Sewage treatment method and treatment system for effective distribution before and after combination of AOA and carbon source

Abstract

The invention provides a sewage treatment method and treatment system utilizing effective distribution before and after combination of AOA and a carbon source. Belongs to the technical field of sewage treatment. The method comprises the following steps: sequentially carrying out denitrification, first anaerobic phosphorus release, first nitrification, second nitrification and second anaerobic phosphorus release on sewage to obtain a first nitrification solution; part of the first nitrification liquid flows back to the denitrification process, the remaining first nitrification liquid is precipitated, and purified water and sludge are obtained; or sequentially carrying out denitrification, first anaerobic phosphorus release, first nitrification and second nitrification on the sewage to obtain second nitrification liquid; part of the second nitrification liquid is refluxed into the denitrification process, the remaining second nitrification liquid is sequentially subjected to second anaerobic phosphorus release and precipitation to obtain purified water and sludge, the nitrification liquid is refluxed, nitrate which is not subjected to denitrification is refluxed to be further denitrified, and therefore the concentration of nitrate in treated effluent and the concentration of total nitrogen in the effluent are reduced. The sewage treatment effect is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of sewage treatment, and in particular relates to a sewage treatment method and a treatment system utilizing AOA combined with effective front and back distribution of a carbon source. Background Art

[0002] With the operation of people's lives, industries and enterprises, sewage is constantly generated. Sewage contains a large amount of organic matter, nitrogen and phosphorus, etc. Direct discharge will cause harm to the environment and human body, so it generally needs to be treated.

[0003] Existing sewage treatment methods mainly include physical, chemical and biological methods. The physical method is simple, but it mainly removes suspended particles, colloids and other substances, and the sewage treatment effect is poor; the chemical method requires the addition of chemical agents, and there is a risk of residual agents; and the biological method has a good treatment effect on organic matter, etc. The existing technology uses anaerobic-aerobic-anoxic methods to treat landfill leachate, which has a good treatment effect on landfill leachate. However, with the continuous improvement of environmental awareness, its treatment effect still needs to be further improved. Therefore, a treatment method with better treatment effect on sewage is urgently needed. Summary of the invention

[0004] The purpose of the present invention is to provide a sewage treatment method and treatment system using AOA combined with effective front and back distribution of carbon sources. The sewage treatment method provided by the present invention has a better treatment effect on sewage.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a sewage treatment method using AOA combined with effective front and back distribution of carbon sources, comprising the following steps:

[0007] (1) subjecting the sewage to denitrification, first anaerobic phosphorus release, first nitrification, second nitrification and second anaerobic phosphorus release in sequence to obtain a first nitrification liquid;

[0008] (2) refluxing part of the first nitrification liquid obtained in step (1) into the denitrification process of step (1), and subjecting the remaining first nitrification liquid to precipitation to obtain purified water and sludge;

[0009] Alternatively: 1) subjecting the sewage to denitrification, first anaerobic phosphorus release, first nitrification and second nitrification in sequence to obtain a second nitrified liquid;

[0010] 2) Part of the second nitrified liquid obtained in step 1) is refluxed into the denitrification process of step 1), and the remaining second nitrified liquid is subjected to second anaerobic phosphorus release and precipitation in sequence to obtain purified water and sludge.

[0011] Preferably, the dissolved oxygen concentration during denitrification in step (1) is 0.3-0.4 mg / L.

[0012] Preferably, the denitrification time in step (1) is 3 to 4 hours.

[0013] Preferably, the dissolved oxygen concentration during the first anaerobic phosphorus release in step (1) is 0.09-0.11 mg / L.

[0014] Preferably, the time for the first anaerobic phosphorus release in step (1) is 1 to 2 hours.

[0015] Preferably, the dissolved oxygen concentration during the first nitrification in step (1) is 1 to 2 mg / L.

[0016] Preferably, in step (1), the total COD concentration of the sewage is 40 to 120 mg / L, and the total nitrogen concentration of the sewage is 38 to 55 mg / L.

[0017] Preferably, the reflux ratio in step (2) is 100-200%.

[0018] Preferably, the sludge obtained in step (2) is returned to the denitrification process in step (1).

[0019] The present invention also provides an AOA sewage treatment system suitable for the sewage treatment method using AOA combined with effective front and back distribution of carbon sources as described in the above technical solution, comprising an anoxic tank, an anaerobic tank, an aerobic tank and a secondary sedimentation tank arranged in sequence; the aerobic tank is sequentially provided with a front section of an aerobic zone, a middle section of an aerobic zone and a final section of an anoxic zone connected in series; the final section of the anoxic zone is connected to the anoxic tank by a pipeline; the middle section of the aerobic zone is connected to the anoxic tank by a pipeline; the secondary sedimentation tank is connected to the anoxic tank by a pipeline.

