Biomass carbon source, preparation method and application thereof

Abstract

The present application relates to the technical field of biomass carbon source, more specifically, the present application relates to a kind of biomass carbon source and preparation method and application, by constructing magnetic solid acid catalyst system, algal biomass and residual sludge are chemically catalytic degradation, it is converted into short-chain fatty acid and monosaccharide mainly easy biodegradable organic carbon source.Biomass carbon source COD concentration is greater than or equal to 90g / L, can be used as supplementary carbon source to improve the effect of low carbon nitrogen ratio sewage biological denitrification.Simultaneously, using straw biomass as raw material, magnetic carrier is prepared to strengthen catalyst recovery rate, catalyst recovery rate is greater than or equal to 75%, realizes the recycling of waste resources.The present application converts algae and sludge into high value-added carbon source product, provides a new solution for carbon source supplement of sewage treatment plant, improves the value of biomass resource utilization and the stability of sewage biological denitrification process.

Description

Technical Field

[0001] This invention relates to the field of biomass carbon source technology. More specifically, this invention relates to a biomass carbon source, its preparation method, and its applications. Background Technology

[0002] Wastewater treatment plants currently face a widespread problem of influent carbon-to-nitrogen ratio imbalance. Traditional biological denitrification processes are insufficient to meet denitrification requirements due to insufficient organic matter, necessitating the addition of external carbon sources. While existing carbon sources such as methanol and sodium acetate can improve efficiency in the short term, they suffer from high procurement costs and the risk of secondary pollution. Therefore, biomass carbon sources (i.e., carbon sources processed from natural biomass) have attracted considerable attention due to their renewability and ability to achieve resource utilization of waste. However, their application remains limited by the shortcomings of traditional utilization methods.

[0003] Currently, biomass carbon sources are mainly released slowly through the preparation of slow-release carbon sources (such as straw, sawdust, and other solid forms). However, due to the complex composition of biomass, this method suffers from problems such as uncontrollable decomposition rates, low carbon release efficiency, and susceptibility to environmental factors, leading to fluctuating denitrification effects and difficulty in matching dynamic wastewater treatment needs. In addition, long-term addition of slow-release carbon sources may cause clogging risks and increase the difficulty of operation and maintenance. These shortcomings limit the large-scale application of biomass carbon sources in denitrification processes. Summary of the Invention

[0004] The purpose of this invention is to provide a biomass carbon source, its preparation method, and its application, which combines high efficiency, controllability, and sustainability, providing a new solution for carbon source replenishment in wastewater treatment plants and enhancing the value of biomass resource utilization and the stability of wastewater biological denitrification processes.

[0005] To achieve these objectives and other advantages according to the present invention, a method for preparing a biomass carbon source is provided, comprising the following steps:

[0006] S1. Cultivate Chlorella using urban domestic sewage, achieving an algal density ≥ 6 × 10⁻⁶. 6 When the volume of cells / mL is 0.01-0.02% of the wastewater mass, add chitosan with a degree of deacetylation ≥90%, flocculate, and then centrifuge to obtain algal slurry with a water content ≤90%.

[0007] S2. Add 2-4% of the mass of the magnetic solid acid catalyst to the algal slurry obtained in S1. After ultrasonic catalysis for 2-3 hours, the first mixture is obtained. After centrifugation, the first supernatant containing sugar and the first precipitate containing algal mud and catalyst are obtained.

[0008] S3. Take the residual sludge from the thickening tank of the sewage treatment plant and mix it with the first precipitate obtained in S2 at a mass ratio of 20-30:1 to obtain the second mixture. Adjust the pH to 3-4 and react under microwave for 1-1.5 hours. Stir evenly to obtain the third mixture. After centrifugation, obtain the second supernatant and the second precipitate.

[0009] S4. Add 3-5 times the volume of n-hexane solution to the second supernatant obtained in S3 for extraction. Collect the upper n-hexane solution containing fatty acids, and remove the solvent by distillation to obtain the fourth mixture. The residual n-hexane mass concentration is ≤0.1%.

[0010] S5. Mix the first supernatant obtained in S2 with the fourth mixture obtained in S4 at a volume ratio of 1:2-3, add 0.2% of Tween 80 by mass of the fourth mixture for emulsification, and adjust the pH to 5-6 to obtain the biomass carbon source with a COD concentration ≥90g / L.

