Fate of bromine-containing disinfection by-products precursors during ozone and ultraviolet-based advanced oxidation processes

Abstract

This research evaluates the effect of ultraviolet photolysis, ozonation and ozonation/ultraviolet advanced oxidation processes on different disinfection by-product precursors, during the treatment of water with low organic matter and moderate bromide contents. After different combinations of ultraviolent fluence and ozone, the formation potentials of trihalomethanes and haloacetic acids were investigated. Bromine incorporation factors were used to give specific insight into the behaviour of brominated disinfection by-products, and inorganic bromate formation was also determined. The ozone/ultraviolet process was found to be more effective in reducing the total natural organic matter content than ozonation or ultraviolet photolysis alone. Ultraviolet photolysis was more successful removing the precursors of brominated trihalomethanes than chlorinated trihalomethanes, but slightly increased the precursors of both brominated and chlorinated haloacetic acids. During ozonation, reductions in the haloacetic acid formation potential were significantly better than those of the trihalomethanes formation potential (up to 54 and 27%, respectively). In the combined ozonation/ultraviolet process, increasing the ultraviolet fluence had a varying effect on trihalomethane and haloacetic acid precursor behaviour, depending on the ozone dose applied. Bromine incorporation after ozonation alone increased to up to 38% of the total bromide, largely as a result of bromate formation. The combined process curtailed all bromate formation, but increased the bromine incorporation up to 48% at higher ozone doses, with disinfection by-product formation shifting towards the more toxic brominated species.

The Role of Catalytic Ozonation Processes on the Elimination of DBPs and Their Precursors in Drinking Water Treatment

“…In general, the oxidation changes the nature of NOM structures into more hydrophilic compounds, being hydrophobic fractions (humic and fulvic structures) the main responsible for THMs and trihaloacetic acid formation, whereas the more hydrophilic ones are related to dichloroacetic acid generation and the formation of higher concentration of brominated DBPs [75][76][77]. In this line, even with the highest THMs and HAAs formation potential removal by combined O 3 /UV treatment, brominecontaining DBPs present increased toxicity being the conditions between oxidant and UV dose crucial to minimize the risks [78]. Also, the particular characteristics of the NOM play a key role in the suitability of a specific treatment [70,79].…”

Suppressing Organic Bromine but Promoting Bromate: Is the Ultraviolet/Ozone Process a Double-Edged Sword for the Toxicity of Wastewater to Mammalian Cells?

“…Therefore, UV/O 3 might also produce more AOBr precursors due to its more powerful oxidizing capacity. It has been reported that UV/O 3 has oxidized THM precursors to more hydrophilic substances, which can be easily reacted with bromine . In addition, organic matter transformed by ·OH generated by UV/O 3 process may be more susceptible to halogen incorporation to form AOX …”

Ozone application in different industries: A review of recent developments

“…Another potential drawback is the production of toxic disinfection by-products such as oxidised halide species and bromates (which are carcinogenic) may cause pH depression and hamper fish health [2] . Thus, UV radiation [116] and activated carbon filtration [117] may be adopted for pre-treatment, particularly if sea water (usually high in Br) is to be utilised. These pre-treatment methods are also effective for increasing the decomposition rate of residual ozone in the treated water, before feeding back to the main culture tank of the RAQS.…”