A sewage treatment process for converting river silt into planting soil

Abstract

The invention discloses a sewage treatment process for converting river silt into planting soil, belongs to the field of sewage treatment technology, and comprises the following steps: sieving and filtering muddy water to obtain organic matter-clay composite and sand and gravel components; hydrophobic modification is performed on organic matter-clay composite; composite flora is accessed in hydrophobic organic matter-clay composite, filtered after the second fermentation, chitosan-humic acid composite flocculant is added, filter press dehydration is performed, and active mud cake is obtained; with sand and gravel components as core materials, a porous carrier modified with dopamine on the surface is obtained; potassium persulfate solution and quaternized chitosan solution are sprayed on the surface of active mud cake, surface treatment is performed, and cellulose nanocrystals are added in a twin-screw mixer with the porous carrier to obtain planting soil. The present application constrains its filling space and filling area while ensuring that it can release organic matter by appropriate expansion, so that the wetland soil as a whole still has better water permeability.

Description

Technical Field

[0001] The invention belongs to the field of sewage treatment and relates to a sewage treatment process for converting river silt into planting soil. Background Art

[0002] As the amount of sewage discharge increases, the siltation in the river channel becomes very serious. Therefore, the first operation in the sewage treatment process is to clean the silt in the river channel.

[0003] In order to achieve effective utilization of river silt after dredging, a large number of existing technologies are used to prepare river silt into soil conditioners containing nutrients, which can increase soil fertility and benefit plant growth. However, in actual studies, it was found that when soil conditioners with silt as the core material are used in high-humidity environments, such as wetland soil, the soil conditioners will absorb water and expand, blocking the pores of the wetland soil and reducing the permeability of the wetland soil. Since wetland soil has been in a high-humidity environment for a long time, once the permeability of the soil is reduced, a large amount of water will accumulate in the wetland soil in a short period of time, causing plant root rot. Summary of the Invention

[0004] The purpose of the present invention is to provide a sewage treatment process for converting river silt into planting soil, which solves the problem that when soil conditioners with silt as the core material are used in high-humidity environments, such as wetland soil, the soil conditioners will absorb water and expand, blocking the pores of the wetland soil and reducing the permeability of the wetland soil.

[0005] The technical solution adopted in the present invention is as follows:

[0006] A sewage treatment process for converting river silt into planting soil comprises the following steps:

[0007] S1. Remove impurities, crush, and perform the first enzymatic hydrolysis on the high-silt sewage in the river to obtain muddy water;

[0008] S2. Screening and filtering the muddy water to obtain organic matter-clay complex and sand and gravel components;

[0009] S3, adding a composite anchoring agent to the organic matter-clay complex for hydrophobic modification to obtain a hydrophobic organic matter-clay complex;

[0010] S4, inoculating a composite bacterial community into the hydrophobic organic matter-clay complex, filtering after the second fermentation, adding a chitosan-humic acid composite flocculant, and dehydrating by filter pressing to obtain an active mud cake;

[0011] S5, adding rice husk powder, humic acid powder, magnesium ammonium phosphate, and shell powder to the sand and gravel components, mixing evenly, adding wood vinegar, stirring evenly, and granulating to obtain a first intermediate, calcining the first intermediate to obtain a second intermediate, and surface-modifying the second intermediate with polydopamine to obtain a porous carrier;

[0012] S6. Spraying potassium persulfate solution on the surface of the active mud cake, filtering, washing, and drying after the reaction, and then spraying quaternized chitosan solution, continuing the reaction to obtain a surface-treated active mud cake, and then putting the surface-treated active mud cake and a porous carrier into a twin-screw mixer, adding cellulose nanocrystals, heating to 80° C. and reacting for 1-2 hours to obtain planting soil;

[0013] S7. Evenly spread the planting soil on the surface of the wetland soil and till it to improve the wetland soil by the planting soil.

[0014] When treating silt, the existing technology separates the sand and gravel components in the silt from the organic matter-clay complex. The organic matter-clay complex is used as a soil conditioner, and the sand and gravel components with low nutrient content are used in other fields, such as the construction field. When silt is used as a soil conditioner, the component actually used is only the organic matter-clay complex. Clay materials tend to absorb water and expand, and the defects caused by water absorption and expansion are particularly significant in wetland environments.

