Biological treatments are known also as “bioremediation”, i.e. “utilization of living organisms to reduce or eliminate environmental contaminants” (Adriano et al., 1999). Biological treatments include one or more of the following processes:
a) degradation: contaminant biochemical degradation by soil microorganisms (bacteria, fungi, actinomycetes);
b) transformation: contaminant biochemical conversion to make it less toxic and /or less mobile;
c) accumulation: organic and inorganic contaminants may accumulate in tissues of living organisms (particularly plants);
d) mobilization: a contaminant-bearing solution may be separated form the contaminated soil.
Microorganisms are potentially able to detoxify several contaminated sites, and to bring them back to the original state. Higher plants are utilized to stabilize or remove contaminants (especially heavy metals) from soil and waters. This technology, known as phytoremediation, is potentially little destructive, environmental friendly and cost-effective, and is applicable to large contaminated land.