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 eukary­otic, 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 biotransfor­mation 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 CO2 from waste and exhaust streams (Olguin, 2003), that can accelerate the microalgal biomass propagation (45% to 60% microalgae by dry weight), nucleic acids, and phos­pholipids. Nutrient removal can be further increased by ammonia stripping or phosphorus precipitation due to the increase in the pH associated with photosyn­thesis (Laliberte 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 wastewa­ter treatment are very effective, in that HRAP-cultivated microalgal cultures can assimilate huge amount of nutrients, resulting in a reduction in BOD and chemi­cal 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 micro­algae 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.

The application and advantages of phycoremediation include (Olguin, 2003)

1. Nutrient removal from both municipal and industrial wastewater or effluent enriched with high organic matter

2. Nutrient and xenobiotic compound removal with the aid of algae-based biosorbents

3. Efficient treatment of acidic and heavy-metal wastewater

4. Increasing oxygenation of the atmosphere

5. CO2 sequestration

6. Improving effluent quality

7. Transformation and degradation of xenobiotics

8. Biosensing of toxic compounds by algae