Mathematical modeling of waste heterogeneities in leachate recirculating landfills

Leachate recirculation is an emerging technology for the on-site management of leachate and enhancement of waste degradation. The benefits of leachate recirculation have been well documented by a variety of researchers. However, little work has addressed the hydrodynamic characteristics of the recirculating landfill, specifically the effect of leachate flow rate and waste characteristics upon leachate routing. This paper presents the results of mathematical modeling of homogeneous and heterogeneous waste masses. Leachate was applied via a horizontal infiltration trench, one of the most commonly employed leachate application methods. A modified form of SUTRA, a USGS unsaturated flow and transport model, was used to simulate the forces driving liquid movement. Modeling of both homogeneous and heterogeneous waste masses was conducted. The homogeneous waste mass was modeled using constant permeabilities of 10-3 and 10-4 cm/s. The heterogeneous waste mass was modeled using normal, and exponential probability density functions with average permeabilities of 10-3 and 10-4 cm/s. Leachate was applied intermittently, eight hours per day, for an average rate of 4 m3/day/m of trench. A comparison of the results with respect to moisture distribution is presented