Bioretention device for removing new pollutants and nitrogen pollutants in rainwater runoff

Abstract

The invention discloses a bioretention device for synchronously removing new pollutants and nitrogen pollutants in rainwater runoff, and relates to the technical field of water environment treatment. Six layers of functional units, namely an overflow layer, a protective layer, a seepage layer, a submerging layer, a transition layer and a drainage layer from top to bottom, are vertically constructed in the pool body; the seepage layer is provided with a top guide and drainage system, the drainage layer is provided with a bottom guide and drainage system, and the top of the multifunctional overflow device and a facility top plate keep safe superelevation; the permeation regulation and control layer is provided with a hydraulic linkage control system, and intelligent opening and closing of a top guiding and discharging opening are achieved through a sensing device; the functional unit is filled with a modified matrix loaded with delta-MnO2 and rich Mn element valence states (+ 2, + 3 and + 4) of the delta-MnO2, removal of new pollutants and nitrogen pollutants is enhanced, meanwhile, circulation of manganese oxidation reduction is formed, cyclic supply of manganese elements in a system is guaranteed, and regular additional filler supplement is not needed.

Description

Technical Field

[0001] The present invention relates to the technical field of water environment treatment, and particularly relates to a bioretention device for removing emerging pollutants and nitrogen pollutants in rainwater runoff. Background Art

[0002] Rainwater runoff is an important link for pollutant migration and transportation. Especially with the intensification of industrialization, emerging pollutants generated by the friction between automobiles and road surfaces are highly biotoxic and pose a threat to water environment safety as they migrate with rainwater runoff.

[0003] Rainwater bioretention facilities are an important part of sponge city construction and the last line of defense to prevent pollutants from entering surface water bodies. Therefore, it is particularly crucial to use rainwater bioretention facilities to remove pollutants in runoff. However, traditional rainwater bioretention facilities have disadvantages such as insufficient electron supply and insufficient rainwater residence time.

[0004] The present invention constructs a bioretention facility added with a matrix modified by loaded δ-MnO2 to simultaneously degrade emerging pollutants and conventional pollutants. In the prior art, common modified matrices such as solid carbon sources (wood chips, etc.), sulfur, iron / aluminum-based materials, etc. can achieve pollutant removal by providing denitrification electrons, promoting autotrophic denitrification, or adsorbing and flocculating phosphorus respectively, but all have significant defects: solid carbon sources are prone to organic matter leakage causing secondary pollution, and structural collapse leading to blockage; sulfur causes a sudden drop in system pH and excessive accumulation of sulfates, inhibiting microbial activity; iron / aluminum-based materials have a risk of metal ion dissolution. At the same time, due to the single function of the above materials, either only as an electron donor or relying on adsorption / precipitation, they cannot achieve the synergistic effect of long-term pollutant retention (extended hydraulic residence time) and stable electron supply in the system, resulting in limited synchronous removal efficiency of multi-target pollutants in complex polluted water bodies.

[0005] δ-MnO2 is a layered manganese dioxide crystal material. Characterized by the coexistence of multivalent manganese, high specific surface area, and surface active hydroxyl groups, it has both redox mediation ability and strong adsorption performance, and can efficiently capture pollutants and provide a reaction interface. The rich Mn element valence states (+2, +3, and +4) of δ-MnO2 in the facility can form a manganese redox cycle, which can simultaneously promote the oxidation of NH4 in rainwater + and NO3 in -The reduction process is carried out, and the abundance of surface-active microorganisms in the matrix is increased to achieve efficient extracellular electron transfer; Mn(II) in δ-MnO2 is used to provide electrons for nitrate nitrogen and 6PPD-Q simultaneously, improving the electron transfer efficiency in the system and promoting the reduction and degradation of 6PPD-Q; Mn(II) forms bio-manganese oxides (BMOs) under aerobic conditions in the percolation layer and the action of manganese-oxidizing bacteria, where manganese elements often exist as highly active Mn(III). While strengthening the effective degradation of 6PPD-Q, Mn(IV) generated by the disproportionation reaction of Mn(III) simultaneously participates in the manganese redox cycle to ensure the cyclic supply of manganese elements in the system. Electron recycling is achieved in these processes, and there is no need to regularly supplement additional fillers. Summary of the Invention

[0006] In view of the above-mentioned defects of the prior art, the technical problem to be solved by the present invention is how to provide sufficient electrons for pollutant removal and extend the residence time of pollutants in the system.

