Multi-media abiotic reaction wall for repairing interlayer runoff of soil in mountain and hilly areas and its application method

Abstract

The present invention provides a multi-media abiotic reaction wall for repairing interlayer runoff in mountain and hilly areas, comprising: a buffer anti-blocking layer disposed in the soil for blocking fine soil sand in the interlayer runoff of the soil; a main reaction layer disposed downstream of the buffer anti-blocking layer for removing nitrates in the interlayer runoff of the soil; a primary adsorption layer disposed downstream of the main reaction layer for removing residual nitrates in the interlayer runoff of the soil; and a secondary adsorption layer disposed downstream of the primary adsorption layer for removing ammonia nitrogen in the interlayer runoff of the soil. The method of the present invention is applicable to the targeted repair of nitrogen pollution in the interlayer runoff of mountain and hilly areas, adapts to the characteristics of seasonal runoff generation and sudden changes in pollutant concentration in the interlayer runoff of the soil, and has the advantages of low operating cost, good effect, and convenient replacement.

Description

Technical Field

[0001] The present invention belongs to the technical field of soil water remediation, and particularly relates to a multi-media abiotic reaction wall for repairing soil interlayer runoff in mountain and hilly areas and an application method thereof. Background Art

[0002] Purple soil is one of the important cultivated soil types in mountain and hilly areas in southern China. Due to the loose surface of purple soil in mountain and hilly areas and the obvious soil-bedrock interface, the vertically infiltrating water generated after precipitation can quickly reach the soil-bedrock interface, easily forming soil interlayer runoff. Soil interlayer flow runs through the farmland aquifer and easily exchanges components with farmland soil. After the replenishment of rainfall and irrigation, nitrogen compounds in the soil are easily carried into the aquifer, and the pollutant concentration in soil interlayer runoff will fluctuate and increase. Purple soil has a thin soil layer, and nutrients are easily lost during the rainy season. The nitrogen loss of surface runoff and soil interlayer runoff mainly occurs in the form of NO 3 - -. Soil interlayer runoff is the preferred way for nutrient loss of surface runoff. Under different cultivation methods, the NO 3 - -N concentration in soil interlayer runoff in mountain and hilly areas can reach 20.00 - 50.00 mg / L. China's "Surface Water Environmental Quality Standard" (GB3838—2002) requires that the maximum TN does not exceed 2.00 mg / L, and the standard limit value of NO 3 - -N in surface water source areas is 10.00 mg / L. The nitrate nitrogen pollution brought by soil interlayer runoff is extremely serious. The nitrogen carried by soil interlayer runoff flows into the surrounding water bodies, which will not only cause pollution to the surrounding water bodies, but also affect the groundwater and the water quality of the Yangtze River, resulting in the decline of local drinking water quality.

[0003] Conventional denitrification technologies mainly include physical, chemical, and biological methods. Biological denitrification is the most commonly used method for treating polluted water bodies in urban sewage treatment plants, but it has disadvantages such as the need for electron donors and carbon sources, the need for end treatment (such as ozone oxidation), long maintenance time, long start-up time, being affected by pH and temperature, and membrane fouling. Summary of the Invention

[0004] In view of the above defects, the present invention provides a multi-media abiotic reaction wall for repairing soil interlayer runoff in mountain and hilly areas and an application method thereof, which solves the key technical problems of complex operation and maintenance, limited treatment life, and cross-media pollution of existing soil interlayer runoff denitrification means.

