Low-freezing-point composite biological carbon source, preparation method and application

Abstract

The invention relates to the technical field of sewage treatment, and discloses a low-freezing-point composite biological carbon source and a preparation method and application thereof.The preparation method comprises the steps that by-products obtained through a fermentation technology are smashed, water is added into obtained particles, autolysis is conducted for a certain time, and particle mixed liquid is obtained; adjusting the pH value of the particle mixed solution, adjusting the temperature, then adding an enzyme for reaction, and simultaneously stirring for hydrolysis until the reaction is complete to obtain a mixed material; centrifuging the mixture and taking supernate to obtain a biological carbon source extracting solution; and adding the anti-freezing solution into the biological carbon source extracting solution, mixing and reacting in a ratio of (5-2): (5-8), and then adjusting the pH value to form the low-freezing-point composite biological carbon source. Compared with single carbon sources such as methanol, sodium acetate, glucose and glycerol, the low-freezing-point composite biological carbon source provided by the invention has the advantages that on one hand, resource utilization of wastes in the fermentation industry is realized, meanwhile, the freezing point is low, biological denitrification requirements of sewage plants in winter low-temperature occasions in northern areas are met, and on the other hand, the denitrification effect is good, the adaptability is high, the cost is low, the dosage is low, and the like.

Description

Technical Field

[0001] The invention relates to the technical field of sewage treatment, and in particular to a low-freezing-point composite biological carbon source, a preparation method and an application thereof. Background Art

[0002] With the increasing prosperity and development of industry, the composition of sewage is becoming more and more complex. The original physical and chemical methods are far from meeting the needs of sewage treatment. In recent years, biochemical treatment methods have been applied to many sewage treatment fields. It is favored for its low energy consumption, high efficiency, low cost and simple operation. At present, most sewage denitrification processes use single carbon source organic substances (such as methanol, ethanol, acetic acid, sodium acetate, glycerol, etc.) and sugar substances (glucose, sucrose, xylose, etc.) as liquid carbon sources.

[0003] In the sewage treatment process, the selection of carbon sources for denitrification is crucial; among them: 1. Sodium acetate, acetic acid, glucose, etc. are commonly used carbon sources for denitrification in sewage treatment plants. They show good denitrification performance at room temperature. However, their solutions have a high freezing point. Once the ambient temperature drops below zero in winter, they are very easy to freeze, which significantly hinders the addition and use of carbon sources in sewage treatment plants. 2. Biological carbon sources have good adaptability and strong biodegradability. They can be quickly absorbed and utilized by activated sludge denitrifying bacteria. The denitrification rate is fast, which can effectively meet the carbon source demand in the denitrification process of anoxic tanks. Unfortunately, its freezing point is basically around zero degrees, which greatly limits its application in winter scenes; 3. Organic carbon source solutions containing high concentrations of methanol and ethanol not only have excellent denitrification performance, but also have a low freezing point. However, methanol is highly toxic and volatile, with a flash point of only 12.2°C, which can easily cause fires and pose many unsafe risks to production operators and users. The flash point of ethanol solutions is also low. For example, the flash point of 60% ethanol solution is 22.7°C, which falls into the category of hazardous chemicals. In view of domestic carbon source-related standards, such as the "Carbon Source for Sewage (Waste) Water Treatment" (T / CSTE0001-2021) requires that the carbon source flash point is greater than 70°C, and the "Composite Carbon Source for Sewage (Waste) Water Treatment" (HG / T5960-2021) requires that the carbon source flash point is greater than 93°C, the actual application of methanol and ethanol solutions as carbon sources is strictly restricted; 4. In addition, alcohol substances such as glycerol, ethylene glycol and propylene glycol also have the effect of lowering the freezing point. Among them, glycerol (propylene glycol) has the characteristics of high viscosity, high flash point, low volatility, low toxicity and good biodegradability. However, its effect of lowering the freezing point is slightly inferior to that of methanol and ethanol, and the freezing points of glycerol aqueous solutions of different concentrations are different; while ethylene glycol performs well in lowering the freezing point, and also has the advantages of high boiling point, high flash point, low toxicity and moderate viscosity, but the BOD5 / CODCr of ethylene glycol is less than 0.4, and according to the "Carbon Source for Sewage (Wastewater) Treatment" (T / CSTE0001-2021), the carbon source BOD5 / CODCr≥0.55 is required, and the "Compound Carbon Source for Sewage (Wastewater) Treatment" (HG / T5960-2021) requires the carbon source BOD5 / CODCr≥0.60, so ethylene glycol is not suitable for use alone as a carbon source for biological denitrification.

