Exploration of the dynamic osmotic membrane bioreactor in low-speed rolling motion for membrane fouling mitigation

A specific dynamic osmotic membrane bioreactor (DR-OMBR) in low-speed rolling motion was designed to alleviate membrane fouling. Using a low rotation speed (2 rpm) together with the cross-flow velocity in this designed DR-OMBR, the shear stress (−1.57 × 10⁻⁴ N/m²) and the centrifugal force (1.31 × 10⁻⁴ N) were generated to reduce the attachment of foulant to the membrane surface and achieve a relatively stable water flux. A parallel experiment indicated that the water flux of the conventional OMBR (without rotation) was 10% lower than that of the DR-OMBR, and total organic carbon and phosphate removals still achieved 99.9 and 97.0%, respectively. The ammonium rejection was slightly lower as a result of the Donna effect. Furthermore, compared to rotation speeds (0–5 rpm), the rotation speed of 2 rpm achieved better water flux (6.4 LMH) and lower reversal salt diffusion (3.7 gMH) because the centrifugal force had a positive effect on the reversal salt flux and a negative impact on the water flux, and a higher rotation speed could generate a considerable centrifugal force to limit the water flux and increase the reverse salt flux. Furthermore, the mitigation of membrane fouling was further confirmed by the relatively low amount of extracellular polymeric substances (EPS) and soluble microbial products (SMP) on the membrane surface of the DR-OMBR.