Although the concept of aerobic (with oxygen) degradation is quite simple, it’s difficult and complex to establish and maintain in a landfill environment. State-of-the-art control and monitoring equipment is required, as well as a keen understanding of microbiology. Aicen, South Carolina-based Environmental Control Systems Inc. (ECS) possesses these resources. Along with aerobic landfill technology, the company uses a patented process to stabilize waste faster than traditional anaerobic methods.
It can take up to 30 years for the organic compounds in a landfill to break down naturally. The ECS method injects air and moisture directly into the waste and thereby reduces the degradation period to between just one and three years. Along the way it produces non-toxic material that can be mined, recovered or reused. In addition to improved environmental performance, economic benefits may be derived from increased “airspace” that eliminates the need for costly expansions, new permits and even new facilities.
The in-situ method manipulates indigenous bacteria in the waste under certain set conditions. Automated continuous monitoring shows that the production of methane and volatile organic compounds (VOCs) is greatly reduced (by more than 90 per cent in less than four weeks after complete system start-up). In addition, the heat that’s generated naturally by this process (up to 60 degrees Celsius) evaporates much of the moisture and potential odour to the atmosphere.
Key steps in the ECS method include:
locating wells to inject air and moisture;
increasing and maintaining moisture (from 40 to 70 per cent);
maintaining temperature to 55 to 65 degrees Celsius to sustain degradation and eliminate pathogens; and,
continuously monitoring all elements.
Since 1997, ECS staff has successfully operated aerobic systems in landfills in Georgia and South Carolina where municipal solid waste was rapidly stabilized. The U.S. EPA recognizes this technology as “an emerging ‘Tier II’ (landfill gas) control technology” that “is expected to become a prime candidate technology for landfills in the U.S. and elsewhere that can not generate (landfill gas) in sufficient quality or quantity to economically recover the associated energy.”
On January 13, 2000, the company was awarded a US$650,000 contract by Williamson County, Tennessee to implement its technology at the seven-acre Subtitle D Landfill near Franklin. The purpose of the project was to eliminate the costs to treat and dispose of the leachate produced at the landfill. Before implementation of the aerobic bioreactor the landfill generated 720,000 litres of leachate each month and paid US$0.15 per gallon for disposal and treatment.
“The leachate is consumed onsite, and methane production decreased by more than 98 per cent.”
With approval by the Tennessee Department of Environment and Conservation, the project was initiated.
Today the leachate is consumed onsite, and methane production has decreased by more than 98 per cent. The site will eventually enjoy additional airspace. In fact, the landfill will save over $650,000 in offsite leachate treatment costs over the next two years.
More importantly, ECS is providing these services on a pay-for-performance basis. If the aerobic bioreactor fails to consume the leachate ECS will not get paid. To date, all leachate has been consumed.
Based on the success of this project other landfills have started to integrate this technology. A landfill bioreactor program is currently underway at the 12-acre New River Landfill (Subtitle D) near Gainesville, Florida and ECS has also expanded the Columbia
County Baker Place Road Landfill near Augusta, Georgia into its third phase.
Connie Vitello is editor of this magazine.