Rainwater bioretention equipment with denitrification function

Abstract

The rainwater bioretention equipment with the denitrification function comprises an equipment body, a super high-rise layer, a water storage layer, a soil layer, a sand filter layer and an underground drainage layer are sequentially arranged in the equipment body from top to bottom, and an underground drainage pipe and a lifting drainage pipe are arranged at the bottom of the underground drainage layer and used for drainage. A water outlet of the lifting drainage pipe is lifted to be higher than the sand filtering layer; a microbial electrochemical respirator is further arranged in the equipment body and comprises a carbon felt and a plurality of electric conductors, the carbon felt is arranged in the sand filtering layer, the electric conductors vertically extend to the super high-rise building from the sand filtering layer, the lower ends of the electric conductors abut against the carbon felt, and the upper ends of the electric conductors are exposed out of the super high-rise building so that the electric conductors can make contact with air and rainwater.

Description

Technical Field

[0001] The present invention relates to the field of sponge city construction and low-impact development facilities, and in particular to a rainwater biological retention device with a denitrification function. Background Art

[0002] During rainfall, rainwater runoff will carry pollutants on the road and spread to surrounding water bodies, causing non-point source pollution, thus becoming one of the important factors causing eutrophication of water bodies. Since non-point source pollution is difficult to control and has a great impact on the water environment, effective measures need to be taken to control pollutants to reduce the occurrence of serious consequences. Rainwater runoff usually contains high concentrations of nitrogen-containing pollutants, among which nitrate nitrogen is difficult to be adsorbed by soil and other media, making the removal of nitrate nitrogen a major challenge in the control of non-point source pollution.

[0003] Currently, low-impact development technologies such as bioretention facilities have been widely used in stormwater management. Traditional bioretention facilities mainly rely on physical processes such as filtration and sedimentation to stably remove particulate pollutants in runoff. However, due to the single selection of fillers and limitations in structural design, the removal effect of dissolved pollutants in runoff (such as ammonia nitrogen and nitrate nitrogen) is not ideal. In order to improve the treatment capacity of bioretention facilities for nitrogen-containing pollutants, research usually improves removal efficiency by optimizing facility structure and improving filler characteristics.

[0004] One way to optimize the structure is to raise the outlet pipe to form a flooded area. The flooded area can provide an anoxic environment for denitrifying bacteria, which helps to extend the hydraulic retention time, alleviate the peak flow and improve the removal of nitrogen-containing pollutants. However, this design may fail in heavy rain conditions because rainwater may carry a large amount of dissolved oxygen into the flooded area, destroying the anoxic environment and causing fluctuations in the denitrification effect.

[0005] Methods for improving fillers include adding functional materials to the facility, such as adding highly adsorbent materials such as biochar and zeolite to enhance the adsorption of nitrogen-containing pollutants, using modification technology to improve the adsorption performance of fillers, adding porous structural materials (such as ceramsite) to provide a base for microorganisms to attach, or using coarse sand, volcanic rock, etc. to optimize the gradation of the filter layer to improve permeability. In addition, the chemical action of iron-based and aluminum-based materials is also used to promote the precipitation and chemical adsorption of pollutants. However, these methods may have problems such as filler loss, high cost, unstable removal effect, 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 biological retention facilities, the present invention proposes a rainwater biological retention equipment with denitrification function based on the principle of microbial electrochemical respirator to achieve stable removal of nitrogen-containing pollutants.

[0007] To achieve the above object, the present invention proposes the following technical solutions:

[0008] A rainwater biological retention device with a denitrification function comprises an equipment body, wherein a super high layer, a water storage layer, a soil layer, a sand filter layer, and an underground drainage layer are sequentially arranged in the equipment body from top to bottom, and an underground drainage pipe and an elevated drainage pipe are arranged at the bottom of the underground drainage layer for drainage, wherein the outlet of the elevated drainage pipe is elevated to be higher than the sand filter layer; a microbial electrochemical respirator is also arranged in the equipment body, comprising carbon felt and a plurality of conductors, wherein the carbon felt is arranged in the sand filter layer, and the plurality of conductors extend vertically from the sand filter layer to the super high layer, and the lower ends thereof abut against the carbon felt, and the upper ends thereof are exposed above the super high layer so as to be able to contact air and rainwater.

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

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

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

[0012] Furthermore, the filler 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 to 30 mm.

[0015] The beneficial effects of the technical solution of the present invention are embodied in the following aspects: the present invention adopts common conductive materials (graphite rods, iron rods, biochar, coke, etc.) to construct a microbial electrochemical respirator, and applies the microbial electrochemical respirator to a rainwater biological retention device for the first time. The electrons generated by the bottom microorganisms in the process of decomposing organic matter are received through carbon felt and conductors, and the electrons are transferred to the upper aerobic environment through the conductor. The oxygen in the air / nitric nitrogen in the accumulated water (rainwater) obtains the electrons. In this process, an electric potential difference is formed in the vertical direction of the conductor. Different pollutants have different redox potentials required for decomposition. Therefore, different pollutants can react at different longitudinal positions of the conductor, so that the rainwater biological retention device of the present invention can efficiently and stably remove nitrate nitrogen and other pollutants in rainwater.