[0020] The present invention provides a sewage treatment method using AOA combined with effective front and back distribution of carbon sources, comprising the following steps: (1) sequentially subjecting the sewage to denitrification, first anaerobic phosphorus release, first nitrification, second nitrification and second anaerobic phosphorus release to obtain a first nitrified liquid; (2) partially returning the first nitrified liquid obtained in step (1) to the denitrification process of step (1), and the remaining first nitrified liquid is precipitated to obtain purified water and sludge; or: 1) sequentially subjecting the sewage to denitrification, first anaerobic phosphorus release, first nitrification and second nitrification to obtain a second nitrified liquid; 2) partially returning the second nitrified liquid obtained in step 1) to the denitrification process of step 1), and the remaining second nitrified liquid is sequentially subjected to second anaerobic phosphorus release and precipitation to obtain purified water and sludge. The present invention returns part of the nitrified liquid to the denitrification process, so that the nitrate that has not undergone denitrification is refluxed for further denitrification, thereby reducing the concentration of nitrate and total nitrogen in the effluent after treatment, and improving the treatment effect of the sewage. The results of the examples show that after being treated by the treatment method of the present invention, the nitrate concentration in the purified water is below 8.5 mg / L, and the total nitrogen concentration is below 13.6 mg / L. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A schematic diagram of the structure of the AOA sewage treatment system provided in Example 1;

[0022] Figure 2 A schematic diagram of sewage treatment using the AOA sewage treatment system provided in Example 1;

[0023] Figure 3 COD content of the purified water (effluent) of Examples 3 to 7;

[0024] Figure 4 TN content of the purified water (effluent) of Examples 3 to 7. DETAILED DESCRIPTION

[0025] The present invention provides a sewage treatment method using AOA combined with effective front and back distribution of carbon sources, comprising the following steps:

[0026] (1) subjecting the sewage to denitrification, first anaerobic phosphorus release, first nitrification, second nitrification and second anaerobic phosphorus release in sequence to obtain a first nitrification liquid;

[0027] (2) refluxing part of the first nitrification liquid obtained in step (1) into the denitrification process of step (1), and subjecting the remaining first nitrification liquid to precipitation to obtain purified water and sludge;

[0028] Alternatively: 1) subjecting the sewage to denitrification, first anaerobic phosphorus release, first nitrification and second nitrification in sequence to obtain a second nitrified liquid;

[0029] 2) Part of the second nitrified liquid obtained in step 1) is refluxed into the denitrification process of step 1), and the remaining second nitrified liquid is subjected to second anaerobic phosphorus release and precipitation in sequence to obtain purified water and sludge.

[0030] The present invention provides a sewage treatment method using AOA combined with effective front and back distribution of carbon sources, comprising the following steps:

[0031] (1) subjecting the sewage to denitrification, first anaerobic phosphorus release, first nitrification, second nitrification and second anaerobic phosphorus release in sequence to obtain a first nitrification liquid;

[0032] (2) Part of the first nitrification liquid obtained in step (1) is refluxed into the denitrification process of step (1), and the remaining first nitrification liquid is precipitated to obtain purified water and sludge.

[0033] The invention sequentially performs denitrification, first anaerobic phosphorus release, first nitrification, second nitrification and second anaerobic phosphorus release on sewage to obtain a first nitrification liquid.

[0034] In the present invention, the total COD concentration of the sewage is preferably 40 to 120 mg / L, more preferably 50 to 110 mg / L, and most preferably 70 to 90 mg / L.

[0035] In the present invention, the COD preferably includes at least one of organic nitrogen in C_I (difficult to degrade soluble COD) and C_S (easy to degrade soluble COD).

[0036] In the present invention, 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 30-50 mg / L.

[0037] In the present invention, the total nitrogen concentration of the sewage is preferably 38 to 55 mg / L, more preferably 40 to 50 mg / L, and further preferably 45 to 46 mg / L.

[0038] In the present invention, the total nitrogen preferably includes ammonia nitrogen (C_NH4 + ), nitrate (C_NO3 - ), C_ND (biodegradable soluble organic nitrogen), organic nitrogen in C_I, X_ND (biodegradable particulate organic nitrogen) and at least one of the organic nitrogen in X_S (easily degradable particulate COD).

