EP2643827A1

EP2643827A1 - System for monitoring water quality

Info

Publication number: EP2643827A1
Application number: EP10859949.9A
Authority: EP
Inventors: Sakari Laitinen-Vellonen
Original assignee: Individual
Current assignee: Individual
Priority date: 2010-11-23
Filing date: 2010-11-23
Publication date: 2013-10-02
Also published as: WO2012069688A1

Abstract

The invention relates to a system for monitoring water quality, which system (10) includes one or several measurement units (12) placed at measurement locations and data-transfer means (20), each of which measurement unit (12) contains a measurement sensor comprising electrodes (22) made from several different materials. Each measuring unit (12) includes a transmitter for wireless data transfer and the system (10) includes a local base station (14) located in the vicinity the measuring unit (12 ) for receiving and forwarding the measurement data collected by the measuring unit (12), which local base station (14) is arranged permanently in a telecommunications network and is permanently electrified, and in which system (10) each measuring unit (12) has its own power supply and is arranged to measure changes in the potentials between the electrodes (22).

Description

SYSTEM FOR MONITORING WATER QUALITY

The present invention relates to a system for monitoring water quality, which system includes one or several measurement units placed at measurement locations and data-transfer means for forwarding the measurement data for processing, each of which measurement unit contains a measurement sensor, a transmitter for wireless data transfer, as well as electrodes made from several different materials, for electrochemical measurements.

The quality, and variations in the quality of water, aqueous solutions, and aqueous slurries are important factors in human health, the operation of numerous different processes, and the quality of end products. Such end products include drinking water, foodstuffs, beverages, pharmaceuticals, raw materials, paper, textiles, and so forth. The quality of water and variations in it are also important parameters in water-distribution networks and industrial water circulation. In addition, the system can be used to monitor groundwater and waters in the environment at final disposal sites for nuclear waste.

Water consists of a complex matrix of elements (inorganic + organic substances), which create the quality of water. The electrochemical interactions of the substances are very complex reactions and change continuously. Due to this, there are no reliable, dependable, simple monitoring systems requiring little maintenance, for the real-time measurement of water quality. The problem is to ensure the quality of water continuous and cost effectively.

Nowadays, ensuring water quality is mainly based on laboratory analyses (electrical conductivity, pH, odour, taste, turbidity, iron, manganese, colour, ammonium, oxygen alkalinity, sulphate, chloride, nutrients, as well as COD and BOD) . Water samples are taken according to a separate programme at intervals of weeks (typically 2 - 4 weeks), or even months (typically 3 - 5 months) and the laboratory results are typically obtained weeks after the samples have been taken. During the time between taking samples, the water quality is largely without monitoring. If foreign substances enter the water, for example cyanide, arsenic, or sewage, at present they will go unnoticed to the end user, into products or processes. A good example of this is the town of Nokia in Finland, where sewage entered the drinking-water network, leading to the deaths of a few people and thousands being ill, for up to 6 months. People drank sewage for several days before an epidemic of gastric disease was noticed at a health centre. The delay is of several days, or even weeks before problems in water quality are confirmed.

In systems according to the prior art, online measurements are used, which are typically conductivity, pH, and turbidity. These are very insensitive measurements and demand continual calibration. These measurements cannot measure extensive changes in the ion matrix, but only measure a single parameter. The problem is that the many parameters that are measured in the systems according to the prior art cannot show all the changes that take place in the quality of water, aqueous solutions, and aqueous slurries and how they affect the operations of the treatment process and cleaning processes, the quality of the end product and people's safety. For example, a change in quality arising from reduction in raw water affects the flotation of the water purification process and through it disinfection and finally the quality of the drinking water.

Special analysers are known from the prior art, which measure a few parameters simultaneously at a frequency of more than 15 minutes . Even these devices concentrate on a few known laboratory parameters and cannot report widely on changes in the quality of water. The real-time management of many of the parameters is technically impossible, because water contains hundreds, or even thousands of different compounds and molecules. In order to manage water quality sufficiently well. a large number of different kinds of instruments and different techniques would be required to measure the individual parameters contained in the water. The analysers generally require good sampling, filtering, reagents, and complicated mechanisms. Due to the complex technical solutions, the analyser technologies have in practice proven to be unreliable and expensive to maintain. These devices have therefore been taken out of use in many places . Measurements using electrodes are also known from the prior art, but these generally use a wiring ground to the device casing or the environment, so that the measuring apparatus is in a ground potential . The invention is intended to create a system for monitoring water quality, which is more reliable and requires less maintenance than the prior art . The characteristic features of the present invention are stated in the accompanying Claim 1. This purpose can be achieved by means of a system for monitoring water quality, which system includes one or several measuring units placed at the measuring location and data- transfer means for forwarding the measurement data for processing, of which each measuring unit contains a measuring sensor comprising electrodes made from several different materials for electrochemical measurements . The important feature is that each measuring unit includes a transmitter for wireless data transfer and that the system further includes a local base station placed in the vicinity of one or more measuring unit, for receiving the measurement information collected by the measuring unit and forwarding it for processing. The local base station is arranged permanently in the data-transfer network and is permanently electrified. In the system, each measuring unit has its own power supply and is arranged to measure changes in potential between the electrodes. Thus, the measuring unit is made to consume a very little power, as the transmission distance to the local base station is short, so that the operating life of the measuring unit is typically 1 - 3 years. The measuring unit preferably includes an analog part and a digital part, as well as a galvanic separator between them, in order to isolate the analog part and the digital part from each other. Thanks to the separate parts, leakage currents cannot interfere with the separate parts of the measuring unit.

