[Research progress of free ammonia pretreatment in sewage sludge anaerobic fermentation for resource recovery and hazardous substance removal].

Direct anaerobic fermentation of sewage sludge is often inefficient for the recovery of high-value products such as short-chain fatty acids, hydrogen, and methane, as well as for the simultaneous removal of hazardous substances like hydrogen sulfide, pathogens, and antibiotic resistance genes. Free ammonia (FA), a substance that can be obtained internally within wastewater treatment systems, exhibits environmental friendliness, cost-effectiveness, and sustainability, showing promising prospects in achieving sludge resource recovery and hazardous substance removal. This paper systematically reviews the research progress of FA pretreatment in promoting efficient sludge resource recovery and hazardous substance removal through anaerobic fermentation, discusses the key influencing factors of this process, summarizes the underlying mechanisms, and evaluates the comprehensive benefits of FA technology from the perspectives of energy consumption, economics, and environmental impacts. This review aims to provide a theoretical basis and technical reference for developing an economical, environmentally friendly, and sustainable sludge management approach.