This study attempts to provide an improved fundamental understanding of the self-forming dynamic membrane (SFDM) filtration process in submerged anaerobic bioreactors. Excellent system performances were achieved in terms of high COD removal efficiency (similar to 90%), fast formation/reformation of SFDM (< 1 h), and sustainable low-resistance (3.92 x 10(10) m(-1)) high-flux (10-30 L/m(2).h) filtration. A typical flux-variation profile consisted of an initial abruptly fast decrease followed by a gradually slow reduction, corresponding to the formation and sustainable operation period, respectively. The increase of SFDM resistance in formation period was attributable to the fast deposition of large particles on coarse-pore support materials. After SFDM formation, the subsequent increase of SFDM resistance was controlled more by the increase of specific resistance, which was firstly mainly resulted from the increasing accumulation of small particles with higher hydrophobicity and the external deposition of eEPS but later most attributable to the increase of internal release of eEPS.