A sewage pretreatment system comprising an oil and sand removal and primary settling tank

Abstract

The utility model discloses a sewage pretreatment system, including the oil -removing sand pool and primary sedimentation tank that communicate in proper order. The oil -removing sand pool is composed of water intake area, sand removing area and oil removing area, is used for removing grit and grease in sewage in proper order, and the primary sedimentation tank includes primary sedimentation tank water intake area, the inclined tube precipitation area of built -in inclined tube filler, sludge concentration discharge area and water outlet area, realizes mud water separation and sludge discharge. The primary sedimentation tank water intake area is linked with the oil removing area through the channel, and the channel is fixedly connected with the super outlet pipe, and the super outlet pipe is provided with the super isolation gate plate. The system adopts the split type design, and is convenient for flexible arrangement when the land is tight. The super outlet pipe and the super isolation gate plate are arranged on the channel from the oil -removing sand pool to the primary sedimentation tank, can select whether to super the primary sedimentation tank according to the water inlet suspended solid concentration, directly super when SS is less than or equal to 200mg / L, effectively retains the carbon source, reduces the additional carbon source dosage of subsequent biochemical treatment, reduces the operation cost, and improves the system flexibility and economy.

Description

Technical Field

[0001] This utility model relates to the field of wastewater pretreatment technology, specifically a wastewater pretreatment system including oil and sand removal and a primary sedimentation tank. Background Technology

[0002] The pretreatment unit of a municipal wastewater treatment plant is the first step in the entire treatment process. Its core function is to remove physical pollutants and some organic pollutants from the influent, mainly including suspended solids (SS) and organic matter (indicating BOD and COD). The treatment effect at this stage directly affects the stable operation of subsequent biological treatment units and the final effluent quality. For a long time, grit chambers and primary sedimentation tanks have been the most commonly used pretreatment processes, playing a crucial role in removing SS, some BOD, and COD. Grit chambers are mainly used to remove denser inorganic particles (such as sand). Aerated grit chambers, in particular, separate organic matter from sand particles by controlling the aeration intensity, reducing organic matter loss while removing sand. Primary sedimentation tanks remove suspended solids and some settleable organic matter through gravity settling. Common forms include horizontal flow sedimentation tanks and inclined plate sedimentation tanks; the latter effectively improves treatment efficiency by increasing the sedimentation area.

[0003] A search revealed CN217757087U, which discloses a wastewater treatment pond, but it still has the following drawbacks in practical applications: 1. The high-load and integrated features of the integrated oil and sand removal sedimentation tank make it suitable for wastewater treatment plants with limited space. However, the integrated design also means that the sand removal and sedimentation units must be located together, which makes the layout less flexible. 2. In actual operation, wastewater treatment plants may need to exceed the sedimentation tank depending on the quality of the incoming water. However, the integrated design of the oil and sand removal sedimentation tank cannot exceed the sedimentation unit, resulting in a lack of operational flexibility. Utility Model Content

[0004] The purpose of this invention is to provide a wastewater pretreatment system that includes oil and sand removal and a primary sedimentation tank, in order to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a wastewater pretreatment system including an oil and sand removal tank and a primary sedimentation tank, comprising an oil and sand removal tank and a primary sedimentation tank, wherein the oil and sand removal tank includes an inlet zone, a sand removal zone and an oil removal zone, and the primary sedimentation tank includes a primary sedimentation tank inlet zone, an inclined tube sedimentation zone, a sludge thickening and discharge zone and an outlet zone. The inlet area is used to receive and distribute raw wastewater. The sand removal zone is connected to the inlet water zone and is used to settle and remove sand and gravel from the wastewater. The oil removal zone is connected to the sand removal zone and separates the oil from the wastewater after sand and gravel sedimentation to obtain oil-removed wastewater. The primary sedimentation tank inlet area is connected to the oil removal zone through a channel to receive oil-removed wastewater. An overflow outlet pipe is fixedly connected to the channel, and an overflow isolation gate is installed on the overflow outlet pipe. The inclined tube sedimentation zone is connected to the inlet area of ​​the primary sedimentation tank. The interior of the inclined tube sedimentation zone is equipped with inclined tube packing material that flows water from bottom to top, which is used to separate sludge and water, so that the oil-removed wastewater settles to form pretreated water, which is then discharged through a collection tank. The sludge thickening and discharge zone is connected to and located below the inclined tube sedimentation zone, and is used to collect and discharge sludge. The effluent zone, located at the rear of the inclined tube sedimentation zone, is used to collect and discharge the pretreated water discharged from the collection tank.

