Yellow liquor anaerobic digestion treatment method based on nitrate and manganese-loaded charcoal

Abstract

The invention provides a yellow liquid anaerobic digestion treatment method based on nitrate and manganese-loaded biochar, which comprises a treatment step of adding nitrate and manganese-loaded biochar into cellar bottom yellow liquid to be treated in an anaerobic digestion treatment link. According to the method, the manganese-loaded biochar is in contact with nitrate radicals, the nitrate radicals are converted into nitrogen free radicals with high activity, refractory organics in the yellow liquor are oxidized, and hydrolytic decomposition of the refractory organics in the yellow liquor is promoted. The biochar can also strengthen interspecific electron transfer between bacteria and archaea. Under the combined action of nitrate and manganese-loaded charcoal, not only is the activity level of anaerobic microorganisms driven to be improved, but also the chemical oxidation effect is introduced. Under the combined action of the two, the anaerobic digestion efficiency of the yellow liquid is comprehensively improved.

Description

Technical Field

[0001] The invention belongs to the technical field of wine wastewater treatment and relates to an anaerobic digestion treatment method for yellow liquor based on nitrate and manganese loaded biochar. Background Art

[0002] During the brewing process, baijiu (white liquor) is often brewed with starch-rich raw materials such as sorghum and glutinous rice. After steaming, these raw materials are then fermented with koji (dice yeast). During fermentation, the starch saccharifies and ferments to produce ethanol. Simultaneously, tannins, pigments, soluble starch, yeast extract, and reducing sugars in the raw materials dissolve in water and seep to the bottom of the pit, forming a yellowish-brown, turbid, and viscous liquid with a distinctive odor ("pit bottom yellow liquor"). Furthermore, in some sauce-flavored baijiu (sauce-flavored) liquors, the first and last liquors from the distillation process (the pot bottom liquid) are mixed with the raw materials to increase fermentation yield. This mixed first and last liquors also enter the pit and are partially converted into pit bottom yellow liquor. Every ton of Daqu baijiu produced generates 12-20 tons of brewing wastewater, of which 300-400 kg is pit bottom yellow liquor. Compared to workshop flushing wastewater generated during the baijiu brewing process, pit bottom yellow liquor has higher concentrations of organic matter, ammonia nitrogen, and TP. Under different brewing processes, the COD concentration of yellow liquor at the bottom of the pit ranges from approximately 80,000 to 300,000 mg / L, and the ammonia nitrogen concentration is approximately 2,000 to 4,000 mg / L. Anaerobic digestion is the primary method for treating yellow liquor. Under the action of microorganisms, it converts organic matter in the wastewater into methane and CO2, reducing the COD of the wastewater. In addition to alcohols, yellow liquor also contains a large amount of high-molecular-weight polysaccharides, especially the products of yeast growth and death. These have relatively poor biodegradability and are resistant to anaerobic microbial metabolism, resulting in low anaerobic digestion efficiency.

[0003] During anaerobic treatment, the anaerobic conversion of organic matter is divided into hydrolysis and acidification and methanogenesis stages. The dominant microbial species in these two stages differ: fermentative bacteria dominate the hydrolysis and acidification phase, hydrolyzing organic matter into acetic acid and H2, while methanogenic archaea use the metabolic end products of fermentative bacteria as substrates, converting them into methane for release. Energy acquisition for anaerobic microbial metabolism primarily comes from horizontal phosphorylation, with energy acquisition levels generally maintained at 5 mol ATP / mol glucose. This limits energy acquisition for anaerobic microorganisms and slows their growth during the anaerobic biological treatment process, limiting their ability to secrete more hydrolytic enzymes for the hydrolysis of recalcitrant organic matter. This results in a slow decomposition rate of recalcitrant organic matter in the yellow liquor and a high COD concentration in the final effluent. Summary of the Invention

[0004] The purpose of the present invention is to address the defects of the existing technology and provide a yellow liquor anaerobic digestion treatment method based on nitrate and manganese loaded biochar to improve the anaerobic digestion efficiency of yellow liquor.

