A method for removing humic acid inhibition of anaerobic methanogenesis system

Abstract

The present invention belongs to the technical field of sludge treatment and resource utilization, and specifically relates to a method for removing the anaerobic methanogenesis system inhibited by humic acid; comprising: obtaining biochar particles after washing, drying, grinding and screening the biochar material; obtaining pretreated sludge after sedimentation, screening and heat pretreatment of the remaining sludge; mixing the pretreated sludge with the inoculated sludge to obtain mixed sludge; adding the biochar particles, humic acid and mixed sludge to an anaerobic reactor, and the anaerobic reactor is sealed and placed in a water bath constant temperature oscillator after nitrogen aeration to produce methane until no more methane is generated in the anaerobic reactor. The present invention solves the rate limiting problem of hydrolysis, acidification and methanogenesis stages in the anaerobic digestion process of sludge inhibited by humic acid, and at the same time realizes the improvement of the anaerobic methanogenesis efficiency of sludge inhibited by humic acid.

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 the anaerobic digestion system of sludge. For example, through hydrothermal treatment, part of the structure of humic acid can be destroyed to improve its bioavailability; adding metal cations can combine with some functional groups in humic acid to 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, resulting in an increase in operating costs and limiting its popularization and application in sludge treatment; the high cost and difficult maintenance of the pretreatment technology limit its further application in the sludge treatment process; again, although the binding ability of heavy metal ions and humic acid is very strong, the introduction of heavy metal ions will increase the risk of environmental pollution. Therefore, there is an urgent need 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 relieving the inhibition of the anaerobic methane production system by humic acid, which solves the rate-limiting problems in the hydrolysis, acidification and methane production stages during the anaerobic digestion process of sludge under the inhibition of humic acid, and at the same time realizes the improvement of the anaerobic methane production efficiency of sludge under the inhibition of humic acid.

[0008] To achieve the above object, the present invention adopts the following technical solutions:

[0009] The present invention provides a method for relieving the inhibition of the anaerobic methane production system by humic acid, including:

[0010] Washing, drying, grinding and screening the biochar material to obtain biochar particles;

[0011] Subjecting the excess sludge to sedimentation, sieving and thermal pretreatment to obtain pretreated sludge; mixing the pretreated sludge and inoculated sludge to obtain mixed sludge;

[0012] Adding the biochar particles, humic acid and mixed sludge into an anaerobic reactor, sealing the anaerobic reactor after purging with nitrogen and placing it in a water bath constant temperature oscillator for methane production until no more methane is generated in the anaerobic reactor.

[0013] Preferably, the mass ratio of the volatile suspended solids in the humic acid, biochar particles and mixed sludge is 0.005:1:1.

[0014] Preferably, the preparation method of the biochar material is: pyrolyzing the biomass material under anaerobic conditions at 400-600 °C for 2-4 h to obtain the biochar material.

[0015] Preferably, the drying condition of the biochar material is: drying at no higher than 80 °C for not less than 24 h.

[0016] Preferably, the particle size of the biochar particles is 0.1 - 0.2 mm.

[0017] Preferably, the sedimentation time of the excess sludge is not less than 24 h.

[0018] Preferably, the excess sludge is sieved through a 0.45 mm sieve mesh.

[0019] Preferably, the volume ratio of the inoculated sludge to the pretreated sludge is 1:4.

[0020] Preferably, the conditions for the thermal pretreatment are: thermal pretreatment at 80 °C for not less than 30 min.

