Removal method for inhibiting anaerobic methanogenesis system by humic acid

Abstract

The invention belongs to the technical field of sludge treatment and recycling, and particularly relates to a removing method for inhibiting an anaerobic methanogenesis system by humic acid. Comprising the following steps: cleaning, drying, grinding and screening a biochar material to obtain biochar particles; carrying out sedimentation, sieving and thermal pretreatment on the residual sludge to obtain pretreated sludge; mixing the pretreated sludge with the inoculated sludge to obtain mixed sludge; the biochar particles, humic acid and mixed sludge are added into an anaerobic reactor, the anaerobic reactor is sealed in a water bath constant-temperature oscillator after being subjected to nitrogen aeration, and methane production is performed until no methane is generated in the anaerobic reactor. According to the method, the problem of rate limitation of hydrolysis, acidification and methanogenesis stages in the sludge anaerobic digestion process under the inhibition of humic acid is solved, and meanwhile, the improvement of the sludge anaerobic methanogenesis efficiency under the inhibition of humic acid is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of sludge treatment and resource utilization, and particularly relates to a method for removing a humic acid-inhibited anaerobic methanogenesis system. Background Art

[0002] The residual sludge produced by sewage treatment plants contains a large amount of organic matter, such as polysaccharides, proteins and humic acid, accounting for more than 60% of the dry weight, and is also rich in resources such as nitrogen and phosphorus, which can be used as a carrier of energy and resources. Compared with other sludge treatment and disposal technologies, anaerobic digestion technology can decompose organic matter in sludge, reduce the content of volatile solids, and kill parasite eggs and pathogenic bacteria. It not only achieves the purpose of sludge reduction, stabilization and harmlessness, but also recovers energy and resources, such as methane, hydrogen and short-chain fatty acids. Therefore, anaerobic digestion technology has greater economic, environmental and social benefits, meets the sustainable development needs of residual sludge treatment and disposal, and is expected to achieve green and low-energy operation of sewage treatment plants, thereby promoting the high-quality development of the sewage treatment industry.

[0003] There are two main ways to form humic acid in sewage treatment: first, the sewage itself contains a large amount of humic acid and other difficult-to-degrade substances; second, complex macromolecular organic matter will also form humic acid substances as the degree of humification deepens during the degradation and transformation of microorganisms. Due to the difficulty of biodegradation of humic acid, it will eventually enter the sludge anaerobic digestion system.

[0004] Humic acid, as the main component of sludge organic matter, contains various oxygen-containing functional groups and has an aromatic ring as its carbon skeleton structure. After sludge pretreatment, the complex structure of humic acid is still difficult to destroy. During the anaerobic digestion process, on the one hand, humic acid itself is difficult to be degraded and utilized by microorganisms; on the other hand, its existence will also affect each stage of anaerobic digestion, thereby affecting the conversion efficiency of other organic matter into methane. Based on this, the impact of humic acid accumulation on the anaerobic digestion process of sludge cannot be ignored.

[0005] It has been confirmed that excessive accumulation of humic acid will have a significant inhibitory effect on the anaerobic methanogenesis process. When the concentration of humic acid is too high, on the one hand, they will occupy the active sites of hydrolytic enzymes, and on the other hand, they will compete with anaerobic microorganisms for electrons. This will not only reduce the yield and quality of methane, but also lead to the collapse of the anaerobic system.

[0006] At present, a series of measures have been taken to slow down or eliminate the inhibitory effect of humic acid on anaerobic digestion systems of sludge. For example, thermal hydrolysis can destroy part of the structure of humic acid and improve its bioavailability; the addition of metal cations can combine with certain functional groups in humic acid, change its properties and reduce its inhibitory effect on microbial activity. However, these measures still have certain limitations. For example, the technology of extracting and separating humic acid has the problem of easy clogging of the filter membrane, which leads to an increase in operating costs and limits its promotion and application in sludge treatment; the high cost and difficult maintenance of pretreatment technology limit its further application in the sludge treatment process; for example, although heavy metal ions have a strong binding ability with humic acid, the introduction of heavy metal ions will increase the risk of environmental pollution. Therefore, it is urgent to invent a green, sustainable and low-cost method to relieve the inhibition of humic acid. Summary of the invention

