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Patents ]

wires. One wire of each pair is copper, the other is titanium. A bactericidal tablet is also contained in the intake device.

The water then rises up the hose to the filter cassette, which is in the form of a hollow disc and which contains a pack of membrane filters. After passing through these, the water is finally drawn off by the pump. Patent number: SU 1565495 Date: 23 May 1990 Inventors: Y.S. Veselov, V.A.

Ostrovskii

Immobilized enzyme: self- cleaning membrane? A common problem when operating filtration units is blinding of filtration media by coherent layers of bacteria or fungi. In conventional macro- scale media, physical methods such as backwashing or chemical treatment are often effective. The use of these techniques is usually inappropriate where a membrane is the filtering medium.

This proposed solution employs any of a number of enzymes - peptitase, protease, lysozyme, glucanase, cellulase or pectinase - which become incorporated into the membrane material and remain held there.

This can be accomplished with both ceramic membranes and with polymeric membranes. The membrane is immersed in an aqueous solution of the enzyme appropriate to the biological fouling problem. The enzyme consequently becomes attached to the active layer in the membrane. In some circumstances a chemical pre-treatment of the membrane is necessary so that the enzyme can be held in place by covalent bonding.

The enzyme keeps the

Camping water purifier

hand pump

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water intake

membrane clear by destroying the cell walls of any organism in contact with it. For bacteria, peptitase, protease and lysozyme can be used, while for fungal growth glucanase, cellulase or pectinase are proposed.

It is also appropriate to use this technique to prepare membranes for use in separating fermentation liquids into microbial cells and filtrate: the cells that actually remain on the membrane for any length of time will be destroyed but the majority in the body of the liquid will be unaffected. Patent number: JP 2291264

Date: 3 December 1990 Inventor: Y. Nishida Applicant: NGK Insulators Ltd

Continuous blood fractionation Procedures involving the processing of whole blood, especially those when some part of the blood is returned to its

14 Membrane Technology

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Fig. 1: Continuous blood fractionation equipment

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fractionation unit

Fig. 2: Blood plate

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distribution channels

transfer area

combining channels

human 'owner', require as little damage as possible to red and white blood cells. They also are more acceptable to the patient or donor if a single needle can be used for both withdrawal and return of blood. This can be done using a needle with concentric barrels but these have intrinsic flow rate limitations; a flow- reversal technique is more effective if the pumping action can be kept at energies low enough not to injure corpuscles.

Apparatus to accomplish these desirable aims is shown in Fig. 1. It can be used for dialysis, plasma level adjustment or red blood corpuscle removal, depending on the pore size of the membranes fitted in the fractionation unit.

In outline, blood is initially taken from the donor's arm, then pumped through tubing into the fractionation unit. It traverses that, then flows into a reservoir, from which it is returned to the donor at regular intervals. The apparatus is under the control of a microprocessor to cb-ordinate blood and other liquid flows, and flow-rate monitors and other sensors indicated in outline in Fig.1 report information to the processor.

The fractionation unit is made up of multiple membranes interleaved with distribution plates, one of which is shown in Fig. 2. The design of the plate ensures effective exchange between the blood and the other circulating fluid. Membrane pore size is in the range 50 A to 0.05 microns for the separation of protein-free filtrates and protein fractions, and 1.0 micron for plasma collection. A pump is connected to the fractionator so that the blood makes two passes through it on the way to the reservoir. This allows the use of a smaller fractionator than previously developed, shortening the flow path compared to the earlier device. A typical construction is a stack of five plates separated by four membranes. Patent number: US 4980054 Date: 25 December 1990 Inventor: A.R. Lavender

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