Efficient composite carbon source, preparation method thereof and application of efficient composite carbon source in sewage deep denitrification method

Abstract

The invention relates to the technical field of sewage treatment, and particularly discloses an efficient composite carbon source, a preparation method thereof and application of the efficient composite carbon source in a sewage deep denitrification method. The efficient composite carbon source disclosed by the invention is prepared from the following components: sodium acetate, ethanol, glucose, trace elements, a functional additive and water, a preparation method of the functional additive comprises the following steps: placing starch in an aqueous solution of catechol and diethylenetriamine to obtain modified starch; and then mixing the modified starch with butylated hydroxytoluene and glyceryl distearate to obtain the modified starch. The AAOAO technology is adopted, the carbon source coupling local complete mixing type plug flow aerobic bioreactor is used in a sewage deep nitrogen removal method, and the nitrogen removal efficiency of sewage can be effectively improved.

Description

Technical Field

[0001] The present application relates to the technical field of sewage treatment, and in particular to a high-efficiency composite carbon source and a preparation method thereof and an application thereof in a sewage deep denitrification method. Background Art

[0002] At present, the AAO process is the mainstream process in domestic urban sewage treatment plants, accounting for more than 90% of the total number, and the effluent quality can meet the limit requirements of various indicators in the "Pollutant Discharge Standard for Urban Sewage Treatment Plants" (GB 18918-2002). However, when the effluent quality needs to be further improved, the AAO process cannot meet the requirements. When the internal reflow ratio is increased to 300%, the TN removal rate of the system drops significantly due to the impact of the oxygen-rich reflux liquid on the anoxic section. At this time, the theoretical TN removal rate cannot exceed 75%. In order to meet the requirements of quality improvement and transformation in many regions, the TN removal rate must reach 80% or even more than 90%. Therefore, deep denitrification is the focus and difficulty in the quality improvement and transformation of AAO treatment facilities.

[0003] At present, the main processes of AAO in denitrification and quality improvement are Bardenpho, AOA, multi-stage AO, denitrifying biofilter, etc. 1) The Bardenpho process is to add a second stage AO based on the addition of carbon source on the basis of the AAO process, but because the original AAO has not been changed, the total residence time is prolonged after the addition of AO, and additional construction land is required to place the newly added AO stage. For most of the renovation facilities, the land requirements cannot be met. At the same time, the efficiency of the single carbon source added is low, resulting in increased operating costs; 2) AOA does not need to expand the volume of the biochemical reaction tank during the renovation, but due to the increase in the solid load of the secondary sedimentation tank, the secondary sedimentation tank needs to be expanded, and the feasibility is greatly reduced. In addition, the deep denitrification effect of AOA is highly dependent on the actual The influence of dissolved oxygen in the aerobic tank on the second-stage anoxic tank during actual operation places extremely high demands on operation control, resulting in reduced applicability; 3) Multi-stage AO uses multi-stage water inlet to achieve high utilization of the original carbon source of sewage. Under the condition of low internal recirculation ratio, the more stages there are, the higher the denitrification rate. However, in order to ensure that each stage A meets the anoxic condition, an oxygen elimination stage needs to be set up in the O stage to increase the tank capacity. In addition, the operation of segmented water inlet is complicated under actual working conditions and is not suitable for the transformation of existing treatment facilities; 4) When using the denitrifying biological filter, it needs to be used in conjunction with the nitrification filter. At the same time, the filter has a high risk of compaction, and there is no advantage in terms of land occupation and operation.

[0004] In addition, in terms of carbon source addition, traditional carbon source addition has some shortcomings. For example, using sodium acetate as the carbon source has the fastest denitrification rate and short response time, but the operating cost is high, the sludge yield is high, and the denitrification efficiency is insufficient. Due to the limitation of carbon source utilization efficiency, the carbon source is difficult to be completely consumed in the anoxic tank. In order to avoid excessive COD in the effluent, the dissolved oxygen in the aerobic tank is usually maintained at a high level to consume excess carbon source.

[0005] Therefore, there is an urgent need to develop a method for upgrading denitrification standards that can achieve the goals of saving land, improving denitrification efficiency, and reducing energy and material consumption. Summary of the invention

[0006] In order to solve the above technical problems, the present application provides a high-efficiency composite carbon source and a preparation method thereof and an application thereof in a method for deep denitrification of wastewater.

