Process for treating wastewater after pectin extraction

Abstract

The present application provides a kind of pectin extraction wastewater treatment process, it is related to pectin production technical field.The pectin extraction wastewater treatment process mainly includes: preliminary filtration, preliminary enzymolysis, secondary filtration, secondary enzymolysis, microbial treatment, evaporation concentration, flocculation precipitation and the like steps.The present application overcomes the deficiencies of the prior art, improves the effect of pectin wastewater treatment, improves the efficiency of wastewater treatment, and is convenient for actual operation.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of pectin production, in particular to a wastewater treatment process after pectin extraction. BACKGROUND

[0002] Pectin is generally obtained after multiple treatments of pomace, and a large amount of wastewater is generated during the extraction of pectin. Due to the difference in the process of pectin extraction, the types of wastewater generated are different. Generally, the wastewater contains a large amount of fiber materials, silt, original pectin, cellulose, hemicellulose, etc. If it is discharged at will, on the one hand, it will waste water resources; on the other hand, it will pollute the environment, so the pectin wastewater needs to be treated to meet the discharge requirements.

[0003] Generally, the treatment of pectin wastewater is mostly combined with microbial decomposition and flocculation, and the treatment effect of the related pollutants in the wastewater is not ideal. Usually, repeated operations are required to reach a certain discharge standard, which is time-consuming and laborious, and brings great trouble to actual production. SUMMARY

[0004] In view of the deficiencies of the prior art, the present application provides a wastewater treatment process after pectin extraction, which improves the treatment effect of pectin wastewater and improves the efficiency of wastewater treatment, facilitating actual operation.

[0005] To achieve the above purpose, the technical scheme of the present application is realized by the following technical scheme:

[0006] A wastewater treatment process after pectin extraction, the wastewater treatment process after pectin extraction comprises the following steps:

[0007] (1) Preliminary filtration: the wastewater after pectin extraction is placed in a filter tank, the pH is adjusted to 5.5, and then preliminary grid filtration is carried out by stirring, the filter residue is separated, and the first filtrate is obtained for standby;

[0008] (2) Preliminary enzymolysis: the first filtrate is added into the first composite enzyme prepared by mixing pectinase, cellulase and hemicellulase, and air is introduced for stirring and mixing, and after enzymolysis for 4-6h, the first enzymolysis wastewater is obtained for standby;

[0009] (3) Secondary filtration: active carbon, kaolin, diatomite and medical stone are selected to prepare a filter material, and the enzymolysis wastewater is subjected to secondary filtration through the filter material to obtain a second filtrate;

[0010] (4) Secondary enzymolysis: the second filtrate is added into the second composite enzyme prepared by mixing xylanase, glucose oxidase, acid protease and saccharifying enzyme, and is uniformly stirred, and after enzymolysis for 4-6h, a second enzymolysis liquid is obtained;

[0011] (5) Microbial treatment: the second enzymatic hydrolysate is added into the microbial treatment agent prepared by mixing Pseudomonas aeruginosa, Aspergillus niger, Bacillus laterosporus, Sclerotium rolfsii and yeast, and stirred uniformly, and then treated for 2-4 hours to obtain a microbial treatment liquid for standby;

[0012] (6) Evaporation and concentration: the microbial treatment liquid is placed in an evaporation tank for eight-fold concentration to obtain a concentrated liquid for standby;

[0013] (7) Flocculation and precipitation: the concentrated liquid is added into a flocculating agent, and after being stirred and flocculated, filtered to obtain a treated waste liquid.

[0014] Preferably, the first composite enzyme is added in the step (2) in an amount of 0.005%-0.02% of the mass of the first filtrate.

[0015] Preferably, the mass ratio of pectinase, cellulase and hemicellulase in the step (2) is 2-4:1-1.8:1-2.

[0016] Preferably, the mass ratio of activated carbon, kaolin, diatomite and medical stone in the step (3) is 3-8:1-2:2-3:4-9.

[0017] Preferably, the preparation method of the filtering material in the step (3) is as follows: the kaolin and medical stone are mixed and calcined at a high temperature of 500-600°C for 1.5-2 hours, then the activated carbon and diatomite are added and ground in a grinding machine to be crushed and passed through a 40-mesh sieve, and then a filtering layer with a thickness of 8-12 cm is prepared to obtain the filtering material.

