BE1031355B1 - IMPROVED WATER BALANCE - Google Patents

Abstract

The present invention provides, among other things, a method for automatically controlling the quality of water (7), preferably swimming pool water, comprising the steps of: actively measuring alkalinity of the water (7) with a first sensor, during a first state (101); switching from the first (101) to a second (301, 701) state; measuring pH of the water (7) with the same first sensor, during the second state; calculating, based on said measurement of alkalinity and pH, a water balance index, preferably a Langelier Saturation Index, LSI; determining whether the calculated index meets a predetermined criterion with respect to said quality; if said criterion is not met, generating an instruction for correction of said quality; wherein said first sensor is a pH sensor (8); wherein said first (101) and second (301, 701) states are at least partially non-overlapping in time, preferably non-overlapping in time; whereby said active measuring is related to the automated and metered addition of a measuring fluid to obtain a ready-to-measure solution.

Description

1 BE2023/5119

IMPROVED WATER BALANCE

TECHNICAL DOMAIN

The invention relates to a method and device for automatically controlling the quality of water, and a swimming pool related thereto.

STATE OF THE ART

Measuring water alkalinity is an important consideration in many applications, including monitoring swimming pool water quality.

Existing methods and devices for measuring alkalinity are often too complex and/or require expensive instrumentation, requiring a set of various sensors. In some cases, the measurement is also slow. Also, a form of integration with measurement of other parameters that are important for water quality, and/or a form of correction based on the measurements, is often lacking. In addition, for many applications, including swimming pool applications, it is important that the substances and materials involved are non-toxic, and that a generally safe character can be guaranteed.

FR2935371A1, IN201911044176A, WO2017223365A1 and FR3005742A1 disclose related concepts but require complex implementation and/or are not sufficiently accurate, which is disadvantageous.

There is a need for methods and devices for cost-effective and reliable alkalinity measurement. The invention aims to solve the above-mentioned problems.

SUMMARY OF THE INVENTION

The invention provides an apparatus and method for measuring alkalinity of water, a system, a swimming pool, a use of a pumping device for measuring alkalinity; a method for correcting alkalinity of water, a use of a combination of fluids for automatic and fluid-based correction of alkalinity of a swimming pool, a kit for correcting alkalinity of a swimming pool; a method and apparatus for automatically controlling quality of water, and a related swimming pool.

The various aspects are complementary and are not mutually restrictive. Some aspects are included in the claims, other aspects are referred to in this document as "article" or "clause".

This terminology is not intended to be limiting, and the terms "article" and "clause", known in English as "clause", all serve to indicate aspects and preferred embodiments of the invention which, in addition to the actual claims, are also to be considered as patentable subject matter, with claim-like wording. The presence of a feature in one of the aspects is not limiting for the invention in its other aspects. A feature which is present in one

2 BE2023/5119 aspect but not in one or more of the other aspects is therefore to be considered non-essential for at least all aspects in which the characteristic does not occur. This consideration applies further to all characteristics, in each of the aspects.

In one aspect, the invention provides a method for automatically controlling the quality of water, preferably swimming pool water, comprising the steps of: actively measuring alkalinity of the water with a first sensor, during a first state; switching from the first to a second state; measuring pH of the water with the same first sensor, during the second state; calculating, based on said measurement of alkalinity and pH, a water balance index, preferably a Langelier Saturation Index, LSI; determining whether the calculated index meets a predetermined criterion with respect to said quality; if said criterion is not met, generating an instruction for correction of said quality; wherein said first sensor is a pH sensor; wherein said first and second states are at least partially non-overlapping in time, preferably non-overlapping in time. In preferred embodiments, said active measuring relates to the automated and metered addition of a measuring fluid to obtain a ready-to-measure solution. In alternative embodiments, said active measuring relates to an alkalinity measurement with equivalence point attainment as described, for example, in WO2017223365A1, wherein the alkalinity measurement preferably takes place with a second sensor which at least partially differs from the pH sensor used for the pH measurement.

An advantage of such a method is the far-reaching automation, whereby said switching makes it possible to measure both pH and alkalinity, whereby only a pH sensor is at least required. This is made possible by the active form of measurement, which for example relates to the mixing of a measuring fluid and a sample, but which can also relate to an alkalinity measurement with reaching an equivalence point as described for example in WO2017223365A1. In contrast to WO2017223365A1, a method related to the mixing of a measuring fluid and a sample nevertheless offers both alkalinity measurement and pH measurement using the same one pH sensor, consisting of for example only two electrodes, which is advantageous. This can offer simple maintenance, whereby any wear on sensors can be limited to a small number of sensors, in embodiments only the pH sensor.

Such a method for automatic control of water quality is not described or suggested by the prior art.

3 BE2023/5119

In one aspect, the invention provides an apparatus for automatically controlling water quality, comprising: a first sensor; means for performing an active measurement; a control unit connected to said first sensor; said control unit being configured to: measure, by means of said first sensor, pH of the water, during a first state; actively measure, by means of a second sensor, which is preferably equal to the first sensor, and said means for performing said active measurement, said alkalinity of the water, during a second state; calculating, based on said measurement of pH and alkalinity, a water balance index, preferably a Langelier Saturation Index, LSI; determining whether the calculated index meets a predetermined criterion relating to said quality; if said criterion is not met, generating an instruction for improving said quality; said first sensor being a pH sensor; said first and second states being at least partially non-overlapping in time, preferably being non-overlapping in time; wherein said means for performing the active measurement are preferably associated with the automated and metered addition of a measuring fluid to obtain a ready-to-measure solution.

The advantages of such an arrangement are similar to those of the corresponding method.

In one aspect, the invention provides a swimming pool comprising an apparatus comprising an inlet and outlet and a pool shell comprising said water connected to said apparatus by said inlet and outlet.

This pool has advantages similar to those of the corresponding facility.

Embodiments according to the dependent claims and their respective possible advantages are explained in the detailed description.

4 BE2023/5119

DESCRIPTION OF THE FIGURES

Figure 1 shows a schematic exemplary embodiment of a device according to the invention.

Figures 2A-2B show exemplary embodiments of devices according to the invention. In these,

Figure 2A shows an example embodiment without an incoming flow pump, and Figure 2B shows an example embodiment with an incoming flow pump.

Figures 3A-3B show exemplary embodiments of devices according to the invention in which switching takes place between a first and second state. Figure 3A shows an exemplary embodiment with a valve, and Figure 2B shows an exemplary embodiment with an incoming flow pump.

Figure 4 shows a schematic exemplary embodiment of a device according to the invention with an alka-plus pump.

Figure 5 shows an exemplary embodiment of a device according to the invention with both an alkali-plus pump and a pH-minus pump.

Figure 6 shows an example of a bijective relationship according to the invention, in which the alkalinity of the water is plotted as a function of the acidity of the ready-to-measure solution.

DETAILED DESCRIPTION

Unless otherwise defined, all terms used in the description of the invention, including technical and scientific terms, have the meaning as commonly understood by one skilled in the technical field of the invention. For a better appreciation of the description of the invention, the following terms are explicitly explained. “A,” “an,” and “the” refer in this document to both the singular and the plural unless the context clearly suggests otherwise. For example, “a segment” means one or more than one segment. Quoting numerical intervals through the endpoints includes all integers, fractions, and/or real numbers between the endpoints, including these endpoints.

In this document, the term "water" refers to an aqueous solution that is predominantly H2O. Throughout this document, "water" may be replaced by the term "aqueous solution" without this leading to a re-evaluation of the scope of the invention or the claims. The term "water" is thus a collective term for all aqueous solutions that would be referred to as water in everyday practice. In preferred embodiments, the aqueous solution consists of at least 80% H2O, more preferably at least 90% H2O, most preferably at least 98% H2O. The water may relate to any form of fresh water, salt water, seawater, surface water, groundwater, drinking water, process water. In embodiments, the water relates to water from a swimming pool, pond, swimming pond or breeding pond.

In this document, "alkalinity" is a measure of the acid buffering capacity of water. This can be related to both a qualitative and a quantitative measure. Alkalinity is related to the ability of water, i.e. the aqueous solution, to neutralize acids. Preferably, it is related to the stoichiometric sum of the bases in the aqueous solution, such as hydroxide ions (OH), carbonate ions (CO3) and hydrogen carbonate ions (HCO:"). Alkalinity is a measure of the buffering capacity of water, i.e., the ability to prevent pH fluctuations. If the alkalinity is too low, the pH will fluctuate strongly when acid or base is added. If the alkalinity is too high, the pH will be difficult to correct.

In this document, the term "bijective relationship" preferably refers to a calibration curve, more preferably a calibration line, which defines the relationship between alkalinity and acidity.

In this document, "acidity" is an alternative term for "pH", where the former can be replaced by the latter, while the latter term refers to both acidity and a measurement of acidity. A "measurement of acidity", or a "measurement of pH", corresponds to a pH value.

In this document, the terms "volume" and "flow rate" are interchangeable. In embodiments, the respective known volumes of said sample and said dose are functions of respective known flow rates. The volume then corresponds to the volume that, for the known flow rate, can be pumped by the respective pump during a certain time window, for example a certain cycle (with or without time measurement), or a certain measured time period.

In this document, the term "molar concentration (or molarity)" refers to the degree of dilution of a substance. It is expressed in "M" or "molar", corresponding to moles per liter (mol/l).

In an aspect according to the articles in this document, the invention provides an apparatus for measuring alkalinity of water, preferably swimming pool water, comprising: a first pump for automatically pumping a measuring fluid comprising a known dilution of an acid corresponding to a known acidity; a second pump for automatically pumping a sample of the water; a chamber connected to said first and second pump, for receiving a ready-to-measure solution comprising said sample and said measuring fluid according to a known mixing ratio, the chamber comprising a pH sensor for measuring acidity; a control unit connected to said pH sensor; said control unit being configured to measure said alkalinity based on a measurement of acidity of said ready-to-measure solution by said pH sensor and based on a bijective relationship between acidity of the ready-to-measure solution and alkalinity of the water valid in a working range comprising said known acidity and said measurement of acidity.

