Cause and Control of Baulking Sludge by Microthrix Parvicella in MUCT System

The cause and control of bulking in modified University of Cape Town (MUCT) system were investigated. The results were as follows: (1) Low temperature is the main cause of excessive filamentous bacteria growth, and dominant filamentous bacteria was Microthrix parvicella in the sludge; (2) Biological techniques such as reducing sludge retention time (SRT) and increasing temperature could decrease sludge volume index (SVI) and control bulking; (3) The removal efficiency of COD was constantly higher than 92.4%, and the removal efficiency of TP ranged between 87.4 and 98.0% during experiment, but percentage of TN removal decreased to about 42.2% due to used the lower SRT (6d) after 9 Nov 2006.