Filtering device, filtering system and filtering method

Abstract

To provide a filter device, filter system, and filter method that have high effects of removing refractory substances. The filter device (10) of the present invention has a filter container (11) that has a supply port (4) for a treated liquid (A) and a discharge port (15) for a treatment liquid (B), and a cylindrical filter (12) that is disposed inside the filter container (11), has a filter surface (12f) on the outside and a passage for the treatment liquid (B) on the inside, and has a layer of an adsorbent (N) that adsorbs the refractory substances (E) in a state before filtration accumulated on the filter surface (12f) to form an adsorbent layer (47).

Description

Technical Field

[0001] This invention relates to a filtration device, filtration system, and filtration method for removing recalcitrant substances contained in a liquid being treated. Background Technology

[0002] The Stockholm Convention on Persistent Organic Pollutants (POPs Convention) stipulates the elimination and restriction of the manufacture and use of persistent organic pollutants (POPs), and the reduction of their emissions. POPs are a collective term for chemical substances that are difficult to decompose in the environment, easily accumulate in organisms, and are highly mobile and diffusive. Appendix A of the Convention lists perfluorooctanoic acid (PFOA) as an example of a target substance, while Appendix B lists perfluorooctane sulfonic acid (PFOS) as an example. Japan acceded to the Convention in August 2002 and is committed to fulfilling its obligations under the Convention.

[0003] PFOS and PFOA, substances specified in the POPs Convention, have been included in Japan's water quality management target items since April 1, 2020, with a target value of 0.00005 mg / L (tentative) for the sum of these two substances. The Japanese Ministry of the Environment has also conducted surveys of rivers, lakes, seas, groundwater, and outflows. Thus, there is a widespread public demand for technologies to remove POPs such as PFOS and PFOA.

[0004] In addition, non-POPs (chemical substances that are difficult to decompose in the natural environment) may also be a cause of environmental pollution (e.g., water quality deterioration), and therefore it is desirable to remove them. It should be noted that the determination of whether a chemical substance is readily decomposed or recalcitrant is based on the following criteria recorded in the "Test Methods and Judgment Criteria Related to the Judgment of Compliance with Surveillance Chemical Substances" (final revision April 22, Heisei 23) stipulated by the Japanese National Regulations. That is, readily decomposed means: (1) In three test containers, the degree of decomposition based on BOD is 60% or more in two or more containers, and the average of the three containers is 60% or more. (2) At the same time, it is confirmed by direct analysis methods such as HPLC and GC that no decomposition products are generated. It should be noted that if the test results based on the test methods specified in the document do not meet the above criteria, and if biodegradation continues to occur after the test according to the BOD curve or other indications (such as an upward trend), the determination can be made based on the test results of OECD Test Criterion 302C. On the other hand, recalcitrant means not readily decomposed.

[0005] Examples of methods for purifying liquids containing recalcitrant substances (including POPs, hereinafter the same) as described above include (1) RO membrane treatment, (2) ion exchange resin adsorption, (3) activated carbon adsorption, (4) ozone oxidation decomposition, and (5) ultraviolet / photocatalyst methods.

[0006] In addition, as prior art related to this invention, there are inventions disclosed in Patent Documents 1 to 5.

[0007] Patent Document 1 discloses an operating method for a water treatment device using an impregnated membrane filtration unit. This method involves flowing a powdered activated carbon mixture (pre-added powdered activated carbon to raw water) into a membrane filtration tank, or flowing raw water into the membrane filtration tank and adding powdered activated carbon to form a powdered activated carbon mixture. This allows trace amounts of organic matter and other substances targeted for treatment in the raw water to be adsorbed onto the powdered activated carbon. The impregnated membrane filtration unit, installed within the tank, then performs solid-liquid separation of the powdered activated carbon mixture within the membrane filtration tank. The disclosed method achieves the following effect: the amount of water removed from the membrane filtration tank is at least 99% of the amount of water flowing into the membrane filtration tank, maintaining a high concentration of powdered activated carbon within the membrane filtration tank, thereby promoting the adsorption of the targeted substances.

[0008] Patent Document 2 discloses a wastewater treatment method. In this method, an adsorbent material capable of adsorbing dissolved harmful components is introduced into the raw water through an adsorbent material input section. After at least the dissolved harmful components are adsorbed onto the adsorbent material, the water is filtered using a filtration unit such as a membrane separation device to separate the adsorbent material containing the harmful components from the raw water. Then, the rinsing wastewater from the filtration unit is introduced into an accelerated oxidation treatment section for accelerated oxidation treatment, thereby rendering the harmful components harmless. The method discloses the following advantages: by using this method, dioxins, PCBs, chlorobenzene, trihalomethanes, and other organochlorine compounds and pigments contained in wastewater can be removed efficiently and at low cost.

[0009] Patent document 3 discloses a method for treating polluted water containing recalcitrant substances. This method, characterized by the following steps: adding an inorganic adsorbent to the polluted water containing the recalcitrant substances, and filtering the polluted water with the added inorganic adsorbent using a filter membrane; if necessary, after separating the polluted water by passing it through a reverse osmosis membrane, adding the inorganic adsorbent to the liquid component that did not pass through the reverse osmosis membrane. The method discloses the following advantages: According to this method, by adding an inorganic adsorbent to the polluted water to adsorb the recalcitrant substances, filtration using a filter membrane does not involve oxidative decomposition reactions in the reaction system. Therefore, it can also be applied to wastewater containing reducing agents such as bisulfite, and is not limited by the properties of the recalcitrant substances contained therein. It can efficiently and cost-effectively treat polluted water containing recalcitrant substances to achieve harmless treatment.

[0010] Patent document 4 discloses a method for treating water containing recalcitrant substances. The method includes the following steps: (B) adding an adsorbent to water containing recalcitrant substances (raw water for treatment) to adsorb the recalcitrant substances onto the adsorbent (adsorption treatment step); (C) separating the adsorbent containing the recalcitrant substances using a filtration membrane to obtain water concentrated with the adsorbent containing the recalcitrant substances (membrane filtration treatment step); and (D) without desorbing the recalcitrant substances adsorbed by the separated adsorbent from the adsorbent, but instead contacting the recalcitrant substances with a peroxide to chemically decompose them (chemical decomposition step). The method discloses the following advantages: when concentrating and rendering harmless recalcitrant substances such as dioxins contained in polluted water (raw water for treatment), it is also applicable to water containing reducing substances such as bisulfite that neutralize free chlorine, and is not limited by the properties of the recalcitrant substances contained therein, enabling efficient and low-cost rendering.

[0011] Patent document 5 discloses a method for treating water containing recalcitrant substances. The method includes the following steps: (B) adding an adsorbent to the water containing the recalcitrant substances, causing the recalcitrant substances to be adsorbed onto the adsorbent (adsorption treatment step); (C) using a filtration membrane to separate the permeate and concentrate the adsorbent containing the recalcitrant substances (membrane filtration treatment step); (D) decomposing the recalcitrant substances adsorbed by the concentrated adsorbent (recalcitrant substance decomposition step); and (E) returning the decomposed adsorbent to step (B) of the adsorption treatment step (adsorbent return step). The method discloses the following advantages: when concentrating and rendering harmless recalcitrant substances such as dioxins contained in polluted water, a closed system can be formed that effectively decomposes the recalcitrant substances adsorbed by solids in their original state without desorption or other operations.

[0012] Patent document 6 discloses a filtration device and a filtration method using the filtration device. The filtration device includes: a filtration assembly that houses a filter membrane within a housing and filters filtered water from raw water; a filtered water discharge unit connected to the filtration assembly and discharging filtered water; and an activated carbon suspension supply unit that supplies a suspension of activated carbon to the filtration assembly without introducing raw water, forming an activated carbon membrane or layer on the filter membrane by filtering the suspension, and then introducing raw water into the filtration assembly for filtration. The disclosed effect is that by reliably and uniformly forming an activated carbon membrane on the filter membrane, clogging of the filter membrane caused by turbidity substances in the raw water can be effectively prevented, enabling effective filtration.

[0013] Existing technical documents

[0014] Patent documents

[0015] Patent Document 1: Japanese Patent Application Publication No. 9-285779

[0016] Patent Document 2: Japanese Patent Application Publication No. 2003-266090

[0017] Patent Document 3: Japanese Patent Application Publication No. 2005-205300

[0018] Patent Document 4: Japanese Patent Application Publication No. 2006-192378

[0019] Patent Document 5: Japanese Patent Application Publication No. 2007-021347

[0020] Patent Document 6: Japanese Patent Application Publication No. 2005-193075 Summary of the Invention

[0021] The problem that the invention aims to solve

[0022] However, the aforementioned RO membrane (reverse osmosis) treatment requires a water pressure of approximately 4MPa to 7MPa, necessitating a powerful transfer pump for the treated liquid, resulting in high operating costs. Furthermore, due to the cross-flow method, the flow rate of each RO membrane is small, requiring a large number of membranes and leading to high initial costs. Additionally, the presence of substances other than recalcitrant compounds (such as organic matter) in the treated liquid can easily clog RO membranes, necessitating periodic maintenance to remove these blockages.

[0023] Compared to activated carbon, the ion exchange resin used in the above-mentioned ion exchange resin adsorption method has a higher adsorption capacity per unit volume of recalcitrant substances and superior adsorption performance, but it suffers from a higher unit price. Furthermore, the particle size of ion exchange resin is as small as 0.3 mm to 1 mmΦ (precision scale), thus offering advantages such as high contact efficiency with recalcitrant substances and an adsorption efficiency of over 90%. However, due to its fineness, it results in high water flow resistance. High water flow resistance necessitates slowing down the water flow rate, and to treat a certain amount of liquid, an increased number of bottles filled with ion exchange resin are required, leading to high initial costs. Additionally, the adsorption performance of ion exchange resin is easily degraded due to the presence of substances other than recalcitrant substances (such as organic matter) in the liquid being treated. Moreover, if the turbidity of the liquid being treated (referring to the degree of turbidity, with test methods in JIS K0101) is high, the gaps between ion exchange resin particles are easily blocked, necessitating the installation of a separate filter upstream of the ion exchange resin unit to reduce turbidity. In addition, due to the high cost of bottles filled with ion exchange resin, there are also problems such as high operating costs due to bottle replacement and high costs of waste disposal of used bottles.

[0024] Among the activated carbon adsorption methods described above, a representative approach is to use a device that packs activated carbon into granules (granule packing method). However, this granule packing method suffers from poor adsorption efficiency (adsorption efficiency) when the concentration of recalcitrant substances in the treated liquid is low. Specifically, at a space velocity (SV) of 5–10 (1 / Hr), only about 50–70% of recalcitrant substances can be adsorbed, resulting in high uncertainty regarding the removal of these substances. Furthermore, if the surface of the activated carbon granules is covered (masked) by suspended matter, biofilms, etc., in the treated liquid, the adsorption performance of the activated carbon granules deteriorates. To prevent such masking, a separate filter to remove these substances must be installed upstream of the activated carbon adsorption layer, or hypochlorous acid must be injected into the treated liquid, leading to high initial and operating costs. Additionally, the adsorption performance of activated carbon is also prone to deterioration due to the influence of substances other than recalcitrant substances (such as organic matter) in the treated liquid. Furthermore, the large amount of activated carbon granules required to remove recalcitrant substances results in high costs (both initial and operating). Additionally, activated carbon packing layers tend to become large, leading to the problem of large-scale equipment. Consequently, dehydration and drying devices must be installed downstream of the activated carbon to dispose of the adsorbed recalcitrant substances. For example, in the case of PFOS, since PFOS decomposes when heated to 850 degrees Celsius for 2 seconds, a device for decomposing PFOS must be installed downstream of the activated carbon packing layer.

[0025] In addition, the liquid to be treated can also be treated by the ozone oxidation decomposition method, ultraviolet / photocatalyst method, etc., but the equipment cost is high and the operating cost such as electricity is also high, and the efficiency of removing difficult-to-decompose substances is low, so there is a problem of ineffectiveness.

