Ecological restoration material for polluted bottom mud of rivers and lakes as well as preparation method and application of ecological restoration material

Abstract

The invention discloses a bottom mud ecological restoration material as well as a preparation method and application thereof. The material is composed of a degradable carrier, a treatment flora and a multifunctional filler. The carrier is porous particles die-cast by corn straws and the like; the treatment flora comprises photosynthetic bacteria, bacillus and nitrifying bacteria; the filler is prepared from non-nitrate type hydrotalcite-like compounds, calcium nitrate, nitrate type hydrotalcite-like compounds and a flocculating agent according to a specific mass ratio. The preparation method comprises the following steps: carrying out pressure casting on the carrier, adsorbing the flora, and rolling the filler to form balls. The restoration method comprises the steps that a river channel is cut off in the dry season to form a closed area, materials are put according to the area ratio of 10: 1 for preliminary restoration, and after standing is conducted for 1-5 days, the materials are put along with water flow according to the area ratio of 2: 1 for deep restoration. Through the physical, chemical and biological synergistic effect, the sediment redox environment can be effectively improved, pollutant release and degradation are promoted, operation is easy and convenient, and the risk of secondary pollution is low.

Description

Technical Field

[0001] This invention belongs to the field of environmental governance and ecological restoration technology, specifically relating to an ecological restoration material for polluted sediments in rivers and lakes, its preparation method, and its application. Background Technology

[0002] Endogenous pollution in river and lake sediments (such as excessive nitrogen, phosphorus, sulfur, organic matter, and heavy metals) is a major cause of eutrophication and ecological degradation. Existing treatment technologies each have limitations: physical methods (such as dredging and aeration) are costly and prone to ecological damage; biological methods (such as adding microbial agents) are slow to take effect and have low microbial survival rates; chemical methods (such as adding passivating agents) are fast-acting but easily cause chemical residues and secondary pollution. For example, directly adding nitrates or mineral materials may trigger nitrite (NO2) formation. - -N) and ammonium salts (NH4) + The accumulation of sediment (N-N) threatens aquatic ecosystem security. Therefore, there is an urgent need to develop a sediment ecological restoration technology that can coordinate physical, chemical, and biological processes to achieve high efficiency, long-lasting results, and low environmental risk. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide an ecological restoration material for polluted sediments in rivers and lakes, as well as its preparation method and application. The ecological restoration material provided by this invention has low pollution, is easy to operate, and has a long-lasting restoration effect. Through a unique structural design, this material achieves an organic combination of carrier, functional microbial community and multifunctional filler. When applied, it adopts a step-by-step restoration strategy, which can effectively improve the redox environment of sediments, promote the release and degradation of pollutants, and at the same time minimize secondary pollution.

[0004] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a sediment ecological restoration material, comprising a biodegradable carrier, a remediation microbial community attached to the pores of the carrier, and a filler shell wrapped around the outside of the carrier; The treatment microbial community includes photosynthetic bacteria, Bacillus, and nitrifying bacteria; The components of the filler shell include non-nitrate hydrotalcite, calcium nitrate, nitrate hydrotalcite, and flocculant.

[0005] Preferably, the carrier is a porous particle with through holes inside, and the diameter of the porous particle is 2-3 cm; the material of the carrier is one or more of corn stalks, wheat stalks, paper and wood chips.

[0006] Preferably, the non-nitrate type hydrotalcite and the nitrate type hydrotalcite are independently one or more of magnesium aluminum hydrotalcite, zinc aluminum hydrotalcite and calcium aluminum hydrotalcite; the flocculant is polyaluminum chloride and / or polyacrylamide.

[0007] Preferably, the mass ratio of the non-nitrate type hydrotalcite, calcium nitrate, nitrate type hydrotalcite and flocculant in the filler shell is 0.5:1.5:4.5:3.5.

[0008] Preferably, the volume ratio of the carrier to the outer shell of the filler is 1:0.6.

[0009] This invention also provides a method for preparing the sediment ecological restoration material described in the above technical solution, comprising the following steps: (1) The biodegradable carrier raw material is die-cast into particles with through holes inside to obtain the carrier; (2) The carrier is immersed in a treatment bacterial community solution containing photosynthetic bacteria, Bacillus and nitrifying bacteria for bacterial community adsorption; (3) The particles that have completed the adsorption of bacteria are mixed with the filler, and the filler is wrapped around the particles by rolling to form balls, so as to obtain the bottom sediment ecological restoration material; the filler includes non-nitrate type hydrotalcite, calcium nitrate, nitrate type hydrotalcite and flocculant.

