Anotec Technical Paper - Dynamic Olfactometry A Forced Choice

Dynamic Olfactometry – A Forced Choice?

Anotec Pty Limited 30-32 Chegwyn St Botany NSW 2019 Tel: 02 9700 1222

Victoria Zavras

Anotec Pty Limited is a research company specialising in formulating odour control substances for various industries. The approach is to determine which odours are present and at what concentrations before testing and formulating a substance for recommendation as a suitable odour control product.

Presentation: Clean Air Society Australia New Zealand Odour Special Interest Group Western Australia

ANOTEC PTY LIMITED

ODOUR CONTROL TECHNICAL PAPER

Copyright Victoria Zavras

Anotec Pty Limited PO Box 292 BOTANY NSW 1455 TEL: (02) 9700 1222 FAX: (02) 9700 1771 2

ANOTEC®

Odour Special Interest Group

Section 10. Measurement and Standards

Subject:

Dynamic Olfactometry – A Forced Choice?

Author

Victoria Zavras

INFORMATION PROVIDED IN THIS DOCUMENT IS PROVIDED “AS IS” WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY AND/OR FITNESS FOR A PARTIUCLAR PURPOSE. The user assumes the entire risk as to the accuracy and the use of this Application Note. Copyright Anotec Corporation. All Rights Reserved.

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ANOTEC

®

Odour Special Interest Group

Section 10. Measurement and Standards 10.4 New Developments

Presented at Clear Air Society of Australia and New Zealand, Perth, Australia Subject:

Dynamic Olfactometry – A Forced Choice?

Author

Victoria Zavras

Introduction An inductive venture conscious of its responsibilities cannot but promise scientific advance in its field of activities by every possible means. Failing such a responsibility, an industry would not enjoy the liberty of full exploitation of the results of research. In the odour control industry, the old adage “Seeing is believing” literally translates to “Smelling is perceiving”. It is the human response to odours that relay to the heads of a community that an odour problem exists. It is the human element in society which determines whether an evaluation be sought and regulations be set up to combat the problem. Recent advances in scientific instruments have permitted rigorous study of this phenomenon that humans have always been aware of. For example, about a hundred years ago Japan began modernisation initially in the textile and spinning industries. Subsequently, heavy industries such as iron, steel and shipbuilding were developed. The principal energy source for industry at that time was a coal, which, upon combustion emitted a thick black smoke. This black smoke was considered a symbol of prosperity. Today that thick black smoke, if emitted, is considered a health hazard and an odour nuisance. Californians over-react to the slightest odour; Texans say “Ma’am, that’s just the sweet smell-o-money.” Socially it is unacceptable.

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Anosmia Technologies Pty Limited is a research company specialising in formulating odour control substances for various industries. The approach is to determine which odours are present and at what concentrations before testing and formulating a substance for recommendation as a suitable odour control product. Odorous emissions usually contain significant amounts of various odorous components. The perceived odour is due to the effect of all compounds in the mixture and depends upon the concentration and odorous qualities of the component compounds. Therefore, it is logical that an odorous gas sample be characterised in two ways. Firstly, in the analytical expression, whereby the components and their concentrations are determined and in the sensory expression, where the human response to that odorous mix is measured. This paper deals with the advantages of a combined approach to odour assessment utilising olfactometry and chemical analysis. Anosmia Technologies have utilised these methods in the quest for a better understanding of how to assist in the abatement of malodours within the community and industry alike.

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1.

