Method for improving concentration of volatile fatty acid produced by anaerobic fermentation of municipal sludge and application of method

Abstract

The invention discloses a method for improving the concentration of volatile fatty acid produced by anaerobic fermentation of municipal sludge and application of the method, and relates to the technical field of water treatment. According to the method, after the municipal sludge is pretreated by electrochemistry, anaerobic fermentation is performed to produce volatile fatty acid and inhibit the generation of methane, carbon in the municipal sludge is converted into volatile fatty acid, and the generation of methane and carbon dioxide is inhibited under the condition that no chemical agent is added. The volatile fatty acid is stored in the anaerobic biogas slurry, so that the value of municipal sludge recycling products is improved. According to the method, the carbon fixing amount is increased, the greenhouse gas emission amount is reduced, the environmental protection is promoted, the problems of low value and large greenhouse gas emission amount of existing municipal sludge recycling products are further solved, and a new strategy is provided for efficient treatment of municipal sludge.

Description

Technical Field

[0001] The invention relates to the technical field of water treatment, and in particular to a method for increasing the concentration of volatile fatty acids produced by anaerobic fermentation of municipal sludge and an application thereof. Background Art

[0002] Anaerobic fermentation is currently an effective way to treat municipal sludge, in which anaerobic microorganisms can decompose organic carbon in municipal sludge and produce methane and carbon dioxide, of which about 30% of organic carbon is converted into methane (Dinh et al., 2019), and another 8% of organic carbon is emitted into the air in the form of carbon dioxide (Picot et al., 2003). It is worth noting that both methane and carbon dioxide are greenhouse gases. The combustion of methane to produce carbon dioxide or the direct emission of carbon dioxide will enhance the greenhouse effect, thereby having a negative impact on environmental protection. Therefore, the traditional anaerobic fermentation method of treating municipal sludge to produce methane has the disadvantages of low product economic benefits and emission of greenhouse gases (such as methane and carbon dioxide).

[0003] When recovering carbon from municipal sludge by anaerobic fermentation, more attention should be paid to converting carbon in municipal sludge into higher value substances, such as volatile fatty acids, and reducing the emission of carbon in sludge into the environment as greenhouse gases. Volatile fatty acids are raw materials for many high-value products. For example, volatile fatty acids can be used to prepare biodiesel, bioplastics, single-cell proteins, and as an organic carbon source for use in sewage biological treatment processes (Agnihotri et al., 2022; Szacherska et al., 2021). Traditional anaerobic fermentation produces methane, and its economic benefits (US$3.71 / ton of municipal sludge) are much lower than the economic benefits of anaerobic fermentation with volatile fatty acids as products (US$9.12 / ton of municipal sludge) (Liu et al., 2018).

[0004] Therefore, how to more efficiently convert municipal sludge into volatile fatty acids while reducing greenhouse gas emissions and treat the growing amount of municipal sludge in a more environmentally friendly and economical way is one of the technical problems that need to be urgently solved in this field.

[0005] In view of this, the present invention is proposed. Summary of the invention

[0006] The object of the present invention is to provide a method for increasing the concentration of volatile fatty acids produced by anaerobic fermentation of municipal sludge and its application, so as to solve the above technical problems.

[0007] The present invention is achieved in that:

[0008] In a first aspect, an embodiment of the present invention provides a method for increasing the concentration of volatile fatty acids produced by anaerobic fermentation of municipal sludge, which comprises electrochemically pretreating the municipal sludge, and then subjecting the electrochemically pretreated municipal sludge to anaerobic fermentation;

[0009] The voltage of electrochemical pretreatment is ≥10V, and the time of electrochemical pretreatment is ≥30min;

[0010] After anaerobic fermentation treatment, the volatile fatty acid concentration of electrochemically pretreated municipal sludge increased to ≥97.8mgCOD / L±20.6mgCOD / L.

