In this study, behaviors of pepper mild mottle virus (PMMoV), rotavirus A (RVA), and norovirus GII in an advanced water treatment process and liquid waste treatment system were investigated by analyzing the water samples collected at 11 points in a full-scale drinking water treatment plant. PMMoV and RVA were detected in the raw water at the concentrations of 6.1 and 3.7 log₁₀ copies/L, respectively. PMMoV was detected in the water samples after the coagulation-sedimentation process at the concentration of 3.9 log₁₀ copies/L, while RVA was not. PMMoV was detected in the samples after the ozonation and activated carbon treatment processes at the concentrations of 3.4 and 3.2 log₁₀ copies/L, respectively, and was detected only in 11% of samples after the rapid sand filtration. In the liquid waste treatment system, PMMoV was detected in the supernatant from sludge thickener and dewatering liquid wastes from sludge filter press at the concentrations of 4.2 and 4.3 log₁₀ copies/L, respectively. Based on the flows of drinking water treatment process and waste streams, the load of PMMoV recycled back into the raw water reservoir was estimated to be 0.06% of that contained in the raw water. These results suggested that most of PMMoV removed through the coagulation-sedimentation process were disposed from the plant with dewatered cake.

 Required disinfection strength for wastewater effluent need to be determined based on a mathematical model that connects the operational parameters (e.g., CT value) and log reduction value (LRV) of viruses. However, an inactivation kinetics model applicable to wastewater effluent with fluctuated water quality has not been developed. This study aimed to develop an inactivation kinetics model of which predictors were water quality indices and operational parameters, using regularized regression analysis. The dataset of the LRV of the genus enterovirus and the experimental condition were collected through a literature review to be used in the model construction. We found that automatic relevance determination with interaction terms resulted in better prediction performances. Finally, we performed chloramine disinfection test using a laboratory strain of Enterovirus 71 and secondary treated wastewater in order to validate the developed model, and demonstrated that prediction accuracy was higher and overestimation of LRVs were reduced in Bayesian ridge regression with interaction terms. However, the virus LRV were overestimated especially when the observed LRV was lower than 2 LRV. These results suggested that the prediction performance is affected by the strain-dependent chlorine sensitivity of enteroviruses and other factors which lower the efficacy of chlorine disinfection of wastewater effluent. In order to improve the applicability of the developed model, further studies need to identify the unknown factors that affect the disinfection efficacy.

 Noroviruses are well known as the main causal pathogens of oyster-related outbreaks. To prevent norovirus infection in consuming raw oysters, shellfish farmers generally conduct depuration of oysters to remove the virus before its shipment. However, since the depuration seems to be not effective enough to remove Norovirus from oysters completely, new measures based on different concepts, such as selecting oysters with low capacity to accumulate norovirus, are required to improve the safety to consume raw oysters. In this study, to obtain information for the selecting oysters in which Norovirus are hardly accumulated, we performed an experiment that oysters (Crassostrea gigas) collected from a shellfisheries area were artificially contaminated for 24 h in artificial seawater with a high concentration of Norovirus GII. 2 and GII. 4. After the contamination process, the oysters were depurated in the clean seawater for 24 h. As the result of contamination and depuration, Norovirus GII. 2 (80.0 %) was accumulated in oysters more effectively than GII. 4 (60.0 %). The depuration process only achieved the slight decrease in the percentage of oysters contaminated with GII. 4 from 80.0 % to 60.0 %, while these percentages were higher than in uncontaminated oysters (20.0 %). The difficulty to eradicate Noroviruses accumulated in oysters is consistent with the previous studies. Interestingly, regardless of its genotypes, a part of oysters did not accumulate Norovirus GII during 24 h in the seawater heavily contaminated with this virus. On the other hand, the highest concentration of Norovirus in oysters was 4.08 log copies/g-DT, indicating the huge difference (100 times or higher) in the virus accumulation capability from one oyster to another. The Norovirus GII concentration in oysters was not significantly correlated with the weights of individuals and digestive cecum. This implies the existence of a specific mechanism of virus accumulation which is highly dependent on oyster individuals.

 Effects of SRT and HRT on digestibility of polysaccharides, proteins, and lipids in waste activated sludge were investigated in an anerobic membrane bioreactor (AnMBR). The AnMBR was operated in six different phases. Degradation efficiencies of polysaccharides, proteins, and lipids were increased with prolonged SRT from 30 days to 90 days. Shortening of HRT from 30 days to 15 days lead to increase of organic loading rate, which further increased biogas production rate. Trans-membrane pressure reached to 41 kPa during 154-days continuous membrane filtration of digested sludge. Inorganic irreversible fouling was dominant in the used membrane and Ca, P, and Mg were extracted.

 In this study, we proposed the basic theory of a novel high-efficiency nitrogen recovery method by applying the intracellular organic matter accumulation characteristics of microalgae under nutrient starvation, with the aim of dramatically increasing the efficiency and saving energy of nitrogen resource recovery from sewage, and verified the effectiveness of the method through laboratory scale experiments. By exposing Chlorella sp. MK201 to a phosphorus-starved environment and controlling pH, we artificially inhibited cell division and temporarily increased the accumulation of intracellular organic matter. Subsequently, we observed rapid cell devision of Chlorella by consuming the accumulated organic matter as an energy source. Our novel two-step process method consisted of accumulation and utilization of intracellular organic matter was shown to be effective for highly efficient cultivation of microalgae. These results are expected to contribute to expanding the possibilities of algae utilization in the future.

