A method for improving the accumulation rate of nitrite and the operation stability in a sulfur autotrophic denitrification process

Abstract

The application belongs to the technical field of sewage treatment, and aims to solve the problems of low nitrite accumulation rate in the sulfur autotrophic denitrification process and unstable reactor performance when facing impact load, and provides a method for improving the nitrite accumulation rate and operation stability in the sulfur autotrophic denitrification process. The sulfur autotrophic denitrification system or Anammox-SADN coupling system is inoculated with anaerobic ammonia oxidation sludge and / or anaerobic ammonia oxidation sludge and sulfur autotrophic denitrification sludge, SCAC is added, the influent is artificial water, the pH is adjusted to 8.0, the dissolved oxygen concentration of the influent is less than 0.2 mg·L ‑1 , and the anaerobic environment is maintained; the reactor is continuously operated in the environment at 35 DEG C, 120 r·min ‑1 for 60-104 days, 1g of S 0 powder is added every week; the nitrite accumulation rate in the denitrification process can be significantly improved; when facing impact, the reactor shows faster adaptability. The sludge in the reactor promotes the secretion of EPS, and enriches the sulfur autotrophic denitrification related microorganisms.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of sewage treatment, and particularly relates to a method for improving the nitrite accumulation rate and operation stability in a sulfur autotrophic denitrification process. BACKGROUND

[0002] Anaerobic ammonia oxidation (Anammox) as a new type of biological denitrification technology has attracted much attention due to its high denitrification efficiency and low energy consumption in wastewater treatment. Anammox bacteria use nitrite as an electron acceptor to consume ammonia nitrogen, which is converted into nitrogen gas and nitrate. Nitrite can be obtained through partial nitrification and denitrification. Partial nitrification requires a complex control strategy, including aeration mode, DO set value and optimal temperature, to inhibit nitrite oxidizing bacteria. The efficiency and stability of heterotrophic short-cut denitrification depend on the types of carbon sources and the carbon-nitrogen ratio in wastewater. In addition, a large amount of by-products such as excess sludge and greenhouse gases are produced during the reduction process, increasing the cost of further treatment. At the same time, the high growth rate and biomass of heterotrophic microorganisms make them superior to anammox bacteria in substrate competition, which is not conducive to the growth of anammox bacteria. In contrast, autotrophic denitrification does not require organic matter, and the sludge production is low. Both anammox and autotrophic denitrification are autotrophic reactions, and it is easier to achieve balance between microbial populations by controlling the solid retention time in a single reactor.

[0003] Anammox reaction requires NO2 - as an electron acceptor, and its reaction product contains NO3 - , which cannot be removed by anammox itself, thereby limiting the total nitrogen removal effect.

[0004] Sulfur autotrophic denitrification (SADN) is a denitrification process that uses sulfur-containing compounds (such as S 0 , S 2- and S2O3 2- ) as electron donors to reduce nitrate to nitrogen gas. Among them, sulfur is an efficient, inexpensive and easily accessible denitrification electron donor that can promote nitrite accumulation during sulfur autotrophic denitrification. However, the dissolution rate of sulfur is relatively slow, resulting in a slow reduction rate of nitrate, which limits the production and accumulation of nitrite. Studies have shown that biochar can act as a redox mediator to promote electron transfer or directly provide additional electrons to accelerate denitrification, thereby increasing the reduction rate of nitrate. In addition, sludge-based biochar can act as a carrier to accelerate the formation of granular sludge and enhance the long-term stability of granules. Since sulfur autotrophic denitrification can also utilize NO2 - -N, therefore, NO2 -The accumulation of -N is crucial. In addition, anaerobic ammonia oxidizing bacteria have a long doubling time, are easily lost in the reactor, are difficult to accumulate, and are quite sensitive to external environmental conditions. An unsuitable environment will seriously affect the effectiveness of Anammox. Summary of the Invention

[0005] This invention addresses the issue of nitrite accumulation during sulfur autotrophic denitrification, providing a method to improve nitrite accumulation rate and operational stability during denitrification. The study proposes increasing NO2 production during the sulfur autotrophic denitrification reaction by adding sludge-coal gangue-based activated carbon (SCAC) to the reactor. - This invention aims to explore the promoting mechanisms of α-N accumulation capacity and the stability of anammox-SADN reaction. It seeks to elucidate the role of SCAC in the Anammox-SADN reactor, providing a new approach for the stable operation of the Anammox-SADN coupled system. The invention couples denitrification, using elemental sulfur as an electron donor, with anammox-SADN to provide NO2 for anammox-SADN. - -N, while treating NO3 produced during the reaction. - -N.

[0006] This invention is achieved by the following technical solution: a method for improving the nitrite accumulation rate and operational stability during sulfur autotrophic denitrification, utilizing a sulfur autotrophic denitrification system or an Anammox-SADN coupling system, inoculating the reactor or coupling system with anammox sludge and / or anammox sludge and sulfur autotrophic denitrification sludge, and then adding sludge-coal gangue-based activated carbon (SCAC), with artificially prepared influent at 1 mol·L⁻¹. -1 The pH of the influent was adjusted to 8.0 using HCl and NaOH, and N2 was introduced to reduce the dissolved oxygen concentration in the influent to less than 0.2 mg·L⁻¹. -1 Maintain an anaerobic environment; place the reactor at 35℃ and 120 r·min. -1 The reactor was continuously operated in the environment for 60-104 days, with 1g of S added weekly. 0 Powder; reactor performance is analyzed during this process.

[0007] The influent contains 100~300 mg·L -1 NO3 - -N, 2g·L -1 NaHCO3, 27.6 mg·L -1 KH2PO4, 180 mg·L - 1 CaCl2·2H2O, 300 mg·L -1 MgSO4·7H2O, 1 mL of trace element I and 1 mL of trace element II; the composition of the trace element solution is as follows (g / L):

[0008] .

[0009] Further, the method specifically comprises the following steps:

[0010] (1) Inoculation of sludge and addition of SCAC: The municipal sludge was allowed to stand for 24 h, and the supernatant was discarded. The MLSS was measured to be 7.34 g / L, and the MLVSS was measured to be 4.40 g / L. 150 mL of sludge was inoculated in the reactor, and 1 g of SCAC was added thereto;

[0011] (2) Operation of the reactor: The reactor was placed in a constant-temperature shaking box at 35°C, 120 r·min -1 , and was operated every week by adding 1 g of S 0 . The water was intermittently fed, and the HRT was controlled to be 12 h. The reactor was continuously operated for 60 d, which was divided into three stages. Except that the concentration of NO3 - -N in the influent was different, the other conditions were the same. The first stage was 1-7 d, the concentration of NO3 - -N in the influent was 100 mg·L -1 , the second stage was 8-20 d, the concentration of NO3 - -N in the influent was 200 mg·L -1 , and the third stage was 21-60 d, the concentration of NO3 - -N in the influent was 300 mg·L -1 .

[0012] (3) Performance analysis: The effluent of the reactor was analyzed every day in terms of routine water quality, including NO2 - -N, NO3 - -N, SO4 2- , and pH. The water sample was filtered by using a water filter head with a pore size of 0.45 µm. NO2 - -N was analyzed by using N-(1-naphthyl)-ethylenediamine spectrophotometry, NO3 - -N was analyzed by using ultraviolet spectrophotometry, and SO4 2- was analyzed by using barium chromate spectrophotometry (cold method). The conversion rate of NO3 - -N, the accumulation rate of NO2 - -N, the removal rate of total nitrogen (TN), the reduction rate of NO3 - -N, and the reduction rate of NO2 - -N were determined. After the performance was stable in each reaction stage, the reactor was sampled at intervals of 1 h, and the reaction rate was analyzed. At the end of the operation of the reactor, sludge samples were taken, and the content of EPS, the content of microbial protein, and the concentration of polysaccharide were analyzed by using the Bradford method, the anthrone-sulfuric acid colorimetric method, and microbial sequencing analysis.

