Anaerobic ammonia oxidation enhanced denitrification device and method based on electron mediator type biological carrier and iron oxide

Abstract

The invention belongs to the technical field of sewage treatment, and discloses an anaerobic ammonia oxidation enhanced denitrification device and method based on an electron mediator type biological carrier and iron oxide. The anaerobic ammonia oxidation enhanced denitrification device comprises a reactor main body, a heat preservation circulating water device, a stirring device, a water inlet pipeline and a water outlet pipeline, anaerobic ammonium oxidation bacteria are contained in the reactor main body, a certain proportion of electron mediator type biological carriers are filled in the reactor, and a proper amount of iron oxide is added; wherein the added high-valence iron oxide can be used as an extracellular electron acceptor of anaerobic ammonium oxidation bacteria, the electron mediator type carrier can be used as a redox mediator, and nitrogen removal of the anaerobic ammonium oxidation system is promoted by strengthening the extracellular electron transfer process of the anaerobic ammonium oxidation bacteria.

Description

Technical Field

[0001] The invention belongs to the technical field of sewage treatment, and relates to an anaerobic ammonia oxidation enhanced denitrification device and method based on an electron mediator-type biological carrier and iron oxides. Background Art

[0002] Nitrogen pollution is one of the primary pollution indicators affecting the safety of water quality in my country. Excessive discharge of nitrogen will cause water quality deterioration and eutrophication. The traditional nitrification-denitrification process currently used in sewage treatment plants for denitrification requires aeration and additional carbon source addition, which is not conducive to reducing carbon emissions from sewage. The anaerobic ammonia oxidation process (Anaerobic ammonia oxidation, Anammox) uses nitrite as an electron acceptor to oxidize ammonia to nitrogen and nitrate anaerobically. Compared with traditional biological denitrification technology, it has the advantages of less aeration, less sludge production, less greenhouse gas emissions, and no need for organic carbon sources. However, due to the slow growth and low activity of anaerobic ammonia oxidation bacteria (Anaerobic ammonia oxidation bacteria, AnAOB), this process is limited in actual engineering applications. Therefore, ensuring that it has high retention and high activity in the reactor is very important for the rapid start-up and stable operation of the system.

[0003] Recent studies have shown that AnAOB is an electroactive microorganism with extracellular electron transfer (EET). Its intracellular electrons can pass through the bacterial cell membrane and transfer to extracellular electron acceptors. By strengthening this process, the enrichment effect and metabolic activity of AnAOB can be significantly improved. However, in the actual environment, the extracellular electron transfer process of AnAOB is blocked, mainly due to the lack of extracellular electron acceptors and the low efficiency of electron transfer. Therefore, artificial addition of extracellular electron acceptors and electron mediators is expected to enhance the extracellular electron transfer process of AnAOB. ​​Among them, iron oxides have recently been found to be an extracellular electron acceptor of AnAOB, which promotes the extracellular electron transfer of Anammox by reducing high-valent iron to low-valent iron. In addition, iron is also a trace element necessary for the metabolism and growth of AnAOB. ​​It stimulates the secretion of extracellular polymer EPS, participates in the synthesis of key enzymes in cytochrome c and Anammox reaction process, and regulates the metabolic growth of AnAOB. However, iron oxides are insoluble extracellular electron acceptors with a slow extracellular electron transfer rate, while redox mediators / electron mediators / electron shuttles (RMs) have the ability to act as electron carriers and can promote the transfer of electrons between microorganisms and electron donors / acceptors by being reversibly oxidized and reduced. If electron mediators are added directly, they may be lost from the reactor with the water flow and cannot be recycled. Therefore, we introduce this electron mediator into the biological carrier, so that the electrons generated in the AnAOB attached to the biological carrier can be directly captured by the electron mediator on the carrier, and then transferred to the iron oxide as an extracellular electron acceptor, thereby greatly improving the efficiency of extracellular electron transfer and ultimately strengthening the denitrification of the Anammox system. Summary of the invention

[0004] The purpose of the present invention is to provide an anaerobic ammonium oxidation enhanced denitrification device and method based on electron mediator-type biological carriers and iron oxides, which uses the electron mediator in the biological carrier as a redox mediator and iron oxides as an extracellular electron acceptor to promote the extracellular electron transfer rate, thereby increasing the activity of anaerobic ammonium oxidizing bacteria and ultimately improving the nitrogen removal efficiency in sewage.

