JP2017094228A - Membrane module and water treatment system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a membrane module reducing an operation power in a water treatment system and suppressing the stack and stagnation of sludge on a tubular filter membrane.SOLUTION: A membrane module 1 comprises: a cylindrical casing 2 extended with an axis line A in a vertical direction; a plurality of tubular filter membranes 3 extending in an extending direction and having a single layer structure copolymerized with a hydrophilic monomer at the inside of the casing 2; and a plurality of connection members 34 connecting one ends of the tubular filter membranes 3 with each other and the other ends of the tubular filter membranes 3 with each other so that the plurality of tubular filter membranes 3 are connected in series.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a membrane module and a water treatment system for treating organic wastewater such as human waste.

When organic wastewater such as human waste is treated, it is the mainstream to use membrane separation such as MF (microfiltration) and UF (ultrafiltration) for solid-liquid separation.
As the membrane separation device, a plurality of membrane modules including a cylindrical casing and a plurality of tubular filtration membranes (hollow fiber membranes) accommodated in the casing are used, and raw water is circulated inside the tubular filtration membrane. An apparatus using a filtration method is known (for example, see Patent Document 1). The permeated water that has permeated through the tubular filtration membrane is sucked by a suction pump and stored in, for example, a storage tank and used as appropriate.

JP 2013-052338 A

By the way, in the conventional membrane separation apparatus, the arrangement method of the tubular filtration membranes accommodated in the casings of the plurality of membrane modules is a parallel system. That is, the water to be treated is introduced into the plurality of tubular filtration membranes via the header of the casing.
In the case of such a form, since the amount of the treated water to circulate increases, there is a problem that the driving power increases. In addition, when the water to be treated is not supplied uniformly to each tubular filtration membrane, there is a problem that the membrane surface flow rate becomes non-uniform, and sludge accumulates or stagnates on the tubular filtration membrane. Due to the accumulation and stagnation of sludge, there are problems such as (1) a tubular filtration membrane that is not effectively utilized, (2) a decrease in FLUX (outflow amount), and (3) a blockage of the tubular filtration membrane.

  An object of the present invention is to provide a membrane module and a water treatment system capable of reducing the driving power of the water treatment system and suppressing sludge accumulation or stagnation on the tubular filtration membrane. To do.

  According to the first aspect of the present invention, the membrane module includes a cylindrical casing whose axis extends in the vertical direction, and extends in the extending direction of the casing inside the casing. A plurality of tubular filtration membranes having a copolymerized single-layer structure, one end of the tubular filtration membrane, and the other end of the tubular filtration membrane are connected so that the plurality of tubular filtration membranes are connected in series. A plurality of connecting members.

  According to such a structure, compared with the system which connects a some tubular filtration membrane in parallel, the flow volume of the to-be-processed water which flows through a tubular filtration membrane can be decreased. Thereby, the driving power for circulating treated water can be made small. In addition, since the membrane surface flow rate becomes uniform, it is possible to suppress the accumulation or stagnation of sludge on the tubular filtration membrane.

  In the membrane module, provided at one end in the extending direction of the casing, and having a first partition wall having a plurality of through holes to which one ends of the plurality of tubular filtration membranes are connected, and at the other end in the extending direction of the casing And a second partition wall having a plurality of through holes to which the other ends of the plurality of tubular filtration membranes are connected, and the connecting member may connect the plurality of through holes.

  In the membrane module, the connection member may be a membrane connection plate including a membrane connection groove that connects the plurality of through holes.

  According to such a configuration, the assembly process of the membrane module can be simplified. Moreover, disassembly and cleaning can be facilitated by reducing the number of parts.

