Xu Jingya, Wang Yizhen, Wang Yanzhao, Peng Lai, Xu Yifeng, Yin Hailong, Dong Bin, Dai Xiaohu, Sun Jing
State Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Tongji University, Shanghai, 200092, PR China.
Key Laboratory of Yangtze River Water Environment, School of Environmental Science and Engineering, Tongji University, Shanghai, 200092, PR China.
Water Res X. 2024 Oct 29;25:100273. doi: 10.1016/j.wroa.2024.100273. eCollection 2024 Dec 1.
Dosing iron salts is a widely adopted strategy for sewer odor and corrosion management, and it can affect bioenergy recovery during anaerobic digestion (AD) of sludge in downstream wastewater treatment plants. However, the different impacts of in-sewer iron salt dosing on AD, depending on the types of iron and digestion conditions, remain unclear. Therefore, this study investigated the impact of in-sewer ferrous (Fe(II)) and ferrate (Fe(VI)) dosing on bioenergy recovery in both conventional AD and AD with thermal hydrolysis pretreatment (THP). The results showed that in-sewer Fe(VI) dosing notably enhanced methane production in AD more than in-sewer Fe(II) dosing, with cumulative methane yields of 197.1±1.9 mLCH∙gVSadded for Fe(VI) and 186.5±10.4 mLCH∙gVSadded for Fe(II), respectively. Microbial analyses and iron particle characterizations suggested that the superior promotion with Fe(VI) dosing may be attributed to the smaller particle sizes and higher iron oxide content of Fe(VI) resultant products. This led to a greater enhancement in direct interspecies electron transfer (DIET) between syntrophic bacteria and methanogens, as indicated by the upregulation of and key functional genes involved in CO-utilizing methanogenesis. Additionally, in THP-AD, the methane production enhancement caused by in-sewer iron dosing (35.5 mLCH∙gVSadded) exceeded that in conventional AD (26.9 mLCH∙gVSadded), although organic degradation during THP was unaffected. As THP-AD gains popularity for improved bioenergy recovery from sludge, our findings suggest that in-sewer iron dosing supports this advancement. Furthermore, in-sewer Fe(VI) dosing appears more promising within integrated wastewater management strategies, facilitating energy- and carbon-neutralization of urban water systems.
投加铁盐是一种广泛采用的下水道气味和腐蚀控制策略，它会影响下游污水处理厂污泥厌氧消化（AD）过程中的生物能源回收。然而，下水道内投加铁盐对厌氧消化的不同影响，取决于铁的类型和消化条件，目前仍不清楚。因此，本研究调查了下水道内投加亚铁（Fe(II)）和高铁酸盐（Fe(VI)）对传统厌氧消化和热水解预处理（THP）厌氧消化中生物能源回收的影响。结果表明，下水道内投加Fe(VI)比投加Fe(II)能更显著地提高厌氧消化中的甲烷产量，Fe(VI)的累积甲烷产量为197.1±1.9 mLCH₄∙gVSadded，Fe(II)的累积甲烷产量为186.5±10.4 mLCH₄∙gVSadded。微生物分析和铁颗粒表征表明，投加Fe(VI)的卓越促进作用可能归因于Fe(VI)生成产物的颗粒尺寸更小和氧化铁含量更高。这导致互营细菌和产甲烷菌之间的直接种间电子转移（DIET）得到更大增强，这由参与利用CO₂产甲烷的关键功能基因的上调所表明。此外，在THP-AD中，下水道内投加铁盐引起的甲烷产量提高（35.5 mLCH₄∙gVSadded）超过了传统厌氧消化（26.9 mLCH₄∙gVSadded），尽管THP过程中的有机降解未受影响。由于THP-AD在提高污泥生物能源回收方面越来越受欢迎，我们的研究结果表明下水道内投加铁盐有助于这一进展。此外，在综合废水管理策略中，下水道内投加Fe(VI)似乎更具前景，有助于实现城市水系统的能源和碳中和。
