A wastewater recycling method

Abstract

The application relates to the technical field of sewage treatment, in particular to a wastewater recycling method, which comprises the following steps: cyanide breaking: adding an oxidizing agent to wastewater for oxidation in an alkaline environment; first monitoring: monitoring the oxidation-reduction potential and the free cyanide concentration in real time, adjusting the sodium hypochlorite adding ratio based on the ORP dynamic range and the cyanide concentration decay rate; precipitation: adding a hydroxide for heavy metal precipitation; second monitoring: collecting component information in sewage, and gradiently compensating sodium hydroxide and sodium sulfide after triggering judgment; membrane treatment: filtering and degrading treatment through a biological membrane; third monitoring: dynamically adjusting the aeration intensity and the backwashing period according to the coupling relationship between the differential pressure slope and the sludge concentration; and fourth monitoring: calculating the process capability index, and judging whether the process capability index is less than a third threshold value; if yes, the sodium sulfide adding amount in the precipitation stage is adjusted. The application 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

[0002] At present, industrial wastewater recycling is a key measure to alleviate water resource shortage and reduce environmental pollution. The treatment of electroplating wastewater is significantly more difficult than that of conventional wastewater because it contains cyanide, heavy metals (such as copper, nickel, and chromium), and complex compounds. The traditional electroplating wastewater treatment process usually adopts a multi-stage treatment process of "cyanide breaking and oxidation-chemical precipitation-membrane separation". However, it faces problems such as large water quality fluctuations and complex pollutant forms in actual operation.

[0003] In the prior art, specific operation parameters are set, and a certain amount of material is directly added for multi-stage treatment of wastewater. However, each treatment unit independently detects key parameters, lacks correlation analysis of cyanide conversion rate, heavy metal precipitation efficiency, and membrane flux decay, and it is difficult to achieve coordinated regulation and control of the whole process, resulting in resource waste. SUMMARY

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

[0005] The wastewater recycling method provided by the present application adopts the following technical solution:

[0006] A wastewater recycling method comprises the following steps:

[0007] Cyanide breaking: in an alkaline environment, sodium hypochlorite is added as an oxidizing agent to oxidize the wastewater;

[0008] First monitoring: real-time monitoring of the oxidation-reduction potential and free cyanide concentration in the cyanide breaking stage, adjustment of the sodium hypochlorite addition ratio based on the ORP dynamic range and cyanide concentration decay rate;

[0009] Precipitation: adding a hydroxide to precipitate heavy metals;

[0010] Second monitoring: simultaneously collecting the pH value, copper ion concentration, and nickel ion concentration in the precipitation stage, and triggering gradient compensation addition of sodium hydroxide and sodium sulfide when the pH value is outside the first set range or the heavy metal concentration deviates from the second set range value;

[0011] Membrane treatment: filtering and degrading treatment by a biological membrane to remove impurities and organic matter;

[0012] Third monitoring: continuously tracking the transmembrane pressure difference change rate and sludge concentration in the membrane treatment stage, and dynamically adjusting the aeration intensity and backwashing period according to the coupling relationship between the pressure difference slope and the sludge concentration;

[0013] Fourth monitoring: obtaining monitoring data, calculating process capability index, and judging whether it is less than the third threshold value, if so, process parameter compensation is performed: adjusting the sodium sulfide dosage in the precipitation stage.

[0014] By adopting the above technical scheme, in the cyanide breaking stage, an oxidizing agent (such as sodium hypochlorite) is added under alkaline conditions to break the cyanide structure; real-time feedback data is fed back through an ORP sensor and a cyanide concentration detector to dynamically adjust the oxidizing agent dosage; in the precipitation stage, a hydroxide (such as NaOH) is added to precipitate heavy metals; through a pH meter and a heavy metal ion sensor, gradient compensation addition (such as the addition of sodium sulfide) is triggered; organic matter is filtered through a biological membrane, and the aeration and backwashing frequency are adjusted through transmembrane pressure difference monitoring; the process capability index (Cpk) is calculated to determine whether process compensation is needed.

[0015] The traditional method relies on fixed dosage, and in the cyanide breaking stage, the present application realizes on-demand addition of sodium hypochlorite through double-factor feedback of ORP and cyanide concentration, reduces waste caused by fixed addition, predicts the oxidation endpoint through the cyanide concentration decay rate, avoids excessive oxidation, and shortens the treatment time; in the precipitation stage, pH and heavy metal concentration are linked to compensate for the addition (such as automatically adding NaOH when the pH exceeds the standard, and adding sodium sulfide when the 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 to analyze, to dynamically adjust the aeration intensity to reduce energy consumption and dynamically adjust the backwashing period to reduce membrane pollution rate; the fourth monitoring integrates cyanide, heavy metal, and membrane pollution data through the process capability index (Cpk) to evaluate the overall process efficiency, breaking through the traditional single-parameter compliance mode.

[0016] Through multi-parameter linkage feedback, the barriers of independent control of each unit are broken, realizing the positive transmission chain of cyanide conversion rate, heavy metal precipitation efficiency, and membrane flux; through real-time monitoring and dynamic adjustment in multiple stages, the treatment precision is improved, ORP and cyanide concentration linkage reduces oxidizing agent waste and reduces resource waste; pH and heavy metal linkage improve precipitation efficiency, and transmembrane pressure difference dynamic management prolongs membrane life.

