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Heterotrophic bacteria in drinking water in Tabriz,, Iran

Author(s): Mosaferi M | M Shakerkhatibi | A Mehri

Journal: Journal of School of Public Health and Institute of Public Health Research
ISSN 1735-7586

Volume: 8;
Issue: 4;
Start page: 83;
Date: 2011;
Original page

Keywords: Drinking water | Heterotrophic bacteria | HPC | Tabriz

Background and Aim: Recently the use of heterotrophic plate count (HPC) has received much attention as a supplementary indicator of the MPN test in water quality control. The US Environmental Protection Agency (USEPA) has declared 500 cfu/mL as the maximum acceptable level for heterotrophic bacteria in distribution networks. Currently the HPC determination is not among the routine control items in Tabriz city and there is no published information on the presence of heterotrophic bacteria in that city's potable water. In this study the presence of HPC in potable water main was determined in Tabriz city, Iran.  Materials and Methods: A total of 50 water samples, representing drinking water of the whole city of Tabriz, were taken randomly from different districts of Tabriz city and their HPC, coliform, residual chlorine, turbidity, temperature, and pH were measured. For the heterotrophic bacteria the R2A and Nutrients Agar culture media were used, while the spread plate count method was used for the HPC test. The statistical tests used for data analysis were the t-test and regression.     Results: In 50% of the samples heterotrophic bacteria were present. In 6 districts the HPC was higher than 500 cfu/mL. Based on Nutrient Agar and R2A, the HPC indicator in Tabriz drinking water was 184±340 and 154±315 cfu/mL, respectively, the growth rate being higher in the former medium. There was a significant correlation between the HPC and residual chlorine in both media (for Nutrients Agar, p

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