Method and system for filtering a liquid

Abstract

A method of filtering a liquid through a filtration system and a filtration system are disclosed. The filtration system is configured with filtration parameters, which at least include the filtration time and the filtration flux of the liquid passing through the filtration system. The method includes: determining a fouling index in the filtration system; comparing a set of fouling indices with corresponding set values; operating the filtration system based on the comparison result; and establishing the set values based on the received operating mode, where the operating mode is one of extending the life cycle of the filtration system or maximizing the total volume of the filtered liquid.

Description

[0001] This application claims the benefit of European Patent Application EP19382783, filed on September 9, 2019. Background Art

[0002] This specification relates to a membrane water treatment system or method, for example, using an immersion membrane to treat water in the system. Specifically, methods for mitigating the effects of membrane fouling are disclosed.

[0003] Membrane technologies (such as ultrafiltration UF or microfiltration MF) are complex to operate, and plant managers and operators may handle monitoring systems to follow key parameters and make operating decisions. Membrane fouling is one of the limitations when applying membrane filtration technology. The SCADA system allows passive monitoring of key parameters and is capable of downloading the generated data and analyzing how transmembrane pressure, TMP, permeability, flux, or other metrics change over time to make decisions. Therefore, the system allows corrective decisions that can affect operating resources. Some strategies include adopting a fixed setpoint filtration cycle, which can be adjusted after the water treatment system exhibits non-desired behavior. Description of the Drawings

[0004] Figure 1 is a schematic diagram of an example of a filtration system.

[0005] Figure 2 is a schematic diagram of an example of the method of the present disclosure.

[0006] Figure 3 is a schematic diagram of an example of the method of the present disclosure.

[0007] Figure 4 is a schematic diagram of an example of the method of the present disclosure.

[0008] Figure 5 is a schematic diagram of an example of the method of the present disclosure. Detailed Description

[0009] The present disclosure relates to methods and systems for liquid filtration, wherein the system can respond and adapt to different operating requirements. In a filtration system, presetting the filtration flux or developing regular hydraulic cleaning and / or chemical cleaning may be some strategies for sustainable operation in terms of membrane fouling and cost. In different situations where an event occurs (such as a sudden increase in the contamination of the liquid to be filtered), maximum production may be required.

[0010] Exemplary methods of the present disclosure include methods of filtering a liquid through a filtration system. The liquid can be wastewater or drinking water. The filtration system can be ultrafiltration UF, a membrane system, a sand filtration SF system, microfiltration, a membrane filtration system MF, or filtration through any type of medium.

[0011] In this specification, a chemical cycle can be defined as the time between chemical cleanings, which includes: one or more hydraulic cycles and a chemical cleaning. The hydraulic cycles in this specification include: a production / filtration cycle (also known as a filtration period) and a mechanical or hydraulic cleaning. The hydraulic cycle can be set from 15 minutes to 2 hours, while the chemical cycle can be set to 1 day, 3 days, 5 days, or 10 days. In some examples, one chemical cycle includes a determined number of hydraulic cycles. For example, two consecutive chemical cycles can include:

[0012] - The first chemical cycle: "filtration period - hydraulic wash - filtration period - hydraulic wash - chemical cleaning" (two hydraulic cycles and one chemical cleaning);

[0013] - The second chemical cycle: "filtration period - hydraulic wash - chemical cleaning" (one hydraulic cycle and one chemical cleaning);

[0014] The exemplary method of the present disclosure can include a filtration system configured with filtration parameters. The filtration parameters at least include the filtration time and filtration flux of the liquid passing through the filtration system. Depending on the filtration system employed, the filtration time or filtration cycle may vary. In the ultrafiltration membrane system UF, the filtration cycle or period can include 30 to 120 minutes. In a sand filtration system, depending on the filtration rate of the system, the filtration cycle range may include 30 minutes to several hours. In some examples, the filtration parameters can include some characteristics of the chemical cycle, for example, the frequency and / or intensity and / or product used in the chemical cleaning of the chemical cycle, where the intensity can include the concentration of the chemical product used for chemical cleaning.

[0015] The exemplary method of the present disclosure can include: for example, determining the fouling index of the filtration system by online or offline measurement or by receiving. Online measurement can allow direct control of the filtration system (for example, in real time) based on some parameters of the filtration system or from the liquid to be filtered or the filtered liquid, while offline measurement can allow configuring the filtration system to be installed or analyzing the filtration system in a non-real-time manner. In some examples, determining the fouling index includes performing an online measurement of the fouling index during the hydraulic cleaning of the filtration system. In some examples, determining the fouling index includes performing an online measurement of the fouling index during production.

[0016] In some cases, fouling is quantified by the change in transmembrane pressure TMP during filtration or permeation. Fouling is usually represented by the resistance R calculated according to the following formula:

[0017]

[0018] where R is the resistance (m -1 )

[0019] TMP is the transmembrane pressure (Pa),

[0020] J is the flux of the permeated or filtered liquid (m 3 m -2 s -1 ),

[0021] μ is the viscosity of water (Pa s -1 ).

