A device and method for purifying nitrate-antibiotic compound contaminated groundwater

Abstract

The present application relates to the technical field of groundwater pollution remediation technology, and more particularly to a device and method for purifying groundwater contaminated by nitrate and antibiotics. 0 The reaction container is internally provided with a joint electron donor reaction zone, which is filled with S 0 / FeS2 joint electron donor soaked by denitrifying bacteria solution. The bottom of the reaction container is provided with a water inlet, and the top is provided with a water outlet. The water inlet is connected with a peristaltic pump through a pipeline. The peristaltic pump is used for pumping groundwater into the inside of the reaction container. The top of the reaction container is provided with a gas collection port, which is externally connected with a gas collection bag. The present application realizes efficient utilization of electron donor and synergistic and long-acting removal of nitrate nitrogen and typical antibiotic SMX and TMP composite pollutants based on the coupling of S 0 / FeS2 joint electron donor and autotrophic denitrifying microorganisms.

Description

Technical Field

[0001] This invention relates to the field of groundwater pollution remediation technology, and in particular to a device and method for purifying groundwater contaminated with nitrate-antibiotic complex pollution. Background Technology

[0002] With the acceleration of industrialization and urbanization, and the improvement of agricultural intensification, nitrate pollution has become one of the major environmental problems threatening groundwater quality. Meanwhile, antibiotics are difficult to completely degrade in the environment, generating stable degradation products through a dynamic adsorption-desorption process, forming "pseudo-persistent pollution." Sulfamethoxazole (SMX) and trimethoprim (TMP), as components of commonly used clinical compound preparations (such as compound sulfamethoxazole), are widely used in medical, livestock, and other fields. Antibiotic contaminants have been detected in most rivers, with trimethoprim (TMP) having the widest distribution. Sulfamethoxazole (SMX), due to its high utilization rate and strong environmental persistence, is detected very frequently in aquatic environments. It mainly enters the aquatic environment through wastewater treatment plants (WWTPs), and then seeps into the groundwater system through vadose zone leaching and surface water-groundwater recharge, often coexisting with TMP. In typical areas such as livestock breeding areas and sewage discharge outlets, nitrate and antibiotic pollution often occur simultaneously, forming a complex pollution pattern that seriously threatens human health and the stability of the ecological environment.

[0003] Bioremediation is an environmentally friendly and sustainable remediation technology. Biodenitrification is the removal of NO3. - In the presence of sufficient organic carbon sources, heterotrophic denitrification is a highly effective and common method for removing NO3- from wastewater. - The -N method is difficult to achieve efficient nitrogen removal in low C / N ratio environments such as groundwater. Adding external organic carbon sources (such as methanol and ethanol) increases treatment costs and poses a risk of secondary pollution. In contrast, autotrophic denitrification has significant advantages. This process utilizes chemoautotrophic bacteria to use inorganic matter as electron donors to remove NO3-. - -N is reduced to N2. It has the following significant advantages: (1) No external organic carbon source is required, reducing costs and the risk of secondary pollution; (2) Extremely low cell yield, minimizing sludge production; (3) Strong denitrification capacity, capable of simultaneously removing nitrogen and phosphorus, with good self-buffering performance, and other byproducts (sulfate, N2O, NH4) are also reduced. + (Even low sulfate yield) is considered an economical and efficient biological nitrogen removal process, and has been widely studied and applied in engineering. High sulfate production and a sharp pH decrease are limiting factors for elemental sulfur (S). 0 Key factors in the engineering application of autotrophic denitrification (SAD).

[0004] The pyrite-mediated autotrophic denitrification (PAD) process mainly involves three stages: pyrite surface oxidation, microbial metabolism, and coupled cycling. Pyrite acts as a solid-phase electron donor, undergoing surface oxidation to release electrons and Fe. 2+ and S2 - Fe 2+ It can be further oxidized to Fe 3+ This forms a Fe(II) / Fe(III) redox cycle, providing a bridge for electron transfer; autotrophic denitrifying bacteria adsorb onto the surface of pyrite and capture electrons released by the oxidation of pyrite through the electron transport chain on their cell membranes, thus converting NO3- into electrons. - -N is reduced to N2, while simultaneously using CO2 as a carbon source to complete its own proliferation. The enriched microbial community further promotes the expression of denitrification genes on the pyrite surface, accelerating N conversion; Fe 3+ As an electron carrier, it promotes the transfer of electrons between pyrite and microorganisms. At the same time, the S cycle and N cycle are closely coupled to form a “SN-Fe” synergistic metabolic network, which further enhances the denitrification efficiency.

