers in drinking water treatment plants which employ activated carbon adsorption followed by microfiltration (MF) often ask why the removal ratio of compounds causing musty odors in real plants is smaller than that achieved in laboratory experiments. We investigated whether this difference in removal ratios was due to the release of intracellular geosmin under high pressure from cyanobacteria coexisting on the filter membrane surface. We conducted batch pressurization tests with a cyanobacterium-containing solution, laboratory-scale MF experiments, and pilot-scale experiments designed to remove both the geosmin and cyanobacteria in a hybrid system which used powdered activated carbon adsorption, coagulation, and ceramic microfiltration. Release of intracellular geosmin from cyanobacteria accumulated on the membrane surface was observed in both the laboratory-scale MF experiments and the pilot-scale experiments, but not in the batch pressurization tests. Geosmin was still observed in the MF permeate when the hybrid system was operated with commercially available powdered activated carbon (PAC), and its concentration increased with filtration time owing to the continued release of geosmin. In contrast, operation of the hybrid system with micro-ground PAC completely removed the geosmin.
  • Nobutaka Shirasaki, Taku Matsushita, Yoshihiko Matsui, Koichi Ohno
    JOURNAL OF WATER SUPPLY RESEARCH AND TECHNOLOGY-AQUA 57 7 501 - 506 2008年 [査読無し][通常論文]
     
    We evaluated the removal of virus (bacteriophage Q beta) after hydraulic backwashing and the effects of reversible and irreversible membrane fouling on virus removal by a coagulation microfiltration (MF) system. The rate of virus removal in the coagulation-MF system was low at the beginning of filtration but increased with filtration time, owing to the accumulation of foulant on the membrane. The rate of virus removal thereafter remained high, even after hydraulic backwashing of the membrane to remove reversible membrane foulant. The presence of irreversible, rather than reversible, membrane foulant contributed to the increase in virus removal rate observed at the beginning of filtration. The irreversible membrane fouling maintained a high virus removal rate even after hydraulic backwashing. Moreover, irreversible fouling of the membrane during long-term filtration (1 month) improved virus removal in the coagulation-MF system, and the membrane excluded virus particles even in the absence of coagulation pretreatment. Therefore, the accumulation of irreversible membrane foulant with filtration time played an important role in virus removal by the coagulation-MF system.
  • T. Matsushita, Y. Matsui, S. Taniwaki, K. Ikeba
    WATER SCIENCE AND TECHNOLOGY 58 3 741 - 747 2008年 [査読無し][通常論文]
     
    In the present study, our objectives were (1) using the Ames assay, to evaluate the change in mutagenicity of a fenitrothion-containing solution during aerobic biodegradation, anaerobic biodegradation, and photodegradation, and (2) to identify possible mutagenic transformed products (TPs) that contributed substantially to any increase in mutagenicity. Mutagenicity of the fenitrothion-containing solution did not increase during aerobic biodegradation with any of the tested bacterial strains. In contrast, the mutagenicity increased for strain YG1029 during anaerobic biodegradation because of the generation of a strongly mutagenic TP, aminofenitrothion. During photodegradation, mutagenicities increased slightly for YG1021 and YG1024, possibly owing to the production of a previously unreported mutagenic TIP.
  • Yoshihiko Matsui, Takako Aizawa, Fumiaki Kanda, Naoko Nigorikawa, Satoru Mima, Yuji Kawase
    JOURNAL OF WATER SUPPLY RESEARCH AND TECHNOLOGY-AQUA 56 6-7 411 - 418 2007年09月 [査読無し][通常論文]
     
    Tap water free from unpleasant taste and odour is important for consumer satisfaction. we applied a super-powdered activated carbon (S-PAC) and microfiltration (MF) system to the removal of geosmin, a taste- and odour-causing compound. We used a specially pulverised PAC much smaller than the normal PAC (N-PAC) particle size as an with a submicron particle size,, adsorption pretreatment agent. MF and adsorption pretreatment with S-PAC removed geosmin with considerably greater efficiency and at a much lower dosage rate than with N-PAC. An S-PAC dosage of 2 mg/L was equivalent to an N-PAC dosage of more than 20 mg/L in the treatment of reagent-geosmin-spiked feed water - a dosage saving of 90%, with better removal. in experiments with feed water spiked with cultured Anabaena and geosmin, geosmin removal was attained with S-PAC at a dosage 10% of that of N-PAC. The superiority of S-PAC in removing naturally occurring geosmin from raw water was also confirmed. However, the dosage saving in this case was 75%. S-PAC also helped attenuate trans-membrane pressure increases in both physical backwash and chemical cleaning cycles. No significant trans-membrane pressure increase was observed during 4 months of MF operation with S-PAC addition, suggesting that S-PAC particles did not clog or foul the membrane.
  • Yasumoto Magara, Yoshihiko Matsui, Koichi Ohno
    JOURNAL OF WATER SUPPLY RESEARCH AND TECHNOLOGY-AQUA 56 6-7 365 - 373 2007年09月 [査読無し][通常論文]
     
    The Japanese government published "The Water and Sanitation Broad Partnership initiative (WASABI)" in March 2006. This initiative was based on the policies that Japan will support the self-help efforts of developing countries on water and sanitation, establishing broad partnerships with international organizations, and the other donor agencies, etc. Because water resources are very limited, there are many areas and regions which have to use a heavily polluted water source. Therefore, it is necessary to develop the emergent water treatment technology which can supply safe drinking water from polluted source water at a reasonable cost. In order to anticipate a sustainable development of water service the Japanese ministry of Health, Labor and Welfare published "The Water Works Vision" so as to restructure the water utility management system in 2004. The vision asks to reform the water utility management system so as to mobilize every resource including public private partnership. Therefore, it is necessary to develop an audit system by a third party for risk communication among the stakeholders.
  • Koichi Ohno, Tatsuya Yanase, Yuki Matsuo, Tetsuro Kimura, M. Hamidur Rahman, Yasumoto Magara, Yoshihiko Matsui
    SCIENCE OF THE TOTAL ENVIRONMENT 381 1-3 68 - 76 2007年08月 [査読無し][通常論文]
     
    More and more people in Bangladesh have recently become aware of the risk of drinking arsenic-contaminated groundwater, and have been trying to obtain drinking water from less arsenic-contaminated sources. In this study, arsenic intakes of 18 families living in one block of a rural village in an arsenic-affected district of Bangladesh were evaluated to investigate their actual arsenic intake via food, including from cooking water, and to estimate the contribution of each food category and of drinking water to the total arsenic intake. Water consumption rates were estimated by the self-reporting method. The mean drinking water intake was estimated as about 3 L/d without gender difference. Arsenic intakes from food were evaluated by the duplicate portion sampling method. The duplicated foods from each family were divided into four categories (cooked rice, solid food, cereals for breakfast, and liquid food), and the arsenic concentrations of each food category and of the drinking water were measured. The mean arsenic intake from water and food by all 18 respondents was 0.15 +/- 0.11 +/- mg/d (range, 0.043-0.49), that by male subjects was 0.18 +/- 0.13 mg/d (n=12) and that by female subjects was 0.096 +/- 0.007 mg/d (n=6). The average contributions to the total arsenic intake were, from drinking water, 13%; liquid food, 4.4%; cooked rice, 56%; solid food, 11%; and cereals, 16%. Arsenic intake via drinking water was not high despite the highly contaminated groundwater in the survey area because many families had changed their drinking water sources to less-contaminated ones. Instead, cooked rice contributed most to the daily arsenic intake. Use of contaminated water for cooking by several families was suspected based on comparisons of arsenic concentrations between drinking water and liquid food, and between rice before and after cooking. Detailed investigation suggested that six households used contaminated water for cooking but not drinking, leading to an increase of arsenic intake via arsenic-contaminated cooking water. (c) 2007 Elsevier B.V. All rights reserved.
  • Yoshihiko Matsui, Takayuki Yamagishi, Yoshihiro Terada, Taku Matsushita, Takanobu Inoue
    JOURNAL OF WATER SUPPLY RESEARCH AND TECHNOLOGY-AQUA 56 1 13 - 24 2007年02月 [査読無し][通常論文]
     
    Although advances in water treatment technology have contributed to improved water quality at water treatment plants, treated water is not reaching consumer taps with the same quality. Water quality in service pipes is lower than at the water treatment plants, most likely because rust corrosion particles are generated inside the pipes, accumulated sediments become resuspended or other reasons. in this study, particles suspended in treated water flowing through water mains of various service areas were collected, and their quantity and elemental compositions were analyzed to investigate changes in suspended solid (SS) characteristics over distance and time. in addition to longitudinal changes along water mains, cross-sectional SS changes were investigated by developing a method of directly collecting SS particles flowing through a water main at different vertical locations. SS concentrations and the percentages of inorganics and iron in SS increased as water traveled toward the dead end of a main. Vertical differences of SS in the main cross section were also observed: SS concentrations in the upper part were higher than those in the middle and lower parts. The higher percentages of inorganics and iron in the upper part suggested that scaling in the upper part of the main, which had a stagnant area, caused iron particles to be released into the stream. Temporal variations in SS concentrations were observed for water flowing through the middle and lower parts of the main cross section. SS concentrations increased with increased flow rates, indicating resuspension of sediment at the bottoms of the mains. Overall, SS concentrations, their temporal variations, their cross-sectional changes and the elemental compositions of SS in water were different in various water service areas, and these characteristics could be useful in determining the origin of SS particles in drinking water.
  • Yoshihiko Matsui, Takayuki Yamagishi, Yoshihiro Terada, Taku Matsushita, Takanobu Inoue
    JOURNAL OF WATER SUPPLY RESEARCH AND TECHNOLOGY-AQUA 56 1 13 - 24 2007年02月 [査読無し][通常論文]
     
    Although advances in water treatment technology have contributed to improved water quality at water treatment plants, treated water is not reaching consumer taps with the same quality. Water quality in service pipes is lower than at the water treatment plants, most likely because rust corrosion particles are generated inside the pipes, accumulated sediments become resuspended or other reasons. in this study, particles suspended in treated water flowing through water mains of various service areas were collected, and their quantity and elemental compositions were analyzed to investigate changes in suspended solid (SS) characteristics over distance and time. in addition to longitudinal changes along water mains, cross-sectional SS changes were investigated by developing a method of directly collecting SS particles flowing through a water main at different vertical locations. SS concentrations and the percentages of inorganics and iron in SS increased as water traveled toward the dead end of a main. Vertical differences of SS in the main cross section were also observed: SS concentrations in the upper part were higher than those in the middle and lower parts. The higher percentages of inorganics and iron in the upper part suggested that scaling in the upper part of the main, which had a stagnant area, caused iron particles to be released into the stream. Temporal variations in SS concentrations were observed for water flowing through the middle and lower parts of the main cross section. SS concentrations increased with increased flow rates, indicating resuspension of sediment at the bottoms of the mains. Overall, SS concentrations, their temporal variations, their cross-sectional changes and the elemental compositions of SS in water were different in various water service areas, and these characteristics could be useful in determining the origin of SS particles in drinking water.
  • Yoshihiko Matsui, Takayuki Yamagishi, Yoshihiro Terada, Taku Matsushita, Takanobu Inoue
    JOURNAL OF WATER SUPPLY RESEARCH AND TECHNOLOGY-AQUA 56 1 13 - 24 2007年02月 [査読無し][通常論文]
     
    Although advances in water treatment technology have contributed to improved water quality at water treatment plants, treated water is not reaching consumer taps with the same quality. Water quality in service pipes is lower than at the water treatment plants, most likely because rust corrosion particles are generated inside the pipes, accumulated sediments become resuspended or other reasons. in this study, particles suspended in treated water flowing through water mains of various service areas were collected, and their quantity and elemental compositions were analyzed to investigate changes in suspended solid (SS) characteristics over distance and time. in addition to longitudinal changes along water mains, cross-sectional SS changes were investigated by developing a method of directly collecting SS particles flowing through a water main at different vertical locations. SS concentrations and the percentages of inorganics and iron in SS increased as water traveled toward the dead end of a main. Vertical differences of SS in the main cross section were also observed: SS concentrations in the upper part were higher than those in the middle and lower parts. The higher percentages of inorganics and iron in the upper part suggested that scaling in the upper part of the main, which had a stagnant area, caused iron particles to be released into the stream. Temporal variations in SS concentrations were observed for water flowing through the middle and lower parts of the main cross section. SS concentrations increased with increased flow rates, indicating resuspension of sediment at the bottoms of the mains. Overall, SS concentrations, their temporal variations, their cross-sectional changes and the elemental compositions of SS in water were different in various water service areas, and these characteristics could be useful in determining the origin of SS particles in drinking water.
  • Y. Matsui, T. Aizawa, M. Suzuki, Y. Kawase
    Water Science and Technology: Water Supply 7 5-6 43 - 51 2007年 [査読無し][通常論文]
     
    The musty-earthy taste and odour caused by the presence of geosmin and other compounds in tap water are major causes of consumer complaints. Although ozonation and granular activated carbon (GAC) adsorption have been practiced in water-treatment plants to remove these compounds effectively, two major problems associated with the application of these processes - formation of stringently regulated bromate ions by ozonation and unhygienic invertebrate colonisation of GAC filters - are still to be resolved. This research advanced the process of adsorption by powdered activated carbon (PAC) by reducing its particle size to the submicrometre range for microfiltration pretreatment. Adsorption pretreatment by using this super (S)-PAC removed the geosmin with vastly greater efficiency than by normal PAC. Removal was attained in a much shorter contact time and at a much lower dosage. The S-PAC was also beneficial in attenuating the transmembrane pressure rises that occurred between both physical backwashings and chemical cleanings. © IWA Publishing 2007.
  • Y. Matsui, K. Narita, T. Inoue, T. Matsushita
    WATER SCIENCE AND TECHNOLOGY 56 1 71 - 80 2007年 [査読無し][通常論文]
     
    Verification of a diffuse pollution model involves comparing results actually observed with those predicted by precise model inputs. Acquisition of precise model inputs is, however, problematic. In particular, when the target catchment is large and substantial estimation uncertainty exists, not only model verification but also prediction is difficult. Therefore, in this study, rice-farming data were collected for all paddy fields from all farmers in a catchment and pesticide adsorption and degradation rates in paddy field soil samples were measured to obtain precise model inputs. The model inputs successfully verified the model's capability to predict pesticide concentrations in river water. Sensitivity analyses of the model inputs elucidated the processes significantly affecting pesticide runoff from rice farms. Pesticide adsorption and degradation rates of the soil did not significantly affect pesticide concentrations, although pesticide discharge to river water accounted for less than 50% of the total quantity of pesticide applied to fields, possibly owing to pesticide adsorption and degradation. The timing of increases in pesticide concentrations in river water was affected mostly by the farming schedule, including the time of pesticide application and irrigation, and secondarily by rainfall events.
  • Y. Matsui, K. Narita, T. Inoue, T. Matsushita
    TRANSACTIONS OF THE ASABE 49 6 1723 - 1735 2006年11月 [査読無し][通常論文]
     
    In predicting time-series concentrations of pesticides in river water using diffuse pollution hydrological models, farming schedules (including pesticide application) and pesticide sorption/decomposition rates greatly affect prediction accuracy. For large, basin-scale catchments, precise acquisition of these data is not possible and substantial estimation uncertainty inevitably exists. This article presents the development of a basin-scale diffuse pollution hydrological model, a Monte Carlo method for creating input data, and its effectiveness in predicting the concentrations of paddy-fanning pesticides in river water from a large catchment (1882 km(2)). The Monte Carlo method created input data for numerous compartments of a paddy field in the basin model: the pesticide products, amounts and dates of pesticide application, rice varieties, rice seedling transplanting dates, time variation of water depth in rice paddies, and parameter values for pesticide decomposition and sorption. The model was calibrated with hydrological data only, without reference to observed pesticide concentration data. Results showed that the uncertainty bounds estimated for model outputs with Monte Carlo inputs encompassed observed data and that the model predictions were better with Monte Carlo inputs than with deterministic input. The Monte Carlo method provides a surrogate approach for obtaining precise data on individual farming schedules (including pesticide application dates), degradation rates, and sorption coefficients in each soil.
  • Yoshihiko Matsui, Yoshihiko Matsui, Kentaro Narita, Takanobu Inoue, Taku Matsushita
    Transactions of the ASABE 49 1723 - 1735 2006年11月01日 [査読有り][通常論文]
     
