Slow-release oxygen material for in-situ remediation of farmland drainage water and preparation method and application thereof

Abstract

The application provides a slow-release oxygen material for in-situ remediation of farmland drainage water and a preparation method and application thereof, and relates to the field of sewage treatment. The slow-release oxygen material for in-situ remediation of farmland drainage water comprises the following raw materials in parts by mass: 1-5 parts of an oxygen releasing agent, 1-5 parts of a plastic bonding material, 1-6 parts of an adsorptive mineral, and 1-3 parts of a pH buffer, wherein the oxygen releasing agent comprises calcium peroxide and calcium carbonate. The slow-release oxygen material for in-situ remediation of farmland drainage water is prepared from raw materials such as calcium peroxide, sulfur, tourmaline and calcium carbonate, can efficiently treat low-concentration ammonia-nitrogen wastewater in-situ, has long-lasting aeration time, can reduce the system pH while efficiently releasing oxygen, and solves the problem that the system environment is excessively alkaline due to aeration of a chemical oxygen releasing agent, and microorganisms are difficult to survive.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to a slow-release oxygen material for in-situ remediation of farmland runoff, its preparation method, and its application. Background Technology

[0002] Agricultural runoff, often generated by artificial drainage or rainfall, flows from farmland and contains high levels of nitrogen and phosphorus, essential elements for plant growth. Agricultural sources account for 85-93% of nitrogen and 67-81% of phosphorus in surface water. Direct discharge of agricultural runoff into rivers easily leads to eutrophication, becoming a significant source of agricultural non-point source pollution. Agricultural runoff is widespread and dispersed, impacting surface waters through various channels, making its management challenging and complex. In the highly fragmented, household-based farming model, numerous agricultural runoff outlets exist, and farmers often lack the economic and technical resources to manage the pollution. Therefore, reducing agricultural runoff pollution to rivers requires tailored solutions based on the specific characteristics of agricultural runoff. In-situ remediation of agricultural runoff is currently the most economical and appropriate solution to these problems.

[0003] Currently, there are many effective methods for treating farmland runoff pollution, such as constructing terraces, plant ponds, ecological ditches, oxidation ponds, vegetation buffer zones, and artificial wetlands. However, these methods require large land areas, are susceptible to pests and diseases, and involve high biological and hydraulic complexity. These factors increase the difficulty in understanding their treatment mechanisms, process kinetics, and influencing factors. Furthermore, improper design often results in effluent failing to meet discharge standards, and in some cases, it even becomes a source of pollution. Therefore, it is essential to develop an in-situ, controllable, and cost-effective method for remediating farmland runoff pollution. Farmland drainage ditches are crucial channels connecting agricultural drainage to rivers and lakes. They serve as the initial collection point for agricultural non-point source pollution and the outlet for downstream rivers and lakes, playing multiple roles such as water storage, drainage, and water purification. Therefore, establishing a small-scale A2O process within the drainage ditch, conducting nitrification and denitrification reactions within the runoff channel, can solve the problem of centralized rural wastewater treatment and effectively protect rivers from nitrogen and phosphorus pollution.

[0004] Because farmland uses large amounts of fertilizers and pesticides, the total nitrogen content, especially ammonia nitrogen, in farmland runoff often far exceeds water quality standards, leading to eutrophication. Microbial nitrification is currently the most efficient and pollution-free treatment method for removing ammonia nitrogen. However, this method requires providing sufficient oxygen to the microorganisms. For farmland runoff, traditional physical aeration methods, such as external aeration pumps or aerators, are not widely applicable and would result in economic burdens and energy waste. Directly using chemical oxygen generators like calcium peroxide presents problems such as uneven oxygen release, excessively high pH levels due to water reaction, and inhibition of microbial activity.