6 BE2023/5119

Such a device provides an answer to the problems of the prior art, see for example WO2017223365A1. A whole series of electrodes is required there, which can make it expensive and cumbersome to measure alkalinity. Moreover, the method according to WO2017223365A1 can be slow, because it has to work towards an equivalence point, where the power consumed during the titration is a measure of the alkalinity. The present invention provides an alternative by only requiring a pH sensor for measuring alkalinity, so that for example a pair of electrodes can suffice. Also, the solution obtained by mixing the measuring fluid and the sample is "ready for measurement", so that it is not necessary to work towards an equivalence point during the measurement, which can benefit the speed of measurement, and/or can save electrical energy, and/or can avoid the oxidation inherent in titration.

In one aspect according to the articles in this document, the invention provides a system comprising the apparatus according to the articles in this document, a source of measuring fluid and an assembly of connections for measuring alkalinity according to a closed loop with inlet connected to said second pump, and outlet connected to said chamber.

This system has advantages similar to those of the corresponding facility.

In one aspect according to the articles in this document, the invention provides a swimming pool comprising the system according to the articles in this document comprising said inlet and outlet and a swimming pool shell comprising said water connected to said system through said inlet and outlet.

This pool has advantages similar to those of the corresponding system and the corresponding layout.

In an aspect according to the articles in this document, the invention provides a method for measuring alkalinity of water, preferably swimming pool water, comprising the steps of: mixing a measuring fluid and a sample of water according to a known mixing ratio, the measuring fluid comprising a known dilution of an acid corresponding to a known acidity, to obtain a ready-to-measure solution; performing, with respect to said ready-to-measure solution, a measurement of acidity by means of a pH sensor; measuring said alkalinity of the water, based on said measurement of acidity and based on a bijective relationship between acidity and alkalinity which is valid in a working range comprising said known acidity and said measured acidity.

Such a method is advantageous because it can avoid the disadvantages of prior art alkalinity measurement. In WO2017223365A1, the alkalinity measurement is related to the generation of hydronium using the titrant generating electrode, which allows the

7 BE2023/5119 acidity is changed. The generation is aimed at reaching a predetermined end point of electrochemical titration, i.e. to realize a titration to equivalence point.

In this case, the amount of current or charge that has been consumed, or the amount of hydronium ions that have been generated, is indicative of the alkalinity. This measuring principle is therefore based on a correlation, in which generation and detection are correlated. In the alkalinity measurement according to the present invention, there is no such complex correlation, and the same amount of acid is used as a starting point, so that the mixture of measuring fluid and steel is immediately a ready-to-measure solution. This benefits the simplicity and cost price, can lead to faster and/or energy-saving measurements, and can also lead to a more robust implementation. By avoiding electrochemical titration, the well-known usage problems of electrodes (e.g., as a result of transition resistance) are avoided. The consumption of measuring fluid is also easy to predict, because a dosed amount of measuring fluid is supplied each time. In example embodiments, this is always the same amount.

In one aspect according to the articles in this document, the invention provides a use of a pumping device for measuring alkalinity, by pumping a sample of water and a measuring fluid according to a mixing ratio which is known by means of provisions, belonging to the pumping device, for realizing a mechanically coupled volumetric ratio.

This use can provide an advantageous solution to the problem of realising a ready-to-measure solution according to a known mixing ratio. Rather than working with two pumps whose flow rate is independently adjustable (two degrees of freedom), it can be advantageous to mainly control the mutual ratio, by said mechanically coupled volumetric ratio (one degree of freedom). The dosage is also relevant, but may have less influence on the accuracy of the alkalinity measurement.

In an aspect according to the clauses in this document, the invention provides a method for correcting the alkalinity of water, preferably swimming pool water, comprising the steps of: automatically pumping a sample of said water and a measuring fluid comprising a known dilution of an acid corresponding to a known acidity, according to a known mixing ratio, to obtain a ready-to-measure solution; measuring an acidity of said ready-to-measure solution by means of a pH sensor; measuring, based on said acidity, said alkalinity of the water; performing, based on said measurement, said correction with respect to the alkalinity of the water, by automated and metered addition of an alkalinity-increasing fluid by means of an alka-plus pump.

An advantage of such a method is related to the completely liquid-based measuring and correction of alkalinity, where only a pH sensor is at least required. This can offer easy maintenance, where only two liquids need to be filled, and where

8 BE2023/5119 any wear on sensors may be limited to a small number of sensors, in embodiments only the pH sensor. Such a method for correction is not described or suggested by the prior art.

In one aspect according to the clauses in this document, the invention provides a use of a combination of a measuring fluid comprising a known dilution of an acid corresponding to a known acidity comprising adipic acid and an alkalinity increasing fluid comprising a carbonate or bicarbonate for automatically and fluid-based correction of alkalinity of a swimming pool.

An advantage of such use is related to the completely liquid-based measuring and correction of alkalinity. This can provide easy maintenance, with only two liquids to be replenished, which can be cost-saving due to the similar nature of maintenance.

This allows an operator to coordinate stocks so that both stocks are replenished with just one intervention, which is even more cost-effective.

In an aspect according to the clauses herein, the invention provides a kit for correcting alkalinity of a swimming pool, comprising: a measuring fluid comprising a known dilution of an acid corresponding to a known acidity including adipic acid; and an alkalinity increasing fluid comprising a carbonate or bicarbonate; said alkalinity increasing fluid comprising carbonate, COs*, and/or bicarbonate, HCOs, and said alkalinity increasing fluid comprising said carbonate or bicarbonate at a concentration greater than 0.2 M.

An advantage of such a kit is related to the completely liquid-based measuring and correction of alkalinity. This can provide easy maintenance, where two liquids are replenished simultaneously, where the supplies are matched according to a kit, so that only one delivery is needed.

In embodiments, said known mixing ratio is further related to pumping a known volume of said measuring fluid, with said first pump, and/or a known volume of a sample of said water, with said second pump. This may have the advantage that the mixing ratio is known more accurately, whereby it is calculated both on the basis of the mechanically coupled volumetric ratio between the flow rates of the pumps among themselves, and on the basis of one, or both, of the respective flow rates of the pumps.

In alternative embodiments, said known mixing ratio is not related to a mechanically coupled volumetric ratio between the flow rate of the first pump and the

9 BE2023/5119 flow rate of the second pump, but instead relates to the pumping of a known volume of said measuring fluid, with said first pump, and a known volume of a sample of said water, with said second pump.

In embodiments, measuring alkalinity is related to water quality analysis.

In embodiments, the pH sensor comprises a set of a first and second electrode. These may be either solid-state electrodes or glass electrodes. Furthermore, the invention is not limited thereto, and any means suitable for pHmetry may be used, including holographic pH sensors with colorimetric operation, and including forms of pHmetry without the use of electrodes.

In preferred embodiments, the acid present in the measuring fluid is related to adipic acid. In preferred embodiments, the concentration of adipic acid present in the measuring fluid is between 0.01 g and 10 g per liter, more preferably between 0.1 g and 1 g per liter, most preferably 0.2 or 0.3 or 0.4 or 0.5 or 0.6 or 0.7 or 0.8 or 0.9 g per liter. In preferred embodiments, the mixing ratio of measuring fluid and sample of water is between 1:4 and 4:1, more preferably between 1:3 and 3:1, most preferably 1:2 or 2:3 or 3:4 or 4:5 or 1:1 or 5:4 or 4:3 or 3:2 or 2:1. In preferred embodiments, the mixing ratio is a function of the mechanically coupled volumetric ratio between flow rate of the measuring fluid and flow rate of the sample. This ratio depends on the precise characteristics of the pumps and/or the pumping device, and can be any real number. In preferred embodiments, this number is determined during calibration and is taken into account when calculating an alkalinity measurement value as a function of the acidity measurement.

In WO2017223365A1, a pH-sensing electrode and the titrant-generating electrode for determining alkalinity are mentioned. In contrast to the current invention, a titrant-generating electrode is required, while the current invention starts from a measuring fluid. It is important that the operation of the measurement also differs. In WO2017223365A1, the alkalinity measurement is related to the generation of hydronium using the titrant-generating electrode, which changes the acidity. The generation is aimed at reaching a predetermined end point of electrochemical titration, i.e. to realize a titration to equivalence point. The amount of current or charge consumed, or the amount of hydronium ions generated, is indicative of the alkalinity. This measuring principle is therefore based on a correlation, in which generation and detection are correlated. In the alkalinity measurement according to the present invention there is no such complex correlation, and the same amount of acid is used as a starting point, so that the mixture of measuring fluid and steel is directly a ready-to-measure solution. This benefits the simplicity and cost price, can lead to faster and/or energy-saving measurement, and can also lead to a more robust implementation.

By avoiding electrochemical titration, the well-known problems of using electrodes (e.g., due to contact resistance) are avoided. Also, the consumption of

10 BE2023/5119 measuring fluid easy to predict, because a metered amount of measuring fluid is administered each time. In example embodiments this is always the same amount.

In exemplary embodiments, the cycle of switching between the first and second states in the domain of swimming pools consists of a short-term alkalinity measurement alternating with a long period (e.g. 2-4 hours) of continuous pH measurement. In other exemplary embodiments, the alkalinity measurement is switched rapidly, for example every three or five or ten minutes between an alkalinity measurement for a period of the given duration and a pH measurement for a period of the same duration.

The prior art mentions the use of two electrode sets for the measurement of alkalinity, see for example WO2017223365A1. In contrast to the present invention, the alkalinity measurement is based there exclusively on coulometric titration. The first electrode set monitors the pH and the second electrode set provides the coulometric titration. In the example of WO2017223365A1, the second set relates to a hydronium-generating electrode and a hydroxide ion-generating electrode, whereby the role can be switched (by reversing the current sense). The pH detection electrode and the hydronium (or hydroxide) producing electrode(s) can be called working electrodes. Each of the electrode sets also includes at least one reference electrode and at least one first counter electrode, whereby the set can share the same reference and counter electrodes. Despite this sharing of an electrode, such a setup requires a whole series of electrodes according to WO2017223365A1, which can make it expensive and cumbersome to implement. Moreover, this can be slow, because an equivalence point has to be worked towards, where the power consumed during the titration is a measure of the alkalinity. The current invention offers an alternative by working with only a pH sensor, so that, for example, an electrode pair can suffice. Also, the solution obtained by mixing the measuring fluid and sample is "ready for measurement", so that it is not necessary to work towards an equivalence point during the measurement.

