CN115010336A - Method for producing methane through anaerobic digestion of sludge based on slow-release choline - Google Patents
Method for producing methane through anaerobic digestion of sludge based on slow-release choline Download PDFInfo
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- CN115010336A CN115010336A CN202210744229.0A CN202210744229A CN115010336A CN 115010336 A CN115010336 A CN 115010336A CN 202210744229 A CN202210744229 A CN 202210744229A CN 115010336 A CN115010336 A CN 115010336A
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- choline
- sludge
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- release
- anaerobic digestion
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- OEYIOHPDSNJKLS-UHFFFAOYSA-N choline Chemical compound C[N+](C)(C)CCO OEYIOHPDSNJKLS-UHFFFAOYSA-N 0.000 title claims abstract description 108
- 229960001231 choline Drugs 0.000 title claims abstract description 108
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 title claims abstract description 90
- 239000010802 sludge Substances 0.000 title claims abstract description 87
- 230000029087 digestion Effects 0.000 title claims abstract description 62
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 27
- 238000000034 method Methods 0.000 claims abstract description 41
- 229920001661 Chitosan Polymers 0.000 claims description 55
- 239000000203 mixture Substances 0.000 claims description 37
- 238000011282 treatment Methods 0.000 claims description 24
- 238000000855 fermentation Methods 0.000 claims description 23
- HFJRKMMYBMWEAD-UHFFFAOYSA-N dodecanal Chemical compound CCCCCCCCCCCC=O HFJRKMMYBMWEAD-UHFFFAOYSA-N 0.000 claims description 20
- 238000006243 chemical reaction Methods 0.000 claims description 19
- 238000003756 stirring Methods 0.000 claims description 17
- 239000000463 material Substances 0.000 claims description 14
- 239000010865 sewage Substances 0.000 claims description 14
- 238000011081 inoculation Methods 0.000 claims description 11
- 238000002360 preparation method Methods 0.000 claims description 11
- 239000002244 precipitate Substances 0.000 claims description 10
- 229910000033 sodium borohydride Inorganic materials 0.000 claims description 10
- 239000012279 sodium borohydride Substances 0.000 claims description 10
- 238000013268 sustained release Methods 0.000 claims description 10
- 239000012730 sustained-release form Substances 0.000 claims description 10
- 239000002262 Schiff base Substances 0.000 claims description 9
- 150000004753 Schiff bases Chemical class 0.000 claims description 9
- 238000001035 drying Methods 0.000 claims description 6
- 230000004151 fermentation Effects 0.000 claims description 3
- 238000002156 mixing Methods 0.000 claims description 3
- 239000003431 cross linking reagent Substances 0.000 claims description 2
- 238000007710 freezing Methods 0.000 claims description 2
- 230000008014 freezing Effects 0.000 claims description 2
- 230000001376 precipitating effect Effects 0.000 claims description 2
- 244000005700 microbiome Species 0.000 abstract description 10
- 230000008569 process Effects 0.000 abstract description 10
- 230000007062 hydrolysis Effects 0.000 abstract description 7
- 238000006460 hydrolysis reaction Methods 0.000 abstract description 7
- 230000020477 pH reduction Effects 0.000 abstract description 7
- 230000027756 respiratory electron transport chain Effects 0.000 abstract description 5
- 230000007613 environmental effect Effects 0.000 abstract description 2
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 description 51
- 239000000243 solution Substances 0.000 description 24
- 235000019832 sodium triphosphate Nutrition 0.000 description 16
- 239000000843 powder Substances 0.000 description 12
- 239000007787 solid Substances 0.000 description 9
- 239000007864 aqueous solution Substances 0.000 description 8
- 239000003094 microcapsule Substances 0.000 description 8
- UNXRWKVEANCORM-UHFFFAOYSA-I triphosphate(5-) Chemical compound [O-]P([O-])(=O)OP([O-])(=O)OP([O-])([O-])=O UNXRWKVEANCORM-UHFFFAOYSA-I 0.000 description 8
- 238000005406 washing Methods 0.000 description 8
- 239000006228 supernatant Substances 0.000 description 7
- 230000000694 effects Effects 0.000 description 6
- 230000002829 reductive effect Effects 0.000 description 6
- 238000011160 research Methods 0.000 description 5
- 238000005303 weighing Methods 0.000 description 5
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 4
- 150000001299 aldehydes Chemical class 0.000 description 4
- 238000001914 filtration Methods 0.000 description 4
- 238000004108 freeze drying Methods 0.000 description 4
- 238000000227 grinding Methods 0.000 description 4
- 239000002105 nanoparticle Substances 0.000 description 4
- 239000006259 organic additive Substances 0.000 description 4
- 239000002904 solvent Substances 0.000 description 4
- 239000000725 suspension Substances 0.000 description 4
- 229910021642 ultra pure water Inorganic materials 0.000 description 4
- 239000012498 ultrapure water Substances 0.000 description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 3
