Pigment wastewater treatment process with low excess sludge

Abstract

The invention belongs to the technical field of pigment wastewater treatment, and particularly provides a low-excess-sludge pigment wastewater treatment process which comprises the following steps: 1) performing coagulating sedimentation and micro-electrolysis treatment on to-be-treated wastewater to remove suspended solids and toxic substances to obtain pretreated wastewater; (2) the pretreated wastewater is treated through a biochemical unit, the biochemical unit treatment comprises hydrolytic acidification and two-stage biological contact oxidation, and biological membrane filler is loaded and salicylanilide derivatives are added in the biological contact oxidation treatment process.The treatment process has the advantages of being high in COD treatment efficiency and low in residual sludge amount.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of pigment wastewater treatment, and particularly relates to a pigment wastewater treatment process with low residual sludge. BACKGROUND

[0002] Pigment wastewater mainly comes from process wastewater, washing wastewater and ground flushing wastewater generated in the production process of the industrial fields such as dyes, coatings, inks, textile printing and dyeing, leather processing and plastic coloring. This kind of wastewater contains a large amount of organic pigment molecules and additives, has a very high COD value, and has certain toxicity to microorganisms and the environment, so it is difficult to treat.

[0003] The challenges currently faced by pigment wastewater treatment include: 1) the pigment molecular structure is stable, contains a large number of aromatic structures such as benzene rings and naphthalene rings, and color groups such as azo bonds and conjugated double bonds, and has strong stability to light, heat and chemical oxidation; 2) the degradation of organic matter is not complete, and macromolecular organic matter is difficult to be completely mineralized by conventional biological treatment; 3) heavy metal ions may form complexes with organic matter, increasing the difficulty of treatment; 4) high salt environment inhibits microbial activity, affecting the efficiency of biological treatment; 5) large amount of residual sludge, and a large amount of residual sludge is generated by traditional treatment methods, which is difficult to treat.

[0004] The above problems have comprehensiveness and correlation, and need to be considered comprehensively in the aspect of technical improvement. For example, in the process of treating pigment wastewater, the residual sludge mainly comes from the proliferation of microorganisms, metabolic products of microorganisms, accumulation of incomplete oxidation products and physicochemical precipitates generated in the process of biological treatment. Therefore, high residual sludge is also one of the manifestations of low efficiency and incomplete treatment of pigment wastewater treatment, and high residual sludge will bring subsequent environmental risks and treatment costs. Therefore, how to develop and research the technical method for improving the treatment effect of pigment wastewater and reducing residual sludge is of practical significance. SUMMARY

[0005] In order to further improve the treatment effect of pigment wastewater and reduce residual sludge, the application provides a pigment wastewater treatment process with low residual sludge.

[0006] The application provides a pigment wastewater treatment process with low residual sludge, which comprises the following steps: 1) The wastewater to be treated is first subjected to coagulation sedimentation and micro-electrolysis treatment to remove suspended solids and toxic substances, and pretreated wastewater is obtained. 2) The pretreated wastewater is subjected to biochemical unit treatment, and the biochemical unit treatment comprises hydrolysis acidification and two-stage biological contact oxidation, and the biological contact oxidation treatment process loads biological membrane filler and adds salicylanilide derivatives.

[0007] Furthermore, the salicylaniline derivative is prepared by the following steps: S1: 3,5-Dichlorosalicylic acid reacts with thionyl chloride to obtain crude acyl chloride. Then, the crude acyl chloride is dissolved in THF, followed by the addition of a THF solution of methyl 4-aminobenzoate and triethylamine. The mixture is stirred overnight at room temperature, extracted with ethyl acetate, washed, and dried to obtain an intermediate. S2: Dissolve the intermediate material, 4-(hydroxymethyl)phenylboronic acid pinacol ester, DCC, and DMAP in dichloromethane, stir the reaction at room temperature under nitrogen protection, and then filter, wash, and dry to obtain the final product.

[0008] Furthermore, in step S1, the mass-to-volume ratio of 3,5-dichlorosalicylic acid to thionyl chloride is (2-2.5g):(10-15mL).

[0009] Furthermore, in step S1, the molar ratio of 3,5-dichlorosalicylic acid to methyl 4-aminobenzoate is 1:(1-1.15).

