Sewage treatment system and treatment method suitable for plateau low-pressure environment

Abstract

The invention discloses a sewage treatment system and treatment method suitable for a plateau low-pressure environment, and the sewage treatment system suitable for the plateau low-pressure environment comprises a first SBR reactor which is provided with a water inlet pipe, a stirrer and a first water decanter; the second SBR reactor is provided with an MABR aeration assembly and a second water decanter; a hollow fiber membrane cavity of the MABR aeration assembly is connected with an air supply unit; the control unit is used for coordinating and controlling the periodic operation of the first SBR reactor and the second SBR reactor, and is used for regulating and controlling the output power of the air supply unit or the valve opening degree according to the real-time monitoring value of the DO sensor in the aeration stage of the second SBR reactor; therefore, the air supply pressure in the membrane cavity of the MABR aeration assembly is dynamically controlled. According to the invention, the limitation of low atmospheric pressure is eliminated, the synergistic interaction of nitrogen removal and phosphorus removal is realized, and the aeration requirement is further reduced.

Description

Technical Field

[0001] This invention belongs to the field of wastewater biological treatment technology, specifically a treatment system for denitrification and phosphorus removal of urban wastewater in low-pressure, low-oxygen, and low-temperature environments in plateau regions. Background Technology

[0002] The ecological environment of my country's plateau regions (such as the Qinghai-Tibet Plateau) is fragile, and its environmental characteristics of "low pressure, low oxygen, and low temperature" pose significant challenges to traditional biological wastewater treatment technologies. Traditional activated sludge processes typically employ forced aeration. Under the low-pressure environment of the plateau, oxygen partial pressure and saturated solubility (SPS) are significantly affected. C s The oxygen demand of microorganisms decreases significantly. To meet their oxygen requirements, aeration must be drastically increased, leading to extremely low oxygen transfer efficiency (OTE) and a sharp increase in aeration energy consumption (typically accounting for more than 50% of the total energy consumption of a wastewater treatment plant). Simultaneously, the consistently low temperatures in high-altitude areas (e.g., influent temperatures below 10°C) reduce microbial activity, especially slowing the growth of nitrifying bacteria and polyphosphate-accumulating organisms (PAOs), making it difficult to guarantee the system's nitrogen and phosphorus removal efficiency and increasing the risk of sludge bulking. Sequencing batch reactors (SBRs) offer advantages due to their flexible operation, as they can compensate for the reduced reaction rate caused by low temperatures by extending the reaction time. Membrane aerated bioreactors (MABRs) achieve "bubble-free" oxygen supply through hollow fiber membranes, theoretically offering high oxygen mass transfer efficiency, and their biofilm characteristics help enrich slowly growing nitrifying bacteria at low temperatures. However, how to combine the high-efficiency oxygen supply characteristics of MABR with the flexible operation mode of SBR, and build a process that can simultaneously and efficiently remove nitrogen (N) and phosphorus (P) to systematically solve the problems of energy consumption, efficiency and stability in high-altitude, low-pressure, low-temperature and low-oxygen environments, is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a wastewater treatment system and method suitable for high-altitude and low-pressure environments that reduces aeration energy consumption and improves low-temperature nitrogen and phosphorus removal efficiency.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A wastewater treatment system suitable for high-altitude, low-pressure environments includes: The first SBR reactor, namely the biological phosphorus removal SBR reactor, is equipped with an inlet pipe, a stirrer and a first decanter. The second SBR reactor, namely the MABR-SBR reactor, has its inlet connected to the outlet of the first decanter via a pipeline; the second SBR reactor is equipped with a MABR aeration component and a second decanter; the hollow fiber membrane cavity of the MABR aeration component is connected to an air supply unit. The sludge return pipeline is used to return the sludge discharged from the second SBR reactor to the first SBR reactor; The control unit is connected to the valves of the inlet pipe, the agitator, the first decanter, the inlet valve of the second SBR reactor, the air supply unit, the second decanter, and the pump of the sludge return pipeline. The control unit is also electrically connected to the DO sensor installed in the second SBR reactor and the gas pressure sensor installed on the air supply pipeline of the MABR aeration component. The control unit is used to coordinate and control the periodic operation of the first SBR reactor and the second SBR reactor, and during the aeration stage of the second SBR reactor, it is used to adjust the output power of the air supply unit or the valve opening according to the real-time monitoring value of the DO sensor, so as to dynamically control the air supply pressure in the membrane chamber of the MABR aeration component.

