Method for producing acid by enhancing fermentation of cow dung through coupling of salt-tolerant microorganism and acid-base regulation

Abstract

The application provides a method for enhancing acid production in cow dung fermentation by using salt-tolerant microorganisms and acid-base regulation, which comprises the following steps: heat treatment and domestication of activated sludge, enrichment of salt-tolerant acid-producing microbial flora, and standby; mixing the heat-domicilated activated sludge and cow dung to obtain initial fermentation raw materials, and performing fermentation by regulating the pH and supplementing the domesticated sludge to regulate the total abundance of salt-tolerant acid-producing bacteria in the fermentation system, and obtaining organic acid. The method disclosed in the application uses cow dung as the fermentation material, induces efficient enrichment of salt-tolerant acid-producing bacteria through natural domestication, simultaneously regulates the acid-base degree of the fermentation system and supplements the inoculated sludge in stages, cooperatively controls the metabolic activity of anaerobic methanogenic bacteria in the system through acid-base regulation and salt stress, induces anaerobic acid-producing microorganisms in the salt-tolerant and alkali-tolerant environment to become dominant genera, promotes the rapid acidification of organic matter in the cow dung, reduces the methanation of organic acid, and realizes the directional accumulation of organic acid.

Description

Technical Field

[0001] This invention belongs to the field of high-value utilization technology of waste, specifically relating to a method for enhancing the fermentation and acid production of cow manure by coupling salt-tolerant microorganisms with acid-base regulation. Background Technology

[0002] With the large-scale development of the dairy industry, the production of cow manure has increased year by year. A cattle farm with 1,000 head of cattle can produce 20-30 tons of cow manure per day, with an annual output of 7,000-11,000 tons. Cow manure contains high levels of organic matter (such as cellulose, hemicellulose, and protein) and minerals (such as nitrogen, phosphorus, and potassium), as well as a certain amount of microorganisms (especially anaerobic microorganisms) and undigested feed residue. If cow manure is discharged directly without treatment, it will lead to environmental risks such as eutrophication of water bodies, soil pollution, and foul odors. How to effectively treat and utilize cow manure has become an important environmental and economic issue.

[0003] Domestic and international scholars have conducted in-depth research on the resource utilization of cow manure. Currently, the main methods of cow manure resource utilization include energy production, fertilizer production, and substrate production. While cow manure fertilizer and substrate production can effectively treat the dry matter in cow manure, they are difficult to utilize for wastewater. Energy utilization, primarily through anaerobic digestion to produce biogas, can treat and utilize all of the manure from cattle farms; however, the biogas product has poor economic viability, and there is also the problem of difficult disposal of biogas slurry generated from large-scale biogas projects, which to some extent restricts the sustainable application of this technology. Changing the traditional anaerobic fermentation process, which focuses on biogas production, and directionally converting the organic carbon source in cow manure into organic acid products, which can then be used as a carbon source for wastewater treatment plants or for green chemical synthesis, can improve the economic viability of the products while treating all of the manure.

[0004] Existing technologies disclose methods for fermenting cow dung with straw or kitchen waste to produce acid, but these methods suffer from problems such as a single product, low yield, and complex and costly processes for separating and purifying organic acids from the fermentation liquid. In addition, the poor adaptability of some highly efficient functional bacteria to the cow dung environment is also a key issue restricting the fermentation of cow dung to produce acid. Summary of the Invention

[0005] This application provides a method for enhancing cow manure fermentation and acid production by using salt-tolerant microorganisms coupled with acid-base regulation, aiming to solve the problems of single product, low yield, complex process and high cost in existing cow manure fermentation and acid production.

[0006] This application provides a method for enhancing cow manure fermentation and acid production through salt-tolerant microorganisms coupled with acid-base regulation, comprising the following steps:

[0007] (1) Heat-treat and acclimatize the activated sludge to enrich the salt-tolerant acid-producing microbial community for later use; (2) The activated sludge after thermal domestication and cow manure are mixed to obtain the initial raw material for fermentation. The fermentation process is carried out by adjusting the pH and supplementing the domesticated sludge to regulate the total abundance of salt-tolerant acid-producing bacteria in the fermentation system to obtain organic acids.

