WATER TREATMENT SYSTEM AND METHOD FOR TREATING WATER LOCATED IN A WATER RESERVOIR

Abstract

The invention relates to a water treatment system (1) and a method for treating water (2) located in a water reservoir (3). The water treatment system (1) comprises a recirculation means (4) and a membrane filtration means (9) with a plurality of filter modules (10) disposed in the recirculation means (4). The water treatment system (1) particularly comprises a gas supply means (24) by which gas can be introduced into the filter modules (10) to clean the membranes of the filter modules (10) of the membrane filtration means (9) or by which gas supply means (24) gas can be introduced into the water reservoir (3) at one or more locations, periodically or when required, to circulate and mix up the water (2).

Claims

1-33. (canceled)

34. Method for treating water (2) located in a water reservoir (3), for example in a swimming pool, pond or aquarium, in particular for cleaning and disinfecting the water (2), comprising: removing a pre-settable quantity of water (2) per unit of time from the water reservoir (3) via one or more extraction line(s) (6) of a recirculation means (4); filtering the removed partial quantity of water (2) by means of a membrane filtration means (9) disposed in the recirculation means (4), the membrane filtration means (9) comprising a number of filter modules (10) fluidically connected in a parallel arrangement; returning the water to the'water reservoir (3) via one or more return line(s) (7) of the recirculation means (4); cleaning the membranes of the filter modules (10), periodically or when required, by backwashing with a backwashing liquid by reversing the direction of flow through the filter modules (10) compared with that of the filtration operation and discharging the dirty liquid occurring during backwashing via a discharge (17), wherein in order to clean the membranes of the filter modules (10) of the membrane filtration means (9), gas is introduced by a gas supply means (24) into the filter modules (10) on the intake side or the gas is introduced into the water reservoir (3) at one or more locations by the gas supply means (24), periodically or when required, to circulate the water (2) in the water reservoir (3), the gas supply means (24) being used either to flush the filter modules (10) with gas or to circulate and mix the water (2) in the water reservoir (3).

35. Method according to claim 34, wherein an operation for cleaning the membranes of the filter modules (10) is run in such a way that gas is introduced simultaneously into all the filter modules (10) on the intake side and then presettable partial quantities of the filter modules (10) are sequentially backwashed with the backwashing liquid by reversing the direction of flow through the filter modules (10).

36. Method according to claim 34, wherein an operation for cleaning the membranes of the filter modules (10) is run in such a way that gas is introduced simultaneously into all the filter modules (10) on the intake side, after which each filter module (10) is sequentially individually backwashed with the backwashing liquid by reversing the direction of flow through the filter modules (10).

37. Method according to claim 34, wherein the filter modules (10) are backwashed with mains water.

38. Method according to claim 37, wherein cleaning chemicals are added to the mains water when backwashing a filter module (10).

39. Method according to claim 34, wherein a filter module (10) is backwashed with a flow volume of backwashing liquid of between 70 l/m.sup.2.sub.mem*h and 700 l/m.sup.2.sub.mem*h and with a flow speed of the backwashing liquid through the filter module (10) of between 0.02 m/s and 1.0 m/s.

40. Method according to claim 34, wherein a filter module (10) can be cleaned on the intake side with a gas flow volume of between 0.2 Nm.sup.3/m.sup.2.sub.mem*h and 5.0 Nm.sup.3/m.sup.2.sub.mem*h and a flow speed of the gas through the filter module (10) of between 0.1 m/s and 2 m/s.

41. Method according to claim 36, wherein in order to end an operation for cleaning and flushing a filter module (10), the intake of mains water into the filter module (10) is halted, the backwashing water remaining in the filter module (10) is displaced by the gas and directed away via a discharge (17), and the filter module (10) is filled with mains water before resuming the filtration operation.

42. Method according to claim 34, wherein the flow quantity of water (2) through the filter modules (10) is detected during the filtration process and an operation for cleaning the filter modules (10) is initiated when there is a drop below a pre-settable threshold value for the flow quantity.