[0039] In the present invention, the concentration of ammonia nitrogen in the sewage is preferably 15-25 mg / L, more preferably 20-23 mg / L; the concentration of nitrate in the sewage is preferably 10-20 mg / L, more preferably 14-16 mg / L; the concentration of C_ND in the sewage is preferably 1-3 mg / L, more preferably 2-2.8 mg / L; the concentration of organic nitrogen in C_I in the sewage is preferably 1-3 mg / L, more preferably 2-2.4 mg / L; the concentration of X_ND in the sewage is preferably 1-3 mg / L, more preferably 1.6-2 mg / L; the concentration of organic nitrogen in X_S in the sewage is preferably 0.1-0.3 mg / L, more preferably 0.15-0.2 mg / L.

[0040] The present invention limits the total COD concentration and total nitrogen concentration of sewage within the above ranges, which can further improve the sewage treatment effect. The present invention has no special limitation on the source of the sewage, and sewage from sources well known to those skilled in the art can be used.

[0041] In the present invention, the dissolved oxygen (DO) concentration during denitrification is preferably 0.3-0.4 mg / L, more preferably 0.35 mg / L; the denitrification temperature is preferably 15-25°C, more preferably 20°C; the denitrification time is preferably 3-4 hours, more preferably 3.5-4 hours. The present invention limits the denitrification parameters within the above range, which can further improve the sewage treatment effect.

[0042] In the present invention, the denitrification is preferably carried out in an anoxic tank. In the present invention, the anoxic tank preferably contains initial sludge. The present invention has no particular limitation on the source and type of the initial sludge in the anoxic tank, and the sludge used in the anoxic tank well known to those skilled in the art can be used.

[0043] In the present invention, the volume of the initial sludge is preferably 60-70% of the volume of the anoxic tank, and more preferably 65-68%. The present invention limits the volume of the initial sludge to the above range, which can further improve the sewage treatment effect.

[0044] In the present invention, the dissolved oxygen concentration during the first anaerobic phosphorus release is preferably 0.09-0.11 mg / L, more preferably 0.1 mg / L; the temperature of the first anaerobic phosphorus release is preferably 15-25°C, more preferably 20°C; the time of the first anaerobic phosphorus release is preferably 1-2 hours, more preferably 1.5 hours. The present invention limits the parameters of the first anaerobic phosphorus release to the above range, which can further improve the sewage treatment effect.

[0045] In the present invention, the first anaerobic phosphorus release is preferably carried out in an anaerobic tank. In the present invention, the anaerobic tank preferably contains initial sludge. The present invention has no particular limitation on the source and type of the initial sludge in the anaerobic tank, and the sludge used in the anaerobic tank well known to those skilled in the art can be used.

[0046] In the present invention, the volume of the initial sludge is preferably 60-70% of the volume of the anaerobic tank, and more preferably 65-68%. The present invention limits the volume of the initial sludge to the above range, which can further improve the sewage treatment effect.

[0047] In the present invention, the dissolved oxygen concentration during the first nitrification is preferably 1-2 mg / L, more preferably 1-1.5 mg / L; the temperature of the first nitrification is preferably 15-25°C, more preferably 20°C; the time of the first nitrification is preferably 3-4 hours, more preferably 3.5 hours. The present invention limits the parameters of the first nitrification to the above range, which can further improve the sewage treatment effect.

[0048] In the present invention, the first nitrification is preferably carried out in the front section of the aerobic zone of the aerobic tank. In the present invention, the front section of the aerobic zone of the aerobic tank preferably contains initial sludge. The present invention has no particular limitation on the source and type of the initial sludge in the front section of the aerobic zone of the aerobic tank, and the sludge used in the front section of the aerobic zone of the aerobic tank well known to those skilled in the art can be used.

[0049] In the present invention, the volume of the initial sludge is preferably 60-70% of the volume of the front section of the aerobic zone of the aerobic tank, and more preferably 65-68%. The present invention limits the volume of the initial sludge to the above range, which can further improve the sewage treatment effect.

[0050] In the present invention, the dissolved oxygen concentration during the second nitrification is preferably 0.4-0.6 mg / L, more preferably 0.5-0.6 mg / L; the temperature of the second nitrification is preferably 15-25°C, more preferably 20°C; the time of the second nitrification is preferably 3-4 hours, more preferably 3.5 hours. The present invention limits the parameters of the second nitrification to the above range, which can further improve the sewage treatment effect.

[0051] In the present invention, the second nitrification is preferably carried out in the middle section of the aerobic zone of the aerobic tank. In the present invention, the middle section of the aerobic zone of the aerobic tank preferably contains initial sludge. The present invention has no particular limitation on the source and type of the initial sludge in the middle section of the aerobic zone of the aerobic tank, and the sludge used in the middle section of the aerobic zone of the aerobic tank that is well known to those skilled in the art can be used.

[0052] In the present invention, the volume of the initial sludge is preferably 60-70% of the volume of the middle section of the aerobic zone of the aerobic tank, and more preferably 65-68%. The present invention limits the volume of the initial sludge to the above range, which can further improve the sewage treatment effect.

