A reactor and method for culturing aerobic granular sludge in continuous flow

Abstract

This invention discloses a reactor for continuous flow aerobic granular sludge cultivation, comprising: a sludge contact tank, including an inlet A, a sludge-water mixing device, and an outlet A; a sludge lifting tank, including an aeration system A, an air-lift sludge device, an inlet B, an outlet B, and a gas guide plate A; an aerobic aeration tank, including an aeration system B, an internal circulation device, an inlet C, an outlet C, and a gas guide plate B; a sludge-water circulation pipe A, connecting the outlet A of the sludge contact tank and the inlet C of the aerobic aeration tank; a sludge-water circulation pipe B, connecting the outlet C of the aerobic aeration tank and the inlet B of the sludge lifting tank; and a sludge-water circulation pipe C, connecting the air-lift sludge device and the sludge contact tank. This invention provides technical support for the rapid cultivation of AGS under continuous flow processes.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to a reactor and method for continuously flowing downflow culture of aerobic granular sludge. Background Technology

[0002] Aerobic granular sludge (AGS) has the characteristics of good settling performance, strong shock resistance, and simultaneous nitrogen and phosphorus removal, but it also has limitations such as long cultivation cycle, difficulty in cultivation, and harsh operating conditions.

[0003] Currently, the technology for cultivating aerobic granular sludge (AGS) is mainly based on the sequencing batch reactor (SBR) process.

[0004] For example, under SBR process conditions, AGS was successfully cultivated by alternating between sludge saturation and starvation to increase hydraulic shear force, washing flocculent sludge, and adding flocculants and crystal nuclei.

[0005] However, in actual engineering practice, due to the high requirements for operation and management of the SBR process, the adoption rate of the SBR process is not as high as that of the continuous flow process.

[0006] In particular, most large-scale wastewater treatment plants in China use continuous flow processes.

[0007] However, under continuous flow processes, it is difficult to achieve alternating periods of sludge saturation and starvation, and it is impossible to selectively wash flocculent sludge. Low hydraulic shear force and problems such as the need for pumps to crush granular sludge during sludge recirculation have become bottlenecks limiting the cultivation of AGS.

[0008] Currently, the technology for cultivating AGS in continuous flow processes lags significantly behind that of SBR processes and is mainly in the laboratory research stage. Summary of the Invention

[0009] To address the shortcomings of existing technologies, this invention provides a reactor and method for continuous flow cultivation of aerobic granular sludge. By employing airlift and gravity flow methods, the sludge-water mixture is circulated between the sludge contact tank, the aerobic aeration tank, and the sludge lifting tank, thus solving the problems in the prior art.

[0010] The objective of this invention is achieved as follows: a reactor for continuous flow cultivation of aerobic granular sludge, comprising: The sludge contact tank includes inlet A, sludge mixing device, and outlet A; The sludge lifting tank includes an aeration system A, an air-lift sludge device, an inlet B, an outlet B, and a gas guide plate A. The aeration system A is located at the bottom of the sludge lifting tank, the air-lift sludge device is located above the aeration system of the sludge lifting tank, the inlet B is located above the gas collection hood A, the outlet B is located at the top of the sludge lifting tank, and the gas guide plate A is located below the air-lift sludge device. An aerobic aeration tank includes an aeration system B, an internal circulation device, an inlet C, an outlet C, and a gas guide plate B. The aeration system B is located at the bottom of the aerobic aeration tank, the inlet C is located below the gas collection hood B, the outlet C is located at the top of the aerobic aeration tank, and the gas guide plate B is located below the internal circulation device. Sludge-water circulation pipe A connects the sludge contact tank outlet A and the aerobic aeration tank inlet C. Sludge circulation pipe B connects to the outlet C of the aerobic aeration tank and the inlet B of the sludge lifting tank. Sludge circulation pipe C connects the air-lift sludge device and the sludge contact tank.

[0011] Furthermore, the air-lift sludge device consists of an air-collecting hood A and a spiral rising pipe A, with the rising pipe A vertically connected above the air-collecting hood A and above the designed liquid level; the internal circulation device consists of an air-collecting hood B and a spiral rising pipe B, with the rising pipe B vertically connected above the air-collecting hood B and its outlet located below the designed liquid level of the aerobic aeration tank.