[0008] According to some embodiments of the method for enhancing cow manure fermentation and acid production by coupling salt-tolerant microorganisms with acid-base regulation as described in this application, the activated sludge is derived from an anaerobic reactor using livestock and poultry manure as fermentation raw material, preferably from an anaerobic reactor using dairy cow manure as raw material.

[0009] According to some embodiments of the method for enhancing cow manure fermentation and acid production by coupling salt-tolerant microorganisms with acid-base regulation as described in this application, the volatile organic compound content in the domesticated activated sludge is 4-6% by mass, calculated as VS.

[0010] According to some embodiments of the method for enhancing cow manure fermentation and acid production by coupling salt-tolerant microorganisms with acid-base regulation as described in this application, the operation method of the activated sludge heat treatment includes: placing the activated sludge in an open container, controlling the temperature at 70-80℃ through a water bath or oil bath, and simultaneously adjusting the pH of the activated sludge to 8.5-10.0, and heat treating under these conditions for 1-3 hours to reduce the metabolic activity of the original methanogenic bacteria in the sludge.

[0011] According to some embodiments of the method for enhancing the fermentation and acid production of cow manure by coupling salt-tolerant microorganisms with acid-base regulation as described in this application, the acclimation method includes: mixing heat-treated sludge with cow manure for anaerobic fermentation to acclimate the acid-producing microorganisms in the activated sludge to gradually adapt to the salt and organic matter components in the cow manure.

[0012] According to some embodiments of the method for enhancing cow manure fermentation and acid production by coupling salt-tolerant microorganisms with acid-base regulation as described in this application, the mass ratio of volatile solids in cow manure to volatile solids in activated sludge during the domestication process is 1:(4-6).

[0013] According to some embodiments of the method for enhancing the fermentation and acid production of cow manure by coupling salt-tolerant microorganisms with acid-base regulation as described in this application, in step (2), the mass ratio of the activated sludge to the cow manure in the initial fermentation raw material is (1-3):1, based on volatile solids; after one week of fermentation, acclimatized sludge is added to the fermentation material so that the salt concentration in the fermentation system reaches 6.4-16.0 mg / L; preferably, the salt includes potassium salt, sodium salt and chloride ions.

[0014] According to some embodiments of the method for enhancing the fermentation and acid production of cow manure by coupling salt-tolerant microorganisms with acid-base regulation as described in this application, the solid content of the cow manure is 5wt%-20wt%.

[0015] According to some embodiments of the method for enhancing the fermentation and acid production of cow manure by coupling salt-tolerant microorganisms with acid-base regulation as described in this application, the mass content of volatile organic compounds in the cow manure is 5%-15%.

[0016] According to some embodiments of the method for enhancing the fermentation and acid production of cow manure by coupling salt-tolerant microorganisms with acid-base regulation as described in this application, the crude protein content in the cow manure is 10%-15%.

[0017] According to some embodiments of the method for enhancing the fermentation and acid production of cow manure by coupling salt-tolerant microorganisms with acid-base regulation as described in this application, in step (2), the pH adjustment includes: adjusting the pH to 7-11 during fermentation fluctuations.

[0018] According to some embodiments of the method for enhancing cow manure fermentation and acid production by coupling salt-tolerant microorganisms with acid-base regulation as described in this application, the fermentation fluctuation includes a first fermentation fluctuation stage and a second fermentation fluctuation stage; the first fermentation fluctuation stage is 3-5 days after fermentation starts; the second fermentation fluctuation stage is 8-12 days after fermentation starts.

[0019] According to some embodiments of the method for enhancing the fermentation and acid production of cow manure by coupling salt-tolerant microorganisms with acid-base regulation as described in this application, in step (2), the reagents used to adjust the pH include one or more of hydrochloric acid, sulfuric acid, sodium hydroxide and potassium hydroxide.

[0020] According to some embodiments of the method for enhancing the fermentation and acid production of cow manure by coupling salt-tolerant microorganisms with acid-base regulation as described in this application, in step (2), the phased supplementation of acclimatized sludge includes supplementing acclimatized sludge at 4%-6% of the fermentation volume one week after the start of fermentation, so as to maintain the abundance of salt-tolerant acid-producing bacteria in the fermentation material ≥30%.