[0005] Furthermore, the air supply unit is preferably an adjustable frequency screw compressor or a high-pressure fan.

[0006] The present invention also provides a wastewater treatment method based on the above system, the method comprising: first SBR reactor operation cycle control and second SBR reactor operation cycle control. A) The operation cycle control of the first SBR reactor (biological phosphorus removal SBR) includes, in sequence: 1. Influent stage: The wastewater to be treated is pumped into the first SBR reactor, and the return sludge from the second SBR reactor is pumped in at the same time; 2. Anaerobic reaction stage: Start the agitator and stir under anaerobic conditions without aeration to allow polyphosphate-accumulating bacteria (PAOs) to release phosphates and absorb easily degradable organic matter in the wastewater; 3. Sedimentation stage: Stop stirring and allow the sludge to settle by gravity; 4. Decanting stage: Start the first decanter to discharge the supernatant (rich in ammonia nitrogen and phosphate) and transport it to the second SBR reactor.

[0007] B) Operation cycle control of the second SBR reactor (MABR-SBR), including the following in sequence: 1. Feed stage: Receive the supernatant discharged from the first SBR reactor; 2. MABR Reaction Stage: The MABR aeration components and control unit are started for aeration; the control unit sets the target dissolved oxygen (DO) concentration of the mixed liquor in the second SBR reactor to 0.2~0.5 mg / L; The control unit monitors the DO concentration in real time and adjusts the output of the air supply unit through negative feedback to maintain a low dissolved oxygen (DO) concentration in the mixture. Aerobic organic matter degradation, nitrification, and aerobic phosphorus uptake occur on the surface of the MABR biofilm (aerobic microzone); simultaneous nitrification-denitrification (SND) and denitrification-phosphorus uptake (DPAOs) occur in the bulk of the mixed liquor (anoxic microzone). 3. Settling stage: Aeration is stopped, and the sludge undergoes gravity settling; 4. Decanting stage: Start the second decanter to discharge the supernatant after treatment to meet the standards; 5. Sludge Discharge / Recirculation Stage: Discharge the remaining sludge from the system and start the sludge recirculation pump to return a portion of the sludge rich in polyphosphate-accumulating bacteria to the first SBR reactor for use in the influent stage of the next cycle.

[0008] Beneficial effects of the present invention Compared with the prior art, the present invention has the following significant advantages: 1. Extremely low aeration energy consumption and high oxygen mass transfer efficiency: This invention utilizes a MABR module for aeration of the SBR in a high-altitude, low-pressure environment. By increasing the air pressure within the membrane chamber through the control unit, a high oxygen partial pressure difference can be artificially created, overcoming the limitations of low atmospheric pressure, and achieving an oxygen transfer efficiency (OTE) of over 90%. Compared to traditional blower-aerated SBRs, aeration energy consumption is significantly reduced (saving over 70%).

[0009] 2. Highly optimized process flow for excellent nitrogen and phosphorus removal: This invention employs a two-stage SBR series connection, achieving perfect separation and coupling of functions. The first SBR (anaerobic) is dedicated to anaerobic phosphorus release by polyphosphate-accumulating bacteria and carbon source screening; the second SBR (MABR) is dedicated to nitrification, denitrification, and aerobic / anoxic phosphorus uptake. Clear functional zoning avoids interference from multi-stage switching within a single SBR tank, resulting in more stable treatment performance.

[0010] 3. Enhanced Simultaneous Nitrification-Denitrification (SND) and Denitrification Phosphorus Removal: The core of this invention lies in the low DO (0.2~0.5 mg / L) control during the MABR reaction stage. This creates aerobic microzones (for nitrification and phosphorus uptake) on the surface of the MABR biofilm, while anoxic microzones are formed in the bulk of the mixed liquor. This greatly promotes SND formation and creates favorable conditions for denitrifying polyphosphate-accumulating bacteria (DPAOs), achieving synergistic effects in nitrogen and phosphorus removal and further reducing aeration requirements.

