Method for quickly starting anaerobic ammonia oxidation and improving operation efficiency under low-oxygen condition

Abstract

The invention discloses a method for quickly starting anaerobic ammonia oxidation and improving operation efficiency under a low-oxygen condition. The method comprises the following steps: S1, inoculating anaerobic ammonia oxidation sludge into a reactor; s2, water is fed into the reactor, the fed water is not subjected to deoxidation treatment, the ratio of ammonia nitrogen to nitrite nitrogen in the fed water is (1.5-2.5): 1, and the hydraulic retention time is 3-3.9 h; s3, the reactor is operated until the total nitrogen removal efficiency in the reactor reaches 75% and is kept stable for at least 14 days, meanwhile, the ammonia nitrogen removal efficiency and the nitrite nitrogen removal efficiency are both kept to be 90% or above, and therefore anaerobic ammonia oxidation rapid starting under the low-oxygen condition is achieved; s4, the hydraulic retention time is adjusted to be 2-2.9 h, the reactor continues to run for no more than 20 days, and therefore the running efficiency of the reactor is improved. According to the method disclosed by the invention, quick start of anaerobic ammonia oxidation can be successfully realized within 40 days under a micro-aerobic condition, the operation efficiency of anaerobic ammonia oxidation can be improved within 20 days, and the limitation of long start period and low operation efficiency of traditional anaerobic ammonia oxidation is broken through.

Description

Technical Field

[0001] The present invention relates to the technical field of biological sewage treatment, and in particular to a method for quickly starting anaerobic ammonia oxidation and improving operating efficiency under hypoxic conditions. Background Art

[0002] Anaerobic ammonium oxidation (ANAMMOX) is a highly efficient autotrophic denitrification technology that directly converts ammonia nitrogen and nitrite into nitrogen gas under anaerobic conditions. Compared to traditional nitrification-denitrification processes, ANAMMOX requires no external carbon source, consumes less energy, and produces less sludge, making it a valuable application in wastewater treatment. However, ANAMMOX bacteria grow slowly and are sensitive to environmental conditions, particularly during the initial startup phase. This results in long system startup times and poor stability, limiting their widespread application in actual wastewater treatment projects.

[0003] Currently, anaerobic ammonium oxidation (ANAMMOX) is typically initiated using sludge inoculation or biofilm immobilization, with system stability enhanced through a short-cut nitrification-ANAMMOX process. The short-cut nitrification-ANAMMOX process utilizes ammonia-oxidizing bacteria to oxidize some ammonia nitrogen into nitrite nitrogen, providing an electron acceptor for the ANAMMOX bacteria. However, the short-cut nitrification-ANAMMOX process still presents numerous challenges in practical applications. For example, the ANAMMOX bacteria must contend with the effects of dissolved oxygen present in the preceding short-cut nitrification process or in the wastewater itself, making its practical application undoubtedly difficult.

[0004] Therefore, there is an urgent need to provide a method for quickly starting anaerobic ammonia oxidation and improving operating efficiency under low oxygen conditions. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for rapidly starting anaerobic ammonium oxidation (ANAMMOX) under low-oxygen conditions and improving its operating efficiency. By constructing a "short-range nitrification-ANAMMOX" system under microaerobic conditions and utilizing the synergistic mechanism of ammonia-oxidizing bacteria and ANAMMOX bacteria, the rapid start-up and efficient operation of the ANAMMOX system are achieved. This method can successfully achieve rapid start-up of ANAMMOX under microaerobic conditions within 40 days and improve the operating efficiency of ANAMMOX within 20 days, breaking through the limitations of traditional ANAMMOX, such as the long start-up period and low operating efficiency, and improving the operability of the project.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0007] The present invention provides a method for quickly starting anaerobic ammonium oxidation and improving operating efficiency under hypoxic conditions, comprising the following steps:

[0008] S1. Inoculate anaerobic ammonium oxidation sludge into the reactor;

[0009] S2. feeding water into the reactor, wherein the water has not been deoxygenated and the ratio of ammonia nitrogen to nitrite nitrogen in the water is (1.5-2.5):1, and the hydraulic retention time is 3-3.9 h;

[0010] S3. operating the reactor until the total nitrogen removal efficiency in the reactor reaches 75% and remains stable for at least 14 days, while the ammonia nitrogen removal efficiency and the nitrite nitrogen removal efficiency are both maintained above 90%, thereby achieving rapid start-up of anaerobic ammonium oxidation under hypoxic conditions;

[0011] S4. Adjusting the hydraulic retention time to 2 to 2.9 hours and continuing to operate the reactor for no more than 20 days, thereby improving the operating efficiency of the reactor.

