Reactive transport modeling of clogging in landfill leachate collection system

Abstract

The leachate collection system (LCS) is an important component of the barrier system of landfills. LCS in China is subjected to serious clogging due to the more degradable organics and water in the municipal solid wastes (MSWs). To evaluate the service life of LCS, a reactive transport model is developed to simulate the biogeochemical clogging in LCS. The hydrolysis reactions of degradable components and the kinetic calcium leaching process are taken into account to calculate the generation of VFAs and Ca²⁺ in MSW. The ionization equilibrium of volatile fatty acids (VFAs), dissolution equilibrium of calcium carbonate, and the kinetic biodegradation reactions of VFAs are considered to simulate the pH variation, calcium carbonate precipitation, and biofilm growth during clogging. By comparing with the laboratory experiment data, the proposed numerical model shows the ability to accurately predict the decrease of the porosity in LCS. Parameter analysis indicates that the decrease of the mass fraction of degradable components in MSW, leachate irrigation rate, and calcium ion leaching rate can significantly extend the service life of LCS. The proposed reactive transport model can be the methodological support for the design and service life prediction of leachate collection systems in landfills.