A biological denitrification treatment method for low carbon-nitrogen ratio wastewater

Abstract

The application provides a biological denitrification treatment method for low-carbon-nitrogen-ratio wastewater, and utilizes single-stage nitrification and denitrification to treat ammonia-nitrogen wastewater in a one-piece submerged biological filter (SBAF reactor). The method comprises the following steps: sludge inoculation, sludge biofilm formation, system starting, and stable operation. In the sludge inoculation, sludge meeting the microbial community distribution is selected. In the system starting process, the microbial community distribution in the sludge in the one-piece submerged biological filter (SBAF reactor) is used as the symbol of successful system starting. During the input of the high-concentration ammonia-nitrogen wastewater to be treated, the aerobic nitrifying bacteria and the anaerobic denitrifying bacteria can more stably meet the above microbial community distribution, the system has better stability, the stable operation time is longer, the sludge does not need to be replaced for restarting during the stable operation, the continuous operation time is longer, can reach at least 250 days or more, and the frequency of replacing the sludge for restarting is reduced.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment, and more specifically to a biological denitrification treatment method for wastewater with a low carbon-to-nitrogen ratio. Background Technology

[0002] The pharmaceutical, chemical, fertilizer, petrochemical, coking, smelting, and slaughtering industries are major contributors to ammonia nitrogen wastewater discharge in my country. This wastewater is characterized by a low C / N ratio, making it one of the more difficult types of industrial wastewater to treat. Traditional nitrification-denitrification biological denitrification technologies for treating this type of wastewater face both macroscopic and microscopic technical and economic bottlenecks.

[0003] At a macroscopic level, the nitrification-denitrification process operates in two independent reactors: the first reactor handles nitrification (e.g., reaction 1), and the second reactor handles denitrification (e.g., reaction 2). In the first reactor, nitrification, under aerobic conditions, consumes a large amount of dissolved oxygen to convert all ammonia nitrogen into nitrate nitrogen. Furthermore, due to the generation of hydrogen ions, a significant amount of alkalinity is required to maintain the acid-base balance within the reaction system. Simultaneously, the production of aerobic sludge is substantial. Therefore, this stage presents technical challenges related to high energy and chemical consumption and high sludge production. In the second reactor, denitrification, under anaerobic conditions, consumes a large amount of organic carbon sources and hydrogen ions (which is clearly unsuitable for treating ammonia nitrogen wastewater with a low C / N ratio) to convert nitrate nitrogen into nitrogen gas. Carbon dioxide is also produced as a byproduct. Therefore, this stage suffers from high organic carbon source and chemical consumption and the generation of greenhouse gases.

[0004]

[0005]

[0006] At the microscopic level, in the first reactor, the main functional bacteria for nitrification are nitrifying bacteria. These microorganisms are autotrophic and highly sensitive to environmental factors, such as dissolved oxygen concentration >2 mg / L, alkalinity of 7.14 g / g (based on 1 g N nitrification), pH of 8.0–8.4 (pH changes have a significant impact on nitrifying bacteria), reaction temperature of 20–30°C, low organic matter concentration (nitrifying bacteria are autotrophic, and high organic matter limits their proliferation), sludge age of 3 days, and very low heavy metal content. In the second reactor, the main functional bacteria for denitrification are denitrifying bacteria. These microorganisms are heterotrophic and their environmental requirements differ significantly from those of autotrophic nitrifying bacteria. They require a high organic carbon source (BOD5 / TKN >3–5, which is clearly unsuitable for treating ammonia nitrogen wastewater with a low C / N ratio), a pH of 6.5–7.5, dissolved oxygen <0.5 mg / L, and a reaction temperature of 20–40°C. Therefore, in order to maintain the good survival and reproduction of the two bacteria, they must be acclimatized and operated in two different reactors. This results in a longer process flow for the nitrification-denitrification method, and higher infrastructure investment and operating costs.

[0007] Currently, there are also research on single-stage autotrophic denitrification methods, which enable functional bacteria such as aerobic ammonia oxidizing bacteria and functional bacteria such as anaerobic ammonia oxidizing bacteria to achieve denitrification performance in a single-stage reactor. However, the existing methods are unstable in operation. At most, after 120 to 150 days of stable operation after startup, the removal rate of ammonia nitrogen and total nitrogen drops significantly, and then it is necessary to replace the sludge and restart. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a biological denitrification treatment method for wastewater with a low carbon-to-nitrogen ratio.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is: a biological denitrification treatment method for wastewater with a low carbon-to-nitrogen ratio, the method comprising the following steps:

[0010] (1) The seed sludge, after being aerated by air, is inoculated into an integrated submerged biological filter. The microbial community in the seed sludge includes: Acidobacteria with an abundance of 10.68%~11.80%, Actinobacteria with an abundance of 5.81%~6.41%, Bacteroidetes with an abundance of 13.35%~14.75%, and Chloroflexi with an abundance of 16.64%~18.39%. The abundance of Euryarchaeota was 1.10%–1.20%, Firmicutes was 14.77%–16.31%, Gemmatimonadetes was 2.40%–2.65%, Proteobacteria was 24.20%–26.74%, and Verrucomicrobia was 1.91%–2.11%.

