Plant Processes

Influent Sewage

The influent sewage, or raw wastewater first enters the plant’s pretreatment facilities, which remove large objects and grind sewage solids that could damage equipment if allowed to pass on. These functions are accomplished by the bar screens (rakes/screens) and comminutors (grinders) located in the Raw Wet Well section of the Administration Building.

Pumping and Preliminary Treatment

The wastewater is then pumped up to the grit removal buildings (to remove sand and stone material) using any combination of one 5-million gallon per day capacity, two 9-million gallon per day capacity, or two 18-million gallon per day capacity pumps.

Secondary Treatment

Secondary treatment is achieved in the aeration, final settling tanks and return activated sludge buildings. In the aeration tanks, oxygen supplied by three 4160 volt 600 HP compressors blow air to the biological organisms which feed on the food material present in the wastewater. The organisms form floc, which in turn settle in the circular final settling tanks. A major portion of the settled floc is returned to the aeration tanks to maintain a high concentration of organisms in the aeration tanks. The entire operation of floc formation, food consumption, settling and return of settled floc to the aeration tank is referred to as the activated sludge process.

Disinfection

The portion of the purified wastewater that does not settle in the final settling tanks is disinfected in the chlorine contact tanks. Sodium bisulfite is then added to neutralize the chlorine in the dechlorination reaction basin. This eliminates any potential chlorine toxicity effect on aquatic life in Lake Erie.

Effluent

After the dechlorination reaction basin, the treated wastewater, called effluent, is pumped using any combination of two 9-million gallon per day capacity, or three 18-million gallon per day capacity pumps. Two of the 18-million gallon per day pumps are designed only to run in tandem and provide a maximum pumping rate of 36 million gallons per day. The typical daily flow is 5-6 million gallons per day. The effluent outfall located in Maumee Bay, approximately one mile north of Wynn Road and east of the Corps of Engineers Confined Dredge Disposal Facility.

Biosolids

Sludge, or the portion of the wastewater and heavier material which settle in the final settling tanks are pumped to the aerobic digestion tanks. The biosolids are mechanically dewatered using centrifuges. The dewatered biosolids are hauled to a sanitary landfill for disposal.