A biofilm reactor and method for treating municipal sewage using nanobubble aeration

Abstract

The present invention discloses a biofilm reactor and method for treating municipal sewage with nanobubble aeration, which belongs to the technical field of secondary sewage treatment. A biofilm reactor for treating municipal sewage with nanobubble aeration includes a bioreactor system, an aeration system, and a pump control system; a method for achieving nitritation / anaerobic ammonium oxidation of municipal sewage with nanobubble aeration, which uses the biofilm reactor for treating municipal sewage with nanobubble aeration as described above to treat municipal sewage, so that the municipal sewage achieves nitritation / anaerobic ammonium oxidation, and includes the following steps: cultivating and enriching biofilms related to anaerobic ammonium oxidizing bacteria on biofilm carriers of the bioreactor, cultivating the anaerobic ammonium oxidizing bacteria biofilm carriers to maturity, and the bioreactor entering a municipal sewage treatment mode. The present invention uses a method for achieving nitritation / anaerobic ammonium oxidation of municipal sewage with nanobubble aeration to improve the efficiency of sewage denitrification and reduce the cost of municipal sewage treatment.

Description

Technical Field

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

[0002] With the increasing frequency of human production activities, wastewater containing high levels of nitrogen is continuously discharged into rivers, lakes, and other water bodies. This leads to the continuous accumulation of reactive nitrogen in the biosphere, causing problems such as water pollution and eutrophication. This not only damages the ecological environment but also affects human water safety. Therefore, the key to solving this problem is to rapidly degrade nitrogen in wastewater. Biological denitrification technology has the advantages of being economical, efficient, and pollution-free, and has attracted increasing attention in recent years. Among them, biological denitrification methods include nitrification-denitrification, short-cut nitrification and denitrification, and anaerobic ammonium oxidation.

[0003] Nitrification / anaerobic ammonium oxidation (PN / A) is one of the most promising new denitrification technologies for municipal wastewater treatment. Applied to biofilm processes such as MBBR (Medium-Blocked Bacteria), PN / A fully leverages the advantages of its functional bacterial communities. The AOBs layer in the outer biofilm can fully utilize dissolved oxygen in the external environment while efficiently transferring the majority of the generated nitrous oxide to the inner Anammox layer, creating a favorable anoxic environment within the inner layer. This not only combines the advantages of short-range nitritation and anaerobic ammonium oxidation, saving carbon sources and reducing costs, but also offers excellent treatment results in a biofilm format, effectively addressing production challenges such as sludge bulking. The core mechanism influencing PN / A is primarily reflected in the synergistic and competitive relationships among AnAOB, aerobic ammonia oxidizing bacteria (AOB), nitrite oxidizing bacteria (NOB), and conventional heterotrophic OHOs, which respond to changing external factors. The key to coupling PN / A with Anammox is targeted control of the functional bacterial communities, achieving "effective NOB inhibition and AOB promotion." Currently, methods for targeted control of functional microbial communities to effectively inhibit NOB and promote AOB primarily include maintaining high temperatures and low dissolved oxygen (DO), real-time aeration control, and suppression of free ammonia (FA) or free nitrite (FNA). However, these methods present challenges such as long startup times, difficulty maintaining long-term stable operation, and microbial tolerance to inhibitors. Numerous studies have demonstrated that AOB are more adaptable to reactive oxygen species (ROS) than NOB. Therefore, reactive oxygen species (such as superoxide radicals, hydroxyl radicals, and hydrogen peroxide) could be considered as a control strategy. Nanobubbles, on the other hand, have the ability to generate reactive oxygen species in aqueous environments.

