A system and method for defouling a forward osmosis unit for dialysis

Abstract

A system (1) for defouling a FO-unit arranged for generating treatment fluid for use in dialysis treatment, the system (1) comprising: a fluid path (2) including two or more dialysis concentrate connectors (3a, 3c) each connector configured to be connected to a source of dialysis concentrate fluid (4a, 4c), and an inlet connector (5a) configured to be connected to a fluid line (5) arranged for transportation of effluent fluid from a patient; a forward osmosis- (FO-) unit (6) including a draw side (6a) and a feed side (6b) separated by a FO-membrane (6c), the FO-unit (6) fluidly connected to the fluid path (2), wherein the FO-unit (6) is configured to receive one or more dialysis concentrate fluids (4a, 4c) at the draw side (6a) and to receive the effluent at the feed side (6b), wherein water is transported from the effluent to the one or more dialysis concentrate fluids through the FO-membrane (6c) via an osmotic pressure gradient between the draw side (6a) and the feed side (6b), thereby diluting the one or more dialysis concentrate fluids into a diluted dialysis concentrate fluid; a concentration sensor (8) configured to sense the concentration of the diluted dialysis concentrate fluid; and a control unit (40) configured to cause a relative pressure to be established in the chamber by controlling the flow of effluent fluid with the valve in a closed position Once a threshold relative pressure level is reached, the control unit causes the valve to open, thereby causing fluid in the feed side to accelerate, promoting release of a foulant built up on the FO-membrane.

Description

[0001] A system and method for defouling a forward osmosis unit for dialysis

[0002] Technical field

[0003] The present invention relates to the field of dialysis, and to systems and methods for defouling forward osmosis units used to prepare treatment fluid for use in dialysis.

[0004] Background

[0005] Peritoneal dialysis (PD) is a method for treating patients suffering from renal failure. During PD, the peritoneal cavity of a patient is filled with fresh PD fluid, and waste and fluid is transported from the blood of the patient, via the patient’s peritoneal membrane, to the fresh PD fluid. The used PD fluid (also referred to as “effluent”) is thereafter drained from the patient. There are several kinds of PD. In automated peritoneal dialysis (APD) a machine or cycler is used to fill the peritoneal cavity with fresh PD fluid, and after a specified dwell period, automatically drains the used PD solution from the body. This procedure is repeated several times, typically during overnight.

[0006] Hemodialysis (HD) is another type of dialysis method for treating patients suffering from renal failure. During HD, blood is removed from the patient to a cycler and passed through a dialyzer. In the dialyzer, the removed blood moves along one side of a membrane and dialysis fluid moves in an opposite direction along the other side of the membrane. The dialyzer membrane, which is semipermeable, causes waste and excess water in the blood to be removed to the side of the dialysis fluid. The filtered blood is then returned to the patient.

[0007] Some dialysis cyclers utilize a solution generation device including a forward osmosis unit to dilute concentrated sources of dialysis fluid. The forward osmosis unit promotes the flow of water from a low concentrate source into the concentrated dialysis fluid to prepare the dialysis fluid for use in treatment. Such a system is described in, for example, PCT Publication No. WO2021 / 156429, published August 12, 2021 , which is hereby incorporated by reference in its entirety. The forward osmosis unit contains a membrane used to separate the lowconcentrate source from the concentrated dialysis fluid. This membrane can become fouled or obstructed from chemical build-up of carbonates or phosphates from the patient present in the effluent (referred to as scaling or inorganic scaling), or from surface adherence of biomolecules such as proteins, lipids, fibrine, and others (referred to as fouling). Both mechanisms may be present at once or in combination as well. For example, the inorganic scaling may form a matrix that promotes the build-up of fouling.

[0008] Obstruction of the forward osmosis membrane can cause inaccuracies or difficulty in forming a dialysis fluid with the correct concentration levels for treatment, early obsolescence of a given solution generation device, and inefficient use of feed water resources, amongst other drawbacks. There is accordingly a need to reduce the negative consequences listed above.

[0009]

[0010] It is an objective of the disclosure to alleviate at least some of the drawbacks with the prior art. It is a further objective to provide a cost-efficient solution for defouling forward osmosis membranes in a solution generation machine for generating treatment fluid for use in dialysis. It is a still further objective to provide a solution for producing fluid for dialysis at the point of care, which consumes low amounts of water.

[0011] These objectives and others are at least partially achieved by the system and method according to the independent claims, and by the embodiments according to the dependent claims.

[0012] According to one aspect of the present disclosure, which may be combined with any other aspect or portion thereof, the disclosure relates to a system for defouling a forward osmosis unit. The system is typically included in a solution generation machine for generating treatment fluid for use in dialysis, for example peritoneal dialysis or hemodialysis. The system comprises a fluid path having one or more dialysis concentrate connectors each configured to be connected to a source of dialysis concentrate fluid, and an inlet connector configured to beconnected to a fluid line arranged for transportation of feed fluid from a feed fluid source. The system further comprises a forward osmosis (FO-) unit including a draw side and a feed side separated by a FO-membrane. The FO-unit is fluidly connected to the fluid path. The FO-unit is configured to receive the one or more dialysis concentrate fluids at the draw side and to receive the feed fluid at the feed side, wherein water from the feed fluid is transported to the one or more dialysis concentrate fluids through the FO-membrane by means of an osmotic pressure gradient between the draw side and the feed side. The one or more dialysis concentrate fluids are thereby diluted into a diluted dialysis concentrate fluid. The system further includes a chamber configured to receive effluent fluid from the effluent fluid line upstream of the FO-unit and further configured to allow gas to migrate out of the effluent fluid. The system further comprises an air vent configured to release gas from the chamber. The system also includes a valve disposed between the chamber and the FO-unit. The system further comprises a control unit configured to control a flow of feed fluid on the feed side, control a flow of the one or more dialysis concentrate fluids into the draw side, and control the valve. The control unit is configured to cause a pressure difference to be established between the chamber and the FO-unit by controlling the flow of feed fluid into or out of the chamber with the valve in a closed position. Once a threshold pressure difference level is reached, the control unit causes the valve to open, thereby causing fluid in the feed side to accelerate, promoting release of a foulant built up on the FO-membrane.

[0013] The proposed system allows for the revitalization of FO-unit components. The efficiency of the dialysis fluid preparation process is in turn improved, causing less water demand. Further, the longevity of the FO-unit, and in turn the solution generation device, is improved such that costly and wasteful replacements are minimized.

[0014] According to another aspect of the present disclosure, the control unit is further configured to determine a degree of compliance in the chamber by communicating with one or more level sensors, and wherein if a desired degree of compliance is not met, the system is configured to draw air in from or push air outof the air vent until the desired degree of compliance for the defouling operation is detected.

[0015] According to another aspect of the present disclosure, which may be combined with any other aspect or portion thereof, the degree of compliance in the chamber corresponds to a level of fluid in the chamber.

[0016] According to another aspect of the present disclosure, which may be combined with any other aspect or portion thereof, opening the valve creates a transmembrane pressure (TMP) transient that results in a water transport transient in a reverse direction to a normal operation of the FO-unit that promotes foulant release.

