A raw water turbidity flow rate self-control filtration system
Patent Information
- Application Number
- CN202522091197.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-28
- Publication Date
- 2026-08-28
- Estimated Expiration
- 2035-09-28
AI Technical Summary
[0002]现有生产中，膜过滤虽然能够解决高浊度原水的问题，但是任何膜在过滤过程中，水中的微粒、胶体粒子、微生物或溶质大分子由于与膜存在物理化学相互作用或机械作用而引起的在膜表面或膜孔内吸附、沉积造成膜孔径变小或堵塞，使膜产生透过流量与分离特性的不可逆变化现象所造成的污堵，出水不稳定，一旦膜造成污堵后就必须采用化学清洗才能够恢复至初始状态，如此不停的经过过滤—化学清洗—过滤的过程，久而久之膜经过多次化学清洗后就会造成膜的老化和报废，特别是膜在化学清洗的过程要使用化学药剂，由于化学药剂的使用会造成二次污染，如果处理不当对饮用水源造成污染，对饮用水的安全造成威胁
本实用新型过滤系统在管式膜的基础上构建一层介质膜来进行介质调控，实现介质调控的介质膜本质上是一层可牺牲的抗污染过滤层，由于其具有可再生性，介质层会优先截留胶体、油类、大分子有机物等污染物，避免这些污染物与基膜接触。在抗污染过滤层的保护下，无需对管式膜的基膜进行化学清洗。当膜受到污染后，只需通过低压反冲将抗污染过滤层中失效的介质层及附着污染物剥离，随后重新构建一层抗污染过滤层，即可使膜重新投入使用，真正实现了零化学清洗式的性能恢复。过滤系统设置有介质膜过滤层再生系统、循环产水系统、清洗系统，通过介质膜过滤层再生系统可随时在管式膜上培养覆盖可剥离的介质膜，通过循环产品系统持续产生淡水，通过清洗系统对管式膜及管道进行清洗，剥离已污染介质膜，以此杜绝化学药剂使用，构建出水稳定的过滤系统。
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Figure CN224691898U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of raw water filtration technology, and in particular to a filtration system based on the self-controlled turbidity and flow rate of raw water. Background Technology
[0002] In current production processes, while membrane filtration can solve the problem of high-turbidity raw water, any membrane, during the filtration process, will experience fouling. This is caused by the adsorption and deposition of microparticles, colloidal particles, microorganisms, or large solute molecules on the membrane surface or within the pores due to physicochemical or mechanical interactions with the membrane. This leads to reduced pore size or blockage, resulting in irreversible changes in permeate flow and separation characteristics, resulting in unstable effluent. Once the membrane becomes fouled, chemical cleaning is necessary to restore it to its initial state. This continuous cycle of filtration-chemical cleaning-filtration eventually leads to membrane aging and eventual failure. Furthermore, the use of chemical agents in membrane cleaning can cause secondary pollution, potentially contaminating drinking water sources and threatening drinking water safety if not properly handled. The application range of tubular membrane filtration systems is limited by suitable water pressure and flow rate, and this range changes as impurities accumulate and the membrane becomes clogged. Therefore, we need a raw water filtration system that can solve the problems of chemical reagent use, stable output water, and automatically maintain optimal operating pressure under water quality fluctuations. Utility Model Content
[0003] The purpose of this invention is to address the shortcomings of existing technologies by proposing a self-controlled filtration system based on raw water turbidity and flow rate.
[0004] To achieve the above objectives, a self-controlled filtration system based on raw water turbidity and flow rate includes a raw water tank, a sludge tank, a media storage tank, a freshwater tank, and a tubular membrane. The raw water tank is equipped with a raw water inlet pipe connected to the raw water inlet of the tubular membrane. The concentrated water outlet of the tubular membrane is equipped with a concentrated water return pipe connected to the raw water tank. The freshwater outlet of the tubular membrane is equipped with a freshwater outlet pipe connected to both the media storage tank and the freshwater tank. The freshwater tank is equipped with a freshwater flushing pipe connected to the media storage tank, the freshwater outlet of the tubular membrane, and the raw water inlet. The concentrated water outlet of the tubular membrane is equipped with a concentrated water outlet pipe connected to both the sludge tank and the media storage tank. The media storage tank is also connected to a tap water pipe. A circulation pump is installed on the raw water inlet pipe, and a backwash pump is installed on the freshwater flushing pipe.