[0007] In view of the problems existing in the prior art, the present invention provides a method for releasing the anaerobic methanogenesis system inhibited by humic acid, which solves the rate limitation problems in the hydrolysis, acidification and methanogenesis stages during the anaerobic digestion of sludge under humic acid inhibition, and at the same time improves the anaerobic methanogenesis efficiency of sludge under humic acid inhibition.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions: The present invention provides a method for removing humic acid from inhibiting an anaerobic methanogenesis system, comprising: The biochar material is cleaned, dried, ground and sieved to obtain biochar particles; The residual sludge is subjected to sedimentation, screening and thermal pretreatment to obtain pretreated sludge; the pretreated sludge and the inoculated sludge are mixed to obtain mixed sludge; Biochar particles, humic acid and mixed sludge are added to the anaerobic reactor. After nitrogen aeration, the anaerobic reactor is sealed and placed in a water bath constant temperature oscillator to produce methane until no more methane is produced in the anaerobic reactor.

[0009] Preferably, the mass ratio of the humic acid, the biochar particles and the volatile suspended solids in the mixed sludge is 0.005:1:1.

[0010] Preferably, the method for preparing the biochar material is: pyrolyzing the biomass material under anaerobic conditions at 400-600°C for 2-4 h to obtain the biochar material.

[0011] Preferably, the biochar material is dried at a temperature not higher than 80° C. for not less than 24 hours.

[0012] Preferably, the particle size of the biochar particles is 0.1 to 0.2 mm.

[0013] Preferably, the residual sludge settling time is not less than 24 h.

[0014] Preferably, the excess sludge is sieved using a 0.45 mm sieve.

[0015] Preferably, the volume ratio of the inoculated sludge to the pretreated sludge is 1:4.

[0016] Preferably, the heat pretreatment is performed at 80°C for no less than 30 min.

[0017] Preferably, the shaking speed of the water bath constant temperature oscillator is 120-130 rpm and the temperature is 35±1°C.

[0018] Compared with the prior art, the present invention has the following beneficial effects: The present invention reduces the effect of humic acid on microbial activity by adding biochar. On the one hand, the sites of humic acid adsorbed on the surface of biochar are occupied, thereby reducing the effect of humic acid accumulation on hydrolases, thereby increasing the activity of hydrolases, promoting the hydrolysis process of organic matter, accelerating the consumption of short-chain fatty acids, and promoting the conversion of propionic acid into acetic acid, providing sufficient substrate for methanogens. At the same time, the possibility of humic acid competing with methanogens for electrons is reduced, thereby improving the efficiency and rate of methane production; on the other hand, biochar has a large specific surface area, which provides sufficient space for the proliferation and growth of microorganisms; at the same time, biochar can also mediate the direct interspecies electron transfer process between bacteria and methanogens, further promoting the anaerobic digestion methanogenesis process. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0020] Figure 1 It is a line graph of the methane accumulation of each group in Example 1 of the present invention and the comparative example; Figure 2 It is a line graph of the methane generation rate of each group of Example 1 of the present invention and the comparative example. DETAILED DESCRIPTION

[0021] In order to enable those skilled in the art to understand the characteristics and effects of the present invention, the following is a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used in the text are the common meanings understood by those skilled in the art for the present invention. In the event of a conflict, the definition in this specification shall prevail.

[0022] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, that is, the present invention can be implemented without being limited by any specific theory or mechanism.

[0023] In this article, all features such as values, quantities, contents and concentrations defined in the form of numerical ranges or percentage ranges are for simplicity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to have included and specifically disclosed all possible secondary ranges and individual values ​​within the range (including integers and fractions).

[0024] In this document, unless otherwise specified, “includes,” “including,” “contains,” “has,” or similar terms cover the meanings of “consisting of” and “mainly consisting of,” for example, “A includes a” covers the meanings of “A includes a and other” and “A only includes a.”

[0025] In this document, in order to make the description concise, not all possible combinations of various technical features in various embodiments or examples are described. Therefore, as long as there is no contradiction in the combination of these technical features, the various technical features in various embodiments or examples can be combined arbitrarily, and all possible combinations should be considered to be within the scope of this specification.

