研究者データベース

研究者情報

マスター

アカウント(マスター)

  • 氏名

    白崎 伸隆(シラサキ ノブタカ), シラサキ ノブタカ

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

  • 2020, 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
  • 2020, 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
  • 2020, 流体工学Ⅱ, Fluid Mechanics II, 学士課程, 工学部, 流体,流れ,乱流,管路,ポンプ,拡散
  • 2020, 反応工学, Chemical Reaction Engineering, 学士課程, 工学部, 工業反応速度論,物質収支,流体混合モデル
  • 2020, 反応工学演習, Exercise in Chemical Reaction Engineering, 学士課程, 工学部, 工業反応速度論,物質収支,流体混合モデル
  • 2020, 環境リスク解析学, Human health risk assessment for environmental engineering, 学士課程, 工学部, 健康リスク,有害性の同定,曝露,用量―反応関係,リスクの評価

researchmap

プロフィール情報

学位

  • 博士(工学)(北海道大学)

プロフィール情報

  • 白崎, シラサキ
  • 伸隆, ノブタカ
  • ID各種

    201001099728627820

対象リソース

業績リスト

研究キーワード

  • ウイルス除去   新規ウイルス定量法   水系感染症   ウイルス不活化   セラミック膜   新規凝集剤   新規吸着材   浄水処理   ウイルス   

研究分野

  • 社会基盤(土木・建築・防災) / 土木環境システム

経歴

  • 2020年04月 - 現在 北海道大学 大学院工学研究院 環境工学部門 環境工学分野 准教授
  • 2019年03月 - 2020年03月 北海道大学 大学院工学研究院 環境創生工学部門 水代謝システム分野 准教授
  • 2011年01月 - 2019年02月 北海道大学 大学院工学研究院 環境創生工学部門 水代謝システム分野 助教
  • 2010年04月 - 2010年12月 日本学術振興会特別研究員(PD)
  • 2009年04月 - 2010年03月 日本学術振興会特別研究員(DC2)

学歴

  • 2007年04月 - 2010年03月   北海道大学   工学研究科   環境創生工学専攻
  • 2005年04月 - 2007年03月   岐阜大学   工学研究科   土木工学専攻
  • 2003年04月 - 2005年03月   岐阜大学   工学部   土木工学科
  • 1998年04月 - 2003年03月   福井工業高等専門学校   環境都市工学科

委員歴

  • 2020年 - 現在   札幌市営企業調査審議会   委員
  • 2019年 - 現在   土木学会環境工学委員会   委員
  • 2019年 - 現在   日本水環境学会 北海道支部   会計
  • 2012年 - 現在   北海道大学 衛生工学シンポジウム   実行委員
  • 2017年 - 2018年   日本水環境学会 第52回日本水環境学会年会   実行委員
  • 2013年 - 2015年   日本水環境学会 北海道支部   幹事
  • 2011年   日本水環境学会 第45回日本水環境学会年会   実行委員   日本水環境学会
  • 2010年   日本水環境学会 若手の会   幹事   日本水環境学会

受賞

  • 2021年 北海道大学大学院工学研究院 若手教員奨励賞
     
    受賞者: 白崎伸隆
  • 2021年 遠山椿吉記念 第7回食と環境の科学賞 山田和江賞
     
    受賞者: 白崎伸隆
  • 2019年 平成30年度建設工学研究振興会 建設工学研究奨励賞
     
    受賞者: 白崎伸隆
  • 2017年 平成29年度クリタ水・環境科学研究優秀賞
     
    受賞者: 白崎伸隆
  • 2015年 平成26年度日本水環境学会 論文奨励賞 (廣瀬賞)
     
    受賞者: 白崎伸隆
  • 2013年 土木学会平成25年度全国大会第68回年次学術講演会 優秀講演者表彰
     
    受賞者: 白崎伸隆
  • 2013年 第2回エヌエフ基金 研究開発奨励賞 (環境・エネルギー)
     
    受賞者: 白崎伸隆
  • 2013年 第49回環境工学研究フォーラム 論文賞
     
    受賞者: 白崎伸隆;松下拓;松井佳彦;大芝淳
  • 2013年 平成25年度前田記念工学振興財団 設立20周年記念特別論文賞 最優秀賞
     
    受賞者: 白崎伸隆
  • 2012年 平成24年度前田記念工学振興財団 山田一宇賞
     
    受賞者: 白崎伸隆
  • 2012年 平成24年度文部科学大臣表彰 若手科学者賞
     
    受賞者: 白崎伸隆
  • 2011年 平成22年度土木学会 論文奨励賞
     
    受賞者: 白崎伸隆
  • 2010年 第46回環境工学研究フォーラム 論文奨励賞
     
    受賞者: 白崎伸隆
  • 2009年 第12回日本水環境学会シンポジウム若手研究紹介(オルガノ)セッション 最優秀発表賞
     
    受賞者: 白崎伸隆
  • 2009年 平成21年度日本水環境学会 博士研究奨励賞(オルガノ賞)
     
    受賞者: 白崎伸隆
  • 2008年 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: 白崎伸隆;浦崎稔史;小泓誠;松下拓;松井佳彦;大野浩一
  • 2005年 平成16年度土木学会中部支部 優秀研究発表賞
     
