Waste Water Treatment Process

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Raw Influent
Raw wastewater is collected throughout the City through a complex system of sewers and pump stations and conveyed to the plant. A total of 6 sources discharge into the influent structures at the plant: General Motors, Kingsbury, Maumee, Kettenring, Ayersville, and Defiance County’s Christy Meadows Pump Stations. The combined sewage then flows by gravity to the Grit and Screening Building.

Preliminary Treatment
A bar screen and grit tank removes large debris and heavy grit in the raw influent before preliminary treatment. Material removed in this process is disposed of in a sanitary landfill.

Primary Treatment
Additional settleable solids are removed in the four rectangular and one circular primary settling tanks. Settled solids are recycled in the plant or wasted to the digesters. The primary settling tank effluent flows to the settled flow diversion chamber where it can be directed to the roughing towers or the aeration tanks.

Secondary Treatment
Flow from the primary treatment process is pumped to the two roughing towers for the removal of organics. Roughing tower effluent flows by gravity to the aeration tanks for further biological treatment.

Advanced Secondary Treatment and Final Settling
Ammonia nitrogen is biologically removed in the three aeration basins. Phosphorus is removed by chemical precipitation in the final clarifiers. Activated sludge is returned to the plant or wasted to the digesters.

Disinfection
Final effluent is chemically monitored and disinfected to ensure compliance with the City of Defiance NPDES permit.

Final Effluent
After the effluent is chemically monitored and disinfected to ensure compliance with the City of Defiance NPDES permit. The final effluent is then discharged to the Maumee River.

Solids Stabilization and Storage
Raw sludge or biosolids are removed from the primary clarifiers. It is then pumped to the two anaerobic digesters for volatile solids reduction and stabilization. Digested biosolids are then moved from the digesters to the plants four biosolids storage lagoons where it is dewatered and thickened. On a seasonal basis, the thickened biosolids are then transported to area farmland. These biosolids are then injected into the soil to act as a conditioner and fertilizer. biosolids management, including biosolids storage and handling, is conducted in accordance with both federal and state environmental regulations.

View the Process Design Data