WO2007000747A1

WO2007000747A1 - Water treatment artefact

Info

Publication number: WO2007000747A1
Application number: PCT/IB2006/052158
Authority: WO
Inventors: Leon Buchan
Original assignee: Ppa Water Industries (Proprietary) Limited
Priority date: 2005-06-28
Filing date: 2006-06-28
Publication date: 2007-01-04

Abstract

A water treatment artefact (10) includes a compacted or compressed composite body of an admixture of particulate calcium phosphate {Ca3(PO4)2} and particulate calcium hypochlorite (Ca(OCI)2}.

Description

WATER TREATMENT ARTEFACT

THIS INVENTION relates to a water treatment artefact. The invention also relates to a water treatment device and kit.

HOCI is very useful as a disinfecting or water treatment agent. Although comparatively few investigations appear to have been made on the activity of chlorine in relation to its concentration, it has been stated that the chlorine concentration is of minor importance compared with the influence of pH. Thus, chlorine is in the class of disinfectants which is only a little affected by dilution, meaning that HOCI holds much promise as a disinfecting agent for small volume batch drinking water sanitisation. The inherent chemical properties of both low and high test calcium hypochlorite however cause fast release of the HOCI active germicide and hinder the use of calcium hypochlorite as a slow-dissolving HOCI release agent.

The simple coordinate bonding of the inorganic salts of calcium with electronegative atoms is energetic and active due to its strong hydration properties. So readily does coordination occur that the inorganic salts of calcium are hydrated in holding water of crystallization when Ca⁺² salts are introduced to water, so that the inorganic salts do not readily dissolve, but react with the water molecules in what is called deliquescent dissolution. For example, when unslaked lime (CaO) is dissolved in water it produces Ca(OH)₂ or slaked lime, which is milky in colour and the dissolution in water (deliquescence) is exothermically spontaneous in producing a 6-hexa-hydrated calcium hydroxide. The coordination with water renders a calcium hydroxide molecule of low solubility.

According to one aspect of the invention, there is provided a water treatment artefact which includes a compacted or compressed composite body of an admixture of particulate calcium phosphate (Ca₃(PO₄J₂J and particulate calcium hypochlorite {Ca(OCI)₂}.

The calcium hypochlorite may be low test calcium hypochlorite, which may be included in the composite body as a powder. Instead, or in addition, the calcium hypochlorite may be high test calcium hypochlorite, which may be included in the composite body as granules. Preferably, the calcium hypochlorite is dry calcium hypochlorite.

Commercial calcium hypochlorite (60 % - 72 % by mass available chlorine) contains 30 % - 38 % inert salts, principally NaCI with minor amounts of calcium salts such as Ca(OH)₂ and CaCI₂. Typically, the inert salts are bound in a calcium hypochlorite complex and are thus not in the form of free salts.

The calcium hypochlorite may be commercial calcium hypochlorite comprising 60 % to 72 % by mass available chlorine. The commercial calcium hypochlorite and the calcium phosphate may be present in the composite body in a mass ratio of between about 1 : 0.43 and about 1 : 1.5, preferably between about 1 : 0.7 and about 1 : 1 , more preferably between about 1 : 0.75 and about 1 : 0.8, e.g. about 1 : 0.78.

The composite body may include chloride of lime. The chloride of lime may be present in the composite body in a concentration of between about 10 % by mass and about 40 % by mass, preferably between about 10 % by mass and about 30 % by mass, more preferably between about 15 % by mass and about 25 % by mass, e.g. about 20 % by mass.

The composite body may include a tabletting lubricant, e.g. zinc stearate. Typically, the composite body includes between about 0.5 % and about 2 % by mass of the tabletting lubricant.