[0005] The present invention provides a yellow liquor anaerobic digestion treatment method based on nitrate and manganese-loaded biochar. In the anaerobic digestion treatment link, the method comprises the steps of adding nitrate and manganese-loaded biochar to the yellow liquor at the bottom of the pit to be treated.

[0006] Preferably, the nitrate ion is derived from potassium nitrate and is added with the influent at a ratio of 5-20 mg / L.

[0007] Preferably, the manganese-loaded biochar is prepared by impregnating walnut shells, coconut shells or sawdust with manganese nitrate and then calcining at 400-600° C. under oxygen-free conditions.

[0008] Preferably, the manganese-loaded biochar is prepared by the following method: a) Crush walnut shells, coconut shells or sawdust into 2-5 mm particles; b) impregnating with a manganese nitrate solution at a mass ratio of 1:1 for 24-48 hours; c) heating the mixture to 400-600°C for 2-4 hours at a rate of 5°C / min under nitrogen protection. The pyrolysis process adopts a two-stage temperature control: the first stage is 200-300°C and maintained for 1 hour, and the second stage is raised to 400-600°C and maintained for 1-3 hours.

[0009] Preferably, the dosage of the manganese-loaded biochar is 200-1000 mg / L, and the particle size is controlled at 30-50 μm.

[0010] Preferably, the dosage of the manganese-loaded biochar is 360-920 mg / L.

[0011] Preferably, when adding the potassium nitrate, it is first completely dissolved in water and then mixed into the yellow liquor at the bottom of the pit.

[0012] Preferably, the temperature of the anaerobic digestion process is 30° C. to 40° C., and the pH value is adjusted to between 6.5 and 7.5.

[0013] Preferably, during the anaerobic digestion process, the COD removal rate η is detected every 24 hours. COD , ammonia nitrogen concentration change rate ΔN and methane production rate R CH4 t , and adjust the addition amount of potassium nitrate and manganese loaded biochar according to the test results.

[0014] Preferably, the dosage is adjusted according to the following formula, wherein the potassium nitrate adjustment amount is: ΔK=[(η target -ηCOD ) / η target ]×K0×α; Where: η target is the target COD removal rate; η COD is the real-time COD removal rate; K0 is the initial dosage; α is the ammonia nitrogen concentration compensation factor: α = 0.5 + 0.1 × (ΔN / N0), N0 is the initial ammonia nitrogen concentration, α takes a positive value when ΔN > 0, and takes a negative value when ΔN < 0; the adjustment amount of manganese-loaded biochar is: ΔB=[(R CH4 t - R CH4 t-1 ) / R CH4 t-1 ]×B0×β; Where: R CH4 t is the methane yield in the current detection period; R CH4 t-1 is the methane yield in the previous detection cycle; B0 is the initial dosage; β is the attenuation coefficient: β = β0× e -k·t ×(1-η COD / η max ); Where: β0 is the initial attenuation coefficient (0.8-1.0); k is the time decay constant (0.02-0.05 h -1 ); t is the running time (h); η max is the maximum theoretical COD removal rate of the system.

[0015] Compared with the prior art, the present invention has the following beneficial effects: This method significantly improves the degradation efficiency of organic matter in liquor wastewater treatment: the synergistic effect of nitrate and manganese-loaded biochar optimizes microbial metabolic pathways and enhances the degradation efficiency of complex organic matter. The catalytic activity and high specific surface area of ​​manganese-loaded biochar provide an ideal metabolic environment for microorganisms, significantly improving the overall treatment efficiency of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of outlet water concentration in one embodiment of the present invention. DETAILED DESCRIPTION

[0017] In order to enable those skilled in the art to better understand the technical solution of the present invention, the preferred embodiments of the present invention are described below in conjunction with specific embodiments. However, it should be understood that the drawings are only for illustrative purposes and cannot be understood as limiting this patent; in order to better illustrate this embodiment, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted; the positional relationships described in the drawings are only for illustrative purposes and cannot be understood as limiting this patent.

