INTRODUCTION: Brazil's Federal District (FD) has seen steep population growth in recent years, and this has increased demand for high-quality water. AIM: The present work aims to evaluate the quality of surface water from two water bodies in the FD at six sampling points, three of which are in the Sobradinho River (the receiving body of a sewage treatment plant effluent) and three in the Jardim River (located in an agricultural region). METHODS: Analyses were carried out every thirty days, for twelve months, covering rainy and dry seasons. Parameters were analyzed such as temperature, pH, dissolved oxygen (DO), conductivity, turbidity, total hardness, main ions, total and fecal coliforms (E. coli) in water. Ecotoxicological evaluation was also performed, using the micro-crustacean Ceriodaphnia dubia. RESULTS: Data of physical and chemical determinations showed DO, conductivity, Cl-, NO3-, SO4(2-) and Na+ to be important in indicating contamination by urban effluents. On the subject of biological parameters - E. coli and ecotoxicological evaluation - the former was seen to be more effective in the urban area. However, in the countryside, the assay with C. dubia proved to be the most sensitive, although less than ideal, because the organism is very sensitive to low water hardness. CONCLUSIONS: The fecal coliform indicator (E. coli) was the most effective one for comparing water quality in the two basins, mainly for the urbanized one, while ecotoxicity assays with C. dubia were harmed by the natural chemical composition of the water.
water hardness; ecotoxicology; water resources; calcium; bioindicators
