Research Scholar, School of Civil and Environmental Engineering, Indian Institute of Technology Mandi, Himachal Pradesh, 175005, India.
Associate Professor, School of Civil and Environmental Engineering, Indian Institute of Technology Mandi Himachal Pradesh, 175005, India.
Environ Pollut. 2024 Aug 15;355:124138. doi: 10.1016/j.envpol.2024.124138. Epub 2024 May 9.
Clay-amended barriers are widely used to prevent hazardous leachate percolation from landfill to subsurface. The performance of these barriers is mostly evaluated through numerical simulations with limited experimental investigation through leachate flushing experiments. To bridge this gap, contaminant loading and its flushing experiments were carried out to assess the performance of clay-amended composite materials as landfill liners. River sand (Sa), loamy soil (Ns), and alternative waste materials like fly ash (Fa) and flushed silt (Si) were used to prepare the composites. Composites fulfilling the hydraulic conductivity (<10 cm/s) and compressive strength (200 kPa) criteria were selected for contaminant loading and its flushing experiments to understand the fate of fluoride ions. The experimentally determined hydraulic conductivity (K) values for all the composites were in the order of 10 cm/s. The experimental breakthrough curves exhibited skewed shape, long tailing, and dual peaks. Dual porosity and dual permeability with immobile water models were employed to simulate these curves, revealing that preferential flow pathways and random chemical sorption sites significantly affect solute transport in clay-amended barriers. Further, scanning electron microscopy and energy-dispersive X-ray spectroscopy were employed to trace the preferred path of fluoride ions through the barrier. The removal efficiency and temporal moments were used to determine the percentage mass retained, mean arrival time, and spreading within the barrier. The highest solute mass was retained by sand-clay barrier (SaB30) (91%), followed by loam-clay barrier (NsB30) (59%), fly ash-clay barrier (FaB30) (38%), and silt-clay barrier (SiB30) (4%) with the least mass. The lowest mean arrival time was calculated for NsB30 (269 h) and the highest for SaB30 (990 h), with FaB30 (384 h) and SiB30 (512 h) having values in between. This study concludes that validating the design hypothesis of clay-amended barriers through contaminant loading and its flushing studies leads to an effective and sustainable design.
黏土改良屏障被广泛用于防止危险的渗滤液从垃圾填埋场渗透到地下。这些屏障的性能主要通过数值模拟进行评估，而通过渗滤液冲刷实验进行的实验研究则有限。为了弥补这一差距，进行了污染物加载及其冲刷实验，以评估黏土改良复合材料作为垃圾填埋场衬垫的性能。河沙 (Sa)、壤土 (Ns) 和替代废物材料如粉煤灰 (Fa) 和冲刷淤泥 (Si) 被用于制备复合材料。满足水力传导率 (<10 cm/s) 和抗压强度 (200 kPa) 标准的复合材料被选用于污染物加载及其冲刷实验，以了解氟离子的命运。所有复合材料的实验确定的水力传导率 (K) 值均在 10 cm/s 左右。实验突破曲线呈偏态形状、长尾和双峰。双孔隙度和双渗透率与不可移动水模型一起用于模拟这些曲线，表明优先流途径和随机化学吸附位点对黏土改良屏障中的溶质传输有显著影响。此外，扫描电子显微镜和能量色散 X 射线光谱用于追踪氟离子通过屏障的优先路径。去除效率和时间时刻用于确定保留的质量百分比、平均到达时间和在屏障内的扩散。沙-黏土屏障 (SaB30) 保留的溶质质量最高 (91%)，其次是壤土-黏土屏障 (NsB30) (59%)、粉煤灰-黏土屏障 (FaB30) (38%) 和淤泥-黏土屏障 (SiB30) (4%)，保留的质量最少。NsB30 的平均到达时间最短 (269 h)，SaB30 的最长 (990 h)，FaB30 (384 h) 和 SiB30 (512 h) 的时间在两者之间。本研究得出结论，通过污染物加载及其冲刷研究验证黏土改良屏障的设计假设可导致有效和可持续的设计。
