Device and method for advanced nitrogen removal from sewage

Abstract

The present application belongs to the field of sewage biological treatment, and particularly relates to a device and method for advanced denitrification of sewage. The device for advanced denitrification of sewage comprises a UASB reactor and a SBR aerobic reactor connected in series. The UASB reactor is provided with a first water inlet and a second water inlet. The first water inlet is arranged at the bottom of the UASB reactor, and the second water inlet is arranged on the side wall of the sludge bed area of the UASB reactor. A dynamic membrane is arranged between the overflow port and the water outlet of the UASB reactor. The water outlet of the SBR aerobic reactor is connected to the second water inlet of the UASB reactor through a water outlet barrel. The device can fully utilize the organic matter in raw water, realize advanced denitrification, reduce the production of residual sludge, achieve good water quality, and save operation cost due to low cost of the dynamic membrane.

Description

Technical Field

[0001] The present invention belongs to the field of biological sewage treatment, and in particular relates to a device and method for deep denitrification of sewage. Background Art

[0002] As society progresses and people's living standards improve, the amount of sewage generated also increases. When elements like nitrogen and phosphorus in sewage enter water bodies, they can cause water pollution problems like eutrophication. Therefore, sewage treatment is crucial, and the sewage treatment and discharge standards currently formulated by the state are becoming increasingly stringent.

[0003] Because domestic sewage has a low carbon-to-nitrogen ratio, the organic matter in the raw water is insufficient for denitrification. Therefore, the traditional biological wastewater treatment processes used by sewage treatment plants require a large amount of carbon source and energy to remove pollutants from the wastewater. This significantly increases treatment costs for sewage treatment plants and also produces a large amount of excess sludge, further increasing the burden on wastewater treatment plants to dispose of the excess sludge.

[0004] Therefore, it is of great significance to the field of sewage treatment to research and develop a sewage treatment method that can achieve deep denitrification without the need for an external carbon source and reduce the production of residual sludge. Summary of the Invention

[0005] This invention is based on the inventors' discovery and understanding of the following facts and problems: Currently, most solutions to address the low C / N ratio in domestic sewage involve adding carbon sources or employing complex process combinations, which undoubtedly increase sewage treatment costs. Therefore, it is necessary to develop treatment methods and process devices with simple process combinations to reduce the cost of treating low C / N ratio sewage.

[0006] The present invention aims to address, at least to a certain extent, one of the technical problems in the related art. To this end, embodiments of the present invention provide a device for deep denitrification of wastewater. This device, which does not require an external carbon source, can address the problem of insufficient carbon sources in wastewater, achieving deep denitrification while saving energy and fully utilizing the carbon source in the raw water. Furthermore, by cultivating granular sludge in a UASB reactor equipped with a dynamic membrane, the dynamic membrane can effectively retain the granular sludge. Furthermore, by taking advantage of the granular sludge's ease of sedimentation, the degree and frequency of membrane fouling can be reduced, the number of membrane cleanings can be reduced, and the service life of the dynamic membrane can be extended.

[0007] A device for enhancing deep denitrification of sewage by combining a granular sludge-dynamic membrane bioreactor with a short-cut nitrification according to an embodiment of the present invention comprises a UASB reactor and an SBR aerobic reactor connected in series.

[0008] The UASB reactor is provided with a first water inlet and a second water inlet, wherein the first water inlet is provided at the bottom of the UASB reactor, and the second water inlet is provided on the side wall of the sludge bed region of the UASB reactor; a dynamic membrane is provided between the overflow port and the water outlet of the UASB reactor;

[0009] The water outlet of the SBR aerobic reactor is connected to the second water inlet of the UASB reactor through a water outlet bucket.

