基于盐分累积调控的有机盐汲取液正渗透膜生物反应器性能和膜污染机理与影响机制研究

Osmotic membrane bioreactor (OMBR), which integrates forward osmosis (FO) with conventional activated sludge treatment, is a promising technology for advanced wastewater treatment and water reuse. Compared to conventional MBR, OMBR has several advantages, including lower membrane fouling propensity, less energy consumption and better product water quality. Salinity build-up in the bioreactor is a key issue associated with OMBR due to the high salt rejection from wastewater by the FO membrane, and more importantly, the reverse salt flux from the draw solution. Our previous studies proposed that utilizing organic based draw solutes for OMBR could effectively mitigate salinity build-up in the bioreactor. However, the effect of organic based draw solutes on the performance of OMBR is still largely unknown. Moreover, there is a dearth about the fouling behavior and mechanism of the FO membrane during long-term OMBR operation. Thus, in this project, we will investigate the effect of organic based draw solutes on the performance of a submerged OMBR and build a screening protocol for draw solute selection with the aim to alleviate salinity build-up in the bioreactor. Further efforts will be made to elucidate membrane fouling behavior and mechanism during OMBR operation driven by the optimal organic based draw solute by characterizing dissolved organic substances and sludge properties in the bioreactor as well as the membrane fouling layer.

将正渗透（FO）膜分离技术与生物处理工艺结合的正渗透膜生物反应器（OMBR）在污水深度处理与回用领域具有良好的应用前景。与传统的MBR相比，OMBR具有膜污染倾向低、能耗少、出水水质高等优势。然而，FO膜的高效截留作用和其特有的离子反混现象会造成反应器内盐分累积，影响OMBR的可持续运行。前期的研究表明，有机盐汲取液的选用是控制OMBR反应器内盐分累积的有效途径，但其对OMBR性能的影响尚不清楚。此外，OMBR长期运行过程中，FO膜的污染行为与机理尚不明确。因此，本项目着重面向产业化应用的浸没式OMBR，以反应器内盐分累积的调控为切入点，研究有机盐汲取液驱动的OMBR性能，构建OMBR有机盐汲取液的筛选体系；在此基础上，通过污染物辨别和污泥特性分析，采用先进的膜表征技术，研究有机盐汲取液驱动的OMBR膜污染形成机理与影响机制，为膜污染的有效控制提供理论指导，推进OMBR实际应用的发展。

正渗透膜生物反应器（OMBR）因具有膜污染倾向低、能耗少、出水水质高等优势，近年来已应用于污水深度处理与回用领域。然而，正渗透（FO）膜的高效截留作用和其特有的离子反混现象会造成反应器内盐分累积，影响OMBR的可持续运行。本项目基于前期的研究，系统阐述了OMBR盐分累积的成因、影响及控制措施，表明有机盐汲取液能够有效控制盐分累积，但其对OMBR性能的影响仍需深入研究。随后根据有机盐汲取液的特性，构建了OMBR的有机盐筛选体系，并以常用的氯化钠（NaCl）作为基准，选取筛选后的醋酸钠有机盐作为汲取液，探究其驱动OMBR的污水处理性能。研究表明，在相同的渗透压下，醋酸钠具有较低的离子反混通量，能缓解OMBR运行过程中的盐分累积，但会造成严重的膜污染，降低水通量。为了解决这一问题，进而探究了在有机或无机汲取液中添加有代表性的表面活性剂十二烷基苯磺酸钠（SDBS）来减少离子反混通量。结果发现，添加SDBS对NaCl汲取液的影响大于有机汲取液，特别当添加浓度达到5 mM以上时，能够显著降低NaCl的反向扩散（减少量达69.7%），并且水通量下降相对较小。因此在NaCl汲取液中添加SDBS可以有效缓解OMBR运行过程中的盐分累积，从而实现了稳定的处理性能。在此基础上，采用X射线计算机断层扫描和同步辐射红外光谱成像技术揭示了OMBR运行过程中膜污染机理，并探究了膜污染对有机微污染物截留性能的影响。结果表明，多糖类物质首先在FO膜表面形成，随后蛋白质类物质依附在多糖类污染层表面，通过对FO膜基质内部成像分析，发现蛋白质类物质会透过膜基质，积累在汲取液中。在膜污染过程中大量带负电的溶解性微生物代谢产物（即多糖类和蛋白质类物质）吸附在膜表面，从而通过空间位阻和静电相互作用增加了FO膜对部分有机微污染物的截留效率。本项目的研究结果为控制OMBR中的盐分累积和膜污染提供了重要的理论依据，从而有效推进了OMBR在污水深度处理与回用领域的发展。