Composite carbon source and sewage treatment method

Abstract

The invention discloses a composite carbon source and a sewage treatment method, the composite carbon source comprises a first carbon source and a second carbon source, the first carbon source is ethylene glycol, the second carbon source is selected from at least one of glycerol, molasses, cassava treatment liquid, food waste liquid, vinasse biogas slurry and fermentation liquor, and the mass fraction of ethylene glycol is greater than or equal to 5 wt%. According to the composite carbon source, the first carbon source and the second carbon source are scientifically compounded, so that the sewage treatment efficiency and effect are remarkably improved. Ethylene glycol has the advantages of being stable in chemical property, moderate in biodegradation rate, safe to store and the like, and can provide continuous electron donors for the denitrification process; glycerol, molasses or fermentation liquor is rich in easily degradable organic matters, so that the denitrification reaction can be quickly started, and the defect of relatively slow initial response of ethylene glycol is overcome. Under the synergistic effect of the two, a'quick start-stable supply 'dual-mode carbon source supply mode is formed, the utilization rate of the carbon source is effectively increased, and a higher water treatment effect is achieved within the same hydraulic retention time.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, and more specifically, to a composite carbon source and a wastewater treatment method. Background Technology

[0002] With my country's ever-increasing demands for water environmental quality, wastewater treatment plant effluent must consistently meet or exceed the Class A standard of the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants" (GB18918-2002) (such as Class IV surface water), making nitrogen and phosphorus removal increasingly challenging. However, most urban wastewater suffers from a low carbon-to-nitrogen ratio (C / N), resulting in insufficient external carbon sources for the denitrification process and severely impacting total nitrogen (TN) removal efficiency.

[0003] Currently, wastewater treatment plants generally rely on purchasing commercial carbon sources (such as sodium acetate and methanol) to compensate for insufficient internal carbon sources. However, these purchased reagents are expensive, have high transportation costs, and unstable supply chains, resulting in a continuous increase in operating costs. In 2023, a certain plant spent as much as 53.347 million yuan on carbon source reagents, all of which was purchased from external suppliers. The procurement of carbon source reagents has become a key bottleneck restricting the company's cost reduction, efficiency improvement, and stable operation.

[0004] At the same time, some factories discharge waste that cannot be reused and the treatment costs are high. If waste sludge can be converted into a usable carbon source to achieve "waste treatment", it will become a technological direction that is both economical and sustainable.

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

[0006] The purpose of this invention is to provide a composite carbon source and a wastewater treatment method that can utilize waste while also achieving water treatment effects.

[0007] This invention is implemented as follows: In a first aspect, the present invention provides a composite carbon source, comprising a first carbon source and a second carbon source, wherein the first carbon source is ethylene glycol, and the second carbon source is selected from at least one of glycerol, molasses, cassava treatment liquid, food waste liquid, distiller's grains biogas slurry and fermentation liquid, wherein the mass fraction of the ethylene glycol is ≥5wt%.

[0008] In an optional embodiment, the composite carbon source comprises, by mass fraction, 35-45 wt% glycerol, 25-35 wt% molasses, 5-15 wt% ethylene glycol, and 15-25 wt% water.

[0009] In an optional embodiment, the ethylene glycol is derived from the fan coolant; And / or, the molasses is derived from fermentation or sugar production wastewater, and the molasses includes polysaccharides and organic acids; And / or, the fermentation broth contains volatile fatty acids, including at least one of acetic acid, propionic acid, and butyric acid, and the chemical oxygen demand of the fermentation broth is ≥8000 mg / L.

[0010] In an optional embodiment, the fermentation broth is selected from at least one of the following liquids: a. The supernatant produced during the hydrolysis and acidification stage of sludge separated from wastewater; b. Fermentation residue from alcohol plants; c. Residual liquid of bacterial cells after the production of antibiotics and / or yeast; d. Concentrate of wastewater from the production of monosodium glutamate and / or citric acid.

