Chromium and cadmium removal from wastewater using duckweed - Lemna gibba L. and ultrastructural deformation due to metal toxicity.

Phytoremediation potential of Lemna gibba was evaluated for chromium (Cr) and cadmium (Cd) under laboratory conditions for variable metal load of 1 mg/l, 3 mg/l, 5mgl, 7 mg/l and 9 mg/l, respectively, for 7 and 15 days of treatment period. Effects of both metals on structural attributes of L. gibba were also analyzed by Scanning Electron Microscopic (SEM) study. The metal removal percentage by L. gibba for Cr metal was found in the range of 37.3% to 98.6% and for cadmium it was found within the range of 81.6% to 94.6%. Bio concentration factor (BCF) of L .gibba was observed within the range of 37 to 295 for Cr metal and for Cd metal it ranged from 237 to 1144, which shows that the plant is a hyper accumulator for Cd metal and moderate accumulator for Cr metal. Statistical analysis (Two-way ANOVA) was performed on experimental results to confirm the individual effect of metal concentration and treatment period as well as cumulative effect of both factors together on percentage metal removal and on BCF. Research studies indicated that with the progress of treatment period metal removal percentage increases but increasing metal load during experiment negatively co-relates the metal removal percentage and BCF.