Water Pollution Control Plant

Summary of Operations

The Huntington Water Pollution Control Plant is a 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 wastewater is then pumped by the raw wastewater screw pump station to two gravity feed Head Cell grit tanks. The grit removal process removes heavy and abrasive inorganic materials such as gravel and sand.

Following grit removal, the wastewater flows by gravity 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 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 rotary drum 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 secondary digester to the belt filter press for additional dewatering. Dewatered biosolids from the belt filter press are stored on a covered concrete slab until loaded into trucks and hauled away for agricultural land application.