A backwash control method for multiple biological aeration filters and its application

Abstract

The present invention discloses a backwash control method for linkage of multiple biological aeration filters and its application, belonging to the technical field of sewage treatment. The backwash control method is improved from the original backwashing of multiple biological aeration filters in sequence to the linkage backwashing of two biological aeration filters, which greatly improves the backwash efficiency and can solve the problems of too long backwashing process, idle time and frequent start-stop of backwash fans and backwash pumps during cleaning of multiple biological aeration filters. In addition, the present invention predicts the degree of contamination and blockage of filter materials in the washed filter according to the current value characteristics of the backwash fan in the first half of the air flushing stage, constructs a deviation coefficient and a time adjustment rule, and dynamically adjusts the air flushing stage time and the water flushing stage time, which can ensure the backwashing effect and avoid incomplete backwashing or excessive flushing. The backwash control method provided by the present invention has broad application prospects in the field of sewage treatment.

Description

Technical Field

[0001] The invention belongs to the technical field of sewage treatment, and in particular relates to a backwash control method for linkage of multiple biological aeration filters and an application thereof. Background Art

[0002] Biological aerated filters primarily remove impurities such as suspended solids, ammonia nitrogen, and organic matter from wastewater through a combination of biodegradation and physical filtration. After a period of operation, large amounts of trapped suspended solids, microbial metabolites, and organic pollutants gradually accumulate between the pores of the filter media. This reduces the permeability of the filter layer and significantly increases the resistance to wastewater flow. Backwashing effectively removes these accumulated pollutants and restores the filter media's filtration performance, ensuring efficient filter operation and consistent, standard effluent quality.

[0003] In the prior art, the backwash of the aerated biological filter is triggered by a set time cycle. The backwash process includes three stages: air flushing, air-water mixed flushing, and water flushing. Each stage is carried out at a separately set time, and the time setting value is usually given by experience. Under the condition of a certain backwash intensity, the backwash time has a significant impact on the backwash effect. When the filter influent contains a lot of suspended matter or the filtration time is too long, the suspended matter and detached biofilm retained by the filter material will accumulate and adhere to the filter material and filter plates. When the backwash time is fixed, it is difficult to ensure that the suspended matter and detached biofilm are completely removed during each flushing. Incomplete flushing will lead to excessive accumulation of suspended matter and biofilm, and when it reaches a certain level, the filter material will become compacted. The compacted filter material will cause the fan to trip due to overcurrent during the air flushing stage, and the filter plate will become partially loose or even broken during the air-water mixed flushing stage.

[0004] Chinese patent publications such as CN111672172A and CN102063115A determine backwash time based on the water quality of the filter inlet and outlet, using metrics such as turbidity. While this method utilizes a real-time control strategy to flexibly determine backwash time based on impurity removal during the backwash process, the sequential strategies of performing air flushing alone, air-water mixed flushing alone, or water flushing alone are not suitable for backwashing multiple series-connected biological aerated filters. Backwashing of multiple biological aerated filters is typically performed sequentially in a predetermined sequence. After one filter is flushed, the next filter is flushed, and the process continues until the final filter is flushed. This process is time-consuming and results in idle time for the backwash fan and backwash water pump, impacting backwash efficiency. Furthermore, the backwash fan and backwash pump frequently start and stop within a backwash cycle. This frequent start and stop process accelerates motor insulation aging, shortens motor life, and increases equipment failure rates.

[0005] Therefore, it is necessary to develop a backwash control method with high flushing efficiency, good flushing effect and suitable for multiple aerated biological filters. Summary of the Invention

[0006] In order to solve the above-mentioned deficiencies in the prior art, the present invention provides a backwash control method for multiple biological aeration filters in linkage, which has high flushing efficiency, low energy consumption and good flushing effect.

