A Review on Flux Decline Control Strategies in Pressure-Driven Membrane Processes

Concentration polarization (CP) and membrane fouling are two major drawbacks for pressure-driven membrane filtration processes (PDMPs) because they cause severe flux decline, which requires effective control strategies. Many articles have proposed the diverse potential applications of various control strategies in reducing CP and membrane fouling. This paper reviews various mechanisms and influencing factors on flux decline, as well as their control strategies in PDMPs. Nine effective control strategies are summarized, generalized, and compared in this paper. On the basis of their functions and influences, they can be also classified as the following: (1) modification: pretreatment of feed, modification of feed characteristics, selection and modification of membrane; (2) design: shear-enhanced filtration modules, applied field enhancement and CP drawer; (3) operation: optimization of operating parameters, hydraulic flushing and two-phase flow. Then, the general and practical guidelines are given. On the basis of this review, future research perspectives related to flux decline control strategies are proposed