GB2158060A - Chemical composition - Google Patents

Abstract

The treatment and control of algae and other microorganisms in water, particularly swimming-pool water, are carried out using a copper chelate composition. Also disclosed is a simple filter device, to allow any grade of pool or water treatment chemicals to be used. A mixture (1) of the composition. in a filter container (5), can be located in a filtration area (7), into which the water from a swimming-pool (11) overflows. After treatment in the area (7), the water returns to the pool (11) via an outlet (10), so that the pool water undergoes continuous treatment. <IMAGE>

Description

SPECIFICATION Chemical composition The present invention relates to control of algae in water. More particularly the invention is useful to control algae in swimming pool water.

Since the turn of the century, copper has been known as an effective control upon water borne algae. Not only is it probably one of the most effective chemical algicides it is also safe to use.

As disclosed in "Specification and rate of loss of copper from Lakewater with implications to toxicity" (Water Research Vol. 13 p. 515 - R. Wagman & BR< J. Barcia) copper has been used to clean farm dams of algae. Similarly, it has been used to treat algae in drinking water as disclosed in "Algae in Water Supplies" (U.S. Department of Health, Education and Welfare).

In view of the increasing preponderance of swimming pools, there is a demand for an inexpensive control on algae. Initial investigations have found copper sulphate to be extremely effective in keeping pools clear for up to six (6) months without using other pool algicides. Not only does copper sulphate control algae, but it is apparent that fungal deposits are quickly destroyed helping in the maintenance of "hard to get at" areas in the pool. Typically, the concentration of copper used is 2 parts per million (ppm).

Investigations have also revealed algal control copper does not require supplementary assistance from other pool chemicals such as chlorine. Field trials indicate that at pH's over 8.0 the copper can have its effectiveness reduced by precipitation of its toxic Cu" form. Thus, typical conditions for usage are in the pH range of 7.2 - 7.6, the same as that utilized for pool chlorine.

Whilst copper has been found to control algae in swimming pool applications it will not control or destroy the presence of bacteria or viruses. Accordingly, to protect the swimmer from pathogens an effective sterilizing agent must be used in the water. One known sterilization chemical is calcium hypochlorite which is used widely in the pool industry throughout the world. It is normally dosed in pools to give a chlorine concentration of between 0.5 ppm to 10 ppm for the most effective bacterial control. Other chlorine compounds such as sodium hypochlorite and sodium dichloroisocyanurate have been used as chlorinating chemicals.

Further chlorination of pools has also been used to control algae in the water.

Notwithstanding coppers effectiveness as an algicide, in use problems do arise. In its simple metallic salt form (eg. copper sulphate) its soluability is severely affected by increasing alkaline pH's. At a pH of 7.4 its maximum soluability is approximately 0.7 ppm, and at pH 8.0 its soluability can be less than 0.1 ppm. To be an effective algicide it is normal to maintain the copper concentration at 0.5 ppm or more. Thus, if the pH of pool water is increased to levels in excess of 8.0, the copper may be precipitated from the water and lost through the pool filter. Also at pH levels in excess of 8.0 the copper may form various copper oxides which can leave dark grey stains on the pool surface. This staining problem is the major reason why copper based algicides are not generally used in swimming pools.

One approach attempting to eliminate this staining problem can be found in U.S. Patent No.

2,734,028 which suggest the forming of a copper complex by the reaction of copper sulphate and alkanolamine. In use however this concentrate has not exhibited long storage life thought due to decomposition of the complex under the influence of warm temperatures andlor sunlight. The decomposition results in precipitation of copper and attendant loss of effectiveness.

As disclosed in U.S. Patent No. 3,930,834, in view of the inherent difficulties in using water-soluble copper sources such as copper sulphates, it is proposed to utilize only water- insoluble copper compounds. In doing so, it is necessary to react such insoluble compounds with an acid in aqueous solution and thereafter with a complexing agent.

Whilst a wide range of complexing agents are stated as useful, in U.S. Patent 4, 324,578 by the same inventor it was subsequently found that a mixture of monoethanolamine and triethanolamine was needed to achive the stated copper complex aims of long stability.

in both 834 and 578 it is stated that the increased stability is achieved because of the elimination of sulphate ions in solution, which ions can form sulphuric acid in solution which act on the chelating complex to release copper over extended periods of time.

