Method for preparing greening soil by dehydrating and synchronously fermenting geotechnical tube bags from river and lake dredged mud

Abstract

The invention discloses a method for preparing green soil by dehydrating and synchronous fermentation of a river and lake dredged mud geotube bag, including: S1, pumping a porous biopolymer solution into a mud pipeline, the soil particles of the mud condense, and the mud and water are layered; adding a conditioning agent into the mud pipeline; S2, filling the treated mud into a geotube bag, and under the internal pressure and gravity of the geotube bag, the mud moisture is discharged; under the action of native microorganisms in the mud, the soil enters a micro-fermentation state; 3 to 5 days after the geotube bag is filled, the conditioning agent coating layer disintegrates under the action of moisture, coconut chaff and composite bacterial agent are evenly dispersed in the mud, coconut chaff promotes the decrease of the moisture content of the mud, and the concentrated mud formally enters the fermentation link; regularly transporting air into the geotube bag, and the moisture content of the mud further decreases during the fermentation process; S3, after 30-45 days, the dredged mud is fermented into green planting soil. This method significantly reduces engineering costs and improves the processing efficiency of the mud.

Description

Technical Field

[0001] The invention belongs to the technical field of river and lake bottom mud treatment, and in particular relates to a method for preparing greening soil by dehydrating a geotechnical tube bag and synchronously fermenting the bottom mud dredged from a river or lake. Background Art

[0002] The dredging of rivers, lakes, reservoirs and ponds will inevitably produce a large amount of high-water content sediment. If it is not treated, it will not only cause environmental pollution, but also occupy a large amount of land resources. Therefore, sediment post-treatment is crucial in dredging projects. Sediment post-treatment mainly includes two links: sediment dehydration and sediment disposal. Generally, the sediment dehydration and sediment volume reduction method is selected according to the final treatment method of the sediment.

[0003] Generally speaking, the dredged mud from rivers, lakes, reservoirs and ponds is rich in "nitrogen and phosphorus" nutrients and has good land utilization and resource properties. If the dehydrated mud can be used for greening or soil improvement, it can achieve a virtuous closed loop of the last kilometer of the dredging project, with significant economic and ecological benefits.

[0004] At present, there are methods for preparing green soil by dredging sludge, but most of them consider the sludge dehydration and sludge fermentation separately, which has the problems of long construction period and high cost. At present, there is no method that considers sludge dehydration and fermentation simultaneously. Summary of the invention

[0005] In order to solve the problems existing in the prior art, the present invention provides a method for preparing greening soil by dehydrating and simultaneously fermenting the dredged mud from rivers and lakes using geotechnical tube bags with high efficiency, environmental protection and low cost.

[0006] To this end, the present invention adopts the following technical solutions:

[0007] A method for preparing greening soil by dehydrating and simultaneously fermenting river and lake dredged mud geotube bags, comprising the following steps:

[0008] S1, sludge dehydration and simultaneous fermentation pretreatment, includes the following sub-steps:

[0009] S1-1, sediment dehydration and adjustment: Continuously pump porous biopolymer solution into the sediment pipeline. The amount of porous biopolymer is 10-30g per cubic meter of river and lake dredged sediment. Under the action of the pipeline mixer, the soil particles in the sediment are condensed and the mud and water are separated;

[0010] S1-2, adjustment of the carbon-nitrogen ratio of the sludge: adding a conditioning agent to the sludge pipeline, the amount of the conditioning agent is 1 to 1.6 kg per cubic meter of sludge;

[0011] S2, sludge dehydration and simultaneous fermentation:

[0012] 1) Initial stage: the sludge treated in step S1-2 is filled into the geotube bag. Under the action of the internal pressure and gravity of the geotube bag, the water in the sludge is discharged through the pores on the surface of the geotube bag. At the same time, under the action of the native microorganisms in the sludge, the soil enters a micro-fermentation state;

[0013] 2) Mid-term: 3 to 5 days after the geotube bag is filled, the coating layer of the conditioner in step S1-2 disintegrates under the action of water, and the coconut bran and composite bacterial agent inside the conditioner are evenly dispersed in the bottom mud. The water absorption of coconut bran causes the moisture content of the bottom mud to decrease; at the same time, under the action of the composite bacterial agent, the concentrated bottom mud officially enters the fermentation stage;

[0014] 3) Late stage: During the fermentation process (temperature is 25-30°C), air is regularly supplied to the geotube bag to promote aerobic fermentation of the bottom mud, and the moisture content of the bottom mud is further reduced during the fermentation process;

[0015] S3. Final disposal stage: The dredged sludge is fermented into green planting soil, and after passing the bag breaking, screening and testing, it is bagged.