[0011] 4. Overcoming the limitations of high altitude and low temperature, ensuring stable operation: The biofilm characteristics of MABR allow slow-growing functional bacteria, such as nitrifying bacteria, to be stably enriched at low temperatures. Meanwhile, the SBR operating mode allows for the extension of reaction phases (such as the MABR reaction phase) to compensate for the reduced microbial activity caused by low temperatures, ensuring that the system still has stable and efficient C, N, and P removal capabilities under high altitude and low temperature conditions (such as 8℃). Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the process flow of a high-efficiency oxygen mass transfer membrane aeration bioreactor system suitable for high-altitude and low-pressure environments according to the present invention.

[0013] The diagram shows the following labels: 1-Inlet pipe; 2-First SBR reactor; 3-Agitator; 4-First decanter; 5-Second SBR reactor; 6-MABR aeration assembly; 7-Second decanter; 8-Outlet pipe; 9-Air supply unit; 10-Dissolved oxygen sensor; 11-Gas pressure sensor; 12-Control unit; 13-Sludge return pump; 14-Sludge return pipeline; 15-Excess sludge discharge; 16-Supernatant delivery pipeline. Detailed Implementation

[0014] The following is in conjunction with the appendix Figure 1 The technical solution of the present invention will be further described in detail below with reference to specific embodiments.

[0015] like Figure 1 As shown in the figure, the high-efficiency oxygen mass transfer membrane aeration bioreactor system suitable for high-altitude and low-pressure environments provided in this embodiment of the invention includes a first SBR reactor 2 and a second SBR reactor 5.

[0016] The first SBR reactor 2 is equipped with an inlet pipe 1, a stirrer 3, and a first decanter 4; The second SBR reactor is equipped with a MABR aeration component 6 and a second decanter 7; the hollow fiber membrane cavity of the MABR aeration component 6 is connected to the air supply unit 9. The inlet of the second SBR reactor is connected to the outlet of the first decanter via a pipeline; the sludge discharged from the second SBR reactor is returned to the first SBR reactor via the sludge return pipeline 14.

[0017] The wastewater to be treated first enters the first SBR reactor 2 through the inlet pipe 1. At the same time, phosphorus-rich sludge from the second SBR reactor 5 is pumped into the first SBR reactor 2 through the sludge return pipe 14 and the sludge return pump 13.

[0018] Control unit 12 controls the first SBR reactor 2 to operate cyclically: Influent stage: The wastewater to be treated and the returned sludge enter the tank of the first SBR reactor 2.

[0019] Anaerobic reaction stage: Start agitator 3 and, under non-aeration conditions (about 2 hours), allow polyphosphate-accumulating bacteria in the sludge to release phosphates and absorb easily degradable organic matter such as VFA in the wastewater.

[0020] Sedimentation stage: Stop stirring (about 1 hour) and the activated sludge settles.

[0021] Decanting stage: Start the first decanter 4 to decanter the water rich in NH4. + -N and PO4 3- The supernatant of -P is discharged into the second SBR reactor 5 through the supernatant delivery pipeline 16.

[0022] After receiving the supernatant, the second SBR reactor 5 operates cyclically under the control of the control unit 12: Feed stage: Receive the supernatant from the first SBR reactor 2 (approximately 30 minutes).

[0023] MABR reaction stage: This is the core stage of the invention. Control unit 12 starts air supply unit 9 (such as variable frequency compressor) to supply air to the membrane chamber of MABR aeration component 6 for 4-6 hours.

[0024] The control unit 12 sets the target DO value of the mixture to 0.3 mg / L.

[0025] The DO sensor 10 monitors the DO value in real time. If DO < 0.3 mg / L, the control unit 12 increases the frequency of the air supply unit 9 and increases the supply pressure (monitored by the gas pressure sensor 11); if DO > 0.3 mg / L, the frequency and pressure are reduced.

[0026] Under this "low DO" control, the surface of the MABR biofilm is in an aerobic state due to direct oxygen supply, enabling efficient nitrification (NH4+). + →NO3 _ ( ) and aerobic phosphorus uptake. Meanwhile, the main body of the mixed liquor (the water in the SBR tank) is in an anoxic state, utilizing NO3 diffused from the biofilm. _ Simultaneous nitrification and denitrification (SND) are carried out, while DPAO bacteria utilize NO3. _ It acts as an electron acceptor for denitrification and phosphorus uptake.