- 238000004090 dissolution Methods 0.000 description 3
- 230000002708 enhancing effect Effects 0.000 description 3
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 2
- 229930013930 alkaloid Natural products 0.000 description 2
- 150000003797 alkaloid derivatives Chemical class 0.000 description 2
- 238000006065 biodegradation reaction Methods 0.000 description 2
- 230000015556 catabolic process Effects 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
- 238000006731 degradation reaction Methods 0.000 description 2
- 230000000593 degrading effect Effects 0.000 description 2
- 235000014113 dietary fatty acids Nutrition 0.000 description 2
- 238000003912 environmental pollution Methods 0.000 description 2
- 229930195729 fatty acid Natural products 0.000 description 2
- 239000000194 fatty acid Substances 0.000 description 2
- 150000004665 fatty acids Chemical class 0.000 description 2
- 230000005764 inhibitory process Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 150000007524 organic acids Chemical class 0.000 description 2
- 241000894006 Bacteria Species 0.000 description 1
- 239000002028 Biomass Substances 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 238000009825 accumulation Methods 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 239000002585 base Substances 0.000 description 1
- -1 biochar Chemical compound 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 150000001720 carbohydrates Chemical class 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 230000000536 complexating effect Effects 0.000 description 1
- 239000002361 compost Substances 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000000589 high-performance liquid chromatography-mass spectrometry Methods 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 150000002632 lipids Chemical class 0.000 description 1
- 230000002503 metabolic effect Effects 0.000 description 1
- 230000004060 metabolic process Effects 0.000 description 1
- 230000000813 microbial effect Effects 0.000 description 1
- 235000005985 organic acids Nutrition 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 102000004169 proteins and genes Human genes 0.000 description 1
- 108090000623 proteins and genes Proteins 0.000 description 1
- 238000000197 pyrolysis Methods 0.000 description 1
- 238000009790 rate-determining step (RDS) Methods 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 238000005070 sampling Methods 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F11/00—Treatment of sludge; Devices therefor
- C02F11/02—Biological treatment
- C02F11/04—Anaerobic treatment; Production of methane by such processes
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E50/00—Technologies for the production of fuel of non-fossil origin
- Y02E50/30—Fuel from waste, e.g. synthetic alcohol or diesel
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W10/00—Technologies for wastewater treatment
- Y02W10/20—Sludge processing
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Life Sciences & Earth Sciences (AREA)
- General Chemical & Material Sciences (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Molecular Biology (AREA)
- Hydrology & Water Resources (AREA)
- Environmental & Geological Engineering (AREA)
- Water Supply & Treatment (AREA)
- Organic Chemistry (AREA)
- Treatment Of Sludge (AREA)
Abstract
The invention discloses a method for producing methane by anaerobic digestion of sludge based on slow-release choline, and relates to the technical field of environmental engineering. The invention improves the anaerobic digestion hydrolysis acidification performance of the sludge by preparing the slow-release choline, strengthens the mutual operation relationship of functional microorganisms in a sludge anaerobic digestion system, further improves the electron transfer capacity among functional microorganism flora in the anaerobic digestion process, and improves the yield of methane accumulated in the anaerobic digestion of the sludge added with the slow-release choline by 20-30 percent compared with the yield of methane accumulated in the anaerobic digestion of the sludge treated by common choline.
Description
Technical Field
The invention relates to the technical field of environmental engineering, in particular to a method for producing methane by anaerobic digestion of sludge based on slow-release choline.
Background
Along with the rapid development of economy in China, the sewage treatment scale of urban sewage plants is gradually enlarged, the sludge is used as a byproduct of a sewage biological treatment process, the yield is increased rapidly, and the treatment pressure is huge. If the sludge is not properly treated, it is prone to secondary environmental pollution risks. On the other hand, the sludge is rich in organic matters such as saccharides, proteins and lipids, has great potential for realizing biomass energy recovery by producing methane through anaerobic digestion, and is also an important way for reducing carbon emission.