[0021] Preferably, the shaking speed of the water bath constant temperature oscillator is 120 - 130 rpm, and the temperature is 35 ± 1 °C.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention weakens the influence of humic acid on microbial activity by adding biochar. On the one hand, the sites of the humic acid adsorbed on the surface of the biochar are occupied, thereby reducing the influence of humic acid accumulation on hydrolase, thus improving the hydrolase activity, promoting the hydrolysis process of organic matter, accelerating the consumption of short-chain fatty acids, promoting the conversion of propionic acid to acetic acid, and providing sufficient substrates for methanogens. At the same time, it reduces the possibility of humic acid competing with methanogens for electrons, thereby enhancing the methane production efficiency and rate; on the other hand, the biochar has a large specific surface area, providing sufficient space for the proliferation and growth of microorganisms; at the same time, the biochar can also mediate the direct interspecies electron transfer process between bacteria and methanogens, further promoting the anaerobic digestion methane production process. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for use in the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0025] Figure 1 It is a line graph of the methane cumulative amount of each group in Example 1 and the comparative examples of the present invention;

[0026] Figure 2 It is a line graph of the methane production rate of each group in Example 1 and the comparative examples of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] 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.

[0028] 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.

[0029] 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).

[0030] 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.”

[0031] 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.

[0032] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0033] The present invention provides a method for removing humic acid from inhibiting an anaerobic methanogenesis system, comprising:

[0034] The biochar material is cleaned, dried, ground and sieved to obtain biochar particles;

[0035] 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;

[0036] 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).

[0037] A further optimized solution specifically includes the following steps:

[0038] Pyrolyze the biomass material under anaerobic conditions at 400 - 600 °C for 2 - 4 h to obtain a biochar material; wash the biochar material repeatedly with deionized water until the surface soluble ions are removed; dry the washed biochar material at a temperature not higher than 80 °C for at least 24 h; after drying, obtain biochar particles with a particle size of 0.1 - 0.2 mm by screening. The biochar material is fruit wood, bark, straw, or straw, etc. In the present invention, by decomposing the organic components in the biomass material under anaerobic conditions at 400 - 600 °C, a biochar material (carbon-rich solid substance), volatile gases, and liquid products are generated; by washing the biochar material, the surface soluble ions can be removed, including soluble salts and harmful ions such as sulfide ions and chloride ions, etc.; by grinding and screening the biochar material, its particle size distribution can be adjusted, and it can more effectively adsorb harmful substances in the mixed sludge and reduce its impact on the microbial activity of the sludge anaerobic digestion system.

[0039] Let the excess sludge settle naturally for at least 24 h, and screen the settled excess sludge through a 0.45 mm sieve to remove gravel and large particle impurities; thermally pre-treat the screened excess sludge at 80 °C for at least 30 min to obtain pre-treated sludge; mix the inoculum sludge and the pre-treated sludge according to a volume ratio of 1:4 to obtain mixed sludge. In the present invention, through sedimentation, screening, and thermal pre-treatment of the excess sludge, large particle substances and some refractory organic matters in the excess sludge can be removed, making the excess sludge more uniform and improving its biodegradability; at the same time, thermal pre-treatment can destroy the structure of the excess sludge and release more soluble organic matters, creating more favorable substrate conditions for subsequent methane production. The inoculum sludge is rich in anaerobic functional microorganisms capable of degrading organic matters. After mixing with the pre-treated sludge, it can quickly adapt to the environment and start degrading the organic matters in the sludge, and finally convert the organic matters into methane.

[0040] Add humic acid, biochar particles, and mixed sludge to an anaerobic reactor, where the mass ratio of volatile suspended solids in humic acid, biochar particles, and mixed sludge is 0.005:1:1. After the anaerobic reactor is purged with nitrogen for at least 5 min, seal the anaerobic reactor and place it in a water bath constant temperature oscillator. The shaking speed of the water bath constant temperature oscillator is 120 - 130 rpm, and the temperature is 35 ± 1 °C for methane production until no more methane is generated in the anaerobic reactor. In the present invention, humic acid, biochar particles, and mixed sludge are mixed. Under anaerobic conditions, the humic acid in the mixed sludge will be adsorbed by the biochar, reducing its toxic effect on anaerobic microorganisms. Moreover, under the catalytic action of the biochar particles, anaerobic microorganisms can more effectively convert organic matters into methane, improving the production efficiency and rate of methane.