[0026] The present invention is further described in detail below in conjunction with the accompanying drawings: The present invention provides a method for removing humic acid from inhibiting an anaerobic methanogenesis system, comprising: The biochar material is cleaned, dried, ground and sieved to obtain biochar particles; The residual sludge is subjected to sedimentation, screening and thermal pretreatment to obtain pretreated sludge; the pretreated sludge and the inoculated sludge are mixed to obtain mixed sludge; Biochar particles, humic acid and mixed sludge are added to the anaerobic reactor, which is sealed and placed in a water bath thermostat oscillator after nitrogen aeration to produce methane until no more methane is produced in the anaerobic reactor. Under anaerobic conditions, anaerobic microorganisms produce methane by decomposing complex organic matter (such as organic matter in mixed sludge).

[0027] The further optimized solution specifically includes the following steps: The biomass material is pyrolyzed for 2-4 h under the conditions of anaerobic and 400-600 ° C to obtain a biochar material; the biochar material is repeatedly washed with deionized water until the soluble ions on its surface are removed; the washed biochar material is dried at a temperature not higher than 80 ° C for not less than 24 h; after drying, the biochar particles with a particle size of 0.1-0.2 mm are obtained by screening. The biochar material is fruit wood, bark, straw or stalks. The present invention generates biochar material (carbon-rich solid matter), volatile gas and liquid product by decomposing organic components in the biomass material under the conditions of anaerobic and 400-600 ° C; the surface soluble ions, including soluble salts and harmful ions, such as sulfur ions and chloride ions, can be removed by washing the biochar material; the particle size distribution of the biochar material can be adjusted by grinding and screening the biochar material, which can more effectively adsorb harmful substances in the mixed sludge and reduce its influence on the microbial activity of the anaerobic digestion system of the sludge.

[0028] The residual sludge is allowed to settle naturally for no less than 24 hours, and the residual sludge after settling is sieved with a 0.45 mm sieve to remove gravel and large particle impurities; the sieved residual sludge is heat pretreated at 80 ° C for no less than 30 minutes to obtain pretreated sludge; the inoculated sludge and the pretreated sludge are mixed in a volume ratio of 1:4 to obtain mixed sludge. The residual sludge of the present invention can remove large particles and some difficult-to-degrade organic matter in the residual sludge through sedimentation, sieving and heat pretreatment, so that the residual sludge is more uniform and its biodegradability is improved; at the same time, the heat pretreatment can destroy the structure of the residual sludge, release more soluble organic matter, and create more favorable substrate conditions for subsequent methane production. The inoculated sludge is rich in anaerobic functional microorganisms that can degrade organic matter. After mixing with the pretreated sludge, it can quickly adapt to the environment and begin to degrade the organic matter in the sludge, and finally convert the organic matter into methane.

[0029] Humic acid, biochar particles and mixed sludge are added to an anaerobic reactor, wherein the mass ratio of humic acid, biochar particles and volatile suspended solids in the mixed sludge is 0.005:1:1. After the anaerobic reactor is aerated with nitrogen for no less than 5 minutes, the anaerobic reactor is sealed and placed in a water bath constant temperature oscillator, the shaking speed of the water bath constant temperature oscillator is 120-130 rpm, the temperature is 35±1°C, and methane production is carried out until no methane is generated in the anaerobic reactor. The present invention mixes humic acid, biochar particles and mixed sludge. Under anaerobic conditions, humic acid in the mixed sludge will be adsorbed by biochar, reducing its toxic effect on anaerobic microorganisms. Moreover, under the catalytic action of biochar particles, anaerobic microorganisms can more effectively convert organic matter into methane, thereby improving the efficiency and rate of methane generation.

[0030] On the one hand, humic acid can promote the solubilization process of sludge, thereby improving the dissolution of organic matter and facilitating the anaerobic methanogenesis process; on the other hand, humic acid slows down the hydrolysis process of organic matter by hindering the activity of hydrolytic enzymes. In the presence of biochar particles, it will adsorb free humic acid, thereby weakening the effect of humic acid on the activity of anaerobic microorganisms. At the same time, biochar particles adsorb part but not all of the humic acid, and free humic acid and biochar particles will form a synergistic effect on the anaerobic methanogenesis process of sludge. Specifically, biochar particles adsorb humic acid and occupy its active sites, thereby improving the activity of hydrolytic enzymes. At the same time, it reduces the electron competition process between humic acid and methanogens, improves the electron transfer capacity between microbial species, and the cytochrome C content and coenzyme F420 activity of anaerobic microorganisms, promotes the hydrolysis process of organic matter, and promotes the conversion of propionic acid into acetic acid, providing sufficient substrate for methanogens, and ultimately improving the efficiency of anaerobic methanogenesis.

