Environment & Ecosystem Science (EES)

Laboratory chemical wastewater contains the heavy metals such as Pb and Cr. The removal of Pb from such water in the absence and presence of Cr and other metals using phytoremediation technique with Azolla was studied. A hyperaccumulator Azolla aquatic plant species was grown in a solution of Pb and/or Cr under three experimental settings and the relative growth rate of the plant, the bioconcentration factor and the Pb removal efficiency were measured for a period of 21 days under controlled laboratory environment. In the first experimental setting, the Azolla was planted in Pb solutions of concentrations 2.5 ppm, 5.0 ppm, and 10.0 ppm. A removal efficiency of Pb up to 98% was reported in the solution of 2.5 ppm Pb concentration. In the second experimental setting, when the Pb was mixed with Cr, a decrease in the relative growth rate of Azolla was observed, yet with an increase in the Pb removal efficiency. In the third experiment series, two concentrations (2.5 ppm and 5.0 ppm) of Fe, Mg and Ca in the solution were used in addition to Pb and Cr. Here, a decreased relative growth rate with increasing exposure days, and a rising trend in metal removal efficiency and bioconcentration factor were observed. The results revealed a promising potential of Azolla sp in the phytoremediation of Pb in solution. Further, the Azolla sp was found more effective in removing Pb when it is present individually rather than in a solution with Cr.