An electrochemical system for detecting bacterial growth in a duct

Abstract

An electrochemical system (200) and a corresponding method for detecting bacterial growth in a duct (205) are presented. The electrochemical system (200) includes one or more electrodes (211, 212, 213) and a measurement device (240) adapted to perform an electrochemical measurement using the said one or more electrodes. Each electrode is coupled to an electrolyte to form an electrode-electrolyte assembly (210', 220', 230'). Also presented is a method of removing bacterial growth from a duct using the electrochemical system.

Description

[0001] AN ELECTROCHEMICAL SYSTEM FOR DETECTING BACTERIAL GROWTH IN A DUCT

[0002] Technical Field

[0003] The present disclosure relates to an electrochemical system and method for detecting bacterial growth formation in a duct.

[0004] Background

[0005] Ducts of different size and shapes are used in a variety of applications that may include heating or cooling systems, water treatment and supply, food and drink manufacturing, to name a few.

[0006] Bacterial growth formation, including the formation of biofilms in pipework requires regular maintenance. This may include inspection of the conduit followed by a cleaning procedure. Currently the detection of bacterial formation in pipework is performed using relatively complex techniques such as microscopy.

[0007] It is an object of the disclosure to address one or more of the above mentioned limitations.

[0008] Summary

[0009] According to a first aspect of the disclosure, there is provided an electrochemical system for detecting bacterial growth in a duct, the system comprising: one or more electrodes, wherein each electrode is coupled to an electrolyte; and a measurement device adapted to perform an electrochemical measurement using the said one or more electrodes. The electrochemical system may also be used for removing or destroying bacterial growth in the duct. For instance, the electrochemical system may be used for destroying a biofilm.

[0010] Optionally, the said one or more electrodes are attachable on an outer surface of the duct, so that for each electrode the electrolyte is in contact with the outer surface of the duct.

[0011] For instance the duct may be made of a conducting material such as a metal or a metal alloy material. Alternatively the duct may be made of a non-conducting material , such as plastic.

[0012] For instance, each electrode coupled to the electrolyte may form an electrode-electrolyte assembly. The electrode-electrolyte assembly may be implemented with different configurations. For example the electrode may form a first layer and the electrolyte a second layer in contact with the first layer. Alternatively, the electrode may be a rod, a wire or a plate surrounded at least partially by the electrolyte.

[0013] Optionally, the measurement device comprises a potentiostat.

[0014] The measurement device may be remotely coupled to the electrodes. For instance the measurement device may include a potentiostat and a receiver for receiving data from the electrodes wirelessly.

[0015] Optionally, the electrochemical system comprises a mechanical arrangement adapted to attach the said one or more electrodes to the duct.

[0016] For instance the mechanical arrangement may include a set of clamps for attaching the electrodes to the duct. Optionally, the said at least one electrodes are made of a metal or metal alloy material. For instance, the electrode material may comprise stainless steel, silver, copper or platinum.

[0017] Optionally, the said one or more electrodes are shaped to match a pre-defined geometry of the outer surface of the pipe.

[0018] Optionally, the said one or more electrodes are made of a rigid material or of a flexible material.

[0019] Optionally, the said one or more electrodes are operable up to a temperature of about 90 degree centigrade.

[0020] For instance, the said one or more electrodes may be operable between about 10°C and about 90°C.

[0021] Optionally, the electrolyte is a solid electrolyte.

[0022] Optionally, the solid electrolyte comprises a conducting polymer.

[0023] For instance, the electrodes may be modified with the conducting polymer. For example the conducting polymer may comprise one or more of the following polymers including Polyacetylene (PA), polyaniline (PAN1), polypyrrole (PPy), polythiophene (PT), and poly (3,4- ethylenedioxythiophene) (PEDOT).

[0024] Optionally, the conducting polymer is mixed with metallic nanoparticles or carbon nanotubes CNTS. For instance multi-walled carbon nanotubes MWCNTs may be used.

[0025] Optionally, the electrolyte is a quasi-solid electrolyte.

[0026] Optionally, the quasi-solid electrolyte comprises a conducting hydrogel. For instance, the conducting hydrogel may comprise a natural or synthetic polymer and a conducting fluid.

[0027] Optionally, a membrane may be provided on an active surface of the electrolyte. The membrane may be a protective membrane or filtration membrane. For instance, the membrane may be a polymer membrane.

[0028] Optionally, the electrochemical system comprises a processor configured to process measurement data to identify bacterial growth formation.

[0029] For instance the processor may be configured to execute a software or algorithm to analyse the measurement data.

[0030] Optionally, the electrochemical system is non-invasive.

[0031] For instance, the electrochemical system may be retrofitted on existing pipework without having to penetrate through the pipes or conduits.

[0032] Optionally, the electrochemical system may include an additional electrode to be inserted inside the duct. For instance, the additional electrode may be a metallic rod or a metallic wire.

