Study on Fouling of Nanofiltration Membranes when Treating the MBR Effluent

The source of water in this paper is the effluent of MBR. The pressure of nanofiltration system was monitored during the conditioning phase to check the fouling of nanofiltration membrane. The morphology and distribution of polluants on the membrane surface were examined by scanning electron microscopy (SEM), with additionalenergy dispersive spectrometer (EDS) analysis. Then analyzes the main causes of membrane fouling. And the result of SEM and EDS about membrane showed that, the major foulants of membrane include organic substances and silicon dioxide. And there may be some inorganic substances, which contained magnesium (Mg) and calcium (Ca). Thought cleaning experiments with HCl, STPP (Sodium tripolyphosphate, Na5P3O10) + Na-DDBS (sodium dodecyl benzene sulfonate, C6H5(CH2)(12)-SO3Na) about fouled membrane, cleaning efficiency is up to 87%. As water scarcity and water pollution increasing, water resource has become the dominant factor restricting the economic development. In addition to finding new water sources, the water reuse has been paid more and more attention. To enhance the quality of reclaimed water to meet the different needs, further treatment must be carried out. The municipal sewage has a lot of salts in the Coastal zone, so desalination is an important part of water reuse. Nanofiltration system as one of the main desalination technology has several advantages, such as simply, no phase transition process, and treatment effect significant. However, the high organic content, water quality composition complex, it is likely to cause pollution of nanofiltration membrane, so how to solve the problem of nanofiltration membrane fouling is a critical problem in water treatment systems. In order to investigate the fouling reasons and cleaningmethods of nanofiltration membrane, this paper analyzed theeffluent water quality characteristics of membrane bioreactor(MBR) in the municipal sewage treatment plant, To provide the basis for the application of nanofiltration system.