Analysis of the mixing performance of a full-scale membrane bioreactor for municipal wastewater treatment

High energy consumption remains to be a key problem for application of membrane bioreactor (MBR). Optimization of MBR to save energy requires a compressive understanding of the performance of the reactor, among which the mixing performance is a significant parameter, however received little attention. In this study, a tracer experiment was carried out in a full-scale MBR for municipal wastewater treatment in China. The mixing performance of both the entire plant and the membrane tanks were evaluated. The entire plant was found to be a cascade of 2.15 continuous stirred tank reactors (CSTRs) with 8.02% of dead zones. The membrane tanks were also found to deviate from CSTR. The mixing energy was analyzed and compared with literature data from three aspects: the specific power used per unit of tank volume (P-s,P-v), per unit of permeate volume (P-s,P-p), and per unit of membrane area (P-s,P-m).