A device and method for treating municipal sewage based on short-range denitrification coupled with anaerobic ammonia oxidation continuous flow

Abstract

The application provides a device and method for treating municipal sewage based on short-range denitrification coupled with anaerobic ammonia oxidation continuous flow, the device comprises a water inlet unit, a composite biofilm reactor, a hydroxylamine dosing unit, a backwashing unit and an aeration unit, the composite biofilm reactor comprises an anoxic reaction zone and an aerobic reaction zone in sequence; the water inlet unit is connected with the anoxic reaction zone, the outlet of the aerobic reaction zone is connected to the anoxic reaction zone through an external pipeline, the hydroxylamine dosing unit is connected with the anoxic reaction zone, the backwashing unit is connected with the bottom of the anoxic reaction zone, and the aeration unit is connected with the bottom of the aerobic reaction zone. Through the division of the reaction zone of the composite biofilm reactor and the setting of the structure units such as hydroxylamine dosing, backwashing and aeration, the sewage can be continuously treated, the short-range denitrification can be quickly started through the control of the hydroxylamine dosing process, the ammonia nitrogen removal rate is high, the treatment load is high, the sewage treatment cost can be reduced, and the device is suitable for multiple application scenarios.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology and relates to an apparatus and method for treating urban wastewater based on short-cut denitrification coupled with anaerobic ammonia oxidation in a continuous flow. Background Technology

[0002] With economic development and the enrichment of people's production activities, the discharge of urban sewage is constantly increasing. Urban sewage contains a large amount of nitrogenous pollutants, which, if not treated or treated inadequately, will harm the water, soil, and atmospheric environment. At present, sewage treatment plants usually use biological treatment methods for denitrification, such as nitrification and denitrification. First, ammonia nitrogen in sewage is oxidized into nitrate nitrogen in the aerobic zone. The resulting nitrate nitrogen is then denitrified in the anoxic zone using a carbon source as an electron acceptor. This process consumes a large amount of organic carbon source. However, due to the severe imbalance of carbon-nitrogen ratio in urban sewage in my country, a large amount of external carbon source needs to be added for denitrification, leading to increased operating costs. At the same time, the oxidation of more than 95% of ammonia nitrogen in sewage into nitrate nitrogen by oxygen in this process also consumes a large amount of aeration energy.

[0003] Anaerobic ammonia oxidation (AAO) is an autotrophic nitrogen removal process that uses ammonia nitrogen as an electron donor and nitrite nitrogen as an electron acceptor. This process requires no carbon source and saves aeration energy. Nitrite is an important substrate in this process and a crucial factor in achieving AAO, but obtaining nitrite nitrogen is relatively difficult. Currently, nitrite nitrogen in urban wastewater treatment systems is mainly obtained through short-cut nitrification and short-cut denitrification. However, the former's reaction process is unstable, while the latter is more universal and stable. Therefore, a process based on short-cut denitrification coupled with AAO has emerged to address the problems in biological nitrogen removal from urban wastewater.

[0004] Based on the characteristics of existing urban wastewater, it is not conducive to the start-up and long-term stability of short-cut denitrification, and it is generally not suitable for large-scale treatment in wastewater treatment plants. Hydroxylamine, as an intermediate product of nitrification and anaerobic ammonium oxidation, can help achieve stable operation of short-cut denitrification coupled with anaerobic ammonium oxidation by adding hydroxylamine. CN 115490323A discloses an apparatus and method for achieving short-cut denitrification coupled with anaerobic ammonium oxidation based on hydroxylamine addition. The apparatus includes a raw wastewater tank, a carbon capture SBR, an intermediate tank, a sludge storage tank, a short-cut denitrification coupled with anaerobic ammonium oxidation SBR, a sludge fermentation SBR, and a fermentation broth storage tank. The carbon capture SBR, sludge fermentation SBR, and short-cut denitrification coupled with anaerobic ammonium oxidation SBR are set up separately. The fermentation supernatant of the sludge fermentation SBR is introduced into the short-cut denitrification coupled with anaerobic ammonium oxidation SBR in the form of a carbon source, and hydroxylamine is added to carry out the short-cut denitrification and anaerobic ammonium oxidation reaction. This patent is mainly applicable to SBR devices for small-volume water treatment and uses the sludge activation method, which is not applicable to continuous flow devices and biofilm methods; the method of inoculating sludge and introducing fermentation liquid cannot make full use of the original carbon source in urban sewage.

[0005] CN 110510739A discloses a device and method for achieving semi-short-cut coupling of anaerobic ammonia oxidation via a continuous flow AOA biofilm reactor using hydroxylamine. The device includes a raw wastewater tank, a continuous flow AOA biofilm reactor, a hydroxylamine reagent storage tank, and a sedimentation tank. The continuous flow AOA biofilm reactor includes an anaerobic section, an aerobic section, and an anoxic section. This device can be used in continuous flow processes, but the wastewater treatment process involves semi-short-cut nitrification and anaerobic ammonia oxidation, which is a coupling of short-cut nitrification and anaerobic ammonia oxidation. The former's process of generating nitrite nitrogen is unstable and belongs to a different process from short-cut denitrification. Even if the same substance is added, its effect will be different.

