Role of microalgae and activated sludge in the removal of fats, oils, and grease (FOG) in municipal wastewater

• Co-cultivation of microalgae significantly increases biomass productivity. • FOG presence enhances microalgae growth and nutrient removal efficiency. • Activated sludge integration improves pollutant degradation rates effectively. • High FOG removal efficiency, reaching up to 99 %, was achieved. The increasing demand for sustainable wastewater treatment has driven a shift towards resource recovery, focusing on extracting valuable materials such as energy, nutrients, and biomass. A critical challenge in this domain is the effective removal of fats, oils, and grease (FOG), which can obstruct plant infrastructure and impede biological treatment processes. This study explores the potential of two microalgae strains, Chlorella vulgaris, and Phormidium keutzingium , for FOG and nutrient removal in municipal wastewater. Additionally, it examines the growth performance and nutrient removal efficiency of these microalgae strains when cultured both individually and in symbiosis with activated sludge (AS). The research evaluates the biochemical composition of the resulting biomass, including proteins, carbohydrates, and lipids, to determine their feasibility for value-added applications. Results showed that symbiotic cultivation with AS significantly enhances biomass productivity, achieving up to 247.68 ± 0.64 mg/L.day with 99 % FOG removal. This underscores the synergistic relationship between microalgae and AS, which not only optimized pollutants removal but also enhances biomass yield. The findings provide valuable insights into the utilization of microalgae-AS systems for wastewater treatment processes, contributing to reduced energy consumption and enhanced sustainability. By integrating these approaches, the study supports circular economy objectives in wastewater management, paving the way for improved resource recovery and the development of sustainable value chains.