 Microbial fuel cells (MFCs) can simultaneously treat wastewater and recover renewable energy, but their output voltage and power are low. Therefore, a voltage booster rectifier (LVBR) consisting of a DC/AC voltage booster (LVB) and a rectifier and charger was developed to boost low MFC output voltage to usable levels. In the present study, the electric energy recovery rate from wastewater was evaluated for the following two connection methods of the MFC and LVBR. Three Each individual air-cathode MFC was connected to an LVB (MFC-LVB units), and then three MFC-LVR units were parallelly connected to a rectifier/charger (MFC-LVBR I).Three air-cathode MFCs were parallelly connected to an LVB and then connected to a rectifier/charger (MFC-LVBR II).Asupercapacitor (16.2 V, 83.3 F) was charged for 72 h, and the voltage was increased to 2.68 Vwith a charging efficiency of 31.2 % for MFC-LVBR I and to 3.10 V with a charging efficiency of 35.9 % for MFC-LVBR II, respectively.

 In order to improve the efficiency of CCTV surveys of sewer pipe, the applicability of machine learning for image recognition and object detection was investigated using actual survey videos. For image recognition, the effect of transfer learning and generalization performance of four models, MobileNetV3-Large, ResNet-50, EfficientNet-B4, and EfficientNet-B4 Noisy Student, were compared in a six-class classification using F-means. ResNet-50 was better for the training data set without transfer learning, EfficientNet-B4 Noisy Student was better with transfer learning, and EfficientNet-B4 was better in generalization performance for both without and with transfer learning. For object detection, the mAP was 90.76% for 3-class classification, indicating its applicability.

 Various known and unknown chemicals potentially present in treated wastewaters have raised un urgent needs for a more comprehensive water quality assessment and monitoring tool to ensure the safety and reliability of water reuse systems. In this study, we developed a model of the fluorescence feature of drinking waters using machine learning based anomaly detection, and the similarity between the water quality or the model and those of effluents from advance wastewater treatment processes was evaluated quantitatively. Total 387 samples of actual drinking waters (i.e., tap water, spring water, bottled water) were collected from all over Japan, and their three dimensional fluorescence spectra data were learned by Deep SVDD, one of the machine learning based anomaly detection method. The abnormality (deviation from the model water quality) calculated for drinking water and reclaimed water samples demonstrated that actual drinking water quality itself was not unform, and varied by sampling dates or location. Although the abnormality of the RO permeate slightly exceed the range of variation observed for the actual drinking waters, the deviation was much smaller than the diluted MBR effluents. The inline LC-EEM analysis further revealed that the molecular weight distribution of the fluorescent compounds in the reclaimed waters were smaller than the actual drinking waters. This study first presented the effectiveness of machine learning based anomaly detection method for extracting useful information from the non-target analysis data.

 The United Nations indicated the Sustainable Development Goals (SDGs) as goals to be achieved by 2030. However, due to the complexity of SDGs, there are various interrelationships (synergies and trade-offs) among the goals and targets, which need to be accurately understood in order to improve the progress of SDGs. In this study, we focused on Goal 6 "Clean Water and Sanitation" and investigated the interrelationships of Goal 6 and other goals using explainable machine learning. Totally, 80 indicators were selected for 176 countries, and we used cluster analysis and LIME (Local Interpretable Model-agnostic Explainations) to examine the interrelationships between Target 6.1/6.2-related indicators (population with access to drinking water and sanitation) and other SDGs indicators. The results show that there are synergistic relationships between Target 6.1/6.2-related indicators and other indicators such as electricity, poverty rate, and mortality, and a trade-off with energy consumption and waste. This study proposes the use of explainable machine learning as a method for quantitatively analyzing the interrelationships among various Goals and Targets.

 This study is investigated to the competition between cyanobacterium Microcystis aeruginosa and diatom Nitzschia palea that can increase their cell number in a favorable environment for the occurrence of water bloom. We particularly focused on the temperature and pH effects on the inhibition effects of M. aeruginosa by N. palea. The maximum cell yield of M. aeruginosa reduced by approximately 50 % in the co-culture with N. palea at 15–30 ℃ as compared to that in the monoculture. N. palea also reduced the maximum cell yield of M. aeruginosa by 33, 54 and 66 % at pH 7.0, 8.0 and 9.0, respectively. N. palea reduced M. aeruginosa growth in the culture condition where water bloom is likely to occur. However, M. aeruginosa remained the dominant species in co-culture at 20–30 ℃ or pH 7.0–8.0. It is necessary to artificially increase the relative abundance of N. palea for enhancing the inhibition effect of M. aeruginosa.

 The assessment of secondary productivity is important in terms of proper conservation of biodiversity and fishery management. The object of this study was to evaluate the potential of evaluating the growth processes of oysters, which are one of major secondary producers in coastal marine systems, by shell analysis. Using linear regression analysis, we estimated the relationship between the Mg/Ca ratio of the chalky substance in oyster shells and water temperature. It was also found that one chalky layer was formed in about two month, and the Mg/Ca ratio in the layer reflects the water temperature with timelag one month. The area around the umbo surrounded by a continuous foliate layer from both surfaces of the right shell, including the chalky substance near the umbo, which is considered to record growth, showed a positive relationship with three growth indicators of oyster individuals, shell thickness, shell height and shell cut surface area. Thus, the area around the umbo can be useful, quantitative indicators of oyster growth. These results suggest that comparing the Mg/Ca ratio distribution of the chalky substance near the umbo with field water temperature data, ones can estimate the growth process of oysters at approximately one month resolution.