[0004] In recent years, micro-nanobubbles have been widely studied in the field of environmental pollution control due to their distinctive properties, which differ from those of ordinary bubbles. These include their technical advantages in enhancing mass transfer, interfacial potential, and the release of free radicals. New progress has also been made in the application of micro-nanobubbles in wastewater treatment, such as the adsorption and removal of suspended solids, the enhanced decomposition of difficult-to-degrade organic pollutants, and the promotion of biological purification. Research has also been conducted on the use of micro-nanobubbles in wastewater treatment to achieve effective denitrification, optimize synergy with other strong oxidizing conditions, and develop practical nanobubble generators that are low-cost, low-energy, high-performance, and suitable for widespread use. Summary of the Invention

[0005] The present invention aims to leverage the ability of micro-nano bubbles to generate reactive oxygen species, selectively inhibiting the activity and growth of NOBs. This overcomes the difficulty in effectively inhibiting NOBs in municipal wastewater nitritation / anaerobic ammonium oxidation processes, achieving stable nitritation / anaerobic ammonium oxidation of municipal wastewater. Furthermore, the present invention utilizes the MBBR process to form a nitritation / anaerobic ammonium oxidation biofilm, which, compared to activated sludge, effectively prevents the flotation effect of micro-nano bubbles on sludge.

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

[0007] The present invention discloses a biofilm reactor for treating municipal sewage with nanobubble aeration, comprising a bioreactor system, an aeration system and a pump control system;

[0008] The bioreactor system includes a bioreactor for treating sewage, a biofilm carrier is provided inside the bioreactor, a monitoring device for real-time monitoring of the reaction process is provided on the bioreactor, a water inlet and a water outlet are provided on the outer wall of the bioreactor, and the water outlet is located at a position farthest from the water inlet, and the water inlet and the water outlet are connected to a water inlet pipe and a water outlet pipe respectively;

[0009] The aeration system is connected to the bioreactor system and is used to aerate the bioreactor;

[0010] The pump control system is used to control the operation of the pump connected to the bioreactor.

[0011] Furthermore, the monitoring device includes a temperature monitoring mechanism for real-time monitoring of the reactor temperature and an online real-time monitoring mechanism for real-time monitoring of dissolved oxygen and pH value of the reactor.

[0012] Furthermore, the aeration system includes a micro-nano bubble aeration device, and the micro-nano bubble aeration device includes a micro-nano bubble generator. The micro-nano bubble generator is connected to the bioreactor through an air supply pipeline II, and a rotor flowmeter II is provided on the air supply pipeline II.

[0013] Furthermore, the aeration system includes a combined aeration device, and the combined aeration device includes a common aeration device and a micro-nano bubble aeration device;

[0014] The common aeration equipment includes a common aeration device, which is connected to the bioreactor via a gas pipeline I, and a rotor flowmeter I is provided on the gas pipeline I;

[0015] The micro-nano bubble aeration equipment includes a micro-nano bubble generator, which is connected to the bioreactor via an air delivery pipeline II, and a rotor flowmeter II is provided on the air delivery pipeline II.

[0016] Furthermore, the pump control system includes a plug flow pump and a dosing pump. The plug flow pump is arranged inside the bioreactor near the water inlet, and the dosing pump is arranged on the water inlet pipe.

[0017] Furthermore, the aeration port on the outer wall of the bioreactor is located above the plug flow pump.

[0018] Furthermore, a water suction pipe connected to the micro-nano bubble generator is provided on the outer wall of the bioreactor.

[0019] A method for achieving nitritation / anaerobic ammonium oxidation of municipal sewage using nanobubble aeration, wherein the method uses the above-described biofilm reactor for treating municipal sewage using nanobubble aeration to treat municipal sewage, thereby achieving nitritation / anaerobic ammonium oxidation of the municipal sewage, and comprises the following steps:

[0020] Cultivating and enriching anaerobic ammonia oxygen bacteria-related biofilm on the biofilm carrier of the bioreactor, controlling the initial influent total nitrogen load of the bioreactor to 50 mg / m³ / d, and the bioreactor is in enrichment mode;

[0021] When the ammonia nitrogen concentration of the bioreactor effluent is lower than 5 mg / L, the total nitrogen load of the influent is gradually increased at a rate of 10-20%, and the total nitrogen load of the influent is increased each time and operated stably until the total nitrogen removal rate reaches more than 80%, and then the total nitrogen load of the influent is increased again;

