A method for achieving self-oxygenation of aerobic pools through sludge reflow

Abstract

The present invention discloses a method for achieving self-oxygenation of an aerobic tank through sludge return, comprising: installing multiple dissolved oxygen monitoring probes along the aerobic tank, extracting sludge from the MBR tank and returning it to multiple outlets along the aerobic tank, each outlet being provided with a sludge return valve for controlling the return flow rate Q, each dissolved oxygen monitoring probe being associated with a sludge return valve located at its front end and closest to it; and adjusting the opening / closing and flow rate Q of each sludge return valve accordingly based on the feedback data of each dissolved oxygen monitoring probe. The method of the present invention can achieve stable control of dissolved oxygen in the aerobic tank and save fan energy consumption through a simple batch return technology, and the effect is very significant. Although the invention is only aimed at the activated sludge + MBR system process, the technology is currently a mainstream sewage treatment process and is widely used. Therefore, the invention patent has great market application prospects.

Description

Technical Field

[0001] The invention belongs to the field of sewage treatment, and in particular relates to a method for achieving self-oxygenation of an aerobic tank through sludge reflow. Background Art

[0002] According to surveys, the overall energy consumption of sewage treatment plants is very complex, mainly including electricity consumption, chemical consumption, and sludge disposal. Electricity consumption is one of the main expenses of sewage treatment plants, generally accounting for more than 30%. Aerobic tank aeration fans are the main source of electricity consumption throughout the sewage treatment plant, accounting for 30% to 50% of the total electricity consumption. Therefore, reducing aeration fans in aerobic tanks can effectively reduce the operating energy consumption of the entire sewage treatment plant and is an effective means to reduce pollution and carbon emissions in sewage treatment plants.

[0003] Using precision aeration technology to control the aeration system can not only control the dissolved oxygen of the biological treatment process within a certain range, ensure the stable operation of the sewage treatment system, but also achieve energy conservation and consumption reduction. It is the current mainstream technology for reducing the energy consumption of fans in sewage treatment plants. For example, Chinese patent document CN202210874455.0 discloses a method for controlling the air volume of a precision aeration system. The precision aeration system includes a data collector, a data calculation and analysis unit, and a signal feedback unit. After the staff inputs the control range of dissolved oxygen into the precision aeration system, the data collector collects the required instrument data, and then uses the data calculation and analysis unit to calculate the aeration volume through the data collected by the data collector. The input air volume of the blower is determined based on whether the real-time dissolved oxygen value of the aerobic tank is within the dissolved oxygen control range, and the blower input air volume is fed back to the blower through the signal feedback unit, thereby accurately controlling the aeration volume. The above method can achieve precise control of the aeration system, the fan supplies air on demand, improves operating efficiency, and achieves the purpose of energy saving. This technology uses various theoretical formulas to confirm the actual oxygen demand of the aerobic tank. It requires simultaneous monitoring of indicators such as sludge respiration rate, influent COD value, temperature, and oxygen transfer efficiency. The actual operation is extremely difficult, and each coefficient is determined by empirical values ​​with a large range. The results resulting from different values ​​vary greatly, and cannot effectively meet aeration needs.

[0004] For example, Chinese invention patent document CN202110480137.1 discloses a precise aeration method for a landfill leachate aerobic system, in which an aeration fan combined with a jet water pump is used to control the aerator to aerate the landfill leachate, ensuring that the dissolved oxygen concentration in the nitrification tank is within the set range, so that the landfill leachate can be deeply treated until it reaches the national or local treatment standards before being discharged or comprehensively utilized. The automated and precise control of dissolved oxygen in the leachate aerobic system in this patent document reduces the high energy consumption caused by differences in the technical capabilities of operators, while reducing the impact of uncertain factors. It can reduce the high energy consumption caused by the uneconomical operation of high-energy-consuming electromechanical equipment, and the energy efficiency reduction rate is not less than 25% of the installed capacity. However, this technology only optimizes the aeration volume and the ratio of the jet pump through aeration and dissolution feedback data, which avoids the waste of dissolved oxygen to a certain extent, but the effect of reducing the operating power consumption of the aeration fan is very limited.