[0012] A method for continuously flowing down-cultured aerobic granular sludge, using the aforementioned reactor, includes the following steps: 1) Soak the biodegradable wastewater treatment plant sludge in clean water for a set time, intermittently stirring during the soaking period to produce pre-granulated seed sludge; add the pre-granulated seed sludge to the sludge contact tank, aerobic aeration tank, and sludge lifting tank of the continuous flow reactor respectively; fill the continuous flow reactor with clean water to the designed liquid level; turn on the aeration system of the aerobic aeration tank and sludge lifting tank and the agitator of the sludge contact tank, and aerate for a set time without water intake to activate the sludge in the reactor; 2) After the sludge activation is completed, the wastewater to be treated is introduced into the reactor from the sludge contact tank in a continuous flow manner and is fully mixed with the sludge in the tank. 3) The wastewater to be treated entering the continuous flow reactor circulates in the order of sludge-water lifting tank => aerobic aeration tank => sludge lifting tank. During this process, pollutants in the wastewater to be treated are removed, and the treated wastewater is discharged from the outlet of the sludge lifting tank. In the sludge lifting tank, the settling zone formed around the sludge lifting device uses selective pressure to retain sludge with good settling performance and washes out the flocculent sludge with poor settling performance from the reactor. In the aerobic aeration tank, sludge-water self-circulation is achieved with the internal circulation device as the center, which improves the hydraulic shear force and retains granular sludge with good settling performance in the aerobic aeration tank.

[0013] Furthermore, when it is necessary to improve the washing efficiency of flocculent sludge, the vertical height h1 between the inlet B and outlet B of the sludge lifting tank can be shortened, and vice versa. When it is necessary to increase the self-circulating water volume in the aerobic aeration tank, measures such as increasing the aeration intensity, reducing the inner diameter of the riser pipe B, and increasing the vertical height h3 of the riser pipe B can be taken to increase the sludge-water flow velocity in the riser pipe B and increase the total amount of sludge-water lifted by the internal circulation device. The reverse is also true. When it is necessary to increase the sludge return ratio, measures such as increasing the aeration intensity of the sludge lifting tank, reducing the inner diameter of the riser pipe A, and increasing the vertical height h2 of the riser pipe A can be taken to increase the sludge-water flow velocity of the riser pipe A, increase the total amount of sludge and water lifted by the air-lift sludge device, and increase the hydraulic shear force. The reverse is also true.

[0014] Furthermore, the seed sludge dosage is above 5000 mg / L, and during the start-up and operation of the continuous flow reactor, the MLSS in the high dissolved oxygen zone of the aerobic aeration tank is controlled to be above 4000 mg / L.

[0015] Furthermore, the height-to-diameter ratio of the sludge lifting device should be controlled above 4.

[0016] Furthermore, the ratio of the sludge saturation period to the starvation period should be controlled to be above 1:3.

[0017] Furthermore, the dissolved oxygen in the sludge contact tank is controlled at <0.3 mg / L.

[0018] Furthermore, the dissolved oxygen (DO) at the outlet of the aerobic aeration tank should be controlled at around 2.0 mg / L.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention employs airlift and gravity flow methods to achieve sludge-water circulation between the sludge contact tank, aerobic aeration tank, and sludge lift tank. The reactor: A) achieves alternating sludge saturation and starvation environments through sludge-water circulation between different tanks; B) utilizes the settling zones of the airlift sludge tank and aerobic aeration tank to wash out poorly settling flocculent sludge from the reactor, retaining granular sludge with good settling properties; C) rapidly spirals upwards through the sludge-water flow in riser pipes A and B, increasing hydraulic shear force and achieving regular sludge rotation; D) reduces the crushing and breaking down of granular sludge during sludge circulation through airlift and gravity flow. This invention provides technical support for the rapid cultivation of AGS in continuous flow processes. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the reactor structure of the present invention.

