Trihalomethane formation potential in selected drinking waters of Lebanon

Laboratory-scale simulated distribution system trihalomethane (SDS-THM) tests were conducted on selected public drinking water sources to predict as well as evaluate trihalomethane formations under controlled laboratory conditions. Varying concentrations of SDS-total trihalomethane at any time (SDS-TTHM_T) (2.68–85.78 μg/L) were detected in the two simulated water sources. Evaluating the impact of each test variable on attained SDS-TTHM_T levels revealed that for both water sources, the majority of samples exhibited higher SDS-TTHM_T levels in the presence of higher chlorine doses. For the two sources, 85 to 87.5 percent of the sample pairs exhibited higher SDS-TTHM_T levels at higher incubation temperatures. Incubation periods at which maximum THM levels were attained varied with water source type as well as pH values. All comparable samples exhibited SDS-TTHM_T values higher (1.41 and 7.07 folds) than actual surveyed TTHM levels. Statistically, SDS_T-TTHM showed significant correlations with applied chlorine dose at the 0.05 level, and with TOC, bromides, contact time, and temperature at the 0.01 level. The predictive model, formulated using multiple regression approaches, exhibiting the highest coefficients of determination was logarithmic for the laboratory simulated THM database (r²=0.70; p<0.001) with a very high significance level (<0.01 level).