High-organic-equivalent liquid-phase composite carbon source and preparation and application thereof

Abstract

The invention relates to the technical field of sewage treatment, and discloses a high-organic-equivalent liquid-phase composite carbon source and preparation and application thereof, and the composite carbon source comprises the following components in parts by mass: 5-10 parts of polyglycolide, 10-15 parts of glycerol, 10-15 parts of saccharides, 10-15 parts of propylene glycol, 15-25 parts of glycolic acid and 30-40 parts of water. The prepared composite carbon source is high in COD (Chemical Oxygen Demand) organic equivalent, small in molecular weight, green, environment-friendly, non-toxic and harmless, and suitable for microbial absorption. The flammable, combustible, toxic and harmful risks of methanol and ethanol used as a traditional carbon source are avoided, the risk of filamentous bacterium expansion caused by use of glucose is avoided, the problems of single microbial colony variety and poor load resistance caused by a single carbon source are avoided, and low-cost addition and utilization are realized.

Description

Technical Field

[0001] The invention relates to the technical field of sewage treatment, and in particular to a high organic equivalent liquid phase composite carbon source and preparation and application thereof. Background Art

[0002] Carbon source is a high molecular organic compound that provides necessary nutrients for microbial growth and metabolism. It is widely used in sewage treatment biochemical systems of different processes. The use of carbon source is particularly critical in the fields of urban domestic wastewater, industrial wastewater, municipal sewage, etc. Due to the wide variety of pollutants in sewage and wastewater and the extremely low content of organic matter, the microorganisms in the biochemical system cannot obtain enough organic matter and lack energy for denitrification reaction. Therefore, most sewage treatment plants need to add carbon source to solve the problem of high nitrate nitrogen in effluent caused by insufficient organic matter, thereby improving the biological denitrification and denitrification capacity of the biochemical system.

[0003] Carbon sources can be divided into single carbon sources and composite carbon sources. Single carbon sources mainly include methanol, ethanol, acetic acid, sodium acetate, glucose, etc., while composite carbon sources are mixed with these single carbon sources. However, there are many difficult-to-solve technical problems in the carbon sources currently sold on the market, which seriously affect the effect and safety of sewage treatment.

[0004] 1. Problems with single carbon source:

[0005] Methanol and ethanol: Although these alcohol carbon sources are easy to obtain and relatively cheap, they are highly toxic and can easily poison microorganisms and reduce the sewage treatment plant's ability to resist shock loads. Long-term use can cause drastic fluctuations in effluent quality, and in severe cases can even cause the biochemical system to collapse. In addition, the storage and use of methanol and ethanol present serious safety risks and must be strictly monitored, increasing the complexity and cost of operations.

[0006] Acetic acid and sodium acetate: Although acetic acid and sodium acetate have good denitrification effects, their low organic matter content leads to large dosage and high cost of use. At the same time, a large amount of sludge is produced during microbial metabolism, which increases the burden of sludge treatment and makes it difficult to use on a large scale.

[0007] Glucose: Although glucose is easily used by microorganisms, it can easily cause the proliferation of filamentous bacteria, leading to sludge swelling and affecting the sewage treatment effect. Therefore, glucose cannot be used as the main carbon source for a long time.

[0008] 2. Problems with composite carbon sources:

[0009] Most of the composite carbon sources on the market are mainly based on single carbon sources such as methanol, sodium acetate, glucose, etc., which cannot avoid the above-mentioned shortcomings of single carbon sources. Although these composite carbon sources have improved some problems of single carbon sources to a certain extent, they still have the following main problems:

[0010] 1. Toxicity and safety risks: Composite carbon sources usually contain toxic and harmful alcohols, such as methanol and ethanol, which are easy to poison microorganisms and reduce the shock load resistance of sewage treatment plants. At the same time, safety risks in storage and use still exist and require strict monitoring and management.

[0011] 2. Low organic matter content: Even if multiple single carbon sources are mixed, the organic matter content of the composite carbon source is still low, resulting in large dosage and high use cost. The amount of sludge produced during microbial metabolism is large, which increases the burden of sludge treatment.

[0012] 3. Unstable use effect: Due to the complex composition of the composite carbon source and the difficulty in quality control, its use effect is unstable and it is difficult to ensure the stability and reliability of the effluent water quality.

