A method and apparatus for fast start-up of an AOA process

Abstract

The application provides a method and device for quickly starting an AOA process, and the method provided by the application is directly operated in an anaerobic / anaerobic mode, takes nitrate as an electron acceptor, domesticates denitrification and nitrogen conversion performance while preferentially enriching core bacteria of glycan bacteria, and shortens glycan bacteria enrichment and domestication time.Secondly, during domestication of nitrifying bacteria, the method is operated in an anaerobic / aerobic / anaerobic mode, nitrate is added by means of segmented water feeding, short-term over-aeration is adopted, nitrifying bacteria are successfully stimulated to quickly recover activity, and the AOA system is accelerated to start in combination with the basis that the glycan bacteria have excellent conversion capacity for nitrate nitrogen in the early stage.

Description

Technical Field

[0001] This invention belongs to the field of water treatment technology, specifically relating to a method and apparatus for rapidly starting up an AOA process. Background Technology

[0002] With the rapid development of the social economy and the acceleration of urbanization, my country's wastewater treatment and discharge standards have also been raised. These standards are crucial for environmental protection, water quality improvement, and promoting sustainable development. Urban domestic sewage is a key focus of water treatment, and its discharge volume is closely related to economic development and human activities. Nitrogen and organic matter are the main pollutants in domestic sewage; if discharge does not meet standards, they can harm human health and the environment, including water, soil, and air. Currently, most wastewater treatment plants use biological treatment methods for nitrogen removal, such as anammox, denitrification, and nitrification. Among these, anammox has attracted much attention due to its advantages, including autotrophic nitrogen removal, reduced carbon source requirements, and the elimination of the need for aeration.

[0003] Anaerobic ammonia oxidation (AAO) utilizes anaerobic ammonia-oxidizing bacteria (AnAOB) to convert ammonia into nitrogen gas using nitrite as an electron acceptor, thus achieving nitrogen removal from wastewater. A stable supply of nitrite is crucial for stable nitrogen removal in AAO. Urban wastewater treatment systems typically employ short-cut nitrification or short-cut denitrification processes to obtain nitrite. Short-cut nitrification coupled with AAO offers advantages such as saving carbon sources, low sludge production, and good treatment efficiency; however, prolonged aeration leads to excessive NO2--N production, hindering the full progress of AAO. Even though controlling dissolved oxygen and free ammonia concentrations can mitigate this problem, the stability is poor, making it difficult to provide a stable substrate supply for AAO bacteria. Traditional short-cut denitrification coupled with AAO, given the low-carbon, high-nitrogen characteristics of domestic wastewater in my country, often requires the addition of exogenous carbon sources to supplement organic matter to ensure the reaction proceeds fully, but this incurs high costs. Meanwhile, since organic matter undergoes transformation after a period of aeration, coupling traditional short-cut nitrification with short-cut denitrification wastes organic matter in the raw water and requires the addition of external carbon sources, consuming significant amounts of energy, carbon, and costs. Therefore, the development of green and low-carbon wastewater denitrification technologies is of paramount importance in the current water treatment field.

[0004] In recent years, the anaerobic / aerobic / anoxic (AOA) process has attracted widespread attention in urban wastewater treatment due to its advantages such as high nitrogen removal efficiency, full utilization of organic matter, energy saving, and stable reaction. The AOA process couples anaerobic ammonia oxidation through multiple pathways using a staged approach, with endogenous (short-cut) denitrification being crucial for deep nitrogen removal. In the anaerobic stage, polysaccharitrophs and polyphosphate-accumulating bacteria can absorb organic matter in wastewater and convert it into an internal carbon source. Subsequently, in the aerobic and anoxic stages, this internal carbon source is used for denitrification and phosphorus removal, thereby enhancing the nitrogen removal contribution of the aerobic and anoxic zones. Therefore, for the system to achieve deep nitrogen removal, it is essential to enrich polysaccharitrophs. Compared to polysaccharitrophs, nitrifying bacteria are easier to enrich, while anaerobic ammonia-oxidizing bacteria are often obtained through inoculation. However, polysaccharitrophs grow slowly, making their enrichment process the rate-limiting step in starting the system. This results in a long start-up time for AOA systems using traditional activated sludge, hindering their promotion and application. Therefore, adopting a batch acclimation strategy to establish a rapid start-up method for the AOA process has practical research significance and application value. Summary of the Invention

[0005] This invention addresses the technical problem of how to achieve rapid startup of an AOA system, and provides a method for rapid startup of the AOA process. This invention also provides a device for rapid startup of the AOA process to implement this method.

[0006] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows:

[0007] A method for rapidly starting up an AOA process includes: (1) inoculating activated sludge into the reactor and running it in an anaerobic / anoxic manner to enrich and acclimate polysaccharide bacteria; initially, at the beginning of the anaerobic stage, simulated wastewater without carbon source is introduced to complete the washing of miscellaneous bacteria after a short period of starvation; thereafter, at the beginning of each anaerobic stage, simulated wastewater mainly containing carbon source is introduced; after the drainage is completed at the end of each anaerobic stage, the anoxic stage is entered, and at the beginning of the anoxic stage, simulated wastewater mainly containing nitrate is introduced; during operation, key operating parameters are adjusted to complete the first stage start-up; (2) inoculating activated sludge and anaerobic ammonia oxidizing bacteria into the reactor and using an anaerobic / aerobic / anoxic method. The system operates in a controlled manner. Initially, simulated wastewater containing carbon sources, ammonia nitrogen, inorganic salts, and trace elements is introduced as influent during the anaerobic stage. Nitrate nitrogen is added during the anoxic stage. In the early aerobic stage, over-aeration is employed. As nitrification intensifies, when the nitrate nitrogen concentration at the end of the anoxic stage exceeds a predetermined value, the amount of nitrate nitrogen added during the anoxic stage is gradually reduced until it reaches zero. When nitrate nitrogen addition ceases in the anoxic stage and no ammonia nitrogen remains at the end of the anoxic stage, the aeration rate is gradually reduced until the remaining ammonia nitrogen at the end of the aerobic stage cannot be completely removed by the anaerobic ammonia oxidation process in the anoxic stage, at which point the reduction in aeration rate stops. Key operating parameters are adjusted during operation to achieve rapid startup of the AOA system.

[0008] In step (1), the phosphate concentration in the simulated wastewater introduced at the beginning of the anaerobic stage is 4-5 mg / L, and the COD concentration of the influent is greater than or equal to 120 mg / L; the nitrate concentration in the simulated wastewater introduced during the anoxic stage is 35-50 mg / L.

[0009] When inoculating activated sludge in step (1), the volume of the inoculated sludge accounts for 20% to 30% of the total volume of the reactor. The total suspended solids in the initial mixed liquor formed by stirring are about 2000 to 2500 mg / L, and the mass ratio of volatile suspended solids to total suspended solids in the initial mixed liquor is 0.4 to 0.7.

[0010] In step (1), the amount of carbon source added in the anaerobic stage is adjusted within the range of carbon-nitrogen ratio of 2.7-3.5, the duration of the anaerobic stage is adjusted within the range of 1.5-2.5 hours, and the duration of the anoxic stage is adjusted within the range of 3-6 hours. The system is adjusted to run until the nitrate removal rate is higher than 90% and the nitrite accumulation rate is higher than 50%, thus completing the first stage startup.

[0011] In step (1), the temperature inside the reactor is controlled at 29-31℃.

[0012] In step (2), when inoculating activated sludge and anaerobic ammonia oxidizing bacteria, the volume of sludge after inoculation accounts for 30-40% of the total volume of the reactor, the total amount of suspended solids in the mixed liquid formed by stirring is 2500-3000 mg / L, and the mass ratio of volatile suspended solids to total suspended solids is 0.4-0.7.

[0013] In step (2), over-aeration is carried out in the aerobic stage in the early stage to control the dissolved oxygen concentration at the end of the aerobic process to 1-2 mg / L; when the nitrate concentration at the end of the anoxic stage is higher than 5 mg / L, the amount of nitrate added is gradually reduced until it is reduced to 0.

[0014] The simulated wastewater introduced in step (2) during the anaerobic stage has an ammonia nitrogen concentration of 35-50 mg / L, a phosphate concentration of 9-10 mg / L, and a carbon-nitrogen ratio of the same as that at the end of step (1).

[0015] In step (2), during operation, key operating parameters, including aeration rate and duration of different stages, are adjusted until the total nitrogen removal rate is higher than 95% and the phosphorus removal rate is higher than 80%, thus completing the rapid start-up of the AOA system.

[0016] The AOA process rapid start-up device for implementing the method comprises: a sequencing batch reactor (SBR) equipped with an aeration device; an inlet tank connected to the SBR via an inlet pipe, on which an inlet pump and inlet valve are installed; a carbon source storage tank connected to the SBR via a carbon source delivery pipe, on which a chemical feed pump and chemical feed valve are installed; a nitrate solution storage tank connected to the SBR via a nitrate solution delivery pipe, on which a liquid feed pump and liquid feed valve are installed; and a drain tank connected to the SBR via a drain pipe, on which a drain valve is installed.

[0017] This invention provides a method for rapid startup of the AOA (Automatic Aeration) process, based on the growth characteristics of different key functional bacteria in the system. It offers a device and method for batch-directed acclimatization of traditional activated sludge to achieve rapid startup of the AOA system, solving the problem of slow startup in practical applications. First, a portion of activated sludge is introduced into the SBR reactor. Using an anaerobic / anoxic operating mode, combined with batch influent, mid-term effluent, short-term starvation washing of miscellaneous bacteria, inhibition of polyphosphate accumulation, and constant-temperature heating strategies, polysaccharide-rich bacteria are preferentially enriched, giving them good ability to remove nitrate and nitrite accumulation. Then, a portion of traditional activated sludge and a small amount of anaerobic ammonia-oxidizing bacteria are inoculated. Using an anaerobic / aerobic / anoxic operating mode, combined with short-term over-aeration and a decreasing aeration rate and nitrate dosage strategy, the activity of endogenous denitrifying bacteria and anaerobic ammonia-oxidizing bacteria is maintained, while stimulating the rapid recovery of nitrifying bacteria activity in the activated sludge. Furthermore, the inhibition of polyphosphate-rich bacteria is eliminated, improving the system's phosphorus removal capacity. By combining the successful enrichment of polysaccharide-producing bacteria with their efficient conversion of nitrate nitrogen, the AOA system was able to start up quickly and achieve excellent and stable nitrogen and phosphorus removal performance.