[0017] Optionally, the process capability index is calculated by the following parameters:

[0018] ;

[0019] Wherein: is the mean value of the cyanide oxidation rate, is the standard deviation of the cyanide oxidation rate, ; ; is the upper and lower limit of the heavy metal removal rate; is the transmembrane pressure difference change rate; is a membrane pollution correction factor, and the value range is 0.1-0.3.

[0020] By adopting the technical scheme, Cpk is calculated by a formula, and dynamic correction is combined with cyanide oxidation rate average value, standard deviation and transmembrane pressure difference change rate; a membrane pollution correction factor is introduced to quantify the influence of membrane pollution on the overall process, for example: when increases, the Cpk weight is automatically reduced, the membrane protection strategy is preferentially triggered, and the problem that the traditional Cpk calculation ignores the cross-stage coupling effect is reduced; the heavy metal removal rate and the membrane pressure difference change rate are included in the same evaluation system to improve the system stability.

[0021] Optionally, in the fourth monitoring step, the process parameter compensation further includes:

[0022] The ORP is increased and maintained for 20 minutes in the cyanide breaking stage, and the sodium hypochlorite addition ratio is simultaneously increased; the sodium sulfide addition amount is increased in the precipitation stage, and the aeration intensity is increased to k times of the reference value in linkage with the third monitoring step; the backwashing frequency is increased in the membrane treatment stage, and the washing time is increased.

[0023] By adopting the technical scheme, the ORP is increased and maintained for 20 minutes, the sodium hypochlorite addition ratio is simultaneously increased, the sudden cyanide load impact is responded to, the oxidation rate stability is improved; the sodium sulfide addition amount is increased and the aeration intensity is increased in linkage, the flocculation is promoted through aeration, the heavy metal precipitation speed is accelerated; the backwashing frequency and time are dynamically adjusted, the washing intensity is matched according to the sludge concentration, and the membrane flux recovery rate is improved; the traditional process compensation is single (such as adjusting only pH), and the method forms a compensation closed loop by linkage across stages (such as aeration intensity and backwashing cooperation) to quickly restore the system efficiency.

[0024] Optionally, the method further includes a fifth monitoring step, a first standard judgment step and a second standard judgment step,

[0025] Fifth monitoring: real-time detection of membrane treatment product water conductivity and hexavalent chromium concentration;

[0026] First standard judgment: if the membrane treatment product water conductivity is greater than the second threshold value, the statistical step is executed;

[0027] Statistics: when the conductivity exceeds the standard for three times in succession, the concentrated water reflux ratio is increased, and the membrane system citric acid-EDTA composite cleaning program is triggered;

[0028] Second standard judgment: if the hexavalent chromium concentration is greater than 0.05 mg / L, the ORP threshold value of the first monitoring step is increased in linkage, and the sodium hypochlorite addition amount is increased.

[0029] By adopting the above technical scheme, the concentration water reflux ratio is increased for three times when the concentration exceeds the standard, the risk of membrane surface scaling is reduced, the membrane flux recovery efficiency is improved by citric acid-EDTA composite cleaning, and the membrane filtration effect is maintained; when the hexavalent chromium exceeds the standard, the ORP threshold value of the cyanide breaking stage is increased, so as to ensure the complete oxidation of cyanide and block the generation path of hexavalent chromium; in the traditional process, the water production exceeding the standard only triggers the end treatment (such as repeated filtration), and the present scheme controls by reverse tracing (such as adjusting the cyanide breaking parameter in the upstream), and radically solves the pollution source; and the traditional method passively cleans after membrane pollution, the present method intervenes in advance by counting the number of times of exceeding the standard, and reduces the risk of membrane blockage by combining citric acid-EDTA composite cleaning.

[0030] Optionally, the method further comprises a monitoring and adjusting step;

[0031] Monitoring and adjusting: a dynamic weight distribution model is constructed for optimizing the control priority of each monitoring stage: the cyanide breaking stage weight is set based on the toxicity grade of cyanide; the sedimentation stage weight is set based on the risk of heavy metal exceeding the standard; the membrane treatment stage weight is set based on the membrane flux attenuation rate; when the weight threshold of any stage is triggered, the weights of the sedimentation stage and the membrane treatment stage are automatically reduced, and the resources are concentrated for control.

[0032] By adopting the above technical scheme, a dynamic weight distribution model is constructed, the control priority is distributed according to toxicity, heavy metal risk and membrane flux attenuation, and the weight of other stages is automatically reduced when the threshold is triggered; traditional equal control is easy to cause resource waste, and the present method concentrates resources to deal with high-risk links (such as cyanide toxicity priority) by dynamic adjustment of the weight, so that the cost is reduced on the premise of maintaining efficiency.

[0033] Optionally, after the monitoring and adjusting step, a joint adjusting step is further included;

[0034] Joint adjustment: the weight adjustment in the weight distribution model is participated by the process capability index, when , the cyanide breaking stage weight is forcibly increased to 0.7, and the membrane treatment stage control is frozen; when , the sedimentation stage weight is reduced to 0.1, and the membrane treatment energy consumption is preferentially optimized.