[0011] (2) Inert gas is introduced into the integrated submerged biological filter to carry out biofilm formation. The sludge color changes from yellowish brown (PGB(115,74,18)) to dark brown (PGB(41,36,33)). After stopping the inert gas introduction and letting it stand, the excess sludge is discharged.

[0012] (3) Simulated ammonia nitrogen wastewater is introduced into the reaction system of the integrated submerged biological filter while micro-aeration is performed to start the system. The DO in the reaction system is controlled at 0.6~0.8 mg / L, the pH value is 6.7~8.0, the water temperature is controlled within the range of 30.0~31.5℃, and the hydraulic retention time is controlled at 18~24 h. The parameters of the simulated ammonia nitrogen wastewater include pH 7.60~8.80, CODcr 0.0~16.0 mg / L, and NH4+. + -N 102.0~165.0 mg / L, NO2 - -N 0.0~7.0 mg / L, NO3 - -N 0.6~3.0 mg / L, phosphorus concentration 6.7~8.3 mg / L, the simulated ammonia nitrogen wastewater also contains potassium, magnesium, calcium, sodium, iron, manganese, copper, zinc and cobalt elements. Multiple batches of simulated ammonia nitrogen wastewater are input. When the microbial community in the activated sludge of the integrated submerged biological filter meets the following conditions, the system starts successfully.

[0013] The microbial community in the activated sludge of the integrated submerged biological filter includes the following microorganisms with relative abundance (greater than %): Acidobacteria (4.28%–4.45%), Actinobacteria (1.18%–1.23%), Bacteroidetes (21.90%–22.79%), and Chlorobi (4.32%–4.49%). The abundance of Chloroflexi was 1.69%–1.76%, Firmicutes was 48.12%–50.08%, Fusobacteria was 2.04%–2.12%, Gemmatimonadetes was 1.32%–1.37%, and Proteobacteria was 11.70%–12.17%.

[0014] (4) Input the high-concentration ammonia nitrogen wastewater to be treated into the integrated submerged biological filter that was successfully started in step (3) and run it stably.

[0015] While researching methods for treating ammonia nitrogen wastewater using single-stage nitrification and denitrification in an integrated submerged biological filter (SBAF reactor), the inventors discovered that existing methods for treating ammonia nitrogen wastewater using integrated single-stage nitrification and denitrification have a short stable operating time after startup. At most, after 120-150 days of operation, the removal rates of ammonia nitrogen and total nitrogen decrease significantly, necessitating sludge replacement and restart. Through research, the inventors found that controlling the distribution of microbial communities in the inoculated activated sludge and studying different start-up success indicators during the input of simulated ammonia nitrogen wastewater demonstrated that using the distribution of microbial communities in the sludge of the integrated submerged biological filter (SBAF reactor) as a successful start-up indicator allows aerobic nitrifying bacteria and anaerobic denitrifying bacteria to more stably conform to the aforementioned microbial community distribution during the treatment of high-concentration ammonia nitrogen wastewater. This results in better system stability and a longer stable operating time. The study found that the microbial community in the activated sludge of integrated submerged biological filters included the following microorganisms with relative abundance (greater than %): Acidobacteria (4.28%–4.45%), Actinobacteria (1.18%–1.23%), Bacteroidetes (21.90%–22.79%), Chlorobi (4.32%–4.49%), Chloroflexi (1.69%–1.76%), Firmicutes (48.12%–50.08%), Fusobacteria (2.04%–2.12%), and Gemmatimonadetes. The abundance of 1.32%~1.37% and the abundance of Proteobacteria is 11.70%~12.17%. As the sign of successful system startup in step (3) of the biological denitrification treatment method for low carbon-nitrogen ratio wastewater of the present invention, the startup time is slightly extended to about 45~50 days. At this time, the ammonia nitrogen conversion rate exceeds 90.0% and the total nitrogen removal rate exceeds 70.0%. However, by controlling the distribution of microbial communities, after successful startup, the input of high-concentration ammonia nitrogen wastewater to be treated is stable. The distribution of microbial communities remains basically unchanged. During the stable operation period, there is no need to replace the sludge and restart. The continuous operation time is longer, which can reach at least 250 days. The microorganisms listed in the seed sludge and activated sludge in the biological filter are not all the microorganisms in the seed sludge and activated sludge in the biological filter. However, as long as the activated sludge in the seed sludge and biological filter contains the above-listed microorganisms and the abundance of the biological community meets the above-listed requirements, the purpose of the invention can be achieved.

