AU2003200031A1 - Biocidal treatment method and device therefor - Google Patents

Description

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT (Original) APPLICATION NO:

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RELATED ART: NAME OF APPLICANT: ACTUAL INVENTOR(S): ADDRESS FOR SERVICE: INVENTION TITLE: BIO HEALTH SYSTEMS PTY LTD ANDREW EDMUND FITZ GIBBON MAXWELL EDNEY SCOTT LORD COMPANY, Patent Trade Mark Attorneys, of 4 Douro Place, West Perth, Western Australia, 6005, AUSTRALIA.

BIOCIDAL TREATMENT METHOD AND DEVICE

THEREFOR

DETAILS OF ASSOCIATED PROVISIONAL APPLICATION NO'S: AUSTRALIAN PROVISIONAL APPLICATION NUMBERS PR9873, PS3322, and 2002951828, FILED JANUARY 8, 2002, JULY 3. 2002, and October 7, 2002, respectively.

The following Statement is a full description of this invention including the best method of performing it known to me/us:

TITLE

BIOCIDAL TREATMENT METHOD AND DEVICE THEREFOR FIELD OF THE INVENTION The present invention relates to a biocidal treatment method and device therefor, particularly a heat treatment method for vegetation control by means of pressurised fluids and a device to deliver pressurised fluids for heat treatment of vegetation. The invention, can, however, have various other applications such as, for example, treatment of the ground in order to kill or debilitate unwanted agents such as microorganisms, fungus, plant-life, and animals (such as insects including eggs of such insects) in the soil near its surface. The device may also be used to clean surfaces such as paved areas to remove unwanted agents such as moss, algae and other plant life and fungi.

BACKGROUND OF THE INVENTION It is known to effect vegetation control by direct application of herbicidal preparations, or heat treatment including the application, at elevated temperatures, of water, foam, air or flame. There is extensive concern about the environmental effects of each of these methods of vegetation control, particularly in relation to the residual lifetimes of herbicidal preparations and their toxicity effects. Further, the large energy expenditure involved in various heat treatment methods has been prohibitive in its widespread adoption. Additionally, the application of hot air or flame to vegetation in order to destroy it has only been partially successful as it tends to only scorch the exposed part of the vegetation, leaving the root stock remaining intact.

The application of flame also has the potential to create a fire hazard. The present invention attempts to overcome at least in part some of the aforementioned disadvantages.

SUMMARY OF THE INVENTION In accordance with a first aspect of the present invention there is provided a biocidal treatment device, comprising a fluid directing means for applying biocidal treatment fluids to a subject in need of biocidal treatment, the means having a first directional outlet for a first treatment fluid and at least one second directional outlet for a second treatment fluid, a first treatment fluid supply means in fluid communication with the first directional outlet, and a second treatment fluid supply means in fluid communication with the or each second directional outlet, the second treatment fluid being applied to a subject of biocidal treatment at a higher temperature than the first treatment fluid, wherein the or each second directional outlet is disposed adjacent to the first directional outlet, the arrangement being such that application of the second treatment fluid to the subject facilitates preheating of the subject immediately before application of the first treatment fluid.

In accordance with a second aspect of the invention there is provided a method of biocidal treatment comprising the steps of applying heat to a substrate in need of biocidal treatment and thereafter applying a mixture of hot air and water to the substrate.

In accordance with a third aspect of the invention there is provided a method of killing weeds comprising the steps of applying heat to the weeds to reduce the moisture content thereof and thereafter applying a mixture of hot air and water to the weeds.

In accordance with a fourth aspect of the invention there is provided a mobile biocidal treatment apparatus for traversing an area to undergo biocidal treatment, the mobile biocidal treatment apparatus comprising a first means for generating a supply of heat and discharging the heat at a first discharge location and a second means for generating a mixture of hot air and water and discharging the mixture of a second discharge location, the first discharge location being disposed ahead of the second discharge location with respect to the direction of travel of the mobile biocidal treatment apparatus to facilitate preheating of the area immediately before discharge of the mixture of hot air and water.

DESCRIPTION OF THE DRAWINGS The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a cross sectional view of a biocidal treatment device in accordance with the present invention; and Figure 2 is a schematic view of a mobile biocidal treatment apparatus in accordance with the fourth aspect of the present invention.