[0010] The advantages and technical effects brought by the device for deep denitrification of sewage of the embodiment of the present invention are as follows: 1. In the embodiment of the present invention, a dynamic membrane is provided in the UASB reactor, and the granular sludge and dynamic membrane formed in the UASB reactor can effectively retain anaerobic ammonia oxidizing bacteria. At the same time, due to the formation of granular sludge, anaerobic ammonia oxidizing bacteria grow inside the granular sludge, which can protect the anaerobic ammonia oxidizing bacteria from the impact and influence of organic matter in the influent; 2. In the embodiment of the present invention, a UASB reactor and an SBR aerobic reactor are connected in series, and a second water inlet is provided on the UASB reactor, and part of the effluent of the SBR aerobic reactor is introduced into the sludge bed area of ​​the UASB reactor, dividing the UASB reactor into an anaerobic zone and an anoxic zone. The sewage entering through the first water inlet at the bottom of the UASB reactor undergoes an anaerobic reaction in the anaerobic zone below the second water inlet. The anaerobic digestion bacteria remove organic matter in the sewage in the anaerobic zone and store it in the body as an internal carbon source for subsequent denitrification reaction in the anoxic zone. The sewage enters the anoxic zone above the second water inlet upward, and the NH4 + -N and NO2 produced by the SBR aerobic reactor with reflux from the second water inlet --N reacts under the action of anaerobic ammonia-oxidizing bacteria, further removing nitrogen from the sewage; 3. In the embodiment of the present invention, in the UASB reactor, the granular sludge is combined with the dynamic membrane, which can effectively cope with the impact load of the influent pollutants. Since the granular sludge itself is easy to settle, the possibility and frequency of dynamic membrane pollution can be reduced, and the number of membrane cleanings can also be reduced, which is beneficial to the stable operation of the device; 4. In the embodiment of the present invention, by setting a second water inlet on the UASB reactor, the UASB reactor is divided into an anaerobic zone and an anoxic zone, so that the UASB reactor has the dual functions of removing organic matter and denitrification, which is different from the three-stage AOA or two-stage OA process, it can fully and effectively utilize the carbon source in the raw water, achieve deep denitrification, and reduce the reaction volume and floor space; 5. In the embodiment of the present invention, the traditional UASB reactor is improved by setting a dynamic membrane, and the dynamic membrane is used to intercept sludge, which can reduce the volume of the sludge settling zone, thereby reducing the volume of the reactor and saving operating costs; 6. In the embodiment of the present invention, only one UASB reactor and one SBR aerobic reactor are required to be set in series, which can effectively treat domestic sewage with a low C / N ratio without the need to add additional carbon source. The device is simple, low cost, and easy to industrialize.

[0011] In some embodiments, the distance between the second water inlet and the bottom of the UASB reactor is H1, the sludge bed height of the UASB reactor is H, and H1 and H satisfy: H1 = 1 / 2H to 2 / 3H.

[0012] In some embodiments, the UASB reactor uses constant pressure gravity to discharge water, and the head difference is set to 5 to 8 cm; and / or the supporting material of the dynamic membrane includes non-woven fabric.

[0013] The present invention also provides a method for deep denitrification of wastewater, comprising the following steps:

[0014] (1) Start short-cut nitrification in the SBR aerobic reactor;

[0015] (2) inoculating anaerobic digestion sludge and anaerobic ammonium oxidation granular sludge into a UASB reactor, and starting the UASB reactor, wherein a dynamic membrane is set between the overflow port and the outlet of the UASB reactor;

[0016] (3) After the successful start-up of steps (1) and (2), the sewage is fed into the first water inlet at the bottom of the UASB reactor, and part of the effluent from the SBR aerobic reactor is fed into the sludge bed area of ​​the UASB reactor through the second water inlet on the side wall of the UASB reactor. After the reaction, the effluent from the UASB reactor is fed into the SBR aerobic reactor for treatment, and part of the effluent treated by the SBR aerobic reactor is discharged as the final effluent.

[0017] The advantages and technical effects brought by the method for deep denitrification of sewage in the embodiment of the present invention are as follows: 1. In the embodiment of the present invention, sewage first enters the UASB reactor. In the anaerobic zone at the bottom of the reactor, the organic matter in the sewage is stored in the body by anaerobic bacteria in the form of internal carbon source. Then the muddy water leaves the anaerobic zone and contacts the effluent from the SBR aerobic reactor and enters the anoxic zone. The anoxic zone is the reaction zone of anaerobic ammonia oxidizing bacteria and endogenous denitrifying bacteria. The anaerobic ammonia oxidizing bacteria uses the NO2 produced by the SBR aerobic reactor to - -N is the same as NH4 in the raw sewage water + -N reacts to produce N2 and some NO3 - -N, while endogenous denitrifying bacteria can remove NO3 produced by anaerobic ammonium oxidizing bacteria in the presence of organic matter stored in anaerobic bacteria in sludge. - -N, NO3 - -N is reduced to N2. After that, the muddy water is separated by a dynamic membrane, the activated sludge is intercepted, and the effluent of the UASB reactor enters the SBR aerobic reactor, so that the remaining ammonia nitrogen in the sewage undergoes a short-range nitrification reaction, further denitrifying the sewage and simultaneously producing the NO2 required by the UASB reactor. - -N, achieving continuous and stable operation of the system. 2. The method of the embodiment of the present invention does not require an external carbon source, can solve the problem of insufficient carbon source for domestic sewage, achieve deep denitrification while saving energy and making full use of the carbon source in the raw water, and at the same time cultivates granular sludge in the UASB reactor, uses the dynamic membrane to intercept the granular sludge, and takes advantage of the easy precipitation of the granular sludge, thereby reducing the degree and frequency of membrane fouling of the dynamic membrane set in the UASB reactor, reducing the membrane cleaning coefficient, and extending the service life of the dynamic membrane. In addition, the process combination of the embodiment of the present invention is simple, low-cost, and easy to industrialize.

