Bio-based nylon production wastewater treatment system and treatment method thereof

Abstract

The invention relates to the technical field of industrial wastewater treatment, and discloses a bio-based nylon production wastewater treatment method which comprises the following steps: inputting dodecanol-containing wastewater generated in a bio-based nylon production cell workshop into a static oil separation tank, and separating the dodecanol-containing wastewater into an upper oil item and a bottom clear liquid after precipitation; conveying the bottom clear liquid into an air flotation lifting tank, adding cell secondary condensate water, and dividing the bottom clear liquid mixed with the cell secondary condensate water into the bottom clear liquid and an upper oil item again under the action of an air flotation machine until more than or equal to 90% of dodecanol is removed from the bottom clear liquid. Through preliminary separation of the static oil separation tank and deep treatment of the air floatation lifting tank, 90% or more of dodecanol in the wastewater is removed in stages, and the NF concentrated liquid enriched with dodecanol is reused for production in a cell workshop, so that the defect that high-value components are not recycled in the traditional technology is overcome, the raw material cost is remarkably reduced, and resource waste is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of industrial wastewater treatment, and in particular to a bio-based nylon production wastewater treatment system and a treatment method thereof. Background Art

[0002] Bio-based nylon production wastewater contains high concentrations of dodecanol (1000-2000 mg / L), COD (3000-8000 mg / L) and ammonia nitrogen (500-2000 mg / L). Existing technologies have three major defects: first, dodecanol is difficult to biodegrade, resulting in low efficiency of traditional biochemical methods; second, single-stage membrane treatment is easily polluted by organic / inorganic scaling, resulting in poor separation effect and short membrane life; third, effective recovery of high-value components (such as dodecanol) is not achieved, resulting in waste of resources and high raw material costs. Summary of the Invention

[0003] In order to solve the existing technical problems, the present invention provides a bio-based nylon production wastewater treatment system and a treatment method thereof, which solves the problems of susceptibility to organic or inorganic scaling pollution and short membrane life.

[0004] To solve the above technical problems, according to one aspect of the present invention, more specifically, a method for treating bio-based nylon production wastewater comprises the following steps: S1. The wastewater containing dodecanol generated in the bio-based nylon production cell workshop is fed into a static oil separator tank, where it is separated into an upper oily portion and a bottom clear liquid after sedimentation. S2. The bottom clear liquid is transferred to an air flotation lift tank and the cell secondary condensate is added. The bottom clear liquid mixed with the cell secondary condensate is again separated into a bottom clear liquid and an upper oily portion by the action of an air flotation machine until ≥90% of the dodecanol is removed from the bottom clear liquid. S3, transferring the bottom clear liquid from which ≥90% of the dodecanol has been removed to an acid adjustment tank, and adding sulfuric acid to adjust the pH of the bottom clear liquid in the acid adjustment tank to acidic; S4, sequentially performing multi-media filtration and activated carbon adsorption to remove residual organic matter, and then using a temperature-raising heat exchanger to heat the bottom clear liquid after filtration and adsorption; S5. Use the UF system to ultrafilter the heated bottom clear liquid to remove colloids and macromolecules. The treated UF concentrate enters the NF system for treatment; S6 and NF systems perform nanofiltration on the UF concentrate to intercept small molecular organic matter. The treated NF concentrate is transported to the cell workshop for production.

[0005] Furthermore, the upper oil produced in step S2 is transported back to the static oil separator in step S1 for secondary sedimentation and is discharged after sedimentation.

[0006] Further, the multi-media in the step S4 is a mixture of quartz sand and anthracite, and the mixing ratio of the quartz sand and the anthracite is 1:1.

[0007] Further, the UF system in the step S5 further comprises an ultrafiltration cleaning system, and the NF system in the step S5 further comprises a nanofiltration cleaning system. The ultrafiltration cleaning system and the nanofiltration cleaning system are cleaned by one of alkali, citric acid or bactericide.

[0008] Further, when the UF system transmembrane pressure difference is detected to be increased and the influent COD is greater than 5000 mg / L, only the ultrafiltration cleaning system is used to clean the UF system by one of alkali or bactericide. When the UF system influent hardness is greater than 200 mg / L or the running period exceeds 72 hours, only the ultrafiltration cleaning system is used to clean the UF system by one of citric acid or bactericide.

