A method for promoting acid production by anaerobic fermentation of excess sludge
By subjecting the remaining sludge to natural sedimentation, concentration, and metabisulfite pretreatment, the extracellular polymer structure is destroyed, promoting anaerobic fermentation and acid production, thus solving the problem of low VFA yield and realizing the resource utilization of sludge and environmentally friendly wastewater treatment.
Patent Information
- Application Number
- CN202410518668.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-04-28
- Publication Date
- 2025-11-25
- Estimated Expiration
- 2044-04-28
AI Technical Summary
The existing anaerobic digestion process for producing VFAs from waste sludge has a low hydrolysis rate and low VFA yield, resulting in the underutilization of organic matter resources.
After the residual sludge is allowed to settle and concentrate naturally, it is pretreated with metabisulfite, including adjusting the pH and constant temperature shaking in an anaerobic environment to destroy the extracellular polymer structure and promote the release of organic matter, and then anaerobic fermentation to produce acid.
It increased the production of VFAs, enabled the resource utilization of sludge, reduced disposal costs, alleviated the problem of insufficient carbon sources in wastewater treatment, and reduced environmental risks.
Smart Images
Figure CN118270962B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of environmental protection technology, and in particular to a method for promoting the anaerobic fermentation of waste sludge to produce acid. Background Technology
[0002] Urban wastewater treatment plants generate a large amount of residual sludge annually. Improper treatment of this sludge can cause serious environmental problems. This is because, on the one hand, residual sludge contains pathogens, heavy metals, and persistent organic pollutants, which, if improperly treated, can threaten the environment and human health. On the other hand, residual sludge is rich in organic matter, such as proteins and carbohydrates, which should be treated as resources rather than waste to ensure the sustainable operation of wastewater treatment plants and meet dual-carbon (carbon and carbon) targets. Typically, the cost of residual sludge disposal can reach 20%-50% of the operating costs of a wastewater treatment plant, posing a significant challenge. Therefore, a suitable sludge treatment method is urgently needed.
[0003] Investigations revealed four main approaches to the treatment and disposal of waste sludge in China: anaerobic digestion + land application, aerobic fermentation + land application, drying and incineration + ash landfill or building material utilization, and deep dewatering + emergency landfill. Landfilling is the most prevalent method, which not only increases the pressure on landfill space but also wastes a significant amount of resources. Anaerobic fermentation, on the other hand, can achieve both stabilization and volume reduction of waste sludge, while also recovering high-value byproducts such as methane, hydrogen, and volatile organic acids (VFAs). Compared to methane and hydrogen production, VFAs are safer and more convenient to transport and store. Furthermore, VFAs can be used as a carbon source for nitrogen and phosphorus removal in wastewater treatment plants, providing a new solution to the long-standing problem of insufficient carbon sources in these facilities.
[0004] However, since most of the organic matter in the residual sludge is coated with extracellular polymers and is difficult to be digested and utilized by anaerobic bacteria, the efficiency of traditional anaerobic digestion is very low, and the organic matter resources in the sludge are not fully utilized. Summary of the Invention
[0005] The purpose of this application is to address the problems of low hydrolysis rate and low VFA yield in existing anaerobic digestion processes for producing VFAs from waste sludge, and to provide a method for promoting anaerobic fermentation of waste sludge to produce acid.
[0006] To achieve the above objectives, the technical solution of this application is as follows:
[0007] This application provides a method for promoting anaerobic fermentation and acid production from excess sludge, comprising:
[0008] The remaining sludge is subjected to natural sedimentation and concentration treatment to obtain concentrated sludge.
[0009] The concentrated sludge was pretreated with metabisulfite to obtain pretreated sludge;
[0010] The pretreated sludge is then subjected to anaerobic fermentation to produce acid.
[0011] Preferably, the residual sludge is residual sludge generated by a sewage treatment plant, and the residual sludge settles naturally at room temperature for 4-36 hours.
[0012] Preferably, the concentration of volatile solids in the concentrated sludge is 4.0 g / L to 12 g / L.
[0013] Preferably, the preprocessing includes:
[0014] The pH of the concentrated sludge is adjusted to 8.8-9.2, metabisulfite is added, and then it is placed in an anaerobic environment for constant temperature shaking pretreatment in a constant temperature shaker.
