Sewage treatment system

Abstract

The utility model relates to the technical field of sewage treatment, in particular to a sewage treatment system which comprises an ultrafiltration unit, a reverse osmosis unit and a concentrated water treatment unit which are sequentially communicated, the concentrated water treatment unit comprises an ozone generator and an ozone treatment assembly, and the ozone treatment assembly comprises a plurality of ozone oxidation branches. Each ozone oxidation branch is connected in parallel with the ozone generator, and each ozone oxidation branch is connected in parallel with the reverse osmosis unit. The utility model aims to provide the sewage treatment system aiming at at least one technical problem related in the prior art.

Description

Technical Field

[0001] The present application relates to the technical field of sewage treatment, and in particular to a sewage treatment system. Background Art

[0002] As water resources become increasingly scarce, the demand for recycled water technology is gradually increasing. Compared with mature desalination water treatment technologies, brine treatment technology has become a more urgent problem that needs to be solved, especially the removal of COD from the brine after desalination of the tail water of municipal sewage treatment plants. Utility Model Content

[0003] The purpose of this application is to provide a sewage treatment system to address at least one technical problem involved in the background technology.

[0004] In order to achieve the above objectives, this application adopts the following technical solutions:

[0005] The present application provides a sewage treatment system, comprising an ultrafiltration unit, a reverse osmosis unit and a concentrated water treatment unit connected in sequence, wherein the concentrated water treatment unit comprises an ozone generator and an ozone treatment component, and the ozone treatment component comprises a plurality of ozone oxidation branches, each of the ozone oxidation branches being connected in parallel to the ozone generator, and each of the ozone oxidation branches being connected in parallel to the reverse osmosis unit.

[0006] Optionally, the ozone oxidation branch includes an ozone reactor and a check valve, wherein the check valve is connected to the ozone reactor and is located between the ozone reactor and the ozone generator.

[0007] The beneficial effect of this technical solution is that COD in concentrated water is removed in the ozone reactor, and by setting a check valve, ozone sent from the ozone generator is not easily backflowed back into the ozone generator, thereby avoiding damage to the ozone generator caused by this.

[0008] Optionally, the concentrated water treatment unit further includes a first ozone concentration detector and a second ozone concentration detector, and the ozone generator, the first ozone concentration detector, the ozone treatment component and the second ozone concentration detector are connected in series in sequence.

[0009] The beneficial effect of this technical solution is that: in this way, the concentration of ozone sent to each ozone oxidation branch is detected by the first ozone concentration detector, and then it is known whether the ozone concentration meets the requirements; the concentration of ozone sent out from each ozone oxidation branch is detected by the second ozone concentration detector, and then it is judged whether a sufficient reaction has taken place in the ozone reactor based on the reading of the second ozone concentration detector.

[0010] Optionally, the ultrafiltration unit includes an ultrafiltration device, a raw water pool, a raw water pump and a water production pool, and the ultrafiltration unit also includes an inlet pipe, an outlet pipe and a return pipe.

[0011] The ultrafiltration device includes ultrafiltration membrane filaments. The raw water pool is connected to the outside of the ultrafiltration membrane filaments through the water inlet pipe, and the water production pool is connected to the inside of the ultrafiltration membrane filaments through the water outlet pipe. The raw water pool is also connected to the ultrafiltration device through the return pipe to send the circulating water sent from the ultrafiltration device to the raw water pool. The raw water pump is installed on the water inlet pipe.

[0012] The beneficial effect of this technical solution is that it further realizes the filtration of tail water of a municipal sewage treatment plant in an ultrafiltration unit.

[0013] Optionally, the ultrafiltration unit further includes a filter installed on the water inlet pipe, and the filter is located between the raw water pump and the ultrafiltration device.

[0014] Optionally, the ultrafiltration unit further includes an inlet valve, a production water valve and a concentrated water valve, the inlet valve being installed on the water inlet pipe, the inlet valve being located between the filter and the ultrafiltration device, the production water valve being installed on the outlet pipe, and the concentrated water valve being installed on the return water pipe.

