WO2001018456A1

WO2001018456A1 - Apparatus and method for treatment of air

Info

Publication number: WO2001018456A1
Application number: PCT/SE2000/001748
Authority: WO
Inventors: Kjell Ekberg
Original assignee: Otre Ab
Priority date: 1999-09-08
Filing date: 2000-09-08
Publication date: 2001-03-15
Also published as: SE9903177D0; SE9903177L; AU7566300A

Abstract

The invention resides in a purification and sterilization device having an air inlet (102, 202) and an air outlet (103, 203), said inlet and outlet joined by an air duct, said air duct provided with at least one filter (110, 210) through which essentially all air entering the device has to pass, means (125, 132, 232) provided for mixing ozone into a liquid, preferably water, thereby forming an ozone-water solution at least part of said ozone-water solution recirculated in the device, the filter (110, 210) adapted to be soaked or wetted in or by said solution. The invention also resides in a mixing means for use with the purification and sterilization device. The invention also resides in a method for purification and sterilization of a gas comprising the following steps: providing an ozone-water solution having controlled amounts of ozone therein, by dissolving freshly prepared ozone in a recirculated ozone-water solution in dependence of the ozone-concentration of said recirculated ozone-water solution; said dissolving accomplished by feeding said freshly prepared ozone through micro-porous nozzle arranged in said recirculated solution; withdrawing ozone-water solution from said ozone-water solution having controlled amounts of ozone therein; wetting or soaking one or more filters through which gas is made to pass, thereby forcing said gas in contact with the ozone-water solution.

Description

Apparatus and method for treatment of air.

The present invention relates to an apparatus and a method for treatment of air for the purpose of purifying, disinfection, and or sterilization of air. The word "air" should in the context below be understood as relating to a gas mixture breathable by humans/animals. It is clear that any gas could be treated in this manner for the same purpose using the same equipment.

Background of the Invention A number of factors have contributed towards the growing problem of air- contamination in commercial, industrial and residential buildings. The problems also exist in connection with hospitals, wards for treating infections, operational areas and post-operational wards. Another area of concern is aircraft for transport of passengers etc. Many more areas of interest may be though of and the stated areas may serve as examples only.

In many buildings air-conditioning is installed, often in conjunction with humidifiers of different kinds to make the ambient air comfortable and to exchange stale air for fresh air. For energy conservation reasons the buudings are built to be very tight and to minimized the loss of warm indoor air to the outside and to minimize the intake of cold outside air into the building. The air inside the bunding carries not only contaminants from materials used in the bunding and the materials of the fnπiiture but also dust and spores and other small particles which serve as vehicles to carry microbiological contaminants.

As regards the humidifiers they have sometimes been part of the problem in that the water as such has to be kept clean so that the humidifier doesn't contribute to the contaminants. One example is reported outbreaks of so called humidifier fever. In an aircraft the problem is the same since part of the air is recirculated during the flight and only part of the same is exchanged for new air taken from the outside.

It is well-known that these air-borne contaminants cause different health-problems and also actually may carry disease from one person to the other.

Ehmination of germs, etc through the use of poisonous substances is not allowed in most countries if these substance can reach the space in which persons are present.

Apparatuses for purifying indoor air are known from e.g. DE,A1,33 32 176,

US,5, 186,903, US,4,434,765, US,4,863,687, US,5,656,063, DE,A1,19 513 943, and EP,A2,0 707 178.

The present invention seeks to provide an improved apparatus and method for purification and/or sterilization of air.

According to an aspect of the present invention there is provided a purification and sterilization device having an air inlet and an air outlet, said inlet and outlet joined by an air duct, said air duct provided with at least one filter through which essentially all air entering the device has to pass, means provided for mixing ozone into a liquid, preferably water, thereby forrning an ozone-water solution at least part of said ozone-water solution recirculated in the device, the filter adapted to be soaked or wetted in or by said solution.

According to another aspect of the invention there is provided a method for purification and sterilization of a gas comprising the following steps:

providing an ozone-water solution having controlled amounts of ozone therein, by dissolving freshly prepared ozone in a recirculated ozone-water solution in dependence of the ozone-concentration of said recirculated ozone-water solution said dissolving accomplished by feeding said freshly prepared ozone through micro- porous nozzle arranged in said recirculated solution,

withdrawing ozone-water solution from said ozone-water solution having controlled amounts of ozone therein.

wetting or soaking one or more filters through which gas is made to pass, thereby forcing said gas in contact with the ozone-water solution.