The analog part includes the said electrodes located in the water to be studied, a preamplifier for the electrochemical forces arising between the electrodes, and an AD converter for converting an analog signal into a digital signal. Using such a measuring unit, it is possible to measure accurately the potentials of the electrodes .

At least the analog part is preferably arranged to float electrically, in order to prevent leakage-current interference. The measuring unit can include separate auxiliary power supplies for the said analog part and digital part. Thus, very sensitive measurements can be performed, without errors caused by interference. According to one embodiment, the digital part includes a microcontroller for controlling the analog part, as well as a radio for performing data communications between the measuring unit and the local base station. With the aid of the radio, the measuring unit can be made wireless .

The measuring unit preferably includes means for switching off the current to the analog part and for operating it at intervals. The measuring unit can include means for commanding the digital part to a standby state. With the aid of intermittent operation and a dormant state, the power consumption of the measuring unit can be reduced considerably. Most of the electrodes are preferably made from various noble and base metals. The noble metals can be, for example, gold

(Au) , silver (Ag) , or platinum (Pt) and the base metals lead

(Pb) , tin (Sn) , and iron (Fe) .

According to a third embodiment, at least one of the electrodes of the measuring unit is a reference electrode and most of the electrodes are measuring electrodes. Thus, the measurement result of each pair of measuring electrodes can be checked reliably by comparing it with the reference electrode.

The measuring unit can include two or more series, each with its own reference electrode, one of the electrodes being a bias electrode for comparing the potentials of the reference electrodes . The bias electrode can further be used to assess the functioning and condition of the reference electrodes .

According to a fourth embodiment, there are 5 - 20 electrodes, preferably 7 - 14 electrodes, for each measuring unit. By using a sufficiently large number of electrodes, a sufficient reliability of the measurement results will be achieved, as the same electrochemical forces will be measured simultaneously using several similar electrodes. According to a fifth embodiment, each measuring unit is 1 - 300 m, preferably 5 - 100 m distant from the local base station. The measuring unit's radio transmitter can then have a low power and consume little current. The measuring unit's measuring frequency can be 1/min - 1/d. By using measurements repeated sufficiently frequently, a sudden drop in water quality can be detected quickly and an alarm given, before the drop in quality spreads to a wide area. According to a sixth embodiment, the local base station is a WLAN station. Such a base station is cheap in terms of investment costs . With the aid of the system, the quality of water, aqueous solutions, and aqueous slurries and the processes relating to its monitoring are managed comprehensively in real time and risks are predicted. This takes place by measuring extremely sensitive electrochemical changes in the liquid. The measurement of a change in potential and the structure of the electrically floating measuring unit permit, together with the use of a local base station, the low power consumption of the measuring unit, so that the operating time of the measuring units will be long. The system is sensitive, comprehensive, and wide-cover /wide spectrum, i.e. it measures changes very widely. In addition, the system is robust, economical and easy to maintain, cheap, and consumes little power and has a long operating time. In the following, the invention is described in detail with reference to the accompanying drawings showing some applications of the invention, in which

Figure 1 shows a schematic diagram of the system according to the invention,

Figure 2 shows a schematic diagram of the system according to the invention, when the system is connected to a server and user interface,

Figure 3 shows a diagram of the more detailed construction of the measuring unit of the system according to the invention,

Figure 4 shows a circuit diagram of the analog circuit according to one embodiment,

Figure 5 shows a diagram of the more detailed construction of the server of the system according to the invention, Figure 6 shows a composite indicator in the user interface, transmitted to a user of the system according to the invention, and

Figure 7 shows a schematic diagram of the operation of an alarm application of the system according to the invention.

The system according to the invention can be used for monitoring water quality and predicting risks in raw-water sources (surface water and groundwater), in natural waterways, in water-treatment processes, in industrial processes (mines, fertilizer, paper, metal, etc.) , in drinking water, in drinking-water distribution systems, in circulation water, in the energy industry (including bio-energy, and oil-sand applications) , in the pharmaceutical industry, in groundwater at final disposal sites for nuclear waste, at landfill, as well as in preventing disasters. An example of the prevention of disasters is, among others, the prediction of earthquakes by measuring electrochemical changes in water in the ground, which are caused by geophysical and chemical changes in the ground.

