Municipal Services
Water Quality Control
Water Quality Control Facility
The Turlock Regional Water Quality Control Facility (RWQCF) provides tertiary treatment of wastewater from the City of Turlock, Ceres and the community service districts of Keyes and Denair. Effluent from the facility discharges to the Turlock Irrigation District (TID) Lateral No. 5 Drain (also known as the Harding Drain). The Harding Drain is an open, multipurpose drain that intercepts and conveys irrigation return flows as well as storm drain runoff and the RWQCF’s effluent. The Harding Drain discharges to the San Joaquin River. The San Joaquin River is designated an impaired water body under the authority of the Clean Water Act, Section 303(d). When a water body is listed as an impaired water body, the regulations require that no additional pollutants be discharged to the water body. Dilution credits will no longer be allowed for the effluent discharge from the RWQCF, as the RWQCB determined that the TID Lateral No. 5 Drain was a tributary to the San Joaquin River. The regional Basin Plan requires that tributaries receive the same level of protection as the major water bodies. The discharge requirements include tertiary treatment (coagulation/flocculation and filtration), lower levels of biochemical oxygen demand (BOD), total suspended solids (TSS), ammonia, and more efficient disinfection.
Raw Wastewater Characteristics
The raw wastewater received at the RWQCF is a combination of domestic and industrial wastewater flows. The wastewater facility currently receives an average flow of 13 mgd. Nearly half of the flow comes from food processing and dairy industries. The incoming wastewater is a high-strength waste, with biochemical oxygen demand (BOD) design concentrations averaging 557 milligrams per liter (mg/L), and total suspended solids (TSS) concentrations averaging 532 mg/L. The industrial wastewater loading to the RWQCF accounts for approximately 70% of the organic loading and 30% of the hydraulic loading.
Treatment Process
The RWQCF is a tertiary treatment facility designed to treat 20 mgd. The facility currently treats an average of 13.0 mgd. The treatment process is comprised of the following unit processes: screening, primary treatment (flotation), secondary treatment (activated sludge) that includes biotowers, aeration and nitrification (waste solids are removed via a gravity belt thickener and anaerobic digestion), secondary clarification, high rate clarifier / thickener, cloth disk filters, and chlorine disinfection and sodium bisulfite dechlorination.
NPDES Permit Requirements (CA0078948)
On May 1, 2006, more stringent NPDES discharge requirements came into effect. In particular, turbidity for final effluent may not exceed 2.0 NTU.
During 2006, treatment facility percent removal for BOD and TSS was 99.2 and 98.3 percent respectively. Effluent ammonia concentrations averaged <1.0 mg/L.
POTW Staffing
The treatment facility is staffed 24 hours per day on a year round basis by eleven SWRCB certified operators. Nine mechanical and electrical staff perform required maintenance on the facility’s equipment.
