Method for renewing water treatment facility and membrane separation apparatus

Abstract

To provide a method for renewing a water treatment facility capable of maintaining good treatment efficiency with membrane units even when the number of immersion type membrane units is reduced.SOLUTION: A method of renewing a water treatment facility 1 having a plurality of treatment tanks 7-9 equipped with a first air diffuser 23 includes: a first process of installing an immersion type membrane unit 31 in at least one treatment tank 8 other than the renewal target, subjecting a part of the liquid 2 to be treated supplied to the treatment tank 8 other than the renewal target to solid-liquid separation by the membrane unit 31 and discharging it to the outside of the treatment tank 8, and discharging the remainder of the liquid 2 to be treated to the outside of the treatment tank 8 after diffusing air by a first air diffuser 23; a second process of renewing the treatment tank 7 to be renewed while the first air diffuser 23 of the treatment tank 7 to be renewed is stopped; and a third process of removing the membrane unit 31 from the treatment tank 8 other than the treatment tank to be renewed after the renewal. The first process involves solid-liquid separation by surrounding the lateral perimeter of the membrane unit 31 with an enclosure 32, and the second process is carried out while the first process is carried out.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a renewal method for a water treatment facility having a plurality of treatment tanks equipped with aeration devices, and to a membrane separation device. [Background technology]

[0002] Conventionally, as a method for updating this type of water treatment facility, for example, as shown in FIG. 12, a first step is to install a plurality of floating-type submerged membrane separation devices 126 in a predetermined aerobic tank 122 of a plurality of existing aerobic tanks 122 to 124 equipped with an existing aeration device 121, and operate the predetermined aerobic tank 122 as an aerobic tank using the floating-type submerged membrane separation device 126, and a second step is to operate the other aerobic tanks 122 to 124 in which the floating-type submerged membrane separation device 126 is not installed. a second step of discharging the treated liquid 127 stored in the aerobic tanks 123, 124 to the outside of the aerobic tanks 123, 124 and renewing the other aerobic tanks 123, 124 that have become empty, and then supplying the treated liquid 127 to the other aerobic tanks 123, 124 to operate them; and a third step of removing the floating-type submerged membrane separation device 126 from the specified aerobic tank 122 into which it was introduced in the first step.

[0003] The floating-type submerged membrane separation device 126 is equipped with a floating means and floats in the liquid to be treated 127, and separates the liquid to be treated 127 into solid and liquid by the membrane unit.

[0004] A method for updating water treatment facilities as described above is described in, for example, Patent Document 1 listed below. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2017-104780 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the above conventional system, as shown in Fig. 12, the entire amount of the liquid to be treated 127 supplied to a specific aerobic tank 122 is subjected to membrane separation treatment in the submerged membrane separation apparatus 126 and then discharged outside the aerobic tank 122, so the number of submerged membrane separation apparatuses 126 increases. This leads to an increase in the number of membrane units, which causes problems such as increased initial costs and running costs. In addition, the power required for membrane separation treatment increases, making it difficult to secure a power source.

[0007] As described in Patent Document 1, if the membrane separation apparatus is to be used continuously as the main facility after the modification, an increase in the number of membrane units is not a problem because it is a necessary investment to reach the final form. However, if a treatment method other than the membrane bioreactor (MBR) is adopted as the treatment method after the renewal, it is desirable to keep the number of membrane units used as small as possible.

[0008] An object of the present invention is to provide a method for updating a water treatment facility and a membrane separation device that can maintain good treatment efficiency by the membrane units even if the number of submerged-type membrane units is reduced. [Means for solving the problem]

[0009] In order to achieve the above object, the first invention is a method for updating a water treatment facility having a plurality of treatment tanks each equipped with a first aeration device, A first step of installing a submerged membrane unit in at least one treatment tank other than the treatment tank to be renewed, separating a part of the liquid to be treated supplied to the treatment tank other than the treatment tank into solid and liquid by the membrane unit and discharging the remaining liquid to the outside of the treatment tank after diffusing it with a first air diffuser; A second step of updating the treatment tank to be updated while stopping the first aeration device of the treatment tank to be updated; and a third step of removing the membrane units from the treatment tanks other than the one to be updated after the update. In the first step, the sides of the membrane unit are surrounded by an enclosure to separate solid and liquid, The second step is carried out while the first step is being carried out.

[0010] According to this, in the first step, a part of the liquid to be treated supplied to the treatment tanks other than the one to be renewed is subjected to solid-liquid separation by the membrane unit and discharged to the outside of the treatment tank, and the remainder of the liquid to be treated is diffused by the first air diffuser and then discharged to the outside of the treatment tank. Therefore, the number of membrane units can be reduced compared to the case where the entire amount of the liquid to be treated supplied to the treatment tanks other than the one to be renewed is subjected to solid-liquid separation by the membrane unit and discharged to the outside of the treatment tank.

