| May 22, 2003
News Release Engineers designing facilities to treat wastewater from south Snohomish County and north King County are ready to make a quantum leap in the technology used to protect public health and the environment. It will need less space, be easier to control odors and produce better water quality than traditional wastewater treatment. After an extensive evaluation of emerging technologies for possible use at the planned Brightwater Treatment Plant, engineers for King County's Wastewater Treatment Division selected a process called a membrane bioreactor. Long used in the water treatment industry, membranes have been adapted more recently to treat wastewater. The Brightwater system will combine standard biological wastewater treatment with membrane filters submerged in wastewater. The filters have microscopic pores large enough to let water pass through but small enough to filter out particulate matter and even individual bacteria. The result is treated wastewater that is seven to 10 times cleaner than typical secondary treated wastewater, which already meets tough environmental requirements for discharges into Puget Sound. For example, 36 million gallons of the treated wastewater discharged daily from Brightwater using membrane technology would contain only the same amount of microscopic impurities as 5 million gallons of treated wastewater from a typical secondary treatment plant. Also significant is that this technology takes up substantially less space than conventional treatment systems. It would replace large round settling tanks now used in conventional plants. That more efficient use of space will provide more room for both screening the plant from public view and providing area for public use. The membrane bioreactor process will also be easier to cover so the plant can capture and eliminate odors. "This is an emerging technology that other treatment facilities are implementing internationally," said Stan Hummel, King County's chief engineer for the Brightwater plant. "The environmental benefits of higher quality water and the space savings make it so attractive that we decided to pursue it." The technology meets criteria King County used to evaluate treatment technologies, Hummel said. Although it's a new technology, it has a 10-year record of reliable performance. And it meets and even exceeds regulatory standards for treated wastewater. "Membrane filters are newer to wastewater treatment," Hummel said, "but there are a number of facilities in construction or operation. King County extensively pilot-tested the technology to gain a better understanding of the operating requirements and performance of various membrane systems. That testing provided information that helps build confidence in the technology." Hummel noted that multiple vendors provide the technology, so King County will have a range of choices in selecting and customizing a system that meets the needs of Brightwater. King County has also studied use of membrane bioreactors for reclaiming wastewater for nondrinking water purposes such as landscape and agricultural irrigation, heating and cooling, and industrial processing. Unlike typical secondary treated wastewater, no additional treatment except disinfection would be required to produce reclaimed water suitable for these uses. That would make water reuse more cost-effective. The regional wastewater treatment utility operated by King County protects public health and water quality by serving 18 cities, 15 sewer districts and more than 1.4 million residents in King, Snohomish and Pierce counties. Related Information
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