Composite carbon source for sewage treatment, preparation method and application

Abstract

The present invention discloses a composite carbon source for sewage treatment, a preparation method and an application thereof, and belongs to the technical field of sewage treatment. The composite carbon source is composed of 3 to 20 parts of sodium acetate, 5 to 15 parts of potassium formate, 2 to 10 parts of gelatinized starch, 1 to 5 parts of a saccharide compound, 1 to 5 parts of an inorganic salt, 0.3 to 0.5 parts of a natural cellulose extract, 0.01 to 0.5 parts of a biological enzyme, and 20 to 45 parts of water, by weight. The composite carbon source of the present application can stably and effectively release the carbon source, improve the growth environment of nitrogen- and phosphorus-loving sludge, increase the activity of nitrogen- and phosphorus-loving sludge, reduce the nitrogen and phosphorus content in wastewater, improve sewage treatment efficiency, and has a simple preparation method and is convenient to use.

Description

Technical Field

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

[0002] In recent years, with the decline of water resources and the increasing demand for water in an increasing number of industries, eutrophication has become a serious environmental problem. Following the release of China's "Ten Water Regulations," stricter requirements have been set for nitrogen and phosphorus emissions. Among the many municipal wastewater treatment processes, biological nitrification and denitrification is widely used for wastewater denitrification due to its low cost and high efficiency. Traditional biological denitrification processes are primarily divided into nitrification and denitrification. Denitrification involves the reduction of nitrite and nitrate produced during nitrification into gaseous nitrogen by heterotrophic denitrifying bacteria using an organic carbon source as an electron donor in an anoxic environment. Organic carbon sources are crucial in the denitrification process, and their type and carbon-to-nitrogen ratio influence denitrification effectiveness. Denitrification can only proceed smoothly if sufficient carbon sources are present in the water, generally requiring a BOD / TKN ratio greater than 4. Due to insufficient carbon sources, the effluent quality of sewage treatment plants is difficult to meet the "Class A" standard for pollutant emissions from urban sewage treatment plants. Currently, external carbon sources are added to low-carbon-nitrogen ratio sewage to ensure denitrification. However, different carbon sources have different effects on denitrification. Finding efficient, cheap and environmentally friendly external carbon sources has become an urgent problem to be solved.

[0003] Composite carbon source is a carbon source product for starting and debugging sewage biochemical systems or shortening recovery time. Composite carbon source can be used as a carbon source product in municipal and industrial sewage treatment plants to enhance sludge activity. It can also be used as a carbon source product to improve the efficiency of nitrogen-loving bacteria and phosphophilic bacteria, reduce nitrogen and phosphorus content in wastewater, and ensure that the system's denitrification and phosphorus removal effects meet standards.

[0004] However, existing carbon sources still have problems: glucose is the primary carbon source used in existing wastewater treatment, and the high dosage not only increases system operating costs but can also cause COD levels to exceed standards. Therefore, developing a composite carbon source with significant denitrification effects, high wastewater treatment efficiency, ease of use, and a high cost-effectiveness is an urgent need in this field. Summary of the Invention

[0005] In response to the shortcomings of the prior art, the present invention aims to provide a composite carbon source for sewage treatment. This composite carbon source can stably and effectively release carbon, improve the growth environment of nitrogen- and phosphorus-loving sludge, increase sludge activity, reduce nitrogen and phosphorus content in wastewater, and improve sewage treatment efficiency. It also features a simple preparation method and is easy to use.

[0006] On one hand, the present invention provides a composite carbon source for sewage treatment. The composite carbon source is composed, by weight, of 3 to 20 parts of sodium acetate, 5 to 15 parts of potassium formate, 2 to 10 parts of gelatinized starch, 1 to 5 parts of carbohydrate compounds, 1 to 5 parts of inorganic salts, 0.3 to 0.5 parts of natural cellulose extracts, 0.01 to 0.5 parts of biological enzymes, and 20 to 45 parts of water.

