WO2016092488A1

WO2016092488A1 - Germicidal uv irradiation of liquids

Info

Publication number: WO2016092488A1
Application number: PCT/IB2015/059477
Authority: WO
Inventors: Pieter SWART
Original assignee: Surepure Operations Ag
Priority date: 2014-12-09
Filing date: 2015-12-09
Publication date: 2016-06-16
Also published as: GB201421892D0

Abstract

The invention provides for germicidal treatment of a liquid by passing the liquid through an annular flow passage (18), imparting turbulence to the liquid, and irradiating the liquid with UVC radiation in the germicidal spectral range from one or more LED (12) that has been selected to reduce the UVC radiation emitted in at least one predetermined UVC spectral band that can adversely affect the liquid. The turbulence is imparted to the liquid by supplying the liquid to the annular flow passage (18) at an inlet (20) that is offset from an axis (24) of the annular flow passage (18) and/or by providing an uneven texture on at least one surface of a wall (14) facing the annular flow passage (18).

Description

GERMICIDAL UV IRRADIATION OF LIQUIDS

FIELD OF THE INVENTION

This invention relates to germicidal treatment of liquids with ultra-violet (UV) irradiation.

BACKGROUND TO THE INVENTION

The use of UV irradiation in germicidal treatment or disinfection of liquids is well known, but its use had previously been limited to treatment of transparent or translucent liquids, because insufficient germicidal effects were found in turbid liquids, but International Patent Application Number WO 01 /37675 disclosed a method and device for irradiating turbid liquids with UV to an extent that allowed unprecedented germicidal action. The content of WO 01 /37675 is included herein in its entirety, by reference.

The germicidal treatment of liquids in methods as described in WO 01 /37675 results from exposure of the liquid to UVC (short wave UV), i.e. UV radiation in the range of 200 to 280 nm. More particularly, the highest effectiveness of germicidal action is obtained from UV irradiation in the so-called "germicidal range" between 250 to 290 nm. The distribution of germicidal effectiveness in relation to wavelength typically resembles a bell shaped profile, with a peak normally in the region of 253.7 to 254.1 nm. The germicidal properties of UV radiation are mainly due to inactivation of bacteria and viruses through DNA mutations induced through absorption of UV light by DNA molecules at very specific germicidal wavelengths, which are normally between 253.7 and 254.1 . The distribution of germicidal action in relation to wavelength is illustrated in Figure 1 (which also shows some spectral lines from a low pressure mercury lamp - see below). Commercially, there are two main economically viable UV sources that emit sufficient energy in the germicidal wavelength range (250 to 290 nm) and these are mercury and deuterium lamps. Mercury lamps are available in high pressure (HP- Hg lamp) and low pressure (LP-Hg lamp) versions, each of which emits UV-light of high intensity at very specific wavelengths, called spectral lines, which are shown schematically in Figure 2A and 2B. As can be seen in Figure 2, the spectral emission from a LP-Hg lamp is significantly "cleaner" in the sense that it includes fewer spectral lines outside the germicidal range and includes one very prominent spectral line at a wavelength of 253.7 nm (which is also shown in Figure 2 as

"Germicidal Lamp Output"). The specific high intensity single wavelength emission of the LP-Hg lamp makes it suited for germicidal applications and the preferred UV source for use in the invention of WO 01 /37675.

Deuterium lamps have a significantly broader emission spectrum than mercury lamps (HP and LP) as can be seen in Figure 3, which shows a typical emission spectrum of a deuterium lamp. The UVC emission from a deuterium lamp is not as intense as a mercury lamp, but the deuterium lamp emits UV-light in a broad spectrum covering the whole UVC germicidal wavelength range from 240 to 300 nm.

The major impediment to the application of UVC sterilization, especially to biological liquids, even when using LP-Hg lamps as the source of UV-light, is energy

absorbance and subsequent decomposition of key elements in these sensitive liquids, which adversely affect the quality of the end product.