    In predicting time-series concentrations of pesticides in river water using diffuse pollution hydrological models, farming schedules (including pesticide application) and pesticide sorption/decomposition rates greatly affect prediction accuracy. For large, basin-scale catchments, precise acquisition of these data is not possible and substantial estimation uncertainty inevitably exists. This article presents the development of a basin-scale diffuse pollution hydrological model, a Monte Carlo method for creating input data, and its effectiveness in predicting the concentrations of paddy-farming pesticides in river water from a large catchment (1882 km 2). The Monte Carlo method created input data for numerous compartments of a paddy field in the basin model: the pesticide products, amounts and dates of pesticide application, rice varieties, rice seedling transplanting dates, time variation of water depth in rice paddies, and parameter values for pesticide decomposition and sorption. The model was calibrated with hydrological data only, without reference to observed pesticide concentration data. Results showed that the uncertainty bounds estimated for model outputs with Monte Carlo inputs encompassed observed data and that the model predictions were better with Monte Carlo inputs than with deterministic input. The Monte Carlo method provides a surrogate approach for obtaining precise data on individual farming schedules (including pesticide application dates), degradation rates, and sorption coefficients in each soil. © 2006 American Society of Agricultural and Biological Engineers.
  • Taku Matsushita, Yoshihiko Matsui, Yusuke Matsui
    CHEMOSPHERE 64 1 144 - 151 2006年06月 [査読無し][通常論文]
     
    We aimed to: (1) evaluate the change in mutagenicity of a fenitrothion-containing solution during photolysis and (2) elucidate mutagenic compounds that were possible major contributors to mutagenicity. A batch test involving irradiation by natural sunlight was conducted on the solution, and then HPLC fractionation, mutagenicity testing, and gas chromatography-mass spectrometry (GC-MS) analysis were performed on the irradiated solution. During the 15-day photolysis, fenitrothion was almost completely decomposed, and 34 transformed products (TPs) were generated. Photolysis decreased the mutagenicity of the fenitrothion-containing solution for base-pair-substitution-detecting tester strains (YG1026 and YG1029) but increased mutagenicity for frameshift-detecting tester strains (YG1021 and YG1024). One TP was identified as a potential source of the increased mutagenicity; its molecular formula was estimated to be (CH3O)(2)PS-O-C8H6NO. (c) 2005 Elsevier Ltd. All rights reserved.
  • 清塚雅彦, 竹田憲史, 松井佳彦, 向井藤利, 森康輔, 榊原康之
    環境衛生工学研究 20 1 15 - 20 京都大学環境衛生工学研究会 2006年 [査読無し][通常論文]
  • Y. Matsui, T. Sanogawa, N. Aoki, S. Mima, T. Matsushita
    PARTICLE SEPARATION 2005 - DRINKING WATER TREATMENT 6 1 149 - 155 2006年 [査読無し][通常論文]
     
    Submicron powdered activated carbon (PAC) rapidly adsorbed natural organic matter (NOM) fromwater samples: a batch test of the adsorption kinetics showed that the NOM concentration dropped substantially within 15 s and then leveled off. In a tubular flow reactor test, NOM removal after a 15 s contact time was almost the same as removal values attained at longer contact times. Laboratory-scale and bench-scale pilotplant ceramic microfiltration (MF) experiments with submicron PAC adsorption pretreatment were conducted to evaluate NOM removal and to examine the effect of the PAC on filterability. The laboratory scale IVIF experiment revealed that PAC adsorption pretreatment could be accomplished with a detention (2.4 s) that was much shorter than the time expected from the adsorption kinetics test. This result suggests that adsorption pretreatment for IVIF could be accomplished by adding the submicron PAC directly into the feed line to the membrane and that installation of a special PAC contactor before the membrane unit is unnecessary. Although micron PAC rather than submicron PAC was used unintentionally in the pilot plant experiment, these PAC showed much better NOM removal than normal PAC, and no adverse effects, such as transmembrane pressure buildup and reversible or irreversible membrane fouling, were observed. Keywords Humic substances; membrane; natural organic matter; particle size; powdered activated carbon.
  • T Matsushita, Y Matsui, N Shirasaki
    WATER SCIENCE AND TECHNOLOGY 53 7 199 - 207 2006年 [査読無し][通常論文]
     
    Virus removal experiments using river water spiked with bacteriophages were conducted by an inline coagulation-ceramic microfiltration hybrid system to investigate the effects of filtration flux (62.5 and 125 L/(m(2) x h)) and type of virus (Q beta and MS2) on virus removal. In addition, the mass balance of viruses through the hybrid system was analysed by quantifying the infectious and inactive viruses by a combination of the polymerase chain reaction (PCR) method and the plaque forming units (PFU) method. Even when the system was operated at high filtration flux (125 L/(m(2) x h)), high virus removal (> 6 log) with short coagulation time (2.4 s) was successfully achieved by dosing polyaluminium chloride (PACl) at more than 1.08 mg(.)Al/L. Removal performances were different between Q beta and MS2, although their diameters are almost the same: greater virus removal was achieved for MS2 at PACI dosing of 0.54 mg(.)Al/L, and for Q beta at PACI dosing of more than 1.08 mg(.)Al/L. The combination of the PCR and PFU methods revealed that two phenomena, adsorption to/entrapment in aluminium floc and virucidal activity of PACl, partially account for the high virus removal in the coagulation-MF hybrid system.
  • Y. Matsui, K. Narita, T. Inoue, T. Matsushita
    WATER SCIENCE AND TECHNOLOGY 53 10 173 - 181 2006年 [査読無し][通常論文]
     
    To predict rice-farming pesticide concentrations in river water with imprecise model inputs for screening-level analysis, a basin-scale runoff model was developed. The Monte Carlo method was applied to create estimates of input data regarding agricultural work schedules and parameters for pesticide decomposition and sorption in solids and water. The prediction accuracy of the model was evaluated when used with non-optimised pesticide parameters; the model was calibrated using hydrological data alone without reference to observed pesticide concentration data. Overall, predictions for the pesticide concentrations were successful within order-of-magnitude accuracy. The pesticide rankings according to the predicted concentration roughly agreed with those observed. The success of screening-level analysis indicates that the model prediction can help in selection of pesticides to be monitored and in determining the monitoring schedule for the river basin.
  • Y. Matsui, K. Narita, T. Inoue, T. Matsushita
    WATER SCIENCE AND TECHNOLOGY 53 10 173 - 181 2006年 [査読無し][通常論文]
     
    To predict rice-farming pesticide concentrations in river water with imprecise model inputs for screening-level analysis, a basin-scale runoff model was developed. The Monte Carlo method was applied to create estimates of input data regarding agricultural work schedules and parameters for pesticide decomposition and sorption in solids and water. The prediction accuracy of the model was evaluated when used with non-optimised pesticide parameters; the model was calibrated using hydrological data alone without reference to observed pesticide concentration data. Overall, predictions for the pesticide concentrations were successful within order-of-magnitude accuracy. The pesticide rankings according to the predicted concentration roughly agreed with those observed. The success of screening-level analysis indicates that the model prediction can help in selection of pesticides to be monitored and in determining the monitoring schedule for the river basin.
  • Matsui, Y, Narita, K, Inoue, T, Matsushita, T
    Water Sci. & Tech. 53 10 173 - 181 2006年 [査読無し][通常論文]
  • T Matsushita, Y Matsui, R Saeki, T Inoue
    CHEMOSPHERE 61 8 1134 - 1141 2005年12月 [査読無し][通常論文]
     
    Previous studies have revealed that the mutagenicity of fenitrothion increases during anaerobic biodegradation, suggesting that this insecticide's mutagenicity could effectively increase after it pollutes anaerobic environments such as lake sediments. To investigate possible changes to the mutagenicity of fenitrothion under aerobic conditions after it had already been increased by anaerobic biodegradation, batch incubation cultures were maintained under aerobic conditions. The mutagenicity, which had increased during anaerobic biodegradation, decreased under aerobic conditions with aerobic or facultative bacteria, but did not disappear completely in 22 days. In contrast, it did not change under aerobic conditions without bacteria or under continued anaerobic conditions. These observations suggest that the mutagenicity of anaerobically metabolized fenitrothion would not necessarily decrease after it arrives in an aerobic environment: this would depend on the presence of suitable bacteria. Therefore, fenitrothion-derived mutagenic compounds may pollute the water environment, including our drinking water sources, after accidental pollution of aerobic waters. Although amino-fenitrothion generated during anaerobic biodegradation of fenitrothion was the principal mutagen, non-trivial contributions of other, unidentified metabolites to the mutagenicity were also observed. (c) 2005 Elsevier Ltd. All rights reserved.
  • T Matsushita, Y Matsui, N Shirasaki, Y Kato
    DESALINATION 178 1-3 21 - 26 2005年07月 [査読無し][通常論文]
     
    We studied virus removal from spiked river water by an in-line coagulation-ceramic microfiltration hybrid system to investigate the effects of (1) coagulant dose (0.54,1.08, and 1.62 mg Al/L), (2) pore size of the MF membrane (0.1, 0.5, and 1.0 mu m), and (3) coagulation time (1.1, 2.4, and 60 s). We found that (1) coagulant dose strongly affected virus removal. Whereas 7.4 log removal was achieved with 1.62 mg Al/L PACl dosing, only 2.8 log removal was observed with 0.54 mg Al/L; thus, the larger the coagulant dose, the greater the virus removal. (2) Pore size of the MF membrane also affected virus removal: pore sizes of 0.5 and 1.0 mu m showed about I log less removal than the 0.1-mu m pore-size MF membrane. (3) Coagulation time slightly affected virus removal: the longer the coagulation time, the greater the reduction in virus level, but the effect was not large. Overall, the combination of in-line coagulation prior to microfiltration enables much shorter coagulation times than in conventional treatment plants: dosing with at least 1.08 mg Al/L PACl in the hybrid system allowed the coagulation time to be only 2.4 s.
  • FS Li, A Yuasa, Y Muraki, Y Matsui
    SCIENCE OF THE TOTAL ENVIRONMENT 345 1-3 99 - 113 2005年06月 [査読無し][通常論文]
     
    The impacts of a heavy storm of rain upon the dissolved and particulate organic matter (OM), nitrogen (N) and phosphorus (P) in the main river of the vegetation-rich Nagara River basin were investigated using water samples collected along the river line during a critical typhoon-induced heavy rain storm event. Besides, based on a high performance size-exclusion chromatography (HPSEC) system, the variance of dissolved OM (DOM) in its molecular weight (MW) characteristics was also assessed. From the MW standpoint, DOM components merged into the river along the river line resembled those present in its headwater. The MW range changed only slightly from 1010 to 5900 at the upstream (US), to 1130-5900 and 1200-5900 Da at the midstream (MS) and downstream (DS), respectively, while the corresponding weight-averaged MW (M-w) decreased from 3669 to 3330 and 2962 Da. The heavy storm of rain enhanced the content of DOM; however, apart from a small larger-MW fraction (about 5900-6800 Da), the newly emerged DOM constituents exhibited an MW range similar to those existed before the storm. Due also to the storm of rain, total P and N (TP and TN) changed markedly in the ranges of 6.6-11.9, 8.3-40.6 and 48.4-231.3 mu g/l for TP, and 145.4-296.0, 502.2-1168.7 and 1342.7-1927.3 mu g/l for TN at the US, MS and DS, respectively. The larger values of TP and IN generally appeared for samples at elevated river water levels. The enhanced presence of P was found largely attributed to its particulate form; while, for N, the contribution from its dissolved form was significant. The newly emerged suspended particles via the storm-water contained lower content of OM, N and P, and a general decreasing trend of the particulate OM, N and P along the river line was also confirmed. The C/N ratio in the dissolved form varied in 0.7-6.7 and decreased downstream, while, that in the particulate form 2.3-17.3. Suspended particles that emerged in the river water during the storm exhibited larger C/N values. N/P in both dissolved and particulate forms varied in the ranges of 2.2-17.1 and 12.9-444.9, respectively, and a general trend of either increasing or decreasing in relation to the storm of rain was not revealed. (c) 2004 Elsevier B.V. All rights reserved.
  • 井上隆信, 松下拓, 山田俊郎, 松井佳彦
    水文・水資源学会誌 18 6 681 - 687 2005年 [査読無し][通常論文]
  • 鄭恩貞, 湯浅晶, 李富生, 松井佳彦
    第42回環境工学研究フォーラム論文集 42 253 - 264 Japan Society of Civil Engineers 2005年 [査読無し][通常論文]
     
    Batch activated carbon adsorption experiments were performed for investigation of the adsorption capacity of estrone, 17β-estradiol and estriol using single-solute and mixed-solute solutions. The single-solute isotherm data for all three adsorbates were well described by the Freundlich isotherm expression and the associated adsorption parameters (Freundlich constant K and exponent 1/n) were thus determined. The K values were relatively large, 493.6, 347.8 and 194.4 (mg/g)/(mg/L)1/n for E1, E2 and E3, respectively, which indicated strong adsorbabilities. In regard of 1/n, the determined values fell in a range below 0.3 (0.264, 0.227 and 0.197 for El, E2 and E3, respectively), suggesting strong affinity of these compounds to the activated carbon used (Filtrasorb 400). When subjected to adsorption in mixed solutions with different solute and concentration combinations, the adsorption capacity of all these three compounds decreased obviously, as compared to that in single-solute solutions. However, the order assessed in terms of the magnitude of adsorption capacity was found not changed as it was in single solute solutions, i. e., E1>E2>E3.
  • 松下拓, 小塚信幸, 中務誠, 角田裕樹, 松井佳彦
    環境工学研究論文集 42 463 - 468 Japan Society of Civil Engineers 2005年 [査読無し][通常論文]
     
    In order to investigate the change in the infectivity of virus (bacteriophage Qβ) after dosing of polyaluminum coagulant (PACl), virus concentrations were measured by plaque forming unit (PFU) method and polymerase chain reaction (PCR) method after dissolving aluminum floc which had been formed during coagulation process and would have adsorbed/entrapped virus. The drop of infectious virus concentration after coagulation could not be explained by simple aggregation of infectious virus particles alone, suggesting that the loss of infectivity of virus caused by the PAC1 could partly account for the drop. The irreversible adhesion of virus to the polyaluminum species was enhanced by adding NaCl, MgCl2 and CaCl2 to the virus containing water before dosing PACl, while it was reduced by adding NaHCO3. The addition of NaCl, MgCl2 and CaCl2 decreased the surface charge of the virus so that they might decrease the irreversible adhesion. NaHCO3 increased the surface charge of the virus, and this might decrease the irreversible adhesion.
  • A Yuasa, FS Li, EJ Cheong, Y Matsui
    ADSORPTION-JOURNAL OF THE INTERNATIONAL ADSORPTION SOCIETY 11 243 - 248 2005年 [査読無し][通常論文]
     
    Three NPEO mixtures containing NPEO compounds having attached EO numbers in the ranges of 1-6, 2-12 and 4-19 were subjected to batch activated carbon adsorption experiments in solutions with and without the presence of competing natural organic matter (NOM) existent extensively in drinking water sources. The liquid phase composition of the NPEO mixtures, described in the ratios (C-i/C-T) of the equilibrium concentrations of individual compounds (C-i) to the total mixture (C-T), did not change after adsorption at varied carbon dosages, no matter if NOM was present or not. However, their adsorption capacity was significantly reduced with the adsorption of NOM due to site competition and pore blockage. The adversary impact was found to be greatly dependent upon the initial presence levels of NPEO and NOM as well as the NOM sources.
  • FS Li, A Yuasa, Y Matsui, EJ Cheong
    ADSORPTION-JOURNAL OF THE INTERNATIONAL ADSORPTION SOCIETY 11 691 - 696 2005年 [査読無し][通常論文]
     