[0021] According to some embodiments of the method for enhancing cow manure fermentation and acid production by coupling salt-tolerant microorganisms with acid-base regulation as described in this application, the total abundance of salt-tolerant acid-producing bacteria in the fermentation material is 40%-60%.

[0022] According to some embodiments of the method for enhancing cow manure fermentation and acid production by coupling salt-tolerant microorganisms with acid-base regulation as described in this application, the salt-tolerant acid-producing bacteria include Porphyromonas, halophilic bacteria, and Streptococcus.

[0023] According to some embodiments of the method for enhancing cow manure fermentation and acid production by coupling salt-tolerant microorganisms with acid-base regulation as described in this application, the fermentation temperature is 30-40℃ and the fermentation time is 16-20 days.

[0024] According to some embodiments of the method for enhancing cow manure fermentation and acid production by coupling salt-tolerant microorganisms with acid-base regulation as described in this application, the organic acid includes one or more of acetic acid, propionic acid, isobutyric acid, butyric acid, isovaleric acid, valeric acid, and hexanoic acid.

[0025] The beneficial effects of this application include: The method for enhancing the fermentation and acid production of cow manure by coupling salt-tolerant microorganisms with acid-base regulation described in this application uses cow manure with high salt content and strong acid-producing ability of bovine rumen microorganisms as fermentation material. Through natural domestication, it induces the efficient accumulation of salt-tolerant acid-producing bacteria. At the same time, by adjusting the pH of the fermentation system and supplementing the domesticated inoculated sludge in stages, the metabolic activity of anaerobic methanogenic bacteria in the system is controlled by acid-base regulation and salt stress. This induces salt- and alkali-tolerant anaerobic acid-producing microorganisms to become the dominant bacteria, promotes the rapid acidification of organic matter in dairy cow manure, reduces the methanation of organic acids, and achieves the targeted accumulation of organic acids.

[0026] The products of cow manure fermentation for acid production described in this application are diverse, and the organic acids produced can be widely used in the production of medium-chain fatty acids and the industrial synthesis of downstream chemical products. To a certain extent, this solves the problem that the utilization pathways of cow manure composting and anaerobic biogas production are relatively singular and have low economic value. Detailed Implementation

[0027] The embodiments of the present invention are described in detail below. These embodiments are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0028] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0029] This application provides a method for enhancing cow manure fermentation and acid production through salt-tolerant microorganisms coupled with acid-base regulation, comprising the following steps: (1) Heat-treat and acclimatize the activated sludge to enrich the salt-tolerant acid-producing microbial community for later use; (2) The activated sludge after thermal domestication and cow manure are mixed to obtain the initial raw material for fermentation. The fermentation process is carried out by adjusting the pH and supplementing the domesticated sludge to regulate the total abundance of salt-tolerant acid-producing bacteria in the fermentation system to obtain organic acids.

[0030] The method described in this application for enhancing acid production through the coupled acid-base regulation of salt-tolerant microorganisms in cow manure fermentation uses cow manure as the fermentation substrate (cow manure has a high content of organic components and high salt content). By controlling the salt content during the fermentation process, supplementing activated sludge in stages, and adjusting the pH during the fermentation process, the abundance of salt-tolerant acid-producing microorganisms during the anaerobic fermentation of cow manure is induced and enriched. This enhances the hydrolysis of organic components in cow manure and the targeted acidification of organic carbon sources by the dominant salt-tolerant acid-producing bacteria. At the same time, the metabolic activity and abundance of anaerobic methanogens in the fermentation system are reduced through the above-mentioned regulation methods, further avoiding the methanation of organic acids produced during the hydrolysis fermentation process and promoting the effective accumulation of volatile organic acids such as acetic acid in the fermentation system.

[0031] In some embodiments of this application, the activated sludge is derived from an anaerobic reactor using livestock and poultry manure as fermentation raw material.

[0032] In some embodiments of this application, the activated sludge originates from an anaerobic reactor using cow manure as raw material. Compared to chicken and pig manure, cow manure has a higher C / N ratio, and the ammonia nitrogen concentration in the acidified organic acid solution produced after fermentation is relatively low. Therefore, it can be used directly as a carbon source in wastewater treatment plants without purification, saving carbon source costs and providing a new approach for the harmless treatment and rational utilization of cow manure.