[0005] To address the above issues, the invention patent "A Slow-Release Oxygen Material for Groundwater Remediation and Its Preparation Method" (application number: 201110426869.9) uses calcium peroxide as an oxygen-releasing agent and cement as a binder to prepare a slow-release oxygen material. However, this material significantly increases the pH value of the system during the oxygen release process, failing to maintain pH stability while ensuring oxygen release effectiveness. It cannot be used as an oxygen-releasing agent in microbial nitrification reactions, and the material cannot be reused after complete aeration, easily leading to material waste. The patent "A Preparation Method of Calcium Peroxide Slow-Release Oxygen Particles" (application number: 201910430223.4) uses polylactic acid to encapsulate calcium peroxide, solving the problem of poor oxygen release continuity from calcium peroxide, but it does not solve the problem of pH increase in the system. The patent "Slow-Release Oxygen Composite Material Composition, Slow-Release Oxygen Composite Material and its Preparation Method and Raw Material Composition" (Application No.: 202110956873.X) uses metal peroxide as an oxygen-releasing agent and adds persulfate as an oxygen-releasing agent component, effectively solving the problem of pH increase caused by using a single metal peroxide. Persulfate decomposes to generate sulfate ions, which can provide electron acceptors for microorganisms in groundwater. However, for farmland runoff, the generation of sulfate ions causes a large amount of pollution and burdens the decomposition of ammonia nitrogen. At the same time, this material is mainly used for the degradation of organic pollutants such as petroleum, and the material preparation method is complex, making it unsuitable for the degradation of farmland runoff pollution. The patent "A Preparation Method and Application of a Modified Adsorbent Material for Low Concentration Ammonia Nitrogen in Water" (Application No.: 202211536702.2) is mainly used for the remediation of low concentration ammonia nitrogen in farmland irrigation areas. The components of the adsorbent material are mainly fly ash and sodium hydroxide. However, this adsorbent material is prone to saturation and is difficult to reuse after saturation.Currently, some scholars have also used methods such as loading oxygen nanobubbles for aeration. Li et al. (LI Y, XIONG X, ZHANG C, et al. Sustainable restoration of anoxic freshwater using environmentally-compatible oxygen-carrying biochar: Performance and mechanisms [J]. Water Research, 2022, 214: 118204.) successfully loaded oxygen nanobubbles onto the surface of biochar using vacuum pressure swing adsorption. This oxygen-carrying sediment-based biochar was able to continuously oxygenate anoxic water bodies for 28 days in a simulation experiment. This technology greatly reduces the use of chemical agents and does not cause an increase in the pH of the water body. However, the physical modification process of loading oxygen nanobubbles involves vacuuming and high pressure, which requires high-quality equipment and is complex to prepare. In order to reduce the escape of oxygen adsorbed by porous materials, the oxygen-carrying nanobubble type slow-release oxygen material should be put into use immediately after preparation, which is not conducive to storage and transportation. These shortcomings limit the application of such materials in actual production. Zhou et al. (ZHOU Y, FANG X, ZHANG Z, et al. An oxygen slow-releasing material and its application in water remediation as oxygen supplier [J]. Environmental Technology, 2017, 38(22): 2793-2799.) selected stearic acid as the embedding agent, dissolved stearic acid in CCl4, added a certain amount of CaO2 powder and quartz sand, stirred thoroughly, and then compressed into tablets using a tablet press. Although this improved the utilization rate of CaO2, the organic solvents used in the preparation process are usually toxic and volatile, making recycling difficult, causing environmental pollution, and incurring high costs.

[0006] Therefore, those skilled in the art urgently need to disclose a slow-release oxygen material for in-situ remediation of farmland drainage, in order to solve the problems of existing slow-release oxygen materials having complex preparation processes, easily causing a significant increase in water pH, high preparation costs, and inability to be reused. Summary of the Invention

[0007] The purpose of this invention is to provide a slow-release oxygen material for in-situ remediation of farmland drainage, its preparation method and application, in order to solve the problems of complex preparation processes of existing slow-release oxygen materials, which easily cause the pH value of the water to rise, thus leading to a significant reduction in the treatment effect of nitrifying bacteria.

