Wetland system for non-point source pollution treatment

Abstract

The invention discloses a wetland system for non-point source pollution treatment, and relates to the technical field of environmental engineering. The wetland system comprises a front pond, a first-stage horizontal subsurface flow wetland, a second-stage horizontal subsurface flow wetland, a vertical subsurface flow wetland and a surface flow wetland which are communicated in sequence, the front pond is communicated with a branch, and the surface flow wetland is communicated with the downstream of a main stream or the branch; and the wetland system is used for treating non-point source pollution gathered along the branch flow and discharging purified water into the downstream of the main flow or the branch flow. The two-stage horizontal subsurface flow wetland and the vertical subsurface flow wetland are arranged, so that the pollutant removal capacity of the wetland system is improved, the treatment effect of non-point source pollution is improved, and meanwhile, the cost is relatively low.

Description

Technical Field

[0001] The invention relates to the technical field of environmental engineering, and in particular to a wetland system for treating non-point source pollution. Background Art

[0002] When point source and internal source pollution are effectively controlled, surface source pollution along the river becomes the main factor threatening the safety of river water quality.

[0003] At present, the main means of non-point source pollution control are regulating reservoirs, subsurface wetlands and sponge city construction. Among them, sponge city construction can only be achieved through planning in the urban planning stage and is difficult to transform. There are problems such as high cost of collecting and treating wastewater in regulating reservoirs, difficulty in operating sewage treatment plants, and high operating costs. Artificial wetlands are the preferred process for non-point source pollution control due to their good ecological landscape effects, high purification efficiency, low economic cost, no secondary pollution, and strong nitrogen and phosphorus treatment capabilities.

[0004] Currently, non-point source pollution in small towns can be controlled through a single artificial wetland system, but the control effect is poor. Summary of the invention

[0005] The present invention provides a wetland system for treating non-point source pollution, so as to solve the technical problem that a single artificial wetland system in the related art has a poor treatment effect on non-point source pollution.

[0006] According to one aspect of the present invention, a wetland system for non-point source pollution treatment is provided, comprising a pre-pond, a primary horizontal subsurface wetland, a secondary horizontal subsurface wetland, a vertical subsurface wetland and a surface flow wetland which are connected in sequence, the pre-pond being connected to a tributary, the surface flow wetland being connected to a main stream or a downstream of a tributary; the wetland system is used to treat non-point source pollution collected along the tributary, and discharge purified water into the main stream or the downstream of the tributary;

[0007] A water distribution channel is arranged between the front pond and the first-level horizontal submerged flow wetland, one end of the water distribution channel is connected to the front pond through a pipeline, and the other end is connected to the first-level horizontal submerged flow wetland through a first water distribution main pipe, the first water distribution main pipe is connected to a first water distribution branch pipe, the first water distribution branch pipe is a perforated pipe, which is parallel to the water surface and perpendicular to the water flow direction; a first partition wall is arranged between the first-level horizontal submerged flow wetland and the second-level horizontal submerged flow wetland, a first water collecting pipe is arranged on the upstream side of the first partition wall, and a first water distribution pipe is arranged on the downstream side; the first water collecting pipe is connected to the first water distribution pipe through a plurality of connecting pipes passing through the first partition wall, the first water collecting pipe and the first water distribution pipe are both perforated pipes, which are both parallel to the water surface and perpendicular to the water flow direction;

[0008] A second partition wall is arranged between the secondary horizontal subsurface flow wetland and the vertical subsurface flow wetland, a second water collecting pipe is arranged on the upstream side of the second partition wall, and a second water distribution main pipe is arranged on the downstream side; the second water collecting pipe is connected with the second water distribution main pipe through a plurality of connecting pipes passing through the second partition wall, the second water collecting pipe is a perforated pipe, which is parallel to the water surface and perpendicular to the water flow direction, and the second water distribution main pipe is a perforated pipe;

[0009] The vertical subsurface flow wetland also includes: a water collection main pipe, a plurality of water collection branch pipes connected to the water collection main pipe, and a plurality of second water distribution branch pipes connected to the second water distribution main pipe, the second water distribution branch pipes and the water collection branch pipes are perforated pipes, which are parallel to the water surface and the direction of water flow; a water collection channel is arranged between the vertical subsurface flow wetland and the surface flow wetland, one end of the water collection channel is connected to the water collection main pipe, and the other end is connected to the surface flow wetland.

[0010] The technical solution of the embodiment of the present invention, on the one hand, sets up a pre-pond, can avoid the blockage of each subsurface wetland, and improve the reliability of the wetland system. On the other hand, setting up two levels of horizontal subsurface wetlands and vertical subsurface wetlands, takes advantage of the horizontal subsurface wetlands' strong ability to remove chemical oxygen demand (COD) and not easy to be blocked, and takes advantage of the vertical subsurface wetlands' strong hydraulic and pollutant reduction load, nitrification ability, and phosphorus removal ability, to improve the pollutant removal ability, and then improve the control effect of non-point source pollution. At the same time, since the engineering construction cost of horizontal subsurface wetlands is relatively low and the engineering construction cost of vertical subsurface wetlands is relatively high, setting up two levels of horizontal subsurface wetlands and vertical subsurface wetlands can reduce investment on the basis of ensuring the normal operation of the wetland system. On the other hand, setting up surface flow wetlands improves the water body's reoxygenation capacity and biochemical action, and further improves the pollutant removal capacity. On the other hand, by setting up water distribution channels, water distribution pipes and water collection pipes, and connecting the first-level horizontal subsurface flow wetland with the second-level horizontal subsurface flow wetland by multiple connecting pipes, and connecting the second-level horizontal subsurface flow wetland with the vertical subsurface flow wetland by multiple connecting pipes, the uniformity of water distribution can be ensured, further improving the effect of surface source pollution control.