[0010] Preferably, in step (2), the bacterial community is adsorbed for 3 to 5 hours to allow the bacterial community to fully colonize; after adsorption, the expansion rate of the particulate matter at room temperature is 0.3 to 0.5%.

[0011] In the above preparation method, the adsorption time is 3-5 hours, and the expansion rate of the particles is controlled at 0.3-0.5% at room temperature to ensure sufficient colonization of the microbial community. Through the rolling ball-making process, the filler can be evenly wrapped around the outside of the carrier to form core-shell structured repair material particles.

[0012] This invention also provides a method for remediating polluted river and lake sediments using the sediment ecological restoration material described above, comprising the following steps: (1) Preliminary restoration (surface treatment and environmental modification): During the dry season, the section of the river to be restored is isolated to form a closed restoration area, and the bottom sediment ecological restoration material is put into the closed restoration area. (2) Deep restoration (deep treatment and thorough purification): After the initial restoration is completed and the sediment is left to stand for 1 to 5 days, the bottom sediment ecological restoration material is put back into the closed restoration area with the water flow.

[0013] In the above-mentioned methods for remediating polluted sediments in rivers and lakes, the preliminary remediation stage aims to preliminarily treat the surface sediments, improve the redox conditions and microbial community structure at the interface between the local water body and the sediment, and in the deep remediation stage, the flocculants in the remediation materials expand by 80-110% when they come into contact with water, which can more effectively penetrate into the sediments and flocculate and capture pollutants released from deep layers, which are then ultimately degraded by functional microorganisms.

[0014] Preferably, in step (1), the ratio of the coverage area of ​​the bottom sediment ecological restoration material on the riverbed to the surface area of ​​the water surface in the closed restoration area is 1:10.

[0015] Preferably, in step (2), the ratio of the coverage area of ​​the bottom sediment ecological restoration material on the riverbed to the surface area of ​​the water surface in the closed restoration area is 1:2.

[0016] The sediment ecological restoration material of this invention is a core-shell structured composite particle, comprising: a biodegradable carrier core: porous particles (2-3 cm in diameter) cast from natural materials such as corn stalks, wheat stalks, paper, or wood chips, with internal through-pores. This carrier is used to adsorb and load remedial bacteria, and can be gradually degraded in water without secondary pollution. Remedial bacteria: attached to the pores and surface of the carrier, including photosynthetic bacteria, Bacillus, and nitrifying bacteria, used for the biodegradation of pollutants released into the water. A multifunctional filler shell: encasing the carrier, composed of the following four components in a specific mass ratio: non-nitrate-type hydrotalcite: as a hydrophilic mineral, it provides biofilm attachment space for the remedial bacteria and utilizes its ammonia-loving properties to promote the degradation of ammonia nitrogen (NH4). + Treatment methods include: Calcium nitrate: used to remove nitrogen and phosphorus from water; oxidizing reduced iron (Fe) and sulfur (S) in sediment through autotrophic denitrification, improving the anaerobic environment of the sediment; and simultaneously promoting a shift in the sediment microbial community from being dominated by sulfate-reducing bacteria (SRB) to being dominated by nitrate-reducing bacteria (NRB) or sulfur-oxidizing bacteria (NR-SOB), creating a favorable microecological environment for functional bacteria. Nitrate-type hydrotalcite: used to alter the particle structure of sediment, reducing its particle size and physical cohesion, making the sediment structure loose, thereby promoting the release of solid pollutants into the liquid phase and accelerating the transformation of sediment to an aerobic state. Flocculants: polyaluminum chloride (PAC) and / or polyacrylamide (PAM), used to flocculate and precipitate suspended pollutants released from sediment into the water.

[0017] Compared with the prior art, the present invention has the following advantages: (1) Multi-mechanism synergistic innovation: This invention is not a simple mixture of materials, but creatively constructs a triple synergistic remediation system of "physical adsorption (carrier) + chemical modification (filler) + biodegradation (microbial community)". The components in the filler have clear functions and promote each other: hydrotalcite improves the sediment structure, calcium nitrate improves the redox environment and fixes phosphorus and some heavy metals, flocculant aggregates pollutants, and finally the pre-set treatment microbial community carries out biological removal, realizing a closed loop from "pollution fixation" to "pollution elimination".

