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

•Application of Vetiveria zizanioides and Oryza sativa in VF-CWs was analyzed.•The best effects of NO3−-N removal were for a hydraulic load No. 2 = 241 dm3·m−2·d−1.•The ratio of COD/NO3-N in wastewater affected the efficiency of NO3-N removal.•The best effects of COD removal in the VFCW-1 were for hydraulic load HL2 – 55%.•The best effects of COD removal in the VFCW-2 were for hydraulic load HL1 – 43%.•Vetiveria zizanioides has a good potential in NO3-N and COD removal from sewage.