[0018] Preferably, the second composite enzyme is added in the step (4) in an amount of 0.005%-0.02% of the mass of the second filtrate.

[0019] Preferably, the mass ratio of xylanase, glucose oxidase, acid protease and saccharifying enzyme in the second composite enzyme is 1-2:1-3:2-3:1-2.

[0020] Preferably, the microbial treatment agent is added in the step (5) in an amount of 0.008%-0.01% of the mass of the second enzymatic hydrolysate.

[0021] Preferably, the mass ratio of Pseudomonas aeruginosa, Aspergillus niger, Bacillus laterosporus, Sclerotium rolfsii and yeast in the microbial treatment agent in the step (5) is 1-4:4-8:1-2:1-2:2-3.

[0022] Preferably, the flocculating agent in the step (7) is a polysilicic acid flocculating agent, and the amount of the flocculating agent added is 0.1%-0.5% of the volume of the concentrated liquid.

[0023] The present application provides a kind of pectin extraction wastewater treatment process, compared with prior art advantages are in:

[0024] (1) the present application is first filtered to remove pomace and part of insoluble impurities, then through the enzymolysis of first composite enzyme to reduce the viscosity of waste liquid, and through the filtration material to filter, which can effectively improve the filtration efficiency, and the impurities in waste liquid can be effectively removed and adsorbed by filtration material, which improves the impurity removal efficiency of waste liquid;

[0025] (2) through the treatment of second composite enzyme and microbial treatment agent, the BOD and COD removal rate of wastewater can be effectively improved, and the efficiency of removal can be improved;

[0026] (3) the present application can further reduce the SS content in wastewater by adding flocculating agent after concentration, filtering after flocculation, and reducing resource waste. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and completely below in combination with the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor belong to the scope of protection of the present application.

[0028] Embodiment 1:

[0029] A kind of pectin extraction wastewater treatment process, the pectin extraction wastewater treatment process includes the following steps:

[0030] (1) preliminary filtration: the waste liquid after pectin extraction is placed in a filter tank, the pH is adjusted to 5.5, and then preliminary grating filtration is carried out by stirring, the filter residue is separated, and the first filtrate is obtained for standby;

[0031] (2) preliminary enzymolysis: the first filtrate is added to the first composite enzyme prepared by mixing pectinase, cellulase and hemicellulase in a mass ratio of 2:1:1, and the addition amount of the first composite enzyme is 0.005% of the mass of the first filtrate, and air is introduced for stirring and mixing, and after enzymolysis for 4h, the first enzymolysis waste liquid is obtained for standby;

[0032] (3) secondary filtration: select activated carbon, kaolin, diatomite and medical stone in a mass ratio of 3:1:2:4, mix kaolin and medical stone, calcine at 500 DEG C for 1.5h, then take out, add activated carbon and diatomite, grind and crush in a grinder, pass through a 40 mesh sieve, then prepare a filter layer with a thickness of 8cm as a filter material, and the enzymolysis waste liquid is filtered through the filter material to obtain a second filtrate;

[0033] (4) Secondary enzymatic hydrolysis: the second filtrate is added to a second composite enzyme prepared by mixing xylanase, glucose oxidase, acid protease, and saccharifying enzyme in a mass ratio of 1:1:2:1, and stirred uniformly, the addition amount of the second composite enzyme is 0.005% of the mass of the second filtrate, and the enzymatic hydrolysis is performed for 4 hours to obtain a second enzymatic hydrolysis liquid;

[0034] (5) Microbial treatment: the second enzymatic hydrolysis liquid is added to a microbial treatment agent prepared by mixing Pseudomonas aeruginosa, Aspergillus niger, Bacillus laterosporus, Sclerotium rolfsii, and yeast in a mass ratio of 1:4:1:1:2, and stirred uniformly, the addition amount of the microbial treatment agent is 0.008% of the mass of the second enzymatic hydrolysis liquid, and post-treatment is performed for 2 hours to obtain a microbial treatment liquid for standby;

[0035] (6) Evaporation and concentration: the microbial treatment liquid is placed in an evaporation tank for eight-fold concentration to obtain a concentrated liquid for standby;

[0036] (7) Flocculation and precipitation: the concentrated liquid is added to a polysilicic acid flocculant, the addition amount of the flocculant is 0.1% of the volume of the concentrated liquid, and after sufficient stirring and flocculation, filtration is performed to obtain a treated waste liquid.

