Method for removing and recycling nitrogen and phosphorus based on meat processing wastewater

Abstract

The application provides a method for removing and recycling nitrogen and phosphorus based on meat processing wastewater, and relates to the technical field of industrial wastewater treatment, comprising the following steps: collecting and preprocessing the total phosphorus, ammonia nitrogen, organic matter concentration and pH data of batch wastewater; calculating the wastewater comprehensive treatment difficulty index based on the total phosphorus, ammonia nitrogen and organic matter concentration, calculating the initial magnesium salt addition amount based on the total phosphorus and pH, calculating the initial alkali addition amount based on the ammonia nitrogen and pH, adding the magnesium salt and alkali according to the addition amount to obtain a reaction mixture; continuously collecting the total phosphorus and ammonia nitrogen concentration of the reaction mixture and smoothing filtering, calculating the nitrogen and phosphorus removal synchronism index, and determining whether the cooperation state of total phosphorus removal and ammonia nitrogen removal is normal; calculating the reaction endpoint comprehensive maturity based on the total phosphorus and ammonia nitrogen concentration, determining the reaction endpoint judgment threshold in combination with the wastewater comprehensive treatment difficulty index, and determining whether the reaction is completed after comparison. The application effectively improves the nitrogen and phosphorus removal efficiency and operation stability through on-demand addition and endpoint self-adaptive judgment.

Description

Technical Field

[0001] This invention relates to the field of industrial wastewater treatment technology, specifically to a method for nitrogen and phosphorus removal and recovery based on meat processing wastewater. Background Technology

[0002] The meat processing industry is a vital part of the national economy. The wastewater generated during its production process is characterized by high organic matter concentration, significant total phosphorus and ammonia nitrogen content, and large fluctuations in water quality. Direct discharge without effective treatment will lead to eutrophication of receiving water bodies, causing serious environmental problems such as excessive algal growth and a sharp decline in dissolved oxygen. Chemical precipitation is one of the mainstream processes for nitrogen and phosphorus removal from this type of wastewater. It involves adding magnesium salts and alkaline solutions to the wastewater to induce the formation of magnesium ammonium phosphate precipitate, thereby achieving the simultaneous recovery of total phosphorus and ammonia nitrogen. The treatment effect of this method is highly dependent on precise control of the dosage of reagents, the reaction pH, and the timing of the reaction endpoint. Deviations in any step can directly affect the precipitation efficiency and the effluent compliance rate.

[0003] In the prior art, patent CN120736737A discloses a method and apparatus for treating aquaculture wastewater based on the synergistic guano petrification of red mud and boron mud. This technology includes: firstly, adjusting the pH of the solid-liquid separated aquaculture wastewater to 5.5-7.0; adding boron mud (1-5% of the wastewater volume with a particle size ≤200 mesh) and stirring for 10-60 minutes; utilizing the weakly acidic environment to promote the hydrolysis of boron mud and release active Mg2+, simultaneously precipitating amorphous silicic acid / silica gel. Subsequently, a red mud-boron mud compound agent is added, maintaining the pH at 8.5-9.5 for 20-60 minutes, allowing NH4+, PO43-, and Mg2+ to combine and form struvite; the compound agent continuously raises the pH to 9.0-10.0 to create an optimal crystallization window, where free Ca2+ from the red mud promotes sedimentation and forms calcium-doped struvite, and hematite induces Fe3+ and PO43- to form FePO4 heterogeneous coprecipitation nuclei. Finally, a triple-stable encapsulation structure is constructed by aging at 50-70℃ for 2-4 hours: the inner layer is an Fe-OP chemically bonded layer, the middle layer forms a 50-200nm amorphous silicone coating layer, and the outer layer establishes a Ca-O-Si bridging network to delay the nitrogen and phosphorus release cycle.

[0004] However, in the aforementioned existing technologies, the initial dosage of magnesium salt and alkaline solution is set based on a fixed ratio, without dynamic calculation based on the actual total phosphorus, ammonia nitrogen concentration, and pH of the wastewater, resulting in the reagent dosage deviating from the actual needs; the reaction endpoint is determined using a fixed threshold, which cannot be adaptively adjusted according to changes in the overall pollution load of the wastewater, leading to insufficient treatment of high-load wastewater or overtreatment of low-load wastewater; there is a lack of real-time monitoring methods for the synergistic removal of total phosphorus and ammonia nitrogen during the reaction process, making it impossible to intervene in a timely manner when the removal rates of the two are unbalanced, affecting the stability of the reaction; the endpoint determination relies only on a single concentration index, without combining it with the trend of removal rate changes for comprehensive judgment, which is prone to misjudgment due to local sampling errors or rate decay in the later stages of the reaction, affecting the treatment effect and operational economy.