[0018] (2) Novel structural design: The core-shell structure of "degradable carrier core + multifunctional filler shell" is adopted. The carrier not only serves as a "dormitory" for the microbial community, but its degradation process can also gradually release the microbial community and prolong the action time; the outer shell filler acts as the "vanguard" to first improve the sediment environment and create conditions for microbial activity. This sequential action design significantly improves the remediation efficiency.

[0019] (3) Effectively avoid secondary pollution: By pre-combining chemical materials such as calcium nitrate and hydrotalcite with the microbial community and forming a high ammonia environment in the local area, the activity of the treatment microbial community is stimulated and the nitrogen cycle is accelerated, thereby effectively inhibiting the accumulation of nitrite and ammonium salts caused by the direct addition of chemical agents in traditional methods and reducing the risk of secondary ecology.

[0020] (4) Optimization of remediation process: The proposed "two-step application method" is strategic. The first step, low-density application, aims to "pave the way" and improve the overall environment; the second step, high-density application, is used to "attack" deep pollution. This method overcomes the material waste and uneven remediation problems caused by one-time application, making the remediation process more scientific, economical and thorough. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 The present invention provides a method for the remediation of polluted sediment in rivers and lakes using sediment ecological restoration materials. Detailed Implementation

[0023] Example 1 Preparation of sediment ecological restoration materials: Carrier preparation: Select dry corn stalks, crush and screen them, and then press them into regular spherical particles with a diameter of about 2.5 cm and internal through holes.

[0024] Microbial adsorption: The above-mentioned carrier particles are immersed in a high-concentration compound treatment microbial solution containing photosynthetic bacteria ( 沼泽红假单胞菌 Bacillus subtilis ( 枯草芽孢杆菌 ) and Nitrosomonas spp. 亚硝化单胞菌 The mixed bacterial solution had a total bacterial concentration of 2×10⁻⁶. 8 CFU / mL ~5×10 8 CFU / mL. The carrier particles were immersed and adsorbed at room temperature (25℃) for 4 hours, with the water absorption and swelling rate controlled at 0.4%.

[0025] Filler preparation: Weigh non-nitrate magnesium aluminum hydrotalcite (MgAl-CO3LDH), calcium nitrate (Ca(NO3)2·4H2O), nitrate magnesium aluminum hydrotalcite (MgAl-NO3LDH), and polyaluminum chloride (PAC, Al2O3 content ≥30%) powders in a mass ratio of 0.5:1.5:4.5:3.5, and mix them thoroughly in a mixer to obtain the composite filler.

[0026] Rolling pelletizing: The wet carrier particles adsorbed with the therapeutic bacteria are removed, excess water is drained, and then placed in a rotary granulator. During the rolling process, the mixed filler powder is evenly sprinkled on the surface of the carrier particles, and the rolling process firmly coats the carrier particles, forming a core-shell structure. The final product is controlled so that the volume ratio of the carrier core to the filler shell is 1:0.6, and the filler layer thickness is 2~3 mm.

[0027] Drying and storage: Dry the prepared composite repair material particles in a cool and ventilated place until there is no obvious moisture on the surface, seal the packaging, and store in a dry place at room temperature for later use.

[0028] Example 2 The difference from Example 1 is as follows: Carrier preparation: Porous particles formed by die casting of waste corrugated paper pulp.

[0029] Filler formulation: Non-nitrate type hydrotalcite is zinc aluminum hydrotalcite (ZnAl-CO3LDH), nitrate type hydrotalcite is zinc aluminum nitrate hydrotalcite (ZnAl-NO3LDH), and flocculant is anionic polyacrylamide (PAM, molecular weight approximately 12 million).

[0030] Microbial adsorption: The adsorption time was 3.5 hours, and the expansion rate was controlled at 0.3% at room temperature. The remaining steps and parameters were the same as in Example 1.

