In rivers where farmlands and livestock farms are scattered throughout the watershed, anthropogenic nutrient loading may affect not only water quality but also the river ecosystem. In this study, we evaluated the effects of anthropogenic nutrient loading on the material cycle and food web in the Yukiya River and Setsukinai River using carbon and nitrogen stable isotope ratios (δ¹³C and δ¹⁵N). We collected macroinvertebrates and food sources (attached algae, leaf, suspended particle organic matter (SFPOM) and benthic particle organic matter (BFPOM)) from study sites. The results of δ¹³C and δ15N suggested the impact of anthropogenic nutrient loading at all sites except the upstream of the Setsukinai River.The stable isotope two source mixing model based on δ¹³C revealed that macroinvertebrates consumed mainly attached algae. The significant positive correlation between the δ¹⁵N of attached algae and the δ¹⁵N of each feeding function groups suggested that a food web based on attached algae was constructed in the study rivers. Therefore, it is suggested that the effects of anthropogenic nutrient loading are propagated to macroinvertebrates through attached algae and FPOM derived from attached algae, and that these effects extend downstream to the dam through eutrophication of the dam lake.

 Public concerns have recently emerged due to sanitary microorganisms in combined sewer overflows (CSO) during rainy events. The purpose of this study was to investigate the influence of primary treatment discharge from a combined sewer sewage treatment plant (STP) on sanitary microorganisms in receiving Katsura River. To this end, we investigated the presence of sanitary microorganisms in STP discharge and river water during rainy events. In addition, increase in the load of sanitary microorganisms during rainy events was examined based on our previous study during non-rainfall conditions. It was found that primary treatment discharge during rainy events significantly increased in the microbial load of STP discharge and the receiving water. However, the increasing load of the river reach between upstream and downstream points could not be explained by the increase in the STP discharge alone.

 In this study, to estimate water quality markers and biomarkers on fish reproduction in treated wastewater, a growth test was carried out for Japanese medaka exposed to effluents of secondary treatment and of microbial carrier process, followed by a Target screening analysis on endogenous metabolites in liver and reproduction test for grown medaka. In addition to a general water quality analysis, a Non-target analysis on chemical substances by LC-QTOF/MS was carried out for test waters. A relationship between the water quality parameters and the impacts observed on growth, on reproduction, and on composition of endogenous metabolites was determined by statistical analysis. Decreases in fertilized egg number and fertility were observed in the reproduction test using secondary treated wastewater. Lager changes in metabolites were observed in female fish than in male. Phosphocreatine was among those metabolites that particularly increased in female fish exposed to secondary treated wastewater. The fertilized egg number showed high correlation to the concentration of NH_4-N and of the compound observed at m/z 362.1523 by LC-QTOF/MS. Fertility showed high correlation to the fluorescence intensity (Ex : 345 nm/ Em : 430 nm) and the concentration of the compound observed at m/z 517.0774.

 This study focused on corrosion of cast iron and ductile iron pipes, which are mainly used as water pipes, and attempted to analyze the relationship between the corrosion and the aging of the pipes and the buried ground. For the analysis, we used the data of about 7,000 pipe body surveys of buried pipes in the 23 wards of Tokyo that have been conducted since 1987. As a result of this analysis, the pitting corrosion coefficient (𝑘), which indicates the corrosion strength of the buried ground, was quantified for each ground category. And the results of the pipe body survey demonstrated that weakly corrosive ground (Ground I) and strongly corrosive gorund (Ground II) were classified into western and eastern part of the 23 wards of Tokyo. In addition, the tendency of ground corrosiveness and pitting depth and the corrosion protection effect of polyethylene sleeves were also clarified. Furthermore, we visualized graphically that pitting corrosion of cast iron pipes progressed faster than that of ductile iron pipes. These new findings can be useful for pipeline renewal planning in the target area.

 This study focused on the rehabilitation plan of water distribution main pipelines. The renewal of water distribution mains will be greatly affected by the scale of construction and water outages, and it’s the plan that entails a heavy burden in terms of technologies and cost. Furthermore, the population of Tokyo is expected to decline after 2025, and demand for water supply will decline in the future too. In the previous research, we proposed the new renewal priority evaluation method that takes into account change of long-term water demand. However, since a structure of water distribution networks has wide varieties of shapes and features depending on the topographical conditions and changes in urban developments, it is necessary to confirm the effectiveness and versatility of the new method of renewal. Therefore, in this paper tried to perform a comparative analysis of the renewal priority order of distribution main pipelines in consideration of future changes in water demand for two water distribution area models with different characteristics and shapes. Pipeline renewal scenarios that created by the renewal priority evaluation method are compared with stable supply and cost as indicators. The results showed the effectiveness and variety of the proposed new method of renewal in this paper.

 In this study, we conducted a questionnaire survey in small communities that use and manage water supply systems with a population of less than 100 people, with the aim of identifying the burdens and heavy workloads that community representatives feel toward maintenance work such as inspection and cleaning. In addition, a questionnaire survey was conducted to understand the status of collaboration and cooperation in maintenance work with organizations outside the village and the intention to use support from private organizations.

