Solid composite carbon source for sewage denitrification and application thereof

Abstract

The invention discloses a solid composite carbon source for sewage denitrification and a preparation method thereof. The composite carbon source is prepared from the following components in parts by weight: 10 to 60 parts of sodium acetate, 10 to 30 parts of glucose, 10 to 30 parts of starch, 0.1 to 2 parts of yeast powder, 1 to 5 parts of cellulose and 0.1 to 0.3 part of glycosyl hydrolase. Sodium acetate in the composite carbon source can react quickly, an instantaneous carbon source is provided, glucose and starch can be utilized by microorganisms for a long time, and durability of the carbon source is guaranteed. The invention also provides a sewage treatment method using the composite carbon source, and the method comprises the following steps: adding the composite carbon source into sewage, and carrying out denitrification treatment. The addition amount of the composite carbon source is determined based on the C / N ratio in the sewage. By adding the composite carbon source, the content of nitrate nitrogen in sewage can be effectively reduced, so that the sewage treatment efficiency is improved. The composite carbon source exists in a solid form, is convenient to store and transport, and reduces the influence on the environment. The composite carbon source not only can obviously improve the sewage treatment effect and improve the effluent quality, but also can reduce the operation cost and additional cost, and has important significance for improving the environment.

Description

Technical Field

[0001] The invention relates to the technical field of sewage treatment, in particular to a method for preparing a solid composite carbon source and a method for sewage treatment using the composite carbon source. Background Art

[0002] Under the modern environmental protection system, the water treatment industry faces higher environmental protection requirements, especially the microbial denitrification and phosphorus removal in municipal sewage treatment. However, the organic matter in municipal sewage is consumed in large quantities in the primary and secondary biological treatment, resulting in insufficient biologically available organic carbon sources in the sewage reaching the deep treatment stage, thereby limiting the activity of microorganisms and the efficiency of biological denitrification. Specifically, the types and concentrations of organic matter in municipal sewage are affected by daily life and industrial emissions, which are somewhat unstable, making sewage treatment face greater challenges. In addition, the operating costs of municipal sewage treatment plants, including energy consumption, drug consumption, and sludge treatment costs, are also important factors limiting the widespread application of deep treatment technology. In response to these problems, the research and application of composite carbon sources have begun to receive attention. Composite carbon sources can provide more stable and diverse nutrients, which helps to improve the efficiency of microbial denitrification and phosphorus removal. However, most of the existing composite carbon sources do not consider the physical form and solubility of carbon sources in sewage treatment, and often contain high concentrations of organic matter. Although they can provide sufficient carbon sources, they may cause problems such as increased sludge production, increased treatment costs, and increased effluent COD.

[0003] In the field of environmental engineering, microbial denitrification and phosphorus removal technology is a key part of sewage treatment, which mainly relies on microorganisms in activated sludge to remove nitrogen and phosphorus using biochemical oxygen demand (BOD5) in sewage. However, since BOD5 in municipal sewage cannot meet the comprehensive nutritional needs of microorganisms, exogenous carbon sources need to be added during the biological treatment process. The carbon sources on the current market are mainly single substances, such as sugars, methanol, acetic acid and sodium acetate, but these carbon sources all have certain problems. For example, when methanol is used as a carbon source, its cost is relatively high and it has certain toxic effects on the human body. In addition, the response time of methanol is relatively slow. If emergency treatment is required in the sewage treatment plant, methanol may not be able to provide enough carbon source in time. As carbon sources, acetic acid and sodium acetate have better denitrification effects and can respond to the denitrification process immediately. Denitrifying bacteria are still active at low temperatures and can be used for emergency treatment during water plant operation. However, their prices are relatively high and the amount of sludge produced is also large, which brings greater operating pressure to sewage treatment plants. Glucose has a good effect when used as a carbon source, but it is easy to cause a large number of microorganisms to multiply, resulting in sludge swelling, increasing the chemical oxygen demand (COD) of the effluent, and thus affecting the effluent quality. At the same time, glucose is more likely to produce the phenomenon of nitrite nitrogen accumulation. The use of these single carbon sources often requires an adaptation and domestication process, and it is difficult to meet the needs of various microorganisms, so the effect of sewage treatment cannot be fully exerted. At the same time, a single carbon source cannot adapt to various working conditions in sewage treatment and has poor flexibility.

