Pinheiros River (Brazil) plays a pivotal role in supplying water to Billings Reservoir, which presents multiple uses (human drinking, energy generation, irrigation, navigation, fishing and leisure). An intense monitoring program was performed during the years 2007 and 2008 to find out whether on site flotation is a feasible solution or not for improving the water quality of this urban river, attenuating the pollutants load caused by the water pumping to the reservoir (approximately 10 m3 s−1). The monitoring of 18 variables (13,429 laboratorial analysis during the period of 490 days), suggested that despite the convenience of the on site approach for water treatment, especially for rivers located in fully urbanized areas, the flotation system is not enough itself to recover Pinheiros River water quality, given the several constraints that apply. Total phosphorus removal was high in percentage terms (about 90%), although the remaining concentrations were not so low (mean of 0.05 mg L−1). The removal efficiency of some variables was insufficient, leading to high final mean concentrations of metals [e.g. aluminium (0.29 mg L−1), chromium (0.02 mg L−1) and iron (1.1 mg L−1)] as well as nitrogen-ammonia (25.8 mg L−1) and total suspended solids (18 mg L−1) in the treated water.
Keywords: environmental monitoring, on site treatment, urban rivers, water flotation, water resources management