Bioreduction of Chromate in a Methane-Based Membrane Biofilm Reactor

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• 作者：Chun-Yu Lai ; Liang Zhong ; Yin Zhang ; Jia-Xian Chen ; Li-Lian Wen ; Ling-Dong Shi ; Yan-Ping Sun ; Fang Ma ; Bruce E. Rittmann ; Chen Zhou ; Youneng Tang ; Ping Zheng ; He-Ping Zhao
• 刊名：Environmental Science & Technology
• 出版年：2016
• 出版时间：June 7, 2016
• 年：2016
• 卷：50
• 期：11
• 页码：5832-5839
• 全文大小：542K
• 年卷期：0
• ISSN：1520-5851

文摘

For the first time, we demonstrate chromate (Cr(VI)) bioreduction using methane (CH₄) as the sole electron donor in a membrane biofilm reactor (MBfR). The experiments were divided into five stages lasting a total of 90 days, and each stage achieved a steady state for at least 15 days. Due to continued acclimation of the microbial community, the Cr(VI)-reducing capacity of the biofilm kept increasing. Cr(VI) removal at the end of the 90-day test reached 95% at an influent Cr(VI) concentration of 3 mg Cr/L and a surface loading of 0.37g of Cr m^–2 day^–1. Meiothermus (Deinococci), a potential Cr(VI)-reducing bacterium, was negligible in the inoculum but dominated the MBfR biofilm after Cr(VI) was added to the reactor, while Methylosinus, a type II methanotrophs, represented 11%–21% of the total bacterial DNA in the biofilm. Synergy within a microbial consortia likely was responsible for Cr(VI) reduction based on CH₄ oxidation. In the synergy, methanotrophs fermented CH₄ to produce metabolic intermediates that were used by the Cr(VI)-reducing bacteria as electron donors. Solid Cr(III) was the main product, accounting for more than 88% of the reduced Cr in most cases. Transmission electron microscope (TEM) and energy dispersive X-ray (EDS) analysis showed that Cr(III) accumulated inside and outside of some bacterial cells, implying that different Cr(VI)-reducing mechanisms were involved.