98 Environmental Biotechnology
Table 5.1 Potential for bioremediation of selected contaminants
Readily possible Possible under certain
circumstances
Currently impossibleAcids Chlorinated solvents Asbestos
Alcohols Cyanides Asphalt
Aldehydes and ketones Explosives Bitumen
Ammonia PCBs Inorganic acids
Creosote PAHs
Chlorophenols Pesticides, herbicides
Crude oil and petroleum and fungicides
hydrocarbons Tars
Glycols Timber treatments
Phenols
Surfactants
accessible or less so. The net result produced in either case can, under the right
conditions, be a very effective functional remediation. A list of typical contam-
inants suitable for bioremediation would include the likes of crude oil and its
derivatives, some varieties of fungicides and herbicides, hydrocarbons, glycols,
phenols, surfactants and even explosives.
Developments in bioprocessing continually redefine the definitive catalogue of
what may, and may not, be treated and many chemicals once thought ‘impossible’
are now routinely dealt with biologically. Table 5.1 reflects the current state of
the art, though this is clearly subject to change as new approaches are refined.
As a result, it should be obvious that a large number of opportunities exist
for which the application of remediating biotechnologies could have potential
relevance. Even so, there are a number of factors which affect their use, which will
be considered before moving on to discuss practical treatment issues themselves.
Factors Affecting the use of Bioremediation
It is possible to divide these into two broad groups; those which relate to the
character of the contamination itself and those which depend on environmental
conditions. The former encompass both the chemical nature of the pollutants
and the physical state in which they are found in a given incident. Thus, in
order for a given substance to be open to bioremediation, clearly it must be both
susceptible to, and readily available for, biological decomposition. Generally it
must also be dissolved, or at the very least, in contact with soil water and typ-
ically of a low–medium toxicity range. The principal environmental factors of
significance are temperature, pH and soil type. As was stated previously, biore-
mediation tends to rely on the natural abilities of indigenous soil organisms and
so treatment can occur between 0–50◦C, since these temperatures will be tol-
erated. However, for greatest efficiency, the ideal range is around 20–30◦C, as