CN111500292B

CN111500292B - Composite type soil material and application thereof in preparing greening planting soil from river and lake dredging mud

Info

Publication number: CN111500292B
Application number: CN202010328997.9A
Authority: CN
Inventors: 黄达琦; 张耀; 吴邦硕; 周伟
Original assignee: China Construction Second Engineering Bureau Co Ltd
Current assignee: China Construction Second Engineering Bureau Co Ltd
Priority date: 2020-04-23
Filing date: 2020-04-23
Publication date: 2021-03-26
Anticipated expiration: 2040-04-23
Also published as: CN111500292A

Abstract

The invention discloses a composite type soil material and application thereof in preparing green planting soil from river and lake dredging mud, wherein the composite type soil material comprises the following components in parts by weight: 1-3 parts of cationic polyacrylamide, 4-6 parts of polyferric chloride, 20-40 parts of Portland cement, 25-45 parts of modified fly ash and straws, and an auxiliary agent: 1-2 parts of calcium formate, 2-4 parts of polyglutamic acid and 2-3 parts of activated humic acid. The invention integrates the functions of dehydration decrement, heavy metal stabilization, strength improvement, soil structure and nutrient improvement and the like for the first time, and avoids the repeated process operation when the traditional function is realized singly or compounded; the final outlet problem of the dredging mud treatment is solved in a resource utilization mode of greening planting soil products, the use requirements of planting greening soil in peripheral areas are met, the goal that non-point source pollution collected by river and lake dredging mud returns to the soil in a stable mode is achieved, and the method has good operable application prospect.

Description

Composite type soil material and application thereof in preparing greening planting soil from river and lake dredging mud

Technical Field

The invention belongs to the field of environmental waste treatment and resource utilization, relates to treatment and application of dredging mud, and particularly relates to a composite type soil material and application thereof in preparing greening planting soil from river and lake dredging mud.

Background

In the river and lake water environment treatment engineering, a large amount of dredging mud is inevitably generated in order to eliminate the internal pollution of the river and lake or recover the function of the river. The dredging mud with high water content and flow state has almost no strength, and the conventional disposal treatment mode not only occupies the land for a long time, but also has the pollution risks of nitrogen and phosphorus nutrient elements, heavy metals and the like to the surrounding water body and soil environment. The solution of the reduction, harmlessness and reclamation of the dredged mud is an urgent need in the solution of the problem of river and lake water environment treatment. Under the large background that marine mud throwing is limited and forbidden in all aspects and the land dredging mud stacking field is extremely tense, seeking reasonable and effective outlet becomes a 'neck' problem limiting the treatment and disposal of the mud throwing.

The vacuum preloading treatment of the dredging mud for land reclamation and construction is a common physical construction method for improving the bearing capacity of the dredging mud at present. The consolidation settlement of the dredging mud is accelerated by means of negative pressure, the construction period is 4-6 months more, the strength of the treated mud is generally 0.08-0.25MPa, and the treated mud is easily influenced by precipitation or surface runoff. The sludge solidification technology can obtain relatively higher and more stable unconfined compressive strength, and a framework is constructed for improving the strength of the dredging mud by greatly mixing inorganic materials such as cement, lime, fly ash, slag and the like, so that the conversion of the dredging mud to a soil material is finally realized. The 25-60% high-curing material mixing amount, the strong alkaline property of the soil material, the low unconfined compressive strength, the narrow application range of the soil material product and other factors of the technology determine that the curing material needs to be further integrated and optimized.

The traditional 'retting' process of river and lake dredging mud plays an important role in promoting the agricultural development process in a specific historical period. The dredged mud enriches the pollution loads of organic matters, nitrogen and phosphorus elements and the like from the water body, overcomes part of unfavorable physicochemical properties, and has the potential of being used as greening planting soil due to the own composition and nutrient content. If the conversion of the dredging mud to the greening planting soil can be realized through a proper engineering treatment means, on one hand, the soil requirements for reinforcing and repairing the bank protection slope required in the water environment treatment engineering are met, and on the other hand, the soil can be used as municipal greening and peripheral soil repairing base soil, so that the problem of the outlet of the dredging mud is fundamentally solved. In recent years, measures for solving the problem of treatment of dredging mud are diversified based on engineering requirements, and in terms of final treatment of dredging mud, there are two major categories of occupied site types such as abandonment and stockyard storage and resource utilization types such as building material utilization and soil utilization. The conventional building material treatment measures are obviously restricted by local requirements, the treatment efficiency of the dredging slurry and the like, and relatively speaking, the soil formation is a suitable development direction for the treatment of the dredging slurry in the current stage and in a long period of time in the future.

