Aerobic granular sludge cultivation method and device thereof

Abstract

The present invention discloses a method and device for culturing sludge of an aerobic granular sludge technology with low carbon and energy conservation. The device is mainly used for sewage treatment. The device includes 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 to accommodate a mixed liquid 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 addition state and a second water addition state. The first water flow rate in the first water addition state is V1, and the second water flow rate in the second water addition state is V2, and V2 is greater than V1; the control system is configured to control the working state of the water distribution system, as well as the operation time and water flow rate in the corresponding working state, according to the sludge volume index (SVI<subgt;30< / subgt;) and the mixed liquor suspended solids (MLSS) concentration.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and particularly relates to a method and device for culturing sludge of an aerobic granular sludge technology that is energy-saving and low-carbon. Background Art

[0002] The aerobic granular sludge technology is a sewage treatment technology that has been studied more at home and abroad in the past decade. More than 100 sewage treatment plants abroad have adopted this process. Compared with the traditional process, it can reduce the floor area by about 25% to 70%, reduce the operating energy consumption by about 20% to 50%, and at the same time reduce the investment and construction costs and operating chemical agent costs. The degradation rate of pollutants is better than that of the existing process, which 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 the in-situ cultivation granulation of flocculent sludge. The influent water quality of sewage treatment plants using the aerobic granular sludge process reported at home and abroad is relatively high, about 500 mg / L to 800 mg / L of COD, while the influent COD of most domestic municipal sewage treatment plants is about 150 mg / L to 250 mg / L. This will lead to a longer granulation time of aerobic granular sludge, and the pollutant removal efficiency of the aerobic granular sludge system is related to the degree of sludge granulation. Therefore, in order to shorten the commissioning cycle 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, realizing the simultaneous nitrogen and phosphorus removal of aerobic granular sludge in the EBPR system. However, there are still problems such as long startup time and poor long-term operation stability, which greatly restrict the popularization and use of this technology.

[0004] In view of the above technical problems, for example, the patent with publication number CN107986432A discloses a method and device for culturing aerobic granular sludge, which realizes the switching of each stage including influent water - anaerobic - aerobic - precipitation - effluent water - idle by regulating whether to start stirring, the stirring speed, whether to aerate, etc., and the time of each stage is controllable. Further, the present invention sets multiple reaction conditions, which is helpful for the rapid cultivation of aerobic activated sludge particles and finally realizes the simultaneous removal of nitrogen, phosphorus and organic matter in sewage.

[0005] To overcome the above technical defects, the present invention provides a method for rapid granulation of aerobic granular sludge under the condition of treating low-concentration sewage, effectively solving the problem of long commissioning cycle. Summary of the Invention

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

[0007] In the first aspect of the present application, an aerobic granular sludge cultivation device is provided, including: 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 supplement oxygen into 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 into the reaction tank (1), and has a first water addition state and a second water addition state. The first water flow rate in the first water addition state is S1, and the second water flow rate in the second water addition state is S2, and S2 is greater than S1; the control system is configured to control the working state of the water distribution system, as well as the operation time and water flow rate in the corresponding working state according to the SVI 30 and MLSS concentration.

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

[0013] If the MLSS is 4000 mg / L to 6000 mg / L and the SVI 30 is less than 60 mL / g, then the water distribution system alternately operates the first water addition state and the second water addition 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 addition state is 5 seconds to 10 seconds;

[0014] If the MLSS is greater than 6 or 000 mg / L and the SVI 30 is less than 50 mL / g, then the water distribution system continuously operates in the first water addition 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 bucket, 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 bucket, 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 sizes of S1 and S2 by controlling the working frequency of the variable-frequency water inlet pump.

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

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

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

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

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

[0021] The determination of the water change ratio should preferably satisfy 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 opening or closing of the water distribution system according to the mapping relationship between the water change ratio and the operation time of the water distribution system;

[0023] And / or, the device further includes 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 blower, and the control system is further configured to control the opening and closing of the blower and the operating frequency of the blower in the on state according to the dissolved oxygen concentration in the mixed liquor;

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

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

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

[0028] And / or, when the ammonia nitrogen value is lower than the first threshold a, the operating frequency of the variable frequency blower is reduced to control the dissolved oxygen at 0.5 mg / L to 1 mg / L; where a is 30% to 40% of the influent ammonia nitrogen value or 120% to 140% of the designed effluent ammonia nitrogen;

[0029] And / or, when the ammonia nitrogen value is lower than the second threshold b, the variable-frequency blower is shut down and the stirring mechanism is started; where the value of b is 10% to 20% higher than the designed effluent ammonia nitrogen value.

