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Chapter 7
Nano-bioremediation: An Innovative
Remediation Technology for Treatment
and Management of Contaminated Sites
Ritu Singh, Monalisha Behera, and Sanjeev Kumar
Abstract As every method has its own benefits and setbacks, the integration of
remediation methods could be thought of as a solution to tackle remediation prob-
lems. Integrated approaches could overcome the disadvantages of individual tech-
nologies and provide a better alternative to conventional remediation methods.
Nano-bioremediation is one of such kind of methods which received a lot of
attention in the past few years. It aims at reducing the contaminant concentrations
to risk-based levels, alleviating the additional environmental impacts simulta-
neously. This method brings the benefits of both nanotechnology and bioremediation
together to achieve a remediation that is more efficient, less time taking, and
environment friendly than the individual processes. The present chapter provides a
brief account of nanotechnology and variety of nanostructured materials reported for
removing organic and inorganic contaminants from environmental matrices
followed by detailed description of nano-bioremediation technique, its process,
and applications.
Keywords Environmental contamination · Nano-bioremediation · Nanoparticles ·
Pollutants removal · Environmental safety
1 Introduction
The increasing rate of industrialization, urbanization, and modernization has
brought down unsustainable pollution load on the environment. The toxic pollut-
ants are increasing at alarming levels in the environment which are deteriorating
the quality of environment, disturbing the ecosystem, and adversely impacting the
human health. As per the Outlook on the Global Agenda 2015 report, the problem
of rising pollution in developing countries is the sixth most significant global trend,
R. Singh (*) · M. Behera
Department of Environmental Science, Central University of Rajasthan, Ajmer, Rajasthan, India
S. Kumar
Centre for Environmental Sciences, Central University of Jharkhand, Ranchi, Jharkhand, India
©Springer Nature Singapore Pte Ltd. 2020
R. N. Bharagava, G. Saxena (eds.), Bioremediation of Industrial Waste for
Environmental Safety,https://doi.org/10.1007/978-981-13-3426-9_7
165
and in Asia, it is third (World Economic Forum). In response to this, several in situ
and ex situ technologies were proposed by different groups of researchers for
taking up large-scale clean-up of contaminated sites. However, certain limiting
factors such as high operational and maintenance cost, high energy requirements,
destructive methodologies, time constraints, etc. restrict their widespread applica-
tion (Zelmanov and Semiat 2008).
In the past few decades, nanotechnology application has occupied various
sectors of our life such as medicine, textiles, pharmaceutics, electronics, optics,
cosmetics, sports, and many more. The area of environmental remediation also has
not been left untouched by nanotechnology. It is evident from the research ongoing
and number of articles published in this field that nanotechnology could take up
remediation tasks and challenges efficiently (Tratnyek and Johnson 2006;Mueller
and Nowack 2010; Singh and Misra 2014;2016; Patil et al. 2016). Recently, the
concept of sustainable remediation has acquired a great importance, as it essen-
tially aims at reducing the contaminant concentrations to risk-based levels and
alleviating the additional environmental impacts. Recent development made in this
arena has incorporated multiple technologies together in single system so that a
complete solution could be provided that can decontaminate the site economically
in a time efficient manner as well as improve the quality of the site through
restoration. Among restoration methods, bioremediation is one which could com-
bat contamination issues in an economic and environment-friendly way. Bioreme-
diation essentially uses the microorganisms to remediate the pollutants present in
water and soil matrices (Saxena et al. 2019; Bharagava et al. 2017a,b;Gautam
et al. 2017; Saxena et al. 2016; Chandra et al. 2015; Saxena and Bharagava 2017;
Saxena and Bharagava 2015;Perelo2010;Mosaetal.2016).Accordingtothe
EPA, bioremediation is a “treatment that uses naturally occurring organisms to
break down hazardous substances into less toxic or non toxic substances.”It has
several advantages over physicochemical methods such as high selectivity, spec-
ificity, cost and energy efficiency, minimal requirement, etc. However, bioreme-
diation has its limitation too, that is, it takes a long period of time for carrying out
degradation of a toxic compound, typically several months to over a year. More-
over, its application becomes restricted in cases of sites severely contaminated with
highly toxic and hazardous pollutants (Azubuike et al. 2016).
