Dietary utilization of cyanobacteria by B. longirostris is expected to suppress cyanobacterial blooms. We investigated the stomach contents and fatty acid compositions of the pond smelt (Hypomesus nipponensis) to examine the predation on B. longirostris and to evaluate feeding selectivity in Lake Hachiro, Akita. As a result, we found that the main dietary sources of the pond smelts were B. longirostris which accounted for 90.2 % of the total stomach contents of the pond smelts during the summer when cyanobacterial blooms were observed. In particular, B. longirostris were selectively preyed by the pond smelts less than 5 cm. Predation of B. longirostris by the pond smelts was also supported by the increase of cyanobacterial fatty acids in B. longirostris and pond smelts in summer. These results indicate that catching the pond smelts would contribute to decrease the predation pressure on B. longirostris, consequently the effects of suppressing cyanobacteria is strengthened.

 Fast Repetition Rate Fluorometry (FRRF) is one of the methods for quantifying primary production in aquatic environment, and it has the advantages in terms of quick measurement and being able to obtain the large amounts of data. In this study, FRRF has been applied to monitor the primary production from 2016 to 2019 in Lake Kasumigaura. Algal abundance and photosynthetic activity are assumed to be the factors affecting primary production. In Lake Kasumigaura, it was shown that primary production and the algal abundance had the causal relationship with the annual variation of strength. On the other hands, correlation analysis revealed that the extinction coefficient of light under the water (K_d) have much influenced on the photosynthetic activity in the lake. Furthermore, especially near the estuary, it was found that nitrate from the inflowing rivers during the rainfall events also affect the photosynthetic activity.

 In this study, the authors aimed at clarifying river environment functions of spur dike focusing on swimming behaviors of Tribolodon hakonensis in normal flow. Therefore, we carried out behavior experiments and hydraulics experiments using fish and columns with relatively large diameters. Results revealed that the presence points of fish mainly were two patterns, 1) a column group and 2) downstream site of the column group. Further, fish was mainly presented the downstream site of the columns in the case of the column group. The flow rate of the place was less than 4BL/s and the fish chose the flow that was lower than the cruising velocity, we presume. Further, difference occurred between the cases in the flow of the transverse direction in the downstream site of the columns although difference did not occur in time of fish's presence in the column group of the fish in each case. This is because the flow rate v of the downstream site of the column was less than 2BL/s and the fish were not affected by the flow rate, we infer. Further, the column installation interval in the identical y-axis was wider than the fish's length, which made it easier for the fish to present in the column group, we presume.

 The Japanese medaka (Oryzias latipes) is an endangered species. The mosquitofish (Gambusia affinis) is an invasive species native to North America that is designated as an invasive alien species in Japan. In this study, laboratory experiments were conducted to clarify the difference in the avoidance behavior and use of refuge against running water between Japanese medaka and mosquitofish, by observing their behaviors with respect to swimming speed, swimming distance and residence time in the observation section.

 The results showed that the Japanese medaka changed its swimming behavior according to the flow velocity. On the other hand, no rheotactic reactions were observed of the mosquitofish, and refuges were used even at a low flow velocity. In conclusion, we believe that the Japanese medaka is able to adapt to changes in water flow, and that the mosquitofish tends to be more lentic than the Japanese medaka.

 A questionnaire survey was conducted on small-scale communities using and managing a water supply system with a water supply population of less than 100 people in order to understand the current status of the maintenance and management of the water supply system. In the survey, we asked about the existence of records of inspection and management of facilities and maintenance manuals, the status of cooperation with the government and other communities, the existence of training workshops, and their perception of the burden of management work such as inspection and cleaning.

 As a result, it was found that although few communities have documentation such as inspection records and maintenance manuals, they face various difficulties in the stable water supply and maintenance of facilities, such as frequent water interruptions caused by natural disasters and facility failures. We were also able to understand that they felt the training workshops were useful, although there were few examples of actual practice. In addition, we were able to identify the works that they felt were a heavy burden in the maintenance and management work.

 Slow sand filtration process is frequently used for water treatment using a variety of microorganisms including photosynthetic organisms which is dependent on sunlight. In this study, for proposing a technology to cover the filtration pond and equip it with blue LED as the light source, effects of the LED on quality of treated water and biological filtration membrane (BFM) were investigated in a lab-scale experiment of slow sand filtration, comparing with sunlight and dark conditions. The result of experiment demonstrated both blue LED and sunlight contributed to growth of BFM and maintained aerobic condition on the surface of the membrane. Microbial community analysis of BFM revealed these lights did not change the density of bacteria in the membrane but reduced the diversity of microbes probably due to increase of photosynthesis bacteria like Cyanobacteria. The analysis also found Cyanobacteria related to nitrate assimilation in the conditions of LED and sunlight, resulting in a lower concentration of nitrates in the treated water than in the dark condition. The findings obtained in this study lead to our expectation that blue LED can contribute to a stable performance of slow sand filtration process, even if the filtration pond is covered for a security reason, by increase of photosynthesis bacteria and slower growth of BFM than sunlight.

 As reported in Cape Town in 2018, the rapid population growth in urban areas has made the municipal water security more fragile especially in developing countries. The urban aggromeration of Chennai, India, experienced a severe drought in June 2019 called ‘Day Zeo’, literally meaning no municipal water supply. This study aimed to find the causes of Day Zero and the fraws and deficiency of water governance in Chennai. The population in Chennai has tripled since the 1960s, which has caused chronic shortages of water supply. Although the annual precipitation of 2019 was close to the average, the 18-month Standardized Precipitation Index (SPI-18) in June 2019 showed a severe dryness that may occur once in 20 years. In addition, the late arrival of the Southwest monsoon was also a cause of Day Zero.

