Reduction of microbiological growth in pipes

Abstract

The proposed technology relates to a system (8) for preventing microbiological growth in a conduit conveying a liquid. The system (8) comprises a multi-layered pipe (10) constituting said conduit and having an inner layer (12) that covers the complete inside (16) of the pipe (10) and is formed of an electrically conductive polymer material. A liquid in the pipe (10) is in direct contact with the inner layer (12). The system further has a first electrical connector (18) and a second electrical connector (19) connecting to the inner layer (12) from outside the pipe (10), wherein the first electric connector (18) and the second electric connector (19) are spaced apart along the pipe (10). The system further has an electric power source (20) operationally connected to the first electrical connector (18) and the second electrical connector (19) and configured for supplying an electric current to the inner layer (12).

Claims

1. A system for preventing microbiological growth in a conduit conveying a liquid, wherein the system comprises: a multi-layered pipe constituting said conduit and having an inner layer and an outer layer, wherein the inner layer is formed of an electrically conductive polymer material and covers an inside surface of the pipe so as to be directly contacted by liquid in the pipe, wherein the inner layer has an outside, a portion of which is covered by the outer layer, and wherein the outer layer is formed of an electrically insulating polymer material; a first electrical connector connecting to a first exposed portion of the inner layer from outside the pipe, and a second electrical connector connecting to a second exposed portion of the inner layer from outside the pipe, wherein the first electrical connector and the second electrical connector are electrically connected to each other by the inner layer; and an electric power source operationally connected to the first electrical connector and the second electrical connector, the electric power source being configured for supplying an electric current to the inner layer.

2. The system according to claim 1, wherein the electric current is a direct current.

3. The system according to claim 2, wherein the electric current is between 0.1 mA and 10 mA.

4. The system according to claim 1, wherein the electric current is supplied at a voltage between the first electrical connector and the second electrical connector that is between 20 V and 150 V.

5. The system according to claim 1, wherein the electric current is an alternating current.

6. The system according to claim 5, wherein the electric current is between 0.1 mA and 10 mA.

7. The system according to claim 5, wherein the electric current is supplied at a voltage between the first electrical connector and the second electrical connector that is between 20 V and 80 V.

8. The system according to claim 5, wherein the alternating current has a frequency between 1 kHz and 5 kHz.

9. The system according to claim 1, wherein the power source is further configured for supplying a pulsed electric current.

10. The system according to claim 9, wherein the pulses have a combined pulse length over a period of time that is equal to or less than 50% of the length of the period.

11. The system according to claim 1, wherein the electrically conductive polymer material of the inner layer is carbon-black filled polyethylene.

12. The system according to claim 1, wherein the multilayered pipe is a flexible hose.

13. The system according to claim 12, wherein the electrically conductive polymer material of the inner layer is carbon-black filled polyethylene.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) A more complete understanding of the proposed technology and other features and advantages of the proposed technology, will be apparent from the following detailed description of the figures, where:

(2) FIGS. 1a-c schematically illustrate the a setup of an embodiment of the proposed system,

(3) FIG. 2 schematically illustrates an embodiment of the proposed system in a liquid transportation application,

(4) FIG. 3 schematically illustrates an embodiment of the proposed system in a liquid dispensing application,

(5) FIG. 4 schematically illustrates an embodiment of the proposed system in a liquid recycling application,

(6) FIG. 5 schematically illustrates an embodiment of a beverage dispensing system including the proposed system for preventing microbiological growth,

(7) FIG. 6 schematically illustrates an embodiment of a beverage dispensing system including a retrofitted proposed system for preventing microbiological growth, and

(8) FIG. 7 is a graph illustrating the results of an investigation of the function of the proposed technology.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE PROPOSED TECHNOLOGY

(9) The setup of an embodiment of a system for reducing microbiological growth in a conduit is schematically illustrated in FIGS. 1a-c. A multi-layered pipe 10 is provided having an inner layer 12 and an outer layer 14. The inner layer 12 is composed of carbon-black filled polyethylene with a 20 weight percentage of carbon-black. The outer layer is composed of polyethylene. This means that the inner layer 12 is electrically conductive and the outer layer 14 is electrically insulating. The inner layer 12 and the outer layer 14 have been co-extruded in a manner such that the inner layer 12 covers the complete inside 16 of the pipe 10 and the outer layer 14 covers the complete outside of the inner pipe 12, as is shown in FIG. 1c. There is no material between the inner pipe 12 and a liquid conveyed by the pipe 10.