Embodiments of the invention will be described below, by way of example.

Brief Description of the Drawings:

Fig. 1 shows a first embodiment of an apparatus according to the invention in section. Fig. 2 shows the embodiment in Fig. 1 in section along A - A.

Fig. 3 shows a plane view of an embodiment of a filter for use in an apparatus according to the invention.

Fig. 3 a shows a side view of the filter according to Fig. 3.

Fig. 3b shows a side view of a further embodiment of the filter according to Fig. 3. Fig. 4 shows in section part of an embodiment of the ozone generating and mixing part of the apparatus shown in Fig. 1.

Fig. 5 shows in section part of a further embodiment of the ozone generating and mixing part of the apparatus shown in Fig. 1.

Fig. 6a shows an embodiment of a mixing chamber for use in the apparatus in Fig. 1.

Fig. 6b shows the mixing chamber according to Fig. 6a partly in section.

Fig. 7 shows a second embodiment of an apparatus according to the invention in section.

Fig. 8 shows the embodiment in Fig. 7 in section along B - B. Detailed Description of Preferred Embodiments

Referring to Fig.l an air treatment system includes a housing 101 having an air inlet 102 for air to be treated and an air outlet 103 for treated air, a fan 104 for drawing air into the system, an interior duct passage connecting the air inlet 102 with the air outlet 103. At the outlet 103 an ozone destruction filter 105 is arranged through which the treated air is forced to pass.

Within the interior duct passage a filter 110 is arranged through which the air to be treated is passed. The filter 110 is in the form of a rotating filter. The filter may be formed from a stainless steel net. In the figure the filter 110 is shown arranged on a shaft 111, driven by a motor 112 via a shaft coupling 113 and a transmission 114. The filter is disk-formed and arranged in a stepped up cylindrical segment 115 of the interior duct passage arranged between an inlet segment 116 of the interior duct passage and an outlet segment 117 of the interior duct passage.

The outlet section 117 is inclined from the outlet 103 towards the stepped up cylindrical segment 115 of the interior duct passage, thus providing for any condensed liquid to be transported back to the cylindrical segment.

The lower portion of the cylindrical segment 115 reaches below the inlet segment 116 and outlet segment 117 of the interior duct passage thereby forming a tank 118. The tank 118 is arranged to hold a liquid medium 119 into which the filter 110 dips. This liquid medium is according to one embodiment of the invention "ozone-water", which term refers to water comprising a solution of ozone. Other chemicals may be added to the water in other embodiments, either in combination with ozone or without ozone.

Further within the housing 101 an ozone generator 120 is arranged having a control unit 121 comprising the control circuits and power supply for the electrode etc., a unit 122 comprising the ozone generating electrode/s and a unit 123 comprising air/oxygen pump for pumping air oxygen to the ozone generator. A non-return valve 124 is provided at the outlet from the ozone generator unit 122. This will be further described in connection with Fig. 4.

Further a dissolving means 125 may be seen at the bottom of the tank 118 provided to dissolve the ozone produced in the liquid present in the tank 118.

In Fig. 2 is shown a section along the line A-A in Fig. 1 looking from the outlet segment 117 of the internal duct towards the wider cylindrical segment 115 of the interior duct passage, the bottom part of which forms the tank 118, in which the filter 110 is disposed. The liquid medium 119 in the tank 118 is shown as well as the wall of the outlet segment 117 of the interior duct passage. The shaft 111 holding the filter 110 is also shown.

In Fig. 3 two embodiments of the filter 110 according to the invention are shown. The filter 110 according to the described embodiment of the invention generally comprises a filter surface made from e.g. stainless steel net or other for the purpose sufficient material. In fig 3 a the filter in Fig. 3 is seen in a side view. One or several essentially circular flat units 110a, 110b, etc. may make up the filter as is shown in Fig. 3B. The net may be pleated radically or axially in order to increase the working surface of the filter. When several filter units are used they may be arranged adjacent to each other or spaced from each other as is shown in Fig. 3b.

Generally the filter used according to the invention may exhibit mesh-sizes chosen such that it is ascertained that all air comes into contact with the liquid medium. The mesh-sizes also depend on the number of consecutive filters used.