[0007] To achieve the above object, the present invention provides a bioretention device for synchronously degrading new pollutants and conventional pollutants based on δ-MnO2 modified matrix. The device includes a pool body 12.

[0008] Six functional units are vertically constructed in the pool body, which are, from top to bottom, an overflow layer 1, a protection layer 2, a percolation layer 3, a submerged layer 4, a transition layer 5, and a drainage layer 6.

[0009] The percolation layer is equipped with a top drainage system 7, and the drainage layer is provided with a bottom drainage system 8. Both sets of drainage pipes adopt a porous pipe structure; the outlet elevation of the bottom drainage pipe is flush with the top surface of the saturated water-holding layer.

[0010] A multi-functional overflow device is arranged inside the device, which consists of a shaft 10 structure and a detachable grille cover 11, and there is a safety freeboard of 5-10 cm between the top and the facility roof slab.

[0011] Both outlets of the drainage system are connected to the overflow device and finally converge into the municipal drainage network.

[0012] The infiltration regulation layer is equipped with a hydraulic linkage control system 9, and the intelligent opening and closing of the top drainage outlet are realized through a sensing device.

[0013] The opening and closing of the valve 91 are controlled by the induction device 92 to sense the water level.

[0014] The starting regulation water level H of the top drainage system is determined by the following relational formula:

[0015]

[0016] In the formula: is the comprehensive runoff coefficient of the catchment area, F is the service area of the facility, t pis the design water accumulation time, P is the design recurrence period, ranging from 5 to 30 years, A is the facility infiltration area, t is the rainfall duration, K u is the overall permeability of the protective layer and the seepage layer;

[0017] The overflow device discharge capacity must meet the following requirements:

[0018]

[0019] Where: n k The number of holes in the overflow well width direction, l is the grate hole length, b is k is the grate hole width, C is the orifice coefficient, g is the gravity acceleration, h is the flooding depth above the wellhead, K w is the blocking coefficient, K b is the overall permeability of the facility, and P is the maximum recurrence period, ranging from 30 to 100 years.

[0020] During operation, for normal rainfall conditions (P = 1-5 years): the top drainage system remains closed, and the runoff is gradually infiltrated and purified through each functional layer before being introduced into the overflow device by the bottom drainage system.

[0021] For heavy rainfall conditions (P = 5-30 years): when the accumulated water reaches the starting water level, the sensor device will open the top drainage port in a linked manner to form a fast drainage channel from the infiltration control layer to the overflow device, shortening the runoff migration path.

[0022] Extreme rainstorm conditions (P>30 years): When the accumulated water overflows the top cover of the overflow device, a surface runoff direct discharge channel is formed to ensure the flood control safety of the system. This design achieves a functional balance between infiltration purification and flood discharge and risk elimination.

[0023] In a preferred embodiment of the present invention, the protective layer matrix is selected from pebbles with a particle size of 1 cm to 3 cm;

[0024] In a preferred embodiment of the present invention, the seepage layer is filled with 90% sand + 10% δ-MnO2 loaded gravel matrix;

[0025] In a preferred embodiment of the present invention, the flooded layer is filled with 80% sand + 20% δ-MnO2 loaded gravel matrix;

[0026] In a preferred embodiment of the present invention, the transition layer is composed of homogeneous quartz sand (4 mm to 8 mm) to prevent the filter medium from entering the drainage layer;

[0027] In a preferred embodiment of the present invention, the drainage layer substrate is made of 1cm to 2cm pebbles.

