WO1998051394A1

WO1998051394A1 - Water distiller system for medical applications

Info

Publication number: WO1998051394A1
Application number: PCT/US1998/009423
Authority: WO
Inventors: John M. Swancara
Original assignee: Pure Water, Inc.
Priority date: 1997-05-16
Filing date: 1998-05-08
Publication date: 1998-11-19
Also published as: AU7374098A

Abstract

A water purification system (10) which is capable of meeting pharmacological and medical quality requirements in high-volume includes a water distillation unit (12) having a boiling tank (18) which converts raw water into steam and a condenser (26) which converts steam to condensate. The system (10) further includes a post-treatment system (44) which removes residual minerals and bacteria from the condensate and an output system (46). The system (10) may further include filters such as activated carbon filter (60) which is connected to output line (58).

Description

WATER DISTILLER SYSTEM FOR MEDICAL APPLICATIONS

BACKGROUND OF THE INVENTION This invention relates generally to producing purified water and, in particular, to a water distillation unit capable of producing water which is useable in applications requiring ultra-pure water, such as pharmaceutical applications, medical applications, biomedical laboratory applications, and the like. The invention is also adaptable to applications requiring multiple levels of water quality, such as drinking water, on one hand, and ultra-pure water, on the other hand. Ultra-pure water is required in many applications. One such application is the pharmaceutical and medical laboratory environment in which processed water is required to meet United States Pharmacopoeia (USP) standards, as well as American Society for Testing and Materials (ASTM) Class 1 standards. On a large scale, such as in a production facility in which pharmaceuticals are manufactured, expensive water purification systems are installed which are capable of meeting the high- volume requirements of the manufacturing processes.

Because of the high cost, such systems are impractical on a smaller scale. When small amounts of ultra-pure water are required, filtration systems are available which process tap water to a state which generally meets these rigid requirements. However, such small scale systems are capable of producing only an extremely limited quantity of ultra-pure water. Furthermore, to produce this ultra-pure water requires a very frequent changing of the filters utilized to remove minerals and bacteria from the tap water.

Many applications require a quantity of ultra-pure water which is greater than that which can be produced from filtration of tap water, but which cannot support the high cost of the systems of the type utilized in manufacturing processes. In addition to the pharmaceutical and medical laboratory environment, there are applications in the medical care field in which an even stricter standard for water purity must be met.

SUMMARY OF THE INVENTION The present invention provides a water purification system which is capable of meeting many diverse applications in the pharmacological industry and medical laboratory, and hospital environments, without the extensive cost required for known high-volume systems, yet without the drawbacks of low-volume, high-maintenance systems. This is accomplished, according to an aspect of the invention, by a water purification system including a water distillation unit having a boiler which converts raw water into steam and a condenser which converts steam to condensate. The water distillation unit further includes a holding tank which holds condensate from the condenser. According to this aspect of the invention, a condensate filtration system is provided which removes residual minerals and bacteria from the condensate from the holding tank. The condensate filtration system may include a deionization resin bed, which removes the residual minerals from the condensate, and a submicron filter, which removes bacteria from the condensate. The condensate filtration system may also include a bacteria destruction unit which destroys or inactivates bacteria in the condensate. Preferably, the destruction unit includes an ultraviolet radiation source. According to another aspect of the invention, a water purification system includes a water treatment unit, which converts raw water into treated water, and a holding tank, which holds treated water from the water treatment unit. A delivery system is provided for delivering treated water from the holding tank to a use, such as a pharmaceutical use, a laboratory use, a medical use, a drinking water use, or the like. The delivery system includes a post-treatment system which removes minerals and bacteria from the water in the holding tank and an output which dispenses post-treated water to the use. The system further includes a water quality assurance system including a water quality measuring device and a recirculation system. The recirculation system recirculates water from the holding tank through the post-treatment system and back to the holding tank in response to the water quality measuring device determining that water quality is inadequate. In this manner, a water purification system, according to this aspect of the invention, is capable of providing significant volumes of ultra-pure water in a manner which ensures that water quality is maintained at a desired level.

A water purification system according to the invention is capable of meeting the demands of many applications which require a significant volume of ultra-pure water, but which cannot support the cost of large production units. Furthermore, a water purification system according to the invention is capable of concurrently producing such ultra-pure water and supplying treated water for human consumption as drinking water. In this manner, not only the requirements of the applications are met but also the water quality consumed by the occupants of the premise is increased. The present invention also provides a compact unit which may be made portable on wheels and easy to install so that it can be moved from location to location.

