Urban sewage treatment system and method based on high / low DO alternating MBBR

Abstract

The invention relates to an urban sewage treatment system and method based on a high / low DO alternating MBBR (Moving Bed Biofilm Reactor). According to the system and the method, long-sludge-age autotrophic nitrogen removal microorganisms and short-sludge-age phosphorus-accumulating bacteria are separated by utilizing the MBBR, and through alternate operation of high / low DO, a suitable growth environment is created for different microorganisms, so that synchronous and efficient nitrogen and phosphorus removal is realized. According to the system and the method, short-cut nitrification-anaerobic ammonia oxidation and biological phosphorus removal reaction are enhanced, the operation energy consumption is reduced, and the problems that urban sewage carbon sources are insufficient, the nitrogen and phosphorus removal effect of a traditional process is not ideal and the like are solved. The system is simple in device, simple in process, compact in arrangement and wide in application prospect. Compared with the prior art, the method has the advantages that the reaction rate is increased, a good nitrogen and phosphorus removal effect is ensured, the energy consumption is reduced, and the operation convenience is optimized.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and in particular to an urban sewage treatment system and method based on high / low DO alternating MBBR. Background Art

[0002] With the rapid development of my country's economy and the continuous improvement of environmental protection requirements, sewage discharge standards are becoming increasingly stringent. At present, sewage treatment has entered the advanced treatment stage of nitrogen and phosphorus removal from the stage of simple removal of organic matter.

[0003] In the traditional biological denitrification and phosphorus removal process, the removal of nitrogen and phosphorus is completed by nitrifying bacteria, denitrifying bacteria and polyphosphate bacteria in the sludge respectively. However, there are significant differences in the living habits of these bacteria. For example, the sludge age of nitrifying bacteria is longer than that of polyphosphate bacteria. In order to ensure the nitrification effect, a longer sludge age is usually adopted in the process design, which limits the phosphorus removal effect to a certain extent. In addition, the organic matter in urban sewage often cannot meet the needs of polyphosphate bacteria and denitrifying bacteria at the same time, making it difficult for traditional denitrification and phosphorus removal processes to achieve good removal effects.

[0004] As a new autotrophic nitrogen removal process, short-cut nitrification-anaerobic ammonium oxidation (ANAMMOX) is a new type of autotrophic nitrogen removal process. Under low dissolved oxygen (DO) conditions, short-cut nitrifying bacteria oxidize ammonia nitrogen in sewage into nitrite nitrogen. At the same time, anaerobic ammonium oxidizing bacteria use nitrite nitrogen as an electron acceptor and the remaining ammonia nitrogen in sewage as an electron donor, converting both into nitrogen gas for removal. This process does not require organic matter, so the organic matter in sewage can be mainly used for biological phosphorus removal, thus overcoming the shortcomings of insufficient organic matter in traditional nitrogen and phosphorus removal processes, and can significantly save aeration energy consumption. However, low DO will limit the activity of short-cut nitrifying bacteria, thereby affecting the reaction rate of short-cut nitrification-anaerobic ammonium oxidation, and is also not conducive to aerobic phosphorus absorption reactions by polyphosphate bacteria.

[0005] MBBR reactor is a composite reactor in which biofilm and flocculent sludge coexist by adding biological carrier fillers to ordinary activated sludge SBR reactor. It can separate different types of microorganisms. Among them, polyphosphate-accumulating bacteria and denitrifying bacteria with faster growth and shorter sludge age mainly grow in flocculent sludge; anaerobic ammonia-oxidizing bacteria and short-range nitrifying bacteria with slower growth and longer sludge age attach to and grow on the fillers to form biofilm.

