CN115010336B - Method for producing methane by sludge anaerobic digestion based on slow-release choline - Google Patents
Method for producing methane by sludge anaerobic digestion based on slow-release choline Download PDFInfo
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- CN115010336B CN115010336B CN202210744229.0A CN202210744229A CN115010336B CN 115010336 B CN115010336 B CN 115010336B CN 202210744229 A CN202210744229 A CN 202210744229A CN 115010336 B CN115010336 B CN 115010336B
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- OEYIOHPDSNJKLS-UHFFFAOYSA-N choline Chemical compound C[N+](C)(C)CCO OEYIOHPDSNJKLS-UHFFFAOYSA-N 0.000 title claims abstract description 111
- 229960001231 choline Drugs 0.000 title claims abstract description 111
- 239000010802 sludge Substances 0.000 title claims abstract description 91
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 title claims abstract description 70
- 230000029087 digestion Effects 0.000 title claims abstract description 60
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 20
- 238000000034 method Methods 0.000 claims abstract description 35
- 230000008569 process Effects 0.000 claims abstract description 15
- 229920001661 Chitosan Polymers 0.000 claims description 49
- 238000000855 fermentation Methods 0.000 claims description 23
- 238000011282 treatment Methods 0.000 claims description 22
- 239000000203 mixture Substances 0.000 claims description 20
- 238000003756 stirring Methods 0.000 claims description 19
- 238000006243 chemical reaction Methods 0.000 claims description 16
- 239000010865 sewage Substances 0.000 claims description 14
- HFJRKMMYBMWEAD-UHFFFAOYSA-N dodecanal Chemical compound CCCCCCCCCCCC=O HFJRKMMYBMWEAD-UHFFFAOYSA-N 0.000 claims description 12
- 238000002360 preparation method Methods 0.000 claims description 11
- 229910000033 sodium borohydride Inorganic materials 0.000 claims description 10
- 239000012279 sodium borohydride Substances 0.000 claims description 10
- 238000011081 inoculation Methods 0.000 claims description 9
- 238000004108 freeze drying Methods 0.000 claims description 6
- 238000002156 mixing Methods 0.000 claims description 6
- 239000002244 precipitate Substances 0.000 claims description 6
- 230000004151 fermentation Effects 0.000 claims description 4
- 230000001376 precipitating effect Effects 0.000 claims description 3
- 239000003431 cross linking reagent Substances 0.000 claims description 2
- 244000005700 microbiome Species 0.000 abstract description 11
- 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
- 230000003993 interaction Effects 0.000 abstract description 3
- 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 22
- 235000019832 sodium triphosphate Nutrition 0.000 description 16
- 239000000463 material Substances 0.000 description 12
- 239000000843 powder Substances 0.000 description 12
- 239000007787 solid Substances 0.000 description 9
- 239000007864 aqueous solution Substances 0.000 description 8
- LQZZUXJYWNFBMV-UHFFFAOYSA-N dodecan-1-ol Chemical compound CCCCCCCCCCCCO LQZZUXJYWNFBMV-UHFFFAOYSA-N 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
- 239000002262 Schiff base Substances 0.000 description 6
- 150000004753 Schiff bases Chemical class 0.000 description 6
- 230000000694 effects Effects 0.000 description 6
- 230000015556 catabolic process Effects 0.000 description 5
- 238000006731 degradation reaction Methods 0.000 description 5
- 230000002829 reductive effect Effects 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
- 238000004090 dissolution Methods 0.000 description 4
- 238000001914 filtration Methods 0.000 description 4
- 238000000227 grinding Methods 0.000 description 4
- 239000002105 nanoparticle Substances 0.000 description 4
- 230000001105 regulatory effect Effects 0.000 description 4
- 239000002904 solvent Substances 0.000 description 4
- 238000005728 strengthening Methods 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
- 238000001291 vacuum drying Methods 0.000 description 4
- 238000005303 weighing Methods 0.000 description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 3
- 238000011160 research Methods 0.000 description 3
- 241000894006 Bacteria Species 0.000 description 2
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 2
- 230000009471 action Effects 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
- 239000003795 chemical substances by application Substances 0.000 description 2
- 235000014113 dietary fatty acids Nutrition 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 230000002708 enhancing effect Effects 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
- 230000002503 metabolic effect 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
- 239000006259 organic additive Substances 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 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
- 230000002411 adverse Effects 0.000 description 1
- 239000003513 alkali Substances 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
- 229910052799 carbon Inorganic materials 0.000 description 1
- 238000010668 complexation reaction Methods 0.000 description 1
- 238000009264 composting Methods 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000000593 degrading effect Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000003912 environmental pollution 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
- 230000000696 methanogenic 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
- 238000011084 recovery Methods 0.000 description 1
- 238000005070 sampling 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 sludge anaerobic digestion based on slow-release choline, and relates to the technical field of environmental engineering. According to the invention, the slow-release choline is prepared to improve the anaerobic digestion hydrolysis acidification performance of the sludge, strengthen the interaction relation of functional microorganisms in the anaerobic digestion system of the sludge, and further improve the electron transfer capability among functional microorganism flora in the anaerobic digestion process, so that the accumulated methane yield of the anaerobic digestion of the sludge added with the slow-release choline is improved by 20-30% compared with that 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 sludge anaerobic digestion based on slow-release choline.
