Method for strengthening formation of salt-tolerant aerobic granular sludge and its denitrification performance in high-salinity wastewater treatment

Abstract

The application discloses a method for strengthening salt-tolerant aerobic granular sludge formation and its denitrification performance in high-salinity wastewater treatment, and specifically comprises the following steps: taking activated sludge of a municipal wastewater treatment system and salt-tolerant sludge of an industrial wastewater treatment system as mixed inocula to culture S-AGS, optimizing SBR reactor operation conditions, identifying S-AGS core species by 16S rRNA high-throughput sequencing and co-occurrence network analysis, providing a theoretical basis for directional strengthening of the structural stability and denitrification performance, screening and expanding core functional strains, compounding Thauera T-1 and Pseudofulvimonas P-1 obtained by screening and expansion to prepare a composite functional microbial agent, and putting the composite functional microbial agent into the reactor on the basis of the mixed inocula and reactor conditions to synergistically strengthen the denitrification performance of the S-AGS.

Description

Technical Field

[0001] This invention belongs to the field of biological enhancement treatment technology for high-salt organic wastewater, specifically relating to a method for enhancing the formation of salt-tolerant aerobic granular sludge and its denitrification performance in the treatment of high-salt wastewater. Background Technology

[0002] Aerobic granular sludge (AGS) technology boasts advantages such as good settling performance, high load tolerance, and strong resistance to salt stress, making it highly promising for the treatment of high-salt organic wastewater. However, under high salt stress, the AGS process faces engineering challenges, including unstable particle structure and limited removal of pollutants (especially nitrogen pollution), hindering its engineering application. Cultivating structurally stable and highly efficient nitrogen-removing salt-tolerant aerobic granular sludge (S-AGS) is crucial. Current S-AGS cultivation methods mostly involve first cultivating granular sludge using conventional activated sludge as inoculum, and then gradually increasing salinity to improve the community's salt tolerance. However, a single sludge inoculum source is insufficient to cultivate stable, salt-tolerant S-AGS. Researchers typically use biochemically activated sludge, known for its rich species diversity and good settling properties, as inoculum for cultivating AGS. However, AGS has limited salinity tolerance and exhibits unstable performance under high-salt stress. Compared to conventional activated sludge, microbial communities originating from high-salt environments such as industrial wastewater have higher salinity tolerance and more diverse metabolic pathways. However, these communities have poor self-flocculation capabilities, making it difficult to form structurally stable granular sludge. Furthermore, as salinity increases progressively, microbial activity generally decreases, and sludge loss becomes severe, especially for denitrifying bacteria (such as denitrifying bacteria, ammonia oxidizing bacteria, and nitrite oxidizing bacteria), which are highly sensitive to salinity. Their metabolism is severely inhibited, leading to a collapse in the process's denitrification performance. To address these issues, the characteristics of AGS microbial community zoning, colonization, and functional interactions should be fully utilized. From the perspectives of inoculum sludge selection, operational condition optimization, and functional agent enhancement, a method for enhanced cultivation of S-AGS should be proposed to achieve efficient and stable denitrification of S-AGS under high-salt stress. Summary of the Invention

[0003] To address the aforementioned problems, the present invention aims to provide a method for enhancing the formation and denitrification performance of salt-tolerant aerobic granular sludge in the treatment of high-salt wastewater.

[0004] This invention proposes a method for cultivating S-AGS using a mixture of activated sludge from urban wastewater treatment systems and salt-tolerant sludge from industrial wastewater treatment systems as inoculum. Based on the optimization of the inoculum sludge, this invention develops a method for cultivating S-AGS with strong aeration, short settling time, and gradient salinity acclimatization. Then, 16S rRNA high-throughput sequencing and co-occurrence network analysis are used to identify the core species of S-AGS, providing a theoretical basis for targeted enhancement of its structural stability and denitrification performance. Core functional strains are screened and expanded. Thaurera T-1 and Pseudofulvimonas P-1 obtained from the screening and expansion are combined to prepare a compound functional bacterial agent, which is then introduced into an SBR reactor to leverage the synergistic enhancing effect of Thaurera spp. and Pseudofulvimonas spp. on the denitrification performance of S-AGS, endowing S-AGS with the potential for simultaneous nitrification and denitrification under high salt stress, and enhancing the denitrification performance of high-salt wastewater treatment processes.

