MBBR (Moving Bed Biofilm Reactor) sewage treatment method for efficiently supplying oxygen by nano bubbles

Abstract

The invention discloses an MBBR (Moving Bed Biofilm Reactor) sewage treatment method capable of efficiently supplying oxygen through nanobubbles, and relates to the technical field of sewage treatment. A required treatment system comprises an MBBR reaction tank, a suspended carrier fluidization system, a suspended carrier interception system and a nano aeration system, the MBBR reaction tank is filled with suspended carriers, the suspended carrier interception system comprises a tiled interception screen and an effluent interception screen, and the tiled interception screen is located on the bottom surface of the MBBR reaction tank and is parallel to the bottom surface; the nano aeration system comprises a nano aerator and a nano gas generating device, the nano gas generating device is positioned outside the MBBR reaction tank and is connected with the nano aerator positioned in the MBBR reaction tank, and the aeration rate of the nano aerator is calculated according to a formula. According to the invention, the synchronous energy-saving and high-efficiency decontamination process is realized by fully utilizing the characteristics of a biofilm method and the advantages of the nanobubbles.

Description

Technical Field

[0001] The invention relates to the technical field of sewage treatment, and in particular to an MBBR sewage treatment method with nanobubbles providing efficient oxygen. Background Art

[0002] Biochemical process is the core process unit of sewage treatment, responsible for more than 80% of pollutant removal. It is also the process unit with the largest land area and the highest energy consumption in sewage treatment plants. 60% to 80% of the land in sewage treatment plants is used for the construction of biochemical processes, and 50% of the electricity consumption comes from biochemical processes. Therefore, biochemical processes are the key to achieving sustainable development of sewage treatment plants and energy conservation and carbon reduction. From the perspective of biochemical processes, the biofilm method has become the first choice for the construction and operation of sewage treatment plants in the new era due to its efficient pollution removal performance. From the perspective of the oxygen supply system of biochemical core equipment, micro-nano bubbles have a wide range of application prospects in water treatment due to their slow rising speed, long residence time, high dissolution efficiency, self-oxygenation, negative charge and rich in strong oxidizing free radicals. The combination of the two processes can not only improve oxygen utilization and reduce energy consumption, but also improve pollution removal performance and reduce land occupation. It is the key to the transformation of sewage treatment plants to green and low-carbon.

[0003] At present, the research reports on micro-nano aeration in the field of water treatment are as follows:

[0004] CN110143664B discloses a micro-nano aeration BAF treatment device and treatment process, including a BAF device, a micro-nano bubble generator, and a backwash device. The BAF device includes a sewage inlet pump, a BAF reaction tank, a sewage circulation pump, and a basket filter. The micro-nano bubble generator includes a micro-nano bubble generator housing, a nano-grade ceramic membrane tube, a liquid flow meter, a gas rotor flow meter, a gas pressure gauge, and a gas control valve. By supplying micro-nano bubbles to the system, the gas utilization rate is improved, and COD in sewage is removed with high removal efficiency and low energy consumption, and at the same time, the surface of the BAF reaction tank will not be caused to roll. The main technical problems that exist in the treatment device and treatment process are: 1. Uneven gas supply. The filter material of the BAF device is fixed. Since the supplied micro-nano bubbles rise very slowly and are blocked by the filter material during the rising process, the distribution resistance of the bubbles is increased, which easily leads to an anaerobic environment on the upper layer of the filter material, thereby affecting the removal effect; 2. The biofilm is thickened and the operation control is complicated. Micro-nano bubbles will strengthen the mass transfer process and improve the removal efficiency. Therefore, for the BAF process, the biofilm grows faster than the traditional process. Therefore, in order to control the thickness of the biofilm, the backwashing frequency is increased compared with the traditional process, which indirectly increases the complexity of operation control; ③ Whether the energy consumption problem can be reduced remains to be verified. The energy consumption of BAF comes from aeration on the one hand and backwashing on the other hand. The nano aeration method reduces the energy consumption of aeration, but increases the energy consumption of backwashing. Therefore, whether the total energy consumption can be reduced by combining the two remains to be verified by engineering.