[0005] The information disclosed in the background section is only intended to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0006] The purpose of this invention is to provide a nitrogen and phosphorus removal and recovery method based on meat processing wastewater, thereby solving the problems mentioned in the background section. This invention achieves on-demand addition by calculating the initial addition amounts of magnesium salts and alkaline solution based on total phosphorus and pH, and ammonia nitrogen and pH, respectively; it calculates the comprehensive treatment difficulty index of the wastewater based on the initial pollution load and dynamically adjusts the reaction endpoint determination threshold to adapt to different water quality conditions; it monitors the synergistic state of nitrogen and phosphorus removal in real time during the reaction process and triggers control commands, and determines the endpoint by combining the comprehensive maturity of the reaction endpoint and its rate of change. This invention achieves refined intelligent control of the entire reaction process, improving treatment efficiency and stability, ensuring effluent meets standards, and reducing operating costs.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A method for nitrogen and phosphorus removal and recovery from meat processing wastewater:

[0009] S1: Collect initial water quality parameters of batches of meat processing wastewater at a preset sampling frequency within a preset time window. The initial water quality parameters include total phosphorus concentration data, ammonia nitrogen concentration data, organic matter concentration data, and pH data, which respectively constitute initial total phosphorus concentration sequences, initial ammonia nitrogen concentration sequences, initial organic matter concentration sequences, and initial pH sequences. Preprocess the initial total phosphorus concentration sequences, initial ammonia nitrogen concentration sequences, initial organic matter concentration sequences, and initial pH sequences.

[0010] S2: Based on the initial concentration sequences of total phosphorus, ammonia nitrogen, and organic matter after pretreatment, calculate the difficulty index of comprehensive wastewater treatment. Calculate the initial amount of magnesium salt to be added based on the initial concentration sequences of total phosphorus and pH after pretreatment, and calculate the initial amount of alkali solution to be added based on the initial concentration sequences of ammonia nitrogen and pH after pretreatment. Add magnesium salt and alkali solution to the batch of meat processing wastewater according to the calculated initial amounts of magnesium salt and alkali solution to obtain a reaction mixture.

[0011] S3: Continuously collect total phosphorus concentration data and ammonia nitrogen concentration data of the reaction mixture at the preset sampling frequency, and perform smoothing filtering on the collected total phosphorus concentration data and ammonia nitrogen concentration data. Calculate the nitrogen and phosphorus removal synchronicity index based on the smoothed total phosphorus concentration data and ammonia nitrogen concentration data, and determine whether the synergistic state of total phosphorus removal and ammonia nitrogen removal in the reaction mixture is normal based on the nitrogen and phosphorus removal synchronicity index.

[0012] S4: Based on the total phosphorus concentration data and ammonia nitrogen concentration data after smoothing and filtering, calculate the overall maturity of the reaction endpoint. Based on the wastewater comprehensive treatment difficulty index, determine the reaction endpoint judgment threshold. Compare the overall maturity of the reaction endpoint with the reaction endpoint judgment threshold, and determine whether the reaction process is completed based on the comparison result.

[0013] Furthermore, the method for preprocessing the initial concentration sequences of total phosphorus, ammonia nitrogen, organic matter, and pH is as follows:

[0014] Outliers in the initial concentration sequences of total phosphorus, ammonia nitrogen, organic matter, and pH were identified using statistical methods. These outliers were then removed, and missing values ​​in the initial concentration sequences of total phosphorus, ammonia nitrogen, organic matter, and pH were filled using linear interpolation.

[0015] Furthermore, the formula used to calculate the difficulty index of comprehensive wastewater treatment is as follows:

[0016]

[0017] in, The difficulty index for comprehensive wastewater treatment;

[0018] This represents the arithmetic mean of the initial total phosphorus concentration sequence after pretreatment.

[0019] The preset total phosphorus baseline concentration;

[0020] This represents the arithmetic mean of the initial ammonia nitrogen concentration sequence after pretreatment.

[0021] The preset ammonia nitrogen baseline concentration;

[0022] This represents the arithmetic mean of the initial concentration sequences of organic matter after pretreatment.

[0023] This is the preset organic matter baseline concentration;

[0024] , , These are the preset weighting coefficients for total phosphorus, ammonia nitrogen, and organic matter, respectively, and they satisfy the following conditions: , >0, >0, >0.

[0025] Furthermore, the formula used to calculate the initial amount of magnesium salt added is as follows:

[0026]

[0027] in, This refers to the initial amount of magnesium salt added.

[0028] The preset magnesium salt reference addition amount;

[0029] A correction factor is added to the magnesium salt determined based on the pH-magnesium salt correction mapping relationship established by laboratory calibration. The value of the magnesium salt correction factor is determined based on the arithmetic mean of the pretreated initial pH sequence.

[0030] The total phosphorus response index is a preset value, and 0.5 ≤ ≤1.5.

[0031] Furthermore, the formula used to calculate the initial amount of alkali solution added is as follows:

[0032]

[0033] in, This is the initial amount of alkali solution added;

[0034] The amount of alkali solution added is the preset standard amount;

[0035] A correction factor is added to the alkali solution determined based on the pH-alkali solution correction mapping relationship established by laboratory calibration. The value of the alkali solution correction factor is determined based on the arithmetic mean of the initial pH sequence after pretreatment.

[0036] The preset ammonia nitrogen response index is given, and 0.5 ≤ ≤1.5.

[0037] Furthermore, the method for smoothing and filtering the collected total phosphorus concentration data and ammonia nitrogen concentration data is as follows:

[0038] Using the sampling time corresponding to the preset sampling frequency as the reference time point, an equally spaced reference time axis is formed. The total phosphorus concentration data and ammonia nitrogen concentration data of the collected reaction mixture are matched with the reference time axis according to their original timestamps to form the total phosphorus concentration time series and the ammonia nitrogen concentration time series of the reaction mixture, respectively. Median filtering is performed on the total phosphorus concentration time series and the ammonia nitrogen concentration time series of the reaction mixture using a single-sided sliding window of length N, where N is a preset odd number and N≥3.