[0011] In the first step, the membrane unit is surrounded by an enclosure on the sides to perform solid-liquid separation, so that the liquid to be treated inside the enclosure is concentrated, and the concentration of suspended solids in the liquid to be treated inside the enclosure becomes higher than the concentration of suspended solids in the liquid to be treated outside the enclosure. This makes it possible to increase the concentration of suspended solids in the liquid to be treated inside the enclosure to a level suitable for membrane separation treatment, and to maintain good treatment efficiency by the membrane unit.

[0012] The method for updating a water treatment facility according to the second invention involves, in a first step, performing solid-liquid separation of the liquid to be treated using a membrane unit while diffusing aeration using a first air diffuser in a treatment tank other than the one to be updated.

[0013] This makes it possible to prevent a temporary decrease in the treatment capacity of the water treatment facility when the treatment tank to be updated is being updated in the second step.

[0014] In the method for updating a water treatment facility according to the third invention, the enclosure has a lower end that is submerged below the liquid level in the treatment tank and an upper end that protrudes above the liquid level.

[0015] The method for renewing a water treatment facility according to the fourth aspect of the present invention provides a communication part that communicates between the inside and outside of an enclosure below the liquid level.

[0016] The method for updating water treatment facility according to the fifth aspect of the present invention is provided with a discharge device for discharging the liquid to be treated inside the enclosure to the outside.

[0017] According to this, by discharging the liquid to be treated inside the enclosure to the outside by the discharge device, the liquid to be treated outside the enclosure flows into the enclosure through the communication part, and therefore the concentration of suspended solids in the liquid to be treated inside the enclosure can be adjusted to a concentration suitable for membrane separation treatment.

[0018] The method for updating a water treatment facility in the sixth aspect of the present invention uses a discharge device to adjust the MLSS concentration of the liquid to be treated inside an enclosure.

[0019] This makes it possible to maintain the MLSS concentration of the liquid to be treated inside the enclosure at a level suitable for membrane bioreactor treatment.

[0020] In the seventh aspect of the present invention, there is provided a method for updating a water treatment facility, wherein the membrane unit has a membrane element and a second air diffuser that generates a swirling flow that swirls in a vertical direction along the membrane element, The enclosure has a peripheral wall surrounding the side periphery of the membrane unit and a bottom wall provided at a lower part of the peripheral wall and covering the lower part of the membrane unit, The bottom wall is located above the first air diffuser in the treatment tank.

[0021] According to this, by operating the second air diffuser to diffuse air, a swirling flow is generated along the membrane element inside the enclosure, and the surface of the membrane element is cleaned.

[0022] In this case, since the lower part of the membrane unit is covered by the bottom wall of the enclosure, when the first air diffuser in the treatment tank is operated to diffuse air, it is possible to prevent a large amount of air bubbles released from the first air diffuser from entering the inside of the enclosure from below.

[0023] This makes it possible to prevent a large amount of air bubbles released from the first air diffuser from entering the inside of the enclosure and disrupting the smooth flow of the swirling flow, thereby maintaining good cleaning efficiency of the membrane element.

[0024] The method for updating a water treatment facility in the eighth aspect of the present invention includes a fourth step of activating a first aeration device of the treatment tank after the renewal to resume operation of the treatment tank after the renewal, The second step is carried out while the first step is carried out, and then the third and fourth steps are carried out simultaneously or at different times.

[0025] The ninth invention relates to a membrane separation device including a membrane unit and an enclosure used in the water treatment facility renewal method according to the first invention, The membrane unit and the enclosure are mounted on a support frame, The support frame body has a submerged portion that is submerged below the liquid surface in the treatment tank and an exposed portion that is exposed above the liquid surface, The exposed portion of the support frame has a supported portion that is supported by the treatment tank, A floating body that generates buoyancy is provided on the support frame body.

[0026] According to this, when the membrane unit is installed in the treatment tank in the first step, the supported portion of the support frame of the membrane separation device is supported by the treatment tank. In this state, buoyancy is generated by the float provided on the support frame, so the load (self-weight) of the membrane separation device acting on the treatment tank via the supported portion of the support frame is reduced by the amount of buoyancy. This makes it possible to eliminate the need for reinforcement work for the treatment tank or to significantly reduce the amount of reinforcement work required.