[0017] According to another aspect of the present disclosure, which may be combined with any other aspect or portion thereof, the control unit controls the flow of feed fluid on the feed side by at least one feed pump.

[0018] According to another aspect of the present disclosure, which may be combined with any other aspect or portion thereof, a pressure sensor in operable communication with the control unit and disposed along the feed side is arranged to measure an amount of the relative pressure in the chamber.

[0019] According to another aspect of the present disclosure, which may be combined with any other aspect or portion thereof, at least one feed pump is arranged for pumping effluent fluid from an effluent container toward a drain line, wherein the at least one feed pump is arranged to dispose released foulant through the drain line.

[0020] According to another aspect of the present disclosure, which may be combined with any other aspect or portion thereof, the system further comprises an effluent container disposed between the inlet connector and the chamber.According to another aspect of the present disclosure, which may be combined with any other aspect or portion thereof, the pressure difference is a negative relative pressure of the chamber compared to the FO-unit.

[0021] According to another aspect of the present disclosure, which may be combined with any other aspect or portion thereof, the acceleration of the fluid in the feed side is a negative acceleration relative to the downstream direction of the feed side.

[0022] According to another aspect of the present disclosure, which may be combined with any other aspect or portion thereof, the negative acceleration causes fluid to flow in the upstream direction of the feed side.

[0023] According to another aspect of the present disclosure, which may be combined with any other aspect or portion thereof, the pressure difference is a positive relative pressure of the chamber compared to the FO-unit.

[0024] According to another aspect of the present disclosure, which may be combined with any other aspect or portion thereof, the acceleration of the fluid in the feed side is a positive acceleration relative to the downstream direction of the feed side.

[0025] According to another aspect of the present disclosure, which may be combined with any other aspect or portion thereof, the positive acceleration causes fluid to flow in the downstream direction of the feed side more rapidly than during a normal operation of the FO-unit.

[0026] According to another aspect of the present disclosure, which may be combined with any other aspect or portion thereof below, the system, typically included in a solution generation machine for generating treatment fluid for use in dialysis, for example peritoneal dialysis or hemodialysis, comprises a fluid path having one or more dialysis concentrate connectors, each connector configured to be connected to a source of dialysis concentrate fluid, a diluted dialysis concentrate connectorconfigured to be connected to a source of diluted dialysis concentrate fluid, an inlet connector configured to be connected to a feed fluid line arranged for transportation of feed fluid from a source of feed fluid, a forward osmosis (FO-) unit including a draw side and a feed side separated by a FO-membrane, the FO-unit fluidly connected to the fluid path, wherein the FO-unit is configured to receive one or more dialysis concentrate fluids at the draw side and to receive the feed fluid at the feed side, wherein water is transported from the feed fluid to the one or more dialysis concentrate fluids through the FO-membrane via an osmotic pressure gradient between the draw side and the feed side, wherein the osmotic pressure gradient where water is transported from the feed side to the draw side through the FO-membrane comprises a normal osmotic pressure gradient, thereby diluting the one or more dialysis concentrate fluids into a diluted dialysis concentrate fluid, a first three-way valve fluidly connecting at least one source of dialysis concentrate fluid to the feed side upstream of the FO-unit, a second three-way valve fluidly connecting the feed fluid line to the draw side upstream of the FO-unit, an air vent in fluid communication with the draw side downstream of the FO-unit, and a control unit configured to control a flow of feed fluid on the feed side, control a flow of the one or more dialysis concentrate fluids on the draw side, and control the valves, wherein the control unit is configured to cause an osmotic backwash by emptying the draw side by pulling air in through the air vent by a first pump disposed on the draw side in fluid communication with the air vent to the source of diluted dialysis concentrate, priming the feed side with a dialysis concentrate by means of the first pump and the first three-way valve, and sending a low concentration fluid by means of a feed pump disposed on the feed side and the second three-way valve through the draw side of the FO-unit, thereby creating an osmotic pressure gradient in an opposite direction of the normal osmotic pressure gradient wherein water is transported from the draw side to the feed side through the FO-membrane, wherein the osmotic backwash promotes release of a foulant built up on the FO-membrane.

[0027] According to another aspect of the present disclosure, which may be combined with any other aspect or portion thereof, the control unit is configured to continue to pump low concentrate fluid to the draw side and dialysis concentrate to the feedside, and is configured to control the flow rates of the low concentrate fluid and the dialysis concentrate.

[0028] According to another aspect of the present disclosure, which may be combined with any other aspect or portion thereof, controlling the flow rates of the low concentrate fluid and the dialysis concentrate is used to ensure that the entire draw side becomes primed to achieve osmotic backwash of the entire FO-membrane.

[0029] According to another aspect of the present disclosure, which may be combined with any other aspect or portion thereof, the system further comprises a conductivity sensor disposed on the draw side and in operable communication with the control unit. The conductivity sensor is used to determine full priming of the draw side.

[0030] According to another aspect of the present disclosure, which may be combined with any other aspect or portion thereof, the low concentrate fluid is water.

[0031] According to another aspect of the present disclosure, which may be combined with any other aspect or portion thereof, the low concentrate fluid is effluent fluid.

[0032] According to another aspect of the present disclosure, which may be combined with any other aspect or portion thereof, at least one feed pump is arranged for pumping feed fluid from an effluent container toward a drain line wherein the at least one feed pump is arranged to dispose released foulant through the drain line.

[0033] According to another aspect of the present disclosure, which may be combined with any other aspect or portion thereof, the system is arranged to dispose released foulant through a drain line.According to another aspect of the present disclosure, which may be combined with any other aspect or portion thereof, wherein the drain line is also used to dispose spent feed fluid.

[0034] According to another aspect of the present disclosure, which may be combined with any other aspect or portion thereof, the system further comprises an effluent container disposed between the inlet connector and the chamber.

[0035] Brief description of the drawings

[0036] Figs. 1 and 3 illustrate different embodiments for a system for defouling a forward osmosis unit for dialysis according to some embodiments.

[0037] Figs. 2, 4, and 5 are flowcharts of methods for defouling a forward osmosis unit for dialysis according to some embodiments.

[0038] Detailed description

[0039] In the following disclosure, several embodiments of systems and methods for defouling a forward osmosis (FO-) unit for preparing dialysis fluids such as peritoneal dialysis (“PD”) and hemodialysis (“HD”) fluids will be described. The embodiments may each make use of forward osmosis to dilute one or more dialysis concentrates using water transported over a FO-membrane from used dialysis fluid or “effluent”. A source of fresh water can also be used as the source of water to transport over the FO-membrane in alternative embodiments. The term “feed fluid” as used within refers to either or both of effluent or fresh water as desired to carry out the forward osmosis process. It is therefore contemplated that “effluent” or “water” may be interchangeable or described more generally as “feed fluid” in alternative embodiments. In embodiments where effluent is used as the feed fluid, water from the effluent is reused for mixing with dialysis concentrates to provide new dialysis fluid. The solution may be used for different variants of automated dialysis, including on-line mixing of dialysis fluid and batch-wise mixing of dialysis fluid. Performance tests of the system have indicated that it is possible to reduce novel pure water demand by 50-70% or higher compared to a system not using the present structure and methodology.A plurality of systems for producing fluids for dialysis are described herein, with reference to Figs. 1 and 3. References that are the same throughout the figures may not be textually described in each embodiment but include all of the structure, functionality and alternatives that are described.