43. Method according to claim 34, wherein the pressure loss across the filter modules (10) is detected during the filtration process and an operation for cleaning the filter modules (10) is initiated when a pre-settable threshold value for the pressure loss is exceeded.

44. Method according to claim 34, wherein in order to circulate the water (2) in the water reservoir (3), gas is introduced into the water reservoir (3) with a gas flow volume of between 0.05 Nm.sup.3/m.sup.3.sub.wr*h and 5 Nm.sup.3/m.sup.3.sub.wr*h at periodic time intervals.

45. Method according to claim 34, wherein the water (2) is directed through an activated carbon filter (31) fluidically incorporated in the recirculation means (4).

46. Method according to claim 34, wherein ionic nutrients are removed from the water (2) by means of an ion exchanger (34) fluidically incorporated in the recirculation means (4).

47. Method according to claim 34, wherein fragrances are added to the water (2) by means of a metering device (22).

48. Method according to claim 34, wherein substances with an antimicrobial effect are added to the water (2) by means of a metering device (37).

49. Method according to claim 34, wherein the partial quantity of water (2) removed from the water reservoir (3) by the recirculation means (4) per unit of time is selected so that a removal rate of microorganisms that is greater than the growth rate of microorganisms in the water (2) over the same period can be achieved by recirculating and filtering the water (2).

50. Method according to claim 34, wherein the partial quantity of water (2) removed from the water reservoir (3) by the recirculation means (4) per unit of time is selected so that the volume of water (2) contained in the water reservoir (3) overall can be filtered by the membrane filtration means (9) at least once a day and preferably between 2 times and 10 times.

51. Water treatment system (1) for implementing the method according to claim 34, comprising a recirculation means (4) having a pumping device (5), one or more extraction line(s) (6) for removing a pre-settable quantity of water (2) from the water reservoir (3) per unit of time, and one or more return line(s) (7) for returning the water (2) to the water reservoir (3); a membrane filtration means (9) disposed in the recirculation means (4), which comprises a number of filter modules (10) fluidically connected in a parallel arrangement, and the filter modules (10) are connected to the extraction line or lines (6) by pipes that can be selectively shut off or opened to permit circulation on the intake side and on the filtrate side are connected to the return line or lines (7) by pipes that can be selectively shut off or opened to permit circulation, and in order to clean the filter modules (10), the filter modules (10) are connected to a backwashing liquid source (16) by pipes that can be selectively shut off or opened to permit circulation on the filtrate side and on the intake side are connected to a discharge (17) by pipes that can be selectively shut off or opened to permit circulation, wherein it comprises a gas supply means (24), which, for cleaning the filter modules (10) of the membrane filtration means (9), is connected to the filter modules (10) by pipes that can be selectively shut off or opened to permit circulation on the intake side so that all of the filter modules (10) can be flushed with gas, and which gas supply means (24) is connected to the return line or lines (7) of the recirculation means (4) by pipes that can be selectively shut off or opened to permit circulation for circulating and mixing the water (2) in the water reservoir (3).

52. Water treatment system according to claim 51, wherein the filter modules (10) comprise at least two gas inlet connectors (28).

53. Water treatment system according to claim 51, wherein a shut-off member (15) co-operates with every filter module (10) of the membrane filtration means (9) on the filtrate side so that the filter modules (10) can be backwashed independently of one another in each case by means of the backwashing liquid source (16).

54. Water treatment system according to claim 51, wherein the filter modules (10) of the membrane filtration means (9) are connected to the extraction line or lines (6) via a common shut-off or flow-regulating member (14) on the intake side, and the filter modules (10) are connected to the discharge (17) via a common flow-regulating or shut-off member (18) on the intake side, and on the filtrate side, the filter modules (10) are connected to the return line or lines (7) of the recirculation means (4) and to the backwashing liquid source (16) via at least one switching means (19).

