A method for rapidly improving sandy soil using river sediment

Abstract

The present invention provides a method for rapidly improving sandy soil by using river sediment. The collected river sediment is subjected to freezing, thawing, centrifugal and drying conditions, and then applied at a ratio of 1.5 to 6.0 kg / m 2 Mix well with sand, compact, level the surface of the mixed soil, irrigate with water, let the mixed soil properties stabilize for 1 month, and then test relevant indicators. The method of the present invention promotes the removal of heavy metals and salts in the sediment, reduces the number of bacteria in the sediment, improves the mud-water separation effect, increases the sediment dehydration rate, and reduces the sediment volume. The harmless, reduced and resource-based utilization of river sediments is achieved, and the properties of sand are improved. The method of the present invention reduces the bulk density of sand and increases the clay content and fertility level.

Description

Technical Field

[0001] The invention belongs to the technical field of harmless treatment, reduction and resource utilization of river sediment, and specifically relates to a method for rapidly improving sandy soil by utilizing river sediment. Background Art

[0002] With the vigorous development of industry, the output of urban residual sludge has gradually increased, which has led to an increase in river sediment. At the same time, a large amount of sewage is directly discharged into the river without treatment, and the pollutants in the sewage naturally settle down, resulting in the gradual accumulation of pollutants in the sediment, and the pollution is becoming more and more serious. Therefore, the effective treatment of river sediment is an environmental problem that needs to be solved urgently.

[0003] Sandy soil is soil mixed with a large amount of sand and a small amount of clay. The sandy soil in the present invention comes from Zhanggutai Town, Fuxin City (42°43′N, 122°22′E), and its mechanical composition is relatively coarse. Its basic properties are shown in Table 1. This sandy soil is loose and has good water permeability and air permeability, but it is poor in nutrients such as N and P, and has poor water and fertilizer retention capacity, which is not conducive to plant growth. Therefore, it is necessary to find an economical and effective method for improving the properties of sandy soil.

[0004] Table 1 Basic properties of sandy soil

[0005]

[0006] The resource utilization of river sediment is to apply dredged sediment to farmland, forest land, landscaping and severely disturbed land restoration and reconstruction, etc. It has the advantages of low investment and low energy consumption. The organic part of the sediment can be converted into soil conditioner components during the disposal process, which is considered to be the most promising resource utilization method. The chemical composition of river sediment is similar to clay and close to the structural properties of soil. The rational application of river sediment in sand is an effective and scientific disposal method. However, river sediment not only contains rich nutrients such as organic carbon, nitrogen, phosphorus, but also contains harmful substances such as heavy metals, which must be stabilized, reduced and harmless. The river sediment in the present invention comes from the Nujiang Bridge section of Xinkai River in Shenyang, Liaoning Province, and the basic properties are shown in Table 2. With the proposal of the goal of ecological civilization construction in my country and the continuous improvement of relevant laws and regulations, dehydration, drying, sterilization and resource comprehensive utilization of river and lake dredged sediment is an inevitable choice in the future. Therefore, a method for rapidly improving sand using river sediment is proposed, which is of great significance to the resource utilization of river sediment and sand improvement.

[0007] Table 2 Basic properties of river sediment

[0008] Summary of the invention

[0009] In order to solve the problems of harmless, reduced and resourceful treatment of river sediment on the one hand, and to improve the properties of sand on the other hand, the present invention provides a method for rapidly improving sand using river sediment.

[0010] The technical solution adopted by the present invention is:

[0011] A method for rapidly improving sandy soil by using river sediment comprises the following steps:

[0012] 1) Set 5 sampling points in the sampling river section, use Peterson mud sampler, collect 1 kg of bottom mud at the depth of 0 to 15 cm at each sampling point, after sampling, evenly mix the bottom mud collected at each sampling point, and take part of the river bottom mud for freezing treatment;

[0013] 2) thawing and melting the river sediment treated in step 1);

[0014] 3) centrifuging the river sediment treated in step 2);

[0015] 4) drying the river sediment treated in step 3);

[0016] 5) mixing the river sediment treated in step 4) with the sand at a depth of 20 cm on the surface to obtain mixed soil;

[0017] 6) Compact the mixed soil, level the surface of the mixed soil, irrigate it thoroughly with water, and allow the mixed soil to stabilize for 1 month;

[0018] 7) Test the relevant indicators of the mixed soil after its properties have been stabilized.

