Kirksville’s waste water treatment processes essentially accelerate nature’s own clean-up methods, through the use of bacteria and enzymes which "eat" the harmful pollutants in the water. Water velocity also effects treatment because the speed of the flow of the water will determine how much settling occurs. For example, if you stir sugar into tea, the action of stirring causes the sugar to be suspended in the tea. If you leave the tea for a while, some of the sugar will settle our. It follows that the flow of water must be monitored in sewer lines. If the water is moving too slowly the solids settle out and the in will become stopped up.
The objectives of waste water treatment include:
- Prevention of disease;
- Prevention of nuisances;
- Avoiding water supply contamination;
- Maintaining clean waters for the propagation and survival of fish and other wildlife;
- Conservation of water for all uses.
Lift Stations:
There are twelve lift stations in Kirksville. Lift stations are low points where gravity takes sewer water. The station then lifts the water by pumping it up to a point where gravity can carry it to the waste water plant. "Good" bacteria and enzymes are added at the lift stations to reduce odors and hydrogen sulfide which can build up in sewers. This gas will corrode the collection system used to transport water if it is not controlled. Each lift station has two pumps and a basin that can hold excess waste water should there be an emergency.
The Treatment Process:
Once the collection system takes waste water from the lift stations to the waste water treatment plant, two screw pumps lift the raw water to levels where gravity can take it through the plant. From there it goes to a grit chamber which settles out some of the heavier materials in the waste water. Further filtering is done by a mechanical bar screen which removes things like rags, stick and other debris.
From there the flow splits to two primary clarifiers. These performs similar functions to the clarifiers used at the Water Treatment plant. Floating debris is skimmed off the top and settled solids from the bottom are sent to two above ground tanks called digester. These digester are similar to a human stomach in that they decompose any organic materials. This process gives off methane gas which is captured and used to heat the digester tanks and to heat a portion of the plant itself. The sludge created by the digester is ultimately hauled to farmers’ fields for fertilization.
Biological Treatment:
To this point treatment has been limited to the removal of solids from the waste stream. The water flow is now pumped to a packed tower, which is an above ground tank filled with corrugated plastic media. The media give millions of microorganisms something to stick to as water is trickled down through the tower by a motorless rotating arm. As the water trickles over the media, the microorganisms consume dissolved particles that are in the water and this causes the dissolved particles to stick together, become heavy, and settle out of the water.
From the tower, waste water is sent inside the plant to flow through a series of rotation biological contactors (RBC). These provide more surface area for microorganisms to attach. More cleaning occurs through each of the Waste Water plant’s twenty RBC’s.
Exiting the Treatment Plant:
Water finally leaves the plant through a partial flume. This is where water is measured. The water that leaves the plant feeds into Bear Creek and then the Salt River Basin, and eventually the Mark Twain Reservoir. This means that our neighbors downstream depend on us to maintain a level of cleanliness in the water we treat.
This waste water treatment process requires extensive monitoring. The plant can treat 5 million gallons of water per day, but currently averages 3 ½ million per day. Treated water discharged to Bear Creek must be tested for nutrient levels weekly. Other tests must be performed daily to make sure everything is working properly. The industries in Kirksville are also monitored to make sure they don’t put any pollution into the waste water system.
Maintenance of Operations:
Extensive maintenance also comes with extensive monitoring. The equipment must continually by checked and if any of the breaks down, the back up systems must be put into operation immediately. One person checks lift stations each day to make sure the 22 pumps with 22 large motors are working properly. The gases produced in the sewer are very corrosive and would severely damage the pipes of they were not maintained properly. Hauling the sludge to farmers’ fields is also time consuming and costly.
Plant Operators’ Qualifications:
All operators are licensed by the state of Missouri to handle waste and waste water and are required to have several years of experience before they can upgrade their license. A lot of time and effort are put into this facility to insure that the water is properly treated.
How this Division Benefits You:
Because the City’s Waste Water treatment accelerates the natural processed of cleaning, it does not have a lot of harmful by-product to pollute your environment. Without proper treatment procedures the health and well being of the community and downstream water users will suffer.
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