  According to the second aspect of the present invention, the membrane module has a cylindrical casing and a single layer structure in which the hydrophilic monomer is copolymerized in the casing in the extending direction of the casing. A plurality of tubular filtration membranes, a first partition wall provided at one end in the extending direction of the casing, and having a plurality of through holes to which one ends of the plurality of tubular filtration membranes are connected, and in the extending direction of the casing A second partition wall provided at the other end and having a plurality of through-holes connected to the other ends of the plurality of tubular filtration membranes, one ends of the tubular filtration membranes, and the other ends of the tubular filtration membranes A pair of membrane connection plates provided with membrane connection grooves that are connected so that the tubular filtration membranes are connected in series.

  According to the third aspect of the present invention, the water treatment system includes a biological treatment water tank that treats organic matter contained in the treated water, and a raw water tank that accommodates the treated water discharged from the biological treatment water tank. A membrane separation device having the membrane module according to any one of the above, separating the treated water supplied from the raw water tank into permeated water and concentrated water, and returning the concentrated water to the biologically treated water tank A return line that does not return the concentrated water to the raw water tank.

  In the water treatment system, the membrane separation device may include a plurality of the membrane modules connected in series to each other.

  According to such a configuration, the number of pipes connected to the membrane separation device is one, and the flow rate of water to be treated circulating through the water treatment system can be reduced. Thereby, the driving power for circulating treated water can be made small.

  According to the present invention, it is possible to reduce the flow rate of the water to be treated flowing through the tubular filtration membrane as compared with a method of connecting a plurality of tubular filtration membranes in parallel. Thereby, the driving power for circulating treated water can be made small. In addition, since the membrane surface flow rate becomes uniform, it is possible to suppress the accumulation or stagnation of sludge on the tubular filtration membrane.

It is a schematic block diagram of the water treatment system of 1st embodiment of this invention. It is a schematic sectional drawing of the membrane module of 1st embodiment of this invention. It is a schematic block diagram of the water treatment system of 2nd embodiment of this invention. It is a disassembled perspective view of the 1st partition and membrane connection board of the membrane module of 3rd embodiment of this invention. It is a schematic sectional drawing of the 1st partition and membrane connection board of the membrane module of 3rd embodiment of this invention.

(First embodiment)
Hereinafter, the water treatment system 10 having the membrane module 1 of the first embodiment of the present invention will be described in detail with reference to the drawings.
As shown in FIG. 1, the water treatment system 10 of the present embodiment includes a biological treatment water tank 11 for treating organic substances contained in the water to be treated W1 (organic wastewater including human waste and septic tank sludge), and a biological treatment water tank 11. The raw water tank 12 in which the treated water W2 discharged is accommodated, and the membrane separation device 13 that separates the treated water W3 (raw water) supplied from the raw water tank 12 into the permeated water PW and the concentrated water W4. ing.

  The biological treatment water tank 11 is a device that decomposes and removes BOD, nitrogen compounds, etc. in the liquid by the action of nitrifying bacteria and denitrifying bacteria, for example. To-be-treated water tank 11 is supplied with treated water W <b> 1 through first pipe 15. The biological treatment water tank 11 and the raw water tank 12 are connected by a second pipe 16.

The membrane separation device 13 includes a plurality of membrane modules 1. The plurality of membrane modules 1 are arranged in parallel. The plurality of membrane modules 1 are arranged vertically in the housing of the membrane separation device 13. That is, the axis A of the cylindrical casing 2 (see FIG. 2) of the membrane module 1 extends in the vertical direction.
As shown in FIG. 2, the membrane module 1 has a casing 2 and a plurality of tubular filtration membranes 3 arranged inside the casing 2. The membrane separation device 13 is a device that takes out the permeated water PW from the water to be treated W3 by using a method of filtering the water to be treated W3 while circulating it inside the tubular filtration membrane 3.

