Vertical subsurface flow constructed wetland system for enhancing removal of antibiotics

Abstract

The invention provides a vertical subsurface flow constructed wetland system for enhanced antibiotic removal, which comprises a pool body and a high-level water tank, the pool body is filled with a matrix, the matrix comprises a supporting layer matrix, a quartz sand matrix and an amino modified Fe-MOFs composite matrix from bottom to top, the lower part of the pool body is provided with a water inlet, and the upper part of the pool body is provided with a water outlet; a discharge outlet is formed in the lower part of the high-level water tank and is connected with the water inlet of the pool body through a water inlet pipe; the particle size of the matrix meets the requirement that the particle size of the supporting layer matrix is larger than that of the quartz sand matrix is larger than that of the amino-modified Fe-MOFs composite matrix; wetland plants are planted in the amino modified Fe-MOFs composite matrix. By adopting the technical scheme provided by the invention, antibiotic pollutants in wastewater can be effectively removed, particularly, the method has a remarkable removal effect on antibiotics such as sulfamethoxazole and the like, the reaction rate is higher, and the purification efficiency is higher.

Description

Technical Field

[0001] The invention relates to the technical field of environmental protection and water treatment, and in particular to a vertical subsurface flow artificial wetland system for enhancing the removal of antibiotics. Background Art

[0002] Antibiotics, as a new type of pollutant, are widely present in a variety of environmental media, such as sewage, soil, surface water and sludge. Antibiotics have a relatively short half-life in the environment, but human or veterinary antibiotics are continuously discharged into the environment, causing pseudo-persistent pollution. The long-term presence of antibiotics at a certain concentration level in the environment may not only have toxic effects on some sensitive organisms, but also lead to the production, maintenance, transfer and spread of antibiotic resistance genes (ARBs) and resistance genes (ARGs) under selective pressure, which will have an impact on the ecosystem and reduce the therapeutic potential of antibiotics against human and animal pathogens.

[0003] Antibiotics ingested into the body cannot be completely absorbed or metabolized. It is estimated that 50% to 90% of antibiotics will be excreted from the body in the form of original compounds or conjugates. In aquaculture and livestock farming, these antibiotics will directly enter the soil or water environment, causing non-point source pollution. More excrement will be collected through the municipal pipe network and enter the sewage treatment plant. If the antibiotics cannot be effectively removed, the sewage treatment plant will become an important source of antibiotic pollution in the environment. Traditional sewage treatment processes can effectively remove carbon and nitrogen and control microbial pollution, but they have limited effects on the removal of trace organic pollutants such as antibiotics.

[0004] Constructed wetlands have a certain effect on the removal of antibiotics, but the removal efficiency of different types of antibiotics in constructed wetlands may vary, depending on their chemical structure, hydrolysis and photolysis stability, and the interaction with the physical, chemical and biological effects in the constructed wetland system. At present, the removal efficiency of antibiotics by constructed wetlands is limited, and the sewage in the existing operation mode enters in a predetermined order, with obvious hydraulic retention stratification, resulting in reduced nitrogen removal performance. At the same time, the carbon source in the sewage is continuously consumed during the hydraulic retention time, further resulting in reduced nitrogen removal performance. Summary of the invention

[0005] In view of the above technical problems, the present invention discloses a vertical subsurface flow artificial wetland system for enhanced removal of antibiotics, which can be used to enhance the treatment and removal of antibiotic wastewater and has low carbon emission characteristics; in particular, it is for the removal of sulfamethoxazole (SMX).

[0006] To this end, the technical solution adopted by the present invention is:

[0007] A vertical subsurface artificial wetland system for enhanced removal of antibiotics, comprising a pool body and a high-level water tank, wherein the pool body is filled with a matrix, wherein the matrix is ​​respectively a supporting layer matrix, a quartz sand matrix and an amino-modified Fe-MOFs composite matrix from bottom to top, wherein a water inlet is arranged at the bottom of the pool body, and a discharge port is arranged at the bottom of the high-level water tank, wherein the discharge port is connected to the water inlet of the pool body through an inlet pipe; wherein the particle size of the matrix satisfies the supporting layer matrix>quartz sand matrix>amino-modified Fe-MOFs composite matrix; and wherein the amino-modified Fe-MOFs composite matrix is ​​planted with wetland plants. Among them, the amino-modified Fe-MOFs is an amino-modified iron-based metal organic framework material.

