A nitrate pollution in-situ remediation system and method for riverbank water source

Abstract

The application provides a nitrate pollution in-situ remediation system and method for a river-adjacent water source, which comprises a groundwater source exploitation well adjacent to a river, at least one nitrification unit arranged between the river and the exploitation well and comprising a control well, an oxygen release material storage device and a first control system, at least one denitrification unit arranged between the nitrification unit and the exploitation well and comprising 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 and connected with the first control system and the second control system respectively, and at least one second monitoring well arranged between the denitrification unit and the exploitation well and connected with the second control system. The nitrate pollution in-situ remediation system and method for the river-adjacent water source can be used for in-situ remediation of composite nitrogen pollution and realizes synchronous operation of remediation and exploitation.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of groundwater remediation, in particular to a nitrate pollution in-situ remediation system and method for river-adjacent water source. BACKGROUND

[0002] Groundwater nitrate pollution has become a global environmental problem, especially in river-adjacent water source, affected by agricultural non-point source pollution and surface water-groundwater interaction, nitrate is transported to the aquifer through hydraulic migration, threatening drinking water safety. At present, the permeable reactive barrier (PRB) technology is a widely used in-situ groundwater remediation technology, which realizes the reduction of nitrate by filling reaction medium (such as zero-valent iron, activated carbon), but there are problems of medium blockage and short service life in practical application. And PRB technology is difficult to control the reduction products due to uncontrollable carbon source diffusion, which is easy to cause secondary pollution, and is not suitable for the treatment of nitrate pollution in river-adjacent water source which is the source of drinking water.

[0003] The microbial treatment method is accepted and widely used by people because of its simple operation, no secondary pollution, high remediation efficiency and stable operation, but due to the diversification trend of pollutants in water body, especially for river-adjacent water source, due to the complex nitrogen pollution caused by the mutual contact of surface water and groundwater, a single treatment and remediation process is difficult to cope with the complex nitrogen pollution (ammonia nitrogen, nitrate and nitrite coexist) under the dynamic hydrological conditions of river-adjacent area, and lacks precise control mechanism, cannot realize synchronous operation of remediation and exploitation, and the blockage problem leads to poor long-term operation stability. SUMMARY

[0004] The present application provides a nitrate pollution in-situ remediation system and method for river-adjacent water source, which can in-situ remediate complex nitrogen pollution under dynamic hydrological conditions of river-adjacent area, realize synchronous operation of remediation and exploitation, reduce the content of nitrogen in water, ensure stable and safe water quality, provide reliable water source, and avoid the blockage problem caused by microbial growth.

[0005] To solve the above technical problems, the present application provides a nitrate pollution in-situ remediation system for river-adjacent water source, which at least comprises:

[0006] A groundwater water source exploitation well adjacent to a river;

[0007] At least one nitrification unit is arranged between the river and the exploitation well, the nitrification unit comprises a control well, an oxygen release material storage device and a first control system;

[0008] at least one denitrification unit arranged between the nitrification unit and the exploitation well, the denitrification unit comprising an injection well, a carbon source storage device and a second control system;

[0009] at least one first monitoring well arranged between the nitrification unit and the denitrification unit and connected to the first control system and the second control system respectively;

[0010] at least one second monitoring well arranged between the denitrification unit and the exploitation well and connected to the second control system.

[0011] In an embodiment of the present application, the distance between the injection well and the exploitation well is greater than or equal to the influence radius R; and / or

[0012] The ratio of the distance between the control well and the injection well to the distance between the injection well and the exploitation well is greater than or equal to 3.

[0013] In an embodiment of the present application, 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, and the in-situ remediation system comprises a plurality of in-situ reaction units arranged at equal intervals, and the distance between adjacent in-situ reaction units is a, then a is greater than or equal to 2R.

[0014] In an embodiment of the present application, 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

[0015] The distance between the second monitoring well and the injection well is 75%-85% of the distance between the injection well and the exploitation well.

[0016] In an embodiment of the present application, the oxygen-releasing material storage device stores slow-release oxygen-releasing material, the slow-release oxygen-releasing material comprises an oxygen-releasing source and a buffer, the oxygen-releasing source comprises one or more combinations of calcium peroxide, magnesium peroxide, sodium peroxide, zinc peroxide or sodium percarbonate, and the buffer comprises one or more combinations of potassium dihydrogen phosphate, ammonium sulfate, disodium hydrogen phosphate, sodium dihydrogen phosphate, sodium bicarbonate or ammonium acetate.

[0017] In an embodiment of the present application, the oxygen-releasing material storage device is arranged on one side of the control well, a first delivery device is arranged between the oxygen-releasing material storage device and the control well, and the first delivery device is connected to the first control system.

[0018] In an embodiment of the present application, 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

[0019] The carbon source storage device stores carbon sources, which include one or more combinations of ethanol, sodium succinate, sodium acetate, sodium malate, or glucose.

[0020] In an embodiment of the present application, a first sensor is arranged in the first monitoring well, which is used to detect the concentrations of ammonia nitrogen, nitrate, and nitrite in water during the wet season, and 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 according to the ammonia nitrogen concentration data of the first sensor, feeds back the target data to the first delivery device, and the first delivery device controls the input amount of the oxygen material storage device into the control well according to the target data. The second control system obtains the initial addition amount of carbon source according to the nitrate and nitrite concentration data of the first sensor, feeds back the initial addition amount to the second delivery device, and the second delivery device controls the input amount of the carbon source storage device into the injection well according to the initial addition amount.