[0037] Example 2:

[0038] A wastewater treatment process after pectin extraction, the wastewater treatment process after pectin extraction comprises the following steps:

[0039] (1) Preliminary filtration: the wastewater after pectin extraction is placed in a filtration tank, the pH is adjusted to 5.5, and then preliminary grid filtration is performed by stirring to separate the filter residue, and a first filtrate is obtained for standby;

[0040] (2) Preliminary enzymatic hydrolysis: the first filtrate is added to a first composite enzyme prepared by mixing pectinase, cellulase, and hemicellulase in a mass ratio of 4:1.8:2, and the addition amount of the first composite enzyme is 0.02% of the mass of the first filtrate, and air is introduced for stirring and mixing, and the enzymatic hydrolysis is performed for 6 hours to obtain a first enzymatic hydrolysis waste liquid for standby;

[0041] (3) Secondary filtration: activated carbon, kaolin, diatomite, and medical stone are selected in a mass ratio of 8:2:3:9, the kaolin and medical stone are mixed, placed in a high-temperature furnace at 600°C for calcination for 2 hours, taken out, added with activated carbon and diatomite, and ground and pulverized in a grinding machine to pass through a 40-mesh sieve, and then a filter layer with a thickness of 12 cm is prepared as a filtration material, and the enzymatic hydrolysis waste liquid is subjected to secondary filtration through the filtration material to obtain a second filtrate;

[0042] (4) Secondary enzymatic hydrolysis: the second filtrate is added to a second composite enzyme prepared by mixing xylanase, glucose oxidase, acid protease, and saccharifying enzyme in a mass ratio of 2:3:3:2, and stirred uniformly, the addition amount of the second composite enzyme is 0.02% of the mass of the second filtrate, and after enzymatic hydrolysis for 6 hours, a second enzymatic hydrolysis solution is obtained;

[0043] (5) Microbial treatment: the second enzymatic hydrolysis solution is added to a microbial treatment agent prepared by mixing Pseudomonas aeruginosa, Aspergillus niger, Bacillus laterosporus, Sclerotium rolfsii, and yeast in a mass ratio of 4:8:2:2:3, and stirred uniformly, the addition amount of the microbial treatment agent is 0.01% of the mass of the second enzymatic hydrolysis solution, and after post-treatment for 4 hours, a microbial treatment solution is obtained for standby;

[0044] (6) Evaporation and concentration: the microbial treatment solution is placed in an evaporation tank for eight-fold concentration, and a concentrated solution is obtained for standby;

[0045] (7) Flocculation and precipitation: the concentrated solution is added to a polysilicic acid flocculant, the addition amount of the flocculant is 0.5% of the volume of the concentrated solution, and after sufficient stirring and flocculation, the treated waste liquid is obtained by filtration.

[0046] Example 3:

[0047] A wastewater treatment process after pectin extraction, the wastewater treatment process after pectin extraction comprises the following steps:

[0048] (1) Preliminary filtration: the wastewater after pectin extraction is placed in a filter tank, the pH is adjusted to 5.5, and then preliminary grid filtration is performed by stirring, and the filter residue is separated, and a first filtrate is obtained for standby;

[0049] (2) Preliminary enzymatic hydrolysis: the first filtrate is added to a first composite enzyme prepared by mixing pectinase, cellulase, and hemicellulase in a mass ratio of 3:1.4:1.5, and the addition amount of the first composite enzyme is 0.012% of the mass of the first filtrate, and air is introduced for stirring and mixing, and after enzymatic hydrolysis for 5 hours, a first enzymatic hydrolysis waste liquid is obtained for standby;

[0050] (3) Secondary filtration: activated carbon, kaolin, diatomite, and medical stone are selected in a mass ratio of 5:1.5:2.5:7, kaolin and medical stone are mixed, placed in a high-temperature furnace at 550°C, calcined for 1.8 hours, taken out, activated carbon and diatomite are added, and ground and pulverized in a grinding machine to pass through a 40-mesh sieve, and then a filter layer with a thickness of 10 cm is prepared as a filter material, and the enzymatic hydrolysis waste liquid is subjected to secondary filtration through the filter material, and a second filtrate is obtained;

[0051] (4) Secondary enzymolysis: the second filtrate is added into a second composite enzyme prepared by mixing xylanase, glucose oxidase, acid protease, saccharifying enzyme in a mass ratio of 1.5:2:2.5:1.5, and stirred uniformly, the addition amount of the second composite enzyme is 0.012% of the mass of the second filtrate, and after enzymolysis for 5 hours, a second enzymolysis liquid is obtained;

