COMMUNITY ODOR SURVEY

The paper will describe one of the techniques for odor assessment in a two community odor survey with a case studies performed at a waste water treatment plant in Ontario, Canada.The first indication that a potential odor problem may exist in the community is odor complaints.Addressing community odor complaints requires an objective definitions of the odor character, intensity, and frequency. Without such definitions, meaningful action cannot be expected. Through the community odor survey, these odor parameters are measured and documented.The intensive community odor survey can be an effective alternative or supplement to source testing for odor, particularly in cases where there are a number of potential odor emission sources in a community, and where there are sources which are difficult to sample. It is also useful when sources are expected to vary with meteorological conditions.A community odor survey consists of the evaluation of odors by experienced and trained observers in a structured observation session, in which the odors are rated using a standard intensity scale at prescribed locations downwind of the selected plant.For a given observation session, five or six routes are selected, covering a sector centered directly downwind based on the observed wind direction at the start of the session. Odors are evaluated at each of the observation points, starting away from the plant and progressing towards it, to minimize the potential for olfactory fatigue. Odor intensities are rated using a standard point scale (0- no odor to 4- extreme odor).The survey results in a large database of several thousand odor observations which can provide a reliable indication of the impact of odors in the area surrounding the plant. The results can include the percentage of the time that odors above a certain intensity level were detected at a given distance from the plant, the maximum distance at which odors attributable to the plant were detected, and a breakdown of the relative contribution of specific odor categories to the total number of odor observations.The resulting data can be used to confirm dispersion modeling results.This paper will include three case studies–community odor surveys performed at two separate wastewater treatment plants in Ontario.