[0008] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0009] This invention provides a slow-release oxygen material for in-situ remediation of farmland drainage, comprising the following raw materials in parts by weight:

[0010] 1-5 parts oxygen release agent, 1-5 parts plastic binder, 1-6 parts adsorbent minerals, and 1-3 parts pH buffer;

[0011] The oxygen-releasing agent includes calcium peroxide and calcium carbonate;

[0012] The pH buffer comprises tourmaline and sulfur;

[0013] Preferably, the mass ratio of calcium peroxide to calcium carbonate is 1~20:1.

[0014] Preferably, the plastic binder material includes cement and river sand;

[0015] The mass ratio of cement to river sand is 0.5~10:1;

[0016] The particle size of the river sand is 10-40 mesh.

[0017] Preferably, the adsorbent mineral is zeolite;

[0018] The particle size of the zeolite is 20-200 mesh.

[0019] Preferably, the sulfur has a particle size of 10-60 mesh.

[0020] Preferably, the mass ratio of tourmaline to sulfur is 0.5 to 10:1.

[0021] This invention also provides a method for preparing a slow-release oxygen material for in-situ remediation of farmland drainage, comprising the following steps:

[0022] The oxygen-releasing agent, plastic binder, adsorbent minerals, pH buffer, and water are mixed, granulated, and dried to obtain a slow-release oxygen material for in-situ remediation of farmland drainage.

[0023] Preferably, the mass of each granulated slow-release oxygen material used for in-situ remediation of farmland drainage is 3-7g.

[0024] This invention also provides an application of a slow-release oxygen material for in-situ remediation of farmland runoff, characterized by the following application method:

[0025] The ammonia nitrogen in farmland runoff is treated by adding slow-release oxygen materials for in-situ remediation of farmland runoff and by inoculating nitrifying sludge.

[0026] Preferably, the mass-to-volume ratio of the farmland drainage, the slow-release oxygen material used for in-situ remediation of farmland drainage, and the nitrified sludge is 1L: 1~15g: 2~10mL;

[0027] The ammonia nitrogen concentration in the farmland drainage water is 1.5~10.5 mg / L;

[0028] The processing temperature is 25~30℃, and the processing time is 1~5 days.

[0029] The present invention has at least the following beneficial effects:

[0030] This invention utilizes calcium peroxide, calcium carbonate, tourmaline, and sulfur as raw materials to prepare a slow-release oxygen material for in-situ remediation of farmland runoff. It can efficiently treat low-concentration ammonia nitrogen wastewater in situ, with a long aeration time. It can reduce the system pH while efficiently releasing oxygen, solving the problem of excessive alkalinity in the system caused by chemical oxygenation agents, which makes it difficult for microorganisms to survive. Sulfur and calcium carbonate are excellent sulfur-autotrophic denitrification raw materials. After complete aeration, they are allowed to air-dry for 1-2 days before being directly added to the denitrification reaction section. At this point, the material loses its original strong aeration environment, thus serving as both a microbial attachment material and providing sufficient sulfur and inorganic carbon sources for denitrification, further promoting denitrification. This achieves synergistic nitrification and denitrification, and the material can be reused after oxygen release.

[0031] The raw materials used in this invention are low in cost, the granulation method is simple, the operation is convenient, and the dried material has high hardness and large particle size, which can further solve the problems of small particle size, complicated granulation, and low utilization rate of existing materials. Attached Figure Description

[0032] Figure 1 The figure shows the statistical change of pH value over time when the SO slow-release oxygen material prepared in Example 1 and the O oxygen-releasing material prepared in Comparative Example 2 are used to treat farmland runoff.

[0033] Figure 2 The figure shows the statistical change of dissolved oxygen content over time in the system when the SO slow-release oxygen material prepared in Example 1 and the O oxygen-releasing material prepared in Comparative Example 2 are used to treat farmland runoff.

