HOW MICROSLUDGE® AND ANAEROBIC DIGESTION OR AEROBIC STABILIZATION OF WASTE ACTIVATED SLUDGE CAN SAVE ON SLUDGE MANAGEMENT COSTS

Waste activated sludge (WAS) is a waste by-product that is generated in large quantities in air-activated sludge or UNOX effluent treatment plants (ETPs) in pulp and paper mills. Currently, WAS is managed as a waste and is either burned (in spite of its high water content and negative fuel value), landfilled, or land-applied. However, WAS has both economic and environmental value: it is a potential source of both renewable energy and nutrients that can reduce the net costs of sludge management as well as a pulp mill's environmental footprint. Anaerobic digestion converts only a small portion of untreated WAS to form biogas, and the process is slow. Aerobic stabilization of raw WAS occurs in ETPs during long solids retention times, but results in high aeration costs. MicroSludge is a sludge pre-treatment process that ruptures the microbial cell membranes of WAS. This study shows that MicroSludge significantly increases the rate of anaerobic digestion of pulp and paper WAS, reduces the amount of waste sludge for disposal, and enables recovery of fertilizer that otherwise would need to be purchased to operate the ETP. This study also indicates that aerobic stabilization of MicroSludge-processed WAS results in rapid destruction of the sludge for disposal.