The water treatment artefact may have less than about 35 % available chlorine. When the water treatment artefact has less than 35 % available chlorine, it is unlikely to react with contaminant-substances that may generally be considered to be incompatible with calcium hydrochlorite and the composite body will also not combust, nor meaningfully contribute to a conflagration. Under these conditions, it may be possible for the water treatment artefact of the invention to be declassified to be acceptable as air freight, as the Applicant expects that the water treatment artefact will not demonstrate the hazards associated with oxidisers. The water treatment artefact may include a housing of water-impervious material located snugly around the composite body, with a water access opening being provided in the housing so that water can reach a portion of the surface of the composite body. If desired, the water access opening may have a closure member which can be removed or pierced prior to use of the water treatment artefact.

By "snugly" is meant that the housing, at least initially, holds the composite body firmly so that the composite body cannot readily move relative to the housing and so that in use water can not freely enter between the composite body and the housing.

In one embodiment of the invention, the housing is of latex. Advantageously, latex is resistant to chlorine. In another embodiment of the invention, the housing is of a synthetic plastics or polymeric material, e.g. polyethylene or the like, and may be shrink- wrapped, e.g. heat shrink-wrapped, around the composite body.

The composite body may be elongate and cylindrical, e.g. circular cylindrical, and may have a length or thickness greater than its diameter. Typically, one or both ends of the elongate composite body are in use exposed to water, with the surface of the composite body between the ends being covered by the housing.

The housing may be in the form of a sleeve or wrapper.

The housing may include an attachment formation to attach the housing to the housing of another of said water treatment artefacts, or to a buoyant body or float. Preferably, the housing includes at least two attachment formations that are complementary or cooperating and circumferentially spaced, so that one water treatment artefact can be attached to one or more other water treatment artefacts by engaging an attachment formation on the one water treatment artefact with the complementary or cooperating attachment formation on the other water treatment artefact.

The invention extends to a water treatment kit which includes a buoyant body or float, with an attachment formation; and at least one water treatment artefact which includes a compacted or compressed composite body of an admixture of particulate calcium phosphate {Ca₃(PO₄)₂} and particulate calcium hypochlorite {Ca(OCI)₂}, and a complementary or cooperating attachment formation so that the water treatment artefact can be attached to the buoyant body, via the attachment formation of the buoyant body.

The water treatment artefact may be as hereinbefore described.

Preferably, the kit includes a plurality of the water treatment artefacts, the artefacts being configured also to be attachable to each other via attachment formations.

According to another aspect of the invention, there is provided a water treatment device which includes a buoyant holder having at least one water treatment artefact compartment for holding a water treatment artefact, the water treatment compartment having at least one opening to allow water to enter the compartment; and a water treatment artefact as hereinbefore described, in the compartment of the holder.

The compartment may be complementary shaped and dimensioned to the water treatment artefact, to receive the water treatment artefact without clearance. The compartment may be of more-or-less elongate cylindrical form, e.g. circular cylindrical, with at least one open end.

The device may include a float, with the compartment being located on an operative underside of the float.

The invention will now be described, by way of example only, with reference to the following examples and the drawings in which

Figure 1 shows a three-dimensional view of a water treatment artefact in accordance with the invention; and

Figure 2 shows a three-dimensional view of a water treatment device in accordance with the invention; Figure 3 shows a three-dimensional view of a water treatment kit in accordance with the invention;

Figure 4 shows a further three-dimensional view of the water treatment kit of Figure 3; and Figure 5 shows a three-dimensional view of a pair of water treatment artefacts in accordance with the invention.

A water treatment artefact in accordance with the invention, as shown in Figure 1 of the drawings and generally indicated by reference numeral 10, was prepared. An admixture of low test calcium hypochlorite in the form of a powder and particulate calcium phosphate, together with chloride of lime and zinc stearate were tabletted to form a compacted circular cylindrical composite tablet body 12. The calcium hypochlorite (including impurities), chloride of lime and calcium phosphate were in a mass ratio of about 45 : 20 : 35. The tablet body 12 included about 2 % zinc stearate.

