A hematite-based nitrate wastewater treatment method

Abstract

The present application belongs to the technical field of wastewater treatment, and specifically discloses a nitrate wastewater treatment method based on hematite. The present application first adds hematite in a nitrate wastewater treatment reactor and inoculates sludge; then performs sludge domestication; then keeps inorganic carbon source and sulfur source in the treatment system, takes the nitrate wastewater to be treated as influent, and inputs the nitrate wastewater treatment reactor to perform sulfur autotrophic denitrification treatment, thereby completing the treatment of the nitrate wastewater. The present application adds hematite, which plays a role in enriching bacterial flora, promoting sulfur oxidation and Fe 2+ / Fe 3+ cycle in the sulfur autotrophic denitrification treatment of the nitrate wastewater, improves the electron supply and electron transfer efficiency of denitrification, shortens the system start-up period, promotes microbial cooperation, and improves the effect of operation stability.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to a method for treating nitrate wastewater based on hematite. Background Technology

[0002] With the continuous improvement of wastewater discharge standards and increasingly stringent requirements for water pollution control in my country, the demand for nitrogen removal efficiency in nitrate wastewater is constantly rising. High-efficiency nitrogen removal has become a pressing technical problem in the wastewater treatment field. Biological nitrogen removal technology is widely used in municipal sewage and various industrial wastewater treatments due to its low operating costs and stable treatment effects. Current nitrate wastewater treatment mainly employs heterotrophic denitrification technology, using organic matter such as methanol, sodium acetate, and glucose as electron donors to reduce nitrates to nitrogen gas under the action of denitrifying microorganisms. This process has high nitrogen removal efficiency, but requires continuous addition of external organic carbon sources, resulting in high operating costs and potentially increasing sludge production and effluent organic matter concentration. For nitrate wastewater with a low C / N ratio (C / N), additional organic carbon sources are usually required to maintain stable denitrification, further increasing operating costs and the risk of secondary pollution.

[0003] Sulfur autotrophic denitrification technology uses inorganic sulfur compounds such as sulfides, thiosulfates, and elemental sulfur as electron donors. Under the action of sulfur-oxidizing autotrophic denitrifying microorganisms, inorganic sulfur-containing compounds are oxidized to release electrons, while nitrates are reduced to nitrogen gas, without the need for additional organic carbon sources. Compared with heterotrophic processes, this technology can significantly reduce sludge production (approximately 55%), reduce greenhouse gas emissions (95-100%), and reduce operating costs (approximately 80%). It can be applied to the treatment of low C / N ratio nitrate wastewater, such as municipal wastewater deep denitrification, industrial wastewater, groundwater, aquaculture wastewater, and landfill leachate. Existing sulfur autotrophic denitrification technologies mainly rely on sulfur autotrophic denitrifying microorganisms such as Thiobacillus and Sulfurimonas to oxidize inorganic sulfur-containing compounds to release electrons and complete nitrate reduction through microbial metabolism. Therefore, this process is highly dependent on the enrichment of sulfur autotrophic denitrification functional bacteria, while the enrichment rate of functional bacteria is relatively slow. The synergistic effect between sulfur oxidizing bacteria, denitrifying bacteria and other functional microorganisms is limited, resulting in a long system start-up period and easy fluctuations in denitrification performance during operation.

[0004] To improve the nitrogen removal performance of sulfur autotrophic denitrification systems, existing technologies employ the addition of iron-containing materials such as ferric ions, pyrite, magnetite, and siderite to enhance the electron transfer process, thus improving the system's nitrogen removal efficiency to some extent. However, these iron-containing materials generally suffer from slow mineral dissolution rates, limited electron release capacity, and susceptibility to passivation on their surfaces, making it difficult to maintain high electron transfer efficiency. Furthermore, some iron-sulfur minerals may undergo abiotic nitrate reduction reactions during the reaction, generating byproducts such as ammonium nitrogen, reducing electron utilization efficiency and increasing the difficulty of byproduct control.

