A method for in situ enrichment of anaerobic ammonia-oxidizing bacteria

Abstract

The present invention discloses a method for in-situ enrichment of anaerobic ammonium oxidizing bacteria, which uses a biofilm reactor, wherein the carrier of the biofilm is made of a material with good electrical conductivity and biological affinity; a DC power supply continuously outputs a weak voltage below 1.0V; special wastewater is prepared as the inlet water of the reactor; sludge containing anaerobic ammonium oxidizing bacteria is selected as the inoculated sludge, and the hydraulic retention time of the reactor is controlled so that the microorganisms in the reactor mainly grow by attaching to the carrier to form a biofilm, and suspended sludge is eliminated as much as possible; the reactor is aerated, and water is continuously fed in and out of the reactor. The enrichment of anaerobic ammonium oxidizing bacteria by the present invention is carried out under microaerobic conditions, and the nitrogen source is only ammonia nitrogen. Nitrite nitrogen is produced during the conversion of ammonia nitrogen rather than being supplied externally. This approach has revolutionized the paradigm of anaerobic ammonium oxidizing enrichment culture and effectively solved the problem that anaerobic ammonium oxidizing bacteria cannot be enriched in actual wastewater treatment processes due to the lack of an external supply of nitrite nitrogen.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental protection and relates to a method for in-situ enrichment of anaerobic ammonia-oxidizing bacteria. Background Art

[0002] The anaerobic ammonium oxidation (ANAMMOX) process has attracted increasing attention worldwide. The principle of ANAMMOX is that ANAMMOX bacteria use nitrite as an electron acceptor to convert ammonia nitrogen into nitrogen gas. Compared with traditional nitrification and denitrification processes, ANAMMOX reduces oxygen demand by 60%, requires no organic carbon source, and is significantly more efficient. However, ANAMMOX bacteria grow slowly, are sensitive to the environment, and often compete poorly with other microorganisms, making their enrichment a challenge. In particular, in-situ enrichment of ANAMMOX bacteria during the primary wastewater treatment process remains a significant challenge.

[0003] Anaerobic ammonium oxidizing bacteria grow slowly and are difficult to retain in suspended growth systems. However, attached growth on carriers effectively separates sludge retention time from hydraulic retention time, facilitating their retention. Under microaerobic conditions, the carrier biofilm provides an anoxic niche for anaerobic ammonium oxidizing bacteria to survive. Simultaneously, the ammonia-oxidizing bacteria in the biofilm can utilize limited dissolved oxygen to oxidize some ammonia nitrogen into nitrite nitrogen. Denitrifying bacteria can also produce nitrite nitrogen through nitrate reduction. The anaerobic ammonium oxidizing bacteria in the biofilm can then utilize the remaining ammonia nitrogen and newly generated nitrite nitrogen to complete the denitrification process.

[0004] Given that electrical stimulation can increase the activity of microbial functional enzymes, studies in recent years have attempted to enhance the anaerobic ammonium oxidation process by applying electricity. For example, in a bioelectrolysis cell (MEC) system, ammonia nitrogen and nitrite nitrogen are directly added to the influent, and the applied voltage effectively increases the activity and relative abundance of marine anaerobic ammonium oxidation bacteria. In addition, some studies have found that the electrochemical action of the anode under an applied voltage can convert ammonia nitrogen into nitrite nitrogen, thereby promoting anaerobic ammonium oxidation. Studies similar to the above are conducted in MEC, and such studies are inseparable from the anode and cathode. In addition, some studies used a DC power supply directly connected to a titanium wire mesh to perform weak electrical stimulation on the sludge. In this study, there was no anode and cathode. The titanium wire mesh only served as a conductor, and no film could form on the titanium wire mesh. Microorganisms grew in a suspended state, denitrification and denitrification were enhanced, and no enrichment of anaerobic ammonium oxidizing bacteria was found.

