小水路における水質変化に及ぼす河床生物膜の影響

概要

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Effects of environmental conditions, i.e., amount of riverbed biofilm, flow velocity, dissolved oxygen, and water temperature, on the purification rate of pollutants in a small channel discharging gray water were investigated. In order to investigate the effects, artificial substrata (unglazed tile, 4.6mm×4.6mm) were set on the riverbed. The substrata were taken from the channel once a week, and purification rate, i.e., removal rates of dissolved organic carbon (DOC), dissolved nitrogen (D-N), ammonium nitrogen (NH4-N), nitrate nitrogen (NO3-N), and dissolved phosphorus (D-P), was measured. Removal rates of DOC, D-N and D-P were increased with the increase in the amount of riverbed biofilm under high DO condition although the rate were decreased under low DO condition. Increase in flow velocity improved the removal rates by accelerating the diffusion of DO and substrates from liquid phase to inner parts of riverbed. High water temperature caused the decrease in DO with enhanced oxygen consumption in wastewater and riverbed biofilm, resulting in the decrease in the removal rates. On the other hand, high removal rate of NO3-N was observed under low DO condition.
社団法人　日本水環境学会の論文