In Fig. 4 one embodiment according to the invention of the ozone generating arrangement for dissolving ozone in the liquid medium 119 in the tank 118 shown. The arrangement comprises an air pump 123, an air inlet conduit 126 to the ozone generating unit 122, said unit 122 comprising the ozone generating electrode/s, an ozone generator control unit 121 comprising the control circuits and power supply for the electrode etc. The unit 121 and 122 are electrically connected for control signals and power supply via a connection 130 and the ozone from the ozone generating unit 120 is forwarded to the dissolving means via an ozone outlet conduit 131.

In the tank 118 a dissolving means 125 is arranged at the bottom of the tank. The dissolving means 125 is connected to the ozone producing unit 122 via an outlet conduit 131 connected to the dissolving means 125 via the non-return valve 124. The dissolving means 125 may comprise a nozzle of the type described later in connection with Fig. 6.

Some of the generated ozone will bubble up through the liquid medium (water) 119 in the tank 118 without being dissolved. However, this ozone may be active in gas phase disinfecting the air passing through the interior duct passage and possibly circumventing the filter 110.

This all depends on the construction of the passage at the filter. Several possibilities are open, either to seal of the filtering part such that the air coming through the internal duct passage has to pass through the filter or to let some of the air pass beside the filter depending on the degree of purificatiori/sterilization wanted in each specific instance. There is the option of sterilizing all air entering a specific area or the option to gradually let most of the air in an area repeatedly pass through an embodiment a device according to the invention.

The ozone generated may use air or oxygen as the starting material. Air will of course give a lower ozone concentration.

In Fig 5 a further embodiment according to the invention of the ozone generating arrangement for dissolving ozone in the liquid medium 119 in the tank 118 shown. The arrangement comprises an air pump 123, an oxygen inlet conduit 126 to the ozone generating unit 122, said unit 122 comprising the ozone generating electrode/s, an ozone generator control unit 121 comprising the control circuits and power supply for the electrode etc. The unit 121 and 122 are electrically connected for control signals and power supply via an electrical connection 130.

From the ozone generating unit 122 in which ozone or an ozone-oxygen mixture is generated a conduit 131 exhibiting non-return valve 124 leads to a mixing chamber 132 for dissolving the ozone/air or the ozone/oxygen mixture into the liquid medium, e.g. water present in the tank 118. The mixing chamber exhibits a return conduit 136 for the liquid medium having dissolved ozone to the tank 118. From the tank 118 a suction conduit 133 is arranged for drawing water from the tank, a pump 134 for pumping said water further on through a feed conduit 135 to the mixing chamber 132. In the tank 118 there will thus exist a re-circulating liquid solution having ozone therein. The ozone-solution will in this embodiment be more stable than in the first embodiment.

However, the choice between the two embodiments and any further embodiment within the scope of the appended claims will depend on the circumstances and the expected degree of sterilization.

In Fig. 6a and 6b is shown an embodiment of a inixing chamber according to the invention. The numbers used for details in Fig. 6a and 6b correspond to each other. In Fig. 6a the chamber is shown from the outside displaying an inlet 1 for water and one inlet 2 for ozone and an outlet 3 for the water/gas solution. In Fig 6b the same chamber is shown in another view and partly in section. In the figures an atomization nozzle 5, preferably made from sintered ceramics or stainless steel is shown, which nozzle is used for dispersing the gas in the water in the chamber. The nozzle exhibits a channel 6 (closed at the end of the nozzle) through which the gas enters the nozzle and therefrom penetrates through the nozzle walls into the chamber 9 in which the gas is dissolved into the liquid. The nozzle is shown being in sealing contact with the inner walls of the walls of the chamber 9. The liquid passes from the liquid inlet 1 to the liquid-gas inixture outlet (3) and thereby a pressure diffenrence is created before and after the nozzle 5 such that the gas i made to diffuse through said porous nozzle.

The important factor in choosing the material in the mixing chambers is that a material is chosen, which, if possible, is inert to ozone and which does not show any catalytic effect on the decay of the ozone. In order to achieve a good mixing of the ozone gas with the water it is essential that the gas is atomized by means of the sintered atomizing nozzle or any other injection means giving the same effect.

