CN117126006A - Sludge compost and preparation method thereof - Google Patents
Sludge compost and preparation method thereof Download PDFInfo
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- CN117126006A CN117126006A CN202311101533.4A CN202311101533A CN117126006A CN 117126006 A CN117126006 A CN 117126006A CN 202311101533 A CN202311101533 A CN 202311101533A CN 117126006 A CN117126006 A CN 117126006A
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- 239000010802 sludge Substances 0.000 title claims abstract description 101
- 239000002361 compost Substances 0.000 title claims abstract description 32
- 238000002360 preparation method Methods 0.000 title claims abstract description 19
- 239000010902 straw Substances 0.000 claims abstract description 34
- 239000007858 starting material Substances 0.000 claims abstract description 20
- 239000003337 fertilizer Substances 0.000 claims abstract description 19
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- 229910052799 carbon Inorganic materials 0.000 claims abstract description 18
- 239000002994 raw material Substances 0.000 claims abstract description 18
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- 238000000034 method Methods 0.000 claims description 18
- 230000001580 bacterial effect Effects 0.000 claims description 17
- 238000009264 composting Methods 0.000 claims description 17
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- 235000002017 Zea mays subsp mays Nutrition 0.000 claims description 3
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- 241000654838 Exosporium Species 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 claims 2
- 229910001385 heavy metal Inorganic materials 0.000 abstract description 36
- 230000007613 environmental effect Effects 0.000 abstract description 4
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- PPNAOCWZXJOHFK-UHFFFAOYSA-N manganese(2+);oxygen(2-) Chemical class [O-2].[Mn+2] PPNAOCWZXJOHFK-UHFFFAOYSA-N 0.000 description 4
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- WQHONKDTTOGZPR-UHFFFAOYSA-N [O-2].[O-2].[Mn+2].[Fe+2] Chemical compound [O-2].[O-2].[Mn+2].[Fe+2] WQHONKDTTOGZPR-UHFFFAOYSA-N 0.000 description 3
- 125000000524 functional group Chemical group 0.000 description 3
- 239000002245 particle Substances 0.000 description 3
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- 239000010865 sewage Substances 0.000 description 3
- 238000001179 sorption measurement Methods 0.000 description 3
- 238000004065 wastewater treatment Methods 0.000 description 3
- XLYOFNOQVPJJNP-ZSJDYOACSA-N Heavy water Chemical compound [2H]O[2H] XLYOFNOQVPJJNP-ZSJDYOACSA-N 0.000 description 2
- 239000002154 agricultural waste Substances 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
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- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 1
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- 239000003575 carbonaceous material Substances 0.000 description 1
- 238000010000 carbonizing Methods 0.000 description 1
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Classifications
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- C—CHEMISTRY; METALLURGY
- C05—FERTILISERS; MANUFACTURE THEREOF
- C05F—ORGANIC FERTILISERS NOT COVERED BY SUBCLASSES C05B, C05C, e.g. FERTILISERS FROM WASTE OR REFUSE
- C05F17/00—Preparation of fertilisers characterised by biological or biochemical treatment steps, e.g. composting or fermentation
- C05F17/10—Addition or removal of substances other than water or air to or from the material during the treatment
-
- C—CHEMISTRY; METALLURGY
- C05—FERTILISERS; MANUFACTURE THEREOF
- C05D—INORGANIC FERTILISERS NOT COVERED BY SUBCLASSES C05B, C05C; FERTILISERS PRODUCING CARBON DIOXIDE
- C05D9/00—Other inorganic fertilisers
-
- C—CHEMISTRY; METALLURGY
- C05—FERTILISERS; MANUFACTURE THEREOF
- C05F—ORGANIC FERTILISERS NOT COVERED BY SUBCLASSES C05B, C05C, e.g. FERTILISERS FROM WASTE OR REFUSE
- C05F17/00—Preparation of fertilisers characterised by biological or biochemical treatment steps, e.g. composting or fermentation
- C05F17/20—Preparation of fertilisers characterised by biological or biochemical treatment steps, e.g. composting or fermentation using specific microorganisms or substances, e.g. enzymes, for activating or stimulating the treatment
-
- C—CHEMISTRY; METALLURGY
- C05—FERTILISERS; MANUFACTURE THEREOF
- C05F—ORGANIC FERTILISERS NOT COVERED BY SUBCLASSES C05B, C05C, e.g. FERTILISERS FROM WASTE OR REFUSE
- C05F17/00—Preparation of fertilisers characterised by biological or biochemical treatment steps, e.g. composting or fermentation
