A biochar-reinforced sediment remediation turf and its preparation method, and sediment remediation method

Abstract

The present invention relates to the technical field of sediment remediation, and in particular, to a sediment remediation turf strengthened by biochar, a preparation method thereof, and a sediment remediation method. The sediment remediation turf prepared by the preparation method of the present invention can not only efficiently adsorb pollutants released from the sediment, but also facilitate the roots of submerged plants to enter the sediment, improve the survival rate of submerged plants, and effectively improve the sediment matrix.

Description

Technical Field

[0001] The present invention relates to the technical field of sediment remediation, and particularly to a sediment remediation turf strengthened by biochar, a preparation method thereof, and a sediment remediation method. Background Art

[0002] As an important part of water bodies, sediment is the "sink" of various pollutants in water bodies, including nitrogen and phosphorus nutrients, heavy metals, and refractory organic compounds, etc. Due to the complex mass exchange with the upper water body at all times, when the pollutant concentration in the upper water body decreases, a large amount of pollutants in the sediment will be re-released into the upper water body through the concentration gradient effect. It is reported that from 2007 to 2016, about 128 Gg of nitrogen was released from the sediment into the Taihu Lake water body, hindering the further improvement of the water quality of the Taihu Lake. Thus, it can be seen that sediment remediation is very necessary for improving water quality and water environment. Common sediment remediation methods include dredging, in-situ chemical remediation, bioaugmentation remediation, in-situ covering, etc. Among them, the in-situ covering technology is widely used to reduce the pollutant flux released by the sediment due to its advantages such as simple operation, high economic efficiency, energy conservation and environmental protection. The selection of in-situ covering materials is the key. Common covering materials include zeolite, activated carbon, fly ash, etc., which show disadvantages such as low efficiency, high cost and ecological risks in engineering practice. As the most common bioaugmentation remediation means, submerged plants can effectively absorb and metabolize various pollutants in the sediment, improve the sediment matrix, and reduce pollutant release, but they often face problems such as terrain condition limitations, difficult construction and low survival rate during planting. In summary, in view of the many deficiencies of existing remediation technologies, it is urgent to develop new sediment remediation materials and methods.

[0003] The Chinese invention patent with the publication number CN111499134A discloses a in-situ sediment remediation blanket and a riverbed sediment remediation method, including a sediment remediation layer, an aquatic plant layer and a substrate layer; the substrate layer is fixedly arranged on the sediment remediation layer, and the aquatic plant layer grows on the substrate layer; the sediment remediation layer includes a support skeleton and a remediation agent layer wrapped outside the support skeleton. The Chinese utility model patent with the publication number CN214218508U discloses an in-situ sealing and underwater ecological remediation ecological blanket for riverbed sediment, which is sequentially provided with a waterproof layer, a weight layer, a nutrient layer and a planting layer from bottom to top. A conduit with one end extending out of the river surface is arranged in the waterproof layer, and ventilation holes are arranged on the side surface of the part of the conduit located in the waterproof layer. The Chinese invention patent with the publication number CN113955855A discloses an ecological blanket for water body remediation and its application, including a waterproof layer, a multi-functional remediation layer, a slow-release nutrient layer and a planting layer arranged in sequence from bottom to top; the waterproof layer, the multi-functional remediation layer, the slow-release nutrient layer and the planting layer are all detachably connected; wherein, the multi-functional remediation layer is prepared from waste bricks, limestone and negatively magnetically modified biochar. The above invention ideas all set the sediment remediation layer - substrate layer - aquatic plant layer (from bottom to top), while reducing the pollutant flux released by the sediment, and at the same time improving the survival rate of aquatic plants by externally setting the substrate layer; since the aquatic plants all grow on the external substrate, the role of aquatic plants in improving sediment and absorbing pollutants cannot be exerted, and there is also a risk of secondary release of pollutants in the external substrate. Summary of the Invention

[0004] The purpose of the present invention is to provide a sediment remediation grass blanket strengthened by biochar, its preparation method and a sediment remediation method. The sediment remediation grass blanket prepared by the preparation method can efficiently adsorb pollutants released by sediment while facilitating the roots of submerged plants to enter the sediment, improving the survival rate of submerged plants and effectively improving the sediment matrix.

