River-side water source nitrate pollution in-situ remediation system and method

Abstract

The invention provides an in-situ remediation system and method for nitrate pollution of a riverside water source. The in-situ remediation system comprises an underground water source mining well adjacent to a river; the nitration unit is arranged between the river and the mining well and comprises a control well, an oxygen release material storage device and a first control system; the denitrification unit is arranged between the nitrification unit and the mining well and comprises an injection well, a carbon source storage device and a second control system; the at least one first monitoring well is arranged between the nitrification unit and the denitrification unit and is respectively connected with the first control system and the second control system; and the at least one second monitoring well is arranged between the denitrification units and between the mining wells and is connected with the second control system. According to the in-situ remediation system and method for nitrate pollution in the riverside water source, in-situ remediation can be carried out on compound nitrogen pollution, and remediation and mining are synchronously carried out.

Description

Technical Field

[0001] The present invention relates to the technical field of groundwater remediation, and in particular to an in-situ remediation system and method for nitrate pollution in a riverside water source. Background Art

[0002] Nitrate contamination of groundwater has become a global environmental problem, particularly in riverside water sources. Affected by agricultural non-point source pollution and surface water-groundwater interactions, nitrates migrate hydraulically into aquifers, threatening drinking water safety. Permeable reactive barrier (PRB) technology is currently a widely used in-situ remediation technique for groundwater contamination. While PRB technology reduces nitrates by filling a reactive medium (such as zero-valent iron or activated carbon), it suffers from media clogging and short lifespan in practice. Furthermore, due to the uncontrollable diffusion of its carbon source, PRB technology struggles to control reduction products, leading to secondary contamination. This makes it unsuitable for treating nitrate contamination in riverside water sources, which serve as drinking water supplies.

[0003] Microbial treatment methods are accepted and widely used because of their advantages such as simple operation, no secondary pollution, high remediation efficiency and stable operation. However, due to the current trend of diversification of pollutants in water bodies, especially for riverside water sources, the complex nitrogen pollution caused by the interconnection between surface water and groundwater, a single treatment and remediation process is difficult to cope with the complex nitrogen pollution (coexistence of ammonia nitrogen, nitrate and nitrite) under the dynamic hydrological conditions of riverside areas, and lacks a precise control mechanism, it is impossible to achieve simultaneous operation of remediation and mining, and the blockage problem leads to poor long-term operation stability. Summary of the Invention

[0004] The present invention proposes an in-situ remediation system and method for nitrate pollution in riverside water sources. The system can perform in-situ remediation of complex nitrogen pollution under the dynamic hydrological conditions of the riverside area, realize the simultaneous operation of remediation and mining, reduce the nitrogen content in the water, ensure stable and safe water quality, provide a reliable water source, and at the same time avoid blockage problems caused by microbial growth.

[0005] To solve the above technical problems, the present invention proposes an in-situ remediation system for nitrate pollution in riverside water sources, which at least comprises: wells mined from groundwater sources adjacent to rivers; at least one nitrification unit disposed between the river and the production well, the nitrification unit comprising a control well, an oxygen-releasing material storage device, and a first control system; at least one denitrification unit, disposed between the nitrification unit and the production well, the denitrification unit comprising an injection well, a carbon source storage device, and a second control system; at least one first monitoring well, disposed between the nitrification unit and the denitrification unit, and connected to the first control system and the second control system respectively; At least one second monitoring well is disposed between the denitrification units and the production wells and is connected to the second control system.

[0006] In one embodiment of the present invention, the distance between the injection well and the production well is greater than or equal to the influence radius R; and / or The ratio of the distance between the control well and the injection well to the distance between the injection well and the production well is greater than or equal to 3.

[0007] In one embodiment of the present invention, one nitrification unit, one denitrification unit, one first monitoring well and one second monitoring well are arranged in a single row, which is an in-situ reaction unit. The in-situ remediation system includes a plurality of equidistantly arranged in-situ reaction units. The distance between adjacent in-situ reaction units is a, and a is greater than or equal to 2R.

[0008] In one embodiment of the present invention, the distance between the first monitoring well and the control well is 75%-85% of the distance between the control well and the injection well; and / or The distance between the second monitoring well and the injection well is 75%-85% of the distance between the injection well and the production well.

[0009] In one embodiment of the present invention, the oxygen-releasing material storage device stores a slow-release oxygen material, and the slow-release oxygen material includes an oxygen-releasing source and a buffer. The oxygen-releasing source includes one or more combinations of calcium peroxide, magnesium peroxide, sodium peroxide, zinc peroxide or sodium percarbonate, and the buffer includes one or more combinations of potassium dihydrogen phosphate, ammonium sulfate, disodium hydrogen phosphate, sodium dihydrogen phosphate, sodium bicarbonate or ammonium acetate.

[0010] In one embodiment of the present invention, the oxygen-releasing material storage device is provided on one side of the control well, a first delivery device is provided between the oxygen-releasing material storage device and the control well, and the first delivery device is connected to the first control system.

[0011] In one embodiment of the present invention, the carbon source storage device is arranged on one side of the injection well, a second delivery device is arranged between the carbon source storage device and the injection well, and the delivery device is connected to the second control system; and / or The carbon source storage device stores a carbon source, and the carbon source includes one or more combinations of ethanol, sodium succinate, sodium acetate, sodium malate or glucose.