- C05F17/80—Separation, elimination or disposal of harmful substances during the treatment
-
- 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
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/40—Bio-organic fraction processing; Production of fertilisers from the organic fraction of waste or refuse
Landscapes
- Chemical & Material Sciences (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Organic Chemistry (AREA)
- Microbiology (AREA)
- Biotechnology (AREA)
- Biochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Molecular Biology (AREA)
- Life Sciences & Earth Sciences (AREA)
- Tropical Medicine & Parasitology (AREA)
- Toxicology (AREA)
- Inorganic Chemistry (AREA)
- Fertilizers (AREA)
- Treatment Of Sludge (AREA)
Abstract
The invention relates to sludge compost and a preparation method thereof, which are used for reducing the bioavailability of heavy metals in sludge, so as to reduce the absorption of plants to the heavy metals and further reduce the environmental risk. The preparation method of the sludge compost comprises the following steps: s100: pretreating sludge; dehydrating and crushing sludge, and regulating the carbon-nitrogen ratio of the sludge to 20-30 by using straw to obtain pretreated sludge; s200: preparing biochar; after the biomass raw material is air-dried, the biomass raw material is placed in a nitrogen atmosphere and heated for 2 hours at 500 ℃, then cooled to room temperature, and the biochar is taken out for crushing and grinding; s300: fermenting; and (3) adding a biological fertilizer starter and the biological carbon obtained in the step (200) into the pretreated sludge obtained in the step (100), regulating the water content of the mixed material to be 50-60%, uniformly stirring, fermenting at 50-60 ℃ for 20-25 days, and then air-drying, crushing and sieving to obtain the sludge compost.
Description
Technical Field
The invention relates to the technical field of sludge treatment, in particular to sludge compost and a preparation method thereof.
Background
The wastewater treatment in China has remarkable effect, the sludge yield is increased as a byproduct of the wastewater treatment, the national sludge yield in 2022 reaches 7288.3 ten thousand tons, and the wastewater treatment burden is increased. The phenomenon of heavy water and light mud exists in China for a long time, so that the recognition of the characteristics of pollutants in the mud is insufficient, the stabilization treatment of the mud is also seriously insufficient, the construction of a mud treatment facility is generally lagged, the mud becomes an important problem for urban environment treatment, and the mud treatment situation is very serious.
At present, the sludge treatment and disposal modes mainly comprise landfill, incineration, building material utilization, land utilization and the like. The landfill not only occupies a large amount of land resources, but also has hidden troubles of groundwater pollution, biogas explosion and the like; the energy consumption of incineration is high; the utilization of building materials can reduce the quality of the materials. Therefore, compared with other treatment modes, the sludge land utilization is an important recycling way. However, the sludge of sewage treatment plants in China usually contains higher heavy metals, so that the sludge land utilization has environmental risks.
Disclosure of Invention
In view of the above analysis, the present invention aims to provide a sludge compost and a preparation method thereof, which are used for reducing the bioavailability of heavy metals in sludge, thereby reducing the absorption of heavy metals by plants and further reducing environmental risks.
In one aspect, the invention provides a method for preparing sludge compost, comprising the following steps:
s100: sludge pretreatment
Dehydrating and crushing sludge, and regulating the carbon-nitrogen ratio of the sludge to 20-30 by using straw to obtain pretreated sludge;
s200: preparation of biochar
After the biomass raw material is air-dried, the biomass raw material is placed in a nitrogen atmosphere and heated for 2 hours at 500 ℃, then cooled to room temperature, and the biochar is taken out for crushing and grinding;
s300: fermentation treatment
And (3) adding a biological fertilizer starter and the biological carbon obtained in the step (200) into the pretreated sludge obtained in the step (100), regulating the water content of the mixed material to be 50-60%, uniformly stirring, fermenting at 50-60 ℃ for 20-25 days, and then air-drying, crushing and sieving to obtain the sludge compost.
