The　innovative　partial　denitrification/anammox　(PD/A)　process　holds　significant　promise　for　treating　industrial　wastewater　containing　nitrate,　yet　it　may　encounter　the　challenge　of　high　salinity’s　inhibitory　impact.　In　this　study,　a　nitrite-producing　PD　process,　crucial　for　stable　and　efficient　anammox,　was　developed.　The　effect　of　salt　on　performance　was　thoroughly　assessed,　and　metabolic　mechanisms　were　dissected.　Results　showed　that　increasing　salinity　to　20　g/L　enhanced　PD　performance,　raising　the　nitrate-to-nitrite　transformation　ratio　from　63.1　to　70.1%　and　the　nitrite　production　rate　from　27.9　to　39.1　mg　of　N/g　VSS/h.　Salinity　also　promoted　sludge　granulation　by　stimulating　extracellular　polymeric　substance　(EPS)　secretion　to　resist　stress.　Microbial　analysis　revealed　the　enrichment　of　PD　functional　bacterium　(Thauera　phenylacetica).　Gene　expression　analysis　showed　upregulation　of　narGHI　(encoding　NO3--N　reductase)　and　downregulation　of　nirS　(encoding　NO2--N　reductase),　which　contributed　to　improved　PD　performance.　Salinity　stress　had　a　limited　impact　on　carbon　metabolism　and　electron　transport　processes.　The　secretion　of　EPS　acted　as　a　compensatory　mechanism,　alleviating　the　inhibitory　effects　of　salinity　on　these　processes　and　providing　microorganisms　with　an　extended　period　for　self-repair.　Overall,　these　findings　offer　new　insights　into　the　salt-effect　PD　process,　showing　the　potential　for　its　application　in　saline　wastewater　treatment.　©　2025　American　Chemical　Society.