title: Membrane installation for enhanced up-flow anaerobic sludge blanket (UASB) performance.
abstract: It is postulated that up-flow anaerobic sludge blanket (UASB) reactor efficiency can be enhanced by a membrane immersed in the reactor to operate it as an anaerobic membrane bioreactor (AnMBR) for low-strength wastewater treatment. This postulate was tested by comparing the performance with and without a hollow fiber microfiltration membrane module immersed in UASB reactors operated at two specific organic loading rates (SOLR). Results showed that membrane filtration enhanced process performance and stability, with over 90% total organic carbon (TOC) removal consistently achieved. More than 91% of the TOC removal was achieved by suspended biomass, while less than 6% was removed by membrane filtration and digestion in the membrane attached biofilm during stable AnMBRs operation. Although the membrane and its biofilm played an important role in initial stage of the high SOLR test, linear increased TOC removal by bulk sludge mainly accounted for the enhanced process performance, implying that membrane led to enhanced biological activity of the suspended sludge. The high retention of active fine sludge particles in suspension was the main reason for this significant improvement of performance and biological activity, which led to decreased SOLR with time to a theoretical optimal level around 2  g COD/g MLVSS·d and the establishment of a microbial community dominated by Methanothrix-like microbes. It was concluded that UASB process performance can be enhanced by transforming such to AnMBR operation when the loading rate is too high for sufficient sludge retention, and/or when the effluent water quality demands are especially stringent.
authors.affiliation: Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China. yinliu@iue.ac.cn
authors.forename: Yin
authors.initials: Y
authors.lastname: Liu
authors.forename: Kaisong
authors.initials: K
authors.lastname: Zhang
authors.forename: Rune
authors.initials: R
authors.lastname: Bakke
authors.forename: Chunming
authors.initials: C
authors.lastname: Li
authors.forename: Haining
authors.initials: H
authors.lastname: Liu
mesh_terms: D000693:Anaerobiosis; D018441:Biofilms; D019149:Bioreactors; D002244:Carbon / Q000302:isolation & purification / Q000378:metabolism; D005374:Filtration / Q000295:instrumentation / Q000379:methods*; D008697:Methane / Q000378:metabolism; D012722:Sewage / Q000382:microbiology*; D014865:Waste Disposal, Fluid / Q000295:instrumentation / Q000379:methods*; D062065:Wastewater / Q000737:chemistry / Q000382:microbiology
chemical_list: D002244:Carbon; D008697:Methane; D012722:Sewage; D062065:Wastewater
keywords: AnMBR; Anaerobic digestion; Biofilm; HAnMBR; HUASB; LAnMBR; LUASB; Low-strength wastewater; MLSS; Membrane filtration; SMA; SOLR; Sludge loading rate; Specific methanogenic activity; UASB; anaerobic membrane bioreactor; high load AnMBR; high load UASB; low load AnMBR; low load UASB; mixed liquor suspended solids; specific methanogenic activity; specific organic loading rate; upflow anaerobic sludge blanket