TWI699235B - Water treatment method and device - Google Patents

Abstract

In order to provide a water treatment method and a water treatment device that treat the backwash drainage, wash drainage, circulating water or concentrated water of the membrane separation device and use it as cooling water for cooling towers. After filtering the discharged water from the cooling tower (1) through the filter (30), it is treated by a pretreatment membrane device (33) such as MF membrane, and then treated by an RO membrane device (reverse osmosis membrane device) (38), Return the RO treated water to the cooling tower (1). The concentrated water, backwash drainage, and washing drainage of the pretreatment membrane device (33) and the RO membrane device (38) are sent back to the water supply piping (11) leading to the side filter (14).

Description

Water treatment method and device

The present invention relates to a method and device for reusing backwashing drainage, washing drainage, circulating water, concentrated water, etc. of a membrane separation device, and particularly to a water treatment method and device suitable for recycling cooling tower discharge water.

In the cooling water system, the boiler water system, etc., the heat transfer surface and the piping that are in contact with water may cause scale obstacles. Especially in the case of high concentration operation by reducing the discharge (blow) of cooling water to the outside of the system based on the standpoint of saving resources and energy, the dissolved salt will be concentrated, making the heat transfer surface easy to corrode and become insoluble Of salt and form scale. If scale adheres to the wall surface of the device, it will cause a decrease in thermal efficiency, blockage of piping, etc., which will cause major obstacles to the operation of the boiler and heat exchanger. In recent years, for the purpose of saving water and energy, the tendency to use water as effectively as possible has become significant. However, in the case of higher concentration operation, there is a limit to suppressing the precipitation of scale.

After passing the cooling water discharge water through the MF membrane or the UF membrane to remove the suspended matter in the discharged water, the RO membrane treatment is performed to remove ions, organic matter, etc., and return to the cooling tower technology is known (Patent Document 1,2).

[Patent Document 1] JP 2002-18437

[Patent Document 2] JP 2003-1255

When using MF membranes, UF membranes, and RO membranes for recycling, the membranes must be cleaned regularly or irregularly. In Patent Documents 1, 2, the backwash drain after washing is discharged to the outside of the system, and therefore the water recovery rate is lowered accordingly. In addition, when backwashing water, circulating water, concentrated water, washing drainage, etc. are discharged out of the system, drainage treatment may be necessary depending on the water quality.

The object of the present invention is to provide a method and device for treating backwash drainage, washing drainage, concentrated water, and circulating water of a membrane separation device and using it as cooling water for a cooling tower.

The water treatment method of the present invention is characterized in that a part or all of the discharge water of the membrane separation device constituted by at least one of backwash drainage, washing drainage, circulating water, and concentrated water of the membrane separation device is supplied to the cooling tower.

The water treatment device of the present invention is a water treatment device with a membrane separation device, and is characterized in that it is equipped with a supplier that is a combination of backwash drainage, washing drainage, circulating water, and concentrated water of the membrane separation device Part or all of the discharged water from the membrane separation device constituted by at least one is supplied to the cooling tower.

Preferably, the membrane separation device includes a pretreatment membrane device and a reverse osmosis membrane device, and the pretreatment device has at least a precision filtration membrane or an ultrafiltration membrane.

In one aspect of the present invention, the cooling tower includes a filtering device for circulating and filtering at least a part of the cooling water.

In the present invention, it is preferable that the discharged water of the aforementioned membrane separation device is filtered and supplied to the cooling tower. In this case, it is preferable that the filtration treatment is performed using a filtration device installed in the aforementioned cooling tower and used for circulating filtration of at least a part of the cooling water.

In one aspect of the present invention, a cooling tower is connected to a water supply pipe, and the water supply pipe is for supplying water to a filtering device for circulating and filtering at least a part of the cooling water from the cooling tower; and supplying the aforementioned membrane separation device discharge water to The water supply pipe or the vicinity of the water supply pipe connection part in the cooling tower.

In one aspect of the present invention, the discharged water from the membrane separation device is temporarily stored in a water tank and then supplied to the cooling tower.

In one aspect of the present invention, the discharge water of the cooling tower is supplied to the aforementioned membrane separation device.

