Rainwater treatment device and rainwater treatment method

Abstract

The present invention discloses a rainwater treatment device and a rainwater treatment method. The rainwater treatment device includes a rainwater gutter, an adjustable power supply, an electric flocculation reactor, a normally open electromagnetic water valve and a ceramic membrane; the device also includes an aeration pipe, which is arranged on a pipe between the electric flocculation reactor and the normally open electromagnetic water valve, and the ceramic membrane is located in a pipe joint behind the electromagnetic water valve; the present invention uses a gravity-driven electric flocculation method to treat rainwater, which has a better floc formation rate than traditional electric flocculation, and can prevent the cathode from generating an oxide film during the reverse aeration process, effectively ensuring the stability of the water flux and extending the service life of the electric flocculation reactor; in addition, combined with the strong mechanical properties and stable chemical properties of the ceramic membrane, the water outlet at the end of the electric flocculation is directly connected to the ceramic membrane for membrane filtration, thereby achieving a fast and convenient water purification and production effect; and in actual use, the device uses the gravity of the water body itself as a driving force, saving energy consumption.

Description

Technical Field

[0001] The present invention relates to the technical field of water treatment, in particular to a rainwater treatment device and a rainwater treatment method. The rainwater treatment device is a pipeline pulse reverse aeration mixed electric flocculation ceramic membrane microfiltration device and a water treatment method using the device. Background Art

[0002] Electrocoagulation is a highly efficient water treatment method that has the advantages of low sludge production, easy solid-liquid separation, no need for external chemicals, and little secondary pollution. The reaction principle is to use metals such as aluminum and iron as anodes. Under the action of direct current, the anodes are corroded to produce Al 3+ 、Fe 2+ Plasma, these ions undergo a series of hydrolysis, polymerization and ferrous oxidation processes, developing into various hydroxyl complexes, polynuclear hydroxyl complexes and even hydroxides. These products help to condense and precipitate colloidal and suspended impurities in sewage, thereby achieving water purification.

[0003] Chinese patent CN210736283U provides an electric flocculation reactor for high-efficiency hydraulic mixing flocculation, which includes an electric flocculation box and an electric flocculation power supply; the electric flocculation box is provided with an electric flocculation reaction zone and a hydraulic flocculation zone separated by a first partition, the electric flocculation reaction zone is provided with a water inlet, the electric flocculation reaction zone is provided with a metal anode plate and a metal cathode plate, the metal anode plate and the metal cathode plate are provided with honeycomb-shaped through holes, and the positive and negative poles of the electric flocculation power supply are electrically connected to the metal anode plate and the metal cathode plate respectively; a water outlet is provided in the hydraulic flocculation zone, and a second partition, a third partition, a fourth partition and a fifth partition are provided in sequence between the first partition and the water outlet in the hydraulic flocculation zone, the upper parts of the first partition, the third partition and the fifth partition are provided with upper flow holes, and the lower parts of the second partition and the fourth partition are provided with lower flow holes.

[0004] Chinese patent CN207713466U provides an electro-flocculation high-density clarifier. This patent uses the flocculation principle to concentrate and separate pollutants in the water, returning the enriched sludge to the mixing tank. The netting and adsorption effects of the returned sludge and electro-flocculation are used to enhance the adsorption and sedimentation of suspended matter in the water. The conventional method of directly adding flocculants and stirring is improved to synthetic mixing through electro-flocculation, which increases the contact area of ​​the reaction, accelerates the flocculation reaction process, saves time, reduces the volume of the structure, and ultimately improves the water output.

[0005] However, in the above patent, the electrocoagulation effect is limited by the residence time, and during long-term use, an impermeable oxide film may form on the cathode, resulting in a loss of electrocoagulation efficiency.

[0006] Ceramic membranes feature high mechanical strength, low energy consumption, strong pollution resistance, and a long service life. They are also widely used in rainwater purification, utilizing the water's own pressure to filter water, achieving low energy consumption. While ensuring effective water purification, electro-flocculation reduces membrane fouling and maintains a stable, high water volume. Summary of the Invention

[0007] In order to solve the problems existing in the above-mentioned prior art, in view of the shortcomings of the existing electric flocculation device and the advantages of ceramic membranes, the main purpose of this application is to provide a pipeline pulse reverse aeration mixed electric flocculation ceramic membrane microfiltration device. In combination with electric flocculation, on the premise of good flocculation effect in rainwater treatment, it is proposed to use gravity drive and use a solenoid valve to control the hydraulic retention time to avoid the formation of an impermeable oxide film on the cathode, increase the collision opportunity of the electric flocculation floc particles, and thus better produce flocs; in addition, the water after electric flocculation is further filtered through the ceramic membrane. As an integrated device, it achieves the purpose of processing and purifying from the source to the direct use of effluent, which can effectively purify rainwater and ensure the effluent water volume.