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

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

[0032] If the proportion of particles is 30% to 50%, the sludge discharge amount is calculated according to a sludge age of 30 to 40 days;

[0033] If the proportion of particles is higher than 50% and the effluent indexes of the device all meet the standards, no sludge is discharged;

[0034] If the proportion of particles 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 designed load, the sludge discharge amount is calculated according to a sludge age of 35 to 45 days.

[0035] In some embodiments of the present application, the sludge discharge mechanism includes a sludge discharge port, and the distance between the sludge discharge port and the water surface is L, L = V1 * e * t, where t is the sedimentation time, L is the sinking distance of granular sludge within the sedimentation time t, V1 is the average sedimentation velocity of granular sludge, and e is the mass proportion of 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; where L2 = V2 * t, L1 = V1 * t, V1 is the average sedimentation velocity of granular sludge, V2 is the average sedimentation velocity of flocculent sludge, t is the sedimentation 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 above L1.

[0038] The second aspect of the present application provides a method for culturing aerobic granular sludge, including the following steps;

[0039] Inlet and outlet water stage: Pulse water inlet is implemented synchronously at the beginning of water inlet. During synchronous inlet and outlet water, the screening process of granular sludge is initially completed. On the premise of meeting a certain sludge load, the water change ratio is adjusted in a timely manner according to SVI 30 and MLSS;

[0040] Anaerobic stage: After the influent water inflow ends, the pollution concentration in the system reaches the maximum value. At this time, the system enters the anaerobic stage. In this stage, the stirring device is started to make the newly incoming sewage fully contact with the sludge;

[0041] Aeration stage: After the anaerobic stage ends, the stirring device is closed, and the variable-frequency blower is started for aeration operation. The opening and closing of the variable-frequency blower and the operating frequency of the variable-frequency blower in the open state are controlled according to the dissolved oxygen concentration and ammonia nitrogen value in the mixed liquor; when the ammonia nitrogen value is lower than the preset threshold, the aeration is shut down, and the stirring device is started to operate for a preset time;

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

[0043] Compared with the prior art, the beneficial effects of the present invention are:

[0044] This application embodiment configures the control system to control the working state of the water distribution system according to the SVI 30 and the MLSS concentration, as well as the running time and water flow velocity in the corresponding working state, creating a "rich-hungry" environment to promote sludge granulation, and being able to timely remove the flocculent sludge, so as to complete the sludge elutriation process while inflowing water, with simple operation, reduced equipment investment, and saved operating power consumption.

[0045] The present invention uses pulsed influent water to elutriate the flocculent sludge, a high water exchange ratio to make up for the shortage of carbon source in low-concentration sewage, adds a stirring device to enhance mass transfer and strengthen the starvation process, precisely controls the dissolved oxygen to ensure total nitrogen removal, and optimizes the setting of the sludge discharge port to intercept the granular sludge to the greatest extent, which can accelerate the granulation cultivation process of the flocculent sludge. In a specific implementation case, when the water temperature is controlled at about 20 °C, with low-concentration municipal sewage as the system influent water through the cooperation of the device, after running for about 30 days, the volume ratio of granular sludge with a size greater than 0.2 mm in the system rises from 6% to about 45%.

[0046] Other features and advantages of the present invention will be described in the subsequent specification, and part of them will become obvious from the specification or be understood by implementing the present invention. The objectives and other advantages of the present invention can be achieved and obtained through the structures pointed out in the specification and the drawings. Brief Description of the Drawings

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

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

[0049] Figure 3 This is a graph showing the changing trend of the proportion of particles during the granulation of the present invention.

