A pilot-scale study on polyhydroxybutyrate-amended electro-assisted biodechlorination of chlorinated ethenes in shallow groundwater

Although biodechlorination has been extensively investigated, most related technologies remain at the laboratory scale, and practical in situ engineering applications still face considerable challenges because of the oligotrophic conditions of groundwater and the inherent characteristics of aquifers. In this study, polyhydroxybutyrate (PHB)-amended electro-assisted biodechlorination (P-EAB) systems were constructed to successfully remove chlorinated ethenes (CEs) from groundwater. After 20 d of P-EAB operation, the concentrations of all detected CEs in the P-EAB systems decreased to below 1 μg/L. The biodechlorination model further indicated that, after 12 d of P-EAB operation, 80% of TCE were removed within a 5-m radius from the reaction center. Microbial community analysis revealed significant enrichment of microorganisms associated with electroactivity and reductive biodechlorination in the P-EAB systems, including Rhodoferax, Dechloromonas, Geobacter, Shewanella, and Dehalogenimonas. Metagenomic analysis revealed a high abundance of reductive dechlorination genes (pceA, tceA, and dhaA) in the P-EAB systems. Weak electrical stimulation enhanced microbial metabolic activity, while hydrogen generated during PHB degradation likely served as an effective electron donor to promote the further transformation of cis-1,2-DCE and trans-1,2-DCE. Ecological risk assessment and life cycle evaluation indicated that P-EAB was a low-impact and environmentally friendly biodechlorination technology. This study confirmed the feasibility and effectiveness of P-EAB technology for CEs removal from groundwater, providing valuable insights for its broader application and promotion.