Method and system for improving cross-flow filtration - Patents.com

Abstract

A method of cross-flow filtration of wastewater from a diagnostic device or laboratory analyzer, the wastewater containing nanoparticles and / or microparticles, the wastewater flowing in a laminar flow across a surface of a filter membrane, the method comprising: (a) flowing the wastewater across the surface of the filter membrane at a flow rate such that the flow of the wastewater is laminar with a Reynolds number (Re) less than 500; (b) flowing the wastewater in pulse cycles across the surface of the filter membrane, each pulse cycle including one active period during which the wastewater is under a duty pressure and one inactive period during which the wastewater is under an inactive pressure, the inactive pressure being less than or equal to 10% of the duty pressure, the active period having a duration greater than 50% of the corresponding pulse cycle; and (c) separating the nanoparticles and / or microparticles from the wastewater as it passes through the filter membrane. Also described is a cross-flow filtration system configured to perform the method.

Description

[Technical field]

[0001]

[0001] The present invention relates to a method for cross-flow filtration of wastewater from a diagnostic device or laboratory analyzer, the wastewater containing nanoparticles and / or microparticles, the wastewater flowing in a laminar flow across a surface of a filter membrane. The present invention also relates to a cross-flow filtration system for carrying out the method. The present invention also relates to a computer program for carrying out the method, and to a computer readable medium having stored thereon the computer program. [Background technology]

[0002]

[0002] The laboratory diagnostics industry uses reagents that contain small particles, e.g., nanoparticles and / or microparticles, with a particle size smaller than 5 mm. The wastewater generated in this industry contains these small particles, which can be harmful to the environment due to their raw material (e.g., microplastics). They also tend to be highly adsorptive and can transfer pollutants to and from the environment, which can cause damage. These particles differ from particulate waste generated in other industries in that they have a well-defined composition and a very uniform particle size. Therefore, it is difficult to efficiently remove them from the wastewater of laboratory analyzers.

[0003]

[0003] Filtration techniques are often used to remove particles from liquids. Cross-flow filtration (also called tangential flow filtration) is a type of filtration in which the liquid to be filtered passes across a filter membrane, rather than directly into the filter as in dead-end filtration. Substances in the liquid that are smaller than the pore size of the filter membrane pass through the membrane, producing a permeate. The liquid passes across the filter membrane with a positive pressure relative to the permeate side. It is this positive pressure that provides the primary driving force for the cross-flow filtration process. The pressure difference on either side of the filter membrane (called the feed / retentate side and the permeate side) is measured as the transmembrane pressure (TMP).

[0004]

[0004] Many cross-flow filtration processes involve turbulent liquid flow (e.g., Reynolds numbers of about 2000 or greater) passing over a filter membrane. In such processes, the flow of liquid near the surface of the filter membrane is turbulent, which can prevent particulates from settling on the surface and forming a filter cake that blocks the pores of the membrane. The turbulent liquid flow in cross-flow filtration is generally generated in filtration devices that have very high liquid flow rates. Such flow rates are usually generated by high-power pumps. These pumps tend to be large in size and have high energy consumption.

[0005]

[0005] When cross-flow filtration is performed with a low flow rate of liquid, laminar flow may pass over the surface of the filter membrane. Since the tangential flow velocity near the surface of the filter membrane is low in laminar flow, there is a problem that the filter membrane is easily clogged by fine particles, for example, when the fine particles aggregate and form a filter cake on the surface of the filter membrane. In such a case, filtration must be stopped and the clogged filter membrane must be replaced with an unclogged filter membrane. In order to reuse the filter membrane, the obstruction must be removed from the filter membrane, which may damage the filter membrane because it is delicate. This is undesirable because the filter membrane is an expensive component of the cross-flow filtration system. Summary of the Invention

[0006] In a first aspect, the present invention provides a method for cross-flow filtration of wastewater from a diagnostic instrument or laboratory analyzer, the wastewater containing nanoparticles and / or microparticles, the wastewater flowing in a laminar flow across an inner surface of a tubular filter membrane (25) having an inlet and an outlet, at a flow rate such that the Reynolds number (Re) of the flowing wastewater is less than 500; the wastewater flows in pulse cycles across the inner surface of the tubular filter membrane (25) from the inlet to the outlet, each pulse cycle including one active period (A') during which the wastewater is subjected to a duty pressure at the inlet and one inactive period (I) during which the wastewater is subjected to an inactive pressure at the inlet, the inactive pressure being less than or equal to 10% of the duty pressure, and the active period having a duration greater than 50% of the corresponding pulse cycle; The filtrate portion of the wastewater passes across the tubular filter membrane (25) and the nanoparticles and / or microparticles are separated from the filtrate portion of the wastewater by the tubular filter membrane (25).

[0007]

[0007] The present invention relates to cross-flow filtration in which a laminar flow of a liquid (in this case wastewater from a diagnostic or laboratory analyzer) is passed or flowed over the surface of a filter membrane. The flow rate of the liquid over the filter membrane is relatively low, especially when compared to systems employing turbulent flow. As further described below, the cross-flow filtration method and system of the present invention are particularly suitable for use with diagnostic or laboratory analyzers to remove small particles from wastewater generated by such devices.

[0008]

[0008] Surprisingly, it has been found that by flowing wastewater across the surface of the filter membrane in pulse cycles, clogging of the filter membrane during cross-flow filtration can be reduced or prevented. This significantly improves the performance and efficiency of cross-flow filtration technology. Cross-flow filtration can be run for longer periods while maintaining a high flow rate of permeate through the filter membrane. This reduces the need to periodically stop filtration to unclog and clean the filter membrane. It can also extend the life of the filter membrane.

[0009]

[0009] It will be appreciated that, in contrast to known cross-flow filtration methods, embodiments of the present invention do not superimpose oscillations or flow pulses on an underlying continuous flow. Rather, embodiments of the present invention impose a flow regime that alternates between active and inactive periods as defined. Embodiments of the present invention can impose flows that do not include backwash or backflow across the filter membrane. Embodiments of the present invention can impose flows where the transmembrane pressure is always greater than or equal to zero. Furthermore, embodiments of the present invention apply pulse cycles with a much lower frequency than that used in known cross-flow filtration methods, and the flows are at very low Reynolds numbers below 500.

[0010]

[0010] Energy is consumed by generating a flow or stream of wastewater over a filter membrane, such as when a pump is used to pump wastewater around a cross-flow filtration system. When the wastewater is pumped in pulsed cycles, energy is consumed primarily during the active phase of each pulse cycle and is conserved during the inactive phase. This avoids the continuous consumption of energy and improves the efficiency of the filtration process.

[0011]

[0011] In embodiments of the present invention, the use of a single pump, e.g., a membrane pump, to implement a flow regime that involves only alternating active and inactive periods means that less energy is required than in prior art systems in which a continuous flow is pumped through a filter device and flow oscillations are superimposed on the underlying continuous flow to create positive and negative flow directions or cycles. Such prior art systems typically require at least two pumps, one to generate the continuous flow and one to superimpose the flow oscillations, and therefore use more energy.

[0012]

[0012] Embodiments of the present invention do not impose alternating positive and negative flows, but instead alternate between gentle positive flow (active phases) and little to no flow (inactive phases). The transmembrane pressure can always be greater than or equal to zero, and is greater during active phases than in inactive phases.

[0013]

[0013] The embodiment of the present invention using laminar flow with a maximum Reynolds number less than 500 avoids cavitation or backwash in the wastewater flow through the tubular filter membrane. Avoidance of cavitation or backwash is facilitated by keeping the transmembrane pressure at or above zero. Avoidance of cavitation or backwash can result in lower mechanical stress on the filter membrane. This can extend the useful life of the filter membrane.

[0014]

[0014] The gentle laminar flow and low pulse cycle frequency of embodiments of the present invention means that the shear action on particulates accumulated inside the tubular filter membrane (filter cake) is much less than in prior art systems. It is currently believed that embodiments of the present invention reduce particulate buildup (filter cake) primarily by diffusing the particles into the wastewater within the tubular filter membrane during the inactive phase of the cycle.

[0015]

[0015] In the present invention, the active phase has a duration of more than 50% of the corresponding pulse cycle. The inventors of the present invention have recognized that the inactive phase can reduce or prevent the formation of filter cake on the filter membrane and keep the surface of the membrane clean on the one hand. On the other hand, the inventors have also realized that the longer the active phase and the shorter the inactive phase of the pulse cycle, the longer the effective transport time per pulse, and therefore the more throughput is possible. In other words, if the duration of the active phase is longer than the duration of the inactive phase in a pulse cycle, more permeate is obtained at the same pressure. Thus, by making the active phase of the pulse cycle longer than the inactive phase, the efficiency of the filtration process is improved and the overall energy consumption is reduced.

[0016]

[0016] The inventors assume that this effect results from the following relationship: during the inactive phase, a portion of the particles forming the filter cake go back into solution. The longer the inactive phase, the more particles dissolve in the liquid. The dissolved particles are then washed away during the active phase. In the case of laminar flow, it is possible that most of the dissolved particles are washed away and only a small portion is reincorporated into the filter cake. Therefore, the inactive phase should not be arbitrarily short. This is also valid for the recovery phase according to step (A) described below.

[0017]

[0017] In some embodiments, the method comprises: (A) applying a recovery period with little wastewater flow and little transmembrane pressure; (B) applying a wash phase during which wastewater is flushed across the surface of the filter membrane with little transmembrane pressure.

[0018]

[0018] The recovery and washout phases may be repeated several times.

[0019]

[0019] Steps (A) and (B) can be carried out to clean and / or rejuvenate the filter membrane. A combination of a rejuvenation phase and a cleaning phase can be used when the filter membrane shows signs of fouling, such as to restore the flow rate of permeate through the filter membrane.

[0020]

[0020] Cross-flow filtration according to the invention can be carried out until the filter membrane shows signs of fouling, after which steps (A) and (B) can be carried out to clean and / or refurbish the filter membrane for further use.

[0021] In a second aspect, the present invention provides a cross-flow filtration system for filtering wastewater from a diagnostic device or laboratory analyzer, containing nanoparticles and / or microparticles, by laminar flow across an inner surface of a tubular filter membrane having an inlet and an outlet, the system comprising: A filter module comprising a tubular filter membrane; a pressure source for flowing the wastewater across a surface of the tubular filter membrane from an inlet to an outlet; a sensor for detecting the flow rate of wastewater; a controller connected to the sensor and configured to control the pressure source to perform the method according to the first aspect; and A flow restrictor is disposed downstream of the filter module on the retentate side of the filter module to provide flow resistance during the active portion of the pulse cycle.

[0022]

[0022] Because the flow rate of wastewater passing over the filter membrane is relatively low, the cross-flow filtration system does not require a pressure source such as a pump with high power.Therefore, the cross-flow filtration system of the present invention can use a smaller and lower power pressure source, which means that the whole system does not occupy a large space and has a small footprint.In some embodiments, only one pump is required.

[0023]

[0023] In certain embodiments, the pressure source may comprise a membrane pump. The membrane pump may be switched on to perform an active phase of a pulse cycle. The membrane pump may be switched off to perform an inactive phase of a pulse cycle.

[0024]

[0024] The combination of pulse cycles, laminar flow with a Reynolds number less than 500, and longer active than inactive periods means that high filtration throughput, efficient filtration, and longer filtration periods can be achieved without interruptions due to clogging of the filter membrane. These advantages can all be achieved with a cross-flow filtration system that has a small footprint due to the use of a small pressure source such as a pump. This small footprint is also advantageous in that the cross-flow filtration system can be incorporated as part of a diagnostic device or laboratory analyzer in locations where there is little available space.

