Device and method for in-situ determination and reduction of greenhouse gas emission in nitrogen and phosphorus removal process of AOA process

Abstract

The invention discloses a device and a method for in-situ determination and reduction of greenhouse gas emission in a nitrogen and phosphorus removal process of an AOA process, and belongs to the field of sewage treatment and carbon neutralization. The device comprises a gas collection type continuous flow AOA reactor, an accurate aeration system, a gas collection system, a microelectrode system and the like. According to the device, a greenhouse gas in-situ monitoring system and a regulation and control system are integrated, the emission condition of greenhouse gases (CO2, CH4 and N2O) in the operation process of the AOA technology can be monitored in real time, then parameters such as dissolved oxygen and the sludge reflux ratio are automatically adjusted, the operation conditions are optimized, and emission of the greenhouse gases is effectively reduced. The method is also combined with a biological enhancement technology, and the ecological niche of the microbial community is adjusted by adding anaerobic ammonia oxidation filler, so that the nitrogen and phosphorus removal efficiency of the AOA process is further improved, and meanwhile, the generation of greenhouse gases is reduced. The device can comprehensively monitor the greenhouse gas in the AOA process, and provides technical support for greenhouse gas research in the biological sewage treatment process.

Description

Technical Field

[0001] The present invention belongs to the field of environmental engineering sewage treatment and carbon neutrality, and in particular, relates to a device and method for in-situ measurement and reduction of greenhouse gas emissions during the AOA process of nitrogen removal and phosphorus removal. The device and method are intended to optimize the sewage treatment process, improve the efficiency of sewage treatment and reduce its impact on the environment by in-situ monitoring of greenhouse gas emissions and taking corresponding measures to reduce emissions. Background Art

[0002] In the context of carbon neutrality, the emission standards of sewage treatment plants have been gradually tightened, including not only sewage indicators but also carbon emissions. Carbon emissions from sewage treatment plants account for about 1% of the total emissions of the whole society, accounting for the largest proportion in the environmental protection industry. Carbon emissions from sewage treatment plants include indirect carbon emissions and direct carbon emissions. Indirect carbon emissions mainly come from energy consumption such as electricity and chemicals, while direct carbon emissions mainly come from greenhouse gases such as CO2, N2O and CH4 produced during biological reactions.

[0003] Most of the N2O produced in sewage treatment plants comes from the biological denitrification process. It is a byproduct of the biological denitrification process and usually escapes into the atmosphere in gaseous form and is discharged with sewage in liquid form. The production of CO2 mainly comes from the oxidative decomposition of organic matter. This process can occur in multiple areas of the biochemical pool and is mainly discharged in the aerobic zone. The production of CH4 mainly comes from the decomposition of organic matter under anaerobic conditions. The anaerobic zone is the main area for CH4 production. In an anaerobic environment, methanogens will use organic matter for anaerobically decomposing and produce CH4 gas.

[0004] The AOA process removes organic matter, releases phosphorus, and denitrifies in the anaerobic zone; nitrification and aerobic phosphorus absorption occur in the aerobic zone to remove NH4 + With PO4 3- ; Endogenous denitrification and denitrification phosphorus removal occur in the anoxic zone. The AOA process does not require an external carbon source for deep nitrogen and phosphorus removal, and can save aeration in the aerobic zone. It has the advantages of deep reduction of pollutants, low sludge production, and carbon saving and consumption reduction. However, greenhouse gases such as CO2, N2O and CH4 are inevitably produced during the whole process.