[0022] When the total nitrogen load of the influent reaches 200-500 mg / m³ / d or more, and the total nitrogen removal rate is maintained at more than 80%, the anaerobic ammonia oxidizing bacteria biofilm carrier is cultivated and mature, and the bioreactor enters the municipal sewage treatment mode;

[0023] Municipal sewage is pre-treated 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 to the bioreactor through the water inlet pipe, and the operating flow of the dosing pump is set and the hydraulic retention time of the bioreactor is controlled to be 3-8 hours;

[0024] When the bioreactor enters the nitrite treatment stage, the aeration system is turned on for aeration to control the dissolved oxygen to be no less than 1.00-8.00 mg / L; during the anaerobic ammonium oxidation treatment stage, the aeration system is adjusted to control the dissolved oxygen to be no more than 0.10-1.00 mg / L;

[0025] The monitoring device is used to detect the dissolved oxygen, pH value, temperature, inlet and outlet ammonia nitrogen of the reactor in real time. )、nitrite nitrogen( ) and nitrate ( ) Concentration: When the ammonia nitrogen concentration in the effluent of the bioreactor 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;

[0026] Dynamically adjusting the plug flow pump in the bioreactor according to the effluent ammonia nitrogen concentration to maintain the effluent ammonia nitrogen concentration of the sedimentation tank at 5-8 mg / L, thereby promoting rapid substrate uptake by the biofilm;

[0027] The online real-time monitoring mechanism detects that the pH value in the bioreactor is between 7.3 and 8.2;

[0028] The temperature monitoring mechanism detects that the temperature in the bioreactor is between 20°C and 34°C;

[0029] Calculate the nitrite accumulation rate NAR: is the nitrite nitrogen concentration in the reactor effluent, TN is the total nitrogen concentration in the reactor effluent, , and determine whether to perform aeration based on the nitrite accumulation rate NAR;

[0030] The concentrations of ammonia nitrogen, nitrite nitrogen and nitrate nitrogen in the effluent of the bioreactor were monitored. After the bioreactor system reached stability, the ammonia nitrogen removal rate in the effluent reached more than 90%, the total nitrogen removal rate reached more than 80%, and it operated stably for more than one month, indicating that the denitrification process of urban sewage was stably achieved.

[0031] Furthermore, when the effluent ammonia nitrogen concentration is higher than 10-20 mg / L, the dissolved oxygen is increased; when the effluent ammonia nitrogen concentration is lower than 5 mg / L, the dissolved oxygen is reduced.

[0032] Furthermore, when NAR>30%, the anoxic period is extended; when NAR<20% and the effluent ammonia nitrogen concentration is higher than 8 mg / L, the aerated aerobic period is extended.

[0033] Compared with the prior art, the present invention has the following beneficial technical effects:

[0034] The present invention provides an autotrophic denitrification process using MBs / NBs aeration, which achieves efficient and stable nitrite-anaerobic ammonium oxidation (ANAOMOX) denitrification of municipal sewage and is a technology urgently needed by municipal sewage treatment plants. The process utilizes the characteristic that ANAOMOX bacteria easily aggregate to form biofilms. By adding a novel biofilm carrier to a bioreactor to form a biofilm, combined with control of parameters such as hydraulic retention time and dissolved oxygen in the bioreactor, the biofilm is formed to promote the niche differentiation of AnAOB and AOB, resulting in efficient enrichment of ANAOMOX bacteria in the inner layer of the biofilm carrier, while AOB are enriched in the outer layer of the biofilm.

[0035] The MBs / NBs aeration technology used in this invention can significantly increase the dissolved oxygen concentration in the water, allowing oxygen molecules to diffuse more quickly 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 nitritation and other life activities, while also improving oxygen utilization and promoting energy conservation.