However, hydrolysis in the anaerobic digestion process of the sludge is the rate-limiting step, and the conversion of macromolecular organic matters in the sludge into small molecular organic matters is seriously hindered, and subsequent acidification, hydrogen production, acetic acid production and methane production are carried out. At present, technologies such as acid-base pretreatment, electrochemical pretreatment, pyrolysis pretreatment, ultrasonic pretreatment, Fenton reaction and the like are mostly adopted for research, so that the hydrolysis and acidification processes of sludge are promoted, and the methane production performance is improved. On the other hand, the electron transfer capacity among system microbial species is weak in the anaerobic digestion process of the sludge, so that the mutual operation relationship among functional microbial floras is insufficient, and the methane production performance is poor. Therefore, researches have been made to improve the electron transfer capacity of the anaerobic digestion system and enhance the methanogenesis performance by adding conductive materials, such as activated carbon, biochar, iron oxide, and the like. Although the above techniques can obtain better experimental results, the problems of higher treatment cost, secondary pollution risk, complex operation, influence on subsequent compost incineration disposal and the like exist, and the method has a great gap from practical application and popularization.
In recent years, researches on promoting the anaerobic digestion and methane production process of sludge by adding an organic additive have been carried out, but in the researches, the organic additive can be rapidly degraded by microorganisms in the early stage of anaerobic digestion of sludge, so that the utilization rate of the organic additive is low, and the effect of the organic additive cannot be fully exerted.
Disclosure of Invention
The invention aims to provide a method for producing methane by anaerobic digestion of sludge based on slow-release choline, which solves the problems in the prior art, enhances the performance of producing methane by anaerobic digestion of sludge, and provides a new technical choice for the method for enhancing the production of methane by anaerobic digestion of excess sludge in municipal sewage treatment plants.
In order to achieve the purpose, the invention provides the following scheme:
the invention provides an application of slow-release choline in methane production by anaerobic digestion of sludge, wherein the slow-release choline is prepared by taking N-alkylated chitosan as a slow-release material and adopting a Schiff base method.
The invention also provides a method for producing methane by anaerobic digestion of sludge based on the slow-release choline, which comprises the following steps:
(1) precipitating and concentrating the excess sludge of the urban sewage plant to obtain sludge to be treated;
(2) mixing the inoculation sludge with the sludge to be treated obtained in the step (1) to obtain an anaerobic fermentation mixture;
(3) and (3) adding slow-release choline into the anaerobic fermentation mixture obtained by the treatment in the step (2), stirring, adjusting the pH value to 6.5-7.5, and then carrying out anaerobic fermentation methane-producing reaction.
Furthermore, the slow-release choline is prepared by taking N-alkylated chitosan as a slow-release material and adopting a Schiff base method.
Furthermore, the slow release period of the slow release type choline is 3-6d, and the release rate of the choline is 75-85%.
Further, the preparation of the slow-release choline comprises the following steps:
reacting chitosan with dodecanal and sodium borohydride to prepare N-alkylated chitosan; and (2) reacting the N-alkylated chitosan with choline in the presence of a cross-linking agent, and after the reaction is finished, freezing and drying the obtained precipitate to obtain the slow-release choline.
Further, the concentration of the slow-release choline in the anaerobic fermentation mixture is 0.2-1.0 g/L.
Further, the mass concentration of the sludge to be treated in the step (1) is 2-4%.
Further, in the step (2), the inoculation mud accounts for 5-15% of the anaerobic fermentation mixture by mass.
Further, the inoculated sludge in the step (2) is digested sludge of an anaerobic digestion tank of a sewage treatment plant, and the mass concentration is 2-3%.
Further, the temperature of the reaction system in the anaerobic fermentation process in the step (3) is 25-35 ℃.
