Composite carbon source, preparation method therefor and use thereof

Abstract

The present invention relates to the technical field of carbon sources used for denitrification for nitrogen removal from waste water, and in particular to a composite carbon source, a preparation method therefor and the use thereof. The preparation method for the composite carbon source comprises the following steps: 1) adding an acid into crude glycerol to carry out acidification treatment, so as to obtain first acidified oil and a first glycerol liquid; 2) adding an alkaline solution into the first glycerol liquid, adjusting the pH value, causing same to stand still for layering, and removing a precipitate to obtain a second glycerol liquid; 3) carrying out reduced pressure distillation on the first acidified oil, and heating same to obtain a third glycerol liquid and first residues; 4) adding water into the first residues, carrying out centrifugal separation and evaporation and condensation to obtain a fourth glycerol liquid and second residues; and 5) mixing the second glycerol liquid and the fourth glycerol liquid, and adding a saccharide, an alcohol, an acid and denitrification promoters, so as to obtain the composite carbon source. Compared with a single carbon source, the crude glycerol composite carbon source has higher utilization rate and selectivity; by means of compositing with other carbon sources, the growth and metabolism of microorganisms can be promoted.

Description

A composite carbon source and its preparation method and application Technical Field

[0001] The present invention relates to the technical field of carbon sources for denitrification of sewage, and in particular to a composite carbon source and a preparation method and application thereof. Background Art

[0002] With the development of the economy and society, eutrophication of water bodies has become increasingly serious, and the nitrogen and phosphorus content in water bodies has increased. Efficient and stable denitrification and phosphorus removal are key links in current sewage treatment, and denitrification biological denitrification using the metabolism of microorganisms is the most economical and effective method.

[0003] Traditionally, biological denitrification of wastewater uses carbon sources such as glucose, sodium acetate, and starch. However, these carbon sources are expensive and pose a burden on the environment. Consequently, in recent years, increasing research has focused on developing low-cost alternative carbon sources.

[0004] Summary of the Invention

[0005] In view of the above-mentioned shortcomings of the prior art, the first aspect of the present invention provides a method for preparing a composite carbon source, comprising the following steps:

[0006] 1) Crude glycerin is mixed with acid and acidified to produce a first acidified oil and a first glycerin liquid. Under alkaline conditions, glycerin, soap, methanol, and methyl ester mix together to form a colloid, making it difficult to separate them individually by sedimentation or centrifugation. Therefore, during the glycerin separation process, the lower layer must be neutralized with acid to an appropriate pH. This allows for separation by sedimentation or centrifugation.

[0007] 2) adjusting the pH of the first glycerol solution obtained in step 1), allowing it to stand for stratification, and removing the precipitate to obtain a second glycerol solution; after the pH adjustment, the pH needs to be adjusted to neutral for better practicality during use.

[0008] 3) distilling the first acidified oil obtained in step 1) under reduced pressure and heating it to obtain a third glycerin liquid and a first residue;

[0009] 4) adding water to the first residue obtained in step 3), centrifuging, evaporating, and condensing to obtain a fourth glycerol liquid and a second residue;

[0010] 5) The second glycerol solution obtained in step 2) and the fourth glycerol solution obtained in step 4) are mixed, and sugars, alcohols, acids and a denitrification promoter are added to obtain the composite carbon source.

[0011] Preferably, it includes at least one of the following technical features:

[0012] 11) In step 1), the acid is selected from one or more of formic acid, acetic acid, hydrochloric acid, and sulfuric acid;

[0013] 12) In step 1), an acid is added to adjust the pH to 4.0-4.5, for example, 4.0-4.1, 4.1-4.2, 4.2-4.3, 4.3-4.4, and 4.4-4.5.

[0014] 13) In step 1), the acidification treatment time is 30-40 min, for example, it can be 30-31 min, 30-32 min, 30-33 min, 30-34 min, 30-35 min, 30-36 min, 30-37 min, 30-38 min, 30-39 min, 30-40 min, etc.

[0015] 14) In step 1), the first glycerol solution is further transferred into a neutralization reactor.

[0016] Preferably, it includes at least one of the following technical features:

[0017] 21) In step 2), the pH adjusting agent is an alkaline solution;

[0018] 22) In step 2), the pH is adjusted to 8.0-8.5;

[0019] 23) In step 2), the second glycerol liquid is subjected to impurity removal treatment.

[0020] Preferably, it includes at least one of the following technical features:

[0021] 211) In feature 21), the alkaline solution is selected from barium hydroxide;

[0022] 231) In feature 23), the impurity removal method is: allowing the second glycerol solution to pass through a cation exchange column, an anion exchange column, and an anion and cation exchange column in sequence.

