JP4820340B2 - 浚 渫 Wastewater purification system - Google Patents

Description

  The present invention relates to a dredging drainage purification system for purifying drainage generated when dredging river or coastal sediment.

In the work of collecting valuable materials such as ore by dripping sediment with high-pressure water, wastewater containing a large amount of sediment fine particles (NORO) can be obtained. Since the rivers are polluted and have a serious impact on the natural environment, the purification process is carried out. For example, Patent Document 1 describes filtering sludge using a gravity filtration device.
Japanese Patent Laid-Open No. 2006-231285

  However, in the above-described conventional filtration device, clogging occurs immediately, so that not only frequent filter cleaning but also filter replacement has to be performed.

  Accordingly, an object of the present invention is to provide a dredging drainage purification system that can easily purify drainage wastewater generated by dredging work and is easy to maintain and manage.

  The object of the present invention includes a plurality of water storage tanks for sedimenting and filtering sludge water, a water distribution pipe for cascading each water storage tank, and a polymer microfilter provided in the middle of the water distribution pipe. The filter includes a porous layer having a scram structure formed of an independent nuclear space serving as a nucleus of the porous space and a continuous fine space communicating between the plurality of independent nuclear spaces. Achieved by the system.

  The dredged wastewater purification system of the present invention includes a first water storage tank that precipitates and filters sludge water, a first polymer microfilter that filters water discharged from the first water tank, and a first polymer microfilter. It is preferable to include a second water storage tank that precipitates and filters the water filtered by the filter, and a second polymer microfilter that filters water discharged from the second water storage tank.

  In the present invention, the first polymer microfilter preferably has a continuous fine space larger than the second polymer microfilter and the thickness of the porous layer is thin. In particular, the thickness of the porous layer of the first polymer microfilter is preferably 10 to 100 μm, and the thickness of the porous layer of the second polymer microfilter is preferably 100 to 1000 μm. Moreover, it is preferable that the average pore diameter of the continuous microspace of the first polymer microfilter is 4 to 8 μm, and the average pore diameter of the continuous microspace of the second polymer microfilter is 0.5 to 4 μm. .

  In the present invention, the porous layer is preferably formed of fibers having a cross-sectional shape that is deformed by one or more convex portions and / or concave portions.

  In the present invention, it is preferable that the porous layer is integrally formed of a nonwoven fabric and a porous resin impregnated in the nonwoven fabric fiber layer.

  In the present invention, the polymer microfilter has a nonwoven fabric intermediate fiber layer having a higher porosity than the porous layer formed on the downstream side of the porous layer, and a support layer formed on the downstream side of the intermediate fiber layer. It is preferable to further have a nonwoven fabric base fiber layer having a higher porosity than the intermediate fiber layer formed on the downstream side of the support layer.

  According to the present invention, it is possible to provide a dredging drainage purification system that can easily purify drainage wastewater generated by dredging work and is easy to maintain and manage.

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

  FIG. 1 is a schematic diagram showing a configuration of a dredged water purification system 100 according to a preferred embodiment of the present invention.

  As shown in FIG. 1, this dredging drainage purification system 100 includes first and second water storage tanks 101 and 102 that are cascade-connected, and a first polymer micro-tube provided at the subsequent stage of the first water storage tank 101. A filter 104 and a second polymer microfilter 105 provided downstream of the second water storage tank 102 are provided. The position of the first water tank 101 is preferably higher than the position of the second water tank 102. By providing such a height difference at the position of the water storage tank, it is possible to perform filtration only with water head pressure.