[0036] The present invention generates ROS through the collapse of MBs / NBs bubbles during MBs / NBs aeration. The ROS generation is controlled by the aeration volume, thereby increasing the intracellular reactive oxygen species (ROS) levels of AOB and AnAOB. ​​Furthermore, based on the fact that AOB and AnAOB have a much greater ability to eliminate reactive oxygen species than nitrite-oxidizing bacteria (NOB), the growth of NOB is selectively inhibited. The present invention combines the control of hydraulic retention time to achieve the elutriation of NOB within the system. Ultimately, the nitritation-anaerobic ammonium oxidation process is completed through the collaboration of the AOB and AnAOB systems, thereby achieving autotrophic denitrification of municipal sewage.

[0037] The present invention uses nanobubble aeration to realize the method of nitrification / anaerobic ammonium oxidation of urban sewage to improve the efficiency of sewage denitrification and reduce the cost of urban sewage treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The present invention will be further described below with reference to the accompanying drawings.

[0039] Figure 1 This is a schematic structural diagram of a biofilm reactor for treating municipal sewage with nanobubble aeration according to the present invention;

[0040] Figure 2 This is a diagram showing the operation of the reactor of the present invention.

[0041] Explanation of the accompanying symbols: 1. Bioreactor; 1-1. Water inlet; 1-2. Water outlet; 2. Biofilm carrier; 3. Plug flow pump; 4. Water inlet pipe; 5. Dosing pump; 6. Water outlet pipe; 7. Temperature monitoring mechanism; 8. Online real-time monitoring mechanism; 9. Ordinary aeration device; 10. Gas pipeline I; 11. Rotor flowmeter I; 12. Micro-nano bubble generator; 13. Gas pipeline II; 14. Rotor flowmeter II; 15. Water suction pipe; 16. Sampling port. DETAILED DESCRIPTION

[0042] like Figure 1 As shown, a biofilm reactor for treating municipal sewage with nanobubble aeration includes a bioreactor system, an aeration system and a pump control system;

[0043] The bioreactor system includes a bioreactor 1 for treating sewage, a biofilm carrier 2 is provided inside the bioreactor 1, a monitoring device for real-time monitoring of the reaction process is provided on the bioreactor 1, a water inlet 1-1 and a water outlet 1-2 are provided on the outer wall of the bioreactor 1, and the water outlet 1-2 is located at the position farthest from the water inlet 1-1 to ensure that the sewage has sufficient residence time in the reactor, and the water inlet 1-1 and the water outlet 1-2 are respectively connected to the water inlet pipe 4 and the water outlet pipe 6;

[0044] The aeration system is connected to the bioreactor system and is used to aerate the bioreactor 1;

[0045] The pump control system is used to control the operation of the pump connected to the bioreactor 1 .

[0046] Specifically, the biofilm carrier 2 mainly serves to provide an attachment medium for the microbial community in the bioreactor 1. The biofilm carrier material mainly adopts artificial synthetic high molecular 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). The main models of the carriers are classified according to the specific surface area of ​​the carriers: K series, NATRIX series, F series, BiofilmChip series, Z series and Activecell series, etc. This embodiment recommends the use of a hydrophilic modified biofilm carrier, that is, a hydrophilic K3 biofilm carrier with a water-solid-liquid interface contact angle of 41° made of an oxidized composite PHBV / PVA material, and its specific surface area is 300 to 600 m² / m³.

[0047] The monitoring device includes a temperature monitoring mechanism 7 for real-time monitoring of the reactor temperature and an online 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 online real-time monitoring mechanism 8 are arranged near the water outlet 1-2 to monitor the ammonia nitrogen, nitrite nitrogen, nitrate nitrogen, temperature, pH, dissolved oxygen and other parameters of the outlet water in real time; a sampling port 16 is also designed at the water outlet 1-2.

[0048] Specifically, the online real-time monitoring mechanism 8 is recommended to use a Hach 40d detector. The dissolved oxygen level in the reactor is controlled according to the operating steps. The dissolved oxygen level in the aerobic zone is generally 1.00-8.00 mg / L, and the dissolved oxygen level in the anaerobic zone is generally 0.10-1.00 mg / L. The pH value is controlled between 7.3 and 8.2. The temperature monitoring mechanism 7 is a thermometer used to monitor the temperature within the bioreactor 1. The recommended temperature range is 20-34°C.