    受賞者: 白崎伸隆
  • 2005年 岐阜大学工学部土木工学科 平成16年度優秀卒業研究賞
     
    受賞者: 白崎伸隆
  • 2003年 全国高等専門学校土木工学会 近藤賞
     
    受賞者: 白崎伸隆

論文

  • Yoshifumi Nakazawa, Taketo Abe, Yoshihiko Matsui, Koki Shinno, Sakiko Kobayashi, Nobutaka Shirasaki, Taku Matsushita
    Water Research 203 2021年09月15日 
    One of the main purposes of drinking water treatment is to reduce turbidity originating from clay particles. Relatively little is known about the removal of other types of particles, including conventionally sized powdered activated carbon (PAC) and superfine PAC (SPAC), which are intentionally added during the treatment process; microplastic particles; and viruses. To address this knowledge gap, we conducted a preliminary investigation in full-scale water treatment plants and then studied the removal of these particles during coagulation-flocculation, sedimentation, and rapid sand filtration (CSF) in bench-scale experiments in which these particles were present together. Numbers of all target particles were greatly decreased by coagulation-flocculation and sedimentation (CS). Subsequent rapid sand filtration greatly reduced the concentrations of PAC and SPAC but not the concentrations of viruses, microplastic particles, and clay particles. Overall removal rates by CSF were 4.6 logs for PAC and SPAC, 3.5 logs for viruses, 2.9 logs for microplastics, and 2.8 logs for clay. The differences in removals were not explained by particle sizes or zeta potentials. However, for clays, PAC and SPAC, for which the particle size distributions were wide, smaller particles were less efficiently removed. The ratios of both clay to PAC and clay to SPAC particles increased greatly after rapid sand filtration because removal rates of PAC and SPAC particles were about 2 logs higher than removal rates of clay particles. The trend of greater reduction of PAC concentrations than turbidity was confirmed by measurements made in 14 full-scale water purification plants in which residual concentrations of PAC in treated water were very low, 40–200 particles/mL. Clay particles therefore accounted for most of the turbidity in sand filtrate, even though PAC was employed. The removal rate of microplastic particles was comparable to that of clays. Sufficient turbidity removal would therefore provide comparable removal of microplastics. We investigated the effect of mechanical/photochemical weathering on the removal of microplastics via CSF. Photochemical weathering caused a small increment in the removal rate of microplastics during CS but a small reduction in the removal rate of microplastics during rapid sand filtration; mechanical weathering decreased the removal rate via CS but increased the removal rate via rapid sand filtration. The changes of removal of microplastics might have been caused by changes of their zeta potential.
  • Shun Saito, Yoshihiko Matsui, Yasuhiko Yamamoto, Shuhei Matsushita, Satoru Mima, Nobutaka Shirasaki, Taku Matsushita
    Water Research 202 2021年09月01日 
    The authors regret that an error has occurred in this paper. On the pilot plant system described in section 2.2.1, “the hydraulic retention time for the coagulation in the pipe mixing of Line B was 3 min” should be changed to “the hydraulic retention time for the coagulation in the pipe mixing of Line B was 4.4 min”. Because of the error, several corrections noted below should be conducted. In abstract, section 3.1, and conclusion (1), SPAC and chlorine contact time of 4 min is replaced by 5.4 min. In Panel A of Fig. 8, the yellow plots of the pilot experiment (Run 1), to be exact their y-axis positions, are somewhat changed. The corrected figure is presented here. In section 3.4, “The kC values of the pilot experiment were higher than those of the batch experiments” is changed to “The kC values of the pilot experiment were similar to those of the batch experiments". The authors would like to apologise for any inconvenience caused. DOI of original article: < https://doi.org/10.1016/j.watres.2020.116412 >
  • Taku Matsushita, Yuji Kikkawa, Kei Omori, Yoshihiko Matsui, Nobutaka Shirasaki
    Chemical Research in Toxicology 2021年08月10日
  • Gang Shi, Shota Nishizawa, Taku Matsushita, Yuna Kato, Takahiro Kozumi, Yoshihiko Matsui, Nobutaka Shirasaki
    Water Research 197 2021年06月01日 
    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.
  • Yoshifumi Nakazawa, Taketo Abe, Yoshihiko Matsui, Nobutaka Shirasaki, Taku Matsushita
    Water Research 190 2021年02月15日 
    © 2020 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-chambered-reactor 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.
  • Kentaro Narita, Yoshihiko Matsui, Taku Matsushita, Nobutaka Shirasaki
    Science of the Total Environment 751 2021年01月10日 [査読有り][通常論文]
     
    © 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.
  • Shun Saito, Yoshihiko Matsui, Yasuhiko Yamamoto, Shuhei Matsushita, Satoru Mima, Nobutaka Shirasaki, Taku Matsushita
    Water Research 187 2020年12月15日 [査読有り][通常論文]
     
    © 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.
  • Taku Matsushita, Yuki Fujita, Kei Omori, Yuxiang Huang, Yoshihiko Matsui, Nobutaka Shirasaki
    Chemosphere 261 2020年12月 [査読有り][通常論文]
     
    © 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.
  • N. Shirasaki, T. Matsushita, Y. Matsui, S. Koriki
    Water Research 186 2020年11月01日 [査読有り][通常論文]
     
    © 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.
  • Shota Nishizawa, Taku Matsushita, Yoshihiko Matsui, Nobutaka Shirasaki
    Science of the Total Environment 737 2020年10月01日 [査読有り][通常論文]
     
    © 2020 Elsevier B.V. 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.
  • Yize Chen, Yoshifumi Nakazawa, Yoshihiko Matsui, Nobutaka Shirasaki, Taku Matsushita
    Water Research 183 2020年09月15日 [査読有り][通常論文]
     
    © 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.
  • Akiko Nakayama, Asuka Sakamoto, Taku Matsushita, Yoshihiko Matsui, Nobutaka Shirasaki
    Water Research 182 2020年09月01日 [査読有り][通常論文]
     
    © 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.
  • Yuanjun Zhao, Ryosuke Kitajima, Nobutaka Shirasaki, Yoshihiko Matsui, Taku Matsushita
    Water Research 177 2020年06月15日 [査読有り][通常論文]
     
    © 2020 Elsevier Ltd Commercially available powdered activated carbon (PAC) with a median diameter of 12–42 μm was ground into 1 μm 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.
  • Taku Matsushita, Wataru Sugita, Tomoya Ishikawa, Gang Shi, S. Nishizawa, Yoshihiko Matsui, Nobutaka Shirasaki
    Water Research 164 2019年11月01日 [査読有り][通常論文]
     
    © 2019 Elsevier Ltd 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•, nitrate became influential only after being transformed into nitrite by concomitant UV light (λ = 254 nm) irradiation. Cl-related radicals (Cl• and Cl2•−) 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.
  • Shunto Nishikawa, Yoshihiko Matsui, Taku Matsushita, Nobutaka Shirasaki
    Regulatory Toxicology and Pharmacology 106 43 - 49 2019年08月 [査読有り][通常論文]
     