[0012] In one embodiment of the present invention, a first sensor is provided in the first monitoring well, and the first sensor is used to detect the concentrations of ammonia nitrogen, nitrate and nitrite in water during the flood season. The first sensor is communicatively connected to the first control system and the second control system respectively. The first control system obtains target data for adjusting the slow-release oxygen material based on the ammonia nitrogen concentration data of the first sensor, and feeds the target data back to the first dosing device. The first dosing device regulates the amount of the oxygen-releasing material storage device added to the control well based on the target data; the second control system obtains the initial addition amount of the carbon source based on the nitrate and nitrite concentration data of the first sensor, and feeds the initial addition amount back to the second dosing device. The second dosing device controls the amount of the carbon source storage device added to the injection well based on the initial addition amount.

[0013] In one embodiment of the present invention, a second sensor is provided in the second monitoring well, and the second sensor is used to detect the concentration of nitrate and nitrite in the water during the wet season and the dry season. The second sensor is communicatively connected to the second control system. During the wet season, the second control system obtains target data for adjusting the carbon source based on the nitrate and nitrite concentration data from the second sensor, and feeds the target data back to the second feeding device. The second feeding device regulates the amount of carbon source storage device fed into the injection well based on the target data. During the dry season, the second control system obtains the initial addition amount of the carbon source based on the nitrate and nitrite concentration data of the second sensor, and feeds the initial addition amount back to the second delivery device. The second delivery device controls the amount of carbon source storage device delivered to the injection well based on the initial addition amount.

[0014] In one embodiment of the present invention, the in-situ remediation system also includes a third sensor, which is arranged in the river. The third sensor is used to detect the ammonia nitrogen concentration in the water during the flood season. The third sensor is communicated with the first control system. The first control system obtains the initial input amount of the slow-release oxygen material based on the ammonia nitrogen concentration data of the third sensor, and feeds the initial input amount back to the first delivery device. The first delivery device controls the input amount of the oxygen-releasing material storage device to the control well based on the initial input amount.

[0015] The present invention also provides an in-situ remediation method for nitrate pollution in riverside water sources, which includes setting up the above-mentioned in-situ remediation system between the river and the groundwater source mining well to remove nitrate pollution.

[0016] In summary, the present invention proposes an in-situ remediation system and method for nitrate pollution in riverside water sources. Through in-situ cascade remediation by nitrifying and denitrifying microorganisms, it can be suitable for the complex nitrogen pollution situation in riverside water sources, realize in-situ remediation of nitrate pollution in riverside water sources, ensure the stability and safety of water quality, and provide more reliable water source protection. In the in-situ remediation, the slow-release oxygen material can slowly release oxygen, and complete nitrification occurs under the action of nitrifying bacteria, oxidizing ammonia nitrogen to nitrate, improving the anoxic condition of groundwater without causing a pH surge. Intelligent control of carbon source and slow-release oxygen material input is adopted, and the system operation and processing status are monitored in real time to avoid problems such as waste of resources, secondary pollution and poor treatment effect, thereby improving the efficiency and stability of in-situ remediation. Sufficient distance is reserved for nitrification and denitrification reactions to improve the remediation effect. At the same time, buffer space is reserved to deal with dynamic factors such as water quality fluctuations and microbial activity decay, ensuring that the denitrification process is stable and efficient under complex working conditions. At the same time, the system can achieve a backwashing effect, solving the blockage problem caused by microbial growth due to lack of flushing during the flood season and dry season. Through in-situ microbial cascade remediation, the complex nitrogen pollution in riverside water sources can be solved, restoration and mining can be carried out simultaneously, the nitrogen content in the water can be reduced, eutrophication of water bodies can be avoided, the stable and safe water quality can be ensured, and a reliable water source can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0018] Figure 1 Schematic diagram of an in-situ repair system during a flood season according to an embodiment of the present invention.

[0019] Figure 2 Schematic diagram of an in-situ repair system during the dry season according to one embodiment of the present invention.

[0020] Figure 3 Schematic diagram of a control well in one embodiment of the present invention.

[0021] Description of labels: 10. Control well; 101. Casing; 11. Oxygen-releasing material storage device; 111. Slow-release oxygen material; 12. First control system; 13. First monitoring well; 14. Injection well; 15. Carbon source storage device; 16. Second control system; 17. Second monitoring well; 18. Production well; 19. Third sensor. DETAILED DESCRIPTION

[0022] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0024] In the description of this specification, it should be understood that the directions or positional relationships indicated by terms such as "center," "upper," "lower," "front," "back," "left," and "right" are based on the directions or positional relationships shown in the accompanying drawings and are intended solely to facilitate the description of this solution and simplify the description. They do not indicate or imply that the devices or components referred to must have a specific direction, be constructed, or operate in a specific direction. Therefore, they should not be construed as limitations on this solution. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0025] Riverside water extraction involves deploying wells along riverbanks, exploiting the relationship between surface water and groundwater. Surface water infiltration constitutes the primary component of extracted water. The relationship between river water and groundwater at the source varies with the river's hydrological dynamics, such as the wet and dry seasons. The wet season is when river flow is primarily recharged by rainfall or snowmelt, typically during the rainy season or the period of rising spring temperatures. During this period, river water levels rise above groundwater levels, leading to groundwater recharge. During this period, ammonia nitrogen, the primary pollutant in the river, is transported into the groundwater with the flow of water. The dry season is when surface water dries up within a basin, leaving groundwater as the primary source of recharge. During this period, nitrate, the primary pollutant in groundwater, is transported into the river with the flow of water. The duration of the dry season varies throughout the year depending on the basin's natural geography and meteorological conditions. The present application provides an in-situ remediation system and method for nitrate pollution in riverside water sources, which can perform in-situ cascade remediation through nitrification and denitrification microorganisms. In response to the complex nitrogen pollution situation in riverside water sources, different remediation methods are adopted during the flood season and the dry season to achieve in-situ remediation of nitrate pollution in riverside water sources, thereby ensuring the stability and safety of water quality and providing a more reliable water source guarantee.

