In recent years, the PDA process, a new nitrogen removal method combining the partial denitrification (PD) reaction and the anammox reaction, has attracted attention worldwide. In this study, focusing on the existence of denitrifying bacteria in anammox sludge, we investigated the possibility of starting up the PDA process using anammox sludge. Moreover, the treatment effect of the PDA process was studied and the microbial composition of granule sludge was analyzed by 16S rRNA gene sequencing. As a result, by controlling the COD/NO₃-N ratio, the EGSB continuous-flow PDA process was successfully started up quickly. Furthermore, the PDA process achieved a high nitrogen removal rate of 99% when treating low-strength nitrogen wastewater. In addition, based on the result of specific activity test for nitrate reduction, nitrite reduction and anammox reaction and the analysis of changes in microbial community structure, we found that the nitrate reduction rate and the nitrite accumulation rate increased, and the dominant species in anammox granule sludge changed from AnAOB and denitrifying bacteria to AnAOB and Thauera, indicating that the PDA process had been successfully started up.

 In this study, advanced oxidation process experiments were conducted on solution of linear alkylbenzene sulfonate (LAS) at initial concentrations of 3 mg/L and 6 mg/L. The experiments employed a 222 nm ultraviolet (UV) lamp and hydrogen peroxide (H₂O₂) with the initial concentrations ranging from 0 to 100 mg/L were used for the experiments. In particular, the experimental results were analyzed focusing on the UV absorption energy of each substance rather than the surface UV energy. Regarding the UV absorption energy of LAS, the amount of LAS decomposition increased as the initial H₂O₂ concentration increased, but no difference was observed between the initial LAS concentrations. The relationship between the UV absorption energy of H₂O₂ and the LAS concentration removal ratio was shown by a first-order reaction equation. It was considered to be a useful index because the UV absorption energy of H₂O₂ can be used to estimate LAS decomposition, unaffected by the by the initial concentration of H₂O₂.

 Semibatch ozonation treatment and its post soil batch experiment for secondary effluent of sewage treatment were conducted to comprehend the reduction characteristics of trihalomethane formation potential (THMFP) and haloacetic acids formation potential(HAAFP). The target effluents were Membrane bioreactor (A2O-MBR) and Conventional activated sludge (CAS) ones. Before the ozonation, the THMFP and HAAFP in the effluents were 90~120 μg/L and 90~100 μg/L, respectively, whereas the THMFP and HAAFP were reduced by the ozonation with approximately 0.5 mgO₃/mgC₀ ozone consumption. The HAAFP in A2O-MBR and CAS at the ozone consumption were 40~65 μg/L and 55~92 μg/L, respectively. Comparing to CAS effuluent, the higher reduction was obtained in A2O-MBR effuluent. The fractions of HoN, HoA and HiN contributed to the THMFP and HAAFP in both effluents, and HoN & HoA reduction occurred by the ozonation due to the decrease of these fractions. In the soil batch experiment, the reduction of the THMFP and HAAFP was observed regardless of ozonation in both effluents. Most reduction of the THMFP was found in the samples of A2O-MBR effuluent with 1.65 mgO₃/mgC₀ ozone consumption for 7 days SAT treatment(from 80 μg/L to 25 μg/L). This result indicated the ozonation promoted the reduction of THMFP in soil aquifer treatment.

 In drinking water treatment, 2-methylisoborneol (2-MIB) removal rate by powdered activated carbon (PAC) can be reduced by natural organic matter (NOM). Algal organic matter (AOM) is a part of NOM in water environment. But the competitive effects of AOM on 2-MIB removal by PAC treatment under non-equilibrium conditions have not been investigated. In order to clarify competitive effects of AOM on 2-MIB removal by powdered activated carbon treatment under non-equilibrium conditions, we evaluated the competitive effects of organic matter produced by Microcystis aeruginosa and estimated the competing compounds in M. aeruginosa-produced organic matter. M. aeruginosa-produced organic matter contained some competitive compounds for the removal of 2-MIB by PAC treatment. It is suggested that these compounds are tryptophan-like fluorescent substances and fulvic acid-like fluorescent substances. The results obtained in this study suggested that culture solutions of all M. aeruginosa strains (NIES-87, 102, 604, 1053) effected competitive adsorption on PAC treatment, indicating that competitive compounds are present in the M. aeruginosa-produced organic matter.

 The purpose of this study is to focus on the pitting corrosion of the outer water pipe surface, which was obtained in the external corrosion survey conducted by the Tokyo Metropolitan Waterworks Bureau. The relationship between the material, buried environment and the deterioration of the water pipe was analyzed using the survival time analysis. Therefore, we tried a new analysis of water pipe deterioration using the Kaplan-Meier method and Cox regression analysis, which have been applied in the fields of medicine and pharmacy in recent years. Based on these survey data, since there are cases in which pitting corrosion has been confirmed even in pipes coated with polyethylene sleeves (PS), analyzing the effects of the presence or absence of PS coating on the survival curve. As a result of the analysis, in the case of non-PS, it was newly revealed that the survival rate started to decrease from 40 years after the pipe laying, and decreased to 0.7 in about 70 years. Furthermore, it was shown by Cox regression analysis showed that the variables of geological features and pipe’s material did not contribute to the life extension effect of pipe with PS.

 Membrane fouling is strongly influenced by biopolymers, which are characterized by their high molecular weights and hydrophilic nature in application of membrane technology to both drinking water treatment and wastewater treatment. However, there is little knowledge about the differences between biopolymers present in drinking water sources and wastewater, mainly because of the unavailability of isolated biopolymer samples. In this study, biopolymers were isolated from surface water and MBR supernatants, and their membrane fouling potentials and physicochemical properties were investigated. Biopolymers isolated from MBR supernatants exhibited much more severe membrane fouling than biopolymers isolated from surface water. Affinities between biopolymers and a membrane polymer (i.e., PVDF) assessed by QCM were consistent with the results obtained in the filtration tests. LC-OCD/UVD/OND and FT-IR analyses revealed clear differences in physical/chemical properties of the biopolymers isolated from the surface water and the MBR supernatants. It is suggested that amino sugars and/or lipopolysaccharide-like components in biopolymers can cause severe membrane fouling.