Other algicides which are not copper based are generally less effective in swimming pools because they do not kill or control as wide a spectrum of algae. Further, they have a short life necessitating constant additions to maintain usefulness. By their nature it is uncommon for such an algicide to also exhibit fungicide characteristics.

Chlorine based sterilizing agent and especially calcium hypochlorite has also been used to control algae growths in pools.However, unless the pool water is thoroughly and continuously chlorinated algae reappears on pool surfaces and in the water within a few days of cessation of chlorination or if the doses of chlorine are too low. This is particularly problematic for pool owners at holiday times and at other periods when the pool cannot be easily and continuously chlorinated.

In view of the above it is common to combine copper and chlorine in the pool to achieve excellent algal control and disinfection. However, chlorine compounds such as calcium hypochlorite have a natural tendency to cause increased alkaline conditions in the pool which cause the copper stains to appear. Further, the addition of calcium into the pool also results in formation of insoluble calcium salts. These salts (eg. calcium carbonate) have a naturally high pH which causes copper stains to occur on the areas where the salts are spread. In some pools the surface lining of the pool is manufactured from calcium carbonate crystals which similarly promote appearance of copper stains.

Thus, whilst a combined composition of copper and chlorine is potentially useful, the resultant rise in pH and associated appearance of copper stains limits its practical usefulness.

Accordingly, it is an object of the present inven tion to minimize the problems of copper staining in swimming pools whilst maintaining the algicidal and fungicidal properties of copper.

In pursuing this object it has been surprisingly found that, water-soluble copper compounds 4 chelated by particular agents reduce the aforemen tioned stains more satisfactorily than heretofore known. The chelate is believed to release and maintain the toxic forms of copper, i.e. Cu and other associated compounds, in the pool water. It also is believed to protect copper from precipitat ing out as greylblack oxide stains on the pool sur faces.

Accordingly there is provided a composition for the control of algae in water comprising: (a) a source of water soluble copper, and (b) a chelating agent selected from water soluble organic acids containing 1 to 22 carbon atoms their salts and mixtures thereof, said chelating agent combining with the copper to inhibit formation of copper oxide or similar dark coloured compounds in water whilst permitting release of toxic copper ions into the water body to substantially control or kill algae and fungus forming therein. More partic ularly hydroxy acids or alkyl carboxylic acids have been found to inhibit copper precipitation quite un expectedly having regard to the prior art (U.S. Pat ent 3,930,834) regarding same as uneffective upon water soluble copper source.

As it is common to use chlorine disinfectants, es pecially calcium hypochlorite, it is desirable for the chelate to be compatible therewith. Combining the algicidal and fungicidal properties of a copper che late with the disinfection provided by common bacteriacides (eg. chlorine) provides a new means of maintaining a clear unmarked and disinfected swimming pool. Experiments have revealed that such a combination exhibits greater effectiveness than either one of the products used by itself.

Nevertheless, it is clear that a copper chelate is ef fective with or without the bacteriacide.

The copper chelate solution has a pH in the range of 1 to 6 and as an additive has the ability to tolerate wide variations in pool pH and inhibit cop per from precipitating and being lost from the pool if the pH rises above 8.0. Such rises in pH may be caused by the addition of the common bacteria cides, eg. alkaline calcium hypochlorite, or by the surface reaction of calcium carbonate "hardness" or by the precipitation with other calcium salts.

Nothwithstanding the stabilizing effect of the chelate it is still desirable to maintain the pH of the pool water below 8. In this respect, the preferred active range of pH is 6.5- 8.0. Similarly, in this range of pH little adverse effect is noticed due to water hardness or salinity in marked contrast to the low pH stability of complexes of the admitted prior art.

In another preferred embodiment of the inven tion use of the chelate promotes a long active service life with algicidal and fungicidal properties which can last for between one (1) and eight (8) months irrespective of whether chlorinating com pounds are added to the pool water.

Copper concentration is also important. If it is low, its algicidal properties will not be as effective.