In embodiments, the known mixing ratio mentioned is related to a mechanically coupled volumetric ratio between the flow rate of the first pump 10 and the flow rate of the second pump 70. In embodiments with a common pump body, it can be, for example, a diaphragm pump or a hose pump; however, it can be any other way. It can also be, for example, a fixed transmission ratio, for example with pulleys and/or gears, where the actuation of one pump is, for example, done by transmitting the revolution of the shaft of the other pump. Such a mechanical coupling can be advantageous because it exhibits predictable behavior, and does not require separate monitoring of the mixing ratio. It can also be advantageous that it is the ratio that is coupled, and not the individual volumes (or, equivalently, flow rates). After all, when holding or controlling individual volumes, there are two degrees of freedom, while the invention makes it possible to take only the mixing ratio into account, i.e. one degree of freedom,

11 BE2023/5119 without being too sensitive to the precise volume of the ready-to-measure solution. If this mixing ratio is also achieved by mechanical coupling, it can advantageously be constant over time, or at least exhibit predictable behaviour, whereby a dependency on, for example, temperature can be overcome by software (e.g., in the calculations made by the control unit). Such predictability allows the mixing ratio of the first and second pump to be determined during calibration, and then taken into account when further calibrating the device. The mixing ratio obtained in this way can, for example, be used as input when calibrating the control unit.

In other examples, further calibration of the control unit can even be avoided, by adjusting the dilution of the acid present in the measuring fluid. The latter can even be done completely manually, which is convenient and fast, and therefore economical.

In embodiments, said transmission of revolutions relates to: pulleys, said transmission ratio relating to a ratio of respective diameters of said pulleys; and/or gears, said transmission ratio relating to a ratio of respective number of teeth of said gears.

In embodiments with pulleys, the transmission is preferably associated with at least one drive belt. In embodiments, the drive belt is associated with a smooth belt or V-belt, and the pulleys preferably comprise a V-shaped cross-section on their outer surface for guiding the belt. In embodiments, the drive belt is, either alternatively or additionally, associated with a toothed belt, and the pulleys preferably comprise an external toothing on their outer surface which is adapted for a slip-free connection between the outer surface and the toothed belt.

In embodiments, the transmission involves both gears and pulleys.

In embodiments, the device comprises an outlet connected to said chamber, configured to drain the ready-to-measure solution to the water in a closed loop.

In embodiments, the device comprises a mixing coil provided between said first pump and second pump and said chamber for mixing said measuring fluid and said sample of water to form said ready-to-measure solution.

In embodiments, the device comprises a temperature sensor for measuring the temperature of said ready-to-measure solution; said control unit being further configured to measure the temperature of said ready-to-measure solution by means of the temperature sensor and to convert said measurement of acidity thereon to obtain a

12 BE2023/5119 equivalent pH, whereby said bijective relationship between acidity and alkalinity is applied to said equivalent pH for said measurement of alkalinity.

In embodiments, the device comprises means for switching between a first state and a second state, said first state corresponding to measuring alkalinity of the water by means of said pH sensor; and said second state corresponding to measuring acidity of the water by means of the same pH sensor.

In embodiments, said means for switching are associated with a valve, preferably a three-way valve; said first state being associated with actuation of said first pump and second pump and with maintaining, by means of said valve, an incoming flow of water without passage through the chamber, for said measuring of alkalinity by means of the pH sensor; and said second state being associated with non-actuation of said first pump and second pump and with directing, by means of said valve, the incoming flow of water through the chamber, for said measuring of acidity by means of the pH sensor.

In embodiments, said means for switching is associated with an incoming flow pump; said first state being associated with actuation of said first pump and second pump and with non-actuation of the incoming flow pump, for said measuring alkalinity by means of the pH sensor; and said second state being associated with non-actuation of said first pump and second pump and with actuation of the incoming flow pump for directing the incoming flow of water through the chamber, for said measuring acidity by means of the pH sensor.

In embodiments, the device comprises an alka-plus pump, i.e., a dosing pump for automatically adding, based on said measurement of alkalinity of the water, an alkalinity-increasing liquid to the water. In embodiments, the alka-plus pump is used to increase the alkalinity. In embodiments, the alka-plus pump is used, alternatively or additionally, to increase the acidity of the water, wherein the alkalinity-increasing liquid is related to a base such as bicarbonate.

In doing so, the influence of alkalinity-increasing liquid on both alkalinity and acidity is preferably taken into account, preferably by converting it based on the index.

In embodiments, the control unit is configured to correct at least one of alkalinity and acidity of the water, preferably both alkalinity and acidity, by a selection of adding the alkalinity increasing fluid and/or the acidity decreasing fluid.

13 BE2023/5119 fluid. For example, this relates to correcting alkalinity using the acidity reducing fluid. In another example, this relates to correcting acidity using the alkalinity increasing fluid. In yet another example, this relates to correcting acidity using both the acidity reducing fluid and the alkalinity increasing fluid. In yet another example, this relates to correcting alkalinity using both the acidity reducing fluid and the alkalinity increasing fluid. This may have the advantage of allowing for a more accurate correction.

In embodiments, the device comprises a pH-min pump for automatically adding, based on one of said acidity measurements, an acidity-reducing liquid to the water, said acidity measurement being related to: said acidity measurement of said ready-to-measure solution; and/or if available, said acidity measurement of the water.

In embodiments where only the acidity of the ready-to-measure solution is measured and not the acidity of the water itself, the addition is based on the alkalinity measurement, which is determined based on at least the acidity measurement of the ready-to-measure solution. In embodiments, the pH-min pump is used to reduce the acidity of the water.

In embodiments, the pH-min pump is used, alternatively or additionally, to reduce alkalinity. In doing so, the influence of acidity-reducing fluid on both alkalinity and acidity is preferably taken into account, preferably via conversion based on the index.

In embodiments, the device comprises a salt-plus pump for automatically adding, based on said alkalinity measurement and/or based on one of said acidity measurements, a salinity-increasing liquid to the water. In embodiments where only the acidity of the ready-to-measure solution is measured and not the acidity of the water itself, the addition is based on the alkalinity measurement, which is determined based on at least the acidity measurement of the ready-to-measure solution.

In embodiments, the apparatus comprises said alka-plus pump and said pH-minus pump; wherein said control unit is further configured to, based on a repeated performance of said measurement of water alkalinity and water acidity, perform a correction with respect to the water, wherein the correction comprises both the possibility of adding said alkalinity-enhancing fluid by means of said alka-plus pump and the possibility of adding said acidity-reducing fluid by means of said pH-minus pump and, preferably, further comprising the possibility of adding said salinity-enhancing fluid by means of said salt-plus pump.

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In embodiments, said adding of alkalinity-increasing fluid is done as a priority over at least said adding of acidity-reducing fluid in order to allow the correction to proceed gradually.

In embodiments, said correction comprises the possibility of adding said salinity-increasing fluid by means of said salt-plus pump, and wherein said adding of salinity-increasing fluid is done as a priority over at least said adding of acidity-reducing fluid in order to allow the correction to proceed gradually.

In embodiments, said mixing is accomplished by means of a first pump for said measuring fluid and a second pump for said sample, the first and second pumps being mechanically coupled according to a volumetric ratio between the flow rate of the first pump and the flow rate of the second pump.

In embodiments, said steps are preceded by the steps of: calibrating the pH sensor with at least two pH calibration solutions which correspond to a pH-related bijective calibration curve which relates pH and a quantity measured with said pH sensor, preferably the voltage between a pair of electrodes belonging to the pH sensor; calibrating with respect to alkalinity with at least two alkalinity calibration solutions which correspond to said bijective relationship between acidity of the ready-to-measure solution and alkalinity of the water.

In embodiments, said alkalinity enhancing fluid comprises carbonate, CO:%, and/or bicarbonate, HCO:.

In embodiments, said alkalinity-enhancing liquid comprises said carbonate or bicarbonate at a concentration greater than 0.2 M.

In embodiments, said alkalinity increasing fluid comprises potassium, preferably potassium derived from dissolving potassium carbonate, K2CO3, and/or potassium bicarbonate, KHCO:3, in water, to obtain the alkalinity increasing fluid.

In embodiments, said alkalinity-enhancing liquid comprises sodium, preferably sodium derived from dissolving sodium carbonate, Na2CO3, in water, and/or sodium bicarbonate,

NaHCO:3, to obtain the alkalinity increasing liquid.

In embodiments, said automated pumping of respective samples of water and of measuring fluid and measuring of acidity of said ready-to-measure solution and

15 BE2023/5119 alkalinity of the water is repeated periodically, whereby said correction is carried out by adding alkalinity-increasing liquid when a difference between a target value for alkalinity and the measured alkalinity exceeds a certain threshold.

In embodiments, said dosage for correction of alkalinity of the water with addition of alkalinity increasing liquid corresponds to a corrected value which is not higher than said target value, preferably lower than said target value.

In embodiments, said measuring of said acidity is done by means of said pH sensor on the basis of a bijective relationship between acidity of the ready-to-measure solution and alkalinity of the water which is valid in a working range comprising said known acidity and said measurement of acidity.

In embodiments, said dilute acid belonging to said measuring fluid relates to bicarboxylic acid, preferably adipic acid, CeH1004.

In embodiments, said bicarboxylic acid is adipic acid, said dilution preferably being between 0.01 and 10 g/l, more preferably between 0.1 and 1 g/l, most preferably 0.2 or 0.3 or 0.4 or 0.5 or 0.6 or 0.7 or 0.8 g/l.

In embodiments, said known mixing ratio is between 1:10 and 10:1, preferably between 1:5 and 5:1, more preferably between 1:4 and 4:1 or between 1:3 and 3:1 or between 1:2 and 2:1, most preferably between 2:3 and 3:2 or between 3:4 and 4:3.

In embodiments, the method further comprises the step of: measuring temperature of said ready-to-measure solution by means of a temperature sensor; wherein said measurement of acidity of said ready-to-measure solution is converted based on said temperature measurement to obtain an equivalent pH, wherein said bijective relationship between acidity and alkalinity is applied to said equivalent pH for said measurement of alkalinity.

