Method for diagnosing state of separation membrane module, program, and method for operating water treatment plant

Abstract

Provided is a method for clarifying factors in the deterioration of a separation membrane module. The present invention provides a method for diagnosing the state of a separation membrane module comprising a step for determining the amount of change in the performance of a separation membrane module on the basis of the difference between the performance measurement result for a first state of the separation membrane module and the performance measurement result for a second state of the separation membrane module, a step for obtaining an analysis result and / or a measurement result correlated with the degree of deterioration for each of a plurality of deterioration factors arising in the change from the first state to the second state, a step for quantifying the analysis result for each deterioration factor as an amount corresponding to a portion of the amount of change in performance, and a step for indicating the contribution amount of each deterioration factor to the amount of change in performance by integrating the results calculated in the quantification step.

Description

Method for diagnosing the condition of a separation membrane module, a program for this, and a method for operating a water treatment plant.

[0001] The present invention relates to a method for diagnosing the condition of a separation membrane module, a program for diagnosing the condition of a separation membrane module, and a method for operating a water treatment plant.

[0002] In recent years, the depletion of water resources has become a serious problem, and the utilization of previously unused water sources is being considered. Furthermore, as a technology for this purpose, separation membranes with significantly higher separation efficiency compared to conventional sand filtration and evaporation methods, such as microfiltration membranes, ultrafiltration membranes, nanofiltration membranes, reverse osmosis membranes, and ion exchange membranes, are being applied to water treatment. Applications of separation membranes include seawater desalination technology for producing drinking water from seawater, and reuse technology for purifying wastewater and regenerating treated water. Among separation membranes, reverse osmosis membranes are attracting considerable attention.

[0003] Reverse osmosis is a water production method that obtains desalinated water by applying pressure exceeding the osmotic pressure to water containing solutes such as salt, causing it to permeate a reverse osmosis membrane. This technology can be used to obtain drinking water from seawater and brine, and can also be used for the production of industrial ultrapure water, wastewater treatment, and the recovery of valuable materials. However, the performance of various water treatment plants using reverse osmosis membranes can deteriorate during operation due to various reasons. For example, chemical deterioration of the reverse osmosis membrane can occur when disinfectants used to sterilize the raw water taken in, coagulants used in pretreatment, or other residues come into contact with the reverse osmosis membrane surface, or when a contaminated reverse osmosis membrane is chemically cleaned with strong acids or strong alkalis. In addition, the surface of the reverse osmosis membrane can be physically damaged when foreign matter in the water being treated, scale, foulant, etc., that have been generated during operation come into contact with the membrane surface.

[0004] Patent Document 1 describes a method for investigating the presence or absence of physical damage to a reverse osmosis membrane, which involves disassembling a reverse osmosis membrane element, passing a staining solution under pressure through a sample of the reverse osmosis membrane for 30 minutes or more, and visually observing whether there are any stained areas. Non-Patent Document 1 discloses a method for investigating the presence or absence of chemical deterioration of a reverse osmosis membrane, which involves disassembling a reverse osmosis membrane element, immersing the extracted reverse osmosis membrane in a solution of alkaline aqueous solution and pyridine, and identifying chemical deterioration, particularly oxidative deterioration, based on whether or not the solution develops color.

[0005] Patent Document 2 describes a method for determining the contribution of physical damage and chemical degradation to a reverse osmosis membrane, which involves creating a chemical degradation profile in which the separation performance deteriorates when the separation membrane module is exposed to chemicals, and a physical damage profile in which the separation performance decreases when physical scratches are made on the shared side of the separation membrane module, and comparing these with the measured separation performance of the separation membrane module. When measuring the performance of the separation membrane module, the method involves supplying test water containing at least two types of solutes (for example, sodium chloride and magnesium sulfate) to the separation membrane module, or supplying two types of test water to the separation membrane module individually, and measuring the separation performance based on the concentration of solutes contained in the permeate.

[0006] International Publication No. 2022 / 203078, International Publication No. 2023 / 127810

[0007] R. Sandin et al. / Desalination and Water Treatment. 51 (2013), 318-327.

[0008] According to the inventors' research, when performance degradation occurs in reverse osmosis membrane elements, degradation is likely to be caused by multiple types of phenomena. In the case of physical damage as described above, sudden changes in operating conditions can cause wrinkles on the membrane surface to come into strong contact with the flow channel material, or strong contact between the membrane surface and the flow channel material can cause physical damage. In addition, performance degradation can occur when reverse osmosis membranes are exposed to high pressure for extended periods during normal operation in various water treatment plants, or when foulant coats the surface of the reverse osmosis membrane. Therefore, it is necessary to periodically inspect the performance of reverse osmosis membranes to diagnose the occurrence of performance degradation factors such as chemical degradation and physical damage, and to take appropriate measures when problems are found. In such cases, it is ideal to take measures against all degradation factors. However, due to time and financial cost issues, the measures that can be realistically adopted are sometimes limited. Simply identifying the presence or absence of impact for each degradation factor does not allow for the identification of which type of degradation factor should be prioritized for countermeasures, making it difficult to take optimal measures.

[0009] For example, while it is possible to investigate the presence or absence of physical damage and chemical degradation of a reverse osmosis membrane using the method described in Patent Document 1 and the method described in Non-Patent Document 1, respectively, there is a problem in that it is not possible to compare the magnitude of the influence of each degradation factor. Furthermore, the technology described in Patent Document 2 is a method for determining the contribution of physical damage and chemical degradation of a reverse osmosis membrane, but it requires a pre-prepared degradation profile and has the problem of not being able to determine the degree of contribution of other degradation factors. The present invention has been made in view of the above-mentioned prior art, and aims to provide a method for clarifying the magnitude of the influence of each degradation factor on a separation membrane module, even when there may be multiple degradation factors in the separation membrane module, and for quantitatively diagnosing the influence of each degradation factor on the separation membrane module.

[0010] To solve the above problems, the present invention has the following configuration: (1) A method for diagnosing the state of a separation membrane module for separating water to be treated into concentrated water and permeate water, comprising the steps of: determining the amount of change in the performance of the separation membrane module due to the change from the first state to the second state based on the difference between the performance measurement result of the separation membrane module in a first state and the performance measurement result of the separation membrane module in a second state; obtaining analysis results that correlate with the degree of deterioration for each of a plurality of deterioration factors that occurred in the change from the first state to the second state; quantifying the analysis result of each deterioration factor as an amount corresponding to a part of the change in the performance of the separation membrane module; and indicating the amount of contribution of each deterioration factor to the change in the performance of the separation membrane module by accumulating the plurality of quantitative results calculated in the quantification step.

[0011] (2) The method for diagnosing the condition of a separation membrane module according to (1), wherein the first state is the state of the separation membrane module before use and / or before storage, and the second state is the state of the separation membrane module after use and / or after storage. (3) The method for diagnosing the condition of a separation membrane module according to (1) or (2), characterized in that the change in the performance of the separation membrane module is the change in water permeability and / or the change in solute removal performance. (4) The method for diagnosing the condition of a separation membrane module according to any one of (1) to (3), characterized in that the plurality of deterioration factors include physical damage, chemical deterioration and deposits.

[0012] (5) A method for diagnosing the condition of a separation membrane module according to any one of (1) to (4), characterized in that, in the step of obtaining analytical results that correlate with the degree of deterioration for each of the plurality of deterioration factors, the amount of performance influence due to deposits and the amount of performance influence due to compaction are quantified, the remaining change in performance is calculated by subtracting the amount of performance influence due to deposits and the amount of performance influence due to compaction from the change in performance of the separation membrane module, test water containing at least two types of solutes is supplied to the separation membrane module in order to calculate the contribution ratio of physical damage and the contribution ratio of chemical deterioration, the separation performance of the separation membrane module for each solute is measured, the contribution ratio of physical damage and the contribution ratio of chemical deterioration are calculated by comparing the separation performance for each solute with pre-created deterioration relation formulas for physical damage and chemical deterioration, and the amount of performance influence due to physical damage and the amount of performance influence due to chemical deterioration are calculated by multiplying the remaining change in performance by the respective contribution ratios. (6) The method for diagnosing the condition of a separation membrane module according to (5), further comprising the step of cleaning the separation membrane module with a chemical solution before the step of calculating the contribution ratio of physical damage and the contribution ratio of chemical deterioration.