[0033] According to a second aspect of the disclosure, there is provided a method of detecting bacterial growth in a duct, the method comprising connecting one or more electrodes to the duct, wherein each electrode is coupled to an electrolyte; performing an electrochemical measurement using the said one or more electrodes; and identifying a level of bacterial growth based on the electrochemical measurement. Optionally, wherein connecting the one or more electrodes comprises attaching the one or more electrodes on an outer surface of the duct so that for each electrode the electrolyte is in contact with the outer surface of the duct.

[0034] Optionally, wherein connecting the one or more electrodes comprises embedding the one or more electrodes within a wall of the duct.

[0035] Optionally, the method comprises identifying formation of a biofilm based on the electrochemical measurement.

[0036] Optionally, wherein the electrochemical measurement comprises at least one of an impedance, a current cycling, a chronoamperometry, a chronopotentiometry, a differential pulse voltammetry, a square wave voltammetry, and a cyclic voltammetry measurement.

[0037] Optionally, wherein the electrochemical measurement comprises measuring a current, or a measuring a voltage between two electrodes or between the duct and at least one electrode.

[0038] Optionally, wherein the electrochemical measurement comprises applying a voltage across the duct and the said one or more electrodes.

[0039] According to a third aspect of the disclosure, there is provided the use of an electrochemical system according to the first aspect for detecting and / or removing bacterial growth in a duct.

[0040] According to a fourth aspect of the disclosure, there is provided a system comprising a duct fitted with and an electrochemical system according to the first aspect for detecting bacterial growth in the duct.

[0041] Optionally, the duct may act as a working electrode. Optionally, the system is part of an industrial processing plant, or part of a heating system, or part of an energy plant, or part of a temperature conditioning system, or part of a water treatment system, or part of a food and drink manufacturing system.

[0042] According to a fifth aspect of the disclosure, there is provided a method of removing bacterial growth from a duct, the method comprising providing the duct with an electrochemical system according to the first aspect; filling at least partially the duct with a salt solution; applying a voltage across the duct and the said at least one electrodes; and rinsing the duct with an aqueous solution.

[0043] Optionally, the method comprises performing an electrochemical measurement.

[0044] Optionally, wherein one of the electrodes is placed inside the duct; and wherein for this electrode the electrolyte is provided by a liquid inside the duct.

[0045] Description of the drawings

[0046] The disclosure is described in further detail below by way of example and with reference to the accompanying drawings, in which: figure 1 is a flow chart of a method for detecting bacterial growth in a duct; figure 2 is a diagram of an electrochemical system for detecting bacterial growth in a duct; figure 3A is a cross section of an electrode / electrolyte assembly fitted onto the surface of a conducting duct; figure 3B is a cross section of another electrode / electrolyte assembly fitted onto the surface of a conducting duct; figure 3C is a cross section of an electrode / electrolyte assembly fitted on a non-conducting duct; figure 4A is a plot showing several impedance spectra obtained with a copper working electrode in waste water using an open circuit potential configuration; figure 4B is a model for fitting the impedance spectra of figure 4A; figure 4C is a plot of the resistance of the biofilm as a function of time; figure 5 is a plot showing several impedance spectra obtained with a copper working electrode waste water using open circuit potential configuration; figure 6A is a plot showing open circuit potential evolution of a copper electrode in waste water; figure 6B is a plot showing the open circuit potential evolution of a copper electrode in distilled water; figure 7A is an atomic force microscopy profile image of untreated copper; figure 7B is an atomic force microscopy profile image of copper in wate water after 15 days using a closed circuit potential of -0.3 V; figure 7C is an atomic force microscopy profile image of copper in wate water after 15 days using an open circuit potential (0V); figure 7D is a plot of the roughness factor profile of the image of figure 7C; figure 7E is an atomic force microscopy profile image of copper in distilled water after 15 days using an open circuit potential (0V); figure 7F is a plot of the roughness factor profile of the image of figure 7E; figure 8A is a plot of the current measured as a function of time between a stainless steel working electrode and a platinum counter electrode in waste water using closed circuit potential of -0.3V; figure 8B is a plot showing the impedance spectra obtained using the setup of figure 8A at 0 days, 4 days, 8 days, and 11 days; figure 8C is a plot showing the capacitance measurements obtained using the setup of figure 8A at 0 days, 4 days, 8 days, and 11 days; figure 9 is a plot of the current measured as a function of time between a stainless steel WE and a stainless steel CE, obtained in both a duct without water and with water, respectively; figure 10 is a plot showing the cyclic voltammetry measurements of water contaminated with bacteria obtained before and after biofilm formation; figure 11 is a plot showing the differential pulse voltammetry of water contaminated with bacteria obtained before and after biofilm formation; figure 12 is another plot showing the cyclic voltammetry measurements of water contaminated with bacteria obtained before and after biofilm formation; figure 13 is a plot showing the differential pulse voltammetry of water contaminated with bacteria obtained before and after biofilm formation; figure 14 is a plot showing the cyclic voltammetry measurements of tap water obtained before and after biofilm formation; figure 15 is a plot showing the differential pulse voltammetry of tap water obtained before and after biofilm formation; figure 16 is a plot showing the OCP evolution of a stainless steel electrode in 10 ml of water contaminated with bacteria and tap water, respectively; figure 17 is a flow chart of a method for removing bacterial growth from a duct; figure 18A is a plot showing the OCP evolution of a stainless steel electrode in 10 ml of water contaminated with bacteria; figure 18B is a plot showing the contaminated water as in figure 18A but after applying a voltage between the duct and the electrode to remove the biofilm at various stages of its formation ; figure 19A is a cross section of an exemplary electrode-electrolyte assembly connected to a duct as shown in the system of figure 2; figure 19B is a diagram of an electrode provided with a circuit for wireless communication; figure 20A is a picture of a flexible modified electrode; figure 20B is a picture of a rigid modified electrode; figure 21 is a plot showing cyclic voltammograms obtained during electro-polymerisation for modifying an electrode; figure 22A shows a pipe filled with tap water and with a reference / counter electrode positioned above the water level; figure 22B shows a pipe filled with tap water and with a reference / counter electrode positioned below the water level; figure 23 is a plot showing the OCP evolution obtained in a pipe with the reference / counter electrode provided in different locations; figure 24A is a plot of a chronoamperometric measurement showing the current as a function of time before and after biofilm formation; figure 24B is a plot showing current measurements using chronoamperometry without bacteria and with bacteria after equilibrium; figure 25 is a chronoamperometric measurement illustrating the formation of a biofilm.