DETAILED DESCRIPTION OF AN EMBODIMENT OF THE INVENTION Referring to Figure 1, there is shown a biocidal treatment device 10. The biocidal treatment device 10 includes a fluid directing means 100 for applying biocidal treatment fluids to a subject having a first directional outlet 20 for a first treatment fluid and a second directional outlet 30 for a second treatment fluid, a first treatment fluid supply means 40 in fluid communication with the first directional outlet 20, and a second treatment fluid supply means 50 in fluid communication with the or each second directional outlet In a preferred embodiment of the present invention, the fluid directing means 100 comprises a hand-held elongate member 110 having a first internal cylindrical void 112 extending along a central longitudinal axis of the elongate member 110 and terminating at the first directional outlet 20 disposed in a distal end 111 of the elongate member 110. The elongate member 110 is also provided with a second internal annular void 114 concentrically disposed around the first internal cylindrical void 112 and extending along the length of the elongate member 110, as shown in Figure 1. The second internal annular void 114 terminates at a plurality of second directional outlets 30 disposed in the distal end 111 of the elongate member 110.

Preferably, the second directional outlets 30 are spaced equiangularly around the first directional outlet Alternatively, the elongate member 110 may be provided with a plurality of second internal cylindrical voids 114 concentrically disposed around the first internal cylindrical void 112 and extending along the length of the elongate member 110. The second internal cylindrical voids 114 terminate at respective second directional outlets disposed in the distal end 111 of the elongate member 110. Preferably, the second directional outlets 30 are spaced equiangularly around the first directional outlet The first and second directional outlets 20, 30 may take the form of a nozzle 22, 32 or a plurality of closely spaced cylindrical apertures in the distal end 111 of the elongate member 110 disposed in an arrangement to facilitate a directional spray pattern. The first and second directional outlets 20, 30 are disposed adjacent to one another such that the spray pattern emerging from the first directional outlet 20 overlaps extensively with the spray pattern emerging from any one of the second directional outlets 30, as shown in Figure 1.

The first internal cylindrical void 112 is arranged in use to receive heated water through a first inlet port 116 disposed in a proximal end 113 of the elongate member 110 and in fluid communication with the first internal cylindrical void 112. The first internal cylindrical void 112 is also arranged in use to receive pressurised air through a second inlet port 118 disposed in a proximal end 113 of the elongate member 110 and in fluid communication with the first internal cylindrical void 112. The first and second inlet ports 116, 118 are coupled with the first treatment fluid supply means via a first fluid delivery line 42 and a second fluid delivery line 44, respectively.

The first treatment fluid supply means 40 comprises a hot water supply and pump arranged to provide heated water to the first internal cylindrical void 112 via the first fluid delivery line 42 and a source of compressed air arranged to provide pressurised air to the first internal cylindrical void 112 via the second fluid delivery line 44.

Preferably, the water is heated to a temperature range of between 95 OC to 120 0

C.

Traditionally, the generation of heated water by a hot water supply in prior art devices has been through the use of vehicle mounted diesel fuel and diesel fired burners which have proved to be unreliable, expensive to produce and heavy factors that have prohibited their widespread adoption.

Typically, the hot water supply of the present invention preferably comprises a first liquid petroleum gas (LPG) or natural gas instantaneous hot water heater in a coupled serial arrangement with a second LPG or natural gas instantaneous hot water heater.

The first heater heats water from an ambient temperature to a maximum of 95°C. The second heater is provided with a much heavier grade heating coil or chamber to withstand boiling water and steam, such that the second heater is arranged to raise the temperature of water received from the first heater from 95 0 C to between 100 120 0 C. The effect of using two heaters in series is to maintain the weight of the combined heaters as low as possible in comparison to other alternative hot water supplies such as a steam boiler, electric heater, or generator of considerably higher weight and volume.

In use, water at ambient temperature is provided to an inlet of the first heater at a rate of approximately 5 to 50 litres per minute. The water is circulated through a series of heating coils of the first heater, whereupon the temperature of the water is raised to about 95'C. The first and second heaters are coupled and in fluid communication with one another via a pipe that provides a conduit from the first heater to the second heater. Upon entering the second heater, the water from the first heater circulates through a series of heavy grade heating coils in the second heater, whereupon the temperature of the water is raised to about 100 120 0 C. An outlet of the second heater is coupled to the first fluid delivery line 42.

