Method for monitoring growth and renewal of biological membrane in denitrification deep bed ceramsite filter

Abstract

The invention discloses a method for monitoring growth and renewal of a biological membrane in a denitrification deep bed ceramsite filter tank, and belongs to the technical field of water treatment. On the basis of the quality of inlet and outlet water of the biological filter, the growth degree of the biological membrane, the blockage degree of the filter and the blockage coefficient of a filter layer of the filter are calculated, so that the growth and renewal state of the biological membrane in the filter is relatively accurately judged; and the filter operation stages are divided based on the fitting slope of the filter layer blockage coefficient of the filter, so that the blockage degree of the filter can be more accurately judged, and a reasonable backwashing period is set according to the blockage degree. Meanwhile, the backwashing period is optimized based on the normal distribution of the effluent turbidity, so that the backwashing time can be accurately controlled, the backwashing is prevented from being too frequent or insufficient, the energy consumption is saved, and the operating efficiency of the filter tank is guaranteed.

Description

Technical Field

[0001] The present invention belongs to the technical field of water treatment, and more specifically, relates to a method for monitoring the growth and renewal of biofilms in a denitrifying deep-bed ceramsite filter. Background Art

[0002] With the acceleration of the industrialization and urbanization processes, the discharge of a large amount of sewage has become an environmental burden. In particular, the content of nitrogen oxides in sewage has been continuously rising, seriously polluting water bodies. This not only affects the balance of water bodies, but also poses a threat to the domestic and industrial water used by humans. To meet the increasingly strict sewage discharge standards, traditional sewage treatment processes are no longer sufficient to meet the requirements. Therefore, the denitrifying deep-bed filter, as an advanced sewage treatment technology, has emerged. This technology utilizes the biofilm formed on the packing in the filter to achieve denitrification under anoxic conditions, effectively removing nitrogen oxides in sewage, and simultaneously achieving the purpose of filtering and purifying water quality. Due to its high efficiency, environmental protection and other characteristics, it has been widely used in the fields of municipal sewage treatment, industrial wastewater treatment, etc. However, due to the difficulty in monitoring the growth of biofilms in denitrifying deep-bed filters, the filter cannot provide stable treatment performance. In addition, some filters cannot operate normally due to frequent blockages, which undoubtedly limits the application potential of denitrifying deep-bed filters.

[0003] The formation of biofilms involves a series of complex steps, such as cell deposition, cell adsorption / desorption, intercellular signal transduction, and the production, replication, growth, and secretion of extracellular polymeric substances, as well as the shedding of biofilms. For denitrifying deep-bed filters, during the start-up stage of the denitrifying deep-bed filter, the biofilm is naturally cultivated with nitrate and organic carbon. However, in the actual treatment process, due to the lack of monitoring and measurement of biofilms, it is very difficult to determine the operation timing, flushing intensity, and duration of filter backwashing. In this case, there may be situations of over-backwashing or untimely backwashing. In recent years, most of the research on denitrifying deep-bed filters has focused on treatment effects and optimizing the backwashing procedure, while research on optimizing denitrifying deep-bed filters based on biofilm growth and removal degree is relatively scarce. Thus, it can be seen that it is very necessary to invent a method for online monitoring the growth of biofilms in denitrifying deep-bed filters and to be able to perform real-time control and optimization for biofilm formation and growth, which will help to further play the role of denitrifying deep-bed filters in water treatment.

[0004] Upon retrieval, in the patent of CN106745719A, a method and device for repairing the microbial film in a denitrifying deep bed filter are disclosed. This application monitors the highest nitrate nitrogen concentration in the effluent after the air-water backwashing ends and compares it with the preset effluent control nitrate nitrogen concentration; adjusts the air backwashing intensity based on the comparison result, indirectly adjusting the air-water backwashing intensity; enabling the aged microbial film to fall off as much as possible and promoting the rapid growth of the new microbial film to repair the microbial film in the denitrifying deep bed filter. The essence of this application is achieved by monitoring the terminal nitrate nitrogen concentration and combining with the backwashing procedure; it is not an improvement made based on the growth situation of the organisms themselves. Therefore, there is still a need for a more diverse design in the industry to solve the problem that the existing denitrifying deep bed filter lacks the monitoring of the biofilm growth process, resulting in the filter being unable to provide stable treatment performance. Summary of the Invention

[0005] 1. Problems to be Solved

[0006] In view of at least some of the above problems existing in the prior art, the present invention proposes a method for monitoring the growth and renewal of biofilm in a denitrifying deep bed ceramsite filter, aiming to solve the problem that the growth of biofilm in the existing denitrifying deep bed filter is difficult to monitor, resulting in the filter being unable to provide stable treatment performance.

