Bench scale treatability tests with ferric chloride coagulation were conducted to assess effects of pre-ozonation, inter-ozonation on water quality variables of water samples in several stages of treatment: free chlorine demand (FCD), absorbance of Ultra Violet light in the 254 nm wavelength (UV254 abs) and organic matter (OM) concentration. Regarding settling, ozonation favored OM removal but did not seem to influence FCD reduction, as compared with tests without ozonation. Regarding filtration, tests with ozonation led to higher OM removals and FCD/OM ratios than tests without ozonation. However, tests without ozonation were more efficient in reducing the FCD. Raw water ozonation decreased OM and UV254 abs values but not FCD values. The immediate FCD was obtained for raw water and it did not seem to depend on contact time.
Water quality; ozone; organic matter; free chlorine demand
