Biofilm reactor and method for treating urban sewage by nano-bubble aeration

Abstract

The invention discloses a bio-membrane reactor and method for treating urban sewage through nano-bubble aeration, and belongs to the technical field of secondary sewage treatment, the bio-membrane reactor for treating urban sewage through nano-bubble aeration comprises a bioreactor system, an aeration system and a pump control system; a method for realizing nitrosation / anaerobic ammonia oxidation of urban sewage by nano-bubble aeration adopts the bio-membrane reactor for treating the urban sewage by nano-bubble aeration to treat the urban sewage, so that nitrosation / anaerobic ammonia oxidation of the urban sewage is realized. Comprising the following steps: culturing and enriching anaerobic ammonium oxidation bacteria related biological membranes on a biological membrane carrier of a bioreactor, and when the anaerobic ammonium oxidation bacteria biological membrane carrier is cultured to be mature, enabling the bioreactor to enter an urban sewage treatment mode. According to the method for realizing nitrosation / anaerobic ammonia oxidation of urban sewage by using nanobubble aeration, the sewage denitrification efficiency is improved, and the urban sewage treatment cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of secondary sewage treatment, and in particular to a biofilm reactor and method for treating urban sewage by nanobubble aeration. Background Art

[0002] With the increasingly frequent production activities of humans, sewage containing high nitrogen is continuously discharged into water bodies such as rivers, lakes, etc., resulting in the continuous accumulation of reactive nitrogen in the biosphere, causing problems such as water environmental pollution and water eutrophication. This not only damages the ecological environment but also affects the water use safety of humans. Therefore, rapidly degrading nitrogen in sewage is the key to solving this problem. The biological nitrogen removal technology has the advantages of economy, high efficiency and no secondary pollution, and has received more and more attention in recent years. Among them, the biological nitrogen removal methods include: nitrification-denitrification, shortcut nitrification-denitrification and anaerobic ammonium oxidation, etc.

[0003] Partial nitrification / anaerobic ammonium oxidation (PN / A) is one of the new nitrogen removal technologies with the greatest development potential in the future of urban sewage treatment processes. The application of the PN / A technology in biological membrane methods such as the MBBR process can give full play to the advantages of the functional flora in the PN / A technology. The AOBs bacterial layer on the outer layer of the biofilm can make full use of the dissolved oxygen in the external environment, and at the same time transfer most of the generated nitrite better to the inner layer of the Anammox bacterial layer and create a good anoxic environment for the inner layer. This not only combines the advantages of shortcut nitrification and anaerobic ammonium oxidation, saves carbon sources and costs, but also has good treatment effects in the form of biofilms, and well solves problems in engineering production such as sludge bulking. The core mechanism affecting PN / A is mainly reflected in the response of the synergistic competition relationship among AnAOB, aerobic ammonia-oxidizing bacteria (AOB), nitrite-oxidizing bacteria (NOB) and conventional heterotrophic OHOs to changes in external factors. The key to coupling the PN technology with Anammox is to conduct directional control over the functional flora, that is, to achieve "effective inhibition of NOB and effective promotion of AOB". At present, the methods for directional control of the functional flora for "effective inhibition of NOB and effective promotion of AOB" mainly include maintaining high temperature and low dissolved oxygen (DO), real-time aeration control, inhibiting free ammonia (FA) or free nitrous acid (FNA). However, the above means have problems such as long startup time, difficulty in maintaining long-term stable operation, and tolerance of microorganisms to inhibitors. And numerous current studies have shown that AOB has a stronger adaptability to reactive oxygen species ROS than NOB. Therefore, reactive oxygen species (such as superoxide radicals, hydroxyl radicals, hydrogen peroxide, etc.) can be used as a control strategy, and nanobubbles have the ability to generate reactive oxygen species in the water environment.