[0053] In the present invention, the dissolved oxygen concentration during the second anaerobic phosphorus release is preferably 0-0.2 mg / L, more preferably 0-0.1 mg / L; the temperature of the second anaerobic phosphorus release is preferably 15-25°C, more preferably 20°C; the time of the second anaerobic phosphorus release is preferably 3-4 hours, more preferably 3.5 hours. The present invention limits the parameters of the second anaerobic phosphorus release to the above range, which can further improve the sewage treatment effect.

[0054] In the present invention, the second anaerobic phosphorus release is preferably carried out in the last section of the anoxic zone of the aerobic tank. In the present invention, the last section of the anoxic zone of the aerobic tank preferably contains initial sludge. The present invention has no particular limitation on the source and type of the initial sludge in the last section of the anoxic zone of the aerobic tank, and the sludge used in the last section of the anoxic zone of the aerobic tank that is well known to those skilled in the art can be used.

[0055] In the present invention, the volume of the initial sludge is preferably 60-70% of the volume of the end section of the anoxic zone of the aerobic tank, and more preferably 65-68%. The present invention limits the volume of the initial sludge to the above range, which can further improve the sewage treatment effect.

[0056] After obtaining the first nitrification liquid, the present invention returns part of the first nitrification liquid to the denitrification process, and precipitates the remaining first nitrification liquid to obtain purified water and sludge.

[0057] The present invention returns part of the first nitrification liquid to the denitrification process, so that the nitrate that has not been denitrified is returned for further denitrification, reducing the concentration of nitrate ions in the treated sewage and the total nitrogen in the effluent, thereby improving the sewage treatment effect.

[0058] In the present invention, the reflux ratio of the reflux is preferably 100-200%, more preferably 130-170%, and most preferably 150%. The present invention limits the reflux ratio within the above range, which can further improve the sewage treatment effect.

[0059] In the present invention, the precipitation temperature is preferably 15-25°C, more preferably 20°C; the precipitation time is preferably 1.5-4.0h. The present invention limits the precipitation temperature and time within the above range, which can further improve the sewage treatment effect.

[0060] In the present invention, the precipitation is preferably carried out in a secondary sedimentation tank.

[0061] After obtaining the sludge, the present invention preferably returns the sludge to the denitrification process.

[0062] In the present invention, the reflux ratio during reflux is preferably 50-70%, more preferably 55-65%, and most preferably 60%. The present invention limits the reflux ratio within the above range, which can further improve the sewage treatment effect.

[0063] The present invention also provides a sewage treatment method using AOA combined with effective front and back distribution of carbon sources, comprising the following steps: 1) subjecting the sewage to denitrification, first anaerobic phosphorus release, first nitrification and second nitrification in sequence to obtain a second nitrified liquid;

[0064] 2) Part of the second nitrified liquid obtained in step 1) is refluxed into the denitrification process of step 1), and the remaining second nitrified liquid is subjected to second anaerobic phosphorus release and precipitation in sequence to obtain purified water and sludge.

[0065] The invention sequentially performs denitrification, first anaerobic phosphorus release, first nitrification and second nitrification on sewage to obtain a second nitrified liquid.

[0066] In the present invention, the parameters of the denitrification, the first anaerobic phosphorus release, the first nitrification and the second nitrification are preferably the same as those of the denitrification, the first anaerobic phosphorus release, the first nitrification and the second nitrification described in the above technical solution, and will not be described in detail here.

[0067] After obtaining the second nitrification liquid, the present invention returns part of the second nitrification liquid to the denitrification process, and the remaining second nitrification liquid is subjected to second anaerobic phosphorus release and precipitation in sequence to obtain purified water and sludge.

[0068] The present invention returns part of the second nitrification liquid to the denitrification process, so that the nitrate that has not been denitrified is returned for further denitrification, reducing the concentration of nitrate ions in the treated sewage and the total nitrogen in the effluent, thereby improving the sewage treatment effect.

[0069] In the present invention, the reflux ratio of the reflux is preferably 100-200%, more preferably 130-170%, and most preferably 150%. The present invention limits the reflux ratio within the above range, which can further improve the sewage treatment effect.

[0070] In the present invention, the various parameters of the second anaerobic phosphorus release and precipitation are preferably the same as the various parameters of the second anaerobic phosphorus release and precipitation in the above technical solution, and will not be described in detail here.

[0071] In the present invention, the difference between the two sewage treatment methods is that the reflux positions of the nitrification liquid are different, one is to reflux from the middle section of the aerobic zone, and the other is to reflux from the end section of the anoxic zone.