In embodiments, the method further comprises the step of: switching between a first state and a second state, said first state corresponding to measuring alkalinity of the water by said pH sensor; and said second state corresponding to measuring acidity of the water by the same pH sensor, said correcting alkalinity being based on both said measurement of alkalinity of the water and said measurement of acidity of the water.

16 BE2023/5119

In embodiments, the method further comprises the step of: performing, based on both said measurement of alkalinity of the water and said measurement of acidity of the water, a correction with respect to the acidity of the water, by automated and metered addition of an acidity-reducing liquid by means of a pH-min pump.

In embodiments, said water is the water of a swimming pool.

In embodiments, said water balance index concerns the LSI.

In embodiments, said criterion is related to a warning interval, whereby if the calculated index is not within said interval, an instruction being a warning to an operator is generated.

In embodiments, said criterion relates to an interval for correction, wherein if the calculated index is not within said interval, an instruction for correction is generated, and wherein said method further comprises at least one of the following two steps: if said instruction for correction comprises increasing alkalinity, the automated and metered addition of an alkalinity-increasing liquid to the water by means of an alka-plus pump; and/or if said instruction for correction comprises decreasing acidity, the automated and metered addition of an acidity-reducing liquid to the water by means of a pH-minus pump. Preferably, the method comprises both of said two steps.

In embodiments, said measuring of said acidity is done by means of said pH sensor on the basis of a bijective relationship between acidity of the ready-to-measure solution and alkalinity of the water which is valid in a working range comprising said known acidity and said measurement of acidity.

In embodiments, said active measuring involves mixing a measuring fluid and a sample of water according to a known mixing ratio, the measuring fluid comprising a known dilution of an acid corresponding to a known acidity, to obtain the ready-to-measure solution.

In embodiments, said known mixing ratio is between 1:10 and 10:1, preferably between 1:5 and 5:1, more preferably between 1:4 and 4:1 or between 1:3 and 3:1 or between 1:2 and 2:1, most preferably between 2:3 and 3:2 or between 3:4 and 4:3.

In embodiments, the method further comprises the step of:

17 BE2023/5119 measuring the temperature of said ready-to-measure solution by means of a temperature sensor; wherein said measurement of acidity of said ready-to-measure solution is converted on the basis of said temperature measurement to obtain an equivalent pH, wherein said bijective relationship between acidity and alkalinity is applied to said equivalent pH for said measurement of alkalinity.

In embodiments, said method further comprises the step of: repeatedly switching between the first state and the second state; wherein said steps are repeatedly performed based on repeated measurement of alkalinity of the water, during the first state, and of acidity of the water, during the second state.

In embodiments, said criterion is related to an interval for correction, whereby if the calculated index is not within said interval, an instruction for correction is generated, and whereby said method comprises the following step: if said instruction for correction comprises increasing the salinity, the automated and metered addition of a salinity-increasing liquid to the water by means of a salt-plus pump.

In embodiments, said adding of alkalinity-increasing fluid is done as a priority over at least said adding of acidity-reducing fluid in order to allow the correction to proceed gradually.

In embodiments, said method further comprises the following step: if said instruction for correction comprises increasing the salinity, the automated and metered addition of said salinity-increasing liquid to the water by means of said salt-plus pump; wherein said adding of salinity-increasing liquid takes place as a priority over at least said adding of acidity-reducing liquid in order to allow the correction to proceed gradually.

In embodiments, said device regulates the quality of the water with the aid of a ready-to-measure solution, and said swimming pool comprises a further pump which realizes an incoming flow through said device for draining the ready-to-measure solution to the swimming pool shell.

In preferred embodiments, the dilute acid present in the measuring fluid is related to adipic acid or, equivalently, hexanedioic acid. An advantage of this can be the ready availability of this acid, with a large global production annually, which is related to the usefulness of this

18 BE2023/5119 acid in certain nylon production processes. A further advantage is the non-toxic nature, as evidenced by the E number for adipic acid as a food additive, E355. The non-toxic nature is advantageous for general applications, and is particularly advantageous for use in swimming pool water.

In preferred embodiments, the Langelier saturation index or Langelier saturation index (LSI) is used as an index for water quality or water balance. The LSI is a measure for saturation of calcium carbonate (CaCO:). A too low LSI value is related to corrosion (corosive), a too high value to scale formation. Perfect saturation corresponds to 0.00 LSI, and an acceptable range of LSI is for example a value between -0.30 and +0.30 LSI. By keeping the water quality within the acceptable range, both corrosion and scale formation can be prevented as much as possible.

The LSI is a function of a set of different parameters, for example five or six, and provides a holistic picture of the water balance, where the influence of the different parameters is calculated into a single value. In this way, the LSI offers a pragmatic tool for monitoring water quality, as a predictor of corrosion or scale deposits. This is superior to the current method in the state of the art, to monitor only certain intervals, where the pH should be between 7.2 and 7.8, preferably between 7.4 and 7.6, and/or where Calcium should be kept in the range 200-400 ppm, or the total alkalinity should be kept between 80 and 120 ppm. Monitoring such intervals is a complex challenge, which can be disadvantageous.

Furthermore, monitoring intervals only provides an incomplete picture, which can lead to poor results. Corrosion and/or limescale deposits are not determined by the intervals separately, but by the values in combination. It is therefore possible that certain combinations of values are all in their respective intervals, but corrosion or limescale deposits still occur.

In implementations, the LSI is a function of a set of two or more different parameters of: pH, water temperature (T) (expressed in °C), calcium hardness (CH) (expressed in ppm), carbonate alkalinity (CA), cyuranic acid / stabilizer (CYA) (expressed in ppm), total alkalinity (ALKA, expressed in ppm), total dissolved solids (TDS) (expressed in ppm), and electrical conductivity (EC) (expressed in ppm).

In six-parameter versions, the index, preferably the LSI, is related to, for example, pH, water temperature (T) (expressed in °C), calcium hardness (CH) (expressed in ppm), carbonate alkalinity (CA), cyuranic acid / stabilizer (CYA) (expressed in ppm), and total dissolved solids (TDS) (expressed in ppm).

19 BE2023/5119

In five-parameter versions, the index, preferably the LSI, is related to, for example, pH, water temperature (T) (expressed in °C), calcium hardness (CH) (expressed in ppm), total alkalinity (ALKA, expressed in ppm), and electrical conductivity (EC) (expressed in ppm). Here, total alkalinity (ALKA) is related to carbonate alkalinity (CA), cyanuric acid/stabilizer (CYA), and pH. Electrical conductivity (EC) is related to total dissolved solids (TDS). The conductivity measurement is performed with an electronic sensor in micro/milli-Siemens per centimeter or ppm, preferably in ppm. Conductivity increases with increasing ion content, meaning that in most cases a simple relationship exists with a TDS measurement, for example with a conversion factor CF of 1 ppm = CFuS/cm, where CF is for example 2.

Conductivity is temperature sensitive and is typically standardized to 25°C.

In example embodiments, the LSI is related to the following formula:

LSI= (pH) + (-0.00014554*(T in°C)*(T in°C) + 0.02808929*(T in°C) + 0.00408167) + (0.43475046*In(Calcium hardness in ppm) - 0.39514691) + (0.43475046*In(ALKA in ppm) + 0.00485309) - (-0.0000000100*(EC in ppm)*(EC in ppm) + 0.000122*(EC in ppm) - 12.08)

In variants, the LSI is expressed in °iW, which is a scaled version of the LSI, according to the conversion: °IW= 5/3*LSI + 100.

The professional takes into account possible small deviations and variants in the appearance of the LSI function, both in terms of the coefficients and the precise nature of proportionality (linear vs. non-linear, logarithm or other elementary function, etc.).

Embodiments with deviations and variants with regard to the form of the LSI function remain fully within the scope of the invention.

In preferred embodiment, water balance control is done according to threshold values. In exemplary embodiments, this is related to one or more, preferably all, of the following values: - LSI

Maximum: M1 (Scale forming)

High warning level: W1

Ideal: 0

Low warning level: w1

Minimum: m1 (corrosive) - SiW

Maximum: M2 (Scale forming)

High warning level: W2

Ideal: 100

20 BE2023/5119

Low warning level: w2

Minimum: m2 (corrosive)

Preferably, M1 and -m1 are in the range 0.2-0.4, more preferably in the range 0.25-0.35, and most preferably equal to 0.3. Preferably, M1=-m1.

Preferably, W1 and -w1 are in the range 0.05-0.3, more preferably in the range 0.10-0.20, and most preferably equal to 0.15. Preferably, W1=-w1.

Preferably, M2 is in the range 100-250, more preferably in the range 120-180, and most preferably M2 is equal to 150. Preferably, m2 is in the range 0-100, more preferably in the range 25-75, and most preferably m2 is equal to 50. Preferably, M2-100=100-m2.

Preferably, W2 is in the range 100-150, more preferably in the range 115-135, and most preferably W2 is equal to 125. Preferably, w2 is in the range 50-100, more preferably in the range 65-85, and most preferably w2 is equal to 75. Preferably, W2-100=100-w2.

In embodiments, monitoring water balance, e.g. via the LSI, relates to performing a correction with respect to the water. In the present invention, this correction preferably relates to the addition of alkalinity-enhancing fluid. This is in contrast to the approach in the prior art, such as in, for example, IN201911044176A and FR3005742A1.

In IN201911044176A, monitoring of the LSI is described, but corrections are only performed with chlorine, algaecides and stabilizers. As a result, it is not possible to directly compensate for low alkalinity in methods according to IN201911044176A, which means that in many cases the LSI cannot be brought back into a desired range.

In contrast, the present invention, in embodiments related to water balance monitoring, offers the possibility of direct and automated correction of alkalinity, using the alkalinity-increasing fluid. In FR3005742A1, a "TAC+ product" (TAC: titre alkalimétrique complet) is mentioned, but precise correction is not possible for various reasons. In methods according to FR3005742A1, the LSI is not used, and only intervals are used. Furthermore, alkalinity measurement according to FR3005742A1 is carried out via observation of CO2 concentration, which is complex and/or inaccurate.