[0005] While achieving efficient denitrification, pyrite tailings can also be utilized as a resource, making it a research hotspot in environmental engineering and groundwater pollution control in recent years. The mineralogical properties of pyrite are the core determinants of denitrification performance, including sulfur content and surface area, particle size and pretreatment, and crystal phase characteristics. Smaller particle size results in a larger specific surface area and a higher reaction rate; pyrite with more exposed (111) and (210) crystal faces exhibits higher electron release efficiency. 0 The synergistic effect of PAD and SAD has been demonstrated in the FeS2 mixed system (PSAD). 0 The coupling of PAD and SAD in the FeS2 co-electron donor system enhanced the conversion of sulfur and iron, expanded the reaction zone, and improved the simultaneous removal rate of N and P. The PSAD system accumulated more biomass and enhanced the stability of microbial denitrification, including the interaction of FeS2 and S. 0 Electron transfer and consumption on the particle surface. The feasibility and mechanism of simultaneous conversion of SMX in the PSAD system have also been reported, involving sulfur vacancies and Fe on the FeS2 surface. 3+ The •OH generated promotes the anaerobic autodegradation of SMX, and the microbial oxidation of Fe 2+ Fe 3+ This may support sustainability. Pyrite-mediated degradation mitigates the enrichment and spread of antibiotic resistance genes (ARGs) by reducing the selectivity of SMX for the PSAD system. 0 The combined electron donor bioremediation technology with FeS2 shows promising engineering application potential in the synergistic deep remediation of nitrate-antibiotic complex pollution in groundwater. Summary of the Invention

[0006] The purpose of this invention is to provide a groundwater purification device and method for nitrate-antibiotic compound pollution, which achieves efficient utilization of electron donors and synergistic long-term removal of pollutants while paying attention to greenhouse gas generation, and obtaining S... 0 The key parameters of the FeS2 optimal electron donor system provide an efficient, economical, and sustainable scheme for constructing a combined electron donor for groundwater purification devices, so as to achieve the goal of synergistic and long-term remediation of groundwater complex pollution.

[0007] This invention provides a groundwater purification device for nitrate-antibiotic compound pollution, comprising a reaction vessel, the upper and lower ends of which are filled with quartz sand layers to simulate the underground aquifer medium; the reaction vessel contains a combined electron donor reaction zone, which is filled with S-type bacteria soaked in denitrifying bacteria solution. 0 / FeS2 combined electron donor, the S 0 Elemental sulfur in the FeS2 combined electron donor 0 The mass ratio of FeS2 in pyrite is (2:1) ~ (1:5); The reaction vessel has an inlet at the bottom and an outlet at the top. The inlet is connected to a peristaltic pump via a pipe. The peristaltic pump is used to pump groundwater into the reaction vessel. The top of the reaction vessel has a gas collection port, which is connected to a gas collection bag for periodically collecting greenhouse gases generated by the device.

[0008] Furthermore, the reaction vessel is a cylindrical plexiglass column, and the filling thickness of the quartz sand layer is 10~20cm.

[0009] Furthermore, the height of the combined electron donor reaction region is 10~20cm.

[0010] Furthermore, the S 0 Elemental sulfur in the FeS2 combined electron donor 0 The particle size of FeS2 in pyrite is 10-200 mesh.

[0011] This invention provides a method for purifying groundwater contaminated with nitrate-antibiotic complex pollution, based on the aforementioned purification device, comprising the following steps: S1. Prepare groundwater that simulates nitrate-antibiotic compound pollution; S2. The anaerobic sludge is placed in a culture solution for cultivation and acclimatization to obtain a denitrifying bacteria solution; S3. The S 0 / FeS2 combined electron donor is soaked in the denitrifying bacteria solution prepared in step S2 and then filled into the combined electron donor reaction zone of the reaction vessel; nitrogen gas is continuously introduced into the groundwater prepared in step S1 to maintain the anaerobic environment, and the groundwater is pumped into the reaction vessel by a peristaltic pump; the inlet and outlet are sampled at regular intervals to analyze the changes in water quality indicators over time. S4. Collect greenhouse gases generated during operation periodically using gas collection bags, and analyze the components and concentration changes of the greenhouse gases.

