Abstract

One of the important operational factors affecting the fouling of membrane bioreactors (MBR) is the critical flux which is defined as the flux above which the cake layer formation on the membrane surface is seen. So, to prevent severe fouling in MBR, it is important to determine the critical flux and operate at a flux below it. The evaluation of critical flux and pollutant removal in a lab-scale submerged membrane bioreactor was performed for a real oil refinery wastewater. Transmembrane pressure (TMP) and flux behavior in a period of time via a so-called flux step method were studied to determine the critical flux of the membrane and to investigate of the effect of TiO₂ nanoparticles (NPs) incorporation into Polyvinylidene fluoride (PVDF) matrix, on the membrane filterability. The effectiveness of MBR for treating effluent stream of Dissolved Air Floatation (DAF) unit of Tehran oil refinery wastewater plant has been studied and the results showed that TiO₂ NPs improved the phenol removal efficiency in such wastewater. About 70% enhancement in critical flux of PVDF/TiO₂ membrane was observed as a result of TiO₂ NPs tendency to reduce fouling of PVDF membranes. It was concluded that the effect of TiO₂ incorporation in the membrane matrix is more significant in fouling reduction than permeability improvement and that the surface charge of the membrane plays much more important role than other surface modification strategies such as hydrophilicity enhancement, in fouling mitigation of MBRs. The results also demonstrated that TiO₂ has no significant effect on the microorganism destruction or growth, since the amount of total soluble microbial products (SMP) and extracellular polymeric substance (EPS) remained almost stable during MBR operation for both membranes.

中文翻译：

---

TiO2 纳米颗粒对膜生物反应器中 PVDF 膜过滤性的影响：结垢减少和临界通量增强

摘要

影响膜生物反应器 (MBR) 结垢的重要操作因素之一是临界通量，其定义为在膜表面上可以看到滤饼层形成的通量。因此，为了防止 MBR 中的严重结垢，重要的是确定临界通量并在低于它的通量下运行。对真实的炼油厂废水进行了实验室规模浸没式膜生物反应器中临界通量和污染物去除的评估。通过所谓的通量阶梯法研究了一段时间内的跨膜压力（TMP）和通量行为，以确定膜的临界通量并研究了TiO _2的影响纳米粒子 (NPs) 掺入聚偏二氟乙烯 (PVDF) 基质中，对膜的过滤性有影响。研究了 MBR 处理德黑兰炼油厂废水处理厂溶解气浮 (DAF) 装置流出物的有效性，结果表明 TiO ₂ NPs 提高了此类废水中苯酚的去除效率。由于 TiO ₂ NPs 倾向于减少 PVDF 膜的污染，因此观察到 PVDF/TiO ₂膜的临界通量提高了约 70% 。结论是 TiO _2的影响与改善渗透性相比，膜基质中的掺入在减少污染方面更显着，并且膜的表面电荷在减少 MBR 污染方面比其他表面改性策略（例如亲水性增强）起更重要的作用。结果还表明，TiO ₂对微生物的破坏或生长没有显着影响，因为在两种膜的 MBR 操作期间，总可溶性微生物产物 (SMP) 和细胞外聚合物 (EPS) 的量几乎保持稳定。