[0005] The filtration system incorporates a media membrane layer on top of the tubular membrane for media regulation. This media membrane is essentially a sacrificial antifouling filter layer. Due to its regenerability, the media layer preferentially traps contaminants such as colloids, oils, and large organic molecules, preventing these contaminants from contacting the base membrane. Protected by the antifouling filter layer, chemical cleaning of the tubular membrane base is unnecessary. When the membrane becomes fouled, low-pressure backwashing removes the failed media layer and attached contaminants from the antifouling filter layer, allowing for the membrane to be reused. This truly achieves zero-chemical-cleaning performance recovery. The filtration system includes a media membrane regeneration system, a circulating water system, and a cleaning system. The media membrane regeneration system continuously cultivates and covers the tubular membrane with a peelable media membrane. The circulating water system continuously produces fresh water. The cleaning system cleans the tubular membrane and pipes, removing the fouled media membrane, thus eliminating the need for chemical agents and creating a stable filtration system. Media membrane filtration layer regeneration system: A certain amount of tap water is introduced into the media storage tank through a tap water pipe, and the corresponding composite media is added. The backwash pump is turned on, and the liquid in the media storage tank flows into the tubular membrane through the freshwater flushing pipe, then returns to the media storage tank through the freshwater outlet pipe and the concentrated water outlet pipe, forming the media membrane filtration layer regeneration system. A media membrane is then constructed on the tubular membrane support layer. Circulating permeate system: Raw water from the raw water tank is input into the tubular membrane for filtration through the raw water inlet pipe. The resulting freshwater flows into the freshwater tank through the freshwater outlet pipe. The unfiltered concentrated water in the tubular membrane flows back to the raw water tank through the concentrated water return pipe, forming a circulating permeate system to produce freshwater. Cleaning system: Freshwater from the freshwater tank flows backward into the freshwater outlet of the tubular membrane module through the freshwater flushing pipe, flushing out the contaminated media membrane. The flushing wastewater flows into the sludge tank through the concentrated water outlet of the tubular membrane and the concentrated water outlet pipe for discharge.
[0006] Preferably, the raw water inlet pipe is equipped with a manual working valve and a first working valve at both ends before and after the circulating pump, the concentrated water return pipe is equipped with a second working valve, the fresh water outlet pipe is equipped with a first fresh water valve and a second fresh water valve on the pipes connecting to the media storage tank and the fresh water tank respectively, the fresh water flushing pipe is equipped with a first backflushing valve, the fresh water flushing pipe is equipped with a second backflushing valve, a third backflushing valve and a fourth backflushing valve on the pipes connecting to the media storage tank, the fresh water outlet of the tubular membrane and the raw water inlet respectively, the concentrated water outlet pipe is equipped with a first concentrated water valve and a second concentrated water valve on the pipes connecting to the sludge tank and the media storage tank respectively, a first check valve is equipped on the pipe at the front end of the manual working valve, and a switch valve is equipped on the tap water pipe.
[0007] To ensure the independent operation of the media membrane filter layer regeneration system, circulating water system, and cleaning system, when the media membrane filter layer regeneration system is operating, all valves are closed, and only the second backflush valve, fourth backflush valve, first freshwater valve, second concentrated water valve, and backflush pump are opened to form an independent circulation loop; when the circulating water system is operating, all valves are closed, and only the manual operating valve, first operating valve, second operating valve, second freshwater valve, and circulating pump are opened to form an independent circulation loop; when the cleaning system is operating, all valves are closed, and only the first backflush valve, third backflush valve, first concentrated water valve, and backflush pump are opened to form an independent cleaning pipeline.
[0008] Preferably, the first working valve, the second working valve, the first fresh water valve, the second fresh water valve, the first backflush valve, the second backflush valve, the third backflush valve, the fourth backflush valve, the first concentrate valve, the second concentrate valve, and the switching valve are solenoid valves. A turbidity meter is installed on the raw water inlet pipe, a frequency converter is connected to the circulating pump, and pressure sensors are respectively installed at the raw water inlet and the concentrate outlet of the tubular membrane.