[0013] (7) A separation membrane module condition diagnosis program, wherein the computer functions as a data input means for inputting performance measurement results in a first state and a second state of the separation membrane module and analysis results correlated with each degradation factor into the computer, a performance change amount calculation means for calculating the performance change amount from the performance measurement results of the first state and the second state, a quantification means for quantifying each analysis result correlated with each degradation factor as an amount corresponding to a part of the performance change amount, a data recording means for recording the input and calculated data in the computer, and a condition diagnosis means for determining the degree of each degradation factor in the performance change amount by accumulating the quantified results of each degradation factor based on the input and / or recorded data.

[0014] (8) A recording medium on which the separation membrane module condition diagnosis program described in (7) is recorded. (9) A method for operating a water treatment plant, characterized in that, based on the separation membrane module condition diagnosis method described in (4) to (6), if it is determined that the deterioration factor is physical damage, at least one of the following is performed: checking the inflow status of foreign matter and preventing its inflow, preventing a sudden rise or fall in operating pressure, and replacing the deteriorated separation membrane module; if it is determined that the deterioration factor is deposits, at least one of the following is performed: checking the inflow status of deposits and preventing their inflow, performing separation membrane module cleaning according to the type of deposits, adding a chemical to prevent deposit formation, and replacing the deteriorated separation membrane module; and if it is determined that the deterioration factor is chemical deterioration, at least one of the following is performed: checking the inflow status of oxidizing agents and preventing their inflow, checking the inflow status of strong acids or strong bases and preventing their inflow, and replacing the deteriorated separation membrane module.

[0015] The separation membrane module condition diagnosis method of the present invention allows for the quantitative diagnosis of multiple degradation factors occurring in the separation membrane module. Based on the diagnosis results, optimal countermeasures can be taken to improve the operation of the water treatment plant, enabling stable operation of the separation membrane module in the water treatment plant.

[0016] This is a partially exploded perspective view of a typical spiral-type reverse osmosis membrane element. This is a side cross-sectional view of a reverse osmosis membrane module in which spiral-type reverse osmosis membrane elements are loaded into a pressure vessel. This is a diagram showing the configuration of a pressure vessel and apparatus used for performance evaluation or staining of reverse osmosis membranes. This is an example of the condition diagnosis results of the separation membrane module of the present invention. This is an example of the condition diagnosis results of the separation membrane module of the present invention. This is an example of the condition diagnosis results of the separation membrane module of the present invention.

[0017] The present invention will be described in detail below, but these are merely examples of desirable embodiments, and the present invention is not limited to these. [Method for diagnosing the state of a separation membrane module] The present invention is a method for diagnosing the state of a separation membrane module for separating water to be treated into concentrated water and permeate water, comprising the steps of: determining the amount of change in the performance of the separation membrane module due to the change from a first state to a second state based on the difference between the performance measurement result of the separation membrane module in a first state and the performance measurement result of the separation membrane module in a second state; obtaining analysis results and / or measurement results that correlate with the degree of deterioration for each of a plurality of deterioration factors that occurred in the change from the first state to the second state; quantifying the analysis result of each deterioration factor as an amount corresponding to a part of the amount of change in performance; and indicating the amount of contribution of each deterioration factor to the amount of change in performance by accumulating the plurality of quantitative results calculated in the quantification step.

[0018] Figure 1 shows an example of a separation membrane module to which the present invention is applied, and is a partially exploded perspective view of an element used as a typical spiral-type reverse osmosis membrane module. In this spiral-type reverse osmosis membrane element, a reverse osmosis membrane unit including a reverse osmosis membrane 1, a permeate flow channel material 2, and a water to be treated flow channel material (net spacer) 3 is generally wound spirally around a water collection pipe 4 having a water collection hole, and the outside of the reverse osmosis membrane unit is covered with a film or glass fiber impregnated with a curable resin, and a telescopic prevention plate 5 is attached to at least one end of this fluid separation element.

[0019] For the water to be treated channel material, net-like or mesh-like lattice channel material, grooved sheet, corrugated sheet, etc., can be used. For the permeate water channel material, net-like or mesh-like lattice channel material, grooved sheet, corrugated sheet, etc., can be used. In either case, the net or sheet may be independent of the separation membrane, or it may be integrated by bonding or fusing. The water to be treated 6 is supplied from the telescopic prevention plate 5, passes through the water to be treated channel material 3 and is supplied to the reverse osmosis membrane, where it is separated into permeate water 7 and concentrated water 8 through membrane separation treatment. The permeate water 7 is collected inside the water collection pipe 4 through holes on the side of the water collection pipe, passes through the water collection pipe, and the permeate water 7 is collected from the mouth of the water collection pipe. This spiral element can be used by loading it into the pressure vessel 9 as shown in Figure 2. When inspecting the reverse osmosis membrane element, if the performance of only the reverse osmosis membrane collected from the reverse osmosis membrane element is to be measured, the reverse osmosis membrane can be inspected by loading it into the pressure vessel as shown in Figure 2.

[0020] Figure 3 shows the flow path configuration used for evaluating the performance of the reverse osmosis membrane. The water to be treated 11 is supplied from the water to be treated tank 12 through the water to be treated supply line 13 and via the pressurized supply means 14 to the reverse osmosis membrane 15, which is loaded into the reverse osmosis membrane evaluation cell 16, which is a pressure vessel. Here, the water to be treated is separated by membrane separation treatment into concentrated water 17 and permeate 18. The permeate 18 is collected from the permeate drain valve 202 through the permeate line 20. In addition, a portion of the concentrated water 17 is collected from the concentrated water drain valve 201 through the concentrated water line 19, and the remainder is circulated back to the water to be treated tank 12 via the concentrated water circulation valve 101 and used again for performance measurement. The evaluation operating conditions are measured using a pressure gauge 21 and a concentrated water flow meter 22.

[0021] In one embodiment of the present invention, the first state is preferably the state of the separation membrane module before use and / or before storage, and the second state is preferably the state of the separation membrane module after use and / or after storage. Typical factors that affect the performance of the separation membrane module include use and / or storage. Therefore, based on the performance differences at any timing before and after these state changes, the degradation factors can be measured more accurately by measuring analysis results and / or measurement results that correlate with the degree of degradation for each of the multiple degradation factors that occurred during the state change.

[0022] The first state may be the initial state of the separation membrane module. This initial state is any state in which the separation membrane module exhibits its initial performance, similar to the state when new, the state at the time of manufacture, or the state showing performance at the time of plant startup, and is not limited to whether or not it is unused. The use of the separation membrane module here includes, but is not limited to, using it in the water treatment operation of a water treatment plant, unpacking the separation membrane module from its storage state, loading the separation membrane module into a pressure vessel installed in a water treatment plant or water treatment device, and supplying pressurized water to the separation membrane module in the pressure vessel. The storage of the separation membrane module here includes, for example, leaving the separation membrane module unattended in a sealed state, leaving the separation membrane module unpacked from its sealed state, and leaving the separation membrane module unattended in a pressure vessel.

[0023] The change in performance of the separation membrane module refers to the difference between the performance measurement results in the first state and the performance measurement results in the second state. Here, the performance of the separation membrane module includes the weight of the separation membrane module, the operating pressure during operation of the separation membrane module, the water permeability performance of the separation membrane module, and the solute removal performance of the separation membrane module. Among these, from the viewpoint of direct evaluation of the separation membrane module and quantitative accuracy, it is preferable that the performance measurement results of the separation membrane module be the water permeability performance and / or the solute removal performance of the separation membrane module. Therefore, it is preferable that the change in performance of the separation membrane module in the present invention be the change in water permeability and / or the change in solute removal performance.

[0024] In the present invention, permeability performance is preferably a physical quantity expressed in units indicating the amount of water permeated per unit time, per unit area, or per unit pressure, but is not limited to these. Measured values ​​obtained under certain conditions may be converted to performance at specific solute concentrations, temperatures, pH, pressures, or flow rates. As a method of conversion, for example, the dependence of permeability performance on the concentration, temperature, pH, and pressure of the test water can be determined experimentally in advance, and then converted to performance under specific conditions based on the relational equations derived from these.

