JP2022077113A - Water treatment apparatus and washing method of water treatment apparatus - Google Patents

Abstract

To provide a water treatment apparatus capable of performing uniform washing treatment by the chemical solution of a membrane separation device.SOLUTION: A sewage water treatment apparatus 1 as a water treatment apparatus comprises: a storage tank 2 storing water to be treated such as sewage containing solid matter and the like; a membrane separation device 3 being immersed in the storage tank 2 and separating and removing the solid matter; and a washing chemical solution tank 6 storing a chemical solution 5 washing the membrane separation device 3. The membrane separation device 3 has a hollow fiber membrane 3a having a hollow part surrounded with fibers provided with fine pores, a water collection part 3b connected to one end of the hollow fiber membrane 3a and a water collection part 3c connected to the other end of the hollow fiber membrane 3a. The washing chemical solution tank 6 is connected to the water collection part 3b via a pump P3 and connected to the water collection part 3c via a pump P4. The circulation flow of the chemical solution 5 successively flowing such parts as the washing chemical solution tank 6, the water collection part 3c, the hollow part of the hollow fiber membrane 3a, the water collection part 3b and the washing chemical solution tank 6 is formed when the pumps P3, P4 are driven.SELECTED DRAWING: Figure 1

Description

The present invention relates to a water treatment apparatus and a method for cleaning the water treatment apparatus.

Conventionally, a storage tank that stores water to be treated such as sewage containing solid matter, a membrane separation device that is immersed in the storage tank and separates and removes solid matter from the water to be treated, and aeration that supplies air in contact with the water to be treated. A sewage treatment device including the device is known (for example, Patent Document 1). The membrane separation device of Patent Document 1 includes a long hollow fiber membrane having a hollow portion surrounded by fibers in which micropores are formed, a first water collecting portion connected to one end of the hollow fiber membrane, and a first water collecting portion. A second water collecting portion connected to the other end of the hollow fiber membrane is provided, and the solid matter contained in the water to be treated is separated and removed by the hollow fiber membrane, and the solid matter is separated and removed (hereinafter referred to as “water to be treated”). The "membrane permeated water") sequentially passes through the micropores and the hollow portion of the hollow fiber membrane, and is collected in the first water collecting portion or the second collecting portion. The membrane permeated water collected in the first water collecting part and the second water collecting part is discharged to the outside of the storage tank.

When the membrane separation device separates and removes solid matter from the water to be treated, the aeration device supplies air to the water to be treated, and the air is exposed to the membrane separation device. As a result, the solid matter does not adhere to the surface of the hollow fiber membrane, so that the filtration function of the hollow fiber membrane that separates and removes the solid matter from the water to be treated does not immediately deteriorate. On the other hand, if the membrane separation device is continuously used, fouling substances such as minute solids are accumulated in the fibers of the hollow fiber membrane, and the filtration function of the hollow fiber membrane is gradually deteriorated. In order to restore the filtering function of the hollow fiber membrane deteriorated by the fouling substance, chemical cleaning of the membrane separation device is known (see, for example, Patent Document 2). The chemical cleaning of the membrane separation device of Patent Document 2 is performed by sequentially passing the chemical liquid through the first water collecting portion, the hollow portion and the micropores of the hollow fiber membrane, and permeating the outside of the hollow fiber membrane.

JP-A-2019-205987 Japanese Unexamined Patent Publication No. 2019-188276

However, since a large number of micropores in the hollow fiber membrane are formed on the entire surface of the fibers constituting the hollow fiber membrane, even if the chemical solution is introduced into the hollow portion from the first water collecting portion or the second water collecting portion, the chemical liquid is formed. Most of the water is discharged to the outside of the hollow fiber membrane from the micropores around the first water collecting part or the second water collecting part. Therefore, for example, it is difficult for the chemical solution to reach the middle of the first water collecting portion and the second water collecting portion of the hollow fiber membrane, and cleaning spots due to the chemical solution of the hollow fiber membrane may occur, and the chemical solution of the hollow fiber membrane may occur. The cleaning spots caused by the hollow fiber membranes were remarkably generated when the length of the hollow fiber membrane in the longitudinal direction was, for example, 3 m or more.

That is, there is a problem that a uniform cleaning treatment with a chemical solution of the membrane separation device cannot be performed.

An object of the present invention is to provide a water treatment device and a method for cleaning the water treatment device, which can perform a uniform cleaning treatment with a chemical solution of the membrane separation device.

