Aerobic granular sludge culture method and device

Abstract

The invention discloses a low-carbon and energy-saving sludge culture method and device of an aerobic granular sludge technology, the device is mainly used for sewage treatment, and the device comprises a reaction tank (1), an aeration mechanism, a sludge discharge mechanism, a water distribution system and a control system (2); the reaction tank is used for accommodating a mixed solution containing activated sludge; the aeration mechanism is configured to supplement oxygen into the mixed liquid; the sludge discharge mechanism is configured to discharge the mixed liquid in the reaction tank; the water distribution system is configured to add water into the reaction tank (1) and has a first water adding state and a second water adding state, the first water flow speed of the first water adding state is V1, the second water flow speed of the second water adding state is V2, and V2 is greater than V1; the control system is configured to control the working state of the water distribution system according to the sludge volume index (SII30) and the concentration of the mixed liquid suspended solids (MLSS), and the running time and the water flow speed in the corresponding working state.

Description

Technical Field

[0001] The invention relates to the technical field of sewage treatment, and in particular to a sludge cultivation method and a device of an energy-saving and low-carbon aerobic granular sludge technology. Background Art

[0002] Aerobic granular sludge technology is a sewage treatment technology that has been widely studied at home and abroad in the past decade. More than 100 sewage treatment plants abroad have adopted this process. Compared with traditional processes, it can reduce the floor space by about 25% to 70%, reduce the operating energy consumption by about 20% to 50%, and reduce the investment and construction costs and operating agent costs. The degradation rate of pollutants is better than the existing process, and it has great social and economic benefits. In recent years, this technology has also moved from the laboratory exploratory research stage to the engineering application stage in China. At present, if this process is to be applied to domestic sewage treatment plants, the granular sludge mainly comes from flocculent sewage. In-situ cultivation and granulation of sludge. It is currently reported at home and abroad that the influent water quality of sewage treatment plants using aerobic granular sludge process is relatively high, with COD of about 500mg / L to 800mg / L, while the influent COD of most domestic municipal sewage treatment plants is about 150mg / L to 250mg / L, which will lead to a longer granulation time of aerobic granular sludge. The removal efficiency of pollutants by aerobic granular sludge system is related to the degree of sludge granulation. Therefore, in order to shorten the debugging period and make the effluent water quality meet the standards as soon as possible, it is extremely important to study a rapid granulation method under the condition of low COD concentration influent water quality.

[0003] At present, granular sludge has been successfully cultivated in the EBPR system, and the simultaneous nitrogen and phosphorus removal of aerobic granular sludge in the EBPR system has been achieved. However, there are still problems such as long start-up time and poor long-term operation stability, which largely restrict the promotion and use of this technology.

[0004] In response to the above technical problems, announcement number CN107986432A discloses an aerobic granular sludge cultivation method and a cultivation device, which realizes the switching of each stage including water inlet-anaerobic-aerobic-sedimentation-water outlet-idle by adjusting whether to start stirring, stirring speed, aeration, etc., and the time of each stage is controllable. Furthermore, the present invention sets multiple reaction conditions, which is conducive to the rapid cultivation of aerobic activated sludge particles, and ultimately realizes the synchronous removal of nitrogen, phosphorus and organic matter in sewage.

[0005] In order to overcome the above technical defects, the present invention provides a method for rapid granulation of aerobic granular sludge in treating low-concentration sewage, which effectively solves the problem of long debugging cycle. Summary of the invention

[0006] The object of the present invention is to provide an aerobic granular sludge cultivation device, aiming to solve at least one of the above technical problems.

[0007] The first aspect of the present application provides an aerobic granular sludge cultivation device, comprising: a reaction tank (1), an aeration mechanism, a sludge discharge mechanism, a water distribution system and a control system (2);

[0008] The reaction tank is used to accommodate a mixed liquid containing activated sludge;

[0009] The aeration mechanism is configured to add oxygen to the mixed liquid;

[0010] The sludge discharge mechanism is configured to discharge the sludge in the reaction tank;

[0011] The water distribution system is configured to add water to the reaction tank (1), and has a first water adding state and a second water adding state, the first water flow rate in the first water adding state is S1, the second water flow rate in the second water adding state is S2, and S2 is greater than S1; the control system is configured to adjust the water flow rate according to SVI 30 and MLSS concentration to control the working state of the water distribution system, as well as the operating time and water flow rate under the corresponding working state.

[0012] In some embodiments of the present application, if the MLSS is 1000 mg / L to 3000 mg / L, SVI 30 If the flow rate is greater than 100 mL / g, the water distribution system alternately operates the first water adding state and the second water adding state, wherein S1 is not higher than 4 m / h; S2 is 8 m / h to 10 m / h, and the water distribution system operates the second water adding state for 3 to 5 seconds at a time;

[0013] If the MLSS is 4000mg / L to 6000mg / L, SVI 30 If the flow rate is less than 60 mL / g, the water distribution system alternately operates the first water adding state and the second water adding state, wherein S1 is not higher than 4 m / h, S2 is 10 m / h to 12 m / h, and the operation time of the water distribution system in the second water adding state is 5 seconds to 10 seconds;

[0014] If the MLSS is greater than 6000 mg / L, SVI 30 If the flow rate is less than 50 mL / g, the water distribution system continues to operate in the first water adding state, wherein S1 is not higher than 4 m / h.

[0015] In some embodiments of the present application, the water distribution system includes a water storage tank, a water inlet pipe, a variable frequency water inlet pump and a multi-point water distribution head, the water inlet pipe connects the water storage tank, the variable frequency water inlet pump and the multi-point water distribution head, and the multi-point water distribution head is arranged at the bottom of the reaction tank; the control system controls the size of S1 and S2 by controlling the operating frequency of the variable frequency water inlet pump.