[0039] Furthermore, the formula used to calculate the nitrogen and phosphorus removal synchronicity index is as follows:

[0040]

[0041] in, for Nitrogen and phosphorus removal synchronicity index at time;

[0042] for The total phosphorus removal rate of the reaction mixture at time t, the total phosphorus removal rate The calculation formula is: ,in, After smoothing filtering Total phosphorus concentration data of the reaction mixture at any given time. After smoothing filtering Total phosphorus concentration data of the reaction mixture at any given time. The time interval corresponding to the preset sampling frequency;

[0043] for The ammonia nitrogen removal rate of the reaction mixture at time t, wherein the ammonia nitrogen removal rate The calculation formula is: ,in, After smoothing filtering ammonia nitrogen concentration data of the reaction mixture at any given time. After smoothing filtering Data on ammonia nitrogen concentration in the reaction mixture at any given time.

[0044] Furthermore, the determination logic for whether the synergistic state of total phosphorus removal and ammonia nitrogen removal in the reaction mixture is normal is as follows:

[0045] when < And lasting longer than When the reaction mixture is found to be in an abnormal state of synergy between total phosphorus removal and ammonia nitrogen removal, a dosing control command is triggered.

[0046] when ≥ ,or < However, the duration did not exceed At that time, the synergistic state of total phosphorus removal and ammonia nitrogen removal in the reaction mixture was determined to be normal;

[0047] in, The preset synchronicity index threshold is 0 < <1;

[0048] The preset duration threshold, and >0.

[0049] Furthermore, the formula used to calculate the overall maturity at the reaction endpoint is as follows:

[0050]

[0051] in, for The overall maturity level at the endpoint of the response at any given moment;

[0052] The preset total phosphorus concentration threshold;

[0053] The preset ammonia nitrogen concentration threshold;

[0054] , These are the preset weighting coefficients for total phosphorus compliance and ammonia nitrogen compliance, respectively. , >0, >0;

[0055] The value is set to a positive number to prevent the denominator from being zero.

[0056] The method for determining the reaction endpoint threshold is as follows:

[0057] when < When the reaction endpoint determination threshold is = ;

[0058] when ≥ When the reaction endpoint determination threshold is ;

[0059] in, The threshold for determining the reaction endpoint;

[0060] The preset threshold for determining the reaction endpoint;

[0061] The upper limit of the preset reaction endpoint determination threshold is met, and the following conditions are satisfied: < <1;

[0062] This is a preset processing difficulty threshold;

[0063] The adjustment coefficient is the preset endpoint determination threshold, and >0.

[0064] Furthermore, the logic for determining whether the reaction process is complete based on the comparison results is as follows:

[0065] when ≥ And 0≤ < When the reaction process is complete, it is determined that the reaction process is finished.

[0066] when < If the reaction process is determined to be incomplete, the current reaction process will be maintained.

[0067] when ≥ ,but ≥ or If the value is less than 0, the reaction process is considered incomplete, and the current reaction process continues.

[0068] in, for The overall maturity level at the endpoint of the response at any given moment;

[0069] This is the preset threshold for the rate of change in maturity.

[0070] Compared with the prior art, the beneficial effects of the present invention are:

[0071] This invention calculates the initial magnesium salt addition amount based on the initial total phosphorus concentration and pH, and the initial alkali addition amount based on the initial ammonia nitrogen concentration and pH, enabling on-demand dosing of reagents. This avoids reagent waste or insufficient dosing due to water quality fluctuations, reduces operating costs, and improves reaction efficiency. Based on the initial concentration sequences of total phosphorus, ammonia nitrogen, and organic matter after pretreatment, a comprehensive wastewater treatment difficulty index is calculated. The threshold for determining the reaction endpoint is adjusted differentially based on the comparison between this index and a preset treatment difficulty threshold, thus adapting to the actual treatment needs of water with different pollution loads. During the reaction, total phosphorus and ammonia nitrogen concentration data are continuously collected. Through smoothing filtering and the calculation of the nitrogen and phosphorus removal synchronicity index, the synergistic state of total phosphorus and ammonia nitrogen removal can be monitored in real time, triggering dosing control commands in case of anomalies, thereby improving the stability and controllability of the reaction process. Furthermore, the comprehensive maturity of the reaction endpoint is calculated, and the endpoint is determined by comparing its rate of change with a preset rate of change threshold, ensuring that the reaction terminates in a timely manner when the expected removal effect is achieved. This improves the precision of process control and operational efficiency while ensuring stable effluent compliance. Attached Figure Description

[0072] Figure 1 This is a schematic diagram of the overall process for a nitrogen and phosphorus removal and recovery method based on meat processing wastewater. Detailed Implementation

[0073] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0074] It should be noted that, unless otherwise defined, the technical or scientific terms used in this invention should have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0075] Example:

[0076] Please see Figure 1 The present invention provides a technical solution:

[0077] A method for nitrogen and phosphorus removal and recovery from meat processing wastewater:

[0078] S1: Within a preset time window, initial water quality parameters of a batch of meat processing wastewater are collected at a preset sampling frequency. The initial water quality parameters include total phosphorus concentration data, ammonia nitrogen concentration data, organic matter concentration data, and pH data. These parameters can comprehensively reflect the water pollution load characteristics of the wastewater and constitute initial total phosphorus concentration sequences, initial ammonia nitrogen concentration sequences, initial organic matter concentration sequences, and initial pH sequences, respectively. The preset sampling frequency is based on the measurement cycle of the instrument with the longest measurement cycle among the monitoring instruments corresponding to each water quality parameter, and is used as a unified sampling frequency to ensure that the four initial concentration sequences can be synchronized in time. The duration of the preset time window is determined according to the preset sampling frequency, and its value should ensure that the number of data points in each sequence of the initial total phosphorus concentration sequence, initial ammonia nitrogen concentration sequence, initial organic matter concentration sequence, and initial pH sequence is not less than 5. The initial total phosphorus concentration sequence, initial ammonia nitrogen concentration sequence, initial organic matter concentration sequence, and initial pH sequence are preprocessed.

