AAOA sewage treatment system and method

Abstract

The invention provides an AAOA sewage treatment system and method, and relates to the technical field of sewage treatment. The AAOA sewage treatment system provided by the invention comprises an anoxic tank, an anaerobic tank, an aerobic tank and a secondary sedimentation tank which are sequentially arranged according to the flow direction of sewage, an aerobic zone front section, an aerobic zone middle section and an anoxic zone tail section are sequentially arranged in the aerobic tank. On the basis of the original AAO sewage treatment system, the anoxic zone is added to the last section of the aerobic tank. Compared with an AAO (anaerobic-anoxic-oxic) sewage treatment system, the AAOA sewage treatment system disclosed by the invention is used for treating sewage, so that the nitrate radical and the total nitrogen concentration of effluent can be reduced, the dosage of an external carbon source is reduced, the sewage treatment cost is reduced, the nitrogen removal effect is improved, and the effluent quality is obviously improved.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and in particular to an AAOA sewage treatment system and method. Background Art

[0002] At present, the influent of my country's sewage treatment plants is generally low in carbon-nitrogen ratio, so additional carbon sources need to be added to meet the requirements of denitrification. The AAO (Anaerobic-Anoxic-Oxic) sewage treatment process is an efficient biological denitrification and phosphorus removal process. It purifies sewage through three key stages, namely anaerobic tanks, anoxic tanks and aerobic tanks. Each stage promotes specific biochemical reactions to remove organic matter, nitrogen, phosphorus and other pollutants in sewage. However, the existing AAO sewage treatment process has a large amount of carbon source addition, but the total nitrogen in the effluent, including nitrate, has not decreased significantly. Summary of the invention

[0003] In view of this, the object of the present invention is to provide an AAOA sewage treatment system and method. The AAOA sewage treatment system provided by the present invention is used to treat sewage, with low carbon source consumption, low nitrate concentration in effluent, and low total nitrogen concentration.

[0004] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0005] The present invention provides an AAOA sewage treatment system, which comprises an anoxic tank, an anaerobic tank, an aerobic tank and a secondary sedimentation tank which are arranged in sequence according to the sewage flow direction; the aerobic tank is provided with an aerobic zone front section, an aerobic zone middle section and an anoxic zone end section in sequence; the anoxic tank and / or the anoxic zone end section is provided with a carbon source addition port.

[0006] Preferably, a nitrification liquid reflux pipeline is connected between the end section of the anoxic zone and the anoxic pool.

[0007] Preferably, a sludge external return pipeline is connected between the secondary sedimentation tank and the anoxic tank.

[0008] The present invention also provides an AAOA sewage treatment method, which is carried out using the AAOA sewage treatment system described in the above technical solution, and comprises the following steps:

[0009] A carbon source is added, and the sewage is sequentially denitrified in an anoxic tank, anaerobic phosphorus release is carried out in an anaerobic tank, the first nitrification is carried out in the front section of the aerobic zone, the second nitrification is carried out in the middle section of the aerobic zone, the anaerobic phosphorus release-denitrification is carried out in the last section of the anoxic zone, and sedimentation is carried out in a secondary sedimentation tank to obtain purified water; the carbon source is added to the anoxic tank and / or the last section of the anoxic zone.

[0010] Preferably, the total COD concentration in the sewage is 40-120 mg / L, and the total nitrogen concentration is 38-55 mg / L.

[0011] Preferably, the nitrified liquid obtained by anaerobic phosphorus release-denitrification is refluxed into the anoxic tank; the reflux ratio of the nitrified liquid is 100-200%.

[0012] Preferably, the dissolved oxygen concentration in the anoxic tank is 0.3-0.4 mg / L.

[0013] Preferably, the dissolved oxygen concentration in the anaerobic tank is 0.09-0.11 mg / L.

[0014] Preferably, the dissolved oxygen concentration in the front section of the aerobic zone is 1 to 2 mg / L;

[0015] The dissolved oxygen concentration in the middle section of the aerobic zone is 1 to 2 mg / L;

[0016] The dissolved oxygen concentration in the final section of the anoxic zone is 0.3-0.4 mg / L.

[0017] Preferably, the sludge obtained by the precipitation is returned to the anoxic tank; the return ratio of the sludge is 50-70%.