[0011] In an optional embodiment, the composite carbon source further includes a sludge alkaline hydrolysis carbon source, and the preparation method of the sludge alkaline hydrolysis carbon source includes: sequentially performing alkaline hydrolysis, hydrolysis acidification and solid-liquid separation on waste sludge from a sewage treatment plant, and the resulting liquid phase is the sludge alkaline hydrolysis carbon source.

[0012] In an optional embodiment, the alkaline hydrolysis is performed at a temperature of 25-70°C, a pH of 11-12, and a time of 1-2 hours. And / or, the hydrolysis acidification temperature is 33-37℃, the pH is 9.8-10.2, and the time is 9-11h.

[0013] In an optional embodiment, after hydrolysis and acidification and before solid-liquid separation, struvite precipitation is performed. The pH of the struvite precipitation step is 8.5-9.5, and a magnesium source is added during the struvite precipitation process to precipitate the struvite.

[0014] In an optional embodiment, before alkaline hydrolysis, the waste sludge from the wastewater treatment plant is diluted to a TSS of 75-105 g / L.

[0015] Secondly, the present invention provides a wastewater treatment method, comprising: using A 2 Wastewater treatment using the / O process involves adding the composite carbon source described in any of the aforementioned embodiments to A. 2 Oxygen-deficient section of the / O process.

[0016] In an optional embodiment, the carbon-to-nitrogen ratio of the anoxic zone is 2.0-5.0:1, the residence time of the anoxic zone is 60-180 min, and the residence time of the aerobic zone is 180-240 min.

[0017] The present invention has the following beneficial effects: The composite carbon source provided by this invention significantly improves the efficiency and effectiveness of wastewater treatment by scientifically combining ethylene glycol as the first carbon source with at least one second carbon source selected from glycerol, molasses, or fermentation broth. Ethylene glycol has advantages such as chemical stability, moderate biodegradation rate, and safe storage, providing a continuous electron donor for the denitrification process; while glycerol, molasses, or fermentation broth are rich in easily degradable organic matter, which can quickly initiate the denitrification reaction, compensating for the slow initial response of ethylene glycol. The synergistic effect of the two forms a dual-mode carbon source supply model of "fast start-up - stable supply," effectively improving carbon source utilization and achieving higher water treatment efficiency within the same hydraulic retention time. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a process flow diagram for preparing the carbon source for sludge alkaline hydrolysis according to the present invention.

[0020] Figure 2 The composite carbon source of this invention is in A 2 Schematic diagram of dosing and function in the / O process.

[0021] Figure 3 This is a curve comparing the total nitrogen (TN) removal effects of the composite carbon source in Example 1 of the present invention with those of Comparative Example 1 (sodium acetate). Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially. The following abbreviations apply to this document: Carbon-to-nitrogen ratio (C / N) - Carbon-to-nitrogen ratio; Total nitrogen (TN) - Total nitrogen; The ratio of B / C-BOD5 to COD (also known as a biodegradability index); VFAs - Volatile fatty acids; A 2 / O process - anaerobic-anoxic-aerobic process; C:N ratio - carbon-nitrogen ratio; COD - Chemical Oxygen Demand; SCOD - Dissolved Chemical Oxygen Demand; BOD5 - Five-day biochemical oxygen demand; NH3-N-ammonia nitrogen; TP - Total Phosphorus.

[0023] The present invention provides a composite carbon source, including a first carbon source and a second carbon source. The first carbon source is ethylene glycol, and the second carbon source is selected from at least one of glycerol, molasses, cassava treatment liquid, food waste, distiller's grains biogas slurry and fermentation liquid, wherein the mass fraction of the ethylene glycol is ≥5wt%.