[0041] On the one hand, humic acid can promote the solubilization process of sludge, thereby enhancing the dissolution of organic matter, which is beneficial to the anaerobic methane production process; on the other hand, humic acid slows down the hydrolysis process of organic matter by hindering the activity of hydrolase. In the presence of biochar particles, they will adsorb free humic acid, thereby weakening the impact of humic acid on the activity of anaerobic microorganisms. At the same time, the biochar particles adsorb only part of the humic acid rather than all of it, and the free humic acid and biochar particles will have a synergistic promoting effect on the anaerobic methane production process of sludge. Specifically, the biochar particles adsorb humic acid and occupy its active sites, thereby increasing the activity of hydrolase. At the same time, it reduces the electron competition process between humic acid and methanogens, enhances the electron transfer ability 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 propionate to acetate, providing sufficient substrates for methanogens, and ultimately improving the anaerobic methane production efficiency.

[0042] In addition, biochar particles have good electrical conductivity, which can mediate the electron transfer process between microbial species, strengthen the syntrophic metabolic relationship between microbial species, accelerate the electron transfer efficiency between syntrophic microorganisms, and further promote the anaerobic digestion methane production efficiency.

[0043] The following will further illustrate the present invention in combination with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not 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 also fall within the scope defined by the appended claims of this application.

[0044] Conventional instrument equipment in the art is used in the following embodiments. For the experimental methods without specific conditions noted in the following embodiments, they are usually carried out under conventional conditions or according to the conditions recommended by the manufacturer. Various raw materials are used in the following embodiments. Unless otherwise stated, commercially available products are used, and their specifications are conventional specifications in the art. In the specification of the present invention and the following embodiments, unless otherwise specified, "%" represents weight percentage, "parts" represents weight parts, and the ratio represents weight ratio.

[0045] Example 1

[0046] The fruit wood was pyrolyzed under anaerobic conditions at 500 °C for 2 h to obtain a biochar material; the biochar was repeatedly washed with deionized water until the surface soluble ions were removed; the washed biochar material was dried at 70 °C for 26 h; after drying, biochar particles with a particle size of 0.2 mm were obtained by sieving;

[0047] The excess sludge was allowed to settle naturally for 26 h, and the settled excess sludge was sieved through a 0.45 mm sieve to remove gravel and large particulate impurities; the sieved excess sludge was thermally pretreated at 80 °C for 40 min to obtain pretreated sludge; the inoculum sludge and the pretreated sludge were mixed at a volume ratio of 1:4 to obtain mixed sludge;

[0048] Humic acid, biochar particles and the mixed sludge were added to an anaerobic reactor, where the mass ratio of volatile suspended solids in humic acid, biochar particles and the mixed sludge was 0.005:1:1. After the anaerobic reactor was purged with nitrogen for 7 min, the anaerobic reactor was sealed and placed in a water bath thermostatic shaker. The shaking speed of the water bath thermostatic shaker was 130 rpm and the temperature was 35 °C for methane production until no more methane was produced in the anaerobic reactor. The cumulative methane production was 132.6 mLCH 4 / gVSS, and the maximum daily methane production rate was 10.6 mL / d.

[0049] Example 2

[0050] The bark was pyrolyzed at 600 °C under anaerobic conditions for 3 h to obtain a biochar material; the biochar was repeatedly washed with deionized water until the surface dissolved ions were removed; the washed biochar material was dried at 75 °C for 25 h; after drying, biochar particles with a particle size of 0.15 mm were obtained by screening;

[0051] The excess sludge was allowed to settle naturally for 24 h, and the settled excess sludge was sieved through a 0.45 mm sieve to remove gravel and large particulate impurities; the sieved excess sludge was thermally pretreated at 80 °C for 35 min to obtain pretreated sludge; the inoculum sludge and the pretreated sludge were mixed at a volume ratio of 1:4 to obtain mixed sludge;

[0052] Humic acid, biochar particles and the mixed sludge were added to an anaerobic reactor, where the mass ratio of volatile suspended solids in humic acid, biochar particles and the mixed sludge was 0.005:1:1. After the anaerobic reactor was purged with nitrogen for 6 min, the anaerobic reactor was sealed and placed in a water bath thermostatic shaker. The shaking speed of the water bath thermostatic shaker was 125 rpm and the temperature was 35 °C for methane production until no more methane was produced in the anaerobic reactor. The cumulative methane production was 131.8 mLCH 4 / gVSS, and the maximum daily methane production rate was 10.6 mL / d.