Yet, if the copper concentration is too high, then there is a risk of the appearance of copper stains.

For these reasons the most preferred chelating agent is of a type that combines with the copper to hold it in solution and prevent it forming copper oxide and after copper staining compounds on the pool lining surface. Such agent should also be able to release Cu and similar toxic copper ions to the water body to substantially control or kill the algae and fungus. In this respect, if the chelating effect is too great, algae and fungus will appear in the water due to the absence of toxic forms of copper.

Accordingly, it is preferred that the ratio of copper chelate to source of chlorine be between the range 1 1 to 50 1. As a practical rule it is typical to mix 0.2 - 5.0 milligrams per litre of copper as a copper chelate into the pool water together with 0.2 to 10 milligrams per litre of chlorine as a sodium or calcium salt. This mixture controls and kills bacteria, algae and fungus without the deposition of copper stains on the pool surface. Whilst reference has been made to the use of a bacteriacide eg. chlorine, in the above mixture, it may be dispensed with in which case, the copper as a copper chelate still kills or controls algae and fungus without the deposition of copper stains on the pool surface.

Typical of chelating agents as defined above, found to exhibit the desired characteristics are ethylene diamine tetra acetic acid, sodium citrate, citric acid, sodium acetate, triethylamine, and other similar chemicals which combined with the copper ion in various concentrations to kill or control algae and fungus and be used in the presence of calcium or sodium hypochlorite (for disinfection) without staining occurring on the pool surface.

The concentration of both the copper and chelating agent have to be adjusted according to the water hardness and calcium scaling present in the pool.

The invention is now further illustrated with reference to the following comparitive example.

500mis of secondary treated domestic effluent were collected from a waste stabilisation pond discharge and added to each of five sets of conical flasks. A known strength of algicide was added to four of the flasks as follows: 1. Control 2. CuSO4 (2g/m3) 3. CuSo4 (1g/m3) (10glum3) Citric acid or equivalent salt 4. CuSo4 (1g/m3) (15g/m3) Sodium Citrate 5. CUSo4 (0.5g/m3) (15git3) Citric acid Each flask opening was closed with a cotton wool pad. The five flasks were illuminated continuously by a 15w fluorescent light during the study period.

1 my. samples were taken from the side of each of the flasks in turn, at the 200 ml. mark and pipetted into a Sedgwick Rafter counting cell. The com position and abundance of algal taxa were identified and counted for each set of samples using a Zeiss compound microscope. Samples were taken at the beginning of the bioassay and at intervals over a three day period.

The total number of algae per ml. for each sample is recorded in figure 1. Only flasks 2 and 3 showed a continuous reduction in total numbers of algae/ml. over the 3 day period. Zero numbers were recorded in flask 2 after 72 hours. There was a rise in total numbers of algae/ml. beyond the initial counts in flask 5 after 65 hours and in flasks 1 and 4 after 72 hours.

Flask 2 showed the best killing potential, however, it deposited black stains as is typical of the use of copper only. Flask 3 however, with chelating agent added exhibited a similar killing potential without the appearance of stains. When the amount of chelating agent was increased as in Flask 4, a decline in effectiveness was noted. This was thought due to an excess of chelating agent inhibiting cu++ availability. Nevertheless no black stains were apparent. The less effective composition of Flask 5 whilst again not exhibiting staining, showed that the chelating agent can further inhibit copper availability thereby reducing effectiveness of the composition as an algicide.

Accordingly by use of chelated copper, existing problems of staining can be substantially reduced if not eliminated without undue influence on is algicidal characteristics. Further, it is possible to successfully combine same with commonly known bacteriacides to provide a composition which can cope with variances in pH, water hardness and salinity.

In a separate aspect there is provided a chlorine filter which substantially inhibits ingress of insoluble compounds into water being chlorinated.

In recent years pools, both of the above ground and recessed type, have gained popularity. With such increase has come an increased demand for chlorination chemicals. At present there are only limited sources of chlorine, which are usually supplied in powder or tablet form.

