A bioretention device for removing emerging and nitrogen contaminants in stormwater runoff

Abstract

The application discloses a biological retention device for synchronously removing new pollutants and nitrogen pollutants in rainwater runoff, and relates to the technical field of water environment treatment. The biological retention device comprises a pool body, six functional units are vertically constructed in the pool body from top to bottom, and the six functional units are overflow layer, protection layer, seepage layer, submerged layer, transition layer and drainage layer in sequence. The seepage layer is provided with a top drainage system, the drainage layer is provided with a bottom drainage system, and the top of the multifunctional overflow device is kept at a safe superheight from the top plate of the device. The seepage control layer is provided with a hydraulic linkage control system, and the intelligent opening and closing of the top drainage opening is realized through a sensing device. The modified substrate loaded with δ-MnO2 is filled in the functional units, the rich Mn element valence state (+2, +3 and +4) of the δ-MnO2 strengthens the removal of the new pollutants and the nitrogen pollutants, simultaneously forms the manganese oxidation-reduction cycle, guarantees the cyclic supply of the manganese element in the system, and does not need to be regularly supplemented with fillers.

Description

Technical Field

[0001] This invention relates to the field of water environment management technology, and in particular to a bioretention device for removing new pollutants and nitrogen pollutants from rainwater runoff. Background Technology

[0002] Rainwater runoff is a crucial link in the migration and transport of pollutants. In particular, with increasing industrialization, new pollutants released from the friction between vehicles and roads are highly biotoxic and threaten aquatic environmental safety as they migrate with rainwater runoff.

[0003] Rainwater bioretention facilities are an important component of sponge city construction and serve as the last line of defense against pollutants entering surface water bodies. Therefore, utilizing rainwater bioretention facilities to remove pollutants from runoff is particularly crucial. However, traditional rainwater bioretention facilities have drawbacks such as insufficient electronic power supply and insufficient rainwater retention time.

[0004] This invention constructs a bioretention facility with a modified δ-MnO2-loaded matrix to simultaneously degrade both novel and conventional pollutants. In existing technologies, commonly used modified matrices such as solid carbon sources (wood chips, etc.), sulfur, and iron / aluminum-based materials can remove pollutants by providing denitrification electrons, promoting autotrophic denitrification, or adsorbing flocculent phosphorus, respectively. However, all have significant drawbacks: solid carbon sources are prone to organic matter leakage leading to secondary pollution, and structural collapse can cause blockages; sulfur causes a sharp drop in system pH and excessive sulfate accumulation, inhibiting microbial activity; iron / aluminum-based materials pose a risk of metal ion leaching. Furthermore, because these materials have limited functions—either acting only as electron donors or relying on adsorption / precipitation—they cannot simultaneously achieve a synergistic effect of long-term pollutant retention (extending hydraulic retention time) and stable electron supply within the system, thus limiting the efficiency of simultaneous removal of multiple target pollutants in complex polluted water bodies.

[0005] δ-MnO2 is a layered manganese dioxide crystalline material characterized by the coexistence of multiple manganese valence states, high specific surface area, and surface-active hydroxyl groups. It possesses both redox-mediating capabilities and strong adsorption properties, enabling efficient capture of pollutants and providing a reaction interface. The abundant Mn valence states (+2, +3, and +4) in δ-MnO2 within the facility can form a manganese redox cycle, simultaneously promoting the absorption of NH4+ from rainwater. + Oxidation and NO3 -The reduction process enhances the abundance of active microorganisms on the matrix surface, thereby achieving efficient transfer of extracellular electrons. Mn(II) in δ-MnO2 simultaneously provides electrons for nitrate nitrogen and 6PPD-Q, improving electron transfer efficiency and promoting the reductive degradation of 6PPD-Q. Under aerobic conditions in the permeable layer and with the action of manganese-oxidizing bacteria, Mn(II) forms biogenic manganese oxides (BMOs), where manganese often exists as the highly reactive Mn(III). This enhances the effective degradation of 6PPD-Q while simultaneously allowing Mn(IV) generated from the disproportionation reaction of Mn(III) to participate in the manganese redox cycle, ensuring a continuous supply of manganese within the system. Electron circulation is achieved through these processes, eliminating the need for periodic replenishment of packing material. Summary of the Invention

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

[0007] To achieve the above objectives, this invention provides a bioretention device based on a δ-MnO2 modified matrix for the simultaneous degradation of novel and conventional pollutants. The device includes a tank 12.

