A capping layer for in situ remediation of contaminated sediments

Abstract

The application discloses a covering layer for in-situ remediation of bottom sediment pollution, which comprises a covering layer laid on the surface of the bottom sediment and formed by composite particles containing treatment components, for blocking and treating the pollutants in the bottom sediment; an aquatic plant layer located on the covering layer, and the plant root system of the aquatic plant layer extends into the bottom sediment through the covering layer; bacteria dispersed in the covering layer for treating the pollution components and promoting the growth of the plants; and benthic animals which are active in the bottom sediment and form an ecological cycle with the plants of the plant layer for promoting the mixing of the treatment components in the composite particles with the bottom sediment. The covering layer provided by the application has a better remediation effect without destroying the ecological environment of the bottom sediment.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of water environment treatment, in particular to a covering layer for in-situ remediation of contaminated sediment. BACKGROUND

[0002] With the rapid development of industrialization and urbanization, a large amount of pollutants are discharged into water bodies, leading to a decline in water environmental quality and an increasingly serious problem of sediment pollution. Sediment is an important component of water bodies, which not only provides habitat for aquatic organisms, but also purifies water quality through adsorption, sedimentation and other ways. However, when the sediment is contaminated, its ecological environment function will be seriously affected, and even the ecological balance of water bodies may be broken. Therefore, how to effectively treat and remediate contaminated sediment has become an important issue in the fields of environmental engineering, water treatment and ecological remediation.

[0003] Currently, there are mainly two ways to treat and remediate contaminated sediment: one is ex-situ remediation, which involves excavating and transporting contaminated sediment to other places for treatment. Although this method can effectively remove pollutants, it has a large amount of engineering and high cost, and may cause secondary pollution. The other is in-situ remediation, which involves remediation in the original position of contaminated sediment. This method not only reduces the amount of engineering and cost, but also avoids secondary pollution, and is a relatively ideal remediation method.

[0004] In-situ covering is a commonly used in-situ remediation method, which involves constructing a covering layer above the contaminated sediment to prevent the spread of pollutants into the overlying water body. However, the existing in-situ covering technology still has some problems. First, the traditional covering material is mainly a single chemical or mineral material, which has poor impact resistance and stability, and is easily moved or damaged under the action of water flow, affecting the remediation effect. Second, the traditional covering material often cannot effectively dispose of the pollutants in the contaminated sediment, resulting in poor remediation effect. Third, the traditional covering material has poor blocking ability for pollutants, and often requires a large laying thickness to reduce the spread of pollutants in the contaminated sediment. The increase in laying thickness will seriously affect the water storage function of the water body. Finally, the traditional covering material may also have negative effects on the ecological environment of the sediment, such as changing the physical properties of the sediment and affecting the biodiversity in the sediment. SUMMARY

[0005] Therefore, an in-situ remediation structure with better remediation effect without damaging the ecological environment of the sediment is provided.

[0006] An in-situ remediation covering layer for contaminated sediment, comprising:

[0007] a covering layer laid on the surface of the sediment and formed by composite particles containing treatment components, for blocking and treating pollutants in the sediment;

[0008] an aquatic plant layer on the blanket layer, and plant root systems of the aquatic plant layer extending through the blanket layer into the sediment;

[0009] bacteria dispersed in the blanket layer for treating the contaminated components and promoting plant growth;

[0010] benthic animals active in the sediment and forming an ecological cycle with the plants of the plant layer for promoting mixing of the treated components in the composite particles with the sediment.

[0011] The following also provides several optional modes, but not as additional limitations to the above general scheme, merely further supplements or preferences, and in the absence of technical or logical contradictions, each optional mode can be combined with the above general scheme alone, and can also be combined between multiple optional modes.