[0012] Furthermore, the antibiotic in step S1 is at least one of sulfamethoxazole and trimethoprim.

[0013] Further, in step S1, the concentration of antibiotics in the groundwater is 1 μg / L to 1000 μg / L; NO3 - The concentration of -N is 20 mg / L to 100 mg / L, expressed as N.

[0014] Furthermore, in step S3, S 0 The FeS2 combined electron donor was immersed in denitrifying bacteria solution for 22-26 hours.

[0015] Furthermore, in step S3, the influent flow rate of groundwater into the reaction vessel is 0.1 mL / min to 2 mL / min.

[0016] Furthermore, the water quality indicators in step S3 include pollutant concentration, reaction products, pH value, dissolved oxygen concentration, oxidation-reduction potential, and temperature.

[0017] In summary, the present invention has the following advantages: The technical solution provided by this invention is based on S 0 The coupling of FeS2 with electron donors and autotrophic denitrifying microorganisms significantly improves the microbial utilization efficiency and electron transfer efficiency of pyrite, catalyzes the generation of hydroxyl radicals (•OH) on the pyrite surface, strengthens the long-term synergistic remediation mechanism of complex pollution, and constructs S... 0 The FeS2 combined electron donor purification device, using nitrate nitrogen and typical antibiotics sulfamethoxazole and trimethoprim as representatives of compound pollutants, achieved a high average synergistic removal rate after 240 days of operation. The generation of reaction byproducts was significantly reduced, and the system's pH buffering effect was obvious. While efficiently and synergistically purifying compound pollutants, it also realized the resource utilization of pyrite tailings, which is in line with the concepts of low-carbon environmental protection and circular economy. It has good economic benefits and will provide new technical support for the synergistic and long-term remediation of nitrogen and new pollutants in aquatic media, generating good social and environmental benefits. Attached Figure Description

[0018] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the device in Embodiment 1 of the present invention; Figure 2 The diagram shows the effect of the device in Embodiment 1 of the present invention on the removal of nitrate and the generation of nitrite and ammonia after 240 days of continuous operation. Figure 3 This is a diagram showing the removal effect of the device in Embodiment 1 of the present invention on SMX after 240 days of continuous operation; Figure 4 This is a graph showing the pH change of the effluent from the device in Embodiment 1 of the present invention after 240 days of continuous operation. Figure 5 This is a graph showing the variation of dissolved oxygen (DO) in the effluent after 240 days of continuous operation of the device in Embodiment 1 of the present invention. Figure 6 This is a graph showing the ORP (Original Rate of Return) of the effluent from the device during 240 days of continuous operation in Embodiment 1 of the present invention. Figure 7 This is a graph showing the variation of TDS in the effluent after 240 days of continuous operation of the device in Embodiment 1 of the present invention. Figure 8 This is a graph showing the change in outlet water temperature during 240 days of continuous operation of the device in Embodiment 1 of the present invention. Figure 9 This is a graph showing the content of greenhouse gas components generated in Example 1 of the present invention; Figure 10 This is a graph showing the changes in the concentration of greenhouse gas components generated in Example 1 of the present invention.

[0020] Explanation of reference numerals in the attached diagram: 1-Acrylic glass column; 101-Water inlet; 102-Water outlet; 103-Gas collection port; 2-Quartz sand layer; 3-Combined electron donor reaction zone; 4-Peristaltic pump; 5-Water supply device; 6-Water collection device; 7-Gas collection bag. Detailed Implementation

[0021] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used 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. Therefore, they should not be construed as limiting this invention.

[0023] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified. Furthermore, the terms "installed," "connected," and "linked" should be interpreted broadly; for example, they may refer to a fixed connection, a detachable connection, or an integral connection; they may refer to a mechanical connection or an electrical connection; they may refer to a direct connection or an indirect connection through an intermediate medium; and they may 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.

