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

减轻抗生素耐药基因（ARGs）的传播将是未来国际废水处理的主要挑战之一。膜生物反应器（MBR）已被用于废水处理中去除细菌细胞。然而，ARGs不仅出现在细菌细胞内，还以游离DNA的形式出现，可能通过MBR曝气释放。这些游离ARGs在膜生物反应器中的转运和滞留尚不完全清楚。我们假设膜生物污垢层的存在显著改变了mbr对这些游离ARGs的保留特性。虽然生物污染可能降低总体过滤性能，但较厚的生物膜层和孔阻塞增加了ARG吸附的可能性、停留时间和生物降解的可能性，从而增加了游离ARG的去除。另一种假设是，剪切应力的增加会导致压缩，从而提高生物污垢层的密度，从而提高ARG的保留率。为了验证这些假设，将开发一个MBR污垢模拟器平台，该平台允许在可控和可重复的操作条件下整合和解释ARG去除实验。该平台的核心是一个剪切单元，通过可调搅拌器实现与商用MBR相对应的实际流动条件和剪切梯度。将计算不同膜层和污染层特性的传质系数，并将其集成到MBR污染模拟器平台中。实验将用不同的、市售的和先前表征的多孔膜进行。arg将以自由质粒的形式添加到饲料中。为了获得ARG log的去除率，将通过改进的多靶点ddPCR测定膜传膜前后的质粒，同时测定质粒的完整性。为了阐明膜污染对ARG去除的影响，将一个模拟废水群落接种到MBR剪切细胞中。我们认为，主要类型的膜污染（孔隙堵塞，滤饼过滤）可以通过改变膜的物理化学性质（如疏水性，孔径和表面粗糙度）和剪切应力的应用来积极控制。使用光学相干层析成像（OCT）系统表征老化不同阶段的污染层的物理结构。这将允许创建和测试具有代表性的、可重复的、具有不同特性的生物污垢层，用于去除ARG。最后，结果将用于确定和关联操作参数，这些参数对于提高MBR的ARG去除效率至关重要。为了验证从MBR污染模拟器平台获得的见解，将对在真实MBR装置中污染的膜进行表征，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.