Handling waste fluid generated during dialysis therapy

Abstract

An apparatus is provided for handling waste fluid, WF, generated in connection with dialysis therapy, to mitigate the risk that a patient undergoing dialysis therapy is exposed to harmful leakage currents. The apparatus includes a fluid disposal arrangement, FDA (40), which is configured to receive WF and define a fluid flow path (41) for directing WF to a drain. The FDA (40) is operable to combine WF with a dilution fluid, DF, at a supply region (44) in the fluid flow path (41). A control arrangement (50) is configured to operate one or more flow controllers (42, 45) in the FDA (40) to relatively control a first fluid flow of DF and a second fluid flow of WF into the supply region (44) so that a hypothetical homogeneous mixture of DF and WF at the supply region (44) has an electrical conductivity below a first limit value.

Description

[0001] HANDLING WASTE FLUID GENERATED DURING DIALYSIS THERAPY

[0002] Technical Field

[0003] The present disclosure relates generally to dialysis therapy, and in particular to a technique of handling waste fluid generated in connection with dialysis therapy.

[0004] Background Art

[0005] Dialysis therapy is undertaken to replace or supplement the normal blood-filtering function of the kidneys. It is used when the kidneys are not working well, which is known as kidney failure and includes acute kidney injury (AKI) and chronic kidney disease (CKD). Dialysis therapy involves removal of water from the body of the patient suffering from kidney failure, as well as exchange of solutes with the patient's blood. One example of dialysis therapy is extracorporeal (EC) blood therapy, in which blood is circulated outside of the patient and interfaced with one or more treatment fluids. Modalities of extracorporeal blood therapy include hemodialysis (HD), hemofiltration (HF) and hemodiafiltration (HDF). Another example of dialysis therapy is peritoneal dialysis (PD), in which a treatment fluid is infused into the peritoneal cavity of the patient to interface with the blood of the patient through the peritoneal membrane.

[0006] Treatment fluids used in HD and PD are commonly known as dialysis fluids. In HF, the treatment fluid is known as replacement fluid, since it is infused into the blood of the patient to replace fluid removed during therapy. In HDF, both dialysis fluid and replacement fluid are used.

[0007] In connection with dialysis therapy, waste fluid is generated by the dialysis system. The waste fluid may include spent treatment fluid, priming fluid, cleaning fluid, etc., depending on the functionality of the dialysis system. The amount of waste fluid may be considerable, and it is therefore common to install drain tubing that directs the waste fluid from the dialysis system to a drain, for example a sink, toilet, bathtub or any other permanent installation for disposal of liquid. The drain may be heavily contaminated by microorganisms, and there is a risk that microorganisms migrate from the drain into the drain tubing. The waste fluid may contain nutrients for microorganisms, and the drain tube may create an environment that favors growth of microorganisms. There is thus a risk of significant microbial contamination of the drain tubing. If microorganisms enter the dialysis system, the health of the patient is at serious risk. Depending on the functionality of the dialysis system, it is conceivable that the dialysis system comprises more than one outlet for waste fluid, and that separate drain tubings are directed from the respective outlet to the drain. This make installation of the dialysis system more complex, increases the risk for leaks and invades the space where the dialysis therapy is performed. This may be a particularly relevant when the dialysis therapy is to be performed in the home of the patient.

[0008] Summary

[0009] It is an objective to at least partly overcome one or more limitations of the prior art.

[0010] One objective is to provide a simple technique of mitigating the risk of microbial contamination of a system for use in dialysis therapy via one or more flow paths from the system to a drain.

[0011] A further objective is to provide such a technique that provides for simple installation of systems for use in dialysis therapy.

[0012] Another objective is to provide such a technique that can be implemented in relation to existing machines for use in dialysis therapy.

[0013] One or more of these objectives, as well as further objectives that may appear from the description below, are at least partly achieved by an apparatus for handling waste fluid from a system for use in dialysis therapy, a system for use in dialysis therapy, a method of handling waste fluid from a system for use in dialysis therapy, and a computer-readable medium according to the independent claims, embodiments thereof being defined by the dependent claims.

[0014] A first aspect is an apparatus for handling waste fluid from a system for use in dialysis therapy. The apparatus comprises a container configured to be arranged in relation to one or more supply lines of the system to receive, through a top portion of the container, the waste fluid from a respective outlet of the one or more supply lines, the waste fluid defining a top fluid surface in the container. The apparatus further comprises: a drain line, which is fluidly connected to a bottom portion of the container; a pumping device, which is arranged in the drain line to draw the waste fluid from the container along the drain line, and a control arrangement, which is configured to operate the pumping device to maintain at least a minimum spacing between the top fluid surface in the container and the respective outlet of the one or more supply lines so as to impede propagation of microorganisms from the drain line into the system.

[0015] A second aspect is a system for use in dialysis therapy. The system comprises: a first sub-system, which is configured to generate a treatment fluid by mixing product water with one or more concentrates. The first sub-system comprises one or more first fluid lines for disposal of first waste fluid produced by the first sub-system before, during or after generation of the treatment fluid, and the apparatus of the first aspect or any of its embodiments, with the apparatus of the first aspect being arranged to receive the first waste fluid from the one or more first fluid lines.

[0016] A third aspect is a method of handling waste fluid from a system for use in dialysis therapy. The method comprises: receiving, from one or more supply lines of the system, the waste fluid through a top portion of a container; and operating a pumping device, which is arranged in a drain line that is fluidly connected to a bottom portion of the container, to draw the waste fluid from the container along the drain line to maintain at least a minimum spacing between a top fluid surface defined by the waste fluid in the container and a respective outlet of the one or more supply lines, so as to impede propagation of microorganisms from the drain line into the system.

[0017] A fourth aspect is a computer-readable medium comprising program instructions, which when executed by processing circuitry causes the processing circuitry to perform the method of the third aspect.

[0018] These aspects have the technical effect of impeding or mitigating propagation of microorganisms from the drain into the system, since the spacing above the top fluid surface forms a barrier that makes it difficult for microorganisms to migrate from the waste fluid in the container into the outlet of the respective supply line above the top fluid surface. Any supply line that is particularly prone to microbial growth may be intermittently disinfected, for example by the system generating a flow of cleaning fluid through the supply line, whereas the drain line downstream of the drain container needs less or no treatment by disinfection thanks to the barrier in the container. Another technical advantage of the foregoing aspects is that the pumping device ensures a controlled flow of waste fluid through the drain line to the drain. This facilitates installation by allowing the installer to route the drain line freely from the container to the drain without, for example, having to consider the risk for backflow. Yet another technical advantage is that waste fluid from any number of supply lines may be collected in the container, so that it is sufficient to install a single drain line from the container to the drain. This facilitates installation and reduces the risk for undetected leaks since there is only one drain line. Further, the drain line may be automatically checked for disruptions by monitoring the operation of the pumping device, the fluid level in the container, or the fluid pressure downstream of the pumping device.

[0019] Below, embodiments of the apparatus of the first aspect are recited.

[0020] In some embodiments, the apparatus is configured to, when at least part of the system is subjected to a cleaning procedure, receive heated waste fluid in the container from at least one of the one or more supply lines. In some embodiments, the minimum spacing corresponds to a predefined level in the container, and the control arrangement is configured to, during the cleaning procedure, operate the pumping device to arrange the top fluid surface at or above the predefined level.

[0021] In some embodiments, the apparatus comprises a further drain line, which is fluidly connected to one or more further supply lines of the system to receive further waste fluid from a respective outlet of the one or more further supply lines, wherein the further waste fluid has a lower temperature than the heated waste fluid, wherein the further drain line extends to a juncture on the drain line, and wherein the apparatus is operable to generate a mixture of the heated water fluid and the further waste fluid in the drain line.

[0022] In some embodiments, the juncture is located upstream of the pumping device in the drain line.

[0023] In some embodiments, the apparatus comprises a further container, which is configured to be arranged to receive, through a top portion of the further container, the further waste fluid from the respective outlet of the one or more further supply lines, the further waste fluid defining a further top fluid surface in the further container.

[0024] In some embodiments, the apparatus comprises a flow controller in the further drain line, wherein the control arrangement is configured to selectively operate the flow controller to provide the further waste fluid into the drain line.

[0025] In some embodiments, the control arrangement is further configured to selectively operate the flow controller to maintain at least a further minimum spacing between the further top fluid surface in the further container and the respective outlet of the one or more further supply lines so as to impede propagation of microorganisms from the further drain line into the system.

[0026] In some embodiments, the control arrangement is configured to operate at least one of the flow controller or the drain pump, so that a temperature of a resulting fluid in the drain line downstream of the juncture is below a maximum temperature.

[0027] In some embodiments, the apparatus comprises a heat transfer device, which is arranged in the drain line and configured to transfer heat from the heated waste fluid to a flow of product water for use in the cleaning procedure.

[0028] In some embodiments, the heat transfer device is arranged upstream of the juncture.

[0029] In some embodiments, the control arrangement is further configured to operate the pumping device to generate a flow rate of the heated waste fluid through the heat transfer device so as to achieve a target transfer of heat from the heated waste fluid. In some embodiments, the apparatus further comprises a bypass arrangement with a bypass line for fluid communication with the drain line upstream and downstream of the heat transfer device, wherein the control arrangement is configured to intermittently operate the bypass arrangement to direct the heated waste fluid via the bypass line into the drain line downstream of the heat transfer device.

[0030] In some embodiments, the container is operable to be selectively opened and closed to its surroundings, and the control arrangement is configured to close the container to the surroundings during at least part of the cleaning procedure.

[0031] In some embodiments, the container is configured to be permanently open to its surroundings, and the control arrangement is configured to operate the pumping device to empty the container after the cleaning procedure and maintain the container empty for a time period to allow moisture in the container to evaporate into the surroundings.

[0032] In some embodiments, the container is configured to receive the waste fluid from at least two supply lines of the system, and a single drain line is fluidly connected to the bottom portion of the container.

[0033] In some embodiments, the drain line comprises a first line portion and a second line portion, and the first line portion extends from the container to a first terminal connector, which is configured to establish a fluid connection with a second terminal connector on the second line portion.

[0034] In some embodiments, the control arrangement is configured to determine a momentary flow rate of the waste fluid in the one or more supply lines and operate the pumping device based on the momentary flow rate to maintain said at least a minimum spacing.

[0035] In some embodiments, the apparatus comprises a sensor arrangement, which is configured to generate a sensor signal indicative of a momentary level of the top fluid surface in the container, and the control arrangement is configured to operate the pumping device based on the sensor signal to maintain said at least a minimum spacing.

[0036] In some embodiments, the sensor arrangement comprises a pressure sensor, which is arranged to measure a momentary pressure of the waste fluid in the container, and the sensor signal represents the momentary pressure.

[0037] In some embodiments, the control arrangement is configured to perform a calibration procedure, comprising: obtaining an initial pressure value from the sensor signal for a first level of the top fluid surface in the container; obtaining a subsequent pressure value from the sensor signal after receiving an amount of waste fluid from the one or more supply lines resulting in a second level of the top fluid surface in the container; and defining, based on the initial and subsequent pressure values and the first and second levels, a conversion function from pressure to level of the top fluid surface. In some embodiments, the control arrangement is configured to perform a flow rate measurement, comprising: closing the drain line by the pumping device or an optional drain valve in the drain line; determining, based on the sensor signal, an increase in pressure while the container receives the waste fluid from the one or more supply lines for a predefined time period; and calculating a flow rate of the waste fluid based on the increase in pressure and the predefined time period.