[0011] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0013] Figure 1 is a flow chart of a wetland system for non-point source pollution treatment provided by an embodiment of the present invention;

[0014] Figure 2 is a plan view of a wetland system for non-point source pollution treatment provided by an embodiment of the present invention;

[0015] Figure 3 is a cross-sectional view of a primary horizontal subsurface flow wetland provided by an embodiment of the present invention;

[0016] Figure 4 is a cross-sectional view of a secondary horizontal subsurface flow wetland provided by an embodiment of the present invention;

[0017] Figure 5 is a cross-sectional view of a vertical subsurface flow wetland provided by an embodiment of the present invention;

[0018] Figure 6 It is a schematic diagram of an application scenario of a wetland system provided by an embodiment of the present invention.

[0019] Reference numerals:

[0020] 11: front pond; 12: first-level horizontal subsurface wetland; 13: second-level horizontal subsurface wetland; 14: vertical subsurface wetland; 15: surface flow wetland; 16: tributary; 17: downstream of the main stream or tributary; 18: water distribution channel; 19: the first water distribution main pipe; 20: the first water distribution branch pipe; 21: the first partition wall; 22: the first water collection pipe; 23: the first water distribution pipe; 24: connecting pipe; 25: the second partition wall; 26: the second water collection pipe; 27: the second water distribution main pipe; 28: connecting pipe; 29: the water collection main pipe; 30: the water collection branch pipe; 31: the second water distribution branch pipe; 32: the water collection channel; 33: the first ventilation pipe; 34: the second ventilation pipe; 35: the first covering layer; 36: the first valve; 37: the third ventilation pipe; 38: the fourth ventilation pipe; 39: the second covering layer; 40: the third covering layer; 41: the second valve. DETAILED DESCRIPTION

[0021] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0022] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the term "comprising" and any variation thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices. The acquisition, storage, use, processing, etc. of data in the embodiments of the present invention all comply with the relevant provisions of national laws and regulations.

[0023] Figure 1 It is a flow chart of a wetland system for treating non-point source pollution provided by an embodiment of the present invention. Figure 2 FIG. 1 is a plan view of a wetland system for treating non-point source pollution provided by an embodiment of the present invention. Figure 1 As shown, the wetland system provided in this embodiment is used to treat non-point source pollution collected along the tributary 16, and discharge the purified water into the main stream or the downstream 17 of the tributary.

[0024] Please also refer to Figure 1 and Figure 2 The wetland system includes a pre-pond 11, a first-level horizontal subsurface wetland 12, a second-level horizontal subsurface wetland 13, a vertical subsurface wetland 14 and a surface flow wetland 15 which are connected in sequence. The pre-pond 11 is connected to a tributary 16, and the surface flow wetland 15 is connected to a main stream or a downstream tributary 17.

[0025] In this embodiment, the front pond 11 is used as a pretreatment facility for the subsurface wetland, which can filter and intercept suspended matter and degradable particles in the water body to avoid clogging the subsequent subsurface wetlands. In this embodiment, the front pond 11 is set in the wetland system to effectively increase the water intake and the impact load resistance of the water quality, increase the hydraulic retention time, and increase the water distribution uniformity of the subsurface wetland.

[0026] Optionally, in order to facilitate the acquisition of unpurified water from the tributary 16, a water pump is provided between the tributary 16 and the front pond 11 in the present embodiment to realize the pumping of the unpurified water in the tributary 16 into the front pond 11. Non-point source pollution along the river mainly flows into the river through initial rain runoff. Optionally, the unpurified water in the tributary 16 can be initial rainwater. The non-point source pollution in the river has the characteristics of a wide discharge area, random discharge paths, and poor initial rainwater quality, so the collection and treatment of initial rainwater is very necessary. The wetland system provided in the present embodiment can ensure that the initial rainwater is purified before entering the main stream or the downstream of the tributary.

[0027] Figure 3 It is a cross-sectional view of a primary horizontal subsurface flow wetland provided by an embodiment of the present invention. Figure 4 It is a cross-sectional view of a secondary horizontal subsurface flow wetland provided by an embodiment of the present invention. Figure 5 It is a cross-sectional view of a vertical subsurface flow wetland provided by an embodiment of the present invention.

[0028] Please also refer to Figure 1 , Figure 2 and Figure 3 In this embodiment, a water distribution channel 18 is arranged between the front pond 11 and the first-level horizontal submerged flow wetland 12. One end of the water distribution channel 18 is connected to the front pond 11 through a pipeline, and the other end is connected to the first-level horizontal submerged flow wetland 12 through a first water distribution main pipe 19. The first water distribution main pipe 19 is connected to the first water distribution branch pipe 20. The first water distribution branch pipe 20 is a perforated pipe, which is parallel to the water surface and perpendicular to the water flow direction.

