Method for detecting damage to a separation membrane module, method for repairing damage, and damage detection set.

Abstract

This invention provides a simple and efficient method for detecting membrane damage during inspection of separation membrane modules at MBR sites. [Solution] A method for detecting damage to a separation membrane module, wherein the separation membrane module comprises a separation membrane cassette, which is a unit comprising a plurality of sheet-shaped separation membrane elements arranged in parallel, each having a water collection section for discharging permeate water to the outside, and an element block formed by loading one or more of the separation membrane cassettes onto a frame, and the method comprises the steps of: supplying pressurized gas to the separation membrane cassette or the element block while the separation membrane elements are wet in the atmosphere; sealing the pressurized gas to the separation membrane cassette or the element block so that the pressure is within a predetermined range; and determining whether or not the separation membrane cassette or the element block is damaged based on the subsequent pressure change of the pressurized gas.

Description

Technical Field

[0001] The present invention relates to a method for detecting damage to a separation membrane module, a method for repairing the damage, and a damage detection set.

Background Art

[0002] In recent years, flat or hollow fiber separation membranes have come to be used in the water treatment field and the food industry field. For example, a separation membrane element provided with a separation membrane or a separation membrane module in which a plurality of these separation membrane elements are arranged is used in a water purification treatment device. Separation membranes used in the separation method by a separation membrane element include microfiltration membranes, ultrafiltration membranes, nanofiltration membranes, reverse osmosis membranes, forward osmosis membranes, etc. from the viewpoints of their pore diameters and separation functions. These membranes are used, for example, when obtaining drinking water from seawater, brackish water, water containing harmful substances, etc., in the production of industrial ultrapure water, wastewater treatment, recovery of valuable substances, etc., and are properly selected according to the target separation component and separation performance.

[0003] The membrane bioreactor (MBR) is a treatment method in which a separation membrane is immersed in an activated sludge tank and the activated sludge and the treated water are separated by the membrane. Since MBR saves space and can obtain good water quality, it is being introduced into large-scale facilities exceeding 100,000 m 3 / day mainly in small-scale facilities in Japan and is being promoted in large-scale facilities overseas.

[0004] ]Activated sludge treatment requires aeration into the treatment tank to cultivate aerobic microorganisms. By installing an aeration block (ABL) equipped with this aeration device below the membrane unit (hereinafter referred to as "element block"), the gas-liquid mixed flow produced by the aeration rises within the element block, scraping off contaminants from the membrane surface. This allows for solid-liquid separation while cleaning the membrane surface, enabling low-cost membrane filtration operation. In MBRs, an element block typically consists of multiple flat membrane separation elements stacked in parallel and inserted into a rectangular module housing with grooves inside and open at the top and bottom. The element block and aeration block combined are called a separation membrane module.

[0005] Water treatment equipment that uses a high concentration of flat membrane separation elements, as described above, can experience clogging of the diffuser pores due to sludge accumulation, microbial growth, organic matter precipitation, and mineral deposits such as calcium and magnesium, if used continuously. When the diffuser pores become clogged, the air dispersion becomes uneven, leading to localized gas emissions and ultimately damage to the separation membrane module. When the separation membrane module is damaged, sludge leaks from the damaged area, and the system fails to perform its intended separation function. To prevent this, it is necessary to stop the operation of the separation membrane module, remove it from the MBR tank for inspection, and restore it to its original state. Specifically, it is necessary to identify and repair the damaged area of ​​the separation membrane module. In some cases, repairing the damaged area may be difficult, and it may be necessary to replace the separation membrane module or separation membrane cassette.

[0006] In MBRs, damage detection is typically performed after removing the separation membrane module from the MBR tank. Previous inspections required either identifying damage to the separation membrane element by discoloration of the filtered water tubing, or visually checking for water leakage from the damaged area of ​​the separation membrane element by injecting tap water from the filtered water piping side and applying back pressure. However, inspecting the entire separation membrane module outside the MBR tank requires a large amount of water, which can be difficult to secure. Even if sufficient water is available, inspecting each individual separation membrane element is time-consuming. When sufficient water is unavailable, damaged separation membrane elements are identified by discoloration of the tubing; however, identifying discoloration is often difficult, and the detection is unreliable as it doesn't accurately link to the damaged element. Furthermore, after repairs, it was impossible to determine if the filtered water quality had improved until the separation membrane module was reinstalled in the MBR tank and operation resumed. Furthermore, if the water quality did not improve due to overlooked checks or handling errors, the separation membrane module had to be retrieved again, and the inspection and repairs had to be repeated, which required considerable effort and expense.

[0007] Patent Document 1 describes a precision filtration system using a hollow fiber-like water treatment membrane with numerous pores. Unlike MBRs, this system is classified as ultrafiltration (UF, microfiltration: MF) that removes impurities such as bacteria and suspended solids from raw water using a water treatment membrane. In this system, the water treatment membrane may break down after prolonged use. When the water treatment membrane breaks down, raw water leaks from the damaged area, and the filtration system ceases to function properly. Therefore, to detect damage to the water treatment membrane, a method has been proposed in which pressurized gas is supplied to one side of the water treatment membrane immersed in a water tank, and the tank is sealed while maintaining a predetermined pressure. Subsequently, damage to the water treatment membrane is detected based on the pressure change of the pressurized gas.

