Oxigênio dissolvido e demanda bioquímica de oxigênio no Rio Uberabinha: um estudo da poluição orgânica biodegradável

Abstract

The Uberabinha River, located in the region of Triângulo Mineiro, in the state of Minas Gerais, Brazil, is part of the Araguari River sub-basin. From its head in the city of Uberaba to its mouth in the Araguari River, it measures approximately 150 km, spanning about 135 km in the municipality of Uberlândia. The river drains a watershed of about 2.190 km2, from which water is collected to supply a population that approaches half a million inhabitants. Later, the sewage produced by the city is also discharged directly into the river. This research consisted in the analyses of pH, temperature, dissolved oxygen and biochemical oxygen demand of samples collected in five points of the Uberabinha River, from a section starting upstream of the urban area down to 20.5 km downstream the last point of sewage discharge, encompassing approximately 42 km. In this river section, the landforms go from low to medium hills with many rapids and waterfalls. The samples were collected from June 1999 to May 2000 and the water flow was measured on the two extremes of the studied river section. The results show that the dissolved oxygen values are reduced when receiving the sewage and it tends to slowly return to its normal saturation rate. On the other hand, the biochemical oxygen demand follows a reverse path, as a result of the natural phenomenon of self-restoration even though the organic material is not yet completely removed from the studied river section.