[0025]

[0025] An embodiment of the present invention may use or include hollow fiber filter membranes. The hollow fiber filter membrane may include a plurality of hollow fibers connected in parallel in an external manifold. Each hollow fiber is configured as a tubular filter membrane having a tubular wall with an inner surface and an outer surface. Each tubular filter membrane has an inner diameter, which may define a characteristic linear dimension for calculating the Reynolds number of the flow through the hollow fiber filter membrane. The tubular wall is porous and has pores of a desired diameter. Wastewater is fed into the inlet end of each hollow fiber, passes along the interior of the tubular filter membrane and crosses the inner surface. The filtrate component of the wastewater passes through the pores of the tubular wall and may be collected at the outlet end of the manifold of the hollow fiber filter membrane. The remaining liquid fraction of the wastewater, along with any particulate matter that does not pass through the pores, may continue to flow along the interior of the tubular filter membrane and be output at the outlet end of the hollow fiber filter membrane separately from the filtrate. When the filter membrane comprises a plurality of hollow fibers, the filter membrane can have a total number of hollow fibers of at least 10, for example at least 20, for example at least 50, preferably at least 75, for example at least 100. In some embodiments, the filter membrane can have a total number of hollow fibers of up to 2000, or up to 1000, or up to 750, or up to about 500. The total number of fibers depends on the size of the filter membrane. In some embodiments, the filter membrane can include only one fiber or less than 10 fibers. Filter membranes with a low number of fibers, for example less than 10, can be configured as ceramic filter membranes.

[0026]

[0026] It will be understood that when wastewater flows through the interior of the tubular filter membrane, the filtrate fraction of the wastewater passes through the pores of the tubular wall of the tubular filter membrane, resulting in a decrease in the velocity profile of the wastewater flow along the interior of the tubular filter membrane. In the context of this application, the maximum Reynolds number of the flow is determined at the point in the tubular filter membrane where the flow velocity is maximum. This point may be at the inlet of the tubular filter membrane.

[0027]

[0027] The cross-flow filtration system may be retrofitted to or may be part of a diagnostic device or laboratory analyzer, for example, as a module of the diagnostic device or laboratory analyzer.

[0028] A third aspect of the present invention provides a method for cross-flow filtration of wastewater from a diagnostic instrument or laboratory analyzer, the wastewater containing nanoparticles and / or microparticles, the wastewater flowing in a laminar flow across a surface of a filter membrane, the method comprising: (A) applying a recovery period with little wastewater flow and little transmembrane pressure; (B) applying a wash phase during which wastewater is flushed across the surface of the filter membrane with little transmembrane pressure.

[0029]

[0029] The recovery and washout phases may be repeated several times.

[0030]

[0030] A third aspect of the invention relates to a method for cleaning and / or restoring a filter membrane. A combination of a restoring phase and a cleaning phase can be used when the filter membrane shows signs of fouling, such as to restore the flow rate of permeate through the filter membrane.

[0031]

[0031] The method of the third aspect of the present invention can be used independently of the method of the first aspect. For example, conventional cross-flow filtration can be carried out until the filter membrane shows signs of clogging. The method of cleaning and / or repairing the filter membrane in the third aspect of the present invention can then be used to restore the filter membrane for further use.

[0032]

[0032] The present invention further relates to a computer program comprising computer executable code which, when executed on a controller, causes the cross-flow filtration system to carry out the method according to the present invention.

[0033]

[0033] The invention also relates to a computer-readable medium, which stores a computer program according to the invention.

[0034]

[0034] The preferred, advantageous and optional features of any one particular aspect of the invention described below are also preferred, advantageous and optional features of any other aspect.

[0035]

[0035] The present invention will now be further described with reference to the accompanying drawings. [Brief description of the drawings]

[0036] [Figure 1] FIG. 1 is a schematic diagram of a cross-flow filtration system according to the present invention. [Diagram 2] FIG. 1 is a schematic diagram of a cross-flow filtration system according to the present invention. [Diagram 3] FIG. 1 is a schematic diagram of a cross-flow filtration system according to the present invention. [Figure 4] 1 is a graph showing the flow rates of wastewater feed (f), clean water permeate (p), and wastewater retentate (r) over time in a conventional crossflow filtration system. [Diagram 5] 1 is a graph showing the permeate flow rate over time in a cross-flow filtration system operated with a conventional continuous flow wastewater feed (see "60 minutes of pumping") or when the wastewater feed is run in pulsed cycles ("Pulse Protocol") in accordance with the present invention. [Figure 6] 6 is a graph showing the permeate (p) flow rate during the active (A) or inactive (I) phase of a pulse cycle. During the active phase (A), the transmembrane pressure is greater than 0 bar. The average permeate flow rate (M) obtained using a pulse cycle is also shown, which is higher than the flow rate plateau (P) obtained without a pulse cycle. The duration of the active phase in FIG. 6 is longer than in FIG. 7. [Figure 7]Graph showing permeate (p) flux during the active (A) or inactive (I) phase of a pulse cycle. During the active phase (A), the transmembrane pressure is greater than 0 bar. Also shown is the average permeate flux (M) obtained using a pulse cycle, which is higher than the flux plateau (P) obtained without a pulse cycle. [Figure 8] 1 is a graph showing the flow rates over time of wastewater feed (f), retentate (r) and permeate (p) in a cross-flow filtration system in which the wastewater feed is run in a pulsed cycle in accordance with the present invention. [Figure 9] 9 is a graph showing pressure over time for the cross-flow filtration shown in Figure 8. The graph shows the wastewater feed (f) pressure, retentate (r) pressure, permeate (p) pressure, and transmembrane pressure (t). [Figure 10] 11 is a graph showing the effect on the permeate flow rate when the duty cycle of the pulsating laminar flow is changed. [Figure 11] 1 is a graph showing the relationship between flow rate, Reynolds number and a parameter related to a filter membrane, specifically, the surface area of ​​the filter membrane. [Figure 12] 1 is a graph showing the relationship between flow rate, Reynolds number and parameters related to the filter membrane, specifically the number of threads. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037] definition

[0044] The term "laminar flow" as used herein has its conventional meaning in fluid mechanics. It is a type of liquid flow in which the liquid flows in a smooth or regular path (as opposed to turbulent flow, in which the liquid fluctuates and mixes irregularly). In this case, the liquid is wastewater from a diagnostic device or laboratory analyzer. In laminar flow, the velocity, pressure, and other flow characteristics at each point in the liquid are constant.

[0038]

[0045] As used herein, the term "streaming" refers to the flowing or conveying or passing of a liquid (in this case wastewater) across the surface of a filter membrane.

[0039]

[0046] As used herein, the term "pulse cycle" is used to define the manner in which wastewater is flowed across the surface of a filter membrane. The wastewater is flowed across the surface of the filter membrane in a pulsating flow (also called a water-thrust flow). A pulsating flow, as used in fluid mechanics, is a flow (e.g., a wastewater flow) in which the pressure changes periodically. A pulsating flow can be generated by flowing a liquid (e.g., wastewater) in a pulsed manner. A pulse cycle can be represented by a pulsating wave (also called a pulse wave or a pulse train) as shown in Figures 5 to 9.

[0040]

[0047] A pulse cycle has a period, which is the total duration of the pulse cycle. The period of a pulse cycle is related to the frequency of the pulse cycle by the following equation:

number

[0041]

[0048] Each pulse cycle has an active period and an inactive period. The duration of the active period is the active period. The duration of the inactive period is the inactive period. The period of the pulse cycle is the sum of the active period and the inactive period.

[0042]

[0049] In some cases, it is useful to refer to the duty cycle or pulsation of a pulse cycle. As used herein, the term "duty cycle" refers to the ratio of the active period to the total period of the pulse cycle. Duty cycle (D) is defined as:

number

[0043]

[0050] As used herein, the term "active phase" refers to the stage of the pulse cycle during which the wastewater is under duty pressure.

[0044]

[0051] As used herein, the term "inactive phase" refers to the stage of the pulse cycle during which the wastewater is under inactive pressure.

[0045]

[0052] The term "duty pressure" as used herein refers to the pressure of the wastewater on the retentate side of the filter membrane. The duty pressure is a pressure greater, preferably significantly greater, than the inactive pressure (defined below). The duty pressure is the pressure to achieve permeation of the wastewater through the filter membrane, such as when the filter membrane is not blocked or clogged, as in conventional cross-flow filtration. In general, the duty pressure is greater than 0.0 bar, preferably greater than 0.1 bar.

[0046]

[0053] The term "inactive pressure" refers to the pressure of wastewater on the retentate side of the filter membrane. Typically, the inactive pressure is the pressure at which there is little or no wastewater permeation through the filter membrane (e.g., less than 1.0 L / hr), such as when the filter membrane is not blocked or clogged, such as in conventional cross-flow filtration. In general, the inactive pressure may be greater than 0.0 bar, and preferably the inactive pressure is about 0.0 bar, e.g., 0.0 to 0.2 bar.

[0047]

[0054] As used herein, the term "significantly greater" refers to at least 10% greater, preferably at least 25% greater, and more preferably at least 50% greater. This term is used herein to describe the flow rate of the feed during an active phase compared to the flow rate of the feed during an inactive phase, and the flow rate throughput of the permeate during an active phase compared to the flow rate throughput of the permeate during an inactive phase.

[0048]

[0055] As used herein, the term "transmembrane pressure" or "TMP" refers to the pressure difference between the retentate and permeate sides of a filter membrane.

number

[0049]

[0056] When the permeate side pressure is 0.0 bar, the transmembrane pressure may be the same as the duty pressure during the active phase. Similarly, when the permeate side pressure is 0.0 bar, the transmembrane pressure may be the same as the inactive pressure during the inactive phase, particularly when the filter membrane is not blocked or clogged. The transmembrane pressure may be measured by conventional methods known in the art, such as using a flow sensor or a pressure sensor.

[0050]

[0057] The term "feed" as used herein refers to wastewater containing nanoparticles and / or microparticles that is flowed across the surface of a filter membrane. The feed is flowed through an inlet of a filter module that contains the filter membrane.

[0051]

[0058] As used herein, the term "permeate" refers to the clarified wastewater that has passed through the filter membrane.

[0052]

[0059] The term "retentate" as used herein refers to wastewater that has been flushed across the surface of a filter membrane. The retentate is flushed from an outlet of a filter module that includes the filter membrane. From the outlet, the retentate can be flushed into a container (e.g., a liquid retentate storage container). In the container, the retentate can be mixed with wastewater, such as fresh wastewater from a diagnostic device or laboratory analyzer, for recirculation. This wastewater can be flushed across the surface of a filter membrane according to the methods of the present invention.

[0053]

[0060] The term "filter cake" as used herein refers to any substance or material that is retained on or within a filter membrane. Typically, the substance or material is a solid that can clog or contribute to the clogging of the filter membrane. Filter cake may be a collection of nanoparticles and / or microparticles that are retained on or within the filter membrane.

[0054]

[0061] As used herein, the term "disposed" has its conventional meaning and includes the term "located."

[0055]

[0062] The term "diagnostic apparatus" as used herein includes any such device or apparatus for performing a diagnostic function that generates wastewater containing nanoparticles and / or microparticles. Diagnostic apparatus are used, particularly in the medical field, to identify the nature or cause of a particular phenomenon, and the information provided by the apparatus helps a clinician to make a diagnosis about the health condition of a patient. The diagnostic apparatus is preferably a medical diagnostic apparatus.

[0056]

[0063] The term "laboratory analyzer" as used herein includes any device or apparatus (typically automated device or apparatus) for use in a laboratory to qualitatively identify the presence or quantitatively determine the amount (e.g., typically the concentration) of a chemical or substance in a sample, and which generates wastewater containing nanoparticles and / or microparticles. The laboratory analyzer is preferably a medical laboratory analyzer (e.g., a medical laboratory analyzer). The sample may be, for example, serum, plasma, urine or other bodily fluids from a human or animal patient. Analytes or analytes for which the device or apparatus is used may include proteins, metabolites, electrolytes or drugs. The laboratory analyzer may use heterogeneous immunoassays. An example of a laboratory analyzer is the cobas 1000 series manufactured by the applicant. TM e801 module and cobas TM There is a c701 module.