[0018] In some embodiments, in step (1), during the process of starting the short-cut nitrification, the concentration of the inoculated sludge is 3500-4500 mg / L; and / or, the sludge age is 12-18 days, the hydraulic retention time is 5-8 hours, and / or, hypoxic aeration is used, and the hypoxic aeration is to control the dissolved oxygen concentration to below 0.8 mg / L;

[0019] And / or, NH4 + When the -N concentration is lower than 5 mg / L and the nitrite accumulation rate reaches more than 80%, it is considered that the short-term nitrification is successfully started.

[0020] In some embodiments, in step (2), during the start-up of the UASB reactor, the concentration of the mixed sludge of anaerobic digestion sludge and anaerobic ammonium oxidation granular sludge in the reactor is 5000-7000 mg / L, preferably, the mass percentage of the anaerobic ammonium oxidation granular sludge in the mixed sludge is 5-15%; and / or, the temperature in the UASB reactor is 30-35°C, and the hydraulic retention time is 20-24h.

[0021] In some embodiments, in step (2), during the start-up of the UASB reactor, NH4 + -N and NO2 - -N molar ratio is 1: (1 to 1.32), and the internal reflux ratio is adjusted to 0 to 200%;

[0022] And / or, when red granular sludge appears in the UASB reactor and the simultaneous removal rate of ammonia nitrogen and nitrite reaches more than 80%, the UASB reactor is considered to be successfully started.

[0023] In some embodiments, in step (3), the distance between the second water inlet of the UASB reactor and the bottom of the UASB reactor is H1, the sludge bed height of the UASB reactor is H, and H1 and H satisfy: H1 = 1 / 2H ~ 2 / 3H.

[0024] In some embodiments, in step (3), the ratio of the water flow rate of the second water inlet of the UASB reactor to the water flow rate of the first water inlet is 50-100%; and or, hypoxic aeration is used in the SBR aerobic reactor, and the hypoxic aeration is to control the dissolved oxygen concentration to below 0.8 mg / L.

[0025] In some embodiments, in step (3), the sewage is urban sewage with a C / N ratio of 1.1 to 4.5. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of a device for deep denitrification of sewage according to an embodiment of the present invention;

[0027] Figure numerals: 1-water inlet bucket, 2-first water inlet pump, 3-UASB reactor, 31-first water inlet, 32-second water inlet, 33-dynamic membrane, 34-sludge bed, 35-water outlet, 36-overflow port, 4-reflux pump, 5-intermediate water tank, 6-water outlet bucket, 7-second water inlet pump, 8-SBR reactor, 9-agitator, 10-rotor flowmeter, 11-aeration pump. DETAILED DESCRIPTION

[0028] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0029] like Figure 1 As shown, an apparatus for deep denitrification of sewage according to an embodiment of the present invention comprises: a UASB reactor 3 and an SBR aerobic reactor 8 connected in series; the UASB reactor 3 is provided with a first water inlet 31 and a second water inlet 32, the first water inlet 31 is provided at the bottom of the UASB reactor 3, and the second water inlet 32 ​​is provided on the side wall of the sludge bed 34 area of ​​the UASB reactor 3; a dynamic membrane 33 is provided between the water outlet 35 and the overflow port 36 of the UASB reactor 3, and the water outlet of the SBR aerobic reactor 8 is connected to the second water inlet 31 of the UASB reactor 3 through a water outlet bucket 6.