[0006] Preferably, the water inlet area includes a raw water inlet pipe and a water inlet distribution channel. The raw water inlet pipe is connected to the water inlet distribution channel, and the water inlet distribution channel is connected to the sand removal area through an outlet. The outlet of the water inlet distribution channel is equipped with an inlet gate.

[0007] Preferably, there can be multiple oil and sand removal tanks, and all multiple oil and sand removal tanks are connected to the primary sedimentation tank inlet area of ​​the primary sedimentation tank through channels.

[0008] Preferably, the sand removal zone further includes a bubble-cutting aerator head that receives gas from an external air intake pipe, and the bubble-cutting aerator head has a self-closing function when the air supply stops.

[0009] Preferably, the sand removal zone is specifically divided into two interconnected areas, namely a first area and a second area. Wastewater first flows into the first area and then into the second area. Both the first and second areas are equipped with bubble cutting aeration heads. The volume of the second area is larger than that of the first area. The first area is used to wash sand and gravel, and the second area is used to settle sand and gravel.

[0010] Preferably, the bottom of the sand removal zone is provided with a sand discharge hopper for collecting sand and gravel, and the sand and gravel collected in the sand discharge hopper is pumped to the sand-water separator by a sand discharge pump.

[0011] Preferably, the oil removal zone further includes a submersible aerator, which is located in the longitudinal center of the oil removal zone.

[0012] Preferably, an oil and scum collector is provided at the front of the inclined tube sedimentation zone. The oil and scum collector can discharge the oil and scum generated by the submersible aerator to the scum storage tank. The oil in the scum storage tank is sent to the scum-water separation device by the scum discharge pump.

[0013] Preferably, the sludge thickening and discharge zone further includes a drive device, a sludge scraper, a sludge discharge pump, a sludge discharge pipe, and a sludge interface meter. One or more sludge thickening hoppers are provided at the bottom of the sludge thickening and discharge zone. The sludge scraper is located at the bottom of the sludge thickening and discharge zone and is driven by the drive device. The sludge in the sludge thickening hopper is discharged through the sludge discharge pump and the sludge discharge pipe. The sludge interface meter is located above the sludge thickening and discharge zone to monitor the sludge thickness at the bottom of the sludge thickening and discharge zone.

[0014] Preferably, the water outlet area further includes a water outlet channel, which is connected to the water collection tank. The drain outlet of the water outlet channel is fixedly connected to a water outlet pipe, and a water outlet isolation gate is provided at the inlet of the water outlet pipe.

[0015] Beneficial effects This utility model provides a wastewater pretreatment system including oil and sand removal and a primary sedimentation tank, which has the following beneficial effects: 1. This wastewater pretreatment system, which includes oil and sand removal tanks and a primary sedimentation tank, allows for flexible arrangement based on actual needs, especially when the wastewater treatment plant has limited land area.

