DBPs formation and toxicity monitoring in different origin water treated by ozone and alum/PAC coagulation

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, UV254 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 formation potential (THAAFP) increased after each coagulation, ozonation and their combination. 300 µg/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.

Alum and PAC coagulation, ozonation and their combination were performed for the treatment of the raw water samples Buyukcekmece (BC) and Omerli (OM), Istanbul, Turkey and Carmine (CR), Salerno, Southern Italy. The efficiency of processes was evaluated by measuring DBPs, toxicity and TOC parameters. The following conclusions were drawn from the present work: • TOC removal was almost the same at the alum doses over 20 mg/L (ranging from 40 to 100 mg/L) for the OM samples. • TOC removal was almost the same at alum doses over 20 mg/L (ranging from 40 to 100 mg/L) for the OM samples. However, although the same TOC degradation (%22) was achieved using 40 mg/L alum, the change in TTHMFP was insignificant while TTHMFP decreased 40% after coagulation with 80 mg/L of alum. • Pre-ozonation enhanced the efficiency of both alum and PAC coagulation. • Bromide spiking at 0.15 Br–/TOC ratio affected drastically DBPs speciation, in particular THMs.