Phycoremediation by High-Rate Algal Ponds (HRAPs) - Biotechnological Applications of Microalgae - page 185

reported that wastewater provides an ideal medium for potential microbial growth
(Kong et al . , 2010; Cho et al . , 2011; Christenson and Sims, 2011; Park et al . , 2011a;
Pittman et al . , 2011; Rawat et al . , 2011), irrespective of anaerobic or aerobic waste-
water treatment (Abeliovich, 1986).
12.3 PHYCOREMEDIATION
The term phycoremediation was coined by John (2000) to refer to the remediation
of water carried out by algae. Microalgae have high efficacy in wastewater treatment
and can offer possible solutions for environmental problems (Lau et al . , 1994; Craggs
et al . , 1997; Korner and Vermaat, 1998; Harun et al . , 2010). Microalgae are eukary-
otic, autotrophic microorganisms that can adapt to almost any aquatic environment
(including wastewater) and produce biomass rich in various nutrients and minerals.
Microalgae vary greatly in protein (10% to 53%), carbohydrate (10% to 16%), lipid
(15% to 55%), and mineral (5%) constituents (Xu et al . , 2006).
Phycoremediation of wastewater (domestic or industry) refers to any large-scale
utilization of (desirable) microalgae for the removal of pollutants or biotransfor-
mation of hazardous or harmful organic chemical compounds to nonhazardous
end-products, xenobiotics, and removal of pathogens from wastewater. Biomass
consumes considerable amounts of nutrients from freely available sources, such
as wastewater rich in organic nutrients, inorganic chemicals, and CO 2 from waste
and exhaust streams (Olguin, 2003), that can accelerate the microalgal biomass
propagation (45% to 60% microalgae by dry weight), nucleic acids, and phos-
pholipids. Nutrient removal can be further increased by ammonia stripping or
phosphorus precipitation due to the increase in the pH associated with photosyn-
thesis (Laliberté et al . , 1994; Oswald, 2003; Hanumantha Rao et al . , 2011; Rawat
et al . , 2011).
Phycoremediation as a biological tertiary treatment, performed typically to treat
secondary municipal wastewater, has been the focus of research during the past few
decades (Oswald and Gotaas, 1957). High-rate algal ponds (HRAPs) for wastewa-
ter treatment are very effective, in that HRAP-cultivated microalgal cultures can
assimilate huge amount of nutrients, resulting in a reduction in BOD and chemi-
cal oxygen demand (COD). Microalgae are regarded as the most versatile solution
among biological wastewater treatment processes. Domestic wastewater contains the
majority of nutrients such as nitrogen and phosphorous that directly and indirectly
support microalgal productivity and maintain the biomass at levels high enough to
achieve nutrient removal efficiently in wastewater systems. The application of micro-
algae in wastewater treatment for reducing odor, coloring, nitrate, nitrite, phosphate,
ammonia, TDS, TSS, BOD, and increasing pH and heavy metal absorption has been
performed over the past few years. Effluent-treated microalgal biomass can be used
for various purposes (Munoz and Guieysse, 2006). Recently, Kumar et al . (2011)
studied high-rate algal pilot plant cultivated Chlorella vulgaris in confectionery
effluent wastewater treatment, wherein harvested biomass was used for enzymatic
and nonenzymatic antioxidant potential studies. However, the enriched microalgal
biomass needs to be harvested at low cost using a cost-effective nutrient removal
system. These are still in the infancy stage.