A housing or a wrapper 14 was formed for the tablet body 12 by wrapping the circular cylindrical surface of the tablet body 12 in a tape of a synthetic plastics material of which one side is adhesive. Circular end surfaces 16, 18 of the tablet body 12 were thus not covered by the housing 14.

The water treatment artefact 10 had a diameter of about 25 mm and a thickness or height of about 20 mm.

EXAMPLE 1

One of the surfaces 16, 18 of the water treatment artefact 10 was also covered by tape and the water treatment artefact 10 was placed in a container holding about 500 litres of water. The HOCI concentration in the water was measured over a period of time and the results are shown in Table 1. TABLE 1

EXAMPLE 2

The water treatment artefact 10 was placed in a container holding about 500 litres of water. Both of the surfaces 16, 18 of the water treatment artefact 10 were exposed to the water and the HOCI concentration was measured over a period of time. The results are shown in Table 2. TABLE 2

From Table 1 and Table 2, it is apparent that the water treatment artefact 10 is suitable for use as a slow-releasing HOCI disinfecting agent for small volume batch drinking water sanitation purposes. The Applicant expects that the water treatment artefact 10 would find application in the disinfecting of drinking water in quantities from about 500 to 5000 litres to release HOCI into the water in concentrations of up to about 4 ppm. Although not wishing to be bound by theory, the Applicant believes that, when in aqueous solution, the hydration of the tablet body 12 of the water treatment artefact 10, which contains calcium phosphate and calcium hypochlorite, is disturbed on its surface area by the larger anions ^"OCI, PO₄ ^"3 and Cl^" during which the near electroneutral water molecule is gradually displaced as HOCI is released from the tablet surface. As a gradual process, the coordination of a versatile Ca⁺² coordination cation produces small crystals found in biological systems similar to the CaCO₃ in sea shells and the Ca(OH)PO₄ in mammalian bone structure, which results in a hard core or matrix of the tablet remaining after the dissolution of the active HOCI disinfecting ingredient. The ^"OCI anion, although in molecular structure an organic compound (i.e. covalent in chlorine and oxygen-sharing electrons), in holding a negative electric charge is more characteristically an inorganic ionic anion. The HOCI molecule is covalent, and at a pH of 6.9 remains undissociated or unionised, but dissociates or ionises as the pH incrementally increases above 7. When the water treatment artefact 10 is placed in water, surface water hydration occurs by which HOCI disinfectant is released into the surrounding water. When placed in a fixed volume of water, e.g. 1000 litres or 2000 litres, the water provides an independent water source of which the pH optionally can be controlled to increase the efficacy of covalently bonded HOCI being released on dissolution of the tablet. If the water volume has a pH of 7 or less, approximately 80 % of the HOCI released from the tablet will contain neutral covalent HOCI, and only 20 % of the more electronegative ^"OCI and ^"Cl anions. When the pH of the tank is at 8 or above, only about 27 % of active ingredient is produced as HOCI, and at pH 8.5 the HOCI is almost depleted at less than 11 %, resulting in about 89 % of the HOCI in the water being converted to the more electronegative ^"OCI hybrid.

Referring to Figure 2 of the drawings, a water treatment device in accordance with the invention for use with the water treatment artefact of the invention is shown and generally indicated by reference numeral 20. The water treatment device 20 includes a buoyant holder or float 22 with water treatment artefact compartments 24 being located in an operative underside of the float 22. In use, the compartments 24 are submerged. The compartments 24 are elongate and circular cylindrical in shape and are open- ended. The compartments 24 are shaped and dimensioned each to receive an elongate water treatment artefact in accordance with the invention and to allow water to reach the end surfaces of the artefact thereby slowly to release HOCI active disinfecting agent into the water. It is intended that the water treatment artefacts be snugly received inside the water treatment artefact compartments 24. During use, HOCI will be released from the water treatment artefacts located within the water treatment artefact compartments 24. When the water treatment artefacts have been depleted, the water treatment device 20 can be removed from the water, with the hard cores or matrixes of the water treatment artefacts still being located inside the water treatment artefact compartments 24, from which they can then conveniently be removed so that fresh water treatment artefacts can be inserted into the compartments 24.

