Papermaking pulping wastewater anaerobic treatment method and application

Abstract

The invention relates to the technical field of papermaking pulping wastewater treatment, in particular to a papermaking pulping wastewater anaerobic treatment method and application. The method comprises the following steps: carrying out anaerobic treatment on wastewater; the wastewater comprises treated pulping wastewater or untreated pulping wastewater; the content of silicon dioxide in the wastewater is less than 80mg / L. According to the method, the influence of silicon dioxide on the anaerobic granular sludge can be avoided or reduced, the steps are simple, the practicability is high, the activity of the anaerobic granular sludge is remarkably improved, and the anaerobic granular sludge obtained after anaerobic treatment is clear in color, full in granules, good in strength and free of adhesion among the granules.

Description

Technical Field

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

[0002] In the papermaking pulping process, sodium silicate (Na 2 SiO 3 ), can improve the quality of pulp, whiteness of paper, etc., so it is widely used as an important additive in papermaking industry. However, as a result, sodium silicate (Na 2 SiO 3 ) content is too high, which seriously affects the activity of anaerobic granular sludge.

[0003] When the content of sodium silicate in paper pulping wastewater is high, gelled sodium silicate (i.e., gelled silicon dioxide) forms a layer of mucus 2 on the surface of the granular sludge, wrapping the granular sludge 1. Anaerobic bacteria are heterotrophic bacteria, which continue to produce biogas through endogenous respiration after digesting the initially adsorbed COD. This mucus 2 prevents the biogas produced inside from overflowing, and the biogas accumulates inside the granular sludge, causing the granular sludge 1 to form cavitation (as shown in the attached manual). Figure 1 This will cause the density of the granular sludge to decrease, resulting in poor settling performance of the granular sludge, or even the inability of the granular sludge to sink. When the biogas in the particles wrapped by the mucous membrane accumulates to a certain level, the pressure of the biogas is greater than the wrapping force of the mucous membrane, and the granular sludge will explode, breaking into pieces (as shown in the attached manual). Figure 2 As shown in the figure, the flocculated sludge is flocculent. It takes a long time for the flocculated sludge to granulate again, which is not conducive to the treatment of wastewater. In addition, after the surface of the anaerobic granular sludge is wrapped by the gelled sodium silicate film, the wastewater cannot fully contact the anaerobic granular sludge or the wastewater is difficult to penetrate into the anaerobic granular sludge, resulting in the deterioration of the activity of anaerobic bacteria and the reduction of COD removal rate. Summary of the invention

[0004] In order to solve the above problems, the present application proposes a method and application of anaerobic treatment of papermaking and pulping wastewater. The method can solve at least one aspect of the above technical problems.

[0005] This application is implemented through the following technical solutions:

[0006] One of the purposes of this application is to provide a method for anaerobic treatment of papermaking and pulping wastewater, comprising the following steps:

[0007] Anaerobic treatment of wastewater;

[0008] The wastewater includes treated pulping wastewater or untreated pulping wastewater;

[0009] The content of silicon dioxide in the wastewater is below 80 mg / L.

[0010] The method for anaerobic treatment of papermaking pulping wastewater provided in the present application has a silica content in the wastewater of less than 80 mg / L, thereby avoiding or reducing the influence of silica on anaerobic granular sludge. The steps are simple and the practicability is strong. The activity of the anaerobic granular sludge is significantly improved. The anaerobic granular sludge obtained after anaerobic treatment has a clear color, full particles, and no adhesion between the particles.

[0011] In some possible implementations, the content of silicon dioxide in the wastewater is 52.4 mg / L to 75.1 mg / L.

[0012] In some possible implementations, in the anaerobic treatment step, the content of silicon dioxide in the anaerobic system is below 80 mg / L.

[0013] In some possible implementations, after the anaerobic treatment, the mass content of gelled silicon dioxide in the sludge is less than 1% on a dry basis.

[0014] In some possible implementations, the pH value of the wastewater is 8-9.

[0015] In some possible implementations, the step of treating the pulping wastewater includes: flocculating, filtering and adjusting the pH value of the pulping wastewater to obtain the wastewater.

[0016] In some possible implementations, at least one of a flocculant and a coagulant aid is added in the flocculation step.

[0017] In some possible implementations, the flocculant is at least one of an iron salt, a magnesium salt, and an aluminum salt.

[0018] In some possible implementations, activated carbon is further added in the flocculation step; the amount of activated carbon added is 0.5 kg / t to 1 kg / t.

[0019] The second purpose of the present application is to provide an application of the method for anaerobic treatment of papermaking and pulping wastewater provided in the present application in the technical field of papermaking and pulping wastewater treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present drawings or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present drawings. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0021] Figure 1This is a schematic diagram of the structure in which gelled sodium silicate is wrapped around the surface of granular sludge to form a layer of mucous film in an embodiment of the present application.