[0008] The pool is vertically constructed with six functional units, which are, from top to bottom, overflow layer 1, protective layer 2, seepage layer 3, flooding layer 4, transition layer 5 and drainage layer 6.

[0009] The seepage layer is equipped with a top drainage system 7, and the drainage layer is equipped with a bottom drainage system 8. Both 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] The device is equipped with a multi-functional overflow device, consisting of a vertical shaft 10 structure and a detachable grid cover 11, with the top maintaining a safety clearance of 5-10cm from the top of the facility.

[0011] Both outlets of the drainage system are connected to the overflow device, and the water eventually flows into the municipal drainage network.

[0012] The infiltration control layer is equipped with a hydraulic linkage control system 9, which realizes the intelligent opening and closing of the top drainage outlet through a sensor device;

[0013] The opening and closing of valve 91 is controlled by sensing the water level through sensor 92;

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

[0015]

[0016] In the formula: The comprehensive runoff coefficient of the catchment area is given by F, where F is the service area of ​​the facility, and t is the total runoff volume. pThe design water accumulation time is given by P, the design return period (ranging from 5 to 30 years), A is the infiltration area of ​​the facility, t is the rainfall duration, and K is the design return period. u The overall permeability of the protective layer and the seepage layer;

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

[0018]

[0019] Where: n k The number of openings in the width direction of the overflow well, where l is the length of the grate opening, and b is the number of openings in the overflow well. k Where is the grate width, C is the orifice coefficient, g is the gravitational acceleration, h is the water depth above the wellhead, and K is the grate width. w K is the blocking coefficient. b The overall penetration rate of the facility is represented by P, which is the maximum return 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 purified through infiltration at 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 level, the sensor device will activate the top drainage outlet to form a rapid drainage channel from the infiltration control layer to the overflow device, shortening the runoff migration path.

[0022] Extreme rainfall conditions (P>30 years): When floodwater overflows the top cover of the overflow device, it forms a direct discharge channel for surface runoff, ensuring the system's flood control safety. This design achieves a functional balance between infiltration purification and flood discharge and hazard mitigation.

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

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

[0025] In a preferred embodiment of the invention, the flooding layer is filled with a gravel matrix consisting of 80% sand and 20% δ-MnO2 loaded with δ-MnO2.

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

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

[0028] The beneficial effects of this invention are as follows: This invention features three water discharge methods: top drainage pipe discharge, bottom drainage discharge, and overflow discharge, which can automatically adjust the water discharge path of the biological tributary facility according to changes in rainwater flow. When dealing with light to moderate rain, rainwater runoff carries a large amount of pollutants into the facility as it washes away surface water. Within the facility, the abundant Mn element with valence states (+2, +3, and +4) in δ-MnO2 can form a manganese redox cycle, simultaneously promoting the growth of NH4+ in the rainwater. + Oxidation and NO3 - The reduction process is enhanced, and the abundance of active microorganisms on the matrix surface is increased to achieve efficient transfer of extracellular electrons. Mn(II) in δ-MnO2 is used to simultaneously 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. Mn(II) is used to form biogenic manganese oxides (BMOs) under aerobic conditions in the seepage layer and the action of manganese-oxidizing bacteria. Manganese is often present as highly active Mn(III), which enhances the effective degradation of 6PPD-Q. At the same time, Mn(IV) generated by the disproportionation reaction of Mn(III) participates in the manganese redox cycle, ensuring the cyclic supply of manganese in the system. When dealing with rainstorms, the effect of the facility matrix on reducing dissolved oxygen in rainwater runoff is very limited. At this time, the concentration of pollutants in rainwater runoff is relatively low. After the rainwater is treated by the filter layer to remove particulate pollutants, dissolved organic matter and ammonia nitrogen, it flows into the overflow well. When dealing with extreme rainfall conditions, the rainwater runoff flows directly into the overflow well after simple screening of large particulate pollutants by the manhole cover grid. By adjusting the opening of the top back drain pipe to control the water level and the height of the overflow well, the facility can adapt to different rainfall conditions, thereby effectively protecting the flooded layer of the facility, enabling the facility to effectively remove nitrogen and phosphorus, and having a longer service life.

