A multi-stage membrane separation-based chemical wastewater advanced treatment system and method

Abstract

The application provides a kind of multi-stage membrane separation based chemical industrial wastewater advanced treatment system and method, it is related to chemical industrial wastewater treatment technical field, by collecting the pollution load data under the preset membrane flux, by the pollution load data and the real-time pressure index when membrane separation filtering determines the current membrane separation process in the gradient return flow;According to the separation interference deviation, predict the steady-state filtration period of membrane separation filtration grade in constant flux change, carry out synchronous screening to steady-state filtration period, obtain the full-flow separation limit of multi-stage membrane separation unit in different pollution load;According to the gradient return flow and the full-flow separation limit, generate the separation control index when the equivalent flux produces peak shift, and trigger the starting point of the multi-stage membrane separation wastewater treatment process of dirt.This application can balance the adjustment of the advanced treatment process trigger of chemical industrial wastewater under the dynamic working condition of multi-stage membrane separation system, to improve the standard rate of membrane separation chemical industrial wastewater advanced treatment.

Description

Technical Field

[0001] This application relates to the field of chemical wastewater treatment technology, and more specifically, to a deep treatment system and method for chemical wastewater based on multi-stage membrane separation. Background Technology

[0002] Chemical wastewater treatment refers to a process that utilizes a combination of technologies such as physical pretreatment, biochemical degradation, membrane separation, and advanced oxidation. This involves removing large suspended solids through bar filtration, balancing the water quality in an equalization tank to stabilize influent conditions, decomposing organic pollutants in an anaerobic-aerobic biological unit, and using ultrafiltration-reverse osmosis membrane separation to remove heavy metals and high-salt components. If necessary, ozone or Fenton oxidation is employed for deep degradation of recalcitrant substances. Simultaneously, online monitoring instruments collect real-time data on COD, pH, and pollutant concentrations, combined with membrane operating parameters, to achieve compliant discharge or resource recovery of chemical wastewater, preventing pollutants from entering natural water bodies and causing ecological damage.

[0003] However, existing multi-stage membrane separation-based advanced treatment systems for chemical wastewater suffer from several shortcomings. Firstly, they neglect the impact of separation interference deviations caused by the dynamic coexistence of pollutants on the steady-state filtration cycle. Secondly, they lack separation control indicators based on cascade return flow and full-flow separation limits. These shortcomings lead to large fluctuations in membrane influent, accelerated membrane fouling, inaccurate prediction of steady-state filtration cycles, and ambiguity regarding full-flow separation limits. Ultimately, this results in a sharp drop in membrane separation efficiency and a shortened membrane module lifespan, making it impossible to guarantee the continuous and stable treatment of chemical wastewater to meet standards. Therefore, how to balance and adjust the triggering of the advanced treatment process for chemical wastewater under the dynamic operating conditions of a multi-stage membrane separation system to improve the compliance rate of membrane-based advanced treatment of chemical wastewater is a challenge facing the industry. Summary of the Invention

[0004] This application provides a system and method for advanced treatment of chemical wastewater based on multi-stage membrane separation. Under the dynamic operating conditions of the multi-stage membrane separation system, the advanced treatment process of chemical wastewater can be balanced and adjusted to improve the compliance rate of advanced treatment of chemical wastewater by membrane separation.

[0005] In a first aspect, this application provides a method for advanced treatment of chemical wastewater based on multi-stage membrane separation, the method comprising the following steps:

[0006] The wastewater pretreatment system filters and regulates the water quality of chemical wastewater, generating stable water flow information, while injecting backwashing medium into the membrane separation valve of the wastewater inflow section.

[0007] Collect the stable water flow information and the fouling load data under the preset membrane flux when the backwashing medium is acting. Determine the step-by-step return flow rate in the current membrane separation process by using the fouling load data and the real-time pressure index during membrane separation and filtration.

[0008] The separation interference deviation when pollutants coexist dynamically in chemical wastewater is determined. Based on the separation interference deviation, the steady-state filtration cycle of the membrane separation filtration level under constant flux variation is predicted. The steady-state filtration cycle is simultaneously screened to obtain the full-flow separation limit of the multi-stage membrane separation unit under different pollution loads.

[0009] Based on the cascade return flow rate and the full flow separation limit, an equivalent flux is generated, resulting in a peak shift in the separation control index. This separation control index then triggers the multi-stage membrane separation wastewater and sludge treatment process from the start point.

[0010] In this embodiment, the backwashing medium refers to the fluid used to flush the membrane separation valve orifice and the initial contaminants on the membrane surface.

[0011] In this embodiment, collecting the stable water flow information and the fouling load data under the preset membrane flux during the backwashing medium action specifically includes:

[0012] The wastewater concentration characteristics are determined based on the stable water flow information and the backwashing medium.

[0013] The membrane flux is preset based on the wastewater concentration characteristics;

[0014] Obtain the pollution load data under the preset membrane flux.

[0015] In this embodiment, determining the separation interference deviation when pollutants dynamically coexist in chemical wastewater specifically includes:

[0016] Chemical wastewater samples containing multiple target pollutants and potential interfering pollutants were collected, and the membrane separation process was simulated.

[0017] The separation efficiency data of the chemical wastewater samples were measured simultaneously, and the corresponding pollutant combination information was recorded.

[0018] Based on the separation efficiency data and the pollutant combination information, the separation interference deviation when pollutants dynamically coexist in chemical wastewater is determined.

[0019] In this embodiment, the dynamic coexistence of pollutants refers to the state in which multiple target pollutants and potential interfering pollutants coexist in chemical wastewater.

[0020] In this embodiment, the membrane separation filtration level refers to a classification of multi-level membrane module combination levels based on wastewater treatment needs, adapted to pollutant removal requirements to ensure effluent compliance.

[0021] In this embodiment, the steady-state filtration cycle is synchronously screened to obtain the full-flow split limit of the multi-stage membrane separation unit under different pollution loads, specifically including:

[0022] Establish a separation correlation feature based on the steady-state filtration cycle and the synchronously monitored multi-level membrane fouling load;

[0023] The synergistic variation patterns of different membrane separation units under the pollution load gradient were analyzed using the aforementioned separation correlation characteristics.