[0025] In this invention, solute removal performance is a physical quantity expressed as the ratio of the solute concentration in the permeate water to the solute concentration in the test water, or the amount of solute permeate per unit time, but is not limited to these. Furthermore, measured values ​​obtained under certain conditions may be converted to performance at specific solute concentrations, temperatures, pH, pressures, flow rates, or recovery rates. Here, recovery rate refers to the ratio of the permeate flow rate to the flow rate of the treated water. As a method of conversion, for example, the dependence of removal performance on the concentration, temperature, pH, and pressure in the test water can be determined in advance by experiment, and the performance at specific conditions can be converted based on the relationship formula derived from these.

[0026] As a method for measuring the performance of a separation membrane module or separation membrane, as shown in Figure 2, the separation membrane module is loaded into a pressure vessel, or as shown in Figure 3, the separation membrane is loaded into a pressure vessel, and the water to be treated is supplied to the pressure vessel under pressure to separate the water into permeate and concentrated water. In this method, it is preferable to measure the solute concentration, temperature, pH, pressure, flow rate, etc., of the water to be treated, permeate, and concentrated water when the water to be treated is supplied to the pressure vessel under pressure, and calculate the water permeability and solute removal performance from the relationship between the flow rate and solute concentration of the water to be treated, permeate, and concentrated water.

[0027] In this invention, analytical and / or measurement results that correlate with the degree of degradation are obtained for each of the multiple degradation factors. In this invention, degradation factors refer to phenomena occurring in the reverse osmosis membrane itself that cause an increase or decrease in the performance of the reverse osmosis membrane element. Here, the reverse osmosis membrane element is synonymous with the separation membrane module. Specifically, these can be subdivided into physical damage, chemical degradation, deposits, compaction, etc. In order to identify the performance degradation factors of the separation membrane module, it is more preferable to further subdivide and analyze each of these factors. For example, for physical damage, physical damage occurring on the membrane and physical damage occurring outside the membrane may be analyzed separately, and chemical degradation may be further subdivided and analyzed separately for oxidative degradation and other types.

[0028] In the present invention, physical damage includes, but is not limited to, damage to the components of the reverse osmosis membrane element, and rupture, defects, or scratches on the reverse osmosis membrane. Furthermore, the analysis and / or measurement results used to quantify the degree of physical damage, which correlate with the degree of physical damage, preferably include one or more of the following: performance measurement results of the separation membrane module, performance measurement results of the separation membrane taken from the separation membrane module, and staining test results of the separation membrane taken from the separation membrane module. It is preferable to include performance measurement results of the separation membrane module that directly correlate with the degree of deterioration. As a method for obtaining performance measurement results of the separation membrane module and as a method for obtaining performance measurement results of the separation membrane taken from the separation membrane module, it is preferable to use methods (I) and (II) of the examples. As a method for obtaining staining test results of the separation membrane taken from the separation membrane module, it is preferable to use method (III) of the examples.

[0029] Chemical deterioration in the present invention is one of the factors that affect the performance of a reverse osmosis membrane element. It includes deterioration caused by contact of acidic substances, basic substances, oxidizing substances, reducing substances, etc. with the reverse osmosis membrane in the reverse osmosis membrane element, resulting in a change in the chemical structure of the reverse osmosis membrane. Further, the analysis results and / or measurement results correlated with the degree of chemical deterioration, which are used to quantify the degree of chemical deterioration, preferably include any one or more of the performance measurement results of the separation membrane module, the performance measurement results of the separation membrane collected from the separation membrane module, the structural analysis results of the separation membrane, and the elemental composition analysis results of the separation membrane. In particular, it is preferable to include any one of the performance measurement results of the separation membrane module, the structural analysis results of the separation membrane collected from the separation membrane module, or the elemental composition analysis results of the separation membrane, as these are results that particularly accurately correlate with the degree of deterioration. As a method for obtaining the structural analysis results and elemental composition analysis results of the separation membrane collected from the separation membrane module, it is preferable to use X-ray photoelectron spectroscopy, microscopic observation, and infrared spectroscopy. More preferably, it is preferable to use the method (IV) of the examples.

[0030] Next, deposits, which are one of the deterioration factors, will be described. In the flow path of the reverse osmosis membrane element of the separation membrane module and on the surface of the reverse osmosis membrane within the reverse osmosis membrane element, turbidity in raw water such as stones, sand, and mud, biofoulants composed of microorganisms, extracellular matrices, and cell secretions in raw water, chemical substances, etc. accumulate, adhere, and adsorb. These deposits can cause the flow path to be blocked or the membrane surface to be coated, which can be a factor in the performance deterioration of the reverse osmosis membrane element. Further, the analysis results and / or measurement results correlated with the degree of deposits preferably include any one or more of the performance measurement results of the separation membrane module, the performance measurement results of the separation membrane collected from the separation membrane module, the staining test results of the separation membrane collected from the separation membrane module, the weight measurement results of the separation membrane module, the weight measurement results of the deposits collected from the separation membrane module, the structural analysis results of the deposits collected from the separation membrane module, and the elemental composition analysis results of the deposits collected from the separation membrane module. It is preferable to include the performance measurement results of the separation membrane collected from the separation membrane module, which directly correlates with the degree of deterioration.

[0031] Methods for obtaining the weight measurement results of the separation membrane module include methods for measuring the weight in a wet state and methods for measuring the weight in a dry state. Preferably, a method is preferred in which the separation membrane module is filled with pure water or an aqueous solution of a specific concentration, and then the separation membrane module is stood upright for a specific time with the telescopic prevention plate at the bottom to drain the water, and then the weight is measured. Methods for obtaining the weight measurement results of deposits collected from the separation membrane module include methods for measuring the weight of the deposits in a wet state, methods for measuring the weight in an extremely dry state, and methods for measuring the weight after combustion. Preferably, X-ray photoelectron spectroscopy, microscopic observation, and infrared spectroscopy are used as methods for obtaining structural analysis results and elemental composition analysis results of deposits collected from the separation membrane module.

[0032] In this invention, the analysis results of each degradation factor are quantified as an amount corresponding to a portion of the performance change that occurs in the separation membrane module. By quantifying the performance change and the influence of each degradation factor in the same units, it becomes possible to accumulate them, and the breakdown of the performance change can be expressed as the sum of each degradation factor. In other words, it quantifies the extent to which various factors that degrade the performance of the separation membrane module affect the water permeability and solute removal performance, which is separation efficiency. Then, the different measurement results of individual factors are converted into the same units, in this case "water permeability" and "solute removal performance," as the degree of influence on the change in water permeability and the change in solute removal performance, allowing for the diagnosis and inspection of the degradation factors of the separation membrane module. Furthermore, due to time and equipment constraints, it may not be possible to cover all the analysis and measurement results necessary for quantifying the degradation factors. In such cases, when the breakdown of the performance change is shown as the sum of each degradation factor, it may not be possible to bridge the gap between the performance in the first state and the performance in the second state. In this case, by calculating the difference between the performance difference between the first and second states and the cumulative performance impact of all quantified degradation factors, and treating this as the amount of degradation due to unspecified factors, it is possible to quantitatively represent the influence of factors that have not yet been quantified at that point. Unspecified factors include degradation factors that have not been analyzed at that point, analytical errors, measurement errors, and unknown factors for which analytical methods have not been established.

[0033] As a method for quantifying an amount corresponding to a part of the amount of performance change of the present invention, first, using the analysis results and / or measurement results corresponding to each deterioration factor, results related to each deterioration factor are quantitatively obtained. For example, in the case of the ratio of physical damage and chemical deterioration, the measurement results of sodium chloride removal performance and magnesium sulfate removal performance in the second state of the separation membrane module are obtained. In the case of chemical deterioration, particularly oxidation deterioration, for example, the membrane surface element analysis results and the element abundance ratio may be obtained. In the case of deposits, for example, the performance measurement results before and after cleaning the deposits are obtained. In the case of compaction, for example, the plant operation history data and the like are acquired. Further, relational expressions for converting these analysis results and / or measurement results into the same unit as the separation membrane module are derived and used. That is, the performance evaluation method of the separation membrane module of the present invention can quantify how much deterioration has affected the performance evaluation results such as water permeation performance from the results that have been judged separately by separate evaluation results until now, and thereby clearly grasp the strength of the deterioration factors.