In order to achieve the above object, the water treatment apparatus of the present invention is a water treatment apparatus for treating water to be treated containing solid matter, and is a separation / removal means for separating and removing the solid matter from the water to be treated, and the separation. A first water collecting means having one end of the removing means and collecting the permeated water permeating the separation and removing means, and a permeated water having the other end of the separating and removing means and permeating the separation and removing means. Between the second water collecting means for collecting water, the cleaning means used for cleaning the separation / removal means, the storage means for storing the cleaning means, and the storage means and the first water collecting means. A first water feeding means intervening and a second water feeding means intervening between the storage means and the second water collecting means are provided, and the cleaning means includes the storage means and the second water sending means. , The second water collecting means, the separating and removing means, the first water collecting means, and the first water feeding means are sequentially circulated to form a circulating flow.

In order to achieve the above object, the cleaning method of the water treatment apparatus of the present invention comprises a separation / removal means for separating and removing the solid matter from the water to be treated in the water treatment apparatus for treating the water to be treated containing the solid matter. A first water collecting means for collecting the permeated water that has passed through the separation / removal means and the other end of the separation / removal means that has permeated the separation / removal means. A second water collecting means for collecting permeated water, a cleaning means used for cleaning the separation / removal means, a storage means for storing the cleaning means, the storage means, and the first water collecting means. In a method for cleaning a water treatment apparatus including a first water supply means interposed between the water treatment apparatus and a second water supply means interposed between the storage means and the second water collection means, the cleaning means is said to be said. The first infiltration step of infiltrating the second water collecting means from the storage means via the second water feeding means, and the cleaning means passing through the separation / removing means from the second water collecting means. A second infiltration step of infiltrating the first water collecting means and a return step in which the cleaning means returns from the first water collecting means to the storage means via the first water feeding means. It is characterized by having.

According to the present invention, it is possible to carry out a uniform cleaning treatment with a chemical solution of the membrane separation device.

It is a figure which shows schematically the sewage treatment apparatus which concerns on embodiment of this invention. It is a flowchart which shows the procedure of the cleaning process of the hollow fiber membrane performed by the chemical solution stored in the chemical solution tank for cleaning in FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a diagram schematically showing a sewage treatment device 1 according to an embodiment of the present invention.

The sewage treatment device 1 (water treatment device) of FIG. 1 is connected to a storage tank 2 and a storage tank 2 for storing treated water such as sewage containing solid matter, and for sending the treated water to the storage tank 2. Pump P1, a film separation device 3 that is immersed in the storage tank 2 and separates and removes solid matter from the water to be treated, an aeration device 4 that supplies air in contact with the water to be treated, and an aeration device 4 that supplies bubbles to the aeration device 4 (not shown). The film separation device 3 is connected to one end of a long hollow thread film 3a (separation / removal means) having a hollow portion surrounded by fibers in which micropores are formed, and a hollow thread film 3a. It has a water collecting portion 3b (first water collecting means) and a water collecting portion 3c (second water collecting means) connected to the other end of the hollow thread film 3a. The water collecting portions 3b and 3c are directly connected to one end and the other end of the plurality of hollow fiber membranes 3a, respectively, and both are connected to the pump P2 via the three-way cocks C1 and C2.

The fiber of the hollow fiber membrane 3a is, for example, a polytetrafluoroethylene resin (PTFE) or a polyvinylidene fluoride (PVDF) resin, and it is preferable to use a polytetrafluoroethylene resin having excellent chemical resistance and durability. In the present embodiment, the length of the hollow fiber membrane 3a in the longitudinal direction is, for example, 3 m or more and 5 m or less, which is conventionally considered to be prone to wash spots by the chemical solution 5 (cleaning means) of the hollow fiber membrane 3a. ..

When the pump P1 is driven, the water to be treated is sent to the storage tank 2, and the storage tank 2 is filled with the water to be treated. A blower (not shown) supplies air bubbles to the aeration device 4, and the aeration device 4 supplies air that comes into contact with the water to be treated. As a result, the air is exposed to the membrane separation device 3. When the pump P2 is driven, the solid matter contained in the water to be treated is separated and removed by the hollow fiber membrane 3a, and the water to be treated from which the solid matter is separated and removed (hereinafter referred to as "membrane permeated water") is the hollow fiber membrane. It sequentially passes through the micropores and hollow portions of 3a, collects water in the water collecting portions 3b and 3c, and is subsequently discharged to the outside of the storage tank 2. At this time, the three-way cocks C1 and C2 adjust the valves to shut off the pipes connected to the pumps P3 and P4, and only the pipes connecting the pump P2 with the water collecting part 3b and the water collecting part 3c are membrane permeated water. Can be set to pass.