In the water treatment method and device of the present invention, at least one of the backwash drainage, washing drainage, and concentrated water of the membrane separation device installed in various water treatment pipelines is supplied to the cooling tower to be used as cooling water, which can improve water Recovery rate. In particular, the cooling tower discharge water is fed through the membrane separation device It can be reused as cooling water after treatment, and at least one of the backwash drainage, washing drainage, circulating water, and concentrated water of the membrane separation device is used as cooling water, thereby increasing the water recovery rate of the cooling tower .

In one aspect of the present invention, after the discharged water is filtered through an MF membrane or a UF membrane, the RO membrane is used for deionization and organic matter removal, and the RO treated water is used as cooling water for the cooling tower. In addition, the backwash wastewater, circulating water, concentrated water, and RO membrane cleaning wastewater of the MF membrane or UF membrane are filtered and supplied to the cooling tower. This filtering process is performed by a filtering device installed in the cooling tower system to circulate at least a part of the cooling water, thereby making it possible to utilize existing equipment.

1‧‧‧Cooling Tower

4‧‧‧Heat exchanger

14‧‧‧Side filter

25‧‧‧Water treatment device

30‧‧‧Filter

33‧‧‧Pretreatment membrane device

38‧‧‧RO membrane device

Figure 1 is a flowchart showing the water treatment method and device of the embodiment.

Figure 2 is a flowchart showing the water treatment method and device of the embodiment.

Hereinafter, the embodiment will be described with reference to the drawings. Figure 1 shows an example of a cooling tower system using the method and device of the present invention.

The cooling tower 1 of this cooling tower system is configured such that the cooling water sprinkled from the sprinkler pipe 1a is cooled by contact with the air introduced from the louver 1c while flowing through the filler layer 1b, and then is stored in a pit ) In 1d (the water tank at the lower part of the cooling tower), the air containing steam is driven by a fan 1e is discharged into the atmosphere. The cold water in the water storage tank 1d of the cooling tower 1 is supplied to the heat exchanger 4 through the pump 2 and the pipe 3, and the return water from the heat exchanger 4 is sent back to the sprinkler 1a of the cooling tower 1 through the pipe 5.

A part of the water in the water storage tank 1d is supplied to the side filter 14 through the water-feeding side circulation pipe 11, the pump 12, and the valve 13. After filtration, it is sent back to the water storage tank 1d through the return side circulation pipes 15, 17 and valve 16. The side filter 14 is constituted by a filtering device, etc., using a floating filter, a sand filter, and the like. The air for backwash can be introduced into the pipe 15 through the air pump 19 and the valve 18. On the primary side of the side filter 14, a discharge pipe 14 for backwashing drainage with a valve 14a is connected.

When the side filter 14 performs the filtering process, the valves 13, 16 are opened, and the valves 14a, 18 are closed. When the side filter 14 is subjected to air backwashing, the valves 13, 16 are closed, the valves 14a, 18 are opened, the air from the air pump 19 is supplied to the side filter 14, and the backwashing water is discharged through the pipe 14b.

The cooling tower 1 is supplied with make-up water from the make-up water line 8 in such a way that the water level in the water storage tank 1d is finally set to a predetermined water level by the float valve device 7 (or a water supply valve device with a water level sensor).

A conductivity meter for measuring the conductivity of the cooling water in the water storage tank 1d is installed. When the conductivity detected by the conductivity meter becomes more than a predetermined value, the drain valve 21 is opened to increase the salt concentration. Part of the cooling water is discharged through the pipe 22 in the form of drain water. In this embodiment, the drain water is sent to the water treatment device 25 through the pump 23 and the pipe 24. If gravity can be used for water delivery, the pump 23 is unnecessary. The structure of the water treatment device 25 will be described in detail later.

In the cooling tower 1, in order to remove the heat of the process, part of the circulating water evaporates, and the make-up water becomes concentrated. Concentrated cooling water, due to the occurrence of scale and slime, will affect the heat exchange efficiency of the heat exchanger, etc., so it is necessary to add a dispersing agent and a slime removing agent to prevent them from occurring. Medicines.

As the dispersant, it is possible to use: inorganic polyphosphates such as sodium hexametaphosphate and sodium tripolyphosphate; phosphonic acids such as hydroxyethylidene diphosphonic acid and butane tricarboxylic acid phosphonic acid; maleic acid, acrylic acid, Iconic acid and other carboxyl-containing materials; it can be combined with vinylsulfonic acid, allylsulfonic acid, 2-methacrylamide-2-methylpropanesulfonic acid, and other vinyl sulfonic acid groups as necessary It is also possible to use materials other than the materials listed here for copolymers and the like formed by combining nonionic vinyl monomers such as monomers and acrylamide. As the third component of the dispersant, other components are used, and terpolymers can also be used. For example, as the third component, N-tertiary butyl acrylamide or the like is used.

