Figure 4-54: Typical Methanotrophic Biofilm Reactor Diagram
Biofiltration is a low-cost and highly effective air
pollution control (APC) technology in which vapor-phase organic
contaminants are passed through a bed of porous media and sorb to the media surface where they are
degraded by microorganisms in the media. Specific strains of bacteria may be introduced
into the filter and optimal conditions provided to preferentially degrade specific
compounds. The biofilter provides several advantages over conventional activated carbon
adsorbers. First, bio-regeneration keeps the maximum adsorption capacity available
constantly; thus, the mass transfer zone remains stationary and relatively short. The
filter does not require regeneration, and the required bed length is greatly reduced.
These features reduce capital and operating expenses. Additionally, the contaminants are
destroyed not just separated, as with granulated activated carbon (GAC) technologies.
As with other biological treatment processes, biofiltration is highly
dependent upon the biodegradability of the contaminants. Under proper conditions,
biofilters can remove virtually all selected contaminants to harmless products.
Biofiltration is used primarily to treat nonhalogenated VOCs and fuel hydrocarbons.
Halogenated VOCs also can be treated, but the process may be less effective. Biofilters
have been successfully used to control odors from compost piles.
The following factors may limit the applicability and effectiveness of the
- The rate of influent air flow is constrained by the size of the biofilter.
- Fugitive fungi may be a problem.
- Low temperatures may slow or stop removal unless the biofilter is climate-controlled.
- Compounds that are recalcitrant to biodegratation will not be converted to harmless
A detailed discussion of these data elements is provided in Subsection 2.2.3. (Data Requirements for Air
Nonproprietary filters that require low air loading rates for organics
(100 ppm) have been used successfully for more than 20 years. Proprietary designs that
support higher air loadings also are available. Biofilters have been used extensively in
Europe and Japan, but only recently have they received attention in the United States.
levels, pH, temperature, and other filter conditions may have to be monitored to maintain
high removal efficiencies. Filter flooding and plugging as a result of excessive biomass
accumulation may require periodic mechanical cleaning of the filter.
Cost estimates range from $5 to $10 per kilogram of contaminant ($2.27 to
$4.54 per pound).
USAEC, 1997. "Remediation of Air Streams Contaminated with
Trichloroethylene Using Biofiltration at Anniston Army Depot" in Innovative
Technology Demonstration, Evaluation and Transfer Activities, FY 96 Annual Report, Report
No. SFIM-AEC-ET-CR-97013, pp. 19-20.
Points of Contact:
General FRTR Agency Contacts
Technology Specific Web Sites:
Government Web Sites
Non Government Web Sites
A list of vendors offering Air
Emission/Off-Gas Treatment is available from EPA
REACH IT which combines information from three established EPA databases,
the Vendor Information System for Innovative Treatment Technologies (VISITT),
the Vendor Field Analytical and Characterization Technologies System (Vendor
FACTS), and the Innovative Treatment Technologies (ITT), to give users access to
comprehensive information about treatment and characterization technologies and
Health and Safety: