JP4346340B2 - Operation method of coagulation filtration processing device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for operating a coagulation filtration apparatus for filtering water to be treated, which has added flocculant and generated flocs during a filtration step, with a membrane module.
[0002]
[Prior art]
Conventionally, as this type of coagulation filtration processing apparatus, for example, as shown in FIG. 11, a supply pump 12 that supplies water to be treated (water, purified water, sewage, effluent, waste water, etc.) to the membrane module 11 is installed. A mixing tank 13 is installed on the upstream side of the supply pump 12, and an addition unit 14 for adding a flocculant (polyaluminum chloride or the like) to the water to be treated injected into the mixing tank 13 is provided. The mixing tank 13 is provided with a mixer 15 for stirring and mixing the water to be treated and the flocculant. The membrane module 11 contains a straight tubular membrane tube 16.
[0003]
According to this, a flocculant reaction occurs by adding a flocculant to the treated water introduced into the mixing tank 13 from the addition unit 14 during the filtration step, and flocs containing suspended substances are generated in the treated water. The The water to be treated that has generated flocs in this way is supplied from the mixing tank 13 to the membrane module 11 by the supply pump 12, filtered through the membrane tube 16, and then discharged from the membrane module 11 as filtered water.
[0004]
Usually, the addition amount of the flocculant is set to an optimum value based on the improvement of the quality of the water to be treated. For example, several milligrams of the flocculant is added to 1 liter of the water to be treated.
[0005]
However, when the addition amount of the flocculant is set based on the water quality improvement of the water to be treated as described above, flocs generated in the water to be treated have a minute size, and when the membrane module 11 is filtered, As shown in FIG. 12, the minute floc Fs adheres to the inner peripheral side of the membrane tube 16 to form the minute floc layer Ls, and the minute hole of the membrane tube 16 is blocked by the minute floc Fs. There is a problem that even if the membrane module 11 is backwashed, the floc Fs is not easily peeled off from the inner peripheral surface of the membrane tube 16.
[0006]
As a countermeasure for the above problems, increase the amount of the flocculant added during the filtration step by 5 to 10 times the normal amount (that is, the amount set based on the quality improvement of the water to be treated). The method of adding is mentioned (for example, refer patent document 1).
[0007]
[Patent Document 1]
Japanese Patent Laid-Open No. 10-85513
[Problems to be solved by the invention]
However, as described above, since a large amount of flocculant (5 to 10 times the normal addition amount) is always added during the filtration step, an excessive amount of flocculant is present for the quality of the water to be treated. As a result, the operation of the coagulation filtration apparatus becomes uneconomical.
[0009]
An object of this invention is to provide the operation method of the coagulation filtration processing apparatus which can perform backwashing of a membrane module easily and performing economical operation | movement.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the first aspect of the present invention provides a method for operating a coagulation filtration treatment apparatus that supplies water to be treated, which has flocs produced by adding a flocculant during the filtration step, to the membrane module and filters the membrane module. Because
The membrane module is backwashed by increasing the amount of flocculant added above the normal amount added for a certain period of time immediately before the filtration step is completed, and after the filtration step is completed, the backwashing step is performed. It is.
[0011]
According to this, the size of the floc produced | generated during the fixed period of a filtration process becomes coarser than the size of the floc produced | generated during filtration processes other than a fixed period. Accordingly, the coarse floc is supplied to the membrane module during the certain period, and the flocs of the minute size as usual are supplied to the membrane module outside the certain period. Thereby, in the filtration step, first, a minute floc is deposited on the primary side (treated water side) of the membrane surface of the membrane module to form a minute floc layer, and then a coarse floc layer is formed on the minute floc layer. A floc is deposited and a coarse floc layer is formed to overlap.
[0012]
In this state, by performing the backwashing process and backwashing the membrane module, the backwash water flows from the secondary side of the membrane surface to the primary side, and the coarse flocs with weak adhesion easily peel off, At this time, minute flocs adhere to the periphery of the coarse floc and peel off together. Further, when the peeled coarse floc flows together with the backwash water, the coarse floc hits the fine floc layer and scrapes the fine floc layer. For this reason, minute flocs are also easily peeled off, and these coarse flocs and minute flocs can be easily removed from the membrane surface of the membrane module, and backwashing can be performed easily and effectively. In addition, the amount of flocculant added is increased from the normal amount added during a certain period of time during the filtration process, and is reduced to the normal amount added outside of the fixed period. Compared with the case where it is constantly added, economical operation can be performed.