[0011] In a second aspect, an embodiment of the present invention provides an application of the aforementioned method in treating municipal sludge.

[0012] The present invention has the following beneficial effects:

[0013] An embodiment of the present invention provides a method for increasing the concentration of volatile fatty acids produced by anaerobic fermentation of municipal sludge, which uses electrochemistry to pretreat the municipal sludge and then performs anaerobic fermentation to produce volatile fatty acids and inhibit the production of methane, converting carbon in the municipal sludge into volatile fatty acids, and inhibiting the production of methane and carbon dioxide without adding electrolytes and any chemical agents, so that the volatile fatty acids are preserved in the anaerobic sludge, thereby increasing the value of the municipal sludge resource products.

[0014] Compared with traditional anaerobic fermentation of municipal sludge to produce methane, the method provided by the present invention increases carbon fixation, reduces greenhouse gas emissions, promotes environmental protection, and is conducive to further solving the problems of low value of existing municipal sludge resource products and large greenhouse gas emissions, providing a new strategy for the efficient treatment of municipal sludge. DETAILED DESCRIPTION

[0015] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0016] Municipal sludge mainly comes from water supply plant sludge, domestic sewage sludge, industrial sludge, urban water dredging sludge, chemical sludge, etc., and belongs to the freshwater type. Among them, domestic sewage is the main component of urban sewage, and domestic sewage sludge is the main component of municipal sludge. It mainly comes from sewage from residents' lives, including sewage discharged from kitchens, toilets, washing machines, etc., containing a large amount of organic matter, grease, bacteria, viruses, etc.; industrial sludge includes sewage from industrial production, including sewage discharged from chemical, metallurgical, pharmaceutical, papermaking and other industries, containing a large amount of heavy metals, toxic and harmful substances, etc. The components of municipal sludge include organic matter, inorganic matter, bacteria, water and heavy metal elements. Improper treatment will cause secondary pollution to the ecological environment, further sewage water sources, soil, and atmospheric environment, and seriously threaten people's health and environmental safety.

[0017] From 2020 to 2022, the amount of municipal sludge produced by China's sewage treatment plants increased from 36.984 million tons to 47.579 million tons, with an average annual growth of 8.8% (Ministry of Ecology and Environment, 2023). Therefore, how to reasonably treat municipal sludge and convert it into products with higher economic benefits while reducing greenhouse gas emissions is a technical problem that needs to be solved in this field. The present invention uses electrochemical pretreatment to increase the concentration of volatile fatty acids produced by anaerobic fermentation of municipal sludge, which can treat the growing total amount of municipal sludge in a more environmentally friendly and economical way. The details are as follows:

[0018] In a first aspect, an embodiment of the present invention provides a method for increasing the concentration of volatile fatty acids produced by anaerobic fermentation of municipal sludge, which comprises electrochemically pretreating the municipal sludge, and then subjecting the electrochemically pretreated municipal sludge to anaerobic fermentation;

[0019] The voltage of electrochemical pretreatment is ≥10V, and the time of electrochemical pretreatment is ≥30min;

[0020] After anaerobic fermentation treatment, the volatile fatty acid concentration of electrochemically pretreated municipal sludge increased to ≥97.8mgCOD / L±20.6mgCOD / L.

[0021] It should be noted that electrochemical pretreatment of municipal sludge can effectively inhibit the conversion of organic carbon in high-salt (such as chloride ion greater than 5000 ppm) municipal sludge into methane and carbon dioxide, so that the organic carbon is preserved in the anaerobic biogas slurry in the form of volatile fatty acids.

[0022] It should be noted that municipal sludge produces methane, which causes greenhouse gases, fixes carbon and converts carbon into volatile fatty acids during the anaerobic fermentation process; among them, the reduction in methane production will be significantly reduced with the increase of the voltage used in electrochemical pretreatment or the extension of treatment time; the amount of carbon fixation will be significantly increased with the increase of the voltage used in electrochemical pretreatment or the extension of treatment time; and volatile fatty acids will be significantly increased with the increase of the voltage used in electrochemical pretreatment or the extension of treatment time.