[0009] A turbidity meter is installed to detect the turbidity of the raw water in the raw water outlet pipe, and a pressure sensor is installed to detect the pressure at the raw water inlet and concentrate outlet of the tubular membrane. The system is sampled in stages using a frequency converter. A model of the correspondence between turbidity and target operating pressure is established based on the actual detection data. The filtration system is operated according to the optimal data of the set model using any existing PID controller. It can automatically maintain the best operating pressure under water quality fluctuations, significantly improving the intelligence level and economy of the tubular membrane system.
[0010] Preferably, the raw water tank is provided with a sewage pipe connected to the sludge tank, and the sewage pipe is provided with a second check valve, a manual sewage valve and a sludge pump in sequence.
[0011] Installing a drain pipe allows for direct discharge of wastewater from the raw water tank, preventing excessive turbidity in the raw water tank after the water is recycled.
[0012] Preferably, the freshwater flushing pipe at the rear end of the backwash pump is also connected to the sludge tank via a pipeline and a first flushing valve is provided on the pipeline, and the freshwater flushing pipe at the front end of the second backwash valve is also connected to the sludge tank via a pipeline and a second flushing valve is provided on the pipeline.
[0013] The first flush valve can discharge water from the media storage tank alone, or in combination with the second backflush valve, discharge water from both the media storage tank and the freshwater pool simultaneously; the second flush valve can discharge water from the freshwater pool alone.
[0014] Preferably, the freshwater outlet pipe at the front end of the second freshwater valve is equipped with a flow meter and a manual water production valve.
[0015] Preferably, the raw water tank, the medium storage tank, and the fresh water tank are each equipped with a liquid level sensor.
[0016] Preferably, the liquid level sensor is a liquid level float.
[0017] Compared with the prior art, the beneficial effects of this utility model are: This novel filtration system incorporates a media membrane layer on top of a tubular membrane for media regulation. This media membrane is essentially a sacrificial antifouling filter layer. Due to its regenerability, the media layer preferentially traps colloids, oils, and large organic molecules, preventing these contaminants from contacting the base membrane. Protected by the antifouling filter layer, chemical cleaning of the tubular membrane base is unnecessary. When the membrane becomes fouled, low-pressure backflushing removes the failed media layer and attached contaminants from the antifouling filter layer, allowing for the membrane to be reused. This truly achieves zero-chemical-cleaning performance recovery. The filtration system includes a media membrane regeneration system, a circulating water production system, and a cleaning system. The media membrane regeneration system continuously cultivates and covers the tubular membrane with a peelable media membrane. The circulating water production system continuously generates fresh water. The cleaning system cleans the tubular membrane and pipes, removing the fouled media membrane, thus eliminating the need for chemical agents and creating a stable filtration system.
[0018] A turbidity meter is installed to detect the turbidity of the raw water in the raw water outlet pipe, and a pressure sensor is installed to detect the pressure at the raw water inlet and concentrate outlet of the tubular membrane. The system is sampled in stages using a frequency converter. A model of the correspondence between turbidity and target operating pressure is established based on the actual detection data. The filtration system is operated according to the optimal data of the set model using any existing PID controller. It can automatically maintain the best operating pressure under water quality fluctuations, significantly improving the intelligence level and economy of the tubular membrane system. Attached Figure Description
[0019] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the accompanying drawings used in the embodiments will be briefly introduced below.
[0020] Figure 1 This is a schematic diagram of the structure of Embodiment 1 of this utility model.
[0021] Figure 2 This is a schematic diagram of the structure of Embodiment 2 of this utility model.
[0022] Figure 3 This is a schematic diagram of the structure of Embodiment 3 of this utility model.
[0023] Figure 4 This is a schematic diagram of the structure of Embodiment 4 of this utility model. Detailed Implementation
[0024] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to specific embodiments and accompanying drawings. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of this utility model. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concept of this utility model.
