Toxicity Evaluation of Effluents from Dye and Dye Intermediate Producing Industries Using Daphnia Bioassay

Wastewater from seven dye and dye intermediate producing industries and a common effluent treatment plant was assessed to characterize the acute toxicity using Daphnia bioassay. The 24 and 48 h EC50 values and its confidence limits were estimated applying the probit analysis method. The 24 h EC50 values for different dye effluent samples A, B, C, D, E and F were 1.35, 17.32, 17.67, 29.18, 46.49 and 25.11%, and 48 h EC50 values were 1.23, 14.12, 15.52, 24.53, 29.69 and 23.22%, respectively. Result showed linear relationship with high degree of confidence (0.84 100%. Effluent of industry 'A' exhibited highest toxicity causing 100% immobility at 3.13% effluent concentration. Effluent of industry 'G' and 'H' had shown least toxicity, and was found toxic at the concentration of full strength (100%) causing ≤ 20% and 10% immobility in 24 h. Out of 8 industries effluents tested, 5 showed 100% immobility of daphnia at 50% of effluent concentration, while 1 showed highest toxicity (100% immobility) at a very low concentration (3.13%) of the effluent, and 2 showed lowest toxicity. These results clearly indicate that the bioassay reflects the overall toxicity potential of indusial discharge as it provides the complete response of test organisms to all components of water.