[0023] Preferably, it includes at least one of the following technical features:

[0024] 31) In step 3), the vacuum degree of the reduced pressure distillation is controlled at 0.15-0.17 kPa, for example, 0.15-0.16 kPa, 0.16-0.17 kPa.

[0025] 32) In step 3), the heating is to 164-204°C;

[0026] 33) In step 3), the third glycerol liquid is refined glycerol;

[0027] Preferably, it includes at least one of the following technical features:

[0028] 41) In step 4), the volume ratio of the first residue to water is 1:0.75-1.15, for example, it can be 1:0.75, 1:0.85, 1:1, 1:1.05, etc.

[0029] 42) In step 4), the centrifugal separation device is a double-push centrifuge. Preferably, the centrifugal separation speed is 450-550 r / min, for example, it can be 450-460 r / min, 450-470 r / min, 450-480 r / min, 450-490 r / min, 450-500 r / min, 450-510 r / min, 450-520 r / min, 450-530 r / min, 450-540 r / min and 460-550 r / min, etc.

[0030] 43) In step 4), the distillation device is a thin film evaporator;

[0031] 44) In step 4), the second residue is asphaltene.

[0032] Preferably, it includes at least one of the following technical features:

[0033] 51) In step 5), the crude glycerol is derived from a biodiesel byproduct;

[0034] 51) In step 5), the sugar is selected from one or more of glucose, galactose, and fructose;

[0035] 52) In step 5), the alcohol is selected from one or more of methanol, ethanol, ethylene glycol, glycerol, and butanol; 53) In step 5), the acid is selected from one or more of acetic acid, propionic acid, n-butyric acid, and isobutyric acid;

[0036] The aforementioned added sugar substances are all monosaccharide carbon sources. Monosaccharide compounds are an environmentally friendly and efficient external carbon source and can be utilized by microorganisms without a long hydrolysis process; the added acid substances are volatile fatty acids, which are small molecular organic acids and are easily utilized by denitrifying bacteria, with good denitrification effect; the addition of alcohol compounds as an external carbon source has the characteristics of low cost and good denitrification effect.

[0037] 54) In step 5), the total mass of the second glycerol solution and the fourth glycerol solution: mass of sugars: mass of alcohols: mass of acids = (60-70): (5-10): (5-10): (5-10);

[0038] 55) In step 5), the denitrification promoter is sulfur and a metal-modified biochar selected from iron, magnesium, manganese, and nickel. The metal-modified biochar preparation method comprises soaking bamboo or wood blocks in a metal salt solution, drying the blocks, and then carbonizing and pulverizing the blocks to obtain the metal-modified biochar.

[0039] The metal elements in the metal-modified biochar contained in the denitrification promoter play a role in regulating the surface charge of the carbon source, which can promote the adsorption and removal of nitrate. The sulfur contained in the sulfur can provide an electron donor for the process of denitrifying bacteria reducing nitrate, thereby cooperating with the heterotrophic denitrification process to jointly promote the removal of nitrate, which can further improve the efficiency of biological denitrification.

[0040] Preferably, it includes at least one of the following technical features:

[0041] 551) In feature 55), the mass ratio of the sulfur to the composite carbon source is 0.5-1:100, for example, it can be 0.5:100, 0.6:100, 0.7:100, 0.8:100, 0.9:100, etc.

[0042] 552) In feature 55), the mass ratio of the metal bio-modified carbon to the composite carbon source is 0.05-0.1:1, for example, it can be 0.05:1, 0.06:1, 0.07:1, 0.08:1, 0.09:1, etc.

[0043] The second aspect of the present invention provides a composite carbon source, which is prepared using the above-mentioned method for preparing the composite carbon source.

[0044] A third aspect of the present invention provides the application of the composite carbon source in wastewater denitrification.

[0045] As described above, the method for preparing the composite carbon source provided by the present invention has the following beneficial effects:

[0046] 1) The present invention provides a method and composition for fermenting and purifying crude glycerol as the primary raw material and then compounding it into a composite carbon source. This method involves purifying crude glycerol, a byproduct of biodiesel, and compounding it with other carbon sources, thereby eliminating the waste of crude glycerol and simultaneously utilizing the organic matter in biodiesel to increase the utilization and selectivity of the carbon source for microorganisms.

[0047] 2) The crude glycerol in this invention is a low-cost, readily available carbon source that can significantly reduce the production cost of carbon sources for denitrification and nitrogen removal, offering excellent economic benefits when applied on a large scale. Compared to single carbon sources, crude glycerol composite carbon sources offer higher utilization and selectivity. Combining with other carbon sources can promote microbial growth and metabolism, facilitating wastewater denitrification.