[0010] Furthermore, in step S2, the mass ratio of intermediate material, 4-(hydroxymethyl)phenylboronic acid pinacol ester, DCC, and DMAP is (3-3.5):(2-2.5):(2-2.2):(0.08-0.12).

[0011] Furthermore, in step 2), hydrogen peroxide slow-release microspheres are also added when adding the salicylaniline derivative.

[0012] Furthermore, in step 2), the dosage of the salicylaniline derivative is 0.5-2 mg / L.

[0013] Furthermore, in step 2), the salicylaniline derivative is added starting 5 days after the start of the biological contact oxidation treatment.

[0014] Furthermore, in step 2), the biological contact oxidation treatment adopts a gradient dissolved oxygen process, including an aerobic stage, a facultative anaerobic stage, and an anaerobic stage.

[0015] Furthermore, the DO value in the aerobic stage is 2-3 mg / L, the DO value in the facultative anaerobic stage is 0.2-0.5 mg / L, and the DO value in the anaerobic stage is <0.1 mg / L.

[0016] Compared with the prior art, this application has the following beneficial effects: 1. This application, through the rational control of dissolved oxygen, creates and maintains a gradient dissolved oxygen environment at different stages, enabling microbial self-digestion. When the external carbon source is exhausted, microorganisms in the endogenous respiration phase begin to decompose and utilize their own stored substances and cellular material from decaying cells to maintain their life activities. Simultaneously, hydrolytic enzymes secreted by some microbial communities decompose difficult-to-degrade cell debris and organic fragments into reusable small molecules. This process achieves deep mineralization of organic matter and gradual energy consumption, thereby significantly reducing the amount of residual sludge.

[0017] 2. This application employs pretreatment processes such as coagulation sedimentation and micro-electrolysis to remove some suspended solids and toxic substances, increasing the B / C ratio of the wastewater and creating a favorable environment for subsequent biological treatment. Furthermore, it utilizes a hydrolysis acidification + biological contact oxidation main process, employing biofilm packing to cultivate and acclimate a dominant bacterial community that efficiently degrades pigment intermediates, supplemented by gradient dissolved oxygen, forming a multidimensional microenvironment of aerobic, facultative, and anaerobic processes. This not only efficiently degrades COD but also achieves simultaneous nitrification and denitrification. Ultimately, the system can stably reduce the influent COD from several thousand mg / L to below 100 mg / L, significantly decolorizing it, and achieving effluent standards for municipal water supply or reuse. The operating cost is far lower than advanced oxidation and other deep treatment technologies.

[0018] 3. In this application, the addition of salicylaniline derivatives during the biological contact oxidation stage can be responded to by the slow-release hydrogen peroxide microspheres added at an appropriate time. This has a positive promoting effect on the uncoupling activity of the dominant bacterial community and can also form a Fenton-like reaction to treat recalcitrant organic matter, further reducing the amount of residual sludge. Attached Figure Description

[0019] Figure 1 This is a schematic diagram showing the COD removal rate data of Examples 1-2 and Control Group 1 of this application.

[0020] Figure 2 These are schematic diagrams of the UV-Vis spectra of Examples 1-2 and Control Group 1 of this application. Detailed Implementation

[0021] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0023] When using “including,” “having,” and “contains” as described herein, the intention is to cover non-exclusive inclusion, unless an explicit qualifying term such as “only,” “consisting of,” etc., is used, in which case another component may be added.

[0024] The terms "preferred," "more preferably," "better," and "even better" used in this application refer to embodiments of this application that provide certain beneficial effects under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of this application. That is, in this application, "preferred," "more preferably," "better," and "even better" are merely descriptions of implementations or embodiments with better effects, but do not constitute a limitation on the scope of protection of this application.

[0025] In this application, terms such as "further," "even more," and "particularly" are used for descriptive purposes and indicate differences in content, but should not be construed as limiting the scope of protection of this application.

[0026] In this application, "at least one" means one or more, such as one, two, or more. "Multiple" or "several" means at least two, such as two, three, etc., and "multi-layered" means at least two layers, such as two layers, three layers, etc., unless otherwise explicitly specified. In the description of this application, "several" means at least one, such as one, two, etc., unless otherwise explicitly specified.

[0027] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0028] Unless otherwise specified, all steps in this application may be performed sequentially or randomly. For example, the method comprising steps (a) and (b) indicates that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order; for example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc. Unless otherwise stated, singular terms may include plural forms and should not be construed as having a quantity of one.