[0047] Description

[0048] Figure 1 is a flow chart of a method for detecting bacterial growth in a duct. For instance, the duct may be made of a conducting material such as a metal or a metal alloy material. Alternatively the duct may be made of a non-conducting material , such as plastic.

[0049] At step 110 one or more electrodes are connected to the metallic duct. Each electrode is coupled to an electrolyte. When the duct is made of a conducting material various means (for instance mechanical arrangements) may be used to attach the electrodes on the surface of the duct. When the duct is made of a non-conducting material the electrodes may be inserted in the duct’s wall. The electrodes may be distributed along the length of the duct as appropriate depending on the size and shape of the duct.

[0050] At step 120 an electrochemical measurement is performed using the said one or more electrodes. The electrochemical measurement may be performed over an extended period of time, for instance a few hours or a few days.

[0051] At step 130 a level of bacterial growth is identified based on the electrochemical measurement. For instance various phases of biofilm formation may be identified.

[0052] Figure 2 is a diagram of an electrochemical system for detecting bacterial growth in a duct. The duct 205 may be made of different metallic materials, including metal alloys. For instance the duct 205 may be made of stainless steel or copper.

[0053] The system 200 includes one or more electrodes. In this example three electrodes are connected to the duct 205 at different locations along its length, labelled 210, 220 and 230. The electrodes can be attached on the external surface of the duct 205. As a result the electrodes 210, 220 and 230 are not in direct contact with the fluid present in the duct 205.

[0054] Each electrode is coupled to an electrolyte to form an electrode-electrolyte assembly. The electrode 210 is in contact with the electrolyte 211 to form the electrode-electrolyte assembly 210’. Similarly the electrode 220 is in contact with the electrolyte 212 to form the electrode-electrolyte assembly 220’, and the electrode 230 is in contact with the electrolyte 213 to form electrode-electrolyte assembly 230’.

[0055] The electrodes can be made of metallic, or metal allow materials such as stainless steel, silver (Ag), copper (Cu) or Platinum (Pt). It will also be appreciated that the electrodes may be functionalised, for instance with nanoparticles.

[0056] The electrolyte may be a solid electrolyte, also referred to as solid-state electrolyte. The solid electrolyte could be made of a conducting polymer such as Polyaniline (PAN1). The conducting polymer may be mixed with metallic nanoparticles or carbon nanotubes CNTS. Multi-walled nanotubes, for instance multi-walled carbon nanotubes MWCNTs may also be used. MWCNTs are a special form of carbon nanotubes in which multiple singlewalled carbon nanotubes are nested inside one another.

[0057] Alternatively, the electrolyte may be a quasi-solid electrolyte, also referred to as gel polymer electrolyte (GPE). For instance, the gel polymer electrolyte may be made of a conducting hydrogel made of a natural or synthetic polymer and a conducting fluid. The conducting fluid may include a saline solution, a buffer solution or hard water (i.e water with a high mineral content).

[0058] A measurement device 240 is provided to perform an electrochemical measurement using the electrodes 210, 220 and 230. For instance, the measurement device 240 may be a potentiostat. The measurement device 240 may also be configured to communicate with a user device 250 such as a computer, a server, or a mobile phone.

[0059] A processor configured to process the measurement data may be provided to identify bacterial growth formation. The processor may be implemented as part of the measurement device 240 or as part of the user device 250. The processor may be configured to execute a software program to analyse the data. The software program may be used to identify a particular feature in the measurement data indicative of biofilm formation. The processor may also be configured to generate a warning signal upon identification of bacterial growth formation. The system 200 can be installed or retrofitted on existing pipework without having to penetrate through the pipes / conduits. The electrode-electrolyte assemblies may be fitted on the external surface of the duct using various techniques. For instance a mechanical arrangement such as a clamp may be used to attach each electrode-electrolyte assembly onto the duct.