[0018] The method and apparatus for rapidly starting the AOA process according to the present invention have the following advantages:

[0019] (1) The method for rapid startup of the AOA process provided by this invention is based on the growth characteristics of different main functional bacteria in the AOA process system. It selectively and batch-wise acclimatizes traditional activated sludge, avoiding problems such as competition for nutrients and ecological niches among bacterial species caused by direct startup. It achieves rapid startup of the system within 30 days and obtains efficient and stable nitrogen and phosphorus removal performance, with the total nitrogen removal rate maintained at about 95% and the phosphorus removal rate maintained at about 85%. The startup method of the AOA system provided by this invention is based on the advantage of the strong endogenous metabolic activity of traditional activated sludge. It prioritizes the cultivation and enrichment of polysaccharide bacteria, making up for the defects when the AOA system is started directly using activated sludge. This is because exogenous denitrifying bacteria in the activated sludge compete with polysaccharide bacteria for carbon sources, and easy-to-grow nitrifying bacteria and polyphosphate bacteria with growth mechanisms similar to polysaccharide bacteria compete with them for ecological niches. It provides the slow-growing polysaccharide bacteria with the most suitable growth environment, accelerates the enrichment rate, and thus shortens the startup time of the entire system.

[0020] (2) The method for rapid startup of the AOA process provided by this invention does not employ the traditional method of enrichment followed by acclimatization during the rapid enrichment stage of polysaccharide bacteria. Instead, it first operates in an anaerobic / aerobic mode, without adding nitrogen to enrich the polysaccharide bacteria to a certain extent, and then operates in an anaerobic / anoxic mode, eliminating the aerobic stage and using nitrate instead of oxygen as the electron acceptor to acclimatize the denitrification performance of the polysaccharide bacteria. The method provided by this invention operates directly in an anaerobic / anoxic mode, using nitrate as the electron acceptor, enriching the polysaccharide bacteria while simultaneously acclimatizing their denitrification and nitrogen conversion performance, thus shortening the enrichment and acclimatization time. Furthermore, taking advantage of the better endogenous denitrification performance of polysaccharide bacteria at higher temperatures, the reactor is heated by a constant-temperature water bath, and the growth of polyphosphate-accumulating bacteria is inhibited by halving the phosphorus concentration in the mid-term drainage and influent, further accelerating the startup of the endogenous (short-range) denitrification system.

[0021] (3) The method for rapidly starting the AOA process provided by the present invention adopts the method of adding nitrate in stages during the acclimatization of nitrifying bacteria, so as to avoid the problem that the activity of the endogenous denitrifying bacteria enriched in the early stage is weakened due to the lack of substrate caused by the poor activity of nitrifying bacteria in the early stage. At the same time, the endogenous short-range denitrification promotes the rapid recovery of activity of the inoculated anaerobic ammonia oxidizing bacteria.

[0022] (4) The method for rapid startup of the AOA process provided by the present invention successfully stimulates nitrifying bacteria to quickly recover their activity by using short-term over-aeration. Combined with the excellent nitrate conversion ability of polysaccharide bacteria in the early stage, the startup of the AOA system is accelerated. Since the aerobic stage is set for a short period of time and the dissolved oxygen concentration is controlled at 1-2 mg / L, the short-term over-aeration will not pose a threat to the system and the activity of anaerobic ammonia oxidizing bacteria is not significantly affected. Therefore, the system can operate stably.

[0023] (5) The method for rapid start-up of the AOA process provided by this invention eliminates the strategy of halving the phosphorus concentration in the intermediate drainage and influent during the restoration of nitrifying bacteria performance, and restores the cultivation of polyphosphate-accumulating bacteria under the premise that polyphosphate-accumulating bacteria are dominant. In addition, the change in the operating mode, namely the addition of the aerobic stage, provides favorable conditions for phosphorus removal, and ultimately achieves a stable phosphorus removal effect.

[0024] To make the technical solution of the method and apparatus for rapidly starting the AOA process according to the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0025] like Figure 1 The diagram shown is a schematic of the AOA process rapid start-up device described in this invention.

[0026] The attached figures are labeled as follows:

[0027] 1-Inlet tank; 2-Carbon source inlet tank; 3-Nitrogen and nitrate inlet tank; 4-Outlet tank; 5-Integrated AOA system reactor; 51-Stirring device; 52-Inlet valve; 53-Liquid inlet valve; 54-Dosage inlet valve; 55-Outlet valve; 56-Air pump; 57-Rotameter; 58-Aeration device; 6-Inlet pump; 7-Dosage inlet pump; 8-Liquid inlet pump; 9-Online water quality monitoring system. Detailed Implementation Example 1

[0028] This embodiment provides a rapid start-up device for the AOA process, the structure of which is as follows: Figure 1 As shown, the system includes an inlet tank 1, a carbon source inlet tank 2, a nitrate / nitrogen inlet tank 3, an outlet tank 4, an integrated AOA system reactor 5, an inlet pump 6, a chemical inlet pump 7, and a liquid inlet pump 8; a stirring device 51, an aeration device 58, a rotor flowmeter 57, an air pump 56, an online water quality monitoring system 9, an inlet valve 52, a liquid inlet valve 53, a chemical inlet valve 54, and an outlet valve 55, wherein the aeration device 58 is an aeration disc installed inside the reactor. The simulated wastewater in the inlet tank 1 is connected to the integrated AOA system reactor 5 through the inlet pump 6 and the inlet valve 52; the carbon source in the carbon source inlet tank 2 is connected to the integrated AOA system reactor 5 through the chemical inlet pump 7 and the chemical inlet valve 54; the nitrate / nitrogen inlet tank 3 contains NO3-. - -N wastewater is connected to the integrated AOA system reactor 5 via inlet pump 8 and inlet valve 53; the integrated AOA system reactor 5 is connected to the outlet tank 4 via drain valve. In this embodiment, the integrated AOA system reactor 5 is a sequencing batch reactor with an effective volume of 5L. The sensors of the online water quality monitoring system 9 are installed inside the sequencing batch bioreactor to monitor dissolved oxygen, pH, COD, and NO3 in the water. - -N、NH4+ -N and NO2 - Monitoring of -N concentration.

[0029] During startup, the device uses deionized water to prepare three types of feed water for the first stage of startup. Among them, feed water 1 has a composition and concentration of 4 mg / L PO4. 3- -P and a trace element solution of 1 ml / L were added. The main component of influent 2 was a carbon source (5.64 g / L CH3COONa), and the main component and concentration of influent 3 was 40 mg / L NO3. - A solution of -N, 60 mg / L CaCl2, 60 mg / L MgSO4·7H2O, 1000 mg / L KHCO3, and 1 ml / L trace elements was prepared. The pH of influent 1, influent 2, and influent 3 was maintained at approximately 8.0. Two types of influent were prepared using deionized water for the second-stage start-up. Influent 4 contained 158.97 mg / L CH3COONa and 40 mg / L NH4+. + -N, 9 mg / L PO4 3- The influent solution contained P, 60 mg / L CaCl2, 60 mg / L MgSO4·7H2O, 1000 mg / L KHCO3, and 1 ml / L trace elements, with the pH maintained at approximately 8.0; the influent solution contained NO3. - -N concentrate.

[0030] The concentrations of each trace element in the trace element solution are as follows: EDTA, 15000 mg / L; CoCl2·6H2O, 240 mg / L; ZnSO4·7H2O, 430 mg / L; MnCl4·H2O, 990 mg / L; NaMoO4·2H2O, 220 mg / L; CuSO4·5H2O, 250 mg / L; NaSeO4·10H2O, 210 mg / L; NiCl·6H2O, 190 mg / L; and H3BO4, 14 mg / L.

[0031] The specific steps for using the apparatus of this embodiment to quickly start the AOA process are as follows:

[0032] Traditional activated sludge was used as inoculum in the sequencing batch reactor (SBR). The volume of the inoculum sludge accounted for 20% of the total volume of the SBR. After stirring, the total suspended solids in the resulting initial mixture were 2000 mg / L. The ratio of volatile suspended solids to total suspended solids (ρ(VSS) / ρ(SS)) in the initial mixture was 0.4. The SBR was operated in an anaerobic / anoxic mode with a effluent ratio of 50%.

[0033] For the first four days, at the beginning of each anaerobic stage, influent 1 (containing no carbon source) was introduced into the reactor. Then, the stirring, sedimentation, and effluent processes were sequentially initiated. After the effluent from the anaerobic stage was completed, the reactor entered the anoxic stage. At the beginning of the anoxic stage, influent 3 (containing nitrate nitrogen) was introduced, followed by the sequential operation of stirring, sedimentation, effluent, and idle processes. During the first four days, the initial influent to the anaerobic stage contained no carbon source, and the reactor operated under short-term starvation conditions (C / N ratio of 0) to wash away miscellaneous bacteria from the sludge.

[0034] After rinsing, simulated wastewater mainly containing carbon sources is introduced at the beginning of each anaerobic stage. After effluent is discharged at the end of the anaerobic stage, the anoxic stage begins, in which simulated wastewater mainly containing nitrates is introduced. During operation, the first stage is started by adjusting the amount of carbon source added in the anaerobic stage, the duration of different stages, and the hydraulic retention time. In this embodiment, after rinsing, the specific procedures and influent process of the anaerobic / anoxic stages are as follows: at the beginning of the anaerobic stage, influent 1 and influent 2, i.e., influent containing carbon sources, are introduced, and then the stirring, sedimentation, and effluent processes are started in sequence. The C / N ratio when the carbon source is first added in the anaerobic stage is 2.7. The anaerobic / anoxic stage is operated in the form of mid-term effluent discharge. After the effluent discharge of the anaerobic stage is completed, the anoxic stage begins. At the beginning of the anoxic stage, influent 3, i.e., influent containing nitrate nitrogen, is introduced, and then the stirring, sedimentation, effluent, and idle processes are run in sequence. The anaerobic / anoxic cycle includes influent (influent 1 and influent 2) – stirring – sedimentation – effluent – ​​influent (influent 3) – stirring – sedimentation – effluent – ​​idle. During the intermediate drainage stage (after sludge sedimentation at the end of the anaerobic phase), phosphorus-rich wastewater is rapidly discharged to reduce the influent phosphorus concentration to 4-5 mg / L, thus minimizing competition between polyphosphate-accumulating bacteria and polysaccharide-accumulating bacteria. This process is cyclical, and the COD and NO3 levels at different stages of the reactor are monitored throughout the operation. - -N and NO2 - -N concentration was monitored daily. During operation, the carbon source dosage in the anaerobic phase was adjusted within a C / N ratio range of 2.7-3.5; the duration of different phases and hydraulic retention time were adjusted within a range of 1.5-2.5 hours for the anaerobic phase and 3-6 hours for the anoxic phase. Finally, under the conditions of a C / N ratio of 3.1, a 2-hour anaerobic phase, and a 4-hour anoxic phase, the system was operated in an anaerobic / anoxic mode for a total of 18 days. The system was adjusted to achieve a nitrate removal rate of 90% and a nitrite accumulation rate of 50%, completing the start-up of the first stage of the endogenous short-cut denitrification system. This step, based on the anaerobic / anoxic operation mode combined with batch influent and interim effluent operation, reduced the influent phosphorus concentration and decreased competition between polyphosphate-accumulating bacteria and polysaccharide-accumulating bacteria.