[0005] The specific technical solution is as follows:

[0006] A method for enhancing the formation and denitrification performance of salt-tolerant aerobic granular sludge in high-salt wastewater treatment includes the following steps:

[0007] 1) S-AGS was cultured using activated sludge from urban sewage treatment systems and salt-tolerant sludge from industrial wastewater treatment systems as mixed inoculum, and the operating conditions of the SBR reactor were optimized.

[0008] 2) High-throughput sequencing of 16S rRNA and co-occurrence network analysis were used to identify core species with good salt tolerance in S-AGS, providing a theoretical basis for targeted enhancement of their structural stability and denitrification performance;

[0009] 3) Based on the screening and amplification of the core functional strains in step 2), Thaurata T-1 and Pseudofulvimonas P-1 obtained from the screening and amplification were combined to prepare a compound functional bacterial agent. Based on the mixed inoculum and reactor conditions in step 1), the compound functional bacterial agent was added to allow Thaurata spp. and Pseudofulvimonas P-1 to exert their effects.

[0010] Synergistic enhancement of the denitrification performance of S-AGS by Pseudofulvimonas spp.

[0011] Furthermore, in step 1), the salinity of the salt-tolerant sludge is ≥1%, and the mixing mass ratio of activated sludge and salt-tolerant sludge is 2:1-1:1. The salt-tolerant sludge in the industrial wastewater treatment system is taken from wastewater (mother liquor) from production wastewater (pharmaceutical, chemical, fine chemical, coal chemical, petrochemical, etc.) and wastewater regeneration concentrate from wastewater from papermaking, printing and dyeing, power plant desulfurization, etc. The proportion of salt-tolerant sludge in industrial wastewater should not exceed 50%, otherwise the sludge granulation process will be slow and the particle structure will be difficult to stabilize.

[0012] Furthermore, the effective volume of the sequencing batch reactor (SBR) in step 1) is 4.0±0.2L, with a height-to-diameter ratio of 5:1, a volume exchange ratio of 50%, and an ambient temperature of 25±2℃. Oxygen is supplied to the reactor through bottom aerators, with a surface gas velocity of 1.2cm / s and dissolved oxygen of 7.5–8.5mg / L. Unlike conventional operation, stronger aeration generates higher hydraulic shear forces, stimulating microorganisms to secrete extracellular polymeric substances (EPS) and creating higher hydraulic selective pressure to promote particle formation. The operating cycle is 4 hours, including 3 minutes of influent, 35 minutes of settling, 187–192 minutes of aeration, 5–10 minutes of sedimentation, and 5 minutes of effluent. Sludge discharge is not strictly controlled, and the pH value is controlled at 7.0± Setting a shorter settling time (0.2) helps to discharge sludge with poor settling performance as early as possible during the drainage stage, while promoting the retention of high-performance granular sludge in the system. A gradient acclimatization method is used to enhance the salt tolerance of the sludge. The reactor is operated in six stages for a long time, with influent salinity of 0, 10, 20, 30, 35, and 40 g / L (based on NaCl), influent COD of 800–1000 mg / L, and COD / TN ratio of 20:1, to promote microbial growth. Each stage lasts for 15–20 days. After the COD and TN removal performance stabilizes, the salinity can be increased. Gradient salinity conditions are conducive to adaptive changes in the microbial community and avoid cell death caused by high osmotic pressure under instantaneous salt stress.

[0013] Furthermore, in step 2), the dynamic succession of the microbial community structure with changes in salinity was investigated to clarify the impact of salinity on the S-AGS microbial community. 16S rRNA high-throughput sequencing and co-occurrence network analysis were used to identify the salt-tolerant core species Thaurera spp. and Pseudofulvimonas spp.

[0014] Furthermore, in step 3), Thaurata T-1 and Pseudofulvimonas P-1 are compounded in a biomass ratio of 2:1 to 1:2 in the compound functional bacterial agent.