[0060] The system 200 may be used to perform various types of electrochemical measurements including impedance measurements, current cycling measurements, chronoamperometry, chronopotentiometry, differential pulse voltammetry, square wave voltammetry, or cyclic voltammetry, to name a few. The measurements may be performed in a closed circuit potential CCP configuration or in an open circuit potential OCP configuration.

[0061] When using the closed circuit potential configuration, a voltage is applied across the metallic duct and the electrodes. For instance, the measurement device 240 may be used to apply a negative voltage to the duct 205 and a positive voltage to the electrodes 210, 220 and 230. The measurement device 240 is used to measure a current. The current response can then be analysed to identity bacterial growth. Depending on the electrochemical measurement chosen, the metallic duct itself can act as one electrode, for instance as a working electrode (WE) or a counter electrode (CE). The electrode and electrolyte may be arranged using different configurations.

[0062] Figure 3A is a cross section of an electrode / electrolyte assembly fitted onto the surface of a conducting duct. The electrode 310 forms a first layer provided on top the electrolyte 311 which forms a second layer. The electrolyte 311 is in contact with the wall surface 305 of the duct. A liquid 301 is provided inside the duct. The nature of the liquid would depend on the application. The liquid can be any fluid medium that is capable of allowing bacteria to grow, such as water, liquid and viscous food stuffs, sugar solutions, milky fluids, beverages among many other types of liquids. Figure 3B is a cross section of another electrode / electrolyte assembly fitted onto the surface of a conducting duct. In this example the electrode 310’ is a rod or wire provided within the electrolyte 311’. The electrolyte 311’ surrounds the electrode 310’ so that only the electrolyte 311’ is in contact with the surface of the duct 305.

[0063] As mentioned above when the duct is made of a non-conductive material, the electrode / electrolyte assembly may be inserted within a wall portion of the duct.

[0064] Figure 3C is a cross section of an electrode / electrolyte assembly fitted on a non-conducting duct. The same reference numerals have been used as in figure 3B for labelling corresponding components. In this example, an aperture or hole is formed within the duct’ wall 305. The electrode / electrolyte assembly 310’ / 311’ is inserted within the aperture, so that electrolyte 311’ has an active surface that can come into contact with the liquid 301. Optionally, a membrane 312’ may be provided on the active surface of the electrolyte 311’. The membrane 312’ may be a protective or filtration membrane used to prevent contamination between the liquid and the electrolyte. For instance, the membrane 312’ may be a polymer membrane. Examples of polymer membranes may include a sulfonated tetrafluoroethylene based fluoropolymer-copolymer membrane, such as a Nation membrane.

[0065] To illustrate the principle of operation of the proposed system, various electrochemical measurements are described with reference to figures 4 to 19 and 21.

[0066] Figure 4A is a plot showing impedance spectra obtained with a copper working electrode (WE) dipped in in 11 ml of waste water, using a platinum counter electrode (CE) and a Platinum reference electrode (RE). Measurements are provided after 1 hour (waveform 410), 11 days (waveform 420) and 14 days (waveform 430) using the closed circuit potential configuration. Depending on the ionic strength of the solution and the temperature, the voltage applied between the WE and CE can range from about -0.2 V to about -10 V. It is also possible to apply a current at about - 100 mA . For example in saline water at 0.1 M it is 2V , in 0.01 M it is 0.5 V at RT.

[0067] Figure 4B is a model for fitting the impedance spectra of figure 4A.

[0068] The model shows the charge transfer resistance Ret and the biofilm resistance Rbiofilm which can be extracted from the model.

[0069] Figure 4C is a plot of the resistance of the biofilm as a function of time. Once the biofilm has matured the resistance Rbiofilm drops sharply around day 14. The sharp drop in resistance value may be used as an indicator of biofilm formation.

[0070] Figure 5 is a plot showing impedance spectra obtained with a copper working electrode (WE) dipped in 5 ml of waste water, using a platinum counter electrode (CE) and a Platinum reference electrode (RE). Measurements are provided after 1 hour (waveform 510), 6 days (waveform 520), 9 days (waveform 530), 12 days (waveform 540), 13 days (waveform 550) using the open circuit potential OCP configuration (no voltage applied).

[0071] Figure 6A is a plot showing the OCP evolution of a copper electrode in waste water. In this experiment a potential also referred to as OCP potential is measured between the WE and the RE. The Y axes shows the open circuit potential OCP in volts.

[0072] Figure 6B is a plot showing the OCP evolution of a copper electrode in distilled water. Figure 7 A shows the atomic force microscopy (AFM) profile image of a piece of untreated copper.

