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Our services are aimed to help our clients to plan to prevent and minimise odours emitted from existing or new plants. Each project must consider the compatibility of the new plant, or modifications to an existing plant, with current and likely future land uses.
Characterization of odor nuisance
We can conduct field campaigns for characterizing odor nuisance, using artificial instruments as well as setting up a team of selected operators (VDI 3940) to produce a georeferenced map of the impacted areas. We can also charaterize volatile organic compounds that are relevant for odor generation and speciate them to identify the components causing odors.
We can assist our Clients in monitoring odor emissions on the short term and from continuous sources. Also, we can find the abatement strategies that can be applied.
Estimation of odor impact
The estimation of odor impact is carried out evaluating the frequency and magnitude of odour, determining what areas will be affected by odours and evaluating possible mitigation measures.
The tools used to estimate odor impact are air dispersion models, which provide the ability to mathematically simulate the fate of a pollutant into the atmosphere. They are used to calculate spatial and temporal fields of odour concentrations.
Dispersion models can provide concentration estimates due to both existing and future emissions scenarios. Dispersion models can also be used to estimate the cumulative impacts of various industries located in close proximity. The estimated odor concentration is compared with threshold established by local legislation or guidelines.
The dispersion models used by Enviroware are mainly AERMOD, CALMET/CALPUFF and LAPMOD. AERMOD and the CALMET/CALPUFF system belong to the list of preferred/recommended models od the US-EPA, while LAPMOD is a Lagrangian particle model developed by Enviroware. One of the features of LAPMOD is that it is capable to calculate directly averages on short time periods (e.g. 5-10 minutes), which is very important in odor impact. The other models calculate 1-hour averages, and need a peak-to-mean ratio a conversion factor that adjusts model predictions to the peak concentrations perceived by the human nose.
Analysis of the meteorological conditions
Meteorological conditions govern the transport and dispersion of pollutants from emission sources to receptors. When modelling emission sources, it is important to use meteorological data that represent the site. Sufficient meteorological data should be available to ensure that worst case conditions are adequately represented in the model predictions. This requirement is especially important when the predicted concentrations must be reported on a statistical basis (e.g. 98th percentile).
A careful analysis of local meteorological conditions is important for other reasons as, for example:
- Identifying an operation as the source of odour by correlating meteorological data with the time of the complaint.
- Describe the prevailing dispersion meteorology at the site including: wind rose diagrams, or joint frequency distribution of wind speed and wind direction, or 1 year of site-representative records of hourly average wind speed and wind direction.
- Conduct odour-generating activities or use odour-generating equipment during the least sensitive time of day or under the most favourable weather conditions. For example, wait until the wind is blowing away from sensitive receptors before flushing a sewage system.
Mitigations
The results of the dispersion modelling analysis is used to develop control strategies that ensure compliance with the odour assessment criteria.
A combination of several approaches is often necessary to achieve the appropriate level of mitigation. Selecting an appropriate strategy for a proposed project involves:
- Determining the order of magnitude of the odour reduction required to meet the relevant criteria.
- Identifying the specific characteristics of the industry and the site.
- Assessing the range of odour-control strategies available.
- Examining mitigation strategies chosen by similar industries
Examples of commonly used odour-control technologies are: incineration, scrubbing systems, adsorption systems and biofiltration. In some situations, it may be necessary to use more than one of these techniques, for example, scrubbing may be needed before adsorption or biofiltration.