Keyword Biodegradation · Biofuels · Biosorption · Enhanced algal nitrification
process (EANP) · Environmental safety · Life cycle assessment (LCA) · Microalgae ·
Wastewater
1 Introduction
With greater understanding of the impact of wastewater on the environment and
more, a sophisticated advanced technology, an eco-friendly tool for sustainable
wastewater treatment is highly demanded. Industrial wastewater is a major source
of pollution as it carries a variety of highly toxic organic and inorganic chemicals
which may cause serious toxicity in living beings upon exposure (Goutam et al.
2018; Bharagava et al. 2017a, b). Biological treatment processes are relatively
natural processes in which beneficial microbiological agents (e.g., bacteria) or plants
(i.e., phytoremediation) are utilized to treat contaminated water (Saxena et al. 2016,
2018; Gautam et al. 2017; Bharagava et al. 2017c; Saxena and Bharagava 2015,
2017; Chandra et al. 2015). Wastewater treatment using green algae is an innovative
technology with several benefits, which can mitigate greenhouse gas emissions and
produce clean and safe water with less energy consumption (Birol 2007).
Algal biodegradation is an eco-friendly, cost-effective, highly efficient approach
compared to traditional physicochemical methods (e.g., chemical coagulation, filtration, ion exchange, and activated carbon adsorption) which are expensive as well
as unfriendly towards the environment (Javaid et al. 2016). Microalgae are capable
of rapid growth in nutrient-rich wastewater under light with improved removal
efficiency compared to existing biological nutrient removal processes (e.g., 90%
nitrogen [N] and phosphorus [P] removal within 2 days for microalgae compared to
90% of N and 80% of P removal in A
2 O processes) (Jia and Yuan 2016). They can
also sorb inorganic and organic nutrients such as EDCs (Zhou et al. 2014) and heavy
metals (Mallick 2002) from wastewater, representing an environmental safety tool
for advanced wastewater treatment. Several algal systems of different configuration
such as stabilization ponds, hyper-concentrated cultures, and immobilized cell
systems use wastewater for algae cultivation; however, they may generate secondary
pollutants such as hydrocarbons (HC) and nitrogen oxides (NOx) and require
relatively large area of operations. Algae-integrated wastewater treatment processes
emphasize on bioenergy production such as biodiesel (Batan et al. 2010), alcohol
(e.g., butanol and ethanol) (Choi et al. 2011) and biohydrogen production (Hwang
et al. 2014), and capture/sequester CO 2 which is one of the primary greenhouse
gases (GHG). A study by Kim et al. (2013b) showed 60% of biodiesel production
cost saving by downstream processes for algae cultivation. It is suggested that
reducing nutrient cost for algae cultivation by using wastewater ensures the economic feasibility of microalgal biofuel production. However, despite inherent potential as a biofuel resource, there are still many challenges to be resolved which have
impeded the development of algal biofuel technology at commercial scale. For
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J.-H. Hwang et al.
process (EANP) · Environmental safety · Life cycle assessment (LCA) · Microalgae ·
Wastewater
1 Introduction
With greater understanding of the impact of wastewater on the environment and
more, a sophisticated advanced technology, an eco-friendly tool for sustainable
wastewater treatment is highly demanded. Industrial wastewater is a major source
of pollution as it carries a variety of highly toxic organic and inorganic chemicals
which may cause serious toxicity in living beings upon exposure (Goutam et al.
2018; Bharagava et al. 2017a, b). Biological treatment processes are relatively
natural processes in which beneficial microbiological agents (e.g., bacteria) or plants
(i.e., phytoremediation) are utilized to treat contaminated water (Saxena et al. 2016,
2018; Gautam et al. 2017; Bharagava et al. 2017c; Saxena and Bharagava 2015,
2017; Chandra et al. 2015). Wastewater treatment using green algae is an innovative
technology with several benefits, which can mitigate greenhouse gas emissions and
produce clean and safe water with less energy consumption (Birol 2007).
Algal biodegradation is an eco-friendly, cost-effective, highly efficient approach
compared to traditional physicochemical methods (e.g., chemical coagulation, filtration, ion exchange, and activated carbon adsorption) which are expensive as well
as unfriendly towards the environment (Javaid et al. 2016). Microalgae are capable
of rapid growth in nutrient-rich wastewater under light with improved removal
efficiency compared to existing biological nutrient removal processes (e.g., 90%
nitrogen [N] and phosphorus [P] removal within 2 days for microalgae compared to
90% of N and 80% of P removal in A
2 O processes) (Jia and Yuan 2016). They can
also sorb inorganic and organic nutrients such as EDCs (Zhou et al. 2014) and heavy
metals (Mallick 2002) from wastewater, representing an environmental safety tool
for advanced wastewater treatment. Several algal systems of different configuration
such as stabilization ponds, hyper-concentrated cultures, and immobilized cell
systems use wastewater for algae cultivation; however, they may generate secondary
pollutants such as hydrocarbons (HC) and nitrogen oxides (NOx) and require
relatively large area of operations. Algae-integrated wastewater treatment processes
emphasize on bioenergy production such as biodiesel (Batan et al. 2010), alcohol
(e.g., butanol and ethanol) (Choi et al. 2011) and biohydrogen production (Hwang
et al. 2014), and capture/sequester CO 2 which is one of the primary greenhouse
gases (GHG). A study by Kim et al. (2013b) showed 60% of biodiesel production
cost saving by downstream processes for algae cultivation. It is suggested that
reducing nutrient cost for algae cultivation by using wastewater ensures the economic feasibility of microalgal biofuel production. However, despite inherent potential as a biofuel resource, there are still many challenges to be resolved which have
impeded the development of algal biofuel technology at commercial scale. For
284
J.-H. Hwang et al.