**6. Future perspective and conclusion**

In developing countries, almost 80% of the wastewater is discharged untreated to land or waterbodies, which may lead to serious health risks and environmental issues like eutrophication. Due to rapid industrialization and the global population, the requirement for fresh water and wastewater discharge is increasing daily. Conventional sewage treatment processes are not much desired due to their inability to reduce the nutrient concentration to acceptable levels in wastewater.

Microalgae-bacteria-based consortium to recover nutrients from wastewater is an alternative to conventional processes as both organisms establish a symbiotic relationship. Bacteria utilize the organic matter from sewage wastewater and produce CO2 as a by-product. The microalgae, in turn, utilize the bacteria discharges CO2 and produce carbohydrates and O2, required for biomass production, and the latter serves as a terminal electron acceptor for bacterial respiration.

Integrating microalgae-based biorefinery is a promising approach with dual benefits, i.e., wastewater treatment and high-value biomass generation for biofuel production to make the wastewater treatment sustainable, eco-friendly, and economically viable. The microalgae in sewage wastewater treatment have a tri purpose of bioenergy production from generated microalgal biomass, phycoremediation, and organic farming with much less damage to soils and human health than chemical fertilizers.
