The RWRF is located at Jensen and Cornelia in southwest Fresno. Wastewater generated from homes and businesses in the Fresno/Clovis metro area travels through 1,500 miles of sanitary sewer lines to the facility. Currently, the RWRF is a biological, secondary level treatment plant. Future capital improvement projects will upgrade this facility to be able to treat a portion of the incoming wastewater to a tertiary level.
Fresno-Clovis Regional Wastewater Reclamation Facility (RWRF)
The RWRF produces recycled water of secondary treatment level that meets Title 22 California Code of Regulations and can be used to irrigate fields with alfalfa, silage corn, Sudangrass and other fiber crops not used for human consumption. Approximately 12%-15% of the total acre- feet of wastewater that is treated at the reclamation facility goes for direct reuse to farmers leasing land within the RWRF boundaries or to neighboring farmers.
A network of reclamation wells extracts water from the “mound” underneath the percolation pond area and discharges that water into Fresno Irrigation District canals that will be used for irrigation of farmland downstream from the treatment plant.
|Average day maximum month||88|
|BOD 5 and suspended solids|
|Average concentration, mg/L||240|
|Average loading 1,000 lb/day||184|
|Number/capacity, mgd||2 @ 32.4|
|4 @ 46.1|
|Total capacity, mgd||203|
|Mechanical bar screens|
|Bar spacing, in||75|
|Peak capacity (each), mgd||70|
|Total capacity, mgd||210|
|Total capacity, mgd||220|
|Sidewater depth, ft||10|
|Overflow rates, gpd/sf||1,010|
|Detention time, hrs||1.78|
|Primary Sludge Pump Stations Nos. 1 and 2|
|Primary sludge pumps – air diaphragm type|
|Capacity (each), gpm||140|
|Primary scum pumps – air diaphragm type|
|Capacity (each), gpm||140|
|Dewatering pumps – vertical non-clog centrifugal|
|Capacity (each), gpm||1,300|
|Process design flow, mgd||80|
|Volumetric loading, lb BOD 5/1,000 ft/day||48-58|
|Volume per basin, MG||2.7|
|Sidewater depth, ft||15-17|
|Mixed liquor suspended solids,mg/L||2,000-3,000|
|Carbonaceous oxygen requirements lbs O2/lbs BOD||1.125|
|Aeration Air Blowers|
|Air blowers/capacity, cfm|
|Secondary Sedimentation Basins|
|Process design flow, mgd||80|
|Sidewater depth, ft||13-14|
|Overflow rate, gpd/day/ft 2||532-577|
|Weir overflow, gpd/lf||3,000-4,000|
|Pond area, acres||1,400|
|Disposal pond freeboard, ft||2|
|Average pond water depth, ft||4-5|
|Dissolved air flotation thickeners|
|Solids loading, lb/ft 2/day||24|
|Gravity belt thickeners|
|Hydraulic loading, gpm||500|
|Volatile solids loading, lbs/ft^3/day||0.12|
|Min. hydraulic retention time, days||20|
|Sidewater depth, ft||26-29|
|Capacity (each), gpm||5,000|
|Belt filter presses|
|Hydraulic loading, gpm||180|
|Feed solids concentration, %||2-3|
|Cake solids concentration, %||18-20|
|Sludge Storage Silos|
|Solids storage time, hrs||24|
|Steam boiler – horizontal fire tube|
|Air compressors – two-stage reciprocating type|
|Discharge pressure, psig||125|
The process of wastewater treatment requires constant monitoring at the various treatment levels. This ensures that wastewater is being treated properly or if changes need to be made to the process in order to achieve the necessary treatment to meet strict regulatory mandates as specified in the RWRF’s permit to operate (Waste Discharge Requirements).
WMD has its own environmental laboratory on location to handle the day-to-day testing of the various treatment processes. This is a California Department of Health Services (DHS) accredited laboratory (ELAP) for the testing of environmental samples including but not limited to water, groundwater, wastewater and biosolids. The WMD Laboratory is certified to test over 100 constituents including those required to demonstrate regulatory compliance with the Waste Discharge Requirements, the City’s Pretreatment Program and the DHS Water Supply Permit.
The laboratory staff is comprised of chemists, biologists and microbiologists that take care of the daily testing to determine the quality of wastewater from different treatment processes. Timely and accurate data provided by the laboratory to the Operation Team is essential for process control and to determine compliance with environmental regulations. Because of the laboratory’s competitive pricing, the service provided by this laboratory is not limited to the RWRF, but expands to provide service to other Divisions within the City of Fresno and to agencies in neighboring cities.
he Fresno-Clovis Regional Wastewater Reclamation Facility is home to hundreds of birds that live in about 1,300 acres of infiltration ponds. These ponds are habitats for many migratory birds that breed, nest, feed and rear their young at the facility.