[0011] Furthermore, in the method for preparing the biomass carbon source, during centrifugation in S1, the sample is first centrifuged at 3000×g for 10 min, and then centrifuged at 5000×g for 15 min.

[0012] Furthermore, in the method for preparing the biomass carbon source, during centrifugation in step S2, the centrifugation is performed at 3000×g for 10 minutes.

[0013] Furthermore, in the method for preparing the biomass carbon source, during ultrasonic catalysis in S2, the conditions are 60°C, pH 3-4, ultrasonic frequency 40kHz, and ultrasonic power 2W / cm². 2 It is carried out under the following conditions.

[0014] Furthermore, in the method for preparing the biomass carbon source, during centrifugation in step S3, the centrifugation is performed at 5000-8000×g for 15-20 minutes.

[0015] Furthermore, in the method for preparing the biomass carbon source, the method for preparing the magnetic solid acid catalyst includes the following steps:

[0016] (1) Prepare a solution containing Fe(NO3), Al2(SO4)3 and ZrOCl2, wherein the concentrations of Fe(NO3), Al2(SO4)3 and ZrOCl2 are 1 mol / L, 0.5 mol / L and 0.5 mol / L, respectively;

[0017] (2) Add the straw powder treated with phosphoric acid and alkali in sequence to the solution obtained in step (1) at a solid-liquid ratio of 1g:4-5mL, microwave-assisted soaking for 30min, washing and drying to obtain pretreated biomass powder;

[0018] (3) The pretreated biochar obtained in step (2) is placed under N2 protection and heated to 300℃ at a rate of 5℃ / min for 1h for pre-carbonization. Then, the temperature is increased to 600-650℃ and steam is introduced for 30-45min for carbonization. After that, the steam is stopped and the biochar is dried at 105℃.

[0019] (4) The biochar obtained in step (3) is mixed with liquid SO3 at a mass ratio of 3:1, reacted at 40°C for 2 hours, and then reacted at 50°C for 2 hours to sulfonate the biochar.

[0020] (5) The sulfonated biochar obtained in step (4) is washed three times with deionized water and then dried under vacuum at 80°C to obtain the magnetic solid acid catalyst.

[0021] Furthermore, in the method for preparing the biomass carbon source, step (2) of sequentially treating the straw powder with phosphoric acid and alkali includes the following steps:

[0022] Crush the straw to 100 mesh, soak it in 10-15 mol / L phosphoric acid for 8-12 hours, then soak it in 1-2 mol / L NaOH solution for 24 hours, and finally wash it three times with deionized water and dry it.

[0023] Furthermore, the method for preparing the biomass carbon source is characterized by further comprising the following steps:

[0024] S6. Catalyst recovery:

[0025] Add 0.1 mol / L citric acid (10 times its mass) to the second precipitate obtained in S3, and sonicate at a frequency of 20-30 kHz and a power of 0.3-0.5 W / cm². 2 The catalyst is ultrasonically treated for 5 minutes under certain conditions, and then placed in a 0.5-0.8T magnetic field to separate it. Finally, it is washed with water and dried to recover the magnetic solid acid catalyst.

[0026] The present invention also provides a biomass carbon source prepared by any of the above preparation methods.

[0027] The present invention also provides an application of the above-mentioned biomass carbon source in wastewater treatment, comprising the following steps:

[0028] Biomass carbon source is added to the influent of the anoxic section of the wastewater treatment system. After addition, the dissolved oxygen in the anoxic section should be maintained at <0.5mg / L, pH value at 6.5-7.5, and temperature at 20-30℃. The dosage should be adjusted based on the TN and COD concentrations of the influent and effluent.

[0029] The beneficial effects of this invention are:

[0030] 1. This invention utilizes a magnetic solid acid catalyst to catalytically decompose polysaccharides and lipids in microalgae, as well as lipids in residual sludge, to obtain monosaccharides and fatty acids that are easily utilized by microorganisms. Compared with common carbon sources such as sodium acetate or slow-release carbon sources prepared from biomass straw, the biomass carbon source prepared in this invention contains glucose and other sugars that provide rapidly usable carbon sources, while volatile fatty acids prolong carbon release time and promote bacterial proliferation. This composite carbon source, when used as an external carbon source for wastewater treatment, exhibits a better enhanced biological denitrification effect. Compared with biomass fermentation or enzymatic methods for preparing sugar carbon sources, the chemical catalytic method provided by this invention has a faster reaction rate and can simultaneously recover organic matter from sludge.