[0024] The composite carbon source provided in this invention significantly improves the efficiency and effectiveness of wastewater treatment by scientifically combining ethylene glycol as the first carbon source with at least one second carbon source selected from glycerol, molasses, or fermentation broth. Ethylene glycol has advantages such as chemical stability, moderate biodegradation rate, and safe storage, providing a continuous electron donor for the denitrification process; while glycerol, molasses, or fermentation broth are rich in easily degradable organic matter, which can quickly initiate the denitrification reaction, compensating for the slow initial response of ethylene glycol. The synergistic effect of the two forms a dual-mode carbon source supply model of "fast start-up - stable supply," effectively improving carbon source utilization and achieving higher water treatment efficiency within the same hydraulic retention time. Experiments show that when the mass fraction of ethylene glycol is ≥5wt%, the composite carbon source exhibits a significant synergistic effect, with a significantly better nitrogen removal capacity per unit COD than a single carbon source. Under low temperature or low C / N ratio conditions, the composite carbon source still maintains good bioavailability, effectively improving nitrogen and phosphorus removal performance, reducing sludge bulking probability, and enhancing system operational stability.

[0025] Compared to traditional highly toxic methanol carbon sources, this application improves storage, transportation, and operational safety, aligning with the trend of green and low-carbon development. Furthermore, the secondary carbon source, such as fermentation broth, can be prepared using industrial byproducts, further reducing raw material costs and enhancing resource utilization. Therefore, this composite carbon source combines high efficiency, economy, safety, and environmental friendliness, making it suitable for deep denitrification treatment of municipal wastewater and low C / N ratio industrial wastewater, and possessing promising engineering application prospects.

[0026] In an optional embodiment, the composite carbon source comprises, by mass fraction, 35-45 wt% glycerol, 25-35 wt% molasses, 5-15 wt% ethylene glycol, and 15-25 wt% water.

[0027] In an optional embodiment, the ethylene glycol is derived from the fan coolant; And / or, the molasses is derived from fermentation or sugar production wastewater, and the molasses includes polysaccharides and organic acids; And / or, the fermentation broth contains volatile fatty acids, including at least one of acetic acid, propionic acid, and butyric acid, and the chemical oxygen demand of the fermentation broth is ≥8000 mg / L.

[0028] In an optional embodiment, the fermentation broth is selected from at least one of the following liquids: a. The supernatant produced during the hydrolysis and acidification stage of sludge separated from wastewater; b. Fermentation residue from alcohol plants; c. Residual liquid of bacterial cells after the production of antibiotics and / or yeast; d. Concentrate of wastewater from the production of monosodium glutamate and / or citric acid.

[0029] In this application, the composite carbon source includes ethylene glycol, which can be derived from waste cooling liquid from wind farms, providing biodegradable organic matter; glycerol, which can be derived from industrial by-products, has a high carbon content and is easily denitrified; molasses, which can be derived from waste liquid from fermentation or sugar production industries, is rich in polysaccharides and organic acids; food waste liquid refers to liquid waste generated during food production, processing, storage, and consumption, and is a type of organic waste liquid with high organic matter concentration. Its sources include wastewater from food raw material washing, wastewater from production processes (such as canning, beverage brewing, and dairy product production), and leachate from food residues. It is characterized by high BOD5 and COD content, and is rich in biodegradable substances such as sugars, proteins, and oils. Some may contain certain salts or food additives; distiller's grains biogas slurry is the fermentation tail liquid obtained after anaerobic fermentation of distiller's grains (solid or semi-solid fermentation residue) produced in the brewing industry to produce biogas. This type of waste liquid is characterized by the presence of a certain amount of small molecule organic matter, ammonia nitrogen, phosphorus, and trace elements, a high BOD5 / COD ratio, and good biodegradability. It should be noted that when using the aforementioned waste liquid as a second carbon source, materials with good biodegradability (BOD5 / COD≥0.3), high chemical oxygen demand (COD) concentration (usually ≥5,000 mg / L), and free from components that significantly inhibit the activity of microorganisms in wastewater treatment should be preferred. For food waste liquid, concentrated organic wastewater or by-product sugar solutions and fermentation residues from processes such as starch production, sugar refining, brewing, and fermentation are preferred. For distiller's grains biogas slurry, attention should be paid to the nitrogen and phosphorus loads introduced simultaneously and included in the overall system accounting.

