The drinking water taste and odor wheel for the millennium: Beyond geosmin and 2-methylisoborneol

~

Pergamon

War. Sci Tech. Vol.40, No.6, pp. 1-13, 1999 C 19991AWQ Published by ElsevierScienceLtd Printedin Great Bntam. All rightsreserved 0273-1223/99$20.00+ 0.00

PII: S0273-1223(99)00531-4

THE DRINKING WATER TASTE AND ODOR WHEEL FOR THE MILLENNIUM: BEYOND GEOSMIN AND 2-METHYLISOBORNEOL I. H. (Mel) Suffet*, Djanette Khiari** and Auguste Bruchet*** • Environmental Health Sciences, Environmental Scienceand Engineering, UCLA School o/Public Health, Los Angeles, CA 90095, USA •• Metropolitan WaterDistrict ofSouthernCalifornia, WaterQualityDivision, La Verne, CA 91750, USA ••• C.I.R.S.E.E., Suez-Lyonnaise des Eaux, 78230 Le Pecq, France

ABSTRACT The "Taste and Odor Wheel" developed over the last 15 years has been updated to include new compounds identified in the eight classes of odorants, four tastes, and one mouth feel/nose feel category. Over the last 10 years, other types of odors have been identified, in addition to chlorinous and ozonous odors of disinfectants, the earthy compound geosmin, and the musty compound 2-methylisoborneol (2-MIB). Sophisticated instrumental analysis, e.g., gas chromatography/mass spectrometry (GCIMS), and sensory analysis, e.g., flavor-profile analysis (FP A), have been successfully combined with sensory GC to identify various odorants. C 1999 lAWQ Published by Elsevier Science Ltd. All rights reserved

KEYWORDS "Taste and Odor Wheel"; flavor wheel; odor descriptors. INTRODUCTION A better understanding of the chemical causes of tastes and odors in drinking water supplies would help in the control of taste and odor problems. The ''Taste and Odor Wheel" developed over the last 15 years includes eight classes of odors, four tastes, and a mouth feel/nose feel category (Mallevialle and Suffet, 1987; Brady et al., 1988; Suffet eta/., 1988, 1995a; Burlingame etal., 1991a). The identification of odorants is well understood for two groups of chemicals: chlorinous/ozonous and earthy/musty, of the earthy/musty/ moldy category, e.g., geosmin (earthy) and 2-MIB (musty). Over the last 10 years, we have begun to identify other types of odors by utilizing sophisticated GCIMS, FPA (APHA, 1998), and sensory GC analyses. FPA and GCIMS analysis identification must be confirmed by sensory GC analysis, using the appropriate standards (Khiari et al., 1992). However, there is still a general lack of identification of compounds that cause taste and odor problems, especially when compounds are present in complex mixtures at or below an individual odor threshold concentration (OTC). Chemical identification of the odor-causing substance(s) during a taste and odor problem is critical. For example, as algae grow, they can produce odors that progress from cucumber to I

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I H. SUFFET et al.

fishy as their abundance or growth cycle changes (Rashash et al., 1993). Also, odor-causing compounds may hydrolyze, photolyze, or biodegrade during a taste and odor episode or during the sampling and analysis steps (Khiari et al., 1999a). This paper presents the frame of reference of our knowledge of taste and odor problems in drinking water supplies by updating the "Taste and Odor Wheel." The "Taste and Odor Wheel" organizes the relationships between specific taste and odor problems and their causes. The "Year 2000 Taste and Odor Wheel" is shown in Figure I as an upgrade of the "1995 Taste and Odor Wheel" (Suffet et al., 1995a).

\ \

Figure I. Drinking water Taste and Odor Wheel.

Two different philosophies were used as a guide in developing the "Taste and Odor Wheel". First, the "Taste and Odor Wheel" is to be used to help develop a common language for taste and odor sensory panels and drinking water practitioners. Second, the "Taste and Odor Wheel" is devised to present to the water industry the current knowledge about the identification of the "common" organoleptic characteristics found in drinking water. The "Taste and Odor Wheel" describes primary taste and odor categories (inner circle), those common tastes and odors from each primary category that are defined by trained sensory panels in Europe and the USA (outer circle). The chemicals that have been confirmed as the cause of taste and odor problems in drinking water arc noted by a * (outside the circles). All the other chemicals that are listed out-

