DE202022101702U1 - Water treatment plant and use of a water treatment plant - Google Patents

Abstract

Water treatment plant (10) comprising
- a raw water inlet (11) for providing raw water (R),
- a softening device (12) with an inlet (11a), which is connected to the raw water inlet (11), and an outlet (11b), wherein the softening device (12) produces softened water (W) from the raw water (R) and at the outlet (11b) and in particular contains at least one regenerable or exchangeable ion exchanger (13),
- a regenerating device (18) for regenerating the softening device (12), in particular the ion exchanger (13) of the softening device (12), and/or a signaling device which generates a signal when the softening device (12) is exhausted, in order to indicate that the softening device (12) needs to be regenerated Softening device (12) and in particular to display a required regeneration or a required replacement of the ion exchanger (13) and/or to close the outlet (11b) of the softening device (12),
- a control device (14), which is coupled to the regeneration device (18) and/or the signaling device in order to regenerate the softening device (12) when it is exhausted and/or to output or display the signal generated by the signaling device, and
- at least one measuring device (15) connected to the softening device (12) and the control device (14) for detecting a hardness breakthrough in the water (W) provided at the outlet (11b) of the softening device (12), characterized in that the measuring device (15) comprises at least one conductivity sensor (2; 2a, 2b) and an electrolysis cell (1) with at least two electrolysis electrodes (A, K).

Description

The invention relates to a water treatment plant and its use for producing softened water.

The hardness of water is determined by the concentration of the cations of the alkaline earth metals dissolved in the water and, in specific applications, also by the concentration of the associated anionic partners, in particular the hydrogen carbonate. The sum of the concentrations of all dissolved alkaline earth metals (which can be present as carbonates, sulfates, chlorides, nitrites, nitrates and phosphates) is referred to as the total hardness. The proportion that is only bound to carbonic acid is called carbonate hardness (or temporary hardness) and the difference between total hardness and carbonate hardness is called non-carbonate hardness (or permanent hardness), with the majority of the total hardness in drinking water usually being present as carbonate hardness. Calcium and magnesium ions, the so-called hardeners, are the main contributors to the overall hardness of water. The sum of the concentrations of calcium and magnesium ions therefore corresponds to a good approximation of the total water hardness. The other alkaline earth metals, such as strontium and barium, are regularly only present as trace substances in the water and therefore hardly contribute to the water hardness. Carbonate hardness can be removed by removing calcium and magnesium carbonate from the water. The dissolved hardeners calcium and magnesium can form poorly soluble compounds in the water, in particular as carbonates, with the carbon dioxide dissolved in the water, in accordance with the lime-carbonic acid balance.

The formation of poorly water-soluble compounds by the hardeners leads to the formation of scale in household appliances, heating systems and water heaters, especially when water is heated, and reduces the effectiveness of detergents and detergents in (dish) dishwashers and washing machines. Furthermore, the water hardness influences the taste of food and drinks prepared with water. To avoid or reduce these adverse consequences of hard water, i.e. water with a high concentration of alkaline earth metal ions, the calcium and magnesium ions are partially or completely removed from the water, e.g replaced by sodium ions or - in the case of full desalination - completely removed from the water together with all other dissolved ions, e.g. by a combination of cation and anion exchangers or by reverse osmosis.

Since the exchange capacity of ion exchangers is limited, softening devices in which ion exchangers are used must be regenerated in good time before the ion exchanger or ion exchangers become exhausted, in order to avoid hardness breakthrough. An exhausted cation exchange resin is regenerated, for example, with a saline solution (sodium chloride solution). During regeneration, the hardeners (calcium and magnesium ions) absorbed by the ion exchanger during the softening of water are exchanged for sodium ions in the saline solution. The time when an ion exchanger is exhausted depends on the exchange capacity of the ion exchanger material (usually this is an ion exchange resin), the hardness of the raw water and the volume flow rate of the raw water. In order to keep the consumption of regeneration material (e.g. regeneration salt for the production of a common salt solution) as low as possible on the one hand and to prevent hardness breakthrough after the ion exchanger has been exhausted on the other hand, regeneration should take place as soon as possible before the ion exchanger is completely exhausted. In the case of premature regeneration, the consumption of regeneration material increases and if regeneration is too late, the ion exchangers are no longer able to completely remove the hardness-causing ions from the water and hardness breakthrough occurs.

From the DE 198 41 568 A1 a method and an arrangement for determining the regeneration time of a water softening device, in particular for water-carrying, program-controlled household appliances, is known. To determine the hardness of a washing liquid, the conductance of the liquid determined by sensors is measured before and after the softener and a conductance difference is determined from this, with the regeneration of the softener being made dependent on a comparison with conductance values and conductance difference values from previous measurements stored in a memory of a program control. A regeneration of the water softening device is initiated when the conductance difference is equal to zero and the conductance is greater than a predetermined limit value, or if the conductance difference is not equal to zero and tends toward zero. When setting up the device, there is no need to adjust the hardness to the existing fresh or service water, and fluctuating mains water hardness can be automatically taken into account.

Since the electrical conductivity of water is determined by all the ions dissolved in the water and not only by the hardeners dissolved in the water (especially calcium and magnesium ions) and because the exchange of the hardeners due to sodium ions during softening only leads to a slight change in conductivity, the conductivity determined in this known method is only conditionally suitable for calculating the optimal regeneration time. In addition, a hardness breakthrough cannot be reliably prevented with this method, since the regeneration of the ion exchanger only takes place when the conductance difference is zero or tends towards zero, which means that the exchange capacity of the ion exchanger is already (almost) exhausted. The known method is therefore not suitable for use in softening or desalination plants that are intended to permanently provide fully or partially softened water.

From the WO 2009/071066 A2 a water softening device with an ion exchange resin is known, which splits an inflowing raw water flow into two partial flows and subjects one of the two partial flows to full softening and then combines the two partial flows to form a blended water flow, whereby two different conversions are used to determine the water hardness from the electrical conductivity of the raw water the measured electrical conductivity to the raw water hardness. In order to automatically control the regeneration of the ion exchange resin, the measured conductivity is converted into a water hardness using a first calibration curve, which is designed conservatively and reflects the maximum water hardnesses that occur at different conductivities. The conversion with a second calibration curve is designed to be realistic and reflects the average water hardness (ie with the smallest statistical error) at different conductivity values, which is used to control the blending device. As a result, experimentally determined variations in the water composition (and thus different relationships between conductivity and water hardness) can be taken into account in order to optimally determine the regeneration time and to minimize tolerances of the blended water hardness compared to a target value.

The connection between the electrical conductivity and the total hardness of the water must be recorded using characteristic curves, which must be created empirically and laboriously by titrimetric determination of the hardness of various water samples and a measurement of the electrical conductivity. In addition, the connection between the electrical conductivity and the overall hardness of the water is only weakly pronounced, and the replacement of the hardness components by sodium ions during a softening process only leads to a slight change in conductivity. The water hardness that is actually present at a certain conductivity and can be determined titrimetrically can therefore deviate considerably from the hardness value determined via the characteristic curve, especially if the raw water has a relatively high non-carbonate hardness (permanent hardness). If the water hardness of the raw water determined from the calibration characteristic curve deviates from the actual hardness of the raw water, premature regeneration and thus increased consumption of regenerating agent or delayed regeneration with a resulting hardness breakthrough can occur, depending on whether the the raw water hardness determined by the characteristic curve is greater or lower than the actual total hardness of the raw water. For this reason, and also due to the temperature dependence of the electrical conductivity of water, this method for controlling the regeneration of a water softening device is imprecise and can only be applied to raw water qualities that have a course of electrical conductivity from the total hardness of the water that corresponds at least approximately to the characteristic curve used.

For monitoring the exchange capacity of ion exchangers, hardness sensors are also known from the prior art, which contain a swelling or shrinking resin whose volume expansion is used as a measure of the degree of exhaustion of the ion exchanger. Such a hardness sensor for water softening systems is, for example, from the DE 29 53 143 A1 known. However, hardness sensors of this type have insufficient accuracy for many applications.

