Ferric-carbon micro-electrolysis and zeolite reduce CH4 and N2O emissions from the aerated constructed wetland

Aeration has been widely used in constructed wetland (CWs). However, research on greenhouse gas (GHG) emissions and measures to control GHG emissions in aerated CWs is still limited. Therefore, lab-scale aerated CWs were established in this study to explore effects of Fe–C and zeolite on GHG emissions from aerated CWs. Four groups of CWs were filled with gravel (CW-A), zeolite (CW–B), ferric-carbon micro-electrolytic filler (Fe–C) and gravel (CW–C) and Fe–C and zeolite (CW-D). The results showed that compared with CW-A, the other CWs reduced CH4 emissions by 24.39%–51.22%. N2O emissions from CW-C and CW-D were on average 48.53% and 58.20% lower than those from CW-A, respectively, because Fe–C significantly changed abundance of functional genes. Overall, combined use of Fe–C and zeolite as substrate is recommended to optimize aerated CWs, which simultaneously achieved the best treatment performance and the lowest GHG emissions.