[0057]

[0064] The term "wastewater" as used herein refers to an aqueous solution containing nanoparticles and / or microparticles. Wastewater is waste material obtained directly from a diagnostic device or laboratory analyzer. The nanoparticles and / or microparticles are used or unused reagents obtained from a diagnostic or laboratory analysis performed by a diagnostic device or laboratory analyzer. Wastewater can include other waste materials or by-products resulting from a diagnostic or laboratory analysis, such as chemicals or substances being analyzed.

[0058]

[0065] The terms "nanoparticles" and "microparticles" as used herein generally refer to particles having a size of 5 mm or less. Microparticles have a particle size of 5 mm or less (preferably 1 mm or less) and 1.0 μm or more. Nanoparticles have a particle size of less than 1.0 μm (e.g., 999 nm or less) and 1 nm or more. Generally, nanoparticles and / or microparticles are reagents used in diagnostic devices or laboratory analyzers.

[0059]

[0066] The term "Reynolds number" as used herein is the ratio of inertial and viscous forces in a wastewater stream that undergoes relative internal motion due to different fluid velocities within a tubular filter membrane. The Reynolds number is defined as Re=ρuL / μ, where ρ is the density of the wastewater, u is the flow rate, L is the characteristic linear dimension (i.e., the inner diameter of the tubular filter membrane), and μ is the viscosity of the wastewater.

[0060]

[0067] For the avoidance of doubt, all parameters relating to wastewater flow or permeate throughput refer to the temperature at which the method of the present invention is carried out or the system of the present invention is operated. In general, the present invention is carried out or operated at room temperature (e.g., 20° C.). Pressure figures refer to pressures greater than atmospheric pressure unless the context indicates otherwise.

[0061] Detailed Description

[0068] In cross-flow filtration, where laminar flow of liquid passes across the surface of a filter membrane, filtration is often reduced or stopped by blockage or plugging of the filter membrane. An irreversible topcoat can form on the surface of the filter membrane due to absorption, compression, or precipitation of contaminants. This topcoat covers the openings to the pores in the filter membrane, thereby preventing access to these pores. The pores themselves can also become blocked, for example when particles become lodged within the pore channels. Filter membranes can also become clogged or blocked by substances that have an affinity for the membrane material. These substances can enter the pore channels and be adsorbed to the channel walls. Biofouling of filter membranes can also occur, for example by the formation of extracellular polymeric substances (EPS) biofilms produced by microorganisms.

[0062]

[0069] During use of a conventional cross-flow filtration system, the duty pressure and / or transmembrane pressure push particles against the filter membrane. These particles can accumulate on or within the filter membrane, forming a filter cake of particles. This filter cake impedes the flow of liquid into or through the filter membrane, causing the filtration rate to decrease exponentially until a plateau is reached. At this point, filtration reaches a steady state and the filtration rate remains stable at the plateau level, which is the asymptotic value of the steady state, described below. Once the filtration system reaches steady state, the same amount of energy is required as in the initial stages of filtration, but less liquid is filtered, making it less energy efficient.

[0063]

[0070] Therefore, the active period is preferably shorter than the time it takes for the flow throughput of the permeate to decrease from the maximum flow throughput of the permeate in the active phase to the steady-state flow throughput of the permeate. The active period is preferably 80% or less of the time required to reach the steady state, in particular 60% or less, more preferably 50% or less, and even more preferably 40% or less of the time required to reach the steady state. The steady state is an asymptotic value that is never achieved in practice. In the present invention, the steady state is reached when the flow throughput is within 5% of the asymptotic value of the steady state.

[0064]

[0071] This adjustment of the active phase with respect to the steady state can also be applied to other processes of cross-flow filtration of liquids by pulsating flow through a membrane, particularly through hollow fiber membranes.

[0065]

[0072] The present invention specifically relates to cross-flow filtration of a liquid (in this case wastewater from a diagnostic device or laboratory analyzer), where the liquid is passed or transported across the surface of a filter membrane in a laminar flow. Nanoparticles and / or microparticles are removed from the filter membrane by size exclusion. In other words, the pore size of the filter membrane must be small enough to prevent nanoparticles and / or microparticles from entering the pores.

[0066]

[0073] In a first aspect of the invention, the method comprises flowing wastewater across a surface of a filter membrane at a flow rate such that the flow of wastewater is laminar with a Reynolds number (Re) of less than 500. Preferably, the flow of wastewater is laminar with a Reynolds number (Re) of less than 250, more preferably less than 150, even more preferably a Reynolds number (Re) of 100 or less, especially 75 or less. The Reynolds number is determined by the wastewater temperature at which the cross-flow filtration is carried out.

[0067]

[0074] Typically, the flow of the wastewater is a laminar flow with a Reynolds number (Re) of 1 to less than 500. The flow of the wastewater is preferably a laminar flow with a Reynolds number (Re) of 5 to 250, more preferably 10 to 150, and even more preferably 15 to 100, particularly preferably 20 to 75 or 10 to 75.

[0068]

[0075] The present invention avoids or reduces clogging of the filter membrane during cross-flow filtration of a liquid, in this case wastewater from a diagnostic device or laboratory analyzer. When the filter membrane is clogged, the flow rate of permeate through the filter membrane is reduced, reducing the efficiency of the cross-flow filtration process. The present invention improves the performance of the cross-flow filtration system. The wastewater flows across the filter membrane in pulsed cycles, which can inhibit the formation of or aid in the removal of filter cake on and / or within the filter membrane. By reducing or preventing clogging of the filter membrane, cross-flow filtration can be performed for extended periods while maintaining a high flow rate of permeate through the filter membrane. The present invention reduces the need to periodically stop filtration to unclog and clean the filter membrane. This can also extend the life of the filter membrane, which is delicate and easily damaged.

[0069]

[0076] In the method of the present invention, wastewater is passed across the surface of the filter membrane in pulsed cycles. The or each pulsed cycle has an active phase and an inactive phase. The advantages provided by the first aspect of the present invention are related to the use of this combination of active and inactive phases.

[0070]

[0077] It is hypothesized that nanoparticles and / or microparticles on or in the filter membrane can be redispersed in the wastewater during the inactive phase, when there is little or no wastewater flow over the surface of the filter membrane, and the particles redisperse in the wastewater. The pulsing cycle can also create localized disturbances on the surface of the filter membrane, which can prevent particles from settling on or in the filter membrane and / or break up the filter cake formed on or in the filter membrane.

[0071]

[0078] A pulse cycle comprises an active period. Preferably, a pulse cycle comprises a single active period.

[0072]

[0079] The duration of the active phase is the active period. The active period may be at least 5 seconds, such as at least 10 seconds, preferably at least 30 seconds, more preferably at least 60 seconds, even more preferably at least 90 seconds, such as at least 100 seconds.

[0073]

[0080] Typically, the active period is 3600 seconds or less, such as 2800 seconds or less, preferably 1800 seconds or less, more preferably 1200 seconds or less, even more preferably 900 seconds or less, such as 600 seconds or less.

[0074]

[0081] The active period is preferably 5 to 3600 seconds, for example, 10 to 2800 seconds, preferably 30 to 1800 seconds, more preferably 60 to 1200 seconds, for example, 90 to 900 seconds, and further preferably 100 to 600 seconds.

[0075]

[0082] The or each active period has a duration that is greater than 50% of the corresponding pulse cycle. Thus, the active period is greater than 50% of the period of the pulse cycle.

[0076]

[0083] The inventors have found that if the active phase is longer than the inactive phase, the permeate throughput is increased while maintaining the energy efficiency of cross-flow filtration. For the avoidance of doubt, in order for pulse cycles to exist, the inactive period cannot be zero.

[0077]

[0084] The ratio of the duration of the active phase to the total duration of the pulse cycle can be expressed as a parameter called the duty cycle. If the active period is greater than 50% of the period of the pulse cycle, this corresponds to a duty cycle greater than 50%.

[0078]

[0085] The duty cycle may be 51% or more, preferably 55% or more, more preferably 57% or more, such as 60% or more, even more preferably 65% ​​or more, preferably 70% or more, and most preferably a duty cycle of 75% or more.

[0079]

[0086] The duration of the active phase does not exceed 99% of the corresponding pulse cycle, preferably does not exceed 95%, more preferably does not exceed 90%, even more preferably does not exceed 80%. In other words, the duty cycle does not exceed 99%, preferably does not exceed 95%. More preferably, the duty cycle is 85% or less, more preferably 83% or less, for example 82% or less, even more preferably 81% or less, and most preferably a duty cycle of 80% or less.

[0080]

[0087] Any lower duty cycle limit can be combined with any upper duty cycle limit.

[0081]

[0088] The duty cycle may be greater than 50% and not exceeding 99%, preferably 51% to 95%, more preferably 55% to 90%, in particular 55% to 85%, for example 57% to 83%, in particular 57% to 82%, even more preferably 60% to 81%, in particular 65% to 80%, even more preferably 70% to 80%, and most preferably a duty cycle (D) of 75% to 80%.

[0082]

[0089] The optimal duty cycle to provide maximum throughput of permeate while minimizing the energy required to operate the pump will depend on several factors, including the type of filter membrane, the wastewater flow rate, and the nature of the microparticles and / or nanoparticles.

[0083]

[0090] During the active phase, the feed (eg wastewater) has a flow of less than 0.50 m / s, preferably less than 0.35 m / s, more preferably less than 0.25 m / s.

[0084]

[0091] The feed generally has a flow during the active phase of at least 0.01 m / s, preferably at least 0.03 m / s, more preferably at least 0.05 m / s.

[0085]

[0092] Any lower feed flow limit can be combined with any upper feed flow limit.

[0086]

[0093] The feed may have a flow of 0.01 to 0.50 m / s, preferably 0.03 to 0.35 m / s, more preferably 0.05 m / s to 0.25 m / s during the active phase.

[0087]

[0094] In general, the feed flow rate during the active phase is 1.0 to 100 L / h, preferably 2.5 to 75 L / h, more preferably 5.0 to 50 L / h, and further preferably 10.0 to 25 L / h.

[0088]

[0095] The flow rate of the feed during the active phase is preferably significantly greater than the flow rate of the feed during the inactive phase.

[0089]

[0096] Generally, the feed (eg, wastewater) has a flow rate at least as high as or greater than the flow throughput of the permeate.

[0090]

[0097] Typically, during the active phase, there is a permeate flow throughput of greater than 0.0 m / s, preferably greater than 0.5 m / s, and more preferably greater than 1.0 m / s.

[0091]

[0098] During the active phase, it is preferred that there be a permeate flow throughput of greater than 1.0 L / h, preferably greater than 1.5 L / h, and more preferably greater than 2.0 L / h.

[0092]

[0099] The flow throughput of the permeate during the active phase is generally significantly greater than the flow throughput of the permeate during the inactive phase.

[0093]

[0100] When wastewater is flowed across the surface of the filter membrane in pulse cycles, the flow of wastewater during the active phase is laminar and has the Reynolds number defined above. In the active phase, wastewater is flowed across the surface of the filter membrane at the flow rate and duty pressure used in conventional cross-filtration without pulse cycles. In many cross-flow filtration systems, the flow created by the pressure source (e.g., pump) and / or flow restrictor is laminar. If turbulent flow occurs, the flow can be adjusted to laminar by reducing the wastewater flow rate and / or replacing the filter membrane.

[0094]

[0101] During the active phase, wastewater is flowed across the surface of the filter membrane under a duty pressure that is sufficient to effect filtration (e.g., permeation through the filter membrane) of the wastewater during normal, conventional use of the cross-flow filtration system.

[0095]

[0102] The duty pressure may be at least 0.5 bar, preferably at least 1.0 bar, more preferably at least 1.5 bar, and even more preferably at least 2.0 bar.