[0005] Anaerobic ammonium oxidation is a process in which anaerobic ammonium oxidizing bacteria convert NH4 + With NO2 - Converts to N2, fixes CO2 and produces NO3 - The anaerobic ammonium oxidation process does not produce N2O and does not require aeration and organic carbon sources. It is currently the most economical and efficient sewage denitrification technology. In the post-anoxia zone of the AOA process, the intermediate product of the endogenous denitrification process, NO2 -It can be used as an anaerobic ammonium oxidation substrate to couple anaerobic ammonium oxidation denitrification through endogenous reverse short-range nitrification. Combining the AOA process with anaerobic ammonium oxidation can deeply reduce nutrients in urban sewage and reduce the discharge of pollutants such as nitrogen and phosphorus into the water environment. At the same time, it can further save energy and reduce greenhouse gas emissions. At present, there are still deficiencies in the monitoring and reduction technologies for greenhouse gas emissions in the AOA process. On the one hand, there is a lack of equipment for in-situ monitoring of greenhouse gas emissions, and it is impossible to grasp greenhouse gas emissions in real time and accurately; on the other hand, although some studies have tried to reduce greenhouse gas emissions by optimizing AOA process parameters, adding exogenous carbon sources, etc., these methods often have problems such as high cost and unstable results.

[0006] Therefore, developing a device and method that can in situ measure and reduce greenhouse gas emissions during the AOA process of nitrogen removal and phosphorus removal will not only help optimize the AOA process parameters and improve the stability and efficiency of the anaerobic ammonium oxidation process, but also achieve real-time monitoring and effective control of greenhouse gas emissions, which is of great significance for improving sewage treatment efficiency, reducing greenhouse gas emissions, and promoting sustainable development. Summary of the invention

[0007] The object of the present invention is to provide a device and method for in-situ determination and reduction of greenhouse gas emissions during the denitrification and phosphorus removal process of the AOA process. The device can collect all the gases generated by the continuous flow reactor for analysis, and can also collect the gases in different areas for specific research. In addition, the change of liquid phase N2O concentration can be monitored online in real time through a micro-electrode system.

[0008] A device and method for in-situ measurement and reduction of greenhouse gas emissions during the AOA process of nitrogen removal and phosphorus removal, characterized in that: Figure 1As shown, the device includes a water inlet tank (1), an air-collecting continuous flow AOA reactor (2), a precise aeration system (3), a gas collection system (4), a microelectrode system (5) and a secondary sedimentation tank (6); the air-collecting continuous flow AOA reactor includes an anaerobic zone (2.1), an aerobic zone (2.2), an anoxic zone (2.3), a multifunctional port (2.4), a stirring system (2.5) and an anaerobic ammonium oxidation filler (2.6); the precise aeration system includes an aeration head (3.1), an aeration pump (3.2), an ammonia nitrogen online monitor (3.3), a dissolved oxygen online monitor (3.4) and a PCL control system (3.5); the gas collection system includes a drying tube (4.1), a wet gas flow meter (4.2), a gas sampling bag (4.3) and a gas chromatograph (4.4); the microelectrode system includes a N2O microelectrode (5.1), a picoammeter (5.2) and a host (5.3). Influent water enters the gas-gathering continuous flow AOA reactor from the influent tank through the influent pump (1.1), passes through the anaerobic zone, the aerobic zone and the anoxic zone in sequence along the water flow direction, and then enters the secondary sedimentation tank. The sludge at the bottom of the secondary sedimentation tank is returned to the front end of the anaerobic zone through the first sludge return pump (6.1), and is returned to the front end of the anoxic zone through the second sludge return pump (6.2).

[0009] The method for reducing greenhouse gas emissions during the AOA process of nitrogen removal and phosphorus removal is characterized by:

[0010] 1) Dissolved oxygen control strategy:

[0011] The precise aeration system is set at the end of the aerobic zone, and the ammonia nitrogen concentration at the end of the aerobic zone is controlled at 3-5 mg / L through the ammonia nitrogen online monitor, and the dissolved oxygen concentration at the end of the aerobic zone is controlled at 1-2 mg / L through the dissolved oxygen online monitor. When the ammonia nitrogen concentration is greater than 5 mg / L or the dissolved oxygen concentration is lower than 1 mg / L, the aeration volume is increased through the PLC control system, and when the ammonia nitrogen concentration is less than 3 mg / L or the dissolved oxygen concentration is higher than 2 mg / L, the aeration volume is reduced through the PLC control system.

[0012] 2) Second sludge return ratio control strategy:

[0013] The microelectrode system is set at the end of the anoxic zone, and the dissolved N2O concentration is monitored in real time through the N2O microelectrode. When the N2O-N concentration is lower than 0.1mg / L, there is no need to start the second sludge return; when the N2O-N concentration is higher than 0.1mg / L, the second sludge return is turned on to enhance the denitrification performance of the anoxic zone, and the second sludge return ratio is set to 50-100%.