[0021] In an embodiment of the present application, a second sensor is arranged in the second monitoring well, which is used to detect the concentrations of nitrate and nitrite in water during the wet season and the dry season, and 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 according to the nitrate and nitrite concentration data of the second sensor, feeds back the target data to the second delivery device, and the second delivery device controls the input amount of the carbon source storage device into the injection well according to the target data.

[0022] During the dry season, the second control system obtains the initial addition amount of carbon source according to the nitrate and nitrite concentration data of the second sensor, feeds back the initial addition amount to the second delivery device, and the second delivery device controls the input amount of the carbon source storage device into the injection well according to the initial addition amount.

[0023] In an embodiment of the present application, the in-situ remediation system further comprises a third sensor arranged in the river, the third sensor being configured to detect the ammonia nitrogen concentration in the water during the flood season, and the third sensor being in communication with the first control system, and the first control system obtains an initial input amount of the slow-release oxygen material according to the ammonia nitrogen concentration data of the third sensor, and feeds back the initial input amount to the first feeding device, and the first feeding device controls the input amount of the slow-release oxygen material storage device into the control well according to the initial input amount.

[0024] The present application also provides an in-situ remediation method for nitrate pollution of a river-adjacent water source, comprising arranging the in-situ remediation system described above between the river and the exploitation well of the groundwater source to remove the nitrate pollution.

[0025] In summary, the present application provides an in-situ remediation system and method for nitrate pollution of a river-adjacent water source, which can adapt to the complex nitrogen pollution conditions of the river-adjacent water source through in-situ gradient remediation by nitrifying and denitrifying microorganisms, and can achieve in-situ remediation of nitrate pollution of the river-adjacent water source, thereby ensuring the stability and safety of the water quality and providing more reliable water source guarantee. In the in-situ remediation, the slow-release oxygen material can slowly release oxygen, and complete nitrification occurs under the action of nitrifying bacteria, which oxidizes ammonia nitrogen into nitrate, thereby improving the anoxic condition of the groundwater and avoiding excessive increase of pH. The input of the carbon source and the slow-release oxygen material is intelligently controlled, and the system operation and treatment conditions are monitored in real time, thereby avoiding resource waste, secondary pollution, poor treatment effect and other problems, and improving the in-situ remediation treatment efficiency and stability. A sufficient distance is reserved for nitrification and denitrification reactions, thereby improving the remediation effect, and a buffer space is reserved to cope with dynamic factors such as water quality fluctuation and microbial activity attenuation, thereby ensuring stable and efficient denitrification process under complex working conditions. At the same time, the system can achieve reverse flushing effect, thereby solving the problem of blockage caused by microbial growth due to no flushing during the flood season and the dry season. The in-situ microbial gradient remediation can solve the complex nitrogen pollution of the river-adjacent water source, achieve synchronous operation of remediation and exploitation, reduce the nitrogen content in the water, avoid water eutrophication, ensure the stability and safety of the water quality, and provide reliable water source. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0027] Figure 1 FIG. 1 is a schematic diagram of the in-situ remediation system in an embodiment of the present application during the flood season.

[0028] Figure 2Figure 1 is a schematic diagram of an in-situ remediation system in a dry season according to an embodiment of the present application.

[0029] Figure 3 Figure 2 is a schematic diagram of a control well according to an embodiment of the present application.

[0030] BRIEF DESCRIPTION OF DRAWINGS

[0031] 10 control well; 101 casing; 11 oxygen release material storage; 111 slow release oxygen material; 12 first control system; 13 first monitoring well; 14 injection well; 15 carbon source storage; 16 second control system; 17 second monitoring well; 18 production well; 19 third sensor. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0034] In the description of this specification, it is understood that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "front", "back", "left", "right" and the like is based on the orientation or positional relationship shown in the drawings, and is only for the purpose of facilitating the description of the scheme and simplifying the description, and therefore cannot be understood as indicating or implying that the device or component referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the scheme. In addition, the terms "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance.

[0035] River-adjacent water intake is to arrange a mining well on the beach of the river bank, and to obtain water source by using the recharge-discharge relationship between surface water and groundwater. The infiltration recharge of river water becomes the main part of the mining water, and the recharge-discharge relationship between river water and groundwater of the water source changes with the hydrodynamic conditions of river water, such as with the wet season and dry season. Among them, the wet season refers to the period when river flow is mainly supplemented by rainfall or snowmelt, generally in the rainy season or the period when the air temperature continues to rise in spring. In the wet season, the river water level is higher than the groundwater level, and the phenomenon of river water recharging groundwater occurs. At this time, the main pollutant ammonia nitrogen in the river is input into the groundwater with the water flow. The dry season refers to the period when the surface water flow in the basin is exhausted, and the water source is mainly supplemented by groundwater. At this time, the main pollutant nitrate in the groundwater will be input into the river water with the water flow. The duration of the dry season in a year varies with the natural geographical and meteorological conditions of the basin. The present application provides a river-adjacent water source nitrate pollution in-situ remediation system and method, which can realize in-situ gradient remediation by nitration and denitrification microorganisms, and can realize in-situ remediation of river-adjacent water source nitrate pollution by adopting different remediation methods in the wet season and dry season according to the complex nitrogen pollution of the river-adjacent water source, so as to ensure the stability and safety of water quality and provide more reliable water source guarantee.