[0016] In some embodiments of the present application, the control system is further configured to determine a water replacement ratio according to the particle proportion;

[0017] And / or, the control system is further configured to determine the water exchange ratio according to the organic sludge load in the system.

[0018] In some embodiments of the present application, if the particle ratio is less than 10%, the water replacement ratio is 70% to 75%;

[0019] If the particle ratio is 10% to 30%, the water replacement ratio is 60% to 70%;

[0020] If the particle ratio is greater than 40%, the water replacement ratio is 30% to 50%;

[0021] The water exchange ratio should be determined to preferably meet the requirement that the organic sludge load in the system is not less than 0.15 kgCOD / kgMLSS / d.

[0022] In some embodiments of the present application, the control system is further configured to control the water distribution system to be turned on or off according to a mapping relationship between the water exchange ratio and the operating time of the water distribution system;

[0023] And / or, the device further comprises a stirring mechanism, and the control system (2) is configured to start the stirring mechanism after the water distribution system stops.

[0024] In some embodiments of the present application, the aeration mechanism includes a variable frequency fan, and the control system is further configured to control the on / off of the fan and the operating frequency of the fan in the on state according to the dissolved oxygen concentration in the mixed liquid;

[0025] And / or, the aeration mechanism includes a variable frequency fan, and the control system is further configured to start the variable frequency fan after the stirring mechanism is turned off.

[0026] In some embodiments of the present application, the device further comprises a monitoring mechanism, and the monitoring mechanism is used to obtain the dissolved oxygen concentration and the ammonia nitrogen value in the mixed liquid;

[0027] In the early stage of aeration, the dissolved oxygen value is controlled to be 1 mg / L to 1.5 mg / L by the aeration mechanism;

[0028] and / or, when the ammonia nitrogen value is lower than a first threshold value a, reducing the operating frequency of the variable frequency fan so that the dissolved oxygen is controlled at 0.5 mg / L to 1 mg / L; wherein a is 30% to 40% of the ammonia nitrogen value of the inlet water or 120% to 140% of the designed ammonia nitrogen value of the outlet water;

[0029] And / or, when the ammonia nitrogen value is lower than a second threshold value b, the variable frequency fan is turned off and the stirring mechanism is turned on; wherein the b value is 10% to 20% higher than the designed outlet water ammonia nitrogen value.

[0030] In some embodiments of the present application, the control system is further configured to determine the mud discharge amount of the mud discharge mechanism according to the proportion of particles in the mixed liquid.

[0031] In some embodiments of the present application, if the proportion of granular sludge is less than 30%, the sludge discharge amount is calculated based on the sludge age of 20 to 30 days;

[0032] If the particle proportion is 30% to 50%, the sludge discharge volume is calculated based on the sludge age of 30 to 40 days;

[0033] If the proportion of particles is higher than 50% and the water output index of the device meets the standard, no mud will be discharged;

[0034] If the particle proportion is higher than 50%, and the total phosphorus value of the effluent of the device exceeds the preset value or the COD load is lower than 50% of the design load, the sludge discharge volume shall be calculated based on a sludge age of 35 to 45 days.

[0035] In some embodiments of the present application, the mud discharge mechanism includes a mud discharge port, and the distance between the mud discharge port and the water surface is L, L = V1*e*t, wherein t is the sedimentation time, L is the sinking distance of the granular sludge within the sedimentation time t, V1 is the average sedimentation velocity of the granular sludge, and e is the mass percentage of the granular sludge;

[0036] And / or, the sludge discharge mechanism includes a plurality of sludge discharge ports, the plurality of sludge discharge ports are located between L1 and L2, and are arranged at intervals along the height direction of the reaction tank; wherein, L2=V2*t, L1=V1*t, V1 is the average settling velocity of granular sludge, V2 is the average settling velocity of flocculent sludge, t is the settling time, L2 is the sinking distance when the proportion of granular sludge in the activated sludge is 100%, and L2 is the sinking distance when the proportion of particles in the activated sludge is 0;

[0037] And / or, V1 is greater than V2, then L1 is greater than L2, and in the vertical direction, L2 is always located above L1.

[0038] The second aspect of the present application provides an aerobic granular sludge cultivation method, comprising the following steps;

[0039] Inlet and outlet stage: Pulse water inlet is implemented synchronously when water inlet and outlet are started, and the screening process of granular sludge is initially completed during the synchronous inlet and outlet. Under the premise of meeting a certain sludge load, according to SVI 30 and MLSS to adjust the water change ratio in a timely manner;

[0040] Anaerobic stage: After the water inflow is completed, the pollution concentration in the system reaches the maximum value, and the system enters the anaerobic stage. In this stage, the stirring device is started to ensure that the new sewage and sludge are fully in contact;

[0041] Aeration stage: after the anaerobic stage is over, the stirring device is turned off, and the variable frequency fan is started to perform aeration operation. The on and off of the variable frequency fan and the operating frequency of the variable frequency fan in the on state are controlled according to the dissolved oxygen concentration and the ammonia nitrogen value in the mixed liquid; when the ammonia nitrogen value is lower than the preset threshold value, the aeration is turned off, and the stirring device is turned on to run for a preset time;

[0042] Sludge screening stage: After the aeration stage, the sludge discharge port is set at the position corresponding to the flocculent sludge by utilizing the vertical height difference between the granular sludge and the flocculent sludge during the sedimentation process. The flocculent sludge is discharged during the sedimentation stage, and the granular lower sludge is retained to realize the sludge screening process.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] In the embodiment of the present application, the control system is configured according to the SVI 30 The MLSS concentration controls the working state of the water distribution system, as well as the operating time and water flow rate under the corresponding working state, to create a "rich-hungry" environment to promote sludge granulation and to remove flocculent sludge in time, thereby completing the sludge washing process while water is entering, which is simple to operate, reduces equipment investment, and saves operating power consumption.