There is also a third commercial UV source that can be used in the application of UVC sterilization and that is an Amalgam lamp. However, the limitations of the UV sources mentioned above also apply in the case of Amalgam lamps, in that the emitted UV radiation can affect the quality of products adversely.

The sterilizers proposed in WO 01 /37675 have been in commercial use for about fifteen years on ever increasing scale and have been used in most industrialised countries for the purification of turbid beverages and various other liquids and, despite significant delays in obtaining statutory approval in some countries and competing with very entrenched practices such as pasteurization, the invention proposed in WO 01/37675 is currently the international market leader in sterilization of turbid liquids by UV irradiation, under the trade mark SurePure™.

However, despite the success of this technology in the sterilization of turbid liquids, it can still be significantly improved. In particular, the use of fluorescent tubes

(typically LP Hg tubes) as sources of UV irradiation results in uneven distribution of irradiation density along the lengths of the tubes (with maximum irradiation density at the centre of the tube and lower irradiation density closer to the ends). Further, the use of fluorescent tubes requires quartz sleeves installed between the fluorescent tubes and the annular flow passages and the quartz sleeves are prone to breakage - resulting in spillage, product contamination, etc. The fluorescent tubes also have a relatively short useful life span and unexpected failures of these tubes cause disruptions of processed - which can result in discarding a large batch of product, which has been inadequately irradiated. Lastly, the degree to which irradiation intensity from fluorescent tubes can be varied, is fairly limited and in order to vary the UV irradiation exposure of a liquid, the number of fluorescent tubes along which the fluid flows, has to be varied.

The present invention seeks to provide for effective sterilization of liquids, including biological liquids such as turbid liquids, while minimising adverse effects on the liquids and while improving on the versatility, reliability, cost-effectiveness and ease of use of the sterilizers of the prior art.

SUMMARY OF THE INVENTION

According to one aspect of the present invention there is provided a method of treating a liquid, said method comprising:

passing the liquid through an annular flow passage;

imparting turbulence to the liquid flowing in the annular flow passage; and irradiating the liquid in the annular flow passage with UVC radiation in the

germicidal spectral range;

wherein the step of irradiating the liquid in the anular flow passage with UVC

radiation comprises providing electrical power to at least one light emitting diode (LED) and allowing UVC radiation from the LED to pass into the annular flow passage, said LED having been selected so that said UVC radiation emitted has a spectral profile in which radiation in at least one predetermined UVC spectral band that can adversely affect the liquid, has been reduced. The UVC radiation emitted may generally exclude radiation in the predetermined UVC spectral band that can adversely affect the liquid.

The step of irradiating the liquid may include providing power to a plurality of said LEDs and the method may include selecting the LED's to which power is to be supplied, from an array of LEDs.

The method may include controlling the electrical power supplied to the one or more LEDs, to regulate the intensity of UVC radiation emitted from the LEDs. The turbulence may be imparted to the liquid flowing in the annular flow passage by supplying the liquid to the annular flow passage at an inlet that is offset from an axis of the annular flow passage. Instead, or in addition, the turbulence may be imparted to the liquid flowing in the annular flow passage by providing an uneven texture on at least one surface of a wall facing the annular flow passage, e.g. the wall may have a plurality of ribs on its surface facing the annular flow passage.

According to another aspect of the present invention there is provided apparatus for germicidal treatment of a liquid, said apparatus comprising a UVC radiation source and a casing defining an annular flow passage that is exposed to the UVC radiation source, said annular flow passage being configured to impart turbulence to liquids when flowing in the annular flow passage, wherein said UVC radiation source comprises at least one light emitting diode (LED) that emits UVC radiation in the germicidal spectral range, said LED having been selected so that said UVC radiation emitted has a spectral profile in which radiation in at least one predetermined UVC spectral band that can adversely affect the liquid, has been reduced.

