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研究者情報

マスター

アカウント（マスター）

  • 氏名

    松下　拓(マツシタ　タク), マツシタ　タク

所属（マスター）

  • 工学研究院　環境工学部門　環境工学

所属（マスター）

  • 工学研究院　環境工学部門　環境工学

独自項目

syllabus

  • 2021, 水・物質循環工学特論, Water Quality Risk and Control, 修士課程, 工学院, 吸着処理, 汚泥処理
  • 2021, 水・物質循環工学特論, Water Quality Risk and Control, 博士後期課程, 工学院, 吸着処理, 汚泥処理
  • 2021, 環境工学, Environmental Engineering, 学士課程, 工学部, 都市環境、水質汚濁、上下水道、水質保全、大気保全、廃棄物、エネルギー、騒音・振動
  • 2021, 環境工学序論, Introduction to Environmental Engineering, 学士課程, 工学部, 環境問題の歴史，気候変動，SDGs，上下?道，?環境保全，室内環境，廃棄物処分，循環計画システム
  • 2021, 環境工学概論, Introduction to Environmental Engineering, 学士課程, 工学部, 都市環境, 水質汚濁, 上下水道, 水質保全, 大気保全, 廃棄物, エネルギー, 費用便益, 環境管理, 人間の生理機能, 温熱・光, 騒音
  • 2021, 環境毒性学, Environmental Toxicology, 学士課程, 工学部, 毒性物質, 代謝, 生体防御機構, バイオアッセイ
  • 2021, 工学基礎演習, Basic Training for Environmental Engineer, 学士課程, 工学部, 作文技術、和文、英文、プレゼンテーション

researchmap

プロフィール情報

学位

  • 博士（工学）（京都大学）

プロフィール情報

  • 姓

    松下, マツシタ

  • 名

    拓, タク

  • ID各種

    200901091991632712

対象リソース

業績リスト

研究キーワード

  • 浄水処理, 毒性評価, ウイルス除去, 真空紫外線, カルキ臭   Environmental and Sanitary Engineering   

研究分野

  • 社会基盤（土木・建築・防災） / 土木環境システム

経歴

  • 2023年04月 - 現在 北海道大学大学院工学研究院環境創生工学部門 教授
  • 2010年04月 - 2023年03月 北海道大学大学院工学研究院環境創生工学部門（組織名変更） 准教授
  • 2007年04月 - 2010年03月 北海道大学大学院工学研究科環境創生工学専攻 准教授（職名変更）
  • 2006年01月 - 2007年03月 北海道大学大学院工学研究科環境創生工学専攻 助教授
  • 2002年04月 - 2005年12月 岐阜大学工学部社会基盤工学科（組織名変更） 助手
  • 1999年04月 - 2002年03月 岐阜大学工学部土木工学科 助手
  • 1996年04月 - 1999年03月 名古屋大学大学院工学研究科地圏環境工学専攻 助手

学歴

  • 1994年04月 - 1996年03月   京都大学   大学院工学研究科   衛生工学専攻（博士課程）
  • 1992年04月 - 1994年03月   京都大学   大学院工学研究科   衛生工学専攻（修士課程）
  • 1988年04月 - 1992年03月   京都大学   工学部   衛生工学科

委員歴

  • 2015年 - 2021年   日本水環境学会   運営幹事
  • 2015年 - 2017年   土木学会   環境工学委員会委員
  • 2006年 - 2009年   土木学会   環境工学委員会委員兼幹事   土木学会
  • 2005年 - 2009年   日本環境工学教授協会   北海道支部幹事   日本環境工学教授協会
  • 2007年 - 2008年   土木学会   地球温暖化対策特別委員会適応策小委員会委員   土木学会
  • 2008年   日本水環境学会   JWET編集小委員会幹事   日本水環境学会
  • 2008年   日本水環境学会   年会・シンポ等検討委員会委員   日本水環境学会
  • 2008年   日本水環境学会   北海道支部幹事長   日本水環境学会
  • 2007年   土木学会   環境工学委員会地球温暖化小委員会委員   土木学会
  • 2006年   日本水環境学会   北海道支部幹事   日本水環境学会
  • 2005年   日本水環境学会   バイオアッセイによる安全性評価研究委員会幹事   日本水環境学会

受賞

  • 2022年09月 世界水協会（IWA） World Water Congress Best Poster Award
     1,4-Dioxane decomposition with VUV and its computational prediction taking into account effects of inorganic ions 
    受賞者: 松下拓
  • 2019年 日本水環境学会 論文賞
     
    受賞者: 松下 拓
  • 2017年 環境科学会 論文賞
     
    受賞者: 松下 拓
  • 2013年 土木学会環境工学委員会 第49回環境工学研究フォーラム論文賞
     
    受賞者: 松下 拓
  • 2013年 クリタ水・環境科学振興財団 クリタ 水・環境科学研究優秀賞
     
    受賞者: 松下 拓
  • 2008年 土木学会環境工学委員会 第45回環境工学研究フォーラム優秀ポスター発表賞
     
    受賞者: 松下 拓
  • 2003年 日本水環境学会 論文奨励賞（廣瀬賞）
     
    受賞者: 松下 拓

論文

  • D. Shirakawa, N. Shirasaki, Q. Hu, T. Matsushita, Y. Matsui, H. Takagi, T. Oka
    Water Research 236 2023年06月01日 [査読有り]
     
    Here, we examined the efficiencies of drinking water treatment processes for the removal and inactivation of human sapovirus (HuSaV). We applied a recently developed in vitro cell-culture system to produce purified solutions of HuSaV containing virus concentrations high enough to conduct virus-spiking experiments, to develop an integrated cell culture-polymerase chain reaction (ICC-PCR) assay to quantify the infectivity of HuSaV, and to conduct virus-spiking experiments. In virus-spiking coagulation-sedimentation–rapid sand filtration (CS–RSF) and coagulation–microfiltration (C–MF) experiments, HuSaV removals of 1.6–3.7-log10 and 1.2–>4.3-log10, respectively, were observed. The removal ratios observed with CS–RSF were comparable and correlated with those of murine norovirus (MNV, a widely used surrogate for human noroviruses) and pepper mild mottle virus (PMMoV, a potential surrogate for human enteric viruses in physical and physicochemical drinking water treatment processes), and those observed with C–MF were higher than but still correlated with those of MNV and PMMoV, indicating that MNV and PMMoV are both potential surrogates for HuSaV in CS–RSF and C–MF. For astrovirus (AstV, a representative human enteric virus), removal ratios of 1.8–3.3-log10 and 1.1–>4.0-log10 were observed with CS–RSF and C–MF, respectively. The removal ratios of AstV observed with CS–RSF were comparable and correlated with those of PMMoV, and those observed with C–MF were higher than but still correlated with those of PMMoV, indicating that PMMoV is a potential surrogate for AstV in CS–RSF and C–MF. When the efficacy of chlorine treatment was examined by using the developed ICC-PCR assay, 3.8–4.0-log10 inactivation of HuSaV was observed at a CT value (free-chlorine concentration [C] multiplied by contact time [T]) of 0.02 mg-Cl2·min/L. The infectivity reduction ratios of HuSaV were comparable with those of MNV. For AstV, 1.3–1.7-log10 and >3.4-log10 inactivation, as evaluated by ICC-PCR, was observed at CT values of 0.02 and 0.09 mg-Cl2·min/L, respectively. These results indicate that HuSaV and AstV are both highly sensitive to chlorine treatment and more sensitive than a chlorine-resistant virus, coxsackievirus B5 (1.3-log10 inactivation at a CT value of 0.4 mg-Cl2·min/L, as evaluated by the ICC-PCR assay).
  • Yize Chen, Yoshihiko Matsui, Tsutomu Sato, Nobutaka Shirasaki, Taku Matsushita
    Water Research 235 2023年05月15日 [査読有り]
     