Further, the sewage treatment device 1 includes a cleaning chemical solution tank 6 (storage means) for storing the chemical solution 5 for cleaning the membrane separation device 3, and the cleaning chemical solution tank 6 includes a pump P3 (first water supply means) and a cleaning chemical solution tank 6. It is connected to the water collecting portion 3b via the three-way cock C1 and is connected to the water collecting portion 3c via the pump P4 (second water feeding means) and the three-way cock C2. The cleaning chemical tank 6 contains a chemical solution 5, for example, an inorganic acid such as hydrochloric acid, sulfuric acid, nitric acid, sodium hydrogen sulfite, an organic acid such as citric acid and oxalic acid, sodium hypochlorite, sodium hydroxide, a surfactant and the like. At least one of the above is stored, and the type of the chemical solution 5 and the concentration of the chemical solution 5 are adjusted according to the material of the membrane separating device 3 and the properties of the water to be treated.

The pumps P3 and P4 can be driven when the pump P2 is stopped, and when the pumps P3 and P4 are driven, the three-way cocks C1 and C2 cut off the piping connected to the pump P2 by adjusting the valve. The chemical solution 5 can be set to pass only through the pipe connecting the pump P3 and the water collecting portion 3b and the pipe connecting the pump P4 and the water collecting portion 3c. When the pumps P3 and P4 are driven, the chemical solution 5 of the cleaning chemical solution tank 6 sequentially passes through the pump P4 and the three-way cock C2, penetrates into the water collecting portion 3c, and penetrates into the hollow portion of the hollow fiber membrane 3a. At this time, since the pump P3 is driven together with the pump P4, the water collecting portion 3b side in the hollow portion of the hollow fiber membrane 3a has a negative pressure as compared with the water collecting portion 3c side. Therefore, the chemical liquid 5 that has penetrated into the hollow portion of the hollow fiber membrane 3a from the water collecting portion 3c penetrates into the water collecting portion 3b and returns to the cleaning chemical liquid tank 6 via the three-way cock C1 and the pump P3 in sequence. That is, the chemical liquid 5 forms a circulating flow returning from the cleaning chemical liquid tank 6 to the cleaning chemical liquid tank 6 via the water collecting portion 3c, the hollow portion of the hollow fiber membrane 3a, and the water collecting portion 3b in that order.

By the way, when the water collecting portion 3b is connected to the cleaning chemical liquid tank 6 without the intervention of the pump P3, the pump P4 is driven and the chemical liquid 5 of the cleaning chemical liquid tank 6 passes through the pump P4 to collect water. It penetrates into 3c and penetrates into the hollow portion of the hollow fiber membrane 3a. However, there is no pump P3 for forming a mechanism for guiding the chemical solution 5 that has penetrated into the hollow portion of the hollow fiber membrane 3a to the water collecting portion 3b. Therefore, the pump P4 is driven, and the chemical solution 5 of the cleaning chemical solution tank 6 is pushed out from the water collecting portion 3c and enters the hollow portion of the hollow fiber membrane 3a. As a result, the load around the water collecting portion 3c of the hollow fiber membrane 3a increases, so that the chemical solution 5 that has penetrated from the water collecting portion 3c into the hollow portion of the hollow fiber membrane 3a is hollow from the micropores around the water collecting portion 3c. It is discharged to the outside of the thread membrane 3a. Therefore, when all of the pumps P3 and P4 are driven, the chemical solution 5 forms a circulating flow.

Further, in order for the chemical solution 5 to form a circulating flow, it is necessary not only to drive all of the pumps P3 and P4 but also to adjust the pump flow rate (water supply flow rate) of each of the pumps P3 and P4. When the pump flow rate of the pump P3 is smaller than the pump flow rate of the pump P4, the force for guiding the chemical liquid 5 that has entered the hollow portion of the hollow fiber membrane 3a from the water collecting portion 3c to the water collecting portion 3b is small, and the pump P3 has a small force. The chemical solution 5 that has penetrated into the hollow fiber membrane 3a from the water collecting portion 3c is discharged to the outside of the hollow fiber membrane 3a from the micropores around the water collecting portion 3c, and does not form a circulating flow, as in the case of no intervention. ..