[0038] In some embodiments, the container is operable to be selectively opened and closed to its surroundings, and wherein the control arrangement is configured to, upon detection of a need for priming of the pumping device, close the container to the surroundings so that waste fluid entering the container creates a backing pressure in the container, and operate the pumping device when a limit backing pressure is created in the container, as indicated by the sensor signal, to prime the pumping device by waste fluid from the container.

[0039] In some embodiments, the container is operable to be selectively opened and closed to its surroundings, and the control arrangement is configured to perform a temperature measurement, comprising: operating the pumping device to achieve a selected level of the top fluid surface in the container, obtaining a first pressure value from the sensor signal when the waste fluid in the container has a known first temperature, closing the container to the surroundings, operating the pumping device to maintain the selected level in the container while receiving waste fluid from the one or more supply lines, obtaining a second pressure value from the sensor signal, and estimating a temperature of the waste fluid in the container based on the first temperature, and the first and second pressure values.

[0040] In some embodiments, the apparatus further comprises an air flow channel in fluid communication with the top portion of the container, and a control valve which is operable to selectively open and close the air flow channel to thereby open and close, respectively, the container to its surroundings.

[0041] In some embodiments, the control arrangement is configured to, while the air flow channel is open, monitor the sensor signal for detection of a pressure increase corresponding to the waste fluid flowing into the air flow channel, and take dedicated action upon detection of the pressure increase.

[0042] In some embodiments, the container is configured to be permanently open to its surroundings, and the control arrangement is configured to, upon detection of a need for priming the pumping device, operate the pumping device to prime the pumping device by waste fluid from the container when a predefined fluid level is attained in the container, the predefined fluid level corresponding to a predefined fluid pressure at an inlet of the pumping device. In some embodiments, the control arrangement is configured to receive input data indicative of at least one of a drive power of the pumping device, a fluid pressure in the drain line downstream of the pumping device, or a fluid level in the container; evaluate the input data for detection of a disruption in the drain line downstream of the pumping device and generate an alert signal upon detection of the disruption.

[0043] In some embodiments, no further container is fluidly connected in series with the container along the drain line.

[0044] In some embodiments, the control arrangement is configured to enable a continuous flow of waste fluid through the container.

[0045] In some embodiments, the control arrangement is configured to, at least intermittently, operate the pumping device while the waste fluid enters the container as a continuous fluid stream from the one or more supply lines.

[0046] The foregoing embodiments are equally applicable to the second, third and fourth aspects. Some further embodiments of the system of the second aspect are recited below.

[0047] In some embodiments, the system of the second aspect further comprises a second sub- system, which is fluidly connected to receive the treatment fluid from the first subsystem and configured to perform the dialysis therapy by use of the treatment fluid. The second sub-system comprises one or more second fluid lines for disposal of second waste fluid produced by the second sub-system before, during or after the dialysis therapy, with the apparatus of the first aspect being arranged to receive the second waste fluid from the one or more second fluid lines.

[0048] In some embodiments, the system of the second aspect further comprises a third sub- system, which is fluidly connected to receive source water and is configured to generate the product water by purification processing of the source water, with the first sub- system being fluidly connected to receive the product water from the third subsystem. The third sub-system comprises one or more third fluid lines for disposal of third waste fluid produced by the third sub-system before, during or after the purification processing, with the apparatus of the first aspect being arranged to receive the third waste fluid from the one or more third fluid lines.

[0049] A fifth aspect is a system for use in dialysis therapy. The system comprises a subsystem, which is configured to perform the dialysis therapy by use of a treatment fluid. The sub-system comprises one or more fluid lines for disposal of waste fluid produced by the sub-system before, during or after the dialysis therapy, with the apparatus of the first aspect being arranged to receive the waste fluid from the one or more fluid lines.

[0050] A sixth aspect is a system for use in dialysis therapy. The system comprises a subsystem, which is configured to generate product water by purification processing of source water. The sub-system comprises one or more fluid lines for disposal of waste fluid produced by the sub-system before, during or after the purification processing, with the apparatus of the first aspect being arranged to receive the waste fluid from the one or more fluid lines.

[0051] Still other objectives, aspects, embodiments, and technical effects, as well as features and advantages may appear from the following detailed description, from the attached claims as well as from the drawings.

[0052] Brief Description of the Drawings

[0053] FIGS 1A-1B are schematic views of example dialysis systems connected to a patient.

[0054] FIG. 1C is a block diagram of a combination of an example dialysis system, and a waste handling apparatus (WHA) for disposal of waste fluid generated by the dialysis system.

[0055] FIG. 2A is a side view of an installation of an example WHA, and FIG. 2B is a side view of an example WHA during operation.

[0056] FIGS 3A-3B are flow charts of example methods of operating a WHA.

[0057] FIGS 4A-4B are side views of WHAs in accordance with embodiments.

[0058] FIG. 5A is a flow chart of an example pressure-controlled method of operating a WHA, and FIG. 5B is a flow chart of an example calibration method.

[0059] FIG. 6A is a flow chart of an example method of operating a WHA to measure a flow rate, and FIG. 6B is a flow chart of an example method of monitoring operation of a WHA.

[0060] FIGS 7A-7B are flow charts of example methods of priming a drain pump in a WHA.

[0061] FIG. 8 is a block diagram of an example combination of a dialysis system and a WHA.

[0062] FIG. 9 is a flow chart of an example method of operating a WHA during heat treatment.

[0063] FIG. 10 is a flow chart of an example method of operating a WHA to estimate a fluid temperature.

[0064] FIG. 11 A is a block diagram of an example combination of a dialysis system and a WHA, and FIGS 1 IB-11C are flow charts of example methods of operating the combination in FIG. 11 A.

[0065] Detailed Description of Example Embodiments Embodiments will now be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all, embodiments are shown. Indeed, the subject of the present disclosure may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure may satisfy applicable legal requirements.

[0066] Also, it will be understood that, where possible, any of the advantages, features, functions, devices, and / or operational aspects of any of the embodiments described and / or contemplated herein may be included in any of the other embodiments described and / or contemplated herein, and / or vice versa. In addition, where possible, any terms expressed in the singular form herein are meant to also include the plural form and / or vice versa, unless explicitly stated otherwise. As used herein, "at least one" shall mean "one or more" and these phrases are intended to be interchangeable. Accordingly, the terms "a" and / or "an" shall mean "at least one" or "one or more", even though the phrase "one or more" or "at least one" is also used herein. As used herein, except where the context requires otherwise owing to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" is used in an inclusive sense, that is, to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments.

[0067] As used herein, the terms "multiple", "plural" and "plurality" are intended to imply provision of two or more elements. The term "and / or" includes any and all combinations of one or more of the associated listed elements.

[0068] It will furthermore be understood that although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing the scope of the present disclosure.

[0069] Well-known functions or constructions may not be described in detail for brevity and / or clarity. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

[0070] As used herein, "dialysis therapy" refers to any therapy that replaces or supplements the renal function of a patient by use of a medical fluid. Dialysis therapy includes, without limitation, extracorporeal (EC) blood therapy and peritoneal dialysis (PD) therapy.

[0071] As used herein, "treatment fluid" refers to any fluid that is consumed as a result of dialysis therapy. Treatment fluid includes, without limitation, dialysis fluid for infusion into the peritoneal cavity during PD therapy, dialysis fluid for supply to a dialyzer during EC blood therapy, and replacement fluid and substitution fluid for infusion into blood during EC blood therapy.

[0072] As used herein, "waste fluid" refers to any fluid that is discarded as a result of dialysis therapy. Waste fluid may be spent treatment fluid, non-used treatment fluid, a cleaning fluid used for cleaning a dialysis system or part thereof, a priming fluid used for priming a dialysis system or part thereof, any fluid generated as a by-product of a water purification process, etc. Under certain operating conditions of the dialysis system, water may be output as waste fluid from the dialysis system, for example during heat treatment of the dialysis system or part thereof.

[0073] As used herein, "cleaning" refers to a procedure involving at least one of removal (complete or partial) of deposits, or partial removal of microorganisms. The cleaning is performed to ensure the operability of the fluid circuit. Partial removal of microorganisms is also denoted "disinfection" herein. Disinfection may be performed to reduce the number of microorganisms to an appropriate level for the intended use. The cleaning may involve flushing a fluid circuit with a cleaning fluid. The cleaning fluid may be water, which may or may not be heated, depending on the intended type of cleaning. Additionally or alternatively, the water may include a cleaning agent, for example an acid such as citric acid. Disinfection by heated water, with or without cleaning agent, may be performed using time-temperature relationships in accordance with the AO concept.

[0074] Like reference signs refer to like elements throughout.

[0075] The present disclosure relates to a technique of handling waste fluid generated in connection with dialysis therapy performed by one or more machines. The technique is applicable to both peritoneal dialysis (PD) therapy and extracorporeal (EC) blood therapy. For context only, systems for PD therapy and EC blood therapy will be briefly discussed with reference to FIGS 1A-1B.

[0076] FIG. 1A is a generic overview of a dialysis system 10 for PD therapy. The dialysis system 10 is fluidly connected to the peritoneal cavity PC of a patient P. As indicated by a double-ended arrow, the dialysis system 10 is operable to convey fresh dialysis fluid into PC and to receive spent dialysis fluid from PC on a fluid path 11. The fluid path 11 may be defined by tubing that connects to an implanted catheter (not shown) in fluid communication with the peritoneal cavity PC. A drain line 13 is connected to the dialysis system 10 for conveying the spent dialysis fluid to a drain 25. PD therapy is typically implemented as daily treatment sessions, each comprising a number of fluid exchange cycles. The respective fluid exchange cycle may include a fill phase, a dwell phase and a drain phase, performed in sequence. In the fill phase, fresh dialysis fluid is supplied to PC on fluid path 11. In the dwell phase, the dialysis fluid resides in PC. In the drain phase, spent dialysis fluid is extracted from PC on fluid path 11.

[0077] The dialysis system 10 may comprise one or more electrically controlled machines and may be implemented to provide different levels of functionality. In a first implementation, the dialysis system 10 includes a dialysis therapy sub-system which is operable to control the flow of dialysis fluid to and from the PC, and the dialysis system 10 receives pre-made dialysis fluid from a source 20 on a supply path 12. In PD therapy, the dialysis therapy sub-system is commonly known as a "cycler". In a second implementation, the dialysis system 10 includes the cycler and a fluid preparation subsystem that is configured to generate the dialysis fluid for the cycler by mixing one or more concentrates with purified water, which is received from the source 20. In a third implementation, the dialysis system 10 includes the cycler, the fluid preparation subsystem and a water purification sub-system that is configured to generate the purified water based on source water, which is received from the source 20.

