Wastewater recycling method

Abstract

The invention relates to the technical field of sewage treatment, in particular to a wastewater recycling method which comprises the following steps: cyanide breaking: in an alkaline environment, adding an oxidizing agent to oxidize wastewater; first monitoring: monitoring the oxidation reduction potential and the free cyanide concentration in real time, and adjusting the adding proportion of sodium hypochlorite based on the ORP dynamic range and the cyanide concentration attenuation rate; precipitation: adding hydroxide, and carrying out heavy metal precipitation; second monitoring: acquiring component information in the sewage, and adding sodium hydroxide and sodium sulfide in a gradient compensation manner after triggering judgment; membrane treatment: performing filtration and degradation treatment through a biological membrane; 3, monitoring: dynamically adjusting the aeration intensity and the backwashing period according to the coupling relationship between the pressure difference slope and the sludge concentration; and 4, monitoring: calculating a process capability index, judging whether the process capability index is smaller than a third threshold value, and if so, adjusting the sodium sulfide dosage in the precipitation stage. The method has the effect of reducing resource waste in the wastewater treatment process.

Description

Technical Field

[0001] The present application relates to the technical field of sewage treatment, and in particular to a wastewater recycling method. Background Art

[0002] Currently, recycling industrial wastewater is a key measure to alleviate water shortages and reduce environmental pollution. Electroplating wastewater, in particular, is significantly more difficult to treat than conventional wastewater because it contains toxic substances such as cyanide, heavy metals (such as copper, nickel, and chromium), and complexes. Traditional electroplating wastewater treatment processes typically utilize a multi-stage process of "cyanide destruction oxidation—chemical precipitation—membrane separation." However, in practice, this process faces significant fluctuations in water quality and complex pollutant forms.

[0003] In the existing technology, specific operating parameters are often set and a certain amount of materials are directly added to carry out multi-stage wastewater treatment. However, each treatment unit independently detects key parameters, and there is a lack of correlation analysis between cyanide conversion rate, heavy metal precipitation efficiency and membrane flux attenuation. This makes it difficult to achieve coordinated regulation of the entire process, resulting in waste of resources. Summary of the Invention

[0004] In order to reduce resource waste in the wastewater treatment process, the present application provides a wastewater recycling method.

[0005] This application provides a wastewater recycling method, which adopts the following technical solution: A wastewater recycling method comprises the following steps: Cyanide destruction: In an alkaline environment, sodium hypochlorite is added as an oxidant to oxidize the wastewater; First monitoring: Real-time monitoring of the redox potential and free cyanide concentration during the cyanide destruction stage, and adjustment of the sodium hypochlorite dosage ratio based on the ORP dynamic range and cyanide concentration decay rate; Precipitation: Add hydroxide to precipitate heavy metals; Second monitoring: Synchronously collect the pH value, copper ion concentration, and nickel ion concentration during the precipitation stage. When the pH exceeds the first set range or the heavy metal concentration deviates from the second set range, the gradient compensation addition of sodium hydroxide and sodium sulfide is triggered; Membrane treatment: Filtration and degradation through biofilm to remove debris and organic matter; Third monitoring: Continuously track the transmembrane pressure difference change rate and sludge concentration during the membrane treatment stage, and dynamically adjust the aeration intensity and backwash cycle based on the coupling relationship between the pressure difference slope and sludge concentration; Fourth monitoring: obtain monitoring data, calculate the process capability index, and determine whether it is less than the third threshold. If so, perform process parameter compensation: adjust the amount of sodium sulfide added in the precipitation stage.

[0006] By adopting the above technical solution, during the cyanide destruction stage, an oxidant (such as sodium hypochlorite) is added under alkaline conditions to destroy the cyanide structure; real-time feedback data is provided by the ORP sensor and the cyanide concentration detector to dynamically adjust the oxidant dosage; during the precipitation stage, hydroxide (such as NaOH) is added to precipitate heavy metals; a pH meter and a heavy metal ion sensor are used to trigger gradient compensation addition (such as the addition of sodium sulfide); a biofilm is used to filter organic matter, and the aeration and backwash frequency is adjusted by monitoring the transmembrane pressure difference; and the process capability index (Cpk) is calculated to determine whether process compensation is required.

[0007] Traditional methods rely on fixed dosages. In the cyanide breaking stage, this application uses dual-factor feedback of ORP and cyanide concentration to achieve on-demand dosage of sodium hypochlorite, reducing the waste caused by fixed dosage; the oxidation endpoint is predicted by the cyanide concentration decay rate to avoid excessive oxidation and shorten the treatment time; in the precipitation stage, compensation dosage is made by linking pH and heavy metal concentration (such as automatic addition of NaOH when pH exceeds the standard, and addition of sodium sulfide when heavy metal exceeds the standard) to ensure stable precipitation efficiency and reduce residual heavy metal concentration; in the membrane treatment stage, the transmembrane pressure difference change rate and sludge concentration are coupled and analyzed to dynamically adjust the aeration intensity to reduce energy consumption and dynamically adjust the backwash cycle to reduce the membrane fouling rate; the fourth monitoring integrates cyanide, heavy metal and membrane fouling data through the process capability index (Cpk), and evaluates the efficiency of the entire process, breaking through the traditional single parameter compliance model.

