Method for improving remediation of soil using sludge carbon based on land reconfiguration mode

Abstract

The application discloses a method for improving and repairing soil by using sludge carbon based on land reconstruction mode, and belongs to the technical field of soil repair. The method reconstructs the soil to be repaired by improving the structure of the soil to be repaired from top to bottom in sequence, i.e. improving surface soil, surface soil layer, improved subsoil layer soil, subsoil layer and water-retaining subsoil layer; the coarse sandy soil is uniformly mixed with first modified sludge biochar, and the improved surface soil is obtained after stabilization; the subsoil layer soil 25cm to 35cm underground is uniformly mixed with second modified sludge biochar containing biological colonies, and the improved subsoil layer soil is obtained after stabilization; the subsoil layer soil 50cm to 60cm underground is uniformly mixed with second modified sludge biochar, and the water-retaining subsoil layer improved soil is obtained after stabilization. The application reconstructs the soil structure in layers, can improve soil fertility, and improve the contents of organic carbon, available phosphorus and available nitrogen.

Description

Technical Field

[0001] This invention relates to the field of soil remediation technology, and more specifically to a method for improving and remediating soil using sludge peat based on land reconstruction. Background Technology

[0002] A good soil structure can improve soil infiltration capacity, enhance soil erosion resistance, and reduce soil erosion. Biochar can influence soil physicochemical properties, including soil structure and moisture content. Considering the climate and moisture characteristics of the Loess Plateau region, the application of biochar prepared from sludge pyrolysis has potential value in improving the moisture content of loess soils, while its improvement in soil structure may enhance soil erosion resistance and reduce local soil erosion.

[0003] Sludge mainly consists of inorganic particles and organic debris, as well as toxic and harmful substances such as heavy metal ions, pathogenic microorganisms, and parasites (eggs). If not properly disposed of, it will pollute water bodies, soil, and air, causing secondary pollution. The disposal of sludge containing harmful substances in large quantities has become an important research topic in the environmental field.

[0004] Existing technologies only prepare different soil conditioners by focusing on microorganisms, or add sludge peat to certain soil conditioners or fertilizers, without making full use of soil structure or sludge peat to improve soil. Summary of the Invention

[0005] To address the above problems, this invention provides a method for improving and remediating soil using sludge peat based on land remodeling. This invention remodels the soil structure in layers, which can improve soil fertility. The products prepared by pyrolysis of sludge and straw can increase the content of organic carbon, available phosphorus, and available nitrogen. The sludge peat products with improved loading have enhanced adsorption capacity and better adsorption effect on heavy metals.

[0006] The purpose of this invention is to provide a method for improving and remediating soil using sludge peat based on land remodeling. The soil to be remediated is remodeled according to the following structure from top to bottom: improved topsoil, topsoil layer, improved subsoil layer, subsoil layer, and water-retaining subsoil layer.

[0007] The method for preparing improved topsoil is as follows: biomass with a particle size of 3mm~5mm is mixed with sludge and pyrolyzed under a nitrogen atmosphere to obtain the first pyrolyzed sludge biochar; the first pyrolyzed sludge biochar is mixed with potassium hydroxide and undergoes a pore-expansion reaction to obtain the first activated sludge biochar; the first activated sludge biochar is mixed with calcium dihydrogen phosphate, water is added, and the mixture is allowed to stand to undergo an adsorption reaction to obtain the first modified sludge biochar.

[0008] The coarse sandy soil was mixed evenly with the first modified sludge biochar, and water was added to make its moisture content 10%~15%. After stabilization, the improved topsoil was obtained.

[0009] The method for preparing the improved subsoil is as follows: Following the preparation method of the first modified sludge biochar, biomass with a particle size <1mm is treated to prepare the second modified sludge biochar. Specifically, biomass with a particle size <1mm is mixed with sludge and pyrolyzed under a nitrogen atmosphere to obtain the second pyrolyzed sludge biochar; the second pyrolyzed sludge biochar is mixed with potassium hydroxide and undergoes a pore-expansion reaction to obtain the second activated sludge biochar; the second activated sludge biochar is mixed with calcium dihydrogen phosphate, water is added, and the mixture is allowed to stand to undergo an adsorption reaction to obtain the second modified sludge biochar.

[0010] After fermentation treatment of the second modified sludge biochar, a second modified sludge biochar containing biological colonies is obtained.

[0011] The subsoil layer (25cm-35cm below ground) is mixed evenly with modified sludge biochar containing microbial colonies, and water is added to make its moisture content 5%-10%. After stabilization, the improved subsoil layer is obtained.

[0012] The method for preparing water-retaining subsoil improved soil is as follows: mix the subsoil layer soil (50cm-60cm below ground) with the second modified sludge biochar evenly, add water to make its moisture content 7%-15%, and after stabilization, the water-retaining subsoil improved soil is obtained.

[0013] In a preferred embodiment of the present invention, the mass ratio of coarse sand to the first modified sludge biochar is 1:0.05~0.15.

[0014] In a preferred embodiment of the present invention, the mass ratio of the subsoil layer (25cm-35cm below ground) to the second modified sludge biochar containing biological colonies is 1:0.05-0.3.

