Soil improvement method for landscaping engineering

Abstract

The invention provides a soil improvement method for landscaping engineering, and belongs to the technical field of soil improvement. The method comprises the following steps: carrying out thermal desorption remediation treatment on garden polluted soil to obtain soil subjected to thermal desorption remediation; the method comprises the following steps: drying and crushing municipal sludge and garden waste, mixing with an additive, and carrying out anoxic pyrolysis to obtain biochar; and mixing and backfilling the soil subjected to thermal desorption repair, charcoal and green land original soil into a landscaping planting area. The biochar generated by pyrolysis of the municipal sludge and the garden waste can adsorb and stabilize residual pollutants in the soil after thermal desorption, the organic matter content of the green land original soil is increased, and the soil fertility is improved. According to the method, the soil is obtained by screening the dosage proportion of the soil subjected to thermal desorption remediation, the biochar and the green land original soil, and the problems that the green land original soil is low in nutrient content, poor in fertility retention, low in seedling survival rate and the like are solved; the soil can be used as planting soil in urban landscaping engineering and garden green land maintenance and management.

Description

Technical Field

[0001] The invention belongs to the technical field of soil improvement, and in particular relates to a soil improvement method for gardening and greening projects. Background Art

[0002] Garden soil pollution mainly comes from the irrational use and discharge of pesticides, petroleum products, urban garbage, domestic and medical sewage, coal slag, mercury, sulfate oxides and other substances. These behaviors not only affect the function and effective use of soil, but also endanger public health and damage the ecological environment. Garden soil pollution prevention and control is an important basic work to ensure the healthy development of garden greening.

[0003] As a medium for the growth of green space plants and a carrier for their functions, soil is the foundation of the entire green space system and the basis for the high-quality development of the entire urban ecological infrastructure. Urban garden green space soils generally have problems such as poor soil texture, uneven fertility, low organic matter content, and inappropriate moisture content. These problems have affected the healthy growth of garden plants to a certain extent.

[0004] Therefore, there is an urgent need to provide a new soil improvement method to comprehensively utilize urban waste to optimize the construction of urban landscaping projects. Summary of the invention

[0005] In view of this, an object of the present invention is to provide a soil improvement method for landscaping engineering.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a soil improvement method for landscaping engineering, comprising the following steps:

[0008] 1) subjecting the garden contaminated soil to thermal desorption remediation treatment to obtain thermal desorption remediation soil;

[0009] 2) Drying and crushing urban sewage sludge and garden waste, mixing with additives and performing anoxic pyrolysis to obtain biochar;

[0010] 3) Mix the thermally desorbed and repaired soil, biochar and original green land soil and backfill them into the garden planting area.

[0011] Preferably, in step 3), the mass ratio of the soil after thermal desorption repair, biochar and green land original soil is 1:1.5-2.5:2-4.

[0012] Preferably, the temperature of the thermal desorption repair treatment in step 1) is 250-450° C., and the time of the thermal desorption repair treatment is 15-35 minutes.

[0013] Preferably, the moisture content of the soil after thermal desorption repair in step 1) is 10-15%.

[0014] Preferably, in step 2), the mass ratio of the urban sludge to the garden waste is 1.5 to 3:1.

[0015] Preferably, the additives in step 2) are citric acid and sodium carboxymethyl cellulose, the added amount of citric acid is 6-10% of the total mass of urban sludge and garden waste, and the added amount of sodium carboxymethyl cellulose is 6-10% of the total mass of urban sludge and garden waste.

[0016] Preferably, the temperature of the anaerobic pyrolysis in step 2) is 400-600° C.; the time of the anaerobic pyrolysis is 1.5-3 h.

[0017] Preferably, the heating rate of the anaerobic pyrolysis in step 2) is 9-11°C / min.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The present invention provides a method for preparing garden greening soil by using garden polluted soil, urban sludge and garden waste. The biochar produced by pyrolysis of urban sludge and garden waste can adsorb / stabilize the pollutants remaining in the soil after thermal desorption, thereby improving the problems of large-scale ablation of soil organic matter, reduction of fine particles, reduction of plasticity index and residual pollutants after thermal desorption, and reducing the risk of pollution. The original soil of green land has the problems of disordered soil layers, serious soil slag, high soil compaction, poor nutrients and lack of organic matter. The biochar produced by pyrolysis of urban sludge and garden waste can increase the organic matter content of the original soil of green land, increase soil fertility, reduce soil pH value, adjust soil acidity and alkalinity, reduce soil conductivity, improve soil water retention and air permeability, increase nitrogen, phosphorus, potassium and other nutrient elements in the soil, improve soil nutrient content, and promote the rapid growth of seedlings.