[0005] For example, Chinese invention patent document CN202211296805.6 discloses a precision aeration integrated sewage treatment device, which includes a sedimentation tank, an aeration pipe installed in the sedimentation tank, a plurality of branch pipes connected to the aeration pipe, a rotary sealing joint connected between the branch pipe and the aeration pipe, an outlet head evenly distributed on the branch pipe, an air inlet fan connected to the aeration pipe, a lifting device for driving the aeration pipe to rise and fall, and a drive assembly for driving the branch pipe to rotate installed between the side wall of the sedimentation tank and the branch pipe; when the pushing device pushes the aeration pipe to move, the branch pipe is driven by the driving device to rotate, and the outlet head is driven to rotate. When the outlet head rotates, the sedimentation tank can be fully aerated. When the pushing device pushes the aeration pipe to move, the driving assembly is disabled, and the lifting device no longer drives the outlet head to rotate. Through the above operation, the sedimentation tank can be fully aerated during aeration. This technology is mainly used for precise control of aeration points and aeration effects, and does not have any energy-saving and consumption-reducing effects.

[0006] In addition, a large number of patents have proposed control methods that use biological model feedforward + feedback or feedback + hardware integration. Among them, the biological model feedforward is mostly based on the International Water Association ASM series model. However, the above technical control methods are cumbersome and the indicators are complex, requiring a large amount of expensive monitoring systems. In addition, the value range of each coefficient in the model is large, and it is ultimately difficult to accurately determine an accurate dissolved oxygen data. To a large extent, there is no significant energy-saving and consumption-reduction effect. Summary of the Invention

[0007] Biochemical systems typically include anaerobic, anoxic, and aerobic tanks. Aerobic tanks typically require bottom aeration to oxygenate the water, maintaining a dissolved oxygen level of 2.0-4.0 mg / L. This effectively degrades pollutants such as COD and ammonia nitrogen. This process requires the use of aeration fans, which consume a significant amount of energy, typically accounting for 30-50% of the total power consumption of the entire sewage treatment plant.

[0008] MBR tanks are a new type of sludge-water separation technology that has replaced traditional secondary sedimentation tanks. The membrane components in MBR tanks require a constant amount of aeration to clean the membrane fibers and prevent clogging. Since MBR tanks are almost free of pollutants, excessive aeration raises the dissolved oxygen level in the MBR system to over 6 mg / L. This not only wastes dissolved oxygen, but also causes sludge to gradually age in a high dissolved oxygen environment, resulting in poor sludge properties.

[0009] Based on the above problems, the present invention addresses the problem of high power consumption in the operation of the biochemical aeration tank in the sewage treatment plant, utilizes the MBR excess sludge return mode, and effectively solves the problem of dissolved oxygen demand in the biochemical tank.

[0010] Currently, there are no other effective energy-saving and consumption-reducing technologies for aerobic tank aeration modules. However, the method proposed in this invention, which achieves self-oxygenation of aerobic tanks through sludge return, can achieve stable control of dissolved oxygen in aerobic tanks and save fan energy through simple batch return technology, with very significant results. Although this invention only targets the activated sludge + MBR system process, this technology is currently a mainstream sewage treatment process with a very wide range of applications. Therefore, this invention patent has great market application prospects.

[0011] A method for achieving self-oxygenation of an aerobic tank by sludge reflow, comprising:

[0012] Multiple dissolved oxygen monitoring probes are installed along the aerobic tank and multiple outlets are set up. Sludge is extracted from the MBR tank and returned to multiple outlets along the aerobic tank. Each outlet is equipped with a sludge return valve for controlling the return flow rate Q. Each dissolved oxygen monitoring probe is associated with a sludge return valve located in front of and closest to it. The opening / closing and flow rate Q of each sludge return valve are adjusted accordingly based on the feedback data from each dissolved oxygen monitoring probe. The return flow rate of each outlet along the aerobic tank is Q1, Q2...Q n ;Q1+Q2+…+Q n =Total amount of sludge return Q 总 ;

[0013] When the dissolved oxygen concentration fed back by the dissolved oxygen monitoring probes along the process is above X, Q1=Q 总When the dissolved oxygen concentration A fed back by any dissolved oxygen monitoring probe along the process shows that it is lower than X, the sludge return valve at the front end of the dissolved oxygen monitoring probe and associated with the dissolved oxygen probe is opened, and the reflux flow rate of the outlet is controlled to Q = n(XA)*Q 总 , where n is the reflux coefficient, which ranges from 0.21 to 0.35; when the dissolved oxygen concentration A fed back by any dissolved oxygen monitoring probe reaches above 0.5 mg / L, the sludge reflux valve at the front end of the dissolved oxygen monitoring probe and associated with the dissolved oxygen probe is closed.