[0005] Therefore, it is still necessary to develop a mineral-coupled sulfur autotrophic denitrification method that can improve electron transfer efficiency and is applicable to various inorganic sulfur-containing electron donor systems such as sulfides, thiosulfates and elemental sulfur, in order to solve the technical problems of existing sulfur autotrophic denitrification technologies, such as long system start-up cycle, low electron transfer efficiency and unstable denitrification performance. Summary of the Invention

[0006] In view of this, the present invention provides a method for treating nitrate wastewater based on hematite, in order to solve the problems of low electron transfer efficiency, long system start-up cycle, limited denitrification efficiency, insufficient microbial synergy and poor operational stability of existing schemes for improving sulfur autotrophic denitrification systems.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A method for treating nitrate wastewater based on hematite includes the following steps: 1) Add hematite to the nitrate wastewater treatment reactor and inoculate with sludge, then perform sludge acclimatization; 2) With the presence of inorganic carbon and sulfur sources in the treatment system, the nitrate wastewater to be treated is used as influent and fed into the nitrate wastewater treatment reactor for sulfur autotrophic denitrification treatment to complete the treatment of nitrate wastewater.

[0008] Preferably, the hematite has a particle size of 0.5~5 mm and the mass percentage of Fe2O3 in the hematite is ≥50%; The ratio of the amount of hematite added to the effective volume of the nitrate wastewater treatment reactor is 10~100 g / L.

[0009] Preferably, the hematite includes natural hematite and / or modified hematite; The modified hematite includes one or more of acid-washed modified hematite, surface-modified hematite, and hematite modified with a conductive material load.

[0010] Preferably, the sludge includes one or more of anaerobic activated sludge, denitrifying sludge, and sulfur autotrophic denitrifying sludge; The concentration of the inoculated sludge was 6-25 g VSS / L.

[0011] Preferably, the inorganic carbon source includes sodium bicarbonate; The sulfur source includes one or more of elemental sulfur, sulfur-containing fillers supported on a carrier, monosulfides, and thiosulfates.

[0012] Preferably, when the sulfur source is a soluble substance, the nitrate wastewater treatment method involves adding hematite to the nitrate wastewater treatment reactor, inoculating it with sludge, and then performing sludge acclimatization. Inorganic carbon source and sulfur source are mixed with the nitrate wastewater to be treated and used as influent. The mixture is then introduced into the nitrate wastewater treatment reactor to carry out sulfur autotrophic denitrification treatment, thereby completing the treatment of the nitrate wastewater. When the sulfur source is an insoluble substance, the nitrate wastewater treatment method is as follows: add hematite and sulfur source to the nitrate wastewater treatment reactor, inoculate sludge, and then carry out sludge acclimatization. Inorganic carbon source is mixed with the nitrate wastewater to be treated and used as influent. This influent is then fed into the nitrate wastewater treatment reactor for sulfur autotrophic denitrification treatment, thus completing the treatment of the nitrate wastewater.

[0013] Preferably, when the sulfur source is soluble, the amount of inorganic carbon source and sulfur source added in step 2) is to maintain the molar ratio of nitrogen, carbon and sulfur in the influent at 24:8~16:15~30. When the sulfur source is a time-insoluble substance, the amount of inorganic carbon source added in step 2) is to maintain the molar ratio of nitrogen to carbon in the influent at 3:1~2; the amount of sulfur source added is 60~80% of the effective volume of the nitrate wastewater treatment reactor.

[0014] Preferably, the nitrate nitrogen concentration in the nitrate wastewater to be treated is 30~200 mg / L, and the ratio of chemical oxygen demand to total nitrogen mass concentration is 0~2.

[0015] Preferably, the treatment temperature of the sulfur autotrophic denitrification treatment in step 2) is 25~35℃, and the hydraulic retention time is 3~48 h.

[0016] Preferably, the sulfur autotrophic denitrification treatment in step 2) is carried out under light conditions, and the light intensity is 4000~6000 lx.

[0017] As can be seen from the above technical solution, compared with the prior art, the present invention has the following beneficial effects: 1. This invention can significantly enrich sulfur-oxidizing and denitrifying bacteria by adding hematite, thus shortening the system start-up time.