[0015] The planting soil in this application is also a soil conditioner. When developing planting soil with silt as the main material, this application uses an organic matter-clay complex as a nutrient matrix to release organic matter, and then uses the sand and gravel components separated from the silt as the core material to prepare a porous carrier. The porous carrier serves as a support for the organic matter-clay complex. On the one hand, it utilizes the high permeability of sand and gravel to provide a stable permeable channel for wetland soil; on the other hand, it utilizes the rigid structure of sand and gravel to reduce the expansion range of clay through a physical barrier. While achieving the expansion inhibition effect, the porous structure of sand and gravel will also provide a flow channel for the organic matter released by the expansion of clay, allowing the organic matter to enter the overall soil and complete the soil improvement.

[0016] The present application inhibits the expansion of clay particles, not that the clay particles cannot expand after absorbing water, but controls the degree of expansion. While ensuring that the clay particles can release organic matter through moderate expansion, the filling space and filling area are constrained, so that the wetland soil as a whole still has good permeability.

[0017] Furthermore, the composite anchoring agent in step S3 includes nano-metakaolin, hectorite nanosheets, and octadecyltrimethoxysilane, and the mass ratio of nano-metakaolin, hectorite nanosheets, and octadecyltrimethoxysilane is 1:2:1;

[0018] The amount of the composite anchoring agent added in step S3 is 0.5-0.8% of the mass of the organic matter-clay composite.

[0019] Furthermore, in step S6, the concentration of the potassium persulfate solution is 0.1 M, and the spraying amount is 1.5 L / kg of active mud cake; the concentration of the quaternized chitosan solution is 2% w / v, and the spraying amount is 0.5 L / kg of active mud cake; and the amount of cellulose nanocrystals added is 0.5% of the total mass of the surface-treated active mud cake and the porous carrier.

[0020] Furthermore, in step S5, the amount of rice husk powder added is 30-32% of the mass of the sand and gravel component, the amount of humic acid powder added is 15-16% of the mass of the sand and gravel component, the amount of magnesium ammonium phosphate added is 10-12% of the mass of the sand and gravel component, and the amount of shell powder added is 5-6% of the mass of the sand and gravel component.

[0021] Furthermore, in step S5, the second intermediate is surface-modified with polydopamine by the following steps:

[0022] A1. Immerse the second intermediate in a 5% by mass 3-aminopropyltriethoxysilane solution and react at 60° C. for 2 h to obtain a silanized second intermediate.

[0023] A2. Prepare a dopamine solution with a pH of 8.5, mix the dopamine solution with the silanized second intermediate to form a reaction system, add 0.1% FeCl3 catalyst by weight of the reaction system to the reaction system, react at 25°C for 4-5 hours, then raise the temperature to 45°C, continue the reaction for 8-10 hours, filter, and dry to obtain a porous carrier.

[0024] Furthermore, in step S5, the first intermediate is calcined in three stages to obtain the second intermediate, and the three-stage calcination includes:

[0025] The first stage of calcination: calcination at 350 ° C in air for 2 hours;

[0026] Second stage calcination: calcination at 550°C for 1.5 hours under oxygen-limited conditions, wherein the oxygen-limited environment is a nitrogen environment or a low-oxygen environment;

[0027] The third calcination stage: calcination at 700°C in air for 30 minutes.

[0028] Furthermore, in step S6, the mass ratio of the surface-treated active mud cake to the porous carrier is 3:6-7.

[0029] Furthermore, the mass ratio of chitosan to humic acid in the chitosan-humic acid composite flocculant is 1:2.

[0030] Furthermore, the enzymatic agent used for the first enzymatic hydrolysis in step S1 includes the following components: cellulase, xylanase, and laccase.

[0031] Furthermore, the composite bacterial community used in the second fermentation in S4 includes the following components: filamentous fungi Trichoderma reesei and Bacillus subtilis;

[0032] The filamentous fungus Trichoderma reesei has a deposition number of CGMCC 3.3711 and is deposited in the China General Microbiological Culture Collection Center;

[0033] The Bacillus subtilis is deposited in China General Microorganism Culture Collection Center with the accession number of CGMCC 1.3358.

[0034] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0035] 1. A wastewater treatment process for converting river silt into plantation soil uses hydrophobic modification (composite anchoring agents) to reduce the hydrophilicity of clay surfaces, slowing their water absorption and expansion rate. Simultaneously, the rigid skeleton structure of the porous carrier provides physical constraints for clay expansion. This design not only maintains the functional requirement for moderate clay expansion to promote organic matter release, but also avoids blockage of permeable channels caused by disordered clay expansion by limiting the spatial and temporal distribution of expansion.