[0026] In one embodiment of the present invention, the in-situ remediation system for nitrate pollution in a riverside water source at least includes a groundwater source extraction well adjacent to the river; at least one nitrification unit, arranged between the river and the extraction well, the nitrification unit including a control well, an oxygen-releasing material storage device and a first control system; at least one denitrification unit, arranged between the nitrification unit and the extraction well, the denitrification unit including an injection well, a carbon source storage device and a second control system; at least one first monitoring well, arranged between the nitrification unit and the denitrification unit, connected to the first control system and the second control system respectively; at least one second monitoring well, arranged between the denitrification units and the extraction well, connected to the second control system. Through the in-situ remediation system for nitrate pollution in a riverside water source of the present application, it is possible to achieve in-situ remediation of nitrate pollution in a riverside water source, and monitor the operation and processing status of the system in real time, thereby improving the efficiency and stability of the in-situ remediation process.

[0027] See also Figure 1 As shown, in one embodiment of the present invention, water is taken along the river by laying out extraction wells 18 on the beach along the river bank, and utilizing the replenishment and discharge relationship between surface water and groundwater to obtain water. Among them, the extraction wells 18 are, for example, provided with one or more, or they are established in a centralized manner, for example, in the form of parallel layout along the river. This application does not impose specific restrictions. For example, a single row or multiple rows of extraction wells are designed according to specific circumstances, and the well spacing should be designed according to the single-width replenishment volume and the single-well water output. In this embodiment, the depth of the extraction wells 18 is, for example, to the aquiclude, and the well group of the extraction wells 18 is relatively centralized, so that the water source is easy to exploit and manage. In the schematic diagram, only one extraction well is shown to describe the in-situ remediation system.

[0028] See also Figure 1 As shown, in one embodiment of the present invention, a nitrification unit, a denitrification unit, a first monitoring well, and a second monitoring well are arranged in a single row, for example, and are defined as an in-situ reaction unit. In this embodiment, for example, an in-situ reaction unit and a repair process with a single row structure are described, wherein the nitrification unit is arranged between the river and the production well 18 adjacent to the river, and the nitrification unit includes a control well 10, an oxygen-releasing material storage device 11, and a first control system 12. The first control system 12 connects the control well 10 and the oxygen-releasing material storage device 11, and controls the injection of slow-release oxygen material from the oxygen-releasing material storage device 11 into the control well 10 and controls the injection amount. The present application does not limit the distance between the control well 10 and the river, so long as the river does not affect the control well 10 during the flood season.

[0029] See also Figure 1 and Figure 3As shown, in one embodiment of the present invention, the depth of the control well 10 is, for example, to the aquiclude, and the control well 10 is, for example, 40 mm to 100 mm above the ground. The control well 10 is, for example, a perforated pipe, etc., to facilitate water flow and diffusion of dissolved oxygen in the slow-release oxygen material. The present application does not limit the size of the perforations in the control well 10. A casing 101 is provided in the control well 10. The depth and length of the casing 101 above the ground are, for example, the same as those of the control well. The casing 101 is, for example, a perforated pipe with a closed bottom, etc., for placing the slow-release oxygen material 111. The size of the perforations in the casing 101 is smaller than the size of the slow-release oxygen material 111. After the casing 101 is filled with the slow-release oxygen material 111 and the slow-release oxygen material 111 becomes ineffective, the casing 101 is replaced.

[0030] See also Figure 1 As shown, in one embodiment of the present invention, an oxygen-releasing material storage device 11 is provided on one side of the control well 10 for storing a slow-release oxygen material 111. In a specific embodiment of the present invention, the oxygen-releasing material storage device 11 has a waterproof function, and may be, for example, a sealed storage bin or storage tank, etc., but this application does not impose any specific restrictions. A first delivery device (not shown in the figure) is provided between the oxygen-releasing material storage device 11 and the control well 10, such as an automatic feeding device, and may include, for example, a peristaltic pump, an elastic hose, etc. The first delivery device is intelligently connected to the first control system and can automatically adjust the delivery amount of the slow-release oxygen material 111 according to the nitrification demand. The slow-release oxygen material 111 is stored in the oxygen-releasing material storage device 11, and the slow-release oxygen material 111 may include, for example, an oxygen-releasing source, a buffer, a coagulant, and a modifier. The mass ratio of the oxygen release source, buffer, coagulant, and modifier is, for example, (3-3.5): (1-1.5): (3-6): (2.5-3). The oxygen release source includes, for example, one or more combinations of calcium peroxide (CaO2), magnesium peroxide (MgO2), sodium peroxide (Na2O2), zinc peroxide (ZnO2), or sodium percarbonate (2Na2CO3·3H2O), for releasing dissolved oxygen in water. The buffer includes, for example, one or more combinations of potassium dihydrogen phosphate (KH2PO4), ammonium sulfate ((NH4)2SO4), disodium hydrogen phosphate (Na2HPO4), sodium dihydrogen phosphate (NaH2PO4), sodium bicarbonate (NaHCO3), or ammonium acetate (NH4C2H3O2). The H generated by the buffer dissolving in water + Buffers can reduce the alkalinity of water, addressing the increased pH caused by the reaction between the oxygen source and water during the oxygen release process. Furthermore, they provide elements for the growth of microorganisms in soil and water. Coagulants, such as sand and cement, can immobilize the oxygen source and buffer, reducing the area of reaction between the oxygen source and water, slowing the oxygen release rate and ensuring a relatively stable oxygen release rate. Modifiers, such as bentonite, have strong water absorption and swelling properties, effectively improving the agglomeration properties of slow-release oxygen materials during preparation and extending the oxygen release time.

[0031] See also Figure 1 As shown, in one embodiment of the present invention, when preparing a slow-release oxygen material 111, an oxygen release source, a buffer, a coagulant, and a modifier are configured in proportion and mixed evenly, such as by using a blender to fully mix them evenly, and then water is sprinkled to form them into, for example, a spherical or square shape. After air-drying, the slow-release oxygen material 111 is obtained. The diameter or side length of the prepared slow-release oxygen material 111 is, for example, 3m-5cm. In this embodiment, the slow-release oxygen material 111 is, for example, spherical. By making the slow-release oxygen material 111 into a spherical shape, the reaction area is reduced under the same volume, which helps to improve the stability of the oxygen release rate. In a specific embodiment of the present invention, CaO2:KH2PO4:sand:cement:bentonite was prepared in a mass ratio of 3:1.2:3.8:1.8:3 to form slow-release oxygen pellets with a diameter of 4 cm. During an 80-day test, the dissolved oxygen concentration was continuously maintained above 8.5 mg / L and the pH value was around 8.5. An exponential equation y = 36.37e was fitted to show the relationship between the mass of oxygen dissolved in water per two pellets per day and time. -0.02x , where y is the mass of oxygen dissolved in water per day, and x is time. During the in-situ remediation process, slow-release oxygen materials slowly release oxygen, providing ample oxygen. In this oxygen-rich environment, the combined action of naturally occurring nitrifying bacteria in the water and soil allows for complete nitrification, resulting in oxidation of the groundwater into nitrates. Slow-release oxygen materials effectively alleviate the oxygen deficiency in groundwater without causing a pH spike.

[0032] See also Figure 1 As shown, in one embodiment of the present invention, the first control system 12 is, for example, an intelligent control system such as a programmable logic controller (PLC), a distributed control system (DCS), or a programmable automation controller (PAC). In this embodiment, the first control system 12 is, for example, a PLC, which uses sensors to enable online monitoring of indicators such as target groundwater pollutants, with the monitoring results input into the PLC control system. The PLC intelligently controls parameters such as the dosage and timing of the slow-release oxygen material 111, effectively ensuring optimal conditions for the nitrification reaction, improving the stability and utilization of the slow-release oxygen material, addressing the issue of low pollutant removal rates, and reducing raw material waste.

[0033] See also Figure 1 As shown, in one embodiment of the present invention, the denitrification unit is arranged between the nitrification unit and the production well 18. The denitrification unit includes an injection well 14, a carbon source storage device 15 and a second control system 16. The second control system 16 connects the injection well 14 and the carbon source storage device 15, and controls the input of carbon source from the carbon source storage device 15 to the injection well 14 and controls the input amount.

[0034] See also Figure 1As shown, in one embodiment of the present invention, the depth of the injection well 14 is, for example, to the aquiclude, and the injection well 14 is, for example, 40 mm to 100 mm above the ground, and the injection well 14 is, for example, a perforated pipe, etc., to facilitate the flow of water and the diffusion of the carbon source. The present application does not limit the size of the opening on the injection well 14.

[0035] See also Figure 1 As shown, in one embodiment of the present invention, a carbon source storage device 15 is disposed on one side of the injection well 14 for storing the carbon source. In a specific embodiment of the present invention, the carbon source storage device 15 is waterproof, such as, for example, a sealed storage bin or storage tank, but this application does not impose any specific limitations. A second delivery device (not shown) is disposed between the carbon source storage device 15 and the injection well 14, such as an automatic feeding device, such as a peristaltic pump or elastic hose. The second delivery device is intelligently connected to a second control system 16 and can automatically adjust the amount of carbon source delivered according to denitrification needs. The carbon source is stored in the carbon source storage device 15 and may include, for example, one or more combinations of liquid carbon sources such as ethanol, sodium succinate, sodium acetate, sodium malate, or glucose. In this application, a green liquid carbon source is used as a nutrient source for the growth and reproduction of denitrifying bacteria, providing a suitable living environment for the naturally occurring denitrifying bacteria in water and soil, improving reaction efficiency and reducing secondary pollution.

[0036] See also Figure 1 As shown, in one embodiment of the present invention, the second control system 16 is, for example, one of the intelligent control systems such as a programmable logic controller, a distributed control system or a programmable automation controller. In this embodiment, the second control system 16 is, for example, a PLC, which realizes online monitoring of indicators such as groundwater target pollutants through sensors, and the monitoring results are input into the PLC control system. Through the intelligent regulation of the dosage, time and other parameters of the carbon source by PLC, the optimal conditions for the denitrification reaction are effectively guaranteed, the stability and utilization rate of the carbon source are improved, the problem of low pollutant removal rate is solved, and the waste of raw materials is reduced. By adopting intelligent control of the input of carbon source and slow-release oxygen material, the operation and treatment status of the system are monitored in real time, the waste of resources and secondary pollution caused by excessive addition are avoided, and the poor treatment effect caused by too little input is avoided, which can significantly improve the treatment efficiency and stability of the in-situ remediation treatment.

