Double-layer reinforced nitrogen and phosphorus removal constructed wetland system and sewage treatment method thereof

Abstract

The invention belongs to the technical field of constructed wetlands, and particularly relates to a double-layer reinforced nitrogen and phosphorus removal constructed wetland system and a sewage treatment method thereof. The system comprises a constructed wetland, a baffle is vertically arranged in the constructed wetland and divides the interior of the constructed wetland into a filler area and a water collecting area, and the filler area is sequentially provided with an aluminosilicate modified filler layer, a supporting layer and a sulfenyl filler layer from top to bottom; a siphon is arranged in the water collecting area, and a valve is arranged at a water outlet of the siphon to control periodical drainage of the siphon. The two layers of fillers are separated, the upper layer focuses on nitrification, the lower layer focuses on denitrification and phosphorus removal, the siphon arranged in the water collecting area can simulate a tidal flow constructed wetland, conditions are created for ammonia oxidation of the upper layer, denitrification of the lower layer is not affected, synchronous nitrification and denitrification can be realized, and the water collecting area can be used for simulating the tidal flow constructed wetland. And the two layers of fillers can be independently managed and maintained, so that the device has important significance on sewage treatment of the constructed wetland.

Description

Technical Field

[0001] This invention belongs to the field of constructed wetland technology, specifically relating to a two-layer enhanced nitrogen and phosphorus removal constructed wetland system and its wastewater treatment method. Background Technology

[0002] Constructed wetlands are a water purification technology that simulates the ecological functions of natural wetlands. Through the synergistic effect of packing materials, aquatic plants, and microorganisms, pollutants in wastewater are removed through processes such as physical filtration, chemical adsorption, and biodegradation. This system has advantages such as low infrastructure and operating costs, simple maintenance, and ecological and aesthetic benefits. It is widely used in the treatment of domestic sewage and rainwater runoff, and is particularly effective in purifying organic matter, nitrogen, phosphorus, and suspended solids.

[0003] However, traditional constructed wetlands generally suffer from insufficient reoxygenation capacity, which limits their removal efficiency for pollutants such as ammonia nitrogen. To address this, tidal flow constructed wetlands have emerged. This technology simulates tidal rhythms through periodic flooding and drainage, utilizing the passive rise and fall of water levels to achieve efficient reoxygenation: during drainage, air enters the pores of the packing material, and during flooding, the oxygen-laden water permeates the bed, thereby significantly improving oxygen transfer efficiency and enhancing the aerobic microorganisms' ability to degrade ammonia nitrogen and organic matter.

[0004] Despite this, tidal flow constructed wetlands are currently predominantly single-stage structures. In practice, single-stage wetlands generally suffer from a systemic contradiction between uneven dissolved oxygen distribution and insufficient carbon source supply, resulting in limited simultaneous removal efficiency of nitrogen pollutants. Specifically: horizontal subsurface flow constructed wetlands are predominantly anoxic environments, which, while beneficial for denitrification, severely restrict the efficiency of the initial nitrification reaction due to insufficient oxygen supply; while vertical subsurface flow constructed wetlands, although able to supplement oxygen and enhance nitrification through vertical infiltration, often lack sufficient organic carbon sources to support the subsequent denitrification process, making it difficult to improve the total nitrogen removal rate of the system. Furthermore, single-stage wetland structures also face high clogging risks and high maintenance costs. During long-term operation, suspended solids and biofilms easily accumulate in the packing layer, not only exacerbating clogging but also leading to decreased treatment efficiency or even failure. Especially for mixed-packing wetlands, once clogging occurs, it is often necessary to remove and clean or replace the entire packing material, resulting in a large workload, long cycle, and serious impact on the continuous and stable operation of the wastewater treatment system. Summary of the Invention

[0005] The purpose of this invention is to provide a two-layer enhanced nitrogen and phosphorus removal constructed wetland system and its wastewater treatment method, thereby overcoming the shortcomings of the prior art and developing a two-layer enhanced nitrogen and phosphorus removal constructed wetland that can effectively optimize dissolved oxygen distribution, rationally utilize carbon sources, and has anti-clogging and easy-to-maintain characteristics.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows: On one hand, the present invention provides a two-layer enhanced nitrogen and phosphorus removal constructed wetland system, including a constructed wetland, wherein a baffle is vertically installed inside the constructed wetland, the baffle dividing the interior of the constructed wetland into a filling zone and a water collection zone. The filling zone is provided with an aluminosilicate modified filling layer, a support layer and a sulfur-based filling layer from top to bottom. A siphon is provided in the water collection zone, and a valve is provided at the outlet of the siphon to control the periodic drainage of the siphon.

[0007] The system in this application adopts a functionally layered design concept, vertically separating an aluminosilicate-modified packing layer (upper aerobic zone) and a sulfur-based packing layer (lower anoxic / anaerobic zone). The upper aerobic zone, relying on the aluminosilicate-modified packing, efficiently promotes nitrification and precisely removes ammonia nitrogen; the lower anoxic / anaerobic zone utilizes sulfur-based packing to simultaneously drive denitrification and chemical phosphorus removal. This zoned, collaborative working mechanism fundamentally solves the technical bottleneck of traditional single-stage wetlands in achieving simultaneous nitrification and denitrification, significantly improving the removal efficiency of total nitrogen and total phosphorus.

[0008] Furthermore, by using the siphon pipe as a key control unit, the system automatically creates and maintains stratified aerobic / anaerobic environments through periodic drainage and inflow, requiring no external power. More importantly, the modular design of the packing material allows the upper packing layer to be independently removed for maintenance or replacement without emptying the entire system, significantly reducing maintenance costs and workload. This effectively solves the inherent problems of difficult maintenance and easy clogging in traditional wetlands, ensuring the long-term stable operation of the system.

[0009] In some other embodiments, an inlet pipe is provided at one end of the top of the packing area, and the inlet pipe is connected to the sewage in the equalization tank. The inlet pipe is used to discharge the sewage after primary sedimentation treatment in the equalization tank into the constructed wetland for further treatment.

[0010] In some other embodiments, a grid is provided at the bottom of the baffle, the pore size of which is smaller than the particle size of the packing material; the grid occupies 1 / 5 to 1 / 3 of the total height of the baffle. The grid is used to guide the wastewater treated in the packing area into the collection area for storage and to isolate the packing material and other large particles, preventing blockage of the siphon pipe.

[0011] In some other embodiments, the aluminosilicate-modified packing layer is configured as follows: a shell with an open top is provided above the support layer, a perforated filter plate is provided at the bottom of the shell, and the aluminosilicate-modified packing layer is disposed inside the shell. The packing material in the aluminosilicate-modified packing layer can be removed individually for convenient subsequent operation and maintenance.

[0012] In some other embodiments, the support layer is a circular plate with grooves, and the pore size of the perforated filter plate is smaller than the particle size of the aluminosilicate-modified packing. The support layer is used to support the aluminosilicate-modified packing layer. The perforated filter plate allows wastewater to flow from top to bottom into the sulfur-based packing layer while preventing leakage of the aluminosilicate-modified packing.

[0013] In some other embodiments, the connection between the housing and the support layer is a detachable connection, preferably a snap-fit ​​connection.

[0014] In some other embodiments, the horizontal height of the siphon inlet is the same as that of the support layer, the vertical height of the siphon outlet is lower than that of the siphon inlet, and the siphon outlet is equipped with a ball valve.

[0015] This invention is based on the simple physical phenomenon of siphon principle and does not require complex electromechanical equipment or advanced control systems.

[0016] In some other embodiments, the siphon is an inverted U-shaped siphon.

[0017] The internal filling materials (aluminosilicates and sulfur-based fillers) are all conventional or readily available materials. This highly simplified design significantly reduces construction costs, operating energy consumption, and maintenance technical barriers, making it a strong potential application in resource-limited areas.

[0018] The preparation method of aluminosilicate modified filler is as follows: using gravel as aggregate, aluminosilicate inorganic powder is mixed with water to form a wet mixture, which is then uniformly coated on the gravel surface in a granulation device to form a continuous outer coating layer. Subsequently, the wet particles are cured and dried to harden the outer aluminosilicate layer and stably bond it to the gravel surface, thus obtaining the aluminosilicate modified filler.