[0048] 3) The present invention uses crude glycerol as the main raw material to produce a composite carbon source, which has strong economic efficiency and solves the problem of crude glycerol waste disposal, and has a positive promoting significance for economic and social development.

[0049] 4) The preparation method of the composite carbon source provided by the present invention is simple, feasible, and easy to produce and apply on a large scale. DETAILED DESCRIPTION

[0050] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different perspectives and applications without departing from the spirit of the present invention. It should be noted that any process equipment or devices not specifically noted in the following examples are conventional equipment or devices in the art.

[0051] Furthermore, it should be understood that the one or more method steps mentioned in the present invention do not exclude the presence of other method steps before or after the combination step, or the insertion of other method steps between these explicitly mentioned steps, unless otherwise specified. It should also be understood that the combination connection relationship between one or more devices / apparatuses mentioned in the present invention does not exclude the presence of other devices / apparatuses before or after the combination device / apparatus, or the insertion of other devices / apparatuses between two explicitly mentioned devices / apparatuses, unless otherwise specified. Furthermore, unless otherwise specified, the numbering of each method step is merely a convenient tool for identifying each method step, and is not intended to limit the order of arrangement of each method step or to define the scope of the present invention. Changes or adjustments to their relative relationships, without substantially changing the technical content, should also be considered within the scope of the present invention.

[0052] Example 1

[0053] 1) Add 0.32 ml of analytically pure acetic acid to 1000 g of crude glycerol to adjust the pH to approximately 4.0, and perform acidification for 30 minutes to obtain a first acidified oil as an upper layer and a first glycerol liquid as a lower layer. The first glycerol liquid is transferred to a neutralization reactor;

[0054] 2) adding barium hydroxide to the first glycerol solution obtained in step 1) and adjusting the pH to 8.0, allowing the solution to stand and separate into layers to obtain a second glycerol solution, and subjecting the resulting second glycerol solution to a cation exchange column, anion exchange column, and anion and cation exchange column to remove various impurities, and producing a precipitate which is discharged from the bottom of the neutralization reactor;

[0055] 3) subjecting the first acidified oil obtained in step 1) to vacuum distillation at a vacuum degree of 0.15 kPa and heating to 204° C. to obtain a third glycerin liquid and a first residue, which is then transferred to a mixing tank;

[0056] 4) adding water to the first residue obtained in step 4) at a ratio of 1:1.05; centrifuging at a speed of 450 r / min to precipitate salt; and distilling the mixture through a thin film evaporator to obtain a fourth glycerol solution and a second residue;

[0057] 5) The second glycerol liquid obtained in step 2) and the fourth glycerol liquid obtained in step 4) are mixed, and glucose, ethylene glycol and acetic acid are added, wherein the mass fraction of glucose is 10%, the mass fraction of ethylene glycol is 5%, and the mass fraction of acetic acid is 5%; sulfur and iron metal bio-modified carbon are added at the same time, wherein the mass fraction of sulfur is 0.5% and the mass fraction of iron metal bio-modified carbon is 0.05%, thereby obtaining the composite carbon source.

[0058] Experimental testing showed that the composite carbon source had a BOD5 / COD ratio of approximately 0.75, and after dilution, it can be directly used in sewage treatment, with a significant denitrification-promoting effect. BOD5 is an important indicator of the degree of organic contamination in water, indirectly reflecting the amount of dissolved oxygen consumed by microbial metabolism.

[0059] Example 2

[0060] 1) Add 0.32 ml of analytically pure acetic acid to 1000 g of crude glycerol to adjust the pH to approximately 4.0, and acidify for 35 minutes to obtain a first acidified oil as an upper layer and a first glycerol liquid as a lower layer. The first glycerol liquid is transferred to a neutralization reactor;

[0061] 2) adding barium hydroxide to the first glycerol solution obtained in step 1) and adjusting the pH to 8.0, allowing the solution to stand and separate into layers to obtain a second glycerol solution, and subjecting the resulting second glycerol solution to a cation exchange column, anion exchange column, and anion and cation exchange column to remove various impurities, and producing a precipitate which is discharged from the bottom of the neutralization reactor;

[0062] 3) subjecting the first acidified oil obtained in step 1) to vacuum distillation at a vacuum degree of 0.15 kPa and heating to 204° C. to obtain a third glycerin liquid and a first residue, which is then transferred to a mixing tank;

[0063] 4) adding water to the first residue obtained in step 4) at a ratio of 1:1.05; centrifuging at a speed of 450 r / min to precipitate salt; and distilling the mixture through a thin film evaporator to obtain a fourth glycerol solution and a second residue;

[0064] 5) The second glycerol liquid obtained in step 2) and the fourth glycerol liquid obtained in step 4) are mixed, and glucose, ethylene glycol and acetic acid are added, wherein the mass fraction of glucose is 10%, the mass fraction of ethylene glycol is 5%, and the mass fraction of acetic acid is 5%; sulfur and iron metal bio-modified carbon are added at the same time, wherein the mass fraction of sulfur is 0.5% and the mass fraction of iron metal bio-modified carbon is 0.05%, thereby obtaining the composite carbon source.