[0008] Specifically, the support layer matrix is ​​located at the bottom of the pool body. The support layer uses materials with larger particle sizes and has good load-bearing and support capabilities. The gaps between these materials with larger particle sizes are larger, which is conducive to the drainage and ventilation of the upper matrix and maintains the good permeability of the wetland system. At the same time, it can effectively support the upper matrix and prevent it from collapsing or deforming, thereby ensuring the stability and long-term operation effect of the entire artificial wetland system.

[0009] Secondly, the design of the support layer also helps the suspended particles in the water body to settle to the bottom layer. Since the gaps between materials with larger particle sizes are larger, the water flow will be hindered and slowed down to a certain extent when passing through the support layer, so that the suspended particles have more time and opportunities to settle to the bottom of the support layer. In this way, the suspended particles in the sewage can be effectively removed, thereby improving the purification effect and treatment efficiency of the water quality.

[0010] Amino-modified Fe-MOFs is a multifunctional metal-organic framework material whose framework structure consists of an Fe metal center and an organic ligand (such as amino-modified terephthalic acid). This material has a high specific surface area, a porous structure, and excellent stability, and exhibits high catalytic activity and adsorption capacity in the field of water treatment.

[0011] The present invention adopts amino-modified Fe-MOFs metal-organic framework materials (Metal-Organic Frameworks, MOFs) as wetland matrix, synergizes the catalytic degradation of metal active centers (Fe) and the introduction of amino groups (-NH2), and reacts with hydrogen peroxide produced by plant roots, which significantly improves the system's removal efficiency for antibiotics such as sulfamethoxazole (SMX) and exhibits high degradation activity in a wider pH range.

[0012] In this technical solution, the roots of wetland plants provide a surface for microorganisms to attach to, and provide nutrients and hydrogen peroxide for microbial metabolism through root secretions. Wetland plants can produce oxygen through photosynthesis, providing sufficient oxygen for aerobic microorganisms in the root zone, thereby improving the biodegradation capacity of wastewater. The generation of H2O2 is mediated by NADPH oxidase and Fe 2 + / Fe 3+ The NH2 groups in the amino-modified Fe-MOFs composite matrix can effectively promote these reactions, significantly increase the ROS level in the root zone, thereby enhancing the oxidation capacity of the root zone and further promoting the degradation of antibiotics. Under the action of the amino-modified Fe-MOFs composite matrix, wetland microorganisms can use the intermediates produced by decomposition to further degrade antibiotic residues, reducing the risk of the spread of antibiotic resistance genes. At the same time, the high specific surface area of ​​the amino-modified Fe-MOFs composite matrix can provide more surface reaction sites, further improving the removal efficiency of antibiotics. The amino-modified Fe-MOFs composite matrix works together with wetland plants and microorganisms to significantly improve the removal efficiency of the system for antibiotics, especially sulfamethoxazole (SMX) and other antibiotics, and exhibits high degradation activity in a wide pH range.

[0013] During the operation of the system, the amino-modified Fe-MOFs not only act as catalytic degradation materials, but also effectively remove organic pollutants such as antibiotics from the water by physically adsorbing and degrading antibiotics, providing a cleaner environment for wetland plants and microorganisms, making the biological treatment process more efficient.

[0014] The specific principle of the amino-modified Fe-MOFs composite matrix for removing antibiotics is as follows:

[0015] The Fe metal center of amino-modified Fe-MOFs can promote the redox cycle between Fe(III) and Fe(II) in the reaction. This synergistic effect can accelerate the decomposition of H2O2 and generate hydroxyl radicals (·OH) with strong oxidizing properties. The specific reaction is as follows:

[0016] ·Fe(III)+e - →Fe(II) (reduction process)

[0017] ·Fe 2+ +H2O2→Fe 3+ + OH+OH -

[0018] These reactions show the role of Fe in the activation of H2O2, forming a large number of ·OH radicals and promoting the rapid degradation of SMX. In addition, the introduction of Fe3O4 not only enhances the recycling capacity of Fe, but also provides additional active centers, accelerating the generation of free radicals and the reaction rate. The removal rate and rate constant of sulfamethoxazole (SMX) by the amino-modified Fe-MOFs / H2O2 system with the addition of Fe3O4 are 3.2 times and 43.5 times that of the Fe-MOF / H2O2 system without the addition of Fe3O4, respectively. This shows that the synergistic effect of amino-modified Fe-MOFs and Fe3O4 greatly improves the treatment efficiency of the system.

