A wastewater denitrification system based on autotrophic microorganisms

Abstract

The application discloses a wastewater denitrification system based on autotrophic microorganisms and relates to the technical field of biology. The wastewater denitrification system comprises a wastewater supply unit, a strain supply unit and a biofilm unit; the wastewater supply unit and the strain supply unit are connected with the biofilm unit and can supply wastewater and strains to the biofilm unit respectively; the biofilm unit is loaded with fillers; the fillers comprise sulfur and tourmaline; and the strains comprise sulfur autotrophic denitrifying bacteria and tourmaline autotrophic denitrifying bacteria. The wastewater denitrification system is constructed through bacterial community domestication and electron transfer promotion, so that the chemical energy required by the autotrophic denitrification process is reduced, efficient removal of total nitrogen is realized, and the denitrification reaction efficiency under the condition of low carbon-nitrogen ratio is improved.

Description

Technical Field

[0001] This invention relates to the field of biotechnology, and in particular to a wastewater denitrification system based on autotrophic microorganisms. Background Technology

[0002] With increasingly stringent emission standards, addressing the technological bottlenecks in wastewater treatment projects is an urgent need to curb water pollution and protect the aquatic ecosystem. This also poses a significant challenge to the treatment capacity of existing nitrogen removal processes in urban wastewater treatment plants. The wastewater treatment industry faces new challenges, with mainstream wastewater treatment technologies characterized by high energy consumption and high carbon footprints facing obsolescence. Autotrophic denitrification, because it requires no carbon source, is a highly promising deep nitrogen removal technology. Especially as wastewater treatment plants prioritize carbon resource recovery and further reduce the carbon-to-nitrogen ratio in water, autotrophic denitrification offers advantages such as high nitrogen removal efficiency and low operating costs. Therefore, autotrophic denitrification has stronger competitiveness and application value, and can be used as a deep nitrogen removal unit in wastewater treatment plants, possessing significant industry prospects and widespread application potential.

[0003] The main problems with biological nitrogen removal are concentrated in the following key aspects, which significantly hinder its efficient and stable operation:

[0004] (1) Generation duration

[0005] Nitrifying bacteria, especially nitrite-oxidizing bacteria and nitrifying bacilli, grow and reproduce extremely slowly. Compared to common heterotrophic bacteria, their generation time is much longer; for example, the generation time of nitrite-oxidizing bacteria can reach tens of hours. This makes it difficult for nitrifying bacteria to quickly accumulate and form a sufficient population to efficiently complete the conversion of ammonia nitrogen to nitrate nitrogen in microbial denitrification systems. This can easily lead to instability in nitrification, thereby affecting the continuity and efficiency of the entire denitrification process.

[0006] (2) Microorganisms are sensitive to environmental changes

[0007] Various bacteria involved in microbial nitrogen removal, including nitrifying and denitrifying bacteria, are highly sensitive to changes in environmental conditions. They have relatively strict optimal ranges for environmental factors such as temperature, pH, and dissolved oxygen. For example, nitrifying bacteria generally thrive at a pH of 7.5-8.5 and exhibit higher activity at temperatures of 20-30℃; denitrifying bacteria, on the other hand, thrive at a pH of 7-8 and a temperature of 15-25℃. Once these environmental factors deviate from their optimal ranges, the activity of the microorganisms is significantly inhibited, and may even lead to their death, thus preventing the nitrogen removal process from proceeding normally.

[0008] To address common challenges in the wastewater denitrification industry, this invention aims to reveal the efficient coupling deep denitrification mechanism of nitrogen pollutants in wastewater within a power supply medium and an autotrophic microbial system. It will develop a deep wastewater denitrification technology based on autotrophic denitrification engineered bacteria and efficient electron transfer, thereby resolving existing problems such as high energy consumption, the need for external carbon sources, high operating costs, and low total nitrogen removal efficiency in urban wastewater denitrification. Summary of the Invention

[0009] The purpose of this invention is to provide a wastewater denitrification system based on autotrophic microorganisms to solve the problems existing in the prior art. This invention constructs a wastewater denitrification system through microbial domestication and enhanced electron transfer, thereby reducing the chemical energy required for the autotrophic denitrification process, achieving efficient removal of total nitrogen, and improving the denitrification reaction efficiency under low carbon-to-nitrogen ratio conditions.

