WO1998005594A1

WO1998005594A1 - A portable water purification system

Info

Publication number: WO1998005594A1
Application number: PCT/GB1996/001900
Authority: WO
Inventors: Eitan Sharir
Original assignee: Solar Dynamics Limited; Ritter, Stephen, David
Priority date: 1996-08-05
Filing date: 1996-08-05
Publication date: 1998-02-12
Also published as: AU6664496A

Abstract

The invention provides a portable water purification system for use in purifying fresh water containing pathogenic microorganisms, comprising at least one transparent container (14) for the water, the container being exposable to solar radiation (15) including wavelengths in the visible part of the spectrum, for effecting oxidation of said microorganisms. There is also provided a water-dissolvable capsule or tablet (24) comprising inert, non-toxic photosensitizer (26), the photosensitizer being of the type which absorbs visible light and which, in turn, transfers some of the energy from the absorbed visible light to accelerate the oxidation of microorganisms found in the water. The system also includes water delivery means (20) in fluid communication with the lower part of the container.

Description

A PORTABLE WATER PURIFICATION SYSTEM

The present invention relates to an apparatus for the production of drinking water from a water source which is contaminated by pathogenic microorganisms. More particularly, the invention provides a portable apparatus which uses unconcentrated solar energy and which is suitable for use anywhere sunshine is available, no electric power being required.

Many parts of the world have large fresh-water lakes , rivers or underground reservoirs which have been biologically contaminated, due tα natural causes or pcor management. People who drink such water expose themselves to the dangers of various infections, which may lead to life-threatening diseases such as cholera and dysentery. Unfor unately, the appearance of the water is not a reliable guide as to its suitability for drinking. Water may be clear in appearance and yet be contaminated by bacteria or protozoa to a dangerous degree. Conversely, water may be brown with mud and yet pose no danger to the health of a person drinking his fill.

Residential areas are normally supplied with safe drinking water by municipal authorities ; however , at times the supplied water is temporarily contaminated, and then safe water is either delivered tα such an area by tanker, or the residents are asked to boil water used for food preparation and drinking.

The boiling of water before use is dependent on fuel being available. Even so, it is tα be noted that fires are not allowed in many recreational areas, particularly in forests. Furthermore, boil-resistant bacteria have been discovered, and even after boiling, such water requires filtering far removal of impurities .

When it is anticipated that considerable time will be required to restore the supply of safe drinking water, the municipal authority could offer residents the loan of a portable water purification device. Such a device would also be of vital utility in an area suffering from a disaster such as an earthquake which had disrupted water, gas and electricity lines.

Various methods are known for purifying contaminated fresh water to a degree suitable for drinking; most such methods are not suitable for use on small-scale, portable apparatus .

A small, portable unit was developed by Maria Telkes during World War II, to serve the needs of flyers who were forced down at sea. This solar still is inflatable, has a black, porous evaporator, and operates at over 50% efficiency. However, it is designed for the desalination of sea water, and its output serves to supply only the minimum drinking requirements of one person.

Known commercial purification methods such as reverse osmosis, multi-stage flash distillation, and electrodialysis, require electric power and are suitable mainly for large-scale 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 far the removal of microorganisms. Except for the solar stills, none of these plants is suitable for small-scale local operation by unskilled personnel.

Apparatus for purifying water, arranged for the decomposition of organic comtaminants by exposing the water containing said contaminants to a beam of concentrated solar energy, have been disclosed by Inagaki, et al. in U.S. Patent 4,978,458, and by the present inventor in Israel Patent Application 98930 and U.S. Patent Application No. 07/916,700. 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 such concentrating devices is their inability tα utilize the approximately 10% of solar radiation which arrives at ground level in diffuse form after being scattereed by the Earth's atmosphere.

In U.S. Patent 4,008,136, Williams describes and claims a method for the treatment of waste water intended for disposal or subsequent treatment. He claims:

"A process for treating aqueous waste effluents containing organic materials, which comprises adding tα 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."

Williams makes no claim tα a method producing water fit for drinking, nor does he propose any apparatus for producing drinking water.

In co-pending Patent Application there is disclosed a non-portable water purification apparatus, intended to meet medium-scale requirements for drinking water. The device was not intended to provide the very small-scale requirements of a single family, nor waa it intended for mobile applications such as camping, picnics, etc.

It is therefore an objective of the present invention to obviate the disadvantages of the prior art water purification apparatus, and to provide a system which will provide safe drinking water in locations not provided with electricity, gas, or fossil fuels.

A further objective of the present invention is to provide a portable system which can be transported in a typical family automobile, and which can be set up and dismantled in a few minutes.

A still further objective of the present invention is to provide an apparatus which can be manufactured and operated at low cost.

