Imaging biofilm in porous media using X-ray computed microtomography
Imaging biofilm in porous media using X-ray computed microtomography
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DOI：
10.1111/j.1365-2818.2010.03432.x
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发表时间：
2011-04-01
影响因子：
2
通讯作者：
Quintard, M.
中科院分区：
文献类型：
--
作者：
Davit, Y.;Iltis, G.;Quintard, M.
在这项研究中，提出了一种利用x射线计算机微断层扫描对多孔介质内的生物膜进行三维成像的新技术。由于多孔介质（塑料）、生物膜和水相的x射线吸收系数相似，因此需要使用x射线计算机断层扫描技术对实验基质中的生物膜进行x射线造影剂成像。本技术利用医用硫酸钡悬浮液来区分水相和生物膜。将碘化钾添加到悬浮液中，以帮助描述生物膜和实验多孔介质之间的关系。碘化物很容易扩散到生物膜中，而硫酸钡悬浮液仍停留在水相中。这允许在本研究中使用的实验系统内有效区分三个阶段。两种造影剂的行为，特别是硫酸钡的行为，是通过比较(1)光学可视化和(2)x射线吸收成像获得的孔网络内生物膜的二维图像来解决的。我们表明，对比混合物提供了生物膜，水相和固相（珠）之间的对比。然后将成像方法应用于两个三维填充柱，其中生长了生物膜。通过重构图像的实例说明了该方法的有效性。讨论了该技术的局限性和应用。与所提出的方法相关的一个关键好处是，它捕获了大量关于孔隙尺度传输过程拓扑结构的信息。例如，利用特定的放大技术和数值分析，可以量化由生物膜生长引起的多孔介质有效参数（如分散或渗透率）的变化。我们强调，这里提出的结果是对这种新方法的第一次测试；在将该方法用于多孔介质中生物膜几何形状的精确定量分析之前，需要解决图像的准确分割、造影剂的最佳浓度以及使用同步辐射源的潜在需求等问题。
P>In this study, a new technique for three-dimensional imaging of biofilm within porous media using X-ray computed microtomography is presented. Due to the similarity in X-ray absorption coefficients for the porous media (plastic), biofilm and aqueous phase, an X-ray contrast agent is required to image biofilm within the experimental matrix using X-ray computed tomography. The presented technique utilizes a medical suspension of barium sulphate to differentiate between the aqueous phase and the biofilm. Potassium iodide is added to the suspension to aid in delineation between the biofilm and the experimental porous medium. The iodide readily diffuses into the biofilm while the barium sulphate suspension remains in the aqueous phase. This allows for effective differentiation of the three phases within the experimental systems utilized in this study. The behaviour of the two contrast agents, in particular of the barium sulphate, is addressed by comparing two-dimensional images of biofilm within a pore network obtained by (1) optical visualization and (2) X-ray absorption radiography. We show that the contrast mixture provides contrast between the biofilm, the aqueous-phase and the solid-phase (beads). The imaging method is then applied to two three-dimensional packed-bead columns within which biofilm was grown. Examples of reconstructed images are provided to illustrate the effectiveness of the method. Limitations and applications of the technique are discussed. A key benefit, associated with the presented method, is that it captures a substantial amount of information regarding the topology of the pore-scale transport processes. For example, the quantification of changes in porous media effective parameters, such as dispersion or permeability, induced by biofilm growth, is possible using specific upscaling techniques and numerical analysis. We emphasize that the results presented here serve as a first test of this novel approach; issues with accurate segmentation of the images, optimal concentrations of contrast agents and the potential need for use of synchrotron radiation sources need to be addressed before the method can be used for precise quantitative analysis of biofilm geometry in porous media.