Unplanned and planned wastewater reuse are increasing and promising practices for a sustainable surface water resource management. However, pathogenic risk associated with wastewater reuse is a main concern due to the presence of negligible number of infectious enteric viruses in wastewater treatment effluent. A natural inactivation kinetics model of a pathogenic microorganism is essential to fully implement the HACCP approach into the sanitation safety planning. This study aimed to develop a natural inactivation kinetics model of an enteric virus of which predictors were measurable chemical and physical indicators of water matrix. First, the dataset of the time-course decay of the genus enterovirus and the chemical and physical indicators were collected through a literature review to be applied to the model construction. Second, we employed the sparse regression to select the model explanatory variables among temperature, acidic pH, alkaline pH and virus initial concentration. The inactivation rate constant of the Hom model was expressed as a function of alkaline pH, logarithm of the virus initial concentration, squared temperature and squared acidic pH, and the empirical constant was expressed as a function of the inactivation rate constant and temperature. The model parameters were estimated using the hierarchical Bayesian estimation, which provided the 95% credible interval of the time-course decay of enterovirus under varied pH and temperature. Finally, we validated the model with the measured natural decay of Enterovirus 71 (EV71) in buffer solutions (pH 7.0, 7.5, 8.0 and 4oC, 20oC, respectively), and demonstrated that the EV71 concentration was successfully predicted within the 95% credible intervals under the tested environmental conditions. Further studies need to include the contribution of other virucidal factors such as sunlight irradiations and suspended solid to the inactivation kinetics model.

 Methane conversion rate of biomass should be evaluated before methane fermentation of solid biomass. In this study, a simple COD_Cr analysis method based on ‘Testing Methods for Fertilizers’ was proposed, and the COD_Cr values of 142 biomasses were compared with those obtained using JIS. The proposed method showed higher COD_Cr values than conventional methods, especially for high-solid biomasses. Biochemical methane potential (BMP) was measured by a batch experiment. A distinct correlation was observed among the methane conversion rates based on the COD_Cr values obtained by the proposed method and the carbon content. These results indicate that the proposed method can evaluate methane production from solid biomass for introducing methane fermentation process.

 To introduce a methane production process in a small-scale sewer plant, thermophilic high solid codigestion of excess sludge and rice straw was proposed, and the effect of rice straw addition was examined by a pilot scale plant. Under the condition of input sludge concentration 9 % (mixture of excess sludge from an oxidation-ditch 6% and rice straw 3%) at SRT 15 days, stable methane production was observed, though the ammonium nitrogen (TAN) concentration increased over 2,500 mg/L. The methane conversion rate and methane yield were 0.35 and 0.186 Nm³/kgVS, respectively, which were agreed with the calculated vales from the biomethane potential of each biomass obtained by a batch experiment. Uncultured bacteria MBA08 belonging to Class Clostridia occupied 36.7-54.6 % in the digested sludge. High ammonium tolerance archaea, Methanosarcina thermophila was detected at high frequency (84-89%). Even though the viscosity increased by 10 times according to increase in TS concentration, the contents of the digester was well mixed. Although improvement effect of dewaterability of the residue was smaller than that observed in the methophiric digestion, water content of dewatered sludge was lower than those of input sludge and inoculum.

 A regional recycling system of energy and SiO₂ by thermophiric co-ditestion of sewage sludge and rice straw has been proposed. In this study, a continuous thermophilic co-digestion of sewage sludge (row sludge and excess sludge) and rice straw in a laboratory scale digestor was conducted. When 50% of rice straw was mixed to the sludge at the organic loadinlg 3.10 kg-VS/m³/day, stable biogas production was oboserved. Significant differences were observed in both bacterial and ar-chaeal community among monodigestion and co-digestion. The recovered enegty was estimated to increase by 40% by the addition of rice straw from the results of methane yield. The SiO₂ content of rice straw was higher than that of sewage sludge, and SiO₂ could be accumulated in the digested sludge, indicating that SiO₂ can be recycled by fartilizing for rice field.

 Recently, the construction of resource recycling centers of excess sludge has been progressing nationwide when night soil treatment facilities are upgraded. Recycling of energy and resources by methane fermentation and composting of organic wastes, including night soil, johkasou sludge, and kitchen garbage, is being promoted. However, johkasou sludge and kitchen garbage are usually collected independently. In order to reduce the labor and environmental load, a process is developed in which garbage crushed by a disposer is stored in a johkasou, and both johkasou sludge and kitchen garbage are simultaneously and efficiently collected for methane fermentation. Assuming that solids in domestic wastewater and kitchen garbage accumulate in the solid-liquid separation tank of a johkasou, four-week storage experiments were conducted three times continuously using a reactor with a working volume of 0.2 L simulating a solid-liquid separation tank. Degradation behavior of simulated kitchen garbage inoculated with indigenous lactic acid bacteria at 13-25℃ was investigated.

 Lactic acid fermentation resulted in decreased pH of 3.5 and suppressed the solubilization of solids. A preservation ratio of suspended solids was 80%, which shows that decrease in biogas generation potential was suppressed.

 The life cycle CO₂ evaluation of the process revealed that the simultaneous collection of organic waste reduces approximately 140 kg-CO₂/(household • year) compared to the conventional process of independent collection of kitchen garbage and johkasou sludge. In addition, the introduction of the simultaneous collection process reduces the cost of municipal waste treatment by approximately 9,500 JPY/(household•year).

