Rainwater biological retention device with denitrification function

Abstract

The application discloses a rainwater biological retention equipment with a denitrification function, which comprises an equipment main body, wherein an ultrahigh layer, a water storage layer, a soil layer, a sand filter layer and an underground drainage layer are sequentially arranged in the equipment main body from top to bottom, an underground drainage pipe and a raised drainage pipe are arranged at the bottom of the underground drainage layer and used for drainage, the water outlet of the raised drainage pipe is raised to be higher than the sand filter layer, a microbial electrochemical respirator is further arranged in the equipment main body and comprises carbon felt and a plurality of conductive bodies, the carbon felt is arranged in the sand filter layer, the plurality of conductive bodies vertically extend from the sand filter layer to the ultrahigh layer, the lower end of the conductive bodies abuts against the carbon felt, and the upper end of the conductive bodies is exposed above the ultrahigh layer so as to be capable of contacting air and rainwater.

Description

Technical Field

[0001] This invention relates to the field of sponge city construction and low impact development facilities, and particularly to a rainwater bioretention device with denitrification function. Background Technology

[0002] Rainwater runoff carries pollutants from roads into surrounding water bodies during rainfall, causing non-point source pollution and becoming a significant factor in eutrophication. Because non-point source pollution is difficult to control and has a substantial impact on the aquatic environment, effective measures are needed to treat pollutants and reduce serious consequences. Rainwater runoff typically contains high concentrations of nitrogenous pollutants, with nitrate nitrogen being particularly challenging to remove due to its difficulty in being adsorbed by soil and other media.

[0003] Currently, low-impact development technologies such as bioretention facilities are widely used in stormwater management. Traditional bioretention facilities mainly rely on physical processes such as filtration and sedimentation to reliably remove particulate pollutants from runoff. However, due to limitations in the selection of packing materials and structural design, the removal efficiency for dissolved pollutants (such as ammonia nitrogen and nitrate nitrogen) in runoff is not ideal. To improve the treatment capacity of bioretention facilities for nitrogenous pollutants, research typically focuses on optimizing the facility structure and improving the characteristics of the packing materials to enhance removal efficiency.

[0004] One way to optimize the structure is to raise the position of the outlet pipe, creating a flooded zone. This flooded zone provides an anaerobic environment for denitrifying bacteria, helping to extend hydraulic retention time, mitigate peak flow, and improve the removal of nitrogenous pollutants. However, this design may fail under heavy rain conditions because rainwater may carry large amounts of dissolved oxygen into the flooded zone, disrupting the anaerobic environment and causing fluctuations in denitrification efficiency.

[0005] Methods to improve filter media include adding functional materials to the facility, such as enhancing the adsorption of nitrogenous pollutants by incorporating highly adsorbent materials like biochar and zeolite, improving the adsorption performance of the filter media using modification techniques, adding porous materials (such as ceramsite) to provide an attachment substrate for microorganisms, or optimizing the filtration gradation with materials like coarse sand and volcanic rock to improve permeability. Furthermore, the chemical action of iron-based and aluminum-based materials is also used to promote the precipitation and chemisorption of pollutants. However, these methods may suffer from problems such as filter media loss, high costs, unstable removal efficiency, and clogging. Summary of the Invention

[0006] In view of this, in order to solve the problem of poor removal efficiency of nitrogen-containing pollutants in existing bioretention facilities, this invention proposes a rainwater bioretention device with denitrification function based on the principle of microbial electrochemical respirator, so as to achieve stable removal of nitrogen-containing pollutants.

[0007] To achieve the above objectives, the present invention proposes the following technical solution:

[0008] A rainwater bioretention device with denitrification function includes a main body. Within the main body, from top to bottom, are arranged an ultra-high-rise structure, a water storage layer, a soil layer, a sand filter layer, and an underground drainage layer. The bottom of the underground drainage layer is equipped with an underground drainage pipe and a raised drainage pipe for drainage. The outlet of the raised drainage pipe is raised above the sand filter layer. The main body also includes a microbial electrochemical respirator comprising a carbon felt and several conductors. The carbon felt is disposed within the sand filter layer, and the conductors extend vertically from the sand filter layer to the ultra-high-rise structure, with their lower ends abutting against the carbon felt and their upper ends exposed above the ultra-high-rise structure to allow contact with air and rainwater.