[0006] In continuous flow treatment of urban wastewater, the large fluctuations in water volume and the complexity of process operation and control can easily lead to sludge loss. Long-term addition and inoculation are required to maintain the operation of the process. Therefore, when using the short-cut denitrification coupled with anaerobic ammonium oxidation method for continuous treatment of urban wastewater, adjustments need to be made to the structure of the device, the control of hydroxylamine addition, and the improvement of sludge inoculation methods to ensure that the denitrification treatment of urban wastewater can be rapid, efficient, and stable in operation. Summary of the Invention

[0007] To address the problems existing in the prior art, the present invention aims to provide a device and method for continuous flow treatment of urban wastewater based on short-cut denitrification coupled with anaerobic ammonia oxidation. The device, through the division of the reaction zone of the composite biofilm reactor and the setting of structural units such as hydroxylamine dosing, backwashing, and aeration, can effectively achieve continuous treatment of urban wastewater. By controlling the hydroxylamine dosing process, the device enables rapid start-up of short-cut denitrification, making it unaffected by fluctuations in water quantity and quality. It has a high ammonia nitrogen removal rate, a high treatment load, and requires no additional carbon source, effectively reducing equipment and process costs and making it suitable for multiple application scenarios.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] On the one hand, the present invention provides a device for treating urban sewage based on short-cut denitrification coupled with anaerobic ammonia oxidation in a continuous flow. The device includes an influent unit, a composite biofilm reactor, a hydroxylamine dosing unit, a backwashing unit, and an aeration unit. The composite biofilm reactor includes an anoxic reaction zone and an aerobic reaction zone in sequence according to the sewage flow direction. Both the anoxic reaction zone and the aerobic reaction zone are inoculated with packing material that has completed biofilm formation.

[0010] The outlet of the water inlet unit is connected to the inlet of the anoxic reaction zone, the outlet of the aerobic reaction zone is connected to the anoxic reaction zone via an external pipeline, the outlet of the hydroxylamine dosing unit is connected to the inlet of the anoxic reaction zone, the outlet of the backwashing unit is connected to the bottom of the anoxic reaction zone, and the aeration unit is connected to the bottom of the aerobic reaction zone.

[0011] In this invention, to achieve continuous treatment of urban nitrogen-containing wastewater, the device is based on a composite biofilm reactor, which is divided into an anoxic reaction zone and an aerobic reaction zone. Inlet, hydroxylamine dosing, backwashing, and aeration units are connected at different locations within the composite biofilm reactor. In the aerobic reaction zone, ammonia nitrogen is oxidized to nitrate nitrogen. The nitrified liquid from the aerobic reaction zone is then returned to the anoxic reaction zone. Through the precise control of the hydroxylamine dosing unit, short-cut denitrification is rapidly initiated, and then anaerobic ammonia oxidation occurs with the ammonia nitrogen in the wastewater, achieving efficient removal of ammonia nitrogen from the wastewater. The device's structural design eliminates the need to consider fluctuations in influent flow rate and quality, and is unaffected by raw water carbon-nitrogen ratio, pH, COD, etc. It requires no external carbon source and has a high treatment load. The device has a simple structure, low equipment cost, and a wide range of applications.

[0012] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The technical objectives and beneficial effects of the present invention can be better achieved and realized through the following technical solutions.

[0013] As a preferred technical solution of the present invention, the water inlet unit includes a water inlet pool, a water inlet pump and a water inlet flow meter. The water inlet pool outlet pipe passes through the water inlet pump and the water inlet flow meter in sequence, and then connects to the anoxic reaction zone.

[0014] Preferably, the anoxic reaction zone and the aerobic reaction zone are separated by a partition, and the bottom of the partition is provided with a connecting port, and a water inlet valve is provided at the connecting port.

[0015] Preferably, the volume ratio of the hypoxic reaction zone to the aerobic reaction zone is 1:1 to 2:1, such as 1:1, 1.2:1, 1.4:1, 1.5:1, 1.6:1, 1.8:1 or 2:1, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0016] Preferably, the aerobic reaction zone has two outlets, one of which is discharged through an outlet pipe, and the other is connected back to the anoxic reaction zone through an external pipeline.

[0017] Preferably, the external pipeline is equipped with a reflux flow meter and a reflux pump.

[0018] As a preferred embodiment of the present invention, the hydroxylamine dosing unit includes a hydroxylamine storage tank and a hydroxylamine metering pump, wherein the hydroxylamine metering pump is installed on the connecting pipeline between the hydroxylamine storage tank and the anoxic reaction zone.

[0019] Preferably, the backwashing unit includes a backwashing blower and a perforated aeration pipe, the perforated aeration pipe being disposed at the bottom of the anoxic reaction zone, and the outlet of the backwashing blower being connected to the perforated aeration pipe.

[0020] Preferably, the aeration unit includes an aeration blower and an aeration disc, the aeration disc being disposed at the bottom of the aerobic reaction zone, and the outlet of the aeration blower being connected to the aeration disc.

[0021] As a preferred technical solution of the present invention, the device further includes a sludge thickening tank, and a backwash water valve is provided on the side wall of the anoxic reaction zone near the aerobic reaction zone. The anoxic reaction zone is connected to the sludge thickening tank through the backwash water valve, and the upper drain outlet of the sludge thickening tank is connected to the aerobic reaction zone.

[0022] In this invention, the anoxic reaction zone is connected to the sludge thickening tank via a backwashing water valve to achieve the separation of suspended solids and wastewater. The upper drain outlet of the sludge thickening tank is connected to the aerobic reaction zone via a supernatant drain pipe.

[0023] Preferably, the device further includes an intelligent control unit, and the inlet flow meter, the return flow meter and the hydroxylamine metering pump are all connected to the intelligent control unit.

[0024] On the other hand, the present invention provides a method for short-cut denitrification coupled with anaerobic ammonia oxidation continuous flow treatment of municipal wastewater using the above-mentioned apparatus, the method comprising the following steps:

[0025] (1) After inoculating the composite biofilm reactor with activated sludge and packing material, biofilm formation is carried out, and the device is started with continuous water inflow after completion.

[0026] (2) After the device is started normally, it is operated according to the nitrification-denitrification process. During this process, the oxygen-deficient reaction zone is backwashed regularly, and then hydroxylamine solution is added. The addition flow rate of hydroxylamine solution is controlled until the nitrite accumulation rate reaches more than 50%, and the short-cut denitrification is successfully started.

[0027] (3) Reduce the flow rate of hydroxylamine solution until the nitrite accumulation rate stabilizes at 30-40%, then stop adding hydroxylamine and enter the anaerobic ammonia oxidizing bacteria enrichment stage for stable operation;

[0028] (4) During the stable operation of the anaerobic ammonia oxidizing bacteria enrichment stage, the frequency of backwashing is reduced. If the nitrite accumulation rate is less than 30%, return to step (3) and add hydroxylamine solution again until the nitrite accumulation rate is restored.