[0030] In the device for deep denitrification of sewage according to the embodiment of the present invention, a dynamic membrane is provided in the UASB reactor. The granular sludge and the dynamic membrane formed in the UASB reactor can effectively retain anaerobic ammonia-oxidizing bacteria. At the same time, due to the formation of granular sludge, anaerobic ammonia-oxidizing bacteria grow inside the granular sludge, which can protect the anaerobic ammonia-oxidizing bacteria from the impact and influence of organic matter in the influent. In the embodiment of the present invention, a UASB reactor and an SBR aerobic reactor are connected in series, and a second water inlet is provided on the UASB reactor. Part of the effluent from the SBR aerobic reactor is introduced into the sludge bed area of ​​the UASB reactor, and the UASB reactor is divided into an anaerobic zone and an anoxic zone. The sewage entering through the first water inlet at the bottom of the UASB reactor undergoes an anaerobic reaction in the anaerobic zone below the second water inlet. The anaerobic digestion bacteria remove organic matter in the sewage in the anaerobic zone and store it in the body as an internal carbon source for subsequent denitrification reaction in the anoxic zone. The sewage enters the anoxic zone above the second water inlet upward, and the NH4 + -N and NO2 produced by the SBR aerobic reactor with reflux from the second water inlet --N reacts under the action of anaerobic ammonia-oxidizing bacteria, further removing nitrogen from the sewage; in the embodiment of the present invention, in the UASB reactor, the granular sludge is combined with the dynamic membrane, which can effectively cope with the impact load of the influent pollutants. Since the granular sludge itself is easy to settle, the possibility and frequency of dynamic membrane pollution can be reduced, and the number of membrane cleanings can also be reduced, which is beneficial to the stable operation of the device; in the embodiment of the present invention, by setting a second water inlet on the UASB reactor, the UASB reactor is divided into an anaerobic zone and an anoxic zone, so that the UASB reactor has the dual functions of removing organic matter and denitrification, which is different from the three-stage AOA Compared with the two-stage OA process, it can fully and effectively utilize the carbon source in the raw water, achieve deep denitrification, and reduce the reaction volume and floor space. In the embodiment of the present invention, the traditional UASB reactor is improved by setting a dynamic membrane. The dynamic membrane is used to intercept sludge, which can reduce the volume of the sludge settling zone, thereby reducing the volume of the reactor and saving operating costs. In the embodiment of the present invention, only one UASB reactor and one SBR aerobic reactor are required to be set in series, which can effectively treat domestic sewage with a low C / N ratio without the need for additional carbon source. The device is simple, low cost, and easy to industrialize.

[0031] like Figure 1 As shown, when the device of the embodiment of the present invention is specifically used: sewage enters the UASB reactor 3 from the water inlet bucket 1 through the first water inlet pump 2 and the first water inlet 31 at the bottom of the UASB reactor 3. First, in the anaerobic zone, anaerobic digestion bacteria can remove organic matter in the raw water and store the organic matter in the body as an internal carbon source. Then, the muddy water enters the anoxic zone, where anaerobic ammonia oxidizing bacteria and endogenous denitrifying bacteria react. The anaerobic ammonia oxidizing bacteria use the NO2 produced by the SBR aerobic reactor 8 sent through the second water inlet 32 ​​of the UASB reactor 3 to produce - -N, remove NH4 from sewage + -N, the reaction produces NO3 - -N and N2, while endogenous denitrifying bacteria can carry out denitrification reaction in the presence of organic matter stored in anaerobic digestion bacteria, removing NO3 produced by anaerobic ammonium oxidizing bacteria - -N, NO3 - -N is reduced to N2; then the muddy water is further separated by the dynamic membrane 33, and the effluent of the UASB reactor 3 enters the SBR reactor 8 through the intermediate water tank 5 and the second water inlet pump 7. In the SBR aerobic reactor 8, low-oxygen aeration is performed by the aeration pump 11, and under the action of nitrifying bacteria, NH4 + -N is oxidized to NO2 - -N, the effluent from the SBR aerobic reactor 8 flows into the effluent bucket 6, a portion of the effluent enters the anoxic zone of the UASB reactor 3 from the second water inlet 32 ​​on the side of the UASB reactor 3 for denitrification, and the other portion of the effluent is discharged from the system as the final effluent.

[0032] In some embodiments, preferably, the distance between the second water inlet 32 ​​and the bottom of the UASB reactor 3 is H1, the height of the sludge bed 34 of the UASB reactor 3 is H, and H1 and H satisfy: H1 = 1 / 2H to 2 / 3H.

[0033] In the embodiment of the present invention, the position of the second water inlet is preferably selected, which can not only effectively remove organic matter in the anaerobic zone below the second water inlet, but also facilitate the full play of anaerobic ammonia-oxidizing bacteria and endogenous denitrifying bacteria in the anoxic zone above the second water inlet to achieve deep denitrification.

[0034] In some embodiments, preferably, the UASB reactor 3 uses constant pressure gravity flow to discharge water, with a head difference of 5 to 8 cm; and / or the support material of the dynamic membrane comprises a non-woven fabric. Further preferably, when the turbidity of the effluent from the UASB reactor 3 is less than 2 NTU, it indicates that the dynamic membrane has been formed.

[0035] In the embodiment of the present invention, the UASB reactor 3 uses constant pressure gravity self-flowing water, which is easier to clean and replace than traditional membranes, has lower costs, and is easy to promote and apply on a large scale.

[0036] In some embodiments, the device preferably further comprises a rotor flowmeter 10, which is connected to an aeration pump 11. Further preferably, the SBR aerobic reactor 8 is further provided with an agitator 9; and the SBR aerobic reactor 8 and the UASB reactor 3 are further provided with a WTW probe.

