HK1118530B - A device and a method for purifying a liquid with ozone and recirculation - Google Patents

Description

Device and method for purifying and recycling a liquid by means of ozone

Technical Field

The present invention relates to a device and a method for purifying a liquid, in particular water, according to the preambles of the independent patent claims.

Background

In many parts of the world, drinking water sources contain microbial contaminants such as cysts, bacteria and viruses in addition to concentrations of inorganic chemicals such as ferrous iron, manganese, hydrogen sulfide, arsenic and fluoride which pose long-term health hazards or aesthetic problems.

Some regions can only deal with some of these problems or treatment facilities cannot always reliably deliver drinking water that meets the appropriate standards. If the source water contains significant amounts of organic matter such as humates, the sanitary facilities may introduce new toxic chemical contaminants in the form of trihalomethanes (THM's) due to the higher chlorination levels.

The water source may also be a private well for which the user is all responsible for their treatment system. However, few private users have the technical knowledge to properly treat and maintain such water supplies. There is therefore a need to provide an automatic device which is simple and easy to use, which is able to effectively treat water to the potable water standards set by the USEPA (united states environmental protection agency), and which is suitable for use by private individuals or office premises.

It is known in the art to subject water to a multi-stage treatment using a sediment filter, followed by activated carbon filtration to remove chlorine, followed by reverse osmosis to remove most of the salts and finally by activated carbon to remove trace organic compounds. Since reverse osmosis membranes generally have a low water treatment rate, the treated water must be stored in a storage device and the water must be prevented from being re-contaminated with bacteria. This makes periodic sanitization of the storage device necessary due to bacterial growth and the attendant waste and odor problems. These systems are not suitable for use on non-potable water unless the treated water storage is additionally chemically disinfected by ozone or lower levels of chloramine are dosed into the storage.

It is known to chemically sanitize drinking water for use. Ozone is a preferred chemical because of its nature that can be readily generated in situ, does not form potentially toxic halogenated byproducts (THM's), and reverts to molecular oxygen in a short period of time. There are a variety of devices known in the art.

US5,683,576 describes an ozone-based water treatment device suitable for residential use in terms of use and ingress. The apparatus includes a pretreatment filter, a batch ozone reactor (CT chamber), an ozone generator, a storage tank, and a microcontroller to treat water. The raw water passes through a pre-treatment filter to the CT where ozone is dissolved in the water to kill bacteria, viruses and other microorganisms. Ozone is produced in situ by an ozone generator. The treated water is pumped to a storage tank from which it is drawn as required. The storage tank is protected from airborne contaminants by an ozone-rich air blanket located in the gap between the level of the stored water and the top of the storage tank. Water from the CT is poured through the pad as it enters the storage tank. The stored water is periodically recycled back to the CT for reprocessing. Such devices have certain disadvantages. When water is recycled to the CT for reprocessing, ozonation of raw water is not possible because the CT is in use. The production efficiency of the device is therefore limited. Furthermore, the device only solves the problem of removing microbial components. Raw water typically contains inorganic contaminants, which are also considered.

Us6,475,352b2 describes a household water purifier using ozone injected into a recirculation system comprising a prefilter, an activated carbon main filter, a water treatment reactor and optionally an activated carbon polishing filter to filter the water just prior to dispensing. The operation of such a system is performed by a microcontroller and a pump with a valve system. The water must be circulated through the main filter and the reactor at least 3-8 times in order to achieve the proper level of microbial treatment. Although the apparatus will remove colloidal particles (either initially present or generated by oxidation of species during ozonation) and organic chemical contaminants, the apparatus does not provide a solution to the removal problem of inorganic ions such as arsenic or fluoride, which may be present at concentrations that pose a long-term health threat. Furthermore, it is not possible to store purified water while continuously treating raw water.

Disclosure of Invention

The object of the present invention is therefore to overcome the disadvantages of the prior art and in particular to provide a method and a device for purifying a liquid which allow an efficient purification of a liquid, such as raw water, in particular in terms of use during application. Furthermore, in the case where the purified liquid is not dispensed for a certain period of time, the device should automatically ensure that reliable purification is achieved and avoid the problem of recontamination. These and other objects are achieved according to the invention by a device and a method having the features of the independent patent claims.

