FULL-SCALE DEMONSTRATION OF WASTE ACTIVATED SLUDGE HOMOGENIZATION AT THE LOS ANGELES COUNTY JOINT WATER POLLUTION CONTROL PLANT

MicroSludge™ is a patented chemical and pressure pre-treatment process that increases both the rate and the extent that waste activated sludge (WAS) is degraded in a conventional mesophilic anaerobic digester (CMAD). The process uses chemical pre-treatment to weaken cell membranes and a high-pressure homogenizer, or “cell disrupter” to provide an enormous and sudden pressure change to burst the cells. The resulting liquefied WAS is readily stabilized and converted to biogas in a CMAD.Following the demonstration of the first full-scale MicroSludge unit near Vancouver, Canada in 2004, the second full-scale unit was commissioned at the Los Angeles County Sanitation Districts (Districts) Joint Water Pollution Control Plant (JWPCP) in October 2005. The JWPCP is located in Los Angeles County, California and treats 320 MGD of wastewater, serving a population of approximately 3.5 million people. Two 4,000 L/h cell disruption modules are continuously operating for 24 hours per day to process approximately 192 m3/day (50,000 GPD) of thickened WAS (TWAS) at nominally 5 to 6 percent total solids (TS). The processed TWAS is co-digested with primary sludge (PS) in a 75:25 by volume (68:32 by mass) PS:TWAS mix at an approximate 19 day HRT. This is compared with the performance of one of the other 23 CMAD digesters that are operated under similar conditions at the JWPCP, except that the TWAS feed is not pre-treated.This paper outlines the monitoring plan, the performance baseline of the digesters at JWPCP, and the results with and without WAS pre-treatment.