title: Nitrate effects on chromate reduction in a methane-based biofilm.
abstract: The effects of nitrate (NO3-) on chromate (Cr(VI)) reduction in a membrane biofilm reactor (MBfR) were studied when CH4was the sole electron donor supplied with a non-limiting delivery capacity. A high surface loading of NO3-gave significant and irreversible inhibition of Cr(VI) reduction. At a surface loading of 500 mg Cr/m2-d, the Cr(VI)-removal percentage was 100% when NO3-was absent (Stage 1), but was dramatically lowered to < 25% with introduction of 280 mg N m-2-d NO3-(Stage 2). After ∼50 days operation in Stage 2, the Cr(VI) reduction recovered to only ∼70% in Stage 3, when NO3-was removed from the influent; thus, NO3-had a significant long-term inhibition effect on Cr(VI) reduction. Weighted PCoA and UniFrac analyses proved that the introduction of NO3-had a strong impact on the microbial community in the biofilms, and the changes possibly were linked to the irreversible inhibition of Cr(VI) reduction. For example, Meiothermus, the main genus involved in Cr(VI) reduction at first, declined with introduction of NO3-. The denitrifier Chitinophagaceae was enriched after the addition of NO3-, while Pelomonas became important when nitrate was removed, suggesting its potential role as a Cr(VI) reducer. Moreover, introducing NO3-led to a decrease in the number of genes predicted (by PICRUSt) to be related to chromate reduction, but genes predicted to be related to denitrification, methane oxidation, and fermentation increased.
authors.affiliation: Department of Environmental Engineering, College of Environmental and Resource Science, Zhejiang University, Hangzhou, China.
authors.forename: Liang
authors.initials: L
authors.lastname: Zhong
authors.affiliation: Department of Environmental Engineering, College of Environmental and Resource Science, Zhejiang University, Hangzhou, China; Zhejiang Province Key Lab Water Pollut Control & Envi, Zhejiang University, Hangzhou, Zhejiang, China.
authors.forename: Chun-Yu
authors.initials: CY
authors.lastname: Lai
authors.affiliation: Department of Environmental Engineering, College of Environmental and Resource Science, Zhejiang University, Hangzhou, China.
authors.forename: Ling-Dong
authors.initials: LD
authors.lastname: Shi
authors.affiliation: Department of Environmental Engineering, College of Environmental and Resource Science, Zhejiang University, Hangzhou, China.
authors.forename: Kai-Di
authors.initials: KD
authors.lastname: Wang
authors.affiliation: Department of Environmental Engineering, College of Environmental and Resource Science, Zhejiang University, Hangzhou, China.
authors.forename: Yu-Jie
authors.initials: YJ
authors.lastname: Dai
authors.affiliation: Department of Environmental Engineering, College of Environmental and Resource Science, Zhejiang University, Hangzhou, China.
authors.forename: Yao-Wei
authors.initials: YW
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin 150090, China. Electronic address: mafang@hit.edu.cn.
authors.forename: Fang
authors.initials: F
authors.lastname: Ma
authors.affiliation: Biodesign Swette Center for Environmental Biotechnology, Arizona State University, P.O. Box 875701, Tempe, AZ 85287-5701, USA.
authors.forename: Bruce E
authors.initials: BE
authors.lastname: Rittmann
authors.affiliation: Department of Environmental Engineering, College of Environmental and Resource Science, Zhejiang University, Hangzhou, China; Zhejiang Province Key Lab Water Pollut Control & Envi, Zhejiang University, Hangzhou, Zhejiang, China.
authors.forename: Ping
authors.initials: P
authors.lastname: Zheng
authors.affiliation: Department of Environmental Engineering, College of Environmental and Resource Science, Zhejiang University, Hangzhou, China; Zhejiang Province Key Lab Water Pollut Control & Envi, Zhejiang University, Hangzhou, Zhejiang, China; State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin 150090, China. Electronic address: zhaohp@zju.edu.cn.
authors.forename: He-Ping
authors.initials: HP
authors.lastname: Zhao
mesh_terms: D018441:Biofilms; D019149:Bioreactors; D002840:Chromates; D008697:Methane; D009566:Nitrates; D010084:Oxidation-Reduction
chemical_list: D002840:Chromates; D009566:Nitrates; D008697:Methane
keywords: Chromate reduction; Membrane biofilm reactor; Methane; Microorganism; Nitrate