Deep nitrogen and phosphorus removal system for low-carbon-nitrogen-ratio domestic sewage

Abstract

The utility model discloses a deep nitrogen and phosphorus removal system for low-carbon-nitrogen-ratio domestic sewage, belongs to the field of sewage treatment, and solves the problem that the low-carbon-nitrogen-ratio domestic sewage is difficult to treat. The device comprises a main water inlet pipe and a plurality of stages of biochemical reaction tanks which are connected in sequence, the biochemical reaction tank comprises an anaerobic tank, an anoxic tank and an aerobic tank, and the anoxic tank and the aerobic tank are sequentially connected to the rear end of the anaerobic tank at intervals; a plurality of branch water inlet pipes are connected to the main water inlet pipe, water inlet valves are arranged on the branch water inlet pipes, the branch water inlet pipes are connected to the anaerobic tanks and the anoxic tanks in a one-to-one correspondence manner, the first-stage anoxic tank is not provided with the branch water inlet pipes, and the last-stage aerobic tank is connected with a main water outlet pipe; the first-stage anoxic tank is connected with an internal reflux water outlet pipe, the anaerobic tank is connected with an internal reflux water inlet pipe, and an internal reflux pump is connected between the internal reflux water outlet pipe and the internal reflux water inlet pipe. According to the utility model, the denitrification efficiency is improved in a multi-section water inlet manner; and through an internal reflux innovative structure, the dephosphorization effect is enhanced.

Description

Technical Field

[0001] This utility model belongs to the field of wastewater treatment, specifically relating to a deep denitrification and phosphorus removal system for domestic wastewater with a low carbon-to-nitrogen ratio. Background Technology

[0002] Nitrogen and phosphorus in domestic sewage, if released directly into water bodies without treatment, will cause eutrophication, leading to the proliferation of algae and other plankton, ultimately resulting in water quality deterioration. In the process of comprehensive water environment management, due to the regional and complex nature of water pollution, pollution problems are difficult to completely curb. Eutrophication problems still exist, especially in some key reservoirs and slow-flowing lakes, directly impacting the aquatic ecosystem and human health.

[0003] With changes in people's lifestyles, the nature of domestic sewage has also changed. Domestic sewage often has a low carbon-to-nitrogen ratio, which increases the difficulty of treatment and leads to the consumption and addition of a large amount of carbon source materials. At present, most sewage treatment plants have basically completed the Class A upgrade. However, under the national strategy of "carbon peaking and carbon neutrality", the addition of a large amount of carbon source materials to domestic sewage with low carbon-to-nitrogen ratio leads to increased energy consumption and carbon emissions from sewage treatment plants, especially for phosphorus removal, which often requires chemical precipitation. This further increases the consumption of chemical agents and the resulting carbon emissions. Against this background, there is a need to develop sewage treatment processes that can deeply remove phosphorus from influent with low carbon-to-nitrogen ratio. Utility Model Content

[0004] The purpose of this invention is to provide a deep nitrogen and phosphorus removal system for domestic sewage with a low carbon-to-nitrogen ratio, in order to solve the problem of the difficulty in treating domestic sewage with a low carbon-to-nitrogen ratio.

[0005] The technical solution of this utility model is: a deep nitrogen and phosphorus removal system for domestic sewage with low carbon-to-nitrogen ratio, comprising a main inlet pipe and multiple biochemical reaction tanks connected in sequence; the biochemical reaction tanks include an anaerobic tank, an anoxic tank, and an aerobic tank, with the anoxic tank and aerobic tank connected sequentially at intervals at the rear end of the anaerobic tank; multiple branch inlet pipes are connected to the main inlet pipe, each branch inlet pipe is equipped with an inlet valve, and the branch inlet pipes are connected one-to-one to the anaerobic tank and each anoxic tank; the first-stage anoxic tank is not equipped with a branch inlet pipe, and the last-stage aerobic tank is connected to the main outlet pipe; the first-stage anoxic tank is connected to an internal return outlet pipe, the anaerobic tank is connected to an internal return inlet pipe, and an internal return pump is connected between the internal return outlet pipe and the internal return inlet pipe.

[0006] As a further improvement of this utility model, it also includes a sedimentation tank, in which a membrane reactor is installed. The main effluent pipe is connected to the input end of the membrane reactor, and the output end of the membrane reactor is provided with an output pipe, on which an output pump is provided.