[0016] 2. This wastewater pretreatment system, which includes oil and sand removal and a primary sedimentation tank, features an bypass effluent pipe and a bypass isolation gate at the effluent channel of the oil and sand removal tank. This overcomes the limitation of integrated oil and sand removal sedimentation tanks, which cannot bypass the sedimentation unit, making operation more flexible. Furthermore, it can determine whether to bypass the primary sedimentation tank unit based on the raw wastewater quality. Generally, when the raw water suspended solids (SS) concentration does not exceed 200 mg / L, the effluent from the oil and sand removal tank can bypass the primary sedimentation tank. This maximizes the retention of carbon sources in the pretreatment system effluent, reduces the amount of external carbon sources added to the downstream biological treatment system, and saves on wastewater treatment plant reagent consumption. Attached Figure Description

[0017] Figure 1 This utility model presents an overall structural principle diagram of a wastewater pretreatment system including oil and sand removal and a primary sedimentation tank. Figure 2 This is a schematic diagram of the three-dimensional structure of the inclined tube packing material in a wastewater pretreatment system that includes oil and sand removal and a primary sedimentation tank, as proposed in this utility model.

[0018] In the diagram: 1. Raw water inlet pipe; 2. Inlet water distribution channel; 3. Sand removal zone; 4. Oil removal zone; 5. Primary sedimentation tank inlet zone; 6. Inclined tube sedimentation zone; 7. Effluent zone; 8. Effluent pipe; 9. Sludge thickening and discharge zone; 21. Inlet gate; 31. Bubble cutting aeration head; 32. Air inlet pipe; 33. Sand discharge hopper; 34. Sand pump; 35. Sand-water separator; 41. Submersible aerator; 42. Overpass isolation gate; 43. Overpass effluent pipe; 44. Floating oil and scum collector; 61. Drive unit; 62. Sludge scraper; 63. Inclined tube packing; 64. Sludge interface meter; 71. Collection tank; 72. Effluent channel; 73. Effluent isolation gate; 91. Thickened sludge hopper; 92. Sludge discharge pump; 93. Sludge discharge pipe. Detailed Implementation

[0019] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0020] In the description of this utility model, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0021] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0022] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0023] Please see Figure 1-2 This utility model provides a technical solution: a wastewater pretreatment system including an oil and sand removal tank and a primary sedimentation tank, comprising an oil and sand removal tank and a primary sedimentation tank. The oil and sand removal tank includes an inlet zone, a sand removal zone 3 and an oil removal zone 4. The primary sedimentation tank includes a primary sedimentation tank inlet zone 5, an inclined tube sedimentation zone 6, a sludge thickening and discharge zone 9 and an outlet zone 7. The inlet area is used to receive and distribute raw sewage. The raw sewage has the following characteristics: CODcr≤800mg / L, BOD5≤360mg / L, SS≤650mg / L, TP≤8mg / L.

[0024] Sand removal zone 3 is connected to the inlet water zone and is used to remove sand and gravel from wastewater by sedimentation. Oil removal zone 4 is connected to sand removal zone 3 and separates the oil from the wastewater after sand and gravel sedimentation to obtain oil-removed wastewater; The primary sedimentation tank inlet area 5 is connected to the oil removal area 4 through a channel to receive oil removal wastewater. An overpass outlet pipe 43 is fixedly connected to the channel, and an overpass isolation gate 42 is installed on the overpass outlet pipe 43. Inclined tube sedimentation zone 6 is connected to the inlet zone 5 of the primary sedimentation tank. The interior of the inclined tube sedimentation zone 6 is equipped with inclined tube packing material 63 with water flowing from bottom to top, which is used to separate sludge and water, so that the oil-removed wastewater settles to form pretreated water, which is then discharged through the collection tank 71. The inclined tube packing material 63 consists of at least two inclined tube pools, which are composed of multiple inclined tubes arranged in parallel. The length of the inclined tube is 1500mm, the inner diameter of the inclined tube is 80mm, and the inclined installation angle of the inclined tube is 60°.

[0025] Sludge thickening and discharge zone 9 is connected to and located below inclined tube sedimentation zone 6, and is used to collect and discharge sludge. The effluent zone 7 is located behind the inclined tube sedimentation zone 6 and is used to collect and discharge the pretreated water discharged from the collection tank 71.

