Primary rainwater diversion purification ecological ditch

Abstract

The utility model provides an ecological ditch of initial rainwater diversion purification, including the sedimentation unit, initial rainwater diversion unit and primary purification unit that are in series in proper order, the sedimentation unit includes the sedimentation area, and the upper portion of the side wall of sedimentation area is equipped with the water inlet of sedimentation area, and the bottom of sedimentation area is equipped with the sludge discharge mechanism, the initial rainwater diversion unit includes the diversion dam, and the diversion dam from bottom to top includes the sedimentation area limiting platform, filler filter area, rainwater discharge area and flood discharge area in proper order, and rainwater discharge area and flood discharge area are connected with rain flood discharge channel, the primary purification unit includes the primary treatment area, and the primary treatment area is communicated with the sedimentation area through filler filter area, and the water flow direction of primary treatment area is equipped with the water retaining wall of height not less than diversion dam, and the both sides of diversion dam are adjacent with sedimentation area and primary treatment area respectively, through the reasonable setting of structure, the effective diversion of initial rainwater and the efficient exclusion of middle and later period rainwater are realized, the retention time of initial rainwater in ecological ditch is prolonged, and the purification effect of the pollutants in rainwater is improved.

Description

Technical Field

[0001] This invention belongs to the field of urban rainwater treatment, specifically relating to an ecological ditch for initial rainwater diversion and purification. Background Technology

[0002] Ecological ditch technology is an important technique for removing surface runoff pollution, widely used in the treatment of agricultural non-point source pollution from rainfall, and in recent years has been gradually applied to urban stormwater treatment. However, urban stormwater runoff and agricultural stormwater runoff have different pollution characteristics. Urban areas have high underlying surface hardening rates, resulting in large instantaneous runoff volumes, especially during heavy rainstorms, where the flow rate increases dramatically. Furthermore, urban stormwater pollutants are mainly concentrated in the initial stages of rainfall, while the pollutant content in the middle and later stages is lower and can be discharged directly without treatment. Therefore, municipal stormwater ecological ditches cannot be designed using methods for agricultural non-point source runoff pollution. Given that the main pollution in municipal stormwater is concentrated in the initial runoff, effective treatment of the initial runoff is sufficient to meet ecological safety requirements, while preventing erosion and damage to the ecological ditches from flood peaks. However, existing ecological ditch technologies cannot effectively separate initial runoff and suffer from low pollutant removal efficiency, easy clogging of fillers, and high maintenance costs. Summary of the Invention

[0003] To address the aforementioned problems, the purpose of this invention is to provide an ecological ditch for initial rainwater diversion and purification, thereby achieving effective separation and treatment of initial rainwater and solving the problems of existing ecological ditches being unable to adapt to large urban rainwater runoff, having low pollutant removal efficiency, and high system operation and maintenance costs.

[0004] To achieve the above objectives, the technical solution adopted by the present invention includes:

[0005] An ecological ditch for initial rainwater diversion and purification includes a sedimentation unit, an initial rainwater diversion unit, and a primary purification unit connected in series. The sedimentation unit includes a sedimentation zone with an inlet and a sludge removal mechanism at the bottom. The initial rainwater diversion unit includes a diversion dam, which, from bottom to top, includes a sedimentation zone limiting platform, a filter median zone, a rainwater discharge zone, and a flood discharge zone. The rainwater discharge zone and the flood discharge zone are connected to a stormwater discharge channel. The primary purification unit includes a primary treatment zone, which is connected to the sedimentation zone via the filter median zone. The primary treatment zone has a retaining wall at least as high as the diversion dam in the direction of water flow. The diversion dam is adjacent to the sedimentation zone and the primary treatment zone on both sides.

[0006] Preferably, the highest initial rainwater level is located at the junction of the filter area and the rainwater discharge area. The rainwater discharge area is equipped with a rainwater discharge outlet, and the flood discharge area is equipped with a flood discharge outlet. The lowest point of the flood discharge outlet is the water level during heavy rain. The sedimentation zone inlet includes high and low inlets. The bottom of the high inlet of the sedimentation zone inlet is at the same height as the top of the flood discharge outlet, and the bottom of the low inlet of the sedimentation zone inlet is at the same height as the highest initial rainwater level.

