Eficiência de ensaios ecotoxicológicos na detecção de toxicidade em efluentes de refinaria de petróleo

Abstract

One of the main sources of water pollution is industrial wastewater. Among these, stands the waste of oil refinery effluents because is quite complex and of difficult tractability. Therefore, it is evident the need for continuous monitoring of the quality of these effluents, since they are considered high risk waste. In addition to monitoring physical and chemical, biological monitoring is an important tool for assessing the quality of effluents. The aim of this study was to evaluate the effectiveness of four tests in determining the toxicity of treated wastewater of oil refinery. Were performed acute toxicity tests with Daphnia magna and heterotrophic aerobic bacteria (D Test), and chronic toxicity tests with Ceriodaphnia dubia and Caenorhabditis elegans. Tests with D. magna followed the NBR 12713 (ABNT, 2004) and had the mortality as endpoint. The D Test was based on Krebs (1985) and assessed the effects of stimulation or inhibition of biochemical oxygen consumption (BOD). Tests with C. dubia evaluated the mortality rate and reproduction of organisms, according to NBR 13373 (ABNT, 2005). Tests with C. elegans were performed according to ISO / DIS 10872 (2009), and had the growth and reproduction as endpoints. The five evaluated samples were from an oil refinery in the state of Parana, Brazil. The statistical analysis showed that C. elegans was the most sensitive organism to the effluent, presenting the observed effect concentration (OEC) from 12.5%, which classified it as moderately sensitive organism. Tests with C. elegans and the D Test showed low-dose stimulation, a phenomenon known as hormesis. This phenomenon should be considered in environmental assessments because every change in communities composition and structure interferes in the ecosystems integrity.