Ultrafiltration stage for use in a water treatment plant for producing dialysis water

Abstract

The present invention relates to an ultrafiltration stage for use in a water treatment plant for producing purified water for medical or pharmaceutical use, in particular dialysis water, comprising at least one first ultrafilter element and one second ultrafilter element, and a control unit which is designed to monitor at least one functional parameter of at least one of the ultrafilter elements, and, if the at least one functional parameter deviates from a target value or falls outside a tolerance range around said target value, to automatically carry out a backflushing operation of the at least one ultrafilter element. The invention also relates to a system for producing purified water for medical or pharmaceutical use, the system comprising such an ultrafiltration stage.

Description

[0001] 03358-25 He 18.12.2025

[0002] Fresenius Medical Care Deutschland GmbH

[0003] Bad Homburg, Germany

[0004] Ultrafiltration stage for use in a water treatment plant for the production of dialysis water

[0005] The present invention relates to an ultrafiltration stage for use in a water treatment plant for the production of dialysis water.

[0006] It is known according to the state of the art that ultrafiltration stages are used as part of a water treatment plant or cascade, for example in the production of medical water.

[0007] With increasing use, a biofilm forms over time on the membrane of the ultrafiltration stage, reducing the hygiene and function of the stage. Therefore, conventional ultrafiltration stages, or their filter elements or membranes, are usually backwashed at fixed intervals.

[0008] Backwashing the filter elements usually results in a fairly high water consumption, and the production of medical water usually has to be interrupted during the backwashing process.

[0009] Against this background, the present invention aims to mitigate or even completely eliminate the disadvantages of the prior art. A specific object of the invention is to provide an improved, for example more energy-efficient, method for producing medical water, in particular dialysis water.

[0010] This problem is solved by the subject matter of the independent claims. Advantageous embodiments of the invention are the subject matter of the dependent claims.

[0011] Accordingly, an ultrafiltration stage is provided for use in a water treatment plant for the production of pure water for medical or pharmaceutical use, in particular dialysis water, comprising at least a first ultrafilter element and a second ultrafilter element as well as a control unit.

[0012] The control unit is designed to monitor at least one functional parameter of at least one of the ultrafilter elements and, if the at least one functional parameter deviates from a setpoint value or a tolerance range surrounding it, to automatically perform a backwashing process of the at least one ultrafilter element.

[0013] In this way, the backwashing process is preferably only carried out when absolutely necessary. Unnecessary backwashing processes are avoided, which saves energy and water.

[0014] The control unit can be designed to perform the backwashing process of at least one ultrafilter element with filtrate from at least one other ultrafilter element.

[0015] The control unit preferably ensures that the production of purified water or filtrate by the other ultrafilter element is maintained during the backwashing process of one ultrafilter element, so that the production of purified water by the ultrafiltration stage is uninterrupted. By means of a suitable valve arrangement, the filtrate of the active ultrafilter element can be divided between the ultrafilter element being backwashed and another consumer (for example, a downstream fluidic stage in a water treatment plant or cascade, or a consumer such as a dialysis machine).

[0016] The functional parameter of at least one of the ultrafilter elements, monitored by the control unit, can be a filter permeability and / or another parameter such as a transmembrane pressure.

[0017] In this case, the control unit can be designed to automatically perform a backwashing process of the at least one ultrafilter element if the filter permeability falls below a setpoint value or a surrounding tolerance range.

[0018] Preferably, the control unit is designed to perform the backwashing process automatically, i.e. preferably without a user having to initiate it or even being aware of the execution of the backwashing process.

[0019] The control unit can be designed to predict, based on at least one functional parameter, at least one preferably future point in time at which the execution of the backwashing process of at least one of the ultrafilter elements is or will be required.

[0020] In this way, a future backwashing process can be planned, for example as part of "predictive maintenance", and the service life of the ultrafiltration stage can thus be improved.