[0009] Further, when the NF system concentrated water side conductivity is greater than 10 mS / cm and the organic matter rejection rate is decreased, only the nanofiltration cleaning system is used to clean the NF system by one of alkali or bactericide. When the NF system influent calcium and magnesium ion concentration is greater than 150 mg / L or the pH abnormally fluctuates, only the nanofiltration cleaning system is used to clean the NF system by one of citric acid or bactericide.

[0010] Further, when the biological-based nylon production wastewater treatment method is mainly polluted by organic matter, and the COD removal rate is decreased by greater than or equal to 15%, the ultrafiltration cleaning system is used to clean the UF system by alkali, and the nanofiltration cleaning system is used to clean the NF system by citric acid. When the biological-based nylon production wastewater treatment method is mainly polluted by inorganic scaling, and the water production is decreased by greater than or equal to 20%, the ultrafiltration cleaning system is used to clean the UF system by citric acid, and the nanofiltration cleaning system is used to clean the NF system by alkali.

[0011] Further, the membrane washing waste liquid of the UF system cleaned by the ultrafiltration cleaning system, the membrane washing waste liquid of the NF system cleaned by the nanofiltration cleaning system, and the NF clear liquid treated by the NF system are all discharged to a sewage station.

[0012] A biological-based nylon production wastewater treatment system comprises: A static oil separation tank is used to receive dodecanol-containing wastewater and perform sedimentation separation, and outputs an upper oil phase and a bottom clear liquid. A flotation lifting tank receives the bottom clear liquid and injects secondary cell condensate water, separates residual dodecanol through a flotation machine, and outputs secondary bottom clear liquid. Acid adjustment tank, equipped with sulfuric acid dosing device, adjusts the pH of the secondary bottom clear liquid to 3-5; Multi-media filter, filled with quartz sand and anthracite, used to intercept suspended solids; An activated carbon adsorption tower absorbs residual organic matter. A fixed-bed adsorption unit using coal-based activated carbon (surface area ≥ 1000 m² / g) removes dissolved organic matter (such as residual dodecanol and organic acids), reducing COD by 30-50%.

[0013] A plate heat exchanger raises the filtered water temperature to 30-40°C. Its purpose is to reduce water viscosity, increase membrane flux (2-3% increase for every 1°C increase in temperature), and prevent precipitation of dodecanol (freezing point 24°C) due to low temperatures.

[0014] Ultrafiltration membrane group, retaining colloids and macromolecules with a molecular weight cutoff of ≥10 kDa, parallel ultrafiltration cleaning system; Nanofiltration membrane group, retaining small molecule organic matter with molecular weight ≥100 Da, parallel nanofiltration cleaning system; The brine return pipeline is equipped with an online conductivity monitor. When the COD of the brine reaches 5000 mg / L or higher, it is returned to the production workshop. The online conductivity meter detects that the COD of the brine is 5000 mg / L or higher. The brine is then returned to the cell processing plant (because it contains a high concentration of dodecanol, it can replace some raw materials).

[0015] Clean water discharge pipe, discharges NF produced water to sewage station.

[0016] The present invention provides a bio-based nylon production wastewater treatment system and treatment method. Compared with the existing technology, the present method has the following effects: 1. The present invention removes ≥90% of dodecanol in the wastewater in stages through preliminary separation in a static oil separator and deep treatment in a flotation lift tank, and reuses the dodecanol-enriched NF concentrate for cell workshop production, thus solving the defect of traditional technology in not recovering high-value components, significantly reducing raw material costs and avoiding resource waste.

[0017] 2. In view of the difficult biodegradation of dodecanol, the present invention innovatively adopts the "multi-media filtration + activated carbon adsorption + double membrane synergy" process chain. Quartz sand / anthracite filtration intercepts suspended matter, activated carbon adsorbs dissolved organic matter, and the UF-NF system gradedly intercepts colloids and small molecular organic matter, ultimately achieving a COD removal rate of ≥85%, overcoming the technical difficulty of low efficiency of traditional biochemical methods.

