The Performance And Application Of Surface Modified PVDF Hydrophobic Hollow Fiber Membrane In MBFR

Membrane biofilm reactor(MBfR)as a new microbial wastewater treatment technology is based on traditional biological treatment with membrane aeration technology.In MBfR,membrane as microbial adhesion carrier and oxygen transfer media.So membrane materials as the core element in MBfR,it plays a key role in the rapid starting and stable operation of the system.Hydrophobic microporous membrane,compact membrane and composite membrane as the three membrane materials commonly used in MBfR.Composite membrane not only has the high aeration pressure of dense membrane,but the large gas flux of hydrophobic microporous membrane,its research and development becomes one of research hotspots in MBfR.But the membrane designed for MBfR is still rare,making the MBfR technology development and industrial applications restricts.Aiming at the insufficient oxygen supply capacity and bioaffinity property of hydrophobic microporous membrane in MBfR,hydrophobic PVDF hollow fiber membrane was modified by self-polymerization and interfacial polymerization to prepare surface modified composite membrane of PVDF/DO PA and PVDF/TMC-CS that suitable for MBfR technology.And composite membranes had similar mechanical strength with the PVDF original membrane,the total oxygen transfer coefficient(KLa)of PVDF/DOPA was improved from 0.85×10-2min-1 to 1.69×10-2min-1,PVDF/TMC-CS composite membrane increased to 1.24×10-2min-1,the oxygen mass transfer performance of membrane materials has been optimized.The contact angle of PVDF/DOPA and PVDF/TMC-CS composite membrane decreased from 72.3° to 32.8° and 35.7°,respectively,improved the hydrophilicity of the membrane.The results show that the composite membranes meeting the requirements of the MBfR.In this thesis selected mature activated sludge mixture as biological indicator in biological affinity,and studying the attachment on the different membranes,difference of biological affinity between the membranes was evaluated.The preliminary study on the removal characteristics of different membrane for sewage wastewater was carried out.compared with the PVDF original membrane,the microbial film thickness of PVDF/DOPA composite membrane was the highest for 25?m and microbial maturity is high and the quantity is much,indicating that the PVDF/DOPA composite membrane have the highest biological affinity;The effect of PVDF/DOPA composite membrane on TOC and NH4+-N at 93.48%and 84.74%,capacity of sewage treatment and resistance to impact load was significantly better than that of other membranes.And it shown that a poor microorganism adhesion and wastewater treatment capacity in PVDF/TMC-CS composite membrane.It need a further study.Extracellular polymeric substances(EPS)was selected to study the pollution contribution of different hydrophobic organic compounds on membrane.EPS is divided into hydrophobic acids,hydrophobic bases,hydrophobic neutrals and hydrophilic substances by resin grading operation.This four kinds of organic compounds were selected to carry out the experiment of static membrane fouling,and the basic performance and oxygen mass transfer performance of membrane were used as the evaluation criteria.The result demonstrates that,The KLa of PVDF original membrane decreased most obvious cause by the four pollutants.HIS plays a more significant role in the fouling,makes the KLa of PVDF original membrane attenuated by 52.5%.For composite membranes,HOA plays a crucial role in membrane fouling.The adsorption of HOA caused KLa of PVDF original membrane?PVDF/TMC-CS?PVDF/DOPA composite membrane decreased by 41.9%?24.1%and 38.6%respectively.But compared with the PVDF original membrane after HIS pollution,the KLa of the PVDF/TMC-CS composite membrane and the PVDF/DOPA composite membrane is still 1.91 and 2.00 times more.