Enhanced ultrafiltration membrane fouling alleviation by module rotation with Fe-based flocs

The modules of ultrafiltration (UF) membrane always occupy a fixed position during filtration. This results in a gradual aggravation of membrane fouling because of the continuous pollutants deposition. However, it is known that the cake layer is composed of loosely hydrolyzed flocs. Therefore, in this study, the rotation concept of membrane-module was investigated in conjunction with the integrated floc (Fe-based)-UF process. We found that the Fe-based flocs can be easily peeled off the membrane surface during rotation, and the UF membrane fouling was alleviated, particularly with spiral module rotation because of the strong shearing force induced. The fouling behavior after spiral module rotation was similar for different floc dosages because of the looseness cake layer formed. The applied computational fluid dynamics model showed that a greater spiral rotation height corresponded to a larger water velocity distribution and stronger shearing force in the membrane tank, and this resulted in a reduction in the fouling degree due to the thinner cake layer formed. Moreover, in comparison with alkaline conditions, a slightly more severe fouling degree was observed under acidic conditions because of the induced denser cake layer with smaller Fe-based floc sizes; however, a significantly higher humic-acid removal efficiency was observed. In addition, UF membrane performed well with river water samples taken from the South-to-North water diversion project in China (Beijing), thereby indicating the rotating module potential application in membrane-based drinking water treatment.

Automated summary

The study found that rotating membrane modules can effectively alleviate UF membrane fouling, especially with spiral module rotation due to the strong shearing force induced. The computational fluid dynamics model showed that a greater spiral rotation height led to larger water velocity distribution and stronger shearing force, resulting in reduced fouling degree. More severe fouling was observed under acidic conditions with smaller Fe-based floc sizes, although a significantly higher humic-acid removal efficiency was achieved.