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Wastewater Facilities Plan and Upgrades
Plymouth Village Water & Sewer District
Plymouth, New Hampshire

In 2006, the Plymouth Village Water & Sewer District was directed by the New Hampshire Department of Environmental Services to conduct a facilities plan of the existing Plymouth Wastewater Treatment Facility.

The plan addressed two problems: wastewater flows that exceeded 80% of the design flows on a maximum monthly basis; and numerous structural issues with existing tankage and the compost facility.

The District retained Wright-Pierce to evaluate the existing facilities and recommend a long-term plan to address facility needs for 20 years. In addition, the District requested that Wright-Pierce perform a feasibility and cost analysis of regionalizing wastewater treatment with the nearby Town of Ashland, by pumping wastewater from Plymouth to Ashland's aerated lagoons.

Through the regionalization analysis it was determined that it was more cost-effective to upgrade the existing Plymouth WWTF than to pump to the Ashland WWTF.  The District subsequently authorized Wright-Pierce to move forward with design of improvements that include:

  • New channels connecting treatment processes to address hydraulic issues and structural problems
  • New side-car aeration system for improved performance of rotating biological contactors (RBCs)
  • Conversion of an abandoned primary clarifier to a gravity thickener for co-thickening of primary, secondary and septage solids
  • New Fournier rotary press to replace an aging belt filter press for sludge dewatering
  • New lime stabilization facilities for sludge stabilization and a new truck bay
  • New packaged biofilters for odor control of the exhaust air from septage receiving, the gravity thickener, and dewatering

The project, which was operational in the Fall of 2011, received funding under ARRA.

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Project Highlights

Background

  • Wright-Pierce was retained to conduct a facilities plan to address both short-term flow/load and structural issues, as well as long-term facility planning issues
  • Wright-Pierce was then retained to design the recommended improvements

Challenge

  • Variations in flows and loads due to college in user region
  • Analysis of pros and cons of system regionalization
  • Structural integrity issues with existing concrete structures and compost facility

Solutions

  • Regionalization analysis concluded it was more cost-effective to upgrade the existing Plymouth WWTF than pump to nearby town
  • Recommended WWTF upgrade includes new sludge thickening, dewatering and stabilization of facilities