[0096]

[0103] The duty pressure will usually not exceed 25.0 bar, preferably not exceed 20.0 bar, more preferably not exceed 15.0 bar, even more preferably not exceed 10.0 bar.

[0097]

[0104] Any lower duty pressure limit can be combined with any upper duty pressure limit.

[0098]

[0105] Usually, the duty pressure is 0.5 to 25.0 bar, preferably 1.0 to 20.0 bar, more preferably 1.5 to 15.0 bar, and further preferably 2.0 to 10.0 bar.

[0099]

[0106] The transmembrane pressure during the active phase may be at least 0.5 bar, preferably at least 1.5 bar, more preferably at least 1.8 bar, even more preferably at least 2.0 bar.

[0100]

[0107] The transmembrane pressure during the active phase is usually 10.0 bar or less, preferably 6.0 bar or less, more preferably 4.0 bar or less, and further preferably 3.0 bar or less.

[0101]

[0108] Any lower transmembrane pressure limit can be combined with any upper transmembrane pressure limit.

[0102]

[0109] The transmembrane pressure (TMP) during the active phase can be set to 0.5 to 10.0 bar, preferably 1.5 to 6.0 bar, more preferably 1.8 to 4.0 bar, and further preferably 2.0 to 3.0 bar.

[0103]

[0110] In general, the duty pressure may be the transmembrane pressure. The duty pressure can be measured as the transmembrane pressure, such as when the pressure on the permeate side of the filter membrane is 0.0 bar.

[0104]

[0111] The pulse cycle also includes an inactive period during which the wastewater is subjected to an inactive pressure, and therefore there is no or minimal permeation of the wastewater through the filter membrane.

[0105]

[0112] Typically, during the inactive phase, the permeate flow throughput is 1.0 L / h or less, preferably 0.5 L / h or less, and more preferably 0.2 L / h or less.

[0106]

[0113] The flow throughput of the permeate during the active phase is generally significantly greater than the flow throughput of the permeate during the inactive phase.

[0107]

[0114] A pulse cycle can be represented by a pulsating wave. When an active period switches to an inactive period, there is a significant pressure drop as the pressure changes from the duty pressure to the inactive pressure. Similarly, when an inactive period switches to an inactive period, there is a significant pressure increase as the pressure changes from the inactive pressure to the duty pressure.

[0108]

[0115] Typically, the pulsating wave has a discontinuous slope. For example, the pulsating wave is a non-sinusoidal wave. The pulsating wave may be an asymmetric wave. The discontinuous slope may represent a transition between an active period and an inactive period.

[0109]

[0116] The inactive pressure is less than or equal to 10% of the duty pressure, preferably less than or equal to 5% of the duty pressure, more preferably less than or equal to 2% of the duty pressure. The inactive pressure may be greater than or equal to 0.0 bar.

[0110]

[0117] In a first embodiment of the inactive period, the inactive pressure is about 0.0 bar, for example 0.0-0.2 bar. Preferably, the inactive pressure is 0.0 bar.

[0111]

[0118] In this embodiment, the flow rate of the feed during the inactive phase is less than 1.0 L / h, preferably less than 0.5 L / h, more preferably less than 0.2 L / h, and even more preferably about 0.0 L / h. Thus, in the first embodiment of the inactive phase, there is almost no wastewater flow. This allows the nanoparticles and / or microparticles that remain on or in the filter membrane to be redispersed in the wastewater (e.g., feed).

[0112]

[0119] In a second embodiment of the inactive phase, the inactive pressure is between 0.0 and 0.5 bar, for example between 0.1 and 0.3 bar, more preferably about 0.1 bar.

[0113]

[0120] In this embodiment, the flow rate of the feed during the inactive phase is 1.0 to 100 L / h, preferably 2.5 to 75 L / h, more preferably 5.0 to 50 L / h, and even more preferably 10.0 to 25 L / h.

[0114]

[0121] In a second embodiment of the inactive phase, the feed (eg wastewater) has a flow of less than or equal to 0.50 m / s, preferably less than 0.35 m / s, more preferably less than 0.25 m / s.

[0115]

[0122] In a second embodiment of the inactive phase, the feed may have a flow in the active phase of at least 0.01 m / s, preferably at least 0.03 m / s, more preferably at least 0.05 m / s.

[0116]

[0123] In this embodiment, any lower limit of the feed flow can be combined with any upper limit of the feed flow.

[0117]

[0124] In a second embodiment of the inactive phase, the feed may have a flow in the active phase of 0.01 to 0.50 m / s, preferably 0.03 to 0.35 m / s, more preferably 0.05 m / s to 0.25 m / s.

[0118]

[0125] A second embodiment of the inactive phase is when there is a flow of feed across the surface of the filter membrane, but no substantial pressure on the retentate side to effect wastewater permeation. The flow of feed across the surface of the filter membrane can help reduce or prevent clogging, for example, by removing the outer layer of the filter cake that begins to form on the surface.

[0119]

[0126] In general, the flow rate of the feed during the inactive phase, including the first and second embodiments of the inactive phase, is less than the flow rate of the feed during the active phase. Typically, the flow rate of the feed during the active phase is significantly greater than the flow rate of the feed during the inactive phase.

[0120]

[0127] The inactive pressure may generally be the transmembrane pressure. The inactive pressure may be measured as the transmembrane pressure, such as when the pressure on the permeate side of the filter membrane is 0.0 bar.

[0121]

[0128] A pulse cycle may include or consist of an active period and a single inactive period (such as the inactive period of the first embodiment or the inactive period of the second embodiment).

[0122]

[0129] Alternatively, the pulse cycle may include or consist of an active period and two inactive periods, such as an inactive period of a first embodiment (e.g., a first inactive period) and an inactive period of a second embodiment (e.g., a second inactive period). It is preferred that the first inactive period is followed by a second inactive period. Thus, the pulse cycle may include an active period and an inactive period, where the inactive period includes a first inactive period followed by a second inactive period.

[0123]

[0130] The pulse cycle can include an active period and an inactive period including a first inactive period, a second inactive period, and at least one repetition of the first inactive period and the second inactive period.

[0124]

[0131] If the inactive period includes a first inactive period and a second inactive period, the inactive period is the total duration of the inactive periods.

[0125]

[0132] A general feature of the method is that the pulse cycle may have a frequency between 0.0015Hz and 0.0100Hz, preferably between 0.0020Hz and 0.0080Hz, more preferably between 0.0030Hz and 0.0070Hz, for example between 0.0040Hz and 0.0060Hz.

[0126]

[0133] In the present invention, the pulse cycle is adjustable. The pulse cycle can be adjusted using a flow restrictor and / or a pressure source as described herein.

[0127]

[0134] The frequency of the pulse cycle can be adjusted, for example, to optimize the flow throughput of the permeate. Thus, the method of the present invention can include adjusting the frequency of the pulse cycle to optimize the flow throughput of the permeate. The frequency of the pulse cycle can be increased or decreased, and is preferably increased. By varying the pulse cycle, the pressure changes between the active and inactive periods can be more or less frequent, which can change the flow throughput of the permeate. A variable pulse cycle is advantageous because the optimal duty cycle can be determined in one system setup.

[0128]

[0135] The active phase is adjustable. The duty pressure and / or the active period can be adjusted, for example, to optimize (i) the efficiency of filtration in terms of permeate flow throughput, and / or (ii) the energy consumption. Thus, the method of the present invention can include adjusting the duration of the active phase (e.g., the active period) to optimize the efficiency of filtration in terms of permeate flow throughput, and / or the energy consumption.

[0129]

[0136] The inactive period is adjustable. The inactive pressure and / or the inactive period can be adjusted. The inactive period can be adjusted, for example, to allow the filter membrane to recuperate and / or be cleaned.

[0130]

[0137] When adjusting the active and / or inactive periods, it is preferred that the active phase has a duration that remains greater than 50% of the corresponding pulse cycle.

[0131]

[0138] The method can include detecting a decrease in the flow throughput of the permeate through the filter membrane, which can be a lack of flow throughput of the permeate through the filter membrane.

[0132]

[0139] If a decrease in permeate flow throughput is detected, the frequency, active period and / or inactive period of the pulse cycle may be adjusted.

[0133]

[0140] This method is - detecting a decrease in permeate flow throughput through a filter membrane; - adjusting the frequency of the pulse cycle to optimize the permeate flow throughput, and / or adjusting the duration of the active phase to optimize the efficiency of filtration and / or energy consumption in relation to the permeate flow throughput.

[0134]

[0141] The above steps can be repeated. For example, the method can include: - detecting a first decrease in flow throughput of the permeate from the filter membrane; - adjusting a first frequency of pulse cycles to a second frequency of pulse cycles to optimize the permeate flow throughput and / or adjusting a first duration of an active phase (e.g. a first active period) to a second duration of an active phase (e.g. a second active period) to optimize the efficiency of filtration and / or energy consumption in relation to the permeate flow throughput; - detecting a second decrease in flow throughput of the permeate from the filter membrane; and - adjusting the second frequency of the pulse cycles to a third frequency of the pulse cycles to optimize the flow throughput of the permeate, and / or adjusting the second duration of the active phase to a third duration of the active phase (e.g. a third active period) to optimize the efficiency of filtration and / or energy consumption in relation to the flow throughput of the permeate.

[0135]

[0142] In the above method, the first frequency of the pulse cycles is different from the second frequency of the pulse cycles. The second frequency of the pulse cycles is different from the third frequency of the pulse cycles. Preferably, the first frequency of the pulse cycles is different from the third frequency of the pulse cycles. Similarly, the first active period is different from the second active period. The second active period is different from the third active period. Preferably, the first active period is different from the third active period.

[0136]

[0143] The above method can be repeated until no more pulse cycles or active periods can be used to prevent clogging of the filter membrane.

[0137]

[0144] The method further comprises: (A) applying a recovery period with little wastewater flow and little transmembrane pressure; (B) applying a wash phase during which wastewater is flushed across the surface of the filter membrane with little transmembrane pressure.

[0138]

[0145] Steps (A) and (B) can be repeated, for example, several times.

[0139]

[0146] Some embodiments relate to a method for cross-flow filtration of wastewater from a diagnostic device or laboratory analyzer, where the wastewater contains nanoparticles and / or microparticles, and the wastewater is flowing in a laminar flow across a surface of a filter membrane. The method includes: (a) flowing the wastewater across a surface of a filter membrane at a flow rate such that the flow of the wastewater is laminar having a Reynolds number (Re) of less than 500; (b) flowing wastewater across a surface of the filter membrane in pulse cycles, each pulse cycle including one active period during which the wastewater is under a duty pressure and one inactive period during which the wastewater is under an inactive pressure, the inactive pressure being less than or equal to 10% of the duty pressure, and the active period having a duration greater than 50% of the corresponding pulse cycle; (c) separating the nanoparticles and / or microparticles from the wastewater as the wastewater passes through the filter membrane; and Optionally repeating steps (a) to (c), and then (d) applying a recovery period with little wastewater flow and little transmembrane pressure; (e) applying a wash phase during which wastewater is flushed across the surface of the filter membrane with little transmembrane pressure; and optionally repeating steps (d) and (e).

[0140]

[0147] Above steps (d) and (e) are steps (A) and (B), respectively. After steps (d) and (e), steps (a) to (c) can be repeated.

[0141]

[0148] Alternatively, the method of applying the recovery phase (A) and the cleaning phase (B) may be used independently of the method of the first embodiment. For example, conventional cross-flow filtration may be performed until the filter membrane shows signs of clogging. The method of cleaning and / or repairing the filter membrane in the third embodiment of the present invention may then be used to restore the filter membrane for further use.

[0142]

[0149] Step (A) or (d) can include detecting a decrease in permeate flow throughput from the filter membrane and applying a recovery period during which there is little wastewater flow and little transmembrane pressure.