[0029] The following will further explain the concept, specific structure, and technical effects of the present invention in conjunction with the accompanying drawings, so as to fully understand the purpose, features, and effects of the present invention. Attached Figure Description

[0030] Figure 1 This is a preferred embodiment of the present invention, a bioretention device based on a δ-MnO2 modified matrix for the simultaneous degradation of novel and conventional pollutants.

[0031] Overflow layer 1, protective layer 2, seepage layer 3, flooding layer 4, transition layer 5, and drainage layer 6. Top drainage system 7, bottom drainage system 8, hydraulic linkage control system 9, valve 91, sensing device 92, vertical shaft 10, removable grating cover 11, pool body 12. Detailed Implementation

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

[0033] In the accompanying drawings, components with the same structure are indicated by the same numerical designation, and components with similar structures or functions are indicated by similar numerical designations. The dimensions and thicknesses of each component shown in the drawings are arbitrary, and the present invention does not limit the dimensions and thicknesses of each component. To make the illustrations clearer, the thickness of some components has been appropriately exaggerated in the drawings.

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

[0035] The vertical structure consists of six functional units, from top to bottom: overflow layer 1, protective layer 2, seepage layer 3, flooding layer 4, transition layer 5, and drainage layer 6. The seepage layer is equipped with a top drainage system 7, and the drainage layer is equipped with a bottom drainage system 8. Both 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.

[0036] The facility is equipped with a multi-functional overflow device, consisting of a vertical shaft 10 and a removable grating cover 11, with a safety clearance of 5-10cm between the top and the facility's roof. Both outlets of the drainage system are connected to this overflow device, ultimately converging into the municipal drainage network.

[0037] The infiltration control layer is equipped with a hydraulic linkage control system 9, which realizes intelligent opening and closing of the top drain outlet through a sensor. The opening and closing of the valve 91 is controlled by the water level sensed by the sensor 92.

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

[0039]

[0040] In the formula: The comprehensive runoff coefficient of the catchment area is given by F, where F is the service area of ​​the facility, and t is the total runoff volume. p The design water accumulation time is given by P, the design return period (ranging from 5 to 30 years), A is the infiltration area of ​​the facility, t is the rainfall duration, and K is the design return period. u The overall permeability of the protective layer and the seepage layer.

[0041] The overflow device's discharge capacity must meet the following requirements:

[0042]

[0043] Where: n k The number of openings in the width direction of the overflow well, where l is the length of the grate opening, and b is the number of openings in the overflow well. kWhere is the grate width, C is the orifice coefficient, g is the gravitational acceleration, h is the water depth above the wellhead, and K is the grate width. w K is the blocking coefficient. b The overall penetration rate of the facility is represented by P, which is the maximum return period, ranging from 30 to 100 years.

[0044] Operating mechanism:

[0045] Under normal rainfall conditions (P = 1-5 years): The top drainage system remains closed, and the runoff is purified through infiltration at 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 starting level, the sensor device will activate the top drainage outlet to form a rapid drainage channel from the infiltration control layer to the overflow device, shortening the runoff migration path.

[0047] Extreme rainfall conditions (P>30 years): When floodwater overflows the top cover of the overflow device, it forms a direct discharge channel for surface runoff, ensuring the system's flood control safety. This design achieves a functional balance between infiltration purification and flood discharge and hazard mitigation.

[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 a gravel matrix of 90% sand + 10% δ-MnO2 loaded; the flooding layer is filled with a gravel matrix of 80% sand + 20% δ-MnO2 loaded; the transition layer is composed of homogeneous quartz sand (4mm to 8mm) to prevent the filter media from entering the drainage layer; and the drainage layer matrix is ​​made of pebbles with a particle size of 1cm to 2cm.