[0027] The tenth aspect of the present invention is a membrane separation device having a membrane unit that is immersed in the liquid to be treated in a treatment tank and separates the liquid into solid and liquid, and a support frame that supports the membrane unit, The support frame body has a submerged portion that is submerged below the liquid surface in the treatment tank and an exposed portion that is exposed above the liquid surface, The exposed portion of the support frame has a supported portion that is supported by the treatment tank, The support frame is provided with a float that generates buoyancy and an enclosure that surrounds the side periphery of the membrane unit; The enclosure has a lower end that is submerged below the liquid level in the treatment tank and an upper end that protrudes above the liquid level. Effect of the Invention

[0028] As described above, according to the present invention, the number of membrane units can be reduced in step 1. Furthermore, the concentration of suspended solids in the liquid to be treated inside the enclosure can be increased to a level suitable for membrane separation treatment, and good treatment efficiency by the membrane units can be maintained. [Brief description of the drawings]

[0029] [Figure 1] FIG. 1 is a plan view of a water treatment facility according to a first embodiment of the present invention. [Diagram 2] 2 is a view taken along the arrow XX in FIG. [Diagram 3] FIG. 1 is a diagram of a membrane separation device used when updating a water treatment facility. [Figure 4] FIG. 2 is a plan view for explaining a method for updating the water treatment facility according to the first embodiment. [Diagram 5] 5 is a view taken along the arrow XX in FIG. 4. [Figure 6] FIG. 11 is a diagram showing a swirling flow generated inside an enclosure of a membrane separation device when updating a water treatment facility. [Figure 7] FIG. 11 is a diagram showing a membrane separation device used when updating a water treatment facility in a second embodiment of the present invention. [Figure 8] FIG. 11 is a diagram of a membrane separation device used when updating a water treatment facility in a third embodiment of the present invention. [Figure 9] FIG. 13 is a diagram showing a membrane separation device used when updating a water treatment facility in a fourth embodiment of the present invention. [Figure 10] FIG. 13 is a plan view of a membrane separation device used when updating a water treatment facility in a fifth embodiment of the present invention. [Figure 11] FIG. 13 is a diagram showing a membrane separation device used when updating a water treatment facility in a sixth embodiment of the present invention. [Figure 12] FIG. 1 is a plan view for explaining a conventional method for updating a water treatment facility. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0031] (First embodiment) In the first embodiment, as shown in Figs. 1 and 2, reference numeral 1 denotes an existing water treatment facility that biologically treats water to be treated 2 (raw water), such as sewage or industrial wastewater, by a standard activated sludge process.

[0032] The water treatment facility 1 has multiple (e.g., three in FIG. 1 ) existing aerobic tanks 7-9 (an example of a treatment tank) arranged in parallel, a primary sedimentation tank 10 provided upstream of the aerobic tanks 7-9, a final sedimentation tank 11 provided downstream of the aerobic tanks 7-9, and a disinfection tank 12 provided downstream of the final sedimentation tank 11.

[0033] The water to be treated 2 flows from the primary sedimentation tank 10 through a supply line 14 and is supplied to the aerobic tanks 7 to 9. The water to be treated 2 that has been aerobically treated in the aerobic tanks 7 to 9 is discharged as treated water 3 into a discharge line 15 and sent to the final sedimentation tank 11. The treated water 3 discharged from the final sedimentation tank 11 is sent to a disinfection tank 12 where it is disinfected, and then released from the disinfection tank 12 into a river, the ocean, or the like.

[0034] The water treatment facility 1 is provided with a return path 16 for returning the sludge settled in the final settling tank 11 to the aerobic tanks 7-9.

[0035] The aerobic tanks 7 to 9 each have a pair of left and right side walls 20 and a bottom wall 22. A plurality of existing first aeration devices 23 are installed at the bottom of each of the aerobic tanks 7 to 9.

[0036] During normal operation, the water to be treated 2 is supplied from the primary sedimentation tank 10 to each of the aerobic tanks 7-9, aerated by the first aeration devices 23 in each of the aerobic tanks 7-9, and then sent as treated water 3 from each of the aerobic tanks 7-9 to the final sedimentation tank 11.

[0037] When updating the water treatment facility 1, a submerged membrane separation device 30 is used, as shown in Fig. 3. The membrane separation device 30 has a plurality of membrane units 31 for performing solid-liquid separation of the water to be treated 2, an enclosure 32 surrounding the lateral periphery of these membrane units 31, and a support frame body 33.

[0038] The membrane unit 31 is mounted on a support frame body 33 and has a plurality of membrane elements 36 housed in a case 35, a second air diffuser 38 that generates a swirling flow 37 (see Figure 6) that swirls vertically along the membrane elements 36, and a water collection pipe 39 provided above the membrane elements 36.

[0039] The membrane element 36 is a filter membrane attached to a filter plate. The water 2 to be treated that has permeated the filter membrane is collected in a water collection pipe 39 as filtered water 40. The second air diffuser 38 is provided below the membrane element 36.