[0052] (5) Microbial treatment: the second enzymolysis liquid is added into a microbial treatment agent prepared by mixing Pseudomonas aeruginosa, Aspergillus niger, Bacillus laterosporus, Sclerotium rolfsii, and yeast in a mass ratio of 2.5:6:1.5:1.5:2.5, and stirred uniformly, the addition amount of the microbial treatment agent is 0.009% of the mass of the second enzymolysis liquid, and after post-treatment for 3 hours, a microbial treatment liquid is obtained for standby;

[0053] (6) Evaporation concentration: the microbial treatment liquid is placed in an evaporation pool for eight-fold concentration, and a concentrated liquid is obtained for standby;

[0054] (7) Flocculation and precipitation: the concentrated liquid is added into a polysilicic acid flocculant, the addition amount of the flocculant is 0.3% of the volume of the concentrated liquid, and after sufficient stirring and flocculation, the treated waste liquid is obtained by filtration.

[0055] Comparative Example 1:

[0056] The wastewater treatment process after pectin extraction comprises the following steps:

[0057] (1) Preliminary filtration: the wastewater after pectin extraction is placed in a filtration pool, the pH is adjusted to 5.5, and then preliminary grid filtration is performed by stirring, and the filter residue is separated, and a first filtrate is obtained for standby;

[0058] (2) Preliminary enzymolysis: the first filtrate is added into a first composite enzyme prepared by mixing pectinase, cellulase, and hemicellulase in a mass ratio of 3:1.4:1.5, and the addition amount of the first composite enzyme is 0.012% of the mass of the first filtrate, and air is introduced for stirring and mixing, and after enzymolysis for 5 hours, a first enzymolysis waste liquid is obtained for standby;

[0059] (3) Secondary enzymolysis: the first enzymolysis waste liquid is added into a second composite enzyme prepared by mixing xylanase, glucose oxidase, acid protease, and saccharifying enzyme in a mass ratio of 1.5:2:2.5:1.5, and stirred uniformly, the addition amount of the second composite enzyme is 0.012% of the mass of the second filtrate, and after enzymolysis for 5 hours, a second enzymolysis liquid is obtained;

[0060] (4) Microbial treatment: the second enzymatic hydrolysate is added into a microbial treatment agent prepared by mixing Pseudomonas aeruginosa, Aspergillus niger, Bacillus laterosporus, Sclerotium rolfsii and yeast in a mass ratio of 2.5:6:1.5:1.5:2.5, and stirred uniformly, the addition amount of the microbial treatment agent is 0.009% of the mass of the second enzymatic hydrolysate, and the post-treatment is performed for 3 hours to obtain a microbial treatment liquid for standby;

[0061] (5) Evaporation and concentration: the microbial treatment liquid is placed in an evaporation tank to perform eight-fold concentration to obtain a concentrated liquid for standby;

[0062] (6) Flocculation and precipitation: the concentrated liquid is added into a polysilicic acid flocculant, the addition amount of the flocculant is 0.3% of the volume of the concentrated liquid, and after stirring and flocculation, filtration is performed to obtain a treated waste liquid.

[0063] Comparative Example 2

[0064] The wastewater treatment process after pectin extraction includes the following steps:

[0065] (1) Preliminary filtration: the wastewater after pectin extraction is placed in a filter tank, the pH is adjusted to 5.5, and then preliminary grid filtration is performed by stirring to separate the filter residue, and a first filtrate is obtained for standby;

[0066] (2) Preliminary enzymatic hydrolysis: the first filtrate is added into a first composite enzyme prepared by mixing pectinase, cellulase and hemicellulase in a mass ratio of 3:1.4:1.5, and the addition amount of the first composite enzyme is 0.012% of the mass of the first filtrate, and air is introduced for stirring and mixing, and the enzymatic hydrolysis is performed for 5 hours to obtain a first enzymatic hydrolysis waste liquid for standby;

[0067] (3) Secondary filtration: activated carbon, kaolin, diatomite and medical stone are selected in a mass ratio of 5:1.5:2.5:7, kaolin and medical stone are mixed, calcined at 550°C for 1.8 hours, then taken out, activated carbon and diatomite are added and ground and crushed in a grinding machine to pass through a 40-mesh sieve, and then a filter layer with a thickness of 10 cm is prepared as a filter material, and the enzymatic hydrolysis waste liquid is subjected to secondary filtration through the filter material to obtain a second filtrate;