[0072] The present invention controls the specific process of sewage treatment, partially returns the nitrification liquid to the denitrification process, and controls the reflux ratio, reduces the dosage of the added carbon source, reduces the treatment cost, and reduces the concentration of nitrate and total nitrogen in the effluent after treatment, thereby improving the nitrogen removal effect, improving the effluent water quality, and improving the sewage treatment effect.

[0073] In the present invention, a carbon source is preferably added during the sewage treatment process. The present invention has no particular limitation on the specific type and source of the carbon source, and a carbon source for sewage treatment well known to those skilled in the art can be used. In an embodiment of the present invention, the carbon source is a composite carbon source produced by Chongqing Lanjie Environmental Technology Co., Ltd.

[0074] In the present invention, after the carbon source is added, the ratio of the total content of total COD and carbon source to the total nitrogen content in the sewage is preferably (4-5.5):1, more preferably (5-5.5):1.

[0075] In the present invention, the carbon source is preferably added to the anoxic tank or added to the end of the anoxic zone of the aerobic tank or added to the end of the anoxic zone of both the anoxic tank and the aerobic tank.

[0076] In the present invention, when the carbon source is added to the anoxic zone end of the anoxic tank and the aerobic tank at the same time, the mass ratio of the carbon source added to the anoxic zone end of the anoxic tank and the aerobic tank is preferably (1-3): (1-3), more preferably 1: 1. The present invention adds the carbon source at two locations, which can further reduce the amount of carbon source added and improve the effluent water quality.

[0077] The present invention also provides an AOA sewage treatment system suitable for the sewage treatment method using AOA combined with effective front and back distribution of carbon sources as described in the above technical solution, comprising an anoxic tank, an anaerobic tank, an aerobic tank and a secondary sedimentation tank arranged in sequence; the aerobic tank is sequentially provided with a front section of an aerobic zone, a middle section of an aerobic zone and a final section of an anoxic zone connected in series; the final section of the anoxic zone is connected to the anoxic tank by a pipeline; the middle section of the aerobic zone is connected to the anoxic tank by a pipeline; the secondary sedimentation tank is connected to the anoxic tank by a pipeline.

[0078] The AOA sewage treatment system provided by the present invention includes an anoxic tank. In the present invention, the anoxic tank is preferably provided with a first water inlet, a first water outlet, a return nitrification liquid inlet and a return sludge inlet. In the present invention, the first water inlet is a sewage inlet. The present invention has no special limitation on the volume and shape of the anoxic tank, which can be adjusted according to actual sewage treatment needs. In the present invention, the hydraulic retention time of the anoxic tank is preferably 3 to 4 hours, more preferably 3.5 to 4 hours.

[0079] The AOA sewage treatment system provided by the present invention also includes an anaerobic tank. In the present invention, the anaerobic tank is preferably provided with a second water inlet and a second water outlet; the second water inlet is connected to the first water outlet of the anoxic tank through a pipe. The present invention has no special limitation on the volume and shape of the anaerobic tank, which can be adjusted according to the actual sewage treatment needs. In the present invention, the hydraulic retention time of the anaerobic tank is preferably 1 to 2 hours, more preferably 1.5 to 2 hours.

[0080] The AOA sewage treatment system provided by the present invention also includes an aerobic tank.

[0081] In the present invention, the aerobic pool is provided with a front section of an aerobic zone, a middle section of an aerobic zone and a final section of an anoxic zone in series.

[0082] In the present invention, the front section of the aerobic zone is preferably provided with a third water inlet and a third water outlet; the third water inlet is connected to the second water outlet of the anaerobic tank through a pipeline. In the present invention, the hydraulic retention time of the front section of the aerobic zone is preferably 3 to 4 hours, more preferably 3.5 to 4 hours.

[0083] In the present invention, the middle section of the aerobic zone is preferably provided with a fourth water inlet, a fourth water outlet and a nitrification liquid reflux port; the fourth water inlet is connected to the third water outlet of the front section of the aerobic zone. In the present invention, the hydraulic retention time of the middle section of the aerobic zone is preferably 3 to 4 hours, more preferably 3.5 to 4 hours. In the present invention, the nitrification liquid reflux port is connected to the reflux nitrification liquid inlet of the anoxic tank through a nitrification liquid internal reflux pipeline.

[0084] In the present invention, the end section of the anoxic zone is preferably provided with a fifth water inlet, a fifth water outlet and a nitrification liquid reflux port; the fifth water inlet is connected to the fourth water outlet of the middle section of the aerobic zone. In the present invention, the volume ratio of the front section of the aerobic zone, the middle section of the aerobic zone and the end section of the anoxic zone in the aerobic pool is preferably 1:1:1. In the present invention, the hydraulic retention time of the end section of the anoxic zone is preferably 3 to 4 hours, more preferably 3.5 to 4 hours.