[0078] FIG. IB is a generic overview of a dialysis system 10 for EC blood therapy. The dialysis system 10 is fluidly connected to the vascular system of a patient P on a fluid path. In the illustrated example, the fluid path is defined by tubing 11 A for blood extraction and tubing 1 IB for blood return. As indicated by arrows, the dialysis system 10 is operable to draw blood from the patient P through tubing 11 A, process the blood, and return the processed blood to the patient through tubing 1 IB. The tubing 11A, 1 IB is connected to an access device (for example a catheter, graph or fistula, not shown) in fluid communication with the vascular system of the patient P. The dialysis system 10 may be configured to process the blood by any form of EC blood therapy, such as HD, HF or HDF. In HD and HDF, a continuous flow of dialysis fluid is interfaced with the blood of the patient in a filtration unit ("dialyzer"), resulting in a continuous flow of spent dialysis fluid. A drain line 13 is connected to the dialysis system 10 for conveying the spent dialysis fluid to a drain 25. Like in FIG. 1A, the dialysis system 10 may comprise one or more electrically controlled machines and may be implemented to provide different levels of functionality. The first, second and third implementation examples are equally applicable to the dialysis system 10 for EC blood therapy.

[0079] In FIGS 1A-1B, a flow of waste fluid may be guided from the dialysis system 10 through the drain line 13 to the drain 25 before, during and after dialysis therapy. As noted in the Background section, the drain 25 is a potential source of microorganisms that may migrate via the drain line 13 into the dialysis system 10, also denoted "back- contamination" herein. The largest risk for back-contamination occurs when there is no fluid flow in the drain line 13 to the drain 25, for example during the dwell phases in PD therapy, or between therapy sessions of PD therapy or EC blood therapy. Uncontrolled growth of microorganisms in the dialysis system 10 is a health risk for the patient and must be prevented.

[0080] FIG. 1C is a block diagram of an example dialysis system 10 that is combined with a waste handling apparatus (WHA) 40, which is configured to address the problem of back-contamination, as well as other problems. As shown, the WHA 40 is arranged intermediate the dialysis system 10 and the drain 25 to receive waste fluid from the dialysis system 10 and channel the waste fluid towards the drain 25. The WHA 40 is configured to form a barrier to microbial migration from the drain 25 to the dialysis system 10. As described detail below, the WHA 40 is actively controlled by a control arrangement 50 to pump waste fluid produced by the dialysis system 10 to the drain 25.

[0081] The dialysis system 10 in FIG. 1C may be configured for PD therapy or EC blood therapy, for example as shown in FIGS 1A-1B. The dialysis system 10 may be operated by the control arrangement 50, or a separate controller (not shown), in conventional manner to perform dialysis therapy in accordance with a treatment schedule, which may be predefined or entered by a user, such as a caretaker or the patient. In the illustrated example, the dialysis system 10 comprises modules or sub-systems 10A-10C that provide a respective functionality. The sub-systems 10A-10C may be implemented by separate machines or be combined into one or two separate machines.

[0082] Sub-system 10A is operable to generate product water, PW, based on source water, SW, and is denoted "water purification sub-system" or WPS herein. The product water PW is purified water that may be generated to meet criteria of so-called "water for dialysis" "water for injection", or "ultrapure water". Water for dialysis may be defined in accordance with the standard ANSI / AAMI / ISO 23500-3:2019. Requirements for water for injection are for example defined in the Official Monographs for water, United States Pharmacopeia (USP) 39 National Formulary (NF) 34 (Aug. 1, 2016). The requirements include recommended temperature-dependent limits on water conductivity, amount of Total Organic Carbon (TOC), and amount of bacterial endotoxins. The limit on water conductivity is defined in USP 645 (Aug. 1, 2016). For example, at 20°C the conductivity of the water should be less than 1.1 pS / cm, at 25°C the conductivity of the water should be less than 1.3 pS / cm, etc. The amount of TOC should be less than 0.5 mg / L (500 ppb), the amount of bacteria should be less than 10 CFU / mL and the amount of bacterial endotoxins should be less than 0.25 EU / mL. Ultrapure water may be defined as described in the report "Ultrapure water in haemodialysis: a step towards better quality in Lebanon", by Aoun et al., EMHJ, Vol. 25, No. 2 (2019).

[0083] The source water, SW, may be tap water or any other water of insufficient (or at least unverified) purity and / or sterility for use in dialysis therapy. As used herein, the term "water purification" refers to a process of removing undesirable chemicals, biological contaminants, suspended solids, and gases from the water. For example, water purification may involve, in any combination, active carbon filtration, ultrafiltration, membrane filtration, ion exchange, electrodeionization, dechlorination, disinfection, softening, etc. Water purification sub-systems are well-known in the art and need no further description.

[0084] Sub-system 10B is operable to generate treatment fluid, TF, based on PW from the WPS 10A and is denoted "fluid preparation sub-system" or FPS herein. The FPS 10B may be configured to generate TF by mixing PW with one or more concentrates. The skilled person is well aware of fluid preparation sub-systems, integrated or standalone, that have been proposed in both scientific literature and patent literature, for use in PD therapy and EC blood therapy.

[0085] Sub-system 10C performs the dialysis therapy by use of treatment fluid and is denoted "dialysis therapy sub-system" or DTS herein. As understood from FIGS 1A-1B, dialysis therapy involves providing a controlled supply of TF and, at least for some modalities of dialysis therapy, receiving spent treatment fluid, STF. Dialysis therapy sub-systems are well-known in the art and need no further description.

[0086] In the illustrated example, each of the sub-systems 10A-10C provides waste fluid for disposal. The flow rate of waste fluid from the respective sub-system may vary over time, and the composition of the waste fluid from the respective sub-system may vary over time. The WPS 10A provides WF1, which may comprise water with impurities removed from SW by the WPS 10A. At times, WF1 may include a priming fluid during a priming of the WPS, or a cleaning fluid during cleaning the WPS. The FPS 10B provides WF2, which may include non-used TF and, at times, priming fluid or cleaning fluid. The non-used TF may, for example, be provided during start-up of the FPS 10B before the composition of TF has stabilized, or when the composition of TF is changed. The DTS 10C provides WF3, which may include STF and, at times, priming fluid or cleaning fluid.

[0087] FIG. 2A is a section view of a waste handling apparatus (WHA) 40 as installed in fluid connection with a dialysis system (not shown). The WHA 40 comprises a tank or container ("drain container") 41 which defines a chamber for receiving waste fluid. In the illustrated example, two supply lines 111 A, 111 B are arranged with a respective opening or outlet 42A, 42B at the top portion of the tank 41. The supply lines 111A, 11 IB are arranged to convey waste fluid from a respective sub- system in the dialysis system. Any number of supply lines may extend to the tank 41. A supply pump Pl, P2 is arranged in the respective supply line 111 A, 11 IB to pump the waste fluid. The supply lines 111A, 11 IB and the pumps Pl, P2 may be part of the WHA 40 or the dialysis system. In practice, the pumps Pl, P2 are typically controlled as part of the dialysis system. An outlet opening 43 is provided in the bottom portion of the tank 41 and fluidly connected to a drain path 13. In the illustrated example, the drain path 13 is defined by tubing that extends to a toilet, which forms the drain 25. The WHA 40 includes a pumping device 44 ("drain pump") in the drain path 13. The operation of the drain pump 44 is controlled by a control signal Cl, which is generated by the control arrangement 50 (FIG. 1C). The drain pump 44 may be of any type, including but not limited to a peristaltic pump, a gear pump, a screw pump, a lobe pump, a vane pump, a diaphragm pump, etc. In the illustrated example, the WHA 40 includes a level sensor 46, which is arranged to indicate the momentary fluid level in the tank 41 and output a corresponding sensor signal SI. In some embodiments, described further below, the level sensor 46 is a pressure sensor. Alternatively or additionally, the level sensor 46 may include a weight sensor, an electrode-based sensor, an ultrasonic sensor, a capacitance sensor, a float sensor, an optical sensor, or any other sensor that is conventionally used for fluid level detection. The level sensor 46 may be configured to detect a plurality of discrete fluid levels or a continuum of fluid levels. In some embodiments, the level sensor 26 is configured to detect a single fluid level in the tank 41.

[0088] During operation of the WHA 40, the drain pump 44 is operated to maintain a spacing or air gap G between a top fluid surface TS in the tank 41 and the openings 42A, 42B of the supply lines 111 A, 11 IB. If the openings 42A, 42B are arranged at different levels in relation to the tank, the spacing G is defined in relation to the opening that is closest to the fluid level TS (provided there is a spacing / air gap G between the openings 42A, 42B and the top fluid surface TS). The spacing G will form a barrier for migration of microorganisms from the waste fluid in the tank 41 into the supply lines 111A, 1 IB via the openings 42A, 42B. There may be a small risk that microorganisms migrate on the walls of the tank 41 to the openings 42A, 42B but such migration is slow and may be counteracted by regular cleaning of the tank 41, for example by heat treatment as described further below. The Applicant has also verified that migration of microorganisms is minimal when the openings 42A, 42B is in fluid contact with the surface TS via the inflowing waste fluid, for example as shown in FIG. 2B. The directional flow of the waste fluid into the tank 41 will effectively prevent such migration.

[0089] The WHA 40 provides the general advantage of enabling a single drain path to the drain 25, irrespective of the number of outlets for waste fluid on the dialysis system. This facilitates installation of the dialysis system, reduces the risk of leaks and makes it easier to make a discrete installation of the drain path 13 in the facility where the dialysis therapy is performed. Further, the drain pump 44 will drive the waste fluid to the drain, thereby reducing the impact of bends, varying elevation, and other obstacles to the flow through on the drain path 13. It also allows the WHA 40 to be installed at any elevation in relation to the drain 25.

[0090] Further, the WHA 40 enables simple and robust detection of disruptions in the drain path 13 downstream of drain pump 44, by the control arrangement 50. Such disruptions include blockage or leakage of tubing. Blockage may be caused by kinking. To detect a blockage, the drive power (or equivalently, drive current) of the drain pump 44 may be monitored in conjunction with the pressure in the tank 41. A blockage may be detected when the drive power increases whereas the tank pressure is unchanged. The monitoring of the drive power of the pump 44 may be replaced by a monitoring of the pressure downstream of the drain pump 44, given by a dedicated pressure sensor (not shown). To detect a leakage, the drive power of the drain pump 44 or the pressure downstream of the drain pump 44 may be monitored. A leakage may be detected when there is a step-change decrease in the monitored drive current or pressure. Alternatively or additionally, disruptions in the drain path 13 may be detected when the change in fluid level or measured pressure in the tank 41 is unexpectedly small in response to a change in speed of the drain pump 44. Upon detecting a potential disruption, the control arrangement 50 may generate an alert signal and / or cause the operation of the dialysis system to be terminated. Thus, the control arrangement 50 may obtain and evaluate input data for detection of a disruption of the drain line 13 downstream of the drain pump 44. The input data may be in the form of one or more signals and may, for example, be indicative of a drive power of the drain pump 44, a fluid pressure in the drain line 13 downstream of drain pump 44, or a fluid level in the tank 41, or any combination thereof.