[0034] Figure 3 The curves showing the change in ammonia nitrogen content in the system when the SO slow-release oxygen material prepared in Example 1 and the O oxygen-releasing material prepared in Comparative Example 2 are used to treat farmland runoff.

[0035] Figure 4 The figure shows the statistical change of pH value over time when SOO slow-release material prepared in Comparative Example 4 and S&O oxygen-releasing material prepared in different amounts in Comparative Example 1 are used to treat farmland runoff.

[0036] Figure 5 The figure shows the statistical change of pH value over time when the SO slow-release oxygen material prepared in Example 2 and the SOO slow-release material prepared in Comparative Example 4 are used to treat farmland runoff.

[0037] Figure 6 This is a statistical graph showing the change of pH value over time when the SO-Si slow-release oxygen material prepared in Example 3 and the O oxygen-releasing material prepared in Comparative Example 5 are used to treat farmland runoff. Detailed Implementation

[0038] This invention provides a slow-release oxygen material for in-situ remediation of farmland drainage, comprising the following raw materials in parts by weight:

[0039] The mixture comprises 1-5 parts of oxygen-releasing agent, 1-5 parts of plastic binder, 1-6 parts of adsorbent mineral, and 1-3 parts of pH buffer, preferably 2-4 parts of oxygen-releasing agent, 2-4 parts of plastic binder, 2-5 parts of adsorbent mineral, and 1.5-2.5 parts of pH buffer, and more preferably 3 parts of oxygen-releasing agent, 3 parts of plastic binder, 3-5 parts of adsorbent mineral, and 2 parts of pH buffer;

[0040] The oxygen-releasing agent includes calcium peroxide and calcium carbonate;

[0041] The pH buffer includes tourmaline and sulfur. Sulfur is mainly produced by biological or chemical oxidation to generate sulfur oxides, which eventually form a stable form of sulfate, producing hydrogen ions and lowering the pH.

[0042] In this invention, the mass ratio of calcium peroxide to calcium carbonate is 1~20:1, preferably 2~15:1, more preferably 3~10:1, and even more preferably 3~5:1.

[0043] In this invention, the plastic bonding material includes cement and river sand.

[0044] In this invention, the mass ratio of cement to river sand is 0.5 to 10:1, preferably 1 to 8:1, more preferably 1.5 to 5:1, and even more preferably 2 to 3:1.

[0045] In this invention, the particle size of the river sand is 10-40 mesh, preferably 15-35 mesh, and more preferably 20-30 mesh.

[0046] In this invention, the adsorbent mineral is zeolite.

[0047] In this invention, the particle size of the zeolite is 20-200 mesh, preferably 40-150 mesh, and more preferably 80-120 mesh.

[0048] In this invention, the sulfur has a particle size of 10-60 mesh, preferably 20-50 mesh, and more preferably 30-40 mesh.

[0049] In this invention, the mass ratio of tourmaline to sulfur is 0.5 to 10:1, preferably 1 to 8:1, more preferably 1.5 to 5:1, and even more preferably 2 to 3:1.

[0050] This invention also provides a method for preparing a slow-release oxygen material for in-situ remediation of farmland drainage, comprising the following steps:

[0051] The oxygen-releasing agent, plastic binder, adsorbent minerals, pH buffer, and water are mixed, granulated, and dried to obtain a slow-release oxygen material for in-situ remediation of farmland drainage.

[0052] In this invention, the mass of each granulated slow-release oxygen material used for in-situ remediation of farmland drainage is 3-7g, preferably 4-6g, and more preferably 5-6g.

[0053] This invention also provides an application of a slow-release oxygen material for in-situ remediation of farmland runoff, characterized by the following application method:

[0054] The ammonia nitrogen in farmland runoff is treated by adding slow-release oxygen materials for in-situ remediation of farmland runoff and inoculating it with acclimatized nitrified sludge.

