The objectives of this study were to investigate formation of trihalomethane (THM) species in waters treated by different methods and to determine effectiveness of using various methods for controlling disinfection by-product (DBP) precursors in drinking water. Experiments were carried out using batch experimental set-ups. Combinations of pre-ozonation, post-ozonation, enhanced coagulation, rapid sand filtration, activated carbon filtration and UV radiation were performed. Finished waters were analyzed for dissolved organic carbon (DOC), biodegradable dissolved organic carbon (BDOC), ultraviolet absorbance at 254 nM (UV254), total trihalomethane formation potential (TTHMFP), bromide and bromate. The results indicated that using the sequence of pre-ozonation/enhanced coagulation/activated carbon filter is the most effective method for reducing THM precursors. It was also concluded that the formation of THM species primarily related to the characteristics of finished water before chlorination. (c) 2008 Elsevier B.V. All rights reserved.