[0085] In the present invention, a nitrification liquid internal reflux pipe is connected between the end of the anoxic zone and the anoxic pool, and the nitrification liquid reflux port of the end of the anoxic zone is connected to the reflux nitrification liquid inlet of the anoxic pool through the nitrification liquid internal reflux pipe.

[0086] The AOA sewage treatment system provided by the present invention also includes a secondary sedimentation tank.

[0087] In the present invention, the secondary sedimentation tank 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 at the end of the anoxic zone through a pipeline.

[0088] In the present invention, a sludge external return pipe is connected between the secondary sedimentation tank and the anoxic tank, and the sludge outlet of the secondary sedimentation tank is connected to the return sludge inlet of the anoxic tank through the sludge external return pipe. The present invention has no special restrictions on the volume and shape of the secondary sedimentation tank, which can be adjusted according to actual sewage treatment needs.

[0089] In the present invention, the volume ratio of the anoxic tank, the anaerobic tank, the aerobic tank and the secondary sedimentation tank is preferably 2:2:5:1.

[0090] When the AOA sewage treatment system is used for sewage treatment, the sewage enters the anoxic tank from the first water inlet of the anoxic tank for denitrification, and then enters the anaerobic tank from the first water outlet of the anoxic tank through a pipeline from the second water inlet of the anaerobic tank for the first anaerobic phosphorus release, and then enters the front section of the aerobic zone of the aerobic tank from the second water outlet of the anaerobic tank through a pipeline from the third water inlet of the front section of the aerobic zone of the aerobic tank for the first nitrification, and then enters the middle section of the aerobic zone from the fourth water inlet of the middle section of the aerobic zone from the third water outlet of the front section of the aerobic zone through a pipeline for the second nitrification, and then enters the middle section of the aerobic zone from the fourth water inlet of the middle section of the aerobic zone from the fourth water outlet of the middle section of the aerobic zone. The water inlet enters the end of the anoxic zone from the fifth water inlet of the end of the anoxic zone through a pipeline, performs a second anaerobic phosphorus release, obtains a nitrified liquid, and then enters the secondary sedimentation tank from the fifth water outlet of the end of the anoxic zone through a pipeline from the sixth water inlet of the secondary sedimentation tank for precipitation, and then is discharged from the sixth water outlet of the secondary sedimentation tank to obtain purified water and sludge; wherein, part of the nitrified liquid obtained at the end of the anoxic zone of the aerobic tank flows back into the anoxic tank from the nitrified liquid reflux port of the end of the anoxic zone through a pipeline from the reflux nitrified liquid inlet of the anoxic tank; the sludge obtained in the secondary sedimentation tank flows from the sludge outlet of the secondary sedimentation tank through a pipeline from the reflux sludge of the anoxic tank into the sludge outlet of the secondary sedimentation tank. or: the sewage enters the anoxic tank from the first water inlet of the anoxic tank for denitrification, and then enters the anaerobic tank from the first water outlet of the anoxic tank through a pipeline from the second water inlet of the anaerobic tank to perform the first anaerobic phosphorus release, and then enters the front section of the aerobic zone of the aerobic tank from the second water outlet of the anaerobic tank through a pipeline from the third water inlet of the front section of the aerobic zone of the aerobic tank to perform the first nitrification, and then enters the middle section of the aerobic zone from the third water outlet of the front section of the aerobic zone through a pipeline from the fourth water inlet of the middle section of the aerobic zone to perform the second nitrification to obtain the nitrified liquid, and then enters the middle section of the aerobic zone from the fourth water outlet of the middle section of the aerobic zone. The nitrified liquid obtained in the middle section of the aerobic zone of the aerobic tank flows back into the anoxic tank from the nitrified liquid reflux port of the middle section of the aerobic zone through a pipeline and the reflux nitrified liquid inlet of the anoxic tank; the sludge obtained in the secondary sedimentation tank flows back into the anoxic tank from the sludge outlet of the secondary sedimentation tank through a pipeline and the reflux sludge inlet of the anoxic tank.

[0091] Based on the original AO sewage treatment system, the present invention adds an anoxic zone (i.e., the end of the anoxic zone) in the last section of the aerobic tank, which 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 improve the effluent water quality.

[0092] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0093] Example 1

[0094] The structural diagram of the AOA sewage treatment system in Example 1 is as follows: Figure 1 shown.

[0095] The schematic diagram of sewage treatment using the AOA sewage treatment system in Example 1 is as follows: Figure 2 shown.

