The purpose of this study was to develop a bioremediation
method that could be used for soils heavily contaminated with
persistent organic compounds, such as high molecular weight
PAHs. Bioremediation offers a sustainable alternative to other
treatment methods, such as thermal treatment and bitumen stabilization
(Khan et al., 2004). Bioremediation requires much less
energy than thermal treatment. Furthermore, raw material for
bitumen stabilization is derived from petroleum and the solution
cannot be considered as final because the contaminants are not
degraded but only bound to the matrix. The Regulation No 850/
2004 given by the European Community (2004) declares: “The
persistent organic pollutant content in waste is to be destroyed or
irreversibly transformed into substances that do not exhibit similar
characteristics, unless other operations are environmentally preferable.”
Therefore, treatment methods which actually destroy the
contaminants should always be the first choice.
For a bioremediation process to be successful the microorganisms,
or their enzymes, need to be in physical contact with
the organic contaminant. Both properties of the soil and the type of
the contaminant determine bioavailability and bioaccessibility
(Harms, 2011). Bioavailability represents the fraction that is uptaken
by the cells, and can cause toxic effects, or can be biodegraded
by intracellular mechanisms. The term bioaccessibility,
often also called environmental availability, considers the fraction
that is potentially available for biota in soils. From the risk assessment
point of view this phenomenon is more important than the
total concentration, because toxic effects can be attributed to a
contaminant only when it is accessible (Cvancarová et al., 2013).
This is also true for biodegradation phenomena that include the