Method for switching addition of composite carbon source in sewage treatment plant

Abstract

The invention discloses a method for switching addition of a composite carbon source in a sewage treatment plant, and belongs to the field of sewage treatment. The method comprises the following steps: step 1, a step-by-step domestication stage: adding a currently used carbon source and a composite carbon source into a sewage treatment plant, maintaining for a preset duration each time, gradually reducing the adding proportion of the currently used carbon source and gradually increasing the adding proportion of the composite carbon source until the currently used carbon source is completely replaced by the composite carbon source, and completing step-by-step domestication; step 2, an optimization and adjustment stage: after gradual domestication is completed, optimizing and adjusting the addition amount of the composite carbon source according to an effluent TN index internal control value of the sewage treatment plant until the optimal addition amount of the composite carbon source which can meet the requirement that the effluent TN is stabilized at the effluent TN index internal control value is obtained; and step 3, a stable adding stage: stably adding the optimal composite carbon source in the step 2, and finely adjusting the adding amount of the composite carbon source according to the fluctuation of water quality and the internal control value of the effluent TN index of the sewage treatment plant during the adding period. According to the method, the composite carbon source can be switched under the condition that the effluent index is stable.

Description

Technical Field

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

[0002] At present, the actual C / N ratio of most urban sewage is low, and there is a lack of carbon source for denitrification, which limits the denitrification effect and requires external carbon source. The cost of adding carbon source accounts for a certain proportion of the operating cost of sewage treatment plants, especially for large sewage treatment plants with serious imbalance of carbon-nitrogen ratio. The annual cost of adding carbon source is a considerable amount. Therefore, choosing a carbon source with stable denitrification effect and low cost is a key way to reduce the cost of adding carbon source to sewage treatment plants.

[0003] Traditional carbon sources mainly include methanol, sodium acetate, glucose, etc. Methanol is rarely used now due to safety issues; although sodium acetate carbon source has good denitrification effect, the cost of addition is relatively high. Glucose carbon source has a long carbon chain, slow denitrification rate, and high cost. In order to reduce the cost of carbon source addition, a variety of composite carbon sources have appeared on the market. The components of different composite carbon sources vary greatly. Although the quality of composite carbon sources varies, there are also some high-quality composite carbon sources with good denitrification effect and low price, which are more cost-effective than traditional carbon sources. Therefore, more and more sewage treatment plants choose to add more cost-effective composite carbon sources to replace traditional carbon sources. However, there are many types of composite carbon sources and their components are complex and diverse. When switching from traditional carbon sources to composite carbon sources, due to microbial adaptability issues, it is easy to cause an impact on the biochemical system, resulting in poor denitrification effect, resulting in effluent TN and even other indicators exceeding the standard.

[0004] Therefore, how to find a more reliable method of switching and adding composite carbon sources to ensure that the effluent can stably meet the standards is a problem that needs to be solved.

[0005] In view of this, the present invention is proposed. Summary of the invention

[0006] The purpose of the present invention is to provide a method for switching the addition of a composite carbon source in a sewage treatment plant, which can achieve the switch from a traditional carbon source to a composite carbon source without causing a major impact on the biochemical system, ensuring that the effluent is stable and meets the standards, and gradually switching to adding a composite carbon source, thereby reducing the carbon source addition cost of the sewage treatment plant without affecting the effluent standards, thereby solving the above-mentioned technical problems existing in the prior art.

[0007] The objective of the present invention is achieved through the following technical solutions:

[0008] A method for switching and adding a composite carbon source in a sewage treatment plant, comprising:

[0009] Step 1, gradual acclimation stage: adding the current carbon source and the composite carbon source to be switched to the sewage treatment plant to be switched in multiple times, maintaining a predetermined time after each addition of the carbon source, the addition ratio of the current carbon source added from the first to the last gradually decreases and the addition ratio of the composite carbon source gradually increases, until the current carbon source is completely replaced by the composite carbon source, and the gradual acclimation is completed;

[0010] Step 2, optimization and adjustment stage: after completing the gradual domestication of step 1, the dosage of the composite carbon source is optimized and adjusted according to the internal control value of the effluent TN index of the sewage treatment plant, until the optimal dosage of the composite carbon source that can satisfy the effluent TN stability at the internal control value of the effluent TN index is obtained;

[0011] Step 3, stable addition stage: the composite carbon source is stably added according to the optimal composite carbon source dosage in step 2, and the composite carbon source dosage is slightly adjusted according to the internal control value of the effluent TN index of the sewage treatment plant during the addition period according to the water quality fluctuation.