[0031] 2. This invention prepares a magnetic carrier to enhance catalyst recovery and reduce carbon source production costs. In this invention, the impregnated iron ions hydrolyze to generate ferric hydroxide, which is ultimately reduced to elemental iron under high-temperature reducing conditions. This elemental iron then reacts with water vapor at high temperature to generate magnetite (Fe3O4). This invention combines high efficiency, controllability, and sustainability, providing a new solution for carbon source replenishment in wastewater treatment plants and enhancing the value of biomass resource utilization and the stability of wastewater biological denitrification processes.

[0032] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0033] Figure 1 This is a flowchart of the method for preparing biomass carbon source in Example 1 of the present invention;

[0034] Figure 2 This is a scanning electron microscope (SEM) image of the surface of the magnetic solid acid catalyst prepared in Example 1 of this invention.

[0035] Figure 3 The XRD diffraction pattern of the magnetic solid acid catalyst prepared in Example 1 of this invention;

[0036] Figure 4 This is a graph showing the change in acidity value of the magnetic solid acid catalyst prepared in Example 1 of the present invention during solid acid recycling.

[0037] Figure 5 This is a schematic diagram illustrating the effect of adding a carbon source on biological denitrification of wastewater in Example 5 of the present invention;

[0038] Figure 6 This is a schematic diagram illustrating the effect of adding a carbon source on biological denitrification of wastewater in Example 6 of the present invention. Detailed Implementation

[0039] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0040] It should be noted that, unless otherwise specified, the experimental methods described in the following implementation plan are all conventional methods, and the reagents and materials described are all commercially available unless otherwise specified.

[0041] Example 1

[0042] like Figure 1 As shown, an embodiment of the present invention provides a method for preparing a biomass carbon source, comprising the following steps:

[0043] 1. Biomass pretreatment

[0044] Take 1000g of corn stalks, crush them to 100 mesh, and soak them in 12mol / L phosphoric acid for 10h, with a solid-liquid mass ratio of 1:5. Filter out, wash and dry, then soak them in 1.5mol / L NaOH solution for another 24h, wash three times with deionized water, and dry in an oven at 80℃ to constant weight to obtain 800g of biomass powder.

[0045] 2. Preparation of magnetic solid acid catalysts

[0046] (1) Fe(NO3), Al2(SO4)3 and ZrOCl2 were dissolved in deionized water in a molar ratio of 2:1:1 to obtain a mixed solution with concentrations of 1 mol / L, 0.5 mol / L and 0.5 mol / L of Fe(NO3), Al2(SO4)3 and ZrOCl2, respectively.

[0047] (2) Add biomass powder to the mixed solution obtained in step (1) at a solid-liquid mass ratio of 1g:4mL. Microwave-assisted impregnation (power 600W, frequency 2.45GHz, 30min), filter, wash the residue with deionized water 3 times and dry at 105℃ for 2h to obtain pretreated biomass powder.

[0048] (3) The pretreated biomass powder obtained in step (2) is heated to 300°C at a rate of 5°C / min under air-isolated conditions and pre-carbonized at 300°C for 1 hour. Then, the temperature is increased to 625°C and water vapor is continuously introduced. The carbonization process is continued at 625°C for 40 minutes. When the biomass carbonized powder cools down to 105°C, the water vapor is stopped and the powder is kept for 10 hours until it is dried.

[0049] (4) Take the dried biomass carbonized powder obtained in step (3) and add it to a PTFE-lined reactor with stirring. Add liquid SO3 at a mass ratio of SO3:biochar = 1:3. Slowly raise the temperature to 40°C and maintain it for 2 hours while stirring. Then raise the temperature to 50°C and maintain it for 2 hours.

[0050] (5) The sulfonated biochar obtained in step (4) was washed three times with deionized water and then dried under vacuum at 80°C for 10 hours to obtain a magnetic solid acid catalyst with paramagnetic properties.

