Comparison of the efficiency of ~·OH radical formation during ozonation and the advanced oxidation processes O_3/H_2O_2 and UV/H_2O_2

摘要

Comparison of advanced oxidation processes (AOPs) can be difficult due to physical and chemical differences in the fundamental processes used to produce ~·OH radicals. This study compares the ability of several AOPs, including ozone, ozone+H_2O_2, low pressure UV (LP)+H_2O_2, and medium pressure UV (MP)+H_2O_2 in terms of energy required to produce ~·OH radicals. Bench scale ~·OH radical formation data was generated for each AOP using para-chlorobenzoic acid (pCBA) as an 'OH radical probe compound in three waters, Lake Greifensee water, Lake Zurich water, and a simulated groundwater. Ozone-based AOPs were found to be more energy efficient than the UV/H_2O_2 process at all H_2O_2 levels, and the addition of H_2O_2 in equimolar concentration resulted in 35% greater energy consumption over the ozone only process. Interestingly, the relatively high UV/AOP operational costs were due almost exclusively to the cost of hydrogen peroxide while the UV portion of the UV/AOP process typically accounted for less than 10 percent of the UV/AOP cost and was always less than the ozone energy cost. As the ~·OH radical exposure increased, the energy gap between UV/H_2O_2 AOP and ozone processes decreased, becoming negligible in some water quality scenarios.