    Application of poly-aluminum chloride (PACl) coagulant is a popular mode of water treatment worldwide because of the high capacity of PACl to neutralize charge. The manufacture and use of PACls with various basicities in different regions around the world suggest that the characteristics of the raw water are important determinants of the efficacy of PACl application. However, attention has not been fully paid to the effects of water quality other than the substances to be removed. In this study, two typical PACls with different basicities were used to investigate why the performance of PACls depends on the characteristics of the raw water. We focused on the concentrations of inorganic ions in the raw water. Use of high-basicity PACl (HB-PACl) with a high content of polymeric-colloidal species (Alb+Alc) resulted in very slow floc formation and little turbidity removal in raw water with low concentrations of sulfate ions. The performance of the HB-PACl was inferior to that of normal-basicity PACl (NB-PACl), although the charge-neutralization capacity of the HB-PACl was higher. Rates of floc formation were strongly correlated with the rate of aluminum precipitation by hydrolysis reaction, which was identified as an indicator for evaluating the compatibility of raw water with PACl treatment. Among the common ions in natural water, the sulfate ion had the greatest ability to hydrolyze and precipitate PACl because of its divalency and tetrahedral structure. This conclusion followed from experimental results showing similar effects for selenate and chromate ions as for sulfate ions and somewhat smaller effects for thiosulfate ions. Bicarbonate ions and natural organic matter affected PACl hydrolysis-precipitation, but chloride ions, nitrate ions, and cations had little effect on PACl hydrolysis-precipitation. Interestingly, the abilities of sulfate ions to hydrolyze HB-PACl and NB-PACl were very similar, but bicarbonate ions were less effective in hydrolyzing HB-PACl than NB-PACl, and bicarbonate ions contributed little to the hydrolysis-precipitation of HB-PACl in raw water with normal alkalinity. Therefore, sufficient coagulation with HB-PACl therefore usually requires a certain concentration of sulfate ions in water to be treated. The implication is that which anions are most influential to the hydrolysis-precipitation of PACl, and thus to PACl's coagulation ability depends on the constituents of the PACl.
  • Kentaro Narita, Yoshihiko Matsui, Taku Matsushita, Nobutaka Shirasaki
    Journal of Environmental Management 326 2023年01月15日 [査読有り]
     
    Proper selection of new contaminants to be regulated or monitored prior to implementation is an important issue for regulators and water supply utilities. Herein, we constructed and evaluated machine learning models for predicting the detectability (detection/non-detection) of pesticides in surface water as drinking water sources. Classification and regression models were constructed for Random Forest, XGBoost, and LightGBM, respectively; of these, the LightGBM classification model had the highest prediction accuracy. Furthermore, its prediction performance was superior in all aspects of Recall, Precision, and F-measure compared to the detectability index method, which is based on runoff models from previous studies. Regardless of the type of machine learning model, the number of annual measurements, sales quantity of pesticide for rice-paddy field, and water quality guideline values were the most important model features (explanatory variables). Analysis of the impact of the features suggested the presence of a threshold (or range), above which the detectability increased. In addition, if a feature (e.g., quantity of pesticide sales) acted to increase the likelihood of detection beyond a threshold value, other features also synergistically affected detectability. Proportion of false positives and negatives varied depending on the features used. The superiority of the machine learning models is their ability to represent nonlinear and complex relationships between features and pesticide detectability that cannot be represented by existing risk scoring methods.
  • Zhao, Y, Matsui, Y, Kinouchi, Y, Seko, T, Shirasaki, N, Matsushita, T
    Journal of Water Process Engineering 49 103180  2022年10月 [査読有り][通常論文]
     
    Submicron-sized powdered activated carbon (SSPAC, diameter 200 nm) dosed in a pulse after coagulation pretreatment has recently been found to effectively mitigate membrane fouling and thus to suppress the rise of transmembrane pressure (TMP) in the microfiltration process because SSPAC has a higher capacity to adsorb membrane foulants, such as natural organic matter, than conventional PAC and a precoat layer formed by SSPAC on the membrane surface retards membrane fouling. This study investigated the effects of the filtration flux during precoating, the timing of coagulant dosing, and the types of coagulants on the suppression of TMP rise by pulse-dosed SSPAC. The TMP rise was insensitive to the filtration flux during precoating. However, the efficacy of the SSPAC was sensitive to the use of the coagulant polyaluminum-chloride (PACl). Unlike pulse dosing of SSPAC, pulse dosing of coagulant led to excessive aggregation and settling of SSPAC and insufficient formation of a precoating layer. The best filterability was achieved when the coagulant was dosed continuously in the entire operation period. It is also effective to use treated water for feeding during the preparation stage. For sulfated PACl, high basicity (70 %), with its high charge neutralization capacity, was preferred to medium basicity (50 %). Meanwhile, the TMP rise was more effectively suppressed by non-sulfated PACl with a low-to-medium basicity (20–40 %) than zero or high basicity (70 %). This behavior was explained by the fact that, as the basicity increases, hydrolysis of the coagulants is lessened, but the charge neutralization effect becomes stronger.
  • Saito, S, Matsui, Y, Shirasaki, N, Matsushita, T
    Journal of Water Process Engineering 49 2022年10月 [査読有り]
     
    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.
  • Zhao, Y, Matsui, Y, Saito, S, Shirasaki, N, Matsushita, T
    Separation and Purification Technology 296 2022年09月01日 [査読有り][通常論文]
     
    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.
  • Saito, S, Matsui, Y, Shirasaki, N, Matsushita, T
    Water Research X 16 2022年08月01日 [査読有り][通常論文]
     
    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.
  • Shirakawa, D, Shirasaki, N, Matsushita, T, Matsui, Y, Yamashita, R, Matsumura, T, Koriki, S
    Water Research 213 118160 - 118160 2022年04月 [査読有り][通常論文]
     
    Here, we evaluated the reduction efficiencies of indigenous pepper mild mottle virus (PMMoV, a potential surrogate for human enteric viruses to assess virus removal by coagulation-sedimentation–rapid sand filtration [CS–RSF] and coagulation–microfiltration [C–MF]) and representative human enteric viruses in four full-scale drinking water treatment plants that use CS–RSF (Plants A and B) or C–MF (Plants C and D). First, we developed a virus concentration method by using an electropositive filter and a tangential-flow ultrafiltration membrane to effectively concentrate and recover PMMoV from large volumes of water: the recovery rates of PMMoV were 100% when 100-L samples of PMMoV-spiked dechlorinated tap water were concentrated to 20 mL; even when spiked water volume was 2000 L, recovery rates of >30% were maintained. The concentrations of indigenous PMMoV in raw and treated water samples determined by using this method were always above the quantification limit of the real-time polymerase chain reaction assay. We therefore were able to determine its reduction ratios: 0.9–2.7-log10 in full-scale CS–RSF and 0.7–2.9-log10 in full-scale C–MF. The PMMoV reduction ratios in C–MF at Plant C (1.0 ± 0.3-log10) were lower than those in CS–RSF at Plants A (1.7 ± 0.5-log10) and B (1.4 ± 0.7-log10), despite the higher ability of MF for particle separation in comparison with RSF owing to the small pore size in MF. Lab-scale virus-spiking C–MF experiments that mimicked full-scale C–MF revealed that a low dosage of coagulant (polyaluminum chloride [PACl]) applied in C–MF, which is determined mainly from the viewpoint of preventing membrane fouling, probably led to the low reduction ratios of PMMoV in C–MF. This implies that high virus reduction ratios (>4-log10) achieved in previous lab-scale virus-spiking C–MF studies are not necessarily achieved in full-scale C–MF. The PMMoV reduction ratios in C–MF at Plant D (2.2 ± 0.6-log10) were higher than those at Plant C, despite similar coagulant dosages. In lab-scale C–MF, the PMMoV reduction ratios increased from 1-log10 (with PACl [basicity 1.5], as at Plant C) to 2–4-log10 (with high-basicity PACl [basicity 2.1], as at Plant D), suggesting that the use of high-basicity PACl probably resulted in higher reduction ratios of PMMoV at Plant D than at Plant C. Finally, we compared the reduction ratios of indigenous PMMoV and representative human enteric viruses in full-scale CS–RSF and C–MF. At Plant D, the concentrations of human norovirus genogroup II (HuNoV GII) in raw water were sometimes above the quantification limit; however, whether its reduction ratios in C–MF were higher than those of PMMoV could not be judged since reduction ratios were >1.4-log10 for HuNoV GII and 2.3–2.9-log10 for PMMoV. At Plant B, the concentrations of enteroviruses (EVs) and HuNoV GII in raw water were above the quantification limit on one occasion, and the reduction ratios of EVs (>1.2-log10) and HuNoV GII (>1.5-log10) in CS–RSF were higher than that of PMMoV (0.9-log10). This finding supports the usefulness of PMMoV as a potential surrogate for human enteric viruses to assess virus removal by CS–RSF.
  • Pan L, Nakayama, A, Matsui, Y, Matsushita, T, Shirasaki, N
    Water Research 208 117872 - 117872 2022年01月 [査読有り][通常論文]
     