[0049] The aeration system can be designed in two forms:

[0050] (1) The aeration system includes a micro-nano bubble aeration device, which includes a micro-nano bubble generator 12. The micro-nano bubble generator 12 is connected to the bioreactor 1 through a gas pipeline II 13. A rotor flowmeter II 14 is provided on the gas pipeline II 13.

[0051] (2) The aeration system includes a combined aeration device, which includes a common aeration equipment and a micro-nano bubble aeration equipment; the common aeration equipment includes a common aeration device 9, which is connected to the bioreactor 1 through a gas pipeline I 10, and a rotor flowmeter I 11 is provided on the gas pipeline I 10; the micro-nano bubble aeration equipment includes a micro-nano bubble generator 12, which is connected to the bioreactor 1 through a gas pipeline II 13, and a rotor flowmeter II 14 is provided on the gas pipeline II 13.

[0052] Specifically, the micro-nano bubble generator 12 is an aeration device capable of stably generating nanobubbles (air-NBs) with a diameter of 100 to 1000 nm and microbubbles (air-MBs) with a diameter of 1 to 100 µm. The conventional aeration device 9 is an aeration device capable of stably generating conventional bubbles (air-CBs), such as a blower aerator or a centrifugal aerator. A blower aerator is recommended.

[0053] The micro-nano bubbles and the novel biofilm carrier have a good effect of promoting biofilm formation, and the biofilm growth rate is 0.18-0.33±0.02 / d (doubling time of 3.9-2.1 / d).

[0054] Under the action of the micro-nano bubble generator 12 and the plug flow pump 3, the plug flow 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 processing capacity of AOB and AnAOB.

[0055] The pump control system includes a plug flow pump 3 and a dosing pump 5. The plug flow pump 3 is arranged inside the bioreactor 1 near the water inlet 1-1, providing a plug flow effect during the operation of the bioreactor 1 to ensure the fluidity and uniformity of the carrier and substrate in the bioreactor 1; the dosing pump 5 is installed on the water inlet pipe 4.

[0056] The aeration port on the outer wall of the bioreactor 1 is located above the plug flow pump 3. Specifically, the aeration port includes a nano bubble aeration port and a common bubble aeration port, and the aeration volume of the aerobic section of the PN / A is controlled by an air valve.

[0057] A water suction pipe 15 connected to the micro-nano bubble generator 12 is connected to the outer wall of the bioreactor 1 , and the water suction pipe 15 and the gas pipeline II 13 are respectively installed on both sides of the bioreactor 1 .

[0058] A method for achieving nitritation / anaerobic ammonium oxidation of municipal sewage using nanobubble aeration, wherein the method uses the above-described biofilm reactor for treating municipal sewage using nanobubble aeration to treat municipal sewage, thereby achieving nitritation / anaerobic ammonium oxidation of the municipal sewage, and comprises the following steps:

[0059] Cultivating and enriching anaerobic ammonia oxygen bacteria-related biofilm on the biofilm carrier 2 of the bioreactor 1, controlling the initial influent total nitrogen load of the bioreactor 1 to 50 mg / m³ / d, and the bioreactor 1 is in enrichment mode;

[0060] When the ammonia nitrogen concentration of the effluent of the bioreactor 1 is lower than 5 mg / L, the total nitrogen load of the influent is gradually increased by 10-20%, and the total nitrogen load of the influent is increased each time and operated stably until the total nitrogen removal rate reaches more than 80%, and then the total nitrogen load of the influent is increased again;

[0061] When the total nitrogen load of the influent reaches 100 mg / m³ / d or more and the total nitrogen removal rate is maintained at more than 80%, the anaerobic ammonia oxidizing bacteria biofilm carrier is cultivated and mature, and the bioreactor 1 enters the municipal sewage treatment mode;

[0062] The municipal sewage is pre-treated to remove COD, reducing the COD content in the sewage to below 10 mg / L, and converting organic nitrogen in the water into ammonia nitrogen. The municipal sewage after primary treatment is pumped by the water inlet pump and fed into the bioreactor 1 through the water inlet pipe 4. The operating flow rate of the dosing pump 5 is set, and the hydraulic retention time of the bioreactor 1 is controlled to 6 hours.