[0007] Another aspect of the present invention provides a method for preparing a composite carbon source for sewage treatment, the preparation method comprising:

[0008] S1. Add weighed water into the reactor;

[0009] S2. Add weighed sodium acetate, potassium formate, gelatinized starch, and carbohydrate compound to the water in step S1 and stir evenly under constant temperature;

[0010] S3, adding the weighed inorganic salt and natural cellulose extract to the mixed solution of step S2, and stirring evenly under constant temperature;

[0011] S4. Add the biological enzyme to the mixed solution in step S3 and stir evenly under constant temperature to obtain a composite carbon source.

[0012] In another aspect, the present invention provides a composite carbon source for sewage treatment as described above, and / or use of the composite carbon source prepared by the method for preparing the composite carbon source for sewage treatment as described above in sewage treatment.

[0013] The beneficial effects of the present invention include at least one of the following:

[0014] 1. The natural cellulose extract in this application is non-biotoxic and has a large specific surface area. During the denitrification process, it can not only serve as an external carbon source, but also as a carrier of biofilm, enabling efficient denitrification. When the cellulose reacts with water, the oxygen bridges are broken. At the same time, water molecules are added, and the cellulose is converted from long-chain molecules to short-chain molecules until all oxygen bridges are broken and converted into glucose.

[0015] 2. The composite carbon source for water treatment provided by the present application can release carbon sources stably and long-term through the synergistic combination of several components, has high denitrification efficiency and long service life, can significantly reduce the total nitrogen content in water bodies and improve sewage treatment efficiency, and avoids large amounts of sludge output. It is easy to use and can be directly put into sewage treatment equipment for use;

[0016] 3. The preparation method of the composite carbon source of the present application is simple and environmentally friendly, the raw materials are easily obtained, and it has broad prospects for large-scale application;

[0017] 4. The preparation method of the present application uses batch raw materials and industrial equipment, is highly versatile, is easy to produce on a large scale, and has good prospects for industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The figure shows a preparation flow chart of a composite carbon source for sewage treatment according to the present invention. DETAILED DESCRIPTION

[0019] In order to more clearly illustrate the overall concept of the present invention, a detailed description is given below in the form of examples.

[0020] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the scope of protection of the present invention is not limited to the specific embodiments disclosed below.

[0021] In addition, in the description of the invention, it should be understood that the terms "top", "bottom", "inside", "outside", "axial", "radial", "circumferential", etc., indicating orientations or positional relationships, are for the purpose of facilitating the description of the present invention, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0022] In the present invention, unless otherwise expressly specified or limited, terms such as "installed," "connected," "connect," and "fixed" should be interpreted broadly. For example, they may refer to fixed connection, detachable connection, or integration; mechanical connection, electrical connection, or communication; direct connection or indirect connection through an intermediate medium; and internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0023] In the present invention, unless otherwise clearly specified and limited, a first feature "above" or "below" a second feature may be that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in an appropriate manner in any one or more embodiments or examples.

[0024] Hereinafter, the composite carbon source for sewage treatment and the preparation method thereof will be described in detail with reference to exemplary embodiments. Figure 1 The figure shows a preparation flow chart of a composite carbon source for sewage treatment according to the present invention.

[0025] like Figure 1 As shown, in an exemplary embodiment of the present invention, the preparation method of the composite carbon source for sewage treatment can be achieved by the following steps:

[0026] S1. Add the weighed water into the reactor.

[0027] Specifically, the weight portion of water is 20 to 45 parts by weight.

[0028] S2. Add weighed sodium acetate, potassium formate, gelatinized starch, and carbohydrate compound to the water in step S1 and stir evenly under constant temperature.

[0029] Specifically, in parts by weight, the weight portion of sodium acetate is 3 to 20 parts, the weight portion of potassium formate is 5 to 15 parts, the weight portion of gelatinized starch is 2 to 10 parts, and the weight portion of the carbohydrate compound is 1 to 5 parts.

