Method for in-situ enrichment of anaerobic ammonium oxidation bacteria

Abstract

The invention discloses a method for in-situ enrichment of anaerobic ammonia oxidizing bacteria, a bio-membrane reactor is adopted, and a carrier of a bio-membrane is made of a material with good conductivity and biological affinity; the direct-current power supply continuously outputs weak voltage below 1.0 V; preparing special wastewater as inlet water of the reactor; sludge containing anaerobic ammonium oxidation bacteria is selected as inoculation sludge, the hydraulic retention time of the reactor is controlled, microorganisms in the reactor mainly grow on a carrier in an attached mode to form a biological membrane, and suspended sludge is eliminated as much as possible; aeration is performed on the reactor, and water enters and exits the reactor continuously. According to the method, the anaerobic ammonium oxidation bacteria are enriched under the micro-aerobic condition, the nitrogen source is only ammonia nitrogen, nitrite nitrogen is generated in the ammonia nitrogen conversion process instead of being supplied externally, the normal form of anaerobic ammonium oxidation enrichment culture is innovated through the method, and the anaerobic ammonium oxidation enrichment culture efficiency is improved. The problem that anaerobic ammonia oxidizing bacteria cannot be enriched due to lack of external supply of nitrite nitrogen in the actual wastewater treatment process is effectively solved.

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 process has attracted more and more attention worldwide. The principle of anaerobic ammonium oxidation is that anaerobic ammonium oxidizing bacteria use nitrite as an electron acceptor to convert ammonia nitrogen into nitrogen gas. Compared with the traditional nitrification and denitrification process, anaerobic ammonium oxidation can reduce the oxygen demand by 60%, does not require an organic carbon source at all and is more efficient. However, anaerobic ammonium oxidizing bacteria grow slowly, are sensitive to the environment, and are often at a disadvantage in competition with other microorganisms, making the enrichment of anaerobic ammonium oxidizing bacteria a problem. In particular, it is still a huge challenge to enrich anaerobic ammonium oxidizing bacteria in situ in the main process of wastewater treatment.

[0003] Anaerobic ammonium oxidizing bacteria grow slowly and are difficult to retain in a suspended growth system. However, growth on a carrier can effectively separate the sludge retention time from the hydraulic retention time, which is beneficial to the retention of anaerobic ammonium oxidizing bacteria. Under microaerobic conditions, the carrier biofilm can provide an anoxic niche for the survival of anaerobic ammonium oxidizing bacteria. At the same time, the ammonia oxidizing bacteria in the biofilm can use limited dissolved oxygen to oxidize part of the ammonia nitrogen into nitrite nitrogen, and denitrifying bacteria can also produce nitrite nitrogen through nitrate reduction. The anaerobic ammonium oxidizing bacteria in the biofilm can use the remaining ammonia nitrogen and the 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 use electricity to enhance the anaerobic ammonium oxidation process. For example, in the 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 oxidizing 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 this type of research is inseparable from the anode and cathode. In addition, some studies used a direct current power supply to directly connect the titanium wire mesh to perform weak electrical stimulation on the sludge. In this study, there was no anode and cathode. The titanium wire mesh was only used as a conductor, and no film could be formed on the titanium wire mesh. The 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% will 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 show better salt tolerance. For example, marine anaerobic ammonium oxidizing bacteria balance osmotic pressure by accumulating potassium ions in cells and secreting extracellular polymers to protect cells, and can withstand rapid salinity changes from 0 to 5%. Therefore, the purpose of selectively enriching anaerobic ammonium oxidizing bacteria can be achieved by adjusting the salinity of the influent and taking advantage of the difference in the sensitivity of bacteria to salinity. 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 direct current power source (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 source (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 plate (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 1.0 V;

[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, make 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 the reactor adopts a continuous water inlet and outlet mode.

[0021] Furthermore, the material with good electrical conductivity and bioaffinity includes but is not limited to: graphite felt, carbon brush, and carbon felt.