[0008] Through multi-parameter linkage feedback, the barriers of independent control of each unit are broken, and a positive transmission chain of cyanide conversion rate, heavy metal precipitation efficiency, and membrane flux is achieved; through multi-stage real-time monitoring and dynamic adjustment, the processing accuracy is improved, and the ORP and cyanide concentration are coordinated to reduce oxidant waste and reduce resource waste; the pH and heavy metal joint control improves precipitation efficiency, and the dynamic management of transmembrane pressure difference extends membrane life.

[0009] Optionally, the process capability index , calculated using the following parameters: ; in: is the mean cyanide oxidation rate, is the standard deviation of the cyanide oxidation rate, ; ; The upper and lower limits of heavy metal removal rate; is the rate of change of transmembrane pressure difference; is the membrane fouling correction factor, and its value range is 0.1~0.3.

[0010] By adopting the above technical solution, Cpk is calculated by formula, combined with the mean, standard deviation and transmembrane pressure difference change rate of cyanide oxidation rate for dynamic correction; membrane pollution correction factor is introduced to quantify the impact of membrane pollution on the overall process, for example: when When it increases, the Cpk weight is automatically reduced, and the membrane protection strategy is triggered first, reducing the problem of traditional Cpk calculation ignoring the cross-stage coupling effect; the heavy metal removal rate and membrane pressure difference change rate are included in the same evaluation system to improve system stability.

[0011] Optionally, in the fourth detection step, the process parameter compensation further includes: During the cyanide destruction stage, the ORP is increased and maintained for 20 minutes, and the sodium hypochlorite dosage coefficient is simultaneously increased; during the precipitation stage, the sodium sulfide dosage is increased, and the aeration intensity is increased to k times the baseline value in conjunction with the third monitoring step; during the membrane treatment stage, the backwash frequency is increased and the flushing time is increased.

[0012] By adopting the above technical solution, the ORP is increased and maintained for 20 minutes, and the sodium hypochlorite addition coefficient is simultaneously increased to cope with the sudden cyanide load shock, thereby improving the stability of the oxidation rate; the sodium sulfide dosage is increased and the aeration intensity is linked to increase, and floc formation is promoted through aeration, which accelerates the precipitation of heavy metals; the backwash frequency and time are dynamically adjusted, and the flushing intensity is matched according to the sludge concentration, thereby improving the membrane flux recovery rate; the traditional process has a single compensation (such as only adjusting the pH), while this method quickly restores the system efficiency through cross-stage linkage (such as the coordination of aeration intensity and backwashing), forming a compensation closed loop.

[0013] Optionally, it further includes a fifth monitoring step, a first standard judgment step, and a second standard judgment step. Fifth monitoring: Real-time detection of reverse osmosis product water conductivity and hexavalent chromium concentration; First standard judgment: if the conductivity of the reverse osmosis product water is greater than the second threshold, the statistical step is executed; Statistics: When the conductivity exceeds the standard for three consecutive times, the concentrated water return ratio is increased and the membrane system citric acid-EDTA composite cleaning program is triggered; Second standard judgment: If the hexavalent chromium concentration is greater than the third threshold, the ORP threshold of the first monitoring step will be raised and the amount of sodium hypochlorite added will be increased.

[0014] By adopting the above technical solution, three consecutive times of exceeding the standard trigger an increase in the proportion of concentrated water reflux, reducing the risk of scaling on the membrane surface, and through citric acid-EDTA composite cleaning, the membrane flux recovery efficiency is improved, so that the membrane filtration effect can be maintained; when the hexavalent chromium exceeds the standard, the ORP threshold of the cyanide destruction stage is linked to increase to ensure the complete oxidation of cyanide and block the hexavalent chromium generation path; in traditional processes, water production exceeding the standard only triggers terminal treatment (such as repeated filtration), while this solution eliminates the source of pollution through reverse tracing and regulation (such as adjusting upstream cyanide destruction parameters); and the traditional method passively cleans the membrane after contamination, while this method intervenes in advance by counting the number of times the standard is exceeded, combined with citric acid-EDTA composite cleaning to reduce the risk of membrane clogging.

[0015] Optionally, a monitoring and adjustment step is also included; Monitoring and adjustment: Build a dynamic weight allocation model to optimize the control priority of each monitoring stage: the weight of the cyanide breaking stage , based on the cyanide toxicity level; precipitation stage weight , based on the risk setting of heavy metal exceeding the standard; the weight of membrane treatment stage , set based on the membrane flux attenuation rate; when the weight of any stage triggers the weight threshold, the weight of the precipitation stage and the membrane treatment stage is automatically reduced to centrally regulate resources.

[0016] By adopting the above technical solution, a dynamic weight allocation model is constructed to allocate control priorities based on toxicity, heavy metal risk, and membrane flux attenuation, and automatically reduce the weights of other stages when the threshold is triggered. Traditional equal control is prone to waste of resources. This method dynamically adjusts weights to concentrate resources on high-risk links (such as cyanide toxicity priority), thereby reducing costs while maintaining efficiency.

[0017] Optionally, after the monitoring and adjustment step, a joint adjustment step is further included; Joint adjustment: The process capability index is used to participate in the weight adjustment within the weight distribution model. When the weight of cyanide breaking stage is Forced to increase to 0.7, and freeze the membrane processing stage control; when When the weight of the precipitation stage Lower it to 0.1, giving priority to optimizing membrane treatment energy consumption.