[0005] In order to achieve the above invention purpose, the present invention provides the following technical solutions:

[0006] The present invention provides a preparation method of a sediment remediation grass blanket strengthened by biochar, including the following steps:

[0007] Immerse the porous carrier in starch adhesive solution and porous biochar suspension in sequence to obtain a carrier with biochar loaded on the surface;

[0008] Cultivate the carrier with biochar loaded on the surface in a culture solution inoculated with activated sludge to obtain a surface-functionalized carrier;

[0009] Mix submerged plant seeds and water, and then add the surface-functionalized carrier to obtain a carrier with submerged plant seeds deposited thereon;

[0010] Germinate the carrier deposited with submerged plant seeds in a nutrient solution to obtain the biochar-enhanced sediment remediation turf mat.

[0011] Preferably, the impregnation time of the porous carrier in the starch adhesive solution is 10 - 20 min;

[0012] The impregnation time in the porous biochar suspension is 30 - 60 min.

[0013] Preferably, the starch adhesive solution includes a starch binder and water, and the dosage ratio of the starch binder to water is (80 - 150) g : 1 L.

[0014] Preferably, the preparation process of the porous biochar suspension includes the following steps:

[0015] Pyrolyze biomass to obtain biochar;

[0016] Mix the biochar with water to obtain a porous biochar suspension.

[0017] Preferably, the temperature of the pyrolysis is 500 - 700 °C, the time is 2 - 3 h, and the heating rate to the pyrolysis temperature is 10 - 20 °C / min;

[0018] The dosage ratio of the biochar to water is (10 - 50) g : 1 L.

[0019] Preferably, the culture solution includes sodium acetate with a concentration of 800 - 1000 mg / L, ammonium sulfate with a concentration of 200 - 400 mg / L, and sodium dihydrogen phosphate with a concentration of 40 - 50 mg / L;

[0020] The activated sludge is the activated sludge from the secondary sedimentation tank of a sewage treatment plant, and the inoculation amount of the activated sludge is 10 - 30 mL / L;

[0021] The temperature of the culture is 25 - 35 °C, and the time is 2 - 3 d.

[0022] Preferably, the submerged plant seeds include one or more of Vallisneria natans seeds, Hydrilla verticillata seeds, Myriophyllum verticillatum seeds, and Potamogeton crispus seeds;

[0023] The dosage ratio of the submerged plant seeds to water is (0.5 - 1.0) kg : 1 L.

[0024] Preferably, the nutrient solution includes urea at a concentration of 10 - 20 mg / L, calcium nitrate at a concentration of 40 - 80 mg / L, potassium nitrate at a concentration of 40 - 80 mg / L, ammonium dihydrogen phosphate at a concentration of 5 - 8 mg / L, magnesium sulfate at a concentration of 20 - 30 mg / L, sodium EDTA at a concentration of 2 - 5 mg / L, boric acid at a concentration of 0.02 - 0.05 mg / L, manganese sulfate at a concentration of 0.02 - 0.05 mg / L, zinc sulfate at a concentration of 0.02 - 0.05 mg / L, copper sulfate at a concentration of 0.02 - 0.05 mg / L, and ammonium molybdate at a concentration of 0.02 - 0.05 mg / L;

[0025] The temperature for germination is 25 - 30 °C, and the time is 30 - 50 days.

[0026] The present invention also provides a biochar - enhanced sediment - repairing turf mat prepared by the preparation method of the above - mentioned technical solution, which is characterized by comprising a carrier and submerged plants covering the carrier; the carrier includes a porous carrier and an adhesive layer, a biochar layer, and a functional microorganism layer sequentially located on the surface of the pore structure of the porous carrier; the covering density of the submerged plants in the sediment - repairing turf mat is 600 - 900 plants / m 2 , and the length is 30 - 60 cm.

[0027] The present invention also provides a method for sediment repair using the biochar - enhanced sediment - repairing turf mat of the above - mentioned technical solution, which includes the following steps:

[0028] Cover the surface of the sediment to be repaired with the biochar - enhanced sediment - repairing turf mat for repair.