[0035] By adopting the above technical scheme, the Cpk and the weight are linked, the core link (such as cyanide breaking) is preferentially ensured when the system fluctuates, and the energy consumption is optimized after stabilization, and the traditional method lacks this flexible strategy.

[0036] Optionally, the sodium hypochlorite is added in a slow-release manner by loading the sodium hypochlorite on a porous diatomite carrier and adding it to the wastewater in the cyanide breaking stage, setting magnetic particles outside the porous diatomite carrier, applying a magnetic field around the wastewater during addition to adjust the distribution of the porous diatomite carrier, and controlling the disintegration rate of the carrier to prolong the release time of the sodium hypochlorite.

[0037] By using the above technical solution, the sodium hypochlorite is loaded on the porous diatomite to prolong the release time, reduce the fluctuation range of the OPR, reduce the interference with the monitoring step, reduce the local over-concentration or incomplete oxidation, and improve the utilization rate of the oxidant. By coating the magnetic particles on the porous diatomite carrier and applying a magnetic field, the oxidant can be uniformly or concentrated in the wastewater through magnetic field intervention, which facilitates the reaction and can adjust the magnetic field according to the distribution of the sewage substances to make the distribution of the oxidant conducive to the reaction.

[0038] Optionally, the timing control of the oxidant addition and the ORP feedback: 60% of the total amount of sodium hypochlorite is initially added, and the remaining 40% is added in three times according to the ORP change; when the ORP does not reach the fourth threshold value within 5 minutes, an emergency addition mode is triggered, and the remaining amount is added at one time.

[0039] By using the above technical solution, the fluctuation range of the OPR can be reduced, the interference with the monitoring step can be reduced, the local over-concentration or incomplete oxidation can be reduced, the utilization rate of the oxidant can be improved through slow release and phased feedback, and the reagent can be saved.

[0040] Optionally, the first monitoring step further includes dynamically switching the type of oxidant by monitoring the molar ratio of the intermediate product cyanate to the final product carbon dioxide online: when the cyanate accounts for more than half, the magnetic field is changed to gather the porous diatomite carrier, and ozone is supplemented to strengthen the oxidation chain reaction. The ozone is sprayed in a gas-liquid mixed manner and directly injected into the carrier gathering area.

[0041] By adopting the above technical solutions, the molar ratio of cyanate to CO2 is monitored online. When cyanate > 50%, ozone is added to enhance oxidation. Traditional oxidation may remain at the intermediate product (cyanate). To avoid the toxic impact of cyanate residue on subsequent processes, ozone addition promotes complete reaction and improves cyanide removal rate. Sodium hypochlorite-supported diatomaceous earth slow release extends the release time. Combined with the strategy of initial 60% addition and subsequent additions, 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 cyanide mineralization and eliminate the toxic interference of intermediate products on subsequent processes (such as cyanate inhibiting biofilm activity). Slow-release technology ensures normal operating efficiency, ozone addition copes with complex water quality changes, and cyanide removal rate is improved while oxidant cost is reduced. Complete oxidation reduces cyanate residue, avoids biofilm poisoning in subsequent membrane treatment stages, improves sludge activity, and reduces membrane flux decay rate.

[0042] Furthermore, by coating magnetic particles with porous diatomaceous earth and applying a magnetic field, the oxidant can be uniformly or concentrated in the wastewater, facilitating the reaction. When online monitoring detects an excessively high cyanate content, the magnetic field aggregates the carrier, increasing the local catalyst concentration and improving ozone utilization efficiency. Ozone is injected directly into the carrier aggregation area using a gas-liquid mixture, forming a chain reinforcement of "magnetic field guidance - catalyst enrichment - high-efficiency ozone reaction". The porous diatomaceous earth carrier and magnetic particle coating facilitate the adsorption of heavy metal ions, promoting wastewater purification and sedimentation.

[0043] Optionally, a membrane fouling risk index may be introduced in the joint adjustment steps. ;when When the value exceeds the critical value, cross-stage synergistic regulation is triggered: the target value of ORP in the cyanide breaking stage is increased, while the pH fluctuation range in the precipitation stage is reduced.

[0044] By adopting the above technical solution, the traditional single-stage control is prone to neglecting some aspects. This method reduces colloidal pore blockage by adjusting the cyanide-breaking ORP and precipitation pH, thereby reducing membrane fouling at the source, reducing subsequent membrane fouling load, and extending membrane life.

[0045] Optionally, the statistical step introduces a conductivity exceeding trend prediction algorithm, establishes a conductivity change rate model based on time series analysis, and when the predicted probability of exceeding the standard is greater than the fifth threshold in the next 2 hours, the concentrate recirculation ratio increasing mode is started in advance, and the scale inhibitor is injected by loading a porous diatomaceous earth carrier with magnetic particles to delay membrane scaling, and the scale inhibitor is accumulated at the membrane by changing the application position of the magnetic field.