[0010] Nitrogen removal from urban wastewater remains a bottleneck in water treatment. Addressing the challenges of slow growth of autotrophic denitrifying bacteria, poor shock resistance, low process efficiency, and difficulty in maintaining long-term effectiveness in conventional autotrophic denitrification processes, this paper proposes a "community regulation and enhanced electron transfer" denitrification system to solve this technical problem. This system fully leverages the electron-donating ability of the power supply medium to provide electrons to microorganisms, constructing a self-sustaining denitrification system. This allows autotrophic denitrification to overcome the limitations of electron donors and improves denitrification efficiency under low carbon-to-nitrogen ratio conditions by enhancing microbial electron transfer. This provides a basis for the design, commissioning, and operation of deep ammonia removal processes for urban wastewater.

[0011] Based on this, the present invention provides the following solution:

[0012] This invention provides a wastewater denitrification system based on autotrophic microorganisms, comprising a wastewater supply unit, a microbial inoculum supply unit, and a biofilm unit; the wastewater supply unit and the microbial inoculum supply unit are respectively connected to the biofilm unit and can supply wastewater and microbial inoculum to the biofilm unit respectively;

[0013] The biofilm unit is loaded with packing material; the packing material includes elemental sulfur and tourmaline.

[0014] The bacterial strains include sulfur autotrophic denitrifying bacteria and tourmaline autotrophic denitrifying bacteria.

[0015] Furthermore, the sulfur-autotrophic denitrifying bacteria are obtained through enrichment and domestication culture using elemental sulfur as an electron donor.

[0016] Furthermore, the tourmaline autotrophic denitrifying bacteria are obtained by enriching and domesticating tourmaline as an electron donor.

[0017] Furthermore, the elemental sulfur and the tourmaline are alternately loaded in the biofilm unit.

[0018] Furthermore, the mass ratio of the sulfur to the tourmaline is (7-3):(3-7).

[0019] Furthermore, the mass ratio of the sulfur to the tourmaline is 7:3.

[0020] Furthermore, the biofilm unit is an upflow bioreactor.

[0021] The present invention also provides the application of the above-mentioned wastewater denitrification system in wastewater denitrification.

[0022] Furthermore, the application includes reducing the byproduct NO2. - -N and SO4 2- The generation of.

[0023] The present invention also provides a wastewater denitrification method, which includes the step of using the above-described wastewater denitrification system to treat wastewater for denitrification.

[0024] The present invention discloses the following technical effects:

[0025] This invention proposes a denitrification system based on "community regulation and enhanced electron transfer" to solve the technical challenges of microbial denitrification. It fully leverages the electron-donating ability of the power supply medium to microorganisms, constructing a self-sustaining denitrification wastewater treatment device that frees microorganisms in autotrophic denitrification equipment from the burden of electron donors. Compared to conventional denitrification processes, this invention, through microbial domestication and enhanced electron transfer, constructs a sulfur-tourmaline autotrophic denitrification system, reducing the chemical energy required for the autotrophic denitrification reaction and achieving highly efficient total nitrogen removal, thus improving the denitrification reaction efficiency under low C / N ratio conditions. Unlike existing autotrophic denitrification reactions, this invention, on the one hand, reduces the amount of chemical electron donors and accelerates the electron transfer process by screening and constructing the power supply medium; on the other hand, it screens and combines autotrophic microorganisms to enhance their electron-donating ability and applies it to pilot-scale equipment operation.

[0026] This invention, through Chinese-style experiments, confirms that the wastewater denitrification system of this invention achieves the highest NO3 removal rate. - -N removal rate was 3.49 mg / L -1 Compared to sulfur-based autotrophic denitrification alone, the addition of tourmaline increased the nitrogen removal efficiency by 10%. Adjusting the nitrate removal efficiency under different electron donor ratios revealed that a 7 / 3 (sulfur / tourmaline) ratio resulted in a relatively stable average removal efficiency of 0.74 mg / L. -1 N h.