[0013] In summary, there are many difficult-to-solve technical problems in the field of composite carbon source preparation, which seriously affect the effect and safety of sewage treatment. Therefore, seeking a composite carbon source that is non-toxic, harmless, has no safety risks, has a high organic matter content and low addition cost is the focus of the current water treatment industry. Summary of the invention

[0014] The present invention aims to provide a high organic equivalent liquid phase composite carbon source and its preparation and application, so as to solve the problems of potential toxicity and unsatisfactory organic matter content of the composite carbon source in the prior art.

[0015] To achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a high organic equivalent liquid composite carbon source, calculated by mass, includes 5 to 10 parts of polyglycolide, 10 to 15 parts of glycerol, 10 to 15 parts of sugars, 10 to 15 parts of propylene glycol, 15 to 25 parts of hydroxyacetic acid, and 30 to 40 parts of water.

[0016] Preferably, as an improvement, the mixture comprises, by mass percentage, 5-10% polyglycolide, 10-15% glycerol, 10-15% sugar, 10-15% propylene glycol, 15-25% glycolic acid, and 30-40% water.

[0017] Preferably, as an improvement, glycolic acid and propylene glycol are both derived from waste mother liquor or scraps in the reproduction process of the food additive industry.

[0018] Preferably, as an improvement, the carbohydrate is at least one of sodium alginate, sodium gluconate, fructose and sucrose.

[0019] Preferably, as an improvement, the sodium gluconate is food grade and has a content greater than 98%.

[0020] Preferably, as an improvement, the COD equivalent is ≥ 1 million mg / L.

[0021] Preferably, as an improvement, a method for preparing a high organic equivalent liquid composite carbon source comprises the following steps:

[0022] S1. Take glycerol, polyglycolide, propylene glycol and glycolic acid in proportion and place them in a jacketed steam cooker, introduce saturated water vapor to react, and then release the pressure instantly to obtain a well-mixed carbon source substrate for standby use;

[0023] S2. After cooling the carbon source base, inject sugar into the carbon source base, and stir to obtain a high organic equivalent liquid composite carbon source.

[0024] Preferably, as an improvement, in step S1, the reaction temperature is 120° C., the pressure is 1.5 MPa, and the time is 10 to 15 min.

[0025] Preferably, as an improvement, in step S2, the cooling temperature is 30°C, the sugar injection rate is 10 mL / s, the stirring speed is 250-300 rpm, and the stirring time is 10-15 min.

[0026] Preferably, as an improvement, a high organic equivalent liquid composite carbon source is used in the preparation of a sewage treatment agent.

[0027] The principles and advantages of this solution are: in actual application, in the prior art, ethanol, methanol, etc. are often used in the preparation of composite carbon sources, which have certain potential toxicity. This solution selects a combination of alcohols and acids that are not common in the field of water treatment, which overcomes the problem of common carbon sources having alcohol biological toxicity and the danger of containing flammable and explosive substances; the use of glucose is likely to cause the massive reproduction of filamentous bacteria, leading to sludge swelling. This solution creatively uses sodium alginate as the main substance in the sugar composition, lowers the proportion of glucose in the component, and reduces the risk of sludge swelling. Based on this, in this technical solution, a new type of composite carbon source is proposed, and its composition and preparation process are comprehensively optimized. First of all, in the composition of the composite carbon source, the organic equivalent of polyglycolide and glycerol is high, which helps to increase the COD equivalent of the carbon source per unit volume and reduce transportation costs and addition costs. Moreover, polyglycolide is a biodegradable aliphatic polymer with fast degradation rate and good biodegradability. It is easily absorbed by microorganisms after high-temperature dissolution. The metabolites are carbon dioxide and water. There are no toxic and harmful components, which can reduce the metabolic burden of acids and alcohols on microorganisms. In the optimization of sugars, sodium alginate and sodium gluconate are mainly used. Such small molecule sugars help to accelerate bacterial absorption, accelerate intercellular metabolism, and also help to maintain the balance of osmotic pressure between cells, and prolong the survival life of microorganisms. At the same time, avoid using glucose that is easy to cause filamentous bacteria to reproduce, and avoid the secondary problem of sludge swelling in the sewage treatment process. In addition, the glycolic acid used in this technical solution is usually the same as in fishery feed. This technical solution introduces it into the composite carbon source, which can increase the immunity of aquatic organisms, and can also be combined with excessive cations such as calcium and magnesium to form a stable precipitate, which is conducive to controlling the alkalinity and hardness in sewage, thereby playing a role in stabilizing water quality, creating a microenvironment suitable for microbial reproduction, and achieving the dual effects of water improvement and promoting microbial activity. In addition, propylene glycol can be oxidized into propionaldehyde, lactic acid, pyruvic acid and acetic acid under the action of 120℃ steam. After the generated propionaldehyde is fully mixed with other components, it can significantly improve the antifreeze property of the composite carbon source, and there will be no component separation or stratification when used in winter. The high solubility of the carbon source at low temperatures is guaranteed, which is more conducive to the absorption and utilization of microorganisms at low temperatures. Lactic acid can competitively occupy the mucous membrane surface of denitrifying microorganisms, hindering the adhesion and growth of pathogenic microorganisms; in addition, lactic acid and acetic acid can also be decomposed into lactate hydrogen ions and hydrogen ions, thereby reducing the pH value of the environment and creating a weakly acidic environment that microorganisms like.The combination of hydroxyacetic acid and propylene glycol has a significant synergistic strengthening effect. Hydroxyacetic acid participates in the amino acid metabolism process in organisms to form necessary proteins for organisms, while the lactic acid metabolized by propylene glycol can promote the absorption and metabolism of organic matter by organisms, and accelerate the conversion of hydroxyacetic acid to protein, thereby synergistically promoting microorganisms to exponentially accelerate the metabolism of pollutants. The two can also combine with hardness ions such as calcium and magnesium in water to form precipitates, thereby reducing the hardness of the water. At the same time, because the two acids jointly form a weakly acidic environment, the weakly acidic environment has higher resistance to the outside world than when they are used alone, which can enhance the inhibition of the growth of viruses and pathogens and help maintain the normal microbial ecological balance.