[0028] The beneficial effects of the present invention are as follows: The present invention is provided with three water outlet methods, namely, top drainage pipe water outlet, bottom drainage water outlet and overflow water outlet, which can automatically adjust the water outlet path of the biological branch facilities according to the change of rainwater flow. When dealing with light and moderate rain, the rainwater runoff scours the surface and carries a large amount of pollutants into the facilities. In the facilities, the Mn element valence states (+2, +3 and +4) rich in δ-MnO2 can form a manganese oxidation-reduction cycle, which can simultaneously promote the oxidation of NH4 + in rainwater and the reduction process of NO3 - , and improve the abundance of surface active microorganisms in the matrix to achieve efficient extracellular electron transfer; use Mn(Ⅱ) in δ-MnO2 to provide electrons for nitrate nitrogen and 6PPD-Q simultaneously, improve the electron transfer efficiency in the system, and promote the reduction and degradation of 6PPD-Q; use Mn(Ⅱ) to form biological manganese oxides (BMOs) under aerobic conditions in the seepage layer and the action of manganese-oxidizing bacteria. The manganese element in it often exists as Mn(Ⅲ) with extremely strong activity. While strengthening the effective degradation of 6PPD-Q, the Mn(Ⅳ) generated by the disproportionation reaction of Mn(Ⅲ) simultaneously participates in the manganese oxidation-reduction cycle to ensure the cyclic supply of manganese elements in the system. When dealing with heavy rain, the effect of the facility matrix on reducing the dissolved oxygen of rainwater runoff is very limited. At this time, the pollutant concentration in the rainwater runoff is relatively low. After the rainwater passes through the filter layer to treat particulate pollutants, dissolved organic matter and ammonia nitrogen, it flows into the overflow well; when dealing with extreme rainfall conditions, the rainwater runoff directly flows into the overflow well after being simply screened for large particulate pollutants through the manhole cover grille. By adjusting the opening of the top inverted drainage pipe to control the water level and the height of the overflow well wellhead, the facility can adapt to rainfall under different conditions, thereby effectively protecting the submerged layer of the facility, enabling the facility to effectively remove nitrogen and phosphorus, and having a longer service life.

[0029] The concept, specific structure and technical effects of the present invention will be further described below in conjunction with the drawings to fully understand the purpose, features and effects of the present invention. Description of the Drawings

[0030] Figure 1 is a biological retention device for synchronously degrading new pollutants and conventional pollutants based on δ-MnO2 modified matrix in a preferred embodiment of the present invention.

[0031] Overflow layer 1, protective layer 2, seepage layer 3, submerged layer 4, transition layer 5 and drainage layer 6. Top drainage system 7, bottom drainage system 8, hydraulic linkage control system 9, valve 91, induction device 92, shaft 10, detachable grille cover 11, pool body 12. Detailed Embodiments

[0032] The following describes multiple preferred embodiments of the present invention with reference to the accompanying drawings of the specification to make its technical content clearer and easier to understand. The present invention can be embodied in many different forms of embodiments, and the protection scope of the present invention is not limited to the embodiments mentioned in the text.

[0033] In the drawings, components with the same structure are denoted by the same numerical reference signs, and components with similar structures or functions everywhere are denoted by similar numerical reference signs. The size and thickness of each component shown in the drawings are arbitrarily shown, and the present invention does not limit the size and thickness of each component. To make the illustration clearer, the thickness of some parts in the drawings is appropriately exaggerated.

[0034] As Figure 1 shown, the bioretention facility includes a pool body 12.

[0035] The vertical structure is composed of six functional units, which are, from top to bottom in sequence, an overflow layer 1, a protection layer 2, a percolation layer 3, a submerged layer 4, a transition layer 5, and a drainage layer 6. The percolation layer is configured with a top drainage system 7, and the drainage layer is provided with a bottom drainage system 8. Both sets of drainage pipes adopt a porous pipe structure. The elevation of the outlet of the bottom drainage pipe is flush with the top surface of the saturated water-holding layer.

