Department of Biotechnology, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ, Delft, the Netherlands.
Eawag, Swiss Federal Institute of Aquatic Science and Technology, 8600, Dübendorf, Switzerland.
Water Res. 2019 Jun 15;157:335-345. doi: 10.1016/j.watres.2019.03.073. Epub 2019 Apr 2.
Poroelastic fluid-structure interaction models were coupled to experimental data to determine the effects of biofilm spatial distribution of mechanical and hydraulic properties on the biofilm hydraulic resistance and compressibility in membrane filtration processes. Biofilms were cultivated on ultrafiltration membranes for 20 and 30 days under high (0.28 bar) and low (0.06 bar) transmembrane pressure (TMP), in dead-end filtration mode. Subsequently, biofilms were subjected to a compression/relaxation cycles by step-wise TMP changes. Structural deformation of biofilms during compression was observed in-situ using optical coherence tomography. Experimental results show that the observed increase in the biofilm hydraulic resistance during compression is not necessarily accompanied by a detectable biofilm thickness reduction. A dual-layer biofilm model with a dense base and porous top layer could explain these observed results. Because porosity controls indirectly the mechanical response of biofilms under compression, results could be described without assuming a gradient in mechanical properties within the biofilm. The biofilm surface roughness did not significantly influence the water flux in this study. However, the fraction of biofilm base layer directly exposed to bulk liquid could be a good indicator in the determination of water flux. The main implications of this study for the design and operation of low-pressure membrane systems (e.g., MF and UF with fouling layer being the main filtration resistance) lays in the selection of favorable operational TMP and biofilm morphology.
多孔弹性流固耦合模型与实验数据相结合，以确定生物膜的机械和水力性质的空间分布对膜过滤过程中生物膜水力阻力和可压缩性的影响。在死端过滤模式下，采用超滤膜在高（0.28 巴）和低（0.06 巴）跨膜压力（TMP）下培养生物膜 20 和 30 天。随后，通过逐步 TMP 变化对生物膜进行压缩/松弛循环。使用光学相干断层扫描原位观察生物膜在压缩过程中的结构变形。实验结果表明，在压缩过程中观察到的生物膜水力阻力增加不一定伴随着可检测到的生物膜厚度减小。具有致密基底和多孔顶层的双层生物膜模型可以解释这些观察结果。由于孔隙度间接控制生物膜在压缩下的机械响应，因此可以在不假设生物膜内机械性能梯度的情况下描述结果。在这项研究中，生物膜表面粗糙度对水通量没有显著影响。然而，直接暴露于主体液体的生物膜基底层的分数可以作为确定水通量的良好指标。这项研究对低压膜系统（例如，主要过滤阻力为污垢层的 MF 和 UF）的设计和操作的主要意义在于选择有利的操作 TMP 和生物膜形态。