[0055] In this invention, the mass-to-volume ratio of the farmland drainage, the slow-release oxygen material used for in-situ remediation of farmland drainage, and the inoculated and acclimatized nitrified sludge is 1L:1~15g:2~10mL, preferably 1L:3~10g:4~8mL, and more preferably 1L:5~8g:5~6mL.

[0056] In this invention, the ammonia nitrogen concentration in the farmland drainage is 1.5~10.5 mg / L, preferably 3~10 mg / L, and more preferably 5~8 mg / L.

[0057] In this invention, the processing temperature is 25~30℃, preferably 26~29℃, and more preferably 27~28℃; the processing time is 1~5 days, preferably 2~4 days, and more preferably 3 days.

[0058] In this invention, the acclimation method of the nitrified sludge includes the following steps:

[0059] Nitrified sludge is taken from the sludge in the aeration tank of a sewage treatment plant.

[0060] (1) Nitrifying bacteria were initially acclimatized in a culture medium containing glucose, ammonium chloride and potassium dihydrogen phosphate. The COD of the culture medium was 400 mg / L, the ammonia nitrogen content was 20 mg / L, and the phosphorus content was 4 mg / L. The culture medium was changed every two days during the culture process, and the initial acclimatization time was 10 days.

[0061] (2) When the sludge activity and biomass meet the requirements (ammonia nitrogen removal rate reaches more than 85%, COD removal rate reaches more than 85%), the nitrification sludge acclimatization stage begins. Change the water every two days and add ammonium source (ammonium chloride) and phosphorus source (potassium dihydrogen phosphate) to ensure that the mass ratio of N to P in the system is 20:1. Add a certain amount of sodium bicarbonate every two days to keep the pH of the system at around 7. Place the cleaned aeration head at the bottom and ensure continuous aeration throughout the acclimatization process.

[0062] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0063] Example 1

[0064] One part by weight of 20-mesh river sand, two parts of cement (P.O42.5 silicate cement), and 0.8 parts of oxygen-releasing agent were mixed evenly, wherein the mass ratio of calcium peroxide to calcium carbonate in the oxygen-releasing agent was 3:1. Then, 1.1 parts of 200-mesh zeolite powder were added and mixed evenly. After that, one part of 20-mesh sulfur powder and 0.5 parts of 200-mesh tourmaline powder were added and mixed evenly. Finally, 0.5 parts of water were added and kneaded into a dough. After granulation, the dough was naturally air-dried in a well-ventilated place for 2 days to obtain granular slow-release oxygen material with a mass of 5.8 g / particle, which was denoted as SO slow-release oxygen material.

[0065] Example 2

[0066] 1.5 parts by weight of 20-mesh river sand, 0.5 parts by weight of cement (P.O42.5 silicate cement), and 0.5 parts by weight of oxygen-releasing agent were mixed evenly, wherein the mass ratio of calcium peroxide to calcium carbonate in the oxygen-releasing agent was 3:1. Then, 1.1 parts by weight of 200-mesh zeolite powder were added and mixed evenly. After that, 1 part by weight of 20-mesh sulfur powder and 1 part by weight of 200-mesh tourmaline powder were added and mixed evenly. Finally, 0.5 parts by weight of water were added and kneaded into a dough. After granulation, the dough was naturally air-dried in a well-ventilated place for 2 days to obtain granular slow-release oxygen material with a mass of 5.8 g / particle, denoted as slow-release oxygen material SO.

[0067] Example 3

[0068] One part by weight of 20-mesh river sand, two parts of cement (P.O42.5 silicate cement), and 0.5 parts of oxygen-releasing agent were mixed evenly, wherein the mass ratio of calcium peroxide to calcium carbonate in the oxygen-releasing agent was 3:1. Then, 1.2 parts of 200-mesh zeolite powder were added and mixed evenly. After that, one part of 20-mesh sulfur powder and one part of 200-mesh tourmaline powder were added and mixed evenly. Finally, 0.5 parts of water were added and kneaded into a dough. After granulation, the dough was naturally air-dried in a well-ventilated place for 2 days to obtain granular slow-release oxygen material with a mass of 5.8 g / particle, which was denoted as slow-release oxygen material SO-Si.