[0018] In this description, yellow liquor, also known as yellow liquor, is wastewater generated during the liquor brewing process, as described in the background art. Current anaerobic biological treatment processes for yellow liquor suffer from limited energy availability, resulting in low proliferation rates and activity of anaerobic microorganisms. This, in turn, makes it difficult to convert refractory organic matter in the yellow liquor, leading to low anaerobic digestion efficiency.

[0019] The core of the present invention is to add nitrate and manganese-loaded biochar to the yellow liquor at the bottom of the pit to be treated during the anaerobic digestion treatment process.

[0020] Specifically, the nitrate ion can be derived from potassium nitrate and added into the influent at a ratio of 5-20 mg / L.

[0021] In some embodiments, the manganese-loaded biochar is prepared by impregnating walnut shells, coconut shells or sawdust with manganese nitrate and then calcining at 400-600° C. under oxygen-free conditions.

[0022] In some preferred embodiments, the manganese-loaded biochar is prepared by the following method: a) Crush walnut shells, coconut shells or sawdust into 2-5 mm particles; b) impregnating with a manganese nitrate solution at a mass ratio of 1:1 for 24-48 hours; c) heating the mixture to 400-600°C for 2-4 hours at a rate of 5°C / min under nitrogen protection. The pyrolysis process adopts a two-stage temperature control: the first stage is 200-300°C and maintained for 1 hour, and the second stage is raised to 400-600°C and maintained for 1-3 hours.

[0023] It should be noted that, depending on the composition of the yellow liquor, the dosage of the manganese-loaded biochar is 200-1000 mg / L, and the particle size is controlled at 30-50 μm; the preferred range of the dosage of the manganese-loaded biochar is 360-920 mg / L.

[0024] In some preferred embodiments, the potassium nitrate is first completely dissolved in water before being mixed into the yellow liquor at the bottom of the pit.

[0025] As basic process conditions, the temperature of the anaerobic digestion process is 30° C. to 40° C., and the pH value is adjusted to between 6.5 and 7.5.

[0026] In some preferred embodiments, during the anaerobic digestion process, the COD removal rate η is detected every 24 hours. COD , ammonia nitrogen concentration change rate ΔN and methane production rate R CH4 t , adjust the addition amount of potassium nitrate and manganese-loaded biochar according to the test results; specifically, adjust the addition amount according to the following formula, where the potassium nitrate adjustment amount is: ΔK=[(η target -η COD ) / η target ]×K0×α; Where: η target is the target COD removal rate; η COD is the real-time COD removal rate; K0 is the initial dosage; α is the ammonia nitrogen concentration compensation factor: α = 0.5 + 0.1 × (ΔN / N0), N0 is the initial ammonia nitrogen concentration, α takes a positive value when ΔN > 0, and takes a negative value when ΔN < 0; the adjustment amount of manganese-loaded biochar is: ΔB=[(R CH4 t - R CH4 t-1 ) / R CH4 t-1 ]×B0×β; Where: R CH4 t is the methane yield in the current detection period; R CH4 t-1 is the methane yield in the previous detection cycle; B0 is the initial dosage; β is the attenuation coefficient: β = β0× e -k·t ×(1-η COD / η max ); Where: β0 is the initial attenuation coefficient (0.8-1.0); k is the time decay constant (0.02-0.05 h -1 ); t is the running time (h); η max is the maximum theoretical COD removal rate of the system.

[0027] As a preferred embodiment of the present invention, this embodiment provides a method for anaerobic digestion of yellow liquor based on nitrate and manganese loaded biochar, with the high-concentration yellow liquor produced in the liquor brewing process as the treatment object, the initial yellow liquor COD is 247,000 mg / L, the ammonia nitrogen is 2181 mg / L, the initial sludge concentration of the anaerobic reactor is 30,000 mg / L, the anaerobic digestion temperature is 37 degrees, and the treatment load is controlled to 3.5 kg COD / m3 A CSTR reactor was used to start the anaerobic treatment system. After about 40 days of startup, the effluent COD concentration tended to be stable.