[0027] Using the wastewater denitrification system of this invention as a deep wastewater denitrification and treatment system can significantly reduce the cost of adding carbon sources. A wastewater treatment plant with a capacity of 100,000 tons / day can save nearly 6 million yuan annually by using the wastewater denitrification system of this invention for deep denitrification, demonstrating excellent economic benefits. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 Venn diagram of microbial samples;

[0030] Figure 2 A comparison chart of relative abundance at the phylum level;

[0031] Figure 3 The graph shows the changes in nitrogen (A), sulfate (B) concentrations and pH (C) during autotrophic denitrification processes with different sulfur to tourmaline ratios.

[0032] Figure 4 The pilot reactor was operated for 60 days at HRTs of 16 and 12 hours with NO3. - Statistical graph of -N concentration and temperature;

[0033] Figure 5 NO3 for 60 days of pilot reactor operation - A statistical chart of the removal rate of -N;

[0034] Figure 6 SO4 from pilot reactor 2- Concentration statistics chart;

[0035] Figure 7 This is a statistical graph showing the pH changes in the pilot-scale reactor. Detailed Implementation

[0036] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0037] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0038] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0039] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0040] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0041] The tourmaline used in this invention has a mesh size of 8000. It is washed several times with tap water until the supernatant is clear, then ultrasonically vibrated for 30 minutes, followed by rinsing five times with deionized water to remove surface-adhered microparticles. It is then dried at 50°C and stored in a sealed bag for later use. The main components are Na 3.10%, Al 36.48%, Si 40.17%, and Fe 20.25%.

[0042] Example 1

[0043] Enriched microbial culture medium: 3 g / L sulfur (up to 5 g / L), 0.50 g / L NaHCO3, 0.4 g / L KNO3, 0.25 g / L K2HPO4, 0.25 g / L KH2PO4, 0.05 g / L MgCl2, and 2 mL / L trace element solution.

[0044] Autotrophic denitrification medium: 2 g / L sulfur (or tourmaline), 0.35 g / L NaHCO3, 0.2 g / L KNO3, 0.25 g / L K2HPO4, 0.25 g / L KH2PO4, 0.05 g / L MgCl2 and 2 mL / L trace element solution.

[0045] Trace element solution: 1.0 g / L ethylenediaminetetraacetic acid, 0.5 g / L MgSO4·7H2O, 0.5 g / L CuSO4·5H2O, 0.5 g / L FeSO4·7H2O, 0.2 g / L ZnSO4, 0.2 g / L CoCl2·7H2O, and 0.1 g / L MnCl2·7H2O.

[0046] 1. Enrichment and domestication culture of sulfur autotrophic denitrifying bacteria and tourmaline autotrophic denitrifying bacteria

[0047] Sulfate-autotrophic denitrifying bacteria and tourmaline-autotrophic denitrifying bacteria were enriched and cultured from anaerobic sludge of a wastewater treatment plant, using the following method:

[0048] Autotrophic denitrifying bacteria were enriched and acclimatized in anaerobic flasks using enriched microbial culture media and autotrophic denitrification culture media. The enriched microbial culture media, using elemental sulfur and tourmaline as electron donors respectively, were inoculated into anaerobic sludge and cultured anaerobically in a constant-temperature shaker (125 rpm). During the enrichment culture, both sulfur-autotrophic denitrification and tourmaline-autotrophic denitrification processes were maintained at a constant temperature of 30°C and a pH of 7.0–7.5. NO3 levels in the system were monitored periodically. - -N, NO2 - -N, NH4 + Changes in parameters such as -N and pH were monitored, and the pH value within the system was adjusted promptly. The culture medium was periodically replaced with autotrophic denitrification medium. After 40 days of cultivation, sulfur-autotrophic denitrifying bacteria culture solutions and tourmaline-autotrophic denitrifying bacteria culture solutions were obtained, respectively.