 The results of the survey showed that only less than 20% of the villagers were cooperating with organizations outside the village in the maintenance and management of the facilities, and that they felt burdened by the maintenance and management of the facilities. In addition, we were able to understand the frequency of work and the time required for the works that are burdensome in maintenance and management, as well as the needs for support from external organizations and the price range in which the communities would like to use the support.

 In this research, the sewage treatment performance of a pilot-scale multistage constructed wetland with functional filtration media (FFM) bed using zeolite, calcium silicate or activated charcoal with sand and non-functional filtration media (n-FFM) bed using just sand were compared, and the effect of FFM on the water purification performance was elucidated. Under the vertical flow condition suitable for aerated treatment, the BOD removal efficiency of 90.2% was obtained even with n-FFM bed and 99.9% NH⁴⁺_-N removal was attained with FFM bed using zeolite. The effect of FFM was, however, negligible on total nitrogen removal under the hybrid condition comprising both the vertical and horizontal flows. Despite of the filtration media, the total nitrogen removal efficiency under the hybrid condition was around 45%. Although the removal efficiency of phosphorus under the vertical flow condition was 21.6% with n-FFM bed, that under the hybrid condition became below zero. The removal efficiency of phosphorus in FFM bed using calcium silicate was, however, maintained at 18.2% even under the hybrid condition, revealing the effect of calcium silicate to sustain phosphorus removal performance in the constructed wetland.

 The purpose of this study is to make stirring method for controlling nitrous oxide (N₂O) production with successful nitrogen removal in an oxidation ditch reactor with rotator. Continuous measurements of N₂O and water quality were performed under different stirring conditions. As the result, spatiotemporal distribution of dissolved oxygen (DO) and N₂O concentration was different depending on the stirring pattern. In the stirring pattern that adequately makes anoxic zone and aerobic zone in the reactor, dissolved inorganic nitrogen removal ratio was accomplished as 74% and N₂O emission factor was low as 0.31%, respectively. The N₂O production was affected by the profiles of influent, DO, and organic carbon, which implies that existence of anoxic zone and supply of organic carbon promotes the N₂O reduction. Based on the results, strategy for controlling the N₂O emission in full-scale sewage treatment plant based on the stirring methodology was provided.

 Certain antibiotics administered to livestock are released in their excrement. Therefore, antibiotics may combine with livestock wastewater and enter the surrounding water environment, affecting the aquatic ecosystem. In this study, we investigated antibiotics removal from aqueous solution and swine wastewater via contact with clay minerals (zeolite, illite). Furthermore, the safety of the treated water was investigated by a short-term toxicity test using a green alga R. subcapitata. It was observed that zeolite had a higher antibiotics removal rate than illite. Additionally, it was suggested that the removal of tylosin may involve degradation and adsorption. Furthermore, the experimental results of antibiotic removal from swine wastewater indicated that antibiotics can be efficiently eliminated by incorporating the contact treatment using zeolite, after its treatment in constructed wetlands.

 Major component of biofilm is known as extracellular polymeric substances (EPSs) that is produced by microorganisms to survive under various stresses, and it causes problems such as water quality deterioration and pipe corrosion in the water supply system. Ultraviolet (UV) radiation is one of the practical methods to disinfect water, and UV is one of stress factors for bacteria. In this study, the effects of ultraviolet irradiation to bacteria on the subsequent biofilm formation were evaluated. The experimental samples were prepared by mixing UV irradiated and non-irradiated suspensions of Pseudomonas aeruginosa at different ratios, which were then cultured in the microtiter plates to grow biofilms. Amount of biofilm was quantified by crystal violet staining, and metabolic activity of bacteria in the microtiter wells was determined by the adenosine triphosphate (ATP) assay. ATP in the sample containing 100 % of UV irradiated bacteria was decreased by 97 % within first 6 hours after UV exposure, and biofilm growth was subsequently observed. Furthermore, it was estimated that the biofilm growth rate in the 100 % UV-irradiated samples was more than twice of that in the sample of 0 % UV-irradiated samples. These results suggest thatUV-inactivated bacteria stimulated the intact bacteria to produce biofilms and thus indirectly contributed to promote biofilm formation in water supply systems.

 Dead microbial cells derived from sewage sludge (the mixutre of primary sludge and waste activated sludge) cause serious problems on microbial community analysis of anaerobic sludge digesting sewage sludge. In this study, PMA-PCR was employed to inhibit the amplification of DNA derived from dead microbial cells, and microbial community of an anaerobic thermophilic sludge digester was investigated. The results revealed that conventional DNA-based microbial community analysis overestimates the richness and diversity of the anaerobic digester sludge. Microbial members eliminated by PMA-PCR were mainly belonging to Alphaproteobacteria, Gammaproteobacteria (mostly Betaproteobacteriales) and Actinobacteria. Microbial community of the anaerobic thermophilic digester revealed by PMA-PCR was characterized by abundant 15 OTUs (≥1% relative abundance), occupying more than 80% of the community.

