Sewage treatment device and method suitable for low carbon-nitrogen ratio

Abstract

The present invention discloses a sewage treatment device and method suitable for low carbon-nitrogen ratios, comprising an anaerobic zone, an anoxic zone, an aerobic zone I, an aerobic zone II, an aerobic zone III, and a sedimentation zone connected in sequence. Part of the sewage in the aerobic zone III is returned to the anoxic zone, and part of the sludge in the sedimentation zone is returned to the anaerobic zone, while the remaining sludge is discharged. The present invention adopts an intermittent operation mode for the sludge return in the anaerobic zone. When the sludge return is turned on, the anaerobic zone agitator stops working, allowing more sludge to be stored in the anaerobic zone. When the sludge return stops working, the anaerobic zone agitator starts working, allowing the sludge to be fully mixed with the influent. Since there is no large amount of nitrate brought by the sludge return at this time, the polyphosphate bacteria can complete the anaerobic phosphorus release process at this time. Subsequently, the polyphosphate bacteria pass through the subsequent aerobic stage, ultimately achieving efficient removal of phosphorus from the system.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and in particular to a sewage treatment device and method suitable for low carbon-nitrogen ratio sewage. Background Art

[0002] In recent years, with the rapid development of my country's urban economy, the amount of urban sewage has increased rapidly, and urban sewage treatment capacity has also increased rapidly. As of 2018, my country's sewage treatment capacity had reached 228 million cubic meters per day. The activated sludge process, due to its energy efficiency and economic advantages, has been widely used in urban sewage treatment plants.

[0003] The activated sludge method used in existing urban sewage treatment plants mainly relies on the carbon source in the influent to remove nitrogen and phosphorus. However, some sewage treatment plants lack the carbon source in the influent, resulting in insufficient denitrification capacity of the system and a high nitrate concentration in the effluent. The high concentration of nitrate flows back to the anaerobic zone, inhibiting the anaerobic phosphorus release of polyphosphate bacteria, resulting in poor phosphorus removal efficiency of the system, making it difficult for the effluent quality of the sewage treatment plant to meet the increasingly stringent sewage treatment discharge standards.

[0004] In order to solve the problem of insufficient carbon source in the influent of sewage treatment plants, resulting in poor phosphorus removal efficiency of the system, the present invention proposes a sewage treatment device and method suitable for low carbon-nitrogen ratio. Summary of the Invention

[0005] In order to solve the problem that insufficient carbon source in the influent of a sewage treatment plant leads to insufficient denitrification capacity of the system and high nitrate concentration in the effluent, the high concentration of nitrate flows back to the anaerobic zone, inhibits the anaerobic phosphorus release of polyphosphate bacteria, and leads to poor phosphorus removal efficiency of the system, the present invention provides a sewage treatment device and method suitable for low carbon-nitrogen ratio.

[0006] In order to solve the above technical problems, the present invention is implemented through the following technical solutions:

[0007] A sewage treatment device suitable for a low carbon-nitrogen ratio comprises an anaerobic zone, an anoxic zone, an aerobic zone I, an aerobic zone II, an aerobic zone III and a sedimentation zone which are connected in sequence. Part of the sewage in the aerobic zone III flows back into the anoxic zone, part of the sludge in the sedimentation zone flows back into the anaerobic zone, and the other part of the sludge is discharged.

[0008] Preferably, an ammonia nitrogen online monitoring device is provided in the aerobic II zone.

[0009] Preferably, the anaerobic zone, the anoxic zone and the aerobic zone II are all provided with a stirrer; and the aerobic zone I, the aerobic zone II and the aerobic zone III are all provided with an aeration device.

[0010] Preferably, the connection hole between the anaerobic zone and the anoxic zone is located at 1 / 2 to 2 / 3 of the height of the tank body.

[0011] Preferably, the sludge return ratio in the anaerobic zone is 100% to 200%.

