A method for realizing stable operation of a continuous-flow short-cut denitrification reactor

Abstract

The application discloses a method for realizing stable operation of a continuous flow short-range denitrification reactor, which utilizes the short-range denitrification reactor to perform short-range denitrification treatment on nitrate nitrogen in sewage, so as to realize stable accumulation of nitrite, and comprises the following steps: introducing nitrate wastewater and a carbon source into a reactor inoculated with activated sludge to perform continuous flow treatment; the short-range denitrification reactor is rapidly started by adding alkali into the influent to increase pH; after the reactor is successfully started, the high-pH regulation is cancelled, the high pH of the system is maintained by using the alkalinity generated by the denitrification, so that the stable operation of the short-range denitrification reactor is realized. The application only needs to regulate the pH for a short period during the starting stage of the reactor, and in the subsequent operation process, the self-alkalization of the reactor is completely relied on, so that the rapid starting and stable operation of the continuous flow short-range denitrification reactor can be realized, and a large amount of starting time and operation cost is saved for actual engineering application.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment, and in particular to a method for achieving stable operation of a continuous flow short-path denitrification reactor. Background Technology

[0002] Anaerobic ammonia oxidation (AAO) refers to the reaction under anaerobic conditions in which anaerobic ammonia-oxidizing bacteria directly convert ammonia nitrogen and nitrite nitrogen into nitrogen gas and produce a small amount of nitrate nitrogen using inorganic carbon sources. It is considered a revolutionary alternative to traditional nitrification-denitrification processes. However, AAO still faces some challenges in its widespread practical application, one of the bottlenecks being the efficient and stable supply of nitrite substrates. Short-cut denitrification controls the four-step denitrification reaction at the first stage of nitrate nitrogen reduction to nitrite by controlling reaction conditions, thus providing substrates for AAO. Because short-cut denitrification can stably and efficiently produce NO2... - Furthermore, it can reduce the generation of N2O intermediates. Compared with traditional denitrification processes, short-cut denitrification processes have the following advantages: (1) reduced carbon source usage; (2) reduced organic carbon consumption, which also reduces the generation of excess sludge; (3) no NO2. - The reduction of nitrogen oxides can also reduce the risk of N2O emissions. Therefore, the economical, stable, and efficient short-range denitrification technology has attracted increasing attention from scholars and has good application prospects in providing substrates for anaerobic ammonia oxidation.

[0003] However, in practical applications, short-cut denitrification faces challenges such as long start-up times and unstable nitrite accumulation. The key to stable nitrite accumulation is controlling the reduction of nitrate nitrogen to produce only nitrite as the final product, preventing further nitrite reduction. The electron competition between nitrate reductase Nar and nitrite reductase Nir in the system is crucial to this process. Studies show that Nir is highly sensitive to pH, with an optimal pH range of 5.8 to 7; excessively high or low pH levels will deactivate it. When the reactor pH increases from 7.2 to 9, Nir activity is significantly affected, while Nar activity is less affected; high pH conditions favor nitrite accumulation. Therefore, maintaining the reactor system pH is essential for stable operation of short-cut denitrification. However, adjusting the influent pH throughout the entire operation will significantly increase the operating cost of short-cut denitrification. Without pH adjustment, the nitrite accumulation capacity of short-cut denitrification will significantly decrease. Therefore, achieving stable nitrite accumulation by maintaining a stable pH to inhibit nitrite reductase in the treatment of nitrate wastewater is key to the stable operation of the system.

[0004] To ensure the stable operation of short-range denitrification systems, some control methods have been disclosed.

[0005] For example, in Yang Anming's paper "A Short-Cut Denitrification Reactor and a Rapid Start-up Method for a Short-Cut Denitrification Process" (CN106477720A), this invention proposes a short-cut denitrification reactor and a rapid start-up method for short-cut denitrification, using an automatic control system to achieve the start-up and operation of short-cut denitrification. This includes an automatic pH adjustment system consisting of an automatic pH controller and a dosing tank, a dosing pump, and an online pH meter connected to the controller. Simultaneously, it integrates with the influent pump and an online NO3... - An automated reactor operating system, controlled by a -N analyzer, temperature controller, solenoid valve, and pH automatic adjustment controller, enables rapid start-up of short-cut denitrification. However, this method involves complex control conditions and strict temperature and pH regulation, increasing operating costs in subsequent processes, thus making it unsuitable for widespread application in practical engineering.