 To evaluate water governance both qualitatively and quantitatively from the citizens’ viewpoints, SNS data such as tweets and Google trend were analyzed. It was found that the citizens were aware of the water crisis well before the news reports or official warnings of water depletion in the four reservoirs in Chennai. It was also found that, in India, people are more interested in quantity of water rather than quality, and that people in Chennai feel unsatisfied with water services and constantly expressed complaints on distribution systems. Also, citizens are well aware of repeated water crisis in summer. These problems in water governance raised by the citizens were in agreement with those suggested by Japan International Cooporation Agency. The results of this study presented the potential of SNS analysis for a better cooporation between citizens and water supply agencies, which may lead to the improvement of water governance and avoidance or alleviation of water shortages in Chennnai and other mega cities.

 We examined and analyzed indicators of aging and maintenance management of water purification plant. We have selected indicators for aging such as the rate of aged water purification plant and aged water purification equipment. We have also included human and financial resources for indicators, such as number of staffs or water supply revenue. The rate of aged water purification plant and water purification equipment become larger, at larger water utilities where the number of staff and revenue on water supply per facility capacity are large. It was also found that utilities with increasing human and financial resources, had decreased the capacity of water purification plant, increased operation rates and water receiving ratios. It was also suggested for utilities of wide-area cooperation and public-private partnership, that the rate of aged water purification plant was improved and financial resources were secured. There may have a difference for the way to secure human resources between wide-area cooperation and public-private partnership.

 This study evaluated microbial stimulation and decoloization of anaerobic digestion treating sewage sludge with thermally pre-treated waste activated sludge at 150°C for 1 hour. Addition of powdered activated carbon and conditioning with ferric chloride for dewatering were employed for these purposes. The results showed that the addition of activated carbon does not improve overall performance, but is able to siginificantly reduce propionate concentration in digested sludge. Also, the color of digested sludge was reduced by 29.1%. Conditioning of digested sludge by ferric chloride removed the color by approximately 75% at most, without deteriorating dewatering characteristics. Therefore, therse methods were found to be effective for microbial stimulation and decoloization of digested sludge liquor.

 The final objective of this study is to develop highly conductive concrete which effectively mitigates the concentration of hydrogen sulfide (H₂S) in sewer pipe. In the first part of this study, using electricity-producing bacteria (EPB) isolated from sewage sludge from a municipal wastewater treatment plant, the influence of inoculation of these EPB on the decrease in concentration of H₂S was evaluated. Experimental results showed that inoculation of EPB could decrease the concentraton of H₂S, meaning H₂S was biologically oxidized by EPB. In the second part of this study, we developed several types of new conductive concrete containing different amount of acetylene black or magnetite as conductive materials, and evaluated their capabilities to enhance biological oxdatation of H₂S. It was found that newly developed conductive concrete with higher conductivity demonstrated higher capability of decreasing H₂S concentration than commertial conductive concrete.

 In this study, with the aim of developing a method for removing harmful heavy metals from anaerobically digested sewage sludge by using solid chelating agents, the effects of reaction time and pH on the adsorption of soluble heavy metals in acidic simulated wastewater and anaerobically digested sewage sludge were investigated by using a fibrous chelating agent. First, in an adsorption experiment with simulated wastewater, it was found that the chelating agent could adsorb heavy metals in about 1 hour, and fully exerted its adsorption effect when the pH is higher than or equal to 3. Next, in the adsorption experiment of heavy metals eluted by acidifying the sewage digested sludge (pH = 2), the amount of heavy metals adsorbed to the chelating agent was increased by increasing the pH from 2 to 2.5 or 3, although re-adsorption of Cu and Pb to the sludge solid also occurred. Adsorption of heavy metals to chelating agent was observed even at pH 2, indicating that soluble heavy metals could be adsorbed and removed from anaerobically digested sewage sludge using a solid polymeric chelating agent even under strongly acidic conditions.

 This study tried to clarify the relationship between storage conditions and property changes of polymer aqueous solutions using two types of powdery polymer flocculants. Specifically, the determination of the dissolution time when preparing the aqueous solution was examined, firstly. Next, the UV-visible spectrum and the colloid equivalent of each sample were measured by varying the polymer concentration in the aqueous solution, storage temperature and storage time. Then the relationship between properties and deterioration was considered.

 As a result, the dissolution time of the polymer aqueous solution was determined by using the electric conductivity, and the polymer aqueous solution was prepared based on this procedure. In the experiments of the relationship between storage conditions and property, the structural change based on the hydrolysis of polymer aqueous solutions was analyzed by the UV-visible spectrum. The colloidal equivalent tended to decrease significantly with the longer storage time and higher storage temperature, which is considered that the dissociating groups lost their charge as the hydrolysis proceeded.

 Present study examined oxidative stress as biochemical-level response and scope for growth (SFG) as individual-level response in brackish water clam Corbicula japonica exposed to 5× dilution municipal wastewater and its components. Dissolved matters in wastewater had influences on catalase, oxygen radical absorbance capacity and scope for growth, whereas particulate matters stimulated superoxide dismutase and scope for growth. An integrated biomarker responses index (IBR) estimating from the responses of oxidative stress makers used revealed that the most significant stressor was dissolved matters in wastewater. Further, a negative correlation was found between IBR and SFG.

 In this study, secondary treated sewage was used in a short-term toxicity test on zebrafish embryo and sac-fry stage larvae. The relationship between biological responses such as hatch/survival rates and comprehensive gene expression changes, effect on reduced of gene expression by dilution and ozonation treatment were investigated. The levels of gene expression in fish exposed to treated water were compared with those exposed to river water as a control. The highest concentration of secondary treated sewage used (80％) did not appear to influence the hatch rates or survival rates of zebrafish, however, gene expression was altered. The number of differentially expressed genes decreased with reduction in percentage of secondary treated sewage used. Gene ontology (GO) enrichment indicated immunity, metabolism, stress response, and signal transduction pathways were affected by secondary treated sewage. A ten-fold dilution or ozonation treatment of secondary treated sewage demonstrated reduction of these effects on gene expression at level equivalent to these of river water controls.