[0030] The gelatinized starch preparation method comprises: uniformly mixing starch and water in a mass ratio of 1:3 to 5, then adding isopropyl alcohol at 0.1% to 0.3% by mass of the starch, heating to 90°C to 100°C, stirring at a speed of 1000 to 1200 r / min for 2 to 4 hours, and then rotary evaporation and drying to obtain the gelatinized starch. The starch can be any one of corn starch, sweet potato starch, potato starch, and chestnut starch, but the present invention is not limited thereto.

[0031] The sugar compound is any one or more of glucose, sucrose, fructose, galactose and maltose, but the present invention is not limited thereto. The stirring temperature is 30-60° C., and the pH of the system in the reactor is 7.0-7.5.

[0032] S3. Add the weighed inorganic salt and natural cellulose extract to the mixed solution of step S2, and stir evenly under constant temperature.

[0033] Specifically, the inorganic salt is 1 to 5 parts by weight, and the natural cellulose extract is 0.3 to 0.5 parts by weight. The inorganic salt is any one or more of calcium chloride, sodium chloride, potassium chloride, magnesium chloride, and magnesium sulfate, but the present invention is not limited thereto.

[0034] The preparation method of natural cellulose is as follows: corn cobs are crushed and soaked in a 3% sodium hydroxide solution for 24 hours to obtain a mixed solution. Subsequently, the mixed solution is boiled at 100°C for 80 minutes. When the solution is cooled to 70-80°C, a 4% hydrogen peroxide solution is added and the solution is heated for 1 hour while maintaining the temperature at 70-80°C. The mixture is then filtered and the filter residue is washed thoroughly with water until it is neutral. The natural cellulose extract is obtained after drying.

[0035] The stirring temperature is 30-60° C., and the system pH in the reactor is 7.0-7.5.

[0036] S4. Add the biological enzyme to the mixed solution in step S3 and stir evenly under constant temperature to obtain a composite carbon source.

[0037] Specifically, the amount of the biological enzyme is 0.01 to 0.5 parts by weight. The biological enzyme is any one or more of pectin lyase, polygalacturonase, pectate lyase, and pectinesterase, but the present invention is not limited thereto. The stirring temperature is 30 to 60° C., and the pH of the system in the reactor is 7.0 to 7.5.

[0038] Example 1

[0039] This example prepared a composite carbon source for sewage treatment using the following method:

[0040] S1. Corn starch and water are uniformly mixed in a mass ratio of 1:3, and then 0.3% of the mass of corn starch is added with isopropyl alcohol. The mixture is heated to 90° C. and stirred at a speed of 1000 r / min for 2 h. The mixture is then rotary evaporated and dried to obtain gelatinized starch.

[0041] S2. Add 20 g of water, 3 g of sodium acetate, 5 g of potassium formate, 2 g of gelatinized starch, and 1 g of glucose to the water in step S1, and stir evenly at a temperature of 40° C. and a pH of 7.0.

[0042] S3. Add 1 g of calcium chloride and 0.3 g of natural cellulose extract to the mixed solution of step S2, and stir evenly at a temperature of 30° C. and a pH of 7.0.

[0043] S4. Add 0.02 g of pectin lyase to the mixed solution in step S3, and stir evenly at a temperature of 30° C. and a pH of 7.0 to obtain composite carbon source 1#.

[0044] Example 2

[0045] This example prepared another composite carbon source for sewage treatment using the following method:

[0046] S1. Sweet potato starch and water are uniformly mixed in a mass ratio of 1:4, and then 0.2% of isopropyl alcohol by mass of the sweet potato starch is added, heated to 95° C., stirred at a speed of 1100 r / min for 3 h, and then rotary evaporated to dry to obtain gelatinized starch.