[0065] According to experimental tests, the composite carbon source has a BOD5 / CODB / C ratio of about 0.78, can be directly used in sewage treatment after dilution, and has a good denitrification promoting effect.

[0066] Example 3

[0067] 1) Add 0.32 ml of analytically pure acetic acid to 1000 g of crude glycerol to adjust the pH to approximately 4.0, and perform acidification for 40 minutes to obtain a first acidified oil as an upper layer and a first glycerol liquid as a lower layer. The first glycerol liquid is transferred to a neutralization reactor;

[0068] 2) adding barium hydroxide to the first glycerol solution obtained in step 1) and adjusting the pH to 8.0, allowing the solution to stand and separate into layers to obtain a second glycerol solution, and subjecting the resulting second glycerol solution to a cation exchange column, anion exchange column, and anion and cation exchange column to remove various impurities, and producing a precipitate which is discharged from the bottom of the neutralization reactor;

[0069] 3) subjecting the first acidified oil obtained in step 1) to vacuum distillation at a vacuum degree of 0.15 kPa and heating to 204° C. to obtain a third glycerin liquid and a first residue, which is then transferred to a mixing tank;

[0070] 4) adding water to the first residue obtained in step 4) at a ratio of 1:1.05; centrifuging at a speed of 450 r / min to precipitate salt; and distilling the mixture through a thin film evaporator to obtain a fourth glycerol solution and a second residue;

[0071] 5) The second glycerol liquid obtained in step 2) and the fourth glycerol liquid obtained in step 4) are mixed, and glucose, ethylene glycol, and methyl acetate are added, where the mass fraction of glucose is 10%, the mass fraction of ethylene glycol is 5%, and the mass fraction of acetic acid is 5%; sulfur and iron metal bio-modified carbon are also added at the same time, where the mass fraction of sulfur is 0.5% and the mass fraction of iron metal bio-modified carbon is 0.05%, to obtain the composite carbon source.

[0072] According to experimental tests, the composite carbon source has a BOD5 / COD ratio of about 0.80, can be directly used in sewage treatment after dilution, and has a good denitrification promoting effect.

[0073] Example 4

[0074] 1) Add 0.32 ml of analytically pure acetic acid to 1000 g of crude glycerol to adjust the pH to approximately 4.0, and perform acidification for 30 minutes to obtain a first acidified oil as an upper layer and a first glycerol liquid as a lower layer. The first glycerol liquid is transferred to a neutralization reactor;

[0075] 2) adding barium hydroxide to the first glycerol solution obtained in step 1) and adjusting the pH to 8.0, allowing the solution to stand and separate into layers to obtain a second glycerol solution, and subjecting the resulting second glycerol solution to a cation exchange column, anion exchange column, and anion and cation exchange column to remove various impurities, and producing a precipitate which is discharged from the bottom of the neutralization reactor;

[0076] 3) subjecting the first acidified oil obtained in step 1) to vacuum distillation at a vacuum degree of 0.15 kPa and heating to 204° C. to obtain a third glycerin liquid and a first residue, which is then transferred to a mixing tank;

[0077] 4) adding water to the first residue obtained in step 4) at a ratio of 1:1.05; centrifuging at a speed of 450 r / min to precipitate salt; and distilling the mixture through a thin film evaporator to obtain a fourth glycerol solution and a second residue;

[0078] 5) The second glycerol liquid obtained in step 2) and the fourth glycerol liquid obtained in step 4) are mixed, and fructose, glycerol, and propionic acid are added, wherein the mass fraction of fructose is 10%, the mass fraction of glycerol is 5%, and the mass fraction of propionic acid is 5%; sulfur and iron metal bio-modified carbon are added at the same time, wherein the mass fraction of sulfur is 0.5% and the mass fraction of iron metal bio-modified carbon is 0.05%, thereby obtaining the composite carbon source.

[0079] According to experimental tests, the BOD5 / COD ratio of the composite carbon source is about 0.76. After dilution, it can be directly used in sewage treatment and has a good denitrification promoting effect.