    Batch adsorption isotherms of fourteen dissolved organic matrices (DOMs) from river water, ground water, wastewater and commercial sources were measured using lumped quality indices of DOC and UV260, and analyzed using a distributed fictive component method. By accounting for the heterogeneity of DOM constituents with a log-normal distribution of Freundlich K, the adsorption equilibrium of each DOM was characterized by searching for only three parameters. Indicating strong adsorbability dependency upon the sources and types of DOMs, the distribution ranges of the Freundlich K differed markedly. Compared to a river water DOM that had a K range in 10.8-190 (mg/g)/(mg/l)(1/n), a commercial humic acid was found most heterogeneous: K varied in 0.01-1494.3 (mg/g)/(mg/l)(1/n). In addition, based upon chromatographic results measured using a HPSEC system for all DOMs before and after adsorption, preferential adsorption of small molecular weight constituents was revealed for commercial humic acids; for aquatic organic matrices, however, such a trend was not found.
  • Y Matsui, T Inoue, T Matsushita, T Yamada, M Yamamoto, Y Sumigama
    WATER SCIENCE AND TECHNOLOGY 51 3-4 329 - 337 2005年 [査読無し][通常論文]
     
    In the prediction of time-series concentrations of herbicides in river water with diffuse-pollution hydrological models, farming schedules (the dates of herbicide application and drainage of irrigation water from rice paddies) greatly affect the runoff behavior of the herbicides. For large catchments, obtaining precise data on farming schedules is impractical, and so the model input inevitably includes substantial uncertainty. This paper evaluates the effectiveness of using the Monte-Carlo method to generate sets of estimated farming schedules to use as input to a GIS-based basin-scale runoff model to predict the concentrations of paddy-farming herbicides in river water. The effects of using the Monte-Carlo method to compensate for uncertainty in the evaluated parameters for herbicide decomposition and sorption were also evaluated.
  • Y Matsui, R Murase, T Sanogawa, H Aoki, S Mima, T Inoue, T Matsushita
    WATER SCIENCE AND TECHNOLOGY 51 6-7 249 - 256 2005年 [査読無し][通常論文]
     
    Manufacturer-supplied powdered activated carbon (PAC) was ground to produce submicrometre particles (0.8 and 0.6 m median diameter) for use as an adsorbent before microfiltration (MF) for drinking 0 water treatment. Batch tests revealed that the microground PAC adsorbed natural organic matter (NOM) much more rapidly and had a higher adsorptive capacity than ordinary PAC. The water samples pretreated with the submicrometre PAC were subjected to MF, and the results of experiments with different PAC contact times revealed that a 1 min retention time was sufficient for adsorptive removal of NOM. The use of submicrometre PAC permitted not only shorter PAC contact times but also a 75% reduction in dose.
  • T Matsushita, Y Matsui, Y Matsui, T Inoue
    JOURNAL OF ENVIRONMENTAL SCIENCE AND HEALTH PART B-PESTICIDES FOOD CONTAMINANTS AND AGRICULTURAL WASTES 40 6 851 - 861 2005年 [査読無し][通常論文]
     
    The mutagenicity of chlornitrofen (CNP)-containing solutions has been reported to increase during anaerobic biodegradation. In the present study, the fate of this increased mutagenicity under subsequent aerobic and anaerobic incubation conditions was investigated using two Salmonella tester strains, YG1024 (a frameshift-detecting strain) and YG1029 (a base-pair-substitution-detecting strain). Mutagenicity for both YG1024 and YG1029 strains increased during nine-day anaerobic biodegradation. During subsequent anaerobic incubation, the increased mutagenicity decreased gradually for YG1029 but did not change significantly for YG1024. By contrast, the increased mutagenicity decreased rapidly after the conversion to aerobic incubation for both YG1024 and YG1029 strains. The rapid decrease in mutagenicity during aerobic incubation was due to decreases, not only in an identified mutagenic metabolite (CNP-amino) but also in unidentified mutagenic metabolites.
  • Ceramic MF with Submicron-sized Activated Carbon Adsorption and Coagulation Pretreatments for Rapid and Effective NOM Removal
    Yoshihiko Matsui, Yoshitaka Fukuda, Ryota Murase, Nobuhiro Aoki, Satoru Mima, Takanobu Inoue, Taku Matsushita
    Water Intelligence Online 5 23 - 32 2005年 [査読無し][通常論文]
  • T Inoue, Y Matsui, Y Terada, K Baba, T Matsushita
    WATER SCIENCE AND TECHNOLOGY 50 12 71 - 78 2004年 [査読無し][通常論文]
     
    The elemental composition and particle size distribution of suspended particles in raw water, treated water, and distributed water were determined to understand the behavior of particles during the water treatment-distribution process. The weight of suspended particles collected on a 0.6-mum filter was 1.1 times (raw water), 1.4 times (treated water), and 1.5 times (distributed water) that collected on a 2.7-mum filter, suggesting that smaller particles may remain after conventional water treatment. Organic suspended particles were removed less efficiently than inorganic suspended particles. After sand filtration, the Al content in the fixed suspended solids (FSS) markedly increased, indicating that either a small percentage of aluminium floc passed through during sand filtration or dissolved aluminum precipitated after sand filtration. The Mn and Fe concentrations increased after chlorination. The percentages of carbon and nitrogen in the volatile suspended solids (VSS) were roughly the same in the raw, treated, and distributed waters. The carbon/nitrogen/phosphate/VSS ratios indicated that the VSS of the suspended particles consisted of organic, matter originating from microorganisms. The major constituents of the FSS in the treated and distributed waters were compounds of Fe, Al, Ca, Mg, and Mn, but these compounds accounted for only 16% or less of the FSS in raw water, indicating the existence of Si compounds. In distribution pipes, the total suspended solids concentration, especially the FSS concentration, was higher than that of water just after treatment. The Fe concentration in distributed water increased, probably due to oxidation and rusting of iron pipes.
  • T Matsushita, Y Matsui, T Inoue
    WATER SCIENCE AND TECHNOLOGY 50 12 201 - 206 2004年 [査読無し][通常論文]
     
    The infectivity of viruses (Qbeta, MS2, T4, and P1) after dosing virus-contaminated water with 4 types of aluminium coagulant was investigated. The concentrations of infectious viruses were determined after dissolving aluminium hydroxide flocs in alkaline solution. The concentration of infectious viruses did not recover to the initial value after a short floc-dissolution time (5 s). Although the infectious virus concentration increased as the floc-dissolution time was extended to 5 h, it did not recover fully. Irreversible adhesion between virus particles and aluminium coagulant is responsible for the insufficient recovery. We interpret this phenomenon as a virucidal activity of the aluminium coagulant. All tested aluminium coagulants (PACI, alum, and reagent grade aluminium chloride and aluminium sulfate) inactivated all types of viruses tested. PACI had the highest virucidal activity. The virucidal activity of aluminium coagulants was lower in river water, presumably owing to the presence of natural organic matter.
  • Y Matsui, R Murase, T Sanogawa, N Aoki, S Mima, T Inoue, T Matsushita
    NATURAL ORGANIC MATERIAL RESEARCH: INNOVATIONS AND APPLICATIONS FOR DRINKING WATER 4 4 155 - 163 2004年 [査読無し][通常論文]
     
    For the purpose of enhancing the adsorption of natural organic matter (NOM) from water sources, commercially available powdered activated carbon (PAC) was further ground to produce PAC of micrometre-sized particles, and the effects of PAC size on adsorption of NOM were investigated. The micrometre-sized PAC (median particle diameter, 0.8 and 3.8 mum) removed NOM much better than did as-received PAC (33 mum). Only one-tenth the dose of micrometre-sized PAC had the same effect as a full dose of the as-received PAC. The micro-grinding of PAC to micrometre sizes was effective at increasing its adsorption kinetics: adsorption of NOM to the micrometre-sized PAC reached 80% of equilibrium within only 1 min of contact time. The micro-grinding of PAC was also effective at increasing its adsorption capacity for NOM and polystyrene sulfonate-MW1800, but not for the small molecule phenol. This appeared to be due to an increase in mesopore surface area probably by fracture of ink-bottle pore structures during the micro-grinding. The micro-grinding enhanced the adsorption affinity of PAC for NOM that was strongly UV260-absorbent but not for NOM with low UV260 absorbance.
  • Y Matsui, Y Fukuda, T Inoue, T Matsushita, N Aoki, S Mima
    4TH WORLD WATER CONGRESS: INNOVATION IN DRINKING WATER TREATMENT 4 5-6 189 - 197 2004年 [査読無し][通常論文]
     
    The effects of particle size and mixing method of adsorbent during pretreatment in a microfiltration system were investigated. Micrometre-size powdered activated carbons (PACs) obtained by pulverization of an as-received PAC removed natural organic matter (NOM) from water much more efficiently than the as-received PAC, without additional membrane fouling and trans-membrane pressure buildup. The dosage of micrometre-size PAC required for pretreatment was one-sixth the equipollent dosage of the as-received PAC. The coagulant - PAC dosing sequence did not affect the extent of NOM removal, suggesting that the reduction of PAC-pore-blocking macromolecules by coagulation before PAC adsorption was not a key factor in improving the final extent of NOM removal. The mechanism of the enhanced adsorption by micrometre-size PAC seems to involve increases in the adsorption capacity itself, as well as increases in adsorption kinetics.
  • M. Fujisawa, T. Matsushita, Y. Matsui, K. Akasaka, T. Kimura
    Journal of Thermal Analysis and Calorimetry 77 1 225 - 231 2004年 [査読有り][通常論文]
     
    The heat capacities of binary aqueous solutions of 1,2-ethanediol, 1,2-propanediol and 1,2-butanediol were measured at temperatures ranging from 283.15 to 338.15 K by differential scanning calorimetry. The partial molar heat capacities at the infinite dilution were then calculated for the respective alkanediols. For 1,2-ethanediol or 1,2-propanediol, the partial molar heat capacities at the infinite dilution of increased with increasing temperature. In contrast, the partial molar heat capacities of 1,2-butanediol at the infinite dilution decreased with increasing temperature. Heat capacity changes by dissolution of the alkanediols were also determined. Heat capacity changes caused by the dissolution of 1,2-ethanediol or 1,2-propanediol were increase with increasing temperature. On the other hand, heat capacity changes caused by the dissolution of 1,2-butanediol are decrease with increasing temperature. Thus our results indicated that the structural changes of water caused by the dissolution of 1,2-butanediol differed from that of the two other alkanediols.
  • Y Matsui, Y Fukuda, T Inoue, T Matsushita
    WATER RESEARCH 37 18 4413 - 4424 2003年11月 [査読無し][通常論文]
     
    Batch adsorption experiments using powdered activated carbon (PAC) to remove trace synthetic organic chemicals (SOCs) from water containing natural organic matter (NOM) were conducted. The percentage of SOC removed at any contact time and at any PAC dose was observed to be independent of the initial SOC concentration. Equations derived from the ideal adsorbed solution theory and the pore surface diffusion model validated this observation. For the strongly adsorbing SOCs (simazine and simetryn), the percentage of SOC removed was independent only at low initial SOC concentrations. The NOM fraction competing with the weakly adsorbing SOC (asulam) constituted a larger percentage of the total NOM than that competing with the strongly adsorbing SOCs. Although the adsorptive capacities of the SOCs were greatly reduced in water containing NOM compared with those in pure water, the change in the pore diffusion coefficient was insignificant. Therefore, NOM competed with the SOCs for adsorption sites, reducing the adsorptive capacity, but the amount of NOM loading was not so severe that it blocked or filled the pores, hindering the internal diffusion of the SOCs. (C) 2003 Elsevier Ltd. All rights reserved.
  • Y Matsui, T Matsushita, S Sakuma, T Gojo, T Mamiya, H Suzuoki, T Inoue
    ENVIRONMENTAL SCIENCE & TECHNOLOGY 37 22 5175 - 5180 2003年11月 [査読無し][通常論文]
     
    Inorganic aluminum salts, such as aluminum sulfate, are coagulants that cause small particles, such as bacteria and viruses as well as inorganic particles, to destabilize and combine into larger aggregates. In this investigation, batch coagulation treatments of water samples spiked with Qbeta, MS2, T4, and P1 viruses were conducted with four different aluminum coagulants. The total infectious virus concentration in the suspension of floc particles that eventually formed by dosing with coagulant was measured after the floc particles were dissolved by raising the pH with an alkaline beef extract solution. The virus concentrations were extremely reduced after the water samples were dosed with aluminum coagulants. Viruses mixed with and adsorbed onto preformed aluminum hydroxide floc were, however, completely recovered after the floc dissolution. These results indicated that the aluminum coagulation process inactivates viruses. Virucidal activity was most prominent with the prehydrolyzed aluminum salt coagulant, polyaluminum chloride (PACI). Virucidal activity was lower in river water than in ultrapure water-natural organic matter in the river water depressed the virucidal activity. Mechanisms and kinetics of the virus inactivation were discussed. Our results suggest that intermediate polymers formed during hydrolysis of the aluminum coagulants sorbed strongly to viruses, either rendering them inactive or preventing infectivity.
  • FS Li, A Yuasa, H Chiharada, Y Matsui
    WATER RESEARCH 37 16 4027 - 4037 2003年09月 [査読無し][通常論文]
     
    The impacts of a heavy storm of rain on the composition of natural organic matter (NOM) in Nagara River water were studied in terms of molecular weights (MWs) and activated carbon (AC) adsorbabilities using six water samples collected during a critical Typhoon weather condition. The composition in MWs was analyzed using a HPSEC system and that in adsorbabilities was characterized using parameters devised to reflect NOMs average adsorptive strength (K-M), adsorptive strength polydispersity (a), affinity to AC (1/n) and non-adsorbable fraction (C-non/C-T0), respectively. These parameters were determined by model description of observed isotherms with a distributed fictive component method. The heavy storm of rain brought higher content of larger organic components into the river source, thus causing changes of NOMs weight-averaged MWs in the range of 2962-3495 Dalton and MW polydispersity in the narrow range of 1.153-1.226. Comparison of K-M and sigma values for all samples assessed with both indices of TOC and UV260 showed that large proportions of the storm-induced organic components had adsorptive strengths similar to those existent before the storm, with the presence levels for components revealing much strong and weak adsorbabilities being low. Among all organic components brought into the river by the storm of rain, the percentages of non-adsorbable ones was lower (smaller C-non/C-T0 values); and the adsorbable ones had generally more affinity to the adsorbents used (smaller 1/n values). (C) 2003 Elsevier Ltd. All rights reserved.
  • FS Li, A Yuasa, H Chiharada, Y Matsui
    JOURNAL OF COLLOID AND INTERFACE SCIENCE 265 2 265 - 275 2003年09月 [査読無し][通常論文]
     
