Acute toxicity to Daphnia magna of effluents containing Cd, Zn, and a mixture Cd-Zn, after metal removal by Chlorella vulgaris

Daphnia magna was used as a test organism for assessing the toxicity remaining in simulated effluents containing cadmium, zinc, and a cadmium-zinc mixture, after these metals were removed with suspended and immobilized Chlorella vulgaris cultures. The percentage of removal was higher (84.7%) for cadmium in the metal mixture with immobilized cultures. The LC₅₀ value was lower for the residual cadmium (single and in the mixture) in the effluent after treatment with suspended cultures. The acute toxicity response observed in D. magna, indicates that zinc has an antagonistic effect on cadmium toxicity. According to the results, the treatment system can modify the Cd acute residual toxicity. (C) 2000 by John Wiley and Sons, Inc.