Effect of Ion-Exchanging Agent, Zeolite on Removal of Copper in Water and Improvement of Growth in Oreochromis mossambicus (Peters)

Abstract

The effect of different doses of zeolite (0, 0.5, 2, 4 and 8 g zeolite l-1) on reduction of copper toxicity in water and on freshwater fish, Oreochromis mossambicus was studied for 180 days. The 96 h LC50 value of copper for O. mossambicus was 4.27 mg·l-1 . RNA:DNA ratio increased with exposure period in control fish that indicated the growth of fish during the experiment. However, in copper exposed fish the ratio did not show drastic variation when compared to control fish. In zeolite treated fish, RNA:DNA ratio increased like in the control fish. Among the treatments, 2 g zeolite l-1 added treatment showed better performance than the other treatments. When different levels of zeolite were added to copper media, the metal content was completely removed from the medium within a period of 150 days in 0.5 g zeolite l-1 added treatment, while in other treatments (2, 4 and 8 zeolite l-1) it took 120 days. The copper level in Cu treatment was 0.830 mg·l-1 even at the time of the termination of the experiment. The removal of copper from the test media and transfer to sediment were more pronounced in 2 g zeolite l-1 added treatment than in other treatments. A similar trend was also observed in the elimination of accumulated copper from the body tissues. Metal removal from water and body tissues and subsequent improvement of RNA:DNA ratio and protein in fish were maximum in 2 g zeolite l-1 added treatment than in other treatments (0.5, 4 and 8 g zeolite l-1), hence it is considered as an optimum dose.