[0007] As a further improvement of this utility model, a sludge discharge main pipe is provided at the bottom of the sedimentation tank. The sludge discharge main pipe is connected to a return sludge pipe and a discharge pipe. The return sludge pipe is connected to the first-stage anoxic tank. A return sludge pump is provided on the return sludge pipe, and a discharge valve is provided on the discharge pipe.

[0008] As a further improvement of this utility model, the membrane reactor is connected to a backwash pipe, and a backwash pump is installed on the backwash pipe.

[0009] As a further improvement of this utility model, the anaerobic tank and the anoxic tank are equipped with vertical plates, the lower end of which is not connected to the bottom of the tank and is bent.

[0010] As a further improvement of this utility model, each biochemical reaction tank is provided with an arc-shaped plate at its lower corner.

[0011] As a further improvement of this utility model, both the anaerobic tank and the anoxic tank are equipped with a cover plate, and elastic three-dimensional packing material is suspended inside the anaerobic tank and the anoxic tank.

[0012] As a further improvement of this utility model, the top of the aerobic tank is not covered, and the aerobic tank is filled with suspended porous spherical shell packing.

[0013] As a further improvement of this utility model, it also includes an aeration pump, the output end of which is connected to an aeration main pipe, and multiple aeration branch pipes are connected to the aeration main pipe. Each aeration branch pipe is connected to the aerobic tank in a corresponding manner, and an aeration valve is provided on the aeration branch pipe.

[0014] The beneficial effects of this utility model are:

[0015] 1. This utility model designs a multi-stage water intake method for anaerobic and anoxic tanks, which improves carbon source utilization, effectively ensures the carbon source concentration in each stage, and improves denitrification efficiency.

[0016] 2. This invention features an innovative internal recirculation structure. The internal recirculation between the anaerobic tank and the first-stage anoxic tank enhances the alternation of anaerobic and anoxic environments, promoting the accumulation of facultative anaerobic bacteria—denitrifying polyphosphate-accumulating bacteria—and strengthening the system's phosphorus removal. The internal recirculation design solves the problem of increased dissolved oxygen in the anaerobic tank due to sludge recirculation, preventing its damage to the anaerobic environment. This optimized environment encourages polyphosphate-accumulating bacteria and denitrifying polyphosphate-accumulating bacteria to fully release phosphorus, thereby improving the phosphorus uptake effect of both types of microorganisms in the anoxic and aerobic zones, strengthening phosphorus removal, avoiding the high operating costs associated with large-scale chemical dosing, and also enhancing nitrogen removal.

[0017] 3. This invention can effectively increase nitrate concentration, thereby further promoting the phosphorus uptake rate of denitrifying polyphosphate-accumulating bacteria, which is beneficial to improving phosphorus removal efficiency. Compared with the prior art, it also eliminates the internal reflux measure of nitrification liquid, further reducing energy consumption. In addition, it enhances the solid-liquid separation effect and ensures the stability of effluent.

[0018] 4. This invention achieves complete separation of hydraulic retention time and sludge age, which is more conducive to flexible process control. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of this utility model;

[0020] Figure 2 This is a partial enlarged view of the anaerobic tank, anoxic tank, and aerobic tank in this utility model;

[0021] Figure 3 This is a bar chart showing the removal rate of conventional pollutants in Embodiment 1 of this utility model;

[0022] Figure 4 This is a bar chart showing the total phosphorus removal rate of Embodiment 2 of this utility model.

[0023] In the diagram: 101-Anaerobic tank; 102-Anoxic tank; 103-Aerobic tank; 108-Vertical plate; 109-Inlet zone; 110-Outlet zone; 111-Upper water passage; 112-Arc-shaped plate; 113-Middle water passage; 201-Sedimentation tank; 202-Membrane reactor; 205-Backwash pipe; 206-Backwash pump; 301-Sludge discharge main pipe; 303-Return sludge pump; 304-Return sludge pipe; 305-Discharge valve; 306 - Discharge pipe; 401- Aeration pump; 402- Aeration main pipe; 403- Aeration valve; 404- Aeration branch pipe; 501- Main inlet pipe; 502- Branch inlet pipe; 503- Inlet valve; 510- Main outlet pipe; 511- Output pump; 512- Output pipe; 601- Internal return pump; 602- Internal return outlet pipe; 603- Internal return inlet pipe; 701- Elastic three-dimensional packing; 703- Support; 704- Suspended porous spherical shell packing. Detailed Implementation

[0024] The present invention will now be described in detail with reference to the accompanying drawings.