The respective components of the first treatment fluid, namely heated water and pressurised air are delivered to the first internal cylindrical void 112 via the first and second fluid delivery lines 42, 44, respectively, whereupon the heated water and pressurised air mix to form the first treatment fluid. The first internal cylindrical void 112 is provided with a web 116 formed from mesh to assist the dispersion of the heated water with the void 112 and aid efficient mixing therein. In use, the first treatment fluid is discharged from the first directional outlet 20 at a rate of about 4 L per minute at a temperature of about 100 0

C.

The second internal annular void 114 is arranged in use to receive the second treatment fluid through at least one third inlet port 119 disposed in the proximal end 113 of the elongate member 110 and in fluid conunmmunication with the second internal annular void 114. The or each third inlet port 119 is coupled with the second treatment fluid supply means 50 via a second treatment fluid delivery line 52.

It is envisaged that the second internal cylindrical voids 114 would also be arranged in use to receive the second treatment fluid through respective third inlet ports 119 disposed in the proximal end 113 of the elongate member 110 and in fluid communication with the second internal cylindrical voids 114.

The second treatment fluid is pressurised air heated to a temperature range of between about 100 0 C to 1000 0 C, preferably to a temperature range of between 100'C to 400'C. The second treatment fluid supply means 50 comprises a hot compressed air supply, heater and pump arranged to provide pressurised heated air to the second internal annular void 114 via the second treatment fluid delivery line 52. In use, the second treatment fluid is discharged from the or each second directional outlet 320 at a rate of about 100 cubic feet per minute.

The spray pattern emerging from the first directional outlet 20 is arranged to overlap extensively with the spray pattern emerging from any one of the second directional outlets 30. In this way, simultaneous application of the second treatment fluid to the subject of biocidal treatment facilitates preheating of the subject immediately before application of the first treatment fluid, resulting in energy savings since it requires far less energy to provide heated air than the amount of energy required to provide water heated to a similar temperature.

The proximity and overlap of the spray pattern of the second treatment fluid to the spray pattern of the first treatment fluid also serves to maintain the temperature of the first treatment fluid at about 100 0 C. Heat loss inevitably occurs during mixing of heated water and air in the first internal cylindrical void 112 of the fluid directing means 110. Thus, the present invention is particularly advantageous with regard to energy savings, as no further heat needs to be supplied to the first treatment fluid in order for its temperature to have a biocidal effect on the subject of treatment application.

It is envisaged that the hand-held elongate member 110 of the fluid directing means 100 is formed from a material able to withstand high temperature and high pressure fluids received in its internal voids 112, 114. Preferably, an outer surface 115 is provided with a crimped material or non-slip material to assist with holding and manipulation of the fluid directing means 100 by hand.

Typically, biocidal treatment may comprise vegetation control wherein the subject is noxious weeds or unwanted vegetation, sterilisation of top soil or other substrates, fungal and/or mould control, or removal of insects and other pests. Upon application of the first and second treatment fluids by the fluid directing means 110, the high temperature of the second treatment fluid preheats and dehydrates the substrate or subject whilst the first treatment fluid facilitates the biocidal effect.

For example, the heat which is first applied to the vegetation removes the moisture content of the vegetation, so enhancing the ability of the vegetation to accept the water delivered within the mixture of air and hot water, so providing better penetration of the heat for the purposes of killing vegetation. It is believed that the presence of water in the hot air assists in carrying heat contained within the mixture into the ground so as to expose and treat that part of the vegetation located under the ground to heat.

It is also envisaged that several of the biocidal treatment devices 10 of the present invention may be mounted in an array on a mobile structure such that biocidal treatment fluids as described hereinbefore could be conveniently applied to large areas of substrate or subject in need of biocidal treatment. Operation and control of the first and second treatment fluid supply means 40, 50 would be effected by remote control.

The embodiment shown in Figure 2 is directed to a biocidal treatment apparatus used for vegetation control. The biocidal treatment apparatus 210 according to the embodiment is adapted to be mounted on a tractor (not shown) via three-point linkage.

The biocidal treatment apparatus 210 comprises a body 211 having a ground contacting element 213 in the form of a wheel. The wheel 213 travels over ground upon which the body 211 is moved when mounted onto the tractor by way of the three-point linkage as referred to earlier. The wheel 213 is adjustable relative to the body 211 for selectively varying the height of the body 211 relative to the ground over which it travels.

