TARGiM: Transport of Antibiotic Resistance Genes in Membranebioreactors (MBR)

减缓抗生素耐药基因（ARG）的传播将是国际废水处理未来的主要挑战之一。膜生物反应器（MBR）已经建立在废水处理中用于去除细菌细胞。然而，ARG不仅出现在细菌细胞内，而且还以游离DNA的形式出现，可能是通过MBR曝气释放的。这些游离ARGs在膜生物反应器中的运输和保留尚未完全了解。我们假设，膜生物污损层的存在显着改变这些游离精氨酸的MBR的保留特性。虽然生物结垢可能会降低一般的过滤性能，较厚的生物膜层和孔隙堵塞增加的可能性ARG吸附，停留时间和生物降解，从而增加了游离ARG的去除。另一种假设是，增加的剪切应力导致压缩，因此导致生物污垢层的密度更高，从而导致ARG保留改善。为了验证这些假设，将开发MBR污垢模拟器平台，允许在受控和可重现的操作条件下集成和解释ARG去除实验。在其核心，该平台由一个剪切单元，其中现实的流动条件和剪切梯度对应于那些在商业MBR是通过可调搅拌器实现。将针对不同的膜和污染层特性计算传质系数，并将其集成到MBR污染模拟器平台中。将使用不同的市售和先前表征的多孔膜进行实验。ARG将以游离质粒的形式添加到饲料中。为了获得ARG log去除率，将在膜通过之前和之后通过改进的多靶ddPCR测定来定量质粒，该测定同时允许确定质粒完整性。我们认为，主要类型的膜污染（孔堵塞，滤饼过滤）可以通过改变物理化学膜性能（如疏水性，孔径和表面粗糙度）和剪切应力的应用程序进行主动操纵。污垢层的物理结构将在老化的各个阶段使用光学相干断层扫描（OCT）系统的特点。这将允许创建和测试具有代表性的、可重复的生物污垢层，这些生物污垢层具有不同的、确定的ARG去除特性。最后，结果将用于确定和关联对于提高MBR的ARG去除效率至关重要的操作参数。为了验证从MBR污染模拟器平台获得的见解，将表征在真实的MBR设置中污染的膜，预测其传质并测试其ARG去除效率。

Mitigating the spread of antibiotic resistance genes (ARGs) will be one of the major future challenges of international wastewater treatment. Membrane bioreactors (MBR) have been established in wastewater treatment for the removal of bacterial cells. However, ARGs do not only appear inside bacterial cells, but also in the form of free DNA, possibly released by MBR aeration. Transport and retention of these free ARGs in membrane bioreactors are not yet fully understood. We hypothesize that the presence of membrane biofouling layers significantly alters the retention characteristics of MBRs for these free ARGs. While biofouling might reduce the general filtration performance, thicker biofilm layers and pore blocking increase the likelihood of ARG sorption, residence time and biodegradation, thus increasing the removal of free ARGs. Another hypothesis is that increased shear stress leads to the compression and hence higher density of the biofouling layer and consequently to improved ARG retention. To verify these hypotheses, a MBR fouling simulator platform will be developed, that allows integration and interpretation of ARG removal experiments under controlled and reproducible operational conditions. At its core, the platform consists of a shear cell in which realistic flow conditions and shear gradients corresponding to those in a commercial MBR are realized by means of an adjustable stirrer. The mass transfer coefficients will be calculated for different membrane and fouling layer characteristics and integrated into the MBR fouling simulator platform. Experiments will be carried out with different, commercially available and previously characterized, porous membranes. ARGs will be added to the feed in the form of free plasmids. To obtain ARG log removal rates, plasmids will be quantified before and after membrane passage through an improved multi-target ddPCR assay that simultaneously allows determining plasmid integrity.To elucidate the effects of membrane fouling on ARG removal, a model waste water community will be inoculated into the MBR shear cells. We suppose that the predominant type of membrane fouling (pore blocking, cake filtration) can be actively manipulated by altering physico-chemical membrane properties (e.g. hydrophobicity, pore size and surface roughness) and shear stress applications. The physical structure of the fouling layers will be characterized at various stages of ageing using an optical coherence tomography (OCT) system. This will allow creating and testing representative, reproducible biofouling layers of varying, defined properties for ARG removal.Finally, results will be used to determine and correlate operational parameters that are crucial for improving the MBR’s ARG removal efficiency. To validate the insights gained from the MBR fouling simulator platform, membranes fouled in a real MBR setup will be characterized, their mass transfer predicted and their ARG removal efficiency tested.