The device is used essentially to purify liquids such as water from private wells or unreliable public sources that have the potential to be potentially unfit for drinking. The apparatus includes at least one ozonated reactive liquid treatment unit hydraulically connected to the source. The primary function of the ozonation reaction unit is to inactivate microbial contaminants that may be present in the raw water. The ozonation reaction unit generally comprises a batch reactor comprising a treatment tank, a source of ozone gas, an injector for introducing the gas in the form of small bubbles, suitable means for controlling the inflow and outflow of water and its level in the treatment tank, and a timer for controlling the treatment time.

The device is further provided with a storage reservoir hydraulically connected to the ozonation unit for storing the purified water until it is dispensed by a user. According to the invention, the device is further provided with recirculation means for recirculating the treated liquid from the storage reservoir through a recirculation line provided with at least one filtration unit. In contrast to the prior art, the treated liquid is not recycled from the storage reservoir to the ozonation unit. Instead, the treated liquid is fed through the filtration unit arranged in the recirculation line and returned to the storage reservoir. This design has several advantages. First, this makes it possible to recirculate the ozonated liquid from the storage reservoir through the filtration unit multiple times, thereby removing inorganic contaminants still present in the water after ozonation. This allows an optimal utilization of the filter medium due to the prolonged residence time due to the repeated treatment in the filter unit. Second, ozonation of fresh raw water can be performed in parallel with the recirculation cycle, which improves the efficiency of the device in terms of daily water treatment output.

According to a preferred embodiment of the invention, the device is further provided with means for ozonating the liquid in the storage reservoir and/or in the circulation line. If the liquid is ozonated in the storage reservoir during recirculation, dissolved ozone will also be transported through the circulation line and any valves, connections or filter devices arranged therein. Thus, microbial growth processes in components of the hydraulic system and in the filtration unit are inhibited or completely prevented, depending on the frequency and concentration of the ozonation process. Although such ozonation is preferred for a recirculation unit comprising a filtration unit as described above, ozonation of the purified liquid in the storage tank is also preferred without such recirculation. In particular, if the state in which the liquid has not been dispensed has continued for a certain time, it may be preferable to ozonate the liquid contained in the storage tank from time to time. By providing an ozonation unit for ozonating raw water and an additional means for ozonating the purified water in a storage reservoir, ozonation of raw water and re-ozonation of the purified water can be performed in parallel. Consequently, re-ozonation does not have any negative impact on the ozonation process of the raw water in the ozonation reaction unit or on the daily output of the treatment system.

At least a portion of the recirculation line preferably forms part of a hydraulic connection between the ozonation reaction unit and the storage reservoir. It is especially preferred to arrange a filtration unit in the recirculation line so that ozonated water pumped from the ozonation reaction unit to the storage reservoir will be fed through the filtration unit in the recirculation line. It is also possible to use different filter units for transport and recirculation. In this way, contaminants may be removed during transport from the ozonation reaction chamber to the storage reservoir, and the concentration of the contaminants may be further reduced by each pass through the filter while being recycled. The increase in contact time between the filter media and the treated water thus allows for faster treatment with filters of smaller, less effective size or with higher recirculation flow rates.

According to a further embodiment of the invention, the device may be provided with timing and control means for periodically recirculating the liquid through the recirculation line. This is particularly preferred for ozonation of the liquid in the storage reservoir to prevent regrowth of microbial contaminants.

It is also possible, in addition or alternatively, to provide the device with a pump and control means for automatic recirculation of the liquid until the concentration of contaminants to be removed from the liquid by the filter unit has decreased below a predetermined level. Of course, means for periodic recirculation of the liquid and means for initial recirculation of the liquid until a certain concentration of contaminants is achieved may be provided in the same device.

In a preferred embodiment, the filtration unit in the recirculation line is preferably intended for partial or complete removal of inorganic ions such as arsenides and/or fluorides. It has been found that for arsenic in trivalent, arsenite form, ferrous, divalent form, and trivalent, manganous form, ozone treatment of the water in the ozonation reaction unit oxidizes such contaminants to higher valence levels, which contaminants at the valence levels can be removed in subsequent filtration units. In order to remove the resulting soluble pentavalent arsenate ions, the subsequent filtration unit is preferably an activated alumina filter.