[0016] Preferably, in step (1), the microbial community in the seed mud includes: Acidobacteria with an abundance of 11.24%, Actinobacteria with an abundance of 6.11%, Bacteroidetes with an abundance of 14.05%, Chloroflexi with an abundance of 17.52%, Euryarchaeota with an abundance of 1.15%, Firmicutes with an abundance of 15.54%, Gemmatimonadetes with an abundance of 2.53%, Proteobacteria with an abundance of 25.47%, and Verrucomicrobia with an abundance of 2.01%.

[0017] Preferably, in step (1), the sludge concentration of the seed sludge after aeration is 15,000~23,000 mg / L, the MLSS of the seed sludge after aeration is in the range of 10,000~13,000 mg / L, the MLVSS of the seed sludge after aeration is in the range of 4,000~4,500 mg / L, and the pH value of the seed sludge after aeration is in the range of 6.0~8.0.

[0018] Through research, the inventors discovered that the inoculated seed sludge, containing different types of aerobic nitrifying bacteria and anaerobic denitrifying bacteria, has a higher removal efficiency for ammonia nitrogen and total nitrogen in ammonia nitrogen wastewater and a longer stable operating time.

[0019] Preferably, in step (3), the microbial community in the activated sludge includes microorganisms with the following abundances:

[0020] The abundance of Acidobacteria was 4.37%, Actinobacteria was 1.21%, Bacteroidetes was 22.35%, Chlorobi was 4.41%, Chloroflexi was 1.73%, Firmicutes was 49.1%, Fusobacteria was 2.08%, Gemmatimonadetes was 1.35%, and Proteobacteria was 11.94%.

[0021] Preferably, in step (4), the NH4 in the high-concentration wastewater to be treated + The concentration of -N is not less than 100 mg / L.

[0022] The above-mentioned biological denitrification treatment method for low C / N ratio wastewater can treat NH4. + For ammonia nitrogen wastewater with a concentration of -N not less than 100 mg / L, the ammonia nitrogen conversion rate in high-concentration ammonia nitrogen wastewater is 84.4%~100.0%, and the average ammonia nitrogen conversion rate is not less than 96.0%; the total nitrogen removal rate in high-concentration ammonia nitrogen wastewater is 77.8%~98.3%, and the average total nitrogen removal rate is not less than 88.2%.

[0023] Preferably, in step (4), the DO in the reaction system is controlled to be 0.6~0.8 mg / L, the pH is 6.2~8.2, the water temperature is within the range of 29.4~31.5℃, and the hydraulic residence time is 18~20 h.

[0024] Preferably, in step (3), the simulated ammonia nitrogen wastewater includes the following components: NH4Cl 0.38~0.63 g / L, KH2PO4·3H2O 0.00~0.05 g / L, MgSO4 0.00~0.02 g / L, CaCl2 0.00~0.02 g / L, NaHCO3 0.20~1.00 g / L, and trace element solution 0.20~0.40 ml / L; the components and concentrations of the trace element solution are FeCl3·6H2O 3.00~3.50 g / L, MnCl2·4H2O 0.30~0.40 g / L, CuSO4·5H2O 0.07~0.08 g / L, ZnSO4·7H2O 0.02~0.30 g / L, and CoCl2·6H2O 0.30~0.40 ml / L. g / L.

[0025] Preferably, in step (1), the ratio of seed mud usage to the effective volume of the integrated submerged biological filter is 1:1.

[0026] Preferably, in step (2), the inert gas is nitrogen or helium, and the pressure in the integrated submerged biological filter is controlled to be 0.2~0.5 MPa, the aeration time is 24~72 h, and the settling time is 1~2 h.

[0027] Preferably, the integrated submerged biological filter is equipped with a combined packing material, which consists of three parts: a packing disc, a plastic sleeve, and a central copper wire tube. The structure of the combined packing material is to press the plastic disc into a double-ring large plastic ring, and press the polyester filaments on the ring of the double-ring large plastic ring to make the fiber bundles evenly distributed; the inner ring of the double-ring large plastic ring is a snowflake-shaped plastic branch.

[0028] The aforementioned integrated submerged biological filter is equipped with combined packing material, which can both support biofilm formation and effectively cut air bubbles, thereby improving the oxygen transfer rate and utilization rate. As a result, the water-air biofilm is fully exchanged, allowing for efficient treatment of nitrogen in the water.

[0029] Preferably, in step (3), the bottom sediment is not discharged; in step (4), the bottom sediment is not discharged.

