Device and method for rapidly enriching in-situ anaerobic iron ammonia oxidizing bacteria based on ammonia nitrogen and ferric iron substrate concentration regulation strategy

Abstract

The invention discloses a device and a method for rapidly enriching in-situ anaerobic iron ammonia oxidizing bacteria based on an ammonia nitrogen and ferric iron substrate concentration regulation strategy, and belongs to the technical field of biological sewage treatment. The invention aims to solve the technical problems of slow start and difficult in-situ enrichment of anaerobic iron ammonia oxidizing bacteria. The device mainly comprises a sequencing batch reactor, a wastewater storage tank and a water outlet tank. According to the method, the concentrations of ammonia nitrogen and ferric iron in inlet water are regulated and controlled by stages, and three stages of flora adaptation and starting, rapid enrichment under a low-concentration condition and internal iron circulation construction after the addition of exogenous iron is completely stopped are sequentially performed, so that the stable enrichment of the functional flora is finally realized. The whole process is operated under an anaerobic condition, aeration and additional organic carbon sources are not needed, and an efficient and controllable new technical scheme is provided for realizing low-carbon and energy-saving deep denitrification of urban sewage.

Description

Technical Field

[0001] This invention relates to an apparatus and method for the rapid enrichment of in-situ anaerobic iron-oxidizing bacteria based on a strategy of regulating the concentration of ammonia nitrogen and ferric substrate, belonging to the field of wastewater biological treatment technology. Background Technology

[0002] Against the backdrop of the global "carbon neutrality" strategy, urban wastewater treatment plants are transforming from traditional pollutant reduction facilities into low-carbon, energy-saving resource and energy recovery centers. Currently, the vast majority of wastewater treatment plants still rely on traditional nitrification-denitrification biological nitrogen removal processes. Although this process is technologically mature and operates stably, it involves huge aeration energy consumption, a high dependence on external carbon sources, and high greenhouse gas emissions, which has become a key technological bottleneck restricting wastewater treatment plants from achieving energy conservation, emission reduction, and carbon neutrality goals. Therefore, developing economical, efficient, and sustainable new nitrogen removal technologies is crucial for promoting the green transformation of the industry.

[0003] To overcome the drawbacks of traditional processes, autotrophic nitrogen removal technologies, represented by anammox, have become a research hotspot due to their significant advantages such as requiring no organic carbon source, low energy consumption, and low sludge production. Building on this, anammox (Feammox) technology, as an emerging autotrophic nitrogen removal pathway, shows great application potential. This process utilizes iron, a widely available and inexpensive element in nature, as an electron acceptor, coupling the oxidation of ammonia nitrogen under anaerobic conditions to achieve nitrogen removal. Especially under the neutral pH and low C / N ratio conditions common in urban wastewater, Feammox can effectively remove nitrogen, providing a novel low-carbon technology option for wastewater treatment.

[0004] However, anaerobic iron ammonia oxidation technology is still in the early stages of laboratory research, and its large-scale engineering application faces severe challenges. Its core functional microorganisms are mostly anaerobic bacteria with long generation cycles and extremely slow growth rates, making reactor start-up and the enrichment of functional microbial communities exceptionally difficult and time-consuming. Therefore, developing a method for rapid and stable in-situ enrichment of anaerobic iron ammonia oxidizing bacteria has become a key technical problem urgently needing to be solved in this field.

[0005] Based on the above research, this invention provides an apparatus and method for the rapid enrichment of anaerobic iron-oxidizing bacteria in situ based on a strategy of regulating the concentrations of ammonia nitrogen and ferric iron substrates, in order to promote the practical application of anaerobic iron oxidation in wastewater denitrification. Summary of the Invention