The drinking water Taste and Odor Wheel for the millennium

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side the two circles, without a star, have been used by sensory panels as "Representative" standards for the particular organoleptic response (Burlingame et al.; 1991a). CAUSE-AND-EFFECT RELATIONSHIPS IN DRINKING WATER TASTE AND ODOR PROBLEMS The literature is filled with presumptive statements about the causes oftaste and odor problems, which can be misleading to the water industry. For example, the numbers or density of algae or actinomycetes may not affect a taste and odor problem, and the cause of the earthy/musty odor in water is not necessarily geosmin or 2-MIB if algae or actinomycetes are present. The chemical analysis of the water can only prove that geosmin or 2-MIB is present. Rules of evidence must be satisfied before a cause-and-effect relationship can be established between the presence of an organism or chemical and a taste or odor problem in the water. Rules of evidence describing "the scientific method" are used to define presumptive and confirmatory testing procedures to validate the cause of a taste and odor event in drinking water (Mallevialle and Suffet, 1987; Persson, 1992). In short, microbiological causes of taste and odor problems require ecological (concurrence of the organism and the odor in the field), sensory (organism isolated in pure culture must be able to produce the odor in water), and chemical (odorous compound must be isolated from the organism and the original water and chemically identified) evidence. A presumptive test (identifying the organism believed to be the cause of the taste and odor problem and quantifying its population density) must be confirmed by either (1) isolating the organism by culture techniques and determining whether the odor produced by the culture is the same as the original odor problem in the water, as determined by a sensory panel; (2) isolating microbial products associated with the microbial growths in the culture and confirming it by GCIMS, or other chemically accepted confirmatory means for metabolite(s); (3) isolating the microbial product(s) that cause that odor from natural water samples; or (4) developing a relationship between the chemical concentration in actual water samples and the odor intensity detennined by a sensory panel. Determining the chemical causes of taste and odor problems requires developing a presumptive statistical correlation between the chemical compounds in the water sample and the tastes or odors by sensory panel techniques and/or separating and identifying those individual compounds that have the same sensory characteristics as the whole water sample, as described by a sensory panel, by sensory GC analysis (Khiari et al., 1992). Final confirmation is completed by having the sensory panels evaluate the chemical identified by FPA. The relationship between the chemical concentration in actual water samples and the odor intensity is determined by the sensory panel. FPA QUANTITATION The ''Taste and Odor Wheel" presents some reference standards for odors. However, odor descriptions are often related to individual experiences. Also, odors in the earthy/musty category can be produced by several different compounds, such as geosmin, 2-MIB, and 2,4,6-trichloroanisole (TCA). Often, differentiation can be accomplished only by direct comparison between the odor and the chemical. For example, in distilled water, the first description of the odors of geosmin and 2-MIB before training states that geosmin has an earthy, wet mud, muddy, beet, river-bed odor, and 2-MIB has a musty, camphor, moldy, "basement odor" (according to an FPA panel at the Environmental Science and Engineering Program at the University of California, Los Angeles). A third category of reference standards besides the "Known" and "Representative" (Burlingame et al., 1991a) compounds on the outside of the odor wheel is also important for FPA standards: the so-called "Substitutes" are standards that are made from natural materials producing an odor that occurs in water and can be prepared in a consistent manner. Examples include decayed vegetation and septic odors made from aged solutions of grass (APHA, 1998). The ultimate goal is to develop an odor reference stan-dard library and to move representative odorants to identified compounds. For example. the representative compound for the cucumber odor was determined to be trans,cis-2,6nonadienal, which is the actual cause of the cucumber odor in water (Burlingame et al., 1991b). Known reference standards that occur in untreated or finished drinking water need to be evaluated for OTC and for dose-response relationships. An understanding of these relationships can help explain the impact of odorous compounds on the overall sensory quality of drinking water. The relationship between odor intensity and odorant concentration in water can be described by either of the two following models:

I. H. SUFFET er al .

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• Weber-Fechner model (Thiemer, 1982) or • Stevens' Power Law model (Moskowitz et al., 1974)

Intensity =m log (concentration) + b Intensity = k (concentration)"

