The economic effects of the composting of current sewage sludge in Iwamizawa city were investigated compared with the effect of disposing of it. Input-output (IO) tables for each operation, composting or disposing, were compiled and the difference in gross value added (GVA) between the two operations was presented. To create the IO tables, Iwamizawa city’s IO table distributed by the Ministry of the Environment and each operating cost based on past records of Iwamizawa city’s spending were used as original data. Economic ripple effects derived from the operating costs were also included in the compiled tables. As a result, the difference in GVA between the two operations was calculated to be 19.6 million yen year^-1, though the difference in the operational costs was 15.7 million yen year^-1. The use of the sludge dryer was indicated to be a subject of discussion regarding the sustainability of the composting operation. The composting operation can encourage regional demand as local industrial sectors are participating in the operation, and it might lead to larger regional economic ripple effects. The demonstrated analysis could predict an increased amount of GVA, indicating a regional profit. It would be effective for local project assessment.

The objective of this study is to develop a toilet independent of infrastructure, that is, electricity, water and sewerage. The treatment performance of the water purification unit to reclaime wastewater for toilet usage with minimum running energy for the circulation of water was tested. The chromaticity of reclaimed wastewater was maintained at less than 30 degrees after the total number of times of toilet use reached 897 (218 excremental and 679 urinal uses) . Since the complete elimination of Escherichia coli using only the water purification unit was difficult, it was found that some disinfection countermeasure would be necessary to maintain hygienic safety. The removal efficiencies for COD_Mn, total nitrogen and total phosphorus estimated from the total number of times of toilet use and the final water quality of reclaimed wastewater were approximately 99%, 83% and 98%, respectively, despite the frequency of toilet usage. These results confirmed that the water purification unit consisting of a multistage filtration bed could stably reclaim wastewater for reuse in the toilet.

We evaluate the suitability of a fly-ash-ndash;shell blocks (FSBs) for periphytic diatom growth. FSBs and concrete and granite blocks (length 4 cm, width 16 cm, and height 4 cm) were immersed in an aquarium filled with sea water for two weeks. The upper surfaces of the blocks were photographed by digital cameras every weekday. The increase of the periphytic diatom biomass (Chl-a) on the blocks with time was understood from image analysis using a color channel having a high correlation with Chl-a. Factors defining the growth characteristics, such as specific growth rate in the exponential phase and initial recruitment rate, were obtained from the temporal change in the biomass, and were compared among each type of material of the blocks. The results, show that while the diatom recruitment rate was fastest on concrete, the specific growth rate in the exponential phase showed no difference among the materials.

The inner part of Osaka Bay in Japan is affected by eutrophication, and the western part of the bay is affected by oligotrophic conditions. In this study, the distribution, sources, and decomposition rate of organic nitrogen (Org-N) in the estuarine region of Osaka Bay, defined as the region from the mouth of the Yodo River to the bay head, were studied to elucidate the cause of this uneven distribution of nutrients in the bay. Concentrations of Org-N are much higher in the estuary region than in freshwater areas or in the bay itself. Particulate organic nitrogen, which potentially sinks toward the bottom, accounted for 74 ± 11% of Org-N. The decomposition rate of dissolved organic nitrogen over 100 days, which is potentially supplied to the sea with low-salinity water, was 29 ± 4%. These results regarding the decomposition rate of organic matter in the estuarine region of Osaka Bay may improve the accuracy of models of the impact of land-sourced nutrient load on nutrient conditions in the bay.

The objective of this study is to clarify the effects of typhoon 0418 on the macrobenthic community in the tidal flats on the coast of Iwakuni in Hiroshima Bay, using monitoring data from 2001 to 2016. Zostera beds disappeared after typhoon 0418 hit in September 2004. The distribution area of the beds recovered to the pretyphoon level after more than eight years, because of two consecutive years of disturbance by typhoons. The bottom sediment of the tidal flats showed large fluctuations in the mud content, COD (Chemical Oxygen Demand) and IL (Ignition Loss) regardless of changes in the Zostera bed area. Macrobenthic communities showed a drastic decrease in number of species, number of individuals, wet weight and diversity (H’) after typhoon 0418. These values were low during the deterioration period (from just after typhoon 0418 to 2008) of Zostera beds, but became high during the recovery period (2009 and later) . These results show that the presence of Zostera beds is important to the macrobenthic community in tidal flats and that typhoon 0418 had both short- and long-term effects on the macrobenthic community in the tidal flats as it caused physical disturbance and subsequent loss of Zostera beds.

Investigations of microplastic pollution have been conducted in the ocean and coastal areas, but few studies exist for terrestrial waters, such as rivers and lakes in urban areas, which are the main sources of microplastic. In this study, we monitored microplastic pollution in sediments collected from Lake Ezu in Kumamoto City and Ohorikoen Pond in Fukuoka City. As a result, microplastics were detected in sediments at almost all sampling sites, the median concentrations were 725 to 1,034 items kg^-1 dry weight in Lake Ezu and 61 items kg^-1 in Ohorikoen Pond. The difference in microplastic concentrations may be due to the operation of a water treatment facility at Ohorikoen Pond. On the other hand, high concentrations of microplastics were detected in sediments near boat houses on Lake Ezu (36,086 items kg^-1) and Ohorikoen Pond (2,794 items kg^-1) . Polymethyl methacrylate (PMMA) was the dominant component of microplastics in sediments from both sampling sites. The samples of boat paint collected from boat houses were also identified to be PMMA. These results indicate the possibility of boat paints being a potential source of microplastics in an urban freshwater environment.