[0025] Example 1

[0026] like Figure 1 , Figure 2As shown, a deep nitrogen and phosphorus removal system for domestic sewage with a low carbon-to-nitrogen ratio includes a main inlet pipe 501 and multiple biological reaction tanks connected in sequence. The biological reaction tanks include an anaerobic tank 101, an anoxic tank 102, and an aerobic tank 103. The anoxic tank 102 and aerobic tank 103 are connected sequentially at intervals at the rear end of the anaerobic tank 101. The anoxic tank 102 is connected to the previous biological reaction tank through an upper water passage 111, and the anoxic tank 102 is also connected to the previous biological reaction tank through a middle water passage 113. The main inlet pipe 501 is connected to... There are multiple branch inlet pipes 502, each equipped with an inlet valve 503. The branch inlet pipes 502 are connected one-to-one to the anaerobic tank 101 and each anoxic tank 102. The first-stage anoxic tank 102 does not have a branch inlet pipe 502. The last-stage aerobic tank 103 is connected to a main outlet pipe 510. The first-stage anoxic tank 102 is connected to an internal return outlet pipe 602, and the anaerobic tank 101 is connected to an internal return inlet pipe 603. An internal return pump 601 is connected between the internal return outlet pipe 602 and the internal return inlet pipe 603.

[0027] It also includes a sedimentation tank 201, in which a membrane reactor 202 is suspended and installed. A main outlet pipe 510 is connected to the input end of the membrane reactor 202. The output end of the membrane reactor 202 is provided with an output pipe 512, and an output pump 511 is provided on the output pipe 512.

[0028] The sedimentation tank 201 is equipped with a sludge discharge main pipe 301 at the bottom. The sludge discharge main pipe 301 is connected to a return sludge pipe 304 and a discharge pipe 306. The return sludge pipe 304 is connected to the first-stage anoxic tank 102. The return sludge pipe 304 is equipped with a return sludge pump 303, and the discharge pipe 306 is equipped with a discharge valve 305.

[0029] The membrane reactor 202 is connected to a backwash pipe 205, and a backwash pump 206 is installed on the backwash pipe 205.

[0030] The anaerobic tank 101 and the anoxic tank 102 are equipped with vertical plates 108. The lower end of the vertical plate 108 is not connected to the bottom of the tank and is bent. The angle between the bent section and the vertical direction is 60°. The two sides of the vertical plate 108 are the inlet zone 109 and the outlet zone 110, respectively. The volume ratio of the inlet zone 109 to the outlet zone 110 is 1:4.5.

[0031] Each biochemical reaction tank is equipped with an arc-shaped plate 112 at the lower corner to prevent water flow dead zone.

[0032] Both the anaerobic tank 101 and the anoxic tank 102 are equipped with a cover plate. Elastic three-dimensional packing material 701 is suspended in the anaerobic tank 101 and the anoxic tank 102 by a bracket 703.

[0033] The aerobic tank 103 is not covered at the top, and the aerobic tank 103 is filled with suspended porous spherical shell packing 704.

[0034] It also includes an aeration pump 401, the output end of which is connected to an aeration main pipe 402. Multiple aeration branch pipes 404 are connected to the aeration main pipe 402, and each aeration branch pipe 404 is connected to the aerobic tank 103. An aeration valve 403 is provided on each aeration branch pipe 404.

[0035] Anoxic tank 102 contains no dissolved oxygen but contains nitrate nitrogen; anaerobic tank 101 is a non-oxygenated zone, containing neither dissolved oxygen nor nitrate nitrogen. The sludge in anaerobic tank 101 is taken from the anaerobic granular sludge of the anaerobic treatment process section of the beer wastewater treatment plant; the sludge in aerobic tank 103 is taken from the aerobic section of the municipal wastewater treatment plant, and the dissolved oxygen concentration in the aerobic tank is 1.55 mg / L.

