Oxidation of geosmin and MIB in water using O₃/H₂O₂: kinetic evaluation

Tastes and odors (T&Os) of drinking water have been a major issue for water utilities in Korea, due to the ever-increasing consumers' demand on drinking water quality and complaints on T&Os. Among the T&Os causing chemicals in water, the most common and problematic ones are geosmin and 2-MIB, which are produced by blue–green algae and actinomycetes. The odors of the chemicals are characterized earthy and musty/camphorous. Since the reported odor thresholds of geosmin and 2-MIB are as low as 4.0 and 8.5 ng/L, respectively, they are not readily removed by conventional water treatment processes or by simple ozonation. Therefore, oxidation of the chemicals using hydrogen peroxide (H₂O₂) along with ozone (O₃) has been tried as an alternative. In this study, kinetics of geosmin and 2-MIB ozonation at different initial O₃ doses, H₂O₂/O₃ ratios, and temperatures were evaluated. In short, a significant promotion of geosmin and 2-MIB ozonation rate was observed at higher H₂O₂/O₃ ratios at lower temperature; therefore, geosmin and 2-MIB could be successfully removed from water. However, when an ozonation process is designed ozone residual should be considered for satisfactory disinfection; H₂O₂ addition may promote O₃ decomposition and may have an adverse effect on disinfection. Therefore, determination of H₂O₂ and O₃ doses should be carefully made for achieving both disinfection and T&Os removal.