According to a further preferred embodiment of the invention, the recirculation line may be provided with further filtration means arranged upstream of the activated alumina filtration unit. The filter device may preferably be a set of ultra fine glass fibre and activated carbon block filters. Such a filter will remove any colloidal oxides formed from iron and manganese, as well as dissolved organic molecules. The filter also removes potentially carcinogenic bromate ions that may be formed from bromide ions present in the water during ozonation.

The ozonation unit of the present invention is preferably designed to ozonate a certain predetermined amount of liquid in a batch-wise manner. This allows the ozonation process to continue for a time sufficient to reach the desired treatment level even if the user should dispense water from the storage tank. Furthermore, this allows for the purification of water and refilling of the storage reservoir even when purified water is not being dispensed.

According to another preferred embodiment, the device may be provided with a gas conduit between the ozonation reaction unit and the storage reservoir. In the presence of excess ozone, which must be allowed to exit the ozonation reaction unit, can be transported to the storage reservoir through this conduit. This allows a particularly simple ozonation process to be carried out in the storage reservoir by the same ozone generator. According to this preferred embodiment, the storage reservoir is provided with an activated carbon exhaust filter for removing ozone from the carrier gas stream (air or oxygen) being discharged from the storage reservoir, since it is undesirable from the point of view of the health and safety of the user to let large amounts of ozone into the area of the water purifier that is arranged immediately thereafter.

According to another preferred embodiment of the invention, the device may be provided with one single ozone generator. The generator may be connected both to the ozonation reaction unit and to the storage reservoir. Suitable valves may allow for the supply of ozone to either or both of the ozonation unit and the storage reservoir.

The device according to the invention is preferably provided with a pump for supplying the liquid. The pump may be used primarily to feed the liquid from the ozonation reaction unit to the storage reservoir. Since the liquid is to be fed through the filter unit, it is preferred to have the pump feed the liquid at a constant flow rate.

It is particularly preferred that the pump is hydraulically connected to the storage reservoir by valve means, such that in a first mode of operation the pump is adapted to feed liquid from the ozonation unit to the storage reservoir. In a second mode of operation, the pump is adapted to recirculate liquid through the filter unit and the recirculation line. In a third mode of operation, the pump is adapted to supply the purified liquid from the storage reservoir to a dispensing spout. All liquid supplies can be achieved by one and the same pump and by using appropriate valves.

According to a further aspect of the invention, a method for purifying a liquid, in particular water, is provided. In a first step, the liquid is ozonated in an ozonation unit. The ozonated liquid is then transferred to a storage reservoir. Whereby the liquid is preferably fed through at least one filter unit. In a final step, the liquid is recirculated from the storage reservoir through a recirculation line and back to the storage reservoir through at least one filtration unit. The liquid is preferably fed through the same filtration unit during transport from the ozonation unit to the storage reservoir and during recirculation. Suitable piping and valves allow selective connection of the filtration unit to the recirculation line or to a transfer line connecting the ozonation unit to the storage reservoir.

The liquid may be recirculated from time to time, for example periodically. The recirculation is preferably performed if a state in which the amount of purified water dispensed is too low has continued for a predetermined time. This recirculation is combined with periodic ozonation of the storage reservoir to prevent bacterial regrowth when not in use.

Alternatively, it is also possible to recirculate the liquid for a certain time or a certain number of times after it has been delivered from the ozonation reaction unit. The recycling is performed until the amount of contaminants in the liquid is reduced below a predetermined level. The amount of contaminants can be measured directly by measuring their content or empirically by recirculating the water for a certain time. Of course, it is also possible to initially recycle the liquid to reduce the amount of contaminants and thereafter periodically recycle the liquid after ozonation of the storage reservoir to prevent biological material regrowth.

According to a further preferred embodiment of the invention, the ozonized liquid is fed through a double filtration device before entering the storage reservoir, preferably passing the liquid through an activated carbon block filter for removing colloidal particles and dissolved organic matter, followed by an activated alumina filter for removing inorganic ions such as arsenide or fluoride.

