Research On Performance And Mechanism Of Membrane Fouling Mitigation In A Folded Plate MBR

Membrane fouling is a key problem to be solved urgently in MBR. Especially, regarded as the core part of submerged flat sheet MBR, the flat sheet membrane module usually needs frequent membrane cleaning and replacement due to its relatively low antifouling performance, which will greatly increase the running cost. At present, Membrane configuration modification can effectively strengthen the anti-fouling ability of flat sheet membrane module, but the membrane modules designed by configuration modification still have the defect of packing density reduction. Thus, it is very urgent to design a new membrane module which will not reduce the packing density of membrane module, has a simple structure and can effectively mitigate the membrane fouling in MBR at the same time.In order to effectively mitigate membrane fouling, a new folded plate membrane module was designed by modifying the configuration of flat sheet membrane module. In this study, the constant trans-membrane pressure (TMP) membrane filtration experiments were conducted to optimize the vertical inclination angle of folded plate membrane module; the particle image velocimetry (PIV) technology was used to characterize the feature of flow fields near the membrane surface; and effects of operating conditions (namely, aeration intensity, yeast suspension concentration, TMP, membrane spacing and aeration position) on the filtration performance of folded plate membrane module were investigated. Additionally, the constant flux operation experiment of the folded plate membrane module in MBR was conducted to investigate its anti-fouling ability and effluent effect, which can provide the technical support for engineering application of folded plate MBR.The vertical inclination angle optimization experiments of folded plate membrane modules revealed that, compared with flat sheet membrane module, the folded plate membrane module could significantly enhance membrane flux, and the folded plate membrane module with the vertical inclination angle of 15° obtained the highest stable flux enhancement of 57.7%. The PIV measurement results showed that, the biggest zones with high flow velocity, strong turbulent effect and more vortexes existed near the membrane surface of folded plate membrane module with the vertical inclination angle of 15°, which was considered the mechanism that the folded plate membrane module with the vertical inclination angle of 15° could significantly mitigate membrane fouling. The study of effect of operating conditions on filtration performance of folded plate membrane showed that, in the operating conditions set in this study, the higher aeration intensity, the lower yeast suspension concentration and the higher TMP were conducive to obtaining the higher stable flux enhancement for folded plate membrane module. Meanwhile, when the membrane spacing of folded plate membrane module was 30 mm, the folded plate membrane modules obtained the highest stable flux enhancement of above 10%, and aeration position directly below the membrane module could achieve the higher stable flux than that obliquely below the membrane module.Additionally, the constant flux operation experiment of folded plate membrane module in MBR showed that, the TMP rising rate of folded plate MBR was 0.4 times as fast as that of the flat sheet MBR, and CODCr and NH4+-N removal of folded plate MBR were above 90% and 80%, respectively. Moreover, the energy consumption per unit of product water of folded plate MBR was lower than that of flat sheet MBR.