These sources of chlorine are predominately calcium hypochlorite but include insoluble compounds which, if allowed to enter pools, cause the water to take on a cloudy appearance and/or leaves an insoluble precipitate on the bottom of the pool. It is thought these insoluble compounds include calcium hydroxide, calcium carbonate, and other insoluble calcium salts, as well as complexes of iron, aluminium and sodium and other insoluble compounds. In addition to the formation of cloudiness, these insoluble compounds increase the pH of water to unacceptable levels e.g. above 7.6 causing the water to take on an alkaline nature.These compounds have also been found to harden water.

Efforts to eliminate these compounds from chlorine powder or tablets have principally been by chemical purification which has lowered the amount of contaminants but also increased the resultant retail cost of the chlorine. Similarly some sources of chlorine have inherently low amounts of contaminants however at present the retail price is also high.

The present invention is concerned with treatment of the former type of chlorine material which has unacceptable levels of contaminants e.g. 20% calcium hydroxide and 5% calcium carbonate. It should be understood however that the present invention may also be used with chlorine material with low contaminants content, in which case same are further inhibited from entering the pool.

In conventional pools, a filtration compartment is provided in which an open meshed receptacle is placed and through which the pool water passes. It is common to deposit chlorine material of the aforementioned types in this container or in a container which floats on the surface of the pool. In the case of powder, it may be merely scattered into the pool. This material slowly dissolves in the water. Insoluble particles are likewise allowed to enter the pool. In the case of the open meshed container, the mesh is such only to retain twigs and leaves without unduly interfering with water flow. It therefore allows the insoluble compounds to enter the pool.

In contrast to the prior art attempts to reduce the content of insoluble compounds in the material manufacture, the present invention is concerned with the substantial reduction of insoluble compounds entering the pool upon dissolution of the conventional material.

To facilitate this approach, the present invention comprises the provision of a water permeable receptacle into which is placed conventional chlorine material, having either high or low contaminant content, the receptacle permitting soluble compounds to enter the water, and permeate therethrough, whilst simultaneously retaining the bulk of the insoluble compounds within the receptacle.

The receptacle may be of any shape or construction which achieves the above requirements. Typically the receptacle may be sock-like and constructed of closely woven fabric, e.g. industrial filter fabric. A rot-proof variety of this fabric has been found to be most effective. In use the tables or powder are placed into the sock and the open ends of the sock sealed by any known means, e.g.

velco, zip, or pull-closure hook and eye. The sock is then placed into the pool or pool filtration compartment. Water enters the sock and gradually dissolves the soluble compounds of the chlorine material, which then flow into the pool. Insoluble compounds freed from the material are washed against the water permeable fabric and cannot substantially pass therethrough.

After the chlorine material is spent or when further chlorination is required, the sock may be removed and the insoluble compounds are washed out at a remote location away from the pool.

Whilst the above description of the receptacle is as a sock, the form thereof is not so limited. The receptacle may be rigid having a plurality of minute perforations. Further other materials such as fibreglass may be used.

Reference is now made to the accompanying drawings in which: Figure t is a perspective view of one form of the invention; Figure 2 is a perspective view of a second form of the invention; Figure 3 is a cross-sectional view of the second form of the invention in situ.

In Figure 1, a sock 2 of industrial filter material is provided with a closure flap 3 retainable by velco strip 4. Into sock 2 conventional chlorinating mixture 1 is placed and retained.

Similarly as shown in Figure 2 sock 5 is provided with a zip 6 along or adjacent its upper edge. In use sock 5, with mixture 1 contained therein are placed in the filtration area of a pool.

Figure 3 shows in detail the use of sock 5 aforementioned. In particular pool 11 is filled to a level where water flows over dam 9 into the filtration area 7. In this area 7, a filter basket 8 is retained and supports sock 5. Normally water flows through basket 8 and is returned to pool 6 via outlet 10 and inlet 6, floating debris is introduced to basket 8 by reasoning of swinging movement of dam 9.As shown sock 5 is wetted and the soluble compounds of the mixture 1 are brought into solution and pass out of the sock 5. Thereafter the dissolved compound enters pool 6 with recirculated water.lnsoluble compounds liberated in sock 5 are substantially retained therein. After complete dissolution of the soluble compounds of the mixture 1, the sock 5 may be removed and cleaned.For example, cleaning may be carried out by turning the sock 5, inside out and washing the insoluble compounds at a point remote from the pool 6.