[0015] In a preferred embodiment of the present invention, the mass ratio of the subsoil layer (50cm-60cm below ground) to the second modified sludge biochar is 1:0.1-0.4.

[0016] In a preferred embodiment of the present invention, the pyrolysis temperature is 600℃~700℃ when preparing the first pyrolysis sludge biochar.

[0017] When preparing the second pyrolysis sludge biochar, the pyrolysis temperature is 600℃~700℃.

[0018] In a preferred embodiment of the present invention, when preparing the first activated sludge biochar, the mass ratio of the first pyrolysis sludge biochar to potassium hydroxide is 1:0.1~0.2.

[0019] When preparing the second activated sludge biochar, the mass ratio of the second pyrolysis sludge biochar to potassium hydroxide is 1:0.1~0.2.

[0020] In a preferred embodiment of the present invention, when preparing the first modified sludge biochar, the mass ratio of the first activated sludge biochar to calcium dihydrogen phosphate is 10:0.1~0.25.

[0021] When preparing the second modified sludge biochar, the mass ratio of the second activated sludge biochar to calcium dihydrogen phosphate is 10:0.1~0.25.

[0022] In a preferred embodiment of the present invention, when preparing the first activated sludge biochar, the reaction temperature of the pore-expansion reaction is 200℃~250℃ and the reaction time is 2h~3h.

[0023] When preparing the second activated sludge biochar, the reaction temperature for the pore-expansion reaction is 200℃~250℃, and the reaction time is 2h~3h.

[0024] In a preferred embodiment of the present invention, the settling time for preparing the first modified sludge biochar is 2h to 3h.

[0025] When preparing the second modified sludge biochar, the settling time is 2h~3h.

[0026] In a preferred embodiment of the present invention, during fermentation, the fermentation agent is one or a combination of several of actinomycetes, nitrogen-fixing bacteria, phosphate-solubilizing bacteria and Bacillus amyloliquefaciens; the moisture content of the sludge is 50% to 60%.

[0027] Compared with the prior art, the present invention has the following beneficial effects: This invention restructures soil in layers. Large-particle biochar (3mm-5mm) modified with coarse sand improves soil aeration, promotes microbial respiration, and allows water to flow more effectively to the roots. Small-particle biochar (<1mm) modified with microbial communities and then mixed with the 25cm-35cm subsoil layer improves the existing microbial community. The small-particle biochar also provides sufficient organic matter near the roots, ensuring the nutrients needed for root development and providing some water retention. Mixing the small-particle biochar with the 50cm-60cm subsoil layer improves water retention, preventing water loss and better supporting drought conditions. It also provides nutrients for plant growth. Compared to existing methods of applying chemical fertilizers or soil conditioners, this method can transform degraded, unused land, mining areas, and difficult-to-manage land around smelters into soil resources suitable for planting grasses or other plants.

[0028] The improved method of this invention utilizes urban sludge, which can improve the treatment of municipal sludge compared to other soil conditioners.

[0029] The improved method of this invention uses municipal sludge, which reduces the cost of soil improvement compared to other soil conditioners.

[0030] The present invention uses pyrolysis of sludge and straw to prepare sludge char, which increases the organic carbon content and also increases the content of available phosphorus and available nitrogen when mixed into the soil.

[0031] The modified sludge peat of the present invention can improve its adsorption capacity and also improve the P content in the soil.

[0032] The improved sludge carbon of this invention has a better adsorption effect on heavy metals. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the reconstructed soil structure according to the present invention.

[0034] Attached labels: 1-Improved topsoil, 2-Topsoil layer, 3-Improved subsoil layer, 4-Subsoil layer, 5-Water-retaining subsoil layer improved soil. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] This invention targets mining areas or the large amount of degraded and unused land and polluted land around mining areas and smelters in my country. Due to the long-term impact of the surrounding environment, the soil fertility has been reduced, making it unusable and resulting in waste. Therefore, by using low-temperature pyrolysis, sludge is converted into sludge peat rich in nutrients such as nitrogen, phosphorus, potassium, and organic matter. The soil is then reconstructed through a remodeling process, making unusable land resources available for use and further solving the problem of municipal sludge treatment.

[0037] Example 1 A method for improving and remediating soil using sludge peat based on land remodeling, wherein the soil to be remediated is arranged from top to bottom as follows: 0-5cm depth for improved topsoil 1, 5cm-25cm depth for topsoil 2, 25cm-35cm depth for improved subsoil 3, 35cm-50cm depth for subsoil 4, and 50cm-60cm depth for water-retaining subsoil and improved soil 5.

[0038] The improved topsoil 1, improved subsoil 3, and improved water-retaining subsoil 5 are prepared according to the following steps: Step S1: Remove 50% of the water from the sludge by pressure filtration.

[0039] Step S2: Crush the straw into biomass with a particle size of 3mm to 5mm and a particle size of <1mm.

[0040] The large-particle biomass and the dewatered sludge from step S1 are thoroughly mixed at a ratio of sludge to biomass of 1:0.2 to obtain the first mixed sludge.

[0041] The small-particle biomass and the dewatered sludge from step S1 are thoroughly mixed at a ratio of sludge to biomass of 1:0.2 to obtain the second mixed sludge.