[0012] Compared with the prior art, the method for switching the addition of composite carbon source in a sewage treatment plant provided by the present invention has the following beneficial effects:

[0013] By switching from the current carbon source to the composite carbon source in different proportions multiple times during the gradual acclimation stage, the microorganisms have an acclimation adaptation process, gradually transitioning from microbial strains adapted to the current carbon source to microbial strains adapted to the composite carbon source, avoiding the impact of a one-time replacement on the biochemical system of the sewage treatment plant, causing the effluent TN to exceed the standard. After all are replaced with composite carbon sources, the optimization and adjustment stage of the dosage is increased to explore the optimal dosage adapted to the composite carbon source, avoid the waste of carbon sources caused by excessive dosage and increase the dosage cost, and provide dosage data support for the subsequent stable addition of composite carbon sources. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0015] Figure 1 A flow chart of a method for switching the addition of a composite carbon source in a sewage treatment plant provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0016] The following is a clear and complete description of the technical solutions in the embodiments of the present invention in combination with the specific content of the present invention; it is obvious that the described embodiments are only part of the embodiments of the present invention, not all of the embodiments, which does not constitute a limitation of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the protection scope of the present invention.

[0017] First, the terms that may be used in this article are explained as follows:

[0018] The term “and / or” means that either or both of them can be realized at the same time. For example, X and / or Y means both “X” or “Y” and “X and Y”.

[0019] The terms "include", "comprises", "contains", "has" or other descriptions with similar semantics should be interpreted as non-exclusive inclusion. For example, including certain technical feature elements (such as raw materials, components, ingredients, carriers, dosage forms, materials, dimensions, parts, components, mechanisms, devices, steps, procedures, methods, reaction conditions, processing conditions, parameters, algorithms, signals, data, products or products, etc.) should be interpreted as including not only certain technical feature elements explicitly listed, but also other technical feature elements known in the art that are not explicitly listed.

[0020] The term "consisting of..." means excluding any technical feature elements not explicitly listed. If this term is used in a claim, it will make the claim closed, so that it does not contain technical feature elements other than the technical feature elements explicitly listed, except for the conventional impurities related to them. If this term only appears in a clause of a claim, it only limits the elements explicitly listed in the clause, and the elements recorded in other clauses are not excluded from the overall claim.

[0021] The term "parts by mass" refers to the mass ratio relationship between multiple components. For example, if it is described that component X is x parts by mass and component Y is y parts by mass, then the mass ratio of component X to component Y is x:y. 1 part by mass can represent any mass, for example, 1 part by mass can be represented as 1 kg or 3.1415926 kg. The sum of the parts by mass of all components is not necessarily 100 parts, but can be greater than 100 parts, less than 100 parts or equal to 100 parts. Unless otherwise specified, the parts, proportions and percentages described herein are all measured by mass.

[0022] When concentration, temperature, pressure, size or other parameters are expressed in the form of a numerical range, the numerical range should be understood to specifically disclose all ranges formed by the pairing of any upper limit, lower limit, and preferred value in the numerical range, regardless of whether the range is explicitly stated; for example, if a numerical range of "2 to 8" is stated, the numerical range should be interpreted as including ranges such as "2 to 7", "2 to 6", "5 to 7", "3 to 4 and 6 to 7", "3 to 5 and 7", "2 and 5 to 7", etc. Unless otherwise specified, the numerical ranges stated herein include both their end values ​​and all integers and fractions within the numerical range.

[0023] The scheme provided by the present invention is described in detail below. The contents not described in detail in the embodiments of the present invention belong to the prior art known to professionals in the field. If the specific conditions are not specified in the embodiments of the present invention, they are carried out according to the conventional conditions in the field or the conditions recommended by the manufacturer. If the manufacturers are not specified in the reagents or instruments used in the embodiments of the present invention, they are all conventional products that can be purchased commercially.

