The aim of our research was to evaluate the acute and chronic toxicity of wastewater from the pharmaceutical industry to some aquatic organisms. The toxicity of three 24h proportional samples of wastewater was determined with the acute toxicity tests using the bacterium Vibrio fischeri and daphnid Daphnia magna. The inhibition of bacterial luminescence was measured after a 30 min exposure period and the immobility of daphnids was determined after 24 and 48h. The chronic effects on daphnid survival and reproduction were observed for three weeks.

The toxicity tests indicated that all investigated samples were acutely toxic to the organisms, but in each sample the responses of bacteria and daphnids were quite different. Acute and chronic effects on daphnids were observed when testing the first sample of wastewater, but no influence on bacteria was determined. The second sample was acutely toxic to both organisms. The third sample was toxic only to bacteria, while no influence on daphnid survival and reproduction was found. The reason for the different toxicity of the samples lay in their compositions. The comparison between chemical analyses and toxicity data showed that for daphnids the main cause of toxic effects was zinc.