[0008] In a first aspect, the present application provides a pipeline pulse reverse aeration mixed electric flocculation ceramic membrane microfiltration device for rainwater treatment, comprising: a rainwater bucket (1), an aeration tube (4), and an electric flocculation reactor (3).

[0009] Furthermore, an adjustable power supply (2) is provided, and the adjustable power supply (2) is configured to adjust the current density of the electric flocculation reactor (3).

[0010] Furthermore, a normally open electromagnetic water valve (5) is provided, and the normally open electromagnetic water valve is configured to control the electric flocculation reaction time.

[0011] Furthermore, an electric flocculation reactor (3) is provided below the rain gutter (1), the electric flocculation reactor (3) is electrically connected to the adjustable power supply (2), a normally open electromagnetic water valve (5) is connected to the pipe wall below the electric flocculation reactor (3), the aeration pipe (4) is provided on the pipe between the electric flocculation reactor (3) and the normally open electromagnetic water valve (5), the outlet end of the normally open electromagnetic valve is provided with a connecting pipe, and a ceramic membrane (7) is arranged in the connecting pipe.

[0012] Furthermore, the electric flocculation reactor (3) comprises: a first water pipe joint (301), a second water pipe joint (302), and a metal electrode plate, wherein the first water pipe joint (301) and the second water pipe joint (302) are used to fix the metal electrode plate, and the first water pipe joint (301) and the second water pipe joint (302) have an enlarged portion, and the enlarged portion is used to fix the metal electrode plate.

[0013] Furthermore, the electro-flocculation reactor (3) is provided with a first through hole (305) and a second through hole (306), and the metal electrode plate is electrically connected to the adjustable power supply (2) through the first through hole (305) and the second through hole (306), and the adjustable power supply adjusts the electro-flocculation current to 2-4 mA / cm 2 .

[0014] Furthermore, a branch pipe (6) for sampling and testing water quality is provided between the first water pipe joint (301) and the second water pipe joint (302).

[0015] Furthermore, an aeration hole (307) is provided between the electric flocculation reactor (3) and the normally open electromagnetic water valve (5), and the aeration pipe (4) is connected to the electric flocculation reactor (3) via the aeration hole (307).

[0016] Furthermore, dense small holes are provided on the metal electrode plate. Preferably, the diameter of the dense small holes is 2 mm, and the porosity of the dense small holes is 28.2%.

[0017] Furthermore, a normally open electromagnetic water valve (5) is provided between the third water pipe joint (501) and the fourth water pipe joint (502), a fifth water pipe joint joint (701) is connected behind the normally open electromagnetic water valve (5), and a ceramic membrane (7) is placed on the fifth water pipe joint joint (701).

[0018] In a second aspect, the present application provides a method for treating rainwater using the device described in the first aspect, the method comprising the following steps:

[0019] 1) Collect rainwater into the rainwater bucket and enter the electric flocculation reactor;

[0020] 2) Adjust the current density of the electro-flocculation reactor and the normally open electromagnetic water valve to control the electro-flocculation time to complete the electro-flocculation process and obtain the electro-flocculated rainwater;

[0021] 3) Step 3) The rainwater after the electro-flocculation flows into the ceramic membrane for filtration to obtain treated rainwater.

[0022] The current density of the electrocoagulation reactor in step 2) is 2-4 mA / cm 2 , the electric flocculation time is 10-20min.

[0023] Furthermore, in step 2), the rainwater UV 254 The removal rate is 20%-38.7%.

[0024] Furthermore, the device is operated in a pulsed mode, and the membrane flux is measured at an instantaneous constant pressure state of 1 meter head. The membrane flux of the electroflocculation-ceramic membrane group and the ceramic membrane group has a significant downward trend in the first 24 hours. The flux of the electroflocculation-ceramic membrane group of this device is 129.808 L / (m 2 h) (hereinafter referred to as "LMH") decreased to 77.984 LMH;

[0025] Furthermore, on the 12th day of operation, the membrane flux gradually and steadily decreased, and the membrane flux of the electrocoagulation-ceramic membrane group dropped to 19.88 LMH.

