Real-time integration of microalgae-based bioremediation in conventional wastewater treatment plants: Current status and prospects

Abstract

With rising water scarcity leading to a risk of affecting 1.69 to 2.37 billion people in urban residents, the treatment and reuse of wastewater have been identified as one of the main avenues to preserve global water resources. Thus, wastewater treatment plants with capacities ranging from 8000 to 200,000 tons/day have been implemented to treat wastewater and discharge effluent with improved quality parameters. Nonetheless, the generation of 160,000–210,000 tons/year of sludge and the requirement for advanced treatment to achieve non-detectable residues are significant concerns for highly effective wastewater treatment. In this context, microalgae with the potential of effective nutrient removal from wastewater streams have been exploited in wastewater treatment at primary, secondary and tertiary treatment stages. Microalgae-based bioremediation generates valuable biomass with metabolites, namely lipids, proteins, and carbohydrates, which could be utilized in the value-added production of biofuels, biofertilizers, etc. Moreover, microalgae integrated wastewater treatment systems would substantially remove residual pollutants, nutrients, and pathogens with high removal efficiencies. Hence, the integration of microalgae into the conventional wastewater treatment process enhances the process sustainability while contributing to the concept of a circular bioeconomy. Nevertheless, limited studies are available on the potential of integrating microalgae in the conventional wastewater treatment plants for real-world applications, although several reviews are available in the literature focusing the microalgae-based wastewater treatment in a general context. Thus, the current review aims to address this gap in the literature by comprehensively assessing the prospects of integrating phycoremediation as the secondary and tertiary/advanced wastewater treatment processes, while discussing the challenges and future perspectives in the research domain.