[0008] Patent Document 2 describes a blood processing device using hollow fiber membranes. This device is widely used in the field of extracorporeal blood circulation, such as hemodialysis and plasma separation. The device modularizes the membrane, then wets the membrane with water, and measures the leak pressure by applying pressure to the inside and outside of the membrane to determine if a leak exists. This method is also widely used in water treatment technologies for industrial or tap water, such as ultrafiltration membranes and microfiltration membranes. A method has been proposed for determining leaks by using a corrected leak pressure per unit time, which normalizes the total weight of the membrane modules, based on a correlation formula consisting of the total weight of leak-free membrane modules in a wet state and the leak pressure per unit time. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Publication No. 2001-190938 [Patent Document 2] Japanese Patent Publication No. 2005-238096 [Overview of the project] [Problems that the invention aims to solve]

[0010] The damage detection methods described in Patent Documents 1 and 2 have not been applied to MBRs. When the damage detection methods described in Patent Documents 1 and 2, which use hollow fiber membranes, are applied to MBRs using flat membrane separation elements, sludge may adhere to the membrane surface in the MBR tank, and this sludge can block the damaged area of ​​the membrane, hindering accurate damage detection. In addition, since biological reactions and membrane filtration occur simultaneously in the MBR tank, it is necessary to supply pressurized gas for biological treatment and membrane washing. However, supplying pressurized gas for damage detection complicates the supply system, causing fluctuations in supply pressure and making accurate pressure supply difficult. Furthermore, in MBRs, membrane modules are often densely arranged, which further complicates the supply of pressurized gas and makes uniform supply to each module difficult. Moreover, although it may be possible to detect performance degradation due to damage, identifying and repairing the damaged area underwater has been difficult.

[0011] Therefore, the present invention aims to provide a simple and efficient method for detecting membrane damage when inspecting separation membrane modules at an MBR site. [Means for solving the problem]

[0012] To solve these problems, the present invention has the following configuration. [1] A method for detecting damage to a separation membrane module, wherein the separation membrane module comprises a separation membrane cassette, which is a unit comprising a plurality of sheet-shaped separation membrane elements arranged in parallel, each having a water collection section for discharging permeate water to the outside, and an element block formed by loading one or more of the separation membrane cassettes onto a frame, and the method for detecting damage to a separation membrane module is characterized by comprising the steps of: supplying pressurized gas to the separation membrane cassette or the element block while the separation membrane elements are wet in the atmosphere; sealing the pressurized gas to the separation membrane cassette or the element block so that the pressure is within a predetermined range; and determining whether or not the separation membrane cassette or the element block is damaged based on the subsequent pressure change of the pressurized gas. [2] A method for detecting damage to a separation membrane module according to [1], characterized in that, after the step of sealing the pressurized gas, in the step of determining whether or not there is damage, the pressure change of the pressurized gas is measured, and if the pressure after a certain period of time is equal to or greater than a preset judgment criterion pressure, the separation membrane cassette or the element block is determined to be functioning normally, and if the pressure after a certain period of time is less than the judgment criterion pressure, the separation membrane cassette or the element block is determined to be damaged. [3] A method for detecting damage to a separation membrane module according to [1] or [2], characterized in that, in the step of sealing the pressurized gas, the pressure in the predetermined range is 5.1 kPa or more and 6.0 kPa or less, and in the step of determining whether or not there is damage, time measurement is started from when the pressure of the pressurized gas reaches 5.0 kPa, and if the pressure after 1 minute is 1.0 kPa or more, it is determined that the separation membrane cassette or the element block is functioning normally, and if the pressure after 1 minute is less than 1.0 kPa, it is determined that the separation membrane cassette or the element block is damaged. [4] A method for detecting damage to a separation membrane module according to any one of [1] to [3], characterized in that, in the step of determining whether or not there is damage, if it is determined that the separation membrane cassette or the element block is damaged, pressurized gas is supplied to the separation membrane cassette or the element block, and while maintaining a pressurized state at a predetermined pressure, a solution for foam leak airtightness testing is sprayed over the entire surface of the separation membrane element to identify the location of the damage to the separation membrane element in the separation membrane cassette or the element block. [5] The method for detecting damage to a separation membrane module according to [4], characterized in that when maintaining the pressurized state, the predetermined pressure is maintained in a range of 5.1 kPa or more and 6.0 kPa or less. A method for repairing damage to a separation membrane module, characterized by comprising the step of repairing the separation membrane cassette or the element block by identifying the location of the damage to the separation membrane element using the separation membrane module damage detection method described in [6], [4] or [5], and then sealing a portion of the filtered water piping, which includes a water collection section, a filtered water tube, and a tube fitting, from which filtered water is discharged from the damaged separation membrane element. [7] The tube joint is provided with a hollow water inlet that communicates with two or more separation membrane elements, and in the repair step, the separation membrane cassette or the element block is repaired by inserting a sealing material into a part of the water inlet, as described in [6]. [8] A method for repairing damage to a separation membrane module, comprising: a separation membrane cassette comprising a plurality of sheet-shaped separation membrane elements having a water collection section for discharging permeate water to the outside, arranged in parallel, with one or more of the separation membrane cassettes being loaded into a frame to form an element block, wherein the separation membrane elements are moistened in the atmosphere, pressurized gas is supplied to the separation membrane cassette or the element block, the separation membrane cassette or the element block is sealed under a predetermined range of pressure, and the presence or absence of damage to the separation membrane cassette or the separation membrane element block is detected based on the subsequent pressure change of the pressurized gas; and in step 1, the separation membrane cassette or the element block A method for repairing damage to a separation membrane module, comprising: step 2, when it is determined that the element block is damaged, supplying pressurized gas to the separation membrane cassette or the element block again and spraying a foam leak airtightness test solution over the entire surface of the separation membrane element to identify the damaged location of the separation membrane element in the separation membrane cassette or the element block; and step 3, repairing the separation membrane cassette or element block by sealing a part of the water collection portion of the damaged separation membrane element identified in step 2, wherein steps 1 to 3 are repeated until no further damage to the separation membrane element is detected. A separation membrane module damage detection set for use in the method for repairing damage to a separation membrane module described in [9][8], comprising: a device for supplying pressurized gas; an on / off valve for sealing and adjusting the pressure of the pressurized gas; a pressure gauge for measuring the pressure; and a sealing material. [Effects of the Invention]

