Biofilters and air pollution controll by aabid mir
BIOFILTERS: AND CONTROLL
OF AIR POLLUTION.
Aabid Bashir Mir.
M.Sc. 4th sem.
Roll No. 8258.
Department of Environmental Science.
University of Kashmir.
Parameters to be maintained.
Involves passing a
contaminated air stream
through a media bed
that is porous and moist.
As the air passes
through the media, the
adsorbed into the water
within the media.
Bacteria that are present
within the media
80-95% odor reduction of air
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.
Schematics of a Biofilter
Air with H2S
Classification of bioreactors for waste gas
Reactor type Microorganisms Water phase
Biofilter Fixed Stationary
Biotrickling filter Fixed Flowing
Bioscrubber Suspended Flowing
Gas contaminants are
absorbed in a free liquid
phase prior to biodegradation
Operate with the air and
water phase moving either
counter-currently or co-
currently, depending on
Offer greater performance
than biofilters at higher
The degradation of
contaminants is performed
by a suspended consortium
of microbes in separate
Absorption achieved in
packed column, spray
Water transferred to
separate vessel , where
Biofilter Designs Description Feature velocity
First Piles and Pits Compost mixed with wood chips Erratic Performance 3-4 cfm/ft2
Second Enclosed Vessels Similar media as used in "Piles and Improved Performance, 10 cfm/ft2
Generation Pits" but included enclosures around Difficult Expansion and
all sides of the biofilter. Better Maintenance
irrigation and better flow into media
Third Modular Systems Moved from organic medias to Easy 25 cfm/ft2
Generation inorganic medias. Since media is no Installation and Expansion,
longer water soluable, longer media life Easy Media Replacement,
and more aggressive irrigation systems Less Footprint
used, improved mass transfer
A biofilter can be:
open or enclosed.
built directly into the ground or in a reactor
single or multiple bed.
Peat, Compost, Mulch, Wood Chips, etc.
Low Initial Cost .
Prone to Settling, Erratic Performance
Specific Composition and Preparation Process
Higher Initial Cost .
Superior Physical Characteristics .
Superior, Consistent Performance
The useful life of the media is typically up to 5 years.
Fluffing, or turning, of the media material in the biofilter
may be required at shorter intervals to prevent excessive
compaction and settling.
source: Devinny J.S. et al. (1999) “Biofiltration for air pollution control”, Lewis Publishers.
Summary of Important properties
of Common Biofilter Materials
Assimilable nutrient content
Pollutant sorption capacity
perlite, and other
may be expensive
None to H
Parameters that need to be maintained
Moisture Content –
Microorganisms operate best between 30 degrees C and 40 degrees.
Oxygen Level -
Most of degradations are aerobic.
Oxygen is not used directly in the gas form but the microorganisms use the oxygen
present in dissolved form in the media.
For better results must maintain a pH where the microorganisms
are the most efficient.
For aerobic microorganisms, the O/N/P ratio is estimated as 100/5/1.
These are typically nitrogen, phosphorous, and some trace metals.
Microorganisms need a moist environment.
Media has a tendency to dry out because of the air flow.
Optimum 20 -60%.
Pretreatment of Gas Streams
• Besides humidification, heating, or cooling,
other pretreatment necessary may include
• Though the biofilter is capable of removing
particulates, the solid matter can cause
clogging of the biofilter and gas distribution
• Fungi, Bacteria, and Actinomycetes.
• Start up of a biofilter process requires some acclimation time
for the microorganisms to grow specific to the compounds in
the gaseous stream.
• For easily degradable substances, this acclimation period is
typically around 10 days.
• The biomass has been shown to be able to be viable for shut
downs of approximately 2 weeks.
If inorganic nutrient and oxygen supplies are continued, the
biomass may be maintained for up to 2 months.
Movement of the contaminants from the air to the
water phase occurs according to the physical laws.
The contaminants in the gas are either adsorbed onto
the solid particles of the media or absorbed into the
water layer that exists on the media particles.
Concentration of contaminants decreases from inlet to
outlet as they partionised between various phases.
Wastes partition out between soil and gas, so
that the VOC remain in soil longer than in air.
Soil – gas partition coefficients indicate the
relative strength of retention.
The coefficients increase with VOC molecular
weight and the no. of oxygen, nitrogen and
sulphur functional groups in the VOC molecules.
In dry soils the coefficients for VOC is 1 for
methane to 10,000 for octane.
• Diffusion occurs through the water layer to the
microorganisms in the slime layer on the surface
of the media particles.
• Through biotransformation of the food source,
end products are formed, including carbon
dioxide, water, nitrogen, mineral salts, and energy.
• Biotransformation act along with adsorption,
absorption, and diffusion to remove
contaminants from the gaseous stream.
Biotransformation and transport processes in biofilters
• The media of the filter functions both to supply
inorganic nutrients and as a supplement to the
gas stream being treated for organic nutrients.
• The sorbed gases are oxidized by the
microorganisms to CO2.
• The volatile inorganics are also sorbed and
oxidized to form calcium salts.
• Half-lives of contaminants range from minutes to
months. Aliphatics degrade faster than aromatics.