In Fig. 7 yet a further embodiment of the invention is shown in which the filter 210 is stationary. In the figure is shown an air treatment system comprising a housing 201 having an air inlet 202 for air to be treated and an air outlet 203 for treated air, a fan 204 for drawing air into the system, an interior duct passage connecting the air inlet 202 with the air outlet 203. At the outlet 203 an ozone destruction filter 205 is arranged through which the treated air is forced to pass. The ozone destruction filter may e.g. be a carbon filter.

Within the interior duct passage two filters 210 are arranged through which the air to be treated is passed. The filters 210 are stationary filters. There may be one ore more filters arranged after each other depending on the application. The filter/-s 210 may be formed from a stainless steel net. The filters may also be made from any other suitable material which can be used in the environment of the ozone water.

The filter/-s are arranged in a stepped up segment 215 of the interior duct passage between an inlet segment 216 of the interior duct passage and an outlet segment 217 of the interior duct passage. The area of the duct in the stepped up portion measured in the transverse direction may be formed in several ways as long as the filter/^'-s 210 are made to fit to the cήcumference of the duct, such that all air must pass through the filter/'-s 210. The lower portion of the segment 215 reaches below the inlet segment 216 and outlet segment 217 of the interior duct passage thereby forming a tank 218. The tank 118 is arranged to hold a liquid medium 219 into which the filter 210 dips. This liquid medium is according to one embodiment of the invention "ozone-water", which term refers to water comprising a solution of ozone. Other chemicals may be added to the water in other embodiments, either in combination with ozone or without ozone.

There is also a possibility of using this apparatus with other liquids or non-water based solutions for disinfection and/or purification of air or other treatment of gases in general.

The outlet section 217 of the duct is inclined from the outlet 203 towards the stepped up segment 215 of the interior duct passage, thus providing for any condensed liquid to be transported back to the cylindrical segment.

F rther within the housing 201 an ozone generator 220 is arranged having a control unit 221 comprising the control circuits and power supply for the electrode etc., a unit 222 comprising the ozone generating electrode/s and a unit 223 comprising air/oxygen pump for pumping air or oxygen to the ozone generator. A non-return valve 224 is provided at the outlet from the ozone generator unit 222. From the nonreturn valve 224 the ozone generated in passed to a mixing chamber 232, e.g. a mixing chamber as described in connection with Fig. 5 and Fig.6. The ozonated water is transported via conduit/-s 240 to one or more spray nozzles 227 preferably situated near the uppermost part of the stepped-up portion 215 such as to spray the filters with the ozonated water. The ozonated water 219 is thereafter collected in tank 218 formed by the bottom part of the stepped-up portion.

It should be understood that in the embodiment according to Fig. 7 the arrangement present in Fig. 4 may be applied, i.e. the means for dissolving ozone in the liquid may have the form of a micro-porous nozzle placed in the bath 218 for dissolving ozone therein and the ozone-water solution to be sprayed onto the filters be pumped from the bath up to the nozzles 227.

In Fig. 8 the further embodiment according to Fig. 7 is shown in section along the line B - B in Fig. 7 looking from the outlet segment 217 of the internal duct towards the wider segment 215 of the interior duct passage. In the figure the bottom part of the stepped up part of the air duct in which the tank 218 is shown. The filter 210 is shown dipping into the liquid medium 219 in the the tank 218. The wall of the housing 201 of the interior duct passage is shown as well as nozzles 227 which via conduit 240 are provided with the ozone-solution to be sprayed onto the filter 210.

The device according to Fig. 1 and 2 functions in the following way. Contaminated air is sucked in through the opening 102 by the fan 104, passes through the inlet segment 116 of the interior duct passage and through the upper part of the rotating filter 110. The filter 101 which is fixedly fastened to the shaft 111 dips down into the tank 118 provided by the wider cylindrical segment 115 of the interior duct passage and the shaft 111 driven by the motor 112 makes the filter pass through the liquid provided in the tank 118. Bacteria and germs etc which fastens on the filter is killed/destroyed by a sterilizing agent, e.g. ozone, dissolved in the liquid medium. The liquid medium also exerts a rinsing action on the filter. Some of the liquid medium will also stick to the fine-mesh filter. The rotational speed of the filter is adapted to the airflow and type of ambient atmosphere, e.g. a ward for infectious decease or an operational theater. Cleaned/purified air passes through the outlet segment 103 of the interior duct passage. The segment may exhibit a bend as is shown in the figure such that moisture present in the air after the passage through the liquid medium may flow back into the tank 118.

