A municipal rainwater and sewage ecological circulation system

Abstract

The present invention discloses a municipal rainwater and sewage ecological circulation system, comprising an anaerobic tank and an aerobic tank running in series, wherein the anaerobic tank is provided with a flocculation and sedimentation zone and a filter material reactor, wherein filter material is provided in the filter material reactor; a conical inner cylinder is provided at the upper part of the flocculation and sedimentation zone, a conical outer cylinder is provided at the outlet of the conical inner cylinder, an annular baffle is provided at the outer side of the conical inner cylinder and the conical outer cylinder, the upper part of the conical inner cylinder is connected to a water inlet pipe, and the water inlet pipe is connected to a dosing pipe; a filter plate 1 is provided at the bottom of the filter material reactor, inner support rods are vertically fixed on both sides of the filter plate 1 in the longitudinal direction, the outer side of the inner support rods are sleeved with outer support rods, the filter plate 1 is hinged to filter plate 2 on both sides in the transverse direction, a connecting rod is hinged to the middle part of the filter plate 2, the top of the connecting rod is hinged to the outer support rod, a support plate is evenly fixed on the outer side of the filter plate 2 in the transverse direction, and a filter screen is fixed between the support plates and at the top; a filter material reactor is provided at the upper part of the aerobic tank, and an aeration pipe is provided at the lower part of the aerobic tank. The system can centrally flush the filter material, reduce energy consumption, and the filter material is easy to flush with low loss.

Description

Technical Field

[0001] The invention relates to the technical field of municipal drainage, and in particular to a municipal rainwater and sewage ecological circulation system. Background Art

[0002] In recent years, the diversion drainage system has been widely used, but the drainage system in most old urban areas is still a combined pipe system, and most of the domestic sewage from restaurants, food stalls, etc. on municipal roads is directly connected to the rainwater pipe or combined pipe, that is, rainwater and sewage share a pipe system. On sunny days or the beginning of rain, the pipe sewage enters the sewage treatment plant for treatment and discharge; with the increase of rainfall, a large amount of rainwater and sewage pour into the pipe. When it exceeds the conveying capacity of the interception main pipe, the overflowing rainwater and sewage enter the river without any treatment. Since the rainwater runoff carries a large amount of ground pollutants, the mixed sewage is discharged into the river water body, which will cause great pollution to the urban water body. At present, the most commonly used transformation method is to build a regulating reservoir near the river downstream, introduce rainwater and sewage into the regulating reservoir through the interception well, and treat the rainwater and sewage in the regulating reservoir. On the one hand, it can alleviate surface water accumulation and reduce urban waterlogging, and it can also improve water pollution and reduce the operating load of the sewage treatment plant in the rainy season.

[0003] The treatment process of the regulating reservoir generally enters the reaction tank (aerobic reactor-anaerobic reactor) after flocculation and sedimentation to remove N, P and organic pollutants in the water body. The supernatant is returned to the water pool and discharged into the water body or further treated by ultraviolet disinfection. At present, the commonly used filter media in the aerobic-anaerobic reactor of the regulating reservoir are ceramsite, activated carbon, fiber balls, etc. These filter media have large specific surface areas, good biofilm properties, and high removal rates for N, P and organic pollutants. The main problems are: first, the filter media in the filter tank is not easy to collect, and the backwashing water consumption of the filter media layer is high; second, the internal gaps of the filter media are easy to be blocked and remain, and the sewage interception capacity is greatly weakened after backwashing, and the loss is relatively high. Summary of the invention

[0004] In view of this, the purpose of the present invention is to provide a municipal rainwater and sewage ecological circulation system to address the deficiencies in the prior art. The system can centrally flush filter materials to reduce energy consumption, and the filter materials are easy to flush with low loss.