[0028] In summary, the beneficial effects of the technical solution are: the composite carbon source prepared in the technical solution has a high COD organic equivalent, a COD equivalent of about 1 million mg / L, a small molecular weight, is green and environmentally friendly, non-toxic and harmless, and is suitable for microbial absorption. It avoids the risks of flammable and explosive, toxic and harmful use of methanol and ethanol as traditional carbon sources, avoids the risk of filamentous bacteria expansion caused by the use of glucose, and avoids the problems of a single type of microbial colony and poor load resistance caused by a single carbon source, thus achieving low-cost addition and utilization. DETAILED DESCRIPTION

[0029] The following is further described in detail through specific implementations, but the implementation of the present invention is not limited thereto. Unless otherwise specified, the technical means used in the following implementations are conventional means well known to those skilled in the art; the experimental methods used are all conventional methods; the materials, reagents, etc. used can all be obtained from commercial channels.

[0030] Program Overview:

[0031] A high organic equivalent liquid phase composite carbon source comprises, by mass percentage, 5-10% polyglycolide, 10-15% glycerol, 10-15% sugar, 10-15% propylene glycol, 15-25% glycolic acid and 30-40% water.

[0032] Among them, glycolic acid and propylene glycol both come from waste mother liquor and scraps in the reproduction process of the food additive industry; the sugar is at least one of sodium alginate, sodium gluconate, fructose, and sucrose, and the sodium gluconate is food grade with a content greater than 98%.

[0033] A method for preparing a high organic equivalent liquid phase composite carbon source comprises the following steps:

[0034] S1. Take glycerol, polyglycolide, propylene glycol and glycolic acid in proportion and place them in a jacketed steam boiler, introduce saturated water vapor, react with high-temperature steam at 120°C and 1.5MPa pressure for 10-15min, then release the pressure instantly to obtain a well-mixed carbon source substrate for standby use;

[0035] S2. Cool the carbon source base to 30°C, add the sugar into the carbon source base at an injection rate of 10 mL / s, and use a double-axis frame stirrer to stir at a speed of 250-300 rpm for 10-15 min to obtain a high organic equivalent liquid composite carbon source of this scheme.

[0036] Example 1

[0037] A high organic equivalent liquid phase composite carbon source, in terms of mass percentage, includes 8% polyglycolide, 12% glycerol, 15% sugar, 12% propylene glycol, 18% glycolic acid, and 35% water. The sugar in this embodiment is a compound of sodium alginate and sodium gluconate in a mass ratio of 3:1.

