An Integrated Algal Biorefinery Approach for Wastewater Treatment and Biomass Valorisation

Biological wastewater treatment methods are considered suitable due to several advantages, such as fast processing, low operating cost, less secondary pollution, and overall, environmentally friendly. Microalgae-based wastewater treatment has promising potential, as it not only removes pollutants but also produces valuable biomass, which can be further utilised for various applications. In such systems, microalgae bacterial consortia enhance overall treatment efficiency by promoting symbiotic relationships that improve microbial activity, environmental resilience and enhance pollutant removal efficiency. The current review provides an overview of microalgae cultivation in various wastewater streams, CO₂ sequestration and the utilisation of produced microalgal biomass for multiple applications. The manuscript also focuses on the current role of molecular tools in optimisation and the integration of artificial intelligence to enhance microalgae-based wastewater treatment and management. The manuscript highlights recent progress in wastewater treatment, resource recovery, and the contribution of microalgal biomass to the emerging bioeconomy. To address the identified research gaps and promote the practical implementation of integrated algal systems, future research should focus on the combined approach of algae-based wastewater treatment and the concurrent utilisation of algal biomass. Such research should aim to optimise cultivation conditions and operational strategies to improve nutrient removal efficiency, enhance biomass valorisation for biochar, bioplastics, or feed applications, and ensure sustainable economics. This integrated perspective will help bridge the gap between laboratory-scale studies and integration at a larger scale. Overall, this review aims to guide the effective use of microalgae for treating diverse wastewater streams while supporting efforts to mitigate greenhouse gases and reduce pollution.