[0007] In the first aspect, the present application provides a high-efficiency composite carbon source for deep denitrification of sewage. The high-efficiency composite carbon source is made of the following components in parts by weight: 10 to 16 parts of sodium acetate, 10 to 16 parts of ethanol, 2 to 4 parts of glucose, 0.005 to 0.015 parts of trace elements, 0.4 to 1.2 parts of functional additives, and 100 to 140 parts of water; The preparation method of the functional additive is as follows: placing starch in an aqueous solution of 25-35 mmol / L catechol and 1-4 mmol / L diethylenetriamine, soaking at 50-70°C for 10-18 hours, taking out, drying, and grinding to obtain modified starch; and then mixing the modified starch with butylated hydroxytoluene and distearic acid glycerol in a weight ratio of 100:6-12:1-3 to obtain the functional additive.

[0008] The present application provides a high-efficiency composite carbon source for deep denitrification of sewage. Sodium acetate, as a short-chain organic acid salt, is easily utilized by microorganisms and can quickly provide a carbon source to support the denitrification process, thereby accelerating the removal of nitrogen; ethanol can provide a stable carbon source, and its good water solubility helps to be evenly distributed in sewage, thereby improving the utilization efficiency of the carbon source; glucose, as a monosaccharide, is an energy source that is easily utilized by microorganisms. In the process of deep denitrification of sewage, glucose can continuously provide a carbon source for denitrifying bacteria to support their growth and activity; trace elements can improve the metabolic activity and denitrification efficiency of microorganisms. Among the functional additives, the introduction of catechol and diethylenetriamine compounds to modify or react starch can effectively improve the compatibility of starch with other raw materials; the combination of modified starch with butylated hydroxytoluene and distearic acid glycerol can significantly improve the stability of the carbon source, prevent decomposition and deterioration during storage and use, and ensure long-term effectiveness.

[0009] The present application uses sodium acetate, ethanol, glucose, functional additives and trace elements in combination in specific amounts, which can optimize the carbon-nitrogen ratio in sewage, form a slow-release carbon source, meet the long-term denitrification needs of bacteria, and make it more suitable for the growth and activity of denitrifying bacteria; it can also improve the dispersion of the carbon source in water, making it easier to mix with other components in sewage, thereby increasing the nitrogen removal rate; at the same time, it prevents the carbon source from decomposing or deteriorating during storage, further improving the efficient utilization of the carbon source in sewage treatment.

[0010] Compared with traditional carbon sources, the high-efficiency composite carbon source provided in the present application can increase the denitrification rate: the composite carbon source can fully utilize the existing carbon source in the sewage while synergistically and efficiently providing electron donors, greatly improving the electron transfer rate to meet the rapid metabolic needs of microorganisms, thereby increasing the denitrification rate; reducing sludge yield: a single carbon source may have a high sludge yield during use, while the composite carbon source can effectively reduce the sludge yield; improving the stability of the biological system: by adopting a composite carbon source, the diversity and abundance of the denitrifying bacteria in the system are effectively improved, thereby improving the ability to resist load and environmental shocks and improving treatment stability.

[0011] Preferably, the high-efficiency composite carbon source is made of the following components in parts by weight: 12 to 14 parts of sodium acetate, 12 to 14 parts of ethanol, 2.5 to 3.5 parts of glucose, 0.008 to 0.012 parts of trace elements, 0.6 to 1.0 parts of functional additives, and 110 to 130 parts of water.

[0012] Preferably, in the high-efficiency composite carbon source, the preparation method of the functional additive is: placing starch in an aqueous solution of 28-32 mmol / L catechol and 2-3 mmol / L diethylenetriamine, soaking it at 55-65°C for 12-16 hours, taking it out, drying it, and grinding it to obtain modified starch; then mixing the modified starch with butylated hydroxytoluene and distearic acid glycerol in a weight ratio of 100:8-10:1.5-2.5 to obtain the obtained starch.

[0013] Preferably, the trace elements are composed of a mixture of ferrous sulfate, copper sulfate and zinc sulfate in a weight ratio of 1-5:1-5:0.2-0.9.

[0014] In the second aspect, the present application provides a method for preparing the above-mentioned high-efficiency composite carbon source for deep denitrification of wastewater, which specifically includes the following steps in sequence: adding sodium acetate, ethanol, glucose, and trace elements to water and stirring evenly; adjusting the pH to 6.5-8.0, and then adding functional additives, and continuing to stir until completely mixed; that is, the product.

