浸入式超滤膜污染特征与形成机理研究.docx

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浸入式超滤膜污染特征与形成机理研究
摘 要
浸入式超滤膜技术因其卓越的分离性能和可靠的长期运行性，已经被广泛应用于水处理、废水处理、医药、食品等领域。然而，由于膜污染问题的存在，其应用仍面临着严重的挑战。本文通过对浸入式超滤膜污染特征和形成机理的研究，为膜的长期稳定运行提供了一定的理论依据。
通过对浸入式超滤膜的污染特征进行分析，发现膜上主要出现有机污染物、无机污染物和生物污染物等污染物质，其中有机污染物占据污染物的绝大部分。而浸入式超滤膜污染的形成机理主要包括物理阻塞、化学吸附和生物附着等几种机制。其中，物理阻塞是最主要的膜污染机制。由于膜材料和操作条件等因素，会引起膜孔径的变化和分布不均，从而导致物理阻塞。此外，化学吸附和生物附着也与膜污染密切相关。
为了解决浸入式超滤膜的污染问题，多种方法得到了应用，其中包括预处理、后处理、反应性增强等技术。其中，预处理是避免浸入式超滤膜污染的最为有效的方法。可采用物理、化学和生物等方法进行预处理，如粗滤、混凝沉淀、生物膜附着等。此外，后处理也是一种有效的污染控制方法，可采用化学清洗、氧化、还原等后处理方法。反应性增强是利用交联剂等化学方法改变膜性质，以改变膜的阻塞和水通量等性能。
综上所述，浸入式超滤膜污染特征与形成机理的研究，对于保障膜的长期稳定运行和提高其使用效率至关重要。我们需要进一步开展浸入式超滤膜的污染特征和形成机理的深入研究，为膜技术的进一步完善和应用提供更多的理论指导。
关键词：浸入式超滤膜；污染特征；形成机理；水处理；污水处理
Introduction
Water treatment and wastewater treatment are essential for our daily life and social development. However, the traditional treatment methods, such as sedimentation, filtration, and disinfection, cannot remove some of the contaminants effectively. Therefore, membrane technology has become an alternative for water and wastewater treatment in recent decades. Among the membrane technologies, immersed ultrafiltration membrane (IUFM) technology is a promising method for its efficiency and stability. The IUFM has been applied widely in water treatment, wastewater treatment, pharmaceuticals, food, and beverage industries. However, the presence of membrane fouling is still a significant challenge for long-term stable operation. The purpose of this article is to analyze the characteristics and formation mechanisms of the membrane fouling in the IUFM and provide some effective solutions to improve the stable operation of the membrane for water and wastewater treatment.
Characteristics of membrane fouling in the IUFM
Organic substances, inorganic substances, and biological substances are three categories of pollutants that can cause fouling on the membrane surface. Organic pollutants, including humic acids, proteins, and macromolecular composites, are the primary cause of membrane fouling. These organic pollutants can form a macromolecular and gel-like layer on the membrane surface, known as the reversible fouling layer. The reversible fouling layer can reduce the membrane's permeability, which results in a decrease of the water flux.
Besides, inorganic substances, such as calcium carbonate and iron oxide particles, can also cause fouling on the membrane surface. The inorganic substances are usually smaller than the membrane pore size and can easily penetrate into the membrane's internal structure, forming irreversible fouling layers on the membrane surface.
Biological substances, such as microorganisms, bacteria, and algae, are another type of pollutants that can cause fouling on the membrane surface. They can adhere to the surface of the membrane and form a biological fouling layer, which can block the membrane pores and reduce water flux.
Formation mechanisms of membrane fouling in the IUFM
Physical blocking, chemical adsorption, and biological attachment are three types of interactions that can lead to the formation of membrane fouling.
Physical blocking refers to the mechanical occlusion of membrane pores by contaminants. During the operation of the IUFM, the contaminants can accumulate on the surface of the membrane or in the membrane pores, creating a cake or gel layer that reduces the membrane's permeability. The physical blocking is the most common mechanism of membrane fouling, and it is mainly influenced by the pore size distribution of the membrane, the hydrodynamic conditions, and the chemical characteristics of the contaminants.
Chemical adsorption refers to the interaction between the contaminants and the surface of the membrane. The contaminants can interact with the membrane's surface through hydrogen bonds, electrostatic interactions, or Van der Waals forces. The chemical adsorption can cause the aggregation of the contaminants on the membrane surface, reducing the membrane's permeability.
Biological attachment refers to the adhesion of microorganisms on the membrane surface. The microorganisms can adhere to the membrane's surface by secreting extracellular polymeric substances (EPSs). The EPSs can form a biofilm that covers the membrane surface, reducing the membrane's permeability, and increasing the resistance to biocides.
Solutions to control membrane fouling in the IUFM
Several strategies have been developed to control the fouling of the IUFM, including pretreatment, post-treatment, and reactive enhancement.
Pretreatment refers to the methods used to pretreat the influent water before being fed into the IUFM system. The pretreatment methods include coagulation-flocculation, dissolved air flotation, microfiltration, or adsorption. The pretreatment can remove some of the fouling precursors, such as suspended solids, organic matter, and colloids, to prevent membranefouling.
Post-treatment refers to the methods used to restore the membrane's performance after fouling. The post-treatment methods include physical cleaning, chemical cleaning, and biological cleaning. The physical cleaning can remove the fouling layer by applying shear stress on the membrane surface. The chemical cleaning can dissolve the fouling layer by using oxidants, acids, or alkaline solutions. The biological cleaning can remove the biofilm by using microorganisms that can degrade the EPSs.
Reactive enhancement refers to changing the membrane's surface properties or increasing the membrane's hydrophilicity to inhibit or reduce the fouling formation. The reactive enhancement can be achieved by using cross-linking agents, photo-initiators, plasma treatment, or coating materials on the membrane surface.
Conclusion
In conclusion, the characterization and formation mechanisms of membrane fouling in the IUFM have been analyzed in this article. The physical blocking is the dominant mechanism of membrane fouling. The characteristics and formation mechanisms of membrane fouling in the IUFM can be affected by various factors, such as chemical composition, pore size distribution, hydrodynamic conditions, and membrane surface properties. Several strategies, including pretreatment, post-treatment, and reactive enhancement, have been developed to control the fouling of the IUFM effectively. Further studies are required to understand the mechanisms of the different fouling layers and develop more effective control strategies.