Odour modelling using ADMS software

Transcription

1 Odour modelling using ADMS software Presentation by Dr David Carruthers Cambridge Environmental Research Consultants (CERC) Aiga Kāla Estonian, Latvian & Lithuanian Environment (ELLE)

2 Overview Odour units Odour modelling and legal requirements Practical examples

3 Odour units Two types of odour units available in ADMS: ou A value in ou is a ratio. The ou strength is the number of times the mixture must be diluted (at standard temperature and pressure) to reach the detection limit ou E (European odour unit) A value in ou E is a mass measurement. One ou E is the mass of pollutant that, when evaporated into 1m 3 of odourless gas (at standard conditions) results in a mixture with concentration equal to the detection threshold for that pollutant European odour units (ou E ) are more commonly used and olfactometry measurements give odour concentrations in ou E /m 3

4 Odour units (II) The odour concentration of a compound can be estimated by: D = C/T Where: D is the odour concentration of a compound (dimensionless, odour units ou E m -3 ) C is the chemical concentration of a compound in mg m -3 T a is the published odour threshold value of a compound in mg m -3

5 How strong is an odour unit? According to generalised assumptions based upon laboratory-based experiments on perceived intensity: 1 ou E m -3 is the point of detection 5 ou E m -3 is a faint odour 10 ou E m -3 is a distinct odour The recognition threshold is often about three odour units

6 Modelling odours ADMS-Urban and ADMS-Roads 3.1 Many types of installation have the potential for being the cause of an odour nuisance problem Waste water treatment works Landfill sites Livestock farming Paint spray workshops Fuel storage Lithuania User Group Meeting 2012

7 Modelling odours ADMS-Urban and ADMS-Roads 3.1 Odours appears as new option in Setup screen ou E - The mass of pollutant, which when evaporated into 1m 3 of odourless gas at standard conditions (STP) results in a mixture with concentration equal to the detection threshold for that pollutant Detection threshold - the point at which an increasing concentration of an odour sample becomes strong enough to produce a first sensation of odour in 50% of people to whom the sample is presented Lithuania User Group Meeting 2012

8 Modelling odours ADMS-Urban and ADMS-Roads 3.1 Horizontal Guidance for Odour Management (H4) (Environment Agency, April 2011): Classifies relative offensiveness of odours arising from different types of process as High, Medium or Low Odour exposure criteria expressed in terms of 98 th percentile of hourly mean (equivalent to 175 exceedences per year) Offensiveness category Indicative criterion (below which there is no reasonable cause for annoyance ) Examples of installation types High 1.5 ou E /m 3 Waste water treatment, brickworks, oil refining Medium 3 ou E /m 3 Sugar beet processing, intensive livestock rearing Low 6 ou E /m 3 Brewery, chocolate manufacture Lithuania User Group Meeting 2012

9 Modelling odours ADMS-Urban and ADMS-Roads 3.1 Odours are not included in the default pollutants list, so must be added to the palette of pollutants Lithuania User Group Meeting 2012

10 Modelling odours ADMS-Urban and ADMS-Roads 3.1 This will produce output for direct comparison with the indicative odour exposure criteria. The.glt output file contains the long-term average odour concentrations and percentiles of hourly average odour concentrations for all grid points. Lithuania User Group Meeting 2012

11 Modelling odours ADMS-Urban and ADMS-Roads 3.1 Example - Odour release from a group of 5 vents: Olfactometry 125 ou E /m 3 (STP) from each vent Source characteristics: Vent height: 1.75 m Vent diameter: 1 m Exit flow rate: 2 m 3 /s Temperature: 15 C Emission rate: 2 m 3 /s x 125 ou E /m 3 = 250 ou E /s Lithuania User Group Meeting 2012

12 Modelling odours ADMS-Urban and ADMS-Roads 3.1 Contour Plotter used to plot 98 th percentile of hourly average odour concentrations Comparing predicted odour concentrations to indicative odour exposure criteria: No area of exceedence for Low or Medium offensiveness categories Small area of exceedence for High offensiveness category Offensiveness category Indicative criterion High 1.5 ou E /m 3 Medium 3 ou E /m 3 Low 6 ou E /m 3 Lithuania User Group Meeting 2012

13 Legal requirements in Latvia Cabinet of Ministers Regulations No 626 adopted on July 27, 2004 Regulation on the methods for determination of odour, as well order of limitation of odours from polluting activities Odour target value, ou E m -3 Percentile of hourly averages Source of odour th Not specified th Agricultural activities th Permitted industrial activities

14 Examples emission rate Emission factors from literature pig farms (Environmental Protection Agency of Ireland - Odour Impacts and Odour Emission Control Measures for Intensive Agriculture, 2001) Measurements the laboratory of Latvian Environment, Geology and Meteorology Centre determine odour by means of olfactometry uploading oil products pig farms Calculated results based on odour threshold values uploading liquefied gas (methyl mercaptan)

15 Measurements Analytical techniques (chemical analysis) Sensory methods (ie relating to the human response) provides information on the likely population response Selection of a particular method will depend upon: the purpose of the measurement the frequency (once off or frequent/continuous) etc the location at which the odour is sampled whether a point source or surface/area source the complexity of the emission - a single compound or a complex mixture.

16 Case study fish processing

17 Case study fish processing (II)

18 Case study fish processing (III) Main production parameters: Fish for drying t/a Fish for cooking 2324 t/a Source characteristics: Height: 23 and 11 m Diameter: 400 and 500 mm Exit flow rate: m 3 /h and 800 m 3 /h

19 Emission factors for fish processing AP 42, Fifth Edition, Volume I Chapter 9: Food and Agricultural Industries Activity Hydrogen Sulfide (H 2 S), kg/t Trimethylamine ((CH 3 ) 3 N), kg/t Fish cooking: Fresh fish Stale fish Fish drying 0.05 n/d

20 Odour emissions Odour tresholds: For Hydrogen Sulfide ppm ( mg/m 3 ) For Trimethylamine 0.48 ppm (1.16 mg/m 3 ) Activity Odour concentration, (ou E /m 3 ) Odour emission, (ou E /s) Fish drying Fish cooking, H 2 S Fish cooking, (CH 3 ) 3 N

21 Legend

22 Odour assessment: Oil product terminal, Emission rate based on measurement results and information about odour treshold values

23 Odour assessment: pig farm; emission rate calculated from EF (odour units per animal)