[0022] Figure 2 This is a schematic diagram of the structure in which the pressure of the biogas in the embodiment of the present application is greater than the wrapping force of the mucosa, causing the mucosa to rupture.

[0023] Figure 3a For the comparative example of this application, 2 SiO 3 Schematic diagram of the appearance of anaerobic granular sludge in the initial stage of impact;

[0024] Figure 3b For the comparative example of this application, 2 SiO 3 Schematic diagram of the appearance of anaerobic granular sludge during the impact period;

[0025] Figure 3c For the comparative example of this application, 2 SiO 3 Schematic diagram of the appearance of anaerobic granular sludge at the end of the impact period;

[0026] Figure 4 A schematic diagram of a process for anaerobic treatment of papermaking and pulping wastewater in an embodiment of the present application;

[0027] Figure 5 This is a schematic diagram of the appearance of anaerobic granular sludge obtained by a method for anaerobic treatment of papermaking pulping wastewater in an embodiment of the present application.

[0028] Explanation of reference numerals: 1- granular sludge, 2- mucous membrane.

[0029] The purpose, features and advantages of this figure will be further described in conjunction with the embodiments with reference to the accompanying drawings. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application is described and illustrated below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not intended to limit the present application. Based on the embodiments provided in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present application.

[0031] Obviously, the following descriptions are only some examples or embodiments of the present application. For ordinary technicians in this field, the present application can also be applied to other similar scenarios without creative work. In addition, it can also be understood that although the efforts made in this development process may be complicated and lengthy, for ordinary technicians in the field related to the content disclosed in this application, some changes in design, manufacturing or production based on the technical content disclosed in this application are just conventional technical means, and should not be understood as insufficient content disclosed in this application.

[0032] However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of substantially the same structures may be omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the following description is provided for those skilled in the art to fully understand the present application and is not intended to limit the subject matter described in the claims.

[0033] If not otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution, and all technical features and optional technical features of the present application can be combined with each other to form a new technical solution.

[0034] Sodium silicate is a strong base weak acid salt with no fixed composition, and its molecular formula is Na 2 O·mSiO 2 ·xH 2 O, can be strongly hydrolyzed in aqueous solution, and the solution is alkaline. The physical properties of sodium silicate vary with the molar ratio of silicon dioxide to sodium oxide in the product, and the molar ratio is often called the modulus m (generally between 1.5 and 3.5). The modulus is the most important characteristic parameter of sodium silicate. The larger the modulus, the weaker the alkalinity, and the smaller the modulus, the stronger the alkalinity. In addition, the polymerization degree of sodium silicate with different moduli is different, which leads to significant differences in the silicic acid component in its hydrolysis product, which has an important impact on production and application. Amorphous sodium silicate is a mixed solution of many sodium hydrogen polysilicate salts. The main role of its application in papermaking and pulping is the polysilicic acid and its hydrolysis products. Silicate anions include monosilicic acid (orthosilicic acid), disilicate, trisilicic acid, tetrasilicic acid, cyclotetrasilicic acid, cyclohexasilicic acid, cubic octasilicic acid and other low-polymerization silicic acids, as well as the condensation products of cubic octasilicic acid (high-polymer silicic acid). Sodium silicate solution is a metastable system, in which the polysilicic acids are in a complex meta-equilibrium state. When the content of any component changes, the original balance will be broken and a new balance will be established. In other words, the composition (structure and content) of water glass will change immediately.

[0035] In the papermaking and pulping process, sodium silicate not only provides alkalinity, but also plays the role of penetration, buffer and stabilizer. Therefore, sodium silicate is indispensable in the papermaking and pulping process. For the papermaking and pulping wastewater generated by the papermaking and pulping process, anaerobic bacteria in anaerobic reaction are generally used to decompose the organic matter in the wastewater into methane, carbon dioxide and other gases. In the anaerobic reaction system, when the content of sodium silicate is high, anaerobic granular sludge is as shown in the attached manual. Figure 3a , Figure 3b and Figure 3c As shown in the instruction manual, Figure 3a , Figure 3b and Figure 3c These are the initial, middle and final stages of anaerobic granular sludge affected by sodium silicate. As can be seen from the figure, the sludge appears dull grayish white, the particles are wrapped in a layer of milky white colloid, the inside of the particles are hollow, the particles are adhered to each other, and are easily broken by a slight external force.

[0036] In order to reduce the content of sodium silicate in wastewater, thereby improving the activity of anaerobic granular sludge, the present application embodiment proposes a method and application of anaerobic treatment of papermaking and pulping wastewater. The method can avoid or reduce the influence of silicon dioxide on anaerobic treatment, has simple steps, strong practicability, and significantly improves the activity of anaerobic granular sludge. The anaerobic granular sludge obtained after anaerobic treatment has clear color, full particles, strength, and no adhesion between particles.

