94 Environmental Biotechnology
Figure 5.1 Factors affecting technology suitability
option. However, the middle ground between them comprises many more shades
of grey, and the ultimate resolution in these cases is, again, largely dependent on
individual circumstance.
Intensive and Extensive Technologies
Though thein situ/ex situclassification has established historic precedence, of
recent times an alternative approach to categorise remediation activities has
emerged, which has not yet achieved the same widespread recognition or accep-
tance, but does, nevertheless offer certain advantages over the earlier approach.
Perhaps the most significant of these is that it is a more natural division, based
on genuine similarities between technologies in each class. Thus the descriptions
‘intensive’ and ‘extensive’ have been suggested.
Intensive technologies can be characterised as sophisticated, fast-acting, high
intervention strategies, with a heavy demand for resources and high initiation,
running and support costs. Their key factors are a fast response and low treatment
time, which makes them excellent for heavy contamination conditions, since they
can make an immediate lessening in pollutant impact. Soil washing and thermal
treatments are good examples of ‘intensive’ approaches.
Extensive methods are lower-level interventions, typically slower acting, based
on simpler technology and less sophisticated engineering, with a smaller resource
requirement and lower initiation, running and support costs. These technolo-
gies have a slower response and a higher treatment time, but their lower costs
make wider application possible, particularly since extensive land remediation
treatments do less damage to soil quality. Accordingly, they are well suited
to large-scale treatment where speed is not of the essence. Examples include