EP2349932A1 - Sensor arrangement and method for water quality monitoring - Google Patents

Sensor arrangement and method for water quality monitoring

Info

Publication number
EP2349932A1
EP2349932A1 EP08875284A EP08875284A EP2349932A1 EP 2349932 A1 EP2349932 A1 EP 2349932A1 EP 08875284 A EP08875284 A EP 08875284A EP 08875284 A EP08875284 A EP 08875284A EP 2349932 A1 EP2349932 A1 EP 2349932A1
Authority
EP
European Patent Office
Prior art keywords
water
sensor arrangement
flow path
sensors
water flow
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP08875284A
Other languages
German (de)
French (fr)
Inventor
Alejandro Schnyder
Corrado Noseda
Edoardo Charbon
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Age SA
Ecole Polytechnique Federale de Lausanne EPFL
Von Roll Infratec Investment AG
Original Assignee
Age SA
Ecole Polytechnique Federale de Lausanne EPFL
Von Roll Infratec Investment AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Age SA, Ecole Polytechnique Federale de Lausanne EPFL, Von Roll Infratec Investment AG filed Critical Age SA
Publication of EP2349932A1 publication Critical patent/EP2349932A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/18—Water
    • G01N33/1893—Water using flow cells
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2209/00—Controlling or monitoring parameters in water treatment
    • C02F2209/005—Processes using a programmable logic controller [PLC]
    • C02F2209/008—Processes using a programmable logic controller [PLC] comprising telecommunication features, e.g. modems or antennas
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2209/00—Controlling or monitoring parameters in water treatment
    • C02F2209/04—Oxidation reduction potential [ORP]
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2209/00—Controlling or monitoring parameters in water treatment
    • C02F2209/05—Conductivity or salinity
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2209/00—Controlling or monitoring parameters in water treatment
    • C02F2209/06—Controlling or monitoring parameters in water treatment pH
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2209/00—Controlling or monitoring parameters in water treatment
    • C02F2209/11—Turbidity
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2209/00—Controlling or monitoring parameters in water treatment
    • C02F2209/22—O2

Definitions

  • the present invention relates to a sensor arrangement for the permanent remote monitoring of water quality in a water supply line and more particularly in a water supply network.
  • the present invention concerns real-time remote sensing of contamination in water distribution networks.
  • the present invention relates to methods that are based on the application of such a sensor arrangement for the permanent remote monitoring of water quality.
  • the present invention deals with the continuous, on-line monitoring of critical water attributes or parameters; such that any contamination can be detected virtually instantly and all needed countermeasures can be taken as long as they are still effective.
  • Cases of contamination in drinking water supply networks have had serious consequences in the past.
  • Such case was depicted in the movie Erin Brockovich (2000).
  • Other more or less serious cases of contamination have occurred all over the world.
  • One such case has prompted the inventors to find a permanent solution by providing a system for early detection and warning to the operator of a water distribution network.
  • a remote contamination monitoring system for a water supply network is known from the patent EP 1 649 278 Bl.
  • at least one detector is located in each one of a multiplicity of water supply lines.
  • the detectors are ca- pable of monitoring at least one attribute of water flowing through and to provide a signal related to that attribute selected from a wide range of physical or chemical parameters, like pH, temperature, electrical conductivity, chlorine concentration, etc., and from a wide range of biological parameters, like the presence of coliform and other bacteria or microorganisms.
  • Each detector pre- ferably is located at a node within a water supply network, which is also equipped with an access gate that is linked to communicate with an access controller. Specific personal attributes of an access key may allow certain individuals to access the one or more access gates of the monitoring system.
  • a particular shut-off valve may be located at a second node.
  • the local controller compares the incoming specific data with stored model data and based on this comparison, the local controller may decide to cause (again via a wireless link) the particular shut-off valve to close. Such decisions may be also based on cross correlation of data received from different detectors presenting differ- ent attributes; thus, not all detectors for all attributes have to be placed at the same node.
  • a particular sensor arrangement in a multi-parameter monitoring system is known from the patent US 7,007,541 Bl.
  • a plurality of multi-parameter monitoring tool assemblies are connected via a communication network and are further in communication with a central controller.
  • Each one of the multiparameter monitoring tool assemblies is equipped with a plurality of sensor head components and the central controller includes functionality to receive configuration information for each one of these interchangeable sensor head components to extract operational information therefrom.
  • the sensor heads of one multi-parameter monitoring tool may be placed within one restrictor that partially encloses the sensors but provides access openings for the water to reach the sensors. This restrictor also provides physical protection for the sen- sitive detectors when the multi-parameter monitoring tool is used to monitor water quality in location such as ground water or surface water.
  • the sensor heads of one multi-parameter monitoring tool may be placed within a flow cell that comprises input and output lines, thus providing a means to expose the sensors in a tool assembly to a remotely located liquid source.
  • One object of the present invention is the provision of an alternative sensor arrangement that permanently enables remote monitoring of the water quality in water supply lines over long periods of time.
  • One additional object of the pre- sent invention is the provision of an alternative sensor arrangement that is at least partially independent from a central controller.
  • Another object of the present invention is the provision of a method of permanent remote monitoring of water quality in a water supply line.
  • One further object of the present invention is the provision of an alternative sensor arrangement in a system that en- ables water suppliers to detect contaminations the very minute they occur.
  • the sensor arrangement according to the present invention is designed for the permanent remote monitoring of water quality in a water supply line.
  • the sen- sor arrangement comprises a number of sensors for the detection of different attributes of water quality and for providing actual measurement data.
  • the sensor arrangement also comprises a communicating unit for sending the actual measurement data to a central controller.
  • the sensor arrangement comprises a flow cell, which is equipped with a water inlet and with a water outlet that are accomplished to be connectable to a supply tube and respectively to a delivering tube of the water supply line.
  • the sensor arrangement according to the present invention is characterized in that the flow cell comprises a one-way water flow path that links the water inlet to the water outlet, wherein the sensors are arranged one downstream of the other with respect to the water flow path in such a way that their sensing parts, which interact with the flowing water, are located in or at least close to a central axis of the water flow path in each case. Additional preferred and inventive features derive from the dependent claims.
  • a second object is achieved by the provision of a sensor arrangement according to the present invention that further comprises a computing unit for processing the actual measurement data of the sensors, enabling the sensor arrangement to decide carrying out a shut-off action of a valve in the water sup- ply line and/or providing information to another sensor arrangement and to the central controller.
  • a third object is achieved by a method of permanent remote monitoring of water quality in a water supply line with the sensor arrangement according to the present invention.
  • This method is characterized in that a flow cell is mounted in or to a water supply line by connecting a supply tube to the water inlet and a delivering tube to the water outlet of the flow cell.
  • Different attributes of water quality are measured with a number of sensors in a one-way water flow path that links the water inlet to the water outlet, wherein the sensors are ar- ranged one downstream of the other with respect to the water flow path in such a way that their sensing parts, which interact with the flowing water, are located in or at least close to a central axis of the water flow path in each case.
  • a fourth object is achieved by the provision of a system as described hereaf- ter.
  • the system is based on a number of remote sensors located throughout the operator's water supply network.
  • the sensors communicate with each other using a self-organized wireless network, sharing data and control commands.
  • the system enables water suppliers to detect contaminations the very minute they occur. This is of paramount importance to protect the aqueducts from intentional acts, negligence, and accidents.
  • the main purpose for a systematic water quality data collection and management is the ability to counteract possible water contamination events in a timely manner. Also, the collected data can be used to make forecasts of the water quality in the different spots of the network under the influence of external factors or predict the diffusion pattern of a contamination.
  • a "water distribution network” is a network consisting of water sources, pumping and treatment stations, as well as pipes used to supply water to users within a community.
  • a “contamination” is the presence, in critical amounts, of unwanted and/or potentially hazardous substances in drinking or potable water.
  • a “self-organized sensor network” is a network consisting of spatially distributed autonomous devices using sensors to co-operatively monitor physical or environmental conditions, such as temperature, sound, vibration, pressure, motion or pollutants, at different locations.