Background
Along with the rapid development of the economy in China, the sewage treatment scale of urban sewage plants is increasingly enlarged, the sludge is used as a byproduct of the sewage biological treatment process, the yield is rapidly increased, and the treatment pressure is huge. If the sludge is not properly treated, it is liable to cause secondary pollution risks to the environment. On the other hand, the sludge is rich in organic matters such as sugar, protein, lipid and the like, has great potential for realizing biomass energy recovery through anaerobic digestion and methane production, and is also an important way for reducing carbon emission.
However, hydrolysis is a speed limiting step in the anaerobic digestion process of the sludge, and the conversion of macromolecular organic matters in the sludge into micromolecular organic matters is seriously hindered, so that the 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 sludge hydrolysis acidification process is promoted, and the methane production performance is further improved. On the other hand, in the anaerobic digestion process of the sludge, electron transfer capability among microorganism species of a system is weak, so that the interaction relationship among functional microorganism flora is insufficient, and methane production performance is poor. Therefore, research is being conducted on enhancing the electron transfer capability of the anaerobic digestion system and enhancing the methanogenic performance by adding conductive materials such as activated carbon, biochar, iron oxide and the like. Although the technology can obtain better experimental results, the problems of higher treatment cost, secondary pollution risk, complex operation, influence on subsequent composting incineration disposal and the like exist, and a large gap is left between practical application and popularization.
In recent years, there have been studies to promote a sludge anaerobic digestion methanogenesis process by adding an organic additive, but in the studies, it has been found that the organic additive can be rapidly degraded by microorganisms in a sludge anaerobic digestion early stage, resulting in a low utilization rate and failure to fully exert its action and effect.
Disclosure of Invention
The invention aims to provide a method for producing methane by sludge anaerobic digestion based on slow-release choline, which solves the problems in the prior art, strengthens the performance of producing methane by sludge anaerobic digestion, and provides a new technical choice for the strengthening method for producing methane by sludge anaerobic digestion of excess sludge in urban sewage treatment plants.
In order to achieve the above object, the present invention provides the following solutions:
the invention provides an application of slow-release choline in sludge anaerobic digestion for methane production, which is prepared by adopting N-alkylated chitosan as a slow-release material and adopting a Schiff base method.
The invention also provides a method for producing methane by sludge anaerobic digestion based on the slow-release choline, which comprises the following steps:
(1) Precipitating and concentrating the surplus sludge of the municipal sewage plant to obtain sludge to be treated;
(2) Mixing 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 in the step (2), stirring, adjusting the pH to 6.5-7.5, and performing anaerobic fermentation to produce methane.
Further, the slow-release choline is prepared by using N-alkylated chitosan as a slow-release material and adopting a Schiff base method.
Further, the slow release period of the slow release choline is 3-6d, and the choline release rate 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 (3) reacting the N-alkylated chitosan with choline in the presence of a cross-linking agent, and freeze-drying the obtained precipitate after the reaction is finished to obtain the slow-release choline.
Further, the concentration of the slow release choline in the anaerobic fermentation mixture is 0.2-1.0g/L.
Further, the mass concentration of the sludge to be treated in the step (1) is 2% -4%.
Further, in the step (2), the mass ratio of the inoculation mud to the anaerobic fermentation mixture is 5% -15%.
