CN117447038A - Method for promoting anaerobic methane production of excess sludge by using iron-calcium combined pretreatment - Google Patents
Method for promoting anaerobic methane production of excess sludge by using iron-calcium combined pretreatment Download PDFInfo
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- 239000010802 sludge Substances 0.000 title claims abstract description 123
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 title claims abstract description 108
- 238000000034 method Methods 0.000 title claims abstract description 39
- 230000001737 promoting effect Effects 0.000 title claims abstract description 18
- WNQQFQRHFNVNSP-UHFFFAOYSA-N [Ca].[Fe] Chemical compound [Ca].[Fe] WNQQFQRHFNVNSP-UHFFFAOYSA-N 0.000 title claims abstract description 8
- 238000004519 manufacturing process Methods 0.000 title abstract description 22
- 238000000855 fermentation Methods 0.000 claims abstract description 107
- 239000004343 Calcium peroxide Substances 0.000 claims abstract description 45
- LHJQIRIGXXHNLA-UHFFFAOYSA-N calcium peroxide Chemical compound [Ca+2].[O-][O-] LHJQIRIGXXHNLA-UHFFFAOYSA-N 0.000 claims abstract description 45
- 235000019402 calcium peroxide Nutrition 0.000 claims abstract description 45
- UMPKMCDVBZFQOK-UHFFFAOYSA-N potassium;iron(3+);oxygen(2-) Chemical compound [O-2].[O-2].[K+].[Fe+3] UMPKMCDVBZFQOK-UHFFFAOYSA-N 0.000 claims abstract description 42
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 38
- 239000011575 calcium Substances 0.000 claims abstract description 16
- 229910052742 iron Inorganic materials 0.000 claims abstract description 16
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 claims abstract description 13
- 229910052791 calcium Inorganic materials 0.000 claims abstract description 13
- 230000004151 fermentation Effects 0.000 claims description 91
- 239000000758 substrate Substances 0.000 claims description 88
- 239000010902 straw Substances 0.000 claims description 47
- 230000029087 digestion Effects 0.000 claims description 29
- 102000016938 Catalase Human genes 0.000 claims description 28
- 108010053835 Catalase Proteins 0.000 claims description 28
- 210000002966 serum Anatomy 0.000 claims description 25
- 150000001875 compounds Chemical class 0.000 claims description 23
- 238000003756 stirring Methods 0.000 claims description 20
- 238000002156 mixing Methods 0.000 claims description 17
- 238000002203 pretreatment Methods 0.000 claims description 16
- 230000010355 oscillation Effects 0.000 claims description 15
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 12
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 10
- 239000000203 mixture Substances 0.000 claims description 10
- 238000004062 sedimentation Methods 0.000 claims description 10
- 238000005507 spraying Methods 0.000 claims description 10
- 239000007789 gas Substances 0.000 claims description 9
- 230000008569 process Effects 0.000 claims description 9
- 238000007873 sieving Methods 0.000 claims description 9
- 239000006228 supernatant Substances 0.000 claims description 8
- 239000010865 sewage Substances 0.000 claims description 7
- 230000003247 decreasing effect Effects 0.000 claims description 6
- 238000000227 grinding Methods 0.000 claims description 6
- 229910052757 nitrogen Inorganic materials 0.000 claims description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 6
- 239000012153 distilled water Substances 0.000 claims description 5
- 238000001035 drying Methods 0.000 claims description 5
- 230000005484 gravity Effects 0.000 claims description 5
- 238000007789 sealing Methods 0.000 claims description 5
- 238000002791 soaking Methods 0.000 claims description 5
- 238000005303 weighing Methods 0.000 claims description 5
- 238000007781 pre-processing Methods 0.000 claims description 4
- 238000005273 aeration Methods 0.000 claims description 2
- 230000003834 intracellular effect Effects 0.000 abstract description 8
- 238000004090 dissolution Methods 0.000 abstract description 7
- 210000002421 cell wall Anatomy 0.000 abstract description 6
- 238000005336 cracking Methods 0.000 abstract description 6
- 230000003647 oxidation Effects 0.000 abstract description 6
- 238000007254 oxidation reaction Methods 0.000 abstract description 6
- 229920000642 polymer Polymers 0.000 abstract description 6
- 230000000052 comparative effect Effects 0.000 description 20
- 230000000694 effects Effects 0.000 description 20
- 239000007787 solid Substances 0.000 description 14
- 244000005700 microbiome Species 0.000 description 11
- 241000894006 Bacteria Species 0.000 description 7
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 6
- 230000007062 hydrolysis Effects 0.000 description 6
- 238000006460 hydrolysis reaction Methods 0.000 description 6
- 239000001301 oxygen Substances 0.000 description 5
- 229910052760 oxygen Inorganic materials 0.000 description 5
- 230000009286 beneficial effect Effects 0.000 description 4
- 150000004676 glycans Chemical class 0.000 description 4
- 230000005764 inhibitory process Effects 0.000 description 4
- 239000005416 organic matter Substances 0.000 description 4
- 229920001282 polysaccharide Polymers 0.000 description 4
- 239000005017 polysaccharide Substances 0.000 description 4
- 238000002360 preparation method Methods 0.000 description 4
- 102000004169 proteins and genes Human genes 0.000 description 4
- 108090000623 proteins and genes Proteins 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 3
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 3
- 229910052799 carbon Inorganic materials 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 3
- 230000007613 environmental effect Effects 0.000 description 3
- 230000006872 improvement Effects 0.000 description 3
- 230000000696 methanogenic effect Effects 0.000 description 3
- 238000004064 recycling Methods 0.000 description 3
- QJZYHAIUNVAGQP-UHFFFAOYSA-N 3-nitrobicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic acid Chemical compound C1C2C=CC1C(C(=O)O)C2(C(O)=O)[N+]([O-])=O QJZYHAIUNVAGQP-UHFFFAOYSA-N 0.000 description 2
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 description 2
- 241001453382 Nitrosomonadales Species 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- 230000002378 acidificating effect Effects 0.000 description 2
- 230000009471 action Effects 0.000 description 2
- 239000012736 aqueous medium Substances 0.000 description 2
- 239000006227 byproduct Substances 0.000 description 2
- 239000001913 cellulose Substances 0.000 description 2
- 229920002678 cellulose Polymers 0.000 description 2
- 238000000354 decomposition reaction Methods 0.000 description 2
- 230000001627 detrimental effect Effects 0.000 description 2