  • a “sensor node” is a node in a wireless sensor network that is capable of per- forming some processing, gathering sensory information and communicating with other connected nodes in the network.
  • An “actuator” is a mechanical member which is used to control the flow in a section of the water distribution network, such as a slide valve or any other shut-off device.
  • a “physical parameter” is an attribute such as, but not limited to, temperature, turbidity, and conductivity (raw and corrected) of the water that is flowing in the water distribution network.
  • a “chemical parameter” is an attribute such as, but not limited to, oxygen content, pH, redox potential, chlorine concentration, DOC/TOC, CSB / BSB, nitrate concentration.
  • a “biological parameter” is an attribute referring to microorganisms such as, but not limited to, Escherichia coli, Salmonella, Shigella, Pseudomonas, Legionella species.
  • a “triangulation technique” is a technique by which the spatio-temporal origin of an event can be derived by mathematical means from distributed sensor information.
  • Fig. 1 shows a first embodiment of a sensor arrangement for the permanent remote monitoring of water quality according to the present invention
  • Fig. 2 shows the preferred dimensions of the first embodiment of a sensor arrangement for the permanent remote monitoring of water quality of Fig. 1;
  • Fig. 3 shows part of the layout of the water distribution system in the corporation of Chiasso (Switzerland);
  • Fig. 4 shows a plot of the water flow patterns over 24 hours, as measured by two currently operational main inlet flow meters
  • Fig. 5 shows a schematic of a typical water distribution network equipped with a self-organized network of sensors, a network of actuators and centralized or distributed data processing and actuator control units.
  • the Figure 1 shows a first embodiment of a sensor arrangement for the per- manent remote monitoring of water quality according to the present invention.
  • This is a sensor arrangement 1 for the permanent remote monitoring of water quality in a water supply line 2.
  • the sensor arrangement 1 comprises a number of sensors 3 for the detection of different attributes of water quality and for providing actual measurement data, a communicating unit 4 for sending the actual measurement data to a central controller 5, and a flow cell 6.
  • the flow cell 6 is equipped with a water inlet 7 and with a water outlet 8 that are accomplished to be connectable to a supply tube 9 and respectively to a delivering tube 10 of the water supply line 2.
  • the sensor arrangement 1 for the permanent remote monitoring of water quality is characterized in that the flow cell 6 comprises a one-way water flow path 11 that links the water inlet 7 to the water outlet 8, wherein the sensors 3 are arranged one downstream of the other with respect to the water flow path 11 in such a way that their sensing parts 12, which interact with flowing water, are located in or at least close to a central axis 13 of the water flow path 11 in each case.
  • the preferred diameter of the water flow path is 23 mm, whereas its length preferably is not longer than 600 mm.
  • each one of the sensors 3 comprises a thread portion 14 for fastening the sensor 3 from the outside in an adequate nut portion 15 of an insert hole 16 of the flow cell 6.
  • Each one of these insert holes 16 individually opens into the water flow path 11.
  • Providing the sensors 3 with a threaded portion 14 facilitates precise mounting and exchange of the sensors 3.
  • other modes of fixing the sensors 3 to the flow cell 6 are conceivable; such modes e.g. include the utilization of bayonet-type quick lock connections (not shown).
  • the water flow path 11 comprises a number of particular flow path parts 17 that exhibit an essentially circular cross section with a diameter 18 that is adapted to the type of sensor 3, of which the sensing part 12 is located in the particular flow path part 17.
  • the particular water flow path parts 17 preferably are concentrically arranged with respect to the central axis 13 of the water flow path 11. In the first embodiment as shown in Fig. 1, the flow cell 6 of the sensor arrangement 1 is accomplished as a cube.
  • the central axis 13 of the water flow path 11 essentially extends parallel to three straight extensions of the flow cell 6, forming a one-way water flow path 11 in an inverted U-shape.
  • a choke device 19 for regulating the water flow in the water flow path 11.
  • optimal measuring or detection conditions can be achieved for the different sensors 3 that each are located in a cavity of adapted volume.
  • the particular condition for each sensor 3 can be optimized.
  • regulating the water flow also eliminates the danger of accumulation contaminants or biological mass.
  • a particular water flow (of 30 to 50 l/h for drinking water applications) is preferably chosen within the one-way water flow path 11 of a flow cell 6 that is inserted in or attached to a network with a water pressure in the range of e.g. 0.1 to 6 bar for household accommodation.
  • Such water flow provides continuous cleaning of the flow cell 6 in a way that the sensor arrangement 1 can be constantly at- tached to the water distribution network 44 (see Fig. 5) for months and even years.
  • the flow cell 6 could be mounted in any other orientation : In an upside-down position, for example, the one-way water flow path 11 will exhibit an upright U-shape. In a position, where the flow cell 6 is turned by 90° to the left, for example, the one-way water flow path 11 will exhibit an upright C-shape. The actual orientation is left to the decision of the skilled person that mounts the flow cell 6. However, the position as shown in Fig. 1 is preferred, because the choke device 19 can preferably also be used as a ventilation tool for removing most or all present air bubbles in the one-way water flow path 11 of the flow cell 6.
  • the flow cell can be accomplished as a stretched cube (not shown), in which the central axis 13 of the water flow path 11 essentially extends parallel to the length extension of the flow cell 6, forming a straight one-way water flow path 11 (not shown).
  • the individual sensors 3 can be arranged on one, two, three, or on all four sides of such a stretched tube (not shown).
  • the flow cell can be accomplished as a cylinder (not shown), in which the central axis 13 of the water flow path 11 essentially extends parallel to the length extension of the flow cell 6, forming a straight one-way water flow path 11 (not shown).
  • the flow cell 6 preferably is made of a non-corrosive, inert material that is selected from a group of materials comprising brass, light metals, light metal alloys, polymer materials, and polymer composite materials. The skilled person will select the appropriate materials that are labeled and allowed for use in drinking water supply lines.
  • Manufacturing of the flow cell 6 preferably is carried out by injection molding of polymer materials and/or polymer composite materials. This method has the advantage that lightweight flow cells can be produced in large numbers and with high precision; the rather high costs for the molding tool being distributed to the large number of individual flow cells. If however, smaller series of flow cells 6 are to be manufactured block materials of metals or polymers can be utilized and the insert holes 16 and the particular water flow path parts 17 are then accomplished as bore holes. In order to optimize quality and to minimize production costs, combinations of these methods and also the use of molded semi-finished parts of metal or polymer materials can be used.
  • the sensors 3 for mounting to the flow cell 6 preferably are selected from a group comprising pH, redox, chlorine, UV-VIS, turbidimetry, O 2 , and electrical conductivity probes.
  • a pH probe 21, a redox probe 22, a chlorine, chlorine dioxide, or ozone sensor 23, a UV-VIS probe 24, a turbidity sensor 25, an O 2 sensor 27, and a probe to measure electrical conductivity 28 are arranged along the one-way water flow path 11.
  • a pH probe 21, a redox probe 22, a chlorine, chlorine dioxide, or ozone sensor 23, a UV-VIS probe 24, a turbidity sensor 25, an O 2 sensor 27, and a probe to measure electrical conductivity 28 are arranged along the one-way water flow path 11.
  • Void insert holes 16 can be closed with a stopper 26 in order to prevent any leakage of the flow cell 6. If appropriate, all sensors and stoppers are provided with at least one seal 30 for sealingly closing the water flow path 11 against the surroundings.
  • the stopper 26 preferably is also used for maintenance purposes such as cleaning the special coated glass tube of the turbidity meter and for calibrating the turbidity meter with reference calibration glasses.
  • a turbidity meter 25 with an LED transmitter that is po- sitioned in a 90° angle to the receptor (sensor) 25.
  • the transmitter is mounted on the back side oft the flow cell 6.
  • the water flows through an inserted glass tube 48 that is sealed by two O-rings 30 (see Fig. 1).
  • an automatic vent valve 47 is preferably mounted to the water flow path 11 for releasing of all possibly present gas bubbles in the flow cell 6.