[0025] Example 1 This invention provides a self-regulating filtration system based on raw water turbidity and flow rate, such as... Figure 1 As shown, the system includes a raw water tank 1, a sludge tank 2, a media storage tank 3, a freshwater tank 4, and a tubular membrane 5. The raw water tank 1 is equipped with a raw water inlet pipe 6 connected to the raw water inlet of the tubular membrane 5. The concentrated water outlet of the tubular membrane 5 is equipped with a concentrated water return pipe 7 connected to the raw water tank 1. The freshwater outlet of the tubular membrane 5 is equipped with a freshwater outlet pipe 8 connected to both the media storage tank 3 and the freshwater tank 4. The freshwater tank 4 is equipped with a freshwater flushing pipe 9 connected to the media storage tank 3, the freshwater outlet of the tubular membrane 5, and the raw water inlet. The concentrated water outlet of the tubular membrane 5 is equipped with a concentrated water outlet pipe 10 connected to both the sludge tank 2 and the media storage tank 3. The media storage tank 3 is also connected to a tap water pipe 11. A circulation pump 12 is installed on the raw water inlet pipe 6, and a backwash pump 13 is installed on the freshwater flushing pipe 9.
[0026] The filtration system incorporates a media membrane layer on top of the tubular membrane 5 for media regulation. The tubular membrane 5 can be implemented using any existing technology. Essentially, the media membrane for media regulation is a sacrificial antifouling filter layer. Due to its regenerability, the media layer preferentially traps contaminants such as colloids, oils, and large organic molecules, preventing these contaminants from contacting the base membrane. Protected by the antifouling filter layer, chemical cleaning of the base membrane of the tubular membrane 5 is unnecessary. When the membrane becomes contaminated, low-pressure backflushing is sufficient to remove the failed media layer and attached contaminants from the antifouling filter layer. A new antifouling filter layer is then reconstructed, allowing the membrane to be reused, achieving true zero-chemical-clean performance recovery. The filtration system is equipped with a media membrane filter layer regeneration system, a circulating water production system, and a cleaning system. The media membrane filter layer regeneration system can cultivate and cover a peelable media membrane on the tubular membrane 5 at any time. The circulating water production system continuously produces fresh water. The cleaning system cleans the tubular membrane 5 and the pipeline, removing the contaminated media membrane, thereby eliminating the use of chemical agents and creating a filtration system with stable effluent.
[0027] The raw water inlet pipe 6 is equipped with a manual working valve 14 and a first working valve 15 at both ends of the circulating pump 12. The concentrated water return pipe 7 is equipped with a second working valve 16. The fresh water outlet pipe 8 is equipped with a first fresh water valve 17 and a second fresh water valve 18 on the pipes connecting to the media storage tank 3 and the fresh water tank 4, respectively. The fresh water flushing pipe 9 is equipped with a first backflushing valve 19. The fresh water flushing pipe 9 is equipped with a second backflushing valve 20, a third backflushing valve 21, and a fourth backflushing valve 22 on the pipes connecting to the media storage tank 3, the fresh water outlet of the tubular membrane 5, and the raw water inlet, respectively. The concentrated water outlet pipe 10 is equipped with a first concentrated water valve 23 and a second concentrated water valve 24 on the pipes connecting to the sludge tank 2 and the media storage tank 3, respectively. The manual working valve 14 is equipped with a first check valve 25 on the pipe at the front end. The tap water pipe 11 is equipped with a switch valve 26.
[0028] To ensure the independent operation of the media membrane filtration layer regeneration system, the circulating water system, and the cleaning system, when the media membrane filtration layer regeneration system is operating, all valves are closed, except for the on / off valve 26, the second backflush valve 20, the fourth backflush valve 22, the first freshwater valve 17, the second concentrated water valve 24, and the backflush pump 13. A certain amount of tap water is introduced into the media storage tank 3 through the tap water pipe 11, along with the corresponding composite media. The liquid in the media storage tank 3 flows into the tubular membrane 5 through the freshwater flushing pipe 9, and then flows back into the media storage tank 3 through the freshwater outlet pipe 8 and the concentrated water outlet pipe 10, thus forming the media membrane filtration layer regeneration system and constructing a media membrane on the tubular membrane 5. When the circulating water system is operating, all valves are closed, except for the manual operating valve 1. 4. The first working valve 15, the second working valve 16, the second freshwater valve 18, and the circulation pump 12 are used to filter the raw water from the raw water tank 1 into the tubular membrane 5 through the raw water inlet pipe 6. The resulting freshwater flows into the freshwater tank 4 through the freshwater outlet pipe 8. The unfiltered concentrate in the tubular membrane 5 flows back to the raw water tank 1 through the concentrate return pipe 7, forming a circulating water production system to produce freshwater. When the cleaning system is working, all valves are closed, and only the first backwash valve 19, the third backwash valve 21, the first concentrate valve 23, and the backwash pump 13 are opened. The freshwater from the freshwater tank 4 flows back into the freshwater outlet of the tubular membrane 5 through the freshwater flushing pipe 9 to flush out the contaminated media membrane. The flushing wastewater flows into the sludge tank 2 through the concentrate outlet of the tubular membrane 5 and the concentrate outlet pipe 10 for discharge.