[0091] In the illustrated example, the drain path 13 comprises a first line segment or portion ("first drain line") 13A, which is part of the WHA 40, and a second line segment or portion ("second drain line") 13B, which is attached to the first line segment 13A and is arranged to extend to the drain 25. The first line segment 13A is terminated by a terminal connector 45 A. The second line segment 13B comprises a terminal connector 45B, which is configured to establish a fluid connection between the segments 13 A, 13B when joined with the connector 45 A. The combination of line segment 13B and connector 45B forms a replaceable device. Thereby, the length of the drain path 13 may be simply adapted to the needs of a specific installation, by selecting a replaceable device with a suitable length, or by cutting the line segment 13B to a suitable length. If the dialysis system is moved to a new location, a new replaceable device may be attached to the WHA 40 if necessary to reach the drain. The replaceable device may also be simply exchanged, for example if it is damaged, worn or dirty, without the need to also replace the WHA 40.

[0092] FIG. 2B shows the WHA 40 during operation, while first and second waste fluids enter the tank 41 through the respective supply line 111 A, l l lB at a respective flow rate QA, QB. Depending on implementation, the first and second waste fluids may be a respective one of WF1, WF2, WF3 in FIG. 1C. As indicated to the left of the tank 41, the fluid level in the tank 41 may be measured, resulting in a current fluid level He. As shown, He corresponds to a current spacing Ge. Further, a maximum allowable fluid level Hmax in the tank 41 is defined, which corresponds to a minimum allowable spacing Gmin. The minimum spacing Gmin is set to provide a sufficient barrier to transfer of microorganisms from the fluid surface TS to the openings 42A, 42B.

[0093] FIG. 3A is a flow chart of an example method 310 of operating a WHA 40, for example as shown in FIGS 2A-2B. In step 311, waste fluid is received in tank 41. The flow of waste fluid into the tank 41 may be continuous or intermittent. In step 312, the fluid level in the tank 41 (drain container) is monitored based on the signal SI from the level sensor 46. In step 313, the speed of the drain pump 44 is controlled to maintain a spacing (air gap) of at least Gmin in the tank 41 (FIG. 2B). Steps 312-313 are performed by the control arrangement 50 (FIG. 1C), with the speed of the drain pump 44 being set by the control signal Cl (FIG. 2A). As indicated by step 313A, the fluid level in the tank may be held at a fixed and predefined level, or be allowed to reciprocate between two levels. The implementation of the level control may depend on the capabilities of the level sensor 46, for example its accuracy, resolution, number of detected levels, etc. In the method 310, the operation of the drain pump 44 is controlled solely based on the sensor signal SI from the level sensor 46. It is realized that the level sensor 46 serves to decouple the control of the drain pump 44 from the control of the pumps Pl, P2 in the dialysis system. This renders the operation of the WHA 40 independent of the dialysis system, which in turn facilitates integration of the WHA 40 with both new and existing dialysis systems.

[0094] FIG. 3B is flow chart of a method 320, which is an alternative to the method 310 for use when the WHA 40 lacks a level sensor 46. In step 321, waste fluid is received in tank 41. In step 322, the flow rate of incoming waste fluid is monitored to quantify the momentary flow rate. In the example of FIG. 2B, the flow rates QA and QB are monitored. The flow rate of waste fluid into the tank 41 may be monitored in real time based on signals from a flow meter (not shown) in the respective supply line 111 A, 11 IB, based on the speed of the respective pump Pl, P2, or based on a status signal from the dialysis system or its controller. For example, the status signal may include momentary (current) values of the flow rates QA, QB. In step 323, the drain pump 44 is operated to maintain a spacing (air gap) of at least Gmin in the tank 41 (FIG. 2B), by setting the flow rate QD (FIG. 2B) generated by the drain pump 44 relative to the flow rate of incoming waste fluid. For example, the momentary flow rate QD may be set equal to the momentary flow rate of waste fluid into the tank 21, which is the sum of QA and QB in FIG. 2B. Steps 322-323 are performed by the control arrangement 50 (FIG. 1C), with the speed of the drain pump 44 being set by the control signal Cl (FIG. 2A). One potential advantage of the method 320 over the method 310 is that the drain pump 44 may need to be operated less frequently, since the amount of waste fluid to enter the tank 41 at each time point is anticipated through step 322, leading to a reduction of noise from the pump 44 and less wear of the pump 44.

[0095] In the examples of FIG. 3A, it is assumed that the flow rate of waste fluid into the tank 41 cannot be controlled by the control arrangement 50. However, if the control arrangement 50 is operatively connected to the pumps Pl, P2, it is conceivable that the respective speed of the pumps Pl, P2 is controlled instead of, or in addition to, the speed of the drain pump 44 to maintain Gc > Gmin.

[0096] In some embodiments, the WHA 40 is configured to enable a continuous flow of waste fluid through the tank 41. As used herein, a "continuous flow of waste fluid through the tank" implies that waste fluid is pumped out of the tank 41 by the drain pump 44 at the same time as waste fluid flows into the tank 41 via one or more of the supply lines 111 A, 11 IB . There is thus a concurrent flow of waste fluid into and out of the tank 41. It is to be noted that the WHA 40 need not be actively controlled to establish such a continuous throughflow of waste fluid but the WHA 40 may rather be configured without any constraints or limitations in this respect. In other words, the WHA 40 is not intentionally configured and operated to prevent a continuous throughflow. Instead, the WHA 40 "enables" or "allows" a continuous throughflow to be established at any time, as required to maintain the spacing (air gap), while the dialysis system produces waste fluid. Stated differently, the WHA 40 is configured to, at least intermittently, operate the drain pump 44 while waste fluid enters the tank 41.

[0097] One benefit of allowing a continuous throughflow is to make the size of the tank 41 independent of the type of dialysis system and its operation. It also allows for a significant reduction in the size of the tank 41. For example, in PD, the amount of spent treatment fluid (STF) to be extracted during the drain phase is typically 2-3 L. If the STF is continuously extracted and pumped to the WHA 40, and if a continuous throughflow of the tank 41 is prohibited, the tank 41 needs to have a volume of at least 3 L. If the WHA 40 is used with a dialysis system for EC blood therapy, the amount of continuously generated STF may be at least 10 times larger, making the size of the tank 41 an even greater problem. For reasons of usability and ease of installation, it is generally desirable for the WHA 40 to have a small footprint. This is achieved by having a small tank 41, since the footprint of the WHA 40 is largely determined by the tank 41. Another reason for limiting the size of the tank 41 is to facilitate cleaning (below) of the tank 41. A large tank is more difficult to clean than a small tank. Further, if the cleaning involves heat treatment, the available amount of heated fluid may not be sufficient for cleaning a large tank, or an undesirably large amount of heated fluid may need to be provided, resulting in an undesirably high energy consumption.

[0098] In some embodiments, the tank 41 has a size of about 0.1-2 L, for example about 0.3-1 L.

[0099] In some embodiments, for example as shown in FIG. 2A, the WHA 40 includes one and only one tank 41 for handling the waste fluid from the supply lines 111A, 11 IB. In other words, there is no further tank for receiving the waste fluid downstream of the tank 41. Instead, the drain path 13 is formed as a flow channel that extends from the tank 41 to the drain 25. Stated otherwise, the WHA 40 is free of containers or tanks that are fluidly connected in series. The use of a single tank reduces the footprint of the WHA 40 and facilitates cleaning.

[0100] In some embodiments, the respective supply line 111A, 11 IB has an opening 42A, 42B that is configured to generate a continuous stream of waste fluid into the tank 41. As used herein, a "continuous stream" implies that the fluid flow is spatially coherent, so as to form an uninterrupted column of flowing waste fluid between the opening 42A, 42B and the top surface TS in the tank 41. This is believed to improve operational robustness, by limiting the risk that deposits build up at the opening. To ensure a continuous stream of waste fluid the opening 42A, 42B may be unobstructed, for example by being free of any fluid dispersion element, such as a diffuser, atomizer, nozzle, aspirator or the like that would convert fluid flow into a spray or mist.

[0101] FIG. 4A is a side view of a first implementation example of the WHA 40. The tank 41 is a closed vessel which may be selectively opened to its surroundings. In the context of the present disclosure, "opened to its surroundings" implies an atmospheric pressure in the tank 41 above the top surface TS. The supply lines 111A, 11 IB are fluidly connected to the tank 41 at its top, and the drain path 13 extends from the outlet 43. The openings 42A, 42B are spaced from each other to mitigate the risk of crosscontamination, in which microorganisms migrate from one opening to the other. Compared to the example in FIG. 2A, the WHA 40 further comprises an air flow channel 47, which is fluidly connected to the top portion of the tank 41. An on / off valve 48 ("release valve") is arranged in the channel 47. The valve 48 is operable to selectively open the tank 41 to its surroundings. As shown, a flow restrictor 48 A may be arranged in the channel 47, for example intermediate the tank 41 and the valve 48. Further, compared to FIG. 2A, an on / off valve 44A ("drain valve") is arranged in the drain path 13 upstream of the drain pump 44. One purpose of the drain valve 44A is to prevent the tank 41 from being unintentionally drained by siphoning to the drain 25, which may occur if the drain pump 44 is not occluding when stopped. In the example of FIG. 4A, the level sensor 46 is arranged at the bottom of the tank 41. In some embodiments, the level sensor 46 is a pressure sensor. Potential uses of the pressure sensor 46 will be described below with reference to FIGS 5-6.

[0102] FIG. 4B is a side view of a second implementation example of the WHA 40. Here, the tank 41 is an open vessel, which thus is permanently open to its surroundings at its top. The supply lines 111 A, 111 B are arranged with their openings 42A, 42B so that the waste fluid flows into the open top of the tank 41. The openings 42A, 42B may be located at any elevation in relation to the top of the tank 41. To reduce the risk for fluid spillage around the tank 41, the openings 42A, 42B may be arranged to extend into the tank 41. Like in FIG. 4A, a level sensor 46 in the form of a pressure sensor may be arranged at the bottom of the tank 41. In the illustrated example, the WHA 40 comprises an additional level sensor 46', which is configured to output a signal SI' when a predefined fluid level is attained in the tank 41. In a non-limiting example, the sensor 46' is a switch that is responsive to a single fluid level. The predefined fluid level may be located above the maximum allowable fluid level, Hmax (FIG. 2B), and the signal SI' may be used by the control arrangement 50 to detect a malfunction of the WHA 40 that will cause an overflow of waste fluid. Upon detecting the malfunction, the control arrangement 50 may generate an alert signal and / or cause the operation of the dialysis system to be terminated. Like in FIG. 4B, a drain valve 44A is arranged in the drain path 13 upstream of the drain pump 44.

[0103] A corresponding sensor 46' may be installed in the WHA 40 of FIG. 4A and used for detecting a malfunction that will cause the tank 41 to be overfilled.