[0004] The average winter temperature in northern my country is below zero, and the average winter temperature in Heilongjiang is below -11°C, with the lowest temperature reaching -53°C. It can be seen that the low temperature in northern China will inevitably affect the transportation, storage, and addition of liquid carbon sources.

[0005] In summary, how to lower the freezing point of the carbon source without affecting the biological denitrification and denitrification performance of the carbon source has become a key issue in the current research on the use of carbon sources in winter in northern regions. Summary of the invention

[0006] The purpose of the present invention is to provide a low freezing point composite biological carbon source, a preparation method and application thereof, to solve the following technical problems: The freezing point of the carbon source is reduced without affecting the biological denitrification performance of the carbon source.

[0007] The purpose of the present invention can be achieved through the following technical solutions: A preparation method of a low freezing point composite biological carbon source specifically comprises the following steps: The byproducts obtained from the fermentation process are crushed, and the obtained particles are watered to a moisture content of 95.5-98.5%, and are autolyzed for a certain period of time to obtain a particle mixture; The pH of the particle mixture is adjusted to 6-8, and the temperature is adjusted to 25-60° C., and then enzyme is added for reaction, and stirred and hydrolyzed until the reaction is complete to obtain a mixture; The mixture is centrifuged at a speed of 4000-8000 rpm for 5-10 minutes, and then the supernatant is collected to obtain a biocarbon source extract; The antifreeze solution is prepared by mixing ethylene glycol and glycerol in a ratio of 1-10:10-1, wherein 1-10 is 1-10 parts by volume of ethylene glycol and 10-1 is 10-1 parts by volume of glycerol; The antifreeze solution is added to the biocarbon source extract and mixed in a ratio of 5-2:5-8 for reaction, and then the pH is adjusted to 6-9 to form a low freezing point composite biocarbon source, wherein 5-2 is the volume of 5-2 parts of the biocarbon source extract, and 5-8 is the volume of 5-8 parts of the antifreeze solution.

[0008] Preferably, the by-products obtained from the fermentation process are by-products of the fermentation industry process, specifically including beer yeast mud, white wine lees, old wine lees, and alcohol yeast mud.

[0009] Preferably, the by-product crushing is specifically: crushing the particles and agglomerated materials to 80-250 mesh at a rotation speed of 300-1500 rpm.

[0010] Preferably, the autolysis is as follows: the material after adding water is stirred at 40-80 rpm at room temperature, and the autolysis time is 1-2 hours.

[0011] Preferably, the reagent for adjusting pH is 3-5 mol / L NaOH solution.

[0012] Preferably, the enzyme reaction uses wall-breaking enzyme, protein enzyme, papain, chymopapain, papain, alkaline protease, cellulase, β-glucanase; the amount of the enzyme added is: 0.5-3.5%.

[0013] Preferably, the stirring hydrolysis is specifically: hydrolyzing for 6-60 hours under stirring at a rotation speed of 40-80 rpm.

[0014] The invention also provides a method for preparing a low freezing point composite biological carbon source and a low freezing point composite biological carbon source prepared therefrom.

[0015] The present invention also provides the application of the low freezing point composite biological carbon source in denitrification treatment of domestic sewage, municipal sewage, dispersed sewage, industrial sewage and garbage leachate.

[0016] Beneficial effects of the present invention: 1. The present invention utilizes waste by-products from the production process of the fermentation industry, such as distiller's grains and beer mud, for resource utilization, thereby reducing the disposal costs and environmental emissions of waste, while reducing the consumption of chemical resources such as sodium acetate, glucose, glycerol, and ethylene glycol in sewage treatment plants. It has cost advantages over common carbon sources such as sodium acetate, acetic acid, ethylene glycol, glycerol, and glucose on the market. At the same time, the present invention has stable physical and chemical properties, a high flash point, and is non-corrosive. It is safe and convenient to store, transport, and use, and has positive social, economic, and environmental benefits.