As a dispersant, among them, the best are: HAPS (3-allyloxy-2-hydroxy-1-propanesulfonic acid) and copolymer of acrylic acid and/or methacrylic acid, AMPS (2-propenolamine-2 -Methylpropanesulfonic acid) and acrylic acid and/or methacrylic acid copolymer.

The molecular weight of the dispersant is preferably 1,000 or more and 30,000 or less. When the molecular weight is less than 1,000, a sufficient dispersion effect cannot be obtained; when it exceeds 30,000, it may be removed by the pretreatment film. One of the features of the present invention is that the cooling water chemicals contained in the cooling tower discharge water can be reused as chemicals for reverse osmosis membranes, so the aforementioned dispersion can be And the sludge removal agent mentioned later can be effectively used.

As a sludge removal agent, you can use: sodium hypochlorite (NaClO) and other hypochlorite; chlorine, chloramine, chlorinated isocyanurate and other chlorine agents; monochloramine sulfonic acid and other chlorine and sulfonic acid , A combined chlorine agent (stabilizing chlorine agent) obtained by the reaction of a compound with a sulfamic acid group; bromine agents such as dibromohydantoin; bromine and sulfamic acid such as monobutyl cavity sulfonic acid, Bound bromine agent (stabilizing bromine agent) obtained by reacting acid-based compounds; organic agents such as DBNPA (dibromonitrilopropionamide) and MIT (methyl isothiazolinone).

In the combined chlorine agent and the combined bromine agent, the nitrogen compounds bound by free chlorine and free bromine include ammonia or its compounds, melamine, urea, acetamide, sulfonamide, chloramine, sulfonic acid, toluene Sulfonamide, succinimide, phthalimide, isocyanuric acid, N-chlorotoluene sulfonamide, uric acid, saccharin, or salts thereof. The combined chlorine agent used in the present invention is composed of these nitrogen compounds combined with free chlorine. As such a combined chlorine agent, in addition to a combined chlorine agent composed of chloramine, a chlorine-based oxidizing agent and a sulfamic acid compound, there can also be mentioned: chloramine-T (N-chloro-4-methylbenzenesulfonamide Sodium salt), chloramine-B (sodium salt of N-chloro-benzenesulfonamide), sodium salt of N-chloro-p-nitrobenzenesulfonamide, trichloromelamine, mono- or di-chloromelamine sodium Salt or potassium salt, trichloro-isocyanate, sodium or potassium mono- or di-chloroisocyanate, sodium or potassium mono- or di-chlorosulfonic acid, monochlorohydantoin or 1, 3-Dichlorohydantoin, 5,5-alkyl derivatives such as 5,5-dimethylhydantoin, etc. The same applies to the combined bromine agent, except that the chlorine part is changed to bromine.

As the drug that changes the pH, for example, hydrochloric acid, sulfuric acid, nitric acid, sodium hypochlorite, sodium hydroxide, citric acid, oxalic acid, etc. can be selected. The material is not particularly limited.

More than one kind of medicines can be used. It is preferable to measure the concentration of the sludge removing agent in the cooling tower to control the injection amount. Preferably, the pH of the cooling tower is measured and controlled within a certain range.

The water treatment device 25 for treating discharged water will be described next.

The discharged water from the cooling tower is removed by a filter 30 such as a strainer, and then coarse suspended matter and foreign matter are removed. After adding a slime removing agent and a pH adjuster (such as sulfuric acid) to the water tank 31, it is used The pretreatment membrane device 33 performs turbidity removal treatment. The water that has not permeated the membrane 33m is introduced into the aforementioned water-feeding-side circulation pipe 11 through the pipe 34. The impermeable water is preferably returned directly to the water storage tank 1d (the water tank at the lower part of the cooling tower), or may be returned to the water tank 31. The water that has passed through the membrane 33m is supplied to the RO membrane device 38 via the valve 35, the water tank 36, and the pipe 37, and is subjected to deionization treatment. The treated water after the deionization treatment is returned to the cooling tower 1 via the pipe 39. The RO treated water can be sent back to the make-up water pipeline 8, or back to the circulating pipes 11, 15, 17 and so on leading to the side filter 10.

