College of Environmental Science and Engineering, Institute of Carbon Neutrality, State Key Laboratory of Pollution Control and Resources Reuse, Tongji University, 1239 Siping Road, Shanghai 200092, China.
College of Environmental Science and Engineering, Institute of Carbon Neutrality, State Key Laboratory of Pollution Control and Resources Reuse, Tongji University, 1239 Siping Road, Shanghai 200092, China.
Water Res. 2024 Oct 1;263:122133. doi: 10.1016/j.watres.2024.122133. Epub 2024 Jul 22.
Membrane fouling remains a significant challenge in wastewater treatment, hindering both efficiency and lifespan. This study reports a distinct phenomenon of stratified membrane clogging observed in a full-scale cross-flow tubular ultrafiltration (UF) system treating sludge anaerobic digestion (AD) reject water. The distinct stratified structure, comprising inner and outer layers within the cake layer, has not been previously described. This research involved characterizing the filtration performance, analyzing membrane clog composition, and proposing a two-stage formation mechanism for the stratified clogs. It was revealed that higher inorganic and lower organic content in the outer layer compared to the inner layer. Acid and alkali treatments demonstrated the effectiveness of combined cleaning strategies. A mathematical model was developed to determine the critical conditions for stratified clog formation, influenced by membrane flux and cross-flow velocity (CFV). It is proposed that outer layer forms through long-term selective deposition, while the inner layer results from short-term dewatering within limited tubular space. High CFV (>2.5 m/s) prevents inner layer formation. Critical conditions for stratification occur at a flux of 18 L/m/h with a CFV of 0.1 m/s or 65 L/m/h with a CFV of 0.35 m/s. This study contributes a novel understanding of stratified membrane clogging, proposing a two-stage formation mechanism and identifying critical conditions, which provides insights for effective fouling control strategies and maintenance of operational efficiency for membrane systems.
膜污染仍然是废水处理中的一个重大挑战，既影响效率又影响使用寿命。本研究报告了在处理污泥厌氧消化（AD）剩余水的全尺寸错流管式超滤（UF）系统中观察到的分层膜堵塞的明显现象。在饼层内存在内层和外层的明显分层结构以前并未被描述过。本研究涉及表征过滤性能、分析膜堵塞组成，并提出分层堵塞的两阶段形成机制。结果表明，外层的无机含量较高，有机含量较低。酸和碱处理证明了联合清洗策略的有效性。开发了一个数学模型来确定分层堵塞形成的临界条件，这受到膜通量和错流速度（CFV）的影响。提出外层是通过长期选择性沉积形成的，而内层是在有限的管状空间内短期脱水形成的。高 CFV（>2.5 m/s）可防止内层形成。在通量为 18 L/m/h 且 CFV 为 0.1 m/s 或通量为 65 L/m/h 且 CFV 为 0.35 m/s 时会出现分层的临界条件。本研究对分层膜堵塞有了新的认识，提出了两阶段形成机制并确定了临界条件，为有效的结垢控制策略和膜系统的运行效率维护提供了见解。
