jesc.ac.cn Journal of Environmental Sciences 2011, 23(1) 1–13 Treatment of taste and odor causing compounds 2-methyl isoborneol and geosmin in drinking water: A critical review Rangesh Srinivasan, George A. Sorial * Environmental Engineering Program, School of Energy, Environmental, Biological, and Medical Engineering, University of Cincinnati, Cincinnati, OH 45221-0012, USA. E-mail: George.Sorial@uc.edu. Received 26 July 2010; revised 16 October 2010; accepted 17 November 2010 Abstract Problems due to the taste and odor in drinking water are common in treatment facilities around the world. Taste and odor are perceived by the public as the primary indicators of the safely and acceptability of drinking water and are mainly caused by the presence of two semi-volatile compounds – 2-methyl isoborneol (MIB) and geosmin. A review of these two taste and odor causing compounds in drinking water is presented. The sources for the formation of these compounds in water are discussed alongwith the health and regulatory implications. The recent developments in the analysis of MIB/geosmin in water which have allowed for rapid measurements in the nanogram per liter concentrations are also discussed. This review focuses on the relevant treatment alternatives, that are described in detail with emphasis on their respective advantages and problems associated with their implementation in a full- scale facility. Conventional treatment processes in water treatment plants, such as coagulation, sedimentation and chlorination have been found to be ineffective for removal of MIB/geosmin. Studies have shown powdered activated carbon, ozonation and biofiltration to be effective in treatment of these two compounds. Although some of these technologies are more effective and show more promise than the others, much work remains to be done to optimize these technologies so that they can be retrofitted or installed with minimal impact on the overall operation and effectiveness of the treatment system. Key words: adsorption; drinking water; geosmin; 2-methyl isoborneol (MIB); odor; taste DOI: 10.1016/S1001-0742(10)60367-1 Citation: Srinivasan R, Sorial G A, 2011. Treatment of taste and odor causing compounds 2-methyl isoborneol and geosmin in drinking water: A critical review. Journal of Environmental Sciences, 23(1): 1–13. Introduction Drinking water industries, even in most industrialized and developed nations, are facing the necessity for more innovative and cost-effective technologies for water treat- ment and purification. Taste and odor have long been associated with the suitability and safety of our drinking water. It is not uncommon for water utilities, especially those supplied by reservoirs, to be flooded with complaints from consumers about taste and odor in their drinking water, especially during warmer weather. For an average consumer, taste and odor is the only way of determin- ing the safety of tap water (McGuire, 1995). Geosmin (trans-1,10-dimethyl-trans-9 decalol-C 12 H 22 O) and MIB (2-methyl isoborneol-C 11 H 20 O) have been identified to be the major taste and odor-causing compounds in drinking water obtained from surface water (Fig. 1) (Pirbazari et al., 1993). MIB/geosmin in surface water mainly result from the metabolism and biodegradation of certain types of cyanobacteria that normally bloom in the presence of nutrients at warmer temperatures (Watson et al., 2008). * Corresponding author. E-mail: George.Sorial@uc.edu There are currently no regulations for these two com- pounds as they have not been associated with any health effects (Dionigi et al., 1993a). Presence of taste and odor in drinking water may result in decreased consumer trust and subsequently, decreased water consumption and could eventually cause the public to switch to alternate sources of drinking water such as bottled water and in-home treatment systems. The main problem with the presence of MIB/geosmin is associated with their extremely low odor threshold concentrations (OTC) and their persistence to elimination in a conventional water treatment process such as coagulation, sedimentation, filtration and chlorination (Bruce et al., 2002). The OTCs for MIB/geosmin can range from 4 to 20 ng/L (Pirbazari et al., 1993; Lloyd et al., 1998). Another factor that adds to the challenge faced by drinking water facilities in the removal of these contaminants is the presence of natural organic matter (NOM). NOM, a complex mixture of organic compounds derived primarily from the decay of plant and animal materials, is invariably present in all water sources and at much higher concentrations than MIB/geosmin (Pirbazari et al., 1993).