PRB处理酸性矿山废水的地球化学反应模拟研究

Simulation study on geochemical reaction of PRB in treating acid mine drainage

随着工业的迅速发展,矿产资源的需求也随之增加,采矿过程中产生的酸性矿山废水(Acid Mine Drainage,AMD)对周围环境具有严重危害性,可渗透反应墙(Permeable Reactive Barrier,PRB)通过下放置反应材料,利用自然水力梯度拦截污染羽流,该技术已成为有效处理AMD的手段之一。为研究PRB内化学反应堵塞对其处理效果的影响,搭建了规模为60 cm×15 cm×20 cm的箱体装置,模拟石灰石PRB处理AMD的过程;基于箱体实验得到的数据,并利用化学反应输运模型理论开发了一种新的地球化学算法,来描述PRB处理AMD过程中可能会发生的化学反应,最后通过MODFLOW和RT3D的耦合模拟并预测PRB有效处理污染物质的最大寿命。结果表明:①有效地模拟出了PRB中石灰石的酸性中和能力及其对酸性废水中总铁、Al^(3+)的去除效果,并且很好地反映出PRB系统的化学堵塞过程;②模拟结果与实测值吻合程度较好。进口区域、中间区域以及出口区域3个不同位置处出水的pH实测值与预测值的最大误差分别为0.38、0.30和0.29,总铁质量浓度实测值与预测值的最大误差分别为1.570、0.102和0.124 mg/L,Al^(3+)质量浓度实测值与预测值的最大误差分别为1.010、0.374和0.160 mg/L;③预测结果表明,该实验室规模的PRB装置在前30 d出水中的总铁和Al^(3+)质量浓度最低,去除效果最好,且去除能力随着时间逐渐减弱。参照地下水质量标准限制,判断出该石灰石PRB能够有效处理总铁的最大寿命为132 d,有效处理Al^(3+)的最大寿命为63 d。

With the rapid development of industry,the demand for mineral resources also increases.Acid mine drainage(AMD)produced in the mining process is seriously harmful to the surrounding environment.The Permeable Reactive Barrier(PRB)utilizes the natural hydraulic gradient to intercept the pollution plume by placing reactive materials under it,and this technology has become one of the means to effectively deal with AMD.In order to study the effect of chemical reaction blockage in the PRB on its lifespan,a box device with a scale of 60 cm×15 cm×20 cm was built to simulate the process of limestone PRB for AMD treatment.Based on the data obtained from the box experiment,a new geochemical algorithm was developed using the chemical reaction transport model theory to describe the chemical reactions that may occur during the PRB treatment of AMD.Through the coupled simulation of MODFLOW and RT3D,the maximum lifetime of PRB to effectively treat pollutants is predicted.The results show that①The acid neutralization ability of limestone in the PRB and its removal effect on total iron and Al^(3+)in acid wastewater are effectively simulated,and the chemical blocking process of the PRB system is well reflected.②The simulation results are in good agreement with the actual values.The maximum errors between the measured and predicted pH values of the effluent at three different locations in the inlet area,the middle area and the outlet area are 0.38,0.30 and 0.29 respectively.The maximum errors between the actual value and the predicted value of the total iron concentration are 1.570,0.120 and 0.124 mg/L respectively.The maximum error between the actual value and the predicted value of Al^(3+)concentration is 1.010,0.374 and 0.160 mg/L respectively.③The prediction results show that the total iron and Al^(3+)contents in the effluent of this laboratory-scale PRB device are the lowest in the first 30 days,and the removal effect is the best,and the removal capacity gradually weakens with time.With reference to the limit of groundwater quality standard,it is judged that the limestone PRB can effectively treat total iron with a maximum life of 132 days,and effectively treat Al^(3+)with a maximum life of 63 days.