[0030] The beneficial effects of this invention are as follows: This invention provides a biological denitrification treatment method for wastewater with a low carbon-to-nitrogen ratio. This method controls the distribution community of microorganisms in the inoculated activated sludge. During the start-up of simulated ammonia nitrogen wastewater, the distribution of the microbial community in the sludge of the integrated submerged biological filter (SBAF reactor) is used as a sign of successful start-up. During the treatment of high-concentration ammonia nitrogen wastewater, the aerobic nitrifying bacteria and anaerobic denitrifying bacteria can more stably conform to the above-mentioned microbial community distribution, resulting in better system stability, longer stable operation time, no need to replace sludge and restart during stable operation, and a longer continuous operation time of at least 250 days, reducing the frequency of sludge replacement and restart.

[0031] Compared with existing technologies, the biological denitrification treatment method for low carbon-to-nitrogen ratio wastewater of the present invention has the following advantages:

[0032] (1) Superior overall process performance. Conventional biological nitrogen removal technology adopts a combined nitrification-denitrification method, which operates in two different reactors. In actual sludge acclimation and operation, the environmental conditions of different reactors vary greatly, and there are conventional problems such as good nitrification effect but limited denitrification capacity, long process flow, large oxygen consumption and organic carbon source demand, and high residual sludge production, which limit the treatment effect of the integrated nitrification-denitrification biochemical technology on wastewater containing ammonia nitrogen. The integrated SABF reactor selected in this invention enriches Firmicutes and Bacteroidetes, which can effectively remove ammonia nitrogen and total nitrogen in the same reactor, and saves 62.5% of oxygen consumption, 100% of organic carbon source and 50% of alkali consumption, halves the process flow, and reduces sludge production by 90%. These all demonstrate the technical and economic advantages of this biological nitrogen removal method.

[0033] (2) Effective Improvement of Nitrogen Removal Performance. Conventional nitrification-denitrification biological nitrogen removal systems, during startup and operation, employ methods such as controlling temperature, dissolved oxygen, influent ammonia nitrogen load, and hydraulic retention time to achieve an ammonia nitrogen conversion rate of approximately 80% and a total nitrogen removal rate of approximately 67%. Based on this, the present invention adjusts parameters such as temperature, dissolved oxygen, pH, and hydraulic retention time during the system startup and stable operation phases, respectively, without requiring sludge discharge throughout the entire process. During startup, the ammonia nitrogen conversion rate increased from 22.7% to 100.0%, and the total nitrogen removal rate increased from 0.0% to 89.0%. During operation, the ammonia nitrogen conversion rate ranged from 76.3% to 100.0%, with an average conversion rate of 96.0%, and the total nitrogen removal rate ranged from 68.0% to 96.5%, with an average removal rate of 88.1%. This demonstrates the superiority of the present invention.

[0034] (3) Effective suppression of reaction byproducts. In traditional nitrification-denitrification biological denitrification, the growth and accumulation of nitrifying bacteria are affected by the presence of free ammonia and free imine during operation, resulting in incomplete nitrification and affecting the ammonia nitrogen removal performance of the reaction system. The technology of this invention adjusts the parameters of temperature, dissolved oxygen, pH, and hydraulic retention time in the system during the start-up and stable operation stages, respectively. This can effectively stabilize the activity and growth of aerobic nitrite-oxidizing bacteria and nitrifying bacteria, and improve the average ammonia nitrogen removal rate, which has a significant promoting effect on improving the performance of biological denitrification.

[0035] (4) Saving of organic carbon source. In the traditional nitrification-denitrification biological nitrogen removal process, the denitrification stage requires a large amount of organic carbon source to ensure the normal growth and reproduction of denitrifying bacteria and ensure the efficient operation of denitrification. The technology of this invention operates in an integrated SABF reaction system, which does not require the consumption of organic carbon source, thus ensuring the effective growth and reproduction of Firmicutes and Bacteroidetes, ensuring the smooth operation of denitrification, and thereby stabilizing the total nitrogen removal performance.

[0036] (5) Effective Expansion of Technology Application. Traditional nitrification-denitrification biological nitrogen removal requires strict control of key conditions such as temperature, dissolved oxygen, influent ammonia nitrogen load, and hydraulic retention time within very narrow threshold ranges during startup and operation. This places high demands on the design precision of automatic control equipment and the skill level of operators in practical engineering. The technology of this invention addresses the different requirements for the range of condition parameters during the two different stages of system startup and stable operation by adjusting the parameters of temperature, dissolved oxygen, pH, and hydraulic retention time within the system (with a certain expansion of the threshold range) to improve the nitrogen removal performance of the reaction system. This has a more practical and effective feasibility for the design and control of automatic control equipment and the skill level of operators in practical engineering, thus further facilitating the widespread application of this technology.