[0017] 2. The low freezing point composite biological carbon source of the present invention is mainly composed of a variety of easily biodegradable small molecule alcohols, organic acids and sugar substances. The carbon source is rich in variety and has good biodegradability. It can meet the needs of different denitrifying bacteria for organic matter. In the short term, it has strong adaptability and can be quickly absorbed and utilized by activated sludge denitrifying bacteria. In actual use, it does not require special domestication to show high denitrification rate and denitrification effect, and can also meet emergency needs; long-term use can improve and maintain the abundance of the biochemical system flora, thereby improving the denitrification stability and impact resistance of the biochemical system, and showing a higher denitrification rate and denitrification effect.

[0018] In summary, compared with conventional single carbon sources such as methanol, sodium acetate, glucose, and glycerol, the low-freezing-point composite biological carbon source provided by the present invention can realize the resource utilization of waste in the fermentation industry, and at the same time, it has a low freezing point, which can meet the biological denitrification needs of sewage treatment plants in northern regions in low temperatures in winter. On the other hand, it also has the advantages of good denitrification effect, strong adaptability, good stability, low cost, safety, non-toxicity, and low dosage.

[0019] Of course, any product implementing the present invention does not necessarily need to achieve all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0021] Figure 1 This is a flowchart of a method for preparing a low freezing point composite biological carbon source according to the present invention; Figure 2 This is a graph showing the hourly changes in nitrate nitrogen during the anoxic denitrification process of coking wastewater in Example 1 of the present invention; Figure 3 Hourly variation diagram of CODcr in the anoxic denitrification process of coking wastewater in Example 1 of the present invention; Figure 4 This is a graph showing the hourly changes in nitrate nitrogen during the anoxic denitrification process in Example 2 of the present invention. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] In order to reduce the freezing point of the carbon source without affecting the performance of biological denitrification of the carbon source. Figure 1 As shown, the present invention adopts a method for preparing a low freezing point composite biological carbon source: The byproducts obtained from the fermentation process, including beer yeast mud, white wine lees, old wine lees, alcohol yeast mud, etc., are crushed into particles and agglomerated materials at a rotation speed of 300-1500rpm to 80-250 mesh, preferably 250 mesh; then the obtained particles are added with water to adjust the moisture content to 95.5-98.5%, and stirred at 40-80rpm at room temperature (18-25℃), and autolyzed for 1-2 hours to obtain a particle mixture; The pH of the particle mixture is adjusted to 6-8, preferably 7, by a 3-5 mol / L NaOH solution, and the mixture is heated and the temperature is adjusted to 25-60° C., preferably 37-50° C.; then, a wall-breaking enzyme, a protein enzyme, papain, papain, papain peptidase, alkaline protease, cellulase, and β-glucanase are added at a controlled amount of 0.5-3.5%, and then the mixture is stirred at a speed of 40-80 rpm for 6-60 hours until the reaction is complete to obtain a mixture; The mixture is centrifuged at a rotation speed of 4000-8000 rpm for 5-10 minutes, and then the supernatant is taken to obtain a biocarbon source extract, wherein the biocarbon source extract is composed of more than 100 biodegradable small molecule alcohols, organic acids and sugar substances, and contains amino acids and vitamins that are easily absorbed and utilized by microorganisms.

[0024] First, ethylene glycol and glycerol are mixed in a ratio of 1-10:10-1 to form an antifreeze solution, wherein 1-10 is the volume of 1-10 parts of ethylene glycol, and 10-1 is the volume of 10-1 parts of glycerol. Then, the antifreeze solution and the biological carbon source extract are mixed in a ratio of 5-2:5-8, wherein 5-2 is the volume of 5-2 parts of the biological carbon source extract, and 5-8 is the volume of 5-8 parts of the antifreeze solution. Preferably, ethylene glycol: glycerol = 8:2; antifreeze solution: biological carbon source extract is 2-5:8-5.