[0018] By adopting the above technical solution and linking Cpk with weights, core links (such as cyanide breaking) are prioritized during system fluctuations, and energy consumption is optimized after stabilization. Traditional methods lack this flexible strategy.

[0019] Optionally, sodium hypochlorite is added in a slow-release manner by: loading sodium hypochlorite onto a porous diatomaceous earth carrier and adding the sodium hypochlorite to the wastewater in the cyanide destruction stage; arranging magnetic particles on the outside of the porous diatomaceous earth carrier, applying a magnetic field around the wastewater during addition, and adjusting the distribution of the porous diatomaceous earth carrier; and controlling the carrier disintegration rate to extend the release time of the sodium hypochlorite.

[0020] By adopting the above technical solution, sodium hypochlorite is loaded on porous diatomaceous earth, which prolongs the release time and can reduce the OPR fluctuation amplitude, reduce interference with the monitoring step, reduce local excessive concentration or incomplete oxidation, and improve the utilization rate of the oxidant; and by coating the magnetic particles with the porous diatomaceous earth carrier and applying the magnetic field, the oxidant can be uniformly distributed or concentrated in the wastewater through the intervention of the magnetic field, which facilitates the reaction, and the magnetic field can be adjusted according to the distribution of sewage substances so that the distribution of the oxidant is conducive to the reaction.

[0021] Optionally, the timing of oxidant addition and ORP feedback is controlled: 60% of the total amount of sodium hypochlorite is initially added, and the remaining 40% is added in three additional times according to the ORP change; when the ORP does not reach the fourth threshold within 5 minutes, the emergency addition mode is triggered and the remaining amount is added in one go.

[0022] By adopting the above technical solution, the OPR fluctuation amplitude can be reduced, the interference with the monitoring step can be reduced, the local concentration is too high or the oxidation is incomplete, the utilization rate of the oxidant is improved through slow release and phased feedback, and the reagent can be saved.

[0023] Optionally, the first monitoring step also includes dynamically switching the oxidant type by online monitoring of the molar ratio of the intermediate product cyanate to the final product carbon dioxide: when the proportion of cyanate exceeds half, the porous diatomaceous earth carrier is aggregated by changing the magnetic field, and ozone is added to enhance the oxidation chain reaction. The ozone is injected directly into the carrier aggregation area using a gas-liquid mixture spray.

[0024] By adopting the above technical solution, the molar ratio of cyanate to CO2 is monitored online, and ozone is added to enhance oxidation when cyanate is greater than 50%. Traditional oxidation may stay at the intermediate product (cyanate), avoiding the toxic impact of cyanate residue on subsequent processes. The addition of ozone promotes the complete reaction and improves the cyanide removal rate. Sodium hypochlorite is loaded with diatomaceous earth for slow release, and the release time is extended. Combined with the initial 60% addition and the remaining batch addition strategy, it maintains ORP stability and avoids excessive waste of oxidant. Combined with real-time monitoring of the cyanate / CO2 molar ratio, ozone is added when the oxidation path is blocked (cyanate>50%) to promote complete mineralization of cyanide and eliminate the toxic interference of intermediate products on subsequent processes (such as cyanate inhibiting biofilm activity). The slow-release technology ensures normal operation efficiency, and ozone is added to cope with complex water quality mutations. While the cyanide removal rate is improved, the cost of oxidant is reduced. Complete oxidation reduces cyanate residue, avoids biofilm poisoning in the subsequent membrane treatment stage, improves sludge activity, and reduces the membrane flux decay rate.

[0025] By coating the magnetic particles with porous diatomaceous earth carriers and applying a magnetic field, the oxidant can be evenly distributed or concentrated in the wastewater through magnetic field intervention, which facilitates the reaction. When online monitoring detects that the proportion of cyanate is too high, the carriers are aggregated through the magnetic field to increase the local catalyst concentration and improve the ozone utilization efficiency. Ozone is directly injected into the carrier aggregation area using a gas-liquid mixed injection, forming a chain reinforcement of "magnetic field guidance-catalyst enrichment-ozone efficient reaction". The porous diatomaceous earth carrier and the magnetic particle coating facilitate the adsorption of heavy metal ions and the purification and precipitation of wastewater.

[0026] Optionally, in the joint adjustment step, a membrane fouling risk index is introduced ;when When it is greater than the critical value, cross-stage coordinated regulation is triggered: the ORP target value of the cyanide destruction stage is increased, and the pH fluctuation amplitude of the precipitation stage is reduced.

[0027] By adopting the above technical solution, traditional single-stage control is prone to lose sight of one thing while focusing on another. This method reduces colloid blocking of membrane pores by adjusting the cyanide destruction ORP and precipitation pH, thereby reducing membrane pollution at the source, reducing subsequent membrane pollution load, and extending membrane life.

[0028] Optionally, a conductivity exceeding standard trend prediction algorithm is introduced into the statistical step, and a conductivity change rate model is established based on time series analysis. When it is predicted that the probability of exceeding the standard within the next 2 hours is greater than the fifth threshold, the concentrated water return ratio increasing mode is started in advance, and a porous diatomaceous earth carrier with magnetic particles is injected in the form of a scale inhibitor to delay membrane scaling, and the scale inhibitor is accumulated at the membrane by changing the application position of the magnetic field.