[0007] Preferably, the sludge discharge mechanism includes multiple sludge discharge branch pipes, the outlets of each sludge discharge branch pipe are connected through a sludge discharge main pipe, and the outlet of the sludge discharge main pipe is connected to the sludge discharge tank.

[0008] Preferably, the bottom of the sedimentation zone is also equipped with a weir and emergent plants.

[0009] Preferably, the maximum bottom elevation of the sludge discharge main pipe is lower than the liquid level during the rainstorm but higher than the highest liquid level of the initial rainwater, and the highest liquid level of the sludge discharge tank is lower than the highest liquid level of the initial rainwater.

[0010] Preferably, the filter media is hollow and filled with matrix packing material, the sidewall of the filter media is provided with uniformly distributed filter holes, and the sidewall of the filter media is also provided with inspection holes.

[0011] Preferably, the filter media is vertically partitioned inside the filter media, and the partition has water distribution holes. The partition divides the inner cavity of the filter media into two areas along the water flow direction, and the matrix fillers in each area are of different types or different grades.

[0012] Furthermore, it also includes a composite waterfall purification unit connected in series with the primary purification unit. The water-retaining wall faces the composite waterfall purification area, and multiple water outlet branch pipes connected to the primary treatment area are provided on one side of the water-retaining wall. Each water outlet branch pipe is connected through a water outlet main pipe. A control valve is provided near the outlet of the water outlet main pipe, and a water outlet is provided at the outlet of the water outlet main pipe.

[0013] Preferably, the composite cascading purification zone includes packing steps arranged from top to bottom along the water flow direction, with filter holes provided on the surface of the packing steps, matrix material filled inside the steps, and water-blocking bars provided on the surface of each packing step.

[0014] Furthermore, it also includes a secondary purification unit connected in series with the composite cascading water purification unit.

[0015] Compared with the prior art, the advantages of the present invention are:

[0016] (1) The present invention provides an initial rainwater diversion and purification ecological ditch. Through the reasonable setting of the ditch structure, the initial rainwater can be effectively diverted. The runoff entering the rainwater ecological ditch is mainly the runoff formed in the first 15-30 minutes of rainfall, avoiding the strong runoff formed during rainstorms, which will cause scouring and damage to the ecological ditch facilities.

[0017] (2) The present invention provides an initial rainwater diversion and purification ecological ditch. Through the reasonable setting of the ditch structure, under the buffering effect of the sedimentation zone and the primary treatment zone, the speed at which the initial rainwater enters the downstream ecological treatment facility can be adjusted within a certain range, and the residence time of rainwater in the ecological ditch can be extended, thereby achieving efficient purification of the initial rainwater.

[0018] (3) The present invention provides an initial rainwater diversion and purification ecological ditch. Through the reasonable setting of the ditch structure, it realizes static pressure sludge discharge / self-siphon sludge discharge in the sedimentation zone and countercurrent self-backwashing in the filling zone. To a certain extent, it realizes the self-cleaning of the sedimentation zone and the matrix filling of the diversion dam, reduces the maintenance cost of the system, extends the service life of the materials, and improves the system's efficiency in removing pollutants.

[0019] (4) The initial rainwater diversion and purification ecological ditch of the present invention can reduce COD, ammonia nitrogen, phosphorus and SS discharged into the downstream river by more than 57.42%, 50.51%, 54.47% and 46.40% respectively compared with ordinary ecological ditches. Attached Figure Description

[0020] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof. In the drawings:

[0021] Figure 1 Process flow diagram;

[0022] Figure 2 Schematic diagram of the structure of an ecological ditch for initial rainwater diversion and purification;

[0023] Figure 3 Schematic diagram of the sludge removal system in the sedimentation zone;

[0024] Figure 4 Changes in pollutant discharge rates into downstream rivers during rainfall in initial rainwater diversion ecological ditches and ordinary ecological ditches: (a) COD, (b) ammonia nitrogen, (c) phosphorus, (d) SS;

[0025] Figure 5 The concentrations of pollutants entering downstream treatment facilities in rainwater diversion dams with and without filler material and with a mixture of ceramsite and zeolite filler material are: (a) COD, (b) ammonia nitrogen, (c) phosphorus, (d) SS.

[0026] Figure 6 Pollutant concentrations of rainwater entering downstream treatment facilities before and after sludge discharge from the sedimentation zone: (a) COD, (b) ammonia nitrogen, (c) phosphorus, (d) SS;

[0027] Figure 7Pollutant concentrations of rainwater entering downstream treatment facilities before and after countercurrent self-backwashing: (a) COD, (b) ammonia nitrogen, (c) phosphorus, (d) SS.