[0009] Furthermore, the plurality of conductors includes a plurality of columnar conductors.

[0010] Furthermore, the plurality of conductors are uniformly arranged on the carbon felt.

[0011] Furthermore, the specific surface area of ​​the columnar conductor is between 0.05 and 35 cm². 2 / cm 3 .

[0012] Furthermore, the filler material in the soil layer contains biochar.

[0013] Furthermore, the sand filter layer uses silica sand with a gradation of 0.5–1.0 mm.

[0014] Furthermore, the underground drainage layer uses washed gravel with a gradation of 20-30mm.

[0015] The beneficial effects of the technical solution of this invention are reflected in the following: This invention uses common conductive materials (graphite rods, iron rods, biochar, coke, etc.) to construct a microbial electrochemical respirator, and applies the microbial electrochemical respirator to rainwater bioretention equipment for the first time. Through the carbon felt and the conductor, electrons generated during the decomposition of organic matter by microorganisms at the bottom are received and transferred to the upper aerobic environment through the conductor. Oxygen in the air and nitrate nitrogen in the rainwater receive electrons. During this process, a potential difference is formed in the vertical direction of the conductor. Different pollutants require different redox potentials to decompose, so different pollutants can react at different longitudinal positions of the conductor. This allows the rainwater bioretention equipment of this invention to efficiently and stably remove nitrate nitrogen and other pollutants from rainwater.

[0016] In a further technical solution of the present invention, biochar material, which is abundant, inexpensive and readily available, is used and uniformly mixed into the soil medium, which can achieve the dual goals of solid waste resource utilization and stable removal of nitrogen-containing pollutants in rainwater retention facilities.

[0017] In a further technical solution of the present invention, the present invention simultaneously employs a microbial electrochemical respirator and biochar material. Biochar can be stacked as a conductive material to construct the microbial electrochemical respirator, and can also be used as a mixed matrix to improve the lateral electron transfer capability of the system and improve the nitrate nitrogen removal effect of the microbial electrochemical respirator. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of a rainwater bioretention device based on a microbial electrochemical respirator provided in an embodiment of the present invention.

[0019] Figure 2 This is a diagram showing the positional relationship between the graphite rod and the carbon felt in the device of Embodiment 1 of the present invention.

[0020] Figure 3 This is a structural diagram of the control group device in Embodiment 2 of the present invention.

[0021] Figure 4 The graph shows the removal effect of ammonia nitrogen in the experimental group and the control group in Example 2 of this invention.

[0022] Figure 5 The diagram shows the removal effect of nitrate nitrogen in the experimental group and the control group of Example 2 of the present invention.

[0023] Figure 6 The graph shows the total nitrogen removal effect of the experimental group and the control group in Example 2 of this invention.

[0024] Figure 7 The diagram shows the COD removal effect of the experimental group and the control group in Example 2 of this invention. Detailed Implementation

[0025] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be noted that the embodiments provided are for illustrative purposes only and are not intended to impose any limitations.

[0026] Microbial electrochemical respirators are bioelectrochemical systems that transfer electrons generated by microorganisms to a final electron acceptor via conductive materials. Some studies have explored the application of microbial electrochemical respirators in constructed wetlands, leading to the concept of METlands. METlands are wastewater treatment systems that combine microbial electrochemical technology with constructed wetlands. This method replaces gravel with conductive granular materials, enhancing electron transport efficiency and thereby improving the oxidative metabolic capacity of electroactive microorganisms, thus increasing pollutant removal efficiency. Furthermore, studies have found that microbial electrochemical respirators can transfer electrons from sediments to overlying water, effectively removing nitrate nitrogen. However, there are currently no studies applying microbial electrochemical respirators to bioretention facilities to treat nitrogenous pollutants in stormwater runoff.

[0027] This invention addresses the problem of poor removal efficiency of nitrogen-containing pollutants, especially nitrate nitrogen, in bioretention facilities. Based on the principle of microbial electrochemical respirators, it proposes a rainwater bioretention device with denitrification function to achieve stable and effective removal of nitrogen-containing pollutants.

