Department of Environmental Microbiology, Helmholtz Centre for Environmental Research-UFZ, Permoserstr. 15, Leipzig 04318, Germany.
Bundesanstalt für Gewässerkunde, Abteilung Quantitative Gewässerkunde, Am Mainzer Tor 1, Koblenz 56068, Germany.
Environ Sci Technol. 2022 Sep 20;56(18):13008-13018. doi: 10.1021/acs.est.2c01433. Epub 2022 Sep 7.
In situ bioremediation is a common remediation strategy for many groundwater contaminants. It was traditionally believed that (in the absence of mixing-limitations) a better in situ bioremediation is obtained in a more homogeneous medium where the even distribution of both substrate and bacteria facilitates the access of a larger portion of the bacterial community to a higher amount of substrate. Such conclusions were driven with the typical assumption of disregarding substrate inhibitory effects on the metabolic activity of enzymes at high concentration levels. To investigate the influence of pore matrix heterogeneities on substrate inhibition, we use a numerical approach to solve reactive transport processes in the presence of pore-scale heterogeneities. To this end, a rigorous reactive pore network model is developed and used to model the reactive transport of a self-inhibiting substrate under both transient and steady-state conditions through media with various, spatially correlated, pore-size distributions. For the first time, we explore on the basis of a pore-scale model approach the link between pore-size heterogeneities and substrate inhibition. Our results show that for a self-inhibiting substrate, (1) pore-scale heterogeneities can consistently promote degradation rates at toxic levels, (2) the effect reverses when the concentrations fall to levels essential for microbial growth, and (3) an engineered combination of homogeneous and heterogeneous media can increase the overall efficiency of bioremediation.
原位生物修复是许多地下水污染物的常见修复策略。传统上认为（在不存在混合限制的情况下），在更均匀的介质中可以获得更好的原位生物修复，其中基质和细菌的均匀分布有利于更大比例的细菌群落接触到更多数量的基质。这些结论是基于典型的假设，即忽略了基质对高浓度水平下酶代谢活性的抑制作用。为了研究孔隙基质非均质性对基质抑制的影响，我们使用数值方法来解决存在孔隙尺度非均质性时的反应传输过程。为此，开发了一种严格的反应性孔隙网络模型，并用于在具有各种空间相关孔径分布的介质中模拟自抑制基质的瞬态和稳态条件下的反应传输。首次基于孔隙尺度模型方法探索了孔隙尺度非均质性与基质抑制之间的联系。我们的结果表明，对于自抑制基质，（1）孔隙尺度非均质性可以在有毒水平上持续促进降解速率，（2）当浓度下降到对微生物生长至关重要的水平时，这种影响会发生逆转，（3）均匀和非均匀介质的工程组合可以提高生物修复的整体效率。