 Bench-scale experiments were seasonally carried out to understand the effect of sunlight on schutzdecke for the slow sand filtration, with the special focus on its clogging. In spring and winter, the filtration under sunlight was clogged due to the rapid growth of algae in the schutzdecke, while the good performance of filtration was observed in the other seasons. The schmutzdecke in both summer and autumn had Melosira, which is known to help the stable sand filtration, as the dominant species of algae. The diversities of algae and bacteria found in the schmutzdecke were not associated with the performance of sand filtration. In the spring experiment, the irradiation of blue light emitting diode (LED), instead of sunlight, was also examined and it enabled to avoid the clogging of filtration found under sunlight. The additional experiment revealed that intermittent irradiation of blue LED at the interval of 12 hours achieved more stable filtration than its continuous irradication. The schutzdecke, in which Melosira was dominant, under the intermittent irradiation captured a smaller amount of suspended solids than that under sunlight and dark condition, indicating that it was well controlled by blue LED to balance the algal growth and its removal with captured solids.

 We examined the orignins and nutritional value of suspended particulate organic matter (POM) in seawater, which are the potential food source for fouling organisms, in seawater cooling systems of six power stations located in the norseastern Japan. We sampled POM and fouling organisms, and analyzed them for C and N stable isotope ratios (δ¹³C, δ¹⁵N) and the ratio of C/N. As a result, the chemical properties of POM varied between the power stations. POM from the three stations on the Japan Sea coast was considered to have relatively higher contents of POM originating from terrestrial plant and/or riverine producers. POM from the other three stations on the Pacific Ocean coast likely had higher contents of marine phytoplanktons. The POM concentration was generally positively related to dissolved inorganic nitrogen in the seawaters, suggesting that the reduction of anthropogenic nitrogen can potentially be an effective tactics to mitigate the biofoulings in the cooling systems. Furthermore, δ¹³C and δ¹⁵N of the fouling organisms were markedly higher compared with those of POM. This suggests that the fouling organisms selectively assimilated the marine phytoplankton fraction of the bulk POM. Therefore, when the food supply for the fouling ornigsms is evaluated based on bulk POM, that is potentially overestimated. To properly predict effects of nutrient/POM reductions on the production of fouling organisms, further studies are necessaly to accumulate field data and develop reliable, quantitative models describing relationships for POM vs. nutrients as well as fouling organisms vs. POM.

 Diatoms play the main role as primary producer, in tidal flat ecosystems, which have high biological production. Diatoms requires silicon as essential nutrient. Since diatoms in tidal flats mainly obtain dissolved silicon (DSi) loading from a river, it is important to accumurate information about DSi dynamics. In this study, we conducted fieldworks on the basin of Zuibaiji river and evaluated the DSi supply into Imazu tital flat(S0), DSi traping or supply by a reservoir and a sewage treatment plant(T1, S1, respectively). S0 and T1 were estimated as 10.4 ton, and 0.57 ton in December 2022, respectively. It is considered that diatom production and sedimentation to bottom layer in the reservoir was main factor for DSi traping. S1 was also estimated that 2.7 ton of DSi were supplied in December 2022. It is indicated that the reservoirs and the sewage treatment plants have non-regligible influence to DSi supply into tital flats.

 The temporal patterns of nutrient inputs into coastal marine systems are affected by changes in precipitations, hydrological runoff, and release of treated wastewater. Those further affects quantitatively and qualitatively marine primary producers. We conducted a continuous incubation experiment of the diatom species Skeletonema marinoi-dohrnii under two different supply patterns of inorganic nitrogen and phosphorous: short-term intensive supply (pulse treatment) and continuous low-concentration supply (press treatment). In the pulse treatment, the concentration of diatom cells showed apparent production-wethering cycles, and reached relatively higher concentrations at the steady state. While the content of essential fatty acids in the diatom cells was also relatively higher in the pulse treatment, the contents of some of the saturated and monosaturated fatty acids were higher in the diatoms produced under the press treatment. In the press treatment, the continuous depletion of nutrients may have caused an adaptive response of the diatoms leading to their lower growth rate as well as lower contents of the essential fatty acids.

 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 sewage treatment plants with a separate sewage system. We tested DOC, the score value (S_P) of the protein-like component (Comp. 3) of the FDOM, the sum of score values (S_T) for microbial humic-like component (Comp. 1), terrestrial humic-like component (Comp. 2) and Comp. 3 of the FDOM, and FDOM (SP, S_T)/DOC as indicators detecting the change in river water quality due to the inclusion of untreated sewage discharge from the sewage treatment plant during rainy events. Then, we evaluated the suitability of the five 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, that is confusion matrix with accuracy, and F-value. As the results, it was found that the absolute value of FDOM (S_T) was most effective in detecting of the occurrence of primary treatment discharge at the downstream point of the receiving river because of the largest accuracy and F-values.

 Continuous monitoring of influent NH₄-N in a sewage treatment plant was carried out for three years, operation plans were formulated based on these data, and energy saving measures, N₂O control measures, and active management were evaluated using a sewage treatment plant simulator. The seasonal variation of influent NH₄-N tended to be higher in winter, and the range between minimum and maximum values was wide. The daily fluctuation showed a typical fluctuation pattern with the lowest value in the early morning and the highest value in the morning throughout the year. As an operation plan, lowering the DO setting value during low-load hours as an energy-saving measure reduced the aeration air volume by 5.2%, resulting in a 0.5% reduction in GHG emissions for the entire treatment plant. As a water treatment N₂O control measure, doubling the return sludge rate during times of high load reduced N₂O emissions by 12.0%. Active management resulted in a 5% increase in nitrogen supply and a 58% reduction in power consumption CO₂. By continuously monitoring of influent quality and making operation plans, we were able to confirm that improving the operation management of the current process would lead to a reduction in GHG emissions.

