Atmospheric Sublayer Transport and Odor Control

Wastewater treatment plant boundary odor concentrations exceeding 5 ou/scf can cause odor complaints. Highest plant boundary odor concentrations for a given source odor emission rate occur when the stable sublayer temperature at 25 ft. (7.62m) minus that at 5 ft. (1.52m) exceeds 2°F (1.1°C). Another criterion for critical transport may be the occurrence of critical Richardson number conditions within the transporting sublayer. The effectiveness of dispersion-inducing barriers and wind machines is apparently reduced as the net heat flow from air to ground increases. Monitored micrometeorological variables are used to determine the magnitude and frequency of critical transport conditions. (Statistical procedures are used to obtain estimates of the frequency of occurrence of 5 ou/scf odor concentrations at the plant boundary from various odor sources with alternative control systems in use.) Limiting control system operation to critical transport conditions can reduce operating costs to a small fraction of continuous operation costs without incurring additional odor risks.