[0036] Raw water is distributed from the main inlet pipe 501 to the branch inlet pipes 502, and enters the anaerobic tank 101 and other anoxic tanks 102 except for the first-stage anoxic tank 102. The raw water in the anaerobic tank 101 is treated and then enters the subsequent stages of the biochemical reaction tanks. The raw water entering the anoxic tank 102 is mixed with the water treated in the previous stage of the biochemical reaction tank and then enters the subsequent stages of the biochemical reaction tanks. Finally, the water is discharged from the main outlet pipe 510 and enters the membrane reactor 202. The treated water is discharged from the outlet pipe 512 under the action of the outlet pump 511.

[0037] In this embodiment, the anoxic tank 102 and the aerobic tank 103 are each equipped with three stages; there are three water inlet pipes 502, which are respectively connected to the anaerobic tank 101, the second-stage anoxic tank 102 and the third-stage anoxic tank 102. The water inlet flow rate is controlled by the water inlet valve 503, and the water inlet flow rates are 51.5%, 34.5% and 14.0% respectively.

[0038] During operation, the internal recirculation pump 601 is activated to recirculate water from the first-stage anoxic tank 102 back to the anaerobic tank 101, thereby enhancing the alternation of anaerobic and anoxic environments. This promotes the accumulation of facultative anaerobic bacteria—denitrifying polyphosphate-accumulating bacteria—and helps to enhance the system's phosphorus removal. The internal recirculation ratio is 24%.

[0039] Aeration pump 401 aerates the air and delivers it to each aerobic tank 103 via aeration main pipe 402 and aeration branch pipes 404. The aeration flow rate of each aeration branch pipe 404 is controlled by aeration valve 403. Aeration branch pipes 404 are microporous aeration pipes.

[0040] After the sludge settled in the sedimentation tank 201 is discharged through the sludge discharge main pipe 301, part of it is discharged through the discharge pipe 306, and part of it is returned to the first-stage anoxic tank 102 through the return sludge pipe 304 and the return sludge pump 303. The sludge return ratio is 49.5%.

[0041] After running for a period of time, the membrane reactor 202 is backwashed through the backwash pump 206 and the backwash pipe 205.

[0042] The influent conditions in this embodiment are as follows: the influent COD concentration ranges from 215.6 to 358.4 mg / L, with an average concentration of 296.4 mg / L; the TN concentration ranges from 215.6 to 358.4 mg / L, with an average concentration of 296.4 mg / L; and the ammonia nitrogen concentration ranges from 36.4 to 50.9 mg / L, with an average concentration of 44.2 mg / L.

[0043] The removal rates of conventional pollutant indicators such as COD, TN, and ammonia nitrogen in this embodiment are as follows: Figure 3 As shown, the average removal rates were 88.49%, 76.34%, and 94.23%, respectively. The concentrations of conventional pollutants such as COD, TN, and ammonia nitrogen in the effluent all met the Class A discharge standard of the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants" (GB 18918-2002).

[0044] Example 2

[0045] The device in this embodiment is the same as that in Embodiment 1.

[0046] The removal rate of total phosphorus in this embodiment is as follows: Figure 4 As shown, under the conditions of influent TP concentration range of 2.71~6.21 mg / L and average concentration of 4.68 mg / L, the average TP removal rate is 82.85%, and the average TP removal rate reaches 86.71% during the 20th~30th day of stable operation. The average TP concentration in the effluent meets the Class A discharge standard of the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants" (GB 18918-2002).

[0047] On days 10, 20, and 30, the phosphate concentrations during anaerobic phosphorus release were measured and found to be 20.93 mg / L, 26.56 mg / L, and 29.19 mg / L (150 minutes), respectively. In contrast, the phosphate concentration in conventional multi-stage A / O processes increased from 6.11 mg / L to 13.51 mg / L (150 minutes) during anaerobic phosphorus release, demonstrating the superior anaerobic phosphorus release effect of this invention.

[0048] Under anoxic conditions, the phosphorus uptake rates were 0.0710 mg / (g·h), 0.1411 mg / (g·h), 0.2757 mg / (g·h), and 0.3128 mg / (g·h); under aerobic conditions, the aerobic phosphorus uptake rates were 0.3798 mg / (g·h), 0.7211 mg / (g·h), 1.162 mg / (g·h), and 1.246 mg / (g·h). Therefore, the proportion of denitrifying polyphosphate-accumulating bacteria in the system of this invention is 17.89%, 18.95%, 25.02%, and 25.98% of the total polyphosphate-accumulating bacteria. Compared with the conventional multi-stage A / O process, this proportion can be increased from 17.89% to 25.78%. This demonstrates that this invention can significantly increase the number of denitrifying polyphosphate-accumulating bacteria, thereby increasing the denitrification reaction rate and achieving deep phosphorus removal from the influent under low C / N ratio conditions.