 The objective of this study is to reveal the evidence of hydrogen sulfide (H₂S) control by biological oxidation through conducting the long-term experiment of H₂S mitigation by providing electron pathway with highly conductive concrete and bacterial flora analysis of electricity-producing bacteria. The long-term experiment of H₂S mitigation by biological oxidation with rod shaped electrode (anode) of highly conductive concrete was conducted. As the results, it confirmed that H₂S was mitigated. Time-course changes of bacterial flora through this experiment were investigated by PCR-DGGE. From the results, electricity-producing bacteria (Geobacter sp. and Pelobacter sp.) were found around the inner surface of anode. From the results of quantitative analysis of electricity-producing bacteria with metagenomic analysis by next generation sequencer, it was shown that a lot of electricity-producing bacteria (Geobacter sp.) were accumulated around the inner surface of anode. Finally, the evidence of hydrogen sulfide (H₂S) control by biological oxidation (using the oxygen dissolved in surface water as electron accepter nevertheless under anaerobic condition) was revealed.

 Public water supply services in Yangon started in 1842 since British colonial period, however the practice of drinking tap water is uncommon until this moment with public distrust on water supply infrastructure. Yangon city development committee is upgrading the tap water system in accordance with greater Yangon water supply improvement project. At the same time, they are looking for the solutions to improve public acceptance of tap water. Trust is generally assumed to be an essential precondition for improving the consumer’s acceptance of goods. This study aims to provide insight into relationship between trust in water authority and public risk perception on consuming tap water and the mediating demographic factors of this relationship using the questionnaire. It is conducted in central business district area, the heart of Yangon, with the highest population density in which to understand demographic transition in Yangon city. According to our findings, public risk perception on drinking tap water was greatly influenced by level of trust in water authority. In addition, some demographic variables such as gender and family size also had significant impacts on public risk perception on drinking tap water.

 Water supply systems on small islands are fragile and prone to water shortages. Although the Indonesian Government provided assistance to build sea water reverse-osmosis (SWRO) systems on small islands to alleviate water shortages, the inhabitants also have other water sources. Therefore, this study aimed to delineate the inhabitants’ preference and consumption of various water sources, including the SWRO systems, and to find factors affecting water consumption to propose the sustainable operation and management of the SWRO systems. The three islands, namely Belakang Padang Island (BPI), Tanakeke Island (TKI) and Nusa Lembongan Island (NLI), have almost the same SWRO systems with different capacities. In BPI, high pressure pumps (HPP) were broken occasionally, reducing the production capacity significantly. Meanwhile, in TKI and NLI, the SWROs were operated intermittently due to solar power failure and small SWRO water consumption in the rainy season (TKI), and distribution pipe breakage (NLI). The SWRO water consumption by the customers varied significantly: 12, 46, and 110 litters-percapita-per-day (LPCD) on TKI, BPI and NLI, respectively. SWRO water consumption in the dry season was much higher than that in the rainy season when the customers can use rain water. The water consumption of the SWRO systems was also influenced by the operational stability of the SWRO systems, household income levels, and the water tariff levels. About 67% of the surveyed households spent more than 4% of their income for getting water. Since the SWRO systems cannot produce sufficient amounts of water to meet the dry season demand, many customers buy water from other sources that are more expensive than the SWRO water. Therefore, reliable and stable operation of the SWRO systems would lessen the customers’ burden of expenditure for getting water.

 The co-incineration of sewage sludge and municipal solid waste (MSW) as a sewage sludge treatment method has a possibility to decrease lifecycle cost, energy consumption and greenhouse gas (GHG) emission. This study aims to clarify the feasibility on co-incineration of sewage sludge and MSW in Taiwan. This study assumes that sewage sludge is transported to MSWI by vehicles for co-incineration. First, we collected information on WWTPs and MSWIs in Taiwan and established a database using Google My Map. Second, we set the necessary conditions through literature and questionnaires for co-incineration: (1) Operating ratio less than 90%, (2) Mixing ratio less than 3% (dewatered sludge) and 1% (dried sludge), and (3) Distance between WWTP and MSWI is within 30 km. Third, four scenarios (dried sludge or dewatered sludge) were conceived and obtained the possible combination by screening out through necessary conditions. All four scenarios have 39 combinations for co-incineration. Regardless of whether the sludge is dewatered or dried in WWTP, the co-incinerable amount of sludge is the same on a dry basis which accounts for 89.7% of the national sludge generation. Since the amount of sludge in Taiwan is much less than that of MSW, the operating and mixing ratio does not affect the potential of co-incineration. The most critical factors affecting co-incineration are the distance between WWTP and MSWI. The dried sludge can reduce GHG emissions from transportation and incineration, and the generated electricity can also offset GHG emissions. However, the energy consumption of the drying process in the WWTP causes a large amount of GHG emissions than other processes. From the perspective of GHG emissions, dewatered sludge (S1) is the best scenario for co-incineration with MSW. If the drying equipment is installed in MSWI instead of WWTP, the energy required for sludge drying process can be provided from the waste heat of incineration.

 Preparation of alternative soilless organic media with a simple method was investigated to utilize tons of crop residues in a closed loop in agricultural areas. Leaves and stalks of eggplant were used in this study, and the leaves and stalks crudely crushed up to a maximum of 3 cm were soaked into water to reduce electronic conductivity (EC) in the biomass. Water extracts showed their germination and following growth inhibition in a germination inhibition test using grape tomato seeds. Also, heat treatment (e.g., 70oC in a dry oven) reduced the inhibition effect. Then, prepared growing media of eggplant’s leaves and stalks crudely crushed and soaked into water was applied to cultivate grape tomato (cultivation period 53 days; n = 3). Mineral wool, commonly used growing media, was used as a control. Although the average growth of grape tomato in the prepared organic media was lower than that in the mineral wool, one grape tomato was able to grow as much as that in the control case under controlled circumstances. This might indicate that the prepared growing media have the potential to grow plants. Through investigation of characteristics of the prepared growing media, challenges were set to address its high pH, high EC, and low water-holding capacity.

