Abstract
Towards the achievement for the concept that a sewage treatment plant should serve as a base for circulation of materials and energy in a watershed, the solubilization process for enhanced digestion gas production and the acceptance of excess digestion gas at other sewage treatment plant were studied for model cities with a population of 0.5 million population in combination with material(phosphorus) recovery. AS for the region biomass, jyokaso sludge that introduced all model cities was accepted to a sewage treatment plant. Being conscious of the approach that watershed people concerned were united, some scenario was evaluated by the index of the power self-supply ratio in the watershed and the phosphorus recovery ratio in the watershed. As a result of the evaluation for Matsuyama city, Utsunomiya city, Gifu city, it was found that Matsuyama city had 2points higher energy potential utilization ratio(20%) than Utsunomiya city(18%), so Matsuyama city was the most highest power self-supply ratio in the watershed of 57.4%. From the view point of material recycle, because the Gifu city had already carried out phosphorus recovery from incineration ash, the phosphorus recovery ratio in the watershed was highest (46%) because of the high phosphorus removal (615kg/day; removal ratio; 91%) at the wastewater treatment plants. The quantity of present phosphorus recovery was 307kg/day and was calculated to increase by 7kg/day in acceptance of jyokaso sludge.