[0143]

[0150] The method may include a recovery phase. In the recovery phase, there is little wastewater flow and little transmembrane pressure difference. The wastewater is stationary on the filter membrane and there is no pressure difference that causes the wastewater to pass through the filter membrane. Nanoparticles and / or microparticles that are blocking or clogging the filter membrane can be redispersed in the wastewater on the surface of the filter membrane. This allows the filter membrane to recover.

[0144]

[0151] During the recovery phase, there is almost no transmembrane pressure (TMP). Therefore, the TMP is about 0.0 bar, for example, 0.0 to 0.2 bar. The TMP is preferably 0.0 bar.

[0145]

[0152] During the recovery phase, there is almost no wastewater flow, so the wastewater flow rate is less than 0.5 L / h, preferably less than 0.2 L / h, and more preferably about 0.0 L / h.

[0146]

[0153] The recovery phase may have a duration of 30 to 1800 seconds, more preferably 60 to 1200 seconds, for example 90 to 900 seconds, and even more preferably 100 to 600 seconds.

[0147]

[0154] The method may also include a cleaning phase. The cleaning phase involves flowing wastewater across the surface of the filter membrane with little transmembrane pressure difference. There is no pressure difference forcing the wastewater through the filter membrane. There is also no flow resistance, e.g., because the flow restrictor is inactive. Flowing the wastewater over the filter membrane helps to reduce or prevent clogging, e.g., by removing the outer layer of the filter cake that has formed on the surface of the filter membrane.

[0148]

[0155] During the cleaning phase, there is almost no transmembrane pressure (TMP), and therefore the TMP is 0.0 to 0.5 bar, for example 0.1 to 0.3 bar, and more preferably 0.0 to 0.1 bar (for example, about 0.1 bar).

[0149]

[0156] During the cleaning phase, wastewater is passed across the surface of the filter membrane at a flow rate of 1.0-100 L / h, preferably 2.5-75 L / h, more preferably 5.0-50 L / h, and even more preferably 10.0-25 L / h.

[0150]

[0157] The flow of the wastewater during the washing phase may be less than 0.50 m / s, preferably less than 0.35 m / s, more preferably less than 0.25 m / s.

[0151]

[0158] The flow of the wastewater during the washing phase may be at least 0.01 m / s, preferably at least 0.03 m / s, more preferably at least 0.05 m / s.

[0152]

[0159] Any lower limit for wastewater flow can be combined with any upper limit for wastewater flow.

[0153]

[0160] The flow of the wastewater during the washing phase can be 0.01 to 0.50 m / s, preferably 0.03 to 0.35 m / s, and more preferably 0.05 m / s to 0.25 m / s.

[0154]

[0161] The recovery and washout phases may be repeated, for example, several times.

[0155]

[0162] After the filter membrane has been restored, the method of the first aspect of the invention can be carried out.

[0156]

[0163] The present invention relates generally to the filtration of nanoparticles and / or microparticles in wastewater from diagnostic devices or laboratory analyzers.

[0157]

[0164] The nanoparticles and / or microparticles are solids.

[0158]

[0165] Typically, nanoparticles and / or microparticles are monodisperse. Nanoparticles and / or microparticles are monodisperse when the deviation of the particle size range from the average particle size is 10% or less, preferably 8% or less, such as 5% or less, more preferably 3% or less, such as 2% or less, and even more preferably 1% or less.

[0159]

[0166] Generally, nanoparticles have a particle size of 1 nm to 999 nm, preferably 5 nm to 750 nm, more preferably 10 nm to 500 nm, for example, 25 nm to 250 nm.

[0160]

[0167] The microparticles have a particle size of 1000 nm (eg, 1.0 μm) to 5000 μm, preferably 1.5 μm to 1000 μm, for example, 1.5 μm to 999 μm, more preferably 2.0 μm to 500 μm, and even more preferably 2.5 μm to 100 μm.

[0161]

[0168] The nanoparticles and / or microparticles can have, for example, any composition. The nanoparticles and / or microparticles, respectively, may comprise a polymer (e.g., a plastic), an inorganic material, such as a magnetic material, or a biological material, such as a protein.

[0162]

[0169] In principle, any tubular filter membrane can be used in the present invention, provided that it is suitable for removing nanoparticles and / or microparticles from wastewater by particle size-based filtration techniques.

[0163]

[0170] The tubular filter membranes can have a diameter of 5 mm or less, in particular 2 mm or less or 1 mm or less. They usually have a diameter of at least 0.2 mm, in particular at least 0.5 mm or at least 1 mm. Small tubular filter membranes with a diameter of less than 0.2 mm, for example 175 μm, and large tubular filter membranes with a diameter of more than 2 mm or more than 5 mm are also known. Large tubular filter membranes are usually ceramic tubular filter membranes.

[0164]

[0171] The filter membrane is generally porous.

[0165]

[0172] The filter membrane may be a hollow fiber membrane (eg, a tubular membrane filter (TMF)).

[0166]

[0173] The filter membrane may comprise or consist essentially of a polymer, a ceramic material, or a cellulose-containing filter (e.g., a paper filter). Preferably, the filter membrane comprises or consists essentially of a polymer or ceramic material.

[0167]

[0174] The polymer may be selected from polyvinylidene fluoride, polysulfone, polyacrylonitrile, and poly(acrylonitrile)-poly(vinyl chloride) copolymers. When the filter membrane comprises or consists essentially of a polymer, it is preferred that the polymer is polysulfone. More preferably, the polysulfone is polyethersulfone (PES).

[0168]

[0175] The ceramic material may include a material selected from Al2O3, TiO2, ZrO2, ZnO, SiO2, and composite materials including two or more thereof (eg, TiO2-SiO2, TiO2-ZrO2).

[0169]

[0176] The cellulose-containing filter may include cellulose acetate fibers.

[0170]

[0177] The filter membrane has a pore size of at least 0.5 nm, preferably at least 1.0 nm, such as at least 5.0 nm, more preferably at least 50 nm, such as at least 100 nm. The pore size of the filter membrane should be selected to be smaller than the particle size of the nanoparticles and / or microparticles in the wastewater.

[0171]

[0178] The filter membrane typically has a pore size of 25 μm or less, preferably 10 μm or less, for example 5 μm or less, more preferably 1 μm or less, even more preferably 0.5 μm or less.

[0172]

[0179] Any lower pore size limit can be combined with any upper pore size limit. Pore size can be measured using conventional techniques such as evaporation porometry.

[0173]

[0180] According to the inventors' current understanding, the minimum average pore size may be advantageously somewhat smaller than the average size of the smallest nanoparticles or microparticles to be separated from the wastewater by the tubular filter membrane. For example, the minimum average pore size may be 95% or less, or 90% or less, or 75% or less, or 50% or less of the average size of the smallest nanoparticles or microparticles to be separated from the wastewater by the tubular filter membrane. Due to manufacturing tolerances, the pore size of the tubular filter membrane tends to have a normal distribution around the specified pore size. Therefore, if the specified pore size is too close to the average size of the smallest nanoparticles or microparticles, at least some of the pores may be large enough that the smallest nanoparticles or microparticles may enter the largest diameter pores and become clogged in the pores. It may be difficult to remove the clogged nanoparticles or microparticles from the pores using only the flow during the gentle active phase of the pulse cycle without backflow across the filter membrane.

[0174]

[0181] Generally, the filter membrane has a pore size of 0.5 nm to 25 μm, preferably 1.0 nm to 10 μm, for example 5.0 nm to 5 μm, more preferably 50 nm to 1 μm, and even more preferably 100 nm to 0.5 μm. The filtration method is based on size exclusion. Therefore, the pore size of the filter membrane should be selected to be smaller than the particle size of the nanoparticles and / or microparticles in the wastewater.

[0175]

[0182] The filter membrane usually has a nominal molecular weight cut-off of 0.05 kDa to 500 kDa, preferably 0.10 kDa to 250 kDa, and more preferably 0.15 kDa to 200 kDa.

[0176]

[0183] Typically, the filter membrane is 0.010m -2 ~10.00m -2 , preferably 0.025 m -2 ~5.00m -2 , e.g. 0.050m -2 ~1.00m -2 has a surface area of

[0177]

[0184] The filter membrane may include a plurality of hollow fibers connected in parallel. When the filter membrane includes a plurality of hollow fibers, the filter membrane may have a total number of hollow fibers of at least 50, preferably at least 75, for example at least 100. The total number of fibers depends on the size of the filter membrane.

[0178]

[0185] The present invention also provides a cross-flow filtration system, which can be used to carry out the method according to the present invention.

[0179]

[0186] The cross-flow filtration system includes a filter module, which includes a filter membrane as described herein.

[0180]

[0187] The filter module has an inlet for the feed and an outlet for the retentate (e.g., a first outlet), each located on the feed / retentate side of the filter membrane.

[0181]

[0188] The inlet of the filter module is typically fluidly connected to a pressure source, and preferably is fluidly connected to a feed outlet of the pressure source.

[0182]

[0189] The retentate outlet of the filter module is preferably fluidly connected to a flow restrictor.

[0183]

[0190] The pressure source is for driving or causing the wastewater to flow across the surface of the filter membrane. The pressure source can be, for example, (i) a pump, or (ii) a pressure reservoir and a valve for controlled release of the pressurized wastewater. The pressure reservoir can include a pressurized gas cushion to keep the wastewater under pressure.

[0184]

[0191] The cross-flow filtration method and system of the present invention uses a pressure source to drive a feed (e.g., wastewater) across the surface of a filter membrane for filtration. A laminar flow of the liquid feed is generated by the pressure source. Thus, the pressure source can control the flow of the feed. The pressure source can also generate pulse cycles. Because the pressure source is not operated continuously, less energy is used, thereby improving the energy efficiency of the method and system. This increased energy efficiency combined with increased filtration efficiency provides a method and system that significantly improves the overall efficiency of cross-flow filtration.

[0185]

[0192] Preferably, the pressure source is a pump for driving the feed across the surface of the filter membrane, the pump directing the feed to the filter membrane and causing it to flow across its surface.

[0186]

[0193] The flow of the feed (e.g. wastewater) can be controlled by a pump. Because the flow of wastewater over the filter membrane is relatively small, this cross-flow filtration system does not require a pump with high power. The cross-flow filtration system of the present invention can use a smaller and lower power pump, which means that the whole system does not occupy a large space.

[0187]

[0194] The cross-flow filtration system of the present invention may be suitable for incorporation as a module into a diagnostic instrument or laboratory analyzer.

[0188]

[0195] The pumps can be turned on and off sequentially to create the pulsed cycles. Because the pumps are not run continuously, less energy is used, thereby improving the energy efficiency of the method and system. This increased energy efficiency, combined with the increased filtration efficiency, provides a method and system that significantly improves the overall efficiency of cross-flow filtration.

[0189]

[0196] Typically, the system includes a single pump.

[0190]

[0197] The pump has an inlet for the feed (eg, wastewater) and an outlet for the feed.

[0191]

[0198] Typically the pump is a membrane pump or a centrifugal pump. Preferably the pump is a membrane pump.

[0192]

[0199] Typically the pumps, and in particular the membrane pumps, are positive displacement pumps.

[0193]

[0200] The flow restrictor is for providing flow resistance during the active phase of the pulse cycle.

[0194]

[0201] The flow restrictor is disposed downstream of the filter module on the retentate side of the filter module, with the inlet of the flow restrictor typically being fluidly connected to the retentate outlet of the filter module.

[0195]

[0202] The flow restrictor may have an inlet and an outlet.

[0196]

[0203] The outlet of the flow restrictor can be fluidly connected to a liquid retentate reservoir. The liquid retentate reservoir can be a reservoir that provides a source of the feed. The liquid retentate can be recycled and included as part of the feed.

[0197]

[0204] The flow restrictor may be a pressure limiter, a flow resistance means with a switchable bypass (eg, under the control of a controller), or a controllable valve (eg, under the control of a controller).

[0198]

[0205] A flow restrictor can be used to control the transmembrane pressure by controlling the pressure of the feed on the feed / retentate side of the filter membrane.