[0096] use Figure 1 The AOA sewage treatment system shown in the figure performs sewage treatment, and the specific steps are: the sewage is sequentially denitrified in the anoxic tank, the first anaerobic phosphorus release is performed in the anaerobic tank, the first nitrification is performed in the front section of the aerobic zone, the second nitrification is performed in the middle section of the aerobic zone, and the second anaerobic phosphorus release is performed in the end section of the anoxic zone to obtain nitrified liquid, part of the nitrified liquid is returned to the anoxic tank, and the remaining nitrified liquid is precipitated in the secondary sedimentation tank to obtain purified water and sludge, and part of the sludge is returned to the anoxic tank;

[0097] Among them, the anoxic tank, anaerobic tank, the front section of the aerobic zone, the middle section of the aerobic zone and the end section of the anoxic zone in the aerobic tank all contain initial sludge, and the volume of the initial sludge is 2 / 3 of the volume of the front section of the aerobic zone, the middle section of the aerobic zone and the end section of the anoxic zone in the anoxic tank, anaerobic tank and aerobic tank respectively. The volume ratio of the front section of the aerobic zone, the middle section of the aerobic zone and the end section of the anoxic zone in the aerobic tank is 1:1:1. The temperatures of denitrification, the first anaerobic phosphorus release, the first nitrification, the second nitrification, the second anaerobic phosphorus release and precipitation are all 20°C; the nitrification liquid return ratio is 150%; the sludge return ratio is 60%; the DO concentration in the anoxic tank is 0.35mg / L, the DO concentration in the anaerobic tank is 0.1mg / L, the DO concentration in the front section of the aerobic zone in the aerobic tank is 1.0mg / L, the DO concentration in the middle section of the aerobic zone is 0.5mg / L, and the DO concentration in the end section of the anoxic zone is 0.6mg / L. concentration is 0mg / L; the total influent COD concentration is 75mg / L, of which the C_I concentration is 40mg / L and the C_S concentration is 35mg / L; the total influent nitrogen concentration is 46mg / L, of which the ammonia nitrogen concentration is 23mg / L, the nitrate concentration is 16mg / L, the C_ND concentration is 2.8mg / L, the organic nitrogen concentration in C_I is 2.4mg / L, the X_ND concentration is 1.6mg / L, and the organic nitrogen concentration in X_S is 0.2mg / L. The hydraulic retention time (i.e. reaction time) is: 3.7h for the anoxic tank, 1.5h for the anaerobic tank, 3.5h for the front section of the aerobic zone, 3.5h for the middle section of the aerobic zone, and 3.5h for the end section of the anoxic zone. The volume ratio of the anoxic tank, anaerobic tank, aerobic tank and secondary sedimentation tank is 2:2:5:1, and the sedimentation time of the secondary sedimentation tank is 2h.

[0098] Comparative Example 1

[0099] The only difference from Example 1 is that the last section of the anoxic zone in Example 1 is replaced by an aerobic zone, and the other parameters are the same as those in Example 1.

[0100] The concentrations of various components in the purified water (effluent) of Example 1 and Comparative Example 1 are shown in Table 1.

[0101] Table 1 Concentration of each component in purified water (effluent) of Example 1 and Comparative Example 1

[0102]

[0103] As can be seen from Table 1, in the original AAO structure, after 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; although the ammonia nitrogen concentration increased, it was still within the effluent specification range, the total nitrogen concentration was reduced by 9.29%, and the increase in total COD concentration was negligible.

[0104] Example 2

[0105] The only difference from Example 1 is that the nitrification liquid flows back to the anoxic tank from the middle section of the aerobic zone of the aerobic tank.

[0106] Comparative Example 2

[0107] The only difference from Example 2 is that the nitrifying liquid is not refluxed.

[0108] The concentrations of the components in the purified water (effluent) of Example 2 and Comparative Example 2 are shown in Table 2.

[0109] Table 2 Concentration of each component in the purified water (effluent) of Example 2 and Comparative Example 2

[0110]

[0111] It can be seen from Table 2 that the total nitrogen content is reduced after the digestion liquid is refluxed. Refluxing the nitrification liquid and controlling the reflux position can further improve the effluent quality.

[0112] Example 3

[0113] On the basis of Example 1, a composite carbon source was added to the anoxic tank. After the addition, the ratio of the total content of total COD and carbon source to the total nitrogen content in the sewage was 5:1, and purified water was obtained.

[0114] Example 4

[0115] The composite carbon source in Example 3 was added to the end of the anoxic zone of the aerobic tank, and other parameters were the same as in Example 3 to obtain purified water.