 High-rate membrane bioreactor (HR-MBR) can recover >80% of organic matter in municipal wastewater and simultaneously achieve high-quality effluent (>90% removal of COD) However, extremely severe membrane fouling is expected in the operation of HR-MBRs due to very short sludge retention times (SRTs) such as 1 day. In this study, to tackle with the severe fouling in HR-MBRs, intensive physical cleaning with granular materials and chemically enhanced backwashing (CEB) were applied. Influences of different types of granule materials and frequency of CEB on the membrane fouling in HR-MBR was investigated. Sponge cubes exhibited excellent control of reversible fouling in an HR-MBR treating real municipal wastewater. The HR-MBR could be stably operated for 30 days under a membrane flux of 20 LMH (0.48 m/d), which is comparable to that set with conventional aerobic MBRs. It was also demonstrated that frequent CEB tended to accelerate membrane fouling in the HR-MBR.

 Anammox is attracting attention as an energy-efficient and low-carbon nitrogen removal technology and it has been applied worldwide. However, due to the unstable operation and sludge washout, the application of anammox-based process is slow. Recently, the utilizing of the hydroxyapatite (HAP) granules in the anammox process comes with the advantages, including simultaneous removals of nitrogen and phosphorus and better settleability of the sludge. In this study, two continuous one-stage partial nitritation/anammox (PNA) reactors with HAP-enhanced granular sludge were used to treat the synthetic wastewater with varying influent nitrogen concentration and HRT, respectively, to explore the removal performance and operational strategies of nitrogen and phosphorus at 25 °C in a long-term operation. As a result, the formation of HAP granular sludge enabled the maintenance of granular sludge with excellent settling performance, achieving a high nitrogen removal rate (NRR) of 2.0 ± 0.1 kg N/m³/d when the influent ammonium nitrogen concentration was 1200 mg/L, and the highest NRR of 4.8 kg N/m³/d, to the best of our knowledge, under a low hydraulic retention time (HRT) of 2 h and an influent ammonium nitrogen concentration of 500 mg/L. When the calcium concentration was 150 mg/L, the phosphorus removal efficiency (PRE) of 90% could be achieved. To achieve an high nitrogen removal performance stably, sufficient formation of HAP granules was necessary (phosphorus removal rate (PRR)/NRR ratio above 0.02), and a low HRT allowed the discharge of poorly settling sludge for the desired sludge settleability and concentration. The spatial distribution of the functional bacteria in the granular sludge was analyzed with fluorescence in situ hybridization (FISH). Anammox bacteria (AnAOB) and the ammonium oxidizing bacteria (AOB) were the two most abundant bacteria. The study also provides the enhancement strategies for the stability and an excellent nitrogen removal performance in a one-stage PNA process.

 Rural areas of Japan are facing severe declining population and need to consider the recomposing of small-scale waterworks. However there is no reasonable method for these small-scale waterworks to examine the effect of recomposing, especially for the case including community based water management system (CBWMS), whose data is not enough. This study focused on operation cost, which is fundamental information for considering recomposing, and aimed to develop a method for estimating and comparing operation costs for 2 scenarios, continuing current management as CBWMS and combining it into public water system. We developed a forecasting equation to estimate the operating costs of CBWMS based on data collected from local administrative or community. We applied this equation for 16 existing model cases of CBWMS and compared the results of 2 scenarios, and confirmed that this method is able to provide quantitative information about expected cost merit according to each situation of CBWMS.

 This study investigated through a year microbial communities targeting 16S rRNA and 18S rRNA genes using next-generation sequencing in a domestic dam reservoir in order to consider countermeasures against mold odor production. The results showed that the use of next-generation sequencing allowed for the detection of a significantly greater number of microbial species compared to microscopic examination, enabling a more detailed understanding of the microbial communities in the dam reservoir. Furthermore, it was possible to monitor a wide range of mold-producing species and species causing filtration problems in drinking water treatment plants, which were difficult to detect using conventional microscopy. Moreover, in terms of principal coordinate analysis comparing the microbial community similarities between samples, it was revealed that the microbial community in the bottom layer near the dam differed significantly from the surface and another bottom layer from late April to early October. Additionally, the relative abundance of mold-producing species was low during this period. Based on these findings, it was suggested that if the surface water near the dam could be transferred to the bottom layer near the dam using aeration circulation devices during this period to inhibite the growth of mold-producing species, it could potentially effectively reduce the mold odor in the dam reservoir.

 This paper presents bench-scale experiment results of a new coagulant dosage control for water purification processes. The developed new control scheme has a cascade structure where an inner loop Proportional-Integral controller works to determine coagulant dosing rate by using a flocculation image sensor and an outer loop set-point optimizer calculates the set-point of the inner loop controller using the extremum seeking (ES) technique. The image sensor measures the electrophoretic velocity (EV), which is an index of flocculation process performance, and its set-point is optimized by using a performance index consisting of a total operational cost and a treated water quality constraint. Several bench-scale experiment results show that the developed controller works well for both the case that the treated water quality constraint is active and the case that the optimal point is an interior point of the feasible region.

 Yatsu Tidal Flat(Narashino City, Chiba Prefecture), a Ramsar Convention-listed wetland, has been experiencing anaerobic bottom sediment caused by decaying Ulva spp. that grow irregulary during the summer, affecting benthic organisms. However, the specific effects of decaying Ulva spp. and leachate from decaying bottom sediment on ecosystem functions are not made clear. The purpose of this study is to evaluate the ecosystem level effects of decaying Ulva spp. leachate and decaying bottom sediment pore water at the ecosystem level through microcosm-WET test. The results showed that both decaying Ulva spp. and decaying bottom sediment pore water had negative effects on the microbial ecosystem even at concentrations as low as 5% or less. It was suggested that the influence level of decaying Ulva spp. didn’t reduce and it remained in sediment from summer to winter, or it’s influence level in summer was not in significant difference from winter.

