尾崎 博明

Low pressure reverse osmosis (LPRO) membrane filtration has emerged as the best alternative to ordinary reverse osmosis (RO) membrane filtration due to very low operating pressure involved with the former resulting in low cost. However, behaviors of perfluorinated compounds (PFCs) with LPRO membrane filtration are not known since the compounds as water/wastewater contaminants have only a very short history. Therefore, adsorption and diffusion behaviors of selected perfluoroalkyl carboxylate (PFAC) and perfluoroalkyl sulfonate (PFAS) compounds with a tight and a loose LPRO membranes were tested in laboratory experiments. Distribution coefficient (logK_mw) and diffusion coefficient (D_p) values for the compounds were experimentally determined for the first time. The D_p values were about three orders of magnitude larger than those for pharmaceutical and endocrine disrupting compounds. The compounds exhibited similar behaviors to those of pharmaceutical and endocrine disrupting chemicals reported earlier. Adsorption of PFCs to membranes was directly correlated to molecular weight (MW) and carbon-chain length, while their diffusion through membrane pores showed inverse correlations with the parameters. Similarly, their rejections were directly correlated to their logK_mw values and MW. However, significance of carbon-chain length on diffusion was not well understood, and hence further investigations should be devoted to elucidate on the point.

Oseltamivir and zanamivir are the two most prescribed antiviral drugs against influenza in Japan. Oseltamivir and its metabolite are frequently detected in surface water bodies in Japan during the last few years particularly in seasonal influenza period posing a potential threat of emergence of drug-resistant genes in human pathogens. Despite the second largest use of zanamivir as an antiviral drug in Japan, its presence and fate in environmental waters is unknown until now. Accurate assessment on the presence and fates of these drugs in environmental waters is the very first step in countering the potential negative impact on human health. We have recently developed a novel solid-phase extraction (SPE) method for simultaneous recovery of oseltamivir and zanamivir in environmental waters. These antiviral drugs were quantified in Neya River water and a nearby conventional sewage treatment plant (STP) during the 2010/2011 seasonal influenza using the SPE method in this investigation. Oseltamivir and zanamivir concentrations in the river water and STP water samples are discussed and compared with those of the 2009/2010 pandemic influenza in this article. This successful simultaneous quantitation of zanamivir in wastewater and river water with high recovery ratios paves the way for its monitoring in environmental waters.

Presence of the antiviral drug oseltamivir in considerable concentrations in surface waters especially in seasonal and pandemic influenza cases has raised concerns on its possible consequences in the environment and human health. This investigation aimed to elucidate concentration levels of the drug in Neya River in Osaka during 2009/2010 seasonal influenza. Oseltamivir phosphate was detected for the first time in Neya River suggesting the presence of the drug in phosphate form in surface waters is significant only in influenza pandemic cases. Oseltamivir carboxylate concentrations in Neya River were as high as 15-fold the concentrations in Yodo River in 2007/2008 and 3-fold the concentrations in a sewage treatment plant effluent in Kyoto in 2008/2009. The highest oseltamivir carboxylate concentration in Neya River was detected at ST-2 (864.8 ng/L) followed by ST-3. This was possibly due to the inefficiency of the treatment plant upstream and low river water flowrate. Based on the limited information available on the possible environmental risks of the drug in surface waters, the detected concentrations in Neya River may not be an immediate threat to the environment. However, detailed risk assessment studies are essential to clarify the potential environmental risk issue.

塩素系農薬（除草剤）として使用される2,4－ジクロロフェノキシ酢酸(2,4－D)の水中での分解を、光触媒繊維を用いる光触媒法とオゾン法との併用法（O3/UV/TiO2）により試み、副生成物の同定を行った。O3/UV/TiO2の併用法によると、オゾン法単独や光触媒法単独の場合よりも、2,4－Dからの脱塩素および2,4－D分解にともなう副生成物である脂肪族化合物の分解を助長することがわかった。したがって、同併用法は副生成物の分解も可能な有望な方法であると言える。

近年、水環境中から人畜用の医薬品が検出されており、これらは生理活性を有していることから生態系への影響や上水を経由した場合の人体への暴露影響が懸念されている。本研究では、多孔質セラミックス電極を用いた電気分解処理について16種類の医薬品を対象に検討を行った。多孔質セラミックスろ用いた電極分解処理医薬品を電極内に通水する構造にすることで医薬品を吸着した滞留時間を長くすることで効率よく電気分解を行うことが可能となる新しい水処理法である。