[0006] The purpose of this invention is to address the key technical bottlenecks in existing technologies, such as the difficulty and long start-up period of in-situ enrichment of anaerobic iron-oxidizing bacteria (Feammox) in wastewater treatment reactors, by providing a device and method for rapid in-situ enrichment of Feammox based on a substrate concentration control strategy of ammonia nitrogen and ferric iron. This invention aims to rapidly and stably screen and enrich functional bacterial communities in a sequencing batch reactor (SBR) through a staged substrate control scheme, ultimately constructing a low-carbon, energy-saving wastewater treatment system capable of achieving efficient and stable nitrogen removal through internal iron circulation.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A device for rapid enrichment of in-situ anaerobic iron-oxidizing bacteria based on a strategy of regulating the concentration of ammonia nitrogen and ferric substrate, the device comprising: a sequencing batch reactor (1), an artificial wastewater storage tank (2), and an effluent tank (3).

[0009] The sequencing batch reactor is equipped with an inlet (6), an outlet (8), a stirrer (12), an online pH measuring probe (9), an online DO measuring probe (10), and a heating device (13). In addition, the sequencing batch reactor is equipped with an automatic control system, which consists of a computer (15) and a process controller (16) electrically connected to it. The automatic control system is electrically connected to the peristaltic pump (4), the inlet valve (5), the outlet valve (7), and the stirrer (12) to control the peristaltic pump (4), the inlet valve (5), the outlet valve (7), and the stirrer (12).

[0010] The outlet tank (3) is connected to the outlet (8) of the sequencing batch reactor via a drain valve (7); the pH online measuring probe (9) and DO online measuring probe (10) installed on the sequencing batch reactor are both connected to the main unit (11) of the online parameter measuring instrument.

[0011] The artificial wastewater storage tank (2) is connected to the inlet (6) of the sequencing batch reactor (1) by a peristaltic pump (4) and an inlet valve (5); the outlet tank (3) is connected to the outlet (8) of the sequencing batch reactor by a drain valve (7); the nitrogen cylinder (14) is inserted into the underwater space of the artificial wastewater storage tank (2) through a valve and a pipe.

[0012] A method for rapid in-situ enrichment of anaerobic iron-oxidizing bacteria based on the above-mentioned device, characterized by comprising the following steps:

[0013] Operation of the sequencing batch reactor: Each cycle of reactor operation includes five processes: influent, agitation, sedimentation, effluent discharge, and idle. Before influent, the artificial wastewater is aerated using nitrogen cylinders to ensure that its DO is below 0.01 mg / L. The influent time is controlled at 8-10 minutes. During influent, the agitator is turned on, and the sludge uses ferric iron as an electron acceptor to oxidize ammonia nitrogen. The agitation time is adjusted according to the ammonia nitrogen concentration of the influent at different stages. The sedimentation time is controlled at 10-30 minutes. During effluent discharge, the drain valve is opened, and the discharge time is controlled at 5-10 minutes. The idle time is controlled at 60 minutes. The operation of subsequent stages follows the above method, only changing the agitation reaction time.

[0014] During the operation of each of the following stages, the sequencing batch reactors are operated continuously in the periodic manner defined above (i.e., water intake, stirring, sedimentation, drainage, and idle) until the technical indicators or number of operating days set for the corresponding stage are met. Only the set parameters (such as stirring time, water composition, etc.) within each cycle of each stage are different.