[0005] The filter media backwashing efficiency is high and the energy consumption is low; and the filter media used has a large adsorption area, which is convenient for flushing and recycling.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A municipal rainwater and sewage ecological circulation system, comprising an anaerobic tank and an aerobic tank running in series, wherein the anaerobic tank is provided with a flocculation and sedimentation zone and a filter material reactor from bottom to top, and filter material is arranged in the filter material reactor; a conical inner cylinder is arranged at the top of the flocculation and sedimentation zone, a conical outer cylinder is arranged at the outlet of the conical inner cylinder, an annular baffle is arranged at the outer side of the conical inner cylinder and the conical outer cylinder, the upper part of the conical inner cylinder is connected to a water inlet pipe, and the upper part of the water inlet pipe is connected to a dosing pipe; a filter plate is arranged at the bottom of the filter material reactor, and the filter plate is longitudinally two-dimensionally arranged at the bottom of the filter material reactor. The inner support rod is fixed vertically on the side, the outer side of the inner support rod is sleeved with the outer support rod, the filter plate one is hinged to the filter plate two on both sides in the horizontal direction, the middle part of the filter plate two is hinged to the connecting rod, the top of the connecting rod is hinged to the outer support rod, the support plates are evenly fixed on the outer side of the filter plate two in the horizontal direction, and the filter screen is fixed between the support plates and on the top; a filter material reactor is arranged on the upper part of the aerobic tank, and an aeration pipe is arranged on the lower part of the aerobic tank; the overflow port on the upper side of the anaerobic tank is connected to the water inlet at the bottom of the aerobic tank through a pipeline; a mud discharge pipe is arranged at the bottom of the anaerobic tank.

[0008] Furthermore, the extension line of the water inlet pipe is tangent to the inner side of the upper end surface of the conical inner cylinder.

[0009] Furthermore, a spur rack and a gear matching with the spur rack are arranged on the outer side of the upper part of the outer support rod, and the rotating motor drives the gear to rotate.

[0010] Furthermore, the filter material includes a suspension bracket and a fiber composite filter material fixed on the suspension bracket, the suspension bracket includes a central pillar, a V-shaped frame 1 is evenly fixed on the circumference of the central pillar, a V-shaped frame 2 is matchedly arranged on the inner side of the V-shaped frame 1, and the fiber composite filter material is fixed between the V-shaped frame 1 and the V-shaped frame 2.

[0011] Furthermore, positioning columns are symmetrically arranged on the inner side of the outer periphery of the first V-shaped frame, positioning grooves are arranged at corresponding positions of the second V-shaped frame, and through holes are arranged on the fiber composite filter material at positions corresponding to the positioning columns.

[0012] Furthermore, the fiber composite filter material is prepared by the following steps:

[0013] (1) Basalt fiber, cotton fiber and polyphenylene sulfide fiber are mixed in a ratio of 1:1:1-2 by weight to prepare a filter mesh;

[0014] (2) Add chitosan to 3-4 vol% acetic acid solution to prepare a 5-6% chitosan solution, then immerse the filter mesh in the chitosan solution for 5-8 minutes, roll and dry to obtain the product.

[0015] Furthermore, montmorillonite is also added to the chitosan solution in step (2), and the weight ratio of montmorillonite to chitosan is 1:1-2.

[0016] The beneficial effects of the present invention are:

[0017] 1. The present invention discloses a municipal rainwater and sewage ecological circulation system, wherein a flocculation and sedimentation zone is arranged at the lower part of the anaerobic tank, and the flocculation and sedimentation zone includes a conical inner cylinder and a conical outer cylinder from top to bottom. Water and flocculants form a vortex along the inner wall of the conical inner cylinder and flow down to the conical outer cylinder, and then flow upward through the space between the conical inner cylinder and the conical outer cylinder, and gradually settle through the annular baffles arranged in a staggered manner. The flocculation and sedimentation zone has a simple structure and a good sedimentation effect.

[0018] 2. A filter reactor is set on the top of the anaerobic tank and the aerobic tank, and a filter plate 1 is set in the middle of the bottom of the filter reactor, wherein the cross section of the filter plate 1 is a rectangular structure, and the inner support rods are vertically fixed at the symmetrical positions on both sides of the longitudinal direction of the filter plate 1, and the outer support rods are sleeved on the outer side of the inner support rods. The filter plate 1 is hinged to the filter plate 2 on both sides of the transverse direction, and the middle part of the filter plate 2 is hinged to the connecting rod, and the top of the connecting rod is hinged to the outer support rod. The support plate is evenly fixed on the periphery of the filter plate 2, and the filter screen is fixed between the two support plates and at the top. The function of the filter screen is to limit the filter material in the filter reactor. A straight rack and a matching gear are set on the outer side of the upper part of the outer support rod, and the rotating motor drives the gear to rotate. At the same time, the rotating motors on both sides are driven to rotate, which can drive the outer support rods on both sides to move upward, thereby driving the filter plate 2 to fold inward. On the one hand, this structure is convenient for collecting the filter material; on the other hand, the filter material is concentrated and reversed, which can increase the flushing efficiency and reduce energy consumption.