[0073] Figure 7B shows the AFM profile image of copper in wate water after 15 days using a closed circuit potential of -0.3 V. The globular features confirm the presence of the biofilm.

[0074] Figure 7C shows the AFM profile image of copper in wate water after 15 days using an open circuit potential (0V). Figure 7D is a plot of the roughness factor profile of the image of figure 7C. The globular features confirm the presence of the biofilm.

[0075] Figure 7E shows the AFM image of copper in distilled water after 15 days using an open circuit potential (0V). Figure 7F is a plot of the roughness factor profile of the image of figure 7E.

[0076] Figure 8A is a plot showing the electrochemical signal (current) measured as a function of time between a stainless steel working electrode (WE) and a platinum counter electrode (CE). Measurements were obtained by dipping a Platinum reference electrode (RE) in 100 ml of waste water and using a closed circuit potential of -0.3V between the WE and the CE. After 5 days the current signal increases sharply indicating biofilm formation.

[0077] Figure 8B is a plot showing the impedance spectra obtained using the setup of figure 8A at 0 days (waveform 810), 4 days (waveform 811), 8 days (waveform 812), and 11 days (waveform 813).

[0078] Figure 8C is a plot showing the capacitance measurements obtained using the setup of figure 8A at 0 days (waveform 820), 4 days (waveform 821), 8 days (waveform 822), and 11 days (waveform 823). Figure 9 is a plot showing the electrochemical signal (current) measured as a function of time between a stainless steel WE (provided by the duct itself) and a stainless steel CE. Measurements were obtained in both a duct without water and with water using the electrode arrangement described in figure 3A. The electrolyte is provided by a PAN1 / MWCNT solid electrolyte with an electrode / electrolyte arrangement as shown in figure 3A.

[0079] Figure 10 is a plot showing the cyclic voltammetry (CV) measurements of water contaminated with bacteria obtained at 0 hours (waveform 1010 before after biofilm formation) and after 20 hours ( waveform 1020 after biofilm formation). The CV measurements were obtained using stainless steel electrodes.

[0080] Figure 11 is a plot showing the differential pulse voltammetry (DPV) measurements of water contaminated with bacteria obtained at 0 hours (waveform 1110 before after biofilm formation) and after 20 hours ( waveform 1120 after biofilm formation). The CV measurements were obtained using stainless steel electrodes.

[0081] Figure 12 is a plot showing the cyclic voltammetry (CV) measurements of water contaminated with bacteria obtained at 0 hours (waveform 1210 before after biofilm formation) and after 72 hours ( waveform 1220 after biofilm formation). The CV measurements were obtained using carbon electrodes.

[0082] Figure 13 is a plot showing the differential pulse voltammetry (DPV) measurements of water contaminated with bacteria obtained at 0 hours (waveform 1310 before after biofilm formation) and after 72 hours ( waveform 1320 after biofilm formation). The CV measurements were obtained using carbon electrodes. Figure 14 is a plot showing the cyclic voltammetry (CV) measurements of tap water obtained at 0 hours (waveform 1410 before after biofilm formation) and after 20 hours (waveform 1420 after biofilm formation). The CV measurements were obtained using carbon electrodes.

[0083] Figure 15 is a plot showing the differential pulse voltammetry (DPV) measurements of tap water at 0 hours (waveform 1510 before after biofilm formation) and after 20 hours ( waveform 1520 after biofilm formation). The CV measurements were obtained using carbon electrodes.

[0084] Figure 16 is a plot showing the OCP evolution of a stainless steel electrode in 10 ml of water contaminated with bacteria with 0.1M NaCl (waveform 1620), and tap water with 0.1M NaCl (waveform 1610). In this experiment, a potential also referred to as OCP potential is measured between the WE and the RE. The Y axes shows the open circuit potential OCP in volts.

[0085] The electrochemical system of the disclosure can also be used to remove bacterial growth in the duct.

[0086] Figure 17 is a flow chart of a method for removing bacterial growth from a duct.

[0087] At step 1710, the duct is provided with an electrochemical system. The electrochemical system comprises one or more electrodes, each electrode being coupled to an electrolyte; and a measurement device to perform an electrochemical measurement using the said one or more electrodes. For instance the electrochemical system described in figure 2 may be used.

[0088] At step 1720, the duct is filled at least partially with a salt solution. Various concentrations of NaCl may be used, for example 0.1 g / lOOml ; or 0.01 g / 100ml. Alternatively an electrolyte may be used. At step 1730 a voltage is applied between the duct and the one or more electrodes. The voltage applied may vary depending on the NaCl concentration. For instance a voltage of +0.2V may be applied for an NaCl concentration of 0.1 g / lOOml and a voltage of +0.5 V may be applied for an NaCl concentration of 0.01 g / 100ml. Various solutions may be used. To improve reproducibility a constant ionic strength and temperature should preferably be used.

[0089] At step 1740, the duct is rinsed with an aqueous solution.