[0029] As a preferred technical solution of the present invention, the activated sludge in step (1) includes nitrification-denitrification activated sludge, and the packing includes plastic packing.

[0030] Preferably, the initial influent volume of the composite biofilm reactor is 50-70%, such as 50%, 55%, 60%, 65%, or 70%, but not limited to the listed values; other unlisted values ​​within this range are also applicable. The reflux pump is turned on, and the reflux ratio is controlled to be 100-300%, such as 100%, 150%, 200%, 250%, or 300%, but not limited to the listed values; other unlisted values ​​within this range are also applicable. The reflux ratio refers to the ratio of the reflux liquid to the influent volume.

[0031] Preferably, the concentration of activated sludge after the initial influent is 2500–3500 mg / L, such as 2500 mg / L, 2600 mg / L, 2800 mg / L, 3000 mg / L, 3200 mg / L, 3400 mg / L, or 3500 mg / L, but is not limited to the listed values; other unlisted values ​​within this range are also applicable. For example, the filling ratio of the packing material is 60–70%, such as 60%, 62%, 64%, 66%, 68%, or 70%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0032] Preferably, the biofilm formation in step (1) includes a two-stage aeration process. First, after the initial water intake, the biofilm is aerated for 3 to 5 days, for example, 3 days, 3.5 days, 4 days, 4.5 days, or 5 days. Then, after the water is added again to 100% of the volume, the biofilm is aerated for another 3 to 5 days, for example, 3 days, 3.5 days, 4 days, 4.5 days, or 5 days, to complete the biofilm formation.

[0033] Preferably, after the biofilm has been attached, all the activated sludge is discharged.

[0034] In this invention, nitrification-denitrification activated sludge used in urban wastewater treatment plants is inoculated into the anoxic and aerobic reaction zones of the composite biofilm reactor, while blank plastic packing is simultaneously inoculated. After the influent pump is turned on, the suspended sludge concentration and packing ratio are controlled, where the activated sludge concentration and packing ratio are relative to the reactor volume. The biofilm formation of the traditional nitrification-denitrification biofilm is achieved through a semi-aeration operation. Backflow is maintained during the semi-aeration process to prevent activated sludge from accumulating in any one reactor, ensuring uniform distribution of activated sludge throughout the system. This facilitates simultaneous biofilm formation on the packing surfaces in both the anoxic and aerobic reaction zones. Subsequently, all activated sludge is discharged, constructing the composite biofilm reactor as a fully biofilm system. The biofilm forms and grows on the surface of the packing and is related to the material, surface roughness, and specific surface area of ​​the packing.

[0035] As a preferred technical solution of the present invention, the device in step (2) is started by first starting the water inlet unit, the composite biofilm reactor and the aeration unit, and then the backwashing unit is started periodically after it starts running.

[0036] Preferably, after the composite biofilm reactor is started, the reflux pump is started to control the reflux ratio to 100-300%, such as 100%, 150%, 200%, 250% or 300%, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0037] Preferably, during the operation of the nitrification-denitrification process in step (2), the hydraulic retention time of the anoxic reaction zone and the aerobic reaction zone is independently 2 to 3 hours, such as 2 hours, 2.25 hours, 2.5 hours, 2.75 hours or 3 hours, but not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0038] In this invention, the anoxic reaction zone is a fixed bed during normal operation. The biofilm filling ratio of 60-70% can not only achieve denitrification, but also intercept the suspended solids (SS) in the influent. The effluent with SS below 50 mg / L flowing out of this zone enters the aerobic reaction zone.

[0039] Preferably, the backwashing cycle in step (2) is 2 to 4 days, such as 2 days, 2.5 days, 3 days, 3.5 days or 4 days, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable. The backwashing time is 15 to 30 minutes, such as 15 minutes, 18 minutes, 20 minutes, 22 minutes, 25 minutes, 27 minutes or 30 minutes, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0040] Preferably, during backwashing in step (2), water is kept in, the inlet valve between the anoxic reaction zone and the aerobic reaction zone is closed, and the backwash water valve is opened.

[0041] In this invention, to prevent packing material from caking and sludge from clogging, the backwash blower and agitator are periodically turned on to backwash the anoxic reaction zone. During this process, water continues to flow in while the inlet valve is closed and the backwash overflow valve is opened to discharge the backwash wastewater into the sludge thickening tank to separate suspended solids and wastewater. The supernatant from the sludge thickening tank enters the aerobic reaction zone through the supernatant drain pipe. After backwashing, the backwash blower and backwash overflow valve are turned off while the inlet valve is opened, and the anoxic reaction zone continues to operate normally as a fixed bed.

[0042] Preferably, the nitrification-denitrification process in step (2) runs for 15 to 20 days, such as 15, 16, 17, 18, 19 or 20 days, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0043] In this invention, the purpose of the nitrification-denitrification process step is to stabilize the system operation and allow the biofilm to regenerate. Hydroxylamine is then added on the basis of stability.

[0044] As a preferred technical solution of the present invention, the hydroxylamine solution in step (2) is stored in a hydroxylamine storage tank, and the hydroxylamine storage tank is protected from light.

[0045] In this invention, the hydroxylamine storage tank is protected from light, and a hydroxylamine stock solution sufficient for 2 to 3 days is prepared in the tank to prevent the decomposition of hydroxylamine. The concentration of the hydroxylamine solution is denoted as C, and its specific concentration is generally not required, as long as it does not exceed the solubility of hydroxylamine.

[0046] Preferably, the concentration of hydroxylamine after mixing the influent, reflux nitrifying liquid, and hydroxylamine solution is controlled to be 3-5 mg / L, such as 3 mg / L, 3.5 mg / L, 4 mg / L, 4.5 mg / L, or 5 mg / L, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable. Then, the addition flow rate of the hydroxylamine solution is calculated by reading the influent flow rate and the reflux nitrifying liquid flow rate.