[0012] Controlling the ammonia-to-nitrite ratio and hydraulic retention time (HRT) is crucial for the initiation of ANAMMOX. An appropriate HRT helps regulate the competitive relationship between ammonia-oxidizing bacteria, nitrite-oxidizing bacteria, and ANAMMOX. Furthermore, the ammonia-to-nitrite ratio directly impacts the substrate supply for ANAMMOX. Proper regulation optimizes the balance between electron donors and acceptors, promoting the proliferation of ANAMMOX bacteria while preventing the inhibition of ANAMMOX bacteria by excess nitrite, thereby improving the system's denitrification performance.

[0013] In this invention, the inventors innovatively introduce a "short-cut nitrification-anaerobic ammonium oxidation" system into the anaerobic ammonium oxidation rapid startup process for the first time. Under hypoxic conditions, the anaerobic ammonium oxidizing bacteria and ammonia oxidizing bacteria in the anaerobic ammonium oxidation bacterial community cooperate by regulating the ratio of ammonia nitrogen to nitrite nitrogen, oxidizing ammonium ions in the wastewater into nitrite for the anaerobic ammonium oxidizing bacteria. Furthermore, the ammonia oxidizing bacteria, as aerobic bacteria, can consume limited dissolved oxygen, thereby creating the hypoxic conditions necessary for the survival of the anaerobic ammonium oxidizing bacteria. This method achieves rapid startup of the anaerobic ammonium oxidation system and achieves stable and efficient operation without deoxygenating the wastewater, which is of great significance for the practical engineering application of the anaerobic ammonium oxidation process.

[0014] In some preferred embodiments of the present invention, the biomass concentration of the anaerobic ammonium oxidation sludge inoculated in the reactor is 0.5-5 g·L in terms of volatile solid concentration VSS. -1 , for example, it can be 0.5, 1, 2, 3, 4, or 5 g·L -1 wait.

[0015] In some preferred embodiments of the present invention, the reactor is a continuous stirring reactor to ensure that the bacterial flora in the reactor are in full contact with the culture medium.

[0016] In some preferred embodiments of the present invention, the pH of the inlet water is 7.6-7.8, illustratively, it can be 7.6, 7.7, 7.8, etc.; the water temperature of the inlet water is 20-28°C, illustratively, it can be 20, 21, 22, 23, 24, 25, 26, 27, 28°C, etc.

[0017] In step S2 of the present invention, the dissolved oxygen concentration in the influent is ≤0.29 mg·L -1 , for example, can be 0, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29 mg·L -1 wait.

[0018] In step S2 of the present invention, the total nitrogen in the influent is composed of ammonia nitrogen and nitrite nitrogen, wherein the ratio of ammonia nitrogen to nitrite nitrogen needs to be controlled to (1.5-2.5):1. For example, it can be 1.5:1, 2:1, 2.5:1, etc., preferably 2:1.

[0019] Furthermore, when the ratio of ammonia nitrogen to nitrite nitrogen is 2:1, the total nitrogen concentration in the influent is 60-150 mg·L -1 , for example, it can be 60, 70, 80, 90, 100, 110, 120, 130, 140, 150 mg·L -1 The concentration of ammonia nitrogen in the influent is 40-100 mg·L -1 , for example, it can be 40, 50, 60, 70, 80, 90, 100 mg·L -1 The concentration of nitrite nitrogen in the influent is 20-50 mg·L -1 , for example, it can be 20, 30, 40, or 50 mg·L -1 In some preferred embodiments of the present invention, when the ratio of ammonia nitrogen to nitrite nitrogen is 2:1, the total nitrogen concentration in the influent is 90 mg·L -1 , the concentration of ammonia nitrogen is 60 mg·L -1 , the concentration of nitrite nitrogen is 30 mg·L -1 .