Further, in the step S100, the straw is corn straw;
the carbon to nitrogen ratio was 25.
Further, in the step S200, the biomass is placed into a carbonization furnace for carbonization, and nitrogen is filled into the carbonization furnace to form an anoxic environment.
Further, in the step S200, the temperature of the carbonization furnace is raised to 500 ℃ at a speed of 10 ℃/min, and then maintained at 500 ℃ for 2 hours.
Further, in the step S200, the flow rate of the nitrogen in the carbonization furnace is kept between 0.1 and 0.2L/min.
Further, in the step S300, the biological bacterial fertilizer starter includes one or more of bacillus, actinomycetes, saccharomycetes, trichoderma, azotobacter, lactobacillus and exosporium enzymes secreted by microorganisms.
Further, in the step S300, the effective viable count in the biological bacterial fertilizer starter is more than or equal to 100 hundred million/mL.
Further, in the step S300, during the fermentation, when the temperature rises to 50 ℃, the material is turned over and ventilated.
Further, the weight ratio of the sludge, the straw, the biochar and the biological bacterial fertilizer starter is 70-100:15-25:3-6:1.
On the other hand, the invention provides a sludge compost which can be prepared at least by adopting the preparation method, and the sludge compost comprises the following raw materials in parts by weight: 70-100 parts of sludge, 15-25 parts of straw, 3-6 parts of biochar and 1 part of biological bacterial fertilizer starter.
Compared with the prior art, the invention has at least one of the following beneficial effects:
(1) The invention reduces the environmental risk of sludge land utilization by reducing the bioavailability of heavy metals in the sludge;
(2) According to the invention, by adding the biochar, on one hand, the cation exchange capacity of the biochar is higher, so that pollutants such as heavy metals in sludge can be adsorbed more, and the migration and bioavailability of the heavy metals are reduced; on the other hand, the loss of nutrients in the composting process can be reduced, and the humic degree of the pile body can be improved; meanwhile, the rich carbon source can provide nutrients for microorganisms, and the larger porosity and specific surface area can improve water permeability and air permeability, so that the propagation of the microorganisms is facilitated;
(3) The invention takes the sludge, the straw, the biochar and the biological bacterial fertilizer starter as raw materials, the raw materials are easy to obtain, the cost is lower, the preparation process is simple, the operation is easy, the product can be used for landscaping, and meanwhile, the problem of solid waste piling can be solved, and the environment is protected.
In the invention, the technical schemes can be mutually combined to realize more preferable combination schemes. Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and other advantages of the invention may be realized and attained by means of the instrumentalities and particularly pointed out in the specification.
Detailed Description
The sludge subjected to innocent treatment such as composting can be used for landscaping, so that the soil fertility can be improved, and the risk of entering a food chain is avoided.
The invention discloses a preparation method of sludge compost, which comprises the following steps:
s100: sludge pretreatment
Dehydrating and crushing sludge, and regulating the carbon-nitrogen ratio of the sludge to 20-30 by using straw to obtain pretreated sludge;
s200: preparation of biochar
After the biomass raw material is air-dried, the biomass raw material is placed in a nitrogen atmosphere and heated for 2 hours at 500 ℃, then cooled to room temperature, taken out, crushed and ground to obtain biochar;
s300: fermentation treatment
And (3) adding a biological fertilizer starter and the biological carbon obtained in the step (200) into the pretreated sludge obtained in the step (100), regulating the water content of the mixed material to be 50-60%, uniformly stirring, fermenting at 50-60 ℃ for 20-25 days, and then air-drying, crushing and sieving to obtain the sludge compost.
The method has the advantages of easily obtained raw materials and easy operation, can be applied to landscaping, reduces the bioavailability of heavy metals in the sludge, and is an effective way for recycling agricultural and forestry wastes and sludge.
In the step S100:
illustratively, the sludge is dewatered and desiccated sludge from municipal sewage plants (i.e. domestic sewage).
The straw is corn straw, is easy to obtain, has low economic cost and good effect.