The concentrated water of the RO membrane device 38 is preferably discharged through the valve 43 and the pipe 45.

For the RO membrane device 38, washing and washing are performed intermittently, or washing with chemicals using alkali or acid is performed. The washing drainage at this time is also recovered through the pipe 42.

The filter 30 such as the above-mentioned coarse filter can be operated even if it is not installed, but it may cause damage to the pretreatment membrane device 33, so it is better to install it. It is advisable to use an automatic coarse filter that can automatically clean. The shape of the strainer is not particularly limited, and any shape such as Y-shaped and barrel-shaped can be adopted. The pore size of the coarse filter is preferably 100 to 500 μm. When the thickness is less than 100 μm, the clogging of the strainer tends to become serious. When it exceeds 500 μm, the possibility of damage to the pre-treatment film caused by coarse suspended matter and foreign matter after passing through the strainer tends to increase. It is also possible to replace the strainer with a wound filter, a pleated filter, etc. However, considering the frequency of replacement and cleanability, the strainer is better.

The pre-treatment membrane device 33 is used to remove the suspended matter and colloidal components in the water that cause the membrane fouling of the RO membrane device 38. MF membranes and UF membranes can be used. The membrane type is not particularly limited, and hollow fiber type, spiral type and other membrane filtration devices can be used. In addition, the filtering method is not limited, and any method of internal pressure filtering, external pressure filtering, cross-flow filtering, and total filtering can be used. The molecular weight cut-off of MF membrane and UF membrane is preferably 30,000 or more. If it does not reach 30,000, the dispersant may be removed. The upper limit of the molecular weight cut-off is not particularly limited, but when it is 1,000,000 or less, the high molecular polysaccharides that cause clogging of the RO membrane in the cooling water can be removed, so it is preferable. At the beginning of the operation of the pretreatment membrane device, the exhaust step after backwashing, etc., the water injection step and the circulation step of filling the casing with water are performed. At this time, the discharged water (circulating water) is also sent through the pipe 34 Return the water side circulation piping 11, or directly return it to the water storage tank 1d.

Mud removal agent, pH that can be used in the pretreatment membrane device 33 The adjusting agent can be of the same type as that used in the cooling tower. By using the same type, it can be effectively used in the cooling tower. When a combined chlorine agent and a combined bromine agent are used in the cooling tower, by using free chlorine and free bromine in the pretreatment membrane device 33, it can react with the combined chlorine agent (stabilizer) existing in the cooling tower, and Reduce the amount of free chlorine that must be added in the cooling tower.

The pretreatment membrane device 33 performs regular or irregular backwashing treatment, and discharges the suspended matter accumulated in the membrane 33m to the outside of the system. The backwash frequency is generally about once every 10 to 60 minutes, but it is not limited to this. By adding hypochlorous acid and its salt, or hypobromous acid and its salt, organochlorine bactericide, combined chlorine bactericide, combined bromine bactericide and other bactericides, slime control agents, or It is to change the pH to implement backwashing, which can improve the recovery effect.

In order to perform this backwashing, the membrane permeated water in the aforementioned water tank 36 is used in this embodiment. That is, during the backwashing of the membrane 33m, the valves 32 and 35 are closed, the valves 52 and 54 are opened, the pump 50 is activated, and the water in the water tank 36 is supplied to the secondary side of the membrane 33m via the pipes 51 and 53. At this time, a chemical such as NaClO can be added to the pipe 53 to perform chemical washing. The backwash drainage is supplied from the pipe 34 to the aforementioned pipe 11 (the suction side of the pump 12). In addition, instead of water backwashing, air backwashing can be performed. In this case as well, the backwash drainage is collected via the pipe 34. It is possible to perform immersion cleaning by adding a chemical such as NaClO to the primary side of the membrane while backwashing. The washing drainage at this time is also sent back to the water-feeding-side circulation pipe 11 via the pipe 34, or directly sent back to the water storage tank 1d.

The type of the RO membrane 38m of the RO membrane device 38 is not particularly limited, and is appropriately determined according to the quality of the circulating cooling water to be treated (the quality of the raw water supplied to the circulating cooling water system, and the concentration ratio of the circulating cooling water system). The desalination rate of the RO membrane 38m is preferably 80% or more, particularly preferably 85% or more. When the salt rejection rate is lower than this value, the deionization efficiency is poor, and it is difficult to obtain treated water (permeate water) of good water quality. Although the RO film 38m can be made of any material such as polyamide composite film and cellulose acetate film, it is preferable to use polyamide composite film from the viewpoint of removal rate. The shape of the RO membrane 38m is not particularly limited, and both hollow fiber type and spiral type can be used.

