لخّصلي

Heavy metals play an important role in the metabolic processes of the biota, some of them are essential for organisms as micronutrients such as cobalt, chromium, nickel, iron, manganese and zinc.They are involved in redox processes, to stabilize molecules through electrostatic interactions, as catalysts in enzymatic reactions, and regulating the osmotic balance.Physicochemical methods have been used, such as electrochemical treatment, ion exchange, precipitation, reverse osmosis, evaporation, and sorption (Congeevarama et al., 2007).Thus, bioremediation affords a substitute to destroy or reduce the harmful contaminants through biological activity and this method is cost effective (Salem et al., 2012).However, at high levels, both of the essential and non essential metals become toxic to the organisms (Rathnayake et al., 2010).In addition, these metals cannot be degraded to harmless products and hence persist in the environment indefinitely.

Heavy metals play an important role in the
metabolic processes of the biota, some of them are
essential for organisms as micronutrients such as
cobalt, chromium, nickel, iron, manganese and zinc.
They are involved in redox processes, to stabilize
molecules through electrostatic interactions, as
catalysts in enzymatic reactions, and regulating the
osmotic balance. On the other hand, cadmium,
mercury, lead, has no biological role and are
harmful to the organisms even at very low
concentration. However, at high levels, both of the
essential and non essential metals become toxic to
the organisms (Rathnayake et al., 2010). Heavy
metals can produce harmful effects on human
health when they are taken up in amounts that
cannot be processed by the organism. In addition,
these metals cannot be degraded to harmless
products and hence persist in the environment
indefinitely. For these reasons several methods have

been designed for the treatment and removal of
heavy metals in contaminated site (Akhtar et al.,
2013). Physicochemical methods have been used,
such as electrochemical treatment, ion exchange,
precipitation, reverse osmosis, evaporation, and
sorption (Congeevarama et al., 2007).
Bioremediation is a natural process which
depends on bacteria, fungi, and plants to change
pollutants as these organisms carry out their normal
life functions. These organisms have the ability of
using chemical contaminants as an energy source for
their metabolic processes. Thus, bioremediation
affords a substitute to destroy or reduce the harmful
contaminants through biological activity and this
method is cost effective (Salem et al., 2012).