[0028] refer to Figure 1 The rainwater bioretention device with denitrification function based on a microbial electrochemical respirator proposed in this embodiment of the invention includes: a cylindrical device body, in which a super high layer 1, a water storage layer 2, a soil layer 3, a sand filter layer 4, and an underground drainage layer 5 are arranged sequentially from top to bottom. The bottom of the underground drainage layer 5 is provided with an underground drainage pipe 7 and a raised drainage pipe 6 for drainage. The outlet of the raised drainage pipe 6 is raised above the sand filter layer 4 and located between the sand filter layer 4 and the soil layer 3. The device body is also provided with a microbial electrochemical respirator, which includes a carbon felt 9 and several conductors 8. The carbon felt 9 is disposed in the sand filter layer 4. The several conductors 8 extend vertically from the sand filter layer 4 to the super high layer 1. The lower end of the conductors 8 abuts against the carbon felt 9, and the upper end of the conductors 8 is exposed above the super high layer 1 to be able to contact air and rainwater.

[0029] In the above embodiments of the present invention, a microbial electrochemical respirator is constructed in a rainwater bioretention device using a conductor 8 and a carbon felt 9. The conductor 8 and the carbon felt 9 receive electrons generated during the decomposition of organic matter by microorganisms in the sand filter layer 4. These electrons are then transferred through the conductor 8 to the aerobic environment above the super high-rise building 1, where oxygen in the air and nitrate nitrogen in the accumulated water (rainwater) receive electrons. During this process, a potential difference is formed in the vertical direction (e.g., the axial direction of a columnar conductor) of the conductor. Different pollutants require different redox potentials for decomposition, thus allowing different pollutants to react at different longitudinal positions of the conductor. This enables the rainwater bioretention device of the present invention to efficiently and stably remove nitrate nitrogen and other pollutants from rainwater.

[0030] In some preferred embodiments, the number of conductors 8 is multiple (e.g., more than two), but there can also be only one; the present invention does not limit this. Conductors 8 can be made of common conductive materials, such as graphite, biochar, coke, iron, and other highly conductive materials. Conductors 8 can be columnar conductors, such as carbon rods, columnar biochar, graphite rods, iron rods, etc.; they can be cylindrical, prismatic, etc. The present invention does not limit the specific shape, as long as they are vertically arranged within the device to perform the aforementioned electron transfer function. The carbon felt 9 can be circular or square; the present invention does not limit this, its purpose being to increase the contact area with microorganisms.

[0031] Furthermore, in order to maximize the contact area between the conductor and microorganisms in the surrounding environment and increase the range of electron reception, the columnar conductor used in the preferred embodiment of the present invention has a specific surface area of ​​0.05 to 35 cm². 2 / cm 3 .

[0032] Example 1:

[0033] like Figure 1 As shown, the rainwater bioretention device in this embodiment is a cylindrical device with a diameter of 15cm and a height of 100cm. Its interior, from top to bottom, consists of a super-high layer 1, a water storage layer 2, a soil layer 3, a sand filter layer 4, and an underground drainage layer 5. It also includes a raised drainage pipe 6 and an underground drainage pipe 7. The raised drainage pipe 6 extends from the underground drainage layer 5, with its outlet located between the soil layer 3 and the sand filter layer 4. The center of the outlet is 30cm from the bottom of the device, and the pipe diameter is 2cm. The underground drainage pipe 7 is located at the very bottom of the underground drainage layer 5, with a pipe diameter of 2cm. The total height of the super-high layer 1 and the water storage layer 2 is 20cm.

[0034] The filler material in soil layer 3 is a mixture of biochar and soil. The biochar is rice husk biochar made by heating at a rate of 10℃ / min to 500℃ in a vacuum atmosphere. The soil is sandy soil. The two are mixed evenly at a mass ratio of 4:96. The height of soil layer 3 is 50cm.

[0035] The filter media for layer 4 is made of silica sand with a gradation of 0.5-1.0mm and a height of 20cm.

[0036] The underground drainage layer 5 is filled with washed gravel with a gradation of 20-30cm and a height of 10cm.