According to a further preferred embodiment, the liquid is ozonated in batches in the ozonation reaction unit. Thus, a predetermined amount of liquid is treated in the ozonation reaction unit, and the treated amount of liquid is then fed to the storage reservoir after being treated with ozone. This allows for continuous batch mode treatment of raw water in the ozonation unit. Purified water may be dispensed from the storage reservoirs in parallel.

According to a further preferred embodiment, the purified liquid in the storage reservoir is at least temporarily subjected to ozone in the storage reservoir. This temporary treatment, which is performed in addition to the ozonation performed in the ozonation unit, avoids the occurrence of regrowth of biological material.

It is especially preferred that excess ozone in the ozonation unit is fed to the storage reservoir. If the amount of ozone is insufficient, a direct connection can be made between the storage reservoir and the ozone generator.

It is further preferred to remove ozone contained in the storage reservoir in the gas phase from the gas stream that is discharged from the storage reservoir. For this purpose, the gas flow may be fed through an exhaust gas filter. This filtered exhaust gas avoids contamination of the environment surrounding the device with ozone.

The liquid is preferably fed through the filter unit at a constant flow rate. It has been found that by using a constant flow rate, optimal filtration results can be achieved.

According to the invention, the liquid can be moved along different paths. In a first mode of operation, the liquid is movable from the ozonation unit to the storage reservoir. For this delivery, a pump may be used, preferably a pump that supplies the liquid at a constant flow rate. In a second mode of operation, the liquid is circulated through the filtration unit by the pump. In a third mode of operation, the liquid may be dispensed by the same pump. If appropriate valves and piping are utilized, the same pump may be utilized for different purposes.

It is further preferred that the liquid in the storage reservoir is ozonated during or just prior to recirculation. Ozone dissolved in the liquid moves through the filter unit and/or other components of the recirculation device. Thereby preventing re-growth of bacteria in parts of the recirculation device, such as valves, pipes or filter units.

According to the present invention it is further preferred that the raw water is treated by oxidizing contaminants in the liquid during ozonation and that the oxidized contaminants are removed in the filtration unit. It has been found that known filter units using activated alumina show an improved removal efficiency in the treatment of inorganic contaminants, such as arsenides, if the raw water has been previously treated with ozone. Although this removal principle thus has considerable advantages, it is particularly preferred to carry out the above-mentioned recycling, since the removal efficiency is reduced at a pH > 7 and the recycling can restore some of the efficiency lost in a single pass.

According to a further preferred embodiment of the invention, the device further comprises a microprocessor with suitable software programs to place the above-mentioned preferred embodiment in one or more of the following operating modes:

A. reaction & storage mode: -treating raw water in the reactor for a predetermined ozone treatment time, after which the water is pumped through the one or more filters and stored in the storage means.

B. Periodic reservoir ozonation & recirculation: the water in the storage device is subjected to ozone treatment for a predetermined time (storage device treatment time) while recirculating water from the storage device through the filter and back to the storage device. The program further allows the user to set the number of such treatments to be performed on the reservoir and to set a specific number between treatments.

C. Stagnation period ozonation treatment: if the purifier is not in use for a predetermined time, the program automatically ozonates any water located in the reaction chamber and in the reservoir for a predetermined time and after a predetermined stagnation period.

Drawings

The following description is made, by way of example only, with reference to the accompanying drawings, in which preferred embodiments of the invention are shown:

FIG. 1 diagrammatically illustrates the principles of the present invention;

figure 2 schematically shows a device according to the invention; and

fig. 3a to 3e show different modes of operation of the invention of the present patent.

Detailed Description

Fig. 1 schematically shows elements in a device 1 for purifying water according to the invention.

Raw water (raw water) W1 is provided from a water source 10. Particulate and colloidal inorganic matter in the source water W1, which is not suitable for drinking, is first prefiltered by prefilter 16. The pre-filter 16 comprises a layer of ultra-fine glass fibres of nominal thickness of 1 μm, followed by activated carbon blocks to substantially remove any dissolved or colloidal organic material. By reducing the concentration of organic material present, in addition to the aesthetic treatment of the water W1 to remove the haze materials, less ozone will be required at the next stage.