[0029] The first working valve 15, the second working valve 16, the first fresh water valve 17, the second fresh water valve 18, the first backflush valve 19, the second backflush valve 20, the third backflush valve 21, the fourth backflush valve 22, the first concentrate valve 23, the second concentrate valve 24, and the switching valve 26 are all solenoid valves. A turbidity meter 27 is installed on the raw water inlet pipe 6. A frequency converter 28 is connected to the circulating pump 12. Pressure sensors 29 are respectively installed at the raw water inlet and the concentrate outlet of the tubular membrane 5.
[0030] The flow rate control method includes the following steps: Step 1: Install a turbidity meter 27 on the raw water inlet pipe 6 and pressure sensors 29 at both ends of the tubular membrane 5 to monitor the water turbidity and operating pressure in real time; the sampling frequency is once per second. Step 2: Establish a model of the correspondence between turbidity (T) and target operating pressure (P_set) through on-site commissioning; Step 3: The actual pressure (P_actual) is quickly tracked to the operating pressure (P_set) by the PID controller, and a new frequency (F_new) is output to the circulating pump motor; Step 4: Through this feedforward-feedback composite control strategy, the system can automatically maintain the optimal operating pressure according to a predetermined model under water quality fluctuations, significantly improving the intelligence level and economy of the tubular membrane system.
[0031] Example 2 like Figure 2 As shown, this embodiment is basically the same as embodiment 1. The difference is that, considering that the turbidity of the raw water in the raw water tank 1 will continuously increase during the circulation process, and the high turbidity raw water must be discharged after reaching a certain level, the raw water tank 1 is equipped with a sewage pipe 30 connected to the sludge tank 2. The sewage pipe 30 is equipped with a second check valve 31, a manual sewage valve 32 and a sludge pump 33 in sequence. By opening the manual sewage valve 32 and the sludge pump 33, the high turbidity raw water in the raw water tank 1 is discharged into the sludge tank 2.
[0032] Example 3 like Figure 3As shown, this embodiment is basically the same as embodiment 2. The difference is that, considering that the media storage tank 3 and the freshwater tank 4 need to be cleaned regularly, the freshwater flushing pipe 9 at the rear end of the backwash pump 13 is also connected to the sludge tank 2 through a pipeline, and a first flushing valve 34 is installed on the pipeline. Only opening the first backwash valve 19, the second backwash valve 20, the first flushing valve 34 and the backwash pump 13 can empty the water in the media storage tank 3 and the freshwater tank 4, while only opening the second backwash valve 20, the first flushing valve 34 and the backwash pump 13 can empty the water in the media storage tank 3 alone. Considering the need to empty the water in the freshwater tank 4 alone, the freshwater flushing pipe 9 at the front end of the second backwash valve 20 is also connected to the sludge tank 2 through a pipeline, and a second flushing valve 35 is installed on the pipeline. This can be achieved by only opening the first backwash valve 19 and the second flushing valve 35. Since the turbidity in the freshwater tank 4 is low, the discharge can be achieved by setting the height difference between the freshwater tank 4 and the sludge tank 2, without the need for pump assistance.
[0033] Example 4 like Figure 4 As shown, this embodiment is basically the same as embodiment 3, except that the freshwater outlet pipe 8 at the front end of the second freshwater valve 18 is equipped with a flow meter 36 and a manual water production valve 37 for detecting the freshwater output.