55. Water treatment system according to claim 51, wherein the backwashing liquid source (16) is provided in the form of a mains water supply (20).

56. Water treatment system according to claim 55, wherein the filter modules (10) are connected to the mains water supply (20) without a pumping device connected in between.

57. Water treatment system according to claim 55, wherein the mains water supply (20) for the filter modules (10) is provided with a pressure reducer (21).

58. Water treatment system according to claim 54, wherein the mains water supply (20) is provided with a metering device (22) for metering cleaning chemicals into the mains water.

59. Water treatment system according to claim 51, wherein the recirculation means (4) comprises a flow sensor (29) for detecting the quantity of water (2) flowing through the filter modules (10) during the filtration process.

60. Water treatment system according to claim 51, wherein the recirculation means (4) comprises at least two pressure sensors (30) for detecting the loss of pressure across the filter modules (10) during the filtration process.

61. Water treatment system according to claim 51, wherein the recirculation means (4) comprises an activated carbon filter (31).

62. Water treatment system according to claim 51, wherein the recirculation means (4) comprises an ion exchanger (34) for removing ionic nutrients.

63. Water treatment system according to claim 51, wherein it comprises a metering device (37) for adding fragrances to the water (2).

64. Water treatment system according to claim 51, wherein it comprises a metering device (35) for adding substances with an antimicrobial effect to the water (2).

65. Water treatment system according to claim 51, wherein the number and filtration capacity of the filter modules (10) are selected so that a removal rate of microorganisms that is greater than the growth rate of the microorganisms in the water (2) over the same period can be achieved by recirculating and filtering the water (2).

66. Water treatment system according to claim 51, wherein the number and filtration capacity of the filter modules (10) are selected so that the volume of water (2) contained in the water reservoir (3) overall can be filtered by the membrane filtration means (9) at least once a day and preferably between 2 times and 10 times.

Description

[0055] This is a highly simplified, schematic diagram illustrating the following:

[0056] FIG. 1 a water treatment system for treating water located in a water reservoir, based on a very simple, schematic diagram.

[0057] Firstly, it should be pointed out that the same parts described in the different embodiments are denoted by the same reference numbers and the same component names and the disclosures made throughout the description can be transposed in terms of meaning to same parts bearing the same reference numbers or same component names. Furthermore, the positions chosen for the purposes of the description, such as top, bottom, side, etc., relate to the drawing specifically being described and can be transposed in terms of meaning to a new position when another position is being described.

[0058] FIG. 1 illustrates one example of an embodiment of a water treatment system 1 for treating water 2 proposed by the invention, in particular for cleaning and disinfecting water 2. The water to be treated 2 is located in the partially illustrated water reservoir 3. The water reservoir 3 may be a swimming pool, a pond, an aquarium or similar water containers, for example. In principle, it may be an artificial or natural water reservoir 3.

[0059] As illustrated in FIG. 1, the water treatment system 1 comprises a recirculation means 4, by means of which a pre-settable quantity of water 2 can be removed from the water reservoir 3 per unit of time and treated. To this end, at least one pumping device 5 as well as one or more extraction line(s) 6 and one or more return line(s) 7 are provided. The extraction line(s) 6 are preferably connected to the water reservoir 3 at or close to the water surface because in most cases it is at the surface that the water 2 contains the most dirt and contaminants. The return line(s) 7 are preferably connected to the water reservoir 3 at points at a greater depth and at the largest number of points in order to generate better mixing in the water reservoir 3 due to circulation of the water 2. The pumping device 5 may be a feed pump, circulating pump, recirculating pump or similar, for example. The pumping device 5 is preferably a speed controllable pump so that the quantity of water 2 removed from the water reservoir 3 for treatment per unit of time can be adjusted as and when required during ongoing operation.