[0007] 2. Technical Solutions

[0008] To solve the above problems, the technical solutions adopted by the present invention are as follows:

[0009] A method for monitoring the growth and renewal of biofilm in a denitrifying deep bed ceramsite filter of the present invention includes the following processes.

[0010] S1. Monitor the water quality of the influent and effluent of the biological filter in real time.

[0011] S2. Calculate the biofilm growth degree, filter clogging degree, and filter filtration layer clogging coefficient based on the current influent and effluent water quality.

[0012] Biofilm growth degree:

[0013] Filter clogging degree:

[0014] Filter filtration layer clogging coefficient:

[0015] Among them, is the sludge yield coefficient, with a value of 0.74 gVSS / gNO 3 -N;

[0016] n is the data point of the online monitored nitrate concentration.

[0017] Δt is the online monitoring interval, in days;

[0018] Q n is the total influent flow rate, in m 3 / d;

[0019] V filter is the volume of filter media, in m 3 ;

[0020] (NO 3 -N) in 、(NO 3 -N) out are the influent and effluent nitrate concentrations respectively;

[0021] (Turb) in 、(Turb) out are the influent and effluent turbidity values respectively, in NTU;

[0022] S3. Perform a linear regression on the Yc point value in step S2 to obtain the fitting equation Y = kx + b, and divide the filter operation stage according to the slope k. When k < 0.2, it is the initial filtration stage; when 0.2 ≤ k < 0.4, it is the filtration stage; when 0.4 ≤ k < 0.6, it is the clogging stage; when k > 0.6, it is the damaged stage; and when the k value is greater than 0.4, backwashing starts.

[0023] Furthermore, perform a normal distribution fitting on the effluent turbidity during backwashing,

[0024] and determine the start time of backwashing as μ - 3σ and the end time as μ + 3σ according to the formula . Here, μ is the population mean; σ 2 is the population variance; σ is the population standard deviation; x is the actual turbidity value.

[0025] Furthermore, backwashing includes an air washing stage, an air-water combined washing stage, and a water washing stage. The washing time intervals for each stage are [μ - 3σ, μ - σ], [μ - σ, μ + σ], and [μ + σ, μ + 3σ] respectively.

[0026] Furthermore, use the Simpson's formula to calculate the turbidity-time curve during backwashing to determine the area of the turbidity peak, and this area is the actual amount of biofilm detachment S during backwashing,

[0027] where,

[0028] h = (b - a) / N; a is the start time of backwashing; b is the end time of backwashing; N is the number of data points and is an even number.

[0029] Further, according to the shedding ratio coefficients in different flushing stages, calculate the theoretical shedding amount A of the biofilm during the backwashing process,

[0030] A = B1 * G biofilm + B2 * G biofilm + B3 * G biofilm ,

[0031] where B1 is the shedding ratio coefficient in the air flushing stage, and its value range is 0.15 - 0.30;

[0032] B2 is the shedding ratio coefficient in the air-water combined flushing stage, and its value range is 0.30 - 0.50;

[0033] B3 is the shedding ratio coefficient in the water flushing stage, and its value range is 0.05 - 0.15;

[0034] By comparing the actual shedding amount S of the biofilm with the theoretical shedding amount A of the biofilm, determine whether the backwashing process meets the requirements. Specifically:

[0035] When the error range between the actual shedding amount S of the biofilm and the theoretical shedding amount A of the biofilm is within ±15%, it is determined that the result is normal;

[0036] When the actual shedding amount S of the biofilm is lower than the lower limit value, it indicates insufficient film shedding and low flow rate, and the flushing flow rate needs to be increased;

[0037] When the actual shedding amount S of the biofilm exceeds the upper limit value, it indicates excessive film shedding and high flow rate, and the flushing flow rate needs to be decreased.

