[Wastewater Treatment Effects of Ferric-carbon Micro-electrolysis and Zeolite in Constructed Wetlands]

Ferric-carbon micro-electrolysis fillers and zeolite have been increasingly used as substrates in constructed wetlands due to their good wastewater pollution-removal efficiencies. To explore the effects of different fillers on wastewater treatment in constructed wetlands, four constructed wetlands were examined with vertical subsurface flow areas filled with ferric-carbon micro-electrolysis filler+gravel (CW-A), ferric-carbon micro-electrolysis filler+zeolite (CW-B), zeolite (CW-C), and gravel (CW-D). In addition, intermittent aeration was used to improve the dissolved oxygen (DO) environment. The results showed that, compared with CW-D, the ferric-carbon micro-electrolysis filler significantly increased the dissolved oxygen (DO, P<0.05) and pH (P<0.05) of the effluent from the wetlands. The mean removal efficiency of chemical oxygen demand (COD) in the four constructed wetlands were more than 95% (P>0.05). For TN, the mean removal efficiency of CW-A,-B, and-C was 7.94% (P<0.05), 9.29% (P<0.05), and 3.63% (P<0.05) higher than that of CW-D, respectively. The contribution of ferric-carbon micro-electrolysis filler and zeolite to improving the TN removal efficiency of the constructed wetlands was 73.55% and 26.45%, respectively. The mean removal efficiency of NH₄⁺ in the four wetlands ranged from 67.93% to 76.90%, and compared with CW-D, the other treatments significantly improved the removal efficiency of NH₄⁺ (P<0.05). The ferric-carbon micro-electrolysis filler had an excellent removal effect on NO₃^-, with a removal efficiency of more than 99%, which was significantly higher than the constructed wetlands without ferric-carbon micro-electrolysis (P<0.05). Considering the treatment effect of the organic pollutants and the nitrogen-containing pollutants, CW-B achieved the best removal efficiency in constructed wetlands with intermittent aeration.