[0035] During operation, influent 1 is stored in influent tank 1, influent 2 is stored in carbon source influent tank 2, and influent 3 is stored in nitrate / nitrogen influent tank 3. Influent 1 is introduced at the beginning of the anaerobic stage. When influent 1 and influent 2 are introduced simultaneously, influent valve 52 and chemical influent valve 54 are opened, and influent pump 6 and chemical influent pump 7 are started to deliver influent 1 and influent 2 into the reactor. During the anoxic stage, when influent 3 is introduced, influent valve 53 is opened, and influent pump 8 is started to deliver nitrate / nitrogen-containing influent 3 into the reactor.

[0036] (2) Based on step 1, some activated sludge and a small amount of anaerobic ammonia-oxidizing bacteria are inoculated. The volume of the inoculated sludge accounts for 30% of the total volume of the reactor. After the sludge is inoculated, it is stirred. The total suspended solids in the resulting mixture are about 3000 mg / L, and the ratio of volatile suspended solids to total suspended solids (ρ(VSS) / ρ(SS)) in the mixture is 0.5. The anaerobic / anoxic operation mode in step (1) is changed to the anaerobic / aerobic / anoxic operation mode. At the same time, the mid-term drainage mode is cancelled. The process of an anaerobic / aerobic / anoxic cycle in the early stage includes water inlet (water inlet 4) - stirring - sedimentation - stirring and aeration - sedimentation - water inlet (water inlet 5) - stirring - sedimentation - idle. During aeration, air is introduced into the reactor through air pump 56, and the air inlet volume is monitored by rotor flow meter 57. During operation, water inlet 4 is stored in water inlet tank 1, and water inlet 5 is stored in nitrate nitrogen inlet tank 3, which are used for water inlet in the early stage of anaerobic and the anoxic stage, respectively.

[0037] During the initial operation, over-aeration was used in the aerobic phase, with the dissolved oxygen concentration at the end of the aerobic phase reaching 2 mg / L. Simultaneously, a quantitative amount of concentrated nitrate solution (influent 4) was added at the beginning of the anoxic phase to ensure the activity of polysaccharide-producing bacteria and anaerobic ammonia-oxidizing bacteria. After adding nitrate, the nitrate nitrogen concentration in the reactor was controlled at 17.5-25 mg / L. In this embodiment, the addition of nitrate reduced the NO3 concentration in the reactor at the beginning of the anoxic phase. - The -N concentration is 20 mg / L. Subsequently, when the nitrate nitrogen concentration exceeds 5 mg / L at the end of the anoxic stage, the influent flow rate of influent 4 is immediately reduced until influent 4 is completely removed. This results in a single-cycle influent / efluent mode. One cycle of the single-cycle influent / efluent mode is: influent (influent 4) – stirring – sedimentation – stirring and aeration – sedimentation – stirring – sedimentation – idle. After the nitrifying bacteria activity recovers, i.e., when influent 4 has been removed during the anoxic stage and there is no remaining ammonia nitrogen at the end of the anoxic stage, some NH4+ is added during the aerobic stage. + -N is converted to NO3 - -N and NO2 - -N, while polysaccharide bacteria utilize the internal carbon source PHA stored during the anaerobic stage to convert NO3- into NO3-. - -N is further converted into NO2 - -N and N2, part of NO2 - -N is then utilized by anaerobic ammonia oxidizing bacteria to remove some of the NH4+.+ -N. At this point, the aeration rate is gradually reduced according to the different nitrogen concentrations at the end of the aerobic stage, using the remaining NH4+ at the end of the aerobic stage. + -N cannot be completely removed through the anaerobic ammonia oxidation process in the anoxic stage, which is the critical point. The reduction of aeration rate is stopped, and the dissolved oxygen concentration is finally less than 0.5 mg / L at the end of the aerobic stage.

[0038] During operation, COD and NO3 were measured at different stages of the reactor. - -N, NH4 + -N and NO2 - The -N concentration was monitored daily. By adjusting the aeration rate, the duration of different stages within the aerobic period (not exceeding 1 / 4 of the entire cycle), and the hydraulic retention time, the AOA system was quickly started up with a C / N ratio of 3.1, a total nitrogen removal rate of 97%, and an operating cycle of 10 hours (1.5 hours of anaerobic phase, 2 hours of aerobic phase, and 6 hours of anoxic phase). In this embodiment, the start-up time was 25 days. Monitoring showed that after 15 days of operation, the total nitrogen removal rate of the system was still above 97%, and the phosphorus removal rate was 85%, achieving long-term stable operation. Example 2

[0039] The AOA process rapid start-up device in this embodiment is the same as in embodiment 1.