[0020] The present invention obtains soil by screening the usage ratio of soil, biochar and green land original soil after thermal desorption repair, which solves the problems of low nutrient content, poor fertility retention and low survival rate of seedlings in green land original soil; it can be used as planting soil in urban garden greening projects and garden green land maintenance management, and improves economic value relative to the disposal methods such as backfill soil and road soil, and realizes the harmless and resource utilization of garden polluted soil, urban sludge and garden waste. The method of the present invention is simple to operate, safe and effective, has no secondary environmental risks, and effectively reduces soil treatment costs, broadens the source of greening backfill soil, solves the problem of soil resource utilization after repair, and has good promotion value. DETAILED DESCRIPTION

[0021] The present invention provides a soil improvement method for landscaping engineering, comprising the following steps:

[0022] 1) subjecting the garden contaminated soil to thermal desorption remediation treatment to obtain thermal desorption remediation soil;

[0023] 2) Drying and crushing urban sewage sludge and garden waste, mixing with additives and performing anoxic pyrolysis to obtain biochar;

[0024] 3) Mix the thermally desorbed and repaired soil, biochar and original green land soil and backfill them into the garden planting area.

[0025] In the present invention, the garden contaminated soil is subjected to thermal desorption remediation treatment to obtain the thermally desorbed remediation soil. The particle size of the garden contaminated soil is less than 10 mm; the temperature of the thermal desorption remediation treatment is preferably 250-450°C, more preferably 280-420°C; the time of the thermal desorption remediation treatment is preferably 15-35 minutes, more preferably 20-30 minutes; the water content of the thermally desorbed remediation soil is 10-15%.

[0026] In the present invention, after the urban sludge and garden waste are dried and crushed, they are mixed with additives and subjected to anoxic pyrolysis to obtain biochar. The garden waste is preferably plant materials such as tree and shrub trimmings (thinnings), lawn trimmings, fallen leaves, branches, discarded flowers and weeds in gardens and flower beds produced naturally or during the maintenance of green plants in urban green spaces or suburban woodlands; the mesh size of the crushing is preferably 60 to 100 mesh, and more preferably 70 to 90 mesh; the urban sludge is preferably dried at 100 to 110°C for 3 to 5 hours; more preferably, it is dried at 102 to 108°C for 3.5 to 4.5 hours; the garden waste is preferably dried at 50 to 60°C for 6 to 10 hours, and more preferably, it is dried at 52 to 58°C for 7 to 9 hours; the mass ratio of the urban sludge to the garden waste is preferably 1.5 to 3:1, and more preferably, it is dried at 102 to 108°C for 3.5 to 4.5 hours. The ratio of the additives to the waste is preferably 2 to 2.5:1; the additives are preferably citric acid and sodium carboxymethyl cellulose, the amount of the citric acid added is preferably 6 to 10% of the total mass of the urban sludge and garden waste, and more preferably 7 to 9% of the total mass of the urban sludge and garden waste; the amount of the sodium carboxymethyl cellulose added is preferably 6 to 10% of the total mass of the urban sludge and garden waste, and more preferably 7 to 9% of the total mass of the urban sludge and garden waste; the temperature of the anaerobic pyrolysis is preferably 400 to 600°C, and more preferably 450 to 550°C; the time of the anaerobic pyrolysis is preferably 1.5 to 3h, and more preferably 2 to 2.5h; the heating rate of the anaerobic pyrolysis is preferably 9 to 11°C / min, and more preferably 10°C / min.

[0027] In the present invention, the soil after thermal desorption repair, biochar and green land soil are mixed and backfilled into the garden greening planting area. The mass ratio of the soil after thermal desorption repair, biochar and green land soil is preferably 1:1.5-2.5:2-4, and more preferably 1:1.8-2.2:2.2-3.8.