[0030] In an optional embodiment, the composite carbon source further includes a sludge alkaline hydrolysis carbon source. The preparation method of the sludge alkaline hydrolysis carbon source includes: sequentially performing alkaline hydrolysis, hydrolysis acidification, and solid-liquid separation on wastewater treatment plant waste sludge, and the resulting liquid phase is the sludge alkaline hydrolysis carbon source. The flowchart is shown below. Figure 1 As shown.

[0031] Alkaline hydrolysis effectively disrupts the sludge cell structure and extracellular polymers, promoting the dissolution and release of organic matter and significantly increasing the soluble COD (SCOD) concentration, creating favorable conditions for subsequent acid production. The subsequent hydrolysis and acidification stage is conducted under mesophilic, anaerobic conditions, further degrading macromolecular organic matter into volatile fatty acids (VFAs), primarily acetic acid. Acetic acid is the most readily available and high-quality carbon source during denitrification. The final liquid phase obtained through solid-liquid separation methods such as plate and frame filtration—the "sludge alkaline hydrolysis carbon source"—has good biodegradability and can be added to composite carbon sources.

[0032] In an optional embodiment, the alkaline hydrolysis is performed at a temperature of 25-70°C, a pH of 11-12, and a time of 1-2 hours. And / or, the hydrolysis acidification temperature is 33-37℃, the pH is 9.8-10.2, and the time is 9-11h.

[0033] In an optional embodiment, after hydrolysis and acidification and before solid-liquid separation, struvite precipitation is performed. The pH of the struvite precipitation step is 8.5-9.5, and a magnesium source is added during the struvite precipitation process to precipitate the struvite.

[0034] In an optional embodiment, before alkaline hydrolysis, the waste sludge from the wastewater treatment plant is diluted to a TSS of 75-105 g / L.

[0035] The preparation of the composite carbon source in this application may include the following steps: A portion of the carbon source raw materials (solid raw materials need to be pre-treated to a liquid state, such as cassava flour hydrolysis) are initially stirred, dissolved, and mixed in a carbon source raw material mixing tank. Subsequently, the mixture enters a composite carbon source stabilization reaction tank for stabilization treatment under controlled conditions to form the final product. The stabilization treatment includes: mixing at 20-40℃ with continuous mechanical stirring (e.g., 30-120 rpm) for 1-4 hours to homogenize the materials; monitoring and adjusting the pH value of the system to the range of 6.5-8.5; optionally, filtration or the addition of trace stabilizers to prevent microbial growth. This treatment yields a homogeneous, stable, easy-to-store, and easily added liquid composite carbon source product.

[0036] It should be noted that the mass fraction of the first carbon source in the composite carbon source of this application can be any value above 5 wt%, such as 5 wt%, 15 wt%, 25 wt%, 35 wt%, 45 wt%, 55 wt%, 65 wt%, 75 wt% or higher, and the mass fraction of the second carbon source can be 25 wt%, 35 wt%, 45 wt%, 55 wt%, 65 wt%, 75 wt%, 85 wt%, etc.; and the second carbon source can include one source or two or more sources, such as one of glycerol, cassava, fermentation broth or sludge alkaline hydrolysis carbon source, or a combination of glycerol, molasses and cassava, or a combination of distillers' grains biogas slurry, cassava and molasses, etc. When the second carbon source has two or more sources, the second carbon sources from different sources can be combined in any proportion, that is, the mass fraction of any one of the second carbon sources in the second carbon source can be 0-100 wt%, such as 5 wt%, 15 wt%, 25 wt%, 35 wt%, 45 wt%, 55 wt%, 65 wt%, 75 wt%, 85 wt%, 95 wt%, etc.

[0037] This invention also provides a wastewater treatment method, comprising: using A 2 Wastewater treatment using the / O process involves adding the composite carbon source described in any of the aforementioned embodiments to A. 2 The oxygen-deficient section of the / O process, such as Figure 2 As shown.