Further, the inoculation sludge in the step (2) is digested sludge in 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 methanogenesis process of sludge, a large amount of volatile fatty acids are generated in a short period of time due to the action of various hydrolysis/acidification bacteria, so that the pH of the system is rapidly reduced, the metabolic activity of subsequent methanogenesis is influenced (the metabolic proper pH of methanogenesis bacteria is generally between 6.5 and 7.5), and the accumulation of the volatile fatty acids is caused. On the other hand, a large amount of micro-organism degradation-resistant macromolecular organic matters exist in the sludge at the same time, and are not easy to hydrolyze/acidify, so that the methane yield of anaerobic digestion of the sludge is affected. The choline in the alkaloid has been proved to improve the performance of anaerobic digestion and methane production of sludge in such modes as removing acid inhibition effect through complexation effect with small molecular organic acid, reducing and degrading macromolecular organic matters which are difficult to degrade, improving electron transfer capability of an anaerobic system and the like. However, choline is easy to be degraded by microorganisms in the anaerobic sludge digestion process, and research results show that the choline can be degraded after 2-3 days, so that the utilization rate of choline is greatly reduced. According to the invention, the 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 the rapid degradation of the choline by anaerobic microorganisms, so that the utilization rate of the choline is fully improved, the methane production performance of sludge anaerobic digestion is improved, the addition amount of the choline can be reduced, and the system operation cost is reduced.
The invention provides a method for strengthening sludge anaerobic digestion methanogenesis based on slow-release choline, which is characterized in that N-alkylated chitosan is used as a slow-release material to prepare the slow-release choline by adopting a Schiff base method, so that the slow-release choline is slowly released in a sludge anaerobic digestion system, the rapid degradation of choline by anaerobic microorganisms is avoided, the effect of the choline on relieving the inhibition of small molecular organic acid caused by the early stage of anaerobic digestion is fully exerted, the reductive degradation of organic matters difficult to degrade in sludge is enhanced, the anaerobic digestion hydrolysis acidification process of the sludge is promoted, and the methane production performance of the sludge anaerobic digestion is further effectively improved. According to the invention, the slow-release choline is prepared to improve the anaerobic digestion hydrolysis acidification performance of the sludge, strengthen the interaction relation of functional microorganisms in the anaerobic digestion system of the sludge, and further improve the electron transfer capability among functional microorganism flora in the anaerobic digestion process, so that the accumulated methane yield of the anaerobic digestion of the sludge added with the slow-release choline is improved by 20% -30% compared with that of the sludge treated by common choline.
The invention discloses the following technical effects:
1. the invention adopts the slow release type choline adding mode, can more effectively improve the hydrolysis and acidification rate of the sludge, promote the degradation and conversion of organic matters, shorten the anaerobic digestion period of the sludge, reduce the actual adding amount of the choline, and finally can improve the anaerobic digestion accumulated methane yield of the sludge by 20-30 percent compared with the sludge after common choline treatment after the slow release type choline adding.
2. The slow release agent preparation material and the choline are both environment-friendly materials, have biodegradability, cannot cause secondary environmental pollution risk, and cannot cause adverse effects on subsequent treatment and disposal of sludge.
3. The method is simple to operate, can effectively reduce the use amount of choline and the running cost of the system, can improve the methane yield, and can provide technical support for the construction and transformation of anaerobic digestion facilities of sludge.
4. The invention solves the problem of rapid biodegradation of choline in the early stage of anaerobic sludge fermentation by using a slow-release agent method, effectively improves the utilization rate of choline, further strengthens the anaerobic sludge digestion and methane production performance, and provides a new technical choice for the strengthening method of anaerobic sludge digestion and methane production of excess sludge of urban sewage treatment plants.
Detailed Description
Various exemplary embodiments of the invention will now be described in detail, which should not be considered as limiting the invention, but rather as more detailed descriptions 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 this disclosure, it is understood that each intermediate value between the upper and lower limits of the ranges is also specifically disclosed. Every smaller range between any stated value or stated range, and any other stated value or intermediate value within the stated range, is also encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.
Unless otherwise defined, 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 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 invention described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from consideration of the specification of the present invention. The specification and examples of the present invention are exemplary only.
As used herein, the terms "comprising," "including," "having," "containing," and the like are intended to be inclusive and mean an inclusion, but not limited to.
The invention provides a method for strengthening sludge anaerobic digestion methanogenesis based on slow-release choline, which is characterized in that in the sludge anaerobic digestion process, N-alkylated chitosan is used as a slow-release material to prepare the slow-release choline by adopting a Schiff base method, so that the utilization rate of the slow-release choline is effectively improved, and the sludge anaerobic digestion methanogenesis process is further strengthened, and the method specifically comprises the following steps:
(1) Precipitating and concentrating the surplus sludge of the municipal sewage plant to obtain sludge to be treated;
(2) Fully mixing 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 performing anaerobic fermentation to produce methane after regulating the pH.
