Decontamination of industrial wastewater using microalgae integrated with biotransformation of the biomass to green products

Exponential growth in the industrial sector causes the accumulation of toxic wastewater in the ecosystem. The unsafe disposal of such wastewater not only adversely affects the freshwater resources but also pose negative impact on the environment and human health due to the presence of heavy metals, organic/inorganic pollutants, and high amount of nitrogen, phosphorus, and sulfur in it. It demands for the effective wastewater treatment that depends on the effluent quality, industrial process, chemical/energy requirement, economic viability, operational flexibitily, and residual utilization. However, conventional treatment methods are unable to meet all the requriements which demands for the eco-friendly and economical alternatives. Currently, paradigm shift from wastewater treatment and dispoal of, to its utilization in circular biorefinery context is underway. In this context, microalgae-based industrial wastewater is vital option due its pollutant accumulation ability, environmental sustainablity, biorefinery potential, and zero-waste process chain development. This review highlights the characteristics of different industrial effluents and overviews the axenic and binary algal-treatment systems. Economical and technological barriers are the major hindrance in the implementation of algal-based treatment methods; for which biomass valorization has been briefly discussed. This review highlights the need of developing closed-loop integrated processes for wastewater treatment and reuse in sustainable manner. Further research in the development of such schemes specially at large-scale level must be the focus of future studies.