[0038] In an optional embodiment, the carbon-to-nitrogen ratio of the anoxic zone is 2.0-5.0:1, the residence time of the anoxic zone is 60-180 min, and the residence time of the aerobic zone is 180-240 min.

[0039] This invention also provides a wastewater treatment method, comprising: using A 2 Wastewater treatment using the / O process involves adding the composite carbon source described in any of the aforementioned embodiments to A. 2 Oxygen-deficient section of the / O process.

[0040] In an optional embodiment, the carbon-to-nitrogen ratio of the anoxic section is 2.0. 5.0:1, residence time in the hypoxic phase is 60. 180 minutes, the residence time in the aerobic zone is 180 minutes. 240 minutes.

[0041] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0042] Description of raw materials involved in the embodiments of this application: Waste glycerol, derived from chemical byproducts, has a COD of 1,200,000 mg / L; Waste molasses, derived from waste liquid from sugar factories, has a COD of 800,000 mg / L; The fan coolant is derived from waste ethylene glycol coolant and contains ≥95% ethylene glycol. Fermentation broth, derived from fermentation residue of alcohol plants, has a COD ≥ 15,000 mg / L.

[0043] Example 1 This embodiment provides a composite carbon source, which, by mass fraction, comprises 40 wt% glycerol, 30 wt% molasses, 10 wt% ethylene glycol, and 20 wt% water.

[0044] Example 2 This embodiment provides a composite carbon source, which, by mass fraction, comprises 35 wt% glycerol, 30 wt% molasses, 15 wt% ethylene glycol, 5 wt% cassava flour hydrolysate, and 15 wt% water. The cassava flour hydrolysate is obtained by mixing cassava flour and water in a 1:5 ratio, hydrolyzing at 95°C for 2 hours, and then filtering.

[0045] Example 3 This embodiment provides a composite carbon source, which, by mass fraction, comprises 45wt% washing waste liquid (also known as diluted wort, COD≈50,000mg / L) from the saccharification stage of beer production, 25wt% brewer's grains biogas slurry, 12wt% ethylene glycol, and 18wt% water.

[0046] Example 4 This embodiment provides a composite carbon source, which differs from Embodiment 1 mainly in that it replaces glycerol with a sludge alkaline hydrolysis carbon source of equal COD value. The preparation method of the sludge alkaline hydrolysis carbon source specifically includes the following steps: Conditioning involves adding water to the waste sludge from the sewage treatment plant and stirring it evenly to obtain a sludge slurry with a solid content of 8%. Alkaline hydrolysis was performed by adding sodium hydroxide to the sludge at a concentration of 0.1 mol / L, followed by a reaction at 25°C for 60 minutes to obtain an alkaline hydrolysate. Hydrolysis and acidification: The alkaline hydrolysate was placed at (35±2)℃ and a stirring speed of 48rpm, and the pH of the slurry was adjusted to 10±0.2 and the SRT was 10d to obtain the hydrolyzed acidified slurry. The hydrolyzed acidified slurry is filtered by pressure, and the resulting liquid phase is the carbon source for the alkaline hydrolysis of the sludge, with an SCOD of approximately 25,000 mg / L.

[0047] Example 5 This embodiment provides a composite carbon source, which differs from Embodiment 4 mainly in that sodium hydroxide is added to the sludge slurry at a concentration of 0.15 mol / L in the alkaline hydrolysis step, followed by a reaction at 50°C for 90 min, resulting in an SCOD of approximately 32,000 mg / L for the obtained sludge alkaline hydrolysis carbon source.

[0048] Example 6 This embodiment provides a composite carbon source, which differs from Embodiment 1 mainly in that molasses is completely replaced with cassava flour hydrolysate of equal COD value. The final composite carbon source composition is: 40wt% glycerol, 30wt% cassava flour hydrolysate, 10wt% ethylene glycol, and 20wt% water.

[0049] Comparative Example 1 This comparative example provides a carbon source, which is commercial grade sodium acetate solid, prepared as a solution for use, with a COD equivalent concentration of 165,000 mg / L.