[0036] In an embodiment of the present application, the river-adjacent water source nitrate pollution in-situ remediation system at least comprises a groundwater source mining well adjacent to the river; at least one nitrification unit arranged between the river and the mining well, the nitrification unit comprising a control well, an oxygen release material storage device and a first control system; at least one denitrification unit arranged between the nitrification unit and the mining well, the denitrification unit comprising 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 and connected with the first control system and the second control system respectively; and at least one second monitoring well arranged between the denitrification unit and the mining well and connected with the second control system. Through the river-adjacent water source nitrate pollution in-situ remediation system of the present application, in-situ remediation of river-adjacent water source nitrate pollution can be realized, and the system operation and treatment conditions can be monitored in real time, so as to improve the in-situ remediation treatment efficiency and stability.

[0037] Please refer to Figure 1 In an embodiment of the present application, river-adjacent water intake is to arrange a mining well 18 on the beach of the river bank, and to obtain water source by using the recharge-discharge relationship between surface water and groundwater. Among them, the mining well 18 is arranged one or more, or is centrally established, for example, in the form of parallel arrangement along the river, and the present application does not make specific limitation, for example, a single row or multiple rows of mining wells are designed according to specific conditions, and the well spacing should be designed according to the single-width recharge and single-well water yield. In the present embodiment, the depth of the mining well 18 is for example to the aquiclude, and the well group of the mining well 18 is relatively concentrated, so that the water source is easy to mine and manage. In the schematic diagram, only one mining well is shown, and the in-situ remediation system is described.

[0038] Referring to Figure 1 As shown in the figure, in one embodiment of the present application, a nitrification unit, a denitrification unit, a first monitoring well and a second monitoring well are arranged in a single row, defining an in-situ reaction unit. In this embodiment, the in-situ reaction unit in a single row and the remediation process are described, wherein the nitrification unit is arranged adjacent to the river between the river and the exploitation well 18, the nitrification unit comprises the control well 10, the oxygen release material storage device 11 and the first control system 12, the first control system 12 is connected to the control well 10 and the oxygen release material storage device 11, and controls the input of the slow-release oxygen release material from the oxygen release material storage device 11 into the control well 10 and the amount of input. The present application does not limit the distance of the control well 10 from the river, as long as the river does not affect the control well 10 during the wet season.

[0039] Referring to Figure 1 and Figure 3 As shown in the figure, in one embodiment of the present application, the depth of the control well 10 is, for example, to the aquiclude, the control well 10 is, for example, 40mm-100mm above the ground, and the control well 10 is, for example, an open pipe, so as to facilitate the flow of water and the diffusion of dissolved oxygen of the slow-release oxygen release material, and the present application does not limit the size of the openings on the control well 10. A sleeve 101 is arranged in the control well 10, the depth and length of the sleeve 101 above the ground are, for example, the same as the control well, the sleeve 101 is, for example, an open pipe with a closed bottom, etc., for placing the slow-release oxygen release material 111, and the size of the openings on the sleeve 101 is smaller than the size of the slow-release oxygen release material 111, and the sleeve 101 is replaced after being filled with the slow-release oxygen release material 111 and the slow-release oxygen release material 111 is exhausted.

[0040] Referring to Figure 1As shown, in an embodiment of the present application, the oxygen releasing material storage device 11 is arranged on one side of the control well 10 for storing the slow-release oxygen material 111. In a specific embodiment of the present application, the oxygen releasing material storage device 11 has a waterproof function, for example, a sealed storage bin or a storage tank, and the present application does not make specific limitations. A first delivery device (not shown in the figure) is arranged between the oxygen releasing material storage device 11 and the control well 10, for example, an automatic feeding device, for example, including a peristaltic pump, an elastic rubber tube, etc. The first delivery device is intelligently connected with 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 includes, for example, an oxygen releasing source, a buffer, a coagulant and a modifier, etc. The mass ratio of the oxygen releasing source, the buffer, the coagulant and the modifier is, for example, (3-3.5):(1-1.5):(3-6):(2.5-3). The oxygen releasing 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), etc., 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), etc., and the buffer dissolved in water generates H + The alkalinity in water can be reduced, and the problem of pH value rising caused by the reaction of the oxygen releasing source and water in the oxygen releasing process can be solved. In addition, the buffer can also provide elements for the growth of microorganisms in soil and water. The coagulant includes, for example, sand and cement, etc., which can fix the oxygen releasing source and the buffer, reduce the reaction area of the oxygen releasing source and water, slow down the oxygen releasing rate, and ensure that the oxygen releasing rate is relatively stable. The modifier includes, for example, bentonite, etc., which has strong water absorption and swelling properties, can effectively improve the agglomeration performance in the preparation process of the slow-release oxygen material, and achieve the effect of prolonging the oxygen releasing time.