- 235000014113 dietary fatty acids Nutrition 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 239000000194 fatty acid Substances 0.000 description 2
- 229930195729 fatty acid Natural products 0.000 description 2
- 150000004665 fatty acids Chemical class 0.000 description 2
- 239000004021 humic acid Substances 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 230000003301 hydrolyzing effect Effects 0.000 description 2
- 230000004060 metabolic process Effects 0.000 description 2
- 239000007800 oxidant agent Substances 0.000 description 2
- 230000001590 oxidative effect Effects 0.000 description 2
- 230000020477 pH reduction Effects 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 238000005728 strengthening Methods 0.000 description 2
- VTLYFUHAOXGGBS-UHFFFAOYSA-N Fe3+ Chemical compound [Fe+3] VTLYFUHAOXGGBS-UHFFFAOYSA-N 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 239000002585 base Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- AXCZMVOFGPJBDE-UHFFFAOYSA-L calcium dihydroxide Chemical compound [OH-].[OH-].[Ca+2] AXCZMVOFGPJBDE-UHFFFAOYSA-L 0.000 description 1
- 239000000920 calcium hydroxide Substances 0.000 description 1
- 229910001861 calcium hydroxide Inorganic materials 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 238000003421 catalytic decomposition reaction Methods 0.000 description 1
- 238000006555 catalytic reaction Methods 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 230000006957 competitive inhibition Effects 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 230000002939 deleterious effect Effects 0.000 description 1
- 239000003344 environmental pollutant Substances 0.000 description 1
- 239000002803 fossil fuel Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 239000003864 humus Substances 0.000 description 1
- 150000002431 hydrogen Chemical class 0.000 description 1
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 230000002779 inactivation Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 230000000813 microbial effect Effects 0.000 description 1
- 235000015097 nutrients Nutrition 0.000 description 1
- 150000007524 organic acids Chemical class 0.000 description 1
- 230000035699 permeability Effects 0.000 description 1
- 150000002978 peroxides Chemical class 0.000 description 1
- 231100000719 pollutant Toxicity 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 238000009790 rate-determining step (RDS) Methods 0.000 description 1
- 230000008929 regeneration Effects 0.000 description 1
- 238000011069 regeneration method Methods 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F11/00—Treatment of sludge; Devices therefor
- C02F11/02—Biological treatment
- C02F11/04—Anaerobic treatment; Production of methane by such processes
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F11/00—Treatment of sludge; Devices therefor
- C02F11/06—Treatment of sludge; Devices therefor by oxidation
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2303/00—Specific treatment goals
- C02F2303/06—Sludge reduction, e.g. by lysis
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E50/00—Technologies for the production of fuel of non-fossil origin
- Y02E50/30—Fuel from waste, e.g. synthetic alcohol or diesel
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- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Environmental & Geological Engineering (AREA)
- Hydrology & Water Resources (AREA)
- Water Supply & Treatment (AREA)
- Organic Chemistry (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Health & Medical Sciences (AREA)
- General Chemical & Material Sciences (AREA)
- Molecular Biology (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Treatment Of Sludge (AREA)
Abstract
The invention discloses a method for promoting anaerobic methane production of excess sludge by using iron and calcium combined pretreatment, which comprises the following steps: s1, obtaining excess sludge, carrying out pretreatment on S2 and iron calcium in a combined way, and carrying out anaerobic fermentation treatment S3; according to the method for promoting anaerobic methanogenesis of the excess sludge by adopting the combined pretreatment of the potassium ferrate and the calcium peroxide, the sludge cracking efficiency based on advanced oxidation is enhanced by the potassium ferrate, the stability of the potassium ferrate is improved by the alkaline environment created by the calcium peroxide, the extracellular polymer and the cell wall are jointly acted to improve the cracking, the dissolution of intracellular organic matters is promoted, and the anaerobic methanogenesis efficiency of the excess sludge is further improved.
Description
Technical Field
The invention relates to the technical field of sludge treatment, in particular to a method for promoting anaerobic methane production of excess sludge by using iron-calcium combined pretreatment.
Background
In the sewage treatment process, microorganisms utilize organic matters to carry out anabolism to generate a large amount of excess sludge, so that the excess sludge becomes a main byproduct of a sewage treatment plant, and the effective treatment of the excess sludge becomes a serious environmental problem. Among the numerous excess sludge treatment processes, anaerobic biological treatment is attracting attention due to the characteristics of green, low cost, energy generation and the like, and has practical and potential practical and research values. In fact, the surplus sludge has distinct pollution characteristics and the potential of recycling the surplus sludge to change waste into valuable, and because the surplus sludge contains a large amount of carbon and nutrient substances, clean resources such as volatile fatty acid, methane, hydrogen and the like can be generated through anaerobic digestion, thereby being beneficial to realizing the recycling of the surplus sludge, reducing the combustion of fossil fuel, greatly reducing the treatment cost and saving energy.
Anaerobic digestion is generally based on hydrolysis, acidification and methanogenesis, i.e. the organic matter is first hydrolysed and then fermented to produce single chain fatty acids and hydrogen, which are ultimately utilized by heterotrophic and methanogenic bacteria. In general, the excess sludge hydrolysis stage is the rate limiting step of anaerobic digestion, since the protection of dense extracellular polymers and cell walls results in the release of organics in water that is difficult, resulting in the lack of necessary material basis for subsequent microbial life activities and methane production processes. Therefore, if the dissolution and the hydrolysis of the organic matters can be promoted by adopting a proper pretreatment means, the recycling of the surplus sludge is realized, and the method has definitely important significance.