(10) In an alternative embodiment, the polymer of the inner layer 12 and the outer layer 14 is polyethylene, which means that the pipe 10 will have the properties of a hose with respect to manual handling.

(11) The outer layer 14 is removed at the ends of the pipe 10, thereby making the inner layer 12 accessible from outside the pipe 10, as is shown in FIG. 1b. In alternative embodiments, the outer layer 14 is removed at other parts of the pipe 10, for example further in from the ends of the pipes, thus leaving the inner layer 12 covered by the outer layer 14 at the ends of the pipe 10.

(12) A first electrical connector 18 is attached to the exposed inner layer 12 at one end of the pipe 10, and a second electrical connector 19 is attached to the exposed inner layer 12 at the other end of the pipe 10. Both connectors are tightened around the inner layer in a similar manner as a hose clamp is tightened, thus ensuring a good electrical connection between each of the connectors and the inner layer 12.

(13) An electric power source 20 is provided that is operationally connected to the first connector 18 via a first cable 22 and to the second connector 19 via a second cable 24. When installed in an application and with a liquid running through the pipe 10, the electric power source 20 is set to supply a direct current in the inner layer 12 that is between 0.3 mA and 0.7 mA by way of the electric circuit established with the first connector 18, the second connector 19, the first cable 22, and the second cable 24. In an alternative embodiment, the electric power source 20 is also set to generate a stable potential in the range 50 V and 70 V between the first connector 18 and the second connector 19.

(14) In alternative embodiments, the electric power source 20 is set to supply an alternating current in the inner layer 12 that is between 0.4 mA and 0.8 mA. Additionally or alternatively, the electric power source 20 is also set to generate a stable potential in the range 50 V and 70 V between the first connector 18 and the second connector 19.

(15) The electric power source 20 is operated to supply a continuous electric current to the inner layer 12. In an alternative embodiment, the electric current is pulsed or intermittently operated. In one embodiment, the electric current is supplied in a cycle alternating between one week of electric current supply and one week without electric current supply, thus effectively having a combined pulse length over a period of time that is 50% of the length of the period.

(16) An embodiment of the proposed system 8 is shown in FIG. 2. The system 8 is installed in a liquid transportation application 40. It has all the features of the system 8 described above in relation to FIG. 1. At one end, the pipe 10 is connected to a liquid supply 26, for example public water mains. At the other end, the pipe 10 is connected to a liquid recipient 28, such as the water inlet at a domestic or industrial building, or another section of the public water mains.

(17) FIG. 3 schematically illustrates an embodiment of the proposed system 8 in a liquid dispensing application. The system 8 has all the features described above in relation to FIG. 1. At one end, the pipe 10 is connected to a liquid supply 30, for example a hot-water pipe in a domestic building. At the other end, the pipe 10 is connected to a liquid dispenser 32, such as a shower in a domestic or public building.

(18) Another embodiment of the proposed system 8 is shown in FIG. 4. The system 8 is installed in a liquid recycling application 44. It has all the features of the system 8 described above in relation to FIG. 1. At both its ends the pipe 10 is connected to liquid recycler 28, such as the heat exchanger, the circulation pump, and the radiators of a low-temperature heating system of a building.

