The Intensification of Sewage Sludge Anaerobic Digestion by Partial Disintegration of Surplus Activated Sludge and Foam

Large quantities of sludge are produced in biological wastewater treatment. Sludge has a high putrescibility and therefore has to be stabilizsed in order to enable an environmentally safe utilization or disposal. The anaerobic digestion is the standard technique to stabilize the sludge. Digestion produces biogas and reduces the amount of organic matter. The amount of excess sludge production from wastewater treatment plants is continuously increasing. Therefore, minimization of excess sludge is becoming more and more important. The aim of bacterial cell disintegration is the release of the cell contents as an aqueous extract. Mechanical disintegration can activate the biological hydrolysis process and therefore, significantly increase the stabilization rate of the secondary sludge. It has been shown that when subjecting the sludge to 30 min of mechanical disintegration, the COD concentration in the supernatant increased from 61 mg/l to more than 144 mg/l in activated sludge and from 68 to more than 688 mg/l in foam. This study presents an application of mechanical disintegration on sewage sludge (mainly surplus activated sludge) and foam to enhance biodegradability and biogas yield in anaerobic digestion.