[0018] The present invention provides an AAOA sewage treatment system, which includes an anoxic tank, an anaerobic tank, an aerobic tank and a secondary sedimentation tank arranged in sequence according to the flow direction of sewage; the aerobic tank is provided with an aerobic zone front section, an aerobic zone middle section and an anoxic zone end section in sequence; the anoxic tank is provided with a carbon source addition port. Based on the original AAO sewage treatment system, the present invention adds an anoxic zone to the last section of the aerobic tank. Compared with the AAO sewage treatment system, the AAOA sewage treatment system of the present invention is used to treat sewage, which can further denitrify the nitrate brought by the aerobic tank, reduce the concentration of nitrate and total nitrogen in the effluent, reduce the amount of added carbon source, reduce the cost of sewage treatment, improve the nitrogen removal effect, and significantly improve the effluent water quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A schematic diagram of the structure of the AAOA sewage treatment system provided by the present invention;

[0020] Figure 2 This is a diagram of the operation mode of sewage in the anoxic tank, anaerobic tank and aerobic tank in the present invention. DETAILED DESCRIPTION

[0021] The present invention provides an AAOA sewage treatment system, which includes an anoxic tank, an anaerobic tank, an aerobic tank and a secondary sedimentation tank arranged in sequence according to the sewage flow direction; the aerobic tank is provided with an aerobic zone front section, an aerobic zone middle section and an anoxic zone end section in sequence; the anoxic tank and / or the anoxic zone end section is provided with a carbon source addition port. The structural schematic diagram of the AAOA sewage treatment system is shown in FIG. Figure 1 .

[0022] The AAOA sewage treatment system provided by the present invention comprises an anoxic tank, wherein the anoxic tank is preferably provided with a first carbon source addition port, a first water inlet, a first water outlet, a reflux nitrification liquid inlet and a reflux sludge inlet.

[0023] The AAOA sewage treatment system provided by the present invention comprises an anaerobic tank, wherein the anaerobic tank is preferably provided with a second water inlet and a second water outlet, and the second water inlet is connected to the first water outlet.

[0024] The AAOA sewage treatment system provided by the present invention includes an aerobic pool. According to the flow direction of sewage, the aerobic pool is sequentially provided with an aerobic zone front section, an aerobic zone middle section and an anoxic zone end section; the aerobic zone front section is preferably provided with a third water inlet and a third water outlet, and the third water inlet is connected to the second water outlet; the aerobic zone middle section is preferably provided with a fourth water inlet and a fourth water outlet, and the fourth water inlet is connected to the third water outlet; the anoxic zone end section is preferably provided with a second carbon source addition port, a fifth water inlet, a fifth water outlet and a digestion liquid reflux port, and the fifth fourth water inlet is connected to the fourth water outlet. In the present invention, the volume ratio of the aerobic zone front section, the aerobic zone middle section and the anoxic zone end section in the aerobic pool is preferably 1:1:1.

[0025] In the present invention, a nitrifying liquid internal reflux pipe is preferably connected between the end section of the anoxic zone and the anoxic pool, and the digestion liquid reflux port is connected to the reflux nitrifying liquid inlet through the nitrifying liquid internal reflux pipe.

[0026] The AAOA sewage treatment system provided by the present invention includes a secondary sedimentation tank, which is preferably provided with a sixth water inlet, a sixth water outlet and a sludge outlet; the sixth water inlet is connected to the fifth water outlet; the secondary sedimentation tank and the anoxic tank are preferably also connected by a sludge external return pipe, and the sludge outlet is connected to the return sludge inlet through the sludge external return pipe.

[0027] The present invention also provides an AAOA sewage treatment method, which is carried out using the AAOA sewage treatment system described in the above technical solution, including the following steps: adding a carbon source, the sewage is sequentially denitrified in an anoxic tank, anaerobic phosphorus release is carried out in an anaerobic tank, the first nitrification is carried out in the front section of the aerobic zone, the second nitrification is carried out in the middle section of the aerobic zone, the anaerobic phosphorus release-denitrification is carried out in the last section of the anoxic zone, and the second sedimentation tank is used for precipitation to obtain purified water; the carbon source is added to the anoxic tank and / or the last section of the anoxic zone. The operation mode of sewage in the anoxic tank, anaerobic tank and aerobic tank is shown in FIG. Figure 2 .