[0037] (6) Optimization of technical operating costs. During startup and operation, the technology of this invention can effectively save on civil engineering costs (halving the process flow), reduce oxygen consumption and energy costs by 62.5%, save 100% of organic carbon sources and 50% of alkali consumption, and reduce sludge production by 90%. In addition to the above advantages, the technology of this invention also produces extremely low sludge during startup and operation, and there is no need to remove excess sludge throughout the entire process. Attached Figure Description

[0038] Figure 1 This is a diagram showing the abundance of microbial communities in the inoculated sludge during the biological denitrification treatment of low carbon-to-nitrogen ratio wastewater in this invention.

[0039] Figure 2 This is a diagram showing the abundance of sludge microbial communities when the system is successfully started up in the biological denitrification treatment method for low carbon-to-nitrogen ratio wastewater of the present invention.

[0040] Figure 3 This figure shows the stable operation results of the biological denitrification treatment method for low carbon-to-nitrogen ratio wastewater according to the present invention. Detailed Implementation

[0041] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0042] Example 1

[0043] A biological denitrification treatment method for wastewater with a low carbon-to-nitrogen ratio, the method comprising the following steps:

[0044] (1) The seed sludge, after being aerated by air, is inoculated into an integrated submerged biological filter. The microbial community in the seed sludge includes: Acidobacteria with an abundance of 10.68%~11.80%, Actinobacteria with an abundance of 5.81%~6.41%, Bacteroidetes with an abundance of 13.35%~14.75%, and Chloroflexi with an abundance of 16.64%~18.39%. The abundance of Euryarchaeota was 1.10%–1.20%, Firmicutes was 14.77%–16.31%, Gemmatimonadetes was 2.40%–2.65%, Proteobacteria was 24.20%–26.74%, and Verrucomicrobia was 1.91%–2.11%.

[0045] (2) Nitrogen gas is introduced into the integrated submerged biological filter to carry out biofilm formation. When the sludge color changes from yellowish-brown to dark brown, the nitrogen gas is stopped and the sludge is allowed to stand before the excess sludge is discharged. The gas pressure is controlled within the range of 0.2~0.5 MPa and is continuously introduced for 24~72 h.

[0046] (3) Simulated ammonia nitrogen wastewater is introduced into the reaction system of the integrated submerged biological filter while micro-aeration is performed to start the system. The DO in the reaction system is controlled at 0.6~0.8 mg / L, the pH value is 6.7~8.0, the water temperature is controlled within the range of 30.0~31.5℃, and the hydraulic retention time is controlled at 18~24 h. The parameters of the simulated ammonia nitrogen wastewater include pH 7.60~8.80, CODcr 0.0~16.0 mg / L, and NH4+. + -N 102.0~165.0 mg / L, NO2 - -N 0.0~7.0 mg / L, NO3 - -N 0.6~3.0 mg / L, phosphorus concentration 6.7~8.3 mg / L, simulated ammonia nitrogen wastewater also contains potassium, magnesium, calcium, sodium, iron, manganese, copper, zinc and cobalt elements. Multiple batches of simulated ammonia nitrogen wastewater were input. When the microbial community in the activated sludge of the integrated submerged biological filter meets the following conditions, the system will start successfully.

[0047] The microbial community in the activated sludge of the integrated submerged biological filter includes the following microorganisms in abundance: Acidobacteria (4.28%–4.45%), Actinobacteria (1.18%–1.23%), Bacteroidetes (21.90%–22.79%), Chlorobi (4.32%–4.49%), and Chlorobiosis (4.32%–4.49%). The abundance of Chloroflexi was 1.69%–1.76%, Firmicutes was 48.12%–50.08%, Fusobacteria was 2.04%–2.12%, Gemmatimonadetes was 1.32%–1.37%, and Proteobacteria was 11.70%–12.17%.

[0048] (4) Input the high-concentration ammonia nitrogen wastewater to be treated into the integrated submerged biological filter that was successfully started in step (3) and run it stably.

[0049] Trial run

[0050] (a) Seed sludge preparation. Ordinary activated sludge from the secondary sedimentation tank of a municipal wastewater treatment plant was used as seed sludge. The sludge was light yellowish-brown in color, with a pH of 7.4 and a MLSS of 2200 mg / L. After a sedimentation time of 2 h, the MLSS decreased to 12200 mg / L, and the MLVSS decreased to 4100 mg / L. The microbial community distribution in the seed sludge was analyzed as follows: Figure 1 As shown. The microbial community in the seed mud includes: Acidobacteria (11.24%), Actinobacteria (6.11%), Bacteroidetes (14.05%), Chloroflexi (17.52%), Euryarchaeota (1.15%), Firmicutes (15.54%), Gemmatimonadetes (2.53%), Proteobacteria (25.47%), and Verrucomicrobia (2.01%). In addition, the seed mud also contains other microorganisms with extremely low abundance that do not affect the purpose of the invention.