[0045] The present invention can accelerate the granulation process of flocculent sludge by pulse water inlet to wash flocculent sludge, high water exchange ratio to compensate for the lack of carbon source in low-concentration sewage, add a stirring device to enhance mass transfer and strengthen the starvation process, accurately control dissolved oxygen to ensure total nitrogen removal, and optimize the sludge outlet setting to retain granular sludge to the greatest extent. In a specific implementation case, when the water temperature is controlled at about 20°C, low-concentration municipal sewage is used as the system inlet water through the coordination of the device, and it runs for about 30 days. The volume proportion of granular sludge particles larger than 0.2 mm in the system increases from 6% to about 45%.

[0046] Other features and advantages of the present invention will be described in the following description, and partly become obvious from the description, or be understood by implementing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 AGS system device schematic diagram of the present invention;

[0048] Figure 2 It is a schematic diagram of the cycle operation flow chart of the AGS system of the present invention;

[0049] Figure 3 This is a trend diagram of particle proportion changes during the granulation period of the present invention.

[0050] In the figure: 1. AGS reaction tank; 2. Automatic control system; 3. Variable frequency fan; 4. Water distribution system; 5. Ammonia nitrogen detector; 6. DO detector; 7. Variable frequency water inlet pump; 8. Water inlet storage tank; 9. Water inlet pipe; 10. Aeration system; 11. Electric drain valve; 12. Manual mud discharge valve; 13. Electric mud discharge valve; 14. Mud discharge and storage tank; 15. Agitator. DETAILED DESCRIPTION

[0051] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. 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.

[0052] See also Figures 1 to 3 The present invention provides an aerobic granular sludge cultivation method and device, including an AGS reaction tank 1, wherein the interior of the AGS reaction tank 1 is respectively provided with an aeration mechanism, the interior of the AGS reaction tank 1 is also provided with a water adding mechanism and a stirrer 15 for water distribution, a monitoring mechanism is also provided above the AGS reaction tank 1, and the outside of the AGS reaction tank 1 is also provided with a drainage mechanism 11, a sludge discharge mechanism 12, a variable frequency fan 3 and an aeration system 10 connected to the exhaust end of the variable frequency fan 3, and the entire device is equipped with an automatic control system 2.

[0053] The water adding mechanism includes a water distribution system 4, and the water distribution system 4 includes a connecting pipe and a water distribution head. The connecting pipe is located inside the AGS reaction tank 1, and the water distribution head is connected to the top of the connecting pipe.

[0054] Furthermore, the bottom of the connecting pipe is connected to a water inlet pipe 9, one end of the water inlet pipe 9 is connected to a variable frequency water inlet pump 7, and the water inlet end of the variable frequency water inlet pump 7 is connected to a water inlet storage tank 8.

[0055] The monitoring mechanism includes an ammonia nitrogen detector 5 and a DO detector 6. The detection ends of the ammonia nitrogen detector 5 and the DO detector 6 are both located inside the AGS reaction tank 1 and need to be submerged in the mixed liquid placed in the reaction tank 1 during the stirring and aeration stages.

[0056] Furthermore, the discharge mechanism includes an electric drain valve 11, which is connected to one side of the AGS reaction tank 1, and a plurality of valve bodies are connected to the middle of one side of the AGS reaction tank 1. Exemplarily, four groups of valve bodies are connected to the middle of one side of the AGS reaction tank 1. The valve body can be a manual mud discharge valve or an electric mud discharge valve, which is not limited here.

[0057] Specifically, the valve body is a manual mud discharge valve 12 , wherein one end of the manual mud discharge valve 12 is also connected to an electric mud discharge valve 13 through a pipeline, and one end of the electric mud discharge valve 13 is connected to a mud discharge storage bucket 14 .

[0058] The operation mode of the above device is batch operation, and each cycle includes simultaneous water inlet / outlet, anaerobic stirring, aeration, and sedimentation stages, wherein the anaerobic stirring and aeration stages can be operated alternately;

[0059] The water is taken in from the bottom and drained from the top, and the treated water is discharged from the top while the water is taken in;

[0060] In the batch operation cycle of the above-mentioned device, the total operation time of each cycle can be set to 2 hours, 3 hours or 4 hours, among which the water inlet and outlet stage duration is 30 minutes to 80 minutes, and the sedimentation stage duration is 20 minutes to 40 minutes. The anaerobic stirring and aeration time is obtained by deducting the water inlet and outlet time and the sedimentation stage time from the total cycle time. When the total nitrogen and total phosphorus in the effluent exceed the standard, the anaerobic stirring time is gradually extended by 5 minutes. When the anaerobic time is operated in a 2-hour cycle, it generally does not exceed 30 minutes.

[0061] In one aspect, the present invention provides an aerobic granular sludge cultivation device, characterized in that it comprises: a reaction tank (1), an aeration mechanism, a sludge discharge mechanism, a water distribution system and a control system (2);

[0062] The reaction tank is used to accommodate a mixed liquid containing activated sludge;

[0063] The aeration mechanism is configured to add oxygen to the mixed liquid;

[0064] The sludge discharge mechanism is configured to discharge the sludge in the reaction tank;

[0065] The water distribution system is configured to add water to the reaction tank (1), and has a first water adding state and a second water adding state, the first water flow rate in the first water adding state is S1, the second water flow rate in the second water adding state is S2, and S2 is greater than S1; the control system is configured to adjust the water flow rate according to the SVI 30 The MLSS concentration controls the working state of the water distribution system, as well as the operating time and water flow rate under the corresponding working state.

[0066] In the embodiment of the present application, the control system is configured according to the SVI 30 The MLSS concentration controls the working state of the water distribution system, as well as the operating time and water flow rate under the corresponding working state, and can remove flocculent sludge in time, thereby completing the sludge washing process while water is entering. The operation is simple, equipment investment is reduced, the operation is simple, and the accident rate is low.

