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

Abstract

The present application relates to a kind of urban sewage treatment system and method based on high / low DO alternative MBBR.The system and method utilize MBBR reactor to separate long sludge age autotrophic denitrification microorganism and short sludge age phosphorus accumulating organisms, by high / low DO alternative operation, create suitable growth environment for different microorganisms, realize simultaneous efficient denitrification and phosphorus removal.The system and method strengthen short-cut nitrification-anaerobic ammonia oxidation and biological phosphorus removal reaction, reduce operating energy consumption, solve the problems such as carbon source deficiency of urban sewage and unsatisfactory nitrogen and phosphorus removal effect of traditional process.The system device is simple, process is simple, layout is compact, and has broad application prospect.Compared with prior art, the present application improves reaction rate, ensures good denitrification and phosphorus removal effect, saves energy consumption at the same time, and optimizes operation convenience.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to an urban wastewater treatment system and method based on a high / low DO alternating MBBR. Background Technology

[0002] With the rapid development of my country's economy and the continuous improvement of environmental protection requirements, wastewater discharge standards are becoming increasingly stringent. Currently, wastewater treatment has moved from the stage of simply removing organic matter to the stage of advanced treatment involving nitrogen and phosphorus removal.

[0003] In traditional biological nitrogen and phosphorus removal processes, nitrogen and phosphorus removal are accomplished by nitrifying bacteria, denitrifying bacteria, and polyphosphate-accumulating bacteria in the sludge, respectively. However, these bacterial communities differ significantly in their living habits. For example, nitrifying bacteria require a longer sludge age than polyphosphate-accumulating bacteria. To ensure nitrification efficiency, a longer sludge age is typically used in process design, which to some extent limits phosphorus removal efficiency. Furthermore, the organic matter in urban wastewater often cannot simultaneously meet the needs of both polyphosphate-accumulating and denitrifying bacteria, making it difficult for traditional nitrogen and phosphorus removal processes to achieve satisfactory removal results.

[0004] Short-cut nitrification-anaerobic ammonium oxidation (AMO) is a novel autotrophic nitrogen removal process. Under low dissolved oxygen (DO) conditions, short-cut nitrifying bacteria oxidize ammonia nitrogen in wastewater to nitrite nitrogen. Simultaneously, anaerobic ammonium oxidizing bacteria use nitrite nitrogen as an electron acceptor and the remaining ammonia nitrogen in the wastewater as an electron donor, converting both into nitrogen gas for removal. This process does not require organic matter, thus allowing the organic matter in the wastewater to be primarily used for biological phosphorus removal, overcoming the drawback of insufficient organic matter in traditional nitrogen and phosphorus removal processes, and significantly saving aeration energy consumption. However, low DO limits the activity of short-cut nitrifying bacteria, thereby affecting the short-cut nitrification-anaerobic ammonium oxidation reaction rate, and also hindering the aerobic phosphorus uptake reaction of polyphosphate-accumulating bacteria.

[0005] The MBBR reactor is a composite reactor in which biofilm and flocculent sludge coexist, formed by adding biological carrier packing to a conventional activated sludge SBR reactor. It can achieve the separation of different types of microorganisms. Among them, fast-growing polyphosphate-accumulating bacteria and denitrifying bacteria with shorter sludge ages mainly grow in flocculent sludge; while slow-growing anaerobic ammonia-oxidizing bacteria and short-range nitrifying bacteria with longer sludge ages attach and grow on the packing to form a biofilm.

[0006] Against this backdrop, developing MBBR wastewater treatment systems and methods that are tailored to the characteristics of urban wastewater and possess both stable and efficient nitrogen and phosphorus removal effects is of great significance for addressing the current challenges in the wastewater treatment field and improving wastewater treatment efficiency and quality. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of existing technologies. Addressing the issues of insufficient carbon sources in urban wastewater in my country, and the unsatisfactory nitrogen and phosphorus removal efficiency and high energy consumption of traditional denitrification and phosphorus removal processes, this invention develops an urban wastewater treatment system and method based on a high / low DO alternating MBBR. By utilizing an MBBR reactor and combining it with a high / low DO alternating operation mode, favorable growth environments and reaction conditions are created for polyphosphate-accumulating bacteria and denitrifying microorganisms, fully leveraging the advantages of each microbial community. This enables simultaneous and efficient nitrogen and phosphorus removal from urban wastewater, while also saving operating energy consumption. Furthermore, the process is simple and the layout is compact.