    © 2019 Elsevier Inc. 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 μg/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.
  • Hideki Takaesu, Yoshihiko Matsui, Yuki Nishimura, Taku Matsushita, Nobutaka Shirasaki
    Water Research 155 66 - 75 2019年05月15日 [査読有り][通常論文]
     
    © 2019 Elsevier Ltd 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 18O content in the SPAC particles after milling in water-18O indicated that the oxygen in the functional groups originated from the surrounding water.
  • Yoshifumi Nakazawa, Yoshihiko Matsui, Yusuke Hanamura, Koki Shinno, Nobutaka Shirasaki, Taku Matsushita
    Water Research 147 311 - 320 2018年12月15日 [査読有り][通常論文]
     
    © 2018 Elsevier Ltd 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 PACl (poly-aluminum chloride) coagulants, PACl 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. PACls 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 PACl by Al(OH)3-dissolution, and their charge-neutralization capacities were higher. PACls 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.
  • 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]
     
    © 2018 Elsevier Ltd 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.
  • Yoshifumi Nakazawa, Yoshihiko Matsui, Yusuke Hanamura, Koki Shinno, Nobutaka Shirasaki, Taku Matsushita
    Water Research 138 160 - 168 2018年07月01日 [査読有り][通常論文]
     
    © 2018 Elsevier Ltd Superfine powdered activated carbon (SPAC; particle diameter ∼1 μm) 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 μm (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 particles/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 charge-neutralized 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.
  • Megumi Akiyama, Yoshihiko Matsui, Junki Kido, Taku Matsushita, Nobutaka Shirasaki
    Regulatory Toxicology and Pharmacology 95 161 - 174 2018年06月 [査読有り][通常論文]
     
    © 2018 Elsevier Inc. 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).
  • Taku Matsushita, Shiho Honda, Taisuke Kuriyama, Yuki Fujita, Takashi Kondo, Yoshihiko Matsui, Nobutaka Shirasaki, Hirokazu Takanashi, Takashi Kameya
    Water Research 129 347 - 356 2018年02月01日 [査読有り][通常論文]
     
    © 2017 Elsevier Ltd 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.
  • N. Shirasaki, T. Matsushita, Y. Matsui, R. Yamashita
    Water Research 129 460 - 469 2018年02月01日 [査読有り][通常論文]
     
    © 2017 Elsevier Ltd Here, we evaluated the removal of three representative human enteric viruses — adenovirus (AdV) type 40, coxsackievirus (CV) B5, and hepatitis A virus (HAV) IB — and one surrogate of human caliciviruses — murine norovirus (MNV) type 1 — by coagulation–rapid sand filtration, using water samples from eight water sources for drinking water treatment plants in Japan. The removal ratios of a plant virus (pepper mild mottle virus; PMMoV) and two bacteriophages (MS2 and φX174) were compared with the removal ratios of human enteric viruses to assess the suitability of PMMoV, MS2, and φX174 as surrogates for human enteric viruses. The removal ratios of AdV, CV, HAV, and MNV, evaluated via the real-time polymerase chain reaction (PCR) method, were 0.8–2.5-log10 when commercially available polyaluminum chloride (PACl, basicity 1.5) and virgin silica sand were used as the coagulant and filter medium, respectively. The type of coagulant affected the virus removal efficiency, but the age of silica sand used in the rapid sand filtration did not. Coagulation–rapid sand filtration with non-sulfated, high-basicity PACls (basicity 2.1 or 2.5) removed viruses more efficiently than the other aluminum-based coagulants. The removal ratios of MS2 were sometimes higher than those of the three human enteric viruses and MNV, whereas the removal ratios of φX174 tended to be smaller than those of the three human enteric viruses and MNV. In contrast, the removal ratios of PMMoV were similar to and strongly correlated with those of the three human enteric viruses and MNV. Thus, PMMoV appears to be a suitable surrogate for human enteric viruses for the assessment of the efficacy of coagulation–rapid sand filtration to remove viruses.
  • Taku Matsushita, Yoshihiko Matsui, Shohei Ikekame, Miki Sakuma, Nobutaka Shirasaki
    Environmental Science and Technology 51 8 4541 - 4548 2017年04月 [査読有り][通常論文]
     
    © 2017 American Chemical Society. Mechanisms underlying trichloramine removal with activated carbon treatment were proven by batch experiments and theoretical analysis with diffusion-reaction models. The observed values of trichloramine and free chlorine were explained only by the model in which (1) both trichloramine and free chlorine were involved as reactants, (2) the removals of reactants were affected both by the intraparticle diffusion and by the reaction with activated carbon, and (3) trichloramine decomposition was governed by two distinct reductive reactions. One reductive reaction was expressed as a first-order reaction: the reductive reaction of trichloramine with the basal plane of PAC, which consists of graphene sheets. The other reaction was expressed as a second-order reaction: the reductive reaction of trichloramine with active functional groups located on the edge of the basal plane. Free chlorine competitively reacted with both the basal plane and the active functional groups. The fact that the model prediction succeeded even in experiments with different activated carbon doses, with different initial trichloramine concentrations, and with different sizes of activated carbon particles clearly proved that the mechanisms described in the model were reasonable for explaining trichloramine removal with activated carbon treatment.
  • N. Shirasaki, T. Matsushita, Y. Matsui, K. Murai, A. Aochi
    Journal of Hazardous Materials 326 110 - 119 2017年03月15日 [査読有り][通常論文]
     
    © 2016 Elsevier B.V. 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 (PACl, 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-log10). 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 φX174 were comparable with or smaller than those of the CCL viruses. Therefore, φX174 may be a useful conservative surrogate for CCL viruses during coagulation.
  • N. Shirasaki, T. Matsushita, Y. Matsui, T. Marubayashi, K. Murai
    Science of the Total Environment 576 472  2017年01月15日 [査読有り][通常論文]
     
    © 2016 Elsevier B.V. The authors regret that there was an error done in Table 1 of the article. They would like to change it from “mM-Al” to “μM-Al”. Coagulant dosage at sampling day (mM-Al) → “mM” (millimole) is an error and “μM” (micromole) is the correct one. The authors would like to apologise for any inconvenience caused.
  • Yoshihiko Matsui, Nobutaka Shirasaki, Takuro Yamaguchi, Kenta Kondo, Kaori Machida, Taiga Fukuura, Taku Matsushita
    Water Research 118 177 - 186 2017年 [査読有り][通常論文]
     