[0047] In this invention, the inlet flow meter, return flow meter, and hydroxylamine metering pump are connected to an intelligent control unit to read and calculate flow data. The flow values ​​of the inlet flow meter and return flow meter are recorded as Q1 and Q2, respectively, and the flow rate of the hydroxylamine metering pump is adjusted to q. Initially, through calculation, the hydroxylamine concentration C' is maintained after mixing the hydroxylamine solution, inlet water, and return nitrification liquid, thereby determining the flow rate q of the hydroxylamine metering pump. The calculation formula is q = C' * (q + Q1 + Q2) / C. When hydroxylamine is added, the intelligent control unit reads the values ​​of the inlet flow meter and return flow meter every 2 hours and adjusts the flow rate q of the hydroxylamine metering pump accordingly.

[0048] Preferably, the interval between additions of the hydroxylamine solution in step (2) is 24 to 48 hours, such as 24 hours, 28 hours, 32 hours, 36 hours, 40 hours, 44 hours, or 48 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable. The time for each addition is 20 to 28 hours, such as 20 hours, 22 hours, 23 hours, 24 hours, 25 hours, 26 hours, or 28 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0049] Preferably, the nitrite accumulation rate in step (2) reaches 50% or more, such as 50%, 55%, 60%, 65%, 70%, 75%, or 80%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable. The required time is 6 to 8 days, such as 6 days, 6.5 days, 7 days, 7.5 days, or 8 days, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0050] In this invention, there is no need to consider the control of the carbon-nitrogen ratio of the influent. This operating mode can achieve a nitrite accumulation rate (NAR) of more than 50% in the anoxic reaction zone in 6 to 8 days, thereby achieving partial short-cut denitrification in the anoxic reaction zone.

[0051] As a preferred technical solution of the present invention, in step (3), the concentration of hydroxylamine after mixing the influent, reflux nitrification liquid and hydroxylamine solution is reduced to 2-4 mg / L, such as 2 mg / L, 2.5 mg / L, 3 mg / L, 3.5 mg / L or 4 mg / L, but not limited to the listed values. Other unlisted values ​​within this range are also applicable, and the addition flow rate of hydroxylamine solution is then calculated accordingly.

[0052] Preferably, the interval between additions of the hydroxylamine solution in step (3) is 24 to 48 hours, such as 24 hours, 28 hours, 32 hours, 36 hours, 40 hours, 44 hours, or 48 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable. The time for each addition is 20 to 28 hours, such as 20 hours, 22 hours, 23 hours, 24 hours, 25 hours, 26 hours, or 28 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0053] Preferably, the nitrite accumulation rate in step (3) is stable at 30-40%, such as 30%, 32%, 34%, 35%, 36%, 38%, or 40%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable. The required time is 2-3 days, such as 2 days, 2.25 days, 2.5 days, 2.75 days, or 3 days, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0054] In this invention, to prevent the hydroxylamine concentration in the anoxic reaction zone from excessively inhibiting the short-cut denitrification and nitrification reactions in the aerobic reaction zone, while maintaining the accumulation of nitrite in the short-cut denitrification, and to allow hydroxylamine to induce the in-situ enrichment of anaerobic ammonia-oxidizing bacteria in the anoxic reaction zone, the hydroxylamine concentration after mixing the hydroxylamine solution, influent, and return nitrification liquid is reduced to C". Similarly, the flow rate q of the hydroxylamine metering pump is determined.

[0055] As a preferred technical solution of the present invention, in the anaerobic ammonia oxidizing bacteria enrichment stage of step (4), anaerobic ammonia oxidizing bacteria are enriched and grown on the biofilm.

[0056] Preferably, the backwashing frequency in step (4) is once every 6 to 8 days, such as 6 days, 6.5 days, 7 days, 7.5 days or 8 days, but not limited to the listed values. Other unlisted values ​​within this range are also applicable. The backwashing time is 15 to 30 minutes, such as 15 minutes, 18 minutes, 20 minutes, 22 minutes, 25 minutes, 28 minutes or 30 minutes, but not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0057] Preferably, the stable operation time of the anaerobic ammonia oxidizing bacteria enrichment stage in step (4) is 40 to 80 days, such as 40 days, 45 days, 50 days, 55 days, 60 days, 65 days, 70 days, 75 days or 80 days, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0058] Preferably, the abundance of anaerobic ammonia-oxidizing bacteria after enrichment on the biofilm in step (4) reaches 2 × 10⁻⁶. 8 ~3×109 For example, 2×10 8 5×10 8 8×10 8 10 9 1.5×10 9 2×10 9 2.5×10 9 Or 3×10 9 The range of values ​​is not limited to the listed values; other unlisted values ​​within this range also apply. The relative abundance is 1.0 to 10.0%, such as 1.0%, 3.0%, 5.0%, 6.0%, 8.0%, or 10.0%, but is not limited to the listed values; other unlisted values ​​within this range also apply.

[0059] In this invention, under the condition of stabilizing nitrates and influent ammonia nitrogen produced by short-range denitrification in the anoxic reaction zone, the backwashing frequency of the anoxic reaction zone is reduced, thereby providing a longer residence time for the enrichment and growth of anaerobic ammonia-oxidizing bacteria on the biofilm. This process can enrich the Candidatus Brocadia anaerobic ammonia-oxidizing bacteria species in the anoxic reaction zone biofilm within 40–80 days, achieving an abundance of 2 × 10⁻⁶. 8 ~3×10 9 If the short-range denitrification nitrite accumulation rate (NAR) is below 30% during this process, the hydroxylamine dosing strategy can be restarted to restore the NAR to 30-40%.