[0014] The dissolved oxygen limit X value is determined by the estimation formula, specifically: X = BOD 进水 *m, where BOD is the biochemical oxygen demand of the influent, expressed in mg / L, and m is the dissolved oxygen coefficient, ranging from 0.007 to 0.014. The dissolved oxygen coefficient is an empirical value. A coefficient that is too low will result in insufficient dissolved oxygen in the aerobic pool, making it impossible to stably achieve the degradation standards for various pollutants. A coefficient that is too high will result in excessive dissolved oxygen in the aerobic pool, resulting in energy waste and insufficient dissolved oxygen in other areas along the process.

[0015] Optionally, when the dissolved oxygen concentration A fed back by multiple dissolved oxygen monitoring probes along the process is lower than X, and the sum of the corresponding return flow required by each outlet is greater than the total sludge return flow Q 总 When opening, the sludge return valve located at the front of the process is given priority.

[0016] Optionally, the number of the outlets is adapted to the number of dissolved oxygen monitoring probes. A more specific adaptation scheme is that the number of the outlets corresponds one-to-one to the number of dissolved oxygen monitoring probes, a sludge return valve is set for each outlet, and each dissolved oxygen monitoring probe is associated with a sludge return valve.

[0017] Optionally, the aerobic tank should have 4-7 outlets along the entire length of the tank, with the first outlet located at the front end and subsequent outlets evenly distributed. A dissolved oxygen monitoring probe should be placed at the rear end of each outlet. Sludge return outlets are generally configured at 4-7, depending on the scale of the sewage treatment plant. For plants with a capacity of less than 10,000 tons / day, 4 outlets are recommended; for plants with a capacity of more than 100,000 tons / day, 7 outlets are recommended. Too few outlets will result in inaccurate dissolved oxygen control, while too many outlets will make control too complex and meaningless.

[0018] Optionally, the dissolved oxygen monitoring probe is located in the middle between adjacent outlets, and all dissolved oxygen monitoring probes are evenly distributed along the aerobic tank. Dissolved oxygen probes are evenly distributed between each outlet to monitor the dissolved oxygen concentration along the aerobic tank at all times.

[0019] Optionally, the total amount of sludge return Q 总 It is 50% to 100% of the water volume of the aerobic pool.总 It is 50% to 100% of the influent water volume. If the ratio is too low, it will lead to insufficient dissolved oxygen return. If it is too high, it will lead to untimely degradation of pollutants and direct entry into the MBR pool, resulting in direct short-flow effluent and substandard effluent.

[0020] Optionally, all dissolved oxygen monitoring probes are connected to the controller; all sludge return valves are connected to and controlled by the controller.

[0021] Currently, there is no similar product of this invention. Compared with the traditional aeration and oxygenation mode, it has at least one of the following advantages:

[0022] (1) Reduce the energy consumption of aeration fans in aerobic pools by more than 60%, achieving low-consumption sewage treatment;

[0023] (2) The sludge volume in the aerobic tank is increased through the recirculation system, thereby improving the pollutant removal efficiency of the aerobic tank;

[0024] (3) The reflux system reduces the amount of sludge in the MBR pool, reduces the load on the membrane components, and increases their service life;

[0025] (4) The recirculation system reduces the overall dissolved oxygen environment of the aerobic tank + MBR tank, thus avoiding sludge aging. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application.

[0029] A method for achieving self-oxygenation of an aerobic tank through sludge return, which is primarily implemented through the following modules: a sludge return system, a dissolved oxygen monitoring system, a multi-channel automatic valve control system, and a data calculation and analysis unit. The sludge return system extracts sludge from the end of the MBR tank and returns it to the aerobic tank. The return outlets are evenly distributed along the aerobic tank, with the first sludge return outlet located at the very front of the aerobic tank, and subsequent sludge return outlets evenly distributed along the entire length. An automatically controlled sludge return valve is installed at each sludge return outlet, and a dissolved oxygen monitoring probe is installed at each stage where the sludge return valve is located. The feedback data from the dissolved oxygen detection probe is used to adjust the opening / closing and opening flow rate of the corresponding sludge return valve.

