Comparison of the microbiologic quality of point-of-use (POU)-treated water and tap water

Abstract

Activated carbon filtration devices placed on household faucets are used to improve the taste and odour of tap water. However, there has been a concern that the growth of bacteria capable of causing opportunistic infections in these devices might present a public health risk. The water quality from point-of-use (POU) water activated carbon treatment devices and that of tap water with POU-connections and tap water without POU devices were compared. Heterotrophic plate count (HPC) bacteria, total and faecal coliforms, and acid-fast organisms (Mycobacteria spp.), as well as, the opportunistic bacterial pathogens Aeromonas hydrophila, Plesiomonas shigelloides, and Pseudomonas aeruginosa were enumerated. The highest concentration of bacteria was found in POU-treated water. P. aeruginosa, acid-fast organisms, and total coliforms were present in 38.5, 43.8, and 82.4% of the samples, respectively. HPC bacteria were present in all of the POU-treated water samples, with concentrations ranging from 10(2) to 10(7) colony forming units/mL. Neither faecal coliforms nor P. shigelloides were recovered from any samples. Tap water with a POU-connection also had higher numbers of bacteria than tap water samples. It was concluded that tap water without POU devices had lower numbers of A. hydrophila, acid-fast organisms, HPC bacteria, P. aeruginosa and coliforms than POU-treated water, and tap water with a POU-connection. The use of POU-devices may amplify the numbers of bacteria present in the tapwater by promoting biofilm formation. Based on a daily ingestion of two liters of POU treated water, A. hydrophila and P. aeruginosa had a probability of less than 10(-6) of colonizing the gut; however, annual risks could be as much as 100-fold greater.