Electromagnetic field coupled vertical flow constructed wetlands for rural sewage treatment: Performance, microbial community characteristics and metabolic pathways.

Rural sewage management has been a long and difficult task. To overcome this problem, there is an urgent need for efficient, low-maintenance, low-consumption treatment technologies. In this study, an electromagnetic field coupled vertical flow constructed wetland (EMC-VFCW) and a vertical flow constructed wetland (VFCW) were constructed, and the removal performance, microbial changes, and metabolic pathways of both were investigated. The results demonstrated that the EMC-VFCW system achieved removal rates of 88.68% for COD, 92.89% for TP, 83.39% for NH-N, and 94.60% for NO-N. SEM analysis revealed that the lysis of the filler surface in the EMC-VFCW system was rougher and had an increased number of active sites, which provided conditions for microbial attachment. High-throughput sequencing revealed that the EMC-VFCW system was enriched with a greater abundance of microorganisms, including Proteobacteria, Betaproteobacteria, and Acinetobacter, indicating that the presence of the electromagnetic field increased the amount of bacteria associated with phosphate removal and denitrogenation. A KEGG analysis suggested that during decontamination, the electromagnetic field might have released signal molecules that promoted energy metabolism, stimulated membrane transport, and accelerated nitrogen metabolism in the EMC-VFCW system. Additionally, the presence of the electromagnetic field altered nitrogen metabolism pathways and increased the relative abundance of denitrification-related genes (nirB, nirS, nirK). Moreover, the electromagnetic field improved the relationships among microorganisms, nitrogen metabolism functional genes, and pollutant removal in the EMC-VFCW system. Therefore, this study offers valuable insights into the performance and mechanisms of rural sewage disposal.