Complexometric titration methods, e.g. with the disodium salt of ethylenediaminetetraacetic acid (EDTA) as a titrant, can be used to precisely determine the water hardness, which can record the concentrations of the alkaline earth metal ions dissolved in the water and thus the total hardness of the water. Measuring devices are known from the prior art for monitoring the degree of exhaustion of ion exchangers, which photometrically detect the color change point of a titration and trigger a signal as soon as a hardness breakthrough is detected. These measuring devices are characterized by good measuring accuracy, but are complex and expensive to manufacture and require regular maintenance and generate high consumption costs because of the use of the titrant. When detecting a hardness breakthrough with the common titration method, there is also a considerable time delay between the hardness breakthrough and its detection. A soft water sample is usually only taken and analyzed every 5-30 minutes in order to keep reagent consumption low. This takes another 3 - 5 minutes. At this time flows Soft water with unclear quality or already significant hardness breakthrough to the downstream application. A breakthrough in hardness cannot be prevented because the signal that indicates that the ion exchanger needs to be regenerated is only generated when the exchange capacity has already been exhausted.

When determining the optimal point in time for the regeneration of a water softening device that is made available with raw water from the public drinking water supply network, there is also the problem that the water supplier usually has a limited number of different drinking water qualities from different sources and with different compositions and hardness into the network of the public drinking water supply, whereby the introduction of these different drinking water qualities can change within a day or also within longer periods of time, so that the composition and the hardness of the raw water supplied to a softening device correspond to the quality of the water available from the public drinking water supply provided drinking water can change. Such changes in the water quality, which can occur several times during a day, change the remaining exchange capacity of the softening device and thus the optimal time for carrying out a regeneration. In order to be able to quickly adjust the optimum point in time for carrying out regeneration when the water quality of the supplied raw water changes, it is necessary to quickly record any changes in the composition or quality of the raw water during operation of a water treatment plant with a water softening device to allow and adjust the predicted time of exhaustion of the softening device to it.

Proceeding from this, the invention is based on the object of demonstrating a water treatment system and its use for generating softened water, which enable the optimum time for regeneration of the softening device to be determined without the use of chemicals in an automated process during operation of the water treatment system and thereby be able to detect a breakthrough in hardness reliably and as quickly as possible, even if the quality or hardness of the raw water supplied changes.

These objects are achieved with the water treatment system according to claim 1 and the use of a water treatment system for generating softened water with the features of claim 12. Preferred embodiments of the water treatment plant and their use result from the dependent claims.

The water treatment system according to the invention comprises an untreated water inlet, a softening device with an inlet and an outlet and in particular with at least one regenerable or exchangeable ion exchanger, a regeneration device for regenerating the softening device and/or a signaling device which generates a signal when the softening device is exhausted in order to regeneration of the softening device and in particular to display a required regeneration or a required replacement of the ion exchanger, and a control device which is coupled to the regenerating device and/or the signaling device in order to regenerate the softening device when it is exhausted and/or to output the signal generated by the signaling device or display or stop the operation of the softening device, and at least one measuring device connected to the softening device and the control device for detecting a hardness breakthrough in the water provided at the outlet of the softening device. According to the invention, the measuring device comprises at least one conductivity sensor and an electrolysis cell with at least two electrolysis electrodes.

The softening device is supplied with raw water at the inlet via the raw water inlet, from which the softening device produces softened water and makes it available at the outlet, with the measuring device being supplied with water which is made available at the outlet of the softening device, in order to detect a hardness breakthrough in the softening device when the softening device is exhausted water provided at the outlet of the softening device and the control device then initiates regeneration of the softening device by means of the regeneration device and/or outputs or displays a signal generated by the signaling device in order to indicate a required regeneration of the softening device and in particular a required regeneration or a required replacement of the ion exchanger or to stop the operation of the water treatment plant or the softening device in order to prevent non-softened water being provided at the outlet.

With the measuring device, a hardness breakthrough can be recorded conductometrically via the at least one conductivity sensor. the con Ductometric detection of a hardness breakthrough can be detected very quickly and reliably in the measuring device by determining the conductivity difference that results in the electrolytic cell due to electrolytic precipitation of the alkaline earth ions that are contained in the water when hardness breakthrough occurs. For this purpose, the electrical conductivity of the water supplied to the measuring device before entering the electrolytic cell or at an entrance of the electrolytic cell and the electrical conductivity of the water after exiting the electrolytic cell or at an exit of the electrolytic cell are recorded with the measuring device and the difference is formed therefrom in order to to detect the change in electrical conductivity caused by the precipitation of alkaline earth ions in the electrolytic cell. As long as the water supplied to the measuring device is completely softened and therefore does not contain any alkaline earth ions, given proper operation of the water treatment system and in particular when the ion exchanger is not exhausted, the conductivity of the water at the inlet and outlet of the measuring device is at least essentially the same and the measuring device detects a conductivity difference between the input and output of the measuring device of zero or at least approximately zero. If the hardness of the softening device breaks through, however, alkaline earth ions, in particular calcium and magnesium ions, are contained in the water, which are precipitated in the electrolytic cell of the measuring device and lead to a reduction in the electrical conductivity at the outlet of the measuring device compared to the conductivity at the inlet.

The water treatment system according to the invention has the advantage that the water (soft water) provided at the outlet of the softening device is continuously monitored. A time delay in the monitoring is only due to the small distance over which the analyzed water flows through the measuring device, in particular from an inlet to an outlet of the measuring device, with this distance and thus the time delay being able to be kept very short. In preferred embodiments, the electrolytically active residence time of the water (soft water) flowing through the electrolytic cell, which is decisive for precipitation of the alkaline earth metal ions, is in the range from 10 to 120 seconds, preferably between 20 and 50 seconds. For the detection of a hardness breakthrough, there is also a dead time of about 30 to 60 seconds due to the length of the supply lines, so that a change in conductivity is detected within a reaction time of 40 to 180 seconds, in particular 50 to 110 seconds, when a hardness breakthrough begins can be. As a result, an incipient breakthrough in hardness can be detected very early on.

When hardness breakthrough begins, the difference in conductivity of the water recorded at the inlet and outlet of the measuring device can be used to determine the concentration of alkaline earth ions in the water flowing through the electrolytic cell and from this the degree of exhaustion of the softening device. The higher the conductivity difference, the higher the degree of exhaustion or the lower the residual capacity of the softening device, in particular of the ion exchanger or ion exchangers. When hardness breakthrough begins in the water passed through the electrolytic cell, the concentration of alkaline earth ions is still very low, so that even if the alkaline earth ions are completely precipitated, initially only a small change in conductivity between the input and output of the measuring device is measured . However, when there is a complete breakthrough in hardness, there are so many alkaline earth ions in the water that they can no longer be completely precipitated due to the limited residence time in the electrolytic cell Amount continues to depend on the residence time of the water in the electrolytic cell and thus on the flow rate of the water and the length of the electrolytic cell.

The electrolysis electrodes of the measuring device are expediently designed as flat electrodes which are arranged opposite one another in the electrolysis cell. This enables the water to flow evenly through the electrolytic cell between the electrolytic electrodes, which allows a sufficient residence time for the alkaline earth metal ions to precipitate. The electrolysis electrodes are expediently designed in such a way that they can be connected to a DC voltage source.

In order to record the electrical conductivity of the water flowing through the electrolytic cell, the measuring device preferably comprises at least two conductivity sensors. At least one conductivity sensor is particularly preferably integrated in the electrolytic cell. This enables a compact and cost-effective construction of the measuring device. In a preferred embodiment, the measuring device comprises two conductivity sensors, with a first conductivity sensor at an input of the measuring device for measuring the conductivity of the water flowing into the electrolytic cell and a second conductivity sensor at an output of the measuring device for measuring the conductivity of the water flowing out of the electrolytic cell outflowing water is provided. The conductivity sensors can also be arranged outside the electrolytic cell. In this case, for example, a first conductivity sensor is arranged upstream or at an inlet of the electrolytic cell and a second conductivity sensor is arranged downstream or at an outlet of the electrolytic cell.