[0051] Step 2 involves the simultaneous carbonization and sulfonation treatment of straw biomass, which constructs... Acid sites and Lweis acid complex acid sites, phosphoric acid-assisted modification to form medium-strong acid sites, enhance the catalyst's ability to break glycosidic bonds, Al2O3 nanoparticles and Zr 4+ The solid acid provides Lewis acid sites, promoting ester bond cleavage and thus enabling the simultaneous decomposition of polysaccharides and lipids by the solid acid. A microwave field accelerates ion diffusion, and the porous structure of the straw provides a high specific surface area support. The prepared magnetic solid acid catalyst exhibits paramagnetism, facilitating recovery through the addition of an external magnetic field. Figure 2 The image shows a scanning electron microscope (SEM) image of the surface of the prepared magnetic solid acid catalyst. Figure 3 The XRD diffraction pattern of the prepared magnetic solid acid catalyst is shown.

[0052] 3. Preparation of algae-based mixture

[0053] Chlorella was cultivated using domestic wastewater from a wastewater treatment plant until the algal density reached 7 × 10⁻⁶. 6 When the cell / mL ratio is 0.02%, add chitosan with a deacetylation degree ≥90% at a concentration of 0.02% of the Chlorella culture medium. After stirring to form flocs, collect the flocs and centrifuge them in two stages (3000×g centrifugation for 10 min + 5000×g centrifugation for 15 min) to obtain 2 kg of algal slurry with a water content of 89%.

[0054] 4. Biomass carbon source preparation

[0055] Add 4% (by weight) of a magnetic solid acid catalyst to the algae slurry, stir until homogeneous, adjust the temperature of the algae slurry to 60℃ and the pH to 3-4, and then subject it to ultrasonic treatment (40kHz, power density 2W / cm³). 2 The polysaccharides in the algal slurry were decomposed by catalytic reaction for 2.5 h to obtain the first mixture. The mixture was centrifuged at 3000×g for 10 min to obtain the first supernatant containing sugars and the first precipitate containing algal mud and catalyst.

[0056] 5. Take the remaining sludge from the thickening tank of the sewage treatment plant, mix it with the first precipitate at a mass ratio of 25:1 to obtain the second mixture, adjust the pH of the second mixture to 3-4, react it under microwave radiation (800W, frequency 2.45GHz) for 1.2h, stir it evenly to obtain the third mixture, centrifuge it at 5000×g for 15min to obtain the second supernatant and the second precipitate.

[0057] 6. Add four times the volume of n-hexane to the second supernatant, stir for 30 minutes, and let stand for 2 hours. After the solution separates into layers, collect the upper layer containing fatty acids in n-hexane. Remove the n-hexane by heating in a 70°C water bath and distilling. The concentration of residual n-hexane is 0.08% by gas chromatography, resulting in the fourth mixture, which is the concentrated fatty acid mixture.

[0058] 7. Mix the first supernatant and the fourth mixture at a volume ratio of 1:2.5, add 0.2% of Tween 80 by mass of the fourth mixture, stir evenly, and adjust the pH to 5.5 to obtain the fifth mixture, which is the biomass carbon source of the fast and slow carbon source synergistic system. The COD of the carbon source solution is 102 g / L.

[0059] 8. Add 10 times its weight of 0.1 mol / L citric acid to the second precipitate obtained in step 5, stir well, and then heat at 20 kHz with a power density of 0.5 W / cm³. 2 The mixture was ultrasonically treated for 5 minutes and then placed in a 0.5T magnetic field to separate the magnetic solid acid catalyst. The separated material was thoroughly washed with deionized water and then dried at 80°C to recover the magnetic solid acid catalyst with a recovery rate of 80%.

[0060] Using the above method, the separated magnetic solid acid catalyst is reused and then recovered. After each recovery, the acidity value of the magnetic solid acid catalyst is measured by titration as follows: Figure 4 As shown, after 5 cycles of use, the acidity retention rate (i.e., acidity after cycle / original acidity × 100%) is still greater than or equal to 85%.