 We investigated the effect of habitat heterogeneity within river reaches on macroinvertebrate commu-nity structure at upstream and downstream reaches of dams in Miyagi Prefecture, Japan. We compared environmental conditions and macroinvertebrate community structures among four habitat types, i.e., lotic habitat, bar-head lentic habitat, bar-tail lentic habitat and isolated pond, in six river sites. There were sig-nificant differences in water quality, physical parameters and biomass of fine and coarse particulate organic matters among the lotic habitat and lentic habitat types. Spatial variation of spatial factors (dam upstream / downstream, habitat area, and lentic habitat score) and environmental factors (flow velocity and electrical conductivity) between habitat types explained 34% of the variation of macroinvertebrate community struc-ture. Although the lentic habitats had a small space in the river sites, it contributed highly to increasing habitat heterogeneity (β-diversity) within the sites. They also highly contributed to an increase in the overall diversity (γ-diversity) of the upstream and downstream sites of the dams. Our findings suggest that resto-ration of gravel bars to increase habitat heterogeneity in river through the formation of lentic habitats is important for the conservation of riverine ecosystems.

 The applicability of flow cytometry (FCM) for viral particle quantification to membrane challenge testing was examined to identify the performance degradation due to the microstructural changes or microdamage associated with membrane ageing, which is difficult to detect with conventional integrity testing. To evaluate and select a proper purification method for viral particle quantification by FCM, T4 phage purified by ultracentrifugation, medium removal by UF coupled with DNase treatment, medium removal by UF were quantified by FCM, and the effect of purification of host E. coli DNA was evaluated by quantitative PCR. Ultracentrifugation showed a high purification performance, but a viral inactivation was observed. By applying viral particle quantification by FCM with medium removal by UF coupled with DNase treatment to the membrane challenge test, it was revealed that the T4 phage rejection rate (LRV) of the aged membranes was about 2log and was comparable to the rejection rate calculated from the plaque assay method, indicating that the quantification of virus particles by FCM can be applied to the membrane challenge test.

 Membrane properties affect membrane fouling in MBRs. Although many previous studies have investigated the relationship between membrane properties and membrane fouling, there are few studies in which specific membrane properties of interest were varied intentionally and independently. In this study, membranes with the same material and different pore sizes, and membranes with the same structure and different materials were fabricated and used in a bench-scale MBR treating municipal wastewater. In the experiments in which UF and MF membranes made from CPVC were compared, there was almost no difference in fouling between the two membranes. This result implies that effects of pore sizes on fouling in MBRs are limited as long as a local flux imposed on membranes is fixed. In the experiments in which CPVC UF and PVDF UF membranes with the same structure were compared, fouling in the CPVC membrane was faster than that in the PVDF membrane. With the tested flux range of 0.72-0.90 m/d, it was suggested that PVDF is a better membrane material than CPVC in terms of prevention of membrane fouling.

 Membrane bioreactor (MBR) has many advantages over the conventional activated sludge systems, but occurence of membrane fouling is a problem. Our research group found that backwashing utilizing nanobubbles can effectively alleviate membrane fouling in MBRs, but there is plenty of room for the optimization of backwashing using nanobubbles. In this study, we prepared ceramic membranes fouled by sodium alginate, which is often used as model foulant of MBR and investigated factors which can enhance the cleaning efficiency. It was confirmed in this study that cleaning efficiency of backwashing was enhanced by using nanobubbles. Contribution of hydroxyl radical generated from nanobubbles to the enhancement of cleaning efficiency would be limited. Instead, it was suggested that nanobubbles intruded into the fouling layer during backwashing and loosened the structure of it, which led to increase in cleaning efficiency of hydraulic cleaning.

 For the model area, we comprehensively evaluated the energy saving / energy production and GHG reduction measures for the potential of reducing GHG emissions by wide area cooperation and high efficiency technologies using a sewage treatment plant simulator. In the wide area cooperation measures, the integration of village wastewater treatment facilities would decrease to 7,000 kg/day, reduction of 31.4% and the integration of urine treatment plant would decrease to 6,500 kg/day, reduction of 43.5%. As for hige efficiency measures, energy saving measures were reduced to 16,700 kg/day, reduction of 8.2%. Energy production measures reduced to 14,900 kg/day due to the increase in power generation, reduction of 18.1%. As a GHG reduction measure, the fuel reduction would reduced to less than half, resulting in a reduction of 15,400 kg/day, reduction of 15.4%. The incinerator N₂O generation rmeasure which was the largest reduction effect, would reduce to 12,500 kg/day, reduction of 31.3%. GHG emissions in the model area would be expected to be reduced by 57.3% from the current 36,500 kg/day. It was considered necessary to develop and implement further energy-saving and energy-production technologies.

 This study aims to predict the energy consumption of a water-cooled heat pump in a business office with a ground source heat pump system using a lining ground heat exchanger during air cooling with high power consumption. A model to predict COP was developed by applying a multiple regression equation using part load ratio and inlet temperature of the heat pump, which were obtained by the cooling experiment. In addition, simulations were performed to find the effectiveness of the save control systems operation on energy consumption using the model. Results suggest that energy consumption can be reduced by about 30% compared to systems without save control by optimizing the save rate.

 We examined and analyzed indicators of the financial management situation of water utilities. We have selected two indicators from each of the three perspectives of "people, goods, and money," which are generally considered to be important in the management of a business. We also looked at two more indicators for water receiving from the water supply, which was suggested to have an impact on the maintenance and management system in a previous study. The results show that the business condition worsens as the number of the water supply population decreases, and that many of the smaller utilities are unable to fully cover their expenses from water charges alone. In addition, it was found that larger utilities are more likely to reduce fixed assets and utilize outsourced staff to improve operational efficiency, while there is a significant variability among smaller utilities in their current status. In addition, the utilities that have implemented wide-area expansion and public-private partnerships have increased their business efficiency by increasing the ratio of contracted staff, and in particular, the utilities that have implemented wide-area expansion have seen a significant decrease in the ratio of water received, suggesting that although the objectives of the initial measures are reflected in the indicators, the management situation has not yet been significantly improved.