[0069] Comparative Example 1

[0070] 1.5 parts by weight of 20-mesh river sand, 0.5 parts by weight of cement (P.O42.5 silicate cement), and 0.5 parts by weight of oxygen-releasing agent were uniformly mixed, wherein the mass ratio of calcium peroxide to calcium carbonate in the oxygen-releasing agent was 3:1. Then, 1.1 parts by weight of 200-mesh zeolite powder were added and mixed evenly. After that, 1 part by weight of 200-mesh tourmaline powder was added and mixed evenly. Finally, 0.5 parts by weight of water were added and kneaded into a dough. After granulation, the dough was naturally air-dried in a well-ventilated place for 2 days to obtain granular slow-release oxygen material with a mass of 5.8 g / particle. At the same time, 50 g / L and 100 g / L of sulfur particles with a diameter of 50 mm were dispersed and added into the system, which were denoted as slow-release oxygen material S&O.

[0071] Comparative Example 2

[0072] The only difference between this comparative example and Example 1 is that sulfur was not added, and the resulting material is referred to as O-oxygen-releasing material.

[0073] Comparative Example 3

[0074] The only difference between this comparative example and Comparative Example 1 is that the amount of sulfur added in this example is 0 g / L, and the resulting material is denoted as O-releasing oxygen material.

[0075] Comparative Example 4

[0076] The only difference between this comparative example and Example 2 is that the amount of oxygen-releasing agent added is 0.8 parts, and the resulting material is denoted as SOO sustained-release material.

[0077] Comparative Example 5

[0078] The only difference between this comparative example and Example 3 is that the amount of cement added is 0.5 parts, and the resulting material is denoted as SO slow-release oxygen material.

[0079] The slow-release oxygen materials prepared in Example 1 and Comparative Example 1, and their treatment capacity for ammonia nitrogen-containing wastewater, were tested using the following methods:

[0080] Aqueous solutions containing 10 mg / L ammonia nitrogen (ammonium chloride), 10.5 mg / L nitrate nitrogen (potassium nitrate, sodium nitrate), and 1.5 mg / L total phosphorus (potassium dihydrogen phosphate, dipotassium hydrogen phosphate, sodium dihydrogen phosphate, disodium hydrogen phosphate) were used to simulate farmland runoff. Oxygen-releasing materials prepared in Example 1 and Comparative Example 2 were added to two treatment systems at a dosage of 3 g / L, followed by 5 mL of nitrifying sludge. Treatment was carried out at 25°C and 150 r / min. Samples were taken every 24 h to measure the pH, dissolved oxygen content, and ammonia nitrogen content of the systems. Figure 1 This is a statistical graph showing the change in pH value of the system over time. Figure 2 This is a statistical graph showing the change of dissolved oxygen content in the system over time. Figure 3 The graph shows the change curve of ammonia nitrogen content in the system. The horizontal axis represents the reaction time, and the vertical axis represents the change of material indicators during the reaction process.

[0081] The above-mentioned nitrified sludge was prepared using the following method:

[0082] The nitrified sludge was taken from the aeration tank sludge of the Ciqu Wastewater Treatment Plant in Beijing. This wastewater treatment plant uses traditional A... 2 In the O process, activated sludge is mainly composed of bacteria, actinomycetes, fungi, protozoa, and metazoa. The sludge is a mixed microbial community system composed of aerobic heterotrophic bacteria, denitrifying bacteria, and nitrifying bacteria. It involves the combined action of microbial species such as Proteobacteria, Actinomycetes, Firmicutes, Bacteroides, Green Curvularia, Planktonic molds, Acidobacteria, Nitrifying Spirogyra, and Verrucous Microbes. Therefore, to screen out the dominant bacterial species most conducive to nitrification, the collected sludge needs to be acclimatized for one month.