Odour Detection and Measurement – Organoleptic Methods

Organoleptic methods provide direct data on the impact of an odorous sample on the human olfactory senses. The prominent sensory properties of odours are strength, change in strength with dilution, threshold and hedonic tone. The nuisance potential of odours in the context of odorous pollution depends on all these criteria. It is usually not possible to measure the exact concentrations of the components of an odorous mixture by instrumental methods either because the concentration is too low or because of the complexity of the mix. Anosmia Technologies Pty Limited decided that Organoleptic methods be adopted where the human nose is used to estimate odour strength for any given area. Besides, only the human nose can assess synergistic effects, which modify separate odours when they are perceived together in a mix. The use of olfactometers to determine odour strength is both valuable and feasible when considering the extent of an odour problem at a given source. However, olfactometers around the world not only differ in their mechanics but also in the results produced. Three different olfactometers in the U.S. gave results that varied by up to two orders of magnitude for an odour sample that we tested in triplicate on the same day. All three methods however determined similar odour removal efficiencies for treated odour compared to untreated odour. This demonstrates that different methods give similar results irrespective of the range of the odour dilution units for each system. Problems arise when one method gives a relatively low ODU for raw odour and when ANOTEC 0307 was added the result was close to zero. Another method displayed a very high odour dilution unit for raw odour which upon the application of ANOTEC 0307 gave a reduction of 85%. Another method gave a 100% reduction. On the whole, sensory methods used by Anosmia Technologies, showed a significant reduction. Although the aim of utilising organoleptic methods by the Company was solely to demonstrate the effectiveness of its product ANOTEC 0307, questions arose relating to the accuracy of these methods when using the human element as a guide – the odour panel. The main problem was explaining what the Odour Dilution Unit signified and whether part of the ODU were indeed traces of the original malodour. The latter was harder to answer as the methods used were solely for detection of odour strength and not composition. This will be discussed further on. Following are available olfactometers used for odour strength measurement. UTRECHT Olfactometer (Netherlands) Warren Spring Laboratory Olfactometer (Britain) Transportable and Portable Models IPT 1158 Olfactometer (Germany) Proctor and Gamble’s Osmo (USA) ASTM Syringe-Dilution method (USA) ASTM D1391-78 Barneby-Cheney Scentometer (USA) IITRI (USA) Butanol Olfactometer (USA)

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Sensory methods used by Anosmia Technologies Pty Limited failed to concur on the effectiveness of the product. 2.

Comparison of Olfactometers

Sensory methods were compared by the company from practical experience and texts written on the subject. Following are the aforementioned olfactometers and their characteristic qualities. Olfactometer

Static or Dynamic Dilution

On-Site or Laboratory testing

Flow rate of air in Litres per minute to panellist

Dilution ratio achievable

UTRECHT Warren Spring Laboratory (T) Warren Spring Laboratory (P)

dynamic

laboratory

10 litres/min

dynamic

laboratory

dynamic

IPT 1158 ASTM-syringe BarnebeyCheney Butanol OLFAKTOMAT

2 – 500

Number of nose pieces per panellist 2

Materials used in test which contact with odour unknown

190 litres/min

750,000

1

PTFE

laboratory

60 litres/min

25 – 250,000

1

PTFE

dynamic

laboratory

10 litres/min

2 – 25,000

1

unknown

static

laboratory

unknown

unknown

unknown

static dynamic dynamic

on-site on-site laboratory

unknown 15 litres/min 15-20 litres/min

2 – 170 unknown 500,000

1 1 2

syringe clear plastic Teflon Teflon

The table above shows differences in protocol and flow rates associated with each olfactometer. The term “dynamic dilution” depicts a dilution method where dilution is achieved by mixing a flow of odour-free air with the odorous mix. The diluted sample then is presented to the odour panellists at a controlled flow rate. As the table shows, there is a wide range of flow rates of air delivered to each panellist, varying from 10 to 190 litres per minute. Changing the flow rate at which the diluted sample is delivered to the panellist will alter the olfactory sensation. It has been documented that a flow rate of about 10 litres per minute is far too low, making the panellist sniff too hard and therefore inhale extraneous air. It was then considered to increase the rate to 15 litres per minute. A detail such as this creates problems if the differences in flow rates would yield a different result for the same odour source. In “static dilution” methods, it is necessary for the panellists to sniff the air to obtain an odour sensation. Under normal circumstances 5% of the inspired air passes through the olfactory region. Sniffing can increase this figure to as much as 25%. Therefore the degree of sniffing by the odour panellist will inadvertently vary the flow rate in the olfactory area and so the sensation of the odour will also be varied.

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Flow rate variations to panellists using different olfactometers proved to be a major problem. One odour source was tested using different olfactometers. Although the end-results could not be denied and were in fact exact, the different results for the same odour source bred quite a bit of confusion. Absorption of the odours onto the equipment materials also proved to be a problem. Overall the whole procedure associated with olfactometric testing was put into question due to the varying results. 3.

Odour Measurement – Analytical Methods

Analytical data is much more precise than sensory data and may provide information on sources of the various odour components. This is deemed very useful in modifying a manufacturing process or raw materials, also in the selecting of emission treatment methods to reduce the offending odour. For mixtures, the gas-chromatographic separation techniques are widely used to identify the components. Various detectors such as the flame-ionisation detector, the electron-capture detector, the flame photometric detector, the Coulson conductimetric detector (the latter being able to register very low concentrations of the odorous substance), are used. These methods encounter problems during calibration. In the case of sewerage odorous emissions there are a substantial number of components present, and it is usual to utilise the gas chromatograph linked to a mass spectrometer. It is possible to detect 0.1ppb (vol) of hydrocarbons in 100 mL of air allowing effective detection of most odourants at or below their olfactometric threshold. In order to introduce sufficient amounts of compounds with low odour thresholds, concentrating methods are necessary. 4.

