Brazilian environmental regulations are following the international trend to include odor emission control. Today, the only state legislation that determines odor emission limits in Brazil defines that odor generating activities, emitting more that 5×106 O.U/h (odor units per hour), must install odor treatment equipments with at least 85% efficiency for odor removal. This work had the objective to apply dynamic-dilution olfactometry to assess the treatment efficiency of 12 full-scale industrial gas scrubbers and 2 biological filters for the removal of odor during their normal operating conditions, located in five industries in southern Brazil. To determine the odor concentration, a 6-person dynamic-dilution olfactometer was used. Odor emission rates were also measured. Results showed the wide spectrum of efficiency levels that can be found in normal operating conditions for different gas treatment techniques. Overall surprisingly low efficiency rates were found in most wet scrubbers. Biological filters showed relatively higher efficiency rates, but no equipment reached the 85% treatment efficiency level established by law in the case of high odor emissions. As for the odor emission rates, six equipments had an odor outflow higher than the values established by the state regulation.

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