[0023] Taking into account the economy of the method provided by the present invention and the stability of the reaction system during implementation, it is necessary to effectively control the voltage and time of the electrochemical pretreatment, and the specific values ​​can be reasonably adjusted according to the actual amount of material treated. Among them, the voltage of the electrochemical pretreatment can be selected from 10V, 15V, 20V, 25V or other reasonable values ​​greater than 10V, and the time of the electrochemical pretreatment is 30min, 35min, 40min, 50min or other reasonable values ​​greater than 45min.

[0024] In an optional embodiment of the present invention, the voltage of the electrochemical pretreatment is 10V-15V, and the time of the electrochemical pretreatment is 30min-45min.

[0025] In an optional embodiment of the present invention, the electrode material for electrochemical pretreatment is selected from any one of a graphite electrode, a titanium electrode and a carbon brush electrode; further, the electrode material is a graphite electrode; and the shape of the electrode material is a plate.

[0026] In an optional embodiment of the present invention, the electrochemical pretreatment of municipal sludge also includes stirring the municipal sludge, and the stirring speed is 450 rpm-550 rpm. Further, the stirring speed is set to 500 rpm.

[0027] In the above, in the embodiment of the present invention, the specific operation of electrochemical pretreatment of municipal sludge is as follows:

[0028] At room temperature, 1000 mL of municipal sludge filtered through a 4 mm filter was placed in a 1000 mL glass measuring cup, and two electrodes of the same size, shape, and material were placed. The immersion depth of the electrodes was the same, that is, the working area of ​​each electrode was the same. The above two electrodes were used as anode and cathode, respectively, and the distance between the anode and cathode was kept at 10 cm. The electrochemical pretreatment process uses a DC power supply to provide a constant voltage, and the amount of acid produced by the municipal sludge is controlled by controlling the constant voltage size and action time of the above DC power supply.

[0029] In an optional embodiment of the present invention, the temperature of the anaerobic fermentation treatment is 33°C-37°C, further 35°C±1°C.

[0030] The time of anaerobic fermentation treatment is 25 days to 35 days, and further 30 days.

[0031] It should be noted that the anaerobic fermentation treatment also includes charging an inert gas into the reaction system, and the inert gas is preferably nitrogen. The inert gas is used to blow out the oxygen in the reaction system as much as possible to reduce the oxygen content, which is conducive to the efficient anaerobic reaction.

[0032] In an optional embodiment of the present invention, the ratio of the mass of volatile organic solids in the electrochemically pretreated municipal sludge to the mass of volatile organic solids in the acclimated inoculum is controlled to be 1:(1.8-2.3).

[0033] It should be noted that the ratio of the mass of volatile organic solids in municipal sludge to the mass of volatile organic solids in the inoculum of acclimatization treatment within the above range can keep the biological reaction of the anaerobic process normal, thereby ensuring the normal anaerobic fermentation of sludge. If the ratio is too high, it will lead to acidification of the anaerobic digestion reactor, and in severe cases, the anaerobic digestion reactor will fail; if the ratio is too low, it will lead to slow growth of microorganisms in the anaerobic digestion reactor, and in severe cases, the anaerobic digestion reactor will also fail.

[0034] The acclimation process of the inoculum solution is as follows: 2L of biogas slurry is taken from the anaerobic reactor used to treat kitchen waste in the laboratory and placed in a 2L glass batch reactor with constant temperature continuous stirring, the stirring speed is controlled at 100rpm, the temperature is controlled at 35±1°C, 200mL of liquid is taken out from the batch reactor every day and thrown into the designated recovery container of the experiment, and then 200mL of municipal sludge without any treatment is placed. After 30 days, the inoculum solution used in the present invention is obtained.