As every method has its own benefits and setbacks, the integration of remediation
methods could be thought of as a solution to tackle remediation problems. Nano-
bioremediation is one of such kind of methods which received a lot of attention in the
past few years. Nano-bioremediation exploits the benefits of nanotechnology
together with advantages of bioremediation. The present chapter provides a brief
account of nanotechnology and variety of nanostructured materials reported for
removing organic and inorganic contaminants from environmental matrices
followed by detailed description of nano-bioremediation technique, its application
processes, and methods.
166 R. Singh et al.
2 Nanotechnology
Applications of nanoparticles can be seen in almost every field of science like
automobiles, cosmetics, agriculture, food, textiles, space, defense, engineering,
medical fields, and environment. According to the US National Nanotechnology
Initiative (NNI), nanotechnology is defined as “the understanding and control of
matter at dimensions between approximately 1–100 nanometres, where unique
phenomena enable novel nanotechnology applications.”Encompassing nanoscale
science, engineering, and technology, nanotechnology involves imaging, measuring,
modeling, and manipulating matter at this length scale. In the past few years, use of
nanotechnology in contaminant removal has become prominent due to its small
particle size, high surface area to volume ratio, easy injection to the site of action,
flexibility for in situ and ex situ application, etc.
2.1 Shapes, Sizes, and Structures
Nanotechnology basically deals with particles having dimensions within 1–100 nm
range and forms the functional systems that can be used to solve a problem or
perform a specific function. Different properties of nanoparticles like its reactivity,
magnetism, stability, and optical characteristics depend on the distinctive size,
shape, and structure of the nanoparticles. These characteristics of nanoparticles
make them suitable candidates in different fields of application like drug delivery,
textiles, cosmetics, water purification, food packaging, and several other industrial
uses. The nanoparticles can be synthesized in different shapes like rods, spheres,
cubes, triangles, polygons, etc., and depending on their shapes, the nanoparticles are
named as nanospheres, nano-rods, nano-cubes, etc. (Wu et al. 2016). The structure of
the nanomaterials can be organized with respect to their dimensions. The
nanomaterials are mostly found in zero dimension, e.g., fullerenes, atomic clusters;
one dimension, e.g., nanofibers and nanowires; or two dimensions, e.g., nanodisks,
nanolayers, etc. (Benelmekki 2015).
2.2 Synthesis and Characterization
There are mainly two approaches for the synthesis of nanoparticles. One is top-down
approach and the other is bottom-up approach. When a larger system breaks down to
form nanosized particles, it is known as top-down approach such as high energy ball
milling, grinding, etching, laser pyrolysis, lithographic techniques, etc., whereas in
bottom-up approach, atoms combine to form clusters, and these clusters aggregate to
7 Nano-bioremediation: An Innovative Remediation Technology for Treatment... 167
give rise to nanoparticles. Examples of bottom-up approach include coprecipitation,
chemical reduction, etc. (Singh and Misra 2014). The methods for synthesis of
nanoparticles can be classified into physical, chemical, and biological methods.
Figure 7.1 shows various ways/methods of nanoparticle synthesis falling under
physical, chemical, and biological methods. After synthesis, characterization of the
nanoparticle is imperative for the purpose of identification of its size and shape,
surface charge, morphology, crystallographic nature, etc. This characterization can
be done through multiple techniques such as scanning electron microscope (SEM),
transmission electron microscope (TEM), X-ray diffraction (XRD), Fourier trans-
form infrared spectroscopy (FTIR), scanning tunneling microscopy (STM), nuclear
magnetic resonance (NMR), etc. (Sun et al. 2006; Nurmi et al. 2005; Ramamurthy
and Eglal 2014).
2.3 Environmental Remediation via Nanotechnology
Since the environment is deteriorating day by day by pollution, a promising tech-
nology must be developed to remove the harmful pollutants from it. Although there
are a lot of technologies applied for contaminant removal, nanotechnology became
prominent for its high removal efficiency, less time period, and being economical in
comparison to several other technologies.