Therefore, the composite soil material is needed to be provided for conveniently and efficiently realizing the conversion from dredging slurry to planting green soil, and breaking through the requirement of the traditional treatment method on a large-capacity slurry storage primary-sedimentation site.

Therefore, the invention is especially provided.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides a composite type soil material and application thereof in preparing green planting soil from river and lake dredging mud.

The above purpose of the invention is realized by the following technical scheme:

a composite type soil chemical material comprises the following components in parts by weight: 1-3 parts of cationic polyacrylamide, 4-6 parts of polyferric chloride, 20-40 parts of Portland cement, 25-45 parts of modified fly ash and straws, and an auxiliary agent: 1-2 parts of calcium formate, 2-4 parts of polyglutamic acid and 2-3 parts of activated humic acid. Wherein, the cationic polyacrylamide can quickly flocculate fine particles in the dredging mud and quickly promote sedimentation; the polyferric chloride and the cationic polyacrylamide are matched to play a role in flocculation and precipitation; the portland cement can construct a dredging mud solidification framework, improve the unconfined compressive strength after solidification, stabilize the forms of pollutants such as heavy metals and the like, and weaken the leaching risk; the modified fly ash and the straws can enhance the hydration reaction of portland cement, improve the compaction degree and other properties of the solidified sludge, effectively control the dissolution of chloride ions after modification, reduce the salinity and alkalinity of the solidified soil, provide a carrier and a carbon source for the later stage microbial activity of a soil chemical engineering sequence, serve as a phosphorus source substrate fertilizer for plant growth, and improve the air-permeable water-retaining capacity of the soil; calcium formate is beneficial to promoting the rapid construction of a microbial system; the polyglutamic acid provides nutrient components for the growth and the propagation of microorganisms; the alkaline environment of the solidified sludge can be improved in a short time by activating the humic acid, and the germination rate of the plants is improved.

Further, the modified fly ash and the straws are prepared by the following method: taking crop straws, crushing and controlling the length within 5mm, mixing the fly ash and the crushed straws in a mass ratio of 1:2, adding 1-3 wt.% of sodium hydroxide solid, adding water in a solid-liquid ratio of 1kg:10L, carrying out hydrothermal reaction at the temperature of 250-350 ℃ for 5-15min, and carrying out solid phase residue separation, washing and drying to obtain the modified fly ash and the straws.

The composite type soil material is used for preparing greening planting soil from river and lake dredging mud.

Further, the pH value of the river and lake dredging mud is 6.0-8.5, and the water content is 90-99%.

The method for preparing the greening planting soil by using the composite type soil material for the river and lake dredging mud comprises the following steps:

step S1, the main agent and the auxiliary agent of the composite type soil material are separately and uniformly mixed according to the component configuration;

step S2, mixing and stirring the main agent and the auxiliary agent with the dredging mud to be treated simultaneously when in use, and entering a homogenizing pool for homogenizing;

step S3, the homogenized dredging mud pump to be processed is sent into a filter press;

and step S4, the filter-pressed mud cake enters a maintenance process, and the greening planting soil is obtained after screening and packaging.

Further, the amount of the composite type soil chemical material used in the step S2 is 10-30% of the mass of the dredging slurry.

Further, in the step S3, the filtering pressure of the filter press is 0.8-2.0MPa, and the filter pressing time is 5-15 min.

Further, the mud cake curing time in the step S4 is 8-14 d.

Has the advantages that:

1. the composite soil material and the using method provided by the invention are simple and economical in cost, and have excellent adaptability to the soil treatment of the dredged mud as greening planting soil; meanwhile, the method can be applied to the dredged slurry with high water content, thereby breaking through the requirement of the traditional treatment method on a large-capacity slurry storage primary sedimentation site.

2. The composite soil material provided by the invention has good tolerance and stabilization effect on dredging mud polluted by heavy metal to a certain extent, and can fully ensure that the leaching concentration of the heavy metal is lower than the limit value requirement of soil heavy metal content index in national standard for planting green soil (CJT 340-2011).