[0013] The effective volume of the reactor is 400 mL.

[0014] The sludge sample was subjected to microbial sequencing analysis method, the sample DNA was extracted by kit, 16S rRNA V3-V4 region primers were 341F: 5'-CCTACGGGAGGCAGCAG-3' and 805R: 5'-GACTACHVGGGTATCTAATCC-3', and Illumina high-throughput sequencing was carried out.

[0015] NO3 - -N conversion rate, NO2 - -N accumulation rate, total nitrogen TN removal rate, NO3 - -N reduction rate, NO2 - The specific calculation formula of the -N reduction rate is as follows:

[0016] ; wherein, C i refers to the influent substance concentration (mg·L -1 ), C e refers to the effluent substance concentration, C x refers to the substance concentration at x hour.

[0017] The present application proves the feasibility of SCAC in promoting nitrite accumulation and operation stability in the process of sulfur autotrophic denitrification by analyzing nitrogen conversion, reaction rate, EPS secretion and microbial community structure change, and provides a new way for stable operation of Anammox.

[0018] The results show that: adding SCAC not only has a positive effect on the accumulation of NO2 - -N, but also promotes the growth of denitrifying bacteria. Compared with the non-addition, the accumulation rate of NO2 - -N in the reactor is increased by 30.7%; after the impact, the reactor shows a faster adaptability, when the concentration of NO3 - -N is 300 mg·L -1 , the recovery time of the reactor performance (6d) is half (12d) of the control group; the PN content in sludge EPS is significantly increased, increased by 53.2%, which increases the PN / PS by 48.7%; the relative abundance of denitrifying bacteria is improved, Thiobacillus , Sulfurimonas and Thermomonas the relative abundance of denitrifying bacteria is improved,

[0019] The application improves the nitrite accumulation ability and operation stability in the sulfur autotrophic denitrification process by adding sludge-gangue-based biochar to the SBR reactor, and explores the reaction rate, sludge EPS secretion and microbial community structure change in the reaction process. High-efficiency and stable nitrite accumulation is a necessary condition for the stable operation of anaerobic ammonia oxidation, and the application provides a new way. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 For the denitrification effect of the reactor in the cultivation process; in the figure: S1 is the reactor without adding SCAC, S2 is the reactor adding biochar;

[0021] Figure 2 For the SADN reaction rate when the concentration of NO3 - - N is 100 mg·L -1 ;

[0022] Figure 3 For the SADN reaction rate when the concentration of NO3 - - N is 200 mg·L -1 ;

[0023] Figure 4 For the SADN reaction rate when the concentration of NO3 - - N is 300 mg·L -1 ;

[0024] Figure 5 For the change of EPS in the reactor;

[0025] Figure 6 For the microbial community composition in the reactor;

[0026] Figure 7 For the nitrogen change in the Anammox-SADN reactor;

[0027] Figure 8 For the ammonia nitrogen removal rate in the Anammox-SADN reactor;

[0028] Figure 9 For the change of SO4 2- concentration in the Anammox-SADN reactor;

[0029] Figure 10 For the change of pH in the Anammox-SADN reactor;

[0030] Figure 11 For the change of reaction rate in the Anammox-SADN reactor; in the figure: (a) is NH4 + - N; (b) is NO3 - - N; (c) is NO2— N;

[0031] Figure 12 The changes in EPS composition of sludge in AS1 and AS2;

[0032] Figure 13 The relative abundance (phylum level) of microorganisms in AS1 and AS2;

[0033] Figure 14 The community structures of Proteobacteria and Planicillium in AS1 and AS2 are shown (at the horizontal level); in the figure: (a) is Proteobacteria; (b) is Planicillium. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains, and all materials publicly cited herein and cited by them are incorporated herein by reference.

[0036] Equivalent technologies of the specific embodiments described herein that are readily apparent to those skilled in the art through routine experimentation are included in this application.

[0037] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the instruments and equipment used in the following examples are all standard laboratory instruments and equipment; unless otherwise specified, the experimental materials used in the following examples were all purchased from regular biochemical reagent stores.

[0038] The activated carbon used in this invention was prepared according to the method described in the SCAC reference "Preparation and Modification of Sludge and Coal Gangue-Based Activated Carbon and Its Application in Anaerobic Ammonia Oxidation" (Taiyuan University of Technology, 2021-06-01). Specifically, the sludge used in the experiment was taken from the return tank of a wastewater treatment plant, allowed to stand, filtered for 1 minute, dried in an oven at 105±2℃ for 24 hours, cooled to room temperature, and sealed for later use. The coal gangue was taken from a coal mine, crushed, ground to 120 mesh, and sealed for later use.

[0039] Pretreated coal gangue and sludge were mixed at a mass ratio of 6:4 and stirred thoroughly. Carbonized material and ZnCl2 activator (4 mol·L⁻¹) were added to a 50 mL centrifuge tube at a mass ratio of 2:1. -1), centrifugation (15000rpm, 15min) and filtration after 24h of immersion, and drying in a tube furnace (550℃, heating rate 10℃·min -1 ) under N2atmosphere for 1h, and then heated under reflux with 1.2mol·L -1 of hydrochloric acid for 1h, washed with hot deionized water until the pH of the washing liquid was neutral. Finally, an appropriate amount of HF solution was added and reacted for 1min, washed with distilled water until neutral, and dried in vacuum (80℃, 4h) to obtain the finished product.

[0040] Experimental Example 1

[0041] (1) Reaction device and method: Two SBR reaction devices were made of 500mL serum bottles, with a bottom diameter of 7cm and a height of 17cm, and an effective volume of 400mL. Intermittent water feeding was used, and the reactor was placed in a constant temperature shaking box (35℃, 120r·min -1 ). 1.0g of SCAC was added to one of the reactors, which was marked as S2, and the control group was marked as S1.

[0042] 1. Inoculation of sludge and simulated wastewater: The inoculated sludge was taken from the Zhengyang Wastewater Treatment Plant in Jinzhong City, Shanxi Province, and 150mL of flocculent sludge was inoculated into each reactor, with an MLSS of 7.34g·L -1 and an MLVSS / MLSS of 0.60.

[0043] Artificial water was used, which contained NO3 - -N (100~300mg·L -1 ), NaHCO3(2g·L -1 ), KH2PO4(27.6mg·L -1 ), CaCl2·2H2O(180mg·L -1 ), MgSO4·7H2O(300mg·L -1 ), 1mL of trace element I and 1mL of trace element II. The trace element composition is shown in Table 1, and the pH of the influent was adjusted to 8.5 with 1mol·L -1 of HCl and NaOH. The reactor was dosed with 1g of S 0 powder every week.

[0044] Table 1: Trace element solution composition, unit: g / L

[0045]

[0046] 2. Reactor operation parameters: The reactor was operated for 60d, which was divided into three stages, and the time, influent water quality and hydraulic retention time (HRT) of each stage are shown in Table 2.

