AAO-S device and its usage for dealing with wastewater load shocks and reducing external carbon sources

Abstract

This invention relates to an AAO-S device and its usage method for coping with wastewater load shocks and reducing external carbon sources. It includes an anaerobic tank with an inlet on one side. The anaerobic tank is connected to a switching tank I, which is also connected to an anoxic tank. A first sludge removal device is provided between the switching tank I and the anoxic tank. The anoxic tank is connected to an aerobic tank, which is connected to a switching tank II. The switching tank II is connected to a sedimentation tank. One end of the sedimentation tank has an outlet and a second sludge removal device. This invention allows for switching of the tank's process functions. During use, it meets the needs of nitrification liquor replenishment and aerobic tank sludge replenishment while avoiding the impact of dissolved oxygen on denitrification and the interference of nitrate nitrogen on phosphorus removal. The two-stage switching tanks can switch process functions according to the incoming water quality, ensuring and enhancing nitrogen and phosphorus removal while significantly reducing carbon source addition requirements, making it shock-resistant and energy-efficient.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically relating to an AAO-S device and its usage method for coping with wastewater load shocks and reducing external carbon sources. Background Technology

[0002] Referring to Section 6.2.2 of Chapter 6 of the "Water Supply and Drainage Design Manual, Volume 5: Urban Drainage", the BOD5 to TKN ratio in wastewater should ideally be greater than 4 to achieve ideal biological nitrogen removal; the BOD5 to TP ratio in wastewater should ideally be greater than 17 to achieve ideal biological phosphorus removal. However, phosphorus removal has a prerequisite: if nitrogen removal is incomplete, a certain amount of nitrate nitrogen will remain in the system, directly limiting the phosphorus removal effect. Therefore, nitrogen removal is crucial.

[0003] An imbalance in the carbon-nitrogen-phosphorus (C:N:P) ratio, particularly a relative insufficiency of carbon sources, has become a critical issue in wastewater treatment plants. Adding external carbon sources to improve the nutrient ratio is often the preferred approach, but this comes at a high cost. Furthermore, mismatches between operating and design parameters exacerbate system maintenance expenses. We will propose solutions and process models to address these challenges.

[0004] Existing process technology principles:

[0005] A 2 / O process: This process is an improved activated sludge process. By discharging phosphorus-rich excess sludge and nitrification liquor for recirculation, it achieves the purpose of anaerobic chain breaking and phosphorus release, anoxic denitrification and nitrogen removal, aerobic removal of organic matter, and phosphorus removal through sludge discharge, thus achieving the effect of nitrogen and phosphorus removal.

[0006] Improved A 2 / O process: To avoid the adverse effects of nitrate nitrogen on anaerobic phosphorus removal caused by incomplete denitrification of the sludge returned from the secondary sedimentation tank, this process sets up a pre-denitrification tank at the front end of the anaerobic tank. The sludge returned from the secondary sedimentation tank and part of the influent first enter the pre-denitrification zone (the other part enters the anaerobic tank in the same direction) to improve the biological phosphorus removal capacity of the system.

[0007] Bardenpho process: This process technology eliminates the anaerobic stage and is similar to A... 2 Compared to the / O process, the raw water is directly introduced into the anoxic zone to ensure the proportion of carbon source organic matter and improve the denitrification efficiency, but the removal of phosphorus is mainly achieved through biological absorption.

[0008] UCT process: This process technology uses a method of returning sludge and mixed liquor, similar to A... 2 Compared to the O method, the sludge is first returned to the anoxic tank and then returned to the anaerobic tank through the mixed liquor. This is also to avoid the impact of incomplete denitrification on the anaerobic phosphorus release effect of nitrate nitrogen.

[0009] MUCT process: This process adds an anoxic tank to the UCT process, separating the denitrification return area from the sludge return area, resulting in more significant effects and easier management.

[0010] While the aforementioned processes can generally achieve simultaneous nitrogen and phosphorus removal, and each has aspects worth learning and adapting, they still have shortcomings when facing load shocks. Under load shocks, none of these systems can achieve the necessary switching within the tank, such as an increase in total nitrogen (TN), expansion of the anoxic zone, and incomplete nitrogen removal inevitably leads to the release of nitrate nitrogen, which, upon reaching a certain equivalent level, can negatively impact phosphorus removal efficiency. Furthermore, the biological system may disintegrate due to nitrogen poisoning.