3. The invention integrates the functions of dehydration decrement, heavy metal stabilization, strength improvement, soil structure and nutrient improvement and the like for the first time, and avoids the repeated process operation when the traditional function is realized singly or compounded; the final outlet problem of the dredging mud treatment is solved in a resource utilization mode of greening planting soil products, the use requirements of planting greening soil in peripheral areas are met, the goal that non-point source pollution collected by river and lake dredging mud returns to the soil in a stable mode is achieved, and the method has good operable application prospect.

Drawings

FIG. 1 is a process flow chart of the composite type soil material for preparing green planting soil by using river and lake dredging mud.

Detailed Description

The following detailed description of the present invention is provided in connection with the accompanying drawings and examples, but not intended to limit the scope of the invention.

Example 1:

weighing raw material components of the composite type soil chemical material according to the following weight part ratio, wherein the main agent comprises 2.0kg of cationic polyacrylamide, 5.0kg of polyferric chloride, 30.0kg of Portland cement, and 35.0kg of modified fly ash and crushed straw; the auxiliary agents comprise 1.5kg of calcium formate, 3.0kg of polyglutamic acid and 2.5kg of activated humic acid.

The preparation method of the modified fly ash and the straws comprises the following steps: selecting crop straws which are easily obtained in peripheral areas such as corn, rice and the like, crushing and controlling the length within 5mm, mixing fly ash and the crushed straws in a mass ratio of 1:2, adding 1-3 wt.% of sodium hydroxide solid, adding water in a solid-liquid ratio of 1kg:10L, carrying out hydrothermal reaction for 10min at 300 ℃, and carrying out solid phase residue separation, washing and drying to obtain modified fly ash and straws.

Grinding the raw materials of the main agent and the auxiliary agent respectively to about 200 meshes, sieving, and respectively and uniformly mixing to obtain the main agent and the auxiliary agent of the composite type soil chemical material.

The test selects the dredging mud of the Wang Jia river in Yueyang City as a test sample, and the water content of the dredging mud is determined to be 95 percent. The prepared composite type soil material main agent, the prepared auxiliary agent and the dredging mud are sent into a homogenizing pool according to the weight ratio of 6:1:50 to be uniformly mixed, then the mixture is pumped into a plate-and-frame filter press to be subjected to dehydration and decrement treatment, the filtering pressure is 1.6MPa, the filter pressing time is 15min, the dehydrated mud cake enters a maintenance process, the maintenance time is 14d, and the process flow is shown in figure 1.

Example 2:

weighing raw material components of the composite type soil chemical material according to the following weight part ratio, wherein the main agent comprises 2.0kg of cationic polyacrylamide, 5.0kg of polyferric chloride, 30.0kg of Portland cement and 35.0kg of pulverized coal ash and pulverized straws (the mass ratio of the pulverized coal ash to the pulverized straws is 1: 2); the auxiliary agents comprise 1.5kg of calcium formate, 3.0kg of polyglutamic acid and 2.5kg of activated humic acid.

The test sample is the Yueyang Wangjia river dredging mud (the test sample and the test sample in example 1 are collected in the same place and in the same batch), and the water content of the dredging mud is determined to be 95%. The prepared composite type soil material main agent, the prepared auxiliary agent and the dredging mud are sent into a homogenizing pool according to the weight ratio of 6:1:50 to be uniformly mixed, then the mixture is pumped into a plate-and-frame filter press to be subjected to dehydration and decrement treatment, the filtering pressure is 1.6MPa, the filter pressing time is 15min, and the dehydrated mud cake enters a maintenance process for 14 d.

That is, this example differs from example 1 only in that unmodified fly ash and crushed straw are used.

Example 3:

weighing raw material components of the composite type soil chemical material according to the following weight part ratio, namely 7.0kg of polyferric chloride, 30.0kg of Portland cement, and 35.0kg of fly ash and crushed straw (the mass ratio of the fly ash to the crushed straw is 1: 2).

The test sample is the Yueyang Wangjia river dredging mud (the test sample and the test sample in example 1 are collected in the same place and in the same batch), and the water content of the dredging mud is determined to be 95%. The prepared composite soil material and the dredging mud are sent into a homogenizing pool according to the weight ratio of 7:50 to be uniformly mixed, then the mixture is pumped into a plate-and-frame filter press to be subjected to dehydration and decrement treatment, the filtering pressure is 1.6MPa, the filter pressing time is 15min, and the dehydrated mud cake enters a maintenance process for 14 d.