[0034] As a specific method for deriving the relational expression, for example, the contribution ratios of physical damage and chemical deterioration can be calculated by using the method (II) of the examples. The amount of performance influence due to deposits can be calculated by using, for example, the method (V) of the examples. The amount of performance change due to oxidation deterioration among chemical deteriorations can be calculated by using, for example, the method (IV) of the examples. Also, the amount of performance change due to compaction can be calculated by, for example, the method (VI) of the examples.

[0035] In one embodiment of the present invention, it is preferable that the plurality of deterioration factors to be analyzed as the factors causing the difference in the performance measurement results, that is, the amount of performance change, include physical damage, chemical deterioration, and deposits. When broadly classifying the deterioration factors that can occur in a water treatment plant, the main factors can be classified into these three types, and by quantifying the amount of performance influence caused by each of them, the main factors of the performance change that occurred in the separation membrane module can be appropriately specified. In order to clarify the deterioration factors in more detail, it is desirable to distinguish and analyze compaction and other unknown factors for which analysis methods have not been established.

[0036] In this invention, compaction is one of the factors that affect the performance of a reverse osmosis membrane element. The separation membrane of a separation membrane module includes a membrane functional layer near the surface and a support layer that supports that surface layer. The aforementioned physical damage, chemical degradation, and deposits are degradation factors originating from the surface layer. On the other hand, compaction is a degradation factor for the entire separation membrane, including the support substrate. For example, in the case of a reverse osmosis membrane, compaction occurs when the separation membrane is compressed by the pressure difference between the treated water and the permeate, resulting in a change in water permeability or salt permeability. In such cases of compaction, it is preferable that the analysis results and / or measurement results that correlate with the degree of compaction include one or more of the following: performance measurement results of the separation membrane module, performance measurement results of the separation membrane taken from the separation membrane module, measurement results of operating conditions when using the separation membrane module, and structural analysis results of the separation membrane taken from the separation membrane module.

[0037] Furthermore, when calculating the contribution amounts of physical damage and chemical degradation based on the contribution ratios of physical damage and chemical degradation, it is preferable to calculate the performance impact amounts of physical damage and chemical degradation, respectively, by multiplying the result obtained by subtracting the known performance impact amount from the change in performance of the separation membrane module due to the change from the first state to the second state by the contribution ratio of physical damage and the contribution ratio of chemical degradation, respectively. Here, the known performance impact amount refers to the performance impact amount quantified as an amount corresponding to a part of the change in performance. Furthermore, it is preferable that the known performance impact amount includes at least the performance impact amount due to deposits, and more preferably the performance impact amount due to compaction.

[0038] This is a finding discovered by the authors based on the structure and degradation mechanism of reverse osmosis membranes. Physical damage and chemical degradation occur in the membrane's separation functional layer, while deposits cause degradation due to coating and pore blockage of the separation membrane, and compaction causes degradation due to compression of the membrane's support layer; each has a different degradation mechanism. When calculating the impact of physical damage, which is degradation that occurs in the membrane's functional layer, and chemical degradation, which is also degradation that occurs in the membrane's functional layer, based on the contribution ratio of both, it is preferable to multiply the result of subtracting the known performance impact due to degradation occurring outside the functional layer from the total amount of degradation by the contribution ratio of physical damage and the contribution ratio of chemical degradation, respectively, in order to accurately calculate the degradation impact that occurs in the functional layer using the contribution ratio. In particular, deposits are a major degradation factor that can occur in water treatment plants, so it is important to subtract them in advance as a known performance impact.

[0039] Furthermore, in the process of quantifying degradation factors as an amount corresponding to a portion of the performance change of the reverse osmosis membrane element, there are degradation factors that can be quantified as absolute values, independent of the difference between the performance in the first state and the performance in the second state, and degradation factors that depend on the difference between the performance in the first state and the performance in the second state. Examples of the former include the influence of deposits and the influence of compaction, while examples of the latter include the influence of physical damage and the influence of chemical degradation. These can be quantified using the method described in the examples. Here, the influence of physical damage and the influence of chemical degradation are calculated as the relative contribution ratios of physical damage and chemical degradation, so a possible means of quantifying them as an amount corresponding to a portion of the performance change of the reverse osmosis membrane element is to multiply the difference between the performance in the first state and the performance in the second state by the contribution ratio. However, the difference between the performance in the first state and the performance in the second state includes influences from a wide variety of degradation factors, and it is difficult to accurately separate these influences into influences from physical damage and chemical degradation. The separation membrane module condition diagnosis method of the present invention classifies degradation factors by focusing on the main areas affected by degradation.

[0040] Degradation mainly occurring on the separation functional layer includes physical damage and chemical degradation, degradation mainly occurring within the separation functional layer includes deposits, and degradation mainly occurring in the support layer and substrate includes compaction. Considering that physical damage and chemical degradation affect different locations than deposits and compaction, a preferred procedure for accurately calculating the contributions of physical damage and chemical degradation is to subtract the influence of deposits and compaction from the difference between the performance in the first state and the performance in the second state, and then multiply the result by the contribution ratios of physical damage and chemical degradation. For the same reason, in the method for calculating the contribution ratios of physical damage and chemical degradation, it is preferable that the separation performance of the separation membrane module for the two types of solutes used is the separation performance after cleaning the separation membrane module. That is, it is preferable to have a step of chemically cleaning the separation membrane module before the step of calculating the contribution ratios of physical damage and chemical degradation. Here, the separation performance after cleaning the separation membrane module may be determined, for example, by actually cleaning the separation membrane module and then measuring its performance. Alternatively, the membrane taken from the separation membrane module may be cleaned using a method such as that shown in Example (V), and the cleaning recovery rate may be confirmed by comparing the performance before and after cleaning. Based on these results, the post-cleaning performance of the separation membrane module may be estimated.

[0041] [Diagnostic Program for Separation Membrane Module, Recording Medium] Another embodiment of the present invention is a condition diagnostic program for a separation membrane module, which causes a computer to function as a data input means for inputting performance measurement results before and after use of the separation membrane module and analysis results correlated with each degradation factor into the computer; a performance change amount calculation means for calculating the performance change amount from the performance measurement results of a first state and a second state; a quantification means for quantifying each analysis result correlated with each degradation factor as an amount corresponding to a part of the performance change amount, a data recording means for recording the input data in the computer, and a condition diagnostic means for determining the degree of each degradation factor in the performance change amount by accumulating the quantified results of each degradation factor based on the input and / or recorded data. This embodiment causes a computer having each of these means to function for diagnosing the degradation state of the separation membrane module. The program of this embodiment can be recorded in a recording device such as the computer's memory or hard disk, and the form of recording is not particularly limited. Another embodiment of the present invention is a recording medium on which a degradation analysis program for a composite semipermeable membrane is stored.

[0042] [Operation Method of Separation Membrane Module] By utilizing the diagnostic results obtained by the separation membrane module condition diagnosis method of the present invention, the operation method of the separation membrane module and the operation method of a water treatment plant equipped with the separation membrane module can be improved. For example, if the diagnosis determines that physical damage is the main cause, the deterioration factors of the separation membrane module can be eliminated and the operating condition improved by taking at least one of the following measures: checking and preventing the inflow of foreign matter, preventing sudden increases or decreases in operating pressure, and replacing the deteriorated separation membrane module.

[0043] If deposits are determined to be the primary cause, countermeasures such as confirming and preventing the inflow of deposits, cleaning the separation membrane module according to the type of deposit, adding deposit-preventing chemicals, and replacing deteriorated separation membrane modules can be implemented to eliminate the factors causing deterioration of the separation membrane module and improve its operating condition. Typical examples of deposit-preventing chemicals include chemicals that prevent scale formation and chemicals that prevent biofouling. Examples of chemicals that prevent scale formation include scale inhibitors containing polyacrylates, polyphosphates, and phosphonates. Examples of chemicals that prevent biofouling include disinfectants containing 2,2-dibromo-3-nitrilopropionamide, 2-methyl-4-isothiazolin-3-one, and 5-chloro-2-methyl-4-isothiazolin-3-one.