 In this study, to evaluate the possibility of sewage sludge fertilizer and spent mushroom (Agaricus bisporus) substrate application on tea (Camellia sinensis) cultivation, we performed tea cultivation experiments using those materials for 3 years. The yields of tea in the test areas of sewage sludge fertilizer fertilization with spent mushroom substrate were higher than conventional fertilization area (100% of rapeseed wastes with spent mushroom substrate or humus). In particular, test area of sewage sludge fertilizer (50%) and rapeseed waste (50%) fertilization showed the highest yield in this study. Besides, the heavy metals in the sewage sludge fertilizer did not significantly accumulate into the tea leaves. Furthermore, we found that the spent mushroom substrate can be used as soil conditioner for tea cultivation because there was no negative effect of the material compared with conventional soil conditioner (humus). Overall, we found that application of sewage sludge fertilizer at 12 kgN/10a/year could reduce 15% of fertilizer cost compared with conventional fertilizer design, and 88.5% of sewage sludge cake produced in the Kirishima city, Kagoshima, Japan can be utilized in the regional tea cultivation areas.

 Based on our previous studies, we successfully cultivatied protein-rich forage rice in a real-scale field with the area of 30 ale by continuous irrigation using treated municipal wastewater (TWW). The yield (6.58±0.50 t/ha) and protein content (9.76±1.09 %) were significantly higher than those of the same variety of rice harvested in the normal field under the standard practice. An experiment on feeding pigs at the latter growth stage by the protein-rich rice was conducted in this study. Comparing with the general (control) feed composed of corn and soybean cake as sources of energy and protein, respectively, the feed using the protein-rich rice as proxy of corn was tested in the feeding experiment. When the test feed was designed, the usage of soy-bean cake, which is more expensive than corn, could be reduced due to a higher content of proteins in the rice than corn. In the feeding experiment, the pigs fed by the test feed demonstrated a significantly higher yield of dressed carcass than those done by the control feed. The test feed achieved a higher carcass grading than the control feed, although its difference was not significant, and a comparable meat quality indicated by nutritional and physical parameters. To examine its feasibility, the economic evaluation was applied to the project in Tsuruoka municipal wastewater treatment plant to supply TWW to 19 hectale paddy fields cultivating protein-rich rice and to use the rice harvested there for pig farming. It revealed that the investment of 3.5 million JPY/year for TWW supply to the paddy fields can produce the benefit of 5.3 million JPY/year (including bonus for paddy farming) for rice and pig farmers, although the farmland, which are now shared by many rice farmers, has to be consolidated to improve the productivity.

 The objectives of this study were: 1) to develop novel passive sampler (PoP-CoV sampler) that enables the survey in manholes of toilet drainage from individual buildings, 2) to verify the availability of the sampler in actual fields such as a hospital and a quarantine hotel for SARS-CoV-2 patients, and a business office. The results indicated that the PoP-CoV sampler was useful for manhole surveys, because the SARS-CoV-2 was adsorbed on the PoP-CoV sampler regardless of stationary or running waters. Moreover, Ct values for SARS-CoV-2 in samples processed by PoP-CoV sampler were up to 7.0 lower than that in corresponding grab samples. Then, a field investigation using the PoP-CoV sampler was carried out at an office building where 111 people work. Unexpectedly, a positive signal was successfully detected from the building wastewater where later one case was diagnosed SARS-CoV-2 infection with PCR testing of individual specimens. By this method, we may have succeeded in detecting one SARS-CoV-2 patient from 111 people 4 to 5 days before the positive confirmation date (onset date or 1 day before), though we cannot deny that positive signal might have come from asymptomatic patients who were present during the survey period. Therefore, the PoP-CoV sampler is expected to be a powerful tool for wastewater surveillance in individual building SARS-CoV-2 monitoring.

 Wastewater-based epidemiology for SARS-CoV-2, which routinely monitors the virus in wastewater, has been expected as a useful tool to track the dynamics of viral disease prevalence in a population level. However, there is a concern on the infectivity of SARS-CoV-2 in wastewater, which is one of the factors that hamper its widespread use. In the present study, we established an infectivity assay for SARS-CoV-2 based on virus cultivation using VeroE6-TMPRSS cells, which is applicable to investigation of SARS-CoV-2 infectivity in wastewater. Our method enables estimation of the amout of infectious SARS-CoV-2 from the observed SARS-CoV-2 RNA concentrations as determined by PCR, based on the quantitative analysis of the relationship between virus titer and RNA concentration.

