CEST2025

The increasing generation of sewage sludge from urban wastewater treatment plants poses both environmental challenges and opportunities for resource recovery. This study explores the valorization of secondary sludge as a nutrient source for the cultivation of the microalgae Chlorella sorokiniana, with the aim of recovering nitrogen, phosphorus, and proteins. A combined alkaline and ultrasonic pretreatment was applied to enhance the solubilization of organic matter and intracellular compounds. The treated sludge extract was subsequently used as a cultivation medium under mixotrophic conditions. Growth performance and nutrient removal efficiency were assessed through pigment analysis and monitoring of key parameters such as ammonium, nitrate, phosphate, and chemical oxygen demand. The findings support the potential of integrated sludge pretreatment and microalgal cultivation as a sustainable strategy within the framework of circular bioeconomy, offering dual benefits of waste reduction and biomass production with added value.