The effect of antimicrobials in wastewater on the effectiveness of small-scale wastewater treatment is of concern, although the usual concentrations of pharmaceuticals and personal care products (PPCPs) are lower than those that might induce inhibitory effects in large-scale wastewater treatment. The effect of antimicrobials on the operation of a newly designed two-stage membrane bioreactor, which is advantageous for the removal of micropollutants, was investigated. Levofloxacin (5 mg L^-1) and/or clarithromycin (2 mg L^-1) in the feed wastewater decreased the nitrification rate by at least 40％ and promoted membrane fouling. The accumulation of antimicrobials in the sludge phase in the reactors would be the reason for the retardant adverse effects even after stopping the addition of the antimicrobials.

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Papers and reports on investigations of the urban drainage in Japan were collected (1968–2011) and a database of urban runoff loading for each measured precipitation event was prepared. The targeted pollutants were BOD, COD, SS, TN, and TP, and their event mean concentrations (EMC) were included in each data set along with their precipitation event conditions. The distribution of loading and the geographic conditions of the basins were clarified, and the dependence of the EMC values on the precipitation and geographic conditions was modeled using the regression equation of a power law. Using this relation, the predicted yearly loading and coefficients of variation were derived for four representative precipitation conditions in Japan. The required sampling frequency to attain a certain accuracy of the annual loading was estimated by a simulation using the above model. From the results, at least half of the precipitation events must be sampled for the 95% confidence interval of annual loading to be within the range of half to double the true value.

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The relationship between the monitoring plan and the detection of pesticides in raw water at waterworks throughout Japan in fiscal years 2009-2011 was investigated. For analysis, monitoring data of pesticides in the statistics on water supply were used. The number of waterworks at which pesticides monitored were was about 650 and the percentage of waterworks at which pesticides detected were was about 20%. For the waterworks that acquire raw water from surface water, a higher percentage of waterworks detected pesticides in the group of waterworks that frequently monitored many pesticides than in other groups. Additionally, in the group of waterworks that carried out monitoring once a year, a few waterworks detetcted pesticides. Furthermore, most of them detected one pesticide once in the three years. For waterworks that acquire raw water from groundwater, the detection rates of pesticides were low regardless of the monitoring frequency. The number of pesticides detected was 77 among the 102 pesticides listed in the guidelines. However, the pesticieds detected at relatively many waterworks (more than 10) was only about 10. Thus, it was considered that several pesticides might be detected at many waterworks throughout Japan, although many pesticides detected showed regional diversity.

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Arsenic contamination of groundwater resulting from natural processes occurs frequently in the midwestern part of Saitama Prefecture. The chemical composition of groundwater is similar throughout the area, and high concentrations of arsenic and iron are detected under reducing conditions. In this study, the mechanism of arsenic release into groundwater was analyzed by selective extraction of iron oxides from sediments. The revised BCR, Tamm, and revised DC methods were used for extraction from two sediment-core samples (Sites A and B) drilled in an area contaminated by arsenic. From the tests of the extraction of arsenic and iron from sediment-core samples, it was recognized that the revised DC method, in which a mixed dithionite - sodium citrate solution is used as the extracting solvent, is the most suitable technique for the analysis of the arsenic release mechanism in this area. The relationship between arsenic and iron extracted from the two core samples by the revised DC method showed a straight line (Site A: R² = 0.75, n = 19; Site B: R² = 0.65, n = 32) . This result demonstrates that iron oxides are the principal source of arsenic in this area and the dissolution of iron oxides under reducing conditions is a cause of the release of arsenic into groundwater.

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In this study, we applied a water treatment system comprising the coagulation precipitation, membrane filtration, and advanced oxidation processes to the wastewater discharged by the wet decontamination process of incineration plants. As a result, heavy metals and dioxins included in the discharged wastewater were removed to below the environmental standards. In this process, the floc formation process by the coagulation of submicron-sized particles is important as this process affects the decomposition of dioxins in the advanced oxidation process. The existence of large flocs formed from submicron-sized particles might remove the need for the advanced treatment process from the water treatment system. However, it is important to consider the various conditions related to all processes, such as the nature of the target raw water, the constraints of the site, the type of by-product waste, and the cost, to build the optimum water treatment system.

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Because the concentrations of, for example, trihalomethane (THM) , and dissolved organic matter (DOM) in the drinking water of Ogasawara Village were high, a magnetic ion exchange resin (MIEX^®) system was applied for the first time in Japan in an actual drinking water treatment plant, in the new water treatment plant constructed on Chichijima Island. The introduction of the MIEX^® system after the conventional coagulation system was, until then, unprecedented. The objective in this study is to verify the effect of the MIEX^® system. The removal rates of THM and haloacetic acid (HAA) precursors, DOC and other substances rose at this plant. The molecular weight of DOM in the source water decreased with activated carbon -coagulation and additional MIEX^® treatment processes. The concentrations of THM and HAA in tap water from the new water treatment plant decreased to less than half the values in water from the previous water treatment plant. The target values of THM and total organic carbon in the design stage of the plant at Ogasawara Village were achieved.

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