[0024] like Figure 1 As shown, an embodiment of the present invention provides a method for switching the addition of a composite carbon source in a sewage treatment plant, comprising:

[0025] Step 1, gradual acclimation stage: adding the current carbon source and the composite carbon source to be switched to the sewage treatment plant to be switched in multiple times, maintaining a predetermined time after each addition of the carbon source, the addition ratio of the current carbon source added from the first to the last gradually decreases and the addition ratio of the composite carbon source gradually increases, until the current carbon source is completely replaced by the composite carbon source, and the gradual acclimation is completed;

[0026] Step 2, optimization and adjustment stage: after completing the gradual domestication of step 1, the dosage of the composite carbon source is optimized and adjusted according to the internal control value of the effluent TN index of the sewage treatment plant, until the optimal dosage of the composite carbon source that can satisfy the effluent TN stability at the internal control value of the effluent TN index is obtained;

[0027] Step 3, stable addition stage: the composite carbon source is stably added according to the optimal composite carbon source dosage in step 2, and the composite carbon source dosage is slightly adjusted according to the internal control value of the effluent TN index of the sewage treatment plant during the addition period according to the water quality fluctuation.

[0028] Preferably, in step 1 of the above method, the predetermined time after each addition of the carbon source is maintained for 2 days;

[0029] The proportion of the currently used carbon source added from the first to the last is reduced successively according to 70% to 90%, 40% to 70%, 0% to 40%, and 0%. The proportion of the currently used carbon source added refers to the mass proportion of the carbon source COD addition required by the sewage treatment plant;

[0030] The addition ratio of the composite carbon source added from first to last increases successively according to 10%-30%, 30%-60%, 60%-100%, and 100%. The addition ratio of the composite carbon source refers to the mass ratio of the carbon source COD addition required by the sewage treatment plant.

[0031] Preferably, in step 1 and step 2 of the above method, the metering pump dosage of the current carbon source and the metering pump dosage of the composite carbon source are calculated according to the following formula:

[0032] q=C0×K×Q×1000÷(M×24);

[0033] In the above formula, q is the metering pump dosage of the current carbon source or the metering pump dosage of the composite carbon source, in L / h; C0 is the COD dosage of the carbon source in the sewage treatment plant, in mg / L; K is the dosage ratio of the current carbon source or the dosage ratio of the composite carbon source in the dosage ratio; Q is the treated water volume of the sewage treatment plant, in m 3 / d; M is the COD equivalent of the current carbon source or the COD equivalent of the composite carbon source, in mg / L.

[0034] Preferably, in the above method, during the gradual acclimatization period in step 1, the inlet and outlet water quality indicators of the sewage treatment plant, the pH, DO, MLSS, MLVSS, SV 30 , SVI operating parameters, observe the microbial activity, and determine whether the biochemical system has any abnormalities. If not, confirm that the gradual domestication is completed. If so, extend the operating days of the current carbon source and compound carbon source addition ratio or adjust the dosage. If the abnormality persists for more than 3 days, stop adding the compound carbon source. After the system recovers, adjust the addition ratio of the current carbon source and the compound carbon source and switch again.

[0035] Preferably, in step 2 of the above method, the dosage of the composite carbon source is optimized and adjusted according to the internal control value of the effluent TN index of the sewage treatment plant in the following manner until the optimal dosage of the composite carbon source that can satisfy the effluent TN stability at the internal control value of the effluent TN index is obtained, including:

[0036] When the effluent TN of the sewage treatment plant exceeds the upper limit of the internal control value of the effluent TN index χmg / L, the hourly dosage of the composite carbon source is increased by the COD dosage (4-5)×χmg / L at a ratio of 4-5:1 on the basis of the current dosage;

[0037] When the effluent TN of the sewage treatment plant is lower than the lower limit of the internal control value of the effluent TN index χmg / L, the hourly dosage of the composite carbon source is reduced by 4-5:1 based on the current dosage to reduce the COD dosage (4-5)×χmg / L;

[0038] Each time the dosage is adjusted, it is maintained for 2 days until the optimal dosage of the composite carbon source is obtained, which can ensure that the effluent TN is stable at the internal control value of the effluent TN index.

[0039] Preferably, in step 3 of the above method, the method of slightly adjusting the dosage of the composite carbon source according to the internal control value of the effluent TN index of the sewage treatment plant is the same as the method of optimizing and adjusting the dosage of the composite carbon source according to the internal control value of the effluent TN index of the sewage treatment plant in step 2.

