EVALUATION OF THE WATER QUALITY AND AUTO-PURIFICATION FROM THE MEIO STREAM, LEME (SP)

This investigation utilized hydrochemical relations to evaluate possible anthropogenic inputs at Meio Stream, Sao Paulo State. Realized three sampling of water during the months of February, April and July/2005, in five sampling points analyzing: discharge, temperature, turbidity, pH, electrical conductivity (EC), dissolved oxygen ( DO), TDS (total dissolved solids), TSS (total suspended solids), Ca2+, Mg2+, Na+, K+, HCO3-, Cl-, SO42-, PO43- and NO3-. The characteristics of water close to spring until Leme city allow concluding that there is a small interference in its quality, however the absence of treatment of domestic wastewater at Leme city reduced its quality. It was applied the QUAL 2K modeling to evaluate the Meio Stream auto-purification identified the auto-purification zones and indicated the necessity of secondary wastewater treatment, with 76% of efficiency.