[0012] Optionally, the composite particles are of a core-shell structure, wherein the material of the core is at least one of limestone, volcanic stone, and gravel, the particle size of the core material is 5-10 mm, the material of the shell includes a treatment component and a water-absorbing and swelling component, the treatment component includes one of a lanthanum salt, a sulfide, and zero-valent iron, and an adsorption component, the adsorption component is activated carbon, and the water-absorbing and swelling component is at least one of bentonite, swelling clay, and clay mineral. Optionally, the thickness of the blanket layer is calculated using the following formula:

[0013] T=K*1.15*S*C2 / C1+0.5*h / i

[0014] In the formula, T is the thickness of the blanket layer;

[0015] C1 is the cohesion of the blanket material;

[0016] C2 is the cohesion of the sediment;

[0017] S is the maximum disturbance depth of the benthic animals without the blanket layer, in cm;

[0018] h is the water depth, in cm;

[0019] i is an empirical value, and the value range is 70-80;

[0020] K is a disturbance coefficient, and the value of K is as follows:

[0021] When C2 / C1>0.6, and ρ k >150 ind / m 2 , K=0.8;

[0022] When C2 / C1≤0.6, and 100 ind / m 2 ≤ρ k <150 ind / m 2K=0.6 when t=0.5;

[0023] p k The habitat density of the benthic animals.

[0024] Optionally, the plant seed of the aquatic plant layer is 40-50g per square meter of water area, and the plant of the aquatic plant layer is at least one of Vallisneria, Ceratophyllum, Potamogeton.

[0025] Optionally, the plant seed of the aquatic plant layer is mixed with the shell material of the composite particle, and then mixed with the core material to form the composite particle.

[0026] Optionally, the bacteria are any combination of the following:

[0027] a. Microbacterium, Methylophaga WM-1, Bacillus kudriavzevii, Bacillus amyloliquefaciens, Oceanobacillus iheyensis;

[0028] b. Bacillus subtilis, Bacillus methylicus, Bacillus licheniformis.

[0029] Optionally, the bacteria are mixed with the shell material of the composite particle, and then mixed with the core material to form the composite particle, or the bacteria are mixed with the core material of the composite particle, and then mixed with the shell material to form the composite particle.

[0030] Optionally, the benthic animals are at least one of aquatic insect larvae, aquatic mollusks, and aquatic crustaceans, and the habitat density of the benthic animals is not less than 100 ind / m 2 .

[0031] Optionally, the adsorption component in the composite particle is 1-2kg per square meter of water area.

[0032] Optionally, the composite particle is put into the predetermined water area by using a throwing device, and the throwing device comprises:

[0033] A berth, wherein a GPS positioning system is arranged on the berth;

[0034] A bunker arranged on the berth and used for storing the composite particle;

[0035] A spraying barrel connected with the bunker and capable of adjusting the spraying direction and flow.

[0036] Compared with the prior art, the present application has at least the following beneficial effects:

[0037] (1) The water-absorbing and expanding component in the shell material of the composite particles forming the blanket layer expands in the water body, filling the gaps between the cores, forming a relatively impermeable layer, which can effectively block the release of pollutants from the sediment layer to the overlying water, even if the blanket layer is very thin.

[0038] (2) The plant seeds in the shell material of the composite particles forming the blanket layer are increased, and the mutual entanglement of the plant roots and the cores is utilized to enhance the shear strength of the blanket layer, thereby further improving the impact resistance of the blanket layer.

[0039] (3) The treatment component in the composite particles forming the blanket layer can effectively treat the pollutants in the sediment, improving the repair effect.

[0040] (4) The ecological cycle of benthic animals and aquatic plants promotes the growth of each other, and the benthic animals can promote the mixing of pollutants in the sediment and the treatment component in the composite particles when they move, for in-situ treatment of the contaminated sediment, realizing ecological restoration and avoiding the negative impact of traditional covering materials on the ecological environment of the sediment.

[0041] (5) The in-situ repair method is adopted, which does not need to excavate and transport the contaminated sediment, greatly reducing the engineering quantity and cost, and also avoiding the risk of secondary pollution;

[0042] (6) The laying thickness is thinner, avoiding the impact on the water storage capacity of the water body. BRIEF DESCRIPTION OF DRAWINGS

[0043] Figure 1 is a schematic diagram of the composite particles in the present application;

[0044] Figure 2 is a schematic diagram of the composite particles in the present application just put into the water area;

[0045] Figure 3 is a schematic diagram of the composite particles in the present application after hydration in the water area;

[0046] Figure 4 is a schematic diagram of the composite particles in the present application after the growth of plants in the water area;

[0047] Figure 5 is a schematic diagram of the composite particles in the present application after the growth of plants in the water area and the activity of benthic animals;

[0048] Figure 6 is a comparison diagram of the influence of the blanket layer formed by the composite particles in the present application and the blanket layer in the prior art on the concentration of PCBs;

[0049] Figure 7 is a comparison diagram of the influence of the blanket layer formed by the composite particles in the present application and the blanket layer in the prior art on the concentration of Pb;

[0050] Figure 8 Comparison of root length after 3 months with and without inoculants.

