| Vessel oily water is one of the main sources of ocean pollution, in order to protect the ocean, strict rules were made by the International Maritime Organization(IMO), the stable and efficient technology to dispose vessel oily water is extremely urgent. Bringing magnetic technology into MBR to dispose vessel oily water was studied in this thesis. Two sets of the same MBR were used as the contrast test,we call the MP-MBR which added Fe3O4 powder as reactor 1, we call it reactor 2 which upload magnetic field on the basis of the MP-MBR,removal efficiency and membrane fouling was investigated, the optimal magnetic field intensity and duration was determined, the mechanism of membrane fouling was discussed from several aspects.The microbial species, mixed liquor suspended solids(MLSS), sludge volume index(SVI)and other indicators were investigated until the sludge domesticated maturity. Then added Fe3O4 powder 650mg/L into two reactors at the same time, removal efficiency of CODCr and oil were supervised to make sure that the operating conditions and treatment effect were the same in two reactors. Then magnetic field was upload on both side of the reactor 2. The intensity gradient of magnetic field is 0, 15, 25, 35, 45mT, the time was controled by rotary stalling, down-run time is 2min:1min, 2min:2min, 2min:3min. Investigating on the impact of MP-MBR’s removal efficiency and the change of MLSS and TMP with different magnetic field intensity and time, ultimately determined the magnetic field strength of 35mT, rotary down-run time than 2min:2min as the optimal condition of the experiment.Firstly, the effect of magnetic field on the mixture properties was investigated, mixture of MLSS achieved stability and reached 7000mg/L in 25 days of reactor 2, it’s higher 800mg/L than reactor 1 and 12 days in advance to steady; The content of Extracellular Polymers(EPS) in the mixture of reactor 2 is lower 16.64mg/gMLSS than reactor 1, content of Soluble Microbial Products(SMP) is lower 8.45mg/gMLSS than reactor 1, the proportion of protein and polysaccharide decreased 0.2 finally; Floc particle size increased from 146.220nm to 280.179nm of reactor 2 which is two times lager than reactor 1; Specific resistance of sludge is lower 0.09×1013m/kg than reactor 1, this indicated that magnetic field can improve the sludge filtration performance; Zeta potential of absolute value in reactor 2 is smaller 57.17% than reactor 1, the viscosity was reduced by 67.02%, microbial activity increased by 27.07%. The properties of mixture was improved by magnetic field reasonable which slows down the membrane fouling rate.Secondly, the flora about the membrane surface and mixture was investigated and made a detailed classification, it proved that magnetic field can improve the diversity of advantage bacterium group, then enhance the ability to remove contaminants and slow down the membrane fouling rate; The impact of the resistance distribution of pollution by magnetic field was analyzed, the results show that the TMP growth rate was slowed down, cleaning cycle was extended 7 days, Rp and Rc was reduced, Rp/Rt changed little, Rc/Rt was reduced,this suggests the effect on mud cake layer pollution control is greater than the film hole blocking resistance by magnetic field.Ultimately, the microstructure of new film, polluted membrane and the membrane after cleaning were observed by scan electron microscope, it turned out that the viscous material on the membrane surface can be reduce by magnetic field, it can recover the state before the pollution in a larger degree; Fourier Transform Infrared Spectroscopy analysis shows that the production of EPS, SMP, etc can be reduced by magnetic field, thus the content of protein and polysaccharide are decreased and then slow down the membrane fouling rate; Flow field characteristics on the membrane surface were studied using particle image velocimetry (PIV),it proved that magnetic field can control movement of the magnetic particle and distribution of the velocity vector to change the liquid flow field, then promote the magnetic powder to adsorb more sticky and away from the membrane surface, reduce the filter cake layer’s contribution to membrane pollution,so slow down the membrane fouling rate. |
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