[0047] Table 2: Operation parameters of each stage of the experiment

[0048]

[0049] 3. Analytical Methods: Water samples were filtered using a 0.45µm water filter. NO2 - -N was analyzed using the N-(1-naphthyl)-ethylenediamine spectrophotometric method. NO3 - -N was analyzed using ultraviolet spectrophotometry, SO4 2- Barium chromate spectrophotometry (cold method) was used for analysis. MLSS and MLVSS were analyzed using standard methods, and pH was determined using a pH meter. Microbial protein (PN) content was analyzed using the Bradford method, and polysaccharide (PS) concentration was analyzed using the anthrone-sulfuric acid colorimetric method. Additionally, sludge samples were collected at the end of the operation (60 days), and DNA was extracted from the samples using a kit. Primers for the V3-V4 region of 16S rRNA were 341F (5'-CCTACGGGAGGCAGCAG-3') and 805R (5'-GACTACHVGGGTATCTAATCC-3'), and Illumina high-throughput sequencing was performed.

[0050] 4. Calculation method: NO3 mentioned in the text - -N conversion rate, NO2 - -N accumulation rate, total nitrogen (TN) removal rate, NO3 - -N reduction rate, NO2 - The specific formula for calculating the -N reduction rate is as follows:

[0051] Among them, C i This refers to the concentration of substances in the influent (mg·L) -1 ), C e It refers to the concentration of substances in water, C x This refers to the concentration of the substance at hour x.

[0052] (II) Experimental Results

[0053] 1. Performance of SADN without SCAC addition:

[0054] NO2 - -N accumulation: Denitrification performance during the cultivation process of reactor S1 is as follows Figure 1 As shown. Stage I, influent NO3 - -N concentration is 100 mg·L -1 NO3 in the water - -N concentration and NO2 - The concentrations of -N were all 0, and NO3- - -N conversion rate and TN removal rate reached 100%. In Stage II, influent NO3... - -N concentration increased to 200 mg·L⁻¹-1 effluent NO3 - -N concentration and NO2 - The NO-N concentration remained at 0. No NO2 was observed in the first two culture phases. - The accumulation of NO3-. This is because the reaction time is too long relative to the denitrification performance of the reactor, leading to the accumulation of NO3-. - After -N is exhausted, the accumulated NO2 - -N becomes the electron acceptor (see section 2.3 for details). However, in stage III, the influent NO3... - -N concentration was further increased to 300 mg·L⁻¹ -1 Subsequently, due to high influent NO3 - -N concentration shocks reduce denitrification performance, leading to NO3... - -N was not completely consumed, resulting in a noticeable increase in NO2. - -N accumulation phenomenon. From day 21 to 32, NO3- in S1... - The reduction effect of -N is continuously suppressed, with an average NO3- concentration of -N. - -N conversion rate was 59.8%. On day 33, S1 began to gradually recover, and by day 50, its NO3... - -N conversion rate increased to 100%. During this period, the highest NO2 concentration in S1 was... - -N accumulation rate was 48.2%, with an average of 44.5%. After 50 days, NO3 in the influent... - -N was completely consumed again, NO2 - -N continues to participate in the reaction as an electron acceptor, S1 NO2 - -N accumulation rate decreased significantly, and NO2 at the end of stage III. - -N accumulation rate gradually stabilized at 22.3%, and TN removal rate stabilized at 77.7%.

[0055] SO4 2 -Concentration change: S 0 -SADN process with S 0 NO3 acts as an electron donor. - -N / NO2 - -N is the electron acceptor, and the final oxidation product is SO4. 2- Therefore, SO4 2- Changes in concentration can reflect the denitrification performance of the reactor. For example... Figure 1 As shown, in stage I, the average SO4 content in the effluent from reactor S1 is... 2- The concentrations were 876.2 mg·L⁻¹. -1 In the second stage, with the inflow of NO3... - An increase in -N concentration leads to an increase in SO4 in the effluent. 2- The concentration also increases accordingly, with average SO42- The concentration reached 1481.5 mg·L -1 In the third stage, the denitrification performance was inhibited, and the SO4 2- concentration decreased. On the 21st day, the effluent SO4 2- concentration of S1 dropped to 1023.4 mg·L -1 . With the gradual recovery and improvement of the denitrification performance, the effluent SO4 2- concentration gradually increased. Finally, at the end of the third stage, the effluent SO4 2- concentration stabilized at 1842.6 mg·L -1 .

[0056] Changes in pH: Changes in pH in the environment can cause changes in the charge on the surface of microbial cell membranes, affecting the absorption of nutrients by microorganisms and the activity of various enzymes in metabolic activities. Studies have shown that the optimal pH for the reduction of NO3 0 -N in S - -SADN is 8.5, and the optimal pH for the reduction of NO2 - -N is 7. Because H 0 + is produced during the S + -SADN process, the pH of the system gradually decreases as the reaction progresses. In this experiment, the influent pH was controlled at around 8.5, providing the optimal pH for the accumulation of NO2 - -N. In the first stage, the effluent pH of reactor S1 stabilized at 8.2. In the second stage, the effluent pH dropped to 7.8. In the third stage, the effluent pH continued to decrease, eventually stabilizing at 7.5.

[0057] 2. Performance of SADN when SCAC is added

[0058] Accumulation of NO2 - -N: In the first two stages, reactors S2 and S1 showed similar results, with the effluent NO3 - -N concentration and NO2 - -N concentration always being 0. In the third stage, S2 was also impacted by the high influent NO3 - -N concentration. From the 21st to the 26th day, the average NO3 - -N conversion rate of S2 was 63.7%. On the 27th day, it began to gradually recover, and by the 42nd day, its NO3 - -N conversion rate increased to 100%. During this period, the highest NO2 - -N accumulation rate of S2 was 63.0%, with an average of 57.4%. After the 42nd day, NO2 - -N accumulated in NO3 -After the -N is completely consumed, it continues to participate in the reaction as an electron acceptor. With the improvement of denitrification performance, the TN removal rate of S2 reaches 100% on day 50.

[0059] It is noteworthy that, after being suppressed by shock loading, S2 exhibited a faster recovery rate (6 days, compared to 12 days for S1). S2's NO3... - -N conversion reaches 100% within 22 days, while S1 requires 30 days. Meanwhile, at higher NO3 levels... - At the -N conversion rate, S2 also exhibited higher NO2 content. - -N accumulation rate. This indicates that SCAC helps improve S 0 The SADN system's shock resistance allows it to recover denitrification performance more quickly, while significantly improving S... 0 NO2 in the SADN system - -N Accumulation capability.

[0060] SO4 2 - Changes in concentration: such as Figure 1 As shown, in stage I, the average SO4 content in the effluent from reactor S2 is... 2- The concentrations were 876.6 mg·L⁻¹. -1 In Stage II, the average SO4 content in the S2 effluent was... 2- The concentration reached 1481.5 mg·L⁻¹ -1 The SO4 content in the effluent from the first two stages 2- The concentration is not much different from S1. In stage III, the SO42- content of S2... 2- The concentration also decreased. On day 21, the SO4 concentration in the effluent from S2 decreased. 2- The concentration decreased to 1084.5 mg·L⁻¹ -1 In subsequent cultivation, the effluent SO4 2- The concentration gradually increases. Finally, at the end of stage III, the effluent SO4 concentration... 2- The concentration remained stable at 2035.6 mg·L⁻¹ -1 The result is significantly higher than that of S1. This result indirectly confirms that when facing shock loads, S2 has better denitrification performance than S1, and exhibits stronger shock resistance.

[0061] Throughout Stage III, the effluent SO4 from S2... 2- The concentrations of all three components were higher than those of S1, which indirectly confirms that S2 has better denitrification performance than S1 when facing shock loads, and exhibits stronger shock resistance.

