Innovating to improve wastewater treatment

Contact: Mary Connor, 651-757-2629

St. Paul, Minn. — Three Minnesota communities are coming up with new ways to remove contaminants from wastewater discharges, thanks to grants from the Clean Water, Land and Legacy Amendment that are administered by the Minnesota Pollution Control Agency (MPCA).

Minnesota cities can struggle to ensure that their wastewater treatment plants are eliminating the increasing amount of contamination present in municipal wastewater. In St. Cloud, Mankato and Windom, pilot projects are underway to try out new methods. If they prove effective, the methods may help other cities discharge fewer contaminants and treat wastewater in a more cost-effective way.

St. Cloud — The city of St. Cloud has completed a promising pilot project on harvesting usable phosphorus from its waste biosolids to be used as agriculture fertilizer. Removing the phosphorus can help treatment plants reduce the nutrient level in their discharge to surface waters, where phosphorus can cause algae blooms. The process also benefits treatment facility operations by reducing the amount of magnesium ammonium phosphate — also called struvite — in the system, which can cause significant issues by blocking pipes.

Mankato — The city of Mankato is also aiming to reduce the amount of phosphorus in the water it discharges. They are testing the use of a membrane filter and chemical addition to achieve phosphorus reductions. The goal is to reduce the phosphorus concentration in their discharge to levels below what is currently required.

Windom — Windom’s project is looking at processes that would significantly limit the amount of nitrogen they discharge. They plan to try different methods to reduce nitrogen in wastewater, including using a new type of filtration and other alterations in their treatment process. They are aiming to reduce the nitrogen concentration in their discharge to levels below what is currently required. Nitrogen is a problem in Minnesota waters, especially in southwest Minnesota, and contributes to the low-oxygen “dead zone” in the Gulf of Mexico.

To learn more about phosphorus, visit the Phosphorus in wastewater webpage. To learn more about excess nitrogen, visit the Nitrogen study — sources and pathways webpage.