The device according to a further embodiment of the invention may also be use as a humidifier at the same time. The device according to Fig. 7 and Fig. 8 functions in the following way. Contaminated air is sucked in through the opening 202 by the fan 204, passes through the inlet segment 216 of the interior duct passage and through the upper part of the filter 210, which is not below the liquid level in a tank 218. The filter 210 which is fixedly, but removably fastened in the device dips down into the tank 218 provided by the wider segment 215 of the interior duct passage. As the filter/'-s in this embodiment are not rotatable the section of the air duct and the stepped up portion do not necessarily have to have an tubular form, round or oval but may exhibit any form, which is suitable for the purpose. The liquid 219 in the tank 218 works as a water-seal.

A conduit 240 is provided from the mixing chamber 232 in the ozone generator 220. The conduit carries the ozonated water from the mixing chamber 232 to the uppermost part of the stepped up portion 215 of the air duct passage where nozzles are provided. These nozzles are provided to spray the filter/'-s 210 and the space in- between them with ozonated water from the mixing chamber. The ozonated water is then in this embodiment with-drawn from the tank 218 into the nixing chamber 232 in the amount that is needed in order to mix fresh ozone into the water.

It should be born in mind that the ozone in the ozone-water solution is slowly decomposed and also that some of the ozone even escapes from the solution before decomposing. Also the action on bacteria, germs and other substances on which ozone works through its strong oxidizing effect lowers the ozone-content in the solution.

Bacteria and germs etc which fastens on the filter is killed/destroyed by a sterilizing agent, e.g. ozone, dissolved in the liquid medium. The liquid medium also exerts a rinsing action on the filter. Some of the liquid medium will also stick to the fine- mesh filter. The spraying action of the nozzles, the concentration of ozone in the water and the crating in the space in-between the filters of small droplets of the ozonated water will be adapted to the airflow and type of ambient atmosphere, e.g. a ward for infectious decease or an operational theater. The droplets will of course also as well as the filter/'-s contribute to the air cleansing action of the apparatus.

Cleaned/purified air thereafter passes through the outlet segment 217 of the interior duct passage. The segment may exhibit a bend as is shown in the figure such that moisture present in the air after the passage through the filters may flow back into the tank 218.

The device according to this further embodiment of the invention may also be use as a humidifier at the same time.

Excess ozone not spent in the purifymg/sterilizing process may also in this embodiment be eliminated in filter 205, e.g. an active charcoal filter. The device thus may be used immediately adjacent to a person since no ozone will be present in the ambient air. It is possible to allow a certain amount of ozone gas to pass by the ozone filter 205 thus making it possible to sterilize the room in which the device is situated. If humans are present in the room the regulations as to allowable amounts of ozone has to be followed.

The device for making an ozone-water solution "active water" described in the applicants own PCT/SE99/00298 for ascertaining that the ozone content of the ozone-water liquid is kept constant within narrow limits may be used as the ozone generator described in the embodiments above. However, if such constant ozone content in a water-solution may be attained in any other way this solution will also possible to use.

Addition of other chemicals of ozone water should also be considered to be within the scope of the invention.

Changes within the scope of the invention comprises such as, placing the fan after the filter 104,204, the inlet 102,202 may be provided with a pre-filter, the preparation of the sterilizmg/purifying liquid medium may be performed according to Fig.4 or Fig. 5, replenishment with water to the liquid medium may be controlled using automatic controls such as liquid level indicators, refilling valve alternatively manual refilling, and the tank 118,218 comprising the sterilizing liquid medium being coupled to a drain for intermittent withdrawal.

Claims

1. Purification and sterilization device having an air inlet (102,202) and an air outlet (103,203), said inlet and outlet joined by an air duct, said air duct provided with at least one filter (110,210) through which essentially all air entering the device has to pass, means (125, 132,232) provided for mixing ozone into a liquid, preferably water, thereby foiming an ozone-water solution at least part of said ozone-water solution recirculated in the device, the filter (110,210) adapted to be soaked or wetted in or by said solution.

2. Purification and sterilization device according to claim 1, characterized in that an ozone destruction filter (105,205)is provided at the air outlet (103,203).

3. Purification and sterilization device according to claim 1 or 2, characterized in that a fan (104,204) is provided for forcing the air to be purified through the device.

