Bacterial Indicators of Water Quality in Swimming Pools and Their Role

The most significant bacterial indicator of the quality of swimming pool water is the total 35°C agar plate count. Specific bacterial indexes such as Escherichia coli have been used by various agencies, but these indexes are less sensitive than the total 35°C agar plate count. Also, there is no concensus of opinion as to what constitutes acceptable values for these specific indexes. Properly designed, constructed, and operated swimming pools with an adequate level of residual disinfectant can be maintained with total plate counts which are less than 100 colonies/ 1.0 ml. The bacterial quality of swimming pool water is usually a measure of the adequacy of the disinfecting process. Microbiological examination of samples of swimming pool water for specific genus or species are needed usually only in conjunction with a suspected outbreak of disease among the users of a swimming pool.