[0080] Example 5

[0081] 1) Add 0.32 ml of analytically pure acetic acid to 1000 g of crude glycerol to adjust the pH to approximately 4.2, and acidify for 30 minutes to obtain a first acidified oil as an upper layer and a first glycerol liquid as a lower layer. The first glycerol liquid is transferred to a neutralization reactor;

[0082] 2) adding barium hydroxide to the first glycerol solution obtained in step 1) and adjusting the pH to 8.0, allowing the solution to stand and separate into layers to obtain a second glycerol solution, and subjecting the resulting second glycerol solution to a cation exchange column, anion exchange column, and anion and cation exchange column to remove various impurities, and producing a precipitate which is discharged from the bottom of the neutralization reactor;

[0083] 3) subjecting the first acidified oil obtained in step 1) to vacuum distillation at a vacuum degree of 0.15 kPa and heating to 204° C. to obtain a third glycerin liquid and a first residue, which is then transferred to a mixing tank;

[0084] 4) adding water to the first residue obtained in step 4) at a ratio of 1:1.05; centrifuging at a speed of 450 r / min to precipitate salt; and distilling the mixture through a thin film evaporator to obtain a fourth glycerol solution and a second residue;

[0085] 5) The second glycerol liquid obtained in step 2) and the fourth glycerol liquid obtained in step 4) are mixed, and fructose, glycerol, and propionic acid are added, wherein the mass fraction of fructose is 10%, the mass fraction of glycerol is 5%, and the mass fraction of propionic acid is 5%; sulfur and iron metal bio-modified carbon are added at the same time, wherein the mass fraction of sulfur is 0.5% and the mass fraction of iron metal bio-modified carbon is 0.05%, thereby obtaining the composite carbon source.

[0086] According to experimental tests, the composite carbon source has a BOD5 / COD ratio of about 0.78, can be directly used in sewage treatment after dilution, and has a good denitrification promoting effect.

[0087] Example 6

[0088] 1) Add 0.32 ml of analytically pure acetic acid to 1000 g of crude glycerol to adjust the pH to approximately 4.5, and perform acidification for 30 minutes to obtain a first acidified oil as an upper layer and a first glycerol liquid as a lower layer. The first glycerol liquid is transferred to a neutralization reactor;

[0089] 2) adding barium hydroxide to the first glycerol solution obtained in step 1) and adjusting the pH to 8.0, allowing the solution to stand and separate into layers to obtain a second glycerol solution, and subjecting the resulting second glycerol solution to a cation exchange column, anion exchange column, and anion and cation exchange column to remove various impurities, and producing a precipitate which is discharged from the bottom of the neutralization reactor;

[0090] 3) subjecting the first acidified oil obtained in step 1) to vacuum distillation at a vacuum degree of 0.15 kPa and heating to 204° C. to obtain a third glycerin liquid and a first residue, which is then transferred to a mixing tank;

[0091] 4) adding water to the first residue obtained in step 4) at a ratio of 1:1.05; centrifuging at a speed of 450 r / min to precipitate salt; and distilling the mixture through a thin film evaporator to obtain a fourth glycerol solution and a second residue;

[0092] 5) The second glycerol liquid obtained in step 2) and the fourth glycerol liquid obtained in step 4) are mixed, and fructose, glycerol, and propionic acid are added, wherein the mass fraction of fructose is 10%, the mass fraction of glycerol is 5%, and the mass fraction of propionic acid is 5%; sulfur and iron metal bio-modified carbon are added at the same time, wherein the mass fraction of sulfur is 0.5% and the mass fraction of iron metal bio-modified carbon is 0.05%, thereby obtaining the composite carbon source.

[0093] According to experimental tests, the BOD5 / COD ratio of the composite carbon source is about 0.81. After dilution, it can be directly used in sewage treatment and has a good denitrification promoting effect.

[0094] Example 7

[0095] 1) Add 0.32 ml of analytically pure acetic acid to 1000 g of crude glycerol to adjust the pH to approximately 4.0, and perform acidification for 30 minutes to obtain a first acidified oil as an upper layer and a first glycerol liquid as a lower layer. The first glycerol liquid is transferred to a neutralization reactor;

[0096] 2) adding barium hydroxide to the first glycerol solution obtained in step 1) and adjusting the pH to 8.0, allowing the solution to stand and separate into layers to obtain a second glycerol solution, and subjecting the resulting second glycerol solution to a cation exchange column, anion exchange column, and anion and cation exchange column to remove various impurities, and producing a precipitate which is discharged from the bottom of the neutralization reactor;

[0097] 3) subjecting the first acidified oil obtained in step 1) to vacuum distillation at a vacuum degree of 0.15 kPa and heating to 204° C. to obtain a third glycerin liquid and a first residue, which is then transferred to a mixing tank;