[0019] The NH2 groups in the amino-modified Fe-MOFs enhance the ability to transfer electrons to the metal active centers, which helps to accelerate the redox cycle between Fe(III) and Fe(II), overcome the limitation of the slow redox cycle of traditional Fe-based catalysts, and thus improve the catalytic activity. In addition, the surface of the amino-modified material also has a high adsorption capacity and can form a stable complex with antibiotic molecules, thereby improving the adsorption efficiency.

[0020] Through experiments, it was found that the amino-modified Fe-MOFs / H2O2 system showed high SMX degradation activity in the pH range of 3.05 to 7.00. This shows that the material has good pH adaptability and is suitable for the treatment of different types of wastewater, ensuring that the constructed wetland maintains efficient and stable operation.

[0021] In addition, the chemical properties of the surface of the amino-modified Fe-MOFs composite matrix also affect the attachment and growth of microorganisms. The surface of the composite iron matrix may have certain charge characteristics, which may interact with the charge on the surface of the microorganisms and promote the attachment of microorganisms. At the same time, the mineral components of the composite iron matrix may also provide some essential trace elements or nutrients for microorganisms, which is beneficial to their growth and metabolic activities.

[0022] As a further improvement of the present invention, the wetland plant is Canna indica, which is planted in an amino-modified Fe-MOFs composite matrix. Two plants are planted in each pond, with a planting density of about 60 plants / cm 2 .

[0023] As a further improvement of the present invention, the particle size of the supporting layer matrix is ​​6-10 mm, the particle size of the quartz sand matrix is ​​2-3 mm, and the particle size of the amino-modified Fe-MOFs composite matrix is ​​1-2 mm.

[0024] As a further improvement of the present invention, the support layer matrix is ​​gravel.

[0025] As a further improvement of the present invention, a water distribution plate is provided below the support layer matrix, and the water distribution plate is connected to the water inlet to guide and disperse the water flow.

[0026] As a further improvement of the present invention, circular small holes are evenly distributed on the water distribution plate.

[0027] As a further improvement of the present invention, a water inlet is provided at the upper portion of the high-level water tank, and an overflow port is provided at the upper portion of the high-level water tank; and the water inlet pipe is a hose.

[0028] As a further improvement of the present invention, the amino-modified Fe-MOFs are prepared by the following steps:

[0029] Step S1, mixing ferric chloride and N,N-dimethylformamide to obtain a precursor solution;

[0030] Step S2, adding 2-aminoterephthalic acid to the precursor solution, stirring at room temperature until the solution is completely clear, to obtain a reaction solution; the molar ratio of the ferric chloride to the 2-aminoterephthalic acid in the reaction solution is 2:1;

[0031] Step S3, placing the reaction solution in a reaction kettle, reacting at 110-130° C. for more than 15 hours, and cooling naturally;

[0032] Step S4, after the reaction is completed, the amino-modified Fe-MOFs catalyst is recovered by centrifugation, and then washed and dried.

[0033] As a further improvement of the present invention, in step S1, the molar ratio of the ferric chloride to 2-aminoterephthalic acid in the reaction solution is 2:1.

[0034] As a further improvement of the present invention, in step S4, the centrifugal speed is 6000-7000 rpm and the time is 4-6 min.

[0035] As a further improvement of the present invention, in step S4, the cleaning is performed by washing three times with DMF, ethanol and deionized water respectively.

[0036] As a further improvement of the present invention, in step S4, the drying is vacuum drying at 100-120° C. for more than 10 hours.

[0037] The present invention also discloses a method for treating sewage using an artificial wetland, that is, the application of the vertical subsurface artificial wetland system for enhanced removal of antibiotics as described above for water treatment, comprising the following steps:

[0038] Step S1, cultivating microbial cells, filling the pool with sewage, then adding the cultivated microbial cells into the high-level water tank, stopping the water intake and leaving it for 3 days to enhance the adhesion of microorganisms and biofilm formation;

[0039] Step S2, microbial acclimation, first setting the pollutant concentration in the sewage at a low level, and gradually increasing the pollutant concentration as the microorganisms gradually adapt;

[0040] Step S3: After the microorganisms are domesticated, water is continuously introduced and discharged.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] First, the technical solution of the present invention has the function of efficiently removing antibiotics; through the amino-modified Fe-MOFs composite matrix, the system can effectively remove antibiotic pollutants in wastewater, especially has a significant removal effect on antibiotics such as sulfamethoxazole (SMX), and significantly improves the water purification efficiency; the amino-modified Fe-MOFs composite matrix, which is a Fe and Fe3O4 metal system, can synergistically catalyze and promote the decomposition of H2O2, generate a large number of hydroxyl radicals (·OH), accelerate the degradation of organic pollutants, especially antibiotics, and have a faster reaction rate and higher efficiency.

