The residents of one North Dakota city are enjoying the fresh air after a successful three-year project drastically reduced an unpleasant odor caused by the City’s Wastewater Treatment Plant (WWTP). The City of Mandan contracted with AE2S to optimize the processes at the WWTP to address the release of hydrogen sulfide gas from the facility.

“First, we investigated and evaluated the condition of Mandan’s system. Then we determined whether the City’s needs as established in the Capital Improvements Plan (CIP) and Master Plan were still relevant and applicable to our initial evaluation. Finally, we developed a cost-effective improvements approach to meet the needs of Mandan,” says Ken Weber, AE2S Senior Project Manager.WTP

“The improvements to the pretreatment building, including the addition of the odor control system have provided the wastewater staff a safe and reliable operation. Sulfide gases are now under control,” says Justin Froseth, Mandan Director of Planning and Engineering. "Before the upgrades, we were constantly fixing equipment breakdowns, now we can run the Plant in the preventive maintenance mode,” explains Steve Himmelspach, Mandan Wastewater Superintendent.

Ultimately, Mandan saved $400,000 on the project. The construction was estimated to cost $3.1 million and the final construction costs were $2.7 million.

“Since the project’s completion in 2017, there has been a huge reduction in odor complaints in the surrounding area. That was previously an issue for Mandan, and we’re very pleased it has been resolved,” says Jim Neubauer,
Mandan City Administrator.


  • New odor control system that includes a scrubber building and biofilter
  • New ultraviolet disinfection (UV) and flow meter equipment
  • Replaced positive displacement blowers with high efficiency turbo blowers operating on variable frequency drives (VFD)
  • Blower building improvements: pipe insulation, new motor control center, modified blower intake system, modified HVAC system, new roof system, safety equipment and painting of equipment, pipes, and walls
  • Pretreatment building improvements:
    fine screen replacement, addition of a second fine screen, new HVAC to collect and deliver gases to scrubber building, piping improvements, new electrical and control system, new mechanical piping, miscellaneous architectural improvements, roofing system, and coatings
  • New solar power mechanical sludge mixing system
  • Replacement of propeller mixing system with jet pump mixing system in the influent mixing tank
  • Electrical distribution and control updates