 In this study, changes in various nitrogen concentrations in sediment based on a distance from an anode and depth from sediment surface were investigated to evaluate of influences of Sediment Microbial Fuel Cell (SMFC) on sediment. Additionally, changes in the sediment surface layer were investigated by the use of the microsensor measurement technique. By applying the SFC, the NH₄⁺ concentration of the pore water, which was collected at the place of 15 mm away from the anode, reduced to 40% compared with the control operation. Meanwhile, the reduction rate of it at the place of 75 mm away from the anode was 10%. Therefore, it was suggested that SMFC can enhance the degradation rate of NH₄⁺ in sediment within 75 mm from anode at least. An increase of dissolved organic nitrogen (DON) concentration in the pore water of the SMFC was observed compared with the control operation, and this effect was higher as it was closer to the anode. From the result of the microsensor analysis, penetration of dissolved oxygen into the sediment surface in the SMFC was higher than it in the control operation. As the result, the increase of denitrification performance in sediment surfaces with the increase of nitrification performance was suggested.

 The authors showed that cold nocturnal darainage flows break out in the northern part of Osaka Plain, can lower temperature of the part by 2℃ and have velocity profiles similar to those of gravity density currents on inclined plains. In the present study, numerical simulation using the WRF was conducted to examine structures and generation mechanisms of the flows. The accuracy of the calculation was checked by comparison with some existing meteorological data. The simulation results showed that the drainage flow which the authors have been studying is generated by outflow of cold air mass which accumulates in the Tada basin into Osaka Plain and there are other nocturnal drainages which flow on flood plains of the Akutagawa and Aigawa Rivers in the part.

 The aim of this paper is to contribute to developing the prefectures' low-carbon action plan. Utilizing national official statistical microdata, greenhouse gas emissions in the household sector in each prefecture are estimated. These emissions reflected regional conditions, such as the number of households, household size, building type and the presence or absence of elderly people. The CO₂ emission reduction rate per household for each prefecture are also estimated when a uniform 40% reduction is imposed in each prefecture in 2030. As a result, the CO₂ emissions in 2030 increases compared to previous research by considering the presence of elderly people in the household. Furthermore, in prefectures where population decline and aging are progressing at the same time, the CO₂ emissions in 2030 in the BAU (business as usual) case decrease compared to 2015 due to the impact of population decline more than the impact of aging. It is suggested that these Prefectural governments should set higher CO₂ emission reduction targets in their lowcarbon action plan than the national government's reduction targets.

 The generation of scum and foul odor is prominent in the tidal area of an urban small river. This study aims to clarify the contribution of the risk factors causing scum generation through statistical analysis of water quality and scum monitoring data in Shakujii estuary. There are several patterns of scum occurrence in temporal variation such as (1) when salinity is 0 and DO is high during spring tide, (2) when salinity is less than 2 and DO is low during neap tide and (3) when salinity is 0 and DO is 0 two days after rainfall. In univariate analysis of plots between scum coverage and water quality parameters, salinity, SSC, Chl-a and rainfall had clear relationship with scum coverage but not for water temperature, DO and water level.

 Based on the result of logistic regression analysis, the significant parameters to scum occurrence are DO, water temperature, water level, salinity, in the order of strongest contribution. When the values of these variables decrease, the risk of scum occurrence increases. Moreover, the best logistic regression model using these risk factors could properly estimate actual scum with accuracy of 80% during calibration while 65% during validation. Therefore, it was found that the aforementioned risk factors can express 70% of scum occurrence condition.

 Minato City has developed a forecasting system to determine the safety period of bathing at Odaiba Seaside Park using the database of model-calculated E. coli concentration change for each categorized rainfall. However, there are challenges to improve E. coli concentration prediction. Therefore, we revised the characteristics for categorizing rainfall in Tokyo wards area so that they could directly reflect CSO volumes which are related to fecal pollution. First, we estimated the rainfall intensity threshold for CSO occurrence, and defined new rainfall intensity and cumulative rainfall to reflect the CSO volumes. In addition, we proposed the use of net rainfall time which does not contain the no-rainfall period. Then, rainfall categorization results were compared between the revised method and the conventional method considering the maximum hourly rainfall intensity, the whole rainfall duration, and the accumulated rainfall. The revised method significantly reduced the variations of CSO volumes within each rainfall group compared to the conventional one. It indicated that the revised method categorizes rainfall events with similar CSO volumes and spatial distribution.

 Conservation of the surrounding environment is strongly required when civil engineering works in a natural environment. In particular, when using construction light at night, it affects not only the construction area but also a wide area of the surroundings, so that it is prevended by reducing the exposure range and using a light source with low insect attraction. However, it is difficult to quantitatively evaluate the effects on ecosystems, and quantification of the effects by introducing measures was a problem. Therefore, the attraction amount for each insect species was measured by a light trap test using nine kinds of environmental categories and three light sources, and the prediction for quantitatively visualizing the attracting amount of flying insects by nighttime construction lighting was cullied out from the result. As a result, in a lighting plan using Hg, Na and LED lights at a construction site surrounded by deciduous and evergreen forest, it was estimated that 150.7 kg, 41.9 kg and 8.7 kg of flying insects would be attracted to night lighting, respectively, used for 213 days.