[0063] The bioreactor 1 enters the nitrite treatment stage, opens the aeration system for aeration, and controls the dissolved oxygen to be not less than 1.50 mg / L; in the anaerobic ammonium oxidation treatment stage, adjusts the aeration system, and controls the dissolved oxygen to be not more than 0.50 mg / L;

[0064] The monitoring device is used to detect the dissolved oxygen, pH value, temperature, inlet and outlet ammonia nitrogen of the reactor in real time. )、nitrite nitrogen( ) and nitrate ( ) Concentration: 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;

[0065] Dynamically adjust the plug flow pump 3 in the bioreactor 1 according to the effluent ammonia nitrogen concentration to maintain the effluent ammonia nitrogen concentration of the sedimentation tank at 5-8 mg / L, thereby promoting rapid substrate uptake by the biofilm;

[0066] When the effluent ammonia nitrogen concentration is higher than 20 mg / L, the dissolved oxygen is increased; when the effluent ammonia nitrogen concentration is lower than 5 mg / L, the dissolved oxygen is reduced;

[0067] The online real-time monitoring mechanism 8 detects that the pH value in the bioreactor 1 is between 7.3 and 8.2;

[0068] The temperature monitoring mechanism 7 detects that the temperature in the bioreactor 1 is between 20°C and 34°C;

[0069] Calculate the nitrite accumulation rate NAR: is the nitrite nitrogen concentration in the reactor effluent, TN is the total nitrogen concentration in the reactor effluent, , and determine whether to perform aeration based on the nitrite accumulation rate NAR; when NAR>30%, extend the anoxic period; when NAR<20% and the effluent ammonia nitrogen concentration is higher than 8 mg / L, extend the aerobic aeration period; 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 denitrification process of urban sewage is stably achieved, and the reactor operation effect is as shown in the attached figure. Figure 2 shown.

[0070] In the present invention, under the action of the inherent characteristics of micro-nano bubbles (MBs / NBs):

[0071] (1) The size of MBs / NBs is very small, resulting in a large specific surface area. The internal pressure of the bubbles is much greater than the atmospheric pressure. Under the interference of external factors (such as hydraulic shear), the MBs / NBs will collapse and produce ROS.

[0072] (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 internal pressure of the bubble (far greater than atmospheric pressure). In other words, the bubble has a strong driving force for diffusion. The huge specific surface area and high internal pressure make MBs / NBs have strong surface reaction and mass transfer efficiency.

[0073] (3) MBs / NBs have the characteristics of colloidal particles (zeta potential and surface charge): they are negatively charged in a wide pH range, except when the pH is low (strongly acidic). The microorganisms in the bioreactor of this patent are in the pH range of 7.3 to 8.2.

[0074] The effects of using micro-nano bubbles in the present invention are:

[0075] (1) According to the characteristics of MBs / NBs, a plug flow pump is provided in the bioreactor of the present invention, and the carrier and sewage are in a circulating flow state, that is, MBs / NBs will collapse and produce ROS under the interference of external factors. Due to the biological enzyme characteristics of NOBs and Anammox flora, the degradation ability of NOBs biological enzyme to ROS is much lower than that of Anammox flora. At the same time, MBs / NBs can also promote the activity of dehydrogenase in Anammox flora. While inhibiting the activity of NOBs, it also greatly stimulates the biological activity of Anammox flora, thereby increasing the rapid colonization and proliferation rate of Anammox in the biofilm.

