COMMERCIAL SCALE DEMONSTRATION OF THE MICROSLUDGETM PROCESS TO LIQUEFY MUNICIPAL WASTE ACTIVATED SLUDGE
Rob Stephenson, Scott Laliberte, and Peter Elson
Paradigm Environmental Technologies Inc, Canada
(free)
MicroSludge™ is a chemical and physical pretreatment process that significantly increases both the rate and the extent that waste activated sludge (WAS) is degraded in an anaerobic digester. MicroSludge uses alkaline pretreatment to weaken cell membranes and to lower viscosity, and an industrial homogenizer to provide an enormous and sudden pressure change to burst microbial cells. The resulting liquefied WAS is then readily converted to biogas in an anaerobic digester.
The first commercial prototype MicroSludge plant was commissioned in January 2004 in Chilliwack (near Vancouver), British Columbia, Canada. The Chilliwack wastewater treatment plant (WWTP) serves a population of 70,000. During the January to October 2004 demonstration program, a single 4,000 litre per hour homogenizer operated 8 to 10 hours per day to process all of the thickened WAS (TWAS at 4 to 5% total solids) generated at this facility. Treated TWAS was then anaerobically digested at 37ºC both with and without primary solids at HRTs ranging from 6 to 13 days. Volatile solids, volatile fatty acids (VFAs), alkalinity, BOD, COD, gas composition, electrical consumption, chemical consumption, pathogens, ammonia, TKN, and the de-waterability of digested solids were monitored throughout.
This paper is based upon a report written by CH2MHILL [1] on the Chilliwack demonstration. It verifies at a commercial scale that MicroSludge greatly increases both the rate and the extent that WAS is degraded in a conventional mesophilic anaerobic digester. This results in less residual biosolids for disposal and more biogas for energy conversion. Because MicroSludge is a net energy generator, the net operating cost advantage increases with increasing electrical utility cost. The net operating cost advantage also increases with higher biosolids disposal costs. Additionally, since MicroSludge lowers the time needed for anaerobic digestion, digester capacity is increased and therefore fewer anaerobic digesters are required, avoiding plant expansion and associated land and capital costs.
KEY WORDS Biogas, Biosolids Pre-Treatment, Cell Disintegration, Cell Disruption, High Pressure Homogenizer, Anaerobic Digestion, MicroSludge, Sludge Pre-Treatment, Secondary Solids, Waste Activated Sludge
