A Water Treatment Decision Must Be Made

Although levels are believed to be very low in the Green River supply, new regulations will require us to address cryptosporidium (crypto), a naturally-occuring micro organism that can be found in surface water supplies. Although we don't currently have any issues with this organism, we will be required to comply with new laws by 2014. The two effective treatment options for this organism included filtration and ultraviolet light disinfection. Tacoma Water, its policymakers and customers evaluated and weighed the cost, benefits and risks of building a filtration plant against the more moderate cost and lesser benefits of ultraviolet light treatment.

The Public Utility Board recently chose filtration treatment to respond to the new regulation, which requires treatment for cryptosporidium.

Filtration

The Washington State Department of Health determines whether river water supplies must be filtered and conducts annual inspections of Tacoma Water’s facilities, as well as the watershed where we take water from the Green River. Because of the high quality of the Green River water, active watershed control, and ongoing compliance with Federal and State Drinking Water rules, Tacoma Water is one of few water utilities in the United States that currently does not have to filter its water supply.

Filtering the water supply would improve taste, reduce the amount of silt and sand entering the pipe system annually and provide more protection from contaminants like Cryptosporidium, which can cause gastrointestinal difficulties in humans. Filtration also reduces natural organic material found in water, which helps reduce disinfection byproducts.

Ultraviolet Light Treatment

Ultraviolet (UV) light disinfection is a much more moderate cost option to meet future cryptosporidium requirements from the EPA. UV light disinfection effectively kills or sterilizes many organisms found in surface water supplies, including cryptosporidium. Numerous water treatment plants throughout the United States use UV treatment. UV treatment does not offer any other benefits to your water quality other than addressing cryptosporidium.

Treating the Green River supply with UV light disinfection is much less expensive than installing a filtering plant, but it does not offer the additional benefits of filtration discussed earlier.