    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.
  • Nakazawa, Y, Abe, T, Matsui, Y, Shinno, K, Kobayashi, S, Shirasaki, N, Matsushita, T
    Water Research 203 117550 - 117550 2021年09月15日 [査読有り]
  • Matsushita, T, Kikkawa, Y, Omori, K, Matsui, Y, Shirasaki, N
    Chemical Research in Toxicology 34 9 2070 - 2078 2021年08月10日 [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.
  • Shi, G, Nishizawa, S, Matsushita, T, Kato, Y, Kozumi, T, Matsui, Y, Shirasaki, N
    Water Research 197 117086 - 117086 2021年06月01日 [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 full-scale 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.
  • Nakazawa, Y, Abe, T, Matsui, Y, Shirasaki, N, Matsushita, T
    Water Research 190 116786 - 116786 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.
  • Narita, K, Matsui, Y, Matsushita, T, Shirasaki, N
    Science of The Total Environment 751 141636 - 141636 2021年01月10日 [査読有り]
     
    © 2020 Elsevier B.V. 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.
  • Saito, S, Matsui, Y, Yamamoto, Y, Matsushita, S, Mima, S, Shirasaki, N, Matsushita, T
    Water Research 187 116412 - 116412 2020年12月15日 [査読有り]
     
    © 2020 Elsevier Ltd 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 μm may be the most appropriate for Mn(II) removal because particles below this size were aggregated, resulting in reduced removal efficiency.
  • Matsushita, T., Fujita, Y., Omori, K., Huang, Y., Matsui, Y. and Shirasaki, N.
    Chemosphere 261 127743 - 127743 2020年12月 [査読有り]
     
    © 2020 Elsevier Ltd 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.
  • Shirasaki, N., Matsushita, T., Matsui, Y. and Koriki, S.
    Water Research 186 116409 - 116409 2020年11月01日 [査読有り]
     
    © 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.
  • Nishizawa, S, Matsushita, T, Matsui, Y, Shirasaki, N
    Science of The Total Environment 737 140300 - 140300 2020年10月01日 [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.
  • Chen, Y., Nakazawa, Y., Matsui, Y., Shirasaki, N. and Matsushita, T.
    Water Research 183 116093 - 116093 2020年09月15日 [査読有り]
     
    © 2020 Elsevier Ltd Many PACl (poly-aluminum chloride) coagulants with different characteristics have been trial-produced in laboratories and commercially produced, but the selection of a proper PACl 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 AlCl3-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. PACls of high-basicity produced by AlCl3-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 AlCl3-titration PACls did not form large floc particles. High-basicity PACls produced by Al(OH)3-dissolution were superior to low-basicity PACl 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, high-basicity Al(OH)3-dissolution PACl 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 AlCl3-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 AlCl3-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 PACl was hydrolysis-prone, even without sulfate ions. Aluminum species in the high-basicity AlCl3-titration PACl 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 PACl was the least polymerized and contained monomeric species.
  • Nakayama, A, Sakamoto, A, Matsushita, T, Matsui, Y, Shirasaki, N
    Water Research 182 115992  2020年09月01日 [査読有り]
     
    © 2020 Elsevier Ltd 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 MIBs 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 15N-labeled effluent organic matter.
  • Zhao, Y, Kitajima, R, Shirasaki, N, Matsui, Y, Matsushita, T
    Water Research 177 15 115757  2020年06月15日 [査読有り]
     
    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.
  • Matsushita, T, Sugita, W, Ishikawa, T, Shi, G, Nishizawa, S, Matsui, Y, Shirasaki, N
    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.
  • Nishikawa, S, Matsui, Y, Matsushita, T, Shirasaki, N
    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.
  • Takaesu, H, Matsui, Y, Nishimura, Y, Matsushita, T, Shirasaki, N
    Water Research 155 15 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.
  • Nakazawa, Y, Matsui, Y, Hanamura, Y, Shinno, K, Shirasaki, N, Matsushita, T
    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.
  • Takanashia, H, Abiru, K, Hama, T, Shinfuku, Y, Nakajima, T, Ohki, A, Ueda, T, Kondo, T, Matsushita, T, Kameya, T
    Water Research 146 187 - 196 2018年12月 [査読有り][通常論文]
     
    The estimated domestic usage of DD (a typical nematocide) has been the greatest among all the agricultural chemicals in Japan. DD is involved in a document which is used to establish tap water quality standard in Japan. The document indicates that DD is potentially detectable in raw water for tap waters. DD in raw water will be treated with chlorine at waterworks, which raises concerns about formation of mutagenic chlorination by-products through the treatment. The objective of this work was to identify a mutagenic chlorination by-product by using high resolution mass spectrometers and multivariate analyses. Mutagenicity of the chlorination by-product was evaluated with the Ames Salmonella mutagenicity assay. (E)-1,3-Dichloropropene (DCP) was used as a model compound of DD. The mutagenicity of chlorine treated model aqueous solutions of DD increased with increasing chlorine dosages up to 3.00 mol-Cl-2/mol-DCP. From the chlorine treated aqueous solutions of DD, 1,3-dichloroacetone (DCA) was identified as a major mutagen by a cochromatography with an authentic standard, precursor ion analyses and first generation product ion analyses with the high resolution mass spectrometers. The mutagenicity of DCA against TA100 strain without microsomal activation was 160,000 net revertant colony/mu mol (the toxicity equivalent factor was 0.14). Based on the mutagenicity of the chlorine treated DCP sample, the specific mutagenicity of DCA, and the DCA concentration in the sample, the mutagenic contribution of DCA to the chlorine treated DCP sample was calculated. High contribution (98%) clearly shows that DCA is a major mutagen in the chlorine treated DCP sample. Because the exploration of DCA was performed by using the unrealistic high concentration samples of DCP and chlorine, formation of DCA in the practical concentration samples (0-200 mu g-DCP/L, 0.10 or 1.27 mg-Cl-2/L) was examined. It was proven that DCA formation reaction takes place in the practical concentrations of DCA and chlorine. (C) 2018 Elsevier Ltd. All rights reserved.
  • Nakazawa, Y, Matsui, Y, Hanamura, Y, Shinno, K, Shirasaki, N, Matsushita, T
    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.
  • Akiyama, M., Matsui, Y., Kido, J., Matsushita, T. and Shirasaki, N.
    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).
  • Shirasaki, N., Matsushita, T., Matsui, Y. and Yamashita, R.
    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.
  • Matsushita, T, Honda, S, Kuriyama, T, Fujita, Y, Kondo, T, Matsui, Y, Shirasaki, N, Takanashi, H, Kameya, T
    Water Research 129 347 - 356 2018年02月 [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.
  • Pan, L, Nishimura, Y, Takaesu, H, Matsui, Y, Matsushita, T, Shirasaki, N
    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.
  • 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.
  • Matsui, Y, Shirasaki, N, Yamaguchi, T, Kondo, K, Machida, K, Fukuura, T, Matsushita, T
    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.
  • Shirasaki, N, Matsushita, T, Matsui, Y, Murai, K
    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.
  • Pan, L, Takagi, Y, Matsui, Y, Matsushita, T, Shirasaki, N
    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.
  • Matsushita, T, Matsui, Y, Ikekame, S, Sakuma M, Shirasaki, N
    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.
  • Shirasaki, N, Matsushita, T, Matsui, Y, Murai, K, Aochi, A
    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.
  • Pan, L, Matsui, Y, Matsushita, T, Shirasaki, N
    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.
  • 高梨啓和, 浜知広, 中島常憲, 大木章, 上田岳彦, 松下拓, 近藤貴志, 亀屋隆志
    環境科学会誌 29 5 229-237 - 237 社団法人 環境科学会 2016年09月30日 [査読有り][通常論文]
     

    農薬は，施用された後に水環境中で様々な環境変化体（Pesticide Transformation Products in Water environments: PTPWs）に変化し，浄水場における塩素消毒工程において農薬とともに塩素処理され，さらなる変化体を生成する可能性がある。著者らは，すでに，一部の農薬やそのPTPWsの塩素処理実験を行い，変異原性物質生成能（Mutagen Formation Potential: MFP）を測定して報告した。本研究では，すでに報告した物質に加えて，新たに21種類の農薬および27種類のPTPWsの変異原性強度，21種類の農薬および35種類のPTPWsのMFP値を測定し，すでに報告した結果とあわせて再度解析することより，農薬およびPTPWsの変異原性強度が塩素処理によってどのように変化するかを検討した。その結果，多くの農薬やPTPWsの変異原性は陰性であり，問題がないことが確認された。一方，塩素処理前に陰性であった農薬の57％，PTPWsの56％が塩素処理により変異原性が陰性から陽性に転じた。このことから，浄水処理における塩素処理の前に，活性炭吸着処理などで農薬・PTPWsを除去することの重要性が示された。また，農薬からPTPWsへの変化がMFPの削減に繋がるか否かを検討した結果，試験した物質の70％の農薬は，PTPWsに変化することによりMFPが削減されたが，11％の物質のMFP値は10倍以上に上昇した。農薬やPTPWsの部分構造とMFP値の関係を検討した結果，アニリン構造を有する農薬・PTPWsは，塩素処理により変異原性物質を生成しやすいことが示唆された。