[0043] Second, the amino (NH2-) groups introduced into the amino-modified Fe-MOFs composite matrix in the technical solution of the present invention can significantly induce the production of H2O2 in the root zone of the plant, especially at the root tip; the generation of H2O2 improves the oxidation capacity of the root zone, further promoting the degradation efficiency of antibiotics. The amino-modified Fe-MOFs system exhibits high degradation activity in a wide pH range (3.05 to 7.00), is suitable for a variety of wastewater types, and enhances the flexibility and applicability of the system. In addition, the composite matrix not only has physical adsorption capacity, but also synergizes with wetland plants and microorganisms, enhances the removal effect of antibiotics, and ensures the high efficiency and durability of the treatment process.

[0044] Third, the system of the present invention achieves low carbon emission and environmentally friendly effects by reducing the release of greenhouse gases such as nitrous oxide (N2O).

[0045] Fourth, the technical solution of the present invention and the design of the particle size of each layer of the matrix effectively avoid the common clogging problem in traditional wetland systems, ensuring the long-term stable operation of the system. By designing a small high-level water tank and water distribution plate, the water flow distribution is optimized, the hydraulic retention time is reduced, and the sewage treatment speed and efficiency are further improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1Schematic diagram of the structure and principle of the pool body of an embodiment of the present invention; wherein (a) is a schematic diagram of the structure of the pool, and (b) is a schematic diagram of the principle.

[0047] Figure 2 It is a schematic diagram of the connection structure between the pool body and the high-level water tank in an embodiment of the present invention.

[0048] The reference numerals include: 1-cell body, 2-supporting layer, 3-quartz sand matrix, 4-amino-modified Fe-MOFs composite matrix, 5-high-level water tank. DETAILED DESCRIPTION

[0049] The preferred embodiments of the present invention are described in further detail below.

[0050] like Figure 1 and Figure 2 As shown, a vertical subsurface flow artificial wetland system for enhanced removal of antibiotics includes a pool body and a high-level water tank. The pool body is an open hollow cylindrical structure. A water inlet pipe with a hole diameter of 10 mm is set at 25 mm below the pool body, and a water outlet pipe with a hole diameter of 10 mm is set at the upper part of the pool body. Furthermore, the pool body is made of transparent material and is covered with a light-shielding layer on all sides. The light-shielding layer is a white light-shielding plastic film with a thickness of 1 mm, and the inner side is black.

[0051] like Figure 1 As shown, a matrix is ​​filled in the pool body 1, and the matrix is ​​respectively a supporting layer 2, a quartz sand matrix 3, and an amino-modified Fe-MOFs composite matrix 4 from bottom to top; the supporting layer 2 is gravel with a diameter of 6-10mm and a thickness of 50mm; the quartz sand matrix 3 is quartz sand with a diameter of 2-3mm and a thickness of 300mm; the amino-modified Fe-MOFs composite matrix 4 has a diameter of 1-2mm and a thickness of 200mm. A water inlet is provided at the lower part of the pool body, which is connected to the high-level water tank 5 through a pipeline. A horizontally placed water distribution plate is provided in the middle of the supporting layer 2. The water distribution plate is a hollow polyvinyl chloride disc with a diameter of 200mm and a height of 10mm. The water distribution plate is connected to the water inlet, and the water inlet is connected to the water inlet pipe. Circular holes with a diameter of 0.5mm are evenly distributed on the water distribution plate. The water distribution plate located at the bottom of the pool body is connected to the water inlet at the right end of the bottom of the pool body to divert and disperse the water flow. When sewage enters the tank from the water inlet, the circular holes on the water distribution plate disperse the water into multiple streams. This dispersion helps to ensure that the sewage flows evenly inside the tank, prevents the formation of dead water areas, and increases the contact area between the water flow and the microorganisms in the reaction layer, thereby enhancing the treatment efficiency. The tank is planted with wetland plants. In this embodiment, the plants are Canna indica, which is planted in an amino-modified Fe-MOFs composite matrix. Two plants are planted in each tank, and the planting density is about 60 plants / cm 2 .