[0019] 3. The filter material includes a suspension bracket and a fiber composite filter material fixed on the suspension bracket. The suspension bracket includes a central pillar. The outer periphery of the central pillar is evenly fixed with a V-frame 1. The inner side of the V-frame 1 is matched with a V-frame 2. The fiber composite filter material is fixed between the V-frame 1 and the V-frame 2. The specific fixing method is: positioning columns are symmetrically arranged on the inner side of the outer periphery of the V-frame 1, and positioning grooves are arranged at corresponding positions of the V-frame 2. The fiber composite filter material is placed between the V-frame 1 and the V-frame 2, and then the positioning columns are inserted into the positioning grooves to fix the fiber composite filter material. This structure has a large adsorption area, excellent adsorption effect, and is easy to rinse and convenient for recycling.

[0020] 4. Fix the fiber composite filter material on the suspension bracket. The fiber composite filter material is made of basalt fiber, cotton fiber and polyphenylene sulfide fiber. It has high strength, rough surface, gaps, and easy film formation. It has a large contact area with rainwater and sewage, strong pollution interception ability, and the structure is easy to wash and can be reused repeatedly.

[0021] After the filter mesh is impregnated in chitosan, a small amount of montmorillonite is added to the chitosan, and a layer of chitosan film is loaded on the filter mesh. The chitosan surface has a large number of active groups, which can increase the adsorption performance of ammonia nitrogen, and a small amount of montmorillonite can improve the mechanical properties of the membrane, increase the roughness of the fiber surface, and further increase the adsorption performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of the structure of the municipal rainwater and sewage ecological circulation system of the present invention;

[0023] Figure 2 It is a schematic diagram of the top view of the water inlet pipe and the conical inner cylinder;

[0024] Figure 3 It is a structural schematic diagram of the bottom of the filter material reactor;

[0025] Figure 4 It is a schematic diagram of the structure after the filter plate 2 is folded inward;

[0026] Figure 5 It is a structural schematic diagram of the suspension bracket;

[0027] Figure 6 It is a schematic diagram of the structure of fixing the fiber composite filter material on the suspension bracket;

[0028] Figure 7 Schematic diagram of the application test.

[0029] In the figure: 1-anaerobic tank, 2-aerobic tank, 3-conical inner cylinder, 4-conical outer cylinder, 5-annular baffle, 6-water inlet pipe, 7-dosing pipe, 8-filter material reactor, 9-filter plate one, 10-inner support rod, 11-outer support rod, 12-filter plate two, 13-connecting rod, 14-support plate, 15-filter screen, 16-aeration pipe, 17-sludge discharge pipe, 18-spur rack, 19-gear, 20-rotating motor, 21-central pillar, 22-V-frame one, 23-V-frame two, 24-fiber composite filter material. DETAILED DESCRIPTION

[0030] The present invention will be further described below in conjunction with the accompanying drawings and embodiments. Example 1

[0031] like Figure 1-4 As shown, a municipal rainwater and sewage ecological circulation system includes an anaerobic tank 1 and an aerobic tank 2 which are operated in series. The anaerobic tank 1 is provided with a flocculation sedimentation area and a filter material reactor 8 from bottom to top, and filter material is arranged in the filter material reactor 8.

[0032] The upper part of the flocculation and sedimentation zone is provided with a conical inner cylinder 3, and the outer periphery of the conical inner cylinder 3 is fixed to the inner wall of the anaerobic tank 1 through a grid plate. The outlet of the lower part of the conical inner cylinder 3 is a conical outer cylinder 4, and an annular baffle 5 is staggered between the outer side of the conical inner cylinder 3 and the conical outer cylinder 4. The upper part of the conical inner cylinder 3 is connected to a water inlet pipe 6, and the water inlet pipe 6 is connected to a dosing pipe 7, wherein the extension line of the water inlet pipe 6 is tangent to the inner side of the upper end surface of the conical inner cylinder 3 (such as Figure 2 As shown), the incoming water can form a vortex along the inner wall of the conical inner cylinder 3, thereby increasing the mixing effect of the water body and the flocculant.