[0013] This invention enables simple and efficient detection of membrane damage during inspection of separation membrane modules at MBR sites. This allows for pass / fail determination of the separation membrane module's condition before it is installed in the MBR tank. [Brief explanation of the drawing]

[0014] [Figure 1] FIG. 1 is a front schematic view when three separation membrane cassettes arranged in parallel are inspected on the upper stage of a standard element block. [Figure 2] FIG. 2 is a front schematic view when a single separation membrane cassette is inspected. [Figure 3] FIG. 3 is a configuration example of a separation membrane module without using a support plate. [Figure 4] FIG. 4 is a configuration example of a separation membrane cassette without using a support plate.

MODE FOR CARRYING OUT THE INVENTION

[0015] [[ID=1】 Embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the embodiments shown in these drawings.

[0016] The present invention can be suitably applied to a separation membrane module including a separation membrane cassette in which a plurality of flat membrane-like separation membrane elements are bundled, and an element block configured by loading one or more separation membrane cassettes. As an example, a configuration example of a separation membrane module including a bag-shaped separation membrane element without using a support plate is shown in FIG. 3. Here, the separation membrane element 13 has a sealed periphery and a hole is provided in part to form a permeate outlet, and is lightweight and thin. Therefore, a plurality of them can be bundled and used, and these constitute the separation membrane cassette 11. This separation membrane cassette 11 has a high membrane filling rate and becomes the element block 10 when one or more are accommodated in the module frame 14.

[0017] Next, an example of the configuration of the separation membrane cassette 11 will be described with reference to Figure 4. A nozzle 15 for extracting filtered water is provided at the water collection section of the separation membrane element 13, and a water collection pipe 12 is connected to this nozzle 15 via a filtered water tube 16. Since the separation membrane cassette 11 uses multiple separation membrane elements 13 bundled together, the number of filtered water tubes 16 connecting the nozzle 15 and the water collection pipe 12 increases, making the structure complicated and difficult to handle. To avoid this, a tube joint 17 is provided between the nozzle 15 and the water collection pipe 12 to consolidate multiple filtered water tubes 16 into one. This tube joint 17 is provided with a hollow water inlet (not shown) that communicates with each individual separation membrane element.

[0018] In the method for detecting damage of the separation membrane module of the present invention, the separation membrane module is a unit composed of a separation membrane cassette in which a plurality of sheet-like separation membrane elements having a water collection part for discharging permeated water to the outside are arranged in parallel, and includes an element block formed by loading one or a plurality of the separation membrane cassettes into a frame. The method includes: a step of supplying pressurized gas to the separation membrane cassette or the element block in a state where the separation membrane element is moistened in the atmosphere; a step of sealing the pressurized gas so that the pressure of the separation membrane cassette or the element block becomes within a predetermined range; and a step of determining whether or not the separation membrane cassette or the element block is damaged based on the subsequent pressure change of the pressurized gas. In the step of "supplying pressurized gas to the element block", pressurized gas is supplied from the filtrate pipe side of the element block to pressurize all the separation membrane elements in the element block. Next, in the step of "sealing the pressurized gas", the pressurized gas is sealed while being maintained at a pressure within a predetermined range. In the step of "determining whether or not there is damage", the pressure change of the pressurized gas after sealing is monitored to detect damage of the element block. When the separation membrane element is not damaged, the pressurized gas does not leak and the pressure is maintained at a predetermined value. However, when the separation membrane element is damaged, the pressurized gas leaks from the damaged part and the pressure decreases. The degree of pressure drop of the pressurized gas is compared with a previously set determination condition to determine whether the separation membrane element is damaged. By this method, it is possible to efficiently and accurately detect membrane damage.

[0019] Figure 1 is a schematic front view of the inspection target 20, which consists of three separation membrane cassettes 11 arranged in parallel on the upper part of the element block 10. The basic equipment used for inspection in this invention includes a pressurized gas supply device 1, a piping hose 2 for supplying pressurized gas, a gas supply port 3 connected to the water collection pipe of the separation membrane module, a pressure holding valve 4 and a pressure adjustment valve 5 provided in the piping hose 2, and a pressure gauge 6 for measuring the pressure of the pressurized gas sealed inside the element block 10. The gas supply port 3 and the pressure gauge 6 are connected to the water collection pipe 12 of the element block 10 or separation membrane cassette 11 to be inspected. The gas supply port 3 and the pressure gauge 6 may be installed on the same side of the water collection pipe 12 or on opposite sides of the water collection pipe 12.

[0020] Figure 2 is a schematic front view when a single separation membrane cassette 11 is used as the inspection target 20. The equipment configuration is the same as in Figure 1.

[0021] To supply pressurized gas from the filtered water piping side, a gas supply port is connected to the water collection pipe of the element block, and the pressurized gas is distributed to all separation membrane elements through the water collection pipe. This method ensures that pressurized gas is supplied evenly to each separation membrane element, enabling efficient pressurization.

[0022] Since collection pipes are installed for each cassette, it is possible to inspect any separation membrane cassette or group of separation membrane cassettes separately by closing the connection ports of adjacent collection pipes with blind flanges. This method allows for efficient inspection of not only the entire element block, but also groups of separation membrane cassettes or only specific separation membrane cassettes. For example, a standard element block has a cassette configuration of 3 cassettes in parallel x 2 rows, but if one of the 6 separation membrane cassettes is damaged, the 3 parallel cassette groups are inspected first. If damage is found, the separation membrane cassettes containing the damaged separation membrane element can be identified by sequentially inspecting each separation membrane cassette one by one. These inspection methods can be flexibly adjusted according to the lineup of element blocks.

