Three Primary Clarifiers allow smaller particles to settle from wastewater by gravity. This primary wastewater flows out to the next stage of treatment. Scrapers collect the solid matter that remains (called primary sludge). A surface skimmer collects scum or grease floating on top of the basins.
Four Secondary Clarifiers allow the clumps of biological mass (the microorganisms) to settle from the water by gravity. 90 to 95% of this mixture, called “activated sludge” is returned to the aeration basins to help maintain the needed amount of microorganisms. The remaining 5 to 10% is pumped to the anaerobic digester (described later).
Four Aeration Basins supply large amounts of air to the primary wastewater and helpful bacteria and the microorganisms that consume the harmful organic matter. The growth of the helpful microorganisms is speeded up by vigorous mixing of air (aeration) with the concentrated microorganisms (activated sludge) and the wastewater. Adequate oxygen is supplied to support the biological process at a very active level. The ratio of food (organic matter) to organisms to oxygen is continually monitored and adjusted to meet daily variations in the wastewater.
Chlorine Contact Basin
The Chlorine Contact Chamber is provided for sterilization of harmful bacteria that may have survived the treatment process. The flow through the tank is in a snake-like flow to maximize the contact between chlorine and the effluent.
Some of the solids processing occurs by anaerobic digestion. Two large tanks are used to mix and heat the solids. Microorganism process the organic material in the absence of dissolved oxygen. The bi-products of this method of digestion are methane, hydrogen sulfide, and ammonia. The methane produced in this process is used to fuel the boilers and an electrical generator at the plant.
The Waste Activated Sludge continues on to the gravity Belt Thickeners where the solids are concentrated and pumped to the anaerobic digesters. The liquid overflow is returned to the Headworks pump station.
Following the digestion process the biosolids still contain a significant amount of water. Sludge that was removed from the digesters is sent to a belt filter where the water is squeezed out of the solids leaving a 16 to 18 percent biosolids cake.
At the end of the Chlorine Contact Basin, the chlorinated water flows into the Dechlorination Basin where Sulphur Dioxide is added to remove any chlorine still remaining in the plant effluent. Since Sulphur Dioxide removes oxygen from the water, we must aerate the water by cascading it down these falls. This ensures that the water will be safe for the aquatic life when it enters the river.
Out to the Wichita River
Once the water has been biologically and chemically
treated, the water flows straight to the river.