[0061] Example 2

[0062] A method for preparing a magnetic solid acid catalyst includes the following steps:

[0063] (1) Fe(NO3), Al2(SO4)3 and ZrOCl2 were dissolved in deionized water in sequence to obtain a fourth mixture, wherein the concentrations of Fe(NO3), Al2(SO4)3 and ZrOCl2 were 1 mol / L, 0.5 mol / L and 0.5 mol / L, respectively;

[0064] (2) Crush the straw to 100 mesh, soak it in 12 mol / L phosphoric acid for 8 hours, then soak it in 1.5 mol / L NaOH solution for 24 hours, and finally wash it with water 3 times and dry it to obtain biomass powder.

[0065] (3) Add the biomass powder obtained in step (2) to the mixed solution obtained in step (1) at a solid-liquid mass ratio of 1g:5mL. Microwave-assisted impregnation (power 600W, frequency 2.45GHz) for 30min, filter, wash the residue with deionized water 3 times, and dry at 105℃ for 2h to obtain pretreated biomass powder.

[0066] (4) The pretreated biomass powder obtained in step (3) is heated to 300°C at a rate of 5°C / min under air-isolated conditions and pre-carbonized at 300°C for 1 hour. Then, the temperature is increased to 650°C and water vapor is continuously introduced. The carbonization process is continued at 650°C for 30 minutes. When the biomass carbonized powder cools down to 105°C, the water vapor is stopped and the powder is kept for 10 hours until it is dried.

[0067] (5) Take the dried biomass carbonized powder obtained in step (4) and add it to a PTFE-lined reactor with stirring. Add liquid SO3 at a mass ratio of SO3:biochar = 1:3. Slowly raise the temperature to 40°C and maintain it for 2 hours while stirring. Then raise the temperature to 50°C and maintain it for 2 hours.

[0068] (6) After washing the sulfonated biochar obtained in step (5) three times with deionized water, it was placed at 80°C and vacuum dried for 10 h to obtain a magnetic solid acid catalyst.

[0069] Example 3

[0070] A method for preparing a biomass carbon source includes the following steps:

[0071] (1) Chlorella was cultured using urban domestic sewage until the algal density reached 8×10⁻⁶. 6 When the cell / mL ratio is 90%, add chitosan with a deacetylation degree ≥90% at a dosage of 0.01% of the Chlorella culture medium mass. After stirring to form flocs, collect the flocs and centrifuge at 3000×g for 10 min + 5000×g for 15 min to obtain algal slurry with a water content of 90%.

[0072] (2) Add 2% by mass of magnetic catalyst (prepared by the same method as in Example 2) to the algal slurry, at 60°C, pH 3.0, 40 kHz and 2 W / cm². 2 After ultrasonic catalysis for 3 hours, centrifugation at 3000×g for 10 minutes yielded the first supernatant containing sugars and the first precipitate containing algal mud and catalyst.

[0073] (3) Take the remaining sludge from the thickening tank of the sewage treatment plant, mix it with the first precipitate at a mass ratio of 30:1 to obtain the second mixture, adjust the pH to 3-4, react under microwave radiation for 1.5h, stir evenly to obtain the third mixture, centrifuge at 6000×g for 20min to obtain the second supernatant and the second precipitate.

[0074] (4) Add three times the volume of n-hexane to the second supernatant, stir for 30 min and let stand for 2 h. After the solution separates into layers, collect the upper layer containing fatty acid n-hexane solution, heat and distill at 70℃ to remove n-hexane, and use gas chromatography to detect that the mass concentration of residual n-hexane is 0.09%, thus obtaining the fourth mixture, which is the concentrated fatty acid mixture.

[0075] (5) Mix the first supernatant obtained in step (2) and the fourth mixture obtained in step (4) at a volume ratio of 1:3, add 0.2% of Tween 80 by mass of the fourth mixture, stir evenly, adjust the pH to 5-6, and obtain the fifth mixture, which is the biomass carbon source of the fast and slow carbon source synergistic system. The COD of the carbon source solution is 95g / L.

[0076] (6) Add 0.1 mol / L citric acid (10 times its weight) to the second precipitate obtained in step (3), stir well, and then heat at 20 kHz with a power density of 0.3 W / cm³. 2 The mixture was ultrasonically treated for 5 minutes and then placed in a magnetic field of 0.8T to separate the magnetic solid acid catalyst. The separated material was thoroughly washed with deionized water and then dried at 80°C to recover the magnetic solid acid catalyst with a recovery rate of 75%.

