South Bay Water Reclamation Plant
2411 Dairy Mart Road, San Diego, CA 92154
The South Bay Water Reclamation Plant (SBWRP) is located at the intersection of Dairy Mart and Monument roads in the Tijuana River Valley. The plant relieves the South Metro Sewer Interceptor System and provides local wastewater treatment services and reclaimed water to the South Bay. The plant opened in May 2002 and has a wastewater treatment capacity of 15 million gallons a day. The plant design incorporates the newest technologies and meets strict odor control standards.
The Wastewater Treatment Process
The SBWRP Operations Building houses the Control Center which monitors and controls every phase of the treatment process. The facility is staffed from 6 a.m. to 4 p.m., Monday through Friday. Outside these hours, control of the South Bay plant is transferred to Public Utilities' Communications Center in Kearny Mesa. The SBWRP Operations Building also houses Process Control Laboratories where samples of wastewater from every stage of treatment are analyzed.
Untreated wastewater (Influent) enters the plant's Headworks from the South Bay region. In the Headworks, the wastewater passes through large, rake-like Bar Screens to remove solid debris and floating material (called "Rags") such as cloth, wood, and plastic material. These "rags" are dewatered and trucked to a landfill.
Odor Control is an important part of the overall wastewater treatment process. Odor is caused primarily by hydrogen sulfide gas. Throughout the plant, fans draw the foul air off the flow of wastewater and deliver it to Odor Control "Scrubbers." The foul air passes through a bleach solution spray which neutralizes odor-causing sulfide compounds. The "scrubbed" air then passes through carbon filters which remove any additional foul air before being released into the atmosphere.
Following the headworks, the screened wastewater then passes through aerated Grit Chambers where heavier solids such as sand, gravel, coffee grounds and eggshells settle out and are removed. The grit is then dewatered and taken to landfills.
Wastewater then flows into the Primary Sedimentation Basins where the sedimentation process starts. Solids sink to the bottom of the tanks and "scum" (grease and cooking oil) float to the surface. "Raw sludge," which has settled to the bottom of the basins, is returned to the sewer system and sent to the Point Loma Wastewater Treatment Plant. Similarly, the scum is skimmed from the surface and returned to the sewer system.
The wastewater then enters Anoxic Zone Chambers that are oxygen depleted. The wastewater mixes with bacteria ("Bugs") that eat soluble organic material. The wastewater then flows into Aeration Basins where diffused air is pumped into the water. Here, the bugs begin to ingest and digest the organic solids while increasing in number and density.
Wastewater flows from the Aeration Basin into the Secondary Clarifiers where the bacteria and digested solids settle to the bottom as "Secondary Sludge." Some of this Sludge and any remaining scum are removed and returned to the sewer system for treatment at the Point Loma Wastewater Treatment Plant. The remaining sludge is returned to the Anoxic Basins and again mixed with the wastewater.
The water, now treated to a Secondary Treatment level, can either be discharged into the ocean though the South Bay Ocean Outfall or moved on to Tertiary Treatment for reclaimed water applications.
In Tertiary Treatment, the treated wastewater (effluent) flows into Anthracite Coal Beds where it is filtered of remaining solids as it passes through the coal medium. The filtered water then passes through chambers where it is disinfected through exposure to ultraviolet light. At this stage the "reclaimed" water meets State Title 22 full body contact requirements.