[0028] The present invention has no special limitation on the carbon source, and any carbon source known to those skilled in the art can be used, such as one or more of glucose, methanol, acetate and starch. In the present invention, the ratio of the mass of the carbon source to the volume of the sewage is preferably 150-180 g: 1 m 3, more preferably 155 to 175 g: 1m 3 , more preferably 160 to 170 g: 1m 3 .

[0029] In the present invention, the total COD concentration in the sewage is preferably 40-120 mg / L, more preferably 50-110 mg / L, and most preferably 70-90 mg / L; the COD preferably includes at least one of the organic nitrogen in C_I (difficult to degrade soluble COD, COD that is not available to microorganisms) and C_S (easily degradable soluble COD, COD that can provide a carbon source for microorganisms), and the concentration of C_I in the sewage is preferably 10-60 mg / L, more preferably 20-50 mg / L, and most preferably 30-40 mg / L; the concentration of C_S in the sewage is preferably 30-60 mg / L, more preferably 35-55 mg / L, and most preferably 40-50 mg / L.

[0030] In the present invention, the total nitrogen concentration in the sewage is preferably 38 to 55 mg / L, more preferably 38 to 55 mg / L. In the present invention, the total nitrogen preferably includes ammonia nitrogen (NH4 + ), nitrate (NO3 - ), C_ND (biodegradable soluble organic nitrogen), organic nitrogen in C_I, X_ND (biodegradable particulate organic nitrogen) and organic nitrogen in X_S (easily degradable particulate COD). In the present invention, the concentration of ammonia nitrogen in the sewage is preferably 15-25 mg / L, more preferably 20-23 mg / L; nitrate (C_NH4 + ) concentration is preferably 10-20 mg / L, more preferably 14-16 mg / L; C_ND concentration is preferably 1-3 mg / L, more preferably 2-2.8 mg / L; the concentration of organic nitrogen in C_I is preferably 1-3 mg / L, more preferably 2-2.4 mg / L; X_ND concentration is preferably 1-3 mg / L, more preferably 1.6-2, the concentration of organic nitrogen in X_S is preferably 0.1-0.3 mg / L, more preferably 0.15-0.2 mg / L.

[0031] In the present invention, the temperature of denitrification, anaerobic phosphorus release, first nitrification, second nitrification, and anaerobic phosphorus release-precipitation is independently preferably 15-25° C., more preferably 20-25° C. In the present invention, the hydraulic retention time of the anoxic tank is preferably 3.5-4 hours, more preferably 3.7 hours; the hydraulic retention time of the anaerobic tank is preferably 1.2-1.6 hours, more preferably 1.5 hours; the hydraulic retention time of the front section of the aerobic zone is preferably 3.4-3.8 hours, more preferably 3.5 hours; the hydraulic retention time of the middle section of the aerobic zone is preferably 3.4-3.8 hours, more preferably 3.5 hours; the hydraulic retention time of the last section of the anoxic zone is preferably 3.4-3.8 hours, more preferably 3.5 hours.

[0032] In the present invention, the dissolved oxygen (DO) concentration in the anoxic tank is preferably 0.3-0.4 mg / L, more preferably 0.35 mg / L.

[0033] In the present invention, the dissolved oxygen concentration in the anaerobic tank is preferably 0.09-0.11 mg / L, more preferably 0.1 mg / L.

[0034] In the present invention, the dissolved oxygen concentration in the front section of the aerobic zone is preferably 1-2 mg / L, more preferably 2 mg / L; the dissolved oxygen concentration in the middle section of the aerobic zone is preferably 1-2 mg / L, more preferably 1 mg / L; the dissolved oxygen concentration in the end section of the anoxic zone is preferably 0.3-0.4 mg / L, more preferably 0.3-0.35 mg / L. The present invention can slowly reduce the DO value of sewage by controlling the dissolved oxygen concentrations in the front section of the aerobic zone, the middle section of the aerobic zone and the end section of the anoxic zone.

[0035] In the present invention, the nitrified liquid obtained by the second anaerobic phosphorus release is preferably returned to the anoxic tank (internal circulation of the nitrified liquid); the reflux ratio of the nitrified liquid is preferably 100-200%, more preferably 130-170%, and most preferably 150%. By returning the nitrified liquid to the anoxic tank, the present invention can cause the nitrate that has not undergone denitrification to return to the anoxic tank for further denitrification.