Wherein, the slow release choline is prepared by adopting N-alkylated chitosan as a slow release material and adopting a Schiff base method, the slow release period is 3-6d, and the choline release rate is 75-85%.
The mass concentration of the sludge to be treated in the step (1) is 2% -4%;
the mass ratio of the inoculation mud in the step (2) to the anaerobic fermentation mixture is 5% -15%; the inoculation sludge is digested sludge in an anaerobic digestion tank of a sewage treatment plant, and the mass concentration is 2% -3%;
the concentration of the slow-release choline in the step (3) in the anaerobic fermentation mixture is 0.2-1.0g/L.
In the step (3), the pH value of the anaerobic fermentation mixture is adjusted to be 6.5-7.5 after the pH value is adjusted;
the temperature of the reaction system in the anaerobic fermentation process in the step (3) is 25-35 ℃.
The specific preparation steps of the slow release choline are as follows:
(1) Preparation of N-alkylated chitosan
3.6g of chitosan powder is weighed, 200mL of chitosan acetic acid solution with the mass concentration of 1.5% is prepared, and the mixture is stood overnight for defoaming. 9mL of dodecanal (2.5 times the theoretical aldehyde amount) was added dropwise to 200mL of a 1.5% chitosan acetic acid solution, and after stirring for 12 hours, ph=5 was adjusted. Preparing a sodium borohydride aqueous solution (1.5 times of the dodecanol amount) with the mass concentration of 10%, dropwise adding 13.5ml of the sodium borohydride aqueous solution into the reaction system under strong stirring, adjusting the pH=7 of the reaction system after 2 hours, repeatedly washing and filtering with absolute ethyl alcohol, vacuum drying (65 ℃ to constant weight), and grinding to obtain 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 taking 300mL of acetic acid with mass concentration of 3% as a solvent, standing for bubble removal for standby, and adjusting the pH=7 of the solution after dissolution. At 500r/min, choline solution (48-50 wt% in aq.) was added to the reactor and stirred at room temperature for 1h. After stirring was completed, 240mL of 2.5mg/mL sodium Tripolyphosphate (TPP) was taken with a disposable syringe, TPP was added to the system at a rate of 60 drops/min (mass of N-alkylated chitosan: mass of sodium tripolyphosphate = 5:1), and stirring was performed at room temperature for 1h. Centrifuging the obtained suspension at 12000r/min and 4 ℃ for 20min, collecting supernatant, washing the nanoparticles with ultrapure water, centrifuging again to recover precipitate, and freeze-drying in a vacuum freeze dryer for 24h to obtain N-alkylated chitosan-embedded choline microcapsule powder.
The method for measuring the slow release period of the slow release choline comprises the following steps:
adding the slow-release choline prepared by a certain mass into sludge supernatant, preparing a plurality of parallel experimental treatments, sampling at fixed time, measuring the concentration of choline in the sample by utilizing an ultra-high performance liquid chromatography-mass spectrometry, and eliminating the experimental treatments until the concentration of choline in the supernatant is not increased. 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 experimental treatment, the choline concentration measured in the supernatant of the final experimental treatment is taken as the total content of the slow-release choline, namely the choline release rate in the slow-release choline.
The invention is described in further detail below with reference to examples:
example 1
Preparation of slow-release choline:
(1) Preparation of N-alkylated chitosan
3.6g of chitosan powder is weighed, 200mL of chitosan acetic acid solution with the mass concentration of 1.5% is prepared, and the mixture is stood overnight for defoaming. 9mL of dodecanal (2.5 times the theoretical aldehyde amount) was added dropwise to 200mL of 1.5% chitosan acetic acid solution, and after stirring for 12 hours, ph=5 was adjusted. Preparing a sodium borohydride aqueous solution (1.5 times of the dodecanol amount) with the mass concentration of 10%, dropwise adding 13.5ml of the sodium borohydride aqueous solution into the reaction system under strong stirring, adjusting the pH=7 of the reaction system after 2 hours, repeatedly washing and filtering with absolute ethyl alcohol, vacuum drying (65 ℃ to constant weight), and grinding to obtain 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 taking 300mL of acetic acid with mass concentration of 3% as a solvent, standing for bubble removal for standby, and adjusting the pH=7 of the solution after dissolution. 0.6mL choline solution (48 wt% in aq.) was added to the reactor at 500r/min and stirred for 1h at room temperature. After stirring was completed, 240mL of 2.5mg/mL sodium Tripolyphosphate (TPP) was taken with a disposable syringe, TPP was added to the system at a rate of 60 drops/min (mass of N-alkylated chitosan: mass of sodium tripolyphosphate = 5:1), and stirring was performed at room temperature for 1h. Centrifuging the obtained suspension at 12000r/min and 4 ℃ for 20min, collecting supernatant, washing the nanoparticles with ultrapure water, centrifuging again to recover precipitate, and freeze-drying in a vacuum freeze dryer for 24h to obtain N-alkylated chitosan-embedded choline microcapsule powder.