[0006] If short-cut denitrification can be rapidly started up through simple control and pH adjustment during operation can be reduced, it will save significant costs for practical engineering applications and make the engineering of short-cut denitrification technology easier. Furthermore, through the self-alkalization of short-cut / full-cut denitrification, the alkali produced during short-cut / full-cut denitrification raises the pH, thereby inhibiting nitrite-reducing bacteria and achieving stable nitrite accumulation. This allows the short-cut denitrification system to achieve self-equilibrium without pH adjustment during operation. Summary of the Invention

[0007] In view of the shortcomings of existing technologies, the technical problem to be solved by this invention is that existing short-cut denitrification reactors typically require long-term pH control throughout the entire operation to inhibit nitrite reductase activity. This leads to high operating costs and the inhibition of nitrate reduction due to inaccurate pH control. This invention provides a method for achieving stable operation of a continuous-flow short-cut denitrification reactor. During short-cut denitrification operation, the reactor generates its own alkalinity to self-inhibit nitrite reductase. This self-alkalization process maintains the reactor's high pH and the self-equilibrium of short-cut denitrification, thereby achieving stable operation of the short-cut denitrification reactor.

[0008] To achieve the above objectives, the technical solution of the present invention is as follows:

[0009] A method for achieving stable operation of a continuous flow short-path denitrification reactor, characterized by comprising the following steps:

[0010] S1. Startup Phase:

[0011] Nitrate wastewater and carbon source are introduced into a reactor inoculated with activated sludge, so that the microorganisms in the activated sludge can use these carbon sources as electron donors to reduce nitrate.

[0012] Adjust the influent pH to a high level to achieve rapid start-up of the short-cut denitrification reaction;

[0013] S2. Self-alkalization maintenance stage:

[0014] After the reactor is successfully started up, manual pH adjustment is stopped, and the pH value of the system is maintained by the alkalinity generated by the short-range denitrification reaction itself.

[0015] S3. Regulation and Supplementation Phase:

[0016] If short-range denitrification and self-alkalization alone are insufficient to maintain the stable accumulation of nitrite, then by adjusting the COD / NO3--N ratio in the system, the full-process denitrification reaction can be promoted to generate more alkalinity and further increase the pH value of the system, thereby achieving stable accumulation of nitrite.

[0017] Furthermore, the short-term high pH control allows for rapid start-up of the short-range denitrification reactor in 10-20 days.

[0018] Furthermore, after the short-cut denitrification reactor was successfully started up quickly, the nitrite accumulation rate of the system was maintained at 42%-67%.

[0019] Furthermore, the process of maintaining stable nitrite accumulation in the short-cut denitrification self-alkalization system is achieved by removing pH control after the nitrite accumulation becomes unstable during operation, and the alkalinity generated by short-cut denitrification maintains the pH above 8.5, thereby inhibiting nitrite-reducing bacteria.

[0020] Furthermore, the process of maintaining the pH of the system through the self-alkalization of the entire denitrification process is achieved by regulating the system's COD / NO3 ratio. - With -N = 5, denitrification occurs throughout the process, generating alkalinity. This causes the system pH to rise back above 8.5, inhibiting nitrite-reducing bacteria, and then the control is removed.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] This invention provides a method for achieving stable operation of a continuous flow short-cut denitrification reactor, proposing to utilize a self-alkalization process to maintain the self-equilibrium of short-cut denitrification, thereby achieving stable operation of the short-cut denitrification reactor.

[0023] (1) This invention only requires short-term high pH control in the early stage of operation to achieve rapid start-up of short-range denitrification.

[0024] (2) After successful startup, the high pH control is cancelled and the carbon source addition is increased. The short-range denitrification is transformed into full-range denitrification. At the same time, the self-alkalization process of denitrification provides alkalinity to the reactor and inhibits the activity of nitrite reductase, thereby ensuring the stable operation of the system and saving a lot of costs for practical engineering applications.

[0025] (3) Previous operating data shows that without adjusting the influent pH, nitrite reduction may occur in the reactor, leading to full nitrification, which is not conducive to achieving short-cut denitrification. This invention adopts a self-alkalization strategy to maintain the reactor pH within a suitable range, which can effectively alleviate the above problems.

[0026] Combining the three advantages mentioned above, this invention achieves rapid start-up of short-cut denitrification by initially adjusting the pH to a high level. After removing the high pH control, when nitrite accumulation becomes unstable, the pH rises through a self-alkalization process, thereby inhibiting nitrite-reducing bacteria and achieving stable nitrite accumulation and stable operation of the short-cut denitrification reactor. This significantly reduces the cost of pH control. It facilitates the large-scale application of short-cut denitrification technology for nitrite reduction in the future.