[0023] A method for sealing a separation membrane cassette or element block with pressurized gas to a predetermined pressure range involves supplying pressurized gas to the target element block or separation membrane cassette, closing an on-off valve when the predetermined pressure range is reached, and sealing the element block or separation membrane cassette with pressurized gas. After closing the on-off valve, the operation of the pressurized gas supply device may be stopped. Generally, when relatively high-pressure pressurized gas is supplied to a separation membrane, the pressurized gas may leak out from the pores of the separation membrane. Therefore, when sealing with pressurized gas, it is preferable to seal the separation membrane at a pressure slightly lower than the bubble point, which is the pressure at which the pressurized gas does not pass through the separation membrane. To reduce the risk of pore expansion due to the supply of excessive pressurized gas, it is preferable to set the pressure to 5.1 kPa or more and 6.0 kPa or less, and the optimal pressure range is preferably 5.1 kPa or more and 5.5 kPa or less.

[0024] After the step of sealing the pressurized gas, the presence or absence of damage to the separation membrane cassette or element block is determined based on the subsequent pressure change of the pressurized gas. Preferably, after the sealing step, the pressure change of the pressurized gas is measured, and if the pressure after a certain period of time is equal to or greater than a preset judgment criterion pressure, the separation membrane cassette or element block is determined to be functioning normally, and if the pressure after a certain period of time is less than the judgment criterion pressure, the separation membrane cassette or element block is determined to be damaged.

[0025] The above-mentioned pressure thresholds can be arbitrarily determined according to the intended use and treatment water quality standards for each site after MBR treatment. Generally, the following classifications can be used: "strict," "standard (normal)," and "lenient." "Standard (normal)" is a general standard that can accommodate many uses, such as discharge into rivers and cooling water. "Strict" is a stricter standard than standard and can be applied when higher water quality than usual is required. For example, industrial water requires higher quality than standard because it is reused in industrial processes. Boiler feedwater also falls into this category. High-quality water is required to maintain the efficiency and lifespan of boilers. Furthermore, it can be applied when high water quality standards are required, such as when RO treatment is necessary in the subsequent stage, and the quality of water after membrane treatment is strictly controlled. On the other hand, "lenient" is a less strict standard than standard and can be applied when some degree of contamination is acceptable. For example, irrigation water used for agricultural purposes and sludge concentration. These have lower standards than general water quality standards, and some impurities mixed into the treated water are acceptable. These standards may vary depending on the actual use and local regulations, so they should be used as a general guideline.

[0026] While it is essential to limit the supply pressure when determining the degree of pressure drop in a pressurized gas, the criteria for determining the degree of pressure drop may be set arbitrarily.

[0027] In the "Standard" setting, after sealing a pressurized gas between 5.1 kPa and 6.0 kPa, time measurement begins when the pressurized gas pressure reaches 5.0 kPa. If the pressure falls below 1.0 kPa after 1 minute, it is determined that the element block or separation membrane cassette is damaged. In other words, if the pressure is 1.0 kPa or higher, the pressurized state is maintained, and it can be determined that the separation membrane cassette or element block is functioning normally. For the judgment criterion pressure after 1 minute, it is preferable to set it to 3.0 kPa in the "Strict" setting. In the "Less" setting, it is preferable to set it to 0.5 kPa.

[0028] If there is obvious damage to the separation membrane element, such as a damaged nozzle, a detached tube, or a ruptured membrane, the pressure will drop within a few seconds of sealing the pressurized gas, and the holding pressure will become zero. This indicates that the separation membrane element is not functioning properly. On the other hand, if the pressure is maintained for one minute after pressurization, it can be determined that there is no major damage and the element is functioning properly. In this state, it can be guaranteed that the MBR filtered water quality will be satisfactory. In this way, the presence or absence of damage to the separation membrane element can be easily and effectively determined based on the time the pressurized state is maintained.

[0029] In the separation membrane module damage detection method of the present invention, inspections to identify and repair damaged areas of the separation membrane module must be performed outside the MBR tank, i.e., in the atmosphere. On the other hand, since normal inspections become impossible when the separation membrane dries out, the inspection must be performed while it is moist. General hydrophilic separation membranes are prone to structural changes when dry, and even if immersed in water again, they do not easily return to their original state. If re-soaking is incomplete, the performance of the separation membrane deteriorates, and the filtration efficiency worsens. Also, if a hydrophilic membrane remains dry for a long time, it may lose its hydrophilicity and become hydrophobic. This significantly reduces water permeability, and the separation membrane loses its function. Therefore, after removing the separation membrane module from the MBR tank, it is necessary to spray shower water on the separation membrane surface immediately or periodically, and to perform inspections while the separation membrane surface remains moist. In particular, in outdoor environments with strong winds and low humidity, it is essential to spray shower water over the entire separation membrane before supplying pressurized gas to maintain the membrane's moist state.

[0030] Furthermore, if sludge is attached to the membrane surface, the sludge can block the damaged area of ​​the membrane, hindering accurate detection of the damage. Therefore, it is necessary to remove the sludge with shower water or similar before inspection.

[0031] Here, a flat membrane separation membrane to which this invention is applied will be described. Preferably, the separation membrane is one in which a separation function layer is formed on a nonwoven fabric-based substrate. As the separation function layer, a crosslinked polymer is preferably used in terms of pore size control and durability. In terms of component separation performance, a membrane in which a separation function layer formed by polycondensation of a polyfunctional amine and a polyfunctional acid halide, or an organic-inorganic hybrid functional layer, is laminated on a porous support layer is preferably used. Furthermore, a porous support layer such as a cellulose membrane, polyvinylidene fluoride membrane, polyethersulfone membrane, or polysulfone membrane, which has both separation and support functions, can also be used. In other words, the separation function layer and the porous support layer may be realized in a single layer.