[0046] By adopting the technical scheme, the probability of exceeding the conductivity in the future 2 hours is predicted based on time series analysis, when the probability is greater than 70%, the proportion of concentrated water backflow is started in advance, the scaling rate is delayed, the scale inhibitor is added, the protective film is formed, and the scaling risk is reduced; the traditional membrane cleaning relies on after-response, the present scheme 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 over-standard six-valent chromium traceability to the ORP up-regulation in the cyanide breaking stage, to ensure the stability of heavy metal precipitation efficiency; the front section ORP is improved triggered by the membrane pollution index, the organic load is reduced, and the pH fluctuation limit (±0.3) is reduced to reduce colloidal blockage; the conductivity prediction model starts the scale inhibitor addition and concentrated water backflow in advance to delay the scaling rate; the membrane pollution load at the back end is reduced through the optimization of the front-end process (ORP / pH control), the membrane life is prolonged through the predictive maintenance at the back end (scale inhibitor and cleaning), and the comprehensive membrane system operation cost is reduced; the aeration promotes the formation of flocs, the precipitation speed is accelerated, the heavy metal removal rate is greatly reduced through traceability regulation (six-valent chromium generation path blocking); the carrier is fixed near the membrane surface by the magnetic field, the scale inhibitor is slowly released, and the scaling is continuously inhibited (the membrane cleaning period is prolonged).

[0047] In summary, the present application includes at least one of the following beneficial technical effects:

[0048] 1. 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 realized; through multi-stage real-time monitoring and dynamic adjustment, the processing precision is improved, the linkage of ORP and cyanide concentration reduces the waste of oxidizing agent and reduces resource waste; the linkage of pH and heavy metals improves the precipitation efficiency, and the dynamic management of transmembrane pressure difference prolongs the membrane life;

[0049] 2. Sodium hypochlorite is loaded on porous diatomite to prolong the release time, reduce the OPR fluctuation amplitude, reduce the interference with the monitoring steps, reduce the local concentration that is too high or incomplete oxidation, and improve the utilization rate of oxidizing agent. BRIEF DESCRIPTION OF DRAWINGS

[0050] Fig. 1 is a flow chart of the wastewater recycling method in Example 1 of the present application;

[0051] Fig. 2 is a flow chart of the wastewater recycling method in Example 2 of the present application. DETAILED DESCRIPTION

[0052] The present application will be further described below. Figs. 1-2 The present application will be further described below.

[0053] The present application will be further described below.

[0054] Example 1: refer toFig. 1 A wastewater recycling method, comprising the following steps:

[0055] Breaking cyanide: adding an oxidizing agent to the wastewater for oxidation under an alkaline environment;

[0056] The sodium hypochlorite is added in a slow-release manner, which is achieved by loading the sodium hypochlorite on a porous diatomite carrier and adding it to the wastewater in the cyanide breaking stage, and controlling the disintegration rate of the carrier to prolong the release time of the sodium hypochlorite.

[0057] First monitoring: real-time monitoring of the oxidation-reduction potential and free cyanide concentration in the cyanide breaking oxidation stage, and adjusting the sodium hypochlorite addition ratio based on the ORP dynamic range and the cyanide concentration decay rate;

[0058] Time sequence control of oxidizing agent addition and ORP feedback: 60% of the total amount of sodium hypochlorite is initially added, and the remaining 40% is added in three times according to the ORP change; when the ORP does not reach the fourth threshold value within 5 minutes, an emergency addition mode is triggered, and the remaining amount is added at one time.

[0059] Specifically, alkaline environment adjustment: adding NaOH solution to the cyanide-containing wastewater to stabilize the pH at 10.5-11.5; sodium hypochlorite slow-release addition: adsorbing 15% sodium hypochlorite solution on a porous diatomite carrier (pore size 50-100 μm, pretreated with 5% dilute hydrochloric acid to enhance the loading rate), and adding it in the cyanide breaking stage, 60% of the total amount of sodium hypochlorite (calculated according to CN - The initial concentration is calculated according to CN - :ClO - =1:8 mass ratio), the ORP sensor collects the oxidation-reduction potential in real time (target range: +450-+650 mV); the cyanide ion selective electrode monitors the free cyanide concentration (target: <0.2 mg / L); the remaining 40% is added in three times (each time interval is 5 minutes), and when the ORP does not reach +600 mV (the fourth threshold value) within 5 minutes, the remaining amount is added at one time.

[0060] Precipitation: adding a hydroxide to precipitate heavy metals;

[0061] Second monitoring: simultaneously collecting the pH value, copper ion concentration and nickel ion concentration in the chemical precipitation stage, and when the pH value deviates from the first set range or the heavy metal concentration deviates from the second set range value, triggering the gradient compensation addition of sodium hydroxide and sodium sulfide;

[0062] Specifically, Ca(OH)2is added to adjust the pH to 9.0-9.5 (first set range), then 10% NaOH solution is added to maintain the pH, and 0.05 mol / L sodium sulfide (Na2S) is added simultaneously to generate metal sulfide precipitate; real-time feedback is provided by the pH online instrument; during the precipitation stage, wastewater samples are extracted, and the copper / nickel ion concentration is detected online by an atomic absorption spectrometer (AAS) (target: Cu 2+ <0.5 mg / L, Ni 2+ <0.1 mg / L).