[0006] Based on this background, developing MBBR sewage treatment systems and methods tailored to the characteristics of urban sewage and with stable and efficient nitrogen and phosphorus removal effects is of great significance for solving the challenges currently faced in the sewage treatment field and improving sewage treatment efficiency and quality. Summary of the invention

[0007] The purpose of the present invention is to solve the deficiencies in the prior art. In view of the problems of insufficient carbon sources in urban sewage in my country, unsatisfactory nitrogen and phosphorus removal effects of traditional denitrification and phosphorus removal processes, high operating energy consumption, etc., the present invention develops an urban sewage treatment system and method based on high / low DO alternating MBBR. By utilizing an MBBR reactor and combining a high / low DO alternating operating mode, favorable growth environments and reaction conditions are created for polyphosphate bacteria and denitrifying microorganisms, and the advantages of each bacterial community are fully utilized, so that synchronous and efficient denitrification and phosphorus removal of urban sewage can be achieved, while saving operating energy consumption, and the process is simple and the layout is compact.

[0008] In order to achieve the above-mentioned object of the invention, the specific technical scheme of the present invention is as follows:

[0009] The present invention provides an urban sewage treatment system based on high / low DO alternating MBBR, comprising a sewage tank (1) and an MBBR reactor (2) which are sequentially connected in the direction of the sewage treatment process;

[0010] The sewage tank (1) is connected to the MBBR reactor (2) via a peristaltic pump (3);

[0011] The MBBR reactor (2) is provided with a water inlet valve (4), a biological carrier filler (5), a stirrer (6), an aeration pump (7), a gas flow meter (8), a microporous aeration head (9), a DO monitor (10), an ammonia nitrogen / nitrite nitrogen monitor (11), a drainage valve (12) and a mud discharge valve (13).

[0012] In some specific embodiments of the present invention, the biological carrier filler (5) is cylindrical and made of high-density polyethylene.

[0013] In some specific embodiments of the present invention, the density of the biological carrier filler (5) is 0.94-0.97 g / cm 3 , effective specific surface area greater than 800m 2 / m 3 .

[0014] In some specific embodiments of the present invention, the filling rate of the biological carrier filler (5) is 35% to 45%, and the biological carrier filler (5) is suspended and distributed in the MBBR reactor (2).

[0015] In some specific embodiments of the present invention, a controller is further included, which is respectively connected to the peristaltic pump (3), the aeration pump (7), the gas flow meter (8), the microporous aeration head (9), the DO monitor (10), the drain valve (12) and the mud discharge valve (13).

[0016] The present invention also provides a method for treating urban sewage based on high / low DO alternating MBBR, comprising the following steps:

[0017] S1. Municipal sewage enters the MBBR reactor (2) from the sewage tank (1) through the peristaltic pump (3). After the water is inletted, the agitator (6) is turned on and the agitator speed is controlled to be 40-60 r / min to mix the sewage and sludge evenly. At the same time, DO is controlled to be ≤ 0.1 mg / L. At this stage, the denitrifying bacteria growing in the flocculent sludge use the organic matter in the sewage to remove the residual nitrite nitrogen and nitrate nitrogen in the MBBR reactor (2). At the same time, the polyphosphate bacteria perform anaerobic phosphorus release reaction and store the remaining organic matter as intracellular carbon source. The reaction time is 1-1.5 hours.

[0018] S2. After the reaction in step S1 is completed, the agitator (6) is turned off, the aeration pump (7) is turned on, and the DO is controlled to be 2-4 mg / L through the gas flow meter (8). Aerobic phosphorus absorption and short-range nitrification reactions are carried out in the floc sludge and biofilm, respectively, to remove phosphorus in the sewage and convert part of the ammonia nitrogen into nitrite nitrogen. According to the change of nitrogen concentration monitored by the ammonia nitrogen / nitrite nitrogen monitor (11), the aeration time is adjusted to control the ammonia nitrogen to nitrite nitrogen concentration ratio to be 1.5-2:1;