[0034] Liquid level sensors 38 are respectively installed in the raw water tank 1, the medium storage tank 3, and the fresh water tank 4 to detect the actual liquid level. The liquid level sensor 38 is a liquid level float, which can be implemented using any existing technology.
[0035] It should be understood that the specific embodiments described above are merely illustrative or explanatory of the principles of this utility model and do not constitute a limitation thereof. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of this utility model should be included within its protection scope. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.
Claims
1. A self-regulating filtration system based on raw water turbidity and flow rate, characterized in that, The system includes a raw water tank, a sludge tank, a media storage tank, a freshwater tank, and a tubular membrane. The raw water tank is equipped with a raw water inlet pipe connected to the raw water inlet of the tubular membrane. The concentrate outlet of the tubular membrane is equipped with a concentrate return pipe connected to the raw water tank. The freshwater outlet of the tubular membrane is equipped with a freshwater outlet pipe connected to both the media storage tank and the freshwater tank. The freshwater tank is equipped with a freshwater flushing pipe connected to the media storage tank, the freshwater outlet of the tubular membrane, and the raw water inlet. The concentrate outlet of the tubular membrane is equipped with a concentrate outlet pipe connected to both the sludge tank and the media storage tank. The media storage tank is also connected to a tap water pipe. A circulation pump is installed on the raw water inlet pipe, and a backwash pump is installed on the freshwater flushing pipe.
2. The self-regulating filtration system based on raw water turbidity and flow rate according to claim 1, characterized in that, The raw water inlet pipe is equipped with a manual working valve and a first working valve at both ends of the circulating pump. The concentrated water return pipe is equipped with a second working valve. The fresh water outlet pipe is equipped with a first fresh water valve and a second fresh water valve on the pipes connecting to the media storage tank and the fresh water tank, respectively. The fresh water flushing pipe is equipped with a first backflushing valve. The fresh water flushing pipe is equipped with a second backflushing valve, a third backflushing valve, and a fourth backflushing valve on the pipes connecting to the media storage tank, the fresh water outlet of the tubular membrane, and the raw water inlet, respectively. The concentrated water outlet pipe is equipped with a first concentrated water valve and a second concentrated water valve on the pipes connecting to the sludge tank and the media storage tank, respectively. A first check valve is installed on the pipe at the front end of the manual working valve. A switch valve is installed on the tap water pipe.
3. The self-regulating filtration system based on raw water turbidity and flow rate according to claim 2, characterized in that, The first working valve, the second working valve, the first fresh water valve, the second fresh water valve, the first backflush valve, the second backflush valve, the third backflush valve, the fourth backflush valve, the first concentrate valve, the second concentrate valve, and the switching valve are all solenoid valves. A turbidity meter is installed on the raw water inlet pipe. A frequency converter is connected to the circulating pump. Pressure sensors are installed at the raw water inlet and the concentrate outlet of the tubular membrane.
4. The self-regulating filtration system based on raw water turbidity and flow rate according to claim 3, characterized in that, The raw water tank is connected to the sludge tank by a sewage pipe, and the sewage pipe is equipped with a second check valve, a manual sewage valve and a sludge pump in sequence.
5. The self-regulating filtration system based on raw water turbidity and flow rate according to claim 4, characterized in that, The freshwater flushing pipe at the rear end of the backwash pump is also connected to the sludge tank via a pipeline, and a first flushing valve is installed on the pipeline. The freshwater flushing pipe at the front end of the second backwash valve is also connected to the sludge tank via a pipeline, and a second flushing valve is installed on the pipeline.
6. The self-regulating filtration system based on raw water turbidity and flow rate according to claim 5, characterized in that, The freshwater outlet pipe at the front end of the second freshwater valve is equipped with a flow meter and a manual water production valve.
7. The self-regulating filtration system based on raw water turbidity and flow rate according to claim 6, characterized in that, Liquid level sensors are installed in the raw water tank, the medium storage tank, and the fresh water tank.
8. The self-regulating filtration system based on raw water turbidity and flow rate according to claim 7, characterized in that, The liquid level sensor is a liquid level float.