Biofiltration Fundamentals

In the simplest terms, a biofilter is a device that utilizes natural biological oxidation for the destruction and / or removal of hydrocarbons (or CS2, H2S, NH3), that is to say biofiltration is the degradation of organic and inorganic substances by micro-organisms. These micro-organisms live in a biofilm coating that resides on the surface of a media composed of organic or inorganic (or a combination thereof) matter. The micro-organisms are for the stationary in regard to the system as a whole though they are mobile in their localized biofilm area. The process gases containing the contaminants to be treated flow through the media and as these gases flow by molecules of contaminants pass very near to or directly contact the biofilm where they are absorbed into the biofilm. Noting that the biofilm is primarily composed of water one can see clearly that a compounds solubility in water will greatly impact ease of degradation because if the compound does not enter the biofilm then it cannot be decomposed by the micro-organisms in that biofilm. The biofilm also creates a fixed (more or less) inhabitable space that can only be utilized by a finite maximum number of organisms. The organisms will grow and expand until the available space (biofilm) is filled resulting in situation where no more effective growth can occur.. This means that the effective amount of the summation of biomass (dead and alive) in the unit is at a relative constant. An example of this is shown in the graph below.