[0031] In addition, biochar particles have good electrical conductivity, which can mediate the electron transfer process between microbial species, strengthen the symbiotic metabolic relationship between microbial species, accelerate the electron transfer efficiency between symbiotic microorganisms, and further promote the methane production efficiency of anaerobic digestion.

[0032] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0033] The following examples use conventional instruments and equipment in the art. The experimental methods in the following examples where specific conditions are not specified are usually carried out under conventional conditions or under conditions recommended by the manufacturer. The various raw materials used in the following examples are conventional commercial products unless otherwise specified, and their specifications are conventional specifications in the art. In the specification of the present invention and the following examples, unless otherwise specified, "%" means weight percentage, "part" means weight part, and ratio means weight ratio.

[0034] Example 1 The fruit wood was pyrolyzed at 500 °C for 2 h in the absence of oxygen to obtain biochar material; the biochar was repeatedly washed with deionized water until the soluble ions on its surface were removed; the washed biochar material was dried at 70 °C for 26 h; after drying, the biochar particles with a particle size of 0.2 mm were obtained by sieving; The residual sludge was naturally settled for 26 h, and the settled residual sludge was sieved with a 0.45 mm sieve to remove gravel and large particles of impurities; the sieved residual sludge was heat pretreated at 80 °C for 40 min to obtain pretreated sludge; the inoculated sludge and the pretreated sludge were mixed in a volume ratio of 1:4 to obtain mixed sludge; Humic acid, biochar particles and mixed sludge were added into the anaerobic reactor, wherein the mass ratio of humic acid, biochar particles and volatile suspended solids in the mixed sludge was 0.005:1:1. After the anaerobic reactor was aerated with nitrogen for 7 min, the anaerobic reactor was sealed and placed in a water bath constant temperature oscillator with a shaking speed of 130 rpm and a temperature of 35 ℃ for methane production until no more methane was produced in the anaerobic reactor. The cumulative accumulation of methane was 132.6 mLCH4 / gVSS, and the maximum daily methane production rate was 10.6 mL / d.

[0035] Example 2 The bark was pyrolyzed at 600 °C for 3 h in the absence of oxygen to obtain biochar material; the biochar was repeatedly washed with deionized water until the soluble ions on its surface were removed; the washed biochar material was dried at 75 °C for 25 h; after drying, the biochar particles with a particle size of 0.15 mm were obtained by sieving; The residual sludge was naturally settled for 24 h, and the settled residual sludge was sieved with a 0.45 mm sieve to remove gravel and large particles of impurities; the sieved residual sludge was heat pretreated at 80 °C for 35 min to obtain pretreated sludge; the inoculated sludge and the pretreated sludge were mixed in a volume ratio of 1:4 to obtain mixed sludge; Humic acid, biochar particles and mixed sludge were added to the anaerobic reactor, wherein the mass ratio of volatile suspended solids in humic acid, biochar particles and mixed sludge was 0.005:1:1. After the anaerobic reactor was aerated with nitrogen for 6 min, the anaerobic reactor was sealed and placed in a water bath constant temperature oscillator with a shaking speed of 125 rpm and a temperature of 35 ℃ for methane production until no more methane was produced in the anaerobic reactor. The cumulative accumulation of methane was 131.8 mLCH4 / gVSS, and the maximum daily methane production rate was 10.6 mL / d.

[0036] Example 3 The rice straw was pyrolyzed at 400 °C for 4 h in the absence of oxygen to obtain biochar material. The biochar was repeatedly washed with deionized water until the soluble ions on its surface were removed. The washed biochar material was dried at 80 °C for 24 h. After drying, the biochar particles with a particle size of 0.1 mm were obtained by sieving. The residual sludge was naturally settled for 24 h, and the settled residual sludge was sieved with a 0.45 mm sieve to remove gravel and large particles of impurities; the sieved residual sludge was heat pretreated at 80 °C for 30 min to obtain pretreated sludge; the inoculated sludge and the pretreated sludge were mixed in a volume ratio of 1:4 to obtain mixed sludge; Humic acid, biochar particles and mixed sludge were added into the anaerobic reactor, wherein the mass ratio of humic acid, biochar particles and volatile suspended solids in the mixed sludge was 0.005:1:1. After the anaerobic reactor was aerated with nitrogen for 5 min, the anaerobic reactor was sealed and placed in a water bath constant temperature oscillator with a shaking speed of 120 rpm and a temperature of 36 ℃ for methane production until no more methane was produced in the anaerobic reactor. The cumulative accumulation of methane was 130.9 mLCH4 / gVSS, and the maximum daily methane production rate was 10.5 mL / d.

