Reverse osmosis membrane fouling

Binovi R. (1983), A replacement for the silt density index permanganate demand to predict reverse osmosis membrane fouling, Dissertadon, University of Cinciimati. 

Hollow-fiber designs are being displaced by spiral-wound modules, which are inherently more fouling resistant, and require less feed pretreatment. Also, thin-film interfacial composite membranes, the best reverse osmosis membranes available, have not been fabricated in the form of hoUow-fine fibers. 

J. Siler, "Reverse Osmosis Membranes-Concentration Polarization and Surface Fouling Predictive Models and Experimental Verifications," dissertation. University of Kentucky, Lexington, Ky., 1987. 

Reverse Osmosis Membrane Cleaning. Citric acid solutions are used to remove iron, calcium, and other cations that foul ceUulose acetate and other membranes in reverse osmosis and electro dialysis systems. Citric acid solutions can solubilize and remove these cations without damaging the membranes (94—96). 

Jackson, J.M., and Landolt, D., "About the Mechanism of Formation of Iron Hydroxide Fouling Layers on Reverse Osmosis Membranes," Desalination 12, 361-378 (1973). 

Microfiltration cross-flow systems are often operated at a constant applied transmembrane pressure in the same way as the reverse osmosis and ultrafiltration systems described in Chapters 5 and 6. However, microfiltration membranes tend to foul and lose flux much more quickly than ultrafiltration and reverse osmosis membranes. The rapid decline in flux makes it difficult to control system operation. For this reason, microfiltration systems are often operated as constant flux systems, and the transmembrane pressure across the membrane is slowly increased to maintain the flow as the membrane fouls. Most commonly the feed pressure is fixed at some high value and the permeate pressure... 

Zhu, X. and M. Elimelech (1997). Colloidal fouling of reverse osmosis membranes Measurements and fouling mechanisms. Environ. Science Technol. 31, 12, 3654-3662. 

Reverse osmosis membranes prepared by LCVD on porous membrane showed unique but very peculiar reverse osmosis membrane performance [10,13]. In general, the reverse osmosis membrane performance declines with time, i.e., salt rejection and particularly water flux decline with time, which is recognized as membrane fouling. 

Figures 34.16 and 34.17 depict the opposite phenomenon of the membrane fouling, i.e., salt rejection and water flux increases with the operation time during the first 3 months, in which period most reverse osmosis membranes show the beginning of the membrane fouling. The reason for this phenomenon has not been elucidated ...

The main mechanisms of membrane fouling are adsorption of feed components, clogging of pores, chemical interaction between solutes and membrane material, gel formation and bacterial growth. Fet us first consider bacterial growth on membranes. Microbiological fouling of reverse osmosis membranes is one of the main factors in flux decline and loss of salt rejection [25-29] (Table 11.1). 

Sahachaiyunta et al. [38] conducted dynamic tests to investigate the effect of silica fouling of reverse osmosis membranes in the presence of minute amounts of various inorganic cations such as iron, manganese, nickel, and barium, which are present in industrial and mineral processing wastewaters. Experimental results showed that the presence of iron greatly affected the scale structure on the membrane surface when compared to the other metal species. 

Ridgway H.F., Kelly A., Justice C., and Olson B.H., Microbial fouling of reverse osmosis membranes used in advanced wastewater treatment technology Chemical bacteriological and ultrastiuctural analyses. Applied and Environmental Microbiology 46 1983 1066-1084. 

JenkinsM. and Tanner M.B., Operational experience with anew fouling resistant reverse osmosis membrane. Deja/inahon 119 1998 243-250. 

L. Y. Dudley, Membrane autopsies for reversing fouling in reverse osmosis. Membrane Technology 95, 9-12 (1998). 

B. A. Winfield, A study of the factors affecting the rate of fouling of reverse osmosis membranes treating secondary sewage effluent. Water Research 13, 565-569 (1979). 

An effect not considered in the above models is the added resistance, caused by fouling, to solute back-diffusion from the boundary layer. Fouling thus increases concentration polarization effects and raises the osmotic pressure of the feed adjacent to the membrane surface, so reducing the driving force for permeation. This factor was explored experimentally by Sheppard and Thomas (31) by covering reverse osmosis membranes with uniform, permeable plastic films. These authors also developed a predictive model to correlate their results. Carter et al. (32) have studied the concentration polarization caused by the build-up of rust fouling layers on reverse osmosis membranes but assumed (and confirmed by experiment) that the rust layer had negligible hydraulic resistance. 

A further complication arises when the foulant carries a fixed charge, such as whey protein in solutions with pH significantly different from the isoelectric point. Under these conditions, the fouling layer acts as a polyelectrolyte membrane in series with the reverse osmosis membrane, and changes in the salt concentration at the surface of the reverse osmosis membrane would be expected. 

Cohen R.D., Probstein R.F. (1986), colloidal fouling of reverse osmosis membranes. Journal of Colloid and Interface Science, 114, 1, 194-207,... 

Elimelech M., Zhu X., Childress A.E., Hong S. (1997), Role of membrane surface morphology in colloidal fouling of cellulose acetate and composite aromatic polyamide reverse osmosis membranes. 

Jackson J.M., Landolt D. (1973), About the mechanism of formation of iron hydroxide fouling layers on reverse osmosis membranes, Desalination, 12, 361-378. 

Potts D.E., Ahlert R.C., Wang S.S. (1981), A critical review of fouling of reverse osmosis membranes,... 

Zhu X., Elimelech M. (1995), Fouling of reverse osmosis membranes by aluminium oxide colloids. 

Zhu, X. (1996), Colloidal fouling of thin film composite and cellulose acetate reverse osmosis membranes, Dissertation, University of California, Civil Engineering, Los Angeles. 

SILT DENSITY INDEX - A measure of the tendency of a water to foul a reverse osmosis membrane, based on time flow through a membrane filter at constant pressure. 

Louie JS, Pinnau I, Ciobanu I, Ishida KP, Ng A, and Reinhard M, Effects of polyether-polyamide block copolymer coating on performance and fouling of reverse osmosis membranes, Journal of Membrane Science 2006, 280, 762-770. 

Jenkins, M. and Tanner, M.B. 1998. Operational experience with a new fouling resistant reverse osmosis membrane. Desalination 119 243-250. 

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