GB2136790A - Method and apparatus for destroying pyrogenic materials in water - Google Patents

Abstract

A reaction vessel 1 has an upper plate 2 and a lower plate 3. A plurality of ultraviolet lamps 8 are arranged close to the wall of the vessel 1. Each amp is enclosed in a quartz sleeve 7 to isolate the lamp from water in the vessel to enable the ultraviolet production from the lamps to be maximized. Mains water from a de-ionization unit 17 is pumped by pump 10 along a pipe 9 leading to the vessel 1. Ozone from an ozone generator 13 is introduced to the pipe 9 and the combination of ozone and impure mains water passes through a gas injection nozzle 12 into the vessel 1. <IMAGE>

Description

SPECIFICATION Method and apparatus for destroying pyrogenic materials in water This invention relates to the production of water substantially free of pyrogenic materials.

Pyrogenic materials are typically complex molecules, for example, lipopolysaccharides, which are formed as break-down products and debris of bacteria and other organisms. These materials cause a rise in body temperature of animals and humans when they get into the blood stream. In some cases the temperature rise can be enough to cause death.

Consequently solutions which are to be injected into the blood stream are required to be purified to a point where they are substantially free of such pyrogenic material.

A number of methods exist for removing or destroying organic materials in an impure solution.

Ultraviolet light and dissolution of ozone in water to provide ozonated water can to some extent purify water polluted with organic refactories, as described in U.K. Patent Specification 1543225. This method can also be used for the destruction of cyanides as described in U.S. Patent Specification 3920547.

Nevertheless the concentration levels of pyrogenic materials that are permitted for injected solutions are far less than those that can be achieved by the purification methods hitherto disclosed.

To get down to the required concentration levels it is necessary to resort to either ultra filtration or reverse osmosis. Alternatively in the United Kingdom, legislation permits only water that has been triple distilled to be used for intravenous injection.

Naturally the latter method is particularly energy intensive. Additionally it is difficult to maintain water free of pyrogenic material, generally the water must be stored at 80 C. Other purification techniques such as chlorination and irradiation with ultraviolet light kill the bacteria to form sterile solutions. However pyrogenic materials remain in the solution in addition to which other by-products of the sterilisation can be formed which are also detrimental when taken intravenously.

It is an object of the invention to provide a simple, energy efficient method and apparatus for producing water substantially free of pyrogenic materials.

According to one aspect of the invention there is provided a method of destroying pyrogenic materials in water comprising the steps of: ozonating water in which said pyrogenic material is contained, and illuminating the ozonated water with violet ultrasonic light.

Preferably the ozonated water is uniformly illuminated with ultraviolet light, so that the concentration levels of pyrogenic material can be reduced to a level similar to that achieved with the triple distillation method. By increasing the ultraviolet light flux dosage, increased destruction rates of the material can be achieved.-Preferably the water containing pyrogenic material is recycled until either there quired concentration level is attained or until a predetermined time period has passed. Furthermore once the water has been produced substantially free of pyrogenic material it can be maintained in this state by utilising the above-mentioned method without the necessity of keeping the purified water at 80 C.

According to another aspect of the invention there is provided an apparatus for destroying pyrogenic materials in water comprising a reaction vessel, means to ozonate said water, means to introduce the ozonated water into the vessel and means to illuminate the vessel interior with a distribution of ultraviolet light flux to produce destruction of pyrogenic materials in the ozonated water.

Preferably the means to illuminate is adapted to produce a substantially uniform illumination of the vessel interior. The means to illuminate typically comprises at least one ultraviolet lamp, arranged to produce the distribution of ultraviolet light flux by locating the at least one lamp on a wall of the vessel.

The vessel can be a closed cylinder and the at least one lamp arranged to extend between and around the ends of the cylinder. Preferably the apparatus includes a means to recycle water that is removed from the vessel back to the means to ozonate water until either the concentration of pyrogenic material falls below a predetermined level or until a predetermined time period has passed. The apparatus can include a storage means and consequently it can be used to maintain the stored water free of pyrogenic material.

According to a still further aspect of the invention there is provided an apparatus for oxidizing organic materials in water comprising a closed cylinder reaction vessel, means to introduce said water into the vessel being located at the centre of one end of the cylinder, means to remove water from the vessel being located at the centre of the other end of the cylinder, and at least one ultraviolet lamp arranged to extend between the ends of the cylinder and to surround the centre of said ends to thereby illuminate the vessel interior with a distribution of ultraviolet light flux to produce oxidation of organic materials in said water.