[0018] 2. The hematite added in this invention can selectively enrich sulfur-oxidizing bacteria, denitrifying bacteria, and iron-cycling functional bacteria, including dominant genera such as Thiobacillus, Denitratisoma, Geobacter, and Geothrix. It also increases the abundance of sulfur oxidation-related genes (soxA, soxB, soxX, soxY, soxZ), iron redox cycle-related genes (cyc1, coxA, coxB, fpr, petJ), and extracellular electron transport-related genes (pilB-pilZ, ccmF / G / H / Z), thereby enhancing the system's electron generation, electron transport, and electron utilization capabilities. This achieves efficient coupling of the iron cycle, sulfur cycle, and denitrification process, further improving denitrification performance and operational stability.

[0019] 3. The hematite used in this invention is widely available, inexpensive, and chemically stable. It can enhance the sulfur autotrophic denitrification process without the need for additional organic carbon sources. It can be applied to the treatment of nitrate-polluted wastewater such as low C / N ratio industrial wastewater, petrochemical wastewater, groundwater, and municipal tailwater. It has advantages such as low operating costs, low sludge production, high system stability, and ease of engineering implementation. This technology provides a highly efficient, stable, and easily engineering-implemented enhancement strategy for sulfur autotrophic denitrification processes.

[0020] 4. Hematite can optimize electron flow distribution, significantly improve total nitrogen removal efficiency, achieve efficient and stable denitrification, and reduce the production of excess sludge. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0022] Figure 1 This is a comparison chart of the total nitrogen removal effect in Example 1 of the present invention; Figure 2 This is a comparison chart of sludge concentration in Example 1 of the present invention; Figure 3 This is a comparison chart of the total nitrogen removal effect in Example 2 of the present invention; Figure 4 This is a comparison chart of the total nitrogen removal effect in Example 3 of the present invention. Detailed Implementation

[0023] This invention provides a method for treating nitrate wastewater based on hematite, comprising the following steps: 1) Add hematite to the nitrate wastewater treatment reactor and inoculate with sludge, then perform sludge acclimatization; 2) With the presence of inorganic carbon and sulfur sources in the treatment system, the nitrate wastewater to be treated is used as influent and fed into the nitrate wastewater treatment reactor for sulfur autotrophic denitrification treatment to complete the treatment of nitrate wastewater.

[0024] In this invention, hematite is introduced as a functional iron mineral into a sulfur autotrophic denitrification system. By promoting the synergistic effect of iron and sulfur cycles, it enhances the extracellular electron transfer of microorganisms, improves the electron utilization efficiency of inorganic sulfur-containing electron donors, promotes the enrichment of functional microorganisms, and achieves efficient removal of nitrate nitrogen and total nitrogen from nitrate wastewater. It also shortens the system start-up cycle, promotes microbial synergy, and improves operational stability.

[0025] In this invention, the particle size of the hematite is 0.5~5 mm, specifically 0.8 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.2 mm, 3.5 mm, 3.8 mm, 4 mm, 4.2 mm, 4.5 mm, and 4.8 mm; the mass percentage of Fe2O3 in the hematite is ≥50%, specifically 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, and 95%.

[0026] In this invention, the ratio of the amount of hematite added to the effective volume of the nitrate wastewater treatment reactor is 10~100 g / L, specifically 20 g / L, 40 g / L, 50 g / L, 60 g / L, or 80 g / L.

[0027] In this invention, the hematite includes natural hematite and / or modified hematite; the modified hematite includes one or more of acid-washed modified hematite, surface-modified hematite, and hematite modified with conductive materials.

[0028] In this invention, the sludge includes one or more of anaerobic activated sludge, denitrifying sludge, and sulfur autotrophic denitrifying sludge.

[0029] In this invention, the concentration of the inoculated sludge is 6~25 g VSS / L, specifically 8 g VSS / L, 10 g VSS / L, 12 g VSS / L, 15 g VSS / L, 18 g VSS / L, 20 g VSS / L, or 22 g VSS / L.

[0030] In this invention, the sludge acclimation treatment conditions are the same as the sulfur autotrophic denitrification treatment conditions.

