Megacities as Sources for Pathogenic Bacteria in Rivers and Their Fate Downstream

Figure 3

Mean load of thermotolerant coliforms in 2008 along the Tiete River [cfu per 100 mL]. The distance is given in river-km starting from the first sampling site west of Biritiba-Mirim, São Paulo, and the locations of main cities are shown. The onset of input of sewage from the city between km 80 and 120 can clearly be seen in the coliforms load in the river. Downstream from this area the number of coliforms declines considerably but tributaries, for example, Pinheiros River, or cities in the outskirts of São Paulo, for example, Carapicuíba, also dump waste in the river which can be seen by the coliforms number between river-km 130–160. Further down, the number of coliforms declines rapidly but the river is still heavily polluted as judged by the much slower decline in the biochemical oxygen demand (BOD5). As can be seen from the graph, the cities of Salto and Tiete do not contribute significantly to the thermotolerant coliforms load of Rio Tiete. Data taken from the CETESB report 2009 [16].