[0038] A method for preparing a high organic equivalent liquid phase composite carbon source comprises the following steps:

[0039] S1. Take the above-mentioned mass fractions of propylene glycol, polyglycolide, propylene glycol and glycolic acid and place them in a double-layer steam boiler, introduce saturated water vapor, and react with high-temperature steam at 120°C and 1.5MPa pressure for 15 minutes until the above-mentioned substances are fully mixed under high temperature conditions, and then release the pressure instantly to obtain a well-mixed carbon source substrate for standby use.

[0040] S2. Cool the above carbon source base to 30°C, take the above mass fraction of sugar, add it to the carbon source base prepared in step S1 at an injection rate of 10 mL / s, use a double-axis frame stirrer, stir at 250 rpm for 15 minutes to ensure sufficient mixing, and obtain a high organic equivalent liquid composite carbon source.

[0041] Example 2

[0042] A high organic equivalent liquid phase composite carbon source, in terms of mass percentage, includes 5% polyglycolide, 15% glycerol, 12% sugar, 12% propylene glycol, 20% glycolic acid, and 36% water. The sugar in this embodiment is a compound of sucrose and sodium alginate in a mass ratio of 1:1.

[0043] A method for preparing a high organic equivalent liquid phase composite carbon source comprises the following steps:

[0044] S1. Take the above-mentioned mass fractions of propylene glycol, polyglycolide, propylene glycol and glycolic acid and place them in a double-layer steam boiler, introduce saturated water vapor, and react with high-temperature steam at 120°C and 1.5MPa pressure for 10 minutes until the above-mentioned substances are fully mixed under high temperature conditions, and then release the pressure instantly to obtain a well-mixed carbon source substrate for standby use.

[0045] S2. Cool the above carbon source base to 30°C, take the above mass fraction of sugar, add it to the carbon source base prepared in step S1 at an injection rate of 10 mL / s, use a double-axis frame stirrer, stir at 300 rpm for 10 minutes to ensure sufficient mixing, and obtain a high organic equivalent liquid composite carbon source.

[0046] Example 3

[0047] A high organic equivalent liquid phase composite carbon source comprises, by mass percentage, 10% polyglycolide, 13% glycerol, 10% sugar, 12% propylene glycol, 25% glycolic acid, and 30% water. The sugar in this embodiment is glucose.

[0048] A method for preparing a high organic equivalent liquid phase composite carbon source comprises the following steps:

[0049] S1. Take the above-mentioned mass fractions of propylene glycol, polyglycolide, propylene glycol and glycolic acid and place them in a jacketed steam boiler, introduce saturated water vapor, and react with high-temperature steam at 120°C and 1.5MPa pressure for 12 minutes until the above-mentioned substances are fully mixed under high temperature conditions, and then release the pressure instantly to obtain a well-mixed carbon source substrate for standby use.

[0050] S2. Cool the above carbon source base to 30°C, take the above mass fraction of sugar, add it to the carbon source base prepared in step S1 at an injection rate of 10 mL / s, use a double-axis frame stirrer, stir at 280 rpm for 12 minutes to ensure sufficient mixing, and obtain a high organic equivalent liquid composite carbon source.

[0051] Comparative Example 1

[0052] This comparative example uses a commonly used composite carbon source in the prior art as a comparison, and the composite carbon source, in terms of mass percentage, includes 30% methanol, 10% glycerol, 10% glucose, 10% acetic acid, and 40% water. The above-mentioned methanol, glycerol, glucose, acetic acid, and water are placed in a beaker and stirred at a constant speed of 100 rpm for 15 minutes to obtain the carbon source of the comparative example.

[0053] Comparative Example 2

[0054] This comparative example uses a commonly used composite carbon source in the prior art as a comparison, and the composite carbon source, in terms of mass percentage, includes 15% methanol, 10% ethanol, 25% glucose, 20% acetic acid, and 30% water. Methanol, ethanol, glycerol, glucose, acetic acid, and water in the above mass fractions are placed in a beaker and stirred at a constant speed of 100 rpm for 15 minutes to obtain the carbon source of this comparative example.

