Transport of ammonia nitrogen for groundwater pollution control in an informal low-permeability landfill site

Abstract

In informal landfills, leachate leaked into the underlying soil and groundwater has been gaining increasing attention. Recently, an informal low-permeability landfill site in northern China was investigated in detail, and it was found that the groundwater was contaminated by leachate. A groundwater flow and contamination transport model was developed using FEFLOW to forecast contaminant transport and evaluate feasible pollutant control schemes. In this model, good matches between the simulated and observed groundwater level and good matches between the simulated and observed concentration of ammonia nitrogen show that the established model can reproduce the process of groundwater movement effectively. Three kinds of schemes, including natural conditions, pollution source removal, and pump and treatment, were simulated, and the results were compared. The results showed that, under natural conditions, the pollution does not travel far horizontally and vertically. Removal of pollution sources has little effect on the concentration of ammonia nitrogen in groundwater over a period of 100 years. The pump and treatment system can effectively remove high concentrations of ammonia nitrogen in the groundwater of the landfill site, with a maximum decline of over 90%. Therefore, the pump and treatment method may be valid for short-term soil and groundwater remediation.