[0015] 1) First stage, reactor inoculation and adaptation cultivation: Anaerobic sludge and anaerobic ammonia oxidation sludge from the anaerobic zone of a municipal wastewater treatment plant are inoculated into the sequencing batch reactor (SBR) at a volume ratio of 1:1. After inoculation, the total sludge concentration in the reactor is 3000-4000 mg / L. Artificial wastewater is used for influent cultivation, with the ammonia nitrogen concentration controlled at 60 mgN / L and the ferric iron concentration controlled at 90 mgFe / L. Ferric chloride is used to prepare the influent, which is then introduced into the SBR through the influent valve. During operation, the heating device is turned on to maintain the reactor water temperature at 25-28℃. Sufficient sodium bicarbonate is added to provide alkalinity for the anaerobic ammonia oxidation process, while simultaneously controlling the initial alkalinity of the reactor. The initial pH is in the range of 7.5-8.0. During this stage, the stirring time of the reactor is adjusted to 72 hours per cycle. In the initial stage (which can be considered the first few cycles), feedwater containing ferric iron is continuously added until the concentration of bioavailable ferric iron in the reactor accumulates to 500-700 mg Fe / L. Then, the strategy of continuously adding ferric iron is stopped, and the operation mode of intermittent addition of ferric iron is changed. The intermittent addition of ferric iron mode is as follows: when the ammonia nitrogen conversion rate decreases, a higher concentration of ferric iron is added to the feedwater in subsequent cycles. In this case, the concentration of ferric iron in the feedwater is increased to 90 mg Fe / L. The operation continues until the ammonia nitrogen removal rate of the system is stable and the removal rate is >65%. This is considered as successful adaptation of the microbial community and start-up of the process, and the next stage begins.

[0016] 2) Second stage: In-situ rapid enrichment of functional microbial communities: The influent ammonia nitrogen concentration is reduced to 20 mgN / L, and the ferric iron concentration is correspondingly reduced to 20 mgFe / L, and the addition is resumed with the influent. The alkalinity of the system is controlled at 400-450 mg / L using sodium bicarbonate, and the pH of the reaction system is controlled within the range of 7.3-7.5. In this stage, the stirring time of the reactor is adjusted to 48 h for each operating cycle. Screening and enhanced cultivation are carried out under this low concentration ammonia nitrogen substrate condition until the ammonia nitrogen removal rate of the system is stable and greater than 90%. This is considered as the core functional microbial communities have achieved efficient in-situ enrichment, and the next stage begins.

[0017] 3) The third stage is the construction and stabilization of the internal iron circulation system: the addition of external ferric iron is completely stopped, that is, the concentration of ferric iron in the influent is 0, so that the system relies entirely on the iron source accumulated in the sludge for the reaction. At the same time, the concentration of ammonia nitrogen in the influent is gradually increased from 20 mgN / L to 40 mgN / L, and the alkalinity of the system is increased from 400-450 mg / L in the second stage to 800-900 mg / L according to the ammonia nitrogen load. The pH of the reaction system is controlled within the range of 7.5-8.0. The stirring time of the reactor in each cycle is adjusted to 48h in this stage. The system is operated until the ammonia nitrogen removal rate is stable and greater than 90% under the condition of no external addition, and it has been running stably for more than 100 days. The internal iron circulation system is considered to have been successfully constructed.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] 1) Achieved rapid in-situ enrichment of microbial communities: Through a three-stage regulation strategy of "high concentration adaptation - low concentration enrichment - iron-free stabilization", the start-up and enrichment cycle of functional microbial communities in the reactor was significantly shortened, solving the core problem of slow start-up of the process.

[0020] 2) The method is clear and highly operable: A complete and parameter-defined staged control method is proposed, which provides a clear technical route for the stable construction and operation of the Feammox process and is highly operable.

[0021] 3) Achieved stable operation with zero iron source addition: Ultimately, a self-sufficient system relying on internal iron circulation was constructed, which significantly reduced the cost and operational complexity of long-term operation and laid the foundation for engineering applications.

[0022] 4) The process has obvious advantages in low carbon and energy saving: the whole process is carried out under anaerobic conditions and no aeration is required; the use of inorganic trivalent iron as an electron acceptor eliminates the need for an external organic carbon source, which is in line with the development direction of carbon neutrality in wastewater treatment plants. Attached Figure Description

[0023] Figure 1A schematic diagram of a device for the rapid enrichment of in-situ anaerobic iron-oxidizing bacteria based on a strategy of regulating the concentration of ammonia nitrogen and ferric iron substrate.