[0041] Please refer to Figure 1As shown, in an embodiment of the present application, when preparing the slow-release oxygen material 111, the oxygen-releasing source, the buffer, the coagulant and the modifier are proportioned and mixed uniformly, for example, using a blender to mix them thoroughly, and then water is added to form, for example, spherical or cubic shapes, which are then dried and stored for later use, to obtain the slow-release oxygen material 111. The diameter or side length of the slow-release oxygen material 111 prepared is, for example, 3-5 cm. In this embodiment, the slow-release oxygen material 111 is, for example, spherical. By using a slow-release oxygen material in the form of a sphere, the reaction area is reduced at the same volume, which helps to improve the stability of the oxygen release rate. In a specific embodiment of the present application, CaO2: KH2PO4: sand: cement: bentonite are 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. In an 80-day test, the slow-release oxygen pellets can maintain a dissolved oxygen concentration of more than 8.5 mg / L and a pH value of about 8.5, and the exponential equation y = 36.37e -0.02x where y is the daily oxygen mass dissolved in water, and x is the time. In the in-situ remediation process, the slow-release oxygen material can slowly release oxygen to provide sufficient oxygen. In the presence of sufficient oxygen, complete nitrification occurs under the combined action of water and naturally occurring nitrifying bacteria in the soil, and the nitrates are oxidized. The slow-release oxygen material effectively improves the anoxic conditions in the groundwater and does not cause a sharp increase in pH.

[0042] Referring to Figure 1 As shown, in an embodiment of the present application, the first control system 12 is, for example, one of a programmable logic controller (PLC), a distributed control system (DCS), or a programmable automation controller (PAC) or other intelligent control system. In this embodiment, the first control system 12 is, for example, a PLC. The target groundwater pollutants and other indicators are monitored online by sensors, and the monitoring results are input into the PLC control system. The PLC intelligently controls the dosage, time and other parameters of the slow-release oxygen material 111, effectively ensures the optimal conditions for nitrification, improves the stability and utilization rate of the slow-release oxygen material, solves the problem of low pollutant removal rate, and reduces the waste of raw materials.

[0043] Referring to Figure 1 As shown, in an embodiment of the present application, the denitrification unit is arranged between the nitrification unit and the production well 18. The denitrification unit includes the injection well 14, the carbon source storage device 15 and the second control system 16, etc. The second control system 16 is connected to the injection well 14 and the carbon source storage device 15 and controls the input of the carbon source from the carbon source storage device 15 to the injection well 14 and controls the input amount.

[0044] Referring to Figure 1As shown, in one embodiment of the present invention, the depth of the injection well 14 extends to the waterproof layer, and the injection well 14 extends 40mm-100mm beyond the ground surface. The injection well 14 is, for example, an open pipe to facilitate water flow and carbon source diffusion. This application does not limit the size of the opening on the injection well 14.

[0045] Please see 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 carbon sources. In a specific embodiment of the present invention, the carbon source storage device 15 has a waterproof function, and may be, for example, a sealed storage chamber or storage tank, etc., which are not specifically limited in this application. A second dispensing device (not shown in the figure) is provided between the carbon source storage device 15 and the injection well 14, such as an automatic feeding device, or including a peristaltic pump, elastic hose, etc. The second dispensing device is intelligently connected to the second control system 16 and can automatically adjust the amount of carbon source dispensed according to the denitrification requirements. The carbon source is stored in the carbon source storage device 15, and the carbon source includes one or more combinations of liquid carbon sources such as ethanol, sodium succinate, sodium acetate, sodium malate, or glucose. In this application, green liquid carbon sources are 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.

[0046] Please see 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 (PLC), 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 target pollutants in groundwater through sensors, and the monitoring results are input into the PLC control system. By intelligently controlling parameters such as the dosage and time of carbon source addition through the PLC, the optimal conditions for denitrification reaction are effectively guaranteed, the stability and utilization rate of carbon source are improved, the problem of low pollutant removal rate is solved, and raw material waste is reduced. By adopting intelligent control of the input of carbon source and slow-release oxygen material, and monitoring the system operation and treatment status in real time, resource waste and secondary pollution caused by excessive addition are avoided, while poor treatment effect caused by insufficient addition is avoided, which can significantly improve the treatment efficiency and stability of in-situ remediation treatment.

[0047] Please see Figure 1As shown, in an embodiment of the present application, the first monitoring well 13 is arranged between the control well 10 and the injection well 14, the first monitoring well 13 is, for example, to the aquiclude, the first monitoring well 13 is, for example, 40-100mm above the ground surface 40, and the first monitoring well 13 is, for example, an open hole pipe or the like. A first sensor (not shown in the figure) is arranged in the first monitoring well 13, the first sensor is in communication connection with the first control system 12, and the first sensor transmits data such as ammonia nitrogen, nitrate, nitrite concentration and operation condition to the first control system 12 for real-time monitoring. The first control system 12 obtains target data for adjusting the slow-release oxygen material according to the ammonia nitrogen concentration data of the first sensor, feeds back the target data to the first feeding device, and the first feeding device controls the input amount of the slow-release oxygen material storage device 11 to the control well 10 according to the target data. That is, the amount of the slow-release oxygen material 111 input from the slow-release oxygen material storage device 11 to the control well 10 is controlled according to the concentration change of ammonia nitrogen, so as to intelligently control the input of the slow-release oxygen material, to monitor the system operation and treatment in real time, to improve the effect of nitrification treatment, and to reduce the waste of slow-release oxygen material. In the embodiment, the first sensor is, for example, one of three nitrogen sensors such as AE86063 water quality detector or the like, and in other embodiments, the first sensor can also be arranged as multiple sensors for testing the concentrations of ammonia nitrogen, nitrate and nitrite respectively.

