Dual-functional FeMgAl-LDH/peroxydisulfate system for simultaneous carbon and phosphorus recovery from sludge...

The recovery of short-chain fatty acids (SCFAs) and phosphorus (P) from waste activated sludge (WAS) anaerobic fermentation is a promising sustainable strategy for resource valorization. However, its practical application has been hindered by low SCFAs yield and complex P recovery processes. In this study, a FeMgAl-layered double hydroxide (LDH)/peroxydisulfate (PDS) co-treatment strategy was proposed to overcome these challenges. FeMgAl-LDH effectively activated PDS to generate hydroxyl radicals (•OH) and sulfate radicals (SO₄^•-), leading to the disruption of extracellular polymeric substance and a 369.31% increase in dissolved organic matter (measured by SCOD), thus providing abundant substrates for SCFAs production. Furthermore, the system enhanced hydrolytic/acidogenic enzyme activity, enriched functional microbial communities, and activated acidogenic metabolic pathways. Consequently, SCFAs production increased by 7.90-fold (4598.56 vs. 582.27 mg COD/L), and the acetate proportion rose from 23.74% to 66.03%. Simultaneously, the co-treatment facilitated the release of both organic P and Fe-bound P, achieving a total P recovery efficiency of 21.28% via FeMgAl-LDH induced ion exchange, surface complexation, electrostatic attraction, and hydrogen bond. When used as a slow-release fertilizer, the recovered P-loaded FeMgAl-LDH increased the fresh weight of ryegrass by 51.02% in pot experiments. Overall, this synergistic strategy provides an innovative and integrated solution for simultaneous carbon and P resource recovery from WAS, highlighting its potential for advancing sustainable sludge management and circular bioeconomy practices.