    © 2017 Elsevier Ltd 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-Al13 polycation or the δ-Al30 polycation; it is likely to be an aluminum polymer that is unobservable by 27Al 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-Al13 polycation or the δ-Al30 polycation was not indispensable for effective arsenate removal.
  • Long Pan, Yuki Nishimura, Hideki Takaesu, Yoshihiko Matsui, Taku Matsushita, Nobutaka Shirasaki
    Water Research 124 425 - 434 2017年 [査読有り][通常論文]
     
    © 2017 Elsevier Ltd The capacity of activated carbon particles with median diameters (D50s) of >∼1 μm 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 μm have not been thoroughly investigated. Here, we prepared particles with D50s of ∼30 μm–∼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 ∼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.
  • Taku Matsushita, Miki Sakuma, Shiori Tazawa, Taiki Hatase, Nobutaka Shirasaki, Yoshihiko Matsui
    Water Research 125 332 - 340 2017年 [査読有り][通常論文]
     
    © 2017 Elsevier Ltd 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-O 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 15N-labeled phenylalanine suggested that PAC reductively decomposed trichloramine into N2 gas and adsorbed all of the other identified TPs. Superfine PAC (median diameter, 0.7 μm) removed the off-flavor more rapidly than normal-size PAC (median diameter, 8.0 μm).
  • Long Pan, Yuichi Takagi, Yoshihiko Matsui, Taku Matsushita, Nobutaka Shirasaki
    Water Research 114 50 - 58 2017年 [査読有り][通常論文]
     
    © 2017 Elsevier Ltd 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 μm), superfine PAC (SPAC, 0.9–3.5 μm), 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 compounds, 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.
  • N. Shirasaki, T. Matsushita, Y. Matsui, K. Murai
    Water Research 115 29 - 39 2017年 [査読有り][通常論文]
     
    © 2017 Elsevier Ltd 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 φX174) 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 μm 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-log10removal 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 nonsulfated high-basicity PACls containing Al30species had generally a better virus removal (i.e., >4-log10virus removal) than the other aluminum-based coagulants, except for φX174. 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 φX174 were markedly smaller than those obtained for the three human enteric viruses and MNV. However, because MS2 was inactivated after contact with PACl 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 φX174 do not, for the assessment of the efficacy of membrane filtration processes to remove viruses.
  • Long Pan, Yoshihiko Matsui, Taku Matsushita, Nobutaka Shirasaki
    Water Research 102 516 - 523 2016年10月01日 [査読有り][通常論文]
     
    © 2016 Elsevier Ltd 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.
  • N. Shirasaki, T. Matsushita, Y. Matsui, T. Marubayashi, K. Murai
    Science of the Total Environment 563-564 29 - 39 2016年09月01日 [査読有り][通常論文]
     
    © 2016 Elsevier B.V. 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 φX174, 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-log10 and 0.5-2.4-log10, 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 φX174, like AdV and PV, was not inactivated during coagulation, and because the hydrophobicity of φX174 was similar to or somewhat lower than the hydrophobicities of AdV and PV, the φX174 removal ratios tended to be similar to or somewhat smaller than those of the enteric viruses. Therefore, φX174 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.
  • Nobutaka Shirasaki, Taku Matsushita, Yoshihiko Matsui, Takuya Marubayashi
    Journal of Water Supply: Research and Technology - AQUA 65 4 322 - 329 2016年06月 [査読有り][通常論文]
     
    © IWA Publishing 2016. 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.
  • N. Shirasaki, T. Matsushita, Y. Matsui, K. Ohno
    Water Science and Technology: Water Supply 16 3 737 - 745 2016年06月 [査読有り][通常論文]
     
    © IWA Publishing 2016. 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 fromwater 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 recombinantNV 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 nativeNV. 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-VLPswere easy to quantify with a commercially available enzymelinked immunosorbent assay kit, they remained stable for several days at 4 °C after dilution in riverwater, and theywere 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.
  • Taku Matsushita, Masahiro Hashizuka, Taisuke Kuriyama, Yoshihiko Matsui, Nobutaka Shirasaki
    Chemosphere 148 233 - 240 2016年04月 [査読有り][通常論文]
     
    © 2016 Elsevier Ltd. 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 (r2 > 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-{2-3-[(2-hydroxyethoxy)carbonyl]-2,4,6-triiodo-5-nitrobenzoyl}amino)propanoic acid, could be the candidate compounds that contributed to the observed mutagenicity.
  • N. Shirasaki, T. Matsushita, Y. Matsui, T. Marubayashi
    Chemical Engineering Journal 284 786 - 793 2016年 [査読有り][通常論文]
     
    © 2015 Elsevier B.V. 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 Al30 species, indicating that Al30 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.
  • Yoshihiko Matsui, Soichi Nakao, Asuka Sakamoto, Takuma Taniguchi, Long Pan, Taku Matsushita, Nobutaka Shirasaki
    Water Research 85 95 - 102 2015年11月05日 [査読有り][通常論文]
     
    © 2015 Elsevier Ltd. 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.
  • Taku Matsushita, Nozomi Kobayashi, Masahiro Hashizuka, Haruki Sakuma, Takashi Kondo, Yoshihiko Matsui, Nobutaka Shirasaki
    Chemosphere 135 101 - 107 2015年09月01日 [査読有り][通常論文]
     
    © 2015 Elsevier Ltd. 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 96h). The areas of five out of 54 peaks detected on the LC/MS total ion chromatogram had good correlation (r2>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.
  • Masaoki Kimura, Yoshihiko Matsui, Shun Saito, Tomoya Takahashi, Midori Nakagawa, Nobutaka Shirasaki, Taku Matsushita
    Journal of Membrane Science 477 115 - 122 2015年03月01日 [査読有り][通常論文]
     
