Dynamic Water Balance and Geotechnical Stability of BioReactor Landfills Investigator: Krishna R. Reddy, Department of Civil and Materials Engineering Prime Grant Support: NSF, EREF, CReeD & Veolia Environment • In conventional “dry tomb” landfills, waste biodegradation is very slow because of the lack of adequate moisture. These landfills require long-term monitoring for any potential environmental problems (regarding the water and air pollution). • The leachate re-injection or addition of selected liquids to landfill waste (bioreactor) has potential to accelerate waste decomposition and settlement, but will affect the waste properties and slope stability. • Urgent need exists to understand the moisture distribution in the waste and its effects on waste biodegradation and properties as well as geotechnical stability of landfills. • Monitoring several bioreactors to monitor moisture content (with geophysics), biogas and leachate production and quality, waste degradation and properties, and waste settlement. • Developing a mathematical model for: • Understanding the spatial and temporal variations of moisture distribution and landfill settlement • Incorporating change in waste properties caused by decomposition with respect to time • Understanding the influence of leachate recirculation on landfill settlement and slope stability • Optimizing leachate recirculation system designs • Field monitoring at bioreactor landfills is in progress. Studies conducted to date show that dynamic moisture variations within the waste mass during leachate recirculation can be characterized with geophysical methods (electrical resistivity tomography). • Coupled flow and mechanical modeling is in progress for different bioreactor landfill conditions. Preliminary results show that the coupled flow and mechanical modeling can predict both waste moisture and settlement with time under different operational conditions. • Field monitoring and modeling results will be utilized to develop design and monitoring guidelines for bioreactor landfills.