[0051] (b) After aerating the seed sludge with air for 18 h, adjust the sludge concentration to 20,000 mg / L. Take 3.0 L of this sludge and pour it into a submerged biological filter (SBAF) reactor with a suspended combined packing material and an effective volume of 3.2 L.

[0052] (c) Pure nitrogen gas is introduced into the bottom of the SBAF reactor, with the pressure controlled within the range of 0.2~0.5 MPa, and this process is continued for 36 hours. The sludge in the reactor gradually adheres to the surface of the combined packing material. The combined packing material consists of three parts: a single packing disc, a plastic sleeve, and a central copper wire tube. Its structure involves pressing the plastic disc into a double-ringed large plastic ring, pressing polyester filaments onto the rings to ensure even distribution of the fiber bundles; the inner ring consists of snowflake-shaped plastic branches. The sludge color changes from light yellowish-brown to dark brown. At this point, nitrogen gas is stopped, and the mixture is allowed to stand for 1.5 hours. The remaining sludge is then discharged from the sludge discharge port at the bottom of the reactor. The actual ratio of the amount (volume) of sludge used for biofilm formation to the effective volume of the reactor is 1:2.

[0053] (d) Simulated ammonia nitrogen wastewater is introduced into the reaction system of the integrated submerged biological filter while micro-aeration is performed to start the system. The DO in the reaction system is controlled within the range of 0.6~0.8 mg / L, the pH value is controlled within the range of 6.7~8.0, the water temperature is controlled within the range of 30.0~31.5℃, and the hydraulic retention time is within the range of 18 h. The simulated ammonia nitrogen wastewater includes the following components: NH4Cl 0.38~0.63 g / L, KH2PO4·3H2O 0.00~0.05 g / L, MgSO4 0.00~0.02 g / L, CaCl2 0.00~0.02 g / L, NaHCO3 0.20~1.00 g / L, and trace element solution 0.20~0.40 ml / L; the components and concentrations of the trace element solution are FeCl3·6H2O 3.00~3.50 g / L, MnCl2·4H2O 0.30~0.40 g / L, CuSO4·5H2O 0.07~0.08 g / L, ZnSO4·7H2O 0.02~0.30 g / L, and CoCl2·6H2O 0.30~0.40 g / L.

[0054] During system startup, as shown in Table 1, from day 1 to 9, the sludge was in the initial inoculation stage. Low DO severely inhibited the activity of aerobic ammonia-oxidizing bacteria and nitrifying bacteria, resulting in the vast majority of NH4+ being released. + -N failed to be oxidized, and the effluent contained NH4. + -N concentration ranged from 72.0 to 116.0 mg / L, with an average mass concentration of 94.0 mg / L; effluent NO2 - -N concentration ranged from 6.0 to 53.0 mg / L, with an average mass concentration of 23.4 mg / L; effluent NO3 - -N concentrations ranged from 0.7 to 3.1 mg / L, with an average concentration of 2.0 mg / L. From days 10 to 27, a large number of aerobic ammonia-oxidizing bacteria accumulated in the system, while a small number of nitrifying bacteria were present, leading to an increase in NH4+ in the effluent. + -N concentration decreased from 96.0 mg / L to 33.0 mg / L, and NO2 in the effluent decreased. - -N concentration increased from 15.0 mg / L to 56.0 mg / L; effluent NO3 - The -N concentration increased slightly from 1.1 mg / L to 7.2 mg / L, indicating that nitrifying bacteria could be effectively inhibited. From days 28 to 47, the system continued to enrich aerobic ammonia-oxidizing bacteria and began to enrich denitrifying bacteria, causing denitrification. The effluent NH4+ concentration increased significantly. + -N concentration decreased from 33.0 mg / L to 0.0 mg / L, and NO2 in the effluent decreased. --N concentration decreased from 55.0 mg / L to 5.0 mg / L. Around days 45-47, a small amount of sludge was collected, and the microbial community distribution in the sludge was analyzed. The results are as follows: Figure 2 As shown, the microbial community in the activated sludge includes the following microorganisms with relative abundance (greater than %): Acidobacteria (4.37%), Actinobacteria (1.21%), Bacteroidetes (22.35%), Chlorobi (4.41%), Chloroflexi (1.73%), Firmicutes (49.1%), Fusobacteria (2.08%), Gemmatimonadetes (1.35%), and Proteobacteria (11.94%). In addition, there are other microorganisms with extremely low abundance in the sludge that do not affect the experiment. This is used as a sign of successful start-up. After successful start-up, the ammonia nitrogen wastewater to be treated can be introduced for stable operation. After successful startup, NO3 was emitted from the water. - When the nitrogen concentration is in the range of 2.4~8.6 mg / L, the ammonia nitrogen conversion rate increases from 67.7% to 100.0%, and the total nitrogen removal rate increases from 27.5% to 90.0%, indicating successful initiation of partial nitrification-denitrification. During this period, the reactor operates continuously without sludge discharge.

