Effect of Corncobs as External Carbon Sources on Nitrogen Removal in Constructed Wetlands Treating Micro-polluted River Water

Two bench scale constructed wetland were set up in laboratory to evaluate the feasibility and efficiency on denitrification with and without corn cobs as external carbon sources in horizontal subsurface flow constructed wetlands (HFCWs) treating micro-polluted river water that were taken from Jinshui River, Zhengzhou, China. CWs without corn cobs as substrate showed good performance in COD removal (outflow < 40 mg/L) and NH3-N removal (outflow < 0.65 mg/L) but less efficiency in TN and NO3-N removal. The CWs with 1% of corn cobs as external carbon sources (CWs-Corncob) showed significant improvement in TN and NO3-N removal, with the average NO3-N removal efficiency increased from 19% to 71.9%, TN removal efficiency increased from 34.24% to71.9%. The release of organic carbon from corncobs resulted in the improvement of denitrification efficiency. Meanwhile, the effluent concentrations of COD, NH3-N and NO2-N had no obvious change comparing with the CWs without corn cobs.