[0030] Conventional A2O processes include two recirculation modes: sludge recirculation and nitrification solution recirculation. Sludge recirculation is the return from the sedimentation tank to the anaerobic tank, primarily used for phosphorus removal and sludge return. Nitrification solution recirculation is the return from the end of the aerobic tank to the anoxic tank, used for denitrification. The recirculation system of the present invention functions completely differently from these two recirculation modes, primarily replacing the aeration fan to replenish dissolved oxygen in the aerobic tank.

[0031] A schematic diagram of a specific process is as follows Figure 1 As shown in the figure, the influent after treatment in other tanks enters the aerobic tank, which is divided into n zones along the way, namely aerobic tank 1, aerobic tank 2, aerobic tank 3, ... aerobic tank n (named aerobic tank 1, aerobic tank 2, aerobic tank 3, ... aerobic tank n for distinction, but actually representing different zones within the entire aerobic tank, with no partitions between adjacent zones). Aerobic tank n, i.e., the effluent at the end of the aerobic tank, enters the MBR tank. A return sludge outlet is set at the front end of each aerobic tank zone, and a sludge return valve is installed at each return sludge outlet. A dissolved oxygen monitoring probe is installed in the middle of each aerobic tank. All dissolved oxygen monitoring probes can be connected to the control system, and all sludge return valves can be connected to and controlled by the control system. The control system can use a mature controller such as a PLC.

[0032] There are generally 4-7 sludge return outlets, which can also be understood as dividing the aerobic pool into 4 to 7 areas for separate adjustments. It is determined according to the scale of the sewage treatment plant. When the scale of the sewage treatment plant is less than 10,000 tons / day, it is recommended to set up 4; when the scale of the sewage treatment plant is greater than 100,000 tons / day, it is recommended to set up 7.

[0033] Dissolved oxygen monitoring probes are installed at the rear end of each outlet, evenly distributed along the entire length of the aerobic tank to monitor dissolved oxygen concentrations throughout the tank. The sludge return system extracts sludge from the MBR tank and returns it to multiple outlets along the aerobic tank. A sludge return valve controls the return flow rate Q at each outlet. The data calculation and analysis unit (i.e., the control system) automatically controls each Q value, increasing the dissolved oxygen environment in each unit of the aerobic tank by returning sludge from the MBR.

[0034] The return flow rates of the sludge return outlets along the aerobic tank are Q1, Q2, etc. n The reflux flow control method is: Q1+Q2+... +Q n =Total amount of sludge return Q 总 Total sludge return volume Q 总 It is 50% to 100% of the influent water volume. If the ratio is too low, it will lead to insufficient dissolved oxygen return. If it is too high, it will lead to untimely degradation of pollutants and direct entry into the MBR pool, resulting in direct short-flow effluent and substandard effluent.

[0035] When the dissolved oxygen concentration A fed back by the dissolved oxygen monitoring probe along the process is above the preset value X, Q1=Q 总 ; When a certain stage along the process (can also be understood as Figure 1 In a certain aerobic tank area, for example, aerobic tank 2), when the dissolved oxygen concentration A fed back by the dissolved oxygen monitoring probe is lower than X, the sludge return valve in front of the dissolved oxygen probe (for example, the sludge return valve in the aerobic tank 2 area) is opened to control the flow rate Q = n(XA)*Q 总 , where n is the reflux coefficient, ranging from 0.21 to 0.35, which is an empirical value; when a certain stage (also understood as Figure 1 When the dissolved oxygen concentration A fed back by the dissolved oxygen monitoring probe in a certain aerobic tank area (e.g. aerobic tank 3) reaches 0.5 mg / L or above, the sludge return valve in front of the dissolved oxygen probe (e.g. the sludge return valve in the aerobic tank 3 area) is closed. Figure 1 In multiple aerobic pool areas, the dissolved oxygen concentration A was found to be lower than the preset value X, and the total amount of return flow required in each stage was greater than the total amount of sludge return flow Q. 总 When opening, the sludge return valve at the front of the process is given priority.