[0017]
Further, the second invention is an operation method of the flocculation filtration apparatus for supplying the water to be treated, which has added flocculant and generating flocs to the membrane module during the filtration step , and filtering with the membrane module,
A predetermined period immediately before ending a period of time and filtration step immediately after the start of the filtration step, is increased than a normal amount of addition amount of the flocculant, after the completion of the above filtration step, performing the backwash step Thus, the membrane module is backwashed .
[0018]
According to this, at the time of the filtration step, first, coarse flocs are deposited on the primary side of the membrane surface of the membrane module to form the first coarse floc layer, and then, the first coarse floc layer has a minute amount. Flocs are deposited to overlap the micro floc layer, and then the coarse flocs are deposited again on the micro floc layer to form the second coarse floc layer. A floc layer having a sandwich structure in which a minute floc layer is sandwiched between intermediate portions of the second coarse floc layer is formed.
[0019]
In this state, by performing a backwashing process and backwashing the membrane module, backwashing water flows from the secondary side of the membrane surface to the primary side, so that the coarse floc of the second coarse floc layer can be easily obtained. The flocs are peeled off from the fine floc layer. At this time, the fine flocs of the fine floc layer adhere to the periphery of the coarse floc and peel together. Further, when the coarse floc separated from the fine floc layer flows together with the backwash water, the coarse floc hits the fine floc layer and scrapes off the fine floc layer, so that the fine floc is easily peeled off. Further, the coarse floc of the first coarse floc layer is easily peeled off from the film surface, and at this time, the fine floc deposited on the first coarse floc layer is easily peeled off together with the coarse floc. Thereby, coarse flocs and minute flocs can be easily removed from the membrane surface of the membrane module, and backwashing can be performed easily and effectively.
[0020]
Moreover, this 3rd invention sets the addition amount of the flocculant added for a fixed period to 3 to 10 times the normal addition amount.
According to this, it is possible to achieve both easy and effective backwashing and economical operation. In addition, if it is less than 3 times, the merit of carrying out backwashing easily and effectively cannot be obtained sufficiently, and if it exceeds 10 times, the cost increases, and the merit of economical operation is sufficiently obtained. I can't.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. In addition, about the member same as a conventional thing, the same code | symbol is attached | subjected and description is abbreviate | omitted.
[0022]
As shown in FIG. 1, reference numeral 21 denotes a coagulation filtration apparatus that supplies water to be treated, which has added flocculant and generates flocs, to the internal pressure membrane module 22 and filters the membrane module 22 during the filtration step. .
[0023]
As shown in FIGS. 2 and 3, the membrane module 22 includes a plurality of (two) membrane elements 24 inside a casing 23. The membrane element 24 comprises a plurality of straight tubular ceramic membrane tubes 25 whose ends are closed, and a focusing plate for supporting the membrane tubes 25 in a cantilever manner by focusing and fixing the base ends of the membrane tubes 25. 26.
[0024]
Membrane element insertion ports 27 through which the membrane element 24 is taken in and out are formed at both ends of the casing 23, and a cap-shaped water distribution member 28 covering the base end opening 25a side of each membrane tube 25 of the membrane element 24 is attached and detached. It is installed freely. Both water distribution members 28 are provided with raw water supply ports 29 for supplying the treated water sent from the supply pump 12 into the casing 23. Further, the casing 23 is provided with a filtered water discharge port 30 for discharging the filtered water.
[0025]
As shown in FIG. 1, the raw water supply port 29 is connected to a supply flow path 32 for supplying water to be treated in the mixing tank 13, and a supply valve 33 is connected to the supply flow path 32. Is provided. The filtered water discharge port 30 is connected to a discharge flow path 35 for discharging the filtered water to an external treated water tank 34, and a discharge valve 36 is provided in the discharge flow path 35.
[0026]
Further, the coagulation filtration device 21 is provided with a backwash device 40 for backwashing the membrane module 22. The backwashing device 40 branches from the supply channel 32 and joins the backwashing discharge channel 42 for discharging the backwashing water to the drain tank 41 outside the membrane module 22 and the discharge channel 35. A backwashing supply channel 43 for supplying backwashing water to the membrane module 22 and the filtered water discharge port 30 of the membrane module 22 from the backwashing supply channel 43 using the filtered water in the treated water tank 34 as backwashing water. And a backwashing pump 44 to be supplied. The backwash discharge flow path 42 is provided with a backwash discharge valve 45, and the backwash supply flow path 43 is provided with a backwash supply valve 46.
[0027]
Hereinafter, the operation of the above configuration will be described.
