An energy self-sufficient domestic sewage treatment system with deep nitrogen and phosphorus removal

Abstract

The invention discloses an energy-self-sufficient domestic sewage treatment system with deep denitrification and phosphorus removal, wherein a grid, a sedimentation tank, a nitrogen biofilter and a phosphorus biofilter are sequentially connected along the sewage flow direction, the upper part of the sedimentation tank is connected to the inlet of the nitrogen biofilter through a first sewage pump, the bottom of the sedimentation tank is connected to an electrochemical reaction tank through a second sewage pump, and the outlet of the electrochemical reaction tank is connected to the inlet of the phosphorus biofilter; the outlet of the nitrogen biofilter is connected to a first circulating water pump, and the outlet of the first circulating water pump is respectively connected to the inlet of the nitrogen biofilter and the phosphorus biofilter; the outlet of the phosphorus biofilter is connected to a second circulating water pump, and the outlet of the second circulating water pump serves as a sewage discharge outlet and is respectively connected to the inlet of the nitrogen biofilter and the phosphorus biofilter; the sewage treatment system also includes a photovoltaic power supply, which provides electrical energy for all equipment of the sewage treatment system; the system can achieve the advantages of energy self-sufficiency, high denitrification and phosphorus removal efficiency, simple operation and maintenance, and the like.

Description

Technical Field

[0001] The invention relates to the technical field of sewage treatment, in particular to an energy self-sufficient and deep nitrogen and phosphorus removal domestic sewage treatment system. Background Art

[0002] Sewage treatment is a high-energy consumption process, with electricity consumption of approximately 2.7 kWh per ton of water. The operation and maintenance costs are relatively high. How to improve the energy self-sufficiency rate of sewage treatment has been a hot topic in recent years.

[0003] The phosphorus removal effect of the biological filter is poor, and it is impossible to make the sewage meet the discharge standards. At the same time, in order to better remove nitrogen, the biological filter is generally equipped with an aeration system. The aeration process consumes a lot of electricity, making the power consumption of sewage treatment high. In addition, due to the large-scale growth of microorganisms, the biological filter often causes blockage, which requires regular sand cleaning, greatly increasing the difficulty of operation and maintenance.

[0004] Phosphorus removal from sewage is one of the most difficult links in the sewage treatment process. In order to save energy and improve phosphorus removal efficiency, a large amount of research has focused on anaerobic phosphorus removal technology in recent years. However, most of the current research is mainly stagnant in scientific experiments and has not yet been promoted and applied in actual projects. Summary of the invention

[0005] The purpose of the present invention is to provide a domestic sewage treatment system with energy self-sufficiency and deep denitrification and phosphorus removal, which can achieve the advantages of energy self-sufficiency, high denitrification and phosphorus removal efficiency, and simple operation and maintenance.

[0006] The technical solution adopted by the present invention to solve its technical problem is:

[0007] An energy self-sufficient domestic sewage treatment system with deep nitrogen and phosphorus removal, wherein a grid, a sedimentation tank, a nitrogen biofilter and a phosphorus biofilter are sequentially connected along the sewage flow direction, the upper part of the sedimentation tank is connected to the inlet of the nitrogen biofilter through a first sewage pump, the bottom of the sedimentation tank is connected to an electrochemical reaction tank through a second sewage pump, and the outlet of the electrochemical reaction tank is connected to the inlet of the phosphorus biofilter; a first flow control meter is provided between the second sewage pump and the electrochemical reaction tank;

[0008] The outlet of the nitrogen biofilter is connected to a first circulating water pump, and the outlets of the first circulating water pump are respectively connected to the inlets of the nitrogen biofilter and the phosphorus biofilter; a second flow control meter is provided between the first circulating water pump and the inlet of the nitrogen biofilter;

[0009] The outlet of the phosphorus biofilter is connected to a second circulating water pump, which serves as a sewage outlet and is connected to the inlets of the nitrogen biofilter and the phosphorus biofilter respectively; a third flow control meter is provided between the second circulating water pump and the inlet of the nitrogen biofilter;

[0010] The sewage treatment system also includes a photovoltaic power source, which provides electrical energy for all equipment in the sewage treatment system.