[0040] Dialysis Fluid Preparation - Generally

[0041] Fig. 1 illustrates a system 1 according to some embodiments of the disclosure. The system 1 includes a fluid path 2, a plurality of connectors, a forward osmosis-(FO-) unit 6 and a control unit 40. The fluid path 2 may be enclosed inside an enclosure (not shown in Fig. 1). The fluid path 2 may be part of an apparatus or a disposable system. The fluid path 2 includes a plurality of fluid lines. The fluid path 2 may include some or all of the fluid lines as described herein. The connectors include one or more dialysis concentrate connectors 3a, 3c. Each dialysis concentrate connector is configured to be connected to a source of dialysis concentrate fluid 4a, 4c. It should be understood that reference may be made to a source of dialysis concentrate fluid 4a, 4c or the dialysis concentrate 4a, 4c itself. For example, reference character 4a may be used to describe either the dialysis concentrate fluid itself (i.e. "dialysis concentrate fluid” or simply "dialysis concentrate”), or the source of the dialysis concentrate fluid, since both comprise the same fluid. Reference may also be made to a dialysis concentrate bag, which should be understood to refer to a non-limiting example of a source of dialysis concentrate.

[0042] As described herein, then, dialysis concentrate fluid 4a may be considered a first concentrate fluid and dialysis concentrate fluid 4c may be considered a second concentrate fluid. The second concentrate fluid 4c may be an osmotic agent in some embodiments, such as when the system is used for PD. In such embodiments the second concentrate fluid 4c may be referred to as osmotic agent 4c and the second concentrate connector 3c may be referred to as an osmotic agent connector 3c. A source of dialysis concentrate fluid is typically a bag with dialysis concentrate. Each dialysis concentrate connector is then configured to be connected to a corresponding connector provided with thedialysis concentrate fluid bag. The connectors also include an inlet connector 5a. The inlet connector 5a is typically configured to be connected to a fluid line 5 arranged for transportation of feed fluid from a patient.

[0043] The FO-unit 6 comprises a draw side 6a and a feed side 6b separated with a FO-membrane 6c. The FO-unit 6 is fluidly connected to the fluid path 2. The FO-unit 6 is configured to receive one or more dialysis concentrate fluids 4a at the draw side 6a and to receive the feed fluid at the feed side 6b to transport water from the feed fluid to the one or more dialysis concentrate fluids through the FO-membrane 6c by means of an osmotic pressure gradient between the draw side 6a and the feed side 6b. The transportation of water from the feed side 6b to the draw side 6a may be referred to as a normal osmotic pressure gradient, since this is the typical condition that the dialysis cycler utilizes to prepare dialysis fluid. The one or more dialysis concentrate fluids are therefore diluted into a diluted dialysis concentrate fluid 4b. The FO-membrane 6c is a water permeable membrane. It separates the feed side 6b (which contains feed fluid during a normal osmotic pressure gradient) and the draw side 6a (which contains dialysis concentrate during a normal osmotic pressure gradient). The different sides may also be referred to as compartments. The fluids in these sides typically flow in countercurrent flow, but may alternatively flow in co-current flows. In some embodiments, the fluids flow single pass, wherein the fluid passes through the FO-unit 6 only once.

[0044] The water in the feed fluid is transported over the FO-membrane 6c by means of the driving force created by the normal osmotic pressure gradient between the feed fluid (feed solution) and the one or more dialysis concentrate fluids (draw solution). This means that the feed fluid, which initially has about the same osmolarity as final dialysis fluid, will become more concentrated throughout the FO process. The one or more dialysis concentrates 4a will on the other hand be more diluted throughout the FO process. The FO-membrane 6c is typically designed to be more or less exclusively selective towards water molecules, which enables the membrane to separate water from all other contaminants. The geometry of the membrane may be flat-sheet, tubular or hollow fiber.In more detail, a first dialysis concentrate bag 4a is connected via a first bag connector to a first dialysis concentrate connector 3a. A first fluid line 21 is fluidly connected between the first dialysis concentrate connector 3a and an inlet port of the draw side 6a. The first fluid line 21 thus connects the first dialysis concentrate connector 3a and the draw side 6a. A concentrate pump 41 is disposed on the first fluid line 21 primarily to transport dialysis concentrate 4a to the inlet port of the draw side 6a.

[0045] A second fluid line 22 is fluidly connected between an outlet of the draw side 6a and an outlet connector 11a. The second fluid line 22 thus fluidly connects the draw side 6a and the outlet connector 11 a. The outlet connector 11 a is configured to be connected to a corresponding connector of a fluid line 11 , which is configured to transport final dialysis fluid directly to a catheter of a patient, to a cycler for pumping the fluid to a patient, or to a batch container. A third fluid line 25 is connected between the inlet connector 5a and an inlet of the feed side 6b. The third fluid line 25 thus fluidly connects the inlet connector 5a and the feed side 6b. The effluent may optionally be collected in an effluent container 15 before the effluent is fed into the feed side 6b. Thus, the effluent container 15 may be arranged to collect effluent fluid received from the patient before it is transported into the feed side 6b. A fluid line 25a then connects the effluent container 15 to the third fluid line 25. Thus, the effluent container 15 is fluidly connected to the fluid path 2 and the inlet connector 5a. In the embodiment of Fig. 3, the fluid line 25a also connects the effluent container 15 to a source of fresh water 7, connected to the fluid line 2 by a connector 7a. Thus, the effluent fluid from the effluent container 15 may be supplemented with fresh water 7 if the supply of effluent is low or if fresh water 7 is preferred for use in the osmotic process.

[0046] A feed pump 44 is arranged in Fig.1 to control the flow rate of effluent fluid into the feed side 6b. The feed pump 44 is also arranged to control the flow rate of effluent to the effluent container 15. Further, the feed pump 44 is arranged to control the flow rate of effluent from the effluent container 15 into the feed side 6b. Here, the feed pump 44 is arranged to control the flow rate of effluent fluid in the third fluid line 25. A fourth fluid line 26 is connected between an outlet of the feed side 6band a drain 12. Thus, the fourth fluid line 26 connects the feed side 6b and the drain 12. The drain 12 is configured to remove the feed fluid after use. In the embodiment of Fig. 3, a connection fluid line 56 may be connected between the first fluid line 21 and the third fluid line 25. Connection fluid line 56 is for example used during defouling, draining of fluid during flushing, cleaning or as overflow to drain, and may be controlled via valves (as described in further detail below).