[0015] Optionally, the ultrafiltration unit further includes a drug inlet pipe, a cleaning medicine box, a cleaning pump and a drug inlet valve, one end of the drug inlet pipe is connected to the water inlet pipe, and the other end of the drug inlet pipe is connected to the cleaning medicine box, the connection position between the drug inlet pipe and the water inlet pipe is located between the water inlet valve and the ultrafiltration device, the drug inlet valve and the cleaning pump are both installed on the drug inlet pipe, and the cleaning pump is located between the drug inlet valve and the cleaning medicine box.

[0016] The beneficial effect of this technical solution is that: in this way, the drug solution can be sent to the ultrafiltration device to clean the ultrafiltration device.

[0017] Optionally, the ultrafiltration unit further includes a return drug pipe and a return drug valve, one end of the return drug pipe is connected to the water outlet pipe, and the other end of the return drug pipe is connected to the cleaning drug box, and the position where the return drug pipe is connected to the water outlet pipe is located between the ultrafiltration device and the water production valve.

[0018] The beneficial effect of this technical solution is that the drug solution after cleaning the ultrafiltration device can be returned to the cleaning drug box through the drug return pipe and the drug return valve.

[0019] Optionally, the ultrafiltration unit further includes a backwash pipe, a backwash pump and a backwash valve, one end of the backwash pipe is connected to the water outlet pipe, the other end of the backwash pipe is connected to the water production pool, and the backwash pump is installed on the backwash pipe.

[0020] The beneficial effect of this technical solution is that when the ultrafiltration device is in operation, the transmembrane pressure difference of the ultrafiltration will increase due to contamination by various substances in the water, and backwashing is required to reduce the transmembrane pressure difference. The triggering conditions for backwashing are, first, the set transmembrane pressure difference increases, and second, the length of the filtration time. In order to further reduce membrane pollution, the timed backwash mode is conducive to operation management and program control.

[0021] Optionally, the reverse osmosis unit includes a water supply pump, a Y-type filter, a first reverse osmosis membrane element and a second reverse osmosis membrane element, the first reverse osmosis membrane element has a first water inlet, a first concentrated water outlet and a first pure water outlet, the second reverse osmosis membrane element has a second water inlet, a second concentrated water outlet and a second pure water outlet, the ultrafiltration unit includes a water production pool, the water supply pump is connected to the water production pool, the water supply pump, the Y-type filter and the first water inlet are connected in series from upstream to downstream, the first concentrated water outlet is connected to the second water inlet, and the first pure water outlet and the second pure water outlet are both connected to the pure water outlet pipe.

[0022] The beneficial effect of this technical solution is that: in this way, the concentrated water produced after treatment by the first reverse osmosis membrane element enters the second reverse osmosis membrane element, and the concentrated water produced after treatment by the second reverse osmosis membrane element is discharged to the concentrated water tank. The concentrated water in the concentrated water tank will be further sent to the concentrated water treatment unit, and the pure water produced by the first reverse osmosis membrane element and the second reverse osmosis membrane element will be sent to the pure water tank together, and the pure water tank can be connected to the ultrafiltration unit, thereby avoiding insufficient water supply to the backwash system of the ultrafiltration unit.

[0023] The technical solution provided by this application can achieve at least one of the following beneficial effects:

[0024] The sewage treatment system provided by the present application, when in use, the tail water of the municipal sewage treatment plant is sent to the ultrafiltration unit as raw water for ultrafiltration, and then sent to the reverse osmosis unit for treatment. Finally, the concentrated water sent out by the reverse osmosis unit is sent to the concentrated water treatment unit. The ozone generator in the concentrated water treatment unit generates ozone and sends the ozone to each ozone oxidation branch. At the same time, the concentrated water sent out from the reverse osmosis unit is also sent to each ozone oxidation branch, and then the COD in the concentrated water is removed in each ozone oxidation branch. Since the concentrated water treatment unit includes multiple parallel ozone oxidation branches, the reaction of removing COD from the concentrated water can be carried out simultaneously at multiple locations, so that the effect and efficiency of COD removal are significantly improved.