[0019] Furthermore, in the above-mentioned method for rapidly improving sandy soil using river sediment, in step 1), the freezing temperature is controlled at -18°C, and the freezing time is controlled at 4.5 to 6.0 hours.

[0020] Furthermore, in the above-mentioned method of rapidly improving sandy soil using river sediment, in step 3), the centrifugal speed is controlled at 5000-6500 r / min, and the centrifugal time is controlled at 20-30 min.

[0021] Furthermore, in the above-mentioned method for rapidly improving sandy soil using river sediment, in step 4), the drying temperature is controlled at 80-85° C., and the drying time is controlled at 2-3 h.

[0022] Furthermore, in the above method of using river sediment to quickly improve sandy soil, in step 5), the ratio of the river sediment to the sandy soil is 1.5-6.0 kg / m 2 .

[0023] Furthermore, in the above-mentioned method for rapidly improving sandy soil using river sediment, in step 7), the relevant indicators include clay, bulk density, organic carbon, total nitrogen, total phosphorus, heavy metal content, electrical conductivity and total bacterial count.

[0024] The beneficial effects of the present invention are:

[0025] 1. The method of the present invention successively adopts freeze-thaw-centrifugation treatment to the river sediment. Under the freeze-thaw conditions, with the phase change of the sediment, such as the change of the physical properties of the sediment, the sediment is cracked, the solid phase volume is reduced, the liquid phase volume is increased, the volume of the sediment supernatant is increased by 11.76%, and the dehydration rate is increased by 4.00%; at the same time, the freeze-thaw process can promote the removal of heavy metals and salts in the sediment, so that the content of heavy metals and salts in the sediment is reduced, among which the heavy metals Cu, Cd, Pb, and Zn are reduced by 5.63%, 5.45%, 4.98% and 4.47% respectively, and the conductivity is reduced by 32.61%. The river sediment after the river sediment is melted is subjected to centrifugal treatment, which further improves the sediment dehydration rate and reduces its heavy metal and salt content. Among them, the heavy metals Cu, Cd, Pb, and Zn were further reduced by 9.12%, 9.67%, 9.86%, and 10.44%, respectively; the conductivity was reduced by 13.34%; the river sediment dehydration rate increased by 29.00%, and the sediment supernatant volume increased by 85.29%. After freezing-thawing-centrifugation, the method of the present invention dried the sediment, during which the moisture content was further reduced, and most of the harmful microorganisms were removed. Compared with the method before and after the treatment, the total bacterial count was reduced by 97.39%.

[0026] 2. The sandy soil has a small clay content, a high coarse sand content, poor drought resistance and low water holding capacity. The method of the present invention improves the physical properties of the soil after mixing with the sandy soil through the physical properties of the river bottom mud itself, the clay content is increased by 3.49% to 9.19%, the electrical conductivity of the mixed soil is increased by 0.93% to 15.34%, the bulk density is reduced by 14.71% to 23.53%, the organic carbon content is increased by 11.43% to 34.29%, the total nitrogen content is increased by 10.26% to 74.36%, and the phosphorus content is increased by 20.00% to 40.00%, which significantly reduces the bulk density of the sandy soil and improves the clay content and fertility.

[0027] 3. The method of the present invention is simple to operate, has a short improvement cycle, and is easy to implement.

[0028] 4. The present invention provides a method for utilizing river sediment as a resource and improving sandy soil at the same time, providing a new idea for harmless, resource-based utilization and disposal of river sediment, and improving the properties of sandy soil. Among them, the resource utilization of river sediment can solve the problem of sediment outlet, solve the pollution of river water to a certain extent, and reduce the secondary pollution of river water quality. It is a sustainable development path with good application prospects. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0030] Example 1

[0031] A method for rapidly improving sandy soil using river sediment comprises the following steps:

[0032] Five sampling points were set up in the sampling river section, and a Peterson mud sampler was used to collect 1 kg of bottom mud at a depth of 0 to 15 cm at each sampling point. After sampling, the mud collected from each sampling point was evenly mixed, and 0.25 kg of river mud was frozen with the freezing temperature controlled at -18°C and the freezing time controlled at 4.5 to 6.0 h; after thawing, it was centrifuged with the centrifugal speed controlled at 5000 to 6500 r / min and the centrifugal time controlled at 20 to 30 min; the river mud obtained after centrifugation was dried at 80 to 85°C for 2 to 3 hours.