[0005] The present invention provides the following technical solution: A multi-media abiotic reaction wall for repairing interlayer runoff in mountain and hilly areas, comprising: a buffer anti-blocking layer disposed in the soil for blocking fine soil sand in the interlayer runoff of the soil; a main reaction layer disposed downstream of the buffer anti-blocking layer for removing nitrates in the interlayer runoff of the soil; a primary adsorption layer disposed downstream of the main reaction layer for removing residual nitrates in the interlayer runoff of the soil; and a secondary adsorption layer disposed downstream of the primary adsorption layer for removing ammonia nitrogen in the interlayer runoff of the soil and preventing the loss of the main reaction layer and the primary adsorption layer. Among them, the buffer anti-blocking layer includes coarse-grained quartz sand and fine-grained quartz sand, and the mass ratio of coarse-grained quartz sand to fine-grained quartz sand is 1–3:1-3; the main reaction layer includes sponge iron and low-temperature biochar, and the volume ratio of sponge iron to low-temperature biochar is 1:3, and the ratio of the mass ratio is 3.9–4, and the two are uniformly mixed; the primary adsorption layer includes a macroporous adsorption medium; the secondary adsorption layer includes fine-particle zeolite and coarse-particle zeolite, and the coarse-particle zeolite is disposed downstream of the fine-particle zeolite.

[0006] Further, the particle size of the coarse-grained quartz sand is 2mm–4mm, and the particle size of the fine-grained quartz sand is 1mm–2mm.

[0007] Further, the particle size of the sponge iron is 1mm–3mm, and the particle size of the low-temperature biochar is 0.15mm–0.3mm.

[0008] Further, the low-temperature biochar includes low-temperature wood chip biochar fired at a firing temperature of 350°C - 450°C, a firing time of 1h - 4h, and fired in a nitrogen atmosphere.

[0009] Further, the particle size of the fine-particle zeolite is 0.5mm–1mm, and the particle size of the coarse-particle zeolite is 1mm–2mm.

[0010] Further, the main reaction layer further includes an upper baffle and a lower baffle for extending the residence time of the interlayer runoff of the soil in the main reaction layer. The upper baffle is disposed at the upper part in the main reaction layer, and the lower baffle is disposed at the lower part in the main reaction layer.

[0011] Further, the soil permeability coefficient is 0.415cm / min - 0.972cm / min, the permeability coefficient of the multi-media abiotic reaction wall is twice that of the soil permeability coefficient, and the residence time of the interlayer runoff of the soil in the main reaction layer is 2h - 6h.

[0012] Further, the macroporous adsorption medium includes 201*7 type anion exchange resin and calcined hydrotalcite.

[0013] Further, the multi-media abiotic reaction wall for repairing interlayer runoff in mountain and hilly areas includes: 1 part of the buffer anti-blocking layer, 1.5 - 2 parts of the main reaction layer, 1 part of the primary adsorption layer, and 1 part of the secondary adsorption layer.

[0014] The present invention also provides an application method for a multi-media abiotic reaction wall for repairing interlayer runoff of soil in mountainous and hilly areas, comprising the following steps:

[0015] Step S1, arranging an installation space in the soil, with the bottom of the installation space reaching the bedrock layer;

[0016] Step S2, laying a permeable geotextile at the upstream section connection of the installation space, and laying a nylon net at the downstream section connection of the installation space;

[0017] Step S3, placing the multi-media abiotic reaction wall for repairing interlayer runoff of soil in mountainous and hilly areas as described in any one of claims 1-9 into the installation space and located upstream of the nylon net.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] 1. The present invention can in-situ degrade pollutants in the interlayer runoff of soil in mountainous and hilly areas, without the need for the process of first collecting and then treating polluted water bodies, and there is no potential cross-media pollution. By in-situ degrading pollutants, the reaction layer wall of the present invention provides an effective technical effect for pollutant repair, rather than simply controlling pollutant migration.