 Extended spectrum β-lactamase (ESBL)-producing Enterobacteria (ESBL-Ent), which are resistant to a wide range of antibiotics in beta-lactam group, have been recognized worldwide as a threat causing nosocomial infections. To characterize the ESBL-Ent carried by healthy people, we isolated the bacteria from municipal wastewater (MW) and detected genes (bla) cording β-lactamase production. The same analysis was applied to hospital wastewater (HW) for comparison. Wastewater samples were taken from a municipal wastewater treatment plant and a general hospital twice a month throughout a year from February 2019 in Sendai, Miyagi prefecture, Japan. By incubating on CHROMOagar ESBL, 594 and 102 isolates of ESBL-Ent were obtained from MW and HW, respectively. The species identification of each isolate with detection of specific gene (for Escherichia coli) and sequencing of 16S rRNA (for Enterobacteria) found ten bacterial genera including mainly E. coli, Aeromonas, and Klebsiella. Among 20 types tested, 16 types of bla were detected from these isolates. The classification of detected bla demonstrated that Class A was predominant and, in this class, bla_{CTX-M group-9} had the highest prevalence in both wastewaters (MW: 51.9%, HW: 35.6%). ESBL-Ent possessing Class A and Class B genes simultaneously, which can degrade peniciline and carbapenem groups of antibiotics, were detected in both MW (1 isolate) and HW (2 isolates). Two important resistance genes bla_KPC and bla_OXA-1, called overseas carbapenemase in Japan, were also detected from MW and HW isolates. These results indicated that ESBL-Ent, a fraction of which potentially cause infectious diseases difficult to be treated, have been already spread among healthy people living outside hospitals.

 Although seawater desalination can be operated steadily without influence of drought, the high costs and technical requirements make it diffiicult to verify the effectiveness of seawater desalination as a means to alleviate water shortages in developing countries. In this study, we have firstly scraped the internet to collect information on desalination plants using a web scraper and made a database on desalination plants. As a result, it was found that, among the world cities of population over 100 thousands, desalimation plants are in operation in 157 cities, in planning in 27 cities, and under construction in one city, totaling 185 cities. Secondly, four indices were selected out of 1, 386 indices of the World Bank, to incidate the likelihood of seawater desalination plants. Using these four indices, it was estimated that there would be 54 million people who would live in cities in developing countries where desalination plants are likely to be commissioned.

 Using sewage treatment plant simulator, we comprehensively evaluated energy saving, energy production, and phosphorus recovery for the resource and energy circulation base of the sewage treatment plant by wide area cooperation at the model area. For cooperation of domestic wastewater treatment facilities, the agricultural rural sewage treatment facility set up with sewerage connection was the most effective. In the case of A treatment plant, rural sewage treatment facility accounted for 16% of the total power generation of 19,430kWh / day, and the power generation increased about 30%. Phosphorus from three treatment plants was collected in the B treatment plant, therfore the phosphorus recovery amount was 159 kg / day, which was 1.7 times that of the B treatment plant alone(94 kg / day). In the view point of an energy circulation, considering the B treatment plant as the energy base of the three treatment plants, the effect of the digestion gas transportation was large, and the self-sufficiency rate increased to be 82%. Furthermore, in cooperation with the domestic wastewater treatment facilities, the amount of power generation increased to 19,200kWh / day, and it is estimated that the self-sufficiency rate was 104% and power independence is possible.

 This study aims to examine the operation status of a flow-rate controlled ground source heat pump system using a lining borehole ground heat exchanger (LBHE). The system was installed in an office in Kato city, Hyogo prefecture, and the construction tests of the LBHE were conducted in 2019. The construction test results confirmed that the improved construction method reduced the construction time and number of workers as compared to conventional construction methods. Then, we performed cooling demonstration experiments to examine the flow and temperature conditions in the system by controlling the flow rate taken from LBHEs (the circulation flow rate) on extremely hot days in August and September. In these experiments, the ambient air temperature, outlet and inlet water temperatures of the heat pump on the primary side, the circulation flow rate, heat pump power consumption, and room air temperature were measured. The outlet water temperature was maintained almost at the setting temperature (32°C) under experimental conditions, and the circulation flow rate was varied depending on the heat required for the heat pump. However, the output of the heat pump became unstable when the flow rate was close to the minimum flow rate and started fluctuating significantly. Overall, the measured sum of power consumption of the heat pump and auxiliary equipment of the system was 28.4–45.5% lower than the estimated power consumption of the air source heat pump.

 In eutrophic waters such as Mikawa Bay, the bottom water becomes anoxic in summer, and sulfide is leached into the bottom water due to sulfate reduction in the sediment surface layer, leading to environmental problems such as blue tide.As a method to improve the bottom sediment environment, the addition of iron materials to the bottom sediment, inspired by the natural phenomenon of iron curtain (removal of hydrogen sulfide by reaction with iron), has been devised, but its quantitative evaluation has not yet been achieved.In this study, we developed a sediment model focusing on the sulfur circulation process to quantitatively evaluate the inhibitory effect of iron addition on sulfide release, and performed reproducible calculations of sulfide elution experiments.In this study, we developed a sediment model focusing on the sulfur cycling process in order to quantitatively evaluate the effect of iron addition to the sediment.

