A small but energetic group of SAWE members and guests toured the Brightwater Waste treatment plant in Woodinville, Wa. This the a brand new plant and is one of 3 facilities that treats all of the waters in the Greater Seattle area. We had a custom tour from Casey Plank of the Brightwater engineering team.
The plant design integrates landscape, architecture, wildlife habitat, engineering, art, and education.
Casey walked us around the grounds, first describing the waste treatment process, then showing us the facilities of each process
Preliminary
Preliminary treatment removes large objects from the untreated wastewater (influent) as it enters the treatment plant. The equipment includes screens for removing debris and grit facilities for removing sand, gravel and other inorganic matter. The screening and grit removal equipment will be covered and vented for odor control.
Primary
Primary treatment is the process where most of the suspended solids settle out of the wastewater. The conventional primary system consists of rectangular clarifier units equipped with collection systems on the top and bottom. Most of the flows coming into the plant wil be treated here. As with the preliminary process, the primary clarifiers will be covered and the air will be vented to an odor control system.
Secondary Treatment – Membrane Bio-reactor (MBR) technology
Secondary treatment is the process where soluble and fine suspended dissolved materials not already removed at primary treatment are removed. As an alternative to conventional secondary processes (knows as conventional activated sludge), the Brightwater project will use Membrane Bioreactor (MBR) technology.
Split Flows
During times of high flows, flows above a certain design threshold will be split off after preliminary treatment, processed using an enhanced primary treatment and recombined with MBR effluent for disinfection and discharge to Puget Sound. As with the MBR effluent, this combined effluent also provides substantially better effluent quality than conventional secondary treatment.
Disinfection
The purpose of disinfection is to kill remaining pathogens in the effluent to a level that complies with water quality discharge permits. At Brightwater sodium hypochlorite will be used for disinfection.
Odor Control
King County is committed to operating Brightwater with no detectable odors. Stringent design and performance criteria have been established for odor prevention at the facility. All treatment facilities will be covered, including the influent wet well, screening and grit handling, primary clarifiers, aeration basins, membrane tanks, and disinfection. The headworks and solids handling equipment will also be fully enclosed.
Air is collected from these enclosed areas and is then routed to the odor control systems. This air is then treated by multistage chemical and biological scrubbers, followed by a final polishing stage of carbon adsorption. Each stage treats the process air to a greater degree.
Reclaimed Water
Washington state identifies standards for four classes of reclaimed water, with Class A being the highest. Class A reclaimed water can be safely used for many purposes that do not require drinking water, such as industrial processes; irrigation of edible crops, gardens and landscaping; and irrigation of public areas such as parks and recreational fields.
When it comes online, Brightwater will produce about 7 million gallons of Class A reclaimed water each day for off-site uses, and eventually up to 21 million gallons per day as demand requires. The reclaimed water will also be used on-site for irrigation, tank cleaning, and other processes that do not require potable water.
Learn more about Brightwater reclaimed water construction and about the county’s reclaimed water program.
Biosolids
Biosolids are the nutrient-rich organic material produced by treating wastewater solids. After processing and treatment, they can be beneficially recycled as a fertilizer and soil amendment. King County has been safely recycling biosolids for more than 25 years. In 2002, 27,000 dry tons of biosolids from the county’s two regional treatment plants were used for agriculture and forestry applications, and a portion was composted for use in landscaping and gardening.
Biosolids production will include thickening, anaerobic digestion and dewatering of the wastewater solids. The stabilized, dewatered biosolids will then be hauled offsite and beneficially used along with biosolids from the West Point and South Treatment lants. The biosolids facilities will have odor control systems.