[0031] In this invention, the inorganic carbon source includes sodium bicarbonate; the sulfur source includes one or more of elemental sulfur, sulfur-containing fillers supported on a carrier, monosulfides, and thiosulfates.

[0032] In this invention, when the sulfur source is a soluble substance, the nitrate wastewater treatment method involves adding hematite to the nitrate wastewater treatment reactor, inoculating it with sludge, and then performing sludge acclimatization. Inorganic carbon source and sulfur source are mixed with the nitrate wastewater to be treated and used as influent. This influent is then fed into the nitrate wastewater treatment reactor for sulfur autotrophic denitrification treatment, thus completing the treatment of the nitrate wastewater.

[0033] In this invention, when the sulfur source is soluble, the amount of inorganic carbon source and sulfur source added in step 2) is to maintain the molar ratio of nitrogen, carbon and sulfur in the influent at 24:8~16:15~30, preferably 24:10~14:17~25, and more preferably 6:3:5; the carbon element in the ratio is inorganic carbon.

[0034] In this invention, when the sulfur source is an insoluble substance, the nitrate wastewater treatment method is as follows: hematite and sulfur source are added to the nitrate wastewater treatment reactor, and sludge is inoculated, followed by sludge acclimatization. Inorganic carbon source is mixed with the nitrate wastewater to be treated and used as influent. This influent is then fed into the nitrate wastewater treatment reactor for sulfur autotrophic denitrification treatment, thus completing the treatment of the nitrate wastewater.

[0035] In this invention, when the sulfur source is a time-insoluble substance, the amount of inorganic carbon source added in step 2) is to maintain the molar ratio of nitrogen to carbon in the influent at 3:1~2, preferably 3:1.2~1.8, and more preferably 3:1.5; the amount of sulfur source added is 60~80% of the effective volume of the nitrate wastewater treatment reactor, specifically 62%, 65%, 68%, 70%, 72%, 75%, 78%, and the carbon element in the ratio is inorganic carbon.

[0036] In this invention, the nitrate nitrogen concentration in the nitrate wastewater to be treated is 30~200 mg / L, specifically 40 mg / L, 50 mg / L, 80 mg / L, 100 mg / L, 120 mg / L, 150 mg / L, or 180 mg / L; the ratio of chemical oxygen demand to total nitrogen mass concentration is 0~2, specifically 0.1, 0.2, 0.5, 0.8, 1, 1.2, 1.5, or 1.8.

[0037] In this invention, the treatment temperature of the sulfur autotrophic denitrification treatment in step 2) is 25~35℃, specifically 26℃, 28℃, 30℃, 32℃, or 34℃; the hydraulic retention time is 3~48 h, specifically 4 h, 6 h, 8 h, 10 h, 12 h, 18 h, 24 h, 30 h, or 36 h.

[0038] In this invention, the sulfur autotrophic denitrification treatment in step 2) can be carried out under no light conditions or under light conditions. The light intensity is preferably 4000~6000 lx, specifically 4200 lx, 4500 lx, 4800 lx, 5000 lx, 5200 lx, 5500 lx, or 5800 lx; ​​the light is preferably white light.

[0039] In this invention, light is introduced into the sulfur autotrophic denitrification system containing hematite. Through the photoresponse characteristics of hematite and the synergistic effect of the iron redox cycle, the electron transfer process can be promoted, the electron utilization efficiency of inorganic sulfur electron donors can be improved, thereby enhancing the nitrate reduction and denitrification process.

[0040] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] Example 1

[0042] An upflow anaerobic sludge blanket reactor with an effective volume of 5.14 L was used (temperature 31℃, hydraulic retention time 24 h). Natural hematite was used, soaked in a 10% (v / v) hydrochloric acid solution for 1 min to remove surface impurities. The treated hematite was repeatedly washed with deionized water until the wash solution pH was neutral. It was then dried at 105℃ for 12 h, and further crushed and screened to obtain hematite particles with a diameter of 3–5 mm (Fe₂O₃ mass percentage 83.9%). The hematite dosage was 87.5 g / L. Autotrophic denitrification sludge (thickening tank sludge from a chemical refinery wastewater treatment plant) was used as inoculum sludge with a concentration of 11.57 g VSS / L. Artificially prepared nitrate-containing wastewater (with pre-added inorganic carbon and sulfur sources) was used as influent. Sludge acclimation and nitrate wastewater treatment were carried out under conditions without light.