The UVC radiation source may include an array of the LEDs and the apparatus may include electrical circuitry that is configured to provide electrical power to a selection of the LEDs.

The electrical circuitry may be configured to control the electrical power supplied to said LED, to regulate the intensity of UVC radiation emitted from the one or more LEDs.

The casing defining the annular flow passage may include an inlet that defines an inlet passage that is offset from an axis of the annular flow passage. Instead, or in addition, the casing may include at least one wall with an uneven surface facing the annular flow passage, e.g. the wall may have a plurality of ribs on its surface facing the annular flow passage.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, and to show how the same may be carried into effect, the invention will now be described by way of non-limiting example, with reference to the accompanying drawings in which:

Figure 1 is a graph of the relative output or effectiveness against short UVC

wavelengths from a LP-Hg lamp;

Figures 2A and 2B are graphs showing emission spectrums of HP-Hg and LP-Hg lamps, respectively;

Figure 3 is a graph showing is the emission spectrum of a deuterium lamp; and Figure 4 is a schematic longitudinal section of a first embodiment of a germicidal apparatus according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE DRAWINGS

The wavelengths at which undesirable energy absorbance and decomposition occur (referred to herein as "inactivation wavelengths") vary depending on the compounds in the liquid being sterilized and needs to be determined for each compound by UV spectroscopy. To minimise decomposition of UVC sensitive substances during UVC sterilisation, a wavelength within the germicidal range as far removed as possible from the inactivation wavelength should be used.

The inactivation wavelength(s) of a specific biological liquid and the optimal germicidal wavelength for that liquid, need to be determined. This can be done by determining an action spectrum for the liquid by irradiating the liquid with each wavelength in the germicidal range and then to determine the degree of unwanted decomposition of sensitive substances at each wavelength. A graph of wavelength against percentage inactivation can be prepared and such a graph will indicate the "inactivation wavelength" for that liquid. In the case of biological liquids that are mixtures, there could be more than one "inactivation wavelength", some of which could be less prominent than others. Once the inactivation wavelength (or wavelengths) of a liquid has been determined, it is possible to select a preferred germicidal wavelength that is preferably far removed from the inactivation

wavelength, which can be used to irradiate the liquid to yield maximum optimal product stability and germicidal efficiency.

It is believed that most of the adverse effects of UVC irradiation in general and oxidation of proteins and fat in particular, can be substantially limited by sterilising liquids by UVC irradiation with wavelengths in the germicidal range, but removed from UVC wavelengths that cause detrimental product decomposition.

Referring to Figure 4, a first embodiment of a sterilisation device according to the present invention is generally identified by reference number 10 and is similar to that of WO 01 /37675, but configured to allow adjustment of the emission wavelengths, so that the treated fluids are irradiated to optimise germicidal efficiency while keeping product decomposition or degradation to a minimum.

The apparatus 10 includes a UV radiation source in the form of an elongate array of light emitting diodes LEDs 12, and a casing including an outer cylindrical wall or sleeve 14 and an inner cylindrical wall in the form of a quartz sleeve 16, which define an annular flow passage 18 between them. The LED array 12 is disposed inside the quartz sleeve 16 so that UV radiation from the LEDs is emitted through the quartz sleeve to the flow passage 18. The apparatus 10 preferably includes the attributes described in WO 01 /37675 which impart turbulence to a liquid flowing in the flow passage 18, including, but not limited to an inlet 20 and optionally an outlet 22 that define an inlet passage (and outlet passage) that are offset from a longitudinal axis 24 of the annular flow passage 18, to impart swirl to the liquid, as well as an uneven texture, e.g. a ribbed surface on an inner surface of the outer sleeve 14, facing the flow passage 18 which induces turbulence in the flowing liquid in the flow passage 18.

The LED array 12 is shown in Figure 4 as a row of LEDs, supported on a substrate such as a printed circuit board. However, this is merely a diagrammatic

representation of the invention and in practice the LED array will be configured to irradiate the annular passage 18 in all directions, e.g. by supporting the LEDs on the outside of a central, cylindrical substrate.