The raw water tank 12 and the membrane separation device 13 are connected via a raw water supply pipe 17. A circulation pump 21 is provided in the raw water supply pipe 17. The treated water W3 discharged from the raw water tank 12 is supplied to the membrane separation device 13 while being pressurized by the circulation pump 21.
The permeated water PW separated from the membrane separation device 13 is introduced into the permeated water pipe 18. The permeated water pipe 18 is connected to the storage tank 20. That is, the permeate outlet 9 (see FIG. 2) of the membrane module 1 is connected to the permeate pipe 18. A suction pump 22 is provided in the permeate water pipe 18.

The concentrated water W4 separated from the permeated water PW and discharged from the membrane separation device 13 is returned to the biological treatment water tank 11 through the return pipe 19 (return line) except for the excess sludge. That is, the concentrated water discharge port 8 (see FIG. 2) of the membrane module 1 is connected to the return pipe 19.
Therefore, the concentrated water W4 is not returned to the raw water tank 12. The treated water W2 discharged from the biological treatment water tank 11 returns to the biological treatment water tank 11 via the raw water tank 12 and the membrane separator 13. That is, the to-be-processed water W circulates through the piping of the water treatment system 10.

  As described above, the plurality of membrane modules 1 are arranged in parallel. Specifically, the raw water supply pipe 17, the permeate water pipe 18, and the return pipe 19 are connected to each membrane module 1.

As shown in FIG. 2, the membrane module 1 includes a cylindrical casing 2 and a plurality of tubular filtration membranes 3.
The casing 2 includes a cylindrical casing body 4, a first side wall 5 that closes a lower end of the casing body 4, a second side wall 6 that closes an upper end of the casing body 4, and a treatment target formed on the casing body 4. It has a water introduction port 7, a concentrated water discharge port 8 formed in the casing body 4, and a permeate discharge port 9 formed in the casing body 4.

The membrane module 1 includes a first partition wall 30 and a second partition wall 31 that divide the inside of the casing 2 into three spaces. A plurality of insertion holes 32 are formed in the first partition wall 30 and the second partition wall 31. The insertion hole 32 is a through-hole penetrating in the plate thickness direction of the first partition wall 30 and the second partition wall 31. The inner diameter of the insertion hole 32 is slightly larger than the outer diameter of the tubular filtration membrane 3.
The first partition wall 30 is provided at one end in the extending direction of the casing 2, and one end of the plurality of tubular filtration membranes 3 is connected to the plurality of through holes 32. The second partition wall 31 is provided at the other end in the extending direction of the casing 2, and the other ends of the plurality of tubular filtration membranes 3 are connected to the plurality of through holes 32.

The first partition 30 is a plate-shaped member, and is fixed below the extending direction of the casing 2 (on the first side wall 5 side). A space surrounded by the casing body 4, the first partition wall 30, and the first side wall 5 is a lower header space S1.
The second partition wall 31 is a plate-shaped member, and is fixed above the extending direction of the casing 2 (on the second side wall 6 side). A space surrounded by the casing body 4, the second partition wall 31 and the second side wall 6 is an upper header space S2.
A space surrounded by the casing body 4, the first partition wall 30, and the second partition wall 31 is a permeated water space S3. The permeated water PW taken out from the plurality of tubular filtration membranes 3 is discharged into the permeated water space S <b> 3 and then introduced into the permeated water pipe 18 through the permeated water discharge port 9.

The treated water introduction port 7 is an opening that allows communication between the outside of the casing 2 and the lower header space S1. The treated water inlet 7 is formed in the casing body 4. The treated water introduction port 7 is provided between the first partition wall 30 and the first side wall 5 in the axis A direction of the casing 2.
The concentrated water discharge port 8 is an opening that allows communication between the outside of the casing 2 and the upper header space S2. The concentrated water discharge port 8 is formed in the casing body 4. The concentrated water discharge port 8 is provided between the second partition wall 31 and the second side wall 6 in the axis A direction of the casing 2.
The permeated water discharge port 9 is an opening that allows communication between the outside of the casing 2 and the permeated water space S3. The permeated water discharge port 9 is formed in the casing body 4. The permeate discharge port 9 is provided between the first partition wall 30 and the second partition wall 31 in the axis A direction of the casing 2.