[0004] In recent years, in the field of environmental pollution control, micro-nano bubbles have attracted extensive research due to their outstanding characteristics different from ordinary bubbles, such as their technical characteristics in aspects such as enhanced mass transfer, interfacial potential, and the release of free radicals. There have also been new developments in the application of micro-nano bubbles in sewage treatment. For example, in aspects such as the adsorption and removal of suspended solids, the enhanced decomposition of refractory organic pollutants, and the promotion of biological purification functions by micro-nano bubble technology. Research has also been carried out on aspects such as the effective denitrification of sewage treatment using micro-nano bubble technology, optimizing the synergistic conditions with other strong oxidation conditions, and developing practical nano-bubble generating devices with low cost, low energy consumption, excellent performance, and suitable for popularization. Summary of the Invention

[0005] The purpose of the present invention is to utilize the characteristic that micro-nano bubbles can generate reactive oxygen species, and use reactive oxygen species to selectively inhibit the activity and growth of NOBs, thereby breaking through the problem that NOBs are difficult to effectively inhibit in the nitrite / anaerobic ammonium oxidation process of municipal sewage, and achieving the purpose of stable nitrite / anaerobic ammonium oxidation of municipal sewage. At the same time, the present invention uses the MBBR process to form a nitrite / anaerobic ammonium oxidation biofilm, which can effectively prevent the air flotation effect of micro-nano bubbles on sludge compared with activated sludge.

[0006] To solve the above technical problems, the present invention adopts the following technical solutions: A biofilm reactor for treating municipal sewage by nano-bubble aeration according to the present invention includes a biological reactor system, an aeration system, and a pump control system; The biological reactor system includes a biological reactor for treating sewage. A biofilm carrier is arranged inside the biological reactor. A monitoring device for real-time monitoring of the reaction process is arranged on the biological reactor. An inlet and an outlet are arranged on the outer wall of the biological reactor, and the outlet is located at the position farthest from the inlet. The inlet and the outlet are respectively connected to an inlet pipe and an outlet pipe; The aeration system is connected to the biological reactor system for aerating the biological reactor; The pump control system is used to control the operation of the pump connected to the biological reactor.

[0007] Further, the monitoring device includes a temperature monitoring mechanism for real-time monitoring of the reactor temperature and an on-line real-time monitoring mechanism for real-time monitoring of the dissolved oxygen and pH value of the reactor.

[0008] Still further, the aeration system includes a micro-nano bubble aeration device. The micro-nano bubble aeration device includes a micro-nano bubble generator. The micro-nano bubble generator is connected to the biological reactor through a gas transmission pipeline II. A rotor flowmeter II is arranged on the gas transmission pipeline II.

[0009] Furthermore, the aeration system includes a combined aeration device, and the combined aeration device includes a conventional aeration device and a micro-nano bubble aeration device; The conventional aeration device includes a conventional aeration unit, which is connected to the bioreactor through a gas pipeline Ⅰ, and a rotameter Ⅰ is provided on the gas pipeline Ⅰ; The micro-nano bubble aeration device includes a micro-nano bubble generator, which is connected to the bioreactor through a gas pipeline Ⅱ, and a rotameter Ⅱ is provided on the gas pipeline Ⅱ.

[0010] Furthermore, the pump control system includes a pusher pump and a chemical dosing pump. The pusher pump is arranged at a position near the water inlet inside the bioreactor, and the chemical dosing pump is arranged on the water inlet pipe.

[0011] Furthermore, the aeration port on the outer wall of the bioreactor is located above the pusher pump.

[0012] Furthermore, a water suction pipe connected to the micro-nano bubble generator is provided on the outer wall of the bioreactor.

