EXPERIENCES OF DIGESTED-SLUDGE THICKENING BY AERCON

Increasing restrictions on sewage sludge disposal routes and the tight ening of treatment requirements have led to an escalation of sludge-di sposal costs which are out of proportion to other sewage-treatment cos ts: consequently reducing sludge volume is becoming increasingly cost- effective. Consolidation of anaerobically digested sludge has traditio nally been difficult and takes many weeks in secondary digesters or de ep storage tanks. Pre-aeration of the sludge using the Aercon process can enable consolidation to take place in days instead of weeks. This paper reports the results of a pilot-scale plant designed to investiga te further the mechanism by which aeration speeds up consolidation. It was concluded that the rate of consolidation depended on aeration int ensity and cooling of the sludge. Inhibition of anaerobiosis was more important than gas stripping in enhancing consolidation.