Qualidade da água na bacia de contribuição da estação de tratamento de água Sinnott - Pelotas, RS.

Abstract

The catchment area of the Sinnott Water Treatment Plant (SWTP) in Pelotas (RS/Brazil) is used for the abstraction of water for irrigation and human supply for the city, among other uses. To date, few studies related to the factors driving the water quality in the catchment were developed, as well asactions for the management of its waters. In this context, the present study aimed to relate the variation in water quality with rainfall and with the soil types in the catchment of the SWTP. The raw water quality parameters data sets used in this study were obtained from the monitoring carried out by the Autonomous Service ofSanitation of Pelotas (SANEP), including a collection point on the Arroyo Quilombo(31°31'18.62" S; 52°29'9.89" W) and another point on the Arroyo Pelotas (31°35'16.70" S; 52°21'50.67" W). Water samples were collected and analyzed by SANEP, according to the methodology described in Standard Methods for the Examination of Water and Wastewater. Daily and monthly average data were used, covering the period from 2007 to 2012. The physical and chemical parameters used to evaluate the quality of water were: turbidity, temperature, color ,pH, hardness, dissolved oxygen, alkalinity and organic matter. The water quality parameters color, turbidity and organic matter showed a significant positive correlation with rainfall, indicating a likely effect of sediment transport in the catchment area. In relation to thenational water quality standards set by legislation (CONAMA nº 357/2005), for Class 2 freshwater, the parameter color presented the lowest level of achievement, especially at the point of collection on the Arroyo Pelotas, where this parameter, remained 76.2% of the days over the limit in 2009. This result indicates the need for conservation actions in the catchment, especially considering the importance of this parameter for the assessment of water quality for public supply, both in terms of treatment costs as in terms of public health.