[0079] The method for preprocessing the initial concentration sequences of total phosphorus, ammonia nitrogen, organic matter, and pH is as follows:

[0080] Statistical methods were used to identify outliers in the initial concentration sequences of total phosphorus, ammonia nitrogen, organic matter, and pH. Specifically, based on the statistical distribution characteristics of each sequence, the arithmetic mean and standard deviation of each sequence were calculated. The mean ± 3 times the standard deviation was taken as the normal range. Data points falling outside this range were identified as outliers and deleted from the initial concentration sequences of total phosphorus, ammonia nitrogen, organic matter, and pH. This eliminated interference data introduced by factors such as sampling fluctuations or sudden changes in water quality, ensuring the reliability of subsequent calculations. For missing values ​​in the sequences caused by outlier removal or other reasons, linear interpolation was used to fill in the missing values ​​in the initial concentration sequences of total phosphorus, ammonia nitrogen, organic matter, and pH. That is, based on the effective data points adjacent to the missing value, the value at the missing point was estimated along the time axis according to a linear change relationship, so that the sequence restored the complete temporal continuity and maintained the equally spaced distribution characteristics of the data under the original sampling frequency, thereby ensuring the integrity and consistency of each sequence in subsequent calculations.

[0081] S2: Based on the initial concentration sequences of total phosphorus, ammonia nitrogen, and organic matter after pretreatment, a comprehensive wastewater treatment difficulty index is calculated. This index quantifies the overall treatment resistance that the current batch of wastewater needs to overcome in the subsequent nitrogen and phosphorus removal process by comprehensively considering the initial concentration levels of the three pollutants and their deviation from the benchmark value. The higher the index value, the heavier the wastewater pollution load and the greater the treatment difficulty. The initial magnesium salt addition is calculated based on the initial total phosphorus concentration sequence and the initial pH sequence after pretreatment, and the initial alkali solution addition is calculated based on the initial ammonia nitrogen concentration sequence and the initial pH sequence after pretreatment. The initial addition amounts of magnesium salt and alkaline solution are as special agents for environmental pollution treatment. Their types and purity have been screened and confirmed by the laboratory. Magnesium salt and alkaline solution are added simultaneously to batches of meat processing wastewater according to the obtained initial addition amounts of magnesium salt and alkaline solution, so that the two are fully dispersed in the wastewater and come into contact with pollutants, thereby forming a uniform reaction mixture. This creates the initial conditions for the subsequent simultaneous precipitation reaction of nitrogen and phosphorus. Compared with the traditional physicochemical treatment process using high-efficiency activated carbon adsorption, this invention directly recovers nitrogen and phosphorus through chemical precipitation, avoiding adsorption saturation and subsequent hazardous waste disposal problems, and has the advantages of both environmental benefits and resource recovery.

[0082] The formula used to calculate the difficulty index of comprehensive wastewater treatment is as follows:

[0083]

[0084] in, The difficulty index for comprehensive wastewater treatment;

[0085] This represents the arithmetic mean of the initial total phosphorus concentration sequence after pretreatment.

[0086] The preset total phosphorus baseline concentration;

[0087] This represents the arithmetic mean of the initial ammonia nitrogen concentration sequence after pretreatment.

[0088] The preset ammonia nitrogen baseline concentration;

[0089] This represents the arithmetic mean of the initial concentration sequences of organic matter after pretreatment.

[0090] This is the preset organic matter baseline concentration;

[0091] , , These are the preset weighting coefficients for total phosphorus, ammonia nitrogen, and organic matter, respectively, and they satisfy the following conditions: , >0, >0, >0;

[0092] Ratios of each item , , This ratio characterizes the deviation of the initial concentrations of the three main pollutants—total phosphorus, ammonia nitrogen, and organic matter—from their respective preset baseline concentrations. The larger the ratio, the higher the enrichment level of the corresponding pollutant in the wastewater, the greater the absolute amount that needs to be removed in the subsequent chemical precipitation reaction, and the more significant the load impact on the treatment system.

[0093] The formula used to calculate the initial amount of magnesium salt added is as follows:

[0094]

[0095] in, This refers to the initial amount of magnesium salt added.