[0031] Application Example 1 The object of remediation is a closed scenic waterway in a city, approximately 200 meters long, 15 meters wide on average, and 1.2 meters deep on average. The bottom sediment is black and has an odor. Monitoring shows that its organic matter content is 12.5%, total nitrogen (TN) is 1850 mg / kg, total phosphorus (TP) is 650 mg / kg, and oxidation-reduction potential (ORP) is -250 mV, indicating a state of severe anaerobic pollution.

[0032] Repair steps: Step 1 (River Channel Isolation and Preliminary Repair): During the dry season (December), a cofferdam is used to isolate both ends of this section of the river, forming a closed repair area with a surface area of ​​approximately 3000 m². 2The remediation material prepared in Example 1 was uniformly added to the river channel. The initial addition amount was calculated based on a ratio of "sealed river channel surface area: remediation material placement area = 10:1", meaning the material would cover an area of ​​approximately 300 m² on the riverbed. 2 The actual volume of material added was 15 m³. 3 .

[0033] Step 2 (Deep Remediation): After 3 days of settling, an increase in suspended solids was observed on the water surface (due to the release of pollutants from the bottom sediment). A high-pressure water jet (0.5 MPa) was used to create a water flow, flushing up the initially applied remediation material and causing it to redistribute and settle with the water flow. New material was then added at a ratio of 2:1 (sealed river surface area: remediation material area), meaning the additional material covered an area of ​​approximately 1500 m² on the riverbed. 2 The actual volume of material added was 75 m³. 3 After addition, the flocculant component in the repair material can be observed to swell upon contact with water, increasing in volume by approximately 95%.

[0034] Repair effect monitoring: 30 days after remediation: the black and odorous water phenomenon was basically eliminated, and the transparency increased from 10 cm to 45 cm. The ORP of the bottom sediment rose to -50 mV, indicating that the oxidation environment of the bottom sediment was significantly improved.

[0035] Ninety days post-remediation: Sediment samples were collected and analyzed. Results showed that the organic matter content decreased to 6.8%, total nitrogen decreased to 820 mg / kg, and total phosphorus remained stable at 420 mg / kg. Heavy metal analysis indicated that the contents of exchangeable lead (Ex-Pb) and chromium (Ex-Cr) in the sediment decreased by 42% and 35%, respectively, compared to pre-remediation levels (Ex-Pb 6.89 mg / kg and Ex-Cr 5.81 mg / kg). The sediment color changed to yellowish-brown. Microbial community analysis showed a decrease in the dominance of sulfate-reducing bacteria (SRB), while nitrate-reducing bacteria (NRB) and aerobic bacteria became the dominant species.

[0036] Application Example 2 Object of restoration: A nearshore bay area of ​​a suburban lake, affected by the inflow of domestic sewage, covering an area of ​​approximately 500 m². 2 The sediment was severely eutrophic, with monitoring showing an organic matter content of 2.5%, total nitrogen of 2170 mg / kg, ammonia nitrogen of 150 mg / kg, a redox potential of -220 mV, and a total phosphorus release flux of 1.4 mg / (m³). 2 ·d).

[0037] Repair steps: A two-step method similar to Application Example 1 was adopted. First, the bay area was isolated, and the material from Example 2 was applied at a ratio of 10:1 for initial repair. After standing for 2 days, the water flow was stirred using the propeller of a small boat, and a second application was made at a ratio of 2:1 to promote material distribution.

[0038] Restoration effect: After 60 days of restoration, algal blooms in the area were effectively suppressed, and the phosphorus release flux from the sediment was 0.4 mg / (m³). 2 ·d), the redox potential rises to -120mV, ammonia nitrogen (NH4) + The concentration of nitrogen (N) was 18.4 mg / kg, the total nitrogen was 1320 mg / kg, and the organic matter was 1.3%, which verifies the advantages of the material of the present invention in controlling secondary pollution.

[0039] Comparative Example 1 In another polluted area with similar conditions to that in Application Example 1 (monitoring showed an organic matter content of 2.4%, total nitrogen of 2000 mg / kg, ammonia nitrogen of 142 mg / kg, and an oxidation-reduction potential (ORP) of -230 mV), the total phosphorus release flux was 1.32 mg / (m³). 2 •d) Add only one dose of the same amount of repair material (a mixture of calcium nitrate and hydrotalcite) as the total amount used in Application Example 1.