[0060] Compared with the prior art, the present invention has the following beneficial effects:

[0061] (1) The device described in this invention divides the reaction zone of the composite biofilm reactor and sets up structural units such as hydroxylamine addition, backwashing, and aeration. In the aerobic reaction zone, ammonia nitrogen is oxidized to nitrate nitrogen, and then the nitrified liquid in the aerobic reaction zone is returned to the anoxic reaction zone, which can effectively realize continuous biofilm treatment of urban sewage.

[0062] (2) In this invention, by setting up a hydroxylamine dosing unit, the hydroxylamine dosing strategy is precisely controlled, so that short-cut denitrification can be started quickly, and then anaerobic ammonia oxidation occurs with ammonia nitrogen in the wastewater, thereby achieving efficient removal of ammonia nitrogen in the wastewater, with a total nitrogen removal rate of over 76%.

[0063] (3) The precise control of the hydroxylamine addition process in the method described in this invention eliminates the need to consider fluctuations in influent water volume and quality, and is not affected by the carbon-nitrogen ratio, pH value, COD, etc. of the raw water. It can make full use of the carbon source of the raw water for denitrification, and there is no need to add external carbon source.

[0064] (4) The device described in this invention has a simple structure, the method is easy to operate, the equipment and process costs are low, the processing load is high, and it is suitable for a variety of application scenarios. Attached Figure Description

[0065] Figure 1 This is a schematic diagram of the device for treating urban wastewater based on short-range denitrification coupled with anaerobic ammonium oxidation in a continuous flow process, as provided in Embodiment 1 of the present invention.

[0066] Among them, 11-inlet pool, 12-inlet pump, 13-inlet flow meter, 21-anoxic reaction zone, 22-aerobic reaction zone, 23-inlet valve, 24-return flow meter, 25-return pump, 26-sludge thickening tank, 27-backwash water valve, 31-hydroxylamine storage tank, 32-hydroxylamine metering pump, 41-backwash blower, 42-perforated aeration pipe, 51-aeration blower, 52-aeration disc, 6-intelligent control unit. Detailed Implementation

[0067] To better illustrate the present invention and facilitate understanding of its technical solutions, the present invention is further described in detail below. However, the following embodiments are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

[0068] The following are typical but non-limiting embodiments of the present invention:

[0069] Example 1:

[0070] This embodiment provides a device for treating municipal wastewater based on short-cut denitrification coupled with anaerobic ammonium oxidation in a continuous flow process. A schematic diagram of the device is shown below. Figure 1 As shown, it includes an influent unit, a composite biofilm reactor, a hydroxylamine dosing unit, a backwashing unit, and an aeration unit. The composite biofilm reactor includes an anoxic reaction zone 21 and an aerobic reaction zone 22 in sequence according to the sewage flow direction. Both the anoxic reaction zone 21 and the aerobic reaction zone 22 are inoculated with packing material that has completed biofilm formation.

[0071] The outlet of the water inlet unit is connected to the inlet of the anoxic reaction zone 21. The outlet of the aerobic reaction zone 22 is connected to the anoxic reaction zone 21 via an external pipeline. The outlet of the hydroxylamine dosing unit is connected to the inlet of the anoxic reaction zone 21. The outlet of the backwashing unit is connected to the bottom of the anoxic reaction zone 21. The aeration unit is connected to the bottom of the aerobic reaction zone 22.

[0072] The water inlet unit includes a water inlet tank 11, a water inlet pump 12, and a water inlet flow meter 13. The outlet pipe of the water inlet tank 11 passes through the water inlet pump 12 and the water inlet flow meter 13 in sequence, and then connects to the anoxic reaction zone 21.

[0073] The anoxic reaction zone 21 and the aerobic reaction zone 22 are separated by a partition. The bottom of the partition is provided with a connecting port, and a water inlet valve 23 is provided at the connecting port.

[0074] The volume ratio of the hypoxic reaction zone 21 to the aerobic reaction zone 22 is 1:1.

[0075] The packing material is polypropylene hollow ring packing material with a filling ratio of 60%.

[0076] The aerobic reaction zone 22 has two outlets, one of which discharges water through an outlet pipe and the other is connected back to the anoxic reaction zone 21 through an external pipeline; the external pipeline is equipped with a reflux flow meter 24 and a reflux pump 25.

[0077] The hydroxylamine dosing unit includes a hydroxylamine storage tank 31 and a hydroxylamine metering pump 32, which is installed on the connecting pipeline between the hydroxylamine storage tank 31 and the anoxic reaction zone 21.

[0078] The backwashing unit includes a backwashing blower 41 and a perforated aeration pipe 42. The perforated aeration pipe 42 is located at the bottom of the anoxic reaction zone 21, and the outlet of the backwashing blower 41 is connected to the perforated aeration pipe 42.

[0079] The aeration unit includes an aeration blower 51 and an aeration disc 52. The aeration disc 52 is located at the bottom of the aerobic reaction zone 22, and the outlet of the aeration blower 51 is connected to the aeration disc 52.

[0080] The device also includes a sludge thickening tank 26. A backwashing water valve 27 is provided on the side wall of the anoxic reaction zone 21 near the aerobic reaction zone 22. The anoxic reaction zone 21 is connected to the sludge thickening tank 26 via the backwashing water valve. The upper drain outlet of the sludge thickening tank 26 is connected to the aerobic reaction zone 22.

[0081] The device also includes an intelligent control unit 6, and the inlet flow meter 13, the return flow meter 24 and the hydroxylamine metering pump 32 are all connected to the intelligent control unit 6.

[0082] Example 2:

[0083] This embodiment provides a device for treating urban wastewater based on short-cut denitrification coupled with anaerobic ammonia oxidation in a continuous flow. The device is the same as the device in Embodiment 1, except that the volume ratio of the anoxic reaction zone 21 to the aerobic reaction zone 22 is 2:1; and the packing material is polypropylene hollow ring packing material with a filling ratio of 70%.

[0084] Example 3:

[0085] This embodiment provides a device for treating urban wastewater based on short-cut denitrification coupled with anaerobic ammonia oxidation in a continuous flow. The device is the same as that in Embodiment 1, except that the volume ratio of the anoxic reaction zone 21 to the aerobic reaction zone 22 is 2:1.5; the packing material filling ratio of the anoxic reaction zone 21 is 60%, and the packing material filling ratio of the aerobic reaction zone 22 is 70%.