[0011] Biochemical systems are analogous to the digestive process in the human digestive system. Their operation follows certain rules and principles. Anaerobic systems are used for chain breakdown and phosphorus release. The startup of the system and the cultivation of anaerobic bacteria require a certain organic load. Adding recirculation or pre-anaerobic processes weakens the basic functions of anaerobic systems. Aerobic systems typically first undergo heterotrophic carbon removal followed by autotrophic nitrogen removal. When carbon, nitrogen, and phosphorus are imbalanced, the microbial system cannot form, making the sequential process irrelevant. Excessive dissolved oxygen carried by nitrification liquor recirculation can disrupt the anoxic environment, while incomplete nitrogen removal and sludge recirculation can impair anaerobic effects. Furthermore, the denitrification function is not enhanced by anoxic conditions. Summary of the Invention

[0012] The purpose of this invention is to solve the above-mentioned problems. This application proposes an AAO-S device and its usage method to cope with sewage load shocks and reduce external carbon sources. It realizes the switching of process functions in the tank, meets the needs of nitrification liquid replenishment and aerobic tank sludge replenishment, while avoiding the influence of dissolved oxygen on denitrification and the interference of nitrate nitrogen on phosphorus removal. The two-stage switching tank can switch process functions according to the incoming water quality, ensuring and enhancing the nitrogen and phosphorus removal effect while significantly reducing the carbon source addition requirement, resisting shocks and saving energy.

[0013] To achieve the above objectives, the present invention provides the following technical solution: an AAO-S device for coping with wastewater load shocks and reducing external carbon sources, comprising an anaerobic tank, an inlet on one side of the anaerobic tank, the anaerobic tank being interconnected with a switching tank I, the switching tank I being interconnected with an anoxic tank, a first sludge discharge device being provided between the switching tank I and the anoxic tank, the anoxic tank being interconnected with an aerobic tank, the aerobic tank being interconnected with a switching tank II, the switching tank II being interconnected with a sedimentation tank, an outlet and a second sludge discharge device being provided at one end of the sedimentation tank, the output end of the switching tank II forming a nitrification liquid return device with the input end of the first switching tank, the anoxic tank, and the aerobic tank, the output end of the switching tank I and the input end of the anaerobic tank constituting a first sludge return device, and the output end of the sedimentation tank forming a second sludge return device with the input end of the anoxic tank, the aerobic tank, and the switching tank II.

[0014] Furthermore, a flow meter is installed at the water inlet.

[0015] Furthermore, the anaerobic, anoxic, and aerobic tanks are all equipped with an online DO monitoring system and an online dissolved oxygen detection device, and the dissolved oxygen in the anaerobic tank is controlled to be less than 0.2 mg / L; the dissolved oxygen in the anoxic tank is controlled to be 0.2~0.5 mg / L; and the dissolved oxygen in the aerobic tank is controlled to be 3±1 mg / L.

[0016] Furthermore, the anoxic pool is equipped with a stirring device and an online pH monitoring device.

[0017] Preferred: The aerobic tank is equipped with an aeration device, which is configured with a variable frequency.

[0018] Preferred: The nitration liquid reflux device is equipped with a nitration liquid reflux pump, and the nitration liquid reflux pump adopts frequency conversion control.

[0019] Priority: The sludge return ratio in switching tank I should be controlled at 30-50%, the sludge return ratio in sedimentation tank should be controlled at 50-100%, and the nitrification liquor return ratio should be controlled at 100-300%.

[0020] Priority: This device is entirely controlled and managed by a PLC.

[0021] A method for using an AAO-S device to cope with wastewater load shocks and reduce external carbon sources includes the following process:

[0022] 1) Raw water enters the anaerobic tank to ensure the high load required for anaerobic chain breaking and phosphorus release. The DO online monitoring system monitors the influent load, pH, and uniformity of water distribution in the anaerobic tank.