[0048] Please refer to Figure 1 As shown, in an embodiment of the present application, 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, and the inaccuracy of ammonia nitrogen monitoring is reduced. The first sensor is also in communication connection with the second control system 16, so as to transmit information such as monitored nitrate and nitrite concentrations to the second control system 16. The second control system 16 obtains the initial input amount of the carbon source according to the nitrate and nitrite concentration data of the first sensor, feeds back the initial input amount to the second feeding device, and the second feeding device controls the input amount of the carbon source storage device 15 to the injection well 14 according to the initial input amount. In the embodiment, the initial input amount of the carbon source satisfies the C / N mass ratio of, for example, 2 according to the nitrate and nitrite concentrations obtained by the first sensor, so as to provide sufficient carbon source and ensure that the removal rate of nitrate and nitrite reaches more than 90%.

[0049] Please refer to Figure 1As shown, in an embodiment of the present application, the second monitoring well 17 is arranged between the injection well 14 and the exploitation well 18, the second monitoring well 17 is arranged to a depth, for example, to the aquiclude, the second monitoring well 17 is arranged, for example, to be 40-100mm above the ground surface 40, and the second monitoring well 17 is arranged, for example, to be a perforated pipe. A second sensor (not shown in the figure) is arranged in the second monitoring well 17, the second sensor is in communication connection with the second control system 16, and the second sensor transmits data such as nitrate, nitrite concentration and operation condition to the second control system 16 for real-time monitoring. In the wet season, the second control system 16 obtains target data of adjusting the carbon source according to the data of the nitrate and nitrite concentration of the second sensor, feeds back the target data to the second delivery device, and the second delivery device controls the input amount of the carbon source storage device 15 into the injection well 14 according to the target data. In the dry season, the second control system 16 obtains the initial input amount of the carbon source according to the data of the nitrate and nitrite concentration of the second sensor, feeds back the initial input amount to the second delivery device, and the second delivery device controls the input amount of the carbon source storage device 15 into the injection well 14 according to the initial input amount. Through intelligent control of the input of the carbon source, real-time monitoring of the system operation and treatment condition, the effect of denitrification treatment is improved, and the waste of the carbon source is reduced. In the embodiment, the second sensor is, for example, one of the WTW nitrate and nitrite ultraviolet spectrum sensor series or the NT3 series nitrate / nitrite online analyzer, and in other embodiments, the second sensor can also be arranged to be multiple to test the concentration of nitrate and nitrite respectively.

[0050] As shown in the figure Figure 1 As shown, in an embodiment of the present application, 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 exploitation well 18. By increasing the distance between the second monitoring well 17 and the injection well 14, it is ensured that there is enough distance for denitrification reaction, the inaccuracy of nitrate monitoring is reduced, the waste of the carbon source is reduced, and the treatment efficiency is improved.

[0051] As shown in the figure Figure 1 As shown, in an embodiment of the present application, the distance between the injection well 14 and the exploitation well 18 is, for example, greater than or equal to the influence radius R, and the influence radius R is, for example, 1-2 times the distance between the injection well 14 and the exploitation well 18. wherein s wTo design the drawdown, the unit is m, K is the permeability coefficient, the unit is m / d (meter / day), H0 is the static water level of the aquifer from the aquiclude (thickness), the unit is m. The influence radius R is the influence range of the exploitation well on the surrounding groundwater during the pumping process. By reserving a sufficient buffer space by making the distance between the injection well 14 and the exploitation well 18 greater than the influence radius R, for example, the water flow can still ensure the denitrification reaction to proceed under the non-ideal flow state, so as to cope with dynamic factors such as water quality fluctuation and microbial activity attenuation, help to distribute the carbon source uniformly, reduce the influence of dead zones and short flow on the denitrification efficiency, and ensure the stability and high efficiency of the denitrification process under complex working conditions.

[0052] Please refer to Figure 1 As shown in the figure, in an embodiment of the present application, the ratio of the distance between the control well 10 and the injection well 14 and the distance between the injection well 14 and the exploitation well 18 is greater than or equal to 3, for example, to ensure that when the river water is supplied to the exploitation well 18, there is sufficient distance for nitrification reaction, ensuring that ammonia nitrogen pollution can be converted into nitrate, and at the same time, nitrate can be removed in the denitrification process, which can solve the complex nitrogen pollution situation of the river-side water source in situ, and realize synchronous operation of repair and exploitation.

[0053] Please refer to Figure 1 As shown in the figure, in an embodiment of the present application, the in-situ remediation 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 a, for example, a is greater than or equal to 2R, to improve the remediation effect and reduce repeated work, and improve the remediation efficiency.

[0054] Please refer to Figure 1 As shown in the figure, in an embodiment of the present application, the distance between the exploitation well 18 and the river shoreline is greater than 4R, and is also greater than 5R-7R, for example, which creates extremely favorable conditions for the in-situ microbial cascade remediation process of the river water, and further significantly improves the quality of the water obtained by the exploitation well 18. By setting the distance between the exploitation well 18 and the river shoreline, on the one hand, within this specific distance range away from the river shoreline, the river water flow speed is relatively slowed down, so that the suspended matter in the water body has more sufficient time to settle, reducing the content of particulate matter in the water and reducing the turbidity of the water, making the water quality more clear in appearance. On the other hand, there is sufficient distance for the nitrogen pollutants in the river water to be decomposed by microorganisms. In the in-situ nitrification process, ammonia nitrogen is gradually converted into nitrite nitrogen and nitrate nitrogen under the action of nitrifying bacteria, and in the denitrification process, nitrate nitrogen is reduced to nitrogen gas and escapes from the water body.

