contaminants, or pollutant’s adsorption on geologic media. The process is highly
contaminant specific such as for treatment of fuel compounds but not general for
many groups of pollutants (Smets and Pritchard 2003). Bio-stimulation is the process
of bioremediation in which the microorganisms are provided with essential nutrients
(nitrogen, carbon, phosphorous, and potassium) and optimum conditions such as pH
and availability of oxygen to enhance their growth and metabolism (Carberry and
Wik 2001). Bio-augmentation is the process in which bacterial cultures are added for
increasing the biodegradation rate of pollutants (Lamberts et al. 2008). This process
is based on the concept of “soil activation” (by Otte et al. 1994) in which the
biomass/microorganisms are cultivated from a contaminated soil to be used as
inoculum for the treatment of the same contaminated soil.
8.6.1.2 Ex Situ Bioremediation
The commonly used ex situ bioremediation methods include composting, slurry
phase treatment, bioreactors, etc. In composting the organic wastes or contaminated
soil is excavated, layered in composting pad, and biologically degraded at higher
temperatures ranging from 55 to 65
o . To increase the biodegradation the bulking
agents such as wood chips, manure, or vegetable waste are added. Heat production
during the degradation process leads to the contaminant solubility and increase in the
metabolism of organisms in compost. Presence of high substrate levels in compost
can result in the co-metabolism of organic pollutants (Niti et al. 2013). In bioreactors
the polluted soil/organic waste is agitated with nutrients and water in a mechanically
operated bioreactor to enhance the microbial activity of microbes. The bioreactors of
varying configuration can be used such as fermenters, bioslurry reactors, and
prepared bed reactors. The biodegradation extent and rate are generally higher
compared to in situ bioremediation, as these reactors are more manageable and
controllable (Sharma 2012). In slurry-phase treatment the slurry of organic waste,
soil sediments with water, and other bulking additives is prepared. The slurry is
agitated in an engineered confined system to keep solids in suspension and to ensure
the contact of microorganisms with pollutants (Sharma 2012).
8.6.1.3 Removal of Persistent Organic Pollutants
Several studies have reported the potential of removing the persistent organic
pollutants from contaminated soils, sediments, and wastewater. Matsumoto et al.
(2008, 2009) reviewed and reported the removal of endrin and dieldrin through
bioremediation and phytoremediation from soil. Cao et al. (2013) reported the
effective degradation of organochlorine (HCH) and organophosphate (parathion)
pesticides from soil by using genetically modified Sphingobium japonicum UT 26.
The detoxification and biodegradation of endosulfan an organochlorine pesticide by
Alcaligenes faecalis strain JBW4 was reported by Kong et al. (2013, 2014). The
Stain JBW4 effectively degraded about 87.5% and 83.9% of α-endosulfan and
β-endosulfan, respectively. In another study by Odukkathil and Vasudevan (2016)
soil contaminated with endosulfans was bioaugmented with a bacterial consortium
(Bordetella petrii I GV 34, B. petrii II GV 36 and Achromobacter xyloxidans GV 47)
in a glass reactor. Complete removal of α- and β-endosulfan was observed within
8 Persistent Organic Pollutants (POPs): Sources, Types, Impacts, and Their. . .
225
contaminant specific such as for treatment of fuel compounds but not general for
many groups of pollutants (Smets and Pritchard 2003). Bio-stimulation is the process
of bioremediation in which the microorganisms are provided with essential nutrients
(nitrogen, carbon, phosphorous, and potassium) and optimum conditions such as pH
and availability of oxygen to enhance their growth and metabolism (Carberry and
Wik 2001). Bio-augmentation is the process in which bacterial cultures are added for
increasing the biodegradation rate of pollutants (Lamberts et al. 2008). This process
is based on the concept of “soil activation” (by Otte et al. 1994) in which the
biomass/microorganisms are cultivated from a contaminated soil to be used as
inoculum for the treatment of the same contaminated soil.
8.6.1.2 Ex Situ Bioremediation
The commonly used ex situ bioremediation methods include composting, slurry
phase treatment, bioreactors, etc. In composting the organic wastes or contaminated
soil is excavated, layered in composting pad, and biologically degraded at higher
temperatures ranging from 55 to 65
o . To increase the biodegradation the bulking
agents such as wood chips, manure, or vegetable waste are added. Heat production
during the degradation process leads to the contaminant solubility and increase in the
metabolism of organisms in compost. Presence of high substrate levels in compost
can result in the co-metabolism of organic pollutants (Niti et al. 2013). In bioreactors
the polluted soil/organic waste is agitated with nutrients and water in a mechanically
operated bioreactor to enhance the microbial activity of microbes. The bioreactors of
varying configuration can be used such as fermenters, bioslurry reactors, and
prepared bed reactors. The biodegradation extent and rate are generally higher
compared to in situ bioremediation, as these reactors are more manageable and
controllable (Sharma 2012). In slurry-phase treatment the slurry of organic waste,
soil sediments with water, and other bulking additives is prepared. The slurry is
agitated in an engineered confined system to keep solids in suspension and to ensure
the contact of microorganisms with pollutants (Sharma 2012).
8.6.1.3 Removal of Persistent Organic Pollutants
Several studies have reported the potential of removing the persistent organic
pollutants from contaminated soils, sediments, and wastewater. Matsumoto et al.
(2008, 2009) reviewed and reported the removal of endrin and dieldrin through
bioremediation and phytoremediation from soil. Cao et al. (2013) reported the
effective degradation of organochlorine (HCH) and organophosphate (parathion)
pesticides from soil by using genetically modified Sphingobium japonicum UT 26.
The detoxification and biodegradation of endosulfan an organochlorine pesticide by
Alcaligenes faecalis strain JBW4 was reported by Kong et al. (2013, 2014). The
Stain JBW4 effectively degraded about 87.5% and 83.9% of α-endosulfan and
β-endosulfan, respectively. In another study by Odukkathil and Vasudevan (2016)
soil contaminated with endosulfans was bioaugmented with a bacterial consortium
(Bordetella petrii I GV 34, B. petrii II GV 36 and Achromobacter xyloxidans GV 47)
in a glass reactor. Complete removal of α- and β-endosulfan was observed within
8 Persistent Organic Pollutants (POPs): Sources, Types, Impacts, and Their. . .
225