2.7 Integrated Remediation Technologies
Plant microbial–associated bioremediation has been used for agricultural soil remediation. Synergistic interactions between plants and microbial population in the
rhizosphere are effective for the degradation of recalcitrant organochlorines (OCs)
(Vergani et al. 2017). Root exudates (amino acids, flavonones, sugars, enzymes,
phenolic compounds, and other organic substances) could increase the bioavailability of OCs and microbial activities in the immediate vicinity of the roots (Javorska
et al. 2009). Microbial strains capable of breaking down OCs were widespread in the
rhizosphere soils (Chaudhry et al. 2005). Root exudates were found to increase the
degradation of PAHs with increasing ring numbers (Sun et al. 2010).
2.7.1 Surfactant-Enhanced Bioremediation
Bioremediation alone has not been able to quickly remove persistent and highly
toxic pollutants from farm soil in general (Huang et al. 2017). The use of bioremediation is a secondary step after chemical remediation and was found more effective
in PAH removal than the single approach (Kulik et al. 2006). Surfactant-enhanced
bioremediation (SEBR) is a hopeful technology to improve the bioavailability and
removal efficiency of OCs in agricultural soil (Chirakkara et al. 2016; Wang et al.
2016b). Surfactant increased the partition of OCs to microbial cells and also facilitated the transmembrane transportation of OCs into the cells and thus accelerated
intracellular biodegradation (Zhang and Zhu 2012; Li and Zhu 2014; Li et al. 2014).
Different surfactants exerted various effects on the biodegradation of PAHs through
different approaches, such as disrupting bacterial membranes and modifying cell
surface hydrophobicity (Zhang et al. 2013; Ni et al. 2014). Recently, the ringhydroxylating dioxygenase (RHDase) and 1-hydroxyl-2-naphthoate dioxygenase
genes (1H2Nase) were found to be induced in the presence of surfactants, which
played a key role in the decomposition of hydrophobic aromatic compounds
(Li et al. 2015). Surfactants were also found to enhance the degradation of DDT
by microorganisms in agricultural soil (Wang et al. 2016c). Therefore, surfactantenhanced bioremediation could be a promising technology for addressing combined
organic pollution in agricultural soil.
2.7.2 Enhanced Phytodegradation by Plant Growth
Promoting Bacteria
The rhizosphere has a population of microorganisms that can degrade xenobiotic
substances (Donnelly et al. 1994; Macková et al. 2007; Mendez and Maier 2008;
Sindhu and Sharma 2020). Kuiper et al. (2001) reported that inoculation of effective
46
A. Sehrawat et al.
Plant microbial–associated bioremediation has been used for agricultural soil remediation. Synergistic interactions between plants and microbial population in the
rhizosphere are effective for the degradation of recalcitrant organochlorines (OCs)
(Vergani et al. 2017). Root exudates (amino acids, flavonones, sugars, enzymes,
phenolic compounds, and other organic substances) could increase the bioavailability of OCs and microbial activities in the immediate vicinity of the roots (Javorska
et al. 2009). Microbial strains capable of breaking down OCs were widespread in the
rhizosphere soils (Chaudhry et al. 2005). Root exudates were found to increase the
degradation of PAHs with increasing ring numbers (Sun et al. 2010).
2.7.1 Surfactant-Enhanced Bioremediation
Bioremediation alone has not been able to quickly remove persistent and highly
toxic pollutants from farm soil in general (Huang et al. 2017). The use of bioremediation is a secondary step after chemical remediation and was found more effective
in PAH removal than the single approach (Kulik et al. 2006). Surfactant-enhanced
bioremediation (SEBR) is a hopeful technology to improve the bioavailability and
removal efficiency of OCs in agricultural soil (Chirakkara et al. 2016; Wang et al.
2016b). Surfactant increased the partition of OCs to microbial cells and also facilitated the transmembrane transportation of OCs into the cells and thus accelerated
intracellular biodegradation (Zhang and Zhu 2012; Li and Zhu 2014; Li et al. 2014).
Different surfactants exerted various effects on the biodegradation of PAHs through
different approaches, such as disrupting bacterial membranes and modifying cell
surface hydrophobicity (Zhang et al. 2013; Ni et al. 2014). Recently, the ringhydroxylating dioxygenase (RHDase) and 1-hydroxyl-2-naphthoate dioxygenase
genes (1H2Nase) were found to be induced in the presence of surfactants, which
played a key role in the decomposition of hydrophobic aromatic compounds
(Li et al. 2015). Surfactants were also found to enhance the degradation of DDT
by microorganisms in agricultural soil (Wang et al. 2016c). Therefore, surfactantenhanced bioremediation could be a promising technology for addressing combined
organic pollution in agricultural soil.
2.7.2 Enhanced Phytodegradation by Plant Growth
Promoting Bacteria
The rhizosphere has a population of microorganisms that can degrade xenobiotic
substances (Donnelly et al. 1994; Macková et al. 2007; Mendez and Maier 2008;
Sindhu and Sharma 2020). Kuiper et al. (2001) reported that inoculation of effective
46
A. Sehrawat et al.