Emerging trends in sewage sludge pretreatment: Enhancing treatment efficiency and sustainable waste management

Sewage sludge produced from the treatment of municipal wastewater and other liquid wastes requires proper management to diminish environmental impacts. Pretreatment of sewage sludge aims to improve the efficiency of subsequent treatment processes and enhance the quality of treated effluent. This review provides an overview of recent trends and developments in pretreatment techniques for sewage sludge and highlights the significance of anaerobic digestion in its treatment. Pretreatment methods include physical, chemical, combined, and biological processes designed to remove or reduce contaminants in the sludge. Anaerobic digestion reduces the organic content of sludge, producing biogas and eliminating pathogens, thereby minimizing health risks associated with sludge disposal. Additionally, anaerobic digestion generates stabilized bio-solids, which can be used as nutrient-rich soil amendments. However, sludge waste often has a lower methane yield due to its composition, a challenge that can be addressed with various pretreatment techniques. This comprehensive review discusses the constituents of sewage sludge, recent trends in its pretreatment methods, and their biogas potential. Furthermore, it emphasizes the conversion of sewage sludge into valuable products such as biogas, bio-fertilizers, and other waste-to-value products, showcasing the sustainable management and utilization of sewage sludge.