An exponent (n) of less than 1.0 indicates that a change in intensity results from a greater change in odorant concentration (the sensory ratio is smaller than the physical ratio), which is generally true for odors. For the Stevens' Power Law model, an exponent of 0.5 would mean that an increase of I to lOin concentration corresponds to an increase of 1 to 3.2 in odor intensity. Butanol, a frequently used standard, has an exponent of 0.66; therefore, intensity increases about 1.5 times for each doubling of concentration (Thiemer, 1982). Three reference standards were evaluated to obtain a dose-response relationship: geosmin, 2·MIB, and n-hexanal (Burlingame et al., 1991a). The expected concentrations agreed fairly wen at low odor intensities for both the Weber-Fechner and Stevens ' Power Law models. but the Stevens' Power Law model produced less deviation at higher odor intensities. SPECIFIC TASTE AND ODOR CAUSING COMPOUNDS The "Taste and Odor Wheel" and Table I show those tastes and odors that have been confinned to cause taste and odor problems in drinking water. The primary causes of taste and odor problems that have been confirmed in drinking water are highlighted. Earthy/mustY/moldy Geosmin, 2-MIB, and TCA have been identified in water supplies as odorants of this group, with OTCs of < 10 ngfl (Mallevialle and Suffer, 1987). Gerber and co-workers (Table 1) were the first to give an accurate description of the major microbial metabolite, geosmin, responsible for producing the earthy odor in water supplies. Rosen and co-workers (1970) first reported the isolation of geosmin from natural water. Medsker et al. (1969) and Gerber (1969) were the first to identify the musty odor of 2-MIB during taste and odor episodes in natural waters by pure culture techniques. Rosen et al. (1970) isolated 2-MIB not only from pure actinomycete cultures, but also from a natural water. Geosmin and 2-MIB have been isolated metabolites of many genera of algae in drinking water supplies (see Table 1). Recently. TCA has been confirmed to be produced in water distribution systems (Montiel, 1991; Nystrom et al., 1992) and has an OTC of about 20-80 pgfl (UKWIR, 1996). In water distribution systems, trichlorophenols, which are chlorination by-products, can be transformed to trichloranisoles via the methylation process (Montiel et al., 1991). Montiel et al. (1991) showed that a phenol concentration of 0.1 !1g11 was sufficient to produce a musty taste. Other chemicals than geosmin, 2-MIB, and TCA may produce earthyl musty odors, as these types of descriptors are reported by FPA panels when these chemicals are not identified by chemical analysis (Bruchet, 1999). Chlorinous and Olonous Hypochlorous acid and hypochlorite ions have the same odor descriptor. "bleach." Hypochlorous acid has a PIC. of 7.6 and ionizes 10 hypochlorite ion and hydronium ion. Hypochlorous acid (pH < 6) has an OTC of 0.28 mg/l, whereas hypochlorite ion (pH > 9) has an OTC of 0.36 mg/I (Krasner and Barrett, 1984). The breakpoint chlorination curve describes the reaction of chlorine and ammonia. The dominant chlorine species in water prior to the breakpoint are monochloramine and dichloramine, with an odor descriptor of "swimming pool." According to data from the Metropolitan Water District of Southern California, monochloramine at concentrations of 0.5 to 1.5 rng/l has an intensity level to 2.0 (very slight) on the sevenpoint FPA scale. Monochloramine rarely causes taste and odor problems in drinking water unless its concentration exceeds 5 mg/l. The OTC of monochloramine is 0.65 mg/l (Krasner and Barrett, 1984). Dichloramine in concentrations of 0.1 to 0.5 mgIJ in water has an odor intensity level of 4 (slight) to 8 (moderate). However, if the concentration of dichloramine reaches 0.9 to 1.3 mgll, the odor will be described as moderate to very strong, which is offensive and not acceptable. Most people perceive the unpleasant chlorinous smell once the concentration of dichloramine is above 0.5 mg/1(Krasner and Barrett. 1984). Recent studies indicate thaI high levels of dissolved solids can affect the OTe (SutTel, 1999). Also, recent investigations by Welte and Montiel (1999) and Bruchet (1999) have described intense chlorinous