[0032] The separation membrane to which the present invention is applied preferably consists of a substrate and a separation functional layer, and in particular, a separation membrane in which a separation functional layer made of a polyvinylidene fluoride resin is formed is used. Here, it is preferable that a layer in which the resin constituting the separation functional layer and the substrate are mixed is interposed between the substrate and the separation functional layer. As the polyvinylidene fluoride blend resin penetrates from the surface to the interior of the substrate, the separation functional layer is firmly fixed to the substrate by a so-called anchoring effect, and the separation functional layer is prevented from peeling off the substrate. The separation functional layer may be located on one side of the substrate or on both sides. The separation functional layer may have a symmetrical or asymmetrical structure with respect to the substrate. Furthermore, if the separation functional layer is located on both sides of the substrate, the separation functional layers on both sides may be continuous or discontinuous via the substrate.

[0033] In a separation membrane formed from a separation functional layer and a substrate, the substrate has the function of supporting the separation functional layer and providing strength to the separation membrane. The material constituting the substrate is not particularly limited, including organic substrates and inorganic substrates, but organic substrates are preferred because they are easy to lighten. Examples of organic substrates include woven or nonwoven fabrics made of organic fibers such as cellulose fibers, cellulose triacetate fibers, polyester fibers, polypropylene fibers, and polyethylene fibers. Among these, nonwoven fabrics are particularly preferred because their density can be controlled relatively easily.

[0034] Next, a flat membrane separation element suitable for this invention will be described. The separation membrane element is preferably structured so as not to expand when pressurized gas is supplied. Specifically, it is desirable to provide a resin portion that adheres to both opposing permeable surfaces in the permeable surface region of the separation membrane inside the sealed periphery. The shape of the resin portion is suitable to be dot-shaped or linear. By providing this resin portion, a water collection channel through which filtered water flows is secured inside the separation membrane element, and the separation membranes are firmly bound together. As a result, the separation membrane element has the characteristic of not expanding when pressurized gas is supplied inside the separation membrane element.

[0035] On the other hand, in separation membrane elements without a resin portion, the separation membrane may swell under pressure, potentially causing adjacent membranes to stick together during inspection. This can make accurate inspection of the entire surface difficult. Thus, separation membrane elements with a resin portion prevent swelling under pressure and prevent membranes from sticking together, enabling accurate inspection of the entire surface of the separation membrane.

[0036] Typically, pressurized air supplied using a pressurized gas supply device such as a blower or compressor is used as the pressurized gas. It is sufficient to supply a stable pressure at the required level, and it is possible to utilize pressurized air piping permanently installed at the site. Alternatively, portable blowers used in septic tanks and similar applications can be brought to the site and used. The discharge flow rate should be at least 200 L / min per standard separation membrane module.

[0037] While the pressure gauge does not need to be strictly specified, a digital display with a pressure range of 0-50kPa (0-0.5bar) and displaying significant figures to one decimal place is preferable. Any hose can be used for piping, and the hose diameter is not a concern as long as it fits the blower. For the shut-off valves, any valve that can open and close them is acceptable, but two valves are required: one for maintaining pressure and one for regulating pressure.

[0038] In an embodiment of the present invention, pressurized gas is supplied to the separation membrane cassette or the element block, and while maintaining a pressurized state within a predetermined pressure range, a solution for foam leak and airtightness testing is sprayed over the entire surface of the separation membrane element, thereby allowing the location of damage to the separation membrane element in the separation membrane cassette or the element block to be identified.

[0039] The equipment used in the step of determining whether or not the separation membrane module is damaged can be used as is. To maintain the pressurized gas at a predetermined pressure, the pressurized gas is supplied to the target element block or separation membrane cassette, and the opening of the on / off valve is adjusted when the predetermined pressure is reached. With the pressurized gas supply device running, the element block or separation membrane cassette is maintained at a predetermined pressure with pressurized gas. The pressure range is preferably set to 5.1 kPa or more and 6.0 kPa or less, similar to the step of determining whether or not the separation membrane module is damaged, in order to reduce the risk of the pores of the separation membrane expanding due to the supply of excessive pressurized gas, and the optimal pressure range is preferably 5.1 kPa to 5.5 kPa. By maintaining the pressure within this range, the damaged part of the separation membrane module can be identified and appropriate repairs can be carried out.

[0040] Foam leak detection solutions are commonly used to detect leaks in pipes and containers. One example of such a solution consists primarily of water and a foaming agent (e.g., sodium carbonate). When applied to pipes or containers, the solution foams when a leak is detected, allowing the leak's location to be identified. This method is widely used in water and gas pipe inspections. Another example is foam leak detection liquid, a commercially available solution for foam leak detection. It is easy to use; simply apply it to the suspected leak area, and the leak will be detected by foaming. Furthermore, foam detection liquids are solutions containing foaming agents suitable for specific pipes and containers. These solutions contain specialized components to provide optimal leak detection for specific materials and applications.

[0041] A mixture of water and detergent can also be used. Since the detergent helps stabilize the foam, it is suitable for use in this test. The detergent can include household detergents. For general household detergents, a water-to-detergent ratio of 1:10 (1 part detergent to 10 parts water) is sufficient for the test. For improved visibility, a ratio of 1:5 (1 part detergent to 5 parts water) is preferable.

