Wastewater Treatment Facility Biological Process Modification

Allenstown, New Hampshire

Client: Town of Allenstown, New Hampshire


  • Bidding Administration
  • Construction Administration
  • Construction Observation
  • Design
  • Funding Assistance
  • Innovative and Alternative Technology Approvals
  • Permitting
  • Preliminary Design
  • Study and Evaluation

Project Summary

The existing wastewater treatment facility in Allenstown was construction in 1977, has a design average daily flow capacity of 1.05 million gallons/day, and originally designed as an extended aeration process. The facility serves the towns of Allenstown and Pembroke. There was a moratorium in place in both Allenstown and Pembroke from regulatory officials that prohibited connections to the sewer system because the plant was considered to be at or near its design capacity. The upgrade and expansion of the facility was necessary to provide additional hydraulic capacity in order to remove the moratorium.

The upgrade consisted of modifications to the biological treatment process using state-of-the-art innovative/alternate technology to increase the hydraulic capacity without adding new tankage. This was an alternative to a full-scale upgrade of the facility, the funding for which failed to be approved by Town voters 2 consecutive years. The process modifications included a ballasted flocculation process known as the Bio-Mag™ process to significantly enhance solids settling thereby increasing the hydraulic capacity of the secondary clarifiers which was the major limitation.

The project was funded 50 percent with money from the American Recovery and Reinvestment Act (ARRA) of 2009 and 50 percent with capital reserve funds from septage revenues with no resulting financial impact on the taxpayers or the sewer user rates.

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