[0090] Figure 18A is a plot showing the OCP evolution of a stainless steel electrode in 10 ml of water contaminated with bacteria with 0.1M NaCl. In this experiment, a potential also referred to as OCP potential is measured between the WE and the RE. The Y axes shows the open circuit potential OCP in volts. The plot shows the attachment of bacteria .

[0091] Figure 18B is a plot showing the same contaminated water as in Figure 18A but after applying a voltage between the duct and the electrode to remove the biofilm (Step 1730 of figure 17). The plot shows that the biofilm has been removed.

[0092] It is also possible to place an electrode inside the duct. This approach is generally more efficient for removing the biofilm formation on the inner surface of the duct. In this scenario, the electrode provided inside the duct may be a metallic rod or metallic wire. In use the metallic rod or wire is in contact with the fluid present in the duct which includes a liquid electrolyte or slat solution. The voltage applied and the time required for removing the biofilm will depend on the thickness of the film. For instance, a voltage of - 5V may be applied between the pipe (WE) and the electrode inside the pipe (RE) for about 100 seconds. Figure 19A is a cross section of an exemplary electrode-electrolyte assembly connected to a duct as shown in the system of figure 2. Figure 19 is described for the electrode-electrolyte assembly 210’ but would apply equally to 220’ and 230’. As described above, the electrode 210 is in contact with the electrolyte 211 to form the electrode-electrolyte assembly 210’.

[0093] In this example the electrolyte 211 is provided by a conducting polymer composite. The electrolyte 211 connects the outer surface of the duct 205 to the electrode 210. The liquid or fluid inside the duct 205 may also form an electrolyte. For instance milk would conduct electricity through the movement of ions.

[0094] The electrode 210 is adapted to fit around the outer side of a duct 205. The shape and size of the electrode 210 may vary depending on the application, for instance circular, square or semicircular. The substrate can be rigid or flexible. For instance, the electrode may be made of a flexible material that can be bent so that be electrode-electrolyte assembly 210’ clamps onto the outer surface of the duct 205.

[0095] The substrate of the electrode 210 is made of a conducting material which may be a conducting metal or non-metal. The substrate may be passivated and modified with conducting polymers and optionally with metallic or carbon nanomaterials composites as suitable for the application.

[0096] For example the conducting polymer may be Polyacetylene (PA), polyaniline (PAN1), polypyrrole (PPy), polythiophene (PT), poly (3,4- ethylenedioxythiophene) (PEDOT). These conducting polymers have tuneable electrical property and show physical and chemical stability. Thermal stability enables applications in high temperature environments. The conducting polymer can be deposited on the substrate by chemical or electrochemical means. Electrodes modified with a conducting polymer can operate reliably within a relatively wide range of temperatures. For instance up to a temperature of about 90 degree centigrade.

[0097] Electrochemical measurements can be carried out using a two electrode system where the current carrying electrode acts as a working electrode and the second electrode acts as a pseudo reference and counter electrode.

[0098] As explained above with reference to figure 2, the duct 205 itself can act as the working electrode (WE), while any one of the electrodes 211, 212 or 213 can act as the reference and / or counter electrode. Such a two electrode system may be used to measure the complete voltage change across the system formed by the pipe and the electrodes. This set up can be used when currents are very low (for instance a few microamperes) , and the system is in equilibrium, that is once the biofilm is fully matured. Depending on the electrochemical measurement a current may be measured between the WE and the CE. A voltage may also be applied between the WE and the RE. In some cases the reference electrode (RE) and the counter electrode (CE) may also be combined. When the duct itself acts as an electrode, for instance the WE, the WE is in contact with the electrolyte provided by the liquid inside the duct.

[0099] Optionally, an insulating ring (not shown) may be attached to the outer surface of the duct 205. The insulating ring may be made of rubber, fiber glass, plastic or any other insulating material.

[0100] As mentioned above with respect to figure 2 the measurement device 240 may also be configured to communicate with a user device 250 such as a computer, a server, or a mobile phone. The measurement device 240 may also be adapted to communicate remotely with the electrodes. In this case the measurement device 240 does not need to be physically connected to the electrodes. Remote communication between the measurement device 240 and any one of computer, a server, a mobile phone, and the electrodes can be achieved via a wireless link such as WiFi. This approach can be advantageous for field deployable applications. The measurement device may also be provided with a graphical user interface (GUI) for receiving user input and displaying results. It may also be configured to save data in various format. The measurement device may also include a processor for executing a software or algorithm for performing a specific type of electrochemical measurement, such as for instance voltametric and / or amperometric measurements.

[0101] Figure 19B is a diagram of a potentiostat in wireless communication with an electrode.

[0102] The potentiostat is connected to a receiver such as a radio frequency receiver for receiving data from the electrode. It will be appreciated that the potentiostat and the receiver may be implemented as two separate devices or as a single device. The wireless potentiostat and the receiver may be USB powered or battery powered.

