The water body, the object of this study, the creek Grande, located in the city of Boa Vista, Roraima, in northern Brazil. The river has as large tributary to the right bank of the creek Paca, and his mouth in the rio Branco. This study aims to evaluate, through the determination of physico-chemical and biological (chlorophyll-a) the level of contamination of the igarapé Grande after receiving STP effluent/Boa Vista-RR and the environmental impact caused by the injection of substances into the creek and possibly in rio Branco. In this study we selected six collection points considered strategic to the achievement of objectives. Parameters were assessed: color, turbidity, conductivity, pH, temperature, dissolved oxygen, nitrite, ammonia, total phosphorus, chloride, BOD5, COD, chlorophyll-a, copper, manganese, zinc, iron and nickel. The techniques of collection, transportation and preservation of samples and analysis followed the recommendations of the NBR Nº. 9898 of June 1987 and the standard methods described in Standard Methods for Examination of Water and Wasterwater. Through the observations can be verified that the stream is impacted by human removal of vegetation, soil sealing by the occupation of the surroundings and releases of pollutants. Through the results, with the exception of metal species, it was possible to confirm the impact of effluent discharge on igarapé Grande. Parameters such as phosphorus, ammonia, nitrite and chlorophyll-a showed that the creek does not have great capacity to assimilate, especially in periods of drought, nutrient and contaminant species en route to its mouth on the rio Branco.
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