Alkalinity increase may be associated with one or more of bicarbonates (HCO:) and carbonates (COs*), hydroxides (OH), sulfides (S7), silicates (SiOa4*), phosphates (POa43), and borates (BO3%). In embodiments, the alkalinity increase fluid is associated with bicarbonates (HCO+) and/or carbonates (COs?), preferably with bicarbonates.

21 BE2023/5119

According to further aspects of the invention, which are not limiting, the invention relates to the following articles 1-26.

Article 1. Device for measuring alkalinity of water (7), preferably swimming pool water, comprising: a first pump (10) for automatically pumping a measuring fluid (1) comprising a known dilution of an acid corresponding to a known acidity; a second pump (70) for automatically pumping a sample of the water (7); a chamber (6) connected to said first (10) and second pump (70), for receiving a ready-to-measure solution comprising said sample and said measuring fluid (1) according to a known mixing ratio, the chamber (6) comprising a pH sensor (8) for measuring acidity; a control unit connected to said pH sensor (8); said control unit being configured to measure said alkalinity based on a measurement of acidity of said ready-to-measure solution by said pH sensor (8) and based on a bijective relationship between acidity of the ready-to-measure solution and alkalinity of the water (7) valid in a working range comprising said known acidity and said measurement of acidity.

Article 2. Device according to Article 1, wherein said known mixing ratio is related to a mechanically coupled volumetric ratio between the flow rate of the first pump (10) and the flow rate of the second pump (70).

Article 3. Device according to Article 2, wherein said first (10) and second pump (70) belong to one and the same pumping device (100), preferably a diaphragm pump or hose pump, wherein said mechanically coupled volumetric ratio is achieved by means of a joint pump body.

Article 4. Device according to Article 2, in which said second pump (70) is actuated by means of a transmission of revolution of a shaft of the first pump (10) according to a fixed transmission ratio, or vice versa, said mechanically coupled volumetric ratio being achieved by means of said fixed transmission ratio.

Article 5. Device according to Article 4, wherein said transmission of revolutions is related to: pulleys, wherein said transmission ratio is related to a ratio of respective diameters of said pulleys; and/or gears, wherein said transmission ratio is related to a ratio of respective number of teeth of said gears.

22 BE2023/5119

Article 6. Device according to Articles 1-5, wherein said known mixing ratio is related to the pumping of a known volume of said measuring liquid, with said first pump (10), and/or a known volume of a sample of said water (7), with said second pump (70).

Article 7. Device according to Articles 1-6, wherein said pH sensor (8) is associated with an electrode pair (8a, 8b) comprising a first (8a) and second (8b) electrode.

Article 8. Apparatus according to Articles 1-7, further comprising: an outlet (2") connected to said chamber, configured to discharge the ready-to-measure solution to the water according to a closed circuit (2).

Article 9. Apparatus according to Articles 1-8, further comprising: a mixing coil (61) provided between said first pump (10) and second pump (70) and said chamber for mixing said measuring fluid (1) and said sample of water (7) to form said ready-to-measure solution.

Article 10. Apparatus according to Articles 1-9, further comprising: a temperature sensor for measuring the temperature of said ready-to-measure solution; said control unit being further configured to measure the temperature of said ready-to-measure solution by means of the temperature sensor and to convert said acidity measurement thereon to obtain an equivalent pH, said bijective relationship between acidity and alkalinity being applied to said equivalent pH for said alkalinity measurement.

Article 11. Apparatus (300a, 300b) according to Articles 1-10, further comprising means for switching between a first state (101) and a second state (301, 701), said first state (101) corresponding to measuring alkalinity of the water (7) by means of said pH sensor (8); and said second state (301, 701) corresponding to measuring acidity of the water (7) by means of the same pH sensor (8).

Article 12. Apparatus (300a) according to Article 11, wherein said means for switching are associated with a valve (3), preferably a three-way valve; wherein said first state (101) is associated with actuation of said first pump (10) and second pump (70) and with the maintenance, by means of said valve (3), of an incoming flow (700") of water (7) without passing through the chamber (6), for said measuring of alkalinity by means of the pH sensor; and wherein said second state (301) is associated with non-actuation of said first pump (10) and second pump (70) and with the guiding, by means of said valve (3), of the

23 BE2023/5119 incoming flow (700') of water (7) through the chamber (6), for said measurement of acidity by means of the pH sensor.

Article 13. Apparatus (300b) according to Article 11, wherein said means for switching are associated with an incoming flow pump (700); wherein said first state (101) is associated with actuation of said first pump (10) and second pump (70) and with non-actuation of the incoming flow pump (700), for said measuring alkalinity by means of the pH sensor; and wherein said second state (701) is associated with non-actuation of said first pump (10) and second pump (70) and with activation of the incoming flow pump (700) for directing the incoming flow (700") of water (7) through the chamber (6), for said measuring acidity by means of the pH sensor.

Article 14. Device according to Articles 1-13, further comprising an alka-plus pump (40) for automatically adding, on the basis of said measurement of alkalinity of the water (7), an alkalinity-increasing liquid (4) to the water (7).

Article 15. Apparatus according to Articles 1-14, further comprising a pH-min pump (50) for automatically adding, on the basis of one of said acidity measurements, an acidity-reducing liquid (5) to the water (7), said acidity measurement being related to: said acidity measurement of said ready-to-measure solution; and/or if available, said acidity measurement of the water (7).

Article 16. Device according to Articles 1-15, further comprising a salt-plus pump for automatically adding, on the basis of said alkalinity measurement and/or on the basis of one of said acidity measurements, a salinity-increasing liquid to the water (7).

Article 17. Apparatus according to Articles 11-16, comprising said alka-plus pump (40) and said pH-minus pump (50); said control unit being further configured to, based on a repeated performance of said measurement of alkalinity of the water and said acidity of the water, perform a correction with respect to the water (7), the correction comprising both the possibility of adding said alkalinity increasing fluid (4) by means of said alka-plus pump (40) and the possibility of adding said acidity decreasing fluid (5) by means of said pH-minus pump (50) and, preferably, further comprising the possibility of adding said salt content increasing fluid by means of said salt-plus pump.

24 BE2023/5119

Article 18. Installation according to Article 17, in which the said addition of alkalinity-increasing liquid (4) takes place as a priority over at least the said addition of acidity-reducing liquid (5) in order to allow the correction to proceed gradually.

Article 19. Installation according to Articles 17-18, wherein said correction includes the possibility of adding said salinity-increasing liquid by means of said salt-plus pump, and wherein said adding of salinity-increasing liquid takes place as a priority over at least said adding of acidity-reducing liquid (5) in order to allow the correction to proceed gradually.

Article 20. System comprising a device according to Articles 1-19, a source of measuring fluid (1) and a set of connections (2) for measuring alkalinity according to a closed circuit (2) with inlet (2") connected to said second pump (70), and outlet (2") connected to said chamber (6).

Article 21. Swimming pool comprising said system according to Article 20 comprising said inlet (2) and outlet (2") and a swimming pool shell comprising said water (7) connected to said system by means of said inlet (2") and outlet (2").

Article 22. Swimming pool according to Article 21, wherein said system carries out alkalinity measurements with respect to a ready-to-measure solution and wherein said swimming pool comprises a further pump (90) which produces an incoming flow (700") through said system for draining the ready-to-measure solution to the swimming pool shell.

Article 23. Method for measuring the alkalinity of water (7), preferably swimming pool water, comprising the steps of: mixing a measuring fluid (1) and a sample of water (7) according to a known mixing ratio, the measuring fluid (1) comprising a known dilution of an acid corresponding to a known acidity, to obtain a ready-to-measure solution; performing, with respect to said ready-to-measure solution, a measurement of acidity by means of a pH sensor (8); measuring said alkalinity of the water (7), on the basis of said measurement of acidity and on the basis of a bijective relationship between acidity and alkalinity which is valid in a working area comprising said known acidity and said measured acidity.

Article 24. Method according to Article 23, wherein said mixing is carried out by means of a first pump (10) for said measuring liquid and a second pump (70) for said steel, the first and second pumps being mechanically coupled according to a volumetric ratio between the flow rate of the first pump (10) and the flow rate of the second pump.

25 BE2023/5119

Article 25. Method according to Articles 23-24, wherein said steps are preceded by the steps of: calibrating the pH sensor (8) with at least two pH calibration solutions which correspond to a pH-related bijective calibration curve which relates pH and a quantity measured with said pH sensor, preferably the voltage between a pair of electrodes (8a, 8b) belonging to the pH sensor (8); calibrating with respect to alkalinity with at least two alkalinity calibration solutions which correspond to said bijective relationship between acidity of the ready-to-measure solution and alkalinity of the water (7).

Article 26. Use of a pumping device (100) for measuring alkalinity, by pumping a sample of water (7) and a measuring liquid (1) according to a mixing ratio which is known by means of provisions belonging to the pumping device (100) for realising a mechanically coupled volumetric ratio.

According to further aspects of the invention, which are not limiting, the invention relates to the following clauses 1-17.

Clause 1. Method for correcting the alkalinity of water (7), preferably swimming pool water, comprising the steps of: automatically pumping a sample of said water (7) and a measuring liquid (1) comprising a known dilution of an acid corresponding to a known degree of acidity, according to a known mixing ratio, to obtain a ready-to-measure solution; measuring the degree of acidity of said ready-to-measure solution by means of a pH sensor (8); measuring, on the basis of said degree of acidity, said alkalinity of the water (7); carrying out, on the basis of said measurement, said correction with regard to the alkalinity of the water (7), by automated and metered addition of an alkalinity-increasing liquid (4) by means of an alka-plus pump (40).

Clause 2. Method according to clause 1, wherein said alkalinity increasing liquid (4) comprises carbonate, CO”, and/or bicarbonate, HCO:.

Clause 3. Method according to clause 2, wherein said alkalinity increasing liquid (4) comprises said carbonate or bicarbonate at a concentration greater than 0.2 M.

26 BE2023/5119

Clause 4. Method according to clause 3, wherein said alkalinity increasing liquid (4) comprises potassium, preferably potassium derived from dissolving potassium carbonate, KCO3, in water, to obtain the alkalinity increasing liquid.