[0027] The following will further explain the concept, specific structure, and technical effects of the present invention in conjunction with the accompanying drawings, so as to fully understand the purpose, features, and effects of the present invention. Attached Figure Description

[0028] Figure 1 A preferred embodiment of the present invention provides a method for achieving stable operation of a continuous flow short-cut denitrification reactor. In the initial startup phase, the addition of alkali and carbon sources reduces the influent COD / NO3 ratio. - During the adjustment of -N and pH, the influent COD / NO3 - Schematic diagram showing the changes in -N and reactor temperature;

[0029] Figure 2 This invention provides a preferred embodiment of a method for achieving stable operation of a continuous flow short-path denitrification reactor. The invention utilizes pH and COD / NO3... - A schematic diagram showing the nitrate nitrogen concentration and nitrate nitrogen removal efficiency in the reactor influent and effluent during the rapid start-up of short-cut denitrification using the -N control strategy.

[0030] Figure 3 This invention provides a preferred embodiment of a method for achieving stable operation of a continuous flow short-path denitrification reactor. The invention utilizes pH and COD / NO3... - A schematic diagram of nitrite nitrogen concentration and nitrite accumulation rate in the reactor influent and effluent during the rapid start-up of short-cut denitrification using the -N control strategy.

[0031] Figure 4 This is a schematic diagram of the nitrite nitrogen concentration and nitrite accumulation rate in the influent and effluent of the reactor during operation after successful startup of a method for achieving stable operation of a continuous flow short-path denitrification reactor according to a preferred embodiment of the present invention, as well as the nitrite accumulation situation after the reactor becomes unstable and the nitrite accumulation in the reactor is stabilized again through a self-alkalization process.

[0032] Figure 5 This is a schematic diagram illustrating the pH changes of influent and effluent during the entire operation process of a method for achieving stable operation of a continuous flow short-path denitrification reactor, which is a preferred embodiment of the present invention, including the rapid start-up phase and the stable operation phase.

[0033] Figure 6 This is a schematic diagram of a method for achieving stable operation of a continuous flow short-path denitrification reactor according to a preferred embodiment of the present invention. Detailed Implementation

[0034] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0035] A method for achieving stable operation of a continuous flow short-path denitrification reactor includes the following steps:

[0036] The short-cut denitrification reactor is rapidly started up by short-term high pH control of the influent and the addition of a carbon source. Initially, sodium carbonate is added to the influent to regulate the pH, which is then set between 8.5 and 9. An automatic alkali addition method is used to maintain the pH between 8.5 and 9. Additionally, a carbon source is added to the reactor via a dosing tank, using sodium acetate to maintain the influent COD / NO3 ratio. - -N is around 3.

[0037] Specifically as follows:

[0038] After nitrate-containing wastewater is fed into the reactor, to achieve stable nitrite accumulation during short-cut denitrification, nitrite reductase is inhibited by adjusting the pH to a high level, thereby achieving short-cut denitrification. An automatic alkali addition strategy is employed to maintain the pH between 8.5 and 9. Simultaneously, the reactor's heat recovery time (HRT) is maintained at 4 hours.

[0039] During reactor operation, COD / NO3 ratio was maintained by adding sodium acetate. - -N is around 3. Meanwhile, temperature has little effect on short-cut denitrification; therefore, temperature is not controlled during reactor operation, and the temperature varies with room temperature during operation. Figure (1) shows the COD / NO3 ratio during reactor startup. - -N and temperature conditions.

[0040] Through the above strategies, rapid start-up of short-cut denitrification was achieved. As shown in Figure (2), the influent nitrate nitrogen concentration was between 30-40 mg / L. On the first day of short-cut denitrification start-up with high pH control, the effluent nitrate nitrogen concentration was 1.1 mg / L, and the NRE reached 96.8%, indicating that the reactor had good denitrification performance. Within 1-18 days of reactor operation, there was basically no remaining nitrate nitrogen in the effluent, and the average nitrate nitrogen removal rate was 96.6%.

[0041] As shown in Figure (3), the reactor had a nitrite accumulation of 20.4 mg / L on the first day of startup, and the nitrite accumulation rate reached 55%. During the 1-18 days of high pH control, the nitrite accumulation rate was maintained at 42.8%-67.3%, and the short-cut denitrification reactor started up rapidly within 18 days.

[0042] Example 2

[0043] This invention uses a CSTR reactor, which was successfully started up and able to operate stably after 18 days of operation, exhibiting good nitrate removal performance and nitrite accumulation performance. To study the reactor's operation after removing the high pH control, i.e., the nitrite accumulation, and the effect of self-alkalization on maintaining the stable operation of the short-cut denitrification reactor, the high pH control in the reactor was removed on the 19th day of operation, and the pH of the water distribution tank was maintained at around 7.7. At this time, the inhibitory effect of the influent pH on nitrite reductase decreased, as shown in Figure (4). After 8 days of stable operation, the accumulation of nitrite nitrogen gradually began to deteriorate, and the nitrite accumulation rate gradually decreased from an average of 52.6% to 11.1%. On the 30th day, the effluent had only 3.9 mg / L of nitrite accumulation.

