Multi-stage composite extreme denitrification biochemical system

Abstract

The utility model discloses a multistage composite extreme denitrification biochemical system. The system is divided into an activated sludge treatment section, a biological membrane treatment section and an ecological treatment section, wherein the activated sludge treatment section sequentially comprises an anaerobic tank, a primary limit anoxic tank, an aerobic tank and a secondary anoxic tank, and sewage is injected into the anaerobic tank from a sewage pipeline; the biological membrane treatment section comprises a filler filter, and the ecological treatment section comprises an ecological wetland; a sedimentation tank is arranged between the activated sludge treatment section and the biological membrane treatment section, and the bottom of the sedimentation tank is connected to a sewage pipeline through a sludge conveyor. According to the utility model, the problem that the denitrification effect cannot be further improved when the total reflux ratio of the current mainstream denitrification process is increased to a certain value is solved, the removal effect of nitrogen in sewage is improved, and the total nitrogen concentration of treated sewage effluent is lower than 2mg / L.

Description

Technical Field

[0001] The utility model relates to the technical field of sewage treatment, in particular to a multi-stage composite extreme denitrification biochemical system. Background Art

[0002] In recent years, drainage projects have developed rapidly, and the urban sewage treatment rate has increased year by year. At present, sewage treatment has entered a new stage. In order to improve the quality of water environment, various places have successively issued local sewage treatment discharge standards, and implemented the national standard from the first-class A standard to the quasi-class IV water body standard, requiring total nitrogen to be less than 10mg / L. More stringent emission limits have been proposed in economically developed areas and important watersheds that are sensitive to water environment. The most stringent total nitrogen requirement is less than 5mg / L. It can be seen that in the future, the removal of nitrogen in sewage treatment plants is gradually moving from enhanced denitrification to extreme denitrification. The mainstream denitrification processes currently used in existing sewage treatment plants are traditional processes such as AN / O, A / A / O, Bardenpho, oxidation ditch, and UCT. For the quality of ordinary urban sewage, as long as the operation and management are proper, it can reach the "first-class A" standard.

[0003] At present, the mainstream denitrification process adopted by domestic sewage treatment plants mainly increases the nitrogen removal rate by increasing the mixed liquor recirculation ratio. However, when the total recirculation ratio is 4, increasing the recirculation ratio will not significantly improve the denitrification effect. Therefore, it is difficult to further improve the denitrification effect. Although it can reach the "Level A" standard, it cannot reach the higher "limit denitrification" standard of the future trend. Summary of the invention

[0004] The utility model provides a multi-stage composite extreme denitrification biochemical system, which effectively combines the AO multi-stage activated sludge method, the biofilm method and the natural treatment method, makes extreme use of the carbon source in the sewage itself, reduces the aeration oxygen supply, creates a long-duration multi-stage short-range nitrification and denitrification reaction, and advantageously utilizes facultative oxygen, thereby solving the problem that the denitrification effect cannot be further improved when the total reflux ratio of the current mainstream denitrification process increases to a certain value, improves the removal effect of nitrogen in the sewage, and the total nitrogen concentration of the treated sewage effluent is lower than 2 mg / L.

[0005] In order to achieve the above object, the technical solution of the utility model is as follows:

[0006] A multi-stage composite extreme denitrification biochemical system, the system is divided into an activated sludge treatment section, a biofilm treatment section and an ecological treatment section; wherein the activated sludge treatment section comprises an anaerobic tank, a primary extreme anoxic tank, an aerobic tank and a secondary anoxic tank in sequence, and sewage is injected into the anaerobic tank from a sewage pipe; the biofilm treatment section comprises a filler filter tank, and the ecological treatment section comprises an ecological wetland; a sedimentation tank is arranged between the activated sludge treatment section and the biofilm treatment section, and the bottom of the sedimentation tank is connected to the sewage pipe through a sludge conveyor or a sludge pump.

[0007] The sewage first enters the anaerobic tank, mixes with the return sludge to release phosphorus, and then enters the primary extreme anoxic tank. In the primary extreme anoxic tank, the mixed liquid with the return liquid from the aerobic tank undergoes a denitrification process. The effluent from the aerobic tank then enters the secondary anoxic tank and undergoes denitrification reaction again. That is, the sewage is graded for denitrification before and after the aerobic tank.

[0008] The hydraulic retention time of the anaerobic tank should be controlled within 2 hours, the hydraulic retention time of the first-level extreme anoxic tank should be controlled within 3~6 hours, the hydraulic retention time of the second-level anoxic tank should be controlled within 2~3 hours, and the hydraulic retention time of the anoxic / aerobic tank should be controlled within 9~15 hours.