 In non-target LC/MS analysis, solid phase extraction (SPE) is often adopted for a sample pretreatment method, but recovery rate in SPE varies greatly depending on the samples and cartridges used, and some dissolved organic matter (DOM) are lost before LC/MS. In this study, we tried freeze drying (FD) and large volume injection of untreated samples(LVDI) and 4 SPE methods, namely, styrene divinylbenzene polymers, hydrophilic reversed phase polymers and activated carbon, mixed mode cation exchange polymers and anion exchange polymers, primary secondary amine and strong cation exchange, for urban river water at Omokage Bridge, Kanda River, Tokyo, Japan. We compared these six methods in terms of DOC recovery and the number of DOM detected by LC/MS. As results of experiments, two ion-exchange SPE methods showed significant organic leaching from the SPE cartridges and were not suitable for the non-target analysis. DOC recovery of FD were 82.1% to 92.9% and higher than those of SPE methods. Freeze dried samples (FD) detected about 8000 DOMs, which was twice as many DOMs as those detected in SPE samples. Among all DOM components detected by FD, LDVI and two SPE methods, more than half of them were detected by only single method. There was a clear difference in the interquartile range of LC retention times between different pretreatment methods. To choose a single sample pretreatment method, FD was the best suitable method because it had the highest DOC recovery rate and the highest detected number of DOM components. To accomplish further comprehensive analysis, combination of multiple pretreatment methods was also recomendable.

 Formation characteristics of chlorinous odor of 30 nitrogenous compounds were investtegated. Target itmes were odor inteisity, trichloramine (NCl₃) and total purgeable nitrogen (TPN). Formation of chlorinous odor was observed for all target compounds, and it was found that wide varieties of amines and compounds with NH_2- were precursors of chlorinous odor. The odor intensity of eight compounds were higher than that of ammonia (NH₃). From the results of NCl₃ and TPN, it was found that comounds other than NCl₃ were responsible for the chlorinous odor resulting from the chlorination of these eight compounds. For low molecular alkyl amines, the odor intensities of primary amines were higher than those of secondary and tersiary amines. When NH₃ coexisted with bromide (Br^-) (Br^-/NH₃, 0.075-0.5mol/mol), NCl₃ concentration after NH₃ chlorination decreased with increasing Br^- concentration. In case of the odor intensity, it did not change so much at up to 0.25 mol/mol, but decreased at 0.5 mol/mol. Thus, it was suggested that the compouds other than NCl₃ contributed to chlorinous odor in the presence of Br^-.

 Fragmentation behaviors of microplastics (MPs) have been studied in recent years. Studies have been done on the fragmentation behaviors of MPs in seabed and beaches; however, such studies have not been performed on the roadway. The main objective of this study is to evaluate the fragmentation behaviors of MPs on roadway surfaces. In order to simulate the behavior of MPs fragmentation in the roadway environment, three types of plastic bags and three types of plastic straws cut into 1 cm x 1 cm were exposed to ultraviolet light and stepped on by foot. As a result, 3,900 – 5,710 MPs particles with diameters over 20 µm were produced from a piece of plastic bags, and 3 – 1930 were produced from a piece of plastic straw. It is found that 37 – 40% of plastic bags by area ratio have disintegrated into 1.47 million – 1.62 million particles with diameters smaller than 20 µm after 1152 hours of ultraviolet light exposure and 400 times of foot stepping. The present study indicated a possibility that microplastics can be produced on the roadway.

 Most of cesium in soil is strongly fixed, and forest soils may have a lower capacity of Cs fixation because of organic matter. We investigated the vertical distribution of Cs-137 in forest soils and the characteristics of the soils; loss on ignition, CEC, and RIP. Loss on ignition and CEC decreased with depth, and RIP increased. About 90% of the amount of Cs-137 was present within the upper 6cm layer of soil. The concentration of exchangeable Cs decreased with depth, but the ratio of exchangeable Cs to total Cs increased. Most of Cs in forest soils we collected was strongly fixed, however, it is possible that a part of exchangeable Cs remains because organic matter including dissolved organic matter in soil plays a minor role in fixing Cs and also because organic colloides enhance the transfer of Cs.

 In the watershed of the Ogouchi Reservoir, there are water source forests managed by the Tokyo Metropolitan Government Bureau of Waterworks and privately owned forests. The water source forest is expected to be effective in preventing sediment runoff, while the privately owned forest is concerned about sediment runoff due to lack of maintenance, which is a major concern in dam management. In this study, we attempted to extract and analyze the effects of major events by using long-term time series data based on periodic water quality surveys conducted by the water resource management office. Specifically, we attempted to evaluate the data by introducing a new evaluation method using a polar coordinate system to evaluate the scatter plot of the long-term time series data. As a result of the analysis using the devised evaluation index, the effects of the slope, tree density, and understory vegetation on the long-term effects of the water source forest and the forest condition affecting the prevention of sediment runoff were clarified based on the behavior of the ratio θ of flow rate specific turbidity.

 Chlorine injection is strictly controlled so that the residual chlorine level of tap water in the supply and distribution system should be more than 0.1 mg/L. Currently, skilled operators decide the injection volume based on thier experience. However, due to retirement of a large number of veteran operator and a decrease in the number of staff, new methods for managing the injection volume of chlorine that do not depend on experience are required.