[0049] For the cultivation process of sulfur-autotrophic denitrifying bacteria, whenever NO3- appears in the system... - When the NO₂⁻ concentration dropped to 0 mg / L, the bacterial culture was centrifuged and transferred to a new autotrophic denitrification medium. The intervals between seven medium changes were 8 days, 8 days, 4 days, 2 days, 2 days, 3 days, 2 days, and 3 days, indicating a gradual increase in bacterial activity. During the cultivation process, NO₂⁻ in the sulfur-autotrophic denitrification system... - The concentration of -N fluctuates within the range of 0–35.67 mg / L, indicating that there is no accumulation of nitrite.

[0050] Similar to sulfur-autotrophic denitrifying bacteria, the cultivation process of tourmaline-autotrophic denitrifying bacteria involves the presence of NO3 in the system. -When the NO₂-N concentration dropped to 0 mg / L, the bacterial culture was centrifuged, and the inoculum was transferred to a fresh culture medium. During the 40-day culture period, the culture medium was changed only once, a frequency far less than that of sulfur autotrophic denitrification processes. Tourmaline autotrophic denitrification system NO₂ - The -N content hardly increases, indicating that the activity of tourmaline autotrophic denitrifying bacteria is far lower than that of sulfur autotrophic denitrifying bacteria. After enrichment and acclimatization, sulfur autotrophic and tourmaline autotrophic denitrifying bacteria with higher nitrogen removal efficiency were obtained. In summary, the results show that after enrichment and acclimatization, sulfur autotrophic and tourmaline autotrophic denitrifying bacteria with higher nitrogen removal efficiency were obtained. However, the nitrogen removal efficiency of sulfur autotrophic denitrifying bacteria is higher than that of tourmaline autotrophic denitrifying bacteria because sulfur autotrophic denitrifying bacteria grow faster.

[0051] 2. Microbial community analysis

[0052] This study employed Illumina high-throughput sequencing technology to analyze changes in autotrophic microbial diversity, sample similarity, community structure, and community systems during denitrification under the influence of spontaneously generated fields at the phylum, class, order, family, and genus levels, aiming to deeply reveal molecular biological information such as the metabolic activity of autotrophic microorganisms. Samples were extracted from sulfur-autotrophic denitrifying bacteria (S) and tourmaline-autotrophic denitrifying bacteria (T) obtained in step 1 enrichment culture and subjected to high-throughput sequencing. This yielded Venn diagrams of OTUs for both species, comparisons of relative abundance at the phylum level, and sample-species relationships at the class and genus levels, as shown in the figures. Figures 1-2 As shown.

[0053] The two autotrophic denitrifying microorganisms shared 67 operational taxonomic units (OTUs), with a similar number of non-shared OTUs, indicating similar microbial diversity and structure. The relative abundance of bacterial communities within each phylum was assessed. Proteobacteria and Bacteroidetes were the dominant phyla, accounting for over 75% of the total microbial sequence in both samples. Proteobacteria was the most common denitrifying group in denitrifying bioreactors, accounting for 96.7% and 81.4% of tourmaline autotrophic and sulfur autotrophic denitrifying bacteria, respectively. Bacteroidetes were present in anaerobic denitrification, primarily involved in the degradation of high-molecular-weight compounds during nitrate reduction. They accounted for 1.5% and 17.7% of tourmaline autotrophic and sulfur autotrophic denitrifying bacteria, respectively.

[0054] At the class level, the relative abundance of Betaproteobacteria, the most dominant species among tourmaline autotrophic denitrifying bacteria and sulfur autotrophic denitrifying bacteria, was roughly equal, accounting for 42.4% and 41.8%, respectively. The results indicate that both systems are enriched with Betaproteobacteria, which possesses good nitrate removal capabilities. Alphaproteobacteria accounted for 22.8% and 29.3% of both tourmaline autotrophic and sulfur autotrophic denitrifying bacteria, respectively, and are presumably sulfur-producing bacteria that utilize sulfur metabolism for survival.

