Strategies for Simulation, Design, and Management of Solid Wastes Disposal Sites as Landfill Bioreactors

Abstract

The principal objective of this paper is to introduce strategies for modeling, designing, and operating landfills with leachate recirculation. A numerical model capable of predicting leachate quantity and quality, as well as biogas generation at solid wastes is presented for both single-pass leaching and leachate recirculation. The model, PITTLEACH, is based on fundamental relationships among hydrologic, hydraulic, physical/chemical, and biological processes of landfill leaching and stabilization. The principles of unsaturated flow and contaminant transport in porous media were used to predict leachate movement and landfill stabilization in three general areas: moisture distribution and flow, leachate organic characteristics, and overall methane gas production. The microbially mediated processes of solid waste decomposition in landfills were simulated in terms of solublization of solid organic constituents (hydrolysis), acid formation (acidogenesis), and methane fermentation (methanogenesis). The design code and configurations of landfill leachate recirculation were based on the fundamentals of fluid dynamics and applications of Darcy's law, with the leachate recirculation simulation including a surfacial cascade-type distribution network of perforated pipes and a system of vertical recharge wells with horizontal interconnectors. The operational strategy of the leachate recirculation is also presented and discussed.