 This study focused on the time-series data of residual chlorine concentration possessed by water purification plants, and aimed to construct a predictive model that can infer residual chlorine concentration several hours ahead by learning the trend of change in concentration in time series. Specifically, we attempted to construct predictive models of residual chlorine concentrations at 3 hours, 6 hours, 12 hours, and 24 hours ahead using long-term short-term storage networks (LSTM) algorithms.

 We have found that the optimal block for building the model is 24 hours, and the prediction time needs to be 6 hours or less in order to keep the error target less than ±0.025. It was also found that the minimum amount of data required to construct the model was the amount of reduction in residual chlorine concentration for 4 months from April to July.

 From the above, it was found that the residual chlorine concentration 6 hours ahead can be predicted by LSTM if the time series data of 1 hour interval of residual chlorine concentration can be prepared for 4 months.

 Recently, 2-methylisoborneol (2-MIB), which are mold odorants, has been confirmed in the Ara River, and powdered activated carbon has been added for their reduction. However, measurement of the concentration of the odor is difficult, and in many water purification plants, powdered activated carbon has been added empirically.

 In this study, we developed models for short-term predictions of odor concentration by FFANN (Feed Forward Artificial Neural Network) and LSTM (Long Short-term Memory) using the big data held by water purification plants. In FFANN, the odor concentration could be estimated from the basic water quality items at the current time. In addition, in LSTM, a short-term estimate of the concentration of the odor after 3 hours was obtained from the water quality including the concentration of the odor until the current time.

 This suggests that powdered activated carbon can be controlled by inputting the odorant concentrations obtained from FFANN into LSTM.

 Suspended particles in treated water can gradually accumulate in distribution pipes, which cause water discolouration after resuspension due to hydraulic disturbance. This study aimed to estimate the target concentration of suspended particles in treated water from the viewpoint of controlling such discolouration. We investigated the detachment process of accumulated matters triggered by the hydraulic disturbance in a pipe loop facility, and then developed a simple numerical model of detachment. A visual testing of drinking water was also conducted to determine the turbidity threshold at which customers start to perceive the cloudiness or start to complain to water utilities about it. Based on these data, the increase of turbidity during disturbance was simulated in the target network based on the amount of accumulation previously predicted. Then, the discolouration potential score, a new indicator of the possibility of discolouration incorporating the customers' acceptance, was calculated based on the estimated turbidity. The result showed that there were no pipes exceeding the acceptable score at the current concentration of suspended particles (10 μg/L) in treated water. However, pipes with unacceptable score appeared at the concentration of approx. 17 μg/L, which can be considered as a target concentration for controlling the discolouration.

 While water purification using membranes has many advantages over conventional treatment, membrane fouling is still a major problem. Recent studies have suggested that high-molecular-weight hydrophilic organic matters called biopolymers play an important role in the evolution of membrane fouling. In this study, biopolymers were collected and isolated from several drinking water sources with different characteristics, and the properties of the isolated biopolymers were investigated. Degrees of membrane fouling caused by the biopolymers were clearly different depending on the sources, indicating that the characteristics of biopolymers varied with the source. Differences in biopolymers were evident in those molecular weight distribution measurements using LC-OCD and infrared spectra. It was also postulated that biopolymers mainly composed of polysaccharides tended to cause severe irreversible fouling. Analysis of the biopolymers using quartz crystal microbalance with dissipation monitoring(QCM-D) demonstrated an interesting result; the order of affinity of each isolated biopolymers to the membrane material (i.e. PVDF) was consistent with the order of degrees of membrane fouling observed in the membrane filtration test. In addition, viscoelasticity of the biopolymers assessed by QCM-D may explain reversibility of membrane fouling.

 Regular chemical cleaning is conducted in drinking water treatment plants(DWTP) to recover flux declining. In the present experiment, we conducted accererated ageing test by soaking PVDF hollow fiber membrane in sodium hypochlorite, which is common cleaning agent in membrane fitration system. In addition to that, we harvested membranes which were used in a DWTP. We compared virgin membrane, used membrane and soaked membrane by assessing surface structure, selectivity, permeability and pore size distribution. Soaked membrane showed less selectivity than virgin membrane and the decline was similar to used membrane. On the other hand, surface structure and pore size distribution were different between used and soaked membrane. Chages in structure can be different between acceralated ageing test and ageing at DWTP.

 Organic matter and nutrients in municipal wastewater are important resources to be recovered. Direct membrane filtration (DMF) can efficiently recover and concentrate organic matter in municipal wastewater. In most of the previous studies investigating DMF, recovery of nutrients in the treated water (permeate) was not considered. In this study, phosphate ion adsorption was attempted in the pretreatment of DMF in which microbial carriers with zirconium-based phosphate ion adsorbent were placed. As for recovery of ammonium ions in the permeate, use of poly(sodium acrylate) was examined. Experiments were conducted with real municipal wastewater and the results showed that 75% of the phosphate ion and 80% of the ammonium ions could be recovered. The recovery of ammonium ions could be further improved by using nanofiltration that could eliminate the effect of coexisting multivalent ions.

