Grantee Research Project Results
2001 Progress Report: Closing the Gaps in the Regulation of Municipal Solid Waste Landfills: Defining the End of the Post-Closure Monitoring Period and the Future Stability of Leachate Recirculation Landfills
EPA Grant Number: R827580Title: Closing the Gaps in the Regulation of Municipal Solid Waste Landfills: Defining the End of the Post-Closure Monitoring Period and the Future Stability of Leachate Recirculation Landfills
Investigators: Barlaz, Morton A. , Gabr, Mohammed A. , Mohammed, P. E.
Institution: North Carolina State University
EPA Project Officer: Chung, Serena
Project Period: September 13, 1999 through September 12, 2000
Project Period Covered by this Report: September 13, 2000 through September 12, 2001
Project Amount: $145,213
RFA: Futures: Detecting the Early Signals (1999) RFA Text | Recipients Lists
Research Category: Water , Sustainable and Healthy Communities , Land and Waste Management , Aquatic Ecosystems , Ecological Indicators/Assessment/Restoration
Objective:
The objective of this research project is to develop and present a plan to establish the scientific basis for the appropriate regulation and operation of municipal solid waste (MSW) landfills through the post-closure monitoring period, including landfills that utilize leachate recirculation. Issues to be addressed include water management, increased methane emissions and settlement, and waste/cover stability. Specific objectives are to:
· Review data on the composition of leachate associated with well-decomposed refuse and develop criteria for the identification of stable leachate.
· Estimate the quantity and quality of water present in a landfill at the end of the post-closure monitoring period and subsequent leachate generation rates.
· Develop and evaluate strategies for the management of methane emissions that will occur after the end of the post-closure monitoring period.
· Identify techniques for the measurement of geotechnical properties of MSW over time, in terms of compressibility and strength.
· Review models of material compressibility that include biological decomposition and provide a rational analysis of cover system configurations in landfills that utilize leachate recirculation.
A comprehensive research plan has been formulated from which the scientific basis required to manage and regulate landfills in the future can be developed. The plan encompasses a critical review and analysis of existing data and models that describe leachate composition and production, gas generation, geotechnical properties, waste compressibility, waste strength, and cover system stability.
Progress Summary:
Progress has advanced on several fronts, including a literature review of leachate composition data, review and application of methods for evaluating liner efficiencies, estimation of the quantity and quality of leachate from landfills containing well-decomposed refuse, and a review of the mechanics of waste compressibility and strength. In addition, a limited testing program has been developed to measure compressibility and strength properties of MSW while taking into account mechanistic and biological contributions. A model to provide rational analysis of waste settlement in landfills utilizing leachate recirculation is proposed.
Issues addressed due to the increased use of leachate recirculation include water management, gas generation and increased methane emissions, compressibility and strength properties of waste, settlement, cover stability, and cover configuration. Based on a critical review and analysis of existing data, as well as a limited testing program, the following findings are advanced:
· For leachate to safely be released into the environment, certain criteria should be met: (1) the leachate should not contain high concentrations of organics, ammonia, or heavy metals; and (2) the leachate should not exhibit toxicity to organisms in the ecosystem. In addition, the landfill should not be releasing gas that may cause contamination of groundwater supplies, odor nuisances, or explosions. Methodologies to determine acceptable criteria for each parameter have been illustrated.
· The use of organic indicators in leachate is not adequate to define stability.
· Ammonia may be the most significant, long-term pollutant in landfill leachate.
· Heavy metal concentrations in landfill leachate are typically below drinking water standards. Further research is needed to evaluate whether there is any chance of a metals release as the oxidation-reduction potential of a landfill increases.
· Leachate production data from landfills that have received a final cover are needed.
· Landfills do not contribute significant nutrient loads compared to wastewater treatment plants on a population equivalent basis.
· The degradation of MSW over time, and associated settlement, take place at a faster rate in bioreactor landfills. The breakdown of particles changes the waste strength characteristics and adds a compressibility component in these types of landfills as compared to conventional "entombed" cells. There are no data on the strength properties of waste specific to bioreactor landfills. The lack of such data may lead to catastrophic failure of waste slopes and the compromise of cover system integrity and stability.
· A comprehensive model for settlement analysis of bioreactor landfills should take into consideration the increase in void ratio due to solid-to-gas conversion, changes in the degree of saturation, density changes, as well as the physical changes in particle sizes and distribution. As the solid mass is converted to landfill gas in bioreactor landfills, the void ratio increases, hydraulic conductivity decreases, and the degree of saturation increases, which leads to increases in the compressibility characteristic of the waste.
· The issue of adopting Terzaghi's 1-dimensional theory of consolidation for settlement calculations has to be revisited. A mechanistic approach based on evaluating the variation of the waste stiffness as a function of decomposition and taking into account the organic content, moisture content and decomposition profile with depth should be employed to estimate settlement during the early stages of decomposition. In later stages, such a mechanistic model can be coupled with Terzaghi's model to evaluate settlement. Challenges arise from the fact that methods of settlement calculation as well as the properties of each waste sublayer will change with time as a function of decomposition.