[0060] In order to remove relatively large contaminants such as leaves, insects, etc., a filter unit 8 for coarse particles may be provided in the extraction line or lines 6, such as a sand filter or a conventional screen filter, for example. Such filter units 8 are preferably disposed in the extraction line or lines 6 close to the extraction point or points from the water reservoir and thus constitute the first element for removing contaminants from the water 2.

[0061] As also illustrated in FIG. 1, a membrane filtration means 9 is disposed in the recirculation means 4. The membrane filtration means 9 comprises a number of filter modules 10 fluidically connected in a parallel arrangement. By way of example, four filter modules 10 are illustrated in FIG. 1 although the number of filter modules 10 used will obviously depend on the prevailing conditions and various parameters, such as the anticipated extent of contamination of the water 2 or the filtration capacity of an individual filter module 10 etc., for example.

[0062] The number of filter modules 10 used for the water treatment system 1 and their filtration capacity are preferably selected so that a removal rate of microorganisms that can be achieved by recirculating and filtering the water 2 is greater than the rate of growth of microorganisms in the water 2 over the same period. Furthermore, the number of filter modules 10 and their filtration capacity are preferably selected so that the volume of water 2 contained in the water reservoir 3 as a whole can be filtered by the membrane filtration means 9 at least once a day and preferably between 2 times and 10 times.

[0063] In principle, the filter modules 10 of the membrane filtration means 9 may be of various types and/or have various different features. The filter modules 10 are preferably provided in the form of hollow-fiber membrane modules containing a number of hollow-fiber membranes. The hollow fibers may be made from various materials and ceramic hollow fibers or plastic hollow fibers such as hollow fibers of polyethylene, polypropylene, polyether sulfone or similar plastics, for example, are the most commonly used. Such hollow fibers are usually of a tubular shape having two open ends and may be of various lengths. The hollow fibers are porous and water is able to flow through them from the outside to the inside and vice versa. Depending on the selected pore diameter of the hollow fiber material, particles up to a specific size will be able to pass through the membrane walls of the hollow fibers whereas larger particles will be held back on the hollow-fiber membrane walls, this being the filtering effect of a hollow-fiber membrane. For treating water in water reservoirs, hollow-fiber membranes with a pore diameter of between 0.2 m and 0.01 m have been found to be particularly suitable, corresponding to so-called ultrafiltration.

[0064] In the embodiment illustrated as an example in FIG. 1, the type of hollow fibers used may be those which are loosely suspended in the form of bundles or mats disposed in an intake chamber 11 located on the top side of the filter module 10. Accordingly, the respective open ends of the hollow fibers may be embedded in a sealant 12 in such a way that the inner lumens of the hollow fibers open into a filtrate chamber 13 located on the bottom side of a filter module 10. This sealant 12, for example cured epoxy resin or similar, fluidically separates the intake chamber 11 and the filtrate chamber 13 from one another so that the water 2 is only able to pass or be pumped through the hollow-fiber membrane wallsfrom the external surface of the hollow fibers into the inner lumen of the hollow fibersfrom the intake chamber 11 into the filtrate chamber 13 and is thus filtered. The embodiment illustrated in FIG. 1 corresponds to a so-called dead end filtration in outside-in operating mode. The filter modules 10 are preferably fluid-tight and designed to be resistant to high and negative pressure.

[0065] In order to feed the water 2 into the intake chamber 11 of a filter module 10, the filter modules 10 are connected on the intake side to the extraction line or lines 6 of the recirculation means 4 by pipes that can be selectively shut off or opened to permit circulation. In order to shut off and/or open this pipe connection, a common shut-off or flow-regulating member 14 is illustrated in FIG. 1 as an example of an embodiment.

[0066] On the filtrate side, the filter modules 10 are connected to the return line or lines 7 via shut-off members 15 by means of which the pipes can be selectively shut off or opened to permit circulation, as well as to a backwashing liquid source 16. As may be seen from the embodiment illustrated as an example in FIG. 1, it is preferable to provide every filter module 10 with a shut-off member 15 on the filtrate side so that the filter modules 10 can each be backwashed independently of one another by means of the backwashing liquid source 16 by reversing the direction of flow through the filter modules, as will be explained in more detail below.