[0104] Compared to FIG. 4A, the WHA in FIG. 4B has a simpler structure and fewer components. Further, the open tank 41 will automatically dry up when not in use, thereby reducing the risk for microbial growth inside the tank 41. In some embodiments, the WHA may include an air circulation device (not shown), such as a fan or blower, to achieve a forced ventilation of the open tank 41 to speed up the drying process. Further, the risk of microbial growth from the internal wall of the tank 41 into the openings 42A, 42B is minimal since the openings 42A, 42B and the internal wall are physically spaced apart. On the other hand, advantages of the WHA in FIG. 4A include a reduced risk for spillage of waste fluid around the tank 41 and a more controlled containment of odors that may be released from the waste fluid. To mitigate the release of odors, the air flow channel 47 may be connected to a device for odor reduction, for example including activated carbon filter(s), air filter(s), UV radiation source(s), etc. The device for odor reduction may be or include a conventional air purifier. Another advantage of the WHA 40 in FIG. 4 A may be that cleaning of the tank 41, for example for disinfection, is improved and / or facilitated by the use of a closed vessel. Likewise, if the cleaning involves heat treatment, the closed vessel may be operated to prevent uncontrolled release of heat and heated vapor to the surroundings.

[0105] FIG. 5A is a flow chart of an example method 510 of operating the WMA 40 in FIG. 4A or FIG. 4B. The method 510 may be performed by the control arrangement 50. In the method 510, the level sensor 46 is a pressure sensor, which is arranged to measure the hydrostatic pressure in the tank 41. As used herein, the hydrostatic pressure in the tank refers to the pressure exerted by the waste fluid in the tank 41 by the force of gravity. The pressure sensor 46 may be arranged level with the bottom surface of the tank 41, or at a known distance above the bottom surface.

[0106] In some embodiments, the method 510 is performed while the tank 41 is open to its surroundings. Thus, the release valve 48 is opened, if not already open, in step 511. Step 511 is omitted in the example of FIG. 4B. In step 512, the hydrostatic pressure in the tank 41 is determined from the signal SI. Step 512 is performed repeatedly to yield a respective current pressure, Pc. In step 513, the current fluid level He in the tank 41 is calculated as a function of Pc. Step 513 may be performed by use of a level function, which has Pc as a variable: He = fl (Pc). The level function may be determined analytically or experimentally, for example according to the method 520 (below). For an open tank, the hydrostatic pressure at the sensor 46 is given analytically as: Pc = p ■ g ■ (He — HO), with p being the density of the waste fluid, g being the acceleration of gravity, He being the current fluid level relative to the bottom surface of the tank, and H 0 being the distance from the sensor 46 to the bottom surface. Thus, the level function is given, analytically, by: He = HO + Pc / (p ■ g). In step 514, the speed of the drain pump 44 is controlled to maintain He < Hmax (cf. FIG. 2B) in the tank 41, with He being given by step 513.

[0107] FIG. 5B is a flow chart of an example method 520 of calibrating the pressure sensor 46 for level measurements. The method 520 may be performed by the control arrangement 50. The method 520 results in an experimentally determined level function, for use in the method 520. If the method 510 is performed for a tank that is open to its surroundings, so is the method 520. Thus, the release valve 48 is opened, if not already open, in step 521. Step 521 is omitted in the example of FIG. 4B. By steps 522-523, the drain pump 44 is operated to empty the tank 41. When the tank 41 is empty, a first reference pressure value PV1 is obtained from the signal SI in step 524. In step 525, a predefined volume VV2 of fluid is added to the tank 41. The fluid may or may not be waste fluid and may or may not be received via the supply lines 111 A, 11 IB . After step 525, a second reference pressure value PV2 is obtained from the signal SI in step 526. In step 527, the level function is defined based on PV1, PV2 and VV2. For example, assuming that the sensor 46 is arranged at the bottom of the tank 41, the level function may be given by parametrizing the function: He = Bl + B2 ■ Pc, by use of PV1, PV2, and VV2.

[0108] The methods 510 and 520 may alternatively be performed while the tank 41 in FIG. 4A is closed to its surroundings. In this case, the signal SI will represent the sum of the hydrostatic pressure Pc and a backing pressure Pb exerted by the air that is trapped above the fluid in the tank 41. It is realized that Pb will vary with fluid level in the tank 41: Pb = / 2(Hc). The level function He = / I (Pc) may be determined by analogy with the method 520 when performed with the release value 48 closed.

[0109] FIG. 6A is a flow chart of an example method 610 of operating the WHA 40 as a flow meter for measuring the flow rate of waste fluid from the dialysis system into the WHA 40. The method 610 may be performed by the control arrangement 50. The measured flow rate may be used to check the performance of one or more flow meters (not shown) in the dialysis system or to obviate the need to install one or more flow meters in the dialysis system to measure the flow rate of waste fluid from one or more included sub-systems (cf. 10A-10C in FIG. 1C). Like the methods 510 and 520, the method 610 may be performed while the tank 41 is open to its surroundings. Thus, the release valve 48 is opened, if not already open, in step 611. Step 611 is omitted in the example of FIG. 4B. In step 612, the drain path 13 is closed to prevent outflow of waste fluid. The drain path 13 may be closed by use of the drain valve 44A or by controlling the drain pump 44. For example, certain types of pumps will inherently block fluid passage when stopped. In step 613, waste fluid is received from a sub-system of the dialysis system during a measurement period, At. In step 614, a measured pressure increase AP during the measurement period is obtained from the signal SI, as a difference in measured pressure between start and end of step 613. In step 615, the average flow rate of waste fluid, Qw, during the measurement period is calculated: Qw = / 3(AP, At). The conversion function f3 may be determined analytically or experimentally. For example, the skilled person understands that the conversion function f3 may be determined experimentally by use of the level function He = I (Pc) from the method 520.

[0110] The method 530 may alternatively be performed while the tank 41 in FIG. 4A is closed to its surroundings. The conversion function Qw = / 3(AP, At) may be similarly determined based on the level function from the method 520 when performed with the release valve 48 closed.

[0111] FIG. 6B is an example method 620 of detecting an overfilling of the tank 41 in the WHA 40 of FIG. 4A. In step 621, the release valve 48 is opened, whereupon the WHA 40 is operated in accordance with the method 510 (FIG. 5A). While the WHA 40 is operated according to the method 510, the signal SI is monitored in step 622 for detection of a characteristic pressure increase that is indicative of waste fluid having entered the air flow channel 47. The characteristic pressure increase may be detected in relation to a pressure threshold. It is understood that the pressure in the tank 41 will increase drastically when all of the compressible air has been pushed out of the tank 41 via the air flow channel 47. To increase the pressure increase even further, the flow restrictor 48A may be arranged in the air flow channel. The flow restrictor 48A is adapted to cause a small pressure drop for air and a significant pressure drop when waste fluid is about to be pushed into the air flow channel 48. When the characteristic pressure increase is detected in step 622, the control arrangement 50 may generate an alert signal and / or cause the operation of the dialysis system to be terminated in step 623.

[0112] Reverting to FIGS 4A-4B, the drain pump 44 may need to be filled with liquid ("primed") in order to start and operate properly. This need for priming applies to positive-displacement pumps and centrifugal pumps. The need for priming may arise when the tank 41 gets empty of fluid, for example after a cleaning operation or as part of the method 520. FIGS 7A-7B are flow charts of example methods 710, 720 of priming a WHA 40. The methods 710, 720 may be performed by the control arrangement 50.

[0113] The method 710 is applicable to the WHA 40 in FIG. 4A. In step 711, a need for priming the drain pump 44 is detected. The need for priming may be detected based on the fluid level in the tank 41 or by direct monitoring of the operation of drain pump 44. For example, a need for priming may be detected whenever the tank 41 is emptied or when the fluid level changes unexpectedly. In another example, uneven speed or an unexpected change in drive current of the drain pump may be a sign of a need for priming. In step 712, the release valve 48 is closed, so as to close the tank 41. In step 713, the pressure at the inlet of the pump 44 is monitored based on signal SI from sensor 46, which is a pressure sensor in this example. During steps 712-713, the drain pump 44 is stopped, which means that the fluid level in the tank 41 will increase as waste fluid flows into the tank 41 from the dialysis system, causing the hydraulic pressure at the bottom to the tank to increase, as well as the backing pressure (P ) in the tank 41. In step 714, when the inlet pressure reaches a predefined pressure limit, the drain pump 41 is started. The pressure limit is set so that the inlet pressure of the pump 44 is sufficient to prime the pump 44 when started. It is realized that step 712 should be performed when the fluid level in the tank 41 is well below Hmax, to enable a substantial increase of the inlet pressure of the pump 44. The pressure in the tank 41 may alternatively be monitored by a dedicated pressure sensor which is separate from the level sensor 46 and installed anywhere within the tank 41. If the dedicated sensor is not arranged at the bottom of the tank, the measured pressure may be converted into inlet pressure by use of the measured pressure in combination with the measured fluid level, as understood by the skilled person.

[0114] The method 720 is applicable to the WHA 40 in FIG. 4B. In step 721, a need for priming is detected in correspondence with step 711 in the method 710. In step 722, the fluid level He in the tank 41 is monitored by the level sensor 46, which may be of any type. In step 723, when the fluid level reaches a limit value, the drain pump 41 is started. The limit value is set so that the inlet pressure of the pump 44, given by the hydraulic pressure of the fluid upstream of the pump 44, is sufficient to prime the pump 44 when started.

[0115] Priming with open tank 41 (method 720) may be simpler to implement, but the priming with a closed tank (method 710) provides a higher inlet pressure at the drain pump for a given fluid level in the tank 41. This allows for use of a smaller tank and / or faster priming in the method 710 compared to the method 720.

[0116] FIG. 8 is a more detailed example of the combination of a dialysis system 10 and a WHA 40 as shown in FIG. 1C. Like in FIG. 1C, the dialysis system 10 comprises a WPS 10A, an FPS 10B, and a DTS 10C. The WPS 10A is arranged to receive SW on a transfer line 101A and to provide PW to the FPS 10B on a transfer line 101B. The transfer line 101 A may be fluidly connected to the supply path 12 in FIGS 1A-1B. The WPS 10A is arranged to output WF1 on an output line 121. The WPS 10A comprises a purification device 102, which performs at least part of the water purification processing. The waste fluid WF1 that is produced by the WPS 10A may originate at least partly from the device 102. In some embodiments, the device 102 is configured for reverse osmosis (RO), in which an RO membrane is used to separate ions, molecules and larger particles from water. Reverse osmosis inherently generates a flow of so- called reject water, which has a lower purity than the product water PW. In some implementations, the reject water, or part thereof, is discarded. Thus, the reject water may be output as WF1 on output line 121 during operation of the WPS 10A.

[0117] The FPS 10B is configured to generate TF by mixing product water PW with one or more concentrates Cx. The respective concentrate is held in a replaceable container 103, which is connected for communication with the FPS 10B on a supply path 104. The respective concentrate may be in liquid form or in the form of a powder or granules. If the concentrate is a powder or granules, the container 103 may be included in a circulation path, which is operable to dissolve the concentrate in PW. The FPS 10B is arranged to receive PW on the transfer line 101B and to provide TF to the DTS 10C on a transfer line 101C. The FPS 10B is arranged to output WF2 on an output line 122. The FPS 10B comprises a mixing device 105, which performs the final preparation of TF. The waste fluid WF2 that is produced by the FPS 10B originates at least partly from the mixing device 105. In some embodiments, WF2 includes excess treatment fluid, also denoted non-used TF herein. The excess TF is discarded fluid that may be output by the mixing device 105 whenever the composition of the generated TF deviates from a target composition, for example during start-up of the FPS, when a concentrate is replaced, when there is a malfunction in the mixing device 105, etc.