[0026] Furthermore, the methods in Patent Documents 1-5 involve mixing activated carbon or similar materials into the liquid to be treated, adsorbing recalcitrant substances onto the activated carbon, and then filtering the liquid using a filter. However, in these methods, while recalcitrant substances located around the activated carbon (particles) are adsorbed, those located far from the activated carbon (particles) are not. Typically, the liquid to be treated is transported smoothly to the filter without vigorous agitation, thus creating the problem that recalcitrant substances located far from the activated carbon (particles) are not removed and pass directly through the filter.

[0027] The method described in Patent Document 6 is a filtration process designed to effectively prevent clogging of the filter membrane caused by turbidity substances in the raw water. Its purpose is not to remove recalcitrant substances. Patent Document 6 uses a hollow fiber membrane as the filter membrane. In internally pressurized hollow fiber membranes, the flow rate of the suspension inside the membrane is faster, making it difficult to adsorb activated carbon powder inside. Even if adsorbed, it will be stripped off by the rapidly flowing suspension, making it practically impossible to adsorb activated carbon powder. On the other hand, in externally pressurized hollow fiber membranes, the maximum gap between adjacent hollow fiber membranes is typically about 0.5 mm. To ensure the passage of raw water, the maximum thickness of activated carbon that can be adsorbed is actually about 0.15 mm, which is insufficient for adsorbing recalcitrant substances and therefore ineffective. Furthermore, the surface area of ​​a single hollow fiber membrane is typically 50 m². 2 If we assume the thickness of the activated carbon adsorbed on the surface of the hollow fiber membrane is 0.15 mm, then the amount of activated carbon powder held by one hollow fiber membrane is approximately 4 kg. Therefore, to remove a large amount of recalcitrant substances, a large number of hollow fiber membranes must be prepared, increasing the initial cost. Furthermore, it has been disclosed that when adding activated carbon, a low concentration of up to 100 mg / L is used for pre-coating. Assuming 4 kg of activated carbon is added to one hollow fiber membrane, and assuming the number of hollow fiber membranes is 25, then 100,000 g / 0.1 g / 25 LMH / 50 m³ of activated carbon is required. 2 / 25 strands = 32 hours, the adsorption time of activated carbon is too long and impractical. Furthermore, while the disclosed average particle size of the adsorbed activated carbon is preferably 20-200 μm, this average particle size results in poor contact efficiency. Additionally, when cleaning the external pressure hollow fiber membrane, air wiping is performed, but this cleaning method uses filtered water for backwashing, resulting in significant water consumption and waste. As mentioned above, in Patent Document 6, activated carbon particles are thinly adsorbed onto the surface of the hollow fiber membrane, and these activated carbon particles are used as a filter aid, without forming the activated carbon layer (amount of activated carbon) required for the adsorption / removal of recalcitrant substances.

[0028] As mentioned above, the current situation is that a treatment method that can remove recalcitrant substances with a high probability and is economically sound, regardless of the concentration of recalcitrant substances in the treated liquid, has not yet been established. In particular, regarding PFOS, a recalcitrant substance, there are areas where the pollution concentration in rivers, well water, and gushing water is several times to about 170 times the national standard. In addition, it is believed that the concentration of the undiluted and diluted foam fire extinguishing agents (using PFOS) used in bases, ports, airports, etc., is thousands of times higher than the national standard. Therefore, the demand for devices and methods for removing recalcitrant substances is very high in reality.

[0029] Therefore, the main problem to be solved by the present invention is to provide a filtration device and filtration method with high efficiency in removing difficult-to-decompose substances.

[0030] Methods for solving problems

[0031] To address the above issues, the following methods can be employed.

[0032] (Method 1)

[0033] A filtration device for removing recalcitrant substances from a liquid being treated, characterized in that it comprises:

[0034] A filter container having a supply port for the liquid to be treated and a discharge port for the liquid to be treated; and

[0035] A pleated filter is disposed inside the aforementioned filter container. Its outer surface serves as the filter surface, while the interior forms the passageway for the treated liquid. Flat filter media is bent into a corrugated shape to create multiple pleats, forming a cylindrical structure.

[0036] Before filtration, the outer surface of the aforementioned pleated filter has an adsorbent layer.

[0037] The above-mentioned adsorbent layers contain adsorbents that adsorb the aforementioned difficult-to-decompose substances.

[0038] (Effects)

[0039] The first method is characterized in that, before the liquid to be treated is filtered, an adsorbent layer is formed on the outer surface of the filter. With this configuration, when filtering the liquid to be treated, most of the recalcitrant substances in the liquid to be treated can be adsorbed onto the adsorbent in the adsorbent layer formed on the surface of the filter, thereby removing recalcitrant substances from the liquid to be treated at a high ratio.

[0040] As described above, according to the methods in existing patent documents 1-5, an adsorbent is mixed into the liquid to be treated, and the recalcitrant substances contained in the liquid are adsorbed onto the adsorbent. Then, the liquid is filtered using a filter or the like. Therefore, substances close to the adsorbent particles are easily captured, but substances far from the adsorbent particles are difficult to capture. Consequently, recalcitrant substances not captured by the adsorbent particles remain in the treated liquid after passing through the filter. That is, the effect of removing recalcitrant substances from the treated liquid is extremely low.

[0041] On the other hand, in this method, all the liquid to be treated is passed through the filter. That is, by forming an adsorbent layer on the outer surface of the filter, recalcitrant substances in the liquid to be treated must pass through the adsorbent layer before passing through the filter and be adsorbed by the adsorbent during the passage through the adsorbent layer. Therefore, it is possible to reduce the recalcitrant substances that pass through the filter without contacting the adsorbent particles, which are generated in the methods of the above-mentioned prior art documents 1 to 5, and to remove recalcitrant substances in the liquid to be treated at a high ratio.

[0042] Furthermore, in the device described in the aforementioned prior art patent document 6, because a hollow fiber membrane is used as the filter membrane, only an extremely thin adsorbent layer can be formed on its surface (estimated to be at most about 0.15 mm). Therefore, the performance in removing recalcitrant substances from the treated liquid is extremely low. Therefore, the present invention uses a pleated filter as the filter membrane. By using a pleated filter, a thicker adsorbent layer can be formed on its surface (estimated to be at most about 4 mm), resulting in sufficient performance in removing recalcitrant substances from the treated liquid. Typically, to fully absorb recalcitrant substances from the treated liquid, the thickness of the adsorbent layer needs to be 1 mm or more. However, if the adsorbent layer is too thick, the pressure becomes excessive; therefore, 3 mm or less is preferred.

[0043] In addition, compared with a simple flat filter without pleated filter media, the surface area is increased by using a pleated filter, thus significantly improving the removal capacity of difficult-to-decompose substances in the treated liquid.

[0044] Furthermore, after the adsorbent forming the adsorbent layer adsorbs recalcitrant substances, the adsorbent must be removed / discharged, and new adsorbent must be added to the filter membrane. However, as mentioned above, due to the large surface area of ​​the pleated filter, the amount of adsorbent adsorbed on the pleated filter can be increased. As a result, the amount of recalcitrant substances that can be removed increases, and the period requiring adsorbent removal / discharge and re-addition can be delayed. That is, continuous filtration can be performed for a longer period of time. According to the inventors' estimates, even without adsorbent removal / discharge and re-addition, continuous filtration can be performed for more than one year when using a pleated filter.

[0045] (Method 2)

[0046] In the filtration device of the first method described above, the adsorbent layer is composed of multiple layers.

[0047] The average particle size of the first adsorbent in the first adsorbent layer located inside the adsorbent layer is greater than the average particle size of the second adsorbent in the second adsorbent layer located outside the adsorbent layer.

[0048] (Effects)

[0049] The adsorption capacity of an adsorbent decreases as it adsorbs substances that are difficult to decompose. Therefore, when the adsorption capacity drops below a certain level, the adsorbent layer needs to be peeled off and discharged from the surface of the pleated filter, and then a new adsorbent layer needs to be formed. Typically, the average particle size of the adsorbent is small, which can lead to adsorbent entering the gaps in the pleated filter and becoming difficult to peel off.

[0050] To avoid the aforementioned undesirable situations, in this method, the average particle size of the first adsorbent in the first adsorbent layer located inside the adsorbent layer is larger than the average particle size of the second adsorbent in the second adsorbent layer located outside the adsorbent layer. By increasing the average particle size of the first adsorbent in the first adsorbent layer located near the pleated filter, the first adsorbent is less likely to enter the gaps in the pleated filter, and it has the advantage of being easy to peel off when the adsorbent layer is peeled off. On the other hand, by decreasing the average particle size of the second adsorbent in the second adsorbent layer located outside the adsorbent layer, the specific surface area of ​​the second adsorbent increases, thereby improving the removal performance of the second adsorbent for recalcitrant substances. As described above, according to this method, the adsorbent layer is easy to peel off, and the removal performance of recalcitrant substances from the adsorbent layer is improved.

[0051] In particular, a characteristic of pleated filters used as filter membranes is that it is difficult to peel off the adsorbent adhering to the valleys between the pleats. This is especially true if the adsorbent has a small particle size. Therefore, by increasing the average particle size of the first adsorbent in the first adsorbent layer located near the pleated filter, peeling becomes easier, especially the peeling of the adsorbent layer in its valleys, which is a significant advantage.

[0052] It should be noted that, instead of using the first adsorbent layer as in this method, a solution containing a stripping agent that facilitates stripping can be passed into a pleated filter, with a stripping layer placed between the pleated filter and the adsorbent layer. However, such a stripping layer is not used to remove recalcitrant substances and has no purpose other than stripping the adsorbent layer. If the adsorbent layer deposited on the outer surface of the pleated filter becomes thick, the flow performance of the treated liquid decreases. Therefore, the thickness of the adsorbent layer must be kept below a specified thickness. However, with the stripping layer, the thickness of the adsorbent layer must be reduced by the amount of the stripping layer, resulting in a decrease in the removal efficiency of recalcitrant substances. In this method, even the first adsorbent layer, which serves a stripping function, is effective in removing recalcitrant substances, thus offering the advantage of higher removal efficiency compared to the method with a stripping layer.

[0053] Furthermore, this method is not limited to having two adsorbent layers, but also includes having three or more layers. When there are three or more adsorbent layers, the average particle size of the adsorbent in the inner adsorbent layer is greater than the average particle size of the adsorbent in the outer adsorbent layer. For example, when the adsorbent layer consists of three layers, and the laminated adsorbent layers are arranged sequentially from the inside (pleated filter side) to the outside as a first adsorbent layer, a second adsorbent layer, and a third adsorbent layer, it is sufficient that the average particle size of the first adsorbent in the innermost first adsorbent layer is greater than the average particle size of the second adsorbent in the second adsorbent layer located between the first and third adsorbent layers.

[0054] (Method 3)

[0055] A filtration system having a filtration device of the second type, characterized in that it comprises:

[0056] A first solution storage tank, wherein the first solution storage tank stores a first solution containing the first adsorbent described above;

[0057] The first solution delivery path delivers the first solution from the first solution storage tank to the filter container.

[0058] A second solution storage tank, wherein the second solution storage tank stores a second solution containing the aforementioned second adsorbent; and

[0059] The second solution delivery path delivers the second solution from the second solution storage tank to the filter container.

[0060] (Effects)

[0061] In the case of forming a multi-layered adsorbent layer as shown in the second embodiment, for example, a solution containing the first adsorbent needs to be fed to a filter container to form the first adsorbent layer, and a solution containing the second adsorbent needs to be fed to a filter container to form the second adsorbent layer. Regardless of the particle size of the adsorbent, liquids containing the same type of adsorbent are usually stored in the same storage tank. Therefore, typically the first solution containing the first adsorbent and the second solution containing the second adsorbent are stored in the same storage tank.

[0062] However, to ensure that the adsorbent layer on the outer surface of the pleated filter is multi-layered, the timing of supplying the first solution to the filter container needs to be staggered from the timing of supplying the second solution. Therefore, when both the first solution containing the first adsorbent and the second solution containing the second adsorbent are stored in the same storage tank, it is necessary to, for example, empty the storage tank (containing the first solution) after supplying the first solution to the filter container, generate the second solution inside the emptied storage tank, and then supply the second solution from the storage tank to the filter container. However, this results in a large time lag between the completion of the first solution supply and the start of the second solution supply, leading to low efficiency.