[0050] Comparative Example 2 This comparative example provides a carbon source, which is pure ethylene glycol (industrial grade) with a COD equivalent concentration of 1,100,000 mg / L.

[0051] Comparative Example 3 This comparative example provides a carbon source, which is a single waste molasses concentrate with a COD equivalent concentration of 800,000 mg / L.

[0052] Example 7: Comparative Experiment on Denitrification Performance This embodiment provides a denitrification experiment using a carbon source, specifically including: selecting A 2 The aerobic end-of-pipe mixture in the / O process has a total nitrogen concentration of 4 mg / L, SCOD of 36 mg / L, and NH3 concentration of... N is 0.6 mg / L, TP is 1.9 mg / L, and MLSS is 9600 mg / L (water treatment plant test values). Objective: To increase the total nitrogen (TN) of the aerobic terminal mixture to 30 mg / L by adding potassium nitrate; the C / N ratio should be 5:1. The specific experimental steps are as follows: (1) Take 1.5L of aerobic end-of-pipe mixture for each group. To achieve a C / N ratio of 5:1, the required amount of carbon source COD is calculated to be: [5×(30-4)-36]×1.5=141 mg; (2) Stir thoroughly for 120 min; take samples at 0 min and every 60 min to measure pH, chemical oxygen demand (SCOD), total nitrogen (TN), and ammonia nitrogen (NH3). N, and record it, as shown in Table 1 and Figure 3 As shown.

[0053] Table 1 Comparison of denitrification experimental data (C / N=5:1)

[0054] Note: The C / N (SCOD consumed / TN removed) ratio is calculated as: (initial SCOD - SCOD after 2h) / (initial TN - TN after 2h). The lower the value, the higher the carbon source utilization efficiency.

[0055] Example 8: Denitrification effect at different C / N ratios This embodiment provides a denitrification experiment using a carbon source, specifically including: selecting A 2 In the aerobic end-of-pipe mixture of the / O process (water quality as in Example 7), the goal was to increase TN to 30 mg / L. The composite carbon source described in Example 1 was added at C / N ratios of 5:1, 4:1, 3:1, and 2:1, respectively. The specific experimental steps were the same as in Example 7, and the results are shown in Table 2.

[0056] Table 2. Denitrification effect of the composite carbon source in Example 1 at different C / N ratios.

[0057] Example 9: Effect of subsequent treatments during the aeration stage In this embodiment, after the 2-hour denitrification experiment in Example 7, an aeration experiment was conducted on the mixture in the beaker for another 4 hours (simulating A). 2 The study investigated the continuous effects of a composite carbon source on the degradation of residual organic matter, nitrification, and phosphorus removal under aerobic conditions (aerobic section of the / O process). Dissolved oxygen was controlled at 2.0-3.0 mg / L, and the temperature was (20±1)℃. Specific experimental procedures and water quality monitoring are shown in Table 3.

[0058] Table 3 Aeration Stage (3rd) Changes in water quality indicators over 6 hours

[0059] Results analysis: 1. Organic matter degradation: During the aeration stage, the SCOD of all experimental groups using the composite carbon source of this invention (Examples 1-6) decreased to a low level (10-16 mg / L) at the 6th hour, significantly better than the comparative sodium acetate group (24 mg / L) and the control group (21 mg / L). This indicates that the organic matter in the composite carbon source is further efficiently degraded after denitrification, reducing the COD load in the effluent.

[0060] 2. Deep Nitrogen Removal: After 4 hours of aeration, the total nitrogen (TN) in the experimental group dropped to extremely low levels (mostly below 1.0 mg / L), achieving deep nitrogen removal. This was due to the efficient utilization of the composite carbon source during the denitrification stage, which provided a favorable environment for nitrifying bacteria in the aerobic stage and prevented the accumulation of large amounts of nitrate nitrogen.

[0061] 3. Ammonia Nitrification: The rapid decrease in NH3-N indicates that the system's nitrification function is good. The ammonia nitrogen in the effluent from the composite carbon source group is generally below 0.5 mg / L, meeting the high standard effluent requirements.