    The polydisperse composition of nine dissolved organic materials (DOMs) from two river water sources, one ground water source, two biologically treated wastewater sources, and two commercial sources was analyzed based on their adsorbabilities by activated carbon. For each DOM, batch adsorption isotherms measured for both TOC and UV260 were analyzed using an overall isotherm model derived from the IAST-Freundlich expression. By accounting for the heterogeneity of each DOM with a log-normal distribution of the Freundlich parameter (K), its adsorption behavior was characterized with only four parameters (including three fitting ones). The average adsorptive strength (Km) and heterogeneity (a) determined for all DOMs, which were defined by the mean value and the standard deviation of the log-normal distribution of the Freundlich K, changed over the ranges 2.5-62.2 and 0.22-0.97 (mg/g)/(mg/l)(l/n), respectively, when the TOC index was used. Among all DOMs studied, a river water DOM at the upper stream was found least heterogeneous: the Freundlich K of its organic constituents varied in the range 10.8-190 (mg/g)/(mg/l)(l/n), as compared to a commercial humic acid that exhibited the broadest Freundlich K distribution of 0.01-1494.3 (mg/g)/(mg/l)(l/n). K-M and sigma along with other two parameters (the Freundlich exponent l/n and the nonadsorbable organic fraction parameter C-non/C-T0), changed with both indices of TOC and UV260 in a regular manner, indicating that UV-absorbing organic molecules possessed adsorbabilities different from non-UV-absorbing ones. Also based on HPSEC chromatograms measured for solutions before adsorption, the molecular weight composition of all DOMs was also assessed and the molecular size impacts on adsorption characteristics of DOMs were briefly discussed. (C) 2003 Elsevier Inc. All rights reserved.
  • Y Matsui, T Matsushita, T Inoue, M Yamamoto, Y Hayashi, H Yonekawa, Y Tsutsumi
    MEMBRANES IN DRINKING AND INDUSTRIAL WATER PRODUCTION III 3 5 93 - 99 2003年 [査読無し][通常論文]
     
    The performance and mechanism of virus removal by microfiltration with coagulation pretreatment were investigated. We confirmed the unexpectedly high performance of virus removal for two types of ceramic membrane system: a positive pressure-driven dead-end filtration with inside-out configuration and a vacuum pressure-driven dead-end immersed filtration with outside-in configuration. Virus removals by both systems were more than 7 logs, although the size of the tested Obeta virus (23 nm) was much smaller than the membrane nominal pore size of 100 nm. The virus inactivation by the addition of the coagulant (PACl) and the virus adsorption onto the floc retained on the membrane surface mainly contributed the virus removal. No virus accumulation in the retentate was observed, possibly due to the virus inactivation by the coagulant.
  • T Matsushita, Y Matsui, K Ikeba, T Inoue
    CHEMOSPHERE 50 3 275 - 282 2003年01月 [査読無し][通常論文]
     
    The contribution of fenitrothion and its microbial metabolites to the mutagenicity of a fenitrothion-containing solution was investigated during anaerobic biodegradation. Although a mixed culture of bacteria obtained from a paddy field degraded fenitrothion and reduced its concentration from 4.6 to 0. 1 mg/l in 6 days, the indirect mutagenicity of the solution in Salmonella strain YG1029 increased. This increase was found to be partially due to amino-fenitrothion generated during the biodegradation. In addition, other unidentified metabolites contributed to the mutagenicity. In contrast, the indirect mutagenicity in strain YG1042, which was initially large because of fenitrothion, then decreased, and increased again. This increase in mutagenicity was also due to amino-fenitrothion and other unidentified metabolites. The mutagenicity in strains YG1029 and YG1042 decreased after day 6. The greatest contribution of amino-fenitrothion to the mutagenicity was calculated to be 73% and 61% in YG1029 and YG1042 on day 3 of incubation, respectively. That of unidentified metabolites was calculated at 49% and 61% on day 20, respectively. Therefore, because not all the toxic metabolites of a compound can be identified, it is important to evaluate the toxicity of a whole solution in a bioassay such as the Ames assay rather than deducing the toxicity of the solution from the combined toxicities of known metabolites. (C) 2002 Elsevier Science Ltd. All rights reserved.
  • FS Li, A Yuasa, K Ebie, Y Azuma, T Hagishita, Y Matsui
    WATER RESEARCH 36 18 4592 - 4604 2002年11月 [査読無し][通常論文]
     
    Effects of aqueous phase Ca(II) concentrations and pH levels on the adsorption capacity of dissolved organic matters (DOMs) as well as the capacity dependency on the sources and types of DOMs and activated carbons (ACs) were examined. The Ca(II) effect was studied for three coal-based ACs having different pore size distributions (PSDs) and for three DOMs contained in three water samples. For each water sample, four working solutions prepared by adding different dosages of Ca(II) (0-1.5 mM) were used. For the water sample whose adsorption capacity was least affected by Ca(II), the effect of pH was subsequently examined for four water pH levels (pH = 5.5-10) and these three ACs. Isotherm data were analyzed in terms of a modified isotherm model selected from three models developed for normalizing isotherms of heterogeneous organic mixtures. The Ca(II) effect depended obviously on the DOMs used. For all three ACs, increasing Ca(II) greatly enhanced the adsorption capacity of a commercial humic acid. However, the capacity of the DOM in a naturally colored surface water source was much less affected and that of the DOM remaining after precoagulation was not affected. The DOM-Ca(II) interactions, rather than the AC-Ca(II) interactions, seemed to be the predominant mechanism that controlled the extent of the Ca(II)'s impact. Water pH greatly affected the adsorption of the surface water DOM remaining after precoagulation. This effect seemed to be attributed to pH's capability in changing ACs' charge characteristics reflected by zeta-potentials. The adsorption capacity increased as the water pH decreased and was well correlated as a function of pH and the volume of AC pores in sizes of 30-100 Angstrom. ACs having more pores in this size region generally exhibited larger adsorption capacities. (C) 2002 Elsevier Science Ltd. All rights reserved.
  • Y Matsui, DRU Knappe, R Takagi
    ENVIRONMENTAL SCIENCE & TECHNOLOGY 36 15 3426 - 3431 2002年08月 [査読無し][通常論文]
     
    The adsorptive removal of periodic spikes of the trace synthetic organic chemicals (SOCs) simazine and asulam from water containing natural organic matter (NOM) was studied in pilot-scale granular activated carbon (GAC) adsorbers over a period of nearly 3 years. The SOC removal percentage obtained at any preloading time and bed depth was independent of the liquid-phase SOC concentration, and equations derived from the ideal adsorbed solution theory and a pore surface diffusion model validated this observation. The pseudo-steady-state SOC removal rate, (partial derivativeCpartial derivativez), at each preloading time and bed depth was therefore first order with respect to the liquid-phase SOC concentration, C. Furthermore, the removal modulus, k, in the resulting SOC removal rate expression was a reflection of the solid-phase concentration of the NOM fraction that interfered with the adsorption of SOCs. Analysis of the removal modulus values indicated that the mass transfer zone of the NOM fraction competing with asulam traveled more rapidly through the GAC adsorber than that competing with simazine, Given the similar molecular sizes of the targeted SOCs, this result was primarily explained by differences in SOC adsorbabilities, where the more weakly adsorbing asulam was less capable of displacing preloaded NOM. Consequently, the NOM fraction competing with asulam constituted a larger percentage of the total NOM than that competing with simazine.
  • Y Matsui, DRU Knappe, K Iwaki, H Ohira
    ENVIRONMENTAL SCIENCE & TECHNOLOGY 36 15 3432 - 3438 2002年08月 [査読無し][通常論文]
     
    The principal objective of this study was to elucidate mechanisms by which NOM affects the adsorption of a nonpolar (simazine) and a polar (asulam) herbicide on activated carbon. Experiments were carried out in microcolumns that were continuously fed solutions containing NOM with different molecular weight (MW) distributions and intermittently solutions containing the same NOM plus simazine or asulam, The MW distributions of a groundwater NOM were altered by coagulation and ultrafiltration, which resulted in the preferential removal of high-M, UV260-absorbing NOM. At a given NOM loading, the simazine removal efficiency was higher in the column that was preloaded with raw groundwater than in columns receiving coagulated or ultrafiltered water, In contrast, the asulam removal efficiency was similar for all three NOM solutions at a given NOM loading. Therefore, the results suggested that low-MW, UV260-absorbing NOM molecules competed directly with strongly adsorbing pesticides, such as simazine, for adsorption sites, For more weakly adsorbing pesticides, such as asulam, direct competition for adsorption sites originated not only from the strongly adsorbing, low-MW NOM, but also from more weakly adsorbing, higher-MW NOM. Consequently, the competing NOM fraction increases as the adsorbability of the SOC decreases, a result that was confirmed by adsorption data for additional pesticides of similar size. However, a smaller pesticide competed more effectively for adsorption sites than a larger pesticide of similar polarity, suggesting that the concentration of competing NOM decreases as the MW of the SOC decreases.
  • Y Matsui, K Nagaya, G Funahashi, Y Goto, A Yuasa, H Yamamoto, K Ohkawa, Y Magara
    BIOFOULING 18 2 137 - 148 2002年06月 [査読無し][通常論文]
     
    Various antifouling substrata were tested for their effectiveness in inhibiting attachment of Limnoperna fortunei. Field experiments revealed that surface properties affected the antifouling capabilities of nontoxic substrata. Antifouling capabilities were observed for three silicone resin-based coatings with smooth surfaces (<30 mum roughness) and low surface free energy of the hydrogen bonding force component. A further three silicone resin-based coatings tested, as well as other types of nontoxic coatings, did not show any antifouling capabilities. The percentages of juvenile mussels that attached in laboratory experiments correlated with the settling densities of mussels in the field experiments better than those based on adult mussels. This suggests that laboratory experiments with juveniles may be effective as short term preliminary assays to select promising materials/coatings for longer term field experiments. Mussel abundance surveys within a water transmission pipe and pipe current velocity simulation revealed that less infestation was observed in the areas with a wall-vicinity fluid velocity of >1.3 m s(-1). Conversely, pipe surfaces with flows of <1.2 m s(-1) were heavily fouled by L. fortunei.
  • T Matsushita, Y Matsui, S Taniwaki, T Inoue
    CHEMOSPHERE 47 1 9 - 14 2002年04月 [査読無し][通常論文]
     
    In order to investigate changes in the mutagenicity of fenitrothion during its biodegradation in solution, measurements were conducted at intervals in batch cultures incubated under anaerobic or aerobic conditions. Fenitrothion-degrading bacteria were obtained from a green onion field on the west side of Gifu University, Japan. Fenitrothion was almost completely decomposed by day 12 under both types of incubation condition. The indirect mutagenicity of the solution to strains YG1029 and YG1042, however, increased markedly during anaerobic biodegradation. The increase in mutagenicity was partially due to amino-fenitrothion, a metabolite formed during anaerobic biodegradation of fenitrothion. (C) 2002 Elsevier Science Ltd. All rights reserved.
  • T Matsushita, Y Matsui, S Sakuma, T Inoue
    MUTATION RESEARCH-GENETIC TOXICOLOGY AND ENVIRONMENTAL MUTAGENESIS 516 1-2 71 - 79 2002年04月 [査読無し][通常論文]
     
    We used the Ames assay to investigate changes in the mutagenicity of chlornitrofen during its aerobic biodegradation. Although a mixed culture of bacteria obtained from river water degraded chlornitrofen and reduced its concentration from 39 to 6 mug/l in 21 days, the indirect mutagenicity of the solution to Salmonella strains TA98, YG1021, and YG1026 increased gradually. This finding suggests that mutagenic metabolites were produced during the aerobic biodegradation. The increase in the mutagenicity was, however, much smaller under aerobic than under anaerobic conditions. The differing sensitivities of our test strains to the functional groups on the mutagens showed that the mutagenic metabolites were indirect frameshift-type mutagens that might have neither nitro nor amino groups. (C) 2002 Elsevier Science B.V. All rights reserved.
  • Y Matsui, K Iwaki, M Uematsu, A Yuasa
    INNOVATIONS IN CONVENTIONAL AND ADVANCED WATER TREATMENT PROCESSES 2 1 147 - 154 2002年 [査読無し][通常論文]
     
    The removal of hydrophobic and hydrophilic pesticides (simazine and asulum) by granular activated carbon (GAC) adsorbers preloaded with natural organic matter (NOM) was studied through experiments using pilot scale columns and microcolumns. The pesticide concentration increased with time after the pesticide application, and it reached a pseudo-steady-state plateau. Less than 8% of the adsorbed simazine desorbed back into the column effluent by 15 days after the influent was switched to simazine-free water. The simazine desorbed from the upper part of the bed was re-adsorbed in the lower part, keeping the effluent concentration at a low level. In the pseudo-steady-state, the removal rate was described by a first order kinetic reaction for the pesticide concentration. The evaluation of removal rate modulus value revealed the profile of loaded pesticide-competitive NOM with depth. The pesticide-competitive NOMs were different for each pesticide. The percentage of the simazine-competitive NOM to the whole NOM increased after UF membrane filtration (molecular weight cutoff 1 K), but not for the asulum-competitive NOM.
  • Y Matsui, S Itoshiro, M Buma, T Matsushita, K Hosogoe, A Yuasa, S Shinoda, T Inoue
    WATER SCIENCE AND TECHNOLOGY 45 9 141 - 148 2002年 [査読無し][通常論文]
     
    Hydrological diffuse pollution models require calibration before they can be used to make accurate long-term predictions for a range of hydrological and meteorological conditions. As such, the applicability of the models to the dispersion of new pesticides is limited due to the lack of calibration data. In this study, the performance of a GIS-based basin-scale runoff model for predicting the concentrations of paddy-farming pesticides in river water was examined when calibrated using hydrological data alone, without optimization based on empirical pesticide concentration data. The prediction accuracy on a daily or hourly scale was somewhat unsatisfactory due to inevitable compromises concerning rice farming schedules. However, the month-averaged pesticide concentrations were satisfactorily accurate; more than 50% of predicted values were between half and twice the observed values, considering the deficiencies of the input data, particularly for pesticide usage, which may include up to 50% error.
  • T Inoue, S Ebise, A Numabe, O Nagafuchi, Y Matsui
    WATER SCIENCE AND TECHNOLOGY 45 9 121 - 126 2002年 [査読無し][通常論文]
     
    Runoff characteristics of particulate pesticides from paddy fields have been intensively observed in the Koise River in Japan. The 8 pesticides that are applied to paddy fields were analyzed in both particulate and dissolved forms. The concentrations and the detection frequencies of particulate pesticides were lower than those of dissolved pesticides. The particulate pesticide concentrations in the river water were evaluated based on the soil sorption coefficient, particulate organic carbon concentration, and dissolved pesticide concentrations. The particulate pesticide concentrations in the river were higher than evaluated concentrations because the paddy soil contained more pesticides than did suspended solids in the river water discharged during rain events, and because the desorption rates of pesticides were slow. In observations made during rains, the particulate pesticide concentrations increased with the increases in both the discharge rate and the concentrations of suspended solids. The particulate loading was slight compared with dissolved loading, but particulate pesticides may be influenced by enclosed areas such as a lake or estuary because under such conditions particulate matter settles vertically and the pesticide decomposition rate in sediment is slow compared with that in water.
  • Adsorption Isotherm of Nonionic Surfactants onto Activated Carbon: Alkylphenol Polyethoxylates and Alcohol Polyethoxylates
    Akira Yuasa, Fushehg Li, Yoshihiko Matsui
    Fundamentals of Adsorption 7 193 - 200 2002年 [査読無し][通常論文]
  • Removal of Nonionic Surfactants in Activated Carbon Bed: Parameter Estimation and Breakthrough Prediction
    Fushehg Li, Akira Yuasa, Yoshihiko Matsui
    Fundamentals of Adsorption 7 162 - 169 2002年 [査読無し][通常論文]
  • T Matsushita, S Sakuma, K Nakamuro, Y Matsui
    WATER RESEARCH 35 11 2589 - 2594 2001年08月 [査読無し][通常論文]
     