[0029] By adopting the above technical solution, the probability of conductivity exceeding the standard in the next 2 hours is predicted based on time series analysis. When the probability is >70%, the concentrated water return ratio is increased in advance to slow down the scaling rate, add scale inhibitors, form a protective film, and reduce the scaling risk. Traditional membrane cleaning relies on post-event response. This solution reduces the number of unplanned shutdowns and the cleaning frequency through predictive maintenance. The pH and heavy metal concentration are linked to trigger gradient compensation addition (sodium sulfide + aeration enhancement). Combined with the traceability of hexavalent chromium exceeding the standard to the cyanide destruction stage, the ORP is increased to ensure the stability of heavy metal precipitation efficiency. The membrane fouling index triggers the ORP increase in the front section to reduce the organic load. The pH fluctuation limit during precipitation (±0.3) reduces colloid blockage; the conductivity prediction model starts the scale inhibitor addition and concentrated water return in advance to delay the scaling rate; the back-end membrane pollution load is reduced through front-end process optimization (ORP / pH control), and the back-end predictive maintenance (scale inhibitors and cleaning) extends the membrane life, reducing the overall membrane system operating cost; aeration promotes floc formation, accelerates the precipitation rate, and traceability regulation (blocking the hexavalent chromium generation path) greatly reduces the fluctuation of heavy metal removal rate; the magnetic field fixes the carrier near the membrane surface, slowly releases the scale inhibitor, and continuously inhibits scaling (extending the membrane cleaning cycle).

[0030] In summary, this application includes at least one of the following beneficial technical effects: 1. Through multi-parameter linkage feedback, the barriers of independent control of each unit are broken down, achieving a positive transmission chain of cyanide conversion rate, heavy metal precipitation efficiency, and membrane flux. Through multi-stage real-time monitoring and dynamic adjustment, treatment accuracy is improved. The ORP and cyanide concentration are adjusted together to reduce oxidant waste and reduce resource waste. The pH and heavy metal combined control improves precipitation efficiency, and the dynamic management of transmembrane pressure difference extends membrane life. 2. Sodium hypochlorite is loaded on porous diatomaceous earth to extend the release time. At the same time, it can reduce the OPR fluctuation amplitude, reduce interference with the monitoring step, reduce local excessive concentration or incomplete oxidation, and improve the utilization rate of the oxidant. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a flow chart of the wastewater recycling method in Example 1 of the present application; Figure 2 This is a flow chart of the wastewater recycling method in Example 2 of the present application. DETAILED DESCRIPTION

[0032] The following combination Figures 1 to 2 This application is described in further detail.

[0033] This embodiment discloses a wastewater recycling method.

[0034] Example 1: Reference Figure 1 , a wastewater recycling method comprising the following steps: Cyanide destruction: In an alkaline environment, add oxidants to oxidize the wastewater; Sodium hypochlorite is added in a slow-release form by loading the sodium hypochlorite onto a porous diatomaceous earth carrier and adding it to the wastewater in the cyanide destruction stage, controlling the carrier disintegration rate to extend the release time of the sodium hypochlorite.

[0035] First monitoring: Real-time monitoring of the redox potential and free cyanide concentration during the cyanide-breaking oxidation stage, and adjustment of the sodium hypochlorite dosage ratio based on the ORP dynamic range and cyanide concentration decay rate; Timing control of oxidant addition and ORP feedback: 60% of the total amount of sodium hypochlorite is initially added, and the remaining 40% is added in three additional times according to ORP changes; when the ORP does not reach the fourth threshold within 5 minutes, the emergency dosing mode is triggered and the remaining amount is added in one go.

[0036] Specifically, alkaline environment adjustment: add NaOH solution to the cyanide-containing wastewater to stabilize the pH at 10.5-11.5; slow-release sodium hypochlorite addition: adsorb 15% sodium hypochlorite solution on a porous diatomaceous earth carrier (pore size 50-100 μm, pre-treated with 5% dilute hydrochloric acid to enhance the loading rate), and when adding sodium hypochlorite during the cyanide destruction stage, add 60% of the total amount (according to CN - Initial concentration was calculated as CN - :ClO - =1:8 mass ratio calculation), an ORP sensor collects redox potential in real time (target range: +450~+650mV); a cyanide ion selective electrode monitors free cyanide concentration (target: <0.2mg / L); the remaining 40% is added in three doses (each with an interval of 5 minutes). If the ORP does not reach +600mV (the fourth threshold) within 5 minutes, the remaining amount is added in one emergency dose.

[0037] Precipitation: Add hydroxide to precipitate heavy metals; Second monitoring: Synchronously collect the pH value, copper ion concentration, and nickel ion concentration during the chemical precipitation stage. When the pH exceeds the first set range or the heavy metal concentration deviates from the second set range, the gradient compensation addition of sodium hydroxide and sodium sulfide is triggered; Specifically, Ca(OH)2 was added to adjust the pH to 9.0-9.5 (the first setting range), and then 10% NaOH solution was added to maintain the pH. 0.05 mol / L sodium sulfide (Na2S) was added simultaneously to generate metal sulfide precipitation. Real-time feedback was obtained through the pH online instrument. During the precipitation stage, wastewater samples were extracted and the copper / nickel ion concentration (target: Cu) was detected online by atomic absorption spectrometry (AAS). 2+ <0.5mg / L, Ni 2+ <0.1mg / L).

