BIOLOGICAL FOAM MANAGEMENT STRATEGIES AT A PURE-OXYGEN ACTIVATED SLUDGE PLANT WITH NO SELECTOR TECHNOLOGY

摘要

Solids retention time (SRT), biological scum trapping and recycle and the dynamic equilibrium between Nocardioform populations in the foam and the ML are the controlling factors in activated sludge foaming events caused by Nocardioform bacteria. The combination of selective wasting and SRT control can ensure long-term foam control to the operation of a pure-oxygen activated sludge system. Polymer addition to the ML, followed by selective wasting of foam can cure a severely foaming ML in a matter of weeks provided the SRT remains below 1.5 days. SRT control and selective wasting will also alleviate a severely foaming ML, but effects will only be observed after three or four months after implementation. A SRT of 0.3 days will result in the complete wash out of Nocardioform bacteria from the activated sludge system, which can then operate at a SRT of 3 days free of Nocardioform.