A preliminary rainwater treatment system and a preliminary rainwater treatment method

Abstract

This application provides an initial rainwater treatment system and method, which comprises a vortex grit chamber, a mixing reaction tank, and a sedimentation tank. The vortex grit chamber is a single tank, while the mixing reaction tank and sedimentation tank each consist of two tanks, located on the left and right sides of the vortex grit chamber, arranged sequentially according to the flow path. Initial rainwater first enters the vortex grit chamber to remove sand particles, and the sand particles collected in the grit hopper are discharged by gravity through the grit discharge pipe. The initial rainwater flowing out of the vortex grit chamber flows into the mixing reaction tank, where chemicals are added to form flocs. After the chemicals are added, the initial rainwater enters the sedimentation tank for sludge-water separation, and the treated initial rainwater exits from the clear water zone of the sedimentation tank. The sludge collected in the sludge hopper of the sedimentation tank is discharged outside the tank through the bottom sludge discharge pipe, treated, and then transported off-site. This system can effectively remove sand particles, suspended solids, total phosphorus, and some COD from initial rainwater, is easy to maintain and manage, consumes little energy, and reduces operating costs.

Description

Technical Field

[0001] This application relates to the field of wastewater treatment, and more particularly to an initial rainwater treatment system and method. Background Technology

[0002] With the continuous advancement of urbanization in my country, gray infrastructure and paved areas are gradually increasing in cities; simultaneously, the service scope of urban stormwater and sewage pipe networks is expanding. Newly built urban pipe networks generally adopt a separate system, where rainwater and sewage are collected and discharged in different pipes. Sewage is transported to sewage treatment plants for treatment, while rainwater is generally discharged directly into water bodies. In the initial stages of rainfall, rainwater washes down urban roads and roofs, carrying dust and pollutants into the rainwater pipes, and also carrying pollutants from the atmosphere. Therefore, initial rainwater contains a large amount of pollutants, and direct discharge into water bodies would cause significant pollution. The "Outdoor Drainage Design Standard" (GB50014-2021) 4.1.19 also proposes that separate sewage systems should consider partially intercepting rainwater. That is, to control runoff pollution, it is recommended to include some rainwater runoff in the sewage system for treatment. Pollutant concentrations are highest in the initial stages of rainfall runoff, gradually decreasing as rainfall continues. Therefore, the standard recommends that sewage pipe networks consider intercepting a portion of the initial rainwater runoff as appropriate.

[0003] The quality of initial rainwater differs significantly from that of domestic sewage. Initial rainwater has a higher content of inorganic matter, higher chemical oxygen demand (COD) and suspended solids (SS), and lower boron (BOD), making it unsuitable for traditional biological treatment methods used in sewage treatment plants. Treatment of initial rainwater generally employs physical, chemical, or ecological methods, such as hydrocyclone separation, enhanced sedimentation, high-efficiency filtration, storage and sedimentation, constructed wetlands, and disinfection. Initial rainwater contains a large amount of impurities such as stones, garbage, leaves, and silt. Even after large impurities are intercepted by screens, a significant amount of silt and other impurities remain. Therefore, a grit removal process is essential for treating initial rainwater. Commonly used grit chambers include horizontal flow grit chambers, vortex grit chambers, and aerated grit chambers. Vortex grit chambers are more widely used in rainwater treatment due to their smaller footprint. Furthermore, effective removal of suspended solids and COD from rainwater warrants further research. Simply intercepting initial rainwater and treating it throughout the entire wastewater treatment process will inevitably lead to large fluctuations in water quality and quantity during rainy days, resulting in significant shock loads, affecting the growth of microorganisms in the biological treatment system, and hindering the operation and management of the wastewater treatment plant. Constructing initial rainwater treatment structures according to the process of urban wastewater treatment plants would require substantial investment, but the utilization rate would not be proportional to the investment, and maintenance and management would be complex. Currently, my country's wastewater treatment sector is primarily focused on upgrading and renovating wastewater treatment plants; there are few cases of treating initial rainwater separately, and there is a lack of comprehensive treatment processes and technical guidance. Summary of the Invention

[0004] One of the purposes of this application is to provide an initial rainwater treatment system and method, which aims to solve the problem of complex maintenance and management of existing systems that treat initial rainwater separately.

