Comparative evaluation of mass transfer of oxygen in three activated sludge processes operating under uniform conditions.

This investigation was conducted in three laboratory-scale activated sludge processes, namely, the conventional completely mixed activated sludge process (CMAS), the modified Ludzack-Ettinger process (MLE), and the University of Cape Town (UCT) process. These systems were operated under controlled conditions by feeding a uniform influent at a single 10-d solids retention time (SRT). The oxygen transfer parameters (KLaf, α, OTRf, and OTEf) determined indicated that the alpha (α) and oxygen transfer efficiency (OTEf) in processes where the enhanced biological phosphorus removal (EBPR) mechanism was active were higher than in the conventional completely mixed activated sludge (CMAS) process, where such a mechanism was absent. Thus, presenting a clear evidence of improved oxygen utilization in activated sludge processes containing unaerated, anoxic, and anaerobic selector zones. [ABSTRACT FROM AUTHOR]