[0026] Furthermore, when the system was in operation for 30 days, the membrane flux of the electrocoagulation-ceramic membrane group dropped to 12.75LMH.

[0027] Furthermore, under the operating condition that the turbidity of rainwater is 16.3±0.83 NTU, the turbidity of the effluent after treatment by the electro-flocculation-ceramic membrane group of the present invention is less than 0.2 NTU, and the current density of the electro-flocculation is 2-4 mA / cm 2 , the electrocoagulation residence time is 10-20min.

[0028] Furthermore, the test showed that the device has a high purification efficiency for humus macromolecules and aromatic compounds; the UV radiation of simulated roof rainwater 254 It is about 0.045±0.007, and the water output of this device is 0.020±0.005.

[0029] Compared with the prior art, the beneficial effects of this application are:

[0030] (1) The present invention utilizes gravity-driven electroflocculation to treat rainwater. Compared with conventional electroflocculation, the present invention has a better floc formation rate, thereby achieving a better pretreatment effect. In actual use, the gravity of the water body itself is used as the driving force, saving energy. In addition, the reverse aeration process can prevent the cathode from producing an oxide film, effectively ensuring the stability of the water flux and extending the service life of the electroflocculation reactor.

[0031] (2) Compared with ordinary organic low-pressure membranes, ceramic membranes have stronger mechanical strength and longer service life. When treating rainwater, they can adapt to large rainfall and withstand hydraulic shock loads. They are not prone to rupture and can filter out water under low head conditions. Therefore, in actual use, gravity drive can be used to achieve low-energy membrane filtration of water.

[0032] (3) When the present invention is used to treat rainwater, the membrane life can be extended and the cleaning cycle of the device can be extended. Compared with the group using only ceramic membranes, the 24-hour residual membrane flux is twice the membrane flux of the ceramic membrane alone, the 12-day residual membrane flux is 6.5 times the membrane flux of the ceramic membrane alone, and the 30-day membrane flux is 7.68 times that of the ceramic membrane group alone.

[0033] (4) The purification efficiency of the present invention for humic macromolecules and aromatic compounds is 4.27 times higher than that of the control group with a single ceramic membrane. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a schematic structural diagram of the pipeline pulse reverse aeration mixed electro-flocculation ceramic membrane microfiltration device of the present invention;

[0035] Figure 2 This is a schematic structural diagram of the reverse aeration and hydraulic mixing electro-flocculation reactor of the present invention;

[0036] Figure 3 This is a schematic diagram of the structure of a ceramic membrane microfiltration device;

[0037] Figure 4 This is a relationship diagram between the residence time, current density, and UV254 removal rate of the present invention;

[0038] Figure 5 This is a schematic diagram of membrane flux and time changes in a constant pressure state of 1 meter water head according to the present invention;

[0039] Figure 6 This is a graph showing the turbidity of raw water, ceramic membrane device and outlet water of the present invention and their time changes;

[0040] Figure 7 Schematic diagram of raw water, ceramic membrane device and UV254 and time changes of the device;

[0041] Figure 8 Schematic diagram of the total hydraulic membrane resistance Rt of the electrocoagulation-ceramic membrane group and the total hydraulic membrane resistance of the control group.

[0042] In the figure: 1. Rain gutter; 2. Adjustable power supply; 3. Electric flocculation reactor; 301. First water pipe joint; 302. Second water pipe joint; 303. Metal anode plate; 304. Metal cathode plate; 305. First through hole; 306. Second through hole; 307. Aeration hole; 4. Aeration pipe; 5. Normally open electromagnetic water valve; 501. Third water pipe joint; 502. Fourth water pipe joint; 6. Branch pipe; 7. Ceramic membrane; 701. Fifth water pipe joint joint. DETAILED DESCRIPTION

[0043] For a better understanding of the present invention, the following examples are provided to further illustrate the present invention, but the content of the present invention is not limited to the following examples. Example 1

[0044] See also Figure 1-7 , the present invention provides a technical solution for a rainwater treatment device:

[0045] like Figure 1 、 Figure 2 、 Figure 3 As shown:

[0046] The rainwater treatment device is a pipeline pulse reverse aeration mixed electric flocculation ceramic membrane microfiltration device, comprising a rainwater bucket (1), an adjustable power supply (2), an electric flocculation reactor (3), an aeration pipe (4), and a normally open electromagnetic water valve (5); an electric flocculation reactor (3) is provided below the rainwater bucket (1), the electric flocculation reactor (3) is connected to the adjustable power supply (2), an aeration pipe (4) is connected to the pipe wall below the electric flocculation reactor (3), and a normally open electromagnetic water valve (5) is connected to the pipe below the aeration pipe (4), and a connecting pipe is provided at the outlet end of the normally open electromagnetic valve, and a ceramic membrane (7) is arranged in the connecting pipe.

[0047] The rainwater gutter (1) is used to collect rainwater and serves as the water inlet of the entire device. The adjustable power supply (2) supplies power to the electric flocculation reactor (3) and adjusts the current. The electric flocculation reactor (3) is used for electric flocculation to purify the water body. The aeration pipe (4) is used to aerate the water body in the electric flocculation reactor (3). The normally open electromagnetic water valve (5) is used to control the hydraulic retention time.

[0048] In this embodiment, the adjustable power supply (2) can change the current density. The larger the current density, the more flocs are produced, and the higher the electro-flocculation efficiency. However, too high a current density can easily cause excessive polarization of the electrode, accelerate electrode passivation, and increase the consumption of the electrode plate and electricity. Therefore, the adjustable power supply (2) is used to achieve the maximum electro-flocculation efficiency and improve the electro-flocculation efficiency. At the same time, the size of the electro-flocculation density affects the subsequent filtration effect of the ceramic membrane. The appropriate electro-flocculation density will have a positive impact on the filtration effect.

[0049] The electric flocculation reactor (3) comprises a first water pipe joint (301), a second water pipe joint (302), a metal anode plate (303), a metal cathode plate (304), a first through hole (305), and a second through hole (306); the metal anode plate (303) is embedded in the first water pipe joint (301), and the metal cathode plate (304) is embedded in the second water pipe joint (302); the metal anode plate (303) is electrically connected to the positive electrode of the adjustable external power supply (2) through the first through hole (305), and the metal cathode plate (304) is electrically connected to the negative electrode of the adjustable external power supply (2) through the second through hole (306); after the power is turned on, under the action of direct current, the anode is corroded to produce Fe 2+ Ions, after a series of hydrolysis, polymerization and ferrous oxidation processes, develop into various hydroxyl complexes, polynuclear hydroxyl complexes and even hydroxides, which cause the colloidal impurities and suspended impurities in the sewage to condense and precipitate and separate, achieving the effect of purifying the water.

[0050] An aeration hole (307) is provided on the pipe wall between the electric flocculation reactor (3) and the normally open electromagnetic water valve (5), and the aeration pipe (4) aerates the water in the electric flocculation reactor (3) through the aeration hole (307).

[0051] The metal anode plate (303) and the metal cathode plate (304) are provided with dense small holes to increase the contact area between the raw water and the metal sheet, thereby enabling a full electric flocculation reaction and enhancing floc formation.

[0052] In this embodiment, the normally open electromagnetic water valve (5) can control the hydraulic retention time. When the normally open electromagnetic water valve (5) is energized, the valve will be closed, allowing the electro-flocculation reactor (3) to fully react. The normally open electromagnetic water valve (5) is controlled by a timer switch. When the power is cut off, the normally open electromagnetic water valve (5) opens. After the electro-flocculation treatment, the rainwater enters the ceramic membrane (7) of the outlet pipe by gravity. The electro-flocculation frequency is adjusted according to the change in the membrane flux of the ceramic membrane (7), and the pollutants are effectively separated by membrane filtration through the water body's own gravity.

[0053] In this embodiment, a branch pipe (6) is further provided. The branch pipe (6) is arranged between the two stages of the electric flocculation reactor (3) and is used for sampling and testing water quality.

