The Effects of Aging and Sorbent Decomposition on the Bioavailability of Toluene and Xylene in Solid WasteEPA Grant Number: R827131
Title: The Effects of Aging and Sorbent Decomposition on the Bioavailability of Toluene and Xylene in Solid Waste
Investigators: Barlaz, Morton A. , Knappe, Detlef R.U.
Institution: North Carolina State University
Current Institution: North Carolina State University
EPA Project Officer: Lasat, Mitch
Project Period: October 1, 1998 through September 30, 2001 (Extended to March 31, 2002)
Project Amount: $425,000
RFA: EPA/DOE/NSF/ONR Joint Program on Bioremediation (1998) RFA Text | Recipients Lists
Research Category: Land and Waste Management , Hazardous Waste/Remediation
The overall objective of this research is to develop an understanding of factors controlling the bioavailability and fate of organic contaminants sorbed to components of municipal solid waste (MSW). Specific objectives are to: (1) estimate the expected distribution of sorbed contaminants in MSW by measuring the sorptive capacity of the dominant organic refuse components in fresh and biodegraded form, (2) determine whether the sorptive uptake of organic contaminants in MSW is reduced in the presence of leachate as a result of organic contaminant binding by dissolved organic macromolecules, (3) determine the impacts of aging and leachate composition on contaminant desorption rates, (4) compare rates of desorption and biodegradation to determine whether desorption limits bioavailability, (5) determine the effects of refuse decomposition on bioavailability, and (6) identify whether humification is an important sequestration mechanism for aromatic xenobiotics in solid waste.
We hypothesize that kinetically limited sorption/desorption processes and humification control the bioavailability and leaching of organic contaminants in landfills and that humification may be an endpoint in the fate of toluene and xylene. Our hypotheses are supported by our ongoing work on the biodegradation, sorption, and humification of selected organics, including toluene, in refuse excavated from a Superfund site.
Initially, the major organic components of MSW (2 paper types, synthetic food/yard waste, 2 plastic types, a mixture) will be characterized (pore size distribution, BET surface area, elemental analysis). Single-solute batch isotherms will then be measured for each material, and additional tests will be conducted to measure the importance of acid-phase and methane-phase leachate on contaminant sorption. A series of tests will then be conducted with each material in both fresh and anaerobically decomposed form to measure the effect of contaminant aging and refuse decomposition on contaminant desorption, biodegradation, and humification. Finally, live and abiotic column studies will be conducted to extend the research to a dynamic system in which physical, chemical, and biological processes occur concurrently.
This research will provide fundamental information on the effects of contaminant aging and refuse decomposition on bioavailability. In addition, the importance of biological and abiotic humification for contaminant sequestration will be documented. This research will provide information on how contaminants may be expected to behave in landfills over long periods and suggest whether their concentrations in leachate may be expected to increase, decrease or remain stable over time. Our results will support the development of models to predict contaminant fate in landfills. Such models are essential to project contaminant concentrations in leachate, which can then be used to assess the risk to downgradient receptors using groundwater fate and transport models.
Improvement in Risk Assessment or Risk Management: Priority pollutants are being released to groundwater from thousands of unlined landfills, and the EPA must develop strategies to manage these sites in a manner that is both cost-effective and protective of the environment. This research will provide information on contaminant release over time that can be used to evaluate the long-term risk to downgradient receptors and the level of engineering intervention required.