[0035] In an optional embodiment of the present invention, the ratio of the mass of volatile organic solids to the mass of volatile organic solids in the acclimated inoculum is selected from any one of 1:1.8, 1:1.85, 1:1.9, 1:1.95, 1:2 and 1:2.3, or other reasonable values ​​within the range of 1:(1.8-2.3).

[0036] Furthermore, the ratio of the mass of volatile organic solids in the electrochemical pretreated municipal sludge to the mass of volatile organic solids in the acclimated treatment inoculum is controlled to be 1:2.

[0037] In an optional embodiment of the present invention, the methane production of anaerobic fermentation of electrochemically pretreated municipal sludge is reduced by ≥6.9% compared with the methane production of traditional anaerobic fermentation; further, the reduction in methane production is ≥90%.

[0038] It should be noted that the reduction in methane production will be significantly reduced as the voltage used in electrochemical pretreatment increases or the treatment time increases. Methane is a greenhouse gas, and the direct emission of carbon dioxide produced by methane combustion will also aggravate the greenhouse effect, thereby having a negative impact on environmental protection. Therefore, the efficient reduction of methane production has an important impact on environmental protection.

[0039] In an optional embodiment of the present invention, an alkaline solution is used to absorb carbon dioxide gas in the anaerobic fermentation product; the alkaline solution is preferably a sodium hydroxide solution.

[0040] It should be noted that the alkaline solution used in the embodiment of the present invention is a sodium hydroxide solution with a concentration of 3 mol / L. The concentration of the sodium hydroxide solution is reasonably adjusted according to actual needs. In addition, it can also be reasonably adjusted to other soluble alkaline solutions, such as potassium hydroxide solution, etc. according to actual conditions.

[0041] In an optional embodiment of the present invention, after anaerobic fermentation treatment, the carbon fixation amount of anaerobic fermentation of electrochemical pretreated municipal sludge increases by ≥1.0% compared with the carbon fixation amount of traditional anaerobic technology; further, the increase in carbon fixation amount is ≥140%.

[0042] It should be noted that the amount of carbon fixation will increase significantly with the increase of the voltage used in electrochemical pretreatment or the extension of the treatment time. The more carbon fixation, the less carbon material is emitted into the atmosphere, which is beneficial to the control of greenhouse gases and environmental protection.

[0043] In an optional embodiment of the present invention, after anaerobic fermentation treatment, the volatile fatty acid concentration of the electrochemically pretreated municipal sludge increases to ≥2563.1 mg COD / L±307.9 mg COD / L.

[0044] In the above embodiments of the present invention, the municipal sludge pretreated by electrochemical treatment is subjected to anaerobic fermentation treatment, and the specific operation process is as follows:

[0045] After the electrochemically pretreated municipal sludge sample and the inoculum (the inoculum is the domesticated anaerobic sludge) are placed in a 150mL serum bottle, the working volume reaches 120mL, and the ratio of the volatile organic solid mass of the municipal sludge sample to the volatile organic solid mass of the inoculum is controlled to be 1:2. The serum bottle is purged with an inert gas with a purity of >99.9% for 5 minutes to remove oxygen in the top space, and then the serum bottle is placed in a constant temperature water bath set at 35℃±1℃. The electric stirring shaft of the serum bottle stirs the liquid in the serum bottle evenly at a stirring speed of 60 rpm. The anaerobic fermentation time is set to 30 days, and the generated biogas is collected and the carbon dioxide in the biogas is absorbed with an alkaline solution to obtain methane gas.

[0046] It should be noted that the amount of municipal sludge sample and inoculum can be reasonably adjusted according to the actual situation. Stirring can make the reaction system in a uniform state and the reaction more thorough.