 In order to research the detoxification of anearobic salt water containing hydrogen sulfide, we constructed a pipeline for pumping bottom water. It was confirmed by chemical analysis that the bottom water could be pumped up to the land without loss of contained substances in the pipeline. A device for supplying dissolved oxygen was constructed, and temporal water quality changes were investigated by instrumental measurements and chemical analysis when the dissolved oxygen was supplied to pumped water. As a result, it was confirmed that hydrogen sulfide was rapidly oxidized to solid sulfur by supplying oxygen.Moreover, sulfate ions increased in anaerobic condition after supplied oxygen was consumed. When dissolved oxygen was continuously supplied to maintain aerobic conditions, sulfate ion concentration did not change. It was confirmed that conversion to sulfate ion by direct oxidation of hydrogen sulfide does not occur. After completely oxidation of hydrogen sulfide, the increase in sulfate ion concentration was observed under anaerobic condition.

 We compared the feeding and biodepositing rate of the cultivated oysters and fouling mussels by the feeding experiment. The object of this study was to understand the impacts of fouling mussels on the growth of oysters and the load of particulate organic matter (POM) to the sea bottom at the oyster farms. Results showed that the feeding rate of EPA and DHA per the biomass of bivalve were larger in fouling mussels compared with oysters, which implied that fouling mussels can ingest more POM originated from phytoplankton which is essential for their growth. It was also revealed that mussels excrete more POC than oysters per unit biomass and per time. On the other hand, the amount of EPA and DHA per unit POC was lower in biodeposits from mussels than that from oysters. These results imply that removing fouling mussels from oyster farms can reduce the mass of settling POM from farms, although it is possible that the oxygen consumption rate of settling POM increase in the short term. In conclusion, removing fouling mussels from oyster farms can lead to the form of sustainable aquaculture, in terms of the efficient use of phytoplankton resources and the mitigation of the environmental impacts.

 Dissolved organic matter (DOM) transported from terrestrial sources to coastal areas is important for carbon and nutrient cycling as well as trace metal transport. In this study, DOM composition in the Tama River basin was investigated by ultra-high-resolution mass spectrometry, and the mechanisms of DOM formation and transport were discussed. As a result, the molecular composition of CHO was found to be abundant in upstream river water and litter (terrestrial plant) samples. On the other hand, a large proportion of molecular compositions containing heteroatoms (such as N and S) were found in effluent from waste water treatment plant (WWTP), downstream and coastal waters, while common molecular compositions found in all stations accounted for a relatively high proportion (33-58%) in each sampling station. About one-third of the molecular compositions detected in treated wastewater were not detected downstream waters. Many of them contained heteroatoms, suggesting that such compounds may have been decomposed or transformed during the downstream processes.

 In this study, the actual nitrous oxide (N₂O) emissions in four different wastewater treatment systems were investigated at an actual wastewater treatment plant with a small nitrogen influent load and nitrification acceleration operation. As a result, it was estimated that the N₂O emissions of the treatment plant were about 75 % smaller than those calculated using the current official N₂O emission factor. In the all systems, it was estimated that most of the N₂O generated was produced as a byproduct of ammonia nitrification in the aerobic tank. In addition, it was found that N₂O was also generated as a byproduct of the denitrification reaction that proceeds during sludge sedimentation in the final sedimentation tank and during sludge return. Based on these findings, it is necessary to review the N₂O emission factor and develop an operation method to reduce N₂O emissions.

 In this study, the collaborative effects between wastewater treatment plant and municipal solid waste (MSW) incinerator, including the introduction of waste disposers, energy recovery through mixed methane fermentation, and co-incineration of sewage sludge and MSW, were projected to estimate their future impact on greenhouse gas emissions in Satsumasendai City, as a medium-sized city in Japan. In addition to these collaborations, when an increase in wastewater treatment diffusion rates, an emphasis on MSW reduction, particularly in plastic materials and the introduction of waste heat transport to pulp and paper plant were assumed, GHG emissions in 2050 were reduced by 72% from the 2020 level, assuming no progress toward carbon neutralization (CN) of electricity and heat. The factors contributing to this reduction were energy recovery and waste plastic reduction. However, if CN of electricity and heat progresses, GHG emissions are reduced by only 66% because GHG reductions through energy recovery are no longer expected, suggesting that upstream measures such as waste plastic reduction and the introduction of biomass plastics will become even more important.

 Irrigation of treated sewage effluent (TSE) for paddy field should have impact on the emission of GHG such as CH₄ and N2. This study aimed to clarify the impact of the TSE irrigation for paddy field on the GHG emission with dissolved form profile. Survey targeted to the dissolved GHG profile, batch-experiment for CH₄ production potential of soil, and microbial analysis were conducted. The results indicates that dissolved N2 could be decreased in the paddy field contrary to the CH₄ increase, which was caused by biological reduction under anaerobic condition and the CH₄-production promotion due to the inflow of organic carbon from the TSE. This study suggests that the potentially effectiveness of the TSE irrigation for the decrease of dissolved N2 in the TSE, as well as the importance of the concern for the CH₄ production.

 Production of animal feeds using composted sewage sludge (CSS), which can be domestically supplied, is expected to make a great contribution to food security in Japan where almost all of fertilizers and animal feeds need to be imported. This study investigated the emission of greenhouse gases (CH₄ and N₂O) from dent corn fields applied with CSS, comparing with fields applied with chemical fertilizers (CF) and pig manure (PM) as another organic fertilizer. As the results, quite low amount of CH₄ was emitted from the fields regardless of used fertilizer. N₂O was emitted at the beginning of the cultivation, especially from the field applied with CF. The emissions of these gases were converted to that of CO₂ and integrated to calculate the total greenhouse gas emission (TGHG). Although there were no significant differences, using CSS and PM instead of CF could reduce the TGHG from dent corn fields by 33 to 55 %. We also found that dent corn production with application of these organic fertilizers can reduce a larger amount of greenhouse gases emitted in the production of chemical fertilizers than those from the fields. However, the comparable amount of greenhouse gases was emitted in the process of composting sewage sludge, highlighting the importance of controlling the composting process to achieve sustainable production of animal feeds with carbon neutral. In comparison, the emission of greenhouse gases in the transportation of chemical fertilizers produced in foreign countries to Japan was negligible.

