Ecological processes in separated structures of electroactive wetlands: Determinism versus stochasticity

Combined systems are an important direction in electroactive wetlands (EWs) research, with unique advantages in treating high-nutrient wastewater, but neither series nor parallel mode is conducive to system stabilization and performance enhancement. To evaluate the relationships between different series and parallel combined designs and the performance of systems, two combined designs based on two-stage EWs were proposed: pre -multiple parallel (MP) (A) and post -MP (B). The two-stage series design (C) was used as the control. Design A exhibited superior nitrogen (72.81 % +/- 0.30 %) and phosphorus (92.78 % +/- 0.01 %) removal efficiency as well as power production. There was coupling of shortcut nitrification denitrification (SCND) and anaerobic ammonium oxidation (ANAMMOX) in A, which increased the maximum series current density (27.03 mA/m2) and reduced the internal resistance (39.97 Omega). The pre -MP design increased the stochasticity of microbial community assembly (R2 = 0.8781) in accordance with neutral community model, which led to the enhancement of diversity and the functional potential of the microbial community. Proteobacteria was the dominant phylum of the cathodic microbial community and was mainly present in A, accounting for 38.86 %-65.06 %, and played a dominant role in nitrogen removal. Metabolites mediated information exchange between plants and microorganisms; this signaling rate was more rapid in A, which increased the sensitivity of the organisms to environmental changes. This study offers a new approach for practical treatment of rural domestic sewage and engineering applications of EWs.