The drinking waler Taste and Odor Wheel for the millennium

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odors that occurred in the absence of free or combined chlorine. The cause of these odors has not been identified. Fragrant: vegetable/fruity/flowery High-molecular-weight aldehydes, greater than C-7 (heptanal), showed a positive statistical correlation with fruity odors produced during the ozonation drinking water process at the Morsang Treatment Plant, near Paris. This is another example of a presumptive test of a chemical cause of an odor (Anselme et al., 1988). In an independent sensory panel study, a Weber-Fechner relationship was developed between a fruity odor intensity measured by an FPA sensory panel and the logarithm of the total aldehyde concentration in a mixture of seven straight-chain aldehydes (C-6 to C-12). This is a sensory confirmation ofa chemical cause of an odor. The fruity/orange-like odor of decanal can be used to represent this group ofaldehydes. A new addition to the "Taste and Odor Wheel" is the microbial metabolite trans,cis-2,6-nonadienal, which causes the cucumber odor in water supplies. Burlingame et al. (1991b) completed a microbiological confirmation ofthis compound. Because ofits instability, trichloramine is no longer listed as part of this group. It has not been proven that trichloramine has a geranium odor. Medicinal Bromophenols have been added to the "Taste and Odor Wheel." The OTC and flavor descriptors of bromophenols are the same as those of chlorophenols (Whitfield et al., 1988). The bromophenols have the same types of odors as chlorophenols (iodoform, phenolic, medicinal). The OTC order follows approximately the same pattern as the chlorophenols, i.e., 2-bromophenol and 2,6-bromophenol have the lowest OTC, with 30 ngll and 0.5 ng/l, respectively, as reviewed by Suffet et al. (199Sb). The formation of bromophenols is also a function of pH and follow the same pattern as chlorophenols. Bromophenols have been identified in water distribution systems where phenols were leaching from a reservoir coating material and reacting with chlorine in the presence ofbromide ion in the water (Khiari et al., I999b). The chlorine-to-phenol ratio is the major determinant of the production of phenolic by-products of the chlorination process. The highest taste intensity is obtained at a 2: I chlorine-to-phenol ratio because the odorous 2,6-dichlorophenol is the dominant chlorination by-product at this ratio. When the chlorine-tophenol ratio increases to 4:1, and the chlorine concentration increases to 10 ppm, none of these taste and odor compounds can be detected. The formation of odorous chlorophenols is also highly pH-dependent. There is no significant development of chlorophenolic odors at a pH less than 7. The optimum pH value for development of chlorophenols is between pH 8 and 9. When ammonia is present in the phenol solution. it consumes free chlorine and thus lowers the free-chlorine residual level, which may increase the taste and odor ofphenols (Lee, 1967). The formation of iodomethanes in drinking water is related to the organic contents of raw water and the chlorination process. Free chlorine can react with and oxidize both organic and inorganic compounds in water. Trace amounts of bromide and iodide at concentration levels of 0.1 mg/l in the water supplies can be converted into bromine and iodine by chlorination. The natural humic material in water reacts by the haloform reaction to produce noxious brominated and iodinated haloforms. The OTC of iodoform is 300ngll using the FPA method (Bruchet et al., 1989), as shown by Burlingame and Anselme (1995). As a result. the presence of iodinated haloforms at concentrations between 0.30 and 10 I!gIl will cause medicinal taste and odor problems in drinking water (Gittelman and Yohe, 1989; Bruchet et al., 1989). The medicinal character-istics for iodinated trihalomethanes (THMs) increase with the number of iodine atoms in the structure, with iodoform presenting the most characteristic medicinal descriptor (Ventura et al., 1999). For this reason. iodinated THMs have replaced iodoform in this category.

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I. H. SUFFET et al.

