A method for enhancing the domestication of anaerobic ammonia oxidation biofilms using nano-zero valent iron

Abstract

This invention discloses a method for enhancing the acclimatization of anaerobic ammonia oxidation biofilms using nano-zero-valent iron, comprising the following steps: inoculating sludge into an anaerobic biofilm reactor, adding 15-25 mg / L of nano-zero-valent iron particles intermittently, pumping in nitrogen-containing wastewater, and introducing nitrogen gas to ensure an anaerobic environment; performing a hydraulic retention period to achieve rapid acclimatization and stable operation of the anaerobic ammonia oxidation biofilm. This invention, on the one hand, utilizes the promoting effect of nano-zero-valent iron on the growth of anaerobic ammonia oxidation microorganisms, significantly shortening the acclimatization period of the anaerobic ammonia oxidation biofilm; on the other hand, through Fe... 2+ and Fe 3+ The mediated microbial process enhances the deep removal of ammonia and nitrate nitrogen, improves operational stability, and significantly increases total nitrogen removal efficiency; it provides a new strategy for the domestication and stability enhancement of anaerobic ammonia-oxidizing microorganisms.

Description

Technical Field

[0001] This invention relates to a method for biological wastewater treatment, and more particularly to a method for enhancing the domestication of anaerobic ammonia oxidation biofilms using nano-zero valent iron. Background Technology

[0002] Anaerobic ammonia oxidation (AMO) refers to the reaction under anaerobic conditions in which anaerobic ammonia-oxidizing bacteria use nitrite as an electron acceptor to convert ammonia into nitrogen gas. Due to its advantages such as complete autotrophy, no aeration required, high denitrification load, low sludge production, and low greenhouse gas emissions, it is considered the most suitable biological denitrification process under new goals and requirements. However, the long generation cycle of anaerobic ammonia-oxidizing bacteria, their stringent dissolved oxygen requirements, and the production of nitrite in the reaction lead to difficulties in strain domestication and enrichment, poor process stability, and limitations in further improving denitrification efficiency, making this process difficult to apply in mainstream wastewater treatment.

[0003] Nano-sized zero-valent iron (ZVFe) is widely used in environmental remediation due to its strong redox properties. ZVFe can assist cells in synthesizing heme C, lower redox potential, regulate pH within the system, and reduce dissolved oxygen concentration, thus having a positive effect on the growth and metabolism of anaerobic ammonia-oxidizing bacteria. Simultaneously, ZVFe is easily oxidized by dissolved oxygen and nitrate nitrogen in water to form Fe. 2+ and Fe 3 + This, in turn, promotes microbial film formation or granulation through methods such as charge neutralization, compression of the electric double layer structure, promotion of extracellular polymer secretion, and regulation of quorum sensing signaling molecules. Furthermore, Fe... 2+ and Fe 3+ It can mediate the removal of ammonia or nitrate nitrogen by microorganisms under anaerobic conditions through pathways such as ferric oxidation and nitrate-dependent ferrous oxidation. Compared with large-sized zero-valent iron, nano-zero-valent iron has a larger specific surface area and greater dispersibility, making it easier to diffuse into cells, resulting in stronger reactivity and lower dosage. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to provide a method for enhancing the domestication of anaerobic ammonia oxidation biofilms using nano-zero valent iron, which significantly shortens the domestication period, ensures stable operation, and improves nitrogen removal efficiency.

[0005] Technical solution: The method for enhancing the acclimatization of anaerobic ammonia oxidation biofilm using nano-zero valent iron as described in this invention includes the following steps: inoculating sludge into an anaerobic biofilm reactor, adding 15-25 mg / L of nano-zero valent iron particles in an intermittent manner, pumping in nitrogen-containing wastewater, and introducing nitrogen gas to ensure an anaerobic environment, and hydraulically retaining the material for a period of time to achieve rapid acclimatization and stable operation of the anaerobic ammonia oxidation biofilm.

[0006] It is applied once every 40 to 60 days.

[0007] The particle size of the nano-zero valent iron is 30–60 nm.

[0008] Among them, the internal temperature of the biofilm reactor is controlled at 30-35℃.