[0015] More preferably, the anaerobic environment treatment process includes: introducing an inert gas into the fermentation reaction vessel to purge oxygen, wherein the inert gas includes at least one of nitrogen, argon, helium, and neon.
[0016] More preferably, the isothermal oscillation pretreatment time does not exceed 36 hours, and the temperature is 20℃-25℃.
[0017] Preferably, the concentration of metabisulfite added is calculated based on the sulfur content in the concentrated sludge, wherein the sulfur content is 300 mg-S / L to 500 mg-S / L.
[0018] Preferably, before the anaerobic fermentation to produce acid, the method further includes: adjusting the pH of the pretreated sludge to 6.8-7.2 before carrying out the anaerobic fermentation to produce acid.
[0019] Preferably, the anaerobic fermentation acid production time is 5-15 days, and the temperature is 25℃-40℃.
[0020] Preferably, the acid produced by the anaerobic fermentation is a volatile organic acid.
[0021] Preferably, the metabisulfite includes at least one of sodium metabisulfite or potassium metabisulfite.
[0022] The beneficial effects of this application are:
[0023] 1. By using the method proposed in this application, the residual sludge from sewage treatment plants can be utilized to produce acid, saving sludge disposal costs, reducing its potential environmental risks, and achieving sludge reduction, resource utilization, and harmlessness.
[0024] 2. The volatile organic acids obtained after anaerobic fermentation of this application can be reused in the biological system of the sewage treatment process as a carbon source, which can alleviate the problem of insufficient carbon source in urban domestic sewage treatment in my country, reduce the purchase of external carbon sources, and reduce sewage treatment costs.
[0025] 3. Metabisulfite is a commonly used chemical raw material. It is inexpensive and has the function of food preservation and sterilization. Therefore, using metabisulfite to pretreat excess sludge can effectively reduce the biotoxicity of sludge. Attached Figure Description
[0026] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation on the scope of this application.
[0027] Figure 1 A bar chart showing the total cumulative amount of VFAs obtained at the end of the fifth day after anaerobic fermentation to produce acid in Examples 1-2 and Comparative Examples 1-3.
[0028] Figure 2 The cumulative amount of each component in the VFAs obtained at the end of the fifth day after anaerobic fermentation to produce acid in Examples 1-2 and Comparative Examples 1-3 is shown in the bar chart. Detailed Implementation
[0029] As used in this article:
[0030] "Prepared from" is synonymous with "comprising". The terms "comprising", "including", "having", "containing", or any other variations thereof as used herein are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such a composition, step, method, article, or apparatus. The conjunction "composed of" excludes any unnamed elements, steps, or components.
[0031] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1–5” is disclosed, the described range should be interpreted as including ranges “1–4”, “1–3”, “1–2”, “1–2 and 4–5”, “1–3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.
[0032] In these embodiments, unless otherwise specified, the portions and percentages are all by weight.
[0033] "Parts by mass" refers to the basic unit of measurement that expresses the mass ratio of multiple components. One part can represent any unit mass, such as 1g or 2.689g. If we say that component A has "a" parts by mass and component B has "b" parts by mass, it means the ratio of the mass of component A to the mass of component B is a:b. Alternatively, it can mean that the mass of component A is aK and the mass of component B is bK (K is any number representing a multiplier). It is important to understand that, unlike the number of parts by mass, the sum of the mass parts of all components is not limited to 100 parts.
[0034] "And / or" is used to indicate that one or both of the described situations may occur, for example, A and / or B includes (A and B) and (A or B).
[0035] This application provides a method for promoting anaerobic fermentation and acid production from excess sludge, comprising:
[0036] S1. The remaining sludge is subjected to natural sedimentation and concentration treatment to obtain concentrated sludge;
[0037] S2. The concentrated sludge is pretreated with metabisulfite to obtain pretreated sludge;
[0038] S3. The pretreated sludge is subjected to anaerobic fermentation to produce acid.