[0005] The technical solution of this application is:

[0006] An initial rainwater treatment system comprises a vortex grit chamber, a mixing reaction tank, and a sedimentation tank. The vortex grit chamber is a single tank, while the mixing reaction tank and sedimentation tank each consist of two tanks, located on the left and right sides of the vortex grit chamber respectively, arranged sequentially according to the flow path. The vortex grit chamber has an inlet pipe installed on its wall and contains a central pipe, sleeve, support components, a sand discharge pipe, and an annular overflow weir. A passageway is located at the top of the chamber, and a sand hopper and sand discharge pipe are located at the bottom. The sand hopper is connected to the chamber wall by a ramp. The mixing reaction tank consists of two tanks, connected sequentially to the two sides of the vortex grit chamber. The mixing reaction tank contains baffles, short baffles, and a chemical dosing pipe. The sedimentation tank consists of two tanks, connected sequentially to the two sides of the two mixing reaction tanks. Each sedimentation tank contains an ultrasonic generator, an inclined plate, and a π-shaped overflow weir. The ultrasonic generator and inclined plate are fixed by supports, and a sludge hopper and sludge discharge pipe are located at the bottom.

[0007] As one technical solution of this application, the vortex grit chamber consists of an annular overflow weir, a sleeve, and a central pipe from the wall inwards; the central axis of the central pipe is located at the center of the chamber, and it is a closed cylinder with a trumpet-shaped bottom; the sleeve is located outside the central pipe; the annular overflow weir is located on the inner wall of the top of the vortex grit chamber, and the annular overflow weir is a thin-walled weir; the slope at the bottom of the vortex grit chamber has an angle of inclination of 55° to 60° with the horizontal plane; the sand hopper is located below the slope, and it is a tapered cone with a side wall angle of inclination greater than 60° with the horizontal plane; the sand discharge pipe is located at the bottom of the sand hopper, and the connection with the bottom of the sand hopper is in the shape of an inverted trumpet, and the sand discharge pipe is equipped with a solenoid valve.

[0008] As one technical solution of this application, the top of the sleeve is fixed to the passageway at the top of the pool, and a filter screen is provided around the bottom; the filter screen is a sloping annular shape, with the top fixed to the bottom of the sleeve and the bottom vertically fixed to the slope at the bottom of the vortex sedimentation tank; the mesh diameter of the filter screen is 2mm; the bottom of the filter screen, which is close to the slope of the vortex sedimentation tank, has a plurality of spaced small holes, and the height of the small holes is 50mm.

[0009] As one technical solution of this application, the support includes at least four members, which are connected at equal intervals between the central tube and the wall of the vortex grit chamber; one end of each support is fixed to the wall of the vortex grit chamber, and the other end passes through the sleeve and is fixed to the outer wall of the central tube.

[0010] As one technical solution of this application, the annular overflow weir is spaced around the outer peripheral wall of the sleeve, and a first water passage hole is opened at the pool wall where the annular overflow weir connects with the mixing reaction tank; the first water passage hole is rectangular and is set at the same height as the annular overflow weir.

[0011] As one technical solution of this application, the mixing reaction tank is a rectangular tank, and four baffles are vertically arranged inside the tank and fixed to the tank wall in sequence with respect to the water flow direction; there is a gap between the first baffle, the third baffle and the bottom of the mixing reaction tank; one end of the second baffle and the fourth baffle is fixed to the bottom of the mixing reaction tank, and the distance between the first baffle and the tank wall, the distance between the first and second baffles, and the distance between the second and third baffles are equal, the distance between the third and fourth baffles and the distance between the fourth baffle and the tank wall are equal, and the distance between the former is smaller than the distance between the latter; two short baffles perpendicular to the first baffle are installed in the top space between the first baffle and the tank wall, forming a dosing area; the distance between the short baffles is equal to the width of the first water passage, and the top of the short baffle is the same height as the first baffle and the bottom extends 0.5m underwater.

[0012] As one technical solution of this application, the dosing pipe is divided into a main dosing pipe and two branch dosing pipes. Each branch dosing pipe passes through the wall of the mixing reaction tank and a short partition in sequence and extends into the dosing area. The end of the branch dosing pipe is nozzle-shaped. The two branch dosing pipes merge and connect to the main dosing pipe, and a solenoid valve is provided on the main dosing pipe.

[0013] As one technical solution of this application, a second water passage is opened at the bottom of the pool wall at the end of the process flow of the mixing reaction tank. There are two second water passages and they are rectangular in shape. The two second water passages are evenly distributed on the pool wall shared by the bottom of the mixing reaction tank and the sedimentation tank.

