Contaminated Land and Bio-Remediation - Environmental Biotechnology: Theory and Application - page 96

or acceptance, but does, never-the-less offer certain advantages over the earlier
approach. Perhaps the most significant of these is that it is a more natural divi-
sion, 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 technologies
have a slower response and a higher treatment time, but their lower costs make
wider application possible, particularly since extensive land remediation treat-
ments do less damage to soil quality. Accordingly, they are well suited to large
scale treatment where speed is not of the essence. Examples include composting,
the promotion of biological activity in situ within the root-zone, precipitation
of metal sulphides under anaerobic conditions and the cropping of heavy metal
accumulator plants.
All these systems of classification are at best generalisations, and each can be
useful at different times, dependent on the purpose of the consideration. They are
merely a convenient way of looking at the available techniques and should not
be regarded as anything more than a helpful guide. As a final aspect of this, it is
possible to examine the various forms of land remediation technologies in terms
of their overall functional principle. Hence, the approaches may be categorised as
'destructive', 'separating' or 'containing', dependent on their fundamental mode
of operation, as Figure 5.2 illustrates. The principal attraction of this systemisation
is that it is defined on the basis of representing the fate of the pollutant, rather
than the geographical location of the work or the level of complexity of the
technology used, as in the previous cases. In addition, it can also be relatively
easily extended to take account of any given technology.
Process Integration
However they are classified, the fact remains that all the individual technolo-
gies available each have their limitations. As a result, one potential means of
enhancing remediation effectiveness which has become increasingly popular is
the use of a combination approach, integrating different processes to provide an
overall treatment. The widespread application of this originated some years ago
in the USA and the related terms used to describe it, 'bundled technologies' or
'treatment trains' have quickly become commonly used elsewhere. The goal of
process integration can be achieved by combining both different fundamental
technologies (e.g. biological and chemical) and sequences of in situ or ex situ ,