A simple, cost-effective system for treating leachate may be on the horizon. A Louisville, Ky., landfill currently is testing microbial mesh squares, or mats, with blue-green algae that can transform ammonia and degrade organic compounds while isolating heavy metals, according to scientists at Clark Atlanta University in Georgia.
Although the technology could have many environmental applications, landfill leachate treatment appears to be the most immediate use, according to the scientists.
Since the mats are durable and relatively inexpensive to produce, extensive maintenance and controls reportedly are not necessary. The Louisville pilot, which is operated by Waste Management Inc., Oakbrook, Ill., is currently in scale-up planning and is expected to reduce both capital and operating costs at the landfill. Once the pilot project is operating (see diagram), it will produce an effluent for discharge under a NPDES permit.
To date, the mats have removed radionuclides from water in a laboratory pump-and-treat system demonstration. Unlike some conventional biological treatment systems, the mats are not limited to specific contaminants. Other advantages include tolerance for a wide range of pH, salinity and temperature. Because of the multi-species nature of the constructed mats, they offer a wide variety of chemical zones and biological mechanisms for the removal and transformation of both organic and inorganic wastes, according to the scientists.
This new technology has been field-tested in three applications, including a Tennessee Valley Authority coal mine drainage in Alabama and a Bureau of Mines drainage site in Colorado. In the Alabama field test, the mats reportedly removed manganese at five times the conventional rates for almost three years.
In addition, the new technology is being used in a bioreactor to treat a contaminated site in Maryland. This system serves as an alternative to treatment with activated carbon. Although the removal rates of the mats and activated carbon are similar, the constructed mat reportedly leaves no residual contaminant for further treatment. Volatility testing will help determine the treatment's efficiency.
As Subtitle D requirements expand the number of landfills that must now collect and treat leachate, technology options such as the microbial mats may help ease the burden on landfill owners and operators.