[0028] After stabilization, three groups of reactions were taken for comparison. Potassium nitrate, manganese-loaded biochar, and both were added to the three groups of reactors respectively, and the effluent COD and SS concentrations of the reactors after adding different exogenous substances were compared.

[0029] The dosage of potassium nitrate was 10 mg / L, and the dosage of manganese-loaded biochar was 500 mg / L. The manganese-loaded biochar was prepared by impregnating 2-5 mm coconut shell particles with a 1:1 manganese nitrate solution for 24-48 hours. The mixture was then heated to 200-300°C under nitrogen at a rate of 5°C / min and held for 1 hour. The mixture was then heated to 500°C at a rate of 5°C / min and held for 3 hours. The mixture was then pyrolyzed and sieved through a 50 μm filter.

[0030] After 60 days of operation, Figure 1 As shown, it was found that the SCOD of the effluent from the traditional UASB was 4200-4900 mg / L, while that from the effluent from the patented technology was 2873-3100 mg / L, which was significantly lower.

[0031] During the anaerobic digestion process, the COD removal rate η was tested every 24 hours. COD , ammonia nitrogen concentration change rate ΔN and methane production rate R CH4 t , adjust the addition amount of potassium nitrate and manganese-loaded biochar according to the test results; specifically, adjust the addition amount according to the following formula, where the potassium nitrate adjustment amount is: ΔK=[(η target -η COD ) / η target ]×K0×α; Where: η target is the target COD removal rate; η COD is the real-time COD removal rate; K0 is the initial dosage; α is the ammonia nitrogen concentration compensation factor: α = 0.5 + 0.1 × (ΔN / N0), N0 is the initial ammonia nitrogen concentration, α takes a positive value when ΔN > 0, and takes a negative value when ΔN < 0; the adjustment amount of manganese-loaded biochar is: ΔB=[(R CH4 t - R CH4 t-1 ) / R CH4 t-1 ]×B0×β; Where: R CH4 t is the methane yield in the current detection period; RCH4 t-1 is the methane yield in the previous detection cycle; B0 is the initial dosage; β is the attenuation coefficient: β = β0× e -k·t ×(1-η COD / η max ); Where: β0 is the initial attenuation coefficient (0.8-1.0); k is the time decay constant (0.02-0.05 h -1 ); t is the running time (h); η max is the maximum theoretical COD removal rate of the system.

[0032] During the implementation of the above embodiment, the COD removal rate η was detected at 41 days. COD , ammonia nitrogen concentration change rate ΔN and methane production rate R CH4 t The test results are shown in the following table. The amount of potassium nitrate and manganese-loaded biochar to be added is calculated and adjusted according to the above method:

[0033] Through real-time adjustments, the optimal concentration required for nitrate respiration is maintained, ATP production is stabilized at 28-33 mol / glucose, and the polysaccharide degradation rate is increased by 2.3 times. Overall, the treatment cost will be reduced by 38-45% and the catalyst service life will be extended by 2.3 times.

[0034] The present invention provides a process for promoting anaerobic digestion of yellow liquor using nitrate and manganese-loaded biochar. Nitrate addition drives anaerobic microorganisms to rely on nitrate respiration, shifting their ATP acquisition pathway from horizontal phosphorylation to the tricarboxylic acid cycle. This increases ATP acquisition (the tricarboxylic acid cycle ATP acquisition level is 31 mol ATP / mol glucose), thereby enhancing microbial proliferation and activity, and driving them to secrete more hydrolytic enzymes for substrate hydrolysis in the yellow liquor. Furthermore, the introduction of manganese-loaded biochar converts nitrate into highly active nitrogen free radicals through contact with nitrate, which oxidizes and promotes the hydrolysis and decomposition of refractory organic matter in the yellow liquor. Biochar also enhances interspecies electron transfer between bacteria and archaea. The combined effects of nitrate and manganese-loaded biochar not only drive increased anaerobic microbial activity but also introduce chemical oxidation. Together, these two actions comprehensively improve the efficiency of anaerobic digestion of yellow liquor.

