Practical Odour assessm ent Nigel Gibson Odour - the problem The process of concern Local residents 1
Topics covered • Complaints • Off-site survey • Odour/ odorant sampling • Odour/ odorant measurement • Odour assessment Objectives of odour m onitoring • Establish whether nuisance exists • Enable mitigation program to be defined 2
Com plaints • 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 hum an response • Physiological factors - age, sex, health... • Social factors - custom, habit, attitude to source, past experiences... • Meteorological - temperature, humidity... • Local politics 3
Exam ple site - year 1 complants year 1 complaint days complants 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 / / / / / / / / / / / / / / / / / / / / / / / / 1 1 2 2 3 3 4 4 5 5 5 6 6 7 7 8 8 9 9 0 0 0 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 / / / / / / / / / / / / / / / / / / / / / / / / 9 3 6 0 6 0 3 7 1 5 9 2 6 0 4 7 1 4 8 2 6 0 3 7 0 2 0 2 0 2 0 1 0 1 2 1 2 1 2 0 2 0 1 0 1 3 1 2 date Exam ple site - year 2 complaints complaint day complaints 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 / / / / / / / / / / / / / / / / / / / / / / / / 1 2 2 3 3 3 4 4 5 5 6 6 7 7 8 8 9 9 9 0 0 1 1 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 / / / / / / / / / / / / / / / / / / / / / / / / 0 3 7 3 7 1 4 8 2 6 9 3 7 1 4 8 1 5 9 3 7 0 4 8 2 0 1 0 1 3 1 2 1 2 0 2 0 2 0 1 0 1 2 1 2 1 2 0 month 4
Odour Control Param eters v Com plaints Figure 4 odour control parameters v complaints 45 10 9 40 8 35 7 30 6 bed temp. (deg C) bed temperature 25 complaints pH 5 mex temp bed pH 20 acidic pH 4 15 3 10 2 5 1 0 0 21/05/98 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 W ind Speed Direction and Com plaints in June 1998 Figure1 showing wind speed, direction and complaints in June 1998 360.0 14.0 12.0 Wind direction (degrees from north) 270.0 10.0 windspeed (m/s) 8.0 winddirection 180.0 complaints WIND SPEED 6.0 4.0 90.0 2.0 0.0 0.0 3600 3624 3648 3670 3694 3718 3742 3766 3790 3814 3838 3862 3886 3910 3934 3958 3982 4006 4030 4054 4078 4102 4126 4150 4174 4198 4222 4246 4270 4294 4318 4342 4366 Hour 5
Com m unity 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?) Com m unity 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
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 m ethod 1 Method proposed in guidance to WML regulators (EA website) based on assessment of: Intensity + Extent + Sensitivity of Location 7
Off-site survey m ethod 2 I ntensity 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 norm ally, possibly offensive) 4. Strong odour (bearable, but offensive odour - will m y clothes/ hair sm ell?) 5. Very strong odour (this is when you really wish you were som ewhere else) Off-site survey m ethod 3 Extent ( assum ing odour detectable, if not then 0 ) 1. Local and im persistent (only detected during brief periods when wind drops or blows) 2. I mpersistent 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
Off-site survey m ethod 4 Sensitivity of Location w here Odour Detected ( assum ing detectable, if not then 0 ) 1. Rem ote (no housing, com m ercial/ 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 (com plaints arising from residents within area affected by odour) Sam pling • Point sources • Open surfaces - with gas flow • Open surfaces - without gas flow 9
Point sources Open surfaces - w ith gas flow 10
Open surfaces - w ithout gas flow Open surfaces - w ithout gas flow 11
Odour m easurem ent/ quanitification • Compound specific techniques • Complex chemical analysis • Olfactometry Com pound 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
Marker com pounds- landfill Marker com pounds- STW 13
Marker com pounds- brickw orks Figure 1 Odour and H2S concentrations throughout one kiln cycle time 5.E+06 3.5 5.E+06 3 4.E+06 2.5 4.E+06 Odour concentration (ou/m3) H2S concentration (ppm) 3.E+06 tot odour 2 tot h2s 3.E+06 1.5 2.E+06 2.E+06 1 1.E+06 0.5 5.E+05 0.E+00 0 8 0 5 4 3 3 4 4 6 6 5 7 6 5 7 5 1 2 1 1 1 1 1 1 1 1 1 1 1 1 1 1 : : : : : : : : : : : : : : : : 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 1 1 1 1 1 1 1 1 1 1 2 2 time Com plex chem ical analysis Adsorption followed by GC-FID or GC-MS ‘Electronic nose’ 14
Chem ical analysis - GC Gas chromatography is a widely used analytical technique for characterising odour emissions Advantages: • Provides quantitative analysis for a broad range of chemicals Chem ical 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
Chem ical analysis - GC Chem ical 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
Electronic nose 1 Electronic sensors work in 1 of 2 ways: Chem ical reaction: - responds to the products (or starting materials) of reaction Micro- environm entally 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
Electronic nose 3 Olfactom etry 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
Olfactom etry 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 Olfactom etry 3 19
Olfactom etry 4 Olfactom etry 5 Log 10 (Dilution) Vs % Negative response 100 000 9 Log 10 (Dilution) 8 7 6 5 45 000 4 3 2 10 000 50% % Negative response 20
I m pact assessm ent overview Screening or detailed m odelling? • 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
Odour assessm ent 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 m ean ratio, for m ore than Z% of the m eteorological 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
Recommend
More recommend
