Microbial Water Quality of Karaj City in Terms of Heterotrophic Bacteria Count Index: Zoning by the Geographic Information System (GIS)

Background and Purpose: The aim of this study was to evaluate the microbial quality of drinking water in Karaj, Iran in terms of heterotrophic bacteria count index (HPC) and its variation trend using geographic information system (GIS) in 2016. Materials and methods: In this study, water sampling was carried out in Karaj distribution network in all 12 regions and based on this, 3 samples were taken from each region by grab sampling technique. Results: The findings indicated that the mean terms of free residual chlorine, turbidity, and pH in the 12 regions of Karaj were respectively measured 0.2-0.8 mg/l, 0.22-0.94 NTU, and 7.3-7.8. The highest levels of HPC in regions of 3, 6 and 9 of Karaj were detected at 70, 115 and 320 colonies, respectively. The highest turbidity rates were 2.48 and 1.62 NTU in regions 3 and 9, respectively, and the lowest rate was 0.22 NTU in region 5. Conclusion: According to results, in all samples, the obtained HPC levels were within the recommended national standards. Furthermore, the results of water quality zoning using ordinary point kriging represent high quality drinking water and its complete overlap in the studied cases.