[0040] During startup, the device uses deionized water to prepare three types of feed water for the first stage of startup. Among them, feed water 1 has a composition and concentration of 4 mg / L PO4. 3- -P and a trace element solution of 1 ml / L were provided. The main component of influent 2 was a carbon source (5.64 g / L CH3COONa), and the main component and concentration of influent 3 was 40 mg / L NO3. - The solution contains -N, 60 mg / L CaCl2, 60 mg / L MgSO4·7H2O, 1000 mg / L KHCO3, and 1 ml / L of trace elements. The pH of influent 1, influent 2, and influent 3 is maintained at around 8.0.

[0041] Two types of feed water were prepared using deionized water for the second-stage start-up. Feed water 4 contained 153.85 mg / L CH3COONa and 40 mg / L NH4+. + -N, 9 mg / L PO4 3- The influent solution contained P, 60 mg / L CaCl2, 60 mg / L MgSO4·7H2O, 1000 mg / L KHCO3, and 1 ml / L trace elements, with the pH maintained at approximately 8.0; the influent solution contained NO3. - -N concentrate.

[0042] The composition of the trace element solution is the same as that in Example 1.

[0043] The specific steps for using the apparatus of this embodiment to quickly start the AOA process are as follows:

[0044] Traditional activated sludge was used as inoculum, with the inoculum volume accounting for 25% of the total reactor volume. After stirring, the total suspended solids in the resulting initial mixed liquor were 2500 mg / L, and the ratio of volatile suspended solids to total suspended solids (ρ(VSS) / ρ(SS)) in the initial mixed liquor was 0.4. The sequencing batch reactor was operated in an anaerobic / anoxic mode with a effluent ratio of 50%.

[0045] For the first four days, at the beginning of each anaerobic stage, influent 1 (containing no carbon source) was introduced into the reactor. Then, the stirring, sedimentation, and effluent processes were sequentially initiated. After the effluent from the anaerobic stage was completed, the reactor entered the anoxic stage. At the beginning of the anoxic stage, influent 3 (containing nitrate nitrogen) was introduced, followed by the sequential operation of stirring, sedimentation, effluent, and idle processes. During the first four days, the initial influent to the anaerobic stage contained no carbon source, and the reactor operated under short-term starvation conditions (C / N ratio of 0) to wash away miscellaneous bacteria from the sludge.

[0046] After washing, the reactor is operated in an anaerobic / anoxic manner. Simulated wastewater, primarily containing carbon sources, is introduced at the beginning of each anaerobic stage. After effluent discharge at the end of the anaerobic stage, the reactor enters the anoxic stage, where simulated wastewater primarily containing nitrates is introduced. During operation, the first stage startup is achieved by adjusting the carbon-to-nitrogen ratio of the carbon source added in the anaerobic stage, the duration of different stages, and the hydraulic retention time. In this embodiment, the specific procedures and influent process for the anaerobic / anoxic stages are as follows: At the beginning of the anaerobic stage, influent 1 and influent 2, i.e., influent containing carbon sources, are introduced. Then, stirring, sedimentation, and effluent discharge are initiated sequentially. The anaerobic stage is entered for the first time, with the C / N ratio set to 2.7 when adding the carbon source. The anaerobic / anoxic stage operates with mid-stage effluent discharge. After the anaerobic stage effluent discharge is completed, the reactor enters the anoxic stage. At the beginning of the anoxic stage, influent 3, i.e., influent containing nitrate nitrogen, is introduced. Then, stirring, sedimentation, effluent discharge, and idle processes are initiated sequentially. The anaerobic / anoxic cycle includes influent (influent 1 and influent 2) – stirring – sedimentation – effluent – ​​influent (influent 3) – stirring – sedimentation – effluent – ​​idle. During the intermediate drainage stage (after sludge sedimentation at the end of the anaerobic phase), phosphorus-rich wastewater is rapidly discharged to reduce the influent phosphorus concentration to 4-5 mg / L, thus minimizing competition between polyphosphate-accumulating bacteria and polysaccharide-accumulating bacteria. This process is cyclical, and the COD and NO3 levels at different stages of the reactor are monitored throughout the operation. - -N and NO2 --N concentration was monitored daily. During operation, the amount of carbon source added during the anaerobic stage was adjusted within a C / N ratio range of 2.7-3.5; the duration of different stages and hydraulic retention time were adjusted within a range of 1.5-2.5 hours for the anaerobic stage and 3-6 hours for the anoxic stage. Finally, with a C / N ratio of 3.0 and an operating cycle of 7 hours (1.5 hours for the anaerobic stage and 4 hours for the anoxic stage), the system was operated in an anaerobic / anoxic mode for a total of 21 days. The system was adjusted to achieve a nitrate removal rate of 95% and a nitrite accumulation rate of 55%, thus completing the start-up of the first stage of the endogenous short-cut denitrification system.