[0062] pH changes: The pH changes of the effluent from reactor S2 are as follows Figure 1The effluent pH of S2 was stable at 8.2 in the first stage. In the second stage, the effluent pH decreased to 7.7. In the third stage, the effluent pH continued to decrease and finally stabilized at 7.2. In the first two stages, the effluent pH of S2 was similar to that of S1. In the third stage, the effluent pH of S2 was significantly lower than that of S1. This indicates that the denitrification of S2 was more complete than that of S1, and more H + .

[0063] 3. Effect of SCAC on the SADN reaction rate: The denitrification process was divided into two stages according to whether NO3 - -N was depleted. When the concentration was 100 mg·L -1 (see Figure 2 ), the highest NO3 - -N reduction rate of S1 was 45.9 (mg-N·L -1 )·h -1 , and that of S2 was 63.7 (mg-N·L -1 )·h -1 , which was 39% higher than that of S1. Before and after the depletion of NO3 - -N, the highest NO2 - -N reduction rates of S1 were 18.2 and 36.9 (mg-N·L -1 )·h -1 , and those of S2 were 18.6 and 38.2 (mg-N·L -1 )·h -1 , which were 2.2% and 3.5% higher than those of S1. It can be seen that the NO2 - -N reduction rate increased significantly after the depletion of NO3 - -N, because NO2 - -N became the only electron acceptor in the SADN process (this phenomenon also occurred at other concentrations).

[0064] When the concentration was 200 mg·L -1 (see Figure 3 ), the highest NO3 - -N reduction rate of S1 was 61.9 (mg-N·L -1 )·h -1 , and that of S2 was 75.8 (mg-N·L -1 )·h -1 , which was 22.5% higher than that of S1. Before and after the depletion of NO3 - -N, the highest NO2 - -N reduction rates of S1 were 28.2 and 39.7 (mg-N·L -1 )·h -1 , and those of S2 were 31.0 and 42.5 (mg-N·L -1 )·h -1, increased by 9.9% and 7.1%. When the concentration was 300 mg·L -1 (see Figure 4 ), the highest NO3 - -N reduction rate of S1 was 70.6 (mg-N·L -1 )·h -1 , and that of S2 was 107.7 (mg-N·L -1 )·h -1 , increased by 52.5% compared with S1. Before and after the depletion of NO3 - -N, the highest NO2 - -N reduction rate of S1 was 30.5 and 52.6 (mg-N·L -1 )·h -1 , and that of S2 was 35.1 and 62.7 (mg-N·L -1 )·h -1 , increased by 15.1% and 19.2%.

[0065] The results showed that the addition of SCAC made the reactor S2 exhibit higher NO3 - -N reduction rate at each concentration, while the NO2 - -N reduction rate was less improved, which meant that the addition of SCAC could make more NO2 - -N accumulated in the SADN process.

[0066] 4. Changes of EPS in the reactors: The EPS content of the inoculated sludge was (3.97 ± 0.19) mg·gSS -1 , and after 60 d operation, the EPS content in reactors S1 and S2 was (4.89 ± 0.25) mg·gSS -1 and (6.77 ± 0.29) mg·gSS -1 , respectively. The increase of EPS in S2 was 1.88 mg·gSS -1 higher than that in S1. It could be seen from Figure 5 that the PN content in S1 was (3.44 ± 0.18) mg·gSS -1 , and the PS content was (1.45 ± 0.07) mg·gSS -1 ; while the PN content in S2 was (5.27 ± 0.21) mg·gSS -1 , and the PS content was (1.50 ± 0.08) mg·gSS -1PN accounted for 63.0%, 70.3%, and 77.8% of the EPS in the inoculated sludge, S1, and S2, respectively, indicating that PN is the main component of EPS. Compared with the inoculated sludge, the PS content in S1 and S2 did not change significantly, while the increase in PN in S2 was nearly three times that in S1. Furthermore, the PN / PS ratio was 1.70 for the inoculated sludge, 2.36 for S1, and 3.51 for S2, which is 1.5 times that of S1. Adding SCAC significantly increased the PN content in EPS and improved the PN / PS ratio.

[0067] PS is a hydrophilic substance, while PN is a hydrophobic substance. The content and ratio of these two substances affect the relative hydrophobicity of the sludge surface. The higher the PN / PS ratio, the stronger the relative hydrophobicity of the sludge surface, and the more likely it is to form granular sludge. Therefore, adding SCAC makes the sludge in the reactor more likely to form granular sludge, which also explains why S2 has stronger shock resistance.

[0068] 5. Changes in the microbial community structure within the reactor: Figure 6 This study aims to analyze the composition and succession of the microbial community within the reactor. Figure 6 The microbial composition at the phylum level (a) shows that Proteobacteria, Chloroflexi, Bacteroidetes, Myxomycetes, and Campylobacterota are important dominant phyla, with Proteobacteria having the highest relative abundance, accounting for 54.4% and 77.0% in S1 and S2, respectively. Proteobacteria are considered one of the key participants in the denitrification process, participating in various steps of denitrification through different enzymes.

[0069] Figure 6 b represents the composition of genus-level microorganisms. Thiobacillus The dominant bacteria, with the highest relative abundance, accounted for 40.0% and 51.8% in reactors S1 and S2, respectively. Meanwhile, [the following bacteria were also detected]. Sulfurimonas and Thermomonas . Sulfurimonas The relative abundances in S1 and S2 were 0.61% and 2.71%, respectively. Thermomonas The relative abundances in S1 and S2 were 0.03% and 3.47%, respectively. All three genera are closely related to denitrification. Thiobacillus It is the most common functional genus of SADN, and it is related to Thermomonas Contains NO3 - -N reductase and NO2 - -N reductase can convert S 0 and S 2- Reduction of NO3 by electron donor- -N and NO2 - -N. And Sulfurimonas Only NO3 - -N is reduced to NO2 - -N, which cannot be further reduced.

[0070] It was found that the surface of SCAC had obvious sponge-like protrusions, showing uneven and irregular pore structures, and had good capture and adsorption performance. The specific surface area of SCAC reached 146.25 m 2 ·g -1 , and the average pore size was 2.75 nm (mesoporous structure). This large specific surface area and developed pore structure helped to adsorb solutes and enrich microorganisms. As the results showed, the relative abundance of S2 Thiobacillus genus increased by 11.8% compared with S1. At the same time, the relative abundance of S2 Thermomonas increased from 0.03% in S1 to 3.47%. In addition, the relative abundance of S2 Sulfurimonas was significantly higher than that of S1, resulting in a significantly higher NO2 - -N accumulation rate in S2 than in S1.

[0071] Therefore, the addition of SCAC is beneficial to the growth of S 0 -SADN functional bacteria, improves the removal efficiency of NO3 0 -N in S - -SADN, and improves the accumulation efficiency of NO2 - -N. Stable supply of NO2 - -N is a necessary condition for stable operation of Anammox, so in the future, SCAC may be applied to S 0 -SADN-Anammox coupled denitrification process to enhance the coupling effect and improve the operation stability.

[0072] Experimental Example 2:

[0073] (1) Materials and methods: Two SBR reactors were inoculated with anaerobic ammonia oxidation sludge and sulfur autotrophic denitrification sludge. 1.0 g of SCAC was added to one of the reactors, denoted as AS2, and the control group was denoted as AS1. The reactors were placed in a constant temperature incubator (35℃, 120 r·min -1 ) and intermittent water was used. The water composition is shown in Table 3. After water distribution, 1 mol·L -1 of HCl and NaOH was used to adjust the water pH to 8.0, and N2 was used to make the water dissolved oxygen concentration less than 0.2 mg·L -1 , maintaining an anaerobic environment.

