Sewage treatment system

Abstract

The utility model relates to the technical field of sewage treatment, in particular to a sewage treatment system, which comprises a primary sedimentation tank, a synchronous nitrification and denitrification subsystem and a final-stage sedimentation tank which are sequentially communicated, and is provided with an electrolytic dephosphorization device and a liquid conveying device, and a liquid inlet of the electrolytic dephosphorization device is communicated with the bottom of the final-stage sedimentation tank through the liquid conveying device; a liquid outlet of the primary sedimentation tank is connected into the primary sedimentation tank; when the system runs, low-phosphorus turbid liquid at the bottom of the final-stage sedimentation tank is fed into the electrolytic dephosphorization device through the liquid conveying device, the turbid liquid carries metal ions generated by electrolysis to return to the primary sedimentation tank while washing a polar plate, the metal ions are combined with phosphorus in the primary sedimentation tank to form precipitates to realize dephosphorization, and supernate enters a subsequent treatment unit. Due to the low-phosphorus characteristic of the final-stage precipitation solution, the formation of phosphate in the electrolytic dephosphorization device is avoided, and the sewage treatment system does not need to be additionally provided with a sewage storage tank for storing the precipitate in the final-stage precipitation tank, so that the occupied area of the sewage treatment system is reduced.

Description

Technical Field

[0001] This utility model relates to the field of wastewater treatment technology, and in particular to a wastewater treatment system. Background Technology

[0002] Simultaneous Nitrification and Denitrification (SND) in biofilm processes is widely used in rural wastewater treatment due to its simplicity, low energy consumption, lack of sludge production, and small footprint. Its core principle lies in utilizing dissolved oxygen penetration through the packing material to create different anoxic and aerobic zones, thus achieving simultaneous nitrogen removal while removing pollutants. However, it often lacks significant effect on phosphorus removal. To ensure good phosphorus removal, chemical phosphorus removal is typically used, employing methods such as coagulation sedimentation, adsorption, and ion exchange to remove phosphorus from water. While this method offers stable treatment results and is simple to operate, the artificial addition of chemical agents leads to high economic costs, the generation of large amounts of sludge, and carbon dioxide emissions during the chemical production process. Electrochemical phosphorus removal, on the other hand, offers advantages such as small footprint, high phosphorus removal rate, short hydraulic retention time, low sludge production, and the elimination of external dosing and dissolving equipment, making it a promising option for phosphorus removal in rural wastewater treatment.

[0003] In the electrochemical phosphorus removal process, an oxidation reaction occurs at the anode plate, where metal atoms lose electrons to generate metal ions, which are released into the solution. These released metal ions combine with phosphate ions in the solution to form phosphate precipitates, thus achieving phosphorus removal. However, phosphates easily deposit on the electrode surface. As the reaction continues, these phosphates gradually form a dense passivation film. This passivation film blocks direct contact between the metal substrate and the solution, inhibiting further oxidation reactions and resulting in poor electrochemical phosphorus removal efficiency. Utility Model Content

[0004] The technical problem to be solved by this utility model is that in the existing wastewater treatment system, the electrochemical phosphorus removal device is prone to the formation of a passivation film on the surface of the anode plate, which affects the electrochemical phosphorus removal effect.

[0005] To solve the above-mentioned technical problems, the purpose of this utility model is to provide a wastewater treatment system, characterized in that it includes an electrolytic phosphorus removal device, a liquid conveying device, a primary sedimentation tank, a simultaneous nitrification-denitrification subsystem, and a final sedimentation tank. The primary sedimentation tank, the simultaneous nitrification-denitrification subsystem, and the final sedimentation tank are connected sequentially along the water flow direction. The electrolytic phosphorus removal device has an inlet and an outlet. The liquid conveying device has an inlet end and an outlet end. The inlet end is connected to the bottom of the final sedimentation tank, the outlet end is connected to the inlet, and the outlet is connected to the primary sedimentation tank.

[0006] As a preferred embodiment, the electrolytic phosphorus removal device is installed in the primary sedimentation tank, and the liquid outlet is connected to the upper part of the primary sedimentation tank.

