The wastewater treatment facility was originally constructed in 1958 with major renovations occurring in 1985 and 2002. The facility is designed to treat an average flow of 1.9 million gallons per day generated from a population of over 8,800 people. The City oversees 19 lift stations and over 75 miles of gravity sewer lines throughout the City.
There are 5 main steps to treating domestic and industrial wastewater.
- Preliminary treatment
- Primary treatment
- Secondary treatment
- Final clarification
- Solids processing
The majority of the wastewater flows to the main lift station. The main lift station pumps the water to the treatment facility.
Primary treatment is the separation of liquids and solids. The system consists of a bar screen and aerated grit chamber to remove sand and other debris.
Secondary treatment is an activated solids process used to remove suspended solids, dissolved solids, nutrients, and metals. The system is a continuous flow, biological process where microorganisms use the organic material in the wastewater as an energy source. During secondary treatment, organic matter is reduced to carbon dioxide and water.
Similar to primary treatment, final clarification is where solids are allowed settle out. A portion of the solids are used for "seed" and recycled back to the activated solids process. The remaining solids are further processed. The liquid portion is disinfected using chlorine and then discharged to the Mississippi River.
Solids are generated at 2 stages during wastewater treatment; primary treatment and secondary treatment.
The two solids are mixed together and dewatered. The liquid portion is returned to the beginning of the treatment process and the solids portion is sent to an aerobic digester.
During the digestion process, solids are mixed for a minimum of 15 days. The digestion process produces liquid, solids and carbon dioxide gas. The liquid is returned to the head of the treatment process, and the solids portion, called biosolids, are sent to a centrifuge. The centrifuge further dewater the solids before they are land applied.