example, although removal of nutrients by microalgae has been studied for decades,
scale-up of algae-based wastewater treatment is still technically challenging. Currently, it seems that high rate algal ponds (HRAPs), waste stabilization ponds
(WSPs), and algal turf scrubbers (ATSs) are available technologies for scale-up.
However, long water retention time requiring large land area is a major drawback of
these technologies.
This chapter provides information on state-of-the-art technologies and environmentally safe tools for wastewater treatment and subsequent biofuel production from
microalgae. Knowledge gaps are also identified, and future directions of eco-friendly
tools using algae for sustainable wastewater treatment are addressed.
2 History of Microalgae for Wastewater Treatment
The history of the commercial use of microalgae for wastewater treatment started
75 years ago in the early stage of wastewater treatment processes (Abdel-Raouf et al.
2012). A low-cost and environment-friendly algal treatment is an effective method to
treat or remediate the industrial wastewater with high N and P concentrations, and
some of algal species can assimilate heavy metal pollutants and toxic organic
chemicals to some extent (De-Bashan and Bashan 2010) (Table 12.1).
2.1 Biodegradation of Nutrients
2.1.1 Removal of Nitrogen and Phosphorus
Eukaryotic algae have shown their ability to remove N and P, about 90% of
inorganic N and 80% of inorganic P, from wastewater. Many parameters (e.g., biotic
factor, pH, temperature, and light) affect algal nutrient removal, and thus nutrient
removal efficiencies are different depending on wastewater characteristics. In addition, the initial biomass concentration is critical for designing the algae-based
wastewater treatment.
2.1.2 Reduction of Biochemical and Chemical Oxygen Demands
Microalgal species are used to remove organic matters (i.e., biochemical and chemical oxygen demands [BOD and COD]) in wastewater (An et al. 2003; Kong et al.
2010). Improved BOD and COD removal efficiency by algae, which is found
commonly, is associated with food/microorganism (F/M) ratio, typically optimum
F/M ratio range was 0.05–0.1 (Choi and Lee 2012); however, F/M ratio over 0.2
decreases BOD and COD removal less than 80%. It is suggested that F/M ratio can
be a key parameter for algal biodegradation of organic matter in wastewater.
12 Microalgae: An Eco-friendly Tool for the Treatment of Wastewaters for. . .
285
scale-up of algae-based wastewater treatment is still technically challenging. Currently, it seems that high rate algal ponds (HRAPs), waste stabilization ponds
(WSPs), and algal turf scrubbers (ATSs) are available technologies for scale-up.
However, long water retention time requiring large land area is a major drawback of
these technologies.
This chapter provides information on state-of-the-art technologies and environmentally safe tools for wastewater treatment and subsequent biofuel production from
microalgae. Knowledge gaps are also identified, and future directions of eco-friendly
tools using algae for sustainable wastewater treatment are addressed.
2 History of Microalgae for Wastewater Treatment
The history of the commercial use of microalgae for wastewater treatment started
75 years ago in the early stage of wastewater treatment processes (Abdel-Raouf et al.
2012). A low-cost and environment-friendly algal treatment is an effective method to
treat or remediate the industrial wastewater with high N and P concentrations, and
some of algal species can assimilate heavy metal pollutants and toxic organic
chemicals to some extent (De-Bashan and Bashan 2010) (Table 12.1).
2.1 Biodegradation of Nutrients
2.1.1 Removal of Nitrogen and Phosphorus
Eukaryotic algae have shown their ability to remove N and P, about 90% of
inorganic N and 80% of inorganic P, from wastewater. Many parameters (e.g., biotic
factor, pH, temperature, and light) affect algal nutrient removal, and thus nutrient
removal efficiencies are different depending on wastewater characteristics. In addition, the initial biomass concentration is critical for designing the algae-based
wastewater treatment.
2.1.2 Reduction of Biochemical and Chemical Oxygen Demands
Microalgal species are used to remove organic matters (i.e., biochemical and chemical oxygen demands [BOD and COD]) in wastewater (An et al. 2003; Kong et al.
2010). Improved BOD and COD removal efficiency by algae, which is found
commonly, is associated with food/microorganism (F/M) ratio, typically optimum
F/M ratio range was 0.05–0.1 (Choi and Lee 2012); however, F/M ratio over 0.2
decreases BOD and COD removal less than 80%. It is suggested that F/M ratio can
be a key parameter for algal biodegradation of organic matter in wastewater.
12 Microalgae: An Eco-friendly Tool for the Treatment of Wastewaters for. . .
285