The length of the straw is 3-5 cm, so that the straw has better supporting property and structural property, the free airspace of the pile body is better improved, and an attachment point is provided for microorganism growth.
In order to ensure that the aerobic microorganisms have better oxidative decomposition capability, the carbon-nitrogen ratio in the sludge compost is generally controlled between 20 and 30. Too high a carbon to nitrogen ratio can lead to slow decomposition rate and reduced temperature of the compost; too low can lead to the aggravation of volatilization and loss of nitrogen, and can also generate peculiar smell, ammonia gas and the like, thereby influencing the quality and fertilizer efficiency of the compost. Preferably, the carbon-nitrogen ratio of the sludge is adjusted to 25 by using the straw, so that the carbon-nitrogen ratio can be improved due to high organic matter content in the straw.
In the step S200:
the biomass raw material is agricultural waste such as straw, rice hull, livestock manure and the like.
And (3) air-drying and naturally air-drying.
And (3) putting the biomass into a carbonization furnace for carbonization, and filling nitrogen into the carbonization furnace to form an anoxic environment. Preferably, the carbonization furnace is heated to 500 ℃ at a speed of 10 ℃/min and then maintained at 500 ℃ for 2 hours, if the heating speed is too fast, the initial pore formation of the biochar is not favored. Preferably, the flow rate of nitrogen in the carbonization furnace is kept between 0.1 and 0.2L/min (preferably 0.1L/min), so that the equipment is filled with nitrogen, and the cost performance is high.
In the preparation process of the biochar, the high-purity nitrogen is filled in the high-purity nitrogen atmosphere, so that the main function of the high-purity nitrogen is to prevent oxygen from reacting with carbonized substances and avoid oxidation reaction in the pyrolysis process.
And (5) cracking and carbonizing the biomass in a carbonization furnace. After pyrolysis and carbonization are finished, the carbonization furnace is cooled to room temperature (namely 25+/-5 ℃), then the carbonization furnace is opened to obtain pyrolyzed biochar, and the biochar is crushed and ground.
In the grinding process, larger particles are required to be ground, so that the obtained biochar particles are smaller and larger particles are not present.
The biochar is a multi-purpose carbon material with high carbon content, high porosity and strong adsorption capacity, which is formed by high-temperature pyrolysis and carbonization of biomass for a certain time under the anaerobic condition. Biochar can effectively remove heavy metal pollutants, and generally has the combined action of various mechanisms, mainly comprising pi electron coordination action, electrostatic action, proton and ion exchange action, functional group complexation, redox action and the like.
The biochar is used as a conditioner of composting, so that on one hand, the nutrient loss in the composting process can be reduced, the humic degree of the piled body is improved, meanwhile, the rich carbon source can provide nutrient substances for microorganisms, and the water permeability and the air permeability can be improved due to the large porosity and the specific surface area, so that the propagation of the microorganisms is facilitated; on the other hand, the biochar has higher cation exchange capacity, can adsorb pollutants such as heavy metals and the like more, and reduces the mobility and bioavailability of the biochar. Heavy metals are important factors influencing the utilization of sludge land, and the biochar used for sludge composting can improve the composting process, accelerate the degradation of organic matters and improve the passivation effect of the heavy metals, and is a good conditioner for improving the composting environment. Meanwhile, the biochar is also an important mode for recycling agricultural wastes.
The biochar has higher adsorption capacity, and the biochar is used as a conditioner to be added into sludge compost, so that heavy metals in the sludge can be effectively passivated.
In the step S300:
the biological bacterial fertilizer starter comprises one or more of beneficial microorganisms such as bacillus natto, bacillus, actinomycete, saccharomycetes, trichoderma, azotobacter, lactobacillus and the like, and extrasporum enzymes secreted by the microorganisms, wherein the effective viable count is more than or equal to 100 hundred million/mL. The strain can enable the pile body to reach high temperature rapidly, reduce odor generation, shorten composting and decomposing process, and effectively kill pathogens and degrade organic pollutants, thereby improving composting quality.
In the fermentation process, when the temperature rises to 50 ℃, material turning and ventilation are carried out, ventilation is realized through turning, oxygen can be provided for microorganism propagation and metabolism, moisture is removed, heat is taken away, and the temperature of a pile body is controlled. Preferably, the material is turned over once every 5 days to obtain decomposed sludge compost.
