IL112725A - Apparatus for the production of drinking water - Google Patents

Description

AN APPARATUS FOR THE PRODUCTION OF DRINKING WATER The present Invention relates to an apparatus for the production of drinking water from a water source which is contaminated by pathogenic micro-organisms. More particularly, the invention provides an apparatus for the production of drinking water which achieves outstanding economy through the use of high-pressure sodium lamps, in combination with a photosensitizer which is particularly reactive to the radiation produced by said lamps.

Many parts of the world have large fresh-water lakes, rivers or underground reservoirs which have been biologically contaminated, due to natural causes or poor management. A safe supply of drinking water is a basic human requirement, but thirsty people will drink contaminated water if that is all that is available. The resulting epidemics of cholera and dysentery, such as those seen recently in Rwanda and in neighboring states flooded by refugees, require more resources for their control than would have been required originally in order to supply safe drinking water; such diseases take thousands of lives, aside from causing human suffering on a very large scale.

Various methods are known for purifying contaminated fresh water to a degree suitable for drinking, but most such methods are not suitable for use in the underdeveloped areas of the world which need them the most.

Water can be boiled before use, provided that fuel is available. This method of purifying water, however, imposes a surprisingly onerous task on primitive peoples, and therefore cannot be relied upon over the long term. Furthermore, boil-resistant bacteria have been discovered; even after boiling, such water requires filtering for removal of impurities. 2 112,725/2 Known large-scale purification methods, such as reverse osmosis, multistage flash distillation, and electrodialysis, require large amounts of electricity and are suitable mainly for desalination of sea water. Solar distillation is a suitable process for producing drinking water from saline sources for undeveloped areas, but there is no record of this process being effective in removing micro-organisms.

Devices for purifying water, arranged for the decomposition of organic contaminants by exposing the water containing such contaminants to a beam of concentrated solar energy, have been disclosed in U.S. Patent 4,978,458 as well as in Israel Patent 107,329 and U.S.. Patent 5,130,131. Such devices require the construction and maintenance of large lenses or reflectors, and require accurate tracking devices to follow the sun's apparent movement. A further limitation of these concentrating devices is their inability to utilize the approximately 10% of solar radiation arriving at ground level in diffuse form after being scattered by the Earth's atmosphere. A further device using solar energy is described by the present inventor in co-pending Israel Patent Application 111,523. It must be remembered, however, that solar energy-powered devices can operate only during daylight hours, and therefore are suitable mainly for locations where electricity is unavailable.

The use of ultraviolet radiation, typically in the 200-400 nm wavelength range, forms a basis for further known methods of water purification. Such methods, however, suffer from multiple disadvantages, such as sensitivity to dirt in the water being processed and to the water temperature; the need to protect plant operators from excessive exposure; and the relatively short life of lamps producing said radiation, about 7,000 hours. Due to the low efficiency of these lamps, electricity consumption is high.

The U.S. Department of Health, Education and Welfare stated, in a policy ; statement on the use of ultraviolet radiation for disinfection of water: "Ultraviolet treatment does not provide residual bactericidal action. Therefore, there is a need for periodic flushing and disinfection of the water distribution system. Some supplies may require routine chemical disinfection, including the maintenance of a residual bacterial agent throughout the distribution system." U.S. Patent 4,008,136 describes a method for the treatment of waste water intended for disposal or subsequent treatment, and claims as follows: "A process for treating aqueous waste effluents containing organic materials , which comprises adding to said aqueous effluents in the presence of oxygen, a water-insoluble, polymer-based photosensitizer, and then photolyzing the resulting suspension with (light\ having wavelengths between 320 nm and about 800 nm." Said patent makes no claim to a method producing water fit for drinking, nor does it describe any apparatus for producing drinking water.

It is an objective of the present invention to obviate the disadvantages of the prior art water purification devices. Further objectives of the present invention are to provide a water purificatio apparatus which is highly efficient which can be operated using only moderate quantities of electricity, thus being operable at low cost; and which can be operated and maintained by unskilled personnel.

The present invention achieves the above objectives by providing a water purification apparatus for use in purifying pre-filtered water containing pathogenic micro-organisms, comprising an inlet conduit for said water; means arranged to feed a photosensitizer into the water passing through said conduit, said photosensitizer being particularly sensitive to radiation in the range of from about 570-630 nm; a reactor bath receiving said photosensitized water from said conduit at an inlet port, holding said water for a time period allowing treatment thereof, and discharging said water from an exit port; at least one high-pressure sodium lamp, at least half the light radiation output of which is emitted in the wavelength range between 570-630 nm, said light output being directed at the water held in said reactor bath, said radiation causing singlet oxygen to react with, and kill, said microorganisms; and outlet filter means in fluid communication with said exit port, arranged to remove remaining photosensitizer and remaining impurities from the irradiated water, thereby supplying water suitable for drinking.

In a preferred embodiment of the present invention, said photosensitizer is methylene blue.

In a most preferred embodiment of the present invention there is provided an apparatus for water purification, for use in combination with fresh water containing suspended solids and pathogenic micro-organisms, further comprising an inlet filter connected to the inlet conduit for removing these solids from the water entering the apparatus.