[0024] Based on the aforementioned synergistic change pattern, the full-flow separation limit of the multi-stage membrane separation unit under different pollution loads is generated.

[0025] In this embodiment, the diversion control index for generating peak offset when the equivalent flux is generated based on the cascade return flow and the full flow segmentation limit specifically includes:

[0026] The coordinated constraints for flux regulation are determined based on the cascade return flow rate and the full flow separation limit;

[0027] Extract the peak offset characteristics of the equivalent flux during the dynamic separation process from the aforementioned collaborative constraints;

[0028] The separation control index for peak offset generation is generated by the peak offset characteristic.

[0029] In this embodiment, the starting point trigger refers to the initial control action of adjusting the parameters of the multi-stage membrane separation wastewater and sludge treatment process when the real-time data triggers the separation control index threshold.

[0030] Secondly, this application provides a multi-stage membrane separation-based advanced treatment system for chemical wastewater, used to perform a multi-stage membrane separation-based advanced treatment method for chemical wastewater, the advanced treatment system comprising:

[0031] The flushing and regulating module is used to filter and regulate the water quality of chemical wastewater using the wastewater pretreatment system, generate stable water flow information, and inject backwashing medium into the membrane separation valve port of the wastewater inflow section.

[0032] The reflux filtration module is used to collect the stable water flow information and the fouling load data under the preset membrane flux when the backwashing medium is acting, and to determine the step-by-step reflux flow rate in the current membrane separation process by using the fouling load data and the real-time pressure index during membrane separation filtration.

[0033] The filter screening module is used to determine the separation interference deviation when pollutants coexist dynamically in chemical wastewater, predict the steady-state filtration cycle of the membrane separation filtration level under constant flux change based on the separation interference deviation, and simultaneously screen the steady-state filtration cycle to obtain the full-flow separation limit of the multi-stage membrane separation unit under different pollution loads.

[0034] The separation trigger module is used to generate a separation control index when the peak shift occurs due to the equivalent flux generated based on the cascade return flow rate and the full flow separation limit, and then the separation control index is used to trigger the start-up of the multi-stage membrane separation wastewater and sludge treatment process.

[0035] The technical solutions provided by the embodiments disclosed in this application have the following beneficial effects:

[0036] A wastewater pretreatment system is used to filter and regulate the water quality of chemical wastewater, generating stable water flow information. Simultaneously, backwashing medium is injected into the membrane separation valve at the wastewater inflow section. The stable water flow information and pollution load data under a preset membrane flux during the backwashing medium's action are collected. The cascade return flow rate in the current membrane separation process is determined using the pollution load data and real-time pressure indicators during membrane separation filtration. The separation interference deviation when pollutants in the chemical wastewater dynamically coexist is determined. Based on the separation interference deviation, the steady-state filtration cycle of the membrane separation filtration level under constant flux variation is predicted. The steady-state filtration cycle is synchronously screened to obtain the full-flow separation limit of the multi-stage membrane separation unit under different pollution loads. Based on the cascade return flow rate and the full-flow separation limit, a separation control index is generated when the equivalent flux experiences a peak shift. This separation control index then triggers the multi-stage membrane separation wastewater and pollutant treatment process from the start point.

[0037] Therefore, this application demonstrates that, under the premise of large fluctuations in influent water quality and susceptibility to initial membrane fouling in chemical wastewater, the influent stability of a multi-stage membrane separation system can be improved. Specifically, by utilizing a wastewater pretreatment system to filter and regulate the chemical wastewater while simultaneously injecting backwashing media into the membrane separation valve, the shortcomings of existing pretreatment systems—such as unstable water flow and rapid initial membrane fouling—are overcome, providing qualified influent for membrane separation. Furthermore, by collecting stable water flow information and pollution load data during the action of the backwashing media, and combining this with real-time membrane separation pressure indicators to determine the cascade return flow rate, the problem of incomplete return flow rate settings can be avoided. This approach avoids the problems of insufficient reflux leading to increased membrane fouling or excessive reflux reducing treatment efficiency. By identifying the separation interference deviation caused by the dynamic coexistence of pollutants, the steady-state filtration cycle can be predicted and the full-flow separation limit can be screened simultaneously. This addresses the shortcomings of existing technologies, such as ignoring interference, inaccurate cycle prediction, and ambiguous limits. The separation control index is generated from the tiered reflux flow rate and the full-flow separation limit, thereby triggering a multi-stage membrane treatment process. This addresses the shortcomings of existing technologies, such as lack of automated control and delayed response, avoids human judgment errors, significantly reduces the risk of membrane fouling and the probability of substandard effluent, and achieves stable operation of the membrane separation system.

[0038] In summary, the technical solution adopted in this application can balance and adjust the deep treatment process of chemical wastewater under the dynamic operating conditions of a multi-stage membrane separation system, thereby improving the compliance rate of deep treatment of chemical wastewater by membrane separation. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only for this embodiment of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 This is an exemplary flow chart of a method for deep treatment of chemical wastewater based on multi-stage membrane separation provided in this application;

[0041] Figure 2 This is a flowchart illustrating the determination of cascade return flow provided in this application;

[0042] Figure 3 This is a flowchart illustrating the determination of the steady-state filtration cycle provided in this application;

[0043] Figure 4 This is a module structure diagram of a chemical wastewater deep treatment system based on multi-stage membrane separation provided in this application, wherein 100 represents the flushing and adjustment module, 200 represents the reflux filtration module, 300 represents the filter screening module, and 400 represents the separation trigger module. Detailed Implementation

[0044] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0045] This application provides a multi-stage membrane separation-based advanced treatment system and method for chemical wastewater. The core of this system involves using a wastewater pretreatment system to filter and regulate the water quality of chemical wastewater, generating stable water flow information. Simultaneously, backwashing medium is injected into the membrane separation valve at the wastewater inflow section. The system collects the stable water flow information and pollution load data under a preset membrane flux when the backwashing medium is applied. The system determines the cascade return flow rate during the current membrane separation process using the pollution load data and real-time pressure indicators during membrane filtration. It determines the separation interference deviation when pollutants in the chemical wastewater dynamically coexist. Based on the separation interference deviation, it predicts the steady-state filtration cycle of the membrane separation filtration level under constant flux changes. The steady-state filtration cycle is synchronously screened to obtain the full-flow separation limit of the multi-stage membrane separation unit under different pollution loads. Based on the cascade return flow rate and the full-flow separation limit, a separation control index is generated when the equivalent flux experiences a peak shift. This separation control index then triggers the multi-stage membrane separation wastewater and pollutant treatment process.

