State Key Laboratory of Urban Water Resource and Environment (SKLUWRE), School of Environment, Harbin Institute of Technology, Harbin 150090, PR China.
School of Municipal and Environmental Engineering, Shandong Jianzhu University, Jinan 250101, PR China.
Sci Total Environ. 2021 Jun 1;771:145372. doi: 10.1016/j.scitotenv.2021.145372. Epub 2021 Jan 23.
Biological predation has a significant effect on biofouling layers in gravity-driven membrane (GDM) filtration systems. However, the detailed process of predatory activities is still not well known. This study explored the effects of predator movement patterns on the biofouling layer at different temperatures and the factors affecting the stable flux level. The results indicated that Demospongiae, Spirotrichea and Saccharomycetes were the main species, with the body contracting or rotating in one position at 5 °C, and Litostomatea accounted for 55.1% at 10 °C. The weak agility of these species resulted in a less porous biofouling layer with a high extracellular polymeric substance (EPS) concentration, which was responsible for the low permeate flux and the time to reach flux stability. Bdelloidea was dominant at 20 and 30 °C, and the more heterogeneous biofouling layer with a lower EPS concentration was related to their intense creeping and swimming movements and their ability to create current in the water. The grazing of spongy flocs by predators affected the GDM system performance, and a high stable flux was obtained with large and loose flocs. In addition, the diversity of the eukaryotic community decreased after the flux stabilized due to the particular predominance of Bdelloidea at high temperatures, corresponding to a high stable flux. Pollutant removal was less affected by eukaryotes, and decreased ammonia nitrogen removal rates were related to the lower activity of nitrifying bacteria. Moreover, the reliable linear correlation between the temperature and the stable flux implied that the stable flux could be well predicted in the GDM system. The findings are beneficial for developing new strategies for regulating flocs and the biofouling layer to improve the performance of GDM systems.
生物捕食对重力驱动膜（GDM）过滤系统中的生物污垢层有显著影响。然而，捕食活动的详细过程仍不清楚。本研究探讨了捕食者的运动模式在不同温度下对生物污垢层的影响，以及影响稳定通量水平的因素。结果表明，在 5°C 时，主要物种为海绵动物门、旋口虫类和酵母菌，身体在一个位置收缩或旋转，而在 10°C 时，石灰质有孔虫类占 55.1%。这些物种的灵活性较弱导致生物污垢层的孔隙度较低，细胞外聚合物（EPS）浓度较高，这是导致渗透通量低和达到通量稳定时间长的原因。在 20 和 30°C 时，桡足类占主导地位，其具有更低 EPS 浓度的更不均匀的生物污垢层与它们强烈的爬行和游动运动以及在水中产生水流的能力有关。捕食者对海绵絮体的摄食影响了 GDM 系统的性能，由于大而松散的絮体，获得了较高的稳定通量。此外，由于高温下桡足类的特殊优势，稳定通量后真核生物群落的多样性降低，相应地稳定通量也较高。污染物去除受真核生物的影响较小，氨氮去除率降低与硝化细菌活性较低有关。此外，温度与稳定通量之间的可靠线性相关性表明，GDM 系统中的稳定通量可以很好地预测。这些发现有助于开发调节絮体和生物污垢层的新策略，以提高 GDM 系统的性能。