[0050] In the figure: 1. AGS reaction tank; 2. Automatic control system; 3. Variable-frequency blower; 4. Water distribution system; 5. Ammonia nitrogen detector; 6. DO detector; 7. Variable-frequency inlet water pump; 8. Inlet water storage bucket; 9. Inlet pipe; 10. Aeration system; 11. Electric drain valve; 12. Manual sludge discharge valve; 13. Electric sludge discharge valve; 14. Sludge discharge and storage bucket; 15. Stirrer. Specific embodiments

[0051] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0052] Please refer to Figures 1 to 3 , the present invention provides a method and device for culturing aerobic granular sludge, including an AGS reaction tank 1. An aeration mechanism is respectively arranged inside the AGS reaction tank 1. A water addition mechanism for water distribution and a stirrer 15 are also arranged inside the AGS reaction tank 1. A monitoring mechanism is arranged above the AGS reaction tank 1. A drainage mechanism 11, a sludge discharge mechanism 12, a variable-frequency blower 3, and an aeration system 10 communicated with the exhaust end of the variable-frequency blower 3 are arranged outside the AGS reaction tank 1. The whole device is equipped with an automatic control system 2.

[0053] Among them, the water addition mechanism includes a water distribution system 4. 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 communicated with the top of the connecting pipe.

[0054] Furthermore, the bottom of the connecting pipe is communicated with an inlet pipe 9. One end of the inlet pipe 9 is communicated with a variable-frequency inlet water pump 7, and the inlet end of the variable-frequency inlet water pump 7 is communicated with an inlet water storage bucket 8.

[0055] Among them, 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 discharging mechanism includes an electric drain valve 11, which is connected to one side of the AGS reaction tank 1. Several valve bodies are connected to the middle part of one side of the AGS reaction tank 1. Exemplarily, four groups of valve bodies are connected to the middle part of one side of the AGS reaction tank 1. Among them, the valve body can be a manual sludge discharge valve or an electric sludge discharge valve, which is not limited herein.

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

[0058] In the above device operation mode, it is a sequential batch periodic operation. Each cycle period includes simultaneous water inlet / water outlet, anaerobic stirring, aeration, and sedimentation stages. Among them, the anaerobic stirring and aeration stages can operate alternately;

[0059] Adopt the method of bottom water inlet and top water discharge to discharge the treated water at the top while inletting water;

[0060] In the sequential batch operation cycle of the above device operation, the total operation duration of each cycle can be set to 2 hours, 3 hours, or 4 hours. Among them, the duration of the water inlet / outlet stage is 30 min to 80 min, and the duration of the sedimentation stage is 20 min to 40 min. After deducting the water inlet / outlet duration and the sedimentation stage duration from the total cycle duration, it is the anaerobic stirring and aeration duration. When the total nitrogen and total phosphorus in the effluent exceed the standard, the anaerobic stirring duration is gradually extended in units of 5 min. Among them, when operating in a 2-hour cycle, the anaerobic duration generally does not exceed 30 min.

[0061] On the one hand, the present invention provides an aerobic granular sludge cultivation device, which is characterized in that it includes: a reaction tank (1), an aeration mechanism, a sludge discharging mechanism, a water distribution system, and a control system (2);

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

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

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

[0065] 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 rate in the first water adding state is S1, and 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 control the working state of the water distribution system, as well as the operation time and water flow rate in the corresponding working state according to the SVI 30 and the MLSS concentration.

[0066] In the embodiment of the present application, the control system is configured to control the working state of the water distribution system, as well as the running time and water flow velocity in the corresponding working state, according to the SVI 30 and the MLSS concentration, and can timely remove the flocculent sludge, so as to complete the sludge elutriation process while feeding water, with simple operation, reduced equipment investment, simple operation and low accident rate.

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

[0068] It can be understood that when the MLSS is 1000 mg / L to 3000 mg / L and the SVI 30 is greater than 100 mL / g, the overall sedimentation performance of the sludge is poor, and using a low-speed and short-duration pulse will not cause a large loss of sludge.

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

[0070] It can be understood that when the MLSS rises to 4000 mg / L to 6000 mg / L and the SVI 30 is lower than 60 mL / g, it indicates that the sedimentation performance of the sludge has been improved. At this time, the proportion of granular sludge has increased, and the flocculent sludge therein can be further elutriated by extending the pulse duration (8 seconds to 10 seconds) and the pulse speed (10 m / h to 12 m / h), so as to further improve the granulation efficiency of aerobic granular sludge.

[0071] Specifically, if the MLSS is greater than 6000 mg / L and the SVI 30 is less than 50 mL / g, the water distribution system continuously operates in the first water addition state, where S1 is not higher than 4 m / h.

