Study On Effects Of Surface Properties On Membrane Fouling And The Control Of Membrane Fouling

Membrane bioreactor (MBR), which integrates membrane separation with activated sludge system, is a new technology for wastewater treatment. As a new wastewater treatment technology, MBR owns significant advantages, including highly-improved effluent quality, reduced footprint and sludge production, etc. At present, MBR has been increasing used for various wastewater treatment in worldwide. However, membrane fouling is the primary obstacle restricting this technology’s popularization and large-scale applications. During the MBR operation, membrane fouling reduces the quality and production of effluent, increase the energy requirement, which reduces its economy and practicality. Thus, it will be of great significance to explore the mechanism and put forward appropriate control strategy.Based on a continuously operated MBR and XDLVO theory, the key influential factors of membrane fouling were discussed deeply. In this study, effects of surface charge and γAB on interfacial interactions related to membrane fouling based on thermodynamic analysis were explore, and effects of adding powdered activated carbon (PAC) and modified Fe3O4 (m-FesO4) on filtering quality and organic removal efficiency were also researched. The main results are presented as follows:(1) The aim of this study was to investigate effects of surface charge of membrane and sludge foulants on thermodynamic interaction between sludge foulants and membrane in a stable operating SMBR setup. Zeta potential of both membrane and sludge foulants had minor effects on the total interfacial interaction between Soluble Microbial products(SMPs) and membrane (two infinite planar surfaces), but greatly affected the total interfacial interaction between membrane and foulant particals. Eventual adhesion of foulant particles on membrane surface need surmount an energy barrier, and there existed a critical zeta potential below which the energy barrier would disappear.(2) Based on XDLVO theory, membrane surface γAB can influence interaction energy through affecting Lewis acid-base pair force. γAB depend on electron acceptor(γ+)and electron donor (γ), it was indicated that energy barrier increase effectively with the increase of γ+and γ- between foulant particles and smooth membrane. It was also found that the decrease of effect intensity between foulant particles and rough membrane with the increase of γ+andγ-There had a more influence with the change of y compared with y+.(3) There had a decreasing membrane filtration resistance and adding PAC and m-Fe2O3. Microscopic examination showed that the cake layer became more looser and porous after adding two additives especially adding m-Fe3O4. Meanwhile the sludge suspension had higher DOC removal after adding additives especially m-Fe3O4 compared with general sludge. According to thermodynamic analysis, after adding additives the energy barrier between membrane and foulant particles would decrease, which benefits flouant particles adhere to membrane, but at the same time decreasing energy barrier would make foulant particles detach from membrane more easily.