WO2010024742A1

WO2010024742A1 - A method for treatment of circulating water and a swimming pool circulation system having an arrangement for treating water

Info

Publication number: WO2010024742A1
Application number: PCT/SE2008/050965
Authority: WO
Inventors: Lennart Olausson
Original assignee: Lennart Olausson
Priority date: 2008-08-26
Filing date: 2008-08-26
Publication date: 2010-03-04

Abstract

The invention relates to a method for treatment of water circulating in a cycle, in particular water in a swimming pool. The water is passed from a swimming pool (1), through at least one filter (2) and back to the swimming-pool. Chlorine is added to the water and after the water has passed the filter (2), the water is subjected to radiation by ultraviolet light. The invention also relates to a swimming pool having an arrangement for treating water with chlorine and ultraviolet light.

Description

A METHOD FOR TREATMENT OF CIRCULATING WATER AND A SWIMMING POOL CIRCULATION SYSTEM HAVING AN ARRANGEMENT FOR TREATING WATER

FIELD OF THE INVENTION

The invention relates to a method for treatment of circulating water, in particular water that circulates from a swimming pool to a filter and back to the swimming pool. The invention also relates to a swimming pool system having an arrangement for treating the water in the swimming pool.

BACKGROUND OF THE INVENTION

Filters and chemicals are sometimes used for purification of water in a baths establishment e.g., in order to meet hygienic requirements. Various solid contaminants are caught by the filter in order to subsequently be removed. Often, the chemicals used for disinfection are chlorine-containing chemicals. The used filters are mostly sand filters of a certain bed height. Chlorine-containing chemicals for the purification of the bathwater are known to cause troubles both to bathers and employees at baths establishments. For this reason, attempts have been made to find alternatives to the use of chlorine. For example, in WO 2006/130052, it has been suggested that hydrogen peroxide can be used instead of chlorine. However, practical experience of the technology disclosed in WO 2006/130052 suggests that chlorine is still a more effective agent for treatment of water in a swimming pool.

The object of the present invention is to provide a method and an arrangement for purification of water in swimming pools / baths establishments in which the chlorine causes less inconvenience for the users of the swimming pools.

SUMMARY OF THE INVENTION

The inventor of the present invention has found that inconvenience and discomfort to users of a swimming pool caused by chlorine can be reduced by a method for treatment of water circulating in a cycle in which water is passed from a swimming pool, through at least one filter and back to the swimming pool. In the method, chlorine is added to the water. According to the invention, the water is subjected to radiation by ultraviolet light after the water has passed through the at least one filter.

When chlorine is added to water, some of the chlorine will take the form of free chlorine while some of the chlorine will be in the form of bound chlorine such as various chloramines. Without wishing to be bound by theory, the inventor believes that discomfort to users of the swimming pool is caused mainly by bound chlorine in the form of inorganic and/or organic chlorine compounds such as inorganic and/or inorganic chloramines (for example trichloramine). Therefore, while chlorine as such is desirable, the amount of bound chlorine should be reduced as much as possible. Exposure to ultraviolet light causes such compounds to either disintegrate or become bound to solid particles that can be caught by the filter. In turn, removal of particles by the filter means that it becomes easier for the ultraviolet light to reach all parts of the water and thereby causing bound chlorine disintegrate or to become bound to solid particles that may be removed by the filter. In embodiments of the invention, the at least one filter may comprise a layer through which the water passes at a rate of 15 m³ - 20 m³ per square meter of the filter, the layer being 0.30 m - 0.8 m thick. Preferably the layer is 0.30 m - 0.45 m thick. The layer in the filter preferably consists essentially of spherical particles (i.e. round particles) although embodiments of the invention are conceivable where the particles are not spherical.

In some embodiments, at least 70% of the spherical particles in the at least one filter have a diameter in the range of 0.42 mm - 0.84 mm. Preferably, at least 80 % of the spherical particles have a diameter in the range of 0.42 mm - 0.84 mm. Even more preferred, at least 95 % of the particles have a diameter in that range. In some embodiments, the PH level of the circulating water can be regulated such that PH is in the range of 7.2 - 7.6.

In some embodiments, the water receives a dose of ultraviolet light of at least 30 mJ/cm² each time the water is subjected to radiation by ultraviolet light.

The ultraviolet light may suitably have a wavelength of 240 nm - 280 nm although wavelengths less than 240 nm or more than 280 nm may be considered.

In some embodiments, the chlorine level can be monitored. If the chlorine level is monitored, chlorine may be added if the measured chlorine level falls below a predetermined level.