 Although water/wastewater treatment using membrane technology has various advantages over conventional methods, membrane fouling still impedes wide-spread use of the technology. Recent studies have demonstrated that high-molecular-weight hydrophilic organic matters (i.e., biopolymers) play an important role in the evolution of membrane fouling. However, detailed information on biopolymers such as molecular composition and structure is still unknown. In this study, biopolymers were collected and isolated from surface water and municipal wastewater, and their degradability by enzymes was investigated. Enzymes that could degrade specific structures of polysaccharides and proteins (α-amylase, cellulase, protease, and lysozyme) were used in this study. LC-OCD analysis could detect degradation of biopolymers (i.e., shift of molecular weight distribution) caused by enzymes, which cannot be detected by common analytical methods. Biopolymers isolated from surface water were degraded by α-amylase and cellulase, whereas biopolymers isolated from municipal wastewater were degraded by lysozyme. These results clearly indicate that the two biopolymer samples examined in this study had different structures and properties, which has not been clearly shown so far. Use of various combinations of biopolymers and enzymes in the method established in this study may deepen understanding of the structure of biopolymers.

 Disinfection byproducts (DBPs) can be generated from the reaction of natural organic matters (NOM) with halogen during disinfection process. In this study, we used ultra-high resolution mass spectrometry to identify the molecular formulas of deuterium-labeled X_n-DBPs (where X_n is a halogen such as chlorine, bromine, or iodine) to clarify the NOM precursors and reaction pathways of DBPs. The relative contributions of electrophilic addition and substitution reactions to the formation of DBP was found to be dependent on the halogen species involved in the reaction, and the acidity of the hypohalogenic acid species was the important factor affecting the reaction pathway. Furthermore, a binary classification machine learning model (random forest) was constructed to predict the formation of DBP from the molecular properties of NOM. The model showed high prediction accuracy and suggested that the carbon oxidation state of the precursor is an important factor in the formation of iodine containing DBP.

 We investigated changes in dissolved organic carbon (DOC) and the abundance of fluorescent dissolved organic matter (FDOM) components in a river before and after the occurrence of primary treatment discharge from a combined sewage treatment plant. We proposed DOC, the score value of the protein-like component (Comp. 2) of the FDOM, and FDOM/DOC as indicators detecting the change in river water quality due to the inclusion of untreated sewage during rainy events. Then, we evaluated the suitability of the three indicators by comparing their absolute values and their change rates with ratios of estimated primary treatment discharge to river flow. The suitability of the indicators was judged based on binary classification using machine learning, that is confusion matrix with accuracy, and F-value. As the results, it was found that the absolute values of DOC and FDOM were effective in detecting of the occurrence of primary treatment discharge at the downstream point of the receiving river because of the large accuracy rates and F values.

 Optically pure lactate is a raw material for biodegradable polylactic resin. Such lactate is produced by fermentation, and lactate purification from cultivation broth remains a critical issue for reducing the production cost of polylactic resin. Crystallization of calcium lactate is a popular process for its purification; however, the process requires condensed calcium lactate solution, and calcium sulfate is produced as waste in the final step for liberation of lactic acid. This study investigated the purification process via chitosan lactate. Chitosan L-lactate was made using chitosan as a neutralizer in lactate fermentation. Anti-solvent crystallization was applied to recover chitosan lactate, and acetone was worked as an anti-solvent to precipitate chitosan lactate. Finally, ammonium lactate and chitosan were obtained separately by adding chitosan lactate into aqueous ammonia. The recovery ratio of lactate and chitosan was almost 100% when using high molecular chitosan. Recovered chitosan would use as a neutralizer in lactate fermentation again.

 Effects of lactic acid, as an example of organic acids which affects pH and methane fermentation performance, on methane fermentation of waste biomass are evaluated. In batch experiments, when the initial lactic acid concentration was 17.2 gCOD/L, pH dropped from 7.4 to below 6 and methane fermentation was inhibited. When the initial lactic acid concentration was 11.5 gCOD/L, pH dropped to around 6.3, but the inhibitory effect was suppressed with equivalent alkali addition for pH recovery, and the ratio of methane production amount to lactic acid input was about 0.8 on COD base. The calculation of pH based on acid-base equilibrium for sludge from methane fermentation plants treating different substrates was able to reproduce pH change by acid titration. These results confirm that pH under high organic acid concentrations can be predicted by analyses of sludge characteristics. Prediction of pH decrease can be used to evaluate the effect of temporal high loading on methane fermentation performance.

 In this study, a mass production test of a new sewage sludge fertilizer using sewage sludge and regional biomass was carried out on a scale of 5 m³, and the obtained fertilizer was applied to a nitrogen mineralization test, a germination / growth test using Komatsuna (Brassica rapa var. Perviridis) and a tea cultivation test. We were able to mass-produce fertilizers with a total nitrogen content of 3.6 to 3.9% and a low heavy metal content. Since the new sewage sludge fertilizer contains 0.95% ammonia nitrogen, it is considered to be suitable for tea plants of ammonia-philic plants. The nitrogen mineralization test revealed that the new sewage sludge fertilizer has a significantly different mineralization pattern from the organic fertilizer rapeseed meal. In the test plot using the new sewage sludge fertilizer in the germination /growth test, the body mass index of 115 or more (control fertilizer plots 87 to 115, standard plot 100), and it was considered that they did not contain growth inhibitors. Furthermore, the tea cultivation test revealed the effectiveness of new sewage sludge fertilizer with a yield equal to or higher than that of the conventional organic fertilizer (rapeseed meal).

