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Wastewater
throughout the City is conveyed through approximately 80 miles of sanitary
sewers and 60 miles of combined sewers to the treatment facility at the
Foot of E Avenue on the Superior Bay
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The Main Treatment Facility
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The Main Treatment Facility consists of two
independent treatment plants, the main facility and Combined Sewerage
Overflow Plant #2 (CSO #2). The main plant handles all sanitary dry
weather flows up to 5 million gallons per day (MGD). The plant processes
include phosphorus removal, screening, grit removal, primary treatment,
secondary treatment (activated sludge), anaerobic digestion of solids,
disinfection, and dechlorination.
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Preliminary
Treatment
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Raw, unprocessed,
sewage (influent) enters the Main Treatment plant through the Screening Building.
Sewage consists of domestic waste, commercial waste, industrial waste and
stormwater. Septic haulers also bring waste from septic and holding tanks.
The process begins
with a coarse bar screen. Large debris such as boards, branches, rags or
any large items that may damage equipment or plug pipes is removed.
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Screening Building
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Rotomats
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Two automatic rotating screens called Rotomats
screen remaining debris. The rotomats have openings of ¼”. Anything larger
than that will be captured on the screen and scraped off. The collected
solids are dewatered and hauled to the landfill for disposal.
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Ferric Chloride (FeCl3) is added to the
wastewater to act as flocculent, which will aid in the removal of
phosphorus. Phosphorus is a chemical that must be removed to prevent
excessive algae growth in receiving waters.
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Ferric Chloride Tanks
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Grit Chambers
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Inorganic solids like sand, cement, cinders and
eggshells and some dense organic material like grains settle out in the grit
chambers.
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Main Pumping
Station
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Four large pumps inside the main pump building lift the
screened sewage up to the primary clarifiers, the highest point at the
treatment facility.
Pump Capacity: up
to 5 mgd each
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Pump Building
Once the wastewater reaches the primary clarifier,
gravity flow moves the wastewater through the treatment process on its way
to Superior Bay.
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