Iron [Fe(0)]-carbon micro-electrolysis enhances simultaneous nitrogen and phosphorus removal in vertical flow constructed wetlands for advanced treatment of reclaimed water

Constructed wetland is an effective method to remove N and P from reclaimed water, but the treatment effect is restricted by low temperature in winter. In this study, a vertical flow constructed wetland based on Iron [Fe (0)]-carbon micro-electrolysis (IC-ME) (IC-CW) was developed for advanced treatment of reclaimed water. The performance of IC-ME carrier on simultaneous N and P removal under different operational conditions and cold temperature was investigated. Studies have shown that when the HRT is 48 h and the influent C/N ratio is 2.5, the removal efficiencies of TN and TP reach to 88.6% and 92.2%. When operating under low temperature conditions (water temperature at 9.6–18.6 °C and ambient temperature at −14.2 to 8.4 °C), the effluent quality is slightly lower than that at normal temperature, with the TN and TP removal efficiencies of 72.7% and 89.2%. The functional microorganisms in IC-CW were analyzed and the results showed that aerobic bacteria and anaerobic bacteria coexist in the IC-CW, and there are both aerobic nitrification and anaerobic denitrification processes in the IC-CW. In addition, there are more functional denitrifying characteristic microorganisms such as Denitratiosoma attached on the IC-ME carrier (2.18%) than that on the ceramsite (0.92%). The developed IC-CW presented significant potential in the practical application for advanced treatment of reclaimed water.