Grassy/havJstraw/woody Grassy tastes and odors have frequently been reported in drinking water supplies, and now the identification of two grassy compounds has been confirmed in drinking water supplies (Khiari et al., 1999a). Two related chemicals (cis-3-hexen-l-ol and cis-3-hexenyl acetate) have been identified by Khiari et al. (1995a) as the cause of grassy odors when fresh grass is mixed with water for less than a day. In another study, also at the bench scale (Khiari et al., 1997), it was observed that when grass was allowed to decay in water, the first compound to be released in the water was the acetate. The concentration of the corresponding alcohol increased in the later stages of decay. In water, Cotsaris et al. (1995) reported cis-3-hexen-l-01 as a product ofa green alga, Scenedesmus subspicatus. cis-3-Hexen-l-01 and cls-3-hexenyl acetate were identified in a drinking water system from the Metropolitan Water District of Southern California's Oxidation Demonstration Plant. When odor threshold studies were performed, cis-3-hexenyl acetate exhibited a low OTC of 1-2 Ilgfl, only 2-4 percent of the OTC of cis-3-hexen-l-01 (Khiari et al., 1995a). The results obtained in the hydrolysis experiments by Khiari et al. (1999a) indicated that degradation of the chemicals occurs rapidly. Hydrolysis occurs at >pH 6.1. A new compound in this group has been identified as causing hay/woody odors. The compound, 13cyclocitral, was identified in lake and treated water during an algae bloom (Young et al., 1999). This work demonstrates the importance of knowing the relationship of odor type and concentration, as provided by the Weber-Fechner Curve, as 13-cyclocitral changes odor with concentration. Only between 2 and 20 Jlg/l does it have a hay/woody odor in distilled water. 13-Cyclocitral has been described as having a tobacco type of odor (Slater and Block, 1983b) at higher concentrations. Fishv/rancid The only original category of the "Taste and Odor Wheel" that has been modified is fishy. "Fishy" has been changed to "fishy/rancid" because of recent studies in drinking water supplies (Khiari et al., 1995b; Young and Suffet, 1999). Rancid, buttery, and soapy odors have been also observed from ozonation of drinking water in recent studies (Crozes et al., 1999) and are added as unknowns to the "Taste and Odor Wheel." These odors have also been observed during sensory GC analysis (Khiari et al., 1995b). The identification of specific rancid, buttery, and soapy odors needs further study. Fishy odors appear to be occur naturally, as has been shown in algal cultures by many authors (outlined in Table 1). Most recently, Rashash et at. (1993) identified 2-trans-4-cis-7-cis-decatrienal, an alkyl trienal. trans,trans-2,4-Heptadienal, a metabolite of the algae Uroglena americana, is described as contributing to the fishy odor in the Nunobiki reservoir in Japan (Yano et al., 1988). The biological origin of trans.trans2,4-heptadienal was confirmed during the study of natural odor standards (Khiari et al., 1995b) where it was identified in a sample of decaying grass in water. Sensory GC analysis has indicated that trans,4-heptenal is associated with fishy odors, and I-pentene-3-one is associated with rancid odors (Khiari et al., 1995a); however, these identifications need further confirmation. Sensory GC analysis combined with GCIMS allowed the identification of trans,trans-2,4-heptadienal in raw water supplies (Khiari et al., 1995b). The odor at the olfactory port of the GC indicated at low concentrations in one case as a rancid odor and in another case as a fishy odor. The Weber-Fechner Curve for trans.trans-2,4-heptadienal gives an OTC of about 5 Ilg/1 with a rancid fishy odor (Young and Suffer, 1999). This confirms the identification of this compound in raw water supplies. There is a pH dependence on the stability of the trans,trans-2.4-heptadienal (Suffet, 1999). This compound is more stable near pH 9, and samples should be collected and preserved at high pH and refrigerated when collected for analysis. This contrasts with the stability of grassy compounds at low pH (Khiari et al., 1999). Marshvlswampy/septic/sulfurous One component of the decaying vegetation odor has been identified as dimethyl disulfide (Khiari et al., 1997) and added to the "Taste and Odor Wheel" for the first time. Generally, when dimethyl disulfide is present, other compounds present in the sample may contribute to the decaying vegetation odor that an FPA panel observes. The other compounds that have been identified by GC sensory analysis are (1) 2-isobutyl-3-

The drinking water Taste and Odor Wheel for the millennium

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methoxpyrazine, identified as a vegetable odor, and (2) 2-isopropyl-3-methoxypyrazine, identified as a rotten vegetable odor (Khiari et al., 1997). However, the literature indicates that the odors associated with the pure 2-isobutyl-3-methoxypyrazine compound are earthy/musty and bell pepper, and for the pure 2-isopropyl-3-methoxypyrazine compound, they are earthy-musty and potato bin. The effect of concentration of the combination of these chemicals appears to need further investigation in the presence of dimethyl disulfide.

