Survey of Microbial quality of drinking water of distribution system using heterotrophicbacteria plate count index in Zahedan-Iran ۲۰۱۱-۲۰۱۲

Today, heterotrophic bacteria have been considered as HPC index as a supplement to coliformindex in water quality control. In the present study, the HPC index in Zahedan drinking water wasevaluated and determined in accordance with the standard. ۸۰ water samples were preparedaccording to the national standard of Iran No. ۴۲۰۸ based on the population of different areas ofZahedan freshwater distribution network, so that the entire distribution network is covered.Samples were taken separately in two seasons, summer and winter. ۴ areas in areas with newdistribution network and made of polyethylene and ۴ areas in areas with old distribution networkand cast iron were selected and ۱۰ samples were taken from each area. Samples were tested from۸ am to ۱۰ am under standard conditions for HPC, TOC, temperature, turbidity, free residualchlorine, PH and Do. HPC test was performed by plate diffusion method. In only two points, themaximum HPC level in summer was ۳۰۰ CFU / ml, which was lower than the standard and withinthe allowable range. There was a direct relationship between temperature, turbidity, pH and TOCof water with the growth of heterotrophic bacteria. There was also an indirect relationship betweenthe amount of HPC and the amount of chlorine remaining in water and dissolved oxygen. Networkage and material had no effect on HPC.

Keywords:

Heterotrophic , Plate culture , Drinking water , Zahedan