 Treated municipal wastewater (TWW) containing rich nutrients has a potential to be used for incubation of algae. For the goal to produce algae preferred by a zooplankton (Artemia sp.) which is frequently used for aquaculture of shrimps, larval and juvenile fishes, the present study tried to incubate microalgae indigenous in TWW from a municipal wastewater treatment plant in Japan without any exogenous nutrients. The incubation of TWW at 20°C achieved an active growth of microalgae, especially green algae. The dominant species were Monoraphidium sp. and Chlorococcales sp. regardless of sampling dates between August 2019 and January 2020. The concentration of Chl.a as an indicator of green algae had a significant correlation with the concentration of total dissolved nitrogen (TDN) in the initial TWW, indicating the importance to use TDN-rich TWW to obtain a large amount of microalgae biomass. When the TWW was collected in winter, the longer lag time of algal growth was observed in its incubation probably due to dormant cells in such a cold water. The algal growth in the TWW was clearly limited in the incubation at 15°C and diatoms such as Cyclotell meneghiniana and Gomphonema parvulum occupied a larger portion of the algal community after the incubation, which implies the difficulty of open-air production of microalgae relying only on the TWW as both sources of algal cells and substrates in late autumn and winter. As the final step, the microalgae recoverd from the TWW was evaluated by feeding Artemia sp. About 40% of the individuals fed with the microalgae survived for 10 days, while all of non-feeding individuals died. This was a fundamental experiment and the value of this microalgae originated from TWW for aquaculture should be examined by the further experiment of its feeding for a longer period together with nutrient analysis of the grown Artemia cells.

 In this study, to attempt a development of nematodes control method without chemical pesticide for sweetpotato production field, we evaluated Bacillales and free-living nematodes predominated night soil sludge compost application from the aspect of microbial and nematodes community structure changes by DNA sequence analysis, quantitative PCR of parasitic nematodes, and discrimination of nematodes species. As a result of microbial community analysis based on 16S rRNA genes sequence, detection rates of phylotypes belonging to orders Bacillales and Actinomycetales increased in night soil sludge compost fertilized test areas. The result of 18S rRNA genes sequence analysis, ominivorous nematodes of order Dorylaimida were specifically detected in pesticide area and the compost fertilized areas. Besides, approximately 2-fold number of free-living nematodes was observed in the compost fertilized area using Baermann Funnel method compared with control areas. These results suggest that the Bacillales and free-living nematodes predominated night soil sludge compost can be improved microbial and nematodes community structures in sweetpotato cultivation soils.

 Membrane bioreactor (MBR) has some advantages over the activated sludge method, but the membrane fouling that occurs during MBR operation is a big problem. Microbubbles and nanobubbles, which have been reported to have cleaning effects on various types of stains, may be able to efficiently clean fouled membranes. In this study, we conducted a basic study on the membrane cleaning effect of microbubbles and nanobubbles using bench-scale MBR. A large cleaning effect was confirmed in the immersion cleaning using microbubbles. Although nanobubbles did not exhibit a sufficient cleaning effect in the immersion cleaning, it was confirmed that the cleaning effect equal to or higher than that of the backwashing using chemicals was confirmed by mixing the nanobubbles in the backwashing water together with the granular carrier. It was shown that nanobubbles have a small adverse effect on MBR sludge. Membrane cleaning using microbubbles and nanobubbles may be able to solve various problems associated with membrane cleaning using chemicals.

 In ceramic flat-sheet MBRs using a combination of granular scouring and chemically enhanced backwashing (CEB), it is expected that membrane fouling is efficiently controlled, and long-term operation with a high flux may be possible. However, fouling by a transparent gel layer on the membrane became more serious when water temperature was low. Therefore, in this study, we carried out structural and chemical analysis of gel layers formed under different temperatures. The observation using scanning electron microscope (SEM) showed that the gel layer formed under a high temperature had a porous structure, but it was condensed when water temperature was low. Energy dispersive X-ray spectroscopy (EDS) analysis demonstrated that elemental composition of the gel layer changed with water temperature. Fourier transformed infrared spectroscopy analysis showed that proteins and lipids in the gel layer became more significant under a low temperature, and suggested that sub-micron (>0.45μm) particles in mixed liquor supernatants contributed to the formation of the adhesive gel layer when water temperature was low. The ratio of polysaccharides over proteins in the gel layer and that in sludge supernatant decreased when water temperature was low. It was presumed that proteins affected membrane fouling under a low temperature. Inductively coupled plasma (ICP) results indicated that increase of Fe and P in the gel layer was remarkable when water temperature was low.

 In this study, changes of sludge components involved in membrane fouling were continuously monitored (>300 days) at a pilot-scale MBR treating real municipal wastewater. It was found that concentrations of colloidal TOC, dissolved lipopolysaccharides (LPS) and biopolymers in the sludge supernatant are strongly correlated with sludge filterability. Size fractions affecting membrane fouling were also investigated, and the results suggested that colloidal matter ranging 0.45-1.0 m, and 5.0-11 µm has significant impact on MBR fouling. Futhermore, isolation of biopolymers from the MBR sludge supernatant was conducted, and their characteristics were compared with sodium alginate which is commonly used as a model biopolymer. Isolated biopolymers caused more severe membrane fouling than did sodium alginate. It was suggested that biopolymers in MBR supernatant have higher fouling potential than that previously estimated by sodium alginate.

 The activated sludge treatment of sewage has disadvantages such as energy consumption due to aeration and generation of a large amount of excess sludge. The anaerobic membrane bioreactor(AnMBR) is attracting attention as a new wastewater treatment technology because it is energy-saving / energy-creating process and has a small amount of sludge production. In this study, a continuous treatment experiment of AnMBR treatng real sewage was conducted by changing the operating temperature and hydraulic retention time (HRT). The effect of temperature on treatment performance and biogas production was evaluated, and the COD mass balances at different conditions were identified. At a condition of HRT6 h and operating temperature 20 °C, a good treatment performance such as effluent BOD< 20 mg/L, effluent COD< 50 mg/L and removal efficiency >90% was achieved. At a condition of HRT6 h and operating temperature 25 °C, the biogas production was 0.079 L-gas / L-sewage. The amount of sludge produced by AnMBR method was less than that of the activated sludge treatment process even under high load conditions or low temperature conditions.