Preferably, the weight ratio of the sludge, the straw, the biochar and the biological bacterial fertilizer starter is 70-100:15-25:3-6:1; further preferably, the weight ratio of the sludge, the straw, the biochar and the biological bacterial manure starter is 80:20:4:1.
Proper amount of straw is added, so that the carbon-nitrogen ratio of the compost raw material can be adjusted; the water content of the sludge is high, the straws are dry, the water absorption is high, and the water content of the pile can be reduced by taking the sludge as an auxiliary material; the crushed straw has larger porosity, so that the external air can be increased to enter the pile body, and the malodor generated by anaerobic fermentation is avoided. The addition of the biological bacterial fertilizer starter can lead the pile body to reach high temperature quickly, reduce odor generation, shorten the composting process, and effectively kill pathogens and degrade organic pollutants, thereby improving the composting quality.
The preparation method of the invention reduces the bioavailability of heavy metals in the sludge by using the biochar, and simultaneously achieves the purpose of recycling the sludge.
The invention also discloses a sludge compost which at least can be prepared by adopting the preparation method, and the raw materials of the sludge compost comprise the following components in parts by weight: 70-100 parts of sludge, 15-25 parts of straw, 3-6 parts of biochar and 1 part of biological bacterial fertilizer starter. Preferably, the raw materials of the sludge compost comprise 80 parts of sludge, 20 parts of straw, 4 parts of biochar and 1 part of biological bacterial fertilizer starter in parts by weight.
[ example 1 ] A sludge compost, comprising the following raw materials in parts by weight: 4 parts of wheat straw biochar, 20 parts of straw, 80 parts of sludge and 1 part of biological bacterial fertilizer starter. The preparation method comprises the following steps:
s100: sludge pretreatment
Dewatering and crushing 80 parts of sludge, and regulating the carbon-nitrogen ratio of the sludge to about 25 by using 20 parts of straw to obtain a pretreated material;
s200: biochar preparation
Air-drying wheat straw, cutting into sections to about 10cm, putting into a carbonization furnace, filling nitrogen into the carbonization furnace to form an anoxic environment, keeping the flow rate of the nitrogen at 0.1L/min, heating to 500 ℃ at 10 ℃/min for 2 hours, cooling to room temperature after the cracking process is finished, opening the carbonization furnace, taking out biochar, crushing and grinding;
s3, fermentation treatment:
adding 1 part of biological bacterial fertilizer starter and 4 parts of biological carbon obtained in the step S200 into the pretreated sludge obtained in the step S100, adjusting the water content of the mixed material to 50-60% by using water, uniformly stirring, fermenting for 20 days at 50-60 ℃, and then air-drying, crushing and sieving to obtain the sludge compost.
Example 2 the difference from the example is that the biochar is formed from chicken manure, all the other things being equal.
In the fermentation process of examples 1 and 2, the morphological distribution of heavy metals Cd, cu and Zn was measured by sampling every 5 days, and the results are shown in tables 1 to 3.