In a preferred embodiment, the measuring device comprises an input, at which water from the softening device is supplied to the measuring device, and an output, a first conductivity sensor being arranged at the input and a second conductivity sensor being arranged at the output, and the electrolytic cell being arranged between the input and the output . This structure enables a trouble-free measurement of the electrical conductivity of the water flowing into the electrolytic cell at the inlet and the water flowing out of the electrolytic cell at the outlet.

Each conductivity sensor preferably comprises at least one pair of electrodes with two measuring electrodes, designed in particular as rod electrodes, which can be connected or are connected to an AC voltage source. This enables a cost-effective measurement of the electrical conductivity by applying an electrical AC voltage to the measuring electrodes with a compact design of the measuring device.

In a preferred embodiment, the measuring device comprises a first conductivity sensor and a second conductivity sensor, the first conductivity sensor and the second conductivity sensor each comprising a pair of electrodes with two measuring electrodes and the measuring electrodes being connectable or connected to an AC voltage source. The two conductivity sensors can be arranged inside the electrolytic cell or outside of the electrolytic cell. When the conductivity sensors are located within the electrolytic cell, a first conductivity sensor is provided upstream and a second conductivity sensor is provided downstream of the opposed electrolytic electrodes. Arranging the two conductivity sensors within the electrolytic cell enables a compact design and allows the measuring device to be used to determine the hardness of the water in a water sample. An arrangement outside of the electrolytic cell has advantages in terms of metrology, since the conductivity measurement cannot be disturbed by the measuring electrodes due to the local decoupling of the measuring electrodes and the electrolytic electrodes. If the measuring electrodes are arranged within the electrolytic cell, it can be useful to avoid measuring errors to decouple the conductivity measurements using the measuring electrodes and the electrolytic precipitation of the alkaline earth metal ions using the electrolytic electrodes at different times, i.e. to carry them out in consecutive measuring cycles and electrolysis cycles.

The control device of the water treatment system is preferably set up to control the measuring device in such a way that the water provided at the outlet of the softening device is fed to the measuring device at the inlet of the measuring device and the conductivity (Lf _a ) of the water fed in at the inlet is measured with one conductivity sensor or with the first conductivity sensor and then the water is electrolyzed by applying a DC voltage to the electrolysis electrodes and finally the conductivity (Lf _b ) of the electrolyzed water at the outlet of the measuring device is measured using one conductivity sensor or the second conductivity sensor, and in particular a change in the water caused by the electrolysis Conductivity (ΔLf = | Lf _b - Lf _a |) of the water between the input and the output of the measuring device is detected. From the detected change in conductivity (ΔLf) it is possible to conclude that alkaline earth ions exist, in particular if the detected change in conductivity (ΔLf) is above a predetermined limit value. The existence of alkaline earth ions in the water supplied to the measuring device indicates the beginning of a breakthrough in hardness in the softening device, which is why a regeneration process for regenerating the softening device is preferably initiated and/or by the Signal device, a signal is output which indicates a required regeneration of the softening device and in particular a required regeneration or a required replacement of the ion exchanger.

The control device can also control the measuring device in such a way that first the original conductivity (Lf _a ) of the water provided at the outlet of the softening device is recorded, in particular with a first conductivity sensor, and then the alkaline earth metal ions that may be contained therein in the event of a hardness breakthrough are recorded in the measuring device are at least partially precipitated by applying a DC voltage to the electrolysis electrodes and the conductivity (Lf _b ) of the water is measured during and/or after the precipitation of the alkaline earth ions, in particular with a second conductivity sensor. The control device then uses the difference in the measured conductivity values to calculate the change caused by the electrolytic precipitation of the alkaline earth metal ions the conductivity (ΔLf = Lf _b - Lf _a ) is determined and a hardness breakthrough is concluded if the amount of ΔLf is above the specified limit value.

If the control device detects a hardness breakthrough, it or the signaling device can output a signal and/or activate the regeneration device in order to initiate a regeneration process for regenerating the softening device. An operator of the water treatment system is thus informed of a hardness breakthrough and, if necessary, instructed to either manually initiate a regeneration process to regenerate the softening device or to replace the replaceable ion exchanger, which can be designed as a replaceable cartridge, for example.

The control device or the signal device is expediently set up to output a signal if, during the precipitation of the alkaline earth metal ions, in particular over a predetermined period of time (Δt) of the precipitation, there is a change in the measured conductivity compared to the original conductivity of the water provided at the outlet of the softening device is detected, in particular when the change in conductivity (ΔLf) detected over the predefined period of time (Δt) is above a predefined limit value. The signal can be an acoustic signal, for example a warning tone, and/or an optical signal, for example a warning light, and/or a textual and/or symbolized representation of a warning on a display of the control device. The control device or the signaling device can also be set up in such a way that the operation of the softening device is switched off and the outlet of the softening device is closed if hardness breakthrough is detected, for example by closing a valve at the outlet in order to ensure that insufficiently softened water is made available at the prevent exit.

The control device is preferably set up in such a way that it directly initiates a regeneration process by means of the regeneration device as a function of the detected change in conductivity (ΔLf), in particular when a predetermined limit value is exceeded. This enables a fully automatic regeneration of the softening device without the operator of the water treatment system having to intervene manually in the event of a breakthrough in hardness.

In a preferred embodiment of the water treatment system according to the invention, the softening device is designed as a multiple or double system with a first softening device and at least one second softening device, which can be operated in pendulum mode, with the first softening device being operated alternately in a softening or desalination mode in pendulum mode, while the second softening device is operated in a regeneration mode in which regeneration takes place, and vice versa. This oscillating operation of a first and a second softening device makes it possible to change the oscillating operation of one softening device and, for example, initiate the regeneration mode in the first softening device while the second softening device switches to the softening mode when a hardness breakthrough is detected with the measuring device during the softening or desalination mode becomes. This ensures that the water treatment plant can provide partially or fully softened water at any time.

In the use according to the invention of a water treatment system which comprises an untreated water inlet for providing untreated water, a softening device with an inlet and an outlet, a regeneration device for regenerating the softening device and/or a signaling device which generates a signal when the softening device is exhausted in order to Regeneration of the softening device and in particular to display a required regeneration or a required replacement of an ion exchanger, the softening device produces softened water from the raw water and makes this available at the outlet. A control device is provided, which is coupled to the regeneration device and/or the signal device in order to regenerate the softening device in the event of exhaustion and/or to output or display the signal generated by the signal device and/or to close the outlet when a hardness breakthrough is detected. and there is at least one measuring device connected to the softening device and the control device for detecting a hardness breakthrough in the water provided at the outlet of the softening device, with the water provided at the outlet of the softening device being fed at least intermittently or continuously to the measuring device and in the measuring device at least intermittently one electrolytic precipitation of the alkaline earth metal ions in the supplied water is carried out, and the electrical conductivity of the supplied water being recorded at least before and during the electrolytic precipitation of the alkaline earth metal ions and compared with one another, in particular by forming the difference (ΔLF = |Lf _b - Lf _a l) the conductivity (Lf _a ) detected before the electrolytic precipitation and the conductivity (Lf _b ) detected during or after the precipitation.

Raw water, which contains alkaline earth metal ions, in particular calcium and/or magnesium ions, as well as hydrogen carbonate and/or carbonate ions, is supplied to the inlet of the softening device via the raw water inlet.

In the use according to the invention, the electrical conductivity of the water supplied to the measuring device is preferably recorded at an input of the measuring device and an output of the measuring device, and the measuring device preferably comprises an electrolytic cell with at least two electrolytic electrodes, which is arranged in particular between the input and the output of the measuring device, with the Measuring device supplied water is electrolyzed in the electrolytic cell to possibly at a hardness breakthrough in the softening device in the water present alkaline earth ions in the supplied water at least partially, preferably completely, to precipitate. For this purpose, the electrolytic cell comprises at least two electrolytic electrodes, to which DC voltage is applied for the electrolytic precipitation of the alkaline earth metal ions. The measuring device preferably contains at least one conductivity sensor with two measuring electrodes, to which alternating voltage is applied in order to record the conductivity of the water supplied to the measuring device. In order to record the conductivity of the water supplied to the measuring device both at the inlet and at the outlet of the electrolytic cell, the measuring device preferably contains a first conductivity sensor before or at the inlet and a second conductivity sensor after or at the outlet of the measuring device.