  • the sensor arrangement 1 of the present invention further comprises a computing unit 20 for processing the actual measurement data of the sensors 3.
  • the computing unit 20 enables the sen- sor arrangement 1 to decide carrying out a shut-off action of a valve 38 (see Fig. 3 and 5) in the water supply line 2 and/or (preferably wireless) providing information to another sensor arrangement 1 and to the central controller 5 via an antenna 29.
  • an already described sensor arrangement 1 is utilized.
  • the method is characterized in that a flow cell 6 is mounted in or to a water supply line 2 by connecting a supply tube 9 to the water inlet 7 and a delivering tube 10 to the water outlet 8 of the flow cell 6; different attributes of water quality are measured with a number of sensors 3 in a one-way water flow path 11 that links the water inlet 7 to the water outlet 8, wherein the sensors 3 are arranged one downstream of the other with respect to the water flow path 11 in such a way that their sensing parts 12, which interact with the flowing water, are located in or at least close to a central axis 13 of the water flow path 11 in each case.
  • the water flow through the water flow path 11 is monitored and regulated with a choke device 19 of the flow cell 6. If required, e.g. if a too high biological cell content is detected within the flow cell, the water flow can be raised for flushing the flow cell 6. Such flushing can be carried out manually; it is however most preferably also made by remote control. Such remote control can be carried out by the individual computing unit 20 of the particular sensor arrangement 1 or by the central controller 5. In any case, such individual control preferably is monitored by the central controller 5 as well.
  • a particular water flow (of 30 to 50 l/h for drinking water applications) is preferably chosen within the one-way water flow path 11 of a flow cell 6 that is attached to a network with a water pressure in the range of e.g. 0.1 to 6 bar for household accommodation. Such water flow provides continuous cleaning of the flow cell 6 such that the sensor arrangement 1 can be constantly attached to the water distribution network for months and even years.
  • the present invention provides for a method and a system for early detection of contamination in a drinking water supply.
  • the main purpose of the system is to enable the issuance of warnings to the population and to the authorities at an early enough stage of pollution. Thus, counteractions can be taken on time and the exposure of the population to harmful contaminants can be minimized and, possibly, averted all together.
  • the system allows one to set up the means to provide continuous updates on the quality of drinking water. Moreover, as a further development, the system will enable one to automatically control the water flow through the network so as to minimize the effects of a possible contamination.
  • a series of several sensor assemblies or as they are called "sensor arrangements" for on-line water quality monitoring is used. Such sensing units comprise a flow cell 6 and monitor physical, chemical and biological parameters.
  • the physical-chemical parameters include, but are not limited to, temperature, turbidity, conductivity, oxygen content, pH, redox potential, chlorine concentration, DOC/TOC, COD , BOD, (dissolved organic carbons/ total organic carbons, chemical oxygen demand, biological oxygen demand) and nitrate concentration, to name a few.
  • the biological parameters include, but are not limited to, Escherichia coli, Salmonella, Shigella, Pseudomonas, Le- gionella species.
  • the sensing units can be placed in different locations, such as to cover a minimum of principal nodes of the network.
  • the definition of the spatial location of the sensor assemblies or sensor arrangements 1 is the result of a systematic research and optimization taking into account:
  • a solid database and appropriate algorithms allow the water distribution network operator to determine the general picture of the quality of the distributed water by measuring just a few parameters at any time.
  • all the relevant parameters are determined throughout the water supply network by measuring only a few values and using the appropriate correlation algorithms.
  • a main measurement location I for example, all the parameters (1 to n) are measured.
  • Such parameters comprise all those listed above.
  • external sites II and III for instance, secondary measurement locations with only limited measurement capabilities are available. In those external sites II and III, only parameters 1 to p and 1 to q are monitored, respectively, where (p,q) ⁇ n.
  • the correlations found between the data recorded at the main measurement location I allow to extrapolate such parameters in all other sites (here II and III) and at every time, on the basis of the fewer but relevant parameters measured there.
  • the minimization of the number of monitored parameters will hence result in a reduction of the dimension of the sensor assemblies or sensor arrangements 1, which can be fit virtually anywhere within the network 44, for example in fire hydrants (in surface hydrants 35 or in sub-surface hydrants 36; see Fig. 3). Also, a cost reduction of the sensor arrangements 1, which is desirable in view of a widespread use of the sensors 3, is a positive consequence of the minimization of the monitored parameters.
  • While the sensor assemblies or sensor arrangements 1 preferably store the continuously acquired data locally (i.e. in their computing unit 20), they are al- so equipped with wireless transmission modules or communicating units 4 that are used to send the data to a central monitoring and data management station, i.e. to a central controller 5.
  • Wireless data transfer e.g. via antennas 29 has already proved its value.
  • a routine is implemented for the transmission of the data on a regular basis.
  • the area where water sources are located may exhibit geological characteristics that expose them to weather. For example, the karstic nature of some areas may cause water turbidity to increase dramatically as early as only a few hours after the onset of heavy rain. The probability of finding bacteria (dragged from fertilized fields on the surface) may thus increase significantly. This condition makes it yet more urgent to be able to predict the presence of contaminants in the water as it is extracted and fed into the network.
  • weather data such as that taken from the databases of weather forecasters can be used for the refinement of the prediction models.
  • Water demand varies continuously during the course of the day. While it is at its highest in the morning or at lunch and dinner time, it is very low during the night, particularly after 12 midnight. Moreover, the consumption pattern of residential areas is different as compared to business/industrial areas (see Figs. 3 and 4). Flow data from water meters scattered across the network may be used in such a way as to optimize any necessary counteractions (e.g. shut- offs of pipe sections), in case of contamination to areas of the water supply network more likely to be affected by such event.
  • any necessary counteractions e.g. shut- offs of pipe sections
  • the Figure 2 shows the preferred dimensions of the first embodiment of a sen- sor arrangement 1 for the permanent remote monitoring of water quality of Fig. 1. All dimensions are indicated in mm.
  • Table 1 indicates the chemical and physical attributes of the water that preferably are measured as well as the technical data of the sensors preferably used for this purpose. Table 1
  • the computing unit 20 of the sensor arrangement 1 for the permanent remote monitoring of water quality preferably comprises a CPU element with a 32 bit processor and a 128 MB memory running under a LINUX surface.
  • the computing unit 20 preferably further comprises a 128/240 pixel LCD graphic screen with touch panel.
  • Interfaces preferably comprise a CAN bus, through which additional sensors can be hooked up and additional parameters or attributes can be measured.
  • Interfaces preferably also comprise an Ethernet 10/100 MBit interface, a USB contact, and a GSM module.
  • the preferred working tension is 24 V direct current at 2 amperes.
  • the Figure 3 shows part of the layout of the water distribution system in the corporation of Chiasso (Switzerland).
  • the water supply lines 2 of the water distribution network 44 are drawn.
  • a first main flow meter 31 and a second main flow meter 32 are arranged at two extreme positions, namely close to the point where the water enters the network 44 from the water line in direction of "Serbatoio Pignolo" (see arrow 46) and from source 34; "Serbatoio San Giorgio".
  • source 34 "Serbatoio San Giorgio”.
  • a real network 44 of water supply lines 2 is provided here.
  • fire hydrants are positioned in the shape of a surface hydrant 35 or a sub-surface hydrant 36 all numbered with an individual hydrant number 37.
  • a large number of actuators (valves) 38 are distributed all over the network as well. Geographical north is indicated with an arrow labeled with N.
  • the Figure 4 shows a plot of the water flow patterns over 24 hours, as measured by the two currently operational main inlet flow meter 1 (labeled 31 in Fig. 3) and main inlet flow meter 2 (labeled 32 in Fig. 3).
  • the graphs are re- lated to the main flow meters 1 (31) and 2 (32) and demonstrate how a practically continuous feed of water is provided in spite of considerably different flow values from the respective sources.
  • the abscissa of the graph indicates times and dates of the measurements, whereas the ordinate of the graph shows the measured flow in liters per second.