[0020] 2. The present invention uses an abiotic chemical method to remove nitrogen in the interlayer runoff of soil in mountainous and hilly areas, which is suitable for the runoff generation and pollution characteristics of the interlayer runoff of soil. At the same time, the main reaction layer of the present invention includes sponge iron and low-temperature biochar. The rich oxygen-containing functional groups such as phenolic hydroxyl groups, ethers, carboxyl groups, and quinone groups on the surface of the low-temperature biochar have the activities of neutralizing alkali and redox. In the system of the present invention, the low-temperature biochar and sponge iron form a micro galvanic cell, and under the action of the relative potential difference, an electron transfer of Fe→NO 3 - -N is formed. Since the low-temperature biochar has no migration constraint on the N intermediate, the generation rate of NH 4 + -N is inhibited and reduced, and the selective generation rate of N 2 increases, which is beneficial to the removal of total nitrogen in the interlayer runoff of soil. In addition, the primary adsorption layer in the present invention includes a macroporous adsorption medium, and the macroporous adsorption medium has an exchange adsorption effect on nitrate, and is used as a nitrate adsorption layer to cope with sudden nitrate nitrogen pollution and tail water treatment. Moreover, the secondary adsorption layer material includes fine-particle zeolite and coarse-particle zeolite. Zeolite has good ammonia nitrogen adsorption performance and is used to adsorb the ammonia nitrogen generated by the reduction of nitrate by sponge iron-biochar, further improving the total nitrogen removal effect of the main reaction layer. The sponge iron-biochar system in the present invention improves the problem that zero-valent iron cannot effectively remove total nitrogen, can reduce the generation of ammonia nitrogen while maintaining the nitrate removal effect, and generates gaseous nitrogen substances such as nitrogen.

[0021] 3. By optimizing the materials and particle sizes thereof, and optimizing the grading of different particle sizes, the permeability coefficient of the reaction wall is adapted to the interlayer runoff of the soil in mountainous and hilly areas, thereby improving the problem of easy blockage of the reaction wall.

[0022] 4. By adding adjustable baffle plates, the hydraulic retention time of the interlayer runoff of the soil in the main reaction layer of the reaction wall is prolonged, and the pollutant removal effect is improved. At the same time, according to the soil coefficient of the site and the requirements for pollutant effluent, the number and position of the baffle plates can be flexibly adjusted to adapt to various land types. Description of the Drawings

[0023] The present invention will be described in more detail hereinafter based on embodiments with reference to the drawings. Among them:

[0024] Figure 1 is a schematic structural diagram of a multi-media abiotic reaction wall for repairing the interlayer runoff of the soil in mountainous and hilly areas in the experimental simulation scenario provided in Embodiment 1 of the present invention.

[0025] Figure 2 is an installation schematic diagram of a secondary multi-media abiotic reaction wall in a purple soil sloping farmland plot provided in Embodiment 2 of the present invention.

[0026] Figure 3 is a schematic structural diagram of a multi-media abiotic reaction wall for repairing the interlayer runoff of the soil in mountainous and hilly areas provided in Embodiment 2 of the present invention.

[0027] Description of the Reference Numerals in the Drawings:

[0028] 1 - reaction wall; 2 - catchment area; 3 - monitoring well; 4 - buffer anti-blocking layer; 5 - main reaction layer; 6 - primary adsorption layer; 7 - secondary adsorption layer; 8 - adjustable baffle plate; 9 - reaction tank; 10 - water inlet; 11 - water outlet. Detailed Embodiments

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0030] Embodiment 1

[0031] In this embodiment, a multi-media abiotic reaction wall (hereinafter referred to as the reaction wall) for repairing the interlayer runoff of the soil in mountainous and hilly areas is arranged in a reaction tank simulating the interlayer runoff of the soil in mountainous and hilly areas, and the scenario of the interlayer runoff of the soil passing through the reaction wall is simulated to repair the interlayer runoff of the soil.

[0032] Figure 1 It is a schematic structural diagram of a multi-media abiotic reaction wall used to repair the interlayer runoff of soil in mountainous and hilly areas in the experimental simulation scenario provided in Embodiment 1 of the present invention.