[0022] Fouling can be reversible or irreversible and can be further classified as hydraulically or chemically reversible and irreversible. Hydraulically reversible fouling can be removed by physical or mechanical cleaning methods such as backwashing and aeration. Membrane fouling is typically modeled using the series resistance model, which defines the total membrane resistance R T as the sum of the intrinsic membrane resistance Rm and the resistances due to fouling (reversible resistance Rrev and irreversible resistance Rirr), where R T＝ Rm + Rrev + Rirr.

[0023] Fouling control strategies may include mechanical cleaning (also known as hydraulic backwashing) and chemical cleaning. In hydraulic backwashing or mechanical cleaning, the flow of the liquid is reversed to remove any fouling that may have deposited on the membrane surface. Fouling removed by mechanical cleaning can be referred to as hydraulically reversible fouling. The backwash frequency, flux or pressure, duration, or backwash fouling cycle can be adjusted to maximize efficiency. Backwashing may not fully restore the permeability; fouling not removed by mechanical cleaning can be referred to as hydraulically irreversible fouling and is typically supplemented with other physical and / or chemical cleaning methods. Chemical cleaning can include chemically enhanced backwashing CEB and in-situ cleaning CIP. CEB can be performed daily with an oxidant such as sodium hypochlorite. CIP can be performed approximately 10 times per year and often exposes the membrane to various chemicals for enhanced cleaning.

[0024] Exemplary methods of the present disclosure may include determining or measuring fouling metrics, e.g., the total fouling index TFI and / or the hydraulically irreversible fouling index HIFI and / or the change in the reciprocal of the permeability and / or the change in the transmembrane pressure TMP and / or the change in the permeability, where the TFI represents the change in resistance within a single filtration cycle, the HIFI represents the change in resistance between consecutive filtration cycles, and the change in the reciprocal of the permeability can be defined as the change in resistance between filtration cycles. In some examples, the fouling metric includes the time to reach a set value, where the time to reach a set value is the time between the moment at which at least one parameter is measured and the moment at which the parameter is assumed or predicted to reach the set value; in some examples, the set value may be the minimum acceptable permeability MAP or the reciprocal of MAP, or the minimum permeability MPLCC at which chemical cleaning is initiated or the reciprocal of MPLCC. The minimum acceptable permeability can also be defined as the maximum acceptable resistance. In the present disclosure, the fact that the fouling metric is the "time to reach a set value" advantageously allows for a distinction between the following cases:

[0025] -TFI and / or HIFI indicate a high fouling rate, and the system needs to recalibrate the filtration parameters.

[0026] -TFI and / or HIFI indicate the same high fouling rate, but the system remains safe for some time.

[0027] That is, even when membrane fouling accelerates rapidly, the solutions disclosed in this specification allow distinguishing between when an operation needs to be performed immediately or when there is still some time before the operation, thus distinguishing between an acceptable filtration zone or an alarm filtration zone. In addition, since the "time to reach the set value" depends on the value of the set value, and the value of the set value depends on the received "operating mode", the system is intelligent enough to distinguish between warnings or acceptable situations according to the operating mode in which the system is operating (e.g., sustainable operation mode, maximum production or energy saving).

[0028] Exemplary methods of the present disclosure may include determining, receiving, or measuring fouling indicators, e.g., time extrapolation of at least one of the following parameters: resistance between filtration cycles and / or transmembrane pressure TMP and / or TMP with flow rate and / or permeability. In this example, the extrapolation of the parameter represents the time trend or tendency of resistance, TMP, and permeability. In some examples, the fouling indicator includes the parameter and the extrapolation or trend of the parameter. In some examples, the fouling indicator includes the fouling rate of the membrane.

[0029] In some examples of the present disclosure, the fouling indicator is measured during mechanical cleaning or hydraulic backwashing. In other examples of the present disclosure, when multiple consecutive fouling indicator values indicate a rapid fouling event, an alarm signal is received and an automatic operation, such as chemical cleaning, is performed. Advantageously, in the case of an alarm, there is no need to wait for chemical cleaning to restore the membrane permeability or resistance because chemical cleaning is performed automatically.

[0030] Exemplary methods of the present disclosure may include performing a comparison or comparing at least one fouling indicator or a set of fouling indicators with at least one corresponding set value or a plurality of corresponding set values. The set value may include a resistance value that a fouled filtration system may encounter or an acceptable resistance value. In examples of the present disclosure, the set value includes a predetermined value of permeability, such as the minimum acceptable permeability MAP or the reciprocal of MAP, or the minimum permeability MPLCC to initiate chemical cleaning or the reciprocal of MPLCC.

[0031] Exemplary methods of the present disclosure may include: operating the filtration system and / or filtration parameters based on the comparison result. In the exemplary method of the present disclosure, if the fouling indicator reaches or exceeds or is lower than the set value, an operation is performed. In the exemplary method of the present disclosure, if the fouling indicator is between two set values, an operation is performed.