[0042] Step S3: Place the first mixture from step S2 into a tubular furnace, pyrolyze it at 600°C for 3 hours under nitrogen protection, and obtain the first pyrolyzed sludge biochar after cooling.

[0043] The second mixture from step S2 was placed in a tubular furnace and pyrolyzed at 600°C for 3 hours under nitrogen protection. After cooling, the second pyrolyzed sludge biochar was obtained.

[0044] Step S4: The first pyrolysis sludge biochar and potassium hydroxide are heated at 200°C for 3 hours at a weight ratio of 1:0.1, and then dried to constant weight to obtain the first activated sludge biochar.

[0045] The second pyrolysis sludge biochar and potassium hydroxide were heated at 200°C for 3 hours at a weight ratio of 1:0.1, and then dried to constant weight to obtain the second activated sludge biochar.

[0046] Step S5: Add calcium dihydrogen phosphate to the first activated sludge biochar in step S4. Add calcium dihydrogen phosphate at a weight ratio of 10:0.2 of the first activated sludge biochar to calcium dihydrogen phosphate. Stir and mix well, add water to submerge, and let stand at room temperature for 2 hours. After soaking, dry at 105℃ for 12 hours until constant weight is obtained to obtain the first modified sludge biochar.

[0047] Add calcium dihydrogen phosphate to the second activated sludge biochar in step S4 at a weight ratio of 10:0.2. Stir and mix well, add water to submerge, and let stand at room temperature for 2 hours. After soaking, dry at 105℃ for 12 hours until constant weight is obtained to obtain the second modified sludge biochar.

[0048] Step S6: Take an appropriate amount of the second modified sludge biochar from step S5, and add fermentation inoculant accounting for 1% of the total weight of the second modified sludge biochar. Adjust the moisture content of the mixture to 7% with water, stir well, and ferment for 5 days to obtain modified sludge biochar containing biological colonies. The fermentation bacteria consist of phosphate-solubilizing bacteria, actinomycetes, and nitrogen-fixing bacteria in a mass ratio of 1:2:1. The phosphate-solubilizing bacteria are from Aladdin Environmental Protection Co., Ltd., product model HE-M-OP; the actinomycetes are from Ningbo Mingzhou Biotechnology Co., Ltd., product number B81372; and the nitrogen-fixing bacteria are from Ningbo Mingzhou Biotechnology Co., Ltd., product number BMZ132766.

[0049] Step S7: Mix coarse sand with the first modified sludge biochar from step S5 at a weight ratio of 1:0.15, water to a moisture content of 12%, and stabilize for 4 days to obtain improved soil.

[0050] Step S8: Take soil from the lower 25-35cm layer of the subsoil at the designated location and mix it with the modified sludge biochar with small particle size containing biological colonies from Step S6 at a weight ratio of 1:0.2. Water the mixture until the moisture content is 7% and let it stabilize for 5 days to obtain the improved subsoil.

[0051] Step S9: Take soil from the lower 50-60cm layer of the subsoil at the designated location and mix it with the second modified sludge biochar from Step S5 at a weight ratio of 1:0.2. Water the mixture until the moisture content is 10%, compact it, and stabilize it for 5 days to obtain the water-retaining subsoil.

[0052] Example 2 A method for improving and remediating soil using sludge peat based on land remodeling, wherein the soil to be remediated is arranged from top to bottom as follows: 0-5cm depth for improved topsoil 1, 5cm-25cm depth for topsoil 2, 25cm-35cm depth for improved subsoil 3, 35cm-50cm depth for subsoil 4, and 50cm-60cm depth for water-retaining subsoil and improved soil 5.

[0053] The improved topsoil 1, improved subsoil 3, and improved water-retaining subsoil 5 are prepared according to the following steps: Step S1: Remove 50% of the water from the sludge by pressure filtration.

[0054] Step S2: Crush the straw into biomass with a particle size of 3mm to 5mm and a particle size of <1mm.

[0055] The large-particle biomass and the dewatered sludge from step S1 are thoroughly mixed at a ratio of sludge to biomass of 1:0.15 to obtain the first mixed sludge.

[0056] The small-particle biomass and the dewatered sludge from step S1 are thoroughly mixed at a ratio of sludge to biomass of 1:0.15 to obtain the second mixed sludge.

[0057] Step S3: Place the first mixture from step S2 into a tubular furnace, pyrolyze it at 600°C for 3 hours under nitrogen protection, and obtain the first pyrolyzed sludge biochar after cooling.

[0058] The second mixture from step S2 was placed in a tubular furnace and pyrolyzed at 600°C for 3 hours under nitrogen protection. After cooling, the second pyrolyzed sludge biochar was obtained.

[0059] Step S4: The first pyrolysis sludge biochar and potassium hydroxide are heated at 200°C for 3 hours at a weight ratio of 1:0.1, and then dried to constant weight to obtain the first activated sludge biochar.

[0060] The second pyrolysis sludge biochar and potassium hydroxide were heated at 200°C for 3 hours at a weight ratio of 1:0.1, and then dried to constant weight to obtain the second activated sludge biochar.

