Assessment of the quality of surface waters and the sewage treatment system in the city of Rio Claro / SP

Abstract

The preservation of the water quality is essential, considering that only a reduced portion of its total volume is available for direct use. The release of effluents beyond water quality standards can significantly aggravate this scenario. The correct management of wastewater becomes even more important in periods of water crisis, for which a solution is reuse through advanced treatment. Thus, the objective of this work was to evaluate the water quality standard in the city of Rio Claro (SP). Along the rivers Corumbataí and Ribeirão Claro, five sampling points were analyzed in relation to several water quality parameters, including both upstream areas of water catchment and downstream areas of treated sewage discharges . The results were compared to the current environmental legislation to ascertain compliance with the established standards. The Water Quality Index (WQI) presented the classification good for all sites, except the downstream one that received the classification regular. . Dissolved aluminum and iron concentrations were above legal limits in 2018, at all locations, especially in the rain season. In the periods of 2010-2014 and 2013-201: Escherichia coli values were above limit also at all locations, with the worst data for the two sites further downstream; the highest values for total phosphorus, electrical conductivity and biochemical oxygen demand were obtained to the two locations further downstream as well, exceeding legal limits. High organic matter removal efficiencies were reported for two wastewater treatment plants in Rio Claro.