[0037] See also Figure 1As shown, in one embodiment of the present invention, a first monitoring well 13 is disposed between the control well 10 and the injection well 14. The depth of the first monitoring well 13, for example, reaches the aquiclude, and the first monitoring well 13 protrudes 40 mm to 100 mm above the surface. The first monitoring well 13 is, for example, a perforated pipe. A first sensor (not shown) is disposed within the first monitoring well 13 and is in communication with the first control system 12. Data such as the concentrations of ammonia nitrogen, nitrate, and nitrite, as well as operational status, measured by the first sensor is transmitted to the first control system 12 for real-time monitoring. Based on the ammonia nitrogen concentration data from the first sensor, the first control system 12 obtains target data for adjusting the slow-release oxygen material and feeds the target data back to the first dosing device. The first dosing device then regulates the amount of slow-release oxygen material 111 delivered from the oxygen-releasing material storage device 11 to the control well 10 based on the target data. Specifically, the amount of slow-release oxygen material 111 delivered from the oxygen-releasing material storage device 11 to the control well 10 is regulated based on changes in the ammonia nitrogen concentration. This intelligently controls the delivery of slow-release oxygen material, monitors system operation and processing status in real time, improves the effectiveness of nitrification treatment, and reduces waste of slow-release oxygen material. In this embodiment, the first sensor is, for example, one of the three nitrogen sensors such as the AE86063 water quality detector. In other embodiments, the first sensor can also be set to multiple to test the concentrations of ammonia nitrogen, nitrate, and nitrite respectively.

[0038] See also Figure 1 As shown, in one embodiment of the present invention, the distance between the first monitoring well 13 and the control well 10 is, for example, 75%-85% of the distance between the control well 10 and the injection well 14. By increasing the distance between the first monitoring well 13 and the control well 10, it is ensured that there is enough distance for nitrification reaction to be carried out, thereby reducing the inaccuracy of ammonia nitrogen monitoring. The first sensor is also connected to the second control system 16 for communication to transmit information such as the monitored nitrate and nitrite concentrations to the second control system 16. The second control system 16 obtains the initial addition amount of the carbon source based on the nitrate and nitrite concentration data of the first sensor, and feeds the initial addition amount back to the second feeding device. The second feeding device controls the amount of carbon source storage device 15 fed into the injection well 14 based on the initial addition amount. In this embodiment, based on the nitrate and nitrite concentrations obtained by the first sensor, the initial addition amount of the carbon source satisfies the C / N mass ratio of, for example, 2, so as to provide sufficient carbon source and ensure that the removal rate of nitrate and nitrite reaches more than 90%.

[0039] See also Figure 1As shown, in one embodiment of the present invention, a second monitoring well 17 is located between the injection well 14 and the production well 18. The depth of the second monitoring well 17 is, for example, to the aquiclude, and the second monitoring well 17 is, for example, 40 mm to 100 mm above the surface. The second monitoring well 17 is, for example, a perforated pipe. A second sensor (not shown) is located within the second monitoring well 17 and is in communication with the second control system 16. Data such as nitrate and nitrite concentrations and operating status measured by the second sensor are transmitted to the second control system 16 for real-time monitoring. During the wet season, the second control system 16 determines target data for adjusting the carbon source based on the nitrate and nitrite concentration data from the second sensor. This target data is fed back to the second dosing device, which then adjusts the amount of carbon source storage device 15 added to the injection well 14 based on the target data. During the dry season, the second control system 16 determines the initial amount of carbon source added based on the nitrate and nitrite concentration data from the second sensor. This initial amount is fed back to the second dosing device, which then controls the amount of carbon source storage device 15 added to the injection well 14 based on the initial amount. By intelligently controlling carbon source input and monitoring system operation and processing status in real time, the effectiveness of denitrification treatment is improved and carbon source waste is reduced. In this embodiment, the second sensor is, for example, one of the WTW Nitrate and Nitrite UV Spectrometer series or the NT3 series Nitrate / Nitrite Online Analyzer. In other embodiments, multiple second sensors may be provided to measure nitrate and nitrite concentrations separately.

[0040] See also Figure 1 As shown, in one embodiment of the present invention, the distance between the second monitoring well 17 and the injection well 14 is, for example, 75%-85% of the distance between the injection well 14 and the production well 18. By increasing the distance between the second monitoring well 17 and the injection well 14, sufficient distance is ensured for denitrification, thereby reducing inaccurate nitrate monitoring, reducing carbon source waste, and improving treatment efficiency.

[0041] See also Figure 1 As shown, in one embodiment of the present invention, the distance between the injection well 14 and the production well 18 is, for example, greater than or equal to the influence radius R. , where s wis the design drawdown (in meters), K is the permeability coefficient (in meters per day), and H0 is the static water level (thickness) of the aquifer measured from the aquitard (in meters). The influence radius R represents the range of influence of the production well on the surrounding groundwater during the pumping process. By setting the distance between the injection well 14 and the production well 18 larger than the influence radius R, sufficient buffer space is reserved to ensure that the denitrification reaction can proceed even under non-ideal flow conditions. This helps to address dynamic factors such as water quality fluctuations and microbial activity decline, promotes uniform carbon source distribution, reduces the impact of dead zones and short-circuit flow on denitrification efficiency, and ensures the stability and efficiency of the denitrification process under complex operating conditions.

[0042] See also Figure 1 As shown, in one embodiment of the present invention, the ratio of the distance between the control well 10 and the injection well 14 to the distance between the injection well 14 and the production well 18 is, for example, greater than or equal to 3, to ensure that when river water is supplied to the production well 18, there is sufficient distance for nitrification reaction to occur, ensuring that ammonia nitrogen pollution can be converted into nitrate, and at the same time, nitrate is removed during the denitrification process, which can solve the complex nitrogen pollution situation in the riverside water source in situ and realize the synchronous operation of repair and production.

[0043] See also Figure 1 As shown, in one embodiment of the present invention, the in-situ repair system includes a plurality of in-situ reaction units. In this embodiment, the plurality of in-situ reaction units are equidistantly arranged, and the distance between adjacent in-situ reaction units is, for example, a, then a is greater than or equal to 2R, so as to improve the repair effect and reduce duplication of work, thereby improving the repair efficiency.