[0077] Example 4

[0078] A method for preparing a biomass carbon source includes the following steps:

[0079] (1) Chlorella was cultured using urban domestic sewage until the algal density reached 8×10⁻⁶. 6 When the concentration of cells / mL was 90%, chitosan with a degree of deacetylation of 90% was added at a concentration of 0.015% of the Chlorella culture medium mass. After stirring to form flocs, the flocs were collected and centrifuged at 3000×g for 10 min and then at 5000×g for 15 min to obtain algal slurry with a water content of 88%.

[0080] (2) Add 3% by mass of magnetic catalyst (prepared by the same method as in Example 2) to the algal slurry, at 60°C, pH 3.0, 40 kHz and 2 W / cm². 2 After ultrasonic catalysis for 3 hours, centrifugation at 3000×g for 10 minutes yielded the first supernatant containing sugars and the first precipitate containing algal mud and catalyst.

[0081] (3) Take the remaining sludge from the thickening tank of the sewage treatment plant, mix it with the first precipitate at a mass ratio of 27:1 to obtain the second mixture, adjust the pH to 3-4, react under microwave radiation for 1.2h, stir evenly to obtain the third mixture, centrifuge at 6000×g for 20min to obtain the second supernatant and the second precipitate.

[0082] (4) Add four times the volume of n-hexane to the second supernatant, stir for 30 min and let stand for 2 h. After the solution separates into layers, collect the upper layer containing fatty acid n-hexane solution, heat and distill at 70℃ to remove n-hexane, and use gas chromatography to detect the residual n-hexane mass concentration as 0.06%, thus obtaining the fourth mixture, which is the concentrated fatty acid mixture.

[0083] (5) Mix the first supernatant obtained in step (2) and the fourth mixture obtained in step (4) at a volume ratio of 1:3, add 0.2% of Tween 80 by mass of the fourth mixture, stir evenly, adjust the pH to 5-6, and obtain the fifth mixture, which is the biomass carbon source of the fast and slow carbon source synergistic system. The COD of the carbon source solution is 98 g / L.

[0084] (6) Add 0.1 mol / L citric acid (10 times its weight) to the second precipitate obtained in step (3), stir well, and then heat at 30 kHz with a power density of 0.5 W / cm³. 2 The mixture was ultrasonically treated for 5 minutes and then placed in a 0.6T magnetic field to separate the magnetic solid acid catalyst. The separated material was thoroughly washed with deionized water and then dried at 80°C to recover the magnetic solid acid catalyst with a recovery rate of 78%.

[0085] Example 5

[0086] This invention provides an application of biomass carbon source in wastewater treatment. The biomass carbon source used is prepared according to the method in Example 4, using A in the laboratory. 2 The / O wastewater reactor was used as the research object. The COD / TN ratio of the influent to the anoxic tank of the wastewater reactor was 2.5. The carbon source in the denitrification section was insufficient, and the TN removal rate was only 60%. The biomass carbon source obtained in Example 4 was added to optimize the operation.

[0087] 1. Carbon source addition scheme

[0088] Biomass carbon source is added to the inlet of the anoxic section of the wastewater treatment system using a metering pump to ensure that denitrifying bacteria are given priority in utilization.

[0089] 2. Operating parameters

[0090] By monitoring the TN concentration of influent and effluent online and dynamically adjusting the carbon source dosage to maintain the COD / TN ratio of the influent to the anoxic tank of the system at 4.5, the best denitrification effect can be achieved. In actual operation, the influent TN is about 30 mg / L and the raw water COD is about 75 mg / L. After calculation, a COD of 60 mg / L needs to be added, and the volume of biomass carbon source to be added is 0.612% of the wastewater volume.

[0091] Control of reaction conditions: Adjust the aeration valve to ensure DO < 0.5 mg / L in the anoxic zone; add NaHCO3 to maintain pH = 7.0 ± 0.2; control the water temperature to 25 ± 2℃ through the heat exchanger; and ensure uniform dispersion of carbon source through a low-speed flow promoter (50 rpm).

[0092] 3. Running effect

[0093] In this embodiment, a control example 1 was also provided. Except for replacing the added biomass carbon source with sodium acetate carbon source, the other steps and parameters in control example 1 were the same as in example 5.