[0038] Further, in step S1,

[0039] The nitrate and turbidity monitoring instruments installed at the bottom and top of the filter tank sample at each sampling time point, respectively representing the influent and effluent water quality of each index of the filter tank; after a period of detection time, the corresponding parameters are output; the influent flowmeter collects and obtains the water volume data;

[0040] The specific process is as follows: the nitrate concentration and turbidity monitoring instruments will sample at t 1 、t 2 ……t n and output the corresponding data D 1 、D 2 ……D n at the time points of T 1 、D 2 ……D n ; by collecting the real-time data Q 1 、Q 2 ……Q n of each influent pipeline flowmeter, obtain the total influent flow Q 总 = Q1 +Q 2 +……+Q n 。

[0041] Furthermore, when the filter is operating normally with water inlet and outlet, the water quality of each inlet and outlet of the filter needs to be accurately traced back to the monitoring values D of each instrument. The inlet and outlet times and the corresponding inlet and outlet water qualities are represented by t 进 / t 出 、D 进 / D 出 respectively;

[0042] The specific process is as follows: During the data acquisition process, t 进 / t 出 is compared with t 1 、t 2 ……t n at the sampling points of the bottom / top instrument of the filter. The value that meets the solution condition is selected. At this time, the water quality data corresponding to t 进 / t 出 is D 进 / D 出 . Among them, t 进 is solved according to the following formula:

[0043] If 0≤min[t - t 1 - min(|t - t 1 |, |t - t 2 |,......, |t - t n |), t - t 2 - min(|t - t 1 |, |t - t 2 |,......, |t - t n |),......, t - t n - min(|t - t 1 |, |t - t 2 |,......, |t - t n |)]≤0.1, then t 进 = t - min(|t - t 1 |, |t - t 2 |,......, |t - t n |), otherwise t 进 = t + min(|t - t 1 |, |t - t 2 |,......, |t - t n |); At this time, the water quality data D 进 corresponding to t 进 is the influent water quality;

[0044] t 出 = t进 +t', where t' is the residence time of the influent water in the filter; at this time, t 出 The corresponding water quality data D 出 is the effluent water quality.

[0045] Further, when the filter operates normally,

[0046] when a certain cell of the filter is backwashed,

[0047] Further, in step S3, the fitting equation R 2 ≥0.8 means that the fitting is completed.

[0048] Further, each time of fitting takes 100 - 200 continuous Yc point values for fitting, and the fitted Yc point values are no longer involved in the next fitting process.

[0049] 3. Beneficial effects

[0050] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0051] (1) For the method for monitoring the growth and renewal of biofilm in a denitrifying deep - bed ceramsite filter of the present invention, by monitoring the influent and effluent water quality of the biological filter, the biofilm growth degree G biofilm and the filter clogging degree C filter are calculated, and then the clogging coefficient Yc of the filter filter layer is obtained; and linear regression is performed using the Yc point values, and the operation stage of the filter is divided according to the slope k of the fitting equation, so as to relatively accurately judge the state of biofilm growth and renewal in the filter, thereby providing a reference basis for subsequent backwashing to ensure that the filter can provide stable treatment performance.

[0052] (2) For the method for monitoring the growth and renewal of biofilm in a denitrifying deep - bed ceramsite filter of the present invention, when the fitting k value of the Yc point value just exceeds 0.4, the backwashing operation starts. At this time, the filter has experienced a complete filtration cycle, avoiding frequent backwashing operations, which is beneficial to saving energy consumption; at the same time, since the filter layer has just entered the clogging stage, impurities have accumulated in the filter layer but have not been caked and solidified. At this time, when performing the backwashing operation, a large backwashing air - water intensity is not required, and the cleaning difficulty inside the filter layer is small and the cleaning efficiency is high.

[0053] (3) For the method for monitoring the growth and renewal of biofilm in a denitrifying deep - bed ceramsite filter of the present invention, a normal distribution fitting is performed on the effluent turbidity during backwashing, and the maximum effluent turbidity value, the time of air - water combined washing, and the water washing time during backwashing are deduced, so that it can be adjusted independently according to the operation of the filter, saving the energy consumption of the backwashing fan and backwashing water pump, ensuring the operation efficiency of the filter, and taking into account good washing effect and low energy consumption.

