Solubilization and Elimination of Coliforms from Sewage Sludge by Sonication.

Disposal of sewage secondary excess sludge is a great problem globally, and stabilization of this excess sludge by anaerobic digestion is hampered due to its constituents resistant to biodegradation. Sludge pre-treatment enhances the performance of anaerobic digestion. In this study, sewage sludge was collected from a full-scale sewage treatment plant and characterized. Ultrasonic method was used for the excess sludge disintegration of microbial flocks and cells, so as to breakdown the intracellular or extracellular polymeric materials to enhance the anaerobic digestion. The studies related to the effect of sonication on release of nutrients, increase in soluble COD and reduction in pathogenic coliforms as well as heterotrophic microorganisms and the optimization of sonication time were carried out. The results showed that the twenty minutes sonication (25 kHz) increased the soluble COD content, nutrient release and complete disappearance of fecal as well as total coliforms in the treated sludge. The results are presented and discussed in this paper.