[0036] A multifunctional overflow device is provided inside the facility, which is composed of a shaft 10 structure and a detachable grille cover 11, and there is a safety freeboard of 5 - 10 cm between the top and the facility roof slab. Both outlets of the drainage system are connected to this overflow device and finally converge into the municipal drainage network.

[0037] The infiltration regulation layer is equipped with a hydraulic linkage control system 9, and the intelligent opening and closing of the top drainage outlet is realized through a sensing device. The opening and closing of the valve 91 is controlled by the sensing device 92 sensing the water level.

[0038] The starting regulation water level H of the top drainage system is determined by the following relational expression:

[0039]

[0040] In the formula: is the comprehensive runoff coefficient of the catchment area, F is the service area of the facility, t p is the designed ponding time, P is the design return period, and the value range is 5 years to 30 years, A is the infiltration area of the facility, t is the rainfall duration, K u is the overall permeability of the protection layer and the percolation layer.

[0041] The discharge capacity of the overflow device needs to meet:

[0042]

[0043] In the formula: n k is the number of openings in the width direction of the overflow well, l is the length of the grate hole, b kis the grate hole width, C is the orifice coefficient, g is the gravity acceleration, h is the flooding depth above the wellhead, K w is the blocking coefficient, K b is the overall permeability of the facility, and P is the maximum recurrence period, ranging from 30 to 100 years.

[0044] Operation mechanism:

[0045] Normal rainfall conditions (P = 1-5 years): The top drainage system remains closed, and the runoff is gradually infiltrated and purified through each functional layer before being introduced into the overflow device by the bottom drainage system.

[0046] Heavy rainfall conditions (P = 5-30 years): When the accumulated water reaches the start-up water level, the sensor device will open the top drainage port to form a fast drainage channel from the infiltration control layer to the overflow device, shortening the runoff migration path.

[0047] Extreme rainstorm conditions (P>30 years): When the accumulated water overflows the top cover of the overflow device, a surface runoff direct discharge channel is formed to ensure the flood control safety of the system. This design achieves a functional balance between infiltration purification and flood discharge and risk elimination.

[0048] In this example, the protective layer matrix is made of pebbles with a particle size of 1cm to 3cm; the seepage layer is filled with 90% sand + 10% gravel matrix loaded with δ-MnO2; the submerged layer is filled with 80% sand + 20% gravel matrix loaded with δ-MnO2; the transition layer is composed of homogeneous quartz sand (4mm to 8mm) to prevent the filter medium from entering the drainage layer; the drainage layer matrix is made of 1cm to 2cm pebbles.

[0049] The present invention is provided with three water outlet modes: top drainage pipe outlet, bottom drainage pipe outlet and overflow outlet, which can automatically adjust the water outlet path of the biological tributary facility according to the change of rainwater flow. When dealing with light and moderate rain, rainwater runoff washes the surface and carries a large amount of pollutants into the facility. In the facility, the rich Mn element valence states (+2, +3 and +4) of δ-MnO2 can form a manganese redox cycle, which can simultaneously promote the reduction of NH4 + Oxidation and NO3 -The reduction process is carried out, and the abundance of surface-active microorganisms in the substrate is increased to achieve efficient extracellular electron transfer; Mn(II) in δ-MnO2 is used to synchronously provide electrons for nitrate nitrogen and 6PPD-Q, improving the electron transfer efficiency in the system and promoting the reduction and degradation of 6PPD-Q; biological manganese oxides (BMOs) are formed by Mn(II) under aerobic conditions in the percolation layer and the action of manganese-oxidizing bacteria, where manganese elements often exist as highly active Mn(III). While strengthening the effective degradation of 6PPD-Q, the Mn(IV) generated by the disproportionation reaction of Mn(III) simultaneously participates in the manganese redox cycle to ensure the cyclic supply of manganese elements in the system. When dealing with heavy rain, the effect of the facility substrate in reducing the dissolved oxygen in rainwater runoff is already very limited. At this time, the pollutant concentration in rainwater runoff is relatively low. After the rainwater passes through the filter layer to treat particulate pollutants, dissolved organic matter and ammonia nitrogen, it flows into the overflow well; when dealing with extreme rainfall conditions, the rainwater runoff directly flows into the overflow well after large particulate pollutants are simply screened out by the manhole cover grille. By adjusting the opening of the top inverted drain pipe to control the water level and the height of the overflow well opening, the facility can adapt to rainfall under different conditions, thereby effectively protecting the submerged layer of the facility, enabling the facility to effectively remove nitrogen and phosphorus, and having a longer service life.