[0008] To achieve the above-mentioned objectives, the specific technical solution of the present invention is as follows:

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

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

[0011] The MBBR reactor (2) is equipped with an inlet valve (4), biological carrier packing (5), agitator (6), aeration pump (7), gas flow meter (8), microporous aeration head (9), DO monitor (10), ammonia nitrogen / nitrite nitrogen monitor (11), drain valve (12) and sludge 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 / cm³. 3 Effective specific surface area greater than 800 m² 2 / m 3 .

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

[0015] In some specific embodiments of the present invention, a controller is also included, which is communicatively 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 sludge discharge valve (13), respectively.

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

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

[0018] S2. After the reaction in step S1 is completed, turn off the agitator (6), turn on the aeration pump (7), and control the DO to 2-4 mg / L through the gas flow meter (8). Aerobic phosphorus uptake and short-cut nitrification reactions are carried out in the flocculent sludge and biofilm respectively to remove phosphorus from the wastewater and convert some ammonia nitrogen into nitrite nitrogen. According to the nitrogen concentration change 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 gas flow meter (8). The short-range nitrifying bacteria 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 and nitrite nitrogen in the wastewater. When the concentrations of both are below 2 mg / L, aeration is stopped.

[0020] S4. After the reaction in step S3 is completed, the sludge is allowed to settle 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). The age of the flocculent sludge is controlled to be 10-15 days and the sludge concentration is 1800-2300 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 settling time is 10 to 15 minutes.

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

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

[0026] (1) Advantages of microbial isolation and synergistic effects:

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

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

[0029] Alternating high / low DO operation can provide favorable reaction conditions for aerobic phosphorus uptake and short-cut nitrification-anaerobic ammonium oxidation, improve the reaction rate, and achieve simultaneous and efficient nitrogen and phosphorus removal from urban wastewater in a single system.

[0030] (3) Energy saving and microenvironment advantages:

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

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

[0033] By controlling the age of the flocculent sludge, while promoting efficient phosphorus removal from the system, it is possible to effectively wash and inhibit nitrite-oxidizing bacteria, ensuring good anaerobic ammonia oxidation denitrification.

[0034] (5) Advantages of the system:

[0035] The urban wastewater treatment system based on high / low DO alternating MBBR provided by this invention is simple in design, has a concise process, a compact layout, and is easy to operate. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Appendix Figure 1 This is a schematic diagram of a municipal wastewater treatment system based on a high / low DO alternating MBBR reactor. 1-Wastewater tank; 2-MBBR reactor; 3-Peristaltic pump; 4-Inlet valve; 5-Biological carrier packing material; 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 discharge valve. Detailed Implementation

[0038] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention and should not be used to limit the scope of protection of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

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

[0040] The urban wastewater treatment system based on high / low DO alternating MBBR mainly includes a wastewater tank (1) and an MBBR reactor (2) connected sequentially in the wastewater treatment process direction. The MBBR reactor (2) is mainly made of plexiglass with an effective volume of 16L. The wastewater tank (1) is connected to the MBBR reactor (2) via a peristaltic pump (3). The MBBR reactor (2) is equipped with an inlet valve (4), biological carrier packing (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 drain valve (12), and a sludge discharge valve (13). The biological carrier packing (5) is cylindrical, made of high-density polyethylene, with a density of 0.94–0.97 g / cm³. 3 Effective specific surface area greater than 800 m² 2 / m 3 The filling rate is 35% to 45%, and it is suspended in the MBBR reactor (2) to provide a biofilm for anaerobic ammonia oxidizing bacteria and short-range nitrifying bacteria with slow growth and long sludge age to attach and grow.

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

[0042] The urban wastewater treatment system based on high / low DO alternating MBBR, as described in Example 1, mainly includes the following steps:

[0043] 1) Urban sewage enters MBBR reactor (2) from sewage tank (1) via peristaltic pump (3). After the water influent is finished, the agitator (6) is turned on to mix the sewage and sludge evenly. The denitrifying bacteria, which mainly grow in the flocculent sludge, use the organic matter in the sewage to remove the residual nitrite and nitrate nitrogen in the reactor. At the same time, polyphosphate-accumulating bacteria carry out anaerobic phosphorus release reaction and store the remaining organic matter as an intracellular carbon source. The agitator speed is controlled at 40-60 r / min, and the DO is less than 0.1 mg / L. Avoid the speed being too fast to bring air into the water and maintain good anaerobic phosphorus release and anoxic denitrification conditions. The reaction time is 1-1.5 h.