In the anaerobic digestion and methane production process of sludge, a large amount of volatile fatty acid is generated in a short period of time due to the action of various hydrolysis/acidification bacteria in the early stage, so that the pH of a system is rapidly reduced, the metabolic activity of the subsequent methane production is influenced (the proper pH for the metabolism of the methanogen is generally 6.5-7.5), and the accumulation of the volatile fatty acid is caused. On the other hand, a large number of macromolecular organic matters which are difficult to degrade by microorganisms exist in the sludge, and are difficult to hydrolyze/acidify, so that the methane yield of anaerobic digestion of the sludge is influenced. Choline in the alkaloid is proved to improve the methane production performance of anaerobic digestion of sludge by the ways of removing acid inhibition effect through the complexing effect with small molecular organic acid, reducing and degrading difficultly-degraded macromolecular organic matters, improving the electron transfer capacity of an anaerobic system and the like. However, choline is easily degraded by microorganisms in the anaerobic digestion process of sludge, and research results show that choline can be completely degraded within 2-3 days, and the utilization rate of choline is greatly reduced. According to the invention, N-alkylated chitosan is used as a slow-release material to prepare the slow-release choline by adopting a Schiff base method, and the slow release of the choline effectively prevents anaerobic microorganisms from quickly degrading the choline, so that the utilization rate of the choline is fully improved, the performance of methane production by anaerobic digestion of sludge is improved, the addition of the choline can be reduced, and the system operation cost is reduced.
The invention provides a method for enhancing methane production through anaerobic digestion of sludge based on slow-release choline, which is characterized in that the slow-release choline is prepared by taking N-alkylated chitosan as a slow-release material and adopting a Schiff base method, so that the slow-release choline is slowly released in a sludge anaerobic digestion system, the choline is prevented from being rapidly degraded by anaerobic microorganisms, the effect of removing the inhibition of small molecular organic acids caused in the early stage of anaerobic digestion by choline is fully exerted, the reductive degradation effect on organic matters difficult to degrade in sludge is enhanced, the process of hydrolysis and acidification of sludge anaerobic digestion is promoted, and the methane production performance through sludge anaerobic digestion is effectively improved. The invention improves the anaerobic digestion hydrolysis acidification performance of the sludge by preparing the slow-release choline, strengthens the mutual operation relationship of functional microorganisms in a sludge anaerobic digestion system, further improves the electron transfer capacity among functional microorganism flora in the anaerobic digestion process, and improves the yield of methane accumulated in the anaerobic digestion of the sludge added with the slow-release choline by 20-30 percent compared with the yield of methane accumulated in the anaerobic digestion of the sludge treated by common choline.
The invention discloses the following technical effects:
1. according to the invention, the choline is added in a slow-release manner, so that the hydrolysis acidification rate of the sludge can be more effectively improved, the degradation and conversion of organic matters are promoted, the anaerobic digestion period of the sludge is shortened, the actual addition amount of the choline is reduced, and finally, the yield of methane accumulated by anaerobic digestion of the sludge after the slow-release choline is added can be improved by 20-30% compared with that after the choline is treated.
2. The sustained-release agent preparation material and the choline are environment-friendly materials, have biodegradability, do not cause the risk of secondary environmental pollution, and do not cause adverse effects on the subsequent treatment and disposal of the sludge.
3. The method is simple to operate, can effectively reduce the using amount of choline, reduce the system operation cost, improve the methane yield and provide technical support for the construction and the transformation of anaerobic digestion facilities of sludge.
4. The method of the invention utilizes the sustained-release agent, solves the problem of fast biodegradation of choline in the early stage of anaerobic fermentation of sludge, effectively improves the utilization rate of choline, further enhances the performance of methane production by anaerobic digestion of sludge, and provides a new technical choice for the method for enhancing the methane production by anaerobic digestion of excess sludge in municipal sewage treatment plants.
Detailed Description
Reference will now be made in detail to various exemplary embodiments of the invention, the detailed description should not be construed as limiting the invention but as a more detailed description of certain aspects, features and embodiments of the invention.
It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. In addition, for numerical ranges in the present disclosure, it is understood that each intervening value, to the upper and lower limit of that range, is also specifically disclosed. Every smaller range between any stated value or intervening value in a stated range and any other stated or intervening value in a stated range is encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference herein for the purpose of disclosing and describing the methods and/or materials associated with the documents. In case of conflict with any incorporated document, the present specification will control.
It will be apparent to those skilled in the art that various modifications and variations can be made in the specific embodiments of the present disclosure without departing from the scope or spirit of the disclosure. Other embodiments will be apparent to those skilled in the art from consideration of the specification. The description and examples are intended to be illustrative only.
As used herein, the terms "comprising," "including," "having," "containing," and the like are open-ended terms that mean including, but not limited to.