  • knowing the contribution of each source is important for the estimation of the speed of propagation of contaminants in the related network areas.
  • Flow data from water meters scattered across the network e.g. billing meters located at user households, may be used in such a way as to op- timize any necessary counteractions (e.g. shutoffs of pipe sections), in case of contamination, to areas of the water supply network more likely to be affected by such event.
  • the Figure 5 shows a schematic of a typical water distribution network 44 equipped with a self-organized network of sensors 3, a network of actuators 38 and a centralized data processing unit 41 and/or distributed actuator control units 40.
  • the sensors preferably communicate via a sensor network 42 and the actuators preferably communicate via an actuator network 43.
  • the water enters the network 44 from a reservoir 39 that is fed by a source 34.
  • the valves 38 are preferably able to communicate with other valves 38, with sensors 3, and with the control unit 38 as well as with the data processing unit 41. In this way, all participants of the two communication networks are able to address each other. This how- ever, is important, if a network of sensor nodes and actuators shall self- organize. Sensor nodes and self-organizing networks are known per se (see e.g. the patent application US 2007/0180918 Al), they are however applied the first time to water distribution networks as described herein.
  • This self-organized network of sensors 42 preferably uses a link for inter- sensor communication, the link being chosen from an optical link, a wired link, a wireless link, or an arbitrary combination thereof. Especially preferred is the use of a wireless link in each case.
  • identification of the nature of a contamination is carried out.
  • identification of the geographical location of the position of the sensor arrangement 1 is carried out by utilizing a triangulation technique. It is especially preferred that the self-organized network of sensors is automatically updated in the event of:
  • the system for early detection of contamination in a drinking wa- ter supply is permanently actualized and can fulfill its function as a detection and alarm system.
  • This updating is preferably supported in that any one of the events (a) to (d) are communicated to a centralized or distributed data processing and interpretation unit 41 and/or to a centralized or distributed control unit 40 to operate the actuators 38.
  • the actuators 38 in the water distribution network 44 are reorganized, so as to ensure a continuous supply of water to areas not directly concerned by the contamination. In this way, valves 38 in the vicinity of the detected con- tamination are shut-off to stop distribution of contaminated water. The same time, valves 38 in non-contaminated areas can be kept open. It is particularly preferred that a warning message according to the nature of an event selected from a group of events comprising abnormal physical, chemical or biological attributes in relation to a previously defined threshold is distributed to specific sites. Such specific sites can be a centralized or distributed data processing and interpretation unit 41 and/or a centralized or distributed control unit 40 to operate the actuators 38. Other specific sites can be located at police stations, fire fighter stations, hospitals, communal and regional alarm and information centers etc.
  • a system for early detection of pollutants in a water distribution network 44 is described.
  • the system is based on a number of remote sensors 3 located throughout the water supply network 44.
  • the sensors 3 communicate with each other using a self-organized wireless network, sharing data and control commands.
  • the system enables water suppliers to detect contaminations the very minute they occur. This is of paramount importance to protect the aqueducts from intentional acts, negligence, and accidents.

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  • Arrangements For Transmission Of Measured Signals (AREA)

Abstract

A sensor arrangement (1) and a method for the permanent remote monitoring of water quality in a water supply line (2) is disclosed. The sensor arrangement (1) comprises a number of sensors (3) for the detection of different attributes of water quality and for providing actual measurement data, a communicating unit (4) for sending the actual measurement data to a central controller (5), and a flow cell (6), which is equipped with a water inlet (7) and with a water outlet (8) that are accomplished to be connectable to a supply tube (9) and respectively to a delivering tube (10) of the water supply line (2). The sensor arrangement (1) according to the invention is characterized in that the flow cell (6) comprises a one-way water flow path (11) that links the water inlet (7) to the water outlet (8), wherein the sensors (3) are arranged one downstream of the other with respect to the water flow path (11) in such a way that their sensing parts (12), which interact with the flowing water, are located in or at least close to a central axis (13) of the water flow path (11) in each case. Also disclosed is a system for early detection of pollutants in a water distribution network (44). The system is based on a number of remote sensors (3) located throughout the water supply network (44). The sensors (3) communicate with each other using a self-organized wireless network, sharing data and control commands. The system enables water suppliers to detect contaminations the very minute they occur.

Description

Sensor arrangement and method for water quality monitoring
Technical field of the invention
The present invention relates to a sensor arrangement for the permanent remote monitoring of water quality in a water supply line and more particularly in a water supply network. In a preferred embodiment, the present invention concerns real-time remote sensing of contamination in water distribution networks. In addition, the present invention relates to methods that are based on the application of such a sensor arrangement for the permanent remote monitoring of water quality.
All drinking water suppliers in Switzerland are subject to the federal law on foodstuffs, to cantonal laws, and to the guidelines of the Swiss Society of the Gas and Water Industry, as far as ensuring a minimum drinking water quality is concerned. Such regulations demand that the purity of drinking water be verified on a regular basis by means of laboratory tests. For instance, tests to determine the presence of bacteria in drinking water, if any, shall be conducted monthly, while any content of harmful chemicals shall be checked twice a year. These conventional methods, however, do not by any means provide a full safety guarantee, such that any contamination that occur a short time after the lab checks goes undetected until the following tests are performed. In contrast, the present invention deals with the continuous, on-line monitoring of critical water attributes or parameters; such that any contamination can be detected virtually instantly and all needed countermeasures can be taken as long as they are still effective. Cases of contamination in drinking water supply networks have had serious consequences in the past. One famous example, which ended up in court, occurred in California, where the aquifer of the town of Hinkley had been polluted by emissions of solutions containing hexavalent chromium ions, used for cor- rosion protection, from a nearby plant. Such case was depicted in the movie Erin Brockovich (2000). Other more or less serious cases of contamination have occurred all over the world. One such case has prompted the inventors to find a permanent solution by providing a system for early detection and warning to the operator of a water distribution network.
Related prior art
A remote contamination monitoring system for a water supply network is known from the patent EP 1 649 278 Bl. There, at least one detector is located in each one of a multiplicity of water supply lines. The detectors are ca- pable of monitoring at least one attribute of water flowing through and to provide a signal related to that attribute selected from a wide range of physical or chemical parameters, like pH, temperature, electrical conductivity, chlorine concentration, etc., and from a wide range of biological parameters, like the presence of coliform and other bacteria or microorganisms. Each detector pre- ferably is located at a node within a water supply network, which is also equipped with an access gate that is linked to communicate with an access controller. Specific personal attributes of an access key may allow certain individuals to access the one or more access gates of the monitoring system. A particular shut-off valve may be located at a second node. When the detector signals specific data to a central controller via a wireless link, the local controller compares the incoming specific data with stored model data and based on this comparison, the local controller may decide to cause (again via a wireless link) the particular shut-off valve to close. Such decisions may be also based on cross correlation of data received from different detectors presenting differ- ent attributes; thus, not all detectors for all attributes have to be placed at the same node.
A particular sensor arrangement in a multi-parameter monitoring system is known from the patent US 7,007,541 Bl. There, a plurality of multi-parameter monitoring tool assemblies are connected via a communication network and are further in communication with a central controller. Each one of the multiparameter monitoring tool assemblies is equipped with a plurality of sensor head components and the central controller includes functionality to receive configuration information for each one of these interchangeable sensor head components to extract operational information therefrom. The sensor heads of one multi-parameter monitoring tool may be placed within one restrictor that partially encloses the sensors but provides access openings for the water to reach the sensors. This restrictor also provides physical protection for the sen- sitive detectors when the multi-parameter monitoring tool is used to monitor water quality in location such as ground water or surface water. Alternatively, the sensor heads of one multi-parameter monitoring tool may be placed within a flow cell that comprises input and output lines, thus providing a means to expose the sensors in a tool assembly to a remotely located liquid source.