The receptacle of the present invention is cheap and easily manufactured. Unlike prior attempts, it prevents or substantially inhibits, in situ, ingress of unwanted insoluble diluents into a pool. Thus by reason of the invention it is possible to use chlorine material which is highly contaminated with insoluble compound. The expected cloudiness and pH increase is substantially minimized.

The sock preferably is of a material which inhibits from 50 to 99% and more preferably from 75 to 99% of the contaminant insoluble compounds from passing therethrough.

Additionally it will be appreciated that the sock may be adapted to fit in any conventional chlorine mixture dispenser or may be merely suspended by appropriate means at an appropriate place in the pool.

Claims (22)

1. A composition for the control of algae in water comprising: (a) a source of water soluble copper, and (b) a chelating agent selected from water soluble organic acids containing 1 to 22 carbon atoms, their salts and mixtures thereof, said chelating agent combining with the copper to inhibit formation of copper oxide or similar dark coloured compounds in water whilst permitting release of toxic copper ions into the water body to substantially control or kill algae and fungus forming therein.

2. A composition according to claim 1, wherein the water soluble organic acids are hydroxy acids or alkyl carboxylic acids.

3. A composition according to claim 1, wherein the chelating agent is selected from the group comprising ethylene diamine tetra acetic acid, sodium citrate, citric acid, sodium acetate, triethylamine and mixtures thereof.

4. A composition according to claim 1 having a pH in the range 1 to 6.

5. A composition according to claim 4 which further includes a source of chlorine.

6. A composition according to claim 5, wherein the source of chlorine is calcium hypochlorite, sodium hypochlorite and sodium dichloroisocyanurate.

7. An algicide additive for a pool comprising: (a) a source of copper sulphate, (b) a chelating agent selected from the group comprising hydroxy acids, salts and mixtures thereof, the additive having a pH in the range of 1 to 6.

8. An algicide additive according to claim 7 wherein the chelating agent is citric acid.

9. A pool additive comprising an algicide additive according to claims 7 or 8 and a source of chlorine.

10. A pool additive according to claim 9 wherein the ratio of algicide additive to source of chlorine ranges between 1 : 1 to 50 : 1.

11. A pool additive according to claim 10 wherein the source of chlorine is either a sodium or calcium chlorine salt.

12. A method of controlling algae and bacteria in a swimming pool comprising the step of adding to the pool, the pool additive of claims 9 to 11.

13. A method of controlling algae and bacteria according to claim 12 wherein 0.2 to 5 milligram/ litre of the algicide and 0.2 to 10 milligram/litre of the source of chlorine is added as the pool additive.

14. A method of controlling algae in swimming pool water comprising the steps of adding to the pool the algicide additive of claims 7 or 8 in amounts of 0.2 to 5 milligrams/litre of pool water.

15. A receptacle for use in a chlorination system of a pool, in which receptacle a source of chlorine containing soluble and contaminant insoluble compounds is receivable, the receptacle having a water permeable portion which operably permits water to enter the receptacle to disssolve the soluble compounds, the portion further permitting the water and the soluble compounds so dissolved to escape from the receptacle for introduction into the pool, whilst substantially inhibiting passage therethrough of the insoluble compounds.

16. A receptacle according to claim 15 wherein the water permeable portion is fabricated from closely woven material.

17. A receptacle according to claim 16 wherein the closely woven material is industrial filter fabric or perforated rigid materials.

18. A receptacle according to claims 1 or 3 wherein it is sock- like and includes a closable mouth portion.

19. A receptacle according to claim 15 wherein the water permeable portion inhibits at least from 50 to 99% and preferably from 75 to 99% of the contaminant insoluble compounds passing therethrough.

20. A receptacle according to claim 19 wherein the contaminant insoluble compounds comprise up to 25% of the source of chlorine.

21. A receptacle substantially as hereinbefore described with reference to the drawings.

22. A composition according to any of claims 1 to 11 substantially as hereinbefore described.

23 A method of controlling algae and bacteria according to any of claims 12 to 14, substantially as hereinbefore described.