The invention also relates to a swimming pool circulation system that has a swimming pool and an arrangement for treating water. The arrangement for treating water comprises a conduit arranged to lead water from the swimming pool, through at least one filter and back to the swimming pool. The arrangement may also comprise a source of chlorine for adding chlorine to the water and a source of ultraviolet light arranged in the conduit at a location downstream of the at least one filter.

The at least one filter may comprise a particle layer that is at least 0.30 m thick, preferably 0.30 m - 0.45 m thick. The layer may consist essentially of spherical particles.

Preferably at least 70% of the spherical particles have a diameter in the range of 0.42 mm - 0.84 mm.

In embodiments of the invention, the spherical particles may be soda lime glass particles having the following chemical composition in % by weight: 68 - 73 SiO₂, 13 - 15 N₂O + K₂O, 8 - 11 CaO, 3 - 5 MgO and 0.5 - 2 Al₂O₃.

The source of ultraviolet light is preferably arranged inside the conduit through which the water circulates and the source of ultraviolet light is preferably arranged in the centre of the conduit. However, embodiments are conceivable where the source of ultraviolet light is not located inside the conduit. Embodiments are also possible where the source of ultraviolet light is located inside the conduit but not at the centre of the conduit.

The arrangement for treating water may optionally comprise a chlorine level indicator connected to a control unit that controls a source of chlorine such that chlorine is released into the water if the chlorine level indicator signals that the chlorine level has fallen below a predetermined level.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a schematic representation of a swimming pool with an arrangement for treatment of circulating water. Fig. 2 is a schematic representation of a filter used in the invention.

Fig. 3 is a cut-open perspective schematic view of another embodiment of a filter.

Fig. 4 is a cross sectional view of a conduit in which a source of ultraviolet light has been placed. Fig. 5 is a cross sectional view showing the same parts as in Figure 3 but from a direction perpendicular to the direction from which the same parts are showed in Figure 3. DETAILED DESCRIPTION OF THE INVENTION

With reference to Figure 1, a swimming pool 1 is showed that has an arrangement for treating water. The water treatment arrangement comprises a conduit 6 arranged to lead water from the swimming pool 1. In Figure 1, a pump 5 is indicated that forces water in a loop or cycle through the swimming pool 1 and the conduit 6. In Figure 1, only one pump 5 is showed but it should be understood that more than one pump may be used and that pumps 5 may be located at many different places along the conduit 6. The water is forced to pass through at least one filter 2 that is arranged to remove particles from the water. The filter is suitably a filter that uses a layer of fine particles such as, for example, sand or small glass beads. When the water has been passed through the at least one filter 2, the conduit 6 will lead the water back to the swimming pool 1. The arrangement for treating water also comprises a source of chlorine 8 which can be a container arranged to add chlorine to the system if necessary. In the conduit 6, a source of ultraviolet light 3 has been placed at a location downstream of the at least one filter 2. In principle, the filter 2 may have a filtering layer of sand but it has been found that spherical/round particles such as small glass beads are particularly efficient. It has been found that, when spherical glass beads are used, the particle layer can be relatively thin, and that it could be in the range of 0.30 m - 0.45 m. The filtering layer may also comprise a small amount of other particles than spherical particles, i.e. a mixture of spherical and non-spherical particles but it is preferable that it consists essentially of spherical particles (although embodiments are also possible that uses no spherical particles).

Preferably, at least 70% of the spherical particles have a diameter in the range of 0.42 mm - 0.84 mm. The inventor has found that soda lime glass is a particularly suitable material for the spherical particles in the filtering layer 4 used in the filter or filters 2. The soda lime glass spherical particles may have the following composition in % by weight:

SiO₂ 68 - 73

N₂O + K₂O 13 - 15 CAO 8 - 11

MgO 3 - 5

Al₂O₃ 0.5 - 2 With reference to Figure 4 and Figure 5, the source of ultraviolet light can be arranged inside the conduit 6 through which the water circulates and preferably located in the centre or middle of the conduit 6. In Figure 4 and Figure 5, is indicated how the source of ultraviolet light may be held by one or several holders or supporting elements 23. As showed on Figure 1, the arrangement for treating water may comprise a chlorine level indicator 13 connected to a control unit 24 that controls a source of chlorine 8. If the chlorine level indicator 13 detects falling levels of chlorine, a signal from the indicator 13 causes the control unit 24 to release chlorine from the source of chlorine 8 such that chlorine is released into the circulating water. In Figure 1, it is indicated how the chlorine level indicator may be located in a separate first side conduit 25 and how valves 12, 14 may open or close the separate first side conduit 25 in which the chlorine level indicator 13 is located. When the valves 12, 14 are open, some water will pass from the main conduit 6 through the first side conduit 25 and reach the chlorine level indicator 13 such that the chlorine level can be determined. The chlorine level indicator 13 has a connection (not showed in the Figures) to a control unit 24 that is capable of controlling a source of chlorine 8 such that chlorine is released into the water if the chlorine level indicator 13 signals that the chlorine level has fallen below a predetermined level. The connection between the indicator 13 and the control unit 24 may be, for example, wireless communication or an electrical cable. The source of chlorine 8 may be, for example, a container that holds chlorine and the control unit 24 may control a valve (not showed) that can be closed or opened to release chlorine into the water.

As showed in Figure 1, chlorine may be added to the water in a separate loop formed by a second side conduit 7 through which a part of the water may pass in order to receive chlorine before it is sent back to the main conduit 6. The second side conduit 7 conduit can be closed or opened by means of, for example, valves 10, 11 that are placed in the conduit 7.

In principle, the invention may be understood in terms of a method where already chlorinated water is provided instead of a process where water is chlorinated. However, chlorine in the water will gradually disappear due to, for example, sunlight or oxidation. For this reason, it will, in almost all practical cases, be necessary to add chlorine during the process to replace chlorine that has disappeared from the circulating water.

The side conduits 7, 25 may have a diameter that is smaller than the diameter of the main conduit 6 such that the major part of the water will flow through the main conduit 6 and only minor parts of the water will flow through the side conduits 7, 25. In principle, the source of chlorine 8 and the chlorine level indicator 13 may be connected directly to the main conduit 6 but it is easier to add the chlorine in a separate minor flow that is then passed into the main flow. For a correct measurement of the chlorine level, it is also suitable to use a separate loop with a limited flow. To control PH, a source of acid 9 may also be connected to the control unit 24. The PH level may be measured by a separate indicator device 26 that is also in communication with the control unit 24 (the communication may be, for example, through cable or wireless communication). In response to a signal from the indicator device 26 that PH is too high, the control unit 24 may control the source of acid 9 such that an amount of acid is released into the water. The indicator device 26 can thus monitor the PH level and the control unit 24 and the source of acid 9 can be used to regulate the PH level in response to a signal from the indicator device 26. In Figure 1, the same control unit 24 is used for both acid and chlorine. It should be understood that separate control units can be used. The control unit 24 may be, for example, a computer. The acid used to regulate PH may be, for example, hydrochloric acid or carbonic acid.

An embodiment of a suitable filter shall now be explained with reference to Figure 2. As showed in Figure 2, the conduit 6 leads to a filter 2 at an entry point that is located at or near the top of the filter 2. The filter 2 has a shell 22 and contains a filtering layer 4 that may consist of small particles such as sand. Preferably, the particles in the filter 4 are spherical particles such as glass beads/glass balls of soda lime glass. Preferably, the spherical particles, or at least 70% of the spherical particles, have a diameter in the range of 0.42 mm - 0.84 mm. The height H of the filter may be in the range of 0.30m - 0.45 m. In one possible embodiment considered by the inventor, the height H of the filter may be 0.35 m. In this embodiment, the particles used in the filter layer 4 were particles of soda lime glass. The spherical particles had the following composition in % by weight:

SiO₂ 68 - 73

N₂O + K₂O 13 - 15

CAO 8 - 11 MgO 3 - 5

Al₂O₃ 0.5 - 2 Suitable particles can be obtained from, for example, AB TEBECO, Box 49, SE-301 02 HALMSTAD, Sweden. Tebeco sells soda lime glass particles of the kind indicated above.

In principle, the filter layer 4 may contain glass particles that are not spherical. However, spherical particles have been found to be effective for filtering purposes. Moreover, spherical particles do not cause injury to humans coming in contact with them, for example by stepping on such particles.

If sand is used instead of spherical glass particles, the height H should be more than 0.45m. For sand, a suitable height H could be in the range of 0.50 m - 0.75 m since sand is less effective as a filter layer compared to spherical particles.

The filtering layer 4 may be supported on a grating 17.

