JP2001212433A - Pretreating device for raw water fed to reverse osmosis membrane treating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide pretreating device capable of preventing deterioration of water quality of secondary filtered water fed to a reverse osmosis membrane treating device, even in an operation of the device for long hours, as a sealed piping type (a non-open piping type) pretreating device for pretreating raw water fed to the reverse osmosis membrane treating device. SOLUTION: This pretreating device is provided with a flocculant addition device 7, a filter device 8 (a primary filter means), a protection filter 9 (a secondary filter means), a pH adjusting agent addition device 11, a sterilizer addition device 13, a water intake pump 14, a high pressure pump 15, a backward washing device 60, and a germicide addition device 64, and the bite. The backward washing device 60 stores mixed liquid of primary filtered water and a germicide added solution in a backward washing water tank 61, and also adds the germicide added solution via a piping 73 to the mixed liquid taken out from the backward washing water tank 61 with backward washing liquid feed means 63 to be mixed, then feeds it to the filter device 8 to backward wash the filter device 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pretreatment device for raw water supplied to a reverse osmosis membrane treatment device.

[0002]

2. Description of the Related Art As is well known, in seawater reverse osmosis membrane type desalination equipment, seawater is pretreated and supplied to a reverse osmosis membrane treatment apparatus. The treated water is sent to a filter (for example, a sand filter) for primary filtration, and the primary filtered water is temporarily stored in an intermediate storage tank, and if necessary, the primary filtered water is transferred from the intermediate storage tank to a security filter. In addition, pH adjustment treatment and the like are performed on the way, and secondary filtered water having a quality suitable for preventing clogging of the reverse osmosis membrane is obtained, and then sent to the reverse osmosis membrane processing device for processing. .

[0003]

However, in such a pretreatment, since the primary filtered water which has been subjected to the sterilization treatment and the coagulation filtration treatment is temporarily stored in the intermediate storage tank, contaminants from outside are mixed. Or it is easy to cause water quality deterioration due to microbial growth due to stagnation of the primary filtered water, and
Since chlorine is used as a sterilant, organic matter in seawater (raw water) is decomposed into low-molecular-weight organic matter that is easily assimilated by microorganisms, and therefore, the growth of microorganisms in the membrane module of the reverse osmosis membrane treatment device is promoted. In addition, there is a drawback that there is a high risk that harmful trihalomethane is generated by the reaction between chlorine and organic matter in seawater.

[0004] Further, an intermediate storage tank for temporarily storing the primary filtered water subjected to the sterilization treatment and the coagulation filtration treatment is provided between the filter and the security filter, that is, at a stage after the filter (reverse osmosis membrane treatment device side). Therefore, if the pump for raw water (seawater) intake control is turned on and off according to the amount of water stored in the intermediate storage tank, the filtration performance is likely to be unstable, and And the quality of the filtered water deteriorates.

Therefore, the inventors of the present invention applied for a prior application (Japanese Patent Application No.
-89153), one solution is to use a mineral acid in the same manner as in the pH adjustment treatment without using chlorine for the sterilization treatment. It has been proposed to provide a closed pipeline system (non-open pipeline system) in which an intermediate storage tank is not installed, instead of providing a so-called open pipeline system.

However, even in such a case, in the operation of the apparatus for a long time, the prevention of the growth of bacteria in the sand filter itself tends to be insufficient, so that the secondary filtration supplied to the reverse osmosis membrane treatment apparatus is performed. The water quality of water gradually deteriorated, and there was a possibility that the performance would be reduced due to the occurrence of biofouling in the reverse osmosis membrane treatment device.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems and to prevent the deterioration of the quality of the secondary filtered water supplied to the reverse osmosis membrane treatment apparatus even when the apparatus is operated for a long time. An object of the present invention is to provide a pretreatment device that can prevent such a problem.