[0039] Understandably, most of the organic matter in residual sludge is contained within sludge flocs. These flocs are a very stable structure formed by extracellular polymers produced outside the sludge cells. Therefore, appropriate pretreatment methods are needed to disrupt the extracellular polymer structure of the sludge, causing the sludge flocs to disintegrate, promoting the release of intracellular organic matter, and facilitating the efficient utilization of organic matter during anaerobic digestion. The metabisulfite selected in this application can effectively disrupt the extracellular polymer structure and cell wall structure of sludge cells, causing the sludge flocs to disintegrate and the cells to lyse, releasing a large amount of organic matter from the sludge cells. Furthermore, it breaks down the extracellular polymer structure into simpler soluble proteins and polysaccharides, which are easier to hydrolyze and digest, promoting the production of volatile organic acids (VFAs) during anaerobic digestion of the sludge.
[0040] Furthermore, in the system that uses metabisulfite pretreatment of waste sludge to produce VFAs, the abundance of acid-producing bacteria (such as Romboutsia, Clostridium, and Bacillus) increased in the later stages of anaerobic fermentation, while the abundance of methanogenic bacteria (such as Methanosaeta) decreased significantly. This indicates that it has an inhibitory effect on methanogenic bacteria, promoting acid production metabolism while inhibiting methanogenesis during anaerobic digestion, reducing the further metabolism of VFAs, and effectively increasing the accumulation of VFAs.
[0041] Metabisulfite is also a typical food preservative. In the fermentation of waste sludge to produce VFAs, it can inhibit methane production, stimulate protein or polysaccharide release, promote EPS secretion, and induce cell death, all of which are highly correlated with increased VFA yield. Due to its cost-effectiveness and ease of use, sodium metabisulfite has become one of the most effective salts for controlling microbial growth. For example, sodium metabisulfite has been used in the preservation of silage because of its oxygen-scavenging properties and inhibition of oxygen-dependent microorganisms. This partly explains the reduced abundance of some bacteria (such as Proteus) originating from wastewater treatment plants. While inhibiting methane production, metabisulfite also improves sludge dissolution efficiency, indicating its specificity in VFA production and its advantage over sulfite.
[0042] In one embodiment of this application, the residual sludge in S1 is residual sludge generated by a sewage treatment plant, and the residual sludge settles naturally at room temperature for 4-36 hours.
[0043] In one embodiment of this application, the concentration of volatile solids in the concentrated sludge in S1 is 4.0 g / L to 12 g / L, for example, it can be 4.0 g / L, 4.5 g / L, 5.0 g / L, 6 g / L, 8 g / L, 10 g / L, 12 g / L, or any value between 4.0 g / L and 12 g / L. That is, the concentration of the concentrated sludge, expressed as VS, ranges from 4.0 g VS / L to 12 g VS / L.
[0044] In one embodiment of this application, the pretreatment in S2 includes: adjusting the pH of the concentrated sludge to 8.8-9.2, adding the metabisulfite, and then placing it in an anaerobic environment for constant-temperature shaking pretreatment in a constant-temperature shaker. Alternatively, the pH of the concentrated sludge can be adjusted first, then placed in an anaerobic environment, followed by the addition of metabisulfite and shaking pretreatment.
[0045] In one embodiment of this application, the isothermal oscillation pretreatment time does not exceed 36 hours, for example, it can be any value between 1 hour, 6 hours, 12 hours, 24 hours, 36 hours or not exceeding 36 hours; the pretreatment temperature is 20℃-25℃, for example, it can be 20℃, 21℃, 22℃, 23℃, 24℃, 25℃ or any value between 20℃ and 25℃.
[0046] In one embodiment of this application, the anaerobic environment treatment process includes: introducing an inert gas into the fermentation reaction vessel to vent oxygen, wherein the inert gas includes at least one of nitrogen, argon, helium, and neon.
[0047] In one embodiment of this application, the concentration of metabisulfite added in S2 is calculated based on the sulfur content in the concentrated sludge, wherein the sulfur content is 300 mg-S / L-500 mg-S / L, for example, it can be any value between 300 mg-S / L, 350 mg-S / L, 400 mg-S / L, 450 mg-S / L, 500 mg-S / L, or 300 mg-S / L-500 mg-S / L.
[0048] In one embodiment of this application, before anaerobic fermentation to produce acid in S3, the method further includes: adjusting the pH of the pretreated sludge to 6.8-7.2 before carrying out the anaerobic fermentation to produce acid.
