Monitoring of THMs Concentration in Isfahan Water Distribution System and Zoning by GIS, a Case Study in the Center of Iran

Trihalomethanes (THMs) formation in treated water is a consequence of a reaction between the chlorine used for water disinfection and some natural organic matters. The objectives of the present study were monitoring of THMs concentration in Isfahan (A metropolis city in center of Iran) water distribution network (IWDN), evaluation factors that affect the THMs formation potential and identification of critical points by using geographical information system (GIS). The study was performed in summer months of 2014. For sampling point's selection, city divided into 30 zones and water quality parameters such as pH, Electric Conductivity (EC), residual Chlorine, Total Organic Carbon (TOC) and THMs of IWDN measured. Multi regression analysis was used to estimate the correlation between THMs formation and these variables. While the statistical analysis with Spearman non-parametric correlation coefficients showed a positive correlation between distance from treatment plant and THMs concentration(r=0.45, P =0.01) and negative strong correlation(r=-0.95, p>0.001) between THMs and TOC concentrations, there was no strong significant relationship between THMs formation in IWDN and some variables including pH, temperature and residual Chlorine. The results reveal that the average value of the THMs at sampling points for summer attained 42.56 ppb which was lower than the EPA and WHO standards. It is recommended that the distance from the treatment plant was used as an effective parameter for estimation of THMs formation potential.