To illustrate how the invention may be carried into effect reference is made, by way of example only, to the accompanying drawings in which: Figure 1 illustrates an apparatus for destroying pyrogenic materials in water; Figure2 illustrates a cross-section along line I-I of Figure 1.

Referring to the drawings, a reaction vessel 1 comprises a cylinder having a circular wall 11 and an upper end plate 2 and a lower end plate 3. The lower end plate, illustrated in cross-section in Figure 2 includes a central aperture 4 and fifteen identical sockets 5, each surrounded by a space 6 to receive a quartz sleeve 7. The upper plate has a similar arrangement of a central aperture and sockets such that they lie opposite those of the lower plate. Each socket receives an elongate lamp 8 extending across the gap between the upper and lower plates and a quartz sleeve 7 is arranged to enclose the lamp and form a water tight fit with the respective upper and lower plates.

The aperture 4 in the lower plate 3 receives a pipe 9 connected to a circulation pump 10. The pipe 9 has a perforated venturi type gas injection nozzle 12 provided at the pipe end received in the vessel.The pipe 9 is also connected to an ozone generator 13 by a pipe 14; any back pressure in the vessel forces ozone down a further pipe 15, which is connected to the pipe 14. The pipe 15 leads towards an ozone destructor (not shown).

In use, mains water is introduced through an inlet 16 of a de-ionization unit 17. De-ionized water, potentially containing pyrogenic material, is drawn from an outlet 18 of the inlet unit, through an open valve 19 by the pump 10. This impure water is passed to pipe 9 where ozone from the ozone generator 13 is introduced by pipe 14. The combination of ozone and pure water is pumped by the pump 10 through the gas injection nozzle 12 into the chamber, the nozzle mixing the ozone and impure water together such that ozone is dissolved in the impure water and the vessel is saturated with ozone.

The fifteen lamps 8 comprise ultraviolet light emitting tubes, for example germicidal lamps, energized from a supply 20 powered from an electricity source 21. The ultraviolet light causes rapid photolysis of the ozone to form OH radicals by the reaction sequence 03 + hv 254 nm)O2 + O(1D) O(1D) + H2O#2OH The OH radicals react to oxidize pyrogenic materials contained in the ozonated impure water entering through the nozzle 12 thereby making them inactive.

This reaction is assumed to be very rapid. The pyrogenic materials can have a tendency to adhere to the vessel wall 11, therefore the arrangement of the lamps has a number of them as close to the vessel wall as possible. Also, to ensure that the water in all regions of the vessel contain OH radicals it is preferred that the lamps are equally spaced from one another to provide a uniform distribution of UV light such that the water in the vessel is uniformly exposed to the UV photons. In this way mechanical agitation of the vessel contents is not required. In addition to which the UV light increases transfer of ozone from a gas to the liquid phase. The amount of ultraviolet output from the lamps at the 254 nm necessary to drive the above reaction to produce OH radicals is maximised by locating the lamps within the quartz sleeves 7 to isolate them from the water.

Th vapour pressure of the mercury in the lamp can then be stabilized at the optimum working temperature of 10 to 30 C for this wavelength which may not necessarily be the temperature of the water. By providing an appropriate thermal connection to the lamp by means of a mechanical support (not shown) required to maintain the lamp co-axial with the quartz sleeve, the optimum working temperature can be achieved.

The purified water in which the pyrogenic materials have been rendered inactive occurs preferen tiallyatthe upper end of the vessel and is pumped out of the vessel, through the aperture 4 centrally located in the upper plate 2, into a pipe 22.

The water from pipe 22 is diverted by a valve 40 into a pipe 41 connected to pipe 9 so that the water can be recycled at least once until the concentration of pyrogenic material at pipe 22 falls below a predetermined level. If the purity of the water is adequate, that is to say the concentration of pyrogenic material falls below a predetermined level, then the water can be used immediately. It will be apparent that these concentrations in the water removed from the vessel can be altered by changing the residence time of the water in the vessel.

In a system wherein the purified water is stored, the purified water from pipe 22 is fed into a tank 23, the output of pipe 22 being directed at a curved surface 24 provided in the tank to encourage the most recently purified water to travel towards the upper part of the tank. Purified water can then be removed through a valve 25 connected to a pipe 26 provided in the base of the tank. Any excess ozone gas carried into the tank travels to the upper part of the tank, out of a pipe 27 and through to an ozone destroyer 28 driven from a power supply 34. The ozone destroyer can be adjusted to function only when the ozone concentration in the pipe 27 increases above a predetermined level.