The slow release period of the slow release choline is 3 days, and the choline release rate is 75%.
And (3) concentrating the excess sludge of a sewage plant in Shanghai city to adjust the solid content to 2%, inoculating the inoculating sludge with the solid content of 2% in the anaerobic digestion tank into the excess sludge according to the mass ratio of 5%, and uniformly mixing. The prepared slow-release choline is added into an anaerobic fermentation mixture according to the concentration of 0.2g/L, the pH value is regulated to 6.5 after the slow-release choline is uniformly mixed, the slow-release choline is introduced into an anaerobic digestion tank, the anaerobic digestion temperature is set to 25 ℃, and compared with the treatment of adding 0.2g/L choline, the accumulated methane yield of the anaerobic digestion sludge reaches 225.7mL/g volatile solid, and the accumulated methane yield is improved by 23% compared with the conventional treatment of adding choline.
Example 2
Preparation of slow-release choline:
(1) Preparation of N-alkylated chitosan
3.6g of chitosan powder is weighed, 200mL of chitosan acetic acid solution with the mass concentration of 1.5% is prepared, and the mixture is stood overnight for defoaming. 9mL of dodecanal (2.5 times the theoretical aldehyde amount) was added dropwise to 200mL of 1.5% chitosan acetic acid solution, and after stirring for 12 hours, ph=5 was adjusted. Preparing a sodium borohydride aqueous solution (1.5 times of the dodecanol amount) with the mass concentration of 10%, dropwise adding 13.5ml of the sodium borohydride aqueous solution into the reaction system under strong stirring, adjusting the pH=7 of the reaction system after 2 hours, repeatedly washing and filtering with absolute ethyl alcohol, vacuum drying (65 ℃ to constant weight), and grinding to obtain 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 taking 300mL of acetic acid with mass concentration of 3% as a solvent, standing for bubble removal for standby, and adjusting the pH=7 of the solution after dissolution. 0.9mL of choline solution (49 wt% in aq.) was added to the reactor at 500r/min and stirred for 1h at room temperature. After stirring was completed, 240mL of 2.5mg/mL sodium Tripolyphosphate (TPP) was taken with a disposable syringe, TPP was added to the system at a rate of 60 drops/min (mass of N-alkylated chitosan: mass of sodium tripolyphosphate = 5:1), and stirring was performed at room temperature for 1h. Centrifuging the obtained suspension at 12000r/min and 4 ℃ for 20min, collecting supernatant, washing the nanoparticles with ultrapure water, centrifuging again to recover precipitate, and freeze-drying in a vacuum freeze dryer for 24h to obtain N-alkylated chitosan-embedded choline microcapsule powder.
The slow release period of the slow release choline is 4 days, and the choline release rate is 85%.
And (3) concentrating the excess sludge of a sewage plant in Shanghai city to adjust the solid content to 4%, inoculating the inoculating sludge with the solid content of 3% in the anaerobic digestion tank into the excess sludge according to the mass ratio of 15%, and uniformly mixing. The prepared slow-release choline is added into an anaerobic fermentation mixture according to the concentration of 1.0g/L, the pH value is regulated to 7.0 after the slow-release choline is uniformly mixed, the slow-release choline is introduced into an anaerobic digestion tank, the anaerobic digestion temperature is set to 30 ℃, and compared with the treatment of adding 1.0g/L choline, the accumulated methane yield of the anaerobic digestion sludge can reach 323.8mL/g volatile solid, and the accumulated methane yield is improved by 29% compared with the conventional treatment of adding choline.