[0013] A method for realizing nitritation / anammox of urban sewage by nano-bubble aeration uses the biofilm reactor for treating urban sewage with nano-bubble aeration as described above to treat urban sewage, so as to realize nitritation / anammox of urban sewage, and includes the following steps: Cultivate and enrich the biofilm related to anaerobic ammonium-oxidizing bacteria on the biofilm carrier of the bioreactor, control the initial influent total nitrogen load of the bioreactor to be 50 mg / m³ / d, and the bioreactor is in the enrichment mode; When the ammonia nitrogen concentration in the effluent of the bioreactor is lower than 5 mg / L, gradually increase the influent total nitrogen load at a ratio of 10-20%, increase the influent total nitrogen load each time and operate stably until the total nitrogen removal rate reaches more than 80%, and then increase the influent total nitrogen load again; When the influent total nitrogen load reaches more than 200-500 mg / m³ / d and the total nitrogen removal rate is maintained above 80%, the anaerobic ammonium-oxidizing bacteria biofilm carrier is cultivated maturely, and the bioreactor enters the urban sewage treatment mode; The urban sewage is pretreated to remove COD so that the COD in the sewage reaches below 10-20 mg / L, and the organic nitrogen in the water is converted into ammonia nitrogen. The sewage is added into the bioreactor through the water inlet pipe, the operation flow rate of the chemical dosing pump is set, and the hydraulic retention time of the bioreactor is controlled to be 3-8 h; The bioreactor enters the nitrite treatment stage, starts the aeration system for aeration, and controls the dissolved oxygen to be not less than 1.00 - 8.00 mg / L; in the anaerobic ammonium oxidation treatment stage, adjusts the aeration system, and controls the dissolved oxygen to be not higher than 0.10 - 1.00 mg / L. Use the monitoring device to detect the dissolved oxygen, pH value, temperature, influent and effluent ammonia nitrogen concentration NH4-N, nitrite nitrogen N02-N and nitrate nitrogen N03-N concentration in the reactor in real time: when the effluent ammonia nitrogen concentration of the bioreactor is lower than 2 mg / L, adjust the aeration volume of the aeration system, and control the dissolved oxygen to gradually decrease to 0.10 - 0.50 mg / L. Dynamically adjust the pusher pump in the bioreactor according to the effluent ammonia nitrogen concentration to maintain the effluent ammonia nitrogen concentration in the sedimentation tank at 5 - 8 mg / L, and promote the rapid uptake of substrates by the biofilm. The on-line real-time monitoring mechanism detects that the pH value in the bioreactor is between 7.3 and 8.2. The temperature monitoring mechanism detects that the temperature in the bioreactor is between 20 and 34 °C. Calculate the nitrite accumulation rate NAR: NO2-N is the nitrite nitrogen concentration in the reactor effluent, TN is the total nitrogen concentration in the reactor effluent, NAR = [NO2-N] / [TN], and determine whether to aerate according to the nitrite accumulation rate NAR. Monitor the ammonia nitrogen, nitrite nitrogen, and nitrate nitrogen concentrations in the effluent of the bioreactor. After the bioreactor system reaches stability, the ammonia nitrogen removal rate in the effluent reaches more than 90%, the total nitrogen removal rate reaches more than 80%, and it operates stably for more than 1 month, indicating that the denitrification process of urban sewage is stably realized.

[0014] Furthermore, when the effluent ammonia nitrogen concentration is higher than 10 - 20 mg / L, increase the dissolved oxygen; when the effluent ammonia nitrogen concentration is lower than 5 mg / L, decrease the dissolved oxygen.

[0015] Still further, when NAR > 30%, extend the anoxic section time; when NAR < 20% and the effluent ammonia nitrogen concentration is higher than 8 mg / L, extend the aeration aerobic section time.

[0016] Compared with the prior art, the beneficial technical effects of the present invention: An autotrophic nitrogen removal process with MBs / NBs aeration provided by the present invention realizes efficient and stable nitritation-anaerobic ammonium oxidation nitrogen removal from municipal wastewater, which is an urgently needed technology for municipal wastewater treatment plants. By utilizing the characteristic that anaerobic ammonium-oxidizing bacteria are prone to aggregate and form biofilms, a novel biofilm carrier is added to the bioreactor to form biofilms. By controlling parameters such as hydraulic retention time and dissolved oxygen in the bioreactor, the niche differentiation of AnAOB and AOB is promoted, enabling the efficient enrichment of anaerobic ammonium-oxidizing bacteria in the inner layer of the biofilm carrier, while AOB is enriched in the outer layer of the biofilm. The MBs / NBs aeration technology adopted by the present invention can significantly increase the dissolved oxygen concentration in the water body, thereby enabling oxygen molecules to diffuse more rapidly to the surface of the carrier biofilm. This process promotes the uptake of oxygen molecules by ammonia-oxidizing bacteria (AOBs) in the biofilm, thereby accelerating the nitritation reaction and other vital activities, while improving oxygen utilization efficiency and promoting energy conservation. In the present invention, ROS is generated by the collapse of MBs / NBs bubbles in MBs / NBs aeration, and ROS is generated by controlling the aeration volume, increasing the intracellular reactive oxygen species levels of AOB and AnAOB. Based on the fact that the ability of AOB and AnAOB to eliminate reactive oxygen species is much greater than that of nitrite oxidizing bacteria NOB, the growth of NOB is selectively inhibited. By combining the control of hydraulic retention time, the elution of NOB in the system is achieved. Finally, through the cooperation of the AOB and AnAOB systems, the nitritation-anaerobic ammonium oxidation process is completed, realizing autotrophic nitrogen removal from municipal wastewater. The method of using nanobubble aeration to achieve nitritation / anaerobic ammonium oxidation of municipal wastewater in the present invention is used to improve the efficiency of sewage nitrogen removal and reduce the cost of municipal wastewater treatment. Description of the Drawings

[0017] The present invention will be further described below in conjunction with the description of the drawings.

