Toward self-sustaining membrane filtration via manipulating the membrane-surface ecosystem.

Biofouling-induced membrane contamination severely limits the application of membrane filtration systems. Regulating biofilm formation on membrane surfaces can facilitate the development of water channels and help establish a dynamic balance between foulant deposition and biodegradation. In this study, an activated carbon fiber (ACF) barrier and a biofiltration-integrated ACF barrier (BF_ACF) were employed to evaluate their effects on the performance of a gravity-driven membrane (GDM) ultrafiltration (UF) system. The results showed that ACF and BF_ACF, significantly improved dissolved organic matter (DOM) removal, increasing removal efficiencies from approximately 5-13% (for UF alone) to 21-25% and 78-81%, respectively. In addition, the steady-state membrane fluxes of the ACF and BF_ACF systems increased substantially from 1.96 ± 0.15 (UF alone) to 2.84 ± 0.22 and 4.19 ± 0.13 LMH, respectively, corresponding to increases of approximately 44.9% and 214% relative to the control. ACF and BF_ACF were found to alter the heterogeneity of the biofilm layer, resulting in a thinner, looser, and more porous structure. A shift in the microbial community from r-selected to K-selected taxa was also observed, transforming the membrane-surface ecosystem from a "fouling-type" community into a "cleaning-type" community. Overall, this study provides a paradigm for "controlling fouling with microorganisms" through the artificial regulation of the membrane-surface ecological niche, thereby improving the sustainability of membrane-based water treatment systems.