[0050] The preferred specific embodiments of the present invention have been described in detail above. It should be understood that those of ordinary skill in the art can make many modifications and variations based on the concept of the present invention without creative labor. Therefore, all technical solutions that can be obtained by those skilled in the art in the technical field of the present invention through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the protection scope determined by the claims.

Claims

1. A bioretention device for removing new pollutants and conventional pollutants from stormwater runoff, the device comprising a tank body; The pool body is vertically constructed with six functional units, which are overflow layer, protective layer, seepage layer, submerged layer, transition layer and drainage layer from top to bottom; The seepage layer is equipped with a top drainage system, and the drainage layer is equipped with a bottom drainage system. Both sets of drainage pipes adopt a porous pipe structure; the outlet elevation of the bottom drainage pipe is flush with the top surface of the saturated water-holding layer; The device is equipped with a multifunctional overflow device, which is composed of a shaft structure and a removable grid cover, and the top is kept at a safe height relative to the facility roof; Both outlets of the drainage system are connected to the multifunctional overflow device and finally flow into the municipal drainage network; The permeability regulating layer is equipped with a hydraulic linkage control system, and the intelligent opening and closing of the top drainage port is realized through a sensor device; and a modified matrix loaded with δ-MnO2 is filled in the functional unit.

2. The device according to claim 1, characterized in that, The opening and closing of the valve is controlled by the sensing device that senses the water level.

3. The device according to claim 2, wherein, The starting water level H of the top drainage system is determined by the following relationship: In the formula: is the comprehensive runoff coefficient of the catchment area, F is the service area of the facility, and t p is the designed ponding time, P is the design return period, and the value range is 5 years to 30 years. A is the infiltration area of the facility, t is the rainfall duration, and K u is the overall permeability of the protective layer and the seepage layer.

4. The device according to claim 3, wherein The discharge capacity of the overflow device must meet the following requirements: Where: n k The number of openings in the width direction of the overflow well, l is the length of the grate hole, b k is the width of the grate hole, C is the orifice coefficient, g is the acceleration of gravity, h is the depth of the flooded water above the wellhead, K w is the blockage coefficient, K b is the overall permeability of the facility, P is the maximum recurrence period, and the value range is 30 years to 100 years.

5. The device according to claim 4, characterized in that, For normal rainfall conditions, P = 1-5 years: the top drainage system remains closed, and the runoff is guided into the overflow device by the bottom drainage system after being infiltrated and purified step by step through each functional layer; for heavy rainfall conditions, P = 5-30 years: when the accumulated water reaches the starting water level, the sensor device will open the top drainage port in conjunction to form a fast drainage channel from the infiltration control layer to the overflow device, shortening the runoff migration path; for extreme rainstorm conditions, P>30 years: when the accumulated water overflows the top cover of the overflow device, a surface runoff direct discharge channel is formed to ensure the flood control safety of the system; this design achieves a functional balance between infiltration purification and flood discharge and risk removal.

6. The device according to claim 1, wherein The protective layer matrix is made of pebbles with a particle size of 1 cm to 3 cm.

7. The device according to claim 1, characterized in that, The seepage layer is filled with 90% sand + 10% δ-MnO2 loaded gravel matrix.

8. The device according to claim 1, characterized in that The flooded layer is filled with 80% sand + 20% δ-MnO2 loaded gravel matrix.

9. The device according to claim 1, characterized in that, The transition layer is composed of homogeneous quartz sand (4 mm to 8 mm) to prevent the filter medium from entering the drainage layer.

10. The device according to claim 1, characterized in that, The drainage layer substrate is made of 1cm to 2cm pebbles.

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