[0044] See also Figure 1 As shown, in one embodiment of the present invention, the distance between the extraction well 18 and the river bank is, for example, greater than 4R, and for example, 5R-7R, which creates extremely favorable conditions for the in-situ microbial cascade remediation process of river water, thereby significantly improving the quality of water obtained from the extraction well 18. By setting the distance between the extraction well 18 and the river bank, on the one hand, within this specific distance range away from the river bank, the flow rate of the river water is relatively slowed down, allowing suspended matter in the water body more time to settle, reducing the content of particulate matter in the water, reducing the turbidity of the water, and making the water quality appear clearer. On the other hand, sufficient distance allows nitrogen pollutants in the river water more time to be decomposed by microorganisms. During the in-situ nitrification process, ammonia nitrogen is gradually converted into nitrite nitrogen and nitrate nitrogen under the action of nitrifying bacteria, while the denitrification process can reduce nitrate nitrogen to nitrogen gas, which escapes from the water body.

[0045] Among them, nitrification is the process of oxidizing ammonia nitrogen into nitrite nitrogen and nitrate nitrogen under aerobic conditions through the action of autotrophic microorganisms nitrite bacteria and nitrate bacteria naturally present in soil and water. It includes two steps: nitrification and nitrification: Nitrite reaction: Nitrite bacteria participate in the conversion of ammonia nitrogen (NH4 + ) is converted into nitrite (NO2 - ). The reaction equation is: NH4 + +1.5O2→NO2 - +2H + +H2O; Nitrification reaction: Nitrite (NO2 - ) is converted into nitrate (NO3 - ). The reaction equation is: NO2 - +0.5O2→NO3 - ; Denitrification is a process in which denitrifying bacteria naturally present in soil and water reduce nitrite and nitrate to nitrogen gas under anoxic conditions, which then escapes from the water, thereby achieving the purpose of nitrogen removal. In the denitrification process, denitrifying bacteria need an organic carbon source as an electron donor and use NO3 - The reaction process can be simply expressed as follows: 2NO3 - +10H (electron donor organic matter) → N2 + 4H2O + 2OH - ; NO2 - +3H (electron donor organic matter) → 1 / 2N2+H2O+OH - ; This series of complex biochemical reactions can be carried out efficiently within a distance of 5R-7R, effectively reducing the nitrogen content in the water, avoiding the eutrophication problem caused by excessive nitrogen content, reducing the risk of excessive reproduction of algae and other organisms, further ensuring the stability and safety of water quality, and providing more reliable water source security.

[0046] See also Figure 1As shown, in one embodiment of the present invention, a third sensor 19 is installed in the river. The third sensor 19 is connected to the side wall of the river channel, for example, by a rope, and a float is connected to the third sensor 19, allowing the third sensor 19 to float on the water surface. The rope length is sufficient to allow the third sensor 19 to float on the water surface during both wet and dry seasons. The third sensor 19 is in communication with the first control system 12. The third sensor 19 measures the ammonia nitrogen concentration in the river water and transmits data such as the operating status to the first control system 12 for real-time monitoring. During the wet season, the first control system 12 obtains the initial dosage of the slow-release oxygen material based on the ammonia nitrogen concentration data from the third sensor 19. The first control system 12 feeds the initial dosage back to the first dosage device, which controls the dosage of the oxygen-releasing material storage device 11 into the control well 10 based on the initial dosage. In this embodiment, the third sensor 19 is, for example, an ammonia nitrogen sensor.

[0047] In one embodiment of the present invention, the ammonia nitrogen concentration in water measured by the third sensor is, for example, C N (mg / L) The amount of water that needs to be treated is V (L), then the total ammonia nitrogen content is T N =C N *V; required dissolved oxygen DO req =T N *4.57. In this example, the oxygen release of the two balls in x days is y = 36.37e -0.02x Assuming that the oxygen release rates of the two balls are the same and linearly superimposed, the instantaneous oxygen release of n balls in x days is: Y n (x) = n ×18.188e -0.02x If T is the number of days of nitrification reaction, then the oxygen release in T days is: , and because the oxygen release amount of the slow-release oxygen ball should be greater than or equal to the required dissolved oxygen amount, therefore: ; Finally, the required number of slow-release oxygen balls is at least: , where n is rounded up to obtain the initial amount of slow-release oxygen material input.

[0048] The present invention also provides an in-situ remediation method for nitrate contamination at riverside water sources. The in-situ remediation system is installed between the river and the groundwater source's extraction well to remove nitrate contamination. The remediation process differs during wet and dry seasons. The following describes the remediation process for wet and dry seasons.

[0049] See also Figure 1As shown, in one embodiment of the present invention, during the flood season, the river water level is higher than the groundwater level, and the river water recharges the groundwater. At this time, the main pollutants in the river, ammonia nitrogen and nitrate, are transported into the groundwater along with the water flow. The ammonia nitrogen concentration of the river water is obtained by a third sensor 19 and communicated to the first control system 12. The first control system 12 also obtains the initial dosage of the slow-release oxygen material, and the slow-release oxygen material is added to the control well 10 via the first delivery device. The first sensor in the first monitoring well 13 measures the concentrations of ammonia nitrogen, nitrate, and nitrite in the water, as well as operational data, and transmits this data to the first control system 12 and the second control system 16. The first control system 12 monitors and adjusts in real time the amount of slow-release oxygen material 111 delivered from the oxygen-releasing material storage device 11 to the control well 10 by the first delivery device. The second control system 16 controls the initial dosage of the carbon source delivered from the carbon source storage device 15 to the injection well 14 by the second delivery device. The second sensor in the second monitoring well 17 measures the concentration of nitrate and nitrite in the water, as well as data on its operating status. This data is then transmitted to the second control system 16 for real-time monitoring and regulation of the amount of carbon source injected from the carbon source storage device 15 into the injection well 14. The nitrification process from the control well 10 to the injection well 14 constitutes the nitrification zone, while the denitrification process from the injection well 14 to the production well 18 constitutes the denitrification zone. By conducting in-situ microbial cascade remediation of river water, the complex nitrogen pollution in riverside water sources can be remediated, and the removal rate of ammonia nitrogen and nitrate can reach over 90%, ensuring the stability and safety of the water quality in riverside water sources and providing a more reliable water source guarantee.

