Integrationof Odour Emission Measurements from Area Sources

withDispersion Modelling Analysis of Environmental Impacts

ReportNo WSAA 136

September 1999

EXECUTIVESUMMARY

Thereport reviews literature on the development of sampling techniques for areasources. Particular focus was put on the direct sampling using the static USEPA isolation chamber and the dynamic UNSW wind tunnel systems.

Aninvestigation was undertaken to establish the most likely ambient wind velocitypassing across water surfaces of typical wastewater treatment plants at timesof highest recorded levels of odour complaint. The investigation was based onan analysis of odour complaint data for two large wastewater treatment plants.The findings were then used to select an appropriate air velocity for use inthe wind tunnel when used for odour sampling.

Alaboratory investigation, based on three model compounds, to compare resultsobtained using a wind tunnel system with those obtained using an isolationchamber system. The model compounds selected were Acetone in aqueous solution(used to study gas phase controlled volatilization processes), Toluene inaqueous solution (used to study liquid phase volatilization processes) andMethyl ethyl ketone in aqueous solution (used to study both gas and liquidphase controlled volatilization processes).

Afield investigation was carried out at two typical wastewater treatment plantsto compare specific odour emission rates determined on the basis ofolfactometry samples obtained using a wind tunnel system with specific odouremission rates determined on the basis of olfactometry samples obtained usingan isolation chamber system.

Inorder to model community odour impact, an investigation was undertaken at oneof the wastewater treatment plants using the Ausplume dispersion model andspecific odour emission rates determined on the basis of olfactometry samplesobtained using a wind tunnel system. In addition the Ausplume model resultswere interpreted in relation to complaints data available for the plant.

Thestudy concluded that the procedure developed could be used to predict theenvironmental impact for proposed facilities, for augmentation of existingfacilities, and for assessing the odour impact implications of encroachment ofresidential/commercial developments into “buffer zone” area reservations aroundexisting or proposed facilities. The study also concluded that the wind tunnelbased procedures are reproducible, and can be applied to define performancetargets for other, similar, wastewater treatment plant sites. Refinements areproposed to improve the accuracy of the procedures, and to enable approximatelyequivalent performance targets to be defined for emissions from sitesincorporating sources with a range of dispersion characteristics.

Thebasic recommendation of the authors is that the use of the static isolationchamber be discontinued and that the use of portable wind tunnel systems beadopted provisionally for odour (and VOC) emission measurement sampling atwastewater treatment plants.

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