Four-Month Assessment of Water Quality in a Channeled Urban Stream in São Paulo State, Brazil

The Metropolitan Region of São Paulo (MRSP) faces an intense water crisis, which requires measures to guarantee water supply. However, it neglects urban water bodies, often using them as sewage receptors. To improve the quality of urban rivers, it is necessary to study and to mitigate the sources of pollutants. Thus, the objective of this study was to evaluate the Water Quality Index (WQI) of the Comprido stream, an urban freshwater ecosystem which flows into the Tamanduateí River and this to Tietê River, the most important river of São Paulo State, Brazil. Eight occasions over 4 months in 2017 of surface water were conducted at three sampling stations along the longitudinal axis of the stream. The following parameters were evaluated in triplicate: pH, dissolved oxygen, biochemical oxygen demand, chemical oxygen demand (COD), temperature, apparent color, turbidity, total solids, total dissolved solids, total suspended solids, sedimentable solids, electrical conductivity (EC), ammonia nitrogen, total phosphorus, and coliforms. The water quality parameters and the WQI revealed an alarming scenario regarding the environmental and sanitary conditions of Comprido stream. COD (up to 1,000 mg L −1 ) and EC (~ 500 µS cm −1 ) presented very high values. The WQI was always between bad and very bad (20–40), which allows us to conclude that the waters of the Comprido stream are quite degraded. The pollution was associated with sewage discharges. The study points to the need to carry out the integrated management of urban micro-watersheds to preserve streams and, consequently, improve the quality of adjacent water bodies and the maintenance of ecosystem services to the population.