WO2000054817A1

WO2000054817A1 - Method and apparatus for destroying microorganisms in liquid systems

Info

Publication number: WO2000054817A1
Application number: PCT/AU2000/000215
Authority: WO
Inventors: Peter Carter
Original assignee: Enrad Holdings Pty. Limited
Priority date: 1999-03-16
Filing date: 2000-03-16
Publication date: 2000-09-21

Abstract

The present invention provides an apparatus (1) for destroying microorganisms in a liquid system (3). The apparatus includes two electrodes (2) which are in contact with the liquid system (3) and a power source (4) operatively coupled to the electrodes (2). An electric signal generated by the power source passes between the electrodes (2) through the liquid system (3) thereby creating a circuit. The characteristics of the electrical signal are selected according to their ability to destroy a species of microorganisms.

Description

METHOD AND APPARATUS FOR DESTROYING MICROORGANISMS IN LIQUID SYSTEMS

Technical Field

The present invention relates to a new method and apparatus for the treatment of liquid systems, and in particular to a new method and apparatus for removing harmful microorganisms from liquid systems without the use of chemical additives.

Background Art

Airborne dust, atmospheric pollutants, chemical bi-products from human and natural sources, organic material such as leaves and spores and micro-organisms found in all areas of the earth's ecosystem continually find their way into and pollute liquid systems. Often the combined effects of these pollutants is to produce an ideal environment for the propagation of bacteria or organisms harmful and sometimes deadly to human life.

Particular areas of concern where the buildup of organic matter can cause serious health problems are in areas such as drinking water supplies, airconditioning installations, swimming pools and other systems involving the circulation of aqueous solutions. In these environments the pollutants can form what is termed a biofilm which is a layer of organic matter that provides both a habitat and food supply for a wide range of bacteria and other micro-organisms.

As human society becomes increasing urbanised, abundant clean and potable water supplies are becoming increasingly important to support the intensely populated areas. Water supplies intended for drinking and normal household use must be free from any microorganisms that could be a potential threat to human life or well being, and therefore strict monitoring and purifying measures must be in place to ensure the proper management of the resource. Often after heavy rainfall, drinking water supplies may contain excessive levels of harmful micro-organisms such as Giardia and Crypto sporidium which originate from human and animal bodily waste. These micro-organisms are particularly resistant to the more common methods of water treatment and purification, which involve the dosage of chemicals (eg Chlorine), filtration and Ozone treatment. Membrane technology is another alternative, however, the costs associated with this technology are quite high.

Legionellabacteria rarely present a problem to humans, however, when the bacteria is inhaled by a person for example in tiny droplets of water produced from an infected air conditioning system, they can propagate and cause what is referred to as Legionnaires disease, particularly if the person concerned is ill or recovering from a serious medical procedure.

The bacterium Pseudomonαs αeriginosα causes significant infections in humans. People with cystic fibrosis, burn victims, individuals with cancer, and patients requiring extensive stays in intensive care are particularly at risk.

Presently, the usual methods of removal of micro-organisms from liquid systems, involves the dosage of chemicals or biocidal agents and to a lesser extent filtration. Whilst the present known methods have ranging levels of effectiveness in the removal of microorganisms from liquid systems, this identifies a need for, or at least an alternative, apparatus and method for the removal of micro-organisms.

Disclosure of Invention

It is an object of the present invention to provide an alternative method and apparatus, utilising this discovery, for the removal of micro-organisms from liquid systems that does not involve the dosage of chemicals or other biocidal agents. A further object of the invention is to provide a method and apparatus that targets specific micro-organisms that would ideally pose a threat to human life and well being.

Surprisingly, it has been discovered that micro-organisms can be eradicated by introducing a specific wave form into the liquid environment which breaks down the membrane components of the micro-organism necessary for it to survive.

According to the present invention there is a provided an apparatus for destroying micro-organisms in a liquid system which includes: two electrodes in contact with the liquid system, a power source operatively coupled to the electrodes such that an electrical signal can pass between the electrodes through the liquid system thereby creating a circuit, wherein, the characteristics of the electrical signal are selected according to their ability to destroy a species of micro-organism.

Preferably, characteristics include the shape of the wave form, current, frequency and/or duty cycle of said electrical signal

Preferably, the wave form generated from said electrical signal is a triangular, square, sawtooth, delta, rectangular, sinusoidal and/or other shaped wave form.

Preferably, the electrodes are chosen from materials such as for example precious metals including gold or silver.

Preferably the circuit created by the apparatus is reversible such that the polarity of the electrodes is interchangeable.

Preferably the apparatus also provides means for controlling the frequency and/or the current and/or the duty cycle of the electrical signal.

Preferably the frequency is internally or externally selectable from lKhz, 2 KHz, 4

KHz, 16 KHz, 24 KHz, 32 KHz, or 40 KHz; the duty cycle is internally or externally selectable from 10% , 20% , 40%, 50%, 70% , 90% or 100%; and the cycle rate is internally or externally selectable and offers a choice of 5 seconds, 30 seconds, 5 minutes or 15 minutes.