[0054] (4) A monitoring method for the growth and renewal of biofilm in a denitrifying deep-bed ceramsite filter of the present invention can feedback the backwashing effect by comparing the error range between the actual shedding amount S of the biofilm and the theoretical shedding amount A of the biofilm, for the reference of the staff to further ensure that the filter can provide stable treatment performance. Description of the Drawings

[0055] Figure 1 It is a schematic flow chart of a monitoring method for the growth and renewal of biofilm in a denitrifying deep-bed ceramsite filter of the present invention; Detailed Embodiments

[0056] To further understand the content of the present invention, the present invention will be described in detail with reference to the drawings.

[0057] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be understood as a limitation of the present invention. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0058] The present invention will be further described below with specific embodiments.

[0059] A monitoring method for the growth and renewal of biofilm in a denitrifying deep-bed ceramsite filter of this embodiment includes the following steps

[0060] S1. Monitor the water quality of the inlet and outlet of the biological filter in real time

[0061] The nitrate and turbidity monitoring instruments installed at the bottom and top of the filter take samples at each sampling time point, representing the water quality of the inlet and outlet of each index of the filter respectively; after a period of detection time, the corresponding parameters are output; the inlet flowmeter collects and obtains the water volume data. The specific process is as follows: the nitrate concentration and turbidity monitoring instruments will take samples at t 1 t 2 ……t n and after detection, output the corresponding data D 1 T 2 ……T n at the time points; by collecting the real-time data Q 1 Q 2 ……Q n ; through the real-time data Q 1 Q 2 ……Qn , obtain the total influent flow rate Q of the filter 总 = Q 1 + Q 2 + …… + Q n .

[0062] When the filter is operating normally with water inlet and outlet, the water quality of each inlet and outlet of the filter needs to be accurately traced back to the monitoring values D of each instrument. Among them, the inlet and outlet times and the corresponding inlet and outlet water qualities are represented by t 进 / t 出 , D 进 / D 出 respectively. The specific process is as follows: During the data collection process, t 进 / t 出 is compared with t 1 , t 2 ……t n through the sampling points of the bottom / top instruments of the filter. The value that meets the solution conditions is taken. At this time, the water quality data corresponding to t 进 / t 出 is D 进 / D 出 . Among them, t 进 is solved according to the following formula:

[0063] If 0 ≤ min[t - t 1 - min(|t - t 1 |, |t - t 2 |,......, |t - t n |), t - t 2 - min(|t - t 1 |, |t - t 2 |,......, |t - t n |),......, t - t n - min(|t - t 1 |, |t - t 2 |,......, |t - t n |)] ≤ 0.1, then t 进 = t - min(|t - t 1 |, |t - t 2 |,......, |t - t n |), otherwise t 进 = t + min(|t - t 1 |, |t - t 2 |,......, |t - t n |); At this time, the water quality data D 进 corresponding to t 进 is the influent water quality;

[0064] t出 = t 进 + t', where t' is the residence time of the influent water in the filter; at this time, t 出 corresponding water quality data D 出 is the effluent water quality.

[0065] Among them, when the filter operates normally,

[0066] when a certain cell of the filter is backwashed,

[0067] S2. Calculate the biofilm growth rate, filter clogging degree, and filter layer clogging coefficient of the filter according to the current influent and effluent water qualities. Biofilm growth rate:

[0068] Filter clogging degree:

[0069] Filter layer clogging coefficient:

[0070] Among them, is the sludge production rate coefficient, with a value of 0.74 gVSS / gNO 3 -N;

[0071] n is the data point of on-line monitoring;

[0072] Δt is the on-line monitoring interval, in days;

[0073] Q n is the total influent flow rate, m 3 / d;

[0074] V filter is the volume of filter media, m 3 ;

[0075] (NO 3 -N) in and (NO 3 -N) out are the influent and effluent nitrate concentrations respectively;

[0076] (Turb) in and (Turb) out are the influent and effluent turbidity values, in NTU respectively.

[0077] S3. Perform a linear regression on the Yc point value in step S2 to obtain the fitting equation Y = kx + b. When the fitting equation R 2 ≥ 0.8, the fitting is completed. And divide the filter operation stage according to the slope k. When k < 0.2, it is the initial filtration stage; when 0.2 ≤ k < 0.4, it is the filtration stage; when 0.4 ≤ k < 0.6, it is the clogging stage; when k > 0.6, it is the damaged stage.