[0063] Therefore, in this method, it is considered meaningful that even if the first and second solutions contain the same type of adsorbent, the average particle size of the first adsorbent in the first solution differs from that of the second adsorbent in the second solution. Thus, the first and second solutions are stored in different storage tanks. Then, the first solution is transported from the first solution storage tank to the filter container via the first solution transport path, and the second solution is transported from the second solution storage tank to the filter container via the second solution transport path. With this configuration, the time lag from the completion of the first solution transport to the start of the second solution transport can be reduced, resulting in a highly efficient filtration system.

[0064] This method does not limit the number of storage tanks for storing solutions containing adsorbents to two; more than three storage tanks can also be provided. For example, three storage tanks can be provided: a first storage tank for storing the first solution, a second storage tank for storing the second solution, and a third storage tank for storing the third solution.

[0065] (Method 4)

[0066] A filtration system comprising a plurality of filtration devices of the first embodiment described above, arranged side by side, characterized in that it has:

[0067] Multiple extraction paths are provided, located downstream of each filtration unit, to extract the treatment liquid discharged from each filtration unit.

[0068] The set part, which makes the above multiple extraction path sets; and

[0069] A detector, which is installed in the above-mentioned collection section, detects recalcitrant substances contained in the above-mentioned treatment liquid.

[0070] (Effects)

[0071] In cases with multiple filtration units, it is necessary to monitor the filtration function of each unit. For example, if a filtration unit malfunctions, or if the adsorbent layer absorbs a large amount of recalcitrant substances, reducing its adsorption capacity, there is a concern that the treated liquid discharged from the filtration unit may contain high levels of these substances. To prevent this, the treated liquid discharged from each filtration unit is extracted separately. To detect any abnormalities in the amount of recalcitrant substances in this treated liquid (whether the content exceeds a specified value), the same number of detectors as the number of filtration units needs to be installed. This approach, requiring one detector per filtration unit, leads to increased initial costs.

[0072] Therefore, this method employs the following configuration: an extraction path (e.g., a pipe through which the treated liquid passes internally) is provided for extracting the treated liquid discharged from each filtration unit, and this extraction path converges at a later stage (the converged section is called the collection section), where a detector for detecting recalcitrant substances in the treated liquid is installed. By adopting this configuration, it is not necessary to install the same number of detectors as the number of filtration units, thus reducing initial costs. For example, even when multiple filtration units are installed, it is possible to monitor for abnormalities in the amount of recalcitrant substances contained in the treated liquid discharged from each filtration unit by installing only one detector.

[0073] (Method 5)

[0074] A filtration system comprising a plurality of filtration devices of the first embodiment described above, arranged side by side, characterized in that it has:

[0075] A timer that monitors the elapsed time from the start of filtration in each filtration unit; and

[0076] The liquid being treated supply pump stops supplying liquid to a portion of the filtration unit after a predetermined period of time since the start of filtration.

[0077] (Effects)

[0078] In cases with multiple filtration units, it is necessary to monitor whether recalcitrant substances are being adequately removed from each unit. As recalcitrant substances are adsorbed, the adsorption capacity of the adsorbent in the adsorbent layer decreases. Therefore, the adsorbent that has adsorbed a certain amount of recalcitrant substances needs to be replaced with new adsorbent.

[0079] The adsorption capacity of the adsorbent in each filtration unit decreases as the amount of treated liquid passing through the adsorbent layer (flow rate) increases. This flow rate is determined by the speed at which the treated liquid is delivered to the filtration unit (feed rate) and the time elapsed from when the treated liquid begins to pass through the adsorbent layer (flow time). It should be noted that the aforementioned flow time is the same as (or approximately the same as) the elapsed time after the start of filtration; therefore, the flow time is also referred to as the filtration time.

[0080] To utilize the aforementioned relationship, this method incorporates a timer and a control device. For example, after pre-confirming the relationship between the liquid delivery rate, liquid flow time, and the degree of reduction in adsorption capacity through simulation, the actual liquid flow time can be measured using a timer. When the liquid flow time reaches a predetermined time (a certain time), the control device can be used to stop supplying the treated liquid to the filtration device.

[0081] Unlike method 3, this system is cheaper by using a timer to determine when to stop supplying the treated liquid. This is because detectors for recalcitrant substances, typically used in method 3, are expensive, while using a universal timer is much cheaper.

[0082] (Method 6)

[0083] A filtration method, characterized in that it comprises:

[0084] In the adsorbent layer formation process, a solution containing an adsorbent that adsorbs recalcitrant substances is passed through a pleated filter, forming an adsorbent layer on the outer surface of the pleated filter. The outer surface of the pleated filter serves as the filter surface, while the interior is the passageway for the treatment liquid. Flat filter media is bent into a corrugated shape to form multiple pleats and then formed into a cylindrical shape.

[0085] In the adsorption-filtration process, the liquid to be treated is passed through the pleated filter having the adsorbent layer formed thereon, and the recalcitrant substances are adsorbed onto the adsorbent layer while the liquid is filtered.

[0086] (Effects)

[0087] It achieves the same effect as the first method mentioned above.

[0088] (Method 7)

[0089] The filtration method of the sixth method described above, wherein the adsorbent layer forming step comprises:

[0090] In the first adsorbent layer formation step, a first solution containing the first adsorbent is passed through the aforementioned pleated filter, and a first adsorbent layer is formed on the outer surface of the aforementioned pleated filter; and

[0091] In the second adsorbent layer formation step, a second solution containing a second adsorbent with an average particle size smaller than that of the first adsorbent is passed through a pleated filter to form a second adsorbent layer on the outer surface of the first adsorbent layer.

[0092] (Effects)

[0093] It achieves the same effect as the second method mentioned above.

[0094] The effects of the invention

[0095] According to the present invention, a filtration device and filtration method with high efficiency in removing substances that are difficult to decompose can be provided. Attached Figure Description

[0096] Figure 1 This is a structural diagram of the filtering device of the present invention. (A) is a front view, and (B) is a top view (although a pleated filter is present, its representation is omitted in the drawings).

[0097] Figure 2 This is an explanatory diagram of the filter (the cleaning device is not shown).

[0098] Figure 3 These are explanatory diagrams of a modified cleaning unit. (C) is a top view, (D) is an enlarged view of the protrusion, and (E) is a front view.

[0099] Figure 4 This is a structural diagram of the filtration system according to the first embodiment of the present invention.

[0100] Figure 5 This is a structural diagram of the filtration system according to the second embodiment of the present invention.

[0101] Figure 6 This is a structural diagram of the filtration system according to the third embodiment of the present invention.

[0102] Figure 7 In the diagram, (7A) is a cross-sectional view of a portion of the filter in the first and second embodiments. (7B) is a cross-sectional view of a portion of the filter in the third embodiment. Detailed Implementation

[0103] The preferred embodiments of the present invention will now be described. It should be noted that the following description and accompanying drawings illustrate only one embodiment of the present invention and should not be construed as limiting the scope of the invention to this single embodiment.

[0104] (The liquid being treated, A)

[0105] The liquid A to be treated by the filtration device 10 of the present invention is a liquid containing a difficult-to-decompose substance E, such as water from rivers or lakes, seawater, groundwater, gushing water, drainage from factories (semiconductor manufacturing plants or photographic film manufacturing plants, etc.), drainage from ships or vessels, etc.

[0106] (Substance E, which is difficult to decompose)

[0107] Substance E that is difficult to decompose refers to a substance that is not readily decomposed. In this invention, the determination of whether a substance is difficult to decompose or readily decomposed is based on the criteria described in the "Test Methods and Judgment Criteria Related to the Determination of Compliance with Surveillance Chemical Substances" (final revision April 22, 2004) stipulated in Japan.

[0108] The recalcitrant substance E that is the target of this invention can be exemplified by substances listed in the POPs Convention, such as those listed below. Specifically, examples include aldrin, α-hexachlorocyclohexane, β-hexachlorocyclohexane, chlordane, decachlorophenone, decabromodiphenyl ether, dieldrin, isodrin, heptachlorophenone, hexabromobiphenyl, hexabromocyclododecane, hexabromodiphenyl ether, heptabromodiphenyl ether, hexachlorobenzene, hexachlorobutadiene, lindane, mirex, pentachlorobenzene, pentachlorophenol, their salts and esters, polychlorinated biphenyls (PCBs), polychlorinated naphthalenes (including substances with chlorine numbers 2 to 8), short-chain chlorinated paraffins (SCCPs), endosulfan, tetrabromodiphenyl ether, pentabromodiphenyl ether, toxaphene, trichlorfon, perfluorooctanoic acid (PFOA). PFOA and its salts and PFOA-related substances, 1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane (DDT) in Appendix B, perfluorooctane sulfonic acid (PFOS) and its salts, perfluorooctane sulfonyl fluoride (PFOSF), hexachlorobenzene (HCB), hexachlorobutadiene, pentachlorobenzene (PeCB), polychlorinated biphenyls (PCB), polychlorinated dibenzo-dioxins (PCDD), polychlorinated dibenzofurans (PCDF), and polychlorinated naphthalenes (including substances with chlorine numbers 2 to 8) in Appendix C (it should be noted that there are duplicate substances in Appendix A and Appendix C).

[0109] In this invention, examples of the recalcitrant substance E that is particularly targeted include PFOS and its salts, PFOA and its salts and PFOA-related substances, PFHxS (perfluorohexanesulfonic acid) and its salts and PFHxS-related substances, and PFHxA (perfluorohexanoic acid).

[0110] (Adsorbent N)

[0111] It is preferable to use an adsorbent N for adsorbing recalcitrant substances E. The type of adsorbent N is preferably chosen appropriately depending on the type of recalcitrant substance E to be removed. For example, activated carbon is preferred as adsorbent N when it is desired to remove PFOS and its salts, PFOA and its salts and PFOA-related substances, PFHxS and its salts and PFHxS-related substances, and PFHxA. This is because it is inexpensive and readily available compared to other adsorbents N, and it has a high adsorption capacity for these recalcitrant substances E. Furthermore, the activated carbon particles preferably have a particle size of 1 to 30 μm, more preferably 5 to 9 μm. If the activated carbon particle size is less than 1 μm, the gaps between the activated carbon particles are too narrow, thus significantly slowing down the filtration rate of the treatment solution A. On the other hand, if the activated carbon particle size is greater than 30 μm, the gaps between the activated carbon particles become wider, and the recalcitrant substance E is not adsorbed by the activated carbon but passes through the gaps between the activated carbon particles and is mixed into the treatment solution B in large quantities. It should be noted that, as described in the aforementioned existing patent documents, activated carbon is sometimes used to adsorb the recalcitrant substance E. However, in such cases, activated carbon with a particle size of approximately 4 to 6 mm is typically used. In this embodiment, however, activated carbon with a particle size significantly smaller than this is used. By using activated carbon with such a small particle size, the contact efficiency between the recalcitrant substance E and the activated carbon is increased, resulting in a significant improvement in the removal performance of the recalcitrant substance E. Specifically, compared to using activated carbon particles with a particle size of approximately 4 to 6 mm, the specific surface area of ​​the activated carbon particles can be increased by approximately 80,000 to 100,000 times, thus significantly improving the contact efficiency between the recalcitrant substance E and the activated carbon. To increase the specific surface area of ​​the activated carbon, improve the contact efficiency between the recalcitrant substance E and the activated carbon, and further improve the removal effect of the recalcitrant substance E, activated carbon with a particle size of 5 to 9 μm is more preferably used, as described above.

[0112] It should be noted that, as an adsorbent N other than activated carbon, other suitable materials such as ion exchange resins (organic porous materials), zeolite, diatomaceous earth, acid clay, activated clay, carbon black, titanium dioxide (metal oxides or powders), and Prussian blue (cyan) can be used, depending on the type of the recalcitrant substance E. In other words, it is preferable to appropriately change the adsorbent N to one with a high adsorption capacity for the recalcitrant substance E, depending on the type of recalcitrant substance E to be removed.

