Plant power: Muscatine pilots algae water treatment strategy
by Margaret Hurlbert
May 07, 2022

MUSCATINE, Iowa–To preserve the health of Muscatine’s watershed and of communities downstream, the Iowa Department of Natural Resources requires water treatment plants to limit the amount of nitrogen and phosphorous in the water they release. Beginning in late April and continuing through September, the Muscatine Water and Resource Recovery Facility will pilot using algae to remove these nutrients in an effort to save both money and energy.

About 10 years ago, Muscatine Water and Resource Recovery Facility Director Jon Koch saw algae used to treat wastewater in a graduate project in progress at Iowa State University. Now, the company Gross-Wen Technologies has brought the method to market as the Revolving Algal Biofilm System.

The system uses large conveyer belts suspended vertically in wastewater treatment tanks to cycle algae through the wastewater. With each pass, algae remove some of the nitrogen and phosphorous from the water. Once enough algae have built up on the conveyer belt, it gets harvested and replaced with new algae. The water treatment plant can sell the harvested algae for a number of uses, such as serving as an all-natural fertilizer or getting converted into aviation fuel.

Before treated water gets released back into the watershed, the facility adds oxygen to it to benefit aquatic life. Because the process of putting the algae through the water aerates the water without using a lot of energy, it can help reduce the amount of electricity and money it takes to treat wastewater. It also slows the buildup of struvite, caused by high concentrations of certain minerals, on wastewater treatment equipment, reducing the amount of work and expense the plant must do to get it off of their machines and pipes.

For all these reasons, Koch considers it a promising technology: “This will act to remove nitrogen and phosphorous, which we are required to do. It adds oxygen, which we already do, but with very little energy input, which saves us money, and it’s a natural process.”

Over the next six months, the facility will evaluate the cost and effectiveness of using algae to remove nutrients from wastewater and compare it to a variety of other nutrient reduction strategies they have researched. If the results prove satisfactory, they will likely pursue funding from the state revolving fund, which provides low-interest loans for large municipal projects.

Koch would also like to explore utilizing algae to clean the water in the facility’s biosolid storage lagoons. The final solid product of water treatment, the facility uses lagoons to allow the biosolids to settle out from the water before they inject them into neighboring farm fields annually as a fertilizer. After the biosolids settle, the water at the top of the lagoon requires treatment for nutrients before it gets released back into the watershed. Treating it with algae could cost less than running it back through the water treatment plant and allow the facility to get even more usable products from it. Paired with an initiative to create more prairie strips throughout the region to collect nitrogen and phosphorous runoff from farms, Koch believes this additional application for algae could greatly reduce nutrients in area watersheds.

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