[0022] Furthermore, the special wastewater has a sodium chloride concentration of 1.0% to 1.6%, an ammonia nitrogen concentration of ≥50 mg / L, and a carbon-nitrogen ratio of ≤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 it is difficult to retain anaerobic ammonium oxidizing bacteria in the traditional suspended growth method. The present invention creates conditions for the attachment and growth of anaerobic ammonium oxidizing bacteria by selecting materials with good conductivity and biological affinity as carriers. The biofilm provides an ecological niche for anaerobic ammonium oxidizing bacteria, which is conducive to its in situ enrichment;

[0028] 2) Generally, wastewater contains organic matter, which is conducive to the growth and reproduction of heterotrophic bacteria, but easily inhibits anaerobic ammonia oxidizing bacteria. The present invention utilizes the fact that anaerobic ammonia oxidizing bacteria have better salt tolerance than traditional heterotrophic bacteria such as denitrifying bacteria, and uses salinity stress to achieve in-situ enrichment of anaerobic ammonia oxidizing bacteria in the presence of organic matter;

[0029] 3) The traditional view is that dissolved oxygen is an inhibitory factor for anaerobic ammonium oxidation, and the anaerobic ammonium oxidation process must be carried out in an anaerobic environment. In addition, anaerobic ammonium oxidation cannot be separated from the external supply of nitrite nitrogen. These conditions are difficult to meet in actual wastewater treatment. The enrichment of anaerobic ammonium oxidizing bacteria in 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 external supply. This approach has revolutionized the paradigm of anaerobic ammonium oxidation enrichment culture and effectively solved the problem that anaerobic ammonium oxidizing bacteria cannot be enriched in the actual wastewater treatment process due to the lack of external supply of nitrite nitrogen. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It 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 is further described in detail below in conjunction with specific embodiments. The given examples are only for illustrating the present invention, but 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, reagents, etc. 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 a material 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 is: sodium chloride concentration is 1.0% to 1.6%, ammonia nitrogen concentration is ≥50mg / L, carbon nitrogen ratio is ≤5.0;

[0041] The 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 be 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 so that the dissolved oxygen was 1.0 mg / L. A continuous inlet and outlet water operation mode was adopted.

[0042] Figure 2 The changes in the concentration of various forms of nitrogen during the experimental period (84 days) of Example 1 are shown. When the concentrations of ammonia nitrogen and total nitrogen in the influent are 105.07±1.03 mg / L and 105.29±1.08 mg / L, respectively, the concentrations of ammonia nitrogen and total nitrogen during the experimental period are reduced to 0.08±0.02 mg / L and 11.43±1.11 mg / L, respectively, and the removal rate of ammonia nitrogen reaches 99.92%, and the removal rate of total nitrogen reaches 89.14%. Table 1 is a table of the abundance of anaerobic ammonia-oxidizing bacteria in biofilm, inoculated sludge and biofilm 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 change of COD concentration during the experimental period is shown. When the inlet COD concentration is 495.1±2.8mg / L, the effluent COD concentration drops to 17.6±5.6mg / L, and the COD removal rate reaches 96.44%.

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

[0049] Any feature disclosed in this specification (including any additional claims, abstract and drawings), unless otherwise stated, may be replaced by other equivalent or alternative features with similar purposes. 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 above-mentioned 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 device for in-situ enrichment of anaerobic ammonia-oxidizing bacteria, comprising: A direct current power source (1); a conductive carbon-based material biofilm carrier (2); a peristaltic pump (3); an air compressor (8) and a water inlet tank (9); wherein: The DC power source (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; 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 plate (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 device according to claim 1, wherein: The applied weak voltage is a weak voltage of 1.0V or less.

3. A method for in-situ enrichment of anaerobic ammonia-oxidizing bacteria using the device according to claim 1 or 2, 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 1.0 V; Prepare special wastewater as the inlet water of the reactor; Select sludge containing anaerobic ammonium oxidizing bacteria as inoculated sludge, control the hydraulic retention time of the reactor, make 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.

4. The method according to claim 3, wherein: The materials with good electrical conductivity and bioaffinity include: graphite felt, carbon brush, and carbon felt.

5. The method according to claim 3, wherein: The special wastewater is: The sodium chloride concentration is 1.0% to 1.6%, the ammonia nitrogen concentration is ≥50 mg / L, and the carbon-nitrogen ratio is ≤5.

0.

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

7. The method according to claim 3, 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.

8. The method according to claim 3, wherein: The aeration condition is: dissolved oxygen is 0.5-1.0 mg / L.

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