This study leveraged synthesis gas (syngas), a renewable resource attainable through the gasification of biowaste, to achieve efficient chromate removal from water. To enhance syngas transfer efficiency, a membrane biofilm reactor (MBfR) was employed. Long-term reactor operation showed a stable and high-level chromate removal efficiency > 95%, yielding harmless Cr(III) precipitates, as visualised by scanning electron microscopy and energy dispersive X-ray analysis. Corresponding to the short hydraulic retention time of 0.25 days, a high chromate removal rate of 80 µmol/L/d was attained. In addition to chromate reduction, production of volatile fatty acids (VFAs) by gas fermentation was observed. Three sets of batch tests and two groups of batch tests jointly unravelled the mechanisms, showing that biological chromate reduction was primarily driven by VFAs produced from syngas fermentation, whereas hydrogen originally present in the syngas played a minor role. 16 S rRNA gene amplicon sequencing has confirmed the enrichment of syngas-fermenting bacteria (such as ), who performed gas fermentation leading to the synthesis of VFAs, and organics-utilising bacteria (such as ), who utilised VFAs to drive chromate reduction. These findings, combined with batch assays, elucidate the pathways orchestrating synergistic interactions between fermentative microbial cohorts and chromate-reducing microorganisms. The findings facilitate the development of cost-effective strategies for groundwater and drinking water remediation and present an alternative application scenario for syngas.

中文翻译：

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合成气膜生物膜反应器中铬酸盐的生物还原

本研究利用合成气（一种可通过生物废物气化获得的可再生资源）来实现高效去除水中的铬酸盐。为了提高合成气转移效率，采用了膜生物膜反应器（MBfR）。长期反应器运行显示出稳定且高水平的铬酸盐去除效率 > 95%，产生无害的 Cr(III) 沉淀物，如扫描电子显微镜和能量色散 X 射线分析所示。与0.25天的短水力停留时间相对应，获得了80 µmol/L/d的高铬酸盐去除率。除了铬酸盐还原之外，还观察到通过气体发酵产生挥发性脂肪酸（VFA）。三组批次试验和两组批次试验共同揭示了机理，表明生物铬酸盐还原主要是由合成气发酵产生的VFA驱动的，而合成气中原本存在的氢气发挥了次要作用。 16 S rRNA 基因扩增子测序已证实合成气发酵细菌（例如 ）和有机物利用细菌（例如 ）的富集，前者进行气体发酵导致 VFA 的合成，后者利用 VFA 驱动铬酸盐还原。这些发现与批量测定相结合，阐明了发酵微生物群与铬酸盐还原微生物之间协同相互作用的途径。研究结果有助于制定具有成本效益的地下水和饮用水修复策略，并提出了合成气的替代应用场景。