[0103] Figure 20A is a picture of a flexible modified electrode. Figure 20B is a picture of a rigid modified electrode. In this example the electrodes are both made of stainless steel but having different thickness. The electrode 20A is thinner than the electrode 20B, resulting in an electrode that can be bent by hand to fit the geometry of the pipe in use. A rigid electrode has a profile ( inner surface) designed to fit the outer surface of the pipe in use. In the case of a cylindrical pipe, the curvature of the electrode would match the curvature of the pipe.

[0104] Figure 21 is a plot showing cyclic voltammograms obtained during electropolymerisation for modifying an electrode. In this example a stainless steel electrode is modified with PAN1 / MWCNT using 0.002gr MWCNT + 50 ml Sulfuric acid (H2SO4) +0.9 ml aniline. Eleven waveforms are shown each representing a cyclic voltammetry measurement obtained at different time during the electro-polymerisation.

[0105] Figures 22A and 22B show a pipe segment filled with tap water. The pipe is used as a working electrode (WE) and an electrode placed on the outer surface of the pipe is used as a reference electrode (RE). The pipe is filled with tap water up to a level indicated by a dotted line. In figure 22A the RE is positioned above the water level, while in figure 22B the electrode is positioned below the water level.

[0106] Figure 23 is a plot showing the OCP evolution obtained in a pipe segment with the reference / counter electrode provided in different locations. Voltage measurements are made at open circuit potential (OCP) between the WE and the RE. The biofilm formation in the pipe / duct provides a potential difference. Once the potentials across the electrodes are equal, equilibrium is achieved. The pipe / duct is acting as a bipolar electrode.

[0107] The waveform 2310 shows OCP measurement obtained in water before introduction of bacteria, using a reference electrode located above the water level (fig 22A).

[0108] The waveform 2320 shows OCP measurement obtained in water before introduction of bacteria, using a reference electrode located below the water level (fig 22B).

[0109] The waveform 2330 shows OCP measurement obtained in water after introduction of bacteria, using a reference electrode located above the water level (fig 22A).

[0110] The waveform 2340 shows OCP measurement obtained in water after introduction of bacteria, using a reference electrode located below the water level (fig 22B). Figure 24A is a plot of a chronoamperometric measurement showing the current as a function of time before and after biofilm formation. For this experiment a pipe / duct is provided with a counter / reference electrode for performing a chronoamperometric measurement. In this example a solid electrolyte is deposited on a flexible stainless steel counter / reference electrode. The pipe / duct is made of stainless steel and acts as a working electrode. The pipe / duct is filled with tap water.

[0111] Current measurements can be made by applying a potential determined by the solution inside the pipe / duct and other physical conditions such as temperature, pressure and resistance. The current ensuing from the redox reactions associated with biofilm formation can be monitored using chronoamperometric techniques. The current flows mainly through the conducting fluid inside the pipe as the conducting fluid will experience an electric field. The magnitude of the current depends on the conductivity of the fluid, the redox reactions, the potential difference applied and the geometry of the pipe / duct. Most of the current flows through the solution. A background current may be caused by ionic flow from non-redox active ions such as alkali and alkaline earth metals, chloride, carbonates and bicarbonates amongst others. Such a background current will remain steady during the measurement. Any biofilm formation will result in redox reactions from the electroactive metabolites and quorum sensing molecules. The charge transfer on the working electrode will perturb the constant background current indicating onset and maturation of biofilm.

[0112] In figure 24A the equilibrium associated with full maturation of the biofilm is reached after about 200 seconds. It will be appreciated that full maturation may occur be faster or slower depending on the biofilm forming bacterial species and concentration. Figure 24B is a plot showing current measurements using chronoamperometry without bacteria and with bacteria after equilibrium, hence after formation of a biofilm and once the biofilm has matured.

[0113] The waveform 2410 shows current measurement obtained in water before introduction of bacteria, using a reference electrode located above the water level (fig 22A).

[0114] The waveform 2420 shows current measurement obtained in water before introduction of bacteria, using a reference electrode located below the water level (fig 22B).

[0115] The waveform 2430 shows current measurement obtained in water after introduction of bacteria, using a reference electrode located above the water level (fig 22A).

[0116] The waveform 2440 shows current measurement obtained in water after introduction of bacteria, using a reference electrode located below the water level (fig 22B).

[0117] Figure 25 is a chronoamperometric measurement illustrating the formation of a biofilm over time. Initially, a few bacteria or Planktonic cells attach to a substrate that is suitable for biofilm growth such as a carbon-based porous substrate, or a copper substrate among others. In a second stage a mature biofilm is formed. Eventually, in a third stage the biofilm releases bacteria. In turn the dispersed bacteria may attach to the substrate to form another biofilm. The bacteria produce a wide variety of redox-active metabolites. For instance, many bacteria, such as Pseudomonas produce phenazines and phenazines derivatives.

[0118] Ducting used in process industries for movement of fluids such in the food, water, and oil industries and other industrial process can provide substrates for biofilm formation on the inside. Biofilm formation is affected by pH, flow rate, pressure, temperature amongst other factors.

[0119] The proposed systems and corresponding methods of the disclosure permit the detection and potential removal of biofilm formation in a pipe / duct in a non-invasively. The method(s) can be applied to both localised and large areas of biofilm formation.