水汚染物質として問題になり始めている各種の医薬品類及び抗菌剤を対象として、水処理技術開発の一環として低圧逆浸透膜による除去を試み、分離特性を明らかにした。比較的塩阻止能が低い低圧逆浸透膜では、非解離性溶質の阻止は溶質分子の大きさが支配因子となり、溶質の解離度が50％以上の場合に80％を超える高い阻止率を示した。塩阻止能が高い低圧逆浸透膜では、溶質の解離性にかかわらず90％程度以上が除去された。また、極性の低い物質では溶質の疎水性(log Kow)が阻止率に影響を及ぼした。

熱帯地域の下水処理システムについて考究するために、タイ国バンコク市内の大規模下水処理場と、旧来からの小規模下水処理場の流入水と処理状況について調査した。タイ国では伝統的に、家庭排水を一時貯留する浄化槽が設置され、一般にはトイレットペーパーが使われないこと、気温が高く、下水道（管）での滞留時間が長いこと、雨季には多量の雨水により下水が希釈されるなどの特性があり、大規模処理場への流入水の汚濁物質濃度は低く、汚濁物質の分解速度は大きい。大規模処理場は過大に設計されており、気候と伝統をも考慮した下水処理システムの構築について議論した。

PCBsやダイオキシン類等の有害有機物による底質汚染が顕在化している。有害有機物は粘土やシルトに高濃度で吸着しているため、汚染底質は底質を分級し、汚染濃度に応じて処理する方法が効率的である。本研究では比較的低温で底質を間接加熱し、底質中の有害有機物を気化させ浄化する間接熱脱着法に注目した。実験はダイオキシン類・PCBsを含む実汚染底質を全粒径、75-2000μm、20-75μm、20μm以下に分級した後、400℃ で間接加熱した。ダイオキシン類は粒子径が小さくなるほど除去効率が向上し、75μm以下の粒子径から95%以上の除去率を得た。PCBsはどの粒子径においても99%以上の除去率を示した。結果より、間接熱脱着法によるダイオキシン類汚染底質の処理は分級して行う方が効率的である事がわかった。

Dioxin pollution of aquatic sediments has been one of the important environmental problems in Japan.Grain size distribution and organic constituents may play important roles in dioxin contents in sediments, which have not been well investigated. This paper aimed to quantify dioxins (PCDDs/Fs and co-PCBs) in sieved surface sediment fractions obtained from Kizu and Sumiyoshi River in Osaka, Japan. The samples were prepared and analyzed following "the Manual of the Survey and Measurement of Dioxins in Sediment"(Environment Agency in Japan, 2000) and "Method for determination of tetra-through octa-chlorodibenzo-p-dioxins, tetra-through octa-chlorodibenzofutans and coplanar polychlorobiphenyls in industrial water and wastewater"(Japanese Standards Association, 1999) The results showed that TEQ concentrations of dioxins increased with increasing the contents of Ignition Loss (IL) in the sediment fractions. Thus, reporting dioxin contents in sediments without considering grain size distribution may be erroneous, and conventional sediments. This information can be useful for effective remediation of dioxin-contaminated sediments.

This study aimed to investigate the effects of coexisting substances on separation of endocrine disrupting chemicals (EDCs) in water and domestic wastewater effluents using low pressure reverse osmosis (LPRO) membrane. The coexisting substances included calcium chloride, glutamic acid sodium salt, acetic acid and humic substances whose molecular weight ranged up to twenty thousand. The results showed higher rejection of nonylphenol in a mixed solution of the coexisting substances. Thus, the results indicated that coexisting substances can affect rejection properties of EDCs in LPRO membranes. In using higher desalting membranes, much higher rejection rates of EDCs in domestic wastewater effluents were observed compared to rejection of a single solution, which shows over 95% rejection. However, rejection of E2 from domestic wastewater did not increase with relatively loose membrane.

Algal bloom is one of the major environmental problems in closed water bodies. Reduced water currents and high inflow of nutrients to the water bodies are the main reasons behind this problem. Although many researches have been done, effective techniques to minimize the problem are still lacking. The objective of this investigation was to evaluate the effectiveness of mud gels and silver-contained ceramics in growth control of algal bloom. The experimental results showed that use of mud gels and silver-containing ceramics were very effective in controlling algal growth. Bacillus Megaterium was primarily affected while using mud gels. Photo catalysis and silver ions were mainly responsible for algal growth control while using silver-contained ceramics. Effectiveness of this technique increased when mud gels and silver-contained ceramics were used together probably due to synergic effects. This technique of controlling algal bloom can be more effective compared to other available methods.