[0009] The aerobic pool uses short intermittent aeration to control DO at 0.8~2.3mg / L, achieving partial nitritation and nitrification of ammonia nitrogen.

[0010] By controlling the hydraulic retention time, reflow ratio and DO concentration in the aerobic pool, the selective cultivation of anaerobic ammonia-oxidizing bacteria and denitrifying bacteria was achieved in the primary extreme anoxic pool and the secondary anoxic pool. The two bacteria acted synergistically to carry out denitrification, using organic matter and NH3 as electron donors and NO3- and NO2- as electron acceptors to reduce them to N2, thus achieving heterotrophic denitrification and autotrophic denitrification.

[0011] The biofilm treatment section includes a primary filler filter and a secondary filler filter in sequence. The primary filler filter is filled with ceramsite, and the specific surface area of ​​the ceramsite is 500-1000. The secondary filler filter is filled with plastic filler, and the specific surface area of ​​the plastic filler is 500-1000.

[0012] The NO3-N / NO2-N load of the primary filler filter is controlled at 0.74kg / m 3 The NO3--N / NO2-N load in the secondary filler filter is controlled at 0.4kg / m 3 .

[0013] The ecological treatment section includes a primary ecological wetland and a secondary ecological wetland in sequence. The primary ecological wetland is a composite subsurface artificial wetland, and the secondary ecological wetland is mainly an ecological pond type artificial wetland.

[0014] The thickness of the matrix layer in the first-level ecological wetland is 1.0m, and the particle size of the matrix filler increases from bottom to top. The upper layer is 8~15mm volcanic slag with a thickness of 200mm; the middle layer is zeolite with a particle size of 5~10mm and a thickness of 300mm; the lower layer filler is sand and gravel with a particle size of 3~8mm and a thickness of 500mm.

[0015] The water depth of the composite subsurface flow artificial wetland is controlled at 1.0~1.2m; the hydraulic retention time is controlled at 9.0 hours.

[0016] The ecological pond of the ecological pond type artificial wetland is a static pond that imitates natural ecology. Its water depth is controlled at 0.6-1.2 meters. From the edge of the pond to the center of the pond, it is planted with selected wetlands and aquatic plants (mainly Vallisneria). The residual nitrogen and phosphorus elements in the water are further removed through the interception and absorption of wetland fillers (containing zeolite and other fillers with good phosphorus absorption effect) and aerobic and anaerobic coordination of deep-water animals and microorganisms.

[0017] The sewage treatment principle of the utility model is as follows: the sewage purification process of the present invention is as follows: the influent of the sewage treatment plant enters the anaerobic tank after pretreatment, and is mixed with the sludge returned from the sedimentation tank. The phosphorus release of the sludge and partial BOD degradation are mainly carried out in the tank; the effluent of the anaerobic tank enters the primary extreme anoxic tank, and is mixed with the nitro-rich mixed liquid returned from the aerobic tank. The dissolved oxygen in the tank is strictly controlled to be in the anaerobic state of 0.6-0.8 mg / L, and a primary extreme denitrification and denitrification reaction is carried out for 3-6 hours. The main function of this tank is primary extreme denitrification and partial BOD removal; the effluent of the primary extreme anoxic tank enters the aerobic tank, and by controlling the temperature, pH and DO, partial nitrification and nitrite of ammonia nitrogen are achieved to provide nitrate and nitrite for the denitrification reaction, and in addition, BOD oxidation degradation and excessive phosphorus absorption of sludge are also achieved simultaneously; the effluent of the oxidation tank enters the secondary anoxic tank. Since a large amount of BOD in the previous sewage is consumed, in order to ensure the C / N ratio of denitrification, A carbon source is added in this section, and the main function of this pool is to further denitrify the sewage; the effluent from the secondary anoxic pool enters the sedimentation tank for mud-water separation, part of the sludge is returned to the anaerobic tank, and the other part is discharged as residual sludge, and the supernatant effluent enters the next treatment unit; the supernatant effluent from the sedimentation tank enters the primary filler filter and the secondary filler filter in turn, and the pool is provided with filter material, and microorganisms attach to the filter material so that a high biomass can be maintained in the pool. The function of this pool is mainly secondary extreme enhanced denitrification. Since the front-end sewage treatment removes most of the BOD, a carbon source needs to be added to the primary filler filter section to ensure the normal denitrification; the effluent from the secondary biological filter enters the primary ecological wetland and the secondary ecological wetland in turn, and the unique adsorption, degradation and exclusion characteristics of the wetland convert the residual nitrogen in the sewage into resources, and the residual nitrogen in the sewage flowing through the wetland is fixed and deposited in the wetland ecosystem, completing the tertiary extreme denitrification, and the effluent TN of this unit is ≤2mg / L.

