Ultrafiltration What is Ultrafiltration? Ultrafiltration is the removal of fluid from a patient and is one of the functions of the kidneys that dialysis treatment replaces. Ultrafiltration occurs when fluid passes across a semipermeable membrane a membrane that allows some substances to pass through but not others due to a driving pressure. Ultrafiltration in Hemodialysis In hemodialysis, fluid is removed by ultrafiltration using the dialysis membrane. The pressure on the dialysate side is lower so water moves from the blood place of higher pressure to the dialysate place of lower pressure.
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See more details about ultrafiltration. What Is UF? Hollow Fiber Technology Superior to sand filters and traditional media filtration As with most conventional filtration methods, sand filters and media filtration require consistent raw water quality to deliver quality effluent, which is not always possible. Traditional media filters typically remove particles to down to about 5 microns.
Ultrafiltration UF , however, does not suffer from those limitations. This technology uses an ultrafiltration membrane barrier to exclude particles 0. Tolerance to feedwater quality upsets. No use of pretreatment chemicals polymer, coagulant, pH adjustment and associated costs for sludge disposal. Small footprint and less weight than media filters. When used as a pretreatment for reverse osmosis RO , UF also helps reduce fouling of the RO membranes, which can lead to: Reduced chemical cleaning frequency and consequently, lower operating costs and downtime.
The potential to operate RO at higher flux, with fewer membranes and vessels — leading to lower capital cost for the RO system. Rejecting particles, colloids, and macromolecules In ultrafiltration, water and low-molecular-weight substances are passed through an ultrafine membrane by the application of pressure to the system; flow through the membrane is achieved by applying a pressure gradient between the outer and inner walls of the membrane structure.
Ultrafiltration membranes have pore sizes in the range of 0. The process, however, does not reject particles smaller than the pores, such as dissolved salts or organics; nor does it reject other species such as true color, taste, and odor. Ultrafiltration membranes have a service life of three to seven years and potentially longer. They are commercially available in hollow fiber, tubular, plate, and frame, as well as spiral wound configurations. High-filtration performance, high recovery, and energy savings Our ultrafiltration modules are made with high-strength, hollow-fiber ultrafiltration membranes that offer the following features: 0.
PVDF polymeric hollow fibers for high strength and chemical resistance. Hydrophilic PVDF fibers for easy cleaning and wettability to help maintain long-term performance. Outside-in flow configuration for high tolerance to feed solids and the use of air scour cleaning. The outside-in flow configuration is tolerant of wide-ranging feed water qualities and allows air scour cleaning. The dead-end flow offers higher recovery and energy savings. The pressurized vertical shell-and-tube design eliminates the need for separate pressure vessels and allows easy removal of air from cleaning along with integrity testing steps.
The hollow fiber ultrafiltration membranes are 1. The fibers are strong due to a combination of PVDF polymer, an asymmetric membrane with smaller pores in the active filtration area, and a high porosity substructure. PVDF membranes offer high chemical resistance e.
Concentration polarization[ edit ] When filtration occurs the local concentration of rejected material at the membrane surface increases and can become saturated. In UF, increased ion concentration can develop an osmotic pressure on the feed side of the membrane. This reduces the effective TMP of the system, therefore reducing permeation rate. The increase in concentrated layer at the membrane wall decreases the permeate flux, due to increase in resistance which reduces the driving force for solvent to transport through membrane surface. CP affects almost all the available membrane separation processes. In RO, the solutes retained at the membrane layer results in higher osmotic pressure in comparison to the bulk stream concentration. So the higher pressures are required to overcome this osmotic pressure.
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