Low-intensity electrical stimulation enhances phthalate ester biodegradation by activated sludge through real-time...

Phthalate esters (PAEs) are ubiquitous contaminants that are poorly removed by conventional biological treatment processes. This study investigated the enhancement of PAE biodegradation in activated sludge under low-intensity electrical stimulation. A single-chamber electrostimulated aerobic microbial system (EAMS) was established and operated at 0.6-2.1 V to explore the physiological, genetic, and community-level responses of microorganisms. Moderate stimulation (0.9-1.5 V, electric field strength 180-300 V·m^-1, current 10.6-136.0 μA, current density 0.5-6.8 mA·m^-2) increased the biodegradability of the three PAEs by 11%-20%. Electrical stimulation significantly enhanced the physiological activity and community synergy of the microbial community dominated by non-electroactive bacteria. Metagenomic and metatranscriptomic analyses revealed that the genomic abundance of PAE-degrading genes was unchanged, but their expression was strongly upregulated (20-40-fold). Electrical stimulation enhanced PAE biodegradation by activating the metabolic and transcriptional machinery of the resident microbial community, rather than by selecting for specific degraders. This activation led to elevated expression of key degradation genes and consequently improved biodegradation efficiency. These findings suggest that electrical stimulation acts as a functional activator of indigenous microbial communities, providing a rapid and broadly applicable strategy for improving biodegradation efficiency without requiring extensive community restructuring.