[0061] Step S5: Add calcium dihydrogen phosphate to the first activated sludge biochar in step S4. Add calcium dihydrogen phosphate at a weight ratio of 10:0.25. Stir and mix well, add water to submerge, and let stand at room temperature for 2 hours. After soaking, dry at 105℃ for 12 hours until constant weight is obtained to obtain the first modified sludge biochar.

[0062] Add calcium dihydrogen phosphate to the second activated sludge biochar in step S4 at a weight ratio of 10:0.25. Stir and mix well, add water to submerge, and let stand at room temperature for 2 hours. After soaking, dry at 105℃ for 12 hours until constant weight is obtained to obtain the second modified sludge biochar.

[0063] Step S6: Take an appropriate amount of the second modified sludge biochar from step S5, and add fermentation inoculant accounting for 1% of the total weight of the second modified sludge biochar. Adjust the moisture content of the mixture to 7% with water, stir well, and ferment for 5 days to obtain modified sludge biochar containing biological colonies. The fermentation bacteria consist of phosphate-solubilizing bacteria and actinomycetes in a mass ratio of 1:2. The phosphate-solubilizing bacteria are from Aladdin Environmental Protection Co., Ltd., product model HE-M-OP; the actinomycetes are from Ningbo Mingzhou Biotechnology Co., Ltd., product number BMZ132766.

[0064] Step S8: Mix coarse sand with the first modified sludge biochar from step S5 at a weight ratio of 1:0.15, water it until the moisture content is 12%, and stabilize it for 4 days to obtain improved soil.

[0065] Step S9: Take soil from the lower 25-35cm layer of the subsoil at the designated location and mix it with the modified sludge biochar with small particle size containing biological colonies from Step S6 at a weight ratio of 1:0.2. Water the mixture until the moisture content is 7% and let it stabilize for 5 days to obtain the improved subsoil.

[0066] Step S10: Take soil from the lower 50-60cm layer of the subsoil at the designated location and mix it with the second modified sludge biochar from Step S5 at a weight ratio of 1:0.2. Water the mixture until the moisture content is 10%, compact it, and stabilize it for 5 days to obtain the water-retaining subsoil.

[0067] Example 3 A method for improving and remediating soil using sludge peat based on land remodeling, wherein the soil to be remediated is arranged from top to bottom as follows: 0-5cm depth for improved topsoil 1, 5cm-25cm depth for topsoil 2, 25cm-35cm depth for improved subsoil 3, 35cm-50cm depth for subsoil 4, and 50cm-60cm depth for water-retaining subsoil and improved soil 5.

[0068] The improved topsoil 1, improved subsoil 3, and improved water-retaining subsoil 5 are prepared according to the following steps: Step S1: Remove 50% of the water from the sludge by pressure filtration.

[0069] Step S2: Form biomass with a particle size of 3mm~5mm (large particle size) and biomass with a particle size <1mm (small particle size).

[0070] The large-particle biomass and the dewatered sludge from step S1 are thoroughly mixed at a ratio of sludge to biomass of 1:0.15 to obtain the first mixed sludge.

[0071] The small-particle biomass and the dewatered sludge from step S1 are thoroughly mixed at a ratio of sludge to biomass of 1:0.15 to obtain the second mixed sludge.

[0072] Step S3: Place the first mixture from step S2 into a tubular furnace, pyrolyze it at 600°C for 3 hours under nitrogen protection, and obtain the first pyrolyzed sludge biochar after cooling.

[0073] The second mixture from step S2 was placed in a tubular furnace and pyrolyzed at 600°C for 3 hours under nitrogen protection. After cooling, the second pyrolyzed sludge biochar was obtained.

[0074] Step S4: The first pyrolysis sludge biochar and potassium hydroxide are heated at 200°C for 3 hours at a weight ratio of 1:0.1, and then dried to constant weight to obtain the first activated sludge biochar.

[0075] The second pyrolysis sludge biochar and potassium hydroxide were heated at 200°C for 3 hours at a weight ratio of 1:0.1, and then dried to constant weight to obtain the second activated sludge biochar. In step S5, calcium dihydrogen phosphate was added to the first activated sludge biochar in step S4 at a weight ratio of 10:0.25. The mixture was stirred and mixed, then submerged in water and allowed to stand at room temperature for 2 hours. After soaking, the mixture was dried at 105°C for 12 hours until constant weight to obtain the first modified sludge biochar.

[0076] Add calcium dihydrogen phosphate to the second activated sludge biochar in step S4 at a weight ratio of 10:0.25. Stir and mix well, add water to submerge, and let stand at room temperature for 2 hours. After soaking, dry at 105℃ for 12 hours until constant weight is obtained to obtain the second modified sludge biochar.

[0077] Step S6: Take an appropriate amount of the second modified sludge biochar from step S5, and add 1% of the total weight of the second modified sludge biochar as fermentation agent. Adjust the moisture content of the mixture to 7% with water, stir well, and ferment for 5 days to obtain modified sludge biochar containing biological colonies. The fermentation agents consist of actinomycetes, Bacillus amyloliquefaciens, and phosphate-solubilizing bacteria in a mass ratio of 2:2:1. The phosphate-solubilizing bacteria are from Aladdin Environmental Protection Co., Ltd., product model HE-M-OP; the actinomycetes are from Ningbo Mingzhou Biotechnology Co., Ltd., product number BMZ132766; and the Bacillus amyloliquefaciens are from Weifang Yihao Biotechnology Co., Ltd.