[0019] S3. After the reaction in step S2 is completed, the DO is controlled to be 0.2-0.4 mg / L by a gas flow meter (8), and the short-range nitrifying bacteria growing in the aerobic layer on the surface of the biofilm and the anaerobic ammonia-oxidizing bacteria growing in the internal anoxic layer respectively carry out short-range nitrification and anaerobic ammonia-oxidation reactions to remove the remaining ammonia nitrogen and nitrite nitrogen in the sewage. When the concentrations of both are lower than 2 mg / L, aeration is stopped;

[0020] S4. After the reaction in step S3 is completed, the mixture is allowed to stand for sedimentation and then separated into mud and water. The supernatant is discharged through the drain valve (12); the remaining sludge is discharged through the sludge discharge valve (13), and the floc sludge age is controlled to be 10 to 15 days and the sludge concentration is 1800 to 2300 mg / L.

[0021] In some specific embodiments of the present invention, the reaction time of S2 is 1 to 2 hours.

[0022] In some specific embodiments of the present invention, the reaction time of S3 is 2 to 3 hours.

[0023] In some specific embodiments of the present invention, the static precipitation time is 10 to 15 minutes.

[0024] In some specific embodiments of the present invention, the amount of water discharged from the supernatant through the drain valve (12) is equal to the initial water inlet of the system.

[0025] Compared with the prior art, the present invention has the following significant advantages and effects:

[0026] (1) Microbial separation and synergistic advantages:

[0027] MBBR reactor is used to separate autotrophic denitrifying microorganisms with long sludge age and heterotrophic microorganisms with short sludge age, creating a suitable growth environment for different bacterial communities and giving full play to their synergistic effects.

[0028] (2) Reaction conditions and efficiency advantages:

[0029] High / low DO alternating operation can provide good reaction conditions for aerobic phosphorus absorption and short-range nitrification-anaerobic ammonium oxidation, increase the reaction rate, and achieve simultaneous and efficient nitrogen and phosphorus removal from urban sewage in a single system.

[0030] (3) Energy saving and micro-environment advantages:

[0031] As a special microbial aggregation structure, biofilm can form a unique aerobic-anoxic microenvironment under low DO conditions, which is conducive to autotrophic nitrogen removal and reduces operating energy consumption.

[0032] (4) Advantages of phosphorus removal and nitrogen removal:

[0033] By controlling the age of floc sludge, while promoting efficient phosphorus removal in the system, it can effectively wash out and inhibit nitrite oxidizing bacteria, ensuring good anaerobic ammonia oxidation denitrification.

[0034] (5) System advantages:

[0035] The urban sewage treatment system based on high / low DO alternating MBBR provided by the present invention has simple device, concise process, compact layout and convenient operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0037] Attached Figure 1 This is a schematic diagram of the structure of an urban sewage treatment system based on high / low DO alternating MBBR, where: 1-sewage tank; 2-MBBR reactor; 3-peristaltic pump; 4-water inlet valve; 5-biological carrier filler; 6-agitator; 7-aeration pump; 8-gas flow meter; 9-microporous aeration head; 10-DO monitor; 11-ammonia nitrogen / nitrite nitrogen monitor; 12-drain valve; 13-sludge valve. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention and should not be used to limit the protection scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the protection scope of the present invention.

[0039] Example 1: Urban sewage treatment system based on high / low DO alternating MBBR

[0040] The urban sewage treatment system based on high / low DO alternating MBBR mainly includes a sewage tank (1) and an MBBR reactor (2) which are connected in sequence in the direction of sewage treatment process. Among them, the main body of the MBBR reactor (2) is made of organic glass with an effective volume of 16L. The sewage tank (1) is connected to the MBBR reactor (2) through a peristaltic pump (3); the MBBR reactor (2) is provided with an inlet valve (4), a biological carrier filler (5), an agitator (6), an aeration pump (7), a gas flow meter (8), a microporous aeration head (9), a DO monitor (10), an ammonia nitrogen / nitrite nitrogen monitor (11), a drain valve (12), and a mud valve (13); the biological carrier filler (5) is cylindrical and made of high-density polyethylene with a density of 0.94-0.97 g / cm 3 , effective specific surface area greater than 800m 2 / m 3 The filling rate is 35% to 45%, and the sludge is suspended and distributed in the MBBR reactor (2) to provide a platform for the slow-growing anaerobic ammonia-oxidizing bacteria and short-range nitrifying bacteria to attach and grow to form a biofilm.

