The gravity-driven membrane filtration (GDM) process is very suitable for decentralized drinking water or rainwater treatment due to low maintenance (no backwashing, physical flushing and chemical cleaning) and low energy consumption. However, the ultrafiltration process alone seldom satisfies the standard of organics removal. To meet the purpose of water reuse, we applied a powdered activate carbon (PAC) layer and sand layer on the membrane surface of a GDM system to improve the quality of the effluent in this study. In addition, the flux development and fouling layer properties were also systematically investigated. Results show that the presence of a PAC layer enhanced the organics removal by nearly 20%, including the fluorescent organics (such as aromatic proteins, tryptophan proteins and humics) removal. However, the sand layer assisted system did not show any improvement, as observed when compared with the control. With regard to the permeate flux development tendency, the flux could be kept stable in the PAC/GDM system (3.0 L m⁻² h⁻¹) and control system (4.5 L m⁻¹ h⁻¹), whereas the flux of the sand/GDM system did not stabilize with the final value of 2.3 L m⁻² h⁻¹ on day 55. The reason for the lower stable flux in PAC/GDM system was that PAC acted as a bio-carrier and that a large amount of biomass with higher EPS contents (proteins and polysaccharides) developed on the membrane. The main explanation for the unstable flux in the sand/GDM system was the low porosity of the bio-fouling layer, which significantly increased the hydraulically reversible and cake layer resistances. However, the permeate flux could be restored easily in these systems by simple flushing because hydraulically reversible resistance accounted for large proportions (>90%) of the total filtration resistance.

中文翻译：

---

雨水处理过程中PAC颗粒层对重力驱动膜过滤（GDM）系统性能的影响†

重力驱动膜过滤（GDM）工艺由于维护成本低（无需反冲洗，物理冲洗和化学清洁）且能耗低，因此非常适合于分散式饮用水或雨水处理。然而，仅超滤过程很少满足有机物去除的标准。为了满足中水回用的目的，在这项研究中，我们在GDM系统的膜表面上应用了粉末状活性炭（PAC）层和沙层，以提高废水的质量。此外，还对助焊剂的产生和结垢层的性能进行了系统的研究。结果表明，PAC层的存在将有机物的去除率提高了近20％，其中包括荧光有机物（如芳香族蛋白质，色氨酸蛋白和腐殖质）的去除。然而，与对照相比，砂层辅助体系没有显示出任何改善。考虑到渗透通量的发展趋势，在PAC / GDM系统中通量可以保持稳定（3.0 L m^-2 h ^-1）和控制系统（4.5 L m ^-1 h ^-1），而砂/ GDM系统的通量不稳定，最终值为2.3 L m ^-2 h ^-1在第55天，PAC / GDM系统中稳定通量较低的原因是PAC充当了生物载体，并且在膜上形成了大量具有较高EPS含量的生物质（蛋白质和多糖）。砂/ GDM系统中不稳定通量的主要原因是生物污垢层的孔隙率低，这显着增加了水力可逆性和滤饼层的阻力。但是，在这些系统中，通过简单的冲洗即可轻松恢复渗透通量，因为液压可逆阻力占总过滤阻力的很大比例（> 90％）。