In the use according to the invention, this enables reliable detection of a hardness breakthrough on the one hand when a change in the conductivity (ΔLf= Lf _b - Lf _a ) of the supplied water is determined between the inlet and the outlet of the measuring device and on the other hand the effects of a hardness breakthrough that has already taken place at least in part rendered at least partially harmless by the alkaline earth metal ions of the supplied water being at least partially, preferably completely, precipitated. From the amount of the change in conductivity caused by the precipitation of the alkaline earth ions (ΔLf = Lf _b - Lf _a ), the concentration of the alkaline earth ions in the water supplied to the measuring device and thus the hardness slip of the softening device, in particular the ion exchanger, can be determined , getting closed.

In order to detect an incipient hardness breakthrough in good time, the water provided at the outlet of the softening device is preferably conducted continuously from the inlet to the outlet through the measuring device and the conductivity of the water conducted through is recorded at the inlet and outlet. If there is a change in the conductivity between the input and the output of the measuring device, it can be concluded that hardness breakthrough has at least partially occurred or is beginning and a regeneration process for regenerating the softening device can be initiated via the regeneration device and/or a signal can be output by the signaling device, in particular when a predetermined difference limit value of the change in conductivity detected with the measuring device is exceeded. If a difference limit value is exceeded, the water treatment system or the softening device can also be switched off in order to prevent non-softened water or water from being routed to a consumer.

In the use according to the invention, depending on the change in conductivity (ΔLf = Lf _b - Lf _a ) caused by the precipitation of the alkaline earth ions, a regeneration process for regenerating the softening device is automatically initiated and/or a signal is output if the Alkaline earth ions caused difference in conductivity (ΔLf = Lf _b - Lf _a ) exceeds a predetermined difference limit value Δ _G. In this way, it can be ensured that when a hardness breakthrough is detected that is beginning or has already occurred, the softening device is regenerated in good time before a damaging increase in the water hardness of the water provided by the water treatment system for a consumer. At the beginning of a hardness breakthrough, which is particularly evident when there is a low difference in the conductivity (ΔLf = Lf _b - Lf _a ) of the water supplied to the measuring device between the inlet and the outlet of the measuring device, the water hardness of the water from the water treatment plant at the outlet of the measuring device remains supplied water is low and ideally at or near zero, due to the electrolytic precipitation of the alkaline earth ions in the electrolytic cell of the measuring device.

• 1: eine schematische Darstellung eines ersten Ausführungsbeispiels einer erfindungsgemäßen Wasserbehandlungsanlage mit einer Enthärtungsvorrichtung und einer Messvorrichtung zur Erfassung eines Härtedurchbruchs in der Enthärtungsvorrichtung;
• 2: schematische Darstellungen verschiedener Ausführungsformen einer konduktometrischen Messvorrichtung zur Erfassung eines Härtedurchbruchs in einer Enthärtungsvorrichtung, die in der erfindungsgemäßen Wasserbehandlungsanlage eingesetzt und erfindungsgemäß verwendet werden kann;
• 3: ein Diagramm des zeitlichen Verlaufs der in einer der Messvorrichtungen von 2 erfassten elektrischen Leitfähigkeit einer Wasserprobe vor, während und nach einer elektrolytischen Fällung der Erdalkali-Ionen;
• 4: eine schematische Darstellung eines zweiten Ausführungsbeispiels einer erfindungsgemäßen Wasserbehandlungsanlage mit einer Enthärtungssvorrichtung und einer Messvorrichtung zur Erfassung eines Härtedurchbruchs in der Enthärtungsvorrichtung;
• 5: ein Diagramm des zeitlichen Verlaufs der in der erfindungsgemäßen Verwendung erfassten elektrischen Leitfähigkeit des der Messvorrichtung der Wasserbehandlungsanlage von 1 zugeführten Wassers mit einem Härtedurchbruch in der Enthärtungsvorrichtung;
• 6A: eine schematische Darstellung eines weiteren Ausführungsbeispiels einer Elektrolysezelle der Messvorrichtung zur Erfassung eines Härtedurchbruchs in einer Enthärtungsvorrichtung,
• 6B: eine Darstellung des zeitlichen Verlaufs der elektrischen Leitfähigkeit des der Elektrolysezelle von 6A zugeführten Wassers (Weichwasser von der Enthärtungsvorrichtung) vor der Elektrolysezelle (Lf_a) und nach der Elektrolysezelle (Lf_b) sowie der titrimetrisch bestimmten Härte (H) des zugeführten Wassers bei einem Härtedurchbruch in der Enthärtungsvorrichtung (6B);

These and other advantages and applications as well as preferred features of the water treatment system according to the invention and the use according to the invention result from the exemplary embodiments of the invention described below with reference to the drawings. show:

• 1 1: a schematic representation of a first exemplary embodiment of a water treatment plant according to the invention with a softening device and a measuring device for detecting a hardness breakthrough in the softening device;
• 2 1: schematic representations of different embodiments of a conductometric measuring device for detecting a hardness breakthrough in a softening device, which can be used in the water treatment plant according to the invention and used according to the invention;
• 3 : a diagram of the time course of the in one of the measuring devices of 2 detected electrical conductivity of a water sample before, during and after an electrolytic precipitation of alkaline earth ions;
• 4 1: a schematic representation of a second exemplary embodiment of a water treatment plant according to the invention with a softening device and a measuring device for detecting a hardness breakthrough in the softening device;
• 5 : a diagram of the time course of the electrical conductivity recorded in the use according to the invention of the measuring device of the water treatment plant from FIG 1 supplied water with a hardness breakthrough in the softening device;
• 6A : a schematic representation of a further exemplary embodiment of an electrolytic cell of the measuring device for detecting a hardness breakthrough in a softening device,
• 6B : a representation of the time course of the electrical conductivity of the electrolytic cell from 6A supplied water (soft water from the softening device) before the electrolytic cell (Lf _a ) and after the electrolytic cell (Lf _b ) and the titrimetrically determined hardness (H) of the supplied water in the event of a hardness breakthrough in the softening device ( 6B) ;

In 1 a first exemplary embodiment of a water treatment system according to the invention with a softening device 12 is shown, with the water treatment system 10 comprising an untreated water inlet 11 connected to the softening device 12 via a distributor 24 for the provision of untreated water R, a control device 14 and at least one conductometric measuring device 15. The measuring device 15 is arranged downstream of the distributor 24 and is connected to the distributor 24 at an input 15a of the measuring device 15 via a connecting line 20 . The control device 14 is coupled to the distributor 24 and the measuring device 15 in order to control them. The control device 14 controls in particular the volume flows of the water supplied from the raw water inlet 11 into the softening device 12 and the water W softened therein to the connecting line 20.

The softening device 12 is designed as a double system and includes a first softening device 12a and a second softening device 12b, which are operated in alternating operation. The first and the second softening device 12a, 12b each contain an ion exchanger 13 which is arranged in an ion exchange container 8 in each case.