TABLE 1 morphological distribution changes of heavy metals Cd during composting
TABLE 2 morphological distribution changes of heavy metals Cu during composting
TABLE 3 morphological distribution changes of heavy metals Zn during composting
As can be seen from tables 1 to 3, in the original sludge, heavy metal Cd is mainly in a ferromanganese oxide combined state, and accounts for 64.8 percent; cu is mainly in a ferro-manganese oxide bonding state and an organic bonding state, and accounts for 61.5% and 24.1% respectively; zn is mainly in a ferro-manganese oxide bonding state and a carbonate bonding state, and accounts for 52% and 36% respectively; the exchange state contents of the 3 heavy metals are low, and the ratio of the exchange state contents is 1.4%, 0.3% and 3.5% respectively. In the composting process of examples 1 and 2, cd is converted from the combined state of iron and manganese oxides and the combined state of carbonate into a residue state, and compared with the original sludge, the combined state of iron and manganese oxides treated by two biochars is respectively reduced by 33.8 percent and 6.0 percent, and the combined state of carbonate is respectively reduced by 4.6 percent and 0.8 percent; cu is converted from the combined state of the iron and manganese oxides to the organic combined state and the residue state, and compared with the original sludge, the combined state Cu of the iron and manganese oxides treated by the two biochar is respectively reduced by 42.8 percent and 38.9 percent. Example 1 Zn was converted from the iron-manganese oxide bound and exchanged states to the organic bound and residual states, which decreased by 8.7% and 3.0% respectively. Example 2 conversion of Zn from carbonate bound and exchanged to organic bound and residual states in the fermentation treatment was reduced by 8.7% and 3.3% respectively. The exchange state and carbonate bonding state Cd and Zn, carbonate bonding state and ferro-manganese oxide bonding state Cu in the sludge compost added with the two kinds of biochar are obviously different from the original sludge. In addition, in the sludge compost (i.e., example 1) added with the wheat straw biochar, there was a significant difference between the iron-manganese oxide bound state and the organic bound state Cd, and the exchange state and the organic bound state Cu from the sludge as it is. In the sludge compost (i.e. example 2) added with chicken manure biochar, there is a significant difference between the carbonate bound and organic bound Zn and the sludge as such. This shows that the sludge compost of the invention can reduce the bioavailability of Cd, cu and Zn in the raw sludge.
The correlation between the morphological distribution of heavy metals Cd, cu and Zn in the sludge compost of example 1 and example 2, the pH of the heap, the cation exchange capacity and the total organic carbon was analyzed, and the results are shown in tables 4 to 6.
TABLE 4 morphology distribution of heavy metal Cd with respect to bulk pH, cation exchange capacity, total organic carbon
Significant correlation at level 0.05 (two sides), significant correlation at level 0.01 (two sides)
TABLE 5 morphology distribution of heavy metal Cu with respect to bulk pH, cation exchange capacity, total organic carbon
Significant correlation at level 0.05 (two sides), significant correlation at level 0.01 (two sides)
TABLE 6 correlation of Zn morphology distribution of heavy metals with bulk pH, cation exchange capacity, total organic carbon
Significant correlation at level 0.05 (two sides), significant correlation at level 0.01 (two sides)
It can be seen from tables 4 to 6 that the partially unstable morphology of heavy metals is significantly inversely related to the bulk pH. Wherein, the carbonate bonding state Cd, the organic bonding state Cu and the exchange state Zn in the example 1 are extremely strongly and negatively correlated with the pH of the reactor. The exchanged Cd, carbonate bound Cu and exchanged Zn in example 2 are very strongly inversely related to the bulk pH. The detection result shows that compared with the original sludge, the pH of the sludge compost added with the wheat straw biochar and the chicken manure biochar is respectively improved by 2.30 and 1.88. The pH rise of the heap is favorable for the base ions and the heavy metal ions to form oxide and hydroxide precipitates, so that the passivation effect on the heavy metal is improved.
In example 2, the iron-manganese oxide combined state Zn is in negative correlation with the stacked cation exchange amount, because the cation exchange amount of the chicken manure biochar is higher than that of the wheat straw biochar, which indicates that the improvement of the cation exchange amount can reduce the bioavailability of Zn.
The total organic carbon content of the stack can also affect the passivation of heavy metals. In example 1, the partially unstable morphology of the heavy metal was inversely related to the total organic carbon of the heap. The Cu and the organic functional group can undergo a complex reaction, so that the bioavailability of Cu can be reduced by improving the total organic carbon content of the stack. In addition to reacting with anions to form precipitates, zn forms complexes with organic ligands in the stack. Ion exchange and complexation are the primary mechanism of the present invention for passivating heavy metals.
The correlation between the different forms of heavy metals Cd, cu and Zn in examples 1 and 2 was analyzed, and the results are shown in tables 7 to 12.
