Water Pollution Control Plant

Summary of Operations

The Huntington Water Pollution Control Plant is a combined rotating biological contractor/step-feed activated sludge plant. The plant is capable of treating an annual average flow of 7.5 million gallons per day and a peak wet weather flow of 15 million gallons per day. 

Wastewater enters the plant through bar screens where coarse solids such as branches and plastics are physically removed. After screening, the influent proceeds to two detritus-type grit tanks. The grit removal process removes the heavy abrasive inorganic materials such as gravel and sand.

The wastewater is then pumped by the raw wastewater screw pump station to four primary clarifiers where a portion of the suspended solids are removed. Primary treatment is followed by secondary, biological treatment. Biological treatment at the WPCP consists of seven rotating biological contactors and six step-feed aeration basins. The biological processes utilize microorganisms that consume organic waste. Five secondary clarifiers settle suspended solids and microorganisms from the aeration basin effluent before discharging flow to the chlorine contact tank for disinfection. Effluent from the chlorine contact tank is dechlorinated (to protect aquatic life) before the water is discharged to the Wabash River.

Sludge from the primary clarifiers is pumped to the primary anaerobic digester where it is heated and mixed. Microorganisms that thrive in the anaerobic (without oxygen) conditions further break down organic matter contained in the sludge.

Sludge from the secondary clarifiers is either returned to the aeration tanks where it is mixed with incoming wastewater or wasted to the Thickener Building. In the Thickener Building, wasted activated sludge is thickened using a dissolved air flotation thickener. The thickened sludge is pumped to the primary anaerobic digester for further treatment.

Digested sludge from the primary anaerobic digester is transferred to the secondary digester for further stabilization. Digested sludge, now called "biosolids," is pumped from the Digester Building to the two biosolids storage tanks. The biosolids in the storage tanks can then be pumped to the biosolids loading station, loaded into trucks, and hauled away for agricultural land application.