 This paper reports the recovery of phosphorus and potassium from biomass aiming at removing accumulated nutrients in soil in agriculture and to reuse them. At first, the thermodynamic properties were determined for precipitate which contains phosphorus and potassium together in pure chemical solution. The precipitate formed had K:Mg:P ratio of 1:1:1, but different crystalline structure from struvite-K reported so far. The solubility product, ΔrG°, ΔrH° of dissolution reaction of the precipitate were 10^−10.9, −62.4 and −23.0 kJ/mol, respectively. Then, a method to recover P and K from biomass was proposed. The experiment demonstrated that those elements were recovered when KCl solution was used as the initial extraction solvent.

 It is important to determine the infectivity of viruses in waters and foodstuffs so that the risk of viral infection can be assessed. The use of viability markers such as propidium monoazide (PMA), ethidium monoazide (EMA) and more recently cis-dichlorodiammineplatinum (CDDP) has been applied to discriminate between infectious and inactivated viruses by (RT-)qPCR (viability (RT-)qPCR). However, the efficiency of viability (RT-)qPCR in eliminating inactivated viruses can be influenced by viral genome property. The main objective of this study is to evaluate the effects of viral genome types and amplicon lengths on the efficiency of viability (RT-)qPCR. Naked viral genomes extracted from RNA or DNA viruses were treated with PMA (100 µM), EMA (100 µM) or CDDP (1, 000 µM) markers and analyzed by (RT-)qPCR. Among viability markers tested, CDDP was the most effective to remove the detection of the naked viral genomes by (RT)-qPCR. All viability markers tested generally eliminated (RT-)qPCR detections of RNA viral genomes more effectively than those of DNA viral genomes. PMA/EMA/CDDP-(RT-)qPCR was likely to remove the naked viral genomes more efficiently when targeted the longer amplicon lengths than the shorter ones. Thus, the property of viral genomes should be considered as one of the governing factors on the efficiency of viability (RT-)qPCR in exclusion of inactivated viruses.

 This study aims at applying a survey method to offer the presence and coverage of each plant species in field area, so as to develop quantitative evaluation procedure for vegetation structure and diversity. Long-term monitoring surveys and vegetation surveys have been implemented in Harie wetland which is a habitat supporting a large number of rare plant species in Japan from 2011 to 2019. Main results are as follows: 1) vegetation surveys with portable point positioning GPS devices were able to provide the presence and proportion of each species in communities, along with the expansion of Ludwigia grandiflora. 2) Shannon-Wiener diversity index 𝐻 without distinguishing species categories, did not reflect the real abundance change. 3) the evaluation method with periodization presented vegetation diversity with emphasis on various significance is suitable to evaluate the effects of Ludwigia grandiflora on rare species and endemic species.

 Loss of membrane integrity causes deterioration of treated water quality and poses increased risk of microbial diseases. Although there have been several integrity testing methods applied to the full-scale membrane treatment plants, water flow in broken membrane has not been elucidated based on experimental studies. Therefore, this study aimed to directly measure the bypass flow and filtration flow using a novel particle counting method. Nanoparticles greater than the pore size of hollow fiber membrane, but smaller than the inner diameter was suspended to the feed water and both particles deposited on the membrane as a parameter of flux, and the particle in the permeate were measures by the SEM imaging combined with the computer-aided particle conting method, which was verified to be highly accurate. About 0.98% of nanoparticles filtered through the membrane was attached on the membrane, and there was a log-linear relationship between the numbers of particles filtered and the numbers of particles attached on the membrane. The filtration flow was about 20% of the flow rate from the broken end of the membrane, which was about 35% less than the estimated flow by the conventional method. This result indicated that the actual decreases of the log reduction values of the broken membranes are slightly smaller than the ones estimated from the conventional method. The filtration flux from the intact segments of the broken membrane was the lowest at the broken end, and increased along with the length of the membrane to the middle, but the slightly decreased to the outlet, which was considered to be complex flow within the broken hollow fiber membrane.

 We compared the environmental impacts such as waste generation, greenhouse gas emission and water pollution load discharged from various wastewater treatment facilities. The target facilites were septic tanks that are currently widely used abroad, small-scale wastewater treatment systems of which their promotion in the future is expected, overseas adaptable Japanese Johkasou, and centralised sewerage systems. The result suggests that, from the viewpoint of conservation of the water environment, the transition from septic tanks to systems that are able to remove nitrogen is in urgent need. Also, in terms of waste generation mitigation, it is suggested that the overseas adaptation of Japanese Johkasou, which has low sludge discharge volume per removed BOD, appears effective. Difference in greenhouse gas emission volume between centralised systems and decentralised systems decreases as size of treatment facilities becomes smaller. It is showed that when targeted P.E (population equivalent) is lower than 150, decentralised small-scale systems, including the overseas adaptation of Japanese Johkasou, have a lower emission volume than centralised system.

 The effect of reducing environmental impact such as waste generation, greenhouse gas emissions, and water pollution load were compared and examined.

 Organic matter in municipal wastewater should be regarded as a resource for energy production in future wastewater management. Concentration of organic matter in municipal wastewater is necessary for application of anaerobic digestion. Direct membrane filtration (DMF) of municipal wastewater using microfiltration can easily concentrate organic matter in municipal wastewater. However, severe membrane fouling and high concentration of organic matter in treated water have been identified as problems to be solved. In this study, a biofilm process using sponge carriers was used as a pre-treatment, aiming for mitigating membrane fouling and reducing concentration of organic matter in the permeate. The pretreatment worked efficiently when water temperature was low: membrane fouling could be mitigated while recovery of organic matter was maintained. However, when water temperature was high, the pre-treatment accelerated membrane fouling in the subsequent membrane process. It was probably due to production of biopolymers in the pre-treatment process. To control the fouling caused by such biopolymers, use of chemical cleaning by oxidants (e.g., NaClO) would be effective. When the water temperature was high, the BOD concentration in the DMF permeate was reduced to 7 mg/L, which is almost same the level as that in conventional activated sludge process.