[0047] During operation, influent 1 is stored in influent tank 1, influent 2 is stored in carbon source influent tank 2, and influent 3 is stored in nitrate / nitrogen influent tank 3. At the initial stage of the anaerobic phase, influent 1 and influent 2 are introduced by opening influent valve 52 and chemical influent valve 54, and starting influent pump 6 and chemical influent pump 7 to deliver influent 1 and influent 2 into the reactor. During the anoxic phase, when influent 3 is introduced, influent valve 53 is opened, and influent pump 8 is started to deliver nitrate / nitrogen-containing influent 3 into the reactor.

[0048] (2) Based on step 1, some activated sludge and a small amount of anaerobic ammonia-oxidizing bacteria are inoculated. The volume of the inoculated sludge accounts for 30% of the total volume of the reactor. After the sludge is inoculated, it is stirred. The total suspended solids in the resulting mixture are about 3500 mg / L, and the ratio of volatile suspended solids to total suspended solids (ρ(VSS) / ρ(SS)) in the mixture is 0.5. The anaerobic / anoxic operation mode in step (1) is changed to the anaerobic / aerobic / anoxic operation mode. At the same time, the mid-term drainage mode is cancelled. The process of an anaerobic / aerobic / anoxic cycle in the early stage includes water inlet (water inlet 4) - stirring - sedimentation - stirring and aeration - sedimentation - water inlet (water inlet 5) - stirring - sedimentation - idle. During aeration, air is introduced into the reactor through air pump 56, and the air inlet volume is monitored by rotor flow meter 57. During operation, water inlet 4 is stored in water inlet tank 1, and water inlet 5 is stored in nitrate nitrogen inlet tank 3, which are used for water inlet in the early stage of anaerobic and the anoxic stage, respectively.

[0049] During the initial operation, over-aeration was used in the aerobic phase, and the dissolved oxygen concentration at the end of this phase was 1.75 mg / L. Simultaneously, a measured amount of concentrated nitrate solution (influent level 4) was added at the beginning of the anoxic phase to maintain the activity of polysaccharide-producing bacteria. The addition of nitrate reduced the NO3 content in the reactor at the beginning of the anoxic phase. -The -N concentration is 20 mg / L. Subsequently, when the nitrate nitrogen concentration exceeds 5 mg / L at the end of the anoxic stage, the influent flow rate of influent 4 is immediately reduced until influent 4 is completely removed. This results in a single-cycle influent / efluent mode. One cycle of the single-cycle influent / efluent mode is: influent (influent 4) – stirring – sedimentation – stirring and aeration – sedimentation – stirring – sedimentation – idle. After the nitrifying bacteria activity recovers, i.e., when influent 4 has been removed during the anoxic stage and there is no remaining ammonia nitrogen at the end of the anoxic stage, some NH4+ is added during the aerobic stage. + -N is converted to NO3 - -N and NO2 - -N, while polysaccharide bacteria utilize the internal carbon source PHA stored during the anaerobic stage to convert NO3- into NO3-. - -N is further converted into NO2 - -N and N2, part of NO2 - -N is then utilized by anaerobic ammonia oxidizing bacteria to remove some of the NH4+. + -N. At this point, the aeration rate is reduced according to the different nitrogen concentrations at the end of the aerobic stage, using the remaining NH4+ at the end of the aerobic stage. + -N cannot be completely removed through the anaerobic ammonia oxidation process in the anoxic stage, which is the critical point. The reduction of aeration rate is stopped, and the dissolved oxygen concentration is finally less than 0.5 mg / L at the end of the aerobic stage.

[0050] During operation, COD and NO3 were measured at different stages of the reactor. - -N、NH4 + -N and NO2 - The -N concentration was monitored daily. By adjusting the aeration rate, the duration of aerobic phases (not exceeding 1 / 4 of the entire cycle), and the hydraulic retention time, the AOA system was quickly started up with a C / N ratio of 3.0, a total nitrogen removal rate of 95%, and an operating cycle of 10 hours (1.5 hours of anaerobic phase, 2 hours of aerobic phase, and 6 hours of anoxic phase). In this embodiment, the start-up time was 30 days. Monitoring showed that after 15 days of operation, the total nitrogen removal rate was still above 95%, and the phosphorus removal rate reached 83%, achieving long-term stable operation. Comparative Example

[0051] This comparative example was conducted simultaneously with the experiment in Example 1, but the experimental setup differed. The main difference was that a batch-based targeted acclimatization strategy was not adopted. The specific initiation method in the comparative example is as follows:

[0052] (1) Inoculation with conventional activated sludge and anaerobic ammonia oxidizing bacteria: In a 5L SBR reactor, conventional activated sludge and some anaerobic ammonia oxidizing bacteria with good activity were inoculated to make the sludge concentration in the reactor 3500mg / L.

[0053] (2) Operate the reactor in an anaerobic / aerobic / anoxic mode. Before the anaerobic stage, introduce 2.5L of NH4 at a concentration of 40 mg / L. + -N, 9 mg / L PO4 3- The simulated wastewater consisted of P, 60 mg / L CaCl2, 60 mg / L MgSO4·7H2O, 1000 mg / L KHCO3, and a trace element solution of 1 ml / L, along with a suitable carbon source (5.64 g / L CH3COONa). The trace element solution composition was consistent with that in Example 1. After a 1.5-hour anaerobic phase, it entered a 2-hour aerobic phase, with the dissolved oxygen concentration controlled to be less than 0.5 mg / L at the end of the aerobic phase using a flow meter. Finally, it entered a 4-hour anoxic phase.