[0023] 2) During normal operation, Switching Tank I acts as a sedimentation tank, intercepting and removing particulate matter before it is decomposed, while ensuring the concentration of anaerobic sludge replenishment, reducing the frequency of use of the first sludge return device, and ensuring the stability of the system in the anoxic tank; when the influent load changes and the total nitrogen increases, the nitrification liquid return in the nitrification liquid return device is increased, and nitrate and organic matter are added, while Switching Tank I acts as an anoxic tank for denitrification.

[0024] 3) The anoxic tank uses a stirring device to fully mix the returned nitrification liquid, promoting denitrification; the aeration device provides dissolved oxygen to the aerobic tank, promoting the nitrification reaction and also providing the necessary environment for microorganisms in the aerobic tank to absorb polyphosphate, which is conducive to sludge removal and phosphorus removal.

[0025] 4) During normal operation, the aerobic tank and the switching tank II work together to perform nitrification. When the total nitrogen is too high or the carbon source is too low, the sludge concentration in the aerobic tank is increased, and the aeration in the switching tank II is adjusted to air mixing. By controlling the dissolved oxygen value, the switching tank II will perform the denitrification function of the anoxic tank. The sedimentation tank is used for sludge-water separation to meet the requirements of return and sludge discharge.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] This invention enables the switching of process functions in different areas of the tank, ensuring that the anaerobic and anoxic tanks have sufficient carbon sources. The switching of functions does not restrict the original process effect, thus ensuring the integrity of the functions of the anaerobic, anoxic, and aerobic tanks, thereby enhancing the system's resistance to shocks. By controlling the return flow ratio, the denitrification rate and sludge age can be enhanced, which is beneficial for nitrogen removal and reduces the dependence on carbon sources and the cost of adding them.

[0028] Switching tank I not only solves the problem of nitrate nitrogen affecting polyphosphate-accumulating bacteria reaction during anaerobic sludge return, but also avoids the damage to the anoxic environment caused by dissolved oxygen in the returned nitrified liquid. When switching tank II switches to anoxic function, the aerobic tank is directly connected, reducing the energy consumption of the return flow. It operates well, accurately controls the dissolved oxygen in the water, keeps the dissolved oxygen at a low level, reduces the aeration volume, and further saves energy. Attached Figure Description

[0029] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only for more clearly illustrating the technical solutions in the embodiments of the present invention or the prior art. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a structural framework diagram of the present invention. Detailed Implementation

[0031] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention will be further described below with reference to specific embodiments. However, the embodiments are only for illustration and are not intended to limit the present invention.

[0032] An AAO-S device and its usage method (S stands for Switch) for coping with wastewater load shocks and reducing external carbon sources is disclosed. This improved AAO process enables the switching of tank functions, meeting the needs of nitrification liquor replenishment and aerobic sludge replenishment while avoiding the impact of dissolved oxygen on denitrification and the interference of nitrate nitrogen on phosphorus removal. The two-stage switching tank can switch functions according to the incoming water quality, ensuring and enhancing nitrogen and phosphorus removal while significantly reducing the need for carbon source addition, making it shock resistant and energy-saving.

[0033] like Figure 1As shown, an AAO-S device for coping with wastewater load shocks and reducing external carbon sources includes an anaerobic tank with an inlet on one side and a flow meter at the inlet. The anaerobic tank is connected to a switching tank I, which is also connected to an anoxic tank. The anoxic tank is equipped with a stirring device, and a first sludge discharge device is located between the switching tank I and the anoxic tank. The anoxic tank is connected to an aerobic tank, which is equipped with an aeration device. The aerobic tank is connected to a switching tank II, which is also connected to a sedimentation tank. One end of the sedimentation tank has an outlet and a second sludge discharge device. The output end of the switching tank II, together with the input end of the first switching tank, the anoxic tank, and the aerobic tank, forms a nitrification liquid return device. The output end of the switching tank I and the input end of the anaerobic tank constitute a first sludge return device. The output end of the sedimentation tank, together with the input end of the anoxic tank, the aerobic tank, and the switching tank II, constitute a second sludge return device.

[0034] The anaerobic, anoxic, and aerobic tanks are all equipped with an online DO monitoring system and an online dissolved oxygen detection device. The dissolved oxygen in the anaerobic tank is controlled to be less than 0.2 mg / L; the dissolved oxygen in the anoxic tank is controlled to be 0.2~0.5 mg / L; the dissolved oxygen in the aerobic tank is controlled to be 3±1 mg / L; and the pH online monitoring system adjusts the pH value in the anoxic tank to 7.5±1.