[0113] (Adsorbent layer 47)

[0114] Preferably, an adsorbent layer 47 is formed on the outer surface of the filter 12 before the filtration of the treated liquid A begins. By pre-forming the adsorbent layer 47, during the filtration of the treated liquid A, most of the recalcitrant substances E in the treated liquid A can be adsorbed onto the adsorbent layer 47 (the adsorbent N constituting the adsorbent layer), thus enabling the removal of recalcitrant substances E from the treated liquid A at a high proportion. That is, by forming the adsorbent layer 47 on the outer surface of the filter 12, the recalcitrant substances E in the treated liquid A must pass through the adsorbent layer 47 before passing through the gaps in the filter 12, so that during the passage through the adsorbent layer 47, the adsorbent N can adsorb most of the recalcitrant substances E contained in the treated liquid A.

[0115] The thickness of the adsorbent layer 47 can be set arbitrarily, preferably about 1 to 4 mm, more preferably about 1.5 to 4 mm, and even more preferably about 3 to 4 mm. If the thickness of the adsorbent layer 47 is thinner than 1 mm, the recalcitrant substance E in the treated liquid A can easily pass through the gaps between the adsorbent particles constituting the adsorbent layer 47, resulting in an increase in the concentration of the recalcitrant substance E in the treated liquid B. For example, when using activated carbon particles with an average particle size of about 10 μm for adsorption / removal of PFOS, it is difficult to remove PFOS efficiently unless the thickness of the activated carbon layer 47 is at least 1.5 mm, preferably at least 3 mm. On the other hand, if the thickness of the adsorbent layer 47 is thicker than 4 mm, the resistance to allowing the treated liquid A to pass through the gaps between the particles of the adsorbent layer 47 becomes too large, thus placing a heavy load on the pump (8a) used to pressurize the treated liquid A and significantly reducing the filtration speed. It should be noted that the thickness of the adsorbent layer 47 is related to the distance between adjacent pleats of the pleated filter (pleat spacing). That is, in order to avoid filling the gaps between pleats with adsorbent N, the thickness of the adsorbent layer 47 must be reduced when the pleat spacing is small, and increased when the pleat spacing is large. As mentioned above, if the pleat spacing is small, the thickness of the adsorbent layer 47 becomes thinner (limiting the amount of adsorbent N), but the surface area of ​​the pleated filter (the area for adsorbent N) becomes larger, thus increasing the flow rate of the treated liquid A.

[0116] (Filter device 10)

[0117] The filtration device 10 of the embodiment is a full-volume filtration (dead-end filtration) type device as follows: the liquid to be treated A is filtered by the filter 12 in a closed filtration container 11, and the liquid to be treated B (e.g., filtrate, hereinafter referred to as "filtrate B"), the adsorbent N constituting the adsorbent layer 47, and the filter cake K formed on the outer surface of the adsorbent layer 47 are discharged.

[0118] (Filter container 11)

[0119] The filtration device 10 includes a filter container 11 that houses the filter 12. A filter cake discharge chute 11S is provided at the lower part of the filter container 11, and a cylindrical filter housing 11U is formed in a continuous shape above the filter cake discharge chute 11S. The shape of the filter container 11 is not limited to the shape described above, and can be changed to any shape, such as a shape without the filter cake discharge chute 11S.

[0120] (Tubular body 12s)

[0121] Inside the filter container 11, there is a cylindrical body 12s with perforations for filtrate B formed on its wall surface and a filtrate passage 12r formed inside. The figure shows a cylindrical body, positioned within the filter container 11 with its central axis aligned vertically. The shape and orientation of the cylindrical body 12s are not particularly limited; it can be any known shape, such as a square cylinder, or positioned with its central axis horizontal within the filter container 11. It should be noted that the illustrated cylindrical body 12s is formed by molding a perforated metal or other flat plate with perforations into a cylindrical shape, and the space inside the cylindrical body 12s becomes the filtrate passage 12r.

[0122] (12m filter membrane)

[0123] A filter membrane 12m is provided on the outer side of the wall of the aforementioned cylindrical body 12s. Since this filter membrane 12m has a large surface area (filtration area), it is preferable to use a pleated filter formed by bending flat filter media into a serrated (corrugated) shape and wrapping it around the outer circumference of the cylindrical body 12s to create a cylindrical shape. Compared to a simple flat filter without bent filter media, the surface area of ​​the filter is increased by using a pleated filter, thus significantly improving the processing capacity of the treated liquid A per unit time. In order to remove as much of the recalcitrant substance E from the treated liquid A as possible, it is necessary to slow down the speed at which the treated liquid A passes through the filter 12, thus generally tending to result in a lower filtration throughput per unit time. However, even in such cases, by using a pleated filter instead of a flat filter, the reduction in the filtration throughput of the treated liquid A can be prevented.

[0124] It should be noted that, as described above, multiple pleats can be formed by bending the filter media into a serrated shape. This pleated filter has the advantage of easy peeling and discharge of the filter cake K because the spacing between adjacent pleats gradually widens from the inside to the outside. It should also be noted that the length L1 between adjacent pleats and their leading ends can be, for example, 6 mm, and the length L2 from the leading end to the base of the pleat can be, for example, 100 mm.

[0125] The filter membrane 12m can be a single layer or multiple layers. As the material (filter media) for the filter membrane 12m, for example, polytetrafluoroethylene (also known as "Teflon" (registered trademark)), polyester, polyphenylene sulfide (PPS) resin, nylon, stainless steel, etc., can be used. The membrane thickness of the filter membrane 12m is preferably 0.3 mm to 0.7 mm, more preferably 0.6 mm. Furthermore, the fiber diameter of the filter media (referring to the diameter of the projected area equivalent circle, Heywood diameter, hereinafter the same) is preferably 0.1 μm to 3 μm, more preferably 0.1 μm. If fibers with a diameter finer than 0.1 μm are used, the filtration resistance increases, and the apparent surface area narrows. Conversely, if fibers with a diameter coarser than 3 μm are used, adsorbent N particles (e.g., activated carbon particles) will pass through the gaps between the fibers of the filter membrane 12m. Therefore, it is preferable to use filter media with a fiber diameter of 0.1 μm to 3 μm to form a filter membrane 12m with a certain degree of mesh roughness. Through this filter membrane 12m, during filtration, the suspended particles in the treated liquid A attached to the surface of the filter membrane 12m, together with the adsorbent N, function as a filter layer. It should be noted that the length of the filter membrane 12m in the longitudinal direction can be, for example, 300mm to 2000mm.

[0126] In this method, the surface 12f of the filter membrane 12m refers to the surface facing the filter container 11, which is the surface in contact with the liquid being treated A. On the other hand, the back surface 12b of the filter membrane 12m refers to the surface facing the cylindrical body 12s, which is the surface in contact with the filtrate B.

[0127] Furthermore, since cleaning powder F is sprayed onto the surface 12f of the filter membrane 12m, it is preferable to use a filter membrane 12m with a specified strength or higher to prevent damage to the filter membrane 12m due to the shock wave from the sprayed powder F. For example, in the JIS L-1906 test method, tensile strength (N / 5cm) longitudinal: 1200, transverse: 700, and breaking strength (kgf / cm) can be used. 2 Vertical: 25 of the material.

[0128] (Filter support 29)

[0129] Preferably, a support plate (filter support 29) is arranged on the inner surface of the pleats (so that it contacts the back surface 12b of the filter membrane 12m) along the shape of the pleats, in a serrated pattern. As the filter cake K accumulates on the surface 12f of the filter membrane 12m, the pleats of the pleated filter may be crushed, potentially causing "clogging" where the space within the pleats disappears. However, by providing the filter support 29, this clogging can be prevented.

[0130] (Supply of the treated liquid A)

[0131] A supply port 4 for the treated liquid A can be provided on the side of the filter container 11. Figure 1 In one embodiment, the supply port 4 is located at the lower part of the filter container 11, but it can also be located at the upper part or middle part of the filter container 11 (the part between the upper and lower parts in the height direction LD of the filter container 11) or any other location.

[0132] It should be noted that the storage tank 7 for the treated liquid A is connected to the filter container 11 via supply pipes 13 and 14. The treated liquid A is transported from the storage tank 7 to the filter container 11 by a pressure pump 8 (8a). More specifically, the treated liquid A is transported to the coarse filter 9 via the supply pipe 13, and after removing foreign matter such as debris from the treated liquid A, it is transported to the filter container 11 via the supply pipe 14. It should be noted that one pressure pump 8 (8a) is provided in this embodiment, but two or more can be added if it is desired to increase the supply of the treated liquid A. Alternatively, a level gauge (not shown) can be installed in the storage tank 7 to replenish the treated liquid A from the outside when the level in the storage tank 7 is lower than a predetermined value.

[0133] (Discharge of filtrate B)

[0134] A discharge port 15 is provided at the upper part of the filter container 11 for discharging filtrate B outside the filter container 11. Filtrate B flows from the upper opening of the filtrate passage 12r through the discharge port 15 and is guided to the discharge pipe 16. It should be noted that... Figure 1 In this embodiment, as described above, the outlet 15 of the filtrate B is located at the upper part of the filter container 11, but it can also be located at the lower part or middle part of the filter container 11, or any other location.

[0135] (Filter cleaning device 35)

[0136] When filtration is performed using the filter device 10, the recalcitrant substance E in the treated liquid A is adsorbed by the adsorbent N in the adsorbent layer 47. However, there is a limit to the amount of recalcitrant substance E that the adsorbent N can adsorb, and it gradually becomes unable to adsorb the recalcitrant substance E. Therefore, it is necessary to peel off the adsorbent layer 47, which has reduced its adsorption capacity for the recalcitrant substance E, from the filter 12 and discharge it from the filter device 10.

[0137] Furthermore, during filtration using the filter device 10, suspended particles in the treated liquid A (mainly suspended particles other than the recalcitrant substance E; the same applies hereinafter) accumulate on the outer surface of the adsorbent layer 47, forming a filter cake K. Specifically, in the initial filtration stage, a portion of the suspended matter in the treated liquid A is retained inside the adsorbent layer 47. However, as filtration progresses, the gaps within the adsorbent layer 47 become filled with suspended matter, reducing its size. Consequently, most of the suspended matter in the treated liquid A begins to accumulate on the outer surface of the adsorbent layer 47, forming a filter cake K on the outside of the adsorbent layer 47. If a filter cake K forms, the treated liquid A has difficulty reaching the adsorbent layer 47 and the filter 12, reducing filtration capacity. Therefore, it is necessary to peel off the filter cake K when it reaches a predetermined thickness and discharge it from the filter device 10.

[0138] Therefore, in order to remove such adsorbent layer 47 and filter cake K, a filter cleaning device 35 is preferably provided. This cleaning device 35 can be manufactured as a component of the filter device 10, or it can be manufactured as a different product from the filter device 10 and then installed on the filter device 10.

[0139] The cleaning device 35 is located outside the filter 12.

[0140] Figure 1 The cleaning device 35 shown includes: a cleaning liquid tank 36 disposed outside the filter container 11; and a spray outlet 37 disposed in the cleaning liquid tank 36 on the side opposite to the filter 12. The spray outlet 37 is preferably a slit extending axially along the opposite filter 12.

[0141] The cleaning fluid tank 36 is preferably shaped such that at least one side opposite to the filter 12 extends along the axial direction of the filter 12. The illustrated cleaning fluid tank 36 is a hollow prism extending in the same direction as the axial direction of the filter 12. However, it is not limited to this shape and can be changed to any known shape such as a cylinder.

[0142] When configuring the cleaning fluid tank 36, it is preferable that the filter 12 side of the cleaning fluid tank 36 is parallel or substantially parallel to the filter membrane surface 12f. This is to reduce cleaning unevenness in the aforementioned extending direction by making the distance between the nozzle 37 and the filter membrane surface 12f as equal as possible in the extending direction of the filter membrane surface 12f (the direction orthogonal to the circumferential direction of the filter membrane 12m). In addition, the length of the central axis of the cleaning fluid tank 36 is preferably the same as the length of the central axis of the filter membrane 12m, for example, it can be 300mm to 2000mm.

[0143] The outer surface of the filter 12 side of the cleaning fluid tank 36 contacts the outer surface of the filter container 11 (or it can be sandwiched with a gasket, etc.). At their joint, the filter container 11 also has the same hole as the spray outlet 37 (not shown). The cleaning fluid C is sprayed onto the outer surface of the filter 12 through the spray outlet 37 and the hole in the filter container 11. The sprayed cleaning fluid C becomes a shock wave and collides with the filter cake K, the adsorbent layer 47 and the filter 12. Through this impact, the filter cake K and the adsorbent layer 47 are peeled off from the filter 12.

