The Green River water supply gets treated with four chemicals: chlorine, fluoride, caustic soda and starting in 2007, ozone. These treatments assist with secondary aesthetic effects of treatment to improve your water's taste and smell. We do not currently filter our water supply.
Chemical treatment & byproducts
Treating water with chemical disinfectants is especially important when the water comes from an unfiltered surface water source like the Green River. Placing disinfecting chemicals in the water ensures germs and microorganisms normally found in water die, making it safe to drink.
Chlorine is our primary disinfection treatment. While it does an excellent job of killing the microorganisms that may be harmful to you, chlorine also reacts with natural organic material commonly found in surface water sources like lakes, rivers and streams. This reaction forms compounds called "disinfection byproducts." We must meet drinking water standards for two groups of disinfection byproducts compounds. Byproduct levels found in water depend primarily on:
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The amount of natural organic material in the water
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The amount of chlorine used to treat water
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The amount of time it takes water to reach the customer
Byproduct levels vary throughout the year. Byproducts often increase during the warmest months when the water supply has its highest levels of natural organic material and chemical reactions happen faster. We work to minimize byproduct levels and have adjusted portions of our system operations. We will soon place new covered storage tanks at McMillin Reservoir in service, which will replace the last of our open reservoirs. This will improve water quality and help reduce disinfection byproducts. Filtration will remove a percentage of the natural organic material, further reducing byproducts.
The citizens of Tacoma voted in 1988 and 1989 to fluoridate the city’s water supply to improve dental health. Fluoride is added to our drinking water at the rate of 1 milligram per liter.
Customers who prefer unfluoridated water can obtain unfluoridated well water between 8 a.m. and 6 p.m. daily at well 10-C, located just south of South 74th Street on Cedar Street or well SE-8, located behind the former Southeast Mutual Water Company building at 1614 99th Street East. You will need to bring your own container(s).
We began operating our new Ozone Treatment Plant in late summer 2007. This plant is the latest in a long line of major improvements made at the site during the past several years. Ozone was chosen primarily to address objectionable taste and odor issues occasionally seen in the treated Green River. Ozone also provides additional disinfection benefits to help ensure water remains safe to drink. After injecting ozone into the water, the chemical only lasts for a few minutes. Ozone is not present in the water supply when it exits the treatment site.
We treat our Green River water supply with caustic soda to help minimize the amount of lead and copper found in homes. Adding caustic soda into water raises its pH (a measurement of acidity), which helps make water less corrosive on plumbing reducing the amount of lead and copper that can dissolve into drinking water.