[0020] Furthermore, the ratio of ammonia nitrogen to nitrite nitrogen in the influent can be adjusted by adding ammonia nitrogen and nitrite nitrogen to the influent. Ammonia nitrogen and nitrite nitrogen are added to the influent starting from the first day of reactor operation to control the ratio of ammonia nitrogen to nitrite nitrogen in the influent. In some specific embodiments, the ammonia nitrogen source is ammonium chloride, and the nitrite nitrogen source is sodium nitrite.

[0021] Furthermore, the influent can be simulated wastewater. In some preferred embodiments of the present invention, the influent contains NH4Cl, NaNO2, C6H 12 O6, CaCl2·2H2O, MgCl2·6H2O, KHCO3, NaH2PO4, trace element I stock solution, and trace element II stock solution. The trace element I stock solution is prepared from EDTA·2Na and FeSO4·7H2O; the trace element II stock solution contains: MnCl2, ZnSO4·7H2O, CuSO4·5H2O, Na2MoO4·4H2O, H3BO3, CoCl2·6H2O, NiCl2·6H2O, and vitamin tablets.

[0022] In step S2 of the present invention, the hydraulic retention time of the influent needs to be controlled to be 3 to 3.9 hours. For example, it can be 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9 hours, etc., preferably 3.6 hours.

[0023] Furthermore, the time for rapid start-up of the anaerobic ammonium oxidation is no more than 40 days, that is, by controlling the ratio of ammonia nitrogen to nitrite nitrogen in the influent to (1.5-2.5):1 and adjusting the hydraulic retention time to 3-3.9 hours, the anaerobic ammonium oxidation reaction can be successfully started and stabilized within 40 days, thereby achieving efficient denitrification of the system.

[0024] Furthermore, in step S4, after the anaerobic ammonium oxidation reactor is quickly started, the hydraulic retention time is adjusted to 2 to 2.9 hours, and the reactor is continuously operated for no more than 20 days to achieve improved operating efficiency of the reactor. The improved operating efficiency refers to an improvement in the nitrogen removal efficiency of the system.

[0025] In the present invention, after the rapid start of anaerobic ammonia oxidation, the hydraulic retention time needs to be adjusted to 2 to 2.9 hours. For example, it can be 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9 hours, preferably 2.4 hours.

[0026] In this invention, optimizing the hydraulic retention time to 2 to 2.9 hours facilitates the consumption of ammonia nitrogen by ammonia-oxidizing bacteria and converts it into nitrite nitrogen, ensuring sufficient substrate for the anaerobic ammonium oxidation reaction and achieving nitrogen balance. A shorter hydraulic retention time provides nutrients for the anaerobic ammonium-oxidizing bacteria, creating an environment suitable for their growth and thus improving operational efficiency.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. This invention achieves rapid startup and efficient operation of the ANAMMOX system by constructing a "short-range nitrification-ANAMMOX" system under microaerobic conditions and utilizing the synergistic action of ammonia-oxidizing bacteria and ANAMMOX bacteria. Within 40 days, the ANAMMOX reaction was successfully initiated and stabilized, achieving stable system operation and efficient denitrification. This overcomes the limitations of traditional ANAMMOX's long startup cycle, improves engineering operability, and provides a more adaptable startup strategy for practical applications.

[0029] 2. After the rapid start-up of anaerobic ammonium oxidation, the present invention further improves the operating efficiency of the reactor within 20 days by optimizing the hydraulic retention time, ensuring efficient operation, enhancing the stability and adaptability of the anaerobic ammonium oxidation process, and broadening its application range in wastewater treatment.