[0015] In a third aspect, the present application provides the application of the above-mentioned high-efficiency composite carbon source in a method for deep denitrification of wastewater.

[0016] In a fourth aspect, the present application provides a method for deep denitrification of sewage based on a locally fully mixed plug flow aerobic bioreactor coupled with a composite carbon source, which utilizes the above-mentioned high-efficiency composite carbon source for deep denitrification of sewage; specifically, the following steps are included: AAOAO process is used, and the first aerobic pool O 1 It was transformed into a partially fully mixed plug flow aerobic bioreactor SCMAB; Sewage from anaerobic tank A P Enter, converting organic nitrogen in the raw sewage into ammonia nitrogen; then enter the anoxic tank AN1 , mixed with the reflux at the end of SCMAB, and denitrification was carried out using the original carbon source of the sewage; then it entered the aerobic tank O 1 In the reactor SCMAB, ammonia nitrogen is converted into nitrate nitrogen through aerobic nitrification, and part of the mixed liquid is returned to the anoxic tank A. N1 The front part enters the second stage anoxic pool A N2 ; Second stage anoxic pool A N2 The high-efficiency composite carbon source is added into the tank for denitrification and denitrification; then the tank enters the second-stage aerobic pool. 2 , consume the surplus carbon source to ensure that the effluent COD meets the standard.

[0017] In order to solve the problem of denitrification and improvement in the existing process, the present invention splits the existing AAO into five-stage AAOAO without expansion, transforms the first aerobic stage into a locally fully mixed plug flow aerobic bioreactor SCMAB (Segmentally Completely Mixed Aerobic Bioreactor), and adds a high-efficiency composite carbon source to the second stage AO to achieve deep denitrification of sewage, greatly improving the denitrification rate. The method provided in this application only transforms the existing pool body, without the need to requisition additional construction land, saves electricity and drug consumption while ensuring a high denitrification rate, and operates stably and reliably.

[0018] Preferably, the local fully mixed plug flow aerobic bioreactor SCMAB is equipped with a hyperbolic stirrer, which is arranged alternately with the aeration module, and the stirrer is set at an interval of 9 to 12 m; the end of the SCMAB is refluxed to a section of anoxic tank A N1 The front end has a reflux ratio of 300%; the diameter of the hyperbolic stirrer is 1.5 to 3 m, and the stirring intensity is 5 to 6 W / m 3 The blade shape and angle design meet the requirements of fluid mechanics, so that the mixed liquid forms a circulating water flow from top to bottom; the terminal DO of SCMAB is controlled at 0.5-0.8 mg / L.

[0019] In the technical solution provided in the present application, the locally fully mixed plug flow aerobic bioreactor SCMAB eliminates the original aeration device of the aerobic tank; adding a hyperbolic agitator can effectively eliminate the stirring dead corners, prevent local sludge sedimentation, form a local fully mixed effect, and improve the efficiency of the biochemical reaction.

[0020] In the technical solution of this application, after the aerobic tank O1 is transformed into SCMAB, the overall energy consumption per ton of water for aeration and stirring is reduced by 0.03-0.05 kwh / m 3 .

[0021] Preferably, the SCMAB residence time is controlled to be 5.6 to 7.5 hours, and the second stage anoxic tank A N2The residence time is controlled to be 1.2-1.5h, and the second-stage aerobic pool O 2 The residence time is controlled at 0.4-0.6h; the sludge concentration is controlled at 3000-4000.

[0022] Preferably, the anaerobic tank A P The DO of the anoxic tank A is controlled to be below 0.2 mg / L; N1 The DO of the aerobic pool is controlled at 0.4-0.6 mg / L; 1 The DO at the end of the SCMAB reactor is controlled to be 0.5-0.8 mg / L; the post-anoxic zone A N2 The DO of the second-stage aerobic pool is controlled to be below 0.5 mg / L. 2 The terminal DO is controlled at 0.4-0.6 mg / L.

[0023] In summary, the technical solution of this application has the following effects: The method provided in the present application adopts a high-efficiency composite carbon source, and sodium acetate, ethanol, glucose, functional additives and trace elements are added in different proportions. The denitrification rate can reach more than 93%, thereby improving the denitrification rate; avoiding the waste of excessive addition of ordinary carbon sources due to long reaction time, and saving 10-20% of the carbon source addition amount.

