Evaluation of trihalomethanes (THMs) concentration in drinking water of Zanjan in 2013

Trihalomethanes have been known as carcinogen material for human by IARC. Considering the Zanjanś drinking water is supplied from the dam in 2008 and water disinfection with chlorine is performed, this study was carried out to determine THM concentrations in drinking water of Zanjan city.
In this descriptive-cross-sectional research, 32 samples were taken from storage tanks, effluent treatment plant and different points of drinking water distribution system after the city map meshing so that covers all parts of the system in winter and summer seasons in 2013. The reason for these two seasons been variations in the concentration of organic substances in water resources and consequently the concentration of THMs precursors produced and the effect of temperature on the formation of THMs. Gas chromatography technic was used in purge and trap method with electron capture detector for analyzing THM’s samples for each of four components including Chloroform, Bromodichloromethane, Dibromocholoromethane and Bromoform.
The average concentration of THMs in winter for Chloroform, Bromodichloromethane, Dibromocholoromethane and Bromoform, were 4.7±1.44, 4.72±1.25, 3.08±0.43 and 1.98±0.14 µg/Lit and in summer were 4.21±1.83, 4.71±1.8, 3.65±0.81 and 2.22±0.14 µg/Lit, respectively. The average of total THMs in winter equal to 14.19±3.09 µg/Lit and in summer equal to 14.81±4.4 µg/Lit.
Concentration of trihalomethanes and total trihalomethanes in Zanjan drinking water distribution system is lower than the national and international standards and the drinking water consumers arenot at risk of exposure to trihalomethanes.