The present invention achieves the above objectives by providing a portable water purification system for use in purifying fresh water containing pathogenic microorganisms, comprising at least one transparent container for said water, said container being exposable to solar radiation including wavelengths in the visible part of the spectrum, for effecting oxidation of said microorganisms; a water- dissolvable capsule or tablet comprising inert, non-toxic photosensitizer, said photosensitizer being of the type which absorbs visible light and which, in turn, transfers some of the energy from said absorbed visible light to accelerate the oxidation of microorganisms found in said water,- and water delivery means, in fluid communication with the lower υart of said container. In a preferred embodiment of the present invention, there is provided a portable water purification system further comprising a second transparent container, arranged to be in fluid communication with filter means positioned thereabove. Said second container is arranged to receive filtered water from the filter means, and is also exposable to solar radiation including wavelengths in the visible part of the spectrum, to accelerate the oxidation of microorganisms contained therein. Further provided is a water delivery means, for transfer of filtered, irradiated water to the first transparent container.

In a most preferred embodiment of the present invention, there is provided a portable water purification system further comprising a third transparent container, positioned above the second transparent container. Filter means mounted in said third transparent container are arranged to feed filtered water to the second transparent container.

The procedure followed by the present invention is based on dye-sensitized photααxidation reactions, which are further explained as follows:

These reactions, which are also referred to as "photodynamic action," are responsible for the oxidative processes which take place in surface waters exposed to solar radiation. They consist of the combined action of visible light and molecular oxygen (0₂) dissolved in water containing organic matter (OM) such as pathogenic microorganisms, through the intermediary of an appropriate photosensitizer (S). The S is an organic molecule having a special electronic structure which enables it to absorb, and then tα transfer, some of the ligh -radiated energy. The S is added to the aerated and light-exposed contaminated water, and its absorbed energy (S*) is made available for the oxidation of OM. Either one or both of the following mechanisms can operate in aerobic, photosensitized oxidations .

A) Primary interaction of the electronically-excited S* with OM to generate reactive, short-lived intermediates, which subsequently react with 0₂:

S +^■ 1-

S* ÷ OM + 0₂ - transient species _→. oxidation products + S ( 2 )

(Transient species = free radicals, ion pairs, etc.)

B) The presence of 0₂ will compete successfully with CM on receiving the excitation energy from S*. The addition of this energy to 0₂ changes its ground electronic state (triplet state, ³∑g0₂) to the first excited singled state (^Δ O_s) which has a higher energy by 22.5 kcal mole^"2*. When more energy is imparted tα 0₂, another electronic state is formed (^*-^g0₂) which corresponds to a level of 37.5 kcal mole^-3- above the ³∑g0₂. From the properties of singlet oxygen (exceedingly short lifetimes of ^*Σg0₂), it seems likely that only ^*** Δ g0₂ is important in solution photo- oxidations :

S* + ^**Σg0₂ ■_* S + ^***ΔgO_a (3)

^ΔgOz + OM - oxidation products ( 4 ⁾ In both mechanisms, the sensitizer is regenerated and undergoes hundreds of cycles, so that only minute amounts of it are required.

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 cf example and for purposes of illustrative discussion cf the preferred embodiments of the present invention only, and are presented in the cause of providing what is believed tα 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 m ^*"- be embodied in practice.

In the drawings: Fig. 1 is a front elevational view of a preferred embodiment of the water purification system according to the inventio ; Fig. 2 is a front elevational view of a second embodiment of the system of the invention; Fig. 3 is a front elevational view of an embodiment of the system provided with stirring means; Fig. 4 illustrates a system similar to that shown in Fig. 3, but having wind-powered stirring means; ^• 3 -

Fig. 5 is a front elevational view of an embodiment of the system having filter means,- Fig. 6 illustrates a system similar to that shown in Fig. 5, but having improved means for transferring water between the containers, and Fig. 7 is a front elevational view of an embodiment of the system, provided with a third container including filter means.

There is seen in Fig. 1 a portable water purification system 10, for use in combination with fresh water 12 containing pathogenic microorganisms , but not containing harmful solids. If the water to be purified contains solids, the embodiment to be described below with reference to Fig. 5 is used.

A first transparent container 14 for water 12 is arranged to be exposed tα solar radiation 15 including wavelengths in the visible part of the spectrum, for effecting oxidation of said contained microorganisms. A useful container 14 is one having an openable top 18 and a capacity of 20 liters. Water delivery means 20, such as a faucet 22, are in fluid communication with the lower part of container 14.