[0021] Furthermore, better planning is possible because, when backwashing at least one of the ultrafilter elements with the purified water from at least one other ultrafilter element, less purified water is available for each end user. For example, a backwash can be scheduled for a time between 2 and 3 a.m. when fewer dialysis treatments are scheduled.

[0022] Furthermore, in order to achieve better coordination of the individual components, in a case where the ultrafiltration stage is embedded in a water treatment plant or cascade (in other words, a system for producing pure water for medical or pharmaceutical use), the control unit can be designed to transmit at least one time of a completed backwashing process and / or a predicted time of a future backwashing process to at least one component of a system for producing pure water for medical or pharmaceutical use, in particular dialysis water.

[0023] Furthermore, the control unit can be designed to perform an integrity test of at least one ultrafilter element or its membrane, preferably by means of a pressure holding test and / or a determination of the transmembrane pressure.

[0024] For example, a leak test can be performed on at least one ultrafilter element, e.g., to detect an internal leak and / or to check the retention effect of the membrane, i.e., the filter membrane, e.g., a hole in the filter connecting the feed side to the filtrate side can be detected.

[0025] One advantage of integrity testing is that other checks, for example regarding hygiene, need to be carried out less frequently, which leads to reduced manual effort elsewhere.

[0026] Such an integrity test requires sensors that include at least one pressure sensor. A compressed air connection is necessary for a pressure holding test; the air can also be used as a control medium for the valves of the ultrafiltration stage.

[0027] An ultrafiltration stage according to the invention is preferably equipped with at least two parallel-connected, redundant ultrafilter elements, which are identical or different in design, particularly with regard to their membrane properties.

[0028] In principle, any number of ultrafilter elements can be provided.

[0029] The control unit can preferably control or switch the ultrafilter elements separately and individually using appropriate valves.

[0030] In an ultrafiltration stage according to the invention, preferably at least one ultrafiltration element, preferably all ultrafiltration elements, has a membrane in which the molecular weight, determined according to DIN EN ISO 8637:2014 and corresponding to a dextran sieve coefficient of 0.1, is 10-90 kDa, preferably 40-60 kDa, more preferably 30-50 kDa.

[0031] The measurement of the dextran sieving coefficient of a hollow fiber membrane is preferably carried out in accordance with DIN EN ISO 8637:2014 or in accordance with DIN EN ISO 8637:2014 on a fully assembled hollow fiber membrane filter.

[0032] A filter with 10,752 hollow fiber membranes, each with an inner diameter of 185 pm and a wall thickness of 35 pm, is used. The active length of the hollow fiber membrane is 235 mm. The active length of a hollow fiber membrane is defined as the length of the membrane, excluding the potting compound, that is available for determining permeation properties such as sieving coefficient, clearance, and ultrafiltration coefficient. The inner diameter of the hollow fiber membrane filter is 34 mm at its center. Deviating from the standard, an aqueous dextran solution with a broad molecular weight distribution of the dissolved dextran between 1,000 and 100,000 Da, or a mixture of several dextrans within this molecular weight range, is used as the test fluid, resulting in the specified molecular weight distribution.The dextran solution is passed through the fluid inlets through the first chamber of the hollow fiber membrane filter, which encompasses the interior of the hollow fiber membranes, at a flow rate of 446.6 ml / min. In the second chamber of the hollow fiber membrane filter, a flow rate of 89.9 ml / min of pure water is set via the fluid inlets.

[0033] After 12 minutes, the concentration of the dextrans, depending on their respective molecular weight, is determined at the first and second fluid ports of the first chamber of the hollow fiber membrane filter across the entire molecular weight range using gel permeation chromatography. A sieve coefficient curve is then calculated for this entire molecular weight range. The sieve coefficient of a dextran molecule with a specific molecular weight can then be determined from this sieve coefficient curve.

[0034] From these sieve coefficient curves, the corresponding molecular weight at which the sieve coefficient is 0.9 (Molecular weight retention onset, MWRO) and further the corresponding molecular weight at which the sieve coefficient is 0.1 (Molecular weight cut-off, MWCO) can then be determined.

