Key Laboratory of Water and Sediment Sciences of Ministry of Education, State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, China.
Key Laboratory of Water and Sediment Sciences of Ministry of Education, State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, China.
Sci Total Environ. 2021 Sep 15;787:147400. doi: 10.1016/j.scitotenv.2021.147400. Epub 2021 Apr 29.
Addition of ferric oxides into flocculent anaerobic sludge was reported to enhance methanogenesis due to accelerated direct interspecies electron transfer (DIET) between syntrophic microbial communities. However, it is generally hard to incorporate Fe oxides into already matured anaerobic granular sludge (AGS) due to its special aggregated structure. In this study, a novel method was attempted to fast incorporate Fe oxides into AGS through in-situ microbial formation and immobilization of biogenic Fe oxides. Factors influencing the formation of Fe oxides were investigated and effects of Fe oxides on the acidogenic and methanogenic performance of AGS were assessed. Results showed that AGS could form Fe oxides mainly in the form of magnetite and hematite through biological reduction of Fe(III) oxyhydroxide. A maximum loading amount of 83.9 mg Fe/g MLVSS was obtained at pH 7 after contacting with 60 mM Fe(III) oxyhydroxide. The efficiency of electron donors which supported Fe(III) reduction followed the order of pyruvate > propionate > glucose > acetate > lactate > formate. Addition of electron transfer mediators (ETMs) promoted the formation of Fe oxides and their performance followed the order of AQDS > AQC > humics > FMN > riboflavin. Presence of Fe oxides in AGS (134.6 Fe/g VSS) increased the production of volatile fatty acids (VFAs) and methane by 16.28% and 41.94% respectively, comparing to the control. The enhancement may be attributed to increased conductivity and stimulated growth of exoelectrogens (Clostridium and Anaerolinea) and methanogenic endoelectrogens Methanosaeta in granular sludge which may strengthen direct interspecies electron transfer between syntrophic microbial communities. Overall, this study provides an alternative strategy to improve the digestion performance of AGS through in-situ formation and immobilization of biogenic Fe oxides.
向絮状厌氧污泥中添加氧化铁被报道可以增强产甲烷作用，因为这可以加速共生微生物群落之间的直接种间电子转移（DIET）。然而，由于其特殊的聚集结构，通常很难将 Fe 氧化物掺入已经成熟的厌氧颗粒污泥（AGS）中。在这项研究中，尝试了一种通过生物形成和固定生物源 Fe 氧化物将 Fe 氧化物快速掺入 AGS 的新方法。研究了影响 Fe 氧化物形成的因素，并评估了 Fe 氧化物对 AGS 产酸和产甲烷性能的影响。结果表明，AGS 可以通过 Fe(III)氢氧化物的生物还原主要以磁铁矿和赤铁矿的形式形成 Fe 氧化物。在与 60mM Fe(III)氢氧化物接触后，在 pH 7 时获得了 83.9mg Fe/g MLVSS 的最大负载量。支持 Fe(III)还原的电子供体的效率顺序为丙酮酸>丙酸盐>葡萄糖>乙酸盐>乳酸盐>甲酸盐。添加电子转移介质（ETM）促进了 Fe 氧化物的形成，其性能顺序为 AQDS>AQC>腐殖质>FMN>核黄素。AGS 中 Fe 氧化物的存在（134.6 Fe/g VSS）使挥发性脂肪酸（VFAs）和甲烷的产量分别增加了 16.28%和 41.94%，与对照相比。这种增强可能归因于颗粒污泥中增加的电导率和对好氧菌（梭菌属和产甲烷菌属）和产甲烷菌属内电子供体的刺激生长，这可能加强了共生微生物群落之间的直接种间电子转移。总的来说，这项研究提供了一种通过原位形成和固定生物源 Fe 氧化物来改善 AGS 消化性能的替代策略。