[0078] The specific fitting process is as follows: Each time for fitting, 100 - 200 Yc point values are taken for fitting, and the Yc point values that have been fitted are no longer involved in the next fitting process. The reason for taking 100 - 200 Yc point values for fitting is, on the one hand, to ensure the accuracy of the fitting result as much as possible, and on the other hand, to ensure dynamicity and real-time performance. Fewer data points may cause the fitting to not reflect the actual changes in the filter state, while too many data points may cause the details in different stages of the filter to be smoothed out and unable to accurately capture the stage characteristics. At the same time, the Yc point values that have been fitted are no longer involved in the next fitting process. On the one hand, it is to avoid repeated calculations. If the fitted Yc point values are involved in subsequent fittings again, it may lead to the repeated influence of the same data on the fitting result and reduce the sensitivity of the model to new data changes. On the other hand, it is to ensure segmentation. Each fitting only reflects the characteristic changes in the current stage. After excluding the fitted data, the changes in subsequent stages can be captured more accurately, and the states in different stages can be prevented from being confused.

[0079] According to the above-fitted k value and the filter operation stages divided according to the k value, the backwashing cycle of the filter is set between the filtration section and the clogging section. Preferably, when the fitted k value just exceeds 0.4, the backwashing operation is started. At this time, the filter has experienced a complete filtration cycle, avoiding the frequent operation of the backwashing operation, which is beneficial to saving energy consumption; at the same time, since the filter layer has just entered the clogging stage, impurities have accumulated inside the filter layer but have not been caked and solidified. At this time, when performing the backwashing operation, a large backwashing air-water intensity is not required, and the cleaning difficulty inside the filter layer is small and the cleaning efficiency is high.

[0080] In this embodiment, the backwashing includes an air washing stage, an air-water combined washing stage, and a water washing stage. Among them, in the air washing stage, the filter layer is mainly disturbed by an instantaneous impact air flow, and the shear force formed by the mutual collision and friction of the filter materials is used to peel off the sludge and biofilm attached to the surface of the filter materials. The main purpose of air washing is to make the filter layer in a loose state, which is beneficial to the subsequent air-water combined washing.

[0081] The air-water combined washing is the most critical step in filter cleaning. It combines the power of gas and water, and through a strong scouring effect, effectively removes impurities and particulate matters on the filter materials. During the air-water combined washing process, air and water act on the filter together, and the filter layer is kept in a fluidized state through a certain air scouring intensity. At the same time, with a relatively low water scouring intensity, the sludge shed in the air washing stage is effectively lifted to the surface of the filter layer and further washed out.

[0082] Water washing is the last step in filter cleaning. Usually, the filter materials are washed with clean water to remove residual sludge and impurities. The water washing intensity is relatively small because its main purpose is to wash the residues on the surface of the filter materials clean, and to avoid causing too much scouring force on the filter materials and resulting in filter material loss.

[0083] According to the backwashing intensity distribution of the above backwashing procedure, the effluent turbidity starts from the beginning of backwashing and rises until the effluent turbidity starts to increase during the air washing stage. During the combined air-water washing stage, the effluent turbidity further increases and reaches the peak. Subsequently, the water washing cleans the impurities and the aged biofilm, and the effluent turbidity gradually decreases and tends to be stable. Therefore, the variation trend of the effluent turbidity during the entire backwashing cycle conforms to the normal distribution.

[0084] Furthermore, perform a normal distribution fitting on the effluent turbidity during backwashing, and according to the formula the maximum effluent turbidity value, the time of combined air-water washing, and the water washing time during backwashing can be calculated. Different from traditional backwashing, this can be adjusted independently according to the operation conditions of the filter, saving the energy consumption of the backwashing fan and the backwashing water pump, and ensuring the operation efficiency of the filter. Among them, μ: population mean; σ 2 : population variance; σ: population standard deviation; x: actual turbidity value.

