AU2007204601B2 - Method and apparatus for treating roots in and around a conduit - Google Patents

Abstract

In order to kill tree roots (12) which may have entered a sewer pipe (10) through a crack or defective seal (13) between pipe sections (10A), the roots are irradiated with microwave radiation from a portable transmitter mounted on a sewer tractor (18) within the pipe. The transmitter comprises a magnetron (14) having an output port (15). Microwave radiation from the output port (15) is directed towards the tree roots by a parallel plate waveguide (16). The microwave radiation dosage is sufficiently high enough to kill the intruding tree roots and inhibit further growth. A camera (20) may be used on the sewer tractor (18) to provide visual inspection of the interior of the pipe and aid in aligning the transmitter with the roots to be treated.

Description

WO 2007/079542 PCT/AU2007/000026 METHOD AND APPARATUS FOR TREATING ROOTS IN AND AROUND A CONDUIT FIELD OF THE INVENTION 5 The present invention relates generally to a method of, and apparatus for, treating tree or plant roots and other organic matter in and around a conduit. In particular, the invention is directed to a method of and apparatus for killing roots that have penetrated a conduit, by irradiating the roots with microwave radiation. The invention has been developed primarily for treating roots in and around 10 sewer pipes and will be described hereinafter with reference to this application. However, it will be appreciated that the invention is not limited to this particular use. BACKGROUND ART Tree roots often breach underground sewer pipes by entering through defective 15 joints between sections of a pipe, or cracks in the pipe. Over a period of time the roots grow and can cause extensive damage to the pipe. Sometimes the damage is so severe that whole pipes need to be replaced. The replacement of sewer pipes is an expensive and time consuming process. To remedy the problems associated with the invasive growth of tree roots in 20 and around sewer pipes, it is usually necessary to excavate around the pipe in the region of the root breach in order to gain access to the pipe so that the pipe can be repaired. However, the damaged pipe may be in a location that is difficult to excavate. A further problem is that this method of repair tends to be quite costly. Another method consists of treating the problem roots with toxic 25 herbicide/growth inhibitor foam. This method of treatment is usually less expensive than the excavation method, however the foam can cause unwanted environmental damage if it is not properly contained. The use of herbicide treatments also entails the need for specialist vehicles, mixers, protective equipment and the intensive training of personnel. The risk of a toxic spill is also a constant source of concern. 30 Still another method consists of removing root growth within the pipe with a conventional drain-clearing machine such as an 'electric eel'. The electric eel is able to -2 remove the root growth leaving a smooth bore inside the pipe at the site of the root growth. However, the process may need to be repeated within a relatively short period of time if the roots grow back. It is an aim of the present invention to provide a method of, and apparatus for, 5 treating roots in and around a conduit, that substantially overcome, or at least ameliorate, one or more of the deficiencies associated with the prior art, or which at least provides a useful alternative. BRIEF SUMMARY OF THE INVENTION 10 According to a first aspect of the present invention there is provided a method of treating tree or plant roots in and/or around a conduit, comprising the steps of positioning a microwave transmitter within the conduit near the roots to be treated, and irradiating the roots with microwave radiation from the microwave transmitter to kill or inhibit growth of at least the portion of the roots. 