Compared　to　methane,　volatile　fatty　acids　(VFAs)　offer　superior　economic　benefits.　Therefore,　the　extraction　of　VFAs　from　waste　activated　sludge　(WAS)　during　anaerobic　digestion　(AD)　has　garnered　significant　attention.　This　study　demonstrates　that　the　NO2−-PAA　combined　treatment　technology　effectively　promotes　the　accumulation　of　total　volatile　fatty　acids　(TVFAs)　in　the　AD　system,　achieving　a　maximum　VFAs　accumulation　of　1551.2　±　6.6　mg　COD/L　and　an　acidification　rate　(ηa)　of　47.8　±　1.9　%.　Mechanistic　study　indicates　that　the　reactive　oxygen/nitrogen　species　(ROS/RNS,　including　CH3C(O)OO·,·OH,·O2−,　1O2　and　NO·)　induced　by　the　combined　treatment　act　synergistically　to　damage　cell　membranes,　augment　membrane　permeability,　disrupt　protein　structures,　and　stimulate　lipid　peroxidation.　This　significantly　weakens　the　attraction　between　microorganisms　in　WAS,　providing　the　first　mechanistic　explanation　of　how　it　overcomes　the　energy　barrier　of　WAS　dispersion　under　NO2−-PAA　exposure　(extended　Derjaguin-Landau-Verwey-Overbeek　(XDLVO)　theory).　16　S　rDNA　and　metagenomic　analyses　confirmed　that　NO2−-PAA　combined　treatment　promoted　the　selective　enrichment　of　hydrolytic-acidogenic　bacteria,　particularly　Petrimonas　(27.7　%)　and　Macellibacteroides　(17.0　%).　In　addition,　the　increased　abundance　of　VFAs　biosynthesis-related　genes　and　decreased　abundance　of　methanogenic　genes　contribute　to　VFAs　accumulation.　Enhanced　regulation　of　Quorum　Sensing　(QS)　and　Two-Component　Systems　(TCS)　gene　clusters　improved　microbial　adaptation　to　NO2−-PAA　stress.　This　study　elucidated　the　synergistic　effects　of　NO2−-PAA　combined　treatment　on　VFAs　extraction　from　the　perspectives　of　interface　interactions,　functional　potential,　oxidative　stress,　and　adaptive　mechanisms,　and　provided　promising　technical　solutions　for　optimizing　WAS　carbon　flux　and　efficient　VFAs　recovery.　©　2025　Elsevier　Inc.