[0040] Preferably, the above method also includes: setting up an active carbon source storage tank for storing active carbon source in the sewage treatment plant to be switched, monitoring the effluent COD and TN of the sewage treatment plant during the entire composite carbon source switching period, if the online monitored effluent TN exceeds the internal control value for 24 to 48 hours or it is found that the online monitored effluent TN increases by more than 3 mg / L within 6 to 8 hours, emergency measures are taken to immediately stop adding the composite carbon source and replace it with emergency addition of the active carbon source through the active carbon source storage tank.

[0041] In summary, the method of the embodiment of the present invention has at least the following beneficial effects compared with the prior art:

[0042] (1) Use different proportions to gradually switch the addition of composite carbon sources to allow the microorganisms to have an acclimation and adaptation process, gradually transitioning from microbial strains adapted to the current carbon source to microbial strains adapted to the composite carbon source, avoiding a one-time replacement that would have an impact on the biochemical system of the sewage treatment plant and cause the effluent TN to exceed the standard.

[0043] (2) After all the carbon sources are replaced with composite carbon sources, the optimization and adjustment stage of the dosage is increased to find out the optimal dosage suitable for the composite carbon source, avoid the waste of carbon sources caused by excessive dosage and increase the dosage cost, and provide dosage data support for the subsequent stable addition of composite carbon sources.

[0044] (3) Set up emergency measures to timely add the current carbon source when the effluent TN is abnormal, ensuring that the effluent TN of the sewage treatment plant is stable and meets the standard during the entire composite carbon source switching period. Switching to a more cost-effective composite carbon source can reduce the cost of carbon source addition in the sewage treatment plant.

[0045] In order to more clearly demonstrate the technical solution and technical effects provided by the present invention, the solution provided by the embodiment of the present invention is described in detail with specific embodiments below.

[0046] Example 1

[0047] like Figure 1 As shown, this embodiment provides a method for switching the addition of a composite carbon source in a sewage treatment plant, comprising:

[0048] Step 1, gradual domestication stage: add the current carbon source and the composite carbon source to the sewage treatment plant at the same time, the composite carbon source addition ratio is increased by 10% to 30%, 30% to 60%, 60% to 100%, and 100%, and the corresponding current carbon source addition ratio is reduced by 70% to 90%, 40% to 70%, 0% to 40%, and 0%, until the current carbon source is completely replaced by the composite carbon source, that is, the gradual domestication stage is completed. The above-mentioned addition ratio refers to the mass ratio of the carbon source COD addition required by the sewage treatment plant, such as: according to the current carbon source COD addition of the sewage treatment plant, it is distributed according to the mass ratio. If the current sewage treatment plant needs a carbon source COD addition of 30 mg / L, the composite carbon source addition ratio is 30%, then the addition amount is 30×30%=9 mg / L. Similarly, if the current carbon source addition ratio is 70%, then the addition amount is 30×70%=21 mg / L.

[0049] The above-mentioned addition ratios can be taken within the duration of each addition. For example, on the 1st to 2nd day of the gradual acclimation stage, the composite carbon source can take any value between 10% and 30%. If the value is 20%, the current carbon source is 100%-20%=80%. The current carbon source can also be taken between 70% and 90%, such as 70%, and the composite carbon source is 100%-70%=30%. It is sufficient to ensure that the sum of the addition ratios of the two carbon sources is 100%.

[0050] Each dosing ratio is maintained for 2 days, and the gradual acclimatization stage lasts for 6 to 8 days. The specific dosing amount of each dosing ratio is calculated based on the COD dosage of the current carbon source and the COD equivalent of the two carbon sources. The calculation formula is as follows:

[0051] q=C0×K×Q×1000÷(M×24);

[0052] In the above formula, q is the dosage of the composite carbon source or the current carbon source, L / h; C0 is the COD dosage of the sewage treatment plant, mg / L; K is the dosage ratio of the composite carbon source or the current carbon source; Q is the amount of water treated by the sewage treatment plant, m 3 / d; M is the COD equivalent of the composite carbon source or the COD equivalent of the current carbon source, mg / L;

[0053] During the gradual acclimatization period, water quality indicators such as inlet and outlet COD, TN, and biochemical pool pH, DO, MLSS, MLVSS, SV were monitored daily. 30, SVI operating parameters, observe the activity of microorganisms, and determine whether there are any abnormalities in the biochemical system. If not, confirm that the gradual domestication is completed. After gradual domestication, the microorganisms have adapted to the new composite carbon source. If so, extend the operating days of the current dosage ratio of the current carbon source and the composite carbon source or adjust the dosage. If the abnormality persists for more than 3 days, take emergency measures, stop adding the composite carbon source, and after the system recovers, adjust the dosage ratio of the current carbon source and the composite carbon source and switch again.