15 The method is preferably used for treating roots in and around a sewer pipe. It is preferred that any portions of the roots that are inside the conduit are removed prior to the step of positioning the microwave transmitter inside the conduit. This enables the microwave transmitter to be more easily positioned inside the conduit and ensures that a smooth bore will be left inside the conduit. 20 The dosage of microwave radiation to which the roots are exposed is suitably selected so as to be sufficient to cause the irradiated roots to die or otherwise become inactive. Furthermore, the microwave radiation may be of a sufficient strength to affect roots that are situated externally to the conduit. The term "microwave radiation" is intended to mean electromagnetic radiation 25 in that part of the frequency spectrum commonly known as the microwave frequency band, and usually defined as being I GHz to 300 GHz. However, it is to be understood that electromagnetic radiation outside this band may be used in this invention where such radiation is effective to kill or inhibit the growth of tree roots and permitted under codes of practice governing the use of microwave energy in industrial applications. 30 In one embodiment, a microwave transmitter is positioned in the conduit in the vicinity of the roots to be treated. The microwave transmitter may comprise a microwave source or generator, such as a magnetron, having one or more output ports -3 emitting microwave radiation. A reflector or waveguide may suitably be used to direct the radiation to the roots. One or more infrared sensors, and/or a camera in conjunction with a light source, may be used to position the microwave transmitter within the conduit. The infrared 5 sensor(s) may be used for locating a joint between sections of the conduit where root invasion is more likely. Combining the joint location information with knowledge of the root location enables the microwave transmitter to be positioned at the site of root entry. For safety reasons, the microwave transmitter should only be enabled when predetermined conditions are satisfied. Such conditions may include that the microwave 10 transmitter is positioned in a conduit of a recognised size, that substantially no ambient light is present, and that the microwave transmitter is substantially centred relative to the conduit. It is also preferred that flexible microwave absorbent sheeting be placed on the surface above the position of the microwave transmitter in order to reduce any "leakage" of microwave radiation. 15 According to a second aspect of the present invention there is provided a root treatment apparatus for treating tree or plant roots in and/or around a conduit, the apparatus comprising a microwave transmitter, and positioning means for positioning the microwave transmitter at a desired location within the conduit near the roots, wherein the root treatment apparatus is operatively adapted to irradiate the roots with 20 microwave radiation to kill or inhibit growth of at least a portion of the roots. Preferably, the microwave transmitter comprises a source of microwave radiation, such as a magnetron, coupled to a reflector or waveguide to direct the radiation towards the roots. In one embodiment, a parallel plate waveguide is used. Alternately, a conical 25 deflector may be used. Preferably, in either case, the microwave radiation is radiated omni-radially substantially perpendicularly to the longitudinal axis of the conduit. The apparatus may be controlled by a remote controller. The apparatus may include a camera, such as a CCTV camera, whose output is transmitted to a display screen at the remote controller to allow the interior of the 30 conduit to be visually inspected remotely. Additionally, the camera can also assist in positioning the microwave transmitter within the conduit.

