A sustainable solution for dealing with landfill leachate has yet to be devised and implemented, although landfills continue to be used as a primary means of waste disposal throughout the United States. The long-term management of landfill leachate remains a major concern, even after the closure of a landfill site. The need for developing new, low-cost and sustainable solutions for landfill leachates is paramount for assuring the continued management of solid waste and environmental quality. All current methods of leachate treatment are energy and fiscally intensive. Algal bioremediation may provide effective, low-cost, on-site leachate treatment with major benefits over current methods.
Algae bioremediation can reduce pollutants (e.g. ammonia, chemical oxygen demand) and simultaneously generate algae biomass as a by-product, which is of current interest in the production of biofuels (e.g. biodiesel, bio-jet fuel). Because algae harvest solar energy for their metabolic processes, on-site algae remediation may be significantly more sustainable than the conventional method of tanker transport to wastewater treatment facilities. This research project examined the basic biology of algae cultivation within landfill leachate and developed cultivation techniques specifically for the application of algae-based landfill leachate bioremediation. Two strains of algae, isolated from the Alachua County Southwest Landfill in Archer, FL, were characterized. Both algae were inhibited by undiluted leachate from the Alachua County Southwest Landfill at concentrations greater than 10%. The isolated strain of Scenedesmus had a greater tolerance to landfill leachate than the isolated strain of Chlorella. Through empirical testing with pure salts, the primary algae toxicant within landfill leachate was identified as free, unionized ammonia. Methods for algae cultivation, which avoid leachate inhibition by unionized ammonia were developed. Furthermore, leachates from the Citrus County Landfill and the Polk County North Central Landfill were examined to test the potential applicability of algae bioremediation to leachates from other Florida landfills. Laboratory tests demonstrated that algae bioremediation effectively remediated landfill leachate by reducing total ammoniacal nitrogen and chemical oxygen demand by 99.4 and 75.5%, respectively. In the second year of the project, research was continued to determine the bioremediation potential of algae using different landfill leachates and to evaluate the potential for biofuel production from the resultant algal biomass. Algal cultivation in landfill leachate requires minimization of unionized ammonia and comprehensive mixing. Therefore, techniques developed for algae cultivation in landfill leachate added CO2 into an air-sparging system to regulate the pH and simultaneously mix the algae culture, exposing all cells to light. Also, the application of nitrifying bacteria provided an increase in remediation ability and algal productivity within landfill leachate. The Scenedesmus organism being used as the candidate organism for landfill leachate bioremediation was identified by time-domain nuclear magnetic resonance (TDNMR) and conventional solvent extraction as having >35% total lipid content and >30% neutral lipid content by dry weight, which represents a significant biofuel potential. This project has benefits for landfill operators by demonstrating the potential of algae bioremediation of landfill leachate as a novel alternative for sustainable landfill leachate management in the State of Florida.

 

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