[0038] If pH < 9.0, automatically add NaOH solution (flow rate increased by 20%); if Cu 2+ or Ni 2+ If the standard is exceeded (deviates from the second set range), the graded addition of sodium sulfide is triggered: 50% of the design amount is added for the first time, and the remaining amount is added for the second time after 10 minutes.

[0039] Membrane treatment: Filtration and degradation through biofilm to remove debris and organic matter; Third monitoring: Continuously track the transmembrane pressure difference change rate and sludge concentration during the membrane treatment stage, and dynamically adjust the aeration intensity and backwash cycle based on the coupling relationship between the pressure difference slope and sludge concentration; Fourth monitoring: acquiring and monitoring point data, calculating the process capability index, and determining whether it is less than the third threshold. If so, performing process parameter compensation; Specifically, wastewater enters a submerged flat membrane bioreactor (MBR, material: PVDF, pore size 0.1 μm), where organic matter is degraded by aerobic bacteria; a transmembrane pressure (TMP) sensor records ΔP / Δt (pressure change rate); and an optical probe is used to monitor the sludge concentration (MLSS) in real time (target: 8000~12000 mg / L).

[0040] When ΔP / Δt>0.5 kPa / min and MLSS>10000 mg / L, the aeration intensity is increased from the baseline value of 0.8 m³ / (m²·h) to 1.2 times (k=1.2); the backwash cycle is shortened from 30 minutes / time to 20 minutes / time (backwash water: filtered clean water, duration 60 seconds).

[0041] Data source: The integrated DCS system collects data from each monitoring point (cyanide oxidation rate, heavy metal removal rate, TMP slope); The process capability index , calculated using the following parameters: ; in: is the mean cyanide oxidation rate, is the standard deviation of the cyanide oxidation rate, ; ; The upper and lower limits of heavy metal removal rate are USL=99.5% and LSL=98.0%; is the rate of change of transmembrane pressure difference (kPa / min); is the membrane fouling correction factor, ranging from 0.1 to 0.3, and is 0.2 in this embodiment.

[0042] Process parameter compensation also includes: increasing the ORP during the cyanide destruction stage and maintaining it for 20 minutes, and simultaneously increasing the sodium hypochlorite dosage coefficient; increasing the sodium sulfide dosage during the precipitation stage, and linking the third monitoring step to increase the aeration intensity to k times the baseline value; and increasing the backwash frequency and flushing time during the membrane treatment stage.

[0043] Specifically, when Cpk < 1.33 (the third threshold), the following linkage compensation is performed: Enhanced cyanide destruction: ORP is increased to +650mV and maintained for 20 minutes, and the sodium hypochlorite dosage coefficient is increased by 1.3 times; enhanced precipitation: the sodium sulfide dosage is increased by 30%, and the MBR aeration intensity is linked to increase to 1.5 times the baseline value (k=1.0~1.5); enhanced membrane maintenance: backwash frequency is increased by 50%, and the single flushing time is extended to 90 seconds.

[0044] This embodiment prolongs the oxidant action time and reduces the dosage of the reagent through carrier slow release and magnetic field distribution control. A multi-stage dynamic feedback mechanism (ORP / heavy metal / TMP coupling regulation) ensures system stability. Real-time compensation of the Cpk index improves the overall compliance rate, making it suitable for the treatment of high-cyanide and high-heavy metal wastewater in industries such as electroplating and metallurgy.

[0045] Example 2: This example differs from Example 1 in that sodium hypochlorite is added using a porous diatomaceous earth carrier coated with magnetic particles. A magnetic field is applied around the wastewater during addition to adjust the distribution of the porous diatomaceous earth carrier coated with magnetic particles. Specifically, raw material pretreatment: diatomaceous earth raw materials with a silica content of ≥85% and a particle size of 50-100 μm are selected and vibrated to remove impurities through 200 mesh screening; Pickling and pore expansion: put the screened diatomaceous earth into an acid-resistant reactor (lined with PTFE material), and add 5% industrial-grade dilute hydrochloric acid solution at a liquid-to-solid ratio of 5:1; Temperature and time control: Maintain the temperature at 40±2°C and precisely control the temperature by circulating hot water in the jacket; mechanical stirring rate is 120 rpm, and the reaction is continued for 2 hours.

[0046] Washing and drying: After the reaction is completed, wash repeatedly with deionized water until neutral (pH = 6.5 ~ 7.0); dry with hot air at 110 ° C for 30 minutes (belt dryer) to obtain expanded pore diatomite with a specific surface area of ​​≥ 25m² / g.

[0047] Environmental requirements: Closed ventilation system (to prevent HCl volatilization), temperature fluctuation ≤±2℃.

[0048] Magnetic Fe3O4 particle coating: Solution preparation: Under nitrogen protection, press Fe 2+ :Fe 3+ =1:2 molar ratio of ferrous chloride and ferric chloride dissolved in deionized water; Carrier suspension: Disperse the acid-washed diatomaceous earth in water at a ratio of 1:10 (w / v) and subject to high-speed shearing at 2000 rpm for 10 minutes to form a uniform suspension; Co-precipitation reaction: The suspension was transferred to a thermostatic reactor (PTFE-lined) and heated to 60±1°C. Ammonia water was added dropwise until the pH reached 10.5, and 0.5 wt% sodium oleate was added as a dispersant. The reaction was continued at a constant temperature for 45 minutes to complete the deposition of Fe3O4 on the diatomite surface. Magnetic separation and cleaning: Magnetic separation is performed using a 0.5T permanent magnet, and the product is rinsed three times with deionized water to remove free ions. Environmental requirements: Nitrogen protection is used throughout the process to prevent oxidation. Temperature deviations greater than ±1°C will cause particle agglomeration or crystal defects.