[0086] Example 4:

[0087] This embodiment provides a method for treating municipal wastewater based on short-cut denitrification coupled with anaerobic ammonium oxidation in a continuous flow process. The method uses the apparatus described in Embodiment 1, which is a continuous flow pilot-scale device.

[0088] The method includes the following steps:

[0089] (1) After inoculating the composite biofilm reactor with nitrification-denitrification activated sludge and plastic packing, biofilm formation is carried out. The initial influent volume of the composite biofilm reactor accounts for 60%, the reflux ratio is controlled at 300%, and biofilm formation is achieved after one week of aeration. All activated sludge is discharged, and the continuous influent is started after completion. The average influent COD is 120.7 mg / L, the average ammonia nitrogen concentration is 41.2 mg / L, the average influent TN is 45.1 mg / L, and the carbon-nitrogen ratio is 2.67.

[0090] (2) After the device is started normally, hydroxylamine solution is added. The concentration of hydroxylamine after mixing the influent, reflux nitrification liquid and hydroxylamine solution is controlled to be 5 mg / L. The addition flow rate of hydroxylamine solution is calculated to be 0.107 L / h. The interval between additions of hydroxylamine solution is 1 day, and the time for each addition is 1 day. After 6 days of operation, the nitrite concentration in the effluent of anoxic reaction zone 21 rises to 16.8 mg N / L, the nitrate concentration in the effluent of anoxic reaction zone 21 is 13.5 mg N / L, the nitrite accumulation rate reaches 55%, and the partial short-cut denitrification is successfully started.

[0091] (3) After the influent, reflux nitrification liquid and hydroxylamine solution are mixed, the concentration of hydroxylamine is reduced to 3 mg / L. At this time, the addition flow rate of hydroxylamine solution is 0.064 L / h. After 2 days, the nitrite concentration in the effluent of the anoxic reaction zone 21 drops to 12.3 mg N / L, and the nitrite accumulation rate is 40%. The addition of hydroxylamine is stopped, and the system enters the anaerobic ammonia oxidizing bacteria enrichment stage for stable operation.

[0092] (4) The anaerobic ammonia-oxidizing bacteria enrichment stage was stably operated for 62 days until the nitrite effluent in the anoxic reaction zone 21 dropped to 2 mg / L, and the abundance of Candidatus Brocadia in the biofilm reached 2.67 × 10⁻⁶. 9 .

[0093] In this embodiment, the above method was used to treat the wastewater, and the final effluent TN was 10.5 mg N / L, with a total nitrogen removal rate of 76.2%. This achieved partial short-cut denitrification coupled with anaerobic ammonia oxidation reaction, and also showed that the nitrite produced by partial short-cut denitrification in the anoxic reaction zone was used immediately.

[0094] Example 5:

[0095] This embodiment provides a method for treating municipal wastewater based on short-cut denitrification coupled with anaerobic ammonia oxidation in a continuous flow process. The method uses the apparatus described in Embodiment 2, which is a pilot-scale continuous flow composite biofilm device.

[0096] The method includes the following steps:

[0097] (1) After inoculating the composite biofilm reactor with nitrification-denitrification activated sludge and plastic packing, biofilm formation is carried out. The initial influent volume of the composite biofilm reactor accounts for 70%, the reflux ratio is controlled at 200%, and biofilm formation is achieved after 7 days of aeration. All activated sludge is discharged, and the continuous influent is started after completion. The average COD of the influent is 260 mg / L, the average ammonia nitrogen concentration is 45 mg / L, the average TN of the influent is 50 mg / L, and the carbon-nitrogen ratio is 5.2.

[0098] (2) After the device is started normally, it runs for 20 days according to the traditional nitrification-denitrification process. Then, hydroxylamine solution is added. The concentration of hydroxylamine after mixing the influent, reflux nitrification liquid and hydroxylamine solution is controlled to be 4 mg / L. The calculated flow rate of hydroxylamine solution is 0.156 L / h. The interval between additions of hydroxylamine solution is 1.5 days, and the time for each addition is 1 day. After running for 8 days, the nitrite concentration in the effluent of the anoxic reaction zone 21 rises to 14.6 mg N / L, the nitrate concentration in the effluent of the anoxic reaction zone 21 is 14.7 mg N / L, the nitrite accumulation rate reaches 50%, and the partial short-cut denitrification is successfully started.

[0099] (3) After the influent, reflux nitrification liquid and hydroxylamine solution are mixed, the concentration of hydroxylamine is reduced to 2.4 mg / L. At this time, the addition flow rate of hydroxylamine solution is 0.0936 L / h. After 3 days, the nitrite concentration in the effluent of the anoxic reaction zone 21 drops to 5.6 mg N / L, and the nitrite accumulation rate is 39%. Hydroxylamine addition is stopped, and the system enters the anaerobic ammonia oxidizing bacteria enrichment stage for stable operation.

[0100] (4) The anaerobic ammonia-oxidizing bacteria enrichment stage was stably operated for 75 days until the nitrite effluent in the anoxic reaction zone 21 dropped to 2 mg / L and the relative abundance of Candidatus Brocadia in the biofilm was 1.5%.

[0101] In this embodiment, the above method was used to treat the wastewater, and the final effluent TN was 7 mg N / L, with a total nitrogen removal rate of 86%. The effluent met the standards and had low total nitrogen, indicating a high removal rate. This also shows that the nitrite produced by the partial short-cut denitrification in the anoxic reaction zone was used immediately.

[0102] Example 6:

[0103] This embodiment provides a method for treating municipal wastewater based on short-cut denitrification coupled with anaerobic ammonia oxidation in a continuous flow process. The method uses the apparatus described in Embodiment 3, which is a pilot-scale continuous flow composite biofilm device.