[0011] Furthermore, the nitrogen biological filter is provided with a first uniform water distributor, a nitrogen biological filter layer, a first supporting layer and a first water collection tank in sequence from top to bottom, the first uniform water distributor and the nitrogen biological filter layer are arranged at intervals, and a ventilation pipe connecting the water collection tank with the atmosphere is vertically penetrated in the nitrogen biological filter; an exhaust fan is provided outside the first water collection tank, and the exhaust fan is connected to the first water collection tank through an exhaust pipe, and a first liquid level controller and a second liquid level controller are provided inside the first water collection tank, and the first liquid level controller is connected to the exhaust fan to control the operation of the exhaust fan; the second liquid level controller is connected to the first circulating water pump to control the operation of the first circulating water pump, and adjusts the height of the first supporting layer and the water surface in the first water collection tank by 10-60 cm, and the sewage return ratio of the nitrogen biological filter is 100%-600%.

[0012] Furthermore, the phosphorus biological filter tank is provided with a phosphorus biological filter layer, a second supporting layer and a second water collection tank in sequence from top to bottom, a second uniform water distributor is buried on the upper part of the phosphorus biological filter layer, a positive electrode and a negative electrode are vertically buried in the phosphorus biological filter layer, and the positive and negative electrodes are respectively connected to a current controller; a third liquid level controller is provided inside the second water collection tank, the third liquid level controller is connected to the second circulating water pump, controls the operation of the second circulating water pump, and adjusts the height of the water surface in the second supporting layer and the second water collection tank, and the sewage return ratio of the phosphorus biological filter tank is 50%-500%.

[0013] Furthermore, the electrochemical reaction cell is provided with a cathode electrode, an anode electrode and a stirrer.

[0014] Furthermore, the distance between the first uniform water distributor and the top surface of the nitrogen biological filter layer is 5-50 cm.

[0015] Furthermore, the nitrogen biological filter layer includes more than two layers, and the filter diameter of the filter media in each filter layer decreases from top to bottom, the filter media thickness is 30-100cm, and the filter diameter is 10-100mm.

[0016] Furthermore, the number of the air-permeable tubes is more than two.

[0017] Furthermore, the phosphorus biological filter layer comprises more than one layer, and the filter diameter of the filter material in each filter layer decreases from top to bottom, the filter material thickness is 30-80cm, and the filter diameter is 30-120mm.

[0018] Furthermore, the second uniform water distributor is buried at a depth of 5-10 cm in the phosphorus biological filter layer.

[0019] Furthermore, the voltage of the cathode and anode electrodes is 0-400V; and the residence time of the sewage in the electrochemical reaction cell is 10-480min.

[0020] The beneficial effects of the present invention are:

[0021] 1. Photovoltaic power supplies provide electrical energy for all equipment in the sewage treatment system, making the sewage treatment system energy self-sufficient.

[0022] 2. After the larger suspended solids are removed from the sewage through the screen, it enters the sedimentation tank. The supernatant of the sedimentation tank enters the nitrogen biological filter. In the upper filter layer of the nitrogen biological filter, heterotrophic aerobic bacteria use DO to decompose organic matter, and nitrifying bacteria use DO to oxidize ammonia nitrogen into nitrate nitrogen. As DO in the sewage is consumed, anoxic areas will form in the lower filter layer. Denitrifying bacteria use organic matter in the anoxic area to further reduce nitrate nitrogen to nitrogen gas. Finally, the sewage achieves the effect of organic matter decomposition and denitrification.

[0023] 3. Maintain a certain height between the first water collection tank and the first supporting layer, and use the exhaust fan to speed up the air flow between the first water collection tank and the first supporting layer, so as to fully increase the DO in the sewage and provide sufficient DO for the nitrogen filter tank, eliminating the aeration system required for the general biological filter tank and greatly reducing the energy consumption of sewage treatment.

[0024] 4. The first circulating water pump pumps part of the sewage in the first water collection tank of the nitrogen biofilter to the second water distributor of the phosphorus biofilter, and the remaining sewage flows back to the first water distributor, achieving a deep denitrification effect, while reducing the sewage load of the nitrogen biofilter and effectively preventing the nitrogen biofilter layer from being blocked.