[0018] 3. This invention dynamically matches cleaning strategies based on contamination type: When elevated transmembrane pressure in the UF system is detected and the influent COD exceeds 5000 mg / L, an alkaline / biocide cleaning is triggered to degrade organic contaminants. When the NF system's concentrate conductivity exceeds 10 mS / cm and the retention rate decreases, an alkaline cleaning is initiated to restore membrane performance. By integrating real-time parameters such as transmembrane pressure, COD, and hardness with multiple thresholds during the operating cycle, membrane fouling is precisely controlled, extending membrane life by more than three times.

[0019] 4. This invention addresses the scaling risk caused by high hardness and pH fluctuations by inventing a differentiated cleaning combination. When organic contamination is predominant, the UF system uses alkaline cleaning to dissolve grease, while the NF system uses citric acid to break down the "dodecyl alcohol-calcium" complex. When inorganic scaling is predominant, the UF system uses citric acid to chelate calcium and magnesium ions, while the NF system uses alkaline cleaning to dissolve metal hydroxides. This strategy increases system water production by ≥20%.

[0020] 5. The present invention controls the pH value to 3-5 by the acid adjustment tank to prevent calcium and magnesium scaling, and combines the temperature-raising heat exchanger to reduce the viscosity of the water body and reduce the membrane area investment; the concentrated water return pipeline realizes the recycling of high COD components, and the clean water discharge accounts for less than 30% of the treatment volume, which greatly reduces the treatment load and operating costs of the sewage station. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a structural schematic diagram of the present invention; Figure 2 This is a flow chart of Example 1 of the present invention; Figure 3 Flowcharts of Embodiments 2 and 3 of the present invention; Figure 4 Flowcharts of Embodiments 4 and 5 of the present invention; Figure 5 This is a flow chart of Embodiments 6 and 7 of the present invention. DETAILED DESCRIPTION

[0022] In order to make the technical solution of the present invention clearer, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] Example 1

[0024] like Figure 1 、 2 According to one aspect of the present invention, a method for treating wastewater from bio-based nylon production is provided, comprising the following steps: Step 1: The wastewater containing dodecanol generated in the bio-based nylon production cell workshop is fed into a static oil separator tank and separated into an upper oil portion and a bottom clear liquid after sedimentation; A static oil separator is a non-powered device that uses density differences to separate oil and water. When wastewater containing dodecanol (density approximately 0.83 g / cm³) is allowed to stand, the light oil phase rises to form the upper oil phase, while the heavy water phase sinks to form the clear liquid at the bottom. This system initially removes most of the free dodecanol (removal rate ≥70%), reducing the subsequent processing load.

[0025] Step 2: The bottom clear liquid is transported to an air flotation lift tank and cell secondary condensate is added. Under the action of the air flotation machine, the bottom clear liquid mixed with the cell secondary condensate is again separated into the bottom clear liquid and the upper oil item until ≥90% of the dodecanol is removed from the bottom clear liquid; the upper oil item generated in this step is re-transported to the static oil separator in step 1 for secondary precipitation and discharged after precipitation.

[0026] The flotation lift tank injects secondary condensate (containing trace amounts of surfactant) from cells into the wastewater. The flotation machine generates microbubbles, which adsorb residual dodecanol onto the bubble surfaces, forming a scum (the oily substance on the top). This deep separation of the emulsified dodecanol ensures the safety of the subsequent membrane system.

[0027] Step 3: The bottom clear liquid from which ≥90% of the dodecanol has been removed is transferred to an acid adjustment tank, and sulfuric acid is added to adjust the pH of the bottom clear liquid in the acid adjustment tank to acidic. The acid conditioning tank is a reaction vessel where sulfuric acid (98%) is added to adjust the pH to an acidic range of 3-5. This prevents scaling caused by calcium and magnesium ions (CaCO3 / Mg(OH)2 precipitation is likely to occur when the pH is above 5) and improves the subsequent activated carbon adsorption efficiency (acidic conditions enhance the adsorption of organic matter).

[0028] Step 4: Perform multi-media filtration and activated carbon adsorption in sequence to remove residual organic matter, and then use a heating heat exchanger to heat the bottom clear liquid after filtration and adsorption; the multi-media of the multi-media filtration in this step is a mixture of quartz sand and anthracite, wherein the mixing ratio of quartz sand and anthracite is 1:1.

