ABSTRACT
Toxic metals present in groundwater or soil present unique challenges in terms of environmental remediation. The principal aim in the biological treatment of toxic organic chemicals is generally detoxification of the toxic species by complete oxidation to volatile carbon dioxide. The biocolloid formation is distinguished from the processes of sorption or chelation in that colloid formation occurs as a result of microbial transformation of the metal ion. The relevant features for transformation of a metal ion to the base metal state by bacteria include thermodynamic considerations and certain metabolic processes. Characteristic of biological colloids is the negative charge that is usually present on the particle surface and forms the electric double layer surrounding the colloid particle. The reduction of selenite and selenate by bacteria results in the formation of red colloidal elemental selenium. The biocolloid system may be appropriate for a variety of situations; however, the greatest potential is in remediation of groundwaters and flowing surface waters.