It will be realized that while the novel apparatus of the present invention is particularly suited to use in less developed countries where electricity is expensive and available in limited supply, the low operating costs of such a plant make it a viable competitor for water purification tasks anywhere. The extensive use of high-pressure sodium lamps for street lighting is an indication of the economy they provide, and such use in itself has contributed to lowering the manufacturing cost of these lamps.

With regard to safety of operation, there is no known danger of exposure to radiation in the range produced by the sodium lamp; there is also no need for plant operators to be subjected to suc exposure.

The safety aspects of using methylene blue, chemically defined as tetramethylthionine chloride, have been carefully studied. The present invention provides for the removal of the bulk of the methylene blue from the water supplied for drinking. Nevertheless, it is realized that a small quantity of this material will eventually be consumed by users of the produced water.

Methylene blue is an antiseptic material which degrades in the digestive system to a colorless, non-odorous material called leukomethylene blue. Most of the ingested material leaves the body through the kidneys, entrained in urine. The material was found to be poisonous when injected in very high concentrations into cats (40 mg/kg) and mice (67 mg/kg), but standard textbooks do not list this material as a poison consequently, no infomation is available as to what constitutes a harmful dose for humans. The substance is used as a medicine for certain diseases in humans, at a concentration of 1 or 2 mg/kg.

In the process of the present invention, methylene blue is added to the water as a photosynthesizer, at a - o - concentration of from 0.5-10 ppm. The water is filtered after processing to remove up to 99.9% of the photosynthesizer residue before said water is supplied to consumers. It may therefore be concluded that users of the produced water will not be harmed thereby, as they would be unable to drink the massive quantity of water needed to accumulate a harmful quantity of the little remaining photosensitizer material.

The invention will now be described in connection with certain preferred embodiments with reference to the following illustrative figures so that it may be more fully understood.

With specific reference now to the figures in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only, and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice .

In the drawings: Fig. 1 is a schematic view of a preferred embodiment of the water purification apparatus according to the present invention; Fig. 2 is a schematic view of a second embodiment of said apparatus ; Fig. 3 is a schematic plan view of a reactor bath used in said apparatus Fig. 4 is a schematic view of an embodiment of the apparatus of the invention, provided with light reflectors; Fig. 5 ia a schematic view of part of an apparatus including a reservoir , and Fig. 6 is a schematic view of part of an apparatus for use in purifying water containing suspended solids.

Fig. 1 illustrates a water purification apparatus 10, for use in combination with pre-filtered water 12 containing pathogenic micro-organisms. Water 12 enters the apparatus through inlet conduit 14. Means 16 is arranged to feed a controlled quantity of photosensitizer 18, typically 0.6 ppm, into the water 12 passing through conduit 14. Means 16 suitably comprises a small variable output metering pump 20. Suitable pumps which are able to reliably feed very small quantities of liquids are commerically available, for example, from Gorman-Rupp Industries, Ohio, U.S.A.

The dosage of photosensitizer can be varied in response to increased water flow, or to combat higher bacteriological loads at the same flow rate. The photosensitizer 18 is particularly sensitive to radiation in the range of between 570-630 nm, and suitably comprises an organic dye, such as methylene blue ( tetramethylthionine chloride ) . Methylene blue has a bacteriostatic effect which inhibits propagation of bacteria in the apparatus. For this reason, there is no need to add chlorine to the water, as is practiced at present.

A reactor bath 22 is provided with inlet 24 for receiving the photosensitized water 26 from conduit 14. The bath 22 holds water 26 for a sufficient time period to allow its treatment. An exit port 28 is provided for the discharge of treated water 30.

An array of high-pressure sodium lamps 32 is arranged above the water 26 held in reactor bath 22. Lamps 32 have a light output wherein at least half the light radiation is emitted in the wavelength range from about 570-630 nm. A high-pressure sodium lamp is defined as an electric discharge lamp in which radiation is produced by the excitation of sodium vapor, and in which the partial pressure of the vapor during operation is 26,000 N/ma. Lamps of this type have an expected life of 16,000 hours. They have excellent stability, still producing 83% of their rated output after having operated over 70% of their rated lifetime .

The lamps 32 are arranged to direct their emitted light radiation at water 26 held in reactor bath 22, which radiation causes singlet oxygen to react with, and kill, micro-organisms contained in the water. Advantageously, the lower inner surface 34 of the reactor bath 22 is light-reflecting. Thus, incoming radiation passes through the water 26 and, being reflected by surface 34, passes through the water a second time, to achieve an enhanced disinfecting action.

To complete the apparatus 10, outlet filter means 36 is provided in fluid communication with exit port 28. Filter means 36 is a sorption device designed to remove at least 90% of the photosensitizer, and operates by the use of ion exchange resins. The resins can be processed to effect separation of the photosensitizer for recovery and reuse. Filter means 36 preferably comprises several units used in parallel as shown, to achieve a specified flow rate and to facilitate servicing of filter units without shutting down the entire apparatus.