[0052] Due to the principle of the connecting pipe, the height of the sewage in the high-level water tank and the pool body is the same. As the sewage continues to flow in, it passes through the supporting layer, the quartz sand matrix and the amino-modified Fe-MOFs composite matrix and flows out from the outlet at the top of the pool body. The water flow enters the supporting layer after being dispersed by the water distribution plate. In the supporting layer, the water flow is guided into the reaction layer by the pressure. In this process, the water flow comes into contact with the microorganisms in the reaction layer, and the microorganisms will metabolize the organic matter in the water, promote its degradation, and purify the water quality. At the same time, the design of the reaction layer allows the water flow to fully stay in it, which provides the necessary time and space for the reaction between microorganisms and organic matter.

[0053] The water inlet of the high-level water tank is located at the upper part of the water tank, and the discharge port is located at the lower part of the high-level water tank; the discharge port of the high-level water tank and the water inlet of the lower part of the pool body are connected by a hose with a diameter of 12mm. In addition, an overflow port is provided at the upper part of the high-level water tank to prevent system damage caused by system blockage. The discharge port is located 550mm from the bottom of the pool, and the water inlet and the discharge port are both pagoda-shaped interfaces with a diameter of 12mm. The main function of the high-level water tank is to make the water flow into the artificial wetland stably. By keeping the water level at the level of the water level inside the pool body, the high-level water tank can stably control the hydraulic retention time, thereby improving the treatment efficiency and speed. Secondly, the size of the high-level water tank is relatively small. In a system with a long hydraulic retention time, pollutants may stay in the system for a long time, resulting in the generation of odor, bacteria or other undesirable substances. A shorter retention time can reduce this retention and reduce the accumulation of pollutants in the system. Compared with a larger volume water tank, a smaller high-level water tank can control the water flow more flexibly and make it pass through the system faster. In addition, smaller water tanks take up relatively less space, which is beneficial for the design and layout of the overall system.

[0054] The sewage containing antibiotics flows into the lower water inlet of the wetland and is degraded through natural degradation, microbial degradation, plant rhizosphere microbial degradation, and plant absorption.

[0055] The amino-modified Fe-MOFs composite matrix is ​​prepared by the following steps:

[0056] 1. Preparation of Precursor Solution

[0057] First, 2.50 mmol of FeCl3·6H2O was dissolved in 30 mL of N,N-dimethylformamide (DMF) to form a precursor solution.

[0058] Subsequently, 1.25 mmol of 2-aminoterephthalic acid (2-NH2-BDC) was added to the above solution. This organic ligand is used to form the organic framework in the MOF structure.

[0059] The mixture was stirred at 480 rpm with a magnetic stirrer at 25 °C for 35 min until the solution was completely clear.

[0060] 2. Hydrothermal reaction

[0061] The clear solution was transferred to a 100 mL polytetrafluoroethylene (PTFE) lined stainless steel autoclave.

[0062] The reaction was heated at 120°C for 20 hours to complete the formation of the MOF structure.

[0063] After the reaction was completed, the mixture was allowed to stand and cool naturally at room temperature for about 20 hours.

[0064] 3. Catalyst recovery and purification

[0065] After the reaction was completed, the synthesized amino-modified Fe-MOFs catalyst was recovered by centrifugation (the centrifugal speed was set at 6500 rpm for 4.5 min) and washed three times with DMF, ethanol and deionized water, respectively, to remove the residual reactants and solvents.

[0066] Centrifugation is required after each wash.

[0067] After the catalyst was purified, it was dried in vacuum at 110° C. for 12 hours.

[0068] Through this hydrothermal method, amino-functionalized MOFs with Fe metal active centers were synthesized. The catalyst showed significant catalytic activity in Fenton-like reactions and effectively promoted the degradation of organic pollutants through its high specific surface area and functionalized surface.

[0069] In the technical solution of this embodiment, wetland plants are planted on the upper part of the amino-modified Fe-MOFs composite matrix. First, the roots of the wetland plants grow in the matrix, forming a complex root system. These roots absorb water and nutrients through osmosis, promoting nutrient circulation in the wetland. At the same time, the roots of wetland plants also provide abundant organic matter, such as root secretions and plant residues, providing good conditions for the survival and reproduction of rhizosphere microorganisms.