[0040] The enclosure 32 is mounted on a support frame body 33 and is formed by a peripheral wall 41 formed in a rectangular cylindrical shape in a plan view, with its lower end submerged below the water surface 4 in the aerobic tanks 7-9 and its upper end protruding above the water surface 4. The upper and lower ends of the enclosure 32 are each open, so that a communication port 34 (an example of a communication part) is provided at the lower end of the enclosure 32 that communicates with the inside and outside of the enclosure 32 below the water surface 4.

[0041] The support frame body 33 can be suspended and fixed to the aerobic tanks 7 to 9, and has an upper horizontal frame 43, a pair of left and right vertical frames 44 suspended from the upper horizontal frame 43, and a lower horizontal frame 45 provided between the lower ends of the two vertical frames 44.

[0042] The support frame body 33 has a submerged portion 47 that is submerged below the water surface 4 in the aerobic tanks 7-9, and an exposed portion 48 that is exposed above the water surface 4. The upper horizontal frame 43 is included in the exposed portion 48, and has supported portions 43a at both ends that are supported by the upper ends of the side walls 20 of the aerobic tanks 7-9.

[0043] The upper horizontal frame 43 supports a filtered water discharge pipe 50 that sends the filtered water 40 to the downstream side of the disinfection tank 12, and an air supply pipe 51 that supplies air to the second air diffuser 38. The filtered water discharge pipe 50 is connected to the water collection pipe 39 via a first connecting pipe 52. The air supply pipe 51 is connected to the second air diffuser 38 via a second connecting pipe 53.

[0044] The enclosure 32 is attached to the upper horizontal frame 43. The lower horizontal frame 45 is provided with a floating body 55 (float) that generates buoyancy in the support frame body 33. The lower horizontal frame 45 and the floating body 55 are included in the submerged portion 47.

[0045] A lower space 58 through which the water to be treated 2 flows is formed between the lower end of the enclosure 32 and the bottom walls 22 of the aerobic tanks 7 to 9. In addition, a side space 59 through which the water to be treated 2 flows is formed between the outer circumferential surface of the enclosure 32 and the side walls 20 of the aerobic tanks 7 to 9.

[0046] Hereinafter, a method for updating the water treatment facility 1 using the membrane separation device 30 will be described.

[0047] For example, the aerobic tank 7 is the treatment tank to be updated, and the other aerobic tanks 8 and 9 are treatment tanks not to be updated.

[0048] The updating method includes the following first to fourth steps.

[0049] As shown in Figs. 4 and 5, in the first step, a membrane separation device 30 having a membrane unit 31 is installed in one of the aerobic tanks 8 and 9 (or the aerobic tank 9) other than the target for renewal. Then, while air bubbles 60 are released from the first aeration device 23 of the aerobic tanks 8 and 9 other than the target for renewal to perform aeration, the water to be treated 2 is separated into solid and liquid by the membrane unit 31 of the aerobic tank 8. As a result, a part of the water to be treated 2 supplied to the treatment tank 8 is separated into solid and liquid by the membrane unit 31 and discharged to the outside of the treatment tank 8, while the rest of the water to be treated 2 supplied to the treatment tank 8 is aerated by the first aeration device 23 and then discharged from the treatment tank 8 to the final settling tank 11 as treated water 3, and the entire amount of the water to be treated 2 supplied to the aerobic tank 9 is aerated by the first aeration device 23 and then discharged from the treatment tank 9 to the final settling tank 11 as treated water 3.

[0050] At this time, as shown in Figures 3 and 5, the treated water 2 which has permeated the filtration membrane of the membrane element 36 is collected in the water collection pipe 39 as filtrate 40, and is sent from the water collection pipe 39 through the first connecting pipe 52 and the filtrate discharge pipe 50 to the downstream side of the disinfection tank 12, and then discharged into a river, the ocean, or the like.

[0051] In addition, by releasing air bubbles 61 from the second air diffuser 38 of the membrane separation apparatus 30 to diffuse air, a swirling flow 37 is generated along the membrane element 36 as shown in FIG. 6, and the filtration membrane of the membrane element 36 is cleaned by the swirling flow 37.

[0052] In the second step, the supply of the water to be treated 2 from the primary sedimentation tank 10 to the treatment tank 7 to be updated is stopped, and the water to be treated 2 in the treatment tank 7 is discharged to the outside while the first aeration device 23 of the treatment tank 7 to be updated is stopped, to empty the treatment tank 7 and update the treatment tank 7. The update may involve, for example, replacing the first aeration device 23 of the treatment tank 7 with a new one, or adding an additional first aeration device 23 to the treatment tank 7, or performing maintenance, inspection, and repair of the machinery and electrical equipment associated with the treatment tank 7 and the side wall 20 or bottom wall 22 of the treatment tank 7.