[0005] CN214781329U discloses a micro-nano MBBR small integrated rural domestic sewage treatment equipment, which uses nano aeration instead of blower aeration, which can effectively reduce equipment noise and does not affect the daily life of surrounding residents; nano aeration instead of blower aeration can effectively improve the utilization efficiency of oxygen, and the dissolution rate of micro-nano bubbles in water exceeds 85%, which can effectively reduce the operating cost. Nano aeration replaces the traditional aeration head with an atomizer. Compared with traditional aeration equipment, the aeration head is located in the pool, which reduces the difficulty and cost of installation and maintenance; under the same aeration intensity, the nano aerator produces more dissolved oxygen than ordinary aerators, has a higher biochemical oxygen demand and ammonia nitrogen removal rate, and improves the water purification treatment effect. The main technical problems of this treatment device are: nano aeration is used in the aerobic zone, which improves the oxygen utilization rate, but K3 filler is added to the aerobic zone at the same time. As is well known to industry personnel, K3 filler is a suspended carrier, and the aeration intensity of nano aeration cannot maintain the uniform fluidization of K3 filler. The non-fluidization of the filler means that the aerobic zone has no decontamination function, which contradicts the so-called high oxygen utilization rate.

[0006] It can be seen that there are still many problems in the application of micro-nano aeration in the field of water treatment, and the existing technology needs to be further improved. Summary of the invention

[0007] The object of the present invention is to provide an MBBR sewage treatment method with nanobubbles for efficient oxygen supply, which applies nanobubbles to the MBBR sewage treatment method, and achieves a synchronous energy-saving and efficient pollution removal process by optimizing process conditions and operating parameters.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] A nanobubble efficient oxygen supply MBBR sewage treatment method comprises the following steps in sequence:

[0010] a. Prepare the required processing system

[0011] The treatment system includes an MBBR reaction tank, a suspended carrier fluidization system, a suspended carrier interception system and a nano aeration system. The MBBR reaction tank is filled with suspended carriers. The suspended carrier interception system includes a flat interception screen and an outlet interception screen. The suspended carrier fluidization system includes an agitator and a perforated aeration pipe located in the MBBR reaction tank. The nano aeration system includes a nano aerator and a nano gas generator. The nano gas generator is located outside the MBBR reaction tank and is connected to the nano aerator located in the MBBR reaction tank. The flat interception screen is parallel to the bottom surface of the MBBR reaction tank and is located above the nano aerator.

[0012] The specific gravity of the suspension carrier is 1.10 g / cm 3 ~1.20g / cm 3 , is a cylindrical suspension carrier with a thickness of 3mm to 5mm and a suspension carrier pore size of 4mm to 5mm;

[0013] b. The treated sewage enters the MBBR reaction tank, the agitator is turned on, the inlet SS is lower than 50 mg / L, and nano bubbles are provided into the reaction tank through the nano aerator; the aeration rate of the nano aerator is calculated according to formula (1):

[0014]

[0015] In formula (1): α is the oxygen mass transfer correction coefficient, E A is the oxygen transfer efficiency of the nano aerator, AOR is the total oxygen demand, Cs' is the saturated dissolved oxygen of clean water at the actual temperature, Cs is the saturated dissolved oxygen of the wastewater to be treated at the actual temperature, and C is the actual DO of the treatment system;

[0016] c. Run:

[0017] During normal operation, the power density of the agitator is 7.5-10W / m 3 , the aeration volume of the perforated aeration tube is twice the area of ​​the intercepting screen;

[0018] In the strong hydraulic shear stage, the power density of the agitator is 15-20W / m 3 , the aeration volume of the perforated aeration tube is 4 times the area of ​​the intercepting screen;

[0019] For MBBR reaction pools whose core is to remove organic matter, the strong hydraulic shear stage is started every 10 to 15 days, and each time it is turned on for 2 to 3 hours; for MBBR reaction pools whose core is to remove ammonia nitrogen, the strong hydraulic shear stage is started every 20 to 25 days, and each time it is turned on for 1 to 2 hours.

[0020] In the above-mentioned MBBR wastewater treatment method with nanobubble efficient oxygen supply, the effluent interception screen is located at the effluent end of the MBBR reaction tank and is perpendicular to the water flow direction.