[0036] 2. The sand and gravel components in the present invention are not directly used to adsorb organic matter-clay complexes to limit their expansion. Directly adding sand and gravel components to the soil would significantly change the soil hardness, thereby hindering plant root penetration. Therefore, the present invention uses rice husk powder, humic acid powder, magnesium ammonium phosphate, and shell powder mixed with the sand and gravel components and then calcined in three stages. The resulting porous carrier not only provides a basic porous rigid skeleton, but also has a lower hardness than the sand and gravel components alone. At a certain addition amount, it does not increase the difficulty of planting and allows the roots of wetland plants such as reeds to penetrate.

[0037] 3. In the present invention, both the organic matter-clay composite and the porous carrier are surface-modified, forming a high connection strength between the two, and can maintain stable adsorption under conditions such as rain erosion. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be considered as limiting the scope. A person of ordinary skill in the art can also derive other relevant drawings based on these drawings without inventive effort, among which:

[0039] Figure 1This is an SEM image of the sand and gravel components before treatment according to the present invention;

[0040] Figure 2 It is the SEM picture of the porous carrier after treatment of the present invention. DETAILED DESCRIPTION

[0041] In order to make the objectives, technical solutions, and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only intended to explain the present invention and are not intended to limit the present invention. That is, the embodiments described herein are only some embodiments of the present invention, not all embodiments. Generally, the components of the embodiments of the present invention described and illustrated in the drawings herein may be arranged and designed in various different configurations.

[0042] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but is merely intended to represent selected embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative work are within the scope of protection of the present invention.

[0043] It should be noted that relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus comprising the element.

[0044] The features and performance of the present invention are further described in detail below with reference to the embodiments.

[0045] Example 1

[0046] A preferred embodiment of the present invention provides a sewage treatment process for converting river silt into planting soil, comprising the following steps:

[0047] S1. Remove impurities, crush, and perform the first enzymatic hydrolysis on the high-silt sewage in the river to obtain muddy water;

[0048] S2. Screen and filter the mud water to obtain organic matter-clay composite and sand and gravel components. The microscopic picture of the sand and gravel components is as follows: Figure 1 As shown;

[0049] S3, adding a composite anchoring agent to the organic matter-clay complex for hydrophobic modification to obtain a hydrophobic organic matter-clay complex;

[0050] S4, inoculating the composite bacterial community into the hydrophobic organic matter-clay complex, fermenting at 45°C for 5 days for a second fermentation, filtering after the second fermentation, adding a chitosan-humic acid composite flocculant, and dehydrating by filter pressing to obtain an active mud cake;

[0051] S5. Add rice husk powder, humic acid powder, magnesium ammonium phosphate, and shell powder to the sand and gravel components, mix them evenly, add 6% wood vinegar by weight of the mixture to the mixture, stir evenly, and granulate to obtain a first intermediate. The first intermediate is calcined to obtain a second intermediate. The second intermediate is surface-modified with polydopamine to obtain a porous carrier. The microscopic image of the porous carrier is shown in FIG. Figure 2 shown; contrast Figure 1 、 Figure 2 , the pores of the porous support increase and the pore diameter increases;

[0052] S6. Spray potassium persulfate solution on the surface of the active mud cake, react at 50° C. for 1-2 hours, filter, wash, and dry, then spray quaternized chitosan solution, react at 60° C. for 2 hours to obtain a surface-treated active mud cake, then put the surface-treated active mud cake and a porous carrier into a twin-screw mixer, add cellulose nanocrystals, heat to 80° C., react for 1-2 hours, and obtain planting soil;

[0053] S7. Evenly spread the planting soil on the surface of the wetland soil and till it to improve the wetland soil by the planting soil.

[0054] The composite anchoring agent in step S3 comprises nano-metakaolin, hectorite nanosheets, and octadecyltrimethoxysilane, wherein the mass ratio of nano-metakaolin, hectorite nanosheets, and octadecyltrimethoxysilane is 1:2:1;

[0055] The amount of the composite anchoring agent added in step S3 is 0.5% of the mass of the organic matter-clay composite.