[0018] Advantages of utility models

[0019] 1. The utility model effectively combines the AO multi-stage activated sludge method, the biofilm method and the natural treatment method, makes maximum use of the carbon source in the sewage, reduces the aeration oxygen supply, creates a long-duration multi-stage short-range nitrification and denitrification reaction, and advantageously utilizes facultative oxygen, thereby solving the problem that the denitrification effect cannot be further improved when the total reflux ratio of the current mainstream denitrification process increases to a certain value, improves the removal effect of nitrogen in sewage, and the total nitrogen concentration of the treated sewage effluent is lower than 2 mg / L, providing new ideas for the selection of processes for new sewage treatment plants in the future and the upgrading and transformation of existing sewage treatment plants. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of the connection structure of the utility model;

[0021] Figure 2 This is a schematic diagram of the structure of the first-level ecological wetland and the second-level ecological wetland;

[0022] The serial numbers and component names in the figure are: 11-anaerobic tank; 12-first-level extreme anoxic tank; 13-aerobic tank; 14-second-level anoxic tank; 21-sedimentation tank; 22-sludge conveyor; 31-first-level filler filter; 32-second-level filler filter; 41-first-level ecological wetland; 42-second-level ecological wetland. DETAILED DESCRIPTION Example 1

[0023] A multi-stage composite extreme denitrification biochemical system, the system is divided into an activated sludge treatment section, a biofilm treatment section and an ecological treatment section; wherein the activated sludge treatment section comprises an anaerobic tank 11, a primary extreme anoxic tank 12, an aerobic tank 13 and a secondary anoxic tank 14 in sequence, and sewage is injected into the anaerobic tank 11 from a sewage pipe; the biofilm treatment section comprises a filler filter tank, and the ecological treatment section comprises an ecological wetland; a sedimentation tank 21 is arranged between the activated sludge treatment section and the biofilm treatment section, and the bottom of the sedimentation tank 21 is connected to the sewage pipe through a sludge conveyor 22.

[0024] The biofilm treatment section includes a primary filler filter 31 and a secondary filler filter 32 in sequence.

[0025] The ecological treatment section includes a primary ecological wetland 41 and a secondary ecological wetland 42 in sequence.

[0026] The thickness of the matrix layer in the first-level ecological wetland 41 is 1.0m, and the particle size of the matrix filler increases from bottom to top. The upper layer is 8-15mm volcanic slag with a thickness of 200mm; the middle layer is zeolite with a particle size of 5-10mm and a thickness of 300mm; the lower layer filler is sand and gravel with a particle size of 3-8mm and a thickness of 500mm.

Claims

1. A multi-stage composite extreme denitrification biochemical system, characterized in that: The system is divided into an activated sludge treatment section, a biofilm treatment section and an ecological treatment section; wherein the activated sludge treatment section comprises an anaerobic tank (11), a primary extreme anoxic tank (12), an aerobic tank (13) and a secondary anoxic tank (14) in sequence, and sewage is injected into the anaerobic tank (11) from a sewage pipe; the biofilm treatment section comprises a filler filter tank, and the ecological treatment section comprises an ecological wetland; a sedimentation tank (21) is arranged between the activated sludge treatment section and the biofilm treatment section, and the bottom of the sedimentation tank (21) is connected to the sewage pipe via a sludge conveyor (22).

2. The multi-stage composite extreme denitrification biochemical system according to claim 1, characterized in that: The biofilm treatment section comprises a primary filler filter (31) and a secondary filler filter (32) in sequence.

3. The multi-stage composite extreme denitrification biochemical system according to claim 1 is characterized in that: The ecological treatment section includes a primary ecological wetland (41) and a secondary ecological wetland (42) in sequence.

4. The multi-stage composite extreme denitrification biochemical system according to claim 3 is characterized in that: The thickness of the matrix layer in the first-level ecological wetland (41) is 1.0m, and the particle size of the matrix filler increases from bottom to top. The upper layer is volcanic slag with a particle size of 8~15mm and a thickness of 200mm; the middle layer is zeolite with a particle size of 5~10mm and a thickness of 300mm; the lower layer filler is sand and gravel with a particle size of 3~8mm and a thickness of 500mm.

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