[Impacts of different pretreatments on characteristics of excess sludge]

The impacts of three pretreatments (acid, alkaline and thermal treatments) on the characteristics of sludge were discussed. The results showed that the three pretreatments could disintegrate the sludge and the effectiveness of alkaline treatment was the maximum (about 58.46%) and its SCOD release was also the maximum (2934.9 mg/L). The main compositions of soluble organics were proteins, carbohydrates and volatile fatty acids (about 80%-90%, together). The increase of soluble proteins in the alkaline treated sludge was the maximum (2058.6 mg/L), while the increase of soluble carbohydrates in the thermal treated sludge was the maximal (353.2 mg/L). The SS and VSS of sludge were decreased by the treatments and the effectiveness of alkaline treatment was the best and that of acid treatment was the worst. The particle size distribution of sludge showed acid and alkaline treatments could decrease the particle size and increase the consistency of sludge. The solublized mechanism of the three pretreatments was also discussed.