[0015] Furthermore, the amount of compound functional microbial agent added is 3% to 10% of the biomass.

[0016] Further, the screening and amplification process in step 3) is as follows: S-AGS was obtained from a stably operating SBR reactor as the source of salt-tolerant co-culture strains. Granular sludge was thoroughly ground and dispersed, and strains were isolated using a dilution method. The diluted bacterial suspension was uniformly coated onto a solid medium containing 100 mg / L LB, and different concentrations of NaCl were added to simulate a salt stress environment. The medium was then sealed with sealing film and incubated overnight in a constant temperature incubator. After single colonies grew, several salt-tolerant strains were finally screened through multiple plate plating and streaking processes. When the salinity of the medium was 10 g / L, the selected strains were passaged three times and then frozen in 50% glycerol at -80°C. 16S rDNA gene sequencing was then performed, and a phylogenetic tree was generated using the BLAST (basic local alignment search tool) algorithm to screen for the strain most similar to Thaureraspp. (named Thaureras T-1). Similarly, when the culture medium salinity was 30 g / L, the strain most similar to Pseudofulvimonas spp. was screened out (named Pseudofulvimonas P-1) and used as a reserve core functional strain for exogenous enhancement of the reactor.

[0017] The beneficial effects of this invention are as follows:

[0018] 1) This invention proposes to cultivate S-AGS by using activated sludge from urban sewage treatment systems and salt-tolerant sludge from industrial wastewater treatment systems as mixed inoculum. Compared with single sludge inoculation, this method combines the advantages of activated sludge being easy to aggregate and granulate with the strong salt tolerance of industrial sludge, and can cultivate S-AGS with dense particles and good strength, giving it efficient denitrification and carbon removal performance under high salt stress.

[0019] 2) This invention develops a method for cultivating S-AGS with strong aeration, short settling time, and gradient salinity acclimatization. This method can stimulate microorganisms to secrete extracellular polymers and form higher hydraulic selective pressure to promote particle formation. This is beneficial for discharging sludge with poor settling performance as early as possible during the drainage stage and for retaining high-performance granular sludge in the system. It is also beneficial for the microbial community to undergo adaptive changes and avoid cell death caused by high osmotic pressure under instantaneous salt stress. 3) With the goal of directional enhancement of S-AGS structural stability and denitrification performance, this invention targets and identifies the core species of S-AGS and screens and expands them to obtain a compound functional bacterial agent (ThaueraT-1 + Pseudofulvimonas P-1). Both microorganisms are functional bacteria with simultaneous nitrification and denitrification capabilities. Thaurera T-1's strong EPS secretion ability is beneficial for maintaining the stability of S-AGS particles, and Pseudofulvimonas... P-1's strong salt tolerance helps improve the salt stress resistance of S-AGS. The two work synergistically to endow S-AGS with the potential for simultaneous nitrification and denitrification under high salt stress, and enhance the denitrification performance of the process for treating high-salt wastewater. Attached Figure Description

[0020] Figure 1 The following are the performance results under three different sludge inoculation conditions in Example 1: (a) Particle size of salt-tolerant aerobic granular sludge, (b) Influent COD and removal rate, (c) Influent TN and removal rate, (d) NH4+ + -N and removal rate;

[0021] Figure 2 The images are optical microscope images of sludge samples taken at 4% salinity in Example 1. (a) is reactor R1, (b) is reactor R2, and (c) is reactor R3.

[0022] Figure 3 This is a diagram of the collinear microbial network of sludge from reactor R3 at a salinity of 1-4% in Example 2.

[0023] Figure 4 For the nitrogen conversion process of RC and RTP, NH4 + -N, NO2 - -N and NO3 - -N degradation curves, (a) and (e) are the ammonia oxidation process of the RC group and the RTP group, respectively; (b) and (f) are the nitrite oxidation process of the RC group and the RTP group, respectively; (c) and (g) are the nitrite reduction process of the RC group and the RTP group, respectively; (d) and (h) are the nitrate reduction process of the RC group and the RTP group, respectively. Detailed Implementation

[0024] The present invention will be further described below with reference to the embodiments and the accompanying drawings, but the scope of protection of the present invention is not limited thereto.

