CN104787885B - A kind of restoration methods synchronizing nitrosation Anammox and denitrification process - Google Patents

Abstract

The invention discloses a recovery method for synchronous nitrosation anaerobic ammonium oxidation and denitrification process, which belongs to the field of advanced sewage treatment. In SNAD, if the operation is not done properly, it is very easy to cause NOB to proliferate in large quantities, and the denitrification effect of the system will continue to decline or even collapse. The present invention keeps the dissolved oxygen concentration below 0.3 mg·L ^-1 throughout the reaction period by (1) adjusting the aeration rate. (2) Shorten (HRT) so that the reactor effluent always contains NH ₄ ⁺ ‑N (greater than 10mg·L ^‑1 ). (3) Add NaOH solution to the influent to increase the pH of the influent to 7.8-8.0. (4) Inorganic carbon sources are artificially added to the influent to maintain the ratio of alkalinity to ammonia nitrogen concentration above 10 (gCaCO ₃ /gNH ₄ ⁺ ‑N). Maintain the continuous operation of the above strategy until the characteristic ratio (the ratio of the total nitrogen removal amount to the generated nitrate nitrogen amount) is greater than 20, the total nitrogen removal rate is greater than 75%, and it has been continuously operated for more than 10 cycles. And the denitrification process has been effectively restored.

Description

A Recovery Method for Simultaneous Nitrosification Anammox and Denitrification Process

technical field

The invention belongs to the field of advanced sewage treatment. In particular, it relates to a recovery method for a simultaneous nitrosation-anammox and denitrification (SNAD) process. It is suitable for sewage and wastewater treatment with low carbon-to-nitrogen ratio.

Background technique

In the late 1980s, Mulder et al. found that in addition to the well-known denitrification reaction, there was an unknown reaction to make ammonia nitrogen disappear in the biological denitrification fluidized bed reactor, and predicted the anaerobic ammonium oxidation reaction (ANAMMOX) The existence of anammox bacteria was proved more than 10 years later. Third et al. proposed the CANON (completelyautotrophic nitrogen removal over nitrite) process in 1999, which is a single-stage full autotrophic nitrogen removal process. This process is based on the principle of short-range nitrification and anaerobic ammonium oxidation reaction. Compared with the traditional full-process nitrification and denitrification process, it has the advantages of short process flow, small footprint, and low infrastructure investment; it saves oxygen consumption, reduces carbon emissions, and has less residual sludge. ; No need to add carbon source and many other advantages. This process conforms to the concept of low-carbon, efficient and sustainable sewage and wastewater treatment, and is a new process with broad prospects. Its reaction formula is as follows:

Aerobic ammonium oxidizing bacteria (AOB) and anaerobic ammonium oxidizing bacteria (AnAOB) participating in the CANON process are autotrophic bacteria, and their growth and metabolism will be inhibited by organic matter to varying degrees. However, it is impossible to have organic carbon sources in the actual sewage, which poses a challenge to the stable and efficient operation of the CANON process. In addition, the effluent of the CANON process will contain a small amount of NO ₃ ^— N, making it unable to meet the increasingly stringent sewage treatment standards.

Based on the above two points, Huihui Chen et al. proposed the simultaneous nitrification-anammox and denitrification (SNAD) process in 2009. The principle of this process is: first, about 57% of the NH ₄ ⁺ -N in the wastewater is in the AOB Under the action of AnAOB, the reaction produces NO ₂ ^- -N while consuming oxygen; secondly, the produced NO ₂ ^- -N reacts with the remaining 43% NH ₄ ⁺ -N under the action of AnAOB to generate N ₂ and release it, and at the same time, 11 % NO ₃ ^— N; finally, the generated NO ₃ ^— N reacts with organic matter to generate N ₂ under the action of denitrifying bacteria, and completes the whole denitrification process.

The SNAD process can reduce NO ₃ ^— N in the effluent and increase the removal rate of total nitrogen, and at the same time realize the simultaneous removal of NH ₄ ⁺ -N and COD. Therefore, it has extremely wide application value. At present, the SNAD process has been successfully applied in many fields such as sludge digestion liquid, landfill leachate, photoelectric wastewater, and livestock wastewater.

However, in the application process, the SNAD process often results in a large number of nitrite oxidizing bacteria (NOB) in the system due to improper operation, equipment failure and other reasons, resulting in an increase in effluent NO ₃ ^- N, a decrease in the total nitrogen removal rate, and the reactor is moving towards the full nitrification process. The direction of denitrification changes, which eventually leads to the collapse of the SNAD process. Therefore, the present invention provides a recovery method for synchronous nitrosation-anammox and denitrification processes, aiming to provide a strategy for rapid recovery and stabilization of the collapsed or near-collapsed SNAD process.

