Uptake of zinc from water and wastewater by a commonly available macrophyte

Abstract

The removal/uptake of zinc from water and wastewater by a locally available macrophyte, water hyacinth, has been investigated. Batches of water hyacinth were exposed to the water containing different concentrations of zinc. The growth was significant at low metal concentrations i.e. 2.0 and 4.0 mgL -1 of zinc. At higher concentrations the growth of the plant was inhibited. The metal accumulation within the plant tissues increases linearly with increasing initial concentrations of metal in water solutions. The threshold toxicity as per visible symptoms starts at zinc concentrations > 4.0 mgL-1. The variation of the metal uptake as a function of time reveals a biphasic behaviour. Analysis of metal content in the root and top of plant reveals that more of the metal is accumulated in the root than the top of the plant. The values of Relative Growth Rate (RGR) parameters were found to be 8.14 × 10-2 and 2.44 × 10-2 at 2.0 and 12.0 mgL-1 of zinc in the solution. However, the rate of mobility of the metal is slower in the root than that in the top of water hyacinth. The metal accumulation factors in the top as well as in the root were determined and the values were found to be significant.