Toxicity Evaluation of Wastewater Treatment Plant Effluents Using Daphnia magna

Toxicity evaluation is an important parameter in wastewater quality monitoring as it provides thecomplete response of test organisms to all compounds in wastewater. the water flea daphnia magnastraus is the most commonly used zooplankton in toxicological tests. the objective of this study was toevaluate the acute toxicity of effluents from different units of isfahan wastewater treatment plant(iwtp). the samples were taken from four different physical and biological units. the acute toxicitytests were determined using daphnia magna. the immobility of daphnia was determined after 48h.toxicity results showed that 48h-lc50 and atu values for raw wastewater were 30% (v/v) and 3.33,respectively. it was also found that lc50 values after 48 h for preliminary, primary, and secondaryeffluents were 32%, 52% and 85% (v/v), respectively. the atu values for these effluents were 3.1, 1.9,and 1.8, correspondingly. the efficiency levels of preliminary, primary, and secondary units forremoval of toxicity were found as 6%, 38.9% and 8%, in that order. overall, the present investigationindicated that toxicity removal by up to 50% might be achieved in iwpt. based on the obtainedresults and regarding the improvement of water quality standards, coupled with public expectations iniran, it is necessary to consider more stringent water quality policies for regular monitoring and toxicityassessment.