[0024] Currently, the existing AAO process treatment facilities need to be upgraded and renovated, and there is no extra land available for construction. The technical solution provided in this application can be used to renovate the existing facilities without additional land acquisition, thus saving land.

[0025] The method provided in the present application transforms an aerobic section into a partially fully mixed plug flow aerobic bioreactor SCMAB, which strengthens the stirring and mixing effect in the plug flow form, improves the biochemical reaction efficiency, and reduces the aeration energy consumption. The comprehensive power consumption can be reduced by 0.03-0.05 kwh / m 3 And create better conditions for the later stage denitrification. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic diagram of the process for transforming AAO into AAOAO process for deep denitrification of wastewater for this application.

[0027] Figure 2 This is a schematic diagram of the transformation of a section of an aerobic tank into a partially fully mixed plug flow aerobic bioreactor in this application. DETAILED DESCRIPTION

[0028] The present application is further described in detail below in conjunction with examples, comparative examples and performance testing experiments. These examples should not be construed as limiting the scope of protection claimed in the present application. Example

[0029] Example 1 Example 1 provides a method for deep denitrification of wastewater based on a locally fully mixed plug flow aerobic bioreactor coupled with a composite carbon source.

[0030] The method for deep denitrification of sewage in this embodiment is specifically described as follows.

[0031] First, press Figure 1 The process is modified in this way, a part of the tank capacity of the O section in the original AAO is split out as the second section AO, forming an AAOAO two-stage series process, and the first section O is transformed into a local fully mixed plug flow aerobic bioreactor SCMAB. In fact, the process / method can be suitable for the modification method including the basic treatment process based on AAO and its improved process. All the process flow settings that transform the original process into an AAOAO two-stage process flow, and the first aerobic section O is stirred and coupled with aeration, and the second section is enhanced by adding drugs for denitrification, all belong to the protection scope of the present invention. The modified process flow is: (1) Anaerobic tank A: sewage (water quality of inlet water: COD = 138.67 mg / L, ammonia nitrogen (NH 3 -N)=37.94mg / L, nitrate nitrogen (NO 3 - -N)=0、total phosphorus=4.85mg / L) from anaerobic tank A P Entering, the organic nitrogen in the raw sewage is converted into ammonia nitrogen, and the DO of the anaerobic tank is controlled below 0.2mg / L. P The water quality after treatment is: COD = 117.73 mg / L, total nitrogen = 45.25 mg / L, ammonia nitrogen (NH 3 -N)=35.17mg / L, nitrate nitrogen (NO 3 - -N)=0, total phosphorus=10.42mg / L.

[0032] Anoxic pool A: The mixed liquid then enters anoxic pool A N1 The denitrifying bacteria in the activated sludge use the easily degradable organic matter in the sewage and the supplementary external carbon source to carry out denitrification reaction to convert NO in the internal reflux mixed liquor. 3 - -N is converted into nitrogen gas to remove nitrogen from sewage. Anoxic environment is crucial to the efficiency of denitrification. N1 The DO is controlled at 0.5mg / L. N1 The water quality after treatment is: COD = 45.83 mg / L, ammonia nitrogen (NH 3 -N)=11.37mg / L, nitrate nitrogen (NO 3 - -N)=15.79mg / L, total phosphorus=9.35mg / L.

[0033] Aerobic pool O: The mixed liquid then enters aerobic pool O 1 The main function of the activated sludge in the reactor SCMAB (formerly the first aerobic tank O1) is to degrade the anoxic tank A N1 The remaining organic matter in the effluent mixture is converted into NH 3 - -N is converted to NO 3 - -N completes the nitrification reaction, and the polyphosphate bacteria absorb excessive phosphorus in the mixed liquid for biological phosphorus removal. The mixed liquid is returned to the anoxic tank A N1 Denitrification is performed. In order to maintain the anoxic environment of the front anoxic tank and the rear anoxic tank and reduce energy consumption, the SCMAB retention time is controlled at 5.6-7.5h; the DO at the end of the SCMAB is controlled at 0.5-0.8mg / L. The water quality after SCMAB treatment is: COD = 21.37mg / L, ammonia nitrogen (NH 3 -N)=4.96mg / L, nitrate nitrogen (NO 3 - -N)=29.78mg / L, total phosphorus=1.54mg / L.

