THM formation in water supply in South Bohemia, Czech republic

Abstract In recent years attention has been drawn to various aspects related to the influence of disinfection by-products in distribution systems. The formation of trihalomethanes (THMs) and its species which form from the reaction of chlorine with humic substances have caused much alarm because of their carcinogenic and dangerous health effects. This article studies the factors affecting THM formation in pipelines transporting drinking water in the south of Bohemia in the Czech Republic. The residual chlorine in water entering these pipelines is in average 0.75 mg l−1 and decreases with distance until it reaches zero. The low velocity and the large volume of reservoirs increase the residence time and correspondingly provide conditions for more chlorine decay and accordingly an increase in THM formation. The effect of temperature and organic matters on THM formation was also studied in this article. The residence time and decay of chlorine were used as good predictors for the formation of THM and chloroform in this study. There was a linear correlation between the cumulative chlorine decay and the cumulative THMs formed in the pipelines with R2=0.913. Meanwhile, the correlation between THM formation and residence time was exponential with R2=0.91.