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 90,000 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 11.5 million gallons of wastewater flow through the Budd Inlet Treatment Plant on an average day. During the wet months, flows average nearly 15 million gallons per day due to stormwater inputs from older storm drains in downtown Olympia. During the wettest month, flows reached an average of 33.8 million gallons per day (mgd) due to large storm events, but this rate of flow is very unusual.
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 in solids handling.
- Secondary Treatment The plant provides an
environment, which allows naturally present bacteria to
consume and break down additional pollutants.
- 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
As the wastewater is cleaned, remaining solid material is
- 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, which provides heat and power for plant processes.
- 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. The final product, called biosolids, leave the
machine and is carried via screw conveyor to a biosolids
- Hauling and Beneficial Use The resulting
biosolids are trucked to
Lewis County where they are used to fertilize pasture land,
forests and dry-land wheat.