[0033] As Figure 1 shown, the reaction tank 9 is overall in a cuboid structure, with a total length of 360 mm, a total width of 80 mm, a total height of 80 mm, and a total volume of 2304 cm 3 , an internal volume of 1715 mL, an internal length of 350 mm, an internal width of 70 mm, and an internal height of 70 mm. The reaction tank 9 is made of polymethyl methacrylate and is hollow inside, used to fill the reaction wall and the interlayer runoff of the soil. The water inlet 10 and the water outlet 11 are respectively arranged on both sides of the reaction tank 9 and are located at the center points of the two side surfaces of the reaction tank 9. Valves (not shown in the figure) are provided at both the water inlet 10 and the water outlet 11. In the experiment, one side of the water inlet 10 is raised to make an angle of 6° with the horizontal plane to simulate the inclination degree of the interlayer runoff generation of the soil in the actual mountainous and hilly areas, and the influent flow rate is controlled by a micro peristaltic pump.

[0034] In this embodiment, the reaction wall is filled into the reaction tank 9, and soil is filled in the upper and lower parts of the reaction wall. The reaction wall in this embodiment includes: 2 parts of sponge iron with a particle size of 1 - 3 mm and 6 parts of low-temperature pine sawdust biochar as the main reaction layer, 1 part of Mg-Fe 3:1 calcined hydrotalcite-like as the primary adsorption layer, and 2 parts of fine-particle zeolite with a particle size of 0.5 mm - 1 mm and coarse-particle zeolite with a particle size of 1 mm - 2 mm as the secondary adsorption layer. Among them, the sponge iron is pickled with dilute hydrochloric acid for 10 minutes and then evenly mixed with the low-temperature pine sawdust biochar, filled into the reaction tank 9. After the reaction wall is compacted, a layer of soil is covered on the surface. The interlayer runoff of the soil is controlled to permeate through the reaction wall by a micro peristaltic pump, and the hydraulic retention time of the operation is controlled to be 3 h. The reaction wall repairs the interlayer runoff of the soil and operates continuously for 10 days.

[0035] In Embodiment 1, the water quality indexes of the influent and effluent of the reaction tank 9 are measured to verify the pollutant removal effect and capacity of the device. The initial concentration of NO 3 - -N in the influent of the water inlet 10 is about 30 mg / L. The average effluent of TN of the reaction wall is 3.24 mg / L, and the average removal rate reaches 89.20%; the average effluent of NO 3 - -N is 0.71 mg / L, and the average removal rate reaches 97.63%; the average effluent of NH 4 + -N is 2.50 mg / L, and NO 2 --N average effluent is 0.03 mg / L. From the experimental data, it can be seen that in this embodiment, medium and low temperature biochar and sponge iron can form a micro primary battery, and under the action of the relative potential difference, an electron transfer of Fe→NO 3 - -N occurs. Since the low temperature biochar has no migration constraint on N intermediates, the generation rate of NH 4 + -N is inhibited and decreased, and the selective generation rate of N 2 increases, which is beneficial to the removal of total nitrogen in the interlayer runoff of the soil. In addition, the primary adsorption layer in this embodiment includes a macroporous adsorption medium, and the macroporous adsorption medium has an exchange adsorption effect on nitrate, and is used as a nitrate adsorption layer to cope with sudden nitrate nitrogen pollution and tail water treatment. Moreover, the secondary adsorption layer material includes fine particle size zeolite and coarse particle size zeolite. Zeolite has good ammonia nitrogen adsorption performance and is used to adsorb the ammonia nitrogen generated by the reduction of nitrate by sponge iron-biochar, further improving the total nitrogen removal effect of the reaction wall.

[0036] Example 2

[0037] In this embodiment, a multi-media abiotic reaction wall (hereinafter referred to as the reaction wall) for repairing the interlayer runoff of mountain and hilly areas is applied to repair the interlayer runoff of purple soil in a certain county in Sichuan. The soil permeability coefficient of the purple soil in this county is measured to be 0.415 - 0.972 cm / min, and the permeability coefficient of the reaction wall needs to be greater than twice the soil permeability coefficient.

