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

Cristobal Chaidez, Charles P. Gerba

Research output: Contribution to journalArticlepeer-review

45 Scopus citations


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 107 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.

Original languageEnglish (US)
Pages (from-to)253-260
Number of pages8
JournalInternational Journal of Environmental Health Research
Issue number4
StatePublished - Aug 2004


  • Aeromonas hydrophila
  • Bacteria
  • Drinking water
  • Heterotrophic bacteria
  • Point-of-use (POU) devices
  • Pseudomonas aeruginosa
  • Tap water

ASJC Scopus subject areas

  • Pollution
  • Public Health, Environmental and Occupational Health
  • Health, Toxicology and Mutagenesis


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