EFFECTS OF KAOLIN PROCESSING PLANTS ON THE WATER QUALITY OF STREAMS IN BRAZIL

摘要

Brazil is the second largest kaolin producer in the world (reserves of 14%). The discharge of untreated or inadequately treated wastewater from such kind of industry may be harmful to the aquatic ecosystem and human population. Although attention has been intensively focused on the metal contamination of aquatic systems from several pollution sources, there is a worldwide lack of information concerning effluent emissions from kaolin processing plants. Consequently, the significance of metal discharges into stream waters in altering water quality is still unknown. Thus, with the purpose of establishing a preliminary report to trace out industrialisation outcomes at the State of Minas Gerais, Brazil, which are due to kaolin processing plants, samples of stream water and fluvial sediment were collected and analysed to detect metal inputs. The metal examined were Zn, Fe, and Al among others, being selected due to their toxicity and occurrence in wastewater. Metal inputs in the samples analysed appeared to be related to effluent discharges into the streams. High concentrations of metals were found in samples when compared with controls. The stream water showed elevated concentrations (in μg L~(-1)) of Zn (6840), Fe (9700) and Al (5090). The Sediment Enrichment Factors (SEF) investigations indicated heavy enrichment for Zn (SEF= 18.3). The Geoaccumulation Index for this element in sediments accounted for 4 (heavy polluted). The pH and conductivity levels of the stream water samples were also evaluated and are far from those set by the Brazilian Environmental Standards.