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).

1. BIOFILTRATION IN AIR
POLLUTION CONTROL
Guided By Dr. Anil Sharma
Maulana Azad National Institute of
Technology,Bhopal
Presented By
Yogesh Krishna Tiwari
Scholar id : 202111306

2. INTRODUCTION
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).

3. WHY BIOFILTRATION IS IMPORTANT
● Bio filtration is a recent air pollution control (APC) technology in which
off-gases containing biodegradable volatile organic compounds (VOC) or
inorganic air toxics are vented through a biologically active material.
● Normally, bioreactors do not require full-time labor and the only
operating supplies needed are small quantities of macronutrients.
● Bioreactors only use small amount of electrical power to drive two or
three small motors.

4. TYPES OF BIOFILTERS
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 biofilters :
● Required large area.
● Relatively inexpensive.
● Easy maintenance.
Vertical biofilters :
● Use less surface area compared to Horizontal.
● Expensive.
● Not easy to Maintain.

5. Vertical Biofilter
Open-bed Biofilter

6. THEORY OF BIOFILTER OPERATION
● The gas passes upward through perforated pipes and the biofilter media
bed.
● 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.
● The media of the filter functions as a supplement to the gas stream being
treated for organic nutrients.
● The absorbed gases are oxidized by the microorganisms to CO2 .
The process of Bio Degradation is—
● Organic Pollutant + O2 CO2+ H2O + Heat + Biomass

7. Phenomena involved in the operation of biofilters

8. Process Description of Biofiltration
● 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 medium 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.
● In the biofiltration process, contaminated air is moistened by a humidifier
and is pumped into the biofilter through a chamber below the filter medium
passes out of the top of the biofilter and into the atmosphere.

9. Schematic Diagram Of A Biofilter Unit
Adsorption
Absorption
Microbial degradation
Most biofilters that are in operation today can treat odor and VOCs,overall
efficiencies greater that 90%. However, the drawback to this technology is
that it can only handle low concentrations of pollutants (<1000 ppm) and
loading rates between 90-100 m3/m2-hr.

10. Air Bio filter

11. Components Of A Bio-filter Unit
MATERIALS used for bed media –
Peat, composted yard waste, bark, coarse soil, gravel or plastic shapes
Oyster Shells
for neutralizing acid build-up
Fertilizer
for macronutrients(are mixed with bed media)
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.

12. 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 oxygen present in dissolved form in
the media.
PH –
For better results must maintain a pH where the microorganism are the most
efficient.

13. 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.

14. Major considerations when determining the appropriate
filter material include:
● Ability to retain moisture to sustain biofilm layer.
● Large surface area, both for contaminant
absorption and microbial growth;
● Ability to retain nutrients and supply them to microbes as required;
● Low resistance to air flow (minimizes pressure drop and blower power
requirements);
● Physical characteristics, such as physical stability and ease of handling

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

16. Typical Biofilter Operating Conditions for Waste Air
Treatment
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
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)

17. A Few Existing Bio Filters
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.

18. 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.

19. References
● Biofilters in Mitigation of Odour Pollution - A Review ISSN: 0972-6268 Vol. 15 No. 4 pp. 1177-1185
2016
● Head, I. M., Singleton, I., and Milner, M. (2003). Bioremediation: A critical review horizon scientific
press Norfolk.
● Devinny, J. S. ;Deshusses, M. A.,& Webster, T. S.Biofiltration for air pollution control. Lewis
publishers London.
● Sincero, A. P. and Sincero, G. A. Environmental engineering.:PHI learning Private Limited. N. Delhi.
● Evans, G. M. and Furlong, J. C. Environmental Biotechnology.: Wiley & Sons.
● Brown, C. A. ,Karl, B. Air pollution control technology handbook.
● www.globalspec.com/../air biofilter.
● www.gnest.org/journal/vol 11_no2/218.
● www.ambio.ca/operation.php

20. THANK YOU