Nanoparticle
Synthesis
Biological
Methods
Using Microorganisms
Using Plant extracts
Using Protein templates
Using DNA
Chemical
Methods
Sol -Gel Method
Wet Reduction Method
Hydrothermal Synthesis
Sonochemical Synthesis
Langmuir-Blodgett Method
Microemulsions
Microwave Synthesis
Solvothermal Method
Co-Precipitation Method
Physical
Methods
High Energy Ball milling
Laser Abblation
Laser Vapourisation
Laser Pyrolysis
Magnetron Sputtering
Melt Mixing
ECR Plasma Deposition
Ion Beam Techniques
Fig. 7.1 Methods of nanoparticle synthesis
168 R. Singh et al.
There are different varieties of nanomaterials applied for eliminating contaminants
from environmental matrices (Goutam et al. 2018). These nanomaterials can be
classified into nanotubes, nanofibers, nanoshells, nanoclusters, and nanocomposites
depending on their shape, size, structure, and composition. These nanomaterials have
demonstrated successful removal of hazardous pollutants from ground/surface water,
soil, and sediments. For instance, carbon nanotubes are reported to successfully
remove organic contaminants and metal ions from wastewater through adsorption
process (Hadavifar et al. 2014). Nanofibers have also shown their potency in removing
toxic compounds. Nylon 6 electrospun nanofibers not only remove estrogens from
aqueous solution but could be repeatedly used as long as seven times for removal
purposes (Qi et al. 2014). Titanate nanofibers also demonstrated 96% of phenol
degradation (Barrocas et al. 2017). Nanoshells referred to spherical particles having
a dielectric core and a thin metallic shell. Among nanoshells, Ag nanoshells have been
applied efficiently to catalyze the degradation of organic dyes in industrial effluents
(Vellaichamy and Periakaruppan 2016). Nanomaterials like nanoclusters and
nanocomposites have also shown their efficiency in environmental remediation. The
degradation efficiency of nonylphenol was found to be 96.2% within 120 min with
initial dosage of 0.4 g/L and 5 mM persulfate by nZVI nanocomposite (Hussain et al.
2017). Heavy metals like Ni, Zn, Pb, Cd, and Cr are also reported to be successfully
removed from water bodies using nanostructured graphite oxide and silica/graphite
oxide nanocomposite (Sarkar et al. 2018).
One of the significant advantages of using nanoparticles is that it can be used for
both in situ and ex situ remediation of harmful pollutants. In ex situ remediation, the
contaminated soil and water are brought to the treatment plants and treated with
nanoparticles methodically removing the toxic contaminants, whereas in in situ
treatment methods, nanoparticles are either directly injected to the contaminated
site or are introduced inside a permeable reactive barrier (PRB) where it successfully
treats the contaminant plume and removes it (Karn et al. 2009).
Nanoscale zerovalent iron (nZVI) has shown enormous potential in contaminant
reduction and can be successfully used in groundwater remediation either through
direct injection or through permeable reactive barriers (PRBs) (Singh et al. 1998;Oh
et al. 2001). A case study in Czech Republic reported that when nZVI was injected
into a metal fabrication industrial area contaminated with chlorinated ethylenes, it
showed 50% removal of the contaminant within 5–6 months (Lacina et al. 2015).
When an aquifer contaminated with trichloroethylene (TCE) was treated with nZVI,
it successfully removed 95.7% of TCE within 1 month without generating any
chlorinated intermediates. It was also found that nZVI can be reused several times
even after being aged for 5 months (Ahn et al. 2016).
Since the nanoparticles tend to agglomerate easily and oxidize fast, the surface of
nanoparticles can be coated with suitable stabilizers to increase its stability and
reduce agglomeration (Sakulchaicharoen et al. 2010). The surface coatings increase
the adsorbing capacity of nanoparticles decreasing their agglomeration. A report
showed that phosphate can be efficiently removed from water with humic acid-
coated magnetite nanoparticles (Rashid et al. 2017). Titania-coated silica
nanoparticles degraded 93.29% of safranin-O dye from aqueous solution at optimal
7 Nano-bioremediation: An Innovative Remediation Technology for Treatment... 169
conditions (Ekka et al. 2016). Another research shows that gold nanoparticles with
surface coatings can be reused for 6 times with more than 90% conversion efficiency
and keep high activity even after exposing in air for 1 month (Guo et al. 2016).