 The establishment of a more detailed and simple method for clarifying humic substances components in small sample numbers was investigated by LC-EEM using an ultrafast scanning spectrofluorometer. In offline EEM-PARAFAC, the sample water level in the microplate wells could not be kept constant during EEM measurement, and any humic fractions could not be separated. On the other hand, in inline-EEM using the ultrafast scanning fluorescence spectrophotometer as a detector, it was demonstrated that the generated three-dimensional array satisfies the trilinear condition. The 275 EEM spectra obtained from river water samples collected from 11 locations were subjected to PARAFAC analysis, and the spectra were separated into four components, which enabled us to grasp the increase and decrease of humic constituents including fulvic acid, the behavior of which is difficult to grasp. By applying the developed method, it is believed that DBPs-FP can be predicted concisely and with high accuracy in the water treatment process.

 Recently, there has been concern about the impact of declining primary production on material cycles and ecosystems. The primary production depends on phytoplankton photosynthesis, and predictive models have been constructed based on various types of monitoring of the dynamics of phytoplankton. However, it is not easy to predict phytoplankton dynamics in the ocean, which are affected by various environmental factors. In this study, we constructed a prediction model for basic production rate using machine learning, which is good at predicting the future, and evaluated its performance. The results showed that the model could be estimated with a coefficient of determination of 0.75, using dissolved iron, light intensity, PO₄-P, and NOx-N as important variables.

 The trophic pathways of suspended fine particulate organic matter (SFPOM) in streams in the Amami-Oshima Island are still unknown. In this study, we aimed to estimate the origin and the trophic pathways of SFPOM using carbon and nitrogen stable isotope ratios. Within the habitat of Amami Rabbit, Pentalagus furnessi, the contribution of feces to SFPOM was 39%. The density of Ryukyu Ayufish, Plecoglossus altivelis ryukyuensis, also increased in the area of high algal biomass, but the contribution of algae to SFPOM biomass was only 0.5 mg L^-1. In addition, the density of algae-derived SFPOM showed no significant correlation to the density of Plecoglossus altivelis ryukyuensis. These results suggested that Pentalagus furnessi plays a significant role in converting terrestrial plant into SFPOM in the river ecosystem, whereas that Plecoglossus altivelis ryukyuensis has a low contribution to the production of algae-derived SFPOM in the Amami-Oshima Island.

 In recent years, carbon offsetting, which promotes the reduction and absorption of greenhouse gas emissions as a countermeasure against global warming, has been attracting attention. While terrestrial forests have been utilized as a place to absorb greenhouse gases, or carbon negative sites, seagrass beds are expected to play an important role. The carbon absorbed, sequestered, and stored in the ocean and sediments by marine organisms is called blue carbon, which was proposed by the United Nations Environment Programme (UNEP) in 2009, but the exact amount of carbon sequestration is not yet known, and scientific issues remain. This study aimed to analyze the carbon origin of organic matter in the sediments of Shizugawa Bay and to evaluate the effect of seagrass- and seaweed-derived organic matter on the sequestration in the sediments. The carbon and nitrogen stable isotope ratios were measured as indicators of organic matter, and the origin of the organic matter was analyzed. The cellulose, a refractory organic matter, was separated, and its carbon stable isotope ratios were measured. The result indicated that cellulose not only from land plants but also from seaweeds and seagrasses was a component of sediment organic matter may be contained in the bottom sediment.

 In this study, in order to control and reduce nitrous oxide (N₂O) production by nitrifying bacteria, we focused on NO which is a precursor of N₂O in nitrifier denitrification by Ammonia oxidizing bacteria (AOB) and a substance used by AOB in energy acquisition. We conducted an experimental validation to clarify the interrelationship between NO and N₂O emission characteristics of nitrifying bacteria cultivated on artificial substrates. The results showed that temporal changes in NO production by nitrifying bacteria precede temporal changes in N₂O production. Furthermore, abundant NO supply to AOB, indicated increases the rate of ammonia oxidation and decreases the conversion ratio to N₂O from oxidized ammonia. Using NO as an engineering indicator, it may be possible to comprehensively predict and control N₂O production and nitrification activity of nitrifying bacteria.

 To increase the fertilizer value of wastewater, the culture of purple non-sulfur bacteria (PNSB), known as photosynthetic bacteria, was focused on. The effects of ammonium nitrogen concentration on the growth of PNSB and the production of value-added substances were clarified through culture experiments using artificial culture media and actual wastewater samples. The specific growth rate calculated from the increase in the number of pufM genes in the experiments using the artificial culture medium revealed that growth inhibition caused by ammonia was expressed as an inhibition constant ranging from 0.73 to 1.6 g N/L. In the experiment using actual wastewater samples, the concentrations of carotenoids and 5-aminolevulinic acid, which are value-added substances, were found to increase in response to the growth of PNSB. It was estimated that 2.3 kg of carotenoids and 50 kg of 5-aminolevulinic acid are produced annually by PNSB cultivation in the filtrate of anaerobically digested sludge, and its ammonium nitrogen content is equivalent to about 17 % of the nitrogen required as fertilizer on the scale of Town A. These results suggest that PNSB cultivation using wastewater has the potential to produce value-added liquid fertilizer.

 The effect of dissolved oxygen (DO) concentration on aerobic denitrification activity and denitrifying bacterial communities was investigated. Since the conventional shaking culture method cannot control constant DO concentration, in this study, we constructed an apparatus to maintain constant DO concentration by controlling aeration and conducted aerobic denitrification tests under low DO (3 ± 1 mg/L), medium DO (5 ± 1 mg/L), and high DO (7 ± 2 mg/L) conditions. Under all aerobic conditions, NO₃^-_-N concentrations decreased simultaneously with NH₄⁺_-N and COD_Cr, and aerobic denitrification reaction proceeded simultaneously with nitrification reaction. Prokaryotic community structure analysis based on 16S rRNA genes did not confirm the presence of independent aerobic ammonia-oxidizing bacteria/archaea, suggesting that the ammonia oxidation reaction was carried out by aerobic denitrifying bacteria (heterotrophic bacteria). The microbial community structure was simpler under high DO conditions, with Paracoccus spp. and Pseudomonas spp. dominating under high and low DO conditions, respectively.