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

[0073] In some embodiments of the present application, the water distribution system includes a water storage bucket, a water inlet pipe, a variable-frequency water inlet pump, and a multi-point water head. The water inlet pipe connects the water storage bucket, the variable-frequency water inlet pump, and the multi-point water head, and the multi-point water head is arranged at the bottom of the reaction tank; the control system controls the sizes 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 required, and the sludge elutriation process is completed while water is being inlet. The operation is simple, the equipment investment is reduced, and the operating power consumption is saved.

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

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

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

[0078] Exemplarily, when the system is operating, the organic sludge load in the system should preferably be not less than 0.15 kgCOD / kgMLSS / d when determining the water change ratio.

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

[0080] Exemplarily, if the particle proportion is 10 - 30%, the water change ratio is 60 - 70%.

[0081] Exemplarily, if the particle proportion is greater than 40%, the water change ratio is 50 - 60%.

[0082] In some embodiments of the present application, the control system is further configured to control the opening or closing of the water distribution system according to the mapping relationship between the water change ratio and the operating time of the water distribution system.

[0083] In some embodiments of the present application, the device further includes 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 blower, and the control system is further configured to control the opening and closing of the blower and the operating frequency of the blower in the open state according to the dissolved oxygen concentration in the mixed liquid;

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

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

[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 the first threshold a, the operating frequency of the variable frequency blower is reduced to control the dissolved oxygen to be 0.5 mg / L to 1 mg / L; wherein, a is 30% to 40% of the influent ammonia nitrogen value or 120% to 140% of the designed effluent ammonia nitrogen;

[0089] And / or, when the ammonia nitrogen value is lower than the second threshold b, the variable frequency blower is shut down and the stirring mechanism is started; wherein, the value of b is 10% to 20% higher than the designed effluent ammonia nitrogen value. Specifically, the designed effluent ammonia nitrogen value is 2 mg / L - 5 mg / L.

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

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

[0092] If the particle proportion is 30% to 50%, the sludge discharge amount is calculated according to a sludge age of 30 days to 40 days;

[0093] If the particle proportion is higher than 50% and the effluent indexes of the device all meet the standards, no sludge is 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 designed load, the sludge discharge amount is calculated according to a sludge age of 35 days to 45 days.

[0095] In some embodiments of the present application, the sludge discharge mechanism includes a sludge discharge port, and the distance between the sludge discharge port and the water surface is L, L = V1 * e * t, where t is the sedimentation time, L is the sinking distance of granular sludge during the sedimentation time t, V1 is the average sedimentation velocity of granular sludge, and e is the mass proportion of 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 spaced along the height direction of the reaction tank; wherein, L2 = V2 * t, L1 = V1 * t, V1 is the average sedimentation velocity of granular sludge, V2 is the average sedimentation velocity of flocculent sludge, t is the sedimentation 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 particle proportion in the activated sludge is 0;

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

[0098] On the other hand, the present application also provides a method for culturing aerobic granular sludge. In some embodiments of the present application, the method includes the following steps;

[0099] S1, the water inlet and outlet stage.

[0100] At the beginning of water inlet, pulse water inlet is synchronously implemented. During synchronous water inlet and outlet, the screening process of granular sludge is initially completed. On the premise of meeting a certain sludge load, the water change ratio is adjusted in a timely manner according to SVI 30 and MLSS.

[0101] It can be understood that during the cultivation 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 at the same time. This water inlet method can disturb the sludge deposited in the device during water 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 precipitate 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 large specific gravity, it is less affected by the subsequent continuous water inlet interference and thus precipitates again. Based on this, while completing the water inlet of the system, the flocculent sludge with poor settling performance is gradually washed away to achieve the purpose of gradually eliminating the flocculent sludge;