[0036] The dissolved oxygen preset value X is determined by the estimation formula, specifically: X = BOD 进水 *m, where BOD is the biochemical oxygen demand of the influent, expressed in mg / L, and m is the dissolved oxygen coefficient, ranging from 0.007 to 0.014. The dissolved oxygen coefficient is an empirical value. A coefficient that is too low will result in insufficient dissolved oxygen in the aerobic pool, making it impossible to stably achieve the degradation standards for various pollutants. A coefficient that is too high will result in excessive dissolved oxygen in the aerobic pool, resulting in energy waste and insufficient dissolved oxygen in other areas along the process.

[0037] The following is a further explanation with specific application examples:

[0038] A large municipal wastewater treatment plant in Hangzhou, using an A2O+MBR process, originally used blowers to supply oxygen and flush membranes in the aerobic and MBR tanks. The aerobic tank blower consumed 2130 kWh / day (three blowers, two in operation and one in reserve, accounting for 22.8% of the plant's total power consumption), while the membrane tank blower consumed 1680 kWh / day (three blowers, two in operation and one in reserve, accounting for 18.0% of the plant's total power consumption). Under this cloud model, dissolved oxygen levels in the aerobic tank were maintained at 3-4 mg / L, and in the MBR tank at 8 mg / L.

[0039] After the method of the present invention was tested in the sewage treatment plant, the operation of the membrane pool fan remained unchanged. After the aerobic pool was changed to the oxygenation technology of the present invention, the fan operation mode was adjusted to 1 in use and 2 in standby, and the fans used were also operated at a low frequency. The fan operation power consumption was reduced to 685kWh / d. In order to ensure the uniform distribution of sludge in the aerobic pool, 10 submersible mixers (original facilities) were added and started, increasing the power consumption by 528kWh / d, which is equivalent to a total power consumption of 1213kWh / d for the aerobic pool, which is 917kWh / d (~10%) lower than the energy consumption of the original aerobic pool.

[0040] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art could make various modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A method for achieving self-oxygenation of an aerobic tank by sludge reflow, characterized in that: include, Multiple dissolved oxygen monitoring probes are installed along the aerobic tank and multiple outlets are set up. Sludge is extracted from the MBR tank and returned to multiple outlets along the aerobic tank. Each outlet is equipped with a sludge return valve for controlling the return flow rate Q. Each dissolved oxygen monitoring probe is associated with a sludge return valve located in front of and closest to it. The opening / closing and flow rate Q of each sludge return valve are adjusted accordingly based on the feedback data from each dissolved oxygen monitoring probe. The return flow rate of each outlet along the aerobic tank is Q1, Q2...Q n ;Q1+Q2+…+Q n = Total sludge return flow Q 总 ; Total sludge return Q 总 50%~100% of the water volume of the aerobic pool; When the dissolved oxygen concentration fed back by the dissolved oxygen monitoring probes along the process is above the preset value X, Q1= Q 总 When the dissolved oxygen concentration A fed back by any dissolved oxygen monitoring probe along the process shows that it is lower than the preset value X, the sludge return valve at the front end of the dissolved oxygen monitoring probe and associated with the dissolved oxygen monitoring probe is opened, and the reflux flow rate of the outlet is controlled to Q=n(XA)*Q 总 , where n is the reflux coefficient, ranging from 0.21 to 0.35; when the dissolved oxygen concentration A fed back by any dissolved oxygen monitoring probe reaches 0.5 mg / L or above, close the sludge reflux valve at the front end of the dissolved oxygen monitoring probe and associated with the dissolved oxygen probe; Where X = BOD 进水 *m, where BOD is the biochemical oxygen demand of the influent, in mg / L, and m is the dissolved oxygen coefficient, ranging from 0.007 to 0.014; When the dissolved oxygen concentration A fed back by multiple dissolved oxygen monitoring probes along the process is lower than X, and the sum of the corresponding return flow required by each outlet is greater than the total sludge return flow Q 总 When opening, the sludge return valve located at the front of the process is given priority.

2. The method according to claim 1, characterized in that The number of outlets along the aerobic pool is set to 4-7, with the first outlet located at the front end of the aerobic pool and subsequent outlets evenly distributed; the dissolved oxygen monitoring probe is correspondingly set at the rear end of each outlet.

3. The method according to claim 1, characterized in that The dissolved oxygen monitoring probe is located in the middle between adjacent outlets, and all dissolved oxygen monitoring probes are evenly distributed along the aerobic tank.

4. The method according to claim 1, wherein All dissolved oxygen monitoring probes are connected to the controller; all sludge return valves are connected to and controlled by the controller.

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