WO 2007/079542 PCT/AU2007/000026 -4 Furthermore, the apparatus may have at least one light sensor that is operable by a controller and positioned near the radiating means, to determine whether there is any light present, in which case the microwave transmitter is disabled as a safety measure. A light source may be positioned near the microwave transmitter to 5 illuminate the conduit interior for the camera when required and to determine whether the light sensor is operating correctly. Additionally, the apparatus may include a position indicating means for indicating the plan position of the microwave transmitter inside a conduit. The position indicating means may include a location diode positioned near the microwave 10 transmitter. A location sonde may be used to determine the position of the location diode and, hence, the microwave transmitter within the conduit. In the preferred embodiment, the apparatus is positioned by a transporter which can negotiate the conduit to position the microwave transmitter at the site of suspected root growth. Preferably, the transporter is a sewer tractor on which the apparatus is 15 mounted at one end. Alternatively, the apparatus may be supported by at least one wheel and towed or shunted by the transporter. The power supply for the microwave transmitter is preferably placed outside the conduit, with the power transferred to the apparatus via one or more cables. Alternatively, the power supply may be carried down the conduit with the transporter. 20 In a second embodiment, the positioning means includes a semi-rigid cable that enables the microwave transmitter to be fed into the conduit and pushed to the site of suspected root growth. It is preferred that the cable also functions as a protective conduit for any power or control cables. Preferably, the microwave transmitter is centered inside the conduit to ensure 25 uniform irradiation around the conduit. This may be achieved by providing a plurality of radially extending, resiliently flexible ribs around the microwave transmitter to centre it automatically with respect to the conduit. The apparatus of this alternative embodiment may be stored in a purpose-built storage container when not in use. The storage container is preferably constructed of a 30 substantially transparent or translucent material, and cylindrical in shape. The inner dimension of the storage container is preferably not one of the predetermined conduit WO 2007/079542 PCT/AU2007/000026 -5 sizes within which the apparatus is capable of operating. In order that the invention may be more readily understood and put into practice, embodiments thereof will now be described, by way of example only, with reference to the accompanying drawings. 5 BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is schematic sectional side elevation of one embodiment of an apparatus for treating roots in and around a conduit; and Fig. 2 is a schematic sectional side elevation of an alternative embodiment of 10 an apparatus for treating roots in and around a conduit; and Fig. 3 is a front elevation of the alternative embodiment illustrated in Fig. 2. DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION Fig. 1 illustrates one embodiment of an apparatus 1 being used to treat roots in 15 and around a conduit 10 which may be a sewer pipe made up of individual pipe sections 1OA. The joint between two pipe sections may be sealed by a rubber ring or a cement mortar seal 11. If a joint has a defective seal (shown at 13), or there is a crack in the conduit 10 itself, plant roots, and in particular tree roots, are likely to penetrate the conduit 10. 20 In the embodiment shown in Fig. 1, the apparatus 1 comprises a. microwave generator 14 (typically a magnetron) having an output port 15 which transmits microwave radiation to a parallel plate waveguide 16 which directs the radiation generally perpendicularly to the axis of the conduit 10. A protective casing 17, which is substantially transparent to the microwave radiation, is provided around the parallel 25 plate waveguide 16 to shield the output port from dirt and debris. The microwave generator 14 is powered from a remote power supply, typically located above ground, via a power cable 19A. A transporter, such as a sewer tractor 18, is used to position the microwave output port or transmitter 15 at or adjacent the site to be treated inside the conduit 10. 30 The microwave generator 14 and waveguide 16 are suitably mounted to the sewer tractor 18. The sewer tractor 18 is powered and/or remotely controlled from an WO 2007/079542 PCT/AU2007/000026 -6 external controller (not shown) via one or more cables 19C. Such sewer tractors are known and need not be described in detail in this application. Additionally, a closed circuit television camera 20 is mounted on the sewer tractor 18 to allow visual inspection of the interior of the conduit 10. The output of the 5 camera 20 is transmitted via cable 19B to a remote display screen. It is envisaged that the display screen will be located either on, or nearby the external controller. The external controller may be located at a distance from the apparatus. The controller may control and/or monitor the entire apparatus or just selected components. In the preferred embodiment, the controller at least controls the supply of 10 power to the magnetron 15. In use, the parallel plate waveguide 16 directs the microwave radiation towards the root(s) 12 to cause death of the roots, as described below. Figs. 2 and 3 illustrate a microwave treatment device 30 according to an alternative embodiment of the invention. The device 30 comprises a microwave 15 transmitter for transmitting microwave radiation, and positioning means for positioning the microwave transmitter in the conduit 10 at a desired position, normally at a location where roots have penetrated the conduit. The microwave