[0014] As one technical solution of this application, the inclined plate in the sedimentation tank is installed parallel to the flow direction of the water in the tank, and the inclined plate is installed at an angle of 60°. The length of the inclined plate is 1000mm, and the vertical spacing between the inclined plates is between 30 and 40mm. The support is divided into two layers. The upper support is located at the bottom of the inclined plate and is used to support the inclined plate. The lower support is located below the upper support. The space between the lower support and the upper support is the installation space for the ultrasonic generator. The ultrasonic generator is long and narrow, and its installation direction is parallel to the long side of the inclined plate. The π-shaped overflow weir is located in the clear water area above the inclined plate area. It consists of two transverse weirs and one longitudinal weir. The π-shaped overflow weir is a sawtooth weir with a sawtooth height b of 100mm and an angle a of 60° between the sawtooth inclined side and the bottom side. A third water passage is opened at the end of the longitudinal weir of the π-shaped overflow weir where it meets the tank wall. The width of the third water passage is equal to the width of the longitudinal weir, and the height is determined according to hydraulic calculations.

[0015] As one technical solution of this application, the sludge hopper in the sedimentation tank is a double hopper with an inverted triangular cross-section, and the inverted triangle has an angle of 55° to 60° with the horizontal plane. The bottom of the inverted triangle is provided with a sludge slit, which is long and narrow in plan. A sludge discharge pipe is provided at the bottom of the sludge slit. The two sludge discharge pipes are connected to the sludge discharge main pipe after they merge. One end of the sludge discharge main pipe is provided with a solenoid valve and the other end is provided with a vent valve.

[0016] Furthermore, this application also provides a method for treating initial rainwater, which employs the above-described initial rainwater treatment system to treat initial rainwater; it includes the following steps:

[0017] Grit removal; Initially, rainwater enters the vortex grit removal tank to remove sand particles from the water, and the sand particles collected in the sand hopper are discharged by gravity through the sand discharge pipe;

[0018] Mixing reaction: The initial rainwater flowing out of the vortex grit chamber flows into the mixing reaction tank. By adding chemicals to the mixing reaction tank, the water and chemicals react to form flocs.

[0019] Sedimentation: Initial rainwater after the addition of chemicals enters the sedimentation tank for mud-water separation. The treated initial rainwater exits from the clear water zone of the sedimentation tank, and the sludge collected in the sludge hopper of the sedimentation tank is discharged outside the tank through the sludge discharge pipe. After treatment, it is transported off-site. Ultrasonic waves are emitted by an ultrasonic generator to clean the inclined plate.

[0020] The beneficial effects of this application are:

[0021] In the initial rainwater treatment system and method of this application, the initial rainwater enters the sleeve of the vortex grit chamber tangentially, forming a vortex and promoting the sedimentation of sand particles in the water. At the same time, a central pipe is provided in the center of the chamber to help form the vortex, and the funnel-shaped structure at the bottom of the central pipe can promote the direction of water flow. A filter screen is installed at the bottom of the sleeve of the vortex grit chamber. After the initial rainwater reaches the bottom of the vortex grit chamber, it flows upward into the space between the sleeve and the chamber wall under the action of the funnel-shaped structure at the bottom of the central pipe. During this process, it passes through the filter screen, and the sand particles that have not settled are intercepted by the filter screen and fall into the sand hopper. As the rainwater rises in the space between the sleeve and the chamber wall, the fine sand particles that have not been intercepted by the filter screen will settle again. The settled fine sand particles will fall into the sand hopper through the small holes at the bottom of the filter screen, realizing the secondary sand removal of the vortex grit chamber and further reducing the sand content of the initial rainwater. Furthermore, after the initial rainwater enters the mixing reaction tank through the first through-hole, chemicals are added in the dosing area. Due to the small cross-section of the first through-hole and the dosing area, the water flow velocity is high, allowing for thorough mixing of the chemicals and water, resulting in uniform dispersion. The inlet flow direction of the sedimentation tank is parallel to the inclined direction of the inclined plate installation, effectively preventing short-circuiting and ensuring good sedimentation. Moreover, the total length of the sedimentation tank's effluent weir is relatively large, and the hydraulic load of the effluent weir is low, making it less likely that high flow velocities at the weir will cause suction to carry sediment out of the tank, thus ensuring effluent quality. Furthermore, the entire process structure is simple, easy to maintain and manage, and has low energy consumption. The vortex grit chamber has an open top and a passageway for easy cleaning of impurities and floating debris. Additionally, the mixing reaction tank only has baffles inside, making it less prone to clogging. The entire system relies on water level difference and gravity to maintain operation, without mechanical stirring equipment or aeration devices, resulting in low energy consumption and reduced operating costs. Therefore, this application can be widely used in the treatment of initial rainwater runoff from roofs and roads. It can effectively remove sand, suspended solids, total phosphorus (TP) and some COD from the initial rainwater. The system effluent can be discharged into bioretention facilities such as artificial wetlands and rain gardens to purify rainwater, control non-point source pollution, and realize the resource utilization of rainwater to a certain extent. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of an initial rainwater treatment system provided in an embodiment of this application;

[0024] Figure 2 This is a first-angle schematic diagram of the initial rainwater treatment system provided in an embodiment of this application;

[0025] Figure 3 A schematic diagram of a filter provided in an embodiment of this application;

[0026] Figure 4 This is a schematic diagram of the first angle of the filter provided in an embodiment of this application;

[0027] Figure 5 This is a schematic diagram showing the detailed structure of the π-type overflow weir provided in an embodiment of this application.