[0049] Sodium hypochlorite loading: Solution preparation: Prepare a sodium hypochlorite solution (industrial grade) with a 15% effective chlorine content under light-proof conditions; Vacuum negative pressure loading: Place the magnetic diatomaceous earth carrier in a rotary evaporator and evacuate to -0.08 MPa; inject the sodium hypochlorite solution and immerse for 30 minutes; control the jacket cooling water circulation temperature to ≤30°C.

[0050] Low-temperature drying: The loaded wet carrier is transferred to a nitrogen fluidized bed (oxygen content <5%) and dried at 35°C for 20 minutes. Environmental requirements: Strictly avoid light. Temperatures > 30°C will accelerate the decomposition of sodium hypochlorite (2NaClO → 2NaCl + O2↑).

[0051] Sodium alginate cross-linking controls disintegration: Cross-linker spraying: Place the sodium hypochlorite-loaded carrier in a fluidized bed coater and spray a 2% sodium alginate solution at a flow rate of 5 L / min (inlet air temperature 40°C). Two-step calcification fixation: Step 1: Spray a 0.1 mol / L calcium lactate solution to trigger surface cross-linking. Step 2: Curing at room temperature (25°C) for 30 minutes, with relative humidity controlled at 50 ± 5%.

[0052] Disintegration test: The finished product is tested in 30°C water, and the sodium hypochlorite release time is 35±2 minutes (USP disintegration apparatus).

[0053] Specifically, after the magnetic field is introduced, the magnetic field is applied intermittently, and OPR detection is performed in the gaps between the application of the magnetic field. The OPR electrode is processed, a 200nm silicon nitride (Si3N4) coating is sputtered on the surface of the Pt electrode, and in the gaps between the application of the magnetic field, ultrasonic cleaning is used to clean the magnetic particles adsorbed on the electrode surface. The ultrasonic cleaning module can be used as follows: frequency: 40kHz, power density 0.5W / cm²; trigger logic: pulse operation for 10 seconds after each magnetic stop (to remove adsorbed particles); or a pneumatic scrubbing device can be used: N2 bubbles (flow rate 2L / min) are introduced every 4 hours to scrub the electrode surface.

[0054] Reference Figure 2In other embodiments, it further includes a fifth monitoring step, a first standard judgment step, and a second standard judgment step. Fifth monitoring: Real-time detection of reverse osmosis product water conductivity and hexavalent chromium concentration; First standard judgment: if the conductivity of the reverse osmosis product water is greater than the second threshold, the statistical step is executed; Statistics: When the conductivity exceeds the standard for three consecutive times, the brine return ratio is increased and the membrane system citric acid-EDTA composite cleaning program is triggered; the conductivity exceeding standard trend prediction algorithm is introduced into the statistical step, and the conductivity change rate model is established based on time series analysis. When the probability of exceeding the standard within the next two hours is predicted to be greater than the fifth threshold, the brine return ratio increasing mode is started in advance, and a porous diatomaceous earth carrier with magnetic particles is injected to load the scale inhibitor to delay membrane scaling, and the scale inhibitor is accumulated at the membrane by changing the application position of the magnetic field.

[0055] Specifically, data preprocessing includes taking the conductivity data of the most recent two hours with a sliding window width of 10 minutes and performing wavelet transform denoising (db4 wavelet basis, 3-layer decomposition). Based on the above data, a prediction model is constructed. When the predicted probability of exceeding the standard is greater than 85% (the fifth threshold), the concentrated water return ratio is increased in a gradient from 20% to 25% to 30% (adjusted every 30 minutes). Scale inhibitors are injected, and the scale inhibitors can be injected directly without applying a magnetic field. In other embodiments, the scale inhibitor can be applied via a carrier, and the scale inhibitor carrier can be a carrier prepared in the sodium hypochlorite addition step, which is added by adsorption. Alternatively, magnetic powder and scale inhibitor can be mixed and added before applying a magnetic field.

[0056] Second standard judgment: If the hexavalent chromium concentration is greater than the third threshold, the ORP threshold of the first monitoring will be raised and the amount of sodium hypochlorite added will be increased.

[0057] Specifically, the treatment process for excessive hexavalent chromium: When [Cr 6+ ]>0.05mg / L: ORP set value is increased from 650mV to 750mV (oxidation-reduction potential), and the sodium hypochlorite dosage is increased by the following formula: , K=1.2 (empirical coefficient), .

[0058] Linked first monitoring: ORP threshold in cyanide oxidation stage is simultaneously increased to 800mV It also includes monitoring and adjustment steps; Monitoring and adjustment: Build a dynamic weight allocation model to optimize the control priority of each monitoring stage: the weight of the cyanide breaking stage , based on the cyanide toxicity level; precipitation stage weight , based on the risk setting of heavy metal exceeding the standard; the weight of membrane treatment stage , set based on the membrane flux attenuation rate; when the weight of any stage triggers the threshold, the weights of other stages will be automatically reduced by 5%~10% to centrally regulate resources.