4. Purification and sterilization device according to any of the proceeding claims, characterized in that an ozone generating unit (120,220) is provided.

5. Purification and sterilization device according to any of the proceeding claims, characterized in that the air duct is provided with a stepped-up portion

(115,215) in which the at least one filter (110,210) is arranged, the bottom part of said stepped-up portion adapted so as to form a tank (118,218) adapted to hold a bath (119,219)comprising at least part of the ozone-water solution circulated in the device.

6. Purification and sterilization device according to any of the proceeding claims, characterized in that said at least one filter (110) is rotatably arranged in the stepped-up portion (115) such that at least one part of said at least one filter (110) at any moment is soaked or wetted in the ozone-water solution, while the air to be purified and or sterilized is made to pass through the part of the filter (110) that has been soaked or wetted.

7. Purification and sterilization device according to any of the proceeding claims, characterized in that that said at least one filter (210) is stationary arranged in the stepped-up portion (215), such that at least one part of said at least one filter (210), or an elongating part of the same, dips into the ozone-water solution contained in the tank (218), a pump (228) for pumping said ozone-water solution through said means (232) provided for mixing ozone into a liquid to at least one nozzle (227) arranged for soaking or wetting the part of the at least one filter (210) through which the air to be purified and/or sterilized is made to pass.

8. Purification and sterilization device according to any of the proceeding claims, characterized in that said means (125) provided for mixing ozone into a liquid, preferably water, thereby forming an ozone-water solution are provided within the tank.

9. Purification and sterilization device according to any of the proceeding claims 1 - 7, characterized in that said means (132,232) provided for mixing ozone into a liquid, comprises a suction conduit (113,213) to draw Uquid from the tank, a pump (134,228), a mixing chamber (132,232) comprising a micro-porous nozzle (5), and a return conduit (136,236), said means provided outside the tank.

10. Purification and sterilization device according to claims 8 - 9, characterized in that said nozzle is an atomization nozzle (5), preferably made from sintered ceramics or stainless steel.

11. Mixing means for estabtishing a liquid-gas mixture for the device according to claim 1-10, said mixing chamber having a liquid inlet (1), a gas inlet (2) and a liquid-gas mixture outlet (3), and a conduit (9) for joining said liquid inlet (1) and said liquid-gas mixture outlet (3) characterized by a porous member (5), at least at the upstream end of the member (5) being in sealing contact with the inner walls of said conduit (9), said member (5) having a first surface being in contact with the liquid and second surface being in contact with the gas, the dimensions of said conduit (9) being such that a pressure difference is created in the liquid before and after said member (5) such that the gas is made to diffuse through said porous member (5).

12. Mixing means according to claim 11 characterized in said porous member (5) exhibiting a through-bore (7) essentially co-axial with said conduit (9), the bore (7) constituting a constriction of the conduit (9), the inside walls of said through-bore (7) constituting said first surface, said inner walls having an essentially circumferential recess formed in the inner walls of the conduit essentially along the porous member (5) said recess connected with the gas inlet (2) giving the gas access to the outside of the porous member, said outside constituting said second surface.

13. Mixing means according to claim 11 characterized in said porous member (5) exhibiting a blind-bore (7),the blind-bore (7) communicating with the gas inlet (2), the inside walls of the blind-bore (7) thus constituting said second surface, the outer surface of the porous member (5) constituting said first surface in contact with the liquid, said porous member (5) constituting a constriction of the conduit (9).

14. A method for purification and sterilization of a gas comprising the following steps: providing an ozone-water solution having controlled amounts of ozone therein, by dissolving freshly prepared ozone in a recirculated ozone-water solution in dependence of the ozone-concentration of said recirculated ozone-water solution said dissolving accomplished by feeding said freshly prepared ozone through micro-porous nozzle arranged in said recirculated solution, withdrawing ozone-water solution from said ozone-water solution having controlled amounts of ozone therein, wetting or soaking one or more filters through which gas is made to pass, thereby forcing said gas in contact with the ozone-water solution.

15. A method according to claim 14, characterized by the dissolving being accomplished in a withdrawn portion of the recirculated ozone-water solution, the recirculated ozonewater solution thereafter returned to the solution.

16. A method according to claim 14, characterized by the dissolving being accomplished in the recirculated ozone-water solution