Biological air-pollution control technology has been used extensively. The factors that restricted the use of bio -oxidation are:
-the relatively large size of the units
-the weight of these biofilters precluded their placement on a building roof
-the compliance assurance monitoring
(CAM) regulations of the 1990 Clean Air Act
Amendments require verification of control equipment
performance on a continuous basis
The changing landscape
Bio oxidation facilitators in the form of biofilters, biotrickling filters and bioscrubbers have been made available. In a biofilter microorganisms are attached to a substrate
and a non-bioactive humidification system maintains
the proper moisture level.A bioscrubber is a water-scrubbing device with a suspended
microbial component through which water
recirculates. Bioscrubbers may be designed to use the
effluent (non-chlorinated) from an extended-aeration or activated-sludge type wastewater treatment plant. In a biotrickling filter, microbes
are attached to natural or artificial substrates,
and water for humidification and the stream to be
treated flow over the substrates and are recirculated.
The bed of biomass must be neither too dry nor too
wet (flooded).the biomass
will die if dry and the biomass may wash out or be drowned if wet.
Temperature controls the metabolism of the microbes.a warm (approximately 25â€œ35Ã‚Â°C) biooxidation unit will generally support more organisms,
both in terms of the number of organisms and the number
of species, at higher activities (metabolic rates).
can function at pHs ranging from as low as 2â€œ3 to as
high as 8 or 9. careful attention
must be paid to the pH of the system since the chlorinated and sulfur-containing compounds
produce acids upon biological degradation.
for more details, refer the pdf links given in the previous reply in this thread