The ion exchange tank 8 of the first and the second softening device 12a, 12b each comprises an inlet 11a and an outlet 11b, with the inlet 11a being connected to the distributor 24 via an inlet line 7 and the outlet 11b being connected to the distributor 24 via an outlet line 7'. To regenerate the ion exchanger 13 of the softening devices 12a, 12b, the water treatment system also includes a regeneration device 18 which has a regeneration tank 9 in which an aqueous regeneration solution, in particular a sodium chloride solution, is stored. When the ion exchanger 13 of one of the two softening devices 12a, 12b is exhausted, the regeneration solution is conducted into and through the ion exchange tank 8 of the respective softening device 12a or 12b in a regeneration mode, whereby the calcium and magnesium salts absorbed in the ion exchanger 13 when softening the raw water R ions are replaced by sodium ions. During the regeneration mode, the used regeneration solution is fed into a channel 19 via a discharge line 25 connected to the distributor 24 . While one of the two softening devices 12a or 12b is in a regeneration mode, the other softening device 12b or 12a can work in the operating mode in which raw water R is fed via the distributor 24 into the ion exchange tank 8 and is exchanged for the hardness-forming calcium and magnesium ions against sodium ions of the ion exchanger 13 (at least largely) is completely softened. In the operating mode, the softened water W is made available at the outlet 11b of the respective softening device 12a, 12b and is routed via the drain line 7` to the distributor 24, which feeds the softened water W via the connecting line 20 to the inlet 15a of the measuring device 15 on the one hand and to a Connecting line 20 related consumer line 21 passes. The volume flow of the softened water W, which is supplied to the measuring device 15 as a partial flow, is expediently significantly smaller than the total volume flow of the softened water W, which is introduced into the connecting line 20 . The majority of the total volume flow of the softened water W is introduced into the consumer line 21, which is connected to a consumer 22. The consumer 22 can be the drinking water installation, for example a household or a business or a water device or a downstream water treatment system (e.g. a reverse osmosis system), to which the softened water W is fed directly for further treatment.

The supply of the softened water W to the measuring device 15 takes place during the operation of the water treatment system 10 continuously or intermittently in predetermined measuring cycles. In particular, the measurement cycles can be carried out for the first time when a predicted degree of exhaustion of the ion exchanger 13 of the softening device 12 has been reached, e.g. after a predicted degree of exhaustion of 80% has been reached, and then regularly or continuously until it is completely exhausted, in order to detect a hardness breakthrough that is to be expected shortly. The degree of exhaustion of the softening device 12 depends on the total (maximum) exchange capacity of the ion exchanger 13 and the hardness of the raw water R and the total volume of the raw water that has flowed through the softening device 12, and can consequently be calculated from the known data on the exchange capacity and the Volume flow and the detectable by means of the measuring device 15 hardness H of the raw water R are predicted.

After the end of a measurement in the measuring device, the water W supplied to the measuring device 15 is discharged through the outlet 15b of the measuring device into a drain line 26 that can be closed with a valve v1, which drains the water into a channel 19.

The measuring device 15 comprises an electrolytic cell 1 which has a container 5 in which the input 15a and an output 15b are provided. The softened water W supplied from the connecting line 20 is introduced via the inlet 15a into the container 5 of the measuring device 15 and is conducted through the container 5 to the outlet 15b. For complete emptying of the container 5, it has a drain 15c, preferably on the floor. The measuring device 15 also includes a first conductivity sensor 2a at the input 15a and a second conductivity sensor 2b at the output 15b as well as two electrolysis electrodes A, K arranged opposite one another in the container 5, the electrolysis electrodes being connected to a DC voltage source and an electrolysis electrode as the anode A and electrolysis electrodes is designed as a cathode K. The container 5 and the electrolysis electrodes A, K arranged therein, to which a DC voltage is applied from the DC voltage source, form the electrolytic cell 1. The electrolysis electrodes A, K are preferably designed as flat electrodes, which are arranged in the container 5 at a distance and running parallel to one another are, so that the conducted through the container 5 water W between the electrolysis electrodes A, K can flow through.

The measuring device 15 is controlled by the control device 14 . The control device 14 controls in particular the supply of the electrolysis electrodes A, K during predetermined measurement cycles or electrolysis cycles or permanently during the operation of the water treatment system with electrical DC voltage. Furthermore, the detection of the electrical conductivity of the water W supplied via the connecting line 20 at the inlet 15a and at the outlet 15b of the measuring device 15 is controlled by the control device 14 by means of the two conductivity sensors 2a, 2b. Each of the two conductivity sensors 2a, 2b comprises at least one pair of electrodes 3, to which an electrical AC voltage is applied in defined measurement cycles or continuously during operation of the water treatment system and the current intensity is measured in order to detect the conductivity of the water W supplied. The temperature of the water is expediently recorded by means of a temperature sensor, which can be arranged, for example, in the electrolytic cell 1 or can also be integrated in at least one of the conductivity sensors 2a, 2b, and when determining the conductivity, a correction factor is used to correct the temperature to a standard temperature of e.g. 25°C.

In 2 further embodiments of the measuring device 15 are shown, in which the two conductivity sensors 2a, 2b are integrated in the container 5 of the electrolysis cell 1, with the first conductivity sensor 2a upstream of the electrolysis electrodes A, K at the input 15a and the second conductivity sensor 2b downstream of the electrolysis electrodes A, K is arranged at the output 15a. As in the embodiment of the measuring device 15 of FIG 1 the two electrolysis electrodes A, K are connected to a direct voltage source DC and the pair of electrodes 3 of the two conductivity sensors 2a, 2b are each connected to an alternating voltage source AC, with which the measuring electrodes of the electrode pair 3 can be supplied with electrical alternating voltage of a predetermined frequency. The two measuring electrodes of each conductivity sensor 2a, 2b are in 2 The examples shown are each designed as rod electrodes, the longitudinal axis of which runs parallel to the plane of the two electrolysis electrodes A, K designed as flat electrodes.

In the 2A shown embodiment of the measuring device 15 comprises two designed as flat electrodes electrolysis electrodes A, K, in the electrolytic cell parallel and at a distance mutually extending and arranged opposite to each other. The electrolysis electrodes include at least one anode, which is preferably made from platinized titanium sheet or a platinized titanium grid or from a graphite film, and at least one cathode, which is preferably made from steel or titanium or graphite foil. The anode and the cathode are particularly preferably made of the same material, in particular each made of platinized titanium.

in the in 2 B In the embodiment of the measuring device 15 shown, a plurality of electrolysis electrodes A, K are arranged in the electrolysis cell 1 . In particular, the electrolytic cell 1 of the embodiment of FIG 2 B a cascade of electrolysis electrodes in the sequence of an outer anode A, a first cathode K, an inner anode A, a second cathode K and a further outer anode A, as shown in FIG 2 B evident. A cation exchange membrane KAT is arranged between corresponding electrolysis electrodes A, K in each case. The plurality of electrolysis electrodes A, K and the cation exchange membranes KAT arranged between corresponding electrolysis electrodes A, K increase the efficiency of the electrolytic precipitation of the alkaline earth metal ions by precipitation in the form of alkaline earth metal carbonates at the cathodes K (particularly due to a larger electrode area). , whereby a faster precipitation of the alkaline earth ions when flowing through the water W is achieved.

Both the in 1 as well as the in 2 The embodiments of measuring device 15 shown can be used in a water treatment system 10 according to the invention for detecting a hardness breakthrough in the softening device 12, with the water W preferably flowing through the electrolytic cell 1 continuously or only in the time-defined measuring cycles from the inlet 15a to the outlet 15b and the electrical conductivity of the softened water W before and after the electrolytic cell 1 is measured. For this purpose, while the water W is flowing through the electrolytic cell 1, the conductivity Lf _a of the water flow at the inlet 15a and the conductivity Lf _b at the outlet 15b of the measuring device 15 are continuously measured in a measuring cycle with the two conductivity sensors 2a, 2b. The control device 14 calculates the difference ΔLf=Lf _b -Lf _a from the measured values recorded by the two conductivity sensors 2a, 2b and compares the amount of the calculated difference in the electrical conductivity |ΔLf| with a predetermined limit value Δ _G . If the magnitude of the determined difference in electrical conductivity |ΔLf| lies above this limit value Δ _G , it can be concluded that there is a certain amount of hardness-forming alkaline earth metal ions in the water, which indicates a breakthrough in hardness in the softening device 12 .