Objects and summary of the present invention
One object of the present invention is the provision of an alternative sensor arrangement that permanently enables remote monitoring of the water quality in water supply lines over long periods of time. One additional object of the pre- sent invention is the provision of an alternative sensor arrangement that is at least partially independent from a central controller. Another object of the present invention is the provision of a method of permanent remote monitoring of water quality in a water supply line. One further object of the present invention is the provision of an alternative sensor arrangement in a system that en- ables water suppliers to detect contaminations the very minute they occur.
A first object is achieved by the sensor arrangement as herein described. The sensor arrangement according to the present invention is designed for the permanent remote monitoring of water quality in a water supply line. The sen- sor arrangement comprises a number of sensors for the detection of different attributes of water quality and for providing actual measurement data. The sensor arrangement also comprises a communicating unit for sending the actual measurement data to a central controller. In addition, the sensor arrangement comprises a flow cell, which is equipped with a water inlet and with a water outlet that are accomplished to be connectable to a supply tube and respectively to a delivering tube of the water supply line. The sensor arrangement according to the present invention is characterized in that the flow cell comprises a one-way water flow path that links the water inlet to the water outlet, wherein the sensors are arranged one downstream of the other with respect to the water flow path in such a way that their sensing parts, which interact with the flowing water, are located in or at least close to a central axis of the water flow path in each case. Additional preferred and inventive features derive from the dependent claims.
A second object is achieved by the provision of a sensor arrangement according to the present invention that further comprises a computing unit for processing the actual measurement data of the sensors, enabling the sensor arrangement to decide carrying out a shut-off action of a valve in the water sup- ply line and/or providing information to another sensor arrangement and to the central controller.
A third object is achieved by a method of permanent remote monitoring of water quality in a water supply line with the sensor arrangement according to the present invention. This method is characterized in that a flow cell is mounted in or to a water supply line by connecting a supply tube to the water inlet and a delivering tube to the water outlet of the flow cell. Different attributes of water quality are measured with a number of sensors in a one-way water flow path that links the water inlet to the water outlet, wherein the sensors are ar- ranged one downstream of the other with respect to the water flow path in such a way that their sensing parts, which interact with the flowing water, are located in or at least close to a central axis of the water flow path in each case.
A fourth object is achieved by the provision of a system as described hereaf- ter. The system is based on a number of remote sensors located throughout the operator's water supply network. The sensors communicate with each other using a self-organized wireless network, sharing data and control commands. The system enables water suppliers to detect contaminations the very minute they occur. This is of paramount importance to protect the aqueducts from intentional acts, negligence, and accidents. The main purpose for a systematic water quality data collection and management is the ability to counteract possible water contamination events in a timely manner. Also, the collected data can be used to make forecasts of the water quality in the different spots of the network under the influence of external factors or predict the diffusion pattern of a contamination.
Definitions
In the context of the present invention, the following definitions apply: A "water distribution network" is a network consisting of water sources, pumping and treatment stations, as well as pipes used to supply water to users within a community.
A "contamination" is the presence, in critical amounts, of unwanted and/or potentially hazardous substances in drinking or potable water. A "self-organized sensor network" is a network consisting of spatially distributed autonomous devices using sensors to co-operatively monitor physical or environmental conditions, such as temperature, sound, vibration, pressure, motion or pollutants, at different locations. A "sensor node" is a node in a wireless sensor network that is capable of per- forming some processing, gathering sensory information and communicating with other connected nodes in the network.
An "actuator" is a mechanical member which is used to control the flow in a section of the water distribution network, such as a slide valve or any other shut-off device. A "physical parameter" is an attribute such as, but not limited to, temperature, turbidity, and conductivity (raw and corrected) of the water that is flowing in the water distribution network.
A "chemical parameter" is an attribute such as, but not limited to, oxygen content, pH, redox potential, chlorine concentration, DOC/TOC, CSB / BSB, nitrate concentration.
A "biological parameter" is an attribute referring to microorganisms such as, but not limited to, Escherichia coli, Salmonella, Shigella, Pseudomonas, Legionella species. A "triangulation technique" is a technique by which the spatio-temporal origin of an event can be derived by mathematical means from distributed sensor information.
Brief introduction of the drawings
The invention will be better understood with the aid of the description of an embodiment that is given by way of example, that is not limiting the scope of the present invention, and that is illustrated by the attached figures, in which :
Fig. 1 shows a first embodiment of a sensor arrangement for the permanent remote monitoring of water quality according to the present invention;
Fig. 2 shows the preferred dimensions of the first embodiment of a sensor arrangement for the permanent remote monitoring of water quality of Fig. 1;
Fig. 3 shows part of the layout of the water distribution system in the corporation of Chiasso (Switzerland);
Fig. 4 shows a plot of the water flow patterns over 24 hours, as measured by two currently operational main inlet flow meters;
Fig. 5 shows a schematic of a typical water distribution network equipped with a self-organized network of sensors, a network of actuators and centralized or distributed data processing and actuator control units.
Detailed description of the invention
The Figure 1 shows a first embodiment of a sensor arrangement for the per- manent remote monitoring of water quality according to the present invention. This is a sensor arrangement 1 for the permanent remote monitoring of water quality in a water supply line 2. The sensor arrangement 1 comprises a number of sensors 3 for the detection of different attributes of water quality and for providing actual measurement data, a communicating unit 4 for sending the actual measurement data to a central controller 5, and a flow cell 6. The flow cell 6 is equipped with a water inlet 7 and with a water outlet 8 that are accomplished to be connectable to a supply tube 9 and respectively to a delivering tube 10 of the water supply line 2.
The sensor arrangement 1 for the permanent remote monitoring of water quality according to the present invention is characterized in that the flow cell 6 comprises a one-way water flow path 11 that links the water inlet 7 to the water outlet 8, wherein the sensors 3 are arranged one downstream of the other with respect to the water flow path 11 in such a way that their sensing parts 12, which interact with flowing water, are located in or at least close to a central axis 13 of the water flow path 11 in each case. The preferred diameter of the water flow path is 23 mm, whereas its length preferably is not longer than 600 mm.
Preferably, each one of the sensors 3 comprises a thread portion 14 for fastening the sensor 3 from the outside in an adequate nut portion 15 of an insert hole 16 of the flow cell 6. Each one of these insert holes 16 individually opens into the water flow path 11. Providing the sensors 3 with a threaded portion 14 facilitates precise mounting and exchange of the sensors 3. Also other modes of fixing the sensors 3 to the flow cell 6 are conceivable; such modes e.g. include the utilization of bayonet-type quick lock connections (not shown).
Special sensors perform best in an adapted location that provides the sensor with an optimal water volume. In this sensor arrangement 1, it is thus preferred that the water flow path 11 comprises a number of particular flow path parts 17 that exhibit an essentially circular cross section with a diameter 18 that is adapted to the type of sensor 3, of which the sensing part 12 is located in the particular flow path part 17. In order to provide the sensors 3 in the sensor arrangement 1 with an at least nearly homogenous environment, the particular water flow path parts 17 preferably are concentrically arranged with respect to the central axis 13 of the water flow path 11. In the first embodiment as shown in Fig. 1, the flow cell 6 of the sensor arrangement 1 is accomplished as a cube. In order to provide a sensor arrangement 1 with a minimized total volume, the central axis 13 of the water flow path 11 essentially extends parallel to three straight extensions of the flow cell 6, forming a one-way water flow path 11 in an inverted U-shape.
It is especially preferred to equip the flow cell 6 of the inventive sensor arrangement 1 with a choke device 19 for regulating the water flow in the water flow path 11. When regulating the water flow, optimal measuring or detection conditions can be achieved for the different sensors 3 that each are located in a cavity of adapted volume. By adapting the volume of the cavity and by regulating the water flow, the particular condition for each sensor 3 can be optimized. It actually has been found that regulating the water flow also eliminates the danger of accumulation contaminants or biological mass. Thus, a particular water flow (of 30 to 50 l/h for drinking water applications) is preferably chosen within the one-way water flow path 11 of a flow cell 6 that is inserted in or attached to a network with a water pressure in the range of e.g. 0.1 to 6 bar for household accommodation. Such water flow provides continuous cleaning of the flow cell 6 in a way that the sensor arrangement 1 can be constantly at- tached to the water distribution network 44 (see Fig. 5) for months and even years.