[0028] The labels in the diagram represent:

[0029] A. Sedimentation unit; B. Initial rainwater diversion unit; C. Primary purification unit; D. Composite cascade purification unit; E. Secondary purification unit.

[0030] 1-Sedimentation zone inlet, 2-Sedimentation zone, 3-Water weir, 4-Sludge discharge branch pipe, 5-Maximum sludge height during discharge cycle, 6-Diversion dam, 7-Filtration zone, 8-Filter holes, 9-Matrix packing, 10-Partition wall, 11-Inspection hole, 12-Initial rainwater maximum level, 13-Rainwater discharge outlet, 14-Level during heavy rain, 15-Flood discharge outlet, 16-Storm discharge channel, 17-Storm discharge channel support structure, 1 8-Flood level, 19-Primary treatment zone, 20-Water retaining wall, 21-Working liquid level, 22-Flood peak liquid level, 23-Outlet branch pipe, 24-Outlet main pipe, 25-Outlet diffuser, 26-Control valve, 27-Cascade aeration zone, 28-Packing step, 29-Water retaining grid, 30-Vegetation, 31-Sludge discharge main pipe, 32-Maximum pipe bottom elevation, 33-Sludge discharge valve, 34-Sludge discharge tank, 35-Maximum liquid level of sludge discharge tank. Detailed Implementation

[0031] The invention is not limited to the following specific embodiments. All equivalent modifications made based on the technical solutions of this application fall within the protection scope of this invention.

[0032] It should be noted that the directional terms mentioned in this document, such as "internal cavity" and "side wall", are consistent with the specific directions on the paper in the accompanying drawings or the corresponding directions of the space shown in the drawings; all components and devices in this invention, unless otherwise specified, are all components and devices known in the prior art.

[0033] Example 1

[0034] like Figure 1-3As shown in the figure, this embodiment of an initial rainwater diversion and purification ecological ditch includes a sedimentation unit A, an initial rainwater diversion unit B, a primary purification unit C, a composite cascading purification unit D, and a secondary purification unit E connected in series. The sedimentation unit A includes a sedimentation zone 2, with a sedimentation zone inlet 1 on the upper part of the side wall of the sedimentation zone 2 and a sludge discharge mechanism at the bottom of the sedimentation zone 2. The initial rainwater diversion unit B includes a diversion dam 6, which includes, from bottom to top, a sedimentation zone limiting platform, a filler filter zone 7, a rainwater outlet 13, and a flood outlet 15. The rainwater outlet 13 and the flood outlet 15 are connected to a stormwater discharge channel 16. The primary purification unit C includes a primary treatment zone 19, which is connected to the sedimentation zone 2 through the filler filter zone 7. The primary treatment zone 19 has a retaining wall 20 at a height not lower than the diversion dam 6 in the direction of water flow. The diversion dam 6 is adjacent to the sedimentation zone 2 and the primary treatment zone 19 on both sides, respectively.

[0035] Municipal rainwater first enters sedimentation zone A for sedimentation, and the sludge produced during the sedimentation process is discharged through a sludge removal mechanism. After sedimentation, the rainwater is diverted through a diversion dam 6. Initial rainwater passes through a filter media 7 and enters the primary purification unit C, while secondary and later-stage rainwater, or rainwater exceeding the system load, flows into the stormwater drainage channel 16 through rainwater outlet 13 and flood outlet 15. The substrate in primary purification unit C undergoes self-cleaning through a counter-current backwashing process. After treatment in primary purification unit C, the initial rainwater enters the composite cascading purification unit D for further purification and oxygenation, and then enters the secondary purification unit E for further treatment before being discharged.

[0036] The sedimentation zone inlet 1 disclosed in this embodiment is a high / low level inlet. The bottom of the high level inlet 1 is at the same height as the top of the flood discharge outlet 15, and the bottom of the low level inlet 1 is at the same height as the highest liquid level 12 of the initial rainwater. The initial rainwater and the middle and late rainwater with small rainfall flow in from the low level inlet. When the rainfall is large, the rainwater flows in from the high level inlet at the same time to achieve rapid discharge of the middle and late rainwater and reduce the disturbance of the middle and late rainwater and storm runoff to the initial rainwater stored in the sedimentation zone A. At the same time, the sedimentation zone inlet 1 can be equipped with a drop step or slope to reduce the scouring of the facility surface by rainwater.