[0005] Furthermore, studies have shown that salinity in wastewater greater than 1% can have a strong negative impact on nitrifying and denitrifying bacteria. However, compared with other microorganisms such as nitrifying bacteria and denitrifying bacteria, anaerobic ammonium oxidizing bacteria exhibit better salt tolerance. For example, marine anaerobic ammonium oxidizing bacteria balance osmotic pressure by accumulating potassium ions in the cells and secreting extracellular polymers to protect the cells, and can withstand rapid salinity changes from 0 to 5%. Therefore, by adjusting the salinity of the influent and taking advantage of the differences in the sensitivity of bacteria to salinity, the purpose of selectively enriching anaerobic ammonium oxidizing bacteria can be achieved. At present, there are no reports on the selective enrichment of anaerobic ammonium oxidizing bacteria using salt stress.

[0006] In summary, inoculating sludge containing anaerobic ammonium oxidizing bacteria in the reactor, adding carriers to create conditions for the attached growth of microorganisms, and using weak electrical stimulation combined with salinity stress to achieve the enrichment of anaerobic ammonium oxidizing bacteria in the conductive carrier biofilm is a method for in situ enrichment of anaerobic ammonium oxidizing bacteria. Summary of the Invention

[0007] The purpose of the present invention is to solve the problem of difficulty in enriching anaerobic ammonium oxidizing bacteria and to propose a method for in situ enrichment of anaerobic ammonium oxidizing bacteria. The present invention is achieved through the following technical solutions:

[0008] The present invention first discloses a device for in-situ enrichment of anaerobic ammonia-oxidizing bacteria, comprising:

[0009] A DC power supply (1); a conductive carbon-based material biofilm carrier (2); a peristaltic pump (3); an air compressor (8) and a water inlet tank (9); wherein:

[0010] The DC power supply (1) is connected to the conductive carbon-based material biofilm carrier (2) via a conductive device, and a weak voltage can be applied to the conductive carbon-based material biofilm carrier (2) during the reaction process;

[0011] The bottom end of the conductive carbon-based material biofilm carrier (2) is connected to the peristaltic pump (3) and the water inlet tank (9) through the water inlet pipe (7); the top end is discharged to the water outlet tank (11) through the drainage pipe (5);

[0012] There is also a microporous aeration disk (6) at the bottom of the conductive carbon-based material biofilm carrier (2);

[0013] A gas flow meter (4) is provided on the air compressor (8).

[0014] Furthermore, the applied weak voltage is a weak voltage below 1.0V.

[0015] The present invention also discloses a method for in-situ enrichment of anaerobic ammonia-oxidizing bacteria using the above device, comprising:

[0016] A biofilm reactor (10) is used, and the carrier of the biofilm is made of a material with good electrical conductivity and biological affinity;

[0017] The DC power supply (1) continuously outputs a weak voltage below 1.0V;

[0018] Prepare special wastewater as the inlet water of the reactor;

[0019] Select sludge containing anaerobic ammonium oxidizing bacteria as inoculated sludge, control the hydraulic retention time of the reactor, so that the microorganisms in the reactor mainly grow on the carrier to form biofilm, and eliminate suspended sludge as much as possible;

[0020] The reactor is aerated and adopts a continuous water inlet and outlet mode.

[0021] Furthermore, the materials with good electrical conductivity and bioaffinity include but are not limited to: graphite felt, carbon brushes, and carbon felt.

[0022] Furthermore, the special wastewater has the following characteristics: sodium chloride concentration of 1.0% to 1.6%, ammonia nitrogen concentration ≥ 50 mg / L, and carbon-nitrogen ratio ≤ 5.0.

[0023] Furthermore, the relative abundance of anaerobic ammonia-oxidizing bacteria in the inoculated sludge is ≥0.1%.

[0024] Furthermore, the hydraulic retention time of the reactor is controlled by controlling the water flow rate entering the reactor so that the dilution rate of the suspended sludge (i.e. the inverse of the hydraulic retention time) is greater than its proliferation rate, thereby reducing the accumulation of suspended sludge and facilitating the stable growth of the biofilm.

[0025] Furthermore, the aeration condition is: dissolved oxygen is 0.5-1.0 mg / L.