[0021] In the above-mentioned MBBR sewage treatment method with nanobubble efficient oxygen supply, the nano aerator is located between the flat interception screen and the bottom surface of the MBBR reaction tank, and a plurality of nano aerators are evenly spaced.

[0022] In the above-mentioned MBBR wastewater treatment method with nanobubble efficient oxygen supply, the aperture of the nanoaerator is 100nm-500nm, the value of α is 0.95, and E A The value ranges from 0.90% to 0.95%.

[0023] In the above-mentioned MBBR sewage treatment method with nanobubble efficient oxygen supply, the perforated aeration pipe is located 5 cm to 10 cm below the bottom of the effluent interception screen, and the openings of the holes on the perforated aeration pipe face upward.

[0024] The above-mentioned MBBR sewage treatment method with nanobubble efficient oxygen supply, the agitator is a variable frequency agitator, and the installed power density is 7-20W / m 3 .

[0025] The specific gravity of the above-mentioned suspension carrier is 1.15g / cm 3 , thickness is 4mm.

[0026] Compared with the prior art, the present invention brings the following beneficial technical effects:

[0027] (1) The present invention proposes a MBBR sewage treatment method with nanobubble efficient oxygen supply, which applies nanoaerator to MBBR sewage treatment, and adjusts the parameters such as the density, thickness, and pore size of the suspended carrier. For example, the density of the suspended carrier is adjusted to be larger to match the nanoaerator to produce more bubbles; since the nanoaerator has better mass transfer and thick biofilm, the pore size of the suspended carrier is adjusted to be larger. Due to the influence of the nanoaerator on the MBBR, such as strong mass transfer and thickening of the biofilm, strong fluidization flushing is performed during the operation stage, and adjustments are made according to different operation stages. The frequency of decarbonization backwashing is higher when the heterotrophic bacteria grow faster, and the frequency of backwashing is lower when the nitrification grows slower.

[0028] (2) The present invention saves aeration volume, saves energy and reduces consumption. Nano bubbles have a smaller diameter and a larger specific surface area, and the aerator has a higher oxygen transfer efficiency. Compared with traditional aeration methods, nano aeration can save more than 75% of aeration volume, thereby reducing energy consumption.

[0029] (3) The present invention has high pollution removal efficiency and saves land. The nanobubbles stay in the water for a long time, which can provide sufficient oxygen for microorganisms, improve the biofilm mass transfer effect, increase the treatment efficiency, shorten the biochemical reaction time, and reduce the land area by 70% compared with the traditional activated sludge method and further reduce the land area by 20% compared with the traditional MBBR.

[0030] (4) The present invention reduces the energy consumption of fluidization of the suspended carrier. The aerobic zone of the system uses a stirrer instead of the traditional aeration shear, and the fluidization kinetic energy is lower. Taking a sewage treatment plant in the north as an example, the fluidization kinetic energy is reduced by more than 80%. It not only maintains the uniform fluidization of the suspended carrier, but also ensures that oxygen can be evenly and fully transmitted to the sewage for efficient utilization.

[0031] (5) The present invention has flexible operation control and stable effect. By flexibly adjusting the power density at different times, the normal thickness of the biofilm is maintained, which effectively avoids the problem of biofilm thickening under efficient mass transfer, ensures the long-term stable mass transfer and oxygen transfer process of the system, and realizes the stable operation of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The present invention will be further described below in conjunction with the accompanying drawings:

[0033] Figure 1 It is the front view of the processing system of the present invention;

[0034] Figure 2 A top view of the processing system of the present invention;

[0035] Figure 3 This is the operation effect diagram of the pilot system;

[0036] In the figure:

[0037] 1. Agitator, 2. MBBR reaction tank, 3. Nano aerator, 4. Perforated aeration tube, 5. Effluent interception screen, 6. Flat interception screen, 7. Suspended carrier, 8. Nano gas generator. DETAILED DESCRIPTION

[0038] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application.