[0025] 5. The positive and negative electrodes in the phosphorus biofilter can promote the microorganisms in the phosphorus biofilter to use VFA for anaerobic phosphorus removal, reducing phosphate to phosphine gas, and achieving the effect of phosphorus removal from sewage; the metal cations produced in the electrochemical reaction cell undergo chemical flocculation in the phosphorus biofilter, further removing phosphorus from sewage;

[0026] 6. The second circulation pump returns part of the sewage in the phosphorus biofilter to the second water distributor to achieve deep phosphorus removal effect, while reducing the sewage load in the phosphorus biofilter and effectively preventing blockage of the phosphorus filter layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The present invention is further described below in conjunction with the accompanying drawings and embodiments:

[0028] Figure 1 is a system schematic diagram of the present invention;

[0029] Figure 2 It is a top view of the first uniform water distributor in the present invention. DETAILED DESCRIPTION

[0030] Example 1

[0031] The implementation case of the present invention was carried out using domestic sewage from a community in Hefei City. After the sewage was treated, it met the discharge standards. At the same time, all energy consumption was provided by photovoltaic power sources.

[0032] like Figure 1 As shown, the present invention provides an energy self-sufficient domestic sewage treatment system with deep nitrogen and phosphorus removal, wherein a grid 1, a sedimentation tank 2, a nitrogen biofilter 6 and a phosphorus biofilter 11 are sequentially connected along the sewage flow direction, the upper part of the sedimentation tank 2 is connected to the inlet of the nitrogen biofilter through a first sewage pump 4, the bottom of the sedimentation tank 2 is connected to an electrochemical reaction tank 7 through a second sewage pump 3, and the outlet of the electrochemical reaction tank 7 is connected to the inlet of the phosphorus biofilter 11; a first flow controller 5 is provided between the second sewage pump 3 and the electrochemical reaction tank.

[0033] The outlet of the nitrogen biofilter 6 is connected to a first circulating water pump 9, and the outlets of the first circulating water pump 9 are respectively connected to the inlets of the nitrogen biofilter and the phosphorus biofilter 11; a second flow control meter 10 is provided between the first circulating water pump 9 and the inlet of the nitrogen biofilter. Figure 2 As shown, the nitrogen biological filter is provided with a first uniform water distributor 6-2, a nitrogen biological filter layer 6-4, a first supporting layer 6-5 and a first water collection tank 6-7 from top to bottom, the first uniform water distributor 6-2 and the nitrogen biological filter layer are arranged at intervals, and the spacing between the first uniform water distributor and the top surface of the nitrogen biological filter layer is 5 cm. The nitrogen biological filter is vertically penetrated with a ventilation pipe 6-1 that connects the water collection tank with the atmosphere, and the number of ventilation pipes is 2; an exhaust fan 8 is provided outside the first water collection tank, and the exhaust fan 8 is connected to the first water collection tank through the exhaust pipe 6-6. A first liquid level controller 6-8 and a second liquid level controller 6-9 are provided inside the first water collection tank, and the second liquid level controller is connected to the first circulating water pump 9 to control the operation of the first circulating water pump and adjust the height of the water surface in the first supporting layer and the first water collection tank by 10 cm. The first liquid level controller 6-8 is connected to the exhaust fan 8 to control the operation of the exhaust fan 8. When the water surface in the water collection area rises to the exhaust pipe outlet, the exhaust fan 8 is automatically turned off.

[0034] The nitrogen biological filter layer 6-4 comprises two layers, and the filter diameter of the filter media in each filter layer decreases from top to bottom. The filter media in the nitrogen biological filter layer adopts conventional filter media such as quartz sand. The thickness of the upper filter media is 30cm and the filter diameter is 40-60mm; the thickness of the lower filter media is 50cm and the filter diameter is 10-30mm.

[0035] The outlet of the phosphorus biofilter 11 is connected to a second circulating water pump 13, which serves as a sewage outlet and is connected to the inlets of the nitrogen biofilter 6 and the phosphorus biofilter 11 respectively; a third flow control meter 14 is provided between the second circulating water pump 13 and the inlet of the nitrogen biofilter.