The invention provides a method for strengthening methane production by anaerobic digestion of sludge based on slow-release choline, which effectively improves the utilization rate of the slow-release choline prepared by taking N-alkylated chitosan as a slow-release material and adopting a Schiff base method in the anaerobic digestion process of the sludge, and further strengthens the methane production process by anaerobic digestion of the sludge, and specifically comprises the following steps:
(1) settling and concentrating the excess sludge of the urban sewage plant to obtain sludge to be treated;
(2) fully mixing the inoculation sludge with the sludge to be treated obtained in the step (1) to obtain an anaerobic fermentation mixture;
(3) and (3) adding a certain proportion of slow-release choline into the anaerobic fermentation mixture obtained by the treatment in the step (2), uniformly stirring, and carrying out anaerobic fermentation methane-producing reaction after adjusting the pH value.
The slow-release choline is prepared by taking N-alkylated chitosan as a slow-release material and adopting a Schiff base method, wherein the slow-release period is 3-6d, and the release rate of the choline is 75-85%.
In the step (1), the mass concentration of the sludge to be treated is 2-4%;
in the step (2), the mass ratio of the inoculation mud to the anaerobic fermentation mixture is 5-15%; the inoculation sludge is digested sludge of an anaerobic digestion tank of a sewage treatment plant, and the mass concentration is 2-3%;
in the step (3), the concentration of the slow-release choline in the anaerobic fermentation mixture is 0.2-1.0 g/L.
In the step (3), the pH value of the anaerobic fermentation mixture is adjusted to 6.5-7.5;
the temperature of the reaction system in the anaerobic fermentation process in the step (3) is 25-35 ℃.
The preparation method of the slow-release choline comprises the following specific steps:
(1) preparation of N-alkylated chitosan
Weighing 3.6g of chitosan powder, preparing 200mL of chitosan acetic acid solution with the mass concentration of 1.5%, and standing overnight for defoaming. 9mL of dodecanal (2.5 times the amount of theoretical aldehyde) were added dropwise to 200mL of a 1.5% chitosan acetic acid solution, and after stirring for 12 hours, the pH was adjusted to 5. Preparing 10% sodium borohydride aqueous solution (1.5 times of the amount of the dodecanal), dropwise adding 13.5ml of the sodium borohydride aqueous solution into the reaction system under strong stirring, adjusting the pH value of the reaction system to 7 after 2h, repeatedly washing and filtering the mixture by absolute ethyl alcohol, drying the mixture in vacuum (65 ℃ C., to constant weight) and grinding the mixture to obtain the N-alkylated chitosan powder.
(2) N-alkylated chitosan loaded choline microcapsule
3g of the prepared N-alkylated chitosan was weighed, 300mL of 3% by mass acetic acid was used as a solvent to prepare an N-alkylated chitosan acetic acid solution, the solution was left to stand for defoaming, and after dissolution, the pH of the solution was adjusted to 7. Choline solution (48-50 wt% in aq.) was added to the reactor at 500r/min and stirred at room temperature for 1 h. After stirring was completed, 240mL of 2.5mg/mL sodium Tripolyphosphate (TPP) was taken out with a disposable syringe, and the TPP was added to the system (mass of N-alkylated chitosan: mass of sodium tripolyphosphate: 5:1) at a rate of 60 drops/min, and stirred at room temperature for 1 hour. Centrifuging the obtained suspension for 20min at the temperature of 4 ℃ at 12000r/min, collecting supernatant, washing the nanoparticles with ultrapure water, centrifuging again to recover precipitate, placing the precipitate in a vacuum freeze dryer, and freeze-drying for 24h to obtain the N-alkylated chitosan embedded choline microcapsule powder.
The slow release period measuring method of the slow release choline comprises the following steps:
adding a certain amount of prepared slow-release choline into the sludge supernatant, preparing a plurality of parallel experimental treatments, sampling at regular time, determining the concentration of choline in the sampled samples by using an ultra-high performance liquid chromatography-mass spectrometry method, and eliminating the experimental treatments at the same time until the concentration of choline in the supernatant is not increased any more. The experimental period is the slow release period of the slow release choline.
The method for measuring the choline release rate of the slow-release choline comprises the following steps:
based on the above experimental treatment, the percentage of the choline concentration measured in the supernatant of the final experimental treatment to the total amount contained in the sustained-release choline is the choline release rate in the sustained-release choline.