[0055] (e) Input the high-concentration ammonia nitrogen wastewater to be treated into the integrated submerged biological filter that has been successfully started and operate it stably. The DO in the reaction system is controlled within the range of 0.6~0.8 mg / L, the pH value is controlled within the range of 6.2~8.2, the water temperature is controlled within the range of 29.4~31.5℃, and the hydraulic retention time is within the range of 18 h.

[0056] Once the system enters the operational phase, the ammonia nitrogen wastewater to be treated is input, and the operational experiment results are as follows: Figure 3 As shown, from day 48 to 320 (the time is calculated during the start-up phase), the influent NH4... + When the -N mass concentration is in the range of 102.0~186.0 mg / L and the average mass concentration is 147.4 mg / L; the effluent NH4 + -N concentration ranged from 0.0 to 21.0 mg / L, with an average concentration of 5.96 mg / L; effluent NO2 - -N concentration ranged from 0.0 to 10.0 mg / L, with an average concentration of 2.43 mg / L; effluent NH4 +-N and NO2 - -N mass concentration remained consistently low. (Effluent NO3) - The -N concentration ranged from 0.0 to 21.0 mg / L, with an average concentration of 10.62 mg / L, indicating extremely low nitrifying bacteria content in the system. During this operational phase, the ammonia nitrogen conversion rate ranged from 84.4% to 100.0%, with an average conversion rate of 96.0%; the total nitrogen removal rate ranged from 77.8% to 98.6%, with an average removal rate of 88.1%. Furthermore, no organic carbon source was added during the start-up and operation phases, and the reactor operated continuously and stably without sludge discharge. Stable operation lasted for 273 days.

[0057] Table 1. Influent and effluent water quality and reaction system parameters of the present invention (days 1-47, during system startup)

[0058]

[0059] Table 2. Influent and effluent water quality and reaction system parameters of the present invention (d. 48-320, during stable operation)

[0060]

[0061] Table 3 Comparison of Parameters

[0062]

[0063] As shown in Tables 2 and 3, the biological denitrification treatment method for low C / N ratio wastewater of the present invention controls the distribution community of microorganisms in the inoculated activated sludge. During the start-up of simulated ammonia nitrogen wastewater, the distribution of microbial community in the sludge of the integrated submerged biological filter (SBAF reactor) is used as a sign of successful start-up. During the treatment of high-concentration ammonia nitrogen wastewater, the aerobic nitrifying bacteria and anaerobic denitrifying bacteria can more stably conform to the above-mentioned microbial community distribution, resulting in better system stability, longer stable operation time, no need to replace sludge and restart during stable operation, and longer continuous operation time, which can reach at least 250 days, reducing the frequency of sludge replacement and restart.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A biological denitrification treatment method for wastewater with a low carbon-to-nitrogen ratio, characterized in that, The method includes the following steps: (1) The seed sludge after air aeration is inoculated into an integrated submerged biological filter. The microbial community in the seed sludge includes: 10.68%~11.80% abundance of Acidobacteria, 5.81%~6.41% abundance of Actinobacteria, 13.35%~14.75% abundance of Bacteroidetes, 16.64%~18.39% abundance of Chlorobacteria, 1.10%~1.20% abundance of Archaea, 14.77%~16.31% abundance of Firmicutes, 2.40%~2.65% abundance of Bacillus, 24.20%~26.74% abundance of Proteobacteria, and 1.91%~2.11% abundance of Verrucous Microbes. In step (1), the sludge concentration of the seed sludge after aeration is 15000~23000. mg / L, the MLSS of the seed mud after aeration is in the range of 10000~13000 mg / L, the MLVSS of the seed mud after aeration is in the range of 4000~4500 mg / L, and the pH value of the seed mud after aeration is in the range of 6.0~8.