[0025] Example 1: Optimal Formulation of Inoculated Sludge and Optimization of Reactor Operating Conditions

[0026] Three SBR reactors were set up to investigate the effect of inoculated sludge source on the cultivation performance of S-AGS: the inoculated material of reactor R1 was sludge from the aeration tank of a municipal wastewater treatment plant, with a MLSS (mixed liquor suspended solids concentration) of 4000±110 mg / L and an MLVSS (mixed liquor volatile suspended solids concentration) of 2568±70 mg / L; the inoculated material of reactor R2 was sludge from the secondary sedimentation tank of a pharmaceutical and chemical wastewater treatment plant. The sludge was collected, aerated, and then inoculated. The MLSS of the industrial source salt-tolerant sludge was 4000±120 mg / L and the MLVSS was 2238±60 mg / L; to maintain the same biomass, reactor R3 was inoculated with a mixture of the above municipal sludge and industrial sludge, with a MLSS of 2000 mg / L for both.

[0027] The effective volume of the above three SBR reactor systems is 4.0±0.2L, the height-to-diameter ratio (H / D) is 5:1, the volume exchange ratio is 50%, the ambient temperature is 25±2℃, the reactors are supplied with oxygen through bottom aerators, the surface gas velocity is 1.2cm / s, the dissolved oxygen is 7.5~8.5mg / L, and the SBR operation cycle is 4h, including influent (3min), settling (35min), aeration (190min), sedimentation (7min), and effluent (5min). Sludge discharge is not strictly controlled, and the pH value is controlled at 7.0±0.2. The reactors operated for a total of 145 days, divided into six stages. The influent COD was 800mg / L, TN was 40mg / L, and the influent salinity (as NaCl) in the six stages was 0, 10, 20, 30, 35, and 40g / L, respectively.

[0028] like Figure 1 As shown in (a), the AGS particle size difference was small in the initial stage of the reactors, with average particle sizes of 112.2±11 μm (R1), 90.1±13 μm (R2), and 103.5±9 μm (R3), respectively. After 20 days of sludge removal and screening, the sludge particle size in the three reactors increased, and the sludge gradually transformed from the initial flocculent morphology to fine particles. As the salinity continued to increase, the average particle size of the granular sludge in reactor R3 reached about 1200±44 μm, while the final average particle sizes of the sludge in reactors R2 and R1 were only 600±26 μm and 650±33 μm, respectively. This shows that under high salt stress, R3 exhibits stronger aggregation performance after inoculation with mixed sludge, can tolerate higher salinity, and forms larger particles. Figure 2 As shown, optical microscopy observation of sludge samples at 4% salinity revealed that AGS in R3 had a dense structure, clear boundary structure, and a yellow color. Figure 2 In (c) of the sample, the sludge in R1 has less obvious stratification and a relatively loose structure. Figure 2In (a) of the sample, the sludge in R2 still retains more flocculent structure and appears white. Figure 2 (b) above results show that the R3 reactor inoculated with urban-industrial mixed sludge forms granular sludge with larger particles and higher density. This method solves to some extent the problems of poor settling performance and difficulty in retaining functional bacteria when inoculated with single sludge under high stress.

[0029] The COD concentration and COD removal rate of the reactor influent are as follows: Figure 1 As shown in (b), the COD removal rate of the three reactors fluctuated greatly in the initial stage of salinity addition, but it could be stabilized at around 90% within 10 days. Within 2% salinity, all three reactors could maintain good carbon removal efficiency. When the salinity reached 4%, the COD removal rate of R1 and R2 dropped to below 85% and 90%, respectively, which was significantly lower than that of R3 (94.1±0.4%). The results showed that the sludge microorganisms in R3 had a strong tolerance to salinity and their metabolic activity was not significantly inhibited.