  • 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.
  • Shirasaki, N, Matsushita, T, Matsui, Y, Ohno, K
    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.
  • Shirasaki, N, Matsushita, T, Matsui, Y, Marubayashi, T
    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.
  • Shirasaki, N, Matsushita, T, Matsui, Y, Marubayashi, T
    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.
  • Matsui, Y, Nakao, S, Sakamoto, A, Taniguchi, T, Pan, L, Matsushita, T, Shirasaki, N
    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.
  • Matsushita, T, Kobayashi, N, Hashizuka, M, Sakuma, H, Kondo, T, Matsui, Y, Shirasaki, N
    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.
  • Matsushita, T, Nakamura, K, Matsui, Y, Shirasaki, N
    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.
  • Matsushita, T, Hirai, S, Ishikawa, T, Matsui, Y, Shirasaki, N
    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.
  • Kimura, M, Matsui, Y, Saito, S, Takahashi, T, Nakagawa, M, Shirasaki, N, Matsushita, T
    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,
  • Sakuma, M, Matsushita, T, Matsui, Y, Aki, T, Isaka, M, Shirasaki, N
    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.
  • Ikari, M, Matsui, Y, Suzuki, Y, Matsushita, T, Shirasaki, N
    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.
  • Matsui, Y, Sakamoto, A, Nakao, S, Taniguchi, T, Matsushita, T, Shirasaki, N, Sakamoto, N, Yurimoto, H
    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.
  • Shirasaki, N, Matsushita, T, Matsui, Y, Urasaki, T, Kimura, M, Ohno, K
    Water Supply 14 3 429 - 437 2014年06月01日 [査読有り]
     
    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 Al13 species and possibly Al30 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.
  • Takashi KONDO, Saori MIHO, Miho SAITO, Takashi KAMEYA, Koichi FUJIE, Taku MATSUSHITA, Hirokazu TAKANASHI
    Journal of Water and Technology 12 2 123 - 133 Japan Society on Water Environment 2014年04月 [査読有り][通常論文]
     
    Liquid chromatography-triple quadrupole mass spectrometer (LC/MS/MS) using electrospray ionization (ESI) is a commonly used analytical method for environmental safety even though there are limitations to its robustness. One of the limitations, the matrix effect (ME), is defined as the ionization suppression/enhancement by the co-eluting residual component, which creates large uncertainties in quantification. The objective of this study is to address ME in the analysis of pesticides and their transformation products in water matrices. For a set of 164 environmental samples, which were preconcentrated by a solid-phase extraction, ME was estimated by spiking standard solution containing 27 target chemicals. As a result, ionization suppression occurred in most of the analytes/matrix pairs. Variability in ME was also observed and the variability among analytes was derived from co-eluting matrix component rather than the physicochemical property of each analyte. To overcome ME, the preconcentrated samples were successively diluted and the effective dilution factor was determined. The variability among diluted samples was still observed and therefore ME needs to be confirmed in every sample for reliable quantification. Sample dilution worsens the limit of quantification; however, the limits in the method were maintained below 0.01 μg/L.
  • Hirokazu TAKANASHI, Tomohiro HAMA, Tsunenori NAKAJIMA, Akira OHKI, Takashi KONDO, Takashi KAMEYA, Taku MATSUSHITA
    Journal of Water and Environment Technology 12 1 25 - 32 Japan Society on Water Environment 2014年02月 [査読有り][通常論文]
     
    The mutagenicity of one pesticide and 20 pesticide transformation products in water environments (PTPWs), the mutagen formation potential (MFP) of three pesticides and 28 PTPWs were investigated with the Ames Salmonella mutagenicity assay. The mutagenicity of 2-hydroxybenzyl alcohol (a PTPW of iprobenfos) was positive before chlorination. Out of 28 PTPWs, 18 were positive for the MFP. The difference of the MFP distributions between the parent pesticides and their PTPWs was tested statistically, indicating no increase in the MFP through the transformations. Of the 28 couples of parent pesticides and their PTPWs tested, seven couples increased their MFP through the transformations. The greatest ratio of the increase was 38, which was observed for iprobenfos and its PTPW 3-hydroxybenzyl alcohol.
  • Narita, K, Matsui, Y, Iwao, K, Kamata, M, Matsushita, T, Shirasaki, N
    Environment International 63 114 - 120 2014年02月 [査読有り][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.
  • Shirasaki, N, Matsushita, T, Matsui, Y, Oshiba, A, Marubayashi, T, Sato, S
    Water Research 48 375 - 386 2014年01月 [査読有り]
  • Matsui, Y, Ishikawa, T. B, Kimura, M, Machida, K, Shirasaki, N, Matsushita, T
    Separation and Purification Technology 119 58 - 65 2013年11月 [査読有り]
  • Matsushita, T, Shirasaki, N, Tatsuki, Y, Matsui, Y
    WATER RESEARCH 47 15 5819 - 5827 2013年10月 [査読有り][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.
  • Niizuma, S, Matsui, Y, Ohno, K, Itoh, S, Matsushita, T, Shirasaki, N
    Regulatory Toxicology and Pharmacology 67 1 98 - 107 2013年10月 [査読有り][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.
  • Matsui, Y, Nakao, S, Taniguchi, T, Matsushita, T
    Water Research 47 8 2873 - 2880 2013年05月 [査読有り][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.
  • Kimura, M, Matsui, Y, Kondo, K, Ishikawa, T, B, Matsushita, T, Shirasaki, N
    Water Research 47 6 2075 - 2084 2013年04月15日 [査読有り][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.
  • 高梨啓和, 浜崎賢太, 加藤雄介, 中島常憲, 大木章, 近藤貴志, 亀屋隆志, 松下拓
    水環境学会誌 36 2 29-38 - 38 公益社団法人 日本水環境学会 2013年02月 [査読有り][通常論文]
     
    環境水の農薬濃度モニタリングの例は数多く報告されているが，農薬変化体（Pesticide Transformation Products in Water environments: PTPWs）のモニタリングは十分に行われているとは言い難い。その理由の一つとして，PTPWsのリストが見あたらないことがあげられる。環境中に散布された農薬は，ただちに水や二酸化炭素などの最終分解物まで分解されるとは限らず，加水分解物や光分解物などの農薬変化体が水環境中に残留する可能性がある。このため，PTPWsの環境モニタリングや浄水処理特性を検討することが重要と考えられる。そこで本文献研究では，PTPWsの環境モニタリングや浄水処理特性の検討に資することを目的に，農薬評価書をもとに145農薬の610種類のPTPWsを，12,269報の文献および2冊の書籍をもとに14農薬の73種類のPTPWsをリスト化した。
  • Matsui, Y., Nakao, S., Yoshida, T., Taniguchi, T. and Matsushita, T.
    Separation and Purification Technology 113 75 - 82 2013年 [査読有り][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. © 2013 Elsevier B.V. All rights reserved.
  • Takanashi, H, Kishida, M, Abiru, K, Kondo, T, Kameya, T, Matsushita, T, Nakajima, T, Ohki, A
    Journal of Water Supply: Research and Technology–AQUA 62 1 14 - 22 2013年 [査読有り][通常論文]
     