Table 7.1 enlists few other contaminants which have been studied for their remedi-
ation using nanoparticles.
Table 7.1 Nanoparticle-mediated remediation of contaminants
Nanoparticle Contaminant Remarks References
Fe/Ni bimetallic
nanoparticles
Tetracycline (TC) Removal efficiency of TC showed
a decreasing trend with time due
to the aging of Fe/Ni
nanoparticles. The main aging
products are found to be magne-
tite and maghemite
Dong et al.
(2018)
Magnetic nanopar-
ticle adsorbents,
(Mag-PCMA-T)
PAHs and metal
contaminants
Mag-PCMA-T could simulta-
neously remove PAHs and metal
contaminants from water with
efficiency greater than 85%
Huang et al.
(2016)
Hematite
nanoparticles
Carbamazepine Hematite nanoparticles can be
used to adsorb carbamazepine
from water samples which
showed an increasing trend with
time up to 2.5 h. After 2 h 90% of
carbamazepine got desorbed
Rajendran
and Sen
(2018)
Al
2
O
3
nanoparticles
Arsenite Al
2
O
3
nanoparticles adsorbed
maximum arsenite from ground-
water at normal pH and
temperature
Prabhakar
and
Samadder
(2018)
Activated carbon
nanoparticles
(ACNPs)
Sulfate and copper ACNPs increased surface hydro-
philicity of nanofiltration mem-
branes thereby escalating removal
of sulfate and Cu ions from water
Hosseini
et al. (2018)
Polystyrene
nanoparticle
Estrone hormone The efficiency of polystyrene
nanoparticles in estrone removal
were found to be lower than most
nanofiltration/reverse osmosis
(NF/RO) systems, that is around
40% but its final permeability was
five times higher than other filtra-
tion systems
Akanyeti
et al. (2017)
CTAB modified
magnetic
nanoparticles
Chromium (VI) The CTAB modified Fe
2
O
3
nanoparticles can efficiently
remove Cr (VI) from water at
acidic pH in 12-h contact time
Elfeky et al.
(2017)
nZVI Cu, Pb, Sb nZVI increased the soil washing
efficiency showing selective
removal for Cu, Pb, and Sb
Boente et al.
(2018)
(continued)
170 R. Singh et al.
3 Nano-bioremediation: An Integrated Approach Toward
Environmental Clean-up
Nano-bioremediation is an integrated technology that applies both nanotechnology
and bioremediation together to achieve a remediation that is more efficient, less time
taking, and environment friendly than the individual processes. Integrated approach
could overcome the disadvantages of individual technologies and can provide better
Table 7.1 (continued)
Nanoparticle Contaminant Remarks References
Manganese oxide
nanoparticles
17β-estradiol MnO
2
nanoparticles removed
88% of estrogens from soil. The
decreased injection velocity and
increased concentration of
nanoparticles elevated the estro-
gen degradation
Han et al.
(2017)
Palladium
nanoparticles
Pentachlorobiphenyl The stabilized Pd nanoparticles
coupled with supercritical fluid
CO
2
are able to remove all PCBs
from soil at 200 atm and all
existing temperature ranges
Wang and
Chiu (2009)
Reduced graphene
oxide silver
nanoparticles
(rGO-Ag)
Phenol, bisphenol A,
and atrazine
The rGO-Ag shows
photocatalytic degradation of
these organic compounds. When
the reaction is carried out under
visible light, significant decrease
in contaminants is seen promoting
oxidative degradation
Bhunia and
Jana (2014)
Zinc oxide
nanoparticles
Benzophenone-3
(BP-3)
ZnO nanoparticles showed suc-
cessful degradation of
benzophenone-3 (BP-3) which is
a highly persistent EDC
Rajesha et al.
(2017)
TiO
2
nanoparticles EDCs (diclofenac,
metoprolol, estrone,
and chloramphenicol)
The photocatalytic activity of
TiO
2
nanoparticles were able to
degrade the EDCs arising from
PPCPs. However the large particle
size of the nanoparticle and pres-
ence of rutile decrease the
photodegradation efficiency
Czech and
Rubinowska
(2013)
CuO nanoparticles Arsenic(As) CuO nanoparticles adsorb con-
siderable amount of As from
water showing potential to be
applied in field applications
Reddy et al.