[0016] The porous biopolymer used in the present invention is the "porous biopolymer for dehydration of river and lake ecological dredging sludge" recorded in Chinese invention patent ZL 201911275664.8 (authorization announcement number CN 111018282B).

[0017] The conditioning agent used in the present invention is a special conditioning agent for dehydration and synchronous fermentation of river and lake dredged sludge, which is in granular form and includes a core, an outer shell and a coating from the inside to the outside, wherein: the core has a mass fraction of 1.5 to 2 parts and is pressed from coconut bran, and the density of the pressed coconut bran is 0.45-0.50 g / cm 3 The shell is composed of natural sand, corn cob powder and composite bacterial agent, and the mass proportions of the three are 6-8 parts, 2-2.5 parts and 0.5-1 parts respectively, wherein the fineness modulus of the natural sand is 2.5-3.0, and the mass proportion ratio of the kernel to the shell is 1:(5-6); the composite bacterial agent is composed of thermophilic streptococci and thermophilic actinomycetes, and the mass ratio of the two is 1:1; the coating is composed of vinyl acetate-ethylene copolymer and polyvinyl alcohol, and the mass proportions of the two are 0.6-0.8 parts and 0.15-0.2 parts respectively.

[0018] Preferably, the diameter of the conditioning agent particles is 4 to 6 mm and the density is 1.1 to 1.2 g / cm 3 The coconut bran is prepared from coconut shell fiber powder, the coconut shell fiber powder has a medium degree of decomposition, an ash ratio of 6% to 8%, and a bulk density of 0.1 to 0.15 g / cm 3, EC value is 1.30-2.60mS / cm; after washing with clean water 3 to 5 times, control the EC value of coconut bran to ≤0.5mS / cm, and then dry it to a moisture content of ≤15%. The corn cob powder is obtained by grinding the cobs of corn after removing the kernels through a 120-mesh sieve, and the moisture content is 3 to 5wt%. The water content of the composite bacterial agent is ≤8wt%, and the effective viable count is ≥2 billion CFU / gram. The density of the conditioning agent particles is 1.1 to 1.2g / cm 3 .

[0019] The preparation method of the above-mentioned conditioning agent comprises the following steps:

[0020] S1, kernel preparation: the coconut bran is fed into a double-roll shredder pelletizer and pressed into a ball shape at a pressure of 2.5-3 MPa for 5-10 minutes;

[0021] S2, shell preparation: natural sand, corn cob powder, and composite bacterial agent are mixed evenly according to the above raw material ratio to obtain shell material; then the kernel and the shell material are put into a shot blasting granulator according to the proportion to be shelled and granulated, and the particle diameter is 4 to 6 mm;

[0022] S3, coating preparation: the vinyl acetate-ethylene copolymer and polyvinyl alcohol are mixed evenly according to a ratio, and then the particles obtained in step S2 are added and placed in a coating machine for coating, and the coating thickness is 15-20 μm.

[0023] The method of the present invention can, on the one hand, disintegrate the conditioning agent when the geotube bag does not drain water obviously (i.e., 3 to 5 days after filling), so as to quickly absorb the water in the bottom mud and shorten the dehydration period of the geotube bag. On the other hand, the amount of conditioning agent can be adjusted according to the test results of the bottom mud before the work to adjust the C / N ratio of the concentrated bottom mud to meet the technical requirements of the subsequent bottom mud fermentation green soil. The water content of the river and lake dredged bottom mud in the present invention is about 95%, and the density is 1.12g / cm 3 .

[0024] The method of the present invention has the following advantages and positive effects:

[0025] 1. During the filling of geotube bags, add the special conditioner for sediment fermentation directly into the mud pipeline to ensure that the fermentation material and sediment are fully mixed to avoid incomplete fermentation;

[0026] 2. Laying high-strength PVC air supply branch pipes in the geotube bag bottom mud can, on the one hand, provide ventilation for the later fermentation of the bottom mud, and on the other hand, can serve as a water-permeable support material at the bottom of the geotube bag. Compared with the pebble water-permeable support material of the traditional geotube bag dehydration site, it is lower in cost and more environmentally friendly;

[0027] 3. The traditional geotube dehydration process often leaves a part of space after the bottom mud is dehydrated. The present invention makes full use of this part of the volume to ferment the bottom mud, maximizes the use of the geotube, and saves the cost of the fermentation site;

[0028] 4. The entire process is handled in a closed manner and will not cause secondary pollution.

