Biofiltration is the most cost effective, operationally simple technology
with high waste-removal efficiencies; used to purify contaminated air evolved
from volatile organic and inorganic compounds by using microorganisms.
This technique has been industrially successful in Europe and Japan. It is gradually becoming popular. They were first built in U.S.A during 1960's.
The process is carried out in biofilters.These are packed with soil or compost covered by an active bio film, through which gas is blown. Microorganisms make use of the gaseous pollutants that are present in the gas blown and use these pollutants as a source of carbon and energy. This is a very beneficial technique as it does not need large amounts of energy for operation.
This technique has been industrially successful in Europe and Japan. It is gradually becoming popular. They were first built in U.S.A during 1960's.
The process is carried out in biofilters.These are packed with soil or compost covered by an active bio film, through which gas is blown. Microorganisms make use of the gaseous pollutants that are present in the gas blown and use these pollutants as a source of carbon and energy. This is a very beneficial technique as it does not need large amounts of energy for operation.
Microorganisms Used In The Process
Microorganisms that are present in biofilters
are mainly aerobic ones(microorganisms that require oxygen for their growth).
Most common organisms are Bacteria such as coryneforms and endospore formers,
sometimes Protozoa, Invertebrates and few Actinomycetes are also used. most
commonly used fungi are
Alternaria, Aspergillus, Fusarium etc. Microorganisms are the crucial component because they degrade the gaseous pollutants. In specific cases genetically engineered microorganisms are also used.
Alternaria, Aspergillus, Fusarium etc. Microorganisms are the crucial component because they degrade the gaseous pollutants. In specific cases genetically engineered microorganisms are also used.
Biofilter Media
The packing material or the media used should
have some characters which influence the efficient working of Bio-filters.
1. The filter media should allow the
microorganisms to interact with oxygen and water.
2. The media should have fine pores, large surface area and a uniform pore size.A large surface area provides adsorption and support for microbial growth.
3. Should have the capacity to retain moisture to sustain bio film
layer and retain capacity of nutrient supply to microbes that form the bio film.
The most commonly used packing materials are metal oxides, glass or ceramic beads.Polyvinyl chloride is the most efficient packing material.
Natural Bio-filter media include compost, peat, soil, wood chips etc.
2. The media should have fine pores, large surface area and a uniform pore size.A large surface area provides adsorption and support for microbial growth.
3. Should have the capacity to retain moisture to sustain bio film
layer and retain capacity of nutrient supply to microbes that form the bio film.
The most commonly used packing materials are metal oxides, glass or ceramic beads.Polyvinyl chloride is the most efficient packing material.
Natural Bio-filter media include compost, peat, soil, wood chips etc.
Mechanism Involved
Mechanism
involved is a multistage process.First the contaminants are converted into
liquid phase and then transported to the bacterial cell in the bio-film across
the cell membrane of the organism, where the compound is degraded and used in
cell metabolism to produce carbon and energy. After bio degradation the
contaminants are exhausted from the biofilter.The treatment process depends on
two mechanisms:
1. Directly adsorbing to biofilm and degradation.
2. Conversion into aqueous phase and degradation.
1. Directly adsorbing to biofilm and degradation.
2. Conversion into aqueous phase and degradation.
Attachment Of Microorganisms To The Media
The
attachment of microorganisms to the media consists of two processes:
1. self-attachment of cells to the media by the secretion of glycocalyx or by covalent, hydrophobic and electrostatic interactions.
2. Immobilization ( artificial attachment)by carrier-binding method, cross-linking method, entrapment etc.
But the main disadvantage of the technique is that, it is not suitable for halogenated compounds.
Other drawbacks are:
1. very low aerobic degradation.
2. Size of bio degradation is inversely proportional to the degradation rate.
Despite of disadvantages, the process can be used to remove foul smelling compounds from waste water treatment plants or animal farming. This can be achieved by digging trenches, laying an air distribution system and refilling the trenches with soil, wood chips and compost.
1. self-attachment of cells to the media by the secretion of glycocalyx or by covalent, hydrophobic and electrostatic interactions.
2. Immobilization ( artificial attachment)by carrier-binding method, cross-linking method, entrapment etc.
But the main disadvantage of the technique is that, it is not suitable for halogenated compounds.
Other drawbacks are:
1. very low aerobic degradation.
2. Size of bio degradation is inversely proportional to the degradation rate.
Despite of disadvantages, the process can be used to remove foul smelling compounds from waste water treatment plants or animal farming. This can be achieved by digging trenches, laying an air distribution system and refilling the trenches with soil, wood chips and compost.
Plants As Biofilters
Plants can be used as
Bio-filters to make the ponds habitable for fish. Plants such as Sphagnum,
Water lettuce and American shower weed. When the plants are grown in nutrient
deprived conditions and transferred to ponds, they take up nutrients,
specifically nitrates present in pond water.
This is a very old biotechnological process and research has to be done to determine the extent to which biofilters are efficient in removing the pollutants and much information has to be gathered regarding design, construction and implementing this technique.
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