Rhizodegradation
In rhizodegradation, which is also referred to as rhizosphere bioremediation, the
breakdown of pollutions occurs within the rhizosphere or plant root zone. It is
carried out using fungi and bacteria (Yadav et al. 2018). Microorganisms are
widespread in the rhizosphere since the plants exude enzymes, amino acids, sugars,
and other compounds, which are effective to stimulate bacterial growth. It has been
observed (Zhang et al. 2010) that the fungal and microbial degradation is stimulated
by releasing of enzymes/exudates in the root zone of plant. The ideal performance
depends on the association between plants and microorganisms in the rhizosphere,
concentration of pollutions, the temperature, pH, texture and nutrition of soil, and
rate of metabolism of microorganism (Yadav et al. 2018).
Permeable Reactive Barrier
The method is often maintained as a physical technique to treat the pollution in
groundwater due to its mechanism and design to remove contaminants
(Thiruvenkatachari et al. 2008); however, it has been reported that one of the
mechanisms of contaminants removal in permeable reactive barrier methods is the
biological reaction, which includes degradation, precipitation, and sorption (ObiriNyarko et al. 2014). Apart from the proposed alternative terms like passive
bioreactive barrier, biological permeable reactive barrier, and bioenhanced permeable reactive barrier to accommodate the biotreatment or biotechnological aspects of
this method, the microorganisms’ role is mainly to enhance rather than an independent biotechnology (Azubuike et al. 2016; Philp and Atlas 2005). Generally, permeable reactive barrier is an in situ technique to treat the polluted groundwater with
heavy metals and chlorinated compounds. Xin et al. (2013) reported biodegradation
with 84.7–97.8% efficiency for ethylbenzene, p-xylene, toluene, and benzene with
bioaugmented (Pseudomonas sp. and Mycobaterium sp.) permeable reactive barrier.
The inherent gradient of contaminated water causes its flow through the barrier, thus
the contaminants are trapped and enter a series of reactions that result in clean water
from the flow (Obiri-Nyarko et al. 2014; Thiruvenkatachari et al. 2008). An ideal
barrier is reactive enough to trap pollutions, allow water to flow, and penetrate but
prevent the penetration of contaminants, passive with little energy input, low cost,
accessible, and available easily (De Pourcq et al. 2015). The efficiency of the method
is related to the kind of media that is affected by the kind of contaminant, health
effect, biogeochemical conditions, cost, mechanical stability, hydrogeological conditions, and environmental effect (Liu et al. 2015). Today, combining permeable
reactive barrier with other methods like electrokinetics to treat the different kinds of
contaminants has attracted great attention (García et al. 2014; Mena et al. 2015).
Mena et al. (2015) and Ramırez et al. (2015) reported 30% diesel removal and 39%
decrease in biodegradable fractions of diesel where biopermeable reactive barrier
was combined with electrokinetics to treat the contaminated soils by diesel after
14 days, respectively. Folch et al. (2013) observed 97% decay of Orange G dye in a
12 Remediation of Pollution by Oil Spills
473
In rhizodegradation, which is also referred to as rhizosphere bioremediation, the
breakdown of pollutions occurs within the rhizosphere or plant root zone. It is
carried out using fungi and bacteria (Yadav et al. 2018). Microorganisms are
widespread in the rhizosphere since the plants exude enzymes, amino acids, sugars,
and other compounds, which are effective to stimulate bacterial growth. It has been
observed (Zhang et al. 2010) that the fungal and microbial degradation is stimulated
by releasing of enzymes/exudates in the root zone of plant. The ideal performance
depends on the association between plants and microorganisms in the rhizosphere,
concentration of pollutions, the temperature, pH, texture and nutrition of soil, and
rate of metabolism of microorganism (Yadav et al. 2018).
Permeable Reactive Barrier
The method is often maintained as a physical technique to treat the pollution in
groundwater due to its mechanism and design to remove contaminants
(Thiruvenkatachari et al. 2008); however, it has been reported that one of the
mechanisms of contaminants removal in permeable reactive barrier methods is the
biological reaction, which includes degradation, precipitation, and sorption (ObiriNyarko et al. 2014). Apart from the proposed alternative terms like passive
bioreactive barrier, biological permeable reactive barrier, and bioenhanced permeable reactive barrier to accommodate the biotreatment or biotechnological aspects of
this method, the microorganisms’ role is mainly to enhance rather than an independent biotechnology (Azubuike et al. 2016; Philp and Atlas 2005). Generally, permeable reactive barrier is an in situ technique to treat the polluted groundwater with
heavy metals and chlorinated compounds. Xin et al. (2013) reported biodegradation
with 84.7–97.8% efficiency for ethylbenzene, p-xylene, toluene, and benzene with
bioaugmented (Pseudomonas sp. and Mycobaterium sp.) permeable reactive barrier.
The inherent gradient of contaminated water causes its flow through the barrier, thus
the contaminants are trapped and enter a series of reactions that result in clean water
from the flow (Obiri-Nyarko et al. 2014; Thiruvenkatachari et al. 2008). An ideal
barrier is reactive enough to trap pollutions, allow water to flow, and penetrate but
prevent the penetration of contaminants, passive with little energy input, low cost,
accessible, and available easily (De Pourcq et al. 2015). The efficiency of the method
is related to the kind of media that is affected by the kind of contaminant, health
effect, biogeochemical conditions, cost, mechanical stability, hydrogeological conditions, and environmental effect (Liu et al. 2015). Today, combining permeable
reactive barrier with other methods like electrokinetics to treat the different kinds of
contaminants has attracted great attention (García et al. 2014; Mena et al. 2015).
Mena et al. (2015) and Ramırez et al. (2015) reported 30% diesel removal and 39%
decrease in biodegradable fractions of diesel where biopermeable reactive barrier
was combined with electrokinetics to treat the contaminated soils by diesel after
14 days, respectively. Folch et al. (2013) observed 97% decay of Orange G dye in a
12 Remediation of Pollution by Oil Spills
473