[0007] The specific technical solutions adopted are as follows:

[0008] A method for controlling backwashing of multiple biological aerated filters in linkage includes using a backwashing system to sequentially perform backwashing on each biological aerated filter, including an air flushing stage, an air-water mixed flushing stage, and a water flushing stage; the backwashing system includes a backwashing fan and a backwashing pump, and the number of biological aerated filters is denoted as n, where n is ≥ 3;

[0009] In the specific backwashing process, first start the backwash fan to perform air flushing on the first biological aeration filter for T1 time, then start the backwash pump, and perform air-water mixed flushing on the first biological aeration filter for T2 time, then use the backwash pump to perform water flushing on the first biological aeration filter for T3 time, and at the same time use the backwash fan to perform air flushing on the second biological aeration filter for T3 time. At this point, the backwashing of the first biological aeration filter is completed, and then use the backwash fan and backwash pump to perform air-water mixed flushing on the second biological aeration filter for T4 time, then use the backwash pump to perform water flushing on the second biological aeration filter for T5 time, and at the same time use the backwash fan to perform air flushing on the third biological aeration filter for T5 time, and so on, until the backwashing of the nth biological aeration filter is completed, and the backwashing of the nth biological aeration filter is performed for T 2n After the air-water mixture flushing for a period of time, the backwash fan is turned off and the aeration biological filter is operated for T 2n+1 Turn off the backwash pump after flushing with water for a certain period of time;

[0010] Gas flushing time T1, T3, ...T 2n-1 Determine as follows: Calculate the deviation coefficient K. When 0<K<2, the air flushing time is not adjusted based on the reference t time (the reference t time is determined according to the experience value, which is related to the influent water quality, filter material, and degree of contamination during use. Optionally, the reference t time range is set to 4 to 8 minutes). When 2≤K<K max When the gas flushing time is extended based on the reference time t, the closer K is to K max , the longer the extension time;

[0011] The deviation coefficient K is calculated according to the following formula:

[0012]

[0013] I v I is the average current value of the backwash fan at 1 / 2 of the reference time t during actual operation. v The maximum value is the rated current I N , when I v =I N When K=K max ;I b It is the average current value of the backwash fan when the biological aerated filter is running in a completely pollution-free state.

[0014] The method of the present invention can solve the problems of a long backwashing process during cleaning of multiple biological aerated filters (a long backwashing process will further aggravate the problems of filter blockage and filter material compaction), and the problems of idle time and frequent start-stop of backwash fans and backwash pumps. The backwashing control method provided by the present invention is improved from the original backwashing of multiple biological aerated filters in sequence to the linked backwashing of two biological aerated filters, which greatly improves the backwashing efficiency. The method also predicts the degree of contamination and blockage of the filter material in the filter being washed based on the current value characteristics of the backwashing fan in the first half of the air flushing stage, and constructs a deviation coefficient and time adjustment rule to dynamically adjust the air flushing stage time and the water flushing stage time, thereby ensuring the backwashing effect and avoiding incomplete backwashing or excessive flushing.

[0015] Preferably, when 2≤K<4, the gas flushing time is extended by 20%-30% (based on the benchmark t time) on the basis of the benchmark t time, and the specific value is rounded up (for example, if the specific time is extended by more than 1.0 min and is 1.1 min, the actual operation is rounded up to 0.2 min, the same below);

[0016] When 4≤K<5, the gas flushing time is extended by 60%-80% (based on the benchmark t time), and the specific value is rounded up;

[0017] When 5≤K<K max When the gas flushing time is extended by 80%-100% (based on the benchmark t time), the specific value will be rounded up.

[0018] The above control parameters are summarized by the inventors based on a large number of experiments, which are helpful to improve the backwashing effect and avoid incomplete backwashing or excessive backwashing.

[0019] Furthermore, when K≤0, there is a gas leak in the corresponding gas flushing pipeline, and an alarm is sent to the control system; when K≥K max , then the aerated biological filter is clogged or the filter material is severely compacted, and manual intervention is required.

[0020] The air-water mixed flushing time is also determined according to the empirical value, which is related to the water quality, filter material and degree of contamination during use. Optionally, the air-water mixed flushing time is T2, T4, ...T 2n Set it to 5 to 12 minutes.

[0021] Furthermore, the backwash system includes a backwash fan, a backwash pump, an air flush valve, a water flush valve, an inlet valve and a drain valve, wherein the backwash fan and backwash pump are shared by all aerated biological filters, and each aerated biological filter is equipped with a separate air flush valve, water flush valve, inlet valve and drain valve.