One end of each tubular filtration membrane 3 is fixed to the inner peripheral surface of the insertion hole 32 after being inserted into the insertion hole 32 of the first partition wall 30. A space between the inner peripheral surface of the insertion hole 32 and the outer peripheral surface of the tubular filtration membrane 3 is sealed with a sealing material (not shown). As the sealing material, a material that has an initial viscosity and hardens with time, such as an epoxy resin or a urethane resin, is preferable.
The other end of each tubular filtration membrane 3 is fixed to the insertion hole 32 of the second partition wall 31 in the same manner as one end of the tubular filtration membrane 3.

The plurality of tubular filtration membranes 3 of the present embodiment are connected in series. Specifically, the membrane module 1 of the present embodiment connects one end of the tubular filtration membrane 3 and the other end of the tubular filtration membrane 3 so that a plurality of tubular filtration membranes 3 are connected in series. Yes.
The ends of the tubular filtration membrane 3 are connected to each other by a U-shaped membrane connecting pipe 34. The U-shaped membrane connecting pipe 34 is a curved cylindrical connecting member formed of an engineering plastic such as POM, for example. The membrane connecting pipe 34 may be formed of a metal having excellent corrosion resistance such as SUS304. The end of the membrane connecting pipe 34 is connected to the insertion hole 32 of the partition walls 30 and 31. You may connect the edge part of the membrane connection pipe 34 to the tubular filtration membrane 3 directly.

The tubular filtration membrane 3 has a cylindrical shape, and is formed of a polymer filtration membrane having a single layer structure in which a hydrophilic monomer is copolymerized on a single main constituent material.
That is, the tubular filtration membrane 3 is formed of a single material as a main material. That the main material is formed of one kind of material means that one kind of resin occupies 50% by mass or more in the material (for example, resin) forming the tubular filtration membrane 3.
The fact that the main material is formed of one kind of material means that the nature of the one kind of material dominates the nature of the constituent material. Specifically, it means a material in which one kind of resin has 50 mass% to 99 mass%.

  The main materials constituting the tubular filtration membrane 3 include polyolefin chlorides such as vinyl chloride resin, polysulfone (PS), polyvinylidene fluoride (PVDF), polyethylene (PE), polyacrylonitrile (PAN), and polyether. Polymer materials such as sulfone, polyvinyl alcohol (PVA), and polyimide (PI) can be used.

  As a main material constituting the tubular filtration membrane 3, a vinyl chloride resin is particularly preferable. Examples of vinyl chloride resins include vinyl chloride homopolymer (vinyl chloride homopolymer), a copolymer of a monomer having an unsaturated bond copolymerizable with vinyl chloride monomer and vinyl chloride monomer, and vinyl chloride monomer in the polymer. Examples thereof include graft copolymers obtained by graft copolymerization, and (co) polymers composed of chlorinated vinyl chloride monomer units.

Examples of hydrophilic monomers include:
(1) A cationic group-containing vinyl monomer such as an amino group, an ammonium group, a pyridyl group, an imino group or a betaine structure and / or a salt thereof,
(2) Hydrophilic nonionic group-containing vinyl monomers such as hydroxyl groups, amide groups, ester structures, ether structures,
(3) Anionic group-containing vinyl monomer such as carboxyl group, sulfonic acid group, phosphoric acid group and / or salt thereof,
(4) Other monomers may be mentioned.
The tube diameter of the tubular filtration membrane can be appropriately selected depending on the properties of the water to be treated W. For example, when the amount of coarse fiber α in the water to be treated W3 is 200 mg / liter or less, the inner diameter of the tubular filtration membrane 3 is 5 mm. Hereinafter, when the coarse fiber amount α is larger than 200 mg / liter and smaller than 500 mg / liter, the inner diameter of the tubular filtration membrane 3 is 5 mm-10 mm, and when the coarse fiber amount α is 500 mg / liter or more, the inner diameter of the tubular filtration membrane 3 is Can be 10 mm or more. By selecting the tube diameter, blockage of the tubular filtration membrane 3 due to the coarse fibers can be suppressed.