Example 4:

the unconfined compressive strength of the green planting soil obtained after the treatment of the embodiment 1-3 and main physicochemical properties related to national standards for green planting soil (CJT340-2011) and identification of hazardous waste identification standard leaching toxicity (GB 5085.3-2007) are measured. The physical and chemical properties of the treated soil material obtained in the different examples are contrasted with the required limit values of the general lawn in national standards for greening planting soil and identification standards for identifying leaching toxicity of hazardous wastes as shown in the following table.

The detection results in the table 1 show that the soil material obtained after the treatment of the example 1 can achieve higher unconfined compressive strength, and the incorporation of the flocculation material accelerates the consolidation and dehydration process of the dredging slurry and promotes the framework construction of the portland cement-based solidification material; under the synergistic action of the flocculation-solidification-soil-chemical materials, the produced greening planting soil material meets the requirements of various physicochemical properties in national standards for greening planting soil (CJT 340-2011). The composite soil chemical material provided by the invention has good tolerance and stabilization effect on dredging mud polluted by heavy metals to a certain extent, and can fully ensure that the leaching concentration of the heavy metals is lower than the limit value requirement of each heavy metal leaching concentration in 'hazardous waste identification standard leaching toxicity identification' GB 5085.3-2007. The comparison between the example 1 and the example 2 shows that the modified fly ash and the crushed straws have better heavy metal stabilizing effect than the common unmodified fly ash and the crushed straws, and are very suitable for the dredging mud with high heavy metal pollution.

Example 5:

the planting technique of the greening soil prepared in the embodiment 1 to 3 is used as a substrate for planting tall fescue, bermuda grass and green vegetables. The results of the planting tests on the treated soil material obtained in the different protocol tests are shown in the following table.

The greening planting soil prepared in example 1 is most beneficial to plant germination.

In conclusion, the composite soil material and the using method provided by the invention are simple and economical in cost, and have excellent adaptability to the soil treatment of the dredged mud as greening planting soil; meanwhile, the method can be applied to the dredged slurry with high water content, thereby breaking through the requirement of the traditional treatment method on a large-capacity slurry storage primary sedimentation site; the composite soil material has good tolerance and stabilization effect on dredged mud polluted by heavy metal to a certain degree, and can fully ensure that the leaching concentration of the heavy metal is lower than the limit value requirement of the soil heavy metal content index in the national standard for planting green soil (CJT 340-2011); the invention integrates the functions of dehydration decrement, heavy metal stabilization, strength improvement, soil structure and nutrient improvement and the like for the first time, and avoids the repeated process operation when the traditional function is realized singly or compounded; the final outlet problem of the dredging mud treatment is solved in a resource utilization mode of greening planting soil products, the use requirements of planting greening soil in peripheral areas are met, the goal that non-point source pollution collected by river and lake dredging mud returns to the soil in a stable mode is achieved, and the method has good operable application prospect.

The above-described embodiments are intended to be illustrative of the nature of the invention, but those skilled in the art will recognize that the scope of the invention is not limited to the specific embodiments.

Claims

1. The composite type soil chemical material is characterized by comprising the following components in parts by weight: 1-3 parts of cationic polyacrylamide, 4-6 parts of polyferric chloride, 20-40 parts of Portland cement, 25-45 parts of modified fly ash and straws, and an auxiliary agent: 1-2 parts of calcium formate, 2-4 parts of polyglutamic acid and 2-3 parts of activated humic acid; the modified fly ash and the straws are prepared by the following method: taking crop straws, crushing and controlling the length within 5mm, mixing fly ash and crushed straws in a mass ratio of 1:2, adding 1-3 wt.% of sodium hydroxide solid, adding water in a solid-liquid ratio of 1kg:10L, carrying out hydrothermal reaction at 250-350 ℃ for 5-15min, and carrying out solid-phase residue separation, washing and drying to obtain modified fly ash and straws.

2. Use of the composite type materialization of claim 1 for preparing greening planting soil from river and lake dredging mud.

3. Use according to claim 2, characterized in that: the pH value of the river and lake dredging mud is 6.0-8.5, and the water content is 90-99%.