(2013)
Cerium oxide
nanoparticles
Cadmium (II), lead
(II), and chromium
(VI) ions
CeO
2
nanoparticles were effectual
in removing the three toxic heavy
metals from aqueous system. The
removal efficiencies were found
highest at pH 5 and 7
Contreras
et al. (2015)
7 Nano-bioremediation: An Innovative Remediation Technology for Treatment... 171
remediation results. For instance, incorporation of microbial strains in nZVI helps in
more efficient remediation of pollutants. Chlorinated aliphatic hydrocarbons (CAH)
are recalcitrant compounds which can neither be removed completely by nZVI nor
organochlorine respiring bacteria (ORB). Koenig et al. (2016) combined both the
technologies for removal of CAHs and showed that at appropriate dosage, a wide
range of CAHs can be treated efficiently. They further suggested that the spent nZVI
can be regenerated by certain minerals like cysteine and vitamins which remains
available in bacterial environments. A reductive-oxidative strategy consisting of
nZVI and an aerobic bacterium (Sphingomonas sp. PH-07) found to be effective
for degradation of polybrominated diphenyl ethers (PBDEs) in aqueous solution.
The nZVI particles break down the complex PBDEs like deca-BDE to lower BDEs
through reductive debromination which were then degraded easily by microbes
(Kim et al. 2012). Under optimal conditions, nZVI-CA beads showed 91.35% Cr
(VI) removal, and for biofilm-coated nZVI-CA beads, the removal percentage was
found to be 97.84%. When the efficiency of beads was investigated in column
experiments, increased Cr (VI) removal was observed as compared to the free
beads. The height of the column increases the reactive sites of the beads, which in
turn enhance the removal of the toxic metal from the contaminated water. However
in case of real samples, the efficiency of removal got decreased which may be
attributed to the presence of colloidal particles present in the samples (Ravikumar
et al. 2016). It is suggested by a report that permeable reactive Fe
0
barriers might be
an effective approach to degrade RDX plumes and that treatment efficiency could be
enhanced through bioaugmentation. When nZVI and white rot fungi were applied
simultaneously, a substantial increase in RDX degradation as compared to the
individual approach was observed. In addition to that, nZVI corrosion produces
hydrogen gas which favors the growth and metabolic activities of the fungi further
promoting RDX removal (Oh et al. 2001).
Hydrogen is considered as highly favorable electron donor for microorganisms
carrying out biotransformation of contaminants in environmental substrates. The
possibility of using cathodic hydrogen (produced during corrosion of nZVI under
anaerobic conditions) as an electron donor for contaminant-degrading microbes, has
been explored by many researchers (Weathers et al. 1997; Liu et al. 2005). Xiu et al.
(2010b) demonstrated that the degradation of chlorinated solvent can be boosted by
using nZVI as reducing agent along with bacteria that utilize cathodic depolarization
and reductive dechlorination as metabolic niches. In another study wherein
carboxymethyl cellulose (CMC) stabilized bimetallic nanoparticles (CMC-Pd/
nFe
0
) was integrated with Sphingomonas sp. strain NM05 for studying degradation
of γ-HCH, synergistic effect on γ-HCH degradation was reported in case of inte-
grated system, which further indicate that stabilized nanoparticles have some kind of
biostimulatory effect on cell growth (Singh et al. 2013). Shin and Cha (2008) also
observed biostimulatory effect of nFe
0
on nitrate reducing microbial culture. In
addition, nZVI supported microbial reduction was found to remain indifferent to
fluctuating low temperatures, which otherwise is a major disadvantage with abiotic
nitrate reduction.