[0026] The beneficial effects of the present invention are:

[0027] 1) Anaerobic ammonium oxidizing bacteria grow slowly, and traditional suspended growth methods are difficult to retain anaerobic ammonium oxidizing bacteria. The present invention creates conditions for the attachment and growth of anaerobic ammonium oxidizing bacteria by selecting materials with good conductivity and bioaffinity as carriers. The biofilm provides an ecological niche for anaerobic ammonium oxidizing bacteria, which is conducive to their in situ enrichment;

[0028] 2) Generally, wastewater contains organic matter, which is beneficial to the growth and reproduction of heterotrophic bacteria but tends to inhibit anaerobic ammonium oxidizing bacteria. The present invention utilizes the salt tolerance of anaerobic ammonium oxidizing bacteria, which is superior to that of traditional heterotrophic bacteria such as denitrifying bacteria, and uses salinity stress to achieve in-situ enrichment of anaerobic ammonium oxidizing bacteria in the presence of organic matter.

[0029] 3) Traditionally, it is believed that dissolved oxygen is an inhibitory factor for anaerobic ammonium oxidation (ANAMMOX). The ANAMMOX process must be carried out in an anaerobic environment, and ANAMMOX cannot be separated from the external supply of nitrite nitrogen. These conditions are difficult to meet in actual wastewater treatment. The present invention enriches ANAMMOX bacteria under microaerobic conditions, with the only nitrogen source being ammonia nitrogen. Nitrite nitrogen is produced during the conversion of ammonia nitrogen rather than being supplied externally. This approach revolutionizes the paradigm of ANAMMOX enrichment culture and effectively solves the problem of the inability to enrich ANAMMOX bacteria in actual wastewater treatment processes due to the lack of an external supply of nitrite nitrogen. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic diagram of the reactor structure used in the present invention; wherein: 1 is a DC power supply, 2 is a conductive carbon-based material biofilm carrier, 3 is a peristaltic pump, 4 is a gas flow meter, 5 is a drain pipe, 6 is a microporous aeration disk, 7 is a water inlet pipe, 8 is an air compressor, 9 is a water inlet tank, 10 is a biofilm reactor, and 11 is a water outlet tank.

[0031] Figure 2 It is a graph showing the changes in concentration of nitrogen in various forms during the application experiment period of the present invention.

[0032] Figure 3 It is a graph showing the change of COD concentration during the application experiment period of the present invention. DETAILED DESCRIPTION

[0033] The present invention will be further described in detail below in conjunction with specific embodiments. The examples given are only for illustrating the present invention, not for limiting the scope of the present invention.

[0034] The experimental methods in the following examples are conventional methods unless otherwise specified; the materials and reagents used are all commercially available unless otherwise specified.

[0035] Example 1

[0036] The device of the present invention is as follows Figure 1 shown.

[0037] A method for in-situ enrichment of anaerobic ammonia-oxidizing bacteria using the above device comprises:

[0038] A biofilm reactor (10) is used, and the carrier of the biofilm is made of materials with good electrical conductivity and biological affinity, including but not limited to: graphite felt, carbon brush, carbon felt;

[0039] The DC power supply (1) continuously outputs a weak voltage of 0.9V;

[0040] Prepare special wastewater as the inlet water of the reactor. The special wastewater has the following characteristics: sodium chloride concentration of 1.0% to 1.6%, ammonia nitrogen concentration ≥ 50 mg / L, and carbon-nitrogen ratio ≤ 5.0;

[0041] Sludge containing anaerobic ammonium oxidizing bacteria was selected as the inoculated sludge. The sludge in this embodiment was derived from the secondary sedimentation tank of a sewage treatment station of a kimchi enterprise. The relative abundance of anaerobic ammonium oxidizing bacteria in the sludge was ≥0.1%. The total hydraulic retention time of the reactor was controlled to 24 hours. In order to prevent the influent salinity from changing too drastically and causing the death of anaerobic ammonium oxidizing bacteria, the salinity was gradually increased from 1.0% to 1.6%. The wastewater was pumped into the reactor and the reactor was aerated to a dissolved oxygen content of 1.0 mg / L. A continuous inlet and outlet water operation mode was adopted.

[0042] Figure 2 The changes in the concentrations of various forms of nitrogen during the experimental period (84 days) of Example 1 are shown. When the influent ammonia nitrogen and total nitrogen concentrations were 105.07±1.03 mg / L and 105.29±1.08 mg / L, respectively, the ammonia nitrogen and total nitrogen concentrations dropped to 0.08±0.02 mg / L and 11.43±1.11 mg / L, respectively, during the experimental period. The ammonia nitrogen removal rate reached 99.92%, and the total nitrogen removal rate reached 89.14%. Table 1 shows the abundance of anaerobic ammonium-oxidizing bacteria in biofilms, inoculated sludge, and biofilms without applied voltage after 84 days of application of the present invention.