In a water supply sample with flavor-profile descriptors of decaying vegetation (intensity 4), swampy (intensity 2), and seaweed (intensity 2), a vegetable odor detected by sensory GC analysis was identified as 2-isobutyl-3-methoxypyrazine by GCIMS analysis. However, dimethyl trisulfide (swampy odor), which was identified by GCIMS, did not give any odor at the olfactory port. Dimethyl trisulfide may be associated only with the swampy odor (Khiari et al., 1997). It should be noted that sometimes swampy and septic odors are not easy for FP A panelists to differentiate. Sensory GC and GC/MS with flavor-profile descriptors of decaying vegetation (intensity 4), septic (intensity 2), and fishy (intensity 2) identified the decaying vegetation odor as dimethyl disulfide. Dimethyl trisulfide and indole were also present in the sample, but without sensory GC descriptors. Both dimethyl trisulfide and indole present odor characteristics similar to the odors found in the sample analyzed by FPA, but they were not sufficiently extracted to produce odors at the olfactory port of the sensory GC. It is suspected that dimethyl trisulfide and indole may contribute to the septic odor (Khiari et al., 1997). Chemical/hydrocarhon/miscellaneous Two new classes of compounds have been added to this category. By-products of resin manufacturing processes have been reported to be the cause of at least four different taste and odor episodes in drinking water around the world (Pretti et al., 1993; Ventura et al., 1995; Noblet et al., 1999; Schweitzer etal., 1999a; Schweitzer et al., 1999b). The compounds are products of simple aldehydes and glycols. Of particular concern are the OTCs of both sweet (tutti-frutti) - 2-ethyl-5,S'-dimethyl-l,3-dioxane (2-EDD) from propionaldehyde and neopentyl glycol - and sweet (medicinal) - 2-ethyl-4-methyl-I,3-dioxolane (2-EMD) from propionaldehyde and propylene glycol. 2-EDD and 2-EMD have OTCs of
Source

Odor

Actinomycetes, cyanobacteria

Earthy

Reference Gerber and LeChevalier, 1965; Gerber, 1967, 1968,1979; Saffermannet al., 1967; Medsker et al.; 1968;Rosen et al., 1970; Henley, 1970;Piet et al., 1972;Kikuchi et al., 1973aand 1973b;Narayan and Nunez, 1974; Tabachek and Yurkowski, 1976;Tsuchiya et al., 1978, 1981;Persson, 1979; Izaguirre et al., 1982;Berglind et al., 1983;Wood et al., 1983;Burlingameet al.• 1986;Wu and Juttner, 1988a, 1988b;Matsumotoand Tsuchiya, 1988; Izaguirre, 1992;van Breemen et al., 1992.

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I. H. SUFFET et al.

Table 1. Compounds causing tastes and odors in water (continued) Compound 2.2-Methyl isoborneol"

Source Actinomycetes , cyanobacteria

Odor Musty

3. Isopropyl methoxypyrazine 4. Cadinene-ol

Actinomycetes

S.2,4,6-Trichloroanisole-

Biochemical methylation of chlorophenol

Potato-bin musty Woody/ earthy Musty

Actinomycetes

Reference Rosen et al., 1968; Gerber, 1969; Medsker et al., 1969; Collins et al., 1970; Tsuchiya et al., 1978; Izaguirre et al., 1982, 1983; Negoro et al., 1988; Wu and Juttner, 1988b; Martin et al., 1991; Izaguirre , 1992; Buttery and Ling, 1973; Gerber, 1983 Collins, 1971; Gerber, 1971; Montiel et al. , 1991; Nystrom et al., 1992; Welte and Montiel , 1999

Fragrant: Vegetable/Fruity/Flowery 1. Irans,cis-2,6Algae Burlingame et al., 1991b Cucumber nonadienal" 2. Aldehydes Ozonation Anselme et 0/., 1985a, 1988, Fruity! (higher molecfragrant Suffet et al., 1986 ular weight) 3. Unknown Algal decomposition Decaying MacKenthum and Keup, 1970 by fungi and vegetat ion bactena GrassymaylStrawlWoody Sweet 1. cis-3-HexenylLeaching of chemicals Khiari et al., 1995a 1-01 acetatefrom grass and Khiari et 01., 1999 Grassy drinking water Leaching of chemicals 2. cis-3-Hexen· Grassy Khiari et al ., 1995a from grassldnnking water 1-01Khiari et 01., 1999 Cyanobacteria in a 3. !3-Cyclocltralwater supply Tobacco-like Slater and Blok, 1983b 1° SweetJuttner et al.• 1986 Microcystis cyanobacteria culture pipe tobacco 2° Grassy/ Cotsaris et al., 1995 fruity Lake water (algal bloom) Young et al., 1999 and drinking water Fresh grass, <1 ug/l Hay/woody, 2-20 Ilg/l Tobacco-like, >10 1J.g/l FIshy I . n-Hexanal and n-heptanal 2. trans,cis-2,4decadienal 3. 2-trans,4-cis.7cis-decatrienal