[0029] In this application, "above" or "below" includes the number itself. For example, "below 1" includes 1.

[0030] In this application, room temperature refers to 0~40℃, including but not limited to 10~40℃, or further to 20~30℃.

[0031] Based on extensive experimental research, this application provides a pigment wastewater treatment process with low residual sludge, comprising the following steps: 1) The wastewater to be treated is first subjected to coagulation sedimentation and micro-electrolysis to remove suspended solids and toxic substances, thus obtaining pretreated wastewater; 2) The pretreated wastewater is treated by a biochemical unit, which includes hydrolysis acidification and two-stage biological contact oxidation. During the biological contact oxidation process, biofilm packing is loaded and salicylaniline derivatives are added.

[0032] Furthermore, the salicylaniline derivative is prepared by the following steps: S1: 3,5-Dichlorosalicylic acid reacts with thionyl chloride to obtain crude acyl chloride. Then, the crude acyl chloride is dissolved in THF, followed by the addition of a THF solution of methyl 4-aminobenzoate and triethylamine. The mixture is stirred overnight at room temperature, extracted with ethyl acetate, washed, and dried to obtain an intermediate. S2: Dissolve the intermediate material, 4-(hydroxymethyl)phenylboronic acid pinacol ester, DCC, and DMAP in dichloromethane, stir the reaction at room temperature under nitrogen protection, and then filter, wash, and dry to obtain the final product.

[0033] Furthermore, in step S1, the mass-to-volume ratio of 3,5-dichlorosalicylic acid to thionyl chloride is (2-2.5g):(10-15mL).

[0034] In some specific embodiments, in step S1, the mass-to-volume ratio of 3,5-dichlorosalicylic acid to thionyl chloride can be 2g:10mL, 2g:11mL, 2g:12mL, 2g:13mL, 2g:14mL, 2g:15mL, 2.1g:10mL, 2.2g:11mL, 2.3g:12mL, 2.4g:13mL, 2.5g:14mL, 2.2g:10mL, 2.3g:11mL, 2.4g:12mL, 2.5g:13mL, 2.3g:14mL, 2.4g:15mL, 2.5g:10mL, 2.5g:11mL, 2.5g:12mL, 2.5g:14mL, or 2.5g:15mL. More preferably, under normal circumstances, a better technical effect can be obtained when the mass-to-volume ratio of 3,5-dichlorosalicylic acid to thionyl chloride is 2.1 g: 10 mL in step S1.

[0035] Furthermore, in step S1, the molar ratio of 3,5-dichlorosalicylic acid to methyl 4-aminobenzoate is 1:(1-1.15).

[0036] In some specific embodiments, in step S1, the molar ratio of 3,5-dichlorosalicylic acid to methyl 4-aminobenzoate can be 1:1, 1:11, 1:12, 1:13, 1:14, or 1:15. More preferably, under normal circumstances, a molar ratio of 3,5-dichlorosalicylic acid to methyl 4-aminobenzoate of 1:1.2 in step S1 yields better experimental results.

[0037] Furthermore, in step S2, the mass ratio of intermediate material, 4-(hydroxymethyl)phenylboronic acid pinacol ester, DCC, and DMAP is (3-3.5):(2-2.5):(2-2.2):(0.08-0.12).

[0038] In some specific embodiments, in step S2, the mass ratio of intermediate material, 4-(hydroxymethyl)phenylboronic acid pinacol ester, DCC, and DMAP can be 3:2:2:0.08, 3.1:2:2:0.08, 3.2:2:2:0.08, 3.3:2:2:0.08, 3.4:2:2:0.08, 3.5:2:2:0.08, 3:2.1:2:0.08, 3.1:2.2:2:0.08, 3.2:2.3:2:0.08, 3.3:2.4:2:0.08, 3.4:2.5:2:0.08, or 3.5:2.5: 2:0.08, 3:2.1:2.05:0.08, 3.1:2.2:2.1:0.08, 3.2:2.3:2.15:0.08, 3.3:2.4:2.2:0.08, 3.4:2.5:2.2:0.08, 3.5:2.5:2.2:0.08, 3:2.1:2.05:0.09, 3.1:2.2:2.1:0.1, 3.2:2.3:2.15:0.11, 3.3:2.4:2.2:0.12, 3.4:2.5:2.2:0.12, 3.5:2.5:2.2:0.12. Under normal circumstances, when the mass ratio of intermediate material, 4-(hydroxymethyl)phenylboronic acid pinacol ester, DCC, and DMAP in step S2 is 3.2:2.3:2.1:0.1, better experimental results can be obtained.

