Ultrafiltration and microfiltration module and system

Details Ultrafiltration and microfiltration module and system Ultrafiltration and microfiltration module and system

2000-08-25

2003-07-08

Fortuna, Ana (Department: 1723)

Liquid purification or separation

Processes

Liquid/liquid solvent or colloidal extraction or diffusing...

C210S636000, C210S333010, C210S321800, C210S257200, C210S261000, C210S262000

Reexamination Certificate

active

06589426

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to water purification and more particularly it relates to a membrane water filtration system for in-home application, for example, to provide a reliable supply of safe water with only minimum maintenance.
Recent outbreaks of diseases caused by the presence of parasite cysts such as cryptosporidium and Giardia Lambia in municipal water supplies have created a great need for systems that provide potable water without fear of disease. Most municipalities rely on destruction of these pathogens with chlorine which is only partially effective. Some water purification systems use ultraviolet light disinfection but as with chlorine, this technology also is only partially effective in destroying pathogens present in water, especially the parasite cysts mentioned above.
Membrane-based technology has been used for purifying water. However, the use of conventional membranes is subject to fouling and requires frequent chemical cleaning which is not considered safe for residential or commercial use. Small disposable cartridges are sold for point-of-use applications, e.g., kitchen sink tap, but are very high cost and do not provide whole-house protection against impurities.
To improve the flow of permeate through membranes to provide purified water, different techniques have been employed. For example, U.S. Pat. No. 4,921,610 discloses removal of solids from membranes by a series of chemical cleaning cycles. The optimum time and pattern of the cleaning cycles are calculated from the rate of diminution in filtrate flow rate and the time and filtrate lost in each cycle. This is achieved by calculating fiom the rate of diminution of the filtrate flow rate after each application of a pressurised liquid and/or gaseous backwash cleaning cycle an equation expressing the relationship between filtrate flow and time, and, allowing for the time lost in each backwash cycle and the amount of filtrate lost in each backwash cycle, and, calculating from filtrate loss, the tine loss and the relationship between filtrate flow rate and time, the optimum time of application of liquid and/or gaseous backwashes.
Japanese Patent 4-180887 discloses passing water through a hollow yarn membrane from the inside to the outside and washing the inner surface of the membrane with filtered water except during treatment times. Raw water is introduced through a top port and is filtered before being introduced to the hollow membrane and passing out a bottom port. A resin fixed bed and activated carbon are also used.
U.S. Pat. No. 4,414,113 discloses a method and apparatus for removing dissolved solids from a liquid which utilizes the technique of reverse osmosis (RO). The liquid to be treated is directed into a pressure vessel which contains a plurality of filter elements positioned therein. The filter elements have hollow RO fibers wound around foraminous center cores such that the liquid flows in a direction from the outside of the filter elements towards the center cores. The pure permeate liquid passes into the center bores of the fibers and the concentrate liquid passes into the center cores of the elements.
The method and apparatus provide for the backwashing of the filter elements when they become fouled. Further, an outer filter septum may be applied around the hollow RO fibers of the elements to remove particulate matter which would otherwise foul the hollow RO fibers.
U.S. Pat. No. 3,786,924 discloses a water purification system incorporating a reverse osmosis unit for purifying water. The system yields two streams, one of very high purity for drinking and cooking and the like and one of lower quality for use in toilet tanks, lawn watering, garden irrigation and the like. The system provides apparatus and techniques for reconciling the varying flow rates inherent in a domestic water system with the constant flow rate desirable for efficient performance of the reverse osmosis unit. Provision is made for automatic flushing and backwashing of the reverse osmosis element.
U.S. Pat. No. 3,716,141 discloses a solvent-separating apparatus for purifying water by exposing the water, under pressure, to a solvent-separating means including a non-positive displacement pump for elevating the pressure of the water prior to direction into the water-separating means and means including two presized orifices for maintaining the desired pressure and desired flow rate of the water through tile water-separating means and for flushing the water-separating means periodically without the necessity of further adjustments in order to return the system to normal operating conditions.
U.S. Pat. No. 3,992,301 discloses an automatic flushing and cleaning system for membrane separation machines such as reverse osmosis machines having plural modules or membranes. Cleaning may be by way of reducing the pressure to allow the membrane to relax, by the injection of air or inert gas to provide turbulence, and/or by injection of flushing liquid which may include chemical cleaning additives. Pumps, automatic valving, and pressure controls are provided, along with a complete time operated electrical sequencing system whereby desired purging, flushing and cleaning cycles are automatically undertaken at periodic intervals or in response to one or more preferred conditions.
U.S. Pat. No. 4,876,006 discloses a hollow fiber filter device having a filter casing which is partitioned by a horizontal member into a filtered liquid chamber and a filtering chamber and a plurality of filter modules are suspended downwardly from the horizontal member. Each of the modules includes a plurality of hollow fibers having upper ends open to the filtered liquid chamber and also having lower ends open to a liquid-collecting chamber which is sealed from the filtering chamber and is arranged to communicate with the filtered liquid chamber by way of a conduit so that the full length of the fiber is utilized for filtration.
U.S. Pat. No. 5,437,788 discloses a filter assembly which includes a housing divided into a first chamber and a second chamber. A filter element is disposed in the first chamber, and a conduit is disposed in and opens to the second chamber. A weep hole introduces a backwash liquid from the second chamber into the filter element or the conduit. A differential pressure is then established between the opening in the conduit and the exterior of the filter element to force the backwash liquid through the filter element and thereby clean tile filter element and/or strip a precoat layer from the filter element.
U.S. Pat. No 5,053,128 discloses a method of manufacturing a diffusion and/or filtration apparatus, including a housing consisting of a cylindrical open-ended main part closed by two end caps and being provided with an inlet and outlet for a first fluid and at least one outlet for a second fluid, said first fluid being adapted to flow through tile fibers of a bundle of semi-permeable hollow fibers arranged between two end walls within the housing and said second fluid being adapted to be removed from the space outside the fibers through said at least one outlet for the second fluid.
U.S. Pat. No. 5,059,374 discloses a process for sealing a hollow fiber membrane separation module into a case.
U.S. Pat. No. 5,160,042 discloses an annular double ended hollow fiber bundle, a fluid separation apparatus comprising the annular double ended hollow fiber bundle having bores open at both ends of the hollow fibers embedded in the two tube-sheets enclosed in a shell having multiple ports, a fluid entrance port, a non-permeate exit port and at least one permeate exit port, wherein said double ended hollow fiber bundle is encased in an essentially impermeable film barrier except for entrance regions situated in selected areas between the tubesheets and to processes for separating fluids mixtures.
In spite of these disclosures, there is still a great need for membrane-based filtration system suitable for in-home, commercial and institutional applications. That is, there is great need for a membrane filtration system that wil

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