Backwash control method for linkage of multiple biological aerated filters and application of backwash control method

Abstract

The invention discloses a multi-biological aerated filter linkage backwashing control method and application thereof, and belongs to the technical field of sewage treatment.According to the backwashing control method, original independent sequential backwashing of multiple biological aerated filters is improved into linkage backwashing of two biological aerated filters, the backwashing efficiency is greatly improved, and the backwashing time is shortened. The problems that the backwashing process is too long when the multi-aeration biological filter is cleaned, and a backwashing fan and a backwashing pump have idle time and are frequently started and stopped can be solved, and the pollution and blockage degree of a filter material in the flushed filter can be pre-judged according to the current value characteristic of the backwashing fan in the first half time of the gas flushing stage. According to the backwashing control method, the gas washing stage time and the water washing stage time are dynamically adjusted, the backwashing effect can be guaranteed, incomplete backwashing or excessive backwashing is avoided, and the backwashing control method has wide application prospects in the field of sewage treatment.

Description

Technical Field

[0001] The present invention belongs to the technical field of sewage treatment, and particularly relates to an anti-flushing control method for multi-aeration biological filters in linkage and its application. Background Art

[0002] The aerated biological filter mainly removes impurities such as suspended solids, ammonia nitrogen, and organic matter in sewage based on the combination of biodegradation and physical filtration. After the aerated biological filter operates for a period of time, a large amount of intercepted suspended solids, microbial metabolites, and organic pollutants will gradually accumulate in the pores of the filter media, resulting in a decrease in the permeability of the filter media layer and a significant increase in the resistance when sewage passes through. At this time, through the backwashing operation, the pollutants accumulated in the filter media layer can be effectively removed, and the filtration performance of the filter media can be restored, thereby ensuring the efficient operation of the filter and the stable compliance of the effluent quality.

[0003] In the prior art, the backwashing of the aerated biological filter is triggered by a periodic cycle set by a set time. The backwashing process includes three stages: air washing, air-water mixed washing, and water washing. Each stage is carried out according to a separately set time, and the set value of the time is usually given according to experience. Under the condition of a certain backwashing intensity, the backwashing time has a significant impact on the backwashing effect. When there are more suspended solids in the influent of the filter or the filtration time is too long, the suspended solids intercepted by the filter media and the shed biofilm will accumulate and adhere to the filter media and the filter plate. When the backwashing time is fixed, it is difficult to ensure that the suspended solids and the shed biofilm are completely removed each time during washing. Incomplete washing will lead to excessive accumulation of suspended solids and biofilm. After reaching a certain level, the filter media will become compacted. The compaction of the filter media will cause the fan to trip due to overcurrent during the air washing stage, and local loosening or even fracture of the filter plate will occur during the air-water mixed washing stage.

[0004] Chinese patent documents with publication numbers CN111672172A and CN102063115A determine the backwashing time based on the influent and effluent water quality of the filter. The measurement indexes of the water quality include turbidity, etc. Although this method adopts a real-time control strategy and can flexibly determine the backwashing process time according to the removal situation of impurities during the backwashing process, the strategy of sequentially performing separate air washing, separate air-water mixed washing, or separate water washing is not applicable to the backwashing process of multiple series-connected aerated biological filters. The backwashing of multi-aeration biological filters is generally carried out in a fixed order. After one filter is washed, the next filter is washed until the last filter is washed. This takes a long time, and the backwashing fan and the backwashing water pump will have idle time, affecting the backwashing efficiency. At the same time, the backwashing fan and the backwashing pump will start and stop frequently within a backwashing cycle. Frequent starting and stopping will cause the insulation of the motor to age rapidly, shorten the service life of the motor, and increase the failure rate of the equipment.