[0037] Example 4 The straw was pyrolyzed at 500 °C for 2 h in the absence of oxygen to obtain biochar material. The biochar was repeatedly washed with deionized water until the soluble ions on its surface were removed. The washed biochar material was dried at 65 °C for 28 h. After drying, the biochar particles with a particle size of 0.2 mm were obtained by sieving. The residual sludge was naturally settled for 26 h, and the settled residual sludge was sieved with a 0.45 mm sieve to remove gravel and large particles of impurities; the sieved residual sludge was heat pretreated at 80 °C for 45 min to obtain pretreated sludge; the inoculated sludge and the pretreated sludge were mixed in a volume ratio of 1:4 to obtain mixed sludge; Humic acid, biochar particles and mixed sludge were added into the anaerobic reactor, wherein the mass ratio of volatile suspended solids in humic acid, biochar particles and mixed sludge was 0.005:1:1. After the anaerobic reactor was aerated with nitrogen for 7 min, the anaerobic reactor was sealed and placed in a water bath constant temperature oscillator with a shaking speed of 125 rpm and a temperature of 35 ℃ for methane production until no more methane was produced in the anaerobic reactor. The cumulative accumulation of methane was 129.4 mLCH4 / gVSS, and the maximum daily methane production rate was 10.2 mL / d.

[0038] Example 5 The fruit wood was pyrolyzed at 500 °C for 4 h in the absence of oxygen to obtain biochar material; the biochar was repeatedly washed with deionized water until the soluble ions on its surface were removed; the washed biochar material was dried at 60 °C for 30 h; after drying, the biochar particles with a particle size of 0.2 mm were obtained by sieving; The residual sludge was naturally settled for 26 h, and the settled residual sludge was sieved with a 0.45 mm sieve to remove gravel and large particles of impurities; the sieved residual sludge was heat pretreated at 80 °C for 50 min to obtain pretreated sludge; the inoculated sludge and the pretreated sludge were mixed in a volume ratio of 1:4 to obtain mixed sludge; Humic acid, biochar particles and mixed sludge were added into the anaerobic reactor, wherein the mass ratio of volatile suspended solids in humic acid, biochar particles and mixed sludge was 0.005:1:1. After nitrogen aeration for 7 min, the anaerobic reactor was sealed and placed in a water bath constant temperature oscillator with a shaking speed of 120 rpm and a temperature of 34 ℃ for methane production until no more methane was produced in the anaerobic reactor. The cumulative accumulation of methane was 134.1 mLCH4 / gVSS, and the maximum daily methane production rate was 10.7 mL / d.

[0039] Comparative Example 1 The residual sludge was allowed to settle naturally for 26 h, and the settled residual sludge was sieved with a 0.45 mm sieve to remove gravel and large particles of impurities; the sieved residual sludge was heat pretreated at 80 °C for 40 min to obtain pretreated sludge; the inoculated sludge and pretreated sludge were mixed in a volume ratio of 1:4 to obtain mixed sludge; the mixed sludge was added to the anaerobic reactor, and after the anaerobic reactor was aerated with nitrogen for 7 min, the anaerobic reactor was sealed and placed in a water bath constant temperature oscillator with a shaking speed of 130 rpm and a temperature of 35 °C to produce methane until no methane was produced in the anaerobic reactor.

[0040] Comparative Example 2 The residual sludge was naturally settled for 26 h, and the settled residual sludge was sieved with a 0.45 mm sieve to remove gravel and large particles of impurities; the sieved residual sludge was heat pretreated at 80 °C for 40 min to obtain pretreated sludge; the inoculated sludge and the pretreated sludge were mixed in a volume ratio of 1:4 to obtain mixed sludge; Humic acid and mixed sludge were added into the anaerobic reactor, wherein the mass ratio of humic acid to volatile suspended solids in the mixed sludge was 0.005:1. After the anaerobic reactor was aerated with nitrogen for 7 min, the anaerobic reactor was sealed and placed in a water bath constant temperature oscillator with a shaking speed of 130 rpm and a temperature of 35 °C to produce methane until no more methane was produced in the anaerobic reactor.