· The configuration of the cover system for bioreactor landfills should be reconsidered. As leachate recirculation is implemented, waste decomposition will be enhanced, which will lead to large differential settlement and the imposition of unacceptable tensile strains on the cover system components. One thought is to hold placement of the final cover until stability is achieved. Interim covers for odor control and gas collection can be implemented.
Workshop on the Future of Landfills After Waste Stabilization. Representatives of the regulated community of landfill owners, operators and designers, regulators, and leading researchers were invited to a workshop on the long-term stabilization of landfills. The workshop was held in conjunction with the 5th SWANA Landfill Symposium in Austin, TX, in June 2000. The workshop introduced participants to issues related to: (1) determining an appropriate end for the post-closure monitoring period; (2) leachate recirculation; and (3) waste properties and how they are affected by leachate recirculation. After both of the project investigators gave their presentations, a panel of experts participated in a discussion and exchange of information. Approximately 150 people were in attendance.
References:
Bonaparte R, Daniel D, Koerner RM. Assessment and recommendations for optimal
performance of waste containment systems. U.S. Environmental Protection Agency,
Cincinnati, OH (accepted for publication).
Burton SAQ, Watson-Craik IA. Ammonia and nitrogen fluxes in landfill sites: applicability to sustainable landfilling. Waste Management and Research 1998;16(1):41-53.
Chain EWK, DeWalle FB. Evaluation of leachate treatment: volume I, characterization of leachate. United States Environmental Protection Agency, Report No. EPA-600/2-77-186a, Cincinnati, OH, 1977.
Christensen TH, Kjeldsen P, Bjerg PL, Jensen DL, Christensen JB, Baun A, Albrechtsen HJ, Heron G. Biogeochemistry of landfill leachate plumes. Applied Geochemistry (accepted for publication).
Gabr MA, Valero SN. Geotechnical properties of solid waste. ASTM, Geotechnical Testing Journal 1995;18(2):241-251.
Giroud JP, Badu-Tweneboah K, Bonaparte, R. Rate of leakage through a composite liner due to geomembrane defects. Geotextiles and Geomembranes 1992;11:1-28.
Kruempelbeck I, Ehrig HJ. Long term behavior of municipal solid waste landfills in Germany. Presented at the 7th International Waste Management and Landfill Symposium, Sardinia, Italy, October 4-7, 1999.
Kruempelbeck I, Ehrig HJ. Long-term behavior of municipal solid waste landfills in Germany. In: Proceedings of the 7th International Waste Management and Landfill Symposium, Sardinia, Italy, October 4-7, 1999, Volume I, pp. 27-36.
Murray GB, McBean EA, Sykes JF. Estimation of leakage rates through flexible membrane liners. GMWR, Fall 1995, pp. 148-154.
Pohland FG, Harper SR. Critical review and summary of leachate and gas production from landfills. United States Environmental Protection Agency, Cincinnati, OH, EPA/600/2-86/073, 1985.
Robinson HD. A review of the composition of leachates from domestic wastes in landfill sites. A Report for the UK Department of the Environment, Reference: DE0918A/FR1, 1995.
Reinhart DR, Grosh CJ. Analysis of Florida MSW landfill leachate quality. Florida Center for Solid and Hazardous Waste Management, Report # 97-3, 1998.
Smith DC, Sacks J, Senior E. Irrigation of soil with synthetic landfill leachate-speciation and distribution of selected pollutants. Environmental Pollution 1999;106:429-441.
Future Activities:
The major objectives and focus for the subsequent reporting period will include the conclusion of the limited testing program to discern primary, creep, and biological compressibility of waste, the development of a conceptual cover system configuration, and the preparation of additional manuscripts for publication.
Journal Articles on this Report : 1 Displayed | Download in RIS Format
Other project views: | All 7 publications | 2 publications in selected types | All 2 journal articles |
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Type | Citation | ||
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Kjeldsen P, Barlaz MA, Rooker AP, Baun A, Ledin A, Christensen TH. Present and long-term composition of MSW landfill leachate: a review. Critical Reviews in Environmental Science and Technology 2002;32(4):297-336. |
R827580 (2000) R827580 (2001) R827580 (Final) |
Exit Exit |
Supplemental Keywords:
compressibility, landfills, leachate, liners, municipal solid waste, bioreactors, settlement, stability., RFA, Scientific Discipline, Waste, Municipal, Environmental Chemistry, Hazardous Waste, Ecological Risk Assessment, Hazardous, Exp. Research/future, geotechnical properties, emerging environmental problems, hazardous waste disposal, hazardous waste management, leachate recirculation landfills, municipal solid waste landfill regulations, landfill operation, methane emissions, municipal waste, decomposition, municipal solid waste landfills, post-closure monitoring period, environmental policy, landfills, solid waste landfills, municipal solid waste regulations, RCRA, water managementRelevant Websites:
http://www4.ncsu.edu/~barlaz/post_closure/ Exit
Progress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.