[0022] The components are as follows: 1. Stirring motor; 2. Stirring paddle; 3. Sludge contact tank; 4. Sludge sampling port; 5. Inlet A; 6. Inlet B; 7. Gas guide plate B; 8. Sludge-water circulation pipe A; 9. Aerobic aeration tank; 10. Downflow zone; 11. Upflow pipe B; 12. Gas collection hood B; 13. High dissolved oxygen zone; 14. Outlet A; 15. Sedimentation zone; 16. Outlet C; 17. Inlet C; 18. Gas guide plate A; 19. Gas collection hood A; 20. Aeration system B; 21. Aeration system A; 22. Sludge-water circulation pipe C; 23. Outlet B; 24. Sludge lifting tank; 25. Sludge-water circulation pipe B; 26. Upflow pipe A; 27. Valve; 28. Sludge discharge port. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] like Figure 1 The reactor shown is for continuous flow cultivation of aerobic granular sludge, comprising: The sludge contact tank 3 includes an inlet A 5, a sludge mixing device, an outlet A 14, and a sludge sampling port 4. The mixing device includes a mixing blade 2 controlled by a mixing motor 1. The sludge lifting tank 24 includes an aeration system A 21, an air-lift sludge device, an inlet B 6, an outlet B 23, a gas guide plate A 18, and a sludge sampling port 4. The aeration system A 21 is located at the bottom of the sludge lifting tank 24, the air-lift sludge device is located above the aeration system of the sludge lifting tank 24, the inlet B 6 is located above the air collection hood A 19 of the air-lift sludge device, the outlet B 23 is located at the top of the sludge lifting tank 24, the gas guide plate A 18 is located below the air-lift sludge device, and a valve 27 is installed on the sludge discharge port 28. The aerobic aeration tank 9 includes an aeration system B 20, an internal circulation device, an inlet C 17, an outlet C 16, a gas guide plate B 7, and a sludge sampling port 4. The aeration system B 20 is located at the bottom of the aerobic aeration tank 9, the inlet C 17 is located in the high dissolved oxygen zone 13, the outlet C 16 is located at the top of the aerobic aeration tank 9, and the gas guide plate B 7 is located below the internal circulation device. The mud-water circulation pipe A8 connects the outlet A14 of the sludge contact tank 3 and the inlet C17 of the aerobic aeration tank 9. The mud-water circulation pipe B 25 connects the outlet C 16 of the aerobic aeration tank 9 and the inlet B 6 of the sludge lifting tank 24. Sludge circulation pipe C 22 connects the air-lift sludge device and the sludge contact tank 3.

[0025] The air-lift sludge device consists of an air collection hood A19 and a spiral rising pipe A26. The rising pipe A26 is vertically connected above the air collection hood A19 and is above the design liquid level. The internal circulation device consists of an air collection hood B12 and a spiral rising pipe B11. The rising pipe B11 is vertically connected above the air collection hood B12 and its outlet is located below the design liquid level of the aerobic aeration tank 9.

[0026] A method for continuously flowing down-cultured aerobic granular sludge includes: Wastewater treatment plant sludge with good biodegradability (such as dairy wastewater) is soaked in clean water for about one week, with intermittent stirring during the process, to produce pre-granulated seed sludge.

[0027] Pre-granulated seed sludge was added to a continuous flow reactor. Figure 1 ) In sludge contact tank 3, aerobic aeration tank 9 and sludge lifting tank 24.

[0028] The seed sludge dosage is such that, during the start-up and operation of the continuous flow reactor, it can ensure that the MLSS in the high dissolved oxygen zone 13 of the aerobic aeration tank 9 is above 4000 mg / L.

[0029] Fill the continuous flow reactor with clean water to the designed liquid level.

[0030] Turn on the aeration systems of aerobic aeration tank 9 and sludge lifting tank 24, as well as the agitator of sludge contact tank 3, and aerate for about 3 days without water intake to activate the sludge in the reactor.

[0031] The air-lift sludge device in sludge lifting tank 24 generates a density difference from low to high during the gas flow process. This density difference is used as a driving force to lift the sludge and water below the air-lift sludge device to the sludge contact tank 3.

[0032] The sludge and water that are lifted to the sludge contact tank 3 will flow by gravity into the aerobic aeration tank 9 and the sludge lifting tank 24 due to the water level difference.

[0033] Through the aforementioned lifting and gravity flow of sludge, the sludge is circulated among the three reaction tanks of the continuous flow reactor.

[0034] After the sludge activation is completed, the wastewater to be treated (nutrient substrate) enters the reactor from the sludge contact tank in a continuous flow manner, and is fully mixed with the sludge in the tank, creating saturated conditions for the sludge and carrying out denitrification under anoxic conditions.

[0035] In the aerobic aeration tank 9 and the sludge lifting tank 24, pollutants (nutrient substrates) in the wastewater are oxidized and decomposed, creating starvation conditions for the sludge in the tank.

[0036] By circulating the sludge and water between different tanks in the continuous flow reactor, an alternating environment of saturation and starvation is created for the sludge in the reactor.

