Influence of domestic and industrial waste discharges on water quality at Minas Gerais State, Brazil

Abstract

The aquatic contamination from kaolin processing plants, as well as from untreated or inadequately treated municipal sewage, was evaluated in the Ubá Stream and Vermelho Stream, at the Minas Gerais State, Brazil. With this purpose, samples of water, suspended material and vegetation were collected and analysed. The analyses involved the determination of the concentration of metals, nitrite, nitrate, chloride, phosphate, chemical oxygen demand and biochemical oxygen demand. The suspended material showed high concentrations (in mg kg-1) of Zn (2,400) and Fe (14,900), while the vegetation collected closed to the streams was heavily contaminated with Al (7,120). The concentrations of nitrite, nitrate and chloride in stream water were lower than the maximum values established by the Brazilian Environmental Standards. The phosphate and biochemical oxygen demand values exceeded 7 and 3 times respectively, the maximum concentrations for superficial water of satisfactory quality.