[0029] The present invention provides a preparation method for a biochar - enhanced sediment - repairing turf mat, which includes the following steps: impregnate a porous carrier in a starch adhesive solution and a porous biochar suspension in sequence to obtain a carrier with biochar loaded on the surface; culture the carrier with biochar loaded on the surface in a culture solution inoculated with activated sludge to obtain a surface - functionalized carrier; mix submerged plant seeds and water, and then add the surface - functionalized carrier to obtain a carrier with submerged plant seeds deposited thereon; germinate the carrier with submerged plant seeds deposited thereon in a nutrient solution to obtain the biochar - enhanced sediment - repairing turf mat.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1) By setting up a porous carrier for heterotrophic culture with submerged plants, the present invention is beneficial for submerged plants to absorb pollutants through roots while ensuring the survival rate of submerged plants, and at the same time helps the roots of submerged plants grow downward and take root in the sediment, accelerating sediment improvement and pollutant reduction;

[0032] 2) By setting up the porous carrier and loading the biochar-functional microorganisms, it is beneficial for material exchange between the upper water layer - the covering layer - the sediment, maintaining a high material exchange flux. It is conducive to the covering layer adsorbing the pollutants released from the sediment, accelerating the absorption and degradation of the pollutants released from the sediment;

[0033] 3) Loading porous biochar on the surface of the porous carrier can greatly increase the surface area and adsorption capacity of the carrier. At the same time, it provides sites for the attachment of functional microorganisms, accelerates the formation of functional biofilms, improves the metabolic transformation of adsorbed pollutants, and ensures the long-term effectiveness of the function of the covering layer (the sediment remediation grass mat based on biochar strengthening);

[0034] 4) The starch binder in the starch adhesive solution can be used as a slow-release carbon source on the premise of ensuring the stable loading of biochar. On the one hand, it provides nutrients for the growth of submerged plants, and on the other hand, it provides a carbon source for biological denitrification on the surface of biochar, enhancing the denitrification rate;

[0035] 5) It is easy to install and maintain. The submerged grass mat can be regularly lifted by means of peripheral buoys and other means to check the survival rate of submerged plants, which is convenient for replanting and regular harvesting of submerged plants.

[0036] The present invention also provides a method for sediment remediation using the sediment remediation grass mat based on biochar strengthening described in the above technical solution, including the following steps: covering the sediment remediation grass mat on the surface of the sediment to be remediated for remediation. The presence of the porous carrier in the sediment remediation grass mat is conducive to material exchange between the upper water layer - the covering layer - the sediment, adsorbing the pollutants released from the sediment on the biochar interface, facilitating the submerged plants to uptake pollutants through rich roots, and at the same time, it also helps the roots of the submerged plants to grow downward and take root in the sediment, accelerating the activation of the sediment matrix and the reduction of pollutants; the submerged plants provide oxygen for the microorganisms on the surface of biochar through photosynthesis, accelerating the aerobic transformation of the pollutants adsorbed by the covering layer; during the remediation process, the starch as an adhesive can be used as a slow-release carbon source, providing nutrients for the growth of submerged plants on the one hand and a carbon source for the denitrification of the microorganisms on the surface of biochar on the other hand. Description of the Drawings

[0037] Figure 1 It is a schematic structural diagram of the sediment remediation grass mat based on biochar strengthening described in the present invention;

[0038] Figure 2 It is the TN and ammonia nitrogen contents of the experimental group and the control group at different repair times. Detailed Embodiments

[0039] The present invention provides a preparation method of a sediment remediation grass mat based on biochar strengthening, including the following steps:

[0040] The porous carrier is impregnated successively in the starch adhesive solution and the porous biochar suspension to obtain a carrier with biochar loaded on its surface.

[0041] The carrier with biochar loaded on its surface is cultured in a culture solution inoculated with activated sludge to obtain a surface-functionalized carrier.

[0042] After mixing submerged plant seeds and water, the surface-functionalized carrier is added to obtain a carrier with submerged plant seeds deposited thereon.

[0043] The carrier with submerged plant seeds deposited thereon is germinated in a nutrient solution to obtain the biochar-enhanced sediment remediation turf mat.

[0044] In the present invention, unless otherwise specified, all preparation raw materials are commercially available products well-known to those skilled in the art.