[0026] In situations where wastewater treatment plants have limited land, separating the oil and sand removal tank and the primary sedimentation tank allows for flexible arrangement based on actual needs. Installing a bypass effluent pipe 43 and a bypass isolation gate 42 at the effluent channel of the oil and sand removal tank solves the shortcoming of integrated oil and sand removal sedimentation tanks being unable to bypass the sedimentation unit, making operation more flexible. Furthermore, the decision to bypass the primary sedimentation tank unit can be determined based on the raw wastewater quality. Generally, when the raw water suspended solids (SS) concentration does not exceed 200 mg / L, the effluent from the oil and sand removal tank can bypass the primary sedimentation tank, maximizing the retention of carbon sources in the pretreatment system effluent, reducing the amount of external carbon sources added to the downstream biological treatment system, and saving on wastewater treatment plant reagent consumption.

[0027] The water intake area includes a raw water inlet pipe 1 and a water intake distribution channel 2. The raw water inlet pipe 1 is connected to the water intake distribution channel 2. The water intake distribution channel 2 is connected to the sand removal area 3 through the outlet. The outlet of the water intake distribution channel 2 is equipped with an inlet gate 21. The outlet of the water intake distribution channel 2 can be controlled by setting the inlet gate 21.

[0028] There can be multiple oil and sand removal tanks. All of these tanks are connected to the primary sedimentation tank inlet area 5 via channels. By setting up multiple oil and sand removal tanks, single-tank maintenance can be achieved. During maintenance, it is only necessary to close the inlet gate 21 of the corresponding oil and sand removal tank and stop the water inlet before maintenance can be carried out. The other oil and sand removal tanks can operate normally, thus ensuring the continuous and stable operation of the entire system.

[0029] The sand removal zone 3 also includes a bubble cutting aeration head 31, which is supplied with gas by an external air inlet pipe 32. The bubble cutting aeration head 31 has a self-closing function when the air supply stops. The individual diameter of the bubble cutting aeration head 31 is 100 mm, the air volume is 1 to 2 cubic meters per minute, and the pressure is not less than 50 kPa. The air inlet pipe 32 and the bubble cutting aeration head 31 form an aeration system. The aeration system works continuously to meet the needs of sand washing. The bubble cutting aeration head 31 has a self-closing function when the air supply stops. This function can prevent sludge and impurities from clogging the aeration system when the aeration stops.

[0030] The sand removal zone 3 is specifically divided into two interconnected areas: the first area and the second area. Wastewater first flows into the first area and then into the second area. Both the first and second areas are equipped with bubble cutting aeration heads 31. The volume of the second area is larger than that of the first area. The first area is used to wash the sand and gravel, and the second area is used to settle the sand and gravel. The special design of the sand removal zone 3 can maximize the sedimentation of sand particles, ensuring the sand removal effect, while preventing bubbles from entering the inclined tube sedimentation zone 6.

[0031] The bottom of the sand removal zone 3 is equipped with a sand discharge hopper 33 for collecting sand and gravel. The sand and gravel collected in the sand discharge hopper 33 are sent to the sand-water separator 35 by the sand discharge pump 34. The sand-water separator 35 can separate sand and water. The separated sand can be put into the construction industry to realize waste recycling, and the separated water can be reinjected into the water intake zone to realize water reprocessing.

[0032] The oil removal zone 4 also includes a submersible aerator 41, which is located in the longitudinal center of the oil removal zone 4. The submersible aerator 41 is a jet aeration type, and the preferred quantity is 8 sets. The air volume is 7 cubic meters / hour / set, and the pressure is not less than 30 kPa. The aerator generates microbubbles, and the flotation function can float the oil and scum in the sewage to the water surface.

[0033] An oil and scum collector 44 is installed at the front of the inclined tube sedimentation zone 6. The oil and scum collector 44 can discharge the oil and scum generated by the submersible aerator 41 to the scum storage tank. The oil in the scum storage tank is sent to the scum-water separation device by the scum discharge pump. The separated oil can be recycled and reused, thereby avoiding resource waste. At the same time, in order to ensure the removal of oil, the size design of the oil removal zone 4 can be enlarged according to the needs.

