Better water on the way with the implementation of ozone for disinfection
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LIVERMORE — Prodded by long-term taste and health concerns about its Delta drinking water, the supplier for 220,000 Tri-Valley residents is adding a new water disinfectant more effective than chlorine.
Adding ozone gas — an estimated $30 million project — will produce better tasting water with lower levels of a known carcinogen, as well as several chemicals of emerging concern such as endocrine disrupters, says the Alameda County Zone 7 Water Agency.
The district is a relative latecomer to ozone. The disinfectant has been used for years or decades several Bay Area water districts, including Santa Clara Valley, Alameda County, East Bay Municipal and Contra Costa Water.
Read more about the use of ozone in drinking water HERE
Last week, Zone 7 moved to join them. Its water board approved a $2.7 million design contract to draw up plans for ozone equipment at the district’s largest treatment plant. It will take at least three years to finish the installation, officials estimated.
“Ozone will improve our water quality,” said Jill Duerig, the Zone 7 district general manager. “We think it will help a lot in dealing with taste and odor issues related to algae and other organic materials in Delta water.”
The district supplies treated wholesale water to city and local water systems in Livermore, Pleasanton, Dublin and part of San Ramon.The Sacramento-San Joaquin River Delta — where Zone 7 gets its state water supply — is full of organic material and vulnerable to algae blooms. A recent Delta algae bloom resulted in many consumer taste complaints about Tri-Valley water until the last few days.
Ozone, a highly reactive gas, seeks out and breaks up organics that can impart bad smells and odors to drinking water.
Ozone also reduces the formation of disinfection byproducts called trihalomethanes that can cause cancer. The substances form readily when chlorine is added to water.
Zone 7’s concentrations of trihalomethanes is within public health standards, with not with as great a margin to spare as the district would like, Duerig said.
“There is no one silver bullet in water treatment, but this gives an important new tool,” she said.
Zone 7 has moved slowly to embrace ozone because of the high cost and the board’s historical reluctance to borrow money instead of funding new projects on a pay-as-you go basis.
With the ozone equipment planned, however, Zone 7 is looking into selling bonds and other financing alternatives to fund long-term projects.
The ozone project could raise Zone 7’s water rates about 3 percent, Duerig said.
Angela Ramirez Holmes was the only Zone 7 board member to vote against the ozone design contract.
She said Friday she is disturbed the district committed to spend nearly $3 million to design the project without knowing how it will finance the other $27 million of the cost.
“I think we should know the whole picture before we commit to a nearly $3 million down payment,” Ramirez Holmes said.