[0019] The preparation method of sulfur-based filler is as follows: using sulfur-based filler as the core particle, a composite outer coating layer is introduced on its surface through a wet coating method during the granulation process, so that the functional filler is uniformly wrapped around the sulfur core. After curing and drying, a sulfur-based composite filler with a stable structure and an intact outer coating layer is formed.

[0020] Specifically, the preparation of aluminosilicate modified filler involves using gravel with a particle size of approximately 5–25 mm as aggregate, selecting aluminosilicate inorganic powder as the main coating material, and compounding it with approximately 10–30% inorganic cementitious material. This is then mixed with water to prepare a wet mixture, with the water content controlled within a range sufficient to form a plastic wet material. The gravel is added to a granulation or coating device, and the wet mixture is added in stages under rotation, gradually and uniformly coating the gravel surface. This coating process typically lasts 5–20 minutes, forming a continuous aluminosilicate outer coating layer with a thickness of approximately 0.5–2.0 mm. After coating, the particles are cured at 15–35 ℃ for 12–48 h, followed by drying at 40–80 ℃ for 6–24 h to harden the outer coating layer and stably bond it to the gravel surface, resulting in a structurally stable aluminosilicate modified filler.

[0021] Preparation of sulfur-based composite filler: Sulfur-based particles with a particle size of approximately 2–8 mm are used as the core material, and their surface is modified by wet coating in granulation or coating equipment. During the coating process, functional inorganic powder and binder are mixed at a mass ratio of approximately (80–95):(5–20), and an appropriate amount of water is added to form the outer coating material. This material is then uniformly coated onto the outer surface of the sulfur-based core particles during a 10–25 min roller coating process, forming a composite outer coating layer with a thickness of approximately 0.3–1.5 mm. The temperature of the coating process is preferably controlled within the range of 20–40 ℃. After the granules are formed, they are allowed to stand for 2–8 h and then cured for 12–48 h, followed by drying at 30–70 ℃ for 6–24 h to obtain a sulfur-based composite filler with an intact outer coating and good water resistance.

[0022] More specifically, the preparation of the aluminosilicate modified filler involves using gravel with a particle size of approximately 15 mm as aggregate, selecting aluminosilicate inorganic powder as the main coating material, and compounding it with approximately 20% inorganic cementitious material. This is then mixed with water to prepare a wet mixture, with the water content controlled within a range sufficient to form a plastic wet material. The gravel is added to a granulation or coating device, and the wet mixture is added in stages under rotation, gradually and uniformly coating the gravel surface. This coating process typically lasts 10 minutes, forming a continuous aluminosilicate outer coating layer with a thickness of approximately 1.0 mm. After coating, the particles are cured at 25 ℃ for 24 h, followed by drying at 60 ℃ for 12 h to harden the outer coating layer and stably bond it to the gravel surface, resulting in a structurally stable aluminosilicate modified filler.

[0023] Preparation of sulfur-based composite filler: Sulfur-based particles with a particle size of approximately 5 mm were used as the core material, and their surface was modified by wet coating in granulation or coating equipment. During the coating process, functional inorganic powder and binder were mixed at a mass ratio of approximately 80:20, and an appropriate amount of water was added to form the outer coating material. This material was then uniformly coated onto the outer surface of the sulfur-based core particles during a 20-minute roller coating process, forming a composite outer coating layer with a thickness of approximately 0.3–1.5 mm. The temperature of the coating process was preferably controlled within the range of 30 ℃. After the granules were formed, they were allowed to stand for 5 hours and then cured for 24 hours, followed by drying at 60 ℃ for 12 hours to obtain a sulfur-based composite filler with an intact outer coating and good water resistance.

[0024] On the other hand, the present invention provides a method for treating wastewater using a dual-layer enhanced nitrogen and phosphorus removal constructed wetland system as described in the first aspect, comprising the following steps: (1) Wastewater enters the artificial wetland pond and flows from top to bottom through the silicate-aluminate modified packing layer, the support layer and the sulfur-based packing layer to the bottom. After being filtered by the grid, it enters the water collection area; the valve of the siphon outlet is always closed. (2) When the water level in the collection area rises to the top connection pipe of the siphon, the valve opens and the sewage is discharged through the siphon. (3) When the water level in the collection area drops to the top connecting pipe of the siphon, the valve closes and the collection area begins to collect water. When the water level rises again to the top connecting pipe of the siphon, the valve opens again, and this cycle repeats.