[0044] If chemical degradation is determined to be the main cause, the deterioration factors of the separation membrane module can be eliminated and the operating condition can be improved by taking at least one of the following measures: checking and preventing the inflow of oxidizing agents, checking and preventing the inflow of strong acids or strong bases, and replacing the deteriorated separation membrane module. If consolidation is determined to be the main cause, the deterioration factors of the separation membrane module can be eliminated and the operating condition can be improved by taking at least one of the following measures: checking the operating pressure and temperature, operating under conditions that avoid excessively high pressure and temperature, and replacing the deteriorated separation membrane module. Furthermore, in the condition diagnosis method of the present invention, when the ratio of the performance in the second state to the performance in the first state is taken, if the ratio of the water permeability performance is 0.8 times or less or 1.2 times or more, it is determined that a significant change in water permeability has occurred, and it is preferable to take measures focusing on the main cause that affected water permeability in order to improve the operating condition of the plant. It is even more preferable to take measures when the ratio of the water permeability performance is 0.9 times or less or 1.1 times or more.

[0045] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these. First, the analytical and measurement methods used in each example and reference example will be described. (I) Method for measuring the performance of the separation membrane module As shown in Figure 2 above, the method used was to separate the water to be treated into permeate and concentrated water by supplying the water to be treated under pressure to the pressure vessel while the separation membrane module was loaded into the pressure vessel. In addition, the solute concentration, temperature, pH, pressure, flow rate, etc. of the water to be treated, permeate and concentrated water were measured when the water to be treated was supplied under pressure to the pressure vessel. Based on the measurement results, the water permeability and solute removal performance were calculated. The reverse osmosis membrane element loaded into the separation membrane module was measured for performance using the measurement method shown in Figure 3, and this was used as the performance of the reverse osmosis membrane element. Here, pure water was used as the solvent and sodium chloride was used as the solute. The sodium chloride concentration of the water to be treated, permeate and concentrated water was determined by measuring the electrical conductivity of each solution and using the previously determined relationship between electrical conductivity and sodium chloride concentration. The sodium chloride concentration, temperature, pH, pressure, and flow rate conditions of the treated water during measurement are described in the Examples and Reference Examples.

[0046] (II) Method for Analyzing the Effects of Physical Damage and Chemical Degradation As a method for analyzing the effects of physical damage, the method used in Method (I) above was applied, using either a solution containing magnesium sulfate as the solute instead of sodium chloride, or a solution containing both sodium chloride and magnesium sulfate as the solutes. After determining the sodium chloride removal performance and magnesium sulfate removal performance, the contribution rates of physical damage and chemical degradation were calculated based on these results. The calculations used were the degradation relation equations due to physical damage and the degradation relation equations due to chemical degradation. Specifically, the initial performance and the sodium chloride permeability and magnesium sulfate permeability after degradation were plotted on a plane with sodium chloride permeability on the x-axis and magnesium sulfate on the y-axis, respectively, to determine the contribution rates of physical damage and chemical degradation.

[0047] The degradation relationship due to chemical degradation was investigated by immersing multiple unused reverse osmosis membrane pieces in 1.0 wt% hypochlorous acid and collecting them after staggering the immersion time for each piece, thereby creating membrane pieces with different degrees of chemical degradation. Using these membrane pieces, performance evaluation tests were conducted with sodium chloride solution and magnesium sulfate solution to investigate the correlation between the degradation impact of chemical degradation on sodium chloride removal performance and magnesium sulfate removal performance. A linear relationship was confirmed, and a linear function was derived. The degradation relationship due to physical damage was theoretically formulated by assuming a salt permeation phenomenon caused by physical damage to the reverse osmosis membrane. When physical damage occurs to the reverse osmosis membrane, treated water mixes with permeate from the damaged area, resulting in increased salt permeation. At this time, assuming that the amount of salt permeation is constant regardless of the type of salt, a linear function was derived in which the degradation impact of physical damage on sodium chloride removal performance and magnesium sulfate removal performance are equal. The concentration of magnesium sulfate in each solution was determined by analyzing each solution using ion chromatography.

[0048] (III) Method for analyzing the effects of physical damage by staining As a method for analyzing the effects of physical damage to the membrane by staining, a reverse osmosis membrane piece cut from a reverse osmosis membrane element was used, and as shown in Figure 3, the treated water was supplied under pressure to the pressure vessel with the separation membrane loaded into the pressure vessel, thereby separating the treated water into permeate water and concentrated water. Here, a staining solution (dissolved in Basic Violet 1 (manufactured by Tokyo Chemical Industry Co., Ltd.)) was used as the treated water, and the membrane piece was stained by passing the water under pressure at an operating pressure of 1.5 MPa for more than 30 minutes using a cross-flow at a linear velocity of 0.1 to 0.2 cm / sec, and then removing the excess staining solution by passing pure water through it. The stained membrane piece was observed or analyzed.

[0049] (IV) Analysis Method for the Effects of Oxidative Degradation For the analysis of the effects of oxidative degradation, elemental composition analysis was performed using reverse osmosis membrane fragments cut from reverse osmosis membrane elements. The reverse osmosis membranes were rinsed with distilled water and vacuum-dried for 6 hours using LHV-122 (manufactured by ESPEC Corporation) and TSW-50 (manufactured by Sato Vacuum Co., Ltd.). For reverse osmosis membranes collected from reverse osmosis membrane elements used in the plant, surface contaminants were removed by immersion in acid and base chemicals, then the surface to be measured was gently wiped with cotton wool thoroughly moistened with distilled water, the entire reverse osmosis membrane was rinsed with distilled water, and then vacuum-dried. X-ray photoelectron spectroscopy (XPS) was used as the elemental composition analysis method. Specifically, measurements were taken by irradiating the separation functional layer side with a light source using a Quantera SXM (manufactured by ULVAC-PHI, Inc.). The measurement conditions were monochromatic Al K as the excitation X-ray. α１,２ The X-ray beam was set to 1486.6 eV, with an X-ray diameter of 200 μm and a photoelectron detection angle of 90°. Furthermore, 9-point smoothing was performed to correct the horizontal axis, resulting in a C1s main peak of 284.6 eV.

[0050] (V) Method for measuring the effect of deposits As a method for measuring the effect of deposits, a reverse osmosis membrane piece cut from a reverse osmosis membrane element was used, and as shown in Figure 3, the membrane piece was loaded into a pressure vessel, and the water to be treated was supplied to the pressure vessel under pressure, thereby separating the water to be treated into permeate and concentrated water. In addition, values ​​such as solute concentration, temperature, pH, pressure, and flow rate of the water to be treated, permeate, and concentrated water were measured, and the water permeability performance and solute removal performance were calculated from the relationship between the flow rate and solute concentration of the water to be treated, permeate, and concentrated water. Here, pure water was used as the solvent and sodium chloride as the solute. The sodium chloride concentrations of the water to be treated, permeate, and concentrated water were the same as in (I) Method for measuring the performance of the reverse osmosis membrane element. To measure the effect of adhering substances, two groups of membrane samples were prepared: Group A, which were not washed after cutting, and Group B, which were each immersed overnight in one or more solutions containing an acidic solution, an alkaline solution, and a chelating agent solution. The performance of Group A and Group B was then evaluated.

[0051] (VI) Method for Analyzing the Effects of Consolidation As a method for analyzing the effects of consolidation of the separation membrane, we used operating history information from when the reverse osmosis membrane element under analysis was used in a water treatment plant. Consolidation of the separation membrane occurs with the use of the separation membrane, and the degree of consolidation depends on the material and specifications of the separation membrane, the operating time, the temperature of the liquid being treated, the pressure of the liquid being treated, etc. Therefore, by subjecting the separation membrane to operation at various treated water pressures, treated water temperatures, and operating times in advance and determining the performance of the separation membrane, it is possible to experimentally derive a relationship between the treated water pressure, treated water temperature, operating time and the amount of consolidation effect on the separation membrane. By substituting the information on treated water pressure, treated water temperature, and operating time obtained from the operating history into the relationship obtained in this way, the degree of decrease in water permeability caused by consolidation in the reverse osmosis membrane was calculated.