[0039] Furthermore, in step 2), hydrogen peroxide slow-release microspheres are also added when adding the salicylaniline derivative.

[0040] Furthermore, in step 2), the dosage of the salicylaniline derivative is 0.5-2 mg / L.

[0041] Furthermore, in step 2), the salicylaniline derivative is added starting 5 days after the start of the biological contact oxidation treatment.

[0042] Furthermore, in step 2), the biological contact oxidation treatment adopts a gradient dissolved oxygen process, including an aerobic stage, a facultative anaerobic stage, and an anaerobic stage.

[0043] Furthermore, the DO value in the aerobic stage is 2-3 mg / L, the DO value in the facultative anaerobic stage is 0.2-0.5 mg / L, and the DO value in the anaerobic stage is <0.1 mg / L.

[0044] The present application will be further illustrated by the following examples, but these examples do not limit the scope of the present application.

[0045] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in this application, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. All reagents or instruments whose manufacturers are not specified are conventional products that can be purchased commercially. In addition to the specific methods, equipment, and materials used in the embodiments, based on the knowledge of the prior art possessed by one of ordinary skill in the art and the description in this application, any prior art methods, equipment, and materials similar to or equivalent to those described, used, or made by the methods, equipment, and materials in the embodiments of this application may be used to implement this application.

[0046] Example 1 The pigment wastewater treatment process with low residual sludge in this embodiment includes the following steps: 1) The pigment wastewater to be treated (initial COD 3200 mg / L, SS 1100, LAS 45) first undergoes coagulation and sedimentation, including primary flocculation sedimentation, secondary flocculation sedimentation, and a sedimentation tank. The primary flocculation sedimentation retention time is 5 min, and the secondary flocculation sedimentation retention time is 15 min. 10% of the sludge discharged from the sedimentation tank is recycled to the inlet of the primary flocculation sedimentation tank. Then, the wastewater discharged from the sedimentation tank enters the micro-electrolysis treatment, with cast iron powder added at a dosage of 0.35 g / L and a hydraulic retention time of 90 min, controlling the removal of Fe. 2+ At a concentration of 30-50 mg / L, suspended solids and toxic substances are removed through coagulation, sedimentation, and micro-electrolysis to obtain pretreated wastewater. 2) The pretreated wastewater is treated by a biological unit, which includes hydrolysis acidification and two-stage biological contact oxidation. The hydrolysis acidification retention time is 10 hours and the upflow velocity is 0.8-1.2 m / h. The biological contact oxidation treatment employs a gradient dissolved oxygen process, including aerobic, facultative, and anaerobic stages. The dissolved oxygen (DO) value is 2.5 mg / L in the aerobic stage, 0.35 mg / L in the facultative stage, and <0.1 mg / L in the anaerobic stage. During the biological contact oxidation process, a polyolefin biofilm packing material with a specific surface area >750 m² is loaded. 2 / m 3 The loading rate was 65%; after 5 days of biological contact oxidation treatment, salicylaniline derivative was added at a dosage of 1.5 mg / L.

[0047] The salicylaniline derivative in this embodiment was prepared by the following steps: S1: 2.1 g of 3,5-dichlorosalicylic acid and 10 mL of thionyl chloride were refluxed at 80 °C under DNF catalysis to obtain crude acyl chloride. Then, the crude acyl chloride was mixed with 10 mL of dry THF, followed by the addition of a THF solution containing 1.51 g of methyl 4-aminobenzoate and 2 mL of triethylamine. The mixture was stirred overnight at room temperature, extracted with ethyl acetate, washed with sodium bicarbonate solution under organic phase protection, and dried to obtain intermediate material. S2: Dissolve 3.2g of intermediate material, 2.3g of 4-(hydroxymethyl)phenylboronic acid pinacol ester, 2.1g of DCC, and 0.1g of DMAP in dichloromethane. Stir the reaction under nitrogen protection at room temperature, filter, wash the filtrate with saturated sodium bicarbonate solution, and then purify the organic phase by rotary evaporation, chromatography, and drying to obtain the final product.