[0033] In some embodiments of this application, the volatile organic compound (VOC) content in the acclimated activated sludge is 4-6% by mass, expressed as VS. The sludge is primarily composed of microbial cells, with no more than 1% of the organic matter available as a substrate. Its main purpose is to provide functional microorganisms for subsequent hydrolysis and acidification of cow manure.

[0034] In some embodiments of this application, the operation method of the activated sludge heat treatment includes: placing the activated sludge in an open container, controlling the temperature at 70-80℃ through a water bath or oil bath, and simultaneously adjusting the pH of the activated sludge to 8.5-10.0, and heat-treating under these conditions for 1-3 hours to reduce the metabolic activity of the original methanogenic bacteria in the sludge. Adjusting the pH of the activated sludge to 8.5-10.0 during the heat treatment process is mainly based on the tolerance thresholds of anaerobic methanogenic bacteria and anaerobic acidogenic bacteria to high temperatures and high pH. Generally, the tolerance thresholds of anaerobic methanogenic bacteria to high temperatures and pH are 53-55℃ and 7.5-8.1, respectively. Anaerobic acidogenic bacteria, being bacteria, can form sporophytes under high temperature or high pH conditions, thereby maintaining their activity. This pretreatment method can effectively reduce the abundance and metabolic activity of anaerobic methanogenic bacteria in the inoculated activated sludge, promoting anaerobic acidogenic bacteria to become the main active microorganisms, which is beneficial for the rapid start-up of subsequent cow manure fermentation and acid production.

[0035] In some embodiments of this application, the acclimation method includes: mixing heat-treated sludge with cow manure for anaerobic fermentation to acclimate the acid-producing microorganisms in the activated sludge to the salt and organic matter components in the cow manure. Acclimation generally involves mixing heat-treated inoculated activated sludge with cow manure in a suitable ratio, with the initial acclimation ratio being VS0. 牛粪 VS 污泥 =1:(4-6), while maintaining anaerobic mesophilic conditions for acclimatization, so that the acid-producing microorganisms in the inoculated sludge gradually adapt to the salt and organic matter components in the cow manure, thereby achieving the purpose of acclimatization.

[0036] In some embodiments of this application, in step (2), the mass ratio of the activated sludge to the cow manure in the initial fermentation raw materials is (1-3):1, based on volatile solids; after one week of fermentation, acclimatized sludge is added to the fermentation material to bring the salt concentration in the fermentation system to 6.4-16.0 mg / L. The salt composition mainly includes potassium salt, sodium salt, and chloride ions, which further reduces the metabolic activity of methanogens in the system and induces salt-tolerant acid-producing microorganisms to become the dominant microorganisms through salt stress.

[0037] In some embodiments of this application, the solid content of the cow manure is 5wt%-20wt%; for example, 5wt%, 8wt%, 11wt%, 13wt%, 15wt%, 16wt%, 18wt%, 20wt%, etc. This varies depending on the manure collection method.

[0038] In some embodiments of this application, the mass content of volatile organic compounds in the cow dung is 5%-15%, such as 5%, 8%, 11%, 12%, 15%, etc.

[0039] In some embodiments of this application, step (2) includes adjusting the pH to 7-11 during fermentation fluctuations; for example, pH 7, 8, 9, 10, 11, etc. Alkaline conditions can reduce the metabolic activity of methanogens and reduce the formation of molecular states of organic acids produced during fermentation, thereby reducing the risk of product feedback inhibition.

[0040] In some embodiments of this application, the fermentation fluctuation includes a first fermentation fluctuation stage and a second fermentation fluctuation stage; the first fermentation fluctuation stage is 3-5 days after fermentation initiation; the second fermentation fluctuation stage is 8-12 days after fermentation initiation. By adjusting the pH of the fermentation material, the abundance of salt-tolerant acid-producing bacteria in the system is induced again, the abundance and activity of potential methanogenic archaea in the system are reduced, the hydrolysis and acidification of organic carbon sources are promoted, and the targeted accumulation of organic acids is further achieved.

[0041] In some embodiments of this application, in step (2), the reagent used to adjust the pH includes one or more of hydrochloric acid, sulfuric acid, sodium hydroxide, and potassium hydroxide. Low concentration reagents should be selected whenever possible, such as 1 mol / L, 2 mol / L, or 3 mol / L.