[0051] In the figure: 1, cover layer; 2, sediment; 3, aquatic plant layer; 4, benthic animals; 11, treatment component; 12, water-absorbing and expanding component; 13, core; 14, plant seeds. DETAILED DESCRIPTION

[0052] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0053] In order to better describe and illustrate the embodiments of the present application, one or more drawings can be referred to, but additional details or examples used to describe the drawings should not be considered as limiting the scope of any one of the inventions, the presently described embodiments or the preferred modes of the present application.

[0054] It should be noted that when a component is referred to as being "connected" with another component, it can be directly connected with the other component or there can be a middle component. When a component is referred to as being "disposed on" another component, it can be directly disposed on the other component or there can be a middle component.

[0055] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0056] Referring to Figure 5 As shown in the figure, a cover layer for repairing sediment pollution in situ, comprising:

[0057] The cover layer 1 is laid on the surface of the sediment 2 and is formed by composite particles containing a treatment component, for blocking and treating pollutants in the sediment 2;

[0058] The aquatic plant layer 3 is located on the cover layer 1, and the plant roots of the aquatic plant layer 3 extend through the cover layer 1 into the sediment 2;

[0059] Bacteria are dispersed in the cover layer 1 for treating the pollution component and promoting plant growth;

[0060] The benthic animals 4 are active in the bottom mud 2 and form an ecological cycle with the plants of the plant layer to promote the mixing of the treatment components in the composite particles with the bottom mud 2.

[0061] In the present application, the cover layer 1 is laid on the contaminated bottom mud 2, and the cover layer 1 is formed by the composite particles containing the treatment components. After the composite particles are put into the water area in the form of particles, they gradually sink in the water due to the large specific gravity of the composite particles until they cover the contaminated bottom mud 2. The composite particles contain water-swelling components, and the composite particles gradually swell after being exposed to water. After being deposited above the bottom mud 2, the water-swelling components fully swell to fill the gaps between the composite particles, so that the cover layer 1 is continuously distributed as a whole. Water cannot easily pass through the cover layer 1, and the pollutants in the bottom mud 2 cannot easily diffuse through the cover layer 1 into the water above the cover layer 1.

[0062] The cover layer 1 contains treatment components for pollutants, so even if pollutants enter the cover layer 1, the treatment components can be used for adsorption or other forms of treatment to prevent the pollutants from further entering the water above the cover layer 1.

[0063] In order to stabilize the coverage of the cover layer 1, the aquatic plant layer 3 is provided. The aquatic plants are put into the water in the form of plant seeds. During the growth of the aquatic plants, the root systems of the aquatic plants are intertwined with each other in the cover layer 1 and extend into the bottom mud 2. The fixing effect of the root systems of the aquatic plants further stabilizes the position of the cover layer 1.

[0064] The aquatic plants can be plants with deep root systems and or creeping stems. See Figure 4 As shown, through the mutual intertwining of the plant root systems and the composite particles, an impact-resistant layer is formed, which can effectively improve the impact resistance and stability of the cover layer and effectively prevent movement or damage caused by water flow.

[0065] The addition of bacteria in the cover layer 1 can not only treat organic matter in the contaminated components and promote the decomposition of the organic matter, but also produce substances such as ammonia nitrogen and phosphorus to promote plant growth.

[0066] The benthic animals 4 and the aquatic plants form an ecological cycle and promote each other's growth. Moreover, when the benthic animals 4 are active in the bottom mud 2, they can fully mix the pollutants with the composite particles, and the treatment components in the composite particles are fully mixed with the pollutants, so that the treatment of the pollutants by the treatment components is more efficient.

[0067] After the cover layer is formed, regular observation and maintenance are carried out, and the aquatic plants and the benthic animals 4 are increased or reduced as needed to ensure the normal growth of the aquatic plants and the benthic animals 4.

[0068] The covering layer for repairing the pollution of the bottom mud 2 can effectively reduce the negative influence on the ecological environment of the bottom mud 2, does not change the physical properties of the bottom mud 2, and does not affect the biological diversity in the bottom mud 2, and meanwhile, the ecological environment of the bottom mud 2 can be significantly improved through the growth of the aquatic plants, and the ecological restoration of the bottom mud 2 is promoted.