[0047] The system 1 further comprises a container 4b fluidly connected or connectable to the fluid path 2 by a diluted dialysis concentrate connector 3b. The diluted dialysis concentrate fluid 4b may be diluted dialysis concentrate from the action of the FO-unit 6 or separately provided by a user. The container 4b is arranged to receive the diluted dialysis concentrate fluid. A fifth fluid line 18 is connected between the diluted dialysis concentrate connector 3b and the second fluid line 22. The fifth fluid line 18 thus connects the container 4b and the second fluid line 22. The fifth fluid line 18 connects to the second fluid line 22 at a first point 18a of the second fluid line 22. The concentrate pump 41 is arranged to pump fluid in the second fluid line 22. The concentrate pump 41 is also configured to control the flow rate of the one or more dialysis concentrate fluids into the draw side 6a. The concentrate pump 41 is arranged in between a second point 21a of the second fluid line 22, which connects the first fluid line 21 to the second fluid line 22, and the inlet of the draw side 6a. A valve 30 is used to control the flow between the first fluid line 21 and the second fluid line 22 at the second point 21 a.

[0048] A concentration (e.g., conductivity) sensor 8 is arranged to sense a concentration of the fluid in the fifth fluid line 18 between the first point 18a and container 4b, so that the concentration of the fluid leaving the draw side 6a of the FO-unit 6 can be measured. The fluid path 2 includes a mixing system 50. The fluid path 2 further comprises a water source connector 7a configured to be connected to a source of pure water 7. A sixth fluid line 28 is connected between the water source connector 7a and the second fluid line 22. The sixth fluid line 28 thus fluidly connects the water source connector 7a and the second fluid line 22 at the mixing system 50. In the embodiment of Fig. 1 , a water valve 62 controls the flow of water from the source of pure water 7 in the sixth fluid line 28. A seventh fluid line29 is connected between the osmotic agent connector 3c and the second fluid line 22. The seventh fluid line 29 thus fluidly connects the osmotic agent connector 3c and the second fluid line 22 at the mixing system 50.

[0049] A system pump 43 is configured to control a flow rate of the final dialysis fluid in the second fluid line 22. The system pump is depicted in the mixing system 50, but alternatively may be disposed at any place on the second fluid line which enables the flow of the dialysis fluid to the outlet connector 11a. The mixing system 50 is arranged to mix the diluted dialysis fluid from the second fluid line 22 along with fresh water from the sixth fluid line 28 and optionally osmotic agent 4c from the seventh fluid line 29 as needed so that a substantially homogeneous dialysis fluid reaches the outlet connector 11a. The mixing system 50 may comprise a mixing chamber, a concentration sensor, and a heater, among other components. The system pump 43 may also be configured to control a flow rate of the fresh water and the osmotic agent. Although no valve is depicted on the seventh fluid line 29, it is contemplated that a valve could be used to control the flow of osmotic agent into the mixing system 50.

[0050] The control unit 40 is configured to control the various valves, sensors, and pumps of the system 1. Feed fluid fluid control is for example made by means of the feed pump 44. In some embodiments, the control unit 40 is further configured to control a flow rate of the one or more dialysis concentrate fluids into the draw side 6a to a flow rate that matches a certain production rate of a final dialysis fluid with a prescribed concentration of the one or more dialysis concentrate fluids. The final dialysis fluid has a composition of dialysis concentrates and water that is prescribed or predetermined beforehand. It is thus also known, that is prescribed, which concentration of the one or more dialysis concentrates the final dialysis fluid should have. The final dialysis fluid is dialysis fluid that is ready to be delivered to a patient in a PD or HD treatment.

[0051] It is desired to withdraw as much water as needed from the feed fluid to produce final dialysis fluid. In order to achieve such withdrawal in some embodiments, theflow rate of the feed fluid into the feed side 6b is matched with the flow rate of the one or more dialysis concentrates into the draw side 6b. The flow rates are initially set to approximate flow rates based on the desired composition of the dialysis fluid, the concentration of the dialysis concentrate, and the amount of feed fluid at hand and the time available for the FO session. The amount of dialysis concentrates in the desired composition dialysis fluid is known or predetermined beforehand, as well as the concentration of the dialysis concentrate(s). Thus, for each batch of final dialysis fluid, the amount of dialysis concentrate(s) to be supplied into the draw side 6a is known. The amount of effluent is also known from how much effluent the feed pump 44 has been pumping into the effluent bag 15, or from weighting the effluent bag 15. For example, if 100 ml of dialysis concentrate is included in the batch of final dialysis fluid, then 100 ml will be supplied from the dialysis concentrate source 4a and pumped into the FO-unit 6 by means of the first pump 41. During the same time period, as the dialysis concentrate is pumped into the FO-unit 6 (draw side 6a), the feed fluid is pumped from the effluent source 15 into the FO-unit (feed side 6b). The amount of feed fluid is typically larger than the amount of dialysis concentrate, for example 2000 ml compared to the 100 ml dialysis concentrate. The feed fluid is then pumped into the feed side 6b with a flow rate that is 20 times larger than flow rate of the (one or more) dialysis concentrate into the draw side 6a.

[0052] In some embodiments, the diluted dialysis concentrate is directed to the container 4b. By changing the speed of the first pump 41 , the flow rate of the one or more dialysis concentrate fluids into the draw side 6a can be changed such that a desired product of concentration and volume of the diluted dialysis concentrate fluid can be achieved. This desired product of concentration and volume is thus the desired amount of dialysis concentrate to be included in a batch. The concentration sensor 8 is configured to sense the concentration of the diluted dialysis concentrate. The sensed concentration, together with the flow rate provided with the first pump 41 , may be used to calculate an amount of dialysis concentrate pumped to the container 4b. The sensed concentration may also be used for control of the flow rate of the one or more dialysis concentrates into the draw side 6a with the first pump 41. It can then be assured that the correctamount of the one or more dialysis concentrates is supplied for the desired production rate. In some embodiments, the diluted dialysis concentrate may require further dilution before going to the mixing system 50. In such a scenario, the valve 30 is opened to allow the concentrate pump 41 to send diluted dialysis fluid back through the FO-unit draw side 6a another time, and may iterate this process as needed to reach the desired concentration level.

[0053] One of the one or more dialysis concentrate fluids 4a comprises a fluid including one or more of ions and / or salts, such as, lactate, acetate, citrate, bicarbonate, KCI, MgCI2, CaCI2, NaCL For example, the one dialysis concentrate source may include a fluid containing buffer agents, e.g., one or more of lactate, citrate, acetate and bicarbonate. This fluid, when eventually diluted with water and possibly other dialysis concentrates becomes the final dialysis fluid which has a pH applicable for dialysis treatments, and one or more of KCI, MgCI2, CaCI2 and NaCL Final dialysis fluids may be formed having standard glucose levels, such as 1.36% or 2.27% glucose.

[0054] The control unit 40 includes a processor and a memory. The memory typically stores a program that when executed by the processor controls the system 1 as described herein. The control unit 40 may also comprise a communication interface enabling the control unit 40 to communicate data and signals to and from the components of the system 1 , for example, send control signals to valves and pumps, and receive sensed data from concentration sensors and feedback signals from the valves and pumps.