[0042] The recommended amount of solution to use is 0.05L per separation membrane cassette, but this is not a strict rule. A specified amount of detergent can be prepared, and any sprayer can be used depending on the inspection situation. Handheld sprayers are convenient, but prolonged use can easily lead to fatigue. For applications requiring large spray volumes, a pressurized sprayer is preferable.

[0043] These solutions are sprayed onto the entire element block or separation membrane cassette being inspected. If there is a leak, the solution will foam, making the leak location visible. This method allows for immediate determination of whether or not the separation membrane element is damaged.

[0044] Next, we will explain the "steps for repairing damage" to the separation membrane module.

[0045] If the filtered water tube is damaged or detached, it can be easily repaired by replacing the tube and inserting it into the nozzle. On the other hand, if the separation membrane is torn, it is possible to repair the torn area with adhesive, but the damaged area may be in a hard-to-reach place when the separation membrane cassette is in its original state. Therefore, in order to repair it accurately, it is necessary to disassemble the separation membrane cassette and remove the separation membrane element, which is very time-consuming and laborious. Furthermore, if the nozzle part of the separation membrane element is damaged, repair itself is difficult. In such situations, it is recommended to consider replacing the separation membrane element with a new one, but disassembling the separation membrane cassette and replacing the separation membrane element on-site is time-consuming and laborious, making it unacceptable in situations where quick recovery is necessary, such as during troubleshooting. Similarly, sending it back to the factory for repair is also time-consuming and impractical.

[0046] Therefore, in the embodiment of the present invention, by sealing a portion of the filtered water piping, which includes a water collection section, filtered water tube, and tube fittings, from which filtered water is discharged from the damaged separation membrane element, only the damaged separation membrane element, including the damaged separation membrane and nozzle, can be rendered unusable, thereby restoring the separation membrane cassette to a usable state. This is a preferred method for repairing damage to a separation membrane module that can be easily implemented on-site at the MBR site. As an example of a method for sealing a portion of the filtered water piping, one method is to seal a portion of the filtered water tube of the separation membrane element. For example, this could involve bending the filtered water tube and securing it with a cable tie, or sealing adjacent nozzle sections at two points and connecting them in a loop.

[0047] A more preferable method involves inserting a sealant into the hollow water inlet of a tube fitting provided in the filtered water piping. The tube fitting has a hollow water inlet that communicates with two or more separation membrane elements, and when using multiple separation membrane elements bundled together, multiple tubes can be consolidated into one. When sealing, only the water inlet communicating with the damaged separation membrane element can be sealed, or the downstream flow path of the consolidated filtered water can be sealed. Furthermore, while there is a risk that the cable ties may come off due to vibrations caused by aeration when bending the filtered water tube and securing it with cable ties, inserting a sealant into a portion of the water inlet of the tube fitting provides a more reliable seal, allowing for the repair of the separation membrane cassette or element block.

[0048] The sealing material is not particularly limited and can be any material that can seal the water inlet, such as adhesive, putty, clay, or rubber. However, from the standpoint of cost and workability, it is preferable to use a resin sealing material that fits the inner diameter of the tube fitting water inlet. By using this method, the separation membrane element can be repaired quickly and effectively on-site without the time-consuming and laborious process of replacing the separation membrane element. Furthermore, it eliminates the need to return the element block or separation membrane cassette to the factory for repair.

[0049] On the other hand, if the number of separation membrane elements to be sealed increases, the effective membrane area of ​​the separation membrane module decreases, making it difficult to maintain filtration capacity. Therefore, if more than a certain number of separation membrane elements are damaged, it is recommended to replace the entire separation membrane cassette. This number is merely a guideline, and in reality, it needs to be set for each site, taking into account conditions such as filtration flux. For example, a reduction of up to 20% from the initial membrane area is acceptable. In the case of a separation membrane cassette composed of 50 separation membrane elements, the limit for repair would be up to 10 elements.

[0050] This section describes an example of the inspection and repair methods used for a series of separation membrane modules.

[0051] First, pressurized gas is supplied into the element block to determine whether there is any damage to the element block or the separation membrane cassette. In the case of a standard module, pressurized gas is supplied simultaneously to three separation membrane cassettes arranged in parallel, and the pressure drop is monitored. If a pressure drop is detected, the same inspection is sequentially performed on each of the three separation membrane cassettes to identify which one is damaged. This process is repeated until the separation membrane cassette suspected of being damaged is identified.

[0052] Next, a foaming leak test is performed on the suspected damaged separation membrane cassette to identify the location of the damage. First, pressurized gas is supplied into the target separation membrane cassette and the pressure is kept constant. Then, a mixture of water and detergent is uniformly sprayed over the entire surface of the separation membrane cassette. In this state, if there is damage, the detergent will foam, making the leak location visible.

[0053] Subsequently, the separation membrane element that detected foaming is repaired. Specifically, a resin sealant is inserted into the water inlet of the tube fitting corresponding to the damaged separation membrane element. This process renders only the damaged separation membrane element unusable, allowing the entire separation membrane cassette to be restored to a usable state.

[0054] Furthermore, after the repair is complete, pressurized gas is supplied again to monitor the pressure drop and confirm whether the repair was successful. If the pressure drop still does not meet the passing criteria, the initial damage inspection is performed again. By repeating this series of steps, the presence or absence of abnormalities in the separation membrane module can be confirmed quickly and reliably.

[0055] Conventionally, it was impossible to determine whether the filtered water quality had improved until the separation membrane module was installed in the MBR tank and operation was resumed after repairs. This resulted in rework due to missed checks or handling errors, and if the water quality had not improved, the separation membrane module had to be retrieved again, and inspection and repairs had to be repeated, which incurred considerable effort and expense. However, by implementing this series of steps, these inefficiencies are significantly reduced, saving time and ensuring reliability. Thus, in the embodiment of the present invention, in particular, in a separation membrane module with a high concentration of flat membrane-shaped separation membrane elements, a judgment criterion pressure corresponding to the target water quality can be set in advance, and the necessity of repairs can be appropriately determined based on that criterion, enabling efficient repairs.

