5 Bioremediation Approaches for Cadmium Detoxification
from Contaminated Sites
Cadmium can be effectively removed by various physicochemical methods such
as absorption, oxidation/reduction, flocculation, cation/anion exchange, and precipitation. However they have some drawbacks like complexity, uneconomical, and
lack of public acceptance. So efforts are focused on bioremediation process being a
suitable method for removal of cadmium.
5.1 Bioremediation
Bioremediation is biological techniques that completely remove the toxic contaminants from the soil, water, and air by use of microorganisms (bacteria, fungi, algae,
etc.) and green plants (phytoremediation). It is a natural method with wider application in the realm of environment. Mueller et al. (1996) define bioremediation as the
process where organic waste is biologically degraded under controlled condition to
an innocuous state or to level below concentration limits established by regulatory
authorities. Bioremediation can be classified into in situ or ex situ. In situ techniques
involves remediation at the site of contamination while in ex situ contaminants are
removed from the original site and treated elsewhere, it is called as ex situ. Examples
of bioremediation technologies are bioventing, bioleaching, composting,
landfarming, bioreactor, bioaugmentation, biostimulation, and phytoremediation. It
has high public acceptance due to its relatively low-cost and low-technology technique. In the process of bioremediation, microorganism may be indigenous to the
contaminated site or may be isolated from other sources and brought to the contaminated site for heavy metal removal. To make the process effective, microorganism
must enzymatically attack on the pollutants and convert them into harmless products
(Vidali 2001).
Phytoremediation is the use of green plants to remove pollutants from the
environment or to render them harmless (Cunningham and Berti 1993). Mixing
the use of resistant plants and the application of microorganisms with their beneficial
effects to plants and to soil could represent a valid tool for soil remediation (Wenzel
et al. 2003). The main goal of bioremediation is to remove pollutants from the soil
and water and to restore their capacity and functional potential.
5.1.1 Bioremediation of Cadmium Using Bacteria
Microbial bioremediation is an effective approach for removal of heavy metals like
lead, chromium, cadmium, and zinc. Bacteria are small in size and ubiquitous and
grow in wide range of condition, and their ability to grow in controlled condition
makes them suitable candidates for bioremediation process. Use of bacteria for
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S. Saini and G. Dhania
from Contaminated Sites
Cadmium can be effectively removed by various physicochemical methods such
as absorption, oxidation/reduction, flocculation, cation/anion exchange, and precipitation. However they have some drawbacks like complexity, uneconomical, and
lack of public acceptance. So efforts are focused on bioremediation process being a
suitable method for removal of cadmium.
5.1 Bioremediation
Bioremediation is biological techniques that completely remove the toxic contaminants from the soil, water, and air by use of microorganisms (bacteria, fungi, algae,
etc.) and green plants (phytoremediation). It is a natural method with wider application in the realm of environment. Mueller et al. (1996) define bioremediation as the
process where organic waste is biologically degraded under controlled condition to
an innocuous state or to level below concentration limits established by regulatory
authorities. Bioremediation can be classified into in situ or ex situ. In situ techniques
involves remediation at the site of contamination while in ex situ contaminants are
removed from the original site and treated elsewhere, it is called as ex situ. Examples
of bioremediation technologies are bioventing, bioleaching, composting,
landfarming, bioreactor, bioaugmentation, biostimulation, and phytoremediation. It
has high public acceptance due to its relatively low-cost and low-technology technique. In the process of bioremediation, microorganism may be indigenous to the
contaminated site or may be isolated from other sources and brought to the contaminated site for heavy metal removal. To make the process effective, microorganism
must enzymatically attack on the pollutants and convert them into harmless products
(Vidali 2001).
Phytoremediation is the use of green plants to remove pollutants from the
environment or to render them harmless (Cunningham and Berti 1993). Mixing
the use of resistant plants and the application of microorganisms with their beneficial
effects to plants and to soil could represent a valid tool for soil remediation (Wenzel
et al. 2003). The main goal of bioremediation is to remove pollutants from the soil
and water and to restore their capacity and functional potential.
5.1.1 Bioremediation of Cadmium Using Bacteria
Microbial bioremediation is an effective approach for removal of heavy metals like
lead, chromium, cadmium, and zinc. Bacteria are small in size and ubiquitous and
grow in wide range of condition, and their ability to grow in controlled condition
makes them suitable candidates for bioremediation process. Use of bacteria for
370
S. Saini and G. Dhania