[0028] Icons: 1-Swirl grit chamber; 2-Mixing reaction tank; 3-Sedimentation tank; 4-Inlet pipe; 5-Central pipe; 6-Sleeve; 7-Annular overflow weir; 8-Grit hopper; 9-Grit discharge pipe; 10-Passageway; 11-Support component; 12-First water passage; 13-Main dosing pipe; 131-Branch dosing pipe; 14-Short partition; 15-Partition; 16-Second water passage; 17-Sludge zone; 18-Sludge hopper; 19-Sludge gap; 20-Sludge discharge pipe; 21-Lower support; 22-Ultrasonic generator; 23-Inclined plate; 24-π-shaped overflow weir; 25-Third water passage; 26-Vent valve; 27-Main sludge discharge pipe; 28-Filter screen; 29-Small hole; 30-Dosing zone. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can typically be arranged and designed in various different configurations.

[0030] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0031] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0032] In the description of this application, it should be noted that the terms "upper" and "lower" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of the invention is usually placed when in use. They are only used to facilitate the description of this application and to simplify the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0033] Furthermore, in this application, unless otherwise expressly specified and limited, "above or below" the first feature may include direct contact between the first and second features, or contact between the first and second features through another feature between them. Moreover, "above," "over," and "on" the first feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the first feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0034] Furthermore, terms such as "horizontal" and "vertical" do not imply that components must be absolutely horizontal or suspended, but rather that they can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0035] In the description of this application, it should also be noted that, unless otherwise expressly specified and limited, the terms "set up," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0036] Example:

[0037] Please refer to Figure 1 (Refer to) Figures 2 to 5 This application provides an initial rainwater treatment system, which is composed of a vortex grit chamber 1, two mixing reaction tanks 2 and two sedimentation tanks 3. The vortex grit chamber 1 is a single tank located in the center, and the mixing reaction tanks 2 and sedimentation tanks 3 each have two tanks, located on the left and right sides of the vortex grit chamber 1 respectively, arranged in sequence according to the flow.

[0038] The vortex grit chamber 1 has a cylindrical cross-section and is composed of a sand hopper 8, a conical pool, and a rectangular pool connected sequentially from bottom to top. The sand hopper 8 and the rectangular pool are connected by a sloping conical pool. The bottom of the vortex grit chamber 1 is the sand hopper 8, which is connected to the pool wall of the conical pool by a slope with an angle of 55° to 60° to the horizontal plane. An inlet pipe 4 is installed on the pool wall, and from the pool wall inwards are an annular overflow weir 7, a sleeve 6, and a central pipe 5. The central axis of the central pipe 5 coincides with the central axis of the vortex grit chamber 1. The central pipe 5 is a closed cylinder and mainly consists of a trumpet-shaped inverted conical pipe and a cylindrical pipe connected sequentially from bottom to top. The sleeve 6 is located on the outer periphery of the central pipe 5, with its top fixed to the passageway 10 at the top of the vortex grit chamber 1, and a filter screen 28 around its bottom. See also... Figure 3 , Figure 4 The filter screen 28 is a sloping annular shape with a diameter that gradually decreases from bottom to top. Its top is fixed to the bottom of the sleeve 6, and its bottom is vertically fixed to the bottom slope of the vortex sedimentation tank 1. The bottom of the filter screen 28 is closely attached to the slope of the vortex sedimentation tank 1 and has small holes 29. The holes 29 are spaced apart and have a height of 50mm. The mesh size of the filter screen 28 is 2mm. At the same time, its annular overflow weir 7 is installed on the inner wall of the top of the vortex sedimentation tank 1. The annular overflow weir 7 is a thin-walled weir. Four support members 11 are provided on the lower wall of the vortex sedimentation tank 1. The four support members 11 are located above the slope and are connected at equal intervals between the central pipe 5 and the wall of the vortex sedimentation tank 1. One end of each support member 11 is fixed to the tank wall, and the other end passes through the sleeve 6 and is fixed to the outer wall of the central pipe 5. Both ends are fixed radially. The sand hopper 8 is located below the slope and is a tapered cone with its sidewalls at an angle greater than 60° to the horizontal plane. The sand discharge pipe 9 is located at the bottom of the sand hopper 8 and is shaped like an inverted trumpet at the connection point with the bottom of the sand hopper 8. A solenoid valve is installed on the sand discharge pipe 9.