[0049] In one embodiment of this application, the anaerobic fermentation time for acid production in S3 is 5-15 days, for example, it can be any value between 5 days, 8 days, 10 days, 12 days, 15 days, or 5 days and 15 days. The fermentation temperature for acid production is 25℃-40℃, for example, it can be any value between 25℃, 28℃, 30℃, 32℃, 35℃, 38℃, 40℃, or 25℃-40℃.
[0050] In one embodiment of this application, the acid produced by anaerobic fermentation in S3 is a volatile organic acid, including at least one of acetic acid, propionic acid, valeric acid, valeric acid, butyric acid, and isobutyric acid.
[0051] In one embodiment of this application, the metabisulfite added in S2 includes at least one of sodium metabisulfite or potassium metabisulfite.
[0052] The implementation schemes of this application will be described in detail below with reference to specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating this application and should not be regarded as limiting the scope of this application. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.
[0053] Example 1
[0054] This embodiment provides a method for promoting anaerobic fermentation and acid production from excess sludge, specifically including:
[0055] Step 1: After settling the excess sludge generated by the wastewater treatment plant at room temperature for 24 hours, remove the supernatant to obtain concentrated sludge (wherein, the concentrated sludge has a pH of 7.0±0.2 and a volatile solids (VS) concentration of 4.00 g / L), and then adjust the pH of the concentrated sludge to 9.0±0.2.
[0056] Step 2: Take 130 mL of concentrated sludge with adjusted pH and add it to an anaerobic fermenter with a working volume of 150 mL. Aerate it with nitrogen for 10 minutes to remove oxygen and maintain an anaerobic environment in the fermenter. Immediately after aeration, add 0.1158 g of sodium metabisulfite to make the concentration of metabisulfite in the fermenter 300 mg-S / L (based on the sulfur content in the sludge). Seal the fermenter.
[0057] Step 3: Place the fermenter obtained in Step 2 in a constant temperature shaking incubator and pretreat it for 24 hours at a temperature of 25±2℃ and a shaking frequency of 160rpm.
[0058] Step 4: After pretreatment, the pH of the sludge was readjusted to 7.0±0.2 in the fermenter. After purging with nitrogen for 5 minutes, the fermenter was sealed and placed in a constant-temperature shaking reaction chamber. Anaerobic fermentation was carried out for 10 days at a temperature of 37±2℃ and a shaking frequency of 160 rpm. During the anaerobic fermentation, no sludge was added to or removed from the fermenter. Simultaneously, VFAs concentration data were collected in the fermenter. By the end of day 5, the cumulative VFAs concentration reached 121.48 mg / g VS.
[0059] Example 2
[0060] This embodiment provides a method for promoting anaerobic fermentation and acid production from excess sludge, specifically including:
[0061] Step 1: After settling the excess sludge generated by the wastewater treatment plant at room temperature for 24 hours, remove the supernatant to obtain concentrated sludge (wherein, the concentrated sludge has a pH of 7.0±0.2 and a volatile solids (VS) concentration of 4.00 g / L), and then adjust the pH of the concentrated sludge to 9.0±0.2.
[0062] Step 2: Take 130 mL of concentrated sludge with adjusted pH and add it to an anaerobic fermenter with a working volume of 150 mL. Aerate it with nitrogen for 10 minutes to remove oxygen and maintain an anaerobic environment in the fermenter. Immediately after aeration, add 0.19131 g of sodium metabisulfite to make the concentration of metabisulfite in the fermenter 500 mg-S / L (based on the sulfur content in the sludge). Seal the fermenter.
[0063] Step 3: Place the fermenter obtained in Step 2 in a constant temperature shaking incubator and pretreat it for 24 hours at a temperature of 25±2℃ and a shaking frequency of 160rpm.
[0064] Step 4: After pretreatment, the pH of the sludge was readjusted to 7.0±0.2 in the fermenter. After purging with nitrogen for 5 minutes, the fermenter was sealed and placed in a constant-temperature shaking reaction chamber. Anaerobic fermentation and digestion were carried out for 10 days at a temperature of 37±2℃ and a shaking frequency of 160 rpm. During the anaerobic fermentation and digestion, no sludge was added to or removed from the fermenter. Simultaneously, VFAs concentration data were collected in the fermenter. At the end of day 5, the cumulative VFAs concentration reached 144.46 mg / g VS.