[0025] The additional technical features and advantages of this application will be more clearly explained in the following description, or can be understood through the specific practice of this application. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] To more clearly illustrate the technical solutions of the specific embodiments of this application, the following briefly introduces the drawings required for describing the specific embodiments. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be derived from these drawings without inventive effort.

[0027] Figure 1 A schematic structural diagram of an embodiment of an ultrafiltration unit provided in an embodiment of the present application;

[0028] Figure 2 A schematic structural diagram of an embodiment of a reverse osmosis unit provided in an embodiment of the present application;

[0029] Figure 3 This is a structural schematic diagram of an implementation scheme of a concentrated water treatment unit provided in an embodiment of the present application.

[0030] Reference numerals:

[0031] 01-First drainage pipe; 02-Original water pool;

[0032] 03-Second drain pipe; 04-Second drain valve;

[0033] 05-drug inlet pipe; 06-drug inlet valve;

[0034] 07-Cleaning pump; 08-Cleaning medicine box;

[0035] 09-Medicine liquid reflux pipe; 10-First drain valve;

[0036] 11-return pipe; 12-concentrated water valve;

[0037] 13-air compressor; 14-gas storage tank;

[0038] 15-water inlet pipe; 16-filter;

[0039] 17-water inlet valve; 18-ultrafiltration device;

[0040] 19-raw water pump; 20-backwash pump;

[0041] 21-medicine liquid reflux valve; 22-medicine return pipe;

[0042] 23-drug return valve; 24-water production valve;

[0043] 25-outlet pipe; 26-backwash pipe;

[0044] 27-backwash valve; 28-water production pool;

[0045] 29-dosing system; 30-water supply pump;

[0046] 31-Y-type filter; 32-second reverse osmosis membrane element;

[0047] 33-first reverse osmosis membrane element; 34-pure water outlet pipe;

[0048] 35-second reverse osmosis membrane element; 36-ozone generator;

[0049] 37-first ozone concentration detector; 38-flow meter;

[0050] 39-check valve; 40-ozone reactor;

[0051] 41-Second ozone concentration detector. DETAILED DESCRIPTION

[0052] The following will clearly and completely describe the technical solution of this application in conjunction with the accompanying drawings. Obviously, the embodiments described are only part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of this application.

[0053] In the description of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate the description of this application and simplify the description. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0054] In the description of this application, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on the specific circumstances.

[0055] like Figures 1 to 3As shown, the present application provides a sewage treatment system, comprising an ultrafiltration unit, a reverse osmosis unit and a concentrated water treatment unit connected in sequence, the concentrated water treatment unit comprising an ozone generator 36 and an ozone treatment component, the ozone treatment component comprising a plurality of ozone oxidation branches, each of the ozone oxidation branches being connected in parallel to the ozone generator 36, and each of the ozone oxidation branches being connected in parallel to the reverse osmosis unit.

[0056] The sewage treatment system provided by the present application, when in use, the tail water of the municipal sewage treatment plant is sent to the ultrafiltration unit as raw water for ultrafiltration, and then sent to the reverse osmosis unit for treatment. Finally, the concentrated water sent out by the reverse osmosis unit is sent to the concentrated water treatment unit. The ozone generator 36 in the concentrated water treatment unit generates ozone and sends the ozone to each ozone oxidation branch. At the same time, the concentrated water sent out from the reverse osmosis unit is also sent to each ozone oxidation branch, and then the COD in the concentrated water is removed in each ozone oxidation branch. Since the concentrated water treatment unit includes multiple parallel ozone oxidation branches, the reaction of removing COD from the concentrated water can be carried out simultaneously at multiple locations, so that the effect and efficiency of COD removal are significantly improved.