[0104] The method includes the following steps:

[0105] (1) After inoculating the composite biofilm reactor with nitrification-denitrification activated sludge and plastic packing, biofilm formation is carried out. The initial influent volume of the composite biofilm reactor accounts for 65%, the reflux ratio is controlled at 100%, and biofilm formation is achieved after 10 days of aeration. All activated sludge is discharged, and the continuous influent is started after completion. The influent is urban sewage with an average COD of 184.7 mg / L, an average ammonia nitrogen concentration of 38.4 mg / L, an average TN of 41.5 mg / L, an average SS of 239.5 mg / L, and a carbon-to-nitrogen ratio of 4.45.

[0106] (2) The device has been operating stably for more than 2 years using the traditional nitrification-denitrification process with high efficiency biofilm method. A hydroxylamine addition unit was added, and hydroxylamine solution was added. The concentration of hydroxylamine after mixing the influent, reflux nitrification liquid and hydroxylamine solution was controlled to be 5 mg / L. The calculated addition flow rate of hydroxylamine solution was 10.42 L / h. The interval between additions of hydroxylamine solution was 2 days, and the time for each addition was 28 hours. After 8 days of operation, the nitrite concentration in the effluent of anoxic reaction zone 21 rose to 4.2 mg N / L, the nitrate concentration in the effluent of anoxic reaction zone 21 was 1.3 mg N / L, and the nitrite accumulation rate reached 76%. Partial short-cut denitrification was successfully started.

[0107] (3) After 65 days of stable operation, the nitrite concentration in the effluent of the anoxic reaction zone 21 dropped to below 1 mg / L, which was almost undetectable. The hydroxylamine solution was added again, and the concentration of hydroxylamine after mixing the influent, reflux nitrification liquid and hydroxylamine solution was reduced to 3 mg / L. At this time, the hydroxylamine solution was added at a flow rate of 6.25 L / h. After 3 days, the nitrite concentration in the effluent of the anoxic reaction zone 21 recovered to 2.6 mg N / L, and the nitrite accumulation rate was 47%. The hydroxylamine addition was stopped, and the system entered the anaerobic ammonia oxidizing bacteria enrichment stage for stable operation.

[0108] (4) The anaerobic ammonia-oxidizing bacteria enrichment stage was stably operated for 80 days until the nitrite effluent in the anoxic reaction zone 21 dropped to 2 mg / L and the relative abundance of Candidatus Brocadia in the biofilm was 0.9%.

[0109] In this embodiment, the above method was used to treat the wastewater, and the final effluent TN was 8.3 mg N / L, with a total nitrogen removal rate of 80%. Similarly, partial short-cut denitrification coupled with anaerobic ammonia oxidation was achieved in the continuous flow anoxic reaction zone.

[0110] As can be seen from the above embodiments, the device of the present invention, through the division of the reaction zone of the composite biofilm reactor and the setting of structural units such as hydroxylamine addition, backwashing, and aeration, oxidizes ammonia nitrogen to nitrate nitrogen in the aerobic reaction zone, and then returns the nitrified liquid from the aerobic reaction zone to the anoxic reaction zone, which can effectively achieve continuous biofilm treatment of urban sewage. Through the setting of the hydroxylamine addition unit, the precise control of the hydroxylamine addition strategy enables rapid initiation of short-cut denitrification, followed by anaerobic ammonia oxidation with ammonia nitrogen in the sewage, achieving efficient removal of ammonia nitrogen from the sewage, with a total nitrogen removal rate of over 76%. The precise control of the hydroxylamine addition process in the method eliminates the need to consider fluctuations in influent flow rate and quality, and is unaffected by the carbon-nitrogen ratio, pH value, COD, etc. of the raw water, fully utilizing the carbon source of the raw water for denitrification without the need for external carbon source addition. The device has a simple structure, the method is easy to operate, the equipment and process costs are low, the treatment load is high, and it is suitable for various application scenarios.

[0111] The applicant declares that the present invention is illustrated through the above embodiments with detailed apparatus and methods, but the present invention is not limited to the above detailed apparatus and methods, that is, it does not mean that the present invention must rely on the above detailed apparatus and methods to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the apparatus of the present invention, additions of auxiliary devices, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for treating municipal wastewater by a continuous flow based on short-cut denitrification coupled with anaerobic ammonia oxidation, characterized in that, The method is performed according to a device for treating municipal sewage by short-cut denitrification coupled with anaerobic ammonia oxidation continuous flow: The device comprises a water inlet unit, a composite biofilm reactor, a hydroxylamine adding unit, a backwashing unit and an aeration unit, the composite biofilm reactor comprises an anoxic reaction zone and an aerobic reaction zone in sequence along the sewage flow direction, and the anoxic reaction zone and the aerobic reaction zone are both inoculated with fillers on which biofilm is formed; The outlet of the water inlet unit is connected to the inlet of the anoxic reaction zone, the outlet of the aerobic reaction zone is connected to the anoxic reaction zone through an external pipeline, the outlet of the hydroxylamine adding unit is connected to the inlet of the anoxic reaction zone, the outlet of the backwashing unit is connected to the bottom of the anoxic reaction zone, and the aeration unit is connected to the bottom of the aerobic reaction zone. The device further comprises a sludge concentration tank, a backwashing water valve is arranged on the side wall of the anoxic reaction zone close to the aerobic reaction zone, the anoxic reaction zone is connected to the sludge concentration tank through the backwashing water valve, and the upper drainage port of the sludge concentration tank is connected to the aerobic reaction zone. The method comprises the following steps: (1) after the composite biofilm reactor is inoculated with activated sludge and fillers, biofilm formation is performed, and after completion, the device is started by continuous water inlet; (2) after the device is normally started, the device is operated according to the nitrification-denitrification process, the anoxic reaction zone is backwashed regularly in the process, then hydroxylamine solution is added, the addition flow rate of the hydroxylamine solution is controlled, and when the nitrite accumulation rate is greater than 50%, the short-cut denitrification is successfully started; (3) the addition flow rate of the hydroxylamine solution is reduced, and when the nitrite accumulation rate is stably controlled in the range of 30-40%, the addition of the hydroxylamine solution is stopped, and the device is operated in the enrichment stage of the anaerobic ammonia oxidation bacteria; (4) during the stable operation in the enrichment stage of the anaerobic ammonia oxidation bacteria, the frequency of backwashing is reduced, and if the nitrite accumulation rate is less than 30%, the hydroxylamine solution is added again in step (3) until the nitrite accumulation rate is recovered; In step (2), the concentration of the hydroxylamine after mixing of the water inlet, the reflux nitrification liquid and the hydroxylamine solution is controlled to be 3-5 mg / L, and then the addition flow rate of the hydroxylamine solution is calculated by reading the water inlet flow rate and the reflux nitrification liquid flow rate; In step (3), the concentration of the hydroxylamine after mixing of the water inlet, the reflux nitrification liquid and the hydroxylamine solution is reduced to 2-4 mg / L, and then the addition flow rate of the hydroxylamine solution is calculated.