[0096] The preset magnesium salt reference addition amount;

[0097] The magnesium salt addition correction factor is determined based on the pH-magnesium salt correction mapping relationship established by laboratory calibration. The value of the magnesium salt addition correction factor is determined based on the arithmetic mean of the initial pH sequence after pretreatment. Specifically, under laboratory conditions, several groups of simulated wastewater with similar water quality to meat processing wastewater and a gradient pH distribution are prepared. Batch sedimentation tests are conducted to determine the minimum amount of magnesium salt required to achieve the target phosphorus removal rate at each pH value. The magnesium salt addition amount corresponding to the minimum solubility product of magnesium ammonium phosphate and the strongest precipitation driving force in the pH range of 8.5~9.0 is used as the benchmark. The proportionality coefficient of the addition amount at other pH values ​​relative to the benchmark value is calculated, thereby establishing the pH-magnesium salt correction mapping relationship. A one-to-one correspondence between them;

[0098] The total phosphorus response index is a preset value, and 0.5 ≤ ≤1.5;

[0099] The higher the value, the higher the total phosphorus load in the wastewater, and the greater the theoretical magnesium ion consumption required to form magnesium ammonium phosphate precipitate. Therefore, the amount of magnesium salt added needs to be increased accordingly. Conversely, the lower the value, the greater the total phosphorus load in the wastewater. The smaller the value, the less magnesium ions are theoretically consumed, therefore the amount of magnesium salt added needs to be reduced accordingly.

[0100] The formula used to calculate the initial amount of alkali solution added is as follows:

[0101]

[0102] in, This refers to the initial amount of alkali solution added.

[0103] The amount of alkali solution added is the preset standard amount;

[0104] The alkali addition correction factor is determined based on the pH-alkali correction mapping relationship established by laboratory calibration. The value of the alkali addition correction factor is determined based on the arithmetic mean of the initial pH sequence after pretreatment. Specifically, during the laboratory calibration stage, several groups of simulated wastewater with similar water quality characteristics to meat processing wastewater and a gradient pH distribution (covering the actual pH fluctuation range of meat processing wastewater) are prepared. The minimum amount of alkali added required to adjust the reaction system to the target precipitation reaction initiation pH at each pH value is determined by batch titration tests. The amount added when the pH is in the neutral range (pH=7.0~7.5) is used as the benchmark (let this benchmark condition be used). ), calculate the proportionality coefficient of the amount of alkali added relative to the baseline value at each of the other pH values, and establish the pH value and The correspondence between them;

[0105] The preset ammonia nitrogen response index is given, and 0.5 ≤ ≤1.5;

[0106] This ratio represents the degree of deviation of the current ammonia nitrogen concentration in the wastewater from the preset baseline concentration. The larger the ratio, the higher the ammonia nitrogen load in the wastewater, and the greater the theoretical amount of alkali solution required to generate magnesium ammonium phosphate precipitate. This is because high concentrations of ammonia nitrogen require a higher pH environment to drive the reaction equilibrium toward precipitation. Therefore, the initial amount of alkali solution added needs to be increased accordingly. Conversely, the smaller the ratio, the lower the ammonia nitrogen load, and the less alkali solution is required.

[0107] S3: Continuously collect total phosphorus concentration data and ammonia nitrogen concentration data of the reaction mixture at the preset sampling frequency, and perform smoothing filtering on the collected total phosphorus concentration data and ammonia nitrogen concentration data. Calculate the nitrogen and phosphorus removal synchronicity index based on the smoothed total phosphorus concentration data and ammonia nitrogen concentration data. This nitrogen and phosphorus removal synchronicity index quantifies the relative closeness between the total phosphorus removal rate and the ammonia nitrogen removal rate within the same time period, intuitively reflecting the synergistic removal effect of the two in the reaction process. The closer the value is to 1, the more consistent the removal pace of the two is. Based on the nitrogen and phosphorus removal synchronicity index, determine whether the synergistic state of total phosphorus removal and ammonia nitrogen removal in the reaction mixture is normal.

[0108] The method for smoothing and filtering the collected total phosphorus concentration data and ammonia nitrogen concentration data is as follows:

[0109] Using the sampling times corresponding to the preset sampling frequency as reference time points, these time points are arranged sequentially along the reaction process to form a series of equally spaced time nodes, thus constructing a reference time axis. The total phosphorus concentration data and ammonia nitrogen concentration data of the collected reaction mixture are matched with the reference time axis according to their respective original timestamps. Data points whose original timestamps fall on the reference nodes are directly assigned to the corresponding time. Data points whose original timestamps deviate from the reference nodes are assigned to the nearest reference time according to the principle of temporal proximity, thereby unifying the time coordinates of the entire sequence and constructing a reverse time axis. The time series of total phosphorus concentration and ammonia nitrogen concentration in the reaction mixture are used. Median filtering is performed on the time series of total phosphorus concentration and ammonia nitrogen concentration in the reaction mixture using a single-sided sliding window of length N. The window ends at the current sampling time on the reference time axis and covers N consecutive data points in the time back direction. After each filtering calculation, the window slides one sampling step in the positive direction of the time axis and replaces the concentration value at the current sampling time with the median of the N data points in the window. Here, N is a preset odd number and N≥3.

[0110] The formula used to calculate the nitrogen and phosphorus removal synchronicity index is as follows:

[0111]

[0112] in, for Nitrogen and phosphorus removal synchronicity index at time;

[0113] for The total phosphorus removal rate of the reaction mixture at time t, the total phosphorus removal rate The calculation formula is: ,in, After smoothing filtering Total phosphorus concentration data of the reaction mixture at any given time. After smoothing filtering Total phosphorus concentration data of the reaction mixture at any given time. The time interval corresponding to the preset sampling frequency;

[0114] for The ammonia nitrogen removal rate of the reaction mixture at time t, wherein the ammonia nitrogen removal rate The calculation formula is: ,in, After smoothing filtering ammonia nitrogen concentration data of the reaction mixture at any given time. After smoothing filtering Ammonia nitrogen concentration data of the reaction mixture at any given time;

[0115] when and When they are equal, This indicates that the total phosphorus removal rate and the ammonia nitrogen removal rate are completely synchronized, the precipitation processes of the two target pollutants in the reaction system are coordinated and consistent, and the formation reaction of magnesium ammonium phosphate is in an ideal stoichiometric matching state; when and The greater the difference, A value close to 0 indicates that the removal rate of one pollutant is significantly lagging behind or ahead of the other, indicating a clear imbalance in the reaction process.