[0044] 2) After the reaction in step (1) is completed, turn off the agitator (6), turn on the aeration pump (7) and control the DO to 2-4 mg / L through the gas flow meter (8) to carry out high DO aeration. The polyphosphate-accumulating bacteria that mainly grow in the flocculent sludge use oxygen as an electron acceptor and use the stored internal carbon source to carry out aerobic phosphorus uptake reaction to remove phosphorus from the sewage. At the same time, the short-range nitrifying bacteria that mainly grow in the biofilm carry out short-range nitrification reaction to convert some of the ammonia nitrogen in the sewage into nitrite nitrogen. The nitrogen concentration change is monitored by the ammonia nitrogen / nitrite nitrogen monitor (11), the aeration time is adjusted, and the ammonia nitrogen to nitrite nitrogen concentration ratio is controlled 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 the gas flow meter (8). Under low DO conditions, the biofilm forms an aerobic-anoxic microenvironment from the outside to the inside. The short-range nitrifying bacteria that mainly grow on the aerobic layer on the surface of the biofilm and the anaerobic ammonia oxidizing bacteria in the anoxic layer inside the biofilm simultaneously carry out short-range nitrification and anaerobic ammonia oxidation reactions to remove the remaining ammonia nitrogen and nitrite nitrogen produced during high DO aeration in the wastewater. When the concentrations of ammonia nitrogen and nitrite nitrogen are both below 2 mg / L, aeration is stopped. The reaction time is 2-3 hours.

[0046] 4) After the reaction in step (2) is completed, turn off the aeration pump (7) and let it stand for 10 to 15 minutes to separate the sludge and water. The supernatant is discharged through the drain valve (12), and the amount of water discharged is equal to the initial water inflow of the system. The remaining sludge is discharged through the sludge discharge valve (13). The age of the flocculent sludge is controlled to be 10 to 15 days and the sludge concentration is 1800 to 2300 mg / L.

[0047] Example 3: Urban wastewater treatment test based on the wastewater treatment system of the present invention

[0048] The nitrogen and phosphorus removal performance of the system was investigated using the influent of a municipal wastewater treatment plant as the treatment target.

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

[0050]

[0051] The urban wastewater treatment system based on high / low DO alternating MBBR, as described in Example 1, mainly includes the following steps:

[0052] 1) 8L of urban sewage enters the MBBR reactor (2) from the sewage tank (1) via the peristaltic pump (3). After the water influent is finished, the agitator (6) is turned on to mix the sewage and sludge evenly. The denitrifying bacteria, which mainly grow in the flocculent sludge, use the organic matter in the sewage to remove the residual nitrite and nitrate nitrogen in the reactor. At the same time, polyphosphate-accumulating bacteria carry out anaerobic phosphorus release reaction and store the remaining organic matter as an intracellular carbon source. The agitator speed is controlled at 50r / min, and the DO is less than 0.1mg / L. Avoid the speed being too fast to bring air into the water and maintain good anaerobic phosphorus release and anoxic denitrification conditions. The reaction time is 1.5h.

[0053] 2) After the reaction in step (1) above is completed, turn off the agitator (6), turn on the aeration pump (7) and control the DO to 3-4 mg / L through the gas flow meter (8) to carry out high DO aeration. The polyphosphate-accumulating bacteria that mainly grow in the flocculent sludge use oxygen as an electron acceptor and use the stored internal carbon source to carry out aerobic phosphorus uptake reaction to remove phosphorus from the sewage. At the same time, the short-range nitrifying bacteria that mainly grow in the biofilm carry out 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 1.5h.

[0054] 3) After the reaction in step (2) above is completed, the DO is controlled to be 0.2-0.3 mg / L by the gas flow meter (8). Under low DO conditions, the biofilm forms an aerobic-anoxic microenvironment from the outside to the inside. The short-range nitrifying bacteria that mainly grow on 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 and nitrite nitrogen produced during high DO aeration in the wastewater. The concentrations of ammonia nitrogen and nitrite nitrogen are controlled to be below 2 mg / L, and the reaction time is 2 hours.