  Sludge water generated during dredging in a river or the like is put into the first water storage tank 101, and the sludge water is precipitated and filtered in the first water storage tank 101. The first water storage tank 101 is connected to the second water storage tank 102 through the water distribution pipe 103, and since the first polymer microfilter 104 is provided in the middle, the first water storage tank The supernatant portion of 101 is filtered by the first polymer microfilter 104. The water that has passed through the first polymer microfilter 104 is precipitated and filtered in the second water tank 102. The outlet of the second water storage tank 102 is connected to the water distribution pipe 106, and the second polymer microfilter 105 is provided in the middle of the water distribution pipe 106, so that the supernatant portion of the second water storage tank 102 is the first one. The second polymer microfilter 105 is filtered. In this way, more precise filtration is possible by alternately repeating precipitation filtration and filter filtration.

  By repeating the sludge water filtration step, solid content accumulates in the first and second polymer microfilters 104 and 105 and the filtration function deteriorates, so it is necessary to remove the solid content. Therefore, the polymer microfilter 105 is regularly backwashed or washed with a scraper or the like. Although details will be described later, the polymer microfilter 105 of the present embodiment has a scram structure formed by an independent nucleus space that is a nucleus of a porous space and a continuous fine space that communicates between a plurality of independent nucleus spaces. Since the porous layer is provided, not only the filtration performance is high, but also clogging can be eliminated relatively easily.

  Further, as the polymer microfilter of the present embodiment, the pore size of the continuous fine space is larger as it is located upstream and the thickness of the porous layer is thinner, and the void of the continuous fine space is located as it is located downstream. A material having a small pore size and a thick porous layer is used. That is, the first polymer microfilter 104 has a continuous fine space larger than the second polymer microfilter 105, and the thickness of the porous layer is thin.

  Here, the polymer microfilters 104 and 105 used in the present embodiment will be described in detail.

  FIG. 2 is a schematic cross-sectional view showing the structure of the polymer microfilters 104 and 105.

  As shown in FIG. 2, the polymer microfilters 104 and 105 include a porous layer 2 having a scram structure formed by deforming the cross-sectional shape of the fibers of the nonwoven fabric, and a nonwoven fabric on the downstream side of the porous layer 2. A support layer 4 formed on the downstream side of the intermediate fiber layer 3 with a reinforcing material such as an intermediate fiber layer 3 having a higher porosity than that of the porous layer 2 formed of 4 is provided with a lower fiber layer 5 having a higher porosity than the intermediate fiber layer 3 formed of a nonwoven fabric on the downstream side.

  As the material of the nonwoven fabric forming the porous layer 2, the intermediate fiber layer 3, and the lower fiber layer 5, synthetic fibers such as polyamide, polyester, polyolefin, polyacrylonitrile, polyvinyl chloride, polyvinylidene chloride, and polyvinyl alcohol (vinylon) are used. Can be used. The average fiber diameter of each layer can be appropriately selected according to the porosity and the like. The average fiber diameter of the synthetic fibers forming the porous layer 2 is preferably 3 μm to 25 μm. As the average fiber diameter becomes thinner than 3 μm, handling becomes difficult, and the mass productivity and durability of the nonwoven fabric tend to be lacking. As the fiber becomes thicker than 25 μm, the pores increase and the porosity increases, and the filtration performance decreases. This is because it tends to be easier. In view of water resistance, chemical resistance and weather resistance, polyester and polypropylene are preferable.

It is preferred basis weight of the polymer micro-filters 104 and 105 are ^{500g / m 2 ~1000g / m 2} . As the basis weight becomes smaller than 500 g / m ^2, it becomes difficult to withstand the water pressure repeatedly applied over a long period of time, and the durability tends to decrease. As the mass per unit area becomes larger than 1000 g / m ² , mass productivity decreases. This is because it tends to be easy.

  The support layer 4 is preferably formed by disposing a reinforcing material such as a woven fabric, a net, or other porous membrane between the intermediate fiber layer 3 and the lower fiber layer 5. As the reinforcing material, a monofilament or multifilament woven fabric is preferably used, but a spun woven fabric may also be used. In addition, as the material of the reinforcing material, the same material as that of the above-mentioned nonwoven fabric is preferably used. In the case of a net, a composite of a stainless steel wire and polyester may be arranged vertically and horizontally in a mesh shape.

