DETERMINANTS OF THE MICROBIOLOGICAL WATER-QUALITY OF INDOOR SWIMMING-POOLS IN RELATION TO DISINFECTION

A study of microbiological water quality at 12 indoor swimming-pools w as carried out over a three-month period. Chlorination was used as the disinfectant method at seven of them and at the other five electrolyt ically generated copper and silver ions were used. A regression analys is was used to evaluate the association between variables linked to di sinfection and physico;chemical water quality-residual free chlorine ( HOCl + OCl-), Cu, Ag, pH, conductivity, turbidity - and microbiologica l water quality - aerobic plate count, total and fecal coliforms, feca l streptococci, Pseudomonas aeruginosa and Staphylococcus aureus. Anal ysis showed that the sole predictive variable was disinfectant concent ration based on the linear model P = a + bX(P = probability that a sam ple be microbiologically acceptable; a = interception; b = gradient, a nd X = disinfection concentration). At the chlorinated pools 2.6 mg l( -1) of free chlorine (a = 0.34, b = 0.21) was required, and at those u sing Cu-Ag 3.4 mg l(-1) of Cu (a = 0.15, b = 0.22) in order to ensure that there be a 90% probability of the bathing water being microbiolog ically acceptable. The active chlorine concentration (HOCl) failed to present an association with microbiological water quality. (C) 1998 El sevier Science Ltd. All rights reserved.