Practical Odour assessment. Nigel Gibson

Transcription

1 Practical Odour assessment Nigel Gibson Odour - the problem The process of concern Local residents 1

2 Topics covered Complaints Off-site survey Odour/odorant sampling Odour/odorant measurement Odour assessment Objectives of odour monitoring Establish whether nuisance exists Enable mitigation program to be defined 2

3 Complaints Sign of problems with a plant or process Level of complaints may not represent the true feeling of the community Complaint level will vary with time Factors affecting human response Physiological factors - age, sex, health... Social factors - custom, habit, attitude to source, past experiences... Meteorological - temperature, humidity... Local politics 3

4 Example site - year 1 complants year 1 complaint days 09/01/98 23/01/98 06/02/98 20/02/98 06/03/98 20/03/98 03/04/98 17/04/98 01/05/98 15/05/98 29/05/98 12/06/98 26/06/98 date 10/07/98 24/07/98 07/08/98 21/08/98 04/09/98 18/09/98 02/10/98 16/10/98 30/10/98 13/11/98 27/11/98 complants Example site - year 2 complaints complaint day complaints 20/01/99 03/02/99 17/02/99 03/03/99 17/03/99 31/03/99 14/04/99 28/04/99 12/05/99 26/05/99 09/06/99 23/06/99 07/07/99 21/07/99 month 04/08/99 18/08/99 01/09/99 15/09/99 29/09/99 13/10/99 27/10/99 10/11/99 24/11/99 08/12/99 4

5 Odour Control Parameters v Complaints Figure 4 odour control parameters v complaints bed temp. (deg C) ph bed temperature complaints mex temp bed ph acidic ph /05/98 26/05/98 31/05/98 05/06/98 10/06/98 15/06/98 20/06/98 25/06/98 30/06/98 day Wind Speed Direction and Complaints in June 1998 Figure1 showing wind speed, direction and complaints in June Wind direction (degrees from north) windspeed (m/s) winddirection complaints WIND SPEED Hour

6 Community based techniques Diaries: useful, especially if the event is short-term, and out of hours some discretion in assessing usefulness. (Validation by complaints?) Care needed to interpret diaries (some exaggeration possible, Validation by complaints?) Community surveys: Expensive if done well Ideally large population base require Can differentiate between sources. Boundary fence/off-site survey 1 Many authorisations contain: general odour condition..no offensive odour. as perceived by the local authority inspector routine boundary monitoring by operator 6

7 Boundary fence/off-site survey 2 Advantages: cheap easy (?) Disadvantages: positive results only under extremes conditions discrete test are the results believed? observer fatigue Off-site survey method 1 Method proposed in guidance to WML regulators (EA website) based on assessment of: Intensity + Extent + Sensitivity of Location 7

8 Off-site survey method 2 Intensity 1. No detectable odour 2. Faint odour (barely detectable, need to stand still and inhale facing into the wind) 3. Moderate odour (odour easily detected while walking and breathing normally, possibly offensive) 4. Strong odour (bearable, but offensive odour - will my clothes/hair smell?) 5. Very strong odour (this is when you really wish you were somewhere else) Off-site survey method 3 Extent (assuming odour detectable, if not then 0) 1. Local and impersistent (only detected during brief periods when wind drops or blows) 2. Impersistent as above, but detected away from site boundary 3. Persistent, but fairly localised 4. Persistent and pervasive up to 50 m from site boundary 5. Persistent and widespread (odour detected >50 m from site boundary) 8

9 Off-site survey method 4 Sensitivity of Location where Odour Detected (assuming detectable, if not then 0) 1. Remote (no housing, commercial/industrial premises or public area within 500 m) 2. Low sensitivity (no housing, etc. within 100 m of area affected by odour) 3. Moderate sensitivity (housing, etc. within 100 m of area affected by odour) 4. High sensitivity (housing, etc. within area affected by odour) 5. Extra sensitive (complaints arising from residents within area affected by odour) Sampling Point sources Open surfaces - with gas flow Open surfaces - without gas flow 9