[0116] The determination logic for whether the synergistic state of total phosphorus removal and ammonia nitrogen removal in the reaction mixture is normal is as follows:

[0117] when < And lasting longer than This indicates that the imbalance between the removal rates of total phosphorus and ammonia nitrogen is not caused by occasional instantaneous fluctuations or measurement noise, but by a systematic deviation that persists over a certain time scale. That is, the removal rate of one pollutant is lagging behind or ahead of that of the other pollutant for a long time, resulting in a significant asynchrony in the precipitation process of the two target components in the reaction system. If left unchecked, this may lead to problems such as exceeding the standard of a single indicator in the effluent or a decrease in the purity of the precipitate. It is determined that the synergistic state of total phosphorus removal and ammonia nitrogen removal in the reaction mixture is abnormal, triggering a chemical dosing control command. The reaction conditions are adjusted by adding magnesium salts or alkaline solutions, etc., in order to rebalance the removal rates of the two and bring the precipitation reaction back to a coordinated and synchronous track.

[0118] when ≥ This indicates that the removal rate ratio of the two is always within an acceptable deviation range, and the reaction process is coordinated and orderly, or < However, the duration did not exceed When the deviation is within a short period, it indicates that the transient disturbance is acceptable during the reaction process. The system has the potential to restore equilibrium in the short term by virtue of its own reaction buffering capacity, without the need for human intervention. When either of the above two conditions is met, it is determined that the synergistic state of total phosphorus removal and ammonia nitrogen removal in the reaction mixture is normal. The current dosing scheme and reaction conditions remain unchanged, and routine monitoring of the reaction process can continue. This ensures the system's response sensitivity while effectively avoiding operational redundancy and reagent waste caused by frequent triggering of control actions due to occasional fluctuations.

[0119] in, The preset synchronicity index threshold is 0 < <1;

[0120] The preset duration threshold, and >0.

[0121] S4: Based on the total phosphorus concentration data and ammonia nitrogen concentration data after smoothing and filtering, calculate the overall maturity of the reaction endpoint. This overall maturity of the reaction endpoint is used to quantify the degree to which the reaction system as a whole approaches the endpoint state at the current moment. Based on the wastewater comprehensive treatment difficulty index, determine the reaction endpoint judgment threshold, compare the overall maturity of the reaction endpoint with the reaction endpoint judgment threshold, and determine whether the reaction process is completed based on the comparison result.

[0122] The formula used to calculate the overall maturity at the reaction endpoint is as follows:

[0123]

[0124] in, for The overall maturity level at the endpoint of the response at any given moment;

[0125] The preset total phosphorus concentration threshold;

[0126] The preset ammonia nitrogen concentration threshold;

[0127] , These are the preset weighting coefficients for total phosphorus compliance and ammonia nitrogen compliance, respectively. , >0, >0;

[0128] The value is set to a positive number to prevent the denominator from being zero.

[0129] when Much larger hour, Approaching 0 indicates that the current total phosphorus residue concentration is still far from the acceptable threshold, and this pollutant contributes very little to maturity; as the reaction progresses, As the concentration continues to decrease and approaches the target concentration, The ratio gradually increases and approaches 1, indicating that total phosphorus removal has become sufficient;

[0130] The method for determining the reaction endpoint threshold is as follows:

[0131] when < At this point, it indicates that the overall pollution load of the current batch of wastewater is within the conventional treatable range, the concentrations of total phosphorus, ammonia nitrogen, and organic matter are relatively balanced, the precipitation kinetics of the reaction process are relatively stable, and there are few interfering factors. The threshold for determining the reaction endpoint at this point is... = ;

[0132] when ≥ This indicates a high overall pollution load in the wastewater, significantly increasing the difficulty of treatment. The calculation is normalized based on preset total phosphorus and ammonia nitrogen concentration thresholds. Therefore, the absolute compliance concentration standards for different initial water qualities are unified, and the threshold for determining the reaction endpoint is consistent. Typically, a value less than 1 is set to allow for reaction termination when the concentration is close to but has not yet fully reached the target value, thus balancing operational economy. However, for highly challenging wastewater, high concentrations of organic matter and other coexisting ions in the water can interfere with the magnesium ammonium phosphate precipitation reaction, leading to a decrease in removal rate and precipitation stability in the later stages of the reaction. If a lower baseline threshold is used, the reaction will be terminated when the concentration margin is relatively wide. At this point, the reaction often has not yet crossed the kinetic transition zone, and the precipitate formed after intervention is stopped is prone to reverse dissolution and secondary release of phosphorus, increasing the risk of effluent exceeding standards. Therefore, it is necessary to adjust the threshold based on the relative extent to which the difficulty index exceeds the threshold. The threshold for determining the reaction endpoint is raised, i.e. The forced reaction is pushed to a more stringent residual concentration level, leaving sufficient treatment margin for high-difficulty operating conditions and ensuring that the effluent consistently meets the standards;

[0133] in, The threshold for determining the reaction endpoint;

[0134] The preset threshold for determining the reaction endpoint;

[0135] The upper limit of the preset reaction endpoint determination threshold is met, and the following conditions are satisfied: < <1;

[0136] This is a preset processing difficulty threshold;

[0137] The adjustment coefficient is the preset endpoint determination threshold, and >0.