[0053] In the third step, the membrane separation device 30 installed in the aerobic tank 8 in the first step is removed.

[0054] In the fourth step, the treated water 2 is supplied from the primary sedimentation tank 10 into the renewed aerobic tank 7, and the first aeration device 23 of the aerobic tank 7 is operated as shown in FIG. 1 to aerate the treated water 2 in the aerobic tank 7, just as before the renewal, and the operation of the renewed aerobic tank 7 is resumed.

[0055] In the renewal method, the second step is carried out while the first step is being carried out, and after the second step is completed (ie, after the treatment tank 7 is renewed), the third step and the fourth step are carried out simultaneously.

[0056] In the above embodiment, the second step is carried out while the first step is carried out, and after the second step is completed, the third and fourth steps are carried out simultaneously, but the third and fourth steps may be carried out at different times. That is, the third step may be carried out first, and then the fourth step, or the fourth step may be carried out first, and then the third step.

[0057] In the above embodiment, the aerobic tank 7 is the treatment tank to be updated and the aerobic tanks 8 and 9 are treatment tanks other than the treatment tank to be updated, but the above steps 1 to 4 may be carried out in the same manner when the aerobic tank 8 is the treatment tank to be updated and the aerobic tanks 7 and 9 are treatment tanks other than the treatment tank to be updated, or when the aerobic tank 9 is the treatment tank to be updated and the aerobic tanks 7 and 8 are treatment tanks other than the treatment tank to be updated. This allows the multiple aerobic tanks 7 to 9 to be updated in sequence.

[0058] According to the above-mentioned renewal method, in the first step, as shown in Fig. 4 and Fig. 5, a part of the liquid to be treated 2 supplied to one of the treatment tanks 8, 9 other than the renewal target is subjected to solid-liquid separation by the membrane unit 31 and discharged as filtrate 40 downstream of the disinfection tank 12 (an example of the outside of the treatment tank 8), and the remainder of the liquid to be treated 2 supplied to the treatment tank 8 is diffused by the first air diffuser 23 and then discharged as treated water 3 to the final sedimentation tank 11 (an example of the outside of the treatment tank 8). Therefore, the number of membrane units 31 can be reduced compared to the case where the entire amount of the liquid to be treated 2 supplied to the treatment tanks 8 other than the renewal target is subjected to solid-liquid separation by the membrane unit 31 and discharged as filtrate 40 downstream of the disinfection tank 12.

[0059] Furthermore, in the first step, solid-liquid separation is performed by surrounding the sides of the membrane unit 31 with the enclosure 32, so that the liquid 2 to be treated inside the enclosure 32 is concentrated, and the sludge concentration of the liquid 2 to be treated inside the enclosure 32 becomes higher than the sludge concentration of the liquid 2 to be treated outside the enclosure 32. This makes it possible to increase the sludge concentration of the liquid 2 to be treated inside the enclosure 32 to a predetermined concentration suitable for membrane separation activated sludge treatment, and makes it possible to maintain good treatment efficiency by the membrane units 31 even if the number of membrane units 31 is reduced. Also, the design flux of the membrane units 31 can be increased.

[0060] As an example, the MLSS outside the enclosure 32 is kept at about 2000 mg / L, and the MLSS inside the enclosure 32 is kept at about 10000 mg / L, but these values ​​are not limiting.

[0061] Furthermore, in the first step, the first aeration devices 23 of the aerobic tanks 8 and 9 that are not the target of renewal perform aeration while the membrane unit 31 of the aerobic tank 8 separates the treated water 2 into solid and liquid, so that it is possible to prevent a temporary decrease in the treatment capacity of the water treatment facility 1 when the treatment tank 7 that is the target of renewal is emptied and renewed in the second step. Furthermore, the MLSS concentration of the treated water 3 flowing into the final settling tank 11 from the aerobic tanks 8 and 9 that are not the target of renewal is maintained at the same concentration as before, so there is no need to change the water surface load in the final settling tank 11, and solid-liquid separation treatment in the final settling tank 11 can be performed in parallel.

[0062] In addition, in the first step, when the membrane unit 31 is installed in the aerobic tank 8 as shown in Figures 4 and 5, the supported portion 43a of the support frame body 33 of the membrane separation device 30 is supported on the side wall 20 of the aerobic tank 8 as shown in Figure 3. In this state, buoyancy is generated in the support frame body 33 by the float 55, so that the load (own weight) of the membrane separation device 30 acting on the side wall 20 of the treatment tank 8 via the supported portion 43a of the support frame body 33 is reduced by the amount of buoyancy. This makes it possible to eliminate the need for reinforcement work for the side wall 20 of the treatment tank 8, or to significantly reduce the amount of reinforcement work.

