Biosystems and Environmental Engineering Research Group, Department of Agricultural and Biosystems Engineering, University of Zimbabwe, Mt. Pleasant, P.O. Box MP167, Harare, Zimbabwe.
Department of Geography, Geospatial Science and Earth Observation, University of Zimbabwe, Mt. Pleasant, P.O. Box MP167, Harare, Zimbabwe.
Bull Environ Contam Toxicol. 2023 Jun 7;110(6):102. doi: 10.1007/s00128-023-03743-3.
Hydraulic liners are used to restrict hazardous leachates such as acid mine drainage (AMD) from entering the hydrogeological system. In this study, we hypothesized that: (1) a compacted mix ratio of natural clay and coal fly ash with a hydraulic conductivity of at most 1 × 10 ms can be achieved, and (2) mixing clay and coal fly ash in the right proportion can result in increased contaminant removal efficiency of a liner system. The effects of adding coal fly ash to clay on the mechanical behavior, contaminant removal efficiency, and saturated hydraulic conductivity of the liner were investigated. All clay:coal fly ash specimen liners with less than 30% coal fly ash had significantly (p < 0.05) lower cohesion stress values, and were discarded without further tests. Saturated hydraulic conductivity values showed no significant effect (p > 0.05) on the results of clay:coal fly ash (7:3) specimen liners and compacted clay liner. The clay:coal fly ash mix ratios of 8:2 and 7:3 significantly (p < 0.05) reduced the leachate concentration of Cu, Ni, and Mn. The pH of AMD increased from an average of 2.14 to 6.80 after permeating through a compacted specimen of mix ratio 7:3. Overall, the 7:3 clay to coal fly ash liner showed superior pollutant removal capacity and its mechanical and hydraulic properties were comparable to compacted clay liners. This laboratory scale investigation emphasizes potential limitations with column scale evaluation of liners and provides new information on the application of dual hydraulic reactive liners for engineered hazardous waste disposal systems.
水力衬垫用于限制危险浸出液（如酸性矿山排水（AMD））进入水文地质系统。在本研究中，我们假设：（1）可以达到最大水力传导率为 1×10 ms 的压实天然粘土和粉煤灰的混合比；（2）以适当的比例混合粘土和粉煤灰可以提高衬垫系统的污染物去除效率。研究了向粘土中添加粉煤灰对衬垫系统的机械性能、污染物去除效率和饱和水力传导率的影响。所有粘土：粉煤灰含量小于 30%的试样衬垫的粘聚力应力值明显（p<0.05）较低，没有进一步测试就被废弃。饱和水力传导率值对粘土：粉煤灰（7：3）试样衬垫和压实粘土衬垫的结果没有显著影响（p>0.05）。粘土：粉煤灰的混合比例为 8：2 和 7：3 时，显著（p<0.05）降低了 Cu、Ni 和 Mn 的浸出液浓度。AMD 的 pH 值从 2.14 左右增加到 6.80，然后通过 7：3 的压实试样渗透。总体而言，7：3 的粘土到粉煤灰衬垫显示出优越的污染物去除能力，其机械和水力性能与压实粘土衬垫相当。本实验室规模的研究强调了衬垫柱规模评估的潜在局限性，并提供了有关用于工程危险废物处置系统的双水力反应衬垫应用的新信息。