Departing from the presentation in Fig. 1, the flow cell 6 could be mounted in any other orientation : In an upside-down position, for example, the one-way water flow path 11 will exhibit an upright U-shape. In a position, where the flow cell 6 is turned by 90° to the left, for example, the one-way water flow path 11 will exhibit an upright C-shape. The actual orientation is left to the decision of the skilled person that mounts the flow cell 6. However, the position as shown in Fig. 1 is preferred, because the choke device 19 can preferably also be used as a ventilation tool for removing most or all present air bubbles in the one-way water flow path 11 of the flow cell 6.
Also departing from the presentation in the Fig. 1, the flow cell can be accomplished as a stretched cube (not shown), in which the central axis 13 of the water flow path 11 essentially extends parallel to the length extension of the flow cell 6, forming a straight one-way water flow path 11 (not shown). The individual sensors 3 can be arranged on one, two, three, or on all four sides of such a stretched tube (not shown).
Again departing from the presentation in the Fig. 1, the flow cell can be accomplished as a cylinder (not shown), in which the central axis 13 of the water flow path 11 essentially extends parallel to the length extension of the flow cell 6, forming a straight one-way water flow path 11 (not shown). In order to meet the demands of the drinking water quality regulations cited in the beginning, the flow cell 6 preferably is made of a non-corrosive, inert material that is selected from a group of materials comprising brass, light metals, light metal alloys, polymer materials, and polymer composite materials. The skilled person will select the appropriate materials that are labeled and allowed for use in drinking water supply lines.
Manufacturing of the flow cell 6 preferably is carried out by injection molding of polymer materials and/or polymer composite materials. This method has the advantage that lightweight flow cells can be produced in large numbers and with high precision; the rather high costs for the molding tool being distributed to the large number of individual flow cells. If however, smaller series of flow cells 6 are to be manufactured block materials of metals or polymers can be utilized and the insert holes 16 and the particular water flow path parts 17 are then accomplished as bore holes. In order to optimize quality and to minimize production costs, combinations of these methods and also the use of molded semi-finished parts of metal or polymer materials can be used. The sensors 3 for mounting to the flow cell 6 preferably are selected from a group comprising pH, redox, chlorine, UV-VIS, turbidimetry, O2, and electrical conductivity probes.
In the embodiment shown in Fig. 1, a pH probe 21, a redox probe 22, a chlorine, chlorine dioxide, or ozone sensor 23, a UV-VIS probe 24, a turbidity sensor 25, an O2 sensor 27, and a probe to measure electrical conductivity 28 are arranged along the one-way water flow path 11. An overview of useful sensors and attributes to be measured with is given in the patent EP 1 649 278 Bl, which incorporated herein by explicit reference. Thus, any sensor listed in this European patent, i.e. any sensor that is commercially available can be incorporated in the flow cell 6 of the sensor arrangement 1 according to the invention. It is however noted that the sequence of sensors 3 preferably is chosen as depicted in Fig. 1. Void insert holes 16 can be closed with a stopper 26 in order to prevent any leakage of the flow cell 6. If appropriate, all sensors and stoppers are provided with at least one seal 30 for sealingly closing the water flow path 11 against the surroundings. The stopper 26 preferably is also used for maintenance purposes such as cleaning the special coated glass tube of the turbidity meter and for calibrating the turbidity meter with reference calibration glasses.
Especially preferred is a turbidity meter 25 with an LED transmitter that is po- sitioned in a 90° angle to the receptor (sensor) 25. The transmitter is mounted on the back side oft the flow cell 6. In addition, it is to be mentioned that the water flows through an inserted glass tube 48 that is sealed by two O-rings 30 (see Fig. 1). In addition, an automatic vent valve 47 is preferably mounted to the water flow path 11 for releasing of all possibly present gas bubbles in the flow cell 6.
It is especially preferred that the sensor arrangement 1 of the present invention further comprises a computing unit 20 for processing the actual measurement data of the sensors 3. Thus, the computing unit 20 enables the sen- sor arrangement 1 to decide carrying out a shut-off action of a valve 38 (see Fig. 3 and 5) in the water supply line 2 and/or (preferably wireless) providing information to another sensor arrangement 1 and to the central controller 5 via an antenna 29. Any combination of features disclosed in this patent application that is deemed useful by a person skilled in the art belongs to the scope of the present invention.
In the method of permanent remote monitoring of water quality in a water supply line according to the present invention, an already described sensor arrangement 1 is utilized. The method is characterized in that a flow cell 6 is mounted in or to a water supply line 2 by connecting a supply tube 9 to the water inlet 7 and a delivering tube 10 to the water outlet 8 of the flow cell 6; different attributes of water quality are measured with a number of sensors 3 in a one-way water flow path 11 that links the water inlet 7 to the water outlet 8, wherein the sensors 3 are arranged one downstream of the other with respect to the water flow path 11 in such a way that their sensing parts 12, which interact with the flowing water, are located in or at least close to a central axis 13 of the water flow path 11 in each case.
Preferably, the water flow through the water flow path 11 is monitored and regulated with a choke device 19 of the flow cell 6. If required, e.g. if a too high biological cell content is detected within the flow cell, the water flow can be raised for flushing the flow cell 6. Such flushing can be carried out manually; it is however most preferably also made by remote control. Such remote control can be carried out by the individual computing unit 20 of the particular sensor arrangement 1 or by the central controller 5. In any case, such individual control preferably is monitored by the central controller 5 as well. Thus, a particular water flow (of 30 to 50 l/h for drinking water applications) is preferably chosen within the one-way water flow path 11 of a flow cell 6 that is attached to a network with a water pressure in the range of e.g. 0.1 to 6 bar for household accommodation. Such water flow provides continuous cleaning of the flow cell 6 such that the sensor arrangement 1 can be constantly attached to the water distribution network for months and even years.
The present invention provides for a method and a system for early detection of contamination in a drinking water supply. The main purpose of the system is to enable the issuance of warnings to the population and to the authorities at an early enough stage of pollution. Thus, counteractions can be taken on time and the exposure of the population to harmful contaminants can be minimized and, possibly, averted all together. The system allows one to set up the means to provide continuous updates on the quality of drinking water. Moreover, as a further development, the system will enable one to automatically control the water flow through the network so as to minimize the effects of a possible contamination. In one embodiment, a series of several sensor assemblies or as they are called "sensor arrangements" for on-line water quality monitoring is used. Such sensing units comprise a flow cell 6 and monitor physical, chemical and biological parameters. The physical-chemical parameters include, but are not limited to, temperature, turbidity, conductivity, oxygen content, pH, redox potential, chlorine concentration, DOC/TOC, COD , BOD, (dissolved organic carbons/ total organic carbons, chemical oxygen demand, biological oxygen demand) and nitrate concentration, to name a few. The biological parameters include, but are not limited to, Escherichia coli, Salmonella, Shigella, Pseudomonas, Le- gionella species.
In one embodiment, the sensing units can be placed in different locations, such as to cover a minimum of principal nodes of the network. The definition of the spatial location of the sensor assemblies or sensor arrangements 1 is the result of a systematic research and optimization taking into account:
(a) accessibility, (b) wireless coverage, (c) critical spots in the water distribution network, such as population density, average water flow, and presence of sources of potential dangers, to name just a few.
While the interdependence between some parameters is only qualitatively known from experience, it is of fundamental importance to quantify such relationships. One example of such correlation is represented by the reduction of the concentration of free chlorine ions (sodium hypochlorite is added for network protection purposes) in the presence of (general) bacterial content. Fur- thermore, parameters that appear to be normally considered independent of each other might exhibit some slight correlation.