When performing the filtration step, the backwashing discharge valve 45 and the backwashing supply valve 46 are closed and the backwashing pump 44 is stopped, and the supply valve 33 and the discharge valve 36 are opened, and the supply pump 12 and the mixer 15 are operated, and a flocculant is further added from the addition unit 14 to the water to be treated in the mixing tank 13. As a result, flocs containing suspended substances are generated in the water to be treated in the mixing tank 13, and the water to be treated that has generated the flocs thus flows through the supply flow path 32, as indicated by a solid line arrow in FIG. 2. Is supplied into the water distribution member 28 from the raw water supply port 29, flows into the internal flow path 25b (see FIG. 3) from the proximal end opening 25a of each membrane tube 25, and is filtered when permeating from the inside to the outside of each membrane tube 25 Then, the filtered water is discharged from the filtered water outlet 30 through the discharge channel 35 to the treated water tank 34 as filtered water.
[0028]
When performing the backwashing process, addition of the flocculant is stopped, the supply valve 33 and the discharge valve 36 are closed, the supply pump 12 is stopped, and the backwash discharge valve 45 and the backwash supply valve are stopped. 46 and the backwash pump 44 is operated. As a result, the filtered water in the treated water tank 34 is supplied as backwash water in the casing 23 from the backwash supply channel 43 through the filtered water discharge port 30 of the membrane module 22 as shown by the dotted arrow in FIG. , And permeates from the outside to the inside of each membrane tube 25, flows through the internal flow path 25 b of each membrane tube 25, flows out from the proximal end opening 25 a into the water distribution member 28, and discharges for backwashing from the raw water supply port 29. It is discharged to the drainage tank 41 through the flow path 42.
[0029]
Next, an operation method of the aggregation filtration processing device 21 will be described.
That is, as shown in FIG. 4, during the filtration step, the addition amount of the flocculant is set to the normal addition amount A, but the addition amount of the flocculant is set to the normal addition amount for a certain period of time immediately before the completion of the filtration step. It is increased to 3 to 10 times the addition amount A. And after finishing the said filtration process, a backwashing process is implemented. After the backwashing process is completed, the filtration process is performed again. Thereafter, the backwashing process and the filtration process are repeated a predetermined number of times.
[0030]
The normal addition amount A is set to an optimum value based on the quality improvement of the water to be treated, and is determined empirically according to the type and amount of the turbid component contained in the water to be treated. For example, several milligrams of a flocculant is added to 1 liter of water to be treated. The predetermined period De is set to about 10% of the filtration process period.
[0031]
According to the operation method as described above, during the filtration step, coarse (huge) floc Fb is generated in the water to be treated within the predetermined period De, and in the remaining period E other than the predetermined period De, the target is treated. A minute floc Fs is generated in the water. Therefore, as shown in FIG. 5A, at the time of the filtration step, first, the minute floc Fs is deposited on the inner peripheral surface side (primary side) of each membrane tube 25 to form the minute floc layer Ls, and then A coarse floc Fb is deposited on the inner peripheral side of the fine floc layer Ls, and the coarse floc layer Lb is overlapped.
[0032]
In this state, the backwashing process is performed as described above to backwash the membrane module 22 so that the backwash water is outside the secondary tube (secondary side) as shown in FIG. The coarse floc Fb having a weak adhesion force peels easily from the inside to the inside (primary side), and at this time, the minute floc Fs adheres to the periphery of the coarse floc Fb and peels off together. Further, when the peeled coarse floc Fb flows with the backwash water through the internal flow path 25b of each membrane tube 25 toward the proximal end opening 25a, the coarse floc Fb hits the fine floc layer Ls and hits the fine floc layer Ls. Scrape off. For this reason, the minute flocs Fs are also easily separated, and the separated coarse flocs Fb and minute flocs Fs pass through the proximal opening 25a from the internal flow path 25b of the membrane tube 25, and the water distribution member 28. It is discharged inside. Thereby, the coarse floc Fb and the minute floc Fs can be easily removed from the inner peripheral surface of the membrane tube 25, and backwashing can be easily and effectively performed.
[0033]
In addition, by making the addition amount of the flocculant 3 to 10 times the normal addition amount A only for a certain period De, it is possible to achieve both easy and effective backwashing and economical operation. Can do. In addition, if it is less than 3 times, the merit of carrying out backwashing easily and effectively cannot be obtained sufficiently, and if it exceeds 10 times, the cost increases, and the merit of economical operation is sufficiently obtained. I can't.
[0034]
Next, an operation method of the coagulation filtration apparatus 21 in the second embodiment of the present invention will be described with reference to FIGS.