[0046] Example 1: To better understand the above technical solution, the following will provide a detailed description of the technical solution in conjunction with the accompanying drawings and specific implementation methods. (Refer to...) Figure 1 As shown in the figure, this is an exemplary flowchart of a method for advanced treatment of chemical wastewater based on multi-stage membrane separation according to this embodiment of the present application. The method for advanced treatment of chemical wastewater includes the following steps:

[0047] In step S1, the wastewater pretreatment system is used to filter and regulate the water quality of the chemical wastewater to generate stable water flow information, while backwashing medium is injected into the membrane separation valve port of the wastewater inflow section.

[0048] In practice, chemical wastewater is introduced into the inlet pipe of the pretreatment system. A mechanical rotary screen with a mesh size of 0.5-1mm is installed at the front end of the pipe. The screen continuously intercepts suspended particles with a diameter >1mm (such as plastic fragments and catalyst residue) at a speed of 5r / min. The impurities are transported by the screen to the top slag hopper for periodic cleaning. The wastewater then enters a filter tank with an inner diameter of 1.2m and filled with 0.8-1.2mm quartz sand (1.5m high), where it permeates at a filtration rate of 1.5m / h to remove fine suspended solids of 0.1-1mm. Next, the wastewater flows into a 50m³ water quality equalization tank. The tank is monitored in real time by an online pH monitor, a temperature sensor, and an online COD monitor. When the pH is <6, a 0.5m³ / h sodium hydroxide dosing pump (10% concentration) is turned on to adjust the pH to 6-8. When the temperature is <15℃, a 10kW electric heating element is activated to raise the temperature to 15-25℃. When the COD fluctuates by more than ±10%, a 2m³ / h return pump is turned on to dilute the COD with qualified water. Finally, an electromagnetic flow meter and various online instruments were installed on the outlet pipe of the equalization tank to collect flow rate, COD, pH, and temperature data every 10 seconds and transmit them to the PLC to form stable water flow information. This will not be elaborated further here.

[0049] It should be noted that, in this application, stable flow information refers to a set of data reflecting the stability of flow rate, COD, temperature, and pH value of chemical wastewater after pretreatment.

[0050] In addition, in specific implementation, the backwashing medium can be injected into the membrane separation valve port of the sewage inflow section in the following way: Use treated water from the membrane separation unit as the backwashing medium to avoid introducing new impurities. Install a backwashing injection branch pipe at the sewage inflow valve port of the membrane separation unit. Install a metering pump with a flow rate of 0.2–0.5 m³ / h and an automatic solenoid valve sequentially on the branch pipe, and connect it to the central control system. Set the backwashing cycle to 30 minutes / time, with each cycle lasting 5 minutes. When the system timer reaches the preset cycle, the solenoid valve automatically opens, and the metering pump injects treated water into the membrane separation valve port at a fixed flow rate of 0.3 m³ / h. The water flow backwashes the inner wall of the valve port and the inlet of the membrane module, flushing away initial colloids and fine impurities. After flushing, the sewage enters the membrane separation unit along with the original sewage, preventing contaminant accumulation and clogging of the membrane pores. Further details are omitted here.

[0051] It should be noted that, in this application, the backwashing medium refers to the fluid used to flush the membrane separation valve orifice and the initial contaminants on the membrane surface.

[0052] In step S2, the stable water flow information and the fouling load data under the preset membrane flux when the backwashing medium is acting are collected. The cascade return flow rate in the current membrane separation process is determined by the fouling load data and the real-time pressure index during membrane separation and filtration.

[0053] In this embodiment, the acquisition of the stable water flow information and the fouling load data under the preset membrane flux during the backwashing medium can be achieved through the following steps:

[0054] The wastewater concentration characteristics are determined based on the stable water flow information and the backwashing medium.

[0055] The membrane flux is preset based on the wastewater concentration characteristics;

[0056] Obtain the pollution load data under the preset membrane flux.

[0057] In practice, firstly, stable water flow information is retrieved, including parameters such as flow rate, COD concentration, suspended solids concentration, pH value, and temperature. Simultaneously, the injection flow rate and injection cycle data of the backwash medium are retrieved. Water quality analysis software is used to correlate these two types of data to calculate key concentration indicators of the wastewater after dilution by the backwash medium. For example, the average COD concentration of the stable water flow over one hour is taken, and combined with the backwash medium injection flow rate and the stable water flow rate, the concentration is calculated using the formula: "Diluted concentration = (Stable water flow COD concentration × Stable water flow rate) / (Stable water flow rate + Backwash medium flow rate)". Simultaneously, the suspended solids concentration is measured (water samples are filtered through a 0.45μm filter membrane, dried, and weighed). Finally, the concentration ranges of core pollutants such as COD and suspended solids are compiled to form wastewater concentration characteristics. Then, consult the manufacturer's technical manual for the membrane module (such as an ultrafiltration membrane) to obtain the recommended flux range for different water qualities—for example, the manual states "recommended flux of 15-18 L / (m²·h) when COD < 200 mg / L, 12-15 L / (m²·h) when COD 200-400 mg / L, and 10-12 L / (m²·h) when COD > 400 mg / L." Then, compare this with the wastewater concentration characteristics determined in step one. If the wastewater COD concentration is 280 mg / L and the suspended solids concentration is 8 mg / L, then 13 L / (m²·h) is initially selected as the candidate flux. Subsequently, a 1-hour small-scale test is conducted using a small membrane module, monitoring the pressure difference across the membrane during the test (if the pressure difference is stable at 0.1-0.15 MPa, the rejection rate is ≥ 85%). This confirms that the membrane operates stably at this flux, and finally, 13 L / (m²·h) is set as the preset membrane flux. Finally, an automatic sampling valve is installed on the inlet pipe of the membrane separation unit, set to automatically sample once every 30 minutes, with each sample being 50 mL; at the same time, another automatic sampling valve is installed at the corresponding position on the outlet pipe, sampling 50 mL simultaneously; the inlet and outlet samples are sent to the laboratory separately—the COD concentration of the inlet sample is measured using a COD digester, and the suspended solids concentration is measured by gravimetric method (the filter membrane is dried and weighed), and the corresponding concentration of the outlet sample is measured using the same method; the pollution load is calculated according to the formula "pollution load = (total mass of inlet pollutants - total mass of outlet pollutants) / total area of ​​membrane module": first calculate the total mass of inlet pollutants ((COD concentration + suspended solids concentration) × inlet flow rate × sampling interval), then calculate the total mass of outlet pollutants, and divide the difference between the two by the membrane area (e.g., 50 m²) to obtain the pollution load data every 30 minutes, that is, the pollution load data under the preset membrane flux.