[0199]

[0206] A pressure source, such as a pump, can work against a flow restrictor that creates a variable flow resistance. The flow restrictor aims to keep the pressure at its output constant, so it can create a high flow resistance when the pressure at the input side of the flow restrictor limiter is high, and a low flow resistance when the pressure at the input side is low. During the active phase of the pulse cycle, the flow restrictor opposes the pressure created by the pressure source with a high flow resistance, which results in a rapid rise in pressure and a large TMP. During the inactive phase of the pulse cycle, as the pressure drops at the input side of the flow restrictor, the flow resistance decreases, which accelerates the pressure drop and therefore the TMP becomes small rapidly or even drops towards zero. Thus, providing a flow restrictor pressure limiter at the output of the filter module on the retentate side will amplify the pulse, which will greatly increase the steepness of the edges.

[0200]

[0207] The flow restrictor is preferably a pressure limiter, which is a device that controls the pressure on the output side to a certain level as long as the pressure on the input side is above that level.

[0201]

[0208] The pressure limiter is for regulating the pressure or flow rate of the feed. In particular, the pump works against the pressure limiter which creates a variable flow resistance. The pressure limiter is configured to keep the output pressure constant on its output side, so that it creates a high flow resistance when the input pressure on the input side of the pressure limiter is high and creates a low flow resistance when the input pressure is low.

[0202]

[0209] Typically, a pressure limiter comprises a valve. The valve can be controlled depending on the input pressure of the pressure limiter. The higher the input pressure, the more the valve is closed. Conversely, the lower the input pressure, the more the valve is opened. Such types of pressure limiters are well known in the art.

[0203]

[0210] Since the pump is pulsed, during the active part of the pulse cycle the pressure limiter opposes the pressure generated by the pump with a high flow resistance (e.g. by nearly closing the valve), resulting in a rapid pressure rise and a large TMP. During the inactive part of the pulse cycle, as the input pressure falls, the flow resistance is reduced (e.g. by opening the valve), which accelerates the pressure drop and therefore the TMP becomes smaller rapidly or even drops towards zero. Thus, providing a pressure limiter at the output of the retentate filter module will amplify the pulse and thereby greatly increase the steepness of the edges.

[0204]

[0211] For example, as seen in Figure 5, when the pressure limiter valve is nearly closed, a pressure overshoot is caused, resulting in a flow rate peak 200 at the beginning of each active pulse 100. Figure 5 shows the permeate flow rate. Since the permeate flow rate is approximately proportional to the TMP, the flow rate path also corresponds to the pressure path on the retentate side in the filter module.

[0205]

[0212] After the overshoot, the pressure value, and therefore also the TMP or flow rate, drops exponentially to the pressure value provided by the pump. When the pump is switched off, the pressure value, and therefore also the flow rate, drops sharply (see falling edge 400 in FIG. 5).

[0206]

[0213] The provision of a flow restrictor, in particular a pressure limiter, produces a pulse 100 with a steep rising edge 300 and a steep falling edge 400. This creates a pressure impulse that counteracts the formation of a filter cake. It is speculated that the steep rising flank 300 is particularly relevant in this regard. These steep edge related effects, working in combination with the inactive period, can ensure that the filter membrane remains free of clogging.

[0207]

[0214] In principle, such pressure shocks should be avoided in hydraulic systems, since they can lead to damage to the system in the long term. In the present system, the pump 10, the filter module 20 and the pressure limiter 30 are located close to each other, so the masses to be moved are small and the risk of damage is not great. In addition, the filter membrane 25 usually has no stiffness, so pressure peaks or pressure shocks are damped, so that they are not reflected in the system and can affect other components. Conversely, in the present system, small pressure shocks are desirable, since they keep the filter membrane cleaner for longer.

[0208]

[0215] The pressure limiter may be a valve for controlling the pressure of the feed and / or retentate.

[0209]

[0216] The pressure limiter may include a pressure sensor, which may be connected, preferably electrically connected, to the valve.

[0210]

[0217] The pressure limiter is typically located downstream of the outlet (eg, retentate) of the filter module.

[0211]

[0218] The pressure limiter may have an inlet and an outlet.

[0212]

[0219] The inlet of the pressure limiter can be fluidly connected to the outlet (eg, for retentate) of the filter module.

[0213]

[0220] The outlet of the pressure limiter may be fluidly connected to a liquid retentate reservoir. The liquid retentate reservoir may be a reservoir that provides a source of the liquid feed. The liquid retentate may be recycled and included as part of the liquid feed.

[0214]

[0221] The cross-flow filtration system of the present invention further comprises a controller, the controller configured to carry out the method according to the present invention.

[0215]

[0222] Typically, the controller is connected, preferably electrically connected, to a pressure source such as a pump.

[0216]

[0223] The controller is preferably an electronic microcontroller.

[0217]

[0224] The controller is configured to generate the wastewater flow in pulsed cycles, preferably with an active phase having a duration of greater than 50% of the corresponding pulsed cycle, as described above.

[0218]

[0225] Typically, the controller is configured to generate pulse cycles by sequentially switching a pressure source (particularly a pump) on and off to vary the flow rate of the feed.

[0219]

[0226] In general, the pulse cycle is usually generated by a pressure source, such as a pump, optionally combined with a flow restrictor (eg, a pressure limiter).

[0220]

[0227] A pressure source and optionally a flow restrictor may be used to control the length of the active and inactive periods.

[0221]

[0228] A pressure source and optionally a flow restrictor may be used to control the magnitude of the duty pressure.

[0222]

[0229] The controller may be connected, preferably electrically connected, to the flow restrictor, e.g., to a pressure limiter or a pressure sensor of the pressure limiter. The controller is preferably configured to generate pulse cycles by (a) sequentially switching a pressure source, such as a pump, on and off, and (b) adjusting the flow restrictor to vary the flow rate of the feed (e.g., wastewater).

[0223]

[0230] A controller can be used in the methods of the present invention to adjust the pulse cycle to increase the flow throughput of the permeate.

[0224]

[0231] The controller may be configured to generate a recovery phase and / or a wash phase as described herein.

[0225]

[0232] During the recovery phase, the controller can turn off a pressure source, such as a pump, to stop the flow of wastewater across the surface of the filter membrane. The controller can also set a flow restrictor (e.g., close a pressure limiter) to stop the flow of retentate from the filter module. This means that the wastewater is retained on the surface of the filter membrane.

[0226]

[0233] During the cleaning phase, the controller allows the wastewater to flow across the surface of the filter membrane without pulse cycles.

[0227]

[0234] Typically, the cross-flow filtration system may further comprise a sensor for detecting the flow rate of the wastewater, the sensor being connected, preferably electrically connected, to the controller.

[0228]

[0235] The sensor for detecting the flow rate of the wastewater may be a pressure sensor or a flow rate sensor. The pressure of the feed (e.g., wastewater) is related to the flow rate of the feed. Therefore, by measuring the pressure of the feed, the flow rate of the wastewater can be determined. Preferably, the sensor is a pressure sensor.

[0229]

[0236] The sensor is typically located upstream of the inlet of the filter module. Preferably, the sensor is fluidly connected to the inlet of the filter module. More preferably, the sensor is fluidly connected to the inlet of the filter module and the sensor is fluidly connected to the outlet of a pressure source, such as a pump.

[0230]

[0237] The cross-flow filtration system may further include a sensor for measuring or detecting the flow rate or throughput of the permeate. The sensor may be located on the permeate side of the filter membrane.

[0231]

[0238] The filter module can further include an outlet for the permeate (e.g., a second outlet), the outlet being disposed on the permeate side of the filter membrane.

[0232]

[0239] The outlet may be fluidly connected to a sensor for measuring or detecting the flow rate of the permeate.

[0233]

[0240] Typically, a sensor for measuring or detecting the flow rate or throughput of the permeate is connected, preferably electrically connected, to the controller.

[0234]

[0241] Sensors for measuring or detecting permeate flow or throughput can be used in the methods of the invention to detect a decrease in permeate flow throughput from the filter membrane.

[0235]

[0242] The controller can detect a decrease in the permeate flow throughput from the filter membrane using a sensor to measure or detect the permeate flow rate or throughput. The controller can then, for example: - Sequentially switching on and off a pressure source (particularly a pump), and / or - adjusting the pulse cycle by adjusting a flow restrictor, for example a pressure limiter, preferably a valve of the pressure limiter, The flow rate of the feed (e.g., wastewater) can be altered using feedback from a sensor for detecting the wastewater flow rate and / or a sensor for measuring or detecting the permeate flow rate or throughput.

[0236]

[0243] The inlet of a pressure source, such as a pump, can be fluidly connected to a source of wastewater (e.g., a feed). The source of wastewater can be a container, such as a liquid retentate storage vessel, or can be a waste outlet from a diagnostic device or laboratory analyzer. The source can include wastewater containing nanoparticles and / or microparticles.

[0237]

[0244] The cross-flow filtration system may further comprise a pre-filter.

[0238]

[0245] The prefilter may be disposed between an outlet of a pressure source, such as a pump, and an inlet to the filter module. The inlet of the prefilter may be fluidly connected to the outlet of the pressure source, such as a pump, and the outlet of the prefilter may be fluidly connected to the inlet of the filter module. More preferably, the inlet of the prefilter may be fluidly connected to the outlet of the pressure source, such as a pump, and the outlet of the prefilter may be fluidly connected to the inlet of a sensor for detecting the flow rate of the wastewater.

[0239]

[0246] Additionally or alternatively, the prefilter may be disposed upstream of an inlet to a pressure source, such as a pump. The outlet of the prefilter may be fluidly connected to an inlet of the pressure source, such as a pump. The inlet of the prefilter may be fluidly connected to a source of wastewater. If the source of wastewater is a vessel, the prefilter may be disposed within the vessel.

[0240]

[0247] The vessel may be equipped with an overflow sensor for detecting an overflow of the wastewater. The overflow sensor may be connected, preferably electrically connected, to the controller. When the overflow sensor detects an overflow of the wastewater in the vessel, the controller may activate an alarm.

[0241]

[0248] The vessel may be equipped with a sensor for detecting a maximum amount of wastewater. The sensor for detecting a maximum amount of wastewater may be connected, preferably electrically connected, to the controller. When the sensor detects that the maximum amount of wastewater in the vessel has been reached, the controller may issue a notification or may prevent further replenishment of the vessel with wastewater, such as by closing an opening or inlet to the vessel.

[0242]

[0249] The vessel may include a sensor for detecting a minimum amount of wastewater. The sensor for detecting a minimum amount of wastewater may be connected, preferably electrically connected, to the controller. When the sensor detects that the minimum amount of wastewater in the vessel has been reached, the controller may stop the wastewater from the vessel by turning off a pressure source, such as a pump.

[0243]

[0250] Generally, the cross-flow filtration system may further include a bypass valve having an inlet and an outlet.

[0244]

[0251] The bypass valve may be connected, preferably electrically connected, to the controller.

[0245]

[0252] The inlet of the bypass valve is fluidly connected between the outlet of the pressure source and the inlet of the filter module. The bypass valve may be fluidly connected between the outlet of the pressure source and the inlet of the sensor for detecting the flow rate of the wastewater, if the sensor is located upstream of the inlet to the filter module. Alternatively, the bypass valve may be fluidly connected between the outlet of the sensor for detecting the flow rate of the wastewater and the inlet of the filter module. The bypass valve allows the wastewater to bypass the filter module in the event of a failure.

[0246]

[0253] The outlet of the bypass valve may be fluidly connected to a source of wastewater, such as via a conduit connector.

[0247]

[0254] Typically, the cross-flow filtration system may include a flow switch having an inlet, a first outlet, and a second outlet.

[0248]

[0255] The flow switch may be positioned downstream of the outlet of the filter module such that the inlet of the flow switch is fluidly connected to the outlet of the filter module.