[0102] Exemplarily, at the moment when the system starts to inlet water, 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 pulsed high-speed bottom water inlet at 8m / h, 10m / h, 12m / h (that is, the water distribution system 4 is in the second water addition state, and S2 is from 8m / h to 12m / h), and the duration is controlled within several seconds, 3 seconds, 5 seconds, 8 seconds, 10 seconds. Then the water distribution system 4 maintains low-speed uniform 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-speed uniform water distribution). After the high-frequency operation duration of the high-frequency water inlet pump 7 reaches the preset duration, 3 seconds, 5 seconds, 8 seconds, 10 seconds, the water inlet pump is controlled by the automatic control system 2 to reduce the frequency to the preset low-frequency value to reduce the water inlet flow rate and achieve low-speed uniform water distribution. In this method, the upward flow velocity during low-speed uniform water distribution is not higher than 4m / h. The pulse water inlet duration is jointly determined according to the sludge volume index (SVI 30 ) and the mixed liquor suspended solid concentration (MLSS). At the initial stage of startup, MLSS is controlled at 1000mg / L to 3000mg / L. At this time, most of it is flocculent sludge and SVI 30When the value is relatively high, greater than 100 mL / g, the overall sedimentation performance of the sludge is poor. To avoid excessive sludge loss, a low-speed short-duration pulse is advisable, that is, the pulse duration is controlled between 3 seconds and 5 seconds, and the pulse speed is 8 m / h to 10 m / h; when the MLSS rises to 4000 mg / L to 6000 mg / L and the SVI 30 is less than 60 mL / g, it indicates that the sedimentation performance of the sludge has improved. At this time, the proportion of granular sludge has increased, and the flocculent sludge therein can be further washed out by extending the pulse duration to 8 seconds to 10 seconds and the pulse speed to 10 m / h to 12 m / h. When the sludge concentration is greater than 6000 mg / L and the SVI30 is less than 50 mL / g, it indicates that granular sludge occupies a large proportion in the system, and pulse water inlet can be cancelled;

[0103] For the pulse water inlet in this solution, only one variable-frequency water inlet pump 7 is required to assist in completing the sludge washing process while water is being inlet. The operation is simple, the equipment investment is reduced, the operation is simple, and the accident rate is low.

[0104] The higher the water change ratio, the more sewage the system can accept, and the sludge in the system can come into contact with more nutrients, enabling the system to maintain a relatively high COD sludge load. The key link in sludge granulation is the slow-growing heterotrophic bacteria, such as polyphosphate-accumulating organisms, which form the core of the granules. A high water change ratio can ensure that the slow-growing heterotrophic bacteria obtain sufficient carbon sources to form colloidal nuclei, and then gradually form granules through the adsorption of surrounding flocculent sludge or the self-reproduction of microorganisms on the surface of the colloidal nuclei by extracellular polymers, etc. Considering a certain upward flow velocity, the water change ratio can reach 50%, 55%, 60%, 65%, 70%, 75%. Due to the risk of mixed flow at the end of the water outlet with a high water change ratio, the high water change ratio strategy is only applicable to situations where the water outlet does not require compliance. During this period, the wet screening method is used to measure the mass ratio of granular sludge with a particle size (i.e., diameter) greater than 0.2 mm, and the water change ratio is adjusted according to the mass ratio 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. Exemplarily, the mixed liquid (sludge) in the reaction tank 1 can be all poured onto a sieve with a pore size of 0.2 mm for screening, and the sludge retained on 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 standards, it is recommended that the water exchange ratio be lower than 50%. For 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] During the granular culture stage, the water exchange ratio is adjusted by installing a variable-frequency inlet pump 7 in the water inlet pipeline. The water intake is controlled by controlling the duration of the variable-frequency inlet pump 7's operation. The variable-frequency inlet pump 7 is connected to the automatic control system 2, in which the particle ratio is manually entered. Each specific particle ratio range corresponds to a specific start and stop time for the variable-frequency inlet pump 7. Adjusting the particle ratio changes the start and stop times of the variable-frequency inlet pump 7, thereby changing the water intake and, therefore, the water exchange ratio.

[0107] This method adopts a water inlet scheme of gradually reducing the water inlet volume to the design 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 water inflow is complete, the contaminant concentration in the system reaches its maximum, and the system enters the anaerobic phase. In aerobic granular sludge processes, a stable anaerobic environment is crucial for both granule formation and contaminant removal. To ensure sufficient anaerobic time, a stirring device is activated during this phase to ensure full contact between the incoming sewage and the sludge, enhancing the "enrichment" process and promoting sludge granulation.

[0110] During this phase, the phosphate-accumulating bacteria within the system absorb and utilize organic matter in the incoming wastewater without being affected by nitrifying bacteria, promoting phosphorus release and improving subsequent phosphorus removal efficiency. The agitator is activated and stopped by the automatic control system. When the variable frequency inlet pump 7 is shut down, the agitator is activated.

[0111] S3, aeration stage.