[0047] S2. Add 30 g of water, 10 g of sodium acetate, 8 g of potassium formate, 4 g of gelatinized starch, and 3 g of sucrose to the water in step S1, and stir evenly at a temperature of 50° C. and a pH of 7.3.

[0048] S3. Add 3 g of sodium chloride and 0.35 g of natural cellulose extract to the mixed solution of step S2, and stir evenly at a temperature of 40° C. and a pH of 7.3.

[0049] S4. Add 0.3 g of polygalacturonase to the mixed solution in step S3, and stir evenly at a temperature of 40° C. and a pH of 7.3 to obtain composite carbon source 2#.

[0050] Example 3

[0051] This example prepared another composite carbon source for sewage treatment using the following method:

[0052] S1. Potato starch and water are uniformly mixed in a mass ratio of 1:5, and then 0.3% isopropyl alcohol is added based on the mass of the potato starch. The mixture is heated to 100° C. and stirred at a speed of 1200 r / min for 4 h. The mixture is then rotary evaporated and dried to obtain gelatinized starch.

[0053] S2. Add 45 g of water, 20 g of sodium acetate, 15 g of potassium formate, 10 g of gelatinized starch, and 5 g of fructose to the water in step S1, and stir evenly at a temperature of 40° C. and a pH of 7.0.

[0054] S3. Add 3 g of potassium chloride, 2 g of magnesium sulfate, and 0.5 g of natural cellulose extract to the mixed solution of step S2, and stir evenly at a temperature of 60° C. and a pH of 7.5.

[0055] S4. Add 0.1 g of pectate lyase and 0.05 g of pectin lyase to the mixed solution in step S3, and stir evenly at a temperature of 60° C. and a pH of 7.5 to obtain composite carbon source 3#.

[0056] Example 4

[0057] This example prepared another composite carbon source for sewage treatment using the following method:

[0058] S1. Chestnut starch and water are uniformly mixed in a mass ratio of 1:3.5, and then 0.25% of isopropyl alcohol by mass of the chestnut starch is added. The mixture is heated to 93° C. and stirred at a speed of 1050 r / min for 2.5 h. The mixture is then rotary evaporated and dried to obtain gelatinized starch.

[0059] S2. Add 35 g of water, 12 g of sodium acetate, 10 g of potassium formate, 6 g of gelatinized starch, and 3 g of maltose to the water in step S1, and stir evenly at a temperature of 45° C. and a pH of 7.2.

[0060] S3. Add 3.5 g of magnesium chloride and 0.4 g of natural cellulose extract to the mixed solution of step S2, and stir evenly at a temperature of 45° C. and a pH of 7.2.

[0061] S4. Add 0.05 g of pectinesterase to the mixed solution in step S3, and stir evenly at a temperature of 45° C. and a pH of 7.2 to obtain composite carbon source 4#.

[0062] Comparative Example 1

[0063] This comparative example prepared a composite carbon source for sewage treatment using the following method:

[0064] S1. Chestnut starch and water are uniformly mixed in a mass ratio of 1:3.5, and then 0.25% of isopropyl alcohol by mass of the chestnut starch is added. The mixture is heated to 93° C. and stirred at a speed of 1050 r / min for 2.5 h. The mixture is then rotary evaporated and dried to obtain gelatinized starch.

[0065] S2. Add 35 g of water, 12 g of sodium acetate, 10 g of potassium formate, 6 g of gelatinized starch, and 3 g of maltose to the water in step S1, and stir evenly at a temperature of 45° C. and a pH of 7.2.

[0066] S3. Add 3.5 g of magnesium chloride to the mixed solution of step S2, and stir evenly at a temperature of 45° C. and a pH of 7.2.

[0067] S4. Add 0.05 g of pectinesterase to the mixed solution in step S3, and stir evenly at a temperature of 45° C. and a pH of 7.2 to obtain comparative composite carbon source 1#.