[0034] The sludge thickening and discharge zone 9 also includes a drive unit 61, a sludge scraper 62, a sludge discharge pump 92, a sludge discharge pipe 93, and a sludge interface meter 64. One or more sludge thickening hoppers 91 are provided at the bottom of the sludge thickening and discharge zone 9. The sludge scraper 62 is located at the bottom of the sludge thickening and discharge zone 9 and is driven by the drive unit 61. The sludge in the sludge thickening hopper 91 is discharged through the sludge discharge pump 92 and the sludge discharge pipe 93. The sludge interface meter 64 is located above the sludge thickening and discharge zone 9 and is used to monitor the sludge thickness at the bottom of the sludge thickening and discharge zone 9.

[0035] The sludge scraper 62 can be driven by the drive device 61. The sludge scraper 62 can scrape the sludge in the sludge concentration and discharge zone 9 into the sludge concentration hopper 91. Then, the sludge discharge pump 92 can be used to discharge the sludge from the sludge discharge pipe 93.

[0036] In practical applications, a programmable logic controller (PLC) can be used to connect a sludge interface meter 64, a sludge scraper 62, and a sludge discharge pump 92. When the sludge interface meter 64 detects that the sludge thickness is higher than a predetermined value, the sludge discharge pump 92 can be automatically turned on to achieve automated control and operation, thus solving the problem of insufficient automation in existing processes.

[0037] The water outlet area 7 also includes a water outlet channel 72, which is connected to the water collection tank 71. The drain outlet of the water outlet channel 72 is fixedly connected to a water outlet pipe 8, and a water outlet isolation gate 73 is installed at the inlet of the water outlet pipe 8. By installing the water outlet isolation gate 73, the drain outlet of the water outlet channel 72 can be controlled.

[0038] Actual measurements show that the water quality from outlet pipe 8 meets the following standards: CODcr≤450mg / L, BOD5≤250mg / L, SS≤320mg / L, TP≤6.5mg / L, sand removal rate ≥80% with a particle size of 200 micrometers or larger, and oil and grease removal rate ≥80%.

[0039] This invention integrates sand removal, oil removal, and sedimentation into a single treatment system, solving the problem that traditional processes cannot simultaneously perform sand removal, oil removal, and sedimentation within a single processing unit. This reduces the floor space and construction costs. The inclined tube packing 63 in the inclined tube sedimentation zone 6 uses inclined tubes, and the hydraulic load on the inclined tube surface can reach up to 15-21 cubic meters per square meter per hour, which is 5-10 times that of traditional sedimentation tanks. This improves water treatment capacity and reduces the floor space required, solving the problems of low hydraulic load and large floor space in existing processes. Furthermore, the entire pretreatment system does not require the addition of conventional reagents, has fewer mechanical equipment, lower power consumption, and reduces operating costs, solving the problem of high energy consumption in existing processes.

[0040] The accompanying drawings of the embodiments disclosed in this utility model only involve the structures involved in the embodiments disclosed in this utility model. Other structures can refer to the general design. In the absence of conflict, the same embodiment and different embodiments of this utility model can be combined with each other. Finally: The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A wastewater pretreatment system comprising an oil and sand removal tank and a primary sedimentation tank, characterized in that: The oil and sand removal tank includes an inlet zone, a sand removal zone, and an oil removal zone; the primary sedimentation tank includes a primary sedimentation tank inlet zone, an inclined tube sedimentation zone, a sludge thickening and discharge zone, and an outlet zone. The inlet area is used to receive and distribute raw wastewater. The sand removal zone is connected to the inlet water zone and is used to settle and remove sand and gravel from the wastewater. The oil removal zone is connected to the sand removal zone and separates the oil from the wastewater after sand and gravel sedimentation to obtain oil-removed wastewater. The primary sedimentation tank inlet area is connected to the oil removal zone through a channel to receive oil-removed wastewater. An overflow outlet pipe is fixedly connected to the channel, and an overflow isolation gate is installed on the overflow outlet pipe. The inclined tube sedimentation zone is connected to the inlet area of ​​the primary sedimentation tank. The interior of the inclined tube sedimentation zone is equipped with inclined tube packing material that flows water from bottom to top, which is used to separate sludge and water, so that the oil-removed wastewater settles to form pretreated water, which is then discharged through a collection tank. The sludge thickening and discharge zone is connected to and located below the inclined tube sedimentation zone, and is used to collect and discharge sludge. The effluent zone, located at the rear of the inclined tube sedimentation zone, is used to collect and discharge the pretreated water discharged from the collection tank.

