基于数值模拟的某纳污坑塘地下水砷污染修复技术设计

Design of Remediation Technology for Arsenic Pollution of Groundwater in a Pollutant Pond Based on Numerical Simulation

某典型纳污坑塘地下水砷污染严重,直接威胁周边农业地区和下游浅湖的生态环境安全。拟采用“抽出-处理+原位化学氧化含水层镀铁”联合修复技术,分别针对地下水砷污染重度污染区和中低污染区进行分区分阶段修复。对重度污染区,采用Visual MODFLOW软件建立地下水流和溶质运移模型,模拟并预测抽出-处理技术的修复效果,模拟结果表明:按中部抽水井抽水、外缘注水井注水的井群布设方案进行分阶段抽注,230d后地下水中砷的去除率达78%。对中低污染区,向含水层中交替注入FeSO4溶液和NaClO溶液进行原位化学氧化含水层镀铁除砷,试验结果和除砷机理表明:通过发生氧化、吸附和共沉淀反应,5次抽注循环后地下水中砷的去除率为80%,但存在地下水中砷浓度反弹现象。本研究可为其他砷污染地下水的修复提供工程经验和参考依据。

The groundwater arsenic pollution occurs in a part of typical pollutant pond which seriously threatens the safety of the ecological environment of surrounding agricultural areas and downstream shallow lakes.This paper intends to use the combined technology of“pumping-treatment+in-situ chemical oxidation of aquifer iron plating”for heavily polluted areas and low-pollution areas for partitioned remediation in stages.For heavily contaminated areas,the groundwater flow and solute transport models are established using Visual MODFLOW to simulate and predict the groundwater remediation performance,and the results show that when central pumping wells and outer injection wells run for 230days in stages,the arsenic removal rate in groundwater is 78%.For low-medium pollution areas,in-situ iron plating for arsenic removal is carried out by alternately injecting FeSO4solution and NaClO solution into the aquifer,and the test result and arsenic removal mechanism show that through oxidation,adsorption and co-precipitation,the removal rate of groundwater arsenic after 5injection cycles is 80%,but there is a rebound phenomenon of arsenic concentration.The paper provides engineering experience and reference basis for the restoration of other groundwater contaminated by severe arsenic.