[0063] If the pH is less than 9.0, NaOH solution is automatically added (flow rate increased by 20%); if Cu 2+ or Ni 2+ is over the standard (deviation from the second set range), trigger the staged addition of sodium sulfide: first add 50% of the designed amount, and then add the remaining amount after 10 minutes.

[0064] Membrane treatment: filtration and degradation treatment by biological membrane to remove sundries and organic matter;

[0065] Third monitoring: continuously track the transmembrane pressure difference change rate and sludge concentration in the membrane treatment stage, dynamically adjust the aeration intensity and backwashing period according to the coupling relationship between the pressure difference slope and the sludge concentration;

[0066] Fourth monitoring: obtain and monitor point data, calculate the process capability index, and determine whether it is less than the third threshold value, if so, process parameter compensation is performed;

[0067] Specifically, wastewater enters an immersed flat membrane bioreactor (MBR, material: PVDF, pore size 0.1 μm), and organic matter is degraded by aerobic bacteria; the transmembrane pressure difference (TMP) sensor records ΔP / Δt (pressure difference change rate); the sludge concentration (MLSS) is monitored in real time by an optical probe (target: 8000-12000 mg / L).

[0068] 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 backwashing period is shortened from 30 minutes / time to 20 minutes / time (backwashing water: filtered water, duration 60 seconds).

[0069] Data source: integrate DCS system to collect various monitoring point data (cyanide oxidation rate, heavy metal removal rate, TMP slope);

[0070] The process capability index is calculated by the following parameters: ;

[0071] Wherein: the average value of cyanide oxidation rate, the standard deviation of cyanide oxidation rate, the upper and lower limits of heavy metal removal rate, USL = 99.5%, LSL = 98.0%; the transmembrane pressure change rate (kPa / min); the membrane fouling correction factor, the value range is 0.1-0.3, and the value in the embodiment is 0.2.

[0072] The process parameter compensation also includes: the ORP is raised in the cyanide breaking stage and maintained for 20 minutes, and the sodium hypochlorite addition ratio is simultaneously increased; the sodium sulfide addition amount is increased in the precipitation stage, and the aeration intensity is increased to k times of the reference value in the third monitoring step; the backwashing frequency is increased in the membrane treatment stage, and the washing time is increased.

[0073] Specifically, when Cpk < 1.33 (the third threshold value), the following linkage compensation is performed:

[0074] cyanide breaking strengthening: the ORP is raised to +650 mV and maintained for 20 minutes, and the sodium hypochlorite addition ratio is increased by 1.3 times; precipitation strengthening: the sodium sulfide addition amount is increased by 30%, and the MBR aeration intensity is increased to 1.5 times of the reference value (k = 1.0-1.5) in linkage; membrane maintenance strengthening: the backwashing frequency is increased by 50%, and the single washing time is extended to 90 seconds.

[0075] In the embodiment, the carrier slow release, magnetic field distribution control prolongs the oxidant action time, reduces the dosage of reagents, and the multi-stage dynamic feedback mechanism (ORP / heavy metal / TMP coupling regulation) guarantees the system stability; the real-time compensation of Cpk index improves the comprehensive compliance rate, and is suitable for high-cyanide and high-heavy-metal wastewater treatment in the electroplating and metallurgy industries.

[0076] Embodiment 2: The difference between the embodiment and embodiment 1 is that the sodium hypochlorite is added by using the porous diatomite carrier coated with magnetic particles, a magnetic field is applied around the wastewater when the sodium hypochlorite is added, and the distribution of the porous diatomite carrier coated with magnetic particles is adjusted;

[0077] Specifically, the raw material pretreatment: select diatomite raw material with a silicon dioxide content of ≥85% and a particle size of 50-100 μm, remove impurities through a 200-mesh vibrating screen;

[0078] Acid pickling hole expansion: put the screened diatomite into an acid-resistant reaction kettle (PTFE lining), and add 5% industrial-grade dilute hydrochloric acid solution according to a liquid-solid ratio of 5:1;

[0079] Temperature and time control: maintain the temperature at 40±2℃, accurately control the temperature through jacketed hot water circulation; the mechanical stirring rate is 120 rpm, and the reaction lasts for 2 hours. ​​

[0080] Washing and drying: After the reaction, repeatedly wash with deionized water until neutral (pH = 6.5~7.0); hot air drying at 110℃ for 30 minutes (belt dryer), to get the specific surface area ≥ 25m² / g of expanded diatomite.

[0081] Environmental requirements: closed ventilation system (prevent HCl volatilization), temperature fluctuation ≤ ± 2℃.

[0082] Magnetic Fe3O4 particle coating: solution preparation: under the protection of nitrogen, dissolve ferrous chloride and ferric chloride in deionized water according to the molar ratio of Fe 2+ :Fe 3+ =1:2;

[0083] Carrier suspension: after acid washing, disperse diatomite in water at a ratio of 1:10 (w / v), and form a uniform suspension by high-speed shearing at 2000 rpm for 10 minutes;

[0084] Co-precipitation reaction: transfer the suspension to a constant temperature reactor (PTFE lining), and heat to 60±1℃; add ammonia water to pH=10.5, and synchronously add 0.5wt% sodium oleate as dispersant; constant temperature reaction for 45 minutes to complete the deposition of Fe3O4 on the surface of diatomite;

[0085] Magnetic separation and washing: magnetic separation by 0.5T permanent magnet, and rinse with deionized water for 3 times to remove free ions; environmental requirements: nitrogen protection throughout to prevent oxidation, and temperature deviation > ± 1℃ will cause particle agglomeration or crystallization defects.