[0057] Optionally, the ozone oxidation branch includes an ozone reactor 40 and a check valve 39, the check valve 39 being connected to the ozone reactor 40 and located between the ozone reactor 40 and the ozone generator 36. COD in the concentrated water is removed in the ozone reactor 40. The check valve 39 prevents ozone from flowing back into the ozone generator 36, thereby preventing damage to the ozone generator 36. Alternatively, the check valve 39 may be omitted, or another type of control valve may be used to control the flow of ozone. Preferably, a flow meter 38 is also provided upstream of the check valve 39.

[0058] Optionally, the concentrated water treatment unit further includes a first ozone concentration detector 37 and a second ozone concentration detector 41. The ozone generator 36, the first ozone concentration detector 37, the ozone treatment assembly, and the second ozone concentration detector 41 are connected in series. Thus, the concentration of ozone fed into each ozone oxidation branch is detected by the first ozone concentration detector 37 to determine whether the ozone concentration meets the required level. The concentration of ozone discharged from each ozone oxidation branch is detected by the second ozone concentration detector 41 to determine whether the reaction has been fully completed within the ozone reactor 40 based on the reading of the second ozone concentration detector 41.

[0059] Optionally, the ultrafiltration unit includes an ultrafiltration device 18, a raw water pool 02, a raw water pump 19 and a water production pool 28, and the ultrafiltration unit also includes an inlet pipe 15, an outlet pipe 25 and a return pipe 11.

[0060] The ultrafiltration device 18 includes ultrafiltration membrane filaments. The raw water pool 02 is connected to the outside of the ultrafiltration membrane filaments through the water inlet pipe 15. The water production pool 28 is connected to the inside of the ultrafiltration membrane filaments through the water outlet pipe 25. The raw water pool 02 is also connected to the ultrafiltration device 18 through the return pipe 11 to send the circulating water sent from the ultrafiltration device 18 to the raw water pool 02. The raw water pump 19 is installed on the water inlet pipe 15. This realizes the filtration of the tail water of the municipal sewage treatment plant in the ultrafiltration unit. Preferably, a chlorination device for adding chlorine to the raw water pool 02 is provided. Preferably, an air compressor 13 equipped with an air storage tank 14 is provided and connected to the water inlet pipe 15.

[0061] Optionally, the ultrafiltration unit further comprises a filter 16 installed on the water inlet pipe 15, and the filter 16 is located between the raw water pump 19 and the ultrafiltration device 18. In the embodiment of the present application, preferably, the filter 16 adopts a vertical fully automatic self-cleaning filter 16 with a processing capacity of 5m 3 / h, filtration accuracy 100 microns, the main components of the self-cleaning filter 16 are: motor, electric control box, control pipeline, main pipe assembly, filter element assembly, 316L stainless steel brush, frame assembly, transmission shaft and inlet and outlet connection flanges, etc. The self-cleaning filter 16 is provided with motor overload protection, which can effectively protect the motor. The self-cleaning filter 16 automatically drains according to the filtration pressure difference.

[0062] Optionally, the ultrafiltration unit further includes an inlet valve 17, a production water valve 24 and a concentrated water valve 12, the inlet valve 17 is installed on the inlet pipe 15, the inlet valve 17 is located between the filter 16 and the ultrafiltration device 18, the production water valve 24 is installed on the outlet pipe 25, and the concentrated water valve 12 is installed on the return pipe 11.