[0034] Among them, for one section of aerobic pool O 1 The O tank is transformed into a partially fully mixed plug flow aerobic bioreactor SCMAB. The main flow pattern of the entire reaction tank is plug flow, such as Figure 2 As shown in the figure, a hyperbolic stirrer is added at intervals of 9 to 12 m in the aerobic section. The stirring intensity of the hyperbolic stirrer is 5 to 6 W / m 3 The blade shape and angle design are more in line with the requirements of fluid mechanics, which can make the mixed liquid form a top-down circulating water flow, forming a local fully mixed flow state, effectively eliminating the stirring dead corner, preventing local sludge sedimentation, and improving the efficiency of biochemical reactions. The aeration area uses a high-efficiency ultra-microporous aerator with an oxygen utilization rate of more than 26%. Combined with the efficient stirring and mixing effect of the hyperbolic surface, it can ensure the effective degradation of oxygen-consuming pollutants and complete the nitrification process that is highly related to denitrification efficiency. At the same time, under the coupling effect of aeration and stirring, the dissolved oxygen concentration in the aerobic section can be flexibly controlled by adjusting the blower, and the comprehensive power consumption can be reduced by 0.03-0.05kwh / m 3 The DO at the end of SCMAB can be stably controlled at 0.5-0.8 mg / L, which avoids the return of too much dissolved oxygen in the first stage and causes the denitrification effect of the first anoxic stage to deteriorate. At the same time, it also creates better anoxic conditions for the second anoxic tank and improves the denitrification efficiency.

[0035] (2) Split the end of the first aerobic tank into a tank with a capacity of 1.6 to 2.1 hours, which is set as the second AO denitrification unit. N2The residence time is controlled at 1.3h, and the second stage aerobic pool O 2 The residence time is controlled to be 0.5h. The specific process is as follows.

[0036] Anoxic tank A: A portion of the mixed liquid flows back to anoxic tank A. N1 The front part enters the second stage anoxic pool A N2 The activated sludge uses the efficient composite carbon source to further denitrify the untreated NO 3 - -N is completely removed. The post-anoxic tank design theoretically solves the bottleneck of the total denitrification efficiency of the traditional AAO process being limited by the internal recirculation ratio. The post-anoxic tank can further remove TN by denitrification. The anoxic environment is crucial to the efficiency of denitrification. The DO in the post-anoxic zone is controlled below 0.5 mg / L. Second stage anoxic tank A N2 The water quality after treatment is: COD = 52.3 mg / L, ammonia nitrogen (NH 3 -N)=2.01mg / L, nitrate nitrogen (NO 3 - -N)=0.05mg / L, total phosphorus=1.26mg / L.

[0037] The preparation method of the high-efficiency composite carbon source is as follows: 13g sodium acetate, 13g ethanol, 3g glucose, 0.01g trace elements (the trace elements are composed of ferrous sulfate, copper sulfate, and zinc sulfate mixed in a weight ratio of 3:3:0.5) are added to 120g water and stirred evenly; the pH is adjusted to 7.2, and then 0.9g functional additive is added, and stirring is continued until completely mixed; the functional additive is obtained. The preparation method of the functional additive is as follows: 500g starch is placed in an aqueous solution of 30mmol / L catechol and 2.5mmol / L diethylenetriamine at 60℃ and soaked for 14h, taken out and dried, and ground to a particle size of ≤300 mesh to obtain modified starch; then the modified starch is mixed with butylated hydroxytoluene and distearic acid glycerol in a weight ratio of 100:9:2 to obtain the obtained product.

[0038] Aerobic pool O: Finally enter the second stage aerobic pool O 2 Activated sludge continues to remove organic matter and blow off N in the mixed liquor. 2 , improve DO to prevent the secondary sedimentation tank from anaerobic state, improve sludge settling effect, thereby ensuring the DO environment of the secondary sedimentation tank. In order to reduce energy consumption, the DO at the end of the second stage aerobic tank is controlled at about 0.5mg / L. The water quality after O treatment in the second stage aerobic tank is: COD = 21.6mg / L, total nitrogen = 2.19mg / L, ammonia nitrogen (NH 3 -N)=1.05mg / L, nitrate nitrogen (NO 3 - -N)=1.17mg / L, total phosphorus=0.57mg / L.

[0039] Embodiment 2-5 Examples 2-5 respectively provide a method for deep denitrification of wastewater based on a locally fully mixed plug flow aerobic bioreactor coupled with a composite carbon source.

[0040] The difference between the above embodiment and embodiment 1 is that the dosage of each component in the high-efficiency composite carbon source is different, as shown below.