The pretreatment of the excess sludge comprises acid, alkali, mechanical, heating and other methods, wherein the advanced oxidation technology is widely used for breaking the wall and hydrolyzing the excess sludge due to the characteristics of simplicity, high efficiency and the like. Potassium Ferrate (PF) is a novel green, environmentally friendly strong oxidizer that oxidizes organic matter with high efficiency under both acid and base conditions without producing deleterious byproducts, which produce Fe in aqueous media 3+ Or Fe (OH) 3 The organic acid can be used as an exogenous electron acceptor in the subsequent anaerobic digestion process, enriches iron reducing bacteria, further hydrolyzes and acidizes released refractory organic matters, and can be used as excellent floccules of most pollutants. Therefore, the potassium ferrate is utilized for pretreatment, so that the sludge floc structure is effectively destroyed, intracellular organic matters are released, the sludge reduction is promoted, and the subsequent anaerobic digestion is facilitated. In general, potassium ferrate is extremely oxidizing under acidic conditions, but is extremely unstable and readily decomposable, while stability under alkaline conditions can be greatly improved, and its oxidation characteristics under acidic and basic conditions are as followsThe following is shown:
FeO 4 2- +8H + +3e - →Fe 3+ +4H 2 O， E 0 =+2.20V
FeO 4 2- +4H 2 O +3e - →Fe 3+ +5OH - ， E 0 =+0.72V
calcium peroxide (CaO) 2 ) Is an environmentally friendly inorganic peroxide which is thermally stable and slowly releases hydrogen peroxide and calcium hydroxide at a "controlled" rate, compared to H, when contacted with an aqueous medium 2 O 2 Has higher utilization efficiency, is regarded as H 2 O 2 Is a solid form of (c). In addition, released H 2 O 2 Further generates free radicals including OH, HO 2 Sum O 2 - . The release process is as follows:
CaO 2 +2H 2 O→Ca（OH） 2 +H 2 O 2
CaO 2 +2H 2 O→Ca（OH） 2 +O 2
H 2 O 2 +e - →·OH+OH -
·OH+ H 2 O 2 →H 2 O+ HO 2 ·
HO 2 ·→· O 2 - +H +
product H in the above reaction equation 2 O 2 And Ca (OH) 2 Has the functions of destroying extracellular polymers and cell walls of sludge and promoting sludge dissolution, and in addition, the slow release of calcium peroxide is beneficial to providing oxygen required by microorganism growth, and the micro-oxygen environment promotes the further hydrolysis of dissolved organic matters.
The invention provides a method for preparing methane by anaerobic fermentation by taking residual sludge after wall breaking as a substrate, wherein the residual sludge is pretreated by combining potassium ferrate and calcium peroxide to promote hydrolysis of intracellular substances, and environmental conditions required by subsequent anaerobic fermentation are synchronously blended. At present, no research or technical invention for strengthening the hydrolysis of residual sludge to produce methane by combining potassium ferrate and calcium peroxide exists. Based on the method, the invention provides a method for promoting anaerobic methane production of excess sludge by combining iron and calcium.
Disclosure of Invention
In order to solve the technical problems, the invention provides a method for promoting anaerobic methane production of excess sludge by combining iron and calcium.
The technical scheme of the invention is as follows: a method for promoting anaerobic methanogenesis of excess sludge by using iron-calcium combined pretreatment comprises the following steps:
s1, obtaining excess sludge
Sieving activated sludge obtained from a secondary sedimentation tank of a sewage treatment plant, and carrying out gravity sedimentation for 23-25 h, and discarding supernatant to obtain residual sludge serving as a fermentation substrate; detecting the contents of TSS and VSS in a fermentation substrate, wherein the content of TSS (total suspended solids) in the fermentation substrate is 31.5-32.5 g/L, VSS (volatile suspended solids) and the content of TSS/L, VSS is 18.5-19.5 g/L;
s2, iron-calcium combined pretreatment
Weighing 135-145 mL of fermentation substrate, placing the fermentation substrate in a serum bottle, and sequentially preprocessing the fermentation substrate by adopting 0.28-0.32 g/g of calcium peroxide of VSS and 0.2-1 g/g of potassium ferrate of VSS to obtain a preprocessed fermentation substrate;
s3, anaerobic fermentation treatment
Weighing 95-105 mL of pretreated fermentation substrate, placing the fermentation substrate into an anaerobic fermentation bottle, adding hydrochloric acid with the molar concentration of 4-6 mol/L, adjusting the pH of the pretreated fermentation substrate to 6.5-7.5, adding the inoculated anaerobic digestion sludge according to the volume ratio of the pretreated fermentation substrate to the inoculated anaerobic digestion sludge of 1:0.98-1.02, aerating for 18-22 min, sealing, transferring to a constant-temperature oscillating table for anaerobic fermentation at 36-38 ℃, and collecting gas in the anaerobic fermentation process to obtain methane;
description: the fermentation substrate is pretreated by adopting 0.28-0.32 g/g of VSS calcium peroxide and 0.2-1 g/g of VSS potassium ferrate in sequence, so that the potassium ferrate and the calcium peroxide can act on the sludge together efficiently, the cracking of extracellular polymers and cell walls is further improved, and the dissolution efficiency of intracellular organic matters is further improved; the pretreatment effect of the calcium peroxide and the potassium ferrate in the range on the volatile suspended solids is better, so that the purpose of further improving the methane production efficiency of the residual sludge is achieved; when the content of the potassium ferrate obtained by the data of the embodiment is 1g/g VSS, the inhibition effect is generated on the yield of the early methane, the methane production delay period is obviously increased, and excessive addition of the potassium ferrate can generate some refractory organic matters such as humic acid and cellulose, so that the inhibition effect is generated on methanogens, and meanwhile, the economic cost is slightly high; when the content of potassium ferrate is less than 0.2g/g VSS, the generated SCOD, protein and polysaccharide are obviously reduced, and finally the methane yield is obviously reduced.
Further, in step S1, the sieving method is as follows: sieving by using a screen with the aperture of 1-3 mm;
description: the screen mesh with the aperture can effectively remove insoluble impurities in the activated sludge, so that the purity of the activated sludge is improved, and the anaerobic methane production efficiency of the excess sludge is further improved.
Further, in step S2, the preprocessing method includes: firstly placing a serum bottle on a magnetic stirrer, stirring a fermentation substrate at a rotating speed of 250-300 r/min for 10-20 min, adding 0.28-0.32 g/g VSS calcium peroxide into the fermentation substrate, stirring for 5-7 min, adding 0.2-1 g/g VSS potassium ferrate, stirring for 3-5 min, and finally oscillating in a constant-temperature oscillating table for 22-24 h to obtain a pretreated fermentation substrate;
description: according to the pretreatment method, the surplus sludge is treated by combining the potassium ferrate and the calcium peroxide, so that the sludge cracking efficiency based on advanced oxidation is enhanced by the potassium ferrate, the stability of the potassium ferrate is improved by the alkaline environment created by the calcium peroxide, the extracellular polymer and the cell wall are improved by the combined action of the potassium ferrate and the calcium peroxide, the dissolution of intracellular organic matters is promoted, and the methane production efficiency of a fermentation substrate, namely the activated sludge, can be effectively improved.
