Partial　Denitrification　(PD)　producing　nitrite　for　anammox　may　face　the　issue　of　relatively　high　chemical　oxygen　demand　(COD)　loading　(i.e.,　COD/NO3−-N)　due　to　real　wastewater　being　changed　in　substrate　concentration　and　flowrate.　In　this　study,　three　PD　systems　(R1,　R2,　R3)　with　sodium　acetate　providing　electrons　were　developed　to　investigate　the　influence　of　the　relatively　high　COD/NO3−-N　ratios　(4.0,　6.0,　and　8.0)　on　NO2−-N　production　and　the　subsequent　recoverability.　It　was　found　that　a　relatively　high　NO2−-N　production　with　nitrate-to-nitrite　transformation　ratio　(NTR)　of　74.0%　could　be　still　obtained　despite　COD/NO3−-N　even　improving　to　8.0　under　limited　reaction　time　(10　min)　with　small　nitrate　remaining.　However,　a　deteriorated　nitrite　production　was　observed　with　sufficient　reaction　time　(15　min)　with　NTR　being　lowered　to　19.2%.　Delightedly,　when　reducing　influent　COD/NO3−-N　to　a　normal　level　of　3.0,　PD　with　high　nitrite　production　was　rapidly　achieved　after　suffering　from　a　relatively　high　COD/NO3−-N　(4.0–8.0)　for　130　cycles.　Besides,　it　was　found　the　relatively　high　COD/NO3−-N　had　a　minor　influence　on　the　recoverability　of　PD,　as　evidenced　by　the　close　NTRs.　Microbial　analysis　revealed　the　relative　abundance　of　PD　functional　bacteria,　Thauera,　decreased　under　high　COD/NO3−-N,　while　it　is　still　highly　dominated　in　the　systems,　varying　from　75.1%　in　R1　to　62.8%　in　R3　after　around　110-cycles　recovery.　Furthermore,　it　appeared　that　the　high　pH　(9.1–9.2)　induced　by　sodium　acetate　also　likely　played　a　role　in　maintaining　the　excellent　PD.　Overall,　this　study　demonstrated　the　robustness　and　stability　of　acetate-driven　PD　in　response　to　high　COD/NO3−-N,　further　informing　the　technological　superiority　of　PD　in　supplying　stable　and　efficient　nitrite,　which　provided　solid　technical　support　to　apply　it　with　anammox　for　high-efficient　N　removal.　©　2023　Elsevier　Ltd