Phytoremediation potential of Vetiveria zizanioides and Oryza sativa to nitrate and organic substance removal in vertical flow constructed wetland systems

Abstract

The aim of this work was to determine the potential of phytoremediation of Vetiveria zizanioides and Oryza sativa to nitrate (NO3−-N) and organic matter (COD – chemical oxygen demand) removal in subsurface vertical flow constructed wetland systems (VFCWs). The tests were carried out in models of 2 beds with a surface of 0.24 m2 and depth 0.70 m each at various hydraulic loads (HL) and COD constant in influente wastewater. The VFCW-1 bed was planted with the Vetiveria zizanioides and the VFCW-2 bed with the Oryza sativa. During the 22 weeks of research, the hydraulic load of the analyzed beds was: HL1 = 148 dm3·m−2·d−1, HL2 = 239 dm3·m−2·d−1, HL3 = 350 dm3·m−2·d−1, HL4 = 473 dm3·m−2·d−1. The VFCWs were fed from two reservoirs, one with mineral medium and nitrate, and the other one with fructose as organic matter. Based on the conducted tests, it was found that in both analyzed systems (VFCW-1 and VFCW-2) the highest NO3−-N removal rate was found under HL2 – the median is 59 and 42% respectively. The most effective removal of COD in the VFCW-1 system was obtained at a HL2 – 55%, while in the system VFCW-2 at a HL1 – 43%. The research shows that the low HL and high COD/NO3−-N ratio ensures good effects of nitrate and organic matter removal in VF type constructed wetland systems. It has been shown that the analyzed plants, especially Vetiveria zizanioides have good phytoremediation potential in the field of nitrate nitrogen and organic substance removal and can be recommended for use on a full scale of technology.