[0063] Optionally, the ultrafiltration unit further includes a drug feed pipe 05, a cleaning medicine box 08, a cleaning pump 07, and a drug feed valve 06, one end of the drug feed pipe 05 is connected to the water inlet pipe 15, and the other end of the drug feed pipe 05 is connected to the cleaning medicine box 08. The connection position between the drug feed pipe 05 and the water inlet pipe 15 is located between the water inlet valve 17 and the ultrafiltration device 18. The drug feed valve 06 and the cleaning pump 07 are both installed on the drug feed pipe 05, and the cleaning pump 07 is located between the drug feed valve 06 and the cleaning medicine box 08. In this way, the drug solution can be fed into the ultrafiltration device 18 to clean the ultrafiltration device 18. Preferably, an acid adding device for adding acid, a chlorinating device for adding chlorine, and an alkali adding device for adding alkali to the cleaning medicine box 08 are provided.

[0064] Optionally, the ultrafiltration unit also includes a return drug pipe 22 and a return drug valve 23, one end of the return drug pipe 22 is connected to the water outlet pipe 25, and the other end of the return drug pipe 22 is connected to the cleaning medicine box 08, and the position where the return drug pipe 22 is connected to the water outlet pipe 25 is located between the ultrafiltration device 18 and the water production valve 24. This allows the medicinal liquid that has completed cleaning of the ultrafiltration device 18 to return to the cleaning medicine box 08 through the return medicine pipe 22 and the return medicine valve 23; in the embodiment of the present application, a medicinal liquid return pipe 09 connected to the return water pipe 11 can also be provided, and a medicinal liquid return valve 21 can be installed on the medicinal liquid return pipe 09, and the medicinal liquid can be returned to the cleaning medicine box 08 through the medicinal liquid return pipe 09. A first drain pipe 01 can also be provided to be connected to the medicinal liquid return pipe 09, and a first drain valve 10 can be provided on the first drain pipe 01 to discharge the medicinal liquid after cleaning from the ultrafiltration unit. A second drain pipe 03 and a second drain valve 04 installed on the second drain pipe 03 can also be provided. The second drain pipe 03 can be connected to the water inlet of the ultrafiltration device 18, thereby discharging the medicinal liquid after cleaning from the ultrafiltration unit. In the embodiment of the present application, when the ultrafiltration unit filtration cycle reaches a certain number of times, a chemically enhanced backwash procedure can be performed. The chemically enhanced backwash process can make the ultrafiltration membrane filaments better adapt to adverse water conditions. The chemically enhanced backwash cleaning process is divided into two processes: alkaline washing and acid washing. Usually, one acid wash is performed after six alkaline washes. After the chemically enhanced backwash process is completed, the filtration process is entered again. Backwashing is performed before and after the chemically enhanced backwash cleaning. When the membrane flux or transmembrane pressure difference reaches the set value, the ultrafiltration device 18 is shut down for chemical cleaning. The process and flow of chemical cleaning are the same as those of chemically enhanced backwashing, but the concentration and time of the agent are greater than those of chemically enhanced backwashing. In the embodiment of the present application, preferably, the chemical cleaning process is manually triggered and the cleaning is controlled by an automatic program.

[0065] Optionally, the ultrafiltration unit further includes a backwash pipe 26, a backwash pump 20 and a backwash valve 27. One end of the backwash pipe 26 is connected to the outlet pipe 25, and the other end of the backwash pipe 26 is connected to the water production pool 28. The backwash pump 20 is installed on the backwash pipe 26. When the ultrafiltration device 18 is in operation, the transmembrane pressure difference of the ultrafiltration will rise due to the contamination of various substances in the water, and backwashing is required to reduce the transmembrane pressure difference. The triggering conditions for backwashing are, first, the set transmembrane pressure difference rises, and second, the length of the filtration time. In order to further reduce membrane pollution, the timed backwash mode is conducive to operation management and program control. Preferably, the backwash program can be automatically started when the set time is reached. In the embodiment of the present application, preferably, the backwash pump 20 is a horizontal centrifugal pump, and the reverse osmosis displacement of a single backwash pump 20 is 5m 3 / h, head 30m, power 0.75kW, meet the flow and pressure requirements of reverse osmosis flushing, the backwash pump 20 uses SS304 stainless steel for its flow components, and is equipped with inlet and outlet isolation valves of the backwash pump 20, a swing-type rubber-lined check valve 39 at the outlet, a pressure gauge and its connecting pipe instrument valves, etc. An online electromagnetic flowmeter is installed at the outlet of the backwash pump 20; a chlorination device is installed downstream of the backwash pump 20.

