Static magnetic fields unlock extensive microbial-catalyzed dechlorination and partial anaerobic mineralization

Anaerobic microbial dechlorination of chlorinated aromatic compounds is constrained by slow electron transfer and the accumulation of toxic intermediate, which hindered its practical deployment in contaminated water. Here, a static magnetic field (SMF)-based strategy was developed to overcome these bottlenecks using 2,4,6-trichlorophenol (2,4,6-TCP) as the target compound. A SMF-based system integrating SMF (50 mT), humin (2.0 g/L) mainly as an electron shuttle, and low dosage sulfidized nanoscale zero-valent iron (S-nZVI, 0.04 g/L) as a supplementary electron donor achieved rapid and complete removal of 30 mg/L 2,4,6-TCP within 11-13 days under five repeated spikes without repeated supplementation of carbon source, corresponding to a k_obs 3-4 times higher than that of CK (sediment and medium only), and avoided toxic 4-monochlorophenol accumulation. Moreover, partial anaerobic mineralization was triggered, as evidenced by an 87.8% reduction in total organic carbon, a 9.3-fold increase in acetate production compared to CK, and exclusive detection of 4-chlorobenzoic acid. 16S rRNA gene sequencing identified SMF as the dominant driver of community differentiation, selectively enriching key dechlorinators, including Dehalobacter (1.7%), Pseudomonas (5.9%), and Anaeromyxobacter (5.7%), alongside fermenters, iron-cycling bacteria, and phenol degraders. The SMF-based synergistic strategy profoundly stimulated key mediators in electron transfer chain. The concentration of cytochrome c increased by 78.8%, ATP synthase and hydrogenase genes abundances increased by 3900- and 2530-fold, respectively, and putative dechlorinating Chloroflexota increased by two orders of magnitude. These findings provide a new laboratory-scale concept for enhanced chlorophenol dechlorination and warrant further assessment in practical applications.