[0063] (Second embodiment) In the second embodiment, as shown in FIG. 7, the membrane separation device 30 has an air lift device 65 (an example of a discharge device) that discharges the treated liquid 2 inside the enclosure 32 to the outside, and an MLSS concentration meter 66 that measures the MLSS inside the enclosure 32.

[0064] The air lift device 65 has a third air diffuser 67 provided at the inside lower part of the enclosure 32, and an exhaust pipe 68 provided inside the enclosure 32 and above the third air diffuser 67. The exhaust pipe 68 is an upside-down L-shaped pipe with an inlet 69 at its lower end and an outlet 70 at its upper end. The inlet 69 opens to the inside of the enclosure 32 while submerged below the water surface 4, and the outlet 70 opens to the outside of the enclosure 32 at the same height as the water surface 4.

[0065] The operation of the above configuration will now be described.

[0066] The MLSS concentration inside the enclosure 32 is measured by the MLSS concentration meter 66, and if the measured value is higher than an optimum concentration (for example, 10,000 mg / L), the third aeration device 67 is operated to release air bubbles 62 from the third aeration device 67. This generates an upward flow of the liquid 2 to be treated above the third aeration device 67, and the liquid 2 to be treated inside the enclosure 32 flows together with the air bubbles 62 (entrained by the air bubbles 62) from the inlet 69 through the outlet pipe 68 and is discharged from the outlet 70 to the outside of the enclosure 32.

[0067] As a result, the liquid to be treated 2 outside the enclosure 32 flows into the inside of the enclosure 32 through the communication port 34 at the bottom end of the enclosure 32, so that the MLSS concentration inside the enclosure 32 gradually decreases, and when the measured value reaches the optimum concentration, the third aeration device 67 is stopped. As a result, the liquid to be treated 2 inside the enclosure 32 is not discharged from the discharge pipe 68 to the outside of the enclosure 32, and the MLSS concentration inside the enclosure 32 can be adjusted to a predetermined concentration suitable for membrane bioreactor treatment.

[0068] In the above second embodiment, an air lift device 65 is used as an example of a discharge device, but this is not limited to the air lift device 65, and the treated liquid 2 inside the enclosure 32 may be discharged to the outside using an underwater pump or the like.

[0069] In the above second embodiment, the optimum MLSS concentration (for example, 10,000 mg / L) is used as the standard, but the optimum MLSS concentration range (for example, 9,000 to 11,000 mg / L) may also be used as the standard.

[0070] In the above-described second embodiment, the MLSS concentration meter 66 is provided inside the enclosure 32, but a DO meter (dissolved oxygen meter) may also be provided inside the enclosure 32. If the dissolved oxygen concentration (DO) of the water to be treated 2 inside the enclosure 32 becomes low, poor nitrification may occur, the membrane filtration performance of the membrane unit 31 may decrease, and the membrane element 36 may become clogged between the membranes, or the treated water quality may deteriorate.

[0071] For this reason, the dissolved oxygen concentration in the enclosure 32 is measured by a DO meter, and if the measured value is lower than the optimum concentration, the third air diffuser 67 is operated to release air bubbles 62 from the third air diffuser 67. This generates an upward flow of the liquid 2 to be treated above the third air diffuser 67, and the liquid 2 to be treated inside the enclosure 32 flows together with the air bubbles 62 from the inlet 69 through the outlet pipe 68 and is discharged from the outlet 70 to the outside of the enclosure 32.

[0072] As a result, the liquid 2 to be treated outside the enclosure 32 flows into the inside of the enclosure 32 through the communication port 34 at the bottom end of the enclosure 32, so that the dissolved oxygen concentration inside the enclosure 32 gradually increases, and when the measured value reaches the optimum dissolved oxygen concentration, the third aeration device 67 is stopped. As a result, the liquid 2 to be treated inside the enclosure 32 is not discharged outside the enclosure 32 from the discharge pipe 68, and the dissolved oxygen concentration inside the enclosure 32 can be adjusted to a predetermined concentration suitable for membrane bioreactor treatment.

[0073] Although the optimum dissolved oxygen concentration is used as the standard, the optimum range of dissolved oxygen concentration may be used as the standard.

[0074] In addition, both the MLSS concentration meter 66 and the DO meter may be provided inside the enclosure 32.

[0075] (Third embodiment) 8, in the third embodiment, the enclosure 32 has a peripheral wall 41 and a bottom wall 75 that is provided at the lower end of the peripheral wall 41 and covers the lower part of the membrane unit 31. The bottom wall 75 is located above the first aeration devices 23 of the aerobic tanks 7-9.