[0066] Optionally, the reverse osmosis unit includes a water supply pump 30, a Y-type filter 31, a first reverse osmosis membrane element 33 and a second reverse osmosis membrane element 35, the first reverse osmosis membrane element 33 has a first water inlet, a first concentrated water outlet and a first pure water outlet, the second reverse osmosis membrane element 35 has a second water inlet, a second concentrated water outlet and a second pure water outlet, the ultrafiltration unit includes a water production pool 28, the water supply pump 30 is connected to the water production pool 28, from upstream to downstream the water supply pump 30, the Y-type filter 31 and the first water inlet are connected in series in sequence, the first concentrated water outlet is connected to the second water inlet, and the first pure water outlet and the second pure water outlet are both connected to the pure water outlet pipe 34. In this way, the concentrated water produced after treatment by the first reverse osmosis membrane element 33 enters the second reverse osmosis membrane element 35, and the concentrated water produced after treatment by the second reverse osmosis membrane element 35 is discharged to the concentrated water tank. The concentrated water in the concentrated water tank will be further sent to the concentrated water treatment unit, and the pure water produced by the first reverse osmosis membrane element 33 and the second reverse osmosis membrane element 35 will be sent to the pure water tank together, and the pure water tank can be connected to the ultrafiltration unit, thereby avoiding insufficient water supply to the backwash system of the ultrafiltration unit.

[0067] In the embodiment of the present application, preferably, the processing capacity of the water supply pump 30 is 3m 3 / h, the water supply pump 30 delivers the water from the water production pool 28 into the reverse osmosis unit; the Y-type filter 31 plays a role in filtering and intercepting impurities in the incoming water to protect the equipment; the reverse osmosis unit also includes a booster pump, the processing capacity of the booster pump is 3m 3 / h, can play the role of increasing the water inlet pressure to overcome the resistance of the osmotic pressure of each reverse osmosis membrane element, etc., to ensure the normal operation of each reverse osmosis membrane element, and to achieve the designed water production rate; the reverse osmosis unit also includes a dosing system 29, specifically adding scale inhibitors, bactericides and reducing agents, wherein the role of the scale inhibitor is to prevent scaling on the membrane surface, improve water production and quality, and reduce operating costs, the role of the bactericide is mainly to kill bacteria and algae, effectively sterilize, avoid pipeline blockage, equipment corrosion, the role of the reducing agent is to add sodium hypochlorite to the ultrafiltration unit to prevent the proliferation of microorganisms, there will be some residue when entering the reverse osmosis unit, and the hypochlorite needs to be reduced. In the embodiment of the present application, preferably, the displacement of a single booster pump is 3m 3 / h, head 140m, power 2.2kW. The booster pump provides sufficient inlet pressure to the reverse osmosis unit to overcome resistance, such as osmotic pressure, from the reverse osmosis membrane, ensuring proper membrane operation and achieving the designed water production rate. An electric slow-opening valve (controlling valve opening speed) and a pressure switch are installed at the booster pump outlet to protect the membrane assembly from high-pressure water impact. High pressure alarms and pump shutdown are also provided. The pump and accessories are constructed of SS304 stainless steel. The booster pump, safety filter, and reverse osmosis unit are compactly arranged for aesthetic appeal and ease of operation. The booster pump utilizes variable frequency drive (VFD) technology from Schneider and ABB.