    © 2014 Elsevier B.V. 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 (PACl) 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 PACls, floc-size changes did not affect transmembrane pressure (TMP) buildup and thus did not affect irreversible fouling. Differences in PACl basicity, which affected the distribution of aluminum species, resulted in changes to the degree of irreversible fouling.Pretreatment with high-basicity (71%) PACl was superior to pretreatment with normal-basicity (51%) PACl 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, TMP buildup was the same for PACls with basicities of 71% and 90%; therefore, TMP buildup is not simply related to Al breakthrough and deposition. Increasing the basicity of PACls 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.
  • Miki Sakuma, Taku Matsushita, Yoshihiko Matsui, Tomoko Aki, Masahito Isaka, Nobutaka Shirasaki
    Water Research 68 839 - 848 2015年01月01日 [査読有り][通常論文]
     
    © 2014 Elsevier Ltd. 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 15N-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 1μm 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°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.
  • Mariya Ikari, Yoshihiko Matsui, Yuta Suzuki, Taku Matsushita, Nobutaka Shirasaki
    Water Research 68 227 - 237 2015年01月01日 [査読有り][通常論文]
     
    © 2014 Elsevier Ltd. 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 (1mg-Cl2/L) removed 90% of the iodine in NOM-containing water (dissolved organic carbon concentration, 1.5mg-C/L). Iodine removal in NOM-containing water increased with increasing chlorine dose up to 0.1mg-Cl2/L but decreased at chlorine doses of >1.0mg-Cl2/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 IO3- However, the effect of Br- was small in the NOM-containing water because organic-I formed instead of IO3- SPAC (median particle diameter, 0.62μm) had a higher equilibrium adsorption capacity for organic-I than did conventional PAC (median diameter, 18.9μm), 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.
  • T. Matsushita, S. Hirai, T. Ishikawa, Y. Matsui, N. Shirasaki
    Process Safety and Environmental Protection 94 C 528 - 541 2015年 [査読有り][通常論文]
     
    © 2014 The Institution of Chemical Engineers. 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 (GAC) or biological activated carbon (BAC). Nitrite was produced by VUV treatment but disappeared after subsequent BAC treatment. These results suggest that VUV treatment should be combined with GAC or BAC treatment to suppress by-product formation.
  • Taku Matsushita, Keisuke Nakamura, Yoshihiko Matsui, Nobutaka Shirasaki
    Membrane Water Treatment 6 3 225 - 235 2015年 [査読有り][通常論文]
     
    © 2015 Techno-Press, Ltd. 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.
  • Yoshihiko Matsui, Asuka Sakamoto, Soichi Nakao, Takuma Taniguchi, Taku Matsushita, Nobutaka Shirasaki, Naoya Sakamoto, Hisayoshi Yurimoto
    Environmental Science and Technology 48 18 10897 - 10903 2014年09月16日 [査読有り][通常論文]
     
    © 2014 American Chemical Society. Decreasing the particle size of powdered activated carbon may enhance its equilibrium adsorption capacity for small molecules and micropollutants, such as 2-methylisoborneol (MIB) and geosmin, as well as for macromolecules and natural organic matter. Shell adsorption, in which adsorbates do not completely penetrate the adsorbent but instead preferentially adsorb near the outer surface of the adsorbent, may explain this enhancement in equilibrium adsorption capacity. Here, we used isotope microscopy and deuterium-doped MIB and geosmin to directly visualize the solid-phase adsorbate concentration profiles of MIB and geosmin in carbon particles. The deuterium/hydrogen ratio, which we used as an index of the solid-phase concentration of MIB and geosmin, was higher in the shell region than in the inner region of carbon particles. Solid-phase concentrations of MIB and geosmin obtained from the deuterium/hydrogen ratio roughly agreed with those predicted by shell adsorption model analyses of isotherm data. The direct visualization of the localization of micropollutant adsorbates in activated carbon particles provided direct evidence of shell adsorption.
  • Kentaro Narita, Yoshihiko Matsui, Kensuke Iwao, Motoyuki Kamata, Taku Matsushita, Nobutaka Shirasaki
    Environment International 63 114 - 120 2014年02月 [査読有り][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. © 2013 The Authors.
  • N. Shirasaki, T. Matsushita, Y. Matsui, A. Oshiba, T. Marubayashi, S. Sato
    Water Research 48 1 375 - 386 2014年01月01日 [査読有り][通常論文]
     
    We investigated the effects of basicity, sulfate content, and aluminum hydrolyte species on the ability of polyaluminum chloride (PACl) coagulants to remove F-specific RNA bacteriophages from river water at a pH range of 6-8. An increase in PACl basicity from 1.5 to 2.1 and the absence of sulfate led to a reduction of the amount of monomeric aluminum species (i.e., an increase of the total amount of polymeric aluminum and colloidal aluminum species) in the PACl, to an increase in the colloid charge density of the PACl, or to both and, as a result, to high virus removal efficiency. The efficiency of virus removal at around pH 8 observed with PACl-2.1c, a nonsulfated high-basicity PACl (basicity 2.1-2.2) with a high colloidal aluminum content, was larger than that observed with PACl-2.1b, a nonsulfated high-basicity PACl (basicity 2.1-2.2) with a high polymeric aluminum content. In contrast, although extremely high basicity PACls (e.g., PACl-2.7ns, basicity 2.7) effectively removed turbidity and UV260-absorbing natural organic matter and resulted in a very low residual aluminum concentration, the virus removal ratio with PACl-2.7ns was smaller than the ratio with PACl-2.1c at around pH 8, possibly as a result of a reduction of the colloid charge density of the PACl as the basicity was increased from 2.1 to 2.7. Liquid 27Al NMR analysis revealed that PACl-2.1c contained Al30 species, which was not the case for PACl-2.1b or PACl-2.7ns. This result suggests that Al30 species probably played a major role in virus removal during the coagulation process. In summary, PACl-2.1c, which has high colloidal aluminum content, contains Al30 species, and has a high colloid charge density, removed viruses more efficiently (>4 log10 for infectious viruses) than the other aluminum-based coagulants-including commercially available PACls (basicity 1.5-1.8), alum, and PACl-2.7ns-over the entire tested pH (6-8) and coagulant dosage (0.54-5.4mg-Al/L) ranges. © 2013 Elsevier Ltd.
  • N. Shirasaki, T. Matsushita, Y. Matsui, T. Urasaki, M. Kimura, K. Ohno
    Water Science and Technology: Water Supply 14 3 429 - 437 2014年 [査読有り][通常論文]
     