[0024] Example 1 A groundwater purification device for nitrate-antibiotic compound pollution, such as Figure 1 As shown, the reaction vessel consists of a closed-end acrylic glass column 1, with quartz sand layers 2 filling both ends to simulate underground aquifer media. Inside the acrylic glass column 1 is a combined electron donor reaction zone 3, which is filled with S-containing bacteria soaked in denitrifying bacteria solution. 0 / FeS2 combined electron donor, S 0 Elemental sulfur in the FeS2 combined electron donor 0 The mass ratio of FeS2 to pyrite is 1:1, and the elemental sulfur S 0 The particle size of FeS2 in pyrite is 10-200 mesh.

[0025] The plexiglass column 1 has a water inlet 101 at the bottom and a water outlet 102 at the top. The water inlet 101 is connected to a peristaltic pump 4 through a pipe. The peristaltic pump 4 is used to pump groundwater into the plexiglass column 1. The top of the plexiglass column 1 has a gas collection port 103. The gas collection port 103 is connected to a gas collection bag 7 for periodically collecting greenhouse gases generated by the device.

[0026] During installation and use, the peristaltic pump 4 is connected to the water supply device 5 containing groundwater through a pipe, and the outlet 102 of the plexiglass column 1 is connected to the water collection device 6 through a pipe.

[0027] In this embodiment, the plexiglass column 1 is a cylinder with a diameter of 10 cm and a height of 30 cm, the quartz sand layer 2 has a height of 5 cm, and the combined electron donor reaction zone 3 has a filling height of 20 cm. The gas collection port 103 has a diameter of 0.5 cm to 1 cm, and the gas collection bag 7 has a volume of 500 mL to 1000 mL.

[0028] The specific steps of the method for purifying groundwater contaminated with nitrate and antibiotics using the above-mentioned purification device are as follows: S1. Prepare groundwater simulating nitrate-antibiotic co-contamination. The antibiotic in the groundwater is sulfamethoxazole (SMX), with a concentration of 100 μg / L and NO3. - The concentration of -N is 50 mg / L (as N), NO3 - -N represents nitrate nitrogen.

[0029] S2. Activated sludge from the Tsinghua University Zijing Wastewater Treatment Plant was used. 50g of activated sludge was placed in a 2L plastic bottle, and liquid culture medium was added. The mixture was then cultured and acclimatized at a constant temperature of 30℃ to obtain a sulfur-autotrophic denitrifying bacteria solution. The liquid culture medium was prepared by dissolving 5.0g Na₂S₂O₃, 2.5g NaHCO₃, 1.68g NaNO₃, 2.0g KH₂PO₄, 1.0g NH₄Cl, 0.42g MgSO₄, and 0.02g FeSO₄·7H₂O in 1L of ultrapure water. The plastic bottle was kept sealed and stored in the dark at a constant temperature of 30℃ to promote the growth of autotrophic denitrifying bacteria. During the initial acclimatization period, the culture medium was replaced with fresh medium every 3 days, and the nitrate concentration was measured to calculate the removal efficiency. When the nitrate removal rate reached 95% or higher, the culture medium was replaced with fresh medium every day. The autotrophic denitrifying bacteria acclimatization was considered complete when the nitrate removal rate remained consistently above 95% for one day. The acclimatization period was 35 days.

[0030] S3. S 0 After the FeS2 combined electron donor is completely immersed in the sulfur autotrophic denitrifying bacteria solution prepared in step S2 for 24 hours, it is filled into the combined electron donor reaction zone of the plexiglass column. The groundwater prepared in step S1 is put into a brown water supply bottle, and N2 is continuously introduced to maintain an anaerobic environment. The deoxygenated groundwater is pumped into the plexiglass column by a peristaltic pump, with the influent flow rate controlled at 1 mL / min and the hydraulic retention time at 24 hours. The system is operated continuously for 240 days. Samples are taken from the inlet and outlet at regular intervals to analyze the changes in water quality indicators such as the removal rate of SMX and nitrate nitrogen, reaction products, pH value, dissolved oxygen concentration, redox potential, and temperature in the simulated groundwater over time. S4. Collect greenhouse gases generated during operation periodically using gas collection bags, and analyze the components of the greenhouse gases and the changes in the concentration of each component.