[0094] Before adding the carbon source, the total nitrogen (TN) removal rate of the wastewater was around 60-65%. After adding the carbon source on the 5th day, the TN removal rate gradually increased, reaching 82.5% on the 7th day, and then stabilizing at around 82.8%. The denitrification rate increased from 0.05 mg NO3. - -N / (gVSS·h) increased to 0.12mg NO3 - -N / (gVSS·h), effluent TN concentration was consistently <5mg / L. Mixed carbon source consumption rate >90%, no residual fatty acids detected. The effects of Example 5 and Control Example 1 on biological nitrogen removal from wastewater are as follows: Figure 5 As shown, in Control Example 1, the TN removal rate also increased after the addition of sodium acetate carbon source, and finally stabilized at about 83.3%. By comparison, it can be seen that the biomass carbon source of the present invention is comparable to the traditional carbon source sodium acetate in improving the biological denitrification effect.

[0095] Example 6

[0096] This invention provides an application of biomass carbon source in wastewater treatment. The biomass carbon source used was prepared using the method in Example 4. A laboratory SBR wastewater reactor was used as the research object. The raw water influent TN = 40 mg / L, COD = 80 mg / L, and the influent COD / TN = 2.1. The carbon source in the denitrification stage was insufficient, and the TN removal rate was about 52%. The biomass carbon source obtained in Example 4 was added to optimize the operation.

[0097] 1. Carbon source addition scheme

[0098] Biomass carbon source is added to the anoxic treatment stage of the SBR reactor using a metering pump, and mechanical stirring is used to ensure that the added carbon source is mixed evenly with the wastewater.

[0099] 2. Operating parameters

[0100] By monitoring the TN concentration of the influent and effluent in the SBR reactor online, and adjusting the carbon source dosage to maintain the wastewater COD / TN ratio of 5, the optimal denitrification effect can be achieved. In actual operation, the influent TN is around 40 mg / L, and the raw water COD is around 80 mg / L. After calculation, a COD of 120 mg / L needs to be added, and the volume of biomass carbon source to be added is 0.122% of the wastewater volume.

[0101] Control of reaction conditions: Mechanical stirring was used to keep the DO in the wastewater in the SBR < 0.5 mg / L; NaHCO3 was added to maintain pH = 7.0 ± 0.2; water temperature was controlled at 25 ± 2℃ using a heat exchanger; and carbon source was uniformly dispersed by mechanical stirring (30 rpm).

[0102] 3. Running effect

[0103] In this embodiment, a control example 2 was also provided. Except for replacing the added biomass carbon source with glucose carbon source, the other steps and parameters in control example 2 were the same as in example 6.

[0104] Before adding the carbon source, the total nitrogen (TN) removal rate of the wastewater was approximately 52-60%. After adding the carbon source on day 5, the TN removal rate gradually increased, reaching 80% on day 8, and subsequently stabilizing at around 80.2%, with the effluent TN concentration consistently <5 mg / L. The mixed carbon source consumption rate was >90%, and no residual fatty acids were detected. The effects of Example 6 and Control Example 2 on biological denitrification of wastewater are as follows: Figure 6 As shown, in Control Example 2, the TN removal rate also increased after the addition of glucose as a carbon source, and finally stabilized at around 79.5%. The comparison shows that the biomass carbon source effect of the present invention is comparable to that of the traditional carbon source glucose.

[0105] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and embodiments shown and described herein.