[0030] 3 reactors TN, NH4 + -N removal rates are respectively as follows Figure 1 As shown in (c) and (d), before the addition of salinity, the TN removal rates of R1, R2, and R3 were 70.1±3.1%, 64.6±2.2%, and 68.2±1.3%, respectively, and NH4+ removal rates were also shown. + The nitrogen removal rates were 96.0±2.7%, 83.2±1.9%, and 90.6±2.2%, respectively. With progressively increasing salinity, the nitrogen removal performance of all three reactors was affected within a short period. At a salinity of 3%, reactor R3 showed the following nitrogen removal rates: TN and NH4+. + The nitrogen (TN) removal rates eventually stabilized at 81±1.3% and 98±1.2%, while the removal rates of R1 and R2 were only 77±1.9% and 95±2.2%, and 89±0.9% and 91±1.3%, respectively. Under high salinity conditions in the later stages, the TN removal rate of R3 remained at a high level (78.8±0.9%), higher than that of R1 (59.1±0.7%) and R2 (60.3±1.2%). The reactor stability during different salinity gradient acclimation processes was ranked as R3 > R2 > R1 (based on nitrogen and carbon removal performance). This indicates that compared to single-inoculated sludge, inoculating mixed sludge can couple the nitrogen removal function of municipal wastewater activated sludge with the salt tolerance function of industrial wastewater sludge, endowing R3 with highly efficient nitrogen and carbon removal performance under high salinity stress.

[0031] Example 2: Identification of Core Species in Salt-Tolerant Aerobic Granular Sludge

[0032] High-throughput 16S rRNA sequencing was used to focus on the R3 group to investigate the dynamic succession of microbial community structure with changes in salinity (1-4%), in order to clarify the impact of salinity on the S-AGS microbial community. As salinity increased, the relative abundance of dominant AGS genera Rhodobacter spp., Hyphomonas spp., and Flavobacterium spp. under saline-free conditions decreased from 14.25%, 11.98%, and 9.59% to 1.59%, 5.10%, and 1.29%, respectively, indicating that their competitiveness decreased under high salinity and that they could not compete for survival under excessively high salinity. Thauera spp. was significantly enriched at salinity above 2%, and its abundance increased from 4.57% to 38.89% with increasing salinity, while the abundance of Pseudofulvimonas spp. increased from 1.20% to 10.02%. When the salinity reached 4%, the dominant species in the system were Thauera spp. (30.55%) and Pseudofulvimonas spp. (6.95%). Thauera spp. has a strong EPS secretion capacity and plays an important role in the S-AGS stabilization process. It also has the ability to perform simultaneous nitrification and denitrification. Pseudofulvimonas spp. is a heterotrophic nitrifying-aerobic denitrifying bacterium and has been reported to have a stronger tolerance to salinity (above 30 g / L NaCl). Therefore, under salinity stress, the high enrichment of Thaureraspp. functional bacteria stimulates EPS secretion to maintain good sludge aggregation. At the same time, the salt-tolerant denitrification functional bacteria Pseudofulvimonas spp. in the aerobic granular sludge system can ensure that the system can maintain high nitrogen metabolism efficiency and enhance the salt tolerance of the entire aerobic granular sludge reactor system.

[0033] Analysis of the niche breadth and correlation network of the S-AGS microbial community revealed that, under salinity conditions of 1-4%, functional bacteria such as *Thauera* spp. and *Pseudofulvimonas* spp. not only exhibited high abundance (>1%) under high salt stress but also occupied broad niches (top 50 in niche breadth score). Therefore, *Thauera* spp. and *Pseudofulvimonas* spp. are the dominant bacterial groups in S-AGS. Correlation network analysis (…) Figure 3The positive correlation ratio among microbial community networks was 70.15%, and the negative correlation ratio was 29.85%. The S-AGS microbial network includes several important modules, among which modules represented by Thaurea spp. and Pseudofulvimonas spp. are characterized by large nodes and high centrality. As mentioned earlier, Thaurea spp. and Pseudofulvimonas spp. possess important ecological functions, high stability, and adaptability under salinity of 1%–4%, and are the core species of S-AGS, playing a crucial role in the structural stability and functional diversity of aerobic granular sludge.