[0005] The technical solution of the present invention:

[0006] An anaerobic ammonium oxidation enhanced denitrification device based on electron mediator type biological carrier and iron oxide comprises a reactor body, a heat-insulating circulating water device, a stirring device, an inlet pipe and an outlet pipe; the reactor body is provided with a stirring device, on which a pipe interface for inlet and outlet is opened, which is respectively connected with the inlet pipe and the outlet pipe; the reactor body is a double-layer shell, which cooperates with the heat-insulating circulating water device to control the temperature in the reactor body; the reactor body is inoculated with anaerobic ammonium oxidation sludge, the inside of the reactor body is filled with electron mediator type biological carrier, the filling ratio is 10-50% of the effective volume of the reactor, and iron oxide is added, and the addition amount is 1-15g / L of the effective volume of the reactor.

[0007] The electron mediator-type biocarrier is prepared by melt blending a polymer base material and a modified functional material, wherein the addition ratio of the modified functional material does not exceed 20% of the mass fraction of the polymer base material; the polymer base material is any one of polyethylene, polypropylene, polystyrene, and polyvinyl chloride; the modified functional material is any one of carbon-based materials such as biochar, activated carbon, carbon nanotubes, and graphene, and contains rich redox active functional groups such as phenolic hydroxyl, carbonyl, quinone, and carboxyl groups, and can be used as an electron mediator in the extracellular electron transfer process of anaerobic ammonia oxidation, mediating the utilization of exogenous insoluble extracellular electron acceptors by anaerobic ammonia oxidizing bacteria.

[0008] For carbon materials with less redox active functional groups in modified functional materials, preliminary pretreatment operations are required, including acid treatment, alkali treatment, oxidant oxidation and Hummer method. Specifically, acid treatment uses HNO 3 , H 2 SO 4 , HCl, H 3 PO 4 , KOH and NaOH are used for alkali treatment, and H 2 O 2 、HMnO 4, NaOCl single or mixture, reagent concentration 2-65% (mass fraction), soak or suspend the carbon material at room temperature to 120℃ with a ratio of 1:5-1:20 (carbon material mass g: solution volume mL) for 1-24h; Hummer method is specifically as follows: slowly add the carbon material to a mixture of concentrated sulfuric acid and sodium nitrate under an ice bath, add potassium permanganate solution within 1h, stir and cool for 2h, stir vigorously at room temperature for 2-5 days, add sulfuric acid to the obtained dark brown viscous liquid, stir at 80℃ for 30-60min, then stir at 98℃ for 30-120min, lower the temperature to 60℃, then add hydrogen peroxide solution, stir at room temperature for 2h, and stand for 12h; finally wash and dry with sulfuric acid, hydrogen peroxide solution and hydrochloric acid to obtain modified functional materials. Through these pretreatment methods, the number of functional groups with redox activity contained in it is increased, thereby enhancing its redox ability, so that it can more effectively act as a redox mediator and promote extracellular electron transport.

[0009] The iron oxide is any one or more of high-valent iron oxides in powder or block form (with a particle size not exceeding 5 cm) such as ferric hydroxide, ferric oxide, ferroferric oxide, goethite, ferrihydrite, hematite, magnetite, etc., which can serve as extracellular electron acceptors for anaerobic ammonia-oxidizing bacteria and enhance their extracellular electron transfer process.

[0010] A biological denitrification method using an anaerobic ammonium oxidation enhanced denitrification device, wherein sewage enters the anaerobic ammonium oxidation enhanced denitrification device and is fully contacted with anaerobic ammonium oxidizing bacteria, and then the treated sewage flows out from the outlet of the reactor.

[0011] The stirring frequency of the main reactor is 2-6 minutes every 1-2 hours, the dissolved oxygen concentration is below 0.5 mg / L, the temperature is 10-38°C, the pH value is 7.5-8.5, and the sludge concentration is not less than 1000 mg / L.

[0012] The total nitrogen in the influent is 100-1000 mg / L, the ratio of nitrite nitrogen to ammonia nitrogen in the influent is 1-1.32, and the hydraulic retention time is 8-48 h.

[0013] Beneficial effects of the present invention:

[0014] (1) The electron mediator biocarrier of the present invention has a simple preparation process and the added exogenous iron oxide has a low investment cost, which is conducive to large-scale engineering application.