[0037] The following is a detailed description of an optimization method for treating papermaking and pulping wastewater.

[0038] In a first aspect of the present application, a method for anaerobic treatment of papermaking and pulping wastewater is provided, such as Figure 4 As shown, the following steps are included:

[0039] S1. Anaerobic treatment of wastewater;

[0040] The wastewater includes treated pulping wastewater or untreated pulping wastewater;

[0041] The content of silicon dioxide in the wastewater is below 80 mg / L.

[0042] The method for anaerobic treatment of papermaking pulping wastewater provided in the embodiment of the present application has a silica content of less than 80 mg / L in the wastewater, thereby avoiding or reducing the influence of silica on anaerobic granular sludge. The steps are simple and the practicability is strong, which significantly improves the treatment effect of the anaerobic reaction. The anaerobic sludge obtained after anaerobic treatment has a clear color, full particles, and no adhesion between the particles.

[0043] Treated pulping wastewater refers to pulping wastewater generated by the papermaking pulping process, which is obtained after a series of treatments such as flocculation, filtration and pH adjustment, and has a silica content of less than 80 mg / L.

[0044] Untreated pulping wastewater refers to pulping wastewater generated by the paper pulping process, which has not undergone any treatment such as flocculation and has a silica content of less than 80 mg / L.

[0045] In the embodiment, the content of silicon dioxide in the wastewater is below 80 mg / L and can be 0 mg / L, 40 mg / L, 50 mg / L, 60 mg / L, 80 mg / L and other typical but non-limiting contents or a range between any two contents. When the content of silicon dioxide in the wastewater is 52.4 mg / L to 75.1 mg / L, the content of gelled silicon dioxide in the anaerobic granular sludge is 0.38% to 0.58%, but the methane yield is 71.6% to 78.9%, and the methane yield is relatively high. This is because in the wastewater within this silicon dioxide content range, sodium silicate can be grafted (but not wrapped) on the surface of the anaerobic granular sludge, thereby assisting anaerobic bacteria to decompose organic matter in the water and increase the methane yield; when the sodium silicate content is too low, there is no such assisting effect.

[0046] In some embodiments, in the above step S1, the wastewater is generated by a papermaking and pulping process, and the input amount of sodium silicate in the papermaking and pulping process is less than 30 kg / t, wherein:

[0047] (1) In the pure pulping process, the amount of sodium silicate added to the absolute dry pulp is less than 18 kg / t;

[0048] (2) In the papermaking pulping process, the amount of sodium silicate added to the absolute dry pulp is less than 30 kg / t, generally 20 kg / t to 30 kg / t.

[0049] In the above-mentioned papermaking and pulping, the input amount of sodium silicate is relatively low, and the dosage can be more accurately controlled from the source (papermaking and pulping), thereby intuitively reducing the content of sodium silicate in the wastewater. In the papermaking and pulping process, due to the dilution effect of a large amount of papermaking wastewater, the input amount of sodium silicate can be increased to 20kg / t to 30kg / t.

[0050] In some embodiments, in the above step S1, the step of treating the pulping wastewater includes: flocculating, filtering and adjusting the pH value of the pulping wastewater to obtain the wastewater. In this case, after the pulping wastewater undergoes a series of treatments, the content of silica in the wastewater is reduced to below 80 mg / L, thereby avoiding or reducing the impact of silica on anaerobic treatment and improving

[0051] In some embodiments, at least one of a flocculant and a coagulant is added to the flocculation step. In this case, the flocculant can precipitate suspended matter and colloidal substances such as sodium silicate in the pulping wastewater, thereby eliminating turbidity and heterochromatic substances in the water; the coagulant can accelerate the precipitation of suspended matter and colloidal substances such as sodium silicate in the pulping wastewater, improve the clarification effect, and improve the efficiency of pulping wastewater treatment. It should be noted that the flocculant is a conventional material commonly used in the art, and the specific material of the flocculant does not need to be specifically limited in the embodiments of the present application, but as an example, the flocculant can be selected from at least one of iron salt, magnesium salt, and aluminum salt. Iron salt, magnesium salt, and aluminum salt are all metal salt flocculants commonly used in the art, so iron salt, magnesium salt, and aluminum salt do not need to be specifically limited in the embodiments of the present application, and as an example, the iron salt can be ferric chloride, ferric sulfate, magnesium salt can be magnesium chloride, magnesium sulfate, etc., and aluminum salt can be alum, aluminum chloride, aluminum sulfate, etc. These metal sulfates and chlorides can remove suspended matter and colloidal substances such as sodium silicate in pulping wastewater without introducing new impurities that pollute water resources. Similarly, the coagulant is also a conventional material commonly used in the art. The specific material of the coagulant does not need to be specifically limited in the embodiments of the present application, but as an example, the coagulant can be polyacrylamide. In addition, polyacrylamide can also be used as a flocculant. When used as a flocculant, the charge of the polyacrylamide colloid interacts with the charge of the suspended particles in the wastewater, and through electrical neutralization and adsorption bridging, the suspended particles are condensed to form large particles, thereby settling quickly. Furthermore, the amount of flocculant and coagulant added needs to be adjusted according to the actual situation of the pulping wastewater, which is also a conventional adjustment in the art. As an example, the amount of flocculant added can be 1kg / t to 6kg / t, and the amount of coagulant added can be 0.02kg / t to 0.05kg / t.