[0041] Example 2: Urban sewage treatment method based on the sewage treatment system of the present invention

[0042] The method for treating urban sewage using the high / low DO alternating MBBR system of Example 1 mainly includes the following steps:

[0043] 1) Municipal sewage enters the MBBR reactor (2) from the sewage tank (1) through the peristaltic pump (3). After the water inflow is completed, the agitator (6) is turned on to mix the sewage and the sludge evenly. The denitrifying bacteria mainly grown in the flocculent sludge use the organic matter in the sewage to remove the residual nitrite nitrogen and nitrate nitrogen in the reactor. At the same time, the polyphosphate bacteria perform anaerobic phosphorus release reaction and store the remaining organic matter as intracellular carbon source. The agitator speed is controlled to 40-60r / min, and the DO is lower than 0.1mg / L to avoid excessive speed to bring air into the water, so as to maintain good anaerobic phosphorus release and anoxic denitrification conditions. The reaction time is 1-1.5h.

[0044] 2) After the reaction in step (1) is completed, the agitator (6) is turned off, the aeration pump (7) is turned on, and the DO is controlled to be 2-4 mg / L through the gas flow meter (8), and high DO aeration is performed. The polyphosphate-accumulating bacteria mainly grown in the flocculent sludge use oxygen as an electron acceptor and utilize the stored internal carbon source to perform aerobic phosphorus absorption reaction to remove phosphorus from the sewage. At the same time, the short-range nitrifying bacteria mainly grown in the biofilm perform a short-range nitrification reaction to convert part of the ammonia nitrogen in the sewage into nitrite nitrogen. The nitrogen concentration change is monitored by the ammonia nitrogen / nitrite nitrogen monitor (11), and the aeration time is adjusted to control the ammonia nitrogen to nitrite nitrogen concentration ratio to be 1.5-2:1, and the reaction time is 1-2 hours;

[0045] 3) After the reaction in step (2) is completed, the DO is controlled to be 0.2-0.4 mg / L by a gas flow meter (8). Under low DO conditions, an aerobic-anoxic microenvironment is formed from the outside to the inside of the biofilm, and short-term nitrification bacteria mainly growing in the aerobic layer on the surface of the biofilm and anaerobic ammonia-oxidizing bacteria in the internal anoxic layer simultaneously carry out short-term nitrification and anaerobic ammonia-oxidation reactions to remove the remaining ammonia nitrogen in the sewage and the nitrite nitrogen produced during high DO aeration. When the concentrations of ammonia nitrogen and nitrite nitrogen are both lower than 2 mg / L, aeration is stopped, and the reaction time is 2-3 hours.

[0046] 4) After the reaction in step (2) is completed, the aeration pump (7) is turned off and the mixture is allowed to settle for 10 to 15 minutes for mud and water separation. The supernatant is discharged through the drain valve (12) and the amount of water discharged is equal to the initial water intake of the system. The remaining sludge is discharged through the sludge discharge valve (13) and the age of the floc sludge is controlled to be 10 to 15 days and the sludge concentration is 1800 to 2300 mg / L.

[0047] Example 3: Testing of urban sewage treatment based on the sewage treatment system of the present invention

[0048] The influent of a certain city sewage treatment plant was taken as the treatment object to investigate the nitrogen and phosphorus removal performance of the system.