[0035] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for anaerobic digestion of yellow liquor based on nitrate and manganese loaded biochar, characterized in that: The anaerobic digestion treatment process includes the steps of adding nitrate and manganese-loaded biochar to the yellow liquor at the bottom of the pit to be treated.

2. The method for anaerobic digestion of yellow liquor based on nitrate and manganese loaded biochar according to claim 1, characterized in that: The nitrate ion is derived from potassium nitrate and is added with the influent at a ratio of 5-20 mg / L.

3. The method for anaerobic digestion of yellow liquor based on nitrate and manganese loaded biochar according to claim 1, characterized in that: The manganese-loaded biochar is prepared by impregnating walnut shells, coconut shells or sawdust with manganese nitrate and then calcining the mixture at 400-600° C. under oxygen-free conditions.

4. The method for anaerobic digestion of yellow liquor based on nitrate and manganese loaded biochar according to claim 3, characterized in that: The manganese-loaded biochar is prepared by the following method: a) Crush walnut shells, coconut shells or sawdust into 2-5 mm particles; b) impregnating with a manganese nitrate solution at a mass ratio of 1:1 for 24-48 hours; c) heating the mixture to 400-600°C for 2-4 hours at a rate of 5°C / min under nitrogen protection. The pyrolysis process adopts a two-stage temperature control: the first stage is 200-300°C and maintained for 1 hour, and the second stage is raised to 400-600°C and maintained for 1-3 hours.

5. The method for anaerobic digestion of yellow liquor based on nitrate and manganese loaded biochar according to claim 1, characterized in that: The dosage of the manganese-loaded biochar is 200-1000 mg / L, and the particle size is controlled at 30-50 μm.

6. The method for anaerobic digestion of yellow liquor based on nitrate and manganese loaded biochar according to claim 5, characterized in that: The dosage of the manganese-loaded biochar is 360-920 mg / L.

7. The method for anaerobic digestion of yellow liquor based on nitrate and manganese loaded biochar according to claim 2, characterized in that: When adding the potassium nitrate, it is first completely dissolved in water and then mixed into the yellow liquid at the bottom of the pit.

8. The method for anaerobic digestion of yellow liquor based on nitrate and manganese loaded biochar according to claim 1, characterized in that: The temperature of the anaerobic digestion process is 30° C. to 40° C., and the pH value is adjusted to between 6.5 and 7.

5.

9. The method for anaerobic digestion of yellow liquor based on nitrate and manganese loaded biochar according to claim 1, characterized in that: During the anaerobic digestion process, the COD removal rate η was tested every 24 hours. COD , ammonia nitrogen concentration change rate ΔN and methane production rate R CH4 t , and adjust the addition amount of potassium nitrate and manganese loaded biochar according to the test results.

10. The method for anaerobic digestion of yellow liquor based on nitrate and manganese loaded biochar according to claim 9, characterized in that: Adjust the dosage according to the following formula, where the potassium nitrate adjustment amount is: ΔK=[(η target -or COD ) / or target ]×K0×α; Where: η target is the target COD removal rate; η COD is the real-time COD removal rate; K0 is the initial dosage; α is the ammonia nitrogen concentration compensation factor: α = 0.5 + 0.1 × (ΔN / N0), N0 is the initial ammonia nitrogen concentration, α takes a positive value when ΔN > 0, and takes a negative value when ΔN < 0; the adjustment amount of manganese-loaded biochar is: ΔB=[(R CH4 t - R CH4 t-1 ) / R CH4 t-1 ]×B0×β; Where: R CH4 t is the methane yield in the current detection period; R CH4 t-1 is the methane yield in the previous detection cycle; B0 is the initial dosage; β is the attenuation coefficient: β = β0× e -k·t ×(1-η COD / η max ); Where: β0 is the initial attenuation coefficient (0.8-1.0); k is the time decay constant (0.02-0.05 h -1 ); t is the running time (h); η max is the maximum theoretical COD removal rate of the system.

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