With diminished rainfall, a depleted aquifer basin, near-empty recharge ponds, and an earthquake-vulnerable aqueduct system, the Santa Clara Valley Water District (SCVWD) in San Jose, CA, required additional water supplies to maintain regional economic vitality for its growing community.
Scope
The SCVWD Board of Directors determined that water reuse – taking treated wastewater, purifying it through an advanced treatment process, and distributing it for non-drinking purposes – would be critical to establishing a drought-proof, sustainable water supply for the region.
The SCVWD built the eight-million gallon per day (mgd) Silicon Valley Advanced Water Purification Center (AWPC), the first of its kind in northern California, to free up drinking water resources used for irrigation and non-potable uses and reduce dependency on imported water. The advanced treatment process receives treated secondary effluent from the adjacent San Jose-Santa Clara Regional Wastewater facility and applies a multi-barrier treatment process including microfiltration, reverse osmosis filtration, and ultraviolet (UV) disinfection.
Solution
In designing the state-of-the-art facility, engineering firm Black & Veatch focused on technologies that would treat the water to California’s stringent Title 22 unrestricted water reuse standards while paving the way for the future with potable reuse. Key to the high-quality water output at Silicon Valley AWPC is the final step in the treatment process, UV disinfection.
Black & Veatch project director Sanjay Reddy noted, “We didn’t have any specific ideas for which technologies to use when we started; once we decided on microfiltration and reverse osmosis, it just didn’t make sense to chlorinate and degrade the water, so ultraviolet disinfection made perfect sense.”
Xylem’s Wedeco LBX Series is a closed-vessel UV disinfection system designed for energy-efficient disinfection of wastewater, water reuse, surface water, and process water. With more than 1,000 installations worldwide, LBX UV systems have been tested extensively to meet the U.S. Environmental Protection Agency’s UV Disinfection Guidance Manual and the National Water Research Institute’s UV Disinfection Guidelines for Water Reuse, including complying with California’s stringent Title 22 unrestricted water reuse standards for disinfection.
Design engineers considered different UV disinfection systems to provide the critical final disinfection step. Wedeco, a Xylem brand, was found to be uniquely qualified, with more experience in wastewater treatment than other systems on the market.
Result
The new system disinfects potentially harmful pathogens and produces an exceptionally high quality of purified water using a patented dosing control method to monitor operating conditions, including flow, UV transmittance, and UV intensity.