[0025] After the mixing is completed, the pH of the mixed solution containing the antifreeze solution is adjusted to 6-9 with 4 mol / L NaOH, thereby forming the low freezing point composite biocarbon source of the present invention.

[0026] The invention also provides a method for preparing a low freezing point composite biological carbon source and a low freezing point composite biological carbon source prepared therefrom.

[0027] The present invention also provides the application of the low freezing point composite biological carbon source in denitrification treatment of domestic sewage, municipal sewage, dispersed sewage, industrial sewage and garbage leachate.

[0028] The following are specific embodiments: Example 1

[0029] Take the beer yeast slurry and crush the particles and agglomerated materials at a speed of 1500 rpm, add water to adjust the moisture content to 98%, and pass through an 80-mesh sieve; Autolyze at room temperature (22°C) and stirring (60rpm) for 1 hour; adjust the pH to 7 with 4mol / LNaOH and then adjust the temperature of the material to 50°C, add wall-breaking enzyme, papain, papain, papain, alkaline protease, and β-glucanase in an amount of 1%, start stirring (60rpm), and hydrolyze at a constant temperature for 12 hours.

[0030] After the reaction is completed, centrifugation is performed (speed 5000 rpm, centrifugation 10 min) to obtain a supernatant, which is the biocarbon source extract. The prepared antifreeze A (ethylene glycol and glycerol according to 7:3) is added to the biocarbon source extract, wherein the biocarbon source extract is 75% and the antifreeze is 25%. After mixing, the pH value is adjusted to 7, which is the low freezing point composite biocarbon source of the present invention.

[0031] It has been detected that the COD equivalent of the low freezing point composite biological carbon source of the present invention is 440,000 mg / L, and there is no freezing at -20°C.

[0032] A low freezing point composite biological carbon source 1 was prepared by the method of Example 1, and a denitrification test was carried out in an industrial sewage station: a denitrification application test of coking wastewater from a steel plant.

[0033] The test results of sludge mixed liquor indicators in the biochemical process section of coking wastewater treatment in a steel plant are shown in Table 1. Due to the poor biodegradability of organic matter and high total nitrogen content in the coking wastewater, the C / N ratio of the biochemical system influent is low, and the carbon source available to microorganisms is insufficient, resulting in poor biological nitrification and denitrification effect.

[0034] Table 1 Results of the denitrification mixed liquor index test of the carbon source denitrification experiment of the anoxic tank sludge

[0035] The low freezing point composite biological carbon source 1 of the present invention was compared with the sodium acetate carbon source currently used in the biochemical process section of the coking wastewater treatment of the steel plant in a biological denitrification denitrification test. The addition conditions of different denitrification carbon sources and the test results are shown in Tables 2 and 3.

[0036] Table 2 Different carbon source addition conditions and denitrification test results in the anoxic section of coking wastewater treatment in steel plants:

[0037] Table 3 Comparison of denitrification effects of two carbon sources

[0038] See also Figure 1 and Figure 2 ,Depend on Figure 1 , Figure 2 As shown in Table 2, under the same COD concentration, the denitrification rate of the two carbon sources is: biological composite carbon source 1> sodium acetate carbon source, and the nitrate nitrogen removal rate after 6 hours of reaction is: biological composite carbon source 1> sodium acetate carbon source. This shows that the use of biological composite carbon source has a higher denitrification rate and a higher total nitrogen removal rate, and a higher denitrification effect can be quickly achieved within 6 hours of denitrification. The above data show that the composite biological carbon source can be quickly absorbed and utilized by activated sludge denitrifying bacteria, and shows a high denitrification rate and denitrification effect, indicating that the biological composite carbon source has good adaptability.

[0039] In addition, from the carbon source denitrification unit consumption ΔCOD / ΔTN value in Table 3, the amount of carbon source required to remove unit TN or nitrate, the dosage of the low freezing point composite biological carbon source of the present invention is lower than the dosage of the acetic acid carbon source. In general, the biological composite carbon source 1 is less than the sodium acetate carbon source, that is, the denitrification carbon source unit consumption is slightly less than sodium acetate. Therefore, the use of the low freezing point carbon source of the present invention can save operating costs and the amount of excess sludge generated.