[0040] Results: 60 days after remediation, the sediment ORP only increased slightly to -180 mV, and the sediment phosphorus release flux was 1.17 mg / (m³). 2 ·d), ammonia nitrogen (NH4) + The concentration of nitrogen (N) was 118.4 mg / kg, the total nitrogen was 1240 mg / kg, and the organic matter was 1.8%, indicating that the improvement in the bottom sediment structure was not significant.

[0041] The above embodiments and application examples demonstrate that the sediment ecological restoration material and its two-step restoration method provided by this invention can effectively improve the redox environment of sediment through the synergistic effect of multiple components, promote the release and fixation of pollutants, and achieve efficient and stable restoration of contaminated sediment through pre-placed microbial communities for biodegradation. Simultaneously, it effectively avoids the secondary pollution problems that may be caused by traditional chemical methods. This method is simple to operate, environmentally friendly, and has significant ecological benefits and application prospects.

[0042] Although the above embodiments have provided a detailed description of the present invention, they are merely some, not all, embodiments of the present invention. Those skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. All such modifications and alterations should be covered within the protection scope of the present invention.

Claims

1. A sediment ecological restoration material, characterized in that, It includes a biodegradable carrier, a treatment microbial community attached to the pores of the carrier, and a filler shell that surrounds the outside of the carrier; The treatment microbial community includes photosynthetic bacteria, Bacillus, and nitrifying bacteria; The components of the filler shell include non-nitrate hydrotalcite, calcium nitrate, nitrate hydrotalcite, and flocculant.

2. The sediment ecological restoration material as described in claim 1, characterized in that, The carrier is a porous particle with through holes inside, and the diameter of the porous particle is 2-3 cm; the material of the carrier is one or more of corn stalks, wheat stalks, paper and wood chips.

3. The sediment ecological restoration material as described in claim 1, characterized in that, The non-nitrate type hydrotalcite and nitrate type hydrotalcite are independently one or more of magnesium aluminum hydrotalcite, zinc aluminum hydrotalcite and calcium aluminum hydrotalcite; the flocculant is polyaluminum chloride and / or polyacrylamide.

4. The sediment ecological restoration material as described in claim 1, characterized in that, The mass ratio of the non-nitrate type hydrotalcite, calcium nitrate, nitrate type hydrotalcite, and flocculant in the filler shell is 0.5:1.5:4.5:3.

5.

5. The sediment ecological restoration material as described in claim 1, characterized in that, The volume ratio of the carrier to the outer shell of the filler is 1:0.

6.

6. A method for preparing the sediment ecological restoration material according to any one of claims 1 to 5, comprising the following steps: (1) The biodegradable carrier raw material is die-cast into particles with through holes inside to obtain the carrier; (2) The carrier is immersed in a treatment bacterial community solution containing photosynthetic bacteria, Bacillus and nitrifying bacteria for bacterial community adsorption; (3) The particles that have completed the adsorption of bacteria are mixed with the filler, and the filler is wrapped around the particles by rolling to form balls, so as to obtain the bottom sediment ecological restoration material; the filler includes non-nitrate type hydrotalcite, calcium nitrate, nitrate type hydrotalcite and flocculant.

7. The preparation method according to claim 6, characterized in that, In step (2), the bacterial community is adsorbed for 3 to 5 hours; after adsorption is completed, the expansion rate of the particulate matter at room temperature is 0.3 to 0.5%.

8. A method for remediating polluted river and lake sediments using the sediment ecological restoration material according to any one of claims 1 to 5, characterized in that, Includes the following steps: (1) Preliminary restoration: During the dry season, the section of the river to be restored is isolated to form a closed restoration area, and the bottom sediment ecological restoration material is put into the closed restoration area; (2) Deep restoration: After the initial restoration is completed and the sediment is left to stand for 1 to 5 days, the bottom sediment ecological restoration material is put back into the closed restoration area with the water flow.

9. The method according to claim 8, characterized in that, In step (1), the ratio of the coverage area of ​​the bottom sediment ecological restoration material on the riverbed to the surface area of ​​the water surface in the closed restoration area is 1:

10.

10. The method according to claim 8, characterized in that, In step (2), the ratio of the coverage area of ​​the bottom sediment ecological restoration material on the riverbed to the surface area of ​​the water surface in the closed restoration area is 1:2.

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