[0007] As a preferred embodiment, the simultaneous nitrification-denitrification subsystem includes a primary simultaneous nitrification-denitrification zone, a secondary simultaneous nitrification-denitrification zone, and a tertiary simultaneous nitrification-denitrification zone. The primary simultaneous nitrification-denitrification zone, the secondary simultaneous nitrification-denitrification zone, and the tertiary simultaneous nitrification-denitrification zone are sequentially connected along the water flow direction. The outlet of the primary sedimentation tank is connected to the primary simultaneous nitrification-denitrification zone, and the tertiary simultaneous nitrification-denitrification zone is connected to the final sedimentation tank.

[0008] As a preferred embodiment, the infusion device is an air-lift device.

[0009] As a preferred embodiment, the electrolytic phosphorus removal device includes an insulating barrel and multiple electrode plates. The insulating barrel has a bottom wall and side walls, which enclose a barrel cavity. The upper end of the side walls has multiple horizontally spaced slots. Each electrode plate includes a connecting section at the top and a working section at the bottom. Each connecting section is respectively engaged in each slot, and each working section is inserted into the barrel cavity. The liquid inlet communicates with the upper part of the barrel cavity, and the liquid outlet communicates with the lower part of the barrel cavity.

[0010] As a preferred embodiment, the insulating bucket is a rectangular or square bucket, and has a left side wall and a right side wall arranged at intervals. The upper end of the left side wall has a plurality of first slots arranged at intervals along the front-back direction. The left side of each connecting section has a first protrusion protruding to the left beyond the working section, and each first protrusion is respectively engaged in the first slot. The upper end of the right side wall has a plurality of second slots arranged at intervals along the front-back direction. The right side of each connecting section has a second protrusion protruding to the right beyond the working section, and each second protrusion is respectively engaged in the second slot.

[0011] As a preferred embodiment, a buffer shell is fixed to the upper outer side of the left side wall, and the buffer shell and the left side wall form a buffer cavity. The left side wall has a plurality of diversion holes arranged at intervals along the front-back direction. One end of each diversion hole is connected to the buffer cavity and the other end is connected to the barrel cavity. The liquid inlet is provided on the buffer shell and is connected to the buffer cavity.

[0012] As a preferred embodiment, the upper end of each of the connecting segments has an upwardly protruding electrical contact protrusion extending outside the connecting segment.

[0013] As a preferred embodiment, the interval between two adjacent card slots is 5mm.

[0014] As a preferred option, the spacing between two adjacent plates is one of 5mm, 10mm, 15mm, 20mm, 25mm, 30mm, 35mm, or 40mm.

[0015] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0016] This utility model discloses a wastewater treatment system comprising a primary sedimentation tank, a simultaneous nitrification-denitrification subsystem, and a final sedimentation tank connected in sequence, and equipped with an electrolytic phosphate removal device and a delivery device. The inlet of the electrolytic phosphate removal device is connected to the bottom of the final sedimentation tank via the delivery device, while its outlet is connected to the primary sedimentation tank. During system operation, the low-phosphorus turbid liquid at the bottom of the final sedimentation tank is sent to the electrolytic phosphate removal device via the delivery device. The turbid liquid washes the electrode plates while carrying the metal ions generated by electrolysis back to the primary sedimentation tank. The metal ions combine with the phosphorus in the primary sedimentation tank to form precipitates, thus achieving phosphorus removal. The supernatant then enters the subsequent treatment unit. The low-phosphorus characteristics of the final sedimentation liquid prevent the formation of phosphates in the electrolytic phosphate removal device, effectively inhibiting the formation of passivation films on the electrode plates of the electrolytic phosphate removal device. In addition, by recycling the final sedimentation liquid, the wastewater treatment system does not require an additional storage tank for storing the precipitates from the final sedimentation tank, reducing the footprint of the wastewater treatment system. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the wastewater treatment system of this utility model;

[0018] Figure 2 This is a schematic diagram of the electrolytic phosphorus removal device;

[0019] Figure 3 This is a schematic diagram of the insulating barrel.