[0043] Artificial nitrate wastewater was prepared by dissolving sodium nitrate in tap water to obtain a solution of 303.6 mg / L, corresponding to an initial nitrate nitrogen concentration of approximately 50 mg / L. To ensure the supply of nutrients required for microbial growth, 0.05 g / L KH₂PO₄, 0.20 g / L MgCl₂, and a 1 mL / L trace element solution were added to the wastewater. The composition of the trace element solution (per liter) was as follows: 15 mg EDTA, 0.43 mg ZnSO₄·7H₂O, 0.24 mg CoCl₂·6H₂O, 0.99 mg MnCl₂·4H₂O, 0.25 mg CuSO₄·5H₂O, 0.22 mg Na₂MoO₄·2H₂O, 0.19 mg AlCl₃, 0.014 mg H₃BO₃, 0.5 mg FeCl₃·6H₂O, with a chemical oxygen demand (COD) to total nitrogen mass concentration ratio of 0.06–0.1. A sulfide-driven autotrophic denitrification system was established by supplementing artificially prepared nitrate wastewater with NaHCO3 and Na2S·9H2O. NaHCO3 served as an inorganic carbon source, and Na2S·9H2O served as a sulfur source (electron donor). The addition was carried out according to the molar ratio of nitrogen, carbon (inorganic carbon), and sulfur (N:C:S) of 6:3:5.

[0044] Simultaneously, a control group without hematite and an experimental group with pyrite (particle size 3-5 mm, dosage 87.5 g / L, FeS2 mass percentage 87.1%) were set up as controls (except for the differences mentioned above, the control experiment was consistent with the experiment in Example 1). The comparison of the total nitrogen removal effects of the hematite-added experimental group (denoted as the hematite group), the pyrite-added experimental group (denoted as the pyrite group), and the control group is shown in the figure below. Figure 1 As shown in the figure, the comparison chart of sludge concentration is as follows: Figure 2 As shown.

[0045] pass Figure 1 and Figure 2It can be seen that hematite can significantly promote the rapid start-up of sulfide-driven autotrophic denitrification systems. The hematite group established stable nitrogen removal capacity in just 8 days, while the control group required 19 days to reach a stable operating state, indicating that hematite can significantly shorten the system start-up cycle. After entering the stable operation stage, the hematite group showed superior nitrogen removal performance, with an average total nitrogen removal rate of 94.92%, significantly higher than the pyrite group (90.36%) and the control group (77.07%). At the same time, the nitrate nitrogen concentration in the effluent of the hematite group was only 2.76 mg / L, indicating that hematite promoted the reduction of nitrate to nitrogen and improved electron utilization efficiency. Comparing the reactor sludge concentration after 40 days of operation, the sludge concentration in the pyrite group increased by 12.30% compared to the control group, while the sludge concentration in the hematite group decreased by 9.36%, indicating that hematite not only improved the nitrogen removal efficiency but also effectively reduced the amount of excess sludge, which is beneficial to reducing sludge disposal costs.

[0046] Example 2

[0047] The experiment was conducted in an anaerobic bottle, which was placed in a constant-temperature shaker at 31°C and 150 r / min, using a semi-continuous water influent method. Every 48 hours, 50% of the reaction liquid volume in the anaerobic bottle was discharged, and an equal volume of prepared nitrate wastewater (same as in Example 1) was added to maintain a constant total volume of reaction liquid in the anaerobic bottle. Hematite was added to the anaerobic bottle (treatment method same as in Example 1), and white LED light strips were evenly wrapped around the outer wall of the anaerobic bottle to ensure uniform illumination, with the illumination intensity controlled at 5000 lx. The hematite dosage was 10 g / L. Sludge with autotrophic denitrification activity (sludge from the sludge thickening tank of a chemical wastewater treatment plant) was used as inoculum sludge, with an inoculum sludge concentration of 20.62 g VSS / L. Artificially prepared nitrate-containing wastewater (same as in Example 1) was used as influent for sludge acclimation and nitrate wastewater treatment.