[0031] like Figure 2 As shown in the figure (blue line represents influent nitrate NO3), - -N Inf The red dots represent nitrite (NO2) in the effluent. - -N Eff The blue dots represent ammonia nitrogen (NH4) in the effluent. + -N Eff The black spots represent nitrate NO3 in the effluent. - -N Eff The gray bar chart represents NO3. - The system achieved efficient synchronous denitrification within a 240-day operating cycle: During the start-up adaptation buffer phase (0-40 days), the average nitrate removal rate was 97.3%, but the removal effect fluctuated significantly and was unstable. The concentrations of ammonia nitrogen and nitrite, denitrification products, in the effluent were high and fluctuated, but they decreased rapidly with microbial acclimatization, and the denitrification effect tended to stabilize. During the stable degradation and remediation phase (41-120 days), the average nitrate removal rate was 99.7%, and the denitrification effect was efficient and stable. The concentrations of ammonia nitrogen and nitrite, reaction products, in the effluent remained near the detection limit. Sufficient electron donors for denitrification during the denitrification process effectively reduced the accumulation of nitrite. During the continuous stabilization phase (121-240 days), the average nitrate removal efficiency remained stable at over 99%, and there was no imbalance in the nitrification process or a decline in denitrification performance throughout the entire process. The nitrogen index of the effluent was significantly better than that of conventional biological treatment processes.

[0032] like Figure 3 As shown (the black dot in the image represents the inlet SMX), Inf The red dot indicates the SMX water outlet. Eff The blue bars represent the SMX removal rate. The purification device provided in this embodiment achieved long-term, efficient, and synergistic degradation of SMX during 240 days of continuous operation. During the system startup adaptation buffer phase (0-40 days), the effluent SMX concentration rapidly decreased from an initial 100 μg / L, with the average removal rate fluctuating between 60% and 70%. During the stable degradation and repair phase (41-120 days), the effluent SMX concentration remained consistently below 20 μg / L, with the removal rate stabilizing at 70% to 80% or higher. During the sustained stable phase (121-240 days), the average SMX removal efficiency remained stable at over 80%. The blue bars show that the overall SMX removal efficiency generally increased over operating time: initially fluctuating between 60% and 70%, stabilizing at over 80% after 80 days without significant decline, demonstrating the system's good long-term stability in SMX removal and the absence of performance degradation due to long-term operation.

[0033] like Figure 4 As shown, the pH values ​​of the influent and effluent remained within the neutral range of 6.0-8.0 throughout the 240-day operation, representing the optimal pH conditions for denitrification without drastic fluctuations. Even with periodic fluctuations in the influent pH (6.2-7.2), the effluent pH remained stable within the microbiologically suitable range of 6.5-7.5, and was slightly higher than the influent pH, demonstrating the system's excellent acid-base buffering capacity. This also verified the alkalinity compensation effect of the denitrification process, indicating that the acid-base balance of the biochemical reaction could be maintained without the need for additional acid-base regulators.

[0034] like Figure 5 , Figure 6 , Figure 7 and Figure 8 As shown, during 240 days of continuous operation, the effluent DO concentration remained at 0-1 mg / L, and the ORP remained stable within the reducing range of -100mV to -400mV. This provided a suitable anaerobic microenvironment for denitrification and anaerobic degradation of antibiotics, ensuring a stable and complete denitrification process in the system. It effectively inhibited the production of nitrite and the accumulation of the greenhouse gas nitrous oxide. The system temperature was controlled throughout the process within the suitable growth range of mesophilic bacteria, between 20 and 33°C, without extreme temperature fluctuations. The TDS increased slowly with the progress of the biochemical reaction, without any abnormal salinity shocks, verifying the environmental stability and shock load resistance of the device during long-term operation.

[0035] like Figure 9 and Figure 10 As shown, the greenhouse gases produced during the reaction process are 89% CO2 and 11% CH4. During operation, the emissions gradually shifted from a mixture of CO2 and CH4 in the initial stage to a mode dominated by CO2 with no CH4 emissions in the later stage, and no N2O was produced. This indicates that the purification method provided in this embodiment effectively inhibits the generation of greenhouse gases CH4 and N2O, significantly reduces the overall greenhouse effect intensity, and has significant environmental benefits.