These and other objects, advantages and features of this invention will become apparent upon review of the following specification in conjunction with the drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view of a water purification system according to the invention with a portion of the housing removed to reveal internal details thereof;

Fig. 2 is a block diagram of a water purification system according to the invention; Fig. 3 is the same view as Fig. 2 of an alternative embodiment;

Fig. 4a is an enlarged side elevation of an overflow sensing mechanism; and Fig. 4b is the same view as Fig. 4a illustrating the sensing mechanism in the presence of water.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now specifically to the drawings, and the illustrative embodiments depicted therein, a water purification system 10 includes a water treatment unit 12 and a delivery system 14 for delivering treated water from the water treatment unit to one or more uses, such as pharmacological use, medical use, laboratory use, human consumption, or the like (Fig. 1). In the illustrative embodiment, water treatment unit 12 is a water distillation unit, generally shown at 16, structured according to the principles disclosed in commonly assigned United States

Patent 4,805,692, the disclosure of which is hereby incorporated herein by reference. The details of water distillation unit 16 are disclosed in the '692 patent and will not be repeated herein. Suffice it to say that water distillation unit 16 includes a boiling tank 18 made from stainless steel that is completely covered by insulation to prevent loss of heat. An inlet valve (not shown) selectively admits raw tap water to boiler tank 16. An electrical heater 20 heats the water to convert the water to steam. Conductivity sensing probes 22 and 24 extend downwardly from a top wall of the boiler in order to monitor and control the water level in the boiler tank.

Steam generated in the boiler is transferred to a condenser 26 through a steam tube 28. Cooling airflow generated by a fan 30 flows upwardly over the surfaces of tubes making up condenser 26 in order to condense steam into condensate. The condensate, which is water that has been treated by the water distillation unit in order to produce treated water is stored in a holding tank 32. A control unit 34 controls the operation of water purification system 10 including water treatment unit 12 and delivery system 14. Control unit 34 controls the operation of heater 20 and fan 30 and receives inputs from sensing probes 22 and 24 in the boiler tank. A pair of sensing probes 36 and 38 are positioned in holding tank 32 at a point close to the top of the tank in order to control production of water by the water treatment unit in a manner which maintains the holding tank substantially full of treated water. A third sensing probe 40 in a lower portion of holding tank 32 senses if the level of water in holding tank 32 drops to a low enough level to damage a pump 42 which discharges treated water from the holding tank 32 in a manner which is described in more detail below.

Delivery system 14 includes a post-treatment system generally indicated at 44 and an output system 46 which dispenses post-treated water to a particular use (Figs. 2 and 3). The delivery system includes a water quality assurance system 48 in order to ensure that water delivered to a use is of a particular quality level. If the water quality assurance system determines that water is not of a sufficient quality, the water is not dispensed to the use but, rather, is recycled through the holding tank and the post-treatment system in order to improve the quality of the water. The water quality assurance system includes a water quality measuring device 50 and a recirculation system 52 which recirculates water from the holding tank through post-treatment system 44 and back to the holding tank in a manner which will be described below.

In the illustrated embodiment, post-treatment system 44 is a condensate filtration system including a deionization resin bed 54, which removes minerals from the water processed by water treatment unit 12, and a submicron filter 56, which removes bacteria from the treated water. In the illustrated embodiment, deionization resin bed 54 is a cartridge containing Food and Drug Administration (FDA) grade resin which has been subject to additional post- production steps to minimize Total Organic Carbon (TOC) level. In the illustrated embodiment, the output achieved from resin bed 54 is water having a resistivity of 16 megaohms. The output of the deionization resin bed passes through submicron filter 56, which, in the illustrated embodiment, has a capacity in the range of between approximately 0.2 micron absolute and approximately 0.05 micron absolute. Submicron filter 56, in the illustrated embodiment, is constructed of a highly asymmetric hollow fiber polysulfone media in a polypropylene housing. In the illustrated embodiment, submicron filter 56 has a capacity of reducing bacteria below 10 cfu/L.

Water is supplied to post-treatment system 44 from an output line 59 of pump 42 through an inline check valve 90 to prevent backflow of ultra-pure water. Output line 58 of pump 42 is connected with a pulsation damper 64 which is a bladder- lined, air-filled tank which reduces the cycling frequency of pump 42 by filtering the pressure variations on line 58. Output line 58 is also connected with a carbon filter element 60 in order to supply a human consumption use 62. In this manner, water purification system 10 is capable of not only supplying ultra-pure uses, such as pharmaceutical uses, biomedical uses, laboratory uses, medical uses, and the like, but is also capable of treatment of water in a manner which significantly improves the quality of the water for human consumption.