[0039] It is understandable that the connection relationship described in this application refers to direct or indirect connection. For example, the connection between A and B can be either a direct connection between A and B or an indirect connection between A and B through one or more other electrical components. For example, A and C can be directly connected, and C and B can be directly connected, so that A and B are connected through C. It is also understandable that the "A connects B" described in this application can be a direct connection between A and B, or an indirect connection between A and B through one or more other electrical components.

[0040] The technical concept of the present invention is: the moving bed biofilm reactor (MBBR) is used for the biochemical process of water treatment, and its microbial essence is a biofilm, and its hydraulic characteristics are fluidization. Compared with the traditional activated sludge method, the biofilm method has a stronger enrichment ability for functional bacteria. From a microscopic level, the relative abundance of functional bacteria is generally more than 10 times that of activated sludge, but from a macroscopic level, the treatment performance of the biofilm method is only twice that of the activated sludge method. The main reason is that the decontamination process of the biofilm is mainly based on mass transfer and oxygen transfer. Since liquid ions have less transfer resistance and higher transfer rate than gas molecules, for MBBR, it is essentially DO mass transfer that restricts the efficient performance of the decontamination performance of the biofilm. Therefore, the present invention makes full use of the characteristics of the biofilm method and the advantages of nanobubbles to achieve synchronous energy saving and efficient decontamination process.

[0041] Combination Figure 1 and Figure 2 As shown, the present invention provides an MBBR sewage treatment method with nanobubble efficient oxygen supply, and the required treatment system includes an MBBR reaction tank 2, a suspended carrier fluidization system, a suspended carrier interception system and a nano aeration system.

[0042] The MBBR reaction tank includes a tank body, a water inlet and a water outlet. The tank body is filled with a suspended carrier 7, which is an MBBR biofilm filler. In order to cooperate with the nano aerator, the specific gravity of the suspended carrier is adjusted to 1.10 g / cm 3 ~1.20g / cm 3 The shape is a cylindrical suspension carrier, the thickness is adjusted to 3mm~5mm, and the pore size of the suspension carrier is adjusted to 4mm~5mm.

[0043] The suspended carrier interception system includes a flat interception screen 6 and an outlet interception screen 5. The flat interception screen is located on the bottom surface of the MBBR reaction tank and is parallel to the bottom surface. The suspended carrier is located above the flat interception screen and the nano aerator 3 is located below. The suspended carrier fluidization system includes an agitator 1 and a perforated aeration tube 4 located in the MBBR reaction tank. The nano aeration system includes a nano aerator 3 and a nano gas generator 8. The nano gas generator is located outside the MBBR reaction tank and is connected to the nano aerator located in the MBBR reaction tank. The pore size of the nano aerator is 100nm to 500nm.

[0044] Preferably, the stirrer is a variable frequency stirrer with an installed power density of 7 to 20 W / m 3 , air volume of perforated aeration pipe (m 3 / h) is 2 to 4 times the outlet interception screen area (S).

[0045] The operation method of the above system will be described below in conjunction with the above system.

[0046] Step 1: The sewage to be treated enters the MBBR reaction tank, the agitator is turned on, the inlet SS is lower than 50 mg / L, and nano bubbles are provided to the MBBR reaction tank through the nano aerator; the aeration rate of the nano aerator is calculated according to formula (1):

[0047]

[0048] In formula (1): α is the oxygen mass transfer correction coefficient, E A is the oxygen transfer efficiency of the nano aerator, AOR is the total oxygen demand, Cs' is the saturated dissolved oxygen of clean water at the actual temperature, Cs is the saturated dissolved oxygen of the wastewater to be treated at the actual temperature, and C is the actual DO of the treatment system;

[0049] Step 2: Run:

[0050] During normal operation, the power density of the agitator is 7.5-10W / m 3 , the aeration volume of the perforated aeration tube is twice the area of ​​the intercepting screen;

[0051] In the strong hydraulic shear stage, the power density of the agitator is 15-20W / m 3 , the aeration volume of the perforated aeration tube is 4 times the area of ​​the intercepting screen;

[0052] For MBBR reaction pools whose core is to remove organic matter, the strong hydraulic shear stage is started every 10 to 15 days, and each time it is turned on for 2 to 3 hours; for MBBR reaction pools whose core is to remove ammonia nitrogen, the strong hydraulic shear stage is started every 20 to 25 days, and each time it is turned on for 1 to 2 hours.

