APPARATUS AND METHOD FOR PROVIDING PURIFIED WATER

Abstract

A method of providing a dispense purified water stream from a water purification apparatus involving passing a water inlet stream through a first water purification station to provide a first internal purified water stream, passing the first internal purified water stream to an internal reservoir, and providing a second internal purified water stream from the reservoir, passing the second internal purified water stream into a recirculation loop, measuring the conductivity of the second internal purified water stream; passing the second internal purified water stream to a second water purification station to provide a third internal purified water stream passing the recirculated water return stream into the internal reservoir; calculating the purity of the first internal purified water stream using the measurement of the conductivity of the second internal purified water stream.

Claims

1. A method of providing a dispense purified water stream, from a water purification apparatus, comprising at least the steps of: (a) passing a water inlet stream through a first water purification station comprising one or more first water purification process units to provide a first internal purified water stream that is of higher purity than the water inlet stream, (b) passing the first internal purified water stream to an internal reservoir within the water purification apparatus through a water inlet, the internal reservoir holding a volume of second purified water, and providing a second internal purified water stream from the reservoir, (c) passing the second internal purified water stream from the reservoir into a recirculation loop, (d) measuring the conductivity of the second internal purified water stream in the reservoir, or in the recirculation loop, or both; (e) passing the second internal purified water stream to a second water purification station comprising one or more second water purification process units, and providing a third internal purified water stream that is of higher purity than the second internal purified water stream; (f) providing by selecting from the third internal purified water stream, either a dispense purified water outlet stream, or a recirculated water return stream, or both; (g) passing the recirculated water return stream into the internal reservoir from the recirculation loop; (h) calculating the purity of the first internal purified water stream using the measurement of the conductivity of the second internal purified water stream.

2. The method as in claim 1 wherein the measurement of the conductivity of the second internal purified water stream is carried out by a first conductivity measurement device.

3. The method as in claim 1 further including the step of measuring the conductivity of the third internal purified water stream.

4. The method as in claim 3 wherein the measurement of the conductivity of the third internal purified water stream is carried out by a second conductivity measurement device.

5. The method as in claim 1 further including the step of: measuring a time period between reaching a predetermined volume of second purified water in the internal reservoir from first internal purified water stream entering the internal reservoir, and a predetermined conductivity value of the second internal purified water stream.

6. The method as in claim 1 further including the steps of: measuring the rate of fill of the internal reservoir by the first internal purified water stream, and using the measurement rate of fill in calculating the purity of the first internal purified water stream.

7. The method as in claim 1 further including the steps of: measuring the rate of flow of water in the recirculation loop; and using the measurement in calculating the purity of the first internal purified water stream.

8. The method as in claim 1 wherein the dispense purified water outlet stream is ultra-pure water of resistivity>15 MΩ.Math.cm.

9. The method as in claim 1 wherein the first and second water purification stations include at least a deioniser.

10. The method as in claim 9 wherein the deioniser in the first water purification station is selected from a group comprising: a reverse osmosis unit, a capacitive deionisation unit.

11. The method as in claim 9 wherein the deioniser in the second water purification station is selected from a group comprising: ion exchange resin, electrodeionisation.

12. The method as claimed in claim 1 wherein the second water purification station includes an oxidiser.

13. The method as in claim 12 wherein the oxidiser provides oxidation selected from a group comprising: UV oxidation, ozonation, electrochemical oxidation, ultrasonic oxidation.

14. The method as claimed in claim 1 further including the steps of: passing the second internal purified water stream through a UV photo-oxidation chamber and oxidising organic molecules therein, passing the stream from the UV photo-oxidation chamber through a third conductivity measuring device, and calculating the total organic content of the dispense purified water outlet stream using the measurements from the first and third conductivity measuring devices.

15. A water purification apparatus able to provide a dispense purified water stream, that has at least two stages of purification and a reservoir thereinbetween, the second stage of purification being in a recirculation loop and having conductivity determination in the recirculation loop, or reservoir, or both, that is able to determine the conductivity of the water output from the first purification stage.

16. The water purification apparatus as claimed in claim 15 provided within a single housing containing the first and second water purification stations, the internal reservoir, a pump, and first and second water conductivity measurement devices.

17. The water purification apparatus as claimed in claim 15 further including one or more water connections able to extend the dispense purified water stream or the recirculation loop beyond or outside the housing.