Furthermore, the measuring device 15 can be used to detect a change in the electrical conductivity of the supplied water W, which is based, for example, on a change in the water quality of the raw water R that is supplied to the water treatment system 10 via the raw water inlet 11 . For this purpose, the measuring device can have an in 1 bypass line, not shown, is supplied with untreated raw water R, the conductivity of which is measured with at least one of the two conductivity sensors 2a, 2b. If the determined conductivity of the raw water R changes, a different composition and in particular a changed hardness of the raw water R can be inferred.

In 4 a second exemplary embodiment of a water treatment system 10 according to the invention is shown with a softening device 12, which essentially corresponds to the first exemplary embodiment of 1 is equivalent to. In contrast to the first embodiment of the 1 is in the second embodiment of FIG 4 an additional return line 27 is provided, which connects the outflow line 26 to the consumer line 21 and opens into the consumer line 21 at a connection point 28 . The water W, whose conductivity has been detected in the measuring device 15, can be introduced into the consumer line 21 through the return line 27 in order to supply the water W to the consumer 22, as a result of which the loss of softened water W can be reduced. A valve v2 is provided in the return line 27 for opening and closing the return line 27 and another valve v3 is arranged in the consumer line 21 upstream of the connection point 28 for opening and closing the consumer line 21 . By closing the valves v1 and v3 and opening the valve v2, it is possible to conduct only the partial flow of the water W, which has been passed through the measuring device 15, to the consumer 22.

• Zur Inbetriebnahme der Wasserbehandlungsanlage 10 wird zunächst Rohwasser R durch den Rohwasserzulauf 11 über den Verteiler 24 sowie die Zulaufleitung 7 in den Ionenaustauschbehälter 8 der ersten Enthärtungsvorrichtung 12a geleitet, wodurch im Betriebsmodus (Enthärterbetrieb) der ersten Enthärtungsvorrichtung 12a die Calzium- und Magnesium-Ionen in dem Rohwasser R gegen Natrium-Ionen des Ionenaustauschers 13 ausgetauscht und dadurch enthärtetes Wasser W erzeugt wird, welches am Ausgang 11b der über die Ablaufleitung 7' und den Verteiler 24 in die Verbindungsleitung 20 eingeleitet wird. Das enthärtete Wasser W wird über die Verbindungsleitung 20 und die daran angeschlossene Verbraucherleitung 21 zu einem Verbraucher 22 geleitet, der auf diese Weise mit enthärteten Wasser W versorgt wird.

Below is a in the water treatment plant 10 of 1 feasible embodiment of the use according to the invention explained:

• To start up the water treatment system 10, raw water R is first fed through the raw water inlet 11 via the distributor 24 and the inlet line 7 into the ion exchange tank 8 of the first softening device 12a, whereby in the operating mode (softener operation) of the first softening device 12a the calcium and magnesium ions in the Raw water R exchanged for sodium ions of the ion exchanger 13 and thereby softened water W is produced, which is introduced into the connecting line 20 at the outlet 11b via the discharge line 7' and the distributor 24. The softened water W is routed via the connecting line 20 and the consumer line 21 connected to it to a consumer 22, which is supplied with softened water W in this way.

The second softening device 12b can be operated in the regeneration mode during the operating mode of the first softening device 12a, in which the second softening device 12b is supplied with the aqueous regeneration solution stored in the regeneration container 9 of the regeneration device 18, in particular a sodium chloride solution, via the regeneration line 17 and the distributor 24 becomes. In the regeneration mode, the regeneration solution is passed through the ion exchanger 13 in the ion exchange tank 8 of the second softening device 12b in order to regenerate this ion exchanger 13 by exchanging the calcium and magnesium ions bound therein for sodium ions in the regeneration solution. The regenerating solution consumed in the process is conducted via the discharge line 7' and the distributor 24 into the discharge line 25, which leads to a channel 19.

wird auf einen Härtedurchbruch in der ersten Enthärtungsvorrichtung 12a geschlossen und die Steuereinrichtung 14 leitet daraufhin einen Regeneriervorgang in der ersten Enthärtungsvorrichtung 12a ein. Gleichzeitig kann über eine Signaleinrichtung ein Signal angezeigt werden, welches den von der Steuereinrichtung 14 erfassten Härtedurchbruch der ersten Enthärtungsvorrichtung 12a anzeigt. Um während des eingeleiteten Regeneriermodus der ersten Enthärtungsvorrichtung 12a enthärtetes Wasser W mit der Abwasserbehandlungsanlage 10 in der Verbraucherleitung 21 bereitstellen zu können, wird gleichzeitig mit der Umstellung der ersten Enthärtungsvorrichtung 12a vom Betriebsmodus in den Regeneriermodus die zweite Enthärtungsvorrichtung 12b in den Betriebsmodus umgestellt, in dem die zweite Enthärtungsvorrichtung 12b aus dem vom Rohwasserzulauf 11 kommenden Rohwasser R enthärtetes Wasser W erzeugt und über die Ablaufleitung 7' und den Verteiler 24 in die Verbindungsleitung 20 und die damit in Verbindung stehende Verbraucherleitung 21 einspeist. Während die zweite Enthärtungsvorrichtung 12a im Betriebsmodus (Enthärtungsbetrieb) betrieben wird, befindet sich die erste Enthärtungsvorrichtung 12a im Regeneriermodus, in dem die Regenerierlösung aus der Regeneriervorrichtung 18 in den Ionenaustauschbehälter 8 geleitet wird, um den darin befindlichen Ionenaustauscher 13 zu regenerieren.During operation of the first softening device 12a in the operating mode, a partial flow of the softened water W provided at the outlet 11b of the first softening device 12a is conducted via the connecting line 20 to the measuring device 15 . The partial flow of the water W, which is supplied to the measuring device 15, flows through the container 5 of the measuring device 15 from the inlet 15a to the outlet 15b and is discharged into a channel 19 via the outlet line 26 when the valve v1 is open. At least in defined measuring cycles (or continuously during the operation of the water treatment plant), while the water W is flowing through the container 5, the electrolysis electrodes A, K of the measuring device 15 are subjected to electrical DC voltage. At the same time, the electrical conductivity of the water W flowing through the container 5 is recorded at the inlet 15a of the measuring device 15 with the first conductivity sensor 2a and at the outlet 15b with the second conductivity sensor 2b. The detected measured values Lf _a of the first conductivity sensor 2a and Lf _b of the second conductivity sensor 2b are sent to the control device 14 . The difference between the two measured values Lf _a and Lf _b of the electrical conductivity of the first conductivity sensor 2a and the second conductivity sensor 2b is calculated in the control device 14 and compared with a predefined limit value _ΔG . If it is determined in this comparison that the absolute value of the difference in the electrical conductivity ΔLf= | Lfa - Lfbl of the water W flowing through the container 5 is greater than the specified limit value Δ _G , ie if $$\Delta \text{lf}=\left|\text{lfa}-\text{Lfb}\right|>{\Delta }_{\text{G}}\text{is applicable}\text{,}$$

it is concluded that there has been a hardness breakthrough in the first softening device 12a and the control device 14 then initiates a regeneration process in the first softening device 12a. At the same time, a signal can be displayed via a signaling device, which indicates the hardness breakthrough of the first softening device 12a detected by the control device 14 . In order to be able to provide softened water W with the waste water treatment plant 10 in the consumer line 21 during the initiated regeneration mode of the first softening device 12a, at the same time as the first softening device 12a is switched from the operating mode to the regeneration mode, the second softening device 12b is switched to the operating mode in which the second softening device 12b produces softened water W from the raw water R coming from the raw water inlet 11 and feeds it via the outlet line 7' and the distributor 24 into the connecting line 20 and the consumer line 21 connected thereto. While the second softening device 12a is in the operating mode (softening operation), the first softening device 12a is in the regeneration mode, in which the regeneration solution is fed from the regeneration device 18 into the ion exchange tank 8 in order to regenerate the ion exchanger 13 located therein.

During the operation of the second softening device 12b in the operating mode (softening operation), a partial flow of the softened water W fed from the second softening device 12b into the connecting line 20 is in turn conducted to the measuring device 15 in order to detect a hardness breakthrough in the second softening device 12b. This is done in the same way as in the operating mode of the first softening device 12a.