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A sewage treatment system, characterized in that: It includes an ultrafiltration unit, a reverse osmosis unit and a concentrated water treatment unit connected in sequence. The concentrated water treatment unit includes an ozone generator and an ozone treatment component. The ozone treatment component includes multiple ozone oxidation branches, each of which is connected in parallel to the ozone generator, and each of the ozone oxidation branches is connected in parallel to the reverse osmosis unit.

2. The sewage treatment system according to claim 1, characterized in that: The ozone oxidation branch includes an ozone reactor and a check valve. The check valve is connected to the ozone reactor and is located between the ozone reactor and the ozone generator.

3. The sewage treatment system according to claim 2, characterized in that: The concentrated water treatment unit further includes a first ozone concentration detector and a second ozone concentration detector. The ozone generator, the first ozone concentration detector, the ozone treatment component and the second ozone concentration detector are sequentially connected in series.

4. The sewage treatment system according to claim 1, characterized in that: The ultrafiltration unit includes an ultrafiltration device, a raw water pool, a raw water pump and a water production pool, and the ultrafiltration unit also includes an inlet pipe, an outlet pipe and a return pipe. The ultrafiltration device includes ultrafiltration membrane filaments. The raw water pool is connected to the outside of the ultrafiltration membrane filaments through the water inlet pipe, and the water production pool is connected to the inside of the ultrafiltration membrane filaments through the water outlet pipe. The raw water pool is also connected to the ultrafiltration device through the return pipe to send the circulating water sent from the ultrafiltration device to the raw water pool. The raw water pump is installed on the water inlet pipe.

5. The sewage treatment system according to claim 4, characterized in that: The ultrafiltration unit further includes a filter installed on the water inlet pipe, and the filter is located between the raw water pump and the ultrafiltration device.

6. The sewage treatment system according to claim 5, characterized in that: The ultrafiltration unit also includes an inlet valve, a production water valve and a concentrated water valve. The inlet valve is installed on the water inlet pipe and is located between the filter and the ultrafiltration device. The production water valve is installed on the outlet pipe and the concentrated water valve is installed on the return water pipe.

7. The sewage treatment system according to claim 6, characterized in that: The ultrafiltration unit also includes a drug inlet pipe, a cleaning medicine box, a cleaning pump and a drug inlet valve. One end of the drug inlet pipe is connected to the water inlet pipe, and the other end of the drug inlet pipe is connected to the cleaning medicine box. The connection position between the drug inlet pipe and the water inlet pipe is located between the water inlet valve and the ultrafiltration device. The drug inlet valve and the cleaning pump are both installed on the drug inlet pipe, and the cleaning pump is located between the drug inlet valve and the cleaning medicine box.

8. The sewage treatment system according to claim 7, characterized in that: The ultrafiltration unit also includes a return drug pipe and a return drug valve. One end of the return drug pipe is connected to the water outlet pipe, and the other end of the return drug pipe is connected to the cleaning drug box. The position where the return drug pipe is connected to the water outlet pipe is located between the ultrafiltration device and the water production valve.

9. The sewage treatment system according to claim 4, characterized in that: The ultrafiltration unit further includes a backwash pipe, a backwash pump and a backwash valve. One end of the backwash pipe is connected to the water outlet pipe, and the other end of the backwash pipe is connected to the water production pool. The backwash pump is installed on the backwash pipe.

10. The sewage treatment system according to any one of claims 1 to 9, characterized in that: The reverse osmosis unit includes a water supply pump, a Y-type filter, a first reverse osmosis membrane element and a second reverse osmosis membrane element, the first reverse osmosis membrane element has a first water inlet, a first concentrated water outlet and a first pure water outlet, the second reverse osmosis membrane element has a second water inlet, a second concentrated water outlet and a second pure water outlet, the ultrafiltration unit includes a water production pool, the water supply pump is connected to the water production pool, the water supply pump, the Y-type filter and the first water inlet are connected in series from upstream to downstream, the first concentrated water outlet is connected to the second water inlet, and the first pure water outlet and the second pure water outlet are both connected to the pure water outlet pipe.

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