[0029] Optionally, one end of the water distribution channel 18 can be connected to the front pond 11 through a pipeline. It can be understood that the first water distribution main pipe 19 can pass through the partition wall of the water distribution channel 18 and communicate with the first water distribution branch pipe 20 located in the first-level horizontal submerged flow wetland 12. In this embodiment, the water distribution channel 18 is provided between the front pond 11 and the first-level horizontal submerged flow wetland 12, which can improve the uniformity of water distribution in the first-level horizontal submerged flow wetland 12.

[0030] Please also refer to Figure 1 , Figure 2 , Figure 3 and Figure 4 A first partition wall 21 is provided between the primary horizontal submerged flow wetland 12 and the secondary horizontal submerged flow wetland 13. A first water collecting pipe 22 is provided on the upstream side of the first partition wall 21, and a first water distribution pipe 23 is provided on the downstream side. The first water collecting pipe 22 and the first water distribution pipe 23 are connected through a plurality of connecting pipes 24 passing through the first partition wall 21. Both the first water collecting pipe 22 and the first water distribution pipe 23 are perforated pipes, which are parallel to the water surface and perpendicular to the water flow direction.

[0031] In this embodiment, the upstream side of the first partition wall 21 refers to the side of the first partition wall 21 located at the primary horizontal submerged flow wetland 12. The downstream side of the first partition wall 21 refers to the side of the first partition wall 21 located at the secondary horizontal submerged flow wetland 13.

[0032] In this embodiment, the type and arrangement of the first water distribution branch pipe 20 and the first water distribution pipe 23, that is, the first water distribution branch pipe 20 and the first water distribution pipe 23 are perforated pipes, which are parallel to the water surface and perpendicular to the water flow direction, so that the water flow can be evenly distributed after entering the first-level horizontal submerged flow wetland 12 and the second-level submerged flow wetland 13, thereby improving the purification effect. Figure 2As shown by the arrows in the figure, water flows through the front pond 11, the first-level horizontal subsurface wetland 12, the second-level horizontal subsurface wetland 13, the vertical subsurface wetland 14 and the surface flow wetland 15 in sequence.

[0033] In this embodiment, the type and arrangement of the first water collecting pipe 22, that is, the first water collecting pipe 22 is a perforated pipe, which is parallel to the water surface and perpendicular to the water flow direction, can allow the water to flow smoothly into the secondary horizontal submerged flow wetland 13, thereby preventing dead water from forming in the primary horizontal submerged flow wetland 12.

[0034] Please also refer to Figure 1 , Figure 2 , Figure 4 and Figure 5 A second partition wall 25 is provided between the secondary horizontal subsurface wetland 13 and the vertical subsurface wetland 14. A second water collecting pipe 26 is provided on the upstream side of the second partition wall 25, and a second water distribution main pipe 27 is provided on the downstream side. The second water collecting pipe 26 is connected to the second water distribution main pipe 27 through a plurality of connecting pipes 28 passing through the second partition wall 25. The second water collecting pipe 26 is a perforated pipe, which is parallel to the water surface and perpendicular to the water flow direction, and the second water distribution main pipe 27 is a perforated pipe.

[0035] The vertical subsurface wetland 14 also includes: a water collecting main pipe 29, a plurality of water collecting branch pipes 30 connected to the water collecting main pipe 29, and a plurality of second water distribution branch pipes 31 connected to the second water distribution main pipe 27. The second water distribution branch pipes 31 and the water collecting branch pipes 30 are perforated pipes parallel to the water surface and the direction of water flow. A water collecting channel 32 is set between the vertical subsurface wetland 14 and the surface flow wetland 15, one end of the water collecting channel 32 is connected to the water collecting main pipe 29, and the other end is connected to the surface flow wetland 15.

[0036] In this embodiment, the upstream side of the second partition wall 25 refers to the side of the second partition wall 25 located at the secondary horizontal submerged flow wetland 13. The downstream side of the second partition wall 25 refers to the side of the second partition wall 25 located at the vertical submerged flow wetland 14.

[0037] In this embodiment, the type and arrangement of the second water collecting pipe 26, that is, the second water collecting pipe 26 is a perforated pipe, which is parallel to the water surface and perpendicular to the water flow direction, can allow the water to flow smoothly into the vertical submerged flow wetland 14, thereby preventing dead water from forming in the secondary horizontal submerged flow wetland 13.

[0038] The type and arrangement of the second water distribution branch pipe 31 and the water collection branch pipe 30 in this embodiment can make the water flow evenly distributed after entering the vertical subsurface flow wetland 14, thereby improving the purification effect. At the same time, the water collection branch pipe 30 and the water collection main pipe 29 can make the water flow smoothly enter the water collection channel 32, so that no stagnant water is formed in the vertical subsurface flow wetland 14.

[0039] Optionally, in this embodiment, the second water distribution main pipe 27 is disposed at one end of the vertical subsurface flow wetland 14 close to the second partition wall 25. The water collection main pipe 29 is disposed at one end of the vertical subsurface flow wetland 14 away from the second partition wall 25.