[0076] (2) According to the characteristics of MBs / NBs, that is, the huge specific surface area and high internal pressure of micro-nano bubbles under the action of their own diffusion driving force make MBs / NBs have strong surface reaction and mass transfer efficiency. When air-MBs / NBs enter the bioreactor, the oxygen molecules in the air-MBs / NBs enter the water environment at an extremely fast diffusion rate, greatly increasing the dissolved oxygen in the water, thereby allowing the oxygen molecules to enter the surface of the carrier's biofilm faster, promoting the AOBs on the biofilm to absorb oxygen molecules for nitrosation and other life activities.

[0077] MBs / NBs also have a longer-term stability. Even under the influence of external interference, MBs / NBs can stay in the water environment for about 5 to 10 minutes compared to CBs aeration. This means that MBs / NBs can provide a more lasting and stable dissolved oxygen environment. Compared with CBs aeration, the energy consumption of NBs aeration is reduced by nearly 80%.

[0078] (3) MBs / NBs have the characteristics of colloidal particles (zeta potential and surface charge), that is, MBs / NBs have a Tyndall effect in pure water, which can be used to preliminarily judge the formation status of micro-nano bubbles; at the same time, the zeta potential and surface charge properties of MBs / NBs make the redox potential of the water environment in the reactor at a negative potential, promoting the life activities of microorganisms such as the absorption and utilization of electron donors and acceptors, and indirectly improving the activity of biological enzymes.

[0079] Currently, the mechanisms for the generation of micro-nano bubbles mainly include fluid dynamics and acoustic cavitation, electrolysis, porous materials, fluid oscillation, and pressurized dissolution and decompression. The main methods for producing micro-nano bubbles include pressurized dissolved air release, dispersed air, electrolysis, and flotation pump gas generation. In the present invention, the dispersed air method is recommended as the method for generating micro-nano bubbles. Its main principle is to use hydraulic shearing, high-speed vortex flow, etc. to generate shear force and create extreme conditions, repeatedly shearing and crushing the air, causing it to mix with water to generate a large number of micro-nano bubble air-water mixtures. The diameter of the generated micro-nano bubbles ranges from 0.2 to 100 µm.