[0029] 5. The dehydration and simultaneous fermentation of sludge are realized, which effectively shortens the whole process from dredging sludge to greening soil. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a flow chart of the method for preparing greening soil by dehydrating and synchronously fermenting geotechnical tube bags of river and lake dredged mud of the present invention;

[0031] Figure 2 It is a structural diagram of the geotube bag sludge dehydration and synchronous fermentation system;

[0032] Figure 3 It is a structural diagram showing the positional relationship between the geotube bag and the air supply branch pipe.

[0033] In the figure:

[0034] 1. Mud pipeline; 2. Porous biopolymer dosing equipment; 3. Pipeline mixer; 4. Conditioning agent dosing equipment;

[0035] 5. Gate valve; 6. Leather hose; 7. Filling port; 8. Geotextile tube bag; 9. Air supply branch pipe; 10. Branch pipe valve;

[0036] 11. Gas supply pipe; 12. Air compressor; 13. Two cloths and one membrane; 14. Ditch; 15. Delivery pipeline; 16. Residual water treatment equipment DETAILED DESCRIPTION

[0037] The method of the present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0038] The water content of the river and lake dredged mud in this embodiment is about 95%, and the density is 1.12g / cm 3 about.

[0039] Example 1

[0040] Relying on a river dredging project in Yichun City, Heilongjiang Province, dredged mud geotube bags were dehydrated and fermented simultaneously to prepare green soil. First, mud samples were taken from the dredging area, and the physical and chemical properties of the mud were tested and analyzed. It was determined that the water content of the original river mud was 35%, ammonia nitrogen was 56.4 mg / Kg, total nitrogen was 1850 mg / Kg, and organic matter was 42.3 mg / Kg. Then, the mud was transported from the dredging ship to the dehydration area through the mud pipeline. The moisture content of the mud in the mud pipeline was about 95%.

[0041] The porous biopolymer used in this embodiment is the porous biopolymer prepared in Example 1 of Chinese invention patent ZL 201911275664.8 (authorization announcement number CN 111018282B).

[0042] The conditioning agent used in this example was prepared by the following method:

[0043] ① Kernel production: First, wash the coconut bran with clean water for 5 times, control the EC value not to exceed 0.5mS / cm, then dry it to a moisture content of 15%, send the dried coconut bran to a roller shredder, and press it into a ball with a diameter of 2-4mm at a pressure of 2.5Mpa for 8 minutes. The density after compression is about 0.45g / cm 3 ;

[0044] ② Shell production: natural sand, corn cob powder, and composite bacterial agent are mixed evenly in a ratio of 6 parts, 2 parts, and 0.5 parts, and then 1 part of the kernel material and 6 parts of the shell material are put into a shot blasting granulator for shelling and granulation, and the particle diameter is 4-6mm;

[0045] ③ Coating preparation: vinyl acetate-ethylene copolymer and polyvinyl alcohol are uniformly mixed in a ratio of 0.6:0.15 by mass, and then the particles obtained in step ② are added and placed in a coating machine for coating. The coating thickness is 20 μm.

[0046] See also Figure 1-Figure 3 The method for preparing greening soil by dehydrating the dredged mud from rivers and lakes through geotube bags and performing simultaneous fermentation comprises the following steps:

[0047] S1, sludge dehydration and synchronous fermentation pretreatment: The porous biopolymerization agent dosing device 2 continuously pumps the aqueous solution of the porous biopolymerization agent into the sludge conveying pipeline 1, and the amount of the porous biopolymerization agent used is 20g / m 3 Under the action of the pipeline mixer 3, the soil particles in the bottom mud condense and mud-water stratification occurs; then the solid conditioner is added into the mud pipeline 1 through the conditioner adding device 4, and 1.6 kg of conditioner is required for each cubic meter of bottom mud.

