Odor treatment - Curative processes

Along with dust and noise, olfactory nuisance is one of the pollutants most resented by the general public. Even if legislation is not very precise on the subjects of odor flows, odor concentrations or emission limits, and if, due to low concentrations, there is no relationship between toxicity and the sensation of bad odors, olfactory nuisance must be combated. There are many arguments in favor of minimizing and controlling odor emissions. These include improved comfort for neighbors, or the image of a company or industry that is largely disrupted by foul-smelling gaseous emissions.

An odor is a complex, hyperdiluted mixture of organic or inorganic molecules. These include sulfur compounds (hydrogen sulfide, mercaptans, sulfides, etc.), nitrogen products (ammonia, amines, etc.) and oxygenated molecules (organic fatty acids, alcohols, aldehydes, ketones, esters, etc.). Concentrations found are at most a few µg/m ³ , and generally close to a few ng/m ³ or even pg/m ³ for certain products.

These specific features have led to the development of special treatment processes based on the physico-chemical properties of the odor compounds to be eliminated. For example, a soluble product can be transferred to a washing solution, an acidic or basic compound can be eliminated by a base or acid respectively, and a molecule can be adsorbed by activated carbon or biodegraded by microorganisms. In addition, the low concentration of pollutants means that specific sizing and operating conditions have to be defined for this problem. The notion of treatment investment cost is of prime importance in the environmental field. We therefore need to devise and propose processes that are rustic in design and operation.

This article presents the most common processes used to reduce odour nuisance. An identical approach will be proposed, including the operating principle, implementation, some sizing data and examples of applications. Finally, a few elements for choosing a treatment process will be given, including objective and more subjective criteria, as well as notions of relative cost.