TABLE 7 correlation of Cd and Cu morphology distribution in example 1
Significant correlation at level 0.05 (two sides), significant correlation at level 0.01 (two sides)
TABLE 8 correlation of Cd and Zn morphology distribution in example 1
Significant correlation at level 0.05 (two sides), significant correlation at level 0.01 (two sides)
TABLE 9 correlation of Cu to Zn morphology distribution in example 1
Significant correlation at level 0.05 (two sides), significant correlation at level 0.01 (two sides)
TABLE 10 correlation of Cd and Cu morphology distribution in example 2
Significant correlation at level 0.05 (two sides), significant correlation at level 0.01 (two sides)
TABLE 11 correlation of Cd and Zn morphology distribution in example 2
Correlation of Cu and Zn morphology distribution in table 12-example 2
Significant correlation at level 0.05 (two sides), significant correlation at level 0.01 (two sides)
It can be seen from tables 7 to 12 that the different heavy metal ions also interact with each other. The exchanged Cd in example 1 is very strongly positively correlated with the organically bound Cu and Zn; the organic bound Cu and the exchanged Zn are extremely positively correlated. In the example 2, the residual state Cd and the combined state Zn of the ferro-manganese oxide are positively correlated; the exchange state and the ferro-manganese oxide bonding state Cu are positively correlated with the residue state and the organic bonding state Zn respectively. This is due to antagonism between coexisting heavy metal ions, which compete for adsorption sites on the functional groups in the stack.
Therefore, the invention can convert the forms of Cd, cu and Zn in the sludge from the forms which can be directly absorbed and utilized by plants and are potentially absorbed and utilized by plants into the forms which have more stable properties and are difficult to be absorbed and utilized by plants, thereby reducing the bioavailability of heavy metals in the sludge and reducing the environmental pollution risk of the heavy metals in the sludge land utilization process.
The present invention is not limited to the above-mentioned embodiments, and any changes or substitutions that can be easily understood by those skilled in the art within the technical scope of the present invention are intended to be included in the scope of the present invention.
Claims (10)
1. The preparation method of the sludge compost is characterized by comprising the following steps:
s100: sludge pretreatment
Dehydrating and crushing sludge, and regulating the carbon-nitrogen ratio of the sludge to 20-30 by using straw to obtain pretreated sludge;
s200: preparation of biochar
After the biomass raw material is air-dried, the biomass raw material is placed in a nitrogen atmosphere and heated for 2 hours at 500 ℃, then cooled to room temperature, and the biochar is taken out for crushing and grinding;
s300: fermentation treatment
And (3) adding a biological fertilizer starter and the biological carbon obtained in the step (200) into the pretreated sludge obtained in the step (100), regulating the water content of the mixed material to be 50-60%, uniformly stirring, fermenting at 50-60 ℃ for 20-25 days, and then air-drying, crushing and sieving to obtain the sludge compost.
2. The method according to claim 1, wherein in the step S100, the straw is corn straw;
the carbon to nitrogen ratio was 25.
3. The method according to claim 1, wherein in the step S200, the biomass is placed in a carbonization furnace for carbonization, and nitrogen is filled into the carbonization furnace to form an anoxic environment.
4. A production method according to claim 3, wherein in the step S200, the carbonization furnace is heated to 500 ℃ at a rate of 10 ℃/min and then maintained at 500 ℃ for 2 hours.
5. The method according to claim 3, wherein in the step S200, the flow rate of nitrogen in the carbonization furnace is maintained at 0.1-0.2L/min.
6. The method according to claim 1, wherein in the step S300, the biological bacterial manure ferment comprises one or more of bacillus, actinomycetes, saccharomycetes, trichoderma, azotobacter and lactobacillus, and exosporium enzymes secreted by microorganisms.
7. The method according to claim 6, wherein in the step S300, the effective viable count of the biological bacterial fertilizer starter is not less than 100 hundred million/mL.
8. The method according to claim 1, wherein in the step S300, the material is turned and ventilated after the temperature is raised to 50 ℃.
9. The preparation method according to any one of claims 1 to 8, wherein the weight ratio of the sludge, the straw, the biochar and the biological bacterial manure starter is 70-100:15-25:3-6:1.
10. Sludge composting which can be produced at least by the production method according to any one of claims 1 to 9, wherein the raw materials of the sludge composting comprise, in weight percent:
70-100 parts of sludge, 15-25 parts of straw, 3-6 parts of biochar and 1 part of biological bacterial fertilizer starter.
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