[0120] The electrochemical system of the disclosure may be installed or retrofitted on a pipework or a network of ducts that is part of various systems including an industrial processing plant, a heating system, an energy plant, a temperature conditioning system, a water treatment system, a food and drink manufacturing system, to name a few.

[0121] A skilled person will appreciate that variations of the disclosed arrangements are possible without departing from the disclosure. Accordingly, the above description of the specific embodiments is made by way of example only and not for the purposes of limitation. It will be clear to the skilled person that minor modifications may be made without significant changes to the operation described.

Claims

CLAIMS1. An electrochemical system for detecting bacterial growth in a duct, the system comprising one or more electrodes, wherein each electrode is coupled to an electrolyte; a measurement device adapted to perform an electrochemical measurement using the said one or more electrodes; and wherein the said one or more electrodes are attachable on an outer surface of the duct, so that for each electrode the electrolyte is in contact with the outer surface of the duct.

2. The electrochemical system as claimed in claim 1, wherein the measurement device comprises a potentiostat.

3. The electrochemical system as claimed in claim 1 or 2, comprising a mechanical arrangement adapted to attach the said one or more electrodes to the duct.

4. The electrochemical system as claimed in any of the preceding claims, wherein the said at least one electrodes are made of a metal or metal alloy material.

5. The electrochemical system as claimed in any of the preceding claims, wherein the said one or more electrodes are shaped to match a pre-defined geometry of the outer surface of the pipe.

6. The electrochemical system as claimed in any of the preceding claims, wherein the said one or more electrodes are made of a rigid material or of a flexible material.

7. The electrochemical system as claimed in any of the preceding claims, wherein the said one or more electrodes are operable up to a temperature of about 90 degree centigrade.

8. The electrochemical system as claimed in any of the preceding claims, wherein the electrolyte is a solid electrolyte.

9. The electrochemical system as claimed in claim 8, wherein the solid electrolyte comprises a conducting polymer.

10. The electrochemical system as claimed in claim 9, wherein the conducting polymer is mixed with metallic nanoparticles or carbon nanotubes CNTS.

11. The electrochemical system as claimed in any of claims 1 to 7, wherein the electrolyte is a quasi-solid electrolyte.

12. The electrochemical system as claimed in claim 11, wherein the quasi-solid electrolyte comprises a conducting hydrogel.

13. The electrochemical system as claimed in any of the preceding claims comprising a processor configured to process measurement data to identify bacterial growth formation.

14. The electrochemical system as claimed in any of the preceding claims, wherein the electrochemical system is non-invasive.

15. A method of detecting bacterial growth in a duct, the method comprising connecting one or more electrodes to the duct, wherein each electrode is coupled to an electrolyte;performing an electrochemical measurement using the said one or more electrodes; and identifying a level of bacterial growth based on the electrochemical measurement; wherein connecting the one or more electrodes comprises attaching the one or more electrodes on an outer surface of the duct so that for each electrode the electrolyte is in contact with the outer surface of the duct.

16. The method as claimed in claim 15, wherein connecting the one or more electrodes comprises embedding the one or more electrodes within a wall of the duct.

17. The method as claimed in any of the claims 15 or 16, comprising identifying formation of a biofilm based on the electrochemical measurement.

18. The method as claimed in any of the claims 15 to 17, wherein the electrochemical measurement comprises at least one of an impedance, a current cycling, a chronoamperometry, a chronopotentiometry, a differential pulse voltammetry, a square wave voltammetry, and a cyclic voltammetry measurement.

19. The method as claimed in any of the claims 15 to 17, wherein the electrochemical measurement comprises measuring a current or measuring a voltage between two electrodes or between the duct and at least one electrode.

20. The method as claimed in claim 15, wherein the electrochemical measurement comprises applying a voltage across the duct and the said one or more electrodes.

21. Use of an electrochemical system as claimed in any of the claims 1 to 14 for detecting and / or removing bacterial growth in a duct.

22. A system comprising a duct fitted with and an electrochemical system as claimed in any of the claims 1 to 14 for detecting bacterial growth in the duct.

23. The system as claimed in claim 22, wherein the system is part of an industrial processing plant, or part of a heating system, or part of an energy plant, or part of a temperature conditioning system, or part of a water treatment system, or part of a food and drink manufacturing system.

24. A method of removing bacterial growth from a duct, the method comprising providing the duct with an electrochemical system comprising one or more electrodes, wherein each electrode is coupled to an electrolyte; and a measurement device adapted to perform an electrochemical measurement using the said one or more electrodes; filling at least partially the duct with a salt solution; applying a voltage across the duct and the said at least one electrodes; and rinsing the duct with an aqueous solution.

25. The method as claimed in claim 24, comprising performing an electrochemical measurement.

26. The method as claimed in claim 24 or 25, wherein one of the electrodes is placed inside the duct; and wherein for this electrode the electrolyte is provided by a liquid inside the duct.

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