[0041] Comparative Example 3 The fruit wood was pyrolyzed at 500 °C for 2 h in the absence of oxygen to obtain biochar material; the biochar was repeatedly washed with deionized water until the soluble ions on its surface were removed; the washed biochar material was dried at 70 °C for 26 h; after drying, the biochar particles with a particle size of 0.2 mm were obtained by sieving; The residual sludge was naturally settled for 26 h, and the settled residual sludge was sieved with a 0.45 mm sieve to remove gravel and large particles of impurities; the sieved residual sludge was heat pretreated at 80 °C for 40 min to obtain pretreated sludge; the inoculated sludge and the pretreated sludge were mixed in a volume ratio of 1:4 to obtain mixed sludge; Biochar particles and mixed sludge were added to the anaerobic reactor, wherein the mass ratio of volatile suspended solids in the biochar particles and the mixed sludge was 1:1. After the anaerobic reactor was aerated with nitrogen for 7 min, the anaerobic reactor was sealed and placed in a water bath constant temperature oscillator with a shaking speed of 130 rpm and a temperature of 35 °C to produce methane until no methane was produced in the anaerobic reactor.

[0042] Comparative Example 4 The fruit wood was pyrolyzed at 500 °C for 2 h in the absence of oxygen to obtain biochar material; the biochar was repeatedly washed with deionized water until the soluble ions on its surface were removed; the washed biochar material was dried at 70 °C for 26 h; after drying, the biochar particles with a particle size of 0.2 mm were obtained by sieving; The residual sludge was naturally settled for 26 h, and the settled residual sludge was sieved with a 0.45 mm sieve to remove gravel and large particles of impurities; the sieved residual sludge was heat pretreated at 80 °C for 40 min to obtain pretreated sludge; the inoculated sludge and the pretreated sludge were mixed in a volume ratio of 1:4 to obtain mixed sludge; Humic acid was loaded on the surface of biochar particles to obtain biochar particles loaded with humic acid, and the biochar particles loaded with humic acid were added to the anaerobic reactor. After the anaerobic reactor was aerated with nitrogen for 7 minutes, the anaerobic reactor was sealed and placed in a water bath constant temperature oscillator. The shaking speed of the water bath constant temperature oscillator was 130 rpm and the temperature was 35 °C to produce methane until no more methane was produced in the anaerobic reactor. The mass ratio of humic acid, biochar particles and volatile suspended solids in the mixed sludge was 0.005:1:1.

[0043] like Figure 1As shown, it is a line graph of the methane accumulation of Example 1 and Comparative Examples 1 to 4. The methane accumulation of Comparative Example 1 is 100.3 mL CH4 / gVSS, and the methane accumulation of Comparative Example 2 is 90.9 mL CH4 / gVSS, which is 9.37% lower than that of Comparative Example 1, indicating that humic acid has an inhibitory effect on the anaerobic methanogenesis process; the methane accumulation of Example 1 is 132.6 mLCH4 / gVSS, which is 32.2% and 45.9% higher than that of Comparative Examples 1 and 2, respectively, indicating that the addition of biochar can alleviate or remove the inhibitory effect of humic acid on the anaerobic methanogenesis system of sludge, thereby increasing the methane production; the methane accumulation of Comparative Example 3 is 110.8 mL CH4 / g VSS, which is lower than the methane accumulation in Example 1, indicates that the biochar adsorbs part of the humic acid rather than all of the humic acid. On the one hand, since the biochar can adsorb humic acid, the concentration of free humic acid is reduced, and its inhibitory effect on the activity of functional microorganisms and key enzymes is reduced; on the other hand, low concentrations of humic acid can promote the methanogenesis process, and at the same time, biochar can also promote the methanogenesis process. The methane accumulation in Comparative Example 4 is 122.4 mL CH4 / g VSS, which is higher than that in Comparative Example 1 and Comparative Example 2 but lower than that in Example 1, further confirming that when biochar alleviates the inhibitory effect of humic acid on anaerobic methanogenesis in sludge, humic acid and biochar will form a synergistic promotion effect on the anaerobic methanogenesis process.

