抄録
Coagulant dosed and DO controlled intermittent aeration activated sludge process, which treated domestic wastewater, was investigated so as to examine its ability of nitrogen removal and suppression of the emission of N20, one of the greenhouse effect gases. In respect to the N2O emission into the air, that during aerobic period amounted to about 4 times as large as that during anoxic period. N2O emission dissolved into the effluent was about 1/3 of that into the air. DO controlled intermittent aeration activated sludge process could achieve high nitrogen removal and restraint of N2O emission under control of aeration and stirring by measuring DO and water temperature. N2O conversion ratio from the nitrogen influent and that from the removed nitrogen could be reduced to about 0.05 and 0.06%, respectively, under the nitrogen loading of less than 0.021kg-T-N·kg-MLSS-1·day-1. However, each value increased drastically to 0.66 and 1.13%, respectively, under the nitrogen loading of 0.035kg-T-N·kg-MLSS-1·day-1. N2O emission rate was raised over the range of nitrogen loading, at which the influence of higher-nitrogen loading on both the nitrogen removal efficiency and the nitrification ratio came to arise. Consequently, making the treatment under appropriate influent loading, at which satisfactory nitrogen removal efficiency could be obtained, could also restrain N2O emission simultaneously.
