Assessment of microbiological quality for swimming pools in South America

Concerning the great importance of the safety of bathing water, and due to the dispute about the better microbiological indicator to assess the water quality of swimming pools, 1345 samples of water collected from 60 swimming pools in a period of four years were analyzed for total (TC) and fecal coliforms (FC), fecal streptococci (FS), heterotrophic bacteria (HPC), S. aureus (Sa), C. albicans (Ca) and P. aeruginosa (Pa). The frequency of positive results for these indicators ranged up to 70.4% (HPC), 13.3% (TC), 9.1% (Sa), 7.7% (FS), 5.6% (FC) and 2.0% (Pa and Ca). A correlation matrix (Spearman rank correlation) showed strong positive relationship among the levels of these microorganisms and between their densities and bather load and water temperature. As expected, all the microbiological variables presented a negative correlation with chlorine, C. albicans showing to be the more resistant to this disinfectant. Considering the good correlation among all these microbiological parameters, the highest rates of isolation of heterotrophic bacteria and total coliforms and the costs for microbiological analysis, it is possible to achieve an effective monitoring of swimming pool water quality by using only these two indicators, with no need of applying the other ones on a routine basis. P. aeruginosa and C. albicans, besides their high resistance to chlorine, presented a very low incidence and its use for evaluating swimming pool waters quality in routine is not indicated.