[0020] Figure 4 This is a schematic diagram of the electrode plate structure;

[0021] In the diagram, 1. Primary sedimentation tank; 2. Synchronous nitrification-denitrification subsystem; 21. First-stage synchronous nitrification-denitrification zone; 22. Second-stage synchronous nitrification-denitrification zone; 23. Third-stage synchronous nitrification-denitrification zone; 3. Final sedimentation tank; 4. Electrolytic phosphorus removal device; 41. Inlet; 42. Outlet; 43. Insulating tank; 431. Left side wall; 4311. First slot; 432. Right side wall; 4321. Second slot; 433. Diversion hole; 44. Electrode plate; 441. Connecting section; 4411. First protrusion; 4412. Second protrusion; 4413. Electrical connection protrusion; 442. Working section; 45. Buffer shell; 5. Liquid delivery device; 61. First clamp; 62. Second clamp. Detailed Implementation

[0022] The specific embodiments of this utility model will be further described in detail below with reference to the accompanying drawings and examples. The following examples are used to illustrate this utility model, but are not intended to limit the scope of this utility model.

[0023] In the description of this utility model, it should be understood that the terms "upper," "lower," "left," "right," "top," and "bottom," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this utility model and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model. It should also be understood that the terms "first," "second," etc., are used in this utility model to describe various information, but this information should not be limited to these terms. These terms are only used to distinguish information of the same type from each other. For example, without departing from the scope of this utility model, "first" information can also be referred to as "second" information, and similarly, "second" information can also be referred to as "first" information.

[0024] like Figure 1As shown, a preferred embodiment of the wastewater treatment system of this utility model includes an electrolytic phosphate removal device 4, a liquid conveying device 5, a primary sedimentation tank 1, a simultaneous nitrification-denitrification subsystem 2, and a final sedimentation tank 3. The primary sedimentation tank 1, the simultaneous nitrification-denitrification subsystem 2, and the final sedimentation tank 3 are connected sequentially along the water flow direction. The electrolytic phosphate removal device 4 has an inlet 41 and an outlet 42. The liquid conveying device 5 has an inlet end and an outlet end. The inlet end is connected to the bottom of the final sedimentation tank 3, the outlet end is connected to the inlet 41, and the outlet 42 is connected to the primary sedimentation tank 1. The turbid liquid at the bottom of the final sedimentation tank 3 flows into the electrolytic phosphate removal device 4 under the action of the liquid conveying device 5, which can flush the electrode plates 44 of the electrolytic phosphate removal device 4. The metal ions generated by the electrolysis of the electrolytic phosphate removal device 4 are mixed in the turbid liquid. Therefore, the turbid liquid flowing into the primary sedimentation tank 1 contains more metal ions that can combine with phosphates. After entering the primary sedimentation tank 1... Phosphorus removal is achieved by combining metal ions in the turbid liquid with phosphate ions in the primary sedimentation tank 1. The phosphate precipitate formed in the primary sedimentation tank 1 remains in the primary sedimentation tank 1. The supernatant from the primary sedimentation tank 1 flows into the nitrification-denitrification subsystem and the final sedimentation tank 3. Since the turbid liquid in the final sedimentation tank 3 is a solution after phosphorus removal treatment, the turbid liquid flowing into the electrolytic phosphorus removal device 4 contains fewer phosphate ions. This avoids the formation of phosphate precipitate in the electrolytic phosphorus removal device 4, thereby inhibiting the formation of a passivation film on the electrode plate 44 of the electrolytic phosphorus removal device 4. In addition, by passing the turbid liquid in the final sedimentation tank 3 into the electrolytic phosphorus removal device 4 and then into the primary sedimentation tank 1, not only is the turbid liquid in the final sedimentation tank 3 reused, but there is also no need to set up a sludge storage tank next to the final sedimentation tank 3 for extracting the precipitate in the final sedimentation tank 3, making the wastewater treatment system of this utility model occupy a smaller area.

[0025] In this design, the electrolytic phosphorus removal device 4 is installed in the primary sedimentation tank 1. The solid-liquid separation tank allows phosphorus and iron ions in the water to react fully and form a precipitate at the bottom of the tank, with a retention time (HRT) of at least 2 hours. The outlet is connected to the upper part of the primary sedimentation tank 1. In other embodiments of this invention, the electrolytic phosphorus removal device 4 can be installed on one side of the primary sedimentation tank 1, with the liquid flowing from the outlet 42 being piped into the primary sedimentation tank 1. Installing the electrolytic phosphorus removal device 4 in the primary sedimentation tank 1 further reduces the footprint of the wastewater treatment system.