[0028] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0029] Example 1

[0030] The garden contaminated soil with a particle size of 8 mm was subjected to thermal desorption and remediation treatment at a temperature of 350°C for 25 minutes to obtain the thermally desorbed and remediated soil; the urban sludge was dried at 105°C for 4 hours, and the garden waste was dried at a temperature of 55°C for 8 hours. The urban sludge and garden waste were crushed to 80 mesh, mixed with 8% of citric acid and 8% of sodium carboxymethyl cellulose of the total mass of the urban sludge and garden waste, and placed in a tubular furnace, and then nitrogen was introduced into the tubular furnace for 10 minutes for gas washing, and the air in the reactor was discharged to place the modified sludge powder in a nitrogen protective atmosphere, and the temperature was increased to 500°C at a heating rate of 10°C / min, and high-temperature pyrolysis was performed for 2.5 hours to obtain biochar; the thermally desorbed and remediated soil, biochar and green land original soil were mixed in a mass ratio of 1:2:3 and backfilled into the garden greening planting area.

[0031] Example 2

[0032] The garden contaminated soil with a particle size of 7 mm was subjected to thermal desorption and remediation treatment at a temperature of 250°C for 15 minutes to obtain the thermally desorbed and remediated soil; the urban sludge was dried at 100°C for 3 hours, and the garden waste was dried at a temperature of 50°C for 6 hours. The urban sludge and garden waste were crushed to 60 mesh, mixed with 6% of citric acid and 6% of sodium carboxymethyl cellulose based on the total mass of the urban sludge and garden waste, and placed in a tubular furnace, and then nitrogen was introduced into the tubular furnace for 10 minutes for gas washing, and the air in the reactor was discharged to place the modified sludge powder in a nitrogen protective atmosphere, and the temperature was increased to 400°C at a heating rate of 9°C / min, and high-temperature pyrolysis was performed for 1.5 hours to obtain biochar; the thermally desorbed and remediated soil, biochar and green land original soil were mixed in a mass ratio of 1:1.5:2 and backfilled into the garden greening planting area.

[0033] Example 3

[0034] The garden contaminated soil with a particle size of 9 mm was subjected to thermal desorption and remediation treatment at a temperature of 450°C for 35 minutes to obtain the thermally desorbed and remediated soil; the urban sludge was dried at 110°C for 5 hours, and the garden waste was dried at a temperature of 60°C for 10 hours. The urban sludge and garden waste were crushed to 100 mesh, mixed with 10% of citric acid and 10% of sodium carboxymethyl cellulose of the total mass of the urban sludge and garden waste, and placed in a tubular furnace, and then nitrogen was introduced into the tubular furnace for 10 minutes for gas washing, and the air in the reactor was discharged to place the modified sludge powder in a nitrogen protective atmosphere, and the temperature was increased to 600°C at a heating rate of 11°C / min, and high-temperature pyrolysis was performed for 3 hours to obtain biochar; the thermally desorbed and remediated soil, biochar and green land original soil were mixed in a mass ratio of 1:2.5:4 and backfilled into the garden greening planting area.

[0035] Comparative Example 1

[0036] The difference from Example 1 is that no biochar is added.

[0037] Comparative Example 2

[0038] The difference from Example 1 is that the mass ratio of the soil after thermal desorption repair, biochar and green land original soil is 1:1:1.

[0039] Comparative Example 3

[0040] The difference from Example 1 is that the mass ratio of the soil, biochar and green land original soil after thermal desorption repair is 1:3:5.

[0041] Comparative Example 4

[0042] The difference from Example 1 is that the dosage of citric acid and sodium carboxymethyl cellulose is 5% of the total mass of urban sludge and garden waste respectively.

[0043] Comparative Example 5

[0044] The difference from Example 1 is that the dosage of citric acid and sodium carboxymethyl cellulose is 12% of the total mass of urban sludge and garden waste respectively.

[0045] Experimental Example 1

[0046] The pH value, organic matter content, total nitrogen content, total phosphorus content, total potassium content, hydrolyzable nitrogen content, available phosphorus content, and available potassium content of the soil improved in Examples 1 to 3 and Comparative Examples 1 to 5 were measured respectively. The pH value was measured using a pH meter; the detection method of organic matter content can be found in GB 9834-88; the detection method of total nitrogen content can be found in GB 7173-1987; the detection method of total phosphorus content can be found in GB / T13140-2015; the detection method of total potassium content can be found in GB 9836-88; the detection method of hydrolyzable nitrogen content can be found in GB / T 6379.2; the detection method of available phosphorus content can be found in NY / T 1121.7-2014; the detection method of available potassium content can be found in NY / T 889-2004.

[0047] Experimental results: as shown in Table 1.