[0055] The valves described are typically on / off valves. The valves may be two-way or three-way valves. As stated previously, the system 1 in Fig. 1 has the same reference numbers for the same parts or equivalent parts as described in connection with the system in Fig. 3. Fig. 1 further illustrates a plurality of valves. Such valves include one or more of: a diluted dialysis fluid valve 32 operable with the second fluid line 22 downstream of the first point 18a of the second fluid line 22; a dialysis concentrate valve 31 operable with the first fluid line 21 downstream of the first connector 3a and upstream of the concentrate pump 41 ; a draw sideoutlet valve 33 disposed between the outlet of the draw side 6a of the FO-unit 6 and the first point 18a of the fifth fluid line 18; a feed side inlet valve 34 disposed between the chamber 46 and an inlet of the draw side 6b of the FO-unit 6; a container bypass valve 35 is disposed on a container bypass fluid line 25b, where the container bypass fluid line 25b allows fluid to flow between a first point on the third fluid line 25c and second point on the third fluid line 25d without flowing through the fluid line 25a; an effluent valve 37 operable with the third fluid line 25 upstream of the container bypass valve 35 and just downstream of the inlet connector 5a; a valve 30 as described previously; two effluent container valves 36a, 36b, which control the flow of effluent into and out of the effluent chamber 15 and along the fluid line 25a; a chamber valve 39 operable with a fluid line that is fluidly connected between the chamber 46 and the drain 12; an air vent valve 38 operable with an air vent line 58 which fluidly connects an air vent 59 to the fluid line 2; a feed side drain valve 42 which controls the flow of fluid downstream of the feed side 6b of the FO-unit 6; and a water valve 62 which controls the flow of water from the water source 7, and which in the embodiment of Fig. 1 controls the flow of water into the mixing system 50.

[0056] The system 1 is arranged to allow for defouling of the FO-unit membrane 6c. The membrane 6c may become fouled or obstructed during use. Scaling or fouling can cause clogging of the pores in the membrane 6c, which in turn may affect the rate of transmission of water from the feed side 6b to the draw side 6a, or may reduce the longevity of the FO-unit 6 and therefore the system 1 generally. Scaling and fouling often have directional strength because they build up in the presence of a normal osmotic pressure gradient. Figs. 1 and 3 describe two system 1 arrangements which allow for three different methods of membrane defouling: (i) trans-membrane pressure (“TMP”) driven back-wash; (ii) osmotic back-wash; and (iii) feed side flow transients. A combination of any two or more of the methods is also contemplated, as will be appreciated by those skilled in the art. The methods are preferably performed when no production of treatment fluid is ongoing. If production of treatment fluid is ongoing, the production is temporarily stopped to allow for any of the methods to be performed.TMP- Driven Back-Wash

[0057] The embodiment of Fig. 1 is particularly suited to TMP-driven back-wash defouling.

[0058] In particular, the system 1 of Fig. 1 also includes a first pressure sensor 52 disposed at or near a draw side 6a inlet of the FO-unit 6 and a second pressure sensor 53 disposed along the fluid path 2 between the second point on the third fluid line 25d and the effluent valve 37. Further, the system 1 includes level sensors 46a, 46b disposed on the chamber 46 and configured to sense a level of fluid in the chamber 46. The first pressure sensor 52 is configured to sense the pressure on the draw side of the fluid line 2. The second pressure sensor 53 is configured to sense a pressure corresponding to a pressure of the feed side of the fluid line 2, or the pressure of the chamber 46 in certain configurations of the valves, as described below. Using the sensed pressure from the second pressure sensor 53, the system 1 can determine when a desired threshold pressure is reached in the chamber 46. Using the difference in pressure sensed between the first pressure sensor 52 and the second pressure sensor 53, the TMP of the FO-unit can be calculated, where the TMP is the pressure experienced by the FO-membrane 6c. An increase in TMP corresponds to a greater difference between the pressure on the feed side of the fluid line 2 and the pressure on the draw side of the fluid line 2,

[0059] When a defouling operation is started by the control unit 40, the system 1 of Fig. 1 utilizes the level sensors 46a, 46b of the chamber 46 to determine a level of fluid in the chamber 46 (which corresponds to a degree of compliance, wherein compliance refers to the compressibility of air in the chamber 46). If a desired degree of compliance is not met, i.e. if there is not enough volume of air built up to provide a spring effect by its compressibility, the system 1 is configured to draw air in from the air vent 59 until the desired degree of compliance for the defouling operation is detected by the level sensors 46a, 46b. The system 1 then utilizes the feed side inlet valve 34 especially to perform a TMP-driven backwash defouling. Specifically, the system 1 switches the feed side inlet valve 34 to a closed position, ensures that the chamber valve 39 is in the closed position, and pumpsfluid out of the chamber 46 towards the effluent container 15. With the feed side inlet valve 34 and the chamber valve 39 in the closed position, drawing fluid out of the chamber 46 in the upstream direction of the third fluid line 25 will cause a relative decrease in the internal pressure of the chamber 46 (i.e. a vacuum will begin in the chamber 46). Meanwhile, with the feed side inlet valve 34 and the chamber valve 39 closed, the pressure of the fluid in the feed 6b of the FO-unit 6 remains static, at a level relatively higher than that of the chamber 46. The control unit 40 tracks the negative pressure build-up in the chamber 46 using the second pressure sensor 53, and when a predetermined threshold negative pressure is reached the control unit 40 causes the feed side inlet valve 34 to be opened. The higher-pressure fluid in the feed side 6b moves toward the lower pressure chamber 46 as a result, opposite to a direction of flow during a normal operation of the FO-unit 6. Further, the rush of fluid from the feed side 6b creates a negative TMP as measured by the first pressure sensor 52 and the second pressure sensor 53 that causes fluid from the draw side 6a to move across the FO-membrane 6c in a direction opposite to the typical direction of water flow during normal operation of the FO-unit 6. Hence, a backwash is formed that creates shear forces on the walls of the FO-membrane 6c that are atypical during normal operation of the FO-unit and promotes the release of foulant built up on the FO-membrane 6c and in the FO-unit 6 generally.

[0060] The pumps in each of the versions of system 1 described herein may be volumetric pumps, e.g., piston pumps.

[0061] Fig. 2 is a flow chart of a method according to some embodiments of the disclosure. The method may be implemented as instructions of a computer program and saved in the memory of the control unit 40. The method is explained together with the flow chart of Fig. 2.

[0062] The flow chart discloses a method for TMP-driven back-wash defouling of a FO-unit membrane 6c. The system may be any one of the systems 1 as illustrated or described herein, including a combination of the systems 1. In the illustrated embodiment, the method at S101 determines the level of feed fluid in the chamber46 and, if the fluid level is below a certain compliance in the fluid path, at step S101 a air is pulled in with the feed pump 44 from the air vent 59 until level sensors 46a, 46b sense a level of fluid in the chamber associated with a desired compliance in the fluid path. At S102 the method closes the feed side inlet valve 34. In this embodiment it is assumed that the chamber valve 39 is already in the closed position. However, if the chamber valve 39 is open, then the method will close the chamber valve 39 before S103. At S103 fluid is pumped out of the chamber 46 by feed pump 44 in an upstream direction of the feed side 6b (towards the effluent container 15 via the container bypass valve 35 and effluent container valve 36a). Because the valves downstream of the chamber 46 are closed, pumping fluid out of the chamber 46 will cause a negative relative pressure to build in the chamber 46. The pressure in the line during this operation is determined by the control unit 40 using the inlet pressure sensor 53. This negative relative pressure will continue to grow as long as fluid is being pumped out, until at S104 a threshold negative pressure is reached in the chamber 46. Then, at S105, the feed side inlet valve 34 is opened, and the negative relative pressure in the chamber 46 is translated to the FO-unit, causing a TMP that is negative relative to normal operation. This negative TMP causes fluid downstream of the chamber 46 to be pulled toward the chamber, as well as some fluid from the draw side 6a to be forced across the FO-membrane 6c in the opposite direction of normal FO-unit 6 operation (i.e. the concentrate fluid is forced toward the low concentrate fluid through the pores). The backwash may cause scaling or fouling built up on the membrane 6c and its pores to be released, because fluid pressure is applied to the scaling and fouling in a different direction than when the scaling and fouling built up. In this manner, the FO-unit 6 is defouled by a TMP-driven backwash. Once defouled, the scaling and fouling will be sent from the feed side 6b to the drain 12.