In a preferred embodiment the apparatus can be used in conjunction with a water system chosen from for example a swimming pool or a cooling tower.

In a further preferred embodiment, the apparatus can be used in conjunction with one or more water purification or cleaning systems, chosen from for example a water filtration unit, an ionisation unit, membrane technology or chemical dosage.

In another aspect of the present invention there is provided method for destroying micro-organisms in a liquid system which includes the steps of: applying an electrical signal across two electrodes in contact with the liquid system, wherein, the characteristics of the electrical signal are selected according to their ability to destroy a species of micro-organism.

Brief Description of the Drawings

The present invention will become better understood from the following detailed description of a preferred but non-limiting embodiment thereof, described in connection with the accompanying drawings, where in:

Figure 1. illustrates a preferred embodiment of the present invention wherein the figure shows a schematic representation of the micro-organism removal apparatus.

Figure 2. illustrates a graphical representation of the wave form produced by varying the duty cycle of the electrical signal.

Figure 3. illustrates the same graphical representation as shown in figure 2, but showing the polarity revered between probes A and B.

Figure 4. illustrates graphically the results obtained according to example 1 from the initial influent post inoculum.

Figure 5. illustrates graphically the results obtained according to example 1 during the challenge.

Figure 6. illustrates a graphical representation of the wave form according to example 1.

Figure 7 - 14 illustrate several graphical representations of wave forms found to be effective against Pseudomonas aeriginosa and Legionella pneumophila.

Detailed description of the Invention

A preferred, but non-limiting embodiment of the present invention is shown in figure 1. The metallic probes 2 of the apparatus 1 are immersed into the liquid 3 to be treated. An electrical signal is applied to the probes 2. The control unit 4 provides for current adjustment, frequency adjustment and duty cycle adjustment such that the wave form resulting from the electrical signal can be tailored to target a specific micro-organism presumed present in the liquid 3. The polarity of the probes 2 is reversed at regular intervals to prevent premature degradation of the probes 2 from electrochemical corrosion.

The liquid 3 to be treated in accordance with the present invention can be chosen from any suitable liquid such as water, oil or sewage effluent dependent on the particular application.

The maximum Voltage (referred to as +Vmax in figures 2 and 3) in accordance with the present invention typically supplies between +30 V and +80 V but any +Vmax may be provided to suit a particular application.

In accordance with the present invention the current typically provides up to 2 amperes through the fluid, but of course higher currents can be generated if required for specific applications involving liquids with varying conductivities.

Figures 2 and 3 show a typical square wave whose duty cycle is adjustable between 0% and 100% however any mathematical derived waveform may be used for different applications and for targeting specific micro-organisms in keeping with the ambit of the present invention. The signal frequency in accordance with the present invention is nominally at 1000 Hz but may be varied from DC through to the frequency of UN light depending on the particular applications.

The polarity reversal rate is chosen to suit the application for example if long continuous on periods are envisaged, polarity reversal may be several minutes but for short periods such as in domestic appliances, the reversal rate may be as low as 5 seconds.

The present invention will become better understood from the following examples of preferred but non-limiting embodiments thereof.

Example 1

An apparatus according to a preferred embodiment of the present invention was challenged with Legionella pneumophila serogroup 2-14. Influent water was prepared to provide a suitable background of dissolved and suspended material. The influent water was prepared as per AS/ΝZS 4348 (1995), concentrated 100 fold and diluted to operational consistency with tap water to provide a 20L volume of treatment. A laboratory isolate of Legionella pneumophila serotype 2-14 was harvested from a pre-prepared lawn and suspended in sterile distilled water for later inoculation into the apparatus according to the present invention. Samples were taken of the initial influent post inoculum then after one hour reticulation with no current applied. See figure 4.

During the challenge, the water was reticulated continuously and the current operated at 50%. The Duty Cycle was set to 50% . These specifications resulted in a particular wave form as described in figure 6, which was found to have particular effectiveness against Legionella pneumophila.

Samples were withdrawn by dipping after Vi hour, 1 hour, 2 hours and 3 hours of treatment. Samples were analysed immediately after collection using the incubation regime of 37 degrees/7 days. See figure 5

Immediate analysis of sampled water prevented and bias due to delayed processing since bacteria can either proliferate or die off over time. Additionally, any electrolytic change induced during treatment may further affect stored samples. Immediate analysis circumnavigates such artefacts.

Results:

Where cfu/mL = colony forming units per ml-,

Note: The probe Voltage will be negative or positive depending on the cycle when measured.

The initial inoculum approximated a million Legionella per millilitre.

This population remained virtually constant during the first hour when water was reticulated with the current off. The acclimation period was introduced to ascertain the effect of the tank conditions on the Legionella population prior to treatment. No effect was noted in one hour.