That is, the addition amount of the flocculant is set to the normal addition amount A during the filtration step, but the addition amount of the flocculant is 3 to 10 times the normal addition amount A for a certain period Ds immediately after the start of the filtration step. Doubled. And after finishing the said filtration process, a backwashing process is implemented. After the backwashing process is completed, the filtration process is performed again. Thereafter, the backwashing process and the filtration process are repeated a predetermined number of times. The fixed period Ds is set to about 10% of the filtration process period.
[0035]
According to the operation method as described above, during the filtration step, coarse (huge) floc Fb is generated in the water to be treated within the predetermined period Ds, and in the remaining period E other than the predetermined period Ds, the target is treated. A minute floc Fs is generated in the water. Therefore, as shown in FIG. 7A, during the filtration step, first, coarse floc Fb is deposited on the inner peripheral surface side (primary side) of each membrane tube 25 to form coarse floc layer Lb, and thereafter The minute flocs Fs are deposited on the inner peripheral side of the coarse floc layer Lb, and the minute floc layers Ls are overlapped.
[0036]
In this state, the backwashing process is performed as described above to backwash the membrane module 22 so that the backwash water is outside the secondary tube (secondary side) as shown in FIG. 7B. From the inner peripheral surface of the membrane tube 25, and the minute flocs Fs deposited on the coarse floc layer Lb are separated from the coarse flocs Fs. Easily peels off with Fb. The separated coarse flocs Fb and minute flocs Fs pass through the base channel opening 25a from the internal flow path 25b of the membrane tube 25 and are discharged into the water distribution member 28. Thereby, the coarse floc Fb and the minute floc Fs can be easily removed from the inner peripheral surface of the membrane tube 25, and backwashing can be performed easily and effectively.
[0037]
Next, an operation method of the coagulation filtration apparatus 21 in the third embodiment of the present invention will be described with reference to FIGS.
That is, the addition amount of the flocculant is set to the normal addition amount A at the time of the filtration step, but the addition amount of the flocculant only for a certain period Ds immediately after the start of the filtration step and a certain period De immediately before the end of the filtration step. Is increased to 3 to 10 times the normal addition amount A. And after finishing the said filtration process, a backwashing process is implemented. After the backwashing process is completed, the filtration process is performed again. Thereafter, the backwashing process and the filtration process are repeated a predetermined number of times.
[0038]
According to the operation method as described above, during the filtration step, a coarse (huge) floc Fb is generated in the water to be treated in the fixed periods Ds and De, and the remaining period other than the fixed periods Ds and De. In E, a minute floc Fs is generated in the water to be treated. Therefore, as shown in FIG. 9, in the filtering step, first, coarse floc Fb is deposited on the inner peripheral surface side (primary side) of each membrane tube 25 to form the first coarse floc layer Lb1, In addition, a minute floc Fs is deposited on the inner peripheral side of the first coarse floc layer Lb1, and the fine floc layer Ls is formed on the inner peripheral side of the fine floc layer Ls. The floc Fb is deposited and the second coarse floc layer Lb2 is formed to overlap. As a result, a floc layer having a sandwich structure in which the minute floc layer Ls is sandwiched between the first and second coarse floc layers Lb1 and Lb2 is formed on the inner peripheral surface side of the membrane tube 25.
[0039]
In this state, by performing the backwashing process as described above to backwash the membrane module 22, backwash water flows from the outside (secondary side) to the inside (primary side) of each membrane tube 25, The coarse floc layer Fb having a weak adhesion force of the coarse floc layer Lb2 is easily peeled off from the fine floc layer Ls. Peel off.
[0040]
Further, when the coarse floc Fb peeled off from the fine floc layer Ls flows with the backwash water through the internal flow path 25b of each membrane tube 25 toward the proximal end opening 25a, the coarse floc Fb collides with the fine floc layer Ls. Since the minute floc layer Ls is scraped off, the minute floc Fs is also easily peeled off.
[0041]
Further, the coarse floc Fb having a weak adhesive force of the first coarse floc layer Lb1 is easily peeled off from the inner peripheral surface of the membrane tube 25. At this time, the minute flocs deposited on the inner peripheral side of the first coarse floc layer Lb1 The floc Fs easily peels off with the coarse floc Fb. The coarse flocs Fb and the minute flocs Fs peeled in this way pass through the base channel opening 25a from the internal flow path 25b of the membrane tube 25 and are discharged into the water distribution member 28. Thereby, the coarse floc Fb and the minute floc Fs can be easily removed from the inner peripheral surface of the membrane tube 25, and backwashing can be performed easily and effectively.