Clause 5. Method according to clause 3, wherein said alkalinity increasing liquid (4) comprises sodium, preferably sodium derived from dissolving sodium carbonate, Na2CO3, and/or sodium bicarbonate, NaHCO3, in water, to obtain the alkalinity increasing liquid.

Clause 6. Method according to clauses 1-5, wherein said automated pumping of respective samples of water (7) and of measuring fluid (1) and measuring acidity of said ready-to-measure solution and alkalinity of the water (7) is repeated periodically, and wherein said carrying out of correction by addition of alkalinity-increasing fluid (4) occurs when a difference between a target value for alkalinity and the measured alkalinity exceeds a certain threshold.

Clause 7. Method according to clause 6, wherein said dosage for correction of alkalinity of the water (7) with addition of alkalinity increasing liquid (4) corresponds to a corrected value which is not higher than said target value, preferably lower than said target value.

Clause 8. Method according to clauses 1-7, wherein said measuring of said acidity by means of said pH sensor (8) is done on the basis of a bijective relationship between acidity of the ready-to-measure solution and alkalinity of the water (7) which is valid in a working area comprising said known acidity and said measurement of acidity.

Clause 9. Method according to clauses 1-8, wherein said dilute acid belonging to said measuring fluid (1) is related to bicarboxylic acid, preferably adipic acid, C6H10O4.

Clause 10. A method according to clause 9, wherein said bicarboxylic acid is adipic acid, and wherein said dilution is preferably between 0.01 and 10 g/l, more preferably between 0.1 and 1 g/l, most preferably 0.2 or 0.3 or 0.4 or 0.5 or 0.6 or 0.7 or 0.8 g/l.

Clause 11. Method according to clauses 1-10, wherein said known mixing ratio is between 1:10 and 10:1, preferably between 1:5 and 5:1, more preferably between 1:4 and 4:1 or between 1:3 and 3:1 or between 1:2 and 2:1, most preferably between 2:3 and 3:2 or between 3:4 and 4:3.

Clause 12. Method according to clauses 8-11, further comprising the step of: measuring the temperature of said ready-to-measure solution by means of a temperature sensor;

27 BE2023/5119 wherein said measurement of acidity of said ready-to-measure solution is converted on the basis of said temperature measurement to obtain an equivalent pH, wherein said bijective relationship between acidity and alkalinity is applied to said equivalent pH for said measurement of alkalinity.

Clause 13. The method of clauses 1-12, further comprising the step of: switching between a first state (101) and a second state (301, 701), said first state (101) corresponding to measuring alkalinity of the water (7) by means of said pH sensor (8); and said second state (301, 701) corresponding to measuring acidity of the water (7) by means of the same pH sensor (8); said correcting alkalinity being based on both said measurement of alkalinity of the water (7) and said measurement of acidity of the water (7).

Clause 14. Method according to clause 13, further comprising the step of: performing, on the basis of both said measurement of alkalinity of the water (7) and said measurement of acidity of the water (7), a correction with respect to the acidity of the water (7), by automated and metered addition of an acidity reducing liquid (5) by means of a pH-min pump (50).

Clause 15. Method according to clauses 1-14, where said water (7) concerns the water of a swimming pool.

Clause 16. Use of a combination of a measuring fluid (1) comprising a known dilution of an acid corresponding to a known acidity comprising adipic acid and an alkalinity increasing fluid (4) comprising a carbonate or bicarbonate for the automatic and fluid-based correction of alkalinity of a swimming pool, preferably with a method according to clauses 1-15.

Clause 17. Kit for correcting alkalinity of a swimming pool, comprising: a measuring fluid (1) comprising a known dilution of an acid corresponding to a known acidity including adipic acid; and an alkalinity increasing fluid (4) comprising a carbonate or bicarbonate; said alkalinity increasing fluid (4) comprising carbonate, CO:%, and/or bicarbonate,

HCO:, comprises; and wherein said alkalinity increasing liquid (4) comprises said carbonate or bicarbonate at a concentration greater than 0.2 M.

In the following, the invention is described by means of non-limiting examples which illustrate the invention, and which are not intended or should be construed to limit the scope of the invention.

28 BE2023/5119

EXAMPLES

EXAMPLE 1: SAMPLE IMPLEMENTATION

Figure 1 shows a schematic example of an apparatus according to the invention, where the application is a swimming pool. The mixing coil is missing, since it is not essential for the operation of the apparatus according to the invention.

Figures 2A-2B show exemplary embodiments of devices according to the invention, in which a mixing coil 61 is present. This can have the advantage that the mixing of measuring fluid 1 and sample of the water 7 is enhanced, resulting in an even more homogeneous measurement-ready solution.

In this respect, Figure 2A shows an exemplary embodiment of the device 200a without an incoming flow pump, and Figure 2B shows an exemplary embodiment of the device 200b with an incoming flow pump 700. Both embodiments 200a and 200b are largely equivalent in their operation, and the choice between the two is preferably determined by what is already present in the pool.

In concrete terms, the swimming pool installation, or equivalently the swimming pool, in example embodiment 2004 already comprises a further pump 90 which realises a further flow 9, which in turn realises an incoming flow 700'. In this way, in exemplary embodiment 200a, there is no need for an incoming flow pump, since flow 700" is already strong enough to enable proper functioning of the invention. It is irrelevant whether this additional pump 90 was already present prior to installation of the device or not. After all, it is conceivable that pump 90 is provided at the same time as installation of device 200a, or is replaced by a pump with sufficient power, such that flow 700' is sufficiently strong. In addition, pump 90 can realize various functions in the swimming pool, which can be related to further (temperature) distribution of the water and/or cleaning of the water and/or refreshing of the water, and the usefulness of pump 90 need not be limited to merely maintaining incoming flow 700".

Figure 2B shows an exemplary embodiment of the device 200b with incoming flow pump 700,

In this example, embodiment 200b does not require an external pump to generate incoming flow 700', as this is accomplished entirely by incoming flow pump 700. In still other embodiments (not shown), an external pump 90 is provided to contribute to flow 700', and incoming flow pump 700 merely increases, decreases, or smooths flow 700', which may be more power efficient and/or allow for more accurate operation of the device.

A further difference between Figure 2A and 2B is that Figure 2A shows the pool with water 7, while Figure 2B shows the inlet 2' and outlet 2" of the device. This is

29 BE2023/5119 not to show a difference between versions 200a and 200b but merely to illustrate a preferred version with the possibility of coupling and uncoupling the devices, which is preferably possible with detachable connections at the inlet and outlet. Detachable connections can be advantageous during installation and/or repair and/or maintenance and/or calibration.

Figures 1, 2A-2B illustrate all embodiments of the device. The device comprises: a first pump 10 for automatically pumping a measuring fluid 1 comprising a known dilution of an acid corresponding to a known degree of acidity; a second pump 70 for automatically pumping a sample of water 7; a chamber 6 connected to said first 10 and second pump 70, for receiving a ready-to-measure solution comprising said sample and said measuring fluid 1 according to a known mixing ratio, the chamber 6 comprising a pH sensor 8 for measuring degree of acidity; and a control unit connected to said pH sensor 8.

The control unit (not shown) is configured to measure said alkalinity on the basis of a measurement of acidity of said ready-to-measure solution by means of said pH sensor 8 and on the basis of a bijective relationship between acidity of the ready-to-measure solution and alkalinity of the water 7 which is valid in a working range comprising said known acidity and said measurement of acidity. This bijective relationship can be determined, for example, on the basis of what is described in example 4.

Figures 1, 2A-2B illustrate not only the device but also the system to which the device belongs. The system further comprises a source of measuring fluid 1, and a set of connections 2 for measuring alkalinity according to a closed circuit 2 with inlet 2' connected to said second pump 70, and outlet 2" connected to said chamber 6. This system in turn belongs to a swimming pool, comprising a swimming pool tub containing said water 7, and connected to said system by means of said inlet 2' and outlet 2".

Figure 2B further illustrates the possibility of using the device (either exemplary embodiment 200b, or exemplary embodiment 2004, or any other exemplary embodiment) for measuring the alkalinity of a limited amount of water, for example less than 10 | or less than 5 or less than 1! or less than 10 cl. In such examples it may be advantageous to take a sample via the said inlet 2', but not to connect the outlet 2" to the limited amount of water, and to allow the contents of the chamber, which may for example be filled with the ready-to-measure solution, to flow off instead. In such embodiments, the closed circuit 2 is not used, but purely a course from inlet to outlet. An advantage may be, for example, that the limited amount of water is then not disturbed by the addition of the ready-to-measure solution, and/or that the limited amount of water is prevented from flowing over the edges of the container in which it is contained. This is in contrast to embodiments in which the amount of water is considerable, for example more than 1 | or more than 10 |, and in which the operation

30 BE2023/5119 according to closed circuit, with possible addition of measuring fluid to the quantity of water, has only a limited or very limited influence on the composition of the water, due to the considerable dilution. Designs without closed circuit are not discussed further in the examples, but are also part of the invention.

In exemplary embodiment 200b, the swimming pool comprises, in addition to the system which carries out alkalinity measurements with respect to a ready-to-measure solution, also a further pump 90. The further pump realises, or contributes to, an incoming flow 700' through said system. A purpose of this incoming flow is to drain the ready-to-measure solution to the swimming pool shell, and to fill the chamber 6 with a sample of water 7 which consists only of the water itself, and no longer comprises any or as little measuring fluid 1 as possible.

In this example, and also in examples 2 and 3, the first 10 and second 70 pumps are depicted as separate pumps that, although they belong to a common pumping system 100, can be completely separated in space. In embodiments, the first and second pumps are located more than one meter apart, and are physical components that are completely separated from each other. In other exemplary embodiments, not shown in the figures, the first 10 and second 70 pumps belong to one and the same pumping device 100, and the pumping system 100 is therefore an integrated system, with a common pump body. In this case, the pumping system is, for example, a diaphragm pump or hose pump. This allows a fixed transmission ratio to be realized between the first and second pump. In still other embodiments, the second pump 70 is actuated by means of a transmission of revolution of a shaft of the first pump 10 according to a fixed transmission ratio, or vice versa, i.e., the first pump is actuated by the second. This in turn corresponds to a pump system 100 in which there is partial integration between the first and second pump. All these versions, whether with partial mechanical integration or with complete, have the advantage that a mechanically coupled volumetric ratio is realized by means of the said fixed transmission ratio. These versions are not shown but are considered as further examples which are also described in this document.