[0068] Comparative Example 2

[0069] This comparative example prepared another composite carbon source for sewage treatment using the following method:

[0070] S1. Add 35 g water, 12 g sodium acetate, 10 g potassium formate, 6 g chestnut starch, and 3 g maltose to the water in step S1, and stir evenly at a temperature of 45° C. and a pH of 7.2.

[0071] S2. Add 3.5 g of magnesium chloride and 0.4 g of natural cellulose extract to the mixed solution of step S2, and stir evenly at a temperature of 45° C. and a pH of 7.2.

[0072] S3. Add 0.05 g of pectinesterase to the mixed solution in step S3, and stir evenly at a temperature of 45° C. and a pH of 7.2 to obtain comparative composite carbon source 2#.

[0073] Comparative Example 3

[0074] This comparative example prepared another composite carbon source for sewage treatment using the following method:

[0075] S1. Chestnut starch and water are uniformly mixed in a mass ratio of 1:3.5, and then 0.25% of isopropyl alcohol by mass of the chestnut starch is added. The mixture is heated to 93° C. and stirred at a speed of 1050 r / min for 2.5 h. The mixture is then rotary evaporated and dried to obtain gelatinized starch.

[0076] S2. Add 35 g of water, 12 g of sodium acetate, 10 g of potassium formate, 6 g of gelatinized starch, and 3 g of maltose to the water in step S1, and stir evenly at a temperature of 45° C. and a pH of 7.2.

[0077] S3. Add 3.5 g of magnesium chloride and 0.4 g of natural cellulose extract to the mixed solution of step S2, and stir evenly at a temperature of 45° C. and a pH of 7.2 to obtain comparative composite carbon source 3#.

[0078] The composite carbon sources provided in Examples 1-4 and Comparative Examples 1-3 of the present invention were used to treat municipal sewage and industrial wastewater. During wastewater treatment, the stock solution was diluted to a suitable concentration based on the properties of the composite carbon source and the degree of water pollution before addition. For severely polluted wastewater, the stock solution could be added directly. The dosage was primarily determined by the degree of water pollution, the point of addition, and the pilot test results. Typically, 100-500 mg of the composite carbon source was added per liter of wastewater. The degree of wastewater pollution was measured using the total nitrogen index.

[0079] The test method for sewage denitrification performance is as follows:

[0080] The sewage to be treated first enters a sedimentation tank, where colloids and fine suspended matter therein are condensed to form flocs under the action of a coagulant. After the flocs are separated and removed, the sewage enters a biological aeration filter for carbonization and nitrification. The effluent from the biological aeration filter then enters a denitrification filter, where denitrification is carried out with the aid of a composite carbon source to remove total nitrogen from the water. The effluent from the denitrification filter then enters a sand filter and a catalytic oxidation tank in sequence to ultimately obtain purified water. The composite carbon sources provided in Examples 1 to 4 and Comparative Examples 1 to 3 are added to the denitrification filter at a ratio of 300 mg of composite carbon source per liter of sewage. After the treatment is completed, the purified water is collected and tested for total phosphorus content, chemical oxygen demand (COD), total nitrogen content, and ammonia nitrogen content.

[0081] Determination Standards: Chemical Oxygen Demand (COD): Determined using the dichromate method specified in HJ / T 828-2017; Total Nitrogen: Determined using the gas phase molecular absorption spectrometry method specified in HJ / T 199-2005; Ammonia Nitrogen: Determined using the continuous flow salicylic acid spectrophotometry method specified in HJ / T 665-2013; Total Phosphorus: Determined using the ammonium molybdate spectrophotometry method specified in GB 11893-89. The test results are shown in Table 1.

