Operational Aspects of Activated Sludge Process

The main operational problem encountered in a system of this kind is sludge bulking that could be caused through the absence of phosphorus, nitrogen and trace elements and huge fluctuations in pH, temperature or dissolved oxygen (DO). Bulky sludge has poor compactibility and settleability because of the excessive growth of filamentous micro-organisms. This problem could be controlled through chlorination of the return sludge. Conventional activated-sludge processes and various modifications (Figures 13 to 15) are described below.