[0086] Sodium hypochlorite loading: solution preparation: prepare a 15% effective chlorine content sodium hypochlorite solution (industrial grade) under light-proof conditions; vacuum negative pressure loading: place the magnetic diatomite carrier in a rotary evaporator, and vacuum to-0.08MPa; inject sodium hypochlorite solution, and immerse for 30 minutes; jacket cooling water circulation temperature control ≤30℃.

[0087] Low temperature drying: after loading, the wet carrier is transferred to a nitrogen fluidized bed (oxygen content <5%), and dried at 35℃ for 20 minutes. Environmental requirements: strictly operate in the dark, and temperature >30℃ will accelerate the decomposition of sodium hypochlorite (2NaClO→2NaCl+O2↑).

[0088] Sodium alginate cross-linking to control disintegration: cross-linking agent spraying: place the sodium hypochlorite-loaded carrier in a fluidized bed coating machine; spray 2% sodium alginate aqueous solution at a flow rate of 5L / min (inlet air temperature 40℃). Two-step calcification fixation: first step: spray 0.1mol / L calcium lactate solution to trigger surface cross-linking; second step: solidify at room temperature (25℃) for 30 minutes, and control the relative humidity at 50±5%.

[0089] Disintegration test: The finished product is tested in water at 30°C, and the sodium hypochlorite release lasts for 35 ± 2 minutes (USP disintegration apparatus).

[0090] Specifically, after the magnetic field is introduced, the magnetic field is intermittently applied, the detection of OPR is performed in the gap of the magnetic field application, the OPR electrode is processed, a 200 nm silicon nitride (Si3N4) coating is sputtered on the surface of the Pt electrode, and the magnetic particles adsorbed on the surface of the electrode are cleaned in the gap of the magnetic field application by using ultrasonic cleaning. The ultrasonic cleaning module can be as follows: frequency: 40 kHz, power density 0.5 W / cm²; trigger logic: pulse for 10 seconds after each stop of the magnetic field (remove the adsorbed particles); or a pneumatic scrubbing device can be used: N2 bubbles (flow rate 2 L / min) are introduced every 4 hours to scrub the surface of the electrode.

[0091] Reference Fig. 2 In other embodiments, a fifth monitoring step, a first standard judgment step, and a second standard judgment step are further included,

[0092] Fifth monitoring: Real-time detection of membrane treatment product water conductivity and hexavalent chromium concentration;

[0093] First standard judgment: If the conductivity of the membrane treatment product water is greater than the second threshold value, the statistical step is performed;

[0094] Statistics: When the conductivity exceeds the standard for three consecutive times, the concentrated water reflux ratio is increased, and the citric acid-EDTA composite cleaning program of the membrane system is triggered. In the statistical step, a conductivity over-standard trend prediction algorithm is introduced, a conductivity change rate model is established based on time series analysis, when the probability of exceeding the standard in the next 2 hours is greater than the fifth threshold value, the concentrated water reflux ratio incremental mode is started in advance, and the porous diatomite carrier loaded with scale inhibitor with magnetic particles is injected to delay membrane fouling, and the application position of the magnetic field is changed to make the scale inhibitor gather at the membrane.

[0095] Specifically, data preprocessing: take the conductivity data of the last 2 hours, sliding window width = 10 minutes, wavelet transform denoising (db4 wavelet basis, 3 layers of decomposition); according to the above data, a prediction model is constructed, when the prediction over-standard probability > 85% (fifth threshold value): the concentrated water reflux ratio is increased by gradient: 20%→25%→30% (adjusted every 30 minutes), the scale inhibitor is injected, the scale inhibitor can be directly injected without applying a magnetic field; in other embodiments, the scale inhibitor can be added by using a carrier, the carrier can be prepared by the sodium hypochlorite adding step, and the scale inhibitor can be adsorbed and added; or the scale inhibitor can be added by mixing with magnetic powder, and then a magnetic field is applied.

[0096] Second standard judgment: If the concentration of hexavalent chromium is greater than 0.05 mg / L, the ORP threshold value of the first monitoring is up-regulated, and the sodium hypochlorite dosage is increased.

[0097] Specifically, the treatment process for excessive hexavalent chromium: when [Cr 6+ ]>0.05mg / L: the ORP set value is adjusted from 650mV to 750mV (oxidation-reduction potential), and the sodium hypochlorite dosage is increased according to the formula: , K=1.2 (empirical coefficient), .

[0098] Linkage first monitoring: the ORP threshold in the cyanide oxidation stage is synchronously increased to 800mV

[0099] Also includes a monitoring adjustment step;

[0100] Monitoring adjustment: a dynamic weight distribution model is constructed for optimizing the control priority of each monitoring stage: cyanide breaking stage weight , set based on cyanide toxicity grade; sedimentation stage weight , set based on heavy metal over-standard risk; membrane treatment stage weight , set based on membrane flux decay rate; when the weight of any stage triggers the threshold, automatically reduce the weight of other stages by 5%~10%, and concentrate the control resources.

