Considerable attention has been paid in recent years to the recovery and effective utilization of organic matter in municipal wastewater for the establishment of a circular economy. Direct membrane filtration (DMF) of municipal wastewater using microfiltration (MF) or ultrafiltration (UF) membranes to retain and concentrate the organic matter in municipal wastewater could be a practical option for this purpose. However, severe membrane fouling and high concentrations of organic matter remaining in the DMF permeate are concerns to be addressed. Application of a simple pretreatment using fixed biofilms was investigated to address these issues. In this study, experiments were carried out at an existing municipal wastewater treatment plant. A moving bed biofilm reactor (MBBR) process operated under a very short HRT of 1 h and DO concentration of 0.5 mg/L selectively degraded low-molecular-weight dissolved organic matter in municipal wastewater without degradation of membrane-recoverable suspended and colloidal organic matter. Application of the pretreatment did not reduce the amount of organic carbon recovered by DMF using an MF membrane (approximately 70% of the influent COD being recovered), while it dramatically mitigated the membrane fouling probably due to the alteration of characteristics of dissolved organic matter in wastewater. The pretreatment also reduced the concentration of organic matter in the DMF permeate by 41%: COD concentration in the DMF permeate was as low as 40 mg/L. With the established MBBR pretreatment, performances of MF (0.1 µm) and UF (molecular weight cut-off: 150,000) membranes for DMF were compared in parallel. It was found that the increase of the recoverable amount of organic matter by using UF was marginal (about 5%), whereas fouling in UF was much more severe than that in MF. The severe fouling in UF was caused by inorganic colloids such as FeS that could pass through MF membranes but be retained by UF membranes. Based on the results obtained in this study, it is concluded that MF is more suitable than UF for efficient DMF.

近年来，城市污水中有机物的回收和有效利用，为建立循环经济体系而备受关注。使用微滤 (MF) 或超滤 (UF) 膜对城市废水进行直接膜过滤 (DMF) 以保留和浓缩城市废水中的有机物可能是实现此目的的实用选择。然而，DMF 渗透液中残留的严重膜污染和高浓度有机物是需要解决的问题。研究了使用固定生物膜进行简单预处理以解决这些问题。在这项研究中，实验是在现有的市政污水处理厂进行的。移动床生物膜反应器 (MBBR) 工艺在 1 小时的极短 HRT 和 0 的 DO 浓度下运行。5 mg/L选择性降解城市污水中的低分子量溶解有机物，而不降解膜可回收的悬浮和胶体有机物。预处理的应用并没有减少使用 MF 膜通过 DMF 回收的有机碳量（大约 70% 的进水 COD 被回收），但它显着减轻了膜污染，这可能是由于溶解有机物特性的改变废水。预处理还将 DMF 渗透液中的有机物浓度降低了 41%：DMF 渗透液中的 COD 浓度低至 40 mg/L。通过已建立的 MBBR 预处理，并行比较了 MF（0.1 µm）和 UF（截留分子量：150,000）膜对 DMF 的性能。结果发现，使用 UF 对有机物可回收量的增加是微不足道的（约 5%），而 UF 中的结垢比 MF 中的严重得多。超滤中的严重污染是由无机胶体（如 FeS）引起的，这些胶体可以通过 MF 膜但被超滤膜截留。根据本研究中获得的结果，得出的结论是，MF 比 UF 更适合用于有效的 DMF。