[0037] The microbial electrochemical respirator comprises a columnar conductive material 8 and a circular carbon felt 9. The columnar conductive material 8 consists of five graphite rods, each 6 mm in diameter and 80 cm in height, connected to the circular carbon felt 9, each 10 cm in diameter and 3 mm thick. The five graphite rods are evenly distributed on the carbon felt, as shown in the diagram. Figure 2 As shown. The circular carbon felt 9 is located in the sand filter layer, 20cm from the bottom of the device. The graphite rod passes through the sand filter layer 4, the soil layer 3, the water storage layer 2, and the super high layer 1, with its top in contact with the air and accumulated water.

[0038] Example 2:

[0039] Using the present invention and such Figure 3The conventional rainwater bioretention device (control group) shown is used to treat a simulated rainfall runoff event. Artificial rainwater was used, prepared from conventional water quality pollutants and tap water. The simulated rainwater pollutant concentrations were: COD (300 mg / L), TN (11.5 mg / L) (including NH4+)... + -N (5.5 mg / L), NO3 - -N (6 mg / L) and TP (0.5 mg / L) were used in a simulated drought experiment with a drought period of 5 days and an influent flow rate of 3.2 L. NH4+ in the influent and effluent was measured in each experiment. + -N、NO 3- Concentrations of -N, TN, and COD.

[0040] Figure 4 In terms of ammonia nitrogen removal, the experimental group showed significantly better removal performance than the control group, with a removal rate between 90% and 100%.

[0041] Figure 5 In terms of nitrate removal, the experimental group showed a significantly better removal rate than the control group, with the removal rate ranging from 90% to 100% in the later stages, while the removal effect of the control group was unstable.

[0042] Figure 6 In terms of TN removal, the experimental group showed more stable removal performance and a higher removal rate than the control group.

[0043] Figure 7 In terms of COD removal, the experimental group showed significantly better removal performance than the control group, with a removal rate between 95% and 100% except for the first few experiments.

[0044] Through experimental simulation, the removal effect of the experimental group of this invention was better than that of the control group, and gradually tended to stabilize.

[0045] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, several equivalent substitutions or obvious modifications can be made without departing from the concept of the present invention, and all such modifications, achieving the same performance or purpose, should be considered within the scope of protection of the present invention.

Claims

1. A rainwater biological retention device with denitrification function, characterized in that: The device includes a main body containing, from top to bottom, an ultra-high-rise building, a water storage layer, a soil layer, a sand filter layer, and an underground drainage layer. The bottom of the underground drainage layer is equipped with an underground drainage pipe and a raised drainage pipe for drainage. The outlet of the raised drainage pipe is raised above the sand filter layer. The main body also includes a microbial electrochemical respirator, comprising a carbon felt and several conductors. The carbon felt is disposed within the sand filter layer, and the conductors extend vertically from the sand filter layer to the ultra-high-rise building, with their lower ends abutting the carbon felt and their upper ends exposed above the ultra-high-rise building to allow contact with air and rainwater. The conductor and the carbon felt are used to receive electrons generated during the decomposition of organic matter by microorganisms in the sand filter layer, and to transfer the electrons to the aerobic environment above the super high-rise building through the conductor, so that oxygen in the air and nitrate nitrogen in the water can obtain electrons; and in this process, the conductor forms a potential difference in the vertical direction, so that different pollutants can react at different longitudinal positions of the conductor.

2. The rainwater biological retention device as described in claim 1, characterized in that: The plurality of conductors include multiple columnar conductors.

3. The rainwater biological retention device as described in claim 1 or 2, characterized in that: The conductors are evenly arranged on the carbon felt.

4. The rainwater biological retention device as described in claim 2, characterized in that: The specific surface area of ​​the columnar conductor is between 0.05 and 35 cm². 2 / cm 3 .

5. The rainwater biological retention device as described in claim 1, characterized in that: The filler material in the soil layer contains biochar.

6. The rainwater biological retention device as described in claim 1, characterized in that: The sand filter layer uses silica sand with a gradation of 0.5~1.0mm.

7. The rainwater biological retention device as described in claim 1, characterized in that: The underground drainage layer uses washed gravel with a gradation of 20-30mm.

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