[0042] In some embodiments of this application, step (2) includes supplementing the acclimatized sludge in stages by adding acclimatized sludge at 4%-6% of the fermentation volume one week after the start of fermentation, so as to maintain the abundance of salt-tolerant acid-producing bacteria in the fermentation material ≥30%.

[0043] In some embodiments of this application, the total abundance of salt-tolerant acid-producing bacteria in the fermentation material is 40%-60%; for example, 40%, 45%, 48%, 50%, 55%, 60%, etc.

[0044] In some embodiments of this application, the salt-tolerant acid-producing bacteria include *Porphyromonas violaceum*, halophilic bacteria, and streptococci.

[0045] In some embodiments of this application, the fermentation temperature is 30-40°C, such as 30°C, 32°C, 35°C, 38°C, 40°C, etc., and the fermentation time is 16-20 days.

[0046] In some embodiments of this application, the organic acid includes one or more of acetic acid, propionic acid, isobutyric acid, butyric acid, isovaleric acid, valeric acid, and hexanoic acid. The fermentation method described in this application produces a variety of organic acids. These short-chain fatty acids can be further used to synthesize medium-chain fatty acids, degradable materials, and as carbon sources for nitrogen and phosphorus removal biochemical reactions in wastewater treatment plants. This can, to some extent, solve the problem of relatively singular and low-economic-value applications of cattle manure composting and anaerobic biogas production.

[0047] The technical solution of this application will be further described below with reference to specific embodiments.

[0048] Example 1 A method for producing acid through cow manure fermentation includes the following steps: (1) Sludge pretreatment: Activated sludge taken from an anaerobic fermentation tank with cow dung as the main raw material was placed in an open container and heated by a water bath at a temperature of 75°C. The pH of the activated sludge was simultaneously adjusted to 9.0 and heat-treated for 2 hours. The heat-treated sludge was then mixed with cow dung for anaerobic fermentation and acclimation (the mass ratio of volatile solids in cow dung to volatile solids in activated sludge was 1:5) so that the acid-producing microorganisms in the activated sludge gradually adapted to the salt and organic matter components in the cow dung. After acclimation, the mass content of volatile organic compounds in the activated sludge was 5%, calculated as VS.

[0049] (2) The pretreated activated sludge was inoculated into the fermenter. The amount of activated sludge inoculated was 10% (V / V) of the volume of cow manure. The fermentation concentration of cow manure was 5%VS, the salt content of cow manure was 5.8%, and the mass content of volatile organic compounds in cow manure was 10%. The initial pH of fermentation was adjusted to 9.0. At the same time, the abundance of salt-tolerant fermenting bacteria in the fermentation material was detected. After one week of fermentation, 4% of the fermentation volume of acclimated sludge was added. At the same time, the fermentation pH of the fermentation system was adjusted to 9.0 to induce salt-tolerant acid-producing bacteria such as Porphyromonadaceae, Planococcaceae, and Peptostreptococcaceae to become the dominant bacteria in the system. The abundance of salt-tolerant acid-producing bacteria was detected to be 50.7%. The fermentation temperature was controlled at 35±1℃. Fermentation was carried out at this temperature for 20 days to obtain the fermentation liquid.

[0050] The total organic acid yield in the system was 413.5 mg COD / gVS, with yields of acetic acid, propionic acid, isobutyric acid, butyric acid, isovaleric acid, valeric acid, and hexanoic acid of 281.3, 50.0, 12.5, 36.5, 17.6, 8.4, and 7.2 mg COD / gVS, respectively.

[0051] Example 2 The method for enhancing cow manure fermentation and acid production by coupling salt-tolerant microorganisms with acid-base regulation in Example 2 differs from that in Example 1 only in that the pH value during the fermentation process is adjusted from 9.0 to 8.0, and the abundance of salt-tolerant thermophilic fermenting and acid-producing bacteria such as Porphyromonadaceae, Planococcaceae, and Peptostreptococcaceae is induced to be 40.4% during the fermentation process. All other fermentation conditions remain the same as in Example 1.