[0085] Specifically: Perform a normal distribution fitting on the effluent turbidity data collected during backwashing. When the effluent turbidity reaches μ, it is the maximum point of the backwashing turbidity, and the time of the maximum turbidity point can be indexed from this. At the same time, the time difference indexed by the turbidity data corresponding to μ±σ is the time of combined air-water washing; μ - 3σ and μ + 3σ are respectively recorded as the starting point and the ending point of the backwashing cycle, then the time difference indexed by the turbidity data corresponding to [μ - 3σ, μ - σ] is the air washing time, and the time difference indexed by the turbidity data corresponding to [μ + σ, μ + 3σ] is the water washing time.

[0086] At the same time, combined with the variation trend of turbidity during backwashing, the actual shedding amount S of the biofilm during the entire backwashing period can be represented by calculating the turbidity peak area. Specifically, take the turbidity data as the ordinate and the time data as the abscissa, plot the turbidity-time curve, and use the Simpson's formula to calculate the area of the turbidity peak,

[0087] that is where h = (b - a) / N; a is the start time of backwashing; b is the end time of backwashing; y is the turbidity value corresponding to N; N is the number of data points and is an even number.

[0088] Furthermore, according to the shedding proportion coefficients in different washing stages, calculate the theoretical shedding amount A of the biofilm during backwashing as A = B1*G biofilm + B2*G biofilm + B3*G biofilm, where B1 is the shedding ratio coefficient in the air washing stage, with a value range of 0.15 - 0.30; B2 is the shedding ratio coefficient in the air-water combined stage, with a value range of 0.30 - 0.50; B3 is the shedding ratio coefficient in the water washing stage, with a value range of 0.05 - 0.15. By comparing the actual shedding amount S of the biofilm with the theoretical shedding amount A of the biofilm, it is judged whether the backwashing process meets the requirements. When the error range between the actual shedding amount S of the biofilm and the theoretical shedding amount A of the biofilm is within ±15%, the result is judged to be normal. At this time, the air flow velocity in the air washing stage is controlled at 12 - 13.5 m / s; in the air-water combined washing stage, the air flow velocity is 12 - 13.5 m / s and the water flow velocity is 10 - 13.5 m / h; the water flow velocity in the water washing stage is 5 - 6.5 m / h.

[0089] When the actual shedding amount S of the biofilm is lower than the lower limit value (0.85A), it indicates insufficient film shedding and low flow velocity, and the washing flow velocity needs to be increased. Specifically, A: increase the air flow velocity to 13.5 - 15 m / s in the air washing stage; increase the water flow velocity to 13.5 - 15 m / h in the air-water combined washing stage; slightly adjust the flow velocity to 6.5 - 8 m / h in the water washing stage to avoid insufficient scouring.

[0090] When the actual shedding amount S of the biofilm exceeds the upper limit value (1.15A), it indicates excessive film shedding and high flow velocity, and the washing flow velocity needs to be decreased. Specifically, in the air washing stage, decrease the air flow velocity to 10 - 12 m / s; in the air-water combined washing stage, decrease the water flow velocity to 8 - 12 m / h; in the water washing stage: further reduce the flow velocity to 3 - 5 m / h. At the same time, it should be noted that the above flow velocity increment is controlled within 5% - 10% to avoid excessive adjustment at one time and impact on the system.

[0091] A monitoring method for the growth and renewal of biofilm in a denitrifying deep-bed ceramsite filter of the present invention provides basic data for the operation control of the filter by detecting the changes in water quality parameters at the inlet and outlet of the filter in real time. Based on the data collection, through the turbidity numerical inversion technology, key parameters such as the growth degree of biofilm in the filter, the clogging degree of the filter, and the clogging coefficient of the filter layer can be accurately evaluated. These parameters not only reflect the growth and renewal state of the biofilm but also are directly related to the operation efficiency and effluent water quality of the filter. By monitoring the changes in these parameters in real time, problems in the operation of the filter can be detected in a timely manner, such as clogging caused by too thick biofilm and a decrease in treatment efficiency caused by microbial population imbalance. At the same time, the present invention also divides the operation stage of the filter according to the slope k value of the fitting equation and optimizes the backwashing cycle based on the normal distribution of the effluent turbidity. By dividing the operation stage of the filter, the clogging degree of the filter can be judged more accurately, and a reasonable backwashing cycle can be set accordingly. And optimizing the backwashing cycle based on the normal distribution of the effluent turbidity can achieve precise control of the backwashing time, avoid overly frequent or insufficient backwashing, thereby saving energy consumption and ensuring the operation efficiency of the filter.

