Photobioreactors for wastewater treatment: Recent advances

Sustainability of any waste treatment process depends on how a waste, particularly wastewater, is handled. Wastewater treatment is greatly important for the welfare of the environment and of the Earth in general. An integrative approach involving CO2 sequestration, effluent treatment and biomass generation presents a tremendous potential as the overall process in wastewater treatment and is more sustainable compared with conventional treatment. Research on the use of photobioreactors (PBRs) in wastewater treatment has gained momentum in the past decade. The use of photosynthetic microorganisms, such as microalgae and cyanobacteria, in wastewater treatment offers advantages, such as low energy requirement, biomass production and CO₂sequestration. A large amount of inorganic species present in wastewater promotes the growth of various photosynthetic microorganisms. Removal of high concentrations of inorganic compounds is the major requisite in any wastewater treatment process. Some photosynthetic organisms, especially microalgae, play an important role in a treatment process that involves reduction of nitrates, phosphates and sulfates. Literature suggests that the use of PBRs in wastewater treatment considerably reduces the cost of microalgal cultivation and consequently controls water pollution, conserves freshwater resources and produces useful chemicals and biomass. This chapter focuses on research advances in wastewater treatment using PBRs. Different types of wastewater handled, mixed culture systems (e.g., algal.bacterial system employed in wastewater treatment), types of PBRs used, and bottlenecks that must be addressed to scale-up the wastewater treatment process are discussed.