[0040] From the perspective of comprehensive denitrification rate, nitrate nitrogen removal rate and denitrification carbon source consumption, the biological composite carbon source 1 has a better comprehensive denitrification performance than the current sodium acetate carbon source, and can replace the current sodium acetate carbon source to save operating costs.

[0041] Example 2 Take beer yeast mud and crush the particles and agglomerated materials at a speed of 1500rpm, add water to adjust the moisture content to 97%, and pass through an 80-mesh sieve; self-dissolve for 1.5 hours at room temperature (22°C) and stirring (60rpm); adjust the pH to 7 with 4mol / LNaOH, then adjust the temperature of the material to 40°C, add wall-breaking enzyme, papain, papain, papain, cellulase, and β-glucanase, and add the amount of 0.8%, start stirring (60rpm), and hydrolyze at constant temperature for 24h. After the reaction is completed, centrifuge (speed 5000rpm, centrifugation 10min) to obtain a supernatant, which is a biological carbon source extract, and add the prepared antifreeze A (ethylene glycol and glycerol according to 8:2) to the biological carbon source extract, wherein the biological carbon source extract is 42%, the antifreeze is 58%, and the pH value is adjusted to 7 after mixing, that is, the low freezing point composite biological carbon source of the present invention. It was detected that the COD equivalent of the low freezing point composite biological carbon source of the present invention was 820,500 mg / L, and there was no freezing at -50°C.

[0042] The low freezing point composite biological carbon source 2 was prepared by the method of Example 2, and a denitrification test was carried out in an actual sewage plant.

[0043] A sewage treatment plant in Northeast China adopts the "coarse screen-fine screen-sand trap-CASS-denitrification filter-disinfection" process. The carbon source currently used is mk carbon (COD equivalent ≥ 1.1 million mg / L), and the addition method is direct addition of the original solution. The addition points are the water distribution well and the denitrification filter in front of the CASS pool. In order to compare the denitrification and denitrification effects of different carbon sources in the biochemical section of the sewage treatment plant, the commonly used mk carbon (measured 1.1891 million mg / L), glycerol carbon source (1.2 million mg / L) and sodium acetate (analytical grade) carbon sources on the market were selected for equal comparison with the composite biological carbon source 2 of the present invention (measured 820,500 mg / L), among which: 1. The activated sludge mixed liquor was taken from the CASS biochemical pool of a sewage treatment plant in Northeast China. Its MLSS = 6582 mg / L, filtrate COD = 22 mg / L. After adding 12 mg / L of nitrate nitrogen, the nitrate nitrogen concentration was 21.51 mg / L. The test was carried out after the dissolved oxygen was lower than 0.5 mg / L. 2. The above four carbon sources (mk carbon, glycerol carbon source, sodium acetate carbon source and composite biological carbon source 2) were added to the four denitrification reactions respectively, and the COD concentration of the added carbon sources was 72 mg / L; 3. The initial CODcr of the denitrification system with different carbon sources added is the COD of the activated sludge filtrate plus the COD concentration of the added carbon source; the test results are shown in Table 4 and Figure 3 shown.

[0044] Table 4 Denitrification test of different carbon sources

[0045] Table 5 Comparison of denitrification effects of two carbon sources

[0046] from Figure 3 As can be seen from Table 4, under the same COD concentration, the denitrification rates of the two carbon sources are as follows: sodium acetate (analytical pure) > composite biological carbon source > mk carbon > glycerol carbon, and the nitrate nitrogen removal rate after 6.5 h of reaction is as follows: sodium acetate (analytical pure) > composite biological carbon source > mk carbon > glycerol carbon. This shows that the use of composite biological carbon source has a higher denitrification rate and a higher total nitrogen removal rate than the mk carbon currently used in the plant and the glycerol carbon on the market, and a higher denitrification effect can be quickly achieved within 6 hours of denitrification. The above data show that although the low freezing point composite biological carbon source of the present invention is used for the first time, it can be quickly absorbed and utilized by activated sludge denitrifying bacteria, and exhibits an efficient denitrification rate and denitrification effect, indicating that the composite biological carbon source has good adaptability. In addition, pure sodium acetate has a very excellent denitrification effect as a carbon source, but the market price is much higher than that of the composite biological carbon source.