[0067] Specifically, if the MLSS is 1000 mg / L to 3000 mg / L, SVI 30 Greater than 100mL / g, the water distribution system alternately operates the first water adding state and the second water adding state, wherein S1 is not higher than 4m / h; S2 is 8m / h to 10m / h, and the water distribution system operates the second water adding state for 3 seconds to 5 seconds at a time.

[0068] It is understandable that when MLSS is 1000mg / L to 3000mg / L, SVI 30 When it is greater than 100 mL / g, the overall sedimentation performance of the sludge is poor, and the use of low-speed, short-duration pulses will not cause a large amount of sludge loss.

[0069] Specifically, if the MLSS is 4000 mg / L to 6000 mg / L, SVI 30 If the flow rate is less than 60 mL / g, the water distribution system alternately operates between the first water adding state and the second water adding state, wherein S1 is not higher than 4 m / h, S2 is 10 m / h to 12 m / h, and the operation time of the water distribution system in the second water adding state is 8 seconds to 10 seconds.

[0070] It is understandable that when MLSS rises to 4000mg / L to 6000mg / L and SVI 30 When it is lower than 60mL / g, it indicates that the sludge settling performance is improved. At this time, the proportion of granular sludge is increased. The flocculent sludge can be further washed out by extending the pulse duration (8 seconds to 10 seconds) and the pulse speed (10m / h to 12m / h), thereby further improving the efficiency of aerobic granular sludge granulation.

[0071] Specifically, if the MLSS is greater than 6000 mg / L, SVI 30 If the flow rate is less than 50 mL / g, the water distribution system continues to operate in the first water adding state, wherein S1 is not higher than 4 m / h.

[0072] It is understandable that when the sludge concentration is greater than 6000 mg / L and SVI 30 When it is less than 50 mL / g, it indicates that the granular sludge occupies a large proportion in the system, and the pulse water inlet can be cancelled, thereby retaining the granular sludge in the mixed liquid placed in the reaction tank 1.

[0073] In some embodiments of the present application, the water distribution system includes a water storage barrel, a water inlet pipe, a variable frequency water inlet pump and a multi-point water distribution head, the water inlet pipe connects the water storage barrel, the variable frequency water inlet pump and the multi-point water distribution head, and the multi-point water distribution head is arranged at the bottom of the reaction tank; the control system controls the size of S1 and S2 by controlling the operating frequency of the variable frequency water inlet pump.

[0074] In this embodiment, only one variable frequency water inlet pump is needed, and the sludge washing process is completed while water is being taken in. The operation is simple, equipment investment is reduced, and operating power consumption is saved.

[0075] In some embodiments of the present application, the control system is further configured to determine a water replacement ratio according to the particle proportion.

[0076] In some embodiments of the present application, the control system is further configured to determine a water exchange ratio according to an organic sludge load in the system.

[0077] Furthermore, the control system is configured to determine a water exchange ratio according to the particle proportion and the organic sludge load in the system.

[0078] For example, when determining the water exchange ratio during system operation, priority should be given to ensuring that the organic sludge load in the system is not less than 0.15 kgCOD / kgMLSS / d.

[0079] Exemplarily, if the particle ratio is less than 10%, the water replacement ratio is 70-75%.

[0080] Exemplarily, if the particles account for 10-30%, the water replacement ratio is 60-70%.

[0081] Exemplarily, if the particles account for more than 40%, the water replacement ratio is 50-60%.

[0082] In some embodiments of the present application, the control system is further configured to control the water distribution system to be turned on or off according to a mapping relationship between the water exchange ratio and the operating time of the water distribution system.

[0083] In some embodiments of the present application, the device further comprises a stirring mechanism, and the control system (2) is configured to start the stirring mechanism after the water distribution system stops.

[0084] In some embodiments of the present application, the aeration mechanism includes a variable frequency fan, and the control system is further configured to control the on / off of the fan and the operating frequency of the fan in the on state according to the dissolved oxygen concentration in the mixed liquid;

[0085] And / or, the aeration mechanism includes a variable frequency fan, and the control system is further configured to start the variable frequency fan after the stirring mechanism is turned off.

[0086] In some embodiments of the present application, the device further comprises a monitoring mechanism, and the monitoring mechanism is used to obtain the dissolved oxygen concentration and the ammonia nitrogen value in the mixed liquid;

[0087] In the early stage of aeration, the dissolved oxygen value is controlled to be 1 mg / L to 1.5 mg / L by the aeration mechanism;

[0088] and / or, when the ammonia nitrogen value is lower than a first threshold value a, reducing the operating frequency of the variable frequency fan so that the dissolved oxygen is controlled at 0.5 mg / L to 1 mg / L; wherein a is 30% to 40% of the ammonia nitrogen value of the inlet water or 120% to 140% of the designed ammonia nitrogen value of the outlet water;

[0089] And / or, when the ammonia nitrogen value is lower than a second threshold value b, the variable frequency fan is turned off and the stirring mechanism is turned on; wherein the b value is 10% to 20% higher than the designed effluent ammonia nitrogen value. Specifically, the designed effluent ammonia nitrogen value is 2mg / L-5mg / L.

[0090] In some embodiments of the present application, the control system is further configured to determine the mud discharge amount of the mud discharge mechanism according to the proportion of particles in the mixed liquid.

[0091] In some embodiments of the present application, if the proportion of granular sludge is less than 30%, the sludge discharge amount is calculated based on the sludge age of 20 to 30 days;

[0092] If the particle proportion is 30% to 50%, the sludge discharge volume is calculated based on the sludge age of 30 to 40 days;

[0093] If the proportion of particles is higher than 50% and the water output index of the device meets the standard, no mud will be discharged;

[0094] If the particle proportion is higher than 50%, and the total phosphorus value of the effluent of the device exceeds the preset value or the COD load is lower than 50% of the design load, the sludge discharge volume shall be calculated based on the sludge age of 35 to 45 days.