[0009] The inoculated sludge is selected from at least one of activated sludge, anaerobic granular sludge, and freeze-thawed anaerobic ammonia oxidation sludge.

[0010] The sludge inoculation concentration was 4000 mg / L.

[0011] The hydraulic residence time is 23 to 24 hours.

[0012] The packing material used in the anaerobic biofilm reactor is polyethylene biological packing material with a porosity >95% and a specific surface area >500 m². 2 / m 3 The filling ratio is 30-40%.

[0013] The nitrogen in the nitrogen-containing wastewater consists of ammonia nitrogen and nitrite nitrogen. The nitrogen load can be adjusted according to the removal effect. The molar ratio of ammonia nitrogen to nitrite nitrogen is 1:1.3 to 1.34.

[0014] The influent pH is maintained at 7.5–8.5, and the dissolved oxygen concentration is reduced to below 0.2 mg / L by aeration with N2 for 5–10 minutes before influent.

[0015] The nitrogen-containing wastewater contains the following components: NaH2PO4 10 mg / L, NaHCO3 1000 mg / L, MgSO4·7H2O 20 mg / L, and CaCl2 20 mg / L. Trace element stock solution can be added or tap water can be used to prepare the solution to provide trace elements.

[0016] Beneficial effects: Compared with the prior art, the present invention achieves the following significant effects: (1) On the one hand, the present invention utilizes the promoting effect of nano-zero valent iron on the growth of anaerobic ammonia oxidation microorganisms, significantly shortening the acclimatization period of anaerobic ammonia oxidation biofilm; on the other hand, through Fe 2+ and Fe 3+ (1) The mediated microbial process enhances the deep removal of ammonia nitrogen and nitrate nitrogen, improves operational stability, and significantly improves the total nitrogen removal efficiency; (2) The nano zero-valent iron used in this invention has a small single dosage, low addition frequency, low cost, and is easy to apply on a large scale; (3) This invention is suitable for mainstream wastewater biological denitrification, has stable performance, safe operation, and mild conditions, and provides a new strategy for the domestication and enhanced stability of anaerobic ammonia oxidation microorganisms. Attached Figure Description

[0017] Figure 1The graph shows the changes in ammonia nitrogen influent concentration and ammonia nitrogen removal rate in the effluent of R0 and R1 reactors during 100 days of operation of reactors R0 and R1 in Example 1.

[0018] Figure 2 The graph shows the changes in nitrite nitrogen influent concentration and nitrite nitrogen removal rate in R0 and R1 effluent during 100 days of operation of reactors R0 and R1 in Example 1.

[0019] Figure 3 The graph shows the changes in nitrate nitrogen concentration in the effluent of reactors R0 and R1 during 100 days of operation of reactors R0 and R1 in Example 1.

[0020] Figure 4 The graph shows the changes in total nitrogen influent concentration and total nitrogen removal rate in R0 and R1 effluent during 100 days of operation of reactors R0 and R1 in Example 1.

[0021] Figure 5 For the R0 and R1 reactors of Example 1, the nitrogen stoichiometry ΔNO2 was measured over 100 days of operation. - -N / ΔNH4 + -N、ΔNO3 - -N / ΔNH4 + -N variation curve. Detailed Implementation

[0022] The present invention will now be described in further detail.

[0023] Example 1

[0024] (1) Two anaerobic sequencing batch biofilm reactors with an effective volume of 1L were set up, denoted as R0 and R1. Both R0 and R1 were inoculated with freeze-thawed flocculent sludge, which was taken from the secondary sedimentation tank of a sewage treatment plant in Jiangsu Province and frozen at -20℃ for more than 200 days. The initial sludge concentration was 5000 mg / L. R0 was the control reactor without the addition of nano-zero valent iron. On day 0 and day 50 of operation, an additional 20 mg / L of nano-zero valent iron was added to reactor R1. That is, the concentration of nano-zero valent iron in the reaction system after the addition was 20 mg / L. The average particle size of nano-zero valent iron was 35 nm.

