Abstract
The application of subsurface-flow constructed wetlands (SSFCWs) has been restricted by the low nitrogen and phosphorus removal efficiency for several decades. Ferric-Carbon Micro-Electrolysis (Fe/C-M/E) system has gained increasing attention due to its high redox capacity and the function of adsorption and flocculation. Therefore, to apply Fe/C-M/E process in SSFCWs is a promising approach to enhance the removal efficiency of nitrogen and phosphorus of domestic sewage. In this study, a micro-electrolysis-intensified subsurface-flow constructed wetlands (ME-SSFCWs) including iron scraps and biochar were operated to investigate the effect of micro-electrolysis-substrate on nitrogen and phosphorus removal performance together with the related kinetics and possible pathways. The results showed that the removal efficiency of NO3−-N, total nitrogen (TN) and phosphorus by ME-SSFCWs were 99.54 ± 0.80%, 81.45 ± 1.27% and 93.63 ± 5.30%, respectively, for a 3-day hydraulic retention time (HRT), which were much higher than that of the ordinary SSFCWs (NO3−-N: 37%; TN: 38%; TP: 39%) and biochar-added SSFCWs (NO3−-N: 57%; TN: 54%; TP: 21%). These results indicated that micro-electrolysis could supply electrons for the denitrification. Besides, the improvement of phosphorus removal efficiency was due to the galvanic corrosion of numerous micro-scale sacrificial anodes which caused precipitation, adsorption and flocculation of phosphorus. Microbial analysis via real-time quantitative PCR Detecting System (qPCR) revealed that associated microbial abundance could dramatically increase due to the addition of Fe/C-M/E material substrate.
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