[0008]

According to the present invention, there is provided a pretreatment apparatus comprising: a first conduit for pumping raw water to a filter; and a primary filter for directly filtering primary filtered water from the filter. A second conduit for sending the secondary filtered water from the security filter to a reverse osmosis membrane treatment device via a high-pressure pump; and a coagulant solution in the raw water flowing through the first conduit. A pH adjusting agent adding device for adding a pH adjusting mineral acid solution to the primary filtered water flowing through the second pipe, and one of the first to third pipes. A pre-treatment device for supplying raw water to a reverse osmosis membrane treatment device having a sterilizing agent adding device for adding a sterilizing mineral acid solution to the raw water or the filtered water flowing therethrough in one of the pipelines; It also features a backwashing device for washing It is.

As described above, the processing pipeline system equipped with the filter (primary filtration unit) and the security filter (secondary filtration unit) is replaced with a closed pipeline system (non-open pipeline system) in which no intermediate storage tank is installed. ) And a backwashing device for backwashing the filter is installed, so that the quality of the secondary filtered water supplied to the reverse osmosis membrane treatment device is prevented from deteriorating even when the device is operated for a long time. Therefore, it is possible to prevent the performance degradation due to the occurrence of biofouling in the reverse osmosis membrane treatment apparatus, and to perform the stable reverse osmosis membrane treatment.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a seawater desalination facility. The desalination facility includes a pretreatment device 1, a reverse osmosis membrane treatment device 2, a post treatment device 3, a membrane cleaning device 4, and the like. And a pretreatment device 1 includes a coagulant addition device 7 that adds a coagulant solution to seawater (raw water) flowing through the first conduit 6,
A sand filter 8 as a primary filtration means, a security filter 9 as a secondary filtration means, and a pH adjusting agent adding device 1 for adding a mineral acid solution for pH adjustment to primary filtered water flowing through a second pipe 10.
1 and a sterilizing agent addition device 13 for adding a sterilizing mineral acid solution to the secondary filtered water flowing through the third pipe 12.

The first pipe 6 is connected to the water intake pump 14 and the sand filter 8. In addition, the second pipeline 10
It is connected to a sand filter 8 and a security filter 9. Further, the third conduit 12 is connected to the security filter 9 and the first-stage membrane module 17 of the reverse osmosis membrane treatment device 2, and
A high-pressure pump 15 is mounted on the third pipe 12.

Therefore, seawater (raw water) can be sent to the sand filter 8 by the operation of the water intake pump 14, and the secondary filtered water can be highly pressurized by the operation of the high-pressure pump 15, and can be supplied to the reverse osmosis membrane treatment device 2. At this time, a ferric chloride solution (coagulant solution) having a predetermined concentration is added via the line 18 by the coagulant adding device 7, and
A sulfuric acid solution (mineral acid solution for pH adjustment) is added via a line 19 by a pH adjusting agent adding device 11, and a sulfuric acid solution (mineral acid solution for sterilizing) is further added via a line 20 by a sterilizing agent adding device 13. Is done.

The sterilizing acid solution may be added continuously, but is preferably added intermittently (1 to 6 hr / day). Next, it is added so as to adjust the pH of the filtered water to 1 to 5, preferably 2 to 4. On the other hand, the addition of the mineral acid solution for pH adjustment
It is continuously added so as to adjust the pH of the primary filtered water to 6-7.

The coagulant adding device 7 can extract and add the ferric chloride solution from the tank 22 by operating the pump 21, and add the pH adjusting agent adding device 1.
1 can extract and add the sulfuric acid solution from the tank 24 by operating the pump 23, and further, the sterilizing agent adding device 13 can extract and add the sulfuric acid solution from the tank 26 by operating the pump 25. Are provided respectively.

As described above, the pipeline from the water intake pump 14 to the first-stage membrane module 17 of the reverse osmosis membrane treatment device 2 is provided in a closed pipeline system. That is, unlike the related art, an intermediate storage tank for temporarily storing primary filtered water is not provided in the form of an open pipeline system in which the intermediate storage tank is installed, but is provided in a non-open pipeline system.