The system is based on using an electrochemical measuring technique to measure the conditions in water, instead of individual parameters. The measuring method operates without external energy, as the measuring energy required to measure the potential is contained in the measuring event itself. This refers to the electrochemical difference between charged ions in the liquid and various electrodes. The measuring unit based on potential measurement and the use of a local base station gives the measuring unit a low power consumption, which allows the measuring unit to operate wirelessly on dry-cell or rechargeable batteries for typically 12 - 36 months.

Figure 1 shows one simple embodiment of the system according to the invention. In this embodiment, the system 10 includes only two measuring units 12 placed at the operating location, in this case for example a lake 90, and a local base station 14 located permanently in the vicinity of the measuring units 12. In this connection, the term in the vicinity refers to a distance of 1 - 300 m, preferably 5 - 100 m. The measuring units 12 are on the surface of the water, so that their electrodes 22 are below the surface and measure changes taking place in the potential differences. The measuring units are preferably anchored at the measuring location and are wireless . In each measuring unit 12 there is a transmitter and an antenna 84, by means of which the measuring unit 12 transmits information to the local base station 14.

The local base station 14 also includes an antenna 82 , by means of which it receives the low-power transmission of the measuring unit. The local base station 14 is permanently connected by data-transfer means 20 to a telecommunications network, for example, to the internet. The local base station 14 is powered over a permanent network connection 80, so that a high-power transmitter can be used in the local base station to transmit information to the telecommunications network over the data-transfer means 20. The data-transfer means can be, for example, an I/O transductor included in the measuring unit. The local base station 40 can be a widely-used and economical WLAN station, in which case the measuring unit will converse directly with the WLAN state acting as the local base station. The use of other available connection protocols .( for example Bluetooth and infrared) is also not excluded.

Figure 2 shows one embodiment of the system according to the invention. In this embodiment, the system 10 includes a wireless water-quality measuring unit 12 (LEW-100 Detector) , a local base station 14 i.e. a master unit (LEW-HUB) , a server 16 (Remote Service Centre), and a user interface 18. The transfer of measurement data to the server 16 and the production of information for the end user preferably take place over the internet . According to Figure 3, the electronics of the analog part 30 of the measuring unit 12 consist of a preamplifier and pre-filter 24 and 24', AD and DA converters 26 and 26', as well as a galvanic separator 28. The preamplifier is preferably close to the electrodes and data input to the analog part can take place inductively through the galvanic separator. A special feature of the analog part is that the entirely measuring-current circuit is electrically floating and the measurements are differential measurements. Thus, the measurement is made extremely sensitive and at the same time a very interference- free measurement environment is created. In this system, the natural leakage currents cannot interfere with the sensitive electrochemical measurements . The term leakage-current interference refers to small currents between the liquid and the piping and structures of the electrodes, which lead to differences in potential between them and interfere with the reactions taking place on the surface of the electrodes, and thus with the measurement results. The actual energy for the measurement is formed directly by the difference in potential between the solution and the measuring electronics. A separate dry cell, accumulator, or solar panel acts as an auxiliary energy source 40 for the analog part 30. The measuring units are preferably arranged to operate under their own power, so that they can be located in measurement locations that are difficult to access and can operate without maintenance for even long periods of time. The own power is implemented with the aid of an auxiliary energy source. In this connection, the term own power refers to solutions, in which the measuring unit operates without an external power supply, in which case the measuring unit can be battery operated, or it can have a solar cell, a rechargeable battery, and a capacitor, in place of a normal dry-cell battery. Other corresponding solutions producing current independently are possible. The microcontroller 29 of the digital part 32 preferably includes software means, by which the power consumption of the analog part 30 is controlled. The software means operate a switch through a galvanic separator, by means of which the power consumption of the entire analog part is opened and closed periodically, in order to minimize power consumption (not shown) . Current feed takes place in short periods, during which the analog part starts, performs the measurements, and sends the measurement data to the digital part. After this, the current to the analog part can be cut and the digital part itself can be set to a conventional standby state. The measuring part also includes means for commanding the digital part to a standby state. The microcontroller 29 and radio 34 of the digital part form their own electrically floating totality, for which there is a separate auxiliary power supply 42. Thus the feed of the auxiliary energy of the digital part can be implemented without interfering with the sensitive analog part. In all the digital lines optical separation can be used, so that the various leakage currents cannot interfere with the measurement of the analog part. The radio 3 of the digital part can be a low-power transmitter meeting a standard, the power of which is, for example, 10 mW. Such a transmitter consumes only a little current when operating, which permits long operating times on battery operation.