[0025] (2) Both reactors R0 and R1 were operated in the dark, with a hydraulic residence time of 24h and a volume exchange ratio of 0.8. The reactors were placed on a constant temperature magnetic stirring device, with the temperature controlled at 32-34℃ and the stirring speed at 200rpm.

[0026] (3) The initial influent components are: ammonia nitrogen 60 mg / L, nitrite nitrogen 80 mg / L, NaH2PO4 10 mg / L, NaHCO3 1000 mg / L, MgSO4·7H2O 20 mg / L, CaCl2 20 mg / L, and tap water is used to provide trace elements. The dissolved oxygen concentration is <0.2 mg / L.

[0027] Implementation results:

[0028] (1) The acclimatization results of anaerobic ammonia oxidation in reactors R0 and R1 are as follows: Figure 1 , 2 As shown, the introduction of nano-zero valent iron significantly shortened the start-up and enrichment time of anaerobic ammonia oxidizing bacteria; specifically, the R0 reactor took 80 days to complete the domestication of anaerobic ammonia oxidizing bacteria, while the start-up phase of the R1 reactor was significantly shortened, achieving stable operation in just 8 days.

[0029] (2) From startup, reactor R1 showed better overall removal capacity for ammonia nitrogen and nitrite nitrogen in the influent than reactor R0. During stable operation, the average removal rates of ammonia nitrogen and nitrite nitrogen were 95.85% and 95.81%, respectively, compared to 91.65% and 95.23% for reactor R0. Furthermore, as... Figure 3 , 4 As shown, the average effluent nitrate concentrations of R1 and R0 were 10.14 mg / L and 17.38 mg / L, respectively. The average total nitrogen removal rate of R1 was 88.14%, which was consistently better than R0's 81.42%.

[0030] (3) During stable operation, such as Figure 5 As shown, the stoichiometric ratio of nitrogen in R0 is ΔNO2. - -N / ΔNH4 + -N≈1.40, ΔNO3 - -N / ΔNH4 + -N≈0.32, close to the theoretical values ​​of 1.32 and 0.26, indicating that the anaerobic ammonia oxidation system has been successfully established. The stoichiometric ratios in R1 are 1.36 and 0.20, close to the theoretical values, but significantly lower than the relevant values ​​in R0. This is because the addition of nano-zero-valent iron in R1 not only shortened the start-up and acclimatization time of the anaerobic ammonia oxidizing bacteria and achieved their enrichment, but also improved the total nitrogen removal rate by enhancing the removal of ammonia and nitrate nitrogen, thus strengthening the process's operational efficiency and stability.

[0031] Example 2

[0032] (1) Set up an anaerobic sequencing batch biofilm reactor with an effective volume of 1L, and inoculate it with freeze-thawed flocculent sludge. The sludge was taken from the secondary sedimentation tank of a sewage treatment plant in Jiangsu Province and frozen at -20℃ for more than 200 days. The initial sludge concentration was 5000mg / L. On the 0th and 40th days of operation, an additional 15mg / L of nano-zero valent iron was added to the reactor. The average particle size of the nano-zero valent iron was 35nm.

[0033] (2) All reactors were operated in the dark, with a hydraulic residence time of 24h and a volume exchange ratio of 0.8. The reactors were placed on a constant temperature magnetic stirring device, with the temperature controlled at 30-32℃ and the stirring speed at 200rpm.

[0034] (3) The initial influent components are: ammonia nitrogen 60 mg / L, nitrite nitrogen 80 mg / L, NaH2PO4 10 mg / L, NaHCO3 1000 mg / L, MgSO4·7H2O 20 mg / L, CaCl2 20 mg / L, and tap water is used to provide trace elements. The dissolved oxygen concentration is <0.2 mg / L.

[0035] Example 3

[0036] (1) Set up an anaerobic sequencing batch biofilm reactor with an effective volume of 1L, and inoculate it with freeze-thawed flocculent sludge. The sludge was taken from the secondary sedimentation tank of a sewage treatment plant in Jiangsu Province and frozen at -20℃ for more than 200 days. The initial sludge concentration was 5000mg / L. On the 0th and 60th days of operation, an additional 25mg / L of nano-zero valent iron was added to the reactor. The average particle size of the nano-zero valent iron was 35nm.