[0074] Table 3: Water composition of Anammox-SADN reactor

[0075]

[0076] The trace element ratio is the same as above. The reactor operated for a total of 104 days, divided into three stages. The time, influent water quality, and hydraulic retention time (HRT) of each stage are shown in Table 4.

[0077] Table 4: Operating parameters of Anammox-SADN at various stages

[0078]

[0079] (II) Experimental Results

[0080] 1. Performance of Anammox-SADN without SCAC addition

[0081] Changes in denitrification performance: such as Figure 7 and Figure 8 As shown, in stage I (1-22d), the influent NH4 to reactor AS1 + -N concentration is 50 mg·L -1 NO3 - -N concentration is 100 mg·L -1 During this period, AS1's NH4 + -N removal rates have remained low, with a maximum of only 15.2% and an average of 11.4%, while the effluent NO2... - -N concentration and NO3 - -N concentrations were almost zero, NO3 - -N removal rate reached 100%. This may be due to the relatively fast reaction rate of SADN in the reactor at this time, when NO3... - After -N is completely consumed, the accumulated NO2 - -N, becoming the sole electron acceptor of SADN, was quickly consumed, leaving insufficient NO2. - -N is used by Anammox. Therefore, NO3 will be introduced into the water on day 23. - -N concentration increased to 200 mg·L⁻¹ -1 Phase II, NH4 in AS1 + -N removal improved somewhat, but not significantly. (Days 23-37, NH4+) + -N removal rate slowly increased to 22.6% and remained at this level for 38-54 days. On day 55 (stage III), the influent NH4... + -N concentration increased to 100 mg·L⁻¹ -1 NH4 of AS1 + After a brief fluctuation (3 days), the -N removal effect began to show an upward trend. Until day 75, NH4...+ The removal rate of -N increased to 42.4% and maintained at this level from 76 to 104 d (the maximum removal rate was 44.4% during this period).

[0082] In the second and third stages, the effluent NO2 - The concentration of -N and NO3 - The concentration of -N was always 0, indicating that the SADN process in AS1 was complete (all available substrate was consumed) and Anammox was likely in a state of substrate deficiency in the middle and late stages of the reaction cycle, which could be the reason for the low NH4 + The reason for the low removal rate of -N.

[0083] SO4 2- Concentration changes: from 100 mg·L Figure 3 In the first stage, the effluent SO4 2- concentration of reactor AS1 was relatively stable, with an average of 829.0 mg·L -1 In the second stage, because the influent NO3 - -N concentration increased from 100 mg·L -1 to 200 mg·L -1 , the effluent SO4 2- concentration increased significantly, with an average effluent SO4 2- concentration of 1434.2 mg·L -1 from 23 to 54 d. In the Anammox-SADN coupled denitrification system, SO4 2- is mainly produced when SADN reduces NO3 - -N and NO2 - -N, so changes in the SO4 2- concentration can reflect the contribution of SADN to denitrification. The effluent SO4 2- concentration of AS1 was relatively stable in the first two operating stages, which was due to the lack of significant changes in the removal of NH4 + -N (see section 1.1.1), while in the coupled denitrification system, NH4 + -N is mainly removed by the Anammox process, so the proportion of Anammox and SADN contribution to denitrification does not change significantly, resulting in a stable amount of SO4 2- . In the third stage, only the influent NH4 + -N concentration was increased, while the NO3 - -N concentration did not change, so theoretically the effluent SO4 2- concentration should not change. However, the NH4 +The removal efficiency of -N has improved, which means that Anammox's contribution to nitrogen removal has increased. Therefore, the SO4 produced in the SADN process... 2- The amount decreased, and the average effluent SO4 after the reactor performance stabilized (76-104 days) was... 2- The concentration was 1303.0 mg·L⁻¹ -1 .

[0084] 2. Performance of Anammox-SADN when adding SCAC

[0085] Changes in denitrification performance: such as Figure 7 and Figure 8 As shown, reactor AS2 operates similarly to AS1 in stage I, with NH4 + -N removal rates were at a low level (maximum 15.8%, average 13.7%), and the effluent NO2... - -N concentration and NO3 - -N concentrations were almost all 0.

[0086] Phase II, NH4 in AS2 + -N removal efficiency was significantly improved. On day 26, NH4+ + -N removal rate increased to 29.4% and remained relatively stable until day 32. On day 33, NH4+... + -N removal rate suddenly increased significantly, reaching 56.6%, and continued to rise until day 42, when the removal rate reached 74.8%, and then remained at this level until day 54 (during which the removal rate reached a maximum of 77.0%).

[0087] At the beginning of stage III, due to the influent NH4 + Increased -N concentration leads to increased NH4+ in AS2. + -N removal rate decreased significantly, reaching 46.6% on day 55. It wasn't until day 64 that the removal rate improved, reaching 63.9%. On day 78, the removal rate of NH4 in AS2... + -N removal rate recovered to the level at the end of Phase II, reaching 71.6%, and remained at this level until the end of the operation (during which the removal rate peaked at 75.4%).

[0088] Similar to AS1, AS2 has NO2 in stages II and III. - -N and NO3 - -N removal efficiency was the same as AS1, with the effluent concentration consistently at 0. It is worth noting that although AS2 achieved NH4+ removal efficiency at the end of the third stage... + -N removal rate is similar to (or even lower than) that of Stage II, while the influent NH4 in Stage III... +The -N concentration was twice that of stage II, so AS2's denitrification capacity was greatly improved during the third stage of operation.

[0089] It can be seen that during the 104-day operation, the NO2 in both reactors... - -N and NO3 - The removal effect of -N was the same, with the effluent concentration in both AS2 and AS3 reaching 0 and the removal rate reaching 100%. However, compared with AS1, AS2 had a lower NH4 removal rate. + -N removal effect is significantly better (maximum NH4) + -N removal rate increased by 69.8% compared to AS1. This indicates that AnAOB in AS2 is more effective at removing NO2. - -N has a stronger competitive ability, which may be related to the enrichment effect of SCAC on related functional bacterial groups.

[0090] SO4 2- Changes in concentration: such as Figure 9 As shown, the SO4 content of the effluent from reactor AS2 in stage I is... 2- The concentration was similar to AS1, averaging 824.9 mg·L⁻¹. -1 In stage II, the SO4 effluent from AS2... 2- The concentration was significantly lower than that of AS1, which is due to the NH4+ concentration in AS2 during stage II. + -N removal efficiency was significantly improved (see section 1.2.1). After performance stabilized (42-54 days), the average effluent SO4 level of AS2 decreased. 2- The concentration was 1324.4 mg·L⁻¹ -1 Compared with AS1, it decreased by 109.8 mg·L. -1 In stage III, the SO4 effluent from AS2... 2- After the concentration was further reduced and the performance stabilized (78-104 days), the average effluent SO4 concentration was... 2- The concentration was 1173.0 mg·L⁻¹ -1 Compared to Phase II, it decreased by 151.4 mg·L⁻¹. -1 Compared with AS1 in the same period, it decreased by 130 mg·L -1 Although the NH4 in stage III + -N removal rate remained unchanged compared to stage II, but influent NH4 removal rate remained unchanged. + The -N concentration increased by 100%, so NH4+ + The absolute removal of -N also nearly doubled, which means that Anammox's removal of NO2... - -N is more competitive, SADN is more effective against NO2. - The utilization rate of -N decreases, thereby reducing SO42-. 2- The generation of.

