2,6-dichlorophenol
“Chlorophenol , like antiseptic mouthwash”
2,6-dichlorophenol
170 ng per capsule
Technical specification
Assessment
The best way to detect chlorophenol taints in water is as follows. Without covering the glass, swirl the sample to release the aroma. Take a single short sniff. Repeat as necessary. Amount of flavour per capsule
170 ng per capsule Threshold
The flavour threshold of 2,6,-dichlorophenol in water is 55 ng / l. Origins
Chlorophenols are produced in water through reactions involving phenolic compounds (for example from waters associated with peaty soils) and free chlorine. They can also arise through to contamination of water with wood preservatives. Importance
Chlorophenols are disinfection by-products. They impart unpleasant ‘tainted’ notes to water. Waters containing chlorophenols are ddescribed by consumers as ‘medicinal’ or ‘contaminated’, even at low levels. CAS registry number
The CAS registry number of 2,6-dichlorophenol is 87-65-0. Other names
1-hydroxy-2,6-dichlorobenzene
2,6-DCP
2,6-dichlorfenol
Remarks
Water pH is important in determining the rate of formation of chlorophenols. Such compounds can occasionally be produced by bacterial action or by misuse of carbon filters used to purify water and remove chlorine. Threshold distribution
Capsules per pot
10
dimethyl disulphide
“Rotten vegetable , like a sewage treatment plant”
dimethyl disulphide
360 µg per capsule
Technical specification
Assessment
The best way to detect sulphury taints in water is as follows. Without covering the glass, swirl the sample to release the aroma. Take a single short sniff. Repeat as necessary. Amount of flavour per capsule
360 µg per capsule Threshold
The flavour threshold of dimethyl disulphide in water is 120 µg / l. Origins
Dimethyl disulphiide (DMDS) is formed through biochemical decay of grass and vegetation in reservoirs and lakes, or by metabolism of bacteria or moulds. Importance
Dimethyl disulphide Imparts an unpleasant reduced sulphur note, reminiscent of decaying vegetation. The intensity of the odour can be increased by the presence of other sulphur compounds. CAS registry number
The CAS registry number for dimethyl disulphide is 624-92-0. Other names
DMDS
dimethyl disulfide
dimethyl disulfane
2,3-dithiabutane
methyl disulfide
(methyl dithio) methane
methyl dithiomethane
methyldithiomethane
methyldisulfanylmethane
Remarks
Dimethyl disulphide is often found in association with other sulphur compounds and / or methoxypyrazines in contaminated waters. Threshold distribution
Capsules per pot
10
dimethyl trisulphide
“Onion , like stagnant water or decaying vegetation”
dimethyl trisulphide
330 ng per capsule
Technical specification
Assessment
The best way to assess onion flavour in water is as follows. Cover the sample with your hand and swirl the glass to release the aroma. Remove your hand and take a single long sniff. Repeat as necessary. Amount of flavour per capsule
330 ng per capsule Threshold
The flavour threshold of dimethyl trisulphide in water is 110 ng / l. Origins
Dimethyl trisulphide is formed through decay of grass and vegetation in reservoirs and lakes and by bacterial action. It can also arise from decomposition of algae following an episode of algal bloom. Importance
Imparts an unpleasant ‘swampy’ odour to water. The intensity of the odour can be increased by the presence of other sulphur compounds. CAS registry number
The CAS registry number for dimethyl trisulphide is 3658-80-8. Other names
DMTS
1,3-dimethyl trisulfane
methyl trisulfide
methyl trithiomethane
methylsulfanyldisulfanylmethane
methyltrithiomethane
2,3,4-trithiapentane
methylsulfanyldisulfanylmethane
Remarks
Dimethyl trisulphide is often found in water in association with other sulphur compounds such as H2 S and methanethiol. Threshold distribution
Capsules per pot
10
ferrous sulphate
“Metallic , like ink or blood”
ferrous sulphate
2.7 mg per capsule
Technical specification
Assessment
The best way to assess metallic flavour in water is to take a little sample into your mouth, move it around with your tongue for a few seconds then swallow it. To confirm the presence of a metallic taint, rub a little of the water onto the back of your hand and check for a metallic odour. Amount of flavour per capsule
2.7 mg per capsule Threshold
The flavour threshold of ferrous ions in water is 900 µg / l. Origins
Metallic taints are derived from contamination of water with metal ions, either from natural ground and soil conditions or from electrochemical or microbe-mediated corrosion of cast iron pipework. Importance
