Relative Treatment Efficiency Index of Eichhornia crassipes in Removing Cd, Pb and Ni from Wastewater

Abstract

Relative treatment efficiency index (RTEI) is used to identify the efficiency of the treatment by the plant itself. The higher the RTEI indicates the more efficient the treatment by the plant studied. In this research, Eichhornia crassipes were used to evaluate its RTEI value in removing heavy metals cadmium (Cd), nickel (Ni) and lead (Pb) from wastewater. E. crassipes were grown in Faculty of Science & Natural Resources’s (FSNR) lake water and spiked with 1 mg/L, 3 mg/L and 5 mg/L of Cd, Ni and Pb respectively. The experiment were conducted within 14 days period to evaluate its potential in phytoremediation of heavy metals from the wastewater. The results showed that the removal of Cd, Ni and Pb by E. crassipes were highest at 1 mg/L respectively. It was observed that E. crassipes were effective in removing Pb compared to Cd and Ni. Antagonistic effects between heavy metals were found in affecting the removal efficiency of each other except for metal Pb. E. crassipes were able to achieve highest RTEI = 0.91 with 98.2% removal of Pb followed by RTEI = 0.52 with 50.2% removal of Cd and RTEI = 0.62 with 44.7% removal of Ni. After 14 days treatment, E. crassipes show significant toxic effects on plant roots and leaves as the concentration of heavy metal increased. The accumulation of heavy metals in plant tissues were shown in ranged from 7.48 mg/kg to 2864.12 mg/kg (Cd), 46.18 mg/kg to 3628.21 mg/kg (Ni) and 2.69 mg/kg to 6012.68 mg/kg (Pb). The results also revealed that the accumulation of heavy metals was higher in the roots than stalks and leaves. It was found that bionconcentration factor (BCF) of Pb, Cd and Ni in root at 1 mg/L were exceed 1000. Study on translocation factor (TF) of all metals were recorded low in ranged of 0.01-0.79 respectively. This indicates that the phytoremediation mechanism uptakes of E. crassipes is rhizofiltration. This study give a better understanding on the potential of E. crassipes in removing heavy metals from wastewater especially industrial wastewater.