4. Hepta- and deca-dienals 5. trans,lrans-2,4. Heptadienal " 6. Irans,4-Heptenal7. I-Penten-3-one (tentative)

Flagellated algae diatoms Flagellated algae

Fishy Cod liver oil

Collins and Kalnins, 1965a, 1965b, 1966, 1967; Kikuchi et al., 1974, 1986 Juttner, 1981, 1983

Algae-Synura petersenii and Dinobryon cylindricum cultures Dinobryon algae

Fishy/cod liver oil

Rashash et al., 1993

Fishy

Drinking water supplies

Fishy! swampy Fishy Fishy! swampy

Juttner et al., 1986: Bayliss, 1951 Yano et al., 1988. Khiari et 01., 1995b

Drinking water supplies Drinking water supplies

Khiari et al., 1995b Khiari et 01., 1995b

The drinking waterTaste and Odor Wheel for the millennium Table 1. Compounds causing tastes and odors in water (continued) Compound

Source

Odor

Reference

SwampylSulfurousIDecaying Vegetation/Septic I. Mercaptans 2. Dimethyl polysulfides 3. Hydrogen sulfide 4. Dimethyl disulfide, dimethyl bisulfide, 2.isobutyl-3methoxypyrazine and 2-isopropyl-3methoxypyrazine 5. Unknown 6. Dimethyl bisulfide and indole 7. Aldehydes (lowMW)

Decomposed or living blue-green algae Bacteria Anaerobic bacteria (reduce SO/"lo S-) Biochemical decay of grass and drink ing water supplies

Algae (moderate to large amounts) Biochemical decay of grass and drinking water supplies Chlorination of amino acids

Jenkins et al., 1967; Slater and Blok, 1983.

Odorous sulfur Swampy/ fishy Rotten egg

Giger and Schaffuer, 1981; Wajon et al., 1985a, 1985b, 1985c; Krasneret al., 1986 Hack, 1981

Decaying vegetation

Khiari eI al., 1997

Fishy grassy/septic Septic

Palmer, 1962, 1977, 1980

Swampy/ swimming pool

Hrudey et al., 1989

Khiari et al., 1997

Medicinal 1. Chlorophenols 2-CP,4-CP, 2,4·DCP, 2,6-DCP, 2,4,6·TCP 2. Bromophenols 3. Iodinated THMs (iodoformss)

Phenol chlorination! chloramination

Medicinal

Burttschell et al., 1959; Lee, 1967; Bryan et al., 1973; White, 1980;

Phenol chlorination! presence ofBr ion Chloramination

Medicinal

Suffet et aI., 1995b; Whitfield et 01., 1988

Medicinal

Bruchet et al., 1989; Gittelman and Yohe, 1989

Plast ic/ burnt plastic Cat urine

Burnam and Colbourne, 1979; Anselme et al., 1985b, 1985c; Burlingame and Anselme, 1995 Hoehn et al., 1990

Sweet (tutti-frutti) Sweet (medicinal) Turpentine (hydrocarbon)

Pretti et al., 1993; Ventura et al., 1995; Schwe itzer et 01., 1999a Schwe itzer et al., 1999b

ChemicaVllydrocarbonslMisce//aneous 1. Phenolic antioxidants 2. Unknown

3. 2·EDD 4.2·EMD

Polyethylene pipes Chlorine dioxide and new carpet Mixing wastealdehyde and glycol Mixing waste-saldehyde and glycol Gasoline addit ive

5. Methyl t-butyl ether (MTBE) 6. Dicyclopentadienes Industnal chemical

Shen et al., 1997; Dale et al., 1997 Ventura et al., 1997

Chlorinous/O;.onous Krasner and Barrett, 1984 Chlorinous Chlorinous Krasner et al., 1986 Swimming pool Ozonous 4. Ozone" Disinfection of water Update of table from Ibrahim et al. (1990), Suffet et al. (1993, 1996). ·Confirmed in drinking water.

1. Chlorine (free)"

Disinfection of water

2. Monochloramine" Disinfection of water Disinfection of water 3 Dichloramine'"

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