Avaliação espaço-temporal da qualidade da água e simulação de autodepuração na bacia hidrográfica do córrego São Simão, SP/Water quality spatial and temporal evaluation and auto-purification simulation from the São Simão stream watershed, SP

This study evaluated the water of São Simão stream watershed. For this, six sampling points were established and twelve samples of water were collected during the months of March, May, June, July, August, September, October, November, and December of 2005 and January, February, and March of 2006. The following variables were analyzed: discharge, temperature, turbidity, pH, electrical conductivity (EC), dissolved oxygen (DO), alkalinity, chloride and TSS (total suspended solids). The Streter & Phelps model which correlates the variation of the deficit oxygen with the distance was applied to evaluate the São Simão stream auto-purification. The characteristics of the São Simão stream near its spring until it reaches São Simão city allowed concluding that there is low interference in its quality. However, the absence of treatment of domestic wastewater at São Simão city reduced the water quality and increased the degradation process of São Simão stream after passing through the city. The Streeter & Phelps model allowed identifying the auto-purification zones in this stream and indicated the need for primary wastewater treatment, with an efficiency of 30%. [PUBLICATION ABSTRACT]