[0063] Feed-Side Flow Transients

[0064] Although the system 1 of Fig. 1 has been discussed with the method of Fig. 2, the system 1 of Fig. 1 is also particularly suited for defouling by feed-side flow transients as described in Fig. 5.In particular, the feed-side flow transients defouling process shares certain characteristics of the TMP-driven backwash defouling process including the utilization of pressure in the chamber 46 accomplished by closing the feed side inlet valve 34 and the chamber valve 39. As with the TMP-driven backwash defouling, when a defouling operation is started by the control unit 40 configured to cause a feed-side flow transients defouling, the system 1 of Fig. 1 utilizes the level sensors 46a, 46b of the chamber 46 to determine a level of fluid in the chamber 46 (which corresponds to a degree of compliance). If a desired degree of compliance is not met, the system 1 is configured here also to draw air in from the air vent 59 until the desired degree of compliance for the defouling operation is detected by the level sensors 46a, 46b. The system 1 then utilizes the feed side inlet valve 34 especially to perform a feed side flow transients defouling.

[0065] Specifically, the system 1 switches the feed side inlet valve 34 to a closed position, ensures that the chamber valve 39 is in the closed position, and pumps fluid into the chamber 46 by the feed pump 44 (i.e. pump fluid as if a normal operation of the FO-unit 6 were being performed). Because the feed side inlet valve 34 and the chamber valve 39 are closed, fluid pressure internal to the chamber 46 will begin to build-up. In other words, there will be a positive pressure difference between the pressure in the chamber 46 measured by the second pressure sensor 53 and the TMP measured by the first pressure sensor 52 because the fluid in the FO-unit and on the draw side lines is protected from the pressure build-up in the chamber 46 by the closed valves 34, 39. The control unit 40 tracks the positive pressure build-up in the chamber 46 using the second pressure sensor 53, and when a predetermined threshold positive pressure is reached the control unit 40 causes the feed side inlet valve 34 to be opened. The higher-pressure fluid in the chamber 46 moves toward the lower pressure FO-unit 6 as a result, and the flow rate in the FO-unit 6 on the feed side 6b is increased at a rate higher than during a normal operation of the FO-unit 6, causing excess amounts of shear forces on the walls of the FO-membrane 6c and the FO-unit 6 generally. This promotes the release of foulant built up on the FO-membrane 6c and in the FO-unit 6 generally.Fig. 5 is a flow chart of a method according to some embodiments of the disclosure. The method may be implemented as instructions of a computer program and saved in the memory of the control unit 40. The method is explained together with the flow chart of Fig. 5.

[0066] The flow chart discloses a method for feed-side flow transient defouling of a FO-unit membrane 6c. The system may be any one of the systems 1 as illustrated or described herein, including a combination of the systems 1. In the illustrated embodiment, the method at S301 determines the level of feed fluid in the chamber 46 and, if the fluid level is below a certain compliance in the fluid path, at step S101 a air is pulled in with the feed pump 44 from the air vent 59 until level sensors 46a, 46b sense a level of fluid in the chamber associated with a desired compliance in the fluid path. At S302 the method closes the feed side inlet valve 34. In this embodiment it is assumed that the chamber valve 39 is already in the closed position. However, if the chamber valve 39 is open, then the method will close the chamber valve 39 before S303. At S303 fluid is pumped into the chamber 46 by feed pump 44 in the downstream direction of the feed side 6b (i.e. as it is configured for normal FO operation). Because the valves downstream of the chamber 46 are closed, pumping fluid into the chamber 46 will cause a positive relative pressure to build in the chamber 46. The pressure in the line during this operation is determined by the control unit 40 using the inlet pressure sensor 53. This positive relative pressure will continue to grow as long as fluid is being pumped in, until at S304 a threshold positive pressure is reached in the chamber 46. Those skilled in the art will notice that this process is similar to that of Fig. 2 except that a positive relative pressure is obtained in the chamber 46, rather than a negative relative pressure. Then, at S305, the feed side inlet valve 34 is opened, and the positive relative pressure in the chamber 46 is translated to the FO-unit, causing a pressure difference between the feed side 6b inlet and the feed side 6b outlet that is significantly higher relative to normal operation. This extra pressure causes fluid downstream of the chamber 46 to be pushed toward the drain 12 (a flow transient), as well as some fluid from the feed side 6b to be forced across the FO-membrane 6c at a higher velocity than during a normal FO operation. The shear forces from the acceleration of the liquid on the feed side 6amay cause scaling or fouling built up on the membrane 6c and its pores to be released, because fluid pressure is applied to the scaling and fouling in at a higher level than when the scaling and fouling built up. In this manner, the FO-unit 6 is defouled by a feed side flow transient. Once defouled, the scaling and fouling will be sent from the feed side 6b to the drain 12.

[0067] The feed-side flow transient method may be preferable to the TMP-driven backwash method in situations where no solution is present on the draw side 6a, in order to avoid feed side 6b fluid loss and / or build up of a more concentrated layer close to the FO-membrane 6c, since these conditions could decrease the effectiveness of the TMP-driven back-wash method.

[0068] Those skilled in the art will recognize that the system 1 as embodied in Fig. 1 is particularly adapted to perform a TMP-driven backwash and / or a feed-side flow transient defouling, but that other embodiments are possible. Any system 1 or arrangement of the system 1 embodied by Fig. 1 which is capable of creating a negative excess pressure compared to normal operation of a FO-unit 6 upstream of the feed side 6b of the FO-unit 6 and sudden release of that excess pressure is also contemplated. The components and placement of the components of the embodiment of Fig. 1 are a preferred embodiment.

[0069] Osmotic Back-Wash

[0070] The embodiment of Fig. 3 is particularly suited to osmotic back-wash defouling of the FO-unit 6. Because there is no need for a negative or positive relative pressure build-up in this method, no chamber 46 is necessary as a pressure vessel for the feed side 6b. Rather, this method and apparatus uses certain three-way valves with further fluid lines (as discussed in further detail below) to send high concentrate fluid through the feed side 6b and low concentrate fluid through the draw side 6a. This effectively changes the osmotic pressure, since water will flow from the draw side 6a to the feed side 6b (opposite of normal operation). The change of direction of water flow across the FO-membrane 6c causes built up scaling and fouling to detach from the walls and pores of the FO-membrane 6c.Once defouled, the scaling and fouling will be sent from the feed side 6b to the drain 12.