The electronics of both the analog and digital part can be encased in a metal case. Plastic protective casing can be used in addition, which will protect the entire metal case and antenna. In this way, additional protection will be obtained against electric disturbances, such as static electricity. Particularly in the future, the measuring unit can be made very small in size, so that it can be installed directly in a water mains, piping, or inside a tank, or in a drinking-water tap. Thus, the electronics of the measuring unit form a combination, by means of which a very sensitively and precisely measuring system is obtained. In addition, power consumption has been minimized and the operating time made as long as possible. The operating time is typically 1 - 3 years, if the measuring frequency is once a minute. By lengthening the measuring frequency, the operating time can be increased many times over. In general, it can be said that the desired operating time of the measuring unit, the size of the battery, and the transmission frequency are adapted to each other. A suitable measuring frequency can vary, for example, between 1/min - 4/d, depending on the point of application and the criticality of the measurement . Figure 4 shows a circuit diagram of the analog part 30 of a measuring unit according to one embodiment. Naturally, the entire circuit itself is tightly integrated in the measuring unit, so that the circuit's preamplifiers are close to the electrodes. The analog part according to the figure is almost directly the commercially available Analog Devices AD7718 analog circuit, to which the necessary auxiliary components have been added. The RC components in the inputs of the electrodes are not shown. Changes taking place in the water are detected as changes in the potentials arising between the electrodes 22. The electrodes 22 are connected to the inputs AIN 1 - 8 and AINCOM (reference electrode) of the MUX circuit 45, i.e. of the multiplexer and preamplifier. The multiplexer controls the sending of the sample to the AD converter 26, which converts the analog measurement signals to digital signals. The digital signals go from the AD converter 26 through the digital output to the galvanic separator 28 and through it to the digital part of the measuring unit. A galvanic separator 28 is also connected to the digital inputs of the analog part 30. Data transfer in and out of the analog part 30 takes place with the aid of the galvanic separator 28. As auxiliary components of the analog processor circuit AD 7718, the analog part 30 requires a voltage monitoring circuit 41, a circuit 43 for creating the reference voltage, a single or multiple crystal Xtal for the auxiliary energy source 40, as well as the RC components of the inputs. The analog part 30 is electrically floating, in such a way that the - terminal of the analog part of the processor circuit is connected to the + terminal of the digital part, while the + terminal of the analog part is connected the corresponding terminal of the digital part. A + 5 V voltage is fed by a battery to the voltage terminals of the analog and digital parts, through a stabilization circuit 41. The circuit together with the power supplies is electrically floating. The reference-voltage creation circuit 43 creates a very precise 2,5 V voltage for the comparison of the potentials of the electrodes. The measuring circuit can operate in the -2,5 V - +2,5 V voltage ranges. In this case, the auxiliary energy source 40, i.e. the battery, can produce a voltage of 6,6 V. In this embodiment, the analog part does not include a separate preamplifier, as the incoming impedance from the electrodes (at the MUX-circuit preamplifier) is in the order of 1 Gohm, in which case the signals will not normally require separate amplification. Voltage measurements in the Gohm range can be performed using standard circuits. If the water being measured is ultra-pure water, the analog part can include a separate preamplifier before the AD converter, as with ultra-pure water the impedance of the input can be in the order of 1 Pohm.

The system operates in such a way that the system's measuring unit or units 12 are placed in the water to be measured, in which the analog part 30 of an individual measuring unit 12 measures the changes in the electrochemical forces arising between the electrodes 22. The electrochemical force that has arisen is amplified and filtered with the aid of a preamplifier and filter 24, after which the analog signal is converted in a digital signal by the AD converter 26. After this, the radio 34 of the digital part 32 of the measuring unit 12 transmits the signal to the server 16 through the local base station 14. At the server 16, a measurement matrix is created on the basis of the signal, which is compared with a reference matrix created on the basis of the data in the database 44 of the server 16. On the basis of this comparison, the server 16 forms a composite indicator depicting the water quality, which it sends over a telecommunications network to the operator's user interface 18.

In the system, an estimate of the water quality can be achieved by controlling the relative changes taking place in the chemistry of the water matrix, by measuring in real time using typically 5 - 30 electrodes. Here, the term chemical refers to a change (electron transfer) in the electric forces between the ions, even though the concentrations of substances remain constant. In the measurement, one or more electrochemical measurement methods can be used, which are potential, current, impedance, and noise measurements. However, the use of other than potential measurement will demand a direct electrical connection from the measuring unit, due to its greater power consumption. The measurement is preferably performed by measurement directly from a flowing liquid. Measurement of the water matrix takes place using a multi- electrode series, in which the electrodes form an optimal measurement matrix, relative to the water matrix of the application point being measured. The measurement matrix is adapted application-specifically, in such a way that suitable electrode materials are chosen, which measure as widely, sensitively, and reliably as possible changes taking place in the electric forces between the ions in the water matrix and detect the greatest causes of the change. Thus, the measurement produces a sufficiently wide range of data (several different types of electrodes) on the changes in the water matrix. The use of measurement based on a multi-electrode series also ensures that the data are reliable, as changes are measured simultaneously by electrodes that are similar or of the same type. From this extensive and certain data information is processed automatically using data-processing methods to form, for the needs of the end user, unambiguous composite indicators on the change, its magnitude, and its direction.