Further, the oscillation processing parameters are: the oscillation temperature is 36-38 ℃, and the oscillation speed is 145-155 rpm;
description: the oscillation treatment effect under the parameters is better, the residual sludge can be fully acted, the dissolution condition of intracellular organic matters is improved, and the anaerobic methane production effect of the residual sludge is further improved.
Further, in step S2, the fermentation substrate is subjected to a pretreatment before the pretreatment; the pretreatment method comprises the following steps:
s2-1, taking 100-120 g of straw, soaking the straw in distilled water for 20-30 min, naturally drying the straw at 26-28 ℃ for 3-5 h, and grinding the straw in a grinder for 20-25 min to obtain powdery straw;
s2-2, taking 1/2 of powdery straw, measuring 8-10U/m L of catalase solution according to the weight-volume ratio of 40-50 g to 95-100 mL of the catalase solution, spraying the catalase solution on the surface of the powdery straw at the speed of 5-7 mL/min until the spraying is finished, stirring and mixing uniformly, and compressing the mixture into a block mixture with the size of 1cm multiplied by 1cm by using a press to obtain a compound;
s2-3, carrying out microwave irradiation treatment on a fermentation substrate in a serum bottle, wherein the microwave irradiation intensity is 10-300W, the microwave irradiation time is 10-12 min, and sequentially adding the rest 1/2 of powdery straw and the compound obtained in the step S2-2 into the serum bottle during microwave irradiation and uniformly mixing;
description: the complex obtained by mixing the powdery straw and the catalase is used for carrying out pretreatment on a fermentation substrate in cooperation with microwave irradiation, so that the stability of the catalase can be effectively increased, the influence of microwave irradiation on the activity of a catalase solution is reduced, and the catalytic decomposition of the catalase on the calcium peroxide is utilized to ensure that the calcium peroxide acts on sludge better, and the calcium peroxide can promote the degradation of humus and lignocellulose in the sludge to become organic matters easy to degrade, so that the production of methane is promoted; meanwhile, the calcium peroxide has oxidability, can release hydroxyl free radicals as an oxidant, promotes the decomposition of EPS flocs of the residual sludge through chemical oxidation, and can promote the contact between a compound and a fermentation substrate through microwave treatment, so that the catalysis efficiency of the subsequent calcium peroxide on the sludge is further improved; the composite is prepared into blocks, so that the contact area of microwave action can be effectively increased, and the methane yield is further improved.
Further, in step S2-3, the intensity of microwave irradiation is modulated during the microwave irradiation, and the method is divided into the following two stages:
the first stage: the microwave irradiation intensity is initially adjusted to 250-300W, the microwave irradiation time is 3-5 min, then the microwave irradiation intensity is reduced at the rate of 25-30W/min, and the rest 1/2 of powdery straws are added according to the adding amount of 1.8-3.5 g/min until the microwave irradiation intensity is adjusted to 70-80W;
and a second stage: continuously decreasing the microwave irradiation intensity at the speed of 13-15W/min, performing microwave irradiation treatment for 2-4 min, then keeping the microwave irradiation intensity unchanged, adding the compound into the serum bottle according to 2-4 blocks/min, uniformly mixing, and continuing performing microwave irradiation treatment for 2-4 min until the compound is added;
description: firstly, adding a part of powdery straw into a fermentation substrate can provide carbon sources and energy sources required by anaerobic microorganisms, reduce the viscosity of residual sludge and improve the air permeability of the residual sludge, further promote the growth and metabolism of the anaerobic microorganisms, and further improve the anaerobic methane production efficiency of the sludge; after the microwave irradiation intensity is reduced to 70-80W, the second stage treatment is carried out, so that on one hand, the influence of the microwave irradiation treatment on the activity of the compound can be reduced as much as possible, and on the other hand, the influence of the microwave irradiation intensity on the activity of catalase can be gradually weakened by adjusting the microwave irradiation intensity in a decreasing manner under the lower irradiation intensity, so that the methane production effect of the sludge is enhanced.
Further, in the step S2, the purity of the calcium peroxide is 68-72%;
description: the calcium peroxide with the purity can effectively promote the decomposition and conversion of organic matters in the sludge, and further improve the methane production efficiency of the sludge.
Further, in the step S3, nitrogen with the purity of 99.99-99.999% is adopted in the aeration process;
description: the adoption of high-purity nitrogen can maintain a stable anaerobic environment in the anaerobic reactor, is beneficial to the growth and propagation of methane bacteria, and can inhibit the growth and propagation of ammonia oxidizing bacteria, thereby preventing the competitive inhibition of ammonia oxidizing bacteria on methane bacteria.
Further, in the step S3, the inoculated anaerobic digestion sludge is acquired from a sludge anaerobic digestion tank, and the VSS content in the inoculated anaerobic digestion sludge is 19-21 g/L;
description: excessive concentration of volatile suspended solids in inoculated anaerobic digested sludge may result in increased viscosity of the sludge, which is detrimental to the anaerobic digestion process, and high concentration of volatile suspended solids may prevent gas from escaping from the sludge, resulting in reduced yield of digested gas. In addition, too high a volatile suspended solids concentration may also result in a decrease in the activity of microorganisms within the reactor, further affecting the efficiency of sludge methanogenesis. Too small a concentration of volatile suspended solids may result in an insufficient number of microorganisms in the sludge, lacking enough microorganisms to decompose and convert the organic matter, thereby affecting the methanogenic effect of the sludge. And the too low concentration of volatile suspended solids can also make the parameters such as temperature, pH value and the like in the reactor difficult to maintain stable, which is unfavorable for the growth and propagation of methane bacteria.
