The Plant 409 W-3 well in La Mirada can supply up to 1,200 gallons per minute (gpm) and is a critical local water source for the Suburban Water Systems (SWS) La Mirada service area that is less costly and uses less energy than imported water from Northern California or the Colorado River. SWS proactively took the well offline when arsenic was detected. Water treatment is required to remove the arsenic from this water source.
The Plant 409 site has an existing coagulation and filtration treatment system that removes color, iron, manganese, ammonia, and organics naturally occurring in the groundwater. This treatment plant injects “oxidants” to change the chemical nature of the constituents in the raw groundwater and causes them to form solids (precipitate). The treatment plant’s filtration equipment then removes the solids.
The solids collected on the filter media are removed by backwashing, where treated water is forced backwards through the filter. The solids and backwash water are collected in a 70,000-gallon tank that is continually mixed to prevent the solids from settling in the tank. Water from this tank is discharged to the sewer at concentrations that comply with environmental regulations.
A study by an industry-leading engineering consulting firm determined that adding ferric chloride injection to the existing treatment process would remove arsenic. This project scope includes installing a ferric chloride tank and injection system, monitoring equipment, electrical upgrades, control system modifications, and an educator tank mixing system. SWS works closely with the California State Water Resources Board Division of Drinking Water and the Los Angeles County Sanitation District to ensure required permits are in place to serve treated water to customers and discharge backwash water to the sewer.
SWS is scheduled to complete modifications to the treatment system and has the well back online this summer. The Plant 409 Arsenic Treatment Project is one of many projects that supports SWS’s commitment to providing customers with high-quality water that meets or exceeds all federal and state water quality standards. SWS uses proven and innovative treatment technology to upgrade existing equipment to be responsible stewards of the environment and reduce dependency on energy-intensive imported water sources.
Tank Eductor Connection
Conduit Run Installation
Injection Quill for Ferric Chloride
