Ex situ remediation of chlorophenol contaminated soil: comparison of slurry and solid-phase bioreactors with the two-steppolymer extraction-bioregeneration process

BACKGROUND: An innovative approach for ex situ soil bioremediation, based on absorptive polymers extraction combinedwith biological regeneration of the polymer in a two-phase partitioning bioreactor (TPPB),was tested to remediate soil contaminated by chlorophenols. The objective of the study was to evaluate the performance of the proposed technology in comparison with conventional technologies, such as slurry bioreactors and solid-phase bioreactors. RESULTS: A soil highly contaminated (~4gkg-1 for each compound) by amixture of 4-chlorophenol (4CP) and pentachlorophenol (PCP),was treated with different bioremediation systems.Removal efficiencies achieved with polymer extractionwere>70% for a contact time of 24 h; the contaminated polymer was then regenerated in a TPPB (~100 and 85% biodegradation efficiencies for 4CP and PCP, respectively). No degradation of PCP occurred in conventional bioreactors, while, for 4CP, 40 days were required for its biodegradation in the slurry bioreactor, and 80 days to reach 67% removal in the solid-phase bioreactor. CONCLUSION: Advantages of the two-step polymer-based soil treatment in comparison with conventional technologies have been demonstrated for chlorophenols contaminated soils: efficiencies in the range 70-80%for soil decontamination and almost completemineralization of the two compounds were achieved with reaction times suitable for application (<20 days).