In the illustrated embodiment, water quality measuring device 50 measures the resistivity of water from the output of submicron filter 56. Water quality measuring device 50 supplies an input (not shown) to control unit 34 which monitors the output of the resistivity controller and operates a three-way recirculating valve 66 as a function of water quality. Recirculating valve 66, in one position, interconnects the output of post-treatment system 44 with an ultra-pure water use output 68. In another position, recirculating valve 66 interconnects the output of post- treatment system 44 with recirculating system 52. Recirculating system 52 recirculates the output of post-treatment system 44 back to the storage tank 32 at 70. If water quality measuring device 50 determines that the quality of water produced from post-treatment system 44 meets quality levels, namely that its resistivity value exceeds a particular level, recirculating valve 66 directs the output of post-treatment system 44 to use output 68. If water quality measuring device 50 determines that the resistivity of the water is too low, recirculating valve 66 is switched to a recirculating position and the water is cycled in a continuous loop from storage tank 32 through post-treatment system 44 and back to storage tank 32. This continuous recycling of water through the post-treatment system should increase the quality of the water sufficiently that water quality measuring device 50 determines that recirculating valve 66 can be placed in the position in which water is supplied to use output 68.

Recirculating system 52 is additionally useful in periodic sterilization of the system. This sterilization process my be carried out, for example, after filter cartridges 54 and 56 are replaced. In order to sterilize the system, a cold sterilant, such as minncare, can be added to the storage tank and recycled through the system for a period of time. The sterilant can then be flushed from the system and the system can be placed back into use by operating water treatment unit 12 until storage tank 32 is charged with treated water.

Storage tank 32 includes a submicron air filter 72 which provides venting of storage tank 32 while filtering air vented in the tank in order to eliminate the admission of air-borne bacteria and the like. Additionally, storage tank 32 is made of stainless steel which is welded and purged after welding. This minimizes oxidation of the interior of the storage tank from the treated water stored therein. An overflow tray 76 is provided under storage tank 32. An overflow sensing mechanism 78 is provided to sense the presence of water in overflow tray 76 and to instruct control unit 34 to shut down the water purification system in the presence of water in the overflow tray. Sensing mechanism 78 includes a mechanical microswitch 80 and a sensing actuator 82 (Figs. 4a and 4b). Sensing actuator 82 includes an arm 84 and a compressed water absorbing material 86, such as a sponge. Sensing mechanism 78 is very sensitive to even small quantities of water in the overflow tray. This is because the water causes water absorbing material 86 to expand. The expansion of material 86 moves arm 84 which operates microswitch 80, shutting down the water purification unit as illustrated in Fig. 4b.

In an embodiment illustrated in Fig. 3, a water purification system 10' includes a post- treatment system 44' having a bacteria destruction unit 74 positioned in series flow connection downstream of deionization resin bed 54 and upstream of submicron filter 56. The bacteria destruction unit in the illustrated embodiment is an ultraviolet radiation system composed of an ultraviolet radiation source in a stainless steel housing. The source operates at a frequency of 254 nanometers. The bacteria destruction unit destroys or inactivates any bacteria present in the water. The submicron filter 56 removes the destroyed or inactivated bacteria as well as the endotoxins or pyrogens which remain from the destroyed bacteria. In this manner, water purification system 10' is capable of achieving an output to a use 68' which is substantially free of pyrogens as well as meeting high water quality standards of resistivity. Preferably, the capacity of submicron filter 56 of post-treatment system 44' is approximately 0.05 micron. The present invention provides a water purification system which results in a high quality water that meets United States Pharmacopoeia standards for water for injection in patients. It is also capable of meeting National Committee for Clinical Laboratory standards Type 1 reagent grade water for cell culture. A water purification system according to the present invention is compact in construction, reliable and easy to maintain. The water purification system is capable of producing approximately 60 gallons per day of distilled water with an ultra- pure water production rate of 0.25 gallons per minute. Water quality supplied to human consumption output 62 from water distillation unit 16 is in the range of 0 to 10 ppm. The quality of water at ultra-pure use output 68, 68' is approximately 16.67 megaohms.

In the illustrated embodiment, deionization resin bed cartridge 54 is marketed by Ametek under Model No. PCF1-20MB, submicron filter 56 is marketed by Fibercor under Model Nos. 50-104 and 300-104, and bacteria destruction unit 74 is marketed by Ideal Horizons under

Model No. SR-1. Changes and modifications in the specifically described embodiments can be carried out without departing from the principles of the invention, which is intended to be limited only by the scope of the appended claims, as interpreted according to the principles of patent law including the doctrine of equivalents.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A water purification system, comprising: a water distillation unit including a boiler which converts raw water into steam, a condenser which converts steam to condensate and a holding tank which holds condensate from said condenser; and a condensate filtration system which removes minerals and bacteria from condensate from said holding tank.

2. The water purification system in claim 1 wherein said condensate filtration system includes a deionization resin bed which removes minerals from condensate and a submicron filter which removes bacteria from condensate.

3. The water purification system in claim 2 wherein said deionization bed is made according to a process which reduces total organic carbon level of the resin bed.

