A Novel nitrogen removal system by an aerobic activated sludge controlled to low orp

摘要

Effect of low oxidation-reduction potential(ORP) under aerobic condition on nitrogen removal in an activated soludge was examined. The activated sludge was cultivated in a medium controlled to low ORP by adding hydrazine as a reducer under aerobic condition. During the cultivation, ORP was kept between -100 and -200 mV even though dissolved oxygen(DO) was as high as 6.0 mg centre dot l~-1. After acclimation by fill and draw culture mycelium-like microbes became dominant, and NH_4 was decomposed into nitrogen gas(N_2) under the presence ofcarbon source without accumulation both NO_2 and NO_3. Control experiments using fresh sewage or treated wastewater filtrate implied that the NH_4 removal reaction was biological. Mass balance in continuous culture of activated sludge by adding hydrazine showed that 7.4