[0022] Preferably, the backwash fan is a positive displacement fan, the air output does not change with pressure changes, and the back pressure on the backwash fan is positively correlated with its operating current.

[0023] Specifically, under the condition of a certain air volume, the back pressure on the positive displacement fan is positively correlated with the operating current of the fan. The greater the back pressure (i.e., the pressure on the fan outlet during air flushing), the higher the fan current. When the back pressure exceeds the rated pressure of the fan, the fan operating current will exceed its rated current, and the fan will trip due to overcurrent protection. Similarly, when the filter media in the filter tank is severely clogged or compacted, the current in the initial stage of air flushing will increase sharply. In the later stage of air flushing, as the filter media gradually loosens, the fan current will gradually decrease and stabilize. Within the rated pressure range, the degree of blockage or compaction of the filter media is positively correlated with the current in the fan air flushing stage. The degree of contamination of the filter media can be determined based on the operating current in the first half of the fan air flushing stage. Real-time monitoring can be performed to reduce downtime, avoid the installation of additional sensors and other detection components, improve filtration efficiency, and prevent equipment failure.

[0024] Furthermore, the status of each component in the backwash system and the control of each valve are collected and controlled by the programmable logic controller (PLC).

[0025] The present invention also provides application of the multi-biological aeration filter linkage backwash control method in the field of sewage treatment.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) The method of the present invention provides a backwash control method applicable to multiple biological aerated filters, which can dynamically adjust the corresponding air flushing stage and water flushing stage time according to the pollution degree of the biological aerated filter, thereby solving the problem of incomplete flushing or excessive backwashing caused by the different pollution degrees of each filter when the biological aerated filter is backwashed at a fixed time.

[0028] (2) The method of the present invention optimizes and adjusts the backwash process of multiple biological aeration filters, improving the original backwashing of multiple biological aeration filters in sequence to the coordinated backwashing of two biological aeration filters, which greatly improves the backwashing efficiency, eliminates the idle waiting time of the backwashing equipment, and solves the problem of frequent start-up and stop of the backwash fan and backwash pump of the biological aeration filter.

[0029] (3) The method of the present invention predicts the degree of contamination and blockage of the filter media in the filter tank being flushed based on the current value characteristics of the backwash fan in the first half of the air flushing stage, and constructs a deviation coefficient and time adjustment rules to dynamically adjust the air flushing stage time and the water flushing stage time, which can ensure the backwashing effect, avoid incomplete backwashing or excessive flushing, prevent the filter media from accumulating retained matter, and extend the service life of the filter media. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a current change diagram when the backwash blower in Example 1 is running in a completely pollution-free state.

[0031] Figure 2 This is a diagram of current changes during the actual operation of the backwash fan in Example 1.

[0032] Figure 3 This is a diagram of the current changes during the actual operation of the backwash fan during the traditional backwash process. DETAILED DESCRIPTION

[0033] In order to make the objects, features and advantages of the present invention more clearly understood, a detailed description is given below using specific embodiments. In the following description, many specific details are set forth to fully understand the present invention. However, the present invention can be implemented in many other ways than those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below. The technical features in the various embodiments of the present invention can be combined accordingly without conflicting with each other.

[0034] The operating methods in the following examples without specifying specific conditions are generally carried out under conventional conditions or the conditions recommended by the manufacturer. The contents not described in detail in this specification belong to the prior art known to those skilled in the art.