172 R. Singh et al.
As the toxicity of nanoparticles for microorganisms is well documented in
literature (Li et al. 2010;DiaoandYao2009), the dosage of nanoparticles in
integrated system plays a significant role. In case of CAH treatment by nZVI and
ORB, nZVI showed lethal effect on bacteria over 0.5 g/L, but it was found to have
positive impact on ORB activity below 0.1 g/L (Koenig et al. 2016). The issues of
nanoparticle toxicity toward bioagent can be addressed by modifying the surface of
nanoparticles through coating, stabilization, or entrapment. The coating prevents
the adhesion of nanoparticles on microbial cells, which in turn result in enhanced
remediation of contaminants. Li et al. (2010) compared bactericidal effect of bare
nZVI with polyelectrolyte (polystyrene sulfonate and polyaspartate) and natural
organic matter adsorbed nZVI on E. coli and found that surface modification
diminishes the toxicity of nZVI for exposure concentrations below 0.1–0.5 g/L.
The study reported that surface modification diminishes the toxicity of nZVI for
exposure concentrations below 0.1–0.5 g/L. An et al. (2010) while investigating
nitrate reduction with bimetallic nanoparticles and chitosan/sodium oleate modi-
fied iron nanoparticles also observed reduced toxicity of modified nanoparticles
toward microbes. The oxidation of nanoparticles with time or aging of
nanoparticles is also reported to decrease the toxicity of nanoparticles (Phenrat
et al. 2009). Apart from preventing the direct contact of nanoparticle with micro-
bial cell, coating is also observed to enhance the expression of dechlorinating
genes in Dehalococcoides spp., which in turn accelerates the degradation effi-
ciency of TCE in sequential nano-bio treatment system Xiu et al. (2010a).
Le et al. (2015) investigated polychlorinated biphenyls (PCBs) removal by the
nano-bio approach and found that the sequential treatment of PCB with Pd/Fe
nanoparticles followed by bioremediation with B. xenovorans could effectively
transform PCBs to less toxic and innocuous compounds. They further investigated
the toxicity level of PCBs in Escherichia coli DH5αbefore and after treatment using
toxic equivalent values and reported lower cytotoxicity of residual PCBs toward E.
coli after treatment. When nZVI and whey both were injected into groundwater
contaminated with Cr (VI), Němeček et al. (2016) observed 97–99% of Cr
(VI) removal in an integrated system having nZVI and whey generated microbes.
Besides removing the contaminants, microbes were also found to regenerate the
oxidized Fe
0
nanoparticles which further increased the rate of remediation reducing
the dosage of nanoparticles.
Multi-walled carbon nanotubes (CNTs) along with bioremediation are also suc-
cessfully used for contaminant removal. In a study, Shewanella oneidensis MR-1,a
facultative Gram-negative bacterium, was immobilized in calcium alginate beads
containing carbon nanotubes to reduce Cr (VI) to Cr (III) in wastewater. The study
demonstrated four times higher reduction rates in cells immobilized over CNTs
containing beads in comparison to the free cells and the beads without CNTs (Yan
et al. 2013). The reason for enhanced reduction was ascribed to enhanced electron
transfer by the CNTs. Similarly, Pang et al. (2011) immobilized P. aeruginosa in
polyvinyl alcohol (PVA), sodium alginate, and CNTs matrix for carrying out Cr
(VI) reduction. The study showed that CNT-modified immobilized cells reduce Cr
(VI) contaminant more efficiently and can be reused effectively up to nine times.
7 Nano-bioremediation: An Innovative Remediation Technology for Treatment... 173
Pd nanoparticles have also shown their efficiency in integrated system.
Chidambaram et al. (2010) reported in situ synthesis of Pd nanoparticles using
C. pasteurianum BC1 cells, wherein C. pasteurianum reduced the Pd (II) ions to
Pd nanoparticles which were retained in the cell wall and cytoplasm of the cells in
the form of bio-Pd. This bio-Pd system successfully catalyzed the reduction process
of Cr (VI) to insoluble Cr (III) species. One added benefit of bio-Pd system mediated
reduction was the production of hydrogen gas which provides an alternative to the
costly addition of molecular hydrogen to above ground pump and treat systems.
MgO nanoparticles in combination with yeast Candida sp. SMN04 have been
studied for treating Cefdinir in aqueous medium (Adikesavan and Nilanjana
2016). The half-life of Cefdinir in nano-bio system was observed to reach less
than half of the time taken by the individual yeast cell. Incorporation of MgO
nanoparticles in the system was reported to increase the permeability of cell mem-
brane allowing more amount of contaminant to get access to the cells, thereby
accelerating degradation rate in comparison to individual system. Table 7.2 presents
nano-bioremediation methods reported for a variety of environmental contaminants.