[0078] Step S8: Mix coarse sand with the first modified sludge biochar from step S5 at a weight ratio of 1:0.15, water it until the moisture content is 12%, and stabilize it for 4 days to obtain improved soil.

[0079] Step S9: Take soil from the lower 25-35cm layer of the subsoil at the designated location and mix it with the modified sludge biochar with small particle size containing biological colonies from Step S5 at a weight ratio of 1:0.2. Water the mixture until the moisture content is 7% and let it stabilize for 5 days to obtain the improved subsoil.

[0080] Step S10: Take soil from the lower 50-60cm layer of the subsoil at the designated location and mix it with the second modified sludge biochar from step S5 at a weight ratio of 1:0.1-0.4. Water the mixture until the moisture content is 10%, compact it, and stabilize it for 5 days to obtain the water-retaining subsoil.

[0081] Example 4 A method for improving and remediating soil using sludge peat based on land remodeling, wherein the soil to be remediated is arranged from top to bottom as follows: 0-5cm depth for improved topsoil 1, 5cm-25cm depth for topsoil 2, 25cm-35cm depth for improved subsoil 3, 35cm-50cm depth for subsoil 4, and 50cm-60cm depth for water-retaining subsoil and improved soil 5.

[0082] The improved topsoil 1, improved subsoil 3, and improved water-retaining subsoil 5 are prepared according to the following steps: Step S1: Remove 45% of the water from the sludge by pressure filtration.

[0083] Step S2: Crush the straw into biomass with a particle size of 3mm~5mm (large particle size) and biomass with a particle size of <1mm (small particle size).

[0084] The large-particle biomass and the dewatered sludge from step S1 are thoroughly mixed at a ratio of sludge to biomass of 1:0.2 to obtain the first mixed sludge.

[0085] The small-particle biomass and the dewatered sludge from step S1 are thoroughly mixed at a ratio of sludge to biomass of 1:0.2 to obtain the second mixed sludge.

[0086] Step S3: Place the first mixture from step S2 into a tubular furnace, pyrolyze it at 600°C for 3 hours under nitrogen protection, and obtain the first pyrolyzed sludge biochar after cooling.

[0087] The second mixture from step S2 was placed in a tubular furnace and pyrolyzed at 600°C for 3 hours under nitrogen protection. After cooling, the second pyrolyzed sludge biochar was obtained.

[0088] Step S4: The first pyrolysis sludge biochar and potassium hydroxide are heated at 200°C for 2 hours at a weight ratio of 1:0.15, and then dried to constant weight to obtain the first activated sludge biochar.

[0089] The second pyrolysis sludge biochar and potassium hydroxide were heated at 200°C for 2 hours at a weight ratio of 1:0.15, and then dried to constant weight to obtain the second activated sludge biochar.

[0090] Step S5: Add calcium dihydrogen phosphate to the first activated sludge biochar in step S4. Add calcium dihydrogen phosphate at a weight ratio of 10:0.25. Stir and mix well, add water to submerge, and let stand at room temperature for 2 hours. After soaking, dry at 105℃ for 12 hours until constant weight is obtained to obtain the first modified sludge biochar.

[0091] Add calcium dihydrogen phosphate to the second activated sludge biochar in step S4 at a weight ratio of 10:0.25. Stir and mix well, add water to submerge, and let stand at room temperature for 2 hours. After soaking, dry at 105℃ for 12 hours until constant weight is obtained to obtain the second modified sludge biochar.

[0092] Step S6: Take an appropriate amount of the second modified sludge biochar from step S5, and add 1% of the total weight of the second modified sludge biochar as fermentation agent. Adjust the moisture content of the mixture to 7% with water, stir well, and ferment for 5 days to obtain modified sludge biochar containing biological colonies. The fermentation bacteria consist of Bacillus amyloliquefaciens and actinomycetes in a mass ratio of 1:1. The actinomycetes are from Ningbo Mingzhou Biotechnology Co., Ltd., product number BMZ132766. The Bacillus amyloliquefaciens is from Weifang Yihao Biotechnology Co., Ltd.

[0093] Step S7: Mix coarse sand with the first modified sludge biochar from step S5 at a weight ratio of 1:0.15, water to a moisture content of 12%, and stabilize for 4 days to obtain improved soil.

[0094] Step S8: Take soil from the lower 25-35cm layer of the subsoil at the designated location and mix it with the modified sludge biochar with small particle size containing biological colonies from Step S6 at a weight ratio of 1:0.2. Water the mixture until the moisture content is 7% and let it stabilize for 5 days to obtain the improved subsoil.

[0095] Step S9: Take soil from the lower 50-60cm layer of the subsoil at the designated location and mix it with the second modified sludge biochar from Step S5 at a weight ratio of 1:0.2. Water the mixture until the moisture content is 10%, compact it, and stabilize it for 5 days to obtain the water-retaining subsoil.