[0037] The wastewater to be treated entering the continuous flow reactor circulates in the order of sludge lifting tank 3 => aerobic aeration tank 9 => sludge lifting tank 24. During this process, the pollutants in the wastewater to be treated are removed, and the treated wastewater is discharged from the outlet of sludge lifting tank 24.

[0038] In the sludge lifting tank 24, the sedimentation zone 15 formed around the air-lift sludge device is used to selectively pressurize sludge with different settling properties, retaining sludge with good settling properties and washing out flocculent sludge with poor settling properties from the reactor.

[0039] When it is necessary to improve the washing efficiency of flocculent sludge, the vertical height h1 between the inlet B6 and outlet B23 of the sludge lifting tank 24 can be shortened, and vice versa.

[0040] In the aerobic aeration tank 9, the density difference generated during the gas lifting process in the internal circulation device is used to quickly lift the sludge and water in the high dissolved oxygen zone 13 below the internal circulation device to the outlet of the upflow pipe B 11 for release. When the lifted water volume is greater than the inflow volume of the aerobic aeration tank 9, the sludge and water exceeding the inflow volume will flow back to the high dissolved oxygen zone 13 in the downflow 10 formed around the internal circulation device, thus realizing the sludge and water self-circulation centered on the internal circulation device.

[0041] During the sludge-water self-circulation process, firstly, the rapid spiral ascent of sludge-water within the rising pipe B 11 creates high hydraulic shear force for the cultivation of aerobic granular sludge and enables the sludge to rotate regularly; secondly, the descending flow 10 formed around the gas guiding device stores granular sludge with good settling performance in the aerobic aeration tank 9.

[0042] When it is necessary to increase the self-circulating water volume and hydraulic shear force in the aerobic aeration tank 9, measures such as increasing the aeration intensity, reducing the inner diameter of the riser pipe B 11, and increasing the vertical height h3 of the riser pipe B 11 can be taken to increase the sludge flow velocity in the riser pipe B 11 and increase the total amount of sludge and water lifted by the internal circulation device. The reverse is also true.

[0043] When it is necessary to increase the sludge return ratio and hydraulic shear force, measures such as increasing the aeration intensity of the sludge lifting tank 24, reducing the inner diameter of the riser pipe A 26, and increasing the vertical height h2 of the riser pipe A 26 can be taken to increase the sludge-water flow velocity of the riser pipe A 26 and increase the total amount of sludge and water lifted by the air-lift sludge device, and vice versa.

[0044] During the air-lift sludge process, the rapid spiral ascent of sludge and water in the upflow pipe A26 creates high hydraulic shear force for rapid AGS cultivation and enables the sludge to rotate regularly.

[0045] The height-to-diameter ratio (bottom diameter of the gas collection hood A19) of the sludge lifting device should be controlled above 4.

[0046] Gas guide vanes A 18 and B (7, 18) are installed below the gas collection hood A 19 of the gas guide device and the gas collection hood B 12 of the sludge lifting device.

[0047] The ratio of the sludge saturation period (HRT of sludge contact tank 3) to the sludge starvation period (total HRT of aerobic aeration tank 9 and sludge lifting tank 24) should be controlled to be above 1:3.

[0048] The dissolved oxygen (DO) in sludge contact tank 3 is controlled at <0.3 mg / L.

[0049] The DO at the outlet of aerobic aeration tank 9 (C 16) should be controlled at around 2.0 mg / L.

[0050] During the start-up and operation of the continuous flow reactor, the MLSS in the high dissolved oxygen zone 13 of the aerobic aeration tank 9 should be controlled at >4000 mg / L.

[0051] Multiple internal circulation devices can be installed simultaneously in the aerobic aeration tank 9 as needed (e.g., reactor size).

