When already limited safe groundwater is rapidly contaminated with landfillleachate, it is a timely need to investigate feasible remediation techniques. In this scenario, Permeable Reactive Barrier (PRB) is a potential groundwater treatment method. If waste materials can be effectively applied as PRB reactive media, the system can be made more economical. This study was focused on a treatment system with two mixed-media PRB models (PRB 1 and PRB 2) connected in series, in which dewatered alum sludge (DAS), washed quarry dust (WQD), washed sea sand (WSS), red soil (RS), bio char (BC) and saw dust (SD) were emplaced in reactive beds, to treat organic compounds and nutrients of leachate-contaminated groundwater. Wastewater parameters were measured in terms of BOD5, COD, NO-3-N , NH3-N , TN, PO 3-4-P and TP. Mean removal efficiencies of BOD5 (88.2+5.7%), COD (84.2+9.6%) and NH3-N (95.6+4.2%) were phenomenal with 13.1 days of pore volume hydraulic retention time (HRT) during an experimental period of 140 days. Reactive material properties were not much affected by the interaction with landfill-leachate, thus no considerable change in the removal efficiencies occurred within 140 days. The treatment efficiency of the present system with two reactors connected in series is greater than that of a single PRB reactor filled with the same reactive materials in the same packing configuration.

Permeable Reactive Barrier (PRB) is an on-site treatment technique, which can be effectively used for remediating the groundwater contaminated by landfill -leachate. The objective of this study was to investigate the applicability of several low -cost/waste materials as the reactive media in a bench-scale sequential PRB model to treat the contaminated groundwater by landfillleachate. There were two bench-scale sequential PRB models as experimental and control. Dewatered alum sludge (DAS), washed quarry dust (WQD), fire-wood charcoal (FWC), sea sand (SS) and saw dust (SD) were placed in the experimental model whereas the control model was filled with red laterite soil (RLS), and commonly used zero valent ion (ZVI) and granular activated carbon (GAC) as vertical equal layers. The target wastewater parameters were organic matter (COD and BOD5), nitrogenous compounds (NH3-N, NO3 --N and TN) and heavy metals (Cd, Cu, and Fe). The overall removal efficiency of BOD5 and Cd were greater than 90% and almost 100%, respectively. Further, the masses of BOD5 and TN removed during the entire run of the experimental model were almost the same as those of the control model. Hence, it can be concluded that the low -cost/waste materials used in the experimental model have a potential to be used as reactive media in PRBs aiming at treating the landfill -leachate. Further, this would be a sustainable reuse application for waste materials to be dumped.

Heavy metal (HM) is one of the notable contaminants that may contribute to groundwater pollution. Landfill-leachate is a source, discharging HMs to groundwater. It is essential to trap HMs in groundwater to avoid consequential adverse ramifications. Permeable Reactive Barrier (PRB) is an in-situ technique that can be adopted to remove HMs in groundwater contaminated by landfill-leachate. The objective of this study was to investigate removal efficiencies of HMs in groundwater contaminated by landfill-leachate using a pilot-scale PRB system. Dewatered Alum Sludge (DAS), Washed Sea Sand (WSS), Washed Quarry Dust (WQD), Red Soil (RS), Saw Dust (SD) and Bio Char (BC) were used as mixed reactive media in sequentially connected two PRB models. Average removal efficiencies of Pb, Mn, Cu, Cd and Fe were 94 %, 81 %, 71 %, 68 % and 68 %, respectively for 140 days of an experimental run. Treatment efficiencies could be stimulated by the presence of Fe, Al and Si oxides in materials. It is revealed that mixed-media PRB system showed a remarkable treatment efficiency without a significant change of material properties even after the increase of HM loading at the latter stage. This would also be an economically and environmentally sound re-use application for abundant waste materials.