[0095] In some embodiments of the present application, the mud discharge mechanism includes a mud discharge port, and the distance between the mud discharge port and the water surface is L, L = V1*e*t, wherein t is the sedimentation time, L is the sinking distance of the granular sludge within the sedimentation time t, V1 is the average sedimentation velocity of the granular sludge, and e is the mass percentage of the granular sludge;

[0096] And / or, the sludge discharge mechanism includes a plurality of sludge discharge ports, the plurality of sludge discharge ports are located between L1 and L2, and are arranged at intervals along the height direction of the reaction tank; wherein, L2=V2*t, L1=V1*t, V1 is the average settling velocity of granular sludge, V2 is the average settling velocity of flocculent sludge, t is the settling time, L2 is the sinking distance when the proportion of granular sludge in the activated sludge is 100%, and L2 is the sinking distance when the proportion of particles in the activated sludge is 0;

[0097] And / or, V1 is greater than V2, then L1 is greater than L2, and in the vertical direction, L2 is always located above L1.

[0098] On the other hand, the present application also provides an aerobic granular sludge culture method. In some embodiments of the present application, the method comprises the following steps:

[0099] S1, water inlet and outlet stage.

[0100] Pulse water inlet is implemented synchronously at the beginning of water inlet and outlet, and the screening process of granular sludge is initially completed during the synchronous water inlet and outlet. Under the premise of meeting a certain sludge load, according to SVI 30 Adjust the water change ratio according to MLSS.

[0101] It is understandable that, during the cultivation process of aerobic granular sludge, washing away the flocculent sludge with poor settling performance is beneficial to increasing the settling performance of the sludge and promoting the formation of granular sludge. This water inlet method can disturb the sludge settled in the device when the water is inlet. At this time, the sludge with poor settling performance will be in a suspended state. Due to the continuous disturbance of the water inlet, the suspended flocculent sludge with poor settling performance is difficult to settle again, and thus is discharged from the system with the water flow. Although the settled granular sludge will also be disturbed by the high-flow pulse water inlet due to its high specific gravity, it is less affected by the subsequent continuous water inlet and thus settles again. Based on this, while completing the water inlet to the system, the flocculent sludge with poor settling performance is gradually washed out to achieve the purpose of gradually eliminating the flocculent sludge;

[0102] Exemplarily, at the beginning of water inflow into the system, the variable frequency water inlet pump 7 operates in a high frequency state to increase the flow rate of the water distribution system 4, so that the water distribution system 4 implements a pulse high-speed 8m / h, 10m / h, 12m / h bottom water inflow (that is, the water distribution system 4 is in the second water addition state, S2 is 8m / h to 12m / h), and the duration is controlled within a few seconds 3 seconds, 5 seconds, 8 seconds, 10 seconds, and then the water distribution system 4 maintains low uniform speed water distribution (that is, the water distribution system 4 is in the first water addition state, and the first water flow rate of the first water addition state is S1, S1 is less than S2, and S1 is low uniform speed water distribution). After the high-frequency water inlet pump 7 has been running for a preset time of 3 seconds, 5 seconds, 8 seconds, and 10 seconds, the automatic control system 2 controls the water inlet pump to reduce the frequency to the preset low frequency value to reduce the water inflow flow and achieve low uniform speed water distribution. In this method, the rising flow rate is not higher than 4m / h during low uniform speed water distribution. The pulse water inlet duration is based on the sludge volume index (SVI 30 ) and the mixed liquor suspended solids concentration (MLSS). In the initial stage of startup, MLSS is controlled at 1000mg / L to 3000mg / L. At this time, most of the sludge is flocculent and SVI 30When the value is higher than 100mL / g, the overall sedimentation performance of the sludge is poor. In order to avoid excessive sludge loss, it is advisable to use low-speed short-duration pulses, that is, the pulse duration is controlled at 3 seconds to 5 seconds, and the pulse speed is 8m / h to 10m / h; when MLSS rises to 4000mg / L to 6000mg / L and SVI 30 When it is lower than 60mL / g, it indicates that the sludge settling performance is improved, and the proportion of granular sludge is increased. The flocculent sludge can be further washed out by extending the pulse duration from 8 seconds to 10 seconds and the pulse speed from 10m / h to 12m / h. When the sludge concentration is greater than 6000mg / L and SVI30 is less than 50mL / g, it indicates that the granular sludge in the system accounts for a large proportion, and the pulse water inlet can be cancelled;

[0103] The pulse water inlet in this solution only requires one variable frequency water inlet pump 7, which assists in completing the sludge washing process while inletting water, is easy to operate, reduces equipment investment, is simple to run, and has a low accident rate.

[0104] The higher the water exchange ratio, the more sewage the system can accept, and the sludge in the system can be exposed to more nutrients, so that the system maintains a relatively high COD sludge load. The key link in sludge granulation is that slow-growing heterotrophic bacteria, such as polyphosphate bacteria, form the core of the particles, and a high water exchange ratio can ensure that the slow-growing heterotrophic bacteria obtain sufficient carbon sources to form a nucleus, and then gradually form particles by adsorbing the surrounding flocculent sludge or the self-reproduction of microorganisms on the surface of the nucleus through extracellular polymers. Considering a certain rising flow rate, the water exchange ratio can reach 50%, 55%, 60%, 65%, 70%, and 75%. Because there is a risk of mixed flow at the end of the effluent due to the high water exchange ratio, the high water exchange ratio strategy is only applicable to situations where the effluent is not required to meet the standard. During the period, the wet screening method was used to determine the mass proportion of granular sludge with a particle size (i.e., diameter) greater than 0.2 mm, and the water exchange ratio was adjusted according to the mass proportion of granular sludge. It should be noted that the granular sludge in this application refers to activated sludge with a diameter greater than 0.2 mm. For example, the mixed liquid (sludge) in the reaction tank 1 can be poured into a sieve with a pore size of 0.2 mm for sieving, and the sludge retained in the sieve is the granular sludge with a diameter greater than 0.2 mm.