The present invention will be described in further detail with reference to the following examples:
example 1
Preparation of sustained-release choline:
(1) preparation of N-alkylated chitosan
Weighing 3.6g of chitosan powder, preparing 200mL of chitosan acetic acid solution with the mass concentration of 1.5%, and standing overnight for defoaming. 9mL of dodecanal (2.5 times the theoretical amount of aldehyde) was added dropwise to 200mL of a 1.5% chitosan acetic acid solution, and after stirring for 12 hours, the pH was adjusted to 5. Preparing 10% sodium borohydride aqueous solution (1.5 times of the amount of the dodecanal), dropwise adding 13.5ml of the sodium borohydride aqueous solution into the reaction system under strong stirring, adjusting the pH value of the reaction system to 7 after 2h, repeatedly washing and filtering the mixture by absolute ethyl alcohol, drying the mixture in vacuum (65 ℃ C., to constant weight) and grinding the mixture to obtain the N-alkylated chitosan powder.
(2) N-alkylated chitosan loaded choline microcapsule
3g of the prepared N-alkylated chitosan was weighed, 300mL of 3% by mass acetic acid was used as a solvent to prepare an N-alkylated chitosan acetic acid solution, the solution was left to stand for defoaming, and after dissolution, the pH of the solution was adjusted to 7. 0.6mL of choline solution (48 wt% in aq.) was added to the reactor at 500r/min and stirred at room temperature for 1 h. After stirring was completed, 240mL of 2.5mg/mL sodium Tripolyphosphate (TPP) was taken out with a disposable syringe, and the TPP was added to the system (mass of N-alkylated chitosan: mass of sodium tripolyphosphate: 5:1) at a rate of 60 drops/min, and stirred at room temperature for 1 hour. Centrifuging the obtained suspension for 20min at the temperature of 4 ℃ at 12000r/min, collecting supernatant, washing the nanoparticles with ultrapure water, centrifuging again to recover precipitate, placing the precipitate in a vacuum freeze dryer, and freeze-drying for 24h to obtain the N-alkylated chitosan embedded choline microcapsule powder.
The slow release period of the slow release type choline is tested to be 3 days, and the release rate of the choline is 75 percent.
Excess sludge of a certain sewage plant in Shanghai city is taken to be concentrated to adjust the solid content to 2%, inoculation sludge with the solid content of 2% taken from an anaerobic digestion tank is inoculated into the excess sludge according to the mass ratio of 5%, and the mixture is uniformly mixed. The prepared slow-release choline is added into an anaerobic fermentation mixture according to the concentration of 0.2g/L, the mixture is uniformly mixed, the pH value is adjusted to 6.5, and then the mixture is introduced into an anaerobic digestion tank, the anaerobic digestion temperature is set to be 25 ℃, the accumulated methane yield is compared with the treatment of adding 0.2g/L choline, the final accumulated methane yield of anaerobic digestion sludge reaches 225.7mL/g volatile solid, and is improved by 23% compared with the conventional treatment of adding choline.
Example 2
Preparation of sustained-release choline:
(1) preparation of N-alkylated chitosan
Weighing 3.6g of chitosan powder, preparing 200mL of chitosan acetic acid solution with the mass concentration of 1.5%, and standing overnight for defoaming. 9mL of dodecanal (2.5 times the amount of theoretical aldehyde) were added dropwise to 200mL of a 1.5% chitosan acetic acid solution, and after stirring for 12 hours, the pH was adjusted to 5. Preparing 10% sodium borohydride aqueous solution (1.5 times of the amount of the dodecanal), dropwise adding 13.5ml of the sodium borohydride aqueous solution into the reaction system under strong stirring, adjusting the pH value of the reaction system to 7 after 2h, repeatedly washing and filtering the mixture by absolute ethyl alcohol, drying the mixture in vacuum (65 ℃ C., to constant weight) and grinding the mixture to obtain the N-alkylated chitosan powder.