[0080] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for achieving nitritation / anaerobic ammonium oxidation of municipal sewage by nanobubble aeration, wherein the method uses a biofilm reactor with nanobubble aeration to treat municipal sewage, thereby achieving nitritation / anaerobic ammonium oxidation of municipal sewage, and is characterized by: The biofilm reactor includes a bioreactor system, an aeration system and a pump control system; The bioreactor system comprises a bioreactor (1) for treating sewage, a biofilm carrier (2) being provided inside the bioreactor (1), a monitoring device for real-time monitoring of the reaction process being provided on the bioreactor (1), a water inlet (1-1) and a water outlet (1-2) being provided on the outer wall of the bioreactor (1), and the water outlet (1-2) being located at a position farthest from the water inlet (1-1), and the water inlet (1-1) and the water outlet (1-2) being connected to a water inlet pipe (4) and a water outlet pipe (6), respectively; The aeration system is connected to the bioreactor system and is used to aerate the bioreactor (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) via a gas pipeline II (13), and a rotor flowmeter II (14) is provided on the gas pipeline II (13); A water suction pipe (15) connected to the micro-nano bubble generator (12) is provided on the outer wall of the bioreactor (1); The pump control system is used to control the operation of the pump connected to the bioreactor (1); The pump control system comprises a plug flow pump (3) and a dosing pump (5), wherein the plug flow pump (3) is arranged inside the bioreactor (1) near the water inlet (1-1), and the dosing pump (5) is arranged on the water inlet pipe (4); The method comprises the following steps: Cultivating and enriching anaerobic ammonia-oxygen-related biofilms on the biofilm carrier (2) of the bioreactor (1), controlling the initial influent total nitrogen load of the bioreactor (1) to 50 mg / m³ / d, and placing the bioreactor (1) in an enrichment mode; When the ammonia nitrogen concentration of the effluent of the bioreactor (1) is lower than 5 mg / L, the total nitrogen load of the influent is gradually increased at a rate of 10-20%, and the influent total nitrogen load is increased each time and operated stably until the total nitrogen removal rate reaches more than 80%, and then the influent total nitrogen load is increased again; When the total nitrogen load of the influent reaches 200 to 500 mg / m³ / d or more, and the total nitrogen removal rate is maintained at more than 80%, the anaerobic ammonia oxidizing bacteria biofilm carrier is cultivated and mature, and the bioreactor (1) enters the urban sewage treatment mode; Municipal sewage is pre-treated to remove COD, so that the COD in the sewage reaches below 10 to 20 mg / L, and organic nitrogen in the water is converted into ammonia nitrogen. The sewage is added to the bioreactor (1) through the water inlet pipe (4), and the operating flow of the dosing pump (5) is set and the hydraulic retention time of the bioreactor (1) is controlled to be 3 to 8 hours; The bioreactor (1) enters the nitrite treatment stage, opens 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 more than 0.10-1.00 mg / L; The monitoring device is used to detect the dissolved oxygen, pH value, temperature, inlet and outlet ammonia nitrogen, nitrite nitrogen and nitrate nitrogen concentrations of the reactor in real time: when the outlet ammonia nitrogen concentration 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; Dynamically adjusting the plug flow pump (3) in the bioreactor (1) according to the effluent ammonia nitrogen concentration to maintain the effluent ammonia nitrogen concentration of the sedimentation tank at 5 to 8 mg / L, thereby promoting rapid substrate uptake by the biofilm; An online 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°C and 34°C; Calculate the nitrite accumulation rate NAR: is the nitrite nitrogen concentration, TN is the total nitrogen concentration, , and determine whether to perform aeration based on the nitrite accumulation rate NAR; The concentrations of ammonia nitrogen, nitrite nitrogen, and nitrate nitrogen in the effluent of the bioreactor (1) were monitored. After the bioreactor (1) system reached stability, the ammonia nitrogen removal rate in the effluent reached more than 90%, the total nitrogen removal rate reached more than 80%, and the system operated stably for more than one month, indicating that the denitrification process of urban sewage was stably achieved.

2. The method for achieving nitritation / anaerobic ammonium oxidation of municipal sewage by nanobubble aeration according to claim 1, characterized in that: The aeration system includes a combined aeration device, which includes a common aeration device and a micro-nano bubble aeration device; The common aeration equipment comprises a common aeration device (9), the common aeration device (9) is connected to the bioreactor (1) via a gas pipeline I (10), and a rotor flowmeter I (11) is provided on the gas pipeline I (10); The micro-nano bubble aeration device comprises a micro-nano bubble generator (12), the micro-nano bubble generator (12) is connected to the bioreactor (1) via a gas transmission pipeline II (13), and a rotor flowmeter II (14) is provided on the gas transmission pipeline II (13).

3. The method for achieving nitritation / anaerobic ammonium oxidation of municipal sewage by nanobubble aeration according to claim 1, characterized in that: The monitoring device comprises a temperature monitoring mechanism (7) for real-time monitoring of the reactor temperature and an online real-time monitoring mechanism (8) for real-time monitoring of dissolved oxygen and pH value in the reactor.

4. The method for achieving nitritation / anaerobic ammonium oxidation of municipal sewage by nanobubble aeration according to claim 1, characterized in that: The aeration port on the outer wall of the bioreactor (1) is located above the plug flow pump (3).

5. The method for achieving nitritation / anaerobic ammonium oxidation of municipal sewage by nanobubble aeration according to claim 1, characterized in that: When the effluent ammonia nitrogen concentration is higher than 10-20 mg / L, the dissolved oxygen is increased; when the effluent ammonia nitrogen concentration is lower than 5 mg / L, the dissolved oxygen is reduced.

6. The method for achieving nitritation / anaerobic ammonium oxidation of municipal sewage by nanobubble aeration according to claim 1, characterized in that: When NAR>30%, extend the anoxic period; when NAR<20% and the effluent ammonia nitrogen concentration is higher than 8 mg / L, extend the aerated aerobic period.

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