[0050] See also Figure 2 As shown, in one embodiment of the present invention, during the dry season, the groundwater level is higher than the river water level, and the phenomenon of groundwater replenishing the river water occurs. At this time, the nitrate pollutants in the groundwater are input into the river water along with the water flow. In order to avoid this situation, the second sensor in the second monitoring well 17 measures the data such as the nitrate and nitrite concentrations and operating conditions in the water, and transmits them to the second control system 16, which controls the initial input amount of the carbon source from the carbon source storage device 15 into the injection well 14, and denitrification treatment is carried out in the river from the injection well 14, which is a denitrification zone. Through denitrification, the groundwater replenished into the river water can be repaired by in-situ microorganisms, the amount of nitrate can be reduced, and the river water can be purified and repaired. That is, the in-situ remediation system provided by the present invention can successfully complete the removal of nitrate regardless of whether it is in the wet season or the dry season, that is, the feasibility of the system when used in the actual engineering of nitrate in-situ remediation in the riverside area.

[0051] See also Figures 1 to 2As shown, in one embodiment of the present invention, the direction of water flow is opposite during the flood season and the dry season. Compared to the flood season, the direction of water flow during the dry season is equivalent to reverse flushing the control well 10, the first monitoring well 13, the injection well 14, and the second monitoring well 17, which can solve the blockage problem caused by microbial growth. In this application, depending on the length of the flood season and the dry season, water can also be pumped through the first monitoring well 13. During the pumping process, water on both sides flows to the first monitoring well 13 at the same time. The water level in the first monitoring well 13 is the lowest, which can also achieve the effect of reverse flushing, thereby solving the blockage problem caused by microbial growth due to the lack of flushing during the excessively long flood season and dry season.

[0052] In order to verify the effectiveness of the in-situ remediation system for nitrate pollution in riverside water sources of the present invention, an experimental environment was built for testing. Figure 1 A simulated river, nitrification unit, denitrification unit, first monitoring well, first monitoring well, groundwater model, and production well were constructed. The distance between the control well and the injection well was three times the distance between the injection well and the production well, and the distance between the injection well and the production well was equal to the influence radius R. During the simulated flood season, simulated river water was introduced at a flow rate of 3 mL / min, with an ammonia nitrogen concentration of 3 mg / L. Slow-release oxygen material was added, and based on the nitrate and nitrite concentrations measured by the first sensor, a carbon source (ethanol) was added at a C / N mass ratio of 2. Water was sampled from the first monitoring well for testing. Test results showed that the ammonia nitrogen removal rate in the nitrification section exceeded 91%, and the nitrite concentration remained below the groundwater Class III water quality standard (1 mg / L) throughout the experiment. Testing of water sampled from the production well showed that the nitrate removal rate in the denitrification section exceeded 94%. During a simulated dry season, based on the nitrate concentration measured by the second sensor, a carbon source (ethanol) was added at a C / N mass ratio of 2. Testing was conducted in a control well, and the nitrate removal rate exceeded 90%. This demonstrates that the system can successfully remove nitrates in both wet and dry seasons, demonstrating its feasibility for practical in-situ nitrate remediation projects in riverside areas.

[0053] In summary, the present invention proposes an in-situ remediation system and method for nitrate pollution in riverside water sources. Through the in-situ cascade remediation of nitrification and denitrification microorganisms, it can be suitable for the complex nitrogen pollution situation of riverside water sources, realize in-situ remediation of nitrate pollution in riverside water sources, ensure the stability and safety of water quality, and provide more reliable water source protection. In the in-situ remediation, the slow-release oxygen material can slowly release oxygen, and complete nitrification occurs under the action of nitrifying bacteria, oxidizing ammonia nitrogen to nitrate, improving the anoxic condition of groundwater without causing a pH surge. Intelligent control of carbon source and slow-release oxygen material input is adopted, and the system operation and processing status are monitored in real time to avoid waste of resources, secondary pollution and poor treatment effect, and improve the efficiency and stability of in-situ remediation. Sufficient distance is reserved for nitrification and denitrification reactions to improve the remediation effect. At the same time, buffer space is reserved to deal with dynamic factors such as water quality fluctuations and microbial activity decay, ensuring that the denitrification process is stable and efficient under complex working conditions. At the same time, the system can achieve a backwashing effect, solving the blockage problem caused by microbial growth due to lack of flushing during the flood season and dry season. Through in-situ microbial cascade remediation, the complex nitrogen pollution in riverside water sources can be solved, restoration and mining can be carried out simultaneously, the nitrogen content in the water can be reduced, eutrophication of water bodies can be avoided, the stable and safe water quality can be ensured, and a reliable water source can be provided.