Container 14 is suitably manufactured of a transparent thermoplastic such as acrylic, which has clarity comparable to glass, unusual weatherability, and good scratch resistance. Advantageously, container 14 is provided with a lower reflecting surface 16. In another embodiment (not shown), a part of the side wall is also coated to be reflective. Such reflective surfaces redirect the radiation which has passed through water 12 once to transverse the water a second time, and thus to continue its activity during its further passage.

There is provided a water dissolvable capsule or tablet 24 for insertion into the water 12. Said capsule or tablet contains inert, non-toxic photosensitizer 26, of the type which absorbs visible light and which, in turn, transfers some of the energy from this absorbed visible light to accelerate the oxidation of the microorganisms found in water 12. Photosensitizer 25 is selected from the group of such known materials, consisting of methylene blue, riboflavin, rose bengal, etc. Methylene blue is especially preferred. Capsule or table 24 may also contain desirable minerals and flavour-improving ingredients; since it is non-toxic, it will cause no lasting harm, even if it is accidentally swallowed.

A suitable relationship between the volume capacity of container 14 and the amount of active photosensitizer 26 is between 0.5-2.0 pp active ingredient. The capsule or tablet 24 is advantageously made tα correspond to this requirement. Preferably, the relationship between the volume capacity of container 14 and the amount of active photosensitizer 26 is predetermined to be between 0.5-1.0 mg of active photosensitizer 26 per liter of water 12.

In operation, container 14 is filled with pre-filtered water 12, and a capsule or table 24 is dropped into the water. Tablet 24 dissolves and colors the water 12; if necessary, the user can shake container 14 to improve distribution of the photosensitizer 26. The user then positions container 14 for exposure tα the sun. Under cloudy conditions, the process continues a_t a reduced rate, using diffused radiation.

Typically, after about 2 hours of exposure, the water 12 becomes clear, and the disappearance of coloring in the water signifies tα the user that water 12 is ready far drinking. Water 12 is withdrawn for use via faucet 22.

Referring now to Fig. 2, there is shown a portable water purification system 28, further comprising means 30, such as the illustrated small, removable cover 32, arranged to allow introduction of photosensitizer 26 into water 12 contained in the first transparent container 34. The container 34 is shown to have a shape which increases the radiation exposure area tα above that of a cylindrical tank of equivalent capacity, thus purifying water 12 at a faster rate.

Fig. 3 depicts a portable water purification system 36, further comprising a stirring means 38 for agitating water 12 contained therein. Such agitation is useful in achieving even distribution of the photosensitizer material 26. In the embodiment shown, agitator 40 is connected to a handle 42, for manual operation.

There is seen in Fig. 4 a portable water purification system 44, similar to that seen in Fig. 3; however, in system 44, the stirring means 46 is powered by a wind turbine 48. Wind turbine 48 shown is a device of the cup-anemometer type. Being mounted on a vertical axis 50, it requires no specific orientation relative to wind direction, which may vary. The wind turbine 48 has the advantage of providing continuous stirring tα a greater or lesser extent, depending on the prevailing wind conditions. Continuous stirring, however, is not required.

Referring now to Fig. 5, there is shown a portable water purification system 52, similar to that described above with reference tα Fig. 1, but further comprising a second transparent container 54, for prefiltering the water 12. The photosensitizer capsule or tablet 24 is inserted into the second container 54.

Second container 54 is in fluid communication with filter means 56 positioned thereabσve, and receives filtered water 58 from filter means 56. Filter means 56 is suitably comprised of a bed 60 of activated carbon particles. The bed 60 acts as an adsorbent for microscopic particles which are responsible for unwanted taste and odor. Adsorption takes place in the lattices, or on the surfaces, αf the granular carbon. Filter bed 60 is replaced when exhausted.

Advantageously, filter means 56 also comprises a fine filter 62, arranged to reduce the level of entrained solids tα a level below 500 pp . The fine solids filtering material is suitably made αf cellulose fibers or a tightly- woven cottαn fabric, to trap particles as small as 5 microns.

The second transparent container 54 is also exposable to solar radiation 15 including wavelengths in the visible part αf the spectrum, for acceleration of the oxidation of the microorganisms contained in the water. Container 54 is provided with a water delivery means 64, such as the valve 66 shown, for transfer of filtered, irradiated water tα the first transparent container 14. In the present embodiment 52, such a transfer is carried out manually, either using an additional, hand-held vessel (not shown), or by supporting the open, first transparent container 14 under the open valve 66 during filling.

Fig. 6 illustrates a portable water purification system 68, similar to that shown in Fig. 5; however, the first transparent container 70 is connected by a conduit 72 and a valve 74 tα the second transparent container 76. When the second transparent container 76 is positioned at a higher level than that of the first transparent container 70, and valve 74 is open, water will flow through conduit 72. Conduit 72 thus provides a more convenient method of filling the first container 70. For convenience in transporting the system 68, conduit 72 can be disconnected. Port 77 serves to allow the introduction of capsule or tablet 24 into the water in container 70. Advantageously, a stand 79 may be also provided, for supporting the first container 70 at a height below that of second transparent container 75.

