A Profile of Wastewater Odors - Assessor Training and Evaluation of Odors from Facility to the Community

A Profile of Wastewater Odors Assessor training and evaluation of odors from facility to the community. Wastewater treatment source odors move downwind into the community with changing intensity and odor character. Odor profiling with intensity measurements is a sensory evaluation tool used to quantify this phenomenon. Odor Profiling requires assessors to assign intensity to odor characters observed at multiple concentration dilution levels through an olfactometer, simulating the changing odor character and intensity of the source odor transported (carried by wind) to the community. Weber-Fechner-Stevens (WFS) studies explained how wastewater odor types smell differently and also change differently as they travel from the source into the community. The Weber-Fechner-Stevens studies and the resulting graphs illustrate odor intensity decreasing at different rates (slope) for each odor type. Trained odor assessors (odor judges) report odor intensity in accordance with ASTM E544-18, Standard Practice for Referencing Suprathreshold Odor Intensity, and other accepted industry standard practices, e.g. sugar water scales. Training assessors is the essential part of odor profiling studies. St.Croix Sensory odor evaluation laboratory uses a 'metric' 10-point odor intensity referencing scale, listed with words to describe the ascending concentration levels. 0 Level No Odor 1 Level Threshold 2 Level Very Slight 3 Level Slight 4 Level Slightly Moderate 5 Level Moderate 6 Level Slightly Strong 7 Level Moderately Strong 8 Level Strong 9 Level Very Strong 10 Level Extremely Strong Assessors (odor judges) can be trained using an ASTM E544-18 10-point Butanol Scale, incorporating the training technique of 'Feedback Calibration Method' (FCM). FCM provides immediate feedback to the test individual during the training. Odor Profiling embraces 'odor wheels', general and specific to odor site studies. With confident assessor intensity performance and a known uncertainty budget applied, predicting the effects of wastewater treatment source odors will become routine for practitioners, engineers, operators, and decision makers. Two cases are present to illustrate the different outcomes of odor profiling: (1) terpene odor profiles for the hemp industry and (2) sanitary wastewater collection system odor profiles.