The water may exit the filter 2 at a lower end of the filter 2. It should be noted that the flow through the filter may be shut off by valves 15, 16. To clean the filter 2, there is a separate conduit 18 through which water may be sent through the filter 2 and a separate conduit 20 through which cleaning water from the conduit 18 may leave the filter 2 after it has passed through the layer 4 to flush away dirt particles. The conduits 18, 20 can be closed by valves 19, 21. Normally, the valves 15, 16 are open and water from the swimming pool passes though the filter. The valves 19, 21 are then closed. To clean the filter 2, the valves 15, 16 are closed and the valves 19, 21 are opened. Water from the conduit 18 is then flushed through the filter. When the filter 2 has been cleaned, the valves 19, 21 are closed and the valves 15, 16 are opened.

Another embodiment of a suitable filter shall now be explained with reference to Figure 3.In the filter 2 showed in Figure 3, water enters the filter 2 through an entry conduit 26 and flows out from the funnels 28. In Figure 3, the entry conduit has a connection piece 31 for connection to the conduit 6 for water coming from the pool. The funnels 28 may optionally have perforations 30 through which water may flow. From the funnels 28, the water flows through the filtering layer. For the sake of clarity, the filtering layer 4 is not showed in Figure 3 but it should be understood that there is a filtering layer 4 which is just like the filtering layer 4 in Figure 2. In Figure 3, the height of the filtering layer is indicated by the letter H. When the water has passed through the filtering layer 4, the water reaches a bottom that comprises tubes 29 that are provided with a large number of narrow slots. The slots may have a width of, for example, 0.2 mm. The water may enter through the narrow slots but glass particles from the filtering layer cannot pass through the slots. The tubes 29 are connected to an exit conduit 27. The water can then pass from the tubes 29 to the exit conduit 27 and leave the filter 2 through the exit conduit 27. In Figure 3, the exit conduit 27 is showed with a connection piece 32 for connection to the main conduit 6.

It should be understood that a suitable filter 2 could also be designed in other ways than showed in Figure 2 or Figure 3.

In Figure 1, three filters 2 are showed but it should be understood that embodiments are possible with only one or two filters or with more than three filters. In Figure 1, the three filters 2 are arranged in parallel. This arrangement has been found to be suitable but other

can also be considered. With reference to Figures 4 and 5, another aspect of the invention shall now be explained. When the water has passed through the at least one filter 2, it passes a point in the conduit 6 where a source of ultraviolet light 3 has been arranged. The source of ultraviolet light 3 may be a UV lamp placed in the middle of the conduit 6. Suitably, the UV lamp may be arranged to produce light at a wavelength of 240 nm - 280 nm in order to act on bound chlorine (for example chloramines). Possibly, the wavelength may be higher than 289 nm for some applications. For example, wavelengths in the range of 280 nm - 340 nm may be considered.

For optimum effect, the water that passes the UV lamp 3 should receive a radiation dose of at least 30 mJ/cm². The dose is the product of intensity and the time of exposure. When the source of ultraviolet light 3 is placed in the middle of the conduit 6, the ultraviolet light can reach all parts of the water with optimum efficiency.

In use, the swimming pool circulation system functions as follows. Water is passed from the swimming pool 1 in a loop through the conduit 6. The direction of flow is indicated by arrows in Figure 1. The water passes through at least one filter 2 and back to the swimming pool 1 and chlorine is added to the water at some time during the process. It should be understood that, in principle, it may be so that chlorine is added only once. If the chlorine level then remains constant, no more chlorine is added. In practice, small amounts of chlorine must be added now and then. However, it is not necessarily so that chlorine is added continuously. After the water has passed the at least one filter 2, the water is subjected to radiation by ultraviolet light when it passes the source of ultraviolet light 3.

The at least one filter 2 comprises a layer 4 through which the water may pass. In realistic embodiments, water may pass the at least one filter at a rate of 15 m³ - 20 m³ per square meter of the filter 2 when the layer 4 being 0.30 m - 0.8 m thick. For example, the layer 4 may be 0.30 m - 0.45 m thick and consist essentially of spherical particles as explained above. In one embodiment contemplated by the inventor, the layer 4 may have a thickness of 0.35 m. The PH level of the circulating water is regulated such that PH is in the range of 7.2 - 7.6. The control/regulation of the PH level may be achieved by means of the indicator device 26, the source of acid 9 and the control unit 24.

The chlorine level is monitored by means of the chlorine level indicator 13 and chlorine is added if the measured chlorine level falls below a predetermined level. Suitable levels for chlorine are usually laid down in regulations.