[0044] In order to further reveal the effect of biochar on the anaerobic methanogenesis system of sludge under humic acid inhibition, the methanogenesis rate was further analyzed, such as Figure 2As shown, it is a line graph of the methane generation rate of Example 1 and Comparative Examples 1 to 4. It can be obtained that the methane rates of Example 1 and Comparative Example 4 are significantly higher than the methane rate of Comparative Example 2, and both Example 1 and Comparative Examples 1 to 4 reach the maximum daily methane production rate on the 8th day, wherein the maximum daily methane production rate of Comparative Example 2 is 7 mL / d, while the maximum daily methane production rates of Example 1 and Comparative Example 4 are 10.6 mL / d and 7.9 mL / d, respectively. In addition, compared with the methane production lag period of 3.8 days in Comparative Example 1, the methane production lag period of Comparative Example 3 and Comparative Example 2 is shortened to 3.6 days and 3.0 days, respectively; and the lag period of Example 1 and Comparative Example 4 is extended to 4.4 days and 4.0 days, respectively. On the one hand, biochar can shorten the lag period of anaerobic digestion of sludge. This is because biochar has a large specific surface area, which can provide a suitable environment for functional microorganisms, and can also serve as a carrier for direct electron transfer between microbial species to promote the mutual metabolism process between microbial species. On the other hand, humic acid has been proven to play a role in electron transfer during the acidification process, thereby accelerating the acidification process and shortening the lag period of anaerobic digestion. However, when these two substances are introduced into the anaerobic digestion system at the same time, the lag period is extended. This is because the addition of humic acid increases the number of bacteria related to hydrolysis and acidification on the surface of biochar, occupies more attachment space, and forms a competitive growth relationship with methanogens attached to the surface of biochar.

[0045] In summary, combined with the data of Examples 2 to 5, the present invention uses biochar particles to solve the rate limitation problem of humic acid on the hydrolysis, acidification and methanogenesis stages of anaerobic digestion of sludge. The biochar particles significantly improve the inhibitory effect of humic acid on the anaerobic digestion system of sludge, and improve the efficiency and rate of anaerobic methanogenesis, thereby achieving the improvement of the energy recovery efficiency and rate of the anaerobic methanogenesis system of sludge under the inhibition of humic acid.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for removing humic acid from inhibiting an anaerobic methanogenesis system, characterized in that: include: The biochar material is cleaned, dried, ground and sieved to obtain biochar particles; The residual sludge is subjected to sedimentation, screening and thermal pretreatment to obtain pretreated sludge; The pretreated sludge and the inoculated sludge are mixed to obtain mixed sludge; Biochar particles, humic acid and mixed sludge are added to the anaerobic reactor. After nitrogen aeration, the anaerobic reactor is sealed and placed in a water bath constant temperature oscillator to produce methane until no more methane is produced in the anaerobic reactor.

2. The method for removing the humic acid inhibition anaerobic methanogenesis system according to claim 1, characterized in that: The mass ratio of the humic acid, the biochar particles and the volatile suspended solids in the mixed sludge is 0.005:1:

1.

3. The method for removing the humic acid inhibition anaerobic methanogenesis system according to claim 1, characterized in that: The preparation method of the biochar material is as follows: pyrolyzing the biomass material under anaerobic conditions at 400-600°C for 2-4 h to obtain the biochar material.

4. The method for removing the humic acid inhibition anaerobic methanogenesis system according to claim 1, characterized in that: The drying conditions of the biochar material are: drying at a temperature not higher than 80°C for not less than 24 hours.

5. The method for removing the humic acid inhibition anaerobic methanogenesis system according to claim 1, characterized in that: The particle size of the biochar particles is 0.1-0.2 mm.

6. The method for removing the humic acid inhibition anaerobic methanogenesis system according to claim 1, characterized in that: The residual sludge settling time is not less than 24 hours.

7. The method for removing the humic acid inhibition anaerobic methanogenesis system according to claim 1, characterized in that: The excess sludge was sieved using a 0.45 mm sieve.

8. The method for removing the humic acid inhibition anaerobic methanogenesis system according to claim 1, characterized in that: The volume ratio of the inoculated sludge to the pretreated sludge is 1:

4.

9. The method for removing the humic acid inhibition anaerobic methanogenesis system according to claim 1, characterized in that: The heat pretreatment condition is: heat pretreatment at 80°C for no less than 30 min.

10. The method for removing the humic acid inhibition of anaerobic methanogenesis system according to claim 1, characterized in that: The shaking speed of the water bath constant temperature oscillator is 120-130 rpm and the temperature is 35±1°C.

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