[0018] Figure 1 It is a schematic structural diagram of a biofilm reactor for treating municipal wastewater with nanobubble aeration of the present invention; Figure 2 It is the operation effect diagram of the reactor of the present invention.

[0019] Description of the reference numerals: 1. Bioreactor; 1-1. Water inlet; 1-2. Water outlet; 2. Biofilm carrier; 3. Pusher pump; 4. Water inlet pipe; 5. Chemical dosing pump; 6. Water outlet pipe; 7. Temperature monitoring mechanism; 8. Online real-time monitoring mechanism; 9. Ordinary aeration device; 10. Gas transmission pipeline Ⅰ; 11. Rotameter Ⅰ; 12. Micro-nano bubble generator; 13. Gas transmission pipeline Ⅱ; 14. Rotameter Ⅱ; 15. Suction pipe; 16. Sampling port. Detailed Embodiments

[0020] As Figure 1As shown in the figure, a biofilm reactor for treating urban sewage by nano-bubble aeration includes a bioreactor system, an aeration system, and a pump control system; The bioreactor system includes a bioreactor 1 for treating sewage. Inside the bioreactor 1, there is a biofilm carrier 2. On the bioreactor 1, there is a monitoring device for real-time monitoring of the reaction process. On the outer wall of the bioreactor 1, there are an inlet 1-1 and an outlet 1-2, and the outlet 1-2 is located at the position farthest from the inlet 1-1 to ensure sufficient residence time of the sewage in the reactor. The inlet 1-1 and the outlet 1-2 are respectively connected to an inlet pipe 4 and an outlet pipe 6; The aeration system is connected to the bioreactor system and is used to aerate the bioreactor 1; The pump control system is used to control the operation of the pump connected to the bioreactor 1.

[0021] Specifically, the biofilm carrier 2 mainly provides a medium for the attachment of microbial communities in the bioreactor 1. The biofilm carrier material mainly uses synthetic polymer materials (BDPs), such as polylactic acid (PLA), polycaprolactone (PCL), polybutylene succinate (PBS), and polyhydroxyalkanoates (PHAs, including poly-β-hydroxybutyrate PHB and 3-hydroxybutyrate-co-3-hydroxyvalerate PHBV). According to the specific surface area of the carrier, the main models of the carrier are: K series, NATRIX series, F series, BiofilmChip series, Z series, and Activecell series, etc. In this embodiment, a hydrophilic modified biofilm carrier is recommended, that is, a hydrophilic K3 biofilm carrier with a 41° water-solid liquid contact angle of a composite PHBV / PVA material after oxidation treatment, and its specific surface area is 300-600 m² / m³.

[0022] The monitoring device includes a temperature monitoring mechanism 7 for real-time monitoring of the reactor temperature and an on-line real-time monitoring mechanism 8 for real-time monitoring of the dissolved oxygen and pH value of the reactor; The temperature monitoring mechanism 7 and the on-line real-time monitoring mechanism 8 are arranged near the outlet 1-2 to real-time monitor parameters such as ammonia nitrogen, nitrite nitrogen, nitrate nitrogen, temperature, pH, and dissolved oxygen in the effluent; A sampling port 16 is also designed at the outlet 1-2.

[0023] Specifically, the on-line real-time monitoring mechanism 8 is recommended to use a Hach 40d detector. The dissolved oxygen control of the reactor is controlled according to the operating steps. The dissolved oxygen in the aerobic section is generally 1.00-8.00 mg / L, and the dissolved oxygen in the anaerobic section is generally 0.10-1.00 mg / L; The pH value is controlled at 7.3-8.2. The temperature monitoring mechanism 7 is a thermometer for implementing the monitoring of the temperature inside the bioreactor 1, and the recommended temperature range is 20-34 °C.

[0024] The aeration system can be designed in two forms: (1) The aeration system includes a micro-nano bubble aeration device. The micro-nano bubble aeration device includes a micro-nano bubble generator 12. The micro-nano bubble generator 12 is connected to the bioreactor 1 through an air pipeline II 13, and a rotameter II 14 is arranged on the air pipeline II 13.