 The watershed of Lake Ushikunuma, which is located in the southern part of Ibaraki Prefecture, has been urbanized in recent years. The aim of this study was to clarify the factors affecting changes in water quality in this lake. The water quality and phytoplankton community were surveyed and the changes were analyzed. The results showed that the chemical oxygen demand (COD), total nitrogen, and total phosphorus concentrations in the inflow rivers were all decreasing, due to a decrease in the area of the field and diffusion of the sewage system. COD and chlorophyll a concentrations at the center of Lake Ushikunuma were also decreasing. It was shown that the reduction in inflow load due to urbanization resulted in improved water quality in the lake. Moreover, the results indicated that phytoplankton had a significant influence on the COD changes in the lake because the ratio of particulate COD to total COD was greater than 50%, and because COD and chlorophyll a concentrations in the surface layer were significantly correlated. The phosphorus limited phytoplankton production during most of the year. These results suggest that the phosphorus load and phosphorus release flux from the bottom sediment should be monitored carefully to understand the water quality changes in Lake Ushikunuma.

 By analyzing sulfur dioxide, SO₂ concentration data which was observed in the crater floor area of Mt. Aso and various existing meteorological data, relationship between the occurrence of high-concentration events exceeding the SO₂ environmental standard and meteorological conditions. And numerical simulation using the WRF was carried out to investigate mechanism to transport vertically from the Nakadake crater to the bottom of the crater floor. It was found that the high-concentration events occurred by vertical transportation of downslope wind of mountain waves or mountain wind.

 We evaluated the food resource supply for fouling organisms by inflows of suspended particulate organic matter (POM) in 18 cooling systems of 6 power stations based on seawater samplings and analysis of data from 71 cases of waste treatments of fouling organisms. As a result, the ratio of POM influx to the demand for the production of fouling organisms in the cooling systems ranged between 0.48 and 23.8 (3.55 in median) based on a general productivity/biomass ratio, and between 0.21 and 19.2 (1.99 in median) based on a general suspension-feeding rate of organisms. It was estimated that the areas of approximately several 10⁴ m² were necessary in the sea areas adjacent to the seawater intakes of the cooling systems to place facilities of suspensionfeeding oysters to remove the POM amounts equivalent to the supply or demand for the fouling organisms. The oyster-suspension approach would be difficult currently, since development of concensus among the stakeholders around the coasts are expected to be arduous. Further studies are necessary to examine whether this approach become more feasible by complex use of multiple ecosystem functions which are available in this approach.

 Diarrheal diseases are still serious in low- to middle-income nations, and consuming inadequate water is suspected as one of the main factors. However, past interventions failed to significantly reduce diarrhea prevalence, as they often could not trigger behavior changes. Therefore, understanding local public health data and community backgrounds are considered important in planning intervention projects. However, few studies have comprehensively analyzed past projects to clarify sufficient practices for raising awareness on water and sanitation. Therefore, this study aims to analyze and propose combinations of practices to sustainably raise awareness on water and sanitation in developing nations, by evaluating ODA projects with crisp-set Qualitative Comparative Analysis (csQCA). Sixteen projects for the outcome of “Behavioral changes towards domestic water consumption”, and 13 for “Sustainable use and management of sanitation facilities” were selected. Eight and 13 causal conditions were also selected, respectively. csQCA examined individual and combinational relationship between each outcome and causal conditions. The results showed 3 potential combinations, with awareness-raising workshops to residents from health promotors being the main measures to be taken, for “Behavioral changes towards domestic water consumption”. Four combinations of practices, including sanitation awareness-raising workshops, education and capacitiy development of facility management committees, were suggested for “Sustainable use and management of sanitation facilities”, Results for both outcomes indicated the necessity for residents’ participation, while education was also an important factor in the latter outcome. These combinations provide multiple options of interventions for stakeholders to consider, depending on their community backgrounds and resources. Furthermore, they also showed the importance of community participation and basic education on sanitation, which both have been widely systemized and conducted in Japan, indicating that our basic governmental and educational systems may also bring about improvements in developing nations.

 This study investigated the individual implementation and intention of strengthening protection against COVID-19 during the period when the protection was requested by the government based on a questionnaire suvey, clarifying the factors that affected them. The result showed most of respondents did not strengthen the protection or did it at a low level even during that period. This was possibly attributed to the fact that 2 years had passed since the beginning of COVID-19 pandemic.

 Our survey also found the respondents perceived the information that the number of infections in the city was expected to increase to 1,000 over the next week as a serious warning, influencing their intentions to strengthen the protection. Among the users of a website that provides such information based on virus concentration in municipal wastewater, those who had higher perception about their risk of infection, had greater insecurity about their economic future, or were more altruistic felt stronger aversion to the lack of others’ protections, and consequently increased their intentions to strongten the protection. And the present implementation of protection among the users did not affect their intentions to strongthen the protection significanly. This psychological structure to increase the intention to strongthen the protection for the users was different from those for the non-users.

 Recently, the impact of climate change has been the serious effects on water environments. On dam reservoirs, it is concerned to advance eutrophication due to the increase of water temperature and nutrient loadings. Therefore, this study evaluated the impacts of climate change on phytoplankton concentration and the effectiveness of the destratification system as the adaptation measures depending on the size of imaginary dam reservoirs. As a result, the surface Chl-a concentration in May and June was tend to increase in the future climate change scenarios and the trend was stronger for scenarios with larger temperature increases and recognized in all the sizes of imaginary dam reservoirs. Furthermore, the estimation of water quality using the destratification system in the future climate change scenario indicated that it is possible to reduce the increased surface Chl-a concentration due to the impacts of climate change. These results showed the effectiveness of adaptation measures using the destratification system for eutrophication.

