title: Reduced sludge production in a membrane bioreactor by uncoupling metabolism and its effect on phosphorus accumulation in the biomass.
abstract: Due to its limited recycling or reuse, treatment and disposal of excess waste activated sludge has been a major challenge. As a preemptive method, therefore, uncoupling metabolism for reduced sludge production has been investigated recently. In this study, we operated a pilot-scale A2O-membrane bioreactor (MBR) system incorporating an anaerobic sludge holding tank (SHT) in a sludge recycling line to induce uncoupling metabolism, and investigated sludge production and treatment efficiency. After operation for ≥1 year, the Yobsvalue was estimated to be 0.041 g mixed liquor suspended solid (MLSS)/g chemical oxygen demand with 198.7 days of solids retention time (SRT). This Yobsvalue was markedly lower than those reported previously. Since MBR can be operated with a relatively high MLSS and prolonged SRT, the greatest reduction was achieved by combination with uncoupling metabolism. Phosphate fractionation experiments of the MLSS from the pilot MBR suggested the total phosphate content of microorganisms was 47.0 mg P/g mixed liquor volatile suspended solid; 83% higher than that of the activated sludge process and 49% higher than that of the conventional A2O process. Of the increased phosphate contents, that of the acid-insoluble polyphosphate (AISP) fraction was greatest, suggesting that growth inhibition by uncoupling metabolism stimulates AISP synthesis, which can be utilized under growth-limiting conditions.
  
  
  BACKGROUND
  AISP: acid-insoluble polyphosphate; ASP: acid-soluble polyphosphate; BNR: biological nutrients removal; EPS: extracellular polymeric substance; LMH: L/m2h; MBR: membrane bioreactor; OST: oxic-settling-anaerobic; PAO: phosphate accumulation organism; PCA: perchloric acid; SBR: sequencing batch reactor; SHT: sludge holding tank; SRT: solids retention time; TN: total nitrogen; TP: total phosphate; WAS: waste activated sludge.
authors.affiliation: a Technology R&D Institute, Daelim Industrial Co., Ltd. , Seoul , Korea.|b Department of Environmental Engineering , University of Seoul , Seoul , Korea.
authors.forename: Ji-Hun
authors.initials: JH
authors.lastname: Na
authors.affiliation: a Technology R&D Institute, Daelim Industrial Co., Ltd. , Seoul , Korea.
authors.forename: Duck-Hyun
authors.initials: DH
authors.lastname: Nam
authors.affiliation: a Technology R&D Institute, Daelim Industrial Co., Ltd. , Seoul , Korea.|c Department of Civil Engineering , The University of Suwon , Suwon , Gyeonggi-do , Korea.
authors.forename: Byeong-Gon
authors.initials: BG
authors.lastname: Ko
authors.affiliation: c Department of Civil Engineering , The University of Suwon , Suwon , Gyeonggi-do , Korea.
authors.forename: Chae-Young
authors.initials: CY
authors.lastname: Lee
authors.affiliation: a Technology R&D Institute, Daelim Industrial Co., Ltd. , Seoul , Korea.
authors.forename: Ki-Hoon
authors.initials: KH
authors.lastname: Kang
mesh_terms: D018533:Biomass; D019149:Bioreactors; D008567:Membranes, Artificial; D010758:Phosphorus / Q000378:metabolism; D014865:Waste Disposal, Fluid / Q000379:methods*
chemical_list: D008567:Membranes, Artificial; D010758:Phosphorus
keywords: Membrane bioreactor (MBR); phosphate accumulation; polyphosphate fractionation; reduced sludge production; uncoupling metabolism