[0026] The simultaneous nitrification-denitrification (SND) subsystem 2 can be a single-stage, two-stage, or three-stage system. In this embodiment, the SND subsystem 2 includes a single-stage SND zone 21, a two-stage SND zone 22, and a three-stage SND zone 23. These three zones are sequentially connected along the water flow direction. The outlet 42 of the primary sedimentation tank 1 is connected to the single-stage SND zone 21, and the three-stage SND zone 23 is connected to the final sedimentation tank 3. The first stage primarily removes most of the COD, ammonia nitrogen, and nitrate nitrogen, making it the main contributor to the SND process. The second stage contributes slightly more, while the third stage provides deeper treatment, primarily through nitrification. The SND simultaneous denitrification efficiency of the first stage is 30% to 35%; the efficiency of the second stage is 10% to 20%; and the efficiency of the third stage is ≤5%. In this embodiment, conventional domestic water was used, with COD ranging from 265 mg / L to 416 mg / L, averaging 362 mg / L; ammonia nitrogen ranging from 3543 mg / L to 43 mg / L, averaging 39 mg / L; total nitrogen ranging from 39 mg / L to 52 mg / L, averaging 46 mg / L; and total phosphorus ranging from 2.6 mg / L to 6.2 mg / L, averaging 4.4 mg / L. The number of stages in the simultaneous nitrification-denitrification subsystem 2, and the removal efficiency when the electrolytic phosphorus removal device 4 was started and not started are shown in the table below:

[0027]

[0028] In this system, the simultaneous nitrification and denitrification subsystem 2 uses sponge packing material with a diameter of 3cm to 5cm, and the dissolved oxygen in the water is controlled at 3mg / L to 6mg / L. The packing material has distinct aerobic and aerobic zones, enabling simultaneous nitrification and denitrification. The packing material can be in a sulfidated state or a fixed state. In this embodiment, the infusion device 5 is an air-lift device; in other embodiments of this invention, the infusion device 5 can be a pump body.

[0029] In this embodiment, as Figures 2 to 4As shown, the electrolytic phosphorus removal device 4 includes an insulating barrel 43 and multiple electrode plates 44. The insulating barrel 43 has a bottom wall and side walls that enclose a barrel cavity. The upper end of the side walls has multiple horizontally spaced slots. Each electrode plate 44 includes a connecting section 441 at the top and a working section 442 at the bottom. Each connecting section 441 is respectively engaged in its respective slot, and each working section 442 is inserted into the barrel cavity. The liquid inlet 41 communicates with the upper part of the barrel cavity, and the liquid outlet 42 communicates with the lower part of the barrel cavity. Each electrode plate 44 is connected to the insulating barrel 43 by snap-fit. By adjusting the installation position of the electrode plates 44, the spacing between two adjacent electrode plates 44 can be flexibly adjusted, and it is convenient to replace the electrode plates 44. The insulating barrel 43 is made of insulating materials such as plastic. Utilizing the insulation property of the insulating barrel 43, it can insulate two adjacent electrode plates 44 without the need for additional insulators.

[0030] Specifically, the insulating barrel 43 is a rectangular or square barrel. The insulating barrel 43 has a left side wall 431 and a right side wall 432 arranged at intervals on the left and right sides. The upper end of the left side wall 431 has a plurality of first slots 4311 arranged at intervals in the front-back direction. The left side of each connecting section 441 has a first protrusion 4411 protruding to the left beyond the working section 442. Each first protrusion 4411 is respectively locked in the first slot 4311. The upper end of the right side wall 432 has a plurality of second slots 4321 arranged at intervals in the front-back direction. The right side of each connecting section 441 has a second protrusion 4412 protruding to the right beyond the working section 442. Each second protrusion 4412 is respectively locked in the second slot 4321. The connecting section 441 and the working section 442 form a T-shaped structure, which facilitates the installation of the electrode plate 44 and ensures the stability of the electrode plate 44 on the insulating barrel 43.