[0055] At the genus level, *Thiobacillus* is considered the main autotrophic denitrifying agent, involved in the oxidation of inorganic sulfur and promoting nitrate reduction. It accounts for 1.5% and 19.1% of tourmaline autotrophic and sulfur autotrophic denitrifying bacteria, respectively, confirming that sulfur autotrophic denitrification has a higher nitrogen removal rate than tourmaline autotrophic denitrification. *Paracoccus* accounts for 69.7% of total nitrogen (T) and 14.7% of total sulfur (S), representing a typical denitrifying bacterium capable of using nitrate as an electron acceptor to reduce it to nitrogen gas, thus participating in the nitrogen removal process.

[0056] Example 2

[0057] The synthetic wastewater used in this embodiment was prepared according to the following formula: KNO3 0.2g / L, KH2PO4 0.25g / L, K2HPO4 0.25g / L, NaHCO3 0.7g / L, MgCl2 0.05g / L and trace elements 2mL / L;

[0058] Trace element solution: 1.0 g / L ethylenediaminetetraacetic acid, 0.5 g / L MgSO4·7H2O, 0.5 g / L CuSO4·5H2O, 0.5 g / L FeSO4·7H2O, 0.2 g / L ZnSO4, 0.2 g / L CoCl2·7H2O, and 0.1 g / L MnCl2·7H2O.

[0059] 1g of a powder mixture containing different mass ratios of elemental sulfur (S) and tourmaline (T) (S:T ratios of 10:0, 7:3, 5:5, 3:7, and 0:10) was mixed with 50mL of inoculum and 200mL of synthetic wastewater in a 250mL anaerobic flask (the flask was rinsed with nitrogen for 20 minutes before filling to remove oxygen interference). The flask was sealed and placed in a constant-temperature shaker incubator for mixing and accelerated incubation under the following conditions: temperature = 30℃; rotation speed = 130rpm. Approximately 6mL of the mixed solution was sampled from the flask every 6 hours. The water sample was analyzed for pH and NO3. - -N, NO2 - -N, SO4 2-Analysis. All batch experiments were repeated, and the mean and standard deviation of the data are reported. Changes in oxygen nitrogen, sulfate concentration, and pH during autotrophic denitrification processes with different sulfur to tourmaline ratios are shown below. Figure 3 As shown.

[0060] Depend on Figure 3 As shown in section A, when the total oxidized nitrogen (TON) is reduced to zero, the reaction times for complete denitrification at S:T ratios of 10:0, 7:3, 5:5, 3:7, and 0:10 are 138 h, 102 h, 120 h, 126 h, and 150 h, respectively. The average nitrogen removal rate of SAD (representing an S:T ratio of 10:0, i.e., a sulfur autotrophic denitrification system) (0.219 mg / (L·h)) is higher than that of TAD (representing an S:T ratio of 0:10, i.e., a tourmaline autotrophic denitrification system) (0.201 mg / (L·h)). With the change of S:T, the average nitrogen removal rate changes in the following order: S:T 7:3 > S:T 5:5 > S:T 3:7 > S:T 10:0 > S:T 0:10. When the S:T ratio is 7:3, the average nitrogen removal rate of STAD (representing the sulfur-tourmaline autotrophic denitrification system) is higher (0.290 mg / (L·h)).

[0061] In batch tests, under the conditions of S:T 10:0, S:T 7:3, S:T 5:5, S:T 3:7 and S:T 0:10, the following parameters were used: Figure 3 As shown in B, SO4 2- The concentrations of SO4 produced were 165.80, 145.11, 141.38, 136.16, and 14.72 mg / L, respectively, showing a decreasing trend. 2- The order of their concentrations is: S:T 10:0 > S:T 7:3 > S:T 5:5 > S:T 3:7 > S:T 0:10. Therefore, adding tourmaline to the SAD system can effectively reduce SO4 levels. 2- The formation of SO4 reduces 2- The risk of exceeding emission standards.

[0062] Depend on Figure 3 As shown in Figure C, in the STAD system, reducing the same amount of NO3 - -N, the more tourmaline used, the more H it produces. + The less, the better. This is because tourmaline has the ability to regulate pH balance, making the system more alkaline. Therefore, the pH order of the STAD system is S:T 10:0. <S:T 7:3<S:T 5:5<S:T 3:7<S:T 0:10。

[0063] In conclusion, the optimal mass ratio of sulfur to tourmaline was determined to be 7:3.