 This study investigated removal of five types of antibiotics, i.e., roxithromycin (ROX), clarithromycin (CLR), levofloxacin/ofloxacin (LEV), sulfamethoxazole (SMZ), sulfapyridine(SPD), from treated sewage using zeolite. After antibiotic solution was treated for 1 hour, removal ratio was high for ROX and CLR (> 93%), and LEV (> 60%), but low for SMZ and SPD (< 7%). The same trend was observed in antibiotic removal from treated sewage. Ecotoxicity of antibiotics in treated sewage to R. subcapitata was assessed using the total of toxic unit (TU_sum) for each antibiotic. TU_sum of treated sewage contacted with zeolite was much lower than that of treated sewage because zeolite treatment effectively removed CLR which has high TU value. In addition, acute toxic test comfirmed zeolite-treated wastewater had no inhibition effect to R. subcapitata. Meanwhile, since visible humic acid-like-material adsorded on zeolite, it is needed to investigate continuity of effective removal of antibiotics using zeolite.

 We investigated the distribution of E. coli in the Akagawa and Mogami Rivers, both of which flows through in the Shonai region in Yamagata Prefecture, Japan. The samples of river water were monthly collected through a year from April 2021 to March 2022 at six and one sites along the Akagawa River and Mogami River, respectively. The isolates of E. coli obtained from the water samples were classified into seven-phylogenetic group and evaluated for the antimicrobial susceptibility against 12 antibiotics.

 The concentration of E. coli in the two rivers ranged from <1 to 280 CFU/100 mL, demonstrating that all of the survey sites were satisfied with its criterion for Class A rivers set by Ministry of the Environment in Japan. The concentration of E. coli at the month of both rivers increased from October to January probably due to the dense population of migratory birds found in this season. Of a total of 653 isolates, which are identified E. coli based on uidA gene using PCR analysis collected in this study, 217 isolates (33.2 %) were classified into B2 group which is associated with a high pathogenicity. 175 isolates (26.8 %) of the isolates exhibited the resistance to one or more antibiotics, including the third-generation cephem antibiotics (Cefotaxime and Cefazolin) and carbapenem (Imipenem). This suggested the existence of the extended-spectrum beta-Lactamase (ESBL)-producing bacteria and carbapenem-resistant enterobacteriaceae (CRE) in the investigated rivers. Sixty-six isolates (10.1%) were multidrug-resistant (MDR) defined to show resistance to at least three different groups of antimicrobial agents, and an isolate was resistant to a total of seven antimicrobials. The fact that these antibiotic-resistant bacteria (ARB), which are clinically important, were found in the rivers with less fecal contamination motivates further investigations of ARB on the source and fate in the river environment.

 This study aimed to investigate the occurrence and the source of the antimicrobial-resistant E. coli in the Lake Biwa watershed. To achieve this, field survey for antimicrobial-resistant E. coli were carried out at several locations on Lake Biwa in Shiga Prefecture, Japan and its watershed rivers with and without rainfall events. Results indicated that the concentrations of E. coli and antimicrobial-resistant E. coli could increase when the river streamflow increased due to the rainfall. To further investigate the effect of precipitation on the increasing of E. coli concentrations in a river, continuous 5-day samplings were performed at a location on Yasu River during rainfall events. Further, the potential contamination source of tetracycline-resistant E. coli isolated from wastewater treatment plants, rivers, and Lake Biwa was investigated by the whole-genome sequence analysis of E. coli isolates. Correlation between the concentration of antimicrobial-resistant E. coli in waters and the land use in the watershed was also analyzed. Results in this study suggest that both human and livestock influence the presence of antimicrobial-resistant bacteria in the Lake Biwa watershed.

 This study was aimed to develop the methods for target screening (TS) of contaminants of emerging concern (CECs) by LC-QTOF-MS in consideration with its simplicity and rapidness. In the TS database (TS-DB), measured m/z values of fragment ions and retention time index were applied and registered. For the TS analyses condition, mass error range (precursor ion: 10 ppm, fragment ion: 50 ppm) and retention time range (ΔRT=±1.0 min) were applied. By the developed TS-DB with 102 types of CECs and the TS methods, TS was conducted for 15 river water samples in the Kiso Three Rivers Basin. As a result, 30 types of CECs were detected. By the chemical profiling analyses, the occurrences of linear alkyl benzene sulfonates (LASs), Pharma-ceutical and Personal Care Products (PPCPs) and Perfluorinated substances (PFASs) were demonstrated for each of Ibi-River, Nagara-River, Kiso-River and their tributaries. This study indicated that TS results together with usage information and the relative detected intensity may achive in understanding the occurrences and characteristics of the chemical profiles in water environment.

 Dynamics and total emission of microplastics (MPs) were evaluated at 5 wastewater treatment plants that applied an oxidation ditch (OD) process. Number density of MPs with a major diameter of 0.5 to 5 mm in effluent was 2.0 to 4.5×10 pieces/m³, and the mass density was 1.87×10-2 to 7.72 mg/m³. In the OD process, MPs were subdivided and increased in number, but most of them were discharged with sludge. The average MPs removal from the OD and secondary sedimentation tank was 92% in number and 90.6% in mass. The 87% number of MPs and the 96.7 % mass of MPs were removed from the sand filtration on average. Based on the investigation and statistics, the annual MPs emissions from all sewage treatment plants with ODs in Japan are estimated: 1.4×10¹⁰ pieces/year and 1.17×10³kg/year for a major diameter of 0.5 to 5mm, and 7.9×10⁹pieces/year and 1.11×10³kg/year for a major diameter of 1 to 5mm, respectively.