Next, the effect | action of the water treatment system 10 of this embodiment is demonstrated.
First, the water to be treated W1 is treated in the biological treatment water tank 11. Specifically, the organic substance contained in the for-treatment water W1 is decomposed by microorganisms.
Next, the water to be treated W2 discharged from the biological treatment water tank 11 is stored in the raw water tank 12. When the treated water W3 discharged from the raw water tank 12 is supplied to the membrane separation device 13 via the circulation pump 21, it is sent into the tubular filtration membrane 3 of the membrane module 1. On the other hand, the permeated water space S <b> 3 in the casing 2 of the membrane module 1 becomes negative pressure by the operation of the suction pump 22. The suction pump 22 sucks in a direction substantially orthogonal to the flow of the water to be treated W3 flowing through the tubular filtration membrane 3 through the permeate discharge port 9. The permeated water PW permeated from the tubular filtration membrane 3 is stored in the storage tank 20 through the permeated water discharge port 9 and the permeated water pipe 18.

Here, the flow of the to-be-processed water W3 in the membrane module 1 is demonstrated using FIG.
By connecting the plurality of tubular filtration membranes 3 in series, the treated water W3 flowing into the lower header space S1 is introduced into the first tubular filtration membrane 3a. Next, the water to be treated W3 is introduced into the second tubular filtration membrane 3b through the membrane connection pipe 34a. Thereafter, the water to be treated W3 is introduced to the fifth tubular filtration membrane 3e via the third tubular filtration membrane 3c and the fourth tubular filtration membrane 3d. The treated water W3 flows into the upper header space S2 from the fifth tubular filtration membrane 3e, and is then discharged from the concentrated water discharge port 8.
That is, by making the arrangement of the tubular filtration membranes 3 in series, the same amount of treated water W3 always passes through all the tubular filtration membranes 3.
Alternatively, the first tubular filtration membrane 3a, the treated water introduction port 7, and the fifth tubular filtration membrane 3e may be directly connected to the concentrated water discharge port 8 via the connection member 39 and the connection member 40. In this case, it is not necessary to provide the upper header space S2, and the configuration of the casing can be changed, such as eliminating the second side wall 6.

  The total amount of the concentrated water W4 discharged from the membrane separation device 13 is returned to the biological treatment water tank 11 through the return pipe 19, and the treatment is performed again.

According to the said embodiment, compared with the system which connects the some tubular filtration membrane 3 in parallel, the flow volume of the to-be-processed water W3 which flows through the membrane module 1 can be decreased. Thereby, the driving power for circulating the to-be-processed water W can be made small.
Moreover, when not reducing the flow volume of the to-be-processed water W, a membrane surface flow velocity can be improved. Thereby, it is possible to suppress the accumulation of sludge on the membrane surface of the tubular filtration membrane 3.

  Moreover, since the membrane surface flow velocity becomes uniform, it is possible to suppress the accumulation or stagnation of sludge on the tubular filtration membrane 3. Thereby, all the tubular filtration membranes 3 can be used effectively. Moreover, the fall of FLUX (outflow amount) can be suppressed. Further, the tubular filtration membrane 3 can be prevented from being blocked.

  Moreover, the membrane surface flow rate of the to-be-processed water W3 can be made low by forming the tubular filtration membrane 3 with the material which has hydrophilic property. The film surface flow velocity can be set to, for example, 0.15 m / s-0.30 m / s.

