2D Mass Transport Simulation for Evaluation of Groundwater Contamination around an Oxidation Pond in Eastern China

Oxidation ponds are widely used for wastewater treatment in developing countries because of the relative simplicity and low operating costs. Thanks to the permeability of the soil layer at the bottom of ponds, contaminants can go into groundwater from wastewater during its residence period. In this study, about 14 shallow groundwater samples were collected from pumping wells around an oxidation pond in eastern China. The concentrations of chloride, nitrate and permanganate values significantly changed comparing with the historical data, and they correlated with the distances from sampling wells to the pond. Chloride, the concentration of which increased mostly on average, was selected as the plane 2D solute transport simulation factor to evaluate the impact of the oxidation pond on shallow groundwater. The result indicated that the iso-concentration contour of 250 mg/L would extend up to 1.13km from the pond to southwest in 2019, which means the influence would reach to a village after 10 years. The conclusion drawn by Zhao(1992) was verified during the process of calibration that the effective porosity has a significant influence on non-reactive contents transport in groundwater. In order to evaluate the contamination comprehensively, the migration and degradation of reactive contents, such as COD, nitrate and ammonia nitrogen, should be researched in the future.