[0098] 4) adding water to the first residue obtained in step 4) at a ratio of 1:0.95; performing centrifugation at a speed of 450 r / min to precipitate salt; and then distilling the mixture through a thin film evaporator to obtain a fourth glycerol liquid and a second residue;

[0099] 5) The second glycerol liquid obtained in step 2) and the fourth glycerol liquid obtained in step 4) are mixed, and fructose, butanol, and acetic acid are added, wherein the mass fraction of fructose is 10%, the mass fraction of butanol is 5%, and the mass fraction of acetic acid is 5%; sulfur and molybdenum metal bio-modified carbon are added simultaneously, wherein the mass fraction of sulfur is 0.5% and the mass fraction of molybdenum metal bio-modified carbon is 0.05%, thereby obtaining the composite carbon source.

[0100] According to experimental tests, the composite carbon source has a BOD5 / COD ratio of about 0.78, can be directly used in sewage treatment after dilution, and has a good denitrification promoting effect.

[0101] Example 8

[0102] 1) Add 0.32 ml of analytically pure acetic acid to 1000 g of crude glycerol to adjust the pH to approximately 4.0, and perform acidification for 30 minutes to obtain a first acidified oil as an upper layer and a first glycerol liquid as a lower layer. The first glycerol liquid is transferred to a neutralization reactor;

[0103] 2) adding barium hydroxide to the first glycerol solution obtained in step 1) and adjusting the pH to 8.0, allowing the solution to stand and separate into layers to obtain a second glycerol solution, and subjecting the resulting second glycerol solution to a cation exchange column, anion exchange column, and anion and cation exchange column to remove various impurities, and producing a precipitate which is discharged from the bottom of the neutralization reactor;

[0104] 3) subjecting the first acidified oil obtained in step 1) to vacuum distillation at a vacuum degree of 0.15 kPa and heating to 204° C. to obtain a third glycerin liquid and a first residue, which is then transferred to a mixing tank;

[0105] 4) adding water to the first residue obtained in step 4) at a ratio of 1:0.85; centrifuging at a speed of 450 r / min to precipitate salt; and distilling the mixture through a thin film evaporator to obtain a fourth glycerol solution and a second residue;

[0106] 5) The second glycerol liquid obtained in step 2) and the fourth glycerol liquid obtained in step 4) are mixed, and fructose, butanol, and acetic acid are added, wherein the mass fraction of fructose is 10%, the mass fraction of butanol is 5%, and the mass fraction of acetic acid is 5%; sulfur and molybdenum metal bio-modified carbon are added simultaneously, wherein the mass fraction of sulfur is 0.5% and the mass fraction of molybdenum metal bio-modified carbon is 0.05%, thereby obtaining the composite carbon source.

[0107] According to experimental tests, the composite carbon source has a BOD5 / COD ratio of about 0.80, can be directly used in sewage treatment after dilution, and has a good denitrification promoting effect.

[0108] Example 9

[0109] 1) Add 0.32 ml of analytically pure acetic acid to 1000 g of crude glycerol to adjust the pH to approximately 4.0, and acidify for 30 minutes to obtain a first acidified oil as an upper layer and a first glycerol liquid as a lower layer. The first glycerol liquid is transferred to a neutralization reactor;

[0110] 2) adding sodium hydroxide to the first glycerol solution obtained in step 1) and adjusting the pH to 8.0, allowing the solution to stand and separate into layers to obtain a second glycerol solution, and passing the second glycerol solution through a cation exchange column, anion exchange column, and anion and cation exchange column to remove various impurities, and the resulting precipitate is discharged from the bottom of the neutralization reactor;

[0111] 3) subjecting the first acidified oil obtained in step 1) to vacuum distillation at a vacuum degree of 0.15 kPa and heating to 204° C. to obtain a third glycerin liquid and a first residue, which is then transferred to a mixing tank;

[0112] 4) adding water to the first residue obtained in step 4) at a ratio of 1:0.75; centrifuging at a speed of 450 r / min to precipitate salt; and distilling the mixture through a thin film evaporator to obtain a fourth glycerol solution and a second residue;

[0113] 5) The second glycerol liquid obtained in step 2) and the fourth glycerol liquid obtained in step 4) are mixed, and fructose, butanol, and acetic acid are added, wherein the mass fraction of fructose is 10%, the mass fraction of butanol is 5%, and the mass fraction of acetic acid is 5%; sulfur and molybdenum metal bio-modified carbon are added simultaneously, wherein the mass fraction of sulfur is 0.5% and the mass fraction of molybdenum metal bio-modified carbon is 0.05%, thereby obtaining the composite carbon source.