[0052] In other embodiments, activated carbon is also added in the flocculation step. In some embodiments, the amount of activated carbon added is 0.5kg / t to 1kg / t. In the exemplary embodiment, it can be a typical but non-limiting amount such as 0.5kg / t, 0.8kg / t, 1kg / t, or a range between any two amounts. In this case, the activated carbon can promote the formation of large particle precipitation of insoluble metal salts for easy removal. It should be noted that the types of activated carbon are existing materials and can be selected according to actual needs, but as an example, common sources of activated carbon are wood activated carbon, fruit shell activated carbon, and coal activated carbon; the iodine value of the activated carbon is above 800mg / g.

[0053] In other specific embodiments, the average particle size of the activated carbon is 90 μm to 120 μm, and in the exemplary embodiment, it can be a typical but non-limiting average particle size such as 90 μm, 100 μm, 120 μm, or a range between any two average particle sizes. In this case, after the pulping wastewater is filtered, the activated carbon can be retained in the filtrate to provide a substrate for microorganisms to attach to, thereby increasing the reproduction of microorganisms and the activity of degrading organic matter, which is helpful for the biological treatment (anaerobic reactor) process of wastewater.

[0054] In some embodiments, the filtration step adopts a screen filtration, and the mesh number of the screen is 80 mesh to 120 mesh. In the exemplary example, it can be a typical but non-limiting mesh number such as 80 mesh, 90 mesh, 100 mesh, 120 mesh, or a range between any two mesh numbers. In this case, the screen can screen out the sediment generated in the flocculation step and the large suspended particles in the pulping wastewater. It should be noted that the mesh shape of the screen is a conventional shape in the art, and can be selected according to actual needs, but as an example, it can be distinguished by the mesh shape, which can be a round screen, an oblique screen, and a hexagonal rim screen.

[0055] In some embodiments, an acid solution or an alkali solution is used to adjust the pH value of the pulping wastewater. In some specific embodiments, the acid solution includes at least one of sulfuric acid and hydrochloric acid. In some specific embodiments, the alkali solution includes at least one of sodium hydroxide and sodium carbonate. In this case, these acid solutions or alkali solutions are used to adjust the pH value without introducing new impurities.

[0056] In some embodiments, in the above step S1, the pH value of the wastewater is 8 to 9. In this case, the pH value affects the SiO 2 Solubility, when pH value is 8-9, soluble SiO 2 The solubility of silicate is high, thus reducing the formation of single molecule silicate and polysilicate sol.

[0057] The effect of pH on the chemical equilibrium of silicate hydrolysis reaction is obvious. The chemical equilibrium of silicate hydrolysis reaction is shown in the following equations (1) to (6): When pH ≥ 3, equations (2) and (3) dominate the reaction; when pH = 8 to 9, this condensation ability reaches the maximum. When pH ≥ 10, reaction (5) is the main reaction, and orthosilicate ions with good water solubility are generated. The formation of dimers from orthosilicate is a slow process. Once formed, trimers are generated almost immediately, and the rate of formation of tetramers and pentamers is slower. When the hexamers are formed, side group reactions begin to occur, forming isomers and cross-linking, resulting in colloidal SiO 2 Formation, eventual gel and scaling.

[0058] Among them, the chemical equilibrium formula of the silicate hydrolysis reaction is as follows:

[0059]

[0060] It can be seen that when pH = 8-9, the soluble SiO 2 The solubility of silicate is high, thus reducing the formation of single molecule silicate and polysilicate sol.

[0061] In some embodiments, in the above step S1, in the anaerobic treatment step, the content of silicon dioxide in the anaerobic reaction system is 80 mg / L or less, and in the exemplary embodiment, it can be 0 mg / L, 30 mg / L, 40 mg / L, 60 mg / L, 80 mg / L, etc., which are typical but non-limiting contents, or a range between any two contents. In this case, silicon dioxide with a content of 80 mg / L or less has little or no effect on the anaerobic granular sludge, thereby improving the activity of the anaerobic granular sludge.

[0062] In some specific embodiments, in the above step S1, anaerobic treatment is performed using an anaerobic reactor. It should be noted that the anaerobic reactor is a conventional choice in the art and is not particularly limited in the embodiments of the present application, but as an example, the anaerobic reactor can be an IC tower.

