Enhancing phosphorus release from sewage sludge via anaerobic treatment: State-of-art progress and future challenges.

[Display omitted] • Fermentation pH needs optimization based on specific inorganic P species. • Pre-treating sludge improves P release but its cost needs assessment. • Organic chelators boost metal-bound P release, but optimal dosage is essential. • Studies on effective P enrichment, release, recovery and utilization are required. Phosphorus recovery and recycling from waste streams is of great significance to achieve a sustainable phosphorus management. Daily discharged sewage contained a considerable content of phosphorus, which offers a promising phosphorus source for its recovery. Biological phosphorus removal technology is the most widely employed process for treating sewage and how to effectively extract and capture phosphorus from excess sludge becomes essential. In this review, the state-of-art progress on enhancing phosphorus release from sewage sludge via anaerobic digestion are systematically summarized and discussed. First, phosphorus species transformation during sewage treatment process and the corresponding extraction and analytical methods were summarized. Also, the different pretreatments methods and their economic costs for applying to sludge treatment was analyzed. Then, phosphorus release pathways and mechanisms from sludge under anaerobic conditions were summarized and the influence of key operation parameters on phosphorus release performance was discussed. Moreover, the current practices and achievements on enhancing phosphorus release via sludge anaerobic digestion were reviewed. Finally, the challenges associated with improving the phosphorus release efficiency from sludge and problems related to the current methods are analyzed, and major directions for future research are proposed. This review may provide valuable information for advancing the research and engineering application of phosphorus capture and recovery technology. [ABSTRACT FROM AUTHOR]