[0054] The specific working process is as follows: after rainwater is collected and collected into the rainwater bucket (1), under the action of gravity, the rainwater flows from the rainwater bucket (1) into the electric flocculation reactor (3), and the adjustable power supply (2) supplies power to the electric flocculation reactor (3), so that the electric flocculation reactor (3) performs electric flocculation. At the same time, the adjustable power supply (2) can adjust the current density to control the electric flocculation effect, and cooperate with the normally open electromagnetic water valve (5). When the electric flocculation work is completed, the lower end of the electric flocculation reactor (3) controls the water outlet through the normally open electromagnetic water valve (5), and the normally open electromagnetic water valve (5) controls the opening valve. After the electric flocculation, the raw water flows into the ceramic membrane (7) through the outlet pipe under the action of gravity for membrane filtration; at the same time, a branch pipe (6) is provided in the electric flocculation reactor (3) to sample and test the water quality. Example 2

[0055] A method for treating rainwater using the device described in Example 1,

[0056] The method comprises the following steps:

[0057] 1) Collect rainwater into the rainwater bucket and enter the electric flocculation reactor;

[0058] 2) Adjust the current density of the electro-flocculation reactor and the normally open electromagnetic water valve to control the electro-flocculation time to complete the electro-flocculation process and obtain the electro-flocculated rainwater;

[0059] 3) Step 3) The rainwater after the electro-flocculation flows into the ceramic membrane for filtration to obtain treated rainwater.

[0060] The current density of the electrocoagulation reactor in step 2) is 3 mA / cm 2 , the electric flocculation time is 15 minutes.

[0061] In step 2) the rainwater UV after electrocoagulation 254 The removal rate is 38.7%.

[0062] The device is operated in a pulse mode. The membrane flux is measured at an instantaneous constant pressure state of 1 meter head. The membrane flux of the electroflocculation-ceramic membrane group and the ceramic membrane group has a significant downward trend in the first 24 hours. The flux of the electroflocculation-ceramic membrane group of this device is 129.808 L / (m 2 h) (hereinafter referred to as "LMH") decreased to 77.984 LMH;

[0063] On the 12th day of operation, the membrane flux gradually and steadily decreased, and the membrane flux of the electrocoagulation-ceramic membrane group dropped to 19.88LMH.

[0064] On the 30th day of system operation, the membrane flux of the electroflocculation-ceramic membrane group dropped to 12.75LMH.

[0065] Under the operating condition that the turbidity of rainwater is 16.3±0.83 NTU, the turbidity of the effluent after treatment by the electro-flocculation-ceramic membrane group of the present invention is less than 0.2 NTU. At this time, the current density of the electro-flocculation is 3 mA / cm 2 , the electrocoagulation residence time is 15min.

[0066] This device has a high purification efficiency for humus macromolecules and aromatic compounds; it simulates the UV 254 The UV of the water discharged by this device is about 0.052. 254 is 0.020. Comparative Example 1

[0067] Comparative Example 1 uses the same ceramic membrane as that in the device of Example 1 to treat rainwater, except that Comparative Example 1 does not include the electrocoagulation treatment step.

[0068] The experimental conditions were the same as those in Example 2, and the rainwater UV 254 The removal rate is 15.5%.

[0069] The device of Comparative Example 1 operates in a pulsed mode, and the membrane flux is measured at an instantaneous constant pressure state of 1 meter head. The membrane flux of the ceramic membrane group shows a significant downward trend in the first 24 hours, and the flux of the ceramic membrane group decreases from 119.542LMH to 36.260LMH.

[0070] On the 12th day of operation, the membrane flux gradually decreased steadily, and the membrane flux of the ceramic membrane group dropped to 3.071 LMH.

[0071] On the 30th day of system operation, the membrane flux of the ceramic membrane group dropped to 1.66 LMH.

[0072] Under the operating condition that the turbidity of rainwater is 16.3±0.83 NTU, the turbidity of the effluent after being treated by the electro-flocculation-ceramic membrane group of the present invention is less than 0.2 NTU.

[0073] UV simulation of roof rain 254 The UV of the water discharged by this device is about 0.052. 254 It is 0.039.

[0074] Comparing Example 2 with Comparative Example 1, compared to the ceramic membrane group without electro-flocculation treatment, the flocs formed by electro-flocculation pre-treatment can promote the agglomeration of humic macromolecules and aromatic compounds in water. This is because these organic substances carry negative charges in water and are captured by the membrane after the electro-flocculation process, thereby enhancing the electro-flocculation-ceramic membrane group to remove UV 254Combined with the removal of turbidity and humic macromolecules, it can be confirmed that this device can achieve good water purification effect. Therefore, it can be seen that this device can still ensure good water purification effect under the condition of high and stable water flux.