[0105] The basis for adjusting the water exchange ratio is: under the condition that the MLSS concentration in the later stage of the effluent is lower than the set value, a high water exchange ratio corresponds to a low particle ratio. When the particle ratio is lower than 10%, the corresponding maximum water exchange ratio is 70-75%; when the particle ratio is 10-30%, the corresponding water exchange ratio is 60-70%; when the particle ratio is greater than 40%, the water exchange ratio is 50-60%. When the particle ratio is greater than 50%, it indicates that the sludge granulation process is basically completed. At this time, the device has completed the biological acclimation and debugging process and entered the formal operation stage. In the subsequent stage, in order to ensure that the effluent meets the standard, it is recommended that the water exchange ratio is lower than 50%. By way of example, the water exchange ratio can be understood as the ratio of the volume of sewage entering the reaction tank 1 per cycle to the effective volume of the reaction tank 1.

[0106] The water exchange ratio is adjusted in the granular culture stage as follows: a variable frequency water inlet pump 7 is installed on the water inlet pipeline, and the water inlet amount of the system is controlled by controlling the start time of the variable water inlet pump 7. The variable frequency water inlet pump 7 is connected to the automatic control system 2, and the particle ratio value in the automatic control system 2 is manually input. Each specific range of particle ratio corresponds to a specific start and stop time of the variable frequency water inlet pump 7. The particle ratio value is adjusted to change the start and stop time of the variable frequency water inlet pump 7, change the water inlet amount, and then control the water exchange ratio.

[0107] The method adopts a water inlet scheme of gradually reducing the water inlet volume to the designed scale, which makes up for the defect of insufficient carbon source in the aerobic granular sludge device for treating low-concentration sewage and helps to quickly form particles.

[0108] S2, anaerobic stage.

[0109] After the water inflow is completed, the pollution concentration in the system reaches the maximum value, and the system enters the anaerobic stage. In the aerobic granular sludge process, a certain anaerobic environment is crucial for the formation of particles and the removal of pollutants. In order to ensure sufficient anaerobic time, the stirring device is started at this stage to allow the newly-incoming sewage to fully contact with the sludge, strengthen the "rich" process, and promote sludge granulation.

[0110] At this stage, the polyphosphate bacteria in the system will absorb and utilize the organic matter in the newly-input sewage without being affected by the nitrifying bacteria, thus promoting the phosphorus release process and improving the subsequent phosphorus removal efficiency. The start and stop of the stirring device is executed by the automatic control system. When the variable frequency water inlet pump 7 is shut down, the stirring device is started.

[0111] S3, aeration stage.

[0112] After the anaerobic stage is over, the stirring device is turned off and the fan is started. The fan uses a variable frequency fan to perform aeration operation. After the aeration is completed, the aeration is turned off and the stirring device is turned on to strengthen the denitrification and carbon removal process.

[0113] In this stage, real-time ammonia nitrogen monitoring instruments and real-time dissolved oxygen monitoring instruments are installed to obtain real-time data. The concentration of dissolved oxygen in the aerobic granular sludge system directly affects the removal of total nitrogen, so accurate control of dissolved oxygen is extremely important. If dissolved oxygen control is not performed throughout the aeration stage of a cycle, there will be a significant jump in dissolved oxygen in the second half of aeration, indicating that COD and ammonia nitrogen have been degraded to the greatest extent.

[0114] This situation will be detrimental to the removal of total nitrogen, so the dissolved oxygen concentration range needs to be precisely controlled, and the ammonia nitrogen online monitoring instrument value is used as the basis for dissolved oxygen control.

[0115] In the early stage of aeration, the dissolved oxygen is controlled at 1 mg / L to 1.5 mg / L to promote the nitrification process and fully convert ammonia nitrogen. Set the node value a (also known as the first threshold a), which is 30% to 40% of the inlet ammonia nitrogen value or 120% to 140% of the designed effluent ammonia nitrogen. When the ammonia nitrogen value detected by the online instrument is lower than the node value a, reduce the fan operation frequency to control the dissolved oxygen at 0.5 mg / L to 1 mg / L, and continue to degrade ammonia nitrogen. Set the node value b (also known as the second threshold b), which is 10% to 20% higher than the designed effluent ammonia nitrogen value. When the ammonia nitrogen value detected online is lower than the node value b, shut down the aeration and turn on the stirring device, thereby strengthening the denitrification process, decarbonization and further strengthening the starvation process. In this way, by extending the starvation period, the sludge is promoted to secrete extracellular polymers, which is conducive to the formation of granular sludge.

[0116] S4, sludge screening stage.

[0117] Calculate the sinking distance of granular sludge and flocculent sludge, use the height difference between the two in the vertical direction, set the sludge discharge port at the upper part of the flocculent sludge, discharge the flocculent sludge in the sedimentation stage, retain the granular lower sludge, and realize the sludge screening process;

[0118] Sludge screening is an important control method in the process of granular sludge formation. Compared with granular sludge, flocculent sludge has a larger specific surface area and can adsorb substrates in sewage faster, which will form substrate competition with slow-growing microorganisms in granular sludge. In order to reduce the substrate competition with granular sludge, some flocculent sludge needs to be discharged in time, that is, the sludge screening process is implemented. Granular sludge has a higher specific gravity than flocculent sludge, and its average sedimentation speed is greater than that of flocculent sludge. During the sedimentation stage, stratification will occur, with the lower layer being granular sludge with a faster sedimentation speed, and the upper layer being flocculent sludge with a slower sedimentation speed;