[0059] Specifically, the weight distribution matrix is as follows: in the cyanide destruction stage, W1=0.4~0.6. When the cyanide concentration is greater than 1.0 mg / L (emergency threshold), the adjustment ratio is: 1.5×reference value (initial value of the current stage).

[0060] Precipitation stage W2=0.2~0.3, Zn 2+ / Cu 2+ When the exceedance rate is greater than 15%, the adjustment ratio is: 1.2×reference value; when W3=0.1~0.2 in the membrane treatment stage and the membrane flux attenuation is greater than 10L / (m²·h), the adjustment ratio is: 0.8×reference value.

[0061] Dynamic adjustment rules: When W1 is triggered: automatically reduce W2 / W3 to 0.15 / 0.05.

[0062] After the monitoring and adjustment step, a joint adjustment step is also included; Joint adjustment: The process capability index is used to participate in the weight adjustment within the weight distribution model. When the weight of cyanide breaking stage is Forced to increase to 0.7, and freeze the membrane processing stage control; when When the weight of the precipitation stage When Cpk is lowered to 0.1, the membrane treatment energy consumption is prioritized. When Cpk>1.5, the membrane system switches to low-frequency mode: the high-pressure pump frequency is reduced from 50Hz to 45Hz, and the concentrate reflux ratio is reduced from 25% to 20%.

[0063] For example, scenario simulation: handling of continuous conductivity exceeding the standard event, 08:00: conductivity exceeded the standard for the first time to 52μS / cm (<3 times, triggering prediction); the algorithm predicted that the probability of exceeding the standard at 09:30 reached 90%, the concentrate return ratio was increased from 25% to 30%, 50mg / L of magnetic scale inhibitor carrier was injected, and the electromagnet formed a 0.3T gradient magnetic field on the membrane surface. At 09:20, the measured conductivity stabilized at 48μS / cm (to avoid aggravation of membrane pollution).

[0064] In other embodiments, the first monitoring step also includes dynamically switching the oxidant type by online monitoring of the molar ratio of the intermediate product cyanate to the final product carbon dioxide; when the proportion of cyanate exceeds half, the porous diatomaceous earth carrier is aggregated by changing the magnetic field, and ozone is added to enhance the oxidation chain reaction. The ozone is directly injected into the carrier aggregation area by gas-liquid mixed injection.

[0065] Specifically, when the proportion of cyanate is greater than 50%, it is determined that the intermediate product has accumulated excessively, and ozone is introduced, and ozone injection is strengthened. The gas-liquid mixed injection system: an ozone generator produces ozone, and a Venturi ejector and a static mixer are used to spray ozone by positioning the injection head at the center of the magnetic field, and the diameter of the ozone microbubbles is ≤50μm.

[0066] For example, in a cyanide wastewater treatment plant (flow rate of 50 m³ / h), the initial conditions were: ORP = 650 mV, sodium hypochlorite dosage 120 mg / L, and R = 0.62 (lasting 6 minutes). An electromagnet array induced a 0.4 T magnetic field in reaction zone A3, directing the aggregation of diatomaceous earth carrier (100 mg / L). The ozone generator was activated, and the dosage was switched to 300 mg / L. After 15 minutes, the R value dropped to 0.09, and the sodium hypochlorite dosage was automatically reduced to 80 mg / L. In other embodiments, when magnetic carriers are not used, multiple nozzles are installed at the bottom, and ozone is added by aeration.

[0067] In other embodiments, a membrane fouling risk index is introduced in the combined adjustment step. ;when When it is greater than the critical value, cross-stage coordinated regulation is triggered: the ORP target value of the cyanide destruction stage is increased, and the pH fluctuation amplitude of the precipitation stage is reduced.

[0068] Specifically, the critical value is 0.35, when The target ORP value in the cyanide destruction stage is increased by 50-100mV (baseline 650mV); the pH fluctuation range in the precipitation stage is narrowed from ±0.5 to ±0.2 (set point pH=9.0); oxidant compensation: sodium hypochlorite increment: ; Adding buffer increases the flow rate of 0.1 mol / L NaHCO3 solution by 20%.

[0069] For example, taking an electronic wastewater treatment system (membrane area 500m²) as an example: Risk trigger: At 14:30, (critical value 0.35) exceeded the limit continuously for 10 minutes; coordinated response: cyanide destruction stage: ORP target increased from 650mV to 720mV, sodium hypochlorite increased by 18%; precipitation stage: pH control range increased from 8.8-9.2 to 8.9-9.1, NaHCO3 dosage increased by 20%; membrane system: aeration intensity increased from 0.8m³ / (m²·h) to 1.0m³ / (m²·h); at 16:00 down to 0.19, Regression to baseline.

[0070] Over-limit protection: when the voltage is greater than 800mV, emergency injection of dilution water is initiated; pH out-of-control plan: when the pH exceeds the range of 8.5-9.5, the system switches to the spare sedimentation tank.

[0071] This embodiment prolongs the service life of the membrane and reduces the cost of the reagent.

[0072] The above are all preferred embodiments of the present application, and are not intended to limit the scope of protection of the present application. Therefore, any equivalent changes made based on the structure, shape, and principle of the present application should be included in the scope of protection of the present application.