After detection of a hardness breakthrough in one of the two softening devices 12a or 12b by the measuring device 15, the container 5 of the measuring device 15 is emptied by the water in it through the outlet 15b and, with the valve v1 open, through the drain line 26 and/or through the open outlet 15c is discharged into the channel 19. The measuring device 15 is then ready for a subsequent measuring cycle. When the subsequent measurement cycle is initiated, the container 5 is automatically flushed through by the water flowing through.

In 5 FIG. 12 is an example of the course over time of the measured values of the electrical conductivity Lf _a and Lf _b recorded by the two conductivity sensors 2a and 2b during operation of the water treatment device 10 from FIG 1 shown, whereby first the first softening device 12b is operated in the operating mode while the second softening device 12b is regenerated in the regeneration mode and a partial flow of the softened water W provided at the outlet 11b of the first softening device 12b is fed to the measuring device 15 in order to use the first conductivity sensor 2a to determine the electrical Conductivity Lf _a of the water W at the input 15a and with the second conductivity sensor 2b to detect the electrical conductivity Lf _b of the water W at the output 15b of the measuring device. While the electrical conductivity of the water W is recorded at the input 15a and at the output 15b of the measuring device, the electrolysis electrodes A, K are connected to a DC voltage source, so that any alkaline earth metal ions contained in the water as the water flows through the electrolysis cell 1 be precipitated over a predetermined period of time Δt of the precipitation, which depends on the flow rate and the length of the electrolytic cell 1 in the direction of flow.

At a time of t ~ 18 minutes, in 5 a drop in the conductivity Lf _b can be observed at the outlet 15b, which indicates the existence of alkaline earth ions in the softened water W and therefore a breakthrough in hardness. The conductivity Lf _b at the outlet 15b continues to drop until a point in time t˜23 minutes and asymptotically approaches a minimum. The amount of the difference between the electrical conductivity Lf _a at the input 15a and the conductivity Lf _b at the output 15b becomes correspondingly larger and exceeds a predetermined limit value Δ _G at t ~ 22 minutes, from which a hardness breakthrough and exhaustion of the exchange capacity of the first softening devices 12a are concluded becomes. At t = 23 minutes, the second softening device 12b is switched over to the operating mode, so that softened water W is now provided by the second softening device 12b and fed into the connecting line 20, which is why the measured value of the conductivity Lf _b at the output 15b of the measuring device 15 is the same approaches the original reading before recording the hardness breakthrough and has returned to the original reading of 730 µS/cm at t ~ 24 minutes.

In 6A a further exemplary embodiment of an electrolytic cell 1 of the measuring device 15 is shown, which was used in an attempt to detect a hardness breakthrough in a softening device. The electrolytic cell 1 comprises a container 5 with a length L, an inlet 15a and an outlet 15b as well as an anode A arranged centrally in the container 5 and two cathodes K arranged at a predetermined distance d therefrom and running parallel to the anode A. The length L of the container is 6.7 cm in the example and the volume of the container 5 is 8.7 ml. The distance d between the cathodes K and the anode A is 0.2 cm. The water (softened water) provided by a softening device is conducted through the container 5 in a flow direction v along the length L in a predetermined volume flow of preferably 0.6 l/h to 1.4 l/h. A DC voltage of preferably less than 12 V, in particular in the range from 6 to 10 V, is applied to the electrolysis electrodes A, K. The electrolysis current is suitably between 200 and 1000 mA, in particular between 400 and 700 mA. by means of 6A Not shown conductivity sensors, the electrical conductivity of the water supplied to the electrolytic cell 1 (soft water provided by the softening device) is measured at the input 15a of the electrolytic cell (Lf _a ) and at the output 15b of the electrolytic cell (Lf _b ).

In 6B is the time profile of the electrical conductivity measured with the two conductivity sensors and the titrimetrically determined hardness H of the electrolytic cell 1 from 6A supplied water shown in a hardness breakthrough in the softening device. The hardness (H) of the supplied water was determined titrimetrically. At 10:50 a.m., a direct current of 700 mA was generated at electrodes A, K ("current on"). Out of 6B it can be seen that from the time 10:55 the hardness H of the water increases from initially 0°dH to approx. 22°dH within approx. 30 minutes due to a breakthrough in hardness in the softening device. As soon as the hardness breakthrough begins at 10:55 a.m., a reduction in the conductivity Lf _b at the outlet 15b of the electrolytic cell 1 can be observed, which decreases to a conductivity minimum within about 30 minutes. The hardness breakthrough that has taken place can be seen from this. At around 11:38 a.m. the electrolysis current was switched off (“current off”), which is why the value of the conductivity at the outlet 15b of the electrolysis cell 1 rose again to the original value, which roughly corresponds to the conductance Lf _a at the inlet 15a of the electrolysis cell 1.

The invention is not limited to the exemplary embodiments shown in the drawing. For example, a desalination device can be used in addition to the softening device 12, for example a reverse osmosis system or a desalination device with a cation exchanger and an anion exchanger.

Furthermore, in addition to or instead of the regeneration device 18, a signaling device can also be provided, which generates a signal when the water softening device is exhausted to indicate that the water softening device needs to be regenerated. For this purpose, the signaling device is expediently coupled to the control device 14 and forwards the signal to the control device 14, which then emits an acoustic warning signal, for example a warning tone, or displays an optical warning signal. Such a signaling device is expedient, for example, if the softening device does not contain a regenerable ion exchanger and/or no regeneration device for regenerating the softening device but (at least) one replaceable ion exchanger, for example in the form of an ion exchanger cartridge arranged replaceably in the softening device. A signal generated by the signaling device upon detection of a hardness breakthrough indicates to an operator of the waste water treatment plant 10 that the ion exchanger is exhausted and must be replaced by a new ion exchanger, in particular by a new ion exchanger cartridge. It is also possible that the signaling device or the control device automatically shuts down the operation of the entire water treatment system or the softening device when a hardness breakthrough is detected, or at least stops the provision of water at the outlet by closing the outlet of the softening device in order to prevent the water treatment system provides non-softened water at the outlet and directs it to a consumer coupled to the water treatment system.

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 19841568 A1 [0005]
• WO 2009/071066 A2 [0007]
• DE 2953143 A1 [0009]

Claims (19)

