Removal of Some Heavy Metals from Industrial Wastewater by Lemmna Minor

Abstract

Treatment of industrial wastewater by constructed wetland system for the removal of heavy metals consisting of clarification and Lemna minor (duckweed) system was studied under experimental conditions through design, construction and operating pilot plant. This plant was operated with a constant hydraulic retention time of 2 hr and 10 days for clarifier and duckweed tanks respectively. The potential of duckweed has been investigated to accumulate Cd, Cr, Ni and Pb present in a combined industrial wastewater. The experiments results show that the average removal efficiency of Cd, Cr, Ni and Pb were 44.93%, 32.26%, 74.48%, and 79.1 respectively. Duckweed plant is a poor accumulator for Cd. While it is a hyperaccumulator for Pb, Cr and Ni. Also, the removal percentages of these heavy metals have significant positive linear correlation with the pH reduction percentage and increases in acidic solution (pH < 7). Therefore pH highly affects the removal efficiency of these metals from wastewater. Duckweed shows promise for the removal of heavy metals from industrial wastewater which makes duckweed a good species for phytoremediation activities. Duckweed based treatment systems are a cost-effective and reliable supply of acceptable quality water for river rehabilitation and reuse for other purposes.