[0005] Therefore, it is necessary to develop a backwashing control method with high flushing efficiency, good flushing effect and applicable to multi-aeration biological filters. Summary of the Invention

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

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

[0008] A backwashing control method for multi-aeration biological filter linkage includes performing backwashing on each aeration biological filter in turn by using a backwashing system, the backwashing including an air flushing stage, an air-water mixing flushing stage and a water flushing stage; the backwashing system includes a backwashing blower and a backwashing pump, and the number of aeration biological filters is denoted as n, where n≥3;

[0009] In the specific backwashing process, first start the backwashing blower to perform air flushing on the first aeration biological filter for a time of T 1 , then start the backwashing pump to perform air-water mixing flushing on the first aeration biological filter for a time of T 2 , and then use the backwashing pump to perform water flushing on the first aeration biological filter for a time of T 3 while using the backwashing blower to perform air flushing on the second aeration biological filter for a time of T 3 . At this point, the backwashing of the first aeration biological filter is completed. Then, use the backwashing blower and the backwashing pump to perform air-water mixing flushing on the second aeration biological filter for a time of T 4 , and then use the backwashing pump to perform water flushing on the second aeration biological filter for a time of T 5 while using the backwashing blower to perform air flushing on the third aeration biological filter for a time of T 5 . And so on, until the backwashing of the nth aeration biological filter is completed. After performing air-water mixing flushing on the nth aeration biological filter for a time of T 2n , turn off the backwashing blower, and after performing water flushing on the nth aeration biological filter for a time of T 2n+1 , turn off the backwashing pump;

[0010] The air flushing time T 1 , T 3 ,... T 2n-1 is determined according to the following method: calculate the deviation coefficient K. When 0<K<2, the air flushing time is not adjusted on the basis of the reference t time (the reference t time is determined according to experience and is specifically related to the influent water quality, filter media and degree of pollution during use. Optionally, the reference t time range is set to 4 - 8 minutes). When 2≤K<K max , the air flushing time is extended on the basis of the reference t time, and the closer K is to Kmax , the longer the extended time;

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

[0012]

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

[0014] The method of the present invention can solve the problems that the backwash process is too long during the cleaning of multiple biological aerated filters (the too long backwash process will further exacerbate the problems of filter clogging and filter media caking), the backwash fan and the backwash pump have idle time and frequent start and stop. The backwash control method provided by the present invention is improved from the original separate sequential backwash of multiple biological aerated filters to the linked backwash of two biological aerated filters, which greatly improves the backwash efficiency, and judges the degree of pollution and blockage of the filter media in the filter being washed according to the current value characteristics of the backwash fan in the first half of the air backwash stage, and constructs a deviation coefficient and a time adjustment rule to dynamically adjust the time of the air backwash stage and the water backwash stage, which can ensure the backwash effect and avoid incomplete backwash or over-washing.

[0015] Preferably, when 2 ≤ K < 4, the air backwash time is extended by 20% - 30% based on the reference t time (calculated based on the reference t time), and the specific value is rounded up (for example, if the extended specific time exceeds 1.0 min, it is 1.1 min, then the actual operation is to round up to 1.2 min, the same below);

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

[0017] When 5 ≤ K < K max , the air backwash time is extended by 80% - 100% based on the reference t time (calculated based on the reference t time), and the specific value is rounded up.

[0018] The above control parameters are summarized by the inventor based on a large number of experiments, which helps to improve the backwash effect and avoid incomplete backwash or over-washing.

[0019] Further, when K ≤ 0, there is air leakage in the corresponding air flushing pipeline, and an alarm is sent to the control system; when K ≥ K max , there is a blockage or serious hardening of the filter media in the biological aerated filter, and manual intervention is required for treatment.

[0020] The air-water mixing flushing time is also determined according to empirical values, which is specifically related to the influent water quality, filter media, and degree of contamination during use. Optionally, the air-water mixing flushing T 2 , T 4 , …T 2n is set to 5 - 12 minutes.

[0021] Further, the backwashing system includes a backwashing fan, a backwashing pump, an air flushing valve, a water flushing valve, an inlet valve, and a drain valve. Among them, the backwashing fan and the backwashing pump are shared by all biological aerated filters, and each biological aerated filter is equipped with a separate air flushing valve, water flushing valve, inlet valve, and drain valve.

[0022] Preferably, the backwashing fan is a positive displacement fan, and the air output does not change with the pressure. The back pressure received by the backwashing fan is positively correlated with its operating current.