    The mutagenicity and the mutagen formation potential (MFP) of seven fungicides, 15 herbicides and 22 insecticides upon chlorination were measured with the Ames Salmonella assay. All the pesticides except for thiram and dichlorvos were non-mutagenic. However, 75% of the tested pesticides showed significant MFP. This indicated that the chlorination by-products of some pesticides are mutagenic, although the pesticides themselves are not. No significant mutagenicity or MFP was observed for 20% of the pesticides tested in the present study. Thiram and dichlorvos, representing 5% of the tested pesticides, had significant mutagenicity and MFP. The average MFP of asulam, which had the highest MFP in this study, was 860 times greater than the average MFP of propyzamide, which had the lowest MFP (below the detection limit). In addition, the chemical structures of pesticides which had significant MFPs were compared to each other in order to see if there are common characteristics among them, but we could not predict whether pesticides are capable of forming mutagens from their chemical structures, use types or mode of actions. MFP measurements are indispensable in order to know whether pesticides are capable of forming mutagens.
  • Matsushita, T, Suzuki, H, Shirasaki, N, Matsui, Y, Ohno, K
    Separation and Purification Technology 107 79 - 84 2013年 [査読有り][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.
  • Matsui, Y, Yoshida, T, Nakao, S, Knappe, D, Matsushita, T
    Water Research 46 15 4741 - 4749 2012年10月 [査読有り][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.
  • Shirasaki, N, Matsushita, T, Matsui, Y, Urasaki, T, Ohno, K
    Water Supply 12 5 666 - 673 2012年08月01日 [査読有り]
     
    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.
  • Ando, N, Matsui, Y, Matsushita, T, Ohno, K
    Water Research 46 6 2020 - 2020 2012年04月 [査読有り][通常論文]
  • Tani, K, Matsui, Y, Iwao, K, Kamata, M, Matsushita, T
    Water Research 46 3 741 - 749 2012年03月01日 [査読有り][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. © 2011 Elsevier Ltd.
  • A new approach to estimate norovirus removal performance in a membrane filtration process by using virus-like particles and immuno-PCR method
    Nobutaka Shirasaki, Taku Matsushita, Yuichi Tatsuki, Yoshihiko Matsui
    AWWA/AMTA Membrane Technology Conference and Exposition 2012 1024 - 1028 2012年
  • Coagulation by novel high-basicity poly-aluminum chloride effectively reduces ceramic membrane fouling and residual aluminum
    Masaoki Kimura, Yoshihiko Matsui, Taku Matsushita, Nobutaka Shirasaki, Tairyou B. Ishikawa
    AWWA/AMTA Membrane Technology Conference and Exposition 2012 774 - 777 2012年
  • Kondo, T, Saito, M, Kameya, T, Fujie, K, Matsushita, T, Takanashi, H
    Journal of Water and Environment Technology 10 4 409 - 417 2012年 [査読有り]
  • Hirokazu TAKANASHI, Kazuya ABIRU, Hanako TANAKA, Misako KISHIDA, Tsunenori NAKAJIMA, Akira OHKI, Takashi KONDO, Takashi KAMEYA, Taku MATSUSHITA
    Journal of Water and Environment Technology 10 4 437 - 447 Japan Society on Water Environment 2012年 [査読有り][通常論文]
     
    Fenitrothion [O, O-dimethyl O-(3-methyl-4-nitrophenyl)phosphorothioate], a typical organophosphorus pesticide, is widely used as an insecticide in Japan. In this study, 3-methyl-4-nitrophenol (3M4NP), which is a typical hydrolysate of fenitrothion, was focused as a possible mutagen precursor because it is reported as a common contaminant in raw water for water works, and is capable of forming mutagens when it is chlorinated in water works. In order to examine molecular formulae of mutagens produced from 3M4NP, a chlorinated 3M4NP sample was analyzed with a high-resolution LC/MS. Several peaks were found in a base peak chromatogram. A peak of m/z 215.971 was focused to be analyzed, suggesting a formation of C7H4O5NCl (mass error = 0.397 mmu or 1.837 ppm). To examine the chemical structure of the found substance, MS2 experiments were conducted with a collision induced disassociation technique. Four product ions: m/z 198.9679, 187.9757, 170.9731 and 136.0043 which can be attributed to losses of OH, CO, COOH and Cl functional groups were observed. From these fragment ions and the structure of 3M4NP, the substance was extrapolated to be chloro-5-hydroxy-2-nitrobenzoic acid (C5H2NB). The mutagen formation potential (MFP) of 5-hydroxy-2-nitrobenzoic acid, which is considered to be a precursor of C5H2NB, was tested and the MFP of 3,400 net rev./μmol was observed.
  • KAMEYA Takashi, SAITO Miho, KONDO Takashi, TORIUMI Wataru, FUJIE Koichi, MATSUSHITA Taku, TAKANASHI Hirokazu
    Journal of Water and Environment Technology 10 4 427 - 436 Japan Society on Water Environment 2012年 [査読有り]
     
    The organophosphate pesticide fenitrothion and its degradation product 3-methyl-4-nitrophenol (3M4NP), which possesses greater mutagen formation potential (MFP) than fenitrothion, were monitored. A total of 109 samples were collected from 41 sites of 12 rivers in the Tokyo metropolitan area and 71 samples were collected from 4 sites of 2 streams close to paddy fields in Kanagawa, Japan. The concentrations of fenitrothion and 3M4NP were determined by GC/MS with selected ion monitoring after solid-phase extraction and derivatization of 3M4NP with N, O-bis-(trimethylsilyl)trifluoroacetamide (BSTFA). Both fenitrothion and 3M4NP were below 1 μg/L (0 - 0.083 μg/L of fenitrothion and 0 - 0.156 μg/L of 3M4NP) in the river water samples, whereas fenitrothion and 3M4NP reached 0.16 and 1.6 μg/L, respectively, in the stream water samples. Seasonal and areal fluctuations were also observed in the streams. Nevertheless, the maximum concentration of 3M4NP appeared in late May at all sites. Furthermore, among the samples in which fenitrothion and/or 3M4NP were detected, 3M4NP largely contributed to the potential in 56% and 67% of the river and stream samples, respectively. These results strongly support the need for simultaneous monitoring of various pesticides and their degradation products, identification of degradation products and their MFP, and characterization of their behavior in water purification processes.
  • 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 [査読有り][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．
  • Matsushita, T, Shirasaki, N, Matsui, Y, Ohno, K
    Chemosphere 85 4 571 - 576 2011年10月 [査読有り]
  • Matsui, Y, Ando, N, Yoshida, T, Kurotobi, R, Matsushita, T, Ohno, K
    Water Research 45 4 1720 - 1728 2011年02月 [査読有り]
  • Shirasaki, N, Matsushita, T, Matsui, Y, Kobuke, M, Ohno, K
    Journal of Water Supply: Research and Technology-Aqua 59 8 501 - 511 2010年12月 [査読有り]
  • Matsui, Y, Nakano, Y, Ando, N, Sasaki, H, Ohno, K, Matsushita, T
    Water Science and Technology 62 11 2664 - 2668 2010年12月01日 [査読有り]
     
    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.
  • Tani, K, Matsui, Y, Narita, K, Ohno, K, Matsushita, T
    Water Science and Technology 62 11 2579 - 2589 2010年12月01日 [査読有り]
     
    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.
  • Ohno, K, Ishikawa, K, Kurosawa, Y, Matsui, Y, Matsushita, T
    Water Science and Technology 62 11 2694 - 2701 2010年12月01日 [査読有り]
     
    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09月01日 [査読有り]
     
    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.
  • Ando, N, Matsui, Y, Kurotobi, R, Nakano, Y, Matsushita, T, Ohno, K
    Water Research 44 14 4127 - 4136 2010年07月 [査読有り]
  • Ohno, K, Matsui, Y, Itoh, M, Oguchi, Y, Kondo, T, Konno, Y, Matsushita, T, Magara, Y
    Desalination 254 1-3 17 - 22 2010年05月15日 [査読有り][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 μg/L or more, but not when it was lower than 9 μg/L. When pretreated with ferric chloride, no substantial decline of NF membrane permeability was observed residual iron did not affect the permeability. When SiO2 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 NF feed was not high (30 μg/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. © 2010 Elsevier B.V. All rights reserved.
  • Shirasaki, N, Matsushita, T, Matsui, Y, Urasaki, T, Oshiba, A, Ohno, K
    Water Science and Technology 61 8 2027 - 2034 2010年04月01日 [査読有り]
     
    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 Qβ 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 Qβ 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, Qβ is the more conservative surrogate.
  • Shirasaki, N, Matsushita, T, Matsui, Y, Oshiba, A, Ohno, K
    Water Research 44 5 1307 - 1316 2010年03月 [査読有り]
  • Matsui Yoshihiko, Hasegawa Hiroki, Ohno Koich, Matsushita Taku, Mima Satoru, Kawase Yuji, Aizawa Takako
    Water Research 43 20 5160 - 5170 Elsevier 2009年12月 [査読有り]
     
    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 transmembrane 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.
  • Matsui, Y, Ando, N, Sasaki, H, Matsushita, T, Ohno, K
    Water Research 43 12 3095 - 3103 2009年07月 [査読有り]
     