[0027] Settling stage: Aeration is stopped (approximately 1.5 hours), and the sludge settles.

[0028] Decanting stage: Start the second decanter 7 to discharge the treated supernatant from the outlet pipe 8.

[0029] Sludge discharge / recirculation stage: A portion of the remaining sludge 15 is discharged (this is the final path for phosphorus removal in the system), and the sludge recirculation pump 13 is started to return most of the sludge to the first SBR reactor 2, in preparation for the next large cycle.

[0030] Example 1: Small-scale test simulating a high-altitude, low-pressure environment To verify the beneficial effects of the present invention, a small-scale test simulating a plateau environment was conducted in the laboratory.

[0031] 1. Simulation conditions: Low-pressure simulation: The air pressure of the environment in which the test device is located is kept constant at about 65 kPa through a low-pressure environment chamber (this air pressure is equivalent to simulating conditions at an altitude of about 3650 meters).

[0032] Low temperature simulation: The reactor inlet water temperature is kept constant at an average of 9.5℃ by using an external circulating water bath cooling device to simulate the low temperature conditions at high altitudes.

[0033] 2. Test System (Embodiment of the Invention): The two-stage SBR system described in this invention (e.g.) is employed. Figure 1 (As shown), all are placed within the aforementioned low-pressure environment chamber. The treatment capacity is 50 L / d. The first SBR reactor 2 has an effective volume of 15 L; the second SBR reactor 5 has an effective volume of 35 L. The second SBR reactor is equipped with a PDMS hollow fiber membrane aeration module with a total membrane area of ​​0.2 m². 2 .

[0034] 3. Control group: A single-tank SBR process was used, with traditional microporous aeration discs and blower aeration. DO was controlled at 2.0 mg / L during the aerobic phase. The total volume and operating cycle were comparable to the system of this invention. The control group was also placed in the same simulated low-pressure and low-temperature environment described above.

[0035] 4. Operating conditions: Both systems will operate synchronously for 3 months. Influent will be artificially mixed (simulating typical urban wastewater quality): COD 250~350 mg / L; NH4+ + -N 30~45 mg / L; TN 40~55 mg / L; TP 3~5 mg / L. System parameters (example) of this invention: Two-stage SBR total cycle 8 hours (3 cycles per day). First SBR (anaerobic 2h, sedimentation 1h, decanting 0.5h); Second SBR (influent 0.5h, MABR reaction 4.5h, sedimentation 1h, decanting / sludge discharge 0.5h). DO control target value for the MABR reaction stage 0.3 mg / L. Sludge return ratio (R2 to R1) is 50% of the total influent volume. Total SRT controlled at 30 days.

[0036] 5. Experimental Results:

[0037] Results Analysis: (1) Effect Comparison Under simulated plateau low pressure and low temperature conditions, the traditional SBR in the control group had low oxygen mass transfer efficiency due to simulated low pressure, and low temperature inhibited microbial activity. Its nitrification and phosphorus removal effects were unstable and difficult to meet the standards. In the embodiment of the present invention, through the functional separation of two-stage SBR, the anaerobic environment of the first SBR ensured good screening of PAOs; the MABR biofilm of the second SBR stably enriched nitrifying bacteria under simulated low temperature, ensuring stable nitrification. (2) Innovation Effect The core of the present invention (MABR low DO control) successfully constructed a microenvironment of "aerobic membrane surface and anoxic body" in the second SBR, which greatly enhanced the phosphorus removal effects of SND and denitrification, making the removal rates of TN and TP far better than those of the control group, and stably reaching the Class A standard. (3) Energy Consumption Comparison The energy consumption of the aeration system in the embodiment of the present invention is only 0.13 kWh / m3, compared with 0.48 kWh / m3 of the control group, saving about 73% of aeration energy consumption, proving that the present invention can effectively solve the energy consumption bottleneck problem of wastewater treatment in simulated plateau areas.

[0038] In summary, this invention combines the two-stage SBR process with the precise aeration control of MABR in a high-altitude environment. The process flow design is reasonable, the operation mode is innovative, and it effectively solves the problems of nitrogen and phosphorus removal and high energy consumption in wastewater under low pressure and low temperature conditions in high-altitude environments.

