Qualidade microbiológica e índice de estado trófico dos rios Renato e Caiabi, afluentes do rio Teles Pires-MT

Abstract

The evaluation of the water quality of a water body is of paramount importance regarding its environmental management. Water pollution is a worrying factor in most Brazilian rivers, as a consequence of land use and occupation and effluent discharge without prior treatment. Thereore, the monitoring of water quality is of paramount importance because it portrays the reality that water bodies present in relation to the imapcts suffered in hydrografic basins. Thus, the objective of this work was to characterize the microbiological quality and the and Trophic State Index (TSI) of the rivers basins (BH) Renato and Caiabi, tributaries of the right bank of the Teles Pires River – MT. The collections were carried out during the dry and rainy seasons between 2020 and 2021, with 8 collections in rivers of BH Renato defined with points 8 P1 to P8, and 7 collections in the river of BH Caiabi with points P1 to P5. The results of monitoring the pH, electrical conductivity (EC), temperature and biochemical oxygen demand (BOD) parameters indicate that the water of the Renato and Caiabi rivers are, in general, acidic (4.8 and 7.5 and 4.6 and 7.8, respectively), with low EC values, variable temperature according to the climate and acceptable BOD levels for class 2 rivers (values below 5 mg/L). The results of the quantification of thermotolerant coliforms (Cterm) indicated that in some points of the rivers there is non-compliance with the value established in CONAMA Resolution 357/2005, as in the points of headwaters (P1) of the rivers Renato and Caiabi (9300 and 4300 NMP/100 mL, respectively) showing unnatural sources of contamination. The ETI values obtained indicate watercourses as ultraoligotrophic for the BH of the river Renato and oligotrophic or the river Caiabi, indicating a low risk of eutrophication. Although the results found indicate alterations with a low degree of eutrophication, the intensification of land use and occupation can cause greater negative impacts on water quality.