transmitter comprises a microwave generator 34 (typically a magnetron) having a waveguide section 32 connected to its output port. The 20 microwave radiation generated by the magnetron 34 is transmitted through the waveguide section 32 to a conical reflector 33 which directs the radiation radially outwardly to the conduit 10. That is, the radiation is directed generally perpendicularly to the longitudinal axis of the conduit, in an annular or omni-radial pattern. A transparent nose cone 35 houses several components which are used 25 primarily for safety purposes, as described below. The nose cone 35 is generally hemispherical in shape, and is typically attached to the circular base of the conical reflector 33. The positioning means serves to locate the microwave transmitter at a desired location longitudinally within the conduit 10, as well as centrally relative to the 30 conduit 10. The positioning means includes a semi-rigid cable 31 which not only enables the microwave transmitter to be pushed along the conduit 10, but also supplies WO 2007/079542 PCT/AU2007/000026 -7 the magnetron 34 with electrical power, typically at 4 kV DC. A tubular end fitting 41 surrounds the connection of the semi-rigid cable 31 to the magnetron 15. The distal end of the cable 31 (not shown) is connected to a controller which controls the supply of power to the magnetron 34. The cable 31 also includes wires 5 connecting various sensors (described below) in the nose cone 35 to the controller. The positioning means also includes a plurality of circumferentially-spaced radial ribs 36 as shown more clearly in Fig. 3. The ribs extend from the nose cone 35 to a collar 37 which slides longitudinally along the connector portion 41. The radial extension of the ribs can be adjusted by sliding the collar 37 along the connector 10 portion 41. The position of the collar 37 can be controlled remotely by the controller. The ribs 36 are resiliently flexible, and serve as expandable centering vanes for the radiating means. In this manner, the illustrated apparatus can centre itself within a sewer pipe. The ribs 36 can also change shape to enable the microwave transmitter to negotiate pipe bends etc. That is, the expandable vanes can independently expand and 15 contract radially as the microwave tree rooter changes the shape of its envelope to negotiate pipe bends. When the microwave tree rooter 30 is located at the desired location, the ribs 36 are expanded to ensure that the microwave transmitter is located in the centre of the pipe, to thereby provide even treatment of the roots around the conduit 10 wall. The 20 expandable nature of the ribs 36 also permits the apparatus to be used in pipes of different nominal diameters. A closed circuit television camera facility may be provided in the microwave tree rooter 30. This facility comprises a camera 19 at the front of the nose cone 35. The image detected by the camera 19 is converted to an electrical signal which is 25 transmitted through wires in the cable 31 for display on a remote television screen. The microwave tree rooter of either embodiment may incorporate several safety features. These ensure that the radiating means will transmit microwave generation only in controlled, acceptable, conditions. These features are described with respect to Figs. 2 and 3, however the same features can also be provided in the 30 embodiment of Fig. 1. Infrared beam generators and sensors 38 are located in the transparent nose WO 2007/079542 PCT/AU2007/000026 -8 cone 35, and continually monitor the diameter of the conduit 10 in which the microwave tree rooter is inserted. The control system is configured and/or programmed to permit the radiating means to operate only if the conduit 10 has an inside diameter which matches a predetermined diameter. That is, the control system 5 is configured to permit operation only inside a small number of nominal pipe diameters. This helps avoid inadvertent operation of the radiating means outside the pipe environment. The infrared sensors 38 can also be used to locate the joints 11 between sections of the conduit 10, since the sensed diameter is marginally larger at those 10 joints. As most root damage to sewers occurs at the joints 11 of the conduit 10, this feature permits rapid and accurate location of the target zones for treatment. Three independent light sensors 39 are provided in the nose cone 34, the sensor outputs being connected to the controller by electrical conductors within the cable 31. If any one of the sensors 39 detects light, the radiating means is disabled. Again, this 15 helps avoid inadvertent operation of the device outside a pipe. The closed circuit television system provided in the microwave tree rooter includes a light for illuminating the pipe. A fail-safe continual check of the light sensors is provided by the operation of the closed circuit television system. Namely, the CCTV light must be turned off before the roots will be exposed to microwave 20 radiation. All three light sensors must indicate that no light is present before the radiating means can operate. A location diode 40 is also positioned in the nose cone 34. The location diode 40 can be used in conjunction with a commercially available location sonde (not shown) in order to determine a plan location of the device 30 when the device 30 is 25 located within the conduit 10 below ground. The plan position of the microwave tree rooter is required for a number of reasons. First, access to the surface above the microwave tree rooter should be restricted, even if the radiation reaching the surface is less than the prescribed level set by the EMR Human Exposure Standard and Code of Practice. Secondly, an additional barrier to exposure can be provided by laying 30 flexible microwave absorbent sheeting on the ground surface at the plan position indicated by the location diode 40.