[0015] (2) The electron mediator-type biological carrier prepared in the present invention has abundant redox active functional groups (hydroxyl, carbonyl, carboxyl, etc.), which can serve as the redox mediator of anaerobic ammonium oxidizing bacteria, mediate the extracellular electron transfer process, and improve the utilization of exogenous insoluble extracellular electron acceptors by anaerobic ammonium oxidizing bacteria. In addition, the added iron oxide can serve as an extracellular electron acceptor, provide an additional extracellular electron transfer channel, promote its extracellular electron transfer, and thus strengthen the anaerobic ammonium oxidation process and improve the denitrification effect.

[0016] (3) The method of the present invention has a promoting effect on the metabolism of anaerobic ammonium oxidizing bacteria, can promote the secretion of extracellular polymers, store more redox active substances in the extracellular polymers, stimulate the production of cytochrome c in anaerobic ammonium oxidizing bacteria, and increase the activity of functional enzymes in the anaerobic ammonium oxidation reaction, further accelerate the efficiency of extracellular electron transfer in the system, and improve the metabolic activity of anaerobic ammonium oxidizing bacteria. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of an anaerobic ammonium oxidation enhanced denitrification device based on an electron mediator-type biological carrier and iron oxides of the present invention;

[0018] Figure 2 The denitrification conditions of each reactor of the present invention;

[0019] Figure 3 is the cytochrome c content of each reactor of the present invention; wherein (a) is a suspended sludge system, and (b) is a biofilm system;

[0020] Figure 4 is the activity of the electron transfer system in the biofilm system of each reactor of the present invention;

[0021] Figure 5 The key functional enzyme activities in the anaerobic ammonium oxidation reaction process in each reactor of the present invention, wherein (a) is the nitrite reductase activity, (b) is the hydrazine synthase activity; (c) is the hydrazine dehydrogenase activity, and (d) is the nitrate reductase activity.

[0022] In the figure: 1-water inlet pipe, 2-reactor body, 3-insulated circulating water device, 4-stirring device, 5-water outlet pipe, 6-anaerobic ammonium oxidation sludge, 7-electron mediator type biological carrier, 8-iron oxide. DETAILED DESCRIPTION

[0023] The specific implementation of the present invention is further described below in conjunction with the accompanying drawings and technical solutions.

[0024] Preparation Example

[0025] Preparation of electron mediator type biological carrier 1:

[0026] (1) The biochar was acidified with 5% nitric acid for 24 h to increase its oxygen-containing functional groups, then washed repeatedly with ultrapure water until the filtrate was neutral, and dried at 80°C to constant weight and stored for later use.

[0027] (2) 1000 g HDPE powder, 40 g modified biochar and 20 g talcum powder were fully mixed and added to the extruder, and the temperatures of the four parts of the barrel were 170°C, 180°C, 190°C and 170°C respectively. The extruded strip material was then added to the injection molding machine, and the temperatures of the barrel feeding zone, melting zone, mixing zone and molding zone were set to 160°C, 170°C, 165°C and 155°C respectively, and the desired suspended bio-carrier 1 was extruded and molded.

[0028] The ratios of other electron mediator-type bio-carriers are shown in Table 1.

[0029] Table 1 Preparation materials and proportions of electron mediator-type biological carriers

[0030]

[0031] Example 1

[0032] This embodiment provides an anaerobic ammonium oxidation enhanced denitrification device and method based on an electron mediator-type biological carrier and iron oxides, using Figure 1 The treatment device shown in the figure is used, wherein the reactor body adopts an MBBR bioreactor, whose effective volume is 2L, the ratio of inner diameter to height is 1:4, a double-layer insulation layer with a thickness of 1.5cm is set, and the outside is wrapped with tin foil for light protection. Specifically: the sewage in the water inlet pipe is pumped into the water inlet at the lower end of the MBBR reactor, and flows out through the upper outlet after being treated in the reactor.

[0033] The MBBR reactor was filled with 35% (v / v) biochar electron mediator and 2g / L ferric hydroxide was added as the extracellular electron acceptor of AnAOB, and stirred for 4min every 1h. The continuous water inlet mode was adopted, and the hydraulic retention time of the operation was regulated by the rotation of the peristaltic pump. The total nitrogen load rate of the inlet was controlled by changing the substrate concentration or the hydraulic retention time.