• Adsorption sites are continually becoming
available as oxidation by microorganisms occur.
• Overloading of the biofilters results when
adsorption is occurring faster than oxidation..
• The oxidation of organic matter
• The difference between the
amount being degraded and
the amount represented by
carbon dioxide release from
the biofilter gives an indication
of how much carbon is being
incorporated in biomass
(Medina et al., 1995).
Pollutants: BTEX, NH3, Trirmethylamine, Ethanol,
Organic acids, etc.
Emission sources: Various industrial systems
Microorganisms: Pseudomonas, Bacillus, etc.
Abundant water and oxygen.
Temperature: 15-40 ºC, pH: 6-8.
Metabolic product: CO2 , H2O, Biomass
Low pH Biofilters for Sulfide Oxidation
Pollutants: H2S .
Emission sources: various industrial systems,
wastewater collection and treatment facilities .
Microorganisms: Thiobacillus thiooxidans,
pH: 1-3, Temp.: 15-40 ºC.
Abundant water and oxygen.
Metabolic product: H2SO4
Biofilter의 종류Low-Water-Content Biofilters
Pollutants: VOCs, Odorous materials.
Microorganisms: Filamentous fungi
Degradation of pollutants at low water .
Applications: Bench biofilters for treatment of
Tounlene, Ethylbenzene, o-Xylene
Thermophilic Microorganisms: 45-60 ºC.
Higher degradation rate
More economical treatment processes.
Fast decomposition of degradable support media
Reduction of the solubility of pollutants.
Deshusses et al. (1997): 100 g- ethyl acetate/m3•h,
van Groenestijn et al. (1995):
Hot gases containing ethanol, 50-70 ºC
Nitric oxide Nitrite Nitrate
Denitrifying bacteria: NO N2.
Aerobic / Anaerobic Processes.
Apel et al. (1995): Anaerobic removal of nitrogen
oxides from combustion gases using denitrifying
bacteria (NO N2 in thick biofilm ).
Biosaint (1999): Removal of ammonia using
Nitrobacter:95-98% removal at 50-1000 ppm
Biofilters using cometabolism Biofilter의 종류
Growth substrate (CH4, toluene, phenol, etc.)
Microorganism: no energy or other benefits from
degrading co substrate fortuitously degrade
unrelated compounds (similar shape to the active site
of the enzyme)
Typical Biofilter Operating Conditions
for Waste Air Treatment
Biofilter layer height
Waste air flow
Biofilter surface loading
Biofilter volumetric loading
Bed void volume
Mean effective gas residence time
pressure drop per meter of bed height
Inlet pollutant and/or odor concentration
Inlet air relative humidity
Water content of the support material
pH of the support material
Typical removal efficiencies
0.2-1.0 cm water gauge (max. 10cm)
60% by mass
Source: Deshusses, M.A., biodegration of mixtures of ketone vapours in biofilters for the
treatment of waste air, Swiss Federal institute of technology, Zurich, 1994.
Company Location application
S. C. Johnson and Son, Inc. Racine, Wis. Propane and butane
removal from room air.
Monsanto chemical Co. Springfield, Mass. Ethanol and butyraldehyde
removal from dry air. 99%
Dow chemical Co. Midland, Mich. Chemical process gas.
Hoechst Celanese corp. Coventry, R.I. Process gas.
Sandoz. Basel, Switzerland. Chemical process gas.
Esso of Canada. Sarnia, Ontario. Hydrocarbon vapors from
Mobil chemical co. Canandaigua, N. Y. Pentane form polystyrene
foam molding (proposed)
Uphohn CO. Kalamazoo, Mich. Pharmaceutical production
odors: 60000 cfm
Source: H. Bohn, 1992, Consider biofiltration for decominating gases, Chem. Eng. Prog. (April)
Investment costs vs. air flow rate for various
air pollution control technologies
Operating costs vs. air flow rate for various
air pollution control technologies
Full-Scale Biofilters in Parallel
Surface Area = 2,556 ft2 each
Comparison of Biofiltration Technology
Low Operating Cost
Does not require chemicals
Effective removal of compounds
Break-through can occur if air flow or concentration is not
Does not remove ammonia or amines
Relatively large footprint required
Requires continuous air flow
Requires consistent loading
Requires a humid and warm air stream
Often requires an acclimation period for the media
Microbial degradation of substances with intense odors.
Substrate Microbe Degradation product
Methanol Pseudomonas Water, carbon dioxide
Dimethylamines P. aminovorans Methylamine and
Phenol P. putida Acetaldehyde and puyrate.
Benaldehyde Acetobacter ascendens Benzyl alcohol and benzoic
Aniline Nocardia spp. And
Indole Chromobacterium violaceum Pyrocatechol
Camphor P. putida Lactonic acid
• Biofiltration plays very important role in control of air
• Biofilter, like all systems follows laws of conservation &
• Biofilter is successful only when microbial ecosystem is
healthy & vigorous
• The design of biofilter system requires a detailed
understanding of site,conditions,site limitations, system
components & costs
• Monitoring of BF is very important
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