[0101] Specifically, the weight distribution matrix: cyanide breaking stage W1=0.4~0.6, when cyanide concentration >1.0mg / L (emergency threshold), the adjustment ratio is: 1.5x baseline value (current stage initial value).

[0102] Sedimentation stage W2=0.2~0.3, when Zn 2+ / Cu 2+ over-standard rate >15%, the adjustment ratio is: 1.2x baseline value; membrane treatment stage W3=0.1~0.2, when membrane flux decay >10L / (m²·h), the adjustment ratio is: 0.8x baseline value.

[0103] Dynamic adjustment rule: when W1 triggers: automatically reduce W2 / W3 to 0.15 / 0.05.

[0104] After the monitoring adjustment step, it also includes a joint adjustment step;

[0105] Joint adjustment: the weight adjustment in the weight distribution model is participated by the process capability index, when , the cyanide breaking stage weight is forcibly increased to 0.7, and the membrane treatment stage control is frozen; when , the sedimentation stage weight is down-regulated to 0.1, and the membrane treatment energy consumption is optimized preferentially. 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 concentrated water reflux ratio is down-regulated from 25% to 20%.

[0106] For example, scenario simulation: conductivity continuous over-limit event handling, 08:00: conductivity first over-limit to 52 μS / cm (<3 times, trigger prediction); algorithm predicts 09:30 over-limit probability reaches 90%, concentrated water backflow ratio is increased from 25% to 30%, 50 mg / L of magnetic scale inhibitor carrier is injected, 0.3T gradient magnetic field is formed on the membrane surface by the electromagnet, and the actual measured conductivity is stabilized at 48 μS / cm at 09:20 (to avoid membrane pollution aggravation).

[0107] In other embodiments, the first monitoring step further comprises dynamically switching the type of oxidizing agent by monitoring the molar ratio of intermediate product cyanate to final product carbon dioxide in online monitoring; when cyanate accounts for more than half, the magnetic field is changed, the porous diatomite carrier is aggregated, and ozone is supplemented to strengthen the oxidation chain reaction, and the ozone is directly injected into the carrier aggregation area by using a gas-liquid mixed jet.

[0108] Specifically, when the cyanate accounts for > 50%, it is determined that the intermediate product accumulates excessively, ozone is introduced, ozone is strengthened, a gas-liquid mixed jet system is used: an ozone generator is used to produce ozone, a Venturi jet device and a static mixer are used, the ozone is jetted by positioning the jet head at the center point of the magnetic field, and the diameter of the ozone micro-bubbles is ≤ 50 μm.

[0109] For example, taking a certain cyanide-containing wastewater treatment plant (flow rate 50 m³ / h) as an example: initial state: ORP = 650 mV, sodium hypochlorite dosage 120 mg / L, R = 0.62 is monitored (for 6 minutes); the electromagnet array excites a 0.4T magnetic field in the A3 reaction zone, the diatomite carrier (100 mg / L) is directionally aggregated, the ozone generator is started, and the dosage is switched to 300 mg / L. After 15 minutes, the R value decreases to 0.09, and the sodium hypochlorite is automatically reduced to 80 mg / L; in other embodiments, when the magnetic carrier is not used, multiple jet heads are arranged at the bottom, and ozone is added by aeration.

[0110] In other embodiments, in the joint adjustment step, a membrane pollution risk index is introduced ; when is greater than a critical value, cross-stage coordinated regulation is triggered: the target value of ORP in the cyanide breaking stage is increased, and the fluctuation range of pH in the precipitation stage is reduced.

[0111] Specifically, the critical value is 0.35, when , the target value of ORP in the cyanide breaking stage is increased by 50-100 mV (based on 650 mV); the fluctuation range of pH in the precipitation stage is narrowed from ±0.5 to ±0.2 (set point pH = 9.0); the oxidizing agent is compensated: the sodium hypochlorite is increased by ; the buffer is added to increase the flow rate of 0.1 mol / L NaHCO3 solution by 20%.

[0112] For example, take an electronic wastewater treatment system (membrane area 500 m²) as an example: risk trigger: 14:30, (critical value 0.35) continues to exceed for 10 minutes; cooperative response: cyanide breaking stage: ORP target from 650 mV→720 mV, sodium hypochlorite increment 18%; precipitation stage: pH control band from 8.8-9.2→8.9-9.1, NaHCO3 dosage +20%; membrane system: aeration intensity from 0.8 m³ / (m²·h) to 1.0 m³ / (m²·h); 16:00 decreased to 0.19, Return to the baseline.

[0113] Exceeding protection: start dilution water emergency injection when greater than 800 mV; pH out-of-control plan: cut to standby precipitation tank when out of the range of 8.5-9.5.

[0114] This embodiment prolongs the service life of the membrane and reduces the cost of reagents.

[0115] The above are preferred embodiments of the present application, and are not intended to limit the protection scope of the present application, therefore: any equivalent changes made according to the structure, shape, principle of the present application should be covered within the protection scope of the present application.

