Enhanced Nitrogen Removal Performance in Constructed Wetland by Coupling Partial Tide Flow Operation Mode with Iron-Carbon Micro-Electrolysis Process

Constructed wetlands (CWs) with iron-carbon (Fe-C) filler and gravel filler were set up to examine the synthetic effects of partial tide flow operation mode and Fe-C micro-electrolysis on nitrogen removal performance. Submerged emptying ratio (SER) that representing flood and drain period was set to 2:1 and 1:2 respectively for creating aerobic/anoxic alternative conditions. Upper nitrification area of CWs was operated by tide flow mode and the transformation of NH4+-N to NO3--N was greatly enhanced via the extension of emptying time for air dissolution. Fe-C micro-electrolysis could enhance the availability of carbon sources for biological denitrification and facilitated autotrophic denitrification based on iron oxidation and transfer. It made clear that enhanced denitrification in bottom area contributed to NO3--N removal from water body thus facilitating TN removal. Comprehensive and stable COD (84.2 +/- 2.0%), NO3--N (82.1 +/- 2.0%) and TN (55.6 +/- 2.0%) removal efficiencies were simultaneously achieved in partial tide flow CW with Fe-C filler under SER of 1:2. The study provided a novel idea for the efficient nitrogen removal in CWs treating eutrophic water.