[0076] The bottom wall 75 is provided with a communication opening 34 (an example of a communication portion) that communicates with the inside and outside of the enclosure 32 below the water surface 4. The bottom wall 75 is inclined downward from the lower end of the peripheral wall 41 toward the communication opening 34. The communication opening 34 opens to the inside and outside of the enclosure 32 in a horizontal plane.

[0077] The operation of the above configuration will now be described.

[0078] In the first step, while air bubbles 60 are being released from the first air diffuser 23 of the aerobic tanks 8, 9 other than the target for renewal to diffuse air, air bubbles 61 are being released from the second air diffuser 38 of the membrane separation device 30 of the aerobic tank 8 to diffuse air, thereby generating a swirling flow 37 along the membrane element 36, and the filtration membrane of the membrane element 36 is cleaned by the swirling flow 37.

[0079] At this time, since the lower part of the membrane unit 31 is covered by the bottom wall 75 of the enclosure 32, it is possible to prevent a large amount of air bubbles 60 released from the first air diffuser 23 from entering the inside of the enclosure 32 from below.

[0080] This makes it possible to prevent a large amount of air bubbles 60 released from the first air diffuser 23 from penetrating into the inside of the enclosure 32 and disrupting the smooth flow of the swirling flow 37, thereby maintaining good cleaning efficiency of the membrane element 36.

[0081] Furthermore, although there is a possibility that some of the air bubbles 60 released from the first air diffuser 23 will enter the inside of the enclosure 32 through the communication port 34, the amount of air bubbles 60 that enters the inside of the enclosure 32 in this manner is very small, and therefore will not interfere with the smooth flow of the swirling flow 37.

[0082] In addition, because bottom wall 75 is inclined downward from the lower end of peripheral wall 41 toward communication opening 34, air bubbles 60 released from first air diffuser 23 are guided to the outside of peripheral wall 41 while rising along the inclination of bottom wall 75. As a result, air bubbles 60 released from first air diffuser 23 flow smoothly to the outside of enclosure 32 without stagnation.

[0083] In the third embodiment, the communication opening 34 is provided in the bottom wall 75 of the enclosure 32, but it may be provided in the lower part of the peripheral wall 41.

[0084] (Fourth embodiment) In the fourth embodiment, as shown in FIG. 9, the communication opening 34 opens to the inside and outside of the enclosure 32 within a vertical plane.

[0085] This makes it possible to significantly reduce the possibility that some of the air bubbles 60 released from the first air diffuser 23 will enter the inside of the enclosure 32 through the communication opening 34.

[0086] (Fifth embodiment) In the first embodiment described above, as shown in FIG. 4, the peripheral wall 41 of the enclosure 32 is formed in a rectangular shape when viewed in a plane, but this shape is not limited to this. For example, as a fifth embodiment, as shown in FIG. 10, the peripheral wall 41 may be formed in a boat-like shape when viewed in a plane.

[0087] That is, the peripheral wall 41 is formed so that its width W becomes gradually narrower from the upstream side to the downstream side of the liquid 2 to be treated.

[0088] According to this, in a water treatment facility 1 that employs the OD method (oxidation ditch method), the flow velocity of the water to be treated 2 in the aerobic tanks 7-9 is high. In response to this, by forming the peripheral wall 41 of the enclosure 32 into a boat shape as described above, the resistance to the flow of the water to be treated 2 is reduced, and the external force acting on the support frame body 33 of the membrane separation device 30 is alleviated.

[0089] (Sixth embodiment) In the first embodiment described above, as shown in FIG. 3, the float 55 of the membrane separation device 30 is provided below the membrane unit 31 and is completely submerged below the water surface 4. However, in the sixth embodiment described below, as shown in FIG. 11, the float 55 may be provided above the membrane unit 31 and float on the water surface 4.

[0090] The float 55 has a storage section 78 for storing air inside, and also has an opening 79 on its underside, and obtains buoyancy by storing the air bubbles 61 released from the second air diffuser 38 in the storage section 78 through the opening 79.

[0091] According to this, as in the first embodiment described above, when the membrane unit 31 is installed in, for example, the aerobic tank 8 in the first step, the supported portion 43a of the support frame body 33 of the membrane separation device 30 is supported on the side wall 20 of the aerobic tank 8. In this state, buoyancy is generated in the support frame body 33 by the float 55, so that the load (own weight) of the membrane separation device 30 acting on the side wall 20 of the treatment tank 8 via the supported portion 43a of the support frame body 33 is reduced by the amount of buoyancy. This makes it possible to eliminate the need for reinforcement work for the side wall 20 of the treatment tank 8, or to significantly reduce the amount of reinforcement work.

[0092] In each of the above-described embodiments, as shown in FIG. 1, the water treatment facility 1 is provided with three aerobic tanks 7 to 9, but two or four or more tanks may be provided.

