The Improvement of Pollutant Removal in the Ferric-Carbon Micro-Electrolysis Constructed Wetland by Partial Aeration

Subsurface flow constructed wetland (SSFCW) has been applied for wastewater treatment for several decades. In recent years, the combination of ferric-carbon micro-electrolysis (Fe/C-M/E) and SSFCW was proven to be an effective method of multifarious sewage treatment. However, Ferric substrate created a relatively reductive condition, decreased the oxidation efficiency of NH4+-N, and blocked the following denitrification process, which led to the low removal efficiencies of NH4+-N and total nitrogen (TN). In this study, partial aeration was introduced into the ferric-carbon micro-electrolysis SSFCW (Fe/C-M/E CW) system to solve the problem above. The water quality and nitrogen-related functional genes of bacteria on the surface of substrate were measured for mechanism exploration. The results showed that, the removal efficiencies of NH4+-N and total phosphorus (TP) in an aerated Fe/C-M/E CW system were 96.97% +/- 6.06% and 84.62% +/- 8.47%, much higher than 43.33% +/- 11.27% and 60.16% +/- 2.95% in the unaerated Fe/C-M/E CW systems. However, the TN removal in Fe/C-M/E CW system was not enhanced by aeration, which could be optimized by extending more anoxic section for denitrification.