Town of Amherst Water Pollution Control Facility

Natural Gas Engine Drives Main Wastewater Pump, Generating Savings, Reliability, and Useful Heat

When Siemens Building Technologies conducted an energy audit of more than 100 municipally-owned facilities in the Town of Amherst, New York, it recommended switching a 600 hp sewage pump’s variable speed electric motor drive to a natural gas engine drive to

save energy.

The new natural gas engine-driven pump improves overall energy effi ciency because its waste heat can be reused, along with lowering the high electricity usage and bills at the town’s Water Pollution Control Facility (WPCF).

“This (natural gas engine-driven pump) is the main pump – it runs all the time. This reduces electric use,” says James I. Johnson, P.E., Assistant Town Engineer. “Because we can use the engine’s waste heat, the gas that we would have used to heat the boilers is now used to run the engine. The primary function is pumping; an added benefi t is the heat.”

Pump Lets Treatment Plant Operate during Blackouts

The natural gas engine-driven pump does much more. It allows plant operators the fl exibility to switch between operating with the natural gas and electricity to take advantage of fl uctuations in energy prices. It also improves the plant’s reliability by making it possible to keep treating wastewater during electric power outages, when the electric pump shuts off.

“We have a 2.7 MW (fuel oil) generator for emergencies to maintain minimum operational levels during a power outage,” says Johnson. “With the gas engine taking horsepower off the electric side, we can fully run the WPCF with just the gas engines and the generator.”

The natural gas-driven 585 hp Waukesha engine package was purchased from Energen Technologies Inc. It was installed in 2003 at no cost to the town’s taxpayers, under a 10-year performance contract that guarantees energy savings that are used to pay for the project. So far, the energy effi ciency measures are producing more savings than initially anticipated, according to Johnson.

“ It’s been running very well,”declares

James I. Johnson, P.E.,

Assistant Town Engineer. “ It’s been a win-win for us.”

This natural gas Waukesha engine drives the WPCF’s wastewater pump.

• Natural gas engine-driven pump

• Increased reliability and multiple uses for free wasteheat

• Amherst, New York

The new engine at the WPCF was part of an overall Siemens energy performance contract that provided approximately $4 million in improvements to town buildings, with a projected total annual energy savings of $500,000. The New York State Energy Research and Development Authority (NYSERDA) contributed $1.35 million toward the improvements, while National Fuel, the regional natural gas utility, contributed a $25,000 demonstration grant toward the WPCF project.

Innovative Uses for Waste Heat

“This was an opportunity to have something locally to show other customers who are interested in this technology,” says Howard Patton Jr., Senior Energy Consultant at National Fuel. “The project has been performing and meeting expectations.”

“Energen put together the Waukesha drive package,” says Johnson. “They put the two components – the engine and the drive unit – together.” The engine feeds 1.5 million Btus of heat recovered from the engine package’s water cooling, oil cooling and exhaust system through a series of heat exchangers to the plant’s sludge digesters. The digesters require large amounts of heat year round.

“We previously had problems with condensation and corrosion due to excessive humidity in the pipe tunnels during hot humid weather,” explains Johnson. Now the recovered waste heat from the engine is used to regenerate dehumidifi cation equipment in the summer. The dehumidifi er is used to remove moisture from the underground tunnels that accumulates during the hot humid summers, according to Johnson.

The savings from summer tunnel dehumidifi cation alone is considerable, he says.

During the colder months, recovered engine heat is fed into the plant’s boilers, which supply the plant’s hot water loop for comfort heating.

“The cost savings is the thermal – there are endless possibilities (for) what you can do with thermal,” says Patton.

“It’s been running very well,” declares Johnson. “It’s been a win-win for us.”

National Fuel Gas Distribution Corporation

6363 Main Street

Williamsville, NY 14221-5887

The pump is installed in a verticalshaft (above). The controls are shown (right).

Panoramic view of the WPCF’s settling tanks.