The Contaminants Correlation and Curtailment Prospect of Waterhyacinth, Waterlettuce and Vetiver Grass in Wastewater Treatment

Abstract

This study seeks to elaborate the correlation of physicochemical parameters and heavy metals from a wastewater effluent in Zaria. The contaminants reduction capacity of Vetiver grass (C. zizanoides), water hyacinth (E. crassipes) and Water lettuce (P.stratiotes) were analysed.Temperature, pH, EC, TDS, Cl, PO4-, DO, BOD, COD, Na, K, NO3, TSS, NH3, SO4 and Cu, Cd, Pb, Mn, Mg, Co, Ni, Cr and Zn concentrations were determined using standard method,digestion and assessment of heavy metals using atomic absorption spectrophotometry machine. There was positive correlation between TDS with EC, BOD with NO3-N, pH with Temperature, DO with COD and N, and Cl with K. Zn with Pb and Cd, Cr with Co indicating common source of contamination. Negative correlation was observed between HCO3 with NH3.N and SO4-, Temperature with N and DO, K with BOD and NO3-N, Cr with Ni, Mg with Cu and Zn indicating uncommon source of contamination. The significant correlation was verified by using t-test. The systematic calculation of correlation coefficient between water quality parameters and between heavy metals was carried out. Hydroponic method of phytoremediation was adopted to evaluate the curtailment potentials of the three plants.There was significant difference at P ≤ 0.05 (95% confidence) across days 7, 14 and 21 in reduction during treatment with water hyacinth for EC (846.1, 699 .00 and 502.1 mg/L),  TDS (410.5, 340.0 and 259.0 mg/l), NH3 (1.25, 1.04 and 0.84 mg/l) and Cd (0.021, 0.018 and 0.012 mg/l)., with vetiver grass for EC (828.2, 654.1 and 488.1mg/L), TDS (398.6, 282.8 and 198.2 mg/L), COD (476.5, 355.5 and 265.5 mg/L), NO3 (3.34, 2.13 and 1.40mg/L), TSS (11.6, 8.66 and 6.58mg/L) and Cd (0.019, 0.011 and 0.01mg/L)., and with water lettuce for EC (833.0, 709.6 and 587 mg/L), TDS (452.6, 404.0 and 284.0 mg/L), Cr (0.12, 0.10, and 0.79mg/L), Pb (0.21, 0.18 and 0.13mg/L) and Cd (0.019, 0.013 and 0.011 mg/l). Vetiver grass was found to be more prospective in the curtailment of contaminants.