Preparation method and device of underground permeable reactive barrier

Abstract

The invention relates to a preparation method and device of an underground permeable reactive barrier, and the underground permeable reactive barrier comprises the following components in parts by weight: steel slag, water glass, manganese sand, metal-rich biochar, fluorgypsum, fly ash, red mud, ball-milled hematite, gravel and an engineering bacterial agent. Compared with the prior art, the metal-rich biochar is used as an underground permeable reactive barrier material, electrons are released in the metal elementary substance corrosion process, dissolved-out low-valence metal ions can quickly consume dissolved oxygen in the environment, and a reducing environment beneficial to survival of additional strains is created; meanwhile, polymorphic variable valence metal in the metal-rich biochar bulk phase can effectively mediate the electron transfer process of a microbial extracellular respiratory chain, electrons are transferred to terminal receptor metal ions or persistent organic pollutants, and providing of electrons for reducing Cr < 6 + > and removing toxic groups of benzene rings is accelerated. The metal-rich biochar is matched with the engineering bacterium agent, so that efficient removal of various macromolecular organic pollutants and rapid stabilization of high-valence heavy metals can be realized.

Description

Technical Field

[0001] This invention belongs to the technical field of permeable reactive wall materials, specifically relating to a method and apparatus for preparing an underground permeable reactive wall. Background Technology

[0002] Groundwater pollution has become a serious environmental problem in my country, and the remediation of polluted groundwater is urgently needed. Permeable reactive barrier (PRB) technology is an emerging technology for the remediation of polluted groundwater, characterized by good treatment effect, low cost, and minimal impact on the ecological environment. It can effectively remove organic chlorides, heavy metals, and inorganic ions from groundwater.

[0003] Permeable reactive barrier technology involves constructing a reactive barrier composed of reactive materials along the direction of contaminated groundwater flow. The reactive materials remove pollutants from the groundwater through adsorption, sedimentation, chemical degradation, or biodegradation. Permeable reactive barriers are used to intercept and remediate groundwater pollution plumes. The reactive media filling the barrier include zero-valent iron, zeolite, and carbon sources that enhance microbial activity. The treatment process encompasses physical, chemical, or biological processes.

[0004] However, permeable reactive barrier technology also has certain technical limitations. For example, the capacity of the underground reactive barrier medium is limited, making it impossible to remove pollutants indefinitely. For high-concentration pollutants, the removal energy and capacity must be considered, which can sometimes shorten the service life of the permeable reactive barrier. In addition, the effects of the reactive medium may cause precipitation, altering the flow field of groundwater in and around the reactive barrier. Blockage of the reactive medium can lead to the failure of the permeable reactive barrier.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a method and apparatus for preparing an underground permeable reactive wall, so as to solve the technical problems mentioned in the background art.

[0007] To achieve one of the above objectives, the present invention provides the following technical solution:

[0008] A method for preparing an underground permeable reactive barrier, comprising adding the following materials during the construction of the underground permeable reactive barrier:

[0009] By weight, it includes: 10-30 parts steel slag, 10-20 parts water glass, 5-20 parts manganese sand, 20-40 parts metal-rich biochar, 5-10 parts fluorite gypsum, 10-20 parts fly ash, 1-5 parts red mud, 20-30 parts milled hematite, 1-5 parts gravel, and 5-15 parts engineered microbial agent.

[0010] Preferably, the added materials, by weight, include: 20 parts steel slag, 15 parts water glass, 10 parts manganese sand, 30 parts metal-rich biochar, 8 parts fluorite, 15 parts fly ash, 3 parts red mud, 25 parts milled hematite, 3 parts gravel, and 10 parts engineered microbial agent.

[0011] Preferably, the engineered microbial agent is a mixture of electroactive microorganisms and functional microorganisms, including but not limited to Shewanella, Geobacterium, desulfurizing bacteria, denitrifying bacteria, Paecilomyces lilacinus and Bacillus lateralis.

[0012] Preferably, the addition ratio of Shewanella, Geobacterium, desulfurizing bacteria, denitrifying bacteria, Paecilomyces lilacinus and Bacillus retroflexus is 5:5:3:3:1:3.