Measurement takes place using differential measurements between the measuring electrodes and the reference electrodes . By selecting optimally the electrode pairs relative to the references, it is possible, for example, to distinguish what type of situation prevails relative to oxygen and, at the same time, to determine using other electrode pairs, whether there is sulphur in the mixture and in what form the sulphur probably is (sulphide, hydrogen sulphide) . If the equilibrium between these substances changes, for example due to microbial action, an indication of this will be obtained. In the measurement of the electrodes, the electrochemical measuring methods referred to above can be used, which are used either individually, or several simultaneously, as required. The main emphasis is on the measurement of changes taking place in conditions. If more precise information is required on the reasons for a change, several measuring method are used simultaneously or separately. An additional example that can be mentioned is sulphur, the electrochemistry of which is very important through water quality in safety, the functionality of processes, and the final quality in, among other things, nuclear-waste final disposal sites, ore refining, peat bogs, water treatment, the beverage, foodstuffs, and pharmaceutical industries, and in the pulp and fertilizer industries. Sulphur has seven degrees of oxidation, at which sulphur can act as an oxidant or a reducer. In the application, an electrode combination of copper-silver- iron-lead electrodes is selected, which react in different ways to changes in the degrees of oxidation of sulphur. Software can be used to make an indicator of changes in the sulphur from the changes for the end user.

In this connection, potential measurements are used to monitor redox reactions, in which case the main reactions taking place on the surface of the electrodes will be known. By using a voltametric measurement (mV/mA) , the resistance of the reaction products on the surface of the measuring sensor is scanned continuously, which shows the amount and quality of the substance. Impedance measurement is used to determine the impedance of the electrode surface, which shows the structure of the substance on the surface (impedance spectrum) . In this way, information on the quality of the reaction products on the surface of the measuring sensor is obtained continuously and broadly by using the measurement. As the end result, an accurate picture of the quality of and changes in the quality of water, aqueous solutions, and aqueous slurries is obtained. In this case, the term measuring sensor refers to a totality, which can consist of, for example, the electrodes, preamplifier, and AD converter of the measuring unit.

Some aqueous solutions, for example, ultra-pure water, contain so few measurable substances (ions) , that their measurement is, in practice, impossible. Therefore, viruses and bacteria, for example, are collected on the surface of the electrode by polarizing the electrode surfaces to a suitable state. Polarization takes place using a precisely regulated potential window, a correct flow amount, and velocity, so that specifically the desired substances being studied (ions, bacteria, microbes, algae, etc.) are made to react with the measuring-sensor surfaces to be used in the measurement. The microbes are often negatively charged.

The surfaces of the polarized electrode are deflected, in such a way that the products to be collected detach from the surface. Simultaneously the deflection flow is measured, the amount and direction of which show the content of the substances. The flow can be a maximum value, or alternatively a flow peak in the surface-area potential/flow scale. Both direct and alternating current can be used in the control. The electrodes can be controlled remotely and preset parameters set, according to which the measuring unit will operate and perform the sequences relating to the measurement methods optimally, relative to the phenomena. The electrodes are in direct contact with the liquid being measured, so that the system can be used to made measurements without sampling, filtering, reagents, and the complex mechanisms relating to them. A comprehensive and representative spectrum of the water quality and its changes is obtained by measuring their relative electrochemical changes using numerous electrodes .

The measuring electrodes can be of either inorganic or organic materials, such as metals, metal alloys, minerals, plastic, resin, glass, liquid, gas or salts, nanomaterials , oxides, functional surfaces, bone or wood, or mixtures of the aforementioned materials . The electrodes can also be substances precipitated from the water of the actual location being measured. The measurement can be made more sensitive by illuminating the surfaces of the electrode or the liquid itself with UV light. In the sensitization, passive and electrically controlled metal surfaces can be used, such a zinc, in which case arsenic, for example, will be obtained as hydrogen arsenide .

An individual measuring unit of the system preferably contains one or more reference electrodes. The simultaneous comparison of the measuring electrode to several references will tell of the functionality of the reference electrodes and give certainty to the measurement result. By using several different references simultaneously, the various electrochemical reactions of the liquid will be brought out better.

If necessary, one of the reference electrodes can be a known standardized reference electrode, with the aid of which the measurement results can be linked to known theories, which support real-time measurement and the conclusions drawn from it. The theories are mainly indicative, because they have been developed in controlled conditions and using pure substances. The potential of an iron electrode relative to a standard electrode tells what kind of conditions prevail in the location being measured. The reference electrodes can be connected either internally or externally to the water-quality measuring unit .

The system according to the invention differs from other systems, in that the measuring method can contain not only several references and a standardized reference measurement, but also a bias electrode. By means of this electrode, the functioning and condition of the reference electrodes can be ensured, and it can thus be used as a second electrode increasing certainty. A material, which withstands the conditions mechanically, for example the various forms of stainless steel, is used as the bias electrode.