[0012] Preferably, part of the sewage in the aerobic zone III is refluxed into the anoxic zone through a nitrification liquid reflux pump.

[0013] Preferably, part of the sludge in the sedimentation zone is returned to the anaerobic zone through a sludge return pump.

[0014] A method for treating sewage with a low carbon-nitrogen ratio, comprising the following steps:

[0015] Step 1: The sewage enters the anaerobic zone, anoxic zone, aerobic zone I, aerobic zone II, aerobic zone III, and sedimentation zone in sequence;

[0016] Step 2: Part of the sewage from the aerobic III zone flows back to the anoxic zone, and the other part flows into the sedimentation zone;

[0017] Step 3: Part of the sludge in the sedimentation zone is discharged, and the other part is returned to the anaerobic zone through the sludge pump. The agitator in the anaerobic zone does not work;

[0018] Step 4: The agitator in the anoxic zone starts working to complete the mixing of activated sludge and water;

[0019] Step 5: Use a conventional blower to introduce air into the aerobic zone I, aerobic zone II, and aerobic zone III. The aeration device starts working, and the agitator in the aerobic zone II does not work.

[0020] Step 6: Steps 1-5 are run continuously for 2-3 hours. When the ammonia nitrogen concentration in the aerobic zone II is lower than 2 mg / L, the sludge return pump stops working, the agitators in the anaerobic zone and the aerobic zone II start working, the air supply to the aerobic zone I, the aerobic zone II and the aerobic zone III stops, and the aeration device stops working. Among them, the effluent water quality of the sewage treatment plant generally implements the Class A standard, which stipulates that the effluent ammonia nitrogen concentration is 5 mg / L. Studies have found that the aeration process consumes a lot of carbon sources. Considering that the influent carbon source is large, it is necessary to minimize the system's consumption of carbon sources. When the ammonia nitrogen concentration in the aerobic zone II is lower than 2 mg / L, it is then aerobic. During the nitrification in Zone II, the ammonia nitrogen concentration in the system effluent is lower than 1 mg / L, indicating that the system has been fully nitrified and the system aeration is sufficient. In order to minimize the system's consumption of carbon sources, it is considered to stop aerating Zone I, Zone II, and Zone III at this time. On the one hand, it saves energy consumption, and on the other hand, it saves the consumption of carbon sources for aeration, so that the system has more carbon sources for denitrification and denitrification. At the same time, the sludge return pump stops working, and no nitrate nitrogen enters the anaerobic zone, avoiding the competition between polyphosphate bacteria and denitrifying bacteria for carbon sources, so that polyphosphate bacteria have a good living environment, thereby effectively improving the system's phosphorus removal capacity.

[0021] Step 7: During the continuous process of step 6, if the ammonia nitrogen concentration in the aerobic zone II is found to be higher than 4 mg / L, air is introduced into the aerobic zone I, aerobic zone II, and aerobic zone III, and the other processes remain unchanged. After 1 to 2 hours of continuous operation, the process is switched to steps 1 to 5. The effluent quality of the sewage treatment plant generally complies with the Class A standard, which stipulates that the effluent ammonia nitrogen concentration is 5 mg / L. When the ammonia nitrogen concentration in the aerobic zone II is higher than 4 mg / L, the effluent quality is at risk of exceeding the standard. This condition is set to ensure that the effluent quality meets the standard stably. If the ammonia nitrogen concentration in the aerobic zone II is not found to be higher than 4 mg / L, step 6 is run continuously for 1 to 2 hours, and then the process is switched to steps 1 to 5.

[0022] Step 8: Repeat steps 1-7 to complete the efficient removal of pollutants in urban sewage.

[0023] Preferably, the sewage residence time in the anaerobic zone is 0.5-1.5h, the sewage residence time in the anoxic zone is 1.5-3.0h, the sewage residence time in the aerobic zone I is 1.5-5.0h, the sewage residence time in the aerobic zone II is 0.5-1.0h, and the sewage residence time in the aerobic zone III is 1.0-3.0h.