[0118] The DTS 10C is configured to perform the dialysis therapy by supplying TF on a supply line 10 ID and obtaining STF on a return line 10 IE in accordance with a treatment schedule. The supply line 10 ID may be fluidly connected to the tubing 11 in FIG. 1A or the tubing 11A in FIG. IB. The return line 101E may be fluidly connected to the tubing 11 in FIG. 1A or the tubing 1 IB in FIG. IB. The DTS 10C is arranged to receive TF on the transfer line 101C, and to output WF3 on an output line 123. In some embodiments, the waste fluid WF3 that is produced by the DTS 10C includes at least STF.

[0119] The output lines 121-123 are fluidly connected to the WHA 40, which may be configured in accordance with any of the examples described herein. In the examples in FIGS 2A-2B and FIGS 4A-4B, the supply lines 111 A, 111 B may correspond to two of the output lines 121-123 in FIG. 8. In a variant, the examples in FIGS 2A-2B and FIGS 4A-4B are modified to include all or only one of the output lines 121-123.

[0120] A control arrangement 50 is configured to generate one or more control signals, collectively designated Cj, based on one or more input signals, collectively designated Si. In the illustrated example, the control arrangement 50 is a system controller for the dialysis system 10 as well as a WHA controller for the WHA 40. The operation of the WHA 40 is controlled through a control signal Cl for the drain pump 44, based on signal SI from level sensor 46. The operation of the dialysis system 10 is schematically represented by control signals C2-C4, one for each sub-system 10A-10C. It is realized that the control of the dialysis system 10 is far more complex in practice and based on a plurality of input signals from the dialysis system, for example from various sensors therein. With reference to the method 320 in FIG. 3B, it is also realized that the control arrangement 50 may know the momentary flow rate of WF1-WF3, given that the control arrangement 50 controls the operation of the dialysis system 10. However, as noted above, the control arrangement 50 may instead be a dedicated controller for the WHA 40. In a further alternative, the operation of the dialysis system 10 is controlled by two or more controllers, which may be implemented by physically separate units. For example, the control arrangement 50 may include a first controller configured to jointly operate the WPS 10A and the FPS 10B, and a second controller configured to operate the DTS 10C.

[0121] The control arrangement 50 is configured to generate the control signal(s) Cj in accordance with predefined logic of the control arrangement 50. The predefined logic may be implemented by hardware, or a combination of hardware and software. In the example of FIG. 8, the control arrangement 50 comprises processor circuitry 51 and computer memory 52. The processor circuitry 51 may comprise one or more processors, such as a CPU, DSP, ASIC, FPGA, etc. A control program may be stored in the memory 52 and executed by the processor circuitry 51 to perform any of the methods, procedures, or functions as described herein. The control program may be supplied to the control arrangement 50 on a computer-readable medium, which may be a tangible (non-transitory) product (e.g., magnetic medium, optical disk, read-only memory, flash memory, etc.) or a propagating signal.

[0122] It is common practice to intermittently perform a disinfection of one or more of the sub-systems 10A-10C of the dialysis system 10. This may be done through a heat treatment, in which the sub-system is flushed with a heated fluid, for example PW or SW, optionally containing a cleaning agent. The DTS 10C may not need to be disinfected if its hydraulic system is defined by fluid lines that are disposed after use. Disposable hydraulic systems, also known as "line sets" in the art, in the DTS 10C are common in the fields of PD and EC blood dialysis. The WPS 10A and the FPS 10B typically need to be disinfected from time to time. During or after the heat treatment, the heated fluid is output as waste fluid from the sub-system. It is not uncommon for the heated waste fluid to have a temperature of 70°C-95°C.

[0123] The present Applicant has found that it is possible to use the heated waste fluid to disinfect the flow path from the respective sub-system to the tank 41, and possibly also the tank 41. The drain path 13 from the tank 41 to the drain 25 is less relevant to disinfect, since microorganisms are prevented from migrating through the tank 41 by the spacing G.

[0124] FIG. 9 is a flow chart of an example method 910 of operating the dialysis system 10 and the WHA 40 in FIG. 8. The method 910 is performed by the control arrangement 50. In step 911, a heat treatment of one or more of the sub-systems 10A-10C is performed. In step 912, if the WHA 40 comprises a tank 41 with a release valve 48 (FIG. 4A), the release valve 48 is closed to close the tank 41. If the tank 41 in the WHA 40 is permanently open (FIG. 4B), step 912 is omitted. In step 913, the heated waste fluid is received in the tank 41. In step 914, the drain pump 44 is operated to achieve a selected fluid level for heat treatment in the tank 41. This selected fluid level may be Hmax (FIG. 2B), or even higher to cover at much as possible of the internal surface area of the tank 41 by the heated waste fluid. Parts that are not directly wetted may nevertheless be subjected to a heat treatment by vapor heat transfer from the waste fluid to the unwetted parts in the closed tank 41. In step 918, the heat treatment of the tank 41 is terminated. The heat treatment may be inherently terminated when no more heated waste fluid is received by the tank 41 from the dialysis system 10. However, it is conceivable that the heat treatment of the tank 41 is extended beyond the heat treatment of the dialysis system, by the drain pump 44 being stopped for a time period to hold heated waste fluid in the tank 41. When the WHA 40 and the dialysis system 10 are operated by separate controllers, the end of the heat treatment may be signaled to the WHA controller from the system controller, or may be indicated by a temperature sensor in the tank 41 or upstream thereof. It may be noted that while it is not the main purpose of the method 910, the drain path 13 downstream of the tank 41 is also likely to be exposed to heated waste fluid as it is pumped from the tank 41 to the drain 25. Thus, the method 910 has the beneficial side-effect of cleaning the drain path 13 to some degree.

[0125] In some embodiments, the method 910 comprises a step 915 of determining the temperature of the waste fluid in the tank 41. If the fluid temperature is too low, the method 910 may be terminated in advance, even before step 914 to avoid a potential wetting of internal surfaces above Hmax. Optionally, an error message may be presented to the operator on a user interface (not shown) connected to the control arrangement 50. Alternatively or additionally, the fluid temperature may be used in step 916 (below). In a first example of step 915, a temperature sensor (not shown) is arranged to measure the fluid temperature in the tank 41. In a second example, if an upstream temperature of the heated waste fluid is known, for example from a temperature sensor in the dialysis system, the fluid temperature in the tank may be estimated in step 915 based on the upstream temperature and by estimating the heat losses between the location of the upstream temperature and the tank 41. A third example of estimating the temperature will be presented below with reference to FIG. 10.

[0126] A step 916 may be performed to determine a duration of the heat treatment ("heat exposure time"). The duration may be determined as a function of the fluid temperature from step 915, for example in compliance with an applicable standard. In a non-limiting example, a fluid temperature of 80°C may require in heat exposure time of 10 minutes, whereas a fluid temperature of 93°C may require in heat exposure time of 30 seconds.

[0127] When the dialysis system 10 is operated independently of the WHA 40, the available time for performing the heat treatment of the tank 41 is largely given by the operation of the sub-system that produces the heated waste fluid, although it may be possible to extend the duration by stopping the drain pump when the flow of heated waste fluid ends, as noted above. Thus, in some embodiments, the method 910 may comprise a step 917 of operating the drain pump 44 to achieve the heat exposure time. However, if the WHA 40 and the dialysis system 10 are jointly controlled, step 917 may comprise operating the dialysis system 10 to provide the heated waste fluid for the time required by step 916.

[0128] It may be noted that a permanently open tank 41 (FIG. 4B) may not be sufficiently disinfected by the heat treatment, since it may be difficult to subject all internal surfaces of the open tank to sufficient heat. However, this is less of a concern in the permanently open tank 41, if the outlet openings for waste fluid (cf. 42A, 42B in FIG. 4B) are spaced from the internal walls of the tank 41, for example as shown in FIG. 4B. By spacing the outlet openings 42A, 42B from the tank 41, microorganisms are prevented from migrating from the tank 41 into the openings 42A, 42B.

[0129] Further, in relation to the permanently open tank 41 (FIG. 4B), the method 910 may include a step 919 in which at least one of the drain pump 44 or the dialysis system 10 is operated to allow the tank 41 to dry up after the heat treatment. In other words, step 919 ensures that the tank 41 is emptied and maintained empty for a sufficient time period to allow any remaining moisture in the tank 41 to evaporate.

[0130] FIG. 10 is a flow chart of an example method 1010 of estimating the temperature of the fluid in a tank 41 with a release valve 48 (FIG. 4A). During steps 1011-1012, the release valve 48 is open. In step 1011, the fluid level in the tank 41 is maintained at a fixed level. If waste fluid enters the tank during step 1011, the drain pump 41 is operated to maintain the fixed fluid level, for example in accordance with method 310 or method 320 (FIGS 3A-3B). The waste fluid in the tank 41 during step 1011 has a known temperature, Tl, which may be given by a temperature sensor in the dialysis system, or be assumed to have a predefined temperature, for example room temperature. In step 1012, the pressure in the tank 41 is measured, for example by use of the level sensor 46, if implemented by a pressure sensor, or by a separate pressure sensor. Step 1012 results in a first pressure value, PT1. In step 1013, the release valve 48 is closed. In step 1014, waste fluid of another temperature is received in the tank 41, for example heated waste fluid originating from a disinfection of a sub-system. During step 1014, the drain pump 44 is operated to maintain the same fixed fluid level as in the step 1011. In step 1015, the pressure in the tank 41 is measured, by analogy with step 1012, resulting in a second pressure value, PT2. In step 1016, the fluid temperature T2 is estimated: T2 = f4(Tl, PT1, PT 2). Since the fluid level is fixed, it may be assumed that the difference between PT1 and PT2 corresponds to the expansion of trapped air caused by the temperature increase from T1 to T2. Thus, in some embodiments, based on the ideal gas law, T2 is given by: T2 = T1 ■ PT2 / PT1.

[0131] FIG. 11 A is a block diagram of an example WHA 40, which is fluidly connected to receive WF1 from a WPS 10A and WF2 from an FPS 10B. Like in FIG. 8, the WPS 10A is arranged to receive SW on transfer line 101A and output PW on transfer line 10 IB, and the FPS 10B is arranged to receive PW on transfer line 10 IB and output TF on transfer line 101C. The WPS 10A comprises a purification device 102 and is arranged to output WF1 on output line 121. As noted with reference to FIG. 8, WF1 may be generated as result of the production of the PW, for example as reject water from an RO process performed by the purification device 102. The flow of WF1 may or may not be output concurrently with the generation of PW. The FPS 10B comprises a mixing device 105, which is fluidly connected to receive one or more concentrates Cx on a fluid line 104. The FPS 10B is arranged to output WF2 on output line 122. A transfer line 10 IB is arranged to convey PW from the WPS 10A to the FPS 10B. The FPS 10B defines an inlet flow path 107 for directing incoming PW to the mixing device 105. The inlet flow path 107 includes a heating sub-module 106, which is operable to generate and supply heated PW for disinfection of the mixing device 105 (or part thereof). In FIG. 11 A, the heating module 106 includes a first temperature sensor 106 A, an electric heater 106B, a second temperature sensor 106C, and a pump 106D. In the illustrated example, the heating sub-module 106 is operated to provide heated PW to the mixing device 105, resulting in a flow of WF2 in the output line 122. Depending on implementation, WF2 may be output in synchronization with the inflow of PW or be buffered for output at a later time.