[0048] S2, sludge dehydration and synchronous fermentation:

[0049] Initial stage: the bottom mud in step S1 is sent into the geotube 8 through the gate valve 5, the hose 6 and the filling port 7. During the filling process, under the action of the internal pressure and gravity of the tube bag, the water in the bottom mud is discharged through the pores of the geotube bag, and at the same time, the soil enters a micro-fermentation state under the action of the native microorganisms in the bottom mud;

[0050] Mid-term: 5 days after the geotube bag is filled, the coating of the conditioning agent in step S1 finally disintegrates under the action of water. After the disintegration, the coconut bran and the composite bacterial agent inside the conditioning agent are evenly dispersed into the bottom mud. The water absorption of the coconut bran causes the moisture content of the bottom mud to decrease. At the same time, under the action of the composite bacterial agent, the concentrated bottom mud officially enters the fermentation stage;

[0051] Later stage: during the fermentation process (temperature is 25-30°C), air is transported to the inside of the geotube bag through the air supply branch pipe 9 at the bottom of the geotube bag 8 every 3 days to promote aerobic fermentation of the bottom mud. The moisture content of the bottom mud further decreases during the fermentation process.

[0052] The total duration of the above steps S1 and S2 is 45 days.

[0053] like Figure 2 As shown, the air supply branch pipe 9 is connected to the air compressor 12 through the air supply main pipe 11, and air is supplied by the air compressor. A branch pipe valve 10 is installed on the pipeline between the air supply main pipe and the air supply branch pipe. A plurality of air supply branch pipes 9 are provided at the bottom of each geotube bag 8 (4 are shown in the figure). A plurality of air supply holes are provided on the air supply branch pipe 9 at the bottom of the geotube bag 8, and the air supply holes are wrapped with non-woven fabric to prevent impurities falling out of the geotube bag 8 from clogging the air supply holes. Two cloths and one membrane are laid on the site, and the air supply branch pipe 9 is arranged on the two cloths and one membrane. The water flowing out of the geotube bag 8 converges into the ditch 14, and is sent to the residual water treatment equipment through the conveying pipe 15. The water treated by the residual water treatment equipment 16 can be replenished into the dredging area.

[0054] In this embodiment, the air supply branch pipe 9 is a PVC pipe with a diameter of 20-30 mm and a compressive strength of 1.6 Mpa, arranged parallel to the axis of the geotextile tube bag, and a tube spacing of 20 cm. This creates a drainage channel at the bottom of the geotextile tube bag to avoid water accumulation at the bottom, and can also provide oxygen for the bottom mud fermentation process.

[0055] S3, final disposal stage: the dredged sludge is fermented into green planting soil, and then bagged after passing the bag breaking, screening and testing.

[0056] Comparative Example 1

[0057] Relying on a river dredging project in Yichun City, Heilongjiang Province, the bottom mud geotextile bag dehydration test was first carried out, and the bottom mud fermentation test was carried out after the dehydration was completed. The specific implementation steps are as follows:

[0058] S1, Analysis of sediment in dredging area: Samples of sediment in the dredging area were collected to conduct testing and analysis of the physical and chemical properties of the sediment. It was determined that the moisture content of the original sediment in the river was 35%, the ammonia nitrogen was 56.4 mg / Kg, the total nitrogen was 1850 mg / Kg, and the organic matter was 42.3 mg / Kg.

[0059] S2, dredging sludge pipeline transportation link: The sludge is transported from the dredging ship to the dewatering area through the sludge pipeline. The moisture content of the sludge in the sludge pipeline is about 95%.

[0060] S3, sediment conditioning step: anionic polyacrylamide is added into the sludge pipeline through the conditioning agent adding equipment, with the dosage of 30-45ppm. The anionic polyacrylamide and the sediment are fully mixed and reacted under the action of the pipeline mixer.

[0061] S4, geotube bag filling process: Under the action of the internal pressure of the mud conveying pipeline, the bottom mud in step S3 is filled into the geotube bag. After the bottom mud enters the geotube bag, the mud and water are quickly separated, and the tail water is discharged from the pores on the surface of the geotube bag.

[0062] S5, Sediment fermentation: 90 days after the geotube bag was filled, the moisture content of the sediment in the geotube bag was tested to be reduced to 70%, which met the requirements for the fermentation of sediment to prepare green soil. The sediment in the geotube bag was taken out, turned over and crushed, and then a certain proportion of fermentation auxiliary materials (straw, compound bacteria, starch, etc.) were added, and finally transported to the fermentation tank for fermentation.

[0063] S6, final disposal stage: After 45 days, at a temperature of 30°C, the dredged sludge is fermented into green planting soil, and finally the bags are broken, screened and tested before being bagged.

[0064] Compared with Comparative Example 1, the total construction period of Example 1 is only 45 days, which is significantly shortened.

