Before we can drink water that is brought into the county through canals and pipelines from the Sacramento-San Joaquin Delta or that is collected in local reservoirs, the water must undergo an extensive treatment process. The Santa Clara Valley Water District operates three water treatment plants that clean and disinfect imported water and/or water captured in four of our local reservoirs.
The three water treatment plants, Rinconada, Santa Teresa and Penitencia, are located in the foothills around the Santa Clara Valley and rely on the pull of gravity to deliver the treated water to end users. These three plants can produce as much as 220 million gallons of drinking water a day.
Major upgrades were completed at the Santa Teresa and Penitencia plants in 2006. Ozone is now used as the primary disinfectant at these two water treatment plants. Ozone disinfection is more effective than chlorine at inactivating microbial contaminants like Giardia and Cryptosporidium. Also, the use of ozone in place of chlorine can significantly reduce the formation of trihalomethanes (THMs), a byproduct of chlorine disinfection that may be harmful at high levels. While the district has not detected high levels of THMs in our drinking water, ozone virtually eliminates the potential for formation of unsafe levels of THMs.
Another significant benefit of ozone is its effectiveness at removing unpleasant tastes and odors which are often caused by seasonal algae blooms in our source waters. Ozone has enhanced our ability to address this and generally improves the taste of our drinking water.
The district is moving forward with plans to upgrade Rinconada, our oldest water treatment plant, as well. These upgrades will include work to address the plant’s aging infrastructure and needed seismic improvements. Also, the district is currently evaluating options to upgrade the plant’s treatment processes. In this evaluation, ozone disinfection, which had been planned, is being compared to other disinfection technologies.
While surface water, whether from local reservoirs or imported through pipelines, must be treated before it is drinkable, water pumped from wells is naturally filtered through soils and rock formations; particles and pathogens are removed as the water percolates down to underground aquifers. Water retailers in the Santa Clara Valley that use wells to augment their drinking water supplies may provide disinfection to the well water for additional health protection.
The San Jose/Santa Clara Water Pollution Control Plant treats most of the wastewater in the county. Some water from the plant receives advanced treatment and is recycled by South Bay Water Recycling.