The Experiment – Organoleptic and Analytical methods Combined (Laboratory Testing)

It is my opinion of the company that an odour is not a substance but a sensation. To date there is no scientific instrument that may measure both the chemical composition and perception of odours. Four years of intensive research has revealed to the company that the only way we can achieve an accurate presentation of the odorous emission being assessed is by a combination of the sensory and analytical methods available. It is also the opinion of the company that the University of New South Wales CWT and ANSTO provide the necessary scientific equipment to accurately make that assessment.

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The past three decades have seen a variety of methods used to detect odour pollution. Anosmia Technologies Pty Limited formulated odour control substances relying exclusively on sensory methods available at the time to determine effectiveness. It was realised after a couple of years that the olfactometry used was ideal for measuring the problem but provided no information toward the solution. For example, scientists and engineers are cognisant of the composition of sewerage gas emissions. Olfactometric methods are used to determine the strength of these known substances. ANOTEC 0307 is then added as the odour control substance and the olfactometry results depict a substantial reduction. However, what is not known is the chemical composition of the residual odour. What was being asked was “What does the odour dilution unit, (ODU), signify once an odour abatement process is installed?” It is clear what the ODU signifies when measuring a raw odour sample because the composition is known in many cases. The odour remaining after treatment should be examined, especially if the abatement process involves the addition of a chemical substance. It is possible that if the analytical composition of enough samples of a specific odour is known and the odour characteristics of the samples are measured by sensory methods then statistical methods can be used to develop predictive equations relating to the odour intensity. Anosmia Technologies Pty Limited experience with olfactometry was only limited to those methods as set out by the United States of America. It was time to explore the possibility of utilising Australian methods for an Australian product. The Centre for Wastewater Treatment situated at the University of New South Wales proved the place to go as it is fully equipped with a functional odour laboratory. Visits to the laboratory revealed that the latest scientific technology to date was being employed to measure and detect odorous emissions. Although these techniques, described as state-of-theart, were being used to detect odours from any given source with significant success, experience measuring odour abatement products was limited. The company decided that these latest state-of-the-art methods in olfactometry be adopted to design an experiment where a known concentration of foul air (similar to sewerage gas) be passed through a simulated stack or wind tunnel. Anosmia Technologies personnel would then introduce a manifold injecting their product ANOTEC 0307 and olfactometry readings be taken for before and after treatments. To test the performance of the product as well as determine if there is any masking action of ANOTEC 0307, the foul air was challenged with water, an odourless ANOTECT 0307 and a fragrant ANOTEC 0307. Preparation of the foul air (raw odour) was done by the Environmental Science Program of ANSTO at the Lucas Heights Laboratories. Design of the experiment and construction of the windtunnel/simulated stack was done by Mr John Jiang of the Centre for Wastewater Treatment, University of New South Wales. Pump, nozzles and product were supplied by Anosmia Technologies Pty Limited.

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It was suggested by Mr Jiang that the advantages of performing such tests would be to enable Anosmia Technologies Pty Limited to further research their products as well as using the equipment constructed to perform further experiments which could be reproduced with the olfactometer at any time in the future for testing with other formulations and dosing rates. Following is a summary of the olfactometry testing – A simulated stack and the odorous air generation were set up at the ANSTO Laboratories at Lucas Heights. Air samples were subsequently transports to the Centre for Wastewater Treatment’s Odour Laboratory at the University of New South Wales. The synthetic odorous air mixture was introduced at a rate of 20 Litres per minute. The odorous air mixture was generated using a permeation device and the composition was of acetaldehyde, butanol, ethylamine and hydrogen sulfide. The odorous air mixture was introduced continuously. The control, using a plain water spray was tested first, then the odourless ANOTEC 0307 and finally the fragrant ANOTEC 0307. All samples were collected from the open end of the simulated stack. The odorous airs (raw odour) were samples initially prior to the operation of the spraying equipment. The spray was operated for about five minutes during each subsequent test and the three following samples were collected during operation of the spray. There were intervals of about thirty minutes between successive tests. The dynamic olfactometry was undertaken generally in accordance with the Dutch PreStandard (in the absence of an Australian Standard). A panel of eight observers was used to test each of the samples. Calculations of the results were done automatically by the Dravnieks method. Analysis with GC-MS was performed concurrently with the collection of each sample as prepared for olfactometry testing. This ensured that the results obtained from the chemical analysis would be directly correlated with the olfactometry results. 5.

