Water Pollution Control Plant Celebrates 50 Years

WPCP1On Thursday, Aug. 13 , the City of Muscatine Water Pollution Control Plant (WPCP) held a 50 Year Celebration Open House with tours of the plant and laboratory. It was my second time touring the plant and hearing about the process used to remove harmful organisms and other contaminates from wastewater so it may be safely sent to the Mississippi River.

While on each tour, I could not help but realize how little I think about the water I use. As long as it turns on at the sink or in the shower, I assume things are good to go. I think it is safe to say that a majority of the U.S. population is with me. We don’t often think of the “after” when we flush the toilet or run dishwater down the drain. In touring the plant, I got more than a “whiff” of the “after.” Considering the magnitude of waste water that goes through WPCP, the smell was actually not as bad as I would have imagined. The WPCP works hard to keep the odors under control.


I am going to briefly describe the process used at WPCP to filter water to give you a better idea of what actually goes on at the plant. Jon Koch, WPCP Director, is a wealth of knowledge and does a fantastic job giving tours of the plant. WPCP7

  1. Headworks building – This is the first stop at the plant. All of the wastewater that is collected from homes, commercial buildings and industrial facilities comes here via the collection system. Any large material is separated from the wastewater. Mechanically cleaned bar screens remove bigger materials, such as leaves, wood, rocks, baseball caps, etc. Vortex Grit Chambers (or “Tea Cups”) remove finer particles, such as sand, coffee grounds, egg shells, or “grit.” All removed material is taken to the landfill for disposal.
  2. Primary Clarifiers – Once the wastewater goes through the initial screening process, it is sent to the clarifiers to slow the flow. This allows most of the remaining material to settle out. The settled material has strong organic content so it is sent to the digesters (more on that later!) for further treatment. Lighter material, like oil, grease or anything else that floats is skimmed off the top of the clarifiers and is called “scum” – it is also sent to the digesters.
  3. WPCPAeration Basins – Next, the wastewater is mixed with Return Activated Sludge (RAS) in the splitter box, where air is then added to it. This “biomass” is referred to as mixed liquor. As the mixed liquor moves through the basin, actively metabolizing organisms (better known as “bugs”) biodegrade the water.
  4. Final Clarifier – In the final clarifier, the mixed liquor must travel from the middle of the clarifier to the outer ring. This allows the heavier material to sink and the clarified water to proceed to the next step. The heavy settled material becomes RAS that is sent to the beginning of the aeration basin (step 3) or to be mixed with more incoming wastewater. Some of the RAS is also taken away to the Thickener Building. Basically, the “bugs” keep getting reused over and over again in the cycles of filtering wastewater. 
  5. Disinfection – Before sending the water to the Mississippi River, WPCP uses UV disinfection methods. After final clarification, the water passes through the UV array where 254 nanometer wavelengths of UV attack the vital DNA of bacteria left in the water, making bacterial reproduction impossible.


That sums up the process of taking wastewater from homes and businesses and eliminating materials and bacteria so that it can safely enter the Mississippi. I found it really neat that WPCP does not use any type of chemical to accomplish this great task.

The “bugs” used throughout the process are natural and end up reproducing themselves. The UV system has no by-product and is effective in seconds as opposed to 30 minutes of contact required by chlorine. In the past, the Muscatine WPCP used chlorine for disinfection, but the hazardous chemicals are dangerous to handle and require more hazardous chemicals to de-chlorinate.

Now, I’m going to explain one more crucial function of the plant. Remember how I mentioned that some materials would be going to digesters for further treatment? Well, those digesters are anaerobic, meaning “without oxygen.”


The digesters get materials from two places. 1) The settled material and “scum” from the primary clarifiers, 2) Waste Activated Sludge from the Thickener Building.

In the Thickener Building, the solid material in the water is removed by a solids separation device so that as much water can be cleaned and returned as possible. This solid material is the Waste Activated Sludge, which, like I explained above, goes into the digesters.

Let’s go back to the digesters and look into what they do. The anaerobic bacteria in the digester and the incoming material mixture is heated to 95 degrees Fahrenheit and maintaned at a stead pH of 7.0. This creates the environment best suited for creating methane gas. WPCP5

Currently, a portion of the gas is used to fire the boilers that heat the system to 95 degrees. The rest is burned off and released into the atmosphere. There are future plans in place to use this excess gas to power generators that can run other equipment at the plant.

So, we know that the digesters release methane gas. But, what happens to all of the sludge that went into the digesters in the first place?

WPCP 1Once digested and stabilized, the sludge is tested to meet a set of standards. The Muscatine WPCP produces a Class B (II) biosolid, which is safe for specific agricultural applications. This biosolid material is pumped into two large lagoons across the Highway 61 bypass (right across from Lutheran Living Senior Campus). It is stored there until fall when fields have been harvested. Then, it is pumped to a tractor that injects the biosolid material 8 inches into the subsurface of the ground to be used as fertilizer.

It is pretty cool how biosolids are the by-product of wastewater treatment and then can be used as a safe, organic and economical alternative to chemical fertilizers. WPCP is able to provide the service of treating wastewater while using the aftermath of treatment to provide another service to area farmers.


With that, I will wrap up this post about the Water Pollution Control Plant. In the future, I hope to feature information about the WPCP’s state of the art laboratory that was built in 2014. That’s another great advancement for Muscatine.

Thank you for reading!

6 Replies to “Water Pollution Control Plant Celebrates 50 Years”

  1. Nicely done. Glad you enjoyed the tour and we hope to see you back for our next big project coming next year. It will change the way people think about waste and whether we can really call anything “wasted”.


  2. Hello there! This post couldn’t be written any better!
    Reading through this article reminds me of my previous
    roommate! He constantly kept preaching about this.
    I am going to send this information to him. Fairly certain he will have a good read.
    Thank you for sharing!


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