Manchester WWTF Wins ACEC Gold

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Manchester, New Hampshire                  

The City of Manchester owns and operates a wastewater treatment facility servicing the City and surrounding communities. Wright-Pierce was selected to assist the City with secondary system improvements, including upgrades to increase significantly the peak wet weather flow capacity and to take the first step to meeting an effluent phosphorus limit of 236 lbs/day.

The $22 million aeration system upgrade was substantially completed in December 2015 and included the following:

  • Enhanced biological phosphorous removal using a variation of the Modified Johannesburg (VMJ) process with anaerobic selector zones
  • Transition from two-train to four-train configuration to offer more process flexibility and redundancy
  • Replacement of the existing mechanical surface aerators with ultra high-efficiency diffused aeration and integrally-geared blowers
  • New blower building to house the new Siemens single-speed, integrally-geared, centrifugal blowers
    New RAS pumps, hyperboloid mixers, piping and valve upgrades
  • Major electrical upgrade to the southern end of the facility, instrumentation, HVAC and odor control upgrades
  • New secondary bypass structure allowing better process flow control
  • Energy efficiency grants from Eversource

Prior to the upgrade the secondary system capacity was limited to 34 MGD. The upgraded facility can handle over 48 MGD thereby reducing the total amount of bypassed flow and improving water quality on the Merrimack River.


  • Upgrades to the existing aeration basins for enhanced biological phosphorous removal and improved sludge settleability.


  • Phosphorous discharge limit imposed with new NPDES permit.
  • Increase peak flow capacity for CSO abatement.
  • Hydraulic modification required to convert from 2 to 4 trains for enhanced operating flexibility.
  • Aged aeration system needing replacement.


  • Anaerobic selector for enhanced biological phosphorous removal to meet permit limits and to improve settleability to increase peak secondary flow capacity.
  • Hydraulic modifications and gates to control flow for the new four-train operation and new secondary bypass structure.
  • New more energy efficient aeration system.
  • Major electrical systems upgrade.