[0063] In some specific embodiments, the content of silica in the anaerobic reaction system at the bottom of the anaerobic reactor is less than 80 mg / L, and in exemplary examples, it can be a typical but non-limiting content such as 0 mg / L, 30 mg / L, 40 mg / L, 60 mg / L, 80 mg / L, or a range between any two contents; the content of silica in the anaerobic reaction system in the middle is less than 67 mg / L, and in exemplary examples, it can be a typical but non-limiting content such as 0 mg / L, 30 mg / L, 40 mg / L, 60 mg / L, 67 mg / L, or a range between any two contents; the content of silica in the anaerobic reaction system in the upper part is less than 63 mg / L, and in exemplary examples, it can be a typical but non-limiting content such as 0 mg / L, 30 mg / L, 40 mg / L, 60 mg / L, 63 mg / L, or a range between any two contents.

[0064] The bottom refers to the position between 0 and 1 / 3 (excluding 1 / 3) of the total height of the liquid level of the anaerobic reaction system in the anaerobic reactor.

[0065] The middle portion refers to the position between 1 / 3 and 5 / 6 (excluding 5 / 6) of the total height of the liquid level of the anaerobic reaction system in the anaerobic reactor.

[0066] The upper part refers to the position of 5 / 6 to 1 of the total height of the liquid level of the anaerobic reaction system in the anaerobic reactor.

[0067] Exemplarily, the total height of the liquid level of the anaerobic reaction system is 24m, then the bottom is the position with a height of 0m to 9m (not including 9m) in the anaerobic reaction system, the middle is the position with a height of 9m to 20m (not including 20m) in the anaerobic reaction system, and the upper part is the position with a height of 20m to 24m in the anaerobic reaction system.

[0068] In some specific embodiments, after anaerobic treatment, the mass content of gelled silica in the sludge is less than 1% on a dry basis.

[0069] A second aspect of the embodiments of the present application provides an application of a method for anaerobic treatment of papermaking and pulping wastewater in the technical field of papermaking and pulping wastewater treatment.

[0070] The following is further described in conjunction with specific embodiments.

[0071] Example 1

[0072] Example 1 provides a method for anaerobic treatment of papermaking and pulping wastewater, the steps are as follows:

[0073] Anaerobic treatment of wastewater;

[0074] Among them, the source of wastewater includes pulping wastewater generated by paper pulping, and the silica content in the wastewater is 79 mg / L.

[0075] Example 2

[0076] Example 2 proposes a method for anaerobic treatment of papermaking pulping wastewater, and the steps are basically the same as those of Example 1, except that the content of silicon dioxide in the wastewater is 75.1 mg / L.

[0077] Example 3

[0078] Example 3 proposes a method for anaerobic treatment of papermaking pulping wastewater, and the steps are basically the same as those of Example 1, except that the content of silicon dioxide in the wastewater is 69.8 mg / L.

[0079] Example 4

[0080] Example 4 proposes a method for anaerobic treatment of papermaking pulping wastewater, and the steps are basically the same as those of Example 1, except that the content of silicon dioxide in the wastewater is 70.1 mg / L.

[0081] Example 5

[0082] Example 5 proposes a method for anaerobic treatment of papermaking pulping wastewater, and the steps are basically the same as those of Example 1, except that the content of silicon dioxide in the wastewater is 70.5 mg / L.

[0083] Example 6

[0084] Example 6 proposes a method for anaerobic treatment of papermaking pulping wastewater, and the steps are basically the same as those of Example 1, except that the content of silicon dioxide in the wastewater is 70.4 mg / L.

[0085] Example 7

[0086] Example 7 proposes a method for anaerobic treatment of papermaking pulping wastewater, and the steps are basically the same as those of Example 1, except that the content of silicon dioxide in the wastewater is 71.1 mg / L.

[0087] Example 8

[0088] Example 8 proposes a method for anaerobic treatment of papermaking pulping wastewater, and the steps are basically the same as those of Example 1, except that the content of silicon dioxide in the wastewater is 70.9 mg / L.

[0089] Example 9

[0090] Example 9 proposes a method for anaerobic treatment of papermaking pulping wastewater, and the steps are basically the same as those of Example 1, except that the content of silicon dioxide in the wastewater is 68 mg / L.

[0091] Example 10

[0092] Example 10 proposes a method for anaerobic treatment of papermaking pulping wastewater, and the steps are basically the same as those of Example 1, except that the content of silicon dioxide in the wastewater is 72.3 mg / L.

[0093] Embodiment 11

[0094] Example 11 proposes a method for anaerobic treatment of papermaking pulping wastewater, and the steps are basically the same as those of Example 1, except that the content of silicon dioxide in the wastewater is 5.8 mg / L.

