Nanofiltration Natural

Generally, a distinction can be made between membrane bioreactors based on cells performing a desired conversion and processes based on enzymes. In ceU-based processes, bacteria, plant and mammalian cells are used for the production of (fine) chemicals, pharmaceuticals and food additives or for the treatment of waste streams. Enzyme-based membrane bioreactors are typically used for the degradation of natural polymeric materials Hke starch, cellulose or proteins or for the resolution of optically active components in the pharmaceutical, agrochemical, food and chemical industry [50, 51]. In general, only ultrafiltration (UF) or microfiltration (MF)-based processes have been reported and little is known on the application of reverse osmosis (RO) or nanofiltration (NF) in membrane bioreactors. Additionally, membrane contactor systems have been developed, based on micro-porous polyolefin or teflon membranes [52-55]. 

Nghiem LD, Schafer AI, Elimelech M (2004) Removal of natural hormones by nanofiltration membranes measurement, modeling, and mechanisms. Environ Sci Technol 38 1888-1896... 

These compounds are commonly present in complex fermentation media, or even in natural raw materials and subsidiary streams resulting from the processing of these materials. Their recovery is usually difficult due to their low concentration, often vestigiary, and the complexity of the original matrix where they have to be recovered from. This chapter discusses, and illustrates with recent applications, the use of different membrane processes able to deal with the recovery of small biologically active molecules (see Figure 11.2) electrodialysis, pervaporation, and nanofiltration. 

Recovery of valuable bioactive compounds by nanofiltration, from natural products or streams resulting from the processing of natural products, is also gaining an increasing interest. Recent examples include the production of natural extracts from olive oil subproducts, which are rich in the most potent natural antioxidant compound identified so far (hydroxytyrosol) as well as the production of natural extracts from grape pomace residues, which are rich in a number of high-value compounds. 

D. Violleau, H. Essis-Tome, H. Habarou, J.P. Croue, M. Pontie, fouling studies of a polyamide nanofiltration membrane by selected natural organic matter an analytical approach, Desalination 173 (2005) 223-238. 

Schafer, A. I., A. G. Fane, and T. D. Waite, "Nanofiltration of Natural Organic Matter Removal, Fouling, and the Influence of Multivalent Ions," Desalination, 118 (1998). 

Seidel, Arza, and Menachem Elimelech, Coupling Between Chemical and Physical Interactions in Natural Organic Matter (NOM) Fouling of Nanofiltration Membranes Implications for Fouling Control," Journal of Membrane Science, 203 (2002). 

Hong, S. and Elimelech, M., Chemical and physical aspects of natural organic matter (NOM) fouling of nanofiltration membranes, J. Membr. ScL, 132, 159, 1997. 

Nanofiltration is one of promising technologies for the treatment of natural organic matters and inorganic pollutants. Low-pressure operation of nanofiltration is possible [115, 116]. The nanofiltration system, which has a pretreatment process of microfiltration or ultrafiltration, may be applicable to drinking water treatment. 

Replacing the ultrafiltration, nanofiltration pretreatment and reverse osmosis by BAHLM processes in desalination industry is the main idea of this proposal. Rejection characteristics of natural organic matters and inorganic salts in a low pressure nanofiltration (e.g., >99% at 1.5 MPa [115]) and capacity of polyanions to complex monovalent and especially bivalent cations [92, 95, 115-117] make this idea promising. 

Thanuttamavong M, Oh JI, Yamamoto K, and Urase T, Comparison between rejection characteristics of natural organic matters and inorganic salts in ultra low pressure nanofiltration for drinking water production. Proceedings of the Conference on Membranes in Drinking and Industrial Water Production. Paris, Prance, October 2000 Desalination Publications, L Aquila, Italy, 2000 Vol. 1, pp. 269-282. 

For membrane processes involving liquids the mass transport mechanisms can be more involved. This is because the nature of liquid mixtures currently separated by membranes is also significantly more complex they include emulsions, suspensions of solid particles, proteins, and microorganisms, and multi-component solutions of polymers, salts, acids or bases. The interactions between the species present in such liquid mixtures and the membrane materials could include not only adsorption phenomena but also electric, electrostatic, polarization, and Donnan effects. When an aqueous solution/suspension phase is treated by a MF or UF process it is generally accepted, for example, that convection and particle sieving phenomena are coupled with one or more of the phenomena noted previously. In nanofiltration processes, which typically utilize microporous membranes, the interactions with the membrane surfaces are more prevalent, and the importance of electrostatic and other effects is more significant. The conventional models utilized until now to describe liquid phase filtration are based on irreversible thermodynamics good reviews about such models have been reported in the technical literature [1.1, 1.3, 1.4]. 

The concept of coupling reaction with membrane separation has been applied to biological processes since the seventies. Membrane bioreactors (MBR) have been extensively studied, and today many are in industrial use worldwide. MBR development was a natural outcome of the extensive utilization membranes had found in the food and pharmaceutical industries. The dairy industry, in particular, has been a pioneer in the use of microfiltra-tion (MF), ultrafiltration (UF), nanofiltration (NF), and reverse osmosis (RO) membranes. Applications include the processing of various natural fluids (milk, blood, fruit juices, etc.), the concentration of proteins from milk, and the separation of whey fractions, including lactose, proteins, minerals, and fats. These processes are typically performed at low temperature and pressure conditions making use of commercial membranes. 

Applicability of this purification-and-concentration process with a nanofiltration membrane might be high because it is a simple process that requires low cost and low energy consumption. We are planning to apply this process to purification and concentration of value-added components contained in a wide variety of natural resources. 

The focus of this monograph is a comparison of natural organics rejection potential and fouling mechanisms of three membrane processes which are commonly used in water treatment - micro- (MF), ultra- (UU, and nanofiltration (NF). This comparative treatment study is combined with the science of natural organics and surface water systems, including an examination of natural organic-colloid-calcium interactions and solution speciation. 

Agbekodo K.M., Legube B., Dard S. (1996), Atrazine and simazine removal mechanisms by nanofiltration Influence of natural organic matter concentration. Water Research, 30,11,2535-2542. 

Braghetta A., DiGiano F.A., Ball W.P. (1997), Nanofiltration of natural organic matter pH and ionic strength effects. Journal of Environmental Engineering, 123, 7, 628-641. 

Childress A.E., Elimelech M. (1997), Effects of natural organic matter and surfactants on the surface characteristics of low pressure reverse osmosis and nanofiltration membranes, Proc. A WA Membrane Technology Conference, New Orleans, Feb. 97, 717-725. 

DiGiano F.A, (1996), Evaluation of Natural Organic Matter Fouling in Bench-scale, Batch Recycle Tests of Nanofiltration, ICR Workshop on Bench-scale and Pilot-scale Evaluations, AWAVA, Cincinnati, Ohio, March 1996. 

DiGiano F.A., Braghetta A., Nilson J., Utne B. (1994), Fouling of nanofiltration membranes by natural organic matter. National Conference on Environmental Engineering, American Society of Civil Engineers, 320-328. 

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