A solid database and appropriate algorithms allow the water distribution network operator to determine the general picture of the quality of the distributed water by measuring just a few parameters at any time. In an exemplary embodiment, all the relevant parameters are determined throughout the water supply network by measuring only a few values and using the appropriate correlation algorithms. At a main measurement location I, for example, all the parameters (1 to n) are measured. Such parameters comprise all those listed above. At external sites II and III, for instance, secondary measurement locations with only limited measurement capabilities are available. In those external sites II and III, only parameters 1 to p and 1 to q are monitored, respectively, where (p,q) < n. According to such an exemplary embodiment of a sen- sor network 42 applied to a water distribution network 44, the correlations found between the data recorded at the main measurement location I allow to extrapolate such parameters in all other sites (here II and III) and at every time, on the basis of the fewer but relevant parameters measured there.
The minimization of the number of monitored parameters will hence result in a reduction of the dimension of the sensor assemblies or sensor arrangements 1, which can be fit virtually anywhere within the network 44, for example in fire hydrants (in surface hydrants 35 or in sub-surface hydrants 36; see Fig. 3). Also, a cost reduction of the sensor arrangements 1, which is desirable in view of a widespread use of the sensors 3, is a positive consequence of the minimization of the monitored parameters.
While the sensor assemblies or sensor arrangements 1 preferably store the continuously acquired data locally (i.e. in their computing unit 20), they are al- so equipped with wireless transmission modules or communicating units 4 that are used to send the data to a central monitoring and data management station, i.e. to a central controller 5. Wireless data transfer, e.g. via antennas 29 has already proved its value. In addition, a routine is implemented for the transmission of the data on a regular basis.
Are the data once downloaded, they are treated such that an operator is able to easily detect the presence of pollution events (and possibly to rule them out altogether). Also, once treated and made understandable, some of the data can be made available to the general public. Moreover, the data can be up- dated regularly, e.g. by posting them on a web page. In this respect however, one can ensure that the format of the publicly available data is such that it cannot give rise to misinterpretations and manipulations. Also, access to sensitive data shall be granted to selected users only. Data should in general be protected to avoid anyone to post it freely on the web. Well-known techniques of data protection should be used in this case. Such techniques are disclosed e.g. in the patent EP 1 649 278 Bl, which is incorporated herein by explicit reference also for this purpose.
The area where water sources are located may exhibit geological characteristics that expose them to weather. For example, the karstic nature of some areas may cause water turbidity to increase dramatically as early as only a few hours after the onset of heavy rain. The probability of finding bacteria (dragged from fertilized fields on the surface) may thus increase significantly. This condition makes it yet more urgent to be able to predict the presence of contaminants in the water as it is extracted and fed into the network. Hence, weather data, such as that taken from the databases of weather forecasters can be used for the refinement of the prediction models.
Water demand varies continuously during the course of the day. While it is at its highest in the morning or at lunch and dinner time, it is very low during the night, particularly after 12 midnight. Moreover, the consumption pattern of residential areas is different as compared to business/industrial areas (see Figs. 3 and 4). Flow data from water meters scattered across the network may be used in such a way as to optimize any necessary counteractions (e.g. shut- offs of pipe sections), in case of contamination to areas of the water supply network more likely to be affected by such event.
The Figure 2 shows the preferred dimensions of the first embodiment of a sen- sor arrangement 1 for the permanent remote monitoring of water quality of Fig. 1. All dimensions are indicated in mm.
The following table 1 indicates the chemical and physical attributes of the water that preferably are measured as well as the technical data of the sensors preferably used for this purpose. Table 1
The computing unit 20 of the sensor arrangement 1 for the permanent remote monitoring of water quality preferably comprises a CPU element with a 32 bit processor and a 128 MB memory running under a LINUX surface. The computing unit 20 preferably further comprises a 128/240 pixel LCD graphic screen with touch panel. Interfaces preferably comprise a CAN bus, through which additional sensors can be hooked up and additional parameters or attributes can be measured. Interfaces preferably also comprise an Ethernet 10/100 MBit interface, a USB contact, and a GSM module. The preferred working tension is 24 V direct current at 2 amperes.
The Figure 3 shows part of the layout of the water distribution system in the corporation of Chiasso (Switzerland). Along the streets and roads 45, the water supply lines 2 of the water distribution network 44 are drawn. A first main flow meter 31 and a second main flow meter 32 are arranged at two extreme positions, namely close to the point where the water enters the network 44 from the water line in direction of "Serbatoio Pignolo" (see arrow 46) and from source 34; "Serbatoio San Giorgio". In a more central position, there is the well and pump station 33. It is obvious from Fig. 3 that a real network 44 of water supply lines 2 is provided here. At prominent places, fire hydrants are positioned in the shape of a surface hydrant 35 or a sub-surface hydrant 36 all numbered with an individual hydrant number 37. A large number of actuators (valves) 38 are distributed all over the network as well. Geographical north is indicated with an arrow labeled with N.
The Figure 4 shows a plot of the water flow patterns over 24 hours, as measured by the two currently operational main inlet flow meter 1 (labeled 31 in Fig. 3) and main inlet flow meter 2 (labeled 32 in Fig. 3). The graphs are re- lated to the main flow meters 1 (31) and 2 (32) and demonstrate how a practically continuous feed of water is provided in spite of considerably different flow values from the respective sources. The abscissa of the graph indicates times and dates of the measurements, whereas the ordinate of the graph shows the measured flow in liters per second. In the absence of a number of sensor arrangements 1 according to the invention, knowing the contribution of each source (whether it is a spring or a line from a provider) is important for the estimation of the speed of propagation of contaminants in the related network areas. Flow data from water meters scattered across the network, e.g. billing meters located at user households, may be used in such a way as to op- timize any necessary counteractions (e.g. shutoffs of pipe sections), in case of contamination, to areas of the water supply network more likely to be affected by such event.
The Figure 5 shows a schematic of a typical water distribution network 44 equipped with a self-organized network of sensors 3, a network of actuators 38 and a centralized data processing unit 41 and/or distributed actuator control units 40. The sensors preferably communicate via a sensor network 42 and the actuators preferably communicate via an actuator network 43. The water enters the network 44 from a reservoir 39 that is fed by a source 34. As it is apparent from the schematic drawing, the valves 38 are preferably able to communicate with other valves 38, with sensors 3, and with the control unit 38 as well as with the data processing unit 41. In this way, all participants of the two communication networks are able to address each other. This how- ever, is important, if a network of sensor nodes and actuators shall self- organize. Sensor nodes and self-organizing networks are known per se (see e.g. the patent application US 2007/0180918 Al), they are however applied the first time to water distribution networks as described herein.
Of special interest is the real-time detection of pollutants (or contaminants) in a water distribution network 44. Therefore it is implemented a method for real-time detection of pollutants in a water distribution network 44. the method is carried out with a number of sensor assemblies or sensor arrangements 1 according to the present invention. In addition it is provided :
(a) a self-organized network of sensors 42, the sensors 3 measuring a variety of physical and/or chemical and/or biological parameters;
(b) a set of actuators to control the water flow within the water distribution network 44; (c) a centralized or distributed data processing and interpretation unit 41; and (d) a centralized or distributed control unit 40 to operate the actuators 38.
This self-organized network of sensors 42 preferably uses a link for inter- sensor communication, the link being chosen from an optical link, a wired link, a wireless link, or an arbitrary combination thereof. Especially preferred is the use of a wireless link in each case.
While using at least one sensor 3 of the sensor arrangement 1, identification of the nature of a contamination is carried out. Preferably the same time and prior to submitting data to a centralized or distributed data processing and interpretation unit 41 or to a centralized or distributed control unit 40 to operate the actuators 38, identification of the geographical location of the position of the sensor arrangement 1 is carried out by utilizing a triangulation technique. It is especially preferred that the self-organized network of sensors is automatically updated in the event of:
(a) addition or removal of new sensor nodes; or
(b) modification of a sensor parameter set and/or specifications; or (c) accidental downing of a node; or
(d) intentional downing of a node due to, for example, maintenance or tampering.