[0049] This invention enhances the treatment of phosphorus in domestic sewage with a low carbon-to-nitrogen ratio. Through an innovative internal reflux design, it solves the problem of increased dissolved oxygen in the anaerobic tank due to sludge recirculation, preventing damage to the anaerobic environment. This environmental optimization promotes the full release of phosphorus by polyphosphate-accumulating bacteria and denitrifying polyphosphate-accumulating bacteria, thereby improving the phosphorus uptake effect of these two types of microorganisms in both anoxic and aerobic zones. This strengthens phosphorus removal and avoids the high operating costs associated with large-scale chemical dosing. In the context of "dual carbon" (carbon and nitrogen ratio), applying energy-saving technologies to rural sewage treatment is a crucial guarantee for achieving high-quality economic development and offers valuable insights for solving rural sewage treatment challenges.

Claims

1. A system for advanced nitrogen and phosphorus removal from low carbon-nitrogen ratio domestic sewage, characterized in that: It includes total water inlet pipe (501) and multi-stage biochemical reaction tank connected in turn; the biochemical reaction tank includes anaerobic tank (101), anoxic tank (102) and aerobic tank (103), and the anoxic tank (102) and the aerobic tank (103) are connected in turn at the rear end of the anaerobic tank (101); a plurality of branch water inlet pipes (502) are connected to the total water inlet pipe (501), the branch water inlet pipe (502) is provided with a water inlet valve (503), the branch water inlet pipe (502) is connected to the anaerobic tank (101) and each anoxic tank (102) one by one, the first-stage anoxic tank (102) is not provided with a branch water inlet pipe (502), and the last-stage aerobic tank (103) is connected with a total water outlet pipe (510); the first-stage anoxic tank (102) is connected with an internal reflux outlet pipe (602), the anaerobic tank (101) is connected with an internal reflux inlet pipe (603), and the internal reflux outlet pipe (602) and the internal reflux inlet pipe (603) are connected with an internal reflux pump (601); The anaerobic tank (101) and the anoxic tank (102) are provided with vertical plates (108), and the lower ends of the vertical plates (108) are not connected with the tank bottom and are bent; Each biochemical reaction tank is provided with an arc-shaped plate (112) at the corner of the lower end; The anaerobic tank (101) and the anoxic tank (102) are provided with cover plates at the top, and the anaerobic tank (101) and the anoxic tank (102) are suspended with elastic three-dimensional fillers (701); The aerobic tank (103) is not provided with a cover plate at the top, and the aerobic tank (103) is provided with a suspended porous spherical shell filler (704).

2. The system for advanced nitrogen and phosphorus removal of low C / N domestic sewage according to claim 1, characterized in that: It also includes a sedimentation tank (201), a membrane reactor (202) is installed in the sedimentation tank (201), the total water outlet pipe (510) is connected to the input end of the membrane reactor (202), the output end of the membrane reactor (202) is provided with an output pipe (512), and the output pipe (512) is provided with an output pump (511).

3. The system for advanced nitrogen and phosphorus removal of low C / N domestic sewage according to claim 2, characterized in that: The sedimentation tank (201) is provided with a sludge discharge main pipe (301) at the bottom, the sludge discharge main pipe (301) is connected with a reflux sludge pipe (304) and a discharge pipe (306), the reflux sludge pipe (304) is connected to the first-stage anoxic tank (102), the reflux sludge pipe (304) is provided with a reflux sludge pump (303), and the discharge pipe (306) is provided with a discharge valve (305).

4. The system for advanced nitrogen and phosphorus removal of low C / N domestic sewage according to claim 3, characterized in that: The membrane reactor (202) is connected with a backwashing pipe (205), and the backwashing pipe (205) is provided with a backwashing pump (206).

5. The system for advanced nitrogen and phosphorus removal of low C / N domestic sewage according to any one of claims 1-4, characterized in that: It also includes an aeration pump (401), the output end of the aeration pump (401) is connected with an aeration main pipe (402), a plurality of aeration branch pipes (404) are connected to the aeration main pipe (402), and the aeration branch pipes (404) are connected to the aerobic tank (103) one by one, and the aeration branch pipes (404) are provided with aeration valves (403).

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