    The mutagenicity of water, including herbicide CNP, and its time-variation during anaerobic biodegradation were studied through Ames assay using strains with or without. S9 mix: TA98 TA100. YG1021. YG1024, YG1026, and YG1029. The bacteria, for the anaerobic biodegradation, was obtained from a paddy field, and preincubated for a month. The CNP was decomposed in an anaerobic culture inoculated with the bacteria, and finally yielded CNP-amino as one of the CNP metabolites. About 16% of the initial CNP was transformed into CNP-amino bq the 14th day. The mutagenicities to TA98. YG1024. and YG1029 strains with S9 mix increased with cultivating time, the latter two showed the strongest sensitivity to CNP-amino. The contribution of CNP to the mutagenicity decreased as the chemical decomposed, while the contribution of CNP-amino increased. However, the increased mutagenicity was not limited to the contribution of CNP-amino, but also to the contribution of other metabolites. The contributions of other CNP metabolites were 67% of total mutagenicity to the TA98 strain and 30% to the YG1029 strain. These unknown mutagenic metabolites were the indirect frameshift mutagens which did not have nitro- and amino-substituents, and the indirect base-pair mutagens which might possibly have some amino-substituents. (C) 2001 Elsevier Science Ltd All rights reserved.
  • 湯浅 晶, 松井 佳彦, 篠田 成郎, 井上 隆信, 松下 拓
    環境技術 = Environmental conservation engineering 30 6 460 - 465 環境技術学会 2001年06月20日
  • Y Magara, Y Matsui, Y Goto, A Yuasa
    JOURNAL OF WATER SUPPLY RESEARCH AND TECHNOLOGY-AQUA 50 3 113 - 124 2001年06月 [査読無し][通常論文]
     
    The aquatic nuisance mussel, Limnoperna fortunei, arrived in Japan before 1987 possibly with the Asian clam imported as food from mainland China. Now the mussel's distribution has spread to two river systems in central Japan. Water authorities reported several cases of damage caused by L. fortunei. Most cases of damage were caused by dead mussels clogging small diameter pipes for raw water sampling and monitoring and for cooling water. Clogging of cooling water pipes stopped raw water pumping to a water purification plant and caused the shutdown of a turbine dynamo-electric generator in a hydraulic power plant. The attachment of L. fortunei caused the malfunction of a water level gauge. There was a heavy accumulation of dead L. fortunei in slurry treatment facilities and rotten mussels developed an offensive odour. Although the screens and pipes of the raw water intake and transmission were inhabited by L. fortunei, problems relating to their decreased hydraulic capacity were not reported. This may have been due to the low reproduction rate and short lifespan of L. fortunei. There was one reproduction period each year, during May to September and their lifespan was two years at most. The growth rate could be about 15 mm yr(-1) in shell length. Although chlorine in either free or combined form is effective for the control of L. fortunei larvae, so far water supply authorities have not considered prechlorination in the intake, mainly because prechlorination deactivates the biological nitrification along the pipelines.
  • Y Matsui, A Yuasa, K Ariga
    WATER RESEARCH 35 2 455 - 463 2001年02月 [査読無し][通常論文]
     
    Based on the age distributions of powdered activated carbon (PAC) in reactors, the competitive bi-solute isotherm and the pore-surface diffusion mechanism, a model was developed to predict the removal of a trace synthetic organic chemical (SOC) when PAC was applied to an ultrafiltration (UF) membrane system. Independent experiments evaluated the input parameters for the model. The pore diffusion in liquid-filled pore was the dominant internal mass transfer mechanism in a PAC particle and the surface diffusion mechanism was neglected in the model. Model prediction was compared with data from pilot plant experiments treating simazine in natural water. Due to the blending and the increasing PAC in the UF loop, a transient behavior of effluent simazine concentration was observed in the UF effluent. The model predicted successfully this periodical Variation of the simazine concentration in the UF loop effluent, as well as the simazine concentration in the effluent from the PAC slurry contactor. The faithful model prediction required the modeling of the phenomenon of adsorption/desorption of an SOC on membrane itself. (C) 2000 Elsevier Science Ltd. All rights reserved.
  • Y Matsui, F Colas, A Yuasa
    WATER RESEARCH 35 2 464 - 470 2001年02月 [査読無し][通常論文]
     
    This paper describes several application potentials with a recently developed model for predicting the synthetic organic chemical (SOC) removal by powdered activated carbon (PAC) adsorption during ultrafiltration (UF) and discusses the removal mechanism. The model was successfully applied, without any modification, to dead-end mode operation as well as to cross-Row mode operation, validating the assumption of the internal diffusion control mechanism and the continuously-stirred-tank-reactor (CSTR) concept. Even when UF was operated in a cross-how mode, PAC added was re-circulating in suspension for only a short time. Then, solute uptake look place mostly by PAC immobilized in membrane tubes not only for dead-end operation but also for cross-flow operation. Therefore, cross-flow operation did not have any advantage regarding the SOC mass transfer on PAC in UF loop over dead-end operation. The model simulation implied that pulse PAC addition at the beginning of filtration cycle resulted better SOC removal than continuous PAC addition. However, for the pulse PAC addition mode, the model predicted somewhat lower effluent SOC concentration than the observed values, and the benefit of pulse PAC application in terms of reducing SOC over its continuous dosage was not confirmed. Longer detention time of PAC dosed in a pulse than continuously dosed PAC could possibly further decrease internal diffusivity. (C) 2000 Elsevier Science Ltd. All rights reserved
  • 李富生, 湯浅晶, 松井佳彦
    土木学会論文集 678 678 37 - 48 土木学会 2001年 [査読無し][通常論文]
  • Y Matsui, A Yuasa, F Colas
    MEMBRANES IN DRINKING AND INDUSTRIAL WATER PRODUCTION II 1 5-6 39 - 47 2001年 [査読無し][通常論文]
     
    The effects of operational modes on the removal of a synthetic organic chemical (SOC) in natural water by powdered activated carbon (PAC) during ultrafiltration (UF) were studied, through model simulations and experiments, The removal percentage of the trace SOC was independent of its influent concentration for a given PAC dose. The minimum PAC dosage required to achieve a desired effluent concentration could quickly be optimized from the C/C(0) plot as a function of the PAC dosage. The cross-flow operation was not advantageous over the dead-end regarding the SOC removal. Added PAC was recirculated as a suspension in the UF loop for only a short time even under the cross-flow velocity of > 1.0 m/s. The cross-flow condition did not contribute much to the suspending of PAC. The pulse PAC addition at the beginning of a filtration cycle resulted in somewhat better SOC removal than the continuous PAC addition. The increased NOM loading on PAC which was dosed in a pulse and stayed longer in the UF loop could possibly further decrease the adsorption rate.
  • Y Matsui, K Nagaya, A Yuasa, H Naruto, H Yamamoto, K Ohkawa, Y Magara
    BIOFOULING 17 1 29 - 39 2001年 [査読無し][通常論文]
     
    The attachment strength of the freshwater mussel Limnoperna fortunei was studied. The force and energy required for the mussel to detach from various substrata (coatings and materials) were measured by a load test method, and the results were compared and discussed with regard to the surface properties of the substrata (surface roughness and surface free energy). The detachment force and energy were measured from 0.02 to 2.56 N, and from 0.02 to 14.3 mJ, respectively, depending on the type of coating and material used. The mussel attached strongly to polar surfaces, such as glass, and attached weakly to non-polar surfaces, such as silicone. There was a fairly good correlation between the detachment force and the detachment energy, and the detachment force and energy correlated well with the number of secreted threads. The unit detachment energy (the detachment energy divided by the number of secreted threads) was low when the mussel detached through adhesive failure of byssal pads, whereas it was high when the mussel detached through breakage of byssal threads. Byssal pads attached to a substratum with a low hydrogen bonding component of the surface free energy (SITE) were mostly detached by adhesive failure at the pad-substratum interface. The byssal pad adhered firmly to a surface with high hydrogen bonding SFE, and the mussel detached through thread breakage. The energy required to detach one byssal pad increased in proportion to hydrogen bonding SFE, and reached a level equal to the energy required for breaking a byssal thread at a hydrogen bonding SFE of more than 10 mJ m(-2). For a substratum at this level of hydrogen bonding SFE, mussel detachment occurred with 80% of the threads in a byssal bundle broken and 20% detached at the pad-substratum interface. This finding indicates that low hydrogen bonding SFE at the substratum surface was a prerequisite in decreasing the detachment energy of L. fortunei.
  • K Nagaya, Y Matsui, H Ohira, A Yuasa, H Yamamoto, K Ohkawa, Y Magara
    BIOFOULING 17 4 263 - 274 2001年 [査読無し][通常論文]
     
    The attachment strength of the freshwater mussel Lininoperna fortunei against water flow was studied. Newton's expression successfully described the hydrodynamic drag force acting on the mussel with a drag coefficient value of 1.03. The drag-resistant force (defined as hydrodynamic drag force at mussel detachment) was smaller than the detachment force measured using a tensile load test. A fairly good correlation was obtained between the drag-resistant force and the number of secreted threads. The drag-resistant force divided by the number of threads increased with shell size, suggesting that byssal thread strength increased with mussel growth. For the mussel specimens obtained from a water transmission pipe, thread width increased with shell size. However, thread width was not dependent on current velocity. There was no correlation between the number of secreted threads and shell length, which indicated that the number of secreted threads did not change with mussel size. Therefore, the water velocity needed to detach mussels increases with shell size of the mussel when the number of secreted threads is constant. The increases in the water velocity to detach mussels with larger shells suggests that the mussel becomes more resistant to water flow as it grows. It is estimated that a flow velocity of around l m s(-1) is critical for attachment/detachment of a juvenile mussel with a shell length of a few millimeters and one hundred byssal threads.
  • 水のpHが凝集後に残留するフミン質の活性炭吸着に特性に及ぼす影響
    李富生, 海老江邦雄, 東義洋, 湯浅晶, 萩下隆, 松井佳彦
    水道協会雑誌 69 11 9 - 19 2000年 [査読無し][通常論文]
  • Y Matsui, Y Goto
    FLAT-PANEL DISPLAYS AND SENSORS: PRINCIPLES, MATERIALS AND PROCESSES 558 393 - 398 2000年 [査読有り][通常論文]
     
    Tin Oxide transparent conductive oxide(TCO) films of less than 20nm in thickness was developed as a substrate for pen touch screens. The films were deposited using APCVD method by hydrolytic decomposition of stannic chloride. Electrical properties and stability to heat treatment were studied in relation to deposition conditions. We found the both properties depends mainly on fluorine concentration in the films. The stability was much improved at reduced fluorine concentration. The film which showed the stability to heat treatment at 600 degrees C heat treatment was attained at the thickness of 20nm.
  • K Ohkawa, A Nishida, R Honma, Y Matsui, K Nagaya, A Yuasa, H Yamamoto
    BIOFOULING 13 4 337 - 350 1999年 [査読無し][通常論文]
     
    Attachment of the freshwater mussel, Limnoperna fortunei, was tested using non-treated surfaces, viz. glass, nylon, rubber, silicone and Teflon, together with glass surfaces modified with nine kinds of silane coupling agents. Among the surfaces tested, the mussel avoided attaching to Teflon, silicone, and glass modified with 3-bromopropyltrimethoxysilane or 3,3,3-(trifluoropropyl)-trimethoxysilane. With respect to the relationship between the percentage attachment and the surface free energy (sfe) of the substrates, it was found that attachment was considerably reduced on the substrates which exhibited relatively low sfe, as above. The mean number of secreted byssuses per attaching mussel also decreased with decreasing substrate sfe. Furthermore, when the sfe was divided into the dispersion and polar components, the percentage mussel attachment was related to the polar component. These results suggest that effective antifouling towards L. fortunei is achieved on substrates with a low sfe polar component.
  • Y Matsui, A Yuasa, FS Li
    WATER SCIENCE AND TECHNOLOGY 40 9 223 - 230 1999年 [査読無し][通常論文]
     
    Diluted solutions of a peat water and a biological wastewater effluent were subjected to coagulation, ozonation, and chlorination. The effects of these pretreatments on the removal of humic substances by activated carbon adsorption were tested. Batch adsorption isotherms were analyzed using a distributed fictive component method, which assumed a logarithmic normal distribution of Freundlich K and a non-adsorbable fraction in the Ideal Adsorption Solution Theory for multicomponent adsorption. Coagulation treatment not only increased adsorbabilities bur also decreased its heterogeneity in terms of multicomponent adsorbates. Ozonation decreased adsorbabilities and increased heterogeneity in adsorbabilities by producing weakly adsorbing compounds. The average Freundlich K decreased, while the Freundlich exponent, lin, and non-adsorbable fraction was increased with ozone consumption. Chlorination showed the same effects as ozonation, However, after ozonation, equilibrium capacity at low activated carbon doses was increased because of the reduced dissolved organic carbon concentration by ozonation, (C) 1999 Published by Elsevier Science Ltd on behalf of the IAWQ. All rights reserved.
  • K Ohkawa, A Nishida, K Ichimiya, Y Matsui, K Nagaya, A Yuasa, H Yamamoto
    BIOFOULING 14 3 181 - 188 1999年 [査読無し][通常論文]
     
    A Dopa-containing protein was purified from the foot of the Asian freshwater mussel, Limnoperna fortunei, through acid-urea extraction, 36% ammonium sulfate precipitation, Sephacryl S-200 gel filtration, and reversed phase high performance liquid chromatography. The apparent molecular mass of the protein was 96 kDa, and Achromobacter protease I digested this into six major fragments. The amino acid sequences of the fragments were determined as two hexapeptides and four decapeptides. The consensus sequence of the decapeptides was Lys-(Hyp/Pro)-Thr-(Gln/Tyr)-Dopa-(Ser/Thr)-(Asp/Thr)-Glu-Tyr-Lys. These results suggest that the Dopa-containing foot protein mostly consists of repetitive decapeptides and hexapeptides. The Dopa-containing 96 kDa protein is considered to be a byssal precursor in L. fortunei.
  • Y Matsui, A Yuasa, FS Li
    JOURNAL OF ENVIRONMENTAL ENGINEERING-ASCE 124 11 1099 - 1107 1998年11月 [査読無し][通常論文]
     
    Adsorption equilibrium data in lumped water quality indices obtained for diluted solutions of a peat water and effluents from a wastewater treatment were analyzed using the ideal adsorbed solution theory with the Freundlich equation. The use of the same value for Freundlich exponent 1/n in the ideal adsorbed solution theory resulted in a straightforward and less computationally demanding expression to describe an overall batch adsorption isotherm, A fictive component approach, assuming a logarithmic normal distribution of Freundlich K and a nonadsorbable fraction, adequately described and predicted the overall isotherms for different initial concentrations of diluted solutions presented as a lumped water quality index. The parameters in the distributed fictive component approach were independently sensitive to each portion of an isotherm curvature. Preferential adsorption of the smaller molecular weight (MW) components was observed by a size-exclusion high-performance liquid chromatography. Two-dimensional distribution analysis of organics in terms of Freundlich K and MW revealed a weak tendency of the adsorptive strength to decrease with the increase of the MW.
  • Y Matsui, A Yuasa, Y Furuya, T Kamei
    JOURNAL AMERICAN WATER WORKS ASSOCIATION 90 10 96 - 106 1998年10月 [査読無し][通常論文]
     
    The coagulation kinetics of polyaluminum chloride (PACl) and alum applied to kaolin clay suspensions were compared in batch experiments. Increasing aluminium (Al) dosages reduced the time required for particles destabilization and increased the rate at which the number of primary particles decreased. PACl worked faster than alum. Photometric dispersion analysis showed that increasing Al dosages decreased the time required for floc to form. Again, this rate was faster with PACl than with alum. Increasing the Al dosage accelerated the flocculation rate because it increased collision-attachment efficiency and increased particulate volume. The rates of particle destabilized primary particles, and agglomeration varied with mixing intensity and water temperature. Although lower temperature slowed the particle destabilization rate, similar effects on the flocculation rate could be avoided by maintaining a constant G value. PACl was less sensitive to change in pH, implying that PACl performed better than alum in cold water.
  • DRU Knappe, Y Matsui, VL Snoeyink, P Roche, MJ Prados, MM Bourbigot
    ENVIRONMENTAL SCIENCE & TECHNOLOGY 32 11 1694 - 1698 1998年06月 [査読無し][通常論文]
     