[0023] Specifically, under the condition of a certain air volume, the back pressure received by the positive displacement fan is positively correlated with the operating current of the fan. When the back pressure (i.e., the pressure received at the outlet of the fan during air flushing) is greater, the current of the fan is higher. When the back pressure exceeds the rated pressure of the fan, the operating current of the fan will exceed its rated current, and the fan will trip due to overcurrent protection. Similarly, in the case of serious blockage of the filter media in the filter or the presence of filter media hardening, the current at 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. The degree of blockage or hardening of the filter media within the rated pressure range is positively correlated with the current of the fan during the air flushing stage. According to the operating current of the fan during the first half of the air flushing stage, the degree of contamination of the filter media can be judged, real-time monitoring can be carried out, the downtime can be reduced, additional detection components such as sensors can be avoided, the filtration efficiency can be improved, and equipment failures can be prevented, etc.

[0024] Further, the states of the components in the backwashing system and the control of each valve are signal-collected and controlled by a programmable logic controller PLC.

[0025] The present invention also provides an application of the backwashing control method for the linkage of multiple biological aerated filters in the field of sewage treatment.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

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

[0028] (2) The method of the present invention optimizes and adjusts the backwashing process of multiple aerated biological filters, improving the original backwashing of multiple aerated biological filters in sequence to the linkage backwashing of two aerated biological filters, thereby greatly improving the backwashing efficiency, eliminating the idle waiting time of the backwashing equipment, and solving the problem of frequent start and stop of the backwashing fan and backwashing pump of the aerated biological filter.

[0029] (3) The method of the present invention predicts the degree of contamination and blockage of the filter material in the filter tank being flushed according to the current value characteristics of the backwash fan in the first half of the air flushing stage, and constructs a deviation coefficient and a time adjustment rule to dynamically adjust the air flushing stage time and the water flushing stage time, thereby ensuring the backwashing effect, avoiding incomplete backwashing or excessive backwashing, preventing the filter material from accumulating retained matter, and extending the service life of the filter material. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[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 purpose, features and advantages of the present invention more obvious and easy to understand, the following is a detailed description through specific embodiments. In the following description, many specific details are set forth in order to fully understand the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed below. The technical features in each embodiment 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 usually carried out under conventional conditions or under conditions recommended by the manufacturer. The contents not described in detail in this specification belong to the prior art known to professionals in the field.

[0035] Example 1

[0036] In this embodiment, the backwashing system includes a backwashing blower, a backwashing pump, an air flushing valve, a water flushing valve, an inlet valve, and a drain valve. Among them, the backwashing blower and the backwashing pump are shared by all biological aerated filters (n, n≥3). The backwashing blower is a positive displacement blower, and the air output does not change with the pressure. The back pressure received by the backwashing blower is positively correlated with its operating current. Each biological aerated filter is equipped with a separate air flushing valve, water flushing valve, inlet valve, and drain valve, and each control valve generally uses a pneumatic valve. The states of the components in the backwashing system and the control of each valve are collected and controlled by a programmable logic controller (PLC). Usually, the collected signals of the valves include: fully open signal, fully closed signal, and valve opening and closing control signal. The backwashing cycle is set by a human-machine interface (HMI) or a host computer, and the set time is usually 24, 36, or 48 hours. After setting the cycle time and clicking start timing, the cycle timing starts. When the timing time arrives, the backwashing process begins. The specific implementation steps are as follows:

[0037] (1) Close the inlet valve of the first biological aerated filter to stop water inlet. After it is fully open, open the drain valve of this filter. If the inlet valve or the drain valve is not fully open, an alarm is given and the current filter is skipped to enter the backwashing process of the second biological aerated filter. If the inlet valve and the drain valve are fully open, proceed with the backwashing process of this biological aerated filter according to step (2);

[0038] (2) Open the air flushing valve of the first biological aerated filter. After it is fully open, start the backwashing blower. After the backwashing blower is normally opened, start air flushing timing, and conduct air flushing of the first biological aerated filter for T 1 time. Then start the backwashing pump and open the water flushing valve of the first biological aerated filter to conduct air-water mixed flushing of the first biological aerated filter for T 2 time. After the time is up, use the backwashing pump to conduct water flushing of the first biological aerated filter for T 3 time while using the backwashing blower to conduct air flushing of the second biological aerated filter for T 3 time (before the air flushing of the second biological aerated filter, the same operations as those of the first biological aerated filter are carried out, that is, closing the inlet valve, opening the drain valve, and opening the air flushing valve). At this point, the backwashing of the first biological aerated filter is completed, and the air flushing stage of the second biological aerated filter ends. In the same way as the above steps, then use the backwashing blower and the backwashing pump to conduct air-water mixed flushing of the second biological aerated filter for T 4 time, and then use the backwashing pump to conduct water flushing of the second biological aerated filter for T 5 time while using the backwashing blower to conduct air flushing of the third biological aerated filter for T 5 time, and so on, until the backwashing of the nth biological aerated filter is completed. During the backwashing of the nth biological aerated filter, conduct T2n After the air-water mixed flushing for T time, turn off the backwashing fan, and perform T in the nth biological aerated filter 2n+1 After the water flushing for T time, turn off the backwashing pump;