0. (2) Inert gas is introduced into the integrated submerged biological filter to carry out biofilm formation. When the sludge color changes from yellowish brown to dark brown, the inert gas is stopped and the excess sludge is discharged after standing. (3) Simulated ammonia nitrogen wastewater is introduced into the reaction system of the integrated submerged biological filter while micro-aeration is performed to start the system. The DO in the reaction system is controlled at 0.6~0.8 mg / L, the pH value is 6.7~8.0, the water temperature is controlled at 30.0~31.5℃, and the hydraulic retention time is controlled at 18~24 h. The parameters of the simulated ammonia nitrogen wastewater include pH 7.60~8.80, CODcr 0.0~16.0 mg / L, and NH4+. + -N 102.0~165.0 mg / L, NO2 - -N 0.0~7.0 mg / L, NO3 - -N concentration is 0.6~3.0 mg / L, phosphorus concentration is 6.7~8.3 mg / L, and the simulated ammonia nitrogen wastewater also contains potassium, magnesium, calcium, sodium, iron, manganese, copper, zinc and cobalt. Multiple batches of simulated ammonia nitrogen wastewater are input. When the microbial community in the activated sludge of the integrated submerged biological filter meets the following conditions, the system starts successfully: The abundance of Acidobacteria was 4.28%–4.45%, Actinobacteria 1.18%–1.23%, Bacteroidetes 21.90%–22.79%, Aerobacteria 4.32%–4.49%, Chlorophyta 1.69%–1.76%, Firmicutes 48.12%–50.08%, Fusobacteria 2.04%–2.12%, Bacillus 1.32%–1.37%, and Proteobacteria 11.70%–12.17%. (4) Input the high-concentration ammonia nitrogen wastewater to be treated into the integrated submerged biological filter that was successfully started in step (3), and run it stably to treat the high-concentration ammonia nitrogen wastewater. The NH4 in the high-concentration ammonia nitrogen wastewater + The concentration of -N is not less than 100 mg / L.

2. The biological denitrification treatment method for low C / N ratio wastewater according to claim 1, characterized in that, In step (1), the microbial community in the seed mud includes: 11.24% abundance of Acidobacteria, 6.11% abundance of Actinobacteria, 14.05% abundance of Bacteroidetes, 17.52% abundance of Chlorophyta, 1.15% abundance of Archaea, 15.54% abundance of Firmicutes, 2.53% abundance of Bacillus, 25.47% abundance of Proteobacteria, and 2.01% abundance of Verrucous Microbes.

3. The biological denitrification treatment method for low C / N ratio wastewater according to claim 1, characterized in that, In step (3), the microbial community in the activated sludge includes microorganisms with the following abundances: The abundance of Acidobacteria was 4.37%, Actinobacteria was 1.21%, Bacteroidetes was 22.35%, Aerobacteria was 4.41%, Chlorobacteria was 1.73%, Firmicutes was 49.1%, Fusobacteria was 2.08%, Bacillus was 1.35%, and Proteobacteria was 11.94%.

4. The biological denitrification treatment method for low C / N ratio wastewater according to claim 1, characterized in that, In step (4), the DO in the reaction system is controlled to be 0.6~0.8 mg / L, the pH to be 6.2~8.2, the water temperature to be 29.4~31.5℃, and the hydraulic retention time to be 18~20 h.

5. The biological denitrification treatment method for low C / N ratio wastewater according to claim 1, characterized in that, In step (3), the simulated ammonia nitrogen wastewater includes the following components: NH4Cl 0.38-0.63 g / L, KH2PO4·3H2O 0.00-0.05 g / L, MgSO4 0.00-0.02 g / L, CaCl2 0.00-0.02 g / L, NaHCO3 0.20-1.00 g / L, and trace element solution 0.20-0.40 ml / L; the components and concentrations of the trace element solution are FeCl3·6H2O 3.00-3.50 g / L, MnCl2·4H2O 0.30-0.40 g / L, CuSO4·5H2O 0.07-0.08 g / L, ZnSO4·7H2O 0.02-0.30 g / L, and CoCl2·6H2O 0.30-0.40 ml / L. g / L.

6. The biological denitrification treatment method for low C / N ratio wastewater according to claim 1, characterized in that, In step (2), the ratio of the amount of attached biofilm seed mud to the effective volume of the integrated submerged biological filter is 1:

2.

7. The biological denitrification treatment method for low C / N ratio wastewater according to claim 1, characterized in that, In step (2), the inert gas is nitrogen or helium. The pressure in the integrated submerged biological filter is controlled to be 0.2~0.5 MPa, the aeration time is 24~72 h, and the settling time is 1~2 h. The integrated submerged biological filter is equipped with a combined packing material, which consists of three parts: a packing disc, a plastic sleeve, and a central copper wire tube. The structure of the combined packing material is to press the plastic disc into a double-ring large plastic ring, and press the polyester filaments on the ring of the double-ring large plastic ring to make the fiber bundles evenly distributed; the inner ring of the double-ring large plastic ring is a snowflake-shaped plastic branch.

8. The biological denitrification treatment method for low C / N ratio wastewater according to claim 1, characterized in that, In step (3), no bottom sediment is discharged; in step (4), no bottom sediment is discharged, and the stable operation time in step (4) is at least 250 days.

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