Claims

1. A method for recycling wastewater, characterized by: The method comprises the following steps: Breaking cyanide: in an alkaline environment, sodium hypochlorite is added as an oxidizing agent to oxidize the wastewater; First monitoring: real-time monitoring of the oxidation-reduction potential and free cyanide concentration in the cyanide breaking stage, based on the ORP dynamic range and the cyanide concentration decay rate, adjusting the sodium hypochlorite dosage ratio; Precipitation: adding hydroxide to precipitate heavy metals; Second monitoring: simultaneously collecting the pH value, copper ion concentration and nickel ion concentration in the precipitation stage, when the pH value is out of the first set range or the heavy metal concentration deviates from the second set range value, triggering the gradient compensation of sodium hydroxide and sodium sulfide; Membrane treatment: filtering and degrading treatment by biological membrane to remove sundries and organic matter; Third monitoring: continuously tracking the transmembrane pressure difference change rate and sludge concentration in the membrane treatment stage, dynamically adjusting the aeration intensity and backwashing period according to the coupling relationship between the pressure difference slope and the sludge concentration; Fourth monitoring: obtaining monitoring data, calculating the process capability index, and judging whether it is less than the third threshold value, if so, process parameter compensation: adjusting the sodium sulfide dosage in the precipitation stage; The process capability index is calculated by the following parameters: ； Wherein: is the average cyanide oxidation rate, is the standard deviation of the cyanide oxidation rate, ; ; is the upper and lower limit of heavy metal removal rate; is the transmembrane pressure difference change rate; is the membrane fouling correction factor, the value range is 0.1~0.

3.

2. The wastewater recycling method according to claim 1, characterized by: In the fourth monitoring step, the process parameter compensation also includes: The ORP in the cyanide breaking stage is raised and maintained for 20 minutes, and the sodium hypochlorite dosage ratio is simultaneously increased; the sodium sulfide dosage in the precipitation stage is increased, and the aeration intensity is increased to k times of the reference value in the third monitoring step; the backwashing frequency in the membrane treatment stage is increased, and the flushing time is also increased.

3. The wastewater recycling method according to claim 1 or 2, characterized by: It also includes a fifth monitoring step, a first standard judgment step and a second standard judgment step, Fifth monitoring: real-time detection of the conductivity of the membrane treatment effluent and the concentration of hexavalent chromium; First standard judgment: if the conductivity of the membrane treatment effluent is greater than the second threshold value, execute the statistical step; Statistics: when the conductivity exceeds the standard for 3 times in a row, the concentrated water reflux ratio is increased, and the citric acid-EDTA composite cleaning program of the membrane system is triggered; Second standard judgment: if the concentration of hexavalent chromium is greater than 0.05 mg / L, the ORP threshold value in the first monitoring step is increased, and the sodium hypochlorite dosage is also increased.

4. The wastewater recycling method according to claim 3, characterized by: It also includes a monitoring adjustment step; Monitoring adjustment: build a dynamic weight allocation model to optimize the priority of each monitoring stage: cyanide breaking stage weight , set based on cyanide toxicity grade; precipitation stage weight , set based on heavy metal over-standard risk; membrane treatment stage weight , set based on membrane flux decay rate; when the weight threshold of any stage weight is triggered, the weights of the precipitation stage and the membrane treatment stage are automatically reduced to concentrate the control resources.

5. The wastewater recycling method according to claim 4, characterized by: After the monitoring adjustment step, it also includes a joint adjustment step; Joint adjustment: through the process capability index to participate in the weight adjustment in the weight distribution model, when the cyanide breaking stage weight is forced to rise to 0.7, and the membrane treatment stage control is frozen; when the precipitation stage weight is lowered to 0.1, the membrane treatment energy consumption is preferentially optimized.

6. The wastewater recycling method according to claim 3, characterized by: The sodium hypochlorite is added in a slow-release form, which is achieved by the following method: loading sodium hypochlorite on porous diatomite carrier and adding it to the wastewater in the cyanide breaking stage, setting magnetic particles outside the porous diatomite carrier, applying a magnetic field around the wastewater during addition to adjust the distribution of the porous diatomite carrier; controlling the disintegration rate of the carrier to prolong the release time of sodium hypochlorite.

7. The wastewater recycling method according to claim 6, characterized by: Time sequence 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 3 times according to the ORP change; when the ORP does not reach the fourth threshold value within 5 minutes, the emergency addition mode is triggered, and the remaining amount is added at once.

8. The wastewater recycling method according to claim 6, characterized by: In the first monitoring step, the molar ratio of intermediate product cyanate and final product carbon dioxide is monitored online to dynamically switch the type of oxidizing agent: when cyanate accounts for more than half, the magnetic field is changed to gather the porous diatomite carrier, and ozone is supplemented to strengthen the oxidation chain reaction, and the ozone is injected into the carrier gathering area in the form of gas-liquid mixed jet.

9. The wastewater recycling method according to claim 5, characterized by: In the joint adjustment step, a membrane pollution risk index is introduced ; when the critical value is greater than the critical value, trigger cross-stage coordinated regulation: increase the ORP target value of the cyanide breaking stage, and reduce the pH fluctuation amplitude of the precipitation stage.

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