The pretreated water W2 is directed into an ozonation arrangement 8 having an ozone generator 32 and an ozonation reaction chamber 18 (see fig. 2) for sanitizing pretreated water in the ozonation unit 8. As (III +) arsenite is thereby oxidized to the As (V +) arsenite form. Ozonation is carried out in a batch mode for a certain fixed time depending on the production capacity of the ozone generator, the estimated ozone demand and the ct (concentration x time) required to reduce the amount of pollutants to the required extent. For disinfection purposes to meet the guidelines of the U.S. environmental protection agency, cysts&The log reduction for the virus was 4 and for the bacteria was 7 (i.e., 10)⁴Or 10⁷Reaction). Any excess ferrous or manganous ions in the water will also be oxidized to ferric or manganic valence and form colloidal particles. Since the pH of potable water is in the range of 6-8.5, ferric or manganic ions are very poorly soluble in this pH range and therefore form precipitates as hydroxides in the form of colloidal particles.

Ozonated pretreated water W3 is then pumped at a constant flow rate from the ozonation reaction unit 8 through a second set of microglass and activated carbon block filters 56 through which any colloidal oxides and dissolved organic molecules are removed, as well as any bromate ions that may be formed from bromide ions present. An activated alumina cartridge 58 is provided after the filter, through which at least 80% of the As (V +) or fluoride is removed in a single pass of water at a constant flow rate. The purified water W4 is then stored in the storage reservoir 48 for storage of the purified water. The storage device may typically have a volume to hold 40 liters of purified water.

By periodically effecting the ozone O for a relatively short period of time₃The process of bubbling and passing the bubbles into the reservoir 48 and recirculating the water W4 from the storage reservoir 48 through the microglass and activated carbon filter 56 and activated alumina column 58 and back to the storage reservoir 48 maintains the storage reservoir 48 storing the purified water and the hydraulic lines for dispensing the purified water in a near sterile condition.

The recycle flow rate is set based on the efficiency of the activated alumina column 58 and the estimated number of passes required to reduce the concentration of As (V +) or fluoride ions in the storage reservoir 48 to a concentration that can be tolerated by the epa standards. The estimate is based on the type and amount of activated alumina media, the diameter and length of the filter, and the volume of the storage reservoir. Therefore, the easiest way is to determine this estimate by experimental data and errors of a particular system.

The process of bubbling ozone and passing said bubbles into the storage means is carried out periodically if the condition in which the water is not dispensed continues for a predetermined time, for example four hours. The ozonation time will depend on the strength of the ozone generator and the specific volume of the reservoir. For example, in a 20 liter storage facility, and for a 1g/hour ozone generator, the water W4 is typically ozonated in the storage facility 48 for 10 minutes.

A recirculation process is also initially carried out until the contaminant concentration in the raw water has been reduced to the maximum allowable contaminant concentration. The recirculation process is also initiated during a later reservoir ozonation to prevent microbial regrowth in the hydraulic system, such as in carbon and activated alumina filters, in piping, valves, or in the storage reservoir 48.

Figure 2 schematically shows an apparatus suitable for implementing the above method, except for a microcontroller and its accompanying software, and electronic circuitry to control the operation of the various elements. In the following description it will be understood that the sensors that activate the various operating elements are described by a microprocessor program.

The untreated water source, shown at 10, is connected to a constant flow rate pump 12 that is hydraulically connected in series to a solenoid valve 14 and a prefilter cartridge 16. The pre-filter 16 comprises an activated carbon block filter having a nominal pore size of 0.5 microns (KX Industries, USA) wrapped with an ultra fine glass fibre filter material having a nominal pore size of 1 micron. The filter is disposed in a disposable plastic housing or as a replaceable filter element in a standard filter housing (Ametek, USA). For a 10 "size filter element, the pump 12 is typically run at a speed of 2-l/min.

Prefilter 16 is hydraulically connected to ozonation chamber 18 through raw water conduit 17 and through cover 28. Ozonation chamber 18 contains a minimum water level switch 20 that activates pump 12 and opens valve 14 when the water level is below the switch height. Prefiltered water W2 then enters ozonation reaction chamber 18 until it rises to the point where maximum level switch 22 and/or overflow switch 23 are operational, which causes pump 12 to be turned off and valve 14 to be closed.