According to one preferred embodiment, the measuring unit includes eight electrodes, three of which are noble metal electrodes, three base metal electrodes, one is a reference electrode, and one a bias electrode. Each measuring unit contains 5 - 20 electrodes, preferably 7 - 14 electrodes. The electrodes of the measuring unit include both noble and base metal electrodes .

Data transfer from the measuring unit 12 to the local base station 14 takes place preferably wirelessly. The common standard of 868 MHz or 915 MHz is typically used as the data- transfer frequency. Standard circuit series are available for standard- frequency transmission technology from several manufacturers, so that such a technology is economical to implement. The transmission power of the radio 34 of the measuring unit 12 is quite low, so that the local base station 14 is preferably a few tens of metres away from the measuring unit 12. The transmission power of the local base stationl4 is considerably greater and forwards the signal to the server. Thus, data transfer between the measuring unit 12 and the centralized server 16 nearly always takes place through a local base station 14, unless the measuring unit is right next to the server. The communication of the local base station 14 with the internet can take place over a telecommunications network, i.e. for example a mobile network, a WLA , or an ethernet. The local base station 14 transfers the measurement data to the server 16 and relays the control data of the measuring unit from the server 16 to the measuring unit 12. In this connection, the term measurement data refers to the potentials of the electrodes, measured by the measuring unit. The server 16 also provides the local base station 14 with CMT/UTC time data, according to which the measurement data are stamped. The local base station 14 preferably takes care of buffering data, if data transfer to the internet has been interrupted. The server can be a normal computer.

The system preferably includes several measuring units and local base stations. There can be several measuring units to one local base station, if the measuring units are sufficiently close to each other. The system can include, for example, 20 measuring units, each of which has its own local base station, through which information is transferred over a network to a powerful server. In the server 16, the information is compared with historical information, experience, theory, and natural predefined reference values. On the basis of this conclusion, indicators are formed for the end user, which indicators are preferably displayed to the user over the internet by means of a user interface.

In this connection, the term experience refers to a water memory-trace library, in which there are electrode measurement- data combinations collected from numerous different locations, and the related interpretations. The data received from the measuring sensors are compared programmatically/automatically in real time with the system's memory-trace library. On the basis of the results obtained, the system can identify the earlier interpretations . This property improves the ability to grasp complex matters and brings wiseness to, for example, the classification of water types or risk situations. The collection and processing of data, the production of information, and the control of the measuring units is centralized in a single location, i.e. in the centralized server 16. An important part of the system is centralized data refining, in which the data obtained from the measuring units is refined automatically into information. In this way, the system is made more efficient that traditional systems in the production of the correct type of information for the end user.

According to one embodiment, the system can operate globally. The data coming from globally installed measuring units can be stored appropriately in a separate database (DATABASE1 ) . This database looks after the identification of the measuring unit location-specifically . In addition, this database looks after clock operations, such as the time-stamping of the measurement data.

Figure 5 shows the contents of the server 16 in greater detail. The server 16 can include a firewall and an internet connection 69, a database 44, a customer-specific database 58, a global user interface 56, a user identifier 54, a control unit 52, and an analysis unit 50. The control unit 52 can consist of the control of identification of the measuring unit, automatic identification of the measuring unit, control of the measuring- unit clock, as well as control of protection of the data of the measuring unit. The control unit takes care of the control of the measuring unit and identification of the measuring unit. The analysis unit 50 can include a data and information memory, an index calculator, visualization, control of the manner of measuring of the measuring unit, automatic calibration, alarm control, automatic configuration, and virtual calibration levels. The virtual calibration levels include a statistics library, theoretical analysis, and dynamic models.

The parameters, which affect the quality of water, aqueous solutions, and aqueous slurries, are measured with the aid of the system. In the system, other parameters too, such as temperature, obtainable from the processes, can be utilized. From these data, information is refined through matrix forms to an indicator form, by means of which the changes taking place in the water are ensured in real time, and the risks are predicted. If necessary, the information can be used to eliminate possible disturbances in operating locations, for example, water treatment plants, by regulating the process.

In the server, the water quality is processed as a kind of matrix, which consists of several substances and their degrees of oxidation. The substances and their degrees of oxidation have mutual electrochemical interactions with each other. An optimal electrode matrix, which measures changes widely and simultaneously similar or similar types of changes, is formed in this matrix.

Reference matrices, for example, a 'typical good water state' matrix, which acts as a reference level, are defined in the server's database. This virtual level changes and tells of the water's overall state and its stability. Changes are compared with this dynamic level. In addition, the system is taught poor water state matrices, with which the data obtained from the measuring unit is compared. Specific water-quality indicators, which show more specifically the problems and risks in the water quality, can also be made in the database. There are at least two, preferably four to eight reference matrices.