[0071] The system 1 as embodied in Fig. 3 differs from the system 1 embodied in Fig. 1 partially in that the system 1 of Fig. 3 does not include the dialysis concentrate valve 31 , the feed side inlet valve 34, or the chamber valve 39. Instead, certain three-way valves are utilized to allow low concentrate fluid to flow through the draw side 6a and high concentrate fluid to flow through the feed side 6b. The valves include: a feed fluid reverse valve 64 which is a three-way valve connecting the third fluid line 25 to both an feed fluid feed line 51 (which fluidly connects the feed fluid reverse valve 64 to the feed side 6a inlet) and a feed fluid draw line 54 (which fluidly connects the feed fluid reverse valve 64 to the draw side 6a inlet) , selectively; and a concentrate reverse valve 61 which is a three-way valve connecting the first fluid line 21 to both a concentrate draw line 55 (which fluidly connects the concentrate reverse valve 61 to the draw side 6a inlet) and a concentrate feed line 57 (which fluidly connects the concentrate reverse valve 61 to the feed fluid feed line 51), selectively. In other words, the feed fluid reverse valve 64 allows fluid on the feed side of the fluid path 2 to be directed to the draw side 6a inlet, and the concentrate reverse valve 61 allows fluid on the draw side of the fluid path 2 to be directed to the feed side 6b inlet. Other differences in the system 1 as embodied in Fig. 3 include: a secondary water line 27 connects the sixth fluid line 28 to the fluid line 25a, and the water valve 62 is disposed on the secondary water line 27 to control the flow of water to the fluid line 25a on the feed side; and the air vent line 58 is disposed on the draw side 6a of the fluid line 2.

[0072] Fig. 4 is a flow chart of a method according to some embodiments of the disclosure. The method may be implemented as instructions of a computer program and saved in the memory of the control unit 40. The method is explained together with the flow chart of Fig. 4.The flow chart discloses a method for osmotic back-wash defouling of a FO-unit membrane 6c. The system is preferably system 1 as illustrated or described herein in Fig. 3, but may also include a combination of the systems 1. The boxes illustrated in dashed line correspond to alternative or optional functions or procedures. In the illustrated embodiment, the method at S201 empties fluid in the draw side 6a of the fluid line 2, which may be accomplished by the concentrate pump 41 pulling in air from the air vent 59 and sending it through the draw side 6a of the FO-unit 6. At S202 the method adjusts the concentrate reverse valve 61 so that dialysis concentrate 4a flows to the feed side 6b and not to the draw side 6a of FO-unit 6. This is accomplished by closing the concentrate reverse valve 61 to the concentrate draw line 55 and opening the concentrate reverse valve 61 to the first fluid line 21 and the concentrate feed line 57, allowing fluid from the first fluid line 21 (which would typically flow through the draw side 6a to be routed through the feed side 6b At S203 fluid is pumped via the concentrate reverse valve 61 and the concentrate pump 41 into the feed side 6b to prime the feed side 6b.

[0073] Specifically, dialysis concentrate 4a is sent to the feed side to prime it. At S204, feed fluid reverse valve 64 is adjusted so that low concentrate fluid flows to the draw side 6a and not to the feed side 6b of the FO-unit 6. This is accomplished by closing the feed fluid reverse valve 64 to the feed fluid feed line 51 and opening the feed fluid reverse valve 64 to the third fluid line 25 and the feed fluid draw line 54, allowing fluid from the third fluid line 25 (which would typically flow through the feed side 6b) to be routed through the draw side 6a. In particular, feed pump 44 may be employed to pump feed fluid to the bottom inlet of the draw side 6a. The low concentrate fluid is preferably pumped through the FO-unit 6 starting at the bottom end because scaling and fouling is anticipated to be the most concentrated at that location. With low concentrate fluid flowing through the draw side 6a and high concentrate fluid already primed in the feed side 6b, water will tend to move from the draw side 6a to the feed side 6b because of the osmotic pressure (which is opposite of the normal osmotic pressure gradient). This reversal of the direction of the flow of water across the FO-membrane 6c causes scaling and fouling on the walls and pores of the FO-membrane 6c to become dislodged into the feed side 6b and flow into the drain 12. In this manner, the FO-unit 6 is defouled by an osmotic pressure-driven back-wash. Then, at optionalstep S205, the system 1 may ensure the entire draw side 6a becomes primed with low concentrate fluid by measurement of the conductivity sensor 8 to achieve full osmotic back-wash (i.e. make sure that the reverse osmotic pressure is occurring across the entirety of the FO-membrane 6c). The flow rates of the low concentrate solution and the high concentrate solution may also be controlled by control unit 40 to help ensure that the entire draw side 6a becomes primed.

[0074] Those skilled in the art will recognize that the system 1 as embodied in Fig. 3 is particularly adapted to perform an osmotic back-wash, but that other embodiments are possible. Any system 1 or arrangement of the system 1 embodied by Fig. 3 which is capable of changing the direction of osmotic pressure across the FO-membrane 6c is also contemplated. The components and placement of the components of the embodiment of Fig. 3 are a preferred embodiment.

[0075] Furthermore, it is expressly contemplated that these systems 1 as embodied in Figs. 1 and 3 could be combined to create a system 1 with the functionality of any combination of the methods of Figs. 2, 4, and 5. For example, a chamber 46 could be added to the system 1 of Fig. 3, such as for example disposed upstream of the feed fluid reverse valve 64 which would be capable of building and releasing a positive relative pressure or a negative relative pressure on the feed side 6b. The control unit 40, in such a scenario, may be configured to determine which method (TMP-driven back-wash, osmotic back-wash, or feed-side flow transients) or combination of methods to use in order to defoul the FO-unit 6.

[0076] While the invention has been described in connection with what are presently considered to be the most practical and preferred embodiments, it is to be understood that the invention 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 scope of the appended claims.

Claims

26Claims1. A system (1 ) for defouling a forward osmosis unit arranged for generating treatment fluid for use in dialysis treatment, the system (1) comprising:a fluid path (2) including:two or more dialysis concentrate connectors (3a, 3c), each connector configured to be connected to a source of dialysis concentrate fluid (4a, 4c), andan inlet connector (5a) configured to be connected to a feed fluid source;a forward osmosis- (FO-) unit (6) including a draw side (6a) and a feed side (6b) separated by a FO-membrane (6c), the FO-unit (6) fluidly connected to the fluid path (2), wherein the FO-unit (6) is configured to receive one or more dialysis concentrate fluids (4a, 4c) at the draw side (6a) and to receive the feed fluid at the feed side (6b), wherein water is transported from the feed fluid to the one or more dialysis concentrate fluids (4a, 4c) through the FO-membrane (6c) via an osmotic pressure gradient between the draw side (6a) and the feed side (6b), thereby diluting the one or more dialysis concentrate fluids (4a, 4c) into a diluted dialysis concentrate fluid;a chamber (46) configured to receive feed fluid from the feed fluid source upstream of the FO-unit (6) and further configured to allow gas to migrate out of the feed fluid;an air vent (59) configured to release gas from the chamber (46) or allow air to be drawn into the chamber (46);a valve (34) disposed between the chamber (46) and the FO-unit (6); anda control unit (40) configured to:control a flow of feed fluid on the feed side (6b),control a flow of the one or more dialysis concentrate fluids (4a, 4c) on the draw side (6a), andcontrol the valve (34),wherein the control unit (40) is configured to cause a pressure difference to be established between the chamber (46) and the FO-unit (6) by controlling a flowof feed fluid into or out of the chamber (46) with the valve (34) in a closed position, andwherein, once a threshold pressure difference level is reached, the control unit (40) is configured to cause the valve (34) to open, thereby causing fluid in the feed side (6b) of the FO-unit (6) to accelerate and promoting release of a foulant built up on the FO-membrane (6c).

