Effect of dichromate on population and growth of various protozoa isolatedfrom industrial effluents

Three protozoa belonging to genera Euglena. Vorticella and Stylonychia coll ected from industrial wastes were cultured in a medium containing inorganic salts, basically! meant Ibr the growth of algae. Protozoa showed rapid gro wth in the medium Hexavalent chromium (K2Cr2O7) at a concentration of 5 mug /L in the medium adversely affected the growth of protozoa. Al the end of e ight days of Cr administration, the population of Euglena, Vorticella and S tylonychia increased 8-, 4.5- and 10-fold, respectively, as against 30-, 6. 75- and 50-fold increase in the control cultures. No apparent death phase a nd no change in activity or morphology of protozoa was observed at this Cr concentration. The protozoa were also exposed to different metal ions. The Pb (2.42 mmol/L), Cr (0.48 mmol/L). Cd (0.36 mmol/L), administered in the c ulture medium for a period of 2 years. The metal tolerance for S. mytilus a nd V. microstoma was Pb > Cr > Cd. E proxima could nor tolerate any of the long-term metal treatments. Because of the ability of these protozoa to tol erate high concentrations of heavy metals their potential role in remediati on of heavy metals from industrial wastewater is considered.