[0032] In an exemplary method of the present disclosure, the operation may include modifying the filtration time, such as increasing the filtration time and / or decreasing the filtration time; and / or modifying the filtration flux, for example, increasing the filtration flux and / or decreasing the filtration flux; and / or maintaining the filtration parameters. For example, the filtration flux may be 35 LMH, the measured permeability may be 100 LMH / bar (bar), and the set value of the permeability may be 80 LMH / bar; then, since the measured permeability is higher than the set value, an operation may be performed. The operation performed may be to increase the filtration flux to 40 LMH, because the configuration of the filtration system allows for operation at a higher filtration flux until the set value is reached, thereby increasing the yield.

[0033] In other examples of the present disclosure, if the filtration cycle is set to 60 minutes and, based on the irreversible fouling index or the rate of increase or decrease of the irreversible fouling index (also referred to as the irreversible fouling slope), the time to reach the minimum acceptable permeability is less than a predetermined set value, such as less than 1 day, the filtration cycle may be reduced to 45 minutes because the operating mode may include extending the membrane life, and thus, a sustainable longer filtration cycle may be 45 minutes.

[0034] However, if the operating mode is set to maximize the yield, or in other words, increase the volume of the filtered liquid, the filtration cycle may be increased to 80 minutes until the time to reach the minimum acceptable permeability MAP set value is 15 minutes, because the priority is to produce more filtered liquid independent of the condition or wear of the filtration system.

[0035] The method of the present disclosure includes: establishing a setpoint based on the received operating mode, where the operating mode is one of extending the life cycle of the filtration system or maximizing the total volume of the filtered liquid. The operating mode can be received by the exemplary method of the present disclosure. In an example of the present disclosure, the operating mode can be received from a user interface, where the method includes modifying the operating mode according to the operating mode received from the user interface. In some examples, the operating mode can be received from a control system, where the method includes detecting the need to modify production through the control system. In some examples, the operating mode can be received from a provisioning system, where the method includes detecting the need to change the demand for filter elements through the provisioning system. The provisioning system can include a system configured to determine whether the inventory of membranes is ready to respond to increasing membrane demand. In one example, the sustainable operating mode can be understood as a mode that extends the life cycle of the filtration system, which can be received from the provisioning system that detects the need to stop the demand for replacing filter elements (such as filter membranes). In other examples where the sustainable operating mode has been running, the remote or local control system of the filtration system may detect that the demand for the filtered liquid or water has not been met: in this case, the control system may send a "maximize production" operating mode because the sustainable mode that has been running is not sufficient to respond to the demand. In other examples, the operating mode can be received from a user interface, and the user can select the operating mode depending on the utilization demand.

[0036] In some examples, the setpoint can include resistance and can be set as follows:

[0037] For the sustainable operating mode, the setpoint is set to a value of 3E+12m -1 ;

[0038] For the maximize production operating mode, the setpoint can be set to a value of 2E+12m -1 ;

[0039] These setpoints are selected such that in order to obtain the maximum volume of filtered liquid, extending the life cycle of the filtration system can include allowing a more fouled system (3E12m -1 ) rather than allowing the maximum production mode with a lower resistance value (2E12m -1 ).

[0040] In some examples, the fouling index can include the time when the TFI reaches a limit. In this example, the TFI is used to create a regression line and extrapolate the regression line to the reciprocal of the permeability value because the TFI is calculated using the reciprocal of the permeability. Therefore, the TFI can be extrapolated to the reciprocal of the lowest acceptable permeability. In this example, the limit or setpoint includes the reciprocal of the lowest acceptable permeability MAP; for example:

[0041] - For the sustainable operation mode or to extend the life cycle of the filtration system, the fouling index

[0042] may take 80 minutes to reach the MAP setpoint of 90 LMH / bar;

[0043] - For the maximize production mode, the fouling index may take 80 minutes to reach the

[0044] MAP setpoint of 60 LMH / bar.

[0045] Select this setpoint so that in the sustainable operation mode or when extending the life cycle of the filtration system may include not allowing less than 80 minutes to reach the MAP of 90 LMH / bar, in order to obtain the maximum value of the filtered liquid volume, the maximize production mode allows the filtration system to reach a lower MAP setpoint limit in the same amount of time, even if this operation may mean more wear on the filtration system than in the previous case. In other words, if the goal is to maximize production and the MAP is the lowest acceptable permeability, the achieved MAP may be lower than the MAP for operating in a sustainable manner. For example, in ultrafiltration (UF), a possible strategy to extend the membrane life is to avoid reaching extremely low permeabilities (usually the limits recommended by the manufacturer); however, in some operations, if the goal is to maximize production, the membrane is "forced" in response to specific demands.