[0112] After the anaerobic stage is completed, the stirring device is turned off and the fan is started. The fan adopts 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 process of denitrification and carbon removal.

[0113] In this stage, real-time data is obtained by installing real-time ammonia nitrogen monitoring instruments and real-time dissolved oxygen monitoring instruments. The concentration of dissolved oxygen in the aerobic granular sludge system directly affects the removal of total nitrogen, so the precise control of dissolved oxygen is extremely important. If the dissolved oxygen is not controlled throughout the aeration stage in a cycle, there will be an obvious jump in dissolved oxygen in the second half of the aeration, indicating that COD and ammonia nitrogen have been degraded to the maximum extent.

[0114] This situation will be unfavorable for the removal of total nitrogen, so it is necessary to precisely control the dissolved oxygen concentration range, and the value of the ammonia nitrogen on-line monitoring instrument is used as the basis for dissolved oxygen control.

[0115] In the early stage of aeration, the dissolved oxygen is controlled at 1mg / L to 1.5mg / L to promote the nitrification process and fully convert ammonia nitrogen. Set the node value a (i.e., the first threshold a), which is 30% to 40% of the influent ammonia nitrogen value or 120% to 140% of the designed effluent ammonia nitrogen. When the ammonia nitrogen value detected by the on-line instrument is lower than the node value a, the operating frequency of the fan is reduced to control the dissolved oxygen at 0.5mg / L to 1mg / L and continue to degrade ammonia nitrogen. Set the node value b (i.e., the second threshold b), which is 10% to 20% higher than the designed effluent ammonia nitrogen value. When the on-line detected ammonia nitrogen value is lower than the node value b, the aeration is shut down and the stirring device is started to strengthen the denitrification process for nitrogen and carbon removal and further strengthen the starvation process. In this way, by extending the starvation period, it promotes the secretion of extracellular polymers by the sludge, which is beneficial to the formation of granular sludge.

[0116] S4, sludge screening stage.

[0117] Calculate the sinking distances of granular sludge and flocculent sludge, and use the height difference in the vertical direction between the two to set the sludge discharge port at the upper position of the flocculent sludge. During the sedimentation stage, the flocculent sludge is discharged to retain the granular sludge at the lower layer, realizing the sludge screening process;

[0118] Sludge screening is an important control means in the process of granular sludge formation. Compared with granular sludge, flocculent sludge has a larger specific surface area and can adsorb the substrate in sewage faster, which will form substrate competition with the microorganisms growing slowly in granular sludge. To reduce the substrate competition with granular sludge, it is necessary to discharge some flocculent sludge in time, that is, to implement the sludge screening process. The specific gravity of granular sludge is greater than that of flocculent sludge, and the average sedimentation speed is greater than that of flocculent sludge. Stratification will occur during the sedimentation stage, with granular sludge with a faster sedimentation speed at the lower layer and flocculent sludge with a slower sedimentation speed at the upper layer;

[0119] First, calculate the sludge discharge volume. When the proportion of granular sludge is lower than 30%, it indicates that the proportion of granules in the system is not high, and the sludge granulation and sludge screening processes still need to be continued. It is necessary to continue to discharge the flocculent sludge among them. At this time, the sludge discharge volume is calculated according to the sludge age of 20 - 30 days. The calculation method can be referred to the 05th volume of the Design Manual for Water Supply and Drainage - Urban Drainage.

[0120] When the particle proportion is in the range of 30%-50%, the granular sludge state is relatively stable at this time, and the amount of flocculent sludge to be discharged gradually decreases. At this time, the sludge discharge volume is calculated according to a sludge age of 30-40 days. When the particle proportion is higher than 50%, it indicates that the particle proportion in the device is relatively ideal. If the effluent indexes of the device meet the standards at this time, sludge discharge can be selected not to be carried out. At this time, it is necessary to closely observe the total phosphorus value of the effluent and the sludge COD load. If there is a risk of exceeding the standard for the total phosphorus value of the effluent or the sludge COD load is lower than 50% of the design load, appropriate sludge discharge is carried out, and the sludge discharge volume is calculated according to a sludge age of 35-45 days;