[0047] It should be noted that volatile fatty acids will increase significantly with the increase of the voltage used in electrochemical pretreatment or the extension of the treatment time. Volatile fatty acids are the raw materials of many high-value products. The present invention converts carbon in municipal sludge into higher-value substances, reduces greenhouse gas emissions, and processes the growing municipal sludge in a more environmentally friendly and economical way, providing a new strategy for the efficient treatment of municipal sludge.

[0048] In a second aspect, an embodiment of the present invention provides an application of the aforementioned method in treating municipal sludge.

[0049] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0050] Example 1

[0051] This embodiment provides a method for increasing the concentration of volatile fatty acids produced by anaerobic fermentation of municipal sludge, which comprises the following steps:

[0052] (1) At room temperature, two graphite plate electrodes of the same size (5cm×10cm×2mm), shape (plate type), and material (graphite) were immersed in 1000mL of municipal sludge. The immersion depth was 7cm, and the distance between the two electrodes was kept at 10cm. A DC power supply was used to provide a constant voltage of 15V to the two electrodes for 45 minutes. During the electrochemical pretreatment process, an electric stirring shaft was used to stir the municipal sludge to make it uniform, and the stirring speed was set to 500 rpm. The volatile organic solids concentration of the municipal sludge sample after electrochemical pretreatment was 67.6±7.1g / L.

[0053] (2) The acclimation process of the inoculum solution is as follows: 2L of biogas slurry is taken from the anaerobic reactor used to treat kitchen waste in this laboratory and placed in a 2L glass batch reactor with constant temperature and continuous stirring, the stirring speed is controlled at 100rpm, and the temperature is controlled at 35°C±1°C. Every day, 200mL of liquid is taken out from the batch reactor and thrown into the designated recovery container for the experiment, and then 200mL of municipal sludge without any treatment is placed in it. After 30 days, the inoculum solution used in the present invention is obtained.

[0054] The inoculum solution and the municipal sludge sample after electrochemical pretreatment were uniformly mixed in a 150 mL serum bottle (working volume was 120 ml) according to the ratio of volatile organic solids 2:1 for batch methanogenesis potential test.

[0055] (3) The 150 mL serum bottle was placed in a constant temperature water bath at 35°C for fermentation for 30 days, the biogas was collected, and the carbon dioxide in the biogas was absorbed by 3 mol / L NaOH (sodium hydroxide) solution to obtain methane gas.

[0056] Example 2

[0057] This embodiment provides a method for increasing the concentration of volatile fatty acids produced by anaerobic fermentation of municipal sludge, which differs from Embodiment 1 in that:

[0058] (1) A DC power supply is used to provide a constant voltage of 10 V to two electrodes for 30 minutes. The volatile organic solids concentration of the municipal sludge sample after electrochemical pretreatment is 66.6 g / L±6.5 g / L.

[0059] Example 3

[0060] This embodiment provides a method for increasing the concentration of volatile fatty acids produced by anaerobic fermentation of municipal sludge, which differs from Embodiment 1 in that:

[0061] (1) A DC power supply is used to provide a constant voltage of 10 V to two electrodes for 45 minutes. The volatile organic solids concentration of the municipal sludge sample after electrochemical pretreatment is 67.7 g / L±5.9 g / L.

[0062] Example 4

[0063] This embodiment provides a method for increasing the concentration of volatile fatty acids produced by anaerobic fermentation of municipal sludge, which differs from Embodiment 1 in that:

[0064] (1) A DC power supply is used to provide a constant voltage of 15 V to the two electrodes for 30 minutes. The volatile organic solids concentration of the municipal sludge sample after electrochemical pretreatment is 67.4 g / L±7.9 g / L.