[0067] When the filter modules 10 are in filtration mode, the shut-off or flow-regulating member 14 and the shut-off members 15 are opened so that water 2 can be fed out of the water reservoir 3 via the filter modules 10, filtered and fed via the return line(s) 7 back into the water reservoir 3. In order to run a cleaning operation by reversing the direction of flow through the filter modules, the shut-off or flow-regulating member 14 can be closed in order to shut off the pipe connections of the filter module 10 to the extraction line or lines 6.

[0068] In the embodiment illustrated as an example in FIG. 1, the filter modules 10 are also connected on the intake side to a discharge 17 by pipes that can be selectively shut off or opened to permit circulation. A common flow-regulating or shut-off member 18 is provided for this purpose, which can be closed during the filtration process and opened during a cleaning and/or flushing operation.

[0069] In order to switch between filtration mode and a cleaning operation and/or cleaning mode by backwashing and/or to reverse the direction of flow through the filter modules 10, a switching means 19 is provided in the embodiment illustrated as an example in FIG. 1. By this switching means 19, a flow connection can optionally be established on the filtrate side of the filter modules 10 to the return line or lines 7 or optionally a flow connection to the backwashing liquid source 16. In filtration mode, therefore, the filtered water can be returned to the water reservoir 3, whilst in cleaning and/or backwashing mode the backwashing liquid can be introduced into a filter module 10 with the shut-off member 15 simultaneously closed on the filtrate side. During such a backwashing operation, the backwashing liquid can be introduced into the filtrate chamber 13 of a filter module 10, forcing the backwashing liquid into the inner lumens of the hollow fibers. The backwashing liquid then passes through the walls of the hollow-fiber membranes and into the intake chamber 11 of the filter module 10, and can be discharged and disposed of through the discharge 17. This corresponds to a reversal of the flow direction through a filter module 10 compared with that of a filtration operation. As an alternative to the embodiment illustrated as an example in FIG. 1, several switching means may also be provided, for example a shut-off member co-operating with the backwashing liquid source 16 and a shut-off member co-operating with the return line or lines 7.

[0070] The backwashing liquid source 16 may be provided in the form of a supply tank containing a detergent, for example, from which the detergent is conveyed by a pumping device and introduced into a filter module. As illustrated in FIG. 1, the backwashing liquid source 16 is preferably a mains water supply 20, which is in turn connected, preferably without an inter-connected pumping device, to the filter modules 10 via the switching means 19 and the shut-off members 15 can be optionally shut off or opened to permit circulation on the filtrate side. This being the case, the respectively prevailing mains water pressure can be used as the driving force for backwashing the filter modules 10.

[0071] In order to compensate for pressure fluctuations or if the mains water supply 20 has a very high water pressure, it may be expedient to provide a pressure reducer 21 in a common mains water supply for the filter modules 10. As may also be seen from the embodiment illustrated as an example in FIG. 1, it may also be expedient to provide a metering device 22 in the common mains water supply for the filter modules 10 for metering cleaning chemicals. In this manner, detergents such as surfactants or disinfectants for example, can be added to the backwashing and/or mains water in order to improve cleaning efficiency during a flushing operation. The cleaning chemicals used for this purpose may be drawn from one or more chemical source(s) 23, such as chemical tanks or some other containers suitable for storing the corresponding chemicals for example.

[0072] Irrespective of the nature or exact composition of the backwashing liquid, a filter module 10 is preferably backwashed with a flow volume of backwashing liquid of between 70 l/m.sup.2.sub.mem*h and 700 l/m.sup.2.sub.mem*h and with a flow speed of the backwashing water through the filter module of between 0.02 m/s and 1,0 m/s. Flow volumes and flow speeds of the backwashing liquid in the specified ranges have been found to be effective in terms of obtaining an efficient and as complete as possible cleaning of the hollow-fiber membranes of a filter module 10.

