Virtual Tour - Preliminary Treatment

Process Information - A Virtual Tour of the Main Treatment Plant


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.

The Main Treatment Facility


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. The main treatment facility

Preliminary Treatment


Screen Building


Rotomats
Screening Building Rotomats
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.
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.

Ferric Chloride Tanks


Grit Chambers
Ferric Chloride Tanks Grit Chambers
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. Inorganic solids like sand, cement, cinders and eggshells and some dense organic material like grains settle out in the grit chambers.

Main Pumping Station


Pump Capacity: Up to 5 MGD Each


Pump Building


Pumps Main Pump Building
Four large pumps inside the main pump building lift the screened sewage up to the primary clarifiers, the highest point at the treatment facility. Once the wastewater reaches the primary clarifier, gravity flow moves the wastewater through the treatment process on its way to Superior Bay.