    The ability of in-line coagulation pretreatment with high-basicity polyaluminum chloride (PACl) coagulants to enhance virus removal by ceramic microfiltration (MF) was examined by comparing virus removal efficiencies from water pretreated with PACl-2.2 (basicity 2.2) and PACl-2.5 (basicity 2.5) versus alum, a synthetic aluminum chloride (AlCl3) solution, and two commercially available PACls, PACl-1.5 and PACl-1.8. The virus removal ratios for AlCl3, alum, PACl-1.5, and PACl-1.8 decreased markedly when the pH of the treated water shifted from 6.8 to 7.8, but was high at both pHs for PACl-2.2 and PACl-2.5. PACl-2.5 contains 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. © IWA Publishing 2014.
  • Shun Niizuma, Yoshihiko Matsui, Koichi Ohno, Sadahiko Itoh, Taku Matsushita, Nobutaka Shirasaki
    Regulatory Toxicology and Pharmacology 67 1 98 - 107 2013年10月 [査読有り][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%. © 2013 Elsevier Inc.
  • Taku Matsushita, Nobutaka Shirasaki, Yuichi Tatsuki, Yoshihiko Matsui
    Water Research 47 15 5819 - 5827 2013年10月01日 [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 0.1μm could not eliminate NV-VLPs, a 4-log reduction was achieved by UF with a molecular weight cutoff of 1kDa. When MF was combined with precoagulation (≥10μmol-Fe/L for ferric chloride; ≥20μmol-Al/L for polyaluminum chloride; ≥40μmol-Al/L for alum), the performance of the hybrid process in eliminating rNV-VLPs was greater than that achieved by the 1kDa UF. For all processes, the removal ratios of the bacteriophages MS2 and Qβ 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. © 2013 Elsevier Ltd.
  • Masaoki Kimura, Yoshihiko Matsui, Kenta Kondo, Tairyo B. Ishikawa, Taku Matsushita, Nobutaka Shirasaki
    Water Research 47 6 2075 - 2084 2013年04月 [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.
  • Taku Matsushita, Hideaki Suzuki, Nobutaka Shirasaki, Yoshihiko Matsui, Koichi Ohno
    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.
  • Yoshihiko Matsui, Tairyo B. Ishikawa, Masaoki Kimura, Kaori Machida, Nobutaka Shirasaki, Taku Matsushita
    Separation and Purification Technology 119 58 - 65 2013年 [査読有り][通常論文]
     
    The residual aluminum concentration in treated water after aluminum coagulation and solid-liquid separation is one of the key factors in evaluating the effectiveness of water treatments. Polymeric membrane filters have been widely used to operationally define dissolved substances from particulate matter, and have sometimes been employed in laboratories and pilot studies to approximately simulate media filtration. A comparison between media and membrane filters, however, has not yet been fully investigated. This study compared aluminum concentrations in the filtrate after sand bed and membrane filtrations. The aluminum concentration after sand bed filtration was lower than that after filtration using a membrane with a pore size of 0.1 μm, irrespective of the membrane material, with one exception. A PVDF membrane with a pore size of 0.1 μm produced a similar residual aluminum concentration to that obtained using a sand bed. When the natural organic matter concentration was very low, the aluminum concentration in the PVDF membrane (pore size 0.1 μm) and sand bed filtrates was lower than that obtained using other membranes with the same pore size. It is believed that adsorption of dissolved aluminum may enhance aluminum removal by the sand bed and the PVDF membrane when the aluminum exists in an uncomplexed form with natural organic matter. © 2013 Elsevier B.V. All rights reserved.
  • 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 
    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.
  • N. Shirasaki, T. Matsushita, Y. Matsui, T. Urasaki, K. Ohno
    Water Science and Technology: Water Supply 12 5 666 - 673 2012年 [査読有り][通常論文]
     
    Difference in behaviors of F-specific DNA and RNA bacteriophages during coagulation-rapid sand filtration and coagulation-microfiltration (MF) processes were investigated by using river water spiked with F-specific DNA bacteriophage f1 and RNA bacteriophage f2. Because the particle characteristics of f1 (filamentous) and f2 (spherical) are quite different and the surface charge of f1 in the river water was slightly more negative than that of f2, the removal ratios of f1 were approximately 1-log lower than the removal ratio of f2 after any treatment process used in the present study. This result indicates that the behaviors of the two bacteriophages during the treatment processes were different, and that the removal of f1 by the combination of coagulation and filtration processes was more difficult than that of f2. The removal ratios for f1 and f2 were approximately 3-log and 4-log, respectively, in the coagulation-rapid sand filtration process, and 6-log and 7-log, respectively, in the coagulation-MF filtration process. Therefore, as expected, the coagulation-MF process appears to be more effective than the coagulation-rapid sand filtration process for the removal of not only spherical viruses but also filamentous viruses. © IWA Publishing 2012.
  • Taku Matsushita, Nobutaka Shirasaki, Yoshihiko Matsui, Koichi Ohno
    Chemosphere 85 4 571 - 576 2011年10月 [査読有り][通常論文]
     
    We used the bacteriophages Qβ and MS2 to determine whether viruses are inactivated by aluminum coagulants during the coagulation process. We performed batch coagulation and filtration experiments with virus-containing solutions. After filtering the supernatant of the coagulated solution through a membrane with a pore size of 50 nm, we measured the virus concentration by both the plaque forming unit (PFU) and polymerase chain reaction (PCR) methods. The virus concentration determined by the PFU method, which determines the infectious virus concentration, was always lower than that determined by the PCR-based method, which determines total virus concentration, regardless of infectivity. This discrepancy can be explained by the formation of aggregates consisting of several virus particles or by the inactivation of viruses in the coagulation process. The former possibility can be discounted because (i) aggregates of several virus particles would not pass through the 50-nm pores of the filtration membrane, and (ii) our particle size measurements revealed that the virus particles in the membrane filtrate were monodispersed. These observations clearly showed that non-infectious Qβ particles were present in the membrane filtrate after the coagulation process with aluminum coagulants. We subsequently revealed that the viruses lost their infectivity after being mixed with hydrolyzing aluminum species during the coagulation process. © 2011 Elsevier Ltd.
  • N. Shirasaki, T. Matsushita, Y. Matsui, A. Oshiba, K. Ohno
    Water Research 44 5 1307 - 1316 2010年03月 [査読有り][通常論文]
     
