SITE INFORMATION AND CORRESPONDENCE CASE 2

Home Browse Search

� � 3 STAFF REPORT PAT MITCHELL AND CALIFORNIA NATURAL PRODUCTS WASTEWATER TREATMENT AND DISPOSAL FACILITY SAN JOAQUIN COUNTY / V Introduction Pat Mitchell and California Natural Products (hereafter Discharger) operate a wastewater treatment system and land application system in Lathrop, San Joaquin County, to treat and dispose of industrial wastewater. The Discharger primarily processes rice and soy into food products and secondarily produces coffee, tea, and soups. Operations are conducted year round, five days a week, three shifts per day. Wastewater generated in the processing plant is characterized by a high organic matter and solids content. The Discharger has installed a substantial treatment system and has recently optimized the operation of the system resulting in much better quality wastewater than was discharged in the recent past. However, staff still have concerns about nitrogen and hydraulic loading rates. The facility is currently regulated by WDRs Order No. 98-223. The Discharger is presently in compliance with the existing WDRs with the exception of generation of nuisance odor conditions. Domestic wastewater is discharged to the City of Lathrop's domestic wastewater collection system. Stonnwater collected at paved areas and loading docks is piped to the wastewater treatment system. Stormwater which falls on buildings is discharged to stormwater retention basins. Surrounding land uses are primarily industrial, agricultural, and residential. The City of Lathrop operates three drinking water supply wells in the area,the closest of which is approximately 1,600 feet east of the application area. Treatment System Summary CNP's treatment of process wastewater consists of screening using a rotary screen and two 100- micron stainless steel parabolic screens; holding/recycle tank; pH control; Dissolved Air Flotation (DAF) clarifier; a 45-foot diameter, 20-foot high trickling filter; and a 600 gallon per minute (gpm) lamella separator with flocculent metering system. Prior to discharge,the wastewater is stored in a 13,000 gallon tank. Because the process wastewater is high in BOD and low in nitrogen, the Discharger adds ammonium nitrate to the wastewater to optimize BOD removal in the trickling filter. Solids collected on the screens are placed in containers. Solids which are collected in the lamella separator and DAF clarifier are dewatered in a centrifuge. All solids are contained in bins, transported off-site, and used for animal feed or landfilled. After treatment, the wastewater is piped to the land application area which consists of 17.6 acres divided into 16 checks consisting of approximately one acre each. The disposal area has been