    The purpose of this research was to develop a simple method for predicting the powdered activated carbon (PAC) capacity for micropollutants in natural water. The herbicide atrazine and the odor-causing compound 2-methyl-isoborneol served as target compounds. Isotherm data from experiments conducted with a constant initial adsorbate concentration and varying adsorbent doses exhibited nonlinearity in both single- and multi-solute systems. However, at any given adsorbent dose, the PAC capacity for the micropollutant in multi-solute systems was directly proportional to the initial micropollutant concentration. Using the ideal adsorbed solution theory (IAST), an equation was derived that validated the experimentally observed direct proportionality between PAC capacity and initial micropollutant concentration at a given adsorbent dose. The results of this study show that the PAC dose to remove any amount of micropollutant from natural waters can be estimated without the use of mathematical models from a single isotherm experiment conducted in the natural water of interest, provided that the initial target compound concentration is sufficiently low.
  • K Fukushi, Y Matsui, N Tambo
    JOURNAL OF WATER SERVICES RESEARCH AND TECHNOLOGY-AQUA 47 2 76 - 86 1998年04月 [査読無し][通常論文]
     
    Based on the kinetic model of dissolved air flotation processes proposed in our previous paper, an experimental verification was carried out with batch and continuous flow apparatuses. We measured the characteristic properties of air bubbles, floc particles and their agglomerates. Kinetic parameters, such as the contact time and the intensity of turbulence in a contact zone and the bubble-flee collision-attachment factor were estimated and verified by comparing experimental data with kinetic model simulations. A comparison of the experimental data from the floating velocity distribution and the removal rate in a continuous flow apparatus with the simulations calculated from these kinetic parameters showed a good fit. These results supported the proposed kinetic model.
  • Y Matsui, K Fukushi, N Tambo
    JOURNAL OF WATER SERVICES RESEARCH AND TECHNOLOGY-AQUA 47 1 9 - 20 1998年02月 [査読無し][通常論文]
     
    This paper presents the mathematical formulation of a model for bubble-flee agglomeration in the contact zone of dissolved air flotation (DAF). It also contains rising velocity formulae for a bubble-hoc agglomerate in the separation zone of DAF. The bubble-flee agglomeration model is based on the population balance of air bubbles, particles, and bubble-particle agglomerates, and the rate of bubble-flee collision and attachment. The model has been designed for two cases: where particles are larger than bubbles and vice versa. The requirements of pre-treatment (coagulation and flocculation) and the amount of air as bubbles are discussed, with the support of a model simulation. The air supply-consumption ratio (A(sc)) is derived as an important static parameter determining DAF performance, and should be greater than 1. The traditional DAF parameter, the air-solid ratio (A(s)), is proportional to the air supply-consumption ratio. The DAF model parameter evaluation suggested that it should be on the order of 0.01 or more. To ensure a sufficient bubble-flee collision rate, the DAF model simulation revealed, the kinetic parameter (bubble volume concentration times flee diameter, phi(b)d) Should be greater than 6.0 x 10(-8)m. The performance of DAF in treating a high concentration suspension (>100 mg/L) is dependent mainly on the air-solid ratio (or the air supply-consumption ratio). For low concentration suspensions (much less than 100 mg/L), phi(b)d instead of the air-solid ratio is a dominant operational parameter in ensuring an acceptable bubble-flee collision frequency. The bubble volume concentration required for treating a low concentration suspension can be reduced with the increase of flee size by pre-flocculation.
  • Evaluation of the Composition of the Aqueous Background Organics by the IAST-Freundlich Model and the Molecular Weight Distribution
    Akira Yuasa, Fushehg Li, Yoshihiko Matsui
    Fundamentals of Adsorption 6 407 - 412 1998年 [査読無し][通常論文]
  • Describing the Breakthrough Curves of the Total Organic Mixture and its Molecular Weight Fractions by PFPSDML and IAST-Freundlich Model
    Fushehg Li, Akira Yuasa, Yoshihiko Matsui
    Fundamentals of Adsorption 6 1041 - 1046 1998年 [査読無し][通常論文]
  • N Tambo, Y Matsui, K Kurotani, M Kubota, H Akiyama, T Ohto, Y Zaitsu, H Itoh
    WATER SCIENCE AND TECHNOLOGY 36 4 135 - 142 1997年 [査読無し][通常論文]
     
    A coagulation process for water purification plants mainly uses feedforward control based on raw water quality and empirical data and requires operator's help. We developed a new flee sensor for measuring flee size in a flush mixer to be used for flee control. A control system using model predictive control was developed on the floc size data. A series of experiments was performed to confirm controllability of settled water quality by controlling flush mixer floc size. An automatic control with feedback from the coagulation process was evaluated as practical and reliable. Finally this new control method was applied for actual plant and evaluated as practical. (C) 1997 IAWQ. Published by Elsevier Science Ltd.
  • A Yuasa, FS Li, Y Matsui, K Ebie
    WATER SCIENCE AND TECHNOLOGY 36 12 231 - 238 1997年 [査読無し][通常論文]
     
    The competitive adsorption of aqueous humic substance onto activated carbon was characterized, A technique to determine its composition in terms of both the molecular weight and the adsorbability was developed, This technique required the equilibria of molecular weight fractions in the mixture and that of the hypothetical components which could account for the competitive adsorption of the total organics. The former was obtained by measuring the molecular weight distributions of the humic substance remaining in solution over various carbon dosages with size exclusion HPLC. The latter was achieved by using a method developed on the basis of ideal adsorbed solution theory (LAST) to describe the overall adsorption isotherms for background organics of known composition, Using this technique, the adsorption equilibria of all the molecular weight fractions in the mixture were quantitatively described, and the existence of a correlation between the molecular weight and the adsorptive strength was confirmed, This technique was shown to be also effective in clarifying the composition of the remaining humic substance over different carbon dosages. (C) 1997 IAWQ.
  • Adsorption Equilibria of Multicomponent Organic Mixtures of Unknown Composition
    Akira Yuasa, Fushehg Li, Yoshihiko Matsui, Kunio Ebie
    33 123 - 132 1996年 [査読無し][通常論文]
  • Y Matsui, N Tambo
    JOURNAL OF WATER SUPPLY RESEARCH AND TECHNOLOGY-AQUA 44 6 245 - 257 1995年12月 [査読無し][通常論文]
     
    This paper describes the calibration and the verification of the previously proposed filtration model (UF model) with several sets of experimental data obtained with various operating conditions using alum flocs. The model was improved by including a simplified interpore flocculation equation that deals with the growth of flocs flowing through filter pore channels, in order to compensate for differences between calculated and experimental results in a deeper bed. The improved filtration model (UF-PF model) successfully describes a breakthrough curve and a head loss buildup of the filtration process, The variations of removal efficiency and head loss during the filtration process, for various sand grain sizes, filtration velocities, and depths of filter bed, can be predicted by means of numerical simulations of the proposed filtration equations with the parameters relating to flee properties, The optimum operational design which provides a maximum filtrate production during a filter run and its search algorithms, is also discussed for uniform and dual layer fillers by using numerical simulations of the UF-PF model. The design variables considered are grain sizes, filter layer depths and flow rates,
  • Y MATSUI, N TAMBO
    JOURNAL OF WATER SUPPLY RESEARCH AND TECHNOLOGY-AQUA 44 4 166 - 179 1995年08月 [査読無し][通常論文]
     
    This paper depicts the development of a mathematical model for describing removal efficiency and head loss increase during deep-bed filtration. The model is based upon the postulation that a deep bed consists of unit filter (UF) elements in series, the number of which elements decreases with the progress of filtration due to deposition in the filter pore. The model (UF model) includes a formulation which converts mass-specific deposit into volume-specific deposit by consideration of the self-porosity variation of the deposits. The authors also evaluated all unknown parameters and functions included in the proposed model equations. Conductimetric measurements with NaCl tracer were used to evaluate the variations of pore volume and the structure of the filter bed with time. The function of attachment efficiency between suspended particles and sand grains was estimated by measuring filter coefficients in the clean filter.
  • 亀井翼, 松井佳彦, 中埜渡丈嘉, 丹保憲仁, 湯浅晶
    水道協会雑誌 64 8 26 - 33 1995年 [査読無し][通常論文]
  • 外式セラミック膜による色度成分の除去特性
    亀井翼, 松井佳彦, 中埜渡丈嘉, 丹保憲仁, 竹田浩之
    水道協会雑誌 64 7 34 - 40 1995年 [査読無し][通常論文]
  • K FUKUSHI, N TAMBO, Y MATSUI
    WATER SCIENCE AND TECHNOLOGY 31 3-4 37 - 47 1995年 [査読無し][通常論文]
     
    A kinetic model for DAF is presented. The author's kinetic model consists of the equations for describing a process of bubble-flee collision and attachment in a mixing zone, and a rise velocity of bubble-flee agglomerates in a flotation tank. The attachment process is formulated on a population balance model with bubbles and flocs as a flocculation in a turbulent flow. The rise velocity of bubble-flee agglomerates is formulated with size of flocs and composition of flocs including the flee density function and attached bubble number. The experimental verification was carried out, using a batch flotation tester and a mini-plant with synthetic clay suspension and colored water. The results successfully verify the validity of the model. From a given condition such as flee size and attached bubble number, the rate and extent of removal by DAF can be readily assessed by the model. A single-collector collision model, often discussed in some occasions, seems to be not useful to describe the DAF process.
  • K KUROTANI, M KUBOTA, Y ZAITSU, T OHTO, K INOUE, T NAKAYAMA, H ITOH, N TAMBO, Y MATSUI
    IWSA INTERNATIONAL SPECIALIZED CONFERENCE ON ADVANCED TREATMENT AND INTEGRATED WATER SYSTEM MANAGEMENT INTO THE 21ST CENTURY, SELECTED PAPERS 13 3-4 239 - 244 1995年 [査読有り][通常論文]
  • Y MATSUI, T KAMEI, E KAWASE, VL SNOEYINK, N TAMBO
    JOURNAL AMERICAN WATER WORKS ASSOCIATION 86 9 91 - 102 1994年09月 [査読無し][通常論文]
     
    The removal efficiency of intermittently applied pesticides by a granular activated carbon bed preloaded with background organic matter (BOM) was examined using the rapid small-scale column test. Preloading with BOM decreased the removal efficiency of the pesticides. The removal efficiency was a function of the amount of BOM adsorbed, but was unrelated to the influent concentration of the pesticide. A modeling approach employing the ideal adsorbed solution theory and a linear driving-force expression for intraparticle surface diffusion adequately simulated these phenomena.
  • 有機農薬のフミン質共存系における固定層活性炭吸着特性
    松井佳彦, 亀井翼, 川瀬悦郎, 古屋勇治, 丹保憲仁
    水道協会雑誌 63 3 30 - 38 1994年 [査読無し][通常論文]
  • 固定層活性炭吸着処理において間欠的に流入する農薬の除去特性
    松井佳彦, 亀井翼, 川瀬悦郎, 丹保憲仁
    水道協会雑誌 63 2 85 - 93 1994年 [査読無し][通常論文]
  • PDAと微粒子カウンタを用いた最適急速撹拌条件に関する研究
    松井佳彦, 小川和延, 丹保憲仁
    水道協会雑誌 63 4 42 - 50 1994年 [査読無し][通常論文]
  • Determining the Remaining Life of a Granular Activated Carbon (GAC) Filter for Pesticides
    Detlef R.U. Knappe, Vernon L. Snoeyink, Yoshihiko Matsui, Maria Jos, Prados, Marie-Marguerite Bourbigot
    Water Supply 14 1 - 14 1994年 [査読無し][通常論文]
  • Adsorption Capacity of Organic Pesticides on Activated Carbon Bed Adsorber
    Yoshihiko Matsui, Tasuku Kamei, Akira Yuasa, Norihito Tambo
    Water Supply 14 31 - 41 1994年 [査読無し][通常論文]
  • ペレット流動層による高濁水の高速固液分離
    丹保憲仁, 王暁昌, 松井佳彦
    水道協会雑誌 62 2 34 - 48 1993年 [査読無し][通常論文]
  • フミン質共存下における微量有害成分の活性炭吸着特性
    松井佳彦, 亀井翼, 丹保憲仁, 重田猛
    水道協会雑誌 62 1 2 - 12 1993年 [査読無し][通常論文]
  • 松井佳彦, 亀井翼, 丹保憲仁, 谷口和彦
    水環境学会誌 16 7 497 - 506 Japan Society on Water Environment 1993年 [査読無し][通常論文]
     
    The matrix solution behaviors of humic substances were studied by characterizing molecular weight distribution, hydrophilicity and others before and after batch tests of activated carbon treatment. Aquatic humic substances in peat water and pretreated peat water by alum coagulation were classified by size exclusion HPLC and Sep-Pak C-18 cartridge adsorption and extraction. The lower molecular weight and the less hydrophilic group has higher carbon adsorbability. Ideal adsorbed solution theory (IAST) using the Freundlich isotherm equation was used for the evaluation of adsorption isotherms of each classified groups of humic substances in batch adsorption experiments.
  • Kinetic Study of Fluidized Pellet Bed Process I.-Characteristics of Particle Motions
    Xiaochang C. Wang, Norihito Tambo, Yoshihiko Matsui
    Jour. Water Supply Res. & Tech.-Aqua 42 3 146 - 154 1993年 [査読無し][通常論文]
  • Y MATSUI, N TAMBO, T OHTO, Y ZAITSU
    WATER SCIENCE AND TECHNOLOGY 27 11 153 - 165 1993年 [査読無し][通常論文]
     
    A technique to evaluate the coagulation/flocculation process on fluctuating light intensity transmitted through a flowing suspension has been developed recently for online monitoring in a flocculation system. In this paper, the authors tried to expand this technique to perform direct evaluation of floc size, settling velocity, and residual color after aluminum coagulation from the fluctuating light absorption using dual wavelengths. A theoretical study was carried out to establish the data handling algorithms for the evaluation of the above mentioned values from the fluctuating light absorbance. Two specific wavelengths were selected at near infrared and ultraviolet regions in order to characterize suspended matters and soluble colored organics. The usefulness of the proposed theory was verified in a series of batch coagulation tests with a newly developed dual wavelength photometric dispersion analyzer (DPDA). With an improved high precision photometer and data processing circuits, the extent of color colloid removal can be estimated at the beginning stage of coagulation/flocculation. The algorithms for the evaluation of floc size were calibrated and verified in flocculation experiments with micro photography. Flocculation and sedimentation experiments showed that settling velocity was successfully estimated by the proposed algorithms.
  • T OHTO, Y ZAITSU, Y MATSUI, N TAMBO
    WATER SCIENCE AND TECHNOLOGY 27 11 257 - 260 1993年 [査読無し][通常論文]
     
    A new dual-wavelength photometric dispersion analyzer is described which can be applied in the monitoring of coagulation/flocculation processes.
  • 松井佳彦, 亀井翼, 丹保憲仁, 谷口和彦
    水環境学会誌 16 7 497 - 506 Japan Society on Water Environment 1993年 [査読無し][通常論文]
     