[0138] The logic for determining whether the reaction process is complete based on the comparison results is as follows:

[0139] when ≥ And 0≤ < When the reaction system has basically reached equilibrium, all pollution indicators have approached or reached the expected removal level, and the removal process no longer proceeds at a significant rate, the reaction process is considered complete. Thus, this batch of wastewater has completed the entire process of nitrogen and phosphorus removal and recovery. This method is a highly efficient chemical precipitation technology in the field of wastewater treatment and reuse, which can simultaneously achieve water purification and nutrient resource utilization.

[0140] when < This indicates that the residual concentrations of total phosphorus and ammonia nitrogen in the reaction system are still higher than the target requirements, the overall removal effect has not yet met the effluent standards, the reaction is still in progress, the reaction process is determined to be incomplete, and the current reaction process should be maintained.

[0141] when ≥ ,but ≥ or When the value is less than 0, it indicates that although the current maturity value meets the standard, the reaction is still proceeding rapidly and the system is not yet stable. If it is forcibly terminated at this time, it may lead to a rebound or failure to meet the standard in the subsequent water quality. Alternatively, when the maturity change rate is negative, it means that the maturity has decreased compared to the previous moment. This usually indicates that there is an abnormal deviation in the measurement fluctuation or reaction conditions, and the system is in an unsteady state. In both cases, it is determined that the reaction process is not completed. The current reaction process should be maintained until the maturity stabilizes in the low-speed growth range before a final judgment is made, thereby ensuring the reliability of the reaction endpoint and the long-term stability of the effluent water quality.

[0142] in, for The overall maturity level at the endpoint of the response at any given moment;

[0143] This is the preset threshold for the rate of change in maturity.

[0144] The above formulas are all dimensionless calculations. The formulas are derived from software simulations based on a large amount of collected data to obtain the most recent real-world results. The preset parameters in the formulas are set by those skilled in the art according to the actual situation.

[0145] The above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any other combination thereof. When implemented in software, the above embodiments can be implemented, in whole or in part, as a computer program product. Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented by electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution.

[0146] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment, depending on actual needs.

[0147] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application.

Claims

1. A method for nitrogen and phosphorus removal and recovery based on meat processing wastewater, characterized in that: S1: Collect initial water quality parameters of batches of meat processing wastewater at a preset sampling frequency within a preset time window. The initial water quality parameters include total phosphorus concentration data, ammonia nitrogen concentration data, organic matter concentration data, and pH data, which respectively constitute initial total phosphorus concentration sequences, initial ammonia nitrogen concentration sequences, initial organic matter concentration sequences, and initial pH sequences. Preprocess the initial total phosphorus concentration sequences, initial ammonia nitrogen concentration sequences, initial organic matter concentration sequences, and initial pH sequences. S2: Based on the initial concentration sequences of total phosphorus, ammonia nitrogen, and organic matter after pretreatment, calculate the difficulty index of comprehensive wastewater treatment. Calculate the initial amount of magnesium salt to be added based on the initial concentration sequences of total phosphorus and pH after pretreatment, and calculate the initial amount of alkali solution to be added based on the initial concentration sequences of ammonia nitrogen and pH after pretreatment. Add magnesium salt and alkali solution to the batch of meat processing wastewater according to the calculated initial amounts of magnesium salt and alkali solution to obtain a reaction mixture. S3: Continuously collect total phosphorus concentration data and ammonia nitrogen concentration data of the reaction mixture at the preset sampling frequency, and perform smoothing filtering on the collected total phosphorus concentration data and ammonia nitrogen concentration data. Calculate the nitrogen and phosphorus removal synchronicity index based on the smoothed total phosphorus concentration data and ammonia nitrogen concentration data, and determine whether the synergistic state of total phosphorus removal and ammonia nitrogen removal in the reaction mixture is normal based on the nitrogen and phosphorus removal synchronicity index. S4: Based on the total phosphorus concentration data and ammonia nitrogen concentration data after smoothing and filtering, calculate the overall maturity of the reaction endpoint. Based on the wastewater comprehensive treatment difficulty index, determine the reaction endpoint judgment threshold. Compare the overall maturity of the reaction endpoint with the reaction endpoint judgment threshold, and determine whether the reaction process is completed based on the comparison result.

2. The method for nitrogen and phosphorus removal and recovery based on meat processing wastewater according to claim 1, characterized in that: The method for preprocessing the initial concentration sequences of total phosphorus, ammonia nitrogen, organic matter, and pH is as follows: Outliers in the initial concentration sequences of total phosphorus, ammonia nitrogen, organic matter, and pH were identified using statistical methods. These outliers were then removed, and missing values ​​in the initial concentration sequences of total phosphorus, ammonia nitrogen, organic matter, and pH were filled using linear interpolation.

3. The method for nitrogen and phosphorus removal and recovery based on meat processing wastewater according to claim 2, characterized in that: The formula used to calculate the difficulty index of comprehensive wastewater treatment is as follows: ， in, The difficulty index for comprehensive wastewater treatment; This represents the arithmetic mean of the initial total phosphorus concentration sequence after pretreatment. The preset total phosphorus baseline concentration; This represents the arithmetic mean of the initial ammonia nitrogen concentration sequence after pretreatment. The preset ammonia nitrogen baseline concentration; This represents the arithmetic mean of the initial concentration sequences of organic matter after pretreatment. This is the preset organic matter baseline concentration; , , These are the preset weighting coefficients for total phosphorus, ammonia nitrogen, and organic matter, respectively, and they satisfy the following conditions: , >0, >0, >

0.