In this example, and also in examples 2 and 3, the pH sensor 8 is shown as a set of a first 8a and second 8b electrode. However, the invention is not limited thereto, and any means suitable for pHmetry may be used, including holographic pH sensors with colorimetric operation, and including pH sensors with solid-state electrodes instead of conventional glass electrodes. These embodiments are not shown but are considered as further examples which are also described in this document.

In this example, the measuring fluid 1 is introduced from a reagent tank and mixed with the water sample in a fixed ratio. Both flows are conveyed to the chamber 6 via the pumping device 100, with for versions 200a and 200b also the mixing coil 61 in between. The

31 BE2023/5119 Chamber 6 functions as a detection cell, where the pH as well as the temperature are measured with the pH sensor 8. The pH of the mixture (= final pH, which is T-corrected via the temperature measurement) determines the alkalinity of the water.

To link the final pH to an alkalinity, a calibration is first performed, for example the calibration explained in example 4. For this purpose, in this example, the pH sensor 8 is first calibrated with at least 2 pH calibration points (e.g. 4.01 and 7.01 at 25°C), and then calibrated for the alkalinity. For this, the water tank is replaced by at least 2 calibration solutions. The device is activated, which mixes each calibration solution with the measuring fluid, resulting in a final pH per calibration solution. By reconnecting the water tank after calibration, the alkalinity of the water can be determined. The alkalinity of the sample can be measured continuously or per time interval.

The choice of acid for the measuring fluid can be either a strong or weak acid. The advantage of a weak acid can be that it also has a buffering effect within a certain interval. Due to this buffering capacity, the mixing of measuring fluid and sample and the subsequent measurement on ready-to-measure solution is more predictable, and the final pH can possibly be determined more accurately. Adipic acid is particularly advantageous because of its non-toxic properties and ready availability.

The amount of acid can be controlled by changing the mixing ratio and/or by changing the concentration. This can also determine the net consumption of measuring fluid, and also limit it. The amount of acid can be adjusted to the amount of alkalinity of the water. In this way, specific reagents can be made that can determine the alkalinity within a certain range, with e.g. a first solution for the range of 0 to 200 mg/l CaCOs, and a second solution for the range of 200 to 400 mg/l.

After calibration of the device, the alkalinity of a sample can be determined (both with an internal, incoming flow pump 700 and with an external pump 90). The alkalinity measurement can be analyzed per time interval.

EXAMPLE 2: EXAMPLE VERSIONS WITH SWITCHING

Figures 3A-3B show exemplary embodiments of devices according to the invention in which switching takes place between a first and second state. In addition, Figure 3A shows an exemplary embodiment with a valve, and Figure 2B shows an exemplary embodiment with an incoming flow pump 700. The reason for variants 3004 and 300b is the same as for variants 2004 and 200b in example 1.

In this example, alternating measurement of alkalinity and pH is possible, by alternating between first state 101 and second state 301, 701. In embodiment 300a, it concerns a valve 3, or a 3-way valve, which switches alternately with the first 10 and second 70 pump. In embodiment 300b, this is related to the alternating between the pumping device 100 and the incoming flow pump 700.

32 BE2023/5119

This relates to means for switching between a first state 101 and a second state 301, 701, said first state 101 corresponding to measuring alkalinity of the water 7 by means of said pH sensor 8; and said second state 301, 701 corresponding to measuring acidity of the water 7 by means of the same pH sensor 8.

For device 300a, said means for switching are associated with valve 3, preferably a three-way valve; said first state 101 being associated with actuation of said first pump 10 and second pump 70 and with maintaining, by means of said valve 3, an incoming flow 700' of water 7 without passing through chamber 6, for said measuring of alkalinity by means of the pH sensor; and said second state 301 being associated with non-actuation of said first pump 10 and second pump 70 and with directing, by means of said valve 3, the incoming flow 700' of water 7 through chamber 6, for said measuring of acidity by means of the pH sensor.

For apparatus 300b, said means for switching is associated with an incoming flow pump 700; said first state 101 being associated with actuation of said first pump 10 and second pump 70 and with non-actuation of the incoming flow pump 700, for said measuring alkalinity by means of the pH sensor; and said second state 701 being associated with non-actuation of said first pump 10 and second pump 70 and with actuation of the incoming flow pump 700 for directing the incoming flow 700" of water 7 through the chamber 6, for said measuring acidity by means of the pH sensor.

EXAMPLE 3: SAMPLE VERSIONS WITH ALKA-PLUS PUMP

Figure 4 shows a schematic exemplary embodiment of a device according to the invention with an alka-plus pump 40 connected to it with alkalinity-increasing liquid 4.

Figure 5 shows an exemplary embodiment of a device 500 according to the invention with both an alkali-plus pump 40 with alkalinity-increasing liquid 4 and a pH-minus pump 50 with acidity-reducing liquid 5 connected thereto.

With a device 500 and a corresponding system it is possible to measure pH and alkalinity alternately, and also to administer pH- and alka+. For example, it is possible that only pH is measured during start-up, and that the start is therefore in the second state. Also at times when the further pump 90 is inactive or is still starting up, it can be advantageous to measure pH before alkalinity. This can for example be a period of 10 minutes during

33 BE2023/5119 which pH is measured. Preferably, no adjustments are made on the basis of this measurement, because a measurement of alkalinity is required first, and this should be adjusted as a priority, i.e., prior to any adjustment of pH. Measuring or adjusting alkalinity is not initially an issue because there must first be sufficient circulation in the pool. After the first ten minutes, it is preferable to switch to the first state, in which the alkalinity is measured subsequently. Then, there is a cyclically switching between the first and second state, with or without a fixed schedule, in which the alkalinity and pH are alternately measured and adjusted.

The time interval to switch between pH and alkalinity is configurable.

EXAMPLE 4: SAMPLE IMPLEMENTATION OF CALCULATION

This example relates to the measurement of alkalinity according to the invention, where measurement is performed on the basis of an "active measurement". In this example, this concerns a measurement in which a measuring fluid (active) is added to a sample of water, in order to arrive at a ready-to-measure solution. The pH of the ready-to-measure solution is then measured, after which alkalinity is derived on the basis of a bijective relationship between the acidity of the ready-to-measure solution and the alkalinity of the water. Example 4 can be used advantageously for the alkalinity measurement of example 1 and/or 2 and/or 3.

Figure 6 shows an example of a bijective relationship according to the invention, in which the alkalinity of the water (y-axis, expressed in ppm) is plotted as a function of the acidity of the ready-to-measure solution (x-axis, pH).

In this example, the measurement of alkalinity is related to the following steps: calibrating the pH sensor 8 with at least two pH calibration solutions which correspond to a pH-related bijective calibration curve which relates pH and a quantity measured with said pH sensor, in this example the voltage between a pair of electrodes 8a, 8b belonging to the pH sensor 8; calibrating with respect to alkalinity with at least two alkalinity calibration solutions which correspond to said bijective relationship between acidity of the ready-to-measure solution and alkalinity of the water 7; mixing a measuring fluid 1 and a sample of the water 7 according to a known mixing ratio, the measuring fluid 1 comprising a known dilution of an acid corresponding to a known acidity, to obtain a ready-to-measure solution; performing, with respect to said ready-to-measure solution, a measurement of acidity by means of a pH sensor 8; measuring said alkalinity of the water 7, on the basis of said measurement of acidity and on the basis of a bijective relationship between acidity and alkalinity which is valid in a working area comprising said known acidity and said measured acidity.

34 BE2023/5119

In this example, the water in the swimming pool is used, where the working range covers an alkalinity level of 0 to 200 mg/l.

The type of diluted acid for the measuring fluid is adipic acid with a concentration of 0.4 g/l. The mixing ratio is 1:1. The ready-to-measure solution therefore consists of 1 part water and 1 part measuring fluid.

To link the final pH to an alkalinity, the pH sensor is first calibrated. This is done with at least 2 pH calibration points, in this example 4.01 and 7.01, at 25°C. The calibration results in a bijective calibration curve, in this example a calibration line (first-degree curve), which links the obtained mV to the real pH.

Then the calibration with respect to alkalinity is carried out. For this purpose the water tank is replaced by at least 2 calibration solutions, which are sent in via the inlet 2' which is connected to the second pump 70. The device pumps each calibration solution as a sample, whereby mixing takes place with an equal volume of the measuring fluid 1, which is pumped with the first pump 1.

Both together form the ready-to-measure solution, which is guided through the mixing coil 71 and optimally mixed. The ready-to-measure solution then ends up in chamber 6, where the pH of each calibration solution is measured. This results in a final pH per calibration solution. These measurements allow the bijective relationship between acidity and alkalinity to be determined, in this example a lin. In another example, five calibration solutions are used, in accordance with what is shown in Figure 6. These are solutions with a concentration of 0, 47.5, 95, 143 and 190 ppm of NaHCO:. This results in measuring points 61-65 in Figure 6, with numerical values as shown. In another example, unrelated to Figure 6, the same solutions are presented at 0, 47.5, 95, 143, and 190 ppm NaHCO: concentrations, yielding the following numerical values, not shown in Figure 6: ppm NaHCO: Final pH 0 3.55 47.5 4.02 95 4.42 143 4.79 190 5.17

As illustrated in Figure 6, from such measurements an approximate mathematical equation 60 can be calculated, which represents the transformation of the measured final pH to the alkalinity of the aqueous stream, being the bijective relationship 60 between acidity and alkalinity. The calculation can be done using any approximation, in this example R2, or any other regression method, for example /east square error or least absolute error.

35 BE2023/5119

By reconnecting the water tank with water 7 after this double determination, the alkalinity of water 7 can be determined. The alkalinity of the sample can be measured continuously or per time interval. When a bijective relationship has been established, for example the bijective relationship 60 as shown in Figure 60, and then an unknown water sample is analyzed according to the above procedure, and the pH of the ready-to-measure solution is 4.5, then the alkalinity of the water sample is equal to 131 ppm.