[0053] Example 3

[0054] The straw was pyrolyzed under anaerobic conditions at 400 °C for 4 h to obtain a biochar material; the biochar was repeatedly washed with deionized water until the surface soluble ions were removed; the washed biochar material was dried at 80 °C for 24 h; after drying, biochar particles with a particle size of 0.1 mm were obtained by sieving;

[0055] The excess sludge was allowed to settle naturally for 24 h, and the settled excess sludge was sieved through a 0.45 mm sieve to remove gravel and large particle impurities; the sieved excess sludge was thermally pretreated at 80 °C for 30 min to obtain pretreated sludge; the inoculated sludge and the pretreated sludge were mixed at a volume ratio of 1:4 to obtain mixed sludge;

[0056] Humic acid, biochar particles and mixed sludge were added to an anaerobic reactor, and 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 purged with nitrogen for 5 min, 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 120 rpm and the temperature was 36 °C for methane production until no more methane was produced in the anaerobic reactor. The cumulative methane production was 130.9 mLCH 4 / gVSS, and the maximum daily methane production rate was 10.5 mL / d.

[0057] Example 4

[0058] The straw was pyrolyzed under anaerobic conditions at 500 °C for 2 h to obtain a biochar material; the biochar was repeatedly washed with deionized water until the surface soluble ions were removed; the washed biochar material was dried at 65 °C for 28 h; after drying, biochar particles with a particle size of 0.2 mm were obtained by sieving;

[0059] The excess sludge was allowed to settle naturally for 26 h, and the settled excess sludge was sieved through a 0.45 mm sieve to remove gravel and large particle impurities; the sieved excess sludge was thermally pretreated at 80 °C for 45 min to obtain pretreated sludge; the inoculated sludge and the pretreated sludge were mixed at a volume ratio of 1:4 to obtain mixed sludge;

[0060] Humic acid, biochar particles and mixed sludge were added to an anaerobic reactor, and 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 purged with nitrogen for 7 min, 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 125 rpm and the temperature was 35 °C for methane production until no more methane was produced in the anaerobic reactor. The cumulative methane production was 129.4 mLCH 4 / gVSS, the maximum daily methane production rate is 10.2 mL / d.

[0061] Example 5

[0062] The fruit trees were pyrolyzed at 500 °C under anaerobic conditions for 4 h to obtain biochar materials; the biochar was repeatedly washed with deionized water until the surface soluble ions were removed; the washed biochar materials were dried at 60 °C for 30 h; after drying, biochar particles with a particle size of 0.2 mm were obtained by screening.

[0063] The excess sludge was allowed to settle naturally for 26 h, and the settled excess sludge was sieved through a 0.45 mm sieve to remove gravel and large particle impurities; the sieved excess sludge was thermally pretreated at 80 °C for 50 min to obtain pretreated sludge; the inoculated sludge and the pretreated sludge were mixed at a volume ratio of 1:4 to obtain mixed sludge.

[0064] Humic acid, biochar particles and mixed sludge were added to the anaerobic reactor, where 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 purged with nitrogen for 7 min, 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 120 rpm and the temperature was 34 °C for methane production until no more methane was produced in the anaerobic reactor. The cumulative methane production was 134.1 mLCH 4 / gVSS, the maximum daily methane production rate is 10.7 mL / d.

