Abstract

Membrane bioreactors (MBR) with osmotic pressure driven membranes have significant advantages over bioreactors operated with pressure driven membranes. Since no pressure is applied to the membrane, except the concentrate circulation, osmotic membranes are less prone to fouling. Membrane fouling is an important limiting factor in MBRs, resulting in a frequent plantservice and high operating costs. In addition, other issues such as concentrate management and increased demands for reuse of treated wastewater have led to research of new processes such as the use of osmotic membranes in MBRs. In this study, tubular electrospun nanofiber (TuEN) membrane was coated with polyamide layer (PA) and the tubular nanofiber forward osmosis (TuNFO) membrane was manufactured. It operated submerged in a laboratory scale MBR under application of vacuum and concentrate circulation at the same time. The output of MBR was a feed for the reverse osmosis (RO) system. The RO-concentrate recirculated along the submerged membrane. To achieve an increased water flux and low salt flux in the MBR, the vacuum pressure was applied to the submerged membrane by operating the vacuum pump. The MBR system operated for sixteen months without washing and cleaning, and relatively better water fluxes were obtained (averaged 7.35 L m^–2 h^–1) compared to forward osmosis membrane bioreactors. The overall system (MBR + RO) exhibited high removal efficiencies for organic carbon (>99%), total nitrogen (TN) (70.8%), and total phosphorus (TP) (99.8%). With the concentrate management, the waste discharge of the entire system was minimized. The main point to be investigated more detailed in further studies is the relationship between the membrane structure and the operation mode. The pressure assisted circulation of saline concentrate without mixing with low concentrated feed through a membrane with suitable structure such as TuNFO membrane exhibits an important potential in MBR applications.

中文翻译：

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管式纳米纤维正渗透膜在膜生物反应器与反渗透系统耦合中的压力辅助应用

摘要

具有渗透压驱动膜的膜生物反应器（MBR）优于具有压驱动膜的生物反应器。由于除浓缩液循环外没有对膜施加压力，因此渗透膜不易结垢。膜结垢是MBR的重要限制因素，导致频繁的工厂服务和高昂的运营成本。另外，诸如浓缩液管理和对经处理废水的再利用的需求增加等其他问题也导致了对新工艺的研究，例如在MBR中使用渗透膜。在这项研究中，管状电纺纳米纤维（TuEN）膜上涂有聚酰胺层（PA），并制造了管状纳米纤维正向渗透（TuNFO）膜。它同时在真空和浓缩液循环下浸没在实验室规模的MBR中运行。MBR的输出是反渗透（RO）系统的进料。RO浓缩液沿浸没膜再循环。为了在MBR中获得增加的水通量和低盐通量，通过操作真空泵将真空压力施加到浸没膜上。MBR系统无需清洗就可运行16个月，并且获得了相对更好的水通量（平均7.35 L m^–2 h ^–1）与正渗透膜生物反应器相比。整个系统（MBR + RO）对有机碳（> 99％），总氮（TN）（70.8％）和总磷（TP）（99.8％）表现出较高的去除效率。通过浓缩物管理，整个系统的废物排放得以最小化。在进一步的研究中需要更详细研究的要点是膜结构与操作模式之间的关系。在不与低浓度进料混合的情况下，压力浓缩盐浓缩液通过具有适当结构的膜（例如TuNFO膜）混合，在MBR应用中显示出重要的潜力。