[0034] Artificial simulated wastewater was used as the influent, and the influent matrix composition was: NH 4 Cl 160-210mg / L, NaNO 2 160-210mg / L, NaHCO 3 1.0g / L, CaCl 2 ·2H 2 O 0.05g / L, MgSO 4 7H 2O 0.4g / L, trace element I solution 1.0ml / L, trace element II solution 1.0ml / L, further, trace element I solution uses water as solvent and includes the following solute components: EDTA 6.25g / L, ZnSO 4 7H 2 O 0.43g / L, CoCl 2 6H 2 O 0.24g / L, MnCl 2 ·4H 2 O 0.99g / L, CuSO 4 ·5H 2 O 0.25g / L, NiCl 2 6H 2 O0.19g / L, H 3 BO 4 0.014g / L, trace element II solution uses water as solvent and includes the following solute components: FeSO 4 7H 2 O 5.0g / L, EDTA 5.0g / L.

[0035] The MLSS and MLVSS concentrations of the reactor inoculation sludge were 3937±44 mg / L and 1803±47 mg / L, and the temperature in the reactor was controlled at 36±1°C, the pH value was 7.8-8.2, and the DO was 0.2-0.5 mg / L.

[0036] Example 2

[0037] The biological carrier in Example 1 was replaced by biological carrier 2, the extracellular electron acceptor was replaced by ferric oxide, and the other conditions were the same.

[0038] Example 3

[0039] The biological carrier in Example 1 was replaced by biological carrier 3, the extracellular electron acceptor was replaced by ferrosoferric oxide, and the other conditions were the same.

[0040] Example 4

[0041] The biocarrier in Example 1 was replaced by biocarrier 4, the extracellular electron acceptor was replaced by ferrihydrite, and the other conditions were the same.

[0042] Example 5

[0043] The biocarrier in Example 1 was replaced by biocarrier 5, the extracellular electron acceptor was replaced by goethite, and the other conditions were the same.

[0044] Example 6

[0045] The biocarrier in Example 1 was replaced by biocarrier 6, the extracellular electron acceptor was replaced by hematite, and the other conditions were the same.

[0046] Example 7

[0047] The extracellular electron acceptor in Example 1 was replaced by magnetite, and the other conditions were the same.

[0048] Comparative Example 1

[0049] The technical solution of this comparative example is different from that of the embodiment in that no biological carrier is filled in the anaerobic ammonium oxidation reactor.

[0050] Comparative Example 2

[0051] The technical solution of this comparative example is different from that of the embodiment in that the anaerobic ammonia oxidation reactor is filled with a traditional commercial HDPE carrier.

[0052] Effect example

[0053] The embodiment is recorded as R2 (electron mediator group), the comparative example 1 is recorded as R0 (activated sludge group), and the comparative example 2 is recorded as R1 (ordinary HDPE group). The anaerobic ammonia oxidation denitrification performance in the embodiment, comparative example 1 and comparative example 2 is compared, and the following results are obtained:

[0054] (1) Comparison of reactor denitrification effects

[0055] Depend on Figure 2 It can be seen that when the inlet total nitrogen concentration is 320-420 mg / L and the hydraulic retention time is 12h, the average total nitrogen removal rates of R0, R1 and R2 reactors are 53.24%, 59.28% and 65.80%, respectively. The TN removal rate of the R2 reactor is increased by 12.56% and 6.52% compared with R0 and R1, respectively; in addition, the total nitrogen concentration of the effluent of the R2 reactor fluctuates little over time, and the denitrification treatment effect is more stable.

[0056] (2) Comparison of cytochrome c content

[0057] Depend on Figure 3It can be seen that the cytochrome c content in R2 suspended sludge is 0.78μM / (mg·pro), which is higher than R0 (0.67μM / (mg·pro)) and R1 (0.71μM / (mg·pro)), and the cytochrome c content in R2 biofilm is 1.6 times that of R1 (R2 is 1.68μM / (mg·pro), R1 is 1.05μM / (mg·pro)). Cytochrome c has electron transfer function, and its mediated electron transfer is carried out through the reversible change of the iron atom in the center of the structure between reduced divalent iron and oxidized trivalent iron. Cytochrome c is widely distributed in the inner membrane, peristaltic space and outer membrane of bacterial cells. The higher content of cytochrome c in the R2 group helps to form an efficient channel for transferring electrons to extracellular electron receptors across the inner membrane, peristaltic space and outer membrane of the cell.

