Nutrient removal from polluted river water by using vertical and horizontal subsurface flow constructed wetlands

The main purpose of this study was to treat organic pollutants, nitrogen and phosphorus in polluted river water by the use of constructed wetland (CW) systems. A laboratory experiment research was conducted on subsurface flow constructed wetland systems operated in vertical flow (VF) and horizontal flow (HF) mode. The systems were unplanted and hydraulic retention times were identically 2.7 days. The average removal efficiencies for HFCW and VFCW were NH4+-N 64.9% and 75.2%, NO3--N 92.3% and 40.1%, COD 97.5% and 90.1%, TP 94.6% and 96.2%, respectively. The removal of NH4+-N and NO3--N in the different CW units were in order of VFCW (drained) > VFCW (flooded) > HFCW and HFCW > VFCW (flooded) > VFCW (drained), respectively. When the water level in the VFCW was changed, an obvious fluctuation of the effluent NH4+-N and NO3--N concentrations was observed.