 It is known that coliforms and E. coli are removed in the secondary treatment process of johkasou. Since the internal structure of the secondary treatment process of small johkasou differs greatly, we conducted a detailed analysis of the relationship between the removal characteristics by structure and the biological membrane.The results showed that the coliform group and the coliform count were correlated with the secondary treatment SS.The results suggest that SS removal and inactivation of coliforms and E. coli occur simultaneously in the aerobic part of the secondary treatment. In the case of biological filtration, coliforms and E. coli, which are not correlated with SS, may be generated in the secondary treatment section.Although biological membranes play a major role in the removal of coliforms and E. coli, it was found that it is important to prevent the outflow of biological membranes and SS because coliforms and E. coli are maintained within the biological membrane.

 At present, to reduce the volume of decontamination waste, thermal treatment is carried out. In the thermal treatment, cesium (Cs) is volatilized and separated, resulting in fly ash containing much radioactive Cs. Cs in this fly ash is a chloride and is soluble. For safe final disposal, it is preferable that Cs in fly ash is insoluble. In this study, applying the mechanism that alkali feldspar makes Cs insoluble under heating conditions, whether the efficiency of insolubilization of Cs in fly ash improves was investigated by using rotary kiln. Indian feldspar, fly ash, and cesium chloride were mixed and heated at 700°C in a rotary kiln. No effect of rotating speed on Cs insolubilization was observed. After heating at 4 rpm of rotating speed and 700°C of temperature for 15 hours, 99% of the added cesium became insoluble. Even the addition ratio of Indian feldspar is reduced to about 80% of the amount of fly ash, by heating the mixture for 15 hours, 96% insolubilization of Cs was achieved.

 Insolubilization of arsenite (As(III)) in water sample was investigated through a combined treatment using ferrate (Fe(VI)) and water treatment sludge (WTS). Arsenate (As(V)) formed by As(III) oxidation with Fe(VI) was successfully insolubilized by coprecipitation with hydroxide of Al derived from WTS suspension, which was acidified with a dilute HCl solution. Whereas As(V) insolubilized with ferrate only or WTS suspension only was resolubilized under alkali or acidic condition, the combined treatment inhibited the resolubilization of As(V) under weakly acidic and alkali conditions. Furthermore, As(V) insolubilized with Fe(VI) only was resolubilized via Fe(III) reduction under the presence of dithionite as a reducing agent. However, the treatment using WTS suspension only or the combined treatment inhibited As resolubilization under the same reducing condition.

 These results indicate that the combined treatment using Fe(VI) and WTS suspension could prevent the insolubilized As(V) from being resolubilized even though the environmental conditions such as pH or ORP are changed after application of the treated sample to lands.

 This study evaluated Cs mobility in soil from the viewpoint of the inhibition of Cs sorption onto vermiculite by dissolved soil organic matter (DOM) and the Cs sorption onto DOM. Cs sorption isotherms obtained using soil solution and the diluted soil solution to know the effect of DOM showed that inhibition rate of Cs sorption onto vermiculite was 39.0% in the presence of DOM when Cs concentlation in liquit phase was 10^-2mg/L. In addition, to evaluate the Cs mobility as DOM-sorbed Cs in the soil environment, the Cs sorption onto DOM was investigated by three-dimensional fluorescence analysis and experiments using an anion exchange resin. The distribution coefficient of Cs between DOM and liquid phase was 3.08·10⁴L/kg, which is much larger than those of coexisting elements such as Ca and Mg. It suggested that Cs has higher selectivity for sorption onto DOM than Ca and Mg, and the amount of sorbed Cs onto DOM would be easily mobile in soil.

 PFOA is a type of organic fluoride compound that is harmful to human health and living organisms. In this study, the surface of commercial activated carbon was coated with a cationic polymer, polydiallyldime-thylammonium chloride (PolyDADMAC), to carry anion exchange function. The amine-modified carbon material exhibited excellent adsorption capacity and improved adsorption performance at PolyDADMAC addition rates of 33% or higher. The adsorption kinetics were well described by the Freundlich equation, and the maximum adsorption capacity (365 mg/g) was obtained in the initial pH range of 3-4, and the adsorption capacity was stable at environmental water pH (6.5-8.5). The adsorption progressed quickly in the initial 30 minutes and reached equilibrium in about 2 hours. The amine-modified carbon material is expected to efficiently adsorb and remove PFOA, and it will be important to test and evaluate its durability under actual conditions (in the presence of competing substances).

 We studied the effects of discarged sewage water during the seasonal management operation of sewage treatment on the growth condition and quality of Nori laver, by investigating water qulity and the content of nitrogen and phosphorus, quality (color tone, L^* value) in Nori laver around the sewage discharge outlet and Nori cultivation grounds located in Hakata Bay.

 As a result, we found that the L^* value, which is indicated of the quality of Nori laver, was significantly correlated with nitrogen and phosphorus content of Nori laver, and estimated that Nori laver was of the excellent quality with nitrogen and phosphorus content of 5, 0.2 wt%-dry or higher, respectively. Although there remained the problem in quatifying the concentration of inorganic phosphorus required for Nori laver, we suggested that even if the concentration was lower than 0.0124 mg/L, which was the index required for the growth of laver according to Fukuoka Prefecture, it was sufficient for the growth of Nori laver. Fuerhermore, we found that discharged sewage water during seasonally sewage treatment operation was caused the delay in the time when the discoloration of Nori laver was caused, and the suppression of quality degradation at the location near the sewage discharge outlet and the effect was likely to occur in the Myoken cultivation grounds located on the west side of the discharge outlet. In addition, we suggested that increasing the supply of inorganic phosphorus by seasonally management operation was one of the factors of the effects.

