National Grid Project Expeditor Nantucket

Surfside Wastewater Treatment Energy Conservation Measures

Weston & Sampson recently provided Owner’s Project Management (OPM) services to assist the Town of Nantucket to evaluate and implement four energy conservation measures (ECMs) at the Surfside Wastewater Treatment Facility.

ECM-1: Draft Pump System Modifications

The scope of this ECM included replacement of the four existing draft pumps with new 16 HP submersible chopper pumps. The scope  included hydraulic modifications to allow the pumps to operate at more energy efficient flow rates.

ECM-2: Anoxic Tank Mixers

The scope of this ECM included replacement of the four existing 2.3 HP submersible axial flow propeller mixers (2 per tank) with two 3 HP hyperbolic mixers (1 per tank). The new hyperbolic mixers are a more efficient mixer that resulted in energy savings for the treatment facility.

ECM-3: Aeration Blower Controls

This ECM included replacing the current manual controls for the three existing 60 HP aeration blowers. The manual operation includes setting blower speeds based on expected dissolved oxygen (DO) requirements and manually adjusting the flow control valves. As part of the optimization, the three existing sludge holding tank blowers will be tied into the aeration system with the implementation of a new DO control strategy, DO probes, modulating air control valves, and air flow meters. The controls will reduce the aeration blower energy usage by reducing the amount of air provided to the tanks.

ECM-4: MBR Recycle Air

This ECM includes piping modifications to the existing return activated sludge (RAS) pumping system to direct the recycled flow to the aeration tanks instead of the anoxic tanks. This will reduce the oxygen demand and require the aeration blowers to provide less air and increase energy savings.

These projects were eligible for incentives from National Grid under the MassSave program. As a Project Expediter, Weston & Sampson assisted the town in receiving the utility rebate. As a result, the town received a rebate from National Grid in the amount of $183,927.

  • Project Savings from utility rebate: $183,927
  • Estimated kWh annual savings: 282,649 kWh
  • Estimated project cost: $463,000

Estimated Annual Cost Savings: $42,397



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