[0016] In a further technical solution of the present invention, biochar materials, which are abundant, cheap and easily available, are used and evenly mixed into the soil medium, so as to 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 adopts a microbial electrochemical respirator and biochar materials. Biochar can be stacked as a conductive material to construct a microbial electrochemical respirator, and can also be used as a mixed matrix to improve the lateral electron transfer capacity of the system, thereby improving the nitrate nitrogen removal effect of the microbial electrochemical respirator. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It 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 positional relationship diagram of the graphite rod and the carbon felt in the device of Example 1 of the present invention.

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

[0021] Figure 4 This is a diagram showing the removal effect of ammonia nitrogen by the experimental group and the control group in Example 2 of the present invention.

[0022] Figure 5 This is a diagram showing the removal effect of nitric nitrogen by the experimental group and the control group in Example 2 of the present invention.

[0023] Figure 6 This is a diagram showing the removal effect of total nitrogen by the experimental group and the control group in Example 2 of the present invention.

[0024] Figure 7 This is a diagram showing the COD removal effects of the experimental group and the control group in Example 2 of the present invention. DETAILED DESCRIPTION

[0025] The present invention will be further described below in conjunction with the accompanying drawings and specific implementation methods and examples. It should be noted that the purpose of providing the examples is only to illustrate and not to impose any limitation.

[0026] Microbial electrochemical respirator is a bioelectrochemical system that transfers electrons produced by microorganisms to the final electron acceptor through conductive materials. Some studies have attempted to apply microbial electrochemical respirators to artificial wetlands and proposed the concept of METlands. METlands is a wastewater treatment system that combines microbial electrochemical technology with artificial wetlands. This method replaces gravel with conductive granular materials to enhance the efficiency of electron transfer, thereby improving the oxidative metabolism of electroactive microorganisms and improving pollutant removal. In addition, the study also found that microbial electrochemical respirators can transfer electrons from sediments to overlying water bodies, thereby effectively removing nitrate nitrogen. However, there is currently no research on the application of microbial electrochemical respirators to bioretention facilities to treat nitrogen-containing pollutants in stormwater runoff.

[0027] The embodiment of the present invention aims to solve the problem of poor removal efficiency of nitrogen-containing pollutants, especially nitrate nitrogen, in biological retention facilities, and proposes a rainwater biological retention equipment with denitrification function based on the principle of microbial electrochemical respirator to achieve stable and effective removal of nitrogen-containing pollutants.

[0028] refer to Figure 1 The rainwater biological retention equipment with denitrification function based on the microbial electrochemical respirator proposed in the embodiment of the present invention comprises: a cylindrical equipment 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 in sequence from top to bottom, and an underground drainage pipe 7 and a raised drainage pipe 6 are arranged at the bottom of the underground drainage layer 5 for drainage, wherein the outlet of the raised drainage pipe 6 is raised to be higher than the sand filter layer 4 and is located between the sand filter layer 4 and the soil layer 3; a microbial electrochemical respirator is also arranged in the equipment body, and the microbial electrochemical respirator comprises a carbon felt 9 and a plurality of conductors 8, wherein the carbon felt 9 is arranged in the sand filter layer 4, and the plurality of conductors 8 extend vertically from the sand filter layer 4 to the super high layer 1, the lower end of the conductor 8 abuts the carbon felt 9, and the upper end of the conductor 8 is exposed above the super high layer 1 so as to be able to contact the air and rainwater.

[0029] The above embodiment of the present invention uses the conductor 8 and the carbon felt 9 to construct a microbial electrochemical respirator in the rainwater bioretention device. The conductor 8 and the carbon felt 9 receive the electrons generated in the process of microbial decomposition of organic matter in the sand filter layer 4, and transfer the electrons to the aerobic environment above the super-high-rise 1 through the conductor 8, and the oxygen in the air / nitric nitrogen in the accumulated water (rainwater) obtains the electrons. In this process, the conductor will form a potential difference in the vertical direction (for example, the axial direction of the columnar conductor), and the redox potential required for the decomposition of different pollutants is different. Therefore, different pollutants can react at different longitudinal positions of the conductor, so that the rainwater bioretention device of the present invention can efficiently and stably remove nitrate nitrogen and other pollutants in rainwater.

[0030] In some preferred embodiments, the number of conductors 8 is multiple (for example, more than 2), of course, there can be only one, and the present invention is not limited to this. The conductor 8 can be made of common conductive materials, such as graphite, biochar, coke, iron and other highly conductive materials. The conductor 8 can be a columnar conductor, such as a carbon rod, columnar biochar, graphite rod, iron rod, etc.; it can be cylindrical, prismatic, etc. The present invention does not limit the specific shape, as long as it is vertically arranged in the equipment to play the aforementioned electron transfer role. The carbon felt 9 can be round or square, and the present invention is not limited to this. Its purpose is to increase the contact area with the microorganisms.