[0065] Comparative Example 1

[0066] The excess sludge was allowed to settle naturally for 26 h, and the settled excess sludge was sieved through a 0.45 mm sieve to remove gravel and large particle impurities; the sieved excess sludge was thermally pretreated at 80 °C for 40 min to obtain pretreated sludge; the inoculated sludge and the pretreated sludge were mixed at a volume ratio of 1:4 to obtain mixed sludge; the mixed sludge was added to the anaerobic reactor. After the anaerobic reactor was purged with nitrogen for 7 min, 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 for methane production until no more methane was produced in the anaerobic reactor.

[0067] Comparative Example 2

[0068] Let the excess sludge settle naturally for 26 h, and sieve the settled excess sludge through a 0.45 mm sieve to remove gravel and large particle impurities; thermally pre-treat the sieved excess sludge at 80 °C for 40 min to obtain pre-treated sludge; mix the inoculum sludge and the pre-treated sludge in a volume ratio of 1:4 to obtain mixed sludge;

[0069] Add humic acid and the mixed sludge to an anaerobic reactor, where the mass ratio of humic acid to the volatile suspended solids in the mixed sludge is 0.005:1. After purging nitrogen into the anaerobic reactor for 7 min, seal the anaerobic reactor and place it in a water bath thermostatic shaker. The shaking speed of the water bath thermostatic shaker is 130 rpm and the temperature is 35 °C for methane production until no more methane is produced in the anaerobic reactor.

[0070] Comparative Example 3

[0071] Pyrolyze fruit wood under anaerobic conditions at 500 °C for 2 h to obtain biochar material; repeatedly wash the biochar with deionized water until the surface soluble ions are removed; dry the washed biochar material at 70 °C for 26 h; after drying, obtain biochar particles with a particle size of 0.2 mm through screening;

[0072] Let the excess sludge settle naturally for 26 h, and sieve the settled excess sludge through a 0.45 mm sieve to remove gravel and large particle impurities; thermally pre-treat the sieved excess sludge at 80 °C for 40 min to obtain pre-treated sludge; mix the inoculum sludge and the pre-treated sludge in a volume ratio of 1:4 to obtain mixed sludge;

[0073] Add the biochar particles and the mixed sludge to an anaerobic reactor, where the mass ratio of the biochar particles to the volatile suspended solids in the mixed sludge is 1:1. After purging nitrogen into the anaerobic reactor for 7 min, seal the anaerobic reactor and place it in a water bath thermostatic shaker. The shaking speed of the water bath thermostatic shaker is 130 rpm and the temperature is 35 °C for methane production until no more methane is produced in the anaerobic reactor.

[0074] Comparative Example 4

[0075] Pyrolyze fruit wood under anaerobic conditions at 500 °C for 2 h to obtain biochar material; repeatedly wash the biochar with deionized water until the surface soluble ions are removed; dry the washed biochar material at 70 °C for 26 h; after drying, obtain biochar particles with a particle size of 0.2 mm through screening;

[0076] The excess sludge was allowed to settle naturally for 26 h, and the settled excess sludge was sieved through a 0.45 mm sieve to remove gravel and large particulate impurities; the sieved excess sludge was thermally pretreated at 80 °C for 40 min to obtain pretreated sludge; the inoculated sludge and the pretreated sludge were mixed at a volume ratio of 1:4 to obtain mixed sludge;

[0077] Humic acid was loaded onto the surface of biochar particles to obtain biochar particles loaded with humic acid. The biochar particles loaded with humic acid were added to an anaerobic reactor. After the anaerobic reactor was purged with nitrogen for 7 min, the anaerobic reactor was sealed and placed in a water bath thermostatic oscillator. The shaking speed of the water bath thermostatic oscillator was 130 rpm and the temperature was 35 °C for methane production until no more methane was produced in the anaerobic reactor. Among them, the mass ratio of humic acid, biochar particles and volatile suspended solids in the mixed sludge was 0.005:1:1.

