COMPARISON OF THE MICROBIOLOGICAL QUALITY OF WATER-COOLERS AND THAT OF MUNICIPAL WATER-SYSTEMS

The microbiological quality of tap water and that of water from 50 wat er coolers located in residences and workplaces were comparatively stu died. In addition, different factors that might influence the bacterio logical contamination of water dispensers were examined. Aerobic and f acultative anaerobic heterotrophic bacteria, total coliforms, and two indicators for fecal contamination (fecal coliforms and fecal streptoc occi) as well as three types of pathogenic bacteria (Staphylococcus au reus, Pseudomonas aeruginosa, and Aeromonas spp.) were enumerated. It was found that 36 and 28% of the water dispenser samples from the resi dences and the workplaces, respectively, were contaminated by at least one coliform or indicator bacterium and/or at least one pathogenic ba cterium. The respective proportions of tap water samples contaminated in a similar fashion were 18 and 22%, much less than those observed fo r water coolers (chi1(2) = 3.71, P = 0.05). We were unable to discern the dominant factors responsible for the contamination of water cooler s, but cleaning the water dispenser every 2 months seemed to limit the extent of contamination.