Textile dyes and heavy metals cause irritation to the gastrointestinal tract, permanent eye injury, irritation, redness, cancer, and pain to the skin (Kauffman 1970;
Katz and Salem 1993; www.lenntech.com/periodic/elements/co.htm). Since these
heavy metals and dyes are known to cause several health problems, which may
sometimes even be lethal, hence there is increasing emphasis on decontamination of
such wastewaters to standard permissible limits. Decontamination or effective disposal of wastewater has always been challenging with a thrust on cost-effective
treatment technologies showing minimal side effects. Conventional wastewater
treatment technologies for removal of heavy metals and dyes include chemical
precipitation, ion exchange, evaporation, membrane separation, electrodialysis,
and chemical reduction. All these methods are ineffective at lower concentration
of metal ions. These are cost intensive and also generate a large amount of toxic
sludge (Robinson et al. 2001), disposal of which further requires energy and capital.
Bioremediation is considered as a potential alternative to physicochemical technologies for removal and recovery of metals and dyes from effluents. Bioremediation involves the use of biological agents such as microbes and plants or their
enzymes for the remediation purpose and has certain advantages over conventional
methods (Saxena et al. 2019; Bharagava et al. 2017c; Chandra et al. 2015). It is costeffective, is easy to operate, and does not produce chemical sludge, hence
eco-friendly. Biosorption is a common technique that has increasingly been investigated for removal of toxicants from wastewaters. It involves the use of nonliving
(dead) and nongrowing biomass, which does not require nutrients and is metabolism
independent. Biosorption is different from “bioaccumulation,” which is an active
process, and removal of heavy metals requires the metabolic activity of a living
organism (Davis et al. 2003). Both adsorption and absorption occur in
bioaccumulation. A large number of microorganisms like bacteria, fungi, algae,
and yeast have also been used for bioremoval of heavy metals, dyes, pesticides,
COD, etc. There are reports on the removal of pollutants and contaminant by fungal
strains like Rhizopus arrhizus, Mucor miehei, Penicillium chrysogenum, and
Ganoderma lucidum (Lewis and Kriff 1988; Matheickal et al. 1991; Fourest et al.
1994) and bacterial strains like Arthrobacter sp. and Pseudomonas aeruginosa
(Scott and Palmer 1990; Chang et al. 1997). Though relatively fewer reports are
available on cyanobacterial utilization for heavy metal and dye removal, in recent
years, some studies have reported on these aspects (Vijayaraghavan et al. 2005;
Celekli et al. 2009; Mona et al. 2011).
Microbial bioremediation can cost-effectively and expeditiously destroy or
immobilize contaminants in a manner that protects human health and the environment (Heitzer and Sayler 1993; Gheewala and Annachatre 1997; Gadd 2000).
Research is underway at a number of facilities using exogenous, specialized
microbes or genetically engineered microbes to optimize bioremediation (Hassan
et al. 2003).
Cyanobacterial applications showed enormous potential in wastewater treatment,
bioremediation, and detoxification of industrial effluents of chemical, bio-fertilizer,
food, feed, and fuel industries. Nostoc sp., Anabaena sp., Oscillatoria sp.,
Synechococcus sp., Nodularia sp., and Cyanothece sp. are a group of cyanobacterial
396
S. Mona et al.
Katz and Salem 1993; www.lenntech.com/periodic/elements/co.htm). Since these
heavy metals and dyes are known to cause several health problems, which may
sometimes even be lethal, hence there is increasing emphasis on decontamination of
such wastewaters to standard permissible limits. Decontamination or effective disposal of wastewater has always been challenging with a thrust on cost-effective
treatment technologies showing minimal side effects. Conventional wastewater
treatment technologies for removal of heavy metals and dyes include chemical
precipitation, ion exchange, evaporation, membrane separation, electrodialysis,
and chemical reduction. All these methods are ineffective at lower concentration
of metal ions. These are cost intensive and also generate a large amount of toxic
sludge (Robinson et al. 2001), disposal of which further requires energy and capital.
Bioremediation is considered as a potential alternative to physicochemical technologies for removal and recovery of metals and dyes from effluents. Bioremediation involves the use of biological agents such as microbes and plants or their
enzymes for the remediation purpose and has certain advantages over conventional
methods (Saxena et al. 2019; Bharagava et al. 2017c; Chandra et al. 2015). It is costeffective, is easy to operate, and does not produce chemical sludge, hence
eco-friendly. Biosorption is a common technique that has increasingly been investigated for removal of toxicants from wastewaters. It involves the use of nonliving
(dead) and nongrowing biomass, which does not require nutrients and is metabolism
independent. Biosorption is different from “bioaccumulation,” which is an active
process, and removal of heavy metals requires the metabolic activity of a living
organism (Davis et al. 2003). Both adsorption and absorption occur in
bioaccumulation. A large number of microorganisms like bacteria, fungi, algae,
and yeast have also been used for bioremoval of heavy metals, dyes, pesticides,
COD, etc. There are reports on the removal of pollutants and contaminant by fungal
strains like Rhizopus arrhizus, Mucor miehei, Penicillium chrysogenum, and
Ganoderma lucidum (Lewis and Kriff 1988; Matheickal et al. 1991; Fourest et al.
1994) and bacterial strains like Arthrobacter sp. and Pseudomonas aeruginosa
(Scott and Palmer 1990; Chang et al. 1997). Though relatively fewer reports are
available on cyanobacterial utilization for heavy metal and dye removal, in recent
years, some studies have reported on these aspects (Vijayaraghavan et al. 2005;
Celekli et al. 2009; Mona et al. 2011).
Microbial bioremediation can cost-effectively and expeditiously destroy or
immobilize contaminants in a manner that protects human health and the environment (Heitzer and Sayler 1993; Gheewala and Annachatre 1997; Gadd 2000).
Research is underway at a number of facilities using exogenous, specialized
microbes or genetically engineered microbes to optimize bioremediation (Hassan
et al. 2003).
Cyanobacterial applications showed enormous potential in wastewater treatment,
bioremediation, and detoxification of industrial effluents of chemical, bio-fertilizer,
food, feed, and fuel industries. Nostoc sp., Anabaena sp., Oscillatoria sp.,
Synechococcus sp., Nodularia sp., and Cyanothece sp. are a group of cyanobacterial
396
S. Mona et al.