Development of creation technology of tidal flat blotope for reduction of nitrogen and phosphorus loads and efficient use of treated sewage

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In order to develop a creation technology of tidal flat biotope for reduction of nitrogen and phosphorus loads and efficient use of treated sewage, we studied on the self-purification function of tidal flats, such as nutrients uptake by reed wetland, nutrients cycle and denitrification in tidal flat and nutrients uptake by seaweed bed.The results of this study are summarized as follows.1) Reed wetlandThe effect of porosity of the filling carrier on removal capability of nutrients from treated sewage was analyzed. Nitrification and denitrification by the rhizosphere microorganism were important for the nitrogen removal, and the simultaneous reaction of nitrification and denitrification occurred under appropriate conditions of porosity and water surface loading. The removal of phosphorus was mainly carried out by the adsorption to the carrier. Therefore, high removal efficiency was obtained by the carrier with low porosity.2) Tidal flatThe purification function of attached animal that li … More ved for the revetment of the Tokyo inner bay was evaluated. The attached animal purified organic matter of 19t-COD/day at revetment distance of 192km, and this value corresponded to 23% of COD that flows from Tokyo.The environment factors concerning fluctuations of biomass and species of macrobenthos inhabiting in the Kasai artificial beach were analyzed. The benthos was damaged in the rainfall time. It was due to the inflow and retention of river water. When the river water had been increased by rainfall, the water quality in Kasai artificial beach became a low salinity by the structural problem, and some kinds of bivalve died.3) Seaweed bedThe nutrient uptake rate of Sargassum horneri became the highest from May to June in which the growth rate was also the highest We could make the equation of the nutrient uptake rate which was the function of growth stage, nutrient concentration, illumination intensity and temperature. The effect of nutrients uptake by S. horneri on the nutrients cycle of Matsushima Bay was evaluated. The S. horneri bed in May absorbed about 70% of the nutrients inflow load, and it greatly contributes to improving water quality. Less