Fe(II)/Fe(III) cycle actuating a novel process to remove organics in waste pit mud from Maotai: performance and mechanism

In this study, a novel method relying on iron cycle through intermittent aeration was proposed to treat organic matter in waste sealed pit mud from Moutai. Firstly, ferrihydrite was used to verify dissimilatory iron reduction could remove organics from the pit mud; then, the effect of iron cycle induced by intermittent aeration on organics was investigated. The results showed that the removal efficiency of organics was increased by 8.2% after the addition of ferrihydrite, then intermittent aeration was carried out, Fe(II) content decreased after aeration and increased again after stopping aeration, indicating that iron cycle occurred. Additionally, the total chemical oxygen demand (TCOD) content further decreased by18.8% in the reactor with intermittent aeration, significantly higher than that in the unaerated group (11.8%) (p<0.05). Due to the short aeration time (about once a week, 200-500 mL/min, 30 min for each aeration), aerobic microorganisms were undetected, which further indicated that iron cycle enhanced the removal of organics. Finally, intermittent aeration was conducted in the fermentation system of pit mud without adding iron, and the indigenous iron in the pit mud was also recycled. After 31 days, the TCOD removal efficiency increased by 15.6% in the aeration group compared with that in the control group. Microbial analysis showed that some microorganism that degraded refractory organics, including iron reducing bacteria, were enriched in the aerated reactors, such as WCHB1-32, ADurb. bin053-1, Lentimicrobium, and Aneurinibacillus, Geobacteraceae. These indicated that organic matter removal can be enhanced by relying on its indigenous iron

本研究提出了一种依托间歇曝气驱动铁循环的新型方法，用于处理茅台废弃密封窖泥中的有机质。首先，本研究以水铁矿（ferrihydrite）为对象，验证了异化铁还原作用可去除窖泥中的有机质；随后探究了间歇曝气诱导的铁循环对有机质去除的影响。结果显示，添加水铁矿后，有机质去除率提升8.2%；随后开展间歇曝气实验，曝气阶段Fe(II)（亚铁离子）含量下降，停止曝气后再度回升，证实铁循环过程得以发生。此外，间歇曝气反应器内的总化学需氧量（total chemical oxygen demand，TCOD）含量进一步下降18.8%，显著高于未曝气组的11.8%（p<0.05）。由于单次曝气时长较短（约每周1次，流量200~500 mL/min，单次曝气30分钟），体系中未检测到好氧微生物，进一步证实铁循环强化了有机质的去除效果。最后，本研究在未添加外源铁的窖泥发酵体系中开展间歇曝气实验，窖泥自身固有铁也得以循环利用。培养31天后，曝气组的TCOD去除率较对照组提升15.6%。微生物组分析结果显示，曝气反应器中富集了包括铁还原菌在内的多种难降解有机质降解微生物，例如WCHB1-32、ADurb. bin053-1、Lentimicrobium、Aneurinibacillus以及地杆菌科（Geobacteraceae）。上述结果证实，依托窖泥自身固有铁即可强化有机质的去除效果。