OFF-FLAVOR FLAVOR ODOROUS COMPOUNDS IN WATER: DETERMINATION, FORMATION AND CONTROL

Transcription

1 OFF-FLAVOR FLAVOR ODOROUS COMPOUNDS IN WATER: DETERMINATION, FORMATION AND CONTROL Lifeng Zhang Water Quality Office, PUB, Singapore, PUB-JWRC Symposium, 05 July,

2 INTRODUCTION Surface water supplies are more likely to be affected by substances causing undesirable tastes and odors, the largest single class of consumer complaints submitted to water utilities (Levallois, et al., 1999). Objectionable taste and odor in tap water will compromise public confidence in the water quality 2

3 INTRODUCTION For drinking water, objectionable taste and odor in highly treated water is a serious concern because it could undermine consumer confidence. Water treatment plants utilize chemicals or adsorbents to control these problems. The earthy-musty odors are especially troublesome because they are particularly unpleasant and often encountered in water (Suffet et al, 1996). Earthy-musty smell is associated with the presence of geosmin, MIB and haloanisoles (Mallevialle et al., 1987; Jensen et al., 1994 and Bruchet et al., 1999). 3

4 Figure 1. Taste and Odor Wheel 2000 (Suffet et al. 1999) 4

5 OFF-FLAVOR COMPOUNDS IN ODOR WHEEL --- (Burlingame et al. 2004) Earthy/Musty/Moldy Ammonia/fishy Sulfide/cabbage/garlic Rancid/putric Solvent/hydrocarbon Geosmin ammonia Dimethyltrissulfide 2-Hexenal Thiophene 2-Methylisoborneol Butyl amine Dimethyldisulfide 2,4-Decadienal 1,2-Cyclohexanedione 2,3-Diethylpyrazine N-Butyl amine Dimethylsulfide Amylmercaptan Cresols Trichloroanisole Trimethyl amine Carbon disulfide Butanoic acid Naphthalene 2-Ethyl-1-hexanol Isopropylamine Hydrogen sulfide Butyraldehyde Methylallyltrisulfide Grassy/Woody Pyridine Diethyl sulfide Decanoic acid Methylmethacrylate Β-Cyclocitral Trimethylamine Diallylsulfide Dimethylamine Benzene Cis-3-Hexen-1-ol Dimethylamine Diphenylsulfide Heptanal Tetrachloroethylene Cis-3-Hexenyl-1-ol acetate Dibutylamine Thiophene Hexanoic acid Trichloroethylene Hexanal Methylamine Methyl mercaptan Iso-valeric acid Toluene Furfural Diisopropylamine Allyl mercaptan Methyl thiobutyrate Cumene 1,2-Nonenal Triethylamine Phenyl mercaptan Methylamine M-Xylene Fornaldehyde Heptanal Ethyk mercaptan Phenylmercaptan Styrene Soapy/detergent 2,4-Decadienal Crotyl mercaptan Propyl butyrate Indene 1-Dodecanal 2,4-Heptadienal T-Butyl mercaptan Pyridine Heptane Acetaldehyde Hexylamine Furfuryl mercaptan Thiophenol Octane Ethyl Acetate Medicinal/alcohol Acrylonitrile Trimethylamine T-Butyl toluene Isopropyl acetate N-Butanol Thiocresol Valeric acid Toluene Isovaleraldehyde p/m-cresol Oxidant/Chlorinous Fecal/sewery Methylisobutylketone Isobutyraldehyde Chlorophenols Hypochlorous acid Indole P-Dichlorobenzene D-Limonene Bromophenols Monochloramine Skatole Naphthalene Hexanal Cyclohexanol Dichloroamine Iso-Valeric acid Cumene 1-Hexanol Valeric acid Anisole phenol 1-Butanol Iodoform Pyridine 5

6 SOURCES OF OFF-FLAVOR COMPOUNDS 1) Algae, cyanobacteria and microorganism e.g. geosmin, MIB 2) Chlorination e.g. mono-, di-and tri-chlorophenols 6

7 Sensory Method ANALYTICAL METHODS Threshold Odor Numbers (TON) TON: the greatest dilution of sample with odor-free water yielding a definitely perceptible odor. the temperatures of the samples to be tested should all be standardized, a water bath is to be used and 60 o C is an accepted value for analysis. Threshold Odor Numbers Corresponding to Various Dilutions USEPA Secondary Drinking Water Standards Contaminant Secondary Standard Odor 3 threshold odor number 7