[0029] Multi-media filters are filled with quartz sand (particle size 0.5-1.2mm) and anthracite (particle size 0.8-1.6mm), mixed in a 1:1 ratio. The quartz sand intercepts suspended particles larger than 20μm, while the anthracite adsorbs colloidal substances (zeta potential adjustment).

[0030] Step 5: Use the UF system to ultrafilter the heated bottom clear liquid to remove colloids and macromolecules. The treated UF concentrate enters the NF system for treatment. The UF system in this step also includes an ultrafiltration cleaning system, and the NF system also includes a nanofiltration cleaning system. The ultrafiltration and nanofiltration cleaning systems are both cleaned using alkali, citric acid, or a biocide. The membrane washing wastewater from the UF system (from the ultrafiltration cleaning system), the membrane washing wastewater from the NF system (from the nanofiltration cleaning system), and the NF clear liquid from the NF system are all discharged to the sewage station.

[0031] Step 6: The NF system performs nanofiltration treatment on the UF concentrate to intercept small molecular organic matter. The treated NF concentrate is transported to the cell workshop for production.

[0032] The UF system (ultrafiltration membrane group) is used to remove colloids, bacteria and large molecular organic matter (such as protein fragments), and the produced water SDI is ≤3.

[0033] The NF system (nanofiltration membrane group) is used to intercept small molecular organic compounds (such as dodecanol). Its desalination rate is 60-80% (removal of divalent ions).

[0034] Example 2

[0035] like Figure 3 As shown in FIG, when the transmembrane pressure difference of the UF system is detected to be increased and the influent COD is greater than 5000 mg / L, only the ultrafiltration cleaning system is used to clean the UF system using either alkali or bactericide.

[0036] 1. Pollution mechanism and cleaning agent selection basis

[0037] 2. Scientific correlation of triggering conditions Increased transmembrane pressure difference: directly reflects the blockage of membrane pores (accumulation of pollutants leads to increased water flow resistance).

[0038] Influent COD>5000 mg / L: It indicates that the concentration of organic components in the wastewater exceeds the standard (the initial COD upper limit is 8000 mg / L). At this time, the pollutant load far exceeds the membrane tolerance threshold.

[0039] Combination of the two judgments: Avoid mistaken cleaning (if only the pressure difference increases, it may be a temporary particle blockage).

[0040] 3. Core issues to be solved Through real-time monitoring + condition-triggered cleaning, we can accurately combat membrane fouling caused by high organic matter loads and avoid the blindness of traditional regular cleaning.

[0041] It can also overcome the bottleneck of dodecanol recovery. Due to the characteristics of dodecanol, a lipophilic long-chain alcohol (C12), it easily adsorbs on the membrane surface to form a gel layer. Therefore, alkaline cleaning can decompose the dodecanol-oil complex contaminant, ensuring the ultrafiltration membrane's sustained retention capacity for colloids and macromolecules (≥10 kDa).

[0042] Therefore, this embodiment, through a dual-parameter trigger mechanism of transmembrane pressure differential and COD concentration, combined with targeted alkali / fungicide cleaning, fundamentally solves the industry challenge of rapid ultrafiltration membrane fouling caused by high organic matter loading in bio-based nylon wastewater treatment. Its value is not only reflected in membrane flux recovery and reduced operating costs, but also, by ensuring the stability of the UF system, provides core technical support for subsequent precise nanofiltration recovery of dodecanol and concentrated water reuse, ultimately achieving the dual goals of wastewater treatment and resource utilization.

[0043] Example 3

[0044] like Figure 3 As shown in Figure 2, when the inlet water hardness of the UF system is greater than 200 mg / L or the operation cycle exceeds 72 hours, only the ultrafiltration cleaning system is used to clean the UF system using either citric acid or a bactericide.

[0045] 1. Pollution mechanism and cleaning agent selection basis

[0046] 2. Scientific correlation of triggering conditions Influent hardness > 200 mg / L: far exceeds the membrane tolerance limit (conventional wastewater hardness < 100 mg / L), directly leading to a surge in scaling risk (Document 2 Background Technology: Ammonia nitrogen 500-2000 mg / L, suggesting high alkalinity water quality).

[0047] Operation period>72 hours: Based on the UF system processing load in Example 1 (10 m 3 / h) and the pollutant retention amount (colloids / macromolecules) to estimate the critical time of membrane fouling.

