Quest for better ways to manage pollutants at WDE Landfill finds technology that extracts some for use in fuel blend

For release: April 25, 2013

Contact: Sam Brungardt, 651-757-2249

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Quest for better ways to manage pollutants at WDE Landfill finds technology that extracts some for use in fuel blend

St. Paul, Minn. -- Years ago, few people lived near the Waste Disposal Engineering (WDE) Landfill in Andover. But as the city grew, more and more housing was built near the landfill, until today it is surrounded by homes.

Those close neighbors are the reason the landfill is of special concern to the Minnesota Pollution Control Agency (MPCA). As part of the state’s Landfill Cleanup Act of 1994, the agency’s Closed Landfill Program assumed responsibility for remediation activities and long-term care at the WDE Landfill.

The WDE Landfill was operated as a commercial dump in the 1960s. From 1971 to 1983, it was a MPCA-permitted sanitary landfill that received mixed municipal solid waste and some hazardous wastes. Hazardous wastes, such as spent oils, paints and degreasers, in 6,600 containers of various sizes were accepted at the landfill from 1972 to 1974, when the MPCA ordered closure of the landfill’s hazardous waste pit due to operational concerns. The containers are in a lined pit 240 feet long, 90 feet wide, and 20 feet deep that is separate from the area where the solid waste is buried.

Gas-extraction system draws methane, other gases from buried waste. According to MPCA Project Manager John Moeger, the MPCA has two main challenges at the WDE Landfill. The first is keeping methane and other gases that are produced when organic materials decay from migrating off site. Methane can move through soil and cause problems if it makes its way into poorly ventilated basements or storm or sanitary sewers. Although some methane movement has been detected at the landfill, methane has not moved beyond the 200-foot compliance boundary.

In 1997, the MPCA installed an active gas-extraction system that quickly and efficiently draws methane and other gases from the buried solid waste. The gases are then burned in a controlled manner inside an enclosed flare.

Moeger said the MPCA’s other challenge at the WDE Landfill is removing the volatile organic compounds (VOCs) from the hazardous waste pit and preventing the leaching of polychlorinated biphenols (PCBs) into the groundwater beneath the pit. Some VOCs and PCBs are known carcinogens.

GAC system removes polychlorinated biphenols from groundwater. Over the years, leakage from the containers of hazardous wastes dissolved the floor of the hazardous waste pit. Last spring, MPCA staff for the first time detected PCBs in groundwater from beneath the pit that was being discharged to the landfill’s treatment pond. The MPCA immediately quit pumping groundwater from beneath the pit because the agency’s discharge permit does not allow PCBs at any concentration.

To deal with the PCB problem, the MPCA first had a pilot granulated activated carbon (GAC) system designed and installed to determine the proper capacity for a permanent system. Last summer, the MPCA replaced the pilot system with an appropriately sized permanent GAC system that removes all PCBs from the groundwater so the groundwater can again be discharged to the landfill’s treatment pond and, ultimately, to Andover’s sanitary sewer.

Volatile organic compounds drawn from pit are used in blended fuel. That left the problem of the VOCs in the hazardous waste pit to be dealt with. After two years of study, the MPCA selected a technology known as a C3 (cryogenic, compression and condensing) vapor-extraction system to deal with this problem.

“We wanted a technology that would be able to recover the VOCs from the pit and convert them to something that could be productively used with minimal discharge of pollutants to the atmosphere,” Moeger said. “The beauty of this technology is that the VOCs, which have high Btu content, can be recycled or reused in a fuel-blending process.”

The C3 vapor-extraction system at the WDE Closed Landfill began operating Feb. 1.

Moeger explained how the C3 system works: “The VOC vapors we extract from the pit are compressed and cooled to minus 40 degrees F. and then pumped through a proprietary processing system that turns them into a dense, heavy liquid. The condensed product is then transferred to a 4,000-gallon above-ground storage tank, where it is kept until it can be hauled to a licensed facility in Eau Claire, Wis. There the product is blended into a fuel that is burned in the boilers of cement kilns across the country.”

Moeger looks forward to a time when there will no longer be a hazardous waste pit at the WDE Landfill: “Our ultimate goal is to excavate the contents of the pit sometime in the future and ship the hazardous wastes to a licensed facility outside Minnesota. Using this system, we’ll be able to stabilize the pit by removing as much of the hazardous vapors as possible, which will lessen the danger to the workers who will excavate the pit.”

Moeger said the C3 system has already recovered more than 2,000 gallons of liquid product, in his opinion, a “very exciting number that shows how effective it is.”

Persons who want more information about the operation and remediation of the WDE Landfill may contact John Moeger at the MPCA (phone 651-757-2574, email john.moeger@state.mn.us). More information is available also in an MPCA fact sheet, Waste Disposal Engineering Closed Landfill update (http://www.pca.state.mn.us/index.php/view-document.html?gid=2444).

Broadcast version:

The Minnesota Pollution Control Agency is using new technologies to make the Waste Disposal Engineering Landfill in Andover a better neighbor.

At the landfill, an active gas-extraction system efficiently draws landfill gases from the buried mixed municipal solid waste. The landfill gases, mainly methane, are burned in an enclosed flare on site, thereby preventing the possible migration of these potentially dangerous gases to nearby homes and sewers.

Since the W-D-E Landfill is the only landfill in Minnesota that was ever permitted to accept hazardous wastes, the M-P-C-A must also deal with problems associated with the landfill’s hazardous waste pit.

Over the years, leakage from the containers of a variety of hazardous substances, such as used paints and solvents, stored in the hazardous waste pit dissolved the floor of the pit. Last spring, the M-P-C-A found polychlorinated biphenols, or P-C-Bs, in groundwater that was being pumped from beneath the pit into the landfill’s treatment pond. The agency stopped pumping groundwater from beneath the hazardous waste pit until it had installed a granulated activated carbon treatment system that removes the P-C-Bs before the extracted groundwater is sent to the treatment pond.

Disposing of volatile organic compounds, or V-O-Cs, in the hazardous waste pit was also a challenge. The M-P-C-A solved this problem by installing a system that removes these gases from the pit, cools, compresses, and condenses them into a B-T-U-rich liquid. This is stored in a tank at the landfill until it can be hauled to a licensed facility in Wisconsin that uses it in a blended fuel that’s burned in cement kilns across the country.

Eventually the hazardous waste pit at the W-D-E Landfill will be excavated and the remaining hazardous wastes will be shipped to a licensed disposal facility outside Minnesota. Removing the V-O-Cs from the hazardous waste pit will make the pit less dangerous for workers who will excavate it.

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