Ex situ remediation of polluted soils by absorptive polymers, and acomparison of slurry and two-phase partitioning bioreactors forultimate contaminant degradation

tThe present study has provided a comparison between a conventional ex situ method for the treatmentof contaminated soil, a soil slurry bioreactor, with a novel technology in which a contaminant is rapidlyand effectively removed from the soil by means of absorptive polymer beads, which are then added to atwo-phase partitioning bioreactor (TPPB) for biodegradation of the target molecule. 4-nitrophenol (4NP)was selected as a model contaminant, being representative of a large class of xenobiotics, and the DuPontthermoplastic HytrelTM8206 was utilized for its extraction from soil over ranges of soil contaminationlevel, soil moisture content, and polymer:soil ratios. Since the polymers were able to rapidly (up to77% and 85% in 4 and 24 h respectively) and selectively remove the contaminant, the soil retained itsnutrient and microflora content, which is in contrast to soil washing which can remove these valuablesoil resources. After 4 h of reaction time, the TPPB system demonstrated removal efficiency four timeshigher (77% vs 20%) than the slurry system, with expected concomitant savings in time and energy. Avolumetric removal rate of 75 mg4NP h-1L-1was obtained in the TPPB, significantly greater than thevalue of 1.7 obtained in the slurry bioreactor. The polymers were readily regenerated for subsequentreuse, demonstrating the versatility of the polymer-based soil treatment technology.