[0035] Example 1

[0036] In this embodiment, the backwash system includes a backwash fan, a backwash pump, an air flush valve, a water flush valve, an inlet valve and a drain valve, wherein the backwash fan and the backwash pump are shared by all aerated biological filters (n, n≥3), the backwash fan is a volumetric fan, and the air output does not change with pressure changes. The back pressure exerted on the backwash fan is positively correlated with its operating current; each aerated biological filter is equipped with a separate air flush valve, a water flush valve, an inlet valve and a drain valve, and each control valve generally adopts a pneumatic valve. The status of each component in the backwash system and the control of each valve are signal collected and controlled by the programmable logic controller PLC. Usually, the valve collection signal includes: open position signal, close position signal and valve switch control signal. The backwash cycle is set by the human-machine interface (HMI) or the host computer, and the set time is usually 24, 36, or 48 hours. After setting the cycle time, click Start Timing to start the cycle timing. After the timing time is up, the backwash process starts. The specific implementation steps are as follows:

[0037] (1) Close the water inlet valve of the first biological aerated filter to stop water inflow. After the water inlet valve is fully opened, open the drain valve of the filter. If the water inlet valve or the drain valve is not fully opened, an alarm is sounded and the current filter is skipped to enter the backwash process of the second biological aerated filter. If the water inlet valve or the drain valve is fully opened, the backwash process of the biological aerated filter is carried out according to step (2);

[0038] (2) Open the air flush valve of the first biological aeration filter, and after it is fully opened, start the backwash fan. After the backwash fan is normally turned on, start the air flushing timer, and perform air flushing on the first biological aeration filter for T1 time. Then start the backwash pump, open the water flush valve of the first biological aeration filter, and perform air-water mixed flushing on the first biological aeration filter for T2 time. After the time is reached, use the backwash pump to perform water flushing on the first biological aeration filter for T3 time. At the same time, use the backwash fan to perform air flushing on the second biological aeration filter for T3 time (the second biological aeration filter is flushed with the first biological aeration filter before air flushing). The filter tanks are the same, and the water inlet valve is closed, the drain valve is opened, and the air flushing valve is opened); at this point, the backwashing of the first biological aeration filter is completed, and the air flushing stage of the second biological aeration filter is completed; the same as the above steps, the backwashing fan and the backwashing pump are used to perform air-water mixed flushing on the second biological aeration filter for T4 time, and then the backwashing pump is used to perform water flushing on the second biological aeration filter for T5 time, and the backwashing fan is used to perform air flushing on the third biological aeration filter for T5 time, and so on, until the backwashing of the nth biological aeration filter is completed, and the backwashing of the nth biological aeration filter is performed for T 2n After the air-water mixture flushing for a period of time, the backwash fan is turned off and the aeration biological filter is operated for T 2n+1 Turn off the backwash pump after flushing with water for a certain period of time;

[0039] Gas flushing time T1, T3, ...T 2n-1 Determine as follows: Calculate the deviation coefficient K. When 0<K<2, the gas flushing time is not adjusted based on the reference t time (the reference t time range is 4 to 8 minutes). When 2≤K<K max When the gas flushing time is extended based on the reference time t, the closer K is to K max , the longer the extension time; when 2≤K<4, the gas flushing time is extended by 20%-30% of the base t time on the basis of the base t time, and the value is rounded up; when 4≤K<5, the gas flushing time is extended by 60%-80% of the base t time on the basis of the base t time, and the value is rounded up; when 5≤K<K max When the gas flushing time is 100% longer than the reference t time, the gas flushing time is extended by 80%-100% of the reference t time, and the value is rounded up.

[0040] The deviation coefficient K is calculated according to the following formula:

[0041]

[0042] I v I is the average current value of the backwash fan at 1 / 2 of the reference time t during actual operation. v The maximum value is the rated current I N , when I v =I N When K=K max ;I b It is the average current value of the backwash fan when the biological aeration filter is running in a completely pollution-free state;

[0043] When K≤0, there is leakage in the corresponding air flushing pipeline, and an alarm is sent to the control system; when K≥K max , then the aerated biological filter is clogged or the filter material is severely compacted, and manual intervention is required.

[0044] Specifically, the backwash fan used in this embodiment has a rated power of 75KW and a rated current of 142A. When the current cycle is 1s, the current changes in a completely pollution-free state (backwashing in a clean water state) and in the actual operation process are as shown in the figure below: Figure 1 and Figure 2 As shown, specifically, Figure 2 The corresponding reference time is 4 minutes, and the calculated deviation coefficient is 2≤K<4. The air flushing time is extended by 26% based on the reference t time, and the corresponding air flushing time is 6 minutes. The current change diagram of the backwash fan in actual operation during the traditional backwashing process is as follows: Figure 3 As shown, the corresponding problem of backwash fan overcurrent protection tripping due to filter material blockage frequently occurs, and the fan current remains at a high level during normal backwashing.

