title: An Exploratory Study on the Pathways of Cr (VI) Reduction in Sulfate-reducing Up-flow Anaerobic Sludge Bed (UASB) Reactor.
abstract: Electroplating wastewater contains both Cr (VI) and sulfate. So Cr (VI) removal under sulfate-rich condition is quite complicated. This study mainly investigates the pathways for Cr (VI) removal under biological sulfate-reducing condition in the up-flow anaerobic sludge bed (UASB) reactor. Two potential pathways are found for the removal of Cr (VI). The first one is the sulfidogenesis-induced Cr (VI) reduction pathway (for 90% Cr (VI) removal), in which Cr (VI) is reduced by sulfide generated from biological reduction of sulfate. The second one leads to direct reduction of Cr (VI) which is utilized by bacteria as the electron acceptor (for 10% Cr (VI) removal). Batch test results confirmed that sulfide was oxidized to elemental sulfur instead of sulfate during Cr (VI) reduction. The produced extracellular polymeric substances (EPS) provided protection to the microbes, resulting in effective removal of Cr (VI). Sulfate-reducing bacteria (SRB) genera accounted for 11.1% of the total bacterial community; thus they could be the major organisms mediating the sulfidogenesis-induced reduction of Cr (VI). In addition, chromate-utilizing genera (e.g. Microbacterium) were also detected, which were possibly responsible for the direct reduction of Cr (VI) using organics as the electron donor and Cr (VI) as the electron acceptor.
authors.affiliation: School of Natural and Applied Sciences, Northwestern Polytechnical University, Xi'an, China.|Department of Civil and Environmental Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.
authors.forename: Jin
authors.initials: J
authors.lastname: Qian
authors.affiliation: Department of Civil and Environmental Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.|Wastewater Treatment Laboratory, FYT Graduate School, The Hong Kong University of Science and Technology, Nansha, Guangzhou, China.
authors.forename: Li
authors.initials: L
authors.lastname: Wei
authors.affiliation: Department of Civil and Environmental Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.
authors.forename: Rulong
authors.initials: R
authors.lastname: Liu
authors.affiliation: School of Chemistry &Environment, South China Normal University, Guangzhou, China.
authors.forename: Feng
authors.initials: F
authors.lastname: Jiang
authors.affiliation: Beijing University of Civil Engineering and Architecture, Beijing, China.
authors.forename: Xiaodi
authors.initials: X
authors.lastname: Hao
authors.affiliation: Department of Civil and Environmental Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.|Water Technology Center, The Hong Kong University of Science and Technology, Hong Kong, China.|Hong Kong Branch of Chinese National Engineering Research Center for Control &Treatment of Heavy Metal Pollution, The Hong Kong University of Science and Technology, Hong Kong, China.|Wastewater Treatment Laboratory, FYT Graduate School, The Hong Kong University of Science and Technology, Nansha, Guangzhou, China.
authors.forename: Guang-Hao
authors.initials: GH
authors.lastname: Chen
mesh_terms: D001421:Bacteria, Anaerobic / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D019149:Bioreactors / Q000382:microbiology*; D002857:Chromium / Q000737:chemistry* / Q000378:metabolism; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004595:Electroplating; D007700:Kinetics; D010084:Oxidation-Reduction; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D015203:Reproducibility of Results; D017422:Sequence Analysis, DNA; D012722:Sewage / Q000737:chemistry / Q000382:microbiology*; D013431:Sulfates / Q000737:chemistry* / Q000378:metabolism; D013455:Sulfur / Q000737:chemistry / Q000378:metabolism; D014865:Waste Disposal, Fluid / Q000379:methods*
chemical_list: D004269:DNA, Bacterial; D012336:RNA, Ribosomal, 16S; D012722:Sewage; D013431:Sulfates; D002857:Chromium; C074702:chromium hexavalent ion; D013455:Sulfur