18. The water purification apparatus as claimed in claim 15 being a portable water purification apparatus.

19. The water purification apparatus as claimed in claim 18 having a mass of <22 kg with a full reservoir of water.

20. The water purification apparatus as claimed in claim 18 having an empty mass of <15 kg.

21. The water purification apparatus as claimed in claim 15 comprising; a water inlet for a water inlet stream; a first water purification station comprising one or more first water purification process units to provide a first internal purified water stream that is of higher purity than the water inlet stream; the reservoir able to hold a volume of second purified water comprising at least the first internal purified water stream, and able to provide a second internal purified water stream from the reservoir; a recirculation loop for the second internal purified water stream from the reservoir into the recirculation loop; a first conductivity measurement device able to measure the conductivity of the second internal purified water stream; a second water purification station comprising one or more second water purification process units, able to receive the second internal purified water stream, and able to provide a third internal purified water stream that is of higher purity than the second internal purified water stream; a valve able to select from the third internal purified water stream either a dispense purified water outlet stream or a recirculated water return stream, or both; a passage to pass the recirculated water return stream into the internal reservoir from the recirculation loop; a calculator able to calculate the purity of the first internal purified water stream using the measurement of the conductivity of the second internal purified water stream.

22. A water purification apparatus as claimed in claim 21 further comprising a second conductivity measurement device to measure the conductivity of the third internal purified water stream.

Description

[0125] FIG. 1 is a simplified schematic view of a first water purification apparatus and method for providing purified water according to embodiments of the present invention; in particular a water purification apparatus that has at least two stages of purification, the second stage of purification being in a recirculation loop and having conductivity determination in the recirculation loop that is used to also determine the conductivity of the water output from the first purification stage;

[0126] FIG. 2 is a chart detailing conductivity as measured by a first conductivity cell used to indirectly determine the conductivity of a first internal purified water stream involved in the present invention;

[0127] FIG. 3 is a schematic view of a section of a water purification apparatus for determining the total organic content of the purified water produced by the water purification apparatus; and

[0128] FIG. 4 is a schematic view of a second water purification apparatus and method according to a further embodiment of the present invention wherein an in-line conductivity measurement is used for determining the water conductivity at two different locations as well as determining the total organic content of one of the waters.

[0129] Referring to the drawings, FIG. 1 is a schematic diagram of one embodiment of the present invention. It shows a water purification apparatus 10 having an inlet for connection to a supply of potable or similar water from within a laboratory. The pipe for the water inlet stream 12 is connected to an inlet electrically activated valve 13, such as a solenoid valve, to control the flow of water into the apparatus 10. The outlet from the inlet solenoid valve 13 is connected to the first water purification station 14, able to purify the water inlet stream 12 to create a first purified water, which exits the first water purification station 14 as a first internal purified water stream 18.

[0130] The first water purification station 14 contains one or more deionising technologies, such as reverse osmosis or capacitive deionisation, to achieve the purification, and a grey water outlet 16 able to provide a water stream that may be used for general purposes in the laboratory where water purity is not of concern.

[0131] The first water purification station 14 may also contain other technologies able to filter the inlet water stream 12, to remove particles prior to the deionising technology.

[0132] The first water purification station 14 may further contain technologies such as activated carbon, to remove chlorine or chloramines from the inlet water stream 12 prior to the deionising technology.

[0133] The first water purification station 14 may further contain technologies such as ion exchange resin to soften the inlet water stream 12 by exchanging divalent ions for sodium ions after the deionising technology.

[0134] The skilled man can see that the first water purification station 14 may include one or more water purification process units able to provide one or more of the above technologies, and generally known in the art.

[0135] The first internal purified water stream 18 is passed to an internal reservoir 20 without passing through any conductivity measuring device.

[0136] The internal reservoir 20 can be any suitable shape and design and volume. Optionally, the internal reservoir has a volume in the range of 3 to 10 litres, and has a first water inlet 22 for the first internal purified water stream 18. The internal reservoir 20 also has an outlet 24 for water to exit into a recirculation loop 32, and a second inlet 26 for the returning recirculated water as described hereinafter.

[0137] The internal reservoir 20 also contains a level sensor 30 to determine the amount of water in the reservoir. This may be by any means such as measuring the water pressure, optical measurement, use of floats or any such method known in the art.

[0138] The internal reservoir 20 contains a second purified water 28, being a mixture of first internal purified water stream 18 that has entered by first water inlet 22, and water that has entered by the second water inlet 26 which is more purified than the first internal purified water stream 18 as described hereinafter.

