This　study　explored　the　application　of　shale　ceramsite　(SC)　overlaid　onto　active　alumina　(AA)　to　function　as　a　double-layer　substrate　in　tidal　flow　constructed　wetland　(TFCW,　SC-AA-TFCW)　for　decentralized　domestic　sewage　treatment　This　was　compared　to　AA　or　SC　substrate　alone　(AA-TFCW　or　SC-TECW)　for　nitrogen　removal,　variation　of　dissolved　oxygen　and　porosity　in　TECWs,　as　well　as　structure　of　bacterial　communities　at　varied　hydraulic　load　(HL)　of　0.204-2.448　m(3)/m(2)　d　with　time　ratio　of　the　wet　and　dry　phase　of　3:1.　The　results　demonstrate　that　SC-AA-TFCW　removed　86%　NH4+-N　and　79%　total　nitrogen　at　HL　of　0.612　m(3)/m(2)　d,　which　was　better　than　AA-TFCW(76%)　or　SC-TFCW(49%).　The　higher　nitrogen　removal　performance　in　SC-AA-TECW　was　mainly　attributed　to　enhanced　oxygen　transportation　due　to　non-uniform　flow　field　and　irregular　gap　distribution　in　layered　structure,　as　well　as　less　pore　blockage　during　long-term　operation.　Denitrifying　bacteria　including　Dechloromonas,　Acidovorax,　Chryseobacterium　and　Thermomonas　species　took　up　32%　of　the　microbiome　in　SC-AA-TFCW,　which　was　higher　than　in　AA-TFCW　(17%)　and　SC-TFCW　(7.7%).　This　study　highlighted　the　importance　of　layered　structures　and　determined　an　optimal　HL　of　TFCW　to　achieve　an　efficient　and　stable　nitrogen　removal　for　domestic　sewage　treatment.　(C)　2019　Elsevier　B.V.　All　rights　reserved.