As a result, it is possible to prevent contamination by contaminants from the outside and to perform treatment while continuously supplying water, so that the growth of microorganisms can be effectively prevented. Subsequent fluctuations in flow rate can be dealt with by changing the flow velocity in each component of the pretreatment device 1, so that the water can always be kept in a flowing state, and no stagnation occurs and continuous Processing (processing without ON-OFF operation) can be performed by operation, and stable operation of the sand filter 8 can be performed.

Further, in such a closed pipeline system,
The coagulation filtration process and the pH adjustment process using a sulfuric acid solution, which is a kind of mineral acid, are performed at a stage before the filtration process (secondary filtration process) by the security filter 9 and at a later stage of the secondary filtration process. As in the case of the pH adjustment process, a sterilization process using a sulfuric acid solution is performed. Therefore, there is no danger that harmful trihalomethane is generated.

The above-mentioned pretreatment device 1 is further provided with a backwashing device 60 for backwashing the sand filter 8, and the backwashing device 60 removes the primary filtered water from the second pipe 10. Filtered water extracting means 62 for extracting and supplying the filtered water to backwater tank 61
Backwashing liquid supply means 6 for supplying a mixed solution of the primary filtered water and the disinfectant-added solution from the backwashing water tank 61 to the sand filter 8
3, a disinfectant addition device 64 that supplies the disinfectant addition solution to the backwash water tank 61 and supplies the disinfectant addition solution to the mixed solution supplied from the backwash water tank 61 to the sand filter 8. It is composed of

Then, the filtered water extracting means 62 is connected to the second
Valve 6 mounted on line 65 branched from line 10
The valve 66 is provided so that the opening and closing of the valve 66 is controlled based on a detection signal from a liquid level gauge 67 attached to a backwash water tank 61 provided in a closed structure. In controlling the opening and closing of the valve 66, the liquid level gauge 67 sends a detection signal for closing the valve 66 when the liquid level of the mixed liquid reaches the specified liquid level, and opens the valve 66 when the mixed liquid level falls below the specified liquid level. Send a signal to

The backwash liquid supply means 63 includes a pump 69 mounted on a pipe 68 connected to the backwash water tank 61 and the sand filter 8.
Primary filtered water extracted from the second conduit 10 by the filtered water extracting means 62 and supplied to the backwash water tank 61 and a disinfectant-added solution supplied to the backwash water tank 61 by a disinfectant addition device 64 described below. (For example, sodium hypochlorite solution)
(Backwash liquid) can be supplied from the backwash water tank 61 to the sand filter 8.

The disinfectant adding device 64 includes a pipe 71 connected to a tank 70 for storing a disinfectant added solution and a backwashing water tank 61 and a pump 72 mounted on the pipe 71.
And a pipe 73 connected to the tank 70 and the pipe 68, and a pump 74 mounted on the pipe 73. When the valve 66 is opened, the pump 72 is operated to put the disinfectant into the backwash water tank 61. The pump 6 can supply the additive solution.
In operation 9, the pump 74 is operated to supply the germicide-added solution to the conduit 68. In addition, the concentration and the amount of the disinfectant added solution are appropriately
It is adjusted to a predetermined value.

Therefore, according to the backwashing device 60, a fixed amount of the mixed solution of the primary filtered water and the bactericide-added solution is constantly adjusted so that the amount of liquid stored in the backwashing water tank 61 does not become insufficient.
The mixed solution that can be stored and is drawn out of the backwashing water tank 61 by the backwashing solution supply means 63 is connected to the line 7.
The disinfectant added solution via 3 can be additionally mixed and supplied to the sand filter 8 for backwashing.

The backwashing is performed as necessary. In this case, a mixed solution (backwashing solution) of the primary filtered water and the bactericide-added solution is temporarily stored in the backwashing water tank 61. Therefore, the growth of bacteria in the tank can be prevented, and a bactericide-added solution can be further added to such a mixed solution, whereby the sand filter 8 can be backwashed. Therefore, the sterilization in the sand filter 8 can be performed more sufficiently, and the backwashing effect can be further enhanced.