[0037] In an embodiment of the present invention, a rotor flowmeter 10 is installed in the device to control the intensity of aeration so as to achieve low-oxygen aeration. The installed agitator 9 is used to mix mud and water to make the water treatment more uniform. The installed WTW probe can detect the pH value and dissolved oxygen concentration so as to monitor the sewage treatment status in real time, make timely adjustments to the equipment, and ensure the water quality of the effluent.

[0038] The present invention also provides a method for deep denitrification of wastewater, comprising the following steps:

[0039] (1) Start short-cut nitrification in the SBR aerobic reactor;

[0040] (2) inoculating anaerobic digestion sludge and anaerobic ammonium oxidation granular sludge into a UASB reactor, and starting the UASB reactor, wherein a dynamic membrane is set between the overflow port and the outlet of the UASB reactor;

[0041] (3) After the successful start-up of steps (1) and (2), the sewage is fed into the first water inlet at the bottom of the UASB reactor, and part of the effluent from the SBR aerobic reactor is fed into the sludge bed area of ​​the UASB reactor through the second water inlet on the side wall of the UASB reactor. After the reaction, the effluent from the UASB reactor is fed into the SBR aerobic reactor for treatment, and part of the effluent treated by the SBR aerobic reactor is discharged as the final effluent.

[0042] It should be noted that, in the method of the embodiment of the present invention, there is no restriction on the starting order of step (1) and step (2), and either the SBR aerobic reactor of step (1) or the UASB reactor of step (2) can be started first.

[0043] In the method for deep denitrification of sewage in the embodiment of the present invention, the sewage first enters the UASB reactor. In the anaerobic zone at the bottom of the reactor, the organic matter in the sewage is stored in the body by anaerobic bacteria in the form of internal carbon source. Then the muddy water leaves the anaerobic zone and contacts the effluent from the SBR aerobic reactor and enters the anoxic zone. The anoxic zone is the reaction zone of anaerobic ammonia oxidizing bacteria and endogenous denitrifying bacteria. The anaerobic ammonia oxidizing bacteria uses the NO2 produced by the SBR aerobic reactor to produce nitrogen dioxide. - -N is the same as NH4 in the raw sewage water + -N reacts to produce N2 and some NO3 - -N, while endogenous denitrifying bacteria can remove NO3 produced by anaerobic ammonium oxidizing bacteria in the presence of organic matter stored in anaerobic bacteria in sludge. - -N, NO3 - -N is reduced to N2. After that, the muddy water is separated by a dynamic membrane, the activated sludge is intercepted, and the effluent of the UASB reactor enters the SBR aerobic reactor, so that the remaining ammonia nitrogen in the sewage undergoes a short-range nitrification reaction, further denitrifying the sewage and simultaneously producing the NO2 required by the UASB reactor. - -N, achieving continuous and stable operation of the system; the method of the embodiment of the present invention does not require an external carbon source, can solve the problem of insufficient carbon source for domestic sewage, achieve deep denitrification while saving energy and making full use of the carbon source in the raw water, and at the same time cultivates granular sludge in the UASB reactor, uses the dynamic membrane to intercept the granular sludge, and takes advantage of the easy precipitation of the granular sludge, thereby reducing the degree and frequency of membrane fouling of the dynamic membrane set in the UASB reactor, reducing the membrane cleaning coefficient, and extending the service life of the dynamic membrane. In addition, the process combination of the embodiment of the present invention is simple, low-cost, and easy to industrialize.

[0044] In some embodiments, preferably, in the step (1), during the process of starting the short-cut nitrification, the concentration of the inoculated sludge is 3500-4500 mg / L; and / or, the sludge age is 12-18 days, and the hydraulic retention time is 5-8 hours. Further preferably, in the step (1), during the process of starting the short-cut nitrification, low oxygen aeration is used, and the concentration of dissolved oxygen is controlled below 0.8 mg / L during the low oxygen aeration process. NH4 + When the -N concentration is lower than 5mg / L and the nitrite accumulation rate reaches more than 80%, it is considered that the short-term nitrification is successfully started. The nitrite accumulation rate refers to the NO2 - -N and NO x - -N ratio.

[0045] In the embodiment of the present invention, by controlling various parameters, the NH4 + -N concentration was lower than 5 mg / L, and the nitrite accumulation rate reached more than 80%, which successfully started the short-range nitrification stage.