[0091] It can be seen that, starting from stage II, the SO4 content in the effluent of AS2... 2- The concentration was significantly lower than that of AS1, which actually reflects that Anammox's contribution to denitrification in AS2 was higher than that in AS1, which means that AnAOB gradually became the dominant bacteria in the reactor.

[0092] pH changes within the reactor: In the Anammox-SADN coupled denitrification system, the Anammox reaction is an alkali-inducing reaction, while the SADN reaction is an acid-inducing reaction. Therefore, pH changes within the reactor can indirectly reflect the degree of reaction of these two reactions. Figure 10 As shown, in the initial stage of reactor operation, the effluent pH of both reactors was similar, around 7.1, indicating that the SADN reaction was dominant in the reactors. In stage II, the effluent pH of AS1 fluctuated between 7.1 and 7.3, not significantly different from stage I, while the effluent pH of AS1 reached 7.6. This difference corresponds to the NH4+ reaction in AS2. + The removal efficiency of -N was significantly improved in Stage II, and the Anammox reaction concentration increased, thereby raising the pH within the reactor. In Stage III, the influent NH4+ to both reactors... + The concentrations of -N were increased, and compared with the first two stages, the denitrification effect of AS1 was improved, while AS2 could still maintain a high level of NH4. + -N removal rate, therefore the pH of both reactors increased to varying degrees. After the reaction in stage III stabilized, the effluent pH of AS1 was 7.4-7.6, while the effluent pH of AS2 was 7.8-7.9.

[0093] Throughout the operation, except for the first stage, there was a significant difference in the effluent pH of the two reactors, indicating a significant difference in the degree of Anammox reaction within the reactors. The effluent pH of AS2 was higher than that of AS1 after day 32, indicating that after the addition of SCAC, the degree of Anammox reaction in AS2 was higher than that in AS1, and the coupling effect with SADN was better, which was also confirmed by the denitrification effect.

[0094] Total nitrogen removal efficiency in the Anammox-SADN reactor: The Anammox process generates 11% NO3. - -N, resulting in a maximum TN removal rate of only 89%. In contrast, the Anammox-SADN coupled denitrification system can remove NO3 generated by Anammox. - -N is reduced to NO2 - -N is available for reuse by Anammox.

[0095] Depend on Figure 11It can be seen that, compared with single Anammox denitrification system, the TN removal effect of Anammox-SADN coupled denitrification system is obviously better, whether SCAC is added or not. Even in the early stage of reactor operation, when the coupling degree of Anammox and SADN is low, the reactor can maintain a TN removal rate of more than 65%. In contrast, when the nitrogen removal rate of the Anammox reactor is low at the beginning of operation, the TN removal rate is all below 40%. In the later stage of reactor operation, after the denitrification effect is stable, the TN removal rate of the Anammox system with SCAC added is as high as 83.2%, while the TN removal rate of the coupled system is stable at 91.7%, which exceeds the theoretical upper limit of Anammox denitrification.

[0096] This shows that, compared with single Anammox denitrification system, Anammox-SADN coupled denitrification system has better total nitrogen removal effect, and is suitable for practical wastewater containing NH4 + -N and NO3 - -N, and has a wider application range. It is worth noting that, compared with single denitrification system, the operation of coupled denitrification system in the same reactor is more complex, and as known from the foregoing, SCAC has obvious strengthening effect on the coupling of Anammox and SADN, which may provide a new idea for the application of Anammox in practical wastewater.

[0097] Effect of SCAC on Anammox-SADN reaction rate: In order to clarify the effect of SCAC on the reaction rate of Anammox and SADN in the reactor, after the reaction was stable in the third stage, the reactors AS1 and AS2 were sampled and analyzed every hour in a reaction period, and the removal rates of NH4 + -N, NO3 - -N and the accumulation amount of NO2 - -N in the two reactors were studied, and the results are as follows:

[0098] As shown in Figure 11 (a), the NH4 + -N removal rate of reactor AS2 is higher than that of AS1 in each time period, and the highest removal rates of the two are 8.4 and 6.3 (mg-N·L -1 )·h -1 , respectively, and the average removal rates are 6.0 and 3.4 (mg-N·L -1 )·h -1 , respectively. In the first hour of the reaction period, the difference between the NH4 + -N removal rates of the two reactors is the smallest, which is 0.6 (mg-N·L -1 )·h -1The largest difference was observed within the 8th hour, at 4.6 mg N·L. -1 )·h -1 NO3 in the two reactors - The removal rate of -N is shown in the figure. Figure 11 (b) NO3 in AS1 and AS2 - -N concentrations decreased to 0 at 8h and 9h, respectively. At 1h of the reaction cycle, the NO3 concentrations in both reactors... - The removal rates of -N were all at their maximum values, with AS1 and AS2 being 44.4 and 36.6 (mg-N·L), respectively. -1 )·h -1 The NO3 content of AS1 decreased to varying degrees during the subsequent reaction process. Throughout the entire reaction cycle, the NO3 content of AS1... - The overall NO2 removal rate was higher than that of AS2. - For the case of -N accumulation, see Figure 11 (c) NO2 in the first 3 hours of the two reactors - The accumulation of -N is similar, but in the subsequent reaction process, AS2 is lower than AS1. When NO3... - After -N is completely consumed, NO2 - The accumulation of -N decreased significantly, which is due to the fact that NO2 accumulation was reduced at this time. - -N becomes the sole electron donor for SADN. In the Anammox-SADN coupled denitrification system, NO2... - -N is mainly produced by the reaction of SADN. These NO2 - -N is partially utilized by SADN itself, partially by Anammox, and only the remainder accumulates in the reactor. Although AS2's NO2... - -N accumulation is lower than AS1, but its NO3 accumulation is lower. - The removal rate of -N is lower than that of AS1 (the generated NO2). - -N less), while NH4 + -N removal rate is significantly higher than that of AS1 (Anammox consumes NO2). - -N many), therefore, the actual NO2 of AS2 - The accumulation rate of -N is higher than that of AS1.

[0099] It can be seen that the addition of SCAC significantly increased the NH4+ concentration in the Anammox-SADN reactor. + -N removal rate, although NO3 - The removal rate of -N decreased slightly, but more NO2 accumulated during the reaction, which became available for Anammox to utilize. --N. This indicates that SCAC can enrich both AnAOB and SADN bacteria, but in the coupled denitrification system, the enrichment degree of the two bacteria is different, and it is obvious that the enrichment degree of AnAOB is greater than that of SADN bacteria. It is worth noting that compared with single SADN and Anammox reactors, the reaction rate of Anammox-SADN reactor is reduced, which may be because the coupled denitrification system requires two denitrification reactions to cooperate with each other, and compared with single denitrification system, the reaction itself is more complex. Secondly, the operating conditions of single denitrification system are the most suitable conditions for microbial growth, while the operating conditions of coupled system need to consider the growth conditions of two kinds of microorganisms, thus leading to a lower reaction rate than the former.