    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 [査読有り][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 [査読有り]
  • Ohno, K, Kadota, E, Matsui, Y, Kondo, Y, Matsushita, T, Magara, Y
    Journal of Water Supply: Research and Technology - AQUA 58 7 476 - 487 2009年 [査読有り][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. © IWA Publishing 2009.
  • Ohno, K, Matsuo, Y, Kimura, T, Yanase, T, Rahman, M. H, Magara, Y, Matsushita, T, Matsui, Y
    WATER SCIENCE AND TECHNOLOGY 59 2 195 - 201 2009年 [査読有り][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.
  • Shirasaki, N, Matsushita, T, Matsui, Y, Kobuke, M, Ohno, K
    Journal of Membrane Science 326 2 564 - 571 2009年01月 [査読有り][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.
  • Matsui, Y, Murai K, Sasaki H, Ohno K, Matsushita, T
    Journal of Water Supply: Research and Technology–AQUA 57 8 577 - 583 2008年12月 [査読有り][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.
  • Shirasaki, N, Matsushita, T, Matsui, Y, Ohno, K
    Journal of Water Supply: Research and Technology-Aqua 57 7 501 - 506 2008年11月 [査読有り]
  • Matsui, Y, Ozu, T, Inoue, T, Matsushita, T
    Desalination 226 1-3 215 - 221 2008年06月 [査読有り][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.
  • 活性炭の微粉化が活性炭吸着に与える効果
    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 2008年 [査読有り]
  • Matsushita, T, Matsui, Y, Taniwaki, S, Ikeba, K, Matsui, Y
    Water Science and Technology 58 3 741 - 747 2008年 [査読有り][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.
  • Matsushita, T, Matsui, Y, Ohno, K, Sawaoka, D
    ournal of Water Supply: Research and Technology–AQUA 57 7 481 - 487 2008年 [査読有り][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.
  • Matsui, Y, Yamagishi, T, Terada, Y, Matsushita, T, Inoue, T
    Journal of Water Supply: Research and Technology–AQUA 56 1 13 - 24 2007年02月 [査読有り][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.
  • Matsui, Y, Narita, K, Inoue, T, Matsushita, T
    Water Science and Technology 56 1 71 - 80 2007年 [査読有り][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.
  • N. Shirasaki, T. Matsushita, Y. Matsui, K. Ohno, M. Kobuke
    Water Science and Technology: Water Supply 7 5-6 1 - 8 2007年 [査読有り][通常論文]
     
    Virus removal performance and mechanisms were investigated in a hybrid coagulation - microfiltration (MF) system by using river water spiked with bacteriophage Qβ. Virus removal increased with filtration time: the rate of virus removal was 4 log at the beginning of filtration and gradually increased to 6 log over 5 h, probably because of the growth of a cake layer that accumulated on the membrane surface. Quantification of the virus particles in the MF compartment by a combination of a polymerase chain reaction (PCR) method and a plaque forming unit (PFU) method revealed that most of the virus (> 99.999%) in the MF compartment was entrapped in the aluminium floc and then located in the solid phase most of the virus (> 99.9%) in the solid phase was inactivated. The rate of recovery of virus particles from the MF compartment decreased with filtration time: after 3 h of filtration approximately half of the virus particles in the MF compartment were not recovered by hydraulic backwashing, indicating that the virus might have been retained on the MF membrane as part of an irreversible foulant. © IWA Publishing 2007.
  • 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.
  • Matsushita, T, Le-Clech, P, Chen, V, Wickramasinghe, S.R
    Desalination 199 1-3 105 - 107 2006年11月 [査読有り][通常論文]
  • Matsui, Y, Narita, K, Inoue, T, Matsushita, T
    Transactions of the ASABE 49 6 1723 - 1735 2006年11月 [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-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.
  • Matsushita, T, Matsui, Y, Matsui, Y
    Chemosphere 64 1 144 - 151 2006年06月 [査読有り][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.
  • Matsui, Y, Narita, K, Inoue, T, Matsushita, T
    Water Science and Technology 53 10 173 - 181 2006年 [査読有り][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.
  • Matsushita, T, Matsui, Y, Shirasaki, N
    Water Science and Technology 53 7 199 - 207 2006年 [査読有り][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.
  • Matsui, Y, Sanogawa, T, Aoki, N, Mima, S, Matsushita, T
    Water Science and Technology: Water Supply 6 1 149 - 155 2006年 [査読有り][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.
  • Matsushita, T, Matsui, Y, Saeki, R, Inoue, T
    Chemosphere 61 8 1134 - 1141 2005年12月 [査読有り][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.
  • Matsushita, T, Matsui, Y, Shirasaki, N, Kato, Y
    Desalination 178 1-3 21 - 26 2005年07月 [査読有り][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.
  • 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 THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES 2005年 [査読有り]
     
    酸性雨の影響等による水質変化を的確に捉えその現象を解明するためには，水質の連続観測データが必要となる．pHと電気伝導率(EC)は水質の代表的な指標であるが，特にpHの連続観測は測定が難しいため行われてこなかった．本研究では，pHの連続観測手法の確立を目的に，岐阜県伊自良湖流入河川の伊自良川で，pHとECについて，2001年から4年間の長期間にわたり河川水中にセンサーを設置して連続観測を行った．連続観測によるpH値と採水した試水のpH測定値では異なっていたが，試水のpH測定値を用いて連続観測データを補正することで，降雨時を含めた長期間のpHの変化を連続的に観測することができた．ただし，降雨時にpHが低下した後の上昇時には，連続観測値に一時間程度の遅れが生じていた．ECは，補正することなく連続観測が可能であった．降雨時には，他の渓流河川での観測と同様に流量増加時のpHとECの低下，流量減少時の上昇が見られ，この変化を短い時間間隔で観測することができた．融雪時には，pHの低下に対してECが上昇する傾向も見られ，降雨時とは流出パターンが異なり，降雨時よりも複雑な反応が生じている可能性が示唆された.
  • 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 [査読有り]
     
    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.
  • Enhancing adsorption-membrane hybrid system with microground activated carbon
    Matsui, Y, Fukuda, Y, Inoue, T, Matsushita, T, Aoki, N, Mima, S
    Water Science and Technology: Water Supply 4 5-6 189 - 197 2005年 [査読有り][通常論文]
  • Matsui, Y, Inoue, T, Matsushita, T, Yamada, T, Yamamoto, M, Sumigama, Y
    Water Science and Technology 51 3-4 329 - 337 2005年 [査読有り][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.
  • Ceramic MF with submicron-sized activated carbon adsorption and coagulation pretreatments for rapid and effective NOM removal
    Matsui, Y, Fukuda, Y, Murase, R, Aoki, N, Mima, S, Inoue, T, Matsushita, T
    Water and Environmental Management Series (WEMS) 8 23 - 32 2005年 [査読有り][通常論文]
  • Matsushita, T, Matsui, Y, Matsui, Y, Inoue, T
    Journal of Environmental Science and Health Part B 40 6 851 - 861 2005年 [査読有り][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.
  • Matsui, Y, Murase, R, Sanogawa, T, Aoki, N, Mima, S, Inoue, T, Matsushita, T
    Water Science and Technology 51 6-7 249 - 256 2005年 [査読有り][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.
  • Matsushita, T, Matsui, Y, Inoue, T
    Water Science and Technology 50 12 201 - 206 2004年 [査読有り][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.
  • Matsui, Y, Murase, R, Sanogawa, T, Aoki, N, Mima, S, Inoue, T, Matsushita, T
    Water Science and Technology: Water Supply 4 4 155 - 163 2004年 [査読有り][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.
  • Inoue, T, Matsui, Y, Terada, Y, Baba, K, Matsushita, T
    Water Science and Technology 50 12 71 - 78 2004年 [査読有り][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.
  • Matsui, Y, Fukuda, Y, Inoue, T, Matsushita, T
    Water Research 37 18 4413 - 4424 2003年11月 [査読有り][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.
  • Matsui, Y, Matsushita, T, Sakuma, S, Gojo, T, Mamiya, T, Suzuoki, H, Inoue, T
    Environmental Science & Technology 37 22 5175 - 5180 2003年11月 [査読有り][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.
  • Matsushita, T, Matsui, Y, Ikeba, K, Inoue, T
    Chemosphere 50 3 275 - 282 2003年01月 [査読有り][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.
  • Matsui, Y, Matsushita, T, Inoue, T, Yamamoto, M, Hayashi, Y, Yonekawa, H, Tsutsumi, Y
    Water Science and Technology: Water Supply 3 5 93 - 99 2003年 [査読有り][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.
  • Matsushita, T, Matsui, Y, Taniwaki, S, Inoue, T
    Chemosphere 47 1 9 - 14 2002年04月 [査読有り][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.
  • Matsushita, T, Matsui, Y, Sakuma, S, Inoue, T
    Mutation Research 516 1-2 71 - 79 2002年04月 [査読有り][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.
  • Matsui, Y, Itoshiro, S, Buma, M, Matsushita, T, Hosogoe, K, Yuasa, A, Shinoda, S, Inoue, T
    Water Science and Technology 45 9 141 - 148 2002年 [査読有り][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.
  • Matsushita, T, Sakuma, S, Nakamuro, K, Matsui, Y
    Water Research 35 11 2589 - 2594 2001年08月 [査読有り][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
  • 松下拓, 中道広隆, 伊藤禎彦, 住友恒
    環境工学研究論文集 34 29 - 34 Japan Society of Civil Engineers 1997年 [査読有り]
     
