Microalgae are drawing significant attention for their role as renewable energy sources and their wide-ranging utility in both industry and agriculture. These single-celled autotrophs help produce oxygen while manufacturing essential biomolecules. Microalgae can survive in multiple environments and effectively remove nutrients from wastewater, positioning them as essential tools in wastewater treatment and circular economy systems. This chapter examines new harvesting techniques and methods to recover important organic compounds from wastewater, thereby emphasizing the combination of microalgae-based treatment systems with bioenergy production. Economically valuable products emerge from wastewater when microbiological processes convert it into sustainable solutions for water scarcity and pollution. This chapter illustrates the innovations in bioprocessing and wastewater treatment by highlighting the significant contributions of microalgae to environmental protection and renewable energy production. Microalgae play an essential role in the bio-circular economy where they support resource recovery and global sustainability initiatives through the ability to connect wastewater management and bioenergy production.