[0046] Exemplary methods of the present disclosure may include: operating the filtration system further based on the predicted energy consumption of each operation. In some examples, an energy consumption monitoring system local or remote to the filtration system may send an activation command for an energy-saving mode, in which the operations performed based on the fouling index are selected from a list of possible operations, and the selected operations are those with less energy consumption. In other examples, if the predicted energy consumption indicates that the filtration system will not exceed the limit, then the operations performed may be operations that consume more energy to provide better system performance. For example, if a high fouling state is determined in a case where the fouling index shows a high fouling rate compared to the setpoint, an operation of reducing the filtration time by 5% or reducing the filtration flux by 5% may reduce the fouling rate of the filtration system. The filtration system may be default-configured to always perform reducing the filtration flux; however, in the case of activating the energy-saving mode through an internal or external control system of the filtration system, the selected operations will be those with less energy consumption. Examples of operations with less energy consumption may increase the filtration flux in a low fouling state, meaning higher water production and thus lower energy consumption expressed in kWh / m3. In some examples of the present disclosure, the energy consumption is determined by determining the following parameters:

[0047] Energy consumption [kWh / m 3

[0048]

[0049] Instantaneous power (W) = W [kW] = TMP(t)·V(t)

[0050] where TMP can be provided by SCADA and V(t) is the volume generated during the duration Δt.

[0051] Instantaneous energy consumption (W') = W' [kWh] = W(t)·△t

[0052] Specific energy consumption (EC)

[0053]

[0054] In some examples, the energy cost EC' can be evaluated as follows:

[0055]

[0056] where E T is the energy tax adopted provided by the user or a remote or local pricing system.

[0057] In some examples, the energy consumption is measured during the filtration cycle or the production cycle.

[0058] In some examples, when performing chemical cleaning, the chemical cost CC of the chemical cleaning can be evaluated:

[0059]

[0060] where V CIP is the volume of the chemical solution transferred to the filtration system, CC is the chemical dosage concentration in the chemical cycle (i) [kg / m 3 , and C T is the chemical cost [€ / kg].

[0061] This calculation of the chemical cost can allow for changing certain parameters of the chemical cycle of the filtration system.

[0062] In some examples, the set values include the minimum acceptable permeability MAP and / or the minimum permeability MPLCC for initiating chemical cleaning.

[0063] In some examples, the fouling indicators include at least one of the following parameters: the total fouling index TFI and / or the hydraulic irreversible fouling index HIFI and / or the change in resistance between filtration cycles or during mechanical cleaning and / or the change in transmembrane pressure TMP and / or the change in the reciprocal of permeability and / or the change in permeability and / or the time to reach the set value.

[0064] ​In some examples, the fouling index includes the time extrapolation of at least one of the following parameters: the total fouling index TFI and / or the hydraulic irreversible fouling index HIFI and / or the change in resistance between filtration cycles or during mechanical cleaning and / or the change in transmembrane pressure TMP and / or the change in the reciprocal of the permeability and / or the change in the permeability.

[0065] In some examples, the fouling index includes the time for the filtration system to reach either MAP or MPLCC.

[0066] In some examples, the fouling index is measured during backwashing or hydraulic cleaning of the filtration system. In these examples, the state of the filtration system (e.g., filtration or production, or hydraulic / mechanical cleaning or backwashing or air scouring or chemical cleaning state) can be read from the SCADA connected to the filtration system controller. Advantageously, no calculations need to be performed in the filtration system to detect the filtration system state. In other examples, the state of the filtration system can be detected or evaluated by measuring whether certain conditions are met; for example, the effective permeation cycle conditions can be measured to detect whether the permeation or filtration state is activated in the filtration system so that some fouling parameters can be evaluated only at this time.

[0067] In some examples, after multiple consecutive fouling index values indicate a high fouling state, an alarm signal is received and chemical cleaning is initiated. In this example, advantageously, there is no need to wait until a subsequent chemical cleaning to restore the membrane to a healthy state and return to a low fouling state. In the case of receiving an alarm signal, the system automatically initiates chemical cleaning to quickly respond to some events, such as a change in water quality.

[0068] Figure 1 A filtration system (100) according to some examples of the present disclosure is shown. Figure 1 An interface (101) or display for communicating with a processor (102), an interface (103) for receiving an operating mode, and a device for performing the exemplary method of the present disclosure are shown. Specifically, Figure 1 the system is an optimized membrane ultrafiltration system (104) including one or more membranes. The exemplary method of the present disclosure can be implemented by any type of ultrafiltration UF and microfiltration MF membranes or in any type of ultrafiltration UF and microfiltration MF membranes, and can be applied to any available configuration: immersed or externally pressurized modules. The method can also be implemented by other filtration systems (e.g., sand filter SF).

[0069] In some examples, the filtration system (100) includes a processor (102). In some examples, the device for performing the exemplary method of the present disclosure is included in the processor (102). In Figure 1 the example, the interface (103) for receiving the operating mode may include a user interface, such as a screen.

[0070] The processor may include a computer-readable medium storing executable instructions that, when implemented, cause the processor (102) to perform the method as described in this disclosure.