 In Japan, on-site household wastewater treatment facilities consisting anaerobic and aerobic tanks are called Johkasou. The water temperature is well known as one of the important parameters for wastewater treatment. However, no correlation between temperature and effluent water quality of Johkasou in the period of temperature increase has been reported. In this study, influence of the current and the previous water temperature on treatment performance of Johkasou was investigated. The dissolved oxygen concentration in the aerobic tank and the residual chlorine concentration in the disinfection tank had high correlations with current water temperature, whereas the biochemical oxygen demand and total nitrogen concentration of treated water, among other items, were influenced by moving average of the previous water temperature. The numbers of months used for the moving average calculation that showed the highest correlations were four to five months. This temperature hysteresis effect was found in not only the quality of Johkasou-treated water but also the amount of scum in the anaerobic filter tank. These results suggest that the sludge accumulated in the anaerobic filter tank decomposed and solubilized over a period of 4-6 months, then influenced the Johkasou performance.

 Chlorine inactivation is commonly used in Johkasou, however, its human health risk and environmental impact are concerned. In recent years, small UV-LED with low voltage has been developed, then it is expected to be an alternative way for inactivation in Johkasou. In this research, effects of UV-LED inactivation on three indicator bacteria; coliforms, E.coli, and enterococci in the effluent from Johkasou were examined. Although the removal rates of all three indicator bacteria increased with the increase in UV irradiation time, enterococci showed higher resistance to UV. Since a positive correlation between Abs 280 nm and BOD concentration in the effluent water was observed, it would be important to reduce BOD concentration before the inactivation tank for improving UV irradiation efficiency. The inverse relation between water depth of the inactivation tank and removal rates of indicator bacteria suggests that the use of a shallow inactivation tank would be effective to increase coefficient WF.

 Business feasibility and environmental load were evaluated in operation of water management system for saving cost based on the results of breeding experiments for two weeks. We focused on circulation rate, water replacement period and water replacement rate as experimental factors. As a results, bad effect to feed conversion ratio and cortisol were not confirmed. Based on the results, we calculated the cost, it was possible to save cost of total 867 yen/kg. It was also possible to reduce nitrate nitrogen and wastewater by 0~13.6% and 14.7~20.1%, respectively. It was possible to improve the business feasibility and environmental load in operation of water management system for saving cost.

 Experimental study was carried out in Lake Abashiri where is brackish lake with double-layered formation of freshwater and saltwater. In order to reduce anaerobic salt water layer, we installed the oxygen dissolving device (WEP) in the actual waters. The effect of oxygenation was confirmed at approximately 210,000 m² during the two-month operation of the device. On the other hand, it was confirmed that the amount of residual dissolved oxygen depended on the operating time of device and the concentration of hydrogen sulfide, and that the water mass movement and the supplied dissolved oxygen were important. In addition, it was confirmed that the durability of the device casing would be damaged in water in a strongly reduced state within about two years. In case of installation conditions for this paper, it becomes clear that operating costs, maintenance and repair costs every two years are required, and annual maintenance costs of 3.9 to 5.5 million yen are required. From this result, water quality of anaerobic brackish waters could be improved by dissolved oxygen supply. However, it was suggested that the operation with limited capacity such as isolated water pools was advantageous for actually installation.

 In order to assess the effectiveness of gluconate as a hydrogen donor for biological reductive dechlorination of chloroethenes, an in situ bioremediation study with injection of a remediation agent that is mainly composed of gluconate was conducted in a chloroethenes-contaminated site where groundwater was contaminated with trichloroethene, cis-1, 2-dichloroethene and vinyl chloride. As a result of twice injections of the remediation agent, all of the chloroethenes were reduced below the groundwater standards within 620 days, which demonstrated the usefulness of gluconate as the hydrogen donor in in situ bioremediation of chloroethenes-contaminated groundwater. In addition, it was suggested that effects of gluconate injection on the groundwater quality are temporary and can be recovered to the original level. Comparison with other hydrogen donors previously applied for biological chloroethenes dichlorination demonstrated that gluconate may have advantages to other hydrogen donors in terms of the cost, dechlorination speed and duration of the effect as the hydrogen donor.

 High rates of non-revenue water (NRW) are the main obstacle against improvements of water utility management in many Asian cities. Yangon City, Myanmar, has a high NRW rate of ca. 60%. Previously billed-unmetered consumption, which is often caused by damaged water meters, was classified to revenue water by International Water Association, but later it was redefined as non-recovered revenue water. Although billed-unmetered consumption could cause a significant revenue loss if there is a large discrepancy between billed and real water consumption, there has been no report of estimating the amounts of billed-unmetered consumption in Asian cities including Yangon. Therefore, this study aimed to estimate the revenue increase by replacing damaged water meters with new meters, and thereby to estimate the factors influencing water consumption. The water consumption in three townships with large or ordinary houses were measured on site and the water consumption before and after meter replacement was measured in a pilot study area. The water consumption per connection was influenced by the number of persons per house, but the per-capita consumption was significantly greater and varied in the large houses than the ordinary houses due to non-essential water consumption such as watering gardens and filling swimming pools at the fixed rates of water bills. After water meter replacement, the revenue increased by 2.6 times or 1.8 times in large or ordinary houses, respectively. Thus, the cost of meter replacement could be recovered in eight or 25 months for large and ordinary houses, respectively. Therefore, it was found that, despite limited budget of water utilities and rules of private ownership of water meters, it is recommended to replace water meters to increase their revenue and to save non-essential water consumption by raising the awareness of the consumers through sending bills of their real water consumption.