    The matrix solution behaviors of humic substances were studied by characterizing molecular weight distribution, hydrophilicity and others before and after batch tests of activated carbon treatment. Aquatic humic substances in peat water and pretreated peat water by alum coagulation were classified by size exclusion HPLC and Sep-Pak C-18 cartridge adsorption and extraction. The lower molecular weight and the less hydrophilic group has higher carbon adsorbability. Ideal adsorbed solution theory (IAST) using the Freundlich isotherm equation was used for the evaluation of adsorption isotherms of each classified groups of humic substances in batch adsorption experiments.
  • 急速撹拌時のPDA出力に基づく成長フロックの沈降速度の評価
    松井佳彦, 丹保憲仁
    水道協会雑誌 61 1 20 - 25 1992年 [査読無し][通常論文]
  • 急速過過程の破過と圧力損失の変化過程の数値シミュレーション
    松井佳彦, 丹保憲仁
    水道協会雑誌 61 7 14 - 26 1992年 [査読無し][通常論文]
  • 急速過過程の数値シミュレーションのための諸係数の算定
    松井佳彦, 丹保憲仁
    水道協会雑誌 61 3 2 - 12 1992年 [査読無し][通常論文]
  • 急速過プロセスの数式モデル
    松井佳彦, 丹保憲仁
    水道協会雑誌 61 2 17 - 27 1992年 [査読無し][通常論文]
  • 急速過の設計・操作条件に関する研究
    松井佳彦, 丹保憲仁
    水道協会雑誌 61 8 2 - 12 1992年 [査読無し][通常論文]
  • マイクロカラム法による固定層吸着過程の迅速評価
    松井佳彦, 亀井翼, 丹保憲仁, 川瀬悦郎, 谷口和彦
    水道協会雑誌 61 4 13 - 22 1992年 [査読無し][通常論文]
  • 2波長の吸光度変動を用いた凝集・フロック形成の計測
    松井佳彦, 丹保憲仁, 小川和延, 大戸時喜雄, 財津靖史
    水道協会雑誌 61 9 1 - 9 1992年 [査読無し][通常論文]
  • 松井佳彦, 丹保憲仁, 阿部和之, 大戸時喜雄, 財津靖史
    水質汚濁研究 14 8 539 - 546 Japan Society on Water Environment 1991年 [査読無し][通常論文]
     
    凝集機構の解明やモデル化に際して, 凝集の進行過程を的確に把握することが肝要である。本稿では, 凝集過程にある複数の成分を含む試料液の流れに波長の異なる光を同時に照射して, 各凝集成分に特有なもしくは支配的な吸収や散乱を生じさせる波長の透過光量を同時計測し凝集剤を含む複数成分の凝集の進行状態を経時的に解析することを試みた。2波長の吸光度の平均値, 変動成分の標準偏差, 相関係数より, 水中成分を長波長に散乱を示す懸濁性成分, 短波長にのみ吸収・散乱を示す懸濁性成分 (不溶化水酸化アルミニウム等), 短波長に吸収を示す溶解性成分 (水酸化アルミニウムコロイド等) の3成分に分けて, 各々の濃度を紫外部の吸光度として推算する方法を提案した。提案された計測理論に基づいて製作された機器を用いて, 粗懸濁質 (Sephadex粒子) がアルミニウム水酸化物によりSweep型で凝集される過程を実測例として取り上げ, 計測方式の有効性を説明した。
  • 2波長の吸光度変動を用いた有機着色成分の凝集沈澱除去の計測
    松井佳彦, 丹保憲仁, 阿部和之, 大戸時喜雄, 財津靖史
    水道協会雑誌 679 2 - 9 1991年 [査読無し][通常論文]
  • Y MATSUI, N TAMBO
    WATER SUPPLY, VOL 9, NO 1 8 71 - 78 1991年 [査読無し][通常論文]
  • 凝集制御のためのフロック径のオンライン計測(?)−係数の評価と実験的検討−
    松井佳彦, 丹保憲仁
    水道協会雑誌 666 2 - 1 1990年 [査読無し][通常論文]
  • 凝集制御のためのフロック径のオンライン計測(?)−解析法の理論的考察−
    松井佳彦, 丹保憲仁
    水道協会雑誌 664 12 - 19 1990年 [査読無し][通常論文]
  • Performance of Fluidized Pellet Bed Separator for High-Concentration Suspension Removal
    Tambo N, Matsui Y
    Jour. Water Supply Res. & Tech.-Aqua 38 1 16 - 22 1989年 [査読無し][通常論文]
  • ペレット流動層による硬水軟化の動力学的研究−準安定領域処理によるカルシウムの除去−
    丹保憲仁, 松井佳彦, 牧谷邦昭, 杉本隆仁
    水道協会雑誌 646 10 - 20 1988年 [査読無し][通常論文]
  • A Kinetic Study of Dissolved Air Flotation
    Tambo N., Matsui Y., Fukushi K.
    Proc. of World Congress III of Chemical Engineering. III 200 - 203 1986年09月 [査読有り][通常論文]
  • 塩素マンガン砂法によるマンガン除去の動力学(?)−除去過程の速度論的解析−
    松井佳彦, 丹保憲仁, 佐藤昌之, 杉沢滋
    水道協会雑誌 622 31 - 43 1986年 [査読無し][通常論文]
  • 塩素マンガン砂法によるマンガン除去の動力学(?)−マンガン砂の基礎的性質−
    松井佳彦, 丹保憲仁, 築地原康志, 藤村功
    水道協会雑誌 621 15 - 22 1986年 [査読無し][通常論文]
  • 加圧浮上法の微気泡付着過程の解析−溶解空気浮上法の基礎的研究(5)
    丹保憲仁, 福士憲一, 松井佳彦
    水道協会雑誌 610 2 - 11 1985年 [査読無し][通常論文]
  • 高容量濾過池の研究(?)−ラシヒリング床の除去機構の解析−
    丹保憲仁, 松井佳彦, 岡本裕三
    水道協会雑誌 598 16 - 23 1984年 [査読無し][通常論文]
  • Performance of High Capacity Depth Filter
    Norihiko Tambo, Yoshihiko Matsui
    Jour. of Water Supply Res. & Tech.-Aqua 33 2 96 - 101 1984年 [査読無し][通常論文]
  • Norihito Tambo, Mitsuna Kobayashi, Yoshihiko Matsui
    北海道大学工学部研究報告 118 118 119 - 128 北海道大学 = Hokkaido University 1984年 [査読無し][通常論文]

その他活動・業績

受賞

  • 2017年04月 文部科学大臣表彰 科学技術賞(開発部門)(筆頭)
     
    受賞者: 松井佳彦
  • 2014年06月 日本水環境学会 日本水環境学会学術賞
     
    受賞者: 松井佳彦
  • 2014年03月 北海道大学 北海道大学研究総長賞
     
    受賞者: 松井佳彦
  • 2004年06月 日本水環境学会 日本水環境学会論文賞
     
    受賞者: 松井佳彦

共同研究・競争的資金等の研究課題

  • 文部科学省:科学研究費補助金(基盤研究(S))
    研究期間 : 2012年 -2012年 
    代表者 : 松井 佳彦
  • 文部科学省:科学研究費補助金(基盤研究(A))
    研究期間 : 2009年 -2012年 
    代表者 : 松井 佳彦, 大野 浩一, 松下 拓
     
    セラミック膜ろ過の前処理として,市販の粉末活性炭より遥かに粒径の小さい微粉炭を用いた場合の極性物質の吸着容量の著しい増加,吸着剤内部細孔容積の増加,フロック形成の促進効果,膜ファウリング抑止機構などの吸着剤の超微粒度化効果のメカニズムの解明を目的に研究を行っている.本年度は,自然由来有機物(NOM)のモデル物質としてポリスチレンスルホン酸(PSS)を用い,吸着材内部の吸着量分布の直接観察をさらに進めた.その結果,PSSは活性炭内部に吸着せず,活性炭粒子表面付近に蓄積していることを定量的に確認した.さらに,このことをShell Adsorption Modelとして定量的に表現し,活性炭の微粉化に伴う吸着量増加を定量的に説明した.また,臭気物質2-メチルイソボルネオールとジェオスミンについても,微粉化に伴ってそれほど大きくはないが2倍程度の吸着量増加が実測され,細孔分布などを計測しこの理由についてさらに検討を進めている.さらに,自然水中では,共存するNOMの吸着のため,臭気物質の吸着除去性が低下することが知られているが,微粉炭はNOMを多く吸着するにも関わらず,臭気物質の吸着除去性は大きく低下しないことが分かってきた.また,活性炭粒度を臭気物質の除去率の定量関係を求めることができように,吸着平衡・速度実験と行い,モデル化の検討を行っている.ウイルスの活性炭吸着性には表面の荷電と...
  • 文部科学省:科学研究費補助金(挑戦的萌芽研究)
    研究期間 : 2011年 -2011年 
    代表者 : 松井 佳彦
  • 文部科学省:科学研究費補助金(基盤研究(B))
    研究期間 : 2007年 -2008年 
    代表者 : 松井 佳彦, 松下 拓, 大野 浩一
     
    市販の粉末活性炭(Powdered activated carbon, PAC)を微粉砕し粒径が1μm以下のサブミクロン粒度の微粉炭(Suoper-powdered activated carbon, S-PAC)を製造し, 臭気物質ジェオスミンや2-メチルイソボルネオール(2-MIB), 自然由来有機物質(NOM)の吸着性, セラミック膜ろ過の吸着前処理として用いた際のそれらの除去性, および微粉炭添加が膜ろ過のろ過性に及ぼす影響について検討した. その結果, サブミクロン粒度まで微小化した微粉炭は, 少添加量, 短時間で吸着が進行し, 市販粉末活性炭に比べて, NOM やジェオスミン, 2-MIB の除去性が格段に優れていることが分かった. さらにNOM の吸着除去性の向上には, 吸着容量の増加によるものであることを見出した. 特に, NOM の中でもSUVA 値が高いフミン質的なNOM において吸着量の増加が顕著に見られた. 活性炭の微粉砕の前後で活性炭内部の細孔分布・容量に変化が見られず, 吸着容量の増加は, 高分子モデル物質ポリスチレンスルホン酸(PSS)では見られ, より分子量の大きいポリエチレングリコール(PEG)では見られないことから, 吸着容量増加は吸着質の化学的な性質が関与していると推定された. ジェオスミンを対象に微粉炭に対する吸着速度をhomogene...
  • 文部科学省:科学研究費補助金(基盤研究(B))
    研究期間 : 2005年 -2006年 
    代表者 : 松井 佳彦, 松下 拓
     
    MF膜処理は,設置面積が小さく,バクテリア等の懸濁物がほぼ確実に除去できる優れた特徴を有するが,自然由来有機物(NOM)や臭気物質のような溶存性物質に対しての効果が低いという弱点も有する.そこで,溶存性物質の除去率を高めるために凝集処理や活性炭処理を前処理とした複合MF膜処理が提案されている.ところが,凝集により微粒子を膜孔径以上の大きさにするために要する時間は極めて短い反面,活性炭吸着に要する時間が長いため,MF膜処理の利点である設置面積の省スペース性と相容れない.研究では,粒径1μm以下のサブミクロンサイズまで超微粉化した活性炭により吸着速度を飛躍的に増加させ,高速度運転が可能な吸着・MF膜複合処理法を検討した.サブミクロンサイズまで超微粒度化した活性炭をMF膜の前処理に用いることによって,NOM除去に必要な添加濃度と接触時間の大幅な削減が可能であることを示した.活性炭接触時間としては2.4秒で十分であり,さらに添加量も従来の粉末活性炭に比べて75%削減できることがわかった.この理由は,超微粒度化は粒子外表面の比表面積の増加みならず活性炭内部のメソ孔の増加による活性炭自体の吸着容量と活性炭粒子内の細孔拡散係数をも増加する効果があることを見出した.さらに,臭気物質のジェオスミンとその生成原因藻類であるアナベナの除去について検討しとところ,サブミクロン粒度まで微小化した微粉炭...
  • 文部科学省:科学研究費補助金(萌芽研究)
    研究期間 : 2004年 -2005年 
    代表者 : 松井 佳彦, 井上 隆信, 松下 拓
     
    本年度は,セラミックMF膜を用いた凝集MF膜処理について,異なる条件下におけるウイルス除去の比較・検討を行った.また,ウイルス除去のメカニズムについて調べるために,凝集MF膜処理におけるウイルスの物質収支をとることを試みた.PAC添加濃度,凝集時間,膜孔径,流束がウイルス除去に与える影響について検討した結果,凝集MF膜処理においてはPAC添加濃度の影響が最も大きかった.また,1.08mg/L as Al以上のPAC添加濃度では,どの条件下においても5log以上の高い除去率が得られた.原水間の比較では,濁度成分の高い原水の除去率は他の原水と比べて1log程度低くなった.また,ウイルス間においては,QβとMS2で除去率に差が見られた.さらに,全ての実験結果で,処理時間が経過するにつれて除去率が向上するという傾向が見られた.凝集MF膜処理におけるウイルスの物質収支については,逆圧洗浄を行うことによりMF膜エレメント内に保持されていると考えられるウイルス量の13%を回収することができた.また,未回収の87%については,ファウリング物質として膜の表面でなく膜孔内部に不可逆的に捕捉されている可能性,ならびに処理水中に流出されている可能性の二つが考えられた.
  • 文部科学省:科学研究費補助金(基盤研究(B))
    研究期間 : 2002年 -2004年 
    代表者 : 松井 佳彦, 松下 拓, 井上 隆信
     
    大腸菌ファージQβおよびMS2を用いて、アルミニウム系凝集剤による不活化実験を行い,さらにフロック溶解法を検討した。その結果,以下の結論が得られた.(1)研究で検討したフロック溶解法では、フロック溶解時間を延長することにより、フロックが溶解され、フロック溶解時間を5時間とした場合にウイルスの回収が最大となるため、溶解時間を5時間と設定することが妥当であると考えられた。(2)本研究で用いた4種類の凝集剤(PAC、AlCl_3、硫酸バンド、Al_2(SO_4)_3)はいずれもQβ、MS2を不活化させた。(3)凝集剤間では、PACが他の凝集剤に比べ、最も不活化効果が高かった。(4)同じ条件下ではMS2よりもQβの方が不活化された。(5)河川水中では、Qβの不活化効果が抑制された。本研究では、pH9.5のBE溶液と混合後5時間のボルテックス攪拌を行うという、凝集フロックからの適切なウイルス回収法を確立した。このことから、本研究で確立したウイルス回収法を用いて昨年と同じ不活化実験を検証したところ、アルミニウム系凝集剤によってウイルスが不活化されることがわかった。しかし、そのウイルス不活化のメカニズムを解明するまでは至っていない。今後、ウイルス不活化について更なる検討が必要であり、これらの知見がウイルス不活化のメカニズムを考える上で一つの材料となると期待される。
  • 文部科学省:科学研究費補助金(基盤研究(C))
    研究期間 : 2002年 -2004年 
    代表者 : 井上 隆信, 松下 拓, 松井 佳彦
     
    明谷川および長良川流域で調査採取した河川水中懸濁物質および流域土壌を用いて、化学的連続抽出法による懸濁態リンの分画実験と藻類増殖試験を行った。連続抽出法では懸濁態リンを9成分に分画し、藻類増殖試験では、リン源として懸濁態リンのみを添加した。その結果以下の知見を得た。1)降雨時流出懸濁態リンの主成分は塩基可溶性無機リン、有機態リン、Fe,Mn結合無機態リンであり、全体の75〜90%を占めた。また微生物分解などにより比較的早く利用される有機態リンは概ね30〜40%程度であった。2)森林表層土壌は有機態リンが50%ほど含まれており、ほぼ100%が生物利用可能であった。水田土壌は施肥由来と考えられるFe,Mn結合無機リン、吸着リンが40%を占め、90%が生物利用可能であった。3)懸濁態リンの流出源である流域の土壌や底質中のリンを用いた藻類増殖試験により、懸濁態リンが藻類増殖に利用されていることが明らかになった。4)藻類増殖試験では、森林表層土壌に含まれるリンは60%程度が藻類に利用され、水田土壌は90%近くが利用された。5)藻類に利用可能と考えられている分画から求めた藻類利用可能態リンの懸濁態リンに占める比率は75〜90%であり、藻類増殖試験から求めた値は30%程度であった。流域土壌の藻類利用可能態リンの比率も連続抽出法で求めた場合が、藻類増殖試験で求めた場合よりも高くなった。これら...
  • 文部科学省:科学研究費補助金(基盤研究(B))
    研究期間 : 2001年 -2003年 
    代表者 : 湯浅 晶, 佐藤 三生男, 李 富生, 井上 隆信, 松井 佳彦, 松下 拓, 佐藤 三生男
     
