Variaciones temporales y espaciales de coliformes y de Escherichia coli en aguas recreativas fluviales (RÝo Salado, Santa Fe, Argentina). Relación con los estßndares de calidad / Temporal and spatial variations of coliforms and Escherichia coli in fluvial recreational waters (Salado River, Santa Fe, Argentina). Relationship with the quality standards

RESUMO

There are no standards accepted by all the countries to fix top concentrations of microbiological indicators in recreational waters. Even now there is still a considerable discussion either in USA as in Europe. The universal application of a bacteriological quality criterion is hard due to several environmental factors that affect the relation between the indicator, the exposition and the health risks. Our purpose was to present a case study as an example of the influence of the climatic conditions in the application of the most known standards (Environmental Protection Agency of USA, Council of European Communities, World Organization of Health, and others from Canada, South Africa and Hong Kong). The pluvial rainfall increased the number of E. coli, thermotolerant coliforms (C Te), and total coliforms (CT) 6-10 fold, in comparison to the number registered during the steady-state conditions of the system. However, not all the standards included that factor. In Summer, hourly, daily and weekly variations were proved, therefore the standards that suggest fortnightly sampling frequencies would not be convenient in that system. Although the main source of variation was time, spatial variability was also detected. The percentage of E. coli among the C Te was very variable, but the average resulted low (26) compared to the levels in temperate regions of other countries (> 90). According to the directives proposed by the Commission of European Communities, the parameter has been changed (C Te for E. coli), but the standard has remained (2000/100 ml). Thus, the directive would be more permissive.