[Study on treatment of excess sludge under alkaline condition]

Disintegration of alkaline treatment on excess sludge and its influencing factors were investigated. The results show that alkaline treatment can increase the soluble chemical demand oxygen (SCOD) by releasing the organic materials from cells to water and converting the insoluble ones to soluble ones. The floc structures and the cell structures of sludge were destroyed in the process of alkaline treatment when the treated pH value was above 11.0. OH- played the role in the alkaline treatment and the cation would impact the efficiency. The maximal removal of volatile solid (VS) were 48.01% and 40.40% for total solid (TS) when the pH value was 13.0. Sludge size reduced with the increase of pH value. Sludge concentration, pH value and treatment time were three important factors of alkaline treatment. The results of orthogonal experiment indicated that the sludge concentration was a marked factor of affecting the efficiency of alkaline treatment, but the SCOD of unit sludge was almost similar.