4. The method for nitrogen and phosphorus removal and recovery based on meat processing wastewater according to claim 3, characterized in that: The formula used to calculate the initial amount of magnesium salt added is as follows: ， in, This refers to the initial amount of magnesium salt added. The preset magnesium salt reference addition amount; A correction factor is added to the magnesium salt determined based on the pH-magnesium salt correction mapping relationship established by laboratory calibration. The value of the magnesium salt correction factor is determined based on the arithmetic mean of the pretreated initial pH sequence. The total phosphorus response index is a preset value, and 0.5 ≤ ≤1.

5.

5. The method for nitrogen and phosphorus removal and recovery based on meat processing wastewater according to claim 4, characterized in that: The formula used to calculate the initial amount of alkali solution added is as follows: ， in, This refers to the initial amount of alkali solution added. The amount of alkali solution added is the preset standard amount; A correction factor is added to the alkali solution determined based on the pH-alkali solution correction mapping relationship established by laboratory calibration. The value of the alkali solution correction factor is determined based on the arithmetic mean of the initial pH sequence after pretreatment. The preset ammonia nitrogen response index is given, and 0.5 ≤ ≤1.

5.

6. The method for nitrogen and phosphorus removal and recovery based on meat processing wastewater according to claim 1, characterized in that: The method for smoothing and filtering the collected total phosphorus concentration data and ammonia nitrogen concentration data is as follows: Using the sampling time corresponding to the preset sampling frequency as the reference time point, an equally spaced reference time axis is formed. The total phosphorus concentration data and ammonia nitrogen concentration data of the collected reaction mixture are matched with the reference time axis according to their original timestamps to form the total phosphorus concentration time series and the ammonia nitrogen concentration time series of the reaction mixture, respectively. Median filtering is performed on the total phosphorus concentration time series and the ammonia nitrogen concentration time series of the reaction mixture using a single-sided sliding window of length N, where N is a preset odd number and N≥3.

7. A method for nitrogen and phosphorus removal and recovery based on meat processing wastewater according to claim 6, characterized in that: The formula used to calculate the nitrogen and phosphorus removal synchronicity index is as follows: ， in, for Nitrogen and phosphorus removal synchronicity index at time; for The total phosphorus removal rate of the reaction mixture at time t, the total phosphorus removal rate The calculation formula is: ,in, After smoothing filtering Total phosphorus concentration data of the reaction mixture at any given time. After smoothing filtering Total phosphorus concentration data of the reaction mixture at any given time. The time interval corresponding to the preset sampling frequency; for The ammonia nitrogen removal rate of the reaction mixture at time t, wherein the ammonia nitrogen removal rate The calculation formula is: ,in, After smoothing filtering ammonia nitrogen concentration data of the reaction mixture at any given time. After smoothing filtering Data on ammonia nitrogen concentration in the reaction mixture at any given time.

8. The method for nitrogen and phosphorus removal and recovery based on meat processing wastewater according to claim 7, characterized in that: The determination logic for whether the synergistic state of total phosphorus removal and ammonia nitrogen removal in the reaction mixture is normal is as follows: when < And lasting longer than When the reaction mixture is found to be in an abnormal state of synergy between total phosphorus removal and ammonia nitrogen removal, a dosing control command is triggered. when ≥ ,or < However, the duration did not exceed At that time, the synergistic state of total phosphorus removal and ammonia nitrogen removal in the reaction mixture was determined to be normal; in, The preset synchronicity index threshold is 0 < <1; The preset duration threshold, and >

0.

9. A method for nitrogen and phosphorus removal and recovery based on meat processing wastewater according to claim 8, characterized in that: The formula used to calculate the overall maturity at the reaction endpoint is as follows: ， in, for The overall maturity level of the response endpoint at any given moment; The preset total phosphorus concentration threshold; The preset ammonia nitrogen concentration threshold; , These are the preset weighting coefficients for total phosphorus compliance and ammonia nitrogen compliance, respectively. , >0, >0; The value is set to a positive number to prevent the denominator from being zero. The method for determining the reaction endpoint threshold is as follows: when < At that time, the threshold for determining the reaction endpoint is = ; when ≥ At that time, the threshold for determining the reaction endpoint is ; in, The threshold for determining the reaction endpoint; The preset threshold for determining the reaction endpoint; The upper limit of the preset reaction endpoint determination threshold is met, and the following conditions are satisfied: < <1; This is a preset processing difficulty threshold; The adjustment coefficient is the preset endpoint determination threshold, and >

0.

10. A method for nitrogen and phosphorus removal and recovery based on meat processing wastewater according to claim 9, characterized in that: The logic for determining whether the reaction process is complete based on the comparison results is as follows: when ≥ And 0≤ < When the reaction process is complete, it is determined that the reaction process is finished. when < If the reaction process is determined to be incomplete, the current reaction process will be maintained. when ≥ ,but ≥ or If the value is less than 0, the reaction process is considered incomplete, and the current reaction process continues. in, for The overall maturity level of the response endpoint at any given moment; This is the preset threshold for the rate of change in maturity.

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