In the water supply of the RO membrane device 38, it is preferable to add a slime removing agent. In the case of polyamide composite film, as a slime removing agent, it is advisable to use a combined chlorine agent, a combined bromine agent, and an organic agent. The aforementioned chlorine and bromine agents may cause film deterioration, which is not ideal. This step can be omitted by sharing the cooling water medicine with the dispersant and the slime removing agent. Although the pH adjuster is added to the water tank 31 in this embodiment, depending on the type of dispersant, the polymer may cause clogging of the pretreatment membrane. Therefore, it is preferable not to in the front stage of the pretreatment membrane device but during the RO water supply Add a pH adjuster (for example, sulfuric acid).

As mentioned above, by returning the backwashing drainage and concentrated water to the pipe 11, the suspension components in the backwashing drainage and concentrated water are removed by the side filter 14 to prevent the concentration of the suspension in the cooling water system. , Concentration rises. When the side filter 14 is not provided, a filter device may be additionally provided in the return line.

The total water volume per hour of the backwash drainage, circulating water, washing drainage, and concentrated water sent back to the cooling tower, and the cooling water treatment system The ratio of retained water is preferably 1:100 or more. That is, when the backwash drainage and concentrated water are returned, the amount of water retained in the cooling tower is preferably 100 times or more of the returned amount. If there is more than 100 times the amount of water, the increase in concentration can be suppressed at the time of return to a level without any problems. In the case of returning backwash drain and concentrated water, in order to prevent the water quality of the cooling water from fluctuating, a pH measuring device, an adjusting device, or a chlorine measuring device and adjusting device can be installed.

In this embodiment, a water tank is installed in a water treatment device that treats discharged water, but it may not be installed. In the present invention, as shown in FIG. 2, in order to level the inflow load, the backwash drainage, concentrated water, circulating water, and washing drainage can be temporarily stored in the water tank 55, and then sent back quantitatively through the pump 56 and the piping 57 Piping 11, cooling tower.

The water quality of backwash drainage, circulating water, washing drainage, and concentrated water can be detected by the detector, and it will not be recovered if the concentration is above the specified concentration.

As described above, in this embodiment, the backwash drainage, circulating water, concentrated water, and chemical washing wastewater from the pretreatment membrane device 33 are recovered. The flushing drainage, chemical washing wastewater, and circulating water from the RO membrane device 38 are recovered.

In the above description, although the pretreatment membrane device 33 and the RO membrane device 38 are used, other membranes and filtration means can also be used, and all of the concentrated water of the washing means is the object of recovery. Washing wastewater can be supplied to the cooling tower via a pipeline branched from the drainage pipeline, or directly to the cooling tower side via a supply pipeline. Concentrated water is the same, can be from the circulation line If it is divided and supplied to the cooling tower, all concentrated water can also be supplied to the cooling tower.

Although in the above embodiment, concentrated water, backwash drainage, etc. are sent back to the circulating water supply piping 11 to the side filter 14, it can also be sent back to other parts and can be directly sent back to the water storage tank 1d, such as the water storage tank 1d. The piping 11 is near the connection part. By arranging the return destination at the connection part of the pipe 11 of the water storage tank 1d, that is, near the suction port, when the water containing suspended matter enters the water storage tank, it can be sent to the side filter 14 through the pipe 11 immediately. deal with. Depending on the water quality, it may be returned via the pipe 3.

In the above embodiment, the water treatment device for recovery is equipped with a filter 30, a pre-treatment membrane device 33 such as a UF membrane device, and an RO membrane device 38. Filters, UF membranes, MF membranes, and nanofiltration membranes may also be used. And one of RO membranes or any combination of two or more.

In the present invention, the amount of suspended matter in the backwash drainage, circulating water, washing drainage, and concentrated water is preferably less than 1000 degrees (turbidity). The turbidity of the backwash drainage can reach up to about 300 degrees instantaneously, and can be reduced to less than 1 degree by filtering. The pH of backwash drainage, circulating concentrated water, and washing drainage is preferably 2-12.