[0040] Optionally, the water collecting branch pipe 30 can be higher than the second water distribution branch pipe 31, so that the water in the vertical submerged flow wetland 14 can flow from the bottom of the water to the surface of the water, and no stagnant water is formed. It should be noted that in the vertical submerged flow wetland 14, water can flow from the bottom of the water to the surface of the water, and can also flow from the second partition wall 25 to the water collecting channel 32. The water flow direction in the vertical submerged flow wetland mentioned in this embodiment refers to the direction of flow from the second partition wall 25 to the water collecting channel 32.

[0041] Furthermore, in order to make the water distribution more uniform, the second water distribution main pipe 27 can be parallel to the water surface and perpendicular to the water flow direction. The water collection main pipe 29 can be a perforated pipe, which can be parallel to the water surface and perpendicular to the water flow direction.

[0042] The working process of the wetland system provided in this embodiment is as follows: the water body including non-point source pollution in the tributary 16 enters the front pond 11. The front pond 11 filters and intercepts suspended matter and degradable particulate matter in the water body. The water body treated by the front pond 11 flows through the first-level horizontal subsurface wetland 12, the second-level horizontal subsurface wetland 13 and the vertical subsurface wetland 14 in turn. These subsurface wetlands purify the water body. After the water flowing out of the vertical subsurface wetland 14 flows into the surface wetland 15, it can directly contact with the air, thereby improving the water body's reoxygenation capacity and biochemical action, and can achieve the degradation of ammonia nitrogen (NH3-N) in the water body, and form a wetland park, providing a landscape place for surrounding residents to play, entertain and learn in wetlands. At the same time, in addition to the function of purifying wetlands, the biggest advantage of surface flow wetlands is that they are close to natural wetlands, which can provide a good and diverse environment for the growth, reproduction and habitat of aquatic organisms while purifying water quality. The purified water after treating non-point source pollution flowing out from the surface flow wetland 15 flows into the downstream 17 of the main stream or tributary.

[0043] In the wetland system provided in this embodiment, on the one hand, the provision of a pre-pond can avoid clogging of each subsurface wetland, thereby improving the reliability of the wetland system. On the other hand, the provision of two levels of horizontal subsurface wetlands and vertical subsurface wetlands utilizes the advantages of horizontal subsurface wetlands in terms of strong COD removal capacity and not being easily clogged, as well as the advantages of vertical subsurface wetlands in terms of hydraulic power and pollutant load reduction, nitrification capacity, and phosphorus removal capacity, thereby improving the pollutant removal capacity, and further improving the control effect of non-point source pollution. At the same time, since the engineering construction cost of horizontal subsurface wetlands is relatively low and the engineering construction cost of vertical subsurface wetlands is relatively high, the provision of two levels of horizontal subsurface wetlands and vertical subsurface wetlands can reduce investment on the basis of ensuring the normal operation of the wetland system. On the other hand, the provision of surface flow wetlands improves the water body's reoxygenation capacity and biochemical action, further improving the pollutant removal capacity. On the other hand, by setting up water distribution channels, water distribution pipes and water collection pipes, and connecting the first-level horizontal subsurface flow wetland with the second-level horizontal subsurface flow wetland by multiple connecting pipes, and connecting the second-level horizontal subsurface flow wetland with the vertical subsurface flow wetland by multiple connecting pipes, the uniformity of water distribution can be ensured, further improving the effect of surface source pollution control.

[0044] Optionally, the water surfaces of the front pond 11, the first-level horizontal subsurface wetland 12, the second-level horizontal subsurface wetland 13, the vertical subsurface wetland 14 and the surface flow wetland 15 are lowered in order. That is, the water bodies in the wetland system are all gravity flows, which can save energy and reduce costs.

[0045] Optionally, please also refer to Figure 3 , Figure 4 and Figure 5 The wetland system provided in this embodiment also includes at least one of the following: a first ventilation pipe 33 , a second ventilation pipe 34 , a third ventilation pipe 37 and a fourth ventilation pipe 38 .

[0046] The first ventilation pipe 33 is disposed on the upstream side of the first partition wall 21 . The first ventilation pipe 33 is communicated with the first water collecting pipe 22 . The first ventilation pipe 33 is perpendicular to the water surface and is higher than the water surface.

[0047] The second ventilation pipe 34 is disposed on the downstream side of the first partition wall 21 . The second ventilation pipe 34 is communicated with the first water distribution pipe 23 . The second ventilation pipe 34 is perpendicular to the water surface and higher than the water surface.

[0048] The third ventilation pipe 37 is disposed on the upstream side of the second partition wall 25 . The third ventilation pipe 37 is communicated with the second water collecting pipe 26 . The third ventilation pipe 37 is perpendicular to the water surface and higher than the water surface.

[0049] The fourth ventilation pipe 38 is disposed on the downstream side of the second partition wall 25 . The fourth ventilation pipe 38 is communicated with the second water distribution main pipe 27 . The fourth ventilation pipe 38 is perpendicular to the water surface and is higher than the water surface.

[0050] The purpose of setting up various ventilation pipes is to ensure air circulation inside the wetland and stabilize the pressure, so as to achieve uniform water distribution.

