Mechanical Cell Lysis and Recycle to Reduce Waste Activated Sludge, 1999 Environmental Conference Proceedings

Allan Springer Ph.D.

Miami University

John Higgins P.E.

KADY International

This paper presents results of full-scale pilot testing of a sludge lysis and recycle process at the Portland (Maine) Water District’s 56,870 m 3 /day (15MGD dry weather flow) Marginal Way Activated Sludge Wastewater Treatment Facility (WWTF). Initial research by Springer, et al.1 , demonstrated that through microbial disintegration (lysis) it was possible to recycle all waste activated sludge (WAS), and operate an activated sludge process (ASP), while maintaining acceptable biological oxygen demand (BOD) and total suspended solids (TSS) removal efficiencies. The purpose for pilot testing was to demonstrate at full-scale that by disintegrating cells and other particulates in WAS, using a proprietary adaptation of a KADY mill, excess secondary biosolids produced could be returned to the aeration system of an ASP wastewater treatment plant, without substantially affecting existing BOD and SS removal efficiencies.

In the full-scale test, observed yield values were reduced from 0.75 to 0.33 kg TSS/kg of BOD5 removed resulting in a daily total saving in operation and solids disposal costs of US$291. This savings would pay for the capital cost of the lyse and recycle units in about 2 years. The system operated trouble free with less bulking than in the untreated waste streams. It required more aeration, however the operating cost of this was offset by savings in the cost of sludge disposal, polymer and lime usage and a reduction in the usage of the gravity belt sludge thickener and belt filter press. The lyse and recycle technique was demonstrated to be readily retrofitted to an activated sludge plant.