2. The wastewater pretreatment system according to claim 1, comprising oil and sand removal and a primary sedimentation tank, is characterized in that: The water intake area includes a raw water inlet pipe and a water inlet distribution channel. The raw water inlet pipe is connected to the water inlet distribution channel, and the water inlet distribution channel is connected to the sand removal area through an outlet. The outlet of the water inlet distribution channel is equipped with an inlet gate.

3. A wastewater pretreatment system comprising oil and sand removal and a primary sedimentation tank according to claim 2, characterized in that: The number of oil and sand removal tanks can be multiple, and all multiple oil and sand removal tanks are connected to the inlet area of ​​the primary sedimentation tank through channels.

4. A wastewater pretreatment system comprising oil and sand removal and a primary sedimentation tank according to claim 3, characterized in that: The sand removal zone also includes a bubble-cutting aerator head that receives gas from an external air intake pipe, and the bubble-cutting aerator head has an automatic shut-off function when the gas supply is interrupted.

5. A wastewater pretreatment system comprising oil and sand removal and a primary sedimentation tank according to claim 4, characterized in that: The sand removal zone is specifically divided into two interconnected areas: a first area and a second area. Wastewater first flows into the first area and then into the second area. Both the first and second areas are equipped with bubble cutting aeration heads. The volume of the second area is larger than that of the first area. The first area is used to wash sand and gravel, and the second area is used to settle sand and gravel.

6. A wastewater pretreatment system comprising oil and sand removal and a primary sedimentation tank according to claim 5, characterized in that: The bottom of the sand removal zone is equipped with a sand discharge hopper for collecting sand and gravel. The sand and gravel collected in the sand discharge hopper are pumped to the sand-water separator by a sand discharge pump.

7. A wastewater pretreatment system comprising oil and sand removal and a primary sedimentation tank according to claim 3, characterized in that: The oil removal zone also includes a submersible aerator, which is located in the longitudinal center of the oil removal zone.

8. A wastewater pretreatment system comprising oil and sand removal and a primary sedimentation tank according to claim 7, characterized in that: A set of oil and scum collectors is installed at the front of the inclined tube sedimentation zone. The oil and scum collectors can discharge the oil and scum generated by the submersible aerator to the scum storage tank. The oil in the scum storage tank is sent to the scum-water separation device by the scum discharge pump.

9. A wastewater pretreatment system comprising oil and sand removal and a primary sedimentation tank according to claim 1, characterized in that: The sludge thickening and discharge zone also includes a drive unit, a sludge scraper, a sludge discharge pump, a sludge discharge pipe, and a sludge interface meter. One or more sludge thickening hoppers are provided at the bottom of the sludge thickening and discharge zone. The sludge scraper is located at the bottom of the sludge thickening and discharge zone and is driven by the drive unit. The sludge in the sludge thickening hopper is discharged through the sludge discharge pump and the sludge discharge pipe. The sludge interface meter is located above the sludge thickening and discharge zone and is used to monitor the sludge thickness at the bottom of the sludge thickening and discharge zone.

10. A wastewater pretreatment system according to claim 1, comprising oil and sand removal and a primary sedimentation tank, characterized in that: The water outlet area also includes a water outlet channel, which is connected to the water collection tank. The outlet of the water outlet channel is fixedly connected to a water outlet pipe, and a water outlet isolation gate is installed at the inlet of the water outlet pipe.

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