It is preferred apparent density of the polymer micro-filters 104 and 105 are ^{0.35g / cm 2 ~0.55g / cm 2} . As the apparent density becomes smaller than 0.35 g / cm ^2, the filtration area in contact with the sewage becomes insufficient, and the filtration efficiency tends to decrease. As the apparent density becomes larger than 0.55 g / cm ² , the water flow rate becomes larger. This is because it tends to be insufficient and it becomes difficult to filter a large amount of sewage.

The polymer microfilters 104 and 105 are formed such that the air passage amount when a pressure difference of 98 kPa is applied is 1 (cm ³ / s) / cm ² to 10 (cm ³ / s) / cm ^2. Preferably it is. As the air flow rate becomes smaller than 1 (cm ³ / s) / cm ² , the water flow rate becomes insufficient, and it becomes difficult to filter a large amount of sewage, and 10 (cm ³ / s) / cm ^{This is because} as the ratio becomes larger than ^{2, the} amount of fibers in contact with the sewage becomes insufficient, and the filtration efficiency tends to decrease.

  FIG. 3 is a cross-sectional view of an essential part schematically showing the structure of the porous layer 2 of the polymer microfilters 104 and 105.

  As shown in FIG. 3, the porous layer 2 has a scram structure, a porous resin 15 impregnated into a nonwoven fabric fiber layer forming the porous layer 2 and integrated with the nonwoven fabric, and a porous layer An independent nucleus space 15a serving as a nucleus of the two porous spaces and a continuous fine space 15b communicating between the plurality of independent nucleus spaces 15a.

  Here, the structure of the porous layer in the first polymer microfilter 104 and the second polymer microfilter 105 will be described in detail with reference to FIG. 4A is a schematic cross-sectional view of the porous layer 2a in the first polymer microfilter 104, and FIG. 4B is a schematic cross-section of the porous layer 2b in the second polymer microfilter 105. FIG.

As shown in FIGS. 4A and 4B, the porous layer 2a of the first polymer microfilter 104 and the porous layer 2b of the second polymer microfilter 105 have different thicknesses. . That is, the thickness t ₂ of the porous layer 2b is thicker than the thickness t ₁ of the porous layer 2a.

The average pore diameter _{d 1} of the continuous fine space 15b ₁ in the porous layer 2a is different from the average pore diameter _{d 2} of the continuous fine space 15b ₂ in the porous layer 2b. That is, the average pore diameter d ₂ of the continuous micro spaces of the porous layer 2b is smaller than the average pore diameter d ₁ of the continuous microporous space of the porous layer 2a.

More specifically, the thicknesses t ₁ and t ₂ of the porous layers 2a and 2b and the average pore diameters d ₁ and d ₂ of the continuous fine space are preferably as follows.

The thickness t ₁ of the porous layer 2a of the first polymer microfilter 104 is preferably about 10 to 100 μm. If the thickness t ₁ of the porous layer 2a is smaller than 10 μm, the continuous fine space 15b ₁ cannot be sufficiently secured, the filtration capacity is insufficient, and the porous layer 2a is easily damaged by physical cleaning. The life may be shortened. Further, when the thickness of the porous layer 2a is larger than 100 μm, the water permeability in the first polymer microfilter 104 is not sufficiently increased, and the water permeability of the second polymer microfilter 105 is further insufficient. This is because the filtration efficiency tends to decrease.

The thickness _{t 2} of the porous layer 2b of the second polymer micro filter 105 is preferably about 100 to 1000 [mu] m. When the thickness t ₂ of the porous layer 2b is smaller than 100 μm, the continuous fine space 15b ₂ cannot be sufficiently secured, and fine substances that cannot be captured by the first polymer microfilter 104 are sufficiently filtered. The possibility of not being able to be increased. Moreover, when the thickness of the porous layer 2b is larger than 1000 μm, the water permeability is insufficient and the filtration efficiency tends to be lowered.