 Power to Gas (PtG) technology, which converts surplus electricity into hydrogen gas by water electrolysis, has been attracting attention. One of the methods to utilize this hydrogen gas by converting it into methane gas is bio-methanation in anaerobic digesters at wastewater treatment plants. Laboratory experiments are conducted to evaluate the effect of hydrogen supply on organic acid accumulation during anaerobic digestion by varying the hydrogen supply rates. In mesophilic anaerobic digestion of organic substrate at a loading rate of 0.75 g-volatile solids/(L•d), acetic acid, propionic acid, and isovaleric acid accumulated when the hydrogen supply rate was 26 NL/(L•d). Under the hydrogen supply rate of less than 18 NL/(L•d), no significant accumulation of organic acids was observed, indicating that the conversion of the supplied hydrogen to methane is possible under continuous operation conditions. Microbial structure analysis showed that detected ratios of hydrogen-utilizing methanogens increased under stable operation with hydrogen supply, while detected ratios of acetic acid-utilizing methanogens decreased under acid accumulation conditions. The results show that hydrogen supply for converting carbon dioxide produced from anaerobic digestion of sewage sludge is applicable.

 To introduce a methane production process in a small-scale sewer plant which employ oxidation process or extended aeration activated sludge process, it is effective to gather dewatered sludge from several wastewater treatment plants. In this study, biochemical methane potential (BMP) of dewatered sludge collected from eight small-scale plants was evaluated. BMP remarkably decreased in summer season in lower scale plants, though the variation of BMP in higher scale plants was small. BMP increased remarkably by coagulation\dewatering process. Increasing ratio of BMP did not depend on the treatment process, dewatering devise, and season. As the results of EPS extraction, EPS increased by coagulation/dewatering process. Especially, carbohydrate contents in LB-EPS decreased and those in Total-EPS increased, suggesting that LB-EPS strongly bund to the cell surface, and polysaccharide inside the cell was eluted to EPS fraction by damage of cells. Since the pH value of coagulant solution was low, combination of acid addition and mechanical force might be effective on increase in BMP. These results indicated that coagulation/dewatering process was effective as pre-treatment of methane production of sewage sludge. Collection of sewer sludge after dewatering would be useful to introduce methane production process.

 In this study, the material and energy balances were clarified for an energy-saving small-scale methane fermentation facility. As a result, the facility was operating with a long residence time at a design acceptance rate of about 27%. Furthermore, the organic matter decomposition rate decreased due to the decrease in the amount received and the change in the properties of the food waste. In the energy balance analysis, the amount of methane fermentation received was about 0.8 tons per day, and the self-sufficiency rate of electricity was about 113%, indicating that the methane fermentation facility is energy independent.

 In order to develop a new process for lowering harmful heavy metals from anaerobically digested sewage sludge, the adsorption and recovery of heavy metals from acidified sewage sludge were investigated using a fibrous chelating agent enwrapped with a nylon mesh bag. First, heavy metals in simulated wastewater were adsorbed to the chelating fiber through the nylon mesh with opening of 30 μm. Heavy metals adsorbed to the fiber were successfully desorbed with dilute sulfuric acid at a pH of 1. Next, the leaching of heavy metals from anaerobically digested sewage sludge was conducted by adjusting the pH of the sludge to 2 with sulfuric acid for 48 hours. And then, the pH of the acidified sludge was adjusted to 2.5, 3 and 4 after the addition of nylon mesh bag including the fiber. The optimum pH values in the adsorption with the fiber were 2.5 for Cu, 3 for Pb, and 4 for Cd, Cr, Ni and Zn, respectively. The application of the fibrous chelating agent would be useful for the recovery of soluble heavy metals from acidified sludge without using an acid tolerant solid-liquid separator.

 Prevention of leaching of heavy metals from a simulated sediment was studied using a steelmaking slag. A mixture was created with a standard solution of metals (Ca, Cd, Cr, Cu, Mn, and Zn) and clay, and a stabilized sediment was prepared by adding converter steelmaking slag. Diffusion tests were performed on these samples to evaluate different leaching behaviors for 64 days. The cumulative leaching ratio of all the elements decreased significantly. In addition, the effective diffusion coefficients of the metals in the simulated and stabilized sediments were calculated based on the diffusion. The effective diffusion coefficient of Ca, Cd, Cr, Cu, Mn, and Zn was approximately 1/25, 1/261, 1/4.7, at least 1/(1.3 x 10⁷), 1/2619, and at least 1/(1.8 x 10⁷) respectively, in the stabilized sediment than in the simulated sediment.

 The relationship between the composition of inorganic components in sewage sludge, their melting points, and the amount of molten material was investigated with differential thermal analysis in order to elucidate the mechanism of the clogging phenomenon caused by adhered materials in the sludge incineration system of a sewage treatment plant and to develop a countermeasure. The sludge in the sewage treatment plant where the clogging phenomenon occurred contained substances with a melting point of around 860°C throughout the year. During the winter season, the melting point of the sewage sludge dropped to nearly 800°C, which is below the sludge combustion temperature, indicating that the presence of low-melting-point compounds plays a significant role in the occurrence of the clogging phenomenon. The melting point decreased and the amount of melt tended to increase as the P₂O₅ content in the sludge increased, indicating that P was an component that promoted the clogging phenomenon. From the results of differential thermal analysis on simulated samples in which reagents were added stepwise to calcined real sewage sludge, it was estimated that the higher the Mg, Al, Ca and Si content and the lower the Na content, the less likely the clogging phenomenon occurred.