[0014] 3) Biofortification strategy:

[0015] The sludge concentration in the reactor is increased and stabilized at 5000-8000 mg / L. In addition, anaerobic ammonium oxidation filler is added to the anoxic zone with a filling ratio of 20-30%.

[0016] The characteristics are as follows: the gas collection system can collect the headspace gases in the anaerobic zone and the anoxic zone together through the positive pressure provided by the aerobic zone, and further directly measure the volume concentrations of CO2, CH4 and N2O in the gas phase through a gas chromatograph.

[0017] It is characterized by: Figure 2 As shown, a liquid sealing groove is provided below the stirring port, and the liquid sealing groove is filled with water to prevent gas from escaping from the stirring port.

[0018] It is characterized by: Figure 3 As shown, the reactor sealing cover and the continuous flow water treatment reactor are sealed with sealant to prevent gas from escaping from the gap.

[0019] The N2O concentration in the liquid phase is directly measured by the microelectrode system. The dried gas is collected in a gas sampling bag and the volume concentrations of CO2, CH4 and N2O in the gas phase are directly measured by a gas chromatograph. The formula for converting volume concentration to mass concentration is as follows:

[0020]

[0021] Where, M is the molecular weight of CO2, CH4 and N2O; C V is the volume concentration, ppm; Pa is the air pressure during measurement, Kpa; T is the temperature during measurement, ℃

[0022] The present invention has the following advantages:

[0023] (1) AOA process technology can fully store internal carbon sources in the anaerobic zone and reduce CH4 emissions in the aerobic zone; precise regulation of dissolved oxygen in the aerobic zone can significantly reduce aeration energy consumption and reduce CO2 emissions; endogenous denitrification in the post-anoxic zone can completely remove dissolved N2O;

[0024] (2) The gases generated in the continuous flow AOA reactor can be collected separately according to functional areas or all of them can be collected;

[0025] (3) Capable of online monitoring of liquid phase N2O production in each functional zone of continuous flow;

[0026] (4) The reactor sealing cover can ensure a better anaerobic environment in the non-aerated area, so that anaerobic microorganisms can function better;

[0027] (5) The gas collected by the present invention can be used not only for CO2, CH4 and N2O analysis, but also for analyzing other gases produced in the reactor, such as H2S, etc.;

[0028] (6) Combined with anaerobic ammonium oxidation technology, it reduces dependence on external carbon sources, improves denitrification efficiency, and reduces greenhouse gas emissions during the denitrification process. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a device for in-situ measurement of greenhouse gas emissions during the nitrogen and phosphorus removal process of the AOA process.

[0030] 1 indicates water inlet tank, 2 indicates gas-collecting AOA continuous flow reactor, 3 indicates precise aeration system, 4 indicates gas collection system, 5 indicates microelectrode system, 6 indicates secondary sedimentation tank; 1.1 indicates water inlet pump; 2.1 indicates anaerobic zone, 2.2 indicates aerobic zone, 2.3 indicates anoxic zone, 2.4 indicates multifunctional port, 2.5 indicates stirring system, 2.6 indicates anaerobic ammonia oxidation filler; 3.1 indicates aeration head, 3.2 indicates aeration pump, 3.3 indicates ammonia nitrogen online monitor, 3.4 indicates dissolved oxygen online monitor, 3.5 indicates PCL control system; 4.1 indicates drying tube, 4.2 indicates wet gas flow meter, 4.3 indicates gas sampling bag, 4.4 indicates gas chromatograph, 5.1 indicates N2O microelectrode, 5.2 indicates picoammeter, 5.3 indicates host; 6.1 indicates the first sludge return pump, 6.2 indicates the second sludge return pump.

[0031] Figure 2 It is a specific schematic diagram of the liquid seal groove below the stirring port.