(19) An embodiment of a beverage dispensing system 6 is schematically illustrated in FIG. 5. The dispensing system 6 has a liquid dispenser or tapping station for the beverage in the form of a beer tap 32 attached to a bar counter 34. It further has a beverage conduit 36 for conveying a beverage from a liquid supply or container containing the beverage in the form of a beer keg 30. A system 8 for preventing microbiological growth having the features of the embodiment described above in relation to FIG. 1 forms part of the dispensing system 6. The pipe 10 constitutes a portion of the beverage conduit 6. At one end, the pipe 10 is connected to the beer keg 30 via a beverage hose 37. At its other end, the pipe 10 is connected to the beer tap 32. When the electric power source 20 is operated as described above in relation to FIG. 1, microbiological growth is prevented in the pipe 10.

(20) Another embodiment of a beverage dispensing system 6 is schematically illustrated in FIG. 6. The dispensing system 6 has a liquid dispenser or tapping station for the beverage in the form of a beer tap 32 attached to a bar counter 34. A system 8 for preventing microbiological growth, having the features of the embodiment described in relation to FIG. 1, forms part of the dispensing system 6. However, the system 8 differs in that the pipe 10 is a hose. The dispensing system 6 has an existing conduit 38 in the form of a rigid pipe 38. The hose 10 has been retrofitted in the rigid pipe 38 by the insertion of the hose 10 through the receiving end of the rigid pipe 38 and by connecting the hose 10 to the beer tap 32. At one end, the hose 10 is connected to a beer keg 30 via a beverage hose 37. Thus, the hose 10 forms part of a beverage conduit 36 conveying beer from the keg 30 to the beer tap 32. When the electric power source 20 is operated as described above in relation to FIG. 1, microbiological growth is prevented in the hose 10.

(21) Proof-of-Concept

(22) An investigation of the proposed technology has been performed including three different setups. Three pipes of identical length and diameter were used. The length was 25 meter and the inner diameter was 63 mm. In the first setup, the pipe was a single-layer polyethylene pipe. In the second and third setups the pipes were identical multi-layered pipes with an inner layer of carbon-black-filled polyethylene. Electrical connectors were attached to the inner layer of the pipes at the ends of the pipes. Sweet water from public water mains was introduced in and allowed to flow through the pipes. An electric current of 0.5 mA was supplied to the electrical connectors of the third setup at a voltage in the range 60 V to 65 V.

(23) The investigation was divided into two periods, the first period covering weeks 1 to 10 and the second period covering weeks 10 to 25.

(24) Microbiological growth was monitored weekly by the taking of samples of the biofilm from the inner walls of the pipes. The samples were cultivated for 48 hours and the number of bacteria colonies was then calculated in each sample and used to represent the microbiological growth in the corresponding setup.

(25) In the first period, the microbiological growth was allowed to settle on the inner walls and allowed to adjust to the environment inside the pipes. No conclusive results were achieved in the first period. The three setups were then moved and connected to the public mains at another point before the second period of investigation started.

(26) The results of the second period are shown in FIG. 7. The weeks are indicated on the abscissa and the number of counted bacteria is indicated on the ordinate. For each week, the left bar represents the measurement from the first setup, i.e. with a single layer polyethylene pipe, the middle bar represents the measurement from the second setup, i.e. with an inner conductive layer without an electric current, and the right bar represents the measurement from the third setup, i.e. with an inner conductive layer with an electric current. It should be noted that no sampling was performed in the weeks without any bars.

(27) As can be clearly seen in FIG. 7, after week 16 when the microbiological growth had established itself in the pipes, the microbiological growth in the second setup was greater than in the third setup, thus showing that the supplied electric current reduces the microbiological growth. It is contemplated that the high initial counts of the second and third setups is a result of an initial adaption to the environment inside the pipes with carbon-black in the inner layer.

ITEM LIST

(28) 6 beverage dispensing system 8 system 10 pipe or hose 12 inner layer 14 outer layer 16 inside of the pipe 18 first electrical connector 19 second electrical connector 20 electric power source 22 first cable 24 second cable 26 liquid supply 28 liquid recipient 30 liquid supply 32 liquid dispenser 34 bar counter 36 a beverage conduit 37 beverage hose 38 existing conduit 40 liquid transportation application 42 liquid dispensing application 44 liquid recycling application