[0013] Preferably, the metal-rich biochar is prepared by the following method:

[0014] S100. Siberian irises are planted in a solution containing iron, manganese, cobalt, cerium and zinc ions, and harvested and dried after two months of cultivation.

[0015] S200. The dried plant was washed, dried, and pulverized in a 1 mmol / L hydrochloric acid solution to obtain dry biomass containing metals.

[0016] S300: Metal-rich biochar is obtained by calcining dry biomass containing metals.

[0017] Preferably, in step S100:

[0018] The solution containing metal ions is a solution of ferric chloride, manganese chloride, cobalt chloride, cerium chloride, zinc chloride, and sodium nitrate, all with a concentration of 300 mg / L.

[0019] Preferably, in step S300:

[0020] Dry biomass containing metals was calcined for 2 hours in a nitrogen atmosphere at 900°C.

[0021] Preferably, the engineered microbial agent and metal-rich biochar are encapsulated in sodium alginate microspheres.

[0022] To achieve the second objective mentioned above, the present invention provides the following technical solution:

[0023] An underground permeable reactive wall device is constructed according to the aforementioned method for preparing an underground permeable reactive wall.

[0024] Compared with the prior art, the method and apparatus for preparing an underground permeable reactive wall provided by the present invention have the following advantages:

[0025] 1. In this invention, metal-rich biochar is used as a material for preparing underground permeable reactive barriers. The ferrous ions generated during dissolution can rapidly consume dissolved oxygen in the environment, creating a reducing environment conducive to the survival of added microorganisms. Simultaneously, the multi-element single atoms and intermetallic compounds (especially solid solution γ-Fe) in the bulk phase of the metal-rich biochar can effectively mediate the electron transfer process of the extracellular respiratory chain of microorganisms, transferring electrons to terminal acceptor metal ions (such as Cr) or persistent organic pollutants, thus accelerating the reduction of Cr(VI) and the removal of toxic groups from the benzene ring. When combined with engineered microbial agents, metal-rich biochar can achieve the removal of chlorinated aromatic hydrocarbons, increasing the removal rate by 60% compared to traditional natural biodegradation.

[0026] 2. In this invention, the metal-rich biochar exhibits a homogeneous distribution of active components γ-Fe and α-Fe in the bulk structure of porous biochar, which can simultaneously form numerous Fe / C and Fe / Fe15.1C dual nano-galvanic cell effects, and provide electrons stably for long-term reduction to remove toxic groups (such as halogenated groups) of organic matter. It can promote the bond breaking and mineralization of toxic groups (such as carboxyl COOH, azo group -N=N-), and solve the problems of scaling, caking, passivation, and dead bed of traditional zero-valent iron fillers and iron-carbon fillers.

[0027] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 The flowchart illustrates the preparation process of metal-rich biochar in a method for preparing an underground permeable reactive wall, as provided in this embodiment of the invention. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. 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 claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0031] Example 1: Synergistic remediation of a site contaminated with a combination of chlorinated hydrocarbons and heavy metal chromium

[0032] (1) Precise preparation of metal-rich biochar

[0033] Siberian irises were planted in a mixed nutrient solution containing FeCl3·6H2O, MnCl2·4H2O, CoCl2·6H2O, CeCl3·7H2O, and ZnCl2, with the concentration of each metal ion precisely controlled at 300±10 mg / L, for a cultivation period of 60 days. During cultivation, the pH was maintained within the range of 5.8-6.2, and the nutrient solution was changed every 7 days. After harvesting, plant samples were ultrasonically washed three times with 1 mmol / L HCl solution, dried at 80℃ to constant weight, and pulverized to a particle size of 2-3 mm. Pyrolysis was carried out in a vertical tube furnace at a N2 flow rate of 200 mL / min, with the temperature increased to 900℃ at a rate of 10℃ / min and held at that temperature for 2 hours to obtain biochar rich in multiple metal active sites of Fe, Mn, Co, Ce, and Zn.

