Santa Monica Sustainable Water Infrastructure Project Advanced Water Treatment Facility
This presentation addresses a unique stormwater harvesting program achieved through a multi-benefit system that provides alternative sources of water through blending harvested stormwater with raw wastewater and the treatment processes used to achieve purified water for groundwater augmentation to increase the resiliency of the City’s water supply. A discussion will also be included on designing a stormwater / dry weather runoff harvesting system and treatment facility in a highly urbanized area with minimal impact to surrounding stakeholders.
The City of Santa Monica’s (City) Sustainable Water Infrastructure Project (SWIP) is a key component of the City’s goal to maximize local water resources and reduce reliance on costly imported water supplies. The SWIP consists of upgrades to the Santa Monica Urban Runoff Recycling Facility (SMURRF) to treat dry weather urban runoff and stormwater to California Title 22 Groundwater Replenishment Reuse Project diluent water quality standards and a new Advanced Water Treatment Facility (AWTF) that will treat a mixture of raw wastewater from the City’s sewer collection system as well as stormwater harvested from the City’s stormwater drainage system for groundwater augmentation via direct injection. The project will produce 1.5 million gallons per day (MGD) of purified water for groundwater augmentation, with the SMURRF producing 0.5 MGD and the AWTF producing the remaining 1.0 MGD of purified water. This alternative source of water diversifies and increases the resiliency of the City’s water supply portfolio by reducing its dependency on imported water. This innovative project is being delivered through a Progressive Design-Build-Operate model.
Typical influent to the AWTF will consist of a mixture of raw wastewater and dry weather runoff/ stormwater that will be processed at a blend of up to 30% stormwater/dry weather runoff to 70% wastewater. A 1.5 million gallon storage tank will be located adjacent to the AWTF to allow harvesting of stormwater during storm events with the flow later metered into the AWTF at a controlled rate.
Many advanced treatment facilities to date are solely water purification facilities that take treated effluent from an existing wastewater treatment plant and then purify the water to meet potable reuse regulations. The City’s AWTF is unique since it will be one of the first facilities that takes in raw wastewater, fully oxidizes the stream via biological treatment, and provides the pathogen reduction requirements all within one facility. The AWTF is also setting a new standard for potable reuse source water since harvested stormwater and dry weather runoff will comprise a large portion of the raw water supply, which has not typically been utilized for potable reuse facilities, and allows for the beneficial use of a valuable resource that has historically be discharged to the ocean.
The AWTF and stormwater harvesting tank are situated in a highly urbanized area and will be a completely subterranean facility located below the parking lot of the City’s Civic Center to minimize impact to the surrounding community. Two small buildings at ground level provide staircase/elevator access and several hatches in the parking lot are used for access to large equipment items. The AWTF’s first level below ground serves as the mechanical treatment area that houses the screens, pumps, membrane skids, ultraviolet disinfection reactors, chemical storage, and odor control system. An administrative area on the first level is provided for office space, laboratory, control, and electrical room. The AWTF’s second level below ground serves as the process tanks, including the biological treatment tanks, membrane tanks, filtrate storage, chlorine contact tank, and purified water clearwell. The stormwater harvesting tank is a separate, single level structure from the AWTF and is located under the same parking lot with access provided through hatches at ground level.