[0036] In the present invention, the sludge obtained by the precipitation is preferably returned to the anoxic tank (external circulation of sludge); the return ratio of the sludge is preferably 50-70%, preferably 55-65%, and most preferably 60%. The present invention controls the return ratio of the sludge within the above range, and can replenish sludge for the system.

[0037] The present invention transforms part (e.g., one-third) of the corridors in the original aerobic zone into anoxic tanks to form an AAOA process mode. The influent undergoes denitrification and anaerobic phosphorus release in the anaerobic tank and the anoxic tank, and nitrification occurs in the aerobic tank. Compared with the AAO process, the method provided by the present invention can reduce the concentration of nitrate and total nitrogen in the effluent, reduce the dosage of the added carbon source, reduce the cost of sewage treatment, improve the nitrogen removal effect, and significantly improve the effluent water quality.

[0038] In order to further illustrate the present invention, an AAOA sewage treatment system and method provided by the present invention are described in detail below in conjunction with embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0039] Example 1

[0040] use Figure 1 The device shown in the figure is used for sewage treatment. The specific steps are as follows: glucose is added to the anoxic tank (recorded as the pre-addition of carbon source), the sewage is sequentially denitrified in the anoxic tank, the first anaerobic phosphorus release is carried out in the anaerobic tank, the first nitrification is carried out in the front section of the aerobic zone, the second nitrification is carried out in the middle section of the aerobic zone, the second anaerobic phosphorus release and denitrification are carried out in the last section of the anoxic zone, and the second sedimentation tank is used for precipitation to obtain purified water. The volume ratio of the front section of the aerobic zone, the middle section of the aerobic zone and the last section of the anoxic zone in the aerobic tank is 1:1:1. Among them, the ratio of the glucose addition mass to the sewage volume is 170g:1m 3 ; The sewage treatment temperature is 20℃; The DO concentration in the anoxic tank is 0.3mg / L, the DO concentration in the anaerobic tank is 0.1mg / L, the DO concentration in the front section of the aerobic zone is 2mg / L, the DO concentration in the middle section of the aerobic tank is 1.0mg / L, and the DO concentration in the end section of the anoxic zone is 0.3mg / L. The nitrification liquid does not return, and the sludge return ratio is 60%. The total COD concentration of the influent is 75mg / L, of which C_I is 40mg / L and C_S is 35mg / L; The total nitrogen concentration of the influent is 46mg / L, of which ammonia nitrogen is 23mg / L, nitrate ion is 16mg / L, C_ND is 2.8mg / L, organic nitrogen in C_I is 2.4mg / L, X_ND is 1.6mg / L, and organic nitrogen in X_S is 0.2mg / L. Hydraulic retention time: 3.7h in anoxic tank, 1.5h in anaerobic tank, 3.5h in the first section of aerobic zone, 3.5h in the middle section of aerobic zone, and 3.5h in the last section of anoxic zone. The concentration of each component in the purified water (effluent) is shown in Table 1.

[0041] Comparative Example 1

[0042] The only difference from Example 1 is that Figure 1 The end of the anoxic zone is adjusted to the end of the aerobic zone, and the DO concentration in the end of the aerobic zone is 2 mg / L.

[0043] Table 1 Water composition of Example 1 and Comparative Example 1

[0044]

[0045] The requirements in Table 1 are the Level A requirements of the Pollutant Discharge Standard for Urban Wastewater Treatment Plants (GB18918-2002).

[0046] As can be seen from Table 1, in the original AAO structure, after the end of the aerobic zone in the aerobic pool was changed into anoxic zone, it can be clearly seen in the nitrogen pollution indicators that the nitrate concentration was reduced by 28.65%, and the nitrate concentration was significantly reduced; the ammonia nitrogen concentration increased, but within the effluent specification (GB18918-2002), the total nitrogen concentration decreased by 9.29%, and the increase in total COD concentration was negligible.

[0047] Example 2

[0048] The only difference from Example 1 is that the reflux ratio of the nitrification liquid is 150%. The concentrations of the components in the effluent are shown in Table 2.

