Contaminated Land and Bioremediation 91compromise a company’s ability to channel sufficient funds to deal with others.
The goal of treating land is to make it suitable for a particular purpose or so
that it no longer poses unacceptable risk and, once the relevant aim has been
achieved, further treatment is typically not a good use of these resources. Gen-
erally it would be judged better to devote them to cleaning up other sites, which
maximises the potential reuse of former industrial land thereby protecting urban
open spaces and the countryside from development pressure. In the long term,
the sustainable use of land largely depends on making sure that it is maintained
at a level which enables its continued best use for its current or intended pur-
pose. In this respect, discussions of absolute quality become less relevant than a
consideration of minimum acceptable standards.
The choice of method and the determination of the final remediation standard
will always be chiefly governed by site-specific factors including intended use,
local conditions and sensitivities, potential risk and available timeframe. For this
reason, it is appropriate to take a brief overview of the available technologies at
this point, to set the backdrop for the discussions of the specifically biotechno-
logical methods to come.
Remediation Methods
The currently available processes for soil remediation can be divided into five
generalised categories:
- biological;
- chemical;
- physical;
- solidification/vitrification;
- thermal.
Biological
Biological methods involve the transformation or mineralisation of contaminants
to less toxic, more mobile, or more toxic but less mobile, forms. This can include
fixation or accumulation in harvestable biomass crops, though this approach is
discussed more fully later in Chapter 7.
The main advantages of these methods are their ability to destroy a wide range
of organic compounds, their potential benefit to soil structure and fertility and
their generally nontoxic, ‘green’ image. On the other hand, the process end-point
can be uncertain and difficult to gauge, the treatment itself may be slow and not
all contaminants are conducive to treatment by biological means.
Chemical
Toxic compounds are destroyed, fixed or neutralised by chemical reaction. The
principal advantages are that under this approach, the destruction of biologically