[0055] Among them, the nitrification reaction is a process of oxidizing ammonia nitrogen into nitrite nitrogen and nitrate nitrogen under aerobic conditions through the action of naturally occurring autotrophic microorganisms nitrite bacteria and nitrate bacteria in soil and water, including two steps of nitrosation and nitrification:

[0056] Nitrosation: Involving nitrite bacteria, ammonia nitrogen (NH4 + ) is converted into nitrite (NO2 - ). The reaction equation is: NH4 + + 1.5O2→ NO2 - + 2H + + H2O;

[0057] Nitrification: Involving nitrate bacteria, nitrite (NO2 - ) is converted into nitrate (NO3 - ). The reaction equation is: NO2 - + 0.5O2→ NO3 - ;

[0058] Denitrification is a process in which naturally occurring denitrifying bacteria in soil and water reduce nitrite and nitrate to nitrogen gas and escape from water under anaerobic conditions, thereby achieving the purpose of nitrogen removal. In the process of denitrification, denitrifying bacteria need organic carbon source as electron donor to utilize the oxygen in NO3 - for anaerobic respiration. The reaction process can be simply represented by the following formula:

[0059] 2NO3 - + 10H (electron donor organic matter)→ N2 + 4H2O + 2OH - ;

[0060] NO2 - + 3H (electron donor organic matter)→ 1 / 2N2 + H2O + OH - ;

[0061] This series of complex biochemical reactions are efficiently carried out within the distance of 5R-7R, effectively reducing the content of nitrogen in water, avoiding the problem of water eutrophication caused by high nitrogen content, reducing the risk of overpopulation of algae and other organisms, further ensuring the stability and safety of water quality, and providing more reliable water supply guarantee.

[0062] Please refer to Figure 2As shown, in an embodiment of the present application, a third sensor 19 is arranged in the river, the third sensor 19 is connected to the side wall of the river channel through a rope or the like, and a floating ball is connected to the third sensor 19, so that the third sensor 19 can float on the water surface, and the length of the rope can satisfy the condition that the third sensor 19 can float on the water surface in the wet season and the dry season. The third sensor 19 is in communication connection with the first control system 12, the third sensor 19 measures the ammonia nitrogen concentration and operation condition data in the river water and transmits the data to the first control system 12 for real-time monitoring. In the wet season, the first control system 12 obtains the initial input amount of the slow-release oxygen material according to the ammonia nitrogen concentration data of the third sensor 19, and the first control system 12 feeds back the initial input amount to the first feeding device, and the first feeding device controls the input amount of the oxygen releasing material storage device 11 to the control well 10 according to the initial input amount. In this embodiment, the third sensor 19 is, for example, an ammonia nitrogen sensor.

[0063] In an embodiment of the present application, the ammonia nitrogen concentration measured by the third sensor is, for example, C N (mg / L), the water amount to be treated is V (L), and the total ammonia nitrogen amount T N = C N * V; the required dissolved oxygen amount DO req = T N * 4.57. In this embodiment, the oxygen releasing amount of two small balls in x days is y = 36.37e -0.02x . Assuming that the oxygen releasing rates of the two small balls are the same and linearly superimposed, then the instantaneous oxygen releasing amount of n small balls in x days is: Y n (x) = n × 18.188e -0.02x . Assuming that T is the number of days of nitrification reaction, then the oxygen releasing amount in T days is: , and because the oxygen releasing amount of the slow-release oxygen small ball should be greater than or equal to the required dissolved oxygen amount, it is:

[0064] ;

[0065] Finally, the required number of slow-release oxygen small balls is at least: , wherein n is rounded up to obtain the initial number of the input slow-release oxygen material.

[0066] The present application also provides a nitrate pollution in-situ remediation method for a river-side water source, in which an in-situ remediation system is arranged between a river and a groundwater source exploitation well to remove nitrate pollution. In the wet season and the dry season, the remediation processes are different, and the remediation processes in the wet season and the dry season are described below.

[0067] Please refer to Figures 1 to 2As shown, in an embodiment of the present application, in the wet 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 input into the groundwater with the water flow. The ammonia nitrogen concentration of the river water is obtained by the third sensor 19 and communicated to the first control system 12, and the initial input amount of the slow-release oxygen material is obtained by the first control system 12, and the slow-release oxygen material is added into the control well 10 by the first feeding device. The ammonia nitrogen, nitrate, nitrite concentration and operation data in the water are measured by the first sensor in the first monitoring well 13 and transmitted to the first control system 12 and the second control system 16, the first control system 12 performs real-time monitoring and adjustment of the amount of slow-release oxygen material 111 from the oxygen release material storage device 11 into the control well 10 by the first feeding device, and the second control system 16 controls the initial input amount of the carbon source from the carbon source storage device 15 into the injection well 14 by the second feeding device. The nitrate and nitrite concentrations and operation data in the water are measured by the second sensor in the second monitoring well 17 and transmitted to the second control system 16 for real-time monitoring and adjustment of the amount of carbon source from the carbon source storage device 15 into the injection well 14. The nitrification process is carried out from the control well 10 to the injection well 14, which is the nitrification zone, and the denitrification process is carried out from the injection well 14 to the exploitation well 18, which is the denitrification zone. By in-situ microbial cascade repair of river water, the complex nitrogen pollution of the river water source can be repaired, and the removal rate of ammonia nitrogen and nitrate can reach more than 90%, which ensures the stability and safety of the water quality of the river water source and provides more reliable water source guarantee.