[0031] In addition, in order to maximize the contact area between the conductor and the microorganisms in the surrounding environment and increase the range of receiving electrons, the specific surface area of ​​the columnar conductor used in the preferred embodiment of the present invention is 0.05 to 35 cm 2 / cm 3 .

[0032] Embodiment 1:

[0033] like Figure 1 As shown, the rainwater bioretention device of this embodiment is a cylindrical device with a diameter of 15 cm and a height of 100 cm. From top to bottom, the interior thereof includes 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, and also includes an elevated drainage pipe 6 and an underground drainage pipe 7. The elevated drainage pipe 6 is led out from the underground drainage layer 5, and the drainage port is located between the soil layer 3 and the sand filter layer 4. The center of the drainage port is 30 cm away from the bottom of the device, and the pipe diameter is 2 cm; the underground drainage pipe 7 is located in the underground drainage layer 5, at the bottom of the device, and the pipe diameter is 2 cm. The total height of the super high layer 1 and the water storage layer 2 is 20 cm.

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

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

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

[0037] The microbial electrochemical respirator includes a columnar conductive material 8 and a circular carbon felt 9. The columnar conductive material 8 includes a total of 5 graphite rods with a diameter of 6 mm and a height of 80 cm. The graphite rods are connected to a circular carbon felt 9 with a diameter of 10 cm and a thickness of 3 mm. The 5 graphite rods are evenly distributed on the carbon felt. The distribution of the graphite rods on the carbon felt is shown in FIG. Figure 2 The circular carbon felt 9 is located in the sand filter layer, 20 cm from the bottom of the device, and 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, and the top is in contact with the air and the accumulated water.

[0038] Embodiment 2:

[0039] Using the present invention and Figure 3 The conventional rainwater bioretention device (control group) shown in the figure treats simulated rainfall runoff events. Artificial simulated rainwater is used, and the simulated rainwater is composed of conventional water pollution indicators and tap water. The simulated rainwater pollutant concentrations are: COD (300 mg / L), TN (11.5 mg / L) (NH4 + -N(5.5mg / L), NO 3 - -N (6 mg / L), TP (0.5 mg / L), the simulated experimental drought period was 5 days, the water volume was 3.2 L, and the NH 4 + -N, NO 3- -N, TN, COD concentrations.

[0040] Figure 4 In terms of ammonia nitrogen removal, the removal effect of the experimental group was significantly better than that of the control group, and the removal rate of the experimental group was between 90-100%.

[0041] Figure 5 In terms of nitrate nitrogen removal, the removal rate of the experimental group was significantly better than that of the control group. In the later period, the removal rate was between 90-100%, while the removal effect of the control group was unstable.

[0042] Figure 6 In terms of TN removal, the removal effect of the experimental group was relatively stable, and the removal rate was better than that of the experimental group.

[0043] Figure 7 In terms of COD removal, the experimental group had significantly better removal effects than the control group, and except for the first few experiments, the removal rates were between 95-100%.

[0044] Through experimental simulation, the removal effect of the experimental group of the present invention is better than that of the control group, and gradually tends to be stable.

[0045] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art of the present invention, several equivalent substitutions or obvious variations can be made without departing from the concept of the present invention, and the performance or use is the same, which should be regarded as belonging to the protection scope of the present invention.

Claims

1. A rainwater biological retention device with denitrification function, characterized in that: The device body comprises an equipment body, in which a super-high layer, a water storage layer, a soil layer, a sand filter layer and an underground drainage layer are arranged in sequence from top to bottom, and an underground drainage pipe and a raised drainage pipe are arranged at the bottom of the underground drainage layer for drainage, wherein the water outlet of the raised drainage pipe is raised to be higher than the sand filter layer; the device body is also provided with a microbial electrochemical respirator, comprising a carbon felt and a plurality of conductors, wherein the carbon felt is arranged in the sand filter layer, and the plurality of conductors extend vertically from the sand filter layer to the super-high layer, with the lower end abutting against the carbon felt and the upper end exposed above the super-high layer so as to be able to contact the air and rainwater.

2. The rainwater bioretention device according to claim 1, characterized in that: The plurality of electrical conductors include a plurality of columnar conductors.

3. The rainwater bioretention device according to claim 1 or 2, characterized in that: The plurality of conductors are evenly arranged on the carbon felt.

4. The rainwater bioretention device according to claim 2, characterized in that: The specific surface area of ​​the columnar conductor is between 0.05 and 35 cm 2 / cm 3 .

5. The rainwater bioretention device according to any one of claims 1 to 4, characterized in that: The filler of the soil layer comprises biochar.

6. The rainwater bioretention device according to any one of claims 1 to 4, characterized in that: The sand filter layer uses silica sand with a gradation of 0.5-1.0 mm.

7. The rainwater bioretention device according to any one of claims 1 to 4, characterized in that: The underground drainage layer uses washed gravel with a gradation of 20 to 30 mm.

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