[0034] (2) Combination and immobilization of engineered microbial agents

[0035] Shewanella oneidensis MR-1, Geobacter sulfurreducens PCA, Desulfovibrio vulgaris Hildenborough, Pseudomonas stutzeri ATCC 17588, Purpureocillium lilacinum, and Brevibacillus laterosporus were mixed in a viable ratio of 5:5:3:3:1:3. Ten parts by weight of this composite bacterial agent were thoroughly mixed with 30 parts by weight of the metal-rich biochar prepared in step (1). The mixture was then encapsulated in a 2% sodium alginate solution to form microspheres with a diameter of 3-5 mm, and cross-linked and cured in a 0.1 M CaCl2 solution for 30 minutes.

[0036] (3) Optimized ratio of PRB reaction medium

[0037] The PRB filling medium is precisely prepared according to the following parts by weight: 20 parts 20-40 mesh steel slag, 15 parts water glass (modulus 2.4), 10 parts 30-60 mesh manganese sand, 30 parts immobilized bacterial agent-biochar composite, 8 parts 200 mesh fluorogypsum, 15 parts Grade II fly ash, 3 parts red mud, 25 parts ball-milled hematite (specific surface area >800 m² / kg), and 3 parts 5-10 mm gravel. All components are mixed in a twin-screw mixer for 30 minutes until homogeneous.

[0038] Applications of complex pollution remediation engineering:

[0039] A 20m long, 12m deep, and 2.5m thick PRB (Plasma Reinforced Bench) was constructed at an electronic equipment decommissioning site. The main pollutants in the site's groundwater were trichloroethylene (TCE, initial concentration 5.8 mg / L) and hexavalent chromium (Cr(VI), initial concentration 12.5 mg / L). An open-cut and backfill process was used for construction, with the wall's permeability coefficient controlled at (8.5±0.5)×10⁻⁻⁻⁻⁶. 4 cm / s.

[0040] After 12 months of stable system operation, effluent monitoring data showed that the TCE concentration decreased to <0.005 mg / L, with a removal rate >99.9%; the Cr(VI) concentration decreased to 0.08 mg / L, with a removal rate of 99.4%. Microbial community analysis indicated that a stable dechlorination-reduction functional bacterial community had formed inside the wall. No obvious clogging was observed in the wall, and permeability remained stable.

[0041] Example 2: Remediation of nitrate-contaminated groundwater in an agricultural area

[0042] (1) Preparation of slow-release carbon source composite biochar

[0043] Based on the preparation of metal-rich biochar, the pyrolysis temperature was adjusted to 600℃, and after pyrolysis, 20% by weight of polylactic acid (PLA) was loaded as a slow-release carbon source using a vacuum impregnation method. At the same time, the proportion of metal-rich biochar in the basic filler was adjusted to 15 parts, and 30 parts of biochar prepared from pine wood chips (pyrolyzed at 500℃) were added as the main solid carbon source.

[0044] (2) Construction of highly efficient denitrifying bacteria agents

[0045] The engineered bacterial agent mainly consists of highly efficient denitrifying bacteria Pseudomonas stutzeri STR-18 and Paracoccus denitrificans PD-22, which are mixed in a 1:1 ratio and cultured to a total bacterial concentration of 10^10 CFU / mL. The bacterial agent is immobilized by adsorption onto a modified zeolite carrier (2-4 mm).

[0046] (3) Anti-clogging structural design

[0047] The PRB employs a gradient gradation design: a 50cm thick layer of 10-20mm gravel is placed on the upstream side as a pretreatment layer, and a 30cm thick layer of 3-5mm quartz sand is placed on the downstream side as a stabilizing layer. The particle size of the packing material in the main reaction zone is controlled at 2-8mm, and a sedimentation and oil separation tank is installed in front of the wall.

[0048] Applications in nitrate contamination remediation projects:

[0049] A 50m long, 8m deep, and 3m thick PRB (Plasma Burden) is to be constructed downstream of a certain intensive agricultural area. The initial nitrate nitrogen concentration in the groundwater is 25 mg / L, and the hydraulic retention time is designed to be 24 hours.

[0050] After one year of hydrological operation, monitoring data showed that the effluent nitrate nitrogen concentration remained stable at <5 mg / L, with a removal rate >80%. Wall pressure loss monitoring indicated a head loss of <10 cm and no biological blockage. Quantitative microbial analysis showed that the abundance of denitrification functional genes (nirS, nirK) increased by two orders of magnitude.