Example 3
Preparation of slow-release choline:
(1) Preparation of N-alkylated chitosan
3.6g of chitosan powder is weighed, 200mL of chitosan acetic acid solution with the mass concentration of 1.5% is prepared, and the mixture is stood overnight for defoaming. 9mL of dodecanal (2.5 times the theoretical aldehyde amount) was added dropwise to 200mL of 1.5% chitosan acetic acid solution, and after stirring for 12 hours, ph=5 was adjusted. Preparing a sodium borohydride aqueous solution (1.5 times of the dodecanol amount) with the mass concentration of 10%, dropwise adding 13.5ml of the sodium borohydride aqueous solution into the reaction system under strong stirring, adjusting the pH=7 of the reaction system after 2 hours, repeatedly washing and filtering with absolute ethyl alcohol, vacuum drying (65 ℃ to constant weight), and grinding to obtain 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 taking 300mL of acetic acid with mass concentration of 3% as a solvent, standing for bubble removal for standby, and adjusting the pH=7 of the solution after dissolution. 1.2mL of choline solution (50 wt% in aq.) was added to the reactor at 500r/min and stirred for 1h at room temperature. After stirring was completed, 240mL of 2.5mg/mL sodium Tripolyphosphate (TPP) was taken with a disposable syringe, TPP was added to the system at a rate of 60 drops/min (mass of N-alkylated chitosan: mass of sodium tripolyphosphate = 5:1), and stirring was performed at room temperature for 1h. Centrifuging the obtained suspension at 12000r/min and 4 ℃ for 20min, collecting supernatant, washing the nanoparticles with ultrapure water, centrifuging again to recover precipitate, and freeze-drying in a vacuum freeze dryer for 24h to obtain N-alkylated chitosan-embedded choline microcapsule powder.
The slow release period of the test slow release choline is 6 days, and the choline release rate is 80%.
And (3) concentrating the excess sludge of a sewage plant in Shanghai city to adjust the solid content to 3%, inoculating the inoculating sludge with the solid content of 2% in the anaerobic digestion tank into the excess sludge according to the mass ratio of 10%, and uniformly mixing. The prepared slow-release choline is added into an anaerobic fermentation mixture according to the concentration of 0.7g/L, the pH value is regulated to 7.5 after the slow-release choline is uniformly mixed, the slow-release choline is introduced into an anaerobic digestion tank, the anaerobic digestion temperature is set to 35 ℃, and compared with the treatment of adding 0.7g/L choline, the accumulated methane yield of the anaerobic digestion sludge can reach 278.6mL/g volatile solid, and the accumulated methane yield of the anaerobic digestion sludge 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 prior alkaloid on the anaerobic digestion of sludge to produce methane, and adopts the Schiff alkali method to prepare the slow-release choline by taking N-alkylated chitosan as a slow-release material, so as to promote the slow release of choline in the anaerobic digestion process of sludge, fully improve the utilization rate of choline, and finally improve the yield of the accumulated methane of the anaerobic digestion of the sludge after the slow-release choline is added by 20% -30% compared with that after the common choline is treated.
The above embodiments are only illustrative of the preferred embodiments of the present invention and are not intended to limit the scope of the present invention, and various modifications and improvements made by those skilled in the art to the technical solutions of the present invention should fall within the protection scope defined by the claims of the present invention without departing from the design spirit of the present invention.
Claims (5)
1. A method for producing methane by sludge anaerobic digestion based on slow-release choline, which is characterized by comprising the following steps:
(1) Precipitating and concentrating the surplus sludge of the municipal sewage plant to obtain sludge to be treated;
(2) Mixing inoculation sludge with the sludge to be treated obtained in the step (1) to obtain an anaerobic fermentation mixture;
(3) Adding slow-release choline into the anaerobic fermentation mixture obtained in the step (2), stirring, adjusting the pH to 6.5-7.5, and performing anaerobic fermentation to produce methane;
the slow release period of the slow release choline is 3-6d, and the choline release rate is 75-85%;
the preparation of the slow release choline comprises the following steps: reacting chitosan with dodecanal and sodium borohydride to prepare N-alkylated chitosan; reacting the N-alkylated chitosan with choline in the presence of a cross-linking agent, and freeze-drying the obtained precipitate after the reaction is finished to obtain the slow-release choline;
the temperature of the reaction system in the anaerobic fermentation process in the step (3) is 25-35 ℃.
2. The process according to claim 1, wherein the concentration of the slow-release choline in the anaerobic fermentation mixture is 0.2-1.0g/L.
3. The method according to claim 1, wherein the mass concentration of sludge to be treated in the step (1) is 2% -4%.
4. The process according to claim 1, wherein in step (2) the inoculation sludge is present in an amount of 5% to 15% by mass of the anaerobic fermentation mixture.
5. The method according to claim 1, wherein the inoculation sludge in the step (2) is digested sludge in an anaerobic digester of a sewage treatment plant, and the mass concentration is 2% -3%.
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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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