[0052] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A reactor for culturing aerobic granular sludge in continuous flow, characterized in that, include: The sludge contact tank includes inlet A, sludge mixing device, and outlet A; The sludge lifting tank includes an aeration system A, an air-lift sludge device, an inlet B, an outlet B, and a gas guide plate A. The aeration system A is located at the bottom of the sludge lifting tank, and the air-lift sludge device is located above the aeration system A. The air-lift sludge device consists of an air collection hood A and a spiral rising pipe A. The rising pipe A is vertically connected above the air collection hood A and is above the design liquid level. The inlet B is located above the air collection hood A, the outlet B is located at the top of the sludge lifting tank, and the gas guide plate A is located below the air-lift sludge device. The aerobic aeration tank includes an aeration system B, an internal circulation device, an inlet C, an outlet C, and a gas guide plate B. The aeration system B is located at the bottom of the aerobic aeration tank. The internal circulation device consists of a gas collection hood B and a spiral rising pipe B. The rising pipe B is vertically connected above the gas collection hood B, and the outlet of the rising pipe B is located below the designed liquid level of the aerobic aeration tank. The inlet C is located below the gas collection hood B, the outlet C is located above the aerobic aeration tank, and the gas guide plate B is located below the internal circulation device. Sludge-water circulation pipe A connects the sludge contact tank outlet A and the aerobic aeration tank inlet C. Sludge circulation pipe B connects to the outlet C of the aerobic aeration tank and the inlet B of the sludge lifting tank. Sludge circulation pipe C connects the air-lift sludge device and the sludge contact tank.

2. A method for culturing aerobic granular sludge in continuous flow, using a reactor according to claim 1, characterized in that, Includes the following steps: 1) Soak the biodegradable wastewater treatment plant sludge in clean water for a set time, with intermittent stirring during the soaking period, to produce pre-granulated seed sludge; Pre-granulated seed sludge is added to the sludge contact tank, aerobic aeration tank, and sludge lift tank of the continuous flow reactor, respectively. The continuous flow reactor is filled with clean water to the designed liquid level. The aeration system of the aerobic aeration tank and the sludge lift tank and the agitator of the sludge contact tank are turned on. Under the condition of no water intake, the sludge in the reactor is activated by aeration for a set time. 2) After the sludge activation is completed, the wastewater to be treated is introduced into the reactor from the sludge contact tank in a continuous flow manner and is fully mixed with the sludge in the tank. 3) The wastewater to be treated entering the continuous flow reactor circulates in the order of sludge contact tank => aerobic aeration tank => sludge lift tank. During this process, pollutants in the wastewater to be treated are removed, and the treated wastewater is discharged from the outlet of the sludge lift tank. In the sludge lift tank, sludge with different settling properties is selected, and sludge with good settling properties is retained, while flocculent sludge with poor settling properties is washed out of the reactor. In the aerobic aeration tank, sludge-water self-circulation is achieved with the internal circulation device as the center, which improves the hydraulic shear force while retaining granular sludge with good settling properties in the aerobic aeration tank.

3. The method for culturing aerobic granular sludge in continuous flow down according to claim 2, characterized in that, When it is necessary to improve the washing efficiency of flocculent sludge, the vertical height h1 between the inlet B and outlet B of the sludge lifting tank is shortened, and vice versa. When it is necessary to increase the self-circulating water volume in the aerobic aeration tank, measures such as increasing the aeration intensity, reducing the inner diameter of the riser pipe B, and increasing the vertical height h3 of the riser pipe B can be taken to increase the sludge flow velocity in the riser pipe B and increase the total amount of sludge and water lifted by the internal circulation device. The reverse is also true. When it is necessary to increase the sludge return ratio, measures such as increasing the aeration intensity of the sludge lift tank, reducing the inner diameter of the riser pipe A, and increasing the vertical height h2 of the riser pipe A can be taken to increase the sludge-water flow rate of the riser pipe A and increase the total amount of sludge and water lifted by the air-lift sludge device. The reverse is also true.

4. The method for culturing aerobic granular sludge in continuous flow down according to claim 2 or 3, characterized in that, The dosage of seed sludge is above 5000 mg / L.

5. The method for culturing aerobic granular sludge in continuous flow down according to claim 2 or 3, characterized in that, The height-to-diameter ratio of the sludge lifting tank should be controlled above 4.

6. The method for culturing aerobic granular sludge in continuous flow down according to claim 2 or 3, characterized in that, The ratio of the sludge's saturation period to its starvation period should be controlled to be above 1:

3.

7. The method for culturing aerobic granular sludge in continuous flow down according to claim 2 or 3, characterized in that, The dissolved oxygen in the sludge contact tank should be controlled at <0.3 mg / L.

8. The method for culturing aerobic granular sludge in continuous flow down according to claim 2 or 3, characterized in that, The dissolved oxygen (DO) at the outlet of the aerobic aeration tank should be controlled at 2.0 mg / L.

9. A method for culturing aerobic granular sludge in continuous flow down according to claim 2 or 3, characterized in that, The sludge concentration in the high dissolved oxygen zone below the circulation device in the aerobic aeration tank of the continuous flow reactor is controlled at >4000 mg / L.

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