Using CO2 and oxidants for in situ regeneration of permeable reactive barriers for leachate–contaminated groundwater.

• A CO 2 combined oxidant method for PRB regeneration is proposed for leachate–contaminated areas near landfill. • CO 2 well-washing technology is used for improving PRBs permeability. • The optimal ratios of oxidants and PRB fillers are proposed to achieve the best regeneration effect. Groundwater contamination near landfills is commonly caused by leachate leakage, and permeable reactive barriers (PRBs) are widely used for groundwater remediation. However, the deactivation and blockage of the reactive medium in PRBs limit their long-term effectiveness. In the current study, a new methodology was proposed for the in situ regeneration of PRB to remediate leachate-contaminated groundwater. CO 2 coupled with oxidants was applied for the dispersion and regeneration of the fillers; by injecting CO 2 to disperse the fillers, the permeability of the PRB was increased and the oxidants could flow evenly into the PRB. The results indicate that the optimum filler proportion was zero-valent iron (ZVI)/zeolites/activated carbon (AC) = 3:8:10 and the optimum oxidant proportion was COD/Na 2 S 2 O 8 /H 2 O 2 /Fe2+ = 1:5:6:5; the oxidation system of Fe2+/H 2 O 2 /S 2 O 8 2− has a high oxidation efficiency and persistence. The average regeneration rate of zeolites was 72.71%, and the average regeneration rate of AC was 68.40%; the permeability of PRB also increased. This technology is effective for the remediation of landfills in China that have large contaminated areas, an uneven pollutant concentration distribution, and a long pollution duration. The purification mode of long-term adsorption and short-time in situ oxidation can be applied to the remediation of long-term high-concentration organically polluted groundwater, where pollution sources are difficult to cut off. [ABSTRACT FROM AUTHOR]