On the basis of the measurement data of the measuring units, the server compares the measurement matrices formed with the reference matrices in the database. On the basis of the differences and changes, the server creates an indicator depicting the water and its current quality. The refining of data into indicators is based on virtual and dynamic reference values, which are created on the basis of the data obtained from the measurement subject, the laws of thermodynamics (Pourbaix diagrams) , or from other measuring units monitoring the water quality.

The system differs from earlier systems, in that the reference values or reference matrices in the server's database change according to the situation, so that the reference matrix to be used in computation is typically dynamic. The compound indicators depicting water quality are thus dynamic indicators, the reference level of which changes according to the situation, for example, according to seasonal water-quality variations. The reference levels can be experientially defined or statistically defined. By means of this system, undesirable changes can be easily and reliably indicated and the water quality can be controlled and, if necessary, the process can be regulated better than by using any known system. Traditional measurements and methods are calibrated against a known calibration liquid. The information available from the indicators can be presented as numbers, trends, diagrams, or colour changes . In the system, different indicators of good and bad situations are typically calculated continuously and the results obtained are compared to each other in real time. On the basis of the results obtained, it can be decided what state or states are prevailing at any moment. For example, water can be stated to be typical so-called 'summer water', in which there are sulphur compounds and thus a risk that the water can easily smell bad, but is harmless. In another example, there is so-called 'winter water', which is of very even quality and contains a great deal of an oxidizing substance (chloride) , but at the same time contains cyanide. In this case, the risk is detected and an alarm forwarded. In other words, the system detects whether the matter is one of a natural change in water quality, or some other disturbing factor.

In the server, indicators are computed automatically requirement-, phenomenon-, sub-process-, or area-specifically. A visual presentation is created for the end user from the indicators obtained from several locations . The information (indicators) is transferred to end users or other systems by wire or wirelessly, for example through the internet. The indicator (Water Quality Index) can be presented to the user, for example as a percentage. An index of 100 % means that the water quality is the same as that defined in the system on the basis of predefined material (historical data, theory, a virtual reference) . When the water quality begins to change, i.e. deviate from 100 %, the value of the index decreases towards zero. For example, when the water quality is good, the value of the index will be near to 100 %, as in the case according to Figure 6, in which the index is 89,3 %, and, when the water quality becomes poorer, the value of the index drops to 52,3 %.

According to Figure 6, the magnitude of the change 72 in the indicator 70 is shown in the display 100 of the user interface, which shows the magnitude of the change 72 as a percentage. The change can be, for example that the water quality has diminished by - 0,2 % over the last 40 minutes. At the same time, the individual identifier data 68 of the measuring unit is shown in the display. The time periods 74, from which the changes are calculated, can be adjusted in such a way that the change can be calculated, for example, for the last day. If the water quality becomes poorer, the number will be negative and the colour red. If the water quality has, in turn, improved by 0,1 %, the number will be positive and the colour blue. In addition, there can be a visual indicator 66 in the user interface, which shows the direction of the change. In this example it is an arrow. A blue arrow facing upwards shows that the water quality is improving while a red arrow facing downwards shows that the water quality is getting poorer. The user interface can be a software application for example in a mobile telephone, a laptop computer, or a similar device linked to the internet. The information can be utilized in real time, for example, in alarm and control systems, in operators' networks, or directly by the action of the end user.

By means of the information obtained from the system, the water quality and the related treatment processes can be controlled over a geographically wide area. Water-quality maps can be produced from this water-quality measuring network (grid) , which can be illustrated on a map base. The reading and utilization of the information preferably takes place through the internet or a mobile network.

For example, a measuring-unit network can be constructed from measuring units to a water network and the progression of changes in quality can be followed from a map in real time. At a point where a measuring unit notes a change and the colour of the indicator changes, the colour of its tube will change to red, for example. If the change continues, the measuring unit gives an alarm, which can be transmitted wirelessly through the local base sation to the nearest mobile-telephone base station. If the change in quality proceeds to the next measuring unit, the next measuring unit gives a change indication at the next location and possibly a next alarm. In this way, a wide picture can be obtained of water-quality changes in a water-mains network and the spread of lower-quality water can be monitored. If, on the basis described above, the system decides, for example, that cyanide is spreading, an alarm can be transmitted to the base station in the problem area, which in turn sends an alarm to the wired and wireless terminal devices in the area. In water- intake facilities and groundwater areas too, comprehensive maps can be made of the measuring-unit network, showing changes in water quality. Another form of presentation can be the adding of water-quality information not only to the measuring-unit's identification number, but also to location information, in which case the information can be displayed visually, for example, in a Google Earth-type application in real time.

Figure 7 shows the stages of the system from measuring unit to user, when there is an alarm in the system. The measuring units 12 measure the electrochemical forces of the water and transmit the data through the local base station to the server 16. From the measurement data, the server 16 creates an indicator depicting the water quality, on the basis of which an alarm 62 is given. The alarm 62 is send to the user's user interface 18, for example, as email, a text message, a voice call, or directly to the production facility using the water.