[0056] In step S6, the concentration of the potassium persulfate solution is 0.1 M, and the spraying volume is 1.5 L / kg of active mud cake; the concentration of the quaternized chitosan solution is 2% w / v, and the spraying volume is 0.5 L / kg of active mud cake; the amount of cellulose nanocrystals added is 0.5% of the total mass of the surface-treated active mud cake and the porous carrier.

[0057] In step S5, the amount of rice husk powder added is 30% of the mass of the sand and gravel component, the amount of humic acid powder added is 15% of the mass of the sand and gravel component, the amount of magnesium ammonium phosphate added is 10% of the mass of the sand and gravel component, and the amount of shell powder added is 5% of the mass of the sand and gravel component.

[0058] In step S5, the second intermediate is surface-modified with polydopamine by the following steps:

[0059] A1. Immerse the second intermediate in a 5% by mass 3-aminopropyltriethoxysilane solution and react at 60° C. for 2 h to obtain a silanized second intermediate.

[0060] A2. Prepare a dopamine solution with a pH of 8.5, mix the dopamine solution with the silanized second intermediate to form a reaction system, add 0.1% FeCl3 catalyst by weight of the reaction system to the reaction system, react at 25°C for 4-5 hours, then raise the temperature to 45°C, continue the reaction for 8-10 hours, filter, and dry to obtain a porous carrier.

[0061] In step S5, the first intermediate is calcined in three stages to obtain the second intermediate, and the three-stage calcination includes:

[0062] The first stage of calcination: calcination at 350 ° C in air for 2 hours;

[0063] Second stage calcination: calcination at 550°C for 1.5 hours under oxygen-limited conditions, wherein the oxygen-limited environment is a nitrogen environment or a low-oxygen environment;

[0064] The third calcination stage: calcination at 700°C in air for 30 minutes.

[0065] The mass ratio of the surface-treated active mud cake to the porous carrier in step S6 is 3:6.

[0066] The mass ratio of chitosan to humic acid in the chitosan-humic acid composite flocculant is 1:2.

[0067] The enzymatic agent used for the first enzymatic hydrolysis in step S1 includes the following components: cellulase, xylanase, and laccase, with the mass ratio of cellulase, xylanase, and laccase being 6:2:1. The enzymatic hydrolysis conditions and dosage refer to the prior art.

[0068] The composite bacterial community used in the second fermentation in S4 includes the following components: filamentous fungi Trichoderma reesei and Bacillus subtilis; the amounts used refer to those used in the prior art.

[0069] The filamentous fungus Trichoderma reesei has a deposition number of CGMCC 3.3711 and is deposited in the China General Microbiological Culture Collection Center;

[0070] The Bacillus subtilis is deposited in China General Microorganism Culture Collection Center with the accession number of CGMCC 1.3358.

[0071] The organic matter in the silt mainly includes plant residues, humus, microbial remains, etc. The organic matter content in the organic matter-clay complex is ≥30%.

[0072] Example 2

[0073] This embodiment is based on Example 1, but differs from Example 1 in that the mass ratio of the surface-treated active mud cake to the porous carrier in step S6 of this embodiment is 3:6.5.

[0074] Example 3

[0075] This embodiment is based on Example 1, but differs from Example 1 in that the mass ratio of the surface-treated active mud cake to the porous carrier in step S6 of this embodiment is 3:7.

[0076] Example 4

[0077] This embodiment is based on Example 1, but differs from Example 1 in that the amount of the composite anchoring agent added in step S3 of this embodiment is 0.7% of the mass of the organic matter-clay composite.

[0078] Example 5

[0079] This embodiment is based on Example 1, but differs from Example 1 in that the amount of the composite anchoring agent added in step S3 is 0.8% of the mass of the organic matter-clay composite. Increased hydrophobicity reduces the release rate of organic matter after water absorption and swelling.

[0080] Example 6

[0081] This embodiment is based on Example 4, but differs from Example 4 in that the amount of rice husk powder added in step S5 is 31% of the mass of the sand and gravel component, the amount of humic acid powder added is 15% of the mass of the sand and gravel component, the amount of magnesium ammonium phosphate added is 11% of the mass of the sand and gravel component, and the amount of shell powder added is 5% of the mass of the sand and gravel component. Taking all factors into consideration, this embodiment can be preferably selected as the optimal solution.