[0054] Step 2, optimization and adjustment stage: optimize and adjust the dosage of composite carbon source according to the internal control value of effluent TN index.

[0055] When the effluent TN exceeds the upper limit of the internal control value χmg / L, the hourly dosage of the composite carbon source is increased by the COD dosage (4-5)×χmg / L at a ratio of 4-5:1 based on the current dosage;

[0056] When the effluent TN is lower than the lower limit of the internal control value χmg / L, the hourly dosage of the composite carbon source is reduced by 4-5:1 based on the current dosage to reduce the COD dosage (4-5)×χmg / L;

[0057] Each adjustment of the dosage is maintained for 2 days until the optimal dosage of the composite carbon source is obtained to ensure that the effluent TN is stable at the internal control value, which takes 6 to 8 days.

[0058] Step 3, stable dosing stage: Stable dosing according to the optimal composite carbon source dosage in step 2. During this period, slight adjustments are made according to water quality fluctuations, and the adjustment method is the same as step 2.

[0059] In order to ensure that the TN of the sewage treatment plant effluent is stable and meets the standard, the sewage treatment plant reserves a current carbon source storage tank to store the current carbon source. During the entire composite carbon source switching period, the effluent COD and TN are observed. If the effluent online monitoring TN exceeds the internal control value for 24 to 48 hours or the effluent online monitoring TN is found to rise by more than 3 mg / L within 6 to 8 hours, emergency measures should be taken to immediately stop adding the composite carbon source and replace it with the current carbon source for emergency addition to ensure the stability of the effluent indicators.

[0060] Example 2

[0061] A sewage treatment plant has a treatment capacity of 100,000 tons / day, and the main biochemical process adopts A 2 O process, the current carbon source is 30% sodium acetate, the COD dosage is 30mg / L, the sewage treatment plant effluent standard implements the Beijing landmark "Urban Sewage Treatment Plant Water Pollutant Discharge Standard" (DB11 / 890-2012) in the B standard, TN effluent limit is 15mg / L, the internal control value is 9-11mg / L. Now it is necessary to replace it with a more cost-effective composite carbon source to reduce the cost of carbon source addition, and the COD equivalent of the composite carbon source is 500,000. The specific information of the current carbon source and composite carbon source of the sewage treatment plant is shown in the following table.

[0062] Table 1 is the information table of carbon sources and composite carbon sources currently used in sewage treatment plants

[0063]

[0064] The specific switching method from sodium acetate to composite carbon source is as follows, see Figure 1 :

[0065] Step 1, gradual acclimation stage: Add sodium acetate carbon source and composite carbon source currently used in sewage treatment plant at the same time, and the addition ratio of composite carbon source shall be gradually increased by 10%, 30%, 60%, and 100%, and the corresponding addition ratio of current carbon source shall be gradually reduced by 90%, 70%, 40%, and 0% until all are replaced by composite carbon source. Each addition ratio is maintained for 2 days, and the gradual acclimation stage is 8 days in total. The specific dosage of each ratio is calculated according to the COD dosage of the current carbon source and the COD equivalent of the two carbon sources. The calculation formula is as follows:

[0066] q=C0×K×Q×1000÷(M×24);

[0067] In the above formula, q is the dosage of the composite carbon source or the current carbon source, L / h; C0 is the COD dosage of the sewage treatment plant, mg / L; K is the dosage ratio of the composite carbon source or the current carbon source; Q is the amount of water treated by the sewage treatment plant, m 3 / d; M is the COD equivalent of the composite carbon source or the current carbon source, mg / L.