Contents of the invention

The invention provides a recovery method for synchronous nitrosation-anammox and denitrification processes. It is characterized in that,

For the synchronous nitrification-anammox and denitrification (SNAD) system whose system collapses due to the massive proliferation of nitrite oxidizing bacteria (NOB), the following strategies are adopted: (1) adjust the aeration rate to dissolve the The oxygen concentration was always kept below 0.3 mg·L ^-1 . (2) Shorten the hydraulic retention time (HRT), so that the reactor effluent always contains a certain concentration of NH ₄ ⁺ -N (greater than 10 mg·L ^-1 ). (3) Add a certain amount of NaOH solution to the influent to increase the pH of the influent to 7.8-8.0. (4) Artificially add a certain amount of inorganic carbon source in the influent, so that the ratio of alkalinity to ammonia nitrogen concentration is maintained above 10 (gCaCO ₃ /gNH ₄ ⁺ -N). Maintain the operation of the above strategy until the characteristic ratio (that is, the ratio of total nitrogen removal to the amount of nitrate nitrogen produced) is greater than 20, the total nitrogen removal rate is greater than 75%, and it has been continuously operated for more than 10 cycles. It is considered that synchronous nitrification-anammonia Oxidation and denitrification processes are effectively restored.

The present invention provides an effective recovery method of the SNAD process. The reason why the rapid recovery of the SNAD process is realized is that the AOB is promoted by maintaining a certain concentration of NH ₄ ⁺ -N and a higher concentration of inorganic carbon source all the time. and AnAOB activity, while lower dissolved oxygen is also conducive to promoting the activity of AnAOB and denitrifying bacteria; through lower dissolved oxygen to achieve AOB's competitive advantage over NOB, and continuously elutriate NOB out of the reactor, while improving The pH in the reactor and the maintenance of a certain concentration of effluent NH ₄ ⁺ -N make the concentration of free ammonia (FA) in the reactor between the inhibitory concentration of NOB and the inhibitory concentration of AOB, and the inhibition of NOB by FA is used to achieve NOB disuse. Finally, the effective recovery of simultaneous nitrification-anammox and denitrification processes was realized.

In the process of simultaneous nitrification-ANAMMOX and denitrification, AOB, AnAOB and denitrifying bacteria have achieved synergistic denitrification and COD removal. If the gas is too high, etc.), it is easy to cause a large number of NOB to proliferate, and the denitrification effect of the system will continue to decline or even collapse. Therefore, it is particularly important to provide a simple and effective SNAD recovery strategy. However, there are few reports on how to effectively restore the synchronous nitrosation-anammox and denitrification process, so the present invention will have wide application value in the actual engineering application of SNAD.

Description of drawings:

Fig. 1 is a denitrification effect diagram before the recovery of the SNAD process in a specific example of the present invention.

Fig. 2 is a denitrification effect diagram in the recovery stage of the SNAD process in a specific example of the present invention.

Fig. 3 is a denitrification effect diagram after the recovery of the SNAD process in a specific example of the present invention.

detailed description

The present invention will be further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto.

Example

This experiment adopts SBR reactor, which is made of plexiglass, and a circulating water bath system is installed outside to maintain the temperature in the reactor (28-32°C). The inner diameter of the reactor is 9cm, the height is 1000cm, the effective volume is 5.4L, The exchange ratio is 50%, the bottom is equipped with an aeration head, and the dissolved oxygen is regulated and controlled through a rotameter and an online dissolved oxygen analyzer. The reactor is equipped with a simple automatic control device to realize the continuous automatic operation of water intake, reaction, precipitation, drainage, idle and other stages. The experiment is based on septic effluent from a community: NH ₄ ⁺ -N=90±5mg/L, COD=160±25mg/L, pH=7.3±0.1, alkalinity=370±50gCaCO ₃ . Runs 2 cycles per day. The contents of NH ₄ ⁺ -N, NO ₂ ^— N, NO ₃ ^— N in the influent and effluent were measured every cycle, and the total nitrogen removal rate and characteristic ratio were calculated. Measure the temperature, dissolved oxygen, pH, etc. in each cycle, and calculate the free ammonia (FA) concentration at the beginning and end of each cycle. The main calculation formula is as follows:

Total nitrogen removal rate = (influent total nitrogen - effluent total nitrogen) / influent total nitrogen × 100%

