Institute of Environment Pollution Control and Treatment, Zhejiang University, Hangzhou, 310058, China.
Hangzhou Urban & Rural Construction Design Institute Co., LTD, Hangzhou, 310004, China.
Water Res. 2019 Nov 1;164:114925. doi: 10.1016/j.watres.2019.114925. Epub 2019 Jul 28.
Increasing studies indicate that magnetite addition could accelerate the methanogenesis via enhancing direct interspecies electron transfer (DIET)-based anaerobic syntrophy. However, magnetite is found to run off in continuous bioreactor, and the effect of magnetite loss on syntrophic aggregates is still underreported. In this study, two EGSB reactors (RM with magnetite-enhanced sludge, and RB as a control) were operated to investigate the magnetite behavior in continuous bioreactor and the corresponding response of syntrophic aggregates. Results showed that magnetite in RM was washed out gradually in form of iron ions, and a slightly acidic niche was supposed to be the major cause. Nevertheless, candidate DIET partners like Geobacter and Methanothrix along with syntrophic volatile fatty acids (VFAs)-degrading microbes were enriched in RM. In addition, the improved redox activity of extracellular polymeric substance (EPS), higher sludge conductivity and electron transport activity suggested that the DIET ability of sludge in RM was still enhanced, which favors the syntrophic metabolism of VFAs. Interestingly, syntrophic partners were loosely combined under the condition of high organic loading rate (OLR) in the presence of magnetite, but with gradual loss of magnetite, dense and active anaerobic granular sludge (AGS) was formed in RM. This study provided a comprehensive understanding of magnetite behavior in continuous bioreactor and the response of syntrophic aggregates. The robust DIET-based syntrophy after magnetite adding could favor the high-efficient anaerobic wastewater treatment and resource recovery in the future, and further investigations on magnetite resupply and the mechanism of magnetite enriching candidate DIET partners are recommended.
越来越多的研究表明，添加磁铁矿可以通过增强基于直接种间电子传递（DIET）的厌氧共代谢来加速产甲烷作用。然而，在连续生物反应器中发现磁铁矿会流失，并且磁铁矿损失对共代谢聚集体的影响仍报道较少。本研究采用两个 EGSB 反应器（RM 中添加磁铁矿增强污泥，RB 作为对照）来研究连续生物反应器中磁铁矿的行为及其对共代谢聚集体的相应响应。结果表明，RM 中的磁铁矿逐渐以铁离子的形式流失，而略微酸性的小生境可能是主要原因。然而，像 Geobacter 和 Methanothrix 这样的候选 DIET 伙伴以及共代谢挥发性脂肪酸（VFAs）降解微生物在 RM 中得到了富集。此外，细胞外聚合物（EPS）的氧化还原活性提高、污泥电导率和电子传递活性增加表明 RM 中污泥的 DIET 能力仍然增强，有利于 VFAs 的共代谢。有趣的是，在高有机负荷率（OLR）条件下，磁铁矿的存在使共代谢伙伴松散结合，但随着磁铁矿的逐渐损失，RM 中形成了致密且活跃的厌氧颗粒污泥（AGS）。本研究全面了解了连续生物反应器中磁铁矿的行为及其对共代谢聚集体的响应。添加磁铁矿后基于 DIET 的共代谢增强，有利于未来高效的厌氧废水处理和资源回收，建议进一步研究磁铁矿的补充和磁铁矿富集候选 DIET 伙伴的机制。