[0082] Example 7

[0083] This embodiment is based on Example 4, but differs from Example 4 in that: in step S5 of this embodiment, the amount of rice husk powder added is 32% of the mass of the sand and gravel component, the amount of humic acid powder added is 16% of the mass of the sand and gravel component, the amount of ammonium magnesium phosphate added is 12% of the mass of the sand and gravel component, and the amount of shell powder added is 6% of the mass of the sand and gravel component.

[0084] Comparative Example 1

[0085] This comparative example provides a sewage treatment process for converting river silt into planting soil, comprising the following steps:

[0086] S1. Remove impurities and crush the high-silt sewage in the river to obtain muddy water;

[0087] S2. Screening and filtering the muddy water to obtain organic matter-clay complex and sand and gravel components;

[0088] S3. Dehydrating and drying the organic matter-clay complex to obtain a mud cake; the mud cake is the target substance and is used as a soil conditioner. The soil conditioner is evenly spread on the surface of the wetland soil and plowed to achieve the improvement of the wetland soil by the planting soil.

[0089] Comparative Example 2

[0090] Based on Example 1, the sewage treatment process for converting river silt into planting soil provided in this comparative example is different from that in Example 1: this comparative example does not add rice husk powder, humic acid powder, ammonium magnesium phosphate, and shell powder to the sand and gravel components. The sand and gravel group powder is directly calcined at 600-700°C and then surface-modified with polydopamine to obtain a porous carrier.

[0091] Comparative Example 3

[0092] Based on Example 1, the sewage treatment process for converting river silt into planting soil provided in this comparative example is different from that in Example 1 in that rice husk powder is not added to the sand and gravel components in this comparative example.

[0093] Comparative Example 4

[0094] Based on Example 1, the sewage treatment process for converting river silt into planting soil provided in this comparative example is different from that in Example 1 in that humic acid powder is not added to the sand and gravel components in this comparative example.

[0095] Comparative Example 5

[0096] Based on Example 1, the sewage treatment process for converting river silt into planting soil provided in this comparative example is different from that in Example 1 in that this comparative example does not add magnesium ammonium phosphate to the sand and gravel components.

[0097] Comparative Example 6

[0098] Based on Example 1, the sewage treatment process for converting river silt into planting soil provided in this comparative example is different from that in Example 1 in that no shell powder is added to the sand and gravel components in this comparative example.

[0099] Comparative Example 7

[0100] Based on Example 1, the sewage treatment process for converting river silt into planting soil provided in this comparative example is different from that in Example 1 in that this comparative example does not perform the first enzymatic hydrolysis in step S1.

[0101] Comparative Example 8

[0102] Based on Example 1, the sewage treatment process for converting river silt into planting soil provided in this comparative example is different from that in Example 1 in that: this comparative example does not perform a second fermentation in step S4.

[0103] Comparative Example 9

[0104] Based on Example 1, the sewage treatment process for converting river silt into planting soil provided in this comparative example is different from that in Example 1: in step S6, the surface of the activated mud cake is not treated, and the activated mud cake prepared in step S4 and the porous carrier are directly put into a twin-screw mixer, cellulose nanocrystals are added, and the temperature is raised to 80°C and reacted for 1-2 hours to obtain planting soil.

[0105] Comparative Example 10

[0106] Based on Example 1, the sewage treatment process for converting river silt into planting soil provided in this comparative example is different from that in Example 1 in that: this comparative example does not perform step S3, adds a composite anchoring agent to the organic matter-clay complex for hydrophobic modification to obtain a hydrophobic organic matter-clay complex, and does not perform hydrophobic modification on the organic matter-clay complex. The organic matter-clay complex in step S4 is a complex that has not been hydrophobically modified.

[0107] Comparative Example 11

[0108] Based on Example 1, the sewage treatment process for converting river silt into planting soil provided in this comparative example is different from that in Example 1 in that polydopamine is not used to perform surface modification on the second intermediate in step S5 of this comparative example.

[0109] Comparative Example 12

[0110] Based on Example 1, the sewage treatment process for converting river silt into planting soil provided in this comparative example is different from that in Example 1 in that the mass ratio of the surface-treated active mud cake to the porous carrier in step S6 of this comparative example is 3:5.

[0111] Comparative Example 13

[0112] Based on Example 1, this comparative example provides a wastewater treatment process for converting river silt into planting soil. This process differs from Example 1 in that the mass ratio of the surface-treated activated mud cake to the porous carrier in step S6 is 3:8. Excessive porous carrier significantly increases soil hardness, making planting more difficult and reducing root penetration.