[0037] The sedimentation zone 2 disclosed in this embodiment is equipped with a weir 3 at the bottom and is planted with emergent plants to reduce the impact of incoming water, retain suspended solids, and play a role in water purification. The sludge discharge mechanism includes multiple sludge discharge branch pipes 4 located between adjacent weirs 3. The outlets of each sludge discharge branch pipe 4 are connected through a sludge discharge main pipe 31. The outlet of the sludge discharge main pipe 31 is equipped with a sludge discharge valve 33 and connected to the sludge discharge pool 34. The maximum top elevation 32 of the sludge discharge main pipe 31 is lower than the liquid level 14 during heavy rain but higher than the highest liquid level 12 of the initial rainwater.

[0038] The sludge discharge system of sedimentation zone 2 disclosed in this embodiment is equipped with a sludge discharge tank 34, which controls the highest liquid level 35 of the sludge discharge tank. Sludge can be discharged by utilizing the static pressure of rainwater and the self-siphon effect. When the liquid level in the sedimentation zone is higher than the maximum top elevation 32 of the sludge discharge main pipe, the sludge discharge valve 33 can be opened to start the sludge discharge process as needed. Specifically, during the sludge discharge process, when the liquid level in the sedimentation zone is higher than the maximum top elevation 32 of the sludge discharge main pipe, sludge is discharged by static water pressure. When the liquid level in the sedimentation zone is lower than the bottom elevation of the sludge discharge main pipe, the system continues to discharge sludge by utilizing the generated self-siphon effect.

[0039] The solid part of the sedimentation zone limiting platform at the bottom of the diversion dam 6 disclosed in this embodiment has its highest point being the maximum height 5 of the sludge in the sedimentation zone during the discharge cycle, and a certain buffer area is appropriately considered to intercept sludge and suspended solids, while preventing sludge from entering the packing filter zone 7. After the rainwater undergoes sedimentation to remove particulate matter and suspended solids in the sedimentation zone, it enters the diversion dam 6. When the liquid level in the sedimentation zone is higher than the height of the sedimentation zone limiting platform at the bottom of the diversion dam 6, the rainwater begins to enter the primary ecological treatment zone 19 through the packing filter zone 7 in the diversion dam.

[0040] The filter media 7 disclosed in this embodiment has filter holes 8 evenly distributed on the sidewall surface. The sidewall can be made of porous brick as the main strength structure, and other load-bearing structures can be set inside according to the load requirements. The filter media 7 is hollow and filled with matrix filler 9. The matrix filler 9 includes, but is not limited to, adsorption and filtration materials such as ceramsite, zeolite, quartz sand, and anthracite. At the same time, the matrix filler 9 can be biologically enhanced to remove pollutants such as ammonia nitrogen, phosphorus, COD, and SS in the initial rainwater through adsorption, filtration, and biological action. A partition wall 10 can be set inside the filter media 7. The partition wall 10 has water distribution holes. The partition wall 10 can be made of perforated flower wall or porous brick. The partition wall 10 divides the inner cavity of the filter media 7 into two areas along the water flow direction to be filled with different types or graded matrix fillers 9, thereby enhancing the pollutant removal effect. Inspection holes 11 are provided on both sides of the sidewall 8. The inspection holes 11 are used for inspection, filling, and replacement of matrix filler 9.

[0041] The diversion dam 6 disclosed in this embodiment has a rainwater discharge outlet 13 and a flood discharge outlet 15 on the upper part of the filling area 7. The lowest point of the flood discharge outlet 15 is the liquid level 14 during heavy rain. The rainwater discharge outlet 13 and the flood discharge outlet 15 are connected to the stormwater and flood discharge channel 16. The rainwater discharge outlet 13 and the water retaining wall 20 and its effluent facilities in the downstream primary treatment area work together to achieve normal diversion and discharge of rainwater in the middle and late stages and rainwater exceeding the load of the ecological ditch. The flood discharge outlet 15 is used to discharge flood runoff when the water level rises during heavy rain.

