DMU Wastewater Treatment Plant Improvements

Aerial of DMU wastewater treatment plant

DMU Wastewater Treatment Plant Improvements

Providing a Foundation for Future Nutrient Removal and Economic Growth

Denison Municipal Utilities operates the DMU Wastewater Treatment Plant, which originally consisted of a trickling filter system constructed in the mid-1960s and an activated sludge system built in the early 1980s. A significant portion of the plant loading comes from industrial sources, which creates unique challenges for the administration and operation of the treatment plant. 

To address frequent National Pollutant Discharge Elimination System permit violations due to exceedances of the industrial waste load allocation, a plan was developed in 2013 to confirm available capacity and develop pretreatment requirements for the major industries. As a result, several improvements were identified for Smithfield Foods, including optimizing the pretreatment system and operating their lagoons more consistently. Iowa Department of Natural Resources was engaged for support, and DMU started the re-rating process, with HDR’s assistance. The re-rating process involved formalizing flows and loads, as well as a capacity assessment. The team performed an anti-degradation analysis, industrial waste load allocation and condition assessment. An improvements project was identified that would increase the capacity of the plant above what the existing industries were discharging. 

Before design could begin, Smithfield Foods recognized a need for additional capacity beyond what they were allocated and they had hoped they could increase treatment at their facility. After a review of options to improve pretreatment capabilities at the Smithfield facility, the parties reconvened and agreed on a collaborative approach that developed alternatives that benefited both parties. 

As a result, treatment agreements and a consent order were negotiated between DMU, Smithfield and IDNR. The capacity evaluation and the re-rating process was restarted and expanded to include a new facility planning effort and new industrial waste load allocations. As part of this effort, our team, DMU and Smithfield developed alternatives to address both capacity and reliability and age- and condition-related issues.

The final product is the best project for both Smithfield and DMU and provides a foundation for future nutrient removal and economic growth. The project was completed in 2020 for a total construction cost of just over $16 million. 

Aerial of DMU wastewater treatment plant
Denison Municipal Utilities

Denison, IA
United States



National Recognition Award (2023)
Engineering Excellence Awards
American Council of Engineering Companies
Honor Award (2023)
American Council of Engineering Companies of Iowa