[0047] In addition, judging from the carbon source denitrification unit consumption ΔCOD / ΔTN value in Table 5, the amount of carbon source required to remove unit TN is: composite biological carbon source < glycerol carbon < mk carbon source, that is, the composite biological carbon source can save about 20% COD equivalent carbon source compared with the mk carbon source.

[0048] In terms of comprehensive denitrification rate, nitrate nitrogen removal rate and denitrification carbon source consumption, the composite biological carbon source of the present invention has better comprehensive denitrification performance than the currently used MK carbon source, and can replace the currently used MK carbon source to save operating costs.

[0049] The above contents are merely examples and explanations of the concept of the present invention. The technicians in this technical field may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the concept of the invention or exceed the scope defined by the claims, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing a low freezing point composite biological carbon source, characterized in that: The specific steps include: The byproducts obtained from the fermentation process are crushed, and the obtained particles are watered to a moisture content of 95.5-98.5%, and are autolyzed for a certain period of time to obtain a particle mixture; The pH of the particle mixture is adjusted to 6-8, and the temperature is adjusted to 25-60° C., and then enzyme is added for reaction, and stirred and hydrolyzed until the reaction is complete to obtain a mixture; Centrifuging the mixture, and then taking the supernatant to obtain a biocarbon source extract; The antifreeze solution is prepared by mixing ethylene glycol and glycerol in a ratio of 1-10:10-1, wherein 1-10 is 1-10 parts by volume of ethylene glycol and 10-1 is 10-1 parts by volume of glycerol; The antifreeze solution is added to the biocarbon source extract and mixed in a ratio of 5-2:5-8 for reaction, and then the pH is adjusted to 6-9 to form a low freezing point composite biocarbon source, wherein 5-2 is the volume of 5-2 parts of the biocarbon source extract, and 5-8 is the volume of 5-8 parts of the antifreeze solution.

2. The method for preparing a low freezing point composite biological carbon source according to claim 1, characterized in that: The by-products obtained by the fermentation process are by-products of the fermentation industry process, specifically including beer yeast mud, white wine lees, old wine lees, and alcohol yeast mud.

3. The method for preparing a low freezing point composite biological carbon source according to claim 1, characterized in that: The by-product crushing is specifically: crushing the particles and agglomerated materials to 80-250 meshes at a rotation speed of 300-1500 rpm, and the mixed material is centrifuged specifically: centrifuged at a rotation speed of 4000-8000 rpm for 5-10 minutes.

4. The method for preparing a low freezing point composite biological carbon source according to claim 1, characterized in that: The self-dissolution is as follows: the material after adding water is stirred at 40-80 rpm at room temperature, and the self-dissolution time is 1-2 hours.

5. The method for preparing a low freezing point composite biological carbon source according to claim 1, characterized in that: The reagent for adjusting pH is 3-5 mol / L NaOH solution.

6. The method for preparing a low freezing point composite biological carbon source according to claim 1, characterized in that: The enzyme reaction uses wall-breaking enzyme, protein enzyme, papain, chymopapain, papain peptidase, alkaline protease, cellulase, beta-glucanase; the amount of the enzyme added is: 0.5-3.5%.

7. The method for preparing a low freezing point composite biological carbon source according to claim 1, characterized in that: The stirring hydrolysis specifically comprises: hydrolyzing for 6-60 hours under stirring at a rotation speed of 40-80 rpm.

8. The method for preparing a low freezing point composite biological carbon source according to claim 1, characterized in that: The biological carbon source extract is composed of biodegradable small molecule alcohols, organic acids and sugar substances.

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

10. Application of the low freezing point composite biological carbon source according to claim 9 in denitrification treatment of domestic sewage, municipal sewage, dispersed sewage, industrial sewage and landfill leachate.

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