[0034] Example 3: Enhanced Salt Tolerance and Denitrification Function of S-AGS with Compound Functional Microbial Agent

[0035] S-AGS was obtained from a stably operating SBR reactor as a source of salt-tolerant co-culture strains. Granular sludge was thoroughly ground and dispersed, and strains were isolated using a dilution method. The diluted bacterial suspension was uniformly coated onto solid medium containing 100 mg / L LB, and salt stress was simulated by adding different concentrations of NaCl. The medium was then sealed with sealing film and incubated overnight in a constant temperature incubator. After single colonies grew, several salt-tolerant strains were screened through multiple plating and streaking processes. When the medium salinity was 10 g / L, the selected strains were subcultured three times and then frozen in 50% glycerol at -80°C. 16S rDNA sequencing was then performed, and a phylogenetic tree was generated using the BLAST (basic local alignment search tool) algorithm to screen for the strain most similar to Thaurea spp. (named Thaurea T-1). Similarly, when the culture medium salinity was 30 g / L, the strain most similar to Pseudofulvimonas spp. was screened out (named Pseudofulvimonas P-1) and used as a reserve core functional strain for exogenous enhancement of the reactor.

[0036] Two bacterial strains, Thaurata T-1 and Pseudofulvimonas P-1, were obtained from S-AGS and compounded at a 1:1 biomass ratio to prepare a composite functional bacterial agent. Batch experiments were conducted to evaluate the enhancing effect of the functional agent on the nitrification / denitrification pathway of S-AGS under high salt stress. The RTP group was treated with 5% (bacterial percentage, w / w) of the composite functional agent, while the control group (RC group) was treated with heat-inactivated strains. The specific sludge activity of ammonia oxidation, digestion, and denitrification was analyzed. A total of 10 batch experiments were conducted, and NH4+ was monitored. + -N, NO2 - -N, NO3 -The concentration change of -N was used to obtain the consumption rate of the substrate in the system through linear fitting, and related calculations were performed to evaluate its denitrification performance.

[0037] NH4 + -N, NO2 - -N and NO3 - -N degradation curve Figure 4 As shown, the RTP group rapidly removed nitrogen under 2% salinity conditions, essentially completely removing nitrogen pollutants within 2 hours. Furthermore, the denitrification process followed first-order reaction kinetics. In contrast, the control group showed NH4+ observed in Rc. + A small amount of -N with NO2 - The large accumulation of -N indicates that ammonia oxidation and nitrification processes are inhibited by salinity. Analysis of the denitrification process in group Rc ( Figure 4 NO2 was found in (b) to (d) of the middle section. - -N reduction was unaffected, but NO3 reduction was affected. - -N accumulation indicates NO2 - -N oxidation is inhibited. Compared to nitrification, ammonia oxidation is less affected by salinity, and nitrite-oxidizing bacteria (NOB) obtain less energy from ammonia and nitrite oxidation. Therefore, salt stress has an adverse effect on the activity and enrichment of NOB. In this case, Rc sludge mainly achieves nitrogen conversion through short-cut nitrification-denitrification.

[0038] Calculations of the specific activities of nitrogen transformation-related processes based on sludge nitrogen degradation curves revealed that, compared to the control group, the RTP sludge exhibited significantly higher specific activities for ammonia oxidation, nitrite oxidation, nitrite reduction, and nitrate reduction, at 4.18, 3.62, 4.47, and 5.82 mg N / (g·VSS·h), respectively, representing increases of 19.8±0.8%, 19.1±0.3%, 22.1±1.1%, and 38.9±1.2% compared to the control group (RC). The significantly increased nitrite oxidation rate in RBCs led to rapid nitrite utilization, thus no nitrite accumulation was observed in the batch experiments. Thauera T-1 and Pseudofulvimonas P-1 are both heterotrophic nitrifying-aerobic denitrifying bacteria, possessing simultaneous nitrification-denitrification capabilities under aerobic conditions. Compared to conventional denitrifying bacteria, HN-AD bacteria have a faster growth rate, higher tolerance to nitrogen load, and greater denitrification potential under salt stress. As an emerging bioaugmentation strain, its addition and enrichment can help improve the nitrification / denitrification nitrogen removal efficiency of biological treatment processes under salt stress, and it has good environmental adaptability to support the nitrogen conversion potential of simultaneous nitrification and denitrification.