[0054] On the 6th day of reactor operation, nitrification began to appear in the aerobic stage, producing NO3. - Due to the low nitrogen content, no endogenous (short-cut) denitrification was observed in either the aerobic or anoxic phases. On day 17, nitrification stabilized and anaerobic ammonium oxidation occurred in the aerobic phase. However, due to the short duration of the aerobic phase and the NO2 produced by short-cut nitrification, [failure to observe the denitrification process]. - The amount of -N is low, and there is still a large amount of NH4 at the end of the aerobic stage. + -N and a small amount of NO3 - -N remained. On day 23, endogenous denitrification began to appear during the anoxic phase, but it was unable to eliminate the NO3 remaining from the end of the aerobic phase. - -N was completely removed. By day 55 of reactor operation, endogenous denitrification was significant, with a total nitrogen removal rate of 80% in the AOA system. By adjusting the aeration rate, carbon source addition, duration of different phases, and hydraulic retention time, a total nitrogen removal rate of 90% was finally achieved on day 68, with a C / N ratio of 3.5 and an operating cycle of 10 hours (1.5 hours anaerobic, 2 hours aerobic, and 6 hours anoxic), thus completing the startup of the AOA system. Compared to the comparative example, the method of batch-directed acclimation of traditional activated sludge in this invention for rapid AOA system startup significantly shortens the startup time.

[0055] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the claims.

Claims

1. A method for fast start-up of an AOA process, characterized by, Comprise: (1) inoculate activated sludge into the reactor, and run in a way of anaerobic / anoxic to enrich and domesticate glycan bacteria; In the early stage, the simulated wastewater without carbon source is introduced at the beginning of the anaerobic stage, and the washing of miscellaneous bacteria is completed by short-term starvation. Thereafter, the simulated wastewater mainly containing carbon source is introduced at the beginning of each anaerobic stage. The phosphate concentration in the simulated wastewater introduced at the beginning of the anaerobic stage is 4-5 mg / L, and the influent COD concentration of the simulated wastewater mainly containing carbon source is greater than or equal to 120 mg / L. After the drainage at the end of each anaerobic stage, the anoxic stage is entered. The simulated wastewater mainly containing nitrate is introduced at the beginning of the anoxic stage. The nitrate concentration of the simulated wastewater introduced in the anoxic stage is 35-50 mg / L. The key operation parameters are adjusted during the operation. The carbon source amount in the anaerobic stage is adjusted in the range of 2.7-3.5 of carbon-nitrogen ratio. The anaerobic stage time is adjusted in the range of 1.5-2.5 hours. The anoxic stage time is adjusted in the range of 3-6 hours. The system operation is adjusted until the nitrate removal rate is higher than 90% and the nitrite accumulation rate is higher than 50%, and the first stage start-up is completed. (2) inoculate activated sludge and anammox bacteria into the reactor, and run in a way of anaerobic / aerobic / anoxic. The simulated wastewater containing carbon source, ammonia nitrogen, inorganic salt and trace element is introduced as influent at the beginning of the anaerobic stage. The ammonia nitrogen concentration of the simulated wastewater is 35-50 mg / L. The phosphate concentration is 9-10 mg / L. The carbon-nitrogen ratio is the carbon-nitrogen ratio at the end of step (1). Nitrate is added in the anoxic stage. Over-aeration operation is adopted in the early stage of the aerobic stage. The dissolved oxygen concentration at the end of the aerobic process is controlled to be 1-2 mg / L. As the nitrification is enhanced, when the nitrate concentration at the end of the anoxic stage is higher than 5 mg / L, the nitrate addition amount in the anoxic stage is gradually reduced until it is reduced to 0. When the nitrate addition in the anoxic stage is stopped and there is no ammonia nitrogen left at the end of the anoxic stage, the aeration amount is gradually reduced. The critical point is that the residual ammonia nitrogen in the aerobic stage cannot be completely removed by the anoxic ammonium oxidation process in the anoxic stage. The aeration amount is stopped. The key operation parameters including aeration amount and time length of different stages are adjusted during the operation until the total nitrogen removal rate is higher than 95% and the phosphorus removal rate is higher than 80%, and the rapid start-up of the AOA system is completed.

2. The method for fast start-up of AOA process according to claim 1, wherein, In step (1), the volume of the inoculated sludge accounts for 20%-30% of the total volume of the reactor. In the initial mixed liquid formed by stirring, the total suspended solids are 2000-2500 mg / L. The mass ratio of volatile suspended solids to total suspended solids in the initial mixed liquid is 0.4-0.

7.

3. The method for fast start-up of AOA process according to claim 2, wherein, In step (1), the temperature in the reactor is controlled to be 29-31 ℃.

4. The method for fast start-up of AOA process according to any one of claims 1-3, characterized in that, In step (2), the volume of the inoculated sludge accounts for 30-40% of the total volume of the reactor. In the mixed liquid formed by stirring, the total amount of suspended solids is 2500-3000 mg / L. The mass ratio of volatile suspended solids to total suspended solids is 0.4-0.7.

Images