[0065] Comparative Example 1
[0066] This comparative example provides a method for promoting anaerobic fermentation and acid production from excess sludge, specifically including:
[0067] Step 1: After settling the excess sludge generated by the wastewater treatment plant at room temperature for 24 hours, remove the supernatant to obtain concentrated sludge (wherein, the pH of the concentrated sludge is 7.0±0.2 and the concentration of volatile solids (VS) is 4.00 g / L).
[0068] Step 2: Add 130mL of concentrated sludge to an anaerobic fermenter with a working volume of 150mL, aerate it with nitrogen for 10 minutes to remove oxygen and maintain the anaerobic environment of the fermenter. Seal the fermenter immediately after aeration.
[0069] Step 3: Place the fermenter obtained in Step 2 in a constant temperature shaking incubator and pretreat it for 24 hours at a temperature of 25±2℃ and a shaking frequency of 160rpm.
[0070] Step 4: After pretreatment, the fermenter was placed in a constant temperature shaking reaction chamber and anaerobic fermentation was carried out for 10 days at a temperature of 37±2℃ and a shaking frequency of 160 rpm. During the anaerobic fermentation, no sludge was added to or removed from the fermenter, and the concentration data of VFAs in the fermenter were collected. At the end of day 5, the cumulative concentration of VFAs was 55.17 mg / g VS.
[0071] Comparative Example 2
[0072] This comparative example provides a method for promoting anaerobic fermentation and acid production from excess sludge, specifically including:
[0073] Step 1: After settling the excess sludge generated by the wastewater treatment plant at room temperature for 24 hours, remove the supernatant to obtain concentrated sludge (wherein, the concentrated sludge has a pH of 7.0±0.2 and a volatile solids (VS) concentration of 4.00 g / L), and then adjust the pH of the concentrated sludge to 9.0±0.2.
[0074] Step 2: Take 130 mL of concentrated sludge with adjusted pH and add it to an anaerobic fermenter with a working volume of 150 mL. Aerate it with nitrogen for 10 minutes to remove oxygen and maintain the anaerobic environment of the fermenter. After aeration, seal the fermenter.
[0075] Step 3: Place the fermenter obtained in Step 2 into a constant temperature shaking incubator and pretreat it for 24 hours at a temperature of 37±2℃ and a shaking frequency of 160rpm.
[0076] Step 4: After pretreatment, the pH of the sludge was readjusted to 7.0±0.2 in the fermenter. After purging with nitrogen for 5 minutes, the fermenter was sealed and placed in a constant-temperature shaking reaction chamber. Anaerobic fermentation and digestion were carried out for 10 days at a temperature of 25±2℃ and a shaking frequency of 160 rpm. During the anaerobic fermentation and digestion, no sludge was added to or removed from the fermenter. Simultaneously, VFAs concentration data were collected in the fermenter. At the end of day 5, the cumulative VFAs concentration was 56.29 mg / g VS.
[0077] Comparative Example 3
[0078] This comparative example provides a method for promoting anaerobic fermentation and acid production from excess sludge, specifically including:
[0079] Step 1: After settling the excess sludge generated by the wastewater treatment plant at room temperature for 24 hours, remove the supernatant to obtain concentrated sludge (wherein, the pH of the concentrated sludge is 7.0±0.2 and the concentration of volatile solids (VS) is 4.00 g / L).
[0080] Step 2: Take 130 mL of the concentrated sludge obtained in Step 1 and add it to an anaerobic fermenter with a working volume of 150 mL. Aerate it with nitrogen for 10 minutes to remove oxygen and maintain an anaerobic environment in the fermenter. Immediately after aeration, add 0.19131 g of sodium metabisulfite to make the concentration of metabisulfite in the fermenter 500 mg-S / L (based on the sulfur content in the sludge). Seal the fermenter after aeration.
[0081] Step 3: Place the fermenter obtained in Step 2 in a constant temperature shaking incubator and pretreat it for 24 hours at a temperature of 25±2℃ and a shaking frequency of 160rpm.