[0046] In some embodiments, preferably, in step (2), during the process of starting the UASB reactor, the concentration of the mixed sludge of anaerobic digestion sludge and anaerobic ammonium oxidation granular sludge in the reactor is 5000-7000 mg / L, preferably, the mass percentage of the anaerobic ammonium oxidation granular sludge in the mixed sludge is 5-15%; the temperature in the UASB reactor is 30-35°C, and the hydraulic retention time is 20-24h. Further preferably, the NH4 + -N and NO2 - The molar ratio of -N is 1:(1 to 1.32), and the internal reflux ratio is adjusted to 0 to 200%. In step (2) of the embodiment of the present invention, the effluent from the upper end of the UASB reactor is refluxed to the bottom to promote the flow of activated sludge. The internal reflux ratio refers to the ratio of the water flow rate of the effluent return from the UASB reactor to the water flow rate of the inlet water to the UASB reactor. The UASB reactor is considered to be successfully started when red granular sludge appears in the UASB reactor and the simultaneous removal rate of ammonia nitrogen and nitrite reaches more than 80%.

[0047] In some embodiments, in step (3), the distance between the second water inlet of the UASB reactor and the bottom of the UASB reactor is H1, the sludge bed height of the UASB reactor is H, and H1 and H satisfy: H1 = 1 / 2H to 2 / 3H. In the embodiments of the present invention, the preferred position of the second water inlet is not only conducive to the effective removal of organic matter in the anaerobic zone below the second water inlet, but also conducive to the full play of anaerobic ammonia-oxidizing bacteria and endogenous denitrifying bacteria in the anoxic zone above the second water inlet, thereby achieving deep denitrification.

[0048] In some embodiments, in step (3), the NO2 in the effluent of the SBR aerobic reactor fed back into the anoxic zone of the UASB reactor is - -N concentration, and adjusting the water flow rate of the second water inlet of the UASB reactor to the water flow rate of the first water inlet to be 50-100%. The water flow rate in the present invention refers to the volume flow rate.

[0049] In the embodiment of the present invention, controlling the water flow rate ratio of the second water inlet and the first water inlet of the UASB reactor is beneficial to providing sufficient NO2 for the anoxic zone of the UASB reactor. - -N, to effectively remove ammonia nitrogen from sewage raw water.

[0050] In some embodiments, a low oxygen aeration strategy is adopted in the SBR aerobic reactor, and the low oxygen aeration is to control the concentration of dissolved oxygen to below 0.8 mg / L.

[0051] In the embodiment of the present invention, the method of the present invention can be realized by using low-oxygen aeration to perform short-cut nitrification in the SBR aerobic reactor, which effectively saves the aeration volume and reduces the cost of sewage treatment.

[0052] In some embodiments, in step (3), the sewage is urban sewage with a C / N ratio of 1.1 to 4.5.

[0053] The method of the embodiment of the present invention does not require an external carbon source and can be used to treat sewage with a low C / N ratio, effectively solving the problem of insufficient carbon source in sewage.

[0054] In the embodiment of the present invention, when the equipment is in stable operation, the treated effluent can be controlled to have COD ≤ 50 mg / L and NH4 + -N≤5mg / L, TN≤15mg / L, the effluent quality can meet the discharge requirements and avoid damage to the environment.

[0055] The technical solution of the present invention is described in detail below with reference to specific embodiments and drawings.

[0056] The effective volume of the UASB reactor 3 used in the following examples is 5.6 L, and the effective volume of the SBR aerobic reactor 8 is 6 L. Both the UASB reactor 3 and the SBR aerobic reactor 8 are made of organic glass.

[0057] Example 1

[0058] use Figure 1The sewage deep denitrification device shown is used for sewage treatment, wherein the distance H1 from the second water inlet of the UASB reactor 3 to the bottom of the reactor is 1 / 2H, wherein H is the height of the sludge bed 34 of the UASB reactor 3 .

[0059] (1) Start short-cut nitrification: inoculate the full-process nitrification sludge of the municipal sewage plant into the SBR reactor 8, and maintain the sludge concentration at 3500 mg / L; adopt the low-oxygen aeration strategy to control the dissolved oxygen concentration at 0.6 mg / L; control the sludge age at 12 days and the hydraulic retention time at 6 hours; when the NH4 + When the -N concentration is lower than 5 mg / L and the nitrite accumulation rate reaches more than 80%, the startup of this stage can be considered successful;

[0060] (2) Start UASB reactor 3: inoculate anaerobic digestion sludge and anaerobic ammonium oxidation granular sludge in UASB reactor 3, the concentration of mixed sludge is controlled at 5000 mg / L, the mass percentage of anaerobic ammonium oxidation granular sludge in the mixed sludge is 10%, the temperature is maintained at 30℃ by a temperature control device, the hydraulic retention time is controlled at 20h, the influent uses artificial water distribution, and the NH4 + -N and NO2 - The molar ratio of nitrogen to nitrite was controlled at 1:1.32 to facilitate the growth of anaerobic ammonium-oxidizing bacteria. At the same time, the influent organic load was continuously increased and the internal reflux ratio was adjusted to 50% to 100% to promote the formation of granular sludge. When red granular sludge was observed in UASB reactor 3 and the simultaneous removal rate of ammonia nitrogen and nitrite reached above 80%, the startup phase was considered successful.

