Biofiltration is an air pollution control technique that uses microorganisms to degrade contaminants in a moist environment, effectively targeting malodorous gases and volatile organic compounds. The document outlines the history, components, types, and operational mechanisms of biofilters, emphasizing the need for optimal conditions such as moisture, temperature, and nutrient supply for microbial effectiveness. Case studies highlight successful applications of biofilters in various industries, demonstrating their significance in controlling air pollution.

1. BIOFILTRATION FOR CONTROL OF
AIR POLLUTION
Given by-Ashish kumar yadav
M.Tech 1st year
Roll No. 3140912
Department of Civil Engineering
NIT Kurukhshetra

2. Biofiltration
 Biofiltration is an air pollution control technique
which Involves bio degradation of contaminants
under the action of microorganisms diffused in a
thin layer of moisture known as “BIOFILM”, mainly
used for elimination of malodorous gas emissions
and low concentrations of Volatile Organic
Compounds (VOCs).
 The process of Bio Degradation is—
Organic Pollutant + O2 CO2+ H2O + Heat +
Biomass

3. History of Biofilters
The following is a brief timeline of the development of biofilters:
 1923 -- Biological methods were proposed to treat odorous emissions.
 1955 -- Biological methods were applied to treat odorous emissions in low
concentrations in Germany.
 1960’s -- Biofiltration was used for the treatment of gaseous pollutants both in
Germany and US.
 1970’s -- Biofiltration is used with high success in Germany.
 1980’s -- Biofiltration is used for the treatment of toxic emissions and volatile
organic compounds (VOCs) from industry.
 1990’s -- Today, there are more than 500 biofilters operating both in
Germany and Netherlands and it is widely spreading in US.

4. Components Of A Bio-filter Unit
 MATERIALS used for bed media – peat,
composted yard waste, bark, coarse soil, gravel
or plastic shapes.
 SUPPORT RACK -perforated – allow air from the
plenum to move into the bed media -to contact
microbes that live in the bed. Perforations also permit
excess, condensed moisture to drain out of the bed
to the plenum.
 FAN - Used to collect contaminated air, As the
emissions flow through the bed media, the pollutants
are absorbed by moisture on the bed media .
Microbes reduce pollutant concentrations by
consuming and metabolizing pollutants.

5. Schematic Diagram Of A
Biofilter Unit

6. Differentiation Between Bio
Filtration , Chemical oxidation &
Thermal Processes

7. Types Of Bio Filters
ON THE BASIS OF LAYOUT
 Open Bed : Uncovered and Exposed to all Weather conditions.
 Closed Bed : Enclosed with a small exhaust port for venting of cleaned air
ON THE BASIS OF SHAPE
 Horizontal :
1. With Larger footprints
2. Relatively inexpensive
3. Easy maintenance
 Vertical :
1. Designed to reduce the footprint required.
2. Use less surface area compared to Horizontal
3. Expensive
4. Not easy to Maintain
ON THE BASIS OF SUPPORT MEDIA
 Compost Bio Filter : Soil , Peat, Compost material is used
 Synthetic Bio Filter : Ceramic , Plastic .

8. Vertical
biofilter
Open-bed
biofilter

9. Biofiltration media
 The media used in biofilters can
include peat, heather, bark,
composted sewage sludge,
granular carbon or other
suitable materials
 The useful life of media is
typically 5 years.

10. Parameters that need to be
maintained
 Moisture Content –
Microorganisms need a moist environment.
Media has a tendency to dry out because of the air flow.
Optimum 20 -60%.
 Temperature – Microorganisms operate best between
30 °C and 40°C.
 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.
 pH –For better results must maintain a pH where the
microorganism are the most efficient.
 Nutrient Supply: For aerobic microorganisms, the O:N:P
ratio is estimated as 100:5:1.These are typically nitrogen,
phosphorous, and some trace metals.

11. Microorganisms
 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.

12. Mechanism
 Movement of the contaminants from the air to the
water phase occurs.
 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 partitioned between various
phases.
 Wastes partition out between soil and gas, so that
the VOC remain in soil longer than in air.

13. Process Diagram of a Biofilter

14. Phenomena involved in the operation of biofilters

15. Mechanism cont..
 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.

16. Biotransformation and transport
processes in biofilters

17. Mechanism cont..
 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.
 The oxidation of organic matter generates heat.

18. Typical Biofilter Operating
Conditions for Waste Air Treatment
Parameter
 Biofilter layer height
 Biofilter area
 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
 Operating temperature
 Inlet air relative humidity
 Water content of the support
material
 pH of the support material
 Typical removal efficiencies
Typical value
 1-1.5 m
 1-3000m2
 50-300,000m3h-1
 5-500m3m-2 h-1
 5-500m3m-2 h-1
 50%
 15-60 s
 0.2-1.0 cm water gauge (max.
10cm)
 0.01-5gm-3, 500-50,000OUm-3
 15-30 °C
 >98%
 60% by mass
 pH 6-8
 60-100%

19. Comparison of Biofiltration Technology
 „Benefits:
1. Low Operating Cost
2. Does not require chemicals
3. Effective removal of compounds
 Drawbacks:
1. Break-through can occur if air flow or concentration is not
consistent
2. Large area required to treat contaminated source
3. Requires large acclimation time for microbial population.
 „Requirements:
1. Requires continuous air flow
2. Requires consistent loading
3. Requires a humid and warm air stream

20. Case Study
This case study of PPC Industry ,Texas which conducted Biofiltration as
a VOC Control for Serigraph Inc.(a screen printer and sheet fed offset
printer located in West Bend, Wisconsin, about 30 miles northwest of
Milwaukee , US).

21. A Few Existing Bio Filters
 McMinnville, Oregon: The installation in McMinnville, Oregon perhaps
best demonstrates the capabilities as the levels of odorous compounds
to be treated were among the highest ever reported from the
wastewater treatment environment.
 Long Sault, Ontario: Although a small (1500 cfm), indoor, container-
type system, this installation demonstrates several key aspects that are
relevant to any installation.
 Sarnia, Ontario: This biofilter was installed in 2001 and treats 12,500 cfm
of air coming from a sludge liming and drying operation.
 Brookfield, P.E.I. : This biofilter was installed in 2002, at a composting
plant in P.E.I., that treats 60,000 cfm of air from the composting process.
 Toronto, Ontario: This biofilter was installed in 2002 in the north end of
Toronto at the Toronto Mixed Waste Recycling and Organics Processing
Facility.

22. CONCLUSION
 Biofiltration plays very important role in control
of air pollution
 Biofilter, like all systems follows laws of
conservation & mass balance
 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