4 Application Methods and Process
There are two ways which have been reported for application of integrated nano-bio
process in treatment system. First is sequential method wherein the contaminant is
subjected to nanoparticles first and later on bioagent is added to carry out further
process. The second method is concurrent or combined method where both nano-
particle and biological agent are added to the system simultaneously. The examples
of both methods along with their process are given below:
4.1 Sequential Method
Bokare et al. (2010) developed a sequential hybrid treatment system with bimetallic
nanoparticle (Pd/nFe) and an enzyme for studying degradation of triclosan (TCS)
which is an antimicrobial agent used widely in personal care products. In the first
step, triclosan (5 mg/L) was reduced with Pd/nFe nanoparticles (1 g/L) under
anaerobic conditions which resulted in dechlorination of TCS to 2-phenoxyphenol.
In the next step, nanoparticles were separated from the system, and the dechlorinated
product was subjected to oxidation by laccase enzyme isolated from Trametes
versicolor in presence of syringaldehyde (a natural redox mediator). The study
reported complete transformation of TCS through redox process to nontoxic oligo-
mers. Similar kind of reductive-oxidative hybrid strategy was successfully employed
to demonstrate degradation of polybrominated diphenyl ethers (PBDEs) in aqueous
solution using nZVI along with diphenyl ether-degrading bacteria Sphingomonas
sp. PH-07 (Kim et al. 2012). Debromination of deca-BDE (5 g/L) was carried out
174 R. Singh et al.
Table 7.2 Remediation of environmental contaminants using nano-bioremediation
Nanoparticle Bioagent Contaminant Remark References
Fe
3
O
4
nanoparticles/
gellan gum gel beads
Sphingomonas sp. strain
XLDN2–5 cells
Carbazole The microbial cells immobilized in Fe
3
O
4
nanoparticles/gellan gum gel beads degraded higher
carbazole than the free cells and the
non-magnetically immobilized cells. This integrated
system showed progressive increase in degradation
when being recycled
Wang et al.
(2007)
Pd/nFe Laccase derived from
Trametes versicolor
Triclosan The remediation of triclosan was solely achieved by
Fe nanoparticles. However the degraded by-products
were further converted to nontoxic compounds by
the laccase secreted from T. versicolor strain
Bokare et al.
(2010)
Bio-Pd nanoparticle C. pasteurianum BC1 Cr(VI) C. pasteurianum reduced the Pd(II) ions to Pd
nanoparticles which stayed in the form of bio-Pd in
the cell membrane and cytoplasm of the organism. It
successfully catalyzed the Cr(VI) reduction reaction
and also produced hydrogen gas
Chidambaram
et al. (2010)
Pd/nFe Sphingomonas wittichii
RW1 (DSM 6014)
2,3,7,8-tetrachlorodibenzo-
p-dioxin (2,3,7,8-TeCDD
The highly toxic dioxin isomer is recalcitrant in
nature and its degradation could not be acquired
easily through a single technique. The degradation
was accomplished by using the Pd/nFe nanoparticles
and the Sphingomonas strain sequentially
Bokare et al.
(2012)
Pd/nFe Burkholderia xenovorans
LB400
Polychlorinated biphenyl
(PCB) Aroclor 1248
Pd/nFe nanoparticles efficiently dechlorinated the
bi-, tri-, tetra-, penta-, hexa-chlorinated biphenyls
into biodegradable intermediates which were then
easily degraded by Burkholderia xenovorans
Le et al.
(2015)
nZVI-C-A beads Bacillus subtilis,E. coli,
and Acinetobacter junii
Cr(VI) The thin biofilm covering the nZVI entrapped cal-
cium alginate beads removed around 92% of Cr
(VI) showing enhanced removal by the combined
technology
Ravikumar
et al. (2016)
(continued)
7 Nano-bioremediation: An Innovative Remediation Technology for Treatment... 175
Table 7.2 (continued)
Nanoparticle Bioagent Contaminant Remark References
Carbon nanotubes Shewanella oneidensis
MR-1
Cr(VI) The MR-1 strain immobilized by CNT infused CA
beads could remove four times higher Cr (VI) than
the free cells or CNTs or CA beads
Yan et al.
