Comparison between ozone and ferrate in oxidising geosmin and 2-MIB in water G. Park, M. Yu, J. Go, E. Kim and H. Kim The University of Seoul, Dept. of Environmental Engineering, 90 Jeonnong-dong, Dongdaemun-gu, Seoul 130-743, South Korea (E-mail: h_kim@uos.ac.kr) Abstract Among the chemicals causing taste and odour (T&O) in drinking water, the most commonly identified and problematic ones are geosmin and 2-MIB (2-methylisoborneol). Since the reported odour thresholds of geosmin and 2-MIB are as low as 4 and 8.5 ng/L, respectively, they are not readily removed by conventional water treatment processes. In this study, ozone (O 3 ) and ferrate (Fe(VI)) were applied to oxidise geosmin and 2-MIB. Their performances were compared in terms of removal efficiency of geosmin and 2-MIB. In the case of O 3 , removal efficiency of geosmin and 2-MIB ozonation at different initial O 3 doses, H 2 O 2 /O 3 ratios and water temperatures were evaluated. The oxidation rates of geosmin and 2-MIB by Fe(VI) were measured within pH 6–8. The effect of H 2 O 2 addition was also evaluated. In summary, O 3 , especially with H 2 O 2 , could almost completely oxidise geosmin and 2-MIB, while Fe(VI) could not oxidise them more than 25% at any pH that was considered in this study. This was attributed to the structure of the organics and high reaction selectivity of Fe(VI). Further study should be conducted to find the reason of inhibition of oxidation by Fe(VI). Keywords Ferrate; geosmin; hydrogen peroxide; 2-methylisoborneol; oxidation; ozone; taste and odour Introduction The potability of water is determined by various parameters including pathogen contents, organic and inorganic pollutants and aesthetic parameters such as colour, hardness, turbid- ity and taste. Among them, the aesthetic parameters, in particular taste and odour (T&O), are receiving more attention from water utilities since they are the most frequent cause of customer complaints. Among the chemicals causing T&O in drinking water, the most com- monly identified and problematic ones are geosmin and 2-MIB, which are produced by blue-green algae (cyanobacteria) and actinomycetes. Therefore, the level of these com- pounds is elevated when the organisms proliferate in water reservoir. The odours of the chemicals are characterised as earthy and musty, respectively. Since the reported odour thresholds of geosmin and 2-MIB are as low as 4 and 8.5 ng/L, respectively (Pirbazari et al., 1993), they cannot be easily detected by conventional laboratory techniques. In order to supply aesthetically pleasing water to customers, these compounds should be removed. However, the conventional treatment process is not effective in removing these compounds. Therefore, more advanced treatment processes have been suggested to manage these compounds. The advanced oxidation process (AOP) is the process to utilise strong oxidants, such as hydrogen peroxide (H 2 O 2 ) and ozone (O 3 ), to decompose recalcitrant chemicals and has been applied to oxidise various pollutants in drinking water (e.g. MTBE (Mitani et al., 2002) phenolic and indolic compounds (Wu and Masten, 2002). O 3 also has been applied to oxidation of geosmin and 2-MIB in water (Atasi et al., 1999; Ho et al., 2002; 2004). Previous studies showed ozonation could not completely oxidise these chemicals in water, if used alone. This is partly because these compounds are saturated cycled tertiary alcohols which are resistant to oxidation (Ho et al., 2002). Therefore, H 2 O 2 has been Water Science & Technology Vol 55 No 5 pp 117–125 Q IWA Publishing 2007 117 doi: 10.2166/wst.2007.170 Downloaded from https://iwaponline.com/wst/article-pdf/55/5/117/439508/117.pdf by guest on 27 November 2018