[0037] (2) All reactors were operated in the dark, with a hydraulic retention time of 24h and a volume exchange ratio of 0.8. The reactors were placed on a constant temperature magnetic stirring device, with the temperature controlled at 33-35℃ and the stirring speed at 200rpm.

[0038] (3) The initial influent components are: ammonia nitrogen 60 mg / L, nitrite nitrogen 80 mg / L, NaH2PO4 10 mg / L, NaHCO3 1000 mg / L, MgSO4·7H2O 20 mg / L, CaCl2 20 mg / L, and tap water is used to provide trace elements. The dissolved oxygen concentration is <0.2 mg / L.

[0039] Comparative Example 1

[0040] Based on Example 1, the difference from Example 1 is that 5 mg / L: nano zero-valent iron is used.

[0041] Comparative Example 2

[0042] Based on Example 1, the difference from Example 1 is that 50 mg / L nano zero-valent iron is used.

[0043] Comparative Example 3

[0044] Based on Example 1, the difference from Example 1 is that 100 mg / L nano zero-valent iron is used.

[0045] For the short-term pre-experiments conducted on Comparative Examples 1-3, the results showed that after the acclimatization process was started, the addition of 5 mg / L of nano-zero ferric iron to Comparative Example 1 did not significantly improve the ammonia removal efficiency of the system in the long term; while the reactors of Comparative Examples 2 and 3, which were added with 50 mg / L and 100 mg / L of nano-zero ferric iron respectively, did not significantly reduce the concentrations of ammonia nitrogen and nitrite in the wastewater for a period of time. In the later stage of the experiment, a large amount of iron compounds were deposited on the surface of the biofilm, the treatment efficiency gradually decreased, and the concentration of nitrogen pollutants in the wastewater hardly changed significantly.

Claims

1. A method for enhancing the domestication of anaerobic ammonia oxidation biofilms using nano-zero valent iron, characterized in that, Includes the following steps: Sludge is inoculated into the anaerobic biofilm reactor, and 15~25 mg / L of nano zero-valent iron particles are added intermittently. Nitrogen-containing wastewater is pumped in, and nitrogen gas is introduced to ensure the anaerobic environment. The hydraulic retention time is extended to achieve rapid acclimatization and stable operation of the anaerobic ammonia oxidation biofilm. Add the sludge every 40-60 days; the sludge inoculation concentration is 3500-4000 mg / L; the hydraulic retention time is 23-24 h.

2. The method for enhancing the domestication of anaerobic ammonia oxidation biofilms using nano-zero-valent iron according to claim 1, characterized in that, The particle size of the nano-zero valent iron is 30~60 nm.

3. The method for enhancing the domestication of anaerobic ammonia oxidation biofilms using nano-zero valent iron according to claim 1, characterized in that, The inoculated sludge is selected from at least one of activated sludge, anaerobic granular sludge, and freeze-thawed anaerobic ammonia oxidation sludge.

4. The method for enhancing the domestication of anaerobic ammonia oxidation biofilms using nano-zero-valent iron according to claim 1, characterized in that, The internal temperature of the biofilm reactor is controlled at 30~35℃.

5. The method for enhancing the domestication of anaerobic ammonia oxidation biofilms using nano-zero-valent iron according to claim 1, characterized in that, The packing material used in the anaerobic biofilm reactor is polyethylene biological packing material with a porosity >95% and a specific surface area >500 m². 2 / m 3 The filling ratio is 30-40%.

6. The method for enhancing the domestication of anaerobic ammonia oxidation biofilms using nano-zero-valent iron according to claim 1, characterized in that, The nitrogen elements in nitrogen-containing wastewater include ammonia nitrogen and nitrite nitrogen, and the molar ratio of ammonia nitrogen to nitrite nitrogen is 1:1.3~1.

34.

7. The method for enhancing the domestication of anaerobic ammonia oxidation biofilms using nano-zero-valent iron according to claim 1, characterized in that, The pH of the influent is maintained at 7.5-8.

5. Before the influent is introduced, it is aerated with N2 for 5-10 minutes to reduce the dissolved oxygen concentration to below 0.2 mg / L.

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