UV treatment for the removal of bromate formed during ozonation of groundwater. Influence of the oxidation process on the removal efficiency

• We verify the conditions of ozonation of groundwater containing bromide.
• We assess the removal efficiency of bromate from groundwater through UV.
• We compare the above results with those obtained from bromate spiked solutions.
• We assess the effects on matrix composition of the both abovementioned treatments.
• Results show the role of composition variation due to oxidation on removal efficiency of UV.

The presence of bromide ions in waters treated with ozone can lead to bromate ions and brominated compounds formation, potentially carcinogenic. This poses a need to remove the bromates through other treatment, as UV. In this work the effects of the water composition, and the corresponding variation due to oxidation, on the UV efficiency for the reduction of bromate to bromide ions in groundwater (GW) were investigated. For this purpose an experimental apparatus was specifically designed and experimental tests with ozone and with a UV lamp 6 W were performed. The experimental results show that the reduction of the bromates to bromides by UV is max 41% in GW, depending on ozone dose and initial bromate concentration. The experimental data were fitted with a first order model and the kinetic constant determined. The effects of the ozone and UV treatment on others groundwater components, as TOC and inorganic nitrogen, were taken into account and the corresponding influence on the bromate removal efficiency was evaluated. To this aim, comparative tests with UV in purified water (PW) (reagent grade) and GW spiked with controlled amount of bromates were performed. It was verified that the removal efficiency of bromate by UV increases with increasing of ammonia concentration, but decreases with increasing of TOC and when intermediate bromide species, produced by ozonation, are presents.