[0054] The above description is only a preferred embodiment of the present application and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to the technical solutions formed by the specific combination of the above-mentioned technical features, but should also cover other technical solutions formed by any combination of the above-mentioned technical features or their equivalent features without departing from the inventive concept, such as the technical solutions formed by the mutual replacement of the above-mentioned features with (but not limited to) technical features with similar functions disclosed in this application.

[0055] Except for the technical features described in the specification, the remaining technical features are known technologies to those skilled in the art. In order to highlight the innovative features of the present invention, the remaining technical features will not be described here in detail.

Claims

1. An in-situ remediation system for nitrate pollution in riverside water sources, characterized in that: At least: wells mined from groundwater sources adjacent to rivers; at least one nitrification unit disposed between the river and the production well, the nitrification unit comprising a control well, an oxygen-releasing material storage device, and a first control system; at least one denitrification unit, disposed between the nitrification unit and the production well, the denitrification unit comprising an injection well, a carbon source storage device, and a second control system; at least one first monitoring well, disposed between the nitrification unit and the denitrification unit, and connected to the first control system and the second control system respectively; At least one second monitoring well is disposed between the denitrification units and the production wells and is connected to the second control system.

2. The in-situ remediation system for nitrate pollution in riverside water sources according to claim 1 is characterized in that: The distance between the injection well and the production well is greater than or equal to the influence radius R; and / or The ratio of the distance between the control well and the injection well to the distance between the injection well and the production well is greater than or equal to 3.

3. The in-situ remediation system for nitrate pollution in riverside water sources according to claim 2, characterized in that: One nitrification unit, one denitrification unit, one first monitoring well and one second monitoring well are arranged in a single row, forming an in-situ reaction unit. The in-situ remediation system includes a plurality of equidistantly arranged in-situ reaction units. The distance between adjacent in-situ reaction units is a, and a is greater than or equal to 2R.

4. The in-situ remediation system for nitrate pollution in riverside water sources according to claim 1, characterized in that: The distance between the first monitoring well and the control well is 75%-85% of the distance between the control well and the injection well; and / or The distance between the second monitoring well and the injection well is 75%-85% of the distance between the injection well and the production well.

5. The in-situ remediation system for nitrate pollution in riverside water sources according to claim 1 is characterized in that: The oxygen-releasing material storage device stores a slow-release oxygen material, which includes an oxygen-releasing source and a buffer. The oxygen-releasing source includes one or more combinations of calcium peroxide, magnesium peroxide, sodium peroxide, zinc peroxide or sodium percarbonate, and the buffer includes one or more combinations of potassium dihydrogen phosphate, ammonium sulfate, disodium hydrogen phosphate, sodium dihydrogen phosphate, sodium bicarbonate or ammonium acetate.

6. The in-situ remediation system for nitrate pollution in riverside water sources according to claim 1, characterized in that: The oxygen-releasing material storage device is arranged at one side of the control well. A first delivery device is arranged between the oxygen-releasing material storage device and the control well. The first delivery device is connected to the first control system.

7. The in-situ remediation system for nitrate pollution in riverside water sources according to claim 6, characterized in that: The carbon source storage device is arranged on one side of the injection well, a second delivery device is arranged between the carbon source storage device and the injection well, and the delivery device is connected to the second control system; and / or The carbon source storage device stores a carbon source, and the carbon source includes one or more combinations of ethanol, sodium succinate, sodium acetate, sodium malate or glucose.

8. The in-situ remediation system for nitrate pollution in riverside water sources according to claim 7, characterized in that: A first sensor is provided in the first monitoring well. The first sensor is used to detect the concentrations of ammonia nitrogen, nitrate and nitrite in water during the flood season. The first sensor is communicatively connected to the first control system and the second control system respectively. The first control system obtains target data for adjusting the slow-release oxygen material based on the ammonia nitrogen concentration data of the first sensor, and feeds the target data back to the first delivery device. The first delivery device regulates the delivery amount of the oxygen-releasing material storage device to the control well based on the target data; the second control system obtains the initial addition amount of the carbon source based on the nitrate and nitrite concentration data of the first sensor, and feeds the initial addition amount back to the second delivery device. The second delivery device controls the delivery amount of the carbon source storage device to the injection well based on the initial addition amount.

9. The in-situ remediation system for nitrate pollution in riverside water sources according to claim 7, characterized in that: A second sensor is provided in the second monitoring well, and the second sensor is used to detect the concentration of nitrate and nitrite in the water during the wet season and the dry season. The second sensor is in communication with the second control system. During the wet season, the second control system obtains target data for adjusting the carbon source based on the nitrate and nitrite concentration data of the second sensor, and feeds the target data back to the second feeding device. The second feeding device regulates the amount of the carbon source storage device fed into the injection well based on the target data. During the dry season, the second control system obtains the initial addition amount of the carbon source based on the nitrate and nitrite concentration data of the second sensor, and feeds the initial addition amount back to the second delivery device. The second delivery device controls the amount of carbon source storage device delivered to the injection well based on the initial addition amount.

10. The in-situ remediation system for nitrate pollution in riverside water sources according to claim 7, characterized in that: The in-situ remediation system also includes a third sensor, which is arranged in the river. The third sensor is used to detect the ammonia nitrogen concentration in the water during the flood season. The third sensor is communicated with the first control system. The first control system obtains the initial input amount of the slow-release oxygen material based on the ammonia nitrogen concentration data of the third sensor, and feeds the initial input amount back to the first feeding device. The first feeding device controls the input amount of the oxygen-releasing material storage device to the control well based on the initial input amount.

11. A method for in-situ remediation of nitrate pollution in riverside water sources, characterized in that: The method comprises installing the in-situ remediation system according to any one of claims 1 to 9 between a river and a groundwater source extraction well to remove nitrate pollution.

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