ارزیابی کیفیت باکتریولوژیکی آب تولیدی دستگاه‌های تصفیه آب خانگی

Background and purpose: Awareness of people about drinking water impurities and the demand for better water quality have led to widespread application of point-of-use (POU) water treatment devices. The aim of this study was to investigate the bacteriological quality of water produced by household water treatment devices. Materials and methods: This cross-sectional descriptive study was performed on 18 household water treatment devices in 2014. Thirty-six inlet and outlet water samples were collected. Bacterial quality of the samples were determined by total and fecal coliform multiple-tube fermentation techniques, heterotrophic plate count (HPC) was done using membrane filter technique on blood agar medium and gram-negative bacteria analysis was performed via membrane filtration technique on EMB agar medium. Isolated colonies were identified using standard biochemical tests. Results: Total and fecal coliform bacteria were negative at all inlet samples, but were positive at two of the outlet samples. HPC were higher than the maximum limits of 500 cfu/ml at 67% of the outlet samples. Pseudomonas, Alcaligenes, Serratia and Shigella genus were found with higher frequencies at both inlet and outlet samples. However, frequencies of Proteus and gram positive Bacillus have increased in the outlet samples. Conclusion: The removal of residual chlorine by household water treatment devices causes developing biofilm on the filters and storage tank of the devices by the bacteria present in distribution network. Consequently, the number and variety of bacteria are increased in water produced by POU water treatment devices.