[0113] Test Example 1

[0114] The planting soils (soil conditioners) prepared in Examples 1-7 and Comparative Examples 1-13 were subjected to water permeability testing and organic matter release flux testing; the results are shown in Table 1.

[0115] Water permeability test: Refer to GB / T 50123-2019 and record the amount of water passing through the planting soil per unit area per unit time (cm 3 cm -2 ·s -1 );

[0116] Organic matter release flux: The planting soil was placed in a simulated wetland environment (constant temperature of 25°C, humidity of 70%) and continuously monitored for 30 days. The daily organic matter release (mg·m -2 ·d -1 ), and take the average value.

[0117] Table 1 Test results of water permeability and organic matter release flux:

[0118] Group <![CDATA[Water permeability (×10 -5 cm / s)]]> <![CDATA[Organic matter release flux (mg·m -2 ·d -1 )]]> Examples 1-7 ≥5 ＞90 Comparative Example 1 ＜1.2 100 ± 10 Comparative Example 2 ＜5 ＜90 Comparative Examples 3-6 ＜5 ＞90 Comparative Example 7 ＞5 ＜70 Comparative Example 8 ＞5 ＜70 Comparative Example 9 ＜5 75-80 Comparative Example 10 ＜2 ＜50 Comparative Example 11 ＜5 75-80 Comparative Example 12 ＜5 ＜90 Comparative Example 13 ＞5 ＞90 .

[0119] Water permeability and organic matter release flux are influenced by numerous factors, and there is no linear relationship (either directly or inversely proportional). The pore structure of the porous carrier affects both water permeability and organic matter release flux. Even after the organic matter-clay complex fully expands to release organic matter, if the carrier's pore size and porosity are insufficient for organic matter to pass through, the carrier becomes a physical barrier to the organic matter, easily accumulating it and preventing it from being expelled. This reduces the organic matter release flux and water permeability. When the organic matter-clay complex fully expands and the carrier forms no physical barrier, water permeability is low but organic matter release flux is high. Furthermore, organic matter release is also affected by enzymatic hydrolysis and fermentation processes, with their presence or absence affecting the organic matter release flux. The present invention integrates a porous structure with organic matter treatment to achieve a high organic matter release flux while increasing air permeability.

[0120] Test Example 2

[0121] The penetration of reed roots using the planting soils prepared in Examples 1-7, Comparative Example 2, and Comparative Example 13 was tested. The results are shown in Table 2.

[0122] The detection method is: place the planting soil in a transparent planting container with a depth of 35 cm. The bottom of the transparent planting container is provided with drainage holes. 100 reed seedlings are planted. The lower end of the reed seedlings is inserted into the planting soil to a depth of 10 cm. Water is replenished at 6 o'clock in the morning every day. The flooding level after replenishment is 5 cm. After 30 days, the number of reed plants whose roots reach the bottom of the transparent planting container is counted. The proportion of reed plants whose roots reach the bottom of the transparent planting container in the total planting volume is the penetration rate of the reed roots; the reed plants whose roots reach the bottom of the planting container are selected, and the longest root length that can be achieved is counted.

[0123] Table 2 Penetration test of planting soil:

[0124] Examples 1-7 Comparative Example 2 Comparative Example 13 Penetration ＞96% ＜50% ＜70% Maximum root length 42-44cm 37cm 39cm .

[0125] The invention has good root penetration and no root rot, and all the roots survive.

[0126] The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions and improvements made by any technician familiar with the field within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A sewage treatment process for converting river silt into planting soil, characterized by: The following steps are involved: S1. Remove impurities, crush, and perform the first enzymatic hydrolysis on the high-silt sewage in the river to obtain muddy water; S2. Screening and filtering the muddy water to obtain organic matter-clay complex and sand and gravel components; S3, adding a composite anchoring agent to the organic matter-clay complex for hydrophobic modification to obtain a hydrophobic organic matter-clay complex; S4, inoculating a composite bacterial community into the hydrophobic organic matter-clay complex, filtering after the second fermentation, adding a chitosan-humic acid composite flocculant, and dehydrating by filter pressing to obtain an active mud cake; S5, adding rice husk powder, humic acid powder, magnesium ammonium phosphate, and shell powder to the sand and gravel components, mixing evenly, adding wood vinegar, stirring evenly, and granulating to obtain a first intermediate, calcining the first intermediate to obtain a second intermediate, and surface-modifying the second intermediate with polydopamine to obtain a porous carrier; S6. Spraying potassium persulfate solution on the surface of the active mud cake, filtering, washing, and drying after the reaction, and then spraying quaternized chitosan solution, continuing the reaction to obtain a surface-treated active mud cake, and then putting the surface-treated active mud cake and a porous carrier into a twin-screw mixer, adding cellulose nanocrystals, heating to 80° C. and reacting for 1-2 hours to obtain planting soil; S7. Evenly spread the planting soil on the surface of the wetland soil and till it to improve the wetland soil by the planting soil.

