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Pumps Move Leachate, Help Recover Landfill Gas
From Pollution Engineering

Lake landfill, operated by Waste Management and located in Northbrook, IL, has served the disposal needs of residents and businesses throughout Cook County since 1970. Now the landfill - closed since 1993 - includes a golf course, a driving range and practice tees. Gas from the non-hazardous waste is used to produce electricity.

The collection system for the gas, which is 55 percent methane and 45 percent carbon dioxide, includes 107 drilled boreholes and 24,000 linear feet of piping. Pumps are used to remove the extracted leachate and recover the landfill gas.

"Our research led us to a surface-driven, positive displacement piston pump," says John Schrott, wellfield technician at Lake Landfill. The Anchor Pump, developed and manufactured by Blackhawk Environmental Co., Glen Ellyn, IL, was selected.

Designed for shallow or deep well recovery, the pump's vertical and horizontal pumping capabilities allow for recovery from non-vertical, bent or twisted wells. The pumps operate wet or dry and can pull down liquid to the bottom of the pump or zero submergence. The self-cleaning piston drive assembly resists malfunction caused by dissolved mineral encrustation and biological slime. Its bottom inlet can draw liquid from the bottom of the well, and it does not need any liquid head to fill the pumping cylinder. The pump is not influenced by pressure changes in the well. It lifts liquid from depths of up to 300 feet, operates using standard quality air and can be installed in wells as small as 2 inches in diameter.

"The Anchor Pump is working great," says Schrott. "It not only removes leachate but also aids in gas recovery. The pumps we previously were using had a much wider diameter, which made boreholes difficult to replace. Because the land often shifts and boreholes can become crooked, the new pump's smaller diameter allows for easier repairs and replacements. Also, the pump does not introduce air into the gas wells, and all its working mechanisms are aboveground, making it easier to maintain."

The gas is compressed and fed into four turbines powering generators that produce up to 13.2 million watts of electricity, enough to serve the needs of 22,000 homes in the area. The project is reported to be the first in Illinois to produce electricity directly from landfill gas.

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