[0045] In the present invention, the porous carrier is impregnated successively in the starch adhesive solution and the porous biochar suspension to obtain a carrier with biochar loaded on its surface.

[0046] In the present invention, the porosity of the porous carrier is preferably 0.7 - 0.96, more preferably 0.8 - 0.9, and most preferably 0.88. In the present invention, the porous carrier preferably uses a foamed sponge synthesized from polyester fiber as the raw material. The vertical thickness of the foamed sponge is preferably 10 - 20 cm, and the PPI index is preferably 15 - 40.

[0047] In the present invention, the starch adhesive solution preferably includes a starch binder and water. The dosage ratio of the starch binder to water is preferably (80 - 150) g:1 L, more preferably 100 g:1 L. In the present invention, the starch binder preferably includes starch, cooked starch paste, ferric sulfate, caustic soda, and borax. The mass percentage of starch in the starch binder is preferably 70 - 80%, more preferably 72 - 78%, and most preferably 74 - 76%. The mass percentage of cooked starch paste in the starch binder is preferably 10 - 15%, more preferably 11 - 14%, and most preferably 12 - 13%. The mass percentage of ferric sulfate in the starch binder is preferably 3 - 5%, more preferably 3.5 - 4.5%, and most preferably 3.8 - 4.2%. The mass percentage of caustic soda in the starch binder is preferably 2.5 - 3.5%, more preferably 2.8 - 3.2%. The mass percentage of borax in the starch binder is preferably 2.6 - 3.5%, more preferably 2.8 - 3.2%.

[0048] In the present invention, the temperature for impregnating the porous carrier in the starch adhesive solution is preferably 50 - 80°C, more preferably 70 - 77°C; the time is preferably 10 - 20 min, more preferably 12 - 18 min, and most preferably 14 - 16 min.

[0049] In the present invention, the purpose of impregnating the porous carrier in the starch adhesive solution is to use starch as an adhesive to improve the biochar loading rate, ensure the loading stability of the biochar layer, and prevent it from falling off in the actual water environment; at the same time, as a slow-release carbon source, it provides nutrients for functional microorganisms and provides electrons for the denitrification and nitrogen removal of functional microorganisms.

[0050] In the present invention, the preparation process of the porous biochar suspension preferably includes the following steps:

[0051] Pyrolyze the biomass to obtain biochar;

[0052] Mix the biochar with water to obtain a porous biochar suspension.

[0053] The present invention does not have any special limitation on the type of the biomass, and any type well-known to those skilled in the art can be used. In the present invention, the biomass is more preferably biomass waste, and the biomass waste is preferably one or more of wood chip waste, coconut shell waste, peach shell waste, and bamboo chip waste. When there are two or more of the above specific selections for the biomass waste, the present invention does not have any special limitation on the ratio of the above specific substances, and they can be mixed in any ratio.

[0054] Before pyrolysis, the present invention also preferably includes crushing the biomass. The present invention does not have any special limitation on the crushing process, and it is carried out using a process well-known to those skilled in the art, and the particle size of the crushed biomass is ≥10 mesh (more preferably 30 - 50 mesh).

[0055] In the present invention, the temperature of the pyrolysis is preferably 500 - 700 °C, more preferably 550 - 650 °C, and most preferably 580 - 620 °C; the time is preferably 2 - 3 h, more preferably 2.2 - 2.8 h, and most preferably 2.4 - 2.6 h; the heating rate for heating to the pyrolysis temperature is preferably 10 - 20 °C / min, more preferably 12 - 18 °C / min, and most preferably 14 - 16 °C / min. In the present invention, the pyrolysis is preferably carried out in a nitrogen atmosphere.

[0056] In the present invention, the porosity of the biochar is preferably >0.2, more preferably >0.25, and most preferably >0.3.

[0057] After the pyrolysis is completed, the present invention also preferably includes grinding and sieving in sequence. The present invention does not have any special limitation on the grinding and sieving processes, and they are carried out using processes well-known to those skilled in the art, and it is only necessary to ensure that the biochar powder obtained after sieving is ≥50 mesh.