[0048] Simultaneously, a control group without hematite and an experimental group without illumination were set up. The comparison graph of the total nitrogen removal effect of the experimental group with added hematite and provided illumination (denoted as the hematite-coupled illumination group), the experimental group with added hematite but without illumination (denoted as the hematite-uncoupled illumination group), and the control group is shown below. Figure 3 As shown.

[0049] pass Figure 3It can be seen that both hematite and hematite-coupled light irradiation can promote the sulfide-driven autotrophic denitrification system to reach a higher nitrogen removal level more quickly. After 15 days of operation, the total nitrogen removal rates of the uncoupled and coupled hematite groups reached 80.7% and 87.5%, respectively, and remained stable above 80% during subsequent operation. In contrast, the control group only reached a total nitrogen removal rate of 80.7% on day 21. Furthermore, the coupled hematite group reached 91.70% on day 17, while the total nitrogen removal rates of the control and uncoupled hematite groups did not reach 90% throughout the entire operation cycle. This indicates that coupled hematite irradiation can accelerate the start-up and improve the nitrogen removal performance of the sulfur-driven autotrophic denitrification system, enabling the system to reach a higher total nitrogen removal level more quickly.

[0050] Example 3

[0051] An upflow anaerobic sludge blanket reactor with an effective volume of 4 L was used (temperature 31℃, hydraulic retention time 24h). 4 kg of sulfur packing material (94% elemental sulfur content, particle size 3-6 mm, accounting for 60% of the reactor's effective volume) and 240 g of hematite (dosage 60 g / L, treatment method the same as in Example 1) were added to the reactor. Sulfide-driven autotrophic denitrification sludge, acclimated and cultured in the laboratory under nitrate nitrogen concentration of 50 mg / L, was used as inoculum sludge with a concentration of 12.3 g VSS / L. Artificially prepared nitrate-containing wastewater (with pre-added inorganic carbon source) was used as influent, and sludge acclimation and nitrate wastewater treatment were carried out under conditions without light.

[0052] Artificial nitrate wastewater was prepared by dissolving sodium nitrate in tap water to obtain a solution of 607.1 mg / L, corresponding to an initial nitrate nitrogen concentration of approximately 100 mg / L. To ensure the supply of nutrients required for microbial growth, 0.05 g / L KH₂PO₄, 0.20 g / L MgCl₂, and a 1 mL / L trace element solution were added to the wastewater. The composition of the trace element solution (per liter) was as follows: 15 mg EDTA, 0.43 mg ZnSO₄·7H₂O, 0.24 mg CoCl₂·6H₂O, 0.99 mg MnCl₂·4H₂O, 0.25 mg CuSO₄·5H₂O, 0.22 mg Na₂MoO₄·2H₂O, 0.19 mg AlCl₃, 0.014 mg H₃BO₃, 0.5 mg FeCl₃·6H₂O, with a chemical oxygen demand (COD) to total nitrogen mass concentration ratio of 0.03–0.05. The inorganic carbon source required for sulfur autotrophic denitrification is supplemented by adding NaHCO3 to artificially prepared nitrate wastewater. The dosage is based on a molar ratio of nitrogen to carbon (inorganic carbon) of 2:1.

[0053] A control group without hematite was also set up. The comparison of total nitrogen removal effects between the hematite-added experimental group (denoted as the sulfur-hematite group) and the control group without hematite (denoted as the sulfur group) is shown in the figure below. Figure 4 As shown.

[0054] Depend on Figure 4 It was found that the total nitrogen removal rate of the sulfur group was below 90% from day 1 to day 16, only reaching 90.56% for the first time on day 17. In contrast, the total nitrogen removal rate of the sulfur-hematite group reached 91.54% on day 4 and remained between 91.34% and 95.10% thereafter. Over the entire 22-day operating cycle, the average total nitrogen removal rate of the sulfur-hematite group was 92.15%, an increase of 3.32 percentage points compared to the sulfur group's 88.83%. These results indicate that the addition of hematite enables the system to reach a higher nitrogen removal level more quickly and improves the system's total nitrogen removal performance.