[0070] Secondly, a complex symbiotic relationship is formed between rhizosphere microorganisms and wetland plant roots. Wetland rhizosphere microorganisms include a variety of microbial communities such as bacteria, fungi, and actinomycetes. They exchange substances and interact with plant roots through media such as rhizosphere biofilms. These microorganisms degrade organic matter in sewage by decomposing organic matter released by plant roots, thereby promoting the release and circulation of nutrients in the soil.

[0071] In addition, rhizosphere microorganisms are also involved in the transformation of nutrients such as nitrogen and phosphorus. For example, some nitrogen-fixing bacteria can form a symbiotic relationship with the roots of wetland plants, converting nitrogen in the air into ammonia nitrogen or nitrate nitrogen that can be absorbed by plants, providing a nitrogen source for plant growth. In addition, some phosphate-dissolving bacteria and fungi can promote the release and transformation of phosphorus in sewage.

[0072] The amino-modified Fe-MOFs / H2O2 system exhibited excellent degradation efficiency and reaction rate in the removal of the antibiotic SMX. The system achieved effective removal of antibiotics through the following aspects:

[0073] 1) Activation of hydrogen peroxide: Amino-modified Fe-MOFs as catalysts can effectively activate H2O2 to produce a large number of hydroxyl radicals (·OH). These free radicals have strong oxidizing properties and can non-selectively attack organic molecules, destroying the molecular structure of the antibiotic SMX, thereby achieving its rapid degradation.

[0074] 2) Acceleration of electron transfer: The introduction of amino groups (-NH2) accelerates the transfer of electrons from organic pollutants to metal active centers (Fe), enhances the decomposition efficiency of H2O2, and enables the redox reaction to occur rapidly. This electron transfer process plays a decisive role in the generation of hydroxyl radicals, thereby significantly increasing the degradation rate of antibiotics.

[0075] 3) Accelerate redox: Fe, as a metal active center, can form an efficient catalytic system. Specifically, Fe can promote the reduction of Fe(III) to Fe(II), thereby accelerating the Fe(II) / Fe(III) cycle, while Fe can catalyze the decomposition of H2O2 to produce more hydroxyl radicals in this process. The synergistic effect of metals significantly improves the oxidation capacity and reaction rate of the system, making up for the problem of insufficient activity of a single metal catalyst.

[0076] 4) Overcoming the limitations of Fe-based catalysts: The traditional Fe-MOF system has a relatively slow redox cycle between Fe(III) and Fe(II), which limits the efficient utilization of H2O2 and reduces the degradation efficiency. In the amino-modified Fe-MOFs / H2O2 system, the Fe3O4 contained therein can effectively overcome this limitation, promote the rapid conversion of Fe(II) and Fe(III), and significantly improve the decomposition rate of H2O2 and the rate of free radical generation.

[0077] In addition, amino (NH2) groups can significantly induce the accumulation of reactive oxygen species in plant root tips, especially causing a large amount of enrichment of hydrogen peroxide (H2O2) in the elongation and maturation zones of the root tips.

[0078] When amino-modified Fe-MOFs materials are filled in artificial wetland matrix, the amino groups can enhance the enrichment and generation of H2O2 in the plant root zone through the following mechanism: NH2 groups can coordinate with the metal center (Fe) through lone pair electrons, promoting the redox cycle of the metal center. As a catalytic active center, Fe usually needs to undergo Fe in the process of catalyzing the generation and decomposition of hydrogen peroxide. 2+ / Fe 3 The NH2 group can accelerate the redox cycle of these metal centers through the transfer of electrons, thereby significantly increasing the rate of hydrogen peroxide generation.

[0079] The NH2 group not only enhances the catalytic activity of the metal center, but also promotes the generation and activation of H2O2 by accelerating the electron transfer process. Especially in the root tip, the generation of H2O2 is mediated by NADPH oxidase and Fe 2+ / Fe 3+ The NH2 group can effectively promote these reactions, which greatly increases the ROS level in the root zone.