[0056] The separation membrane module damage detection set, which includes a device for supplying pressurized gas, an on-off valve for sealing and regulating the pressure of the pressurized gas, a pressure gauge for pressure measurement, and a sealing material, offers significant advantages in terms of portability. Because this set is lightweight and easily transportable, it can be easily brought to the site where the separation membrane module damage detection method of the present invention is being implemented, enabling a rapid response. Furthermore, even at sites where securing pressurized gas is difficult, the integrated detection set eliminates the need for additional equipment, allowing for efficient detection of damaged areas. This improves work efficiency and enables rapid on-site troubleshooting. Moreover, it can be used without special skills or expertise, making it easy for field workers to operate. [Examples]

[0057] The following describes in detail an example of an embodiment of the present invention. However, the present invention is not limited in any way to the following examples.

[0058] The following describes the separation membrane module applied to the following examples and comparative examples. As the separation membrane, a composite flat membrane (pore size 0.08 μm, thickness 200 μm) was used, consisting of a polyester nonwoven fabric coated with a polyvinylidene fluoride membrane. Two separation membranes were bonded together on both sides using adhesive resin on the permeable side of the separation membrane surface, resulting in a membrane measuring 800 mm in length, 480 mm in width, and with an effective membrane area of ​​0.7 m². 2 These were used as separation membrane elements. Fifty of these separation membrane elements were bundled together and arranged parallel to each other so that the gap between adjacent separation membrane elements was 6 mm, thereby creating a separation membrane cassette. Three of these separation membrane cassettes were arranged in parallel in an element block, which was then used in two layers, upper and lower, to form a separation membrane module.

[0059] (Example 1) An element block that had been in operation for approximately 5 years at one MBR site was removed from the MBR tank and inspected. The filtered water turbidity before the inspection was 1.5 NTU. A portable blower, connecting piping, hoses, two on / off valves for pressure holding and adjustment, and a pressure gauge were assembled into a unit and brought to the MBR site as a damage detection kit for the inspection, and the work was carried out. Since the MBR treated water is discharged into a river, the judgment standard pressure was set to "standard."

[0060] To determine which separation membrane cassette in the element block was damaged, pressurized gas was supplied to the upper element block, which has three separation membrane cassettes in parallel, and the pressure drop was monitored. The pressurized gas pressure was set to 5.1 kPa, and time measurement was started when the pressurized gas pressure reached 5.0 kPa. After 1 minute, the pressure was 4.1 kPa. If the pressure falls below 1.0 kPa after 1 minute, it is determined that the element block or separation membrane cassette is damaged. However, in this case, the pressure remained above 1.0 kPa after 1 minute, i.e., the pressurized state was maintained, so it was determined that there were no damaged separation membrane elements in these three separation membrane cassettes.

[0061] Next, the lower element block was inspected in the same way as the upper block. The pressurized gas pressure was set to 5.1 kPa, and time measurement was started when the pressure reached 5.0 kPa. After 1 minute, the pressure was 0.0 kPa. Since the pressure was less than 1.0 kPa after 1 minute, it was determined that there was a damaged element somewhere in the three separation membrane cassette groups in the lower section.

[0062] Furthermore, to narrow down the possibilities to individual membrane cassettes, the same inspection was performed on each one. In two of the three membrane cassettes, the pressure after holding pressurized gas for one minute was 0 kPa. Based on this result, it was determined that these two membrane cassettes were damaged.

[0063] Next, a foaming leak test was performed on the two separation membrane cassettes suspected of being damaged to identify the location of the damage. First, pressurized gas was supplied to the inside of the two separation membrane cassettes, and the pressure was kept constant at 5.0 kPa. Next, approximately 5 liters of a mixture of water and detergent (1 part detergent to 5 parts water) was prepared and sprayed uniformly over the entire surface of the two separation membrane cassettes. After that, the separation membrane cassettes were visually inspected, and five foaming spots were found in one separation membrane cassette and three foaming spots in the other, all of which were caused by tears in the separation membrane surface.

[0064] To repair the identified damage, a resin sealant was inserted into the water inlet of the tube fitting corresponding to the separation membrane element where foaming was detected. This repaired the separation membrane cassette by rendering only the damaged separation membrane element unusable.

[0065] Furthermore, after the repair was completed, pressurized gas was supplied again to monitor the pressure drop. Pressurized gas was supplied simultaneously to all separation membrane cassettes in the element block, and the pressure drop was monitored. The pressurized gas pressure was set to 5.1 kPa, and time measurement was started when the pressurized gas pressure reached 5.0 kPa. After 1 minute, the pressure was 4.3 kPa. As a result, all separation membrane cassettes, including the two damaged ones, met the pass criteria, confirming that the repair was successful. Then, the element block was returned to the MBR tank and operation was restarted, and the filtered water turbidity was 0.2 NTU, confirming that the filtered water quality had returned to a normal level. The inspection and repair, including the removal and installation of the element block, took approximately 2 hours, demonstrating that the work could be carried out efficiently.

[0066] (Comparative Example 1) A similar element block, which had been in operation for approximately four years at a different MBR site than that used in Example 1, was removed from the MBR tank and tested. The filtered water turbidity before testing was 2.4 NTU.