[0114] According to experimental tests, the BOD5 / COD ratio of the composite carbon source is about 0.82. After dilution, it can be directly used in sewage treatment and has a good denitrification promoting effect.

[0115] Example 10

[0116] 1) Add 0.32 ml of analytically pure acetic acid to 1000 g of crude glycerol to adjust the pH to approximately 4.5, and perform acidification for 40 minutes to obtain a first acidified oil as an upper layer and a first glycerol liquid as a lower layer. The first glycerol liquid is transferred to a neutralization reactor;

[0117] 2) adding barium hydroxide to the first glycerol solution obtained in step 1) and adjusting the pH to 8.0, allowing the solution to stand and separate into layers to obtain a second glycerol solution, and subjecting the resulting second glycerol solution to a cation exchange column, anion exchange column, and anion and cation exchange column to remove various impurities, and producing a precipitate which is discharged from the bottom of the neutralization reactor;

[0118] 3) subjecting the first acidified oil obtained in step 1) to vacuum distillation at a vacuum degree of 0.15 kPa and heating to 204° C. to obtain a third glycerin liquid and a first residue, which is then transferred to a mixing tank;

[0119] 4) adding water to the first residue obtained in step 4) at a ratio of 1:0.75; centrifuging at a speed of 450 r / min to precipitate salt; and distilling the mixture through a thin film evaporator to obtain a fourth glycerol solution and a second residue;

[0120] 5) The second glycerol liquid obtained in step 2) and the fourth glycerol liquid obtained in step 4) are mixed, and fructose, butanol, and acetic acid are added, wherein the mass fraction of fructose is 10%, the mass fraction of butanol is 5%, and the mass fraction of acetic acid is 5%; sulfur and molybdenum metal bio-modified carbon are added simultaneously, wherein the mass fraction of sulfur is 0.5% and the mass fraction of molybdenum metal bio-modified carbon is 0.05%, thereby obtaining the composite carbon source.

[0121] According to experimental tests, the BOD5 / COD ratio of the composite carbon source is about 0.85. After dilution, it can be directly used in sewage treatment and has a good denitrification promoting effect.

[0122] Example 11

[0123] The wastewater treatment station of a certain electronics company uses nitric acid in the production process, so the total nitrogen content of the production line wastewater is high. The total nitrogen content of the influent of the wastewater treatment station is 200 mg / L, the COD content is 50 mg / L, and the biodegradability of the influent COD is poor, requiring the addition of an external carbon source for denitrification. Sodium acetate, glucose, and the composite carbon sources of Examples 3, 6, 9, and 10 were added to six pilot plants using the company's wastewater. The influent flow rate of the pilot plants was maintained at 100 m 3 / h.

[0124] Sodium acetate, glucose, and the composite carbon sources of Examples 3, 6, 9, and 10 were prepared into denitrification carbon source solutions with the same COD equivalent concentration. The six carbon sources were added at the same volume, maintaining the same dosing pump flow rate. The removal efficiency comparison between the control group and the experimental group is shown in Table 1.

[0125] Table 1 Removal effects of comparison group and experimental group

[0126] The above data show that the composite carbon source of the present invention can be used as a denitrification carbon source for sewage treatment, and compared with the carbon source in the prior art, the composite carbon source of the present invention significantly improves the removal rate of nitrate nitrogen when the same mass of COD is added.

[0127] At the same time, the market price of similar types of sodium acetate and glucose is between 4,000 and 5,000 yuan per ton, while the price of crude glycerol is less than 1,000 yuan per ton. In comparison, under similar conditions, the composite carbon source produced by purifying crude glycerol is more economical.

[0128] Example 12

[0129] A Zhejiang industrial wastewater treatment plant with an inlet flow of 50,000 m 3 / d, with an influent COD concentration of 200 mg / L and a total nitrogen concentration of 40 mg / L. Due to the insufficient C / N ratio of the influent, it was necessary to add an appropriate amount of carbon source to complete the denitrification process. Sodium acetate, glucose, and Examples 3, 6, 9, and 10 were configured to form denitrification carbon source solutions with the same COD equivalent concentration. The six carbon sources were added in equal volumes, maintaining a consistent dosing pump flow rate. A comparison of the removal effects of the control and experimental groups is shown in Table 2.

[0130] Table 2 Comparison of removal effects between the control group and the experimental group

[0131] The above data show that the composite carbon source of the present invention can be used as a denitrification carbon source for sewage treatment, and compared with the carbon source in the prior art, when the same mass of COD is added, the composite carbon source of the present invention can make the effluent of the sewage treatment plant stably reach the Class A emission standard, significantly improve the removal rate of total nitrogen, and has good economic efficiency when used on a large scale in sewage treatment plants.