[0082] Step 4: After pretreatment, open the fermenter and readjust the pH of the sludge to 7.0±0.2. After purging with nitrogen for 5 minutes, seal the fermenter and place it in a constant temperature shaking reaction chamber. Anaerobic fermentation and digestion will proceed for 10 days at a temperature of 37±2℃ and a shaking frequency of 160 rpm. During anaerobic fermentation and digestion, no sludge will be added to or removed from the fermenter. Simultaneously, VFAs concentration data will be collected in the fermenter. At the end of day 5, the cumulative VFAs concentration was 64.08 mg / g VS.
[0083] In the above examples and comparative examples, experiments were conducted to test the changes in parameters and conditions in the method for promoting anaerobic fermentation and acid production of excess sludge. Specifically, in Examples 1-2, as the amount of sodium metabisulfite added increased, the cumulative VFAs concentration increased significantly at the end of the fifth day. Especially after pretreatment with 500 mg / L sodium metabisulfite followed by anaerobic fermentation and acid production, the cumulative VFAs concentration at the end of the fifth day reached 144.46 mg / g VS, which was 1.25-1.6 times higher than the cumulative VFAs in Comparative Examples 1-3.
[0084] Figure 1 The total cumulative amount of VFAs obtained after the fifth day is given for Examples 1-2 and Comparative Examples 1-3. Among them, the cumulative amount of Example 2 is the highest, while the cumulative amount of Comparative Example 1 is the lowest. Figure 2 The cumulative amounts of each component in VFAs at the end of the fifth day after anaerobic fermentation and acid production in Examples 1-2 and Comparative Examples 1-3 are presented. Among them, the VFAs tested in Examples 1-2 and Comparative Example 3 have the highest ethanol content, while the VFAs tested in Comparative Examples 1 and 2 have the highest propionic acid content.
[0085] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.
[0086] Furthermore, those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of this application and form different embodiments. For example, any of the embodiments claimed above can be used in any combination. The information disclosed in this background section is intended only to enhance the understanding of the general background of this application and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.
Claims
1. A method for promoting anaerobic fermentation and acid production from excess sludge, characterized in that, include: The remaining sludge is subjected to natural sedimentation and concentration treatment to obtain concentrated sludge. The concentrated sludge was pretreated with metabisulfite to obtain pretreated sludge; The pretreatment includes: adjusting the pH of the concentrated sludge to 8.8-9.2, adding the metabisulfite, and then placing it in an anaerobic environment for constant temperature shaking pretreatment in a constant temperature shaker; the concentration of the added metabisulfite is calculated based on the sulfur content in the concentrated sludge, and the sulfur content is 300 mg-S / L-500 mg-S / L. The pretreated sludge is subjected to anaerobic fermentation to produce acid; the anaerobic fermentation time for producing acid is 5 days.
2. The method for promoting anaerobic fermentation and acid production of excess sludge as described in claim 1, characterized in that, The residual sludge is the residual sludge generated by the sewage treatment plant, and the residual sludge settles naturally at room temperature for 4-36 hours.
3. The method for promoting anaerobic fermentation and acid production of excess sludge as described in claim 1, characterized in that, The concentration of volatile solids in the concentrated sludge is 4.0 g / L to 12 g / L.
4. The method for promoting anaerobic fermentation and acid production of excess sludge as described in claim 1, characterized in that, The anaerobic environment treatment process includes: introducing an inert gas into the fermentation reactor to purge oxygen, wherein the inert gas includes at least one of nitrogen, argon, helium, and neon.
5. The method for promoting anaerobic fermentation and acid production of excess sludge as described in claim 1, characterized in that, The isothermal oscillation pretreatment time shall not exceed 36 hours, and the temperature shall be 20℃-25℃.
6. The method for promoting anaerobic fermentation and acid production of excess sludge as described in claim 1, characterized in that, Before the anaerobic fermentation to produce acid, the method further includes: adjusting the pH of the pretreated sludge to 6.8-7.2 before carrying out the anaerobic fermentation to produce acid.
7. The method for promoting anaerobic fermentation and acid production of excess sludge as described in claim 1, characterized in that, The temperature for anaerobic fermentation to produce acid is 25℃-40℃.
8. The method for promoting anaerobic fermentation and acid production of excess sludge as described in any one of claims 1-7, characterized in that, The metabisulfite includes at least one of sodium metabisulfite or potassium metabisulfite.