 This study is the first effort to depict the situation of solid waste landfill management in Vietnam. A comprehensive-nationwide-survey was conducted at 13 Vietnamese landfill sites in 2018 to clarify problems of landfill sites under impacts of heavy rain. The survey started with an overview of the landfill management situation along with investigation of the potential contamination of landfill leachate by computing the leachate pollution index (LPI). As a result, owing to the inadequate management of the facilities and high LPI value, the occurrence of heavy rain potentially induces the overload of leachate through its infiltration into landfill body leading it to pose risks to environment. Additionally, the actual incidents caused by heavy rain and the existing strategy to tackle the problems were reported. Based on this, we proposed suggestions to contribute to dealing with heavy rain events ahead. Landfill No. 8 with high leachate monitoring frequency system, provided 5-year leachate monitoring data (2013-2017). Statistical analysis applied on this data set showed a significant relationship between cumulative rainfall and leachate component concentration. The 2013-2015 period showed a negative correlation between rainfall and COD concentration, whereas the 2016-2017 period depicted a positive correlation between them. This can be explained by the starting of a new cell in the landfill to accept wastes in the 2016-2017 period. The remaining leachate components (BOD₅, TN, NH⁴⁺_-N, and Cl^-) had weaker correlation with rainfall compared to COD. Welch t-test was used to further investigate the impacts of heavy rain intensities on leachate component concentration. Results indicated that the impact of heavy rain intensity on COD, Cl^- (2013-2015) and COD, BOD₅ (2016-2017) has statistical significance.

 Previous models of membrane filtration processes required simplification of the membrane structures; thus, it was difficult to characterize the actual porous membranes. Therefore, this study aimed to develop a model that can delineate features of the actual porous membranes and deposited particles. Convolutional neural networks (CNN) were used as the architecture of the deep-learning models developed in this study. After tuning hyperparameters, the CNN models were able to classify the SEM images of polyvinylidene difluoride (PVDF) flat sheet membranes of different pore sizes, i.e. 0.1 µm and 0.45 µm, with high accuracy. The accuracy improved with the epoch size and reached the 100% accuracy after 50 epochs. The CNN model was modified and applied to classification of 0.45 µm pore-sized membranes filtered with feed waters containing 2, 5 and 8 mg/L of nanoparticles. Although the overall classification accuracy was 93%, the classification of 2 and 5 mg/L was less accurate (84% and 88%, respectively) due to small differences of particles deposited on the membranes. The heatmaps of the membranes were drawn by gradient class activation mapping (Grad-CAM) of the CNN models. The Grad-CAM heatmaps output by the CNN model with a kernel size of 3x3 was able to clearly extract detailed features of the membranes, such as aggregates of PVDF spherical crystalline structures and aggregates of particles deposited on the membranes, whereas a 7x7 model featured wide areas including deep pores, top and intermediate layers. Thus, it was found that the CNN models can extract the features of both intact and fouled membranes without any simplification of the membrane structures. By adjusting the model structure, the kernel size and epochs, the CNN models can be used for feature extraction and comparison of different membranes and for improving our understandings of membrane fouling processes.

 Preparation of alternative soilless organic media was investigated to utilize tons of crop residues in Japanese agricultural areas. Leaves and stalks of eggplant were used in this study, and the effect of solvent extraction process for clearing plant growth inhibitors was examined as a secondary processing for soilless media making. Presumably phenolics associated with easily oxidative degradation was confirmed in water, methanol, ethanol, and acetone extracts by HPLC-electrochemical detector analysis. Germination tests using grape tomato seeds presented its delay especially in the case of methanol extracts addition. Finally, grape tomato was cultivated using crop residue media and mineral wool, commonly used growth media, as a control (cultivation period 33 days). The early stage of its cultivation using the crop residues after acetone extraction provided similar plant height and stem diameter to that in the control. This study could indicate the availability of solvent extraction process to produce organic soilless media from crop residues.

 Aiming development of the recovery process of rare earth elements from waste phosphors by biosorption, microalgae Actodesmus acuminatus was used as biosorbent for rare earths elements. Europium and yttrium were leached from a commercially available light-emitting diode (LED) 3-wave form phosphor by strong acid solution. Adsorption of europium was inhibited when aluminum and calcium coexisted at a higher concentration than europium. Living algal cells as adsorbents have a complex adsorption mechanism of chemisorption on cell surface. Further, the inactivated cells by autoclave treatment or ultraviolet treatment lost a part of adsorption mechanism, and decreased adsotion amount of yttrium. However, The decrease of adsorption amount of aluminum and gallium was limited. Europium leached from phosphors by citric acid. However, it was difficult to separate europium from leaching solution by biosorption because metal complex adsorped on only cell surface.

 Using open data, the nutrients supply function (active management) of the sewage treatment plant was comprehensively evaluated with the energy recovery function using a sewage treatment plant simulator, According to the calculation using the operation data in winter, which is the target of seasonal operation, the nitrogen concentration (NO₃-N) in the treated water increased to 10-13 mg/L and the nitrogen supply increased by 62% in the denitrification suppression operation. In the nitrification suppression operation, the treated water nitrogen concentration (NH₄-N) increased to 12-15 mg/L, and the nitrogen supply increased by 85%. The electric power consumption increased slightly in the denitrification suppression operation and decreased in the nitrification suppression operation. By introducing the active management method of "Always suppress nitrification +Duckweed culture", 16-20 mg/L of nitrogen could be supplied in the winter under the condition of nitrogen recovery rate of 70%, and the nitrogen concentration of discharged water was 5.3 mg/L by calculating from the annual discharge load. On the other hand, the annual average power generation was 39,670kWh/day, and the power self-sufficiency rate was 104%, so it was estimated that the power independence could be achieved even in a year.

 In Japan, green tuff is often used for construction materials, and large amount of wasted green tuff is produced during processing. Besides, green tuff has several positive characteristics for plant cultivation such as porous structures and containing several minerals. Therefore, to effectively utilize the green tuff, we performed cultivation test of Solanum lycopersicum var. cerasiforme (cherry tomato) and Daucus carota subsp. sativus (carrot) supplemented with green tuff into cultivation soil, and evaluated the effects of yields, soil chemical parameters, and soil microorganisms. As a result of cultivation tests, significant increase of yield of cherry tomato and length of carrot root in green tuff supplemented areas (p<0.05). In the result of soil chemical analysis, significant increase of NO₃^-–N and Ca²⁺ concentration was caused in green tuff supplemented cherry tomato cultivation field (p<0.05). Microbial community analysis indicated that minor microbial populations (< 0.11% abundance rate) were different between green tuff supplemented areas and no supplemented area at cherry tomato and carrot cultivation tests. Besides, significant increase of family Koribacteraceae was observed in carrot cultivation field without green tuff (p<0.05), which is known as indicator of soil deterioration.