[0071] By operating the method according to this disclosure, certain metrics can be determined and used for further calculations. The determination of parameters may include at least measuring, by the processor (102), the following parameters of one or more membranes:

[0072] - Feed flow rate (105) and / or permeate flow rate (106); a flow meter may be located in the permeate pipeline of the submerged ultrafiltration membrane or in the feed pipeline of the externally pressurized ultrafiltration membrane;

[0073] - Transmembrane pressure TMP; a pressure transmitter may be located on the feed side of the membrane and in the permeate pipeline to measure the pressure gradient across the membrane;

[0074] - Temperature of the water flowing through the membrane; a temperature transmitter may be located in Figure 1 a feed tank not shown. The temperature of the water flowing through the membrane can be used to normalize the flux and permeability;

[0075] - The operating condition or state of the membrane is at least:

[0076] - Filtration or production; or

[0077] - Backwash or hydraulic cleaning or mechanical cleaning, depending on the membrane configuration (submerged or pressurized), which can be in accordance with backwash, forward flush, or air scouring;

[0078] - Maintenance cleaning, which can be a frequent chemical cleaning to control irreversible fouling and restore permeability;

[0079] - Restorative cleaning (also known as enhanced chemical cleaning), which can be applied at a lower frequency but with higher intensity, or using a higher dose of chemicals to restore permeability;

[0080] - Production stop.

[0081] The condition or state can be obtained via SCADA and received by the processor (102) implementing the exemplary method of this disclosure.

[0082] If the operating state is filtration or production, the TMP, permeate flow rate, flux, and permeability may be normalized by temperature because at lower temperatures, the viscosity is higher and a greater pressure is required to force water through the membrane. This operation can explain that membrane fouling is independent of temperature or season. In some examples, these variables are normalized as follows:

[0083] Viscosity normalization:

[0084]

[0085] Normalized permeation flux:

[0086]

[0087]

[0088] Where:

[0089] Q p is the measured permeation flux;

[0090] Q p,25 is the normalized permeation flux at 25 °C;

[0091] TMP is the measured transmembrane pressure;

[0092] TMP 25 is the normalized TMP at 25 °C;

[0093] μ(T) is the calculated viscosity at the measured water temperature.

[0094] Normalized permeation flux (J):

[0095]

[0096] where A is the membrane area [m2 membrane], the input information about the UF series capacity provided by the user.

[0097] Normalized permeability (K 25 ):

[0098]

[0099] where the TMP (transmembrane pressure in "bar") can be directly provided by the SCADA.

[0100] K' calculation:

[0101]

[0102] where K(t) is the measured permeability and Ko is the assumed initial or baseline permeability.

[0103] If the status is backwashing, the fouling index can be measured, such as the reversible fouling index – TFI or the total fouling index. TFI can be calculated as: d(1 / K’) / dt with respect to the filtration cycle or time, corresponding to the duration of a hydraulic cycle, where K' is the normalized permeability. The information obtained from TFI is the “slope” of the regression line, which is calculated from the reciprocal of the permeability monitored along the hydraulic cycle and refers to the “total fouling rate” of the membrane.

[0104] In the backwashing state, other parameters can be calculated, such as the water yield WY or the productivity PR:

[0105] The water yield WY represents the volume % / total filtration volume produced. WY can be calculated as follows:

[0106] WY1: The net volume produced along a hydraulic cycle divided by the total filtration volume.

[0107]

[0108] where V HC is the permeate volume used during backwashing, and V’ HC is the excess inlet volume used for tank filling and emptying in hydraulic cleaning. These volumes can be constant / set values introduced by the user.

[0109] WY2: The net volume produced along a chemical cycle divided by the total filtration volume.

[0110]

[0111] where V MC is the permeate volume used in the CIP tank (in - place cleaning tank), and V’ MC is the excess inlet volume used for tank filling and emptying in MC. These volumes are constant / set values introduced by the user.

[0112] WY3: The net volume produced along an enhanced chemical cycle (restorative cleaning (RC)) divided by the total filtration volume.

[0113]

[0114] where V RC is the permeate volume used in the CIP tank (in - place cleaning tank), and V’ RC is the excess inlet volume used for tank filling and emptying in RC. These volumes are constant / set values introduced by the user.

[0115] In the backwashing state, the productivity PR refers to the percentage of time dedicated to production relative to the total operating time and can be calculated as follows:

[0116]

[0117]

[0118]

[0119] If the status is maintenance or restorative chemical cleaning, another fouling index can be measured, such as the irreversible fouling index HIFI. HIFI can be calculated as: d(1 / K’) / dt along a chemical cycle, where the chemical cycle includes multiple hydraulic cycles, and K’ is the normalized permeability. The information provided by HIFI is the “slope” of the regression line, which is calculated from the reciprocal of the permeability monitored along the chemical cycle and refers to the “irreversible fouling rate” of the membrane.

