Biofiltration is actually, clearing bacteria or the contaminants present in the air. The fact that the bacteria or the contaminants can be “bio-degraded” by using active bacteria was known to the scientist for a longer time, but it is the last ten years when this process is being used as for treating various contaminates in the industries.
Mechanism of a bio-filter:
There are many transport mechanisms that work simultaneously in a bio-filter. The mechanisms of these filters are:
1. Diffusion of the bacteria or the contaminants to the “active bio-film surface” to the “bulk gas flow”
2. Absorbing the bacteria directly on the bio-film surface.
3. Dissolving the bacteria in the water of the bio-films
4. The bacteria get directly absorbed by the surface of the support media
5. Biodegradation and diffusion of the bacteria in the “active bio-film.”
6. Surface biodegradation of the bacteria in the media surface.
7. Back degradation of the absorbed bacteria in the “active bio-films” from the media surface.
Few advantages of various support media:
Bio-filter media on soil:
• Technology, well established
• Suitable for odor control
• Low cost
Bio-filters on pest:
• It is a commercial technology
• Suitable for odor control
• Low costing
Synthetic support media:
• Can be cleaned easily
• One of the fast “start-up” of biofilters.
• Can handle contamination of high level.
• Cost much lower than the “activated carbon-coated media.”
• The pH level can be controlled easily
• With the help of tickling liquid, both the micro and the macro nutrients can be supplied
• Very high “degradation capacity.”
Few effects of Bio-filters:-
1. There was no height limitation for biofilters, and hence one could have designed it as a tower, with a proper diameter. The problem of “support media drying” that used to arise in “compost bio-filters” was not applicable to the bio-tickling features because the “aqueous nutrient steam” used to trickle down the “synthetic media.”
2. For compost, the media never needs replacement, since an external head is supplying the minerals. For compost, once the phosphorus and the nitrogen present in the “compost” get exhausted, it needs to be replaced. After this, the compost becomes itself contaminated and needs to be treated like a solid waste.
3. The compost becomes dense, despite adding wooden chips for support. The growth of microorganisms because of diffusion also makes the compost much heavier and settles down. The settling down increases the “gas-phase pressure drop”. But for the bio-trickling filters, settling is not an issue. However, the major problem of these filters is that the plugging of “the media” because of the growth in the biomass results in “increased gas-phase pressure”.
Bio-filtration will act as a major component in the treatment of inorganic and organic emissions from the various industries. When the bio-filtration was compared with other technologies, it proved to be more cost effective and technical. The compost biofilters are the best one for the treatments of odor contamination. A significant advantage of the bio-trickling filters over the compost bio-filters is that they are skillful of handling “higher contaminant concentrations”.