Modeling the formation of trihalomethanes in drinking waters of Lebanon Lucy Semerjian & John Dennis & George Ayoub Received: 18 September 2007 / Accepted: 23 January 2008 / Published online: 6 February 2008 # Springer Science + Business Media B.V. 2008 Abstract The current research aims at developing predictive models for trihalomethane (THM) forma- tion in Lebanon based on field-scale investigations as well as laboratory controlled experimentations. Sta- tistical analysis on field data revealed significant correlations for TTHM with chlorine dose, Specific UV-A, and UV 254 absorbing organics. Simulated dis- tribution system-THM tests showed significant cor- relations with applied chlorine dose, total organic carbon, bromides, contact time, and temperature. Pre- dictive models, formulated using multiple regression approaches, exhibiting the highest coefficients of de- termination were quadratic for the directly after chlorination (DAC; r 2 =0.39, p <0.036) and network (r 2 =0.33, p <0.064) THM databases, and logarithmic for the laboratory simulated THM database (r 2 =0.70, p <0.001). Computed r 2 values implied low correla- tions for the DAC and network THM database, and high correlation for the laboratory simulated THM database. Significance of the models were at the 0.05 level for DAC database, 0.10 level for the network database, and very high (<0.01 level) for the laboratory simulated THM database. It is noteworthy to mention that no previous attempts to assess, monitor, and predict THM concentrations in public drinking water have been reported for the country although a large fraction of the population consumes chlorinated public drinking water. Keywords Chlorination . Lebanon . Regression modeling . Trihalomethanes Introduction In view of the discovery of trihalomethanes (THM) as undesirable by-products of chlorination, several countries have specified maximum allowable levels for such disinfection by-products (DBPs) in drinking waters. Consequently, an interest in developing mathematical models to describe or predict THM formation in chlorinated waters was sparked. It is clear that properly developed quality models to simulate the temporal and spatial variations of THM in water treatment plant (WTP) outlets and distribu- tion systems can serve as planning tools that potentially assist utility operators in complying with the new strict quality rules by adopting proper source water management strategies. In fact, numerous empirical models have emerged during the last decade exhibiting varying levels of success in their predictive Environ Monit Assess (2009) 149:429–436 DOI 10.1007/s10661-008-0219-4 L. Semerjian (*) : G. Ayoub Department of Civil and Environmental Engineering, American University of Beirut, Beirut, Lebanon e-mail: ls07@aub.edu.lb J. Dennis Department of Community Health Sciences, University of Calgary, Calgary, Alberta, Canada