[0041] In Example 2, the dosage of each component in the high-efficiency composite carbon source is: 10g sodium acetate, 16g ethanol, 2g glucose, 0.015g trace elements, 0.4g functional additives, and 120g water.

[0042] In Example 3, the dosage of each component in the high-efficiency composite carbon source is: 16g sodium acetate, 10g ethanol, 4g glucose, 0.005g trace elements, 1.2g functional additives, and 120g water.

[0043] In Example 4, the dosage of each component in the high-efficiency composite carbon source is: 12g sodium acetate, 14g ethanol, 2.5g glucose, 0.012g trace elements, 0.8g functional additives, and 120g water.

[0044] In Example 5, the dosage of each component in the high-efficiency composite carbon source is: 14g sodium acetate, 12g ethanol, 3.5g glucose, 0.008g trace elements, 1.0g functional additives, and 120g water.

[0045] The other process parameters in the above embodiment are the same as those in embodiment 1.

[0046] Embodiment 6-11 Examples 6-11 respectively provide a method for deep denitrification of wastewater based on a locally fully mixed plug flow aerobic bioreactor coupled with a composite carbon source.

[0047] The difference between the above embodiment and embodiment 1 is that the preparation method of the functional additive is different, as shown below.

[0048] In Example 6: The preparation method of the functional additive is as follows: 500g of starch is placed in an aqueous solution of 25mmol / L catechol and 4mmol / L diethylenetriamine at 60°C and soaked for 14h, taken out, dried, and ground to a particle size of ≤300 mesh to obtain modified starch; then the modified starch is mixed with butylated hydroxytoluene and distearic acid glycerol in a weight ratio of 100:9:2 to obtain the modified starch.

[0049] In Example 7: The preparation method of the functional additive is as follows: 500g of starch is placed in an aqueous solution of 35mmol / L catechol and 1mmol / L diethylenetriamine at 60°C and soaked for 14h, taken out, dried, and ground to a particle size of ≤300 mesh to obtain modified starch; then the modified starch is mixed with butylated hydroxytoluene and distearic acid glycerol in a weight ratio of 100:9:2.

[0050] In Example 8: The preparation method of the functional additive is as follows: 500g of starch is placed in an aqueous solution of 30mmol / L catechol and 2.5mmol / L diethylenetriamine at 60°C and soaked for 14h, taken out, dried, and ground to a particle size of ≤300 mesh to obtain modified starch; then the modified starch is mixed with butylated hydroxytoluene and distearic acid glycerol in a weight ratio of 100:6:3 to obtain the modified starch.

[0051] In Example 9: The preparation method of the functional additive is as follows: 500g of starch is placed in an aqueous solution of 30mmol / L catechol and 2.5mmol / L diethylenetriamine at 60°C and soaked for 14h, taken out, dried, and ground to a particle size of ≤300 mesh to obtain modified starch; then the modified starch is mixed with butylated hydroxytoluene and distearic acid glycerol in a weight ratio of 100:12:1 to obtain the modified starch.

[0052] In Example 10: The preparation method of the functional additive is as follows: 500g of starch is placed in an aqueous solution of 30mmol / L catechol and 2.5mmol / L diethylenetriamine at 60°C and soaked for 14h, taken out, dried, and ground to a particle size of ≤300 mesh to obtain modified starch; then the modified starch is mixed with butylated hydroxytoluene and distearic acid glycerol in a weight ratio of 100:8:2.5.

[0053] In Example 11: The preparation method of the functional additive is as follows: 500g of starch is placed in an aqueous solution of 30mmol / L catechol and 2.5mmol / L diethylenetriamine at 60°C and soaked for 14h, taken out, dried, and ground to a particle size of ≤300 mesh to obtain modified starch; then the modified starch is mixed with butylated hydroxytoluene and distearic acid glycerol in a weight ratio of 100:12:1.5.

[0054] The other process parameters in the above embodiment are the same as those in embodiment 1.

[0055] Comparative Example Comparative Examples 1-4 Comparative Examples 1-4 respectively provide a method for deep denitrification of sewage based on a locally fully mixed plug flow aerobic bioreactor coupled with a composite carbon source.

[0056] The differences between the above comparative example and Example 1 are specifically as follows.

[0057] In Comparative Example 1: the dosage of each component in the high-efficiency composite carbon source is: 10g sodium acetate, 16g ethanol, 2g glucose, 0.015g trace elements, 120g water (no functional additives are added).