[0095] Example 12

[0096] Example 12 proposes a method for anaerobic treatment of papermaking pulping wastewater, and the steps are basically the same as those of Example 1, except that the content of silicon dioxide in the wastewater is 10.6 mg / L.

[0097] Embodiment 13

[0098] Example 13 proposes a method for anaerobic treatment of papermaking pulping wastewater, and the steps are basically the same as those of Example 1, except that the content of silicon dioxide in the wastewater is 15.9 mg / L.

[0099] Embodiment 14

[0100] Example 14 proposes a method for anaerobic treatment of papermaking pulping wastewater, and the steps are basically the same as those of Example 1, except that the content of silicon dioxide in the wastewater is 21.5 mg / L.

[0101] Embodiment 15

[0102] Example 15 proposes a method for anaerobic treatment of papermaking pulping wastewater, and the steps are basically the same as those of Example 1, except that the content of silicon dioxide in the wastewater is 31.6 mg / L.

[0103] Example 16

[0104] Example 16 proposes a method for anaerobic treatment of papermaking pulping wastewater, and the steps are basically the same as those of Example 1, except that the content of silicon dioxide in the wastewater is 42.8 mg / L.

[0105] Embodiment 17

[0106] Example 17 proposes a method for anaerobic treatment of papermaking pulping wastewater, and the steps are basically the same as those of Example 1, except that the content of silicon dioxide in the wastewater is 52.4 mg / L.

[0107] Embodiment 18

[0108] Example 18 proposes a method for anaerobic treatment of papermaking pulping wastewater, and the steps are basically the same as those of Example 1, except that the content of silicon dioxide in the wastewater is 58.6 mg / L.

[0109] Embodiment 19

[0110] Example 19 proposes a method for anaerobic treatment of papermaking pulping wastewater, and the steps are basically the same as those of Example 1, except that the content of silicon dioxide in the wastewater is 62.1 mg / L.

[0111] Embodiment 20

[0112] Example 20 proposes a method for anaerobic treatment of papermaking pulping wastewater, and the steps are basically the same as those of Example 1, except that the content of silicon dioxide in the wastewater is 65.7 mg / L.

[0113] Embodiment 21

[0114] Example 21 proposes a method for anaerobic treatment of papermaking and pulping wastewater, the steps are as follows:

[0115] (1) Select the source of wastewater: pulping wastewater generated by paper pulping process. In paper pulping, the input amount of sodium silicate in the absolute dry pulp is 28 kg.

[0116] (2) 345 tons of papermaking wastewater were selected, aluminum chloride was used as the flocculant, and the addition amount was 1 kg / t; polyacrylamide was used as the coagulant aid, and the addition amount was 1 kg / t.

[0117] (3) Adding a mixture of flocculant and coagulant aid into papermaking pulping wastewater under stirring conditions.

[0118] (4) Filter through a 100-mesh sieve to obtain a filtrate and a filter residue, where the filtrate is wastewater.

[0119] (5) The pH value of the wastewater was adjusted to 9 and then anaerobic treatment was carried out. The silica content in the wastewater was 62.3 mg / L.

[0120] Embodiment 22

[0121] Example 22 proposes a method for anaerobic treatment of papermaking pulping wastewater, the steps are basically the same as those of Example 21, except that:

[0122] The source of the wastewater selected in step (1) is: pulping wastewater generated by a pure pulping process. In the pure pulping process, the input amount of sodium silicate in the absolute dry pulp is 18 kg.

[0123] The silica content in the wastewater is 59.1 mg / L.

[0124] Embodiment 23

[0125] Example 23 proposes a method for anaerobic treatment of papermaking pulping wastewater, the steps are basically the same as those of Example 21, except that:

[0126] The source of the wastewater selected in step (1) is: pulping wastewater generated by a pure pulping process. In the pure pulping process, the input amount of sodium silicate in the absolute dry pulp is 10 kg.

[0127] The silica content in the wastewater is 38.3 mg / L

[0128] Embodiment 24

[0129] Example 24 proposes a method for anaerobic treatment of papermaking pulping wastewater, the steps are basically the same as those of Example 21, except that:

[0130] Activated carbon is also added in step (3), wherein the source of the activated carbon is wood activated carbon (iodine value is 800 mg / g), the average particle size is 100 μm, and the amount of activated carbon used is 276 kg.

[0131] The silica content in the wastewater is 58.6 mg / L

[0132] Comparative Example 1

[0133] Comparative Example 1 proposes a method for anaerobic treatment of papermaking and pulping wastewater, the steps are as follows:

[0134] The wastewater is treated anaerobically; the source of the wastewater is pulping wastewater generated by paper pulping, and the content of silicon dioxide in the wastewater is 121 mg / L.

[0135] Comparative Example 2

[0136] Comparative Example 2 proposes a method for anaerobic treatment of papermaking and pulping wastewater, and the steps are basically the same as those of Comparative Example 1, except that the content of silicon dioxide in the wastewater is 99.3 mg / L.