[0033] The bottom structure of the filter reactor 8 is as follows: Figure 3 As shown, a filter plate 9 is arranged in the middle, and two inner support rods 10 are vertically fixed at symmetrical positions on both sides of the filter plate 9 in the longitudinal direction, and the outer side of the inner support rods 10 is sleeved with the outer support rods 11, and the filter plate 19 is hinged to the filter plate 2 12 on both sides of the lateral direction, and the middle part of the filter plate 2 12 is hinged to the connecting rod 13, and the top end of the connecting rod 13 is hinged to the outer support rod 11. Two inner support rods 10 are arranged, which can increase the stability of supporting the filter plate 2 12.

[0034] Three support plates 14 are evenly fixed on the sides of the filter plate 12, and a filter screen 15 is fixed between the support plates 14 to form a side enclosure. In addition, a layer of filter screen 15 is fixed on the top of all the support plates 14, which is used to limit the filter material in the filter material reactor 8; the support plate 14 and the connecting rod 13 are staggered to prevent the position of the filter plate 12 from being limited when it is folded inward (such as Figure 3 as shown).

[0035] A filter reactor 8 is arranged at the upper part of the aerobic tank 2, and an aeration pipe 16 is arranged at the lower part of the aerobic tank; the overflow port at the upper side of the anaerobic tank 1 is connected to the water inlet at the bottom of the aerobic tank 2 through a pipeline; a mud discharge pipe 17 is arranged at the bottom of the anaerobic tank 1, and a water outlet is arranged at the upper side of the aerobic tank 2.

[0036] A spur rack 18 and a gear 19 matching the spur rack 18 are arranged on the outer side of the upper part of the outer support rod 11 , and a rotary motor 20 drives the gear 19 to rotate.

[0037] The rainwater and sewage overflowing from the interception well, after filtering out large particles through the grid, enter the conical inner cylinder 3 through the water inlet pipe 6, and the flocculant enters through the dosing pipe 7. Since the extension line of the water inlet pipe 6 is tangent to the inner side of the upper end surface of the conical inner cylinder 3, the flocculant and the rainwater and sewage swirl into the conical inner cylinder 3, and then swirl down through the conical inner cylinder 3, fully mixed, and descend to the conical outer cylinder 4 for further mixing, and then ascend through the space between the conical inner cylinder 3 and the conical outer cylinder 4, and gradually settle through the staggered annular baffles 5.

[0038] The clarified liquid continues to flow upward to the filter media reactor 8 for anaerobic reaction, and the sludge at the bottom is processed in the next step through the sludge discharge pipe 17; the rainwater and sewage after anaerobic reaction enter the aerobic tank 2 through the overflow port on the upper side of the anaerobic tank 1 for aerobic reaction, and the rainwater and sewage after aerobic treatment flows out through the outlet on the upper side of the aerobic tank 2 or flows back to the anaerobic tank 1 for circulation treatment.

[0039] The filter material reactor 8 of the present application has support plates 14 evenly fixed on the sides, and filter screens are fixed between the support plates 14 on the sides. In addition, a filter screen is also fixed on the top of the support plate 14. The filter material is placed in the area within the filter screen to form a reaction zone to prevent the filter material from being lost. In addition, the support plate 14 is designed to be staggered with the connecting rod 13 in the horizontal direction to prevent the connecting rod 13 and the support plate 14 from influencing each other when the filter plate 12 is folded inward. A backwashing device is provided on the top of the filter material reactor 8. When the filter material needs to be backwashed, the two rotating motors 20 on both sides of the longitudinal direction are controlled to drive the gear 19 to rotate, drive the outer support rod 11 to move upward, and thus drive the filter plate 12 to fold inward. Figure 4 As shown, the filter media are concentrated for backwashing, which can reduce the energy consumption of backwashing; furthermore, during the inward folding of the filter plate, the filter media is turned over to increase the efficiency of backwashing.

[0040] The filter material in this embodiment is PP porous rotating spherical suspended filler with a diameter of 80 mm and built-in fiber balls. Example 2

[0041] like Figure 5-6 As shown, the filter material includes a suspension bracket and a fiber composite filter material 24 fixed on the suspension bracket. The suspension bracket includes a central pillar 21. A V-frame 1 22 is evenly fixed on the periphery of the central pillar 21. A V-frame 23 is matched inside the V-frame 1 22. The fiber composite filter material 24 is fixed between the V-frame 1 22 and the V-frame 23.