[0025] The wastewater treatment process of this invention is simple and has high treatment efficiency.

[0026] The beneficial effects of this invention are: (1) This invention controls the periodic rise and fall of water level through a siphon drainage device, naturally forming a microenvironment within the wetland where an upper aerobic zone and a lower anoxic / anaerobic zone coexist. In the upper aerobic zone, nitrification of ammonia nitrogen is efficiently carried out with the synergistic effect of aluminosilicate-modified packing material; the sulfur-based packing material in the lower anaerobic zone not only provides a reducing environment for denitrification, but its unique chemical properties also enable efficient and stable removal of total phosphorus through precipitation with phosphates, thus simultaneously achieving the dual goals of nitrogen and phosphorus removal within a single system. This zoning design fundamentally overcomes the technical bottleneck of single-stage wetlands in simultaneously addressing nitrification and denitrification, significantly improving the total nitrogen removal rate of the system.

[0027] (2) The present invention places the upper packing material in an independent container. This design allows the packing material to be replaced, cleaned or replenished without disturbing the lower structure, which greatly reduces the maintenance difficulty and cost, effectively solves the problem of traditional wetland maintenance requiring shutdown and dredging, and ensures the long-term stable operation of the system.

[0028] (3) The present invention adopts a vertically stacked double-layer structure instead of the traditional multi-level parallel or series layout. Under the premise of achieving the same treatment effect, it significantly reduces the land area occupied, which is particularly suitable for areas with scarce land resources and provides a new path for the intensive application of artificial wetlands. Attached Figure Description

[0029] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0030] Figure 1 This is a schematic diagram of the overall structure of the double-layer enhanced nitrogen and phosphorus removal constructed wetland in Embodiment 1 of the present invention; Figure 2 This is a graph showing the changes in the concentrations of various pollutants in Example 1. The components include: 1. Inlet pipe; 2. Siphon pipe; 3. Shell; 4. Support layer; 5. Perforated filter plate; 6. Grille; 7. Water collection area; and 8. Ball valve. Detailed Implementation

[0031] Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be construed as limiting the scope of the invention. Specific conditions not specified in the embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Components whose manufacturers are not specified are all commercially available conventional products.

[0032] Currently, single-stage constructed wetlands suffer from uneven dissolved oxygen distribution and insufficient carbon sources, making it difficult to achieve simultaneous nitrification and denitrification. This invention presents a double-layer constructed wetland for enhanced nitrogen and phosphorus removal, which separates the two layers of packing material to achieve simultaneous nitrification and denitrification. Compared to traditional single-stage constructed wetlands, the siphon design in this invention allows the wetland to encompass both an upper aerobic environment and a lower anaerobic environment. Under aerobic conditions and with the combined action of aluminosilicate-modified packing material, the upper layer can remove the vast majority of ammonia nitrogen, while the lower layer, under anaerobic conditions and with sulfur-based packing material, can significantly remove nitrate nitrogen and phosphorus. Furthermore, the upper packing material is contained in a container and can be removed separately, facilitating subsequent maintenance without affecting the treatment effect. In addition, this constructed wetland requires a much smaller footprint than multi-stage constructed wetlands, requiring only increased depth.

[0033] The solution of the present invention will be further described below with reference to specific embodiments: Example 1 A two-layer enhanced nitrogen and phosphorus removal constructed wetland system, such as Figure 1 As shown, the structure includes an artificial wetland. A vertically installed baffle divides the interior of the wetland into a packing zone and a collection zone 7. A grid 6 is located at the bottom of the baffle, with an aperture smaller than the packing particle size; the grid occupies 1 / 5 to 1 / 3 of the total height of the baffle. The grid 6 is used to guide the wastewater treated in the packing zone into the collection zone 7 for storage and to isolate the packing material and other large particles, preventing blockage of the siphon pipe 2.