[0144] It should be noted that during filtration, since the adsorbent N is in a state of surface filtration on the surface of the filter membrane, the possibility of the adsorbent N penetrating into the filter membrane from its outer surface is low. Furthermore, during stripping, the surface of the filter membrane becomes easy to peel off (especially significant when the filter membrane is a PTFE membrane), thus eliminating the need to form a stripping layer.

[0145] (Powder / Particle F)

[0146] Preferably, particulate matter F is mixed into the cleaning solution C. The particulate matter F in the cleaning solution C collides with the filter cake K, the adsorbent layer 47 and the filter 12, thereby facilitating the separation of the filter cake K and the adsorbent layer 47 from the filter 12.

[0147] The powder / granule F refers to powders and particles, such as spherical plastic beads, spherical perlite beads, spherical sponges such as spherical polyvinyl chloride sponges, and sand such as silica sand. The powder / granule F is sprayed onto the filter 12 while mixed with the cleaning liquid C. Therefore, from the perspective of preventing deterioration of the filter 12, the powder / granule F is not preferably angular particles such as sand, but preferably spherical or ellipsoidal particles with rounded corners. Furthermore, from the same perspective, the powder / granule F preferably has low hardness. Specifically, the hardness of the powder / granule F is preferably R20 to R110. In addition, the powder / granule F is preferably uniformly dispersed in the cleaning liquid C. Therefore, the specific gravity of the powder / granule F is preferably, for example, 0.8 to 1.2 g / cm³. 3 In addition, the particle size of powder F is preferably suitable for recycling and reuse, i.e., for grading. Specifically, the particle size is preferably 0.2 mm to 1 mm, more preferably 0.4 mm to 0.7 mm, but even particles of the above-mentioned size can be fully utilized as powder F. It should be noted that the particle size of powder F is a value measured according to JIS Z8800.

[0148] (Cleaning solution C)

[0149] As the cleaning fluid C, purified liquids such as tap water can be used. However, since the cleaning fluid C used for cleaning the filter 12 needs to be purified by filtration, etc., the liquid to be treated A is preferred from the perspective of economy and efficiency.

[0150] (Gap 50)

[0151] It should be noted that cleaning of filter 12 is preferably performed when the treated liquid A has been discharged from the gap 50 between filter container 11 and filter 12. After the treated liquid A is discharged from the gap 50, the gap 50 is filled with gas, so the momentum of the cleaning liquid C is not significantly reduced, and the cleaning liquid C comes into contact with the filter cake K, adsorbent layer 47, and filter 12. Therefore, the peeling force of filter cake K and adsorbent layer 47 is increased. Conversely, if the cleaning liquid C is sprayed when the gap 50 is filled with the treated liquid A, the momentum of the cleaning liquid C is weakened due to the treated liquid A in the gap 50, and therefore the peeling force of filter cake K and adsorbent layer 47 is reduced.

[0152] (Rectifier baffle 51)

[0153] Preferably, a flow-rectifying baffle 51, formed by bending a flat plate into a V-shape, is installed near the supply port 48 of the cleaning fluid tank 36, extending downwards from the upper end of the cleaning fluid tank 36. As shown in the figure, the bent portion can be positioned on the supply port 48 side, and the front end on the slit 37 side. By installing this flow-rectifying baffle 51, the cleaning fluid C supplied from the supply port 48 into the cleaning fluid tank 36 comes into contact with the flow-rectifying baffle 51, changing its flow direction. Specifically, a portion of the cleaning fluid C bypasses the side of the flow-rectifying baffle 51 and sprays out from the upper part of the slit 37, while another portion flows downwards from the cleaning fluid tank 36 and sprays out from the middle or lower part of the slit 37. By installing the flow-rectifying baffle 51 in this way, the amount of cleaning fluid C sprayed from the slit 37 can be uniform, regardless of whether it is sprayed from the upper, middle, or lower part of the slit 37.

[0154] (other)

[0155] The differential pressure of the slit nozzle 37 (the differential pressure between the cleaning fluid tank 36 and the filter container 11) is preferably 80 kPa to 150 kPa. Below 80 kPa, the filter cake K is difficult to peel off. Furthermore, above 150 kPa, the filter membrane 12m will be damaged due to the impact of the cleaning fluid C. This ejection pressure can be determined taking into account the adhesion of the filter cake K (the type of particles constituting the filter cake K, the moisture content of the filter cake K, etc.).

[0156] Furthermore, in order to remove the filter cake K without any omissions, it is preferable to make the cleaning liquid C contact the entire outer peripheral surface of the filter 12. Therefore, during cleaning, the filter 12 can be rotated around its axis by a motor M located at the top of the filter device 10.

[0157] (Modified Example)

[0158] like Figure 3As shown, the periphery of the slit 37 can be shaped to protrude toward the filter 12. More preferably, the two transverse ends of the periphery of the slit 37 can protrude toward the filter 12, and the gap S between the two ends of the protrusion 45 has a structure that narrows as it moves toward the filter 12. Furthermore, it is preferable that the length of the gap between the two ends of the protrusion 45 closest to the front end of the filter 12 is 0.5 mm to 1.5 mm, more preferably 1 mm. With such a structure, the filter cake K can be effectively peeled off. In addition, since the cleaning fluid C is always pressured from the inside to the outside of the cleaning fluid tank 36, the width S of the slit 37 is prone to expand due to the internal pressure, but by making the slit 37 a protruding shape, the resistance to internal pressure is increased, and the expansion of the width S can be suppressed.

[0159] (Filtering method)

[0160] The following is for reference Figure 4 An example of a filtering method is illustrated.

[0161] (Mixed liquid generation process)

[0162] First, adsorbent N and diluent H are placed in the mixture storage tank 24, and they are stirred using a manual mixer 65 (or a stirring device other than a mixer) to generate mixture G. Tap water, the treated liquid A, etc., can be used as the diluent H. Using the treated liquid A has the advantage of lower operating costs compared to using tap water as the diluent H. However, since the treated liquid A contains a recalcitrant substance E, if the mixture G is to be conveyed to the filter 12 to form an adsorbent layer 47, the recalcitrant substance E in the mixture G may pass through the filter 12. To prevent this, it is preferable to ensure that almost all the recalcitrant substance E in the diluent H (treated liquid A) is adsorbed by the adsorbent N in the mixture storage tank 24 before conveying the mixture G to the filter 12. Thus, the adsorbent N, having adsorbed the recalcitrant substance E contained in the diluent H (treated liquid A), remains on the outer surface of the filter 12, thereby eliminating the problem of the recalcitrant substance E in the mixture G passing through the filter 12. It should be noted that, in order to ensure that almost all the recalcitrant substance E in the diluted solution H (the solution being treated A) is adsorbed by the adsorbent N, increasing the amount of adsorbent N placed in the mixed solution storage tank 24, or thoroughly stirring using the mixer 65, is effective. As described above, the process of mixing the adsorbent N and the diluted solution H to generate a mixed solution is called the mixed solution generation process.

[0163] (Adsorbent layer formation process)

[0164] Next, an adsorbent layer 47 is formed (adsorbent layer formation step). This adsorbent layer 47 is preferably formed completely on the entire outer surface (the entire surface) of the filter 12. This is because if there are portions on the outer surface of the filter 12 where the adsorbent layer 47 is not formed, when the liquid to be treated A is supplied to the filter device 20, the recalcitrant substances E in the liquid to be treated A will not be adsorbed by the adsorbent N in the portions where the adsorbent layer 47 is not formed, but will pass through the filter 12 and be discharged while entering the liquid to be treated B. Furthermore, the adsorbent layer 47 is preferably formed on the entire outer surface (the entire surface) of the filter 12 with a uniform thickness (uniform density). If the thickness of the adsorbent layer 47 is uneven, the liquid to be treated A is less likely to pass through the thicker portions of the adsorbent layer 47, and therefore tends to pass through the thinner portions of the adsorbent layer 47. Moreover, in the thinner portions of the adsorbent layer 47, the amount of adsorbent N is insufficient, so some of the recalcitrant substances E in the liquid to be treated A may not be adsorbed by the adsorbent N and may pass through the filter 12.

[0165] To form an adsorbent layer 47 of uniform thickness and without any omissions on the entire outer surface (the entire surface) of the filter 12, the following operation is performed, for example. First, the adsorbent layer 47 is placed in the supply pipe 14 (in Figure 1 In the filtration system, a common supply pipe 14 is used as the supply pipe for the treated liquid A and the mixed liquid G (but different supply pipes may also be used). Valve V1 and valve V2, located on the discharge pipe 16, are opened, while other valves V3 to V5 are closed. Then, the mixed liquid supply pump 8b is driven to transport the mixed liquid G from the mixed liquid storage tank 24 to the supply pipe 14. After the mixed liquid supply pump 8b is started, the treated liquid supply pump 8a is driven to transport the treated liquid A from the treated liquid storage tank 7 to the supply pipe 14. Then, the treated liquid A and the mixed liquid G are mixed in the supply pipe 14, the mixed liquid G is diluted with the treated liquid A, and the diluted mixed liquid G is transported to the filtration device 10.

[0166] It should be noted that the reason for mixing the treated liquid A and the mixed liquid G in the supply pipe 14, diluting the mixed liquid G with the treated liquid A, and then supplying the diluted mixed liquid G to the filter device 10 is as follows: To ensure that the thickness (density) of the activated carbon layer 47 formed on the outer surface of the pleated filter 12 is approximately uniform across all outer surfaces of the pleated filter 12, it is necessary to increase the differential pressure between the outer and inner sides of the pleated filter. This differential pressure is related to the flow rate; in the case of clean water, it is approximately 10 kPa at 100 LMH and approximately 30 kPa at 300 LMH. However, when activated carbon N is added to the pleated filter, it is approximately 30 kPa at 100 LMH and rises to approximately 80 kPa at 300 LMH. While it is possible to uniformize the amount of activated carbon N added at around 300 LMH, a flow rate of 15 m³ / h is required to achieve such a differential pressure. 3 A flow rate of / H is too high to be maintained by the mixture G alone. Therefore, it is preferable to mix the liquid to be treated A with the mixture G to increase the flow rate, and then use the diluted mixture G to add activated carbon N.

[0167] As described above, the diluted mixture G supplied to the filter device 10 preferably has an adsorbent N concentration of approximately 3000–5000 mg / L. To achieve this concentration, the flow rate of the mixture G supplied to the mixture supply pump 8b and the flow rate of the treated liquid A supplied to the treated liquid supply pump 8a can be adjusted. In the mixture G supplied to the filter device 10, the adsorbent N contained in the mixture G accumulates on the outer surface of the filter 12 to form an adsorbent layer 47. It should be noted that when the adsorbent layer 47 is formed, a large differential pressure is generated between the outer (upstream) and inner (downstream) sides of the filter 12. By generating this differential pressure, uneven adsorbent N relative to the filter 12 can be suppressed (the areas with large adsorbent N accumulation and the areas with small adsorbent N accumulation become smaller), and the thickness of the adsorbent layer 47 can be made uniform. That is, during the formation of the adsorbent layer 47, even if a region with a low amount of adsorbent N is temporarily formed, the amount of mixture G passing through that region naturally increases, thus naturally homogenizing the thickness of the adsorbent layer 47. Furthermore, the liquid portion of the mixture G passes through the filter 12 and exits through the discharge pipe 16 (in...) of the residual liquid J (the liquid after the adsorbent N has been removed from the mixture G). Figure 1 In the filtration system, a common discharge pipe 16 is used as the discharge pipe for both the treated liquid B and the residual liquid J (but different discharge pipes can also be used to discharge them outside the filtration system). When the thickness of the adsorbent layer 47 reaches the specified thickness, the operation of pump 8b is stopped, the delivery of the mixed liquid G is stopped, and the adsorbent layer formation process ends. The thickness of the adsorbent layer 47 is not particularly limited and can be arbitrarily determined. Preferred values ​​for the thickness of the adsorbent layer 47 are as described above, and therefore are omitted here.