[0055] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0056] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for treating nitrate wastewater based on hematite, characterized in that, Includes the following steps: 1) Add hematite to the nitrate wastewater treatment reactor and inoculate with sludge, then perform sludge acclimatization; 2) With the presence of inorganic carbon and sulfur sources in the treatment system, the nitrate wastewater to be treated is used as influent and fed into the nitrate wastewater treatment reactor for sulfur autotrophic denitrification treatment to complete the treatment of nitrate wastewater.

2. The method for treating nitrate wastewater based on hematite according to claim 1, characterized in that, The hematite has a particle size of 0.5~5 mm and the mass percentage of Fe2O3 in the hematite is ≥50%; The ratio of the amount of hematite added to the effective volume of the nitrate wastewater treatment reactor is 10~100 g / L.

3. The method for treating nitrate wastewater based on hematite according to claim 2, characterized in that, The hematite includes natural hematite and / or modified hematite; The modified hematite includes one or more of acid-washed modified hematite, surface-modified hematite, and hematite modified with a conductive material load.

4. A method for treating nitrate wastewater based on hematite according to any one of claims 1 to 3, characterized in that, The sludge includes one or more of anaerobic activated sludge, denitrifying sludge, and sulfur autotrophic denitrifying sludge; The concentration of the inoculated sludge was 6-25 g VSS / L.

5. The method for treating nitrate wastewater based on hematite according to claim 4, characterized in that, The inorganic carbon source includes sodium bicarbonate; The sulfur source includes one or more of elemental sulfur, sulfur-containing fillers supported on a carrier, monosulfides, and thiosulfates.

6. The method for treating nitrate wastewater based on hematite according to claim 5, characterized in that, When the sulfur source is a soluble substance, the nitrate wastewater treatment method is to add hematite to the nitrate wastewater treatment reactor, inoculate sludge, and then carry out sludge acclimatization. Inorganic carbon source and sulfur source are mixed with the nitrate wastewater to be treated and used as influent. The mixture is then introduced into the nitrate wastewater treatment reactor to carry out sulfur autotrophic denitrification treatment, thereby completing the treatment of the nitrate wastewater. When the sulfur source is an insoluble substance, the nitrate wastewater treatment method is as follows: add hematite and sulfur source to the nitrate wastewater treatment reactor, inoculate sludge, and then carry out sludge acclimatization. Inorganic carbon source is mixed with the nitrate wastewater to be treated and used as influent. This influent is then fed into the nitrate wastewater treatment reactor for sulfur autotrophic denitrification treatment, thus completing the treatment of the nitrate wastewater.

7. The method for treating nitrate wastewater based on hematite according to claim 6, characterized in that, When the sulfur source is soluble, the amount of inorganic carbon source and sulfur source added in step 2) is to maintain the molar ratio of nitrogen, carbon and sulfur in the influent at 24:8~16:15~30. When the sulfur source is a time-insoluble substance, the amount of inorganic carbon source added in step 2) is to maintain the molar ratio of nitrogen to carbon in the influent at 3:1~2; the amount of sulfur source added is 60~80% of the effective volume of the nitrate wastewater treatment reactor.

8. A method for treating nitrate wastewater based on hematite according to claim 6 or 7, characterized in that, The nitrate nitrogen concentration in the nitrate wastewater to be treated is 30~200 mg / L, and the ratio of chemical oxygen demand to total nitrogen mass concentration is 0~2.

9. A method for treating nitrate wastewater based on hematite according to claim 8, characterized in that, The treatment temperature for the sulfur autotrophic denitrification process described in step 2) is 25~35℃, and the hydraulic retention time is 3~48 h.

10. A method for treating nitrate wastewater based on hematite according to claim 9, characterized in that, The sulfur autotrophic denitrification treatment described in step 2) is carried out under light conditions, with a light intensity of 4000~6000 lx.

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