Kinetic Study on Clogging of a Geothermal Pumping Well Triggered by Mixing-Induced Biogeochemical Reactions,Environmental Science & Technology

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Kinetic Study on Clogging of a Geothermal Pumping Well Triggered by Mixing-Induced Biogeochemical Reactions
Environmental Science & Technology ( IF 10.8 ) Pub Date : 2019-05-10 , DOI: 10.1021/acs.est.9b00453
Luc Burté _{1,

2} , Charles A. Cravotta ₃ , Lorine Bethencourt _{1,

4} , Julien Farasin ₁ , Mathieu Pédrot ₁ , Alexis Dufresne ₄ , Marie-Françoise Gérard ₁ , Catherine Baranger ₂ , Tanguy Le Borgne ₁ , Luc Aquilina ₁

Affiliation

The sustainability of ground-source geothermal systems can be severely impacted by microbially mediated clogging processes. Biofouling of water wells by hydrous ferric oxide is a widespread problem. Although the mechanisms and critical environmental factors associated with clogging development are widely recognized, effects of mixing processes within the wells and time scales for clogging processes are not well characterized. Here we report insights from a joint hydrological, geochemical, and metagenomics characterization of a geothermal doublet in which hydrous ferric oxide and hydrous manganese oxide deposits had formed as a consequence of mixing shallow groundwater containing dissolved oxygen and nitrate with deeper, anoxic groundwater containing dissolved iron (Fe^II) and manganese (Mn^II). Metagenomics identify distinct bacteria consortia in the pumping well oxic and anoxic zones, including autotrophic iron-oxidizing bacteria. Batch mixing experiments and geochemical kinetics modeling of the associated reactions indicate that Fe^II and Mn^II oxidation are slow compared to the residence time of water in the pumping well; however, adsorption of Fe^II and Mn^II by accumulated hydrous ferric oxide and hydrous manganese oxide in the well bore and pump riser provides “infinite” time for surface-catalyzed oxidation and a convenient source of energy for iron-oxidizing bacteria, which colonize the surfaces and also catalyze oxidation. Thus, rapid clogging is caused by mixing-induced redox reactions and is exacerbated by microbial activity on accumulated hydrous oxide surfaces.

中文翻译：

混合诱导生物地球化学反应触发地热泵井堵塞的动力学研究

微生物介导的堵塞过程会严重影响地源地热系统的可持续性。含水三氧化二铁对水井的生物污染是一个普遍的问题。尽管与堵塞发展有关的机制和关键环境因素已得到广泛认可，但井内混合过程的影响以及堵塞过程的时间尺度尚未得到很好的表征。在这里，我们从地热双重峰的联合水文，地球化学和宏基因组学表征报告中得出的见解，其中由于将含有溶解氧和硝酸盐的浅层地下水与含有溶解铁的深层缺氧地下水混合而形成了含水三氧化二铁和含水氧化锰矿床（Fe ^II）和锰（Mn ^II）。元基因组学在抽水井的缺氧和缺氧区域识别出不同的细菌群落，包括自养铁氧化细菌。分批混合实验和相关反应的地球化学动力学模型表明，与水在抽水井中的停留时间相比，Fe ^II和Mn ^II的氧化速度较慢。但是，Fe ^II和Mn ^II的吸附井筒和泵立管中积聚的含水三氧化二铁和含水氧化锰为表面催化的氧化提供了“无限”的时间，并且为铁氧化细菌提供了方便的能源，铁使细菌定居在表面并催化氧化。因此，快速堵塞是由混合引起的氧化还原反应引起的，并且由于积累的含水氧化物表面上的微生物活性而加剧了堵塞。

更新日期：2019-05-16

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