In the above-mentioned embodiment, the cooling tower discharge water is treated by a membrane separation device and recovered. Even if it is the cleaning drainage of membrane treatment equipment such as water and drainage installed in factories, factories, etc., as long as it is suitable as a cooling tower Any water supplier can be treated by the water treatment device 25 and used as cooling water for the cooling tower 1. However, if it is cooling tower discharge water, the suspended matter in the washing wastewater is the same composition. It has the advantage of being easier to use.

Although it is sent to the water treatment device via the discharge pipe 22 in the above embodiment, the pressure of the pump 2 can also be used to convey from the position of the transfer pipe 3 and the return pipe 5 leading to the heat exchanger.

[Example] [Example 1]

In a cooling tower that uses industrial water from Chiba City, Japan as raw water with a circulating water volume of 5,000m ³ /h and a retained water volume of 1,000m ³ /h, the cooling tower discharge water is recovered at a concentration rate of 3.5 times.

In the dispersant treatment of cooling water, a copolymer of acrylic acid and AMPS (molar ratio 70:30) and a dispersant with an average weight and molecular weight of 10,000 are used. The dispersant in the initial system maintains a concentration of 3mg/L. As a slime removing agent, a mixture of alkali, sulfamic acid and hypochlorous acid described in WO11/125762 is used. Add sludge removal agent so that the initial combined chlorine concentration in the system becomes 1.0 mg/L. In the cooling tower, a light filter manufactured by Kurita Kogyo is installed as a side filter system, and the filtration is performed at 150m ³ /h to remove the predetermined amount of suspended matter in the system.

The flow of the recovery treatment is to use a strainer, an MF device, and an RO membrane device like the water treatment device 25 in FIG. 1 to recover the entire amount of discharged water of 20 m ³ /h. The strainer has a mesh size of 400 μm, and the MF membrane uses Pyuria GS (hydrophilized PVDF, pore size 0.02 μm, external pressure type) manufactured by Kuraray. The RO membrane used KROA-2032-SN (polyamide ultra low pressure RO membrane) manufactured by Kurita Kogyo. The backwash frequency of the MF device is every 30 minutes, and sodium hypochlorite is added at a concentration of 100mg/L during the backwash. The backwash water of the MF device is sent back to the cooling tower. By returning the backwash water of the MF device, the water recovery rate becomes 100%. The amount of backwash water per one time is 1m ³ .

The pH of the discharged water is 8.5 to 8.7, and sulfuric acid is added in front of the RO membrane device to make the pH 5.5. Every 3 months, as the water volume of the RO membrane device decreases, the RO membrane device is cleaned with a sodium hydroxide solution adjusted to pH 11, and the cleaned liquid is sent back to the cooling tower. The water volume of the washing liquid is 4m ³ . The water recovery rate of RO membrane device is 70~75%. By recovering the backwash water and washing wastewater, the washing treatment does not affect the water recovery rate, and the total water recovery rate becomes 70~75%.

The suspended matter during backwashing is removed by the side filter, so that the turbidity is stably maintained in the range of 5 to 7 degrees. The sodium hypochlorite added during backwashing is consumed in the cooling tower, and the chlorine concentration is 0.1~0.2mg/L. The combined chlorine concentration is 0.8~1.0mg/L.

[Comparative Example 1]

The backwash wastewater of the MF device and the washing wastewater of the RO membrane device were discharged out of the system without being sent back to the cooling tower, except that the same treatment as in Example 1 was performed. The water recovery rate of MF membrane is 90%, and that of RO membrane device is 68~73%. Therefore, the total water recovery rate becomes 61~65%.

In order to discharge the backwash drainage and washing drainage to the outside of the system, reduction treatment and pH neutralization treatment are required.

[Example 2]

Except that the side filter 14 was not provided in the cooling tower system, the same treatment as in Example 1 was performed in the same cooling tower system as in Example 1. As a result, the amount of suspended matter in the system gradually increased and became 50 degrees (turbidity) or higher after 10 days, and the treatment was stopped.

[Example 3]

The same treatment as in Example 1 was performed except that the holding water amount of the cooling tower was 100 m ³ . The effect of returning the backwash water of the MF device is not visible. However, the pH will change when the clean water discharged from the RO membrane device is returned, and CaCO ₃ scale will precipitate in the system, so the return is stopped.

[Inspection]

As explained above, according to the circulating cooling water treatment method and treatment device of the present invention, the water recovery rate can be improved by returning the backwashing drainage and washing drainage in the recovery process to the cooling tower without additional implementation. It can perform stable treatment with excellent economic efficiency and high recovery rate.