[0024] Figure 1 In the middle: 1-Sequencing batch reactor, 2-Artificial wastewater storage tank, 3-Outlet tank, 4-Peristaltic pump, 5-Inlet valve, 6-Inlet, 7-Drain valve, 8-Outlet, 9-pH online measurement probe, 10-DO online measurement probe, 11-Online parameter measuring instrument host, 12-Agitator, 13-Heating device, 14-Nitrogen cylinder, 15-Computer, 16-Process controller. Detailed Implementation

[0025] Combination Figure 1 The specific implementation methods of the present invention are as follows:

[0026] Figure 1 A schematic diagram of an in-situ anaerobic iron-oxidizing bacteria rapid enrichment device based on a strategy of controlling the concentration of ammonia nitrogen and ferric iron substrate is given. The device includes: a sequencing batch reactor (1), an artificial wastewater storage tank (2), and an effluent tank (3); the artificial wastewater storage tank (2) is connected to the inlet (6) of the sequencing batch reactor (1) by a peristaltic pump (4) and an inlet valve (5); the effluent tank (3) is connected to the outlet (8) of the sequencing batch reactor (1) by a drain valve (7); a nitrogen cylinder (14) is connected to the sequencing batch reactor (1); the upper part of the sequencing batch reactor is equipped with an online pH measurement probe (9) and an online DO measurement probe (10) connected to the main unit (11) of an online parameter measuring instrument.

[0027] The sequencing batch reactor is equipped with an inlet (6), an outlet (8), a stirrer (12), an online pH measuring probe (10), an online DO measuring probe (11), and a heating device (13). In addition, the sequencing batch reactor is equipped with an automatic control system, which consists of a computer (15) and a process controller (16) connected to it, used to control the peristaltic pump (4), the inlet valve (5), the outlet valve (7), and the stirrer (12).

[0028] A method for rapid in-situ enrichment of anaerobic iron-oxidizing bacteria based on the above-mentioned device, with a specific implementation scheme:

[0029] Operation of the sequencing batch reactor (SBR): The reactor operation includes five processes: influent, agitation, sedimentation, effluent discharge, and idle. Before influent, the artificial wastewater is aerated using nitrogen cylinders to ensure that its dissolved oxygen (DO) is below 0.01 mg / L. The influent time is controlled at 10 minutes, during which the agitator is turned on. The sludge uses ferric iron as an electron acceptor to oxidize ammonia nitrogen. The agitation time is adjusted according to the different influent ammonia nitrogen concentrations. The sedimentation time is controlled at 25 minutes. During effluent discharge, the drain valve is opened, and the discharge time is controlled at 5 minutes. The idle time is controlled at 60 minutes. Subsequent stages are operated in the same manner, only the agitation reaction time is changed.

[0030] During the operation of each of the following stages, the sequencing batch reactors operate continuously in the aforementioned periodic manner (i.e., water intake, stirring, sedimentation, drainage, and idle) until the technical indicators or operating days set for that stage are met. Only the set parameters (such as stirring time, water composition, etc.) within each cycle of each stage are different.

[0031] 1) Reactor inoculation and adaptation culture: Anaerobic sludge and anaerobic ammonia oxidation sludge from the anaerobic zone of the municipal wastewater treatment plant were inoculated into the sequencing batch reactor at a volume ratio of 1:1. The sludge concentration in the reactor after inoculation was 3000-4000 mg / L. Artificial wastewater was used for cultivation, with ammonia nitrogen concentration controlled at 60 mgN / L and ferric iron concentration controlled at 90 mgFe / L. Ferric chloride was used for preparation and introduced into the sequencing batch reactor (SBR) via the inlet valve. During operation, the heating device was activated to maintain the reactor water temperature at 25-28℃. Sufficient sodium bicarbonate was added to provide alkalinity for the anaerobic iron ammonia oxidation process, while simultaneously controlling the initial pH of the reactor within the range of 7.5-8.0. The reactor stirring time was adjusted to 72 hours during this stage. Initially, ferric iron was continuously added until the bioavailable ferric iron concentration in the reactor accumulated to 500-700 mgFe / L. Then, the continuous addition of ferric iron was stopped, and an intermittent addition mode was adopted. When the ammonia nitrogen conversion rate decreased, 90 mgFe / L of ferric iron was added again in the next cycle. When the ammonia nitrogen removal rate of the system was consistently >65%, the microbial community adaptation and process start-up were considered successful, and the process proceeded to the next stage.