[0031] Furthermore, each connecting segment 441 has an upwardly protruding electrical contact protrusion 4413 at its upper end. The upper left and upper right ends of the electrode plate 44 also have electrical contact protrusions 4413. Connecting wire clamps to the electrical contact protrusions 4413 enables electrical connection. During connection, a first wire clamp 61 is connected to every other electrical contact protrusion 4413 on the left side, and a second wire clamp 62 is connected to every other electrical contact protrusion 4413 on the right side. Each first wire clamp 61 is electrically connected to a third wire clamp, and each second wire clamp 62 is electrically connected to a fourth wire clamp. By switching the polarity of the power connectors connected to the third and fourth wire clamps, the polarity of the electrode plate 44 can be switched. The positive and negative terminals should generally be changed every 6 to 24 hours to prevent passivation of the electrode plate 44. The electrode plate 44 is made of iron or aluminum plate, with a length of 200mm to 500mm, a width of 100mm to 200mm, and a thickness of 3mm to 5mm. This design aims to keep the maximum weight of a single electrode plate 44 to around 10kg, making it easy for a single person to handle. In this embodiment, the spacing between two adjacent slots is 5mm. By changing the number of slots between adjacent electrode plates 44, the spacing can be adjusted to one of the following: 5mm, 10mm, 15mm, 20mm, 25mm, 30mm, 35mm, or 40mm. This addresses the different resistances formed by the electrode plates 44 under different water conductivity conditions, preventing short circuits caused by excessive density in high conductivity water, while simultaneously minimizing power consumption by reducing the plate spacing.

[0032] In this embodiment, a buffer shell 45 is fixed to the upper outer side of the left side wall 431. The buffer shell 45 and the left side wall 431 form a buffer cavity. The left side wall 431 has multiple diversion holes 433 arranged at intervals along the left-right direction. One end of each diversion hole 433 is connected to the buffer cavity, and the other end is connected to the barrel cavity. The liquid inlet 41 is provided on the buffer shell 45 and is connected to the buffer cavity. The arrangement of the buffer cavity and the diversion holes 433 enables the turbid liquid in the final sedimentation tank 3 to uniformly flush each electrode plate 44, ensuring that the lifespan of each electrode plate 44 is similar and facilitating the control of the electrode plate 44 replacement cycle.

[0033] In summary, the wastewater treatment system of this utility model includes a primary sedimentation tank 1, a simultaneous nitrification-denitrification subsystem 2, and a final sedimentation tank 3 connected in sequence, and is equipped with an electrolytic phosphorus removal device 4 and a delivery device 5. The inlet 41 of the electrolytic phosphorus removal device 4 is connected to the bottom of the final sedimentation tank 3 through the delivery device 5, and its outlet 42 is connected to the primary sedimentation tank 1. During system operation, the low-phosphorus turbid liquid at the bottom of the final sedimentation tank 3 is sent to the electrolytic phosphorus removal device 4 through the delivery device 5. While the turbid liquid washes the electrode plates 44, it carries the metal ions generated by electrolysis back to the primary sedimentation tank 1. The metal ions combine with the phosphorus in the primary sedimentation tank 1 to form precipitates and achieve phosphorus removal. The supernatant then enters the subsequent treatment unit. The low-phosphorus characteristics of the final sedimentation liquid prevent the formation of phosphate in the electrolytic phosphorus removal device 4 and effectively inhibit the formation of passivation film on the electrode plates 44 of the electrolytic phosphorus removal device 4. In addition, by recycling the final sedimentation liquid, the wastewater treatment system does not need to set up an additional storage tank for storing the precipitates of the final sedimentation tank 3, thus reducing the footprint of the wastewater treatment system.

[0034] The above description is only a preferred embodiment of the present utility model. It should be noted that for those skilled in the art, several improvements and substitutions can be made without departing from the technical principles of the present utility model, and these improvements and substitutions should also be considered within the protection scope of the present utility model.