[0058] It should be noted that, in this application, the preset membrane flux refers to the target operating flux of the membrane separation unit set based on the characteristics of wastewater concentration; the wastewater concentration characteristics refer to the set of parameters of the types, contents and distribution patterns of pollutants in chemical wastewater; and the pollution load data refers to the mass data of pollutants attached to a unit area membrane module under the preset membrane flux operating conditions.

[0059] Preferably, in this embodiment, the cascade reflux rate in the current membrane separation process is determined by the pollution load data and the real-time pressure index during membrane separation filtration, with reference to... Figure 2 As shown in the figure, this is a schematic diagram of the process for determining the cascade return flow rate in some embodiments of this application. In this embodiment, the determination of the cascade return flow rate can be achieved by the following steps:

[0060] In step S21, the pollution status index during the current membrane separation filtration is determined based on the pollution load data;

[0061] In step S22, the real-time pressure index during the membrane separation and filtration process is obtained;

[0062] In step S23, the cascade filtration information in the current membrane separation process is determined based on the contamination status index and the real-time pressure index.

[0063] In step S24, the cascade reflux flow rate in the current membrane separation process is determined using the cascade filtration information.

[0064] In practice, firstly, the pollution load data under the preset membrane flux is obtained, and at the same time, the allowable pollution load (e.g., 0.02 mg / cm²) provided by the membrane module manufacturer is retrieved. The deviation rate is calculated according to the formula "Pollution State Deviation Rate = (Current Pollution Load Data - Allowable Pollution Load) / Allowable Pollution Load × 100%". If the deviation rate is ≤ -10%, the pollution state index is set as "light pollution"; if the deviation rate is between -10% and 10%, it is set as "moderate pollution"; if the deviation rate is > 10%, it is set as "heavy pollution". The final determined pollution state index is then used. Next, a high-precision pressure transmitter is installed on the inlet pipe of the membrane module in the membrane separation unit, and a low-pressure transmitter is installed on the outlet pipe. The two transmitters are set to collect pressure data every 5 seconds and transmit it to the central control system via the 485 communication protocol. The system automatically calculates "real-time membrane pressure difference = inlet pressure value - outlet pressure value" and generates a pressure change curve for nearly 10 minutes (e.g., pressure rises from 0.18MPa to 0.22MPa). The real-time membrane pressure difference value and the pressure change curve are used together as the real-time pressure indicator. Then, a matrix corresponding to "pollution status index - real-time pressure index - cascade filtration information" is preset in the central control system: if the pollution status index is "light pollution" and the real-time membrane pressure difference is ≤0.2MPa, the cascade filtration information is determined as "no need to adjust the reflux, maintain the current filtration status"; if it is "moderate pollution" and the real-time membrane pressure difference is between 0.2-0.23MPa, it is determined as "retrofit needs to be slightly increased to dilute the influent concentration"; if it is "heavy pollution" and the real-time membrane pressure difference is >0.23MPa, it is determined as "retrofit needs to be significantly increased to urgently alleviate pollution"; the system substitutes the current pollution status index and the real-time pressure index into the matrix, automatically matches and outputs the corresponding cascade filtration information in the current membrane separation process. Finally, the system retrieves the baseline feed water volume of the current membrane separation unit and determines the reflux adjustment range based on the cascade filtration information: if the information is "small increase in reflux", the reflux range is set to 10% to 15% of the baseline feed water volume; if it is "large increase in reflux", it is set to 20% to 25%. The reflux flow rate is calculated using the formula "cascade reflux flow rate = baseline feed water volume × reflux range". For example, if the baseline feed water volume is 5 m³ / h and the range is 12%, then the cascade reflux flow rate = 5 × 12% = 0.6 m³ / h. The system sends the calculation results to the reflux pump frequency converter on the effluent side of the membrane separation unit. The frequency converter adjusts the pump speed to stabilize the actual reflux flow rate at 0.6 m³ / h, while simultaneously monitoring the membrane pressure difference after reflux in real time. If the pressure difference does not decrease, the range is finely adjusted.

[0065] It should be noted that, in this application, the real-time pressure index refers to the pressure difference and pressure change trend between the inlet and outlet sides of the membrane module during the membrane separation and filtration process; the fouling status index refers to the parameters that quantify the degree of fouling on the membrane surface during the current membrane separation and filtration process; the cascade filtration information refers to the set of parameters that guide the adjustment of cascade reflux to ensure the stability of membrane separation; and the cascade reflux flow rate refers to the flow rate of wastewater that needs to be returned to the pretreatment system during the wastewater treatment process.