(2) N-alkylated chitosan loaded choline microcapsule
Weighing 3g of the prepared N-alkylated chitosan, preparing an N-alkylated chitosan acetic acid solution by using 300mL of acetic acid with the mass concentration of 3% as a solvent, standing for defoaming for standby, and adjusting the pH value of the solution to 7 after dissolving. 0.9mL of choline solution (49 wt% in aq.) was added to the reactor at 500r/min and stirred at room temperature for 1 h. After stirring was completed, 240mL of 2.5mg/mL sodium Tripolyphosphate (TPP) was taken out with a disposable syringe, and the TPP was added to the system (mass of N-alkylated chitosan: mass of sodium tripolyphosphate: 5:1) at a rate of 60 drops/min, followed by stirring at room temperature for 1 hour. Centrifuging the obtained suspension for 20min at the temperature of 4 ℃ at 12000r/min, collecting supernatant, washing the nanoparticles with ultrapure water, centrifuging again to recover precipitate, placing the precipitate in a vacuum freeze dryer, and freeze-drying for 24h to obtain the N-alkylated chitosan embedded choline microcapsule powder.
The slow release period of the slow release type choline is tested to be 4 days, and the release rate of the choline is 85%.
Excess sludge of a certain sewage plant in Shanghai city is taken to be concentrated to adjust the solid content to 4%, inoculation sludge with the solid content of 3% taken from an anaerobic digestion tank is inoculated into the excess sludge according to the mass ratio of 15%, and the mixture is uniformly mixed. The prepared slow-release choline is added into an anaerobic fermentation mixture according to the concentration of 1.0g/L, the mixture is uniformly mixed, the pH value is adjusted to 7.0, and then the mixture is introduced into an anaerobic digestion tank, the anaerobic digestion temperature is set to be 30 ℃, the accumulated methane yield is compared with the treatment of adding 1.0g/L choline, the final accumulated methane yield of anaerobic digestion sludge can reach 323.8mL/g volatile solid, and the treatment is improved by 29% compared with the conventional treatment of adding choline.
Example 3
Preparation of sustained-release choline:
(1) preparation of N-alkylated chitosan
Weighing 3.6g of chitosan powder, preparing 200mL of chitosan acetic acid solution with the mass concentration of 1.5%, and standing overnight for defoaming. 9mL of dodecanal (2.5 times the amount of theoretical aldehyde) were added dropwise to 200mL of a 1.5% chitosan acetic acid solution, and after stirring for 12 hours, the pH was adjusted to 5. Preparing 10% sodium borohydride aqueous solution (1.5 times of the amount of the dodecanal), dropwise adding 13.5ml of the sodium borohydride aqueous solution into the reaction system under strong stirring, adjusting the pH value of the reaction system to 7 after 2h, repeatedly washing and filtering the mixture by absolute ethyl alcohol, drying the mixture in vacuum (65 ℃ C., to constant weight) and grinding the mixture to obtain the N-alkylated chitosan powder.
(2) N-alkylated chitosan loaded choline microcapsule
3g of the prepared N-alkylated chitosan was weighed, 300mL of 3% by mass acetic acid was used as a solvent to prepare an N-alkylated chitosan acetic acid solution, the solution was left to stand for defoaming, and after dissolution, the pH of the solution was adjusted to 7. 1.2mL of choline solution (50 wt% in aq.) was added to the reactor at 500r/min and stirred at room temperature for 1 h. After stirring was completed, 240mL of 2.5mg/mL sodium Tripolyphosphate (TPP) was taken out with a disposable syringe, and the TPP was added to the system (mass of N-alkylated chitosan: mass of sodium tripolyphosphate: 5:1) at a rate of 60 drops/min, followed by stirring at room temperature for 1 hour. Centrifuging the obtained suspension for 20min at the temperature of 4 ℃ at 12000r/min, collecting supernatant, washing the nanoparticles with ultrapure water, centrifuging again to recover precipitate, placing the precipitate in a vacuum freeze dryer, and freeze-drying for 24h to obtain the N-alkylated chitosan embedded choline microcapsule powder.
The slow release period of the slow release type choline is tested to be 6 days, and the choline release rate is 80%.
Excess sludge of a certain sewage plant in Shanghai city is taken to be concentrated to adjust the solid content to 3%, inoculation sludge with the solid content of 2% taken from an anaerobic digestion tank is inoculated into the excess sludge according to the mass ratio of 10%, and the mixture is uniformly mixed. The prepared slow-release choline is added into an anaerobic fermentation mixture according to the concentration of 0.7g/L, the mixture is uniformly mixed, the pH value is adjusted to 7.5, and then the mixture is introduced into an anaerobic digestion tank, the anaerobic digestion temperature is set to 35 ℃, and the accumulated methane yield is compared with the treatment of adding 0.7g/L choline, so that the final accumulated methane yield of anaerobic digestion sludge can reach 278.6mL/g volatile solid, and is improved by 25% compared with the conventional treatment of adding choline.