[0073] As may be seen from FIG. 1, the water treatment system 1 in particular comprises a gas supply means 24. To enable the filter modules 10 to be cleaned, the gas supply means 24 is connected on the one hand to the filter modules 10 of the membrane filtration means on the intake side by pipes that can be selectively shut off or opened to permit circulation. In addition, the gas supply means 24 is also connected to the return line or lines 7 of the recirculation means 4 by pipes that can selectively shut off or opened to permit circulation in order to circulate and mix the water 2 in the water reservoir 3.

[0074] The gas supply means 24 may be provided in the form of various types of gas source, for example gas bottles or gas cartridges containing suitable gases for flushing the filter modules with gas. For example, suitable gas sources in particular are those containing compressed inert gases. The gas can be fed from such gas sources to the filter modules 10 via pressure-reducing valves, for example. The gas supply means 24 is preferably provided in the form of an air blower 25.

[0075] In the embodiment illustrated as an example in FIG. 1, a common shut-off member 26 is provided as a means of selectively shutting off or opening the pipe connections between the gas supply means 24 and the intake chamber 11 of the filter modules 10. At least one other shut-off member 27 is provided as a means of selectively shutting off or opening the pipe connections between the gas supply means 24 and the return line or lines 7 of the recirculation means 4. On the one hand, this enables the hollow-fiber membranes of the filter modules 10 to be flushed with gas on the intake side. On the other hand, gas can be introduced into the water reservoir 3 from one or more points for circulating or mixing the water 2 in the water reservoir 3 periodically or when required. To ensure that the water 2 in the water reservoir 3 is sufficiently well mixed, gas is preferably introduced into the water reservoir 3 at periodic time intervals at a gas flow volume of between 0.05 Nm.sup.3/m.sup.3.sub.wr*h and 5 Nm.sup.3/m.sup.3.sub.wr*h. The gas supply means 24 may be used either to flush the filter modules 10 or to circulate and mix the water 2 in the water reservoir 3.

[0076] The filter modules 10 are preferably flushed with gas at the same time as the filter modules 10 are being backwashed in the manner described above, and in order to improve the cleaning efficiency of the filter modules 10, the gas is preferably introduced into the filter modules 10 from the intake side of the filter modules 10 via at least two gas inlet connectors 28.

[0077] To enable the filtration operation to be interrupted for the cleaning operation, the shut-off or flow-regulating member 14 may be closed to enable the filter modules 10 to be fluidically disconnected from the extraction line or lines 6. At the same time, the shut-off member 18 can be opened so that the filter modules can be fluidically connected to the discharge 17. Furthermore, the switching means 19 can be switched in order to fluidically disconnect the filter modules 10 from the return line or lines 7 and fluidically connect the filter modules 10 to the backwashing liquid source 16. In order to introduce gas into the intake chamber 11 of the filter modules 10, the shut-off member 26 can be opened so that all the filter modules 10 can be flushed with gas simultaneously and the flushing gas passes through the intake chamber 11 from the bottom to the top and can be fed away via the discharge 17.

[0078] An operation for cleaning the membranes of the filter modules 10 is preferably run in such a way that gas is introduced into all of the filter modules 10 simultaneously from the intake side, after which a pre-settable partial number of filter modules 10 are backwashed with the backwashing liquid by reversing the direction of flow through the filter modules 10. To this end, shut-off members 15 co-operating with partial numbers of filter modules 10 can be sequentially opened and closed from the filtrate side. For example, in cleaning mode, the two filter modules 10 illustrated on the left-hand side in FIG. 1 can be flushed with the backwashing liquid by opening the shut-off members 15 co-operating with these two filter modules 10. The backwashing operation for the two filter modules 10 illustrated on the left-hand side in FIG. 1 can then be terminated by closing the these two shut-off members 15, after which the two filter modules 10 illustrated on the right-hand side can also be flushed with backwashing liquid by opening the shut-off members 15 co-operating with these two filter modules 10. The backwashing operation for these two filter modules 10 illustrated on the right-hand side in FIG. 1 can then also be terminated by closing the shut-off members 15 co-operating with these two filter modules 10.