[0092] This embodiment also provides a biofilm growth and renewal system in a denitrifying deep-bed ceramsite filter, which includes a denitrifying deep-bed filter main body, a carbon source dosing system, a backwashing system, and a control system.

[0093] Among them, nitrate, turbidity monitoring instruments and pressure sensors are arranged at both the bottom and the top of the denitrifying deep-bed filter main body. The carbon source dosing system can dose sodium acetate or methanol. The backwashing system is mainly used to remove impurities and dirt in the filter layer, restore the filtering ability of the filter layer, and extend the service life of the filter layer. The control system consists of a detector, a computer, a sensor interface, and a control unit. The control unit is composed of a programmable logic controller (PLC) and a process control system (PCS). The detector is mainly responsible for detecting or measuring specific physical quantities and transmitting these analog signals or digital signals to the control unit. The sensor interface can convert the output signal of the detector into a format that the control unit can understand. As a bridge between the detector and the control unit, the sensor interface ensures the accurate transmission of signals and realizes functions such as signal amplification, filtering, and conversion to adapt to the output characteristics of different detectors and the processing requirements of the control unit. The computer is used to implement functions such as data processing, algorithm implementation, and user interface display. The connection between the computer and the control unit (especially the PLC) is usually realized through a communication interface (such as Ethernet, serial communication, etc.) to exchange data and instructions. At the same time, inside the control unit, the PLC and the PCS are connected to each other through an internal bus or a communication interface. The PLC is responsible for logic control and sequence control, while the PCS focuses on the monitoring and control of continuous process variables. It should be noted that each component in this embodiment can adopt existing technologies, and its main purpose is to process the monitored data and visualize it on the user interface.

[0094] The above schematically describes the present invention and its implementation manners. This description is not restrictive. What is shown in the drawings is only one of the implementation manners of the present invention, and the actual structure is not limited thereto. Therefore, if those of ordinary skill in the art are inspired by it and design similar structural manners and embodiments without creative efforts without departing from the purpose of the present invention, they shall fall within the protection scope of the present invention.

Claims

1. A method for monitoring biofilm growth and renewal in a denitrification deep bed ceramsite filter, characterized in that: Including the following process, S1. Real-time monitoring of water quality of inlet and outlet water of biological filter; S2. According to the current inlet and outlet water quality, calculate the biofilm growth degree, filter pool blockage degree and filter pool filtration layer blockage coefficient. Biofilm growth: Filter blockage degree: Filter layer clogging coefficient: Among them, Y NO3-N is the sludge yield coefficient, and its value is 0.74gVSS / gNO3-N; n is the data point of online monitoring; Δt is the online monitoring interval, day; Q n is the total inlet flow, m 3 / d; V filter is the filter volume, m 3 ; (NO3-N) in 、(NO3-N) out are the inlet and outlet nitrate concentrations, respectively; (Turb) in , (Turb) out are the inlet and outlet turbidity values, NTU; S3. Perform linear regression on the Yc point value in step S2 to obtain the fitting equation Y=kx+b, and divide the filter operation stage according to the slope k, k<0.2, which is the primary filtration stage; 0.2≤k<0.4 is the filtration stage; 0.4≤k<0.6 is the clogging stage; k>0.6 is the damaged stage; and when the k value is greater than 0.4, start backwashing.

2. The method for monitoring biofilm growth and renewal in a denitrification deep bed ceramsite filter according to claim 1, characterized in that: The effluent turbidity during backwashing was fitted with a normal distribution, and according to the formula The starting time of backwashing is determined as μ-3σ and the ending time is μ+3σ; where μ is the overall mean; σ 2 : population variance; σ: population standard deviation; x: actual turbidity value.

3. The method for monitoring biofilm growth and renewal in a denitrification deep bed ceramsite filter according to claim 2, characterized in that: Backwashing includes an air washing stage, an air-water combined washing stage and a water washing stage. The washing time intervals of each stage are [μ-3σ, μ-σ], [μ-σ, μ+σ] and [μ+σ, μ+3σ] respectively.

4. The method for monitoring biofilm growth and renewal in a denitrification deep bed ceramsite filter according to claim 3, characterized in that: The Simpson formula was used to integrate the turbidity-time curve during the backwashing process to calculate the area of ​​the turbidity peak, which is the actual amount of biofilm shedding S during the backwashing process. in, h=(ba) / N; a is the backwash start time; b is the backwash end time; N is the number of data points and is an even number.

