Treatment Process Description

Raw wastewater is pumped to the headworks structure from the Fischer Road pump station.  The Fischer road pump station presently has a capacity of about 2100 gpm (gallons per minute), with both 100 hp pumps operating. Upon entering the headworks, the flow is divided evenly between the two primary ponds, ponds 1A and 1B.

The primary ponds have been constructed so that two distinct activities can take place. The initial part of the primary ponds, generally the southerly square area includes a digester section at the bottom of the ponds. The digesters are five feet deep with the influent pipe discharging the raw sewage directly above them. The digestion section allows the incoming solids to settle out and to be anaerobically digested. The wastewater then flows in a northerly direction through the pond.

The primary ponds are tapered at the northern end to allow for maximum detention time. Since this treatment facility works using natural processes, maximum treatment is achieved by maximizing the detention time within the ponds. Wastewater leaves the primary ponds through baffles in the north end. These baffles are 3 feet in diameter and surround 18-inch outlet pipes. The baffles serve to retain floatables in the ponds.

Flows leaving ponds 1A and 1B are then transferred to the secondary ponds through Transfer Structure #1. This structure, located between ponds 1A, 1B, 2, and 3, has the ability to direct all or a portion of the flow to either ponds 2, 3, or 4. Normal operation has all of the flow going to pond 2. However, should pond 2 become overloaded or require repairs, the flow can be directed to either Ponds 3 or 4 or both. Normally, flow is transferred to pond 3 through Transfer Structure #2. Transfer Structure #2 is located at the north end of the site, between ponds 2 and 3. The flow leaves pond 3 and is transferred to pond 4 by Transfer Structure #1. The flow then enters pond 4 at the southeasterly end of the pond. Flow out of pond 4 is controlled by an outlet structure, located at the northwesterly end of the pond. The outlet structure has three outlets, each at a different elevation. This allows the operator to minimize the discharging of algae.

The final step in the treatment process involves disinfection. This occurs at the Chlorine Contact Basin, which is located west of the main control building. Flow from pond 4 goes through the outlet structure and then through an 18-inch diameter pipe to the chlorine contact basin. Just prior to entering the chlorine contact basin, the flow rate is measured by a magnetic flow meter. This meter is then used to pace the amount of chlorine required for disinfection. Chlorine gas is withdrawn for one-ton cylinders, located in the control building, and is mixed with the wastewater. The treated wastewater then flows through the long and narrow channels of the chlorine contact basin to the outlet weir. When discharging to the Mad River, Sulfur Dioxide is added to the wastewater just before leaving the chlorine contact basin. Sulfur Dioxide serves to remove any residual chlorine from the water.