[0075] As the experiment progressed, the membrane surface's adsorption of pollutants reached its limit, causing the accumulation of particles on the surface, forming a filter cake layer. As the filtration continued, the filter cake layer gradually thickened. In the later stage of the experiment, the ceramic membrane surface was physically cleaned and wiped with a sponge. The total hydraulic membrane resistance of the two systems was calculated using Darcy's law and the series resistance model. Figure 8 It can be seen that the total hydraulic membrane resistance Rt of this device (electrocoagulation-ceramic membrane group) is 126.43×10 4 m -1 ) was significantly lower than the total hydraulic membrane resistance of the control group (1292.24×10 4 m -1 ), which further confirms that the flocculation process helps to aggregate small molecules in the water into large molecular flocs, reducing membrane fouling, and the pollutant flocs are easy to be removed by hydraulic cleaning.

[0076] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is limited by the appended claims and their equivalents.

Claims

1. A rainwater treatment device, comprising: A rainwater bucket (1), an aeration pipe (4) and an electric flocculation reactor (3); characterized in that: an adjustable power supply (2) is also provided, and the adjustable power supply (2) is configured to adjust the current density of the electric flocculation reactor (3); a normally open electromagnetic water valve (5) is also provided, and the normally open electromagnetic water valve is configured to control the electric flocculation reaction time; An electric flocculation reactor (3) is provided below the rainwater gutter (1), the electric flocculation reactor (3) is electrically connected to the adjustable power supply (2), a normally open electromagnetic water valve (5) is connected to the pipe wall below the electric flocculation reactor (3), the aeration pipe (4) is provided on the pipe between the electric flocculation reactor (3) and the normally open electromagnetic water valve (5), the outlet end of the normally open electromagnetic water valve (5) is provided with a connecting pipe, and a ceramic membrane (7) is arranged in the connecting pipe; The electric flocculation reactor (3) comprises: a first water pipe joint (301), a second water pipe joint (302) and a metal electrode plate, wherein the first water pipe joint (301) and the second water pipe joint (302) are used to fix the metal electrode plate, and the first water pipe joint (301) and the second water pipe joint (302) have an enlarged portion, and the enlarged portion is used to fix the metal electrode plate; The electro-flocculation reactor (3) is further provided with a first through hole (305) and a second through hole (306), and the metal electrode plate is electrically connected to the adjustable power supply (2) through the first through hole (305) and the second through hole (306), and the adjustable power supply can adjust the electro-flocculation current to 2-4 mA / cm 2 ; An aeration hole (307) is provided between the electric flocculation reactor (3) and the normally open electromagnetic water valve (5), and the aeration pipe (4) is connected to the electric flocculation reactor (3) via the aeration hole (307); The metal electrode plate is provided with dense small holes; The electric flocculation reactor (3) further comprises a third water pipe joint (501) and a fourth water pipe joint (502); A normally open electromagnetic water valve (5) is provided between the third water pipe joint (501) and the fourth water pipe joint (502), a fifth water pipe joint joint (701) is connected behind the normally open electromagnetic water valve (5), and a ceramic membrane (7) is placed on the fifth water pipe joint joint (701).

2. A rainwater treatment device according to claim 1, characterized in that: A branch pipe (6) for sampling and testing water quality is also provided between the first water pipe joint (301) and the second water pipe joint (302).

3. A method for treating rainwater using the device according to any one of claims 1 to 2, characterized in that The steps include: 1) Collect rainwater into the rainwater bucket and enter the electric flocculation reactor; 2) Adjust the current density of the electro-flocculation reactor and the normally open electromagnetic water valve to control the electro-flocculation time to complete the electro-flocculation process and obtain the electro-flocculated rainwater; 3) In step 2), the rainwater after the electro-flocculation flows into the ceramic membrane for filtration to obtain treated rainwater.

4. The method according to claim 3, wherein: The current density of the electrocoagulation reactor in step 2) is 2-4 mA / cm 2 , the electric flocculation time is 10-20min.

5. The method according to any one of claims 3 to 4, characterized in that: In step 2) the rainwater UV after electrocoagulation 254 The removal rate is 20%-38.7%.

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