[0132] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form or substance. It should be pointed out that ordinary technicians in this technical field can make several improvements and supplements without departing from the method of the present invention. These improvements and supplements should also be regarded as the scope of protection of the present invention. Any equivalent changes, modifications and evolutions made by technicians familiar with this profession without departing from the spirit and scope of the present invention by using the technical content disclosed above are all equivalent embodiments of the present invention; at the same time, any equivalent changes, modifications and evolutions made to the above embodiments based on the essential technology of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a composite carbon source, characterized in that: The following steps are involved: 1) mixing crude glycerol with acid and performing acidification treatment to obtain a first acidified oil and a first glycerol liquid; 2) adjusting the pH of the first glycerol solution obtained in step 1), allowing it to stand for stratification, and removing the precipitate to obtain a second glycerol solution; 3) subjecting the first acidified oil obtained in step 1) to vacuum distillation and heating to obtain a third glycerol liquid and a first residue; 4) adding water to the first residue obtained in step 3), centrifuging, evaporating and condensing to obtain a fourth glycerol liquid and a second residue; 5) The second glycerol liquid obtained in step 2) and the fourth glycerol liquid obtained in step 4) are mixed, and sugars, alcohols, acids and a denitrification promoter are added to obtain the composite carbon source.

2. The method for preparing a composite carbon source according to claim 1, characterized in that: Include at least one of the following technical features: 11) In step 1), the acid is selected from one or more of formic acid, acetic acid, hydrochloric acid and sulfuric acid; 12) In step 1), adding acid to adjust the pH to 4.0-4.5; 13) In step 1), the acidification treatment time is 30-40 minutes; 14) In step 1), the first glycerol liquid is also transferred into a neutralization reactor.

3. The method for preparing a composite carbon source according to claim 1, characterized in that: Include at least one of the following technical features: 21) In step 2), the pH adjusting agent is an alkaline solution; 22) In step 2), the pH is adjusted to 8.0-8.5; 23) In step 2), the second glycerol liquid is subjected to impurity removal treatment.

4. The method for preparing the composite carbon source according to claim 3, characterized in that: Include at least one of the following technical features: 211) In feature 21), the alkaline solution is selected from barium hydroxide; 231) In feature 23), the impurity removal method is: allowing the second glycerol solution to pass through a cation exchange column, an anion exchange column, and an anion and cation exchange column in sequence.

5. The method for preparing a composite carbon source according to claim 1, characterized in that: Include at least one of the following technical features: 31) In step 3), the vacuum degree of the reduced pressure distillation is controlled at 0.15-0.17 kPa; 32) In step 3), the heating is to 164-204°C; 33) In step 3), the third glycerol liquid is refined glycerol; 34) In step 3), the third glycerol liquid is recycled.

6. The method for preparing a composite carbon source according to claim 1, characterized in that: Include at least one of the following technical features: 41) In step 4), the volume ratio of the first residue to water is 1:0.75-1.15; 42) In step 4), the centrifugal separation device is a double-push centrifuge, and preferably, the rotation speed of the centrifugal separation is 450-550r / min; 43) In step 4), the distillation device is a thin film evaporator; 44) In step 4), the second residue is asphaltene.

7. The method for preparing a composite carbon source according to claim 1, characterized in that: Include at least one of the following technical features: 51) In step 5), the crude glycerol is derived from a biodiesel byproduct; 51) In step 5), the sugar is selected from one or more of glucose, galactose, and fructose; 52) In step 5), the alcohol is selected from one or more of methanol, ethanol, ethylene glycol, glycerol, and butanol; 53) In step 5), the acid is selected from one or more of acetic acid, propionic acid, n-butyric acid, and isobutyric acid; 54) In step 5), the total mass of the second glycerol liquid and the fourth glycerol liquid: mass of sugars: mass of alcohols: mass of acids = (60-70): (5-10): (5-10): (5-10); 55) In step 5), the denitrification promoter is sulfur and any one metal bio-modified carbon selected from iron, magnesium, manganese and nickel.

8. The method for preparing a composite carbon source according to claim 7, characterized in that: Include at least one of the following technical features: 551) In feature 55), the mass ratio of the sulfur to the composite carbon source is 0.5-1:100; 552) In feature 55), the mass ratio of the metal bio-modified carbon to the composite carbon source is 0.05-0.1:

1.

9. A composite carbon source, characterized in that The composite carbon source is prepared by the preparation method of any one of claims 1 to 8.

10. The composite carbon source according to claim 9 is used for wastewater denitrification.

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