[0068] On the 1st to 2nd day, the dosage of composite carbon source q1 = 30 × 10% × 100000 × 1000 / (500000 × 24) = 25 L / h, the dosage of sodium acetate q2 = 30 × 90% × 100000 × 1000 / (234000 × 24) = 480.8 L / h.

[0069] On the 3rd to 4th day, the dosage of composite carbon source q1 = 30 × 30% × 100000 × 1000 / (500000 × 24) = 75 L / h, the dosage of sodium acetate q2 = 30 × 70% × 100000 × 1000 / (234000 × 24) = 373.9 L / h.

[0070] On the 5th to 6th day, the dosage of composite carbon source q1 = 30 × 60% × 100000 × 1000 / (500000 × 24) = 150 L / h, the dosage of sodium acetate q2 = 30 × 40% × 100000 × 1000 / (234000 × 24) = 213.7 L / h.

[0071] On the 7th to 8th day, the dosage of composite carbon source q1=30×100%×100000×1000 / (500000×24)=250 L / h, and the addition of sodium acetate was stopped.

[0072] During the gradual acclimatization period, water quality indicators such as inlet and outlet COD, TN, and biochemical pool pH, DO, MLSS, MLVSS, SV were monitored daily. 30 , SVI operating parameters, and observe microbial activity. By monitoring water quality indicators and operating parameters, the effluent COD, TN and other indicators can be stably discharged up to standard, and there are no abnormal changes in the biochemical system. After gradual domestication, the microorganisms have adapted to the new composite carbon source.

[0073] Step 2, optimization and adjustment stage: optimize and adjust the dosage of composite carbon source according to the internal control value of effluent TN index. The internal control value of TN is 9-11 mg / L. When the effluent TN exceeds the upper limit of the internal control value of 1 mg / L, the hourly dosage of composite carbon source is increased by 5 mg / L of COD dosage at a ratio of 5:1 on the basis of the current dosage, and the corresponding metering pump flow rate increases by 41.7 L / h. When the effluent TN is lower than the lower limit of the internal control value of 1 mg / L, the hourly dosage of composite carbon source is reduced by 5 mg / L of COD dosage at a ratio of 5:1 on the basis of the current dosage, and the corresponding metering pump flow rate decreases by 41.7 L / h. Each adjustment of dosage is maintained for 2 days. After 8 days of adjustment, the optimal dosage of composite carbon source is 235 L / h when the effluent TN is stable at the internal control value of 10-12 mg / L.

[0074] Step 3, stable addition stage: Stable addition according to the optimal composite carbon source dosage of 235L / h in step 2. During this period, slight adjustments are made according to the fluctuation of effluent TN, and the adjustment method is the same as step 2.

[0075] During the entire composite carbon source switching period, the on-site operators closely observed the effluent COD and TN conditions. The effluent TN was able to be maintained within the internal control value, and the effluent COD, ammonia nitrogen and other indicators were able to stably meet the discharge standards. After the sewage treatment plant switched to a more cost-effective composite carbon source, it can save about 24% of the carbon source addition cost for the sewage treatment plant.

[0076] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed in the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims. The information disclosed in the background technology section of this article is only intended to deepen the understanding of the overall background technology of the present invention, and should not be regarded as an admission or in any form that the information constitutes prior art known to those skilled in the art.

Claims

1. A method for switching the addition of a composite carbon source in a sewage treatment plant, characterized in that: include: Step 1, gradual acclimation stage: adding the current carbon source and the composite carbon source to be switched to the sewage treatment plant to be switched in multiple times, maintaining a predetermined time after each addition of the carbon source, the addition ratio of the current carbon source added from the first to the last gradually decreases and the addition ratio of the composite carbon source gradually increases, until the current carbon source is completely replaced by the composite carbon source, and the gradual acclimation is completed; Step 2, optimization and adjustment stage: after completing the gradual domestication of step 1, the dosage of the composite carbon source is optimized and adjusted according to the internal control value of the effluent TN index of the sewage treatment plant, until the optimal dosage of the composite carbon source that can satisfy the effluent TN stability at the internal control value of the effluent TN index is obtained; Step 3, stable addition stage: the composite carbon source is stably added according to the optimal composite carbon source dosage in step 2, and the composite carbon source dosage is slightly adjusted according to the internal control value of the effluent TN index of the sewage treatment plant during the addition period according to the water quality fluctuation.