[0049] The influent water quality during the experiment was as follows:

[0050]

[0051] The method for treating urban sewage using the high / low DO alternating MBBR system of Example 1 mainly includes the following steps:

[0052] 1) 8L of urban sewage enters the MBBR reactor (2) from the sewage tank (1) through the peristaltic pump (3). After the water inflow is completed, the stirrer (6) is turned on to mix the sewage and the sludge evenly. The denitrifying bacteria mainly growing in the flocculent sludge use the organic matter in the sewage to remove the residual nitrite nitrogen and nitrate nitrogen in the reactor. At the same time, the polyphosphate bacteria perform anaerobic phosphorus release reaction and store the remaining organic matter as intracellular carbon source. The stirrer speed is controlled to 50r / min and the DO is lower than 0.1mg / L to avoid excessive speed to bring air into the water. Good anaerobic phosphorus release and anoxic denitrification conditions are maintained. The reaction time is 1.5h.

[0053] 2) After the reaction in the above step (1) is completed, the agitator (6) is turned off, the aeration pump (7) is turned on, and the DO is controlled to be 3-4 mg / L through the gas flow meter (8), and high DO aeration is performed. The polyphosphate-accumulating bacteria mainly grown in the flocculent sludge use oxygen as an electron acceptor and utilize the stored internal carbon source to perform aerobic phosphorus absorption reaction to remove phosphorus from the sewage; at the same time, the short-range nitrifying bacteria mainly grown in the biofilm perform a short-range nitrification reaction to convert part of the ammonia nitrogen in the sewage into nitrite nitrogen. The nitrogen concentration change is monitored by the ammonia nitrogen / nitrite nitrogen monitor (11), and the ammonia nitrogen to nitrite nitrogen concentration ratio is controlled to be 1.5:1, and the reaction time is 1.5 hours;

[0054] 3) After the reaction in the above step (2) is completed, the DO is controlled to be 0.2-0.3 mg / L by a gas flow meter (8). Under low DO conditions, an aerobic-anoxic microenvironment is formed from the outside to the inside of the biofilm, and the short-range nitrifying bacteria mainly growing in the aerobic layer on the surface of the biofilm and the anaerobic ammonia-oxidizing bacteria in the internal anoxic layer simultaneously carry out short-range nitrification and anaerobic ammonia-oxidation reactions to remove the remaining ammonia nitrogen in the sewage and the nitrite nitrogen produced during high DO aeration, and the concentrations of ammonia nitrogen and nitrite nitrogen are controlled to be less than 2 mg / L. The reaction time is 2 hours.

[0055] 4) After the reaction in step (3) is completed, the aeration pump (7) is turned off and the mixture is allowed to settle for 10 minutes for mud and water separation. 8L of the supernatant is discharged through the drain valve (12), and the amount of water discharged is equal to the initial water intake of the system; the remaining sludge is discharged through the sludge discharge valve (13), and the floc sludge age is controlled to be 12 days, and the sludge concentration is about 2000mg / L.

[0056] Under this operating condition, the average COD and NH4 + -N, TN, and TP were 31.6, 1.1, 8.9, and 0.2 mg / L respectively, and all effluent indicators stably reached the national Class A emission standards.

[0057] The above-mentioned specific implementations are only specific cases of the present invention. The patent protection scope of the present invention includes but is not limited to the product form and style of the above-mentioned specific implementations. Any appropriate changes or modifications made to them by ordinary technicians in the technical field that conform to the claims of the present invention shall fall within the patent protection scope of the present invention.

Claims

1. An urban sewage treatment system based on high / low DO alternating MBBR, characterized by: It comprises a sewage tank (1) and an MBBR reactor (2) which are connected in sequence according to the sewage treatment process direction; The sewage tank (1) is connected to the MBBR reactor (2) via a peristaltic pump (3); The MBBR reactor (2) is provided with a water inlet valve (4), a biological carrier filler (5), a stirrer (6), an aeration pump (7), a gas flow meter (8), a microporous aeration head (9), a DO monitor (10), an ammonia nitrogen / nitrite nitrogen monitor (11), a drainage valve (12) and a mud discharge valve (13).