[0069] Referring to Figure 1 As shown in the figure, the composite particle is a core-shell structure, wherein the material of the core 13 is at least one of limestone, volcanic stone and gravel, the particle size of the core material is 5-10mm, the material of the shell includes the treatment component 11 and the water-absorbing and swelling component 12, the treatment component includes one of lanthanum salt, sulfide and zero-valent iron, and the adsorption component is activated carbon, and the water-absorbing and swelling component is at least one of bentonite, swelling clay and clay mineral.

[0070] The composite particle is a core-shell structure, referring to Figure 2 As shown in the figure, when the composite particle is just put into the water body, there is a gap between each composite particle, referring to Figure 3 As shown in the figure, after the composite particle is put into the water, the water-absorbing and swelling component in the shell swells after absorbing water, fills the gap between the cores, forms a continuous distribution of the covering layer, and meanwhile, the treatment component in the shell is dispersed in the gap of the core, and the pollutants in the contacted bottom mud are treated.

[0071] After the composite particle is put into the water, the treatment component in the shell is gradually released, and the treatment component and the adsorption component continuously adsorb and treat the pollutants in the water in the process of entering the water and settling in place, so as to reduce the concentration of the pollutants in the water body.

[0072] The specific gravity of the material of the core in the composite particle is large, so that the composite particle can be quickly settled on the bottom mud, and has a certain anti-impact capacity, after the composite particle is settled, each component in the shell material is gradually diffused into the covering layer structure under the driving of the water-absorbing and swelling effect of the shell structure, but the structure of the core is always stable, the root system of the aquatic plant is wound and connected to the core, and the anti-impact capacity and stability of the covering layer are improved.

[0073] The thickness of the covering layer should be appropriate, which can effectively cover and block the bottom mud, the root system of the aquatic plant can smoothly penetrate the covering layer and penetrate into the bottom mud, and meanwhile, the activity of the benthic animals is not affected.

[0074] Through test observation, in the case that there is no covering layer, the maximum disturbance depth of the water worms, crayfish, snails and loaches in the silt is 6cm, 18cm, 12cm and 16cm respectively, under the condition of the same water depth and the same silt thickness, the influence of the migration activity of the benthic animals on the covering layer with different thicknesses is observed, so as to ensure that the migration of the benthic animals will not damage the covering layer.

[0075] Through the experimental data collection and formula coupling, the thickness formula of the cover layer is obtained, and the thickness of the cover layer is calculated by using the following formula:

[0076] T = K * 1.15 * S * C2 / C1 + 0.5 * h / i

[0077] In the formula: T is the thickness of the cover layer;

[0078] C1 is the cohesion of the cover material;

[0079] C2 is the cohesion of the bottom mud;

[0080] S is the maximum disturbance depth of benthic animals without a cover layer, in cm;

[0081] h is the water depth, in cm;

[0082] i is an empirical value, ranging from 70 to 80;

[0083] K is the disturbance coefficient, and the value of K is as follows:

[0084] When C2 / C1>0.6, and ρ k >150ind / m 2 , K = 0.8;

[0085] When C2 / C1≤0.6, and 100ind / m 2 ≤ρ k <150ind / m 2 , K = 0.6;

[0086] ρ k is the habitat density of benthic animals.

[0087] When the habitat density of benthic animals is less than 100ind / m 2 , it is supplemented to 100ind / m 2 by releasing.

[0088] Taking a certain artificial lake project as an example, C2 / C1 = 0.83, and ρ k = 175ind / m 2 , the water depth is 10m, the released benthic animals are snails, and the maximum disturbance depth of snails without a cover layer is 12cm, and the thickness T of the cover material can be calculated as follows:

[0089] T = 0.8 * 1.15 * 12 * 0.83 + 0.5 * 1000 / 70

[0090] = 9.16 + 7.14

[0091] = 16.30cm

[0092] T=0.8*1.15*12*0.83+0.5*1000 / 80

[0093] =9.16 + 6.25

[0094] =15.41cm

[0095] Therefore, the thickness of the artificial lake cover can be between 15.41 and 16.30 cm.