[0039] In addition, a first water passage hole 12 is opened on the pool wall where the annular overflow weir 7 connects to the mixing reaction tank 2. The first water passage hole 12 is rectangular and has the same height as the annular overflow weir 7. The mixing reaction tank 2 is a rectangular pool with four vertical baffles 15 installed inside. The four baffles 15 are fixed to the pool wall of the mixing reaction tank 2 in sequence along the water flow direction. Among them, there is a gap between the first baffle 15, the third baffle 15 and the bottom of the mixing reaction tank 2. One end of the second baffle 15 and the fourth baffle 15 are fixed to the bottom of the mixing reaction tank 2. Two short baffles 14 perpendicular to the baffle 15 are installed in the top space between the first baffle 15 and the starting end of the pool wall of the mixing reaction tank 2. The two short baffles 14 form a chemical dosing area 30 here. The distance between the short baffles 14 is equal to the width of the first water passage hole 12. The top of the short baffle 14 is the same height as the first baffle 15, and its bottom extends 0.5m underwater.

[0040] Meanwhile, the dosing pipe includes a main dosing pipe 13 and two branch dosing pipes 131. Each branch dosing pipe 131 passes through the wall of the mixing reaction tank 2 and a short partition 14 in sequence and extends into the dosing area 30. The end of the branch dosing pipe 131 is nozzle-shaped. The two branch dosing pipes 131 merge and connect to the main dosing pipe 13. A solenoid valve is installed on the main dosing pipe 13.

[0041] At the bottom of the wall at the end of the process flow of the mixing reaction tank 2, there are two second water passage holes 16. The second water passage holes 16 are rectangular in shape and are evenly distributed on the bottom of the mixing reaction tank 2 and the wall shared by the sedimentation tank 3.

[0042] Furthermore, the sedimentation tank 3, from top to bottom, consists of: a π-shaped overflow weir 24, an inclined plate 23, an ultrasonic generator 22, a support 21, a sludge zone 17, a sludge hopper 18, a sludge slit 19, and a sludge discharge pipe 20. The inclined plate 23 is installed parallel to the water flow direction within the tank, with an installation angle of 60° and a length of 1000mm. The vertical spacing between the inclined plates 23 is between 30 and 40mm. The support consists of a lower support 21 and an upper support. The upper support is located at the bottom of the inclined plate 23 and supports it. The space between the lower and upper supports is for the installation of the ultrasonic generator 22. The ultrasonic generator 22 is elongated and installed parallel to the long side of the inclined plate 23. The π-shaped overflow weir 24 is located in the clear water zone above the inclined plate zone and consists of two transverse weirs and one longitudinal weir. (See [reference]). Figure 5 The π-shaped overflow weir 24 is a sawtooth weir with a sawtooth height b of 100 mm and an angle a of 60° between the hypotenuse and the bottom edge. A third water passage 25 is opened at the longitudinal outlet end of the π-shaped overflow weir 24 where it connects to the pool wall. The width of the third water passage 25 is equal to the width of the longitudinal weir, and its height is determined based on hydraulic calculations. The sludge hopper 18 on the sedimentation tank 3 is a double hopper with an inverted triangular cross-section. The angle between the hypotenuse and the horizontal plane is 55°–60°. A sludge slit 19 is located at the bottom of the inverted triangle, which is elongated in plan. A sludge discharge pipe 20 is located at the bottom of the sludge slit 19. The two sludge discharge pipes 20 merge to form a main sludge discharge pipe 27. One end of the main sludge discharge pipe 27 is equipped with a solenoid valve, and the other end is equipped with a vent valve 26.

[0043] The purification steps and working principle of this system for initial rainwater are as follows:

[0044] S1, Sedimentation: Initial rainwater must first pass through a screen to filter out impurities such as branches, garbage, and large stones before entering this system. Initial rainwater enters the upper part of the vortex sedimentation tank 1 tangentially from the inlet pipe 4, flowing within the space formed by the central pipe 5 and the sleeve 6. Under the influence of gravity and centrifugal force, a vortex is formed, and sand particles settle into the bottom sand hopper 8. After reaching the bottom of the vortex sedimentation tank 1, the initial rainwater is redirected by the funnel-shaped structure at the bottom of the central pipe 5, flowing towards the space between the tank wall and the sleeve 6, continuing to flow upwards. During this process, the initial rainwater passes through the filter screen 28. At this point, sand particles larger than the mesh size of the filter screen 28 that have not settled are intercepted by the filter screen 28 and fall into the sand hopper 8. As the initial rainwater rises within the space between the sleeve 6 and the tank wall, the fine sand particles in the residual water experience a combination of the lift force and gravity. Conversely, the cross-sectional area of ​​this space is larger than that of the space inside the sleeve 6, resulting in a decrease in water flow velocity. Fine sand particles that are not intercepted by the filter screen 28 will settle again. This space is equivalent to a vertical flow grit chamber. The filter screen 28 is installed perpendicular to the slope at the bottom of the vortex grit chamber 1. Small holes 29 are spaced apart at the bottom of the filter screen 28 near the slope. After the fine sand particles fall onto the slope, they will fall into the sand hopper 8 through the small holes 29, realizing secondary sand removal in the vortex grit chamber 1 and further reducing the sand content of the initial rainwater. After the initial rainwater enters the top of the vortex grit chamber 1, it enters the annular overflow weir 7 at the top. The annular overflow weir 7 has first water passage holes 12 on the pool walls on both sides that connect with the mixing reaction tank 2. The initial rainwater that has undergone sand treatment enters the mixing reaction tank 2 through the first water passage holes 12. The solenoid valve on the sand discharge pipe 9 at the bottom of the sand hopper 8 is opened, and the sand particles collected in the bottom sand hopper 8 are discharged out of the pool.

[0045] S2, Mixing Reaction: Initial rainwater enters the mixing reaction tank 2 from the vortex grit chamber 1 through the first water passage 12. It first enters the dosing zone 30 formed by two short baffles 14, the width of which is the same as the width of the first water passage 12. Due to the limited size of the water passage, the water flow velocity is relatively high, resulting in a large velocity gradient G. The chemicals are injected into the water at a high velocity through the nozzle at the end of the dosing branch pipe 131. With the help of this high flow velocity, the chemicals and initial rainwater mix rapidly. The nozzle at the end of the dosing branch pipe 131 is less prone to clogging due to the scouring effect of the water flow. The mixed liquid flows back and forth between the baffles 15 within the tank, making the mixing reaction tank 2 essentially... The flocculation tank with baffles is placed vertically, which also serves to mix and partially flocculate the mixture. During the flow of the mixture in the tank, the first three channels have small cross-sectional areas, while the last two channels have large cross-sectional areas. The velocity gradient G value of the water flow gradually decreases, which is conducive to the reaction between suspended solids in the initial rainwater and the chemicals to form flocs. At the same time, it can also carry some COD. If there is a large amount of inorganic phosphorus in the initial rainwater, adding coagulants can also promote the precipitation of inorganic phosphorus. The chemicals generally used are coagulants and coagulant aids, or high-efficiency composite coagulants can be used to promote the stable aggregation of suspended solids in the initial rainwater to form flocs and promote the precipitation of pollutants in the sedimentation tank 3.

[0046] S3, Sedimentation: When the water flows to the end of the mixing reaction tank 2, the initial rainwater containing flocs enters the sedimentation tank 3 above the sludge zone 17 at the bottom through the two second water passages 16 at the bottom of the mixing reaction tank 2. The water flows upward, passing through the inclined plate 23. The flocculent sludge in the rainwater settles to the upper surface of the inclined plate 23 under gravity. After the sludge accumulates to a certain extent, it slides down to the bottom sludge zone 17 of the sedimentation tank 3 under gravity and accumulates in the sludge hopper 18, thus achieving sludge-water separation. The inclined plate 23 is installed at a 60° angle, and the vertical spacing between the inclined plates 23 is between 30 and 40 mm to ensure smooth sludge discharge and prevent clogging. The water continues to rise to the clear water zone above the inclined plate 23. The clear water zone is designed with a π-shaped overflow weir 24, which consists of two transverse overflow weirs and one longitudinal overflow weir. The system consists of a sawtooth weir at the sludge-water separation point. Initial rainwater, after sludge-water separation, first enters two transverse overflow weirs, then flows into the longitudinal overflow weir. Due to the water level difference, the water in the longitudinal overflow weir flows to the end and exits the pool through the third water passage 25 on the pool wall, thus ending the water purification process. The π-shaped overflow weir 24 in the sedimentation tank 3 has a relatively large total length and a low hydraulic load at the outlet, making it less likely to be drawn out of the pool by the high flow velocity at the weir, thus ensuring the quality of the effluent. Once the sludge in the sludge hopper 18 has accumulated to a certain thickness, the solenoid valve on the sludge discharge main pipe 27 is opened. Under the influence of the gravity of the sludge in the sludge hopper 18 and the pressure of the water flow above, the sludge is drawn from the sludge slit 19 into the sludge discharge pipe 20, then converges back into the sludge discharge main pipe 27 and is discharged out of the pool for further treatment and transportation.