The tank is filled with purified water until a level detector 29 indicates that the water level in the tank has reached a maximum predetermined level. A control unit 33, in response to this indication causes the valve 29 to be switched off.

The water can be maintained in its pure state by recycling the water back to the vessel. Therefore when the valve 19 is closed the water is removed through the tank under the action of pump 10 through an open valve 30, connected by a pipe 31 to the base of the tank, The pump 10 then recycles this water th rough the pipe 9, adding ozone before the water reaches the vessel 1. In this way the water in the tank is kept free of pyrogenic materials without recourse to heating the water to 80or.

When the water level has dropped to a predetermined level in the tank, a level detector 30 indicates this state to the control unit 33 which closes valve 30 and opens valve 19 again to let more impure water be purified through the vessel 1 until level detector 29 is activated to indicate again to the control unit that the maximum level has been reached. The valve 19 is again closed and valve 30 again opened to restart the cycle of maintaining the tank water pure.

It will be apparent that the capability of opening valve 25 can be limited by the control unit only to periods when valve 19 is closed. If the water in the tank requires a predetermined temperature a cooling or heating system 35 can be wrapped around pipe 9 or at another location in the apparatus. Generally cooling is required as a consequence of the heat generated from the UV tubes 8 in addition to which the solubility of ozone decreases with increased temperature. Consequently as low as possible temperature needs to be maintained to effect efficient dissolution of the ozone gas in the water.

It has been found that with a light intensity of 3 watts per one litre of reaction volume in the vessel and an ozone concentration of 6 ppm in aqueous phase the following producion times for water free from pyrogenic material were achieved.

Initial Concentration E.COLI 10 mgm per ml - 8 minutes Initial Concentration E.COLI 30 ngm per ml - 14 minutes Initial Concentration E.COLI 100 ngm per ml 30 minutes With 15 watts per 1 litre of reaction volume two minutes was required to achieve pure water from 100 ngm per ml initial concentration of E.COLI. The rate of destruction of pyrogenic material was found to be increased with increased UV light intensity and increased uniformity of illumination. It was dependent on the concentration of pyrogen and not particularly dependent on ozone concentration or the addition of saline solution.

The water was considered free of pyrogenic material if it passed the Limulus Amoebosyte Lysate (LAL) test as described in "Pyrogent for detection of Endotoxins" Mallinckrodt Inc 1978. This detects when the concentration per ml of solution is less than approximately 0.2 - 0.8 ngm. In this description pure water is defined as passing the LAL test and impure water as failing the LAL test.

Alternatively the rectal temperature of rabbits can be monitored as a test. This test is described in European Pharmacopoeia it, 1971, page 58. The results of the apparatus in accordance with the invention were found to be an improvement on triple distillation.

The apparatus described is generally automatic and has assumed a batch production of suitably pure water from the vessel 1. If recycling of the water through the vessel is required then the valve 25 can be maintained shut until a testing means (not shown) indicates to the control unit that suitably pure water is being stored in the tank. Alternatively the cycling of the water can be arranged to occur for a predetermined time period. It will be apparent that the apparatus can be run manually.

It will also be apparent that other shapes of the reaction vessel could be employed, for example, a spherical (or rectangular) vessel and an axial ultraviolet lamp can be employed. In addition, the apparatus and method described hereinabove could be applied to the destruction, oxidation or inactivation of organic materialsotherthan pyrogenic ones, with orwithoutozonation of the water or with other suitable photoxidants.

The apparatus in accordance with the invention eliminates the necessity for triple distillation and results in a consequent saving of energy. If a 1 to 100 ratio of pyrogenic material concentration to ozone is assumed then for an initial pyrogenic concentration of 100 ngm per ml, then 10 grammes of ozone are required to purify a cubic meter of water. The energy to produce 10 grammes of ozone is typically 106 Joules. It has been found that a 30 litre reaction vessel would purify 300 litres per hour of the above concentration of impure water The 30 litre reaction vessel used 15 watts per litre of UV energy. Consequently for 1 cubic metre of water the energy consumption is 3.3. x 15 x 30 x 3600 or approximately 5 x 106 Joules. Therefore the apparatus in accordance with the invention consumes approximately 6 x 106 Joules to produce one cubic metre of pure water. With single distillaton approximately 2.8 x 109 Joules are required to produce steam from one cubic metre of water at 20 C. For triple distillation where some heat recovery is obtained, the energy requirement can be reduced to approximately 6 x 108 Joules. It is therefore apparent that the apparatus and method in accordance with the invention can achieve considerable energy savings with respect to the energy consumed for distillation.