[0055] Experimental example

[0056] The organic equivalent and effectiveness of the high organic equivalent liquid composite carbon source prepared in the above embodiments were verified, wherein the organic equivalent was measured in terms of COD equivalent concentration, and the detection method was referred to HJ828-2017; the effectiveness was evaluated by conducting a denitrification experiment under the same test conditions of influent water quality, reaction time, dosage, etc. The test conditions for the denitrification experiment were as follows: using the usual municipal sewage influent water quality parameters, controlling the sludge concentration of the water body to 3000 mg / L, controlling the total nitrogen of the influent to 30 mg / L, and the temperature to 20°C. The carbon sources used in the experiment were all added at a carbon-nitrogen ratio of 5:1, and the addition position was the water inlet of the anoxic tank; the detection method was HJ636-2012. At the same time, methanol and glucose were set for comparison with two commonly used composite carbon sources in the prior art (Comparative Examples 1 and 2), and the test results are shown in Table 1:

[0057] Table 1

[0058]

[0059]

[0060] From the experimental results in Table 1, under the conditions of the same influent water quality, reaction time and dosage, the denitrification effect of Examples 1 to 3 is higher than that of the traditional high equivalent liquid carbon source and the common composite carbon source, and the total nitrogen removal rate is about 39.3% higher than that of methanol, 22.3% higher than that of glucose (food grade), and about 27% higher than that of the common composite carbon source. The effluent COD concentration is lower, which proves that Examples 1 to 3 are more easily absorbed and utilized by microorganisms, the denitrification reaction is carried out more thoroughly, and the microbial metabolism is faster, because the synergistic effect of glycolic acid and propylene glycol accelerates the biological metabolism. In addition, Examples 1-3 crystallize out from the water body at about 0°C, which proves that under low temperature conditions, the solubility with water is better, which is conducive to the denitrification microorganisms to attract nutrients in a low temperature environment, thereby realizing low temperature denitrification.

[0061] The high organic equivalent liquid composite carbon source in the embodiment of the present invention is obtained from waste mother liquor and scraps from the food industry, which is easily available and more environmentally friendly in terms of acquisition. It does not contain flammable and explosive substances such as methanol and ethanol, and there is no major production risk during preparation. It is safer to store and use, has good denitrification effect, and has a high organic equivalent.

[0062] The above is only an embodiment of the present invention, and the common knowledge such as the known specific technical solutions and / or characteristics in the solution is not described in detail here. It should be pointed out that for those skilled in the art, without departing from the technical solution of the present invention, several modifications and improvements can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A high organic equivalent liquid composite carbon source, characterized in that: Calculated by mass, it includes 5-10 parts of polyglycolide, 10-15 parts of glycerol, 10-15 parts of sugars, 10-15 parts of propylene glycol, 15-25 parts of glycolic acid, and 30-40 parts of water.

2. A high organic equivalent liquid composite carbon source according to claim 1, characterized in that: Calculated by mass percentage, it includes 5-10% of polyglycolide, 10-15% of glycerol, 10-15% of sugar, 10-15% of propylene glycol, 15-25% of glycolic acid, and 30-40% of water.

3. A high organic equivalent liquid composite carbon source according to claim 2, characterized in that: The glycolic acid and propylene glycol are both derived from waste mother liquor or scraps in the reproduction process of the food additive industry.

4. A high organic equivalent liquid composite carbon source according to claim 3, characterized in that: The sugar is at least one of sodium alginate, sodium gluconate, fructose and sucrose.

5. A high organic equivalent liquid composite carbon source according to claim 4, characterized in that: The sodium gluconate is food grade and has a content greater than 98%.

6. A high organic equivalent liquid composite carbon source according to claim 5, characterized in that: COD equivalent ≥ 1 million mg / L.

7. The method for preparing a high organic equivalent liquid composite carbon source according to any one of claims 1 to 6, characterized in that: The steps include: S1. Take glycerol, polyglycolide, propylene glycol and glycolic acid in proportion and place them in a jacketed steam cooker, introduce saturated water vapor to react, and then release the pressure instantly to obtain a well-mixed carbon source substrate for standby use; S2. After cooling the carbon source base, inject sugar into the carbon source base, and stir to obtain a high organic equivalent liquid composite carbon source.

8. The method for preparing a high organic equivalent liquid composite carbon source according to claim 7, characterized in that: In step S1, the reaction temperature is 120°C, the pressure is 1.5 MPa, and the time is 10 to 15 minutes.

9. The method for preparing a high organic equivalent liquid composite carbon source according to claim 8, characterized in that: In step S2, the cooling temperature is 30°C, the sugar injection rate is 10 mL / s, the stirring speed is 250-300 rpm, and the stirring time is 10-15 min.

10. Use of a high organic equivalent liquid composite carbon source according to any one of claims 1 to 6 in the preparation of a sewage treatment agent.

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