  When the tubular filtration membrane 3 is hydrophobic, it is necessary to increase the membrane surface flow velocity (for example, 2.5 m / s). For this reason, the circulation flow rate increases, and it becomes necessary to return the concentrated water W4 discharged from the membrane separation device 13 to the raw water tank 12 and the biological treatment water tank 11. In order to return to the raw water tank 12 and the biological treatment water tank 11, a distribution tank that distributes the concentrated water W4 to the raw water tank 12 and the biological treatment water tank 11 and a pipe that returns the concentrated water W4 to the raw water tank 12 are required. .

Since the water treatment system 10 of the present embodiment can reduce the membrane surface flow velocity, the circulation flow rate of the water to be treated W can be reduced. Thereby, the power of the circulation pump 21 can be reduced. Moreover, the distribution tank which distributes the to-be-processed water W4 to the raw | natural water tank 12 and the biologically-treated water tank 11, and the return pump which returns the to-be-processed water W4 from the raw | natural water tank 12 to the biologically-treated water tank 11 become unnecessary.
In addition, the diameter of the pipe can be reduced by reducing the flow rate. In addition, by reducing the flow rate, it is possible to reduce equipment such as a flow meter.

(Second embodiment)
Hereinafter, the water treatment system 10B of 2nd embodiment of this invention is demonstrated based on drawing. In the present embodiment, differences from the first embodiment described above will be mainly described, and description of similar parts will be omitted.
As shown in FIG. 3, in the water treatment system 10B of the present embodiment, a plurality of membrane modules 1 are connected in series with each other. For example, when the membrane separator 13 includes three membrane modules 1, the water to be treated W3 discharged from the raw water tank 12 is introduced only into the first membrane module 1a and discharged from the first membrane module 1a. The treated water is introduced only into the second membrane module 1b. The treated water discharged from the second membrane module 1b is introduced only into the third membrane module 1c, and the concentrated water W4 discharged from the third membrane module 1c is introduced into the return pipe 19.

  According to the said embodiment, the raw | natural water supply piping 17 connected to the membrane separator 13 and the return piping 19 become one place each, and can reduce the flow volume of the to-be-processed water W which circulates through the water treatment system 10B. Thereby, the driving power for circulating the to-be-processed water W can be made small.

(Third embodiment)
Hereinafter, a membrane module according to a third embodiment of the present invention will be described with reference to the drawings. In the present embodiment, differences from the first embodiment described above will be mainly described, and description of similar parts will be omitted.
As shown in FIGS. 4 and 5, the membrane module 1C of the present embodiment includes a pair of membrane connection plates 36 (see FIGS. 4 and 5) instead of the membrane connection tube 34 (see FIG. 2) of the first embodiment. Shows one of the pair of membrane connecting plates 36). The membrane connecting plate 36 has a plate shape and is attached in close contact with the surface of the first partition 30 opposite to the surface facing the second partition 31.
The membrane connecting plate 36 is also attached to the surface of the second partition wall 31 opposite to the surface facing the first partition wall 30, but the description thereof is omitted because it has the same structure.

The membrane connecting plate 36 is connected to the first partition wall 30 so that the main surface is in close contact with the surface of the first partition wall 30 opposite to the surface facing the second partition wall 31. A surface of the membrane connecting plate 36 that is in close contact with the first partition wall 30 is referred to as a contact surface 36a. A plurality of membrane connection grooves 37 are formed in the close contact surface 36 a of the membrane connection plate 36. Further, the membrane connection plate 36 is formed with a to-be-treated water insertion hole 38 penetrating the contact surface 36a and the surface on the opposite side.
The membrane connecting groove 37 is a bottomed groove formed in the close contact surface 36 a of the membrane connecting plate 36. The membrane connection groove 37 has the same function as the membrane connection tube 34 of the first embodiment. That is, the to-be-processed water W flowing through one tubular filtration membrane 3 flows to another tubular filtration membrane 3 through the membrane connection groove 37. The treated water insertion hole 38 is a hole that allows the tubular filtration membrane 3 to communicate with the header space.