 A main objective of this study is to know impact factors on reproduction of an invasive alian species Ludwigia grandiflora. Vegetation surveys with portable point positioning GPS devices were carried out for Ludwigia grandiflora at Yabase district on Lake Biwa shore. Area where the species grew well was 49,569 m² winter 2014, then extermination by heavy machines was conducted, however the area had expanded to 136,198 m² winter 2015. Furthermore, as a result of 240 samples reproduction experiments from fragments of the species in a laboratory, it was found that presence or absence of nodes is the main factor of reproduction. Three-way layout (nutrients, length, and diameter) analysis of variance was carried out for growth rates of the species with nodes after 10 days elapsed showed that contribution of diameter was 37.7%. It was a significant impact factor of reproduction of the species. Three-way layout ANOVA was carried out for the growth rates with nodes after 2 days, 4 days, 6 days, and 8 days elapsed, respectively. As the results, the growth rates at 2nd day with nutrients tended to be higher than that without nutrients significantly. It was found that nutrients contribute in the early stages of their reproduction.

 In small and medium-sized rivers, deterioration of landscape and water flow capacity due to overgrowth of vegetation such as reeds are problems. Vegetation control by hydraulic factors is not easy. In this study, we focused on the solar radiation as a factor of controlling overgrowth. According to the solar shading experiment on a reed overgrowing sandbar in a small river, the higher the shading ratio is, the smaller the total length of the reeds is. When the shading ratio exceeds 76%, the reeds density became smaller. When 60% shading, the reeds fell more easily during flooding, and at 94% shading, almost all reeds fell. From the reed coverage survey and solar radiation analysis of the river, it was found that most of the reed coverage can be explained by open sky ratio caused by trees and direct solar radiation ratio determined by topographical factors. From these results, it was shown that the solar radiation may limit the growth of reeds even in actual rivers. Thus the possibility of controlling the overgrowth of reeds by solar shading was demonstrated.

 Freshwater cyanobacterial blooms are mainly composed of Microcystis spp. Cyanobacteria settle down when their cellular activity declines and are subsequently deposited on the lake bottom. In this study, we investigated the process of decomposition of Microcystis spp. and its availability as a food source for macrobenthos, using Microcystis spp. labeled by ¹³C and ¹⁵N. Labeled Microcystis spp. settled immediately with re-suspended sediment. The decomposition rate of Microcystis spp. was increased by mixing with bottom sediment. However, the results of δ¹³C and δ¹⁵N analyses suggested that the organic matter of Microcystis spp. in the sediment remained as detritus or as heterotrophic bacteria. Moreover, the results of the feeding experiment of sediments, containing decomposed Microcystis spp., demonstrated that three kinds of macrobenthos, Chironomidae spp. larvae, Anodonta spp., and Corbicula leana, fed on the organic matter of Microcystis spp. origin. The results of feeding experiment on two kinds (fresh and old) of sediment containing decomposed Microcystis spp. suggested that Corbicula leana, and especially Chironomidae spp. larvae, fed on fresh Microcystis spp.

 This study is to investigate the effect of nutrients, temperature, and pH on the growth characteristics of diatom Nitzschia palea which may be the competitors of bloom forming cyanobacteria. This may be the basis for an ecological engineering method using by N. palea. The maximum specific growth rate (𝜇_𝑚𝑎𝑥) and the half-saturation constant of nitrogen (𝐾_𝑁) for N. palea were estimated as 0.52 day^-1 and 0.12 mgN L^-1, respectively. 𝜇_𝑚𝑎𝑥 and 𝐾_𝑃 of phosphorus for N. palea were estimated as 0.62 day^-1 and 0.035 mgP L^-1, respectively. 𝜇_𝑚𝑎𝑥 and 𝐾_𝑆𝑖 of silicon for N. palea were estimated as 0.68 day^-1 and 0.48 mgSi L^-1, respectively. The temperature for optimal growth was 15~25 ℃. Moreover N. palea maintained high growth rate at 30 ℃. The optimal pH for the growth of N. palea was 7.0-9.0. Therefore N. palea can be used as competitors for bloom forming cyanobacteria in the temperature during summer and an alkaline condition, in which the bloom usually occurs.

 It is known that cesium in clay minerals is dissolved by bacteria. Generally, plants live symbiotically with bacteria. However, little is known about synergetic effect of plants and symbiotic bacteria on cesium dissolution from soil. In this study, we first determined an organic acid produced by a model plant, clover, which was lactic acid. Next, a symbiotic bacterium isolated from clover was cultured with or without addition of lactic acid in a medium containing biotite powder. Addition of lactic acid enhanced dissolution of biotite by the bacterium. As for cesium dissolution from biotite, the cesium concentrations in the liquid phases of the bacterial culture media were lower than those in blank media with no bacterial cells. A possible reason of this lower cesium concentration could be cesium absorption by bacterial cells as magnesium was absorbed.

 On April in 2018, huge eruption at Iouyama in Kirishima mountain range was happened, and the mountain erupted for the first time in 250 years. By this large explosion, many of eruptions were contaminated into rivers, which killed massive amount of fishes due to lower pH and contamination of several heavy metals and anions. Therefore, people who live close to the rivers decided to stop cultivation in paddy fields because the cultivation requires river water. In this study, to understand actual in situ situation, we evaluated influence of water contaminated with eruption of Iouyama in Kirishima mountain range into river environments and rice cultivation. Water quality analysis during 2019–2020 indicated that concentration of Fe and Mn were often higher than threshold of Japanese environmental standard of river. For the As, although beginning concentration was higher than the standard, the concentration became lower than the standard after October in 2019. By 16S rRNA gene analysis, species richness of sediment observed from upstream river closer to Iouyama were significantly lower than downstream rivers, and strong acidophilic bacteria and archaea were predominant in the sediments. Rice cultivation test indicated that total As concentration in brown rice was 0.40 ± 0.11 mg/kg using 10-fold diluted Akago river water during 2018–2019, suggesting that some brown rice may contain As equal to or higher than codex standard value (0.35 mg/kg). Overall, we could assess in situ situation closer to Iouyama in terms of water quality, microbiology, and plant cultivation.