[0048] Table 1 Determination of soil indicators in different treatment groups

[0049]

[0050] As can be seen from Table 1, compared with Comparative Examples 1 to 5, Examples 1 to 3 have higher contents of soil organic matter, total nitrogen, total phosphorus, total potassium, hydrolyzable nitrogen, available phosphorus and available potassium, which greatly improves soil fertility. Biochar plays a vital role in the process of soil improvement, and improper mass ratio of soil, biochar and green land original soil after thermal desorption repair will also greatly reduce the effect of soil improvement. The addition amount of citric acid and sodium carboxymethyl cellulose needs to be strictly controlled. When the addition amount of citric acid is too little, the porosity of the final biochar is too low and the adsorption effect is poor; when the addition amount of citric acid is too much, the etching effect of citric acid and the like on the mechanical strength of biochar is too large, affecting the molding and subsequent use of sludge biochar. If the addition amount of sodium carboxymethyl cellulose is too little; the mechanical strength of the biochar obtained is insufficient; if the addition amount of sodium carboxymethyl cellulose is too much, it is easy to block the gaps inside the biochar and reduce the adsorption effect of the sludge biochar.

[0051] Experimental Example 2

[0052] In Liulin County, Luliang City, Shanxi Province, the soil improvement methods of Examples 1 to 3 and Comparative Examples 1 to 5 were used to plant roses with a plant spacing of 12 to 15 cm. The rose planting method was carried out according to a conventional method. The plant height and base diameter were recorded for 60 days in the early stage of plant growth, and then recorded every 30 days, with an observation period of 8 months.

[0053] Experimental results: as shown in Table 2.

[0054] Table 2 Determination of plant height and base diameter of roses in different treatment groups

[0055]

[0056] Experimental results: As can be seen from Table 2, the roses planted in the soil improved by Examples 1 to 3 have good overall growth compared to Comparative Examples 1 to 5, and the growth rates of the rose plant height and base diameter are fast. The plant height growth rate of the roses planted in the soil improved by Example 1 is 86.75%, and the base diameter growth rate is 10.20%; the plant height growth rate of the roses planted in the soil improved by Example 2 is 86.42%, and the base diameter growth rate is 8.33%; the plant height growth rate of the roses planted in the soil improved by Example 3 is 86.59%, and the base diameter growth rate is 8.16%.

[0057] It can be seen from the embodiments and experimental examples that the soil improved by the present invention has high nutrient contents such as soil organic matter, total nitrogen, total phosphorus, total potassium, hydrolyzable nitrogen, available phosphorus and available potassium, has strong soil fertility, and can promote the rapid growth of seedlings.

[0058] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A soil improvement method for landscaping engineering, characterized in that: The following steps are involved: 1) subjecting the garden contaminated soil to thermal desorption remediation treatment to obtain thermal desorption remediation soil; 2) Drying and crushing urban sewage sludge and garden waste, mixing with additives and performing anoxic pyrolysis to obtain biochar; 3) Mix the thermally desorbed and repaired soil, biochar and original green land soil and backfill them into the garden planting area.

2. The soil improvement method according to claim 1, characterized in that: Step 3) The mass ratio of the thermally desorbed and repaired soil, biochar and green space original soil is 1:1.5-2.5:2-4.

3. The soil improvement method according to claim 1, characterized in that: Step 1) The temperature of the thermal desorption repair treatment is 250-450° C., and the time of the thermal desorption repair treatment is 15-35 minutes.

4. The soil improvement method according to claim 1, characterized in that: Step 1) The moisture content of the soil after thermal desorption repair is 10-15%.

5. The soil improvement method according to claim 1, characterized in that: Step 2) The mass ratio of the urban sludge to the garden waste is 1.5 to 3:

1.

6. The soil improvement method according to claim 1, characterized in that: Step 2) The additives are citric acid and sodium carboxymethyl cellulose, the amount of citric acid added is 6-10% of the total mass of urban sludge and garden waste, and the amount of sodium carboxymethyl cellulose added is 6-10% of the total mass of urban sludge and garden waste.

7. The soil improvement method according to claim 1, characterized in that: Step 2) The temperature of the anaerobic pyrolysis is 400-600° C.; the time of the anaerobic pyrolysis is 1.5-3 hours.

8. The soil improvement method according to claim 1 or 7, characterized in that: The heating rate of the anaerobic pyrolysis in step 2) is 9-11°C / min.

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