[0065] Comparative Example 1

[0066] This comparative example provides a method for treating municipal sludge using a traditional anaerobic technique, which comprises the following steps:

[0067] In this comparative example, the municipal sludge sample without electrochemical pretreatment and the inoculum (the inoculum is the anaerobic sludge after domestication) are placed in a 150mL serum bottle to reach a working volume of 120mL, and the ratio of the volatile organic solid mass of the municipal sludge sample to the volatile organic solid mass of the inoculum is controlled to be 1:2. The serum bottle is purged with an inert gas with a purity of >99.9% for 5 minutes to remove oxygen in the top space, and then the serum bottle is placed in a constant temperature water bath set at 35°C±1°C. The electric stirring shaft of the serum bottle stirs the liquid in the serum bottle evenly at a stirring speed of 60 rpm. The anaerobic fermentation time is set to 30 days, and the generated biogas is collected and the carbon dioxide in the biogas is absorbed with an alkaline solution to obtain methane gas.

[0068] Test Example 1

[0069] This test example uses different electrode materials, sets different voltages and different times to test the effect of electrochemical pretreatment of municipal sludge under different conditions for anaerobic fermentation to produce volatile fatty acids. The relevant information is as follows:

[0070] The electrode materials include titanium plate electrode, carbon brush electrode and graphite plate electrode. The size of the titanium plate electrode and the graphite plate electrode is 5cm×10cm×2mm, and the size of the carbon brush electrode is 10cm long and 3cm in diameter.

[0071] The electrochemical pretreatment voltage is 10V and 15V; the electrochemical pretreatment time is 30min and 45min.

[0072] In the relevant test results, the volatile fatty acid concentration of the experimental groups of titanium plate electrode and carbon brush electrode was 0 after 30 days; the relevant results of the experimental group of graphite plate electrode are shown in Table 1.

[0073] Test Example 2

[0074] This test example tests the cumulative methane production, carbon fixation and volatile fatty acid concentration produced by Examples 1-4 and Comparative Example 1, wherein the test method for methane production is the sludge methanogenic activity determination method in Appendix B of the National Environmental Protection Standards of the People's Republic of China (HJ2013-2012), and the test method for volatile fatty acid concentration is the National Environmental Protection Standards of the People's Republic of China (HJ 810-2016), the carbon fixation is calculated based on the production of methane and volatile fatty acids. For example, if 100 mL of methane is produced and the density of methane at 25°C and 1 atm is 0.648 mg / mL, the carbon fixation corresponding to methane is 64.8 mg. The carbon fixation of volatile fatty acids needs to be calculated based on whether it is acetic acid, propionic acid, butyric acid or valeric acid. For example, the carbon content in acetic acid is 40% (12*2 / 60=40%). If 100 mg of acetic acid is measured, the carbon fixation corresponding to acetic acid is 40 mg. Similarly, the carbon fixation corresponding to propionic acid, butyric acid and valeric acid is calculated and then summarized and added to obtain the carbon fixation of volatile fatty acids. The methane production of Comparative Example 1 was 397.1±28.8 mg COD / g volatile organic solids (theoretically 1 g COD≈350 mL methane), the carbon fixation was 67.5±2.5 mg C / g volatile organic solids, and the volatile fatty acid concentration was 0. The results of Examples 1-4 compared with Comparative Example 1: the reduction in methane production, the increase in carbon fixation, and the volatile fatty acid concentration are summarized in Table 1.

[0075] Table 1

[0076]

[0077] It can be seen from Table 1 that when the electrochemical pretreatment time is the same, as the voltage increases, the methane production decreases, the carbon fixation increases, and the volatile fatty acid concentration also increases; at the same time, if the voltage of the electrochemical pretreatment is the same, as the treatment time is extended, the methane production decreases, the carbon fixation increases, and the volatile fatty acid concentration also increases; and the effect of the extension of the electrochemical pretreatment time on the final volatile fatty acid production is greater than that of increasing the voltage. It should be noted that, considering the practical applicability, stability and economy of the experiment, the electrochemical pretreatment time and voltage are optimally set; at this time, the cumulative methane production of the anaerobic technology using electrochemical pretreatment of municipal sludge in Example 1 is reduced by 94.1% compared with the traditional anaerobic technology, the carbon fixation is increased by 149.8% compared with the traditional anaerobic technology, and the volatile fatty acid concentration is increased to 2563.1±307.9mg COD / L.

