Zone 7 rolls out ozonation water treatment process at Patterson Pass Water Treatment Plant

Zone 7 Water Agency announced that it has completed facility upgrades at the Patterson Pass Water Treatment Plant which improves treated water quality with the added ozonation project, and an increase of the treated water storage capacity. This is the latest investment to make the treatment process more efficient and improve water quality to better serve the community.   

“By investing in best-in-class technology, Zone 7 demonstrates our commitment to high-quality water,” said Board President Angela Ramirez Holmes. “Ozonation is a proven, successful treatment method that will improve our water, making it cleaner, safer and better tasting – straight from the tap.” 

The Patterson Pass Water Treatment Plant, which has been serving Zone 7 since 1962, has been treating imported surface water from the adjacent South Bay Aqueduct using dual-media filtration and chlorine treatment techniques. In recent years, treating this water supply has become increasingly difficult due to the high levels of organic matter and more frequent algae bloom that can cause taste and odor problems.  

The blooms are normal but are becoming more frequent. After reviewing various treatment technologies, Zone 7 selected ozone to replace chlorine as the main disinfectant, resulting in higher quality water provided to customers by reducing chlorine-related byproducts and killing even more pathogens than chlorine.

The upgrades have also replaced aging equipment and have increased treated water storage capacity with the addition of a new, five-million-gallon tank and double the amount of treated water the plant can produce, from 12 million gallons of water a day to 24 million gallons a day. 

The Ozonation Project, which is part of Zone 7’s capital improvement plan, represents a capital investment of $110 million, funded by water rates, new connection fees and bonds.

Photo 1:  Zone 7 Ribbon Cutting (Zone 7 Board of Directors left to right: Director Olivia Sanwong, President Ramirez Holmes, Director Sandy Figuers, Director Laurene Green)

Photo 2:  Zone 7 Ribbon Cutting (Zone 7 Board of Directors/Assemblymember 16th District left to right: Director Olivia Sanwong, President Ramirez Holmes, Director Sandy Figuers, Director Laurene Green and Assemblymember Rebecca Bauer-Kahan)

Photo 3:  Pump Station at Patterson Pass Water Treatment Plant

Photo 4:  Pipe Infrastructure at Patterson Pass Water Treatment Plant

Photo 5:  CO2 and Liquid Oxygen Facility at Patterson Pass Water Treatment Plant