The average pore diameter d ₁ of the continuous microspace 15b ₁ of the first polymer microfilter 104 is preferably 4 to 8 μm. If the average pore diameter d ₁ of the continuous fine space 15b ₁ is smaller than 4 [mu] m, through water is reduced, the filtration efficiency of the second polymeric microfilter 105 tends to decrease. When the average pore diameter d ₁ of the continuous fine space 15b ₁ is greater than 8 [mu] m, it is difficult to capture the fine material, it is closed fine material is caught in the pores, is to remove backwashing or cleaning It becomes difficult. Furthermore, this is because the water permeability in the second polymer microfilter 105 is likely to decrease.

The average pore diameter _{d 2} of the continuous fine space 15b ₂ of the second polymeric microfilter 105 is preferably 0.5 to 4 .mu.m. If the average pore diameter d ₂ of the continuous fine space 15b ₂ is smaller than 0.5 [mu] m, filtration efficiency tends to lower water permeability is greatly reduced. Moreover, it is because filtration performance will fall easily when it becomes larger than 4 micrometers.

  FIGS. 5A to 5C are schematic perspective views showing the structure of the fibers forming the porous layer 2 (2a, 2b).

  FIG. 5A is an example in which a plurality of convex portions 11 are formed on the circumference of the fiber 10 that forms the porous layer 2, and FIG. 5B shows the fiber 10 a that forms the porous layer 2. 5 (c) shows an example in which a plurality of substantially spherical convex portions 11b are formed on the outer peripheral surface of the fiber 10b forming the porous layer 2. FIG. This is an example. These convex portions 11, 11a, and 11b can be formed by passing the fibers 10, 10a, and 10b between rolling rollers that have irregularities corresponding to the convex portions 11, 11a, and 11b formed on the surface.

  The size of the protrusions 11, 11a, 11b depends on the fiber diameter of the fibers 10, 10a, 10b, but when the fiber diameter is 10 μm to 25 μm, the diameter of the protrusions 11, 11a, 11b is 2 μm to 5 μm. It is preferable. As the diameter of the convex parts 11, 11a, 11b becomes smaller than 2 μm, the effect of deforming becomes insufficient, the water permeability tends to decrease and the filtration efficiency tends to decrease, and the convex parts 11, 11a, 11b This is because as the diameter becomes larger than 5 μm, it becomes difficult to maintain the cross-sectional shape and the productivity tends to decrease, and the porosity tends to increase and the filtration performance tends to decrease.

  In the step of forming the porous layer 2 of the polymer microfilters 104 and 105, the fibers 10, 10a, 10b having a cross-sectional shape deformed by one or more convex portions 11, 11a, 11b are made into needle punches, water jet needles, etc. By forming the porous layer 2 by being entangled three-dimensionally by the above method, a substantially uniform continuous microspace 15b communicating with the independent nucleus space 15a can be formed, and the continuous microspace ( The average pore diameter of the fine pores) 15b can be formed to the aforementioned 0.5 μm to 8 μm.

  FIGS. 6A to 6F are schematic cross-sectional views showing modifications of the structure of the fibers forming the porous layer 2 (2a, 2b).

  FIG. 6 (a) is an example in which five convex portions 11c are formed on the outer periphery of the fiber 10c, and FIG. 6 (b) is an example in which four convex portions 11d are formed on the outer periphery of the fiber 10d. FIG. 6C is an example in which three convex portions 11e are formed on the outer periphery of the fiber 10e, and FIG. 6D is an example in which four concave portions 11f are formed on the outer periphery of the fiber 10f. 6 (e) is an example in which three concave portions 11g are formed on the outer periphery of the fiber 10g, and FIG. 6 (f) is an example in which two concave portions 11h are formed on the outer periphery of the fiber 10h.