[0082] Table 1 Test results

[0083]

[0084] As can be seen from Table 1, the composite carbon source prepared by Examples 1 to 4 of the present invention is used for sewage treatment with high denitrification efficiency, and can reduce the total nitrogen content of sewage from more than 38 mg / L to less than 10.10 mg / L, or even as low as 8.05 mg / L, with a total nitrogen removal rate of 79%. The total ammonia nitrogen content of sewage is reduced from 8.61 mg / L to 1.84-2.16 mg / L, and the ammonia nitrogen removal rate reaches more than 74.9%, with a good denitrification effect. The total phosphorus content of sewage is reduced from 2.39 mg / L to 0.23-0.31 mg / L, and the total phosphorus removal rate reaches more than 87%. The COD of the water after treatment with the composite carbon source provided by Examples 1 to 4 of the present invention is 31.41-36.63 mg / L, which fully meets the water quality requirements after purification.

[0085] The composite carbon sources provided in Comparative Examples 1 to 3 lack at least one component of natural cellulose extract, biological enzyme, and gelatinized starch, resulting in a significant decrease in denitrification efficiency, a total nitrogen removal rate of less than 67%, and a COD of the treated water quality higher than 50 mg / L, which does not meet the ideal water purification requirements.

[0086] The foregoing is merely an embodiment of the present invention and is not intended to limit the present invention. It will be apparent to those skilled in the art that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are intended to be included within the scope of the claims of the present invention.

Claims

1. A composite carbon source for sewage treatment, characterized in that: The composite carbon source is composed of 3 to 20 parts of sodium acetate, 5 to 15 parts of potassium formate, 2 to 10 parts of gelatinized starch, 1 to 5 parts of carbohydrate compounds, 1 to 5 parts of inorganic salts, 0.3 to 0.5 parts of natural cellulose extract, 0.01 to 0.5 parts of biological enzymes, and 20 to 45 parts of water in parts by weight; The gelatinized starch preparation method comprises: uniformly mixing starch and water in a mass ratio of 1:3-5, then adding isopropyl alcohol in an amount of 0.1%-0.3% by mass of the starch, heating to 90°C-100°C, stirring at a speed of 1000-1200 r / min for 2-4 hours, and then performing rotary evaporation drying to obtain the gelatinized starch; The preparation method of the natural cellulose extract comprises the following steps: crushing corn cobs and soaking them in a 3% sodium hydroxide solution for 24 hours to obtain a mixed solution; then, boiling the mixed solution at 100°C for 80 minutes; and adding a 4% hydrogen peroxide solution when the solution temperature cools to 70-80°C. The mixture is then heated for 1 hour while maintaining the temperature at 70-80°C. The mixture is then filtered, and the residue is thoroughly washed with water until neutral, and dried to obtain the natural cellulose extract. The biological enzyme is any one or more of pectin lyase, polygalacturonase, pectate lyase and pectinesterase; The sugar compound is any one or more of glucose, sucrose, fructose, galactose and maltose.

2. The composite carbon source according to claim 1, characterized in that The starch is any one of corn starch, sweet potato starch, potato starch and chestnut starch.

3. The composite carbon source according to claim 1, characterized in that The inorganic salt is any one or more of calcium chloride, sodium chloride, potassium chloride, magnesium chloride, and magnesium sulfate.

4. A method for preparing a composite carbon source for sewage treatment according to any one of claims 1 to 3, characterized in that: The preparation method comprises: S1. Add weighed water into the reactor; S2. Add weighed sodium acetate, potassium formate, gelatinized starch, and carbohydrate compound to the water in step S1 and stir evenly under constant temperature; S3, adding the weighed inorganic salt and natural cellulose extract to the mixed solution of step S2, and stirring evenly under constant temperature; S4. Add the biological enzyme to the mixed solution in step S3 and stir evenly under constant temperature to obtain a composite carbon source.

5. The preparation method according to claim 4, characterized in that The temperature under the constant temperature condition is 30-60° C., and the pH value of the system in the reactor is 7.0-7.

5.

6. Use of the composite carbon source according to any one of claims 1 to 3, and / or the composite carbon source prepared by the method for preparing the composite carbon source for sewage treatment according to any one of claims 4 to 5 in sewage treatment.

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