[0120] Figure 2 Shows an example of a schematic diagram of HIFI and TFI graphs. In Figure 2 the normalized permeability curve of the membrane and the reciprocal of the specific volume of filtration [m3 / m2] are represented for two consecutive cycles (cycle 1 and cycle 2). For each antifouling curve, the linear regression is represented as “y”, where the first linear regression is represented as y = ax + b, where “a” is the slope of the first linear regression, TFI is represented as d(1 / K’) / dVs, and b is the initial 1 / K’(t) value of the hydraulic cycle. Note that “t” and “Vs” are related by the equation Qs = Vs / t. The second linear regression of the second curve is represented as y = cx + d, where “c” is the slope of the second linear regression representing HIFI, and “d” is the initial 1 / K’(t) value of the hydraulic cycle. The second curve is the line connecting the points where the antifouling has become irreversible (or in other words, mechanical cleaning or hydraulic backwashing cannot remove membrane fouling). In this theoretical example, to illustrate how the equation is calculated visually, chemical cleaning follows two consecutive hydraulic cycles (i.e., cycle 1 and cycle 2). In a real filtration system, chemical cleaning can usually be carried out daily, and thus, in 24 one-hour hydraulic cycles.

[0121] Figure 3 and Figure 4 respectively show other representations of TFI and HIFI during 3 hydraulic cycles.

[0122] The combination of the two indices TFI and HIFI provides the following information: which hydraulic cleaning strategy can be activated: increasing or decreasing the hydraulic cleaning frequency; and the time of the next maintenance or restorative cleaning can be predicted.

[0123] Depending on the received operating mode: maximum production operation or sustainable operation of the membrane, upper limits of TFI and HIFI can be established respectively:

[0124] - Minimum Acceptable Permeability MAP and

[0125] - Minimum Permeability to Initiate Chemical Cleaning MPLCC.

[0126] For example, for the maximized production operation mode, MAP can be set to 60 [LMH / bar], and MPLCC can be set to 100 [LMH / bar]. For example, in the sustainable operation mode, MAP can be set to 90 [LMH / bar], and MPLCC can be set to 120 [LMH / bar]. These values can be selected as reference values that can be calculated by the operator of the filtration system or the algorithm implementing the method of the present invention. These values can vary. MAP and MPLCC are generally set values that can be determined by the user or can be defined by an artificial intelligence AI system, and they can vary based on the received operation mode. These values define the operations performed through the filtration system.

[0127] In the example shown in the drawings, two values of MAP and MPLCC are presented.

[0128] The "maximized production" operation mode can refer to an extreme non-conservative operation mode, so the membrane can be forced, and a lower permeability level than alternative operation modes can be considered "acceptable". The driving force or goal of this operation mode is to meet the water demand by increasing the production volume, despite the possible negative impact on the lifespan caused by "stressing" the membrane.

[0129] The "sustainable operation" operation mode can make the filtration system operate in a conservative manner. To extend the lifespan of the membrane and keep the filtration system in a sustainable operation state, it may be necessary to avoid reaching a low permeability level. Therefore, the driving force may be to avoid reaching a certain "non-conservative" permeability value.

[0130] If the TFI is calculated as the reciprocal of the permeability, based on the linear regression of TFI and HIFI, the TFI can be extrapolated to the reciprocal of the MAP, and the HIFI can be extrapolated to the reciprocal of the MPLCC, and the "time to reach the reciprocal of MAP / MPLCC" can be predicted. Different levels of fouling can be defined, for example, "high fouling and low fouling", or "high fouling, acceptable fouling and low fouling". In some examples, when it is predicted that the reciprocal of the permeability reaches the reciprocal of the relevant MAP set value in less than 80 minutes, it can be regarded as high fouling or a high fouling rate; in other words, when it is predicted that the TFI extrapolation reaches the MAP limit (or the reciprocal of the MAP) in less than 80 minutes, the system is considered to have a high fouling rate. In some examples, when it is predicted that the irreversible reciprocal of the permeability reaches the reciprocal of the relevant MPLCC set value in less than 2 days; in other words, when it is predicted that the HIFI extrapolation reaches the MPLCC or the reciprocal of the MPLCC limit in less than 2 days, it can be regarded as high fouling or a high fouling rate. In some examples, when it is predicted that the permeability reaches the MAP set value in more than 160 minutes, it can be regarded as low fouling or a low fouling rate. In some examples, when it is predicted that the irreversible permeability reaches the MPLCC in more than 5 days, it can be regarded as low fouling or a low fouling rate.

[0131] The following table shows some examples of high fouling rate, acceptable fouling rate or low fouling rate in matrix representation:

[0132]

[0133] Once the set values of MAP and MPLCC limits are established, the combination of set values provides different exemplary operations that can be performed:

[0134] - If there is high irreversible fouling HIFI and high fouling rate TFI, reduce the filtration time by 5% or reduce the filtration flux by 5%; in this case, the filtration system or membrane will foul rapidly, and the system needs to reduce production. This can be regarded as a warning state;

[0135] - If there is acceptable irreversible fouling HIFI and high fouling rate TFI, or if there is acceptable TFI and high HIFI, reduce the filtration time by 2% or reduce the filtration flux by 2%; in this case, the fouling rate of the membrane is moderate, and the system can be set to produce at a slower speed; this can be regarded as a warning state;

[0136] - If there is high TFI and low HIFI, or if there is low TFI and high HIFI, reduce the filtration time by 1% or reduce the filtration flux by 1%; this can be regarded as a warning state;

[0137] - If both TFI and HIFI are acceptable, maintain or do not perform an operation; in this case, the system may continue to produce as it is;

[0138] - If TFI is low and HIFI is acceptable, or if TFI is acceptable and HIFI is low, increase the filtration time by 2% or increase the filtration flux by 2%; in this case, the membrane fouling rate is moderate, and the system can be set to produce at a higher speed; this can be regarded as a state where the filtration system can further optimize production;

[0139] - If both TFI and HIFI are low, increase the filtration time by 5% or increase the filtration flux by 5%; in this case, the membrane fouling rate is very low, and the system can be set to produce at a higher speed because it can be regarded as underutilized. This can be regarded as a state where the filtration system can further optimize production.