[0048] Example 2 The pigment wastewater treatment process with low residual sludge in this embodiment includes the following steps: 1) The pigment wastewater to be treated (initial COD 3200 mg / L, SS 1100, LAS 45) first undergoes coagulation and sedimentation, including primary flocculation sedimentation, secondary flocculation sedimentation, and a sedimentation tank. The primary flocculation sedimentation retention time is 5 min, and the secondary flocculation sedimentation retention time is 15 min. 10% of the sludge discharged from the sedimentation tank is recycled to the inlet of the primary flocculation sedimentation tank. Then, the wastewater discharged from the sedimentation tank enters the micro-electrolysis treatment, with cast iron powder added at a dosage of 0.35 g / L and a hydraulic retention time of 90 min, controlling the removal of Fe. 2+ At a concentration of 30-50 mg / L, suspended solids and toxic substances are removed through coagulation, sedimentation, and micro-electrolysis to obtain pretreated wastewater. 2) The pretreated wastewater is treated by a biological unit, which includes hydrolysis acidification and two-stage biological contact oxidation. The hydrolysis acidification retention time is 10 hours and the upflow velocity is 0.8-1.2 m / h. The biological contact oxidation treatment employs a gradient dissolved oxygen process, including aerobic, facultative, and anaerobic stages. The dissolved oxygen (DO) value is 2.5 mg / L in the aerobic stage, 0.35 mg / L in the facultative stage, and <0.1 mg / L in the anaerobic stage. During the biological contact oxidation process, a polyolefin biofilm packing material with a specific surface area >750 m² is loaded. 2 / m 3 The loading rate was 65%. After 5 days of biological contact oxidation treatment, salicylaniline derivative and hydrogen peroxide slow-release microspheres were added. The dosage of salicylaniline derivative was 1.5 mg / L and the dosage of hydrogen peroxide slow-release microspheres was 200 mg / L.

[0049] The salicylaniline derivative in this embodiment was prepared by the following steps: S1: 2.1 g of 3,5-dichlorosalicylic acid and 10 mL of thionyl chloride were refluxed at 80 °C under DNF catalysis to obtain crude acyl chloride. Then, the crude acyl chloride was mixed with 10 mL of dry THF, followed by the addition of a THF solution containing 1.51 g of methyl 4-aminobenzoate and 2 mL of triethylamine. The mixture was stirred overnight at room temperature, extracted with ethyl acetate, washed with sodium bicarbonate solution under organic phase protection, and dried to obtain intermediate material. S2: Dissolve 3.2g of intermediate material, 2.3g of 4-(hydroxymethyl)phenylboronic acid pinacol ester, 2.1g of DCC, and 0.1g of DMAP in dichloromethane. Stir the reaction under nitrogen protection at room temperature, filter, wash the filtrate with saturated sodium bicarbonate solution, and then purify the organic phase by rotary evaporation, chromatography, and drying to obtain the final product.

[0050] The hydrogen peroxide slow-release microspheres of this embodiment were prepared by the following steps: 2g of calcium chloride was dissolved in 20mL of deionized water or distilled water, and the pH value was adjusted to about 10 with ammonia. Then, 10mL of hydrogen peroxide (30%) was added, and after mixing evenly, the pH value was adjusted to 11 with NaOH solution. Then, 0.258g of dopamine hydrochloride was added, and the pH value was adjusted to 8.5 with NaOH solution. After stirring continuously for 2 hours, the solid and liquid were separated by high-speed centrifugation. The product after centrifugation was washed three times with ethanol and dried in a vacuum drying oven at 60℃ for 24 hours to obtain the final product.

[0051] Control group 1 The pigment wastewater treatment process in this control group includes the following steps: 1) The pigment wastewater to be treated (initial COD 3200 mg / L, SS 1100, LAS 45) first undergoes coagulation and sedimentation, including primary flocculation sedimentation, secondary flocculation sedimentation, and a sedimentation tank. The primary flocculation sedimentation retention time is 5 min, and the secondary flocculation sedimentation retention time is 15 min. 10% of the sludge discharged from the sedimentation tank is recycled to the inlet of the primary flocculation sedimentation tank. Then, the wastewater discharged from the sedimentation tank enters the micro-electrolysis treatment, with cast iron powder added at a dosage of 0.35 g / L and a hydraulic retention time of 90 min, controlling the removal of Fe. 2+ At a concentration of 30-50 mg / L, suspended solids and toxic substances are removed through coagulation, sedimentation, and micro-electrolysis to obtain pretreated wastewater. 2) The pretreated wastewater is treated by a biological unit, which includes hydrolysis acidification and A / O treatment. The hydrolysis acidification retention time is 10h and the upflow velocity is 0.8-1.2m / h. During the A / O treatment, the dissolved oxygen in the A tank is maintained at 0.5mg / L, the dissolved oxygen in the aeration tank is controlled at 2-4mg / L, and the MLSS is 2500-4000mg / L.

