is a cheaper technique and has obtained popularity especially to restore the sites
contaminated by light spilled products (Höhener and Ponsin 2014).
Biosparging
In this method, air is injected with pressure below the water table in order to increase
the concentration of oxygen in groundwater and enhance the rate of biotreatment
using natural microorganisms. Biosparging increases the contact between soil and
groundwater as a result of increasing the mixing in the saturated zone. The advantage
of this method is that the installation of the small-diameter air injection points is easy
with low cost and therefore the design and construction of the system is flexible.
Phytoremediation
In this method, plants are used to remove pollutants from water and soil via physical,
biological, chemical, biochemical, and microbiological interactions. Depending on
the contaminant, the types of phytoremediation include rhizofiltration,
phytoextraction, phytovolatilization,
phytodegradation,
phytostabilization,
rhizodegradation, and hydraulic control (Mahajan and Kaushal 2018; Yadav et al.
2018; Muthusaravanan et al. 2018). The factors to select a plant as a phytoremediator
are: the required time to obtain the desired level of cleanliness of root system,
toxicity of contaminant for plant, rate of plant growth, site monitoring, resistance
of plant against disease and pests (Lee 2013). Based on the study of Miguel et al.
(2013), the treatment by plants involves the uptake, displacement from roots to
shoots accomplished by xylem flow, and accumulation in shoot (Azubuike et al.
2016). Moreover, accumulation and replacement are dependent on partitioning and
transpiration between neighbor tissues and xylem sap, respectively. However, the
process can be different based on the nature of pollution and type of plant. Most
plants that grow in the contaminated site perform phytoremediation very well. Thus,
the efficiency of phytoremediation method depends on the optimization of treatment
by indigenous plants that grow in contaminated site by biostimulation or
bioaugmentation using exogenous or endogenous plant rhizobacteria (Azubuike
et al. 2016). Also, plant growth-promoting rhizobacteria is a factor that might play
an important role in phytoremediation. It increases the biomass production and the
ability of plants to tolerate the undesirable soil situations (Yancheshmeh et al. 2011;
De-Bashan et al. 2012). Based on the study of Grobelak et al. (2015), the plant root
growth, plant height, and plant stem growth increased when Festuca ovinia L. and
Brassica napus L. subsp. napus were inoculated with exogenous plant growthpromoting rhizobacteria through germination of seeds, 14 days after plant growth,
therefore protect the plants and seeds inhibition in heavy metal contaminated soil.
Mesa et al. (2015) investigated phytoremediation of polluted site by metal with
Spartina maritime in a similar way. They concluded that bioaugmentation with
endogenous rhizobacteria increased metal accumulation and enhanced metal
12 Remediation of Pollution by Oil Spills
469
contaminated by light spilled products (Höhener and Ponsin 2014).
Biosparging
In this method, air is injected with pressure below the water table in order to increase
the concentration of oxygen in groundwater and enhance the rate of biotreatment
using natural microorganisms. Biosparging increases the contact between soil and
groundwater as a result of increasing the mixing in the saturated zone. The advantage
of this method is that the installation of the small-diameter air injection points is easy
with low cost and therefore the design and construction of the system is flexible.
Phytoremediation
In this method, plants are used to remove pollutants from water and soil via physical,
biological, chemical, biochemical, and microbiological interactions. Depending on
the contaminant, the types of phytoremediation include rhizofiltration,
phytoextraction, phytovolatilization,
phytodegradation,
phytostabilization,
rhizodegradation, and hydraulic control (Mahajan and Kaushal 2018; Yadav et al.
2018; Muthusaravanan et al. 2018). The factors to select a plant as a phytoremediator
are: the required time to obtain the desired level of cleanliness of root system,
toxicity of contaminant for plant, rate of plant growth, site monitoring, resistance
of plant against disease and pests (Lee 2013). Based on the study of Miguel et al.
(2013), the treatment by plants involves the uptake, displacement from roots to
shoots accomplished by xylem flow, and accumulation in shoot (Azubuike et al.
2016). Moreover, accumulation and replacement are dependent on partitioning and
transpiration between neighbor tissues and xylem sap, respectively. However, the
process can be different based on the nature of pollution and type of plant. Most
plants that grow in the contaminated site perform phytoremediation very well. Thus,
the efficiency of phytoremediation method depends on the optimization of treatment
by indigenous plants that grow in contaminated site by biostimulation or
bioaugmentation using exogenous or endogenous plant rhizobacteria (Azubuike
et al. 2016). Also, plant growth-promoting rhizobacteria is a factor that might play
an important role in phytoremediation. It increases the biomass production and the
ability of plants to tolerate the undesirable soil situations (Yancheshmeh et al. 2011;
De-Bashan et al. 2012). Based on the study of Grobelak et al. (2015), the plant root
growth, plant height, and plant stem growth increased when Festuca ovinia L. and
Brassica napus L. subsp. napus were inoculated with exogenous plant growthpromoting rhizobacteria through germination of seeds, 14 days after plant growth,
therefore protect the plants and seeds inhibition in heavy metal contaminated soil.
Mesa et al. (2015) investigated phytoremediation of polluted site by metal with
Spartina maritime in a similar way. They concluded that bioaugmentation with
endogenous rhizobacteria increased metal accumulation and enhanced metal
12 Remediation of Pollution by Oil Spills
469