Green tides, in which Ulva spp. overgrow and deposit on the coastline, cause various adverse environmental effects. We investigated seasonal and tidal changes in the distribution of Ulva spp. using a drone and an underwater camera for 2 years on Ohama beach of Innoshima Island in the Seto Inland Sea.

 Ulva spp. were distributed from the tidal flat (datum level: 0 m or more) to the sublittoral zone (datum level: -2.2 m) year-round. The Ulva spp. distribution on tidal flats changed due to the movement of the shoreline with the tide. Ulva spp., which had accumulated over a wide area of the tidal flat at low tide, moved to the shore side while accumulating near the shoreline as it moved due to the rising tide, but remained near the change point of the slope of the tidal flat even at high tide. In addition, the Ulva spp. distribution changed seasonally, and the coverage area expanded from spring (March‒April) and decreased from mid-August. The Ulva spp. distribution changes not only seasonally but also according to tides and topographic slopes, so it was considered necessary to consider all these factors to accurately estimate the abundance of these species.

 This study was conducted to explore the effectiveness of thermally enhanced in situ bioremediation of the groundwater contaminated with chlorinated ethenes in reducing the treatment time. First, the soilcolumn experiments were used to evaluate the effects of elevated temperatures on the dechlorination of tetrachloroethene under semi-static flow conditions. Then, a field test of thermally enhanced in situ bioremediation of the groundwater contaminated with chlorinated ethenes in Japan was conducted using groundwater circulation. The abundance of Dehalococcoides, the bacteria responsible for the dechlorination of cis-1, 2-dichloroethene and vinyl chloride to ethene, increased rapidly at 30°C than at 15°C in the column experiments. This increase greatly improved dechlorination performance of cis-1, 2-dichloroethene and vinyl chloride. In the field test, the temperature and nutrient concentrations (as total carbon) in the contaminated aquifer were controlled at 23°C–30°C and above 100 mg/L, respectively, through repeated injection and pumping during the demonstration period. The chlorinated ethenes in the groundwater decreased to below the groundwater standards after 378 days. The total chlorinated ethene removal rate obtained in the field test was higher than those obtained in previous studies of in situ bioremediation without thermal treatment. The results demonstrated the effectiveness of thermally enhanced in situ bioremediation of groundwater contaminated with chlorinated ethenes in Japan.

 The purpose of this study is twofold. One is to examine hydraulic characteristics and swimming behavior of fish in the stream-type fishway with longitudinal slope of 1/20 and 1/10. The other is to propose a roughness arrangement that makes fish easier to run up in a fishway of steep slope. The experiments were conducted. As the results, the flow velocity of the stream-type fishway with a gradient of 1/10 was approximately twice as fast as that with a gradient of 1/20, and the run-up ratio of the Tribolodon hakonensis was low at 3.3%. Based on the results, the authors suggested the roughness arrangement combining aligned and zigzag, which was expected to improve the run-up ratio even if the flow velocity is fast. However, the run-up ratio was not improved. Accordingly, the authors proposed to set the roughness as a group, expecting that the roughness groups block the water flow, and the flow velocity around there decrease, which forms a resting place for fish. As a result, the run-up ratio was improved to 26.7%, which is eight times that of the previous case.

 Tap water system in Japan is now in management stage rather than new construction. In this study, we focus on the problem that many waterworks are small in scale and have a weak management base, and analyze the characteristics of waterworks nationwide by type of water source and population size. We used the water supply statistics of the Japan Water Works Association to analyze the use of chemicals such as sodium hypochlorite and polyaluminum chloride, which are related to water quality. A comparison was made based on selected indicators such as water supply revenue (net), the number of technical staff per annual water intake, and relevant water quality items. As a result, it was found that, water supply revenue (net) and the number of technical staff tended to be higher in utilities with excessive chemical injection volume, and that utilities with excessive chemical use may not be operating chemicals efficiently.

 In the wake of the Great East Japan Earthquake, efforts to build smart communities are being promoted in various places. Among them, the heat utilization of woody biomass resources, which are abundant in the disaster area, is expected to be promising, but the utilization of woody biomass is not progressing because of the high initial cost such as facility introduction cost. Therefore, in this study, we verified the possibility of introducing a district heating system using a wood boiler and wood CGS for discrete villages that are widely distributed in the mountainous areas, where the use of district heat has hardly been studied so far. Environmental, economic and social impacts of utilization of wood resources and issues in business realization were clarified.