Trichloroethylene Detoxification in Low-Permeability Soil Via Electrokinetic-Enhanced Bioremediation Technology: Long-Term Feasibility and Spatial-Temporal Patterns

Abstract

To in-situ remediate low-permeability soil contaminated with trichloroethylene (TCE), the electrokinetic-enhanced bioremediation (EK-BIO) system offers an innovative technology. While previous studies have demonstrated microbial succession and TCE removal, knowledge gaps remain regarding prolonged dechlorination performance operation and the interactions between electrode reactions and anaerobic dechlorination.   In this study, five one-dimensional columns were constructed in parallel, each operated for a different period (28, 42, 56, 84 and 138 days) to illustrate the spatial and temporal patterns. Continuous TCE degradation was observed, with 46.52% of TCE recovery. The first-step dehalogenation process (TCE to DCE) was accelerated by increased electrokinetic time. Even though Dehalococcoides was widespread in the soil column at 138 days (2.30% - 5.74%), the damage caused by oxygen exposure was irreversible, necessitating secondary inoculation. The presence of typical aerobic bacteria (Comamonas and Pseudomonas) indicated new detoxification pathways in electrode chambers. The expression of tceA, vcrA and Dhc16S further proved the loss of 2nd and 3rd dehalogenation activity (DCE to ethene) with continuous operation. Overall, this study contributes to the field application of the EK-BIO system for maintaining long-term biodegradation and improving detoxification performance by inducing various pathways, which is particularly beneficial for the remediation of low-permeability soils.

Keywords: EK-BIO, TCE Dechlorination, Anaerobic reduction, Aerobic degradation