[0083] The domestication methods are as follows:

[0084] (1) Nitrifying bacteria were initially acclimatized in a culture medium containing glucose, ammonium chloride and potassium dihydrogen phosphate. The COD of the culture medium was 400 mg / L, the ammonia nitrogen content was 20 mg / L, and the phosphorus content was 4 mg / L. The culture medium was changed every two days during the culture process, and the initial acclimatization time was 10 days.

[0085] (2) When the sludge activity and biomass meet the requirements (ammonia nitrogen removal rate reaches more than 85%, COD removal rate reaches more than 85%), the nitrification sludge acclimatization stage begins. The water is changed every two days, and ammonium source (ammonium chloride) and phosphorus source (potassium dihydrogen phosphate) are added to ensure that the mass ratio of N element to P element in the system is 20:1. A certain amount of sodium bicarbonate is added every two days to keep the pH of the system at around 7. The cleaned aeration head is placed at the bottom, and continuous aeration is ensured throughout the acclimatization process.

[0086] Depend on Figure 1It is known that traditional oxygen-releasing materials that use calcium peroxide as an oxygen-releasing agent and cement as a binder will generate a large amount of calcium hydroxide when they come into contact with water. The free hydroxide ions in the water will cause the pH of the water to rise sharply to about 11, making the system an extremely alkaline environment where microorganisms cannot survive. Therefore, the ammonia nitrogen in the system cannot be degraded, and oxygen will also be wasted. In contrast, the pH of the SO oxygen-releasing material system can always be maintained at the optimal pH for nitrifying microorganisms, and the pH is always below 8.7.

[0087] Depend on Figure 2 It is known that, due to the addition of sulfur to the material, some of the sulfur will be oxidized into sulfur oxides by dissolved oxygen in the water. Therefore, the dissolved oxygen in the system with SO oxygen-releasing material will gradually decrease. Compared with O oxygen-releasing material, the dissolved oxygen stability is poor. However, for nitrifying sludge, the reaction can be completed when the ambient dissolved oxygen is above 4. Therefore, SO oxygen-releasing material has more practical application prospects.

[0088] Depend on Figure 3 It can be seen that the ammonia nitrogen degradation effect of SO oxygen-releasing materials is better than that of O oxygen-releasing materials.

[0089] The above experiments show that after adding sulfur, the pH of the system can be stabilized at around 8, and the material can continuously provide sufficient dissolved oxygen. The degradation effect of ammonia nitrogen is also far superior to that of traditional materials that use calcium peroxide as an oxygen generator and cement as a binder. It has broad application prospects in in-situ remediation of farmland runoff and in-situ nitrification reaction to degrade ammonia nitrogen.

[0090] The slow-release oxygen materials prepared in Comparative Examples 1 and 3, and their treatment capabilities for ammonia-nitrogen-containing wastewater, were tested using the same methods as in Examples 1 and 2. Figure 4 It is known that in the dispersed S&O oxygen-releasing material system, pH is significantly inhibited only when the sulfur dosage is 100 g / L. The sulfur dosage of 50 g / L has no significant effect on the pH regulation of the system. Compared with S&O oxygen-releasing materials, SO oxygen-releasing materials not only require less sulfur, thus solving the problems of material waste and environmental pollution, but also effectively solve the pH problem within the material itself, preventing some sludge from becoming too alkaline, and have broad application prospects.

[0091] The slow-release oxygen materials prepared in Example 2 and Comparative Example 4 were tested for their ability to treat ammonia-nitrogen-containing wastewater. The testing methods were the same as those in Example 1 and Comparative Example 2. Figure 5 It is known that excessive oxygen-releasing agents do not bring benefits to the system's oxygenation; on the contrary, they make the system's pH more difficult to control. Furthermore, when applied to denitrification experiments, the high oxygen-releasing capacity of nitrification experiments will bring certain operational pressures and limitations to the application of denitrification. Therefore, SO oxygen-releasing materials have more practical application prospects.