    Safety of herbicide CNP during aerobic biological treatment. was evaluated. Batch biodegradation experiments with bacteria which was accumulated from Lake Biwa water were carried out. It was found that these bacteria decomposed CNP releasing all chlorine atoms of CNP in the culturemedium within 96 hours of cultivation. A by-product of CNP, C6H2Cl3-O-C6H5 was found by mass spectrum analysis with gas chromatograph. Chromosomal aberration test using Chinese hamster lung (CHL) cell was carried out to evaluate mutagenic activity of aerobic biological treated water including CNP. It was found that thecontribution of CNP to activity inducing aberrations of biological treated water decreased. On the other hand, the contribution of the by-products of CNP was increased. As a result, activity inducing aberrations of treated waterdid not reach the control test level.

MISC

所属学協会

  • 土木学会   日本水環境学会   International Water Association (IWA)   

共同研究・競争的資金等の研究課題

  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2022年04月 -2025年03月 
    代表者 : 白崎 伸隆, 松下 拓
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2021年04月 -2024年03月 
    代表者 : 松井 佳彦, 松下 拓, 白崎 伸隆
  • 遺伝子組換と非ウイルスベクター技術を用いた培養に頼らないウイルスの浄水処理性評価
    日本学術振興会：基盤研究(A)（代表）
    研究期間 : 2022年 -2024年 
    代表者 : 松下 拓
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2021年07月 -2023年03月 
    代表者 : 松井 佳彦, 松下 拓
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2019年04月 -2022年03月 
    代表者 : 白崎 伸隆, 松井 佳彦, 松下 拓
     
    本研究では，PCR法に加えて，ウイルスの外殻タンパク質の損傷を捉えることが可能なPMAxx-Enhancer-PCR法を適用することにより，水道原水における病原ウイルスの存在実態を詳細に把握した．また，凝集-MF膜ろ過処理を実施している実浄水処理場における病原ウイルスの処理性と病原ウイルスの代替指標として期待されているトウガラシ微斑ウイルスの処理性を比較することに成功した．加えて，金ナノ粒子に遺伝子を複数結合させた遺伝子結合金ナノ粒子を用いることにより，PCR法にて高感度に定量可能な遺伝子封入ウイルス様粒子（遺伝子封入VLPs）の作製に成功した．
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2016年05月 -2021年03月 
    代表者 : 松井 佳彦, 松下 拓, 白崎 伸隆
     
    超微粉炭はバイオポリマーの吸着除去に優れ、膜ファウリングを抑制した超微粉炭プレコート膜ろ過法を提案した。微粉炭は塩素共存下で酸化の触媒として有効であり、溶存２価マンガンを表面に酸化析出し、膜で分離除去する新規処理方法を提案した。経年使用した粒状活性炭の微粉砕により再利用可能である。ヒ素や微粉炭、ウイルスの除去に優れた高塩基度ポリ塩化アルミニウム凝集剤に成功し、原水中の硫酸イオンにより適用性が異なること、さらに微粉炭やマイクロプラスチック粒子の凝集・沈殿・砂ろ過後の残留性と制御因子を明らかにした。VUV・オゾンマイクロバブルによる促進酸化分解と、さらに還元的な分解も生じていることを明らかにした。
  • 培養に頼らないウイルスの浄水処理性評価手法と高効率浄水ウイルス処理システムの構築
    日本学術振興会：基盤研究(A)（代表）
    研究期間 : 2018年 -2021年 
    代表者 : 松下 拓
  • 「見える」ファウリング物質を用いた膜ファウリングメカニズムの根本的解明
    日本学術振興会：挑戦的研究（萌芽）（代表）
    研究期間 : 2019年 -2020年 
    代表者 : 松下 拓
  • 代謝を考慮したコリンエステラーゼ活性阻害試験の構築とそれを用いた有機リン系農薬由来分解物の毒性評価
    フソウ技術開発振興基金：フソウ技術開発振興基金研究助成（代表）
    研究期間 : 2018年 -2019年 
    代表者 : 松下 拓
  • ＤＮＡを封入したウイルス外套蛋白粒子を用いた培養困難なウイルスの浄水処理性評価
    日本学術振興会：挑戦的研究（萌芽）（代表）
    研究期間 : 2017年 -2018年 
    代表者 : 松下 拓
  • 有機リン系農薬の塩素処理工程における毒性の変動と毒性に寄与する分解生成物の同定
    フソウ技術開発振興基金：フソウ技術開発振興基金研究助成（代表）
    研究期間 : 2017年 -2018年 
    代表者 : 松下 拓
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2012年05月 -2017年03月 
    代表者 : 松井 佳彦, 松下 拓, 白崎 伸隆
     
    微粉炭が示す吸着容量増加のメカニズムとしてShell Adsorption Modelを実証し，さらに低競合吸着性を解明し，超微粒子吸着材の最適粒度を推定した．放射性ヨウ素の高い除去性，使用済粒状活性炭を微粉砕により再利用可能なことを示した．低アルミニウム残留性や高いウイルス除去性などを可能とするための凝集剤ポリ塩化アルミニウムの有効成分とその製造反応条件などが分かった．紫外線酸化分解の基本的分解性能を把握し，酸化分解副生成物の安全性評価を行った．高塩基度ポリ塩化アルミニウム凝集剤による前凝集処理が膜処理における膜ろ過ファウリングを抑制し，アルミニウムのサイズやSiの関連を見出した．
  • 遺伝子組換で発現した外套タンパクを用いた培養不可能なウイルスの浄水処理性の評価
    日本学術振興会：基盤研究(B)（代表）
    研究期間 : 2015年 -2017年 
    代表者 : 松下 拓
  • ヒト嗅覚を検出器としたGC/MS法の確立とそれを用いた浄水異臭味の全体像の把握
    日本学術振興会：挑戦的萌芽研究（代表）
    研究期間 : 2015年 -2016年 
    代表者 : 松下 拓
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2013年04月 -2015年03月 
    代表者 : 松井 佳彦, 松下 拓
     
    粉末活性炭を微粒度化すると平衡吸着容量が増加することがジェオスミンなどいくつかの物質で見られるが，これは活性炭粒子内の吸着量の偏在を仮定したShell Adsorption Model（SAM）で説明されてきた．本研究では，同位体顕微鏡と重水素標識した吸着質を用い，活性炭粒子内の吸着分布を直接観察した．その結果，吸着容量が増加する場合は，吸着量指標の重水素／水素比が活性炭内部よりも外表面付近で高いことが分かった．吸着等温線をSAMで解析して予測した活性炭内部の吸着量分布は，重水素／水素比から求めた分布と概ね一致した．活性炭粒子内の吸着量の偏在を直接観察し，吸着容量増加のメカニズムを検証した．
  • VLPsを用いた培養不可能なウイルスの浄水処理性評価
    日本学術振興会：基盤研究(B)（代表）
    研究期間 : 2012年 -2014年 
    代表者 : 松下 拓
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2009年05月 -2013年03月 
    代表者 : 松井 佳彦, 松下 拓, 大野 浩一
     
