Impact of Local Odor Regulations on Odor Control Requirements

Where they exist, odor regulations around the world vary widely. Some are based on a specific contaminant, such as hydrogen sulfide (H2S), or an odor concentration, such as dilution to threshold (D/T). They can allow various exposure times, such as minutes or hours. The location or type of receptor, for example, urban, rural, commercial, or sensitive may also play a role. Given this variation, it is difficult to apply standardized or universal control recommendations for a process or facility that emits odors since odors that might be considered acceptable in one location may be totally unacceptable if situated in another location. Understanding what the applicable regulations or odor criteria are is a key factor in developing an effective odor control strategy for a facility. This paper presents the results of an odor modeling study which evaluated the compliance status of different odor-emitting processes at a medium-sized municipal secondary wastewater treatment plant (WWTP) against an array of regulatory odor standards, criteria, and guideline values. Odor emissions from the process sources were determined using onsite sampling, and refined dispersion modeling was used to assess the offsite impacts of the odor-causing processes at different types of receptor locations. These offsite receptor impacts were then compared to different odor regulations and criteria in order to determine which sources might require odor control depending upon where the plant was located.