[0058] (3) Comparison of electron transport system activity

[0059] The electron transport system activity (ETSA) in the biofilm was measured and it was found that the ETSA in the R2 group was 44% higher than that in the R1 group (ETSA in R2 was 0.80 μg O 2 / (gVSS·min), ETSA in R1 is 0.52μgO 2 / (gVSS·min)), it can be seen that the electron transfer system of R2 group is more active.

[0060] (4) Comparison of anaerobic ammonium oxidation functional enzyme activities

[0061] The enzyme activity of key functional enzymes of the Anammox reaction in the biofilm system was much higher than that in the suspended sludge, indicating that the biological carrier was conducive to the improvement of enzyme activity. In addition, the activity of these four enzymes was higher in the R2 system, indicating that the redox mediator and iron oxides could increase enzyme activity and promote AnAOB metabolism.

[0062] In summary, the anaerobic ammonium oxidation enhanced denitrification device and method based on electron mediator-type biological carriers and iron oxides of the present invention can enhance the extracellular electron transfer process of anaerobic ammonium-oxidizing bacteria, promote the growth and metabolism of AnAOB, and thus enhance the nitrogen removal effect of sewage.

[0063] Finally, it should be noted that the above embodiments are only preferred embodiments of the present invention and are not limitations on the implementation methods. The scope of protection of the present invention should be based on the scope defined by the claims. Other different forms of changes or modifications can be made on the basis of the above description, and the obvious changes or modifications derived therefrom are still within the scope of protection created by the present invention.

Claims

1. An anaerobic ammonium oxidation enhanced denitrification device based on electron mediator-type biological carriers and iron oxides, characterized in that: The anaerobic ammonium oxidation enhanced denitrification device comprises a reactor body, a heat-insulating circulating water device, a stirring device, an inlet pipe and an outlet pipe; the reactor body is provided with a stirring device, on which a pipe interface for inlet and outlet is opened, which is respectively connected with the inlet pipe and the outlet pipe; the reactor body is a double-layer shell, which cooperates with the heat-insulating circulating water device to control the temperature in the reactor body; the reactor body is inoculated with anaerobic ammonium oxidation sludge, and the inside of the reactor body is filled with electron mediator-type biological carriers, the filling ratio of which is 10-50% of the effective volume of the reactor, and iron oxide is added, and the addition amount is 1-15g / L of the effective volume of the reactor.

2. The anaerobic ammonium oxidation enhanced denitrification device according to claim 1, characterized in that: The electron mediator type biological carrier is prepared by melt blending a polymer base material and a modified functional material, and the added proportion of the modified functional material does not exceed 20% of the mass fraction of the polymer base material.

3. The anaerobic ammonium oxidation enhanced denitrification device according to claim 2, characterized in that: The polymer base material is any one of polyethylene, polypropylene, polystyrene and polyvinyl chloride.

4. The anaerobic ammonium oxidation enhanced denitrification device according to claim 2, characterized in that: The modified functional material is any one of carbon-based materials such as biochar, activated carbon, carbon nanotubes, graphene, etc.

5. The anaerobic ammonium oxidation enhanced denitrification device according to claim 4, characterized in that: The modified functional material is treated with acid, alkali, oxidant or Hummer.

6. The anaerobic ammonium oxidation enhanced denitrification device according to claim 1, characterized in that: The iron oxide is one or a combination of two or more of ferric hydroxide, ferric oxide, ferroferric oxide, goethite, ferrihydrite, hematite and magnetite.

7. A biological denitrification method using the anaerobic ammonium oxidation enhanced denitrification device according to any one of claims 1 to 6, characterized in that: The sewage enters the anaerobic ammonium oxidation enhanced denitrification device and is fully contacted with the anaerobic ammonium oxidation bacteria. Subsequently, the treated sewage flows out from the outlet of the reactor.

8. The biological denitrification method according to claim 7, characterized in that: The stirring frequency of the main reactor is 2-6 minutes every 1-2 hours, the dissolved oxygen concentration is below 0.5 mg / L, the temperature is 10-38°C, the pH value is 7.5-8.5, and the sludge concentration is not less than 1000 mg / L; The total nitrogen in the influent is 100-1000 mg / L, the ratio of nitrite nitrogen to ammonia nitrogen in the influent is 1-1.32, and the hydraulic retention time is 8-48 h.

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