2. The urban sewage treatment system based on high / low DO alternating MBBR according to claim 1, characterized in that: The biological carrier filler (5) is cylindrical and made of high-density polyethylene.

3. The urban sewage treatment system based on high / low DO alternating MBBR as claimed in claim 2, characterized in that: The density of the biological carrier filler (5) is 0.94-0.97 g / cm 3 , effective specific surface area greater than 800m 2 / m 3 .

4. The urban sewage treatment system based on high / low DO alternating MBBR as claimed in claim 3, characterized in that: The filling rate of the biological carrier filler (5) is 35% to 45%, and it is suspended and distributed in the MBBR reactor (2).

5. The urban sewage treatment system based on high / low DO alternating MBBR according to claim 1, characterized in that: The invention also comprises a controller, which is respectively connected to the peristaltic pump (3), the aeration pump (7), the gas flow meter (8), the microporous aeration head (9), the DO monitor (10), the ammonia nitrogen / nitrite nitrogen monitor (11), the drain valve (12) and the mud discharge valve (13) for communication.

6. A method for treating urban sewage based on high / low DO alternating MBBR, characterized in that: The steps include: S1. Municipal sewage enters the MBBR reactor (2) from the sewage tank (1) through the peristaltic pump (3). After the water is inletted, the agitator (6) is turned on and the agitator speed is controlled to be 40-60 r / min to mix the sewage and sludge evenly. At the same time, DO is controlled to be ≤ 0.1 mg / L. At this stage, the denitrifying bacteria growing in the flocculent sludge use the organic matter in the sewage to remove the residual nitrite nitrogen and nitrate nitrogen in the MBBR reactor (2). At the same time, the polyphosphate bacteria perform anaerobic phosphorus release reaction and store the remaining organic matter as intracellular carbon source. The reaction time is 1-1.5 hours. S2. After the reaction in step S1 is completed, the agitator (6) is turned off, the aeration pump (7) is turned on, and the DO is controlled to be 2-4 mg / L through the gas flow meter (8). Aerobic phosphorus absorption and short-range nitrification reactions are carried out in the floc sludge and biofilm, respectively, to remove phosphorus in the sewage and convert part of the ammonia nitrogen into nitrite nitrogen. According to the change of nitrogen concentration monitored by the ammonia nitrogen / nitrite nitrogen monitor (11), the aeration time is adjusted to control the ammonia nitrogen to nitrite nitrogen concentration ratio to be 1.5-2:1; S3. After the reaction in step S2 is completed, the DO is controlled to be 0.2-0.4 mg / L by a gas flow meter (8), and the short-range nitrifying bacteria growing in the aerobic layer on the surface of the biofilm and the anaerobic ammonia-oxidizing bacteria growing in the internal anoxic layer respectively carry out short-range nitrification and anaerobic ammonia-oxidation reactions to remove the remaining ammonia nitrogen and nitrite nitrogen in the sewage. When the concentrations of both are lower than 2 mg / L, aeration is stopped; S4. After the reaction in step S3 is completed, the mixture is allowed to stand for sedimentation and then separated into mud and water. The supernatant is discharged through the drain valve (12); the remaining sludge is discharged through the sludge discharge valve (13), and the floc sludge age is controlled to be 10 to 15 days and the sludge concentration is 1800 to 2300 mg / L.

7. The method for treating urban sewage based on high / low DO alternating MBBR according to claim 6, characterized in that: The reaction time of S2 is 1 to 2 hours.

8. The method for treating urban sewage based on high / low DO alternating MBBR according to claim 6, characterized in that: The reaction time of S3 is 2 to 3 hours.

9. The method for treating urban sewage based on high / low DO alternating MBBR according to claim 6, characterized in that: The static sedimentation time is 10 to 15 minutes.

10. The method for treating urban sewage based on high / low DO alternating MBBR according to claim 6, characterized in that: The amount of water discharged from the supernatant through the drain valve (12) is equal to the initial water intake of the system.

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