FULL SCALE AND LABORATORY SCALE RESULTS FROM THE TRIAL OF MICROSLUDGE AT THE JOINT WATER POLLUTION CONTROL PLANT AT LOS ANGELES COUNTY

MicroSludge® is a patented chemical and pressure pre-treatment process that liquefies waste activated sludge (WAS) to increase both the rate and extent that WAS is degraded in an anaerobic digester. The process uses chemical pre-treatment to weaken cell membranes and then a high-pressure homogenizer, or “cell disrupter”, to provide an enormous and sudden pressure change to burst the cells in WAS. The resulting liquefied WAS is then more readily converted to biogas.Following demonstration of the first full-scale MicroSludge unit near Vancouver, Canada in 2004, a second full-scale unit was commissioned at the Los Angeles County Sanitation Districts' (LACSD's) Joint Water Pollution Control Plant (JWPCP) in October 2005. The JWPCP is located in Carson, California, with capacity to treat 400 MGD of wastewater, serving a population of approximately 3.5 million. The JWPCP services a large industrial base: approximately 20% of the total organic load to the WWTP is contributed by seven oil refineries in Los Angeles County. The JWPCP also treats solids from the LACSD's upstream water reclamation facilities, for a solids loading population equivalent of approximately 5 million.A MicroSludge system with two 4,000 L/h cell disruption modules was continuously operated for 24 hours per day to process approximately 192 m3/day (50,000 GPD) of thickened WAS at 5 to 6% total solids (TS) concentration. The processed WAS was co-digested with primary sludge (PS) in a 75:25 by volume (approximately 68:32 by mass) PS:WAS mix at a nominal HRT of 19 days. The MicroSludge fed digester performance was compared to that of one of the other 23 digesters operated under similar conditions at the JWPCP, except that the WAS feed was not pre-treated.