[0032] Figure 3 Diagram showing the separation of the reactor sealing cover and the continuous flow AOA reactor. DETAILED DESCRIPTION

[0033] The present invention is further described below in conjunction with the accompanying drawings and embodiments: A device and method for in-situ measurement and reduction of greenhouse gas emissions during the denitrification and phosphorus removal process of the AOA process, characterized in that: Figure 1As shown, the device includes a water inlet tank (1), an air-collecting continuous flow AOA reactor (2), a precise aeration system (3), a gas collection system (4), a microelectrode system (5) and a secondary sedimentation tank (6); the air-collecting continuous flow AOA reactor includes an anaerobic zone (2.1), an aerobic zone (2.2), an anoxic zone (2.3), a multifunctional port (2.4), a stirring system (2.5) and an anaerobic ammonium oxidation filler (2.6); the precise aeration system includes an aeration head (3.1), an aeration pump (3.2), an ammonia nitrogen online monitor (3.3), a dissolved oxygen online monitor (3.4) and a PCL control system (3.5); the gas collection system includes a drying tube (4.1), a wet gas flow meter (4.2), a gas sampling bag (4.3) and a gas chromatograph (4.4); the microelectrode system includes a N2O microelectrode (5.1), a picoammeter (5.2) and a host (5.3). The influent enters the gas-collecting continuous flow AOA reactor from the inlet tank through the inlet pump (1.1), passes through the anaerobic zone, aerobic zone and anoxic zone in the direction of the water flow, and then enters the secondary sedimentation tank. The sludge at the bottom of the secondary sedimentation tank is returned to the anaerobic zone through the sludge return pump (5.1). In the anoxic zone, N2O in the liquid phase is directly measured by the microelectrode system. In the aerobic zone, the mixed gas in the gas phase is collected in a gas sampling bag and measured by a gas chromatograph. Figure 2 As shown, a liquid seal groove is provided below the stirring port, and the liquid seal groove is filled with water to prevent gas from escaping from the stirring port. Figure 3 As shown, the reactor sealing cover and the continuous flow AOA reactor are sealed with sealant to prevent gas from escaping from the gap.

[0034] The specific operations are as follows:

[0035] The method for reducing greenhouse gas emissions during the AOA process of nitrogen removal and phosphorus removal is characterized by including the following strategies:

[0036] 1) Dissolved oxygen control strategy:

[0037] The precise aeration system is set at the end of the aerobic zone, and the ammonia nitrogen concentration at the end of the aerobic zone is controlled at 3-5 mg / L through the ammonia nitrogen online monitor, and the dissolved oxygen concentration at the end of the aerobic zone is controlled at 1-2 mg / L through the dissolved oxygen online monitor. When the ammonia nitrogen concentration is greater than 5 mg / L or the dissolved oxygen concentration is lower than 1 mg / L, the aeration volume is increased through the PLC control system, and when the ammonia nitrogen concentration is less than 3 mg / L or the dissolved oxygen concentration is higher than 2 mg / L, the aeration volume is reduced through the PLC control system.

[0038] 2) Second sludge return ratio control strategy:

[0039] The microelectrode system is set at the end of the anoxic zone, and the dissolved N2O concentration is monitored in real time through the N2O microelectrode. When the N2O-N concentration is lower than 0.1mg / L, there is no need to start the second sludge return; when the N2O-N concentration is higher than 0.1mg / L, the second sludge return is turned on to enhance the denitrification performance of the anoxic zone, and the second sludge return ratio is set to 50-100%.

[0040] 3) Biofortification strategy:

[0041] The sludge concentration in the reactor is increased and stabilized at 5000-8000 mg / L. In addition, anaerobic ammonium oxidation filler is added to the anoxic zone with a filling ratio of 20-30%.

[0042] The use of the microelectrode system is characterized by comprising the following steps: before measuring the liquid phase N2O concentration, the microelectrode system is polarized and calibrated, and then the N2O microelectrode is placed in the multifunctional port at the end of the anoxic zone.

[0043] The use of the gas collection system is characterized by comprising the following steps: firstly, the drying tube and the wet flow meter are connected to the multifunctional port for gas collection, and the specifications of the gas sampling bag to be used are determined according to the size of the wet flow meter. Before collecting the gas, the gas sampling bag is not connected first, and is connected again after ventilation for a period of time to discharge the original gas in the passage. After the gas is collected, the volume concentration is measured by a gas chromatograph.

