Pollutant removal potential of single-size root zone media using Vetiveria zizanioides as emergent macrophyte and its validation

The purpose of this study was to evaluate the performance of horizontal flow constructed wetland system made up of single-size gravel media root zone using Vetiver ( Vetiveria zizanioides ) as emergent plant with focus on removal of biochemical oxygen demand, chemical oxygen demand, nitrate and orthophosphate of sewage in microcosms scale test bed. In this study, wetland was made of RCC tank [1.8 m (L) × 0.8 m (W) × 0.7 m (H)] and planted with vetiver in 20 mm gravel root zone media and another setup without plants was maintained as a control. Constructed wetland was subjected to a flow rate of 0.18 m 3 /day and 0.12 m 3 /day corresponding to hydraulic retention time of 2 and 3 days, respectively, and pollutant loading rates in gm/m 3 /d in the range of 20.04–30.8, 45.59–49.2, 3.48–4.94 and 1.13–1.4, respectively, for biochemical oxygen demand, chemical oxygen demand, nitrate and orthophosphate. Removal efficiency achieved for biochemical oxygen demand, chemical oxygen demand, nitrate and orthophosphate was in the range of 88.87–92.25%, 77.65–81.07%, 44.97–51.43% and 49.17–53.33%, respectively, for 2 and 3 days of hydraulic retention time for the wetland system. Removal efficiency of horizontal flow constructed wetland system with vetiver is statistically significant ( p