[0004] In response to these problems, we invented a new composite carbon source, which not only contains a variety of nutrients and meets the needs of a variety of microorganisms, but is also in solid form, which is more convenient to store and transport than conventional liquid carbon sources. Starch and cellulose are widely present in the environment and are easy to obtain, so the cost of carbon sources can be greatly reduced. Yeast powder can increase the activity of microorganisms and further improve the sewage treatment effect. In addition, compared with alcohol carbon sources that require a longer adaptation and domestication time, this composite carbon source has stronger adaptability and almost no domestication time. Another advantage of solid composite carbon sources is that they have a long shelf life, can be stored for a long time, are not easy to produce odor, and will not reduce the denitrification effect due to long-term storage. The application of this new composite carbon source can effectively improve the operating status of sewage treatment plants, improve effluent quality, reduce sludge generation, and reduce operating costs. This composite carbon source has important application value in the current environmental protection issues due to its advantages in treatment effect, cost and environmental friendliness. This composite carbon source can provide a continuous and stable supply of carbon sources, can adapt to various working conditions, and can effectively reduce the amount of sludge generated, reduce operating costs, and protect the environment. At the same time, the use of the composite carbon source will not cause drastic changes in the microbial community in the sewage, and will not destroy the stability of the sewage treatment system. This is of great significance for ensuring the normal operation of the sewage treatment plant and improving the effluent quality. Summary of the invention

[0005] One object of the present invention is to provide a composite carbon source for wastewater denitrification and a preparation method thereof, which optimizes the stability and diversity of the carbon source, meets the needs of microbial denitrification, and makes wastewater treatment more effective.

[0006] The composite carbon source provided by the invention is composed of sodium acetate, glucose, starch, yeast powder, cellulose and glycosyl hydrolase, and comprises the following components in parts by weight: 10-60 parts of sodium acetate, 10-30 parts of glucose, 10-30 parts of starch, 0.1-2 parts of yeast powder, 1-5 parts of cellulose and 0.1-0.3 parts of glycosyl hydrolase.

[0007] The sodium acetate in the composite carbon source can react quickly to provide an instantaneous carbon source, while glucose and starch can be utilized by microorganisms for a relatively long time, thus ensuring the persistence of the carbon source.

[0008] The cellulose and yeast powder in the composite carbon source can improve the activity and biodiversity of microorganisms, more fully utilize organic matter in sewage, and improve denitrification efficiency.

[0009] The composite carbon source exists in a solid form, which is convenient for storage and transportation and reduces the impact on the environment.

[0010] The glycosyl hydrolase in the composite carbon source can accelerate the hydrolysis process of starch and cellulose, and further improve the efficiency of converting COD into BOD5.

[0011] The efficiency of converting COD into BOD5 of the composite carbon source is as high as over 80%, which is significantly better than that of a conventional single carbon source.

[0012] The composite carbon source can significantly improve the sewage treatment effect, not only improve the effluent quality, but also reduce the operating cost and additional cost. By optimizing the carbon source supply of microbial denitrification, the denitrification effect is improved, which is of great significance to improving the environment.

[0013] The present invention will be further described below in conjunction with specific embodiments.

[0014] During the implementation process, the selection of raw materials for composite carbon sources should take into account the durability, cost-effectiveness and environmental friendliness of their carbon source supply. The selection of sodium acetate, glucose, starch, yeast powder, cellulose and glycosyl hydrolase is mainly based on their respective characteristics and their role in the denitrification process. Specifically, sodium acetate is the preferred fast carbon source because it can quickly provide an available carbon source; glucose and starch are the main slow carbon sources because they can provide a long-lasting carbon source supply; yeast powder and cellulose can improve the activity of microorganisms and are important biological activity enhancers; glycosyl hydrolases can promote the hydrolysis of starch and cellulose and improve the efficiency of COD conversion to BOD5.

[0015] The specific implementation process is as follows:

[0016] Step 1: Raw material selection: According to the COD and BOD5 values ​​of each raw material, sodium acetate, glucose and starch are selected as the main raw materials of the composite carbon source.

[0017] Step 2: Sample analysis: Analyze the actual COD and BOD5 test values ​​of each raw material. Select 1 gram of each raw material and dissolve it in 1 liter of distilled water. The COD test method adopts HJ 828-2017 "Determination of Chemical Oxygen Demand of Water Quality - Potassium Dichromate Method"; the BOD5 test method adopts HJ 505-2009 "Determination of Five-Day Biochemical Oxygen Demand (BOD5) of Water Quality - Dilution and Inoculation Method". The actual COD and BOD5 test values ​​of each component are shown in Table 1.

[0018] Table 1: COD and BOD5 measured values ​​of sodium acetate, glucose and starch

[0019] Serial number name COD value (mg / l) BOD5 value (mg / l) Remark 1 Sodium acetate 465 380 60% content 2 glucose 1050 930 99% content 3 starch 1110 890

[0020] Step 3: Prepare multiple embodiments of solid composite carbon sources (see Table 2: the content of each component in each embodiment), and change the COD and BOD5 test results of different embodiments (see Table 3: analysis of the test results of each embodiment).