[0036] The phosphorus biological filter 11 is provided with a phosphorus biological filter layer 11-5, a second supporting layer 11-6 and a second water collecting tank 11-7 in sequence from top to bottom. A second uniform water distributor 11-3 is buried on the upper part of the phosphorus biological filter layer. A positive electrode 11-1 and a negative electrode 11-2 are vertically buried in the phosphorus biological filter layer. The positive and negative electrodes are respectively connected to the current controller 12; a third liquid level controller 11-8 is provided inside the second water collecting tank. The third liquid level controller 11-8 is connected to the second circulating water pump 13 to control the operation of the second circulating water pump 13 and adjust the height of the water surface in the second supporting layer and the second water collecting tank.

[0037] The phosphorus biological filter layer includes one layer, and the filter diameter of the filter media in each filter layer decreases layer by layer from top to bottom. The filter media thickness is 30cm and the filter diameter is 30-50mm. The filter media adopts conventional filter materials such as quartz stone.

[0038] The buried depth of the second uniform water distributor in the phosphorus biofilter layer is 5 cm.

[0039] The electrochemical reaction cell 7 is provided with an anode electrode 7 - 1 , a cathode electrode 7 - 2 and a stirrer 7 - 3 .

[0040] The sewage treatment system further comprises a photovoltaic power source 15, which provides electrical energy to all equipment in the sewage treatment system, and the photovoltaic material is preferably polycrystalline silicon.

[0041] The sewage enters the sedimentation tank 2 after the larger suspended solids are removed through the grille 1. The supernatant of the sedimentation tank is sent to the nitrogen biofilter 6 by the first sewage pump 4. Through biological action, the organic matter and total nitrogen in the sewage are removed. The treated sewage mainly contains the pollutant phosphorus. A part of it is returned to the nitrogen biofilter 6 by the first circulating water pump 9, and the flow rate is controlled by the second flow controller 10 for deep denitrification. The other part is sent to the phosphorus biofilter 11; the mud-water mixture at the bottom of the sedimentation tank is sent to the electrochemical reaction tank 7 by the second sewage pump 3, and the flow rate is controlled by the second flow controller 10. The particulate organic matter and complex organic matter in the mud-water mixture are electrochemically reacted. The wastewater after the reaction contains VFA and iron ions, and flows to the phosphorus biofilter 11 by gravity; the microorganisms in the phosphorus biofilter 11 carry out anaerobic phosphorus removal under the promotion of the electric field, and at the same time, the flocculation effect of iron ions is used to enhance the removal of phosphorus. The second circulating water pump 13 returns part of the treated wastewater to the nitrogen biofilter 6, and the flow rate is controlled by the third flow controller 14 to carry out deep denitrification and phosphorus removal, and part of it is discharged in the form of effluent. The electricity used in the entire sewage treatment system is supplied by the photovoltaic power supply 15, realizing energy self-sufficiency and deep denitrification and phosphorus removal in sewage treatment.

[0042] The first circulating water pump 9 pumps part of the sewage in the water collection tank 6-7 to the second uniform water distributor 11-3, and the remaining sewage flows back to the first uniform water distributor 6-2. The nitrogen filter layer 6-4 and the first supporting layer 6-5 serve as the nitrogen biological filtration area 6-3 to achieve a deep denitrification effect, while reducing the sewage load of the biological filtration area 6-3, effectively preventing the nitrogen filter layer 6-4 from being blocked, and the sewage return ratio is 100%, which is controlled by the second flow controller 10; the second liquid level controller 6-9 controls the first circulating water The operation of pump 9 ensures the height of the first supporting layer 6-5 and the water surface of the collection tank 6-7; heterotrophic aerobic bacteria in the upper filter layer in the biological filtration area 6-3 use DO to decompose organic matter, and nitrifying bacteria use DO to oxidize ammonia nitrogen into nitrate nitrogen. As DO in the sewage is consumed, an anoxic area will be formed in the lower filter layer. Denitrifying bacteria use organic matter in the anoxic area to further reduce nitrate nitrogen to nitrogen gas. Finally, the sewage achieves the effect of organic decomposition and denitrification. At this time, the main pollutant in the sewage in the collection tank 6-7 is phosphorus.

