Odour modelling using ADMS software

Presentation by Dr David Carruthers

Cambridge Environmental Research Consultants (CERC)

Aiga Kāla Estonian, Latvian & Lithuanian Environment

(ELLE)

Overview

Odour units

Odour modelling and legal requirements

Practical examples

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

ouE (European odour unit) – A value in ouE is a mass measurement. One ouE is the mass of pollutant that, when evaporated into 1m3 of odourless gas (at standard conditions) results in a mixture with concentration equal to the detection threshold for that pollutant

European odour units (ouE) are more commonly used and olfactometry measurements give odour concentrations in ouE/m3

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 ouE m -3)

C – is the chemical concentration of a compound in mg m -3

Ta – is the published odour threshold value of a compound in mg m -3

How “strong” is an odour unit?

According to generalised assumptions based upon laboratory-based experiments on perceived intensity: – 1 ouE

m -3 is the point of detection – 5 ouE

m -3 is a faint odour – 10 ouE

m -3 is a distinct odour

The recognition threshold is often about three odour units

Lithuania User Group Meeting 2012

Modelling odours

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

ADMS-Urban and ADMS-Roads 3.1

Lithuania User Group Meeting 2012

Modelling odours

ouE - The mass of pollutant, which when evaporated into 1m3 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

ADMS-Urban and ADMS-Roads 3.1

Odours appears as new option in Setup screen

Lithuania User Group Meeting 2012

Modelling odours

Offensiveness category

Indicative criterion (below which there is ‘no reasonable cause for annoyance’)

Examples of installation types

High 1.5 ouE/m3 Waste water treatment, brickworks, oil refining

Medium 3 ouE/m3 Sugar beet processing, intensive livestock rearing

Low 6 ouE/m3 Brewery, chocolate manufacture

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 98th percentile of

hourly mean (equivalent to 175 exceedences per year)

ADMS-Urban and ADMS-Roads 3.1

Lithuania User Group Meeting 2012

Modelling odours

Odours are not included in the default pollutants list, so must be added to the palette of pollutants

ADMS-Urban and ADMS-Roads 3.1

Lithuania User Group Meeting 2012

Modelling odours

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.

ADMS-Urban and ADMS-Roads 3.1

Lithuania User Group Meeting 2012

Modelling odours

Example - Odour release from a group of 5 vents: • Olfactometry 125 ouE/m3 (STP) from each vent • Source characteristics:

– Vent height: 1.75 m – Vent diameter: 1 m – Exit flow rate: 2 m3/s – Temperature: 15 °C

• Emission rate: 2 m3/s x 125 ouE/m3 = 250 ouE/s

ADMS-Urban and ADMS-Roads 3.1

Lithuania User Group Meeting 2012

Modelling odours

Offensiveness category Indicative criterion

High 1.5 ouE/m3

Medium 3 ouE/m3

Low 6 ouE/m3

• Contour Plotter used to plot 98th 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

ADMS-Urban and ADMS-Roads 3.1

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, ouE

m -3 Percentile of

hourly averages Source of odour

5 98.08th Not specified 8 98.08th Agricultural

activities 10 98.08th Permitted industrial

activities

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)

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.

Case study – fish processing

Case study – fish processing (II)

Case study – fish processing (III)

Main production parameters: – Fish for drying - 7260 t/a – Fish for cooking – 2324 t/a

Source characteristics:

– Height: 23 and 11 m – Diameter: 400 and 500 mm – Exit flow rate:1200-1800 m3/h and 800

m3/h

Emission factors for fish processing

Activity Hydrogen

Sulfide (H2S), kg/t

Trimethylamine ((CH3)3N), kg/t

Fish cooking: Fresh fish 0.005 0.15

Stale fish 0.1 1.75

Fish drying 0.05 n/d

AP 42, Fifth Edition, Volume I Chapter 9: Food and Agricultural Industries

Odour emissions Odour tresholds:

– For Hydrogen Sulfide 0.003 ppm (0.0042 mg/m3)

– For Trimethylamine– 0.48 ppm (1.16 mg/m3)

Activity Odour

concentration, (ouE/m3)

Odour emission,

(ouE/s)

Fish drying 4690.48 1547.86

Fish cooking, H2S 4773.81 1050.24

Fish cooking, (CH3)3N 310.73 68.36

Legend

Odour assessment: • Oil product terminal, • Emission rate based on measurement results and information about

odour treshold values

Odour assessment: • pig farm; • emission rate

calculated from EF (odour units per animal)