Budd Inlet Treatment Plant

The heart of LOTT's system is the Budd Inlet Treatment Plant. Wastewater flowing to the Plant currently comes from almost 50,000 homes, apartments, and commercial/industrial connections served by the sewer utilities of Lacey, Olympia, and Tumwater. From homes and businesses, the wastewater flows through a series of underground pipes to the Plant. The Treatment Plant is located at the north end of Adams Street, between Downtown Olympia and the Port of Olympia.

About 10-12 million gallons of wastewater flow through the Budd Inlet Treatment Plant on an average day. During the wettest months, flows have averaged as high as 22.3 million gallons per day (mgd). The quality of the water LOTT discharges is regulated by the Washington State Department of Ecology under a National Pollutant Discharge Elimination System (NPDES) permit.

Treatment Process Overview

LOTT offers the highest level of wastewater treatment on Puget Sound, treating to an advanced secondary standard. Both physical and biological processes are used to clean LOTT's wastewater as it moves through a series of cleaning stages:

• Screening – First, a mechanical screening process removes large materials such as sticks, rocks, rags, toys, and countless other untreatable items.


• Primary Treatment – Additional solid material and its related pollutants are removed from the wastewater by allowing them to float to the surface or sink to the bottom of large tanks. "Floaters and sinkers" are removed and processed separately.


• Secondary Treatment – The Plant provides an environment which allows naturally present bacteria to consume additional pollutants during secondary treatment.


• Nitrogen Removal – The treatment process at the Budd Inlet Plant includes removal of nitrogen from the water (April to October) to prevent the nitrogen from feeding excessive algae growth after the treated water is discharged.


• Disinfection – The final treatment step is disinfection with ultraviolet light, which turns any remaining pathogens sterile.


• Discharge – The cleaned water is discharged into Budd Inlet through an outfall off the north end of the Port peninsula.

As the wastewater is cleaned, remaining solid material is removed.

• Thickening – The material removed in the primary and secondary treatment processes is sent to the solids handling building to a Dissolved Air Flotation Thickener, which concentrates the sludge and separates it from the liquid before it goes to the digesters.


• Digestion – The thickened sludge is fed to the two primary digesters. The sludge is heated, mixed, and held for at least 15 days to further reduce pathogens. This process also produces methane gas for beneficial reuse within the Plant. The methane is used as fuel for boilers within the Treatment Plant, which produce hot water for the digesters and the HVAC system.


• Dewatering – The digested sludge is sent to a centrifuge for dewatering after its pathogens have been sufficiently reduced. This machine spins to create centrifugal force, which further separates liquids from the solids. As the solids (also called biosolids) leave the machine, they are carried via screw conveyor to a biosolids hauling truck.


• Hauling and Beneficial Use – The resulting biosolids are trucked to locations in Eastern Washington and Lewis County where they are used to fertilize pastureland, forests and dry-land wheat. A small portion of LOTT Biosolids is used to produce compost.