ODOR TESTING BIOSOLIDS FOR DECISION MAKING

The measurement of odors from wastewater treatment facilities is usually a requirement for compliance monitoring, planning, site expansion, and review of operational practices. These odor measurements are often focused on the “front end” of the facility, i.e. head works, primaries, and aeration processes. Sometimes attention is also placed on digesters and dewatering processes. However, the odor of the biosolids material is often overlooked as a parameter in decision-making at the wastewater treatment facility.Odor is a serious issue in the acceptance of biosolids at a landfill and, more so, a critical issue in public acceptance for land application of biosolids. The biosolids industry recognizes a wide variability in the odor from different biosolids. In the search for operational parameters that influence biosolids odor, the need to select and trust odor measurement methods is critical.Research on biosolids odor includes identifying the origin, mechanisms, and parameters for odor production, quantifying odor generation, defining “low odor” processes, and measuring odor in the ambient air surrounding land application operations. All of these research objectives need common, standard, and trustworthy “odor testing” methods (standard practices). Equally important to defining and accepting standard methods, is the over riding need to understand the odor testing results for decision making within the Environmental Management System.Odors have measurable parameters that are not always understood. The parameters of odor include: “odor concentration” (thresholds), “odor intensity” (intensity referencing), “odor character” (standard descriptors), “odor persistency” (the “hang time” of the odor), and “odor Hedonic Tone” (subjective measure of pleasantness/unpleasantness). Each of these parameters have certain limits of “accuracy” that must be understood for appropriate decision making. Without consideration for parameter variability, two odor test results may appear to be different, but may not be statistically different. Likewise, two odor test results may appear to be “nearly the same”, but the differences may be significant when all the odor parameter results are presented in combination for decision-making. Biosolids odors need to be tested with reference to the facility's processes and with reference to the environmental situations at the time of land application.