[0119] First, calculate the amount of sludge discharged. When the proportion of granular sludge is less than 30%, it indicates that the proportion of particles in the system is not high, and the sludge granulation and screening process still needs to be continued, and the flocculent sludge needs to be discharged. At this time, the amount of sludge discharged is calculated based on the sludge age of 20-30 days. The calculation method refers to the Water Supply and Drainage Design Manual 05 Urban Drainage;

[0120] When the particle ratio is in the range of 30%-50%, the state of the granular sludge is relatively stable, and the amount of flocculent sludge to be discharged gradually decreases. At this time, the amount of sludge discharged is calculated based on the sludge age of 30-40 days. When the particle ratio is higher than 50%, it indicates that the particle ratio in the device is relatively ideal. If the effluent indicators of the device meet the standards at this time, you can choose not to discharge sludge. At this time, you need to closely observe the effluent total phosphorus value and sludge COD load. If the effluent total phosphorus value is at risk of exceeding the standard or the sludge COD load is lower than 50% of the design load, then appropriate sludge discharge is required, and the amount of sludge discharge is calculated based on the sludge age of 35-45 days;

[0121] Secondly, calculate the mud discharge time. Mud discharge time = mud discharge volume / mud discharge port flow rate, where the mud discharge port flow rate is measured by installing a flow meter or manually measured. The manual measurement method is: use a container with a precise scale to receive the outflow of the mud discharge port for 15 seconds or 30 seconds, calculate the flow rate per second based on the received volume, and then calculate the mud discharge time based on the calculated mud discharge port flow rate. The mud discharge time is the opening time of the mud discharge port valve;

[0122] Finally, select the location of the sludge outlet. The location of the sludge outlet is mainly determined by the speed difference between the granular sludge and the flocculent sludge when they sink. The sinking distance is calculated as follows:

[0123] During the aeration period, 100 mL of sludge was taken out from the device, and the sludge in the device was screened by wet screening method. The average settling speeds V1 and V2 of granular sludge and flocculent sludge with a particle size greater than 0.2 mm were measured in a 1L measuring cylinder. After determining the settling speed of the sludge, the sinking heights of granular sludge and flocculent sludge were calculated according to the different settling times. The average settling speed of granular sludge is V1; the average settling speed of flocculent sludge is V2, the sedimentation time is t, and the sinking distance L is the distance between the sludge interface and the water surface above.

[0124] The distance that the granular sludge sinks during the sedimentation period is: L1 = V1*t; if the proportion of granular sludge with a particle size greater than 0.2 mm is 100%, then the distance between the mud-water boundary and the upper water surface at the end of the sedimentation period is L1;

[0125] The distance that flocculent sludge sinks during the sedimentation period is: L2 = V2*t. Since V1>V2, obviously, if the sludge particle size in the system is less than 0.2 mm, the distance between the mud-water boundary and the upper water surface during the sedimentation period is L2.

[0126] During the sludge granulation and normal operation, the proportion of sludge particles larger than 0.2 mm is in a dynamic state, and the sludge settling speed varies at different times, so the sludge sinks at different distances. Therefore, multiple sludge discharge ports need to be set, and the distance between the sludge discharge port and the water surface is between L1 and L2. The position Ln of each sludge discharge port is determined according to the proportion of granular sludge e and the settling speed:

[0127] Ln=V1*e*t

[0128] Ln is the distance between the sludge outlet and the water surface when the proportion of granular sludge is e. As shown in the device diagram, during sedimentation, the proportion of granular sludge in the bottom area of ​​the device is high, and the proportion of flocculent sludge at the height positions L2 and L3 in the upper area is high. Discharging sludge from sludge outlets such as L2 and L3 can maximize the discharge of flocculent sludge in the device, retain the granular sludge in the system to the greatest extent, and realize the sludge screening process, which is conducive to the rapid granulation of sludge and the maintenance of the stability of the granular sludge system.

[0129] In summary, the granulation process of flocculent sludge can be accelerated by pulse water inlet to wash the flocculent sludge, high water exchange ratio to make up for the lack of carbon source in low-concentration sewage, adding a stirring device to enhance mass transfer and strengthen the starvation process, precise control of dissolved oxygen to ensure total nitrogen removal, and optimization of the sludge outlet setting to maximize the retention of granular sludge.

[0130] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An aerobic granular sludge cultivation device, characterized in that: include: Reaction tank (1), aeration mechanism, mud discharge mechanism, water distribution system and control system (2); The reaction tank is used to accommodate a mixed liquid containing activated sludge; The aeration mechanism is configured to add oxygen to the mixed liquid; The sludge discharge mechanism is configured to discharge the sludge in the reaction tank; The water distribution system is configured to add water to the reaction tank (1), and has a first water adding state and a second water adding state, the first water flow rate in the first water adding state is S1, the second water flow rate in the second water adding state is S2, and S2 is greater than S1; the control system is configured to adjust the water flow rate according to SVI 30 and MLSS concentration to control the working state of the water distribution system, as well as the operating time and water flow rate under the corresponding working state.

2. The device according to claim 1, characterized in that If the MLSS is 1000 mg / L to 3000 mg / L, SVI 30 If the flow rate is greater than 100 mL / g, the water distribution system alternately operates the first water adding state and the second water adding state, wherein S1 is not higher than 4 m / h; S2 is 8 m / h to 10 m / h, and the water distribution system operates the second water adding state for 3 to 5 seconds at a time; If the MLSS is 4000mg / L to 6000mg / L, SVI 30 If the flow rate is less than 60 mL / g, the water distribution system alternately operates the first water adding state and the second water adding state, wherein S1 is not higher than 4 m / h, S2 is 10 m / h to 12 m / h, and the operation time of the water distribution system in the second water adding state is 5 seconds to 10 seconds; If the MLSS is greater than 6000 mg / L, SVI 30 If the flow rate is less than 50 mL / g, the water distribution system continues to operate in the first water adding state, wherein S1 is not higher than 4 m / h.

