very expensive and may also have several other disadvantages, such
as unpredictable levels of metal ion removal, high reagent requirements,
and the generation of toxic sludge, which requires extreme
caution in disposal because of the risk of secondary environmental
pollution. These disadvantages are more pronounced when the
metal concentrations being removed are low. Moreover, conventional
remediation technologies require that treatments for removal
of contaminants take place at a separate treatment facility (ex-situ
technologies). As a result, for better protection of human health it
remains important to develop new techniques for reduction of
heavy metal concentrations to acceptable environmental levels, but
at more manageable costs.