[0078] As Figure 1 shown, it is a line graph of methane cumulative production of Example 1 and Comparative Examples 1-4. The methane cumulative production of Comparative Example 1 was 100.3 mL CH 4 / gVSS. The methane cumulative production of Comparative Example 2 was 90.9 mL CH 4 / gVSS, which was 9.37% lower than that of Comparative Example 1, indicating that humic acid had an inhibitory effect on the anaerobic methane production process; the methane cumulative production of Example 1 was 132.6 mLCH 4 / gVSS, which was 32.2% and 45.9% higher than that of Comparative Example 1 and Comparative Example 2 respectively, indicating that the addition of biochar could alleviate or relieve the inhibitory effect of humic acid on the sludge anaerobic methane production system, thereby increasing methane production; the methane cumulative production of Comparative Example 3 was 110.8 mL CH 4 / g VSS, which was lower than the methane cumulative production of Example 1, indicating that biochar adsorbed part of the humic acid rather than all of the humic acid. On the one hand, since biochar could adsorb humic acid, the concentration of free humic acid was reduced, and its inhibitory effect on the activity of functional microorganisms and key enzymes was alleviated; on the other hand, low-concentration humic acid could promote the methane production process, and at the same time, biochar could also promote the methane production process. The methane cumulative production of Comparative Example 4 was 122.4 mL CH 4 / g VSS, which was higher than that of Comparative Example 1 and Comparative Example 2 but lower than that of Example 1, further confirming that when biochar alleviated the inhibitory effect of humic acid on sludge anaerobic methane production, humic acid and biochar would form a synergistic promotion effect on the anaerobic methane production process.

[0079] To further reveal the effect of biochar on the sludge anaerobic methane production system inhibited by humic acid, the methane production rate was further analyzed. As Figure 2As shown in the figure, it is a line graph of the methane production rate of Example 1 and Comparative Examples 1-4. It can be obtained that the methane rates of Example 1 and Comparative Example 4 are significantly higher than that of Comparative Example 2, and both Example 1 and Comparative Examples 1-4 reached the maximum daily methane production rate on the 8th day. Among them, 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 periods of Comparative Example 3 and Comparative Example 2 were shortened to 3.6 days and 3.0 days respectively; while the lag periods of Example 1 and Comparative Example 4 were extended to 4.4 days and 4.0 days respectively. On the one hand, biochar can shorten the lag period of sludge anaerobic digestion 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 interspecies electron transfer between microorganisms to promote the syntrophic metabolism process between microorganisms; on the other hand, humic acid has been proven to be able 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 because the addition of humic acid increases the bacteria related to hydrolysis and acidification on the surface of biochar, occupying more attachment spaces and forming a competitive growth relationship with the methanogens attached to the surface of biochar.

[0080] In summary, combined with the data of Examples 2-5, the present invention uses biochar particles to solve the rate limitation problem of humic acid on the hydrolysis, acidification and methanogenesis stages of sludge anaerobic digestion. Biochar particles significantly improve the inhibitory effect of humic acid on the sludge anaerobic digestion system, and improve the anaerobic methane production efficiency and rate, realizing the improvement of the energy recovery efficiency and rate of the sludge anaerobic methane production system under the inhibition of humic acid.

[0081] 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 foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features. And 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; Mixing the pretreated sludge and the inoculated sludge to obtain mixed sludge; The biochar particles, humic acid and the mixed sludge are added to an anaerobic reactor, and the anaerobic reactor is sealed and placed in a water bath constant temperature oscillator after nitrogen aeration to produce methane until no more methane is generated in the anaerobic reactor; The mass ratio of the humic acid, the biochar particles and the volatile suspended solids in the mixed sludge is 0.005:1:

1.

2. 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: pyrolyzing the biomass material under anaerobic conditions at 400-600° C. for 2-4 h to obtain the biochar material.

3. 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.

4. 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.

5. 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.

6. 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.

7. 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.

8. 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.

9. The method for removing the humic acid inhibition 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.

Images