[0045] The embodiments described above provide a detailed description of the technical solutions of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, supplements or similar substitutions made within the scope of the principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A backwash control method for multiple biological aeration filters, characterized in that: include: The backwashing system is used to sequentially perform backwashing on each biological aeration filter, including an air flushing stage, an air-water mixed flushing stage and a water flushing stage; The backwash system includes a backwash fan and a backwash pump. The number of biological aeration filters is n, n≥3; In the specific backwashing process, first start the backwash fan to perform air flushing on the first biological aeration filter for T1 time, then start the backwash pump, and perform air-water mixed flushing on the first biological aeration filter for T2 time, then use the backwash pump to perform water flushing on the first biological aeration filter for T3 time, and at the same time use the backwash fan to perform air flushing on the second biological aeration filter for T3 time. At this point, the backwashing of the first biological aeration filter is completed, and then use the backwash fan and backwash pump to perform air-water mixed flushing on the second biological aeration filter for T4 time, then use the backwash pump to perform water flushing on the second biological aeration filter for T5 time, and at the same time use the backwash fan to perform air flushing on the third biological aeration filter for T5 time, and so on, until the backwashing of the nth biological aeration filter is completed, and the backwashing of the nth biological aeration filter is performed for T 2n After the air-water mixture flushing for a period of time, the backwash fan is turned off and the aeration biological filter is operated for T 2n+1 Turn off the backwash pump after flushing with water for a certain period of time; Gas flushing time T1, T3, ...T 2n-1 Determine as follows: Calculate the deviation coefficient K. When 0<K<2, the gas flushing time is not adjusted based on the reference t time. When 2≤K<K max When the gas flushing time is extended based on the reference time t, the closer K is to K max , the longer the extension time; The deviation coefficient K is calculated according to the following formula: I v I is the average current value of the backwash fan at 1 / 2 of the reference time t during actual operation. v The maximum value is the rated current I N , when I v =I N When K=K max ;I b It is the average current value of the backwash fan when the biological aerated filter is running in a completely pollution-free state.

2. The backwash control method for multiple biological aeration filters according to claim 1, characterized in that: When 2≤K<4, the gas flushing time is extended by 20%-30% based on the reference t time; when 4≤K<5, the gas flushing time is extended by 60%-80% based on the reference t time; when 5≤K<K max When the gas flushing time is extended by 80%-100% based on the benchmark t time.

3. The backwash control method for multiple biological aeration filters according to claim 1, characterized in that: When K≤0, there is leakage in the corresponding air flushing pipeline, and an alarm is sent to the control system; when K≥K max , then the aerated biological filter is clogged or the filter material is severely compacted, and manual intervention is required.

4. The backwash control method for multiple biological aeration filters according to claim 1, characterized in that: The reference t time range is set to 4 to 8 minutes; the air-water mixed flushing time is T2, T4, ...T 2n Set it to 5 to 12 minutes.

5. The backwash control method for multiple biological aeration filters according to claim 1, characterized in that: The backwash system includes a backwash fan, a backwash pump, an air flush valve, a water flush valve, an inlet valve and a drain valve, wherein the backwash fan and backwash pump are shared by all aerated biological filters, and each aerated biological filter is equipped with a separate air flush valve, water flush valve, inlet valve and drain valve.

6. The backwash control method for multiple biological aeration filters according to claim 1, characterized in that: The backwash fan is a positive displacement fan, and the air output does not change with pressure changes. The back pressure on the backwash fan is positively correlated with its operating current.

7. The backwash control method for multiple biological aeration filters according to claim 5, characterized in that: The status of each component and the control of each valve in the backwash system are collected and controlled by the programmable logic controller (PLC).

8. Application of the backwash control method for multiple biological aeration filters linked together according to any one of claims 1 to 7 in the field of sewage treatment.

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