[0064] Example 3

[0065] This embodiment constructs a sulfur-tourmaline autotrophic denitrification system comprising a wastewater supply unit, a microbial inoculum supply unit, and a biofilm unit. The wastewater supply unit and the microbial inoculum supply unit are connected to the biofilm unit, supplying wastewater and microbial inoculum respectively. The biofilm unit uses a sulfur-tourmaline autotrophic denitrification reactor, which is an upflow bioreactor made of steel with a columnar structure. The filter diameter is 600 mm, the height is 2500 mm, the filter bed height is 1000 mm, the outlet height is 2331.5 mm, and the effective volume is 659 L. It is filled with sulfur granules and tourmaline polyurethane (i.e., tourmaline powder loaded on a polyurethane carrier), which are alternately added to the reactor. The mass ratio of sulfur to tourmaline is 7:3. Subsequently, 200 L of sulfur autotrophic denitrifying bacteria solution and 300 L of tourmaline autotrophic denitrifying bacteria solution are added (the two bacterial solutions are obtained by diluting the two culture solutions obtained from the enrichment and domestication culture in Example 2 by 10 times, and the OD is measured). 600 (They are 0.071 and 0.068 respectively).

[0066] The process follows a four-stage cycle: water inlet – circulating biofilm formation – shutting off the circulation pump – static reaction – water inlet (or effluent). Initially, the daily water exchange volume is 200L. Nitrate levels in the influent and effluent are monitored daily, and the water exchange volume is gradually increased based on a nitrate nitrogen removal rate of over 50%. Biofilm formation is considered complete when the daily water exchange volume reaches over 500L. On day 26, biofilm formation is considered complete when the daily water exchange volume reaches over 500L and the nitrate nitrogen removal rate reaches 100% (exceeding 50%).

[0067] Under a residence time of 18 h, the reactor operated well, with a stable nitrate nitrogen removal efficiency of 94.04 ± 2.33%. Ammonia nitrogen concentrations in both the influent and effluent remained stable between 0.7 and 0.9 mg / L, indicating that microbial activity remained at a stable level. Low concentrations of nitrite nitrogen (0.01–0.02 mg / L) were detected in the effluent, indicating that NO2 was almost absent. - The accumulation of -N leads to the rapid reduction of nitrogen to nitrogen gas. The average COD concentration in the effluent was 23.81 mg / L, while the average COD concentration in the influent was 20.80 mg / L. The slight decrease in COD concentration indicates that the process may have consumed some organic matter. - The removal of -N is accompanied by SO42- 2- The formation of tourmaline (i.e., the reduction of 1g of nitrogen produces 5.713g of sulfate ions) should theoretically result in 283.79mg / L of sulfate ions, but only 225.21mg / L was produced. This demonstrates that the addition of tourmaline reduces SO42-. 2- The generation of.

[0068] The reactor operated for 120 days, divided into two stages based on hydraulic retention time (HRT). The HRTs for the first and second stages were 16 and 12 hours, respectively. During operation, the water temperature ranged from 21.1 to 24.1℃, with average temperatures of 23.53±1.53℃ and 23.05±0.49℃ for the first and second stages, respectively. During the 120-day operation, the average NO3- concentration in the influent and effluent... - -N and its removal rate were 18.25±2.36 mg / L, 4.94±2.68 mg / L, and 72.74±16.00%, respectively. Notably, at each HRT, when the reactor was operating stably, the nitrate removal rate could reach over 80%, indicating stable denitrification. - The removal efficiency of NO3- was 82.83 ± 12.67% in the first stage of the experiment. Reducing the HRT is one way to treat more wastewater in the same amount of time, but this will affect the denitrification efficiency. This invention gradually shortens the retention time to find a compromise that maintains the reactor's excellent denitrification performance. After 27 days of operation, the HRT of SLADB was adjusted from 16 hours to 12 hours. The results showed that the average NO3- removal efficiency was 82.83 ± 12.67%. - The nitrogen removal rate dropped to 72.7±7.58%, which indicates that the efficiency and rate of autotrophic denitrification may be affected and decreased at this stage, but the nitrogen removal efficiency is still excellent.