[0051] Optionally, please also refer to Figure 3 and Figure 5 The wetland system in this embodiment also includes: a first valve 36 and a second valve 41.

[0052] The first water distribution main pipe 19 is connected to the first water distribution branch pipe 20 through the first valve 36. The first valve can ensure that the water can be cut off during the maintenance of the single-grid wetland, and at the same time can control the flow entering the single-grid wetland. The single-grid wetland in this embodiment refers to the pre-pond 11, the first-level horizontal submerged wetland 12, the second-level horizontal submerged wetland 13, the vertical submerged wetland 14 and the surface flow wetland 15 that are connected in sequence. The wetland system provided in this embodiment may include multiple parallel single-grid wetlands.

[0053] The water collecting main pipe 29 is connected to the water collecting channel 32 through the second valve 41. The second valve 41 can be provided to control the operating water level in the wetland system.

[0054] Optionally, the first valve 36 may be disposed in the first valve well. The second valve 41 may be disposed in the second valve well.

[0055] Optionally, see Figure 3 The first-level horizontal subsurface flow wetland 12 includes, along the water flow direction, a first water distribution area, a first coarse filtration area, a first fine filtration area and a first water collection area.

[0056] The first water distribution main pipe 19 and the first water distribution branch pipe 20 are arranged in the first water distribution area.

[0057] The first water distribution area, the first coarse filtration area and the first fine filtration area all include fillers, and the particle size of the filler in the first water distribution area, the particle size of the filler in the first coarse filtration area and the particle size of the filler in the first fine filtration area decrease successively. This arrangement can make the particle size of the filler at the front end of the primary horizontal submerged flow wetland larger, that is, the gaps between the fillers are larger, and the water permeability is better. Since the water flowing into the front end of the primary horizontal submerged flow wetland is not yet purified by the primary horizontal submerged flow wetland, there are more impurities in the water. This implementation method can avoid the blockage of the front end of the primary horizontal submerged flow wetland. In addition, the particle size of the filler in the first fine filtration area is smaller, which can improve the purification effect. Therefore, this implementation method can improve the purification effect while avoiding the blockage of the primary horizontal submerged flow wetland.

[0058] The first water collecting pipe 22 is arranged in the first water collecting area. Optionally, in the scenario where the first ventilation pipe 33 is arranged, the first ventilation pipe 33 is also arranged in the first water collecting area.

[0059] Optionally, see Figure 3When the wetland system is located in a relatively low temperature area, in order to solve the problem of high heat conduction rate of the filler in the wetland system in winter and to ensure the purification effect in the wetland system at low temperatures in winter, the first water distribution area, the first coarse filtration area, the first fine filtration area and the first water collection area are provided with a first covering layer 35 on the side away from the bottom of the water. The first covering layer 35 can form an insulating layer on the surface of the first-level horizontal submerged flow wetland, block the influence of low temperature in the air on the purification effect of the wetland, avoid water temperature dissipation in the wetland, and effectively reduce the influence of low temperature in winter on the northern wetlands.

[0060] Optionally, the following principles can be referred to when selecting fillers in subsurface wetlands: 1. The fillers are rough and porous, with a large specific surface area; 2. They have a high content of active substances such as iron, magnesium, calcium, and aluminum; 3. Rational use of local available waste resources, such as construction waste recycled materials, discarded red brick blocks, and steel slag, etc., to achieve the effect of waste treatment under the premise of ensuring the treatment effect and not affecting the environment; 4. The fillers can be easily obtained at the project implementation site, and the price is low to reduce the cost of wetland construction. Therefore, in this embodiment, under the premise of fully considering the purification effect, the pursuit of economy and practicality, combined with the requirements of inlet and outlet water quality and the geographical location of the wetland system, fillers of different materials and particle sizes are organically combined. In this embodiment, taking into full consideration the construction cost and purification efficiency, the subsurface wetland selects graded crushed stone and limestone as the main fillers, and at the same time, it is supplemented by ceramsite, volcanic rock, zeolite, etc., which are easier to form a film, to optimize the removal effect of the wetland system on five-day biochemical oxygen demand (BOD5), NH3-N, total phosphorus (TP), and total nitrogen (TN). Table 1 shows the filler type, filler particle size, and thickness of each functional area in the primary horizontal subsurface flow wetland.

[0061] Table 1 Filler type, filler particle size and thickness of each functional area in the primary horizontal subsurface flow wetland

[0062]

[0063] That is, the particle size of the filler in the first water distribution area is greater than 16 mm and less than or equal to 32 mm. The particle size of the filler in the first coarse filtration area is greater than 8 mm and less than or equal to 16 mm. The particle size of the filler in the first fine filtration area is greater than or equal to 4 mm and less than or equal to 8 mm.

[0064] Optionally, see Figure 4 The secondary horizontal subsurface flow wetland 13 includes, along the water flow direction, a second water distribution area, a second coarse filtration area, a second fine filtration area and a second water collection area.

[0065] The first water distribution pipe 23 is arranged in the second water distribution area. Optionally, in the scenario where the second ventilation pipe 34 is arranged, the second ventilation pipe 34 is also arranged in the second water distribution area.