The beneficial effects of the invention are as follows:
(1) According to the invention, the potassium ferrate and the calcium peroxide are combined to pretreat the surplus sludge, the potassium ferrate strengthens the sludge cracking efficiency based on advanced oxidation, the alkaline environment created by the calcium peroxide improves the stability of the potassium ferrate, the combination of the potassium ferrate and the alkaline environment improves the cracking of extracellular polymers and cell walls, the dissolution of intracellular organic matters is promoted, the released SCOD is 10.3 times that of the single use of the calcium peroxide, 3.2 times that of the single use of the potassium ferrate, the concentration of supernatant protein and polysaccharide is 12.4 times and 14.4 times that of the single use of the calcium peroxide, and 2.0 times and 10.0 times that of the single use of the potassium ferrate.
(2) The calcium peroxide of the invention slowly releases oxygen to provide a micro-oxygen environment, improves the activity of facultative bacteria, and reduces the product Fe (OH) of potassium ferrate under the alkaline condition created by the calcium peroxide 3 As electron acceptor enriched iron reducing bacteria, the two act together to further strengthen the hydrolytic acidification of refractory organic matters and provide high quality substrate for methanogen. Notably, the slow release of oxygen from the calcium peroxide oxidizes the iron oxide reduction compared to the potassium ferrate aloneThe Fe (II) produced promotes the circulation of iron and realizes the regeneration of Fe (III). The methane yield is increased by 112.0% when the calcium peroxide is singly used, and is increased by 133.8% when the potassium ferrate is singly used.
(3) The method has the advantages of simple operation condition, low operation cost, easy obtainment of ferrate and calcium peroxide, environmental friendliness and no secondary pollution.
Drawings
FIG. 1 is a flow chart of the method of the present invention;
FIG. 2 is a bar graph showing the release concentration of intracellular substances after pretreatment in examples 1, 6, 7 and 1-3 according to the present invention;
FIG. 3 is a line graph showing anaerobic methane production in the pretreatment of excess sludge of examples 1, 6, 7 and comparative examples 1 to 3 for 0 to 12 days.
Detailed Description
The invention will be described in further detail with reference to the following embodiments to better embody the advantages of the invention.
Example 1: a method for strengthening anaerobic methanogenesis of excess sludge by using iron and calcium combined pretreatment comprises the following steps:
s1, obtaining excess sludge
Sieving activated sludge obtained from a secondary sedimentation tank of a sewage treatment plant by using a screen with the aperture of 2mm, performing gravity sedimentation for 24 hours, and discarding supernatant to obtain residual sludge serving as a fermentation substrate; detecting the contents of TSS and VSS in the fermentation substrate; the TSS content of the fermentation substrate is measured to be 32g/L, VSS and 19g/L;
s2, iron-calcium combined pretreatment
Measuring 140mL of fermentation substrate, placing the fermentation substrate in a 300mL serum bottle, and sequentially preprocessing the fermentation substrate by adopting 0.3g/g of calcium peroxide of VSS and 0.6g/g of potassium ferrate of VSS to obtain a preprocessed fermentation substrate;
the pretreatment method comprises the following steps: firstly placing a serum bottle on a magnetic stirrer, stirring a fermentation substrate at a rotating speed of 275r/min for 15min, adding 0.3g/g of calcium peroxide with VSS purity of 70% into the fermentation substrate, stirring for 6min, adding 0.5g/g of potassium ferrate with VSS, stirring for 4min, and finally oscillating in a constant-temperature oscillating table with an oscillating temperature of 37 ℃ and an oscillating speed of 150rpm for 23h to obtain a pretreated fermentation substrate;
pre-treating the fermentation substrate before pre-treating; the pretreatment method comprises the following steps:
s2-1, taking 110g of straw, soaking the straw in distilled water for 25min, naturally drying the straw at 27 ℃ for 4h, and grinding the straw in a grinder for 23min to obtain powdery straw;
s2-2, taking 1/2 of powdery straw, measuring the catalase solution with the mass concentration of 9U/mL according to the weight-volume ratio of 45g to 98mL of the catalase solution, spraying the catalase solution on the surface of the powdery straw at the speed of 6mL/min until the spraying is finished, stirring and uniformly mixing, and compressing the mixture into a blocky mixture with the size of 1cm multiplied by 1cm, thus obtaining a compound;
s2-3, carrying out microwave irradiation treatment on the fermentation substrate in the serum bottle, wherein the microwave irradiation intensity is 150W, the microwave irradiation time is 11min, and sequentially adding the rest powdery straw and the compound obtained in the step S2-2 into the serum bottle during the microwave irradiation period, and uniformly mixing;
s3, anaerobic fermentation treatment
Weighing 100mL of pretreated fermentation substrate, placing the fermentation substrate in a 300mL anaerobic fermentation bottle, adding hydrochloric acid with the molar concentration of 5mol/L, adjusting the pH of the pretreated fermentation substrate to 7, adding the inoculated anaerobic digestion sludge according to the volume ratio of the pretreated fermentation substrate to the inoculated anaerobic digestion sludge of 1:1, aerating for 20min by adopting nitrogen with the purity of 99.995%, sealing, transferring to a constant-temperature oscillating table at 37 ℃ for anaerobic fermentation, and collecting gas in the anaerobic fermentation process to obtain methane;
the inoculated anaerobic digestion sludge is collected from a sludge anaerobic digestion tank, and the VSS content in the inoculated anaerobic digestion sludge is 20g/L.
Example 2: unlike example 1, in step S1,
sieving activated sludge obtained from a secondary sedimentation tank of a sewage treatment plant by using a screen with the aperture of 1mm, performing gravity sedimentation for 23 hours, and discarding supernatant to obtain residual sludge serving as a fermentation substrate; detecting the contents of TSS and VSS in the fermentation substrate; the TSS content of the fermentation substrate was determined to be 31.5g/L, VSS and 18.5g/L.
Example 3: unlike example 1, in step S1,
sieving activated sludge obtained from a secondary sedimentation tank of a sewage treatment plant by using a screen with the aperture of 3mm, performing gravity sedimentation for 25h, and discarding supernatant to obtain residual sludge serving as a fermentation substrate; detecting the contents of TSS and VSS in the fermentation substrate; the TSS content of the fermentation substrate was measured to be 32.5g/L, VSS and 19.5g/L.