The body 211 includes a lower casing 215 having side walls 217 and a top wall 219 defining a compartment 221 having an open bottom 223. A partition wall 224 is provided within the lower casing 215 to divide the compartment 221 into a first chamber 225 and a second chamber 227.

The first compartment 225 has an outlet 229 defined by that section of the open bottom 223 associated with the first chamber 225. Similarly, the second chamber 227 has an outlet 231 defined by that section of the open bottom 223 associated with the second compartment 227. Typically, the outlet 231 is in the form of a slot of width between about 3mm and 20 mm.

The outlet 229 provides a first discharge location, and the outlet 231 provides a second discharge location, the purposes of which will be explained later. With this arrangement, the two discharge locations are immediately adjacent one another, with the first discharge location defined by the outlet 229 being ahead of the second discharge location defined by the outlet 231 in the direction of travel of the treatment apparatus 210 as indicated by directional arrow 233 depicted in the drawing.

Because of the inclination of the barrier wall 224 within the casing 215 the first chamber 225 expands in the direction towards the outlet 229 and the second chamber 227 contracts in the direction towards its outlet 231.

An upper casing 235 is mounted on the lower casing 215. The upper casing 235 includes a burner chamber 237, and an air chamber 239 which is separated from the burner chamber 237 by way of a wall 241. The air chamber 239 opens onto the second chamber 227.

Air is delivered under pressure into the air chamber 239 by way of a fan 243 accommodated in a casing 245 which communicates with the air chamber 239.

Typically, the fan 243 delivers air at a rate of 10 cmph and 30 cmph. The fans 243, 249 are hydraulically driven through the hydraulic power system of the tractor.

The burner chamber 237 is fitted with gas burners 247 which operate with LPG.

Typically, the gas burners 247 have a capacity of between about 50,000 btuph and 150,000 btuph.

A fan 249 is provided for delivering air under pressure into the burner chamber 237.

The fan 249 is accommodated in a casing 251 having an outlet communicating with the burner chamber 237. Typically, fan 249 has a capacity of between about 5 cmph and 40 cmph.

The burner chamber 237 communicates with the first chamber 225 by way of an air flow path defined by a plurality of conduits 253 arranged in parallel, with one end of each conduit opening onto the burner chamber 237 through wall 241 and the other end of each conduit opening onto the first chamber 225 through partition wall 224.

In extending between the wall 241 of the burner chamber 237 and the partition wall 224 between the first and second chambers 225, 227, the conduits 253 extend through the air chamber 239 and the second chamber 227.

The conduits 253 provide a heat exchanger, as will be explained in more detail later.

A spray nozzle 257 is provided for injecting water into the second chamber 227 at a location adjacent the outlet 231, as shown in the drawing. Water injected into the second chamber 227 through the nozzle 257 is supplied from a tank mounted on the tractor. Typically, water is injected at a rate of about 1.8 litres per minute. The air flow rate at the location at which water is sprayed into the air is typically between mps and 20 mps.

In operation, the apparatus 210 traverses ground to be treated typically at a speed of between 0.5 and 10 kilometres per hour, depending on the nature of the vegetation to be controlled. The height of the lower casing 215 above the ground is adjusted by way of the roller 213. Typically, the apparatus operates at a clearance of between 1 cm and 7 cm width above the ground. Air is delivered into the burner chamber 237 by way of fan 249. As the air passes through the burner chamber 237, it is heated by the burners 241. The heated air passes through the conduits 253 to the first chamber 225. Because the bottom of the first chamber 225 is open by way of outlet 229, the hot air is projected onto vegetation over which the apparatus 210 travels. The hot air serves to dry the vegetation in readiness for an application of a mixture of heated air and water, as will be explained. The fan 243 supplies air to the air chamber 239 from where it flows to the second chamber 227. As the air moves through the air chamber 239 and the second chamber 227, it passes over the heat exchanger defined by the conduits 253. In this way, the air is heated by heat received from the air passing through the conduits 253 from the burner chamber 237 to the first chamber 225. The heated air in the second chamber 227 flows towards, and ultimately discharges through, the outlet 231. As the air approaches the outlet 231, it receives water sprayed through nozzle 257, with the result that there is created a mixture of water and hot air. The mixture of water and hot air discharges through the outlet 231 and onto the vegetation previously dried by the air discharging through outlet 229 from chamber 225.