[0066] In step S3, the separation interference deviation when pollutants coexist dynamically in chemical wastewater is determined. Based on the separation interference deviation, the steady-state filtration cycle of the membrane separation filtration level under constant flux variation is predicted. The steady-state filtration cycle is synchronously screened to obtain the full-flow separation limit of the multi-stage membrane separation unit under different pollution loads.

[0067] In this embodiment, the separation interference deviation when pollutants dynamically coexist in chemical wastewater can be determined by the following steps:

[0068] Chemical wastewater samples containing multiple target pollutants and potential interfering pollutants were collected, and the membrane separation process was simulated.

[0069] The separation efficiency data of the chemical wastewater samples were measured simultaneously, and the corresponding pollutant combination information was recorded.

[0070] Based on the separation efficiency data and the pollutant combination information, the separation interference deviation when pollutants dynamically coexist in chemical wastewater is determined.

[0071] In practice, firstly, a 500mL glass sampling bottle can be used to collect a sample at the inlet of the membrane separation unit after the pretreatment of chemical wastewater, ensuring that the sample contains both the target pollutant and potential interfering pollutants. The sample is then poured into a small membrane separation experimental device, and the experimental parameters are set to match the actual membrane separation system—temperature 25℃, inlet pressure 0.2MPa, and flow rate 1L / h. The device is then started to simulate the membrane separation process and run continuously for 2 hours, during which the parameters are kept stable. Then, during the simulated membrane separation process, two operations were performed simultaneously every 20 minutes: First, samples were collected from the inlet and outlet of the device using 10mL sampling tubes. The phenol concentration was measured using a high-performance liquid chromatograph, and the copper ion concentration was measured using an atomic absorption spectrophotometer. The separation efficiency data was calculated using the formula "Retention rate = (Inlet concentration - Outlet concentration) / Inlet concentration × 100%". Second, the amount of permeate collected at the outlet within 20 minutes was weighed using an electronic balance, and the real-time membrane flux was calculated based on the membrane area. Simultaneously, the real-time concentration of potential interfering pollutants in the samples was measured using a concentration meter, and the combined information of "Target pollutant concentration + Potential interfering pollutant concentration" was recorded, i.e., the pollutant combination information. Finally, the theoretical retention rate of a single target pollutant provided by the membrane module manufacturer was retrieved. Then, the actual retention rate under the corresponding pollutant combination was extracted from the separation efficiency data. The separation interference deviation was calculated separately using the formula "Separation interference deviation = Theoretical retention rate - Actual retention rate", yielding, for example, a phenol deviation of 7% and a copper ion deviation of 6%. Subsequently, the average value of all target pollutant deviations was calculated, and this average value was used as the separation interference deviation when pollutants dynamically coexist in chemical wastewater.

[0072] It should be noted that, in this application, the target pollutant refers to a specific pollutant in chemical wastewater that needs to be removed by membrane separation; potential interfering pollutants refer to other pollutants in chemical wastewater that affect the separation effect of the target pollutant; dynamic coexistence of pollutants refers to the state in which multiple target pollutants and potential interfering pollutants coexist in chemical wastewater, and their concentrations change with the treatment process, affecting the membrane separation effect; chemical wastewater sample refers to a water sample containing target and potential interfering pollutants, taken from a specific location such as after pretreatment of chemical wastewater, used to simulate membrane separation and analysis; separation efficiency data refers to parameters of the membrane separation process on the pollutant removal effect and operational stability; pollutant combination information refers to the types, concentrations, and proportions of target pollutants and potential interfering pollutants in the chemical wastewater sample; separation interference deviation refers to the difference between the actual rejection rate of membrane separation and the theoretical rejection rate of a single target pollutant when pollutants coexist dynamically.

[0073] Preferably, in this embodiment, the steady-state filtration cycle of the membrane separation filtration level under constant flux variation is predicted based on the separation interference deviation, with reference to... Figure 3 As shown in the figure, this is a schematic flowchart of determining the steady-state filtering period in some embodiments of this application. In this embodiment, the steady-state filtering period can be determined by the following steps:

[0074] In step S31, membrane flux change data within a preset time series are collected under constant flux change.

[0075] In step S32, the dynamic accumulation trend of pollutants on the multi-stage membrane surface is determined based on the separation interference deviation;

[0076] In step S33, the critical fouling load is determined based on the dynamic cumulative trend and the membrane flux change data;

[0077] In step S34, the steady-state filtration cycle of the membrane separation filtration level under constant flux variation is predicted based on the critical contamination load.

[0078] In practice, firstly, based on the membrane separation filtration level (such as ultrafiltration-reverse osmosis two-stage filtration), three sets of constant flux values ​​of 12, 14, and 16 L / (m²・h) are set, with each set corresponding to the standard flux range of one filtration level. A membrane flux monitor is installed on the effluent side of the membrane separation experimental device, with a preset time series of 8 hours and a sampling frequency of once every 10 minutes. The device is then adjusted to each set of constant flux. After startup, the membrane flux monitor collects and records the actual membrane flux value at each moment in real time. For example, with an initial flux of 14 L / (m²・h), the value becomes 13.8 L / (m²・h) after 1 hour and 13.5 L / (m²・h) after 2 hours. Finally, an 8-hour flux change dataset corresponding to each set of constant flux is formed, which is the membrane flux change data within the preset time series. Next, the separation interference bias was obtained to clarify the promoting effect of potential interfering pollutants on the accumulation of target pollutants under this bias. Pollutant mass sensors were installed on the surface of each stage of the multi-stage membrane module (ultrafiltration membrane + reverse osmosis membrane), and the amount of pollutant adhering to the membrane surface was collected every 30 minutes. The membrane separation experimental device was started and operated at a set constant flux, recording the amount of pollutant adhering to each stage membrane in real time at 0.5, 1, 1.5…8 hours. The data was imported into data analysis software, and a pollutant adhering amount-time curve was plotted, with the curve slope representing the dynamic accumulation trend of pollutants on the multi-stage membrane surface. Then, from the membrane flux change data, the time point at which "membrane flux drops to 80% of the initial value" under each constant flux was identified. The amount of pollutant adhering to the membrane surface corresponding to this time point was extracted from the dynamic accumulation trend curve. The maximum amount of pollutant adhering to the multi-stage membrane was taken, and combined with the membrane area, the critical fouling load was calculated according to "critical fouling load = maximum adhering amount of a single-stage membrane × total membrane area," and the calculated result was taken as the critical fouling load under the current constant flux. Finally, the pollutant accumulation rate is extracted from the dynamic accumulation trend (e.g., in linear accumulation, the rate = slope of the dynamic accumulation trend curve); then the amount of pollutant adhering to the single-stage membrane corresponding to the critical pollution load is retrieved; the steady-state filtration cycle is calculated according to "steady-state filtration cycle = amount of adhering to the single-stage membrane corresponding to the critical pollution load ÷ pollutant accumulation rate"; the above calculation is repeated for each set of constant flux to obtain the steady-state filtration cycle under different constant fluxes, forming the steady-state filtration cycle of the membrane separation filtration level under constant flux variation.