On the other hand, when the pump flow rate of the pump P3 is excessive than the pump flow rate of the pump P4, the chemical liquid 5 that has entered the hollow portion of the hollow fiber membrane 3a from the water collecting portion 3c enters the water collecting portion 3b, so that the circulating flow is generated. Although it is formed, the membrane permeation water also penetrates into the hollow portion through the micropores of the hollow fiber membrane 3a and joins the circulating flow. As a result, the concentration of the chemical solution 5 forming the circulating flow decreases, so that the membrane separation device 3 is not sufficiently washed. Further, the concentration of the chemical solution 5 and the chemical solution 5 until the chemical solution 5 returns from the cleaning chemical solution tank 6 to the cleaning chemical solution tank 6 via the water collecting portion 3c, the hollow portion of the hollow fiber membrane 3a and the water collecting portion 3b in sequence. Since the amount changes, the chemical solution 5 cannot be controlled.

Therefore, the pump flow rate of the pump P3 is preferably equal to the pump flow rate of the pump P4, for example, the pump flow rate of the pump P4 is preferably 95% by volume or more and 105% by volume or less of the pump flow rate of the pump P3. In order to surely prevent the membrane permeated water from merging with the circulating flow, the pump flow rate of the pump P4 should be 100% by volume or more and 105% by volume or less of the pump flow rate of the pump P3. As a result, a circulating flow is formed in which the amount of liquid flowing from the cleaning chemical liquid tank 6 toward the pump P4 and the amount of liquid returning from the pump P3 to the cleaning chemical liquid tank 6 are equal to each other, and the hollow fiber membrane 3a is hollow. Since the chemical solution 5 having a constant concentration passes continuously through the portion, the chemical solution 5 used for cleaning the membrane separation device 3 can be easily managed, and the hollow portion of the hollow fiber membrane 3a can be easily controlled with the chemical solution having a constant concentration. It is possible to prevent the hollow fiber membrane 3a from being continuously passed through and causing cleaning spots due to the chemical solution 5 of the hollow fiber membrane 3a.

FIG. 2 is a flowchart showing a procedure for cleaning the hollow fiber membrane 3a executed by the chemical solution 5 stored in the chemical solution tank 6 for cleaning in FIG. 1.

In the cleaning process (cleaning method of the water treatment apparatus) of FIG. 2, first, the pumps P1 and P2 are stopped, and the pumps P3 and P4 are driven (S1). Here, the pump flow rate of the pump P4 is 95% by volume or more and 105% by volume or less of the pump flow rate of the pump P3. Next, the chemical solution 5 of the cleaning chemical solution tank 6 infiltrates into the water collecting portion 3c via the pump P4 and infiltrates into the hollow portion of the hollow fiber membrane 3a (S2, first infiltration step). The pump P3 guides the chemical liquid 5 that has penetrated into the hollow portion of the hollow fiber membrane 3a to the water collecting portion 3b, and the chemical liquid 5 that has penetrated into the hollow portion of the hollow fiber membrane 3a from the water collecting portion 3c penetrates into the water collecting portion 3b ( S3, second infiltration step), return to the cleaning chemical tank 6 (S4, return step). As a result, the chemical liquid 5 forms a circulating flow that sequentially passes through the cleaning chemical liquid tank 6, the water collecting portion 3c, the hollow portion of the hollow fiber membrane 3a, the water collecting portion 3b, and the cleaning chemical liquid tank 6. When the pumps P3 and P4 are driven and a certain period of time required for cleaning the membrane separation device 3, for example, 30 minutes has elapsed, the pumps P3 and P4 are stopped (S5), and this process is completed.

According to the cleaning treatment of the hollow fiber membrane 3a of FIG. 2, the circulating flow sequentially passes through the cleaning chemical liquid tank 6, the water collecting portion 3c, the hollow portion of the hollow fiber membrane 3a, the water collecting portion 3b, and the cleaning chemical liquid tank 6. It is formed (S2 to S4). Here, since the pump flow rate of the pump P4 is 95% by volume or more and 105% by volume or less of the pump flow rate of the pump P3, the amount of liquid flowing from the cleaning chemical liquid tank 6 toward the pump P4 and the liquid from the pump P3 in the circulating flow. The amount of liquid returned to the cleaning chemical tank 6 is about the same, and the chemical liquid 5 having a substantially constant concentration continuously passes through the hollow portion of the hollow fiber membrane 3a and also passes through the hollow portion of the hollow fiber membrane 3a. The chemical solution 5 is hardly discharged to the outside of the hollow fiber membrane 3a, and the membrane permeated water hardly joins the circulating flow. As a result, the chemical solution 5 used for cleaning the membrane separation device 3 can be easily managed, and the cleaning spots caused by the chemical solution 5 of the hollow fiber membrane 3a can be prevented. In the present invention, the chemical solution 5 that passes through the hollow portion of the hollow fiber membrane 3a is hardly discharged to the outside of the hollow fiber membrane 3a, but the fine fouling substance accumulated in the fibers of the hollow fiber membrane is such that the chemical solution 5 is the hollow fiber membrane 3a. It is sufficiently removed in the process of passing through the hollow fiber of the membrane.