[0047] It should be noted that when the inclined plate 23 has been used for a long time and a large amount of sludge has accumulated on it, several ultrasonic generators 22 on the support below the inclined plate 23 can be activated. The generated ultrasonic waves cause the inclined plate 23 and the sludge to vibrate, and the sludge falls off the inclined plate 23 and into the sludge hopper 18, realizing automatic cleaning of the inclined plate 23, saving time and effort, solving the problem of easy clogging of the inclined plate 23, and eliminating the need for high-pressure water flushing. At the same time, the support for the inclined plate 23 and the ultrasonic generators 22 can be made of reinforced concrete strip structure or high-strength corrosion-resistant metal material. The principle is not to significantly reduce the water flow area on the plane of the sedimentation tank 3. This application does not specify the details, but its setting method and function are within the protection scope of this application.

[0048] Specifically, the top of the vortex grit chamber 1 in this application is mostly open space, allowing for easy observation of floating debris accumulation and timely cleaning. The passageway 10 on the top provides space for cleaning. The grit discharge pipe 9 of the vortex grit chamber 1 can be designed with multiple outlets, serving as an empty pipe when the vortex grit chamber 1 is emptied. Sedimentation tanks 3 typically use perforated pipes or mechanical sludge discharge methods. Mechanical sludge discharge requires mechanical equipment such as scrapers, resulting in a complex tank structure. Perforated pipe sludge discharge often experiences clogging problems in the later stages. The sedimentation tank 3 in this system uses a combination of sludge slits 19 and sludge discharge pipes 20, eliminating the need for mechanical equipment and avoiding the common clogging problems of perforated sludge discharge pipes. Furthermore, an empty valve is installed at the other end of the main sludge discharge pipe 27, allowing the sedimentation tank 3 to be emptied during maintenance. Furthermore, the solenoid valves used in this system for chemical dosing, sand removal, and sludge removal can all be remotely controlled using existing PLC control cabinets.

[0049] This system has no complex structure and is easy to maintain and manage. The entire system relies on water level difference and gravity to maintain its operation. There are no mechanical mixing equipment or aeration devices, so it consumes less energy and reduces operating costs. It can be widely used for the treatment of initial rainwater runoff from roofs and roads. It can effectively remove sand, suspended solids, total phosphorus (TP) and some COD from initial rainwater. The system effluent can be discharged into artificial wetlands, rain gardens and other bioretention facilities to purify rainwater, control non-point source pollution and realize the resource utilization of rainwater to a certain extent.

[0050] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. An initial rainwater treatment system, characterized in that, The system includes a vortex grit chamber, two mixing reaction tanks, and two sedimentation tanks. The two mixing reaction tanks are respectively located on opposite sides of the vortex grit chamber, and each sedimentation tank is located outside its corresponding mixing reaction tank. The vortex grit chamber is located at the center and contains a central pipe and a sleeve. The central pipe is coaxially aligned with the vortex grit chamber and located within the inner cavity of the sleeve. The top of the sleeve is fixed to a passageway at the top of the vortex grit chamber, and a filter screen is installed around its bottom circumference. The bottom of the filter screen is vertically fixed to the slope at the bottom of the vortex grit chamber. The vortex grit chamber is composed of a sand hopper, a conical tank, and a rectangular tank connected sequentially from bottom to top. The sand hopper and the rectangular tank are connected via the sloping conical tank, and the bottom of the sand hopper is connected to a sand discharge pipe. An inlet pipe is installed on the upper part of the vortex grit chamber wall, and the tank contains supporting components and an annular overflow weir. The central pipe... The system comprises an inverted conical tube and a cylindrical tube connected sequentially from bottom to top. The top of the cylindrical tube is connected to the passageway and is closed. The annular overflow weir is located on the top of the inner wall of the vortex sedimentation tank and is a thin-walled weir. The slope of the conical tank has an inclination angle of 55° to 60° with the horizontal plane. The sand hopper is located at the bottom of the slope of the conical tank and is a tapered cone with an inclination angle greater than 60° with the sidewall of the horizontal plane. The sand discharge pipe is located at the bottom of the sand hopper and its connection with the bottom of the sand hopper is an inverted funnel shape. The sand discharge pipe is equipped with a solenoid valve. The diameter of the filter screen gradually decreases from bottom to top, and its top is fixed to the bottom of the sleeve, while its bottom is vertically fixed to the slope at the bottom of the vortex sedimentation tank. The mesh diameter of the filter screen is 2 mm, and the bottom of the filter screen, which is in close contact with the slope of the vortex sedimentation tank, has multiple spaced small holes with a height of 50 mm.

