Study on Activated Sludge Bulking and Sludge Characteristics in A~2/O Process

Filamentous sludge bulking,which occurs more frequently in biological nutrients removal(BNR) systems,is a severe problem restricting the development of activated sludge process.Taking the A2/O process currently used in WWTP as research object,the filamentous sludge bulking and its inducement likely occurred in this process were investigated,and the characteristics of bulking sludge were studied.The results show that the filamentous sludge bulking may occur in the A2/O process if the operation is unsuitable.The increasing of DO concentration in the aerobic zone can improve sludge settleability to a certain extent,and the increasing of the organic loading rate in the aerobic zone is more important for control of sludge bulking.The sludge with good settleability has wide particle size distribution,is partly about 15 μm and 50 μm,and the majority of bacteria are cocci.The particle size of bulking sludge is mainly less than 10 μm,the majority of bacteria are filamentous bacteria,and the minority of cocci are embedded inside filamentous bacteria.