2017). This is an unrestrained microbial technology in which soils removed are
mixed with soil amendments and placed on a treatment area, and bioremediation
using forced aeration is carried out. The basic biopile system includes a treatment bed, an aeration system, an irrigation/nutrient system, and a leachate
collection system. Factors such as moisture, heat, nutrients, oxygen and pH
are controlled to enhance the rate of biodegradation (Shukla et al. 2010; Niti
et al. 2013). Soil piles can be up to 20 feet high and can be covered with plastic
to control the runoff, evaporation, and volatilization. Cost of maintenance and
operation and the lack of power supply especially at remote which would enable
uniform distribution of air in contaminated piled soil via air pump are some of
the setbacks of biopiles (Azubuike et al. 2016).
(c) Land Farming: In this process, uncovered polluted soils are dispersed to form a
thin layer on the surface of the ground. The metabolic activity of the indigenous
microflora is stimulated via providing proper aeration, nutrients and moisture for
the remediation of contaminants present in soil (Agwu and Kalu 2012; Niti et al.
2013). It is among one of the easiest bioremediation techniques because of its
low-cost and less equipment requirement, which can be adopted owing to
sufficient land availability (Das and Adholeya 2012; Azubuike et al. 2016).
Due to the site of treatment, it is mostly considered as ex situ bioremediation,
whereas in some cases, it is regarded as an in situ bioremediation technique
(Azubuike et al. 2016). To enhance degradation, increased oxygen supply as
well as mixing is done by ploughing, harrowing or milling at regular intervals
(Das and Adholeya 2012). The area is also tilled to enhance aeration as well as to
ensure that degradation and immobilization of contaminants within the upper
and underlying soil layers occur (Whiteley and Lee 2006). Land farming is best
suited for pesticide-contaminated soils, because of full-scale bioremediation
technology in which the size and location of the spreading operation are decided
based upon the application rate of pesticides to avoid concentrations that would
be unsafe in soil, groundwater or crops (Niti et al. 2013).
(d) Biocell Treatment: This technique resembles farming of land except, the method
in which the polluted soil has placed the form of a pile with alternative vent
layers to enhance the air provision which is needed for the growth of bacteria
(Agwu and Kalu 2012).
(e) Composting: It is a method in which a mixture of contaminated soil and organic
materials is left into a pile of bed-type treatment with the microorganism to act
on the highly contaminated sites, mostly used against hydrocarbon contaminants
(Whiteley and Lee 2006; Agwu and Kalu 2012). This is a specific method
involving a succession of mesophilic and thermophilic microorganisms and
mixing with an organic bulking agent, such as straw or wood chips. The pile
is aerated by forced aeration or pile turning. On the other hand, factors such as
moisture content, pH and nutrient content are controlled (Whiteley and Lee
2006). The temperature is increased due to heat during the process of
composting of organic compounds by microorganisms, and it may range from
55
C to 65
C. (Shukla et al. 2010; Das and Adholeya 2012; Niti et al. 2013).
428
G. Kaur et al.
mixed with soil amendments and placed on a treatment area, and bioremediation
using forced aeration is carried out. The basic biopile system includes a treatment bed, an aeration system, an irrigation/nutrient system, and a leachate
collection system. Factors such as moisture, heat, nutrients, oxygen and pH
are controlled to enhance the rate of biodegradation (Shukla et al. 2010; Niti
et al. 2013). Soil piles can be up to 20 feet high and can be covered with plastic
to control the runoff, evaporation, and volatilization. Cost of maintenance and
operation and the lack of power supply especially at remote which would enable
uniform distribution of air in contaminated piled soil via air pump are some of
the setbacks of biopiles (Azubuike et al. 2016).
(c) Land Farming: In this process, uncovered polluted soils are dispersed to form a
thin layer on the surface of the ground. The metabolic activity of the indigenous
microflora is stimulated via providing proper aeration, nutrients and moisture for
the remediation of contaminants present in soil (Agwu and Kalu 2012; Niti et al.
2013). It is among one of the easiest bioremediation techniques because of its
low-cost and less equipment requirement, which can be adopted owing to
sufficient land availability (Das and Adholeya 2012; Azubuike et al. 2016).
Due to the site of treatment, it is mostly considered as ex situ bioremediation,
whereas in some cases, it is regarded as an in situ bioremediation technique
(Azubuike et al. 2016). To enhance degradation, increased oxygen supply as
well as mixing is done by ploughing, harrowing or milling at regular intervals
(Das and Adholeya 2012). The area is also tilled to enhance aeration as well as to
ensure that degradation and immobilization of contaminants within the upper
and underlying soil layers occur (Whiteley and Lee 2006). Land farming is best
suited for pesticide-contaminated soils, because of full-scale bioremediation
technology in which the size and location of the spreading operation are decided
based upon the application rate of pesticides to avoid concentrations that would
be unsafe in soil, groundwater or crops (Niti et al. 2013).
(d) Biocell Treatment: This technique resembles farming of land except, the method
in which the polluted soil has placed the form of a pile with alternative vent
layers to enhance the air provision which is needed for the growth of bacteria
(Agwu and Kalu 2012).
(e) Composting: It is a method in which a mixture of contaminated soil and organic
materials is left into a pile of bed-type treatment with the microorganism to act
on the highly contaminated sites, mostly used against hydrocarbon contaminants
(Whiteley and Lee 2006; Agwu and Kalu 2012). This is a specific method
involving a succession of mesophilic and thermophilic microorganisms and
mixing with an organic bulking agent, such as straw or wood chips. The pile
is aerated by forced aeration or pile turning. On the other hand, factors such as
moisture content, pH and nutrient content are controlled (Whiteley and Lee
2006). The temperature is increased due to heat during the process of
composting of organic compounds by microorganisms, and it may range from
55
C to 65
C. (Shukla et al. 2010; Das and Adholeya 2012; Niti et al. 2013).
428
G. Kaur et al.