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 ${\overline{\mathrm{R}}}_{\text{air}}$. 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 90min and the backwash duration is 60s. 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.

在膜过滤工艺水处理中，工艺设计、操作、结垢等诸多因素都会影响膜通量。但往往被忽视的通量下降归因于空气阻力。在这项研究中，已经观察到，在启动时最初截留的空气以及从渗透液中释放的空气引起​​的空气阻力对水处理中的膜过滤和反洗过程有不利影响。在这项研究中，一种新的原位监测方法——超声波相控阵（UPA）被用来研究释放空气在中空纤维膜组件中的分布。研究了反洗间隔、持续时间和强度等操作参数。还提出了一种策略来减轻空气阻力的不利影响。${\overline{\mathrm{R}}}_{\text{空气}}$. 放风主要分布在离出口较远的地方，而随着反洗间隔和强度的增加，放风分布范围逐渐扩大。我们还找到了反洗间隔为90min，反洗持续时间为60s的最小排风量的最佳运行参数。此外，空气阻力与释放的空气有很好的正相关关系。此外，释放的空气迁移结果表明，空气分散和再溶解有利于降低反洗过程中的空气阻力。综上所述，优化操作可以减轻水处理中可变膜过滤模式下的空气阻力。