[0052] After 20 days of fermentation, the total organic acid yield in the system was 362.4 mg COD / gVS, with yields of acetic acid, propionic acid, isobutyric acid, butyric acid, isovaleric acid, and valeric acid of 217.9, 46.9, 13.8, 54.7, 17.7, and 11.5 mg COD / gVS, respectively. Compared with Example 1, the total organic acid concentration decreased by 12.4%.

[0053] Example 3 The method for enhancing cow manure fermentation and acid production by coupling salt-tolerant microorganisms with acid-base regulation in Example 3 differs from that in Example 1 only in that the pH value during the fermentation process is adjusted from 9.0 to 10.0, and the abundance of salt-tolerant thermophilic fermenting and acid-producing bacteria such as Porphyromonadaceae, Planococcaceae, and Peptostreptococcaceae is induced to be 25.1% during the fermentation process. All other fermentation conditions remain the same as in Example 1.

[0054] After 20 days of fermentation, the total organic acid yield in the system was 357.3 mgCOD / gVS, with the yields of acetic acid, propionic acid, isobutyric acid, butyric acid, isovaleric acid, and valeric acid being 257.6, 25.4, 11.5, 41.5, 15.7, and 8.9 mgCOD / gVS, respectively. Compared with Example 1, the total organic acid concentration decreased by 13.6%.

[0055] Comparative Example 1 The method for enhancing cow manure fermentation and acid production by coupling salt-tolerant microorganisms with acid-base regulation described in Comparative Example 1 differs from that in Example 1 only in that the pH value of the fermentation process is adjusted from 9.0 to 11.0 during the enhanced cow manure fermentation and acid production by coupling salt-tolerant microorganisms with acid-base regulation. At the same time, the proliferation of salt-tolerant thermophilic fermenting and acid-producing bacteria such as Porphyromonadaceae, Planococcaceae, and Peptostreptococcaceae is induced during the fermentation process, with an abundance of only 5.2%. All other fermentation conditions are consistent with those in Example 1.

[0056] After 20 days of mesophilic fermentation, the total organic acid yield in the system was 262.7 mgCOD / gVS, of which the yields of acetic acid, propionic acid, isobutyric acid, butyric acid and isovaleric acid were 207.3, 14.8, 7.7, 19.2 and 13.6 mgCOD / gVS, respectively; compared with Example 1, the total organic acid concentration decreased by 36.5%.

[0057] Comparative Example 2 The method for enhancing cow manure fermentation and acid production by coupling salt-tolerant microorganisms with acid-base regulation described in Comparative Example 2 differs from that in Example 1 only in that the pH value during the fermentation process is adjusted from 9.0 to 7.0. The dominant microbial community during the fermentation process consists mainly of cellulose-degrading microorganisms and halophilic bacteria such as Planococcaceae, Porphyromonadaceae, and Peptostreptococcaceae, accounting for 35.2%. All other fermentation conditions remain the same as in Example 1.

[0058] After 20 days of mesophilic fermentation, the total organic acid yield in the system was 325.1 mg COD / gVS, with yields of acetic acid, propionic acid, isobutyric acid, butyric acid, isovaleric acid, valeric acid, and hexanoic acid of 157.9, 42.0, 16.4, 74.7, 16.8, 8.9, and 8.3 mg COD / gVS, respectively. Compared with Example 1, the total organic acid concentration decreased by 21.3%.

[0059] Comparative Example 3 The method for enhancing cow manure fermentation and acid production by coupling salt-tolerant microorganisms with acid-base regulation described in Comparative Example 3 differs from that in Example 1 only in that the pH value during the fermentation process of enhancing cow manure fermentation and acid production by coupling salt-tolerant microorganisms with acid-base regulation in Comparative Example 3 is adjusted from 9.0 to 4.0. During the fermentation process, the abundance of salt-tolerant thermophilic fermenting and acid-producing bacteria such as Planococcaceae, Porphyromonadaceae, and Peptostreptococcaceae is significantly reduced to only 14.7%. All other fermentation conditions are consistent with those in Example 1.

[0060] After 20 days of mesophilic fermentation, the total organic acid yield in the system was 76.4 mgCOD / gVS. Only acetic acid, propionic acid, butyric acid and isovaleric acid were detected in the product distribution, with yields of 54.1, 6.9, 8.6 and 6.9 mgCOD / gVS, respectively. Compared with Example 1, the total organic acid concentration was only 18.5% of that in Example 1.