[0137] Comparative Example 3

[0138] Comparative Example 3 proposes a method for anaerobic treatment of papermaking pulping wastewater, and the steps are basically the same as those of Comparative Example 1, except that the content of silicon dioxide in the wastewater is 97.4 mg / L.

[0139] Comparative Example 4

[0140] Comparative Example 4 proposes a method for anaerobic treatment of papermaking pulping wastewater, and the steps are basically the same as those of Comparative Example 1, except that the content of silicon dioxide in the wastewater is 119 mg / L.

[0141] Comparative Example 5

[0142] Comparative Example 5 proposes a method for anaerobic treatment of papermaking pulping wastewater, and the steps are basically the same as those of Comparative Example 1, except that the content of silicon dioxide in the wastewater is 87.5 mg / L.

[0143] Comparative Example 6

[0144] Comparative Example 6 proposes a method for anaerobic treatment of papermaking pulping wastewater, and the steps are basically the same as those of Comparative Example 1, except that the content of silicon dioxide in the wastewater is 88.6 mg / L.

[0145] Comparative Example 7

[0146] Comparative Example 7 proposes a method for anaerobic treatment of papermaking pulping wastewater, and the steps are basically the same as those of Comparative Example 1, except that the content of silicon dioxide in the wastewater is 89.1 mg / L.

[0147] In order to verify the progressiveness of the method for anaerobic treatment of papermaking pulping wastewater proposed in the embodiment of the present application, the following tests were performed on the method for anaerobic treatment of papermaking pulping wastewater provided in the embodiment and the comparative example:

[0148] ① The test results of the silica content of the wastewater at the inlet, bottom, middle, top and outlet of the anaerobic reactor are shown in Table 1. The test of the silica content in the liquid at the inlet, middle, top and outlet is carried out according to 4.2 Determination of constant silicon content and 4.3 Determination of trace silicon content in GB / T12149 "Determination of silicon in industrial circulating cooling water and boiler water"; the test of the silica content in the bottom sludge is carried out according to 6.7 Determination of silicon dioxide-ammonium chloride weight method (reference method) in GB / T176 "Cement Chemical Analysis Method".

[0149] ② Taking Example 1 and Comparative Example 1 as examples, the appearance of the anaerobic granular sludge obtained according to the method of Example 1 is as shown in the attached manual. Figure 5 As shown, the appearance of the anaerobic granular sludge obtained by the method of Comparative Example 1 is as shown in the attached manual. Figure 3a to Figure 3c The content (mass fraction) of gelled silica in the anaerobic granular sludge obtained after anaerobic treatment was tested for the examples and comparative examples, and the test results are shown in Table 2 below.

[0150] The content of gelled silica is tested according to 4.2 Determination of constant silicon content and 4.3 Determination of trace silicon content in GB / T12149 "Determination of silicon in industrial circulating cooling water and boiler water".

[0151] ③ In the anaerobic treatment steps of the embodiment and the comparative example, the actual methane production was detected and compared with the theoretical methane production to obtain the methane yield. The actual methane production and yield are shown in Table 3 below.

[0152] Among them, the theoretical production of methane is calculated based on the consumption of COD, as follows:

[0153] According to the chemical reaction formula: CH 4 +2O 2 =CO 2 +2H 2 O, it is known that 1g of COD can produce 0.35L of COD under standard conditions (273.15K, 101.325kPa), so 1t of COD can produce 350m 3 CH 4 .

[0154] The actual methane production is tested according to the standard NY / T 1700 “Gas chromatography method for determination of methane and carbon dioxide in biogas”.

[0155] Table 1

[0156]

[0157]

[0158] Note: In Table 1 above, "influent" refers to the silica content in the wastewater at the inlet of the anaerobic reactor, "bottom" refers to the silica content in the wastewater at the bottom of the anaerobic reactor, "middle" refers to the silica content in the wastewater in the middle of the anaerobic reactor, and "upper" refers to the silica content in the papermaking and pulping wastewater at the upper part of the anaerobic reactor.

[0159] Table 2

[0160]

[0161]

[0162] Note: In Table 2 above, "gelled silica" means the content of gelled silica in anaerobic granular sludge on a dry basis.

[0163] Table 3

[0164]

[0165]

[0166] From Tables 1 to 3 above, the instructions attached Figure 3a , Figure 3b , Figure 3c and Figure 5 At least the following conclusions can be drawn:

[0167] ① From Table 1, Table 2, and the Appendix to the Instruction Manual Figure 3a , Figure 3b , Figure 3c and Figure 5 It can be seen that when the content of sodium silicate is high, the anaerobic granular sludge after anaerobic reaction is as shown in the attached manual. Figure 3a , Figure 3b and Figure 3c As shown, Figure 3a , Figure 3b and Figure 3c Anaerobic granular sludge affected by sodium silicate has a dull grayish-white appearance, and the particles are covered with a layer of milky white colloid (gel sodium silicate). The particles are adhered to each other and are easily broken by external force. When the content of sodium silicate is low, the anaerobic granular sludge after anaerobic reaction is as shown in the attached manual. Figure 5 As shown, Figure 5 The anaerobic sludge is in good condition, with clear and full particles, and no adhesion between particles. It can be seen that reducing the sodium silicate content in wastewater can significantly improve the activity of anaerobic sludge particles.

