What is the wastewater treatment process?
There are two steps to treating wastewater at either of the City of Moline plants. The first step, called primary treatment, removes about half of the solids from wastewater. Primary treatment first involves screens to collect trash as water passes. Next water flow is slowed to allow heavy solids to settle and lighter greases too rise where each can be removed.


In the second stage, or secondary treatment, 85 - 95% of pollutants are removed. Air is mixed with wastewater, along with bacteria and other microorganisms that are grown and maintained at the treatment plant. These organisms consume harmful organic matter. A sedimentation tank allows the microorganisms and the solid wastes, which they have converted to, settle and separate from wastewater. Chlorine is added to wastewater as a disinfectant before it is discharged.


The solids that were removed from both primary and secondary treatment are sent for further processing in digestion tanks where they decompose. When stabilized, these bio-solids meet all local, state and federal regulations for utilization for beneficial land application reuse as fertilizer.


Three main by-products are created by wastewater treatment: bio-solids, methane gas, and water. Bio-solids can be used to fertilize land, as discussed below. As solids decompose in the digestion process, they produce methane gas. Methane gas is now used to heat process tanks at the treatment plant. It will eventually be utilized to produce a portion of the electrical and heating energy needs of the plant.


Bio-solids are the treated solid material left over from the wastewater treatment process. Currently, Moline's South Plant bio-solids are applied to farmland as fertilizer. The solids from the North Plant are taken to the landfill, as they are not reducible by digestion and contain a low percentage of organic material, making them less beneficial for land application.

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1. What can I do about sewer odor?
2. How can I report a sewer backup?
3. What is Moline's Basement Backup Prevention Program?
4. How can I establish a new sewer connection?
5. How can I report a missing manhole?
6. How do I eliminate sewer charges for lawn watering or swimming pool purposes?
7. How do I report a sinkhole?
8. What is undermining?
9. What is wastewater?
10. What is the wastewater treatment process?
11. How do I locate the water or sewer line on my property?