5. The method for monitoring biofilm growth and renewal in a denitrification deep bed ceramsite filter according to claim 4, characterized in that: According to the shedding ratio coefficients at different flushing stages, the theoretical shedding amount A of the biofilm during backwashing is calculated. A=B1*G biofilm +B2*G biofilm +B3*G biofilm , Among them, B1 is the shedding ratio coefficient in the air washing stage, with a value range of 0.15-0.30; B2 is the shedding ratio coefficient in the gas-water combined stage, ranging from 0.30 to 0.50; B3 is the shedding ratio coefficient in the water washing stage, ranging from 0.05 to 0.15; By comparing the actual shedding amount S of the biofilm with the theoretical shedding amount A of the biofilm, it is judged whether the backwashing process meets the requirements, specifically: The result is considered normal if the error range between the actual biofilm shedding amount S and the theoretical biofilm shedding amount A is within ±15%; When the actual biofilm shedding amount S is lower than the lower limit, it means that the biofilm is not removed enough and the flow rate is too low, and the flushing flow rate needs to be increased; When the actual biofilm shedding amount S exceeds the upper limit, it means that the biofilm is excessively removed and the flow rate is too high, and the flushing flow rate needs to be reduced.

6. A method for monitoring biofilm growth and renewal in a denitrification deep bed ceramsite filter according to any one of claims 1 to 5, characterized in that: In step S1, The nitrate and turbidity monitoring instruments installed at the bottom and top of the filter tank take samples at various sampling time points, which represent the inlet and outlet water quality of the filter tank respectively; after a period of detection time, the corresponding parameters are output; the inlet flow meter collects and obtains water volume data; The specific process is as follows: the nitrate concentration and turbidity monitoring instruments will be at t1, t2...t n Sampling is performed and after testing, at T1, T2, ..., T n Output corresponding data D1, D2...D at time point n ; By collecting the real-time data Q1, Q2...Q of each water inlet pipeline flow meter n , get the total water flow Q of the filter 总 =Q1+Q2+……+Q n .

7. The method for monitoring biofilm growth and renewal in a denitrification deep bed ceramsite filter according to claim 6, characterized in that: When the filter tank is inflowing and outflowing normally, the water quality of each inflow and outflow of the filter tank needs to be accurately traced back to the monitoring value D of each instrument, where the inflow and outflow time and the corresponding inflow and outflow water quality are expressed as t 进 / t 出 , D 进 / D 出 express; The specific process is as follows: During the data collection process, t 进 / t 出 With t1, t2, ... t n Compare the sampling points of the instrument at the bottom / top of the filter pool at all times and take the value that meets the solution condition. At this time, t 进 / t 出 The corresponding water quality data is D 进 / D 出 , where t 进 Solve according to the following formula: If 0≤min[t-t1-min(|t-t1|,|t-t2|,...,|tt n |), t-t2-min(|t-t1|, |t-t2|, ..., |tt n |),......,tt n -min(|t-t1|, |t-t2|, ..., |tt n |)]≤0.1, then t 进 =t-min(|t-t1|, |t-t2|,...,|tt n |), otherwise t 进 =t+min(|t-t1|, |t-t2|,...,|tt n |); At this time, t 进 Corresponding water quality data D 进 It is the inlet water quality; t 出 =t 进 +t', t' is the residence time of the influent in the filter tank; at this time, t 出 Corresponding water quality data D 出 That is the outlet water quality.

8. The method for monitoring biofilm growth and renewal in a denitrification deep bed ceramsite filter according to claim 7, characterized in that: When the filter is operating normally, When a cell of the filter is backwashed, 9. The method for monitoring biofilm growth and renewal in a denitrification deep bed ceramsite filter according to claim 1, characterized in that: In step S3, the fitting equation R 2 The fitting is complete when ≥0.

8.

10. The method for monitoring biofilm growth and renewal in a denitrification deep bed ceramsite filter according to claim 8, characterized in that: Each time fitting, 100-200 Yc point values ​​are taken for fitting, and the fitted Yc point values ​​will no longer participate in the next fitting process.

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