[0092] The slow-release oxygen materials prepared in Example 3 and Comparative Example 5 were tested for their ability to treat ammonia-nitrogen-containing wastewater. The testing methods were the same as those in Example 1 and Comparative Example 2. Figure 6 It is known that cement is a silicate substance, which will undergo a hydration reaction with water to produce alkaline hydrates, which will also put some pressure on the pH control of the system. At the same time, the cement content of SO oxygen-releasing material is sufficient to make the material have good adhesion and hardness. Therefore, whether from the perspective of cost or effect, SO oxygen-releasing material has more practical application prospects.

[0093] The above experiments show that the SO oxygen-releasing material of this invention, after adding sulfur powder, can stabilize the pH of the system at around 8, and the material can continuously provide sufficient dissolved oxygen. The degradation effect of ammonia nitrogen is also far superior to that of traditional materials using calcium peroxide as an oxygen generator and cement as a binder. It has broad application prospects in in-situ remediation of farmland drainage and in-situ nitrification degradation of ammonia nitrogen.

[0094] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A slow-release oxygen material for in-situ remediation of agricultural field drainage water, characterized by, The raw materials include the following mass fractions: 1-5 parts of oxygen releasing agent, 1-5 parts of plastic binding material, 1-6 parts of adsorptive mineral, and 1-3 parts of pH buffer; The oxygen releasing agent includes calcium peroxide and calcium carbonate; The pH buffer includes tourmaline and sulfur.

2. The slow-release oxygen material for in-situ remediation of farmland drainage water according to claim 1, characterized in that, The mass ratio of the calcium peroxide and the calcium carbonate is 1-20:

1.

3. The slow-release oxygen material for in-situ remediation of farmland drainage water according to claim 2, characterized in that, The plastic binding material includes cement and river sand; The mass ratio of the cement and the river sand is 0.5-10:1; The particle size of the river sand is 10-40 mesh.

4. The slow-release oxygen material for in-situ remediation of farmland drainage water according to claim 3, characterized in that, The adsorptive mineral is zeolite; The particle size of the zeolite is 20-200 mesh.

5. The slow-release oxygen material for in-situ remediation of agricultural field drainage water according to claim 4, characterized in that, The particle size of the sulfur is 10-60 mesh.

6. The slow-release oxygen material for in-situ remediation of agricultural field drainage water according to claim 5, characterized in that, The mass ratio of the tourmaline and the sulfur is 0.5-10:

1.

7. The method for producing the slow-release oxygen material for in-situ remediation of farmland drainage water according to any one of claims 1 to 6, characterized by, The method includes the following steps: Mixing the oxygen releasing agent, the plastic binding material, the adsorptive mineral, the pH buffer, and water, granulating, and drying to obtain the slow-release oxygen material for in-situ remediation of farmland drainage water.

8. The method of claim 7, wherein the method further comprises the step of adding a binder to the mixture of the porous oxygen carrier and the water-soluble polymer. The mass of each granule of the slow-release oxygen material for in-situ remediation of farmland drainage water is 3-7 g.

9. Use of the slow-release oxygen material for in-situ remediation of farmland runoff water according to any one of claims 1 to 6 or the slow-release oxygen material prepared by the preparation method according to any one of claims 7 to 8 for remediation of farmland runoff water, characterized in that, The application method is as follows: Adding the slow-release oxygen material for in-situ remediation of farmland drainage water and inoculating nitrifying sludge to the farmland drainage water to treat the ammonia nitrogen in the farmland drainage water.

10. The use of a slow-release oxygen material for the remediation of agricultural runoff in situ according to claim 9, characterized in that, The mass-volume ratio of the farmland drainage water, the slow-release oxygen material for in-situ remediation of farmland drainage water, and the nitrifying sludge is 1 L:1-15 g:2-10 mL; The ammonia nitrogen concentration in the farmland drainage water is 1.5-10.5 mg / L; The treatment temperature is 25-30℃, and the treatment time is 1-5 days.

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