[0043] The first uniform water distributor 6-2 evenly distributes the sewage in the biological filtration area 6-3, at a height of 5 cm from the upper surface of the filter layer 6-4, which effectively increases the residence time of the sewage in the air, thereby increasing the DO in the sewage.

[0044] The height between the first supporting layer 6-5 and the water surface in the water collection tank 6-7 is 10 cm. The exhaust fan 8, the exhaust pipe 6-6 and the air permeable pipe 6-1 are used to accelerate the air renewal speed between the first supporting layer 6-5 and the water collection tank 6-7, further improving the DO in the sewage.

[0045] The second circulating water pump 13 returns part of the sewage in the phosphorus biofilter 11 to the second uniform water distributor 11-3, thereby achieving a deep phosphorus removal effect and reducing the sewage load in the biological filtration area 6-3, effectively preventing the blockage of the nitrogen filter layer 6-4. The sewage return ratio is 500%, and the sewage return ratio is controlled by the third flow controller 14; the third liquid level controller 11-8 controls the operation of the second circulating water pump 13. When the liquid level in the second water collection tank 11-7 is low, the second circulating water pump 13 is automatically shut down.

[0046] The second water distributor 11-3 is buried in the phosphorus filter layer 11-5 at a depth of 5 cm. The phosphorus filter layer 11-5 and the second supporting layer 11-6 together serve as the second biological filtration area 11-4. Sewage flows evenly into the second biological filtration area 11-4, effectively suppressing DO in the sewage and putting the biological filtration area 11-4 in an anaerobic state.

[0047] The phosphorus filter material filter layer 11-5 is one layer, with a thickness of 30 cm and a filter diameter of 30-50 mm.

[0048] The positive electrode 11-1 and the negative electrode 11-2 are preferably made of graphite as electrode material; the current controller 12 controls the current to 0 mA, at which time the phosphorus biofilter 11 undergoes anaerobic phosphorus removal, and after detection, the concentration of phosphine gas is 50-100 ng / L; the iron ions produced in the electrochemical reaction cell 7 undergo chemical flocculation in the phosphorus biofilter 11 to further remove phosphorus in the sewage.

[0049] A stirrer 7-3 is provided inside the electrochemical reaction cell 7 to prevent the mud-water mixture from settling. The hydraulic retention time is 480 minutes. The voltage between the positive electrode and the negative electrode is 0V. The particulate organic matter and complex organic matter in the mud-water mixture are decomposed into VFA, and the anode releases iron ions. The positive electrode material is iron, and the negative electrode material is graphite. The electrode material of the positive electrode 7-1 is regularly replaced.

[0050] The raw water quality and treated effluent quality of domestic sewage in a community in Hefei are shown in Table 1. The SS, COD, and NH 4 + -N, TN, TP all meet the Class A effluent standards.

[0051] Table 1 Water quality of influent and effluent in sewage in Example 1

[0052]

[0053] Example 2

[0054] The implementation case of the present invention was carried out using domestic sewage from a community in Hefei City. After the sewage was treated, it met the discharge standards. At the same time, all energy consumption was provided by photovoltaic power sources.

[0055] The energy self-sufficiency and deep denitrification and dephosphorization domestic sewage treatment system provided in this embodiment is basically the same as that in embodiment 1, except that:

[0056] The number of the air permeable tube 6-1 is one.

[0057] The nitrogen biofilter wastewater return ratio is 600%.

[0058] The distance between the first uniform water distributor 6-2 and the top surface of the nitrogen biological filter layer 6-4 is 50 cm.

[0059] The nitrogen biological filter layer 6-4 is one layer, the filter material thickness is 80cm, and the filter diameter is 50-80mm.

[0060] The height between the first supporting layer 6-5 and the water surface in the first water collecting pool 6-7 is 60 cm.

[0061] The wastewater return ratio of the phosphorus biofilter is 50%.