[0025] (2) The aeration system includes a combined aeration device. The combined aeration device includes a conventional aeration equipment and a micro-nano bubble aeration equipment. The conventional aeration equipment includes a conventional aeration device 9. The conventional aeration device 9 is connected to the bioreactor 1 through an air pipeline I 10, and a rotameter I 11 is arranged on the air pipeline I 10. The micro-nano bubble aeration equipment includes a micro-nano bubble generator 12. The micro-nano bubble generator 12 is connected to the bioreactor 1 through an air pipeline II 13, and a rotameter II 14 is arranged on the air pipeline II 13.

[0026] Specifically, the micro-nano bubble generator 12 is an aeration device that can stably generate nano-bubbles (air-NBs) with a diameter of 100 - 1000 nm and micro-bubbles (air-MBs) with a diameter of 1 - 100 µm. The conventional aeration device 9 is an aeration device that can stably generate conventional bubbles (air-CBs), such as a blower aerator, a centrifugal aerator, etc. A blower aerator is recommended.

[0027] The micro-nano bubbles and the novel biofilm carrier have a good effect on promoting biofilm formation. The growth rate of biofilm hanging is 0.18 - 0.33 ± 0.02 / d (doubling time of 3.9 - 2.1 / d).

[0028] Under the action of the micro-nano bubble generator 12 and the flow-pushing pump 3, the flow-pushing effect of the biofilm carrier 2 in the bioreactor 1 is significantly improved, which promotes the diffusion and transfer of the substrate matrix in the biofilm and improves the absorption rate and treatment capacity of AOB and AnAOB.

[0029] The pump control system includes a flow-pushing pump 3 and a chemical dosing pump 5. The flow-pushing pump 3 is arranged inside the bioreactor 1 near the water inlet 1-1, providing a flow-pushing effect during the operation of the bioreactor 1 to ensure the fluidity and uniformity of the carrier and substrate in the bioreactor 1. The chemical dosing pump 5 is installed on the water inlet pipe 4.

[0030] The aeration ports on the outer wall of the bioreactor 1 are located above the flow-pushing pump 3. Specifically, the aeration ports include nano-bubble aeration ports and conventional bubble aeration ports, and the aeration volume of the aerobic section of PN / A is controlled by an air valve.

[0031] A water suction pipe 15 connected to the micro-nano bubble generator 12 is connected to the outer wall of the bioreactor 1. The water suction pipe 15 and the gas transmission pipeline II 13 are respectively installed on both sides of the bioreactor 1.