[0140] The filtration flux can be changed by sending an electronic command from the processor (102) to the valve (not shown) of the filtration system.

[0141] In matrix form, the above operations can be as shown in the following table:

[0142]

[0143] The set values can be modified according to system requirements. For example, an artificial intelligence AI system can determine that if the established set values force the filtration flux or time to decrease more than twice a day, the set values can be recalibrated.

[0144] As shown in the above example, the operation mode selection triggers the MAP and MPLCC set value definitions, which in turn can trigger the definition and / or modification of the fouling index value (such as the time to reach the set value).

[0145] In the observed example, the set values are MAP or MPLCC, and the time for the fouling index to reach the set value is based on extrapolation and depends on the received operation mode.

[0146] In the above example, the energy-saving mode can allow continuous evaluation and comparison of which operation, modifying the filtration flux operation or modifying the filtration time operation, has a significant impact on the energy consumption of the filtration system.

[0147] Figure 3 and Figure 4 show that the set values vary based on the operation mode. Figure 3 and Figure 4 represent the reciprocal of the permeability 1 / K, the reciprocal of MAP in each figure: MAP_1, MAP_2, the reciprocal of MPLCC in each figure: MPLCC_1, MPLCC_2. The TFI and HIFI regression lines are shown as increasing with time or the filtration volume "specific volume".

[0148] As shown, the irreversible fouling after each hydraulic cleaning (or, in other words, during the hydraulic cycle) is represented by a "growth" curve, representing an increase in the reciprocal of the permeability. The regression line "y" of each curve representing the evolution of the reciprocal of the permeability is obtained. The regression line "y" represents the minimum values of the deviation from the irreversible fouling index after each hydraulic cleaning. The extrapolation of the line "y" is represented by a dashed line, which corresponds to the predicted values of the regression of the regression line "y" or the total fouling index TFI and / or the hydraulic irreversible fouling index HIFI over a period of time.

[0149] Figure 3 Shows the behavior of the filtration system when the operating mode is set to the maximum production operating mode. The setpoints can be MAP_1 and MPLCC_1, corresponding to the first MAP reciprocal and the first MPLCC reciprocal. In Figure 3 , MAP_1 and MPLCC_1 are higher than Figure 4 MAP_2 and MPLCC_2 in (where the sustainable operating mode is set).

[0150] Figure 4 Represents the behavior of the filtration system when the operating mode is set to the sustainable operating mode, where the setpoints MAP_2 and MPLCC_2 corresponding to the second MAP reciprocal and the second MPLCC reciprocal are set. In Figure 4 , MAP_2 and MPLCC_2 are lower than Figure 3 MAP_1 and MPLCC_1 of.

[0151] As shown, the time to reach MAP_1 measured at the time point when the regression line TFI is assumed to reach MAP_1 is greater than the time to reach MAP_2, and the time to reach MPLCC_1 is greater than the time to reach MPLCC_2.

[0152] These results show the adaptability of the filtration system. For example, Figure 4 the sustainable operation shown, where, in order to protect the membrane or the filtration system, the method of the present invention operates on the filtration parameters (increasing or decreasing the filtration flux or filtration time) to avoid reaching the low permeability MAP_2 and MPLCC_2 or the high 1 / K' value, or the method of the present invention operates before reaching the low permeability MAP_2 and MPLCC_2 or the high 1 / K' value. In the example shown, the fact of not reaching MAP or MPLCC can be performed by changing MAP and MPLCC and establishing the "time to reach the setpoint", which has been set to 80 minutes and 160 minutes in some examples. Other times to reach the setpoint can be set based on factory or user needs.

[0153] Figure 5Shows alternative graphical representations where the permeability K, MAP, and MPLCC are represented instead of their reciprocals. In this case, the regression of TFI and HIFI decreases over time, and TFI is calculated as dK / dt instead of d(1 / K) / dt. Figure 5 Shows an example where, if the goal is to maximize production and the MAP is the lowest acceptable permeability, the achieved MAP may be lower than the MAP for sustainable operation. For example, in ultrafiltration (UF), a possible strategy to extend membrane life is to avoid reaching extremely low permeabilities (usually the limits recommended by the manufacturer); however, during some runs, if the goal is to maximize production, the membrane is "forced" in response to specific demands. For visualization, in Figure 5 MAP refers to the permeability and not the reciprocal of the permeability.