[0058] After obtaining the biochar, the present invention mixes the biochar with water to obtain a porous biochar suspension.

[0059] In the present invention, the dosage ratio of the biochar to water is preferably (10 - 50) g: 1 L, more preferably (15 - 45) g: 1 L, and most preferably (25 - 40) g: 1 L.

[0060] In the present invention, the impregnation time in the porous biochar suspension is preferably 30 - 60 min, more preferably 35 - 55 min, and most preferably 40 - 50 min.

[0061] After the impregnation in the porous biochar suspension is completed, the present invention preferably further includes washing and drying in sequence; the washing is preferably carried out with clear water 3 - 5 times; the drying method is preferably drying in an oven, the drying temperature is preferably 65 °C, and the time is preferably 5 h.

[0062] In the present invention, the purpose of impregnation in the porous biochar suspension is to uniformly load the porous biochar on the surface of the carrier, perform surface functionalization on the carrier, and form a functional biochar layer.

[0063] After obtaining the carrier with biochar loaded on its surface, the present invention cultures the carrier with biochar loaded on its surface in a culture solution inoculated with activated sludge to obtain a surface-functionalized carrier.

[0064] In the present invention, the specific process of the culture is preferably to place the carrier with biochar loaded on its surface in the culture solution and inoculate activated sludge for culture.

[0065] In the present invention, the culture solution preferably includes sodium acetate, ammonium sulfate, and sodium dihydrogen phosphate; the concentration of sodium acetate is preferably 800 - 1000 mg / L, more preferably 850 - 950 mg / L, and most preferably 880 - 920 mg / L; the concentration of ammonium sulfate is preferably 200 - 400 mg / L, more preferably 250 - 350 mg / L, and most preferably 280 - 320 mg / L; the concentration of sodium dihydrogen phosphate is preferably 40 - 50 mg / L, more preferably 42 - 48 mg / L, and most preferably 44 - 46 mg / L.

[0066] In the present invention, the activated sludge preferably uses the activated sludge from the secondary sedimentation tank of a sewage treatment plant, the inoculation amount of the activated sludge is preferably 10 - 30 mL / L, more preferably 15 - 25 mL / L, and most preferably 20 mL / L; the culture temperature is preferably 25 - 35 °C, more preferably 30 - 35 °C, and most preferably 35 °C; the time is preferably 2 - 3 d, more preferably 2.5 d.

[0067] In the present invention, in the surface-functionalized carrier, the carrier surface includes a starch binder layer, a biochar layer, and a functional microorganism layer arranged in sequence.

[0068] In the present invention, the effect of culturing the carrier with biochar loaded on its surface in a culture solution inoculated with activated sludge is to colonize functional microorganisms with nitrification and denitrification functions on the surface of the carrier loaded with biochar.

[0069] After obtaining the surface-functionalized carrier, in the present invention, submerged plant seeds and water are mixed, and then the surface-functionalized carrier is added to obtain a carrier deposited with submerged plant seeds.

[0070] In the present invention, the submerged plant seeds preferably include one or more of vallisneria seeds, hydrilla verticillata seeds, myriophyllum verticillatum seeds, and potamogeton crispus seeds. When there are two or more of the above specific selections for the submerged plant seeds, the present invention does not have any special limitations on the specific material ratios of the above, and they can be mixed in any ratio.

[0071] In the present invention, the dosage ratio of the submerged plant seeds to water is preferably (0.5 - 1.0) kg: 1 L, more preferably (0.6 - 0.8) kg: 1 L, and most preferably (0.65 - 0.75) kg: 1 L.

[0072] In the present invention, the immersion time after adding the surface-functionalized carrier is preferably 10 - 30 min, more preferably 15 - 25 min, and most preferably 18 - 22 min.

[0073] In the present invention, in order to ensure that the submerged plant seeds are fully attached to the surface of the surface-functionalized carrier, repeated impregnation is preferably carried out. The present invention does not have any special limitations on the process of the repeated impregnation, and a process well-known to those skilled in the art can be used.

[0074] After obtaining the carrier deposited with submerged plant seeds, in the present invention, the carrier deposited with submerged plant seeds is germinated in a nutrient solution to obtain the biochar-enhanced sediment remediation turf.