[0039] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A wastewater treatment system suitable for high-altitude, low-pressure environments, characterized in that, include: The first SBR reactor is equipped with an inlet pipe, a stirrer, and a first decanter; The second SBR reactor has its inlet connected to the outlet of the first decanter; the second SBR reactor is equipped with a MABR aeration assembly and a second decanter; the hollow fiber membrane cavity of the MABR aeration assembly is connected to an air supply unit. The sludge return pipeline is used to return the sludge discharged from the second SBR reactor to the first SBR reactor; The control unit is connected to the valves of the inlet pipe, the agitator, the first decanter, the inlet valve of the second SBR reactor, the air supply unit, the second decanter, and the pump of the sludge return pipeline. The control unit is also electrically connected to the DO sensor installed in the second SBR reactor and the gas pressure sensor installed on the air supply pipeline of the MABR aeration component. The control unit is used to coordinate and control the periodic operation of the first SBR reactor and the second SBR reactor, and during the aeration stage of the second SBR reactor, it is used to adjust the output power of the air supply unit or the valve opening according to the real-time monitoring value of the DO sensor, so as to dynamically control the air supply pressure in the membrane chamber of the MABR aeration component.

2. The wastewater treatment system for high-altitude, low-pressure environments according to claim 1, characterized in that, The control unit sets the target DO concentration of the mixture in the second SBR reactor to 0.2~0.5 mg / L.

3. The wastewater treatment system for high-altitude, low-pressure environments according to claim 1, characterized in that, The air supply pressure inside the membrane chamber of the MABR aeration module is 20-25 kPa.

4. The wastewater treatment system for high-altitude, low-pressure environments according to claim 1, characterized in that, The air supply unit is an adjustable frequency screw compressor or a high-pressure fan.

5. A treatment method based on the wastewater treatment system suitable for high-altitude, low-pressure environments as described in any one of claims 1-4, characterized in that, This includes the operation cycle control of the first SBR reactor and the operation cycle control of the second SBR reactor: The operation cycle control of the first SBR reactor includes, in sequence: Influent stage: Wastewater to be treated is pumped into the first SBR reactor, and return sludge from the second SBR reactor is pumped in simultaneously. Anaerobic reaction stage: Start the agitator and stir under anaerobic conditions without aeration to allow polyphosphate-accumulating bacteria to release phosphates and absorb easily degradable organic matter in the wastewater. Sedimentation stage: Stop stirring and allow the sludge to settle by gravity; Decanting stage: Start the first decanter to discharge the supernatant rich in ammonia nitrogen and phosphate and transport it to the second SBR reactor; The operation cycle control of the second SBR reactor includes, in sequence: Feed stage: Receive the supernatant decanted from the first SBR reactor; MABR reaction stage: The MABR aeration components and control unit are started for aeration; the control unit sets the target value of DO concentration in the mixed liquor in the second SBR reactor to 0.2~0.5 mg / L; The control unit monitors the DO concentration in real time and adjusts the output of the air supply unit through negative feedback to maintain the DO concentration of the mixture. Aerobic organic matter degradation, nitrification, and aerobic phosphorus uptake occur in the aerobic microzones on the surface of the MABR biofilm; simultaneous nitrification-denitrification and denitrification phosphorus uptake occur in the anoxic microzones of the mixed liquor. Sedimentation stage: Aeration is stopped, and the sludge undergoes gravity settling; Decanting stage: Start the second decanter to discharge the supernatant after treatment to meet the standards; Sludge discharge / recirculation stage: Discharge the remaining sludge from the system and start the sludge recirculation pump to return a portion of the sludge rich in polyphosphate-accumulating bacteria to the first SBR reactor for use in the influent stage of the next cycle.

6. The processing method according to claim 5, characterized in that, The MABR reaction stage of the second SBR reactor lasts for 4-6 hours.

7. The processing method according to claim 5, characterized in that, The anaerobic reaction stage of the first SBR reactor lasts for 1-3 hours.

8. The processing method according to claim 5, characterized in that, The control unit sets the target DO concentration of the mixture in the second SBR reactor to 0.3 mg / L.

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