In this study, aluminium sulphate (alum) and polyaluminum chloride (PAC) coagulation were used for coagulation of different origin water (Buyukcekmece, BC and Omerli, OM in Istanbul, Turkey and Carmine, CR in Salerno, Italy) treatment. The effect of pre-ozonation alone and combined with coagulation on NOM removal which was characterized by TOC, UV 254 was investigated. DBPs formation and acute toxicity on Daphnia magna of chlorinated raw and treated samples were defined in parallel. Moreover, bromide spiking was evaluated for DBPs speciation. Optimum alum dose for TOC removal was found to be 40 mg/L for OM while 80 mg/L of alum exhibited the lowest total trihalomethane formation potential (TTHMFP). Pre-ozonation enhanced the removal of TOC and reduction of TTHMFP when it was used in combination with both coagulants. In contrast, total haloacetic acid fort-nation potential (THAAFP) increased after each coagulation, ozonation and their combination. 300 mu g/L bromide spiking (around the same level with BC) in raw sample collected from CR increased the formation of brominated disinfection byproducts. Raw and treated samples displayed acute toxicity on Daphnia magna in different pattern and practically "no dose-response behavior" was observed.