Study on the effect of municipal solid landfills on groundwater by combining the models of variable leakage rate, leachate concentration, and contaminant solute transport.

The landfill with low economic cost and technical barrier has become a popular option for municipal solid waste treatment, but it is likely to seriously pollute groundwater by solute leaching. In this study, the pollutants concentration model, leakage rate model, and the solute transport model were coupled to investigate the effect of municipal solid waste landfill on groundwater quality. Major results obtained are, (1) the leakage rate of leachate differs significantly among the landfilling stage, covering stage and completely covered stage as the leachate depth varies with the infiltration rainfall. The contact condition between HDPE and CCL was found to be a key factor in determining the leakage rate of leachate. Ensuring good connection between HPDE and CCL is thus critical in protecting groundwater from being polluted by landfill. (2) The NH3-N as a proxy for organic pollutants was generated via the degradation process, and Cl- as a proxy for inorganic pollutants is a leachable fraction of mobilized substances. The concentration of Cl- is higher than that of NH3-N before 7600 days, then the concentration of NH3-N becomes roughly stable while that of Cl- continues to decrease. (3) The load of NH3-N as a proxy for organic pollutants declines linearly downwards before the completely covering stage. The load of Cl- as a proxy for inorganic pollutants increased during the first five years, and then declined. (4) In the case study, the path of maximum pollutants concentration is perpendicular to the groundwater contour, and the maximum pollutants concentration has two peaks, occurring on 7106 days and 11,554 days, respectively. The change laws of maximum pollutants concentration are similar for different connections between HPDE and CCL.