[0075] In the present invention, the nutrient solution preferably comprises urea, calcium nitrate, potassium nitrate, ammonium dihydrogen phosphate, magnesium sulfate, sodium EDTA, boric acid, manganese sulfate, zinc sulfate, copper sulfate and ammonium molybdate; the concentration of the urea is preferably 10-20 mg / L, more preferably 12-18 mg / L, and most preferably 14-16 mg / L; the concentration of the calcium nitrate is preferably 40-80 mg / L, more preferably 50-70 mg / L, and most preferably 55-65 mg / L; the concentration of the potassium nitrate is preferably 40-80 mg / L, more preferably 50-70 mg / L, and most preferably 55-65 mg / L; the concentration of the ammonium dihydrogen phosphate is preferably 5-8 mg / L, more preferably 5.5-7.5 mg / L, and most preferably 6-7 mg / L; the concentration of the magnesium sulfate is preferably 20-30 mg / L, more preferably 22-28 mg / L, and most preferably 24-26 mg / L; the concentration of the sodium EDTA is preferably 2-5 mg / L, more preferably 2.5-4.5 mg / L, and most preferably 3-4 mg / L; the concentration of the boric acid is preferably 0.02-0.05 mg / L, more preferably 0.03-0.04 mg / L; the concentration of the manganese sulfate is preferably 0.02-0.05 mg / L, more preferably 0.03-0.04 mg / L; the concentration of the zinc sulfate is preferably 0.02-0.05 mg / L, more preferably 0.03-0.04 mg / L; the concentration of the copper sulfate is preferably 0.02-0.05 mg / L, more preferably 0.03-0.04 mg / L; the concentration of the ammonium molybdate is preferably 0.02-0.05 mg / L, more preferably 0.03-0.04 mg / L.

[0076] In the present invention, the temperature for germination is preferably 25-30 °C, more preferably 26-29 °C, and most preferably 27-28 °C; the time is preferably 30-50 days, more preferably 35-45 days, and most preferably 38-42 days.

[0077] As Figure 1 shown, the present invention also provides a biochar-enhanced sediment remediation grass mat prepared by the preparation method described in the above technical solution. The sediment remediation grass mat comprises a carrier and submerged plants covering the carrier; the carrier comprises a porous carrier and an adhesive layer and a biochar layer sequentially located on the surface of the pore structure of the porous carrier; the coverage density of the submerged plants in the sediment remediation grass mat is 600-900 plants / m 2 , and the length is 30-60 cm.

[0078] In the present invention, the roots of the submerged plants are located in the pore structure of the carrier, and the submerged plants are wrapped around each other.

[0079] The present invention also provides a method for sediment remediation using the biochar-enhanced sediment remediation grass mat described in the above technical solution, including the following steps:

[0080] Cover the surface of the sediment to be remediated with the biochar-enhanced sediment remediation grass mat for remediation.

[0081] In the sediment remediation grass mat of the present invention, the presence of the porous carrier facilitates the material exchange between the upper water body - the covering layer - the sediment, adsorbs the pollutants released from the sediment on the biochar interface, facilitates the submerged plants to uptake pollutants through their rich root systems, and also helps the submerged plant roots to grow downward and take root in the sediment, accelerating the activation of the sediment matrix and the reduction of pollutants; the submerged plants provide oxygen for the microorganisms on the biochar surface through photosynthesis, accelerating the aerobic transformation of the adsorbed pollutants in the covering layer; during the remediation process, the starch as the binder can serve as a slow-release carbon source, providing nutrients for the growth of submerged plants on the one hand and providing a carbon source for denitrification of the microorganisms on the biochar surface on the other hand.

[0082] The following examples are used to illustrate in detail the biochar-enhanced sediment remediation grass mat and its preparation method and sediment remediation method provided by the present invention, but they should not be construed as limiting the protection scope of the present invention.