Ferrous ions Impart a metallic mouthfeel to water. High levels of ferrous ions may be associated with discolouration of the water supply and – in the extreme – the formation of ‘red water’. Addition of one capsule of this flavour standard to one litre of water produces a colourless solution, whereas use of two capsules in one litre of water produces a discoloured solution. CAS registry number
The CAS registry number for ferrous sulphate is 7782-63-0. Other names
ferrous sulfate
iron(2+) sulfate
iron(2+) sulphate
ferrous sulphate heptahydrate
ferrous sulfate heptahydrate
iron(2+) sulfate heptahydrate
iron(II) sulfate heptahydrate
iron(II) sulphate heptahydrate
Remarks
Copper, manganese and other metals can also be responsible for metallic notes in water. Occasionally, lipid oxidation products can give rise to ‘non-metallic’ metallic odours. Threshold distribution
Capsules per pot
10
geosmin
“Geosmin , like sugar beets or damp soil”
geosmin
35 ng per capsule
Technical specification
Assessment
Geosmin odour in water is best detected as follows. Without covering the glass, swirl the sample to release the aroma. Take a single short sniff. Repeat as necessary. Amount of flavour per capsule
35 ng per capsule Threshold
The flavour threshold of geosmin in water is 10 ng /. Origins
Geosmin is formed in water by Actinobacteria, Cyanobacteria and algae. These can be found in lakes, reservoirs and water distribution systems. Geosmin is produced by both actively-growing organisms and through cell lysis and decomposition. Importance
Geosmin imparts an unpleasant earthy odour to water which is reminiscent of sugar beets or damp soil. Extremely odour-active and for that reason one of the most common flavour faults in potable water. CAS registry number
The CAS registry number for geosmin is 23333-91-7. Other names
2beta,6alpha-dimethyl bicyclo(4.4.0)decan-1beta-ol
octahydro-4,8a-dimethyl-4a(2H)-naphthol
2b,6a-dimethyl bicyclo[4.4.0]decan-1b-ol
2beta,6alpha-dimethyl bicyclo[4.4.0]decan-1beta-ol
1,10-(E)-dimethyl-(E)-(9)-decalol
(E)-1,10-dimethyl-(E)-decalin-9-ol
2b,6a-dimethyl bicyclo(4.4.0)decan-1b-ol
2,6-dimethyl bicyclo(6.4.4.06)decan-1-ol
4,8a-dimethyl decalin-4a-ol
4,8a-dimethyl-1,2,3,4,5,6,7,8-octahydronaphthalen-4a-ol
octahydro-4,8a-dimethyl-4a(2H)-naphthalenol
octahydrodimethyl-4alpha-naphthol
Remarks
Geosmin flavour problems are most commonly associated with surface abstracted waters. Its formation can be influenced by weather conditions, when concentration of organic materials in the water can lead to growth of microorganisms. Threshold distribution
Capsules per pot
10
hydrogen sulphide
“H2 S , like boiled or rotten eggs”
hydrogen sulphide
18 µg per capsule
Technical specification
Assessment
The best way to detect hydrogen sulphide in water is as follows. Without covering the glass, swirl the sample to release the aroma. Take a single short sniff. Repeat as necessary. Amount of flavour per capsule
18 µg per capsule Threshold
The flavour threshold of hydrogen sulphide in water is 4 µg / l. Origins
H2 S is formed by anaerobic sulphate-reducing bacteria from sulphate, by Clostridium or Bacillus from sulphite or proteins, or by electrochemical action through corrosion of pipes in systems with very low flow rates. Importance
H2 S imparts an unpleasant sulphury note to water. H2 S is easily oxidized to less odour-active species, so its presence is indicative of the failure of water treatment processes or post-treatment contamination. CAS registry number
The CAS registry number of H2 S is 7783-06-4. Other names
H2 S
hydrogen sulfide
dihydrogen monosulfide
dihydrogen monosulphide
hydrogen sulfuric acid
hydrogen sulphuric acid
sulfur hydride
Remarks
H2 S is often found in association with other sulphur compounds such as methanethiol and dimethyl trisulphide. Be careful not to overexpose yourself to samples with H2 S. The more you look for it the less likely you are to find it. Threshold distribution
Capsules per pot
10
2-isobutyl-3-methoxypyrazine
“Earthy , like green pepper”
2-isobutyl-3-methoxypyrazine
30 ng per capsule
Technical specification
Assessment
The best way to detect green pepper pyrazine in water is as follows. Without covering the glass, swirl the sample to release the aroma. Take a single short sniff. Repeat as necessary. Amount of flavour per capsule
30 ng per capsule Threshold
The flavour threshold of 2-isobutyl-3-methoxypyrazine in water is 10 ng / l Origins
2-Isobutyl-3-methoxypyrazine is formed by Actinobacteria in lakes, reservoirs and water distribution systems. It may occur in admixture with other methoxypyrazines. Importance