[0061] Although the above embodiments have been shown and described, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Any changes, modifications, substitutions and variations made to the above embodiments by those skilled in the art are within the protection scope of the present invention.

Claims

1. A method for enhancing cow manure fermentation and acid production through salt-tolerant microorganisms coupled with acid-base regulation, characterized in that, Includes the following steps: (1) Heat-treat and acclimatize the activated sludge to enrich the salt-tolerant acid-producing microbial community for later use; (2) The activated sludge after thermal domestication and cow manure are mixed to obtain the initial raw material for fermentation. The fermentation process is carried out by adjusting the pH and supplementing the domesticated sludge to regulate the total abundance of salt-tolerant acid-producing bacteria in the fermentation system to obtain organic acids.

2. The method for enhancing cow manure fermentation and acid production by coupling salt-tolerant microorganisms with acid-base regulation according to claim 1, characterized in that, The activated sludge is derived from an anaerobic reactor using livestock and poultry manure as fermentation raw material, preferably from an anaerobic reactor using dairy cow manure as raw material. And / or, the volatile organic compound content in the acclimated activated sludge is 4-6% by mass, expressed as VS.

3. The method for enhancing cow manure fermentation and acid production by coupling salt-tolerant microorganisms with acid-base regulation according to claim 1, characterized in that, The operation method of the activated sludge heat treatment includes: placing the activated sludge in an open container, controlling the temperature at 70-80℃ through a water bath or oil bath, and simultaneously adjusting the pH of the activated sludge to 8.5-10.0, and heat treating it for 1-3 hours under these conditions to reduce the metabolic activity of the original methanogenic bacteria in the sludge. And / or, the acclimation method includes: mixing heat-treated sludge with cow manure for anaerobic fermentation to acclimate the sludge, so that the acid-producing microorganisms in the activated sludge gradually adapt to the salt and organic matter components in the cow manure; Preferably, the mass ratio of volatile solids in cow dung to volatile solids in activated sludge during the acclimation process is 1:(4-6).

4. The method for enhancing cow manure fermentation and acid production by coupling salt-tolerant microorganisms with acid-base regulation according to claim 1, characterized in that, In step (2), the mass ratio of the activated sludge and the cow manure in the initial fermentation raw materials is (1-3):1, based on volatile solids.

5. The method for enhancing cow manure fermentation and acid production by coupling salt-tolerant microorganisms with acid-base regulation according to claim 1, characterized in that, The solid content of the cow dung is 5wt%-20wt%; And / or, the mass content of volatile organic compounds in the cow manure is 5%-15%.

6. The method for enhancing cow manure fermentation and acid production by coupling salt-tolerant microorganisms with acid-base regulation according to claim 1, characterized in that, In step (2), adjusting the pH includes adjusting the pH to 7-11 during fermentation fluctuations.

7. The method for enhancing cow manure fermentation and acid production by coupling salt-tolerant microorganisms with acid-base regulation according to claim 1, characterized in that, In step (2), the reagents used to adjust the pH include one or more of hydrochloric acid, sulfuric acid, sodium hydroxide, and potassium hydroxide.

8. The method for enhancing cow manure fermentation and acid production by coupling salt-tolerant microorganisms with acid-base regulation according to claim 1, characterized in that, In step (2), the phased replenishment of acclimatized sludge includes replenishing acclimatized sludge at 4%-6% of the fermentation volume one week after the start of fermentation, in order to maintain the abundance of salt-tolerant acid-producing bacteria in the fermentation material at ≥30%; Preferably, the total abundance of salt-tolerant acid-producing bacteria in the fermentation material is 40%-60%; Preferably, the salt-tolerant acid-producing bacteria include *Porphyromonas violaceum*, halophilic bacteria, and streptococci.

9. The method for enhancing cow manure fermentation and acid production by coupling salt-tolerant microorganisms with acid-base regulation according to claim 1, characterized in that, The fermentation temperature is 30-40℃, and the fermentation time is 16-20 days.

10. The method for enhancing cow manure fermentation and acid production by coupling salt-tolerant microorganisms with acid-base regulation according to claim 1, characterized in that, The organic acid includes one or more of acetic acid, propionic acid, isobutyric acid, butyric acid, isovaleric acid, valeric acid, and hexanoic acid.