[0093] In each of the above-described embodiments, as shown in FIG. 4, in the first step, the membrane separation device 30 is installed in the aerobic tank 8 or the aerobic tank 9 out of the aerobic tanks 8 and 9 that are not the target of renewal. However, the membrane separation device 30 may be installed in both the aerobic tank 8 and the aerobic tank 9.

[0094] The drawings are mainly schematic illustrations of the components, and the thickness, length, number, spacing, etc. of each illustrated component may differ from the actual ones for convenience of drawing. Also, the shapes, values, etc. of each component shown in each of the above embodiments are merely examples and are not particularly limited, and various modifications are possible within the scope of the present invention without substantially departing from the configuration thereof. [Explanation of symbols]

[0095] 1. Water treatment facilities 2. Water to be treated (liquid to be treated) 4 Water surface (liquid surface) 7~9 Aerobic tank (treatment tank) 23 1st air diffuser 30 Membrane separation equipment 31 Membrane Unit 32 Enclosure 33 Support frame 34 Communication port (communication part) 36 Membrane element 37 Swirling flow 38 Second air diffuser 41 Peripheral wall 43a Supported part 47 Submerged section 48 Exposed part 55 Floating Body 65 Air lift device (exhaust device) 75 Bottom wall

Claims

1. A method for updating a water treatment facility having a plurality of treatment tanks each equipped with a first aeration device, comprising: A first step of installing a submerged membrane unit in at least one treatment tank other than the treatment tank to be renewed, separating a portion of the liquid to be treated supplied to the treatment tank other than the treatment tank into a solid-liquid state by the membrane unit and discharging the remaining liquid to the outside of the treatment tank, and diffusing the remaining liquid with a first air diffuser and then discharging it to the outside of the treatment tank; A second step of updating the treatment tank to be updated while stopping the first aeration device of the treatment tank to be updated; and a third step of removing the membrane units from the treatment tanks other than the one to be updated after the update. In the first step, the lateral periphery of the membrane unit is surrounded by an enclosure to separate solid and liquid, A method for updating a water treatment facility, comprising carrying out a second step while carrying out a first step.

2. The method for renewing a water treatment facility according to claim 1, characterized in that in the first step, the liquid to be treated is separated into solid and liquid using a membrane unit while diffusing air using a first air diffuser in a treatment tank other than the one to be renewed.

3. 2. The method for updating a water treatment facility according to claim 1, wherein the enclosure has a lower end submerged below the liquid level in the treatment tank and an upper end protruding above the liquid level.

4. 2. The method for updating a water treatment facility according to claim 1, further comprising providing a communication part that communicates between the inside and outside of the enclosure below the liquid level.

5. 5. The method for updating a water treatment facility according to claim 4, further comprising the step of providing a discharge device for discharging the liquid to be treated inside the enclosure to the outside.

6. 6. The method for updating a water treatment facility according to claim 5, further comprising the step of adjusting the MLSS concentration of the liquid being treated inside the enclosure using a discharge device.

7. The membrane unit includes a membrane element and a second air diffuser that generates a swirling flow that swirls vertically along the membrane element, The enclosure has a peripheral wall surrounding the side periphery of the membrane unit and a bottom wall provided at a lower part of the peripheral wall and covering the lower part of the membrane unit, 2. The method for updating a water treatment facility according to claim 1, wherein the bottom wall is located above the first aeration device of the treatment tank.

8. A fourth step of operating the first aeration device of the treatment tank after the renewal to resume operation of the treatment tank after the renewal, 2. The method for renewing a water treatment facility according to claim 1, characterized in that the second step is carried out while the first step is being carried out, and then the third step and the fourth step are carried out simultaneously or at different times.

9. A membrane separation device including a membrane unit and an enclosure used in the water treatment facility renewal method according to claim 1, The membrane unit and the enclosure are mounted on a support frame, The support frame body has a submerged portion that is submerged below the liquid surface in the treatment tank and an exposed portion that is exposed above the liquid surface, The exposed portion of the support frame has a supported portion that is supported by the treatment tank, A membrane separation device characterized in that a support frame is provided with a floating body that generates buoyancy.

10. A membrane separation apparatus having a membrane unit that separates a liquid to be treated into a solid-liquid separation state while being immersed in the liquid to be treated in a treatment tank, and a support frame that supports the membrane unit, The support frame body has a submerged portion that is submerged below the liquid surface in the treatment tank and an exposed portion that is exposed above the liquid surface, The exposed portion of the support frame has a supported portion that is supported by the treatment tank, The support frame is provided with a float that generates buoyancy and an enclosure that surrounds the side periphery of the membrane unit; A membrane separation device characterized in that the enclosure has a lower end that is submerged below the liquid level in the treatment tank and an upper end that protrudes above the liquid level.

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