[0053] The present invention will be further described below in conjunction with specific embodiments.

[0054] Embodiment 1:

[0055] The design scale of a sewage plant in the north is 10000m 3 / d, treating municipal sewage, using MBBR-based AO process system, with a total residence time of 10h, including 5h for aerobic and 5h for anoxic. The aerobic zone adopts traditional aeration method, and air is supplied based on the inlet and outlet water quality requirements. The anoxic zone adopts a stirrer method. The air demand in the aerobic zone is designed according to the inlet water quality, and the installed power density of the stirrer in the anoxic zone is 10W / m 3 The long-term energy consumption is shown as 0 according to the test. In actual operation, the aeration of the aerobic zone is 0.387kWh / m 3 , stirring in the anoxic zone 0.050kWh / m 3 The power energy consumption in the anoxic zone is 13% of that in the aerobic zone.

[0056] Table 1 Energy consumption of different fluidization kinetic energy

[0057] Serial number Functional area Suspended carrier fluidization dynamics Tons of water and electricity consumption 1 Aerobic Aeration 0.387 2 Hypoxia Stirring 0.050

[0058] It can be seen from Example 1 that the energy consumption of using a stirrer for suspended fluidization is lower than that of aeration.

[0059] Embodiment 2:

[0060] Based on different aeration methods, the effects on the nitrification performance of MBBR and activated sludge method were studied. The test water was taken from the inlet of the aerobic pool of the mud membrane composite MBBR of a sewage plant, in which the COD was less than 50mg / L. The activated sludge used in the test was taken from the end of the aerobic pool, and the suspended carrier was taken from the aerobic pool. The test adopted the SBR method, the MBBR reaction pool capacity was 50L, and the temperature was controlled at 20℃. The activated sludge method controlled the sludge concentration to 4000mg / L, and the MBBR system controlled the filling rate to 50%. Agitators were installed to promote fluidization, and then nano-aeration was provided to the system. Regular sampling was performed to detect the ammonia nitrogen situation in the system until the ammonia nitrogen was lower than 1.5mg / L, the reaction stopped, and the nitrification load was calculated, and the result was 0.

[0061] It can be seen from 0 that under the premise of the same aeration volume, for the activated sludge system, the use of microporous aeration has a certain improvement over the perforated tube aeration, but the further use of nano aeration has no obvious improvement in nitrification performance. The main reason is that the limiting factor for the load increase of the activated sludge system is the amount of functional bacteria, not oxygen. For the biofilm system, the nitrification performance is basically the same when using perforated tube aeration and microporous aeration, and is significantly higher than that of the activated sludge system. On the one hand, the reason is that the biofilm has a high efficiency in enriching functional bacteria and has a higher treatment efficiency; on the other hand, since the suspended carrier will cut the bubbles during the fluidization process, even if the perforated tube aeration provides large-aperture bubbles, it will become smaller due to the cutting of the suspended carrier. Therefore, the nitrification load of the system under perforated tube aeration and microporous aeration is basically the same. And the further use of nano aeration has significantly improved the nitrification performance, which is 1.54 times that of microporous aeration. The main reason is that smaller bubbles improve oxygen utilization, promote DO mass transfer, and stimulate the activity of functional bacteria in the inner layer of the biofilm, thereby increasing the nitrification load.

[0062] Table 2 Effects of different aeration modes on activated sludge and biofilm performance

[0063]

[0064]

[0065] Embodiment 3:

[0066] In order to verify the effect of SS in the test system on nano aeration, a comparative test was conducted. The effective tank capacity of the test system is 5m 3 The influent was the aerobic pool in a municipal sewage plant in the north. The SS was controlled at 30mg / L, 50mg / L, 80mg / L, and 100mg / L. The system was aerobic and the same air volume was introduced. A pressure gauge was connected to one end of the nano aerator. The system was operated continuously for a total of 6 months.