[0032] A method for realizing nitritation / anaerobic ammonium oxidation of urban sewage by nano-bubble aeration. This method uses the biofilm reactor for treating urban sewage by nano-bubble aeration as described above to treat urban sewage, so as to realize nitritation / anaerobic ammonium oxidation of urban sewage, and includes the following steps: Cultivate and enrich the biofilm related to anaerobic ammonium oxidizing bacteria on the biofilm carrier 2 of the bioreactor 1, control the initial influent total nitrogen load of the bioreactor 1 to be 50 mg / m³ / d, and the bioreactor 1 is in the enrichment mode; When the ammonia nitrogen concentration in the effluent of the bioreactor 1 is lower than 5 mg / L, gradually increase the influent total nitrogen load at a ratio of 10-20%. Each time the influent total nitrogen load is increased and stable operation is carried out until the total nitrogen removal rate reaches more than 80%, then the influent total nitrogen load is increased again; When the influent total nitrogen load reaches more than 100 mg / m³ / d and the total nitrogen removal rate is maintained above 80%, the anaerobic ammonium oxidizing bacteria biofilm carrier is cultivated maturely, and the bioreactor 1 enters the urban sewage treatment mode; The urban sewage is pretreated to remove COD so that the COD in the sewage reaches below 10 mg / L, and the organic nitrogen in the water is converted into ammonia nitrogen. The urban sewage after primary treatment is lifted by the influent pump and added into the bioreactor 1 through the influent pipe 4. Set the operation flow rate of the dosing pump 5 and control the hydraulic retention time of the bioreactor 1 to be 6 h; The bioreactor 1 enters the nitritation treatment stage, turn on the aeration system for aeration, and control the dissolved oxygen to be not less than 1.50 mg / L; in the anaerobic ammonium oxidation treatment stage, adjust the aeration system and control the dissolved oxygen to be not higher than 0.50 mg / L; Use the monitoring device to real-time detect the dissolved oxygen, pH value, temperature, influent and effluent ammonia nitrogen concentration NH4-N, nitrite nitrogen N02-N and nitrate nitrogen N03-N concentration in the reactor: when the ammonia nitrogen concentration in the effluent of the bioreactor 1 is lower than 2 mg / L, adjust the aeration volume of the aeration system and control the dissolved oxygen to gradually decrease to 0.10-0.50 mg / L; Dynamically adjust the push flow pump 3 in the bioreactor 1 according to the effluent ammonia nitrogen concentration to maintain the ammonia nitrogen concentration in the effluent of the sedimentation tank to be 5-8 mg / L and promote the rapid uptake of substrates by the biofilm; When the effluent ammonia nitrogen concentration is higher than 20 mg / L, increase the dissolved oxygen; when the effluent ammonia nitrogen concentration is lower than 5 mg / L, decrease the dissolved oxygen; The on-line real-time monitoring mechanism 8 detects that the pH value in the bioreactor 1 is between 7.3 and 8.2; The temperature monitoring mechanism 7 detects that the temperature in the bioreactor 1 is between 20 and 34 °C; Calculate the nitrite accumulation rate NAR: NO2-N is the nitrite nitrogen concentration in the reactor effluent, TN is the total nitrogen concentration in the reactor effluent, NAR = [NO2-N] / [TN], and determine whether to aerate according to the nitrite accumulation rate NAR; when NAR > 30%, extend the anoxic section time; when NAR < 20% and the ammonia nitrogen concentration in the effluent is higher than 8 mg / L, extend the aeration aerobic section time; monitor the ammonia nitrogen, nitrite nitrogen, and nitrate nitrogen concentrations in the effluent of the bioreactor 1. After the bioreactor 1 system reaches stability, the ammonia nitrogen removal rate in the effluent reaches more than 90%, the total nitrogen removal rate reaches more than 80%, and it operates stably for more than 1 month, indicating that the urban sewage denitrification process is stably achieved, and the operation effect of the reactor is as attached Figure 2 shown.

[0033] In the present invention, under the action of the self-characteristics of micro-nano bubbles (MBs / NBs): (1) The size of MBs / NBs is very small, resulting in a very large specific surface area. The pressure inside the bubble is much greater than the atmospheric pressure. Under the interference of external factors (such as hydraulic shear), MBs / NBs will collapse to generate ROS reactive oxygen species.

[0034] (2) MBs / NBs have the unique property of long-term stability. The smaller the size of MBs / NBs, the larger the specific surface area, and the greater the pressure inside the bubble (much greater than the atmospheric pressure), that is, the bubble has a large diffusion driving force. The huge specific surface area and high internal pressure make MBs / NBs have strong surface reaction and mass transfer efficiency.

[0035] (3) MBs / NBs have the characteristics of colloidal particles (ζ potential and surface charge): they are negatively charged in a wide pH range, except when the pH is small (strongly acidic). The microorganisms in the bioreactor of this patent are in the pH range of 7.3 to 8.2.

[0036] The effects of applying micro-nano bubbles in the present invention are: (1) According to the characteristics of MBs / NBs, there is a push-flow pump in the bioreactor of the present invention, and the carrier and the sewage are in a circulating flow state, that is, MBs / NBs will collapse under the interference of external factors to generate ROS. Due to the biological enzyme characteristics of NOBs and Anammox bacteria, the ability of NOBs biological enzymes to degrade ROS is much lower than that of Anammox bacteria biological enzymes. At the same time, MBs / NBs can also promote the activity of dehydrogenases in Anammox bacteria, while inhibiting the activity of NOBs, it also greatly stimulates the biological activity of Anammox bacteria and improves the rapid colonization and proliferation rate of Anammox in the biofilm.

[0037] (2) According to the characteristics of MBs / NBs, that is, under the action of its own diffusion driving force, the huge specific surface area and high internal pressure of micro-nano bubbles make MBs / NBs have strong surface reaction and mass transfer efficiency. When air-MBs / NBs enter the interior of the bioreactor, the oxygen molecules in air-MBs / NBs enter the water environment at an extremely fast diffusion rate, greatly increasing the dissolved oxygen in the water, so that the oxygen molecules can enter the biofilm surface of the carrier faster, promoting the AOBs on the biofilm to uptake oxygen molecules for nitrosation and other life activities.

