Control of Microthrix parvicella foaming in activated sludge

A series of investigations including plant monitoring, batch experiments, laboratory scale continuous flow experiments and final field application, were carried out for controlling Microthrix parvicella foaming on the surface of aeration basins in an activated sludge system. In the monitoring of the plant, a very characteristic seasonal pattern was observed in the foaming, and neither metabolic nor kinetic selections such as the mean cell residence time (MCRT), sludge age and food-to-microorganism (F/M) ratio, were effective in suppressing the foaming during the overproliferation of M. parvicella. Three investigated chemical agents, namely chlorine, acrylamide-based cationic polymer, and quaternary ammonium-based anti-filament polymer (AFP), were used in batch experiments and continuous flow experiments for physico-chemically reducing M. parvicella, of which AFP was found be most effective. Sufficient control of the foaming, as well as control of M. parvicella growth was also enabled by AFP in the actual application of foaming plant, with no deterioration in the effluent quality.