[0079] It should be noted that, in this application, membrane separation filtration level refers to a classification of multi-stage membrane module combination levels based on wastewater treatment needs to adapt to pollutant removal requirements and ensure effluent compliance; constant flux variation refers to multiple sets of fixed membrane flux values ​​set to simulate different operating conditions; membrane flux variation data refers to the set of values ​​showing the actual membrane permeate flux changing over time during constant flux operation; dynamic accumulation trend refers to the pattern of pollutant adhesion on the multi-stage membrane surface changing over time under the influence of separation interference deviation; critical fouling load refers to the maximum mass of pollutants adhering to the membrane surface when the membrane flux drops to the initial flux threshold; and steady-state filtration cycle refers to the time required for the membrane to reach the critical fouling load from startup.

[0080] In this embodiment, the simultaneous screening of the steady-state filtration cycle to obtain the full-flow split limit of the multi-stage membrane separation unit under different pollution loads can be achieved by the following steps:

[0081] Establish a separation correlation feature based on the steady-state filtration cycle and the synchronously monitored multi-level membrane fouling load;

[0082] The synergistic variation patterns of different membrane separation units under the pollution load gradient were analyzed using the aforementioned separation correlation characteristics.

[0083] Based on the aforementioned synergistic change pattern, the full-flow separation limit of the multi-stage membrane separation unit under different pollution loads is generated.

[0084] In practice, firstly, in a laboratory or pilot-scale facility, different contamination load gradients (e.g., COD 200, 300, 400, 500, 600 mg / L) are set, and multi-stage membrane separation units are operated at a constant flux. Contamination load data and corresponding steady-state filtration cycles for each membrane stage are recorded simultaneously. The data from each membrane stage at the same load level are then aggregated, and regression analysis or piecewise fitting methods are used to establish a relationship curve between contamination load and steady-state filtration cycle, which is the separation correlation characteristic. Then, based on the separation correlation characteristic, the steady-state filtration cycle change curves of each membrane stage under the same contamination load gradient are compared to analyze whether they exhibit proportional shortening, premature decay of a particular membrane stage, or delayed decay. Simultaneously, combined with membrane flux changes and rejection rate data, the contamination transfer and interference effects between different membrane stages are determined, and the characteristics within different contamination load ranges are summarized. This characteristic is used as the synergistic change law of different membrane separation units under the contamination load gradient. Finally, based on the synergistic change law, the longest steady-state filtration cycle of each membrane stage under different pollution loads is determined; combined with the system design rejection rate requirements, the influent flow rate is gradually increased until the rejection rate of a certain membrane stage is lower than the design value for the first time, and the flow rate at this time is recorded as the full flow separation limit under the pollution load; repeating this test process, the full flow separation limit of the multi-stage membrane separation unit under different pollution loads is obtained.

[0085] It should be noted that, in this application, synchronous screening refers to a screening method that simultaneously processes steady-state filtration cycle and multi-stage membrane fouling load data to accurately determine the full-flow separation limit under different fouling loads; multi-stage membrane separation unit refers to a membrane system unit composed of multiple functional membrane modules that treats pollutants in stages to ensure that the effluent meets standards; fouling load refers to the mass of pollutants borne by a unit area of ​​membrane module per unit time; fouling load gradient refers to multiple sets of different fouling load levels set for actual operating conditions; separation correlation characteristics refer to the quantitative characteristic curves of the operating cycles of membranes at different levels under different fouling load conditions; synergistic change law refers to the mutual influence and synchronous change trend of the operating cycles and fouling rates among multi-stage membrane separation units during the process of fouling load changes; full-flow separation limit refers to the maximum treated water volume that the multi-stage membrane separation unit can maintain the design rejection rate and stable operation under specific fouling load conditions.

[0086] In step S4, a separation control index is generated based on the cascade return flow rate and the full flow separation limit to determine when the equivalent flux causes a peak shift. The separation control index is then used to trigger the multi-stage membrane separation wastewater and sludge treatment process.

[0087] In this embodiment, the diversion control index for generating peak offset based on the equivalent flux generated by the cascade return flow and the full flow segmentation limit can be achieved by the following steps:

[0088] The coordinated constraints for flux regulation are determined based on the cascade return flow rate and the full flow separation limit;

[0089] Extract the peak offset characteristics of the equivalent flux during the dynamic separation process from the aforementioned collaborative constraints;

[0090] The separation control index for peak offset generation is generated by the peak offset characteristic.

