Microalgae-Based Wastewater Treatment as a Circular Solution for Sustainable Resource Recovery

The need for sustainable and circular wastewater management solutions has increased due to water scarcity and environmental degradation. A promising eco-biotechnological strategy that can lower carbon emissions, recover valuable resources, and purify wastewater is microalgae-based systems. Along with important operational parameters that control process efficiency, like light intensity, temperature, CO 2 availability, and hydraulic retention time, the metabolic ability of microalgae to absorb nitrogen, phosphorus, and organic matter is investigated. The energy consumption, carbon footprint, and effluent quality of various cultivation configurations— such as open ponds, photobioreactors, and hybrid systems—are contrasted with conventional wastewater treatment technologies. This chapter examines how microalgae contribute to biomass valorization, nutrient recycling, and pollution removal in order to demonstrate these processes as essential elements of a circular bioeconomy. The benefits of turning energy into biofuels and recovering resources by recycling nutrients into biofertilizers are also highlighted in the chapter. Furthermore, future possibilities for process automation, integration with smart cities, and adherence to international carbon neutrality targets are critically looked at, along with difficulties like biomass collection, contamination hazards, and large-scale feasibility.