Prospects, recent advancements and challenges of different wastewater streams for microalgal cultivation.

Microalgae are recognized as one of the most powerful biotechnology platforms for many value added products including biofuels, bioactive compounds, animal and aquaculture feed etc. However, large scale production of microalgal biomass poses challenges due to the requirements of large amounts of water and nutrients for cultivation. Using wastewater for microalgal cultivation has emerged as a potential cost effective strategy for large scale microalgal biomass production. This approach also offers an efficient means to remove nutrients and metals from wastewater making wastewater treatment sustainable and energy efficient. Therefore, much research has been conducted in the recent years on utilizing various wastewater streams for microalgae cultivation. This review identifies and discusses the opportunities and challenges of different wastewater streams for microalgal cultivation. Many alternative routes for microalgal cultivation have been proposed to tackle some of the challenges that occur during microalgal cultivation in wastewater such as nutrient deficiency, substrate inhibition, toxicity etc. Scope and challenges of microalgal biomass grown on wastewater for various applications are also discussed along with the biorefinery approach.

Assessment of municipal wastewaters at various stages of treatment process as potential growth media for Chlorella sorokiniana under different modes of cultivation.

Wastewater utilization for microalgal biomass production is potentially the most economical route for its fuel and feed applications. In this study, suitability of various wastewater streams within a domestic wastewater treatment plant was evaluated for microalgal cultivation. Pre-treatment methods were evaluated to minimize bacterial load. Biomass, cell physiology, nutrient removal efficiencies and biochemical constituents of Chlorella sorokiniana were investigated in influent (INF) and anaerobic tank centrate (AC) under mixotrophic (Mixo) and heterotrophic (Hetero) cultivation. Promising biomass (77.14mgL-1d-1), lipid (24.91mgL-1d-1), protein (22.36mgL-1d-1) and carbohydrate (20.10mgL-1d-1) productivities were observed in Mixo AC with efficient ammonium (94.29%) and phosphate (83.30%) removal. Supplementation of urea at a concentration of 1500mgL-1 further enhanced biomass (162.50mgL-1d-1), lipid (24.91mgL-1d-1), protein (22.36mgL-1d-1) and carbohydrate (20.10mgL-1d-1) productivities in Mixo AC. Urea supplemented mixotrophic cultivation of microalgae in AC is developed as a biomass production strategy.