[0068] Please refer to Figure 1 As shown, in an embodiment of the present application, in the dry season, the groundwater level is higher than the river water level, and the groundwater recharges the river water, at this time, the nitrate pollutants in the groundwater are input into the river water with the water flow. In order to avoid this situation, the nitrate and nitrite concentrations and operation data in the water are measured by the second sensor in the second monitoring well 17 and transmitted to the second control system 16, the initial input amount of the carbon source from the carbon source storage device 15 into the injection well 14 by the second feeding device is controlled, and the denitrification process is carried out from the injection well 14 to the river, which is the denitrification zone. By denitrification, the groundwater recharged into the river water can be repaired in-situ by microorganisms, and the amount of nitrate can be reduced, which can purify and repair the river water. That is, the in-situ repair system provided by the present application can successfully remove nitrate in the wet season and the dry season, that is, the feasibility of the system in the actual engineering application of nitrate in-situ repair in the river area.

[0069] Please refer to ​As shown, in one embodiment of the present invention, the water flow direction is opposite during the wet and dry seasons. Compared to the wet season, the water flow direction during the dry season is equivalent to reverse flushing of 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 wet and dry seasons, water can also be pumped through the first monitoring well 13. During the pumping process, water from both sides flows simultaneously into the first monitoring well 13, where the water level is lowest, achieving the same reverse flushing effect. This solves the blockage problem caused by microbial growth due to the lack of flushing during excessively long wet and dry seasons.

[0070] To verify the effectiveness of the in-situ remediation system for nitrate pollution in riverside water sources according to this invention, an experimental environment was constructed for testing. The system was tested in the laboratory according to the attached... ​ A simulated river, nitrification unit, denitrification unit, first monitoring well, groundwater model, and extraction well were constructed. The distance between the control well and the injection well was three times the distance between the injection well and the extraction well, and the distance between the injection well and the extraction well was equal to the radius of influence R. During the simulated high-water 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 was added at a C / N mass ratio of 2. Ethanol was selected as the carbon source. Water samples were taken from the first monitoring well for testing. The test results showed that the ammonia nitrogen removal rate in the nitrification section was higher than 91%, and the nitrite concentration remained below the Class III groundwater quality standard (1 mg / L) throughout the experiment. Water samples were taken from the extraction well, and the nitrate removal rate in the denitrification section was higher than 94%. During a simulated dry season, based on the nitrate concentration measured by the second sensor, a carbon source was added at a C / N mass ratio of 2. Ethanol was selected as the carbon source. Water samples were taken from the control well for testing, and the nitrate removal rate was over 90%. This demonstrates that the system can successfully remove nitrates regardless of whether it is a wet or dry season, indicating the feasibility of applying this system in actual engineering projects for in-situ nitrate remediation in riverside areas.

[0071] In summary, the present application provides a kind of nitrate pollution in-situ remediation system and method of river water source, by nitration and denitrification in-situ gradient repair of microorganism, can be suitable for the complex nitrogen pollution situation of river water source, realize nitrate pollution in-situ remediation of river water source, guarantee the stability and safety of water quality, can provide more reliable water source guarantee.And in in-situ remediation, slow-release oxygen material can slowly release oxygen, complete nitrification occurs under the action of nitrifying bacteria, oxidize ammonia nitrogen into nitrate, improve the anoxic condition of groundwater and do not cause pH surge, adopt intelligent control carbon source and slow-release oxygen material input, real-time monitoring system operation processing condition, avoid resource waste, secondary pollution and poor treatment effect, improve in-situ remediation treatment efficiency and stability.Reserve enough distance for nitrification and denitrification reaction, improve repair effect, at the same time reserve buffer space, respond to water quality fluctuation, microbial activity attenuation and other dynamic factors, ensure that denitrification process is stable and efficient under complex working conditions.At the same time, the system can achieve reverse flushing effect, solve the problem of blockage caused by microbial growth due to no flushing in wet season and dry season.Through in-situ microbial gradient repair, complex nitrogen pollution of river water source can be solved, repair and exploitation can be operated synchronously, nitrogen content in water can be reduced, water eutrophication can be avoided, water quality stability and safety can be guaranteed, and reliable water source can be provided.

[0072] The above description is only the preferred embodiment of the present application and the explanation of the applied technical principles, and those skilled in the art should understand that the scope of the application involved in the present application is not limited to the technical solutions formed by the specific combination of the above technical features, and should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the inventive concept, for example, the technical solutions formed by replacing the above features with the technical features disclosed in the present application (but not limited to) having similar functions.

[0073] In addition to the technical features described in the specification, the remaining technical features are known to those skilled in the art, and in order to highlight the innovative features of the present application, the remaining technical features will not be described here.