Claims

1. A wastewater treatment system, characterized in that, It includes a primary sedimentation tank (1), a simultaneous nitrification and denitrification subsystem (2), a final sedimentation tank (3), an electrolytic phosphorus removal device (4), and a liquid delivery device (5); the primary sedimentation tank (1), the simultaneous nitrification and denitrification subsystem (2), and the final sedimentation tank (3) are connected sequentially along the water flow direction; the electrolytic phosphorus removal device (4) has an inlet (41) and an outlet (42); the liquid delivery device (5) has an inlet end and an outlet end; the inlet end is connected to the bottom of the final sedimentation tank (3); the outlet end is connected to the inlet (41); and the outlet (42) is connected to the primary sedimentation tank (1).

2. The wastewater treatment system according to claim 1, characterized in that, The electrolytic phosphorus removal device (4) is installed in the primary sedimentation tank (1), and the liquid outlet is connected to the upper part of the primary sedimentation tank (1).

3. The wastewater treatment system according to claim 1, characterized in that, The simultaneous nitrification and denitrification subsystem (2) includes a primary simultaneous nitrification and denitrification zone (21), a secondary simultaneous nitrification and denitrification zone (22), and a tertiary simultaneous nitrification and denitrification zone (23). The primary simultaneous nitrification and denitrification zone (21), the secondary simultaneous nitrification and denitrification zone (22), and the tertiary simultaneous nitrification and denitrification zone (23) are connected sequentially along the water flow direction. The outlet (42) of the primary sedimentation tank (1) is connected to the primary simultaneous nitrification and denitrification zone (21), and the tertiary simultaneous nitrification and denitrification zone (23) is connected to the final sedimentation tank (3).

4. The wastewater treatment system according to claim 1, characterized in that, The infusion device (5) is an air-lift device.

5. The wastewater treatment system according to claim 1, characterized in that, The electrolytic phosphorus removal device (4) includes an insulating barrel (43) and multiple electrode plates (44). The insulating barrel (43) has a bottom wall and a side wall, which enclose a barrel cavity. The upper end of the side wall has multiple slots arranged horizontally at intervals. Each electrode plate (44) includes a connecting section (441) located at the upper part and a working section (442) located at the lower part. Each connecting section (441) is respectively locked in each slot, and each working section (442) is inserted into the barrel cavity. The liquid inlet (41) is connected to the upper part of the barrel cavity, and the liquid outlet (42) is connected to the lower part of the barrel cavity.

6. The wastewater treatment system according to claim 5, characterized in that, The insulating barrel (43) is a rectangular barrel or a square barrel; The insulating barrel (43) has a left side wall (431) and a right side wall (432) arranged at intervals on the left and right sides. The upper end of the left side wall (431) has a plurality of first slots (4311) arranged at intervals in the front-back direction. Each connecting section (441) has a first protrusion (4411) protruding to the left outside the working section (442) on the left side. Each first protrusion (4411) is respectively locked in each first slot (4311). The upper end of the right side wall (432) has a plurality of second slots (4321) arranged at intervals along the front-back direction. Each connecting section (441) has a second protrusion (4412) protruding to the right outside the working section (442) on the right side. Each second protrusion (4412) is respectively engaged in each second slot (4321).

7. The wastewater treatment system according to claim 6, characterized in that, A buffer shell (45) is fixed to the upper outer side of the left side wall (431). The buffer shell (45) and the left side wall (431) form a buffer cavity. The left side wall (431) has a plurality of diversion holes (433) arranged at intervals along the front-back direction. One end of each diversion hole (433) is connected to the buffer cavity and the other end is connected to the barrel cavity. The liquid inlet (41) is provided on the buffer shell (45) and is connected to the buffer cavity.

8. The wastewater treatment system according to claim 5, characterized in that, Each of the connecting segments (441) has an electrical contact protrusion (4413) protruding upwards out of the connecting segment (441) at its upper end.

9. The wastewater treatment system according to claim 5, characterized in that, The interval between two adjacent slots is 5mm.

10. The wastewater treatment system according to claim 9, characterized in that, The interval between two adjacent plates (44) is one of 5mm, 10mm, 15mm, 20mm, 25mm, 30mm, 35mm, or 40mm.

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