10 Point sources Open surfaces - with gas flow 10

11 Open surfaces - without gas flow Open surfaces - without gas flow 11

12 Odour measurement/quanitification Compound specific techniques Complex chemical analysis Olfactometry Compound specific techniques Specific odorants e.g. NH 3, RNH 2, H 2 S, RHS Marker compounds H 2 S, methane etc. Not necessarily a direct correlation with odour 12

13 Marker compounds- landfill Marker compounds- STW 13

14 Marker compounds- brickworks Figure 1 Odour and H2S concentrations throughout one kiln cycle time 5.E E E+06 Odour concentration (ou/m3) 4.E+06 3.E+06 3.E+06 2.E+06 2.E+06 tot odour tot h2s H2S concentration (ppm) 1.E+06 5.E E :18 7:20 8:15 9:14 10:13 11:13 12:14 13:14 14:16 15:16 16:15 17:17 18:16 19:15 20:17 21:15 time Complex chemical analysis Adsorption followed by GC-FID or GC-MS Electronic nose 14

15 Chemical analysis - GC Gas chromatography is a widely used analytical technique for characterising odour emissions Advantages: Provides quantitative analysis for a broad range of chemicals Chemical analysis - GC Disadvantages Does not detect inorganic species, e.g. ammonia & hydrogen sulphide Poor detection of highly reactive species Time resolution of passive sampling is poor 15

16 Chemical analysis - GC Chemical Analysis (3) Does not take into account additive effects, e.g. Compensation I ab <I a or I b (whichever smaller) Compromise I ab <I a or I b (whichever greater) Independence I ab =I a or I b (whichever greater) Partial addition I a +I b >I a or I b (whichever greater) Complete addition I ab =I a +I b Hyper-addition I ab >I a +I b 16

17 Electronic nose 1 Electronic sensors work in 1 of 2 ways: Chemical reaction: - responds to the products (or starting materials) of reaction Micro-environmentally sensitive: - functions by reaction changes occurring in electrical properties. Mixture not substance specific Electronic nose 2 In the future the electronic nose may offer a practical solution for objectively assessing odours. Unlike gas chromatography the electronic nose measures all components in a mixture at any one time. 17

18 Electronic nose 3 Olfactometry 1 It involves the step-wise dilution of a sample of odour-free air and subsequent presentation to a panel of observers in order to determine the number of dilutions required for odour to be perceived by 50% of the members of the panel. 18

19 Olfactometry 2 1 odour unit = The amount of odorant(s) that, when evaporated into 1 cubic metre of odourless gas at STP, causes a physiological response from a panel (detection threshold) equivalent to that elicited by 40ppb (0.123mg/m3) of n-butanol Source: CEN TC264/WG2 Olfactometry 3 19

20 Olfactometry 4 Olfactometry 5 Log 10 (Dilution) Log 10 (Dilution) Vs % Negative response % % Negative response 20

21 Impact assessment overview Screening or detailed modelling? Screening emission factor data, e.g. for pig farming: weaners 6 ou/animal/s dry sow 19.1 ou/animal/s boar 22.6 ou/animal/s simple model (d max ) Detailed - full measurement (olfactometry) and modelling study (ADMS, AERMOD) 21

22 Odour assessment criteria Two components: a concentration component, and a percentage compliance component. E.g. Odour concentration shall not exceed X OU/m 3, corrected for the appropriate peak to mean ratio, for more than Z% of the meteorological conditions. Criteria used in UK 5 ou/m 3 as a 98th%ile of 1 hour averages set using pre-1995 Dutch data Dutch correction factor: 1 ou E /m 3 =2 GE/m 3 therefore criteria should now read: 2.5 ou/m 3 as a 98th%ile of 1 hour averages 22

23 Dutch criteria (NER 2000) Process Target 98 th %ile Limit 98 th %ile Bakeries 5 Breweries 1.5 Slaughterhouse Meat processing Grass drying 2.5 Coffee roaster 3.5 Animal feed plant 1 composting wwtw Example output as a 98 th %ile

24 Summary Nuisance assessment Mitigation program complaints Off-site assessment Monitoring Impact assessment Yes Yes Possibly Yes Possibly Possibly Yes Yes 24