Effectiveness of drainage blanket for leachate recirculation in bioreactor landfills

Hanumanth S. Kulkarni, Krishna R. Reddy

In the proceedings of: GEO2011: 64th Canadian Geotechnical Conference, 14th Pan-American Conference on Soil Mechanics and Geotechnical Engineering, 5th Pan-American Conference on Teaching and Learning of Geotechnical Engineering

Session: Geoenvironmental Engineering

ABSTRACT: Leachate recirculation in a bioreactor landfill helps distribute the moisture, nutrients and microbes required for the enhanced biodegradation of MSW. The moisture distribution is dependent on the leachate recirculation system (horizontal trenches, vertical wells and drainage blankets), hydraulic properties of MSW and leachate injection rate. The main objective of this paper is to evaluate the effect of leachate injection rate and the saturated hydraulic conductivity on moisture distribution using drainage blanket as leachate recirculation system. A two-phase unsaturated flow model is elative permeabilities computed by van Genuchten function. The model is validated based on published laboratory experiments and mathematical modeling studies. A typical bioreactor landfill cell is selected with a single drainage blanket, and leachate injection is performed continuously until steady-state conditions are achieved. The dynamic changes in the wetted width, wetted MSW area, saturation levels, pore water distribution and outflow into leachate collection system are determined under different hydraulic properties of MSW and leachate injection rates. It is shown that as the hydraulic conductivity decreases, the wetted area increases slowly, but excessive pore water/gas pressures are generated. Higher leachate injection rate under low MSW permeability conditions shows the possibility of leachate migration in both upward and downward directions. Thus, leachate injection should be properly controlled as the permeability of MSW decreases with increased degradation.

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