The invention is mainly based on the problems of rapid biodegradation, low utilization rate and the like of the existing alkaloid on methane production by anaerobic digestion of sludge, adopts N-alkylated chitosan as a slow-release material and adopts a Schiff base method to prepare the slow-release choline, promotes the choline to be slowly released in the anaerobic digestion process of sludge, fully improves the utilization rate of the choline, and finally can improve the yield of methane accumulated by anaerobic digestion of sludge by 20-30 percent compared with that after the methane is treated by common choline after the slow-release choline is added.
The above-described embodiments are only intended to illustrate the preferred embodiments of the present invention, and not to limit the scope of the present invention, and various modifications and improvements made to the technical solution of the present invention by those skilled in the art without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.
Claims (10)
1. The application of the slow-release choline in methane production by anaerobic digestion of sludge is characterized in that the slow-release choline is prepared by taking N-alkylated chitosan as a slow-release material and adopting a Schiff base method.
2. A method for producing methane by anaerobic digestion of sludge based on slow-release choline is characterized by comprising the following steps:
(1) precipitating and concentrating the excess sludge of the urban sewage plant to obtain sludge to be treated;
(2) mixing the inoculation sludge with the sludge to be treated obtained in the step (1) to obtain an anaerobic fermentation mixture;
(3) and (3) adding slow-release choline into the anaerobic fermentation mixture obtained by the treatment in the step (2), stirring, adjusting the pH value to 6.5-7.5, and then carrying out anaerobic fermentation methane-producing reaction.
3. The method as claimed in claim 2, wherein the slow-release choline is prepared from N-alkylated chitosan as a slow-release material by a Schiff base method.
4. The method as claimed in claim 2, wherein the sustained release choline has a sustained release period of 3-6d and a choline release rate of 75-85%.
5. The method according to claim 2, wherein the preparation of the sustained-release choline comprises the steps of:
reacting chitosan with dodecanal and sodium borohydride to prepare N-alkylated chitosan; and (2) reacting the N-alkylated chitosan with choline in the presence of a cross-linking agent, and after the reaction is finished, freezing and drying the obtained precipitate to obtain the slow-release choline.
6. The method of claim 2, wherein the concentration of the slow release choline in the anaerobic fermentation mixture is 0.2-1.0 g/L.
7. The method according to claim 2, characterized in that the mass concentration of the sludge to be treated in the step (1) is 2-4%.
8. The method according to claim 2, wherein in the step (2), the inoculation mud accounts for 5-15% of the anaerobic fermentation mixture by mass.
9. The method according to claim 2, wherein the inoculation sludge in the step (2) is digested sludge of an anaerobic digester of a sewage treatment plant, and the mass concentration is 2-3%.
10. The method as set forth in claim 2, wherein the temperature of the reaction system in the anaerobic fermentation process in the step (3) is 25 to 35 ℃.
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| GB9224101D0 (en) * | 1992-11-17 | 1993-01-06 | Sandoz Ltd | Improvements in or relating to organic compounds |
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| WO2013009142A2 (en) * | 2011-07-14 | 2013-01-17 | Bio Pharmartis Co., Ltd. | Sustained/release pharmaceutical composition comripising choline alfoscerate or pharmaceutically acceptable salt thereof and method for manufacturing the same |
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| CN109574434A (en) * | 2018-12-13 | 2019-04-05 | 上海交通大学 | A method of strengthening excess sludge anaerobic digestion methane phase using alkaloid |
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| GB9224101D0 (en) * | 1992-11-17 | 1993-01-06 | Sandoz Ltd | Improvements in or relating to organic compounds |
| CN1803852A (en) * | 2005-12-21 | 2006-07-19 | 华侨大学 | Method for preparing organic solvent soluble amphiphilic N,N-dilong chain alkyl chitosan |
| WO2013009142A2 (en) * | 2011-07-14 | 2013-01-17 | Bio Pharmartis Co., Ltd. | Sustained/release pharmaceutical composition comripising choline alfoscerate or pharmaceutically acceptable salt thereof and method for manufacturing the same |
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