[0067] After removing the separation membrane module from the MBR tank, we attempted to visually check for water leakage from damaged parts of the separation membrane elements by injecting tap water from the filtered water piping side and applying back pressure. However, due to insufficient water volume at the site, it was difficult to inspect the entire element block, i.e., all six separation membrane cassettes, simultaneously. Therefore, we decided to inspect each separation membrane cassette one by one. In addition, due to insufficient water pressure, it was difficult to visually confirm water leakage from damaged parts, and it took about 30 minutes to inspect one separation membrane cassette. For separation membrane elements suspected of being damaged, the same repair procedures as in the example were carried out.

[0068] Afterward, the element block was returned to the MBR tank and operation was resumed, but the turbidity of the filtered water was 1.3 NTU, indicating that the filtered water quality was still abnormal. Therefore, it was necessary to remove the element block from the MBR tank again and repeat the series of operations, which required considerable effort to identify the new damaged part. The entire process of returning the filtered water quality to a normal level took approximately 10 hours in total. [Explanation of Symbols]

[0069] 1. Pressurized gas supply device 2. Piping hoses 3. Gas supply port 4. Pressure-holding valve 5. Pressure regulating valve 6. Pressure gauge 10 Element Blocks 11 Separation membrane cassette 12 Water collection pipe 13 Separation membrane element 14 Module Frames 15 nozzles 16 Filtration tubes 17 Tube fittings 20 subjects of testing

Claims

1. A method for detecting damage to a separation membrane module, The separation membrane module comprises an element block in which one or more sheet-shaped separation membrane elements, each having a water collection section for discharging permeate to the outside, are arranged in parallel, and one separation membrane cassette is mounted on a frame. The steps include: supplying pressurized gas to the separation membrane cassette or the element block while the separation membrane element is moistened in the atmosphere; The steps include sealing the pressurized gas into the separation membrane cassette or the element block so that the pressure is within a predetermined range, A step of determining whether the separation membrane cassette or the element block is damaged based on the subsequent pressure change of the pressurized gas, A method for detecting damage to a separation membrane module, characterized by comprising the following:

2. The method for detecting damage to a separation membrane module according to claim 1, characterized in that, after the step of sealing the pressurized gas, in the step of determining whether or not there is damage, the pressure change of the pressurized gas is measured, and if the pressure after a certain period of time is equal to or greater than a preset judgment criterion pressure, the separation membrane cassette or the element block is determined to be functioning normally, and if the pressure after a certain period of time is less than the judgment criterion pressure, the separation membrane cassette or the element block is determined to be damaged.

3. A method for detecting damage to a separation membrane module according to claim 1 or 2, characterized in that, in the step of sealing the pressurized gas, the pressure in the predetermined range is 5.1 kPa or more and 6.0 kPa or less, and in the step of determining whether or not there is damage, time measurement is started from when the pressure of the pressurized gas reaches 5.0 kPa, and if the pressure after 1 minute is 1.0 kPa or more, it is determined that the separation membrane cassette or the element block is functioning normally, and if the pressure after 1 minute is less than 1.0 kPa, it is determined that the separation membrane cassette or the element block is damaged.

4. The method for detecting damage to a separation membrane module according to claim 1 or 2, characterized in that, in the step of determining whether or not there is damage, if it is determined that the separation membrane cassette or the element block is damaged, pressurized gas is supplied to the separation membrane cassette or the element block, and while maintaining a pressurized state at a predetermined pressure, a solution for foam leak and airtightness testing is sprayed over the entire surface of the separation membrane element to identify the location of the damage to the separation membrane element in the separation membrane cassette or the element block.

5. The method for detecting damage to a separation membrane module according to claim 4, characterized in that when maintaining the pressurized state, the predetermined pressure is maintained in a range of 5.1 kPa or more and 6.0 kPa or less.

6. A method for repairing damage to a separation membrane module, characterized by comprising the step of repairing the separation membrane cassette or the element block by identifying the location of the damage to the separation membrane element using the separation membrane module damage detection method described in claim 4, and then sealing a portion of the filtered water piping, which includes a water collection section, a filtered water tube, and a tube fitting, from which filtered water is discharged from the damaged separation membrane element.

7. The tube joint is provided with a hollow water inlet that communicates with two or more separation membrane elements. The method for repairing damage to a separation membrane module according to claim 6, characterized in that, in the repair step, the separation membrane cassette or the element block is repaired by inserting a sealing material into a part of the water inlet.

8. A method for repairing damage to a separation membrane module, The element block comprises a separation membrane cassette, which is a single unit consisting of multiple sheet-shaped separation membrane elements arranged in parallel, each having a water collection section for discharging permeate water to the outside, and one or more of these separation membrane cassettes loaded onto a frame. Step 1 involves wetting the separation membrane element in the atmosphere, supplying pressurized gas to the separation membrane cassette or the element block, sealing the separation membrane cassette or the element block under a predetermined pressure range, and then detecting whether or not the separation membrane cassette or the separation membrane element block is damaged based on the subsequent pressure change of the pressurized gas. Step 2 involves determining in step 1 that the separation membrane cassette or the element block is damaged by supplying pressurized gas to the separation membrane cassette or the element block again, maintaining a pressurized state at a predetermined pressure, and spraying a foam leak and airtightness test solution onto the entire surface of the separation membrane element, thereby identifying the location of the damage to the separation membrane element in the separation membrane cassette or the element block. Step 3 involves repairing the separation membrane cassette or element block by sealing a portion of the water collection section of the separation membrane element having the damage identified in step 2, A method for repairing damage to a separation membrane module, characterized by repeating steps 1 to 3 until no further damage to the separation membrane element is detected.

9. A separation membrane module damage detection set for use in the method for repairing damage to a separation membrane module according to claim 8, comprising: a device for supplying pressurized gas; an on / off valve for sealing and adjusting the pressure of the pressurized gas; a pressure gauge for measuring the pressure; and a sealing material.

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