Members of the Fresno Audubon Society visit the reclamation facility to watch water birds including Mallards, Pin-tailed Ducks, Canadian Geese, American Avocets and Green-winged Teals. While driving through the Reclamation Facility you may spot Red-tailed Hawks scanning the scene from posts and nearby trees and Burrowing Owls making the ponding area their home. Cattle Egrets and Herrings can also be found near the
For more information or to schedule a tour of the facility, call (559) 621-5100
WASTE TO ENERGY – RECYCLING METHANE GAS FOR ENERGY PRODUCTION
Conservation is not always using less of a resource; it is also getting the maximum out of a resource, in this case a byproduct of wastewater treatment. In the process of cleaning sewage, the wastewater plant produces large amounts of methane, the primary component in natural gas. Two of the highest monthly costs in treating sewage are electricity and natural gas. The wastewater plant captures the methane produced and burns it in gas turbines to produce approximately 3.3 Megawatts of electricity. The electricity produced is approximately 75% of total required by the treatment facility.
In addition, heat from this process is captured and run through a heat exchanger where the waste heat is transferred to a hot water loop which is used for heat in the processing of wastewater. If this heat was not captured it would be necessary to purchase more natural gas for heat in the process.
Wastewater Management Division finds good use of this process byproduct.
The City of Fresno initiated its first sewer system in 1891 with the construction of a 24-inch outfall sewer to a 40-acre ‘sewer farm’ located southwest of Fresno, east of the existing treatment facility. The acreage proved to be inadequate for the growing town, and an additional 40 acres was purchased to increase capacity. Eight septic tanks were constructed in 1907 to provide partial treatment of the sewage prior to land spreading and irrigation (at the time, the sewage was used for irrigating alfalfa crops).
By 1910, Fresno had an estimated population of 25,000, necessitating an expansion of the sewer farm to meet the treatment needs of this burgeoning society. A major expansion began in 1909 with the purchase of an additional 812 acres and the construction of another 24-inch outfall sewer running parallel to the original outfall. This expansion is the current site of the Regional Wastewater Reclamation Facilities.
Expansion of the Sewer Treatment Plant kept pace with the demands of the City. In 1917, a 60-inch outfall sewer and eight additional septic tanks were constructed and an additional 500 acres of adjacent land, made available by dairies forced to vacate by the State Health Department due to sewage overflow onto their properties, were rented. This system proved inadequate resulting in an odor and fly nuisance.
In 1922, the City Council recognized the dire situation and commissioned a study to recommend a solution to the sewage crisis. The study recommended lowering the groundwater elevation to increase percolation capacity. This would allow water to be extracted and used on local water irrigation systems. Construction began on nine extraction wells in 1924. The project was successful and temporarily solved the sewage crisis.
In 1933, Sewer Farm Management began a new enterprise to raise cattle feed (mostly alfalfa) irrigated by treated sewage, but the operation ended in 1960 due to cost constraints. A major new treatment plant, Plant 1, was constructed in 1947 to provide primary treatment to sewage prior to continued land disposal and local irrigation. This plant consisted of a Headworks, Primary Clarifiers, Anaerobic Digester, and Sludge Drying Beds. The City’s increasing population required the construction of a second plant, Plant 2, in 1958.
In 1966, the City of Fresno was designated as the sewering agency for the local metropolitan area and assumed the role of developing a long-range, area-wide wastewater treatment and disposal plan. As a result, an engineering report recommended a five-stage program to meet long-range metropolitan needs. In 1970, construction began on the first stage of the wastewater treatment facility improvements. Due to odor problems from excessive winery wastes, the City set limits on winery waste discharge until a separate system was developed.
In 1972, the Regional Water Quality Control Board (RWQCB) imposed sanctions on the treatment plant because of past odor problems. New waste discharge limits were issued which required a higher level of treatment. As a result, the treatment plant underwent major construction to meet RWQCB requirements. In 1975, a biological secondary wastewater treatment process was added to Plant 1. Additional anaerobic digesters and sludge drying beds were constructed, which increased the treatment and disposal capacity to 46 million gallons per day (MGD) on 2,000 acres. A separate winery waste collection, transport, and disposal facility was also constructed to help the Treatment Facility meet RWQCB requirements. 1976 saw the addition of a flotation clarifier and trickling filter to Plant 2.
In an effort to reuse the raw material coming into and created by the facility, a cogeneration facility installed in April 2004 utilizes the methane gas produced by the anaerobic digesters, which partially supplies the plant’s energy requirements.
In February of 1996, the RWQCB adopted a cease and desist order requiring the facility to increase capacity to meet demands. A major project that included the rehabilitation of the existing facilities, a new headworks, biosolids dewatering equipment, and additional process units to increase capacity were already under construction. The new facilities came online in the fall of 1996 with an increase in capacity to 68 MGD. By the time the 68 MGD project was started up, the flow to the plant was already in excess of 70 MGD. Thankfully, another phase of expansion to increase capacity to 80 MGD started immediately after the 68 MGD project began, and the 80 MGD expansion was completed in February of 1998.