2. The sewage treatment process for converting river silt into planting soil according to claim 1, characterized in that: The composite anchoring agent in step S3 comprises nano-metakaolin, hectorite nanosheets, and octadecyltrimethoxysilane, wherein the mass ratio of nano-metakaolin, hectorite nanosheets, and octadecyltrimethoxysilane is 1:2:1; The amount of the composite anchoring agent added in step S3 is 0.5-0.8% of the mass of the organic matter-clay composite.

3. The sewage treatment process for converting river silt into planting soil according to claim 2, characterized in that: In step S6, the concentration of the potassium persulfate solution is 0.1 M, and the spraying volume is 1.5 L / kg of active mud cake; the concentration of the quaternized chitosan solution is 2% w / v, and the spraying volume is 0.5 L / kg of active mud cake; the amount of cellulose nanocrystals added is 0.5% of the total mass of the surface-treated active mud cake and the porous carrier.

4. The sewage treatment process for converting river silt into planting soil according to claim 1, characterized in that: In step S5, the amount of rice husk powder added is 30-32% of the mass of the sand and gravel component, the amount of humic acid powder added is 15-16% of the mass of the sand and gravel component, the amount of magnesium ammonium phosphate added is 10-12% of the mass of the sand and gravel component, and the amount of shell powder added is 5-6% of the mass of the sand and gravel component.

5. The sewage treatment process for converting river silt into planting soil according to claim 1 is characterized by: In step S5, the second intermediate is surface-modified with polydopamine by the following steps: A1. Immerse the second intermediate in a 5% by mass 3-aminopropyltriethoxysilane solution and react at 60° C. for 2 h to obtain a silanized second intermediate. A2. Prepare a dopamine solution with a pH of 8.5, mix the dopamine solution with the silanized second intermediate to form a reaction system, add 0.1% FeCl3 catalyst by weight of the reaction system to the reaction system, react at 25°C for 4-5 hours, then raise the temperature to 45°C, continue the reaction for 8-10 hours, filter, and dry to obtain a porous carrier.

6. The sewage treatment process for converting river silt into planting soil according to claim 1 is characterized by: In step S5, the first intermediate is calcined in three stages to obtain the second intermediate, and the three-stage calcination includes: The first stage of calcination: calcination in air at 350 ° C for 2 hours; The second calcination stage is calcined at 550°C for 1.5 hours under oxygen-limited conditions, wherein the oxygen-limited environment is a nitrogen environment or a low-oxygen environment; The third calcination stage: calcination at 700°C in air for 30 minutes.

7. The sewage treatment process for converting river silt into planting soil according to claim 1, characterized in that: The mass ratio of the surface-treated active mud cake to the porous carrier in step S6 is 3:6-7.

8. The sewage treatment process for converting river silt into planting soil according to claim 1 is characterized by: The mass ratio of chitosan to humic acid in the chitosan-humic acid composite flocculant is 1:

2.

9. The sewage treatment process for converting river silt into planting soil according to claim 1, characterized in that: The enzymatic agent used for the first enzymatic hydrolysis in step S1 includes the following components: cellulase, xylanase, and laccase.

10. The sewage treatment process for converting river silt into planting soil according to claim 1, characterized in that: The composite bacterial consortium used in the second fermentation in S4 includes the following components: filamentous fungi Trichoderma reesei and Bacillus subtilis; The filamentous fungus Trichoderma reesei has a deposition number of CGMCC 3.3711 and is deposited in the China General Microbiological Culture Collection Center; The deposit number of Bacillus subtilis is CGMCC 1.3358, and it is deposited in the China General Microbiological Culture Collection Center.

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