[0024] Preferably, the sampling and monitoring time interval of the ammonia nitrogen online monitoring device in the aerobic II zone is 15 minutes to 30 minutes.

[0025] Compared with the prior art, the present invention has the following advantages and effects:

[0026] The system of the present invention has a strong phosphorus removal and nitrogen removal capability: the present invention adopts an intermittent operation mode for the anaerobic zone sludge return. When the sludge return is turned on, the anaerobic zone agitator stops working, allowing more sludge to be stored in the anaerobic zone. When the sludge return stops working, the anaerobic zone agitator starts working, so that the sludge and the influent are fully mixed. Since there is no large amount of nitrate brought by the sludge return at this time, the polyphosphate bacteria can complete the anaerobic phosphorus release process at this time. Subsequently, the polyphosphate bacteria will pass through the subsequent aerobic stage and finally achieve efficient phosphorus removal in the system. At the same time, an ammonia nitrogen online monitoring device is provided in the aerobic zone. The aeration of the aerobic zone of the system is controlled by the ammonia nitrogen concentration, which reduces the consumption of carbon source by excessive aeration of the system and effectively enhances the phosphorus removal and nitrogen removal capability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the planar layout structure of the integrated sewage treatment device of the present invention.

[0028] In the figure: 1- anaerobic zone; 2- anoxic zone; 3- aerobic zone I; 4- aerobic zone II; 5- aerobic zone III; 6- sedimentation zone; 7- nitrification liquid return pump; 8- sludge return pump; 9- ammonia nitrogen online monitoring device. DETAILED DESCRIPTION

[0029] To help those skilled in the art better understand the technical solutions of the present invention, the preferred embodiments of the present invention are described below in conjunction with specific examples. However, it should be understood that the drawings are for illustrative purposes only and are not to be construed as limiting this patent. To better illustrate this embodiment, some components in the drawings may be omitted, enlarged, or reduced, and do not represent the dimensions of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions may be omitted in the drawings. The positional relationships described in the drawings are for illustrative purposes only and are not to be construed as limiting this patent.

[0030] like Figure 1 As shown, a sewage treatment device suitable for a low carbon-nitrogen ratio includes an anaerobic zone 1, an anoxic zone 2, an aerobic zone I 3, an aerobic zone II 4, an aerobic zone III 5 and a sedimentation zone 6 connected in sequence. Part of the sewage in the aerobic zone III 5 is returned to the anoxic zone 2 through a nitrification liquid return pump 7, and part of the sludge in the sedimentation zone 6 is returned to the anaerobic zone 1 through a sludge return pump 8, and the other part of the sludge is discharged.

[0031] The anaerobic zone 1, anoxic zone 2, and aerobic zone II 4 are each equipped with agitators; the aerobic zone I 3, aerobic zone II 4, and aerobic zone III 5 are each equipped with aeration devices. An ammonia nitrogen online monitoring device 9 is installed in the aerobic zone II 4 to monitor the ammonia nitrogen concentration in the aerobic zone II. Its specific structure and operating principle can be selected from conventional techniques in the art.

[0032] The connection hole between the anaerobic zone 1 and the anoxic zone 2 is located at 1 / 2 to 2 / 3 of the tank body height. The sludge return ratio in the anaerobic zone 1 is 100% to 200%.

[0033] The present invention is implemented according to the following steps:

[0034] 1) Influent water quality COD is 108mg / L, NH4 + -N is 24mg / L, TN is 28mg / L, and TP is 2.6mg / .