[0036] Example 2 A method for purifying groundwater contaminated with nitrate and antibiotics is disclosed in this embodiment. This embodiment uses the purification device described in Example 1, with the only difference being that the antibiotics in the groundwater in step S1 of this embodiment are a mixture of SMX and TMP (trimethoprim), with a concentration of 100 μg / L, and SMX and TMP each at 50 μg / L. NO3... - The -N concentration is 50 mg / L. The remaining steps can be performed according to the steps in Example 1.

[0037] After 240 days of continuous operation, the purification unit achieved an average nitrate removal rate of 97.3%, with average concentrations of ammonia nitrogen and nitrite of 2.32 mg / L and 2.77 mg / L, respectively, significantly higher than in Example 1. The average removal rates of SMX and TMP were 81.5% and 64.6%, respectively, demonstrating good degradation and removal effects. The average pH of the effluent was 7.07, which is suitable for the growth of denitrifying bacteria and sulfur-oxidizing bacteria and maintains high activity, ensuring long-term nitrogen removal. The average effluent DO was 4.97 mg / L. This high DO concentration inhibits the activity of nitrite reductase (NiR) and nitric oxide reductase (NoS), leading to nitrite accumulation and the formation of the greenhouse gas N2O. The average ORP was -59.42 mV, and the TDS was significantly increased, averaging 1035.4 mg / L. The generated greenhouse gases were 86% CO2, 13% CH4, and 1% N2O.

[0038] Example 3 A method for purifying groundwater contaminated with nitrate and antibiotics is described in this embodiment. The operation steps are basically the same as those in Embodiment 2, except that the antibiotic in the groundwater prepared in step S1 is only TMP, and the concentration of TMP is 100 μg / L. NO3- - -N concentration is 50 mg / L.

[0039] After 240 days of continuous operation, the purification unit achieved an average nitrate removal rate of 91.6%, with average concentrations of ammonia nitrogen and nitrite of 3.55 mg / L and 1.77 mg / L, respectively, higher than in Example 1 but lower than in Example 2. The average TMP removal rate was 78.3%, higher than in Example 2. The average effluent pH was 7.47, indicating a significant buffering effect. The average effluent DO was 1.27 mg / L, slightly higher than in Example 1. The average ORP was -139.42 mV, indicating a strictly reducing environment within the unit. This provided a suitable anaerobic microenvironment for denitrification and antibiotic anaerobic degradation, ensuring a stable and complete denitrification process, effectively inhibiting nitrite production and the accumulation of the greenhouse gas nitrous oxide, demonstrating a good long-term synergistic denitrification effect. The generated greenhouse gases were 86% CO2 and 14% CH4, with no N2O generated.

[0040] Comparative Example 1 A groundwater purification method is described. The purification device used in this comparative example has the same structure as the purification device in Example 1, except that the combined electron donor in this comparative example is only elemental sulfur (S). 0 .

[0041] After 240 days of continuous operation, the purification unit achieved an average nitrate removal rate of 90.3%, with average concentrations of ammonia nitrogen and nitrite of 8.32 mg / L and 4.77 mg / L, respectively. Elemental sulfur (S) 0As an electron donor, it exhibits good microbial utilization efficiency, but a significant short-cut denitrification process occurs, resulting in high ammonia nitrogen production. The average removal rate of SMX is 71.5%, indicating good degradation and removal efficiency. The average effluent pH is 5.67, showing poor pH buffering capacity, which significantly inhibits the denitrification effect of the device during long-term operation. The average effluent DO is 6.35 mg / L. Similar to Example 2, the high DO concentration leads to nitrite accumulation and the formation of the greenhouse gas N2O. The average ORP is 60.32 mV, and the average TDS is 1285.4 mg / L, originating from elemental sulfur (S). 0 SO4 is oxidized as an electron donor. 2- The large-scale generation of these gases results in 82% CO2, 14% CH4, and 3% N2O as greenhouse gases.

[0042] Comparison document 2 A groundwater purification method is described. The purification device used in this comparative example has the same structure as the purification device in Example 1, except that the combined electron donor in this comparative example is only pyrite FeS2.

[0043] The average nitrate removal rate was only 30.3%, and the purification device lost its denitrification effect after 80 days of operation. This was due to the low bioavailability of pyrite FeS2 by microorganisms in the device, which showed the significant limitations of pyrite FeS2 as an electron donor alone.