[0030] 3. Experiments have shown that the method of the present invention can effectively overcome the problem of slow growth of anaerobic ammonia-oxidizing bacteria, accelerate their enrichment, and significantly improve the denitrification performance of the system. DETAILED DESCRIPTION

[0031] The present invention will be further described below with reference to specific examples so that those skilled in the art can better understand the present invention and implement it, but the examples are not intended to limit the present invention.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meanings as commonly understood by those skilled in the art to which this invention pertains. The terms used in this specification are for the purpose of describing specific embodiments only and are not intended to limit the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0033] In the following examples and comparative examples, the specific components of the simulated wastewater used are as follows: ammonia nitrogen (configured according to experimental requirements), nitrite nitrogen (configured according to experimental requirements), KHCO3 1500 mg·L -1 , MgCl2·6H2O 1500mg·L -1 , CaCl2·2H2O56mg·L -1 , NaH2PO410mg·L -1 , Trace element I stock solution and trace element II stock solution, the solvent is water. Trace element I stock solution composition is: EDTA·2Na 5g·L -1 , FeSO4·7H2O 9.14g·L -1 The composition of trace element II stock solution is: MnCl2 0.63g·L -1 , ZnSO4·7H2O 0.43g·L -1 , CuSO4·5H2O 0.219g·L -1, Na2MoO4·4H2O 0.184g·L -1 , H3BO30.014g·L -1 , CoCl2·6H2O 0.228g·L -1 , NiCl2·6H2O0.195g·L -1 , vitamin tablets 0.317g·L -1 .

[0034] Unless otherwise specified, the experimental methods used in the following examples and comparative examples are conventional methods, and the materials, reagents, etc. used are all commercially available unless otherwise specified.

[0035] Experiment 1

[0036] This experiment provides a method for rapid startup and improved operational efficiency of anaerobic ammonium oxidation under hypoxic conditions. The specific steps are as follows:

[0037] S1. A continuous stirred tank reactor with an effective volume of 1 L was used. Mature anaerobic ammonium-oxidizing sludge containing 7.14% relative abundance of Candidatus Kuenenia and 0.04% relative abundance of Candidatus Brocadia and nearly 0 relative abundance of Nitrosomonas was used as the inoculum source. After inoculation, the biomass in the reactor, expressed as volatile solids concentration (VSS), was 1.20 g·L. -1 .

[0038] S2. Set up four continuous stirred tank reactors (CSRs) with an effective volume of 1.0 L each, designated Y1, Y2, Y3, and Y4. Y1 served as the experimental group, while Y2, Y3, and Y4 served as the control group. Simulated wastewater without deoxygenation was used as the influent, and the ammonia nitrogen:nitrite nitrogen ratio in the influent was adjusted according to Table 1. The hydraulic retention time (HRT) was controlled at 3.6 h, and the sludge was primed at 24°C and an influent pH of 7.6.

[0039] Table 1 Ammonia nitrogen: nitrite nitrogen ratio and dosage in influent

[0040]

[0041] (1) After 40 days of incubation, the average denitrification efficiency of Y1 was 80.27%, the ammonia nitrogen removal rate reached 93.09%, and the nitrite nitrogen removal rate reached 92.18%. The average denitrification efficiency of Y2 and Y4 was around 65%, of which the ammonia nitrogen removal rate of Y2 reached 73.12%, and the nitrite nitrogen removal rate reached 68.18%. The ammonia nitrogen removal rate of Y4 reached 82.37%, and the nitrite nitrogen removal rate reached 76.95%. The average denitrification efficiency of Y3 was 60.84%, the ammonia nitrogen removal rate reached 90.66%, and the nitrite nitrogen removal rate reached 86.47%. Since the denitrification efficiency of Y1 gradually increased and remained stable during the entire incubation period, it can be considered that the anaerobic ammonium oxidation was successfully started. However, the total nitrogen denitrification efficiency of Y2, Y3, and Y4 fluctuated and continued to decline, which can be considered as a failure of the anaerobic ammonium oxidation start-up.

[0042] (2) On the 40th day, a 6-hour ex situ batch experiment was conducted on the sludge in the four reactors to detect the anaerobic ammonium oxidation activity and ammonia oxidation activity. The results showed that the total nitrogen removal rate of Y1 reached the highest 75.46%, and the ammonia nitrogen removal rate reached 93.09%; the total nitrogen removal rate of Y2 was 62.47%, and the ammonia nitrogen removal rate reached 86.09%; while the total nitrogen removal rate of Y3 was only 53.52%, and the ammonia nitrogen removal rate reached 68.09%; the total nitrogen removal rate of Y4 was 63.85%, and the ammonia nitrogen removal rate reached 85.20%.

