Sulfate reduction may inhibit methane production during anaerobic treatment of sulfate-containing wastewater. The purpose of this study was to establish direct interspecies electron transfer (DIET) between iron-reducing bacteria (IRB) and methanogens with Fe oxides to alleviate the inhibition of sulfate in anaerobic digestion. Effects of ferrihydrite on the digestion performances with various sulfate concentrations (1034 mg L⁻¹, 1551 mg L⁻¹, and 3171 mg L⁻¹) were investigated in this study. Results showed that addition of ferrihydrite decreased methane production but enhanced sulfate reduction (P < 0.05) at low concentrations of influent sulfate since ferrihydrite alleviated the inhibition to cause sulfate reducing bacteria to outcompete methanogens for capturing electrons. When increasing the influent sulfate to 3171 mg L⁻¹ with a COD/SO₄²⁻ ratio of 0.54, ferrihydrite increased methane production (P < 0.05) because IRB enriched with ferrihydrite might couple with methanogens to cause DIET for methanogenesis. Ferrihydrite increased the secretion of humic acid-like substances of EPS to enhance electron transfer capacity. During the process, conductive iron minerals such as pyrite were formed to promote the DIET. Accordingly, microbial community analysis revealed that IRB (e.g. Clostridium) were enriched in the presence of ferrihydrite.

中文翻译：

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亚硫酸氢盐对UASB反应器处理高硫酸盐废水甲烷化反应的影响：反应器性能和微生物群落

硫酸盐还原可抑制含硫酸盐废水的厌氧处理过程中甲烷的产生。这项研究的目的是建立还原铁细菌（IRB）和产甲烷菌与Fe氧化物之间的直接种间电子转移（DIET），以减轻厌氧消化中硫酸盐的抑制作用。对消化的表演用硫酸各种浓度（1034毫克的L水铁矿的影响^-1，1551毫克的L ^-1，和3171毫克的L ^-1在本研究中进行了调查）。结果表明，加入三水铁矿可降低甲烷生成量，但可提高硫酸盐还原率（P<0.05）在低浓度的进水硫酸盐中，因为亚铁酸盐减轻了抑制作用，使还原硫酸盐的细菌胜过产甲烷菌以捕获电子。当将进水硫酸盐增加到3171 mg L ^-1且COD / SO ₄ ^2-的比率为0.54时，亚铁水合物增加了甲烷产量（P <0.05），因为富含亚铁水合物的IRB可能与产甲烷菌结合而导致DIET产甲烷。水铁矿可增加EPS的腐殖酸样物质的分泌，从而增强电子转移能力。在此过程中，形成了导电铁矿物质（例如黄铁矿）以促进DIET。因此，微生物群落分析表明IRB（如梭菌））在三水铁矿存在下富集。