 Road dust is considered to be one of the main sources of MPs washed out into the ocean, and rubber pieces from tires can have adverse effects on the ecosystem. However, tires are a mixture of synthetic rubber and natural rubber, and carbon black causes an increase of the absorption residue in IR spectrum, which limits material identification by ATR-FTIR. Therefore, in this study, we proposed a method to judge whether the black samples are tire debris or not by registering the spectrum of tire debris in the library for ATR-FTIR. The spectral shapes differ depending on the tire part. Furthermore, application of tire spectrum library was useful to analyze black MPs in the environmental samples collected from an urban area, improving the detection of tire debris and the material identification.

 Monitoring of orthophosphate (PO_4-P) concentrations in rivers and lakes is important to conserve water environment. Grab sampling followed by general instrumental analysis cannot provide representative concentration of PO_4-P exists in low concentration range in water environment. In this study, passive sampling of orthophosphate was conducted in Sakusyukotoni River and Lake Barato to obtain time-averaged concentration of PO_4-P. As a result, obtained time-averaged concentration of PO_4-P with passive sampling in Sakusyukotoni River coincided with concentrations of dissolved phosphorus in samples obtained by grab sampling. In Lake Barato, vertical profiles of time-averaged concentration of PO_4-P were obtained using passive sampling.

 The consumption of dissolved oxygen by settling particulate organic matter (POM) leads to the formation of hypoxia near the sea bottom in coastal marine systems. The goal of this study was to understand the changes of chemical properties of settling POM and its oxygen comsumption rate applying analyses of fatty acid compositions. We sampled the settling and suspend POM from four depth layers in Shizugawa Bay. Results showed that settling POM have relatively larger contents of C_≧20 PUFA than suspended POM. This suggests the POM which is rich in long-chained essential fatty acids selectively deposited. The contents of C_≧20 PUFA and C_≧20 PUFA/SFA of settling POM decreased significantly with depth, suggesting the POM which contain are mainly degraded in their settling process. Moreover the significant positive relationships between the content of C_≧20 PUFA and the oxygen consumption rate of settling POM imply that the potential of oxygen consumption of settling POM decreased due to its degradation during the deposition. These findings support that the fatty acid analysis help to understand the change of the chemical properties and oxygen consumption of settling POM due to the decomposition even in relatively shallow coastal systems.

 In order to understand the amount of elution of nutrients from the sediment, which is important when considering the environment of the Seto Inland Sea, elution data and environmental data were collected from existing literature. We tried to estimate the elution amount of nutrients from the three items of water temperature, dissolved oxygen concentration in the bottom layer, and amount of organic matter in the bottom layer. Total organic carbon and ignition loss were used as indicators of the amount of sediment organic matter, and the estimated nutrients were dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP). From the prepared formula and the environmental data of the Seto Inland Sea, the elution amount of DIN and DIP in the entire Seto Inland Sea was estimated. The elution amount in the entire Seto Inland Sea increased from around 1980 and then began to decrease, and by around 2015 it was lower than around 1980. It was suggested that the decrease in elution amount of entire Seto Inland Sea in recent years is largely due to the decrease in elution amount in the sea area where the elution amount is large.

 Today the inputs of anthropogenic nitrogen into aquatic environments increase globally, which result from the mass production of chemical fertilizers and their consumptions. The variations in chemical compositions of phytoplankton potentially affect their nutritional values for secondary producers as well as potential impacts on the sea bottom environments via their depositions and oxygen consumptions. We experimentally cultured a diatom species at six levels of inorganic nitrogen concentrations, and examined the response of the algae in terms of their chemical compositions and oxygen consumptions. As a result, the content of essential fatty acids in the diatom cells increased with the nitrogen concentration in ≤3.0 mgN/L, but decreased in >3.0 mg-N/L. The optimum ratio of inorganic nitrogen to phosphorus, at which the diatoms efficiently produce the essential fatty acids, was estimated at 12:1. Furthremore, the oxygen consumption rate of the diatoms increased with the nitrogen concentration, whereas we found no significant effects of the experimental settings of seawater nitrogen cocenration on the settling velocity of the cultured diatoms.

 Environmental DNA (eDNA) analysis is becoming widespread to reduce the effort for fish survey in fish friendly river works. However, the sampling method for obtaining a representative sample in cross-section, and eDNA flow-down distance are unknown. In this study, by performing metabarcoding analysis at 6 points per one cross-section, sampling method was examined. Then by performing the qMiFish method at 10 cross-sections in a river, cases of fish species detected upstream but not detected downstream were collected. Using these data, eDNA decomposition coefficient was determined, and flow-down distance was estimated. It was shown that to acquire a representative sample at a cross-section, sampling surface water at three points or more in a cross-section was necessary. eDNA decomposition coefficient was 3.55 [hr^-1], and the flow-down distance varied from 0.1 to 3.5 km depending on eDNA concentration and flow velocity.

 Estuary weir was constructed in the Nagara River to prevent saltwater intrusion, but high-salinity water often stagnates in bottom layer of downstream area of estuary weir. Because of formation of density stratification in downstream area of estuary weir and in fishway, it is assumed that Anguilla japonica suddenly encounter different salinity conditions during migration. In this study, Anguilla japonica acclimated to environmental water of salinity of 3.5% were put into experimental water of different salinities and analyzed swimming behavior of Anguilla japonica. As a result, it was found that Anguilla japonica which acclimated to saltwater of salinity of 3.5% could not follow environmental change when the salinity difference suddenly changed less than 2.0%. Therefore, it is suggested that once Anguilla japonica are acclimated in buffer zone of well-mixed type by using baffle blocks, it can migrate smoothly.