[0038] Based on the above soil permeability coefficient, the reaction wall 1 in this embodiment includes: 8 parts of coarse quartz sand with a particle size of 2 - 4 mm and 8 parts of fine quartz sand with a particle size of 1 - 2 mm as the buffer and anti-blocking layer 4; a uniform mixture of 6.75 parts of sponge iron with a particle size of 1 - 3 mm and 20.25 parts of low temperature wood chip biochar with a particle size of 0.15 - 0.3 mm, a total of 27 parts as the main reaction layer 5; 16 parts of 201*7 type anion exchange resin as the primary adsorption layer 6; 8 parts of zeolite with a particle size of 0.5 - 1 mm and 8 parts of zeolite with a particle size of 1 - 2 mm as the secondary adsorption layer 7.

[0039] In addition, for the purple soil sloping farmland in this county, two groups of reaction walls as shown in Figure 2 are installed in this embodiment. The first-stage reaction wall 1 and the second-stage reaction wall 1 are respectively placed in the middle and the downstream end of the runoff generation area of the soil interlayer. And stones are filled in the downstream of the second-stage reaction wall as the water collection area 2. The upper end of the reaction wall is covered with purple soil. The purple soil area including the soil covering the upper end of the reaction wall can all be planted with seasonal crops without affecting the actual use of the cultivated land.

[0040] Applying a multi-media abiotic reaction wall (hereinafter referred to as the reaction wall) for repairing the interlayer runoff of mountain and hilly areas to repair the interlayer runoff of purple soil in a certain county in Sichuan in this embodiment includes the following steps:

[0041] Step S1, set up an installation space in the soil, and the bottom of the installation space reaches the bedrock layer.

[0042] An installation space for the reaction wall was excavated in a purple soil sloping cultivated land plot in a certain county in Sichuan. The bottom of the installation space was dug to the bedrock layer to ensure that the pollution plume of this section completely flowed through the reaction wall.

[0043] Step S2, lay a permeable geotextile at the upstream section connection of the installation space, and lay a nylon net at the downstream section connection of the installation space;

[0044] Step S3, place the reaction wall 1 in the installation space and upstream of the nylon net.

[0045] In this embodiment, the treatment of soil interlayer runoff is detected by the monitoring well 3. After precipitation, soil interlayer runoff is generated in the purple soil sloping cultivated land. The generated soil interlayer runoff flows through the soil and the reaction wall 1, and penetrates through the reaction layer wall 1. The impurities in the soil interlayer runoff are intercepted by quartz sands with different gradations. Nitrate reacts with sponge iron and wood chip biochar to generate gaseous nitrogen and ammonia nitrogen. The resin adsorbs the residual nitrate. Finally, the soil interlayer runoff flows through zeolite and the ammonia nitrogen is adsorbed. It is verified that the reaction wall 1 in this embodiment has a strong removal effect on the pollution in the soil interlayer runoff. The influent TN of the system is 5 - 30 mg / L. After the effluent of the first-stage reaction wall and the second-stage reaction wall is stable, the TN of both is lower than 2 mg / L, and most of the effluent TN is less than 1.5 mg / L, meeting the standard of Class IV water in the Environmental Quality Standards for Surface Water (GB3838—2002).

[0046] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

[0047] In addition, those skilled in the art can understand that although some of the embodiments herein include certain features included in other embodiments rather than other features, the combination of the features of different embodiments means that it is within the scope of the present invention and forms different embodiments. For example, in the claims above, any one of the claimed embodiments can be used in any combination. The information disclosed in this background art section is only intended to deepen the understanding of the overall background art of the present invention, and should not be regarded as admitting or implying in any form that this information constitutes the prior art known to those skilled in the art.