[0035] Exemplary values ​​for membranes used in an ultrafilter element are: MWRO between 2-10000 Da and / or MWCO between 10-70000 Da. For example, a membrane can have an MWRO of 6000 Da and an MWCO of 35000 Da.

[0036] Furthermore, at least one ultrafiltration element, preferably all ultrafiltration elements of the ultrafiltration stage, can have a membrane with a pore size between 0.1 nm and 15 nm, determined according to DIN EN ISO 8637:2014 and using the Einstein-Stokes equation. An ultrafiltration stage according to the invention can be designed without a pump, i.e., the ultrafiltration stage preferably does not have its own pump by means of which water is pressurized and moved into or through the ultrafiltration stage.

[0037] However, a pump fluidically connected to the ultrafiltration stage and located externally to the ultrafiltration stage can be used to move fluid / water through or into the ultrafiltration stage.

[0038] In contrast to ultrafiltration setups used in dialysis treatment, an ultrafiltration stage according to the invention preferably does not have a designated ultrafiltration pump.

[0039] Another aspect of the present invention relates to a system for producing pure water for medical or pharmaceutical use, in particular dialysis water, comprising a water pretreatment stage, a pure water stage and an ultrafiltration stage arranged upstream of the pure water stage according to the present invention.

[0040] In such a system, a pump can be fluidically present upstream of the ultrafiltration stage, by means of which water can be introduced into the ultrafiltration stage under pressure.

[0041] In principle, the pump can also be positioned downstream of the ultrafiltration stage, so that water is moved through the ultrafiltration stage by means of the suction effect of the pump.

[0042] It should be noted here that the terms "ein" and "eine" do not necessarily refer to exactly one of the elements, although this is a possible interpretation, but can also denote a plurality of elements. Likewise, the use of the plural also includes the presence of the element in question in the singular, and conversely, the singular also includes several of the elements in question.

[0043] Furthermore, all features of the invention described herein can be combined with one another or claimed separately from one another as desired.

[0044] In the context of this disclosure, the term “ultrafiltration” preferably refers to a process in which water is purified by passing it through a membrane with defined pores at a relatively low pressure (between 1 and 3 bar).

[0045] Ultrafiltration is therefore comparable to nanofiltration, however, nanofiltration preferably uses membranes with a smaller pore size.

[0046] Unlike ultrafiltration and nanofiltration, reverse osmosis uses significantly higher water pressures, for example, in the range of 25 to 35 bar. The membranes used in reverse osmosis preferably do not have defined pores; due to the high pressures, water molecules migrate preferentially through the gaps between the polymer chains of a continuous polymer membrane.

[0047] Further advantages, features and effects of the present invention will become apparent from the following description of preferred embodiments with reference to the figure. Here, the figure shows...

[0048] Fig. 1 shows a schematic diagram of an ultrafiltration stage according to the invention. The ultrafiltration stage shown in Fig. 1 has a first ultrafilter element 1 and a second ultrafilter element 2. Each of the ultrafilter elements 1 and 2 is equipped with a membrane, which is not visible in the figure.

[0049] Water to be purified, for example from a municipal water connection, is fed to the ultrafiltration stage via a line 3 and via a distribution line 4, from which branch lines 5 branch off, to the ultrafilter elements 1 and 2.

[0050] A controllable valve 6 is arranged in the distribution line 4. At least one of the branch lines 5 is equipped with a pressure sensor 7 and a flow sensor 8.

[0051] The flow of water to the ultrafilter elements 1 and 2 can be regulated by means of the valves VF2I, VF22, VFH and VFI2.

[0052] The flow path for water to be purified is shown in Fig. 1 in solid lines.

[0053] The purified water (also called filtrate or permeate) produced by the ultrafilter elements 1 and 2 flows via purified water lines 9 into a collecting line 10, which leads into a product water line 11.

[0054] The outflow of pure water or permeate from the ultrafilter elements 1 and 2 can be regulated by means of the valves Vp2i, Vp22, Vpn and Vpi2.