[0049] Example 3

[0050] The only difference from Example 1 is that the reflux ratio of the nitrification solution is 150%, and the carbon source is added to the last section of the anoxic zone (recorded as post-addition of the carbon source). The concentrations of the components in the effluent are shown in Table 2.

[0051] Example 4

[0052] The only difference from Example 1 is that the nitrification liquid reflux ratio is 150%, and the carbon source is added to the anoxic pool and the end of the anoxic zone at 50 wt% each (recorded as equal addition of carbon source). The concentrations of the components in the effluent are shown in Table 2.

[0053] Example 5

[0054] The only difference from Example 1 is that the nitrification liquid reflux ratio is 150%, 25 wt% of the carbon source is added from the anoxic tank, and 75 wt% is added from the end of the anoxic zone. The concentrations of the components in the effluent are shown in Table 2.

[0055] Example 6

[0056] The only difference from Example 1 is that the nitrification liquid reflux ratio is 150%, 75 wt% of the carbon source is added from the anoxic tank, and 25 wt% is added from the end of the anoxic zone. The concentrations of the components in the effluent are shown in Table 2.

[0057] Table 2 Effect of nitrification solution reflux mode and carbon source addition point on effluent composition in Examples 1 to 6 and Comparative Example 1

[0058]

[0059] It can be seen from Tables 1 and 2 that the total nitrogen in the effluent can be reduced by refluxing the nitrification solution. The total nitrogen in the effluent can be further reduced by adding the carbon source from the anoxic pool and the end of the anoxic zone, thereby achieving cost reduction and efficiency improvement in sewage treatment.

[0060] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. An AAOA sewage treatment system, comprising an anoxic tank, an anaerobic tank, an aerobic tank and a secondary sedimentation tank arranged in sequence according to the sewage flow direction; the aerobic tank is provided with an aerobic zone front section, an aerobic zone middle section and an anoxic zone end section in sequence; the anoxic tank and / or the anoxic zone end section is provided with a carbon source addition port.

2. The AAOA sewage treatment system according to claim 1, characterized in that: A nitrification liquid reflux pipeline is also connected between the end section of the anoxic zone and the anoxic pool.

3. The AAOA sewage treatment system according to claim 1, characterized in that: A sludge external return pipeline is also connected between the secondary sedimentation tank and the anoxic tank.

4. A method for treating AAOA wastewater, using the AAOA wastewater treatment system according to any one of claims 1 to 3, comprising the following steps: A carbon source is added, and the sewage is sequentially denitrified in an anoxic tank, anaerobic phosphorus release is carried out in an anaerobic tank, the first nitrification is carried out in the front section of the aerobic zone, the second nitrification is carried out in the middle section of the aerobic zone, the anaerobic phosphorus release-denitrification is carried out in the last section of the anoxic zone, and sedimentation is carried out in a secondary sedimentation tank to obtain purified water; the carbon source is added to the anoxic tank and / or the last section of the anoxic zone.

5. The AAOA wastewater treatment method according to claim 4, characterized in that: The total COD concentration in the sewage is 40-120 mg / L, and the total nitrogen concentration is 38-55 mg / L.

6. The AAOA wastewater treatment method according to claim 4 or 5, characterized in that: The nitrified liquid obtained by the anaerobic phosphorus release-denitrification is refluxed into the anoxic tank; the reflux ratio of the nitrified liquid is 100-200%.

7. The AAOA wastewater treatment method according to claim 4 or 5, characterized in that: The dissolved oxygen concentration in the anoxic tank is 0.3-0.4 mg / L.

8. The AAOA wastewater treatment method according to claim 4 or 5, characterized in that: The dissolved oxygen concentration in the anaerobic tank is 0.09-0.11 mg / L.

9. The AAOA wastewater treatment method according to claim 4 or 5, characterized in that: The dissolved oxygen concentration in the front section of the aerobic zone is 1-2 mg / L; The dissolved oxygen concentration in the middle section of the aerobic zone is 1 to 2 mg / L; The dissolved oxygen concentration in the final section of the anoxic zone is 0.3-0.4 mg / L.

10. The AAOA wastewater treatment method according to claim 4 or 5, characterized in that: The sludge obtained by the precipitation is returned to the anoxic tank; the return ratio of the sludge is 50-70%.

Images