4. The water purification system in claim 2 wherein said submicron filter comprises a highly asymmetric hollow fiber polysulfone media.

5. The water purification system in claim 2 wherein said submicron filter has a capacity in the range of between approximately 0.2 micron absolute and approximately 0.05 micron absolute.

6. The water purification system in claim 2 wherein said condensate filtration system includes a bacteria destruction unit which destroys or inactivates bacteria in condensate.

7. The water purification system in claim 6 wherein said bacteria destruction unit includes an ultraviolet radiation source.

8. The water purification system in claim 6 wherein said bacteria destruction unit is positioned in serial flow downstream of said deionization resin bed and upstream of said submicron filter.

9. The water purification system in claim 1 including a submicron filtered vent for said holding tank.

10. The water purification system in claim 9 wherein said submicron filtered vent has a capacity of approximately 0.2 micron.

11. The water purification system in claim 1 wherein said water purification system has a capacity of at least approximately 50 gallons of water a day.

12. The water purification system in claim 11 wherein said water purification system has a capacity of at least approximately 60 gallons of water a day.

13. The water purification system in claim 1 including an output from said holding tank for providing condensate for human consumption.

14. The water purification system in claim 1 including a tray below said water distillation unit and a sensor which disables said water distillation unit in response to water in said tray.

15. The water purification system in claim 14 wherein said sensor compressed includes a water absorbent material which expands in the presence of liquid and a switch which responds to expansion of said material.

16. A water purification system, comprising: a water treatment unit which converts raw water into treated water and a holding tank which holds treated water from said water treatment unit; a delivery system for delivering treated water from said holding tank to a use including a post-treatment system which removes minerals and bacteria from water in said holding tank and an output which dispenses post-treated water to the use; and said delivery system including a water quality assurance system having a water quality measuring device and a recirculation system which recirculates water from said holding tank through said post-treatment system and back to said holding tank in response to said water quality measuring device determining that water quality is below a particular value.

17. The water purification system in claim 16 wherein said water quality assurance system diverts water from said output in response to said water quality measuring device determining that water quality is below said particular value.

18. The water purification system in claim 16 wherein said water quality measuring device measures water conductivity to determine water quality.

19. The water purification system in claim 16 wherein said post-treatment system includes a filtration system which removes minerals and bacteria from treated water.

20. The water purification system in claim 19 wherein said filtration system includes a deionization resin bed which removes minerals from treated water and a submicron filter which removes bacteria from treated water.

21. The water purification system in claim 20 wherein said deionization bed is made according to a process which reduces total organic carbon level in the resin bed.

22. The water purification system in claim 20 wherein said submicron filter comprises a highly asymmetric hollow fiber polysulfone media.

23. The water purification system in claim 20 wherein said submicron filter has a capacity in the range of between approximately 0.2 micron absolute and approximately 0.05 micron absolute.

24. The water purification system in claim 19 wherein said filtration system includes a bacteria destruction unit which destroys or inactivates bacteria in treated water.

25. The water purification system in claim 24 wherein said bacteria destruction unit comprises an ultraviolet radiation source.

26. The water purification system in claim 24 wherein said filtration system includes a deionization resin bed which removes minerals from treated water and a submicron filter which removes bacteria from treated water.

27. The water purification system in claim 26 wherein said bacteria destruction unit is positioned in serial flow downstream of said deionization resin bed and upstream of said submicron filter.

28. The water purification system in claim 16 wherein said water treatment unit comprises a water distillation unit including a boiler which converts raw water into steam and a condenser which converts steam to treated water.

29. The water purification system in claim 16 including a submicron filtered vent for said holding tank.

30. The water purification system in claim 29 wherein said submicron filtered vent has a capacity of approximately 0.2 micron.

31. The water purification system in claim 16 wherein said water purification system has a capacity of at least approximately 50 gallons of water a day.

32. The water purification system in claim 31 wherein said water purification system has a capacity of at least approximately 60 gallons of water a day.

33. The water purification system in claim 16 including another output which dispenses treated water from said holding tank for human consumption.

34. The water purification system in claim 16 including a tray below said water treatment unit and a sensor which disables said water treatment unit in response to water in said tray.

35. The water purification system in claim 34 wherein said sensor compressed includes a water absorbent material which expands in the presence of liquid and a switch which responds to expansion of said material.

36. A water purification system, comprising: a water distillation unit including a boiler which converts raw water into steam, a condenser which converts steam to condensate, and a holding tank which holds condensate from said condenser; a human use output which dispenses condensate from said condenser; and a condensate filtration system which removes minerals and bacteria from condensate from said holding tank sufficiently to produce water having a purity sufficient to meet at least one of ASTM Class 1 requirements and United States Pharmacopeia standards.