[0043] Combining the average denitrification efficiency and the results of the ex situ batch experiment, it can be shown that the ratio of ammonia nitrogen to nitrite nitrogen is 2:1 (ammonia nitrogen concentration 60 mg·L -1 , nitrite nitrogen concentration 30 mg·L -1 ), the anaerobic ammonium oxidation reaction of the reactor was successfully started.

[0044] (3) On the 40th day, the microbial community diversity of each reactor in (2) was sequenced and analyzed, and the results are shown in Table 2.

[0045] Table 2 Relative abundance of various bacterial genera in the reactor

[0046]

[0047] As shown in Table 2, the relative abundance of anaerobic ammonium oxidizing bacteria and ammonia oxidizing bacteria in Y1 is more balanced compared with Y2, Y3 and Y4. This shows that due to the presence of dissolved oxygen, the increase in the influent matrix ratio (ammonia nitrogen: nitrite nitrogen ratio) promotes the increase in the activity of ammonia oxidizing bacteria, making ammonia oxidizing bacteria dominate the anaerobic ammonium oxidation system, so excessive nitrite nitrogen is produced, nitrogen accumulation occurs, and the anaerobic ammonium oxidation reaction is unbalanced. However, when the conventional influent matrix ratio is used, the activity of ammonia oxidizing bacteria is low, so that ammonia oxidizing bacteria cannot be used to consume the dissolved oxygen in the water, and thus the anaerobic ammonium oxidation reaction is affected.

[0048] Therefore, through the experiment of optimizing the ratio of ammonia nitrogen to nitrite nitrogen in the influent, it was proved that anaerobic ammonia oxidation started quickly when the ratio of ammonia nitrogen to nitrite nitrogen was 2:1.

[0049] Experiment 2

[0050] This experiment provides a method for rapid startup and improved operational efficiency of anaerobic ammonium oxidation under hypoxic conditions. The specific steps are as follows:

[0051] Three continuous stirred tank reactors with an effective volume of 1 L were set up, named R1, R2, and R3. The anaerobic ammonium oxidation sludge in the Y1 reactor was used as the inoculum source. After inoculation, the biomass in the reactors, expressed as volatile solids concentration (VSS), was 1.44 g·L. -1 . With a content of 60mg·L -1 Ammonia nitrogen and 30 mg·L -1 The reactor's operating efficiency was improved using simulated wastewater containing nitrite nitrogen and not undergoing deoxygenation treatment at 24°C and an inlet pH of 7.6. R1 was the experimental group with a hydraulic retention time of 2.4 hours; R2 and R3 were the control groups with hydraulic retention times of 3.6 hours and 1.2 hours, respectively.

[0052] (1) After 20 days of operation, the average denitrification efficiency of R1 was 88.23%, the average denitrification efficiency of R2 was 79.41%, and the average denitrification efficiency of R3 was 71.26%. This shows that when the hydraulic retention time is 2.4h, ammonia oxidizing bacteria can consume part of the ammonia nitrogen and convert it into nitrite nitrogen, so that the substrate of the anaerobic ammonia oxidation reaction is sufficient and nitrogen balance is achieved. The shorter hydraulic retention time provides nutrients for the anaerobic ammonia oxidizing bacteria. However, too short a hydraulic retention time has a greater impact on the survival of microorganisms in the reactor, causing the operating efficiency to fluctuate and decrease.