[0044] After removing the high pH control, the influent pH was around 7.7, but the effluent pH was generally greater than 8.0. This is because denitrification is an alkali-producing process. During the 8-day stable short-cut denitrification process, the pH of the reactor effluent increased due to the generation of alkalinity.

[0045] Meanwhile, after the reactor had been running stably for 8 days, increasing the amount of carbon source added to the influent reduced the COD / NO3 ratio. --N is maintained at around 5. At this time, short-cut denitrification is transformed into full-cut denitrification. Due to the increase in carbon source, nitrite-reducing bacteria use organic carbon source to gradually reduce nitrite to nitrogen gas, thereby reducing the nitrite accumulation rate in the reactor. At the same time, due to the denitrification process and the reduction of nitrite, the pH in the reactor increases, thus providing an alkaline environment for inhibiting nitrite reductase and gradually restoring nitrite accumulation. As shown in Figure (5), during the stage of deterioration of nitrite accumulation performance in the reactor, due to the production of alkali by denitrification, the pH of the reactor effluent rises to around 8.5. After running for a period of time, the short-cut denitrification performance in the reactor is strengthened, and the nitrite-reducing bacteria are washed away due to long-term substrate limitation. As shown in Figure (4), after 16 days of instability, the nitrite accumulation rate in the reactor gradually recovers to over 40%. After 13 days of stable operation, the nitrite accumulation becomes unstable again. At this time, COD / NO3 is adjusted again. - From -N to 5, through a self-alkalization process, nitrite reductase is inhibited, and after a brief period of instability, stable nitrite accumulation is restored. After undergoing two self-alkalization processes, the short-cut denitrification reactor can operate stably, achieving nitrite accumulation rate of 49.9% and nitrate nitrogen removal rate of 96.1%.

[0046] This indicates a strong correlation between pH and nitrite accumulation, suggesting that short-cut denitrification can be achieved by adjusting the pH within the system. Furthermore, the pH within the reactor can be controlled by utilizing the self-regulation of the denitrification alkali production process. Through the self-alkalization process of denitrification, the pH within the reactor can be regulated, thereby achieving self-equilibrium in short-cut denitrification and further ensuring the stable operation of the short-cut denitrification reactor.

[0047] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A method for achieving stable operation of a continuous flow short-path denitrification reactor, characterized in that, The steps include the following: S1. Startup Phase: Nitrate wastewater and carbon source are introduced into a reactor inoculated with activated sludge, so that the microorganisms in the activated sludge can use these carbon sources as electron donors to reduce nitrate. Adjust the influent pH to a high level to achieve rapid start-up of the short-cut denitrification reaction; S2. Self-alkalization maintenance stage: After the reactor is successfully started up, manual pH adjustment is stopped, and the pH value of the system is maintained by the alkalinity generated by the short-range denitrification reaction itself. S3. Regulatory Supplementation Phase: If short-range denitrification and self-alkalization alone are insufficient to maintain stable nitrite accumulation, then adjusting the COD / NO3 ratio in the system is necessary. - The -N ratio promotes the entire denitrification reaction, generating more alkalinity to further increase the pH value of the system and achieve stable accumulation of nitrite. In step S2, when the pH of the system is maintained above 8.5, it will inhibit nitrite-reducing bacteria, thereby preventing further reduction of nitrite and achieving stable accumulation of nitrite. The process of maintaining the pH of the system through self-alkalization during full-process denitrification is a way to regulate the COD / NO3 ratio of the system. - With -N = 5, denitrification occurs throughout the process, generating alkalinity. This causes the system pH to rise back above 8.5, inhibiting nitrite-reducing bacteria, and then the control is removed.

2. The method for achieving stable operation of a continuous flow short-path denitrification reactor as described in claim 1, characterized in that, In step S1, the pH value of the influent is adjusted to a high level for 10-20 days, with the high pH value being 8.5 to 9.

3. The method for achieving stable operation of a continuous flow short-path denitrification reactor as described in claim 2, characterized in that, The pH of the initial influent was adjusted by adding sodium carbonate.

4. The method for achieving stable operation of a continuous flow short-path denitrification reactor as described in claim 1, characterized in that, After the short-range denitrification reactor described in step S1 is successfully started up, the nitrite accumulation rate of the system is maintained at 42%-67%.

5. The method for achieving stable operation of a continuous flow short-path denitrification reactor as described in claim 1, characterized in that, During reactor operation, the COD / NO3 ratio in the influent is continuously maintained by adding sodium acetate. - -N ratio.

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