Although the present invention is described in detail with a specific aspect, it is well known to those skilled in the art that various changes can be made without departing from the scope of the present invention.

This application is based on Japanese Patent Application 2015-072960 filed on March 31, 2015, and the entirety of it is used in the present invention by reference.

1‧‧‧Cooling Tower

1a‧‧‧Water Sprinkler

1b‧‧‧Filling material layer

1c‧‧‧Blinds

1d‧‧‧Water storage tank

1e‧‧‧Fan

2‧‧‧Pump

3‧‧‧Piping

4‧‧‧Heat exchanger

5‧‧‧Piping

7‧‧‧Float valve device

8‧‧‧Supply water pipeline

11‧‧‧Circulating piping on the water supply side

12‧‧‧Pump

13‧‧‧Valve

14‧‧‧Side filter

14a‧‧‧valve

14b‧‧‧Piping

15‧‧‧Return side circulation piping

16‧‧‧Valve

17‧‧‧Return side circulation piping

18‧‧‧valve

19‧‧‧Air pump

21‧‧‧Drain valve

22‧‧‧Piping

23‧‧‧Pump

24‧‧‧Piping

25‧‧‧Water treatment device

30‧‧‧Filter

31‧‧‧Sink

32‧‧‧valve

33‧‧‧Pretreatment membrane device

33m‧‧‧membrane

34‧‧‧Piping

35‧‧‧valve

36‧‧‧Sink

37‧‧‧Piping

38‧‧‧RO membrane device

38m‧‧‧RO membrane

39‧‧‧Piping

41‧‧‧Valve

42‧‧‧Piping

43‧‧‧valve

44‧‧‧Piping

45‧‧‧Piping

50‧‧‧Pump

51‧‧‧Piping

52‧‧‧Valve

53‧‧‧Piping

54‧‧‧Valve

Claims (6)

A water treatment method is to supply the discharged water of a cooling tower to a membrane separation device and supply the permeated water of the membrane separation device to the cooling tower, and supply part or all of the discharged water from the membrane separation device of the membrane separation device to The cooling tower is characterized in that the membrane separation device includes a pretreatment membrane device and a reverse osmosis membrane device, the pretreatment membrane device has at least a precision filtration membrane or an ultrafiltration membrane, and the membrane separation device discharges water from the front Treat at least one of the backwash drainage, circulating water, concentrated water, and pharmaceutical washing wastewater of the membrane device. The circulating water is used to remove the shell at the start of the operation of the pretreatment membrane device or the exhaust step after the backwash The water discharged during the water injection step and the circulation step where the body is filled with water, the water discharged from the membrane separation device is directly supplied to the cooling tower from the membrane separation device. The water treatment method described in claim 1, wherein the cooling tower is provided with a filtering device for circulating and filtering at least a part of the cooling water. The water treatment method described in claim 1, wherein a water supply pipe is connected to the cooling tower, and the water supply pipe sends water to a filter device for circulating and filtering at least a part of the cooling water from the cooling tower; The discharge water from the membrane separation device is supplied to the vicinity of the water supply pipe connection part in the cooling tower. A water treatment device with a membrane separation device and a cooling tower A mechanism for supplying discharged water to the membrane separation device, and a mechanism for supplying part or all of the discharged water from the membrane separation device of the membrane separation device to the cooling tower, characterized in that the membrane separation device includes a pretreatment membrane device And a reverse osmosis membrane device, the pre-treatment membrane device has at least a precision filtration membrane or an ultra-filtration membrane, and the membrane separation device discharges water from the backwash drainage, circulating water, concentrated water and pharmaceutical washing wastewater from the pre-treatment membrane device At least one of, the circulating water is the water discharged during the water injection step of filling the casing with water at the start of the operation of the pretreatment membrane device or the exhaust step after backwashing, and the The water discharged from the membrane separation device is directly supplied to the cooling tower from the membrane separation device. The water treatment device described in claim 4, wherein the cooling tower is equipped with a filtering device for circulating and filtering at least a part of the cooling water. The water treatment device described in claim 4, wherein a water supply pipe is connected to the cooling tower, and the water supply pipe sends water to a filtering device for circulating and filtering at least a part of the cooling water from the cooling tower; The discharge water from the membrane separation device is supplied to the vicinity of the water supply pipe connection part in the cooling tower.

Images