Odor Dispersion Barrier Walls – Theory and Practical Application

In the late 1970's, extensive research was conducted at Sacramento Regional County Sanitation District on means to control odorous emissions from their sludge storage basins (SSBs), which are part of the solids handling and treatment system for the Sacramento Regional Wastewater Treatment Plant. Odor emissions from these sludge lagoons were a major concern due to the location of nearby residences, less than half of a mile from the plant. Because of the large surface area of the SSBs, typical gas-phase capture-and-treat odor control was not feasible. An alternate means of odor control was researched and installed for the SSBs which incorporated diverting foul air away from the nearby residences using physical barriers and principles of atmospheric dispersion only.The research at Sacramento Regional resulted in construction of a 15-foot tall barrier wall around the perimeter of the SSBs. Research showed that the wall increased vertical dispersion of odorous plumes as they traveled downwind, which resulted in decreased odor concentrations at the surface in the location of the nearby receptors. This effect was most notable under “puff transport” conditions, in which a temperature inversion keeps odorous air close to the ground, and more concentrated than under normal atmospheric conditions.The odor dispersion barrier wall technology can also be applied to other wastewater treatment facilities that utilize large area sources for wastewater storage or treatment. In 2010, a utility in the San Francisco Bay Area constructed a barrier wall adjacent to its secondary clarifiers, which had higher than typical hydrogen sulfide emissions, as a means of increasing vertical dispersion. Furthermore, the odor dispersion wall technology has been applied to non-wastewater treatment operations, in particular agricultural applications such as swine farms and compost systems that also contain large areas of odorous material. These applications have been in existence for decades, and research documenting their benefits continues to this day.The odor dispersion barrier wall technology is a low-cost option that wastewater utilities may consider for better dispersion of odors emitted by large processes such as sludge lagoons. For these odor sources, gas-phase treatment is not feasible and liquid-phase treatment may be expensive; this technology could be used to dramatically reduce complaints.