[0168] It should be noted that when using a pleated filter, the pre-coating with water at a suspended concentration of 5000 mg / L and 300 LMH is used. Therefore, the dosage is 100000 / 5g / 300 LMH / 50m 2 The coating process takes 1.33 hours, which is significantly faster than that described in Patent Document 6.

[0169] (Adsorption-filtration process)

[0170] After the adsorbent layer 47 is formed on the surface of the filter 12, the treated liquid A is filtered. Specifically, the treated liquid supply pump 8a installed in the treated liquid storage tank 7 is started without changing the opening and closing of valves V1 to V5. Then, the treated liquid A is transported to the coarse filter 9 through the treated liquid A supply pipe 13, and the waste contained in the treated liquid A is removed in the coarse filter 9. Afterwards, the treated liquid A discharged from the coarse filter 9 is supplied to the filter container 11 through the supply pipe 14. It should be noted that the flow rate of the treated liquid A supplied to the filter container 11 is preferably about 0.001 m / s to 0.004 m / s (flux of 50 LMH to 200 LMH), and more preferably about 0.0017 m / s to 0.0025 m / s. Regarding the efficiency of adsorbent N in adsorbing the recalcitrant substance E (adsorption efficiency), the contact efficiency between the adsorbent N particles and the treated liquid A is an important factor. The contact efficiency depends on the contact area and contact time (i.e., the flow rate of the treated liquid A) between the adsorbent N particles and the treated liquid A. Therefore, to improve the adsorption efficiency, it is necessary to reduce the particle size (average particle size) of the adsorbent N particles and slow down the flow rate of the treated liquid A, thus slowing down the speed at which the treated liquid A passes through the adsorbent layer 47. Therefore, as described above, it is preferable to slow down the flow rate of the treated liquid A.

[0171] The treated liquid A, arriving at the filter container 11, is then filtered by the filter 12. More specifically, the recalcitrant substances E in the treated liquid A are captured by the adsorbent N of the adsorbent layer 47, and the treated liquid A, with the recalcitrant substances E removed, is filtered by the filter 12. Through this filtration, the liquid of the treated liquid A moves through the filter membrane 12m to the filtrate passage 12r and is discharged from the outlet 15 as filtrate B. The filtrate B discharged from the outlet 15 is discharged outside the system through the discharge pipe 16. On the other hand, the solids (suspended particles) of the treated liquid A adhere to and accumulate on the surface 12f of the filter membrane 12m, resulting in the formation of a filter cake K. It should be noted that the liquid flow resistance per unit area of ​​the filter 12 increases proportionally to the cumulative liquid flow (i.e., the amount of solid components separated from the treated liquid A).

[0172] The filter cake K formed on the surface of filter 12 has a certain degree of liquid permeability, giving it the advantage of functioning as an auxiliary filter for filter 12. However, it also has the disadvantage that its liquid permeability decreases as the filter cake thickens. That is, the liquid flow resistance increases proportionally as the filter cake thickens. Therefore, if a certain amount of filter cake K accumulates, it is necessary to reduce the liquid flow resistance of filter 12 and increase the filtration flow rate. Thus, the filtration process ends when the amount of filter cake K increases to a predetermined level, i.e., when filter 12 becomes clogged.

[0173] The amount of filter cake K generated is proportional to the turbidity of the treated liquid A and the cumulative water flow (i.e., the amount of solid components separated from the treated liquid A). Therefore, the interval from the start of the filtration process to the clogging of filter 12 and the subsequent cleaning process is determined by the generation time of filter cake K. It should be noted that the filter clogging pressure resistance is, for example, 200 kPa.

[0174] When filtration is stopped due to the formation of filter cake K, the following configuration can be used: A pressure gauge (not shown) is used to measure the internal pressure at the supply port 4 of the treated liquid A in the filter container 11, and simultaneously, a pressure gauge (not shown) is used to measure the internal pressure at the discharge port 15 of the treated liquid B. The filtration process ends when the differential pressure reaches a certain value. Alternatively, other methods can be used to determine whether to stop filtration. For example, a flow meter (not shown) can be used to measure the discharge volume of filtrate B per unit time, and the filtration process ends when this volume falls below a certain value. Furthermore, the determination can be made based on whether a predetermined time has elapsed since the start of the filtration process, or by measuring the thickness of the filter cake K. When the filter cake thickness reaches approximately 1 mm to 2 mm, it can be determined that the filter cake K is no longer suitable for filtration.

[0175] Furthermore, if filtration is performed using the filter device 10, the recalcitrant substance E in the treated liquid A is adsorbed by the adsorbent N in the adsorbent layer 47. However, there is a limit to the amount of recalcitrant substance E that the adsorbent N can adsorb, and it gradually becomes unable to adsorb the recalcitrant substance E. Therefore, if the adsorption capacity of the recalcitrant substance E decreases to a certain extent, the filtration process ends in order to peel the adsorbent layer 47 off the filter 12 and discharge it.

[0176] When filtration is stopped due to a decrease in the adsorption performance of the recalcitrant substance E in the adsorbent layer 47, for example, a concentration meter 25 can be installed in the discharge pipe 16 of the treated liquid B to measure the concentration of the recalcitrant substance E in the treated liquid B. The filtration process ends when the concentration of the recalcitrant substance E in the treated liquid B exceeds the allowable value. The timing for ending the filtration process can also be determined by other methods. For example, it can be determined based on whether a predetermined time has elapsed since the start of the filtration process.

[0177] As mentioned above, the main reasons for stopping filtration can be cited as (1) the formation of filter cake K and (2) the reduction in the adsorption capacity of adsorbent N for the recalcitrant substance E. Of these two main reasons, the main reason mentioned above (2) is particularly important. This is because it is a top priority to prevent the recalcitrant substance E in the treated liquid B from exceeding a predetermined allowable value. Therefore, it is preferable to immediately end the filtration process when the adsorption capacity of adsorbent N decreases to an unacceptable level. In addition, even if the adsorption capacity of adsorbent layer 47 still has some capacity, the filtration process can be ended at this stage when the filter cake K becomes a predetermined thickness or more and the filtration rate of the treated liquid A slows down to an unacceptable level.

[0178] As described above, the recalcitrant substance E in the treated liquid A is simultaneously adsorbed by the adsorbent layer 47, and the treated liquid A is filtered by the filter 12. This process is called the adsorption-filtration process.

[0179] It should be noted that the attached diagram shows a flow sensor 46. This flow sensor 46 can detect the flow rate of the processed liquid B passing through the pipe 16 per unit time and the cumulative flow rate of the processed liquid B after filtration begins. If the flow rate of the processed liquid B per unit time is abnormally low, or if the cumulative flow rate of the processed liquid B after filtration begins exceeds a specified value, it can control the filtration process by stopping the drive of the pump 8a.

[0180] (Purge process)

[0181] Next, the purging process using gas (also known as the "gas purging process") performed after the filtration process will be described.

[0182] First, close valves V1, V2, and V4, open valves V3 and V5, and start compressor 6. The pressure of compressor 6 can be, for example, around 20 kPa. Then, gas D (e.g., air; when using air, this is called air purging. Alternatively, other gases such as nitrogen can be used instead of air) from compressor 6 is guided into the filtrate passage 12r via air supply pipes 19 and 16 (air supply pipe 16 also serves as the discharge pipe for filtrate B). At the end of the filtration process, filtrate B remains in the filtrate passage 12r, but is squeezed outwards from the inside of the filter membrane 12m by the supplied gas D. As a result, filtrate B falls to the lower part of the filter container 11 and is returned to the cleaning liquid storage tank 66 via return pipe 22. As this purging process continues, the space (gap 50) outside the pleated filter 12r within the filter container 11 becomes filled with gas D.

[0183] It should be noted that the purging process can be set to last between 5 and 15 seconds. Specifically, with a compressor 6 air supply capacity of 2.5 L / min and a filter container 11 volume (excluding the portion lower than the bottom of the filter 12) of 190 L, the purging process will take 190 L ÷ 2500 × 60 seconds = 4.56 seconds to complete. Considering the time required to open valves V2 and V3, the air resistance of the filter 12, etc., the purging process will end in approximately 10 seconds. Through this air purging process, the filter container 11 is filled with gas, thus enabling cleaning in the gas during the subsequent cleaning process.

[0184] (Cleaning process)

[0185] Next, the cleaning process following the purging process will be explained.

[0186] In the cleaning process, the filter cake K and adsorbent layer 47 formed on the filter membrane surface 12f are peeled off, restoring the filter membrane surface 12f to its initial state. During this cleaning process, the compressor 6 continues to operate, valves V1, V2, and V5 are closed, and valves V3 and V4 are opened. The cleaning liquid C stored in the cleaning liquid storage tank 66 is sent to the cleaning liquid tank 36 through the cleaning liquid supply pipe 30 via the cleaning liquid supply pump 8c. The cleaning liquid tank 36 is temporarily filled with cleaning liquid C, but the filled cleaning liquid C is sprayed out from the slit 37 into the filter 12 due to the pressure of the pump 8. At this time, the differential pressure of the slit nozzle 37 (the differential pressure between the cleaning liquid tank 36 and the filter container 11) is preferably 80 kPa to 150 kPa. Preferably, the nozzle spray velocity is 8 m / s when the differential pressure is 80 kPa, and 12 m / s when the differential pressure is 120 kPa. It should be noted that when the filter cake K and the adsorbent layer thickness are 47, the spray pressure of the cleaning solution C needs to be increased, for example, when the filter cake thickness is 2mm (2000g / m³). 2 At this pressure, 150 kPa (15 m / s) is required. The sprayed cleaning fluid C collides with the filter 12, and this impact peels off the filter cake K and adsorbent N adhering to the filter 12. In addition, since the cleaning fluid C contains particulate matter F, the peeling effect of filter cake K and adsorbent N is high. It should be noted that since the slit 37 extends along the extension direction of the cleaning fluid tank 36, the cleaning fluid C is sprayed out from the slit 37 in a flat plate shape and contacts the filter 12 in a linear manner along the axial direction, which can peel off the filter cake K and adsorbent N without any omissions.

[0187] The filter cake K adhering to the filter 12, especially those located away from the slit 37 of the cleaning liquid tank 36, cannot be impacted. Therefore, it is preferable to rotate the filter 12 around its axis. The time required for the filter 12 to rotate once is determined by the diameter of the filter 12, the number of pleats (in the case of a pleated filter), and the surface area. For example, a filter with a diameter of 400 mm and a surface area of ​​50 m² can be used.2 The filter 12 rotates at 0.5 RPM (once every 120 seconds). By spraying cleaning fluid C from the slit 37 while the filter 12 is rotating, the filter cake K adhering to the entire circumference of the filter 12 can be peeled off. It should be noted that, without the rotation mechanism of the filter 12, the cleaning fluid tank 36 can also be a mechanism that rotates around the filter 12. Alternatively, multiple cleaning fluid tanks 36 can be provided along the circumference of the filter container 11, spraying cleaning fluid C from a 360-degree direction, thereby achieving the same effect as when a rotation mechanism is provided.

[0188] The filter cake K and adsorbent N, which fall into the discharge chute 11S of the filter container 11, are transported together with the cleaning liquid C to the cleaning liquid storage tank 66 via the return pipe 22. It should be noted that the detached filter cake K and adsorbent N can be sent to the cleaning liquid storage tank 66 immediately, or they can be stored in the filter cake discharge chute 11S and transported after accumulating to a certain amount.

[0189] It should be noted that during the cleaning process, the gas supplied from the compressor 6 is also discharged from the inside to the outside of the filter membrane 12m after being guided to the filtrate passage 12r. Therefore, the filter cake K formed on the surface 12f of the filter membrane is not only peeled off by the impact force of the cleaning liquid C from the outside of the filter membrane, but also by the gas D discharged from the inside to the outside of the filter membrane. Therefore, compared with the case where only the cleaning liquid C is used, it is easier to peel off the filter cake K and the adsorbent N. In addition, since the cleaning liquid C is sprayed while the filter container 11 is filled with gas D, the impact force of the cleaning liquid C is greater than that of the conventional case where the filter container 11 is filled with liquid (the liquid being treated A), and the amount of filter cake K and adsorbent N peeled off is greater. Furthermore, even when the spraying force of the cleaning liquid C is strong, since the gas D is discharged from the inside to the outside of the filter membrane, the cleaning liquid C and the powder particles F in the cleaning liquid are less likely to enter the filtrate passage 12r, and even if they do enter, they can be immediately pushed back into the gap 50. The cleaning process ends when all the filter cake K is discharged as described above.