Referring now to Fig. 2, there is depicted a further embodiment 38 of a water purification apparatus. A circulation mixer 40 is positioned in the inlet conduit 42 downstream of metering pump 20, to ensure even distribution of photosensitizer 18 in the water passing through said conduit.

Two transparent windows 44, 46 are provided for visual inspection of water flowing within the apparatus. A first window 44 is positioned in the inlet conduit upstream of the bath inlet 24, thus allowing a plant operator to check that the water mixture is correctly colored by the photosensitizer 18. A second window 46 is positioned downstream of filter means 36, to allow a plant operator to check water transparency as an indication that filter means 36 are operating correctly and removing the remaining photosensitizer 18 from the purified water.

Fig. 3 shows a further embodiment of a reactor bath 48, similar to bath 22 shown in Fig. 1. Reactor bath 48 is configured to form a long, serpentine flow path 50, leading from inlet port 52 to outlet port 54. The water mixture is pumped through flow path 50 at a rate no higher than that calculated to ensure adequate exposure time to the light radiation provided.

Referring now to Fig. 4 , there is seen a detail of an embodiment 56, having enhanced operating efficiency. Said efficiency is achieved by providing each sodium lamp 32 with a reflector 58, arranged to direct the lamp's light output towards reactor bath 22. Good results are obtained with parabolic reflectors, either aluminum or painted with white enamel.

Fig. 5 depicts a part of a further, similar water purification apparatus 60, which is provided with a reservoir 62 for receiving irradiated water 64 from reactor exit port 28, and which then supplies said water to outlet filter means 36. Reservoir 62 allows continuous, steady flow operation of the reactor bath, even while filter means 36 are being serviced. It is to be noted that water contained in reservoir 62 remains sanitized, due to the bacteriostatic effect of the contained photosensitizer 18 (seen in Fig. 1). Reservoir 62 also provides a convenient location for water pump 66, used to provide pressure in filter means 36.

Shown in Fig. 6 is part of a water purification apparatus 68, for use in combination with water containing suspended solids 70 and pathogenic micro-organisms. Inlet filter 72 is connected to inlet conduit 14, for removing solids from water entering apparatus 68. Inlet filter 72 is advantageously built as a two-stage unit. A sedimentation basin 74 serves as a first stage filter for large solids, and a sand filter 76 is the second stage filter, used to remove fine solids.

Table 1 gives test results, using an apparatus as described with reference to the drawings. Test conditions were as follows: TABLE 1 Water flow rate: 1-4 L/min Quantity of photosensitizer added: 5 ppm Wattage of lamp: 400 W Number of lamps used: 1 Lamp reflectors used: Aluminum Initial E. coli count: 1x10s cpu/ml Test Results: Flow L/min Test according to ATCC 25922 for Log Reduction of E. coli 4 3 2 4 1 5 It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrated embodiments and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims (10)

WHAT IS CLAIMED IS:

1. A water purification apparatus, for use in purifying pre-filtered water containing pathogenic micro-organisms, comprising: an inlet conduit for said water; means arranged to feed a photosensitizer into the water passing through said conduit, said photosensitizer being particularly sensitive to radiation in the range of from about 570-630 nm; a reactor bath receiving said photosensitized water from said conduit at an inlet port, holding said water for a time period allowing treatment thereof, and discharging said water from an exit port; at least one high-pressure sodium lamp, at least half the light radiation output of which is emitted in the wavelength range between 570-630 nm, said light output being directed at the water held in said reactor bath, said radiation causing singlet oxygen to react with, and kill, said micro-organisms; and outlet filter means in fluid communication with said exit port, arranged to remove remaining photosensitizer and remaining impurities rom the irradiated water, thereby supplying water suitable for drinking.

2. A water purification apparatus es claimed in claim 1, wherein said photosensitizer is an organic dye.

3. A water purification apparatus as claimed in claim 2, wherein said photosensitizer is methylene blue .

4. A water purification apparatus as claimed in claim 1, wherein said means arranged to feed a photosensitizer into the water passing through said conduit includes a mixer.

5. A water purification apparatus as claimed in claim 1, further provided with at least one transparent window for visual inspection of the water flowing through said apparatus.

6. A water purification apparatus as claimed in claim 1, wherein said reactor bath is configured to form a long, serpentine flow path between said inlet and exit ports.

7. A water purification apparatus as claimed in claim 1, wherein the inner lower surface of said reactor bath is light-reflecting.

8. A water purification apparatus as claimed in claim 1, wherein said sodium lamp is provided with a reflector, arranged to direct the light output of said lamp towards said reactor bath.

9. A water purification apparatus as claimed in claim 1, further comprising a reservoir for receiving treated water from said reactor exit port and supplying water to said outlet filter means.

10. A water purification apparatus as claimed in claim 1 for purifying fresh water containing suspended solids and pathogenic micro-organisms , further comprising an inlet filter connected to said inlet conduit for removing said solids from the water entering said apparatus. for the Applicant: WOLFF, BREGMAN AND GOLLER