Therefore, it is possible to prevent the quality of the secondary filtered water supplied to the reverse osmosis membrane treatment apparatus from being deteriorated even in the operation for a long period of time, and to thereby generate biofouling in the reverse osmosis membrane treatment apparatus. And a stable reverse osmosis membrane treatment can be performed by preventing the performance degradation caused by the reverse osmosis.

During the backwash, the valve 66 is closed and the pump 72 is stopped. During the supply of the primary filtered water and the bactericide-added solution to the backwash tank 61, the pumps 69 and 74 are stopped. Further, the additional mixing of the bactericide-added solution via the pipe 73 is performed as necessary, and therefore, the growth of bacteria can be prevented only by adding the bactericide-added solution to the primary filtered water in the backwash water tank 61. If sufficient, the supply of the disinfectant solution via line 73 may be discontinued.

When backwashing with only a mixture of the primary filtered water and the bactericide-added solution is always sufficient, the bactericide-adding device 64 is not equipped with the pump 74 and the pipe 73. There may be.

Further, the reverse osmosis membrane treatment apparatus 2 includes a second-stage membrane module 30 and a turbocharger (a booster pump) 31 in addition to the first-stage membrane module 17, and is discharged from the first-stage membrane module 17. The permeated water can be sent to a desalination water tank 33 via a pipe 32 and the concentrated water discharged from the first-stage membrane module 17 is passed through a pipe 34, a turbocharger (a booster pump) 31 and a pipe 35. It is provided so that it can be supplied to the second stage membrane module 30.

The permeated water discharged from the second-stage membrane module 30 passes through a pipe 36 to the first-stage membrane module 17.
And the concentrated water discharged from the module 30 is circulated to a turbocharger (pressure boosting pump) 31 via a pipe 37, and a part of the concentrated water is shown via a pipe 38. Sent to an undischarged water tank.

The above-mentioned backwashing device 60 may be provided with a concentrated water extracting means 75 in addition to the filtered water extracting means 62, but the concentrated water extracting means 75 is branched from the pipe 38. Valve 77 installed in the conduit 76
Is provided so that the valve 77 is controlled to open and close based on a detection signal from the liquid level gauge 67. In such open / close control, the liquid level gauge 67 indicates that the liquid level of the mixed liquid is equal to the specified liquid level. Is reached, a detection signal for closing the valve 77 is sent, and a signal for opening the valve 77 is sent when the liquid level falls below a specified level.

On the other hand, the membrane cleaning device 4 extracts the cleaning liquid from the tank 41 by operating the pump 40 and
12 to the first-stage membrane module 17 and to the pipeline 4
2, 35 to the second stage membrane module 30 and via lines 34, 37, 32 and 43,
It is provided so that it can be collected in the tank 41.

The post-processing device 3 includes a pipe 53 for supplying the slaked lime solution from the tank 51 to the mixing and adjusting tank 52 by operating the pump 50, a hopper 54 for storing slaked lime, a stirring device 55, and the like. In the figure, reference numeral 56 denotes a cleaning drainage pipe.

In the above, the case of seawater desalination has been described. In the present invention, the raw water may be other than seawater, for example, groundwater. The mineral acid used is
Sterilization treatment with a mineral acid solution other than sulfuric acid, for example, hydrochloric acid, etc., is not limited to being performed only on the secondary filtered water flowing through the third conduit 12, and the raw water flowing through the first conduit 6 may be used. Alternatively, it may be performed on the primary filtered water flowing through the second pipe 10.

Furthermore, if necessary, a chemical-free filtration treatment may be performed instead of the coagulation filtration treatment, and the disinfectant-added solution may be other than a sodium hypochlorite solution.
Note that the present invention basically does not continuously add chlorine for sterilization as in the past, but depending on the quality of raw water, intermittent use of chlorine sterilization may not be possible. It does not hinder.