[0058] In Comparative Example 2: In the high-efficiency composite carbon source, the preparation method of the functional additive is: starch, butylated hydroxytoluene and distearic acid glycerol are mixed in a weight ratio of 100:12:1.5.

[0059] In Comparative Example 3: In the high-efficiency composite carbon source, the preparation method of the functional additive is as follows: 500g of starch is placed in an aqueous solution of 15mmol / L catechol and 5mmol / L diethylenetriamine at 60°C and soaked for 14h, taken out, dried, and ground to a particle size of ≤300 mesh to obtain modified starch; then the modified starch is mixed with butylated hydroxytoluene and distearic acid glycerol in a weight ratio of 100:9:2.

[0060] In Comparative Example 4: The preparation method of the functional additive is as follows: 500g of starch is placed in an aqueous solution of 30mmol / L catechol and 2.5mmol / L diethylenetriamine at 60°C and soaked for 14h, taken out, dried, and ground to a particle size of ≤300 mesh to obtain modified starch; then the modified starch is mixed with butylated hydroxytoluene and distearic acid glycerol in a weight ratio of 100:2:9.

[0061] The other process parameters in the above comparative example are the same as those in Example 1.

[0062] Performance testing According to the water quality (total nitrogen, ammonia nitrogen (NH 3 -N), nitrate nitrogen (NO 3 - -N) content), total nitrogen and ammonia nitrogen (NH 3 -N), nitrate nitrogen (NO 3 - -N) content), calculate the corresponding removal rate of water pollutants.

[0063] Test results: as shown in Table 1.

[0064] Table 1 Two-stage anoxic pool A in the examples and comparative examples N2 Test results of pollutants in treated water Combined with the test results in Table 1, it can be seen that: no functional additives are added to the high-efficiency composite carbon source in Comparative Example 1; the preparation method of the functional additive in the high-efficiency composite carbon source in Comparative Example 2 is to mix unmodified starch with butylated hydroxytoluene and distearic acid glycerol in a weight ratio of 100:12:1.5. The preparation method of the functional additive in the high-efficiency composite carbon source in Comparative Example 3 is as follows: 500g of starch is placed in an aqueous solution of 15mmol / L catechol and 5mmol / L diethylenetriamine at 60°C and soaked for 14h, taken out, dried, and ground to a particle size of ≤300 mesh to obtain modified starch; then the modified starch is mixed with butylated hydroxytoluene and distearic acid glycerol in a weight ratio of 100:9:2; In Comparative Example 4: the preparation method of the functional additive is to mix the modified starch with butylated hydroxytoluene and distearic acid glycerol in a weight ratio of 100:2:9; the above high-efficiency composite carbon source does not meet the technical requirements of the present application, and is used in the deep denitrification method for sewage, and the nitrogen removal efficiency of the sewage is low.

[0065] In contrast, the present application adopts the method of placing starch in an aqueous solution of catechol-diethylenetriamine with a specific concentration to obtain modified starch; then the modified starch is mixed with dibutyl hydroxytoluene and distearic acid glycerol in a specific weight ratio to obtain a functional additive, and sodium acetate, ethanol, glucose, and trace elements are combined to prepare a high-efficiency composite carbon source; the high-efficiency composite carbon source obtained by this technical solution is coupled with a locally fully mixed plug flow aerobic bioreactor, which is used in a wastewater deep denitrification method, and can effectively improve the nitrogen removal efficiency of wastewater.

[0066] Although the present invention has been described in detail above with general descriptions and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements may be made thereto based on the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection claimed by the present invention.

Claims

1. A high-efficiency composite carbon source for deep denitrification of sewage, characterized in that: The high-efficiency composite carbon source is made of the following components in parts by weight: 10-16 parts of sodium acetate, 10-16 parts of ethanol, 2-4 parts of glucose, 0.005-0.015 parts of trace elements, 0.4-1.2 parts of functional additives, and 100-140 parts of water; The preparation method of the functional additive is as follows: placing starch in an aqueous solution of 25-35 mmol / L catechol and 1-4 mmol / L diethylenetriamine, soaking at 50-70°C for 10-18 hours, taking out, drying, and grinding to obtain modified starch; and then mixing the modified starch with butylated hydroxytoluene and distearic acid glycerol in a weight ratio of 100:6-12:1-3 to obtain the functional additive.

