maintenance and provide wildlife habitat, as well as human recreational opportunities and a reuse and recycling option for wastewater treatment facility. CWs are more
favored in developing countries due to easily available and less costly land and
tropical environment, which help to flourish the microbial communities responsible
for the degradation/detoxification of organic and inorganic contaminants in wastewaters and therefore high treatment efficiency (Zhang et al. 2015). Thus, increasing
use of CWs can successfully remediate heavy metal pollution and solve various
water quality issues in the world. In addition, integrating CWs with a microbial fuel
cell (MFC) for wastewater treatment and electricity generation could be an innovative approach for the improved degradation of pollutants. According to a recent
study, a maximum power density of 15.73 mW m
À2 and maximum current density
of 69.75 mA m
À2 could be achieved during the treatment of synthetic wastewater
containing methylene blue dye (1000 mg l
À1 765) with 75% COD removal in an
integrated CW-MFC system planted with an ornamental plant, Canna indica (Yadav
et al. 2012). Moreover, CWs may have great potential for bioenergy production and
carbon sequestration, if planted with energy crops. According to a study, the
incineration of harvested biomass (16,737 kg with C content, 6185 kg) of Ludwigia
sp. and Typha sp. recovered from a subtropical CW could produce 11,846 kWh for
1 month (Wang et al. 2011). However, the future research should be focused on
(a) understanding of microbiological dynamics and correlation of biological and
non-biological processes in CWs, (b) knowledge of element cycle dynamics that will
help to understand the fundamental processes of greenhouse gas emission in CWs,
and (c) understanding of microbial community and plant-microbe interactions to
know the underlying mechanism of pollutant removal in CWs (Carvalho et al. 2017).
Furthermore, researches are underway to expand the scope and efficacy of CWs for
treatment of metal-contaminated wastewaters.
2.6 Microbial Fuel Cells
A microbial fuel cell (MFC) is a bioelectrochemical device that harnesses the power
of respiring microbes to convert organic substrates directly into electrical energy.
MFC can be a suitable alternative to the conventional activated sludge process
based-treatment systems in terms of energy consumption and excess sludge generation. MFCs offer several advantages over conventional treatment systems related to
energy (like direct electricity generation, energy savings by anaerobic treatment due
to elimination of aeration, low sludge yield), environmental (water reclamation, low
carbon footprint, less sludge generation), economic (revenue through energy and
value-added products (chemicals), low operational costs), and operational benefits
(self-generation of microorganisms, good resistance to environmental stress, and
amenable to real-time monitoring and control) (Li et al. 2014; Gude 2016).
MFCs are environmentally friendly technologies as they can produce clean
electricity directly from organic matter in wastewater without any need for separation, purification, and conversion of the energy products and function at mild
5 Emerging and Ecofriendly Technologies for the Removal of Organic and. . .
119
favored in developing countries due to easily available and less costly land and
tropical environment, which help to flourish the microbial communities responsible
for the degradation/detoxification of organic and inorganic contaminants in wastewaters and therefore high treatment efficiency (Zhang et al. 2015). Thus, increasing
use of CWs can successfully remediate heavy metal pollution and solve various
water quality issues in the world. In addition, integrating CWs with a microbial fuel
cell (MFC) for wastewater treatment and electricity generation could be an innovative approach for the improved degradation of pollutants. According to a recent
study, a maximum power density of 15.73 mW m
À2 and maximum current density
of 69.75 mA m
À2 could be achieved during the treatment of synthetic wastewater
containing methylene blue dye (1000 mg l
À1 765) with 75% COD removal in an
integrated CW-MFC system planted with an ornamental plant, Canna indica (Yadav
et al. 2012). Moreover, CWs may have great potential for bioenergy production and
carbon sequestration, if planted with energy crops. According to a study, the
incineration of harvested biomass (16,737 kg with C content, 6185 kg) of Ludwigia
sp. and Typha sp. recovered from a subtropical CW could produce 11,846 kWh for
1 month (Wang et al. 2011). However, the future research should be focused on
(a) understanding of microbiological dynamics and correlation of biological and
non-biological processes in CWs, (b) knowledge of element cycle dynamics that will
help to understand the fundamental processes of greenhouse gas emission in CWs,
and (c) understanding of microbial community and plant-microbe interactions to
know the underlying mechanism of pollutant removal in CWs (Carvalho et al. 2017).
Furthermore, researches are underway to expand the scope and efficacy of CWs for
treatment of metal-contaminated wastewaters.
2.6 Microbial Fuel Cells
A microbial fuel cell (MFC) is a bioelectrochemical device that harnesses the power
of respiring microbes to convert organic substrates directly into electrical energy.
MFC can be a suitable alternative to the conventional activated sludge process
based-treatment systems in terms of energy consumption and excess sludge generation. MFCs offer several advantages over conventional treatment systems related to
energy (like direct electricity generation, energy savings by anaerobic treatment due
to elimination of aeration, low sludge yield), environmental (water reclamation, low
carbon footprint, less sludge generation), economic (revenue through energy and
value-added products (chemicals), low operational costs), and operational benefits
(self-generation of microorganisms, good resistance to environmental stress, and
amenable to real-time monitoring and control) (Li et al. 2014; Gude 2016).
MFCs are environmentally friendly technologies as they can produce clean
electricity directly from organic matter in wastewater without any need for separation, purification, and conversion of the energy products and function at mild
5 Emerging and Ecofriendly Technologies for the Removal of Organic and. . .
119