Claims

1. A wastewater recycling method, characterized in that: The following steps are involved: Cyanide destruction: In an alkaline environment, sodium hypochlorite is added as an oxidant to oxidize the wastewater; First monitoring: Real-time monitoring of the redox potential and free cyanide concentration during the cyanide destruction stage, and adjustment of the sodium hypochlorite dosage ratio based on the ORP dynamic range and cyanide concentration decay rate; Precipitation: Add hydroxide to precipitate heavy metals; Second monitoring: Synchronously collect the pH value, copper ion concentration, and nickel ion concentration during the precipitation stage. When the pH exceeds the first set range or the heavy metal concentration deviates from the second set range, the gradient compensation addition of sodium hydroxide and sodium sulfide is triggered; Membrane treatment: Filtration and degradation through biofilm to remove debris and organic matter; Third monitoring: Continuously track the transmembrane pressure difference change rate and sludge concentration during the membrane treatment stage, and dynamically adjust the aeration intensity and backwash cycle based on the coupling relationship between the pressure difference slope and sludge concentration; Fourth monitoring: obtain monitoring data, calculate the process capability index, and determine whether it is less than the third threshold. If so, perform process parameter compensation: adjust the amount of sodium sulfide added in the precipitation stage.

2. The wastewater recycling method according to claim 1, characterized in that: The process capability index , calculated using the following parameters: ； in: is the mean cyanide oxidation rate, is the standard deviation of the cyanide oxidation rate, ; ; The upper and lower limits of heavy metal removal rate; is the rate of change of transmembrane pressure difference; is the membrane fouling correction factor, and its value range is 0.1~0.

3.

3. The wastewater recycling method according to claim 2, characterized in that: In the fourth detection step, the process parameter compensation further includes: During the cyanide destruction stage, the ORP is increased and maintained for 20 minutes, and the sodium hypochlorite dosage coefficient is simultaneously increased; during the precipitation stage, the sodium sulfide dosage is increased, and the aeration intensity is increased to k times the baseline value in conjunction with the third monitoring step; during the membrane treatment stage, the backwash frequency is increased and the flushing time is increased.

4. The wastewater recycling method according to any one of claims 1 to 3, characterized in that: It also includes a fifth monitoring step, a first standard judgment step and a second standard judgment step, Fifth monitoring: Real-time detection of reverse osmosis product water conductivity and hexavalent chromium concentration; First standard judgment: if the conductivity of the reverse osmosis product water is greater than the second threshold, the statistical step is executed; Statistics: When the conductivity exceeds the standard for three consecutive times, the concentrated water return ratio is increased and the membrane system citric acid-EDTA composite cleaning program is triggered; Second standard judgment: If the hexavalent chromium concentration is greater than the third threshold, the ORP threshold of the first monitoring step will be raised and the amount of sodium hypochlorite added will be increased.

5. The wastewater recycling method according to claim 4, characterized in that: It also includes monitoring and adjustment steps; Monitoring and adjustment: Build a dynamic weight allocation model to optimize the control priority of each monitoring stage: the weight of the cyanide breaking stage , based on the cyanide toxicity level; precipitation stage weight , based on the risk setting of heavy metal exceeding the standard; the weight of membrane treatment stage , set based on the membrane flux attenuation rate; when the weight of any stage triggers the weight threshold, the weight of the precipitation stage and the membrane treatment stage is automatically reduced to centrally regulate resources.

6. The wastewater recycling method according to claim 5, characterized in that: After the monitoring and adjustment step, a joint adjustment step is also included; Joint adjustment: The process capability index is used to participate in the weight adjustment within the weight distribution model. When the weight of cyanide breaking stage is Forced to increase to 0.7, and freeze the membrane processing stage control; when When the weight of the precipitation stage Lower it to 0.1, giving priority to optimizing membrane treatment energy consumption.

7. The wastewater recycling method according to claim 4, characterized in that: Sodium hypochlorite is added in a slow-release form, which is achieved by: loading sodium hypochlorite on a porous diatomaceous earth carrier and adding it to the wastewater in the cyanide destruction stage; arranging magnetic particles on the outside of the porous diatomaceous earth carrier, applying a magnetic field around the wastewater during addition, and adjusting the distribution of the porous diatomaceous earth carrier; controlling the carrier disintegration rate to extend the release time of sodium hypochlorite.

8. The wastewater recycling method according to claim 7, characterized in that: Timing control of oxidant addition and ORP feedback: 60% of the total amount of sodium hypochlorite is initially added, and the remaining 40% is added in three additional times according to ORP changes; when the ORP does not reach the fourth threshold within 5 minutes, the emergency dosing mode is triggered and the remaining amount is added in one go.

9. The wastewater recycling method according to claim 7, characterized in that: The first monitoring step also includes dynamically switching the oxidant type by online monitoring of the molar ratio of the intermediate product cyanate to the final product carbon dioxide: when the proportion of cyanate exceeds half, the porous diatomaceous earth carrier is aggregated by changing the magnetic field, and ozone is added to enhance the oxidation chain reaction. The ozone is injected directly into the carrier aggregation area using a gas-liquid mixture injection.

10. The wastewater recycling method according to claim 6, characterized in that: In the joint adjustment step, the membrane fouling risk index is introduced ;when When it is greater than the critical value, cross-stage coordinated regulation is triggered: the ORP target value of the cyanide destruction stage is increased, and the pH fluctuation amplitude of the precipitation stage is reduced.

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