Slow-growing heterotrophic pigmented bacteria as an indicator of water quality in potable water samples

The occurrence of pigmented bacteria in heterotrophic plate counts of treated drinking water generally goes unnoticed because most of these organisms grow slowly and require a longer incubation period than the standard 48 hours. Although not considered primary pathogens, strains of pigmented bacteria have been shown to be hazardous to human health. Their presence in recirculating, chilled drinking fountain water can indicate poor water quality. This study focused on drinking water samples from eight different drinking fountains located in five different buildings on Ohio Wesleyan's campus. These fountains differ in usage, age, and placement along the water distribution route. The water quality was determined by taking weekly samples from each fountain, measuring the free chlorine residual from each sample, and plating the water onto R2A medium. After seven days of incubation, the total number of bacterial colonies from each sample was recorded, as well as the total number from each pigment. Age and usage of fountains appeared to be factors influencing water quality, as the older and less used fountains had higher plate counts. As expected, there was also a direct correlation between the amount of free chlorine in the water at the time of sampling and the total number of bacteria contained in the water sample. Fungus growth was noted on plates from certain fountain samples. A preliminary identification of typical pigmented strains is underway, as also is an analysis of the fluctuations of total bacterial counts over the sampling period.