Northern California facility utilizes UV treatment to produce effluent for non-potable use
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, Calif., required additional water supplies to maintain regional economic vitality for its growing community.
The SCVWD board of directors determined that water reuse—taking treated wastewater, purifying it through an advanced treatment process and then distributing it for non-drinking purposes—would be critical to establishing a drought-proof, sustainable water supply for the region.
The SCVWD built the 8-mgd Silicon Valley Advanced Water Purification Center (AWPC), the first of its kind in northern California, to free up drinking water resources designated 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.
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.
“We didn’t have any specific ideas for which technologies to use when we started,” said Black & Veatch Project Director Sanjay Reddy. “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, 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 standards, including complying with California’s stringent Title 22 unrestricted water reuse standards for disinfection.
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.
The UV system at the facility is “very, very simple and works well,” said Silicon Valley AWPC plant supervisor Sam Bogale. “Manual maintenance is not required, and technical support from the group has been excellent; they are very responsive.”
Operation of the entire system is automatic, with minimal input from operators.
The highly purified reuse water is blended with conventionally treated recycled water from the San Jose–Santa Clara Regional Wastewater Facility, which previously produced water with average total dissolved solids (TDS) of 750 ppm. By blending the water produced from each facility, TDS levels are reduced to 500 ppm—higher-quality water preferred by many industrial and irrigation customers.
WEDECO’s 12 LBX 1000 UV reactors, commissioned in 2014, are delivering a safe and reliable water supply for SCVWD.