[0035] The entire device is controlled by PLC. The sludge return ratio in switching tank I is controlled at 30-50%, the sludge return ratio in sedimentation tank is controlled at 50-100%, and the nitrification liquid return ratio is controlled at 100-300%. When the total nitrogen is too high, the dissolved oxygen can be adjusted to 300-600% by combining it with the online dissolved oxygen detection device.

[0036] A method for using an AAO-S device to cope with wastewater load shocks and reduce external carbon sources includes the following process:

[0037] 1) Raw water enters the anaerobic tank to ensure the high load required for anaerobic chain breaking and phosphorus release. (Generally, domestic sewage does not need to be equipped with an online pH monitoring device, but industrial water needs to be specially equipped.) The DO online monitoring system monitors the influent load, pH, and whether the water distribution is uniform. Uniform water distribution and reasonable upward flow velocity are the key to the effectiveness of the anaerobic system.

[0038] 2) During normal operation, Switching Tank I acts as a sedimentation tank, intercepting and removing particulate matter before it is decomposed, while ensuring the concentration of anaerobic sludge replenishment, reducing the frequency of use of the first sludge return device, releasing oxygen, and ensuring the stability of the system in the anoxic tank; when the influent load changes and the total nitrogen increases, the nitrification liquor return in the nitrification liquor return device is increased, and nitrate and organic matter are added, while Switching Tank I acts as an anoxic tank for denitrification.

[0039] 3) The anoxic tank uses a stirring device to fully mix the returned nitrification liquid, promoting denitrification; the aeration device provides dissolved oxygen to the aerobic tank, promoting the nitrification reaction and also providing the necessary environment for microorganisms in the aerobic tank to absorb polyphosphate, which is conducive to sludge removal and phosphorus removal.

[0040] 4) During normal operation, the aerobic tank and the switching tank II work together to perform nitrification. When the total nitrogen is too high or the carbon source is too low, the sludge concentration in the aerobic tank is increased, and the aeration in the switching tank II is adjusted to air mixing. By controlling the dissolved oxygen value, the switching tank II will perform the denitrification function of the anoxic tank. The sedimentation tank is used for sludge-water separation to meet the requirements of return and sludge discharge.

[0041] This device system uses A during normal operation. 2 In the / O operation mode, each process step performs its respective function. When abnormalities are detected in the incoming water or there are different load shocks, the system can switch modes at any time to reduce carbon source demand. Furthermore, this system also has a backup dosing device to enhance the nutrient ratio adjustment capability. The external carbon source uses sodium acetate or industrial white sugar, nitrogen and phosphorus are supplemented using compound fertilizer, and pH is adjusted using sodium carbonate, supplementing alkalinity while adjusting acidity and alkalinity. The aeration device uses a variable frequency drive (VFD) configuration, the nitrification liquor return pump uses VFD control, and the entire system is managed by a PLC.

[0042] Implementation Case:

[0043] This device has been adopted in projects in northern Shaanxi and some parts of Gansu Province. Due to dietary habits, the intake of meat and legumes in northern Shaanxi and Gansu is relatively high. While the CODcr level in local domestic wastewater is far below the commonly used standard selection criteria, the total nitrogen (TN) is as high as 70-90 mg / L. With seasonal changes, water quality and temperature fluctuate significantly, leading to excessive total nitrogen levels. This technology effectively solves the system shock-related problems.

[0044] Located in Gansu Province, the project upgraded its discharge standard from Class B of the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants" (GB18918-2002) to Class A. The original process was an oxidation ditch process. Due to dietary habits and local water quality, the total nitrogen (TN) in domestic sewage in this area is high and exhibits seasonal variations. Before the upgrade, the system had poor operational controllability and frequently experienced unstable effluent TN levels. After the upgrade, during trial operation, the system could switch tank functions based on the influent water quality, resulting in effluent quality that was consistently better than Class A. Even under the most unfavorable winter temperature conditions, the TN remained stable below 12 mg / L. Annual chemical costs were reduced by approximately 40%, with carbon source chemical costs reduced by approximately 55%.