Ozonation reaction chamber 18 can typically have a volume to hold 4-8 liters of raw water, depending on the strength of the ozone generator, the physical limitations imposed by the design and size of the purifier, and the method utilized to inject the ozone/air mixture into the water in the reaction chamber. The ozonation reaction chamber is designed to have a cylindrical shape for efficient operation with a minimum height to diameter ratio of 7: 1, and preferably 10: 1 or higher.

At the bottom 19 of the ozonation reaction chamber 18, means 26 for introducing an ozone/air mixture in the form of fine bubbles are provided. The device may be a porous ceramic stone or other device known in the art. Bubbler 26 is connected to an ozonation solenoid valve 30 through an ozonation pipe 29. Ozonation pipe 29 is integrally sealed through lid 28. An ozone delivery line 31 hydraulically connects ozonation valve 30 to an ozone generator 32. After activation of the maximum water level switch 22, the ozonation solenoid valve 30 is opened, the ozone generator 32 is activated and the process of bubbling the ozone/air mixture and passing bubbles through the device 26 continues for a predetermined time, typically 5-12 minutes for an ozonation reaction chamber 18 having a volume of 4 liters with a height to diameter ratio of 7. A delivery solenoid valve 34 connected to lid 28 is simultaneously opened to allow excess air and ozone to exit ozonation reaction chamber 18.

Excess air and ozone from ozonation reaction chamber 18 is directed through delivery solenoid valve 34 and delivery pipe 45 and through reservoir lid 46 into the headspace of storage reservoir 48 where treated water is stored. The gas is vented to the atmosphere through a Granular Activated Carbon (GAC) air filter cartridge 50 disposed in the reservoir cap 46. The particulate active filter cartridge 50 may, for example, be of the type sold by Ametek Ltd for air purification purposes.

The ozone generator 32 has an air pump 36 connected in series to a cooling element 38, followed by an air drying column 40, an air flow switch 42 and a corona dispensing tube and power supply 44. The cooling element 38 is a thermoelectric cooled metal block containing a tortuous flow path for air, which is arranged to remove excess humidity from the ambient air and reduce the air temperature to about 10 ℃. The partially dried and cooled air a1 enters the air drying column 40 which is filled with a moisture absorbing medium such as Zeochem 4A molecular sieves or silica gel beads. The air a2 exiting the column 40 had a relative humidity of no more than 5% at a temperature of 20C. The humidity and air temperature sensors 43 input data relating to each of these parameters to the aforementioned microcontroller. In the event that the measured value deviates from the predetermined value, the microcontroller indicates a system error and stops the water treatment process in the ozonation reaction chamber by shutting off power supply 44 and ozonation valve 30. Thus, the already treated water in the reservoir 48 may be dispensed for a period of time until the ozone generator is required to ozonate the reservoir 48. At this point, the process of dispensing water from reservoir 48 will also be stopped in a timely manner.

At the end of a predetermined ozonation period, the microcontroller opens a delivery valve 52 for delivering ozonated water, which is hydraulically connected between the bottom 19 of the ozonation chamber 18 and a constant flow rate pump 54. Water W3 from ozonation chamber 18 is delivered at a constant flow rate through activated carbon filter 56 and activated alumina filter 58 by activating pump 54 and opening inlet valve 60 of the reservoir. Purified water W4 is delivered through reservoir inlet conduit 61 and reservoir lid 46 and into storage reservoir 48 where treated water is stored. The maximum flow rate of the pump 54 is determined by the maximum flow rate allowable to reduce dissolved organic material at a predetermined level through the filter 56 and inorganic ions (arsenic or fluoride) at a predetermined level through the filter 58. For a 10 "filter cartridge element, the flow rate is typically 1 liter/minute.