The LEDs 12 may be selected to emit UVC radiation in selected, relatively narrow spectral bands, to optimise the germicidal effect of irradiation of a particular liquid, while minimising degradation of the liquid. However, in a preferred embodiment, the LEDs 12 include a variety of LEDs that can emit UVC radiation in different spectral bands. Further, the electrical circuitry that provide power to the LEDs 12 is configured to control the power supplied to the LEDs separately, so that LEDs can be switched on and off or can be dimmed individually or in groups. Accordingly, for each liquid that needs to be sterilised in the apparatus 10, the UVC radiation emitted by the array of LEDs 12 can be selectively controlled, both by selective control of the spectral distribution of UVC irradiation (be selecting LEDs according to their UVC emission characteristics) and by selective control of electrical power supplied to the LEDs, to control the intensity of UVC radiation from the LEDs. The use of the LED array 12 as source of UVC radiation allows more precise control of the spectral distribution of UVC irradiation of liquids in the annular flow passage 18, than with currently commercially used sources of UVC radiation. As a result, undesirable effects of UVC irradiation can be limited by avoiding irradiation with harmful wavelengths, while optimising the germicidal effect of irradiation.

Further, the present invention offers the versatility of allowing the spectral distribution and/or the intensity of irradiation to be adjusted while optimising a process, and this can be done while the apparatus 10 is in use, without any need for stoppage, changes of equipment, or the like.

This versatility not only allows for optimisation of UVC sterilisation of a particular liquid, but also allows the apparatus 10 to be used for different liquids, without a need to modify the apparatus and it allows the apparatus to be used to identify the optimal germicidal wavelength(s) and/or the inactivation wavelength(s) of a specific liquid, as described above. The invention also holds a number of additional advantages over commercially used sources of UVC radiation, particularly LP-Hg lamps, in that the LED array 12 does not contain mercury (Hg) in substantial quantities, generates less heat that the LP- Hg lamps and does not require a run-up period from being switched on, until it can be used to irradiate the liquid.

In another embodiment of the present invention, instead of defining an annular flow passage between a quartz sleeve and a ribbed outer cylindrical sleeve, the LED array can be supported directly on a tubular wall of an inner sleeve. Preferably, a more robust structure such as a stainless steel (or other durable material) inner tube can be substituted for the quartz sleeve, with the LEDs supported on the inside or outside of the inner tube's wall. In a preferred embodiment, a plurality of apertures are defined in the inner tube, with the array of LED's fitted on the inner tube in a liquid tight manner, so that each LED is configured to emit UV irradiation outwards from one of the apertures. In such a configuration, electronic circuitry for the LEDs can be housed inside the inner tube. The inner tube can also be made so that it can be opened and sealed in a liquid tight manner, e.g. the inner tube can have longitudinal seams along which it can be opened to access the electronic circuitry inside the tube, to replace LEDs, or the like and the tube can be re-sealed and returned to service in the sterilizing apparatus.

Numerous variations of the support of the LEDs on the sleeve are possible, but some of the main advantages from this embodiment of the invention stem from the fact that no quartz sleeve is required and the LEDs can be supported directly on a robust wall that also forms the inside wall of the annular flow passage. In the event that one or more of the LEDs fail, this will be detected in the electronic control circuitry for the LEDs and the intensity of the remaining LEDs can be increased and/or redundant LEDs can be powered, to compensate for the loss of irradiation from the failed LED or LEDs. Accordingly, even though the absence of a quartz sleeve prevents the easy withdrawal and replacement of the UV radiation source inside the quartz sleeve, the use of an LED array according to the present invention drastically reduces the frequency with which such replacements are required - to the extent that replacements can be deferred until a convenient time during equipment downtime.