[0062] The current controller 12 controls the current to be 500 mA. At this time, the phosphorus biofilter 11 undergoes anaerobic phosphorus removal. After detection, the concentration of phosphine gas is 200-350 ng / L.

[0063] The second water distributor 11 - 3 is buried in the phosphorus filter layer 11 - 5 at a depth of 10 cm.

[0064] The hydraulic retention time in the electrochemical reaction cell 7 is 10 minutes. The materials of the anode and cathode are both aluminum. The voltage is 400 V. The particulate organic matter and complex organic matter in the mud-water mixture are decomposed into VFA, and the anode releases aluminum ions.

[0065] The raw water quality and treated effluent quality of domestic sewage in a community in Hefei in this example are shown in Table 2. The SS, COD, and NH 4 + -N, TN, TP all meet the Class A effluent standards.

[0066] Table 2 Water quality of influent and effluent in sewage in Example 2

[0067]

[0068] Example 3

[0069] The implementation case of the present invention was carried out using domestic sewage from a community in Hefei City. After the sewage was treated, it met the discharge standards. At the same time, all energy consumption was provided by photovoltaic power sources.

[0070] The energy self-sufficiency and deep denitrification and dephosphorization domestic sewage treatment system provided in this embodiment is basically the same as that in embodiment 1, except that:

[0071] The number of the air-permeable tubes 6 - 1 is five.

[0072] The nitrogen biofilter wastewater return ratio is 300%.

[0073] The distance between the first uniform water distributor 6-2 and the top surface of the nitrogen biological filter layer 6-4 is 20 cm.

[0074] The nitrogen biological filter layer 6-4 consists of three layers, wherein the filter material thickness of the upper layer is 80cm, and the filter diameter is 60-120mm; the filter material thickness of the middle layer is 40cm, and the filter diameter is 40-60mm; the filter material thickness of the lower layer is 30cm, and the filter diameter is 10-30mm.

[0075] The height between the first supporting layer 6-5 and the water surface in the first water collecting pool 6-7 is 40 cm.

[0076] The wastewater return ratio of the phosphorus biofilter is 300%.

[0077] The phosphorus filter material filter layer 11-5 is 2 layers, the upper filter material thickness is 80cm, the filter diameter is 60-120mm, the lower filter material thickness is 30cm, the filter diameter is 40-60mm.

[0078] The current controller 12 controls the current to be 100 mA. At this time, the phosphorus biofilter 11 undergoes anaerobic phosphorus removal. After detection, the concentration of phosphine gas is 150-230 ng / L.

[0079] The second water distributor 11 - 3 is buried in the phosphorus filter layer 11 - 5 at a depth of 8 cm.

[0080] The hydraulic retention time in the electrochemical reaction cell 7 is 60 minutes, the anode material is iron, the cathode material is aluminum, the voltage is 100V, the particulate organic matter and complex organic matter in the mud-water mixture are decomposed into VFA, and the anode releases iron ions.

[0081] The raw water quality and treated effluent quality of domestic sewage in a community in Hefei in this example are shown in Table 3. The SS, COD, and NH 4 + -N, TN, TP all meet the Class A effluent standards.

[0082] Table 3 Water quality of inlet and outlet water in Example 3

[0083]

[0084] The above is only a preferred embodiment of the present invention, and does not limit the present invention in any form; any technician familiar with the art can make many possible changes and modifications to the technical solution of the present invention by using the above disclosed methods and technical contents without departing from the scope of the technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Therefore, any simple modification, equivalent replacement, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of protection of the technical solution of the present invention.