[0038] MBs / NBs also have long-term stability. Even under the action of external interference, compared with CBs aeration, MBs / NBs can stay in the water environment for about 5 - 10 minutes, which means that MBs / NBs can provide a more persistent and stable dissolved oxygen environment. Comparing CBs aeration with NBs aeration, the energy consumption of NBs aeration is reduced by nearly 80%.

[0039] (3) According to the characteristics of MBs / NBs having colloidal particles (ζ potential and surface charge), that is, MBs / NBs exhibit the Tyndall effect in pure water, which can be used to preliminarily judge the formation status of micro-nano bubbles; at the same time, the ζ potential and surface charge properties of MBs / NBs make the redox potential of the water environment in the reactor in a negative potential, promoting the absorption and utilization of electron donors and acceptors by microorganisms and other life activities, and indirectly improving the activity of biological enzymes.

[0040] Currently, the main mechanisms of micro-nano bubble generation include hydrodynamic and acoustic cavitation, electrolysis, porous materials, fluid oscillation, and pressure dissolution and decompression, etc. The main methods for producing micro-nano bubbles include the pressure dissolution and gas release method, the dispersed air method, the electrolysis method, the air flotation pump gas production method, etc. In the present invention, the recommended method for generating micro-nano bubbles is the dispersed air method. Its main principle is to use methods such as hydraulic shear and high-speed swirling flow to form a shear force and create an extreme condition to repeatedly shear and break the air, so that it is mixed with water to generate a large amount of micro-nano bubble gas-water mixture, and the generated micro-nano bubbles have a diameter range of 0.2 - 100 µm.

[0041] The embodiments described above are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the spirit of the present invention's design, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A biofilm reactor for treating municipal sewage by nanobubble aeration, characterized in that: It includes a bioreactor system, an aeration system and a pump control system; The bioreactor system includes a bioreactor (1) for treating sewage. A biofilm carrier (2) is arranged inside the bioreactor (1). A monitoring device for real-time monitoring of the reaction process is arranged on the bioreactor (1). An inlet (1-1) and an outlet (1-2) are arranged on the outer wall of the bioreactor (1), and the outlet (1-2) is located at the position farthest from the inlet (1-1). The inlet (1-1) and the outlet (1-2) are respectively connected to an inlet pipe (4) and an outlet pipe (6); The aeration system is connected to the bioreactor system for aerating the bioreactor (1); The pump control system is used to control the operation of the pump connected to the bioreactor (1).

2. The biofilm reactor for treating municipal sewage by nano-bubble aeration according to claim 1, wherein: The aeration system includes a micro-nano bubble aeration device. The micro-nano bubble aeration device includes a micro-nano bubble generator (12). The micro-nano bubble generator (12) is connected to the bioreactor (1) through an air delivery pipeline II (13). A rotameter II (14) is arranged on the air delivery pipeline II (13).

3. The biofilm reactor for treating urban sewage by nano-bubble aeration according to claim 1, wherein: The aeration system includes a combined aeration device. The combined aeration device includes a common aeration device and a micro-nano bubble aeration device; The common aeration device includes a common aeration device (9). The common aeration device (9) is connected to the bioreactor (1) through an air delivery pipeline I (10). A rotameter I (11) is arranged on the air delivery pipeline I (10); The micro-nano bubble aeration device includes a micro-nano bubble generator (12). The micro-nano bubble generator (12) is connected to the bioreactor (1) through an air delivery pipeline II (13). A rotameter II (14) is arranged on the air delivery pipeline II (13).

4. The biofilm reactor for treating municipal sewage by nano-bubble aeration according to claim 2 or 3, characterized in that: A water suction pipe (15) connected to the micro-nano bubble generator (12) is arranged on the outer wall of the bioreactor (1).

5. The biofilm reactor for treating urban sewage by nanobubble aeration according to claim 1, characterized in that: The monitoring device includes a temperature monitoring mechanism (7) for real-time monitoring of the reactor temperature and an on-line real-time monitoring mechanism (8) for real-time monitoring of the dissolved oxygen and pH value of the reactor.

6. The biofilm reactor for treating urban sewage by nano-bubble aeration according to claim 5, wherein: The pump control system includes a propelling pump (3) and a chemical dosing pump (5). The propelling pump (3) is arranged at a position inside the bioreactor (1) close to the inlet (1-1). The chemical dosing pump (5) is arranged on the inlet pipe (4).