[0044] The multi-function port can be used flexibly according to needs, such as for sampling, mud collection, etc.

[0045] The above are specific embodiments of the present invention, which are convenient for technicians in this technical field to better understand and apply the present invention. The implementation of the present invention is not limited to this, so simple improvements made to the present invention by technicians in this technical field are within the scope of the present invention.

Claims

1. A device for in-situ measurement and reduction of greenhouse gas emissions during the AOA process of nitrogen removal and phosphorus removal, characterized by: The invention comprises a water inlet tank (1), an air-gathering continuous flow AOA reactor (2), an aeration system (3), a gas collection system (4), a microelectrode system (5) and a secondary sedimentation tank (6); the air-gathering continuous flow AOA reactor comprises an anaerobic zone (2.1), an aerobic zone (2.2), an anoxic zone (2.3), a multifunctional port (2.4), a stirring system (2.5) and an anaerobic ammonium oxidation filler (2.6); the precise aeration system comprises an aeration head (3.1), an aeration pump (3.2), an ammonia nitrogen online monitor (3.3), a dissolved oxygen online monitor (3.4) and a PCL control system (3.5); The gas collection system includes a drying tube (4.1), a wet gas flow meter (4.2), a gas sampling bag (4.3) and a gas chromatograph (4.4); the microelectrode system includes a N2O microelectrode (5.1), a picoammeter (5.2) and a host (5.3); the influent enters the gas-collecting continuous flow AOA reactor from the influent tank through the influent pump (1.1), passes through the anaerobic zone, the aerobic zone and the anoxic zone in sequence along the water flow direction, and then enters the secondary sedimentation tank. The sludge at the bottom of the secondary sedimentation tank is returned to the front end of the anaerobic zone through the first sludge return pump (6.1), and is returned to the front end of the anoxic zone through the second sludge return pump (6.2).

2. A method for reducing greenhouse gas emissions during nitrogen and phosphorus removal by AOA process using the device as claimed in claim 1, characterized in that: 1) Dissolved oxygen control strategy: The aeration system is set at the end of the aerobic zone. The ammonia nitrogen concentration at the end of the aerobic zone is controlled at 3-5 mg / L through an online ammonia nitrogen monitor, and the dissolved oxygen concentration at the end of the aerobic zone is controlled at 1-2 mg / L through an online dissolved oxygen monitor. When the ammonia nitrogen concentration is greater than 5 mg / L or the dissolved oxygen concentration is lower than 1 mg / L, the aeration volume is increased through the PLC control system. When the ammonia nitrogen concentration is less than 3 mg / L or the dissolved oxygen concentration is higher than 2 mg / L, the aeration volume is reduced through the PLC control system. 2) Second sludge return ratio control strategy: The microelectrode system is set at the end of the anoxic zone, and the dissolved N2O concentration is monitored in real time through the N2O microelectrode; when the N2O-N concentration is lower than 0.1 mg / L, there is no need to start the second sludge return; when the N2O-N concentration is higher than 0.1 mg / L, the second sludge return is started to enhance the denitrification performance of the anoxic zone, and the second sludge return ratio is set to 50-100%; 3) Biofortification strategy: The sludge concentration in the reactor is increased and stabilized at 5000-8000 mg / L. In addition, anaerobic ammonium oxidation filler is added to the anoxic zone with a filling ratio of 20-30%.

3. The device according to claim 1, characterized in that: The gas collection system can collect the headspace gases in the anaerobic and anoxic zones through the positive pressure provided by the aerobic zone, and directly measure the volume concentrations of CO2, CH4 and N2O in the gas phase through a gas chromatograph.

4. The device according to claim 1, characterized in that: A liquid sealing groove is provided below the stirring port and is filled with water to prevent gas from escaping from the stirring port.

5. The device according to claim 1, characterized in that: The reactor sealing cover and the continuous flow water treatment reactor are sealed with sealant to prevent gas from escaping from the gap.

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