2. The method for switching and adding a composite carbon source in a sewage treatment plant according to claim 1, characterized in that: In the step 1, each time the carbon source is added, the predetermined time is maintained for 2 days; The proportion of the currently used carbon source added from the first to the last is reduced successively according to 70% to 90%, 40% to 70%, 0% to 40%, and 0%. The proportion of the currently used carbon source added refers to the mass proportion of the carbon source COD addition required by the sewage treatment plant; The addition ratio of the composite carbon source added from first to last increases successively according to 10%-30%, 30%-60%, 60%-100%, and 100%. The addition ratio of the composite carbon source refers to the mass ratio of the COD dosage required by the sewage treatment plant.

3. The method for switching and adding a composite carbon source in a sewage treatment plant according to claim 2, characterized in that: In step 1 and step 2, the dosage of the current carbon source by the metering pump and the dosage of the composite carbon source by the metering pump are calculated according to the following formula: q=C0×K×Q×1000÷(M×24); In the above formula, q is the metering pump dosage of the current carbon source or the metering pump dosage of the composite carbon source, in L / h; C0 is the COD dosage of the carbon source in the sewage treatment plant, in mg / L; K is the dosage ratio of the current carbon source or the dosage ratio of the composite carbon source in the dosage ratio; Q is the treated water volume of the sewage treatment plant, in m 3 / d; M is the COD equivalent of the current carbon source or the COD equivalent of the composite carbon source, in mg / L.

4. The method for switching the addition of a composite carbon source in a sewage treatment plant according to any one of claims 1 to 3, characterized in that: During the gradual acclimatization period in step 1, the inlet and outlet water quality indicators of the sewage treatment plant, the pH, DO, MLSS, MLVSS, SV of the biochemical pool were monitored every day. 30 , SVI operating parameters, observe the microbial activity, and determine whether there is any abnormality in the biochemical system. If not, confirm that the gradual domestication is completed. If so, extend the operating days of the current carbon source and compound carbon source addition ratio or adjust the dosage. If the abnormality persists for more than 3 days, stop adding the compound carbon source. After the system recovers, adjust the addition ratio of the current carbon source and the compound carbon source and switch again.

5. The method for switching the addition of a composite carbon source in a sewage treatment plant according to any one of claims 1 to 3, characterized in that: In the step 2, the dosage of the composite carbon source is optimized and adjusted according to the internal control value of the effluent TN index of the sewage treatment plant in the following manner until the optimal dosage of the composite carbon source that can satisfy the effluent TN being stable at the internal control value of the effluent TN index is obtained, including: When the effluent TN of the sewage treatment plant exceeds the upper limit of the internal control value of the effluent TN index χmg / L, the hourly dosage of the composite carbon source is increased by the COD dosage (4-5)×χmg / L at a ratio of 4-5:1 on the basis of the current dosage; When the effluent TN of the sewage treatment plant is lower than the lower limit of the internal control value of the effluent TN index χmg / L, the hourly dosage of the composite carbon source is reduced by 4-5:1 based on the current dosage to reduce the COD dosage (4-5)×χmg / L; Each time the dosage is adjusted, it is maintained for 2 days until the optimal dosage of the composite carbon source is obtained, which can ensure that the effluent TN is stable at the internal control value of the effluent TN index.

6. The method for switching the addition of a composite carbon source in a sewage treatment plant according to any one of claims 1 to 3, characterized in that: In step 3, the method of slightly adjusting the dosage of the composite carbon source according to the internal control value of the effluent TN index of the sewage treatment plant is the same as the method of optimizing and adjusting the dosage of the composite carbon source according to the internal control value of the effluent TN index of the sewage treatment plant in step 2.

7. The method for switching the addition of a composite carbon source in a sewage treatment plant according to any one of claims 1 to 3, characterized in that: The method also includes: setting up an active carbon source storage tank for storing active carbon sources at the sewage treatment plant to be switched, monitoring the effluent COD and TN of the sewage treatment plant during the entire composite carbon source switching period, and if the online monitored TN of the effluent exceeds the internal control value for 24 to 48 hours or it is found that the online monitored TN of the effluent exceeds 3 mg / L within 6 to 8 hours, emergency measures are taken to immediately stop adding the composite carbon source and replace it with emergency addition of the active carbon source through the active carbon source storage tank.

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