The WLSSD website allows you to see how the plant works.
You can also see current values for the wastewater flow (mgd = million gallons per day) and the influent and effluent temperature, turbidity, pH and the effluent's dissolved oxygen concentration.
Use our plotting utility to
see the effect of precipitation on the volume of wastewater
entering the plant.
WLSSD can be contacted at:
2626 Courtland Street, Duluth MN 55806
(218) 722-3336 http://www.wlssd.com
to find out more about the city of Superior main wastewater treatment facility. Watch a powerpoint about Superior's watewater streament history.
Download this map
(261 KB pdf file)
Most communities operate a municipal wastewater treatment
plant to clean wastewater created by homes and businesses.
Wastewater moves through the
sewer pipes by gravity or with the use of pumping stations.
Wastewater flowing to a treatment plant will typically go
through four phases of treatment, described below:
Primary Treatment: As wastewater arrives at the treatment
plant, it passes through a series of grinders and screens
to remove large debris, like sticks and rags. When the wastewater
flow is slowed down, coarse sediment (sand and gravel) settles
out and grease is skimmed off the top. Debris removed from
wastewater is disposed of in a landfill.
Secondary Treatment: Microbes break down organics and pollutants
in the wastewater as they feed on the nutrients. The wastewater
is aerated to allow microbes to thrive in the wastewater
environment. Solids, or “sludge”, settle to
the bottom and are removed. This process mimics what happens
naturally in rivers and streams.
Tertiary Treatment: Water passes through a filter to remove
fine particles and it may also be disinfected. Before the
water is released to a river or lake, it is must first meet
strict regulatory standards for pollutants.
Solids Management: Solids that are removed during the treatment
process may either be disposed of in a landfill or processed
into biosolids (what we used to call “sludge”).
Biosolids are treated further to remove disease causing
microorganisms (pathogens) and can then be safely used as
a fertilizer and soil amendment.
Here are some more specific details on the City of Duluth sanitary sewer collection system.
The City of Superior is the largest contributor of wastewater to Lake Superior in the state of Wisconsin. Wastewater throughout
the City is conveyed through approximately 80 miles of sanitary sewers and 80 miles of combined sewers to the treatment facility
at the foot of E Avenue on Superior Bay. The Operations Section of the Wastewater Treatment Division of Superior's Public Works
Department is responsible for operating and maintaining collection and treatment equipment that handles 3 to 5 million gallons of
sewage entering the system each day. The main structures include 16 lift stations, one advanced secondary treatment plant, and 3
combined sewage overflow facilities. The Collection System Section is responsible for maintaining the City's 10,000 manholes and
catch basins and over 160 miles of sewer pipelines.
The main treatment facility site contains of two independent treatment plants, the advanced secondary main facility and combined
sewerage overflow plant #2 (CSO #2; see below). Plant processes include screening, grit removal, primary treatment, secondary
treatment (activated sludge), anaerobic digestion of solids, phosphorus removal, disinfection and dechlorination. The main plant
handles all sanitary dry weather flows up to 5 million gallons per day (MGD). This facility can also treat up to 12 MGD for short
periods of time during wet weather events.
Like its neighbor Duluth, large increases in water enter Superior's wastewater system when it rains. Rainfall can enter sanitary
sewer systems as inflow from yard, footing and roof drains and as infiltration from leaking sewer pipes, joints and manholes.
Inflow and infiltration (I&I) of relatively clean water into the sewer pipes has caused sanitary sewer overflows (SSOs). Excess
flow of water into wastewater plants can reduce effectiveness of the treatment process and exceed facility capabilities.
The City of Superior's flat topography combined with predominately clay soil, cause the sewer system to act as a trench drain
at times. The City began a sewer separation project in 1975, which was intended to eliminate combined sewer overflows by
installing stormwater relief lines. Approximately 50% of the combined sewers were technically infeasible or too expensive or
to separate. The City also constructed retention basins adjacent the lift stations along the East 2nd street interceptor
to prevent SSOs. (See the EPA website for more information.)
The City of Superior was one of the first municipalities in the nation to construct and operate combined sewer overflow (CSO)
facilities. Three CSO facilities store and treat combined wastewater from sewer districts #2, #5, and #6. CSO2 serves the
downtown area of Superior. CSO5 is located in South Superior. Billings Park is served by CSO6. Whenever significant rainfall
occurs and the combined sewers fill to capacity, dilute wastewater in the combined districts flow to these CSO facilities to be
stored until the waste stream can be pumped back to the main treatment plant. If needed, stored wastewater can be treated at each
CSO facility prior to release to the environment.
Critical elements of Superior's pollution prevention program include a comprehensive pretreatment program, its membership in the
Regional Stormwater Protection Team and other projects
to educate and involve the public.
Visit the websites for the Western Lake Superior Sanitary District (servicing Duluth and
surrounding communities) and the City of Superior
for a more detailed description of their wastewater treatment processes. For more information about wastewater treatment in other communities,
contact local officials.