Claims

1. A method for enhancing the formation and denitrification performance of salt-tolerant aerobic granular sludge in high-salt wastewater treatment, characterized in that, Includes the following steps: 1) Using activated sludge from urban wastewater treatment systems and salt-tolerant sludge from industrial wastewater treatment systems as mixed inoculum to cultivate salt-tolerant aerobic granular sludge and optimize the operating conditions of the SBR reactor. 2) High-throughput sequencing of 16S rRNA and co-occurrence network analysis were used to identify the core species with good salt tolerance in salt-tolerant aerobic granular sludge, providing a theoretical basis for targeted enhancement of its structural stability and denitrification performance; 3) Based on step 2), the core functional strains were screened and amplified, and the strains obtained from the screening and amplification were used. Thauera T-1 and Pseudofulvimonas P-1 was compounded to prepare a compound functional bacterial agent. Based on the mixed inoculum and reactor conditions in step 1), the compound functional bacterial agent was added to give full play to the synergistic enhancement effect of the core functional strains on the denitrification performance of salt-tolerant aerobic granular sludge. In step 1), the SBR reactor provides oxygen through bottom aeration heads, with a surface gas velocity of 1.2 cm / s and dissolved oxygen of 7.5~8.5 mg / L. The operating cycle is 4 h, including 3 min of influent, 35 min of settling, 187~192 min of aeration, 5~10 min of sedimentation, and 5 min of effluent. The pH value is controlled at 7.0±0.

2. A gradient acclimatization method is used to enhance the salt tolerance of the sludge. The influent salinity is 0, 10, 20, 30, 35, and 40 g / L (based on NaCl), the influent COD is 800~1000 mg / L, and the COD / TN ratio is 20:

1. Step 2) investigates the dynamic succession of microbial community structure with salinity changes to clarify the impact of salinity on the saline-tolerant aerobic granular sludge microbial community. 16S rRNA high-throughput sequencing and co-occurrence network analysis are used to identify core species with good salinity tolerance. Thauera spp. and Pseudofulvimonas spp.; Step 3) involves the screening and propagation process as follows: Salt-tolerant aerobic granular sludge is obtained from a stably operating SBR reactor as the source of salt-tolerant co-culture strains. The granular sludge is thoroughly ground and dispersed, and strains are isolated using the dilution method. The diluted bacterial suspension is evenly coated onto a solid medium containing LB. Different concentrations of NaCl are added to simulate a salt stress environment. The medium is sealed with sealing film and incubated overnight in a constant temperature incubator. After single colonies have grown, several salt-tolerant strains are screened through repeated plate plating and streaking. When the salinity of the medium is 10 g / L, the selected strains are passaged three times and then frozen in 50% glycerol at -80°C. 16S rDNA gene sequencing is then performed, and a phylogenetic tree is generated using the BLAST algorithm to screen strains related to... Thauera The most similar strain to spp., denoted as Thauera T-1, when the culture medium salinity is 30 g / L, screened for products similar to... Pseudofulvimonas The most similar strain to spp. is denoted as Pseudofulvimonas P-1.

2. The method for enhancing the formation and denitrification performance of salt-tolerant aerobic granular sludge in high-salt wastewater treatment as described in claim 1, characterized in that, In step 1), the salinity of the treated salt-tolerant sludge is ≥1%, and the mixing mass ratio of activated sludge and salt-tolerant sludge is 2:1-1:

1.

3. The method for enhancing the formation and denitrification performance of salt-tolerant aerobic granular sludge in high-salt wastewater treatment as described in claim 1, characterized in that, In step 3), the compound functional microbial agent Thauera T-1 and PseudofulvimonasP -1 is compounded in a biomass ratio of 2:1 to 1:

2.

4. The method for enhancing the formation and denitrification performance of salt-tolerant aerobic granular sludge in high-salt wastewater treatment as described in claim 1, characterized in that, The amount of compound functional microbial agent added is 3% to 10% of the biomass.

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