[0045] This invention enables the switching of process functions within the tank, ensuring that the anaerobic and anoxic tanks have sufficient carbon sources available. The switching of functions does not restrict the original process effect, thereby ensuring the integrity of the functions of the anaerobic, anoxic, and aerobic tanks and enhancing the system's resistance to shocks. By controlling the return flow ratio, the denitrification rate and sludge age can be enhanced, which is beneficial for nitrogen removal and reduces the dependence on carbon sources and the cost of addition.

[0046] All content not described in detail in this invention is prior art.

[0047] The above description is merely a preferred embodiment of the present invention and is not limited to the description in the specification and embodiments. Therefore, all equivalent changes or modifications made to the structure, features, and principles described in the claims of this invention should be included within the scope of this patent application.

Claims

1. A method for using an AAO-S device to cope with wastewater load shocks and reduce external carbon sources, the AAO-S device including an anaerobic tank, characterized in that: An inlet is provided on one side of the anaerobic tank. The anaerobic tank is connected to the switching tank I. The switching tank I is connected to the anoxic tank. A first sludge discharge device is also provided between the switching tank I and the anoxic tank. The anoxic tank is connected to the aerobic tank. The aerobic tank is connected to the switching tank II. The switching tank II is connected to the sedimentation tank. An outlet and a second sludge discharge device are provided at one end of the sedimentation tank. The output end of the switching tank II is connected to the input end of the switching tank I, and together with the switching tank I, the anoxic tank and the aerobic tank, they form a nitrification liquid return device. The output end of the switching tank I is connected to the input end of the anaerobic tank to form a first sludge return device. The output end of the sedimentation tank is connected to the input end of the anoxic tank, and together with the anoxic tank, the aerobic tank and the switching tank II, they form a second sludge return device. The method of using the AAO-S device includes the following steps: During normal operation, switching tank I functions as a sedimentation tank. When the influent load changes and the total nitrogen increases, the nitrification liquid return in the nitrification liquid return device is increased, and nitrate and organic matter are added. Switching tank I then functions as an anoxic tank for denitrification. During normal operation, the aerobic tank and the switching tank II simultaneously perform nitrification. When the total nitrogen is too high, the sludge concentration in the aerobic tank is increased, and the aeration in the switching tank II is adjusted to air mixing. By controlling the dissolved oxygen value, the switching tank II can perform the denitrification function of the anoxic tank.

2. The method of using the AAO-S device for responding to wastewater load shocks and reducing external carbon sources according to claim 1, characterized in that: A flow meter is installed at the water inlet.

3. The method of using the AAO-S device for responding to wastewater load shocks and reducing external carbon sources according to claim 1, characterized in that: The anaerobic, anoxic, and aerobic tanks are all equipped with an online DO monitoring system, which controls the dissolved oxygen in the anaerobic tank to less than 0.2 mg / L; the dissolved oxygen in the anoxic tank to 0.2~0.5 mg / L; and the dissolved oxygen in the aerobic tank to 3±1 mg / L.

4. The method of using the AAO-S device for responding to wastewater load shocks and reducing external carbon sources according to claim 1, characterized in that: The anoxic tank is equipped with a stirring device and an online pH monitoring device.

5. The method of using the AAO-S device for responding to wastewater load shocks and reducing external carbon sources according to claim 1, characterized in that: The aerobic tank is equipped with an aeration device, which is configured with a variable frequency.

6. The method of using the AAO-S device for responding to wastewater load shocks and reducing external carbon sources according to claim 1, characterized in that: The nitration liquid reflux device is equipped with a nitration liquid reflux pump, which is controlled by frequency conversion.

7. The method of using the AAO-S device for responding to wastewater load shocks and reducing external carbon sources according to claim 1, characterized in that: The sludge return ratio in switching tank I is controlled at 30-50%, the sludge return ratio in sedimentation tank is controlled at 50-100%, and the nitrification liquor return ratio is controlled at 100-300%.

8. The method of using the AAO-S device for responding to wastewater load shocks and reducing external carbon sources according to claim 1, characterized in that: The AAO-S device is managed by a PLC.

Images