Membrane fouling is one of the most investigated topics in the field of membrane processes because it is the main weakness that prevents membrane bioreactors (MBRs) from being widely applied. With a view to reduce membrane fouling, all the phenomena involved in the operation are worth understanding through a fine-tuned and deep examination. In the present paper, the study focused on the hydrodynamics in an air-lift MBR with a flat sheet membrane, taking into account the application of a specific method for biofouling mitigation adding free-moving particles in addition of bubbles injection. The application of this technique creates a complex three-phase gas–liquid–solid contactor in the MBR in terms of hydrodynamics. Therefore, the main objective of this work was to properly characterize, using a Particle image velocimetry (PIV) technique, such a system in order to clarify the potential effect of the addition of free-moving solid particles on the hydrodynamics and the performances of the MBR. Three different shapes of particles have been tested: beads, hollow cylinders, and flat sheets. Local hydrodynamic parameters, such as the liquid velocity, the liquid shear stress, or the bubble sizes and velocities, were analyzed with and without the presence of solid particles. Specific conclusions are drawn to help future users of this antifouling technique to optimize the design of the solid particles.

中文翻译：

---

空气提升膜生物反应器中自由运动颗粒的撞击的流体力学表征

膜结垢是膜工艺领域研究最多的主题之一，因为它是阻止膜生物反应器（MBR）广泛应用的主要弱点。为了减少膜污染，通过微调和深入检查，值得了解操作中涉及的所有现象。在本文中，该研究集中在带有平板膜的气举式MBR中的流体动力学方面，同时考虑到了一种特殊的生物污损缓解方法的应用，该方法除了注入气泡外还添加了自由移动的颗粒。该技术的应用在流体动力学方面在MBR中创建了一个复杂的三相气液固接触器。因此，这项工作的主要目的是使用粒子图像测速技术（PIV）正确表征，这种系统是为了阐明添加自由移动的固体颗粒对MBR的流体动力学和性能的潜在影响。测试了三种不同形状的颗粒：珠子，空心圆柱体和平板。在有或没有固体颗粒的情况下，分析了局部流体动力学参数，例如液体速度，液体剪切应力或气泡大小和速度。得出特定结论以帮助该防污技术的未来用户优化固体颗粒的设计。例如，在有或没有固体颗粒的情况下，对液体速度，液体剪切应力或气泡大小和速度等液体进行分析。得出特定结论以帮助该防污技术的未来用户优化固体颗粒的设计。例如，在有或没有固体颗粒的情况下，对液体速度，液体剪切应力或气泡大小和速度等液体进行分析。得出特定结论以帮助该防污技术的未来用户优化固体颗粒的设计。