[0032] 2) Rapid in-situ enrichment of functional microbial communities: The influent ammonia nitrogen concentration was reduced to 20 mg N / L, and the ferric iron concentration was correspondingly reduced to 20 mg Fe / L, and the addition was resumed as a continuous addition with the influent. The alkalinity of the system was controlled at 400 mg / L using sodium bicarbonate, and the pH of the reaction system was controlled within the range of 7.3-7.5. The stirring time of the reactor was adjusted to 48 h during this stage. Under these low-concentration substrate conditions, the ammonia nitrogen removal rate of the system was consistently greater than 90%, and the core functional microbial communities were efficiently enriched in situ, moving into the next stage.

[0033] 3) Construction and stabilization of the internal iron circulation system: Completely stop the addition of external ferric iron, so that the system relies entirely on the iron source accumulated in the sludge for the reaction. At the same time, gradually increase the influent ammonia nitrogen concentration from 20 mgN / L to 40 mgN / L, and correspondingly increase the system alkalinity from 400 mg / L to 800 mg / L according to the ammonia nitrogen load. The pH of the reaction system is controlled within the range of 7.5-8.0. The stirring time of the reactor is adjusted to 48h during this stage. When the ammonia nitrogen removal rate is stably greater than 90% under the condition of no external addition and the system has been running stably for more than 100 days, the internal iron circulation system is successfully constructed.

[0034] In the final stage of this embodiment, the reactor operated continuously and stably for 100 days under conditions of no external iron addition and an influent ammonia nitrogen concentration of 40 mgN / L. During this period, the effluent ammonia nitrogen concentration remained below 2 mg / L, and the average ammonia nitrogen removal rate reached 97.5%, indicating that the method described in this invention can successfully achieve in-situ rapid enrichment of anaerobic iron-oxidizing bacteria and construct an efficient and stable internal iron circulation denitrification system.

Claims

1. A device for in-situ rapid enrichment of anaerobic iron-oxidizing bacteria based on ammonia nitrogen and trivalent iron substrate concentration regulation strategy, characterized in that, It comprises: a sequencing batch reactor (1), an artificial wastewater storage tank (2), and a water outlet tank (3); The sequencing batch reactor is provided with a water inlet (6), a water outlet (8), a stirrer (12), an on-line pH measuring probe (9), an on-line DO measuring probe (10), and a heating device (13). In addition, the sequencing batch reactor is provided with an automatic control system, which is composed of a computer (15) and a process controller (16) electrically connected thereto. The automatic control system is electrically connected with the peristaltic pump (4), the water inlet valve (5), the water outlet valve (7), and the stirrer (12) to control the peristaltic pump (4), the water inlet valve (5), the water outlet valve (7), and the stirrer (12); The water outlet tank (3) is connected with the water outlet (8) of the sequencing batch reactor through the water outlet valve (7). The on-line pH measuring probe (9) and the on-line DO measuring probe (10) provided on the sequencing batch reactor are both connected with an on-line parameter measuring instrument host (11). The artificial wastewater storage tank (2) is connected with the water inlet (6) of the sequencing batch reactor by the peristaltic pump (4) and the water inlet valve (5). The water outlet tank (3) is connected with the water outlet (8) of the sequencing batch reactor through the water outlet valve (7). A nitrogen cylinder (14) extends into the artificial wastewater storage tank (2) underwater through a valve and a pipeline.