[0048] Dual-condition independent judgment: covers two scenarios: "sudden high-hardness water ingress" and "gradual pollution accumulation", avoiding excessive cleaning.

[0049] 3. Core issues to be solved Through real-time hardness monitoring + operation time control, inorganic scale can be removed in a targeted manner, solving the pain point that traditional cleaning cannot completely remove hard scale.

[0050] To ensure the synergistic efficiency of the double membranes. Adding sulfuric acid to the acid adjustment tank (pH 3-5) may introduce (sulfate), which combines with calcium ions to form a hard calcium sulfate scale (CaSO4·2H2O, with a solubility of only 0.21 g / 100 mL). This allows citric acid to efficiently dissolve calcium sulfate scale (chelation constant log K = 3.5), ensuring the ultrafiltration membrane's stable retention of macromolecules ≥ 10 kDa.

[0051] Therefore, this embodiment uses a dual trigger mechanism of inlet water hardness threshold + operating time, combined with citric acid / fungicide directional cleaning, to completely solve the industry problem of "high hardness scaling and long-term operation pollution leading to ultrafiltration membrane failure" in the treatment of bio-based nylon wastewater.

[0052] Example 4

[0053] like Figure 4 As shown in Figure 2, when the conductivity of the concentrated water side of the NF system is greater than 10 mS / cm and the organic matter retention rate decreases, only the nanofiltration cleaning system is used to clean the NF system using either alkali or bactericide.

[0054] 1. Pollution mechanism and cleaning agent selection basis

[0055] 2. Scientific correlation of triggering conditions The conductivity of the concentrated water side is greater than 10 mS / cm: far exceeding the tolerance limit of the nanofiltration membrane (conventional design value is less than 5 mS / cm), indicating excessive salt concentration (initial ammonia nitrogen 500-2000 mg / L, equivalent to a conductivity of about 4-8 mS / cm).

[0056] Decreased organic matter retention rate: directly reflects membrane pore blockage or surface contamination (especially failure to retain small molecule organic matter with a molecular weight ≥100 Da) Dual-parameter collaborative judgment: avoids misjudgment of increased conductivity alone (possibly harmless salts), ensuring that cleaning targets organic-biological composite pollution.

[0057] 3. Core issues to be solved By monitoring dual signals—conductivity and retention—the system accurately identifies the coupled effects of salt concentration and organic contamination, overcoming the blind spots of traditional methods that rely solely on pressure. It also retains small organic molecules with a molecular weight ≥100 Da (dodecanol has a molecular weight of 188.3 Da). However, high conductivity reduces the membrane surface zeta potential, increasing dodecanol penetration.

[0058] Therefore, this embodiment fundamentally solves the industry problem of "nanofiltration membrane failure caused by high salinity and organic matter coupling pollution" in bio-based nylon wastewater treatment through a dual-threshold trigger mechanism of concentrated water side conductivity + organic matter retention rate, combined with alkali / bactericide directional cleaning.

[0059] Example 5

[0060] like Figure 4 As shown in Figure 2, when the calcium and magnesium ion concentrations of the NF system influent are greater than 150 mg / L or the pH fluctuates abnormally, only the nanofiltration cleaning system is used to clean the NF system using either citric acid or a bactericide.

[0061] 1. Pollution mechanism and cleaning agent selection basis

[0062] 2. Scientific association of triggering conditions Calcium and magnesium ions > 150 mg / L: far beyond the anti-fouling limit of the nanofiltration membrane (usually < 50 mg / L is tolerated). Combined with the pre-treatment sulfuric acid dosing (acid adjusting tank), a direct formation of a supersaturated solution of calcium sulfate (Ksp = 2.4 x 10 -5 ) Abnormal pH fluctuation: acidic enhancement (pH < 3) aggravates CaSO4 precipitation (solubility decreases). Alkaline deviation (pH > 5) induces Mg(OH)2 precipitation (Ksp = 1.8 x 10 -11 ).

[0063] "Or" logical judgment: covers two types of independent risk sources, avoiding missing sudden conditions.

[0064] 3. Core problem solved Through real-time ion concentration monitoring + pH linkage control, targeted cleaning at the early stage of fouling, solving the passivity of traditional acid washing "after-treatment".