[0034] An inlet pipe 1 is installed at the top end of the packing zone, connecting to the equalization tank. The inlet pipe 1 is used to transport the wastewater to be treated, after primary sedimentation in the equalization tank, to the shell for further treatment. From top to bottom, the packing zone consists of an aluminosilicate-modified packing layer, a support layer 4, and a sulfur-based packing layer. The aluminosilicate-modified packing layer is used for ammonia oxidation, thereby promoting nitrification and reducing the ammonia nitrogen concentration in the wastewater. The support layer 4 is a grooved circular plate used to support the aluminosilicate-modified packing layer. The sulfur-based packing layer performs denitrification while also reducing total phosphorus concentration, significantly reducing nitrate nitrogen and total phosphorus concentrations in the wastewater. A siphon pipe 2 is installed in the collection zone 7. The horizontal height of the inlet of the siphon pipe 2 is the same as that of the support layer, while the vertical height of the outlet of the siphon pipe 2 is lower than that of its inlet. A ball valve 8 is installed at the outlet of the siphon pipe 2. Siphon pipe 2 uses pressure difference to siphon and drain water, simulating a tidal flow artificial wetland, and finally discharges the treated wastewater into an external drainage ditch. Ball valve 8 is used to control the closing of siphon pipe 2, thereby enabling siphon pipe 2 to drain water periodically.

[0035] Specifically, ball valve 8 is closed from the start of water inlet. After sewage enters the collection area 7, when the liquid level rises to just cover the top packing material, a large pressure difference is formed inside and outside the siphon pipe 2. Ball valve 8 is then opened, and the treated sewage in the collection area 7 is discharged through the siphon pipe 2 due to the pressure difference, forming a siphon to simulate a tidal flow artificial wetland. The finally treated sewage is discharged into the external drainage ditch. At this time, the water level drops, and the siphon ends when it is below the inlet of the siphon pipe. Ball valve 8 is then closed, and it is opened again when the water level covers the top packing material, and the cycle repeats.

[0036] To facilitate the replacement and maintenance of the packing material, a shell 3 with a top opening is provided above the support layer 4. A perforated filter plate 5 is provided at the bottom of the shell 3, and an aluminosilicate modified packing layer is provided inside the shell 3. The pore size of the perforated filter plate 5 is smaller than the particle size of the aluminosilicate modified packing material, which allows wastewater to flow from top to bottom into the sulfur-based packing layer, while preventing leakage of the aluminosilicate modified packing material.

[0037] The above-mentioned method for treating wastewater using a two-layer enhanced nitrogen and phosphorus removal constructed wetland system includes the following steps: (1) After the initial sedimentation treatment in the equalization tank, the sewage undergoes nitrification and denitrification in sequence through the aluminosilicate modified packing layer, the support layer 4 and the sulfur-based packing layer from top to bottom via the inlet pipe 1, thereby achieving efficient removal of pollutants such as nitrogen and phosphorus from the discharged sewage.

[0038] (2) After the sewage is filtered by the screen, it enters the water collection area. The ball valve 8 installed at the outlet of the siphon pipe 2 is always closed. When the water level in the water collection area rises to the bend of the siphon pipe 2, the ball valve 8 opens and the sewage is discharged through the siphon pipe 2 by the pressure difference. (3) When the water level in the collection area 7 drops to the bend of the siphon pipe 2, the ball valve 8 closes and the collection area begins to collect water. When the water level rises again to the bend of the siphon pipe 2, the ball valve 8 opens, and this cycle repeats.

[0039] Application Example 1 Construct an artificial wetland 8 m long, 5 m wide, and 2 m deep. Vertically install a baffle inside the wetland, dividing it into a packing zone and a catchment zone. Install a grid along the entire length of the baffle, 1 m from the rear of the wetland and up to 25 cm above the ground. The grid aperture should be smaller than the minimum particle size of the packing material in the packing zone. Install an inverted U-shaped siphon on the wall behind the catchment zone, with the bend positioned 5 cm above the top of the packing material. The siphon inlet should be located approximately 1 m above the ground, at the junction of two packing layers. Install an electric ball valve at the siphon outlet, ensuring the lowest point of the outlet is below the inlet level. Enclose the artificial wetland with a support layer 1 m above the ground, protruding approximately 20 cm. Construct an 8 m wide, 5 m deep, 1 m iron container, filled with aluminosilicate modified packing material. Fill the wetland with sulfur-based packing material up to the support layer, then place the container on top, covering the sulfur-based packing material.