2. The method of claim 1, wherein, The water inlet unit comprises a water inlet tank, a water inlet pump and a water inlet flow meter, and the outlet pipeline of the water inlet tank sequentially passes through the water inlet pump and the water inlet flow meter and is then connected to the anoxic reaction zone.

3. The method of claim 1, wherein, The anoxic reaction zone and the aerobic reaction zone are separated by a partition plate, the bottom of the partition plate is provided with a communication port, and the communication port is provided with a water inlet valve.

4. The method of claim 1, wherein, The volume ratio of the anoxic reaction zone to the aerobic reaction zone is 1:1-2:

1.

5. The method of claim 2, wherein, The outlet of the aerobic reaction zone is provided with two outlets, one of which is discharged through a water outlet pipe, and the other of which is connected back to the anoxic reaction zone through an external pipeline.

6. The method of claim 5, wherein, The external pipeline is provided with a reflux flow meter and a reflux pump.

7. The method of claim 6, wherein, The hydroxylamine adding unit comprises a hydroxylamine storage tank and a hydroxylamine metering pump, and the hydroxylamine metering pump is arranged on the connecting pipeline of the hydroxylamine storage tank and the anoxic reaction zone.

8. The method of claim 7, wherein, The backwashing unit comprises a backwashing blower and a perforated aeration pipe, the perforated aeration pipe is arranged at the bottom of the anoxic reaction zone, and the outlet of the backwashing blower is connected to the perforated aeration pipe.

9. The method of claim 1, wherein, The aeration unit comprises an aeration blower and an aeration disc, the aeration disc is arranged at the bottom of the aerobic reaction zone, and the outlet of the aeration blower is connected to the aeration disc.

10. The method of claim 7, wherein, The device further comprises an intelligent control unit, and the water inlet flow meter, the backflow flow meter and the hydroxylamine metering pump are connected to the intelligent control unit.

11. The method of claim 1, wherein, In step (1), the activated sludge comprises nitrification-denitrification activated sludge, and the filler comprises plastic filler.

12. The method of claim 1, wherein, The initial water inlet volume ratio of the composite biofilm reactor is 50-70%, and the backflow pump is started, and the backflow ratio is controlled to be 100-300%.

13. The method of claim 12, wherein, The concentration of the activated sludge after the initial water inlet is 2500-3500 mg / L, and the filling ratio of the filler is 60-70%.

14. The method of claim 1, wherein, In step (1), the biofilm membrane formation comprises a two-stage muffled exposure process, first muffled exposure for 3-5 days after the initial water inlet, and then continue muffled exposure for 3-5 days after the second water inlet to 100% volume, and complete the biofilm membrane formation.

15. The method of claim 14, wherein, After the biofilm membrane formation is completed, the activated sludge is completely discharged.

16. The method of claim 1, wherein, In step (2), the device is started by starting the water inlet unit, the composite biofilm reactor and the aeration unit, and then the backwashing unit is started periodically after starting operation.

17. The method of claim 1, wherein, After the composite biofilm reactor is started, the backflow pump is started to control the backflow ratio to be 100-300%.

18. The method of claim 1, wherein, In step (2), when the nitrification-denitrification process is running, the hydraulic retention time of the anoxic reaction zone and the aerobic reaction zone is independently 2-3 h.

19. The method of claim 1, wherein, In step (2), the backwashing cycle is 2-4 days, and each backwashing time is 15-30 min.

20. The method of claim 1, wherein, In step (2), when backwashing, keep water inlet, close the water inlet valve between the anoxic reaction zone and the aerobic reaction zone, and open the backwashing water valve.

21. The method of claim 1, wherein, In step (2), the nitrification-denitrification process runs for 15-20 days.

22. The method of claim 1, wherein, In step (2), the hydroxylamine solution is stored in a hydroxylamine storage tank, and the hydroxylamine storage tank is subjected to light shielding treatment.

23. The method of claim 1, wherein, In step (2), the interval time of the hydroxylamine solution addition is 24-48 h, and the addition time of each time is 20-28 h.

24. The method of claim 1, wherein, In step (2), the time required for the nitrite accumulation rate to reach more than 50% is 6-8 days.

25. The method of claim 1, wherein, In step (3), the interval time of the hydroxylamine solution addition is 24-48 h, and the addition time of each time is 20-28 h.

26. The method of claim 1, wherein, In step (3), the time required for the nitrite accumulation rate to be stabilized at 30-40% is 2-3 days.

27. The method of claim 1, wherein, In step (4), in the anaerobic ammonia oxidation bacteria enrichment stage, the anaerobic ammonia oxidation bacteria grow and enrich on the biofilm.

28. The method of claim 1, wherein, In step (4), the backwashing frequency is once every 6-8 days, and each backwashing time is 15-30 min.

29. The method of claim 1, wherein, In step (4), the time required for the anaerobic ammonia oxidation bacteria enrichment stage to be stably running is 40-80 days.

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