[0061] (3) Operation stage: Prepare domestic sewage for testing: C / N is 2.5-2.83, COD is 200-220 mg / L, NH4 + -N is 70-80 mg / L.

[0062] Domestic sewage enters the UASB reactor 3 from the water inlet barrel 1 through the first water inlet pump 2 from the bottom first water inlet 31 of the UASB reactor 3. The sewage is in the anaerobic zone below the second water inlet 32. The anaerobic digestion bacteria can remove the organic matter in the raw water and store the organic matter in the body as an internal carbon source. Then the muddy water enters the anoxic zone above the second water inlet 32. In the anoxic zone, anaerobic ammonia oxidizing bacteria and endogenous denitrifying bacteria react. The anaerobic ammonia oxidizing bacteria use the NO2 produced by the SBR aerobic reactor 8 sent through the second water inlet 32 ​​to produce - -N, remove NH4 from sewage water + -N, while endogenous denitrifying bacteria can remove NO3 produced by anaerobic ammonium oxidizing bacteria --N; After that, the muddy water is further separated by the dynamic membrane 33, and the effluent of the UASB reactor 3 enters the SBR reactor 8 through the intermediate water tank 5 and the second water inlet pump 7. In the SBR aerobic reactor 8, low-oxygen aeration is performed by the aeration pump 11 to control the dissolved oxygen concentration to 0.6 mg / L. Under the action of nitrifying bacteria, NH4 + -N is oxidized to NO2 - -N, the effluent from the SBR aerobic reactor 8 flows into the effluent bucket 6, a portion of the effluent enters the anoxic zone of the UASB reactor 3 from the second water inlet 32 ​​to undergo anaerobic ammonia oxidation reaction and endogenous denitrification reaction, and the other portion of the effluent is discharged from the system as the final effluent, and the ratio of the water flow rate of the second water inlet 32 ​​to the water flow rate of the first water inlet 31 is controlled to be approximately 70%.

[0063] After the treatment in this embodiment, the system stabilized for 40 days, and the COD in the effluent of reactor 8 was 22-25 mg / L, and NH4 + -N is 0.2-0.8mg / L, NO2 - -N is 4.9-5.6mg / L, NO3 - -N is 0.2-0.5mg / L, TN≤8mg / L.

[0064] Example 2

[0065] The method is the same as that of Example 1, except that the second water inlet 32 ​​of the UASB reactor 3 is located at a different position, H1=2 / 3H.

[0066] After the treatment in this embodiment, the system was stable for 40 days, and the COD of the effluent of reactor 8 was 25-31 mg / L, and NH4 + -N is 0.5-1.2mg / L, NO2 - -N is 5.5-6.5mg / L, NO3 - -N is 0.5-1.5mg / L, TN≤10mg / L.

[0067] Example 3

[0068] The method is the same as that of Example 1, except that the dissolved oxygen concentration in the SBR reactor 8 in steps (1) and (3) is controlled at 0.8 mg / L.

[0069] After the treatment in this embodiment, the system was stable for 40 days, and the COD of the effluent of reactor 8 was 25-29 mg / L, and NH4 + -N is 0.1-0.6mg / L, NO2 - -N is 4.5-5.5mg / L, NO3 - -N is 0.5-1.5mg / L, TN≤10mg / L.

[0070] Example 4

[0071] The method is the same as that of Example 1, except that the C / N ratio of the test water prepared in step (3) is 2.2-2.3, wherein the COD is 100-120 mg / L, and the NH4 + -N is 45-55 mg / L.

[0072] After the treatment in this embodiment, the system stabilized for 40 days, and the COD in the effluent of reactor 8 was 20-25 mg / L, and NH4 + -N is 0.5-1.5mg / L, NO2 - -N is 4.2-5.5mg / L, NO3 - -N is 0.5-1.3mg / L, TN≤9mg / L.

[0073] Comparative Example 1

[0074] The method is the same as that of Example 1, except that the second water inlet is removed from the UASB reactor 3 , that is, the effluent from the SBR aerobic reactor 8 is not introduced into the UASB reactor 3 .

[0075] After the treatment of comparative example 1, the system was stable for 40 days, and the COD of the effluent of reactor 8 was 25-28 mg / L, and NH4 + -N is 0.8-1.1mg / L, NO2 - -N is about 21-23 mg / L, NO3 - -N is 3.5-5mg / L, TN is about 25mg / L or more. The UASB reactor lacks NO2 - -N substrate, cannot carry out anaerobic ammonium oxidation reaction, can only remove organic matter, and cannot carry out denitrification; while the SBR process only sets the aerobic time, can only carry out nitrification reaction, and cannot achieve deep denitrification.