[0079] However, it may also be expedient to run an operation for cleaning the membranes of the filter modules 10 in such a way that gas is introduced into all of the filter modules 10 simultaneously on the intake side and then each filter module 10 is backwashed with backwashing liquid individually in sequence by reversing the direction of flow through the filter modules 10.

[0080] During the operation of cleaning the filter modules 10, a gas flow volume of between 0.2 Nm.sup.3/m.sup.2.sub.mem*h and 5.0 Nm.sup.3/m.sup.2.sub.mem*h is preferably introduced into every filter module 10 at a flow speed of the gas in the filter module of between 0.1 m/s and 2 m/s. A cleaning operation involving backwashing and simultaneously flushing the membranes of a filter module 10 with gas is preferably terminated by halting the intake of mains water to the filter module, displacing any backwashing water remaining in the filter module with gas and feeding it away via a discharge, after which the filter module is filled with mains water prior to resuming the filtration operation.

[0081] The filter modules can be cleaned at periodic, pre-settable time intervals, for example. However, it may also be expedient to clean and/or backwash the filter modules 10 assisted by gas as and when necessary. In particular, it is expedient to run a gas-assisted backwash of the filter modules 10 wheneverdue to deposits on the membrane wallsa drop in the flow quantity passing through a filter module 10 is detected during the filtration operation.

[0082] In order to detect the quantity of water flowing through the filter modules 10 during the filtration process, the recirculation means 4 in the embodiment illustrated as an example in FIG. 1 comprises a flow sensor 29. Accordingly, cleaning of the filter modules 10 and/or backwashing with gas can be initiated if there is a drop below a pre-settable threshold value for the flow quantity. In principle, a cleaning operation can be initiated both manually and on an automated basis. A cleaning operation is preferably initiated and run by an appropriately programmed control device of the water treatment system 1, thereby making operation of the water treatment system 1 particularly efficient.

[0083] Alternatively and/or in addition, the recirculation means 4 may comprise at least two pressure sensors 30 for detecting the pressure loss across the filter modules 10 during the filtration process and an operation for cleaning the filter modules 10 can be initiated and run when a pre-settable threshold value for the pressure loss across the filter modules 10 is exceeded.

[0084] In order to resume the filtration operation after backwashing all the filter modules 10, the shut-off member 18 can be closed and the switching means 19 switched back to filtration mode in order to fluidically connect the filter modules 10 to the return line or lines 7 and fluidically disconnect the filter modules 10 from the backwashing liquid source 16. After opening the shut-off or flow-regulating member 14 and opening all the shut-off members 15, the filtration operation can be started again.

[0085] To further improve treatment of the water 2 in the water reservoir 3, the recirculation means 4 of the water treatment system 1 may comprise an activated carbon filter 31, as is the case with the example of an embodiment illustrated in FIG. 1. By means of such an activated carbon filter 31, non-particulate substances dissolved in the water 2, in particular low-molecular organic compounds, can be removed from the water in particular. As illustrated in FIG. 1, an activated carbon filter 31 is preferably connected to the pipes of the recirculation means 4 by pipes than can be selectively shut off or opened to permit circulation. As a result, the water 2 can be selectively directed through the activated carbon filter 31by opening the valves 32 and closing valve 33or the water 2 can be circulated in the water reservoir 3 without passing through the activated carbon filter 31by opening valve 33 and closing valves 32. This may be expedient, for example, as a means of preventing the removal of desired substances from the water, for example whilst the water reservoir 3 is being used for bathing.