2. The high-efficiency composite carbon source for deep denitrification of sewage according to claim 1, characterized in that: The high-efficiency composite carbon source is prepared from the following components in parts by weight: 12 to 14 parts of sodium acetate, 12 to 14 parts of ethanol, 2.5 to 3.5 parts of glucose, 0.008 to 0.012 parts of trace elements, 0.6 to 1.0 parts of functional additives, and 110 to 130 parts of water.

3. The high-efficiency composite carbon source for deep denitrification of sewage according to claim 1, characterized in that: In the high-efficiency composite carbon source, the preparation method of the functional additive is: placing starch in an aqueous solution of 28-32 mmol / L catechol and 2-3 mmol / L diethylenetriamine, soaking it at 55-65°C for 12-16 hours, taking it out, drying it, and grinding it to obtain modified starch; then mixing the modified starch with butylated hydroxytoluene and distearic acid glycerol in a weight ratio of 100:8-10:1.5-2.5 to obtain the functional additive.

4. The high-efficiency composite carbon source for deep denitrification of sewage according to claim 1, characterized in that: The trace elements are composed of ferrous sulfate, copper sulfate and zinc sulfate in a weight ratio of 1-5:1-5:0.2-0.

9.

5. A method for preparing a high-efficiency composite carbon source for deep denitrification of sewage as claimed in any one of claims 1 to 4, characterized in that: Specifically, the method comprises the following steps in sequence: adding sodium acetate, ethanol, glucose and trace elements into water and stirring evenly; adjusting the pH value to 6.5-8.0, then adding functional additives and continuing stirring until completely mixed; and obtaining the product.

6. Use of the high-efficiency composite carbon source as described in any one of claims 1 to 4 in a method for deep denitrification of wastewater.

7. A method for deep denitrification of sewage based on a locally fully mixed plug flow aerobic bioreactor coupled with a composite carbon source, characterized in that: Using the high-efficiency composite carbon source described in any one of claims 1 to 4 to carry out deep denitrification of sewage; specifically comprising the following steps: The AAOAO process was adopted, and the aerobic tank O1 was transformed into a partially fully mixed plug flow aerobic bioreactor SCMAB; Sewage from anaerobic tank A P Enter, converting organic nitrogen in the raw sewage into ammonia nitrogen; then enter the anoxic tank A N1 , mixed with the reflux at the end of SCMAB, and denitrification is carried out using the original carbon source of the sewage; then it enters the reactor SCMAB of the aerobic tank O1, where ammonia nitrogen is converted into nitrate nitrogen through aerobic nitrification, and a part of the mixed liquid is returned to the anoxic tank A N1 The front part enters the second stage anoxic pool A N2 ; Second stage anoxic pool A N2 The high-efficiency composite carbon source is added internally for denitrification and denitrification; and then enters the second-stage aerobic pool O2 to consume the surplus carbon source to ensure that the effluent COD meets the standard.

8. The deep denitrification method according to claim 7, characterized in that: The local fully mixed plug flow aerobic bioreactor SCMAB is equipped with a hyperbolic stirrer, which is arranged alternately with the aeration module, and the stirrer is set at an interval of 9 to 12 meters; the end of the SCMAB is refluxed to a section of anoxic tank A N1 At the front end, the reflux ratio is 300%; The diameter of the hyperbolic stirrer is 1.5~3m, and the stirring intensity is 5~6W / m 3 The blade shape and angle design meet the requirements of fluid mechanics, so that the mixed liquid forms a circulating water flow from top to bottom; the terminal DO of SCMAB is controlled at 0.5~0.8mg / L.

9. The method for deep denitrification of sewage according to claim 7, characterized in that: The SCMAB residence time is controlled to be 5.6-7.5h, and the second stage anoxic tank A N2 The residence time is controlled at 1.2~1.5h, the O2 residence time in the second-stage aerobic tank is controlled at 0.4~0.6h; the sludge concentration is controlled at 3000~4000.

10. The method for deep denitrification of sewage according to claim 7, characterized in that: The anaerobic tank A P The DO of the anoxic tank A is controlled to be below 0.2 mg / L; N1 The DO of the reactor SCMAB in the aerobic tank O1 is controlled at 0.5~0.8mg / L; the DO of the anoxic zone A is controlled at 0.5~0.8mg / L. N2 The DO is controlled below 0.5mg / L, and the DO at the end of the second-stage aerobic pool O2 is controlled at around 0.5mg / L.

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