[0190] (Pulp dewatering process)

[0191] After the above processes, filter cake K, adsorbent N, powder F, treated liquid A, and filtrate B are supplied to the cleaning liquid storage tank 66 (these are referred to as waste liquid U. The same applies hereinafter.). Additionally, a powder classification device 34 is installed near the cleaning liquid storage tank 66 to classify the powder F. The waste liquid U supplied to the cleaning liquid storage tank 66 is pumped by the waste liquid transfer pump 8d through the powder recovery pipe 33 and sent to the powder classification device 34, where the powder F in the waste liquid U is recovered. The recovered powder F is returned to the cleaning liquid storage tank 66. Furthermore, the waste liquid U, from which the powder F has been removed by the powder classification device 34, is pumped by the waste liquid transfer pump 8d through the waste liquid discharge pipe 31 to the dewatering device 27. The dewatering device 27 consists of various filters, filter presses, etc., and is used to capture the filter cake K and adsorbent N in the waste liquid U. The filter cake K and adsorbent N captured by the dewatering device 27 are discharged outside the filtration system and discarded. This process is referred to as the slurry dewatering process. It should be noted that, preferably, not all the waste liquid U in the cleaning liquid storage tank 66 is sent to the powder and particle classification device 34, but rather a portion of the waste liquid U remains in the cleaning liquid storage tank 66. This is because the waste liquid U in the cleaning liquid storage tank 66 is used as the cleaning liquid C in the cleaning process.

[0192] Afterwards, the process returns to the adsorbent layer formation step described above, and performs a series of additional steps. It should be noted that if there is no mixed liquid in the mixed liquid storage tank 24 or if the mixed liquid level decreases, the process returns to the mixed liquid generation step instead of the adsorbent layer formation step. Furthermore, the liquid (purified liquid) from which the filter cake K and adsorbent N have been removed via the dewatering device 27 is discharged from the slurry dewatering device 27 in the new adsorption-filtration step by the drive of the purified liquid delivery pump 8e. It then passes through the purified liquid discharge pipe 32, merges with the treated liquid A flowing in the treated liquid supply pipe 14, and is transported to the filtration device 10 for adsorption-filtration.

[0193] (Vertical dehydration and drying equipment and horizontal dehydration and drying equipment)

[0194] In the above description, a vertical filter device 10 with the axis of filter 12 running longitudinally was described, but it can also be a horizontal filter device 10 with the axis of filter 12 running transversely. In this horizontal filter device 10, the cleaning liquid tank 36 can be positioned below the filter 12, and the cleaning liquid C can be sprayed from below. This is because the filter cake K detached from the filter 12 easily falls into the discharge chute 11S due to gravity.

[0195] (Multiple filtration units 10)

[0196] The number of filter devices 10 installed is not limited to one; it can also be as follows: Figure 5As shown in the second embodiment, multiple filter devices 10 are used. Alternatively, a filtration method using a filtration system with multiple filter devices 10 arranged in parallel may be employed. After the adsorption-filtration step, a stripping-discharge step is performed to remove the adsorbent N, which has adsorbed the recalcitrant substance E through filtration, from the filter 12 and to discharge the stripped adsorbent N from the filter container 11. While some of the filter devices 10 perform the adsorbent layer formation step or the stripping-discharge step, the other filter devices 10 perform the adsorption-filtration step, and the system continues to be filtered by the treatment liquid A within the overall filtration system.

[0197] When multiple filtration units 10 are installed, it is preferable that while some filtration units 10 are performing the stripping-discharge process, other filtration units 10 are performing the adsorption-filtration process. That is, among the multiple filtration units 10, it is preferable that the execution periods of each process, such as the adsorbent layer formation process, the adsorption-filtration process, and the stripping-discharge process, are staggered. In this way, even when some filtration units 10 are performing the formation of the adsorbent layer 47, the stripping of the adsorbent layer 47, and the discharge of the adsorbent N, adsorption-filtration can still be performed by other filtration units 10, thus providing the advantage that the filtration system as a whole can continue to perform the adsorption-filtration treatment of the treated liquid A without stopping.

[0198] In multiple filtration units 10, if the execution times of the adsorbent layer formation step, adsorption-filtration step, and stripping-discharge step are exactly the same, the filtration system as a whole must simultaneously perform adsorbent layer 47 formation and adsorption-filtration to prevent the adsorption-filtration treatment of the treated liquid A from stopping. However, when the adsorbent layer formation step and adsorption-filtration step are performed simultaneously, the treated liquid A is filtered while the surface of the filter 12 cannot form a sufficient adsorbent layer 47, potentially increasing the amount of recalcitrant substance E contained in the treated liquid B. Figure 5 This method can prevent such adverse situations from occurring.

[0199] Furthermore, when multiple filtration units 10 are used, it is necessary to monitor whether the filtration process of each filtration unit 10 is functioning properly. For example, if a filtration unit 10 malfunctions, or if the adsorbent N in the adsorbent layer 47 absorbs a large amount of the difficult-to-decompose substance E and its adsorption capacity decreases, there is a concern that the treated liquid B discharged from the filtration unit 10 may contain a large amount of the difficult-to-decompose substance E. To prevent this from happening, the treated liquid discharged from each filtration unit 10 is extracted separately. To detect whether the amount of the difficult-to-decompose substance E in the treated liquid B is abnormal (whether the content of the difficult-to-decompose substance E is higher than a specified value), it is preferable to provide an extraction tube 42 for extracting the treated liquid B discharged from each filtration unit 10, and to have the extraction tubes 42 converge at a later section. A detector 44 for detecting the difficult-to-decompose substance E in the treated liquid B is installed at this convergence section 43 (or at the later section of the convergence section 43). With this configuration, it is not necessary to install the same number of detectors 44 as the number of filtration units 10, thus reducing initial costs. For example, even when multiple filtration devices 10 are installed, it is possible to monitor whether there is any abnormality in the amount of recalcitrant substance E contained in the treatment liquid B discharged from each filtration device 10 by installing only one detector 44.

[0200] In addition, when there are multiple filter devices 10, other methods can be used to determine whether the difficult-to-decompose substance E can be properly removed in each filter device 10.

[0201] The adsorption capacity of the adsorbent N in each filter device 10 decreases as the amount of treated liquid A passing through the adsorbent layer 47 (flow rate) increases. This flow rate is determined by the speed at which the treated liquid A is delivered to the filter device 10 (feeding speed) and the time elapsed from when the treated liquid A begins to pass through the adsorbent layer 47 (flow time).

[0202] Therefore, for example, after confirming the relationship between the liquid delivery rate, the liquid flow time, and the degree of reduction in adsorption capacity through simulation, the actual liquid flow time can be measured using timer 61. When the liquid flow time reaches a predetermined time (a certain time), the control device 62 can be used to stop driving pump 8a and stop supplying the treated liquid A to the filter device 10. As described above, timer 61 is cheaper than devices that detect the concentration of the recalcitrant substance E in the treated liquid B, thus offering the advantage of reducing the overall initial cost of the filtration system.

[0203] (Third Implementation)

[0204] like Figure 7As shown in 7B, the adsorbent layer 47 can also be composed of multiple layers. In the example shown in 7B, the adsorbent layer 47 has a two-layer structure. In this case, it is preferable that the average particle size of the first adsorbent N1 in the first adsorbent layer 47A located on the inner side of the adsorbent layer 47 is greater than the average particle size of the second adsorbent N2 in the second adsorbent layer 47B located on the outer side of the adsorbent layer 47.

[0205] Specifically, it is preferable that the average particle size of the first adsorbent N1 is about 20 to 50 μm, more preferably about 20 to 30 μm. If the average particle size of the first adsorbent N1 is less than 20 μm, the first adsorbent N1 will penetrate deep into the gaps of the pleated filter 12 and will be difficult to remove from the pleated filter 12. On the other hand, if the average particle size of the first adsorbent N1 is greater than 50 μm, the second adsorbent N2 will penetrate through the gaps of the first adsorbent layer 47A and penetrate deep into the gaps of the pleated filter 12, making it difficult to remove from the pleated filter 12. Thus, the average particle size of the first adsorbent N1 is preferably such that it does not penetrate into the gaps of the pleated filter 12, and therefore the average particle size of the first adsorbent N1 is preferably about 5 to 20 times the size of the gaps of the pleated filter 12, more preferably about 5 to 10 times.

[0206] It should be noted that the pleated filter 12 has numerous gaps, but it is preferable that the average size of each gap is 0.1 to 3 μm. 2 The thickness is approximately 0.15–0.5 μm, more preferably 0.15–0.5 μm. 2 Left and right. If the size of the above gap is less than 0.1μm. 2 If the liquid being treated (A) has difficulty passing through the gaps in the pleated filter 12, the filtration process for the liquid being treated (A) becomes excessively time-consuming. Furthermore, if the size of the aforementioned gaps is greater than 3 μm... 2 If this happens, suspended matter in the treated liquid A may pass through the gaps in the pleated filter 12 and be mixed into the treated liquid B in large quantities.

[0207] The average particle size of the second adsorbent N2 is preferably about 1 to 15 μm, more preferably about 5 to 9 μm. If the average particle size of the second adsorbent N2 is less than 1 μm, the second adsorbent N2 will penetrate through the gaps in the first adsorbent layer 47A and enter deep into the gaps in the pleated filter 12, making it difficult to peel off from the pleated filter 12. On the other hand, if the average particle size of the second adsorbent N2 is greater than 15 μm, the specific surface area of ​​the second adsorbent N2 is large, thus reducing its adsorption capacity for the recalcitrant substance E. Therefore, the average particle size of the second adsorbent N2 is preferably such that the second adsorbent N2 does not penetrate through the first adsorbent layer 47A. Therefore, the average particle size of the second adsorbent N2 is preferably about 1.5 to 5 times the size of the gaps in the first adsorbent layer 47A, more preferably about 1.5 to 3 times. That is, the average particle size of the second adsorbent N2 is preferably about 1.5 to 1.5 of the average particle size of the first adsorbent N1, and more preferably about 1.5 to 1.3.

[0208] Furthermore, the thickness (length in the thickness direction) of the first adsorbent layer 47A is preferably about 0.05 to 0.1 mm, more preferably about 0.07 to 0.1 mm. If the thickness of the first adsorbent layer 47A is thinner than 0.05 mm, the possibility of the second adsorbent N2 entering the gaps of the pleated filter 12 increases. On the other hand, the specific surface area of ​​the first adsorbent N1 is smaller than that of the second adsorbent N2, and its adsorption capacity for the recalcitrant substance E is lower than that of the second adsorbent N2. Therefore, if the thickness of the first adsorbent layer 47A is thicker than 0.1 mm, the adsorption capacity of the recalcitrant substance E as a whole as the adsorbent layer 47 may decrease.

[0209] When the above adsorbent layer 47 is formed, such as Figure 6 As shown, firstly, the first adsorbent N1 and diluent H are added to the first solution storage tank 24A, and the mixture is stirred using a manual mixer 65 to generate the first solution G1. Similarly, the second adsorbent N2 and diluent H are added to the second solution storage tank 24B, and the mixture is stirred using a manual mixer 65 to generate the second solution G2. Here, the average particle size of the first adsorbent N1 is larger than the average particle size of the second adsorbent N2.

[0210] Next, the first solution supply pump 8bA is operated to deliver the first solution G1 in the first solution storage tank 24A to the filter container 11 via the first solution supply path 23A and the mixed liquid supply pipe 14. At this time, it is preferable to operate the treated liquid supply pump 8a to deliver the treated liquid A in the treated liquid storage tank 7 to the mixed liquid supply pipe 14, where the treated liquid A is used to dilute the first solution G1 inside the mixed liquid supply pipe 14. Thus, the first solution G1 entering the filter container 11 passes through the pleated filter 12 from the outside to the inside, thereby forming a first adsorbent layer 47A on the outer surface of the pleated filter 12. Specifically, for example, it is preferable to attach 70-100 g / m³ of first adsorbent N1 with an average particle size of about 15-30 μm to the outer surface of the pleated filter 12. 2 about.