[0132] One objective of the WHA 40 in FIG. 11 A is to avoid that waste fluid is provided to the drain 25 at a temperature that may potentially damage individuals or the drain itself. This is achieved by separately handling hotter waste fluid and colder waste fluid, and mixing the hotter and colder waste fluids before sending the mixture to the drain.

[0133] In FIG. 11A, the WHA 40 comprises a tank 41, which is arranged to receive WF2 from the FPS 10B via the output line 122. A drain path 13 extends from the outlet of the tank 41 to the drain 25. A further (second or auxiliary) tank 41" is arranged to receive WF1 from the WPS 10A via the output line 121. A further (second or auxiliary) drain path or line 13" extends from the outlet of the second tank 41" to a juncture or intersection point 60 on the drain path 13. The juncture 60 is thus a location where the flows of WF1 and WF2 meet. The juncture 60 may, for example, be formed by a 3-way connector, a tank, a static or dynamic mixer, etc. A drain pump 44 is arranged in the drain path 13 downstream of the juncture 60. A respective flow controller 44A, 44B is arranged upstream of the juncture 60 in the drain path 13 and the second drain path 13", respectively. The flow controllers 44A, 44B may be on / off valves or adjustable flow restrictors. The drain pump 44 and the flow controllers 44A, 44B are jointly operated to maintain a spacing G in the tank 41 and in the tank 41", by analogy with method 310 or method 320 in FIGS 3A-3B. In a variant, the flow controller 44B is a pump. In this variant, the drain pump 44 may be moved upstream of the juncture 60 in the drain path 13, and the respective drain pump 44, 44B may be operated to maintain the spacing G in the respective tank 41, 41". The further tank 41" serves to decouple the operation of the WHA 40 from the operation of the WPS 10A, since colder waste fluid (WF1) may be collected in the tank 41" to be available for mixing with hotter waste fluid (WF2) from the FPS 10B. However, the tank 41" may be omitted if the WPS 10A is known or operable to supply a timely and sufficient amount of colder waste fluid to be mixed with the hotter waste fluid from the FPS 10B. However, this presumes that the risk of microbial migration from the juncture 60 to the WPS 10A is deemed acceptable, since the protective air gap G is omitted together with the further tank 41".

[0134] It is realized that, in connection with a heat treatment of the FPS 10B, the tank 41 will receive heated WF2, whereas the second tank 41" will receive and / or contain WF1, which has a lower temperature than WF2 in the tank 41. To make use of the thermal energy of WF2, a heat transfer device 49 may be arranged in the drain path 13, intermediate the tank 41 and the juncture 60, to transfer thermal energy from the heated WF2 to PW conveyed from WPS 10A to FPS 10B. The transfer of thermal energy will reduce the power consumption of the WPA 10 during heat treatment of the FPS 10B, and may also ensure that a maximum power limit of the FPS 10B is not exceeded by the operation of the heating sub-module 106. The installation of the heat transfer device 49 is relevant when heated WF2 flows out of the FPS 10B while heated PW is generated by the heating sub-module 106. The heat transfer device 49 may be a heat exchanger, as shown, which defines one or more first flow channels 49A for WF2 and one or more second fluid channels 49B for PW, and is configured to perform a heat transfer HT from the first flow channel(s) 49A to the second flow channel(s) 49B, as indicated by a block arrow. In a variant, the heat transfer device 49 is a heat pump that uses a refrigeration cycle to transfer thermal energy. The use of a heat pump may provide increased flexibility in the design of the WHA 40.

[0135] In a variant, not shown, the FPS 10B may be operable, by a valve arrangement, to selectively receive PW on the transfer line 101B, which passes the heat transfer device 49, or on a further transfer line, which extends from the WPS 10A to the FPS 10B without passing the heat transfer device 49. The FPS 10B may be configured to receive PW on the transfer line 10 IB during heat treatment, and to receive PW on the further transfer line during normal operation, i.e., when the mixing device 15 is operated to generate and output TF. This may facilitate temperature control of TF, since the incoming PW is unaffected by the temperature of WF2.

[0136] In the example of FIG. 11 A, the WHA 40 further comprises a bypass arrangement 61, which is provided in the drain path 13 and is selectively operable to redirect the flow of heated WF2 into a bypass line 62, which is arranged to bypass the heat transfer device 49. The drain path 13 is configured for fluid communication with the bypass line 62 at a first location upstream of the heat transfer device 49 and a second location downstream of the heat transfer device 49. The bypass arrangement 61 comprises the bypass line 62 and a valve arrangement. As shown, the valve arrangement may comprise a respective 3-way valve 63A, 63B at the first and second locations. The skilled person understands that other configurations of the valve arrangement are conceivable. By the bypass arrangement 61, the WHA 40 is operable to direct the heated WF2 into the drain path 13 downstream of the heat transfer device 49, so as to intermittently expose this downstream portion of the drain path 13 to the heated WF2. Such a heat treatment operation may be performed at any suitable time point to counteract microbial growth and accumulation of deposits in the downstream portion of the drain path 13. This heat treatment operation is typically performed quite infrequently. Since the heat treatment operation entails disposal of hot waste fluid into the drain 25, a warning to the user may be generated before and during the heat treatment, for example via a user interface (not shown) connected to the control arrangement 50.

[0137] It is likely that a residual amount of heated WF2 remains in the FPS 10B and / or the WHA 40 when the heat treatment of the mixing device 105 is terminated. At least part of the residual amount of heated WF2 may be supplied for heat treatment of the downstream portion of the drain path 13. Thus, in some embodiments, the drain pump 44 and the bypass arrangement 61 are operated to direct heated waste fluid, which remains in the tank 41 at the end of the heat treatment of the mixing device 105, via the bypass line 62 into the drain path 13 downstream of the heat transfer device 49.

[0138] Alternatively or additionally, the WHA 40 is operated to minimize the residual amount of heated WF2 in the tank 41 when the heat treatment of the mixing device 105 is terminated, by operating the pump 44 during the heat treatment of the mixing device 105 so as to maximize the spacing G at the end of the heat treatment. This will reduce the waste of heat energy. For example, the spacing may be at Gmin at the end of the heat treatment, or the tank 41 may be completely empty.

[0139] FIG. 1 IB is a flow chart of an example method 1110 of operating the WHA 40 in FIG. 11A. The method 1110 is performed by the control arrangement 50. In step 1111, the temperature of WF2 in the tank 41 is obtained. In step 1112, the temperature of WF1 in the second tank 41" is obtained. These fluid temperatures may be obtained in any suitable way, for example as described above with reference to the methods 910 and 1010. In step 1113, a maximum temperature (Tmax) is obtained for the fluid in the drain path 13, at a selected point downstream of the juncture 60, for example at the end of the drain path 13. In step 1115, the WHA 40 is operated to provide WF1 and WF2 into the drain path 13 so as to ensure that the fluid temperature at the selected point is below Tmax. Step 1115 involves adjusting the flow rate of WF1 and / or WF2 into the juncture 60, based on the fluid temperatures obtained in steps 1112, 1113. As indicated by a dashed box, the method 1110 may also include a step 1114 of selectively supplying SW to the drain path 13, downstream of the tank 14 and, if present, downstream of the heat transfer device 49. Although not shown in FIG. 11A, a supply line for SW may extend to the juncture 60 or a further juncture on the drain path 13. An on / off valve in this supply line may be selectively opened to supply the SW. Step 1114 may be performed if the control arrangement 50 finds that it is not possible to meet Tmax based on the current fluid temperatures in the tanks 41, 41".

[0140] FIG. 11C is a flow chart of an example method 1210 of operating the combination of WPS 10A, FPS 10B and WHA 40 in FIG. 11A. The method 1210 may be performed by the control arrangement 50 in FIG. 8. In step 1211, the WPS 10A is operated to produce PW. In step 1212, WF1 is directed from the WPS 10A to the second tank 41". WF1 may be generated as a result of the production of PW. In step 1213, the FPS 10B is operated to perform a heat treatment of the mixing device 105 by use of PW. In step 1214, WF2 is directed from the FPS 10B to the tank 41. In the FSB 10B, during step 1214, WF2 is generated as a result of the heat treatment and is heated to an elevated temperature. In step 1215, which is optional, thermal energy is transferred from the heated WF2 to PW, which is produced by the WPS 10A and conveyed to the FPS 10B for use in the heat treatment. The PW is thereby heated, reducing the required electric power to heat PW by the heating sub-module 106 in the FPS 10B. It is conceivable that the flow rate of heated WF2 may be controlled to optimize the transfer of thermal energy in the heat transfer device 49. Thus, the drain pump 44 in FIG. 11 A, optionally together with the flow controller 44A (if present), may be operated with the dual purposes of maintaining a spacing G in the tank 41 and achieving a target flow rate of WF2 through the heat transfer device 49, where the target flow rate results in a desired ("target") heat transfer HT in the heat transfer device 49. In some embodiments, the target flow rate of WF2 is set in relation to the flow rate of PW into the through the heat transfer device 49, so as to achieve the target heat transfer. The flow rate of PW may be known to the control arrangement 100 or given by a flow meter (not shown) in the dialysis system or the WHA 40. In step 1216, the WHA 40 is operated to mix WF1 and WF2 and pump the resulting mixture to the drain 25. Step 1216 may be performed in accordance with the method 1110 in FIG. 1 IB.

[0141] It is conceivable that step 1215 may replace step 1216. For example, if step 1215 is known to result in a temperature of WF2 at the drain 25 that is not harmful to individuals, it may be convenient to dispense with the temperature-based control of the flow rates of WF1 and / or WF2 in accordance with the method 1110 of FIG. 1 IB. This also means that the flow controllers 44A, 44B may be omitted.

[0142] In the examples described herein, the WHA 40 is connected to receive waste fluid from a plurality of sub-modules of a dialysis system. It is to be understood, though, that the WHA 40 may be arranged to receive waste fluid from any system for use in dialysis therapy, for example containing only one or two of the sub-modules 10A-10C. As noted above, a sub-module may be implemented as a free-standing machine. Thus, the WHA 40 may be combined with any free-standing machine for use in dialysis therapy.

[0143] While the subject of the present disclosure has been described in connection with what is presently considered to be the most practical embodiments, it is to be understood that the subject of the present disclosure is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and the scope of the appended claims.

[0144] Further, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results.

Claims

CLAIMS1. An apparatus for handling waste fluid from a system for use in dialysis therapy, said apparatus comprising: a container (41) configured to be arranged in relation to one or more supply lines (121-123; 111A, 11 IB) of said system to receive, through a top portion of the container (41), the waste fluid from a respective outlet of the one or more supply lines (121-123; 111A, 11 IB), the waste fluid defining a top fluid surface (TS) in the container (41), a drain line (13), which is fluidly connected to a bottom portion of the container (41), a pumping device (44), which is arranged in the drain line (13) to draw the waste fluid from the container (41) along the drain line (13), and a control arrangement (50), which is configured to operate the pumping device (44) to maintain at least a minimum spacing (Gmin) between the top fluid surface (TS) in the container (41) and the respective outlet of the one or more supply lines (121-123; 111A, 11 IB) so as to impede propagation of microorganisms from the drain line (13) into said system.