[0055] The flow path for the produced purified water is shown in Fig. 1 in dashed lines.

[0056] The purified water produced can be supplied directly to a consumer via the product water line 11 or directed to a downstream water treatment or purification stage. A pressure sensor 12 is arranged in at least one of the purified water lines 9.

[0057] Furthermore, the ultrafiltration stage is equipped with a drainage line 13, which leads into an outlet 14. Retentate from the ultrafilter elements 1 and 2 can be removed via the drainage line 13.

[0058] The outflow of retentate from ultrafilter elements 1 and 2 to outlet 14 can be regulated by means of valves VD2I, VD22, VDH and VDI2.

[0059] To control the flows in the hydraulic layout in Fig. 1, the control unit of an ultrafiltration stage according to the invention can control at least some, or even all, of the valves shown in Fig. 1.

[0060] In the configuration shown in Fig. 1, air is used as the control medium for the valves. However, this is only an example, and any other control medium or a completely different control system is possible.

[0061] In Fig. 1, valve 15 is connected to a line 16 containing the control medium air. Valve 17 is also connected to line 16.

[0062] The flow path of the control medium air is shown in Fig. 1 as a dash-dot line. Line 16 is connected to the atmosphere (ATM) via line 18.

[0063] Fig. 1 shows a very simple embodiment of an ultrafiltration stage according to the invention. For example, a further ultrafilter element could be arranged "back to back" on each of the ultrafilter elements 1 and 2. In the embodiment shown in Fig. 1, the corresponding mounting points are covered with end caps 19. The valves shown in Fig. 1 make it possible to switch the flow paths of the water so that each of the membranes of the ultrafilter elements 1 and 2 can be subjected to forward and reverse flow.

[0064] The membranes of the ultrafilter elements 1 and 2 can be independently subjected to flow, so that different flow directions can be implemented simultaneously in the parallel ultrafilter elements 1 and 2.

[0065] For example, both ultrafilter elements 1 and 2 can filter, one ultrafilter element filters and one ultrafilter element is backwashed (preferably with filtered water from the other ultrafilter element), or one ultrafilter element filters and one ultrafilter element is blocked.

[0066] Simultaneously supplying filtered water to a consumer and to an ultrafilter element undergoing backwashing preferably requires throttling the water flow to the backwashing ultrafilter element. Problems caused by excessive pressure in the backwash flow path can lead to damage to the ultrafilter element due to excessive pressure / flow rates and simultaneously cause a pressure drop on the consumer side, meaning the consumer may receive insufficient purified water.

[0067] The control unit can be designed to control some or all of the backwashing valves of the ultrafiltration stage depending on measured values.

[0068] Furthermore, the control unit can display information regarding the status of the ultrafiltration stage, for example, the operating mode of the ultrafiltration stage and, in particular, when action may be required by the user, such as a yellow light indicating that a filter will soon need to be replaced or a red light indicating a complete pressure drop / hydraulic leak, etc. An ultrafiltration stage according to the invention can have a sensor group for permeability monitoring; for example, the transmembrane pressure can be measured with two pressure sensors and a flow sensor. Optionally, the water temperature can be measured with a temperature sensor, e.g., at the inlet or outlet water, and this measurement can also be taken into account.

[0069] Furthermore, the control unit can be designed to perform water detection in the compressed air line, for example, to detect when at least one ultrafilter element is full, i.e., when water has flowed out of the ultrafilter element. The filling of the ultrafilter element could also be controlled or monitored via a timer or mechanically.

[0070] The control unit is preferably designed to capture a parameter for all ultrafilter elements simultaneously or to capture it for each ultrafilter element individually.

[0071] Using the valves, the control unit can, for example, measure the transmembrane pressure for all ultrafilter elements simultaneously or each ultrafilter element individually.

[0072] The ultrafiltration stage shown in Fig. 1 is preferably chemically disinfectable; the corresponding flow paths are therefore preferably suitable for circulating disinfectant.