[0042]
In each of the above embodiments, immediately after the start of the filtration step or immediately before the end, the fixed periods Ds and De for increasing the addition amount of the flocculant are set, but in the middle of the filtration step (medium, in the middle) You may set the fixed period which increases the addition amount of an agent.
[0043]
In each of the above embodiments, the internal pressure type membrane module 22 that filters the water to be treated from the inside to the outside of the membrane tube 25 during the filtration step has been described. However, as the fourth embodiment of the present invention, As shown in FIG. 10, an external pressure type membrane module 51 that filters the water to be treated from the outside to the inside of the membrane tube 25 may be used.
[0044]
In the external pressure membrane module 51, water collecting members 52 having the same shape as the water distribution member 28 are provided at both ends of the casing 23, and the base end openings 25 a of the respective membrane tubes 25 are covered by the water collecting members 52. It has been broken. The raw water supply port 29 is provided in the casing 23, and the filtered water discharge port 30 is provided in both water collecting members 52.
[0045]
According to this, at the time of a filtration process, to-be-processed water flows into the inner side from the outer side of the membrane tube 25, and the flock layers Lb and Ls are formed in the outer peripheral surface of the membrane tube 25. In addition, backwash water flows from the inside to the outside of the membrane tube 25 during the backwash process.
[0046]
In each of the above embodiments, the membrane module 22 is provided with the straight tubular membrane tube 25, but may be provided with a flat membrane. The material of the membrane tube 25 is not limited to ceramic, and may be an organic material such as cellulose acetate or polyvinylidene fluoride.
[0047]
【The invention's effect】
As described above, according to the present invention, during the back washing process, coarse flocs and minute flocs are easily removed from the membrane surface of the membrane module, so that back washing can be performed easily and effectively. Moreover, economical operation can be performed as compared with the case where a large amount of flocculant is always added to the water to be treated during the filtration step as in the prior art.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a flocculation filtration apparatus in a first embodiment of the present invention.
FIG. 2 is a cross-sectional view of the membrane module of the coagulation filtration apparatus.
FIG. 3 is a sectional view of a membrane element of the membrane module of the coagulation filtration apparatus.
FIG. 4 is a graph showing the relationship between the operation time of the coagulation filtration apparatus and the amount of coagulant added.
FIG. 5 is an enlarged cross-sectional view of the membrane tube of the membrane module of the coagulation filtration apparatus, where (a) shows the time of the filtration step and (b) shows the time of the backwashing step.
FIG. 6 is a graph showing the relationship between the operation time of the coagulation filtration apparatus and the addition amount of the coagulant in the second embodiment of the present invention.
7 is an enlarged cross-sectional view of the membrane tube of the membrane module of the coagulation filtration apparatus, where (a) shows the filtration step and (b) shows the backwash step.
FIG. 8 is a graph showing the relationship between the operation time of the coagulation filtration apparatus and the amount of coagulant added in the third embodiment of the present invention.
FIG. 9 is an enlarged cross-sectional view of the membrane tube of the membrane module during the filtration step of the coagulation filtration apparatus.
FIG. 10 is a cross-sectional view of a membrane module of a coagulation filtration apparatus in a fourth embodiment of the present invention.
FIG. 11 is a diagram showing a configuration of a conventional coagulation filtration apparatus.
FIG. 12 is an enlarged cross-sectional view of the membrane tube of the membrane module of the coagulation filtration apparatus.
[Explanation of symbols]
21 Coagulation filtration apparatus 22, 51 Membrane module A Normal addition amount Ds, De Fixed period E Remaining period

Claims (3)

In the filtration step, the water to be treated, which has added flocculant and generated floc, is supplied to the membrane module, and is a method for operating the agglomeration filtration treatment device for filtering through the membrane module,
Increase the addition amount of the flocculant from the normal addition amount for a certain period immediately before finishing the filtration step, and after the filtration step is completed, perform the backwashing step to backwash the membrane module. The operation method of the coagulation filtration processing apparatus characterized by these. In the filtration step, the water to be treated, which has added flocculant and generated floc, is supplied to the membrane module, and is a method for operating the agglomeration filtration treatment device for filtering through the membrane module,
Increase the amount of flocculant added from the normal amount only for a certain period immediately after starting the filtration step and for a certain period just before ending the filtration step. The membrane module is then back-washed, and the operation method of the coagulation filtration apparatus is characterized in that The operation method of the coagulation filtration apparatus according to claim 1 or 2, wherein the addition amount of the flocculant added for a certain period is set to 3 to 10 times the normal addition amount .

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