Impacts of electrochemical disinfection on the viability and structure of the microbiome in secondary effluent water

Abstract

Electrochemical disinfection (ECD) is a promising disinfection technique for wastewater reclamation; however, the impacts of ECD on the microbiome in secondary effluent wastewater remain unknown. In this study, Propidium monoazide-qPCR (PMA-qPCR) and the plate count method were used to evaluate the inactivation performance, and the PMA-16S rRNA gene sequences of living cells were targeted to study the microbiome. A discrepancy was found between PMA-qPCR and the plate count method in the evaluation of cell count, with increases of 1.5 to 2.2 orders of magnitude in the disinfection rate after 150 s of disinfection. However, the cell count recovered and occasionally exceeded original levels within 3 d after disinfection. Biodiversity was suppressed after ECD, but the microbiome after 150 s disinfection retained a higher level of evenness and stability in the community with a median Shannon index (> 3.7). Pathogenic bacteria remained high in relative abundance even after 150 s of 25 V disinfection, but the biofilm-forming population was effectively suppressed by ECD. The co-occurrence network revealed a centralized and fragile network as disinfection persisted, demonstrating the destabilizing effects of ECD on the microbiome. Functional pathways for cell membrane synthesis and organic compound degradation were enriched after ECD. The reaction of the microbiome after ECD was similar to other disinfection techniques in terms of community structure.