[0076] Comparative Example 2

[0077] The method was identical to that of Example 1, except that the order of installation of the UASB reactor 3 and the SBR aerobic reactor 8 was adjusted. The wastewater first entered the SBR aerobic reactor 8 for short-cut nitrification, then entered the UASB reactor 3 through the first water inlet at the bottom of the UASB reactor 3. The second water inlet of the UASB reactor 3 was omitted. The effluent from the UASB reactor 3 was discharged from the system as the final system effluent.

[0078] After the treatment of comparative example 1, the system was stable for 40 days, and the COD of the effluent of reactor 8 was 25-28 mg / L, and NH4 + -N is 0.6-1.2mg / L, NO2- -N is 20-25mg / L, NO3 - -N is 1.5-3.0mg / L, TN is about 22mg / L or more. The raw water first enters the SBR reactor, aeration removes organic matter, and short-term nitrification produces NO2 - -N, and then the effluent enters the UASB reactor. Due to the low ammonia nitrogen concentration, anaerobic ammonia oxidation reaction cannot be carried out. In addition, due to the lack of organic matter, denitrification cannot be carried out. The UASB loses its function and is neither used to remove organic matter nor to achieve deep denitrification.

[0079] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples without contradiction.

[0080] Although the above embodiments have been shown and described, it is understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. Changes, modifications, substitutions and variations of the above embodiments by those skilled in the art are all within the scope of protection of the present invention.

Claims

1. A method for deep denitrification of sewage, characterized in that: The following steps are involved: (1) Start short-cut nitrification in the SBR aerobic reactor and use low-oxygen aeration. The NH4 + When the -N concentration was lower than 5 mg / L, the nitrite accumulation rate reached more than 80%, and the short-range nitrification was considered to have been successfully started; (2) Anaerobic digestion sludge and anaerobic ammonium oxidation granular sludge are inoculated into the UASB reactor, and the UASB reactor is started. A dynamic membrane is set between the overflow port and the outlet of the UASB reactor. When red granular sludge appears in the UASB reactor and the simultaneous removal rate of ammonia nitrogen and nitrite reaches more than 80%, the UASB reactor is considered to be successfully started; (3) After the steps (1) and (2) are successfully started, the sewage with a low C / N ratio is fed into the first water inlet at the bottom of the UASB reactor, and part of the effluent from the SBR aerobic reactor is fed into the sludge bed area of ​​the UASB reactor through the second water inlet on the side wall of the UASB reactor. After the reaction, the effluent from the UASB reactor is fed into the SBR aerobic reactor for treatment, and part of the effluent treated by the SBR aerobic reactor is discharged as the final effluent system, wherein the distance between the second water inlet of the UASB reactor and the bottom of the UASB reactor is H1, the sludge bed height of the UASB reactor is H, H1 and H satisfy: H1=1 / 2H~2 / 3H, and the ratio of the inlet flow rate of the second water inlet of the UASB reactor to the inlet flow rate of the first water inlet is 50~100%.

2. The method for deep denitrification of sewage according to claim 1, characterized in that: In the step (1), during the process of starting the short-cut nitrification, the concentration of the inoculated sludge is 3500-4500 mg / L; the sludge age is 12-18 days, and the hydraulic retention time is 5-8 hours; the hypoxic aeration is to control the dissolved oxygen concentration to below 0.8 mg / L.

3. The method for deep denitrification of sewage according to claim 1, characterized in that: In the step (2), during the start-up of the UASB reactor, the concentration of the mixed sludge of anaerobic digestion sludge and anaerobic ammonium oxidation granular sludge in the reactor is 5000-7000 mg / L, the temperature in the UASB reactor is 30-35°C, and the hydraulic retention time is 20-24 h.

4. The method for deep denitrification of sewage according to claim 3, characterized in that: In the step (2), the mass percentage of the anaerobic ammonium oxidation granular sludge in the mixed sludge is 5-15%.

5. The method for deep denitrification of sewage according to claim 1 or 3, characterized in that: In the step (2), during the start-up of the UASB reactor, NH4 + -N and NO2 - The molar ratio of -N is 1:(1~1.32), and the internal reflux ratio is adjusted to 0~200%.

6. The method for deep denitrification of sewage according to claim 1, characterized in that: In the step (3), hypoxic aeration is used in the SBR aerobic reactor, and the hypoxic aeration is to control the concentration of dissolved oxygen to below 0.8 mg / L.

7. The method for deep denitrification of sewage according to claim 1, characterized in that: In the step (3), the sewage is urban sewage with a C / N ratio of 1.1-4.5.

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