Filter for purifying domestic drinking water

Details Filter for purifying domestic drinking water Filter for purifying domestic drinking water

2000-04-26

2002-11-05

Cintins, Ivars (Department: 1724)

Liquid purification or separation

Particulate material type separator, e.g., ion exchange or...

With spaced non-particulate separating means

C210S282000, C210S283000, C210S502100, C210S503000, C210S505000

Reexamination Certificate

active

06475386

ABSTRACT:

FIELD OF INVENTION
The present invention relates to a filter for the removal of contaminants from domestic drinking water. In particular, the present invention relates to a gravity-flow filter containing adsorbents to remove a plurality of contaminant species from domestic drinking water.
BACKGROUND OF THE INVENTION
Complaints have been noted that domestic drinking water, in particular from household water taps, often carries a disagreeable taste or has an odor of chlorine. In addition, drinking water also may have low levels of chlorinated organics which are a result of the chlorination of the drinking water sources and, in some older homes, of lead leached from household piping systems. Many filters have been proposed or used to eliminate these objections or to remove these contaminants. Since the types of contaminants are diverse, different filtering materials, each designed to eliminate a particular objection, must be incorporated in the same filter. In a filter of limited size, a combination of filtering materials means a compromise sometimes must be adopted, leading to an inefficient removal of one or more contaminants.
The use of gravity-flow filters for domestic water purification using carafes or pitchers is well known. Typically, the carafe consists essentially of an upper chamber, a lower chamber, and a gravity-flow filter which is disposed tightly but removably between the chambers such that the filtered water is separated from the feed water. The carafe treats water in batches. Feed water is poured into the upper chamber and permeates by gravity through the gravity-flow filter. The filtered water is collected in the lower chamber.
Systems and filters that have been patented or are currently being practiced remove some but not all of the contaminants from domestic drinking water. Typically, chlorine as well as bad taste and odor are removed from the water using activated carbon. Dissolved cationic species, such as lead, are removed using ion exchange media. A gravity-flow filter cartridge also has been designed to remove biological contaminants. However, no gravity-flow filter cartridge for water pitchers or carafes has been developed to remove the dissolved organic chemicals effectively when it must also remove another type of contaminants such as cationic species.
As concern grows over the presence of trihalomethanes (“THMs”) such as chloroform, in drinking water and as the drinking water regulations lower the recommended limit of THMs in drinking water, further removal of these dissolved organic chemicals at the point of use would be desirable. With the current filter designs, the combination of activated carbon and ion exchange resin will not effectively remove the dissolved organic chemicals.
Therefore, it is an object of the present invention to provide a filter that effectively removes a variety of contaminants found in domestic drinking water and overcomes many disadvantages of prior-art water filter cartridges. It is a further object of the present invention to provide a gravity-flow filter for the purification of domestic drinking water, which filter can remove cationic metal species without compromising its ability to remove dissolved organics. It is still a further object of the present invention to provide a filter having high efficiency of contaminant removal through a novel and efficient use of filtering materials. These and other objects of the present invention will become apparent upon a perusal of the present disclosure.
SUMMARY OF THE INVENTION
The present invention provides a filter comprising at least two adsorbents for reducing the levels of contaminants found in domestic drinking water. The filter efficiently removes cationic species, free chlorine and organic chemicals and substantially eliminates bad taste and odor. Adsorbents suitable for use in the present invention include, for example, oxidized activated carbon, activated carbons, zeolites, ion exchange resins, silica gel, and activated alumina. One embodiment of the present invention combines oxidized activated carbon to advantageously remove cationic species with activated carbon to adsorb organic chemicals and contaminants responsible for bad taste and odor and to react with free chlorine. Preferably, the oxidized activated carbon comprises oxidized activated carbon fibers or fabric, or activated carbon cloth (“ACC”). The filter of the present invention is designed to optimally direct water through the adsorbents to minimize potential for flow by-pass and efficiently use the adsorbents in the filter.
In one embodiment, the filter comprises a filter housing containing an elongated envelope longitudinally disposed within for retaining the adsorbents therein. The filter housing and the envelope are spaced apart from each other to define a space therebetween. Optionally, a particulate filtering means comprising, for example, filter paper is disposed in the space between the filter housing and the envelope to retain any dust which may escape from the adsorbents. The filter housing has an inlet port for feeding unheated domestic drinking water into the filter and an outlet port for discharging the filtered or treated water from the filter. The envelope may be made of any inert plastic material such as polyethylene, polypropylene, polyvinylchloride, or polytetrafluoroethylene. The envelope includes at least one means for retaining the adsorbents therein located near the inlet port the filter. An additional retaining means is preferably included near the outlet port of the filter. The retaining means may be screens, which can be of an inert plastic material or a non-corrodible metal, or perforated plates such that the adsorbents are contained and, preferably, packed tightly inside the envelope without substantially inhibiting the water flow.
In a preferred embodiment, the envelope is filled with activated carbon, that is of granular, pelletized or spherical form, and includes at least one layer of oxidized ACC, preferably near the inlet end of the filter housing. Preferably, a plurality of layers of oxidized ACC are positioned between the inlet and the activated carbon. In this way, the oxidized ACC layers receive inflow to remove cationic species before water traverses activated carbon bed in the envelope which removes dissolved organic materials, contaminants and free chlorine.
Alternatively, the oxidized activated carbon or ACC may be interspersed throughout the activated carbon bed. When the oxidized carbon is in the granular, pelletized, or spherical form it may be mixed with the activated carbon to effectively remove cationic species and organic materials. Further, use of oxidized activated carbon eliminates the need to employ an ion exchange resin and provides increased overall capacity and capability of the filter to remove organic materials. This efficiency stems from the large micropore volume which is useful for adsorption of organic materials in addition to cationic species. The filter design further promotes efficient use of adsorbents by directing the water to flow axially through the envelope and substantially eliminates flow by-pass, which is a common problem for liquid flow in filters comprising particulate materials.
Optimal flow and filtration rates can be achieved by adjusting the diameter of the envelope in relation to the diameter of the filter housing and the distance between the second retaining means of the envelope and the bottom of the filter housing. Furthermore, activated carbon also may be disposed in the space between the envelope and the filter housing to provide additional capacity for removal of contaminants. In this case, perforations may be formed into the envelope and located throughout its length. The sizes of the perforations may be selected such that they ensure a water flow throughout the adsorbent. For example, the size of the perforations may increase in the direction away from the inlet of the filter housing so that water does not preferentially flow out of the envelope through the perforations near the inlet port of the housing.
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