[0055] 4) After the reaction in step (3) above is completed, turn off the aeration pump (7), let it stand for 10 minutes to separate the mud and water, and discharge 8L of supernatant through the drain valve (12). The amount of water discharged is equal to the initial water inflow of the system. The remaining sludge is discharged through the sludge discharge valve (13). The age of the flocculent sludge is controlled at 12 days and the sludge concentration is about 2000mg / L.

[0056] Under these operating conditions, the average COD and NH4 in the effluent are + -N, TN, and TP were 31.6, 1.1, 8.9, and 0.2 mg / L, respectively, and all effluent indicators consistently met the national Class A discharge standard.

[0057] The above-described specific embodiments are merely specific examples 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-described specific embodiments. Any appropriate changes or modifications made by a person skilled in the art that conform to the claims of the present invention should fall within the patent protection scope of the present invention.

Claims

1. A method for treating urban wastewater based on a high / low DO alternating MBBR, characterized in that, Includes the following steps: S1. Urban sewage enters MBBR reactor (2) from sewage tank (1) via peristaltic pump (3). After the water influent is finished, the agitator (6) is turned on and the agitator speed is controlled at 40~60 r / min to make the sewage and sludge mix evenly. At the same time, DO is controlled to be ≤0.1 mg / L. During this stage, the denitrifying bacteria growing in the flocculent sludge use the organic matter in the sewage to remove the residual nitrite and nitrate nitrogen in MBBR reactor (2). At the same time, polyphosphate-accumulating bacteria carry out anaerobic phosphorus release reaction and store the remaining organic matter as an intracellular carbon source. The reaction time is 1~1.5 h. S2. After the reaction in step S1 is completed, turn off the agitator (6), turn on the aeration pump (7), and control the DO to 2~4 mg / L through the gas flow meter (8). Aerobic phosphorus uptake and short-cut nitrification reactions are carried out in the flocculent sludge and biofilm respectively to remove phosphorus from the wastewater and convert some ammonia nitrogen into nitrite nitrogen. According to the nitrogen concentration change 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 gas flow meter (8). The short-range nitrifying bacteria 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 and nitrite nitrogen in the wastewater. When the concentrations of both are below 2 mg / L, aeration is stopped. S4. After the reaction in step S3 is completed, the sludge is allowed to settle 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). The age of the flocculent sludge is controlled to be 10~15 days and the sludge concentration is 1800~2300 mg / L.

2. The urban wastewater treatment method based on high / low DO alternating MBBR as described in claim 1, Its features are, The reaction time of S2 is 1~2 h.

3. The urban wastewater treatment method based on high / low DO alternating MBBR as described in claim 1, Its features are, The reaction time of S3 is 2-3 h.

4. The urban wastewater treatment method based on high / low DO alternating MBBR as described in claim 1, Its features are, The settling time is 10-15 minutes.

5. The urban wastewater treatment method based on high / low DO alternating MBBR as described in claim 1, Its features are, The amount of water discharged through the drain valve (12) is equal to the initial water intake of the system.

6. A municipal wastewater treatment system based on a high / low DO alternating MBBR, characterized in that: The system is configured to perform the method as described in any one of claims 1-5; It also includes a wastewater tank (1) and an MBBR reactor (2) connected sequentially in the direction of the wastewater treatment process. The wastewater tank (1) is connected to the MBBR reactor (2) via a peristaltic pump (3); The MBBR reactor (2) is equipped with an inlet valve (4), biological carrier packing (5), agitator (6), aeration pump (7), gas flow meter (8), microporous aeration head (9), DO monitor (10), ammonia nitrogen / nitrite nitrogen monitor (11), drain valve (12) and sludge discharge valve (13). It also includes a controller, which is communicatively 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 sludge discharge valve (13).

7. The urban wastewater treatment system based on high / low DO alternating MBBR as described in claim 6, Its features are: The biological carrier filler (5) is cylindrical and made of high-density polyethylene.

8. The urban wastewater treatment system based on high / low DO alternating MBBR as described in claim 7, Its features are: The density of the biological carrier filler (5) is 0.94~0.97 g / cm³. 3 Effective specific surface area greater than 800 m² 2 / m 3 .

9. The urban wastewater treatment system based on high / low DO alternating MBBR as described in claim 8, Its features are: The biocarrier packing material (5) has a filling rate of 35%~45% and is suspended in the MBBR reactor (2).

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