In yet further embodiments of the present invention, the positions and functions of the inner and outer sleeves defining the annular flow passage can be inverted. In particular, at least one of the inner and outer sleeve must have a texture that imparts the necessary turbulence to the flow in the annular flow passage and this can be achieved most practically by providing circumferential or helical ribs in the inner or outer sleeve. The other sleeve (whether the inner of outer sleeve) is preferably a smooth tube, although it can also be ribbed or have any texture, but it includes a plurality of the apertures described above, through which UV is radiated into the annular flow passage.

Claims

1 . A method of treating a liquid, said method comprising:

passing the liquid through an annular flow passage (18);

imparting turbulence to the liquid flowing in the annular flow passage (18); and

irradiating the liquid in the annular flow passage (18) with UVC radiation in the germicidal spectral range;

characterised in that the step of irradiating the liquid in the annular flow

passage (18) with UVC radiation comprises providing electrical power to at least one light emitting diode (LED) (12) and allowing UVC radiation from the LED to pass into the annular flow passage (18), said LED (12) having been selected so that said UVC radiation emitted has a spectral profile in which radiation in at least one predetermined UVC spectral band that can adversely affect the liquid, has been reduced.

2. A method according to claim 1 , characterised in that said UVC radiation

emitted generally excludes radiation in the predetermined UVC spectral band that can adversely affect the liquid.

3. A method according to claim 1 or claim 2, characterised in that the step of irradiating the liquid includes providing power to a plurality of said LEDs (12).

4. A method according to any one of the preceding claims, characterised by selecting the LED's (12) to which power is to be supplied, from an array of LEDs (12).

5. A method according to any one of the preceding claims, characterised by controlling the electrical power supplied to said LED (12), to regulate the intensity of UVC radiation emitted from the LED (12).

6. A method according to any one of the preceding claims, characterised by imparting turbulence to the liquid flowing in the annular flow passage (18) by supplying said liquid to the annular flow passage (18) at an inlet (20) that is offset from an axis (24) of the annular flow passage (18).

7. A method according to any one of the preceding claims, characterised by

imparting turbulence to the liquid flowing in the annular flow passage (18) by providing an uneven texture on at least one surface of a wall (14) facing the annular flow passage (18).

8. A method according to claim 7, characterised in that said wall (14) has a

plurality of ribs on its surface facing the annular flow passage (18)

9. Apparatus (10) for germicidal treatment of a liquid, said apparatus (10)

comprising a UVC radiation source (12) and a casing (14,16) defining an annular flow passage (18) that is exposed to the UVC radiation source (12), said annular flow passage (18) being configured to impart turbulence to liquids when flowing in the annular flow passage (18), characterised in that said UVC radiation source comprises at least one light emitting diode (LED) (12) that emits UVC radiation in the germicidal spectral range, said LED having been selected so that said UVC radiation emitted has a spectral profile in which radiation in at least one predetermined UVC spectral band that can adversely affect the liquid, has been reduced.

10. Apparatus (10) according to claim 9, characterised in that the UVC radiation source includes an array of said LEDs (12).

1 1 . Apparatus (10) according to claim 9 or claim 10, characterised in that said apparatus (10) includes electrical circuitry that is configured to provide electrical power to a selection of said LEDs (12).

12. Apparatus (10) according to claim 1 1 , characterised in that the electrical

circuitry is configured to control the electrical power supplied to said LED (12), to regulate the intensity of UVC radiation emitted from the LED (12).

13. Apparatus (10) according to any one of claims 9 to 12, characterised in that said casing (14,16) defining the annular flow passage (18) includes an inlet (20) defining an inlet passage that that is offset from an axis (24) of the annular flow passage (18).

14. Apparatus (10) according to any one of claims 9 to 13, characterised in that said casing (14,16) includes at least one wall (14) with an uneven surface facing the annular flow passage (18).

15. Apparatus (10) according to claim 14, characterised in that said wall (14) has a plurality of ribs on its surface facing the annular flow passage (18).