[0065] Therefore, the embodiment solves the industry problem of "high hardness fouling and pH fluctuation leading to rapid failure of nanofiltration membranes" in biological-based nylon wastewater treatment by a calcium and magnesium ion concentration + pH double threshold independent triggering mechanism combined with citric acid / sterilizing agent targeted cleaning.

[0066] Example 6

[0067] As Figure 5 shown, when the biological-based nylon production wastewater treatment method is mainly polluted by organic matter, and the COD removal rate decreases by ≥ 15%, the ultrafiltration cleaning system cleans the UF system by alkali, and the nanofiltration cleaning system cleans the NF system by citric acid.

[0068] 1. Pollution mechanism and cleaning agent selection basis

[0069] 2. Scientific association of triggering conditions COD removal rate decrease ≥ 15%: sign of serious overall organic pollution of the system (initial COD removal rate ≥ 85%, decreased to ≤ 70%).

[0070] Based on the series characteristics of UF + NF system: UF rejection failure will lead to a sudden increase in NF load.

[0071] "Organic pollution mainly" comprehensive judgment: dodecanol ≤ 100 mg / L after oil separation-gas flotation. And if the COD still exceeds the standard after multi-medium filtration / activated carbon adsorption, it indicates that soluble organic matter penetrates into the membrane system.

[0072] 3、Solved core problem The prior art adopts "single cleaning" for membrane pollution, which cannot cope with the organic-inorganic matter of bio-based nylon wastewater.

[0073] Therefore, the embodiment quantifies the threshold value of COD removal rate to determine the organic matter dominant pollution working condition, and innovatively adopts the differential combination strategy of UF alkali washing + NF citric acid washing.

[0074] Embodiment 7

[0075] As Figure 5 shown, when the bio-based nylon production wastewater treatment method is dominated by inorganic scaling, and the water production decreases by ≥20%, the ultrafiltration cleaning system cleans the UF system by citric acid, and the nanofiltration cleaning system cleans the NF system by alkali.

[0076] 1、Pollution mechanism and cleaning agent selection basis

[0077] 2、Scientific association of trigger conditions Water production decrease ≥20%: Directly reflects system flux attenuation (initial water production 10 m³ / h → ≤8 m³ / h). And the typical sign of inorganic scaling (organic pollution usually first shows a decrease in interception rate) "Mainly inorganic scaling" comprehensive judgment: UF inlet water hardness > 200 mg / L or NF calcium and magnesium > 150 mg / L.

[0078] System characteristics: The heat exchanger (30-40℃) aggravates salt crystallization (CaSO4 solubility decreases by 40% at 40℃ compared to 25℃).

[0079] 3、Solved core problem Traditional cleaning uses the same acid cleaning for all membrane systems, but cannot remove metal hydroxide / silicon scale (alkali-soluble scale) in the NF system.

[0080] Therefore, the embodiment quantifies the threshold value of water production to determine the inorganic scaling dominant working condition, and innovatively adopts the reverse combination strategy of UF citric acid washing + NF alkali washing.

[0081] The above-described embodiments only express several embodiments of the present application, and the description is more specific and detailed, but it cannot be understood as limiting the scope of the present patent. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are within the scope of the present application. Therefore, the protection scope of the present patent should be subject to the appended claims.

Claims

1. A method for treating wastewater from bio-based nylon production, characterized in that: The following steps are involved: S1. The wastewater containing dodecanol generated in the bio-based nylon production cell workshop is fed into a static oil separator tank, where it is separated into an upper oily portion and a bottom clear liquid after sedimentation. S2. The bottom clear liquid is transferred to an air flotation lift tank and the cell secondary condensate is added. The bottom clear liquid mixed with the cell secondary condensate is again separated into a bottom clear liquid and an upper oily portion by the action of an air flotation machine until ≥90% of the dodecanol is removed from the bottom clear liquid. S3, transferring the bottom clear liquid from which ≥90% of the dodecanol has been removed to an acid adjustment tank, and adding sulfuric acid to adjust the pH of the bottom clear liquid in the acid adjustment tank to acidic; S4, sequentially performing multi-media filtration and activated carbon adsorption to remove residual organic matter, and then using a temperature-raising heat exchanger to heat the bottom clear liquid after filtration and adsorption; S5. Use the UF system to ultrafilter the heated bottom clear liquid to remove colloids and macromolecules. The treated UF concentrate enters the NF system for treatment; S6 and NF systems perform nanofiltration on the UF concentrate to intercept small molecular organic matter. The treated NF concentrate is transported to the cell workshop for production.