[0068] (4) Microbial treatment: the second filtrate is added into a microbial treatment agent prepared by mixing Pseudomonas aeruginosa, Aspergillus niger, Bacillus laterosporus, Sclerotium rolfsii and yeast in a mass ratio of 2.5:6:1.5:1.5:2.5, and stirred uniformly, the addition amount of the microbial treatment agent is 0.009% of the mass of the second enzymatic hydrolysate, and the post-treatment is performed for 3 hours to obtain a microbial treatment liquid for standby;

[0069] (5) Evaporation and concentration: the microbial treatment liquid is placed in an evaporation tank to perform eight-fold concentration to obtain a concentrated liquid for standby;

[0070] (6) flocculation and sedimentation: the concentrated solution is added to a polysilicic acid flocculant, the amount of the flocculant added is 0.3% of the volume of the concentrated solution, after sufficient stirring and flocculation, filtration is performed, and a treated waste liquid is obtained.

[0071] Comparative Example 3

[0072] A wastewater treatment process after pectin extraction, the wastewater treatment process after pectin extraction comprises the following steps:

[0073] (1) preliminary filtration: the waste liquid after pectin extraction is placed in a filter tank, the pH is adjusted to 5.5, and then preliminary grid filtration is performed by stirring, the filter residue is separated, and a first filtrate is obtained for standby;

[0074] (2) preliminary enzymatic hydrolysis: the first filtrate is added to a first composite enzyme prepared by mixing pectinase, cellulase, and hemicellulase in a mass ratio of 3:1.4:1.5, the amount of the first composite enzyme added is 0.012% of the mass of the first filtrate, air is introduced for stirring and mixing, and after 5h of enzymatic hydrolysis, a first enzymatic hydrolysis waste liquid is obtained for standby;

[0075] (3) secondary filtration: activated carbon, kaolin, diatomite, and medical stone are selected in a mass ratio of 5:1.5:2.5:7, the kaolin and medical stone are mixed, calcined at 550℃ for 1.8h, then taken out, activated carbon and diatomite are added and ground and crushed in a grinding machine to pass through a 40-mesh sieve, and then a filter layer with a thickness of 10cm is prepared as a filter material, the enzymatic hydrolysis waste liquid is subjected to secondary filtration through the filter material, and a second filtrate is obtained;

[0076] (4) secondary enzymatic hydrolysis: the second filtrate is added to a second composite enzyme prepared by mixing xylanase, glucose oxidase, acid protease, and saccharifying enzyme in a mass ratio of 1.5:2:2.5:1.5, stirring is performed until uniform, the amount of the second composite enzyme added is 0.012% of the mass of the second filtrate, and after 5h of enzymatic hydrolysis, a second enzymatic hydrolysis liquid is obtained;

[0077] (5) microbial treatment: the second enzymatic hydrolysis liquid is added to Aspergillus niger and stirred uniformly, the amount of Aspergillus niger added is 0.009% of the mass of the second enzymatic hydrolysis liquid, and after 3h of treatment, a microbial treatment liquid is obtained for standby;

[0078] (6) evaporation and concentration: the microbial treatment liquid is placed in an evaporation tank, and eight-fold concentration is performed, and a concentrated solution is obtained for standby;

[0079] (7) flocculation and sedimentation: the concentrated solution is added to a polysilicic acid flocculant, the amount of the flocculant added is 0.3% of the volume of the concentrated solution, after sufficient stirring and flocculation, filtration is performed, and a treated waste liquid is obtained.

[0080] Detection:

[0081] The wastewater obtained from the same batch of pectin production was treated by the treatment methods of the above Examples 1-3 and Comparative Examples 1-3, respectively, and the removal rates of SS, BOD and COD in the wastewater treatment were detected, and the results are shown in the following table:

[0082] Group SS removal rate BOD removal rate COD removal rate Example 1 99.3％ 94.6％ 93.8％ Example 2 98.9％ 94.8％ 94.5％ Example 3 99.1％ 94.7％ 94.3％ Comparative Example 1 97.8％ 92.2％ 91.5％ Comparative Example 2 98.1％ 91.3％ 90.2％ Comparative Example 3 98.5％ 90.5％ 90.6％

[0083] From the above table, it can be seen that the wastewater treatment method adopted in the present application can effectively improve the removal rates of SS, BOD and COD in the pectin wastewater.