[0049] This invention features three water discharge methods: top drainage pipe discharge, bottom drainage discharge, and overflow discharge. These methods automatically adjust the water discharge path of the biological tributary facility according to changes in rainwater flow. During light to moderate rain, rainwater runoff carries a large amount of pollutants into the facility as it washes away surface sediment. Within the facility, the abundant Mn valence states (+2, +3, and +4) in δ-MnO2 can form a manganese redox cycle, simultaneously promoting the growth of NH4+ in the rainwater. + Oxidation and NO3 -The reduction process is enhanced, and the abundance of active microorganisms on the matrix surface is increased to achieve efficient transfer of extracellular electrons. Mn(II) in δ-MnO2 is used to simultaneously 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. Mn(II) is used to form biogenic manganese oxides (BMOs) under aerobic conditions in the seepage layer and the action of manganese-oxidizing bacteria. Manganese is often present as highly active Mn(III), which enhances the effective degradation of 6PPD-Q. At the same time, Mn(IV) generated by the disproportionation reaction of Mn(III) participates in the manganese redox cycle, ensuring the cyclic supply of manganese in the system. When dealing with rainstorms, the effect of the facility matrix on reducing dissolved oxygen in rainwater runoff is very limited. At this time, the concentration of pollutants in rainwater runoff is relatively low. After the rainwater is treated by the filter layer to remove particulate pollutants, dissolved organic matter and ammonia nitrogen, it flows into the overflow well. When dealing with extreme rainfall conditions, the rainwater runoff flows directly into the overflow well after simple screening of large particulate pollutants by the manhole cover grid. By adjusting the opening of the top back drain pipe to control the water level and the height of the overflow well, the facility can adapt to different rainfall conditions, thereby effectively protecting the flooded layer of the facility, enabling the facility to effectively remove nitrogen and phosphorus, and having a longer service life.

[0050] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A bioretention device for removing novel and conventional pollutants from rainwater runoff, characterized in that, The device includes a pool body; The pool is vertically constructed with six functional layers, which, from top to bottom, are an overflow layer, a protective layer, an infiltration layer, a flooding layer, a transition layer, and a drainage layer. The seepage layer is equipped with a top drainage system, and the drainage layer is equipped with a bottom drainage system. Both drainage systems adopt a porous pipe structure. The elevation of the bottom drainage pipe outlet is flush with the top surface of the saturated water-holding layer. The device is equipped with a multi-functional overflow device, which consists of a vertical shaft structure and a detachable grid cover plate, and the top is kept at a safe height from the top plate of the facility. Both outlets of the drainage system are connected to the multi-functional overflow device, and the water eventually flows into the municipal drainage network. The device also includes a permeation control layer, which is equipped with a hydraulic linkage control system that enables intelligent opening and closing of the top drain outlet through a sensor. The seepage layer is filled with a gravel matrix consisting of 90% sand and 10% δ-MnO2 loaded. The flooding layer is filled with a gravel matrix consisting of 80% sand and 20% δ-MnO2 loaded. The valence state of Mn in δ-MnO2 can form a manganese redox cycle, ensuring the cyclic supply of manganese in the system.

2. The apparatus as claimed in claim 1, characterized in that, The starting water level H of the top drainage system is determined by the following formula: In the formula: The comprehensive runoff coefficient of the catchment area. For the area served by the facilities, To design the water accumulation time, The design return period is defined as a value ranging from 5 to 30 years. For the area of ​​facility penetration, For the duration of rainfall, The overall permeability of the protective layer and the seepage layer.

3. The apparatus as described in claim 2, characterized in that, The discharge capacity of the multi-functional overflow device must meet the following requirements: In the formula: Number of openings in the width direction of the overflow well The length of the grate hole. The width of the grate opening. The orifice coefficient, It is the acceleration due to gravity. The water depth above the wellhead is [missing information]. The blocking coefficient is... For the overall penetration rate of facilities, The maximum return period is 30 to 100 years.

4. The apparatus as described in claim 3, characterized in that, For normal rainfall conditions, P=1-5 years: the top drainage system remains closed, and the runoff is purified through infiltration at each functional layer before being introduced into the multifunctional overflow device by the bottom drainage system; for heavy rainfall conditions, P=5-30 years: when the accumulated water reaches the starting level, the sensor device opens the top drainage port in conjunction with the system, forming a rapid drainage channel from the infiltration control layer to the multifunctional overflow device, shortening the runoff migration path; for extreme rainstorm conditions, P>30 years: when the accumulated water overflows the top cover of the multifunctional overflow device, a direct surface runoff channel is formed, ensuring the system's flood control safety; this design achieves a functional balance between infiltration purification and flood discharge and hazard mitigation.

5. The apparatus as claimed in claim 1, characterized in that, The protective layer matrix is ​​made of pebbles with a particle size of 1cm to 3cm.

6. The apparatus as claimed in claim 1, characterized in that, The transition layer is composed of homogeneous quartz sand of 4mm to 8mm to prevent the filter media from entering the drainage layer.

7. The apparatus as claimed in claim 1, characterized in that, The drainage layer substrate is made of 1cm to 2cm pebbles.

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