Determination the effects of point of use treatment systems in reduction of gram - negative bacilli (E.coli, Pseudomonas aeruginosa and Aeromonas) from Tabriz drinking water supply network

Abstract

Introduction: Raise of people awareness about drinking water contaminants impurities and the demand for better water quality have led to widespread application of point-of-use (POU) water treatment devices. The aim of this study was to investigate the effects of point of use treatment systems in reduction of gram negative bacilli (Escherichia coli, Pseudomonas aeruginosa and Aeromonas) from Tabriz drinking water supply network. Materials and methods: In this study, thirty-six inlet and outlet water samples from household water treatment devices and twenty four samples were obtained from the inlet and outlet of the water treatment systems of hemodialysis centers. Bacterial quality of the samples were determined by total and fecal coliform multiple-tube fermentation techniques, heterotrophic plate count (HPC) using membrane filter method on blood agar medium and E.coli, Pseudomonas aeruginosa and Aeromonas via membrane filtration technique on EMB agar, Cetrimid agar and Aeromonas selective agar medium, respectively. Developed bacteria were identified using standard biochemical tests. The pH, residual chlorine and temperature parameters were determined in sampling place. Also, quries were distributed between 180 the holder of household water treatment devices to investigate their perceptions and attitudes about drinking water quality and the performance of these devices and collected after completion. The results were analyzed by using descriptive and analytical statistics. Results: The results of microbial quality analysis of input and output water of household water treatment devices indicated that total and fecal coliform bacteria were negative at all inlet samples, but were positive at two of the outlet samples. Heterotrophic plate count were higher than maximum limits (500 cfu/ml) at 67% of the outlet samples. Nonfermentative gram-negative bacteria (Pseudomonas and Alcaligenes( were found with higher frequencies at both inlet and outlet samples and Escherichia was only observed both in the inlet and outle samples of one device. Total and feacal coliform bacteria were posetive in the outlet samplesXXVI from hemodialysis water treatment systems in Sina hospital. HPC bacteria in Emam Reza and Sina hospitals outlet samples were higher than standard limits of Association for the Advancement of Medical Instrumentation. Alcaligenes faecalis and Pseudomonas bacteria were found with higher frequencies at inlet and outlet samples respectively. 65% of the holders of treatment devices have stated that distrust to the network water quality as a main reason for using these devices. According to the results of this study, 57% and 65% of the POU holders were satisfied with the appearance and taste and odor of produced water by devices respectively. Conclusion: Gradually formation of biofilm on the filters and the storage tank by the bacteria present in the distribution network are caused to increase in the number and variety of the bacteria in produced water from these devices. Also water treatment systems at hemodialysis centers at some of the studied hospitals do not provide enough efficiency for water supply according to the microbial quality standards. The user of household water treatment devices should be trained about operation and maintenance of these systems to reduce exposure to the microbs agents. Replacement of filters and daily discharge of reservoir water could be considered some of these proceedings