Waste and stormwater
National finalist:
Gold Award

CH2M Hill

Project: Brightwater treatment plant
Client: King County Wastewater Treatment Division

Photo by Benjamin Benschneider, courtesy of CH2M Hill
Treatment facilities at Brightwater are completely enclosed and equipped with odor-treatment systems.

Facing population growth and the requirement to add capacity to its regional wastewater system by 2011, King County developed the Brightwater wastewater treatment and reclamation facility in Woodinville.

CH2M Hillís involvement with Brightwater began with siting studies and environmental impact statement assistance during the initial stages of project planning in 2002, and the firm ultimately became the prime consultant during design.

The heart of the new plant is the split-flow liquids treatment process, which incorporates chemically enhanced primary clarification ahead of the largest membrane bioreactor in North America.

The process protects the membranes from excessive flows, which reduces the annual mass discharge of biochemical oxygen demand and total suspended solids into Puget Sound by more than 1 million pounds compared with traditional secondary treatment. The split-flow process also uses new energy-efficient direct-drive turbo blowers for the aeration basins, which reduce costs and minimize the facilityís carbon footprint.

Odor control was incorporated into the earliest designs. Facilities at Brightwater are completely enclosed and coupled to multiple-stage odor-treatment systems with 13 parallel treatment trains, each rated for 40,000 cubic feet per minute of foul air flow.

The odor-control system provides 99.97 percent removal efficiency of hydrogen sulfide, resulting in less than one part per billion at the property line. This is good news for the hikers and joggers who use the 3 miles of trails built on the site.

An interesting challenge arose well after the initial siting and design of the plant. New data suggested that an active earthquake fault crossed the north portion of the site, so CH2M Hill conducted extensive seismic trenching at the site. Consequently, Brightwater is designed to resist larger ground motions than any other wastewater facility in the Puget Sound region.

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