The Results – Olfactometry & GC-MS (Laboratory Testing)

Olfactometry Results: TEST DESCRIPTION

ODOUR STRENGTH DILUTION UNITS)

Odourous air mixture

(ODOUR 18,227

Control – plain water spray

4,092

ANOTEC 0307 – Odourless ANOTEC 0307 – Fragrant

1,736 6,190

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TEST DESCRIPTION

ODOUR REMOVED (%)

Control – Plain water spray

78%

ANOTEC 0307 – Odourless

90%

ANOTEC 0307 – Fragrant

66%

These olfactometry results showed a marked reduction with water and even more so with the odourless ANOTEC 0307. However the ANOTEC 0307 fragrant was shown to be less effective. It was expected that the fragrance would contribute to the perceived odour and a proper assessment of this product could not be achieved. We anticipated that the chemical analysis would enable removal efficiency for each of the compounds to be determined because the method concentrates on the effect of the product on the odorous compounds while choosing to ignore the fragrance component of the product. This selective ability cannot be achieved by sensory methods. GC-MS Results COMPONENT (ppm) Hydrogen Sulfide Acetaldehyde Methylamine 2-butenal Butanol ODOUR Hydrodgen Sulfide Acetaldehyde Methylamine 2-butenal Butanol TOTAL ODOUR

RAW WATER ANOTEC 0307 – ANOTEC 0307 ODOUR SPRAY - Fragrant Odourless 0.566 0.068 0.000 0.000 9.818 0.037 0.000 0.000 3.000 0.500 <0.05 <0.05 5.630 2.770 0.770 0.260 40.540 14.590 0.790 0.320

2832.35

341.47

0

0

1636.36 300.00 938.29 506.76

6.11 50.00 461.71 182.33

0 0 128.37 9.84

0 0 43.91 4.02

6214

1042

139

48

Odours resulting after spraying with either ANOTEC solutions showed a total elimination of hydrogen sulfide, acetaldehyde and methylamine compared to the raw odour.

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However, both Butanol and 2-butenal were still present at considerably reduced concentrations after treatment with the spraying system. The essential oil mixture in ANOTEC 0307 “fragrant” was ignored in the calculation of results since the analysis was required to be confined to the removal of the odour component generated from the permeation system.

Acknowledgements Dr David J M Stone (ANSTO) Mr John Zavras (Chief Chemist, Anosmia Technologies Pty Limited) Mr Stephen Walker (Walker Associates, Managing Director A.T. Products Corp. Milwaukee USA) Ms Nancy Washburn (Operations, A.T. Products Corp. Milwaukee USA) Mr Ralph Kaye (CWT) Mr John Jiang (CWT) Mr John Drakoulis (ANOTEC Pty Limited)

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REFERENCES: Cox, J. P. Odour Control and Olfaction, Pollution Sciences Publ. Co. Lynden, Washington 1975. Croker, E. C. and L. F. Henderson. Analysis and classification of odours. An effort to develop a workable method. Amer. Perf. Essent. Oil Rev. 22:325-327 1927 Dravnieks, A. Development of a Dynamic Forced Choice Method for the Measurement of Emission and Ambient Odours. Institute of Illinois Research Project 1976 96pp Lauren, O.B. Odour Modification, Industrial Odour Technology, Ann Arbor Science Publ. Inc. 1975 Lundberg, C.A. Dynamic Triangle Olfactometer Evaluation Project, 3M Company St Paul Minnesota 31pp 1975. Marrone W.A. Evaluation of Odour Measurement Techniques: Vol 1, EPA No. 650/274-008-a, USEPA 1974. Neilson, A.J., Kendall D.A., Correlation of Subjective and Objective Odour Responses. Ann. N.Y. Academy of Science 567 1964. National Research Council Committee, Odours from Stationary and Mobile Sources. 1978. Sanders, G The Measurement of Maladour in a Community of Dynamic Olfactometry. Third Karolinska Institute Symposium on Environmental Health 1970. Sereno D. J. Moghaddam O., Harrison D. S., Jacobs P. G., Evaluation of Odour/VOC Control Technologies for dewatered Sludge Storage. Water Pollution Control Federation 63rd Annual Conference Washington DC 1990. Wade, W.A. III, Technical Report to the Illinois Environmental Protection Agency on the Evaluation of Four Odour Measurement Systems. The Research Corporation of New England, Project 32390 1974. Wenzill B.M Techniques in Olfactometry: A critical review of the last one hundred years. Psych. Bull. 45. 1948. Zavras, J. History, Mystery and Chemistry of Odour Control Substances (unpublished), presented at Clean Air Society of Australia and New Zealand Training Activities Committee, Sydney 1992. Zwaardemaker, H. The Physiology of Odours 1895.

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