Water Plant Energy Conservation

Water Treatment Plant Energy Conservation

The Town of Essex Water Treatment Plant (WTP) was constructed in 1982. It is a modified conventional treatment plant with granular activated carbon filters. The plant is designed to treat an average of 500,000 gallons per day and has a maximum hydraulic capacity of 1,500,000 gallons per day. The town has three gravel packed groundwater wells, which supply raw water to the plant. The three wells are all located within ½ mile of the WTP.

This project included work designed to conserve energy and reduce operating costs at the WTP and the well sites. The work at the WTP included upgrading the pump motor starters, installing three 40‑horsepower (HP) Variable Frequency Drives (VFDs), controls, and four programmable thermostats. Well #1 received a new 7.5‑HP VFD, new circuit breaker, controls, flow meter, and one programmable thermostat. At Well #2, a new 15‑HP VFD was installed along with a new circuit breaker, controls, remote communications device, flow meter, and programmable thermostat. Work at Well #3 included a new 10‑HP VFD, circuit breaker disconnect, controls, flow meter, and programmable thermostat. Startup and testing was performed at all of the project locations.

Operating the pumps on VFDs will allow the pumps to run at the desired flow rate, but at a reduced head. This will eliminate pump throttling and result in less energy consumption. The pump curves were evaluated to locate the design point and estimated efficiency for each pump. The energy consumption was then evaluated for existing conditions and post-VFD installation. The total estimated kWh savings is estimated at 82,000 per year for all of the installed measures.


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