[0096] Example 5 A method for improving and remediating soil using sludge peat based on land remodeling, wherein the soil to be remediated is arranged from top to bottom as follows: 0-5cm depth for improved topsoil 1, 5cm-25cm depth for topsoil 2, 25cm-35cm depth for improved subsoil 3, 35cm-50cm depth for subsoil 4, and 50cm-60cm depth for water-retaining subsoil and improved soil 5.

[0097] The improved topsoil 1, improved subsoil 3, and improved water-retaining subsoil 5 are prepared according to the following steps: Step S1: Remove 60% of the water from the sludge by pressure filtration.

[0098] Step S2: Crush the straw into biomass with a particle size of 3mm to 5mm and a particle size of <1mm.

[0099] The large-particle biomass and the dewatered sludge from step S1 are thoroughly mixed at a ratio of sludge to biomass of 1:0.2 to obtain the first mixed sludge.

[0100] The small-particle biomass and the dewatered sludge from step S1 are thoroughly mixed at a ratio of sludge to biomass of 1:0.2 to obtain the second mixed sludge.

[0101] Step S3: Place the first mixture from step S2 into a tubular furnace, pyrolyze it at 600°C for 3 hours under nitrogen protection, and obtain the first pyrolyzed sludge biochar after cooling.

[0102] The second mixture from step S2 was placed in a tubular furnace and pyrolyzed at 700°C for 3 hours under nitrogen protection. After cooling, the second pyrolyzed sludge biochar was obtained.

[0103] Step S4: The first pyrolysis sludge biochar and potassium hydroxide are heated at 250°C for 2.5 hours at a weight ratio of 1:0.1, and then dried to constant weight to obtain the first activated sludge biochar.

[0104] The second pyrolysis sludge biochar and potassium hydroxide were heated at 250°C for 2.5 hours and dried to constant weight to obtain the second activated sludge biochar. The weight ratio of the second pyrolysis sludge biochar to potassium hydroxide was 1:0.2.

[0105] Step S5: Add calcium dihydrogen phosphate to the first activated sludge biochar in step S4. Add calcium dihydrogen phosphate at a weight ratio of 10:0.25. Stir and mix well, add water to submerge, and let stand at room temperature for 3 hours. After soaking, dry at 105℃ for 12 hours until constant weight is obtained to obtain the first modified sludge biochar.

[0106] Add calcium dihydrogen phosphate to the second activated sludge biochar in step S4 at a weight ratio of 10:0.25. Stir and mix well, add water to submerge, and let stand at room temperature for 3 hours. After soaking, dry at 105℃ for 12 hours until constant weight is obtained to obtain the second modified sludge biochar.

[0107] Step S6: Take an appropriate amount of the second modified sludge biochar from step S5, and add fermentation inoculant accounting for 1% of the total weight of the second modified sludge biochar. Adjust the moisture content of the mixture to 7% with water, stir well, and ferment for 5 days to obtain modified sludge biochar containing biological colonies. The fermentation bacteria consist of phosphate-solubilizing bacteria, actinomycetes, and nitrogen-fixing bacteria in a mass ratio of 1:2:1. The phosphate-solubilizing bacteria are from Aladdin Environmental Protection Co., Ltd., product model HE-M-OP; the actinomycetes are from Ningbo Mingzhou Biotechnology Co., Ltd., product number B81372; and the nitrogen-fixing bacteria are from Ningbo Mingzhou Biotechnology Co., Ltd., product number BMZ132766.

[0108] Step S7: Mix coarse sand with the first modified sludge biochar from step S5 at a weight ratio of 1:0.1, water until the moisture content is 10%, and stabilize for 4 days to obtain improved soil.

[0109] Step S8: Take soil from the lower 25-35cm layer of the subsoil at the designated location and mix it with the modified sludge biochar with small particle size containing biological colonies from Step S6 at a weight ratio of 1:0.3. Water the mixture until the moisture content is 5% and let it stabilize for 5 days to obtain the improved subsoil.

[0110] Step S9: Take soil from the lower 50-60cm layer of the subsoil at the designated location and mix it with the second modified sludge biochar from Step S5 at a weight ratio of 1:0.1. Water the mixture until the moisture content is 7%, compact it, and stabilize it for 5 days to obtain the water-retaining subsoil.

[0111] Example 6 A method for improving and remediating soil using sludge peat based on land remodeling, wherein the soil to be remediated is arranged from top to bottom as follows: 0-5cm depth for improved topsoil 1, 5cm-25cm depth for topsoil 2, 25cm-35cm depth for improved subsoil 3, 35cm-50cm depth for subsoil 4, and 50cm-60cm depth for water-retaining subsoil and improved soil 5.

[0112] The improved topsoil 1, improved subsoil 3, and improved water-retaining subsoil 5 are prepared according to the following steps: Step S1: Remove 55% of the water from the sludge by pressure filtration.

[0113] Step S2: Crush the straw into biomass with a particle size of 3mm to 5mm and a particle size of <1mm.

[0114] The large-particle biomass and the dewatered sludge from step S1 are thoroughly mixed at a ratio of sludge to biomass of 1:0.2 to obtain the first mixed sludge.