  By stretching the fiber from a mold having a cross-sectional shape similar to the cross-sectional shape of the fibers 10c to 10h shown in FIG. 6, the cross-sectional shape of the fiber can be made irregular, and the convex shape is continuous in the longitudinal direction of the fiber. A shape or a concave shape can be formed. Further, by twisting the fiber during stretching, a convex shape or a concave shape can be formed in a spiral shape as shown in FIG. By stretching the fiber in the liquid, the deformed cross-sectional shape can be reliably maintained, and the productivity is excellent.

  In FIG. 6, the cross-sectional shape is modified by two to five convex portions 11c to 11e and concave portions 11f to 11h, but the number of convex portions 11c to 11e and concave portions 11f to 11h is two to two. Eight can be formed. As the number of the convex portions 11c to 11e and the concave portions 11f to 11h is less than two, the effect of deforming becomes insufficient, the water permeability tends to decrease, and the filtration efficiency tends to decrease. As the number of 11e and recesses 11f to 11h increases from eight, it becomes difficult to maintain the cross-sectional shape and the productivity tends to decrease, and the porosity tends to increase and the filtration performance tends to decrease. Because. In addition, each fiber 10a thru | or 10h shown in FIG.6 and FIG.7 may each be used independently, and may be used in combination of multiple types.

  The polymer microfilters 104 and 105 configured as described above have the following operations. First, by narrowing the eyes of the upstream porous layer 2 having a scram structure, particles in the sewage can be reliably captured at the surface portion to prevent entry into the interior, and the filtration performance is excellent. In addition, by adjusting the porosity of each layer so that the porosity increases from the porous layer 2 side that is the upstream side to the lower fiber layer 5 side that is the downstream side during filtration, In addition, it can be surely captured and filtered on the surface of the porous layer 2, and the filtered water of the filtered sewage can be quickly discharged from the lower fiber layer 5 side, and the filtration efficiency is excellent.

  In addition, the suspended material adhered to the surface of the porous layer 2 by backwashing or physical peeling by narrowing the eyes of the upstream porous layer 2 and making the downstream lower fiber layer 5 rough. Can be easily removed, clogging hardly occurs, it can be used continuously for a long period of time, and it is excellent in maintainability and practicality.

  Moreover, by having the support layer 4 formed between the intermediate | middle fiber layer 3 and the lower fiber layer 5, it can reinforce the whole and can prevent a vertical / horizontal deformation, and is excellent in durability. In addition, the lower fiber layer 5 can adjust the overall thickness and strength of the polymer microfilters 104 and 105, and when it is washed with a scraper, a brush or the like, it can absorb the impact with its cushioning property, It is difficult for the porous layer 2 to be broken, and the filtered water can be freely moved and discharged, thereby improving water permeability.

  Furthermore, the fibers 10 to 10h forming the porous layer 2 have a cross-sectional shape deformed by one or more convex portions 11 to 11e and concave portions 11f to 11h, so that the porous layer 2 is substantially uniform. A continuous fine space can be formed, and the uniformity of filtration performance is excellent. In addition, since the porous layer 2 has a scram structure in which substantially uniform continuous fine spaces are formed in multiple layers, even if the fibers 10 to 10 h are torn on the surface of the porous layer 2, the inner fibers Filtration can be carried out continuously by a continuous fine space formed in 10 to 10 hours, and the reliability of filtration performance and long life are excellent.

  The polymer microfilters 104 and 105 can perform gravity filtration, are less likely to clog, and can release suspended substances with a small external stimulus. It can be cleaned by a brush cleaning method, a water jet cleaning method, a suction cleaning method, a scraper cleaning method, etc., and can deal with sewage with a high concentration and is excellent in versatility. In addition, it is possible to separate suspended substances adhering to the surface of the porous layer 2 (2a, 2b) in an agglomerated state by sedimentation cleaning such as brush cleaning or scraper cleaning, and to settle on the bottom of a filtration tank or the like. The concentration of sewage can be prevented from increasing, and a stable filtration flow rate can be obtained.