[0042] Positioning columns are symmetrically arranged on the inner side of the outer periphery of the V-shaped frame 1 22, positioning grooves are arranged at corresponding positions of the V-shaped frame 23, and through holes are arranged on the fiber composite filter material 24 at positions corresponding to the positioning columns for positioning the fiber composite filter material 24. The suspension bracket in this application is made of polypropylene.

[0043] The fiber composite filter material 24 is prepared by the following steps:

[0044] (1) Basalt fiber, cotton fiber and polyphenylene sulfide fiber are mixed in a ratio of 1:1:1 by weight to prepare a filter mesh, wherein basalt fiber: 1.86 dtex, 2.63 g / cm 3 , polyphenylene sulfide fiber: 2.40dtex, 1.35g / cm 3 , cotton fiber: 1.40dtex, length 25-35mm.

[0045] The preparation method adopts the traditional needle punching process, and is made through the processes of opening, combing, laying, pre-punching, main-punching and calendering. The prepared filter mesh has a thickness of 1.5 mm and a square meter mass of 220 g / m 2 ;

[0046] (2) Chitosan was added to a 3.5 vol% acetic acid solution to prepare a 6% chitosan solution, and then the filter mesh was immersed in the chitosan solution for 5 minutes, rolled and dried at 100°C to obtain the product.

[0047] In step (2), montmorillonite is also added to the chitosan solution, wherein the weight ratio of montmorillonite to chitosan is 1:1. Example 3

[0048] The difference between Example 3 and Example 2 is that:

[0049] The fiber composite filter material 24 is prepared by the following steps:

[0050] (1) Basalt fiber, cotton fiber and polyphenylene sulfide fiber are mixed in a ratio of 1:1:2 by weight to prepare a filter mesh;

[0051] (2) Chitosan was added to a 4 vol% acetic acid solution to prepare a 5% chitosan solution, and then the filter mesh was immersed in the chitosan solution for 8 minutes, rolled and dried at 100°C to obtain the product.

[0052] In step (2), montmorillonite is also added to the chitosan solution, wherein the weight ratio of montmorillonite to chitosan is 1:2.

[0053] Application test:

[0054] Two plexiglass columns with a height of 100 cm and an inner diameter of 25 cm, an overflow port at the upper end and a water outlet at the lower end were used to simulate the anaerobic tank and aerobic tank in this application (such as Figure 7 As shown), the adsorption performance of the filter material in this application is tested. A filter plate is set 15 cm away from the bottom of the organic glass column, and 70 cm of the filter material prepared in Example 2 of this application is loaded on the filter plate (the filter material height b is 80 mm, the outer diameter a is 40 mm, and the center pillar radius is 15 mm), and a water outlet is set 8 cm above the top of the anaerobic tank filter material.

[0055] The aerobic pool is first biofilmed before the system is put into operation, and the sludge from the sewage treatment plant is mixed with artificial wastewater (COD300mg / L, TN 35 mg / L, ammonia nitrogen (NH4 + -N) 25 mg / L, TP 7 mg / L) are mixed evenly in a volume ratio of 1:1, and poured into the aerobic tank from the top until the mixture covers the filter surface. Then, aeration begins with an air intake of 10 L / h. After continuous aeration for 8 hours, stop aeration for 1 hour. Discharge half of the mixture every 24 hours and add artificial wastewater. After 5 days of aeration, drain the muddy water in the reactor.

[0056] The test water was pumped into the system, and the inlet water concentration was: COD 300 mg / L, TN 35 mg / L, ammonia nitrogen (NH4 +-N) 25 mg / L, TP 7 mg / L, HRT is 12h, and the air-water ratio of the aerobic pool is 3:1.

[0057] After the system is stable, the filter material in Example 2 of the present application is tested to have a TP removal rate of 96.4%, a COD removal rate of 95.8%, a TN removal rate of 83.6%, and an ammonia nitrogen removal rate of 93.7%, with excellent performance.

