Microbial communities and functional genes of nitrogen cycling in an electrolysis augmented constructed wetland treating wastewater treatment plant effluent

Abstract To enhance nitrogen removal efficiency, a new electrolysis augmented constructed wetland (E-CW) was applied for nitrogen removal from waste water treatment plant (WWTP) effluent. This work demonstrated that E-CW could remove NO 3 − efficiently (45.5%–83.4%) under low C COD /N ratio (average 2.29 ± 0.45) with little amount of NH 4 + and NO 2 − generation. High throughput 16S rRNA sequence analysis revealed that Proteobacteria, Actinobacteria, Cyanobacteria, Bacteroidetes, and Verrucomicrobia were the dominant phyla in the E-CW. However, abundance of denitrifiers and denitrification genes decreased along with the operation of E-CW. Four functional gene pairs of anammox- amoA , ( narG  +  napA )-( nirK  +  nirS ), ( narG  +  napA )- nosZ and qnorB - nosZ showed positive correlations with each other. Co-occurrence network analysis results indicated that functional guilds of FeOB and FeRB coupled with denitrifiers and contributed to the process of nitrogen removal in the E-CW. Overall, this work illustrated E-CW was a feasible and effective technology for enhancing nitrogen removal, and provided a theoretical basis for better design and operation of E-CW.