Liquid purification or separation – Particulate material type separator – e.g. – ion exchange or... – With spaced non-particulate separating means
Reexamination Certificate
2000-09-28
2004-11-16
Lithgow, Thomas M. (Department: 1724)
Liquid purification or separation
Particulate material type separator, e.g., ion exchange or...
With spaced non-particulate separating means
C210S243000, C210S492000, C210S335000, C210S323200, C210S501000, C210S509000
Reexamination Certificate
active
06818130
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an apparatus and process for the removal of undesired particulates and microorganisms from water and other liquids. More particularly, the present invention relates to an apparatus and process for the more efficient filtration of liquids such as water.
BACKGROUND OF THE INVENTION
Water intended for human consumption is expected to be either free of harmful constituents or contain concentrations of such constituents that are below harmful levels. To provide potable water for use in homes and businesses, municipalities utilize industrial scale processes in an effort to eliminate or reduce harmful constituents present in water drawn from large, naturally occurring water sources. Potable water is also frequently obtained on a smaller scale from wells and springs and usually without any treatment prior to consumption.
Unfortunately, the potability of a particular water supply is sometimes questionable. The consistency and efficiency of treatment by municipalities may vary due to numerous factors such as heavy rainfall, equipment failures, and usage levels. Depending upon the seriousness of a variation in treatment, a municipality may be forced to notify its consumers that further treatment of the water supplied, e.g. boiling, is required at the point of use before consumption is safe. Water obtained directly from a natural source may also become suspect depending upon environmental conditions near the source. For examples, wells and springs can be contaminated due to rain water run-off washing a contaminant into the source. Accordingly, a need exists for liquid filtration devices suitable in size and scale for residential or office use.
In response, liquid filtration devices have been developed. Such devices range from those located at the point-of-use (e.g. the spigot of a kitchen sink, gravity-flow dispensers such as water pitchers, and low-pressure dispensers such as sports bottles) to the generally bulkier point-of-entry units hidden from view within the plumbing of a home or office. Many of these devices use activated charcoal in at least one stage of the filtration process. Activated charcoal helps to remove strong odors and tastes from water. More specifically, activated charcoal can remove chlorine, and sediment from water.
A problem associated with the use of activated charcoal (also referred to as activated carbon) is that certain microorganisms, like bacteria, propagate rapidly within activated charcoal. This problem has at least three undesirable effects. First, the growth of bacteria within the charcoal may inhibit the flow of water through this stage of the filter. Second, and more importantly, the use of activated charcoal can actually increase the concentration of bacteria present in the water by providing a moist, nutrient-rich environment that is conducive to bacterial reproduction as described in Daschner et al.,
Microbiological Contamination of Drinking Water in a Commercial Household Water Filter System,
15 Eur. J. Clin. Microbiol. Infect. Dis. 233—37 (1996). Third, for those uses that are intermittent, the first flow of water through the activated charcoal after a period of nonuse will contain a spike concentration of bacteria.
Typically, a certain concentration of bacteria is present in all water supplies. This concentration can increase in activated charcoal that is not flushed by the periodic use of water from a particular filter. The result is a spike concentration present in each intermittent use as the bacteria is flushed form the activated charcoal. Increased bacteria concentration is the opposite result intended by the filter installation. While many filtrations mechanisms are available, none address all of these challenging problems without frequent replacement of the activated charcoal.
U.S. Pat. No. 5,271,837 describes a multistage system for the filtration of drinking water utilizing a central filter cartridge constructed of activated charcoal impregnated with silver, a cation exchange resin, and an anion exchange resin. The activated charcoal is the first stage of the filtration system, followed by the resins. To prevent particulates from clogging the central filter cartridge, U.S. Pat. No. 5,271,837 discloses a particulate filter located prior to the central filter cartridge. This patent, however, does not address any problems unique to the filtration of microorganisms or the prevention of bacteria growth on the activated charcoal.
U.S. Pat. No. 5,891,333 describes a modular, multistage water filter for use in countertop or below-countertop applications. This patent is directed to a device with removable, replaceable cartridges containing filter media within a configuration that permits changes in size scale depending upon the filtration capacity desired. The disclosure does not specify any particular filter media or constituent filtration sequence. The removal of any particular constituent from a water supply is not taught.
U.S. Pat. No. 5,318,703 describes a water filter module for use in coffee brewing that is designed to remove residual chlorine, odors, foul tastes, impurities, and unspecified other sediments from water prior to contact with the coffee grinds. The filter media disclosed is activated carbon which is held in place by mesh screens. The mesh screens, which may be a polymer material, are included to remove large particulate impurities, such as sediment and other dirt particles, by mechanical filtration. The removal of microorganisms or any specific problems associated therewith is not addressed.
A disposable filter constructed of a paper filter media is presented in U.S. Pat. No. 5,554,288. Finely-divided adsorbents are uniformly distributed throughout a pulp from which a paper filter media is created for use in variety of configurations. Various adsorbents are claimed, including activated carbon. U.S. Pat. No. 5,554,288 specifically recognizes that carbon filter cartridges that remain immersed in the water being treated may become a hospitable medium for bacteria growth. However, as claimed, this particular problem is avoided because the filters of U.S. Pat. No. 5,554,288 are discarded after use rather than remaining immersed in the water. This solution, however, requires the user to frequently replace the filter, and requires disposal of the spent filter.
Therefore, a need has existed for an improved method and apparatus for the removal of undesired particulates and microorganisms, such as bacteria, viruses, protozoans, yeast, fungi, and microbiological cysts, from liquids such as water. More particularly, a need for an improved method and apparatus for the filtration of liquids with greater filtration efficiency and the elimination of spike concentrations of microorganisms has existed that is not addressed by the prior art.
SUMMARY OF THE INVENTION
The present invention addresses some of the problems identified above by providing a method and apparatus for filtering fluids such as water that reduces bacteria contact with the activated charcoal stage of the filter. More specifically, a filter stage is placed in the water stream of a multistage filter at a point in flow prior to the activated carbon such that the microorganisms are substantially removed from the water prior to the filtration by the activated carbon.
By consequently preventing bacteria contact with the activated charcoal, the problems of increased bacteria concentration and associated flow reduction are avoided. For uses that are intermittent, the problem of spike concentrations is avoided by preventing the in microorganisms from reaching the activated carbon where conditions for reproduction may be conducive during periods of no water flow.
Multiple embodiments of the invention may be employed. For example, the filter may consist of stages in the form of beds of material in a stacked configuration within a cylindrically- or otherwise-shaped chamber. The liquid may enter the chamber from one end, pass longitudinally through the various stages of filter media, and then exit the chamber to a point of use. Ot
Brunner Michael S.
Lyng Robert J.
Varriale Monica G.
Dority & Manning
Kimberly--Clark Worldwide, Inc.
Lithgow Thomas M.
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