[0211] Then, the second solution supply pump 8bB is operated to deliver the second solution G2 in the second solution storage tank 24B to the filter container 11 via the second solution supply path 23B and the mixed liquid supply pipe 14. At this time, it is preferable to operate the treated liquid supply pump 8a to deliver the treated liquid A in the treated liquid storage tank 7 to the mixed liquid supply pipe 14, where the treated liquid A is used to dilute the second solution G2 inside the mixed liquid supply pipe 14. In this way, the second solution G2 entering the filter container 11 passes through the first adsorbent layer 47A and the pleated filter 12 from the outside to the inside, thereby forming a second adsorbent layer 47B on the outer surface of the first adsorbent layer 47A. Specifically, for example, it is preferable to attach 1000-2000 g / m² of second adsorbent N2 with an average particle size of about 5-9 μm to the outer surface of the first adsorbent layer 47A. 2 about.

[0212] It should be noted that the first adsorbent N1 and the second adsorbent N2 can be of the same type or different types. For example, activated carbon can be used as the first adsorbent N1 and activated carbon (with an average particle size smaller than that of the activated carbon in the first adsorbent N1) can be used as the second adsorbent N2. Alternatively, Prussian blue can be used as the first adsorbent N1 and activated carbon (with an average particle size smaller than that of the Prussian blue in the first adsorbent N1) can be used as the second adsorbent N2.

[0213] It should be noted that the particle size of adsorbent N, such as adsorbent N1 and adsorbent N2, refers to the projected equivalent circle diameter (the diameter of a circle with the same projected area as the particle), which is the average of the projected equivalent circle diameters of all particles (average particle size). This average particle size is determined by measuring the particle size distribution using a laser diffraction / scattering particle size distribution measuring device (e.g., the commercial LA-960V2 series, manufactured by Horiba Corporation), and the particle size at which the cumulative volume is equivalent to 50% is defined as the average particle size.

[0214] It should be noted that, in Figure 6 The third embodiment shown illustrates an example where the first solution G1 and the second solution G2 are stored in different mixing tanks 24 (solution storage tanks 24), but is not limited to this example. For instance, the first solution G1 is first stored in the solution storage tank 24, and a portion of the first solution G1 is conveyed to the filter container 11. Then, the first solution G1 remaining in the solution storage tank 24 is further stirred using a mixer 65, and the first adsorbent N1 in the first solution G1 is pulverized by the stirring force. The first adsorbent N1 with thus reduced average particle size is used as the second adsorbent N2. That is, the first adsorbent N1 can also be converted into the second adsorbent N2 by stirring using a mixer 65, and a second solution containing the second adsorbent N2 thus generated is conveyed to the filter container 11.

[0215] In addition to the first adsorbent layer 47A and the second adsorbent layer 47B, a third adsorbent layer 47C or the like can also be provided, making the adsorbent layer 47 have three or more layers. In this case, the adsorbent layers 47 are numbered sequentially from the inside out, with the innermost adsorbent layer being the first adsorbent layer 47A, the adsorbent layer adjacent to the outer side of the first adsorbent layer 47A being the second adsorbent layer 47B, and the adsorbent layer adjacent to the outer side of the second adsorbent layer 47B being the third adsorbent layer 47C, and so on. When the adsorbent layer 47 consists of only the first adsorbent layer 47A and the second adsorbent layer 47B, it is preferable that the average particle size of the first adsorbent N1 in the first adsorbent layer 47A is larger than the gaps in the pleated filter 12. Furthermore, it is preferable that the average particle size of the second adsorbent N2 in the second adsorbent layer 47B is larger than the gaps in the first adsorbent layer 47A. Therefore, even if we attempt to reduce the average particle size of the second adsorbent N2 in the second adsorbent layer 47B, there are inherent limitations. It should be noted that the smaller the average particle size of adsorbent N, the larger the specific surface area of ​​adsorbent N, thus improving the adsorption capacity of the recalcitrant substance E. Therefore, from the perspective of improving the adsorption capacity of the recalcitrant substance E, it is preferable to minimize the average particle size of the adsorbent N constituting the adsorbent layer 47 as much as possible. However, when the adsorbent layer 47 has two layers, the aforementioned limitations exist. Therefore, by further providing a third adsorbent layer 47C using a third adsorbent N3 with an average particle size smaller than that of the second adsorbent N2 on the outside of the second adsorbent layer 47B, the adsorption capacity of the recalcitrant substance E can be further improved. Similarly, if a fourth adsorbent layer 47D using a fourth adsorbent N4 with an average particle size smaller than that of the third adsorbent N3 is further provided on the outside of the third adsorbent layer 47C, the adsorption capacity of the recalcitrant substance E can be further improved. By increasing the number of layers constituting the adsorbent layer 47 in this way, the adsorption capacity of the recalcitrant substance E can be improved. At this time, it is preferable that the average particle size of the adsorbent N (first adsorbent N1, second adsorbent N2, third adsorbent N3...) in each layer (first adsorbent layer 47A, second adsorbent layer 47B, third adsorbent layer 47C...) constituting the adsorbent layer 47 gradually decreases from the inside to the outside of the adsorbent layer 47.

[0216] (Effects of the invention)

[0217] Regardless of the concentration of the recalcitrant substance E in the treated liquid A, E can be removed with a high probability. Furthermore, recalcitrant substances other than PFOS (such as PFOA, PFHxS, bisphenol A, trihalomethanes, PCBs, trichloroethylene, tetrachloroethylene, DDT, benzene, etc.) have different molecular weights than PFOS, but they can all be adsorbed and removed regardless of the molecular weight difference. Additionally, by using a pleated filter as filter 12, the overall filtration device becomes more compact, thus reducing the footprint. Furthermore, using activated carbon as adsorbent N has the following advantages: activated carbon N has high adsorption efficiency (adsorption efficiency) for recalcitrant substance E, and even when activated carbon N adsorbs recalcitrant substance E, its adsorption capacity is unlikely to decrease. Additionally, activated carbon N has low liquid flow resistance, thus reducing the power consumption of the transfer pump and lowering operating costs. Furthermore, when using activated carbon as adsorbent N, the activated carbon is combustible, making disposal easy. Moreover, the entire filtration system can operate fully automatically, saving manpower.

[0218] Symbol Explanation

[0219] 4…supply port, 6…compressor, 7…(treated liquid) storage tank, 8a…treated liquid supply pump, 8b…solution (mixture) supply pump, 8bA…first solution (first mixture) supply pump, 8bB…second solution (second mixture) supply pump, 8c…cleaning fluid supply pump, 8d…waste liquid transfer pump, 8e…purified liquid transfer pump, 9…coarse filter, 10…filtration device, 11…filter container, 11S…discharge chute, 11U…filter housing, 12…filter, 12b…back side of filter membrane (inner surface of filter), 12f…surface of filter membrane (outer surface of filter), 12m…pass Filter membrane, 12r… filtrate passage, 12s… cylindrical body, 13… (treated liquid) supply pipe, 14… (treated liquid) supply pipe (can also serve as a mixed liquid supply pipe), 15… (filtrate) outlet, 16… discharge pipe (can also serve as an air supply pipe), 19… air supply pipe, 23… (mixed liquid) supply pipe, 23A… first solution supply pipe (first solution supply path), 23B… second solution supply pipe (second solution supply path), 24… solution (mixed liquid) storage tank, 24A… first solution (first mixed liquid) storage tank, 24B… second solution (second mixed liquid) storage tank, 25… concentration meter 29…Filter support, 30…Cleaning fluid supply pipe, 31…Waste liquid discharge pipe, 32…Purified liquid discharge pipe, 33…Powder and granular material recovery pipe, 34…Powder and granular material classification device, 35…Cleaning device, 36…Cleaning fluid tank, 37…Spray outlet (slit), 42…Extraction pipe, 43…Collection section, 44…Detector, 45…Protrusion, 46…Flow sensor, 47…Adsorbent layer, 47A…First adsorbent layer, 47B…Second adsorbent layer, 48…Supply port, 50…Gap, 51…Rectifying baffle, 61…Timer, 62…Control device, 65…(Manual) mixer, 66…Cleaning fluid storage Tank, A…processed liquid, B…processed liquid (filtrate), C…cleaning liquid, D…gas, E…difficult-to-decompose substances, F…powder, G…solution (mixture), G1…first solution (first mixture), G2…second solution (second mixture), H…diluent, J…residue, K…filter cake, M…motor, N…adsorbent, N1…first adsorbent, N2…second adsorbent, U…waste liquid, V1~V5…valve, LD…height direction, US…upper side (height direction), DS…lower side (height direction), TD…thickness direction, IS…inner side (thickness direction), OS…outer side (thickness direction).

Claims

1. A filtration device for removing recalcitrant substances contained in a liquid being treated, characterized in that, It has the following characteristics: A filter container having a supply port for the liquid to be treated and a discharge port for the liquid to be treated; and A pleated filter is disposed inside the filter container. Its outer surface serves as the filter surface, while the interior forms the passageway for the treated liquid. Flat filter media is bent into a corrugated shape to create multiple pleats, forming a cylindrical shape. A cleaning device, disposed on the outside of the pleated filter, sprays cleaning fluid onto the outer surface of the pleated filter. In its pre-filtration state, the outer surface of the pleated filter has an adsorbent layer. The adsorbent layers are composed of adsorbents that adsorb the recalcitrant substances. The adsorbent layer consists of multiple layers. In the adsorbent layer A second adsorbent layer is deposited on the outer surface of a first adsorbent layer. The first adsorbent layer contains particles of a first adsorbent that adsorb the recalcitrant substance, and the second adsorbent layer contains particles of a second adsorbent that adsorb the recalcitrant substance. The average particle size of the first adsorbent in the first adsorbent layer is larger than the average particle size of the second adsorbent in the second adsorbent layer. The average particle size of the first adsorbent particles in the first adsorbent layer is larger than the gaps in the pleated filter.

2. The filtration device as claimed in claim 1, wherein, The first adsorbent is activated carbon, and the second adsorbent is activated carbon with an average particle size smaller than that of the first adsorbent.

3. The filtration device as claimed in claim 1, wherein, The first adsorbent is Prussian blue, and the second adsorbent is activated carbon containing Prussian blue with an average particle size smaller than that of the first adsorbent.

4. A filtration method, characterized in that, It has the following characteristics: In the adsorbent layer formation process, a solution containing an adsorbent that adsorbs substances that are difficult to decompose is passed through a pleated filter, and an adsorbent layer is formed on the outer surface of the pleated filter. The outer surface of the pleated filter is the filter surface, and the inside is the passageway for the treatment liquid. The flat filter material is bent into a corrugated shape to form multiple pleats and to form a cylindrical shape. The adsorption-filtration process involves passing the liquid to be treated through a pleated filter having an adsorbent layer formed thereon, thereby filtration in which the recalcitrant substances are adsorbed onto the adsorbent layer; and The cleaning process involves spraying cleaning liquid from a cleaning device located on the outside of the pleated filter onto the outer surface of the pleated filter, thereby peeling off the filter cake and the adsorbent layer formed on the outer surface of the pleated filter. The adsorbent layer forming process includes: The first adsorbent layer forming process involves passing a first solution containing particles of a first adsorbent with an average particle size larger than the gaps in the pleated filter through the pleated filter, thereby forming a first adsorbent layer of the first adsorbent particles on the outer surface of the pleated filter. and In the second adsorbent layer formation step, a second solution containing particles of a second adsorbent with an average particle size smaller than that of the first adsorbent is passed through the pleated filter to form a second adsorbent layer of particles of the second adsorbent on the outer surface of the first adsorbent layer.

5. The filtering method as described in claim 4, wherein, After the adsorption-filtration process is completed and before the cleaning process begins, a purging process is performed to supply gas into the passage of the treatment liquid inside the pleated filter, so as to fill the passage of the treatment liquid and the gap between the outer surface of the pleated filter and the filter container with gas.

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