  According to the said embodiment, compared with the membrane module 1 of 1st embodiment using the some membrane connection pipe | tube 34, the assembly process of a membrane module can be simplified. Moreover, disassembly and cleaning can be facilitated by reducing the number of parts.

The embodiment of the present invention has been described in detail above, but various modifications can be made without departing from the technical idea of the present invention.
For example, regarding the number of the tubular filtration membranes 3, five tubular filtration membranes 3 are shown in FIG. 2 and the like, but the number of the tubular filtration membranes 3 is not limited to this.

  The membrane module 1 may be placed horizontally. That is, the membrane module 1 may be arranged such that the axis A of the membrane module 1 extends in the horizontal direction. By placing the membrane module 1 horizontally, the membrane module 1 can be easily replaced even when a plurality of membrane modules 1 are arranged.

DESCRIPTION OF SYMBOLS 1 Membrane module 2 Casing 3 Tubular filtration membrane 4 Casing main body 5 1st side wall 6 2nd side wall 7 To-be-processed water inlet 8 Concentrated water outlet 9 Permeated water outlet 10 Water treatment system 11 Biologically treated water tank 12 Raw water tank 13 Membrane separation Equipment 15 First piping 16 Second piping 17 Raw water supply piping 18 Permeated water piping 19 Return piping (return line)
20 Reservoir 21 Circulation Pump 22 Suction Pump 30 First Bulkhead 31 Second Bulkhead 32 Insertion Hole (Through Hole)
34 Membrane connection pipe (connection member)
36 Membrane connection plate (connection member)
36a Contact surface 37 Membrane connection groove 38 Water to be treated insertion hole A Axis PW Permeated water S1 Lower header space S2 Upper header space S3 Permeated water space W1 to W3 Water to be treated W4 Concentrated water

Claims (6)

A cylindrical casing whose axis extends in the vertical direction;
A plurality of tubular filtration membranes having a single layer structure in which hydrophilic monomers are copolymerized, extending in the casing extending direction inside the casing;
A membrane module comprising: a plurality of connecting members that connect one end of the tubular filtration membrane and the other end of the tubular filtration membrane so that the plurality of tubular filtration membranes are connected in series. A first partition wall provided at one end in the extending direction of the casing and having a plurality of through-holes connected to one end of the plurality of tubular filtration membranes;
A second partition wall provided at the other end in the extending direction of the casing and having a plurality of through holes to which the other ends of the plurality of tubular filtration membranes are connected,
The connecting member is
The membrane module according to claim 1, wherein the plurality of through holes are connected to each other.   The membrane module according to claim 1 or 2, wherein the connection member is a membrane connection plate including a membrane connection groove that connects the plurality of through holes. A cylindrical casing;
A plurality of tubular filtration membranes having a single layer structure in which hydrophilic monomers are copolymerized, extending in the casing extending direction inside the casing;
A first partition wall provided at one end in the extending direction of the casing and having a plurality of through-holes connected to one end of the plurality of tubular filtration membranes;
A second partition wall provided at the other end of the casing in the extending direction and having a plurality of through holes to which the other ends of the plurality of tubular filtration membranes are connected;
A pair of membrane connection plates provided with membrane connection grooves that connect one end of the tubular filtration membrane and the other end of the tubular filtration membrane so that the plurality of tubular filtration membranes are connected in series. Membrane module. A biological treatment water tank for treating organic substances contained in the water to be treated;
A raw water tank in which treated water discharged from the biological treatment water tank is stored;
A membrane separation apparatus comprising the membrane module according to any one of claims 1 to 4, and separating water to be treated supplied from the raw water tank into permeate and concentrated water;
And a return line for returning the concentrated water to the biologically treated water tank, wherein the concentrated water is not returned to the raw water tank.   The water treatment system according to claim 5, wherein the membrane separation device includes a plurality of the membrane modules connected in series to each other.

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