[0052] <Reference Example 1> In a seawater desalination plant using reverse osmosis membrane elements as separation membrane modules, a deterioration in the quality of the permeate was observed. Therefore, the reverse osmosis membrane elements used in the plant were removed from the vessels and inspected. The measurement methods (I) and (II) were used, and the conditions in Table 1 were applied. The performance of the reverse osmosis membrane elements was measured, and the results, converted to performance at a recovery rate of 8%, showed a sodium chloride removal rate of 99.52% (permeability 0.48%) and a permeate volume of 22.60 m³. ３ / d, the removal rate of magnesium sulfate was 99.95% (transmission rate 0.05%). The initial performance measured under the same conditions beforehand showed a sodium chloride removal rate of 99.85% (transmission rate 0.15%) and a permeate volume of 33.20 m³. ３ / d, the removal rate of magnesium sulfate was 99.95% (permeability 0.05%). From these results, the permeability of sodium chloride was 3.2 times the initial ratio, and the permeability of magnesium sulfate was 1.0 times the initial ratio. Since the decrease in magnesium sulfate decomposition performance was smaller than the decrease in sodium chloride separation performance, it was determined that chemical degradation occurred, rather than physical damage. Furthermore, using the method described in (II) above, the contribution ratio of physical damage to chemical degradation was calculated to be 0:100, and it was determined that the decrease in separation performance was due solely to chemical degradation.

[0053] The effect of adhering substances was investigated using the method described in (V) above. For the preparation of membrane group B, the membranes were immersed overnight at 25°C in citric acid solution, oxalic acid solution, sodium hexametaphosphate solution, sodium hydroxide solution, tetrasodium ethylenediaminetetraacetate solution, and pure water, respectively. Table 2 shows the conditions and the sodium chloride removal rates for membrane group A and membrane group B.

[0054]

[0055] The sodium chloride removal rate for membrane group A was an average of 99.38% (transmittance 0.62%), and the membrane permeation flux was 0.82 m. ３ / m ２ The result was / d. In the membrane sample immersed in citric acid, which showed the highest membrane permeation flux, the removal rate of sodium chloride was an average of 99.46% (permeability 0.54%), and the membrane permeation flux was 0.92 m. ３ / m ２The result was / d. Immersion in citric acid improved the sodium chloride permeability to 0.87 times and the membrane permeation flux to 1.12 times, confirming that the performance was restored by washing. Since the membrane performance was restored by washing, it was determined that fouling on the membrane surface is one of the factors causing deterioration of the reverse osmosis membrane element. The effect of physical damage was analyzed using the method described in (III) above. When the stained membrane pieces were observed visually, no stained areas were found on the membrane pieces. From this, it was determined that no physical damage had occurred on the membrane surface. The effect of compaction was analyzed using the method described in (VI). The operating history of the reverse osmosis membrane element under analysis was 2.5 years of operation, with a maximum treated water temperature of 37.4°C, a minimum treated water temperature of 18.4°C, and a maximum treated water pressure of 70.0 bar. From this, it was estimated that the water permeability performance decreased to 0.76 times the initial performance due to compaction, and it was determined that compaction is one of the factors causing deterioration. The effects of oxidative degradation were analyzed using method (IV). The ratio of halogen elements to carbon elements in the elemental composition ratio of the film surface was 0.0072. Since halogens were detected, it was determined that oxidative degradation of the film surface was one of the degradation factors. Taking these inspection results together, it was determined that fouling, oxidative degradation, and compaction were factors in the performance degradation. However, it was not possible to calculate the contribution rate or amount of each of these multiple factors, i.e., the amount corresponding to the performance impact on the separation membrane module, and therefore the main cause could not be identified.

[0056] <Example 1> Using the analysis results of consolidation in Reference Example 1, the performance impact on the reverse osmosis membrane element due to consolidation was calculated. By multiplying the initial performance of the reverse osmosis membrane element by 0.76 times as estimated in Reference Example 1 and taking the difference from the initial performance, the amount corresponding to the impact on water permeability, i.e., the performance impact, was -7.3 m ３It was estimated to be / d. Also, the amount corresponding to the influence of salt permeability due to the decrease in water permeability, that is, the performance influence amount, was estimated to be 0.04%. Using the evaluation results of the reverse osmosis membrane in Reference Example 1, the performance influence amount caused by fouling on the reverse osmosis membrane element was calculated. Since the sodium chloride permeability was improved by 0.87 times and the membrane permeation flux was improved by 1.12 times by immersion in citric acid, it was assumed that the entire membrane in the reverse osmosis membrane element was uniformly affected by fouling. Based on this assumption, the performance of the reverse osmosis membrane element in the fouled state was calculated by multiplying the initial salt permeation performance of the reverse osmosis membrane by the reciprocal of 0.87 and multiplying the initial water permeation performance of the reverse osmosis membrane by the reciprocal of 1.12, and the difference from the initial performance was taken. The water permeability influence amount was -5.7 m ３ / d, and the salt permeability influence amount was determined to be 0.04%.

[0057] Furthermore, in Reference Example 1, since the ratio of physical damage to chemical degradation was 0:100, the performance difference between the first state: before use of the separation membrane module and the second state: after use of the separation membrane module was divided into physical damage and chemical degradation. First, the performance difference between the first state and the second state was calculated, and then the amount of influence due to physical damage and the amount of damage due to chemical degradation were calculated by multiplying the value obtained by subtracting the performance influence amount due to deposits and the performance influence amount due to densification from the performance difference by the ratio of physical damage to chemical degradation. As a result, out of the 0.25% change in the sodium chloride permeability, it was quantified that the physical damage was 0.00% and the chemical degradation was 0.25% as the factors. Also, out of the water permeability influence, 0.0 m ３ / d corresponds to the amount of performance influence due to physical damage, and 2.4 m ３ / d was quantified as the amount corresponding to the performance impact due to chemical degradation. Furthermore, in order to subdivide the breakdown of physical damage, the ratio of stained areas in the membrane staining results in Reference Example 1 was determined by image analysis, and the amount corresponding to the performance impact was calculated using the previously determined relationship between the stained area ratio and the reverse osmosis membrane performance change, thereby quantifying only the physical damage that occurred in the membrane. As a result, no physical damage occurred in the membrane. Furthermore, in order to subdivide the breakdown of chemical degradation, the performance impact on the reverse osmosis membrane element was calculated using the halogen abundance ratio value from the XPS analysis results in Reference Example 1. Based on the previously determined relationship between the halogen abundance ratio of the reverse osmosis membrane and the performance change, the water permeability impact (amount corresponding to the performance impact) was calculated to be -0.8 m ３ The effect of salt permeability (corresponding to the performance impact) was quantified as -0.04%.

[0058] Based on the above, the performance impact of each degradation factor was quantitatively calculated as a portion of the change in performance of the reverse osmosis membrane element. The difference in performance of the reverse osmosis membrane element before and after use is shown by the cumulative change in performance due to the degradation factors (Table 3). Figure 4 illustrates the results of Table 3 as a waterfall chart, allowing for a quantitative comparison of the change in performance due to all degradation factors. From Figure 4(a) NaCl permeability, the decrease in desalination rate was determined to be due to consolidation, fouling, and chemical degradation, with chemical degradation being the primary cause. From Figure 4(b) permeate water volume, the decrease in permeability was determined to be due to consolidation and fouling, with consolidation being the primary cause. Based on these quantitative results, the permeability decreased to 0.68 times, and the salt permeability increased to 3.20 times. Therefore, focusing on the main causes of both the decrease in permeability and the decrease in desalination rate, methods for improving plant operation were considered. Focusing on chemical degradation and compaction, the plant's operating condition was improved by implementing operational improvements such as preventing the inflow of oxidizing agents, changing pH conditions during membrane cleaning, reviewing operating pressure, and replacing deteriorated reverse osmosis membrane elements.

