Sewage Collection, Treatment, and Disposal
IRWD has an extensive sewage collection system. IRWD collects and treats nearly all the sewage generated within the IRWD service area. Sewage collected through IRWD’s system is sent to one of the two IRWD water recycling plants, the Michelson Water Recycling Plant (MWRP) or the Los Alisos Water Recycling Plant (LAWRP). The majority of the sewage generated in IRWD’s service area is treated to disinfected, tertiary recycled water standards. It is used within the service area for non-potable purposes thus offsetting potable water demands. A few small portions of IRWD’s service area are not served by the MWRP or LAWRP sewage collection and treatment systems. A small percentage of sewage generated within IRWD’s service area is currently collected by neighboring Orange County Sanitation District (OCSD) where facilities treat the sewage for subsequent reuse. Additionally, there are two small areas outside of IRWD’s water service area, from the City of Santa Ana and the El Toro Water District, where IRWD currently collects a small amount of sewage flows. MWRP, the largest treatment plant, is located in Irvine and uses both activated sludge and membrane bio-reactor technology to produce disinfected tertiary recycled water – resulting in high-quality recycled water. This processing system earned IRWD the first unrestricted use permit issued in the State of California, allowing recycled water to be used for virtually everything but drinking. The permitted tertiary treatment capacity of MWRP is currently 28.0 million gallons per day (mgd). The efficiency of MWRP recycled water production is estimated at 90% of the sewage inflow to the plant. IRWD recently completed construction of a biosolids and energy recovery facility at MWRP. The biosolids facility allows IRWD to digest and dehydrate sludge from MWRP which is converted to pelletized form that can be used as a fertilizer. IRWD also owns and operates the LAWRP, located in Lake Forest, which is a separate sewage treatment system with tertiary treatment capacity of 5.5 mgd. The Lake Forest sewer collection system consists of 105 miles of pipe and one lift station which delivers sewage to LAWRP. Secondary effluent from the treatment plant is pumped to the tertiary treatment facility where it is treated for reuse in IRWD’s Lake Forest recycled water distribution system. If recycled water demands are low (typically during the winter), excess recycled water is pumped to the South Orange County Wastewater Authority (SOCWA) pump station which directs the flows to the SOCWA effluent transmission mains and subsequent ocean outfall. Treated effluent produced at both MWRP and LAWRP meet the water quality standards set forth in the California Administrative Code (CAC), Title 22, Division 4 (Title 22) for use as recycled water. IRWD operates four recycled water seasonal storage reservoirs which store excess recycled water during the winter months when irrigation demands are low for later use in the peak summer months. IRWD can deliver excess recycled water from MWRP to the OCWD Green Acres Project (GAP), as well as provide excess recycled water from LAWRP to neighboring Santa Margarita Water District (SMWD) on an as-needed and as-available basis. Some IRWD sewage is subsequently diverted to OCSD for treatment and either reused or passed on as ocean discharge. IRWD joined OCSD in order to secure backup sewage treatment capacity and disposal as needed. IRWD maintains a connection to OCSD where wastewater
6 - 10
IRWD – 2025 Urban Water Management Plan
Powered by FlippingBook