[0066] The second water distribution area, the second coarse filtration area and the second fine filtration area all include fillers, and the particle size of the fillers in the second water distribution area, the particle size of the fillers in the second coarse filtration area and the particle size of the fillers in the second fine filtration area decrease in sequence. The beneficial effects of this arrangement are similar to the beneficial effects of the filler arrangement in the primary horizontal submerged flow wetland, and will not be repeated here.

[0067] The second water collecting pipe 26 is arranged in the second water collecting area. Optionally, in the scenario where the third ventilation pipe 37 is arranged, the third ventilation pipe 37 is also arranged in the second water collecting area.

[0068] The second water distribution area, the second coarse filtration area, the second fine filtration area and the second water collection area are provided with a second covering layer 39 on one side away from the bottom of the water. The effect of providing the second covering layer is similar to that of providing the first covering layer, and will not be repeated here.

[0069] Table 2 shows the filler type, filler particle size, and thickness of each functional area in the secondary horizontal subsurface flow wetland.

[0070] Table 2 Filler type, filler particle size and thickness of each functional area in the secondary horizontal subsurface flow wetland

[0071]

[0072] Optionally, see Figure 5 The vertical subsurface wetland 14 includes, in order from the bottom of the water to the surface of the water, a water distribution layer, a purification layer, a water collection layer, and a third covering layer 40. The water distribution layer in this embodiment may also be referred to as a water distribution supporting layer.

[0073] The second water distribution main pipe 27 and the second water distribution branch pipe 31 are disposed in the water distribution layer.

[0074] The water collecting branch pipe 30 and the water collecting main pipe 29 are arranged in the water collecting layer.

[0075] Optionally, the water distribution layer, the purification layer and the water collection layer all include fillers, and the particle size of the filler in the water distribution layer, the particle size of the filler in the purification layer and the particle size of the filler in the water collection layer decreases in sequence. This arrangement can improve the purification effect while avoiding clogging of the vertical subsurface flow wetland. Table 3 shows the filler type, filler particle size and thickness of the functional area in each functional area of ​​the vertical subsurface flow wetland.

[0076] Table 3 Filler type, filler particle size and thickness of each functional area in the vertical subsurface flow wetland

[0077]

[0078]

[0079] That is, in the vertical subsurface flow wetland, the particle size of the filler in the water distribution layer is greater than 16 mm and less than or equal to 32 mm. The particle size of the filler in the purification layer is greater than 8 mm and less than or equal to 16 mm. The particle size of the filler in the water collection layer is greater than or equal to 4 mm and less than or equal to 8 mm.

[0080] Optionally, aquatic plants are provided in the wetland system. Aquatic plants are a key element in water purification. The wetland system can remove pollutants from the water or reduce their toxicity through aquatic plants directly adsorbing and absorbing pollutants, cooperating with microorganisms to decompose pollutants, etc., so as to further improve the purification effect.

[0081] Optionally, the primary horizontal subsurface flow wetland, the secondary horizontal subsurface flow wetland and the vertical subsurface flow wetland adopt emergent plants, and the surface flow wetland adopts emergent, floating leaf and submerged plants.

[0082] Optionally, the screening principles for aquatic plants in this embodiment are: 1. Select species with strong purification ability, wide adaptability, rapid survival and growth in patches, and well-developed root systems; 2. Select species that are resistant to load shock; 3. When the wetland system is located in an area with lower temperatures in winter, select species that can successfully survive the winter at low temperatures; 4. Select species with good landscape effects; 5. Select species that are not prone to rampant growth.

[0083] In this embodiment, considering the water purification capacity, low temperature adaptability and landscape effect of each subsurface wetland and surface wetland, emergent plants such as reed, calamus, cattail, oriental water plantain, yellow iris, and loosestrife, floating leaf plants such as water lily, water chestnut, and water nymph, and submerged plants such as Vallisneria, duckweed, black algae, and foxtail algae are preferred.

[0084] Furthermore, in order to ensure the landscape effect of the wetland system, in this embodiment, aquatic plants such as reeds, calamus, cattails, water plantain, and pink-green foxtail algae can be arranged at the front end of the wetland water inlet and in areas away from people. Aquatic plants such as calamus, yellow calamus, loosestrife, water lilies, valuable grass, and duckweed can be arranged in the hydrophilic and ornamental areas in combination with the park landscape.

[0085] Optionally, in winter, operational measures such as harvesting aquatic plants to cover the upper part of the wetland and operating at a low water level can be adopted to further block the impact of low temperatures in the air on the purification effect of the wetland, avoid water temperature dissipation in the wetland, and effectively reduce the impact of low temperatures in winter on northern wetlands.

[0086] Optionally, see Figure 2 In the wetland system of this embodiment, the number of first-level horizontal subsurface flow wetlands can be two. The two first-level horizontal subsurface flow wetlands share a water distribution channel and adopt a water flow method of middle water distribution and peripheral water discharge, so that the wetland has strong flexibility, and the wetland side wall is less restricted by hydraulic conditions, so it can be set into different shapes according to landscape needs.

