From Mary Bellis,
Your Guide to Inventors.
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Biological treatment or biofiltration is now the mainstay of wastewater management systems. Patent applications for odor control using biofiltration have been filed since the 1950s for soil filters and large biological trickling filter plants.

Biofilters have been designed primarily for odor control at wastewater treatment plants, rendering plants, and composting operations. They are becoming more popular in the treatment of VOCs (volatile organic compounds), as an innovative method to treat toxic air emissions from commercial processes.

What Does a Biofilter Do?

Biofilters perfom the removal and oxidation of compounds from contaminated air using microorganisms. Smelly air emissions generally contain low concentrations of hydrogen sulfide, mercaptons, and other reduced sulfur compounds.

During the 1990s, biofilters were also used to remove airborne contaminants, including aliphatic and aromatic hydrocarbons, alcohols, aldehydes, organic acids, acrylate, carbolic acids, amines and ammonia. These substances are not just smelly, they are dangerous as well.

Timeline: History of Biofilters

• 1923: The first proposition to use biological methods to treat odorous compounds was as early as 1923. Bach thought of using a biologically active biofilter to control emissions of H2S from a waste water treatment plant.
• 1955: Biological methods were first applied to treat odorous emissions in low concentrations in Germany.
• 1959: A soil bed was installed at a sewage treatment plant in Nuremberg for the control of odors from an incoming sewer main.
• 1960's: Biofiltration was first used for the treatment of gaseous pollutants both in Germany and US; research was intensified.
• 1970's: Biofiltration becomes widespread in Germany.
• 1980's: Biofiltration is used for the treatment of toxic emissions and volatile organic compounds (VOCs) from industry.
• 1990's: There are more than 500 biofilters operating both in Germany and Netherlands, and it is spreading in the US.