[0139] The second purified water 28 is drawn from the internal reservoir 20 as a second internal purified water stream 34, and passed around a recirculation loop 32 by an in-line pump 36. The recirculation loop 32 contains a second water purification station 42.

[0140] The first water purification apparatus 10 further includes a first in-line water quality measurement device 38 for measuring the conductivity of the second internal purified water stream 34 provided from the internal reservoir 20 and pump 36. The first water quality measurement device 38 may be a conductivity cell as known in the art, preferably with a cell constant of 0.02 or less.

[0141] The recirculation loop 32 may further contain a flowrate measuring device 54 to accurately determine the rate of flow of the water around the recirculation loop 32.

[0142] The second water purification station 42 contains one or more deionising technologies, such as ion exchange resin or electrodeionisation, able to remove ions and dissolved carbon dioxide from the water therein, to create a third purified water, which exits the second water purification station 42 as a third internal purified water stream 44. The second water purification station 42 may have a waste stream (not shown), that can return water containing ions removed from the second purified water to a point prior to the first water purification station 14, or pass the waste stream from the unit through the grey water outlet 16.

[0143] The second water purification station 42 may further contain oxidative technologies such as UV oxidation or ozone or peroxide production to remove viable bacterial contamination from the water.

[0144] The second water purification station 42 may further contain oxidative technologies such as UV, ozone, peroxide, sonolysis or electrochemical oxidation to break down organic molecules from the water.

[0145] The second water purification station 42 may further contain molecular filtration by size exclusion, such as microfiltration or ultrafiltration or by charged filters, to remove bacteria, molecules and particulate contamination from the water.

[0146] The third internal purified water stream 44 exiting the second water purification station 42 is passed through a second in-line water quality measurement device 46 for measuring the conductivity of the third internal purified water stream 44. The second water quality measurement device 46 may be a conductivity cell as known in the art, preferably with a cell constant of 0.02 or less.

[0147] The third internal purified water stream 44 is then passed to a to a dispense valve 48, optionally an electrically activated valve, such as a solenoid valve, from which it is either returned to the internal reservoir 20 through the second water inlet 26 as a recirculated water return stream 52, or some or all of the third internal purified water stream 44 may be passed from the water purification apparatus 10 as a dispense purified water outlet stream 50.

[0148] The first water purification apparatus 10 further includes a control system, not shown, such as a printed circuit board including a microprocessor. Readings from the first and second water quality measurement device 38, 46 are processed by the microprocessor and water purity is output to a user by display means as known in the art.

[0149] FIG. 2 shows a curve of how the conductivity of water measured at the first water quality measurement conductivity device 38 of the apparatus shown in FIG. 1, based on a volume in the recirculation loop 34 of 0.5 litres, and a recirculation flow rate of 1.0 l/min, will vary when 5 litres are taken from a 7 litre reservoir, and the reservoir is refilled back to 7 litres at a rate of 167 ml/min with a first purified water with a conductivity of 20 μS/cm.

[0150] At time=0, the internal reservoir 20 starts to fill with water from the first water inlet 22 and the conductivity of the second purified water 28 in the internal reservoir 20 increases to a conductivity approaching a steady level. At time A at 30 minutes, the reservoir becomes full, and a measurement of the conductivity “C(full)”, as measured by the first conductivity device 38, is taken. The microprocessor can then compare conductivity C(full) to a lookup table or use an algorithm to determine the conductivity of the first internal purified water stream 18 that has been fed into the reservoir 20.

[0151] For any particular equipment the volume of the reservoir and recirculation loop are fixed. The curve of conductivity approaches a steady level, presuming that the fill is for a long enough period. In the example described above, a fill of over 2.5 litres corresponding to 15 minutes is suitable.

[0152] Conductivity C(full) may be affected by changes in flow rate of the first purified water filling the reservoir 20, and/or of the rate of flow of the recirculated water return stream 52. Fill flow rate can be determined by monitoring the rate of change of level sensor 30. Variation in flow rate can then be added to the algorithm, or adjustment made to the lookup table.

[0153] It is preferable to use a positive displacement pump 36 for the recirculation loop 32 to provide a constant flow therein. Greater certainty of the flow can be achieved by the addition of a flow rate monitor 54 in the recirculation loop, and one may be desirable in the water purification system to provide a user with information regarding the amount of water the user is dispensing.

[0154] An additional or alternative method for determining the conductivity of the first purified water 18 is to measure the time taken to purify the second purified water 28 to a known conductivity. An example in FIG. 2 is the time taken for the second purified water 28 to reduce from C(full) to 0.5 μS/cm i.e. from t=A to t=B. Again a lookup table or algorithm can be used to determine the conductivity of the first purified water.

