Water Treatment by Microfiltration and Ultrafiltration
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This chapter contains sections titled: Introduction Materials, Module Configurations, and Manufacturers Microfiltration/Ultrafiltration Pretreatment Membrane Applications Membrane Fouling and Cleaning Integrated Membrane Systems (MF or UF + RO or NF) Backwash Water Reuse, Treatment, and Disposal ReferencesKeywords:
Ultrafiltration (renal)
Membrane Fouling
Fouling has continued to be a problem that hinders the effectiveness of membrane properties. To solve this problem of reducing fouling effects on membrane surface properties, different and innovative types of membrane patterning has been proposed. This article reviews on the progress of patterned membranes and their separation process concerning the fouling effects of membranes. The types of separation processes that utilize the maximum effectiveness of the patterned membranes include nanofiltration (NF), reverse osmosis (RO), microfiltration (MF), ultrafiltration (UF), and pervaporation (PV). Using these separation processes have shown and prove to have a major effect on reducing fouling effects, and in addition, they also add beneficial properties to the patterned membranes. Each patterned membrane and their separation processes gave notable results in threshold towards flux, salt rejections, hydrophilicity and much more, but there are also some unsolved cases to be pointed out. In this review, the effects of patterned membrane for separation processes will be discussed.
Nanofiltration
Ultrafiltration (renal)
Membrane Fouling
Membrane Technology
Pervaporation
Separation process
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Control of membrane fouling is important for more efficient use of membranes in water treatment. Control of physically irreversible fouling, which is defined as fouling that requires chemical cleaning to be cancelled, is particularly important for reduction of operation cost in a membrane process. In this study, a long-term filtration experiment using three different types of MF and UF membranes was carried out at an existing water purification plant, and the evolution of physically irreversible fouling was investigated. The experimental results demonstrated that the extent of physically irreversible fouling differed significantly depending on the membrane type. Cleaning of the fouled membranes with various chemical reagents demonstrated that organic matter was mainly responsible for physically irreversible fouling. Organic matter that had caused physically irreversible fouling in the long-term operation was desorbed from the fouled membranes and was subjected to Fourier transform infrared and 13C nuclear magnetic resonance analyses. These analyses revealed that carbohydrates were dominant in the membrane foulant regardless of the type of membrane. Based on measurements of molecular weight distribution of organic matter in the feedwater and the permeates from the membranes, a two-step fouling mechanism is proposed to explain the dominance of carbohydrates in the foulant: hydrophobic (humic-like) components with small molecular weight are first adsorbed on the membrane and, consequently, narrow the size of micro-pores of membranes, and then hydrophilic (carbohydrate-like) compounds with larger molecular weight plug the narrowed pores or the hydrophilic compounds are adsorbed onto the membrane surface conditioned by the hydrophobic components.
Ultrafiltration (renal)
Membrane Fouling
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Ultrafiltration (renal)
Polysulfone
Membrane Fouling
Synthetic membrane
Filtration (mathematics)
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Citations (157)
The performance of three different low-pressure water treatment membrane pilot plants was evaluated on a low-turbidity, low-colour water in British Columbia. All membrane units were hollow-fibre, hydrophilic membranes with nominal pore sizes of 0.01 to 0.2 µm. In addition to finished water quality, specific flux of each membrane was used to compare the performance of the three membrane units. The effect of feed pretreatment on the performance of the membranes and removal of disinfection byproduct (DBP) precursors was evaluated using chemical coagulation and powdered activated carbon (PAC) addition. Chemical coagulation proved to be very effective in removing DPB precursors and reducing the rate of membrane fouling. Powdered activated carbon addition, on the other hand, resulted in moderate removal of DBP precursors but increased the rate of membrane fouling. The nature and causes of membrane fouling as well as the impact of pretreatment methods on membrane fouling are discussed. Key words: ultrafiltration, microfiltration, coagulation, PAC, fouling, hollow fibre membranes, pretreatment, water treatment.
Membrane Fouling
Ultrafiltration (renal)
Turbidity
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The overall objective of our work is to identify the organic fraction responsible for fouling of lowpressure (microfiltration and ultrafiltration) membranes, and to understand fouling mechanisms. Several natural organic matter (NOM) fractions isolated from Ribou Reservoir have been ultrafiltered with two different 100 KD membranes (regenerated cellulose and polyethersulfone) using a non-stirred cell unit. Results have shown that the organic colloidal fraction (bacterial peptidoglycan residue) shows the most significant fouling. The dissolved fraction (<0.45 μm) of NOM, which contains solutes larger and smaller than the pore size of 100 KD membranes, contributes to fouling through pore blockage and/or adsorption mechanisms. Atomic force microscopy (AFM) examination reveals morphological changes during membrane fouling. The polyethersulfone and regenerated cellulose membranes are relatively smooth. However, based on AFM, some of the fouled membrane surfaces appear rougher than the corresponding clean membrane surface. These results demonstrate the role of surface coverage in ultrafiltration membranes. It appears that membrane roughness is a key physical parameter in membrane fouling. More analysis is being undertaken with scanning electron microscopy images to determine pore size distribution for the clean and the fouled membranes, providing more information in terms of fouling mechanisms.
Ultrafiltration (renal)
Membrane Fouling
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Membrane Fouling
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Ultrafiltration (renal)
Filtration (mathematics)
Membrane Fouling
Cross-flow filtration
Protein Adsorption
Membrane Technology
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Citations (80)
Membrane fouling has been recognized as a serious barrier in microfiltration and ultrafiltration of secondary effluent. Feed pre-treatment is a frequent use for fouling extenuation. Numerous techniques have been employed to monitor membrane fouling. These include: Pre-treatment of the feedwater, modification of membrane properties, optimization of module configuration and operating conditions, periodic membrane cleaning, evaluation of system performance using pilot plant, and use of predictive models. However, membrane fouling remains complicated task for both technico-economic reasons depending on water characteristics and pre-treatment processes and efficiencies. The large majority of the membranes employed in water and wastewater treatment are produced of polymeric materials. Nevertheless, it has been expected that ceramic membranes will be competitive options in the following years.
Membrane Fouling
Ultrafiltration (renal)
Boiler feedwater
Membrane Technology
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Concentration polarization
Ultrafiltration (renal)
Membrane Fouling
Membrane Technology
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Citations (29)
Ultrafiltration (renal)
Membrane Fouling
Filtration (mathematics)
Membrane Technology
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Citations (599)