垃圾渗滤液对地下水水质影响的数值模拟预测——以冕宁县漫水湾生活垃圾填埋场为例

APPLICATION OF NUMERICAL SIMULATION TO EVALUATE THE IMPACT OF LEACHATE ON THE GROUNDWATER QUALITY: A CASE STUDY OF MANSHUIWAN LANDFILL IN MIANNING COUNTY

垃圾填埋场的渗滤液渗漏是周围地下水环境的主要威胁之一。以冕宁县漫水湾垃圾填埋场为例,预测垃圾渗滤液对浅层地下水环境的危害程度,通过Modflow和MT3D模拟分析了正常工况和事故工况条件下渗滤液中COD和NH_3-N在地下水中的运移过程。结果表明:在垃圾场运行中,地下水中污染物浓度增加并向下游扩展。正常工况下,污染物NH_3-N的最大迁移距离为141 m,最大浓度为3.5 mg/L;事故工况下,污染物NH_3-N的最大迁移距离为290 m,最大浓度为7.0 mg/L。随着污染物迁移距离的扩大,污染物浓度开始下降。垃圾场封场20年后,渗滤液中ρ(COD)和ρ(NH_3-N)分别为0.06,0.006 mg/L。

The landfill has been recognized as one of the major threats to the surrounding groundwater environment due to the emission of leachate. In this paper,the Manshuiwan Landfill in Mianning County as the research object,in order to evaluate the impact of leachate on the groundwater environment,the Modflow and MT3 D were used to simulate the transportation processes of COD and NH3-N in groundwater due to the emission of leachate under the normal operation and accident conditions. The results showed that the concentration of pollutants in groundwater increased and the pollutants transported downstream during the operation of landfill. Under the condition of normal operation,the maximum concentration and migration distance of pollutants was 3. 5 mg/L and 141 m,respectively. Under the accident condition,the maximum concentration and migration distance of pollutants was 7. 0 mg/L and 290 m,respectively. Then the concentration of pollutants decreased with the transportation. Tuenty years later after the landfill closed,the concentration of COD and NH3-N decreased to 0. 06 mg/L and 0. 006 mg/L,respectively. This study has important practical significance to evaluate of groundwater environment around the landfill.