[0100] Changes of sludge EPS: From Table 5 and Figure 12 It can be seen that after 48 d of operation, the EPS contents of AS1 and AS2 sludge were (9.51 ± 0.51) mg·gSS -1 and (12.78 ± 0.67) mg·gSS -1 , respectively, and the PN accounted for 76.3% and 80.3%, respectively, which were the main components of sludge EPS. On the 104th day, the EPS contents of AS1 and AS2 sludge were (10.25 ± 0.53) mg·gSS -1 and (14.05 ± 0.68) mg·gSS -1 , respectively, and the PN accounted for 76.9% and 81.6%, respectively. With the progress of the reaction, the EPS content in both reactors increased, mainly the PN content. Compared with AS1, the EPS content and PN content of AS2 sludge were always higher than those of AS1.

[0101] On the 48th day, the PN contents of AS1 and AS2 sludge EPS were (7.26 ± 0.38) mg·gSS -1 and (10.26 ± 0.50) mg·gSS -1 , respectively, the PS contents were (2.25 ± 0.13) mg·gSS -1 and (2.52 ± 0.17) mg·gSS -1 , respectively, and the PN / PS was 3.23 and 4.07, respectively; on the 104th day, the PN contents of AS1 and AS2 sludge EPS were (7.88 ± 0.41) mg·gSS -1 and (11.47 ± 0.55) mg·gSS -1 , respectively, the PS contents were (2.37 ± 0.12) mg·gSS -1 and (2.58 ± 0.13) mg·gSS -1, PN / PS were 3.33 and 4.44, respectively. In contrast, the PS content in the EPS of the sludge in the two reactors showed no significant change in the middle and end of the operation stage, while the increment of PN in AS2 was about 2 times that of AS1, and the increase of PN / PS was 3.7 times that of AS1. The above shows that the addition of SCAC promotes the secretion of EPS, increases the PN content, promotes the aggregation of sludge in the reactor and enhances the impact resistance.

[0102] Table 5: EPS components and contents in AS1 and AS2

[0103]

[0104] 3. Microbial community structure changes

[0105] A. Comparison of microbial community structure at the phylum level: As shown in Figure 13 Table 6, the bacterial phyla with higher abundance in AS1 and AS2 were Proteobacteria, Bacteroidota, Chloroflexi, Planctomycetota, etc., which were similar to single Anammox. The relative abundance of Proteobacteria and Planctomycetota in AS1 was 66.01% and 0.35%, respectively, and in AS2 was 59.36% and 5.01%, respectively (see Table 6). Among them, the SADN-related flora belongs to Proteobacteria, and the AnAOB belongs to Planctomycetota. The relative abundance of Proteobacteria in AS2 was 6.65% lower than that in AS1, while the relative abundance of Planctomycetota was 9.34% higher than that in AS1, indicating that in the Anammox-SADN coupled denitrification system, SCAC has a more obvious enrichment effect on AnAOB than SADN bacteria, which also explains why the contribution of Anammox to denitrification in AS2 is significantly greater than that in AS1.

[0106] The foregoing part shows that, during the reaction process, the NO3 - - N removal rate of AS2 was slightly lower than that of AS1, while the NH4 + - N removal rate was significantly higher than that of AS1. Therefore, this is exactly the influence caused by the change of microbial community structure in the reactor after adding SCAC.

[0107] Table 6: Community composition of main bacterial phyla in AS1 and AS2

[0108]

[0109] B. Comparison of microbial community structure at genus level: In order to further study the influence of SCAC on the microbial community structure of the coupled system, the differences between Proteobacteria and Planctomycetota, two types of denitrification-related microorganisms, will be further discussed below. Figure 14 In (a), the community structure of Proteobacteria at the genus level was compared. The genera with high proportions were Thiobacillus , Sulfurimonas , Limnobacter are all denitrifying bacteria, in addition to Denitratisoma and Comamonas and other denitrifying bacteria. As can be seen from Table 7, Thiobacillus the relative abundance in AS1 and AS2 was 48.03% and 44.99% respectively, Sulfurimonas the relative abundance was 3.17% and 3.33% respectively, Limnobacter the relative abundance was 0.58% and 2.33% respectively. It can be seen that the relative abundance of Thiobacillus in AS2 is lower than that in AS1, Sulfurimonas the relative abundance is higher than that in AS1. Thiobacillus and Sulfurimonas are both common genera in the SADN process, but Thiobacillus has both NO3 - -N reductase and NO2 - -N reductase, while Sulfurimonas only has NO2 - -N reductase, Sulfurimonas a higher relative abundance means that more NO2 - -N can be accumulated in the SADN process, which is conducive to the coupling of Anammox denitrification.

[0110] As can be seen from Figure 14 (b), in AS1 and AS2, Candidatus Brocadia is the main AnAOB, with a relative abundance of 0.16% and 3.58% respectively in AS1 and AS2 (see Table 7), and the proportion of AnAOB in AS2 is significantly higher than that in AS1.

[0111] It can be seen that under the action of SCAC, the relative abundance of AnAOB has increased significantly, while the relative abundance of SADN bacteria has increased very limitedly, even decreased. This shows that in the Anammox-SADN denitrification system, SCAC is more conducive to the enrichment of AnAOB. Another possible reason is that SCAC can significantly improve the NO2 - -N accumulation capacity of the SADN reaction process, which makes the supply of NO2 - -N in the reactor more sufficient, which is also more conducive to the growth of AnAOB.

[0112] Table 7: Community composition of main nitrogen conversion bacteria (genus level)

[0113]

[0114] The present application verifies that: adding SCAC makes the denitrification performance of Anammox-SADN reactor more efficient. In the whole running process, the denitrification efficiency of AS2 is obviously higher than that of AS1, and the highest NH4 + - removal rate is 44.4%, and the highest of AS2 is 75.4%, which is increased by 69.8%.

[0115] Compared with AS1, the NH4 + - removal rate of AS2 is obviously improved, and the maximum removal rate is increased by 33.3%, and the average removal rate is increased by 76.5%. In addition, the removal rate of NO3 - - is slightly decreased, but more NO2 - - that can be used by Anammox is accumulated in the reaction process, which provides favorable conditions for Anammox to remove NH4 + -.

[0116] Compared with the single Anammox system, the total nitrogen removal effect of the Anammox-SADN coupled system is obviously better, and after the reactor runs stably, the TN removal rate of the coupled system with SCAC is stabilized at 91.7%, which exceeds the theoretical upper limit value 89% of the Anammox system.

[0117] SCAC promotes the sludge to secrete more EPS and PN, and significantly improves the PN / PS value in the sludge. Compared with AS1, the EPS content of the sludge in AS2 is increased by 37.1%, the PN content is increased by 45.6%, and the PN / PS value is increased by 33.3%. After running for 104d, the EPS content of the sludge in AS1 and AS2 is 10.25mg·gSS -1 and 14.05mg·gSS -1 respectively. Among them, the PN content is 7.88mg·gSS -1 and 11.47mg·gSS -1 respectively, accounting for 76.9% and 81.6% respectively; the PS content is 2.37mg·gSS -1 and 2.58mg·gSS -1 respectively; and PN / PS is 3.33 and 4.44 respectively.