[0042] When the water level in sedimentation zone 2 reaches the initial rainwater maximum level 12, the rainwater level continues to rise until it is discharged through rainwater outlet 13 into stormwater drainage channel 16. Simultaneously, the rainwater continues to pass through the filter media. When the rainwater level in the sedimentation zone continues to rise to the level 14 during heavy rain, it begins to flow into stormwater drainage channel 16 through flood outlet 15. Stormwater drainage channel 16 directly discharges the collected, less polluted rainwater from the later stages. Stormwater drainage channel 16 can be constructed attached to diversion dam 6, in which case a supporting structure 17 can be installed for support. Alternatively, it can be connected to rainwater outlet 13 and flood outlet 15 via pipelines, thus allowing for independent construction.

[0043] Initial rainwater passing through the filter zone 7 enters the primary ecological treatment zone 19. This zone is planted with different types of plants 29 according to purification needs and hydraulic conditions, and undergoes substrate filling and biological enhancement to treat the initial rainwater. The primary ecological treatment zone 19 is connected to the sedimentation zone 2 via a diversion dam 6. A retaining wall 20 is installed at the end of the primary ecological treatment zone 19. The peak flood level 22 within the retaining wall 20 is equal to the flood level 18 in the stormwater discharge channel 16 to prevent the peak flow from continuously passing through the filter zone 7 and entering the downstream area. The normal operating level 21 within the retaining wall is equal to the bottom height of the rainwater discharge outlet 13 within the diversion dam.

[0044] The water-retaining wall 20 disclosed in this embodiment has multiple outlet branch pipes 23 connected to the primary treatment area 19 on the side facing the composite cascading water purification area D. Each outlet branch pipe 23 is connected through an outlet main pipe 24. The outlet main pipe 24 is equipped with a control valve 26 and an outlet spout 25 near the outlet. Rainwater flows out through the outlet branch pipes 23 at different heights, merges and enters the outlet main pipe 24. The water flow rate in this area is controlled by the control valve 26, and finally the rainwater is discharged to the composite cascading water purification area 27 through the outlet spout 25 of the main pipe.

[0045] By adjusting the opening degree of control valve 26, the effluent flow rate and liquid level of primary purification unit C can be controlled, ensuring that the effluent flow rate of primary treatment zone 19 meets the downstream inflow requirements. Simultaneously, it can be closed during backwashing to enhance the reverse flow of water from primary purification unit C to the sedimentation zone. Specifically, control valve 26 controls the rate at which initial rainwater enters the next treatment facility. The effluent velocity of primary purification unit C is generally much lower than the discharge velocity of rainwater and storm runoff from rainwater outlet 13 and flood outlet 15 in the later stages. During the later stages of heavy rainfall, high-level rainwater in the sedimentation zone in front of the diversion dam is rapidly discharged through rainwater outlet 13 and flood outlet 15, creating a reverse liquid level difference between sedimentation zone 2 and primary ecological treatment zone 19, thereby self-backwashing the diversion dam packing. The intensity and duration of self-backwashing can also be adjusted by reducing the opening degree of control valve 26 until it is closed, and by implementing synchronous sludge discharge from the sedimentation zone.

[0046] The ecological ditch disclosed in this embodiment also includes a composite cascading purification unit D connected in series with the primary purification unit C.

[0047] The composite cascading water purification unit D disclosed in this embodiment includes a packing step 28 arranged from top to bottom along the water flow direction. The surface of the packing step 28 can be made of materials such as porous bricks, perforated plastic plates, and stainless steel plates, and the interior is filled with functional materials such as ceramsite. Each packing step surface is provided with a water-blocking grid 29, with a height of about 10-20mm, which causes some water to enter the interior of the step vertically and be purified by the packing. The remaining water overflows directly from the water-blocking grid, falls, and undergoes oxygen-enriched aeration. At the same time, emergent plants and wetland grasses can be planted on the steps to enhance the water purification process and disperse the water flow to enhance the aeration effect. After the initial rainwater passes through the composite cascading water purification zone, it enters the next ecological treatment stage for treatment and is finally discharged into the receiving water body.