In this way, the system for early detection of contamination in a drinking wa- ter supply is permanently actualized and can fulfill its function as a detection and alarm system. This updating is preferably supported in that any one of the events (a) to (d) are communicated to a centralized or distributed data processing and interpretation unit 41 and/or to a centralized or distributed control unit 40 to operate the actuators 38.
In case of an accident or a contamination of the water in the water supply lines, the actuators 38 in the water distribution network 44 are reorganized, so as to ensure a continuous supply of water to areas not directly concerned by the contamination. In this way, valves 38 in the vicinity of the detected con- tamination are shut-off to stop distribution of contaminated water. The same time, valves 38 in non-contaminated areas can be kept open. It is particularly preferred that a warning message according to the nature of an event selected from a group of events comprising abnormal physical, chemical or biological attributes in relation to a previously defined threshold is distributed to specific sites. Such specific sites can be a centralized or distributed data processing and interpretation unit 41 and/or a centralized or distributed control unit 40 to operate the actuators 38. Other specific sites can be located at police stations, fire fighter stations, hospitals, communal and regional alarm and information centers etc.
A system for early detection of pollutants in a water distribution network 44 is described. The system is based on a number of remote sensors 3 located throughout the water supply network 44. The sensors 3 communicate with each other using a self-organized wireless network, sharing data and control commands. The system enables water suppliers to detect contaminations the very minute they occur. This is of paramount importance to protect the aqueducts from intentional acts, negligence, and accidents.
List of reference numbers
1 sensor arrangement 27 O2 sensor
2 water supply line 28 electrical conductivity probe
3 sensor 29 antenna
4 communicating unit 30 seal
5 central controller 31 main flow meter 1
6 flow cell 32 main flow meter 2
7 water inlet 33 well and pump station
8 water outlet "PRA' TIRO"
9 supply tube 34 from source
10 delivering tube "ROVAGINA" via filter sta¬
11 one-way water flow path tion "MORBIO INF."
12 sensing part of 3 35 surface hydrant
13 central axis of 11 36 sub-surface hydrant
14 thread portion 37 hydrant number
15 nut portion 38 valve (actuator)
16 insert hole 39 reservoir
17 particular flow path parts 40 control unit to operate 38
18 diameter of 17 41 data processing unit
19 choke device 42 sensor network
20 computing unit 43 actuator network
21 pH probe 44 water distribution network
22 redox probe 45 streets and roads
23 chlorine or chlorine dioxide 46 arrow; direction of or ozone sensor "Serbatoio Pignolo"
24 UV-VIS spectrometer 47 automatic vent valve
25 turbidity sensor 48 glass tube
26 stopper

Claims

Claims
1. A sensor arrangement (1) for the permanent remote monitoring of water quality in a water supply line (2), the sensor arrangement (1) comprising a number of sensors (3) for the detection of different attributes of water quality and for providing actual measurement data, a communicating unit (4) for sending the actual measurement data to a central controller (5), and a flow cell (6), which is equipped with a water inlet (7) and with a water outlet (8) that are accomplished to be connectable to a supply tube (9) and respectively to a delivering tube (10) of the water supply line (2), characterized in that the flow cell (6) comprises a one-way water flow path (11) that links the water inlet (7) to the water outlet (8), wherein the sensors (3) are arranged one downstream of the other with respect to the water flow path (11) in such a way that their sensing parts (12), which interact with the flowing water, are located in or at least close to a central axis (13) of the water flow path (11) in each case.
2. The sensor arrangement (1) of claim 1, characterized in that each one of the sensors (3) comprises a thread portion (14) for fastening the sen- sor (3) from the outside in an adequate nut portion (15) of an insert hole
(16) of the flow cell (6), all insert holes (16) individually opening into the water flow path (11).
3. The sensor arrangement (1) of claim 1 or 2, characterized in that the water flow path (11) comprises a number of particular flow path parts
(17) that exhibit an essentially circular cross section with a diameter (18) that is adapted to the type of sensor (3), of which the sensing part (12) is located in the particular flow path part (17).
4. The sensor arrangement (1) of claim 3, characterized in that the particular water flow path parts (17) are concentrically arranged with respect to the central axis (13) of the water flow path (11).
5. The sensor arrangement (1) of one of the preceding claims, characterized in that the flow cell (6) is accomplished as a cube or as a cylinder, the central axis (13) of the water flow path (11) essentially extending parallel to at least one straight extension of the flow cell (6).
6. The sensor arrangement (1) of one of the preceding claims, characterized in that the flow cell (6) comprises a choke device (19) for regulating the water flow in the water flow path (11).
7. The sensor arrangement (1) of one of the preceding claims, characterized in that the flow cell (6) is made of a non-corrosive, inert material that is selected from a group of materials comprising brass, light metals, light metal alloys, polymer materials, and polymer composite materials.
8. The sensor arrangement (1) of claim 7, characterized in that the insert holes (16) and the particular water flow path parts (17) are accomplished as bore holes.
9. The sensor arrangement (1) of one of the preceding claims, character- ized in that the sensors (3) are selected from a group comprising pH, redox, chlorine, UV-VIS, turbidimetry, O2, and electrical conductivity probes.
10. The sensor arrangement (1) of one of the preceding claims, character- ized in that it further comprises a computing unit (20) for processing the actual measurement data of the sensors (3), enabling the sensor arrangement (1) to decide carrying out an shut-off action of a valve (38) in the water supply line (2) and/or providing information to another sensor arrangement (1) and to the central controller (5).
11. A method of permanent remote monitoring of water quality in a water supply line with a sensor arrangement (1) according to one of the claims 1 to 10, characterized in that a flow cell (6) is mounted in a water supply line (2) by connecting a supply tube (9) to the water inlet (7) and a delivering tube (10) to the water outlet (8) of the flow cell (6); different attributes of water quality are measured with a number of sensors (3) in a one-way water flow path (11) that links the water inlet (7) to the water outlet (8), wherein the sensors (3) are arranged one downstream of the other with respect to the water flow path (11) in such a way that their sensing parts (12), which interact with the flowing water, are located in or at least close to a central axis (13) of the water flow path (11) in each case.
12. The method of claim 11, characterized in that the water flow through the water flow path (11) is monitored and regulated with a choke device
(19) of the flow cell (6).
13. The method of one of the claims 11 or 12, characterized in that realtime detection of pollutants in a water distribution network (44) is carried out in that it is provided :
(a) a self-organized network of sensors (42), the sensors (3) measuring a variety of physical and/or chemical and/or biological parameters;
(b) a set of actuators to control the water flow within the water distribution network (44); (c) a centralized or distributed data processing and interpretation unit
(41); and
(d) a centralized or distributed control unit (40) to operate the actuators (38).
14. The method of claim 13, characterized in that the self-organized network of sensors (42) uses a link for inter-sensor communication, the link being chosen from an optical link, a wired link, a wireless link, or an arbitrary combination thereof.
15. The method of one of the claims 13 or 14, characterized in that identification of the nature of a contamination is carried out using at least one sensor (3) of the sensor arrangement (1) and identification of the geographical location of the position of the sensor arrangement (1) is carried out by utilizing a triangulation technique.
16. The method of one of the claims 13 or 14, characterized in that the self-organized network of sensors is automatically updated in the event of: (a) addition or removal of new sensor nodes; or
(b) modification of a sensor parameter set and/or specifications; or
(c) accidental downing of a node; or
(d) intentional downing of a node.
17. The method of claim 16, characterized in that the any one of the events (a) to (d) are communicated to a centralized or distributed data processing and interpretation unit (41) and/or to a centralized or distributed control unit (40) to operate the actuators (38).
18. The method of one of the claims 13 or 14, characterized in that the actuators (38) in the water distribution network (44) are reorganized, so as to ensure a continuous supply of water to areas not directly concerned by the contamination.
19. The method of one of the claims 13 to 18, characterized in that a warning message according to the nature of an event selected from a group of events comprising abnormal physical, chemical or biological attributes in relation to a previously defined threshold is distributed to specific sites.
EP08875284A 2008-11-05 2008-11-05 Sensor arrangement and method for water quality monitoring Withdrawn EP2349932A1 (en)

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