 To evaluate of the effect of MgO on insolubilizaiton of heavy metals in volcanic deposit, the raw deposit sampled from five points in Akako River in Miyazaki prefecture, Japan was treated with MgO, and leaching test, pH dependence test and sequential extraction test were performed. B and As were leached from the raw deposit and the concentrations exceeded the Environmental Quality Standards for soil. By adding MgO of 6% into the raw deposit, leaching concentrations of As, B, Cd, F and Pb satisfied the Environmental Quality Standards for soil. The results of pH dependence test indicated that MgO treatment could be highly effective at a pH of 2 for Cd and F; however, it was much less effective less than a pH of 7 for B, As, T-Cr and Pb. It was suggested that As and B could be adsorbed on MgO, Mg(OH)₂ and Fe(OH)₃ to be insolubilized.

 Clay minerals may change under the influence of heat treatment as follows: loss of adsorbed water, interlayer water and constitution water of clay minerals, and decomposition and recrystallization of clay minerals. Cs and Sr are adsorbed on clay minerals with different behavior and strength.Therefore, in this study, it was examined whether structural changes of clay minerals influenced on the characteristics of Cs and Sr elution by heat treatment. XRD peak intensity of kaolinite, dickite, montmorillonite and hydrobiotite changed remarkably by heat temperature. CEC of most clay minerals decreased with high temperature, however, CEC of hydrobiotite increased. The elution rate of Cs in the heated clay minerals decreased and Sr elution rate of some clay minerals increased by heat treatment. This study indicated that the physical and chemical characteristics of clay minerals were changed by heat treatment and that those changes influenced on Cs and Sr elution in the heated clay minerals.

 Effects of sunlight and salinity inactivation on the fate of three types of fecal indicator bacteria (E. coli, Fecal coliform, and Enterococcus) and two types of potential viral indicators (F-specific bacteriophage and Somatic coliphage) in raw sewage were examined by laboratory experiments. F-specific bacteriophage was inactivated by salinity and the inactivation was accelerated by sunlight, and E. coli, Fecal coliform, and Enterococcus were inactivated by sunlight. The overall sunlight inactivation coefficient (k_I) ranking was as follows: E. coli > Fecal coliform > Enterococcus > F-specific bacteriophage. Somatic coliphage was not inactivated by salinity or sunlight. Furthermore, E. coli and Fecal coliform also exhibited a synergistic inactivation effect by salinity and sunlight. The significance of analyzing multiple indicators for understanding fecal pollution was found because the resistance of each indicator to salinity and sunlight was different.

 Viruses are highly diverse even in a genotype. This may affect the required chlorine intensity (CT value: chlorine concentration × contact time) to achieve a sufficient inactivation of viruses in drinking water treatment plant. Recently, it was reported that some environmental strains were more resistant against chlorination than a lab strain. However, few studies have assessed the effect of intratypic variability in free chlorine resistance on the estimation of required CT values for virus inactivation. The objectives of this study were (i) to examine a total of 35 environmental stains of F-RNA phage genotype GI collected in Tama and Sagami rivers for free chlorine resistance, and (ii) to develop the inactivation model to predict the overall inactivation efficiency of heterogeneous F-RNA phage GI strains by assuming a probability density function of free chlorine resistance. The results indicated that most environmental strains of F-RNA phage GI exhibited higher free chlorine resistance than MS2 and fr, laboratory strains of GI phage. The developed model suggested that the overall inactivation efficiency of GI phages was limited to 5.6 log and 5.3 log in Tama and Sagami river, respectively, in the case that 8 log MS2 inactivation was expected. Therefore, the heterogeneity in free chlorine resistance within specific reference pathogens should be incorporated into the model to accurately predict the inactivation efficiency in environmental water.

 This study is aiming at clarifying the behavior of antimicrobial resistant E. coli discharged on a watershed where livestock farming is active. To this end field investigations in non-rainy events and rainy events were carried out at several locations on Yasu River and Hino River in Shiga Prefecture. The results indicated that increase in the concentarations of E. coli and anitimicrobial E. coli was observed in increasing river flow due to rainy events. To investigate the effect of rainfall to the increase of E. coli concentrations in a river, a continuous sampling campaign at a location on Yasu River was performed in a rainy event. As the results, 1) during a rainy event, E. coli and antimicrobial resistant E. coli concetrations were elevated, 2) the behaviors in rainy runoff of the river were different among E. coli, ampicillin resistant E. coli, and tetracycline resistant E. coli, which suggests the diffenece in their origins and runoff mechanisms, and 3) the relastionship between pollutant loads (L) of E. coli, anitimicrobial resistant E. coli and river flow (Q) was clarified based on actual field measurements for the first time.

 The occurrences of primary treatment discharge from sewage treatment plants (STPs) including CSOs and SSOs have been frequently reported in recent years. However, it is still unclear how much pathogen are discharged along with primary treatment discharge into receiving waters. Therefore, this research was aiming at understanding of the pathogen load discharged from a STP which receives sewage from separate sewers with partially-combined sewer drainage areas. This STP facitates biological treatment as well as high-speed coagulation sedimentation treatment. Concentrations of Escherichia coli (E. coli) and F-phage in wastewater were measured before and after chlorination tank, and at high-speed coagulation sedimentation treatment facility, both in rainy and fine weather. Based on the concentrations and statistical model, the annual loads of E. coli and F-phage discharged from each facility were estimated. As a result, primary treatment discharge in rainy day occupied almost half of both E. coli and F-phage loads from the biological treatment facility, which was followed by biological treatment effluent in rainy whether without primary treatment discharge, and the load in the fine weather. The high-speed coagulation sedimentation facility of E. coli was about 1% of the total load from the STP, while that of F-phage was about half of the total load. This is the first study to incestigate the load of microbials discharged from the STP, and demonstrate the impact of the primary treatment discharge in rainy day.