[0096] See Figure 7 As shown, Figure 7 The left-middle region, from bottom to top, includes a bottom sediment layer, a composite hydrated fossil layer, a fine sand layer, and a water layer. The composite hydrated fossil layer is a cover layer formed by composite particles. Figure 7 The right-hand area consists of a bottom sediment layer, a fine sand layer, and a water layer from bottom to top. Hollow circles indicate that when there is a composite hydration layer, the concentration of PCBs in the water layer is extremely low. In other words, a relatively thin cover layer can effectively block and treat PCBs in the bottom sediment. Solid dots indicate that when there is only a fine sand layer, even if the thickness of the fine sand layer is increased, it cannot effectively block and treat PCBs in the bottom sediment.

[0097] See Figure 8 As shown, Figure 8 The left-middle region, from bottom to top, includes a bottom mud layer, a composite hydrated fossil layer, a fine sand layer, and a water layer. The composite hydrated fossil layer is a cover layer formed by composite particles. Figure 8 The right-hand area consists of a bottom sediment layer, a fine sand layer, and a water layer from bottom to top. Hollow circles indicate that when there is a composite hydration layer, the Pb concentration in the water layer is extremely low. In other words, a relatively thin cover layer can effectively block and treat Pb in the bottom sediment. Solid dots indicate that when there is only a fine sand layer, even if the thickness of the fine sand layer is increased, it cannot effectively block and treat Pb in the bottom sediment.

[0098] The amount of plant seeds added to the aquatic plant layer should be appropriate, ensuring that the roots of the aquatic plants can stabilize the cover layer without compromising its barrier effect on the bottom sediment or hindering the activity of benthic animals. The amount of plant seeds added to the aquatic plant layer is 40-50g per square meter of water. The plants used in the aquatic plant layer should be at least one of the following: Vallisneria natans, Ceratophyllum demersum, and Potamogeton crispus.

[0099] The seeds of aquatic plants need to be properly dispersed in the cover layer; therefore, see [reference needed]. Figure 1 As shown, the aquatic plant layer is introduced by mixing the plant seeds 14 with the shell material of the composite particles, and then mixing them with the core material to form composite particles. When the composite particles enter the water, the plant seeds in the composite particles are evenly dispersed in the cover layer.

[0100] The bacteria are Bacillus, which promote the growth of aquatic plant roots. Different formulations of bacterial additives have different effects on plant growth. The effects of two bacterial formulations on the growth of aquatic plant roots are examined.

[0101] Bacterial formulation A: Microbacterium (2 parts), Methylobacterium WM-1 (5 parts), Bacillus chihua-nanensis (1 part), Bacillus amyloliquefaciens (2 parts), Bacillus iheyensis (3 parts).

[0102] Bacterial formulation B: Bacillus subtilis (5 parts), Bacillus methylicus (2 parts), Bacillus licheniformis (1 part).

[0103] The effects of different bacterial formulations on plant growth are as follows:

[0104] Step 1: Prepare four glass cultivation boxes with the same volume. The cultivation box is 0.6m long, 0.4m wide, and 0.5m high, and is numbered 1-4.

[0105] Step 2: Place 10cm thick river bottom mud at the bottom of the cultivation box. The 1-4 cultivation boxes are treated as follows:

[0106] 1. The 1st cultivation box is used as a reference group, without using a mulch layer and adding bacterial agents.

[0107] 2. The 2nd cultivation box uses a 5cm thick mulch layer without adding bacterial agents.

[0108] 3. The 3rd cultivation box uses a 5cm thick mulch layer and adds bacterial formulation A.

[0109] 4. The 4th cultivation box uses a 5cm thick mulch layer and adds bacterial formulation B.

[0110] Step 3: Plant 5 Vallisneria and 5 Ceratophyllum in each cultivation box.

[0111] Step 4: Check and record the vegetation every week.

[0112] After one growth cycle (from the time of planting the plant seedlings to the time of plant wilting and death), the plant root length in the 1st and 2nd cultivation boxes is about 1cm (see the upper part of the plant shown in Figure 8 ), and the leaves are short and small. The plant root length in the 3rd and 4th cultivation boxes is about 3cm (see the lower part of the plant shown in Figure 8 ), and the leaves are thick and have good tillering. The growth of Vallisneria in the 3rd box is better than that in the 4th box, and the growth of Ceratophyllum in the 4th box is better than that in the 3rd box. It can be concluded that adding bacterial agents to the mulch layer can promote the growth and development of plant roots and promote the growth of vegetation. Different bacterial formulations have different effects on the growth of different plants.