[0155] FIG. 3 shows a section of a water purification apparatus for determining the total organic content (TOC) of the dispense purified water outlet stream 50.

[0156] The first in-line water quality measurement device 38 is used to measure the conductivity of an inlet stream 40 to a photo-oxidation chamber 60 located either before, within or after the second water purification station 42. As the water passes through the chamber it is irradiated with UV light from one or more suitable UV irradiation devices, such as LEDs designed to emit specific wavelengths, or discharge tubes that emit some of their radiation at the required wavelengths. The radiation causes the bonds in the organic molecules to fracture creating smaller species typically ionic or ionisable species which can be removed in downstream processes prior to dispense. The ionic or ionisable species cause a decrease in the resistivity of the water passing through the photo-oxidation chamber. The photo-oxidation outlet stream 64 from the photo-oxidation chamber 60 passes through a third in-line water quality measurement device 62 for measuring the conductivity of the photo-oxidation outlet stream 64. From the measurement of the first in-line water quality measurement device 38 and third in-line water quality measurement device 62, and knowing the oxidative efficiency of the photo-oxidative chamber 60, the water purification apparatus control system can calculate the TOC of the dispense purified water outlet stream 50.

[0157] FIG. 4 shows a second embodiment of a water purification apparatus of the present invention. Apparatus may be used incorporating any combination of the components and features of FIG. 4 where they differ from those shown in FIG. 1.

[0158] The second water purification system 110 has the same or similar components and features of the first water purification apparatus 10 in FIG. 1 and the section for TOC determination in FIG. 3, and so uses some notation numbering of +100 to represent such similar components and features.

[0159] The second water purification apparatus 110 includes the photo-oxidation chamber 160 and third in-line water quality measurement device 162 from FIG. 3 in the recirculation loop 134 before the second water purification station 142 such that the ions and ionisable that are generated in the photo-oxidation chamber 160 are removed in the second water purification station 142 prior to the water being dispensed as the dispense purified water outlet stream 150 or returned to the reservoir 120.

[0160] The second water purification apparatus 110 further includes outputs from the water purification apparatus 110 of a first purified water outlet stream 170 and a second purified water outlet stream 172.

[0161] The first internal purified water stream 118 is passed to a first purified water valve 174, preferably an electrically actuated valve such as a solenoid valve, for selectively passing the first internal purified water stream, 118 to either a first purified water outlet as a first purified water outlet stream 170 from the water purification apparatus 110, or to the internal reservoir 120 as a first continuing water stream 180.

[0162] A first tee or tee-junction 182 in the recirculation loop 132, preferably located after the pump 136 (so that the second internal purified water stream 134 is under pressure or ‘pressurised’ relative to atmospheric pressure), allows the second internal purified water stream 134 to pass towards the photo-oxidation chamber 160 and second water purification station 142 or some of the second internal purified water stream 134 may also be passed via a flow limiter 184 and a second purified water valve 176, preferably an electrically operated valve, as a second dispense purified water stream 172 from the water purification apparatus 110.

[0163] The flow limiter 184 ensures that only part of the second internal purified water stream 134 exiting the pump 136 can be output as the second dispense purified water stream 172, and that the flow is maintained to the photo-oxidation chamber 160 and second water purification station unit 142.

[0164] In FIG. 4 an alternative way of controlling the dispense is shown to that in FIG. 1, and each may be used in either apparatus. In FIG. 4 the third internal purified water stream 144 is passed to a second tee 178 from where it may be passed through a 2-way dispense valve 148 to create the dispense purified water outlet stream 150, or returned to the reservoir 120 as the recirculated water stream 152, or both. The pressure for dispensing the outlet water is maintained within the recirculation loop 132 by a pressure sustaining device 186 known in the art. With this arrangement greater control of the rate of output of the dispense purified water outlet stream 150 can be achieved by the use of variable valves such as proportional or stepper motor valves.

[0165] The second water purification apparatus 110 further includes locations 190, 192 for connecting a remote dispenser, or for extending the recirculation loop 132 around a laboratory. If no remote dispenser or recirculation loop extension is required, then a link 194 is present.

[0166] The internal reservoir 120 also contains a composite vent filter 196 to allow air passage into and out of the reservoir 120, thus equilibrating the air pressure inside and outside the reservoir 120, while also preventing particles, bacteria or carbon dioxide to enter the reservoir 120.