The present invention relates to membrane filtration systems and, more particularly, to an improved method and apparatus for gas scouring filtration membranes.
Gas scouring systems have been used with membrane filtration systems to clean membranes and allow such systems to operate effectively over long periods with a reduced need for regular backwashing or high backwashing efficiency. Such systems typically employ pressurized gas generated by a blower or pump to produce gas bubbles which flow along the membrane surfaces and scour accumulated solids and impurities therefrom. The need for a pressurised source of gas normally requires an expensive pump and a power supply. While this is not of concern with large commercial systems, the cost of the gas supply is seen as disadvantageous to be able to provide such scouring methods to smaller systems, for example home filter systems. Such advantages are seen as having application in remote areas (farms, remote villages, expeditions) where it is hard to get electricity and pressurized air but where sufficient water pressure (about 50 to 400 kPa) is available to operate the system.
The present invention seeks to provide a gas scouring system to run without the need for a pressurized gas supply.
According to one aspect the present invention provides a method of cleaning a membrane in a membrane filtration system by flowing gas bubbles past the surfaces of said membrane to scour accumulated solids therefrom, the method including:
Preferably, the reduced pressure is created in an eductor or venturi device.
For preference, the liquid includes feed liquid supplied to the membrane filtration system.
Preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawing in which:
Referring to
In use, the untreated water enters through valve V1 and through the eductor 8 into the membrane module 5. Under normal operating conditions the drain valves V2 and V3 are closed. When treated water (filtrate) is required valve V4 (tap) is opened and the water pressure pushes the water through the membranes 6 to the filtrate side and the filtrate produced flows through valve V4 and filtrate line 10. As the flow rate is limited by the membrane resistance, the speed of the water flowing in the eductor 8 is not high enough to suck air into the water stream. Instead the water pressure will cause the check valve V5 to close. If necessary, the flow rate can be further controlled by valve V4, V1 or an optional flow control valve installed between V4 and the module. If the membranes begin to block up, the following procedure may be used to clean the membranes:
It will be appreciated by those skilled in the art of membrane filtration that a variety of sequencing of the valves can be used in order to achieve a desired outcome.
The eductor 8 is a piece of equipment that uses the dynamic flow of water to create a partial vacuum which causes air to enter into the water flow. Typically this is a venturi pipe or some kind of jet.
If a chemical clean of the membrane is required, an additional liquid connection to the eductor 8 may be used to suck any cleaning chemical into the liquid stream during cleaning. After a short period of time the liquid flow may be stopped by shutting valve V1 in order to save chemicals and to allow the membrane to soak in the solution of the chemical.
The cleaning system may be applied to any form of membrane including fibre, flat sheet, spiral wound, pleated or plate types.
The filter system may be combined with an appropriate activated carbon filter or the like to remove taste and odour.
It will be appreciated that further embodiments and exemplifications of the invention are possible without departing from the spirit or scope of the invention described.
Number | Date | Country | Kind |
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2004907390 | Dec 2004 | AU | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/AU2005/001959 | 12/22/2005 | WO | 00 | 6/21/2007 |