[0067] During the operation of each reaction tank, when SS was controlled at 30mg / L and 50mg / L, the long-term operation pressure gauge showed a basically stable state between 2.10 and 2.15Mpa. When SS was increased to 80mg / L, the pressure gauge showed a continuous increase from the 159th day. After 6 months of operation, the final pressure was 2.18Mpa. When SS was increased to 100mg / L, the pressure increase time was advanced to the 135th day, and the final pressure was 2.22Mpa. The main reason for the pressure increase is that SS particles blocked the aperture of the nano aerator, thereby increasing the aeration resistance. From the test process, the time is relatively short compared with the engineering operation, but from the results, when SS is greater than 80mg / L, the impact on the nano aerator has been shown as the test system is running, so the actual control should ensure that the system inlet SS is below 50mg / L.

[0068] Embodiment 4:

[0069] Through experiments, the study determined the effects of three key parameters, namely, specific gravity, pore size, and thickness of the suspended carrier, on the performance of nano-aeration.

[0070] (1) First, the specific gravity of the suspended carrier. The specific gravity of the suspended carrier selected in the experiment is 0.96 g / cm 3 , 1.05g / cm 3 , 1.15g / cm 3 , 1.25g / cm 3 Four specifications all use cylindrical suspended carriers with a diameter of 25mm, a thickness of 10mm, and a pore size of 5-6mm. The test water is the inlet water of the aerobic pool of a municipal sewage plant in the north. The SS is controlled below 50mg / L, the ammonia nitrogen is 40mg / L, the effective pool capacity of the MBBR reaction pool is 500L, the filling rate is 50%, and the continuous flow operation is controlled to control the same aeration volume and stirring power to ensure oxygen supply and fluidization of the suspended carrier. It runs for a total of 1 month, and the test results are shown in 0. It can be seen from 0 that the influence of the specific gravity of the suspended carrier on the test system is mainly fluidization, and fluidization indirectly affects the biofilm and treatment effect. The better the fluidization, the more uniform the distribution of the suspended carrier, the better the biofilm, and the higher the treatment performance. For the nano aeration system, the nano bubbles will attach to the suspended carrier during the rising process, thereby increasing the buoyancy of the suspended carrier, which is equivalent to reducing a part of the specific gravity. Therefore, the specific gravity of the suspended carrier itself is relatively large, 1.15g / cm 3 The suspended carrier is suitable for nano aeration system.

[0071] Table 3 Effect of suspended carrier specific gravity on system processing performance

[0072]

[0073] (2) The second is the study of the pore size of the suspension carrier. The test selected three specifications with an average pore size of 3.5mm, 4.5mm and 5.5mm. The diameter of the suspension carrier is 25mm, the thickness is 5mm, and the specific gravity is 1.15g / cm 3 . The test water is the inlet water of aerobic pool of a municipal sewage plant in the north. SS is controlled below 50mg / L, ammonia nitrogen is 40mg / L, the effective pool capacity of the reaction pool is 500L, the filling rate is 50%, and the continuous flow operation is controlled. The same aeration volume and stirring power are controlled to ensure oxygen supply and fluidization of suspended carriers. It runs for a total of 1 month. The test results are shown in 0. MBBR biofilm is a film on the material. The biofilm is attached to the protected area inside the suspended carrier. Due to the good mass transfer of nanobubbles, the biofilm is thicker than the traditional method, so the actual pore size is smaller, the surface tension is greater, and the mass transfer resistance inside the pore size is higher; on the contrary, the larger the pore size, the smaller the effective specific surface area. Although the large pore size can ensure the mass transfer process, the overall treatment performance of the system is low. It can be seen from 0 that the treatment performance is optimal when the pore size is 4.5mm.