[0033] The river sediment after the above treatment is mixed with the sand at a depth of 20 cm on the surface. The proportion of river sediment applied is 1.5-6.0 kg / m 2 After mixing, compact and level the surface of the mixed soil, irrigate it with water, and allow the mixed soil to stabilize for 1 month. Then, test related indicators including clay, bulk density, organic carbon, total nitrogen, total phosphorus, heavy metal content, electrical conductivity and total bacteria count.

[0034] After the river sediment was treated by freeze-thaw-centrifugation-drying, the changes in the properties of the supernatant are shown in Table 3, and the changes in the sediment property indicators are shown in Table 4. Under freeze-thaw conditions, with the phase change of the sediment, such as the change in the physical properties of the sediment, the sediment was cracked, the solid phase volume decreased, the liquid phase volume increased, the sediment supernatant volume increased by 11.76%, the dehydration rate increased by 4.00%, the conductivity increased by 18.46%, and the turbidity decreased from 181.2NTU to 168.8NTU; at the same time, the freeze-thaw process can promote the removal of heavy metals and salts in the sediment, so that the heavy metal content and conductivity in the sediment are reduced. Among them, the heavy metals Cu, Cd, Pb, and Zn were reduced by 5.63%, 5.45%, 4.98%, and 4.47%, respectively, and the conductivity was reduced by 32.61%, and the salt removal effect was obvious. After the melted river sediment was centrifuged, the sediment dehydration rate was further improved, and its heavy metal content and conductivity were reduced. The heavy metals Cu, Cd, Pb, and Zn were further reduced by 9.12%, 9.67%, 9.86%, and 10.44%, respectively, and the conductivity was further reduced by 13.34%. The river sediment dehydration rate increased by 29.00%; the sediment supernatant volume increased by 85.29%, the conductivity was further increased by 21.83%, and the turbidity was reduced from 168.8NTU to 8.85NTU. After freezing-thawing-centrifugation, the sediment was dried. During this process, the moisture content was further reduced and most of the harmful microorganisms were removed. Compared with before and after treatment, the total bacterial count was reduced by 97.39%.

[0035] Table 3 Effects of freeze-thaw-centrifugation on the properties of sediment supernatant

[0036]

[0037] Table 4 Effects of freeze-thaw-centrifuge-drying treatment on sediment properties

[0038]

[0039] Note: “——” means the indicator is not involved.

[0040] The test results of the mixed soil properties of the treated river sediment and sand after stabilization for one month are shown in Table 5: the clay content of the mixed soil increased, with an increase of 3.49% to 9.19%; the electrical conductivity of the mixed soil increased, with an increase of 0.93% to 15.34%; the bulk density of the mixed soil decreased, with a decrease of 14.71% to 23.53%; the organic carbon of the mixed soil increased significantly, with an increase of 11.43% to 34.29%; the total nitrogen content and total phosphorus content of the mixed soil increased significantly, with increases of 10.26% to 74.36% and 20.00% to 40.00%, respectively.

[0041] Table 5 Mixed soil properties

[0042]

[0043] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. The protection scope of the present invention is not limited thereto, and any technician familiar with the technical field can make equivalent replacements or changes according to the technical solution and inventive concept of the present invention within the technical scope disclosed by the present invention, and any modifications and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for rapidly improving sandy soil using river sediment, characterized in that: The steps include: 1) Set 5 sampling points in the sampling river section, use Peterson mud sampler, collect 1 kg of bottom mud at a depth of 0-15 cm at each sampling point, and evenly mix the bottom mud collected from each sampling point. Take part of the river bottom mud for freezing treatment, and control the freezing temperature at -18℃ and the freezing time at 4.5-6.0 h; 2) Thawing and melting the river sediment treated in step 1); 3) Centrifuging the river sediment treated in step 2) at a speed of 5000-6500 r / min and a time of 20-30 min; 4) Drying the river sediment treated in step 3) at a temperature of 80-85°C and a drying time of 2-3 h; 5) Mix the river sediment treated in step 4) with the sand at a depth of 20 cm on the surface, with the ratio of river sediment to sand being 1.5-6.0 kg / m 2 , to obtain mixed soil; 6) Compact the mixed soil, level the surface of the mixed soil, irrigate it thoroughly with water, and allow the mixed soil to stabilize for 1 month; 7) Test relevant indicators of the mixed soil after its properties have been stabilized.

2. The method for rapidly improving sandy soil by using river sediment according to claim 1, characterized in that: In step 7), the relevant indicators include clay, bulk density, organic carbon, total nitrogen, total phosphorus, heavy metal content, electrical conductivity and total bacteria count.

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