[0048] Example 2

[0049] This embodiment tested the ecological ditch model disclosed in Example 1 and compared the treatment effects of ordinary ecological ditches and initial rainwater diversion ecological ditches. The model was made of plexiglass, with an effective width of 300 mm and a depth of 500 mm. The maximum initial rainwater interception capacity was approximately 44 L. During the experiment, the average simulated rainwater inflow was approximately 88 L / h. Zeolite and ceramsite were used as fillers. The treated rainwater runoff duration was 90 min. The maximum pollutant concentrations at the initial stage of rainfall were approximately ammonia nitrogen = 10 mg / L, phosphorus = 3 mg / L, COD = 200 mg / L, and SS = 1000 mg / L. The pollutant concentrations in the middle and later stages of rainfall were approximately ammonia nitrogen = 1.5 mg / L, phosphorus = 0.5 mg / L, COD = 30 mg / L, and SS = 100 mg / L. This model did not include the effects of plants and microorganisms. The initial rainwater diversion effect, filler effect, sludge removal effect, and self-washing effect of the ecological ditch were verified. The main results are as follows: Figures 4 to 7 As shown.

[0050] Figure 4 The rate of pollutants discharged into rivers changes over time between ecological ditches and ordinary ecological ditches used for initial rainwater interception. In ordinary ecological ditches, rainwater runoff flows directly into rivers. The high flow velocity in these ditches causes erosion and damage to the ditches' banks and vegetation. Furthermore, due to the short contact time, only a small portion of the pollutants in the rainwater is intercepted by the ecological ditches, with a large amount being directly discharged into the rivers. Figure 1It can be seen that in the first 45 minutes of runoff inflow, especially at the beginning of rainfall, the rate of pollutants discharged into the river from ordinary ecological ditches is much higher than that from the initial rainwater separation ecological ditches. When the initial rainwater is intercepted, only a small amount of rainwater is discharged through the outlet pipe of the rainwater interception system in the first 20 minutes, and the amount of pollutants discharged into the river is relatively small. Afterwards, as the runoff flows out of the system's rainwater inlet in the middle and later stages, the rate of pollutants discharged into the river through the rainwater pipes increases. The area below the curve in the figure can be approximated as the total amount of pollutants discharged into the river during the runoff inflow process. Calculations show that during rainfall, the COD, ammonia nitrogen, phosphorus, and SS discharged into the downstream river from the initial rainwater diversion and purification ditches are 42.58%, 49.49%, 45.53%, and 53.60% of those from ordinary ecological ditches, respectively. It should be noted that this effect does not take into account the role of ditches plants and microorganisms. Because the amount and velocity of water entering the ecological ditches will be greatly reduced after interception, this provides favorable conditions for further removal of pollutants from the ecosystem, so the effect will be more significant in the actual system.

[0051] Figure 5 This study investigated the changes in pollutant concentrations flowing into downstream ecological ditches during rainfall, under conditions of both filling with and without substrate materials. To ensure effective removal of both ammonia nitrogen and phosphorus, zeolite and ceramsite were used as fillers in the experiment. As shown in the figure, the addition of the fillers significantly reduced the pollutant concentrations entering the downstream ecological ditches, particularly suspended solids (SS), which even fell below 20 mg / L after filtration.

[0052] Figure 6 The figure shows the operational effects of the system before and after sludge discharge. As can be seen from the figure, the effluent pollutant concentration was high before sludge discharge, with SS reaching 600 mg / L at one point. After sludge discharge, the effluent pollutant concentration decreased significantly. This demonstrates the reliability of the sludge discharge system and the necessity of installing a sludge discharge system in ecological ditches.

[0053] Figure 7 The experiment compared the system's operational performance before and after counter-current self-backwashing. When the rainwater level in the primary ecological treatment zone reached its maximum, and the flow rate of rainwater into the sedimentation zone began to decrease continuously, the sludge removal system was simultaneously activated (to eliminate the influence of sedimentation, the experiment was conducted after the sludge deposited in the sedimentation zone had been cleaned). At this point, the maximum counter-current liquid level difference between the sedimentation zone and the primary ecological treatment zone could reach 20% of the rainwater level, lasting for 1.5 to 2.0 minutes. Afterward, the liquid levels on both sides gradually became equal. The backwashing duration depended on the sludge discharge volume and the inflow rate of the ecological ditch. The figure shows that after counter-current self-backwashing, the concentration of pollutants in the effluent, especially ammonia nitrogen and initial SS concentration, significantly decreased. This indicates that the self-backwashing effect formed by the system can effectively clean the substrate packing.

[0054] The preferred embodiments of the present disclosure have been described in detail above with reference to the accompanying drawings. However, the present disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present disclosure, various simple modifications can be made to the technical solutions of the present disclosure, and these simple modifications all fall within the protection scope of the present disclosure.