8 ANALYTICAL METHODS Sensory Method Flavor Profile Analysis (FPA) FPA is a technique for identifying sample odou(s). FPA Analysis Laboratory FPA Analysis Work Sheet FPA Analysis Results 8

9 ANALYTICAL METHODS Instrumentation GC-MS Closed Loop Gas Stripping GC-MS Thermo-desorption GC-MS Stirring Bar GC-MS P&T GC-MS.. 9

10 CHALLENGES IN ANALYTICAL METHODS TO OFF-FLAVOR COMPOUNDS Name/ Abbreviation Taste Odor Threshold (ng/l) 2-Methylisoborneol (MIB) Earthy 5-10 Geosmin (GSM) Camphor ,4,6-Trichloroanisole (2,4,6-TCA) Musty ,3,6-Trichloroanisole (2,3,6-TCA) Musty ,3,4-Trichloroanisole (2,3,4-TCA) Musty ,4,6-Tribromoanisole (2,4,6-TBA) Musty isopropyl-3-methoxypyrazine Green, floral, decay isobutyl-3-methoxypyrazine Green pepper β-ionone Violet, woody 7 2-bromophenol medicinal 30 2,6-dibromophenol Medicinal, hospital

11 ANALYSIS OF OFF-FLAVOR COMPOUNDS 11

12 ANALYSIS OF OFF-FLAVOR COMPOUNDS Traditionally, the analysis of odourants and measurement of odours are performed separately. Olfactometry GC-MS enables the identification and linking of odourant compounds and human sensory perception. Olfactometry GC-MS 12

13 Target Odorants in Reservoir Waters R1 R2 R3 R4 R5 R8 DOMINANT Geosmin and 2-MIB detected R6 R7 MINOR IPMP and 26DBP occasionally detected 13

14 Target Odorants in Treated Water G DOMINANT A B C Only 2-MIB occasionally D E F MINOR 26DBP randomly detected due to chlorination No other target compounds were detected above the odor threshold in treated water. 14

15 Target Analytes in Reclaimed Water Ratio [Conc/OTC min ] 26DBP 2MIB geosmin 246TBA secondary effluent samples Dominant 246TCA and geosmin 246TCA Minor 2MIB, 26DBP, 246TBA, IPMP, IBMP, β-ionone, 234TCA 15

16 Anisole Formation in WWTP precursor product raw sewage 2 o effluent Decrease of known precursor 2,4,6-trichlorophenol was consistently observed along with formation of 2,4,6- trichloroanisole. raw sewage 2 o effluent 16

17 Anisole Formation in WWTP activated sludge MW: RT: min Target ion: m/z 202, 204 MW: RT: min Target ion: m/z 201,

18 Treatment of Off-flavor Compounds DILUTION Dil 0x Dil 2x Dil 4x Dil 16x Dil 64x OZONATIO N AERATION Inlet Stripping UV Maybe Maybe OZONATI ON Inlet Ozonated REVERSE OSMOSIS Feed Permeate CHLORINATION Good Maybe Fluence 0 Fluence 500 Fluence C*T 0 C*T 200 C*T Limited Limited UV peroxide Fluence 0 Fluence 500 Fluence BIOLOGICAL A.C. Inlet no-o3 & BAC Maybe CHLORAMINATION C*T 0 C*T 200 C*T Poor O3 & BAC Inlet Pre-O3 & BAC Good Good Environmental Science &Technology, 2011, 24(21),

19 Conclusions 2-MIB and geosmin are the dominant off-flavor compounds in reservoir waters; To the second effluent waters, 246-TCA is the major off-flavor compound, which could be formed during wastewater treatment process; Ozonation, UV/peroxide and ozonation/bac have been proven to be efficient techniques to remove the off-flavor compounds in water 19

20 Acknowledgement Prof. David Sedlak, UC Berkeley Dr. Eva Agus, UC Berkeley Dr. Lim Mong Hoo, WQO/PUB Qian Xiaoqing, WQO/PUB Hu Ruaikang, WQO/PUB Emily See, WQO/PUB Dr. Wu Jingming, WQO/PUB Dr. Yue Junqi, WQO/PUB Lu Qinglin, WSP/PUB 20

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