[0115] The small-particle biomass and the dewatered sludge from step S1 are thoroughly mixed at a ratio of sludge to biomass of 1:0.2 to obtain the second mixed sludge.

[0116] Step S3: Place the first mixture from step S2 into a tubular furnace, pyrolyze it at 600°C for 3 hours under nitrogen protection, and obtain the first pyrolyzed sludge biochar after cooling.

[0117] The second mixture from step S2 was placed in a tubular furnace and pyrolyzed at 650°C for 3 hours under nitrogen protection. After cooling, the second pyrolyzed sludge biochar was obtained.

[0118] Step S4: The first pyrolysis sludge biochar and potassium hydroxide are heated at 200°C for 3 hours at a weight ratio of 1:0.1, and then dried to constant weight to obtain the first activated sludge biochar.

[0119] The second pyrolysis sludge biochar and potassium hydroxide were heated at 200°C for 3 hours at a weight ratio of 1:0.15, and then dried to constant weight to obtain the second activated sludge biochar.

[0120] Step S5: Add calcium dihydrogen phosphate to the first activated sludge biochar in step S4. Add calcium dihydrogen phosphate at a weight ratio of 10:0.1 of the first activated sludge biochar to calcium dihydrogen phosphate. Stir and mix well, add water to submerge, and let stand at room temperature for 2.5 hours. After soaking, dry at 105℃ for 12 hours until constant weight is obtained to obtain the first modified sludge biochar.

[0121] Add calcium dihydrogen phosphate to the second activated sludge biochar in step S4 at a weight ratio of 10:0.1. Stir and mix well, add water to submerge, and let stand at room temperature for 2.5 hours. After soaking, dry at 105℃ for 12 hours until constant weight is obtained to obtain the second modified sludge biochar.

[0122] Step S6: Take an appropriate amount of the second modified sludge biochar from step S5, and add fermentation inoculant accounting for 1% of the total weight of the second modified sludge biochar. Adjust the moisture content of the mixture to 7% with water, stir well, and ferment for 5 days to obtain modified sludge biochar containing biological colonies. The fermentation bacteria consist of phosphate-solubilizing bacteria, actinomycetes, and nitrogen-fixing bacteria in a mass ratio of 1:2:1. The phosphate-solubilizing bacteria are from Aladdin Environmental Protection Co., Ltd., product model HE-M-OP; the actinomycetes are from Ningbo Mingzhou Biotechnology Co., Ltd., product number B81372; and the nitrogen-fixing bacteria are from Ningbo Mingzhou Biotechnology Co., Ltd., product number BMZ132766.

[0123] Step S7: Mix coarse sand with the first modified sludge biochar from Step S5 at a weight ratio of 1:0.05, water until the moisture content is 15%, and stabilize for 4 days to obtain improved soil.

[0124] Step S8: Take soil from the lower 25-35cm layer of the subsoil at the designated location and mix it with the modified sludge biochar with small particle size containing biological colonies from Step S6 at a weight ratio of 1:0.05. Water the mixture until the moisture content is 10% and let it stabilize for 5 days to obtain the improved subsoil.

[0125] Step S9: Take soil from the lower 50-60cm layer of the subsoil at the designated location and mix it with the second modified sludge biochar from Step S5 at a weight ratio of 1:0.4. Water the mixture until the moisture content is 15%, compact it, and stabilize it for 5 days to obtain the water-retaining subsoil.

[0126] Pot experiments were conducted using the reconstructed soils from Examples 1 to 4. Eight ryegrass seeds were evenly sown in each pot and watered regularly. A control group and a blank control group were set up. Control group 1 was treated with commercially available urea. Control group 2 was directly applied to the soil with the same mass of the first modified sludge biochar, the second modified sludge biochar, and the modified sludge biochar with small particle size containing biological colonies prepared in this invention at a mass ratio of 1:1:1. The applied mass was consistent with the mass of the sludge biochar in the experimental group. No substances were applied to the blank control group. Ryegrass seeds were evenly sown in the improved soil and watered regularly. See Table 1 for details.

[0127] Table 1. Rye growth in soil under different treatments As shown in the table above, the germination rate and plant height of rye crops planted in the soils improved in Examples 1-4 of the soil remediation method proposed in this invention are significantly higher than those planted in the control groups 1 and 2 treated with existing soil conditioners. The abundant nitrogen, phosphorus, potassium, and organic matter in the applied peat moss allows plants to obtain more nutrients from the soil, promoting higher germination rates and plant heights. After reconstruction according to the method of this invention, the soil has a more rational structure. The upper soil layer has better aeration, promoting the respiration of microorganisms near the roots, decomposing organic matter in the soil into nutrients that can be absorbed by the roots. The lower soil layer has better moisture retention, better coping with drought conditions and supplying the plant roots with the necessary water.

[0128] The following are the soil physicochemical properties of Examples 1-4 and Control Groups 1-2, as shown in Table 2.

