This invention relates to the storage of liquids, particularly but not exclusively water. For convenience it will be described below with specific reference to water. 5
There have been numerous proposals for the treatment of water to purify it and many of these proposals have been devised bearing in mind that water quality and purity vary considerably from location to location and that a relatively simple treatment means is required that can be used in a wide variety of situations and that is, preferably, renewable.
Many of the known treatments involve filtration and heat stages and are successful to greater and lesser degrees in providing a convenient, economical means of providing 15 water of acceptable purity in respect not only of content of chlorine, heavy metals, organics, carbonates and the like but also in respect of microbiological quality.
Regardless of the actual treatment method used, many treatment processes are devised to provide a reservoir of 20 treated water which can be drawn off for use as and when required, i.e. the treated water is not used immediately but must be stored for varying periods of time. One specific example is in the treatment of water for post-mix beverage dispensers in which a beverage is mixed from a concentrate 25 and a diluent, usually water, at the point of sale. The water to be used may have been subjected to a purification treatment and it may then be stored in a suitable reservoir before being drawn off in a required amount for each beverage dispense.
Although such stored water may be of high purity and of 30 high microbiological quality on entering the reservoir or other storage system, neither it nor the reservoir will normally be sterile. There is, therefore, always a risk that the microbiological state of the stored water will deteriorate with time. Simple addition of microbiocidal material to the reservoir has 35 not proved to be a satisfactory solution as adequate contact is difficult to achieve.
It is, therefore, an object of the present invention to provide a liquid storage apparatus in which this problem may be ameliorated or eliminated. 40
Accordingly the invention provides a liquid storage apparatus, the apparatus comprising a reservoir for the liquid, the reservoir containing a microbiological agent to kill or deter microbiological growth, the microbiological agent being in a 45 physical form to present a sufficient contact area with the liquid to provide the required effect.
In a first general embodiment the wall of the reservoir may be formed of material, usually plastics material, in which the microbiological agent is present or onto which it is coated. 50 Thus the agent may conveniently have been compounded into the composition used to form the walls of the reservoir. The "walls" may, of course, include the floor and roof and the agent may similarly be incorporated in conduits and fittings of the reservoir. However, we have found that such an 55 arrangement does not by itself provide the desired degree of contact time and area to effectively treat all the water or other liquid that may be contained in the reservoir.
Thus in this embodiment of the invention, we have found that it is preferable to provide agitation means within the 60 reservoir to promote increased water/wall contact or recirculation means to pass the water out of and back into the reservoir. Both means may be used in combination. Where the water is recirculated, it may also be passed through, e.g. a cartridge, containing further microbiological agent, to further 65 improve the treatment and contact time. The further microbiological agent may be in any convenient form, e.g. granular
or in a reticulated foam. A labyrinth may be provided in the cartridge in the recirculation line to further improve flow path contact time with the agent.
In a second general embodiment, the microbiological agent is present in the tank in an open cell, e.g. reticulated, foam, in fibre, or in granular form to provide the required surface area to allow adequate contact. It may be coated onto the foam, fibres or granules but it may be found more convenient for it to be compounded into the compositions from which these bodies are formed.
The microbiological agent may be any suitable biocide or biostatic agent and examples include triclosan, zinc pyrithione, silver compounds and KDF. The latter is a metallic combination of copper and zinc, which is available in a variety of forms including granules, wool and reticulated foam.
The agent may be incorporated in a variety of readily available plastics materials which can be processed by conventional means including injection moulding, blow moulding, rotational moulding and extrusion for use in the first embodiment of the invention. Alternatively it may be incorporated in plastics compositions which are processed to a carrier form, e.g. reticulated foam, granule or fibrous form for insertion into the reservoir in the second embodiment.
In the second embodiment of the invention, the carrier form of the agent may be of volume to completely fill the reservoir, in which case a vent will be needed to allow filling of and drawing from the reservoir. For example, the reservoir may be completely filled with reticulated foam containing the agent and the water enters to fill the voids in the foam and thereby ensures a good and sufficient contact area for the agent to work. An air filter may be fitted into the vent.
Alternatively the reservoir may be a sealed tank, i.e. unvented, with sufficient headspace left during use to allow filling and emptying to take place or it may contain a collapsible membrane as a barrier to atmosphere.
Alternatively the carrier may form a layer in the reservoir through which the water must pass on its travel from the reservoir inlet to the outlet. The layer may be attached to the reservoir walls or take the form of a floating layer of, e.g., foam or granules. Again the reservoir may be vented, with a filter, if desired.
In another arrangement the carrier may form a layer on the floor of the reservoir or be in a "sump" in the base of the reservoir.
Where a foam is used as the carrier for the agent, it may be used in compressed or uncompressed state whereby the volume to surface area ratio may be enhanced by changing the cell size.
It will be appreciated that the carrier, e.g. the foam, can present an extremely large surface area to contact the water. Reticulated foam, for example, can absorb almost up to its own volume of liquid thereby ensuing maximum effective use of the microbiological agent.
Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings in which:
FIG. 1 is a diagrammatic representation of a reservoir tank according to the invention;
FIG. 1A is an enlarged view of an alternative form of a portion of the apparatus of FIG. 1;
FIG. 2 is a similar view to FIG. 1 of a second reservoir tank of the invention;
FIG. 3 is a similar view of a third reservoir tank of the invention;
FIG. 4 is a similar view of a fourth reservoir tank of the invention;