The combined effect of initially drying the vegetation with hot air and then applying heat to the dried vegetation by way of the mixture of water and hot air has been found to be particularly effective in killing weeds and other vegetation. It is believed that the action of initially drying the vegetation with heat enhances the ability of the vegetation to later accept the water contained within the mixture of water and hot air.

The presence of the water in the mixture serves to assist the heat contained therein to penetrate the vegetation, so enhancing its ability to kill the vegetation. Furthermore, the presence of the water assists heat contained in the mixture to penetrate the soil and so have an effect on that part of the vegetation below the ground.

From the foregoing, it is evident that the present invention provides a simple yet highly effective arrangement for delivering a supply of heat to vegetation and subsequently applying a mixture of hot air and water to the vegetation in order to kill it.

It should be appreciated that the scope of the invention need not be limited to the scope of the embodiment described. The treatment apparatus has been described in the embodiment as being adapted for attachment to a tractor by way of a three-point linkage. It should be appreciated that any appropriate system can be used to propel the treatment apparatus over the ground. Indeed, it may be possible in certain circumstances for the treatment apparatus to be manually propelled over the ground.

While the treatment apparatus has been described in the embodiment as an independent unit, it should be appreciated that it can be incorporated into other equipment. For example, it may be possible to incorporate the treatment apparatus into a rotary hoe where a protective hood covering the rotor of the rotary hoe would define the first compartment through which heat is applied to the ground and any soil and vegetation disturbed by the rotary hoe.

Furthermore, as alluded to earlier, it should be understood that the invention is not limited to killing weeds and otherwise controlling vegetation as described in the embodiment. The treatment apparatus may have various other applications including cleaning surfaces, and treating soil with the intention of killing micro-organisms, seeds, insects and other life forms therein.

The various flow rates of air and water, and temperatures to which the air flows are heated, can vary according to the particular application of the treatment apparatus.

The necessary flow rates for any particular application can be determined experimentally during use if necessary.

Throughout the specification, unless the context requires otherwise, the word "comprise" or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

Modifications and variations as would be apparent to a skilled addressee are deemed to be within the scope of the present invention.

Claims (25)

1. A biocidal treatment device comprising a fluid directing means for applying biocidal treatment fluids to a subject in need of biocidal treatment, the means having a first directional outlet for a first treatment fluid and at least one second directional outlet for a second treatment fluid, a first treatment fluid supply means in fluid communication with the first directional outlet, and a second treatment fluid supply means in fluid communication with the or each second directional outlet, the second treatment fluid being applied to a subject of biocidal treatment at a higher temperature than the first treatment fluid wherein the or each second directional outlet is disposed adjacent to the first directional outlet, the arrangement being such that application of the second treatment fluid to the subject facilitates preheating of the subject immediately before application of the first treatment fluid.

2. The device according to claim 1, wherein the fluid directing means comprises an elongate member having a first internal cylindrical void extending along a central longitudinal axis of the elongate member and terminating at the first directional outlet disposed in a distal end of the elongate member, and a second internal annular void concentrically disposed around the first internal cylindrical void extending along the length of the elongate member and terminating at the or each second directional outlet disposed in the distal end of the elongate member.

3. The device according to claim 1, wherein the fluid directing means comprises an elongate member having a first internal cylindrical void extending along a central longitudinal axis of the elongate member and terminating at the first directional outlet disposed in a distal end of the elongate member, and a plurality of second internal cylindrical voids concentrically disposed around the first internal cylindrical void extending along the length of the elongate member and terminating at respective second directional outlets disposed in the distal end of the elongate member.

4. The device according to any one of claims 1 to 3, wherein the second directional outlets are spaced equiangularly around the first directional outlet. The device according to any one of claims 1 to 4, wherein the first and second directional outlets comprise a nozzle or a plurality of closely spaced apertures disposed in an arrangement to facilitate a directional spray pattern.

6. The device according to claim 5, wherein the first and second directional outlets are disposed adjacent to one another such that the spray pattern emerging from the first directional outlet overlaps extensively with the spray pattern emerging from any one of the second directional outlets.

7. The device according to any one of the preceding claims, wherein the first treatment fluid comprises water heated to between 95 0 C to 120 0 C and pressurised air, and the second treatment fluid is pressurised air heated to between 100 C to 1000 0 C.