Claims

1. A method for preparing a biomass carbon source, characterized in that, Includes the following steps: S1. Using urban domestic sewage to cultivate Chlorella, at the specified algal density... Add 0.01-0.02% (by weight) of chitosan with a degree of deacetylation ≥90% to the wastewater, and after flocculation and centrifugation, obtain algal slurry with a water content ≤90%. S2. Add 2-4% of the mass of the magnetic solid acid catalyst to the algal slurry obtained in S1. After ultrasonic catalysis for 2-3 hours, the first mixture is obtained. Centrifuge to separate the first supernatant containing sugars and the first precipitate containing algal mud and catalyst. The preparation method of the magnetic solid acid catalyst includes the following steps: (1) Preparation containing , and The solution in which , and The concentrations were 1 mol / L, 0.5 mol / L, and 0.5 mol / L, respectively. (2) Add the straw powder treated with phosphoric acid and alkali in sequence to the solution obtained in step (1) at a solid-liquid ratio of 1g:4-5mL, microwave-assisted soaking for 30min, washing and drying to obtain pretreated biomass powder; (3) Place the pretreated biomass powder obtained in step (2) into Under protection, the temperature is raised to 300℃ at a rate of 5℃ / min for pre-carbonization for 1 hour, then the temperature is raised to 600-650℃ and steam is introduced for carbonization for 30-45 minutes. After steam is introduced, the carbonization is stopped and the biochar is dried at 105℃. (4) Combine the biochar obtained in step (3) with liquid The mixture was mixed at a mass ratio of 3:1, reacted at 40℃ for 2 hours, and then reacted at 50℃ for 2 hours to obtain sulfonated biochar. (5) The sulfonated biochar obtained in step (4) is washed three times with deionized water and then dried under vacuum at 80°C to obtain the magnetic solid acid catalyst. S3. Take the residual sludge from the thickening tank of the sewage treatment plant and mix it with the first precipitate obtained in S2 at a mass ratio of 20-30:1 to obtain a second mixture. Adjust the pH to 3-4 and react under microwave for 1-1.5 hours. Stir until uniform to obtain a third mixture. After centrifugation, obtain the second supernatant and the second precipitate. S4. Add 3-5 times the volume of n-hexane solution to the second supernatant obtained in S3 for extraction, collect the upper n-hexane solution containing fatty acids, and distill to remove the solvent until the residual n-hexane mass concentration is ≤0.1% to obtain the fourth mixture. S5. Mix the first supernatant obtained in S2 with the fourth mixture obtained in S4 at a volume ratio of 1:2-3, add 0.2% of Tween 80 by mass of the fourth mixture for emulsification, and adjust the pH to 5-6 to obtain the biomass carbon source.

2. The method for preparing biomass carbon source as described in claim 1, characterized in that, During centrifugal separation in S1, first... After centrifuging for 10 minutes under the specified conditions, then... Centrifuge for 15 minutes under the specified conditions.

3. The method for preparing biomass carbon source as described in claim 1, characterized in that, During centrifugation in S2, Centrifuge for 10 minutes under the specified conditions.

4. The preparation method according to claim 1, characterized in that, During ultrasonic catalysis in S2, the conditions were: 60℃, pH 3-4, ultrasonic frequency 40 kHz, and ultrasonic power [missing information]. It is carried out under the following conditions.

5. The method for preparing biomass carbon source as described in claim 1, characterized in that, During centrifugation in S3, Centrifuge for 15-20 minutes under the specified conditions.

6. The method for preparing biomass carbon source as described in claim 1, characterized in that, Step (2) involves sequentially treating the straw powder with phosphoric acid and alkali, including the following steps: Crush the straw to 100 mesh, soak it in 10-15 mol / L phosphoric acid for 8-12 hours, then soak it in 1-2 mol / L NaOH solution for 24 hours, and finally wash it three times with deionized water and dry it.

7. The method for preparing biomass carbon source as described in claim 1, characterized in that, It also includes the following steps: S6. Catalyst recovery: Add 0.1 mol / L citric acid (10 times its mass) to the second precipitate obtained in S3, and then perform an ultrasonic treatment at a frequency of 20-30 kHz and an ultrasonic power of [missing value]. The catalyst is ultrasonically treated for 5 minutes under certain conditions, and then placed in a 0.5-0.8T magnetic field to separate it. Finally, it is washed with water and dried to recover the magnetic solid acid catalyst.

8. The biomass carbon source prepared by the method according to any one of claims 1-7, characterized in that, The carbon source COD concentration is ≥90g / L.

9. The application of the biomass carbon source according to claim 8 in wastewater treatment, characterized in that, Includes the following steps: Biomass carbon source is added to the influent of the anoxic section of the wastewater treatment system. After addition, the dissolved oxygen in the anoxic section should be maintained at <0.5mg / L, pH value at 6.5-7.5, and temperature at 20-30℃. The dosage should be adjusted based on the TN and COD concentrations of the influent and effluent.

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