[0051] Example 3: Multi-stage remediation of a petroleum hydrocarbon contaminated site

[0052] (1) Development of solubilized-degradable functional materials

[0053] A 5% by weight ratio of hydroxypropyl-β-cyclodextrin (HP-β-CD) was added as a solubilizer to the PRB medium formulation. Simultaneously, a pre-oxidation zone was set up before the main reaction zone, filled with slow-release oxidant particles loaded with persulfate (ammonium persulfate / bentonite = 1:4).

[0054] (2) Design of aerobic-anaerobic zone system

[0055] PRB adopts a functional partition design:

[0056] Upstream aerobic zone (1m thick): filled with metal-rich biochar (20 parts), manganese sand (15 parts), and activated persulfate (5 parts).

[0057] Downstream anaerobic zone (1.5m thick): filled with immobilized anaerobic bacteria (15 parts), zero-valent iron (20 parts), and slow-release carbon source (10 parts).

[0058] (3) Screening of effective degrading bacteria agents

[0059] Rhodococcus erythropolis PET-12 and Pseudomonasaeruginosa OIL-8 were screened from petroleum-contaminated soil and compounded with basic bacterial agents at a ratio of 2:1, with a total inoculum amount of 10^8 CFU / g filler.

[0060] Applications in petroleum hydrocarbon pollution remediation engineering:

[0061] A multi-stage PRB (Plasma Reinforced Bioreactor) was constructed in the leak area of ​​a gas station, measuring 15m long, 6m deep, and 2.5m thick. The initial concentration of total petroleum hydrocarbons (TPH) in the groundwater was 85 mg / L, and the concentration of benzene series compounds (BTEX) was 28 mg / L.

[0062] After 6 months of operation, the effluent TPH concentration decreased to <5 mg / L and the BTEX concentration decreased to <0.1 mg / L, with removal rates both >95%. Microbial community analysis showed that Rhodococcus was the dominant microorganism in the aerobic zone (relative abundance 35%), while Geobacter had a relative abundance of 28% in the anaerobic zone.

[0063] Example 4: Synergistic Removal of High-Arsenic Groundwater by Multiple Mechanisms

[0064] (1) Optimization of arsenic removal functional materials

[0065] The PRB medium is designed with a triple arsenic removal mechanism:

[0066] Adsorbent material: Iron-rich biochar (40 parts, pyrolysis at 600℃)

[0067] Reduction precipitate material: zero-valent iron (20 parts, 100 mesh)

[0068] Coprecipitation material: Goethite-coated quartz sand (10 parts, coating rate >90%)

[0069] (2) Redox environment regulation

[0070] The oxidation-reduction sequence is achieved through the wall structure design: the incoming water first passes through a 50cm thick manganese sand layer (to promote the oxidation of As(III)) and then enters the main reaction zone (to promote the adsorption and co-precipitation of As(V)).

[0071] (3) Enhancement of functional microbial agents

[0072] Iron-reducing bacteria Shewanella oneidensis AR-1 and arsenic-converting bacteria Bacillus arsenicus AS-5 were added in a 3:2 ratio, with an inoculum size of 10^7 CFU / g packing material.

[0073] Applications in high-arsenic groundwater remediation projects:

[0074] A 30m long, 10m deep, and 2m thick PRB (Plasma Burden Reduction) was constructed in a high-arsenic area. The initial total arsenic concentration in the groundwater was 500 μg / L, with As(III) accounting for 60%.

[0075] After 12 months of operation, the total arsenic concentration in the effluent stabilized at <10 μg / L, meeting drinking water standards. Synchrotron radiation analysis showed that arsenic was mainly fixed on the surface of the packing material as As(V)-Fe(III) coprecipitates.

[0076] Example 5: Advanced treatment of antibiotic-contaminated groundwater

[0077] (1) Advanced oxidation-biodegradation coupling system

[0078] A pre-activation zone (0.5 m thick) was set up upstream of the PRB and filled with a sodium persulfate / attapulgite composite slow-release agent (1:2). 5% Cu-Fe bimetallic biochar was added to the packing material in the main reaction zone as a Fenton-like reaction catalyst.