[0083] Example 1

[0084] Preparation method of the sediment remediation grass mat:

[0085] Crush the coconut shell biomass waste materials with a particle size of 5 - 10 meshes and pyrolyze them at 600 °C for 2 h (heating rate: 10 °C / min), grind them, and pass through a 50-mesh sieve. Mix the obtained biochar (specific surface area: 540 m 2 / g) with water to obtain a biochar suspension (solid-liquid ratio: 40 g / L);

[0086] Mix 100.0 g of starch binder (including 75.6% by mass of starch, 13.8% by mass of cooked starch paste, 4.4% by mass of ferric sulfate, 3.5% by mass of caustic soda, and 2.7% by mass of borax) with 1.0 L of water to obtain a starch adhesive solution;

[0087] Immerse a porous carrier with a thickness of 15.1 cm and a coverage range of 1.0 m 2 (porosity: 0.87, foamed sponge synthesized from polyester fiber, PPI index: 35) in the starch adhesive solution for 20 min, then place it in the biochar suspension (solid-liquid ratio: 40 g / L) for 60 min, wash it 5 times in clean water, and dry it at 60 °C for 5 h to obtain a carrier loaded with biochar;

[0088] Immerse the carrier loaded with biochar in a culture solution (including 1000 mg / L of sodium acetate, 200 mg / L of ammonium sulfate, and 40 mg / L of sodium dihydrogen phosphate), inoculate the activated sludge from the secondary sedimentation tank of a sewage treatment plant in Hangzhou (inoculation amount is 25 mL / L), and culture for 3 days to obtain a surface-functionalized carrier;

[0089] According to a solid-liquid ratio of 1.0 kg / L, mix Vallisneria natans seeds and water, add the surface-functionalized carrier for impregnation. After repeating the impregnation 3 times, culture in a nutrient solution (20 mg / L of urea, 70 mg / L of calcium nitrate, 60 mg / L of potassium nitrate, 8 mg / L of ammonium dihydrogen phosphate, 30 mg / L of magnesium sulfate, 5 mg / L of sodium EDTA, 0.05 mg / L each of boric acid, manganese sulfate, zinc sulfate, copper sulfate, and ammonium molybdate) for 45 days (temperature is 25 °C) to obtain a sediment remediation grass mat with a Vallisneria natans coverage density of 730 plants / m 2 , with a length of 35 - 45 cm;

[0090] Collect 0 - 30 cm sediments and the overlying water from a certain location in the Taihu Lake water body in Huzhou for a laboratory in-situ covering experiment; the average concentrations of COD, total nitrogen, ammonia nitrogen, and total phosphorus in the overlying water are 17.3 mg / L, 3.67 mg / L, 1.88 mg / L, and 0.47 mg / L respectively. According to the assessment requirements of the "Surface Water Environment Quality Standard" (GB3838 - 2022), this water body belongs to a class V inferior water body; the TOC, TN, and TP in the sediment are 45.74 mg / g, 43.40 mg / g, and 2.38 mg / g respectively, exceeding the statistical values of nitrogen and phosphorus contents in typical lakes in the eastern region (0.225 - 1.944 mg / g), with a large potential for pollution release, seriously affecting water quality improvement and further improvement of the water environment. The covering material used in the laboratory is the above-mentioned sediment remediation grass mat; the experiment is carried out under natural light at room temperature, using a stirring paddle to stir to simulate normal water agitation, with a rotation speed of 30 r / min for 90 days;

[0091] Take the scheme without covering the sediment remediation grass mat as the control group, and the above-mentioned scheme with the sediment remediation grass mat covered as the experimental group, Figure 2 For the TN and ammonia nitrogen contents of the experimental group and the control group at different repair times, from Figure 2 it can be seen that the TN in the overlying water of the experimental group is reduced by 61.39% compared with the control group, the TN concentration remains below 2.0 mg / L, the ammonia nitrogen concentration remains at 0.8 mg / L, the pollution flux is reduced by more than 57% and is reduced to 20.5 mg / m 2 ·d, and the ammonia nitrogen concentration stably meets the requirements of class V surface water in GB3838 - 2002, indicating that the sediment remediation grass mat strengthened by coupling biochar provided by the present invention has good sediment remediation ability, can significantly improve the water quality of the overlying water, and reduce the pollution flux released from the sediment.

[0092] It can be seen that the present invention can solve the problems of difficult construction of biochar covering in sediment remediation, low survival rate of submerged plants, and great construction difficulty. While reducing the pollution load released by the sediment, it effectively utilizes the roots of submerged plants to improve the sediment matrix, and accelerates the improvement of the sediment habitat and the water quality of the upper water body.