By means of the invention, it is possible to reach very low levels of bound chlorine. According to Swedish regulations, the level of bound chlorine in bathing water (e.g. swimming pools) should not exceed 0.4 mg/1. Tests made by the inventor have showed that the present invention makes it possible to keep the level of bound chlorine below 0.1 mg/1. At this level, many persons will not even notice that there is chlorine in the water. In some tests, the level of bound chlorine was in the range of 0.06 mg/1 - 0.08 mg/1. In another test, the level of bound chlorine was too low to be detected.

The use of spherical soda lime glass particles has been found to result in a very effective filtering effect. By first filtering the water and subsequently exposing the water to ultraviolet light, the water that is exposed to ultraviolet light is free from particles that could block the ultraviolet light. Therefore, the ultraviolet light is free to act on the bound chlorine in the water. In this context, it should be understood that some amount of small particles will always remain, even after filtering. However, the filter 2 can reduce the amount of such particles to a very large extent. The at least one filter 2 is located downstream of the at least one filter 2 but upstream of the swimming pool 1 such that the water fill first pass through the at least one filter 2, then be exposed to ultraviolet light and then reach the swimming pool. If the source of ultraviolet light is placed downstream of the at least one filter 2 and upstream of the swimming pool 1, there will be less precipitation/depositing on the glass of the UV lamp. The use of ultraviolet light at wavelengths in the range of 240 nm - 289 nm has been found to be particularly effective. Without wishing to be bound by theory, the inventor believes that this is because ultraviolet light at those wavelengths causes bound chlorine such as chloramines to disintegrate, form particles or become bound to remaining small particles in the water.

Claims

1. A method for treatment of water circulating in a cycle in which water is passed from a swimming pool (1), through at least one filter (2) and back to the swimming-pool (1), and in which method chlorine is added to the water, characterized in that, after the water has passed the at least one filter (2), the water is subjected to radiation by ultraviolet light.

2. A method according to claim 1, characterized in that the at least one filter (2) comprises a layer (4) through which the water passes at a rate of 15 m³ - 20 m³ per square meter of the filter (2), the layer (4) being 0.30 m - 0.8 m thick, preferably the layer (4) being 0.30 m - 0.45 m thick, and the layer (4) consisting essentially of spherical particles.

3. A method according to claim 2, characterized in that at least 70% of the spherical particles in the at least one filter (2) have a diameter in the range of 0.42 mm - 0.84 mm.

4. A method according to any of claims 1 - 3, characterized in that the PH level of the circulating water is regulated such that PH is in the range of 7.2 - 7.6.

5. A method according to any of claims 1 - 4, characterized in that the water receives a dose of ultraviolet light of at least 30 mJ/cm each time the water is subjected to radiation by ultraviolet light.

6. A method according to claim 5, characterized in that the ultraviolet light has a wavelength of 240 nm - 280 nm.

7. A method according to any of claims 1 - 6, characterized in that the chlorine level is monitored and in that chlorine is added if the measured chlorine level falls below a predetermined level.

8. A swimming pool circulation system having a swimming pool (1) and an arrangement for treating water, the water treatment arrangement comprising a conduit (6) arranged to lead water from the swimming-pool (1), through at least one filter (2) and back to the swimming pool (1), and which arrangement also comprises a source of chlorine for adding chlorine to the water, characterized in that a source of ultraviolet light is arranged in the conduit (6) at a location downstream of the at least one filter (2).

9. A swimming pool according to claim 8, characterized in that the at least one filter (2) comprises a particle layer (4) that is at least 0.30 m thick, preferably 0.30 m - 0.45 m thick, and in that the layer (4) consists essentially of spherical particles.

10. A swimming pool (1) according to claim 9, characterized in that at least 70% of the spherical particles have a diameter in the range of 0.42 mm - 0.84 mm.

11. A swimming pool (1) according to any of claims 9 or 10, characterized in that the spherical particles are soda lime glass particles having the following chemical composition in % by weight: 68 - 73 SiO₂, 13 - 15 N₂O + K₂O, 8 - 11 CaO, 3 - 5 MgO and 0.5 - 2 Al₂O₃.

12. A swimming pool (1) according to any of claims 8 - 11, characterized in that the source of ultraviolet light is arranged inside the conduit (6) through which the water circulates and in that the source of ultraviolet light is arranged in the centre of the conduit (6).

13. A swimming pool (1) according to any of claims 8 - 12, characterized in that the arrangement for treating water comprises a chlorine level indicator (13) connected to a control unit (24) that controls a source of chlorine (8) such that chlorine is released into the water if the chlorine level indicator (13) signals that the chlorine level has fallen below a predetermined level.