Conditions　conducive　to　aerobic　granular　sludge　(AGS)　growth　and　maintenance　are　very　difficult　to　realize　in　continuous-flow　biological　treatment　processes.　This　study　conducted　a　continuous-flow　self-circulating　up-flow　granular　sludge　fluidized　bed　(Zier　process)　treating　real　urban　wastewater　approximately　one　year.　The　substantial　self-circulating　multiple　times　(RSCMT,　8–15　times)　and　up-flow　velocity　(8–15　m/h)　generated　by　aeration,　the　only　power　equipment　in　Zier　process,　facilitated　pollutant　removal,　particle　granulation　and　stabilization.　With　hydraulic　retention　time　of　5　h,　RSCMT　of　9.3–14.4　times　and　chemical　oxygen　demand　(COD)/total　nitrogen　(TN)　ratio　of　5.9　±　1.0,　the　effluent　COD,　ammonia　nitrogen　and　TN　were　28.6　±　7.7,　1.1　±　1.2,　and　13.3　±　1.7　mg/L,　respectively.　The　median　particle　size　was　150–250　μm　and　effluent　suspended　solids　concentration　was　33.4　±　14.5　mg/L.　It　is　unnecessary　to　set　up　sludge　reflux　which　simplifies　the　subsequent　mud-water　separation　facilities.　The　Zier　process　provides　a　new　process　structure　for　implementation　of　continuous-flow　AGS　process.　©　2024　Elsevier　Ltd