2. The system of claim 1 , wherein the control unit (40) is further configured to determine a degree of compliance in the chamber (46) by communicating with one or more level sensors (46a, 46b), and wherein if a desired degree of compliance is not met, the system (1) is configured to draw air in or push air out from the air vent (59) until the desired degree of compliance for the defouling operation is detected.

3. The system of claim 2, wherein the degree of compliance in the chamber (46) corresponds to a level of fluid in the chamber (46).

4. The system of any one of claim 1-3, wherein opening the valve (34) creates a trans-membrane pressure transient that results in a trans-membrane water transport transient in a reverse direction to a normal operation of the FO-unit that promotes foulant release.

5. The system of any one of claim 1-4, wherein the control unit (40) is configured to control the flow of feed fluid on the feed side (6b) by at least one feed pump (44).

6. The system of any one of claim 1-5, wherein a pressure sensor (53) in operable communication with the control unit (40) and disposed along the feed side (6b) is arranged to measure an amount of the relative pressure in the chamber (46).

7. The system of any one of claim 1-6, wherein at least one feed pump (44) is arranged for pumping effluent fluid from an effluent container (15) toward a drainline (12), wherein the at least one feed pump (44) is arranged to dispose released foulant through the drain line (12).

8. The system of any one of claim 1-7, further comprising an effluent container (15) disposed between the inlet connector and the chamber (46).

9. The system of any one of claim 1-8, wherein the pressure difference is a negative relative pressure of the chamber (46) compared to the FO-unit (6).

10. The system of claim 9, wherein the acceleration of the fluid in the feed side (6b) is a negative acceleration relative to the downstream direction of the feed side (6b).

11. The system of claim 10, wherein the negative acceleration causes fluid to flow in the upstream direction of the feed side (6b).

12. The system of any one of claim 1 -8, wherein the pressure difference is a positive relative pressure of the chamber (46) compared to the FO-unit (6).

13. The system of claim 12, wherein the acceleration of the fluid in the feed side (6b) is a positive acceleration relative to the downstream direction of the feed side (6b).

14. The system of claim 13, wherein the positive acceleration causes fluid to flow in the downstream direction of the feed side (6b) more rapidly than during a normal operation of the FO-unit.

15. A system (1 ) for defouling a forward osmosis unit arranged for generating treatment fluid for use in dialysis treatment, the system (1) comprising:a fluid path (2) including:two or more dialysis concentrate connectors (3a, 3c), each connector configured to be connected to a source of dialysis concentrate fluid (4a, 4c),29a diluted dialysis concentrate connector (3b) configured to be connected to a source of diluted dialysis concentrate fluid (4b),an inlet connector (5a) configured to be connected to a feed fluid line (5) arranged for transportation of feed fluid from a source of feed fluid;a forward osmosis- (FO-) unit (6) including a draw side (6a) and a feed side (6b) separated by a FO-membrane (6c), the FO-unit (6) fluidly connected to the fluid path (2), wherein the FO-unit (6) is configured to receive one or more dialysis concentrate fluids (4a, 4c) at the draw side (6a) and to receive the feed fluid at the feed side (6b), wherein water is transported from the feed fluid to the one or more dialysis concentrate fluids (4a, 4c) through the FO-membrane (6c) via an osmotic pressure gradient between the draw side (6a) and the feed side (6b), wherein the osmotic pressure gradient where water is transported from the feed side (6b) to the draw side (6a) through the FO-membrane (6c) comprises a normal osmotic pressure gradient, thereby diluting the one or more dialysis concentrate fluids (4a, 4c) into a diluted dialysis concentrate fluid;a first three-way valve (61 ) fluidly connecting at least one source of dialysis concentrate fluid (4a) to the feed side (6b) upstream of the FO-unit (6);a second three-way valve (64) fluidly connecting the feed fluid line (5) to the draw side (6a) upstream of the FO-unit (6);an air vent (59) in fluid communication with the draw side (6a) downstream of the FO-unit (6); anda control unit (40) configured tocontrol a flow of feed fluid on the feed side (6b),control a flow of the one or more dialysis concentrate fluids (4a, 4c) on the draw side (6a), andcontrol the valves (61 , 64),wherein the control unit (40) is configured to cause an osmotic backwash by:emptying the draw side (6a) by pulling air in through the air vent (59) by a first pump (41) disposed on the draw side (6a) in fluid communication with the air vent (59) to the source of diluted dialysis concentrate (4b);30priming the feed side (6b) with a dialysis concentrate (4a) by means of the first pump (41 ) and the first three-way valve (61 ); andsending a low concentration fluid (7, 15) by means of a feed pump (44) disposed on the feed side (6b) and the second three-way valve (64) through the draw side (6a) of the FO-unit (6), creating an osmotic pressure gradient in an opposite direction of the normal osmotic pressure gradient wherein water is transported from the draw side (6a) to the feed side (6b) through the FO-membrane (6c),wherein the osmotic backwash promotes release of a foulant built up on the FO-membrane (6c).

16. The system of claim 15, wherein the control unit (40) is configured to continue to pump low concentrate fluid (7, 15) to the draw side (6a) and dialysis concentrate (4a) to the feed side (6b), and is configured to control the flow rates of the low concentrate fluid (7, 15) and the dialysis concentrate (4a).

17. The system of claim 16, wherein controlling the flow rates of the low concentrate fluid (7, 15) and the dialysis concentrate (4a) is used to ensure that the entire draw side (6a) becomes primed to achieve osmotic backwash of the entire FO-membrane (6c).

18. The system of claim 17, wherein a conductivity sensor (8) is disposed on the draw side (6a) and in operable communication with the control unit (40), and wherein the conductivity sensor (8) is used to determine full priming of the draw side (6a).

19. The system of any one of claims 15-18, wherein the low concentrate fluid is water (7).

20. The system of any one of claims 15 to 18, wherein the low concentrate fluid is effluent fluid (15).

20. The system of any one of claims 15 to 20, wherein at least one feed pump (44) is arranged for pumping effluent fluid from an effluent container (15) toward a drain line (12), wherein the at least one feed pump (44) is arranged to dispose released foulant through the drain line (12).

21. The system of claims 6 or 20, wherein the drain line (12) is also arranged to dispose spent feed fluid.

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