[0055] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0056] Furthermore, the various implementation methods disclosed in this solution can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content invented by this disclosure.

Claims

1. An ecological ditch for initial rainwater diversion and purification, characterized in that, It includes a sedimentation unit (A), an initial rainwater diversion unit (B), and a primary purification unit (C) connected in series. The sedimentation unit (A) includes a sedimentation zone (2), which is provided with a sedimentation zone inlet (1) and a sludge discharge mechanism at the bottom of the sedimentation zone (2). The initial rainwater diversion unit (B) includes a diversion dam (6), which includes, from bottom to top, a sedimentation zone limiting platform, a filler filter zone (7), a rainwater discharge zone and a flood discharge zone, and the rainwater discharge zone and the flood discharge zone are connected to a rainwater discharge channel (16). The primary purification unit (C) includes a primary treatment zone (19), which is connected to the sedimentation zone (2) through a filler filter zone (7). The primary treatment zone (19) is provided with a water-retaining wall (20) that is no lower than the diversion dam (6) in the direction of water flow. The diversion dam (6) is adjacent to the sedimentation zone (2) and the primary treatment zone (19) on both sides. The highest initial rainwater level (12) is located at the junction of the filter area (7) and the rainwater discharge area. The rainwater discharge area is equipped with a rainwater discharge outlet (13), and the flood discharge area is equipped with a flood discharge outlet (15). The lowest point of the flood discharge outlet (15) is the level (14) during heavy rain. The sedimentation zone inlet (1) includes a high-level inlet and a low-level inlet. The bottom of the high-level inlet of the sedimentation zone inlet (1) is at the same height as the top of the flood discharge outlet (15), and the bottom of the low-level inlet of the sedimentation zone inlet (1) is at the same height as the highest liquid level (12) of the initial rainwater. The sludge discharge mechanism includes multiple sludge discharge branch pipes (4), and the outlets of each sludge discharge branch pipe (4) are connected through a sludge discharge main pipe (31). The outlet of the sludge discharge main pipe (31) is connected to the sludge discharge tank (34). The maximum bottom elevation (32) of the sludge discharge main pipe (31) is lower than the liquid level (14) during the rainstorm and higher than the highest liquid level (12) of the initial rainwater. The highest liquid level of the sludge discharge tank (34) is lower than the highest liquid level (12) of the initial rainwater.

2. The initial rainwater diversion and purification ecological ditch as described in claim 1, characterized in that, Water weirs (3) and emergent plants are also provided in the gaps between the mud discharge branch pipes (4) at the bottom of the sedimentation zone (2).

3. The initial rainwater diversion and purification ecological ditch as described in claim 1, characterized in that, The packing filter zone (7) is hollow and filled with matrix packing (9). The side wall of the packing filter zone (7) is provided with uniformly distributed filter holes (8). The side wall of the packing filter zone (7) is also provided with inspection holes (11).

4. The initial rainwater diversion and purification ecological ditch as described in claim 3, characterized in that, The filter media (7) is vertically equipped with a partition wall (10). The partition wall (10) has water distribution holes and divides the inner cavity of the filter media (7) into two regions along the water flow direction. The matrix fillers (9) in the regions are of different types or different grades.

5. The initial rainwater diversion and purification ecological ditch as described in any one of claims 1-4, characterized in that, It also includes a composite waterfall purification unit (D) connected in series with the primary purification unit (C). The water retaining wall (20) faces the composite waterfall purification area (D), and a plurality of water outlet branch pipes (23) connected to the primary treatment area (19) are provided on one side of the water retaining wall (20). Each water outlet branch pipe (23) is connected through a water outlet main pipe (24). A control valve (26) is provided near the outlet of the water outlet main pipe (24), and a water outlet spout (25) is provided at the outlet of the water outlet main pipe (24).

6. The initial rainwater diversion and purification ecological ditch as described in claim 5, characterized in that, The composite cascading purification zone (D) includes a packing step (28) arranged from top to bottom along the water flow direction. The surface of the packing step (28) is provided with filter holes, the interior of the step is filled with matrix material, and each packing step is provided with a water-blocking grid strip (29).

7. The initial rainwater diversion and purification ecological ditch as described in claim 6, characterized in that, It also includes a secondary purification unit (E) connected in series with the composite cascading purification unit (D).

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