Biomedical Engineering Reference
In-Depth Information
required, to ensure an optimum internal environment for bacterial action. Though
the efficiency of the biotrickling filter is broadly similar to the previous method,
it can deal with higher concentrations of contaminant and has a significantly
smaller foot-print than a biofilter of the same throughput capacity. However,
as with almost all aspects of environmental biotechnology, these advantages are
obtained by means of additional engineering, the corollary of which is, inevitably,
higher capital and running costs.
Bioscrubbers
Although it is normally included in the same group, the bioscrubber (Figure 4.4) is
not itself truly a biological treatment system, but rather a highly efficient method
of removing odour components by dissolving them. Unsurprisingly, then, it is
most appropriate for hydrophilic compounds like acetone or methanol.
The gas to be treated passes through a fine water spray generated as a mist or
curtain within the body of the bioscrubber vessel. The contaminant is absorbed
into the water, which subsequently pools to form a reservoir at the bottom.
The contaminant solution is then removed to a secondary bioreactor where the
actual process of biodegradation takes place. In practice, activated sludge systems
(which are described in detail in Chapter 6) are often used in this role.
As in the preceding case, process control can be achieved by monitoring the
water phase and adding nutrients, buffers or fresh water as appropriate.
Other options
It is important to be aware that biotechnology is not the only answer to controlling
air pollution. A number of alternative approaches exist, though it is clearly beyond
the scope of this topic to discuss them at length. The following brief outline may
Figure4.4
Bioscrubber
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