Claims

1. An in-situ remediation system for nitrate pollution in riverside water sources, characterized in that, At least comprising: a groundwater source exploitation well adjacent to a river; at least one nitrification unit arranged between the river and the exploitation well, the nitrification unit comprising 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 exploitation well, the denitrification unit comprising an injection well, a carbon source storage device and a second control system; the distance between the injection well and the exploitation well is greater than or equal to the influence radius R; the ratio of the distance between the control well and the injection well to the distance between the injection well and the exploitation well is greater than or equal to 3; at least one first monitoring well arranged between the nitrification unit and the denitrification unit and connected to the first control system and the second control system respectively; in the wet season, the first control system controls the input amount of slow-release oxygen releasing material added into the control well by the oxygen releasing material storage device according to the ammonia nitrogen concentration data obtained by the first monitoring well; the second control system controls the input amount of carbon source added into the injection well by the carbon source storage device according to the nitrate and nitrite concentration data obtained by the first monitoring well; at least one second monitoring well arranged between the denitrification unit and the exploitation well and connected to the second control system; in the wet season, the second control system controls the input amount of carbon source added into the injection well by the carbon source storage device according to the nitrate and nitrite concentration data obtained by the second monitoring well; in the dry season, the second control system controls the input amount of carbon source added into the injection well by the carbon source storage device according to the nitrate and nitrite concentration data obtained by the second monitoring well.

2. The in-situ nitrate contamination remediation system of a riverbanked water source according to claim 1, characterized by, One of the nitrification unit, one of the denitrification unit, one of the first monitoring well and one of the second monitoring well are arranged in a single row, forming an in-situ reaction unit, the in-situ remediation system comprises 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.

3. The in-situ nitrate contamination remediation system of a riverbanked water source according to claim 1, characterized by, 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 exploitation well.

4. The in-situ nitrate contamination remediation system of a riverbanked water source according to claim 1, characterized by, The oxygen releasing material storage device stores slow-release oxygen releasing material, the slow-release oxygen releasing material comprises an oxygen releasing source and a buffer, the oxygen releasing source comprises one or more combinations of calcium peroxide, magnesium peroxide, sodium peroxide, zinc peroxide or sodium percarbonate, and the buffer comprises one or more combinations of potassium dihydrogen phosphate, ammonium sulfate, disodium hydrogen phosphate, sodium dihydrogen phosphate, sodium bicarbonate or ammonium acetate.

5. The in-situ nitrate contamination remediation system of a riverbanked water source according to claim 1, characterized by, The oxygen releasing material storage device is arranged on one side of the control well, and a first delivery device is arranged between the oxygen releasing material storage device and the control well, and the first delivery device is connected to the first control system.

6. The in-situ nitrate contamination remediation system of an in-river water source site according to claim 5, characterized by, The carbon source storage device is arranged on one side of the injection well, and a second delivery device is arranged between the carbon source storage device and the injection well, and the delivery device is connected with the second control system; and / or The carbon source storage device stores carbon sources, and the carbon sources include one or more combinations of ethanol, sodium succinate, sodium acetate, sodium malate, or glucose.

7. The in-situ nitrate contamination remediation system of an in-river water source according to claim 6, characterized in that, The first monitoring well is provided with a first sensor for detecting ammonia nitrogen, nitrate, and nitrite concentrations in water during the wet season, and the first sensor is communicatively connected with the first control system and the second control system, respectively. The first control system obtains target data of the slow-release oxygen material according to ammonia nitrogen concentration data of the first sensor, feeds back the target data to the first delivery device, and the first delivery device controls the input amount of the oxygen releasing material storage device into the control well according to the target data. The second control system obtains an initial addition amount of the carbon source according to nitrate and nitrite concentration data of the first sensor, feeds back the initial addition amount to the second delivery device, and the second delivery device controls the input amount of the carbon source storage device into the injection well according to the initial addition amount.

8. The in-situ nitrate contamination remediation system of an in-river water source site according to claim 6, characterized by, The second monitoring well is provided with a second sensor for detecting nitrate and nitrite concentrations in water during the wet season and the dry season, and the second sensor is communicatively connected with the second control system. During the wet season, the second control system obtains target data of the carbon source according to nitrate and nitrite concentration data of the second sensor, feeds back the target data to the second delivery device, and the second delivery device controls the input amount of the carbon source storage device into the injection well according to the target data. During the dry season, the second control system obtains an initial addition amount of the carbon source according to nitrate and nitrite concentration data of the second sensor, feeds back the initial addition amount to the second delivery device, and the second delivery device controls the input amount of the carbon source storage device into the injection well according to the initial addition amount.

9. The in-situ nitrate contamination remediation system of a riverbanked water source according to claim 6, wherein The in-situ remediation system further comprises a third sensor arranged in the river, and the third sensor is used for detecting ammonia nitrogen concentration in water during the wet season, and the third sensor is communicatively connected with the first control system. The first control system obtains an initial input amount of the slow-release oxygen material according to ammonia nitrogen concentration data of the third sensor, feeds back the initial input amount to the first delivery device, and the first delivery device controls the input amount of the oxygen releasing material storage device into the control well according to the initial input amount.

10. A method for in-situ remediation of nitrate contamination at a riverbank water source, characterized by, The in-situ remediation system according to any one of claims 1-9 is arranged between a river and a groundwater source exploitation well to remove nitrate pollution.

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