Referring to Figure 3 of the drawings, reference numeral 30 generally indicates a water treatment kit in accordance with the invention. The kit 30 includes a buoyant body or float 32 with an eyelet 34 to which a string or the like can be attached. A split circular cylindrical female attachment formation 36 is mounted on an underside of the float 32. A water treatment artefact 40 in accordance with the invention is suspended from the float 32. The water treatment artefact 40 also includes a circular cylindrical composite tablet body 42 comprising compressed particulate calcium hypochlorite and particulate calcium phosphate, together with chloride of lime and zinc stearate. The body 42 is surrounded by a circular cylindrical housing 44 of polyethylene, leaving opposed circular faces of the body 42 exposed. Complementary or cooperating male attachment formations 46 that can fit into the female attachment formations 36 are circumferentially spaced on the housing 44. The housing 44 also supports two further female attachment formations 48 which are circumferentially spaced and which are identical to the female attachment formation 36.

As will be appreciated, by inserting one of the male attachment formations 46 into the female attachment formation 36 suspended beneath the float 32, the water treatment artefact 40 can easily be mounted to the float 32, and just as easily be dismounted or removed when the body 42 is depleted of HOCI.

The water treatment artefact 40 also includes an eyelet 50 mounted on the housing 44. By means of the eyelet 50, a string or the like can be tied to the water treatment artefacts 40 allowing the water treatment artefact 40 easily to be retrieved from a water tank, especially when the tank is deep or when the opening into the water tank is above head height. As will be appreciated, when the water tank is deep, or when the access opening to the water tank is above head height, it may be easier simply to suspend the water treatment artefact 40 from a string, instead of mounting the water treatment artefact 40 to the float 32.

Figure 4 illustrates how a plurality of the water treatment artefacts 40 can be assembled in modular fashion and suspended from the float 32. Naturally, the water treatment artefacts 40 may also individually or together be suspended from one or more of the eyelets 50, using a string or strings. The male and female interlocking attachment formations 46, 48 facilitate the addition or removal of water treatment artefacts 40 and allow the water treatment artefacts 40 to be mounted side-by-side or one above the other thereby providing one with the freedom to vary the depth at which the water treatment artefacts 40 are located in the water. When the water treatment artefacts 40 are used in water troughs for animals, it is expected that the water treatment artefacts 40 will be suspended from the float 32, as these kinds of water troughs are usually open enough to allow a unit that floats on the water surface to dispense HOCI evenly through the water.

Referring to Figure 5 of the drawings, reference numerals 60 refer generally to a further embodiment of a water treatment artefact in accordance with the invention.

The water treatment artefacts 60 are similar to the water treatment artefact 40 and unless otherwise indicated, the same reference numerals are used to indicate the same or similar parts or features.

In the water treatment artefact 60, the composite tablet body 42 is also located in a housing 44. As can however be clearly seen in Figure 5, the housing 44 is not entirely open ended. Instead, the housing 44 has a lid 62 which is perforated with water access openings 64. With the table body 42 being completely encapsulated or housed within the housing 44 and lid 62, particles from the tablet body 42 are inhibited from falling out of the housing 44 into the water within which the water treatment artefact 60 is located. The housing 44 and lid 62 also better protect the integrity of the tablet body 42.

The tablet body 42 can be a single elongate composite body. It is however more likely that the housing 44 will contain two or three composite tablets each with a diameter substantially larger than its thickness.

If desired, an end of the housing 44 remote from the lid 62 may also be perforated.

