Modelling landfill leachate-induced clogging of field-scale test cells (mesocosms)

Abstract

A two-dimensional fluid flow and reactive transport model, BioClog, created to predict clogging in landfill leachate collection systems is used to calculate the clogging of gravel and treatment of leachate as it flows through the gravel in two real-scale experimental cells, called mesocosms, which represent the portion of a landfill drainage layer adjacent to a landfill collection pipe. These tests were conducted using real-time flows of landfill leachate and were run for about 6 and 12 years. The model computes spatial and temporal changes in clog quantity and composition. An empirical relationship predicts changes in hydraulic conductivity, and a variable mesh technique allows the surface to be free and dependent on calculated hydraulic heads. Calculated porosity change, effluent chemical oxygen demand (COD), and calcium concentrations, along with porosity and clog film thickness at termination are compared with the observed values and found to be in reasonable agreement given the variability and uncertainties associated with these processes.