ABSTRACT
The underlying mechanisms which allow biofilters to work, and which must be controlled to ensure success, are complex. The biofilter contains a porous medium whose surface is covered with water and microorganisms. Treatment begins with transfer of the contaminant from the air stream to the water phase. The transfer of contaminants from the air to the water and solids in a biofilter is a fundamental step in treatment and is sometimes loosely referred to as adsorption or dissolution. Biofilters are economical only if the air can be passed through them quickly. Transfer of the contaminant to the medium must also be fast. The key element in destroying contaminants is the biofilm. This is a mass of organisms growing on the surface of the solid medium and carrying out the metabolic activities which transform the contaminant to harmless products. If the biofilter is to succeed, these organisms must be very active.
