How we clean your water

Before we can drink water from local reservoirs or imported through canals and pipelines from the Sacramento-San Joaquin Delta, it must undergo an extensive treatment process. The Santa Clara Valley Water District operates three water treatment plants that clean and purify water that is imported from the Sacramento-San Joaquin Delta or captured in one of our 10 local reservoirs. These three plants can produce as much as 210 million gallons of drinking water a day.

The three treatment plants, Rinconada, Santa Teresa and Penitencia, are located in the foothills around the Santa Clara Valley so that the pull of gravity can help deliver the treated water to the end users.

Major upgrades were completed at the Santa Teresa and Penitencia plants in 2006. Ozone is now used as the primary disinfectant rather than chlorine. Ozone disinfection is more effective at inactivating microbial contaminants like giardia and cryptosporidium than chlorine. Also, ozone can significantly reduce trihalomethanes (THM), a byproduct of chlorine disinfection that may be potentially harmful at high levels. While the District has not detected high levels of THM in our drinking water, ozone virtually eliminates the potential for unsafe levels of THMs. Another significant benefit of ozone is that it is very effective at removing negative tastes and odors often caused by seasonal algal blooms in our Delta source waters. Ozone has strengthened our ability to deal with this and also improves the taste of our drinking water.

The district is developing plans to upgrade Rinconada, our oldest water treatment plant, as well. These plans will include work to address the plants aging infrastructure and needed seismic improvements. Currently, staff is evaluating plans to upgrade the plant with a new type of disinfection process. In this evaluation, ozone disinfection, which had been planned, is being compared to other disinfection technologies.

While surface water from local reservoirs or imported through pipelines must be treated through a treatment plant before it is drinkable, the water pumped from wells has been naturally filtered through soils and rock formations to remove particles and pathogens on its way to underground aquifers. Your water retailer 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 is highly treated and recycled by South Bay Water Recycling.