2-Isobutyl-3-methoxypyrazine is a potent off-flavour with a very low flavour threshold. It imparts an unpleasant earthy note to water which is reminiscent of green peppers. CAS registry number
The CAS registry number for 2-isobutyl-3-methoxypyrazine is 24683-00-9. Other names
2-methoxy-3-(2-methylpropyl)pyrazine
isobutyl methoxypyrazine
3-isobutyl-2-methoxypyrazine
galbanum pyrazine
2- methoxy-3-(2-methyl propyl) pyrazine
2-methoxy-3-(2-methylpropyl)pyrazine
2-methoxy-3-isobutyl pyrazine
2-2-methyl propyl-3-methoxypyrazine
Remarks
Green pepper odours in water are usually associated with surface water abstraction. Formation of 2-isobutyl-3-methoxypyrazine in lakes and resevoirs can be influenced by weather conditions leading to concentration of organic materials in the water and growth of microorganisms. Threshold distribution
Capsules per pot
10
2-methylisoborneol
“Earthy , mouldy, like peat or compost”
2-methylisoborneol
260 ng per capsule
Technical specification
Assessment
Earthy taints caused by 2-methylisoborneol can be best detected in the following way, Without covering the glass, swirl the sample to release the aroma. Take a single short sniff. Repeat as necessary. Amount of flavour per capsule
260 ng per capsule Threshold
The flavour threshold of 2-methylisoborneol in water is 85 ng / l. Origins
Methylisoborneol (2-MIB) is formed by Actinobacteria, Cyanobacteria and algae in lakes, reservoirs and water distribution systems. It is produced both by actively-growing organisms and through cell lysis and decomposition. Importance
Methylisoborneol imparts an unpleasant earthy odour to water which is reminiscent of peat or rotting compost. It is extremely odour-active and for that reason is one of the most common flavour faults in potable water. CAS registry number
The CAS registry number of 2-methylisoborneol is 2371-42-8. Other names
1,6,7,7-tetramethylbicyclo[2.2.1]heptan-6-ol
MIB
exo-1,2,7,7- tetramethyl bicyclo(2.2.1)heptan-2-ol
Remarks
Methylisoborneol is most commonly associated with surface-abstracted waters. Its formation can be influenced by weather conditions which lead to concentration of organic materials in the water and growth of microorganisms. Threshold distribution
Capsules per pot
10
skatole
“Skatole , like animal faeces”
skatole
2.0 µg per capsule
Technical specification
Assessment
The best way to detect faecal odour in water is as follows. Cover the sample with your hand and swirl the glass to release the aroma. Remove your hand and take a single long sniff. Repeat as necessary. Amount of flavour per capsule
2.0 µg per capsule Threshold
The flavour threshold of skatole in water is 700 ng / l. Origins
Skatole is formed by bacteria growing in water, or contributed, pre-formed, by ground water pollution. It is produced by bacteria from tryptophan. Importance
In addition to contributing an unpleasant, somewhat nauseating, faecal note to water, the presence of skatole can also indicate contamination of the water supply chain with faecal bacteria. CAS registry number
The CAS registry number for skatole is 83-34-1. Other names
beta-methyl indole
β-methylindole
scatole
skatol
3-methylindole
3-MI
3-methyl-1H-indole
3-methyl-4,5-benzopyrrole
Remarks
Indole and DMS may often be found in water which contains skatole. Threshold distribution
Capsules per pot
10
2,4,6-tribromoanisole
“Musty , like corked wine with a rubbery overtone”
2,4,6-tribromoanisole
230 ng per capsule
Technical specification
Assessment
The best way to detect 2,4,6-tribromoanisole in water is as follows. Without covering the glass, swirl the sample to release the aroma. Take a single short sniff. Repeat as necessary. Amount of flavour per capsule
230 ng per capsule Threshold
The flavour threshold of 2,4,6-tribromoanisole in water is <10 ng / l. Origins
2,4,6-Tribromoanisole is derived from methylation of bromophenols by moulds or Actinobacteria, primarily in water distribution systems. Importance
2,4,6-Tribromoanisole imparts an unpleasant musty odour to water which is reminiscent of damp cellars or corked wine. CAS registry number
The CAS registry number of 2,4,6-tribromoanisole is 607-99-8. Other names
tribromoanisole
TBA
1,3,5-tribromo-2-methoxybenzene
methyl 2,4,6-tribromophenyl ether
Remarks
2,4,6-Tribromoanisole is one of several bromoanisoles that can taint water. The flavour produced by this compound is typical. This compound can be detected, but not recognized at concentrations well below the recognition flavour threshold. Threshold distribution
Capsules per pot
10