[0074] Table 4 Effect of suspended carrier pore size on system processing performance

[0075] Serial number Suspended carrier pore size / mm <![CDATA[Nitrification load / kg·m -3 ·d -1 > 1 5.5 0.327 2 4.5 0.449 3 3.5 0.357

[0076] (3) Finally, the thickness of the suspension carrier was studied. The test selected three thicknesses of the suspension carrier: 10 mm, 4 mm, and 2 mm, with a specific gravity of 1.15 g / cm 3 , with a diameter of 25mm and an average pore size of 4.5mm. The test water is the inlet water of an aerobic pool of a municipal sewage plant in the north. The SS is controlled to be lower than 50mg / L, the ammonia nitrogen is 40mg / L, the effective pool capacity of the reaction pool is 500L, the filling rate is 50%, and the continuous flow operation is controlled. The same aeration volume and stirring power are controlled to ensure oxygen supply and fluidization of the suspended carrier. The test results are shown in 0. The thinner the suspended carrier, the shorter the mass transfer distance in its pore size and the better the mass transfer effect. However, as the suspended carrier becomes thinner, its fluidization form in the water becomes single and becomes a regular flip, which further limits the mass transfer process. It can be seen from 0 that for the same specification of suspended carrier, when the thickness becomes 4mm, its nitrification performance is 1.1 times that of 10mm. When the suspended carrier becomes 2mm, due to the limitation of the fluidization process, its treatment load is only 82% of the suspended carrier with a thickness of 4mm. Therefore, the thickness of 4mm is the best parameter.

[0077] Table 5 Effect of suspension carrier thickness on system processing performance

[0078]

[0079] Embodiment 5:

[0080] The pilot project is located in a municipal sewage plant in the north. The AO process is used and the reaction tank capacity is 10m 3 , install two stirrers and control the stirrer power density to 7.5~20W / m 3 MBBR reaction tank is filled with suspended carrier, the carrier specific gravity is 1.15g / cm 3 , pore size 4.5mm, thickness 4mm, filling rate 50%, influent is the aerobic pool influent of the project, SS is controlled to be less than 50mg / L, ammonia nitrogen is 40mg / L. Continuous flow operation is adopted to observe the biofilm thickness and the nitrification performance of the system. The operation effect diagram is as follows Figure 3 shown.

[0081] At the beginning of operation, the stirrer power density is controlled to 8W / m 3 , the fluidization of the suspended carrier is normal, the system operates normally, the effluent water quality is stable, and the thickness of the biofilm in the aerobic zone is 400-500μm. On the 20th day of operation, the ammonia nitrogen in the effluent of the detection system fluctuated and showed an upward trend. After 5 consecutive days of testing, it was confirmed that the ammonia nitrogen in the effluent of the system continued to increase. By testing the biofilm, it was found that the thickness of the biofilm increased to 750-800μm, and the poor mass transfer affected the treatment load. The method of increasing the power density of the agitator is adopted to enhance the fluidization of the suspended carrier, promote the shedding of the biofilm, and reduce the thickness of the biofilm. On the 26th day, the power density of the agitator was increased to 14W / m 3 After running for 1 hour, the fluidization was visibly intense, but the nitrification performance did not improve, and the SS of the system outlet water did not increase significantly. On the 28th day, the power density of the agitator was increased to 19W / m 3 After running for 1 hour, the suspended carrier fluidization became more intense, and the SS of the effluent from the detection system also increased significantly. After 1 hour, the biofilm thickness was basically restored to the level of 500-600μm, and the effluent ammonia nitrogen also slowly decreased and returned to the initial level on the 30th day.

[0082] Embodiment 6:

[0083] The effluent from a municipal sewage plant in the north complies with the GB18918-2002 Class A standard. The first phase adopts the AAO process based on the activated sludge method with a treatment scale of 4×10 4 m 3 / d, using microporous aeration; the second phase uses AOAO process based on MBBR, with a treatment scale of 1×10 4 m 3 / d, using perforated tube aeration; Phase III uses MBBR-based AOA process with a treatment scale of 2×10 4 m 3 / d, using nano aeration, the design and operation results of each period are shown in 0. As can be seen from the table, the combination of MBBR and nano aeration not only reduces the operating energy consumption, but also improves the treatment performance. Compared with the traditional activated sludge + microporous aeration method, it reduces energy consumption by 55% and reduces land occupation by 73%. Compared with the MBBR + perforated aeration method, it saves 30% of land occupation.