[0091] In practice, firstly, the range of cascade return flow rate and the full flow separation limit corresponding to different pollution loads are obtained; according to the correspondence between "cascade return flow rate - full flow separation limit", the maximum allowable equivalent flux under different return flow rates is calculated (equivalent flux = (membrane separation unit influent flow rate - cascade return flow rate) / membrane area). For example, when the cascade return flow rate is 0.5 m³ / h and the full flow separation limit is 7 m³ / h, the maximum allowable equivalent flux = (7-0.5) / 50 = 0.13 m³ / (m²・h); then, combined with the flux safety threshold recommended by the membrane module manufacturer, such as ≤0.15 m³ / (m²・h)), the correlation boundary of "cascade return flow rate - full flow separation limit - equivalent flux" is finally determined, forming a synergistic constraint condition for flux control. Then, an online equivalent flux monitor was installed in the membrane separation system, and the monitoring frequency was set to once every 5 minutes. Three sets of dynamic separation conditions were simulated according to the parameter range in the synergistic constraint conditions. The change curve of equivalent flux under each set of conditions was recorded, and the peak value of the normal steady state (e.g., 0.13 m³ / (m²·h)) was extracted (occurring after 2 hours of operation). The peak value under the dynamic conditions (e.g., when the cascade return flow is 1.5 m³ / h, the peak value is 0.11 m³ / (m²·h)) was determined to be 0.11 m³ / (m²·h) (occurring after 1.5 hours). The peak shift amplitude (reduction of 0.02 m³ / (m²·h)) and the time shift (0.5 hours earlier) were determined to be the peak shift characteristics of equivalent flux in the dynamic separation process. Finally, based on the peak offset characteristics, two types of control thresholds are set: one is the peak amplitude offset threshold (e.g., a decrease of ≥0.015 m³ / (m²・h) from the normal peak), and the other is the peak time offset threshold (e.g., an advance of ≥0.4 hours from the normal time). Corresponding control actions are matched for each type of threshold. For example, when the amplitude offset threshold is triggered, the cascade return flow is reduced by 0.2 m³ / h to improve the equivalent flux; when the time offset threshold is triggered, the membrane separation unit's throughput is reduced to 90% of the full flow separation limit to delay fouling. The correspondence between the peak amplitude offset threshold and the peak time offset threshold and the control actions is used as the separation control index when the equivalent flux generates a peak offset.

[0092] It should be noted that, in this application, the equivalent flux peak shift refers to the deviation of the peak value and occurrence time of the equivalent flux from the normal steady state in dynamic membrane separation; the cooperative constraint condition refers to the boundary condition that defines the safe fluctuation of the equivalent flux of the membrane separation system; the peak shift characteristic refers to the feature that the peak occurrence time and peak value of the equivalent flux deviate from the normal steady state in the process of dynamic membrane separation; and the separation control index refers to the threshold and corresponding action set that trigger the adjustment of the membrane separation system parameters.

[0093] In addition, in specific implementation, the starting point triggering of the multi-stage membrane separation wastewater and sludge treatment process by the separation control index can be achieved in the following way: First, the separation control index (including thresholds such as peak amplitude offset ≥0.015m³ / (m²・h) and time offset ≥0.4 hours and corresponding actions) is entered into the wastewater pretreatment system. The wastewater pretreatment system acquires real-time data of the equivalent flux peak, cascade return flow, and full flow separation limit of the multi-stage membrane separation unit every 5 seconds through the data acquisition module (transmitted by the equivalent flux online monitoring instrument, return pump flow meter, and membrane treatment capacity sensor). Then, when the wastewater pretreatment system determines that real-time data triggers any threshold, such as a decrease in the equivalent flux peak value of 0.018 m³ / (m²・h) compared to normal, it immediately sends a command to the corresponding execution device: if the trigger amplitude deviates from the threshold, it controls the frequency converter of the ultrafiltration membrane effluent side return pump to reduce the cascade return flow rate from 1.5 m³ / h to 1.3 m³ / h; if the trigger time deviates from the threshold, it adjusts the opening of the reverse osmosis membrane inlet valve to reduce the treatment capacity from 5 m³ / h (full flow separation limit) to 4.5 m³ / h. At the same time, the wastewater pretreatment system starts feedback monitoring, checking every 10 seconds whether the parameters have returned to the normal range until the indicators stabilize, thus completing the initial triggering and dynamic maintenance of the treatment process, which will not be elaborated here.

[0094] It should be noted that, in this application, "start-point trigger" refers to the initial control action of adjusting the parameters of the multi-stage membrane separation wastewater and sludge treatment process when real-time data triggers the threshold of the separation control index.

[0095] Therefore, this application demonstrates that, under the premise of large fluctuations in influent water quality and susceptibility to initial membrane fouling in chemical wastewater, the influent stability of a multi-stage membrane separation system can be improved. Specifically, by utilizing a wastewater pretreatment system to filter and regulate the chemical wastewater while simultaneously injecting backwashing media into the membrane separation valve, the shortcomings of existing pretreatment systems—such as unstable water flow and rapid initial membrane fouling—are overcome, providing qualified influent for membrane separation. Furthermore, by collecting stable water flow information and pollution load data during the action of the backwashing media, and combining this with real-time membrane separation pressure indicators to determine the cascade return flow rate, the problem of incomplete return flow rate settings can be avoided. This approach avoids the problems of insufficient reflux leading to increased membrane fouling or excessive reflux reducing treatment efficiency. By identifying the separation interference deviation caused by the dynamic coexistence of pollutants, the steady-state filtration cycle can be predicted and the full-flow separation limit can be screened simultaneously. This addresses the shortcomings of existing technologies, such as ignoring interference, inaccurate cycle prediction, and ambiguous limits. The separation control index is generated from the tiered reflux flow rate and the full-flow separation limit, thereby triggering a multi-stage membrane treatment process. This addresses the shortcomings of existing technologies, such as lack of automated control and delayed response, avoids human judgment errors, significantly reduces the risk of membrane fouling and the probability of substandard effluent, and achieves stable operation of the membrane separation system.

[0096] In summary, the technical solution adopted in this application can balance and adjust the deep treatment process of chemical wastewater under the dynamic operating conditions of a multi-stage membrane separation system, thereby improving the compliance rate of deep treatment of chemical wastewater by membrane separation.

[0097] Example 2: This application provides a deep treatment system for chemical wastewater based on multi-stage membrane separation, referencing... Figure 4 As shown in the figure, this is a modular structure diagram of a multi-stage membrane separation-based advanced treatment system for chemical wastewater according to this embodiment of the present application. The advanced treatment system for chemical wastewater includes:

[0098] The flushing and regulating module 100 is used to filter and regulate the water quality of chemical wastewater using the wastewater pretreatment system, generate stable water flow information, and inject backwashing medium into the membrane separation valve port of the wastewater inflow section.