[0021] Table 2: Content of each component in the embodiment (parts by weight)

[0022] name Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Sodium acetate 30 30 Not added 30 30 40 50 60 glucose 30 Not added 30 30 30 20 15 15 starch Not added 30 30 30 30 20 15 15 Yeast powder Not added Not added Not added Not added 2 2 2 2 Cellulose Not added Not added Not added Not added 2 2 2 2 Hydrolases Not added Not added Not added Not added 0.1 0.1 0.1 0.1

[0023] Table 3: Test results of the embodiment

[0024] name Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 COD(mg / l) 751 785 1075 868 849 806 755 707 BOD5 (mg / l) 632 630 898 723 723 682 629 596 BOF5 conversion rate (%) 84.15 80.25 83.53 83.29 85.16 84.61 83.31 84.3

[0025] Step 4: Take the water from the front section of the anaerobic denitrification tank of the sewage treatment plant, add the composite carbon source of Example 5 thereto, add the required composite carbon source according to the C\N ratio to denitrify the sewage, and detect the nitrate-nitrogen content of the sewage before denitrification and after 30 minutes, 60 minutes, and 180 minutes of treatment to verify the treatment effect. The nitrate-nitrogen treatment effects at each stage are shown in Table 4.

[0026] Table 4: Nitrate-nitrogen treatment effects of selected examples

[0027] Select the name of the implementation example C\N ratio Nitrate nitrogen content before treatment Nitrate nitrogen content at 30 minutes Nitrate nitrogen content at 60 minutes Nitrate nitrogen content at 180min Example 5 5 26.7mg / l 10.4mg / l 3.7mg / l 1.1mg / l

[0028] The above implementation verification results have verified that this composite carbon source has a high effect in actual sewage treatment. We can confirm that this composite carbon source plays a positive role in improving sewage treatment efficiency, especially in the denitrification process.

[0029] In general, this example demonstrates the practical application effect of our composite carbon source in treating wastewater containing nitrate nitrogen, and shows its ability to effectively reduce the nitrate nitrogen content in wastewater in a short period of time, which is very important for the actual wastewater treatment process.

[0030] Furthermore, we tested the stability of the composite carbon source over a long period of time. The results showed that even after long-term storage, this composite carbon source still maintained its efficient nitrate removal ability, which verified its excellent stability characteristics. Moreover, since it is a solid carbon source, its loss during storage and transportation is extremely small, which greatly increases the convenience of its application.

[0031] Furthermore, we conducted an economic analysis of the composite carbon source. Since the components of the carbon source of the present invention include sodium acetate, glucose, starch and yeast powder, etc., these raw materials are available in large quantities on the market and are relatively low in price, making this composite carbon source have a significant cost advantage. At the same time, due to the high efficiency of this composite carbon source, its cost per unit volume of sewage treatment is better than many traditional carbon sources.

[0032] The above embodiments and contents are only for better illustrating the present invention and are not intended to limit the protection scope of the present invention. All modifications, equivalent substitutions and improvements within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A solid composite carbon source for sewage treatment, characterized in that: The composite carbon source consists of sodium acetate, glucose and starch, and the composite carbon source selects raw materials by selecting COD and BOD5 values ​​of each raw material.

2. The composite carbon source according to claim 1, characterized in that The composite carbon source may also include yeast powder, cellulose and hydrolytic enzymes.

3. The composite carbon source according to claim 1 or 2, characterized in that The composite carbon source is formed into multiple embodiments by mixing different raw material contents to obtain a composite carbon source with different COD and BOD5 values.

4. The composite carbon source according to claim 1, 2 or 3, characterized in that The composite carbon source can be added according to the C / N ratio when treating sewage to carry out sewage denitrification, thereby effectively reducing the nitrate nitrogen content.

5. The composite carbon source according to claim 1, 2, 3 or 4, characterized in that: The composite carbon source has good storage stability and maintains its efficient nitric acid and nitrogen removal ability even after long-term storage.

6. The composite carbon source according to claim 1, 2, 3, 4 or 5, characterized in that: Since its main raw materials are in large supply and relatively low in price on the market, the composite carbon source has a significant cost advantage.

7. A method for treating sewage using the composite carbon source as claimed in claim 1, 2, 3, 4, 5 or 6, the method comprising the steps of: adding the composite carbon source to the sewage to perform denitrification treatment on the sewage.