EXAMPLE 5: EXAMPLE WATER BALANCE EXECUTION

This example considers the control of water quality via water balance. Water quality is controlled and managed based on a combined input of two or more basic parameters, such as pH, alkalinity, temperature, hardness, conductivity, and weather forecast.

In the state of the art, automatic adjustment of a swimming pool, for example, is often provided by means of separate controls per basic parameter. For example, the basic parameter pH is controlled based on an analysis of the pH. If the pH is too high, this single parameter is adjusted. pH- is added to lower the pH to a set fixed value.

In the case of regulation according to the exemplary embodiment of the invention, the water quality is controlled on the basis of an index, preferably on the basis of the LSI.

At least two basic parameters (e.g. pH, alkalinity, hardness, conductivity, temperature, weather forecast) are combined in this index, also called ‘water balance’. The index is (via the algorithm) a calculated numerical value based on at least two basic parameters. This value can take on all values from minus infinity to plus infinity.

In this example, boundary conditions are defined from which adjustment of the water balance is necessary. The limits of the water balance are defined (maximum and minimum, with or without certain warning limits, i.e. an instruction for correction which is for example a warning for an operator.

In this case, the control is performed on the basis of input data from a combination of basic parameters — so on the basis of the water balance (instead of each time separately on 1 specific basic parameter) and where the basic parameters can be adjusted, either in combination or not. When the value of the water balance exceeds a warning limit (or maximum/minimum), adjustments can be made. The adjustment of the water balance is performed on the basis of an adjustment of one or more basic parameters. The adjustment is included in an algorithm executed by the control unit which ensures that the water balance remains within the predetermined limits by adjusting one or more basic parameters. In example embodiments, it is possible to assign a permitted range to each basic parameter

36 BE2023/5119 within which each basic parameter can vary, which allows the water balance to be further controlled and kept within certain limits.

In example implementations, in addition to water quality, disinfection is also measured and, preferably, adjusted.

In an exemplary embodiment, two or more parameters (e.g. pH, alkalinity, hardness, conductivity, temperature, weather forecast...) are translated to the index via a formula. In embodiments, this relates to one or both of the following definitions for water balance:

LSI index: (pH) + (-0.00014554*(T in°C)*(T in°C) + 0.02808929*(T in°C) + 0.00408167) + (0.43475046*In( Calcium hardness in ppm) - 0.39514691) + (0.43475046*In(Total alkalinity in ppm) + 0.00485309) - (-0.0000000100*(EC in ppm)*(EC in ppm) + 0.000122 *(EC in ppm) - 12.08)

IW index: 166.6666 * [(pH) + (-0.00014554*(T in°C)*(T in°C) + 0.02808929*(T in°C) + 0.00408167) + (0 .43475046*In(Calcium hardness in ppm) - 0.39514691) + (0.43475046*In(Total alkalinity in ppm) + 0.00485309) - (-0.0000000100*(EC in ppm)*(EC in ppm ) + 0.000122*(EC in ppm) - 12.08)] + 100

In example versions the limits for water balance are also defined. . LSI

Maximum: 0.3 (Scale forming)

High warning limit: 0.15

Ideal: 0

Low warning level: -0.15

Minimum: -0.3 (corrosive) ° °iW

Maximum: 150 (Scale forming)

High warning level: 125

Ideal: 100

Low warning level: 75

Minimum: 50 (corrosive)

In embodiments where the instruction for correction includes a control, an adjustment is also made.

In an example, there is a drop in temperature (e.g. winter and no further heating of the water) and the water balance drops below the critical value. In the table below an example is given where the temperature causes a critical drop in the water balance, while the other basic parameters remain constant.

Ppm mg/l CaCO3 ppm °C

LSI water balance ALKA pH Ca hardness EC T 0.005 101 110 7.3 375 1503 30 -0.440 27 110 7.3 375 1503 10

37 BE2023/5119

The control algorithm ensures that the water balance returns to within acceptable limits. In this example, priority is given to adjusting the alkalinity in the control, with alka+ (being alkalinity-increasing fluid), with a variation of +10. This change will also change the pH to e.g. 7.35. The pH is still within its limits here (e.g. 7.2 to 7.4), which means that it is not adjusted with pH- (or acidity-reducing fluid). The algorithm can then choose to first increase the conductivity by adding dissolved salt with a variation of 250. This combination has led to an improvement in the water balance, which is now back in order. ppm mg/l CaCO3 ppm °C

LSI water balance ALKA pH Ca hardness EC T -0.318 47 110 7.3 375 1503 15 -0.252 58 120 7.35 375 1750 15

In this way, the water quality is controlled on the basis of combined basic parameters. (END EXAMPLE 5)

It is understood that the present invention is not limited to the embodiments described above and that some modifications or changes may be added to the described examples without reevaluating the appended claims (or articles or clauses). For example, the present invention has been described with water from a swimming pool, but it may also concern any other volume of water for which the alkalinity and/or acidity and/or water balance and/or general quality needs to be monitored. The invention, in its various aspects, is eminently suitable for all applications where it is important that the water is non-toxic and/or fit for human consumption.

Claims (17)

38 BE2023/5119 CONCLUSIONS 1. A method for automatically controlling the quality of water (7), preferably swimming pool water, comprising the steps of: actively measuring alkalinity of the water (7) with a first sensor, during a first state (101); switching from the first (101) to a second (301, 701) state; measuring pH of the water (7) with the same first sensor, during the second state; calculating, based on said measurement of alkalinity and pH, a water balance index, preferably a Langelier Saturation Index, LSI; determining whether the calculated index meets a predetermined criterion with respect to said quality; if said criterion is not met, generating an instruction for correction of said quality; wherein said first sensor is a pH sensor (8); wherein said first (101) and second (301, 701) states are at least partially non-overlapping in time, preferably non-overlapping in time; whereby said active measuring is related to the automated and metered addition of a measuring fluid to obtain a ready-to-measure solution. 2. The method of claim 1, wherein said water balance index is said LSI. A method according to claims 1 or 2, wherein said criterion is related to a warning interval, whereby if the calculated index is not within said interval an instruction being a warning to an operator is generated. 4. Method according to claims 1-3, wherein said criterion is related to an interval for correction, wherein if the calculated index is not within said interval an instruction for correction is generated, and wherein said method further comprises at least one of the following two steps: if said instruction for correction comprises increasing alkalinity, the automated and metered addition of an alkalinity-increasing liquid (4) to the water by means of an alka-plus pump (40); and/or if said instruction for correction comprises decreasing acidity, the automated and metered addition of an acidity-reducing liquid (5) to the water by means of a pH-minus pump (50). 39 BE2023/5119 5. A method according to claim 4, wherein said method comprises both of said two steps. 6. Method according to claims 1-5, wherein said measuring of said acidity by means of said pH sensor (8) is done on the basis of a bijective relationship between acidity of the ready-to-measure solution and alkalinity of the water (7) which is valid in a working range comprising said known acidity and said measurement of acidity. 7. Method according to claims 1-6, wherein said active measuring relates to mixing a measuring fluid (1) and a sample of water (7) according to a known mixing ratio, the measuring fluid (1) comprising a known dilution of an acid corresponding to a known acidity, to obtain the ready-to-measure solution. 8. A method according to claim 7, wherein said known mixing ratio is between 1:10 and 10:1, preferably between 1:5 and 5:1, more preferably between 1:4 and 4:1 or between 1:3 and 3:1 or between 1:2 and 2:1, most preferably between 2:3 and 3:2 or between 3:4 and 4:3. 9. A method according to claims 6-8, further comprising the step of: measuring temperature of said ready-to-measure solution by means of a temperature sensor; wherein said measurement of acidity of said ready-to-measure solution is converted on the basis of said temperature measurement to obtain an equivalent pH, wherein said bijective relationship between acidity and alkalinity is applied to said equivalent pH for said measurement of alkalinity. 10. A method according to claims 1-9, comprising the further step of: repeatedly switching between the first state (101) and the second state (301, 701); said steps being repeatedly performed based on repeated measurement of alkalinity of the water (7) during the first state (101) and of acidity of the water (7) during the second state (301, 701). 11. Method according to claims 1-10, wherein said criterion is related to an interval for correction, wherein if the calculated index is not within said interval an instruction for correction is generated, and wherein said method comprises the following step: if said instruction for correction comprises increasing the salt content, the automated and metered addition of a salt content increasing liquid to the water (7) by means of a salt-plus pump. 40 BE2023/5119 12. Method according to claims 5-11, wherein said adding of alkalinity-increasing liquid (4) is done as a priority over at least said adding of acidity-reducing liquid (5) in order to allow the correction to proceed gradually. 13. Method according to claims 5-12, wherein said method comprises said next step: if said instruction for correction comprises increasing the salinity, adding said salinity-increasing liquid to the water (7) in an automated and metered manner by means of said salt-plus pump; wherein said adding of salinity-increasing liquid takes place with priority over at least said adding of acidity-reducing liquid (5) in order to allow the correction to proceed gradually. 14. Method according to claims 1-13, wherein said water (7) is the water of a swimming pool. 15. Apparatus for automatically controlling the quality of water (7), comprising: a first sensor; means for performing an active measurement; a control unit connected to said first sensor; said control unit being configured for: measuring, by means of said first sensor, pH of the water (7), during a first state; actively measuring, by means of the same first sensor and said means for performing said active measurement, said alkalinity of the water (7), during a second state; calculating, based on said measurement of pH and alkalinity, a water balance index, preferably a Langelier Saturation Index, LSI; determining whether the calculated index satisfies a predetermined criterion relating to said quality; if said criterion is not met, generating an instruction for improving said quality; said first sensor being a pH sensor (8); said first and second states being at least partially non-overlapping in time, preferably being non-overlapping in time; wherein said means for performing the active measurement are associated with the automated and metered addition of a measuring fluid to obtain a ready-to-measure solution. 41 BE2023/5119 16. Swimming pool comprising the device according to claim 15 comprising an inlet (2') and outlet (2") and a pool shell comprising said water (7) connected to said device by means of said inlet (2') and outlet (2"). 17. A swimming pool as claimed in claim 16, wherein said device regulates the quality of the water with the aid of a ready-to-measure solution and wherein said swimming pool comprises a further pump (90) which produces an incoming flow (700") through said device for draining the ready-to-measure solution to the swimming pool shell.