Actually, the pump flow rate of the pump P4 is 2 L per 1 m ² of the membrane area of the hollow fiber membrane 3a, and the pump flow rate of the pump P3 is 2 L per 1 m ² of the membrane area of the hollow fiber membrane 3a. Was carried out for 30 minutes. Further, the pump flow rate of the pump P4 is 2 L per 1 m ² of the membrane area of the hollow fiber membrane 3a, and the pump flow rate of the pump P3 is 2.1 L per 1 m ² of the membrane area of the hollow fiber membrane 3a. Washing was performed for 30 minutes. Further, the pump flow rate of the pump P4 is 2 L per 1 m ² of the membrane area of the hollow fiber membrane 3a, and the pump flow rate of the pump P3 is 1.9 L per 1 m ² of the membrane area of the hollow fiber membrane 3a of 3 m. Washing was performed for 30 minutes. In each case, the amount of the chemical solution 5 and the concentration of the chemical solution 5 in the cleaning chemical solution tank 6 did not change, and no cleaning spots on the hollow fiber membrane 3a were confirmed after the cleaning was completed. As a result, it was found that the management of the chemical solution 5 became easier and that the hollow fiber membrane 3a was surely washed with the chemical solution 5.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments.

P3, P4 Pump 1 Sewage treatment device 3 Membrane separation device 3a Hollow fiber membrane 3b, 3c Water collecting part 5 Chemical solution 6 Cleaning chemical solution tank

Claims (5)

In a water treatment device that treats water to be treated containing solid matter
A separation / removal means for separating and removing the solid matter from the water to be treated,
A first water collecting means having one end of the separating and removing means and collecting the permeated water that has passed through the separating and removing means, and a first water collecting means.
A second water collecting means having the other end of the separating and removing means and collecting the permeated water that has passed through the separating and removing means, and a second water collecting means.
The cleaning means used for cleaning the separation / removal means and the cleaning means.
A storage means for storing the cleaning means and a storage means
A first water sending means interposed between the storage means and the first water collecting means, and
A second water feeding means interposed between the storage means and the second water collecting means is provided.
The cleaning means sequentially circulates a circulating flow that sequentially circulates the storage means, the second water supply means, the second water collection means, the separation / removal means, the first water collection means, and the first water supply means. A water treatment device characterized by forming. The water treatment apparatus according to claim 1, wherein the water supply flow rate of the second water supply means is 95% by volume or more and 105% by volume or less of the water supply flow rate of the first water supply means. The water treatment apparatus according to claim 1, wherein the water supply flow rate of the second water supply means is 100% by volume or more and 105% by volume or less of the water supply flow rate of the first water supply means. The water treatment apparatus according to any one of claims 1 to 3, wherein the separation / removal means has a long shape and has a length of 3 m or more and 5 m or less in the longitudinal direction thereof. In a water treatment apparatus for treating water to be treated containing solid matter, a separation / removal means for separating and removing the solid matter from the water to be treated and one end of the separation / removal means are provided and permeate through the separation / removal means. A first water collecting means for collecting water, a second water collecting means having the other end of the separation / removal means and collecting the permeated water that has passed through the separation / removal means, and the separation / removal means. A cleaning means used for cleaning, a storage means for storing the cleaning means, a first water supply means interposed between the storage means and the first water collecting means, the storage means, and the second water collecting means. In a method of cleaning a water treatment apparatus including a second water feeding means interposed between the water collecting means of the above.
A first infiltration step in which the cleaning means infiltrates the second water collecting means from the storage means via the second water feeding means.
A second infiltration step in which the cleaning means passes through the separation / removal means from the second water collecting means and infiltrates into the first water collecting means.
A method for cleaning a water treatment apparatus, wherein the cleaning means has a regression step of returning from the first water collecting means to the storage means via the first water feeding means.

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