WO 2007/079542 PCT/AU2007/000026 The device 30 may be stored in a cylindrical storage container (not shown) when it is not being used. The storage container preferably has an inner diameter which is not one of the predetermined diameters within which the device 30 is permitted to operate. 5 The storage container is also transparent or translucent so as to enable light to reach the light sensors 39, and hence prevent the radiating means from operating. These features assist in preventing inadvertent operation of the device 30 within its storage container. A method of using the apparatus to treat roots in and around a sewer pipe will 10 now be described. Prior to inserting the apparatus into the conduit 10, any root growth inside the conduit 10 should be removed to eliminate obstructions. A conventional drain-clearing machine such as an 'electric eel' is normally used to remove the root growth and leave a smooth bore inside the conduit 10 at the site of the root growth. During the process 15 of removing the root growth, the distance from the point of entry into the conduit 10 to the root growth is noted so that this information can be used when positioning the apparatus inside the conduit 10. The apparatus will usually be inserted into the conduit 10 via an access point or inspection opening in the conduit 10. The apparatus traverses the conduit 10 to the 20 desired location. The positioning of the apparatus within the conduit 10 can be confirmed visually by using the camera 20. Infrared beam/sensors 38 may be used in conjunction with, or alternatively to, the camera to position the apparatus within the conduit 10 at the site to be treated. (Infrared sensors 38 enable a change in diameter of the conduit 10, such as the change in diameter that occurs at the site of a joint, to be 25 identified. If an approximate location along the pipe of root growth is known, the pipe diameter information provided by the infrared beam/sensors enables the apparatus to be positioned at the site of a joint 11 where root penetration is likely). The corresponding surface position of the apparatus may be checked with a location sonde. The location sonde detects a locating signal that is reflected by the 30 location diode 40. Once the corresponding surface position of the apparatus has been determined, Faraday sheeting (microwave absorbent material) is laid over the WO 2007/079542 PCT/AU2007/000026 -10 corresponding surface position in order to provide additional protection against any undesired exposure to the microwave radiation emitted by the apparatus. It is also desirable to erect access barriers around the surface area corresponding to the position of the apparatus. 5 The control system will determine whether it is safe to emit microwave radiation. It may use light sensors 39 to detect light and infrared sensors 38 to determine the diameter of the conduit 10. If light is detected or the conduit is not of an allowed size, no microwave radiation will be emitted. Otherwise, the apparatus will deliver a dosage of microwave radiation to raise the irradiated tree root cells to a 10 temperature sufficient to cause cell death. After treatment, the woody remnant of the root end remains within the recess of the pipe joint, and the living root behind the treated zone helps maintain this timber plug into position to block further invasion of the joint by root regrowth. Since most commonly used conduit 10 materials are transparent to microwaves, the microwave 15 radiation can also kill roots a small distance outside the conduit 10. In the embodiment shown in Figs. 2 and 3, the following steps may also be required. Prior to administering the treatment, the combination 34,32,33 which forms the microwave radiating means needs to be centred in the conduit 10. To centre the microwave radiating means relative to the conduit 10, the ribs 36 are utilised. 20 Longitudinal movement of the collar 37 along the tubular connector 41 determines the extent to which the ribs 36 extend radially. The position of the collar 37 can be controlled by the controller. When the collar 37 is moved to the left (as shown in Fig. 2), the ribs 36 expand radially to place the radiating means, and in particular, the reflector 33, to be approximately equidistant from the conduit wall, so that the wall is 25 irradiated evenly. The radiating means will not be operated unless centering has occurred. Once the desired dosage of radiation has been delivered, the radiating means cannot be moved unless the centering ribs 36 have been retracted, thereby disabling power to the radiating means. Although the ribs 36 are sufficiently flexible to negotiate around bends in the 30 conduit 10, the collar 37 is normally moved to the right along the connector 35 when the radiating means is being pushed along the conduit 10. This reduces the radial WO 2007/079542 PCT/AU2007/000026 - 11 extent of the ribs 36, facilitating the passage along the conduit 10. After the tree root cells have been dosed with microwave radiation, the control system removes power from the radiating means and the ribs 36 are retracted so that the radiating means can be positioned at the next point of treatment, or removed from 5 the conduit 10. (If the apparatus is to be withdrawn from the conduit 10, the cable 31 is first removed from the controller). The foregoing embodiments are intended to be illustrative of the invention, without limiting the scope thereof. The invention is capable of being practised with various modifications and additions. For example, the magnetron may be located 10 outside the conduit 10, and microwave energy fed to the reflector 33 (or a waveguide antenna) via a coaxial cable or flexible waveguide. Such cable waveguide should be sufficiently durable to withstand the sharp and often jagged surfaces present inside sewer pipes. Further, the conical reflector 33 may be replaced by a waveguide designed to 15 transmit microwave radiation to a localised area of the conduit wall. Even further, the apparatus may be used to cure resins and glues and the like in a conduit, or aid in the drying of surfaces within a conduit. Additionally, the apparatus may be used for pest or insect eradication or the elimination of corrosion causing sulphur-oxidising bacteria and odour-causing bacteria within a conduit. 20 Accordingly, it is to be understood that the scope of the invention is not to be limited to the exact construction and operation described and illustrated, but only by the following claims which are intended, where the applicable law permits, to include all suitable modifications and equivalents within the spirit and concept of the invention. 25 Throughout this specification, including the claims, where the context permits, the term "comprise" and variants thereof such as "comprises" or "comprising" are to be interpreted as including the stated integer or integers without necessarily excluding any other integers.

