Ecotoxicity of raw and treated effluents generated by a veterinary pharmaceutical company: a comparison of the sensitivities of different standardized tests.

Pharmaceutical effluents have recently been recognized as an important contamination source to aquatic environments and the toxicity related to the presence of antibiotics in effluents has attracted great attention. Conventionally, these effluents have been treated using physico-chemical and aerobic biological processes, usually with low rates of pharmaceuticals removal. Due to the complexity of effluents, it is impossible to determine all pharmaceuticals and their degradation products using analytical methods. Ecotoxicity tests with different organisms may be used to determine the effect level of effluents and thus their environmental impacts. The objective of this work was to compare the sensitivities of five ecotoxicity tests using aquatic and terrestrial organisms to evaluate the toxicity of effluents from the production of veterinary medicines before and after treatment. Raw and chemically treated effluent samples were highly toxic to aquatic organisms, achieving 100,000 toxic units, but only few of those samples presented phytotoxicity. We observed a reduction in the toxicity in the biologically treated effluent samples, which were previously chemically pre-treated, however the toxicity was not eliminated. The rank of test organisms' reactions levels was: Daphnia similis > Raphidocelis subcapitata > Aliivibrio fischeri > Allium cepa ~ Lactuca sativa. Effluent treatment employed by the evaluated company was only partially efficient at removing the effluent toxicity, suggesting potential risks to biota. The acute toxicity test with D. similis proved to be the most sensitive for both raw and treated effluents and is a suitable option for further characterization and monitoring of pharmaceutical effluents.