Claims

1. A multi-media abiotic reaction wall for repairing interlayer runoff in mountain and hilly areas, characterized in that, it includes: A buffer anti-blocking layer, which is arranged in the soil and is used to block the fine soil sand in the interlayer runoff of the soil; A main reaction layer, which is arranged downstream of the buffer anti-blocking layer and is used to remove nitrates in the interlayer runoff of the soil. The main reaction layer also includes an upper baffle and a lower baffle, which are used to extend the residence time of the interlayer runoff of the soil in the main reaction layer. The upper baffle is arranged at the upper part in the main reaction layer, and the lower baffle is arranged at the lower part in the main reaction layer; A primary adsorption layer, which is arranged downstream of the main reaction layer and is used to remove the remaining nitrates in the interlayer runoff of the soil; A secondary adsorption layer, which is arranged downstream of the primary adsorption layer and is used to remove ammonia nitrogen in the interlayer runoff of the soil; Wherein, the buffer anti-blocking layer includes coarse-grained quartz sand and fine-grained quartz sand, and the mass ratio of the coarse-grained quartz sand to the fine-grained quartz sand is 1–3:1–3; The main reaction layer includes a mixture of sponge iron and low-temperature biochar, and the volume ratio of the sponge iron to the low-temperature biochar is 1:3, and the ratio of the mass ratio is 3.9–4; The primary adsorption layer includes a macroporous adsorption medium, and the macroporous adsorption medium includes an anion exchange resin and calcined hydrotalcite; The secondary adsorption layer includes fine-particle zeolite and coarse-particle zeolite, and the coarse-particle zeolite is arranged downstream of the fine-particle zeolite.

2. The multi-media abiotic reaction wall for repairing interlayer runoff in mountain and hilly areas according to claim 1, characterized in that, The particle size of the coarse-grained quartz sand is 2mm–4mm, and the particle size of the fine-grained quartz sand is 1mm–2mm.

3. The multi-media abiotic reaction wall for repairing interlayer runoff in mountain and hilly areas according to claim 1, characterized in that, The particle size of the sponge iron is 1mm–3mm, and the particle size of the low-temperature biochar is 0.15mm–0.3mm.

4. The multi-media abiotic reaction wall for repairing interlayer runoff in mountain and hilly areas according to claim 3, characterized in that, The low-temperature biochar includes low-temperature wood chip biochar fired at a firing temperature of 350°C - 450°C, a firing time of 1h - 4h, and fired in a nitrogen atmosphere.

5. The multi-media abiotic reaction wall for repairing interlayer runoff in mountain and hilly areas according to claim 1, characterized in that, The particle size of the fine-particle zeolite is 0.5mm–1mm, and the particle size of the coarse-particle zeolite is 1mm–2mm.

6. The multi-media abiotic reaction wall for repairing interlayer runoff in mountain and hilly areas according to claim 1, characterized in that, The soil permeability coefficient is 0.415cm / min - 0.972cm / min, the permeability coefficient of the multi-media abiotic reaction wall is twice that of the soil permeability coefficient, and the residence time of the interlayer runoff of the soil in the main reaction layer is 2h - 6h.

7. The multi-media abiotic reaction wall for repairing interlayer runoff in mountain and hilly areas according to claim 1, characterized in that, it includes: The buffer anti-blocking layer is 1 part, the main reaction layer is 1.5 - 2 parts, the primary adsorption layer is 1 part, and the secondary adsorption layer is 1 part.

8. An application method of a multi-media abiotic reaction wall for repairing interlayer runoff in mountain and hilly areas Characterized in that It includes the following steps: Step S1, set an installation space in the soil, and the bottom of the installation space reaches the bedrock layer; Step S2, lay a permeable geotextile at the upstream section connection of the installation space, and lay a nylon net at the downstream section connection of the installation space; Step S3, place the multi-media abiotic reaction wall for repairing interlayer runoff in mountain and hilly areas as described in any one of claims 1 - 7 in the installation space and upstream of the nylon net.

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