  Further, since the polymer microfilters 104 and 105 do not require a filtration pressure device, they are excellent in energy saving, the entire filtration device can be reduced in size and weight, and mass productivity and handleability can be improved. Moreover, without using a flocculant etc., it is possible to carry out purification treatment by removing only suspended substances while leaving the minerals contained in the sewage, and it can be discharged into rivers etc. as fresh water So it has excellent environmental protection. Moreover, even if suspended substances in sewage adhere to the surfaces of the porous layers 2 (2a, 2b) of the polymer microfilters 104 and 105, the filtration efficiency is not lowered and excellent filtration performance is maintained. It can be used and has excellent practicality and reliability.

  7A and 7B are cross-sectional views showing a modification of the porous layer 2 of the polymer microfilters 104 and 105, where FIG. 7A is a cross-sectional view of the main part, and FIG. It is an enlarged view of the part shown by A in FIG.

As shown in FIGS. 7A and 7B, in the present embodiment, a part of the nonwoven fabric fibers 10 constituting the porous layer 2 protrudes to the inside of each pore of the continuous microspace 15b. It has become. The average fiber diameter d ₃ of the nonwoven fabric fibers 10 constituting the porous layer 2 is made smaller than the average pore diameter d ₄ of the continuous fine space 15b.

When the porous layer 2 is configured as shown in FIG. 7, the average pore diameter d ₄ of the continuous fine space (open cell) 15 b of the porous layer 2 is preferably 0.5 μm to 8 μm. The average fiber diameter d ₃ of the nonwoven fabric fibers 10 constituting the porous layer 2 is preferably 8 μm or less, and more preferably 4 μm or less. When the average pore diameter d ₄ of the continuous fine space is smaller than 0.5 μm, the water permeability is greatly lowered and the filtration efficiency is deteriorated. Further, when the average fiber diameter d ₃ of the nonwoven fabric fibers 10 constituting the porous layer 2 is larger than 8 μm, the average pore diameter d ₄ of the continuous fine space is made larger than the average fiber diameter d ₃ of the nonwoven fabric fibers 10. Because it is necessary, it becomes difficult to capture a minute solid substance, and it becomes caught in a hole and becomes a closed state, and cannot be removed by backwashing or washing. Therefore, it is particularly preferable that the average pore diameter d ₄ of the continuous fine space is 4 μm or more and the average fiber diameter d ₃ of the nonwoven fabric fiber 10 is 4 μm or less.

  According to such a configuration, even when the fine particles 16 enter the continuous fine space by filtration, the fine particles 16 are caught by the non-woven fibers 10 existing in the continuous fine space. Can be prevented from entering. Thereby, clogging of the polymer microfilter can be prevented. Further, even in the backwashing, since the fine particles 16 do not penetrate deep into the porous layer 2, the cleaning effect can be enhanced.

  As described above, according to the dredged wastewater purification system 100 of this embodiment, since the wastewater is filtered using the polymer microfilters 104 and 105, it is possible to remove fine solids contained in the wastewater. The adverse effect of wastewater on the environment can be greatly reduced. In particular, since the polymer microfilters 104 and 105 are used, fine solids can be reliably removed, clogging can be eliminated relatively easily, and filtration efficiency can be improved. .

Moreover, in wastewater purification system of this embodiment, larger average continuous micro spaces of the porous layer 2a pore diameter d ₁ is the thickness t ₁ is thin (i.e., filtration performance is good but not very high water permeability ) first with a polymer micro filter 104, the average of continuous micro spaces of the porous layer 2b pore diameter d ₂ is small, the thickness t ₂ is thicker second of the polymer micro-filter 105 double-layered polymer microfilters Filtration of sewage using As a result, simple filtration is performed by the first-layer polymer microfilter 104, so that the second-layer polymer microfilter 105 is clogged even if the pore diameter of the continuous fine space of the porous layer is reduced. It does not occur and more precise filtration can be performed.