Claims

1. A method for preparing green soil by dehydrating and simultaneously fermenting river and lake dredged mud geotube bags, comprising the following steps: S1, sludge dehydration and simultaneous fermentation pretreatment, includes the following sub-steps: S1-1, sediment dehydration and adjustment: Continuously pump porous biopolymer solution into the sediment pipeline. The amount of porous biopolymer is 10-30g per cubic meter of river and lake dredged sediment. Under the action of the pipeline mixer, the soil particles in the sediment are condensed and the mud and water are separated; S1-2, adjustment of the carbon-nitrogen ratio of the sludge: adding a conditioning agent to the sludge pipeline, the amount of the conditioning agent is 1 to 1.6 kg per cubic meter of sludge; S2, sludge dehydration and simultaneous fermentation: Initial stage: the treated sediment in step S1-2 is filled into the geotube bag. Under the action of the internal pressure and gravity of the geotube bag, the water in the sediment is discharged through the pores on the surface of the geotube bag. At the same time, under the action of the native microorganisms in the sediment, the soil enters a micro-fermentation state; Mid-term: 3 to 5 days after the geotube bag is filled, the coating layer of the conditioner in step S1-2 disintegrates under the action of water, and the coconut bran and composite bacterial agent inside the conditioner are evenly dispersed in the bottom mud. The water absorption of coconut bran causes the moisture content of the bottom mud to decrease; at the same time, under the action of the composite bacterial agent, the concentrated bottom mud officially enters the fermentation stage; Later stage: During the fermentation process, air is regularly delivered into the geotube bag to promote aerobic fermentation of the bottom mud, and the moisture content of the bottom mud is further reduced during the fermentation process; S3, final disposal stage: dredged sludge is fermented into greening planting soil, and after being tested and sieved, it is bagged; The conditioning agent in step S1-2 is in granular form, and includes a core, a shell and a coating from the inside out, wherein: the core has a mass fraction of 1.5 to 2 parts and is pressed from coconut husk, and the density of the pressed coconut husk is 0.45-0.50 g / cm 3 The shell is composed of natural sand, corn cob powder and composite bacterial agent, and the mass proportions of the three are 6-8 parts, 2-2.5 parts and 0.5-1 parts respectively, wherein the fineness modulus of the natural sand is 2.5-3.0, and the mass proportion ratio of the kernel to the shell is 1:(5-6); the composite bacterial agent is composed of thermophilic streptococci and thermophilic actinomycetes, and the mass ratio of the two is 1:1; the coating is composed of vinyl acetate-ethylene copolymer and polyvinyl alcohol, and the mass proportions of the two are 0.6-0.8 parts and 0.15-0.2 parts respectively.

2. The method according to claim 1, characterized in that: The diameter of the conditioning agent particles is 4-6 mm and the density is 1.1-1.2 g / cm 3 .

3. The method according to claim 1, characterized in that: The coconut bran is prepared from coconut shell fiber powder, the coconut shell fiber powder has a medium degree of decomposition, an ash ratio of 6% to 8%, and a bulk density of 0.1 to 0.15 g / cm 3 , EC value is 1.30-2.60mS / cm; after washing with clean water 3 to 5 times, control the EC value of coconut bran to ≤0.5mS / cm, and then dry it to a moisture content of ≤15%.

4. The method according to claim 1, characterized in that: The corncob powder is obtained by grinding corn cobs after removing the kernels and passing them through a 120-mesh sieve, and has a water content of 3-5 wt%.

5. The method according to claim 1, characterized in that: The water content of the composite bacterial agent is ≤8wt%, the effective viable bacteria count is ≥2 billion CFU / g, and the density of the conditioning agent particles is 1.1-1.2g / cm 3 .

6. The method according to claim 1, characterized in that The preparation method of the conditioning agent comprises the following steps: S1, kernel preparation: the coconut bran is fed into a double-roll shredder pelletizer and pressed into a ball shape at a pressure of 2.5-3 MPa for 5-10 minutes; S2, shell preparation: natural sand, corn cob powder, and composite bacterial agent are mixed evenly according to the above raw material ratio to obtain shell material; then the kernel and the shell material are put into a shot blasting granulator according to the proportion to be shelled and granulated, and the particle diameter is 4 to 6 mm; S3, coating preparation: the vinyl acetate-ethylene copolymer and polyvinyl alcohol are mixed evenly according to a ratio, and then the particles obtained in step S2 are added and placed in a coating machine for coating, and the coating thickness is 15-20 μm.

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