[0040] During normal operation, the ball valve is closed. Wastewater, after initial sedimentation in the regulating tank, enters the wetland through the inlet pipe. The wastewater flows from top to bottom, passes through the screen, and enters the collection area, causing the water level to rise. When the water level just covers the packing material, the ball valve is opened, and the wastewater is discharged through the siphon pipe due to pressure difference, forming a siphon and causing the water level to drop. Once the water level drops below the inlet, the valve is closed, and water collection begins, causing the water level to rise again. This cycle repeats continuously.

[0041] Figure 2 The graph shows the changes in the concentrations of various pollutants. Figure 2 It can be seen that the concentrations of nitrate nitrogen, ammonia nitrogen, and total phosphorus in the effluent treated using this application example are all significantly reduced.

[0042] In summary, this invention, through its zoned oxygen supply design, functional packing material adaptation, and modular structural innovation, can significantly improve treatment efficiency. It not only enables simultaneous nitrification and denitrification but also allows for separate management of the two packing layers, facilitating subsequent maintenance and repair. This provides an advanced and feasible technical solution for efficient, energy-saving, and easy-to-maintain decentralized wastewater treatment.

[0043] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A two-layer enhanced nitrogen and phosphorus removal constructed wetland system, characterized in that, The invention includes an artificial wetland, in which a vertical baffle is installed inside, dividing the interior of the artificial wetland into a filler zone and a water collection zone. The filler zone is provided with a layer of aluminosilicate modified filler, a support layer and a sulfur-based filler layer from top to bottom. The water collection zone is equipped with a siphon pipe, and the outlet of the siphon pipe is equipped with a valve to control the periodic drainage of the siphon pipe.

2. The constructed wetland system for enhanced nitrogen and phosphorus removal in a two-layer configuration according to claim 1, characterized in that, A water inlet pipe is installed at one end of the top of the packing area, and the water inlet pipe is connected to the sewage in the equalization tank.

3. The constructed wetland system for enhanced nitrogen and phosphorus removal in a two-layer configuration according to claim 1, characterized in that, The bottom of the baffle is equipped with a grid, the pore size of which is smaller than the particle size of the filler; the grid occupies 1 / 5 to 1 / 3 of the total height of the baffle.

4. The dual-layer enhanced nitrogen and phosphorus removal constructed wetland system according to claim 1, characterized in that, The aluminosilicate modified filler layer is configured as follows: a shell with an open top is provided above the support layer, a perforated filter plate is provided at the bottom of the shell, and the aluminosilicate modified filler layer is placed inside the shell.

5. The dual-layer enhanced nitrogen and phosphorus removal constructed wetland system according to claim 4, characterized in that, The support layer is a circular plate with grooves, and the pore size of the perforated filter plate is smaller than the particle size of the aluminosilicate modified filler.

6. The dual-layer enhanced nitrogen and phosphorus removal constructed wetland system according to claim 4, characterized in that, The connection between the shell and the support layer is detachable, preferably a snap-fit ​​connection.

7. The dual-layer enhanced nitrogen and phosphorus removal constructed wetland system according to claim 1, characterized in that, The water inlet of the siphon is at the same horizontal level as the support layer.

8. The constructed wetland system for enhanced nitrogen and phosphorus removal in a two-layer configuration according to claim 1, characterized in that... The vertical height of the siphon outlet is lower than the vertical height of the siphon inlet, and the siphon outlet is equipped with a ball valve.

9. The constructed wetland system for enhanced nitrogen and phosphorus removal in a two-layer configuration according to claim 1, characterized in that, The siphon is an inverted U-shaped siphon.

10. A method for treating wastewater using a dual-layer enhanced nitrogen and phosphorus removal constructed wetland system as described in any one of claims 1-9, characterized in that, Includes the following steps: (1) Wastewater enters the artificial wetland pond and flows from top to bottom through the silicate-aluminate modified packing layer, the support layer and the sulfur-based packing layer to the bottom. After being filtered by the grid, it enters the water collection area; the valve of the siphon outlet is always closed. (2) When the water level in the collection area rises to the top connection pipe of the siphon, the valve opens and the sewage is discharged through the siphon. (3) When the water level in the collection area drops to the top connecting pipe of the siphon, the valve closes and the collection area begins to collect water. When the water level rises again to the top connecting pipe of the siphon, the valve opens again, and this cycle repeats.

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