[0052] Performance testing The pigment wastewater treatment process was debugged according to Examples 1-2 and Control Group 1. After stable operation, the effluent indicators and residual sludge content were tested, and the test results were obtained. Figure 1 and Figure 2 As shown in the figure, the pigment wastewater treatment process of this application can achieve a stable effluent COD of around 80 mg / L and a total nitrogen of less than 50 mg / L. Figure 2 It can be seen that as the treatment progresses, the pigments in the wastewater continuously degrade, meeting the discharge standards. The residual sludge production was examined by calculating the sludge yield, which is calculated as MLSS (mg) / COD (mg). The sludge yield of Examples 1-2 in this application is less than 0.25, while the sludge yield of Control Group 1 is greater than 0.6. The pigment wastewater treatment process of this application produces almost no residual sludge after long-term operation.

[0053] Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A pigment wastewater treatment process with low residual sludge, characterized in that: Includes the following steps: 1) The wastewater to be treated is first subjected to coagulation sedimentation and micro-electrolysis to remove suspended solids and toxic substances, thus obtaining pretreated wastewater; 2) The pretreated wastewater is treated by a biochemical unit, which includes hydrolysis acidification and two-stage biological contact oxidation. During the biological contact oxidation process, biofilm packing is loaded and salicylaniline derivatives are added.

2. The pigment wastewater treatment process with low residual sludge according to claim 1, characterized in that: The salicylaniline derivative was prepared by the following steps: S1: 3,5-Dichlorosalicylic acid reacts with thionyl chloride to obtain crude acyl chloride. Then, the crude acyl chloride is dissolved in THF, followed by the addition of a THF solution of methyl 4-aminobenzoate and triethylamine. The mixture is stirred overnight at room temperature, extracted with ethyl acetate, washed, and dried to obtain an intermediate. S2: Dissolve the intermediate material, 4-(hydroxymethyl)phenylboronic acid pinacol ester, DCC, and DMAP in dichloromethane, stir the reaction at room temperature under nitrogen protection, and then filter, wash, and dry to obtain the final product.

3. The pigment wastewater treatment process with low residual sludge according to claim 2, characterized in that: In step S1, the mass-to-volume ratio of 3,5-dichlorosalicylic acid to thionyl chloride is (2-2.5g):(10-15mL).

4. The pigment wastewater treatment process with low residual sludge according to claim 2, characterized in that: In step S1, the molar ratio of 3,5-dichlorosalicylic acid to methyl 4-aminobenzoate is 1:(1-1.15).

5. The pigment wastewater treatment process with low residual sludge according to claim 2, characterized in that: In step S2, the mass ratio of intermediate material, 4-(hydroxymethyl)phenylboronic acid pinacol ester, DCC, and DMAP is (3-3.5):(2-2.5):(2-2.2):(0.08-0.12).

6. The pigment wastewater treatment process with low residual sludge according to claim 1, characterized in that: In step 2), hydrogen peroxide slow-release microspheres are also added when adding salicylaniline derivatives.

7. The pigment wastewater treatment process with low residual sludge according to claim 1, characterized in that: In step 2), the dosage of the salicylaniline derivative is 0.5-2 mg / L.

8. The pigment wastewater treatment process with low residual sludge according to claim 7, characterized in that: In step 2), the salicylaniline derivative is added starting 5 days after the start of the biological contact oxidation treatment.

9. The pigment wastewater treatment process with low residual sludge according to claim 1, characterized in that: In step 2), the biological contact oxidation treatment adopts a gradient dissolved oxygen process, including an aerobic stage, a facultative anaerobic stage, and an anaerobic stage.

10. The pigment wastewater treatment process with low residual sludge according to claim 9, characterized in that: The DO value in the aerobic stage is 2-3 mg / L, the DO value in the facultative anaerobic stage is 0.2-0.5 mg / L, and the DO value in the anaerobic stage is <0.1 mg / L.

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