2. The apparatus of claim 1, which is configured to, when at least part of the system is subjected to a cleaning procedure, receive heated waste fluid in the container (41) from at least one of the one or more supply lines (121-123; 111A, 11 IB).

3. The apparatus of claim 2, wherein the minimum spacing corresponds to a predefined level in the container (41), and wherein the control arrangement (50) is configured to, during the cleaning procedure, operate the pumping device (44) to arrange the top fluid surface (TS) at or above the predefined level.

4. The apparatus of claim 2 or 3, comprising a further drain line (13"), which is fluidly connected to one or more further supply lines (121) of said system to receive further waste fluid from a respective outlet of the one or more further supply lines (121), wherein the further waste fluid has a lower temperature than the heated waste fluid, wherein the further drain line (13") extends to a juncture (60) on the drain line (13), and wherein the apparatus is operable to generate a mixture of the heated water fluid and the further waste fluid in the drain line (13).

5. The apparatus of claim 4, wherein the juncture (60) is located upstream of the pumping device (44) in the drain line (13).

6. The apparatus of claim 4 or 5, comprising a further container (41"), which is configured to be arranged to receive, through a top portion of the further container (41"), the further waste fluid from the respective outlet of the one or more further supply lines (121), the further waste fluid defining a further top fluid surface (TS") in the further container (41").

7. The apparatus of claim 6, comprising a flow controller (44B) in the further drain line (13"), wherein the control arrangement (50) is configured to selectively operate the flow controller (44B) to provide the further waste fluid into the drain line (13).

8. The apparatus of claim 7, wherein the control arrangement (50) is further configured to selectively operate the flow controller (44B) to maintain at least a further minimum spacing between the further top fluid surface (TS") in the further container (41") and the respective outlet of the one or more further supply lines (121) so as to impede propagation of microorganisms from the further drain line (13") into said system.

9. The apparatus of claim 7 or 8, wherein the control arrangement (50) is configured to operate at least one of the flow controller (44B) or the drain pump (44), so that a temperature of a resulting fluid in the drain line (13) downstream of the juncture (60) is below a maximum temperature.

10. The apparatus of any one of claims 2-9, comprising a heat transfer device (49), which is arranged in the drain line (13) and configured to transfer heat from the heated waste fluid to a flow of product water for use in the cleaning procedure.

11. The apparatus of claim 10 in combination with any one of claims 4-9, wherein the heat transfer device (49) is arranged upstream of the juncture (60).

12. The apparatus of claim 10 or 11, wherein the control arrangement (50) is further configured to operate the pumping device (44) to generate a flow rate of the heated waste fluid through the heat transfer device (49) so as to achieve a target transfer of heat from the heated waste fluid.

13. The apparatus of any one of claims 10-12, further comprising a bypass arrangement (61) with a bypass line (62) for fluid communication with the drain line (13) upstream and downstream of the heat transfer device (49), wherein the control arrangement (40) is configured to intermittently operate the bypass arrangement (61) to direct the heated waste fluid via the bypass line (62) into the drain line (13) downstream of the heat transfer device (49).

14. The apparatus of any one of claims 2-13, wherein the container (41) is operable to be selectively opened and closed to its surroundings, wherein the control arrangement (50) is configured to close the container (41) to the surroundings during at least part of the cleaning procedure.

15. The apparatus of any one of claims 2-13, wherein the container (41) is configured to be permanently open to its surroundings, wherein the control arrangement (50) is configured to operate the pumping device (44) to empty the container (41) after the cleaning procedure and maintain the container (60) empty for a time period to allow moisture in the container (41) to evaporate into the surroundings.

16. The apparatus of any preceding claim, wherein the container (41) is configured to receive the waste fluid from at least two supply lines (121-123; 111 A, 11 IB) of said system, and wherein a single drain line (13) is fluidly connected to the bottom portion of the container (41).

17. The apparatus of any preceding claim, wherein the drain line (13) comprises a first line portion (13A) and a second line portion (13B), wherein the first line portion (13A) extends from the container (41) to a first terminal connector (45A), which is configured to establish a fluid connection with a second terminal connector (45B) on the second line portion (13B).

18. The apparatus of any preceding claim, wherein the control arrangement (50) is configured to determine a momentary flow rate of the waste fluid in the one or more supply lines (121-123; 111A, 11 IB) and operate the pumping device (44) based on the momentary flow rate to maintain said at least a minimum spacing (Gmin).

19. The apparatus of any preceding claim, further comprising a sensor arrangement (46, 46', 46"), which is configured to generate a sensor signal (SI) indicative of a momentary level of the top fluid surface (TS) in the container (41),wherein the control arrangement (50) is configured to operate the pumping device (44) based on the sensor signal (SI) to maintain said at least a minimum spacing (Gmin).

20. The apparatus of claim 19, wherein the sensor arrangement (46, 46') comprises a pressure sensor (46), which is arranged to measure a momentary pressure of the waste fluid in the container (41), and wherein the sensor signal (SI) represents the momentary pressure.

21. The apparatus of claim 20, wherein the control arrangement (50) is configured to perform a calibration procedure (520), comprising: obtaining an initial pressure value from the sensor signal (SI) for a first level of the top fluid surface (TS) in the container (41); obtaining a subsequent pressure value from the sensor signal (SI) after receiving an amount of waste fluid from the one or more supply lines (121-123; 111A, 11 IB) resulting in a second level of the top fluid surface (TS) in the container (41); and defining, based on the initial and subsequent pressure values and the first and second levels, a conversion function from pressure to level of the top fluid surface (TS).

22. The apparatus of claim 20 or 21, wherein the control arrangement (50) is configured to perform a flow rate measurement (610), comprising: closing the drain line (13) by the pumping device (44) or an optional drain valve (44 A) in the drain line (13); determining, based on the sensor signal (SI), an increase in pressure while the container (41) receives the waste fluid from the one or more supply lines (121-123; 111A, 11 IB) for a predefined time period; and calculating a flow rate of the waste fluid based on the increase in pressure and the predefined time period.

23. The apparatus of any one of claims 20-22, wherein the container (41) is operable to be selectively opened and closed to its surroundings, and wherein the control arrangement (50) is configured to, upon detection of a need for priming of the pumping device (44), close the container (41) to the surroundings so that waste fluid (41) entering the container (41) creates a backing pressure in the container (41), and operate the pumping device (44) when a limit backing pressure is created in the container (41), as indicated by the sensor signal (SI), to prime the pumping device (44) by waste fluid from the container (41).

24. The apparatus of any one of claims 20-22, wherein the container (41) is operable to be selectively opened and closed to its surroundings, and wherein the control arrangement (50) is configured to perform a temperature measurement (1010),comprising: operating the pumping device (44) to achieve a selected level of the top fluid surface (TS) in the container (41), obtaining a first pressure value from the sensor signal (SI) when the waste fluid in the container (41) has a known first temperature, closing the container (41) to the surroundings, operating the pumping device (44) to maintain the selected level in the container (41) while receiving waste fluid from the one or more supply lines (121-123; 111A, 11 IB), obtaining a second pressure value from the sensor signal (SI), and estimating a temperature (T2) of the waste fluid in the container (41) based on the first temperature, and the first and second pressure values.

25. The apparatus of any one of claims 20-24, further comprising an air flow channel (47) in fluid communication with the top portion of the container (41), and a control valve (48) which is operable to selectively open and close the air flow channel (47) to thereby open and close, respectively, the container (41) to its surroundings.

26. The apparatus of claim 25, wherein the control arrangement (50) is configured to, while the air flow channel (47) is open, monitor the sensor signal (SI) for detection of a pressure increase corresponding to the waste fluid flowing into the air flow channel (47), and take dedicated action upon detection of the pressure increase.

27. The apparatus of claim 1, wherein the container (41) is configured to be permanently open to its surroundings, and wherein the control arrangement (50) is configured to, upon detection of a need for priming the pumping device (44), operate the pumping device (44) to prime the pumping device (44) by waste fluid from the container (41) when a predefined fluid level is attained in the container (41), the predefined fluid level corresponding to a predefined fluid pressure at an inlet of the pumping device (44).

28. The apparatus of any preceding claim, wherein the control arrangement (50) is configured to receive input data indicative of at least one of a drive power of the pumping device (44), a fluid pressure in the drain line (13) downstream of the pumping device (44), or a fluid level in the container (41); evaluate the input data for detection of a disruption in the drain line (13) downstream of the pumping device (44) and generate an alert signal upon detection of the disruption.

29. The apparatus of any preceding claim, in which no further container is fluidly connected in series with the container (41) along the drain line (13).

30. The apparatus of any preceding claim, wherein the control arrangement (50) is configured to enable a continuous flow of waste fluid through the container (41).

31. The apparatus of any preceding claim, wherein the control arrangement (50) is configured to, at least intermittently, operate the pumping device (44) while the waste fluid enters the container (41) as a continuous fluid stream from the one or more supply lines (121-123; 111A, 11 IB).

32. A system for use in dialysis therapy, said system comprising: a first sub-system (10B), which is configured to generate a treatment fluid by mixing product water with one or more concentrates, wherein the first sub-system (10B) comprises one or more first fluid lines (122) for disposal of first waste fluid produced by the first sub-system (10B) before, during or after generation of the treatment fluid, and the apparatus as defined in any one of claims 1 -31 , wherein the apparatus is arranged to receive the first waste fluid from the one or more first fluid lines (122).

33. The system of claim 32, further comprising a second sub-system (10C), which is fluidly connected to receive the treatment fluid from the first sub-system (10B) and configured to perform the dialysis therapy by use of the treatment fluid, wherein the second sub-system (10C) comprises one or more second fluid lines (123) for disposal of second waste fluid produced by the second sub-system (10C) before, during or after the dialysis therapy, wherein the apparatus is arranged to receive the second waste fluid from the one or more second fluid lines (123).

34. The system of claim 32 or 33, further comprising a third sub-system (10A), which is fluidly connected to receive source water and is configured to generate the product water by purification processing of the source water, wherein the first subsystem (10B) is fluidly connected to receive the product water from the third subsystem (10A), wherein the third sub-system (10A) comprises one or more third fluid lines (121) for disposal of third waste fluid produced by the third sub-system (10A) before, during or after the purification processing, wherein the apparatus is arranged to receive the third waste fluid from the one or more third fluid lines (121).

35. A method of handling waste fluid from a system for use in dialysis therapy, said method comprising:receiving (311, 321), from one or more supply lines of said system, the waste fluid through a top portion of a container, and operating (313, 323) a pumping device, which is arranged in a drain line that is fluidly connected to a bottom portion of the container, to draw the waste fluid from the container along the drain line to maintain at least a minimum spacing between a top fluid surface defined by the waste fluid in the container and a respective outlet of the one or more supply lines, so as to impede propagation of microorganisms from the drain line into said system.

36. A computer-readable medium comprising program instructions, which when executed by processing circuitry (51) causes the processing circuitry (51) to perform the method according to claim 35.