    粉末活性炭(PAC)を用いた吸着と限外ろ過(UF)を用いる膜分離を組み合わせたハイブリッドシステム(PAC-UFシステム)による浄水処理において,水中有機物の除去効率に影響する処理操作・運転条件について検討し,処理システムの最適化をはかることを目的として,PAC-UFシステムにおける有機化合物の除去性を予測するシミュレーションモデルを開発した.開発されたモデルは,デッドエンド方式とクロスフロー方式のいずれの方式の膜ろ過操作の場合にも良く適合し,活性炭粒子内拡散律速モデルと連続撹拌反応槽(CSTR)モデルを仮定した解析が有用であることが実証された.膜ろ過がクロスフロー方式で運転される場合であっても,注入添加された粉末活性炭が浮遊状態で再循環するのはほんの短時間に限られることが示された.クロスフロー方式の場合でもデッドエンド方式の場合と同様に粉末活性炭が中空糸膜モジュール内に留まっており,粉末活性炭が膜ろ過装置内をほとんど循環ないことから,有機化合物の吸着速度の観点からはクロスフロー方式の有利さはほとんどないことが明らかにされた.シミュレーションによれば,膜ろ過サイクルにおいて連続的に粉末活性炭(PAC)を注入する方式に比べて,膜ろ過サイクルの開始時にPACを全量注入するパルス注入方式のほうがPACの滞留時間が長くなり,有機化合物の除去性が高くなることが示された.
  • 文部科学省:科学研究費補助金(基盤研究(C))
    研究期間 : 2001年 -2003年 
    代表者 : 湯浅 晶, 井上 隆信, 篠田 成郎, 松井 佳彦, 松下 拓, 李 富生
     
    本研究では,化学物質の移動モデルとその輸送媒体である水分の移動モデルによって流出解析モデルを構成した.流域を縦横1km×1kmのメッシュに分割し,各メッシュを垂直または水平に13個のコンパートメントに区切ったモデルを適用した.解析対象流域内は農薬原体濃度観測が週に約5回の高頻度で行われる筑後川流域であり,水田用農薬の流出予測を行った.流域の標高,土地利用,河川・水路等のデータは国土数値地図情報土地利用データを用いた.気温・日照時間は流域付近の17箇所の地上気象観測点でのアメダスデータ(アメダス観測年報)を利用した.降水量はレーダーアメダス解析雨量を用いて推定した.河川の流量に関するデータは,流量観測点での観測値と,ダムからの流出量と貯水量などから推定した.計算に必要な入力パラメータ値の設定に当たり,農薬の散布場所や田植日,農薬の散布日,水管理日などの農作業に関するデータ,および,農薬の吸着定数や分解係数といった農薬原体の特性に関するデータについて不確実なデータであると考え,ある生起確率分布に従って個々の水田ごとに値を設定するモンテカルロ手法を用いて入力データを構築した.一方で,これらの入力パラメータ値の設定に当たり,決定論的に定めた値を入力データとして用いる場合についても計算を行った.その結果,以下のことが明かとなった.(1)モンテカルロ手法を用いて農作業等の不確実性を考慮し...
  • 文部科学省:科学研究費補助金(基盤研究(B))
    研究期間 : 2000年 -2002年 
    代表者 : 松井 佳彦, 久保 俊裕, 湯浅 晶, 山本 浩之, 松下 拓, 井上 隆信
     
    引張試験機を用いて試験片に付着したカワヒバリガイを脱離するために必要な力とエネルギーを指標として除去性を評価した.その結果,シリコーン樹脂系塗料の脱離力は0.1N未満で,相対的に除去性が高いことを明らかにした.また,脱離過程での足糸の様子を観察した結果,分泌した各足糸が脱離する際,試験片と接着円盤の界面で剥離する場合と,足糸の繊維部が切断する場合があることを確認し,分泌した足糸数が少ないほど,かつ剥離する足糸の割合が大きいほど脱離力や脱離エネルギーが低下することを明らかにした.さらに,除去性と試験片の表面物性の関係を考察した結果,表面自由エネルギーの水素結合力成分値が低い試験片ほど足糸が剥離する割合が大きく,付着力も小さいことが分かった.しかし,試験片の表面粗さと付着力はほぼ無関係であった.本研究ではフィールドで採取した成貝を実験室内で試験片に再付着させた後脱離性を評価している.このため各試験片の除去性の相対的な関係を評価しているため,今後はフィールドで付着,成長したカワヒバリガイに対して試験片の除去性を評価する必要が残された.さらに,水流によってカワヒバリガイの脱離を試み,脱離に必要な流速と成貝に作用する抗力を測定した.その結果,シリコーン樹脂系塗料に付着したカワヒバリガイは比較的低い流速で脱離させることが可能で,相対的に脱離性の優れた塗料であることを確認した.さらに各種試...
  • 文部科学省:科学研究費補助金(基盤研究(C))
    研究期間 : 1997年 -1999年 
    代表者 : 湯浅 晶, 篠田 成郎, 松井 佳彦
     
    水田用農薬の河川流出過程の数理モデルを奥入瀬川流域(青森県,幹線流路延長70km,流域面積844km^2)に適用し,実測データが揃っている1995年と1996年の農薬流出量について解析した.流域を1片5kmのメッシュに分割して,地理情報データから土地利用状況を4種類(山地・水田・畑地・市街地)に分類した.農薬使用データ(農薬の種類・販売量・成分割合・分子量・半減期・土壌吸着平衡係数など)に基づいて農薬成分11種類を解析対象とし,水稲栽培ごよみや農業雑誌の情報から各農薬の使用・散布時期を推定した.水文気象データ(降水量・気温など)は流域内8カ所の観測値からTiessen法により各メッシュに配分した.各メッシュの蒸発散量と融雪量の推定法の検討と多層コンパートメント流出モデルにおける必要最小コンパートメント数について検討した.蒸発散モデルとして検討した5つの推定法のうちで実蒸発散量の日変化を捉えるBrutsaert and Strickerの補完法が適していることを示した.また,積雪・融雪モデルとして積雪の冷却・凍結過程と保水過程をも考慮することにより積雪深や融雪流出量を精度良く計算できるTemperature index法が適していることを示した.水と農薬の流出モデルでは,6個のコンパートメント(河川水・河川底泥・水田水・水田底泥・土壌A層・土壌B層)が最小限必要であることを示し...
  • 文部科学省:科学研究費補助金(一般研究(C), 基盤研究(C))
    研究期間 : 1995年 -1996年 
    代表者 : 松井 佳彦, 湯浅 晶
     
    本研究の成果をまとめると次のようである.HPLC用の機器を固定層吸着実験用に用い,粉末活性炭を充填した微小カラムの破過曲線から,吸着過程の相以則に基づいて実吸着過程の進行を迅速評価することを試みた.この方法によれば,吸着の動力学式と吸着平衡式から誘導される無次元数を一致させることによって大規模な装置とほぼ相似な破過曲線を極短時間に少量の試料から得ることができる.フミン質の吸着除去性に関してはマイクロカラムとパイロットカラムは相似な破過曲線を得た.しかし,シマジンとアシュラムの吸着除去性に関する相似則は成立しないことが示された.フミン質の共存下で微量有害成分の平衡吸着関係や吸着速度がどのように変化するかを,新しい活性炭とフミン質と吸着平衡に達した活性炭を用いて検討し,(1)フミン質の存在下で微量有害成分の吸着性は低下するが,フミン質の吸着は有害成分より影響を受けない.(2)フミン質が吸着することによって,微量有害成分の吸着速度は著しく低下することがあきらかとなった.様々なタイプの農薬のフミン質共存下における固定層吸着特性をマイクロカラム法を用いて検討し,水溶解度が高く親水的な農薬ほど活性炭吸着性は低く,活性炭吸着性が低い農薬ほど,フミン質が共存することによる吸着性の低下の度合が大きいことがあきらかとなった.フミン質を除去している活性炭固定床に農薬が間欠的流入する場合の除去特性を...
  • 文部科学省:科学研究費補助金(重点領域研究)
    研究期間 : 1995年 -1995年 
    代表者 : 湯浅 晶, 松井 佳彦
     
    水不足地域における水道水安定供給のための対応策として海水淡水化浄水処理施設(逆浸透法を主プロセスとし,海水から飲料水を生産する施設)を導入する場合を想定して,その建設と運転・維持管理に要するコストを算定するとともに,地球温暖化などの要因となるエネルギー消費量および二酸化炭素排出量を算定した.水不足は夏の1ヶ月の期間であり,不足量は1万m^3/日であると想定した.新たに建設する海水淡水化施設は1年の内の1ヶ月間は稼働率90%で運転して不足分の飲料水を生産し,残りの11ヶ月間は施設保持のために稼働率20%で運転すると想定した.一方の対策として,ダム(貯留量1ヶ月分30万m^3)と従来型浄水場(通常浄水施設+高度浄水処理施設)を建設する場合を想定し,比較評価の対照とした.海水淡水化施設の建設費は81.5億円であり,ダム・従来型浄水場の1.9倍となる.また,海水淡水化施設の運転・維持管理費は1.72億円/年であり,ダム・従来型浄水場の3.6倍となる.海水淡水化施設の建設に係わるエネルギー消費量と二酸化炭素排出量はそれぞれ715TJと13.3Mkgであり,いずれもダム・従来型浄水場の約2倍となる.また,運転・維持管理に係わるエネルギー消費量と二酸化炭素排出量はそれぞれ42.5TJ/年と0.60Mkg/年であり,いずれもダム・従来型浄水場の約20倍と非常に大きく,地球温暖化などの環境への...
  • 文部科学省:科学研究費補助金(一般研究(C))
    研究期間 : 1994年 -1995年 
    代表者 : 亀井 翼, 藤田 睦博, 藤田 陸博, 湯浅 晶, 藤田 睦博, 松井 佳彦
     
    土壌中の農薬の濃度を予測するためには、土壌に存在する水分の挙動を解析する必要がある。したがって、本研究の内容は、次の二つに分類できる。一つは、不飽和浸透流理論をいかに実流域における流出解析に適用するかという問題である。これについては、藤田が担当した。二つ目は、土壌中の農薬の拡散・輸送現象の解析で、松井が担当した。土壌中の水分の移動現象は、不飽和浸透流理論によって最も物理的に記述できる。しかしながら、この理論を実流域の流出解析に適用しようとすると、いくつかの克服すべき問題が残されている。特に、土壌の不飽和透水層の下端における境界条件をどのように設定するかが、重要な問題となる。この境界条件が、より深層の土壌への浸透を規定するからである。藤田は試験地における流出解析より新しい境界条件を提案している。不飽和浸透流式を解く際に必要なθ(含水率)〜ψ(吸引圧)の関係式と不飽和透水係数は室内試験より得ている。試験地を除くと、このようなθ〜ψの関係式や不飽和透水係数を得ることことができない。このことが、不飽和浸透流式を実流域の流出解析に応用できない理由となっている。藤田はタンクモデルとエントロピー法を用いて計算した深層の土中への浸透が不飽和浸透流式を用いて計算した結果と一致することを指摘している。タンクモデルやエントロピー法は、集中定数系の流出モデルなので、実流における流出解析も容易である。...
  • 文部科学省:科学研究費補助金(一般研究(C))
    研究期間 : 1991年 -1992年 
    代表者 : 亀井 翼, 松井 佳彦, 丹保 憲仁
     
    農薬が上水道水源流域に散布されると、農薬は降雨によって土壌中を移動し河川へ流出する。その場合、(1)どのようなタイプの農薬が、(2)どの様なタイプの土壌から、どの程度流出するかを明らかにすることは、水源水を適切に管理し処理するために重要である。そこで本研究では、始めに(1)上水道水源斜面における降雨の流出経路を検討しついで(2)土壌と土中水における農薬の物質収支式から誘導される拡散項を含まない農薬の移動距離算定式を提案し、提案した式の有用性を確認するために行う実験に必要な測定法として(3)数100μlの少量の試水中の農薬を抽出、濃縮等の前処理をすることなくHPLCにより迅速簡単に測定する方法を提案した。提案した農薬の移動予測式と農薬の迅速、簡単な測定法を用いて数多くの土壌による農薬の吸着実験と農薬の移動距離の算定を行い、得られた結果を土壌の赤外線吸収スペクトル、土壌の1%NaOH抽出可能なE260等と対比し以下のような結果を得た。1)土壌の1%NaOH抽出可能なE260を測定することにより通常の有機土壌の吸着性の大小を簡単に推定することが可能である。2)水酸基量の大きい土壌はカオリンのような無機土壌、新琴似土壌のような有機土壌のいずれの場合でも水酸基量の小さい千歳土壌、石英砂よりも農薬の吸着量が高い。3)土壌中における農薬の物質収支式より誘導された農薬の移動距離算定式により定...
  • 文部科学省:科学研究費補助金(試験研究(B))
    研究期間 : 1990年 -1992年 
    代表者 : 丹保 憲仁, 大戸 時喜雄, 財津 靖史, 中埜渡 丈嘉, 松井 佳彦, 亀井 翼, 伊藤 晴夫
     
    2波長(近赤外部と紫外部)の吸光度の時間変動を凝集・フロック形成系について測定することによって、水処理プロセスの凝集処理をオンラインでモニターし、自動制御することを可能にした。得られた成果を要約すると次のようである。1)マイクロフロックの生成過程をその初期からオンラインで計測でき、フロック粒径の増大を遅滞なく計測できる。2)そのことによって、時間遅れのない自動制御が可能となった。3)マイクロフロックを含む懸濁水の吸光度がランダム変動をすることと、近赤外部と紫外部の光が粗懸濁質と溶解性有機成分(フミン質)に対して異なる吸収特性を持つことを利用して、凝集の進行状態を計測する。すなわち、2種類の波長の示す平均吸光度と吸光度の2乗平均から、凝集剤注入直後に生成したマイクロフロックの粒径と、凝集せずに残留している溶解性のフミン質濁度を算出する。4)実施設に長期間使用し得るフィールド型のセンサーの開発を進め、一年間の耐久試験により、機械的な問題と共にセル汚れの自動保障、洗浄システムを完成することができて実用化に踏み込み得た。5)本センサーを入力機器として、凝集プロセスを制御するためのアルゴリズムを開発し、500m/dのプラントにより実施設の自動制御の実験を繰り返し、生成フロックの設定沈降速度を目標値とした凝集剤添加率の自動制御を可能にした。これらの研究成果によって、現代の浄水場の主プロセ...
  • 文部科学省:科学研究費補助金(一般研究(B))
    研究期間 : 1988年 -1990年 
    代表者 : 丹保 憲仁, 松井 佳彦, 清水 達雄, 亀井 翼
     
    流動床造粒プロセスによる高速度固液分離法を用いてさまざまな原水を処理するための研究を行い次のような成果を得た。1)粘土系県濁質を対象として:カチオン系凝集剤(アルミニウム)と弱アニオンまたはノニオン系高分子凝集剤の2剤の最適用法に関する検討を行い、ALT比とDT比およびALT/DTの比についての適切な造粒操作條件を確立した。ALTについては、マイクロフロックのZPを-20m-付近に設定し、PT/ALT≒0.5となるような手順で注薬率を設定する。2)粘土・色度2成分系について:濁度、色度がほぼ1対1程度もしくは色度の割合がそれ以下の場合には、流動層造粒分離を真のペレットに近い集塊物を生成して、高速で行いうる、濁度が10^2のオーダまで適用しえて、東南アジア、中国、アフリカなどの比較的濁度の高い、色度を共存する原水に対する有力な処理法となりうる。凝集條件は、色成分を凝集するための弱酸領域におけるZPが-10〜13nVであり、弱アニオン系高分子凝集剤をPT/ALT≒0.5で造粒可能である。3)造粒・生物炉床システム:下水処理の最初沈澱池の替りに、アルミニウム添加、弱アニオン高分子添加によるLV100〜200M_oの高速造粒分離槽を用い、高分子成分と懸濁成分を分離した後、低分子BOD成分のみを滞留時間1時間程度の生物炉床で処理し、濁質温度、BOD共に10mf/i以下の良好な処理水を得...

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