A 2 log reduction was found after half an hour of treatment. A further 2 log reduction was recorded after 1 hour and 2 hours treatment respectively, by which time no Legionella was isolated. Example 2

An apparatus according to a preferred embodiment of the present invention was challenged with Pseudomonas aeruginosa strain ATCC 9027. The reason this challenge organism was used is that according to microbiologists, it is one of the hardest to kill, meaning that if this can be eradicated, a broad range of bacteria will also be destroyed. Influent water was prepared to provide a suitable background of dissolved and suspended material. The influent water was prepared as per AS/NZS 4348 (1995), concentrated 100 fold and diluted to operational consistency with tap water (i.e. 1:100).

Prior to sampling, approximately 400 mL was discharged from the outlet at each time interval to ensure samples represented reticulated water. Samples were taken of the initial influent, pre and post inoculum then after reticulation, 1 hour, 3 hours and 24 hours.

During the challenge, the water was reticulated continuously and the current operated at 606 mA. The Duty Cycle was set to 50% . These specifications resulted in a particular wave form as described in figure 7, which was found to have particular effectiveness against Pseudomonas aeruginosa.

Samples were withdrawn by dipping after Vz hour, 1 hour, 2 hours and 3 hours of treatment. Samples were analysed immediately after collection using the incubation regime of 37 degrees/7 days. See figure 5

Samples were analysed immediately after collection as per AS4276.3.1 (1995) using the incubation regime of 37°C/48 hours. Results:

Where cfu/mL = colony forming units per mL

Pseudomonad levels have shown an approximate one log reduction in 1 hour, and a 2 log reduction in 24 hours.

Although several preferred embodiments have been described in detail, it should be understood that various changes, substitutions, and alterations can be made herein by one ordinarily skilled in the art without departing from the spirit or scope of the present invention.

Claims

1. An apparatus for destroying micro-organisms in a liquid system which includes: two electrodes in contact with the liquid system, a power source operatively coupled to the electrodes such that an electrical signal can pass between the electrodes through the liquid system thereby creating a circuit, wherein, the characteristics of the electrical signal are selected according to their ability to destroy a species of micro-organism.

2. An apparatus as claimed in claim 1, wherein said characteristics include the shape of the wave form, current, frequency and/or duty cycle of said electrical signal

3. An apparatus as claimed in claim 1 , wherein the wave form generated from said electrical signal is a triangular, square, sawtooth, delta, rectangular, sinusoidal and/or other shaped wave form.

4. An apparatus as claimed in claim 1, wherein the species of micro-organism is Legionella pneumophila, and the electrical signal has a duty cycle of 50%, a current of 50% and a frequency of 1 kHz.

5. An apparatus as claimed in claim 1, wherein the species of micro-organism is Legionella pneumophila, and the wave form generated from said electrical signal is substantially as hereinbefore described with reference to figures 6, 8, 9, 13 and 14.

6. An apparatus as claimed in claim 1 , wherein the species of micro-organism is Pseudomonas aeruginosa, and the wave form generated from said electrical signal is substantially as hereinbefore described with reference to figures 7 and 10 to 12.

7. An apparatus according to any one of claims 1 to 5, wherein the electrodes are chosen

SUBSTITUTE SHEET from materials such as for example precious metals including gold or silver.

8. An apparatus according to any one of claims 1 to 6 wherein the circuit created by the apparatus is reversible such that the polarity of the electrodes is interchangeable.

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9. An apparatus according to any one of claims 1 to 7 wherein the apparatus also provides means for varying the frequency, the current, the duty cycle and/or other characteristics of the electrical signal.

10 10. An apparatus according to any one of claims 1 to 8 wherein the frequency is internally or externally selectable from 1 KHz, 2 KHz, 4 KHz, 16 KHz, 24 KHz, 32 KHz, or 40 KHz.

11. An apparatus according to any one of claims 1 to 9 wherein the duty cycle is 15 internally or externally selectable from 10%, 20%, 40%, 50%, 70% , 90% or 100% .

12. An apparatus according to any one of claims 1 to 10 wherein the cycle rate is internally or externally selectable and offers a choice of 5 seconds, 30 seconds, 5 minutes or 15 minutes.

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13. An apparatus according to any one of claims 1 to 11 wherein, the apparatus can be used in water system and preferably a swimming pool or a cooling tower.

14. A method for destroying micro-organisms in a liquid system which includes the steps 25 of: applying an electrical signal across two electrodes in contact with the liquid system, wherein, the characteristics of the electrical signal are selected according to their ability to destroy a species of micro-organism. 30

SUBSTITUTE SHEET

15. A method as claimed in claim 13, wherein said characteristics include the shape of the wave form, current, frequency and/or duty cycle of said electrical signal

16. A method as claimed in claim 14, wherein the wave form generated from said electrical signal is a triangular, square, sawtooth, delta, rectangular, sinusoidal and/or other shaped wave form.

17. An apparatus as hereinbefore described with reference to the examples and accompanying drawings.

18. A method for destroying micro-organisms in a liquid system as hereinbefore described with reference to the examples and accompanying drawings.

SUBSTITUTE SHEET