[0078] In summary, an embodiment of the present invention provides a method for increasing the concentration of volatile fatty acids produced by anaerobic fermentation of municipal sludge, which uses electrochemistry to pretreat the municipal sludge and then performs anaerobic fermentation to produce volatile fatty acids and inhibit the production of methane, converting the carbon in the municipal sludge into volatile fatty acids, and inhibiting the production of methane and carbon dioxide without adding electrolytes and any chemical agents, so that the volatile fatty acids are preserved in the anaerobic sludge, thereby increasing the value of the municipal sludge resource products.

[0079] Compared with traditional anaerobic fermentation of municipal sludge to produce methane, the method provided by the present invention increases carbon fixation, reduces greenhouse gas emissions, promotes environmental protection, and is conducive to further solving the problems of low value of existing municipal sludge resource products and large greenhouse gas emissions, providing a new strategy for the efficient treatment of municipal sludge.

[0080] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for increasing the concentration of volatile fatty acids produced by anaerobic fermentation of municipal sludge, characterized in that: The method comprises electrochemically pretreating municipal sludge, and then subjecting the electrochemically pretreated municipal sludge to anaerobic fermentation treatment; The voltage of electrochemical pretreatment is ≥10V, and the time of electrochemical pretreatment is ≥30min; After anaerobic fermentation treatment, the volatile fatty acid concentration of electrochemically pretreated municipal sludge increased to ≥97.8mg COD / L±20.6mg COD / L.

2. The method according to claim 1, characterized in that The voltage of the electrochemical pretreatment is 10V-15V, and the time of the electrochemical pretreatment is 30min-45min.

3. The method according to claim 1, characterized in that The temperature of the anaerobic fermentation treatment is 33°C-37°C, preferably 35°C±1°C; The anaerobic fermentation treatment lasts for 25 to 35 days, preferably 30 days; Preferably, the anaerobic fermentation treatment further comprises charging an inert gas into the reaction system, and the inert gas is preferably nitrogen.

4. The method according to claim 1, characterized in that: In the anaerobic fermentation treatment, the mass ratio of volatile organic solids in the electrochemical pre-treated municipal sludge to the mass ratio of volatile organic solids in the acclimated inoculum is controlled to be 1:(1.8-2.3); preferably 1:

2.

5. The method according to claim 1, characterized in that The methane production of anaerobic fermentation of electrochemically pretreated municipal sludge is reduced by ≥6.9% compared with the methane production of conventional anaerobic fermentation; preferably, the reduction in methane production is ≥90%; Preferably, an alkaline solution is used to absorb carbon dioxide gas in the anaerobic fermentation product; the alkaline solution is preferably a sodium hydroxide solution.

6. The method according to claim 1, characterized in that Compared with the carbon fixation amount of the conventional anaerobic technology, the carbon fixation amount of the electrochemical pretreated municipal sludge anaerobic fermentation is increased by ≥1.0%; preferably, the increase in carbon fixation amount is ≥140%.

7. The method according to claim 1, characterized in that After anaerobic fermentation treatment, the volatile fatty acid concentration of electrochemically pretreated municipal sludge increased to ≥2563.1mg COD / L±307.9mg COD / L.

8. The method according to claim 1, characterized in that The electrode material for electrochemical pretreatment is selected from any one of a graphite electrode, a titanium electrode and a carbon brush electrode; Preferably, the electrode material is a graphite electrode; Preferably, the electrode material is in the shape of a plate.

9. The method according to claim 1, characterized in that: The electrochemical pretreatment process of municipal sludge also includes stirring treatment of the municipal sludge, and the stirring speed is 450 rpm-550 rpm.

10. Use of the method according to any one of claims 1 to 9 in treating municipal sludge.

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