[0059]

[0060] <Reference Example 2> In an industrial water treatment plant using reverse osmosis membrane elements, a trend of deteriorating permeate water quality and decreasing permeate volume was observed. Therefore, the reverse osmosis membrane elements used in the plant were removed from the vessels and inspected. The measurement methods described in (I) and (II) above were used, under the conditions shown in Table 4. The performance of the reverse osmosis membrane elements was measured, and the results, converted to performance at a recovery rate of 15%, showed a sodium chloride removal rate of 93.00% (permeability 7.00%) and a permeate volume of 20.00 m³. ３ / d, the removal rate of magnesium sulfate was 98.44% (transmission rate 1.56%). The initial performance of this reverse osmosis membrane element, measured under the same conditions beforehand, was 99.77% for sodium chloride removal rate (transmission rate 0.23%) and 53.40 m³ of permeate. ３ On day d, the removal rate of magnesium sulfate was 99.92% (permeability 0.08%), the permeability of sodium chloride was 30.4 times that of the initial performance, and the permeability of magnesium sulfate was 19.5 times that of the initial performance. Since the decrease in magnesium sulfate decomposition performance was smaller than the decrease in sodium chloride separation performance, it was determined that chemical deterioration was the main cause of the deterioration compared to physical damage. Furthermore, using the method described in (II) above, the contribution ratio of physical damage to chemical deterioration was calculated to be 0:100, and it was determined that the decrease in separation performance was due solely to chemical deterioration.

[0061] The effect of adhering substances was investigated using the method described in (V) above. For the preparation of membrane group B, the treatment conditions in Table 5 were used, and the sodium chloride removal rates for membrane group A and membrane group B were as shown in Table 5.

[0062]

[0063] The sodium chloride removal rate for membrane group A was an average of 88.39% (transmittance 11.61%), and the membrane permeation flux was 0.89 m. ３ / m ２ The result was / d. The membrane sample with the highest water permeability was the one immersed in citric acid, with an average sodium chloride removal rate of 98.01% (transmission rate of 1.99%) and a membrane permeation flux of 2.29 m ３ / m ２The result was / d. Furthermore, immersion improved the sodium chloride permeability to 0.11 times and the membrane permeation flux to 2.58 times, confirming that the performance was restored by the cleaning effect. Since the membrane performance was restored by cleaning, it was determined that fouling on the membrane surface is one of the factors causing deterioration of the reverse osmosis membrane element.

[0064] The effects of physical damage were analyzed using method (III) above. Visual inspection of the stained membrane fragments revealed no stained areas. Therefore, it was determined that no physical damage occurred on the membrane surface. The effect of consolidation was not determined because the operating history information of the seawater desalination plant was unknown. The effects of oxidative degradation were analyzed using method (IV). As a result, the ratio of halogen elements to carbon elements in the elemental composition ratio of the membrane fragment surface was 0.0087. Since halogens were detected, it was determined that oxidative degradation of the membrane surface was the cause of the performance degradation. Combining these inspection results, it was determined that fouling and oxidative degradation were the causes of the performance degradation. However, it was not possible to calculate the contribution rate or amount of each of these multiple factors, i.e., the amount corresponding to the performance impact of the separation membrane module.

[0065] <Example 2> Using the inspection results from Reference Example 2, the following additional analysis was performed. Using the evaluation results of the reverse osmosis membrane in Reference Example 2, the amount of performance impact on the reverse osmosis membrane element due to fouling was calculated. Since immersion in citric acid improved the sodium chloride permeability to 0.11 times and the membrane permeation flux to 2.58 times, it was assumed that the entire membrane within the reverse osmosis membrane element was uniformly affected by fouling. The performance of the reverse osmosis membrane element under the influence of fouling was calculated by multiplying the initial salt permeability performance of the reverse osmosis membrane by the reciprocal of 0.11 and the initial water permeability performance of the reverse osmosis membrane by the reciprocal of 2.58. By taking the difference from the initial performance, the amount corresponding to the change in water permeability performance was -34.71 m ３ / d, the change in salt permeability performance was 4.28%. In Reference Example 2, the ratio of physical damage to chemical degradation was 0:100, so the difference in performance before and after use of the separation membrane module was divided into physical damage and chemical degradation. First, the difference in performance before and after use was calculated, and then the amount of influence due to physical damage and the amount of damage due to chemical degradation were calculated by multiplying the value obtained by subtracting the performance influence due to deposits from that amount by the ratio of physical damage to chemical degradation. As a result, it was quantified that 0.00% of the change in salt permeability was due to physical damage and 2.49% was due to chemical degradation. In addition, of the influence of permeate water volume, 0.0 m ３ / d is the amount corresponding to the performance impact due to physical damage, 1.31 m ３ / d was quantified as the amount corresponding to the performance impact due to chemical degradation. Furthermore, in order to subdivide the breakdown of physical damage, the same analysis as in Example 1 was performed, and no physical damage occurred to the membrane. In addition, in order to subdivide the breakdown of chemical degradation, the performance impact on the reverse osmosis membrane element was calculated using the halogen abundance ratio value from the XPS analysis results in Reference Example 2. Based on the previously determined relationship between the halogen abundance ratio of the reverse osmosis membrane and the change in performance, the water permeability impact (amount corresponding to the performance impact) was calculated to be 1.82 m ３ The salt permeability effect (equivalent to the performance effect) was quantified as -0.04%.

[0066] Based on the above, the performance impact of each degradation factor was quantitatively calculated as a portion of the performance impact of the reverse osmosis membrane element. The difference in reverse osmosis membrane element performance before and after use is shown by the cumulative performance impact of the degradation factors (Table 6). This made it possible to quantitatively compare the performance impact of all degradation factors. From Figure 5(a), it was determined that the decrease in desalination rate was due to fouling of deposits and chemical degradation, with fouling being the main cause. From Figure 5(b), it was determined that the decrease in water permeability was also mainly due to fouling of deposits. Based on these quantitative results, similar to Example 1, the plant operating condition was improved by implementing operational improvement methods focusing on fouling, such as preventing the inflow of deposit-causing substances, adding chemicals to prevent deposit formation, and replacing deteriorated separation membrane modules.

[0067]

[0068] <Reference Example 3> In a wastewater treatment plant using reverse osmosis membrane elements, a trend of deteriorating permeate water quality and decreasing permeate volume was observed. Therefore, the reverse osmosis membrane elements used in the plant were removed from the vessels and inspected. The measurement methods (I) and (II) were used, and the conditions in Table 7 were applied. The performance of the reverse osmosis membrane elements was measured, and the results, converted to performance at a recovery rate of 15%, showed a sodium chloride removal rate of 98.30% (permeability 1.70%) and a permeate volume of 30.24 m³. ３ / d, the removal rate of magnesium sulfate was 98.47% (transmission rate 1.53%). The initial performance measured under the same conditions beforehand showed a sodium chloride removal rate of 99.86% (transmission rate 0.14%) and a permeate volume of 44.42 m³. ３ On day d, the removal rate of magnesium sulfate was 99.95% (permeability 0.05%). That is, the permeability of sodium chloride was 12.1 times that of the initial performance, and the permeability of magnesium sulfate was 30.8 times that of the initial performance. Since the decrease in magnesium sulfate decomposition performance was greater than the decrease in sodium chloride separation performance, it was determined that physical damage was the main cause of the deterioration compared to chemical damage. Furthermore, using method (II), the contribution ratio of chemical deterioration to physical damage was calculated to be 6:94, and it was determined that the decrease in separation performance was mainly due to physical damage.

[0069] Upon examining the membrane surface after disassembling the separation membrane element, organic matter-based deposits were found, leading to the conclusion that fouling of the membrane surface was a factor in the deterioration of the reverse osmosis membrane element. The effects of physical damage were analyzed using the method described in (III) above. Visual inspection of the stained membrane fragments revealed stained areas. From this, it was determined that physical damage had occurred on the membrane surface.

