Effects of Primary Settling Tank on Denitrifying Phosphorus Removal in a Full-Scale AAO Process

Abstract

Effects of primary settling tank (PST) on phosphorus removal and the ratio of denitrifying phosphorus removing bacteria (DPB) to phosphorus accumulating organisms (PAOs) in a full-scale anaerobic/anoxic/aerobic (AAO) process were investigated by field survey and batch test. The AAO process without PST showed higher phosphorus removal efficiency than that with PST. In the anoxic tank, the phenomenon of anoxic phosphorus uptake and anaerobic phosphorus release were observed in the AAO process without and with PST, respectively. The DBP/PAOs ratio was 46% and 39% in the AAO process with and without PST, respectively. The AAO process with PST yielded higher microbial activities than that without PST.