[0116] Example 5

[0117] The composite carbon source in Example 3 was added to the end of the anoxic zone of the anoxic tank and the aerobic tank, the mass ratio of the carbon source in the end of the anoxic zone of the anoxic tank and the aerobic tank was 1:3, and other parameters were the same as in Example 3 to obtain purified water.

[0118] Example 6

[0119] The composite carbon source in Example 3 was added to the anoxic zone of the anoxic tank and the aerobic tank. The mass ratio of the carbon source in the anoxic zone of the anoxic tank and the aerobic tank was 3:1. The other parameters were the same as those in Example 3. Purified water was obtained.

[0120] Example 7

[0121] The composite carbon source in Example 3 was added to the anoxic zone end of the anoxic tank and the aerobic tank, the mass ratio of the carbon source in the anoxic zone end of the anoxic tank and the aerobic tank was 1:1, and the other parameters were the same as in Example 3 to obtain purified water.

[0122] The COD and TN contents of the purified water (effluent) of Examples 3 to 7 are as follows: Figure 3 and Figure 4As shown, the complete front placement is embodiment 3, the front placement 3 / 4 is embodiment 6, the equal placement is embodiment 7, the rear placement 3 / 4 is embodiment 5, and the complete rear placement is embodiment 4. Figures 3-4 It can be seen that the later the carbon source is added, the worse the COD effect of the effluent. This is because the later the carbon source is added, the less time it stays in the biochemical stage, and the amount of material consumed is relatively reduced. From the total nitrogen in the effluent, it can be seen that the total nitrogen removal efficiency is best when the carbon source is added in an even distribution mode, which is mainly reflected in its NO3 - The concentration is the lowest. Among other TN components, the content of organic nitrogen in soluble inert organic matter and soluble biodegradable organic nitrogen remains basically unchanged. As the proportion of carbon source addition increases, the effluent NH4 + The smaller the content, the smaller the proportion. This may be because there is too little carbon source in the anoxic pool, and the carbon source that should flow to denitrification flows to assimilation, and the microorganisms in the pool use ammonia nitrogen as a nitrogen source to grow and reproduce.

[0123] 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. A method for treating wastewater by effectively distributing AOA in combination with a carbon source, comprising the following steps: (1) subjecting the sewage to denitrification, first anaerobic phosphorus release, first nitrification, second nitrification and second anaerobic phosphorus release in sequence to obtain a first nitrification liquid; (2) refluxing part of the first nitrification liquid obtained in step (1) into the denitrification process of step (1), and subjecting the remaining first nitrification liquid to precipitation to obtain purified water and sludge; Alternatively: 1) sequentially subjecting the sewage to denitrification, first anaerobic phosphorus release, first nitrification, and second nitrification to obtain a second nitrified liquid; 2) Part of the second nitrified liquid obtained in step 1) is refluxed into the denitrification process of step 1), and the remaining second nitrified liquid is subjected to second anaerobic phosphorus release and precipitation in sequence to obtain purified water and sludge.

2. The sewage treatment method according to claim 1, characterized in that: The dissolved oxygen concentration during denitrification in step (1) is 0.3-0.4 mg / L.

3. The sewage treatment method according to claim 1 or 2, characterized in that: The denitrification time in step (1) is 3 to 4 hours.

4. The sewage treatment method according to claim 1, characterized in that: The dissolved oxygen concentration during the first anaerobic phosphorus release in step (1) is 0.09-0.11 mg / L.

5. The sewage treatment method according to claim 1 or 4, characterized in that: The time of the first anaerobic phosphorus release in step (1) is 1 to 2 hours.

6. The sewage treatment method according to claim 1, characterized in that: The dissolved oxygen concentration during the first nitrification in step (1) is 1-2 mg / L.

7. The sewage treatment method according to claim 1, characterized in that: In the step (1), the total COD concentration of the sewage is 40-120 mg / L, and the total nitrogen concentration of the sewage is 38-55 mg / L.

8. The sewage treatment method according to claim 1, characterized in that: The reflux ratio of the reflux in the step (2) is 100-200%.

9. The sewage treatment method according to claim 1, characterized in that: The sludge obtained in step (2) is returned to the denitrification process in step (1).

10. An AOA sewage treatment system suitable for the sewage treatment method using AOA combined with effective front and back distribution of carbon sources as described in any one of claims 1 to 9, comprising an anoxic tank, an anaerobic tank, an aerobic tank and a secondary sedimentation tank arranged in sequence; the aerobic tank is sequentially provided with a front section of the aerobic zone, a middle section of the aerobic zone and a final section of the anoxic zone connected in series; the final section of the anoxic zone is connected to the anoxic tank by a pipeline; the middle section of the aerobic zone is connected to the anoxic tank by a pipeline; the secondary sedimentation tank is connected to the anoxic tank by a pipeline.

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