Spatial and seasonal evolution of trihalomethanes in water distribution systems in Lebanon

Spatial and seasonal changes in trihalomethane concentrations were investigated in various water distribution systems in Lebanon supplied by different water sources. A seasonal sampling program was initiated during which trihalomethanes and various contributing water quality and operational parameters were monitored at points along the distribution system. The majority of samples collected from points within the distribution network exhibited higher trihalomethane concentrations (1–13 folds) when compared to total trihalomethane levels detected in samples collected directly after chlorination. Recorded trihalomethane concentrations in Lebanon were highest in the spring, followed by the summer and winter. Moreover, total trihalomethane concentrations were higher when the abstraction sources were surface waters compared to ground water sources. Also, higher mean trihalomethane values were recorded in chlorinated waters originating from sources subjected to semi-conventional water treatment before the application of chlorine compared to mean trihalomethane values established in chlorinated waters originating from sources subjected to direct chlorination.