[0118] The results of Chao, ACE, Shannon, and Simpson indices showed that there were differences in microbial community structure between AS1 and AS2. Compared with AS1, the species abundance and microbial community diversity were lower in AS2, but the proportion of dominant bacteria was larger. In terms of the dominant phylum with higher abundance, the two were similar, and were Proteobacteria, Bacteroidota, Chloroflexi, Planctomycetota, etc. The main functional genera related to nitrogen transformation belonged to Proteobacteria and Planctomycetota, and their relative abundances in AS1 were 66.01% and 0.35%, respectively, and in AS2 were 59.36% and 5.01%, respectively. The relative abundance of Proteobacteria in AS2 was 6.65% lower than that in AS1 at the same period, but the relative abundance of Planctomycetota was 4.66% higher, indicating that SCAC was more conducive to the enrichment of AnAOB. At the genus level, the dominant SADN bacteria in AS1 and AS2 were Thiobacillus and Sulfurimonas , and the dominant AnAOB were Candidatus Brocadia , although the compositions were similar, but the relative abundances were obviously different. In the total bacterial community of AS1 and AS2, Thiobacillus accounted for 48.03% and 44.99%, respectively, Sulfurimonas accounted for 3.17% and 3.33%, respectively, Candidatus Brocadia accounted for 0.16% and 3.58%, respectively. The relative abundance of Thiobacillus decreased in AS2, but the relative abundance of Sulfurimonas obviously increased, which was conducive to the accumulation of more NO2 - -N in the reactor, and promoted the coupling of Anammox and SADN for denitrification. Moreover, the relative abundance of Anammox bacteria genus in AS2 was also obviously higher than that in AS1, indicating that SCAC was conducive to maintaining a relatively balanced proportion of microorganisms in the reactor, thereby more effectively denitrifying.

[0119] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for improving the accumulation rate of nitrite and the operational stability in the process of sulfur autotrophic denitrification, characterized in that: The influent was artificial water, and the pH of the influent was adjusted to 8.0 by 1 mol·L -1 of HCl and NaOH, and the dissolved oxygen concentration of the influent was less than 0.2 mg·L -1 by passing N2 to maintain an anaerobic environment. The performance of the reactor was analyzed during the process. The reaction of the sulfur autotrophic denitrification system comprises the following steps: (1) inoculating sludge and adding SCAC: the municipal sludge is left standing for 24 hours, the supernatant is discarded, the MLSS is measured as 7.34 g / L, and the MLVSS is measured as 4.40 g / L; 150 mL of sludge is taken to inoculate the reactor, and 1 g of coal gangue-based activated carbon SCAC is added; (2) Reactor operation: the reactor was placed in a constant temperature shaking box at 35℃, 120 r·min -1 , and 1 g of S 0 was added every week; intermittent water feeding was adopted, and HRT was controlled at 12 h; the reactor was continuously operated for 60 d, which was divided into three stages, and other conditions were the same except for the different concentrations of NO3 - -N in the influent; the first stage was 1~7 d, the concentration of NO3 - -N in the influent was 100 mg·L -1 , the second stage was 8~20 d, the concentration of NO3 - -N in the influent was 200 mg·L -1 , and the third stage was 21~60 d, the concentration of NO3 - -N in the influent was 300 mg·L -1 ; (3) Performance analysis: routine water quality analysis was performed on the effluent of the reactor every day, including NO2 - -N, NO3 - -N, SO4 2- , pH, the water sample was filtered with a water filter head of 0.45 pm, NO2 - -N was analyzed by N-(1-naphthyl)-ethylenediamine spectrophotometry, NO3 - -N was analyzed by ultraviolet spectrophotometry, SO4 2- was analyzed by barium chromate spectrophotometry (cold method), the removal rate of NO3 - -N conversion rate, NO2 - -N accumulation rate, total nitrogen TN removal rate, NO3 - -N reduction rate, NO2 - -N reduction rate; after the performance of each reaction stage was stable, the reactor was sampled at intervals of 1 h to analyze the reaction rate; at the end of the reactor operation, sludge samples were taken to analyze the EPS content, microbial protein content was analyzed by Bradford method, polysaccharide concentration was analyzed by anthrone-sulfuric acid colorimetry, and microbial sequencing analysis was performed; The Anammox-SADN coupling system reaction specifically includes the following steps: the ASBR reactor is inoculated with anaerobic ammonia oxidation sludge and sulfur autotrophic denitrification sludge; 1.0 g of SCAC is added to the reactor; the reactor is placed at 35°C, 120 r·min -1 The pH of the influent is adjusted to 8.0 by using 1 mol·L -1 of HCl and NaOH, and the dissolved oxygen concentration of the influent is less than 0.2 mg·L -1 by using N2 to maintain an anaerobic environment; The reactor operated for a total of 104 days, divided into three stages. In each stage, NO3 was added to the influent. - Except for the different NO3- concentrations, all other conditions were the same; Phase I lasted from 1 to 22 days, with influent NO3- - -N concentration is 100 mg·L -1 NH4 inlet water + -N concentration is 50 mg·L -1 The initial HRT is 24 hours; the second stage is 23-54 days, with influent NO3... - -N concentration is 200 mg·L -1 NH4 inlet water + -N concentration is 50 mg·L -1 The HRT is 24h; the third stage is 55-104d, with influent NO3. - -N concentration is 200 mg·L -1 NH4 inlet water + -N concentration is 100 mg·L -1 HRT is 24h; Performance analysis: The effluent of the reactor was analyzed for routine water quality every day, including NO2 - -N, NO3 - -N, SO4 2- , pH, the water sample was filtered with a water filter head of 0.45 pm, NO2 - -N was analyzed by N-(1-naphthyl)-ethylenediamine spectrophotometry, NO3 - -N was analyzed by ultraviolet spectrophotometry, SO4 2- was analyzed by barium chromate spectrophotometry (cold method), and NO3 - -N conversion rate, NO2 - -N accumulation rate, total nitrogen TN removal rate, NO3 - -N reduction rate, NO2 - -N reduction rate; after the performance of each reaction stage was stable, the reactor was sampled at intervals of 1 h to analyze the reaction rate; at the end of the reactor operation, sludge samples were taken to analyze the EPS content, microbial protein content was analyzed by Bradford method, polysaccharide concentration was analyzed by anthrone-sulfuric acid colorimetry, and microbial sequencing analysis was performed.

2. The method of claim 1, wherein: When the reaction is carried out by using the sulfur autotrophic denitrification system, anaerobic anammox sludge is inoculated into the reactor, and the influent contains 100-300 mg·L -1 NO3 - -2 g·L -1 NaHCO3, 27.6 mg·L -1 KH2PO4, 180 mg·L -1 CaCl2·2H2O, 300 mg·L -1 MgSO4·7H2O, 1 mL of trace element I and 1 mL of trace element II; The influent for the Anammox-SADN coupled system reaction contains NH4 + - N(NH4Cl) 25-100 mg·L -1 , NO2-N 130 mg·L -1 , NO3-N 100-200 mg·L -1 , KHCO3 500 mg·L -1 , KH2PO4 27.6 mg·L -1 , CaCl2·2H2O 180 mg·L -1 , MgSO4·7H2O 300 mg·L -1 , 1 mL of trace elements I and 1 mL of trace elements II; The components of the trace element solution are as follows: g / L: 。 3. The method of claim 1, wherein: The effective volume of the reactor is 400 mL.

4. The method of claim 1, wherein: The method for sequencing the sludge sample is to extract sample DNA by using a kit, the V3-V4 region primers of 16S rRNA are 341F: 5'-CCTACGGGAGGCAGCAG-3' and 805R: 5'-GACTACHVGGGTATCTAATCC-3', and Illumina high-throughput sequencing is performed.

5. The method of claim 1, wherein: NO3 - -N conversion, NO2 - -N accumulation rate, total nitrogen TN removal rate, NO3 - -N reduction rate, NO2 - The specific calculation formula of the -N reduction rate is as follows: ； wherein C i refers to the concentration of the substance in the influent (mg L -1 ), C e refers to the concentration of the substance in the effluent, and C x refers to the concentration of the substance at the xth hour.

Images