    Norovirus (NV) is an important human pathogen that causes epidemic acute nonbacterial gastroenteritis worldwide. Because of the lack of a cell culture system or an animal model for this virus, studies of drinking water treatment such as separation and disinfection processes are still hampered. We successfully estimated NV removal performance during a coagulation-rapid sand filtration process by using recombinant NV virus-like particles (rNV-VLPs) morphologically and antigenically similar to native NV. The behaviors of two widely accepted surrogates for pathogenic waterborne viruses, bacteriophages Qβ and MS2, were also investigated for comparison with that of rNV-VLPs. Approximately 3-log10 removals were observed for rNV-VLPs with a dose of 40 μM-Al or -Fe, as polyaluminum chloride at pH 6.8 or ferric chloride at pH 5.8, respectively. Smaller removal ratios were obtained with alum and ferric chloride at pH 6.8. The removal performance for MS2 was somewhat larger than that for rNV-VLPs, meaning that MS2 is not recommended as an appropriate surrogate for native NV. By comparison, the removal performance for Qβ was similar to, or smaller than, that for rNV-VLPs. However, the removal performances for rNV-VLPs and Qβ differed between the coagulation process and the following rapid sand filtration process. Therefore, Qβ also is not recommended as an appropriate surrogate for native NV. © 2009 Elsevier Ltd. All rights reserved.
  • N. Shirasaki, T. Matsushita, Y. Matsui, T. Urasaki, A. Oshiba, K. Ohno
    Water Science and Technology 61 8 2027 - 2034 2010年 [査読有り][通常論文]
     
    Norovirus (NV) is a prototype strain of a group of human caliciviruses responsible for epidemic outbreaks of acute gastroenteritis worldwide. Because of the lack of a cell culture system or an animal model for this virus, studies on drinking water treatment such as separation and disinfection processes are still hampered. In the present study, we investigated NV removal performance as particles during a coagulation-ceramic microfiltration (MF) process by using recombinant NV virus-like particles (rNV-VLPs), which are morphologically and antigenically similar to native NV. We also experimentally investigated the behaviors of two widely accepted surrogates for pathogenic waterborne viruses, bacteriophages 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. © IWA Publishing 2010.
  • Nobutaka Shirasaki, Taku Matsushita, Yoshihiko Matsui, Makoto Kobuke, Koichi Ohno
    Journal of Water Supply: Research and Technology - AQUA 59 8 501 - 511 2010年 [査読有り][通常論文]
     
    The feasibility of in-line coagulation as a pretreatment for ceramic microfiltration (MF) was verified by comparing its efficiency in the removal of viruses with that of the traditional mechanical mixing approach for coagulation, and by examining the effect of coagulant dose and coagulation time on virus removal. The in-line coagulation-ceramic MF system efficiently removed bacteriophage Qβ and MS2: removal ratios were.>8.2 log for infectious viruses and >5.4 log for total (infectious+ inactivated) virus particles. These values were similar to those of the mechanical coagulation-ceramic MF system. The in-line coagulation system has potential as a useful pretreatment for the removal of viruses as an alternative to the mechanical mixing system, because the former efficiently removes viruses and has a smaller footprint in treatment plants. For the in-line coagulation-ceramic MF system, a coagulant dose of 1.08 mg-Al/L and a coagulation time of 1 min were required to achieve a high level of virus removal. Infectious Qβ and MS2 were removed to similar levels by the two precoagulation methods tested, but the removal of total MS2 particles was higher than that of Qβ particles, possibly because of the selective interaction with the cake layer. © IWA Publishing 2010.
  • N. Shirasaki, T. Matsushita, Y. Matsui, T. Urasaki, K. Ohno
    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 Qβ and MS2, were investigated during the coagulation process by using river water spiked with these bacteriophages. The particle size and electrophoretic mobility of Qβ and MS2 were similar, but the removal performances of infectious Qβ and MS2, as measured by a plaque forming unit (PFU) method, differed markedly during the coagulation process. The removal ratio of the infectious Qβ concentration was approximately 2 log higher than that of the infectious MS2 concentration at all coagulant doses tested. The total Qβ 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 Qβ 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 difference was larger for Qβ than MS2, meaning that Qβ 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 Qβ 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. © 2008 Elsevier Ltd. All rights reserved.
  • N. Shirasaki, T. Matsushita, Y. Matsui, M. Kobuke, K. Ohno
    Journal of Membrane Science 326 2 564 - 571 2009年01月20日 [査読有り][通常論文]
     
    The removal performance of two surrogates for pathogenic waterborne viruses, F-specific RNA bacteriophages Qβ 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 Qβ 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 Qβ and MS2 differed markedly. Removal of total MS2 was approximately 2-log larger than that of total Qβ, possibly owing to selective interaction with the cake layer, although the particle diameters and electrophoretic mobilities of Qβ and MS2 were similar. The total number of bacteriophages retained in the microfiltration compartment after 4-h filtration was similar for Qβ and MS2, but there were approximately 3 log fewer infectious Qβ than infectious MS2, probably owing to the difference in sensitivity to the virucidal activity of aluminum coagulant. © 2008 Elsevier B.V. All rights reserved.
  • Nobutaka Shirasaki, Taku Matsushita, Yoshihiko Matsui, Koichi Ohno
    Journal of Water Supply: Research and Technology - AQUA 57 7 501 - 506 2008年11月 [査読有り][通常論文]
     
