Division of Environmental Engineering, Hokkaido University, N13W8, Kita-ku, Sapporo, 060-8628, Japan.
Division of Environmental Engineering, Hokkaido University, N13W8, Kita-ku, Sapporo, 060-8628, Japan.
Water Res. 2019 Mar 1;150:21-28. doi: 10.1016/j.watres.2018.11.030. Epub 2018 Nov 14.
Intensive membrane cleaning can be used with ceramic membranes since they are physically/chemically robust. It might therefore be possible for membrane bioreactors (MBRs) to be operated under the condition of a high membrane flux when ceramic membranes are used with such intensive membrane cleaning. In this study, bench-scale MBRs equipped with flat-sheet ceramic membranes were operated for long periods. Circulation of granular materials (cylindrical polyurethane) in the tank and frequent chemically enhanced backwash (CEB) were used as intensive physical cleaning and chemical cleaning in this study, respectively. Experiments were carried out with synthetic wastewater. The use of granular materials, which can cause significant damage to polymeric membranes (Kurita et al., 2015), was effective for controlling the formation of cake (deposition of microbial flocs) on the surface of the ceramic membranes. When both mechanical cleaning using the granular materials and CEB with 1000 ppm of sodium hypochlorite (NaClO) were applied, contrary to an expectation, evolution of reversible fouling (formation of a transparent gel layer on the membrane surface) became uncontrollable, whereas irreversible fouling was effectively controlled. The use of NaClO induced release of organic macromolecules via biomass decay, leading to the evolution of reversible fouling. When the intensity of CEB with NaClO was adequately lowered, with the aid of the mechanical cleaning using the granules, the bench-scale MBR could be operated stably under an elevated membrane flux for a long period (>70 days). It was postulated that the adjustment of CEB intensity preferably altered properties of organic macromolecules released from biomass: the structure of the gel layer was porous when the CEB intensity was lowered. When CEB is used in MBRs, it is thus important to balance cleaning efficiency and its harmful effect on biomass. When adequate CEB is used with intensive mechanical cleaning, MBRs with ceramic membranes can be operated under high flux conditions.
可以对陶瓷膜进行强化膜清洗，因为陶瓷膜具有物理和化学稳定性。因此，在使用陶瓷膜时，通过强化膜清洗，膜生物反应器（MBR）有可能在高膜通量条件下运行。在这项研究中，使用平板陶瓷膜装备了实验室规模的 MBR 并进行了长期运行。在该研究中，通过在槽内循环颗粒材料（圆柱形聚氨酯）和频繁地进行化学增强反冲洗（CEB），分别对其进行强化物理清洗和化学清洗。实验采用合成废水进行。使用颗粒材料（栗田等人，2015 年）可以有效控制在陶瓷膜表面形成滤饼（微生物絮体的沉积），而颗粒材料可能会对聚合膜造成严重的损害。当同时使用颗粒材料的机械清洗和 1000ppm 次氯酸钠（NaClO）的 CEB 时，与预期相反，可逆污染（在膜表面形成透明凝胶层）的发展变得不可控，而不可逆污染则得到了有效控制。NaClO 的使用通过生物量衰减诱导有机大分子的释放，导致可逆污染的发展。当通过颗粒材料的机械清洗适当降低 NaClO 的 CEB 强度时，在该强度的辅助下，实验室规模的 MBR 可以在高膜通量下稳定运行很长一段时间（>70 天）。可以假设，通过调整 CEB 强度，可以改变从生物量中释放的有机大分子的性质：当降低 CEB 强度时，凝胶层的结构是多孔的。因此，在 MBR 中使用 CEB 时，重要的是要平衡清洗效率及其对生物量的有害影响。当使用足够的 CEB 并结合强化机械清洗时，带有陶瓷膜的 MBR 可以在高通量条件下运行。