Example 4: unlike example 1, in step S2,
140mL of fermentation substrate is measured and placed in a 300mL serum bottle, and the fermentation substrate is pretreated by adopting 0.3g/g of VSS calcium peroxide and 0.2g/g of VSS potassium ferrate in sequence, so as to obtain the pretreated fermentation substrate.
Example 5: unlike example 1, in step S2,
140mL of fermentation substrate is measured and placed in a 300mL serum bottle, and 0.3g/g of VSS calcium peroxide and 1g/g of VSS potassium ferrate are adopted to pretreat the fermentation substrate in sequence, so that the pretreated fermentation substrate is obtained.
Example 6: unlike example 1, in step S2,
the pretreatment method comprises the following steps: firstly placing a serum bottle on a magnetic stirrer, stirring a fermentation substrate at a rotating speed of 250r/min for 20min, adding 0.28g/g of calcium peroxide with VSS purity of 68% into the fermentation substrate, stirring for 7min, adding 0.2g/g of potassium ferrate with VSS, stirring for 5min, and finally carrying out oscillation treatment for 24h in a constant-temperature oscillation table with an oscillation temperature of 36 ℃ and an oscillation speed of 145rpm to obtain the pretreated fermentation substrate.
Example 7: unlike example 1, in step S2,
the pretreatment method comprises the following steps: firstly placing a serum bottle on a magnetic stirrer, stirring a fermentation substrate at a rotating speed of 300r/min for 10min, adding 0.32g/g of calcium peroxide with VSS purity of 72% into the fermentation substrate, stirring for 5min, adding 1g/g of potassium ferrate with VSS, stirring for 3min, and finally carrying out oscillation treatment for 22h in a constant-temperature oscillation table with an oscillation temperature of 38 ℃ and an oscillation speed of 155rpm to obtain the pretreated fermentation substrate.
Example 8: unlike example 1, in the pretreatment method,
s2-1, soaking 100g of straw in distilled water for 20min, naturally drying at 26 ℃ for 5h, and grinding in a grinder for 20min to obtain powdery straw.
Example 9: unlike example 1, in the pretreatment method,
s2-1, soaking 120g of straw in distilled water for 30min, naturally drying at 28 ℃ for 3h, and grinding in a grinder for 25min to obtain powdery straw.
Example 10: unlike example 1, in the pretreatment method,
s2-2, taking 1/2 of powdery straw, measuring the catalase solution with the mass concentration of 8U/m L according to the weight-volume ratio of 40g to 95mL of the catalase solution, spraying the catalase solution on the surface of the powdery straw at the speed of 5mL/min until the spraying is finished, stirring and uniformly mixing, and compressing the mixture into a blocky mixture with the size of 1cm multiplied by 1cm, thus obtaining the compound.
Example 11: unlike example 1, in the pretreatment method,
s2-2, taking 1/2 of powdery straw, measuring the catalase solution with the mass concentration of 10U/m L according to the weight-volume ratio of 50g to 100mL of the catalase solution, spraying the catalase solution on the surface of the powdery straw at the speed of 7mL/min until the spraying is finished, stirring and uniformly mixing, and compressing the mixture into a blocky mixture with the size of 1cm multiplied by 1cm, thus obtaining the compound.
Example 12: unlike example 1, in the pretreatment method,
s2-3, carrying out microwave irradiation treatment on the fermentation substrate in the serum bottle, wherein the microwave irradiation intensity is 10W, the microwave irradiation time is 10min, sequentially adding the rest 1/2 of powdery straw and the compound obtained in the step S2-2 into the serum bottle during the microwave irradiation, and uniformly mixing.
Example 13: unlike example 1, in the pretreatment method,
s2-3, carrying out microwave irradiation treatment on the fermentation substrate in the serum bottle, wherein the microwave irradiation intensity is 300W, the microwave irradiation time is 12min, sequentially adding the rest 1/2 of powdery straw and the compound obtained in the step S2-2 into the serum bottle during the microwave irradiation, and uniformly mixing.
Example 14: unlike example 1, in step S2-3, the intensity of microwave irradiation is modulated during microwave irradiation, and is divided into the following two stages:
the first stage: the microwave irradiation intensity is initially adjusted to 250W, the microwave irradiation time is 5min, then the microwave irradiation intensity is reduced at the speed of 25W/min, and the rest 1/2 of powdery straw is added according to the addition amount of 1.8g/min until the microwave irradiation intensity is adjusted to 70W;
and a second stage: continuously decreasing the microwave irradiation intensity at the speed of 13W/min, performing microwave irradiation treatment for 2min, then keeping the microwave irradiation intensity unchanged, adding the compound into the serum bottle according to 2 blocks/min, uniformly mixing, and continuously performing microwave irradiation treatment for 4min until the compound is added.
Example 15: unlike example 1, in step S2-3, the intensity of microwave irradiation is modulated during microwave irradiation, and is divided into the following two stages:
the first stage: the microwave irradiation intensity is initially adjusted to 275W, the microwave irradiation time is 4min, then the microwave irradiation intensity is adjusted in a descending way according to the speed of 28W/min, and the rest 1/2 of powdery straws are added according to the adding amount of 2.6g/min until the microwave irradiation intensity is adjusted to 75W;
and a second stage: continuously decreasing and adjusting the microwave irradiation intensity at 14W/min, performing microwave irradiation treatment for 3min, keeping the microwave irradiation intensity unchanged, adding the compound into the serum bottle according to 3 blocks/min, uniformly mixing, and continuously performing microwave irradiation treatment for 3min until the compound is added;
example 16: unlike example 1, in step S2-3, the intensity of microwave irradiation is modulated during microwave irradiation, and is divided into the following two stages:
the first stage: the microwave irradiation intensity is initially adjusted to 300W, the microwave irradiation time is 3min, then the microwave irradiation intensity is reduced at the rate of 30W/min, and the rest 1/2 of powdery straw is added according to the adding amount of 3.5g/min until the microwave irradiation intensity is adjusted to 80W;
and a second stage: continuously decreasing the microwave irradiation intensity at the speed of 15W/min, performing microwave irradiation treatment for 4min, then keeping the microwave irradiation intensity unchanged, adding the compound into the serum bottle according to 4 blocks/min, uniformly mixing, and continuously performing microwave irradiation treatment for 2min until the compound is added.