[0043] Table 1

[0044]

[0045]

[0046] According to the results in Table 1, the relative abundance of anaerobic ammonium-oxidizing bacteria in the inoculated sludge was only 0.14%. Compared with the inoculated sludge, the relative abundance of anaerobic ammonium-oxidizing bacteria in the conductive carrier biofilm was increased to 6.78% by adding conductive carriers and using salt stress strategy. The relative abundance of anaerobic ammonium-oxidizing bacteria in the conductive carrier biofilm was further increased to 11.24% by adding conductive carriers and combining salt stress and weak electrical stimulation, and the enrichment effect was more significant.

[0047] Figure 3 The results show the change of COD concentration during the experimental period. When the influent COD concentration was 495.1±2.8 mg / L, the effluent COD concentration dropped to 17.6±5.6 mg / L, and the COD removal rate reached 96.44%.

[0048] All features disclosed in this specification, or all steps in the disclosed methods or processes, except mutually exclusive features and / or steps, can be combined in any manner.

[0049] Any feature disclosed in this specification (including any appended claims, abstract and drawings), unless otherwise stated, may be replaced by other equivalent or similar features. That is, unless otherwise stated, each feature is only an example of a series of equivalent or similar features.

[0050] The present invention is not limited to the aforementioned specific embodiments, but extends to any new features or any new combination disclosed in this specification, as well as any new method or process steps or any new combination disclosed.

Claims

1. A method for in-situ enrichment of anaerobic ammonium oxidizing bacteria using an apparatus for in-situ enrichment of anaerobic ammonium oxidizing bacteria, comprising: A biofilm reactor (10) is used, and the carrier of the biofilm is made of a material with good electrical conductivity and biological affinity; The DC power supply (1) continuously outputs a weak voltage below 1.0V; Prepare special wastewater as the inlet water of the reactor. The special wastewater has the following characteristics: sodium chloride concentration of 1.0% to 1.6%, ammonia nitrogen concentration ≥ 50 mg / L, and carbon-nitrogen ratio ≤ 5.0; Select sludge containing anaerobic ammonium oxidizing bacteria as inoculated sludge, control the hydraulic retention time of the reactor, so that the microorganisms in the reactor mainly grow on the carrier to form biofilm, and eliminate suspended sludge as much as possible; The reactor is aerated and the reactor adopts a continuous water inlet and outlet mode; The device for in-situ enrichment of anaerobic ammonia-oxidizing bacteria comprises: A DC power supply (1); a conductive carbon-based material biofilm carrier (2); a peristaltic pump (3); an air compressor (8) and a water inlet tank (9); the DC power supply (1) and the conductive carbon-based material biofilm carrier (2) are connected via a conductive device, and a weak voltage of less than 1.0 V can be applied to the conductive carbon-based material biofilm carrier (2) during the reaction process; The bottom end of the conductive carbon-based material biofilm carrier (2) is connected to the peristaltic pump (3) and the water inlet tank (9) through the water inlet pipe (7); the top end is discharged to the water outlet tank (11) through the drainage pipe (5); There is also a microporous aeration disk (6) at the bottom of the conductive carbon-based material biofilm carrier (2); A gas flow meter (4) is provided on the air compressor (8).

2. The method according to claim 1, wherein: The materials with good electrical conductivity and bioaffinity include: graphite felt, carbon brushes, and carbon felt.

3. The method according to claim 1, wherein: The relative abundance of anaerobic ammonia-oxidizing bacteria in the inoculated sludge is ≥0.1%.

4. The method according to claim 1, wherein: The hydraulic retention time of the control reactor is: By controlling the water flow rate entering the reactor, the dilution rate of the suspended sludge is made greater than its proliferation rate, thereby reducing the accumulation of suspended sludge and facilitating the stable growth of the biofilm.

5. The method according to claim 1, wherein: The aeration condition is: dissolved oxygen is 0.5-1.0 mg / L.

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