The invention advantageously provides a low water-solubility water treatment artefact which functions as a slow-releasing HOCI source which can advantageously be used for small volume batch drinking water sanitisation. Advantageously, the water treatment artefact retains its integrity and does not disintegrate by unlimited hydration, retaining a rigid structure if dried after release of the active HOCI sanitising agent. The performance of the water treatment artefact according to the invention, as illustrated, relies on the calcium phosphate/calcium hypochlorite matrix to slow the rate of penetration of water in which the water treatment artefact is submerged, into the composite body. This retarded water penetration allows for the slow release and the consistency of the release of the active HOCI ingredient. By controlling the surface area of the composite body exposed to water, the concentration of HOCI in the water can be controlled or set. By increasing the length of the composite body (e.g. when the composite body is in the form of a cylinder), the HOCI release capacity of the water treatment artefact can be increased, i.e. the length of time during which the water treatment artefact will release HOCI, can be increased. The concentration of HOCI in the water, and to some extent the HOCI release capacity, can also be controlled or set by varying the ratio of Ca₃(PO₄^ and Ca(OCI)₂ in the composite body.

Claims

CLAIMS:

1. A water treatment artefact which includes a compacted or compressed composite body of an admixture of particulate calcium phosphate (Ca₃(PO₄M and particulate calcium hypochlorite (Ca(OCI)₂J.

2. The water treatment artefact as claimed in claim 1 , which the calcium hypochlorite is commercial calcium hypochlorite comprising 60 % to 70 % by mass available chlorine, the commercial calcium hypochlorite and the calcium phosphate being present in the composite body in a mass ratio of between about 1 : 0.43 and about 1 : 1.5.

3. The water treatment artefact as claimed in claim 1 or claim 2, in which the composite body includes chloride of lime.

4. The water treatment artefact as claimed in claim 3, in which the chloride of lime is present in the composite body in a concentration of between about 10 % by mass and about 40 % by mass.

5. The water treatment artefact as claimed in any one of the preceding claims, which has less than about 35 % available chlorine.

6. The water treatment artefact as claimed in any one of the preceding claims, which includes a housing of water-impervious material located snugly around the composite body, with a water access opening being provided in the housing so that water can reach a portion of the surface of the composite body.

7. The water treatment artefact as claimed in claim 6, in which the composite body is elongate and cylindrical, and has a length or thickness greater than its diameter, one or both ends of the elongate composite body in use being exposed to water, with the surface of the composite body between the ends being covered by the housing.

8. The water treatment artefact as claimed in claim 6 or claim 7, in which the housing is in the form of a sleeve or wrapper.

9. The water treatment artefact as claimed in any one of claims 6 to 8 inclusive, in which the housing includes an attachment formation to attach the housing to the housing of another of said water treatment artefacts, or to a buoyant body or float.

10. A water treatment kit which includes a buoyant body or float, with an attachment formation; and at least one water treatment artefact which includes a compacted or compressed composite body of an admixture of particulate calcium phosphate (Ca₃(PO₄M ^and particulate calcium hypochlorite {Ca(OCI)₂}, and a complementary or cooperating attachment formation so that the water treatment artefact can be attached to the buoyant body, via the attachment formation of the buoyant body.

11. The kit as claimed in claim 10, in which the water treatment artefact is an artefact as claimed in any one of claims 1 to 9 inclusive.

12. The kit as claimed in claim 10 or claim 11 , which includes a plurality of the water treatment artefacts, the artefacts being configured also to be attachable to each other via attachment formations.

13. A water treatment device which includes a buoyant holder having at least one water treatment artefact compartment for holding a water treatment artefact, the water treatment compartment having at least one opening to allow water to enter the compartment; and a water treatment artefact as claimed in any one of claims 1 to 9 inclusive, in the compartment of the holder.

14. The device as claimed in claim 13, in which the compartment is complementary shaped and dimensioned to the water treatment artefact, to receive the water treatment artefact without clearance.

15. The device as claimed in claim 13 or claim 14, which includes a float, with the compartment being located on an operative underside of the float.