Characteristic ratio = (influent total nitrogen - effluent total nitrogen) / (effluent nitrate nitrogen + effluent nitrous - influent nitrate nitrogen - influent nitrous)

The main control parameters during the experiment are as follows:

The nitrogen removal effect before the collapse of the simultaneous nitrification-ANAMMOX and denitrification process system is shown in Figure 1. In the 1st-166th cycle, the reactor has been running stably, the dissolved oxygen is maintained at 0.4±0.1mg/L, the effluent ammonia nitrogen is 4±2mg/L, the average removal rate of total nitrogen is 89%, the removal rate of COD is 70%, and the average characteristic ratio is 21 . In the 177th-220th cycle, the nitrate nitrogen in the reactor effluent continued to rise (5.9-25.4mg/L), the characteristic ratio continued to decline (16.62-2.94), and the total nitrogen removal rate continued to decline (88%-71%), indicating that NOB continues to increase. If timely strategies are not adopted to suppress the proliferation of NOB, the reactor will proceed in the direction of full nitrification and denitrification, and the proportion of autotrophic denitrification will become smaller and smaller, even leading to the collapse of the SNAD process.

The denitrification effect during the recovery process of simultaneous nitrification-anammox and denitrification process is shown in Figure 2. In the 177th-220th cycle, add a certain amount of NaHCO ₃ to the influent until the measured alkalinity ratio is 12±1 (gCaCO ₃ /gNH ₄ ⁺ -N), and add NaOH solution (1mol/L ) until the pH of the influent water is 7.9±0.1, adjust the aeration rate during operation to stabilize the dissolved oxygen at 0.2±0.1mg/L, and control the aeration time so that the ammonia nitrogen in the effluent water is 14±4mg/L at the end of the operation. During the recovery process, the activity of AOB and AnAOB is promoted by maintaining a certain concentration of NH ₄ ⁺ -N and a high concentration of inorganic carbon source, and at the same time, the activity of AnAOB and denitrification bacteria is promoted by using low dissolved oxygen; in addition , under low dissolved oxygen, because the affinity of AOB to oxygen is stronger than that of NOB to oxygen, therefore, NOB is continuously eliminated from the reactor due to the limitation of dissolved oxygen; at the same time, increase the pH in the reactor and maintain a certain concentration of effluent NH ₄ ⁺ -N to make the concentration of free ammonia (FA) in the reactor between the inhibitory concentration of NOB and the inhibitory concentration of AOB, and use the inhibition of FA to NOB to realize the elimination of NOB. After 12 days of recovery process, the nitrate nitrogen in the effluent continued to decrease, and the characteristic ratio in the reactor continued to rise from 3.82 to 25.3. For 10 consecutive cycles, the characteristic ratio was higher than 20 and the total nitrogen removal rate was higher than 75%. It is considered that simultaneous nitrification-anaerobic Ammonia oxidation and denitrification processes have been restored.

Figure 3 shows the denitrification effect of simultaneous nitrification-anammox and denitrification processes after recovery. In the 221st-250th cycle, adjust the aeration rate to maintain the dissolved oxygen at 0.3±0.1 during the reaction period, and control the aeration time so that the ammonia nitrogen in the reactor effluent is 4±2mg/L. Continuous operation for 30 cycles, the total nitrogen removal rate is average The value is 89%, and the average characteristic ratio is 20.45, indicating that the synchronous nitrosation-anammox and denitrification process after restoration has good stability.

Claims (1)

1. synchronize a restoration methods for nitrosation Anammox and denitrification process, its feature It is:

For cause because NOB breeds in a large number the synchronization nitrosation of system crash- Anammox and denitrification process system, use following strategy: (1) regulation aeration rate makes instead 0.1-0.3mg L should be maintained all the time by dissolved oxygen concentration in phase^-1；(2) hydraulic detention time is shortened, Make reactor water outlet contains all the time 10-20mg L^-1The NH of concentration₄ ⁺-N；(3) in water inlet Add NaOH solution, improve inlet flow-patterm to 7.8 8.0；(4) artificially add in water inlet Inorganic carbon source so that basicity and NH₄ ⁺-N concentration ratio maintains 10-15gCaCO₃/gNH₄ ⁺-N； Maintain above-mentioned strategy to run, until the ratio of the nitrate nitrogen amount of total nitrogen removal amount and generation more than 20, Nitrogen removal rate is more than 75%, and runs more than 10 cycles continuously, it is believed that and synchronization nitrosation- Anammox and denitrification process have obtained effectively recovering.