Example 17: unlike in example 1, in step S3,
measuring 95mL of pretreated fermentation substrate, placing the fermentation substrate in a 300mL anaerobic fermentation bottle, adding hydrochloric acid with the molar concentration of 4mol/L, adjusting the pH of the pretreated fermentation substrate to 6.5, adding the inoculated anaerobic digestion sludge according to the volume ratio of the pretreated fermentation substrate to the inoculated anaerobic digestion sludge of 1:0.98, aerating for 22min by adopting nitrogen with the purity of 99.99%, sealing, transferring to a 36 ℃ constant-temperature shaking table for anaerobic fermentation, and collecting gas in the anaerobic fermentation process to obtain methane.
Example 18: unlike in example 1, in step S3,
weighing 105mL of pretreated fermentation substrate, placing the fermentation substrate in a 300mL anaerobic fermentation bottle, adding hydrochloric acid with the molar concentration of 6mol/L, adjusting the pH of the pretreated fermentation substrate to 7.5, adding the inoculated anaerobic digestion sludge according to the volume ratio of the pretreated fermentation substrate to the inoculated anaerobic digestion sludge of 1:1.02, aerating for 18min by adopting nitrogen with the purity of 99.999%, sealing, transferring to a constant-temperature oscillating table for anaerobic fermentation at 38 ℃, and collecting gas in the anaerobic fermentation process to obtain methane.
Example 19: unlike in example 1, in step S3,
the VSS content in the inoculated anaerobic digestion sludge is 19g/L.
Example 20: unlike in example 1, in step S3,
the VSS content of the inoculated anaerobic digestion sludge is 21g/L.
Experimental example: the pre-treated SCOD release amount, supernatant protein concentration, polysaccharide concentration and methane yield in the process of 0-12 d of each example were tested, and methane yield data in the experimental example table were taken as methane yield in the reaction of 12d, and specifically explored as follows:
the influence of pretreatment of calcium peroxide and potassium ferrate on anaerobic methanogenesis of residual sludge is explored
TABLE 1 influence of example 1, examples 4-5 and comparative examples 1-3 on anaerobic methanogenesis of excess sludge
Comparative example 1: unlike example 1, the fermentation substrate was not treated with calcium peroxide and potassium ferrate as a blank.
Comparative example 2: unlike example 1, only calcium peroxide was added to the fermentation substrate for treatment.
Comparative example 3: unlike example 1, the fermentation substrate was treated with potassium ferrate alone.
Conclusion: as can be seen from the data in table 1, the anaerobic methanogenesis capacity of the excess sludge in the preparation process of comparative examples 1 to 3 is obviously reduced, and as can be seen from the comparison of the data in examples 1, 4 and 5 and fig. 2 and 3, the cost of the agent of 1g/g VSS in example 5 is doubled but the improvement effect of methane yield is not significant, and the lag phase of methane production is seriously increased, while the addition of 1g/g VSS causes the release of a large amount of organic matters such as SCOD, supernatant protein, polysaccharide, etc., but the addition of 1g/g VSS also produces an inhibition effect on the yield of methane, which means that the excessive addition of potassium ferrate may produce some refractory organic matters such as humic acid, cellulose, thereby producing an inhibition effect on methane production, so the comprehensive economic cost and the improvement effect are optimal, while example 7 has been considered as the excessive addition, the economic cost and the potential cost are not in accordance with the low-friendly invention, and the optimal proposal is not made, and the optimal embodiment 1 is further selected.
The influence of pretreatment and pretreatment technology on the yield of anaerobic methane in excess sludge is explored
TABLE 2 final methane yields obtained by the preparation of example 1, examples 8-13 and comparative examples 6-7
Comparative example 6: unlike example 1, the pretreatment method did not grind the straw.
Comparative example 7: unlike example 1, the pretreatment method did not subject the fermentation substrate to microwave irradiation treatment.
Conclusion: as can be seen from the data in table 3, the lack of grinding treatment of the straw and microwave irradiation treatment of the fermentation substrate in comparative example 6 and comparative example 7 both result in a significant decrease in the final methane yield, because the complex obtained by mixing the powdered straw with catalase can effectively increase the stability of catalase, reduce the influence of microwave radiation on the activity of the catalase solution, and the straw directly mixed with catalase has a slightly weaker improvement effect on catalase due to the limited contact area between the straw and catalase, further causes the inactivation of catalase, and reduces the methane yield; whereas the lack of microwave treatment in comparative example 7 limited the contact of the complex with the fermentation substrate, affecting the final yield of methane; based on this, embodiment 1 is selected as the optimal solution.
The influence of a microwave irradiation treatment mode on the anaerobic methane yield of the residual sludge is explored
TABLE 3 final methane yields obtained by the preparation of example 1, examples 14-16 and comparative example 8
Comparative example 8: unlike example 15, the sludge was irradiated with the microwave irradiation intensity of 33W for 10 to 15min.
Conclusion: as can be seen from the data in table 4, the comparison of the data in examples 1 and 14-16 shows that the amount of methane produced in examples 14-16 is slightly better than that in example 1, because the intensity of microwave irradiation is modulated in a staged manner, a part of powdery straw is added to provide carbon source and energy source required by anaerobic microorganisms, so that the growth and metabolism of anaerobic microorganisms are further promoted, and the anaerobic methane production efficiency of sludge is improved; after the microwave irradiation intensity is reduced to 70-80W, performing the second stage treatment can reduce the activity influence of the microwave irradiation treatment on the compound as much as possible, and effectively enhance the methane production effect of the sludge; while the direct use of the microwave irradiation intensity of 33W for the sludge treatment in comparative example 8 can avoid the influence on catalase, it also resulted in a significant increase in methane production time, and only about 30% of the methane yield obtained by the method of example 15 could be obtained after 12d, which is the best mode in example 15.
Exploring the influence of the solid concentration in the inoculated anaerobic digestion sludge on the anaerobic methane yield of the residual sludge
TABLE 4 final methane yields obtained for the preparation of example 15, examples 19-20 and comparative examples 9-10
Comparative example 9: unlike example 1, in step S3, the inoculated anaerobic digested sludge had a VSS content of 17.5g/L.
Comparative example 10: unlike example 1, in step S3, the inoculated anaerobic digested sludge had a VSS content of 21.5g/L.
