Effect Of Non Solvent On The Properties Of Supported Composite Membrane In PVDF/PET And Its Application In MBR System

Membrane bioreactor(MBR), as a new type of highly efficient wastewater treatment technology, has great potential in the field of wastewater resource and reuse, and common concerned by the scholars of the world’s. However, membrane fouling is the main problem that hinders the large-scale use of MBR, which leads to the decrease of membrane flux, the increase of the frequency of the replacement and cleaning of the membrane module, and the operating cost of the reactor. Therefore, it is necessary to develop the membrane that had stronger anti pollution performance and explore the characteristics of membrane fouling, which has great significance for the effective control of membrane fouling and the wide application of MBR. This paper has done two aspects of research: on the one hand, the addition of a non solvent small molecule in the PVDF casting liquid system makes the thermodynamic properties of the system become unstable, and then changes the pore structure, affecting the performance of PVDF/PET composite films. On the other hand, selecting the better performance of membrane and making curtain type components used in an inverted A2O-MBR reactor to treating domestic sewage, and optimizing the operating conditions to explore the characteristics of membrane pollution.Research results show that:(1) Addition of non solvent additives with different concentrations of different components in the casting solution, the hollow fiber composite membrane was prepared through the coating technology and immersion-precipitation technique and the performance of the composite membrane were determined, such as the flux, contact angle, then the best concentration ratio of different non solvent additives was determined. By test specific flux of composite membrane obtained that adding H2 O and TEG composite membrane of specific flux per unit time decay rate is relatively smaller than GI and HAC composite membrane. Unit time decay amplitude is increased by the order of TEG, H2 O, HAc, and GI. Description in TEG content is 5% made the comprehensive performance of the composite membrane best, so the selection of the formula of casting solution spinning silk into membranes were used in the subsequent MBR.(2) In MBR treatment of domestic wastewater COD removal rate of 73.2% above, the impact of hydraulic retention time on the effluent COD is small. When the system is stable, the ammonia nitrogen effluent is stable at 0.25-1.26mg/L, the removal rate of 96% above. The effect of HRT to TN removal rate was less than NH3-N. But compared with the traditional activated sludge process, the inverted A2/O-MBR has a good removal effect of TN.(3) In the MBR system design, HRT is an important design parameter. The shorter HRT promote the accumulation of polysaccharide and protein in the membrane surface, resulting in a more serious membrane fouling. Compared with polysaccharides, protein is a major factor affecting membrane fouling. In the process of membrane fouling, the effect of HRT on biological metabolism is very small. In submerged MBR, due to the degradation of microorganisms, polysaccharides did not cause serious irreversible membrane fouling. The biological degradation of EPS in the reactor is not equal, which may be due to different microorganisms responsible for the degradation of different components.(4) After FTIR analysis, polysaccharide and protein were main compositions of organic pollutants and that were hydrophilic substance. Membrane surface filter cake layer is the most similar to EPS. AFM analysis that the adhesion of membrane and EPS were largest, indicating that EPS was the main pollutant of the membrane, through the QCM-D technology to further from the degree of adsorption and adsorption point of view more intuitive expression of EPS was the main pollutant, consistent with the FTIR analysis.