[0084] It should be noted that in this paper, relational terms such as first and second are used only to distinguish one entity or operation from another, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. Moreover, the terms "include", "contain" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or equipment. Without more limitations, the element defined by the statement "including a" does not exclude the presence of other identical elements in the process, method, article or equipment including the element.

[0085] The above examples are only used to illustrate the technical solutions of the present application, but not to limit it; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solution deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A process for the treatment of wastewater after pectin extraction, characterized in that, The wastewater treatment process after pectin extraction comprises the following steps: (1) preliminary filtration: the wastewater after pectin extraction is placed in a filter tank, the pH is adjusted to 5.5, and then preliminary grid filtration is carried out by stirring to separate the filter residue, and the first filtrate is obtained for standby; (2) preliminary enzymolysis: the first filtrate is added into the first composite enzyme prepared by mixing pectinase, cellulase and hemicellulase, and air is introduced for stirring and mixing, and after enzymolysis for 4-6 h, the first enzymolysis wastewater is obtained for standby; (3) secondary filtration: activated carbon, kaolin, diatomite and medical stone are selected to prepare a filter material, and the enzymolysis wastewater is subjected to secondary filtration through the filter material to obtain a second filtrate; (4) secondary enzymolysis: the second filtrate is added into the second composite enzyme prepared by mixing xylanase, glucose oxidase, acid protease and saccharifying enzyme, and is uniformly stirred, and after enzymolysis for 4-6 h, a second enzymolysis liquid is obtained; (5) microbial treatment: the second enzymolysis liquid is added into a microbial treatment agent prepared by mixing pseudomonas aeruginosa, aspergillus niger, bacillus laterosporus, sclerotium rolfsii and yeast, and is uniformly stirred, and after post-treatment for 2-4 h, a microbial treatment liquid is obtained for standby; the mass ratio of pseudomonas aeruginosa, aspergillus niger, bacillus laterosporus, sclerotium rolfsii and yeast in the microbial treatment agent is 1-4:4-8:1-2:1-2:2-3; (6) evaporation and concentration: the microbial treatment liquid is placed in an evaporation tank for eight-fold concentration to obtain a concentrated liquid for standby; (7) flocculation and precipitation: the concentrated liquid is added into a flocculating agent, is fully stirred and flocculated, and then is filtered to obtain a treated wastewater.

2. The process for treating wastewater after pectin extraction according to claim 1, characterized in that: In step (2), the addition amount of the first composite enzyme is 0.005%-0.02% of the mass of the first filtrate.

3. A process for treating wastewater after pectin extraction according to claim 2, characterized in that: In step (2), the mass ratio of pectinase, cellulase and hemicellulase is 2-4:1-1.8:1-2.

4. The process for treating wastewater after pectin extraction according to claim 1, characterized in that: In step (3), the mass ratio of activated carbon, kaolin, diatomite and medical stone is 3-8:1-2:2-3:4-9.

5. A process for treating wastewater after pectin extraction according to claim 4, characterized in that: In step (3), the preparation method of the filter material is as follows: kaolin and medical stone are mixed, calcined at 500-600℃ for 1.5-2 h, taken out, activated carbon and diatomite are added, ground and crushed in a grinding machine, and then passed through a 40-mesh sieve, and then a filter layer with a thickness of 8-12 cm is prepared, which is the filter material.

6. The process for treating wastewater after pectin extraction according to claim 1, characterized in that: In step (4), the addition amount of the second composite enzyme is 0.005%-0.02% of the mass of the second filtrate.

7. A process for treating wastewater after pectin extraction according to claim 6, characterized in that: In the second composite enzyme, the mass ratio of xylanase, glucose oxidase, acid protease and saccharifying enzyme is 1-2:1-3:2-3:1-2.

8. The process for treating wastewater after pectin extraction according to claim 1, characterized in that: In step (5), the addition amount of the microbial treatment agent is 0.008%-0.01% of the mass of the second enzymolysis liquid.

9. The process for treating wastewater after pectin extraction according to claim 1, characterized in that: In step (7), the flocculating agent is a polysilicic acid flocculating agent, and the addition amount of the flocculating agent is 0.1%-0.5% of the volume of the concentrated liquid.