2. The initial rainwater treatment system according to claim 1, characterized in that, The support includes at least four members, which are connected at equal intervals between the central pipe and the wall of the vortex sedimentation tank; one end of each support is fixed to the wall of the vortex sedimentation tank, and the other end passes through the sleeve and is fixed to the outer wall of the central pipe.

3. The initial rainwater treatment system according to claim 1, characterized in that, The annular overflow weir is spaced around the outer periphery of the sleeve, and a first water passage hole is opened at the pool wall where the annular overflow weir connects with the mixing reaction tank; the first water passage hole is rectangular and is set at the same height as the annular overflow weir.

4. The initial rainwater treatment system according to claim 3, characterized in that, The mixing reaction tank is a rectangular tank with four parallel baffles vertically spaced inside. The distances from the first, second, third, and fourth baffles to the vortex grit chamber gradually increase. The first and third baffles have gaps between themselves and the bottom of the mixing reaction tank, while the bottoms of the second and fourth baffles are fixed to the bottom of the mixing reaction tank. Two short baffles perpendicular to the first baffle are installed between the first baffle and the inner wall of the mixing reaction tank near the vortex grit chamber. These two short baffles, the first baffle, and the mixing reaction tank together form a dosing area. The distance between the two short baffles is equal to the width of the first water passage, and the top of each short baffle is at the same height as the first baffle, with its bottom extending 0.5m underwater.

5. The initial rainwater treatment system according to claim 4, characterized in that, Both of the mixing reaction tanks are equipped with dosing branch pipes, each of which extends into the dosing area and has a nozzle-shaped bottom; the two dosing branch pipes are connected to the main dosing pipe, which is equipped with a solenoid valve.

6. The initial rainwater treatment system according to claim 1, characterized in that, Two spaced-apart second water passages are provided on the bottom side wall of the mixing reaction tank near the sedimentation tank. The second water passages are rectangular.

7. The initial rainwater treatment system according to claim 1, characterized in that, The sedimentation tank is provided with, from bottom to top, a lower support, an ultrasonic generator, an upper support, an inclined plate, and a π-shaped overflow weir. The lower support is located between two opposite inner sidewalls of the sedimentation tank. The ultrasonic generator is elongated and mounted on the lower support, with its installation direction parallel to the long side of the inclined plate. The inclined plate is installed at a 60° angle on the upper support, with its installation direction parallel to the water flow direction in the sedimentation tank. The length of the inclined plate is 1000 mm, and the vertical distance between adjacent inclined plates is 30-40 mm. The π-shaped overflow weir is located in the clear water zone above the area where the inclined plate is located, and consists of two transverse weirs and one longitudinal weir, which are sawtooth weirs. A third water passage is opened at the outlet end of the longitudinal weir where it meets the tank wall of the sedimentation tank, and the width of the third water passage is equal to the width of the longitudinal weir. A sludge hopper is provided at the bottom of the sedimentation tank, and the sludge hopper is connected to a sludge discharge pipe.

8. The initial rainwater treatment system according to claim 7, characterized in that, The sludge hopper has a double-bucket structure with an inverted triangular cross-section. The angle between the hypotenuse of the inverted triangle and the horizontal plane is 55° to 60°. The bottom of the sludge hopper is provided with a sludge slit, and the bottom of the sludge slit is connected to the sludge discharge pipe. The two sludge discharge pipes merge into a sludge discharge main pipe. A solenoid valve is provided at one end of the sludge discharge main pipe, and a vent valve is provided at the other end.

9. A method for treating initial rainwater, comprising using the initial rainwater treatment system according to any one of claims 1 to 8, characterized in that, Includes the following steps: Sand settling; after the initial rainwater enters the vortex sedimentation tank, the sand particles in the water are removed, and the sand particles collected in the sand hopper of the vortex sedimentation tank are discharged by gravity through the sand discharge pipe; Mixing reaction: The initial rainwater flowing out of the vortex grit chamber flows into the mixing reaction tank. By adding a chemical agent to the mixing reaction tank, the water and the chemical agent react to form flocs. Sedimentation: Initial rainwater after the addition of chemicals enters the sedimentation tank for mud-water separation. The treated initial rainwater exits from the clear water zone of the sedimentation tank, and the sludge collected in the sludge hopper of the sedimentation tank is discharged outside the tank through the sludge discharge pipe. After treatment, it is transported off-site. Ultrasonic waves are emitted by an ultrasonic generator to clean the inclined plate.

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