Pressure driven inside feed (PDI) hollow fibre filtration: Optimizing the geometry and operating parameters

Exploring the influence of air resistance on the hollow fiber membrane process in water treatment based on ultrasonic phased array technology

In water treatment with membrane filtration process, a lot of factors such as process design, operation, and fouling affect membrane flux. But it is often neglected the flux decline which attribute to air resistance. In this study, it has been observed that air resistance caused by air trapped initially at startup as well as the release of air from the permeating liquid has an adverse effect on the membrane filtration and backwash process in water treatment. In the study, a new in-situ monitoring method, ultrasonic phased array (UPA), was used to investigate the distribution of released air in the hollow fiber membrane module. The operation parameters such as backwash interval, duration and strength were investigated. A strategy was also proposed to mitigate the adverse effects of air resistance. The results showed that UPA can successfully monitor the distribution of released air, which has a good positive correlation with air sound pressure reflection R¯_air. The released air is mainly distributed far away from the outlet, while as the backwash interval and strength increase, the range of released air distribution gradually expands. We also found the optimal operating parameters for the minimum released air volume that the backwash interval is 90 min and the backwash duration is 60 s. Besides, the air resistance has a good positive correlation with released air. Moreover, the released air migration results show that air dispersion and redissolution are beneficial to reduce the air resistance in the backwash process. In summary, the optimal operation can mitigate the air resistance in the variable membrane filtration mode in water treatment.

Optimizing the Axial Resistance Profile of Submerged Hollow Fiber Membranes

Submerged hollow fiber membranes (SHFMs) are used for a wide variety of applications. Their applicability and their advantages, however, depend crucially on the prevailing hydrodynamics within single fibers. In this respect, the non-uniform distribution of transmembrane flux is a known problem related to inhomogeneous membrane fouling and disadvantages for cleaning. To address this problem, we propose an approach to homogenize transmembrane flux by varying the local membrane resistance using optimal control methods for the first time in SHFM research. Based on an established model, different scenarios are optimized, namely with different fiber lengths and inner radii. In addition, a double-end setup is explored. It is shown that the optimization goal is reached very well in all tested cases, which underlines the general validity of our strategy. Further uses and extensions of the optimization method are provided, as well as hints for the practical implementation of the suggested measures.