[0035] 2) Continuous water inlet and outlet are adopted, and the aeration air-water ratio in the aerobic zone of the biological reactor is 3.6;

[0036] 3) The activated sludge concentration in the biological reactor is maintained at 3800 mg / L;

[0037] 4) Sewage and part of the return sludge enter the anaerobic zone, the agitator in the anaerobic zone does not work, and the residence time is 1.5 hours;

[0038] 5) The sewage and part of the reflux nitrification liquid enter the anoxic zone, and the agitator in the anoxic zone starts working with a residence time of 3.0h;

[0039] 6) The sewage enters the aerobic zone 13 with a residence time of 4.0 h. Aeration is carried out in the aerobic zone by a conventional blower, and the DO in the aerobic zone is controlled at above 1.5 mg / L;

[0040] 7) The sewage enters the aerobic II zone 4 with a residence time of 0.5 h. Aeration is carried out in the aerobic zone by a conventional blower, and the DO in the aerobic zone is controlled at above 1.5 mg / L;

[0041] 8) The sewage enters the aerobic zone III 5, where it stays for 2.0 hours and is aerated by a conventional blower. The DO in the aerobic zone is controlled at above 1.5 mg / L.

[0042] 9) After 2.5 hours of continuous operation according to 2) to 8), the ammonia nitrogen concentration in aerobic zone II 4 is 1.2 mg / L, the sludge return pump stops working, the agitators in the anaerobic zone and aerobic zone II 4 start working, and aeration is stopped in aerobic zone I 3, aerobic zone II 4, and aerobic zone III 5;

[0043] 10) After 1.5 hours of continuous operation according to 9), the ammonia nitrogen concentration in aerobic zone II 4 was 2.4 mg / L, and the reactor was switched to operation according to 2) to 8) again.

[0044] Repeat steps 2) to 10) to run the effluent COD and NH4 + The concentrations of -N, TN and TP are 18 mg / L, 0.46 mg / L, 13.42 mg / L and 0.46 mg / L respectively. The effluent quality is better than the requirements of Level A of the "Pollutant Discharge Standard for Urban Wastewater Treatment Plants" (GB18918-2002).

[0045] When the reactor is operated according to 2) to 8), the effluent COD and NH4 + The concentrations of -N, TN and TP were 16 mg / L, 0.24 mg / L, 15.48 mg / L and 1.15 mg / L respectively. The effluent quality could not meet the requirements of Level A of the "Pollutant Discharge Standard for Urban Wastewater Treatment Plants" (GB18918-2002).

[0046] It can be seen that the method of the present invention is suitable for treating sewage with a low carbon-nitrogen ratio.

[0047] According to the description and drawings of the present invention, those skilled in the art can easily manufacture or use the sewage treatment device and method suitable for low carbon-nitrogen ratio of the present invention, and can produce the positive effects described in the present invention.

[0048] Unless otherwise specified, in the present invention, if there are terms such as "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicating orientation or positional relationships, they are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the orientation or positional relationships in the present invention are only used for illustrative purposes and cannot be understood as limiting this patent. For ordinary technicians in this field, they can understand the specific meanings of the above terms in conjunction with the drawings and according to specific circumstances.

[0049] Unless otherwise specified or limited, the terms "disposed," "connected," and "connected" in this disclosure should be interpreted broadly. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to direct connections, indirect connections through an intermediary, or internal connections between two components. Those skilled in the art will understand the specific meanings of these terms in this disclosure based on the specific circumstances.

[0050] The above is only a preferred embodiment of the present invention, but the present invention is not limited to the above specific embodiment. Those skilled in the art may make several modifications, supplements or use similar methods instead without departing from the principles of the present invention, and these should also be considered as the scope of protection of the present invention.

