Marshalltown, IA

Energy Efficiency

  • Client City of Marshalltown
  • Type Wastewater
  • Services Evaluation, Design, Construction
  • Project Manager Lance Aldrich, P.E., BCEE

CHALLENGE

Performance Edge is the name given to a cooperative effort between the city and Alliant Energy. In 2011, FOX Engineering began a detailed evaluation of the Marshalltown wastewater treatment plant in cooperation with Alliant Energy. The mission was to identify improvements that could be made to the facility that would reduce the plant’s energy consumption with a payback of five to seven years.

Fine bubble air diffusers

Fine bubble air diffusers

SOLUTION

The study revealed that most of the facility was already highly efficient.  Previous projects had upgraded the anaerobic digestion process, raw wastewater pumping, and secondary sludge thickening; little improvement could be found in the industrial SBR plant. The main municipal aeration system process was the single largest power user and was found to be the process with the greatest potential energy savings.  It was also determined that the interior lighting system could be upgraded with a 2-3 year payback.

Aeration basin

Aeration basin

OUTCOME

Construction of the project was complete in 2015. The project included replacing the jet aeration system with a more efficient fine bubble aeration system and a new high efficiency turbo blower.  Interior lights were replaced with multi-lamp T8 fluorescent fixtures, and occupancy sensors were installed in most spaces to control the lighting.  Based on data compiled since the system was put into service, it appears that the plant has reduced its electrical power requirements by approximately 25 to 30 percent.

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