[0053] On the 20th day, a 6-hour ex situ batch experiment was conducted on the sludge in the three reactors to test anaerobic ammonium oxidation (ANAMMOX) and ammonia oxidation (AMOX) activities. The results showed that R1 achieved the highest total nitrogen removal rate of 90.12% and ammonia nitrogen removal of 95.19%. R2 achieved a total nitrogen removal rate of 86.47% and an ammonia nitrogen removal rate of 86.22%. However, R3 achieved a mere 73.42% total nitrogen removal and ammonia nitrogen removal rate of 69.84%. Therefore, it was concluded that shorter hydraulic retention time (HRT) increases ANAMMOX activity and decreases ammonia oxidation activity. When the influent ammonia nitrogen:nitrite nitrogen ratio was 2:1 and the concentration remained constant, increasing the HRT increased the nitrogen load in the reactor and simultaneously boosted the activity of ANAMMOX bacteria. This indicates that the system environment is conducive to the growth of ANAMMOX bacteria, resulting in better treatment results. This demonstrates that a 2.4-hour HRT significantly improves reactor performance.

[0054] In summary, this experiment achieved rapid startup of anaerobic ammonium oxidation by controlling the influent ammonia nitrogen:nitrite nitrogen substrate ratio to 2:1, enabling the system to successfully and stably operate within 40 days. Furthermore, by optimizing the hydraulic retention time to 2.4 hours, the reactor's operating efficiency was significantly improved within 20 days. This invention not only provides new research perspectives and data support for the rapid startup and stable operation of anaerobic ammonium oxidation in practical applications, but also provides a scientific basis for optimizing biological denitrification process parameters and improving engineering applicability.

[0055] The above embodiments are merely preferred embodiments for the purpose of fully illustrating the present invention, and the scope of protection of the present invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are within the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

Claims

1. A method for rapid startup and improved operation efficiency of anaerobic ammonium oxidation under hypoxic conditions, characterized in that: The following steps are involved: S1. Inoculate anaerobic ammonium oxidation sludge into the reactor; S2. Introducing water into the reactor, wherein the influent water has not been deoxygenated, and the ratio of ammonia nitrogen to nitrite nitrogen in the influent water is (1.5-2.5):1, and the hydraulic retention time is 3-3.9h; S3. operating the reactor until the total nitrogen removal efficiency in the reactor reaches 75% and remains stable for at least 14 days, and the ammonia nitrogen removal efficiency and the nitrite nitrogen removal efficiency are both maintained at more than 90%, thereby achieving rapid start-up of anaerobic ammonia oxidation under hypoxic conditions; S4. Adjust the hydraulic retention time to 2-2.9 hours, and continue to operate the reactor for no more than 20 days, thereby improving the operating efficiency of the reactor.

2. The method for rapid startup and improved operation efficiency of anaerobic ammonium oxidation under hypoxic conditions according to claim 1, characterized in that: In step S1, the reactor is a continuous stirring reactor.

3. The method for rapid start-up of anaerobic ammonium oxidation under hypoxic conditions according to claim 1, characterized in that: In step S1, the biomass concentration of the anaerobic ammonium oxidation sludge inoculated in the reactor is 0.5-5 g·L in terms of volatile solid concentration VSS. -1 .

4. The method for rapid startup and improved operation efficiency of anaerobic ammonium oxidation under hypoxic conditions according to claim 1, characterized in that: In step S2, the dissolved oxygen concentration in the influent is ≤ 0.29 mg·L -1 , the pH of the inlet water is 7.6-7.8, and the water temperature is 20-28℃.

5. The method for rapid startup and improved operation efficiency of anaerobic ammonium oxidation under hypoxic conditions according to claim 1, characterized in that: In step S2, the ratio of ammonia nitrogen to nitrite nitrogen in the influent is 2:1, and the hydraulic retention time is 3.6 h.

6. The method for rapid startup and improved operation efficiency of anaerobic ammonium oxidation under hypoxic conditions according to claim 5, characterized in that: In step S2, the total nitrogen concentration of the influent is 60 to 150 mg·L -1 , the concentration of ammonia nitrogen is 40~100mg·L -1 , the concentration of nitrite nitrogen is 20~50mg·L -1 .

7. The method for rapid startup and improved operation efficiency of anaerobic ammonium oxidation under hypoxic conditions according to claim 1, characterized in that: In step S3, the time for the rapid start-up of anaerobic ammonium oxidation does not exceed 40 days.

8. The method for rapid startup and improved operation efficiency of anaerobic ammonium oxidation under hypoxic conditions according to claim 1, characterized in that: In step S4, the hydraulic retention time is adjusted to 2.4 h.

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