[0093] The above are only the preferred embodiments of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the original premise of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of a sediment remediation grass mat based on biochar strengthening, characterized in that, It includes the following steps: The porous carrier is successively impregnated in a starch adhesive solution and a porous biochar suspension to obtain a carrier with biochar loaded on its surface; The carrier with biochar loaded on its surface is cultured in a culture solution inoculated with activated sludge to obtain a surface-functionalized carrier; After mixing submerged plant seeds and water, the surface-functionalized carrier is added to obtain a carrier with submerged plant seeds deposited thereon; The carrier with submerged plant seeds deposited thereon germinates in a nutrient solution to obtain the biochar-enhanced sediment remediation turf; 2. The preparation method according to claim 1, characterized in that, The impregnation time of the porous carrier in the starch adhesive solution is 10 - 20 min; The impregnation time in the porous biochar suspension is 30 - 60 min.

3. The preparation method according to claim 1 or 2, characterized in that, The starch adhesive solution includes a starch binder and water, and the dosage ratio of the starch binder to water is (80 - 150) g : 1 L.

4. The preparation method according to claim 1, characterized in that, The preparation process of the porous biochar suspension includes the following steps: Biomass is pyrolyzed to obtain biochar; The biochar is mixed with water to obtain a porous biochar suspension.

5. The preparation method according to claim 4, characterized in that, The temperature of the pyrolysis is 500 - 700 °C, the time is 2 - 3 h, and the heating rate to the pyrolysis temperature is 10 - 20 °C / min; The dosage ratio of the biochar to water is (10 - 50) g : 1 L.

6. The preparation method according to claim 1, characterized in that, The culture solution includes sodium acetate with a concentration of 800 - 1000 mg / L, ammonium sulfate with a concentration of 200 - 400 mg / L, and sodium dihydrogen phosphate with a concentration of 40 - 50 mg / L; The activated sludge is the activated sludge from the secondary sedimentation tank of a sewage treatment plant, and the inoculation amount of the activated sludge is 10 - 30 mL / L; The temperature of the culture is 25 - 35 °C, and the time is 2 - 3 d.

7. The preparation method according to claim 1, characterized in that, The submerged plant seeds include one or several of Vallisneria natans seeds, Hydrilla verticillata seeds, Myriophyllum verticillatum seeds, and Potamogeton crispus seeds; The dosage ratio of the submerged plant seeds to water is (0.5 - 1.0) kg : 1 L.

8. The preparation method according to claim 1, characterized in that, The nutrient solution includes urea with a concentration of 10 - 20 mg / L, calcium nitrate with a concentration of 40 - 80 mg / L, potassium nitrate with a concentration of 40 - 80 mg / L, ammonium dihydrogen phosphate with a concentration of 5 - 8 mg / L, magnesium sulfate with a concentration of 20 - 30 mg / L, sodium EDTA with a concentration of 2 - 5 mg / L, boric acid with a concentration of 0.02 - 0.05 mg / L, manganese sulfate with a concentration of 0.02 - 0.05 mg / L, zinc sulfate with a concentration of 0.02 - 0.05 mg / L, copper sulfate with a concentration of 0.02 - 0.05 mg / L, and ammonium molybdate with a concentration of 0.02 - 0.05 mg / L; The temperature of the germination is 25 - 30 °C, and the time is 30 - 50 days.

9. The biochar-enhanced sediment remediation turf prepared by the preparation method according to any one of claims 1 to 8, characterized in that, It includes a carrier and submerged plants covering the carrier; the carrier includes a porous carrier and an adhesive layer, a biochar layer, and a functional microorganism layer that are sequentially located on the surface of the pore structure of the porous carrier; the coverage density of the submerged plants in the sediment remediation turf is 600-900 plants / m 2 , and the length is 30-60 cm.

10. The method for sediment remediation using the biochar-reinforced sediment remediation turf described in claim 9, characterized in that, It includes the following steps: Cover the surface of the sediment to be repaired with the biochar-enhanced sediment remediation turf for repair.

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