Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
Water Res. 2010 Apr;44(8):2541-53. doi: 10.1016/j.watres.2009.12.024. Epub 2009 Dec 28.
Shear, in the form of vigorous aeration, is used to control fouling in membrane bioreactor (MBR) systems. However, shear also influences the physicochemical and biological properties of MBR biomass. The current study examines the relationship between the aeration intensity and extracellular polymeric substance (EPS) production in MBRs. Two identical submerged MBRs were operated in parallel but the aeration rate was three times greater in one of the MBRs. The concentrations of floc-associated and soluble EPS were monitored for the duration of the experiment. Microscopic images and floc-size measurements were also collected regularly. The membrane fouling potential of the biomass was quantified using the flux-step method. Increased aeration did not have a direct effect on soluble or floc-associated EPS production in the microfiltration MBRs. However, aeration intensity had a significant effect on predatory organisms. Large aquatic earthworms, Aeolosoma hemprichi, proliferated under lower shear conditions but were never observed in the high shear reactor. Predation by A. hemprichi resulted in increased floc-associated and soluble EPS production. Thus, the mixing conditions in the low shear MBR indirectly resulted in increased soluble EPS concentrations and higher fouling potential. This research suggests that predation can have a significant impact on the production rates of floc-associated and soluble EPS--key parameters driving membrane fouling in MBRs.
剪切作用（如剧烈曝气）可用于控制膜生物反应器（MBR）系统中的结垢问题。然而，剪切作用也会影响 MBR 生物量的物理化学和生物特性。本研究考察了曝气强度与 MBR 中胞外聚合物（EPS）产生之间的关系。两个相同的浸没式 MBR 平行运行，但其中一个 MBR 的曝气速率是另一个的三倍。在整个实验过程中监测了絮体相关和可溶性 EPS 的浓度。还定期收集显微镜图像和絮体尺寸测量结果。使用通量阶跃法定量评估生物量的膜污染潜力。增加曝气对微滤 MBR 中的可溶性或絮体相关 EPS 产生没有直接影响。然而，曝气强度对捕食生物有显著影响。大型水生蚯蚓 Aeolosoma hemprichi 在低剪切条件下大量繁殖，但从未在高剪切反应器中观察到。A. hemprichi 的捕食导致絮体相关和可溶性 EPS 产量增加。因此，低剪切 MBR 中的混合条件间接导致可溶性 EPS 浓度增加和更高的污染潜力。本研究表明，捕食作用会对絮体相关和可溶性 EPS 的产生速率产生重大影响，这是 MBR 中膜污染的关键参数。
