Optimization of Energy Use in a 20-mgd Immersed Membrane Water Treatment Plant

Last Modified: Oct 20, 2006


  • Eileen McCarthy Feldman, Hazen and Sawyer

The paper will describe how the 20-mgd immersed membrane water treatment plant (WTP) that is about to be constructed for the Westchester Joint Water Works (WJWW), NY, at Rye Lake, has been designed to minimize the energy usage.

Immersed membrane treatment is a method of filtering water to a very high standard of cleanliness that has developed rapidly over the last 5 to 10 years.

Immersed membrane plants normally use a relatively inefficient end suction centrifugal pump dedicated to each membrane tank. These pumps create a vacuum of up to 13 psi to generate a flow of water through the hollow fiber membranes. At the Rye Lake WTP the pumps have been replaced by siphons, a wet well, and a smaller number of more efficient vertical turbine pumps under variable frequency drive (VFD) control.

The membrane tanks are aerated by Roots-type blowers that consume electrical power. The control system for these blowers incorporates two modes of operation that save power; air cycling and intermittent air operation. In addition, to optimize air flow in the membrane tanks, the blowers will be controlled by VFDs.

The Rye Lake Pump Station that will feed the new immersed membrane WTP is being upgraded to 20-mgd capacity using VFDs to control flow and thereby reduce power consumption.

Anticipated power consumption at the Rye Lake Water Treatment Plant will be examined to evaluate operating energy costs of this process.

For a copy of the full paper, please contact the author at efeldman@hazenandsawyer.com

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