[0073] In a system for producing pure water, the ultrafiltration stage can be disinfected jointly with, for example, a reverse osmosis stage (RO stage) of the system via a common disinfection line. This simplifies the system because, for example, the disinfectant can then be removed again using the RO stage. At least the following advantages can be achieved with an ultrafiltration stage or system according to the invention:

[0074] In a system according to the invention, the ultrafiltration stage reliably removes fouling-associated particles and microbial load from the water stream upstream of the RO stage, in particular the increased bacterial load downstream of any activated carbon filter.

[0075] The upstream ultrafiltration stage significantly reduces the burden on the RO membrane from biofouling, resulting in a longer service life for the RO membrane.

[0076] Since the RO membrane does not present a complete barrier to microorganisms (leakage), the introduction of microorganisms into a ring main and / or to a consumer is reduced. This results in a reduced need for sanitizing and flushing the RO stage and ring main, saving time and resources.

Claims

03358-25 He 18.12.2025 Fresenius Medical Care Deutschland GmbH Bad Homburg, Germany Ultrafiltration stage for use in a water treatment plant for the production of dialysis water Claims 1. Ultrafiltration stage for use in a water treatment plant for the production of pure water for medical or pharmaceutical use, in particular dialysis water, comprising at least one first ultrafilter element and one second ultrafilter element, as well as a control unit designed to monitor at least one functional parameter of at least one of the ultrafilter elements, and to automatically perform a backwashing process of the at least one ultrafilter element if the at least one functional parameter deviates from a setpoint value or a tolerance range surrounding it.

2. Ultrafiltration stage according to claim 1, wherein the control unit is designed to perform the backwashing process of the at least one ultrafilter element with filtrate from the at least one other ultrafilter element.

3. Ultrafiltration stage according to claim 1 or 2, wherein the functional parameter of the at least one of the ultrafilter elements is a filter permeability and the control unit automatically performs a backwashing process of the at least one ultrafilter element when the filter permeability falls below a setpoint value or a tolerance range surrounding it.

4. Ultrafiltration stage according to one of the preceding claims, wherein the control unit is designed to predict, on the basis of the at least one functional parameter, at least one time at which the execution of at least one of the ultrafilter elements is or will be required.

5. Ultrafiltration stage according to one of the preceding claims, wherein the control unit is designed to transmit at least one time of an executed backwashing process and / or a predicted time of a future backwashing process to at least one component of a system for producing pure water for medical or pharmaceutical use, in particular dialysis water.

6. Ultrafiltration stage according to one of the preceding claims, wherein the control unit is designed to perform an integrity test of at least one ultrafilter element, preferably by means of a pressure holding test and / or a determination of the transmembrane pressure.

7. Ultrafiltration stage according to one of the preceding claims, comprising at least two parallel-connected, redundant ultrafilter elements, which are identical or different in design, in particular with regard to their membrane properties.

8. Ultrafiltration stage according to one of the preceding claims, wherein at least one ultrafiltration element, preferably all ultrafiltration elements, comprises a membrane in which the molecular weight, determined according to DIN EN ISO8637:2014 and corresponding to a dextran sieve coefficient of 0.1, is 10-90 kDa, preferably 40-60 kDa, more preferably 30-50 kDa.

9. Ultrafiltration stage according to one of the preceding claims, wherein at least one ultrafiltration element, preferably all ultrafiltration elements, comprises a membrane having a pore size determined according to DIN EN ISO 8637:2014 between 0.1 nm and 15 nm.

10. Ultrafiltration stage according to one of the preceding claims, wherein the ultrafiltration stage is designed without a pump.

11. System for producing pure water for medical or pharmaceutical use, in particular dialysis water, comprising a water pretreatment stage, a pure water stage and an ultrafiltration stage arranged upstream of the pure water stage according to one of the preceding claims.

12. System according to claim 9, wherein a pump is further provided fluidically upstream of the ultrafiltration stage, by means of which water can be introduced into the ultrafiltration stage under pressure.

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