[0034]

As described above, according to the present invention, with regard to the pretreatment of raw water supplied to the reverse osmosis membrane treatment apparatus, it is possible to solve the problem of harmful trihalomethane formation and to prevent the deterioration of water quality. Pretreatment can be performed well.

Further, even during long-term operation, it is possible to prevent deterioration of the quality of the secondary filtered water supplied to the reverse osmosis membrane treatment apparatus, and therefore, the generation of biofouling in the reverse osmosis membrane treatment apparatus can be prevented. And a stable reverse osmosis membrane treatment can be performed by preventing the performance degradation caused by the reverse osmosis.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a main part of a seawater desalination facility.

[Explanation of symbols]

 1: Pretreatment device 2: Reverse osmosis membrane treatment device 6: First line 7: Coagulant addition device 8: Sand filter (primary filtration unit) 9: Security filter (secondary filtration unit) 10: Second line 11: pH adjusting agent adding device 12: Third conduit 13: Sterilizing agent adding device 15: High pressure pump 17, 30: Membrane module 60: Backwashing device 61: Backwashing water tank 62: Filter water draining means 63: Backwashing Liquid supply means 64: Disinfectant addition device

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C02F 1/50 531 C02F 1/50 531P 540 540B 550 550C 560 560E 560Z 1/52 1/52 Z 1/76 1/76 A F term (reference) 4D006 GA03 KA03 KB13 KB15 KD06 KD08 KD11 KD24 PA02 PB03 PB05 4D015 BA19 BB05 CA20 DA13 EA35 FA02 FA17 FA23 FA28 4D050 AA06 AB06 BB06 BB20 BD03 BD06 CA09 CA13 CA15 CA19 FA19 FA23 FA28

Claims (5)

[Claims] 1. A first pipe for pumping raw water to a filter, a second pipe for directly sending primary filtered water from the filter to a security filter, and a secondary pipe from the security filter. A third conduit for feeding to a reverse osmosis membrane treatment device via a high pressure pump, a flocculant adding device for adding a flocculant solution to the raw water flowing through the first conduit, and the primary fluid flowing through the second conduit. A pH adjusting agent adding device for adding a pH adjusting mineral acid solution to the filtered water; and a sterilizing mineral acid added to the raw water or the filtered water flowing through any one of the first to third pipes. A reverse osmosis membrane treatment apparatus, comprising: a pretreatment apparatus for raw water to be supplied to a reverse osmosis membrane treatment apparatus having a sterilizing agent addition apparatus for adding a solution; Pretreatment device for raw water to be supplied to 2. A backwashing device, comprising: a filter water extracting means for extracting primary filtered water from a second pipe line and supplying the filtered water to a backwash water tank; and a disinfectant additive for supplying a disinfectant-added solution to the backwash water tank. 2. The reverse cleaning device according to claim 1, further comprising an apparatus, and a backwashing liquid supply unit configured to supply a mixed solution of the primary filtered water and the disinfectant-added solution from the backwashing water tank to a filter. 3. Pretreatment equipment for raw water to be supplied to the osmosis membrane treatment equipment. 3. A backwashing device, comprising: a filtered water extracting means for extracting primary filtered water from a second pipe line and supplying the filtered water to a backwashing water tank; Backwashing liquid supply means for supplying a filter from the washing tank to the filter; and a disinfectant for supplying the disinfectant-added solution to the backwashing tank and the mixed solution supplied from the backwashing tank to the filter. The pretreatment device for raw water supplied to the reverse osmosis membrane treatment device according to claim 1, comprising a disinfectant addition device for supplying an addition solution. 4. The pretreatment device for raw water supplied to a reverse osmosis membrane treatment device according to claim 2, wherein the disinfectant-added solution is a sodium hypochlorite solution. 5. The pretreatment device for raw water supplied to a reverse osmosis membrane treatment device according to claim 1, wherein the raw water is seawater.