Gravity-driven membrane (GDM) filtration system is a promising process for decentralized drinking water treatment. During the operation, membrane relaxation and shear stress could be simply achieved by intermittent filtration and water disturbance (created by occasionally shaking membrane model or stirring water in membrane tank), respectively. To better understand the impact of membrane relaxation and shear stress on the biofouling layer and stable flux in GDM system, action of daily 60-min intermission, daily flushing (cross-flow velocity = 10 cm s⁻¹, 1 min), and the combination of the two (flushed right after the 60-min intermission) were compared. The results showed that membrane relaxation and shear stress lonely was ineffective in improving the stable flux, while their combination enhanced the stable flux by 70%. A more open and spatially heterogeneous biofouling layer with a low EPS content and a high microbial activity was formed under the combination of membrane relaxation and shear stress. In-situ optical coherence tomography (OCT) observation revealed that, during intermission, the absence of pushing force by water flow induced a reversible expansion of biofouling layer, and the biofouling layer restored to its initial state soon after resuming filtration. Shear stress caused abrasion and erosion on the biofouling surface, but it exerted little effect on the interior of biofouling layer. Under the combination, however, both the surface and interior of biofouling layer were disturbed because of 1) the water vortexes caused by rough biofouling layer surface, and 2) the porous structure after 60-min intermission. This disturbance, in turn, helped the biofouling layer maintain its roughness and porosity, thereby improving the stable flux of GDM system.

重力驱动膜（GDM）过滤系统是用于分散式饮用水处理的有前途的工艺。在操作过程中，膜的松弛和剪切应力可以通过间歇性过滤和水扰动（分别通过偶尔摇动膜模型或在膜罐中搅动水）来简单地实现。为了更好地了解膜松弛和剪切应力对GDM系统中生物污垢层和稳定通量的影响，每天60分钟间歇，每天冲洗（错流速度= 10 cm s ^-1，1分钟），并比较了两者的组合（中场休息60分钟后立即消失）。结果表明，单独的膜松弛和剪切应力不能有效地提高稳定通量，而它们的结合使稳定通量提高了70％。在膜松弛和剪切应力的共同作用下，形成了具有较低EPS含量和较高微生物活性的更开放的空间异质生物污垢层。原位光学相干断层扫描（OCT）观察表明，间歇期间，水流不存在推动力会导致生物污垢层可逆膨胀，并且在恢复过滤后不久，生物污垢层会恢复到其初始状态。剪切应力导致生物污垢表面发生磨损和腐蚀，但是它对生物污染层内部几乎没有影响。然而，在该组合下，生物污垢层的表面和内部都受到干扰，原因是：1）由粗糙的生物污垢层表面引起的水涡流； 2）间歇60分钟后的多孔结构。反过来，这种干扰又有助于生物污损层保持其粗糙度和孔隙率，从而提高了GDM系统的稳定通量。