8. The device according to claim 7, wherein the first treatment fluid supply means comprises a heated water supply and pump arranged to provide heated water to the first internal cylindrical void via a first fluid delivery line and a source of compressed air arranged to provide pressurised air to the first internal cylindrical void via a second delivery line, whereupon the heated water and pressurised air mix to form the first treatment fluid.

9. The device according to claim 7, wherein the second treatment fluid supply means comprises a compressed air supply, heater and pump arranged to provide pressurised heated air to the or each second internal void via a second treatment fluid delivery line. A mobile biocidal treatment apparatus for traversing an area to undergo biocidal treatment, the mobile biocidal treatment apparatus comprising a first means for generating a supply of heat and discharging the heat at a first discharge location and a second means for generating a mixture of hot air and water and discharging the mixture of hot air and water at a second discharge location, the first discharge location being disposed ahead of the second discharge location with respect to the direction of travel of the mobile biocidal treatment apparatus to facilitate preheating of the area immediately before discharge of the mixture of hot air and water.

11. The mobile biocidal treatment apparatus according to claim 10, wherein the heat generated and discharged by the first means comprises hot air.

12. The mobile biocidal treatment apparatus according to claim 10, wherein the hot air is pressurised.

13. The mobile biocidal treatment apparatus according to any one of claims 10 to 12 wherein the first and second means are housed in a body defining a first chamber having an outlet providing the first discharge location and a second chamber having an outlet providing the second discharge locations.

14. The mobile biocidal treatment apparatus according to claim 13, wherein the first means comprises a first air delivery means for delivering a flow of air to the first chamber along a first flow path. The mobile biocidal treatment apparatus according to claim 14, wherein heating means is provided for heating air delivered to the first chamber along the first flow path.

16. The mobile biocidal treatment apparatus according to claim 15, wherein the second means comprises a second air delivery means for delivering a flow of air to the second chamber along a second flow path, the second flow path being in heat exchange relationship with the first flow path whereby air flowing along the second flow path receives heat from air flowing along the first flow path.

17. The mobile biocidal treatment apparatus according to claim 16, wherein the second means further comprises means for introducing water into the second chamber to mix with the air flowing therethrough towards the outlet thereof

18. The mobile biocidal treatment apparatus according to claim 16 or 17, wherein water is injected into the second chamber at a location adjacent the outlet thereof.

19. The mobile biocidal treatment apparatus according to any one of claims 13 to 18, wherein the first chamber is configured to expand in the direction of air flow towards the outlet thereof. The mobile biocidal treatment apparatus according to any one of claims 13 to 19, wherein the second chamber is configured to contract in the direction of air flow towards the outlet thereof

21. The mobile biocidal treatment apparatus according to any one of claims 15 to wherein the heating means for heating air delivered to the first chamber comprise at least one gas burner, the or each gas burner being located in a burner chamber through which air flows on its passage to the first chamber.

22. The mobile biocidal treatment apparatus according to any one of claims 13 to 21, wherein the first and second chambers are defined within a casing having a compartment with an open bottom and a partition wall being provided within the casing to divide the compartment into first and second chambers, wherein the section of the open bottom of the compartment associated with the first chamber provides the first discharge location, and the section of the open bottom associated with the second chamber provides the second discharge location.

23. The mobile biocidal treatment apparatus according to any one of claims 16 to 22, wherein the first flow path includes one or more conduits extending through the second chamber and opening onto the first chamber through the partition wall, said one or more conduits providing a heat exchanger for the heat exchange relationship between the first and second flow paths.

24. A method of biocidal treatment comprising the steps of applying heat to a substrate in need of biocidal treatment and thereafter applying a mixture of hot air and water to the substrate. The method according to claim 24, wherein heat is applied to the substrate by administering hot air.

32. The method according to claim 25, wherein the hot air is pressurised.

33. A method of killing weeds comprising the steps of applying heat to the weeds to reduce the moisture content thereof and thereafter applying a mixture of hot air and water to the weeds.

34. The method according to claim 27, wherein heat is applied to the weeds by administering hot air. The method according to claim 28, wherein the hot air is pressurised.

36. A biocidal treatment device substantially as hereinbefore described with reference to the accompanying Figures.

37. A mobile biocidal treatment apparatus substantially as hereinbefore described with reference to the accompanying Figures. DATED THIS 7TH DAY OF JANUARY 2002. BIO HEALTH SYSTEMS PTY LTD By their Patent Attorneys LORD AND COMPANY PERTH, WESTERN AUSTRALIA