[0087] Figure 6 Schematic diagram of an application scenario of a wetland system provided by an embodiment of the present invention. Figure 6 As shown, the wetland system provided in this embodiment can work together with the regulating reservoir to solve the problem of regional non-point source pollution and maintain and stabilize the water quality of the river.

[0088] The storage pool will handle part of the initial rainwater and reduce the amount of non-point source pollution entering the river. The remaining initial rainwater will be purified by the wetland system provided in this embodiment. The water purified by the wetland system will be discharged into the main stream or downstream of the tributary to provide ecological water demand for the main stream or downstream of the tributary. In addition, the wetland system provided in this embodiment will not only purify the water quality, but also form a park water system to provide activity space for surrounding residents.

[0089] Initial rainwater storage tanks are mainly set up in built-up areas to collect rainwater runoff generated by the thickest rainfall. This part of runoff has a high concentration of pollutants and needs to be intercepted by initial rain interception and storage facilities before entering the sewage treatment plant for purification.

[0090] Intercepting pipes are built along the rainwater pipes in the river channel of the built-up area. According to the design requirements, part of the initial rainwater is intercepted and enters the newly built storage tank. According to the existing pipeline conditions and the surrounding land use conditions, the storage tank is located in the green space or park green space on both sides of the river, including the grille room and the initial rain storage tank. The grille room can be a fully underground rotary mechanical grille. After passing through the grille, the rainwater enters the water distribution well between the grilles. The water distribution well is equipped with an emptying submersible pump to meet the emptying of the storage tank. Optionally, an initial rainwater storage tank flushing pump can be set in the water distribution well to meet the requirements of silt flushing in the storage tank. According to the characteristics of rainwater precipitation, to meet the initial rain storage requirements of different rainfall processes, the storage tank is divided into 3 compartments: initial rainwater pool 1, initial rainwater pool 2 and initial rainwater pool 3. The initial rainwater enters the initial rainwater pool 1→initial rainwater pool 2→initial rainwater pool 3 in sequence, and finally reaches the designed storage capacity. Overflow holes are used for water distribution between the storage tanks, and the number of overflow holes can be 2. The hole top height is consistent with the highest water level of the initial rain storage tank, and a water drop device is installed at the overflow square hole of the rainwater storage tank. In order to ensure normal pressure and air circulation in the pool, a vent pipe can be installed on the top of the pool.

[0091] At the beginning of rainfall, rainwater first flows into the initial rainwater pool 1, so that the relatively dirty initial rainwater can be intercepted. When the water level of the initial rainwater pool 1 rises to the bottom elevation of the overflow hole, the initial rainwater pool 1 has been collected, and the rainwater overflows into the initial rainwater pool 2; when the water level of the initial rainwater pool 2 rises to the bottom elevation of the overflow hole, the initial rainwater pool 2 has been collected, and the rainwater overflows into the initial rainwater pool 3. When the rainwater rises to the designed maximum water level, the inlet gate is closed. Some of the initial rainwater that cannot be collected in the storage tank is purified by the wetland system.

[0092] Optionally, in this embodiment, in order to further improve the effect of non-point source pollution control, the hydrodynamic model can be used to simulate the flow rate of the initial rain thickness and the comprehensive runoff coefficient of each sub-basin to obtain the simulation results. The simulation results include the water quality and water volume when the river flows into the initial rain. The size and location of the pre-pond, the first-level horizontal subsurface wetland, the second-level horizontal subsurface wetland, the vertical subsurface wetland and the surface flow wetland in the wetland system are determined according to the simulation results. The wetland system provided in this embodiment can be set in the bypass where the tributary flows into the main stream to ensure that the water quality is purified before flowing into the main stream.

[0093] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps described in the present invention can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solution of the present invention can be achieved, and this document does not limit this.

[0094] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A wetland system for non-point source pollution treatment, characterized in that: It includes a pre-pond, a first-level horizontal subsurface wetland, a second-level horizontal subsurface wetland, a vertical subsurface wetland and a surface flow wetland that are connected in sequence, the pre-pond is connected to a tributary, and the surface flow wetland is connected to a main stream or a downstream tributary; the wetland system is used to treat non-point source pollution collected along the tributary, and discharge purified water into the main stream or the downstream of the tributary; A water distribution channel is arranged between the front pond and the first-level horizontal submerged flow wetland, one end of the water distribution channel is connected to the front pond through a pipeline, and the other end is connected to the first-level horizontal submerged flow wetland through a first water distribution main pipe, the first water distribution main pipe is connected to a first water distribution branch pipe, the first water distribution branch pipe is a perforated pipe, which is parallel to the water surface and perpendicular to the water flow direction; a first partition wall is arranged between the first-level horizontal submerged flow wetland and the second-level horizontal submerged flow wetland, a first water collecting pipe is arranged on the upstream side of the first partition wall, and a first water distribution pipe is arranged on the downstream side; the first water collecting pipe is connected to the first water distribution pipe through a plurality of connecting pipes passing through the first partition wall, the first water collecting pipe and the first water distribution pipe are both perforated pipes, which are both parallel to the water surface and perpendicular to the water flow direction; A second partition wall is arranged between the secondary horizontal subsurface flow wetland and the vertical subsurface flow wetland, a second water collecting pipe is arranged on the upstream side of the second partition wall, and a second water distribution main pipe is arranged on the downstream side; the second water collecting pipe is connected with the second water distribution main pipe through a plurality of connecting pipes passing through the second partition wall, the second water collecting pipe is a perforated pipe, which is parallel to the water surface and perpendicular to the water flow direction, and the second water distribution main pipe is a perforated pipe; The vertical subsurface flow wetland also includes: a water collection main pipe, a plurality of water collection branch pipes connected to the water collection main pipe, and a plurality of second water distribution branch pipes connected to the second water distribution main pipe, the second water distribution branch pipes and the water collection branch pipes are perforated pipes, which are parallel to the water surface and the direction of water flow; a water collection channel is arranged between the vertical subsurface flow wetland and the surface flow wetland, one end of the water collection channel is connected to the water collection main pipe, and the other end is connected to the surface flow wetland.

