This　study　focused　on　investigating　reactor　performance,　simultaneous　methanogeneis　and　denitrifiction　(SMD)　process　for　treatment　of　a　sulfate　plus　organic　sulfur　-　rich　3,4,5-Triethoxybenzaldehyde　(TMBA)　manufacturing　wastewater　with　variable　COD/TSO42-　(total　sulfate)　ratio　by　micro-electric　field-　zero-valent-iron　(ZVI)　UASB　for　390　days.　The　initial　COD/TSO42-　was　set　as　1.42,　0.9　and　0.5,　respectively　by　manually　introducing　sulfate.　The　experimental　results　indicated　that　micro-electric　field-　zero-valent-iron　UASB　was　an　attractive　integrated　option　for　satisfactory　COD　removal,　nitrate　reduction　and　a　reasonable　methane　yield　rate　even　at　COD/TSO42-　as　low　as　0.9.　Further　declining　the　COD/TSO42-　to　0.5　can　result　in　a　moderate　inhibition　of　SMD　process.　The　behavior　of　organic　S　release　was　not　inhibited　over　the　entire　experimental　period.　Thus,　surprisingly,　sulfate　concentration　in　the　effluent　was　always　higher　than　that　in　the　influent.　In　comparison　with　sludge　sample　at　Day-1,　sludge　at　Day-390　was　characterized　with　high　abundant　Tissierella　Soehngenia,　Anaerolinaceae　and　Brevundimonas　diminuta,　which　played　critical　role　in　promising　performance　in　COD　abatement.　The　relatively　low　abundance　of　sulfate　reducing　bacteria　(SRB)　such　as　Desulfobulbus　and　Desulfomicrobium　can　explain　the　lower　sulfate　reduction　efficiency　in　term　of　high　concentration　of　sulfate　plus　released　from　organic　S-rich　compounds.