 It is becoming clear that cylindrical protrusions are effective for eel migration. However, it is feared that if nylon tape debris or flexible fragments of long vegetation flow into the fishway, they may become entangled in the cylindrical protrusions and block the gap, making it difficult for eels to migrate upstream. In this study, we proposed a fishway for eels with strip roughness at the bottom. The roughness interval was varied from 50 to 200 mm, and the flow rate was varied from 140 to 540 ml/s. The roughness interval was determined to be appropriate for a 200mm long Anguilla japonica. As a result, a roughness interval of 100 mm, which is 0.5 times the total length, was found to be effective. This was attributed to the fact that the eels behaved differently in climbing over the strip roughness as the spacing changed. It was found that the eels could easily insert their bodies into the grooves of the roughness when the spacing was 0.5 times the total length, and the roughness could be used as an object of the migration reaction force, leading to the improvement of the migration rate. On the other hand, when the spacing was 0.25 times the total length, it is difficult to insert their bodies between the roughness, and when the spacing is more than 0.75 times the total length, it is difficult for the tail to contact the downstream rouguness, resulting in a lower migration rate.

 In this study, experiments were conducted to clarify the effects of colors and illuminance of LED lighting on the nocturnal activity of a rareand nocturnal species of Hynobius tokyoensis. White, blue, green, yellow, and red LEDs were used in the experiment, and the activity of this species under 1 lux and 10 lux illuminance was compared with that of the species when the lights were off.

 In the 1 lux experiment, the activity of this species was 32 % under white light, 42 % under blue light, 44 % under green light, 64 % under yellow light, and 35 % under red light, compared with the case when the lights were off. The results suggest that the magnitude of the suppressive effect on activity of H.tokyoensis at the same illuminance is white ≈ red > green ≈ blue > yellow. In the 10 lux experiment, many individuals were inactive regardless of lighting color, with activity ranging from 0 % to 29 % compared to when the lights were off. Thus, the nocturnal activity of this species was suppressed at higher illuminance, regardless of the color of the light.

 This study involved the introduction of a sludge dewatering system mixed with plant biomass in a sewage treatment plant. The purpose of the study was to collect information to inform the selection of plant biomass mixing points. The investigation items were the mixing conditions of digested sludge, the flocculant, and the plant biomass. Mixing the plant biomass with the sludge first, compared to mixing with the flocculant first, was more effective at reducing the water content of the dewatered cake, suppressing the outflow of the plant biomass into the filtrate, and reducing the amount of dewatered cake. In addition, the results suggested that the condition at which the plant biomass was most effectively mixed in the sludge occurred around the lowest level at which the sludge flocculates. The optimal mixing ratio of the plant biomass was 15% solids, but a wide range from 5% to 15% was effective. In the selection of plant biomass, it is important to investigate the water absorption rate as one of the factors influencing water content reduction.

 Graphitic carbon nitride (CN) is a photocatalyst that is driven by visible light and easy to synthesize. In this study, we developed a novel environmentally friendly and easily solid-liquid separable photocatalyst-impregnated adsorbent (CS/CN) using CN and chitosan (CS), a biodegradable adsorbent. We evaluated the adsorption and degradation characteristics of CS/CN for two organic dyes, acid black 1 (AB1) and malachite green (MG), in water. In the dye decomposition experiment using photocatalyst alone, CN almost completely removed the dyes (removal rate of more than 94%) in 180 to 390 min under UV-visible light irradiation by a xenon lamp; in the dye adsorption and degradation experiments using CS/CN, both AB1 and MG, which were not able to be removed by chitosan adsorbent alone, were removed under light irradiation (removal rate of over 91%). Although there are issues to be addressed, such as improving the photocatalytic activity of CN, CN -impregnated adsorbents may be effective for removing various pollutants in water.

 Heavy metals are adsorbed on clay minerals and their adsorption capacities depend on the type of clay minerals. The physical and chemical characteristics of clay minerals are changed by heat treatment and the adsorption of heavy metals may be influenced by these changes. Therefore, in this study, the selected heavy metals were adsorbed on 1:1 layer silicates such as kaolinite, and 2:1 layer silicates such as hydrobiotite under different pH conditions. The results showed that the adsorption rates of heavy metals on kaolinite, dickite, and pyrophyllite decreased at 500℃, 500℃, and 1000℃, respectively, and that the adsorption rates of them except for Cs on hydrobiotite were approximately constant high levels regardless of heat temperature. The dissolution rates of structural elements from heated clay minerals were different and increased when the heavy metals were adsorbed on the heated clay minerals. The pH of clay minerals was changed because of heat treatment. However, the changes of pH were not related to the adsorption of the heavy metals or the dissolution of the structural elements. This study indicated that the structure and the adsorption capacities of clay minerals were changed by heat treatment and also that their changes effected on heavy metals adsorption on clay minerals.

 In this study, it was investigated that a method for producing porous sodium carbonate from coarse sodium bicarbonate by using vacuum thermal treatment instead of pulverization for the high efficiency of dry-scrubbing of solid waste incineration flue gas. The porous sodium carbonate was obtained by vacuum thermal treatment of coarse sodium bicarbonate which having a higher specific surface area than that was produced by heating the pulverized sodium bicarbonate under normal pressure at 180℃. From the results of SEM analysis and pore distribution analysis, it was found that the lower the pressure, the larger the mesopore and the specific surface area. The acid gas removal performance of the produced porous sodium carbonate increased as the specific surface area increased. In addition, the moisture in the gas leads to an increase in acid gas removal efficiency of porous sodium carbonate.