358
N. Pradhan et al.
strips within a surface water body and pollutant sources. Many researchers (Rosal
et al. 2010; Kim et al. 2005) have reported that removal through biological means
happened through vegetated drainage system and multiple biochemical processes.
Bacteria, fungi, and other extracellular enzyme producers through their biofilm and
other physiological/morphological changes form polymeric cohesive stable matrices
surrounding the particulate/granular form of activated carbon. These can be served
as a biologically active matrix for C-filtration. Biodegradation and adsorption of dissolved contaminants occur on the surface of C-active medium. Physical adsorption
onto the cellular matrices, biodegradation, and bacterial regeneration is the effective
biologically mediated source filtration processes which are employed to harness the
potential of nature biotechnology in the area of contaminant bioremediation.
15.2.3 Sustainable Natural Attenuation Techniques
Natural attenuation can be defined as a natural process which involves several contaminant removal techniques through sorption, dilution, dispersion, and volatilization, different physico-chemical stabilization techniques which happen in streams,
sediments, and water of environmental compartments. Different chemical, physical,
and biochemical processes help in the immobilization of different natural contaminants. The processes are summarized as below and are shown in Fig. 15.3, where
phytovolatilization/stabilization, bioleaching, biomethylationrhizodegradation, and
or abiotic/biotic dissipation processes build up the foundation stone for noxious metal
removal.
a) A strong co-ordination with Fe/Mn oxides and hydroxides may lead to the
precipitation and transformation metal (loids).
b) Oxidation and hydrolysis of minerals can lead to the formation of insoluble
carbonates, oxides, and sulfides of stable complexes.
c) Bacterial reduction can lead to non-mobile forms of metals through changes in
different physico-chemical factors which are particularly true for some metals
like Cr, U, Se, Cu, Pb, Fe, Cd, etc (Kumari et al. 2018a, b; Kumar et al. 2017).
d) Organic matter plays a big role in metal sequestration/chelation properties by
converting them to metallic/non-metallic forms.
e) Plant uptake and biological filtration of suspended solids can lead to conversion of toxic elements into non-toxic forms. Sometimes, aerobic/anaerobic biogenic decontamination processes (such as biomethylation, phytostimulation, and
rhizodegradation) which are facilitated through involvement of plant root exudates, plant metabolic enzymes, and several microbial metabolic processes lead
to attenuation of pollutants in constructed wetlands and aquatic ecosystems,
where translocations and bio augmentation play a big role along with above fundamental processes. Many researchers (Lasat 2002; McGrath and Zhao 2003)
have studied and critically analyzed the usefulness of phytostimulation and phytoextraction for rare earth elements decontamination study (such as U, La, Gd,
N. Pradhan et al.
strips within a surface water body and pollutant sources. Many researchers (Rosal
et al. 2010; Kim et al. 2005) have reported that removal through biological means
happened through vegetated drainage system and multiple biochemical processes.
Bacteria, fungi, and other extracellular enzyme producers through their biofilm and
other physiological/morphological changes form polymeric cohesive stable matrices
surrounding the particulate/granular form of activated carbon. These can be served
as a biologically active matrix for C-filtration. Biodegradation and adsorption of dissolved contaminants occur on the surface of C-active medium. Physical adsorption
onto the cellular matrices, biodegradation, and bacterial regeneration is the effective
biologically mediated source filtration processes which are employed to harness the
potential of nature biotechnology in the area of contaminant bioremediation.
15.2.3 Sustainable Natural Attenuation Techniques
Natural attenuation can be defined as a natural process which involves several contaminant removal techniques through sorption, dilution, dispersion, and volatilization, different physico-chemical stabilization techniques which happen in streams,
sediments, and water of environmental compartments. Different chemical, physical,
and biochemical processes help in the immobilization of different natural contaminants. The processes are summarized as below and are shown in Fig. 15.3, where
phytovolatilization/stabilization, bioleaching, biomethylationrhizodegradation, and
or abiotic/biotic dissipation processes build up the foundation stone for noxious metal
removal.
a) A strong co-ordination with Fe/Mn oxides and hydroxides may lead to the
precipitation and transformation metal (loids).
b) Oxidation and hydrolysis of minerals can lead to the formation of insoluble
carbonates, oxides, and sulfides of stable complexes.
c) Bacterial reduction can lead to non-mobile forms of metals through changes in
different physico-chemical factors which are particularly true for some metals
like Cr, U, Se, Cu, Pb, Fe, Cd, etc (Kumari et al. 2018a, b; Kumar et al. 2017).
d) Organic matter plays a big role in metal sequestration/chelation properties by
converting them to metallic/non-metallic forms.
e) Plant uptake and biological filtration of suspended solids can lead to conversion of toxic elements into non-toxic forms. Sometimes, aerobic/anaerobic biogenic decontamination processes (such as biomethylation, phytostimulation, and
rhizodegradation) which are facilitated through involvement of plant root exudates, plant metabolic enzymes, and several microbial metabolic processes lead
to attenuation of pollutants in constructed wetlands and aquatic ecosystems,
where translocations and bio augmentation play a big role along with above fundamental processes. Many researchers (Lasat 2002; McGrath and Zhao 2003)
have studied and critically analyzed the usefulness of phytostimulation and phytoextraction for rare earth elements decontamination study (such as U, La, Gd,