Development of Advanced Treatment Systems of Rural Sewerage by the Combination of Biogeofilter and Biotope Pond

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As a result of the selection of plants suitable for the advanced treatment of rural sewerage located in Akita City, we clarified that summer plants including forage rice plant, sesbania, Italian rye grass, and fall-winter plants including potherb mustard and nozawana have high nitrogen and phosphorus absorbing ability. And we conducted experiments of advanced treatment of rural sewerage with Biogeofilter (BGF) that was built in a rural sewerage plant. In a BGF filled with zeolite, we demonstrated that in 2004 the growth of forage rice plant was very bad because zeolite absorbed most of nutrition, but that in 2005 its growth and the removal rate of phosphorus were improved. Moreover it was suggested that NH_4-N was almost completely removed by the filled zeolite for two years when the secondary treated water of the average NH_4-N concentration 33mg/L was provided to a BGF at the time interval of one day and a half.We also constructed three series of BGF for the environmental education for elementary school children. We planted flowers, vegetables and resource plants such as sesbania and papyrus in these BGF. In biotope ponds we brought killifish and loaches from the surrounding paddy fields, and observed their growth. We observed that the bio-diversity in the ponds was maintained. After the plantation of plants, the observation of the growth and the final presentation by school children, we clarified that the environmental consciousness of the children was stimulated and that teachers gave a high evaluation to this experiment. These researches suggest that it is important, for effective advanced treatment of rural sewerage, to make up appropriate combination models of filter materials and plants considering their nutrition absorbing abilities so that we could reach the target of treated water quality.