[0121] Secondly, calculate the sludge discharge duration. The sludge discharge duration = sludge discharge volume / flow rate through the sludge discharge port, where the flow rate through the sludge discharge port is measured by installing a flow meter or manually measured. The manual measurement method is as follows: Use a container with precise scales to receive the effluent volume of the sludge discharge port for 15 seconds or 30 seconds, calculate the flow rate per second according to the received volume, and then calculate the sludge discharge duration according to the calculated flow rate through the sludge discharge port. The sludge discharge duration is the opening duration of the sludge discharge port valve;

[0122] Finally, select the position of the sludge discharge port. The position of the sludge discharge port 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] Take out 100 mL of sludge from the device during the aeration period, screen the sludge in the device by the wet screening method, and measure the average sedimentation velocities V1 and V2 of the granular sludge and flocculent sludge with a particle size greater than 0.2 mm in a 1 L graduated cylinder respectively. After determining the sedimentation velocity of the sludge, calculate the sinking height of the granular sludge and the flocculent sludge according to different sedimentation times. The average sedimentation velocity of the granular sludge is V1; the average sedimentation velocity of the 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 sinking distance of the granular sludge during the sedimentation period: L1 = V1 * t; if the proportion of granular sludge with a particle size greater than 0.2 mm is 100%, the distance between the mud-water interface and the water surface above at the end of the sedimentation period is L1;

[0125] The sinking distance of the flocculent sludge during the sedimentation period: L2 = V2 * t. Since V1 > V2, obviously, if the particle size of the sludge in the system is all less than 0.2 mm, the distance between the mud-water interface and the water surface above during the sedimentation period is L2;

[0126] Due to the granulation of the sludge and the dynamic change of the proportion of sludge with a particle size greater than 0.2 mm during the normal operation process, and the difference in the sedimentation velocity of the sludge at different times, the sinking distance of the sludge is different at different times. 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 particle sludge proportion e and the sedimentation velocity:

[0127] Ln = V1 * e * t

[0128] Among them, Ln is the distance between the sludge discharge port 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 is relatively high in the bottom area of the device, and the proportion of flocculent sludge is relatively high at the L2 and L3 height positions in the upper area. Sludge is discharged from sludge discharge ports such as L2 and L3 to maximize the discharge of flocculent sludge in the device and maximize the retention of granular sludge in the system, realizing the process of screening sludge, which helps the rapid granulation of sludge and maintains the stability of the granular sludge system.

[0129] In summary, by pulsing influent to wash out flocculent sludge, using a high water exchange ratio to make up for the shortage of carbon source in low-concentration sewage, adding a stirring device to enhance mass transfer and strengthen the starvation process, precisely controlling dissolved oxygen to ensure total nitrogen removal, and optimizing the setting of the sludge discharge port to maximize the interception of granular sludge, the granulation cultivation process of flocculent sludge can be accelerated.

[0130] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. 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, Including: A reaction tank, an aeration mechanism, a sludge discharge mechanism, a water distribution system and a control system; The reaction tank is used to contain the mixed liquid containing activated sludge; The aeration mechanism is configured to supplement oxygen into 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 into the reaction tank, and has a first water addition state and a second water addition state. The first water flow rate in the first water addition state is S1, and the second water flow rate in the second water addition state is S2, and S2 is greater than S1. The control system is configured to control the working state of the water distribution system, as well as the operation time and water flow rate in the corresponding working state, according to the SVI 30 and MLSS concentration; If the MLSS is 1000 mg / L to 3000 mg / L, SVI 30 is greater than 100 mL / g, then the water distribution system alternately operates in the first water addition state and the second water addition state, where S1 is not higher than 4 m / h; S2 is 8 m / h to 10 m / h, and the time for the water distribution system to operate in the second water addition state once is 3 seconds to 5 seconds; If the MLSS is 4000 mg / L to 6000 mg / L, SVI 30 is less than 60 mL / g, then the water distribution system operates alternately in the first water addition state and the second water addition state, where S1 is not higher than 4 m / h, S2 is 10 m / h to 12 m / h, and the operating time of the water distribution system in the second water addition state is 5 seconds to 10 seconds; If the MLSS is greater than 6000 mg / L and the SVI 30 is less than 50 mL / g, the water distribution system continuously operates in the first water addition state, where S1 is not higher than 4 m / h; The control system controls the sizes of S1 and S2 by controlling the working frequency of the variable-frequency water inlet pump; The control system is further configured to determine the water change ratio according to the particle proportion; And, the control system is further configured to determine the water change ratio according to the organic sludge load in the system; If the particle proportion is less than 10%, the water change ratio is 70% to 75%; If the particle proportion is 10% to 30%, the water change ratio is 60% to 70%; If the particle proportion is greater than 40%, the water change ratio is 30% to 50%; The determination of the water change ratio should preferably satisfy that the organic sludge load in the system is not less than 0.15 kgCOD / kgMLSS / d; The control system is further configured to control the opening or closing of the water distribution system according to the mapping relationship between the water change ratio and the operation time of the water distribution system.