Claims (20)

1. A method of treating tree or plant roots in and/or around a conduit, comprising the steps of positioning a microwave transmitter within the conduit near the roots to be treated, and irradiating the roots with microwave radiation from the microwave transmitter to kill or inhibit growth of at least a portion of the roots.

2. The method of claim 1, wherein the dosage of microwave radiation with which the roots are irradiated is sufficient to cause death of at least the portion of the roots within the conduit.

3. The method of claim 1, further comprising the step of removing any portions of the roots that are inside the conduit prior to positioning the microwave transmitter within the conduit.

4. The method of any preceding claim, wherein the conduit is a sewer pipe.

5. The method of any preceding claim, further comprising the step of centering the microwave transmitter with respect to the conduit to ensure uniform irradiation around the conduit.

6. The method of any preceding claim, wherein the microwave radiation is electromagnetic radiation in the frequency spectrum between 1 GHz to 300 GHz.

7. The method of any preceding claim, wherein the microwave transmitter comprises a microwave generator having an output port, the microwave generator being connected to a remote power supply via an electrical cable.

8. The method of any preceding claim, further comprising means for disabling operation of the microwave transmitter unless predetermined conditions are met. -13

9. Root treatment apparatus for treating tree or plant roots in and/or around a conduit, the apparatus comprising a microwave transmitter, positioning means for positioning the microwave transmitter at a desired location within the conduit near the roots, wherein the root treatment apparatus is operatively adapted to irradiate the roots with microwave radiation to kill or inhibit growth of at least a portion of the roots.

10. The root treatment apparatus of claim 9, further comprising a controller for controlling the microwave transmitter from a remote location.

11. The root treatment apparatus of claim 9 or 10, wherein the microwave transmitter comprises a microwave generator connected to a remote power supply via an electrical cable, the microwave generator having an output port, and a waveguide mounted to the output port for directing microwave radiation from the output port substantially perpendicularly to the longitudinal axis of the conduit.

12. The root treatment apparatus of claim 11, wherein the waveguide is a parallel plate waveguide.

13. The root treatment apparatus of claim 9 or 10, wherein the microwave transmitter comprises a microwave generator having an output port, and a conical deflector for directing microwave radiation from the output port substantially perpendicularly to the longitudinal axis of the conduit.

14. The root treatment apparatus of any one of claims I1 to 13, wherein the microwave generator is a magnetron.

15. The root treatment apparatus of any one of claims 9 to 14, further comprising a camera mounted on the positioning means.

16. The root treatment apparatus of any one of claims 9 to 15, further comprising at least one infrared sensor for determining the conduit size, and/or for -14 locating a joint between sections of the conduit.

17. The root treatment apparatus of any one of claims 9 to 16, further comprising at least one light sensor mounted on the positioning means adjacent the microwave transmitter to detect the presence of light, and means for disabling the operation of the microwave transmitter in response to the output of the light sensor.

18. The root treatment apparatus of any one of claims 9 to 17, further comprising a position indicating means for indicating the plan position of the microwave transmitter within the conduit.

19. The root treatment apparatus of any one of claims 9 to 18, wherein the positioning means is a wheeled carrier.

20. The root treatment apparatus of any one of claims 9 to 18, wherein the positioning means comprises a cable for pushing the microwave transmitter to a desired position along the conduit, and further comprising a plurality of resiliently flexible radially-extending ribs for centering the microwave transmitter with respect to the conduit.