2. The method for treating bio-based nylon production wastewater according to claim 1, characterized in that: The upper oil produced in step S2 is transported back to the static oil separator in step S1 for secondary sedimentation and is discharged after sedimentation.

3. The method for treating bio-based nylon production wastewater according to claim 1, characterized in that: The multi-media used in the multi-media filtration in step S4 is a mixture of quartz sand and anthracite, wherein the mixing ratio of quartz sand to anthracite is 1:

1.

4. The method for treating bio-based nylon production wastewater according to claim 1, wherein: The UF system in step S5 also includes an ultrafiltration cleaning system, and the NF system in step S5 also includes a nanofiltration cleaning system; The ultrafiltration cleaning system and the nanofiltration cleaning system are both cleaned by using one of alkali, citric acid or bactericide.

5. The method for treating bio-based nylon production wastewater according to claim 4, characterized in that: When it is detected that the transmembrane pressure difference of the UF system increases and the COD of the influent is greater than 5000 mg / L, the UF system is cleaned using only the ultrafiltration cleaning system with either alkali or bactericide; When the hardness of the inlet water of the UF system is greater than 200 mg / L or the operation cycle exceeds 72 hours, the UF system is cleaned using only the ultrafiltration cleaning system using either citric acid or a bactericide.

6. The method for treating bio-based nylon production wastewater according to claim 4, characterized in that: When the conductivity of the concentrated water side of the NF system is greater than 10 mS / cm and the organic matter retention rate decreases, the NF system is cleaned using only the nanofiltration cleaning system with either alkali or bactericide; When the calcium and magnesium ion concentrations of the NF system influent are greater than 150 mg / L or the pH fluctuates abnormally, the NF system is cleaned using only the nanofiltration cleaning system using citric acid or a bactericide.

7. The method for treating bio-based nylon production wastewater according to claim 4, characterized in that: When the bio-based nylon production wastewater treatment method is mainly organic pollutant and the COD removal rate decreases by ≥15%, the ultrafiltration cleaning system cleans the UF system with alkali, and the nanofiltration cleaning system cleans the NF system with citric acid; When the bio-based nylon production wastewater treatment method is mainly based on inorganic scaling and the water production decreases by ≥20%, the ultrafiltration cleaning system cleans the UF system with citric acid, and the nanofiltration cleaning system cleans the NF system with alkali.

8. The method for treating bio-based nylon production wastewater according to claim 4, characterized in that: The membrane washing waste liquid after cleaning the UF system by the ultrafiltration cleaning system, the membrane washing waste liquid after cleaning the NF system by the nanofiltration cleaning system, and the NF clear liquid after treatment by the NF system are all discharged to the sewage station.

9. A bio-based nylon production wastewater treatment system, characterized in that: The method for treating bio-based nylon production wastewater according to any one of claims 1 to 8, wherein the bio-based nylon production wastewater treatment system comprises: Static oil separator, used to receive wastewater containing dodecanol and perform sedimentation separation, outputting the upper oil phase and the bottom clear liquid; The flotation lifting tank receives the bottom clear liquid and injects the secondary condensed water of the cells, separates the residual dodecanol through the flotation machine, and outputs the secondary bottom clear liquid; Acid adjustment tank, equipped with sulfuric acid dosing device, adjusts the pH of the secondary bottom clear liquid to 3-5; Multi-media filter, filled with quartz sand and anthracite, used to intercept suspended solids; Activated carbon adsorption tower, adsorbing residual organic matter; The heating heat exchanger heats up the filtered water to 30-40℃; Ultrafiltration membrane group, retaining colloids and macromolecules with a molecular weight cutoff of ≥10 kDa, parallel ultrafiltration cleaning system; Nanofiltration membrane group, retaining small molecule organic matter with molecular weight ≥100 Da, parallel nanofiltration cleaning system; The concentrated water return pipeline is equipped with an online conductivity monitor. When the concentrated water COD is ≥5000 mg / L, it is returned to the production workshop. Clean water discharge pipe, discharges NF produced water to sewage station.

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