[0044] Comparative Example 3 A groundwater purification method is described. The operation steps of this comparative example are basically the same as those of Example 2, except that the groundwater prepared in step S1 contains only antibiotics, simulating groundwater contaminated by antibiotics, and does not contain nitrates. The concentrations of SMX and TMP are 50 μg / L, respectively.

[0045] After 240 days of continuous operation, the average concentrations of nitrate, ammonia nitrogen, and nitrite generated from the degradation of SMX and TMP were 1.96 mg / L, 0.99 mg / L, and 0.05 mg / L, respectively, with significant accumulation observed. The nitrate concentration increased from 0.11 mg / L during the initial adaptation buffer phase (0-40 days) to 3.16 mg / L during the stable phase (121-240 days), while ammonia nitrogen increased from 0.53 mg / L to 1.16 mg / L and nitrite from 0.01 mg / L to 0.08 mg / L during the same period. The average removal rates of SMX and TMP were 45.6% and 38.4%, respectively, indicating unsatisfactory degradation and removal efficiency. The average effluent pH was 7.01, average DO was 4.95 mg / L, average ORP was -321.7 mV, and average TDS was 608.1 mg / L. The generated greenhouse gases were 64% CO2 and 36% CH4.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A groundwater purification device for nitrate-antibiotic compound pollution, characterized in that, The reaction vessel includes a reaction container, both its upper and lower ends of which are filled with quartz sand layers to simulate underground aquifer media. The reaction container also includes a combined electron donor reaction zone, which is filled with S-type bacteria soaked in denitrifying bacteria solution. 0 / FeS2 combined electron donor, the S 0 Elemental sulfur in the FeS2 combined electron donor 0 The mass ratio of FeS2 in pyrite is (2:1) ~ (1:5); The reaction vessel has an inlet at the bottom and an outlet at the top. The inlet is connected to a peristaltic pump via a pipe. The peristaltic pump is used to pump groundwater into the reaction vessel. The top of the reaction vessel has a gas collection port, which is connected to a gas collection bag for periodically collecting greenhouse gases generated by the device.

2. The groundwater purification device according to claim 1, characterized in that, The reaction vessel is a cylindrical plexiglass column, and the quartz sand layer has a filling thickness of 10~20cm.

3. The groundwater purification device according to claim 1, characterized in that, The height of the combined electron donor reaction region is 10~20cm.

4. The groundwater purification device according to claim 1, characterized in that, The S 0 Elemental sulfur in the FeS2 combined electron donor 0 The particle size of FeS2 in pyrite is 10-200 mesh.

5. A method for purifying groundwater contaminated with nitrate-antibiotic complex pollution, characterized in that, The purification device according to any one of claims 1-4 includes the following steps: S1. Prepare groundwater that simulates nitrate-antibiotic compound pollution; S2. The anaerobic sludge is placed in a culture solution for cultivation and acclimatization to obtain a denitrifying bacteria solution; S3. The S 0 / FeS2 combined electron donor is soaked in the denitrifying bacteria solution prepared in step S2 and then filled into the combined electron donor reaction zone of the reaction vessel; nitrogen gas is continuously introduced into the groundwater prepared in step S1 to maintain the anaerobic environment, and the groundwater is pumped into the reaction vessel by a peristaltic pump; the inlet and outlet are sampled at regular intervals to analyze the changes in water quality indicators over time. S4. Collect greenhouse gases generated during operation periodically using gas collection bags, and analyze the components and concentration changes of the greenhouse gases.

6. The purification method according to claim 5, characterized in that, The antibiotic in step S1 is at least one of sulfamethoxazole and trimethoprim.

7. The purification method according to claim 5, characterized in that, In step S1, the concentration of antibiotics in the groundwater is 1 μg / L to 1000 μg / L; NO3 - The concentration of -N is 20 mg / L to 100 mg / L, expressed as N.

8. The purification method according to claim 5, characterized in that, In step S3, S 0 The FeS2 combined electron donor was immersed in denitrifying bacteria solution for 22-26 hours.

9. The purification method according to claim 5, characterized in that, In step S3, the inflow rate of groundwater into the reaction vessel is 0.1 mL / min to 2 mL / min.

10. The purification method according to claim 5, characterized in that, The water quality indicators in step S3 include pollutant concentration, reaction products, pH value, dissolved oxygen concentration, oxidation-reduction potential, and temperature.

Images