    通常の粉末活性炭に比べて超微粉炭は,自然由来有機物質とそのモデル物質であるポリスチレンスルホン酸(PSS)の高い平衡吸着容量を有する.この高い平衡吸着容量は,吸着質が活性炭粒子内部を拡散せず外表面付近に吸着するためであることを明らかにした.さらに,硫黄元素を指標にして,活性炭粒子の外表面付近にPSSが吸着していることを走査型電子顕微鏡/エネルギー分散型X線分析により直接観察した.Shell Adsorption Model(SAM)を提唱し,平衡吸着容量の活性炭粒径依存性を定量的に評価した.SAMをBranched pore kinetic modelに導入することで,吸着速度の活性炭粒径依存性を評価した.また,超微粉炭を膜分離のための凝集前処理の前に添加すると,ろ過運転に伴う膜間差圧の上昇を抑制することを示した.この理由を,フロック形成と膜ファウリング物質から明らかにした.
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2011年 -2012年 
    代表者 : 松井 佳彦, 松下 拓
     
    ジェオスミンと2-メチルイソボルネオールの活性炭吸着容量の活性炭粒径依存性を2種類の活性炭を用いて検討した.重水素で標識したジェオスミンと2-メチルイソボルネオールを吸着した活性炭粒子を同位体顕微鏡で観察し,重水素/水素比を指標にしてジェオスミンと2-メチルイソボルネオールの吸着分布を求めた.その結果,活性炭粒径が小さくなると吸着容量が増加する活性炭では,ジェオスミンと2-メチルイソボルネオールが主に活性炭粒子の外表面付近に吸着していることを明らかにした.この結果は,超微粉炭の高い吸着容量は,ShellAdsorptionMechanism,すなわち,吸着質が活性炭粒子内部へ拡散せず外表面付近に吸着する機序によることを示している.さらに,ジェオスミンと2-メチルイソボルネオールが活性炭粒子内部に吸着する場合は,通常の粉末活性炭に比べて超微粉炭が競合吸着物質である自然由来有機物質を多く吸着しても,ジェオスミンと2-メチルイソボルネオールの吸着性が低下しないことを明らかにした.
  • VLPを用いたノロウイルスの浄水処理性評価
    日本学術振興会：若手研究(A)（代表）
    研究期間 : 2009年 -2011年 
    代表者 : 松下 拓
  • 遺伝子組換で発現した外套タンパクを用いたノロウイルス浄水処理性の評価
    クリタ水・環境科学振興財団：クリタ水・環境科学振興財団助成（代表）
    研究期間 : 2009年 -2010年 
    代表者 : 松下 拓
  • 日本学術振興会：科学研究費助成事業
    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homogeneous surface diffusion model (HSDM)とbranched pore kinetic model (BPKM)で解析したところ, 活性炭粒子の微粒度化に伴い, 吸着除去速度の律速段階が, 粒子内のマクロ孔やメソ孔を通じた半径方向の拡散から, ローカルなミクロ孔の拡散へ移行することがわかった. そのためHSDM では見かけ上拡散係数が減少することになる. 微粉炭の粒度と吸着除去性の関連をBPKMで検討し, 除去対象をジェオスミンに想定した場合の最適粒径は1μm付近であり, 1μm以下まで粉砕しても除去効率の向上はあまりないことがわかった. 微粒度化は市販の木質, ヤシ殻, 石炭系のすべての活性炭で有効であることも確認した. 膜の前処理としての微粉炭の添加は, 薬品洗浄までの長期的膜間差圧上昇のみならず逆洗浄までの短期的膜間差圧上昇の抑制にも効果的なことが分かった. この理由は微粉炭添加により膜ファウリング物質が活性炭へ吸着されるためと, 微粉炭添加により粒子間の衝突頻度が高まりさらに凝集剤消費物質であるNOMが予め吸着除去されるためにより大きな透水性の高いフロック粒子が形成されるためであることを明らかにした.
  • ウイルス外套タンパク粒子を用いたノロウイルスの浄水処理性の検討
    日本学術振興会：若手研究(B)（代表）
    研究期間 : 2007年 -2008年 
    代表者 : 松下 拓
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2005年 -2007年 
    代表者 : 李 富生, 鈴木 譲, 湯浅 晶, 松下 拓
     
    河川や湖沼などの水道水源域には,自然由来のフミン質や下水の生物処理工程で生み出される生物代謝有機物のほかに,産業・社会活動に起因する微量有機化学物質が数多く混入されている.なかには,極微量の濃度であっても,長期間の暴露によって無処置の生物とその子孫に悪影響をもたせるものとして,最近では,人畜由来の17βエストラジオール(E2)やエストロン(E1)などの天然女性ホルモン物質,ヒトと家畜の病気治療や予防に使用されている抗生物質が強く縣念されている.自然水域の保全,特に水道水質のリスクの軽減と未然防止を図るためには,水域内における関係物質の消長挙動を解明し,その挙動を診断・予測しうる手法を構築していくことが大変重要である. そこで本研究では,安全リスクが著しく高く,自然水域で普遍的に検出されている人畜由来の女性ホルモン類物質を主な対象物質とし,岐阜県を流下する長良川本川と支川の水と底泥,および閉鎖性ダム湖水域の底泥を用いた回分式実験・連続流式カラム通水実験を行い,対象物質の消長挙動と消長のメカニズムを評価するとともに,その動態の診断・予測するための数値解析を行った.また,自然水域における微生物の種と密度には下水放流水からの影響を受け,かつ,対象物質の存在量と形態には下水処理工程での生分解効率によって異なるため,半連続流式活性汚泥反応場における女性ホルモンの挙動とそれに与える操作条件や共存生物易分解性物質の影響も評価した.また,家畜の病気の治療や予防に多く用いられている抗生物質の挙動について,長良川の河床微生物を植種した生物活性炭充填カラムを用いて検討を行った.これらの一連の検討を通じて,対象物質の消長挙動と機構を明らかにし,系統的な予測手法の構築に寄与する有用な知見を多く得た.
  • 日本学術振興会：科学研究費助成事業
    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ジェオスミン除去性が格段に優れていることが分かった.膜の前処理としての微粉炭の添加は,薬品洗浄までの長期的膜問間圧上昇のみならず逆洗浄までの短期的膜間差圧上昇の抑制にも効果的なことが分かった.本研究より,分離膜への流入途中に超微粉化活性炭を添加するだけで処理水質が向上することが示唆された.
  • 日本学術振興会：科学研究費助成事業
    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.
  • 環境中での農薬の光／微生物分解に伴う遺伝子毒性の変動
    日本学術振興会：若手研究(B)（代表）
    研究期間 : 2004年 -2005年 
    代表者 : 松下 拓
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2002年 -2004年 
    代表者 : 井上 隆信, 松井 佳彦, 松下 拓
     
    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。 これらの結果から、連続抽出法により、藻類利用可能態リンを定量評価することは可能であると考えられる。ただし、どの分画が藻類に利用されるかは、対応が必ずしも明確にされていないため、今後さらに検討する必要がある。本研究において、藻類利用可能態リンの定量方法の方向性を示すことができた。今後、連続抽出法を改良し、藻類増殖試験を組み合わせてどの分画が藻類利用可能リンかを明らかにすることで、藻類利用可能態リンの定量法が確立できる。
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2002年 -2004年 
    代表者 : 松井 佳彦, 井上 隆信, 松下 拓
     
    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。
  • 嫌気好気条件の変化に伴う環境化学物質の微生物分解代謝物の遺伝子毒性の変動
    日本学術振興会：若手研究(B)（代表）
    研究期間 : 2002年 -2003年 
    代表者 : 松下 拓
  • 日本学術振興会：科学研究費助成事業
    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た流出解析値は河川水中の農薬の観測値に近い値となり,農薬流出予測の精度が高いことが示された. (2)水田ごとの正確な農薬使用量や散布日が不明であっても,流域全体の農薬使用量を把握することができれば,農薬の流出予測が可能であることが示唆された.
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2001年 -2003年 
    代表者 : 湯浅 晶, 李 富生, 井上 隆信, 松井 佳彦, 佐藤 三生男, 松下 拓
     
    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.
  • 日本学術振興会：科学研究費助成事業
    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.さらに各種試験片の脱離に必要な抗力は引張試験で測定した脱離力と比較すると平均で1/5程度であることを確認した.また,脱離時に足糸繊維部が切断する場合に限って,カワヒバリガイの殻長と足糸数からその成貝を脱離するために必要な流速を推定した.その結果,足糸数が一定であると仮定した場合,カワヒバリガイが成長するにしたがって脱離に必要な流速が増加する可能性を確認した.
  • 染色体異常誘発性と遺伝子毒性からみた環境化学物質の微生物分解の安全評価実験
    日本学術振興会：奨励研究(A)（代表）
    研究期間 : 2000年 -2001年 
    代表者 : 松下 拓

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