2. The device according to claim 1, characterized in that, The control system is further configured to determine the sludge discharge amount of the sludge discharge mechanism according to the particle proportion of the mixed liquid.

3. The device according to claim 2, wherein If the proportion of granular sludge is less than 30%, the sludge discharge amount is calculated according to a sludge age of 20 days to 30 days; If the particle proportion is 30% to 50%, the sludge discharge amount is calculated according to a sludge age of 30 days to 40 days; If the particle proportion is higher than 50% and the effluent indexes of the device all meet the standards, no sludge is 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 amount is calculated according to a sludge age of 35 days to 45 days.

4. The device according to claim 1, characterized in that, The sludge discharge mechanism includes a sludge discharge port, a sludge discharge pipeline and a pipeline valve. The distance between the sludge discharge port and the water surface is L, and L = V1 * e * t, where 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 proportion 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 spaced along the height direction of the reaction tank; where L2 = V2 * t, L1 = V1 * t, V1 is the average sedimentation velocity of the granular sludge, V2 is the average sedimentation velocity of the flocculent sludge, t is the sedimentation 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 particle proportion in the activated sludge is 0; And / or, V1 is greater than V2, then L1 is greater than L2. In the vertical direction, L2 is always above L1.

5. The device according to claim 1, characterized in that, The device further includes an aeration mechanism and a stirring mechanism. The control system is configured to start the stirring mechanism after the water distribution system stops or the aeration ends. The aeration mechanism is configured to provide aeration to the device.

6. The device according to claim 5, characterized in that The device further includes a monitoring mechanism. The monitoring mechanism 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 through the aeration mechanism; And / or, when the ammonia nitrogen value is lower than the first threshold a, reduce the operating frequency of the variable frequency blower to control the dissolved oxygen at 0.5 mg / L to 1 mg / L; wherein, a is 30% to 40% of the influent ammonia nitrogen value or 120% to 140% of the designed effluent ammonia nitrogen; And / or, when the ammonia nitrogen value is lower than the second threshold b, shut down the variable frequency blower and start the stirring mechanism; wherein, the value of b is 10% to 20% higher than the designed effluent ammonia nitrogen value.

7. The device according to claim 1, characterized in that, The water distribution system includes an influent storage bucket, an influent pipe, a variable frequency influent pump, and a multi-point water head. The influent pipe connects the influent storage bucket, the variable frequency influent pump, and the multi-point water head, and the multi-point water head is arranged at the bottom of the reaction tank.

8. A method for culturing aerobic granular sludge using the aerobic granular sludge culturing device according to any one of claims 1 to 7, characterized in that, It includes the following steps: Inlet and outlet water stage: When the water inlet starts, S1 and S2 are alternately water-distributed synchronously. During the synchronous water inlet and outlet, the screening process of granular sludge is initially completed. On the premise of meeting the organic sludge load, the water change ratio is adjusted according to SVI 30 and MLSS; Anaerobic stage: After the influent ends, the pollution concentration in the system reaches the maximum value. At this time, the system enters the anaerobic stage. In this stage, start the stirring device to make the newly incoming sewage fully contact with the sludge; Aeration stage: After the anaerobic stage ends, turn off the stirring device and start the variable frequency blower for aeration operation. Control the opening and closing of the variable frequency blower and the operating frequency of the variable frequency blower in the on state according to the dissolved oxygen concentration and ammonia nitrogen value in the mixed liquor; when the ammonia nitrogen value is lower than the preset threshold, stop aeration and start the stirring device to operate for a preset time; Sludge screening stage: After the aeration stage ends, utilize the height difference in the vertical direction between the granular sludge and the flocculent sludge during the sedimentation process, set the sludge discharge port at the position corresponding to the flocculent sludge, and discharge the flocculent sludge during the precipitation stage to retain the granular lower-layer sludge, realizing the sludge screening process.

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