3. The device according to claim 1 or 2, characterized in that The water distribution system includes a water storage tank, a water inlet pipe, a variable frequency water inlet pump and a multi-point water distribution head. The water inlet pipe connects the water storage tank, the variable frequency water inlet pump and the multi-point water distribution head. The multi-point water distribution head is arranged at the bottom of the reaction tank. The control system controls the size of S1 and S2 by controlling the operating frequency of the variable frequency water inlet pump.

4. The device according to claim 1, characterized in that The control system is further configured to determine a water replacement ratio according to the particle proportion; And / or, the control system is further configured to determine the water exchange ratio according to the organic sludge load in the system.

5. The device according to claim 4, characterized in that If the particle ratio is less than 10%, the water replacement ratio is 70% to 75%; If the particle ratio is 10% to 30%, the water replacement ratio is 60% to 70%; If the particle ratio is greater than 40%, the water replacement ratio is 30% to 50%; The water exchange ratio should be determined to preferably meet the requirement that the organic sludge load in the system is not less than 0.15 kgCOD / kgMLSS / d.

6. The device according to claim 1, characterized in that The control system is further configured to control the water distribution system to be turned on or off according to a mapping relationship between the water exchange ratio and the operating time of the water distribution system; And / or, the device further comprises a stirring mechanism, and the control system (2) is configured to start the stirring mechanism after the water distribution system stops.

7. The device according to claim 1, characterized in that The aeration mechanism includes a variable frequency fan, and the control system is further configured to control the on / off of the fan and the operating frequency of the fan in the on state according to the dissolved oxygen concentration in the mixed liquid; And / or, the aeration mechanism includes a variable frequency fan, and the control system is further configured to start the variable frequency fan after the stirring mechanism is turned off.

8. The device according to claim 7, characterized in that The device also includes a monitoring mechanism, which is used to obtain the dissolved oxygen concentration and the ammonia nitrogen value in the mixed liquid; In the early stage of aeration, the dissolved oxygen value is controlled to be 1 mg / L to 1.5 mg / L by the aeration mechanism; and / or, when the ammonia nitrogen value is lower than a first threshold value a, reducing the operating frequency of the variable frequency fan so that the dissolved oxygen is controlled at 0.5 mg / L to 1 mg / L; wherein a is 30% to 40% of the ammonia nitrogen value of the inlet water or 120% to 140% of the designed ammonia nitrogen value of the outlet water; And / or, when the ammonia nitrogen value is lower than a second threshold value b, the variable frequency fan is turned off and the stirring mechanism is turned on; wherein the b value is 10% to 20% higher than the designed outlet water ammonia nitrogen value.

9. The device according to claim 1, characterized in that The control system is also configured to determine the mud discharge amount of the mud discharge mechanism according to the proportion of particles in the mixed liquid.

10. The device according to claim 9, characterized in that If the proportion of granular sludge is less than 30%, the sludge discharge volume is calculated based on the sludge age of 20 to 30 days; If the particle proportion is 30% to 50%, the sludge discharge volume is calculated based on the sludge age of 30 to 40 days; If the proportion of particles is higher than 50% and the water output index of the device meets the standard, no mud will be discharged; If the particle proportion is higher than 50%, and the total phosphorus value of the effluent of the device exceeds the preset value or the COD load is lower than 50% of the design load, the sludge discharge volume shall be calculated based on the sludge age of 35 to 45 days.

11. The device according to claim 1, characterized in that The mud discharge mechanism includes a mud discharge port, a mud discharge pipeline and a pipeline valve. The distance between the mud discharge port and the water surface is L, L = V1*e*t, wherein t is the sedimentation time, L is the sinking distance of the granular sludge within the sedimentation time t, V1 is the average sedimentation velocity of the granular sludge, and e is the mass percentage of the granular sludge; And / or, the sludge discharge mechanism includes a plurality of sludge discharge ports, the plurality of sludge discharge ports are located between L1 and L2, and are arranged at intervals along the height direction of the reaction tank; wherein, L2=V2*t, L1=V1*t, V1 is the average settling velocity of granular sludge, V2 is the average settling velocity of flocculent sludge, t is the settling time, L2 is the sinking distance when the proportion of granular sludge in the activated sludge is 100%, and L2 is the sinking distance when the proportion of particles in the activated sludge is 0; And / or, V1 is greater than V2, then L1 is greater than L2, and in the vertical direction, L2 is always located above L1.

12. An aerobic granular sludge cultivation method, characterized in that: The steps include: Inlet and outlet stage: Pulse water inlet is implemented synchronously when water inlet and outlet are started, and the screening process of granular sludge is initially completed during the synchronous inlet and outlet. Under the premise of meeting the sludge load, according to SVI 30 and MLSS to adjust the water exchange ratio; Anaerobic stage: After the water inflow is completed, the pollution concentration in the system reaches the maximum value, and the system enters the anaerobic stage. In this stage, the stirring device is started to ensure that the new sewage and sludge are fully in contact; Aeration stage: after the anaerobic stage is over, the stirring device is turned off, and the variable frequency fan is started to perform aeration operation. The on and off of the variable frequency fan and the operating frequency of the variable frequency fan in the on state are controlled according to the dissolved oxygen concentration and the ammonia nitrogen value in the mixed liquid; when the ammonia nitrogen value is lower than the preset threshold value, the aeration is turned off, and the stirring device is turned on to run for a preset time; Sludge screening stage: After the aeration stage, the sludge discharge port is set at the position corresponding to the flocculent sludge by utilizing the vertical height difference between the granular sludge and the flocculent sludge during the sedimentation process. The flocculent sludge is discharged during the sedimentation stage, and the granular lower sludge is retained to realize the sludge screening process.

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