[0080] The second aspect of the present embodiment provides a method for treating sewage using the vertical subsurface flow artificial wetland system for enhanced removal of antibiotics. Microbial inoculation is required before the first sewage treatment, and the inoculated microorganisms are usually derived from the natural environment, an existing sewage treatment system or laboratory culture. When selecting the source, the degradation ability, growth rate and environmental adaptability of the microorganism to the target pollutant need to be considered. Under laboratory conditions, the selected microorganisms are first cultured to obtain a sufficient number of bacteria. During the culture process, suitable conditions such as temperature, pH value, and nutrient supply need to be controlled to ensure the rapid growth of microorganisms. During inoculation, the pool is first filled with sewage, and then the cultured microorganisms are added from the water inlet of the artificial wetland, the water intake is stopped and placed for 3 days to enhance the adhesion and biofilm formation of the microorganisms.

[0081] Microbial domestication: At the beginning, the pollutant concentration in the sewage is set at a low level. As the microorganisms gradually adapt, the pollutant concentration is gradually increased to enhance their ability to treat high-concentration pollutants. Ensure that the nutrients such as carbon, nitrogen, and phosphorus required for microbial growth are adequately supplied, but at the same time avoid excessive amounts, so as not to cause excessive growth of microorganisms and affect system efficiency.

[0082] After the microorganisms are domesticated, water can be continuously taken in and out.

[0083] When the above method is actually used, the influent is manually prepared, and the water quality index is the Class B standard in the Pollutant Discharge Standard for Urban Wastewater Treatment Plants (GB 18918-2002), COD is 20 mg / L, ammonia nitrogen is 8 mg / L, nitrate nitrogen is 12 mg / L, and total phosphorus is 1.2 mg / L. It is prepared with glucose, ammonium chloride, potassium nitrate, and potassium dihydrogen phosphate respectively.

[0084] Before starting the device, fill the reactor with wastewater, introduce 5L of activated sludge with a sludge concentration of about 5000mg / L through the high-level water tank, do not add water during this period, air-dry for 3 days, let it settle for 1 hour on the 4th day, then discharge about 1 / 5 of the upper wastewater in the pool, and inject the same amount of fresh sewage. Repeat the three processes of air-drying, settling and water-injection, but the amount of water inflow each time should be increased compared to the last time, and the air-drying time should be shortened compared to the last time. When the indicators of the upper wastewater discharged from the reactor are stable, water can be continuously added.

[0085] Since the sludge has not yet adapted to the environment in the early stage of cultivation, the water flow rate should be small and set at 2L / day. Thereafter, the water flow rate should be gradually increased by 1L per day to 14L / day. When the water flow rate reaches the concentration required by the process, normal operation can begin.

[0086] Taking the artificial wetland without adding the amino-modified Fe-MOFs composite matrix as a comparative example, the other conditions are the same as those in this embodiment. The removal of common pollutants in the two artificial wetlands is shown in Table 1, the removal of the antibiotic SMX is shown in Table 2, and the release of greenhouse gases is shown in Table 3. By comparison, it can be seen that the vertical subsurface flow artificial wetland system using the embodiment of the present invention has better sewage treatment effect, especially higher removal efficiency of antibiotics.

[0087] Table 1 Removal of common pollutants

[0088]

[0089] From Table 1 above, we can find that: NH4 + The removal effects of TP and TP were stable in the experiment, reaching removal rates close to 77.63% and 70.83% respectively.

[0090] Table 2 Removal of antibiotic SMX

[0091]

[0092] Table 3 Greenhouse gas release

[0093]

[0094] Gas was collected using a gas collecting barrel, and CH4 and N2O were detected using an Agilent GC-7980A gas chromatograph. The results showed that the addition of amino-modified Fe-MOFs composite matrix can significantly reduce greenhouse gas emissions, reducing CH4 emissions by 44.1% and N2O emissions by 52.2%.

[0095] By analyzing the effluent from the device by liquid chromatography-mass spectrometry (LC-MS), five main intermediate products (N1-N10) were detected, and the degradation mechanism of SMX was proposed based on these products. The following is a detailed description of the degradation path of SMX: SC bond cleavage:

[0096] SN bond breakage:

[0097] The cleavage of the SN bond produced N1 (m / z = 99.0553), which further demonstrated the strong oxidative effect of hydroxyl radicals (·OH) on SMX. This process is considered to be a key step in the degradation pathway because the destruction of the SN bond directly leads to the disintegration of the SMX molecular structure.

[0098] Sulfamide bond cleavage and ring-opening reactions:

[0099] The cleavage of the sulfamide (-SO2-NH-) bond produced the nitro derivative N2 (m / z=284) and the formation of the ring-opening product N3 (m / z=304), indicating further disintegration of the molecular structure.

