Biofilters are a method of treatment where odor removal is based on the biological process. The air which odor removal process will be carried out passes through a porous media bed. The media used in this media bed ensures a high surface area. It is essential that a suitable pH range and a humidity ratio are ensured so that the microorganisms on the media work at the desired efficiency. Water is supplied to the system to ensure that humidity is present in the environment and that the microorganisms can continue their activities. The presence of water is also important to ensure that contaminants are passed from air to the water.
Biofilters are often used at large capacity wastewater treatment plants. The biggest disadvantage of this system is that a wide area is needed for installation. Biofilters can treat various and high concentrations of contaminants but they cannot react quickly in the case of excessive loads. The best area of working for these is places where input concentrations are relatively stable.