The roles of particles in enhancing membrane filtration: A review

Particles suspended within feed flow or added into membrane-filtration systems may behave as foulant or fouling mitigation agent. The fine boundary between these two roles warrant attention to promote the beneficial role of particles and avoid their undermining impact. The particle back-transport phenomenon is first elucidated, then the four possible enhancing roles of particles in membrane-filtration systems are discussed, namely, mechanical scouring, as adsorbents of organic foulants, as coagulants to form porous flocs, and as dynamic membranes to protect the primary membrane matrix. Process variables governing such phenomena and possible adverse effects that need to be mitigated are also summarized. Finally, future research directions are recommended based on the understanding accumulated, namely, hybridization of the various beneficial roles, development of customized particles, and more understanding/optimization of the energy - fouling mitigation tradeoff.