Water treatment plant (10) comprising - an untreated water inlet (11) for providing untreated water (R), - a softening device (12) with an inlet (11a), which is connected to the untreated water inlet (11), and an outlet (11b), wherein the softening device (12) produces softened water (W) from the raw water (R) and makes it available at the outlet (11b) and in particular contains at least one regenerable or replaceable ion exchanger (13), - a regenerating device (18) for regenerating the softening device (12 ), in particular of the ion exchanger (13) of the softening device (12), and/or a signaling device which generates a signal when the softening device (12) is exhausted to indicate that the softening device (12) needs to be regenerated and in particular that a regeneration or a required to indicate replacement of the ion exchanger (13) and/or to close the outlet (11b) of the softening device (12), - a control device (14) which is coupled to the regeneration device (18) and/or the signaling device in order to control the softening device (12) to regenerate when exhausted and/or to output or display the signal generated by the signaling device, and - at least one measuring device (15) connected to the softening device (12) and the control device (14) for detecting a hardness breakthrough in the water (W) provided at the outlet (11b) of the softening device (12), characterized in that the measuring device (15) has at least one conductivity sensor (2; 2a, 2b) and an electrolysis cell (1) with at least two electrolysis electrodes (A, K). water treatment plant claim 1 , characterized in that the electrolysis electrodes (A, K) are designed as flat electrodes arranged opposite one another in the electrolysis cell (1), the electrolysis electrodes (A, K) being connectable or connected to a DC voltage source. Water treatment plant according to one of Claims 1 or 2 , characterized in that at least one conductivity sensor (2; 2a, 2b) is integrated in the electrolytic cell (1) or that a first conductivity sensor (2a) is arranged upstream and a second conductivity sensor (2b) is arranged downstream of the electrolytic cell (1). Water treatment system according to one of the preceding claims, characterized in that at least one conductivity sensor (2) is integrated in the electrolytic cell (1), the integrated conductivity sensor (2) comprising at least one pair of electrodes (3) with two measuring electrodes designed in particular as rod electrodes, the Measuring electrodes can be connected or are connected to an AC voltage source. Water treatment system according to one of the preceding claims, characterized in that a first conductivity sensor (2a) and a second conductivity sensor (2b) are integrated in the electrolysis cell (1), the first conductivity sensor (2a) and the second conductivity sensor (2b) each having a pair of electrodes (3) with two measuring electrodes, wherein the measuring electrodes can be or are connected to an AC voltage source and are preferably arranged between the opposing electrolysis electrodes (A, K) of the electrolysis cell (1) and are preferably designed as rod electrodes. Water treatment plant according to one of the preceding claims, characterized in that the measuring device (15) contains an inlet (15a), at which water from the softening device (12) is supplied to the measuring device, and an outlet (15b), the inlet (15a) a first conductivity sensor (2a) and a second conductivity sensor (2b) are arranged at the outlet (15b), and the electrolytic cell (1) is arranged between the inlet (15a) and the outlet (15a). water treatment plant claim 6 , The control device (14) controlling the measuring device (15) in such a way that water (W), which is provided at the outlet (11b) of the softening device (12), is supplied to the measuring device (15) at the inlet (15a) and the conductivity (Lf _a ) of the water (W) supplied at the inlet (15a) is recorded with the first conductivity sensor (2a) and then the water (W) supplied to the measuring device (15) is electrolysed by applying a DC voltage to the electrolysis electrodes (A, K) and Finally, the conductivity (Lf _b ) of the electrolyzed water (W) at the outlet (15b) of the measuring device (15) is measured using the second conductivity sensor (2b) and, in particular, a change in conductivity (ΔLf = | Lf _b - Lf _a |) of the water (W) between the inlet (15a) and the outlet (15b) of the measuring device (15) is detected. Water treatment plant according to one of the preceding claims, wherein the control device (14) controls the measuring device (15) in such a way that initially the original conductivity (Lf _a ) of the water (W) provided at the outlet (11b) of the softening device (12) and then the alkaline earth metal ions contained in the water (W) supplied to the measuring device (15) are recorded in the measuring device (15) by applying a DC voltage to the electrolysis electrodes ( A, K) are at least partially precipitated and the conductivity (Lf _b ) of the water (W) supplied to the measuring device (15) is measured during and/or after the precipitation of the alkaline earth metal ions. water treatment plant claim 7 or 8th , characterized in that the control device (14) outputs a signal and/or controls the regeneration device (18) in order to initiate a regeneration process for regenerating the softening device (12) if a difference (ΔLf = | Lf ₂ - Lf ₁ ) between the original conductivity (Lf ₁ ) and the conductivity (Lf ₂ ) of the water (W) supplied to the measuring device (15) measured after or during the precipitation of the alkaline earth ions, in particular if the detected difference in conductivity (ΔLf) is above a predetermined one limit is Water treatment plant according to one of Claims 7 until 9 , characterized in that the control device (14) outputs a signal if, during the precipitation of the alkaline earth metal ions, in particular over a predetermined period of time (Δt) of the precipitation, there is a change in the measured conductivity compared to the original conductivity of the measuring device (15). Water (W) is detected, in particular when the change in conductivity (ΔLf) detected over the specified period of time (Δt) is above a specified limit value (Δ _G ). Water treatment plant according to one of Claims 7 until 10 , wherein the control device (14) is set up in such a way that it initiates a regeneration process of the regeneration device (18) as a function of the recorded change in conductivity (ΔLf), in particular when a predetermined limit value (Δ _G ) of the recorded change in conductivity (ΔLf. Use of a water treatment plant (10) for producing softened water, the water treatment plant (10) - an untreated water inlet (11) for providing untreated water (R) which contains alkaline earth metal ions, in particular calcium and/or magnesium ions, and hydrogen carbonate and/or carbonate ions, - a softening device (12) with an inlet (11a), which is connected to the raw water inlet (11), and an outlet (11b), the softening device (12) being extracted from the raw water (R ) produces softened water (W) and makes it available at the outlet (11b) and in particular contains at least one regenerable or exchangeable ion exchanger (13), - a regeneration device (18) for regenerating the softening device (12), in particular the ion exchanger (13), and/ or a signaling device which generates a signal when the softening device (12) is exhausted in order to indicate that the softening device (12) needs to be regenerated and in particular that the ion exchanger (13) needs to be regenerated or replaced, or that water is made available at the outlet (11b ) sets, - a control device (14), which is coupled to the regeneration device (18) and/or the signaling device in order to regenerate the softening device (12) in the event of exhaustion and/or to output or display the signal generated by the signaling device, - and at least one measuring device (15) connected to the softening device (12) and the control device (14) for detecting a hardness breakthrough in the water (W) provided at the outlet (11b) of the softening device (12), characterized in that water (W), which is provided at the outlet (11b) of the softening device (12), is fed at least intermittently, preferably continuously, to the measuring device (15) and in the measuring device (15) an electrolytic precipitation of the alkaline earth metal ions in the water (W) fed in is carried out, at least before and during the electrolytic precipitation of the alkaline earth metal ions, the electrical conductivity of the supplied water (W) is recorded and compared with one another, in particular by forming the difference (ΔLF = | Lf _b - Lf _a |) of the before the electrolytic conductivity (Lf _a ) detected during precipitation and the conductivity (Lf _b ) detected during or after precipitation. use after claim 12 , characterized in that the electrical conductivity of the measuring device (15) supplied water (W) at an input (15a) of the measuring device (15) and an output (15b) of the measuring device (15) is detected. Use after one of Claims 12 until 13 , characterized in that the measuring device (15) comprises an electrolytic cell (1) arranged in particular between the input (15a) and the output (15b) of the measuring device (15) and having at least two electrolytic electrodes (A, K), the measuring device ( 15) supplied water (W) is electrolyzed in the electrolytic cell (1) in order to at least partially precipitate the alkaline earth metal ions in the supplied water (W). Use after one of Claims 12 until 14 , characterized in that in the Measuring device (15) a partial or complete precipitation of the alkaline earth ions in the supplied water (W) takes place and that the change in conductivity (ΔLf = Lf _b - Lf _a ) of the supplied water (W) caused by the precipitation of the alkaline earth ions is detected. Use after one of Claims 12 until 15 , characterized in that the measuring device (15) comprises an electrolysis cell (1) which contains at least two electrolysis electrodes (A, K) which are subjected to a DC voltage for the electrolytic precipitation of the alkaline earth metal ions in the water fed to the measuring device (15). . use after Claim 16 , characterized in that the measuring device (15) contains at least one conductivity sensor (2) with two measuring electrodes, which are applied to detect the conductivity of the measuring device (15) supplied water with AC voltage, wherein the measuring device (15) preferably a first conductivity sensor ( 2a) and a second conductivity sensor (2b) each with two measuring electrodes. Use after one of Claims 12 until 17 , characterized in that water (W) which is provided at the outlet (11b) of the softening device (12) is continuously passed from an inlet (15a) to an outlet (15b) through the measuring device (15) and the conductivity of the water passed through at the input (15a) and at the output (15b) and when there is a change in the conductivity between the input (15a) and the output (15b), a regeneration process for regenerating the softening device (12) is initiated and/or a signal is output, in particular at Exceeding a specified differential limit value (Δ _G ) of the change in conductivity. Use after one of Claims 12 until 18 , characterized in that depending on a change in conductivity (ΔLf = Lf _b - Lf _a ) caused by the precipitation of the alkaline earth ions, a regeneration process for regenerating the softening device (12) is initiated and/or a signal is output or the water treatment system is shut down, in particular when the difference in conductivity (ΔLf=Lf _b -Lf _a ) caused by the precipitation of the alkaline earth ions exceeds a predetermined difference limit value (Δ _G ).

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