[0113] The bacteria adopt any one of the following combinations:

[0114] a. Microbacterium, Methylophaga WM-1, Bacillus kudouensis, Bacillus amyloliquefaciens, and Bacillus ishinazawai;

[0115] b. Bacillus subtilis, Bacillus methylicus, and Bacillus licheniformis.

[0116] When the aquatic plant is Vallisneria, the combination of the bacterial agents is Microbacterium, Methylophaga WM-1, Bacillus kudouensis, Bacillus amyloliquefaciens, and Bacillus ishinazawai.

[0117] When the aquatic plant is Ceratophyllum, the combination of the bacterial agents is Bacillus subtilis, Bacillus methylicus, and Bacillus licheniformis.

[0118] The bacteria are mixed with the material of the shell of the composite particles, mixed with the core material to form composite particles, or the bacteria are mixed with the material of the core of the composite particles, mixed with the shell material to form composite particles. When the composite particles enter the water, the bacteria in the composite particles are also uniformly dispersed in the mulch layer.

[0119] The bacteria also need to be divided and dispersed in the mulch layer, and the delivery method of different bacterial agents will also affect the growth of aquatic plants. The effect of the delivery method of the bacterial agents on the aquatic plants is verified through the following experimental process.

[0120] Step 1, prepare six glass cultivation boxes with the same volume, the cultivation box bottom is 0.6m long, 0.4m wide, and 0.5m high, numbered 1 to 6, and the cultivation box bottom is covered with 5cm thick river bottom mud.

[0121] Step 2, prepare six portions of composite particles with different components, wherein:

[0122] 1. The core of the composite particles is limestone, and the bacterial agent formula A is fixed on the core.

[0123] 2. The core of the composite particles is limestone, and the bacterial agent formula A is fixed on the shell.

[0124] 3. The core of the composite particles is volcanic rock, and the bacterial agent formula A is fixed on the core.

[0125] 4. The core of the composite particles is volcanic rock, and the bacterial agent formula A is fixed on the shell.

[0126] 5. The core of the composite particles is gravel, and the bacterial agent formula A is fixed on the core.

[0127] 6. The core of the composite particles is gravel, and the bacterial agent formula A is fixed on the shell.

[0128] Step 3, 6 parts of the composite particles are put into the 1st to 6th cultivation boxes respectively, and the thickness of the cover layer is 5 cm;

[0129] Step 4, 5 plants of Vallisneria and 5 plants of Ceratophyllum are planted in each cultivation box;

[0130] Step 5, the growth of the vegetation in each cultivation box is observed for a long time to analyze the influence of the nuclear material and the fixing mode of the bacteria on the growth of the plants.

[0131] When the nuclear material in the composite particles is a porous material, such as volcanic rock, the bacteria are mixed with the volcanic rock and fixed in the pore structure of the nuclear material. When the nuclear material is a non-porous material, the bacteria are mixed with the shell material, and then mixed with the nuclear material to form the composite particles.

[0132] The benthic animals are at least one of aquatic insect larvae, aquatic mollusks and aquatic crustaceans, and the habitat density of the benthic animals is not less than 100 ind / m 2 Too many benthic animals will destroy the stability of the cover layer and cannot form an effective barrier to the bottom mud.

[0133] The amount of the adsorbed component in the composite particles is 1-2 kg per square meter of water area.

[0134] The composite particles are put into the predetermined water area by a throwing device, and the throwing device comprises:

[0135] A boat, and a GPS positioning system is arranged on the boat;

[0136] A bin is arranged on the boat for storing the composite particles;

[0137] A spray barrel is connected with the bin and the direction and flow of the spray barrel can be adjusted.

[0138] The boat is parked at the predetermined water area by the GPS positioning system, and the composite particles in the bin are sprayed into the water body by the spray barrel. The direction of the spray barrel can be adjusted as needed, and the spray flow of the composite particles can also be measured and adjusted.

[0139] The composite particles can be more accurately put into the expected water area by the throwing device, and the thickness of the cover layer is more uniform.

[0140] Any combination of the technical features of the above-mentioned embodiments can be made, and in order to make the description simple, all possible combinations of the technical features in the above-mentioned embodiments are not described, however, as long as the combination of the technical features does not exist contradictory, it should be considered as the scope of the present application.