[0249]

[0256] The flow switch is typically disposed upstream of the flow restrictor. A first outlet of the flow switch may be fluidly connected to an inlet of the flow restrictor.

[0250]

[0257] The flow switch is typically disposed upstream of the source of wastewater. The second outlet of the flow switch may be fluidly connected to the source of wastewater, such as via a conduit connector. For the avoidance of doubt, no flow restrictor is disposed between the second outlet of the flow switch and the source of wastewater.

[0251]

[0258] The flow switch may be connected, preferably electrically connected, to a controller that may be configured to control the flow switch, and in particular, the flow of retentate from the filter module to either a flow restrictor or a source of wastewater.

[0252]

[0259] The flow switch is used to control the flow of retentate from the filter module. In a first position, the flow switch directs the flow of retentate from the filter module to a flow restrictor (e.g., through a first outlet of the flow switch). In a second position, the flow switch directs the flow of retentate from the filter module to a wastewater source, for example, through a conduit connector.

[0253]

[0260] A flow switch may be used in the methods of the present invention.

[0254]

[0261] During the cleaning phase, the flow switch can be switched to a second position, for example to direct the flow of retentate from the filter module to a source of wastewater, for example through a conduit connector. The wastewater is then allowed to flow across the surface of the filter membrane without a pulse cycle and without the flow of wastewater being inhibited. This flow of wastewater over the filter membrane helps to reduce or prevent clogging, for example by removing the outer layer of the filter cake that has formed on the surface of the filter membrane.

[0255]

[0262] When applying a flush phase, the controller may be configured to switch the flow switch from a first position to a second position.

[0256]

[0263] When applying a recovery phase, such as after a cleaning phase, the controller may be configured to switch the flow switch from the second position to the first position.

[0257]

[0264] The cross-flow filtration system may further include a conduit connector having an outlet fluidly connected to a source of wastewater.

[0258]

[0265] The conduit connector can have an inlet (eg, a first inlet) fluidly connected to the outlet of the bypass valve.

[0259]

[0266] The conduit connector can have an inlet (eg, a second inlet) fluidly connected to the outlet of the flow restrictor.

[0260]

[0267] The conduit connector can have an inlet (eg, a third inlet) fluidly connected to the second outlet of the flow switch.

[0261]

[0268] The present invention further relates to a computer program comprising computer executable code that, when executed on a controller (eg, a computer system), causes a cross-flow filtration system to perform the method of the present invention.

[0262]

[0269] The invention also relates to a computer readable medium, which stores a computer program.

[0263]

[0270] 1 illustrates one embodiment of a cross-flow filtration system of the present invention. The pressure source is pump 10. Pump 10 draws wastewater (e.g., feed) through conduit 5 from a vessel 40 through a prefilter 50. The operation of pump 10 is controlled by an electronic microcontroller 80 via electrical coupling S10. The flow rate of wastewater entering filter module 20 is measured using a pressure sensor 70 that is electrically coupled S70 to the electronic microcontroller 80. Wastewater from pump 10 is forced or conveyed into filter module 20 having filter membrane 25.

[0264]

[0271] If the filter membrane is not blocked, permeate is produced and enters conduit 15. The flow rate of the permeate in conduit 15 is measured using flow sensor 60. Flow sensor 60 is electrically connected S60 to electronic microcontroller 80 and provides information regarding the amount of permeate produced during filtration. The permeate passes through flow sensor 60 and may be collected in a container.

[0265]

[0272] Wastewater from the feed that does not pass through the filter membrane 25 becomes the retentate. The retentate exits the filter module 20 in conduit 35 and enters a flow restrictor, in this case a pressure limiter 30. The pressure limiter 30 is used to control the pressure of the feed / retentate on the feed / retentate side of the filter membrane 25. From the pressure limiter 30 the retentate is returned to vessel 40 and recycled as part of the liquid feed.

[0266]

[0273] A signal is sent to pump 10 via electrical coupling S10 to sequentially turn the pump on and off to generate a pulse cycle. Turning the pump on and off controls the length of the active and inactive periods of the pulse cycle. The magnitude of the duty pressure is determined in part by the flow rate output by pump 10.

[0267]

[0274] The pressure in the system is monitored using pressure sensor 70 and adjusted using pressure limiter 30. Pressure limiter 30 can also be used to adjust the active period and magnitude of the pulse cycle. The active period or duty cycle of the pulse cycle can be varied until flow sensor 60 detects permeate having a flow rate that meets some minimum threshold. At this point, the parameters for the pulse cycle can be fixed and cross-flow filtration is performed. If flow sensor 60 detects a decrease in the permeate flow rate below some minimum threshold, the pulse cycle can be adjusted until the permeate flow rate again exceeds the threshold.

[0268]

[0275] The vessel 40 has a sensor 1 for detecting an overflow of wastewater from the vessel. The sensor 1 is electrically connected S1 to an electronic microcontroller 80. When the sensor 1 detects an overflow, the electronic microcontroller 80 can activate an alarm.

[0269]

[0276] The vessel 40 has a sensor 2 for detecting the maximum amount of wastewater in the vessel. The sensor 2 is electrically connected S2 to an electronic microcontroller 80. When the sensor 2 detects that the amount of wastewater has reached a maximum level, the electronic microcontroller 80 can issue a notification. The notification can ask the end user whether to start the cross-filtration process.

[0270]

[0277] The vessel 40 has a sensor 3 for detecting a minimum amount of wastewater in the vessel. The sensor 3 is electrically connected S3 to an electronic microcontroller 80. When the sensor 3 detects that the minimum amount of wastewater has been reached, the electronic microcontroller 80 can activate an alarm and / or switch off the pump 10.

[0271]

[0278] Figure 2 shows an alternative embodiment of a cross-flow filtration system of the present invention, which is the same as the system shown in Figure 1, except that the pre-filter 50 is located between the pump 10 and the pressure sensor 70 rather than within the vessel 40.

[0272]

[0279] Figure 3 illustrates a further embodiment of a cross-flow filtration system of the present invention that can be used to carry out the methods of the present invention.

[0273]

[0280] The embodiment shown in FIG. 3 can be used to carry out the method of the present invention in the same manner as the embodiments shown in FIGS.

[0274]

[0281] The cross-flow filtration system of Figure 3 includes a bypass valve 75 connected between the sensor 70 and the filter module 20. If a problem occurs, the bypass valve 75 can be opened or switched on to divert the flow of wastewater away from the filter module 20. The wastewater is directed through the conduit connector 65 to the vessel 40. The bypass valve is included to protect the filter module from damage.

[0275]

[0282] The outlet from bypass valve 75, the outlet from pressure limiter 30, and the second outlet of flow switch 90 may be connected into a single conduit by conduit connector 65. The single conduit from conduit connector 65 directs flow to vessel 40.

[0276]

[0283] The cross-flow filtration system also includes a flow switch 90 connected to the outlet of filter module 20. Flow switch 90 directs the flow of retentate either through pressure limiter 30 via conduit 35 or through conduit 85 via conduit connector 65 to vessel 40.

[0277]

[0284] In the first position, the flow switch 90 connects the outlet of the filter module 20 to the pressure limiter 30 .

[0278]

[0285] In this first position of the flow switch 90, a first embodiment of an inactive period (e.g., a first inactive period) can be implemented in the method of the present invention. By closing the pressure limiter 30 and switching off the pump 10, the wastewater is subjected to an inactive pressure and the flow rate of the wastewater is zero or near zero.

[0279]

[0286] A second embodiment of an inactive period (e.g., a second inactive period) can also be implemented in the method of the present invention when the flow switch 90 is in a first position (e.g., as in Figures 1 and 2) to connect the outlet of the filter module 20 to the pressure limiter 30. The pressure limiter 30 can be fully open to allow the retentate to pass without resistance, thereby ensuring that the wastewater is subjected to the inactive pressure.

[0280]

[0287] When the flow switch 90 is in the first position, a recovery phase can be performed. As described above, by closing the pressure limiter 30 and switching off the pump 10, the wastewater is subjected to a non-active pressure and the wastewater flow rate is zero or near zero.

[0281]

[0288] In the second position, the flow switch 90 connects the outlet of the filter module 20 to a conduit 85 that bypasses the pressure limiter 30 .

[0282]

[0289] In this second position of the flow switch 90, a second embodiment of an inactive period (e.g., a second inactive period) can be implemented in the method of the present invention. With the pressure limiter 30 bypassed, the pump 10 continues to operate without generating a pump cycle and the retentate flows from the filter module 20 without resistance, thereby ensuring that the wastewater is subjected to the inactive pressure.

[0283]

[0290] When the flow switch 90 is in the second position, a cleaning phase can be performed. The pump 10 operates to generate a flow of wastewater without pulse cycles. The pressure limiter 30 is bypassed and retentate flows from the filter module 20 without resistance, thereby ensuring that there is little or no transmembrane pressure.

[0284]

[0291] The flow switch 90 has an electrical connection S95 to the electronic microcontroller 80.

[0285]

[0292] In response to a signal from the flow sensor 60 indicating no or reduced flow throughput of the permeate, the electronic microcontroller 80 can apply a recovery phase to the filter membrane 25. The electronic microcontroller 80 can send a signal via connection S10 to switch off the pump 10 and can send a signal to the pressure limiter 30 to stop the flow of retentate through the pressure limiter 30. The wastewater rests on the filter membrane 25, redistributing any particles that have accumulated on the filter membrane.

[0286]

[0293] After a predetermined time, the electronic microcontroller 80 can apply a cleaning phase to the filter membrane 25. The electronic microcontroller 80 can send a signal via connection S10 to switch on the pump 10 without generating a pulse cycle, allowing the wastewater to flow through the filter module 20. At about the same time, the electronic microcontroller 80 can send a signal to the flow switch 90 to switch to a second position, which connects the outlet of the filter module 20 to the conduit 85, bypassing the pressure limiter 30. The wastewater passing through the filter module 20 can clean the filter membrane 25. The wastewater is returned to the vessel 40, such as through the conduit connector 65, stopping the flow of retentate through the pressure limiter 30.

[0287]

[0294] The concentration of nanoparticles and / or microparticles in the container 40 may increase over time after performing the recovery and cleaning phases. When the sensor 3 detects a minimum level of wastewater, the nanoparticles and / or microparticles collected in the container 40 may be removed and discarded.

[0288]

[0295] Instead of using pump 10 to generate the pulse cycles in the method of the present invention, flow switch 90 may be rapidly switched between a first position and a second position to generate the pulse cycles. EXAMPLES

[0289]

[0296] The following examples are provided to illustrate the invention and are not intended to limit the scope of the invention described herein.

[0290] Comparative Example

[0297] Cross-flow filtration was simulated using a system equipped with a membrane pump, a filter membrane, a pressure limiter, and a tank with a sensor. The filter membrane was a 150 kDa (pore size 4.54 nm) polyethersulfone (PES) membrane (NX-Filtration). TM) The flow and pressure in the system were measured using high-precision testing equipment (Convergence Industry TM BV) was used.

[0291]

[0298] The system was operated using conventional continuous laminar flow of a microplastic-laden liquid feed (3 L of liquid containing plastic particles with a particle size of 110-120 nm at a concentration of 0.476%). A pump was used to drive the feed through the filtration module. The test was performed for 5 min.

[0292]

[0299] The results are shown in Figure 4, which shows the flow rates of feed (f), permeate (p) and retentate (r) over time.

[0293]

[0300] The results show that when the feed flow rate is set at 18 L / h and the transmembrane pressure (TMP) is 3 bar, a steady state plateau is obtained for the permeate, which remains constant at approximately 1.4 L / h.

[0294] Example 1

[0301] A cross-flow filtration system with the same type of configuration as shown in Figure 1 was simulated. The same type of filter membrane as in the comparative example, namely a polyethersulfone (PES) membrane (NX-Filtration TM ) was used. The same test equipment (Convergence Industry TM BV) was also used.

