Also known as biological filters are devices that remove a wide range of polluting compounds from a stream of fluid (air or water) through a biological process.
How do Biofilters work?
The air is drawn near the center of emanation and usually led to a conditioning chamber. In the chamber the air is saturated with moisture and then guided to a fixed bed of biomass. The pollutants are absorbed to the biofilm of biomass formed over the fill and subsequently are digested by microorganisms. In our research group of bacteria motility we are studying the possible displacement of non-motile bacteria in the presence of chemical compounds such as substrates. The biofilm formed by biomass can be seen as the surface of carbon source in which the bacteria will reside. The possible displacement of these non-motile bacteria by the effect of a gradient concentration can be seen as the driving force that will promote the movement of this organism to the areas in the biofilm that contain the higher concentrations of pollutants – to eventually yield a high efficiency of contaminants removal in the fluid stream. In the process of digestion and metabolism the treated compounds are transformed into compounds that do not smell. The organic compounds are transformed into carbon dioxide and water. In principle this is an oxidation of the contaminants at low temperature.
Where can Biofilters be applied?
Biofilters can be applied to a wide range of volatile substances; from inorganic compounds such as hydrogen sulfide and ammonia; to volatile organic compounds such as toluene, xylens or benzene. For the application of Biofilters air must be provided in biocompatible conditions, this means that:
- there shouldn’t be present disinfectant compounds,
- the temperature must be in a range of about 5 – 40 ° C and
- the concentration of the substances to retain should not be toxic to the organisms.
How efficient Biofilters are?
The overall performance will be better if the conditions are constant. The yields achieved by the Biofilters depend on the nature and concentration of the pollutants and in any other compounds present in the treated mixture. Biofiltration often reaches yield values of 95 – 99% and are therefore comparable with the yields achieved by other deodorizing process as the chemical cleaning or activated carbon filters.
- Joseph S. Devinny, Marc A. Deshusses and Todd S. Webster (1999). Biofiltration for Air Pollution Control. Lewis Publishers. ISBN 1-56670-289-5.
- Beychok, Milton R. (1967). Aqueous Wastes from Petroleum and Petrochemical Plants (1st Edition ed.). John Wiley & Sons Ltd. LCCN 67019834.
Walter G. Rivera Guzmán