(2013)
nZVI Dehalococcoides spp. TCE This study showed that nZVI stimulated the meta-
bolic activity of methanogens but deactivated the
dechlorinating bacteria, but after a lag phase the
dechlorinating bacteria could again remove TCE
producing ethene as by-product
Xiu et al.
(2010b)
Pd(0) nanoparticles Shewanella oneidensis
MR-1
PCBs The bio-Pd formed from the microbial reduction
effectively dechlorinated around 90% of PCBs pro-
ducing less toxic by-products
Windt et al.
(2005)
Fe
3
O
4
nanoparticles Sphingomonas
sp. XLDN2-5 cells
Carbazole The Fe
3
O
4
nanoparticles bound to the surface of the
bacterial strain showed no increased degradation
than the free cells but showed amazing reusability.
Another advantage of using magnetic nanoparticles
is it can be separated from the microorganism using
an external magnet source
Li et al. (2013)
Magnetic Fe
3
O
4
nanoparticles
Pseudomonas delafieldii Dibenzothiophene The magnetic nanoparticle coated microbial cells
showed greater biodesulfurization of
dibenzothiophene than the free cells or cells coated
with celite. It is also observed that it can be reused
more than five times
Shan et al.
(2005)
nZVI Paracoccus sp. strain YF1 Nitrate Lower conc. of nZVI (50 mg/L) enhanced denitrifi-
cation process along with slight microbial toxicity,
while higher conc. (1000 mg/L) significantly
reduced denitrification rate
Liu et al.
(2014)
176 R. Singh et al.
with nZVI (100 mg) under anaerobic condition in 15 ml glass test tube. After
20 days, PH-07 strain was added in reaction mixture and incubated for 4 days.
The sequential system was found to be effective for degradation of deca-BDE
showing reduction up to 67%. The debrominated products were further treated
with PH-07 strain to study their mineralization. He et al. (2009) also reported
sequential treatment of 2, 2
0
4, 5, 5
0
-pentachlorobiphenyl with an anaerobic nZVI
reaction and successive aerobic transformation with bacterium H1.
4.2 Concurrent/Combined Method
In a microcosm study, Xiu et al. (2010a) investigated the effect of nZVI on
dechlorinating microorganism using trichloroethylene (TCE) as model compound.
For experiments, 100 mg of nZVI (1 g/L) and 4 ml of inoculation culture
(Dehalococcoides spp.) along with mineral salt medium were added simultaneously
in reaction vials containing TCE (20 g/L). The reaction mixture was then put over
shaker at 200 rpm. Two other experiments were also carried out under similar
conditions, one with nZVI alone and another with Dehalococcoides spp. only.
Initially, nZVI was observed to inhibit microbial dechlorination, but later on it was
found to have biostimulatory effect on dechlorinating bacteria which in turn could
enhance the overall rate of contaminant degradation. The reason ascribed to this was
the hydrogen which is evolved from nZVI during cathodic corrosion can be utilized
as electron donor by dechlorinating bacteria. In another combined study, nanopar-
ticle (nFe
0
/Pd) was coated with a polymer (carboxymethyl cellulose, CMC) to avoid
direct contact of nanoparticle with bacterial cells, as their direct contact inhibits the
growth of bacteria cells (Singh et al. 2013). The study demonstrated degradation of
γ-HCH in individual and combined system of CMC-Pd/Fe
0
and Sphingomonas
strain NM05. The results revealed that γ-HCH degradation efficiency in combined
system was 1.7–2.1 times greater as compared to system containing either NM05
strain or CMC-Pd/nFe
0
alone.
5 Conclusion
Integration of nanoremediation with bioremediation either sequentially or concur-
rently appears to be a feasible alternative to conventional remediation technologies.
More studies and development actions are still needed for bringing down these kinds
of technologies to the marketplace for full-scale implementation. Moreover, the
effect of environmental factors like pH, temperature, ionic strength, presence of
competing or inhibitory substances, etc. on remediation efficacy of nano-
bioremediation method is also needed.
7 Nano-bioremediation: An Innovative Remediation Technology for Treatment... 177
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