The filter 56 is identical in construction to the earlier described filter 16. The activated alumina filter 58 comprises a column of activated alumina media that is activated prior to use by contacting the filter with 29g/L of aluminum sulfate solution for a period of 1 hour. The solution is then flushed from the filter with pure water before the filter is installed and used in the apparatus. The physical dimensions of the activated alumina filter 58 are determined by the flow parameters of the recirculation loop, the pH of the water from the source and the concentration of arsenic or fluoride in the water, and the total volume of water to be treated, for example, the activated alumina filter may typically be a cylindrical cartridge having a diameter of 60mm and a length of 500 mm.

The storage reservoir 48, which stores treated water, is provided with a minimum level switch 70, a maximum level switch 72 and an overflow switch 74. An air/ozone bubbler element 62 disposed in the reservoir is connected to a reservoir ozonation valve 64 through the lid 46 by means of a reservoir ozonation pipe 63. Valve 64 is hydraulically connected to ozone delivery pipe 31 and thereby to ozone generator 32. At a predetermined time, for example at 4 hour intervals, the microcontroller activates the ozone generator 32 and reservoir ozonation valve 64, thereby bubbling the ozone/air mixture and causing the bubbles to enter the storage reservoir 48 where the treated water is stored.

The reservoir outlet conduit 66 extends through the lid 46 that closes the reservoir 48 storing the treated water to allow water to be drawn from the reservoir 48. A reservoir outlet conduit 66 is hydraulically connected to the inlet of the pump 54 through a reservoir outlet valve 68 and a conduit 69. The treated water is dispensed at spout 78 through dispensing valve 76 and dispensing conduit 75, which is connected to the outlet of pump 54. When a user manually instructs the microcontroller to dispense purified water, for example by pressing a button on the purifier, the reservoir outlet valve 68 and the dispensing valve 76 are opened, the pump 54 is activated, and water W6 is dispensed at the spout 78.

To accomplish the recirculation of water from reservoir 48 through filters 56 and 58, ozonated water delivery valve 52 and dispense valve 76 are maintained in a closed state. Reservoir inlet valve 60 and reservoir outlet valve 68 and pump 54 are activated and the re-treated water is returned to reservoir 48 through reservoir inlet conduit 61. The time of the recirculation period is predetermined by a value set in the microcontroller.

The ozonation process in the storage reservoir and the recirculation process are usually performed in parallel.

Fig. 3a to 3e schematically show different operating modes.

In fig. 3a, pre-filtered water W2 is ozonated in ozonation reaction chamber 18. To do so, ozonation valve 30 is opened and air pump 36 is on. Ozone generated by ozone generator 32 is fed through ozone delivery line 31 and ozonation line 29 and into ozonation reaction chamber 18. Figure 3a shows a first batch of ozonation process. Ozone delivery valve 34 is opened. All other valves are closed. Since this is the initial batch, the storage reservoir 48 contains no water.

Fig. 3b shows the process of delivering ozonated water W3 to the storage reservoir 48 in mode M1. Ozonated water transfer valve 52 and reservoir inlet valve 60 are opened and pump 54 is running. All other valves are closed.

Fig. 3c shows another operating mode M2. In this mode of operation, all of the contents of ozonation reaction chamber 18 have been transferred to storage reservoir 48. To accomplish repeated treatment of the water through filters 56 and 58, ozonated water delivery valve 52 is closed and reservoir outlet valve 68 and reservoir inlet valve 60 are opened. The pump 54 is in operation to recirculate water from the storage reservoir 48 through a recirculation line comprising a reservoir outlet conduit 66 and a reservoir inlet conduit 61 and conduit 69. In this mode of operation, all other valves are closed. However, it is possible to ozonate the raw water contained in ozonation reaction chamber 18 in parallel in a similar way as in fig. 3 a.

Fig. 3d shows another alternative recirculation mode of operation M2'. Reservoir outlet valve 68 and reservoir inlet valve 60 are opened and pump 54 is in operation so that water can be circulated. In comparison with fig. 3c, furthermore, the ozone transfer valve 64 of the reservoir is opened in order to let ozone into the storage reservoir. Ozone will dissolve in the water contained in the storage reservoir 48 and will be fed through the recirculation line, which includes the reservoir outlet pipe 66, the reservoir outlet valve 68, the pipe 69, the pump 54, the filters 56 and 58, and the reservoir inlet valve 60 and the reservoir inlet pipe 61. A new batch of raw water may be ozonated in parallel.

