Modeling of Redox Zonation Downgradient of Landfill Sites

The release of landfill leachate, with its load of organic material, gives rise to a succession of redox zones in the contaminated aquifer. Indigenous microbial populations can couple the oxidation of the organic compounds to the reduction of a number of electron acceptors. The sequence of TEAPs (terminal electron acceptor processes): aerobic respiration, denitrification, Mn(IV)-reduction, Fe(III)-reduction, sulfate-reduction and methanogenesis is determined by the energy yield of each redox reaction. This study presents a kinetic description of these processes using the multispecies reactive transport code RT3D. A user-defined kinetic was developed in order to take into account the principal biogeochemical processes that are likely to occur downgradient of a landfill. This model was tested on simple batch, 1D and 2D problems before applying to a field data set collected at a mixed municipal and industrial landfill site located close to the city of Turin in Italy.