 To investigate the changes in phosphorus and potassium during co-firing of sewage sludge with grass and woody biomass and to assess the potential of incinerated sewage sludge ash as a fertilizer, a laboratory incinerator was used to conduct co-firing tests of sewage sludge with cut grass and tree prunings. The incinerated ash resulting from the tests was subjected to various analyses (XRF, XRD and XAFS) and thermodynamic equilibrium calculations, and the compositional changes due to co-firing were summarized. Furthermore, the properties of incinerated ash as a fertilizer were evaluated through leaching tests. The addition of grass biomass during co-firing was found increase available potassium, which reacted with aluminum and silicate compounds in the sludge to form aluminosilicates. Additionally, phosphorus was transferred to calcium compounds and other compounds during the reaction process. Moreover, co-firing with both grass and woody biomass was found to enhance the citric acid–soluble forms of potassium and phosphorus available to plants, thereby increasing the value of incinerated ash as a fertilizer.

 In this study, in order to clarify the characteristics of the newly developed sewage sludge fertilizer (NSSF) using sewage sludge and regional biomass for tea cultivation, the optimum fertilization amounts (ratios) of NSSF, the optimum fertilizer application period, and the amount of nitrogen leaching to groundwater were investigated. In the tea cultivation test using the NSSF, the tea yields were equal to or better than those of the conventionally fertilized areas, indicating that the NSSF can replace rapeseed cake (conventional organic fertilizer) as a fertilizer (24kgN/10a fertilization out of the maximum annual fertilizer nitrogen amount of 50kgN/10a). The concentration of metals and heavy metals in the NSSF-fertilized soil did not change significantly during the tea cultivation tests, and the values were below the soil environmental standard. When NSSF was fertilized in spring or autumn/spring, the fresh leaf yield and crude tea quality were equal to or better than those of organic mixed fertilizer were obtained. Compared with the control (conventional organic fertilizer), the NSSF had a lower nitrate nitrogen concentration in the infiltrated water (fertilization in autumn and spring : 15-30mg/L, control: 35-100mg/L), indicating that the environmental load is lower than that of the conventional farming system.

 This study aimed to evaluate feasibility of wastewater-based epidemiology in Japan by long-term monitoring of SARS-CoV-2 RNA in wastewater at municipal wastewater treatment plants in 3 cities of Japan. The viral titers in wastewater exhibited significant correlations with clinically reported cases of COVID-19 in all the 3 cities during the 7th wave of outbreak. A viral loading in wastewater, which is normalized the viral titer by multiplying the detected viral concentration with daily quantity of influent wastewater, exhibited better correlations than viral concentrations. Importantly, surges of viral titers in wastewater were found when big sport events were organized during the 6th wave in Ota city. This suggests that wastewater-based epidemiology is effective to detect visit of infected people from outside of the city. In this study a W/C ratio, which is calculated as a ratio of viral titers in wastewater to the number of clinically reported cases was shown to have the potential to forecast probability of increase in clinically reported cases in the following week.

 Antimicrobials are frequently used on livestock farms to treat animal diseases and to promote its growth. Therefore, livestock farms are widely recognized as hotspots for the emergence of antibiotic-resistant bacteria and their relevant genes caused by the frequent administration of antimicrobials. In this study, we investigated the prevalence of antibiotic-resistant Escherichia coli (AR-EC) strains isolated from fatting cattle with minimum use of antimicrobials in a livestock farm affiliated with Yamagata University, Japan. The fecal samples were monthely collected from 6 pairs of fatting cattles, including < 7-month calves and their parents, from January to December 2022. A total of 384 isolates were collected from fattig cattle through the periods and identified as E. coli based on uidA detection. Antimicrobial susceptibility test for the isolates found only two strains (0.52%, 2/384 isolates), both of which were isolated from calves, were resistant to ampicillin (ABPC) or tetracycline (TC), whereas all other strains were susceptible to all other antimicrobials. This percentage of AR-EC was extremely low compared to reported cases in Japan. The two AR-EC strains isolated from calves, ABPC^R-EC and TC^R-EC, were characterized by the typing of antibiotic-resistance genes using PCR analysis. The result showed that ABPC^R-EC and TC^R-EC possessed bla_TEM and tetB, respectively. Both strains were evaluated on the transmission route in livestock farms using the genotyping method such as multi-locus sequencing typing (MLST) and pulsed-field gel electrophoresis (PFGE). According to the MLST analysis, the ABPC^R-EC was identified as ST8333 which is commonly isolated from cattle, whereas TC^R-EC was not assigned to the database (NSM, no strain match). The PFGE analysis was performed on E. coli isolates in the months when ABPC^R-EC and TC^R-EC were obtained. The PFGE type of the ABPC^R-EC isolate did not match those of the seven E. coli strains isolated during the same period. In addition, the PFGE type same as ABPC^R-EC was not detected in the months before and after the month of its detection, suggesting that the AR-EC came from outside the cattle body. In contrast, the PFGE type of the TC^R-EC was determined to be identical (= difference of 0.0) among the seven isolates collected at the same time. This indicated that a part of the dominant strains of E. coli in the feces has acquired TC^R with tetB in the intestinal tract. AR-EC were less likely to occur in this farm with minimum use of antimicrobials, and even when they occured, they seemed to be quickly eliminated.

 A comprehensive culture-independent analysis of drug-resistant bacteria linking drug-resistant genes derived from plasmid DNA with bacterial species has been developed using a combination of high-sensitivity fluorescence in situ hybridization (CARD-FISH) and fluorescence-activated cell sorting (FACS). A model experiment targeting the Class A β-lactamase TEM-1 gene employing E. coli cells and the pCR2.1 TOPO plasmid vector yielded fluorescent detection of E. coli cells harboring the TEM-1 gene. The application of this method to the activated sludge sample and gene quantification by means of real-time PCR led to a 6.2- to 45.3-fold enrichment of the TEM-1 gene in comparison to the pre-sort sample. The heightened prevalence of class Bacilli in the post-sorting samples suggested that the bacteria belonging to class Bacilli constituted the principal pool of TEM-1-harboring drug-resistant bacteria in the activated sludge.