[0062] 4. Biological phosphorus removal: The continuous decrease in TP indicates that polyphosphate-accumulating bacteria have a significant effect on excessive phosphorus uptake in the aerobic stage. The composite carbon source group (especially Examples 4 and 5 which contain sludge alkaline hydrolysis carbon source) not only provides carbon source, but may also enhance the biological phosphorus removal effect due to the presence of suitable VFAs components, and the final effluent TP is mostly below 0.05 mg / L.

[0063] In summary, the composite carbon source of this invention not only exhibits high efficiency of "rapid start-up and stable supply" in the anoxic denitrification stage, but also demonstrates good biocompatibility in the subsequent aerobic stage, promoting rapid system recovery and achieving deep and simultaneous removal of COD, TN, NH3-N, and TP, thus ensuring the overall A 2 The effluent quality of the / O process system consistently meets the standards.

[0064] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A composite carbon source, characterized in that, It includes a first carbon source and a second carbon source, wherein the first carbon source is ethylene glycol, and the second carbon source is selected from at least one of glycerol, molasses, cassava treatment liquid, food waste liquid, distiller's grains biogas liquid and fermentation liquid, wherein the mass fraction of the ethylene glycol is ≥5wt%.

2. The composite carbon source according to claim 1, characterized in that, The composite carbon source comprises, by mass fraction, 35-45 wt% glycerol, 25-35 wt% molasses, 5-15 wt% ethylene glycol and 15-25 wt% water.

3. The composite carbon source according to claim 1, characterized in that, The ethylene glycol is derived from the fan coolant; And / or, the molasses is derived from fermentation or sugar production wastewater, and the molasses includes polysaccharides and organic acids; And / or, the fermentation broth contains volatile fatty acids, including at least one of acetic acid, propionic acid, and butyric acid, and the chemical oxygen demand of the fermentation broth is ≥8000 mg / L.

4. The composite carbon source according to claim 1, characterized in that, The fermentation broth is selected from at least one of the following liquids: a. The supernatant produced during the hydrolysis and acidification stage of sludge separated from wastewater; b. Fermentation residue from alcohol plants; c. Residual liquid of bacterial cells after the production of antibiotics and / or yeast; d. Concentrate of wastewater from the production of monosodium glutamate and / or citric acid.

5. The composite carbon source according to claim 1, characterized in that, The composite carbon source also includes a sludge alkaline hydrolysis carbon source. The preparation method of the sludge alkaline hydrolysis carbon source includes: sequentially performing alkaline hydrolysis, hydrolysis acidification and solid-liquid separation on waste sludge from a sewage treatment plant, and the resulting liquid phase is the sludge alkaline hydrolysis carbon source.

6. The composite carbon source according to claim 5, characterized in that, The alkaline hydrolysis is performed at a temperature of 25-70℃, a pH of 11-12, and a time of 1-2 hours. And / or, the hydrolysis acidification temperature is 33-37℃, the pH is 9.8-10.2, and the time is 9-11h.

7. The composite carbon source according to claim 5, characterized in that, After hydrolysis and acidification and before solid-liquid separation, struvite precipitation is performed. The pH of the struvite precipitation step is 8.5-9.5, and a magnesium source is added during the struvite precipitation process to precipitate the struvite.

8. The composite carbon source according to claim 5, characterized in that, Before alkaline hydrolysis, the waste sludge from the wastewater treatment plant is diluted to a TSS of 75-105 g / L.

9. A wastewater treatment method, characterized in that, include: Using A 2 Wastewater treatment using the / O process involves adding the composite carbon source described in any one of claims 1-8 to A. 2 Oxygen-deficient section of the / O process.

10. The wastewater treatment method according to claim 9, characterized in that, The carbon-to-nitrogen ratio in the anoxic zone is 2.0-5.0:1, the residence time in the anoxic zone is 60-180 min, and the residence time in the aerobic zone is 180-240 min.

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