Dual role of phenol Co-contamination in trichloroethylene detoxification in EK-BIO systems: Microbial inhibition versus stimulated aerobic cometabolism.

Phenol often co-occurs with trichloroethylene (TCE) and can inhibit the activity of organohalide-respiring bacteria, posing challenges for in-situ bioremediation. This study evaluated one-dimensional columns operated under electrokinetic-enhanced bioremediation (EK-BIO) for simultaneous TCE detoxification with phenol co-amendment at 1 mM (replenished every 14 days). EK-BIO achieved effective TCE removal despite 6 injection cycles (2100 μmol total), with pore water concentrations decreasing from 500 μM to 79.03 μM at day 28, and 5.86 μM by day 84. Phenol-free batch experiments exhibited earlier VC-to-ethene conversion and less intermediate accumulation. Soil microbiota achieved complete TCE-to-ethene conversion, with Dehalococcoides 16S rRNA gene copies increased by 13.94-fold in cathode-adjacent zones. The co-occurrence of Dehalobacter and Desulfitobacterium supports that multiple OHRB populations contributed to dechlorination. Phenol co-amended electrolytes selectively enriched oxidative-stress-adaptable aerobic and electroactive genera (Pseudomonas, Comamonas and Delftia), with concurrent upregulation of oxygenase and cytochrome-associated pathways, indicating a redox-stratified metabolic shift from soil dechlorination toward electrolyte-mediated aerobic cometabolism. EK-BIO's spatial compartmentalization enabled continued TCE detoxification while mitigating chronic phenol inhibition, demonstrating field-relevant metabolic flexibility and microenvironment-driven microbial cooperation under co-contamination.