[0084] Table 6 Effects of combined application of different processes and aeration methods

[0085] Compare Projects unit Activated sludge + microporous aeration MBBR+perforated aeration MBBR+Nano Aeration Processing scale <![CDATA[Ten thousand m 3 / d]]> 4 1 2 Aerobic residence time h 13 5 3.5 Effluent ammonia nitrogen concentration mg / L <1.5 <1.5 <1.5 Power consumption in aerobic zone <![CDATA[kWh / m 3 ]]> 0.332 0.337 0.150 Impact resistance - Poor generally excellence

[0086] Parts not described in the present invention can be implemented by referring to the existing technology.

[0087] Those skilled in the art should recognize that the above embodiments are only used to illustrate the present application and are not intended to be limiting of the present application. As long as they are within the spirit of the present application, appropriate changes and modifications to the above embodiments should fall within the scope of protection of the claims of the present application.

Claims

1. A MBBR sewage treatment method with nanobubble efficient oxygen supply, characterized in that: The following steps are included in sequence: a. Prepare the required processing system The treatment system includes an MBBR reaction tank, a suspended carrier fluidization system, a suspended carrier interception system and a nano aeration system. The MBBR reaction tank is filled with suspended carriers. The suspended carrier interception system includes a flat interception screen and an outlet interception screen. The suspended carrier fluidization system includes an agitator and a perforated aeration pipe located in the MBBR reaction tank. The nano aeration system includes a nano aerator and a nano gas generator. The nano gas generator is located outside the MBBR reaction tank and is connected to the nano aerator located in the MBBR reaction tank. The flat interception screen is parallel to the bottom surface of the MBBR reaction tank and is located above the nano aerator. The specific gravity of the suspension carrier is 1.10 g / cm 3 ~1.20g / cm 3 , is a cylindrical suspension carrier with a thickness of 3mm to 5mm and a suspension carrier pore size of 4mm to 5mm; b. The treated sewage enters the MBBR reaction tank, the agitator is turned on, the inlet SS is lower than 50 mg / L, and nano bubbles are provided to the MBBR reaction tank through the nano aerator; the aeration rate of the nano aerator is calculated according to formula (1): In formula (1): α is the oxygen mass transfer correction coefficient, E A is the oxygen transfer efficiency of the nano aerator, AOR is the total oxygen demand, Cs' is the saturated dissolved oxygen of clean water at the actual temperature, Cs is the saturated dissolved oxygen of the wastewater to be treated at the actual temperature, and C is the actual DO of the treatment system; c. Run: During normal operation, the power density of the agitator is 7.5-10W / m 3 , the aeration volume of the perforated aeration tube is twice the area of ​​the intercepting screen; In the strong hydraulic shear stage, the power density of the agitator is 15-20W / m 3 , the aeration volume of the perforated aeration tube is 4 times the area of ​​the intercepting screen; For MBBR reaction pools whose core is to remove organic matter, the strong hydraulic shear stage is started every 10 to 15 days, and each time it is turned on for 2 to 3 hours; for MBBR reaction pools whose core is to remove ammonia nitrogen, the strong hydraulic shear stage is started every 20 to 25 days, and each time it is turned on for 1 to 2 hours.

2. The MBBR sewage treatment method with nanobubble efficient oxygen supply according to claim 1, characterized in that: The effluent interception screen is located at the effluent end of the MBBR reaction tank and is perpendicular to the water flow direction.

3. The MBBR sewage treatment method with nanobubble efficient oxygen supply according to claim 1 is characterized in that: The nano aerator is located between the flat interception screen and the bottom surface of the MBBR reaction tank, and a plurality of nano aerators are evenly spaced.

4. The MBBR sewage treatment method with nanobubble efficient oxygen supply according to claim 3 is characterized by: The pore size of the nano aerator is 100nm-500nm, the value of α is 0.95, and E A The value ranges from 0.90% to 0.95%.

5. The MBBR sewage treatment method with nanobubble efficient oxygen supply according to claim 1, characterized in that: The stirrer is a variable frequency stirrer with an installed power density of 7 to 20 W / m 3 .

6. The MBBR sewage treatment method with nanobubble efficient oxygen supply according to claim 1, characterized in that: The specific gravity of the suspension carrier is 1.15 g / cm 3 , thickness is 4mm.

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