[0086] For all of the shut-off members and/or flow regulating members 14, 15, 18, 19, 26, 27, 32 and 33 mentioned above, it is possible to use a whole range of different shut-off members or valves for shutting off and opening pipe connections, for example so-called on/off valves. In this respect, it is also possible to use both manually operable valves or valves operated on an electronically automated basis. It is preferable to use electronically operated valves to enable the water treatment system 1 to be operated by means of automatic and/or programmable control systems. In the case of a flow regulating member, it is possible to use steplessly adjustable valves in particular.

[0087] As is the case with the embodiment illustrated as an example in FIG. 1, the recirculation means 4 may also comprise one or more ion exchangers 34. For reasons of clarity, only one ion exchanger 34 is illustrated in FIG. 1. Such ion exchangers 34 may be cation exchangers or anion exchangers and these may advantageously be used primarily for removing ionic nutrients from the water 2 by directing the water in the recirculation means 4 through one or more ion exchangers 34.

[0088] It may also be expedient to provide a metering device 35 in the recirculation means 4 of the water treatment system 1, by means of which metering device 35 substances having an antimicrobial effect can be drawn from a chemical source 36 and introduced into the water. For example, this enables silver nanoparticles to be added to the water 2.

[0089] Finally, the water treatment system 1 may comprise a metering device 37 by means of which fragrances from a fragrance source 38 can be added to the water. Such a metering device 37 is disposed in the recirculation means 4 of the embodiment illustrated as an example in FIG. 1. In principle, however, fragrances can also be added to the water reservoir 3 directly.

[0090] The embodiments illustrated as examples represent possible variants of the water treatment system and the method for treating water, and it should be pointed out at this stage that the invention is not specifically limited to the variants specifically illustrated, and instead the individual variants may be used in different combinations with one another and these possible variations lie within the reach of the person skilled in this technical field given the disclosed technical teaching.

[0091] Furthermore, individual features or combinations of features from the different embodiments illustrated and described may be construed as independent inventive solutions or solutions proposed by the invention in their own right.

[0092] The objective underlying the independent inventive solutions may be found in the description.

[0093] All the figures relating to ranges of values in the description should be construed as meaning that they include any and all part-ranges, in which case, for example, the range of 1 to 10 should be understood as including all part-ranges starting from the lower limit of 1 to the upper limit of 10, i.e. all part-ranges starting with a lower limit of 1 or more and ending with an upper limit of 10 or less, e.g. 1 to 1.7, or 3.2 to 8.1 or 5.5 to 10.

[0094] Above all, the individual embodiments of the subject matter illustrated in FIG. 1 constitute independent solutions proposed by the invention in their own right. The objectives and associated solutions proposed by the invention may be found in the detailed descriptions of this drawing.

[0095] For the sake of good order, finally, it should be pointed out that, in order to provide a clearer understanding of the water treatment system, it and its constituent parts are illustrated to a certain extent out of scale and/or on an enlarged scale and/or on a reduced scale.

TABLE-US-00001 List of reference numbers 1 Water treatment system 2 Water 3 Water reservoir 4 Recirculation means 5 Pumping device 6 Extraction line 7 Return line 8 Filter unit 9 Membrane filtration means 10 Filter module 11 Intake chamber 12 Sealant 13 Filtrate chamber 14 Flow regulating member 15 Shut-off member 16 Backwashing liquid source 17 Discharge 18 Shut-off member 19 Switching means 20 Mains water supply 21 Pressure reducer 22 Metering device 23 Chemical source 24 Gas supply means 25 Air blower 26 Shut-off member 27 Shut-off member 28 Gas inlet connector 29 Flow sensor 30 Pressure sensor 31 Activated carbon filter 32 Valve 33 Valve 34 Ion exchanger 35 Metering device 36 Chemical source 37 Metering device 38 Fragrance source