2. The wetland system according to claim 1, characterized in that: The wetland system further includes at least one of the following: a first vent pipe, a second vent pipe, a third vent pipe, and a fourth vent pipe; The first ventilation pipe is arranged on the upstream side of the first partition wall, the first ventilation pipe is communicated with the first water collecting pipe, and the first ventilation pipe is perpendicular to the water surface and higher than the water surface; The second ventilation pipe is arranged at the downstream side of the first partition wall, the second ventilation pipe is communicated with the first water distribution pipe, and the second ventilation pipe is perpendicular to the water surface and higher than the water surface; The third ventilation pipe is arranged on the upstream side of the second partition wall, the third ventilation pipe is communicated with the second water collecting pipe, and the third ventilation pipe is perpendicular to the water surface and higher than the water surface; The fourth ventilation pipe is arranged on the downstream side of the second partition wall, the fourth ventilation pipe is communicated with the second water distribution main pipe, and the fourth ventilation pipe is perpendicular to the water surface and higher than the water surface.

3. The wetland system according to claim 1, characterized in that: The water surface elevations of the front pond, the first-level horizontal subsurface wetland, the second-level horizontal subsurface wetland, the vertical subsurface wetland and the surface flow wetland decrease in sequence.

4. The wetland system according to any one of claims 1 to 3, characterized in that: The wetland system further includes: a first valve and a second valve; The first water distribution main pipe is connected to the first water distribution branch pipe through the first valve; The water collecting main pipe is communicated with the water collecting channel through the second valve.

5. The wetland system according to any one of claims 1 to 3, characterized in that: The first-level horizontal subsurface flow wetland includes, in sequence along the water flow direction: a first water distribution area, a first coarse filtration area, a first fine filtration area and a first water collection area; The first water distribution main pipe and the first water distribution branch pipe are arranged in the first water distribution area; The first water distribution area, the first coarse filtration area and the first fine filtration area all include fillers, and the particle size of the filler in the first water distribution area, the particle size of the filler in the first coarse filtration area and the particle size of the filler in the first fine filtration area decreases in sequence; The first water collecting pipe is arranged in the first water collecting area.

6. The wetland system according to claim 5, characterized in that: The particle size of the filler in the first water distribution area is greater than 16 mm and less than or equal to 32 mm; The particle size of the filler in the first coarse filtration zone is greater than 8 mm and less than or equal to 16 mm; The particle size of the filler in the first fine filtration zone is greater than or equal to 4 mm and less than or equal to 8 mm.

7. The wetland system according to claim 5, characterized in that: A first covering layer is provided on the first water distribution area, the first coarse filtration area, the first fine filtration area, and the first water collection area on a side away from the water bottom.

8. The wetland system according to any one of claims 1 to 3, characterized in that: The secondary horizontal subsurface flow wetland includes, in sequence along the water flow direction: a second water distribution area, a second coarse filtration area, a second fine filtration area and a second water collection area; The first water distribution pipe is arranged in the second water distribution area; The second water distribution area, the second coarse filtration area and the second fine filtration area all include fillers, and the particle size of the filler in the second water distribution area, the particle size of the filler in the second coarse filtration area and the particle size of the filler in the second fine filtration area decreases in sequence; The second water collecting pipe is arranged in the second water collecting area; A second covering layer is provided on the side of the second water distribution area, the second coarse filtration area, the second fine filtration area and the second water collection area away from the water bottom.

9. The wetland system according to any one of claims 1 to 3, characterized in that: The vertical subsurface wetland includes, in order from the bottom of the water to the surface of the water: a water distribution layer, a purification layer, a water collection layer and a third covering layer; The second water distribution main pipe and the second water distribution branch pipe are arranged in the water distribution layer; The water collecting branch pipe and the water collecting main pipe are arranged in the water collecting layer.

10. The wetland system according to claim 9, characterized in that: The water distribution layer, the purification layer and the water collection layer all include fillers, and the particle size of the filler in the water distribution layer, the particle size of the filler in the purification layer and the particle size of the filler in the water collection layer decreases in sequence; The particle size of the filler of the water distribution layer is greater than 16 mm and less than or equal to 32 mm; The particle size of the filler of the purification layer is greater than 8 mm and less than or equal to 16 mm; The particle size of the filler of the water-collecting layer is greater than or equal to 4 mm and less than or equal to 8 mm.

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