Claims (29)

1. A method of destroying pyrogenic materials in water comprising the steps of: ozonating water in which said pyrogenic material is contained, and illuminating the ozonated water with ultraviolet light.

2. A method as claimed in claim 1 including a further step wherein the water is recycled at least once in order to be again ozonated and again illuminated with the ultraviolet light flux.

3. A method as claimed in claim 2 wherein the water recycled for a predetermined time period.

4. A method as claimed in claim 2 wherein the water is recycled until the concentration of pyrogenic material in said water falls below a predetermined level.

5. A method as claimed in any preceding claim including a further step of providing additional illumination of the ozonated water to thereby increase the said flux to achieve increased destruction rate of said pyrogenic materials.

6. A method of maintaining water substantially free of pyrogenic material including a method as claimed in any preceding claim.

7. Apparatus for destroying pyrogenic materials in water comprising a reaction vessel, means to ozonate said water, means to introduce the ozonated water into the vessel and means to illuminate the vessel interior with ultraviolet light to produce destruction of pyrogenic materials in the ozonated water.

8. Apparatus as claimed in claim 7 wherein said means to illuminate comprises at least one ultraviolet lamp.

9. Apparatus as claimed in claim 8 wherein the vessel is cylindrical and an ultraviolet light is provided at the axis of the cylindrical vessel.

10. Apparatus as claimed in claim 8 or 9 wherein the vessel is cylindrical with a plurality of lamps disposed regularly about the axis of the cylindrical vessel.

11. Apparatus as claimed in claim 10 wherein at least some of the lamps are disposed adjacent walls of the vessel.

12. Apparatus as claimed in any one of claims 9 to 11 wherein the ozonated water is introduced at the centre of one end of the cylinder and water is removed at the centre of the other end of the cylinder

13. Apparatus as claimed in claim 12 wherein the ozonated water is introduced at the centre of one end of the cylinder through a perforated nozzle.

14. Apparatus as claimed in claims 9 to 13 wherein the or each lamp extends between the ends of the cylinder.

15. Apparatus as claimed in any one of claims 8 to 14 wherein the or each lamp is separated from the ozonated water by a sheath substantially transparent to ultraviolet light.

16. Apparatus as claimed in any one of claims 7 to 15 including means to recycle water that is removed from a vessel back to said means to ozonate the water.

17. Apparatus as claimed in claim 16 wherein the means to recycle includes timing means adapted to stop the means to recycle after a predetermined time.

18. Apparatus as claimed in claim 16 wherein the means to recycle includes testing means adapted to stop the means to recycle when said testing means detects a concentration of pyrogenic material below a predetermined level.

19. Apparatus as claimed in any one of claims 7 to 18 including storage means capable of storing water removed from the vessel.

20. Apparatus as claimed in any one of claims 7 to 19 including cooling means arranged to maintain water removed from the vessel within a predetermined temperature range.

21. Apparatus for oxidizing organic materials in water comprising a closed cylinder reaction vessel, means to introduce said water into the vessel being located at the centre of one end of the cylinder, means to remove water from the vessel being located at the centre of the other end of the cylinder, and at least one ultraviolet lamp arranged to extend between the ends of the cylinder to thereby illuminate the vessel interior with ultraviolet light to produce oxidation of organic materials in said water.

22. Apparatus as claimed in claim 21 wherein an ultraviolet light is provided at the axis of the cylinder.

23. Apparatus as claimed in claim 21 or 22 wherein the at least one lamp is separated from the water by a sheath substantially transparent to ultraviolet light.

24. Apparatus as claimed in any one of claims 21 to 23 including means to recycle water that is removed from the vessel back to the vessel.

25. Apparatus as claimed in claim 24 wherein the means to recycle includes timing means adapted to stop the means to recycle after a predetermined time.

26. Apparatus as claimed in claim 24 wherein the means to recycle includes testing means adapted to stop the means to recycle when said testing means detects a concentration of organic materials below a predetermined level.

27. A method of destroying pyrogenic materials substantially as herein described.

28. Apparatus for destroying pyrogenic materials substantially as herein described with reference to the accompanying drawings.

29. Apparatus for oxidizing organic materials substantially as herein described with reference to the accompanying drawings.