[0070] The effect of consolidation using method (VI) could not be analyzed because the operating history information of the seawater desalination plant was unknown. The effect of oxidative degradation was analyzed using method (IV). As a result, the ratio of halogen elements to carbon elements in the elemental composition ratio of the membrane surface was 0.0017. Since halogens were detected, it was determined that oxidative degradation of the membrane surface was the cause of the performance degradation. Combining these inspection results, it was determined that fouling, oxidative degradation, and physical damage were the causes of the performance degradation. However, it was not possible to calculate the contribution rate or amount of each of these multiple factors, i.e., the amount corresponding to the performance impact of the separation membrane module, and therefore the main cause could not be identified.

[0071] <Example 3> Using the inspection results from Reference Example 3, the following additional analysis was performed. Taking advantage of the fact that the ratio of physical damage to chemical degradation was 94:6 in Reference Example 3, the performance difference between the first state (before use of the separation membrane module) and the second state (after use of the separation membrane module) was divided into physical damage and chemical degradation. First, the performance difference between the separation membrane module before and after use was calculated. Then, the performance impact due to deposits was subtracted from this difference, and the resulting value was multiplied by the ratio of physical damage to chemical degradation to calculate the impact due to physical damage and the amount of damage due to chemical degradation. As a result, it was found that 1.47% of the change in salt permeability was due to physical damage and 0.08% was due to chemical degradation. Furthermore, of the influence of permeate volume, 0.08 m ３ / d is the amount corresponding to the performance impact due to physical damage, 0.43 m ３ / d was quantified to represent the performance impact due to chemical degradation.

[0072] Furthermore, to further subdivide the physical damage, the ratio of stained areas in the membrane staining results of Reference Example 3 was determined by image analysis, and the amount of performance change was calculated using a previously determined relationship between the stained area ratio and the reverse osmosis membrane performance change, thereby quantifying only the physical damage that occurred in the membrane. As a result, it was determined that the physical damage that occurred in the membrane accounted for almost all of the physical damage. Furthermore, to further subdivide the chemical degradation, the performance impact on the reverse osmosis membrane element was calculated using the halogen abundance ratio values ​​from the XPS analysis results of Reference Example 3. Based on the previously determined relationship between the halogen abundance ratio of the reverse osmosis membrane and the performance change, the water permeability impact (amount equivalent to the performance impact) was calculated to be 0.43 m ３ The salt permeability effect (equivalent to the performance effect) was quantified as -0.04%.

[0073] Based on the above, the performance impact of each degradation factor was quantitatively calculated as a portion of the change in the performance of the reverse osmosis membrane element. The difference in the performance of the reverse osmosis membrane element before and after use is shown by the sum of the performance changes due to each degradation factor (Table 8). Here, for the permeate volume, the difference in the performance of the reverse osmosis element before and after use could not be filled by the sum of the performance changes alone, so this difference was treated as an unspecified factor and was -14.69 m ３ The value was set to / d. This allowed for a quantitative comparison of the performance changes due to all degradation factors. From Figure 6(a), it was determined that the decrease in desalination rate was due to physical damage and chemical degradation, with physical damage being the primary cause. From Figure 6(b), it was determined that the decrease in water permeability was primarily due to an unspecified factor. Based on these quantitative results, the plant's operating condition was improved by implementing measures to improve operation, focusing on physical damage, such as preventing the inflow of foreign matter and replacing the deteriorated separation membrane module. Furthermore, as a breakdown of the unspecified factors, fouling was observed on the membrane surface, so the plant's operating condition was focused on fouling, and the plant's operating condition was improved by implementing measures to prevent the inflow of substances causing fouling and adding chemicals to prevent the formation of fouling.

[0074]

[0075] 1: Reverse osmosis membrane 2: Permeate water channel material 3: Water to be treated channel material (net spacer) 4: Water collection pipe 5: Telescopic prevention plate 6, 6': Water to be treated 7, 7': Permeate water 8: Concentrated water 9: Pressure vessel 11: Water to be treated 12: Water to be treated tank 13: Water to be treated supply line 14: Pressurized supply means 15: Reverse osmosis membrane 16: Reverse osmosis membrane evaluation cell 17: Concentrated water 18: Permeate water 19: Concentrated water line 20: Permeate water line 21: Pressure gauge 22: Concentrated water flow meter 101: Concentrated water circulation valve 201: Concentrated water drain valve 202: Permeate water drain valve

Claims

1. A method for diagnosing the condition of a separation membrane module for separating treated water into concentrated water and permeate, comprising the steps of: determining the amount of change in the performance of the separation membrane module due to the change from the first state to the second state based on the difference between the performance measurement result of the separation membrane module in a first state and the performance measurement result of the separation membrane module in a second state; obtaining analysis results that correlate with the degree of deterioration for each of a plurality of deterioration factors that occurred in the change from the first state to the second state; quantifying the analysis results of each deterioration factor as an amount corresponding to a part of the amount of change in the performance of the separation membrane module; and indicating the amount of contribution of each deterioration factor to the amount of change in the performance of the separation membrane module by accumulating the plurality of quantitative results calculated in the quantification step.

2. The method for diagnosing the condition of a separation membrane module according to claim 1, wherein the first state is the state of the separation membrane module before use and / or before storage, and the second state is the state of the separation membrane module after use and / or after storage.

3. The method for diagnosing the condition of a separation membrane module according to claim 1 or 2, characterized in that the change in the performance of the separation membrane module is the change in water permeability and / or the change in solute removal performance.

4. A method for diagnosing the condition of a separation membrane module according to any one of claims 1 to 3, characterized in that the plurality of deterioration factors include physical damage, chemical deterioration, and deposits.

5. A method for diagnosing the condition of a separation membrane module according to any one of claims 1 to 4, characterized in that, for each of the plurality of deterioration factors, in the step of obtaining an analysis result correlated with the degree of deterioration, the performance influence due to deposits and the performance influence due to compaction are quantified, the remaining change in performance is calculated by subtracting the performance influence due to deposits and the performance influence due to compaction from the change in performance of the separation membrane module, in order to calculate the contribution ratio of physical damage and the contribution ratio of chemical deterioration, test water containing at least two types of solutes is supplied to the separation membrane module, the separation performance of the separation membrane module for each solute is measured, the contribution ratio of physical damage and the contribution ratio of chemical deterioration are calculated by comparing the separation performance for each solute with pre-created deterioration relational formulas for physical damage and chemical deterioration, and the performance influence due to physical damage and the performance influence due to chemical deterioration are calculated by multiplying the remaining change in performance by the respective contribution ratios.

6. The method for diagnosing the condition of a separation membrane module according to claim 5, further comprising the step of cleaning the separation membrane module with a chemical solution before the step of calculating the contribution ratio of physical damage and the contribution ratio of chemical deterioration.

7. A separation membrane module condition diagnosis program, wherein, in order to determine the degree of multiple degradation factors in the performance change amount before and after use of the separation membrane module, the computer is configured to function as: a data input means for inputting performance measurement results in a first state and a second state of the separation membrane module and analysis results correlated with each degradation factor into the computer; a performance change amount calculation means for calculating the performance change amount from the performance measurement results of the first state and the second state; a quantification means for quantifying each analysis result correlated with each degradation factor as an amount corresponding to a part of the performance change amount; a data recording means for recording the input and calculated data in the computer; and a condition diagnosis means for determining the contribution amount of each degradation factor to the performance change amount by accumulating the quantified results of each degradation factor based on the input and / or recorded data.

8. A recording medium that records the state diagnostic program for the separation membrane module described in claim 7.

9. A method for operating a water treatment plant, characterized in that, based on the method for diagnosing the condition of a separation membrane module according to any one of claims 4 to 6, if it is determined that the cause of deterioration is physical damage, at least one of the following is performed: checking the inflow status of foreign matter and preventing its inflow, preventing a sudden rise or fall in operating pressure, and replacing the deteriorated separation membrane module; if it is determined that the cause of deterioration is deposits, at least one of the following is performed: checking the inflow status of deposits and preventing their inflow, performing separation membrane module cleaning according to the type of deposits, adding a chemical to prevent deposit formation, and replacing the deteriorated separation membrane module; and if it is determined that the cause of deterioration is chemical deterioration, at least one of the following is performed: checking the inflow status of oxidizing agents and preventing their inflow, checking the inflow status of strong acids or strong bases and preventing their inflow, and replacing the deteriorated separation membrane module.

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