100 Environmental Biotechnology
Figure 5.3 Modification of effect by edaphic factors
desk top and practical means, empirical data has been obtained, the resident con-
tamination has been characterised and quantified, its extent determined, relevant
risk factors identified and risk assessment has been performed. The next stage
is the formulation of a remediation action plan, making use of the data obtained
to design a response to the contamination which is appropriate, responsible and
safe. At this point, having obtained the clearest possible overview, technology
selection forms a major part of this process.
When this has been done, and approval has been gained from the relevant statu-
tory, regulatory or licensing bodies, as applicable, the last phase is to implement
the remediation work itself.
Biotechnology Selection
Although the primary focus of remediation methods commonly falls on technolo-
gies dependent on a relatively high engineering component, there is one purely
biological treatment option which can be a very effective means of clean-up.
Known variously as ‘natural attenuation’, ‘passive remediation’, ‘bioattenuation’
or ‘intrinsic remediation’, it is appropriate for sites where the contamination does
not currently represent a clear danger to human health or the environment. Though
it is not an engineered solution, neither is it a ‘do nothing’ approach as is some-
times stated, since it is not an exercise in ignoring the problem, but a reasoned
decision on the basis of the necessary site investigations, to allow nature to take
its course. The approach works with natural cycles and the pre-existing indige-
nous microbial community to bring about the required treatment. The need for a
good initial survey and risk assessment is clear, and typically a comprehensive
monitoring programme is established to keep a check on progress.