Claims

1. A method for treating sewage with a low carbon-nitrogen ratio, characterized in that: The sewage treatment device comprises an anaerobic zone (1), an anoxic zone (2), an aerobic zone I (3), an aerobic zone II (4), an aerobic zone III (5) and a sedimentation zone (6) which are connected in sequence, wherein part of the sewage in the aerobic zone III (5) is returned to the anoxic zone (2), part of the sludge in the sedimentation zone (6) is returned to the anaerobic zone (1), and the other part of the sludge is discharged; The sewage treatment method comprises the following steps: Step 1: The sewage enters the anaerobic zone (1), the anoxic zone (2), the aerobic zone I (3), the aerobic zone II (4), the aerobic zone III (5), and the sedimentation zone (6) in sequence; Step 2: A portion of the wastewater from the aerobic zone III (5) flows back to the anoxic zone (2), and the other portion flows into the sedimentation zone (6); Step 3: A portion of the sludge in the sedimentation zone (6) is discharged, and the other portion is returned to the anaerobic zone (1) through the sludge return pump (8), and the agitator in the anaerobic zone (1) does not work; Step 4: The agitator in the anoxic zone (2) starts to work, completing the mixing of activated sludge and water; Step 5: Air is introduced into the aerobic zone I (3), aerobic zone II (4), and aerobic zone III (5) through a conventional blower, and the aeration device starts working, while the agitator in the aerobic zone II (4) does not work; Step 6: Steps 1-5 are run continuously for 2-3 hours. When the ammonia nitrogen concentration in the aerobic zone II is lower than 2 mg / L, the sludge return pump (8) stops working, the agitators in the anaerobic zone (1) and the aerobic zone II (4) start working, the air supply to the aerobic zone I (3), the aerobic zone II (4) and the aerobic zone III (5) stops, and the aeration device stops working; Step 7: During the continuous process of step 6, if the ammonia nitrogen concentration in aerobic zone II is found to be higher than 4 mg / L, air is introduced into aerobic zone I (3), aerobic zone II (4), and aerobic zone III (5), and the other processes remain unchanged until the process continues for 1 to 2 hours, and then the process switches to step 1-5. If the ammonia nitrogen concentration in aerobic zone II (4) is not found to be higher than 4 mg / L, step 6 is continued for 1 to 2 hours, and then the process switches to step 1-5. Step 8: Repeat steps 1-7 to complete the efficient removal of pollutants in urban sewage.

2. The method for treating sewage with a low carbon-nitrogen ratio according to claim 1, wherein: An ammonia nitrogen online monitoring device (9) is provided in the aerobic II zone (4).

3. The method for treating sewage with a low carbon-nitrogen ratio according to claim 1, wherein: The anaerobic zone (1), the anoxic zone (2) and the aerobic zone II (4) are all provided with agitators; and the aerobic zone I (3), the aerobic zone II (4) and the aerobic zone III (5) are all provided with aeration devices.

4. The method for treating sewage with a low carbon-nitrogen ratio according to claim 1, wherein: The connection hole between the anaerobic zone (1) and the anoxic zone (2) is located at 1 / 2 to 2 / 3 of the height of the tank body.

5. The method for treating sewage with a low carbon-nitrogen ratio according to claim 1, wherein: The sludge return ratio in the anaerobic zone (1) is 100% to 200%.

6. The method for treating sewage with a low carbon-nitrogen ratio according to claim 1, wherein: Part of the sewage in the aerobic III zone (5) is returned to the anoxic zone (2) through the nitrification liquid return pump (7).

7. The method for treating sewage with a low carbon-nitrogen ratio according to claim 1, wherein: Part of the sludge in the sedimentation zone (6) is returned to the anaerobic zone (1) through the sludge return pump (8).

8. The method for treating sewage with a low carbon-nitrogen ratio according to claim 1, wherein: The residence time of sewage in the anaerobic zone (1) is 0.5~1.5h, the residence time of sewage in the anoxic zone (2) is 1.5~3.0h, the residence time of sewage in the aerobic zone I (3) is 1.5~5.0h, the residence time of sewage in the aerobic zone II is 0.5~1.0h, and the residence time of sewage in the aerobic zone III (5) is 1.0~3.0h.

9. The method for treating sewage with a low carbon-nitrogen ratio according to claim 1, wherein: The sampling and monitoring time interval of the ammonia nitrogen online monitoring device (9) in the aerobic II zone (4) is 15 minutes to 30 minutes.

Images