As evident from the above results, for all the metals studied, the least metal uptake was recorded at 20 mg l-1 while initial concentration for highest uptake varied in different metals. Among all the metals studied, Cd, Hg and As recorded decrease in the metal uptake at higher concentrations after attaining the maximum values. This appears to be due to the increase in the number of ions competing for the available binding sites in the biomass and also due to the lack of binding sites for the complexation of these ions at higher concentration levels. At lower concentrations, all metal ions present in the solution would interact with the binding sites and thus facilitate maximum adsorption. At higher concentrations, more ions are left unabsorbed in solution due to saturation of binding sites (Ahalya et al., 2005). Also, contact time for minimum uptake was found to be 30 min for all the metals. However, contact time for maximum uptake also differed for different metals.