Investigation of Bacterial Regrowth and Residual Chlorine in Household Stored Water in Saveh- Iran

 Saveh city -located in the semi-arid area in Iran- has brackish water and it was forced to use reverse osmosis desalting systems.  Water is not distributed through the distribution network to homes so, people have to buy water from certain places and transfer water through household storage vessel. They have to buy more water and keep it at home for more than 1 week. Therefore, the probability of microbial contamination or the regrowth of microorganisms rise.  The aim of this study was to evaluate the changes in the free residual chlorine (FRC) and the number of bacteria in desalinated water samples that collected from water kiosk system that provide desalinated water for the public. Samples collected at the beginning and the end of the water network and stay for 9 days at room temperature and similar condition as public stored at home. The samples analyzed for FRC, total coliform (TC), fecal coliform (FC), heterotrophic plate count (HPC) and organic matter for 9 days. The results indicated that FRC concentration at the beginning of water network was 1 mg/L and after 9 days it was reached to 0.5 mg/L at the end of the water network. The amount of UV254 at the end of water network was 0.0134 cm-1 and after 9 days it was reached to 0.0125 cm-1. There aren’t detected any TC and FC in samples even at beginning of the examination and also, after 9 days storage of water. The number of HPC colony for samples at the end of the network it reached 22 CFU/ml, after 9 days. It was concluded that desalinated water that stored at household storage vessel in Saveh has good quality and meets standard limit value until 9 days. It should be noted that this conclusion depends on various conditions, including various environmental factors. However, Water treatment officials need to pay more attention to the amount of chlorine remaining in drinking water in Saveh because after 9 days, there was still 0.5 mg/L of residual free chlorine in the water.