 Optically pure lactate is a raw material for biodegradable polylactic resin. Such lactic acid is produced by fermentation, and lime is commonly used as a neutralizing agent. However, gypsum is generated in the process of releasing lactic acid from calcium lactate produced by lactic acid fermentation, and the cost associated with its treatment is expensive and unfriendly to the environment. Thus, it is necessary to establish the new lactate production, for example, by finding alternative neutralizers. Previous research investigated lactic acid fermentation using chitosan as a neutralizer, although the antibacterial activity of chitosan against the lactic acid-producing bacteria inhibited the fermentation. However, the molecular weight of chitosan might influence the antimicrobial activity; therefore, we elucidated the lactic acid fermentation using various molecular weights of chitosan as a neutralizer. In an antibacterial assay, the molecular weight of 3,000~20,000 Da did not present bactericidal activity against the lactate-producing bacteria. In the lactate fermentation, maintaining the pH of the culture medium at not 5.5 but 6.5 decreased chitosan's antibacterial activity and led to chitosan lactate production when using chitosan oligosaccharide as a neutralizer. Additionally, immobilizing lactate-producing bacteria produced chitosan lactate if using a high molecular weight of chitosan that represents the antibacterial activity.

 Microalga Haematococcus lacustris produces astaxanthin, a carotenoid, under stressful conditions. The alga changes its cells into three main types (flagellate, palmelloid, and cyst) depending on environmental conditions. In the course of studying the method of H. lacustris dominant culture to realize a resource recovery wastewater treatment process that removes and recovers nutrients while producing astaxanthin, image recognition techniques was investigated to understand the cell types. With OpenCV, a classifier that differentiated between spherical cells (palmelloids and cysts) and flagellates with 84% of accuracy. However, a two-step classification was required to further classify palmelloids and cysts which have red color derived from astaxanthin by cell color. Simultaneous recognition of the three cell types by YOLO resulted in a high accuracy of over 90% for all types. The effect of image quality on recognition accuracy was examined. The accuracy decreased significantly when lower quality images were used during recognition than during training.

 To examine the occurrence of sulfur dioxide SO₂ high concentration events exceeding the environmental standard and the relationship between the events and meteorological conditions, SO₂ concentration data which was obtained in the southern part of the crater floor area of Mt. Aso by the special vehicle for atmospheric environmental observation and various existing meteorological data were analyzed. And numerical simulation of SO₂ behavior using the WRF was carried out to clarify mechanism to transport from the Nakadake crater of Mt. Aso to the bottom of the southern part of the crater floor. It was found that the SO₂ high concentration events generated by downslope wind occurring in cold air mass inflow and by valley wind circulation.

 In the report of the Central Environment Council in May 2020, PFOS and PFOA were designated as monitoring items for public water bodies and groundwater, and provisional guideline values were set. Although there are many reported cases of PFASs concentrations in environmental water, the relationship between PFASs contamination in soil and PFASs concentrations in groundwater is not clear. In this study, 21 PFASs (13 PFCAs, 8 PFSAs) and 14 PFASs precursors were analyzed in 37 soil boring samples from Kadena Town, Okinawa Prefecture. The main conclusions are as follows. 1) 20 out of 35 PFASs were detected above the lower limit of quantitation. 2) Main contaminant was PFOS (2,620 ng/kg-dry), the second was PFHxA (2,280 ng/kg-dry), and the third was 8:2FTS (360 ng/kg-dry), and the fourth was 6:2 FTS (222 ng/kg-dry). 3) PFOS concentration in surface soils was 28, 000 ng/kg-dry, it was 180 times higher than the median global background (Rankin et al., 2016) and 74 times higher than the U.S.EPA guidelines for groundwater protection. 4) Up to 1,530 ng/L of PFOS was detected in the surrounding groundwater.

 Recently, pollution of the aquatic environment by microplastics (MPs), which are defined as plastic particles of 5 mm or less in diameter, has been reported. Since tire-derived MPs account for 28% of primary MPs, understanding the occurrence of tirederived MPs will contribute to reducing the discharge of MPs into the ocean. In this study, road dust was sampled at two locations, one at Kotta in Tama City, and another at Kameido, and tire dust-derived MPs were identified using FTIR. Sampling was conducted at two points in a straight road section at Kotta, and at four points within an intersection and two points in a straight road section in Kameido. A comparison of the MPs at both straight section showed that more MPs were obtained at Kotta, where traffic volume was larger. Moreover, the number of MPs was more than twice within the intersection compared with straight section. This result will suggest that the number of MPs may increase at points where vehicles pass from various directions or where curves occur.

 The load of some pesticides into water environments is seriously concerned for its adverse effects on non-target organisms. In this study, we investigated the effects of some neonicotinoid insecticides on diatom (the primary producer in aquatic ecosystems) phototaxis. Neonicotinoids had both positive and negative effects on the phototaxis, depending on the organisms and the chemical species investigated. Imidacloprid promoted Nitzschia sp. phototaxis up to 160 mg L^-1 (the highest concentration in this study), while thiacloprid decreased the relative number of cells exhibiting positive phototaxis in Nitzschia sp. and Mayamaea pseudoterrestris by up to approximately 29 % and 70 %, respectively. However, the decrease in phototaxis is unlikely at the detected concentrations in the environment. Our results suggest that phototaxis is useful as an endpoint for ecotoxicological impact assessment. The method based on counting the number of cells can evaluate the ecotoxicological impact of some neonicotinoids on diatom phototaxis and may be applied to growth inhibition evaluation in an environmental situation where light is irradiated unevenly.

 The monitoring concentration of viruses in sewage can grasp the pandemic of infectious diseases in the catchment area. This study aimed to clarify the effects of COVID-19 predicted number as wastewater-based epidemiological information on the changes of going out behavior. We conducted a questionnaire survey for Sendai citizens and analyzed by covariance structure model about two groups. Group A respondents received information "COVID-19 predicted number is 12,000 people next 1 week in Sendai city", group B respondents received "1,200".

 As a result, there was no significant relationship between the changes of going out behavior and the experience of COVID-19 infection or the number of vaccination doses. In group B, people who had high-level risk perceptions and who were anxious about going out tended to implement new measures and increase the frequency of their measures during going out.