Contaminated Land and Bioremediation 109Figure 5.9 Schematic soil slurry bioreactor system
Process selection and integration
However, when complex mixtures of compounds are required to be treated,
combining a series of different individual process stages within a series of
interlinked bioreactors, may often be a more appropriate and effective response.
Dependent on the specific type of contaminants, this may necessitate a sequence
of both aerobic and anaerobic procedures, or even one which combines biologi-
cal and chemical steps to achieve the optimum remediation system. Under such
circumstances, clearly each bioreactor features conditions designed to optimise
specific biological processes and degrade particular contaminants.
It should be clear from the preceding discussions that the actual process of
bioremediation employed will depend on a number of factors, amongst others
relating to the site itself, the local area, economic instruments, reasons for reme-
diation and the benefits and limitations of the actual technologies. Hence, it
should not be difficult to see that for any given contamination event, there may
be more than one possible individual approach and, indeed, as described earlier,
the potential will often exist for using integrated combinations of technologies to
maximise the effectiveness of the overall response. In this way, though dependent
on many external variables, a mix and match assemblage of techniques may rep-
resent the individual best practicable environmental option (BEPO). The merging
of anex situtreatment, like, for example, soil washing via a slurry reactor, to
offer an intensive and immediate lessening of pollution effect, with a slowerin
situprocess to polish the site to a final level, has much to recommend it, both
environmentally and commercially. Accordingly, it seems reasonable to conclude
that the prevalence and relative importance of such approaches will be likely to
grow over the coming years.