  The present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention, and these are also included in the scope of the present invention. Needless to say.

FIG. 1 is a schematic diagram showing a configuration of a dredged water purification system 100 according to a preferred embodiment of the present invention. FIG. 2 is a schematic cross-sectional view showing the structure of the polymer microfilter 105. FIG. 3 is a cross-sectional view of the main part showing the structure of the porous layer 2 of the polymer microfilter 105. 4A to 4C are schematic perspective views showing the structure of the fibers forming the porous layer 2. FIGS. 5A to 5F are schematic cross-sectional views showing modifications of the structure of the fibers forming the porous layer 2. FIGS. 6A to 6F are schematic cross-sectional views showing modifications of the structure of the fibers forming the porous layer 2 (2a, 2b). 7A and 7B are cross-sectional views showing a modification of the porous layer 2 of the polymer microfilters 104 and 105, where FIG. 7A is a cross-sectional view of the main part, and FIG. It is an enlarged view of the part shown by A in FIG.

Explanation of symbols

2, 2a, 2b Porous layer 3 Intermediate fiber layer 4 Support layer 5 Lower fiber layer 10 Fiber 10a-10h Fiber 11 Convex part 11a-11e Convex part 11f-11h Concave part 15 Porous resin 15a Independent nuclear space 15b, 15b ₁ , 15b ₂ continuous fine space d ₁ , d ₂ average fine pore diameter of flat continuous fine space 100 浚 渫 drainage purification system 101 first water storage tank 102 second water storage tank 103 water distribution pipe 104 first polymer microfilter 105 first 2 polymer microfilter 106 water pipe

Claims (6)

A plurality of water tanks that precipitate and filter sludge water;
A water pipe for cascading each water tank;
A polymer microfilter provided in the middle of the water pipe,
The polymer microfilter includes a porous layer having a scram structure formed by deforming a cross section of a fiber of a nonwoven fabric,
The porous layer communicates between a porous resin impregnated in the fiber layer of the nonwoven fabric and integrated with the nonwoven fabric , an independent nucleus space serving as a nucleus of the porous space, and the plurality of independent nucleus spaces. A dredging drainage purification system characterized by having a continuous fine space. The polymer microfilter is:
An intermediate fiber layer having a higher porosity than the porous layer formed of a nonwoven fabric on the downstream side of the porous layer;
A support layer as a reinforcing material formed on the downstream side of the intermediate fiber layer;
The dredged drainage purification system according to claim 1, further comprising a lower fiber layer having a higher porosity than the intermediate fiber layer formed of a nonwoven fabric on the downstream side of the support layer. A first water tank for precipitating and filtering sludge water;
A first polymer microfilter for filtering water discharged from the first water tank;
A second water storage tank for precipitating and filtering the water filtered by the first polymer microfilter;
A second polymer microfilter for filtering water discharged from the second water tank,
The dredging drainage purification according to claim 1 or 2, wherein the first polymer microfilter has a continuous fine space larger than the second polymer microfilter and the thickness of the porous layer is thin. System . The thickness of the porous layer of the first polymer microfilter is 10 to 100 μm, and the thickness of the porous layer of the second polymer microfilter is 100 to 1000 μm. The dredged waste water purification system according to claim 3. The average pore diameter of the continuous microspace of the first polymer microfilter is 4 to 8 μm, and the average pore diameter of the continuous microspace of the second polymer microfilter is 0.5 to 4 μm. The dredged waste water purification system according to claim 3 or 4. The porous layer has a structure in which a part of the fibers of the nonwoven fabric protrudes to the inside of each pore of the continuous fine space,
The average fiber diameter of the said nonwoven fabric is smaller than the average hole diameter of the said continuous fine space, The dredged waste water purification system as described in any one of the Claims 1 thru | or 4 characterized by the above-mentioned.

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