Fig. 3e shows the process of dispensing purified water W5 in another operating mode M3. A new batch of raw water may be ozonated in parallel.

Claims (16)

1. An apparatus (1) for the purification of a liquid contaminated with microorganisms and/or metal ions oxidizable to a higher oxidation state, said apparatus comprising at least one ozonation unit (8) for the treatment of said liquid (W1) by ozone (O) and

a physically separate storage reservoir (48) of treated liquid hydraulically connected to the ozonation unit (8),

wherein the device (1) is provided with recirculation means for recirculating the ozonized liquid (W4) from the storage reservoir (48) through a recirculation line (66, 69, 61), and

wherein the recirculation line (66, 69, 61) is provided with at least one filtration unit but does not comprise the ozonation unit (8).

2. Device (1) according to claim 1, having at least one ozonation unit (8) for treating a liquid (W1) by ozone (O) and having a storage reservoir (48) for storing the ozone-treated liquid (W4), wherein the device (1) is provided with means (64, 63) for ozonating the liquid (W4) in the storage reservoir (48).

3. The device of claim 1, wherein a portion of the recirculation line (66, 69, 61) forms part of a hydraulic connection between the ozonation unit (8) and the storage reservoir (48).

4. The device according to claim 1, wherein the device (1) is provided with recirculation means for periodically recirculating the liquid through the recirculation line (66, 69, 61).

5. The device according to claim 1, wherein the device (1) is provided with a pump and a control device (54) for recirculating the liquid (W4) until the amount of contaminants to be removed from the liquid (W4) by the filter unit is below a predetermined level.

6. The device according to claim 1, wherein the filtration unit is adapted to remove arsenic compounds and/or fluorides.

7. The apparatus of claim 1, wherein the filtration unit is an activated alumina filter.

8. Device according to one of claims 6 or 7, wherein the recirculation line (66, 69, 61) is provided with further filtering means arranged upstream of the filtering unit.

9. The apparatus of claim 1, wherein the ozonation unit (8) is designed to ozonate a quantity of liquid in a batch-wise manner.

10. The device of claim 1, wherein the device is provided with a connection (45) between an ozonation chamber (18) and the storage reservoir (48), wherein excess ozone in the ozonation chamber (18) can be transported to the storage reservoir (48) through the connection (45).

11. The device of claim 1, wherein the storage reservoir (48) is connected to an ozone generator (32) by a reservoir ozonation connection (63).

12. The device according to claim 1, wherein the storage reservoir (48) is provided with an exhaust filter (50) for removing ozone from the gas as it is exhausted out of the storage reservoir (48).

13. The device according to claim 10, wherein the device (1) is provided with an ozone generator (32) connected both to the ozonation chamber (18) and to the storage reservoir (48).

14. The device according to claim 10, wherein the device (1) is provided with a pump (54) for feeding the liquid from the ozonation chamber (18) to the storage reservoir (48).

15. Device according to claim 14, wherein the pump (54) is hydraulically connected to the storage reservoir (48) by valve means, such that

-in a first mode of operation (M1), the pump (54) is adapted to feed liquid (W3) from the ozonation chamber (18) to the storage reservoir (48),

-in a second operating mode (M2), the pump (54) is adapted to recirculate liquid (W4) in a recirculation line (66, 69, 61) and through the filtration unit, and

-in a third mode of operation (M3), the pump is adapted to supply purified liquid (WL) from the storage reservoir to the dispensing conduit (78).

16. The device of claim 1, wherein the device comprises a control device for placing the device in at least one of the following operating modes, wherein

-in a reaction and storage mode, raw water is treated in the reactor for a predetermined ozone treatment time, after which the water is pumped through one or more filters and stored in the storage reservoir,

-wherein in a periodic reservoir ozonation and recirculation mode, the water in the storage reservoir is subjected to ozonation for a predetermined time, thereby recirculating water from the storage reservoir through the filter and back to the storage reservoir, and

-wherein in a stagnation period ozonation treatment mode, if the purifier is not in use for a predetermined time, ozonation of any water located in the reaction chamber and in the storage reservoir is performed for a predetermined time and after a predetermined stagnation period.