Biofiltration is a relatively new pollution control technology. It is an attractive technique for the elimination of malodorous gas emissions and of low concentrations of volatile organic compounds (VOCs). The most common style biofilter is just a big box. Some can be as big as a basketball court or as small as one cubic yard. A biofilter’s main function is to bring microorganisms into contact with pollutants contained in an air stream. The box that makes up this biofilter contains a filter material, which is the breeding ground for the microorganisms. The microorganisms live in a thin layer of moisture, the "biofilm", which surrounds the particles that make up the filter media. During the biofiltration process, the polluted air stream is slowly pumped through the biofilter and the pollutants are absorbed into the filter media. The contaminated gas is diffused in the biofilter and adsorbed onto the biofilm. This gives microorganisms the opportunity to degrade the pollutants and to produce energy and metabolic byproducts in the form of CO2 and H2O.

This biological degradation process occurs by oxidation, and can be written as follows:

Organic Pollutant + O2  CO2 + H2O + Heat + Biomass

Why Is Bio-filtration Important?

• The process involved (bio reaction) is a green process.

• Thermal and catalytic control units consume large volumes of expensive fuel.

• Bioreactors only use small amounts of electrical power to drive two or three small motors.

• Normally, bioreactors do not require full-time labor and the only operating supplies needed are small quantities of macronutrients.

While the use of bio filtration in India is not used, hundreds of these systems are successfully operating in Europe, Netherlands, New Zealand, Germany, and Japan. Bio filters have been designed primarily for odor control at wastewater treatment plants, rendering plants, and composting operations. However, bio filters are becoming more popular in the treatment of VOCs and other organic compounds.

Biofiltration utilizes a supported media for microbial growth to remove odors and organic contaminants from air streams. The filter consists of a closed chamber containing contaminant degrading microbes and absorbed water suspended in a filter medium. The filter medial is designed to provide a high capacity for water uptake, have a long working life, and provide a low pressure drop for the gases passing through the media.