[0168] ② From the data in Table 1 and Table 3, it can be seen that: when the content of silica in the wastewater is below 42.8 mg / L (excluding 0 mg / L, Examples 11 to 16, Example 23), although the content of gelled silica in the anaerobic granular sludge is low (below 0.39%), the methane yield is also very low; when the content of silica in the wastewater is between 52.4 mg / L and 75.1 mg / L (Examples 2 to 10, Examples 17 to 22, Example 24), the content of gelled silica in the anaerobic granular sludge is 0.38% to 0.58%, but the methane yield is 71.6% to 78.9%; and when the content of silica in the wastewater is above 75.1 mg / L (excluding 75.1 mg / L, 79 mg / L in Example 1), the methane yield decreases. It can be seen that when the silica content in the wastewater is between 52.4mg / L and 75.1mg / L, the content of gelled silica in the anaerobic granular sludge is at a lower level and the methane yield is higher. This is because in the wastewater within this silica content range, sodium silicate can be grafted (but not wrapped) on the surface of the anaerobic granular sludge, thereby assisting anaerobic bacteria to decompose organic matter in the water and increase the methane yield; when the sodium silicate content is too low, there is no such assisting effect. Therefore, when the sodium silicate content in the wastewater is controlled at 52.4mg / L to 75.1mg / L, the methane yield can be increased without affecting the quality of the anaerobic granular sludge.

[0169] ② It can be seen from the data of Examples 21 to 23 in Tables 1 to 3 that the method for anaerobic treatment of papermaking pulping wastewater according to the embodiments of the present application can reduce the sodium silicate content in the wastewater from the source of the wastewater: reducing the input amount of sodium silicate during papermaking pulping, and can also reduce the amount of materials such as flocculants added during the treatment process, thereby reducing the treatment cost.

[0170] ③ From the data of Example 24 in Tables 1 to 3, it can be seen that the addition of activated carbon can significantly reduce the content of silicon dioxide, the content of gel silicon dioxide, and the biogas yield in the wastewater. It can be seen that activated carbon can remove sodium silicate in papermaking wastewater and provide a matrix for microorganisms to attach in anaerobic reactions, thereby increasing the reproduction of microorganisms and the activity of degrading organic matter, which is helpful for the biological treatment (anaerobic reactor) process of wastewater.

[0171] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A method for anaerobic treatment of papermaking and pulping wastewater, characterized in that: The steps include: Anaerobic treatment of wastewater; The wastewater includes treated pulping wastewater or untreated pulping wastewater; The content of silicon dioxide in the wastewater is below 80 mg / L.

2. The method for anaerobic treatment of papermaking and pulping wastewater according to claim 1, characterized in that: The content of silicon dioxide in the wastewater is 52.4 mg / L to 75.1 mg / L.

3. The optimization method for treating papermaking and pulping wastewater according to claim 1, characterized in that: In the anaerobic treatment step, the content of silicon dioxide in the anaerobic system is below 80 mg / L.

4. The optimization method for treating papermaking and pulping wastewater according to claim 1, characterized in that: After the anaerobic treatment, the mass content of gelled silicon dioxide in the sludge is less than 1% on a dry basis.

5. The method for anaerobic treatment of papermaking and pulping wastewater according to claim 1, characterized in that: The pH value of the wastewater is 8-9.

6. The method for anaerobic treatment of papermaking and pulping wastewater according to any one of claims 1 to 5, characterized in that: The step of treating the pulping wastewater comprises: flocculating, filtering and adjusting the pH value of the pulping wastewater to obtain the wastewater.

7. The method for anaerobic treatment of papermaking and pulping wastewater according to claim 6, characterized in that: In the flocculation step, at least one of a flocculant and a coagulant aid is added.

8. The method for anaerobic treatment of papermaking and pulping wastewater according to claim 7, characterized in that: The flocculant is at least one of iron salt, magnesium salt and aluminum salt.

9. The method for anaerobic treatment of papermaking and pulping wastewater according to claim 6, characterized in that: Activated carbon is also added in the flocculation step; the amount of activated carbon added is 0.5kg / t to 1kg / t.

10. Use of the method for anaerobic treatment of papermaking and pulping wastewater as claimed in any one of claims 1 to 9 in the technical field of papermaking and pulping wastewater treatment.

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