The system can also be used for predicting and warning about earthquakes, in such a way that the changes in water quality in an active area are measured by measuring units, which are adapted to measure changes caused by volcanic gas compounds in the ground in water (groundwater, well water, river water, seawater, and lake water) . In the system, on the basis of the above description, a matrix change by volcanic gases is distinguished from a normal water matrix. A dynamic indicator can distinguish between variations in water quality in a volcanic-gas matrix and in normal water. Illustrative risk prediction and alarms of water crises can be implemented on a global level using the Google Earth map application, in which case large alarm areas can be seen easily as colours, texts, or graphic images, combined with sound. Individual values and trends can be made visible by bringing the map globe closer.

The system according to the invention is sensitive to changes, simple, and visual. The measuring technology based on electronic transfer reactions permits the system to be highly sensitive to changes . At the same time as the measuring method is sensitive to changes and reliable, it is also very robust and requires very little maintenance. Maintenance operations can be announced to users over a remote connection and at the same time clear maintenance instructions can be sent to the user's user interface. Clear-text laboratory definitions, which have been made from various water samples, can also be sent to the user interface. These can be time element definitions, nutrients, VOC compounds, and total carbon.

According to one embodiment, in addition to electrochemical measurement, in the measurement of a water-quality matrix artificial-nose measurement based on IMS technology according to Finnish patent FI 113089 can be used above the liquid surface, by means of which reactions taking place in the matrix, which produce gas, can be measured. For example, arsenic creates hydrogen arsenide, which can be detected from the gas phase. In the production of gas, passive metallic surfaces such as zinc, or electrically controlled electrode surfaces are used. Such an embodiment requires, however, that the measuring unit is in a permanent electrical network. In that case, a web camera can be used to monitor the electrode surfaces, by means of which changes taking place on the surfaces of the electrodes can be seen visually.

Claims

1. System for monitoring water quality, which system (10) includes one or several measurement units (12) placed at measurement locations and data- trans fer means (20) for forwarding the measurement data for processing, each of which measurement unit (12) contains a measurement sensor comprising electrodes (22) made from several different materials, for electrochemical measurements, characterized in that each measuring unit (12) includes a transmitter for wireless data transfer and the system (10) further includes a local base station (14) located in the vicinity of one or more measuring unit (12) for receiving the measurement data collected by the measuring unit (12) and forwarding it for processing, which local base station (14) is arranged permanently in a telecommunications network and is permanently electrified, and in which system (10) each measuring unit (12) has an independent power supply and is arranged to measure changes in the potentials between the electrodes (22) .

2. System according to Claim 1, character!zed in that the measuring unit (12) includes an analog part (30) and a digital part (32) , as well as a galvanic separator (28) between them, to isolate the analog part (30) and the digital part (32) from each other.

3. System according to Claim 2, characterized in that the said analog part (30) includes the said electrodes (22) placed in the water being studied, a preamplifier (24) of the electrochemical forces arising between the electrodes (22), and an AD converter (26) for converting the analog signal into a digital signal.

4. System according to Claim 2 or 3 , characterized in that at least the analog part (30) of the measuring unit (12) is arranged to be electrically floating, in order to prevent leakage-current interference.

5. System according to any of Claims 2 - 4, characterized in that the measuring unit (12) includes separate auxiliary energy sources (40, 42) for the said analog part (30) and digital part (32) .

6. System according to any of Claims 2 - 5, character!zed in that the said digital part (30) includes a microcontroller (29) in order to control the analog part (30) , as well as a radio (34) for performing data transfer between the measuring unit (12) and the local base station (14) .

7. System according to any of Claims 2 - 6, characterized in that the measuring unit (12) includes means for switching off the current to the analog part (30) and operating it intermittently.

8. System according to Claim 7, characterized in that the measuring unit (12) includes means for commanding the digital part (32) to a standby state.

9. System according to any of Claims 1 - 8, character!zed in that most of the electrodes (22) are manufactured from various noble and base metals .

10. System according to any of Claims 1 - 9, characterized in that at least one of the electrodes (22) of the measuring unit (12) is a reference electrode and most of the electrodes (22) are measuring electrodes .

11. System according to any of Claims 1 - 10, characterized in that the measuring unit (12) includes two or more series with their own reference electrodes and one of the electrodes (22) is a bias electrode for comparing the potentials of the reference electrodes .

12. System according to any of Claims 1 - 11, characterized in that there are 5 - 20, preferably 7 - 14 of the said electrodes (22) to each of the measuring units (12) .

13. System according to any of Claims 1 - 12, characterized in 5 that each measuring unit (12) is at a distance of 1 - 300 m, preferably 5 - 100 m from a local base station (14) .

14. System according to any of Claims 1 - 13, characterized in that the measuring frequency of the measuring unit (12) is 1/min - 1/d.

10 15. System according to any of Claims 1 - 14, characterized in that the local base station (14) is a WLAN station.