[0058] Due to the special structure of the filter material, the backwash frequency can be set to once every 7 days, air washing: 25 L / (m 2 ·s), 4-5min; water washing 6.00 L / (m 2 ·s), 4-5min, after 24h of backwashing, the removal rates of TP, COD, TN and ammonia nitrogen can reach 90.1%, 88.4%, 70.5% and 71.3% respectively. The adsorption performance recovers quickly and can be maintained at the high level before flushing in 2-3d, with strong pollutant treatment capacity.

[0059] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Other modifications or equivalent substitutions made to the technical solution of the present invention by ordinary technicians in the field should be included in the scope of the claims of the present invention as long as they do not depart from the spirit and scope of the technical solution of the present invention.

Claims

1. A municipal rainwater and sewage ecological circulation system, characterized by: The invention comprises an anaerobic tank (1) and an aerobic tank (2) which are operated in series. The anaerobic tank (1) is provided with a flocculation and sedimentation zone and a filter material reactor (8) from bottom to top. Filter material is arranged in the filter material reactor (8). A conical inner cylinder (3) is arranged at the top of the flocculation and sedimentation zone. A conical outer cylinder (4) is arranged at the outlet of the conical inner cylinder (3). An annular baffle (5) is arranged between the outer side of the conical inner cylinder (3) and the inner side of the conical outer cylinder (4). The upper part of the conical inner cylinder (3) is connected to a water inlet pipe (6). The upper part of the water inlet pipe (6) is connected to a dosing pipe (7). A filter plate (9) is arranged at the bottom of the filter material reactor (8). Inner support rods (10) are vertically fixed on both sides of the filter plate (9). The outer side of the inner support rod (10) is sleeved with the outer support rod (11); the two sides of the filter plate 1 (9) are hinged to the filter plate 2 (12); the middle of the filter plate 2 (12) is hinged to the connecting rod (13); the top of the connecting rod (13) is hinged to the outer support rod (11); the outer side of the filter plate 2 (12) is evenly fixed with a support plate (14); a filter screen (15) is fixed between and at the top of the support plates (14); a filter material reactor (8) is arranged at the upper part of the aerobic tank (2); an aeration pipe (16) is arranged at the lower part of the aerobic tank; an overflow port at the upper side of the anaerobic tank (1) is connected to a water inlet at the bottom of the aerobic tank (2) through a pipeline; and a mud discharge pipe (17) is arranged at the bottom of the anaerobic tank (1).

2. A municipal rainwater and sewage ecological circulation system according to claim 1, characterized in that: The extension line of the water inlet pipe (6) is tangent to the inner side of the upper end surface of the conical inner cylinder (3).

3. A municipal rainwater and sewage ecological circulation system according to claim 1, characterized in that: A spur rack (18) and a gear (19) matching the spur rack are arranged on the outer side of the upper portion of the outer support rod (11), and a rotating motor (20) drives the gear to rotate.

4. A municipal rainwater and sewage ecological circulation system according to claim 1, characterized in that: The filter material comprises a suspension support and a fiber composite filter material (24) fixed on the suspension support, the suspension support comprises a central pillar (21), a V-shaped frame 1 (22) is uniformly fixed in the circumferential direction of the outer periphery of the central pillar (21), a V-shaped frame 2 (23) is matchedly arranged inside the V-shaped frame 1 (22), and the fiber composite filter material (24) is fixed between the V-shaped frame 1 (22) and the V-shaped frame 2 (23).

5. A municipal rainwater and sewage ecological circulation system according to claim 4, characterized in that: Positioning columns are symmetrically arranged on the inner side of the outer periphery of the first V-shaped frame (22) in the upper and lower parts, positioning grooves are arranged at corresponding positions of the second V-shaped frame (23), and through holes are arranged on the fiber composite filter material (24) at positions corresponding to the positioning columns.

6. A municipal rainwater and sewage ecological circulation system according to claim 4, characterized in that: The fiber composite filter material (24) is prepared by the following steps: (1) Basalt fiber, cotton fiber and polyphenylene sulfide fiber are mixed in a ratio of 1:1:1-2 by weight to prepare a filter mesh; (2) Add chitosan to 3-4 vol% acetic acid solution to prepare a 5-6% chitosan solution, then immerse the filter mesh in the chitosan solution for 5-8 minutes, roll and dry to obtain the product.

7. A municipal rainwater and sewage ecological circulation system according to claim 6, characterized in that: Montmorillonite is also added to the chitosan solution in step (2), and the weight ratio of the montmorillonite to the chitosan is 1:1-2.

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