[0154] As shown, the proposed methods and systems can allow for the optimization of UF operation. Membrane fouling is a limitation when applying membrane filtration technology. The disclosed methods allow for the introduction of intelligence in strategy development, which are typically forced as fixed setpoints, as constants, and are not suitable for feed variation scenarios.

[0155] Therefore, the disclosed methods allow for intelligent monitoring of reversible and irreversible membrane fouling based on user or plant needs: maximizing production or economic savings or sustainable operation in terms of fouling. These methods allow for the adaptation of setpoints to plant needs or feed variations. The disclosed methods also perform a set of operations to optimize fouling control strategies: basic operating conditions, hydraulic cleaning, and chemical cleaning, to predict membrane operation and are able to predict enhanced maintenance operations such as chemical cleaning.

[0156] The disclosed methods also allow for the monitoring of high KPI values such as energy consumption, chemical consumption, or OPEX.

Claims

1. A method for filtering a liquid through a filtration system, wherein, The filtration system is configured with filtration parameters, and the filtration parameters at least include the filtration time and filtration flux of the liquid passing through the filtration system; The method includes: - Determining a fouling index in the filtration system; - Comparing at least one fouling index with at least one corresponding set value; - Operating the filtration system based on the comparison result, wherein the operation includes: - Changing the filtration time; and / or - Changing the filtration flux; and / or - Maintaining the filtration parameters; The method further includes: establishing a set value based on the received operating mode, wherein the operating mode is one of extending the life cycle of the filtration system or maximizing the total volume of the filtered liquid, wherein the fouling index includes at least one of the following parameters: - Total fouling index TFI and / or - Hydraulic irreversible fouling index HIFI and / or - Resistance change between filtration cycles and / or - Transmembrane pressure TMP change and / or - Transmembrane pressure TMP change with flow rate and / or - Permeability change and / or - Time to reach the set value, and, wherein, establishing a set value based on the received operating mode includes: selecting a set value so that in order to obtain the maximum volume of filtered liquid, extending the life cycle of the filtration system includes allowing a system with more fouling rather than the maximum production mode with a lower resistance value.

2. The method according to claim 1, wherein Operating the filtration system is also based on the predicted energy consumption of each operation.

3. The method according to any one of the preceding claims, wherein The operating mode is received from at least one of the following: - A user interface, wherein the method includes modifying the operating mode according to the operating mode received from the user interface; and / or - A control system, wherein the method includes detecting the need to modify production through the control system; and / or - A supply system, wherein the method includes detecting the need for a change in the demand for filtration elements through the supply system.

4. The method according to claim 1 or 2, wherein The set value includes: - Minimum acceptable permeability MAP and / or - Reciprocal of MAP and / or - Minimum permeability for starting chemical cleaning MPLCC and / or - Reciprocal of MPLCC.

5. The method according to claim 1 or 2, wherein The fouling index includes the time extrapolation of at least one of the following parameters: - Resistance between filtration cycles and / or - Transmembrane pressure TMP and / or - Transmembrane pressure TMP with flow rate and / or - Permeability.

6. The method according to claim 4, wherein The fouling index includes the time when the filtration system reaches one of MAP or MPLCC or the reciprocal of MAP and / or the reciprocal of MPLCC.

7. The method according to claim 1 or 2, wherein Determining the fouling index includes performing an on-line measurement of the fouling index during production or filtration.

8. The method according to claim 1 or 2, wherein The filtration parameters include the product, frequency, and / or intensity of chemical cleaning.

9. The method according to claim 4, wherein When an alarm signal is received, chemical cleaning is automatically started.

10. A filtration system, the filtration system includes: An interface (101) for communicating with a processor (102); An interface (103) for receiving an operating mode; And wherein the filtration system is configured to: - Determine a fouling index in the filtration system; - Compare at least one fouling index with at least one corresponding set value; - Operate the filtration system based on the comparison result, and the operation includes: - Changing the filtration time; and / or - Changing the filtration flux; and / or - Maintaining the filtration parameters; - and establishing a setpoint based on the received operating mode, wherein the operating mode is one of extending the life cycle of the filtration system or maximizing the total volume of filtered liquid, wherein the fouling index includes at least one of the following parameters: - total fouling index TFI and / or - hydraulic irreversible fouling index HIFI and / or - change in resistance between filtration cycles and / or - transmembrane pressure TMP change and / or - transmembrane pressure TMP change with flow rate and / or - permeability change and / or - time to reach the setpoint, establishing a setpoint based on the received operating mode includes: selecting a setpoint such that, in order to obtain the maximum volume of filtered liquid, extending the life cycle of the filtration system includes allowing a system with more fouling rather than the maximum production mode with a lower resistance value.

11. The filtration system according to claim 10, further comprising a processor (102).

12. The filtration system according to any one of claims 10 and 11, wherein, The interface (103) for receiving the operating mode includes a user interface.

13. A non-transitory computer-readable medium storing executable instructions that, when implemented, cause a processor to perform the method according to any one of claims 1 to 9.

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