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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.

In a period when MP contamination of drinking water is a great concern, this study focused on the size-and morphology-based count, and polymeric identification of plastic particles in tap water sourced from Thailand. A total of 45 human consumable samples (each 1 L) were collected at Thammasat University. The average MP counts sorted by Nile Red tagging were 56.0±14.0 p/L (6.5-53 µm) and 21.0±7.0 p/L (53-300 µm), while those found by optical microscopic observations were 13.0±5.0 p/L (300-500 µm) and 6.0±3.0 p/L (≥ 500 µm). A significantly high MP amount was observed in the 6.5-53 µm fraction. Fibers dominated in all samples, accounting for 58% of the particle count. Most ≥ 300 µm particles tested by ATR-FT-IR spectroscopy were confirmed to be polymeric, identified as PE, PVC, PET, PA, PTFE, PP, and PAM. These particles may have escaped from the treatment plant or were added along the water distribution network. Since MPs in drinking water constitute a potential health risk by exposing humans to direct plastics intake, MP contamination in water supply systems should be controlled.

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.