[0295]

[0302] A pulsating laminar flow of liquid was passed across the filter membrane using a pump and pressure limiter with the same microplastic-containing liquid as in the comparative example. The feed flow rate was set to 18 L / h. The transmembrane pressure was 3 bar during the active phase and 0 bar during the inactive phase. The duty cycle was 80% and the active period was 60 seconds. The generated pulse cycles are shown in Figure 5 along with the results.

[0296]

[0303] Results are also shown for the system operating with a conventional continuous laminar feed (labeled "60 minutes pumping").

[0297]

[0304] It can be seen that the use of a pulsed cycle with a duty cycle of 80% provided superior results compared to the conventional operation of the system with continuous laminar flow (Comparative Example). In the conventional operation of the system, the flow rate reached a plateau and the average permeate obtained during this plateau was approximately 1.4 L / h. In contrast, when the pulsed protocol of the present invention was used, the average permeate was 3.3 L / h.

[0298]

[0305] Because the pump was not operated continuously during the pulse protocol, the cross-flow filtration process of the present invention is more energy efficient than the conventional process. A pressure limiter was used to prevent the overpressure generated by the pump from being applied directly to the system. This overpressure was redistributed within the system when the pump was switched off, again improving energy efficiency.

[0299]

[0306] In the experiment, we succeeded in removing large particles with a diameter of 2.7 μm.

[0300]

[0307] Experiments were also successful with a 140 kDa (4.44 nm pore size) ceramic membrane instead of the PES membrane, and similar improvements were seen with the ceramic membrane when pulse cycles were used.

[0301] Example 2

[0308] Further simulation experiments were performed similar to Example 1 to determine the effect of the active phase duration (eg, active period) on filtration.

[0302]

[0309] In the first experiment, the period of the pulse cycle was 15 min and the duty cycle was 80%. The transmembrane pressure was greater than 0 bar (i.e., duty pressure and active period) for 12 min and approximately 0 bar (i.e., inactive pressure and inactive period) for 3 min. The results are shown in Figure 6. Figure 6 shows a pulse cycle with active phases (A') and inactive phases (I). The effect of these phases on the permeate (p) flow rate is shown. Also shown is the plateau (P) of the permeate flow rate obtained with conventional cross-flow filtration without a pulse cycle. The plateau (P) is also the asymptotic value of the exponential decrease in throughput during each active phase.

[0303]

[0310] In Figure 6, it can be seen that for longer active periods, the permeate flow rate during each individual active phase tends towards a plateau level (P). Nevertheless, an improvement in the mean permeate flow rate (M) above the plateau level (P) is obtained.

[0304]

[0311] In the second experiment, the period of the pulse cycle was 3 min and the duty cycle was 80%. The transmembrane pressure was greater than 0 bar (i.e., duty pressure and active period) for 144 s and approximately 0 bar (i.e., inactive pressure and inactive period) for 36 s. The results are shown in Figure 7. As in Figure 6, Figure 7 also shows the active (A') and inactive (I) phases of the pulse cycle. The effect of these phases on the permeate (p) flux is shown. Also shown is the plateau (P) of permeate flux obtained with conventional cross-flow filtration without a pulse cycle.

[0305]

[0312] As shown in Figure 7, with shorter active periods, the permeate flow rate during each individual active phase does not have time to reach the plateau level (P). This results in a further improvement in the average permeate flow rate (M) obtained when compared to the plateau level (P) and when compared to the relatively long active periods used in Figure 6. In other words, by adjusting the active phase duration to a value significantly shorter than the time required to reach the plateau level (P), the portion of the active phase with low throughput is cut off.

[0306]

[0313] For completeness, Figures 8 and 9 from the same experiment are included. Figure 8 shows the flow rates of the feed (f), retentate (r), and permeate (p). Figure 9 shows the feed (f) pressure, retentate (r) pressure, permeate (p) pressure, and transmembrane pressure (t). Comparing the graphs in Figures 8 and 9, the individual flow rates versus pressure relationships can be seen.

[0307] Example 3

[0314] The experiments using the pulse protocol of Example 1 were repeated, except that the active period for these experiments was set to 2 minutes, and the inactive period was 5 seconds, 30 seconds, 45 seconds, or 90 seconds. The duty cycle of each pulsating wave was plotted against the permeate flow rate. The results are shown in FIG.

[0308]

[0315] Analysis showed that for the parameters and system used, a duty cycle of approximately 80% resulted in the highest filtration rate.

[0309]

[0316] A series of routine experiments were performed to understand the effect of filter membrane parameters on the flow of the liquid feed, which confirmed the presence of laminar flow regions in all examples herein.

[0310]

[0317] The Reynolds number (Re) is closely related to the flow velocity inside the fibers of the filter membrane. The Reynolds number can be changed by changing the diameter of the fibers, the total number of fibers (surface area of ​​the filter membrane), or by changing the feed flow rate.

[0311]

[0318] Figure 11 is a graph showing the relationship between Reynolds number and filter membrane surface area at various liquid feed flow rates. At a Reynolds number of approximately 2300, a dashed line (T) separates the laminar (Re<2300) from the turbulent (Re>2300) flow regions.

[0312]

[0319] FIG. 12 is a graph showing the relationship between the Reynolds number and the number of threads when the thread diameter is 0.7 mm.

[0313]

[0320] The filter membranes used in the examples were PES membranes with 120 or 504 threads and an inner diameter of about 0.8 mm. The membrane surface area was 0.071 m, respectively. 2 and 0.3m 2 At a feed flow rate of 20 L / h the system is in the deep laminar flow regime (Re<70). To achieve the turbulent flow regime the feed flow rate needs to be >625 L / h.

[0314]

[0322] All headings and sub-headings are used herein for convenience only and should not be construed as limiting the invention in any way.

[0315]

[0323] Any examples provided herein, or the use of exemplary language (e.g., "such as"), are intended merely to better illustrate the invention and do not limit the scope of the invention unless otherwise specified. No language in the specification should be construed as indicating any undescribed element as essential to the practice of the invention.

[0316]

[0324] This invention includes all modifications and equivalents of the subject matter recited in the paragraphs appended hereto as permitted by applicable law.

[0317]

[0325] This patent application claims priority to European Patent Application No. 22157842.0, the contents of which are incorporated herein by reference.

[0318]

[0321] In the figures, the following reference numbers are used: [Explanation of symbols]

[0319] 1. Sensor for detecting overflow 2 Sensor for detecting maximum filling level 3. Sensor for detecting minimum feed amount 5 Wastewater feed pipe 10. Pump 15 Permeate conduit 20 Filter Module 25 Filter Membrane(25) 30 Flow Restrictors (e.g., pressure limiters) 35 Retentate conduit 40 containers 50 Pre-filter 60 Flow Sensor 65 Conduit Connector 70 Sensor for detecting wastewater flow rate (e.g., pressure sensor) 75 Bypass valve 80 Controller 85 Bypass duct 90 Flow Switch S1 Signal from sensor 1 to detect overflow S2 Signal from sensor 2 for detecting maximum filling level S3 Signal from sensor 3 for detecting minimum feed amount S10 Signal from controller 80 to pump 10 S60 Signal from flow sensor 60 to controller 80 S70 Signal from sensor 70 to controller 80 S95 Signal from controller 80 to flow switch 90 100 Active Pulse 200 Flow Peak 300 Steep rising edge 400 falling edge A' Active Period I Inactive period p Permeate r Retained f Feed t Transmembrane pressure P Plateau level of permeate flow M Average permeate flow rate T is the threshold value that separates laminar and turbulent flow.

Claims

1. 1. A method for cross-flow filtration of wastewater from a diagnostic device or laboratory analyzer, wherein the wastewater contains nanoparticles and / or microparticles, and the wastewater is flowing in a laminar flow across the interior surface of a tubular filter membrane (25) having an inlet and an outlet at a flow rate such that the Reynolds number (Re) of the flowing wastewater is less than 500; the wastewater flows across the inner surface of the tubular filter membrane (25) from the inlet to the outlet in pulse cycles, each pulse cycle including one active period (A') during which the wastewater is subjected to a duty pressure at the inlet and one inactive period (I) during which the wastewater is subjected to an inactive pressure at the inlet, the inactive pressure being less than or equal to 10% of the duty pressure, and the active period having a duration greater than 50% of the corresponding pulse cycle; a filtrate portion of the wastewater passes across the tubular filter membrane (25), and the nanoparticles and / or microparticles are separated from the filtrate portion of the wastewater by the tubular filter membrane (25); method.

2. 2. The method of claim 1, wherein the transmembrane pressure (TMP) during the active phase is 0.5 to 10.0 bar, preferably 1.5 to 6.0 bar, more preferably 1.8 to 4.0 bar, and even more preferably 2.0 to 3.0 bar.

3. 3. The method of claim 1, wherein the nanoparticles and / or microparticles are monodisperse, preferably the nanoparticles having a particle size of 1 nm to 999 nm and / or the microparticles having a particle size of 1000 nm to 5000 μm.

4. 3. The method according to claim 1 or 2, wherein the duration of the active phase (A') does not exceed 90%, preferably does not exceed 80%, of the corresponding pulse cycle.

5. 3. The method according to claim 1, wherein the pulse cycle has a frequency of 0.0015 Hz to 0.0100 Hz, preferably 0.0025 Hz to 0.0075 Hz.

6. 3. The method of claim 1 or 2, wherein the duration of the active phase (A') is 80% or less of the time required for the flow throughput of the permeate to decrease from a maximum flow throughput of the permeate in the active phase (A') to a steady-state flow throughput of the permeate.

7. adjusting the frequency of the pulse cycle to optimize the permeate flow throughput and / or adjusting the duration of the active phase (A') to optimize the efficiency of the filtration and / or energy consumption in relation to the permeate flow throughput; 3. The method of claim 1 or 2, further comprising:

8. The method comprises: (A) applying a recovery period in which there is little wastewater flow and little transmembrane pressure; (B) applying a wash phase in which the wastewater is flowed across the surface of the filter membrane (25) with little transmembrane pressure; further comprising The method of claim 1 or 2, wherein the recovery and washout periods may be repeated several times.

9. 1. A cross-flow filtration system for filtering wastewater from a diagnostic device or laboratory analyzer, the wastewater containing nanoparticles and / or microparticles, by laminar flow across an interior surface of a tubular filter membrane (25) having an inlet and an outlet, the system comprising: a filter module (20) comprising the tubular filter membrane (25); a pressure source (10) for forcing wastewater to flow across the surface of the tubular filter membrane (25) from the inlet towards the outlet; a sensor (70) for detecting the flow rate of said wastewater; a controller (80) connected to the sensor (70) and configured to control the pressure source (10) to perform the method according to claim 1 or 2; a flow restrictor (30) disposed downstream of the retentate side of the filter module (20), the flow restrictor (30) for providing flow resistance during the active phase (A') of the pulse cycle; A system comprising:

10. The flow restrictor (30) - Pressure limiter, or - flow resistance means with a switchable bypass (90) under the control of said controller (80), or a controllable valve under the control of said controller (80); 10. The cross-flow filtration system of claim 9, wherein:

11. 10. The cross-flow filtration system of claim 9, wherein the filter membrane (25) is a hollow fiber membrane and / or the tubular filter membrane comprises a polymer or ceramic material.

12. 10. A cross-flow filtration system according to claim 9, wherein the tubular filter membrane (25) has a pore size of at least 0.5 nm, preferably at least 1.0 nm, more preferably at least 5.0 nm.

13. 10. A cross-flow filtration system according to claim 9, wherein the tubular filter membrane (25) has a pore size of 25 μm or less, preferably 10 μm or less, more preferably 5 μm or less.

14. 10. A cross-flow filtration system according to claim 9, wherein said pressure source (10) is a pump, preferably a membrane pump.

15. 10. The cross-flow filtration system of claim 9, wherein the sensor (70) is located upstream of the inlet to the filter module (20), preferably the sensor (70) being a pressure sensor or a flow sensor.

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