[0141] The above-described embodiments are merely illustrative of several embodiments of the present application, which are described in more detail and in a specific and detailed manner, but should not be construed as limiting the scope of the patent. It should be noted that for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present application, and these are all within the scope of the present application. Therefore, the scope of protection of the patent of the present application should be subject to the appended claims.

Claims

1. A capping layer for in-situ remediation of contaminated sediment, characterized in that, include: A cover layer, laid on the surface of the sediment and formed of composite particles containing treatment components, is used to block and treat contaminants in the sediment. The aquatic plant layer is located on top of the cover layer, and the roots of the aquatic plants extend through the cover layer into the bottom mud. Bacteria, dispersed in the cover layer, are used to treat contaminants and promote plant growth; Benthic animals, which live in the sediment and form an ecological cycle with the plants in the vegetation layer, are used to promote the mixing of the treatment components in the composite particles with the sediment; The composite particles have a core-shell structure. The core material is at least one of limestone, volcanic rock, and gravel, and the particle size of the core material is 5-10 mm. The shell material includes a treatment component and a water-absorbing and swelling component. The treatment component includes one of lanthanum salt, sulfide, and zero-valent iron, and an adsorption component. The adsorption component is activated carbon, and the water-absorbing and swelling component is at least one of bentonite, expanded clay, and clay minerals. The thickness of the cover layer is calculated using the following formula: T = K * 1.15 * S * C² / C¹ + 0.5 * h / i In the formula: T is the thickness of the cover layer; C1 represents the cohesive force of the cover material; C2 represents the cohesive force of the bottom sediment; S represents the maximum disturbance depth of benthic animals without a cover layer, expressed in cm. h represents the water depth, in cm. i is an empirical value, ranging from 70 to 80; K is the disturbance coefficient, and the rules for determining the value of K are as follows: When C2 / C1>0.6, and ρ k >150ind / m 2 At that time, K=0.8; When C2 / C1≤0.6, and 100ind / m 2 ≤ρ k <150ind / m 2 At that time, K=0.6; ρ k This represents the habitat density of benthic animals.

2. The capping layer for in-situ remediation of contaminated sediment as described in claim 1, characterized in that, The amount of plant seeds placed in the aquatic plant layer is 40-50g per square meter of water area, and the plants in the aquatic plant layer are at least one of Vallisneria natans, Ceratophyllum demersum, and Potamogeton crispus.

3. The capping layer for in-situ remediation of contaminated sediment as described in claim 1, characterized in that, The method of placing the plant seeds in the aquatic plant layer is as follows: the plant seeds are mixed with the shell material of the composite particles, and then mixed with the core material to form composite particles.

4. The capping layer for in-situ remediation of contaminated sediment as described in claim 1, characterized in that, The bacteria are any combination of the following: a. Microbacterium, Bacillus methylophilus WM-1, Bacillus cognac, Bacillus amyloliquefaciens, Bacillus taiyoi of Ihira-Yabashi; b. Bacillus subtilis, Bacillus methyltrophicus, Bacillus licheniformis.

5. The capping layer for in-situ remediation of contaminated sediment as described in claim 1, characterized in that, The bacteria are introduced in the following ways: the bacteria are mixed with the shell material of the composite particles and then mixed with the core material to form composite particles, or the bacteria are mixed with the core material of the bacterial composite particles and then mixed with the shell material to form composite particles.

6. The capping layer for in-situ remediation of contaminated sediment as described in claim 1, characterized in that, The benthic animals are at least one of aquatic insect larvae, aquatic mollusks, and aquatic crustaceans, and the habitat density of the benthic animals is not less than 100 ind / m³. 2 .

7. The capping layer for in-situ remediation of contaminated sediment as described in claim 1, characterized in that, The amount of adsorbent component in the composite particles is 1-2 kg per square meter of water.

8. The capping layer for in-situ remediation of contaminated sediment as described in any one of claims 1 to 7, characterized in that, The composite particles are deployed into a predetermined water area using a dispersing device, which includes: The vessel is moored and equipped with a GPS positioning system. A silo, located on the moored vessel, is used to store the composite particles; The spray nozzle is connected to the hopper and its spray direction and flow rate are adjustable.

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