[0129] Table 2 Physicochemical properties of different improved soils As shown in Table 2, the physicochemical properties of the soils improved by Examples 1-4 of the soil remediation method proposed in this invention are significantly improved compared to the soils treated with existing amendments (Control Groups 1 and 2) in terms of organic matter, total nitrogen, phosphorus, potassium, and available nitrogen and phosphorus. These improvements significantly enhance soil fertility, directly promoting plant growth and development. Compared to the control group and the blank control group, the sludge applied in Examples 1-4 contains richer nutrients such as nitrogen, phosphorus, potassium, and organic matter. Through plant growth activities and the action of soil microorganisms, the improved soil contains more nitrogen, phosphorus, potassium, and other nutrients that can be utilized by plants for growth. Furthermore, because the reconstructed soil has better permeability, it promotes the respiration of soil microorganisms, accelerating the decomposition of organic matter in the sludge and converting it into nutrients that can be absorbed by plants.

[0130] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0131] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for improving and remediating soil using sludge peat based on land remodeling, characterized in that, The soil to be repaired is reconstructed according to the structure from top to bottom as improved topsoil (1), topsoil layer (2), improved subsoil layer (3), subsoil layer (4) and water-retaining subsoil layer improved soil (5); The preparation method of the improved topsoil (1) is as follows: biomass with a particle size of 3mm~5mm is mixed with sludge and pyrolyzed under a nitrogen atmosphere to obtain the first pyrolyzed sludge biochar; the first pyrolyzed sludge biochar is mixed with potassium hydroxide and a pore-expansion reaction is carried out to obtain the first activated sludge biochar; the first activated sludge biochar is mixed with calcium dihydrogen phosphate, water is added, and the mixture is allowed to stand and an adsorption reaction is carried out to obtain the first modified sludge biochar. The coarse sand soil was mixed evenly with the first modified sludge biochar, and water was added to make its moisture content 10%~15%. After stabilization, the improved topsoil was obtained. The preparation method of the improved subsoil (3) is as follows: referring to the preparation method of the first modified sludge biochar, biomass with a particle size <1mm is treated to prepare the second modified sludge biochar; after fermentation treatment of the second modified sludge biochar, the second modified sludge biochar containing biological colonies is obtained. Mix the subsoil layer (25cm-35cm below ground) with the modified sludge biochar containing biological colonies, add water to make the moisture content 5%-10%, and after stabilization, obtain the improved subsoil layer. The preparation method of the water-retaining core soil layer improved soil (5) is as follows: mix the soil of the core soil layer 50cm~60cm below ground with the second modified sludge biochar evenly, add water to make its water content 7%~15%, and after stabilization, the water-retaining core soil layer improved soil is obtained. When preparing the first activated sludge biochar, the reaction temperature for the pore-expansion reaction is 200℃~250℃, and the reaction time is 2h~3h. When preparing the second activated sludge biochar, the reaction temperature for the pore-expansion reaction is 200℃~250℃, and the reaction time is 2h~3h.

2. The method for improving and remediating soil using sludge peat based on land remodeling as described in claim 1, characterized in that, The mass ratio of coarse sand to the first modified sludge biochar is 1:0.05~0.

15.

3. The method for improving and remediating soil using sludge peat based on land remodeling as described in claim 1, characterized in that, The mass ratio of the subsoil layer (25cm-35cm below ground) to the second modified sludge biochar containing biological colonies is 1:0.05-0.

3.

4. The method for improving and remediating soil using sludge peat based on land remodeling as described in claim 1, characterized in that, The mass ratio of the subsoil layer (50cm-60cm below the surface) to the second modified sludge biochar is 1:0.1-0.

4.

5. The method for improving and remediating soil using sludge peat based on land remodeling as described in claim 1, characterized in that, When preparing the first pyrolysis sludge biochar, the pyrolysis temperature is 600℃~700℃; When preparing the second pyrolysis sludge biochar, the pyrolysis temperature is 600℃~700℃.

6. The method for improving and remediating soil using sludge peat based on land remodeling as described in claim 1, characterized in that, When preparing the first activated sludge biochar, the mass ratio of the first pyrolysis sludge biochar to potassium hydroxide is 1:0.1~0.2; When preparing the second activated sludge biochar, the mass ratio of the second pyrolysis sludge biochar to potassium hydroxide is 1:0.1~0.

2.

7. The method for improving and remediating soil using sludge peat based on land remodeling as described in claim 1, characterized in that, When preparing the first modified sludge biochar, the mass ratio of the first activated sludge biochar to calcium dihydrogen phosphate is 10:0.1~0.25; When preparing the second modified sludge biochar, the mass ratio of the second activated sludge biochar to calcium dihydrogen phosphate is 10:0.1~0.

25.

8. The method for improving and remediating soil using sludge peat based on land remodeling as described in claim 1, characterized in that, When preparing the first modified sludge biochar, the settling time is 2h~3h; When preparing the second modified sludge biochar, the settling time is 2h~3h.

9. The method for improving and remediating soil using sludge peat based on land remodeling as described in claim 1, characterized in that, During fermentation, the fermentation agent is one or a combination of several of the following: actinomycetes, nitrogen-fixing bacteria, phosphate-solubilizing bacteria, and Bacillus amyloliquefaciens; the moisture content of the sludge is 50% to 60%.

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