[0079] (2) Construction of specific degrading bacterial agents

[0080] Sphingomonas sp. AMP-12 and Streptomycesrochei ANT-8 were screened from activated sludge in a wastewater treatment plant. They have the ability to specifically degrade sulfonamide antibiotics and were compounded with a basic bacterial agent in a 1:1 ratio.

[0081] (3) Ecological security protection measures

[0082] A 30cm thick granular activated carbon (GAC) protective layer is installed at the end of the PRB, and the effluent is further treated by a UV / hydrogen peroxide advanced oxidation unit to ensure that the ecotoxicity meets the standards.

[0083] Applications of antibiotic pollution remediation engineering:

[0084] A coupled PRB, 25m long, 8m deep, and 2.5m thick, is being constructed downstream of a pharmaceutical factory. The initial concentration of sulfamethoxazole (SMX) in the groundwater is 2.8 mg / L, and the concentration of tetracycline (TC) is 1.5 mg / L.

[0085] After 9 months of operation, the concentrations of SMX and TC in the effluent decreased to <0.05 mg / L and <0.1 mg / L, respectively, with a removal rate of >98%. Acute toxicity tests of the luminescent bacteria showed that the relative luminescence rate of the effluent was >85%, with no ecotoxicity.

[0086] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. In addition, the terms "first," "second," "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0087] Furthermore, terms such as "horizontal," "vertical," and "sag" do not imply that components must be absolutely horizontal or suspended, but rather that they can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal relative to "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0088] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0089] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the scope of protection of the invention. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

Claims

1. A method for preparing an underground permeable reactive wall, characterized in that, The following materials should be added during the construction of underground permeable reactive walls: By weight, it includes: 10-30 parts steel slag, 10-20 parts water glass, 5-20 parts manganese sand, 20-40 parts metal-rich biochar, 5-10 parts fluorite gypsum, 10-20 parts fly ash, 1-5 parts red mud, 20-30 parts milled hematite, 1-5 parts gravel, and 5-15 parts engineered microbial agent.

2. The method for preparing an underground permeable reactive wall according to claim 1, characterized in that, The added materials, by weight, include: 20 parts steel slag, 15 parts water glass, 10 parts manganese sand, 30 parts metal-rich biochar, 8 parts fluorite, 15 parts fly ash, 3 parts red mud, 25 parts milled hematite, 3 parts gravel, and 10 parts engineered microbial agent.

3. The method for preparing an underground permeable reactive wall according to claim 2, characterized in that, The engineered microbial agent is a mixture of electroactive microorganisms and functional microorganisms, including but not limited to Shewanella, Geobacterium, desulfurizing bacteria, denitrifying bacteria, Paecilomyces lilacinus, and Bacillus lateralis.

4. The method for preparing an underground permeable reactive wall according to claim 3, characterized in that, The addition ratio of Shewanella, Geobacterium, desulfurizing bacteria, denitrifying bacteria, Paecilomyces lilacinus and Bacillus retroflexus was 5:5:3:3:1:

3.

5. The method for preparing an underground permeable reactive wall according to claim 4, characterized in that, The metal-rich biochar is prepared by the following method: S100. Siberian irises are planted in a solution containing iron, manganese, cobalt, cerium and zinc ions, and harvested and dried after two months of cultivation. S200. The dried plant was washed, dried, and pulverized in a 1 mmol / L hydrochloric acid solution to obtain dry biomass containing metals. S300: Metal-rich biochar is obtained by calcining dry biomass containing metals.

6. The method for preparing an underground permeable reactive wall according to claim 5, characterized in that, In step S100: The solution containing metal ions is a solution of ferric chloride, manganese chloride, cobalt chloride, cerium chloride, zinc chloride, and sodium nitrate, all with a concentration of 300 mg / L.

7. The method for preparing an underground permeable reactive wall according to claim 6, characterized in that, In step S300: Dry biomass containing metals was calcined for 2 hours in a nitrogen atmosphere at 900°C.

8. The method for preparing an underground permeable reactive wall according to claim 2, characterized in that, Engineered microbial agents and metal-rich biochar were embedded in sodium alginate microspheres.

9. A permeable underground reactive wall device, characterized in that, It is constructed using the method for preparing an underground permeable reactive wall according to any one of claims 1-8.

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