Fungal and bacterial evaluation in drinking water distribution network and their association with physicochemical parameters

Preventing the growth of microorganisms in water distribution network (WDN) is an important public health priority. In this study, 98 water samples were collected from the Gorgan City (Iran) water distribution network (WDN) to assess fungal and bacterial contamination in WDN and their association with physicochemical parameters. All microbiological and physicochemical tests were performed as described in the standard method. The results showed that 15.3 %, 12.2 %, and 2 % of the sample had total coliforms, Clostridium perfringensand fecal coliforms, respectively; however, no Escherichia coliand fecal streptococci were found in samples. The average count of heterotrophic bacteria and fungi was 203.45 CFU/mL and 6.83 CFU/100 mL, respectively. Seven genera of fungi were isolated, of which Candida(19.4 %) and Aspergillus(11.2 %) were the most prevalent, followed by Penicillium(5.1 %), Rhodotorula(3.1 %), Cladosporium(2 %), Acremonium(2 %) and Alternaria(1 %). The mean and Standard deviation of free residual chlorine (FRC), pH, turbidity, temperature, total organic carbon and electrical conductivity were 0.22 ± 0.27 mg/l, 7.28 ± 0.22, 0.61 ± 0.68 NTU, 19.27 ± 2.83 °C, 0.45 ± 0.17 mg/l, and 953.49 ± 207.54 (µs/cm), respectively. The presence of pathogens fungus is a major public health concern for people with lowered immunity. The present study indicated that using microorganisms with different features provides a more reliable evaluation to assess the microbial growth in WDN. Amongst physicochemical parameters, FRC above 0.8 mg/l prevented the fungal and bacterial pathogens growth in WDN. However, further research is required to measure the risks of trihalomethane formation.