- Category: Wastewater Department
1. Inflow to the treatment plant (average 1 million gallons a day) flows in from a main line into our Influent pumping station. A “bar rack” removes all sorts of large material such as bricks, boards, and other large objects.
2. The flow is then pumped up into our headworks building. A slightly finer bar rack removes things like rags and other assorted “large garbage). The flow is then diverted into a grit chamber where finer material such as sand and grit is removed.
3. After the grit and sand removal, flow goes into our oxidation ditch. This is basically a large fish tank that contains microscopic organisms. These organisms use the raw sewage as food. The oxidation ditch has two parts: the anoxic zone (very low oxygen, usually less than one milligram per liter) and of course a zone where aeration takes place. The aeration portion of the tank allows for reduction of solids whereas the anoxic zone promotes nutrient and phosphorous reduction.
4. The mixed liquor (treated sewage solids and water) exits the oxidation ditch into two circular clarifiers. The solids settle to the bottom and flow into a sludge wet well. The supernatant (treated water) flows over into a separate wet well in our intermediate building.
5. There are several processes that occur in the intermediate building. The treated water from the clarifiers goes to a wet well and is then pumped through an ultraviolet disinfection system to kill any remaining microorganisms before the treated water is sent to the Walnut River. The solids that settled out in the clarifiers goes to the sludge wet well. This sludge is then sent two directions: back to the oxidation ditch for more food for the microorganisms, and also “wasted.” The wasted sludge is sent to the sludge thickener where it settles out even more. Water from thickener sludge is decanted off the top and sent right back to the influent building to be pumped back to the thickener. The thickened sludge is then run through a belt filter press to squeeze out the remaing water (this is called "dewatering"). The sludge is then land applied on City owned fields in accordance with EPA Part 503 Regulations.