[0100] Epoxidation:

[0101] The benzene ring and isoxazole ring in SMX were also attacked by OH, and an epoxidation reaction occurred. Hydroxylation of the isoxazole ring generated N4 (m / z=270). This epoxidation reaction not only changed the chemical structure of the SMX molecule, but also triggered further oxidative degradation.

[0102] Decarboxylation reaction:

[0103] N5 (m / z = 173.0878) was detected in the article, and its formation process is related to the oxidative decarboxylation of N4. This reaction is the result of further oxidation after the hydroxyl radical attacks the SMX molecule.

[0104] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A vertical subsurface flow constructed wetland system for enhanced removal of antibiotics, characterized by: It comprises a pool body and a high-level water tank, wherein the pool body is filled with matrix, and the matrix comprises a supporting layer matrix, a quartz sand matrix and an amino-modified Fe-MOFs composite matrix from bottom to top, respectively; a water inlet is arranged at the lower part of the pool body, and a discharge port is arranged at the lower part of the high-level water tank, and the discharge port is connected to the water inlet of the pool body through an inlet pipe; the particle size of the matrix satisfies the supporting layer matrix>quartz sand matrix>amino-modified Fe-MOFs composite matrix; and the amino-modified Fe-MOFs composite matrix is ​​planted with wetland plants.

2. The vertical subsurface flow constructed wetland system for enhanced removal of antibiotics according to claim 1, characterized in that: The particle size of the support layer matrix is ​​6-10 mm, the particle size of the quartz sand matrix is ​​2-3 mm, and the particle size of the amino-modified Fe-MOFs composite matrix is ​​1-2 mm.

3. The vertical subsurface flow constructed wetland system for enhanced removal of antibiotics according to claim 2, characterized in that: The supporting layer matrix is ​​gravel.

4. The vertical subsurface flow constructed wetland system for enhanced removal of antibiotics according to claim 1, characterized in that: A water distribution plate is provided below the support layer matrix, and the water distribution plate is connected to the water inlet to guide and disperse the water flow.

5. The vertical subsurface flow constructed wetland system for enhanced removal of antibiotics according to claim 4, characterized in that: The water distribution plate is evenly distributed with circular small holes.

6. The vertical subsurface flow constructed wetland system for enhanced removal of antibiotics according to claim 1, characterized in that: The upper part of the high-position water tank is provided with a water inlet, and the upper part of the high-position water tank is provided with an overflow port; the water inlet pipe is a hose.

7. The vertical subsurface flow constructed wetland system for enhanced removal of antibiotics according to any one of claims 1 to 6, characterized in that: The amino-modified Fe-MOFs are prepared by the following steps: Step S1, mixing ferric chloride and N,N-dimethylformamide to obtain a precursor solution; Step S2, adding 2-aminoterephthalic acid to the precursor solution, stirring at room temperature until the solution is completely clear, to obtain a reaction solution; the molar ratio of the ferric chloride to the 2-aminoterephthalic acid in the reaction solution is 2:1; Step S3, placing the reaction solution in a reaction kettle, reacting at 110-130° C. for more than 15 hours, and cooling naturally; Step S4, after the reaction is completed, the amino-modified Fe-MOFs catalyst is recovered by centrifugation, and then washed and dried.

8. The vertical subsurface flow constructed wetland system for enhanced removal of antibiotics according to claim 7, characterized in that: In step S1, the molar ratio of the ferric chloride to 2-aminoterephthalic acid in the reaction solution is 2:1; In step S4, the centrifugal speed is 6000-7000 rpm, and the time is 4-6 min; The cleaning is performed by washing with DMF, ethanol and deionized water three times respectively; The drying is vacuum drying at 100-120° C. for more than 10 hours.

9. A method for treating sewage using artificial wetlands, characterized in that: The vertical subsurface flow constructed wetland system for enhanced removal of antibiotics as claimed in any one of claims 1 to 8 is used for water treatment, comprising the following steps: Step S1, cultivating microbial cells, filling the pool with sewage, then adding the cultivated microbial cells into the high-level water tank, stopping the water intake and leaving it for 3 days to enhance the adhesion of microorganisms and biofilm formation; Step S2, microbial acclimation, first setting the pollutant concentration in the sewage at a low level, and gradually increasing the pollutant concentration as the microorganisms gradually adapt; Step S3: After the microorganisms are domesticated, water is continuously introduced and discharged.

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