Conclusion: as can be seen from the data in table 4, the anaerobic digested sludge inoculated in comparative example 9 and comparative example 10 has significantly reduced volatile suspended solids concentration below or above the final methane yield outside the scope of the present invention, because too high a concentration of volatile suspended solids in the inoculated anaerobic digested sludge results in an increase in viscosity of the sludge, which is detrimental to the anaerobic digestion process, and a high concentration of volatile suspended solids may prevent gas from escaping from the sludge, resulting in a reduced yield of digested gas, while too low a concentration of volatile suspended solids results in an insufficient number of microorganisms in the sludge, lacking enough microorganisms to decompose and convert the organic matter, thereby affecting the methanogenic effect of the sludge. Based on this, example 15 remains the optimal solution.
Claims (9)
1. The method for promoting anaerobic methanogenesis of excess sludge by using the combined pretreatment of iron and calcium is characterized by comprising the following steps of:
s1, obtaining excess sludge
Sieving activated sludge obtained from a secondary sedimentation tank of a sewage treatment plant, and carrying out gravity sedimentation for 23-25 h, and discarding supernatant to obtain residual sludge serving as a fermentation substrate; detecting the contents of TSS and VSS in the fermentation substrate;
s2, iron-calcium combined pretreatment
Weighing 135-145 mL of fermentation substrate, placing the fermentation substrate in a serum bottle, and sequentially preprocessing the fermentation substrate by adopting 0.28-0.32 g/g of calcium peroxide of VSS and 0.2-1 g/g of potassium ferrate of VSS to obtain a preprocessed fermentation substrate;
s3, anaerobic fermentation treatment
Measuring 95-105 mL of pretreated fermentation substrate, placing the fermentation substrate into an anaerobic fermentation bottle, adding hydrochloric acid with the molar concentration of 4-6 mol/L, adjusting the pH of the pretreated fermentation substrate to 6.5-7.5, adding the inoculated anaerobic digestion sludge according to the volume ratio of the pretreated fermentation substrate to the inoculated anaerobic digestion sludge of 1:0.98-1.02, aerating for 18-22 min, sealing, transferring to a constant-temperature oscillating table at 36-38 ℃ for anaerobic fermentation, and collecting gas in the anaerobic fermentation process to obtain methane.
2. A method for promoting anaerobic methanogenesis of excess sludge by combined pretreatment of iron and calcium according to claim 1, wherein in step S1, the sieving method is as follows: sieving by using a screen with the aperture of 1-3 mm.
3. The method for promoting anaerobic methanogenesis of excess sludge by using the combined pretreatment of iron and calcium according to claim 1, wherein in the step S2, the pretreatment method is as follows: firstly placing a serum bottle on a magnetic stirrer, stirring a fermentation substrate at a rotating speed of 250-300 r/min for 10-20 min, adding 0.28-0.32 g/g VSS calcium peroxide into the fermentation substrate, stirring for 5-7 min, adding 0.2-1 g/g VSS potassium ferrate, stirring for 3-5 min, and finally oscillating in a constant-temperature oscillating table for 22-24 h to obtain the pretreated fermentation substrate.
4. A method for promoting anaerobic methanogenesis of excess sludge by combined pretreatment of iron and calcium as recited in claim 3, wherein said oscillation treatment parameters are: the oscillation temperature is 36-38 ℃ and the oscillation speed is 145-155 rpm.
5. A method for promoting anaerobic methanogenesis of excess sludge by combined pretreatment of iron and calcium according to claim 1, wherein in step S2, the fermentation substrate is subjected to pretreatment prior to said pretreatment; the pretreatment method comprises the following steps:
s2-1, taking 100-120 g of straw, soaking the straw in distilled water for 20-30 min, naturally drying the straw at 26-28 ℃ for 3-5 h, and grinding the straw in a grinder for 20-25 min to obtain powdery straw;
s2-2, taking 1/2 of powdery straw, measuring 8-10U/mL of catalase solution according to the weight-volume ratio of 40-50 g to 95-100 mL of the catalase solution, spraying the catalase solution on the surface of the powdery straw at the speed of 5-7 mL/min until the spraying is finished, stirring and mixing uniformly, and compressing the mixture into a block mixture with the size of 1cm multiplied by 1cm, thus obtaining a compound;
s2-3, carrying out microwave irradiation treatment on the fermentation substrate in the serum bottle, wherein the microwave irradiation intensity is 10-300W, the microwave irradiation time is 10-12 min, and sequentially adding the rest 1/2 of powdery straw and the compound obtained in the step S2-2 into the serum bottle during microwave irradiation, and uniformly mixing.
6. The method for promoting anaerobic methanogenesis of excess sludge by combined pretreatment of iron and calcium according to claim 5, wherein in step S2-3, the intensity of microwave irradiation is modulated during the microwave irradiation, and the method is divided into the following two stages:
the first stage: the microwave irradiation intensity is initially adjusted to 250-300W, the microwave irradiation time is 3-5 min, then the microwave irradiation intensity is reduced at the rate of 25-30W/min, and the rest 1/2 of powdery straws are added according to the adding amount of 1.8-3.5 g/min until the microwave irradiation intensity is adjusted to 70-80W;
and a second stage: continuously decreasing the microwave irradiation intensity at the speed of 13-15W/min, performing microwave irradiation treatment for 2-4 min, then keeping the microwave irradiation intensity unchanged, adding the compound into the serum bottle according to 2-4 blocks/min, uniformly mixing, and continuously performing microwave irradiation treatment for 2-4 min until the compound is added.
7. The method for promoting anaerobic methanogenesis of excess sludge by using the combined pretreatment of iron and calcium according to claim 1, wherein in the step S2, the purity of the calcium peroxide is 68-72%.
8. The method for promoting anaerobic methanogenesis of excess sludge by using iron and calcium combined pretreatment as claimed in claim 1, wherein in the step S3, high-purity nitrogen with purity of 99.99-99.999% is adopted in the aeration process.
9. The method for promoting anaerobic methanogenesis of excess sludge by using iron and calcium combined pretreatment according to claim 1, wherein in the step S3, the inoculated anaerobic digestion sludge is obtained by collecting in a sludge anaerobic digestion tank, and the VSS content in the inoculated anaerobic digestion sludge is 19-21 g/L.
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