[0039] Air flushing time T 1 , T 3 , …T 2n-1 It is determined by the following method: Calculate the deviation coefficient K. When 0 < K < 2, the air flushing time remains unchanged based on the reference t time (the range of the reference t time is 4 - 8 minutes). When 2 ≤ K < K max , the air flushing time is extended based on the reference t time. The closer K is to K max , the longer the extension time. When 2 ≤ K < 4, the air flushing time is extended by 20% - 30% of the reference t time based on the reference t time, and the value is rounded up. When 4 ≤ K < 5, the air flushing time is extended by 60% - 80% of the reference t time based on the reference t time, and the value is rounded up. When 5 ≤ K < K max , the air flushing time is extended by 80% - 100% of the reference t time based on 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 is the average current value of the backwashing fan at 1 / 2 reference t time during actual operation. The maximum value of I v is the rated current I N . When I v = I N , K = K max ; I b is the average current value of the backwashing fan when operating in a completely pollution-free state in the biological aerated filter;

[0043] When K ≤ 0, there is air leakage in the corresponding air flushing pipeline, and an alarm is sent to the control system. When K ≥ K max , then there is a blockage or serious filter media caking in the biological aerated filter, and manual intervention is required.

[0044] Specifically, the rated power of the backwashing fan used in this embodiment is 75KW, and the rated current is 142A. When the current sampling period is 1s, the current change diagrams in the completely pollution-free state (backwashing in the clear water state) and during actual operation are as shown in Figure 1 and Figure 2 shown. Specifically, Figure 2The corresponding reference time is 4 minutes, and the calculated deviation coefficient is 2 ≤ K < 4. Based on the reference time t, it is extended by 26%, and the corresponding air flushing time is 6 minutes. The current change diagram of the backwashing fan during the actual operation in the traditional backwashing process is as Figure 3 shown. There is a problem that the overcurrent protection of the backwashing fan frequently trips due to filter material blockage, and at the same time, the fan current remains at a relatively high level during normal backwashing.

[0045] The above-described embodiments have detailed 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 used to limit the present invention. Any modification, supplement, or substitution in a similar manner within the principle scope of the present invention shall be included within the protection scope of the present invention.

Claims

1. A backwash control method for multiple biological aerated filters, characterized in that: include: Using the backwashing system, each aerated biological filter is backwashed in sequence, 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 aerated biological filters is n, where n≥3; In the specific backwashing process, first start the backwashing fan to perform air flushing on the first aerated biological filter for T1 time, then start the backwashing pump to perform air-water mixed flushing on the first aerated biological filter for T2 time, then use the backwashing pump to perform water flushing on the first aerated biological filter for T3 time, and use the backwashing fan to perform air flushing on the second aerated biological filter for T3 time. At this point, the backwashing of the first aerated biological filter is completed, and then the backwashing fan and the backwashing pump are used to perform air-water mixed flushing on the second aerated biological filter for T4 time, and then the backwashing pump is used to perform water flushing on the second aerated biological filter for T5 time, and the backwashing fan is used to perform air flushing on the third aerated biological filter for T5 time, and so on, until the backwashing of the nth aerated biological filter is completed, and the backwashing of the nth aerated biological 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 aerated biological filter is aerated for T 2n+1 After flushing with water for a certain period of time, turn off the backwash pump; 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 on the basis of the reference t time, the closer K is to K max , the longer the extension time; The coefficient of deviation 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 aerated biological filter is running in a completely pollution-free state.

2. The backwash control method for multiple aerated biological 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 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 the 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 aerated biological filters according to claim 1, characterized in that: The backwash fan is a positive displacement fan, and the air output does not change with the pressure. 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 aerated biological filters linked together according to any one of claims 1 to 7 in the field of sewage treatment.

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