Shown in Fig. 7 is a portable water purification system 78, similar to that described above with reference to Fig. 5, but further comprising a third transparent container 80. Container 80 acts a a filter housing, and is positioned above the second transparent container 82. Filter means 56 is mounted in the third transparent container 80, and is arranged to feed filtered water 84 to the second transparent container 82. Advantageously, there is further provided a manually-powered air pumping means 86, arranged to allow raising the pressure in the third transparent container 80 and thereby increasing the water filtration rate. Means 86 shown comprise a hand pump 88; a foot pump (not shown) could alternatively be used. The increased pressure in the third container 80 is αf particular benefit when filter means 56 includes a very fine filter 62, which is used to remove very small particles. The additional pressure substantiality reduces the filtering time_*

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 αf equivalency of the claims are therefore intended to be embraced therein.

Claims

CLAIMS:

1. A portable water purification system for use in purifying water containing microorganisms, comprising: a container for said water, said container being adapted to expose water in said container to solar radiation including wavelengths in the visible part of the spectrum, for effecting oxidation of said microorganisms; an inert, non-toxic photosensitizer, said photosensitizer being of the type which absorbs visible light and which, in turn, transfers some of the energy from said absorbed visible light to accelerate oxidation of said microorganisms; and water delivery means, for exit of water from said container.

2. A portable water purification system according to Claim 1 for production of drinking water.

3. A portable water purification system according to Claim 2 wherein the photosensitizer is water-dissolvable.

4. A portable water purification system according to any previous claim for use in purifying fresh water containing pathogenic microorganisms, comprising: at least one transparent container for said water, said container being exposable to solar radiation including wavelengths in the visible part of the spectrum, for effecting oxidation of said microorganisms; a water-dissolvable capsule or tablet comprising inert, non-toxic photosensitizer, said photosensitizer being of the type which absorbs visible light and which, in turn, transfers some of the energy from said absorbed visible light to accelerate the oxidation of microorganisms found in said water; and water delivery means, in fluid communication with the lower part of said container.

5. A portable water purification system according to any previous claim, wherein the relationship between the water volume capacity of said container and the amount of active photosensitizer is predetermined to be between 0.5-2.0 pp active ingredient.

6. A portable water purification system according to any of Claim 1 -4, wherein the relationship between the water volume capacity of said container and the amount of active photosensitizer is predetermined to be between 0.5-1.0 mg of active photosensitizer ingredient per litre of water.

7. A portable water purification system according to any previous claim comprising a capsule or tablet containing said photosensitizer and also containing desirable minerals and flavour-improving ingredients.

8. A portable water purification system according to any previous claim, further comprising means arranged to allow the introduction of said photosensitizer into the water contained in said first transparent container.

9. A portable water purification system according to any previous claim, further comprising a stirring means for agitation of the water contained therein.

10. A portable water purification system according to Claim 9, wherein said stirring means is powered by a wind turbine.

11. A portable water purification system according to any previous claim, wherein said container is provided with a lower reflecting surface.

12. A portable water purification system according to any previous claim, further comprising a second container arranged to be in fluid communication with filter means positioned thereabove, and arranged to receive filtered water from said filter means; said second container also being adapted to expose water therein to solar radiation including wavelengths in the visible part of the spectrum, to accelerate the oxidation of microorganisms contained therein, and being further provided with a water delivery means for transfer of filtered, irradiated water to said first transparent container.

13. A portable water purification system according to Claim 12, wherein a first transparent container is connected by a conduit and a valve to a second transparent container, whereby when said second transparent container is positioned at a higher level than that of said first transparent container and said valve is open, water will flow through said conduit.

14. A portable water purification system according to Claim 12 or 13, further comprising a stand configured to support said first transparent container at a height below that of said second transparent container.

15. A portable water purification system according to any of Claims 12 to 14, wherein said filter means comprises a bed of activated carbon particles.

16. A portable water purification system according to any of Claims 12 to 15, wherein said filter means is a fine filter arranged to reduce the levei of entrained solids to a level below 500 ppm.

17. A portable water purification system according to any of Claims 12 to 16, further comprising a third transparent container positioned above said second transparent container, said filter means being mounted in said third transparent container and being arranged to feed filtered water to said second transparent container.

18. A portable water purification system as claimed in Claim 17, further comprising a manually-powered, air pumping means arranged to allow raising the pressure in said third transparent container, thereby increasing the water filtration rate.