biofiltration uses for voc removal , its advantage and disadvantage and a case study of biofiltration scope for air pollution control.

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