    We evaluated the removal of virus (bacteriophage Qβ) after hydraulic backwashing and the effects of reversible and irreversible membrane fouling on virus removal by a coagulation-microfiltration (MF) system. The rate of virus removal in the coagulation-MF system was low at the beginning of filtration but increased with filtration time, owing to the accumulation of foulant on the membrane. The rate of virus removal thereafter remained high, even after hydraulic backwashing of the membrane to remove reversible membrane foulant. The presence of irreversible, rather than reversible, membrane foulant contributed to the increase in virus removal rate observed at the beginning of filtration. The irreversible membrane fouling maintained a high virus removal rate even after hydraulic backwashing. Moreover, irreversible fouling of the membrane during long-term filtration (1 month) improved virus removal in the coagulation-MF system, and the membrane excluded virus particles even in the absence of coagulation pretreatment. Therefore, the accumulation of irreversible membrane foulant with filtration time played an important role in virus removal by the coagulation-MF system. © IWA Publishing 2008.
  • 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.
  • Taku Matsushita, Y. Matsui, N. Shirasaki
    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/ (m2 × h)) and type of virus (Qβ 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/(m2 × 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 Qβ and MS2, although their diameters are almost the same: greater virus removal was achieved for MS2 at PACl dosing of 0.54 mg-Al/L, and for Qβ at PACl 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. © IWA Publishing 2006.
  • Taku Matsushita, Y. Matsui, N. Shirasaki, Y. Kato
    Desalination 178 1-3 SPEC. ISS. 21 - 26 2005年07月10日 [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 μm), 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 μ showed about 1 log less removal than the 0.1-μm 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. © 2005 Elsevier B.V. All rights reserved.

担当経験のある科目(授業)

  • 流体工学Ⅱ北海道大学
  • 反応工学北海道大学
  • 環境創生工学特別研究北海道大学
  • 環境創生工学特別演習北海道大学
  • 卒業論文北海道大学
  • 環境工学ゼミナールⅡ北海道大学
  • 環境工学ゼミナールⅠ北海道大学
  • 環境工学概論北海道大学
  • 環境工学北海道大学
  • 環境工学序論北海道大学
  • 一般教育演習北海道大学
  • 環境工学実験Ⅱ北海道大学
  • 工学基礎演習北海道大学
  • 反応工学演習北海道大学
  • 環境リスク解析学北海道大学

所属学協会

  • 国際水協会   日本水環境学会   土木学会   International Water Association   Japan Society on Water Environment   Japan Society of Civil Engineers   

共同研究・競争的資金等の研究課題

  • 急速砂ろ過方式から膜ろ過方式への浄水施設更新前後におけるウイルス除去性能の比較
    クボタ若手研究者研究奨励制度(水道分野) 第2回
    研究期間 : 2021年 -2022年 
    代表者 : 白崎伸隆
  • 浄水処理におけるヒト感染コロナウイルスの除去・不活化特性の評価
    フソウ技術開発振興基金 令和2年度研究助成
    研究期間 : 2020年 -2021年 
    代表者 : 白崎伸隆
  • リバースジェネティクス法を用いたウイルス野生株・流行株の塩素消毒不活化特性の把握
    日本学術振興会科学研究費補助金 挑戦的研究(萌芽)
    研究期間 : 2020年 -2021年 
    代表者 : 白崎伸隆
  • 遺伝的多様性を考慮した水道原水中に存在する病原ウイルスの浄水処理性評価
    日本学術振興会科学研究費補助金 基盤研究(B)
    研究期間 : 2019年 -2021年 
    代表者 : 白崎伸隆,松井佳彦,松下拓
  • ヒト感染コロナウイルスの浄水処理性の評価:凝集ろ過分離性及び消毒不活化性の把握
    前田記念工学振興財団 令和3年度研究助成
    研究期間 : 2021年 
    代表者 : 白崎伸隆
  • 遺伝子封入VLPsを用いた培養困難なノロウイルスの浄水処理性評価
    フソウ技術開発振興基金 令和元年度研究助成
    研究期間 : 2019年 -2020年 
    代表者 : 白崎伸隆
  • 水道原水中に高濃度で存在するトウガラシ微斑ウイルスを指標とした実浄水処理場におけるウイルスの処理性評価
    フソウ技術開発振興基金 平成30年度研究助成
    研究期間 : 2018年 -2019年 
    代表者 : 白崎伸隆
  • 水道原水中に高濃度で存在するトウガラシ微斑ウイルスを用いた実浄水処理場における水系感染症ウイルスの処理性の推定
    平成29年度クリタ水・環境科学振興財団 国内研究助成 自然科学・技術(1)
    研究期間 : 2017年 -2018年 
    代表者 : 白崎伸隆
  • 遺伝子型の差異を考慮した培養不可能なウイルス及び消毒耐性ウイルスの浄水処理性評価
    日本学術振興会科学研究費補助金 若手研究(A)
    研究期間 : 2016年 -2018年 
    代表者 : 白崎伸隆
  • カプシドタンパクの精密質量分析によるウイルス消毒不活化・消毒耐性メカニズムの解明
    日本学術振興会科学研究費補助金 挑戦的萌芽研究
    研究期間 : 2016年 -2017年 
    代表者 : 白崎伸隆
  • 遺伝子封入VLPsを用いた培養困難なウイルスの浄水処理性評価
    ノースティック財団・若手研究人材育成事業 若手研究人材・ネットワーク育成補助金(ノースタレント補助金)
    研究期間 : 2017年 
    代表者 : 白崎伸隆
  • PMA-PCR法による水道原水河川における感染性を有する病原ウイルスの存在実態の把握
    河川財団 平成29年度河川基金助成 若手研究者 一般的助成
    研究期間 : 2017年 
    代表者 : 白崎伸隆
  • 水系感染症ウイルスを高度・高効率に処理可能な先端的ウイルス除去システムの開発
    向科学技術振興財団 平成28年度研究助成
    研究期間 : 2017年 
    代表者 : 白崎伸隆
  • Contaminant Candidate Listに掲載された水系感染症ウイルスの浄水処理性評価及びウイルス処理性指標の探索
    平成26年度クリタ水・環境科学振興財団 国内研究助成 自然科学・技術(1)
    研究期間 : 2014年 -2015年 
    代表者 : 白崎伸隆
  • 精密質量分析を応用した新手法による水系感染症ウイルスの消毒不活化メカニズムの解明
    日本学術振興会科学研究費補助金 挑戦的萌芽研究
    研究期間 : 2014年 -2015年 
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