Residents in the Tri-Valley region will start to see and taste a difference in their tap water thanks to upgrades made to the Patterson Pass Water Treatment Plant in Livermore.

The Zone 7 Water Agency held a ribbon-cutting ceremony last Thursday to celebrate the opening of the newly renovated plant, which cost $110 million for planning, design and construction.

Improvements to the plant included installation of ozone treatment facilities, aging equipment and increased treated water storage capacity with the addition of a new, five-million-gallon tank. The plant will now be able to double the amount of treated water the plant can produce, from 12 million gallons of water a day to 24 million gallons a day, according to a Zone 7 news release.

After decades of planning, the project was completed in spring 2022, after the Zone 7 Board of Directors approved the construction in 2019.

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

The ozonation project is the latest investment to make the treatment process more efficient and improve water quality to better serve the community, according to Zone 7. How the new process will work is ozone will be injected into water and immediately start oxidizing and eliminating contaminants.

According to Zone 7, the Patterson Pass Water Treatment Plant, which has been serving the agency since 1962, has been treating imported surface water from the adjacent South Bay Aqueduct using dual-media filtration and chlorine treatment techniques.

But this has not been as effective in recent years at addressing high levels of organic matter and more frequent algae blooms that can cause taste and odor problems. Algae blooms are rapid increases or accumulations in the population of algae in freshwater or marine water systems that can produce dangerous toxins.

"The blooms are normal but are becoming more frequent," according to Zone 7. "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."

Zone 7 supplies water to all of eastern Alameda County and sells wholesale treated water to local retailers, including the cities of Livermore and Pleasanton, the Dublin San Ramon Services District and the California Water Service Company. The public agency is also responsible for flood control in the Livermore and Amador valleys.