Claims

1. An energy self-sufficient domestic sewage treatment system with deep nitrogen and phosphorus removal, It is characterized in that A grid, a sedimentation tank, a nitrogen biofilter and a phosphorus biofilter are sequentially connected along the sewage flow direction; the upper part of the sedimentation tank is connected to the inlet of the nitrogen biofilter through a first sewage pump; the bottom of the sedimentation tank is connected to an electrochemical reaction tank through a second sewage pump; the outlet of the electrochemical reaction tank is connected to the inlet of the phosphorus biofilter; a first flow control meter is provided between the second sewage pump and the electrochemical reaction tank; The outlet of the nitrogen biofilter is connected to a first circulating water pump, and the outlets of the first circulating water pump are respectively connected to the inlets of the nitrogen biofilter and the phosphorus biofilter; a second flow control meter is provided between the first circulating water pump and the inlet of the nitrogen biofilter; The outlet of the phosphorus biofilter is connected to a second circulating water pump, which serves as a sewage outlet and is connected to the inlets of the nitrogen biofilter and the phosphorus biofilter respectively; a third flow control meter is provided between the second circulating water pump and the inlet of the nitrogen biofilter; The sewage treatment system also includes a photovoltaic power source, which provides electrical energy for all equipment in the sewage treatment system.

2. A domestic sewage treatment system with energy self-sufficiency and deep denitrification and phosphorus removal according to claim 1, It is characterized in that The nitrogen biological filter is provided with a first uniform water distributor, a nitrogen biological filter layer, a first supporting layer and a first water collection tank in sequence from top to bottom, the first uniform water distributor and the nitrogen biological filter layer are arranged at intervals, and a ventilation pipe connecting the water collection tank with the atmosphere is vertically penetrated through the nitrogen biological filter; an exhaust fan is provided outside the first water collection tank, and the exhaust fan is connected with the first water collection tank through an exhaust pipe, and a first liquid level controller and a second liquid level controller are provided inside the first water collection tank, and the first liquid level controller is connected with the exhaust fan to control the operation of the exhaust fan; the second liquid level controller is connected with the first circulating water pump to control the operation of the first circulating water pump, and adjusts the height of the first supporting layer and the water surface in the first water collection tank by 10-60 cm.

3. The energy self-sufficient and deep denitrification and dephosphorization domestic sewage treatment system according to claim 1, It is characterized in that The phosphorus biological filter tank is provided with a phosphorus biological filter layer, a second supporting layer and a second water collection tank in sequence from top to bottom; a second uniform water distributor is buried on the upper part of the phosphorus biological filter layer; a positive electrode and a negative electrode are vertically buried in the phosphorus biological filter layer; the positive and negative electrodes are respectively connected to a current controller; a third liquid level controller is provided inside the second water collection tank; the third liquid level controller is connected to the second circulating water pump, controls the operation of the second circulating water pump, and adjusts the height of the water surface in the second supporting layer and the second water collection tank.

4. The energy self-sufficient and deep denitrification and dephosphorization domestic sewage treatment system according to claim 1, It is characterized in that The electrochemical reaction cell is provided with a cathode electrode, an anode electrode and a stirrer.

5. The energy self-sufficient and deep denitrification and dephosphorization domestic sewage treatment system according to claim 2, It is characterized in that The distance between the first uniform water distributor and the top surface of the nitrogen biological filter layer is 5-50 cm.

6. The energy self-sufficient and deep denitrification and dephosphorization domestic sewage treatment system according to claim 2, It is characterized in that The nitrogen biological filter layer includes more than two layers, and the filter diameter of the filter material in each filter layer decreases from top to bottom, the filter material thickness is 30-100cm, and the filter diameter is 10-100mm.

7. The energy self-sufficient and deep denitrification and dephosphorization domestic sewage treatment system according to claim 2, It is characterized in that The ventilation tubes include more than two.

8. The energy self-sufficient and deep denitrification and dephosphorization domestic sewage treatment system according to claim 3, It is characterized in that The phosphorus biological filter layer comprises more than one layer, and the filter diameter of the filter material in each filter layer decreases layer by layer from top to bottom, the filter material thickness is 30-80cm, and the filter diameter is 30-120mm.

9. The energy self-sufficient and deep denitrification and dephosphorization domestic sewage treatment system according to claim 3, It is characterized in that The second uniform water distributor is buried at a depth of 5-10 cm in the phosphorus biological filter layer.

10. The energy self-sufficient and deep denitrification and dephosphorization domestic sewage treatment system according to claim 4, It is characterized in that The voltage of the cathode and anode electrodes is 0-400V; the residence time of the sewage in the electrochemical reaction tank is 10-480min.

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