Potential of Mosquito Fern (Azolla caroliniana Willd.) Plants as a Biofilter for Cadmium Removal from Wastewater

Abstract

The aquatic vascular plant Mosquito Fern (Azolla Caroliania Willd.) was investigated asa potential biological filter for removal of Cd from wastewater. Mosquito Fern plants were grown in and harvested weekly from 0.10 M Hoagland nutrient solutions containing 0.01, 0.04, and 1.03 µg Cd mL-1 or 0.50 M Hoagland nutrient solutions containing 0.02, 1.0, and 9.14 µg Cd mL-1. Dry weights of plants significantly increased when exposed to all three Cd concentrations in 0.10 M Hoagland solution through week three then decreased thereafter. However in plants exposed to Cd treatments in 0.50 M Hoagland solution, dry weights increased only through week one and decreased thereafter. Tissue Cd concentrations in plants grown in 0.10 M Hoagland solution increased during the first two weeks followed by decreases in week 3 and 4. However, tissue Cd increased through week 3 in plants grown in 0.50 M Hoagland solutions. Tissue P in plants grown in 0.10 M Hoagland solution increased over time, and plants exposed to the lowest concentration of Cd showed tissue P greater than controls. Tissue P in both control and treated plants in 0.50 M Hoagland solution increased over time with exception of the medium level (1 µg Cd mL-1). Overall, our results suggest that Mosquito Fern would be useful for absorbing Cd from nutrient-rich water when the solution concentration, were as low as 0.01 and as high as 9.14 µg Cd mL-1. However, the harvest regime would haue to be every one or two weeks to sustain plant vigor and realize maximum uptake of Cd from solution.