7. The biofilm reactor for treating urban sewage by nanobubble aeration according to claim 6, wherein: The aeration port on the outer wall of the bioreactor (1) is located above the propelling pump (3).

8. A method for realizing nitritation / anaerobic ammonium oxidation of urban sewage by nano-bubble aeration. This method uses a biofilm reactor for treating urban sewage with nano-bubble aeration as described in claim 6 to treat urban sewage, so as to realize nitritation / anaerobic ammonium oxidation of urban sewage. It is characterized in that: It includes the following steps: Cultivate and enrich the biofilm related to anaerobic ammonium oxidation bacteria on the biofilm carrier (2) of the bioreactor (1), control the initial influent total nitrogen load of the bioreactor (1) to be 50 mg / m³ / d, and the bioreactor (1) is in the enrichment mode; When the ammonia nitrogen concentration in the effluent of the bioreactor (1) is lower than 5 mg / L, the total nitrogen load of the influent is gradually increased at a ratio of 10-20%. Each time the total nitrogen load of the influent is increased and the operation is stabilized until the total nitrogen removal rate reaches over 80%, the total nitrogen load of the influent is increased again. When the total nitrogen load of the influent reaches above 200-500 mg / m³ / d and the total nitrogen removal rate is maintained above 80%, the anaerobic ammonium oxidation bacteria biofilm carrier is cultivated maturely, and the bioreactor (1) enters the urban sewage treatment mode. The urban sewage is pretreated to remove COD so that the COD in the sewage reaches below 10-20 mg / L, and the organic nitrogen in the water is converted into ammonia nitrogen. The sewage is added into the bioreactor (1) through the influent pipe (4). The operation flow rate of the dosing pump (5) is set and the hydraulic retention time of the bioreactor (1) is controlled to be 3-8 h. The bioreactor (1) enters the nitritation treatment stage, the aeration system is turned on for aeration, and the dissolved oxygen is controlled to be not lower than 1.00-8.00 mg / L; in the anaerobic ammonium oxidation treatment stage, the aeration system is adjusted to control the dissolved oxygen to be not higher than 0.10-1.00 mg / L. The monitoring device is used to detect the dissolved oxygen, pH value, temperature, ammonia nitrogen concentration NH4-N, nitrite nitrogen N02-N and nitrate nitrogen N03-N concentration of the influent and effluent of the reactor in real time: when the ammonia nitrogen concentration in the effluent of the bioreactor (1) is lower than 2 mg / L, the aeration volume of the aeration system is adjusted to control the dissolved oxygen to gradually decrease to 0.10-0.50 mg / L. The pusher pump (3) in the bioreactor (1) is dynamically adjusted according to the ammonia nitrogen concentration in the effluent to maintain the ammonia nitrogen concentration in the effluent of the sedimentation tank at 5-8 mg / L, so as to promote the rapid uptake of the substrate by the biofilm. The on-line real-time monitoring mechanism (8) detects that the pH value in the bioreactor (1) is between 7.3 and 8.

2. The temperature monitoring mechanism (7) detects that the temperature in the bioreactor (1) is between 20 and 34 °C. Calculate the nitrite accumulation rate NAR: NO2-N is the nitrite nitrogen concentration in the effluent of the reactor, TN is the total nitrogen concentration in the effluent of the reactor, NAR = [NO2-N] / [TN], and judge whether to aerate according to the nitrite accumulation rate NAR. Monitor the ammonia nitrogen, nitrite nitrogen and nitrate nitrogen concentrations in the effluent of the bioreactor (1). After the bioreactor (1) system reaches stability, the ammonia nitrogen removal rate in the effluent reaches over 90%, the total nitrogen removal rate reaches over 80%, and it operates stably for over 1 month, indicating that the denitrification process of urban sewage is stably realized.

9. The method for realizing nitritation / anaerobic ammonium oxidation of municipal sewage by nano-bubble aeration according to claim 8, characterized in that: When the ammonia nitrogen concentration in the effluent is higher than 10-20 mg / L, increase the dissolved oxygen; when the ammonia nitrogen concentration in the effluent is lower than 5 mg / L, decrease the dissolved oxygen.

10. The method for realizing nitritation / anaerobic ammonium oxidation of municipal sewage by nano-bubble aeration according to claim 8, characterized in that: When NAR > 30%, extend the anoxic section time; when NAR < 20% and the ammonia nitrogen concentration in the effluent is higher than 8 mg / L, extend the aeration aerobic section time.

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