2. A method for in-situ rapid enrichment of anaerobic iron-ammoxying bacteria using the apparatus of claim 1, characterized in that, The following steps are included: Operation of the sequencing batch reactor: Each cycle of the reactor operation includes water inlet, stirring, sedimentation, water outlet, and idling. Before water inlet, the artificial wastewater is aerated by the nitrogen cylinder to ensure that the DO is lower than 0.01 mg / L. The water inlet time is controlled within 8-10 min. The stirrer is turned on during water inlet. The sludge uses ferric ions as an electron acceptor to oxidize ammonia nitrogen. The stirring time is adjusted according to the ammonia nitrogen concentration of the water inlet at different stages. The sedimentation time is controlled within 10-30 min. The water outlet valve is turned on during water outlet. The water outlet time is controlled within 5-10 min. The idling time is controlled within 60 min. The operation mode of the subsequent different stages is operated in the above-mentioned manner, and only the stirring reaction time is changed. During the operation of each stage, the sequencing batch reactor is continuously operated in the periodic manner defined above until the technical indicators or the operation days set for the corresponding stage are met. 1) The first stage, reactor inoculation and adaptive culture: The anaerobic sludge and anaerobic anammox sludge from the anaerobic zone of a municipal wastewater treatment plant were inoculated into the sequencing batch reactor at a volume ratio of 1:1, and the total sludge concentration in the reactor was 3000-4000 mg / L after inoculation. Artificial wastewater was used for influent culture, wherein the ammonia nitrogen concentration of the artificial wastewater was controlled at 60 mgN / L, and the ferric iron concentration was controlled at 90 mgFe / L, which was prepared by ferric chloride and entered the sequencing batch reactor through the influent valve. During the operation period, the heating device was turned on to control the water temperature in the reactor at 25-28℃. A sufficient amount of sodium bicarbonate was added to provide alkalinity for the anaerobic iron ammonia oxidation process, and the initial pH in the reactor was controlled in the range of 7.5-8.

0. The stirring time of the reactor was adjusted to 72 h for each cycle in this stage. The initial period continued to add influent containing ferric iron, and after the concentration of bioavailable ferric iron in the reactor accumulated to 500-700 mgFe / L, the strategy of continuous addition of ferric iron was stopped, and the intermittent addition mode of ferric iron was changed. The intermittent addition mode of ferric iron was: when the ammonia nitrogen conversion rate decreased, higher concentration of ferric iron was supplemented in the subsequent cycle, wherein the ferric iron concentration in the influent was increased to 90 mgFe / L, and the operation was continued until the ammonia nitrogen removal rate of the system was stable and the removal rate was >65%, which was considered as the success of the adaptation of the bacterial community and the start-up of the process, and the next stage was entered; 2) The second stage, in-situ rapid enrichment of functional bacterial community: The ammonia nitrogen concentration of the influent was lowered to 20 mgN / L, the ferric iron concentration was correspondingly lowered to 20 mgFe / L, and the mode of continuous addition with the influent was restored. The alkalinity of the system was controlled at 400-450 mg / L by sodium bicarbonate, and the pH of the reaction system was controlled in the range of 7.3-7.

5. In this stage, the stirring time of the reactor was adjusted to 48 h for each operation cycle. Under the condition of low concentration of ammonia nitrogen substrate, screening and intensive culture were carried out, and when the ammonia nitrogen removal rate of the system was stable and greater than 90%, it was considered that the core functional bacterial community had achieved efficient in-situ enrichment, and the next stage was entered; 3) The third stage, construction and stabilization of the internal iron cycle system: The addition of external ferric iron was completely stopped, i.e. the ferric iron concentration in the influent was 0, so that the system completely relied on the accumulated iron source in the sludge for reaction, and at the same time, the ammonia nitrogen concentration of the influent was gradually increased from 20 mgN / L to 40 mgN / L, and the alkalinity of the system was increased from 400-450 mg / L in the second stage to 800-900 mg / L according to the ammonia nitrogen load, and the pH of the reaction system was controlled in the range of 7.5-8.

0. The stirring time of the reactor was adjusted to 48 h for each cycle in this stage. When the ammonia nitrogen removal rate of the system was stable and greater than 90% under the condition of no external addition, and the continuous stable operation was more than 100 days, it was considered that the internal iron cycle system was successfully constructed.

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