[0099] The reflux filtration module 200 is used to collect the stable water flow information and the fouling load data under the preset membrane flux when the backwashing medium is acting, and to determine the step-by-step reflux flow rate in the current membrane separation process by the fouling load data and the real-time pressure index during membrane separation filtration.

[0100] The filter screening module 300 is used to determine the separation interference deviation when pollutants coexist dynamically in chemical wastewater, predict the steady-state filtration cycle of the membrane separation filtration level under constant flux change based on the separation interference deviation, and simultaneously screen the steady-state filtration cycle to obtain the full-flow separation limit of the multi-stage membrane separation unit under different pollution loads.

[0101] The separation trigger module 400 is used to generate a separation control index when the peak shift occurs in the equivalent flux based on the cascade return flow rate and the full flow separation limit, and then trigger the multi-stage membrane separation wastewater and sludge treatment process by the separation control index.

[0102] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0103] Those skilled in the art will understand that all or part of the steps in the various methods of the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, including read-only memory (ROM), random access memory (RAM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), one-time programmable read-only memory (OTPROM), electrically-Erasable Programmable Read-Only Memory (EEPROM), compactdisc read-only memory (CD-ROM) or other optical disc storage, disk storage, magnetic tape storage, or any other computer-readable medium capable of carrying or storing data.

[0104] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

Claims

1. A method for advanced treatment of chemical wastewater based on multi-stage membrane separation, characterized in that, The chemical wastewater advanced treatment method comprises the following steps: The chemical wastewater is filtered and water quality is adjusted by using a wastewater pretreatment system to generate stable water flow information, and a backwash medium is injected into a membrane separation valve port of a wastewater inflow section; A wastewater concentration feature is determined according to the stable water flow information and the backwash medium, a preset membrane flux is determined according to the wastewater concentration feature, pollution load data under the preset membrane flux is obtained, and a stepwise backflow amount in a current membrane separation process is determined by using the pollution load data and a real-time pressure index during membrane separation filtration, wherein the stepwise backflow amount refers to a wastewater flow amount that needs to be backflowed to the pretreatment system during wastewater treatment; A chemical wastewater sample containing multiple target pollutants and potential interference pollutants is taken, and a membrane separation process is simulated, separation efficiency data of the chemical wastewater sample are synchronously measured, and corresponding pollutant combination information is recorded, separation interference deviation of the pollutants in the chemical wastewater when the pollutants dynamically coexist is determined according to the separation efficiency data and the pollutant combination information, a stable filtration period of the membrane separation filtration level in constant flux variation is predicted according to the separation interference deviation, a separation correlation feature is established according to the stable filtration period and a multi-stage membrane pollution load synchronously monitored, a cooperative change rule of different membrane separation units under a pollution load gradient is analyzed through the separation correlation feature, and a full-flow separation limit of the multi-stage membrane separation unit in different pollution loads is generated based on the cooperative change rule, wherein the stable filtration period refers to a time required for the membrane to reach a critical pollution load from starting operation, and the full-flow separation limit refers to a maximum treatment water amount that the multi-stage membrane separation unit can maintain a designed interception rate and stable operation under a specific pollution load condition; A cooperative constraint condition of flux regulation is determined according to the stepwise backflow amount and the full-flow separation limit, a peak value offset characteristic of an equivalent flux in a dynamic separation process is extracted from the cooperative constraint condition, a separation regulation index when the equivalent flux generates a peak value offset is generated through the peak value offset characteristic, and a starting point trigger of a wastewater and pollutant treatment process of the multi-stage membrane separation is generated by using the separation regulation index, wherein the equivalent flux=(full-flow separation limit-stepwise backflow amount) / membrane area, and the starting point trigger refers to an initial regulation action of starting parameter adjustment of the wastewater and pollutant treatment process of the multi-stage membrane separation when real-time data triggers a separation regulation index threshold value.

2. The method for advanced treatment of chemical wastewater based on multi-stage membrane separation according to claim 1, characterized in that, The backwash medium refers to a fluid used for flushing initial pollutants of a membrane separation valve port and a membrane surface.

3. The method for advanced treatment of chemical wastewater based on multi-stage membrane separation according to claim 1, characterized in that, The dynamic coexistence of the pollutants refers to a state that multiple target pollutants and potential interference pollutants exist simultaneously in the chemical wastewater.

4. The method for advanced treatment of chemical wastewater based on multi-stage membrane separation according to claim 1, characterized in that, The membrane separation filtration level refers to a classified multi-stage membrane assembly level that is divided according to wastewater treatment requirements, adapts to pollutant removal requirements, and guarantees that effluent meets standards.

5. A multi-stage membrane separation-based advanced chemical wastewater treatment system for performing a multi-stage membrane separation-based advanced chemical wastewater treatment method according to any one of claims 1 to 4, characterized by, The chemical wastewater advanced treatment system comprises: A flushing adjustment module is used for filtering and adjusting water quality of the chemical wastewater by using the wastewater pretreatment system to generate stable water flow information, and a backwash medium is injected into a membrane separation valve port of a wastewater inflow section; A backflow filtering module is configured to collect the stable water flow information and the pollution load data of the backwashing medium under a preset membrane flux, and determine the gradient backflow amount in the current membrane separation process by the pollution load data and the real-time pressure index during the membrane separation filtering; A filtering screening module is configured to determine the separation interference deviation when the pollutants in the chemical wastewater dynamically coexist, predict the steady filtering period of the membrane separation filtering level in the constant flux change according to the separation interference deviation, and synchronously screen the steady filtering period to obtain the full-flow separation limit of the multi-stage membrane separation unit in different pollution loads; A separation triggering module is configured to generate the separation control index when the equivalent flux produces a peak value offset according to the gradient backflow amount and the full-flow separation limit, and then trigger the starting point of the multi-stage membrane separation wastewater treatment process according to the separation control index.

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