[0069] The pilot reactor operated for 60 days at HRTs of 16 and 12 hours with NO3. - -N concentration and NO3 - For the removal rate of -N, see [link to relevant documentation]. Figures 4-5 .

[0070] The average influent and effluent chemical oxygen demand (COD) were 23.14 ± 7.17 and 16.76 ± 5.55 mg / L, respectively. Approximately 6.38 mg / L of COD was removed in the reactor. This indicates that denitrification in the reactor mainly relies on sulfur autotrophic denitrification and tourmaline autotrophic denitrification.

[0071] In a sulfur-autotrophic denitrification process, for every 1 mg / L of NO3 removed... - -N produces 5.7 mg / L of SO4. 2- When a sulfur autotrophic denitrification system is used to treat NO3 - When the NO3- concentration in wastewater is below 48 mg / L, the generated NO3- - -N concentrations are within the safety limits set by the EPA. However, when performing advanced nitrate treatment in wastewater treatment plants, it is still necessary to assess SO4 levels in the effluent during sulfur autotrophic denitrification. 2- The concentration.

[0072] SO4 in the tail water of the present invention 2-The concentration range was 69.77-72.34 mg / L. The results showed that SO4... 2- The actual effluent concentration fluctuates closely around the theoretical effluent concentration and is generally below 250 mg / L. Figure 6 In the sulfur-tourmaline autotrophic denitrification system, tourmaline acts as a pH buffer and a potential substrate for v-trophic denitrification, maintaining acid-base balance and supporting microbial growth. During reactor operation, the pH slightly decreases due to the buffering effect of tourmaline, while the effluent pH remains neutral. The average pH values ​​of the influent and effluent are 7.90±0.27 and 7.54±0.19, respectively. Figure 7 The stability of the pH environment in this system contributes to biomass accumulation and denitrification rate.

[0073] The results of the above experiments show that, in sulfur-tourmaline autotrophic denitrification, the highest NO3 concentration obtained by enhancing sulfur autotrophic denitrification with tourmaline is […]. - -N removal rate was 3.49 mg·L⁻¹ -1 Nh primarily contributes nitrogen removal efficiency under conditions where tourmaline and elemental sulfur are electron donors. Results show that adding tourmaline improves nitrogen removal efficiency by 10% compared to sulfur-only autotrophic denitrification. Adjusting the nitrate removal efficiency under different electron donor ratios revealed that a 7 / 3 (sulfur / tourmaline) ratio resulted in a relatively stable average removal efficiency of 0.74 mg·L-1. -1 N h.

[0074] The sulfur-tourmaline pilot reactor was successfully started up, simultaneously improving denitrification efficiency. Each HRT (16h and 12h) reactor operated stably, achieving a nitrate removal rate of over 80%, thus ensuring stable denitrification. Furthermore, the addition of tourmaline reduced NO2. - -N and SO4 2- Byproduct accumulation is controlled, and the pH level in the environment is adjusted to ensure stable and normal operation of the reaction. The effluent meets the Class A standard (i.e., total nitrogen discharge is less than 10 mg / L).

[0075] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A wastewater denitrification system based on autotrophic microorganisms, characterized in that, It includes a wastewater supply unit, a microbial inoculum supply unit, and a biofilm unit; the wastewater supply unit and the microbial inoculum supply unit are respectively connected to the biofilm unit and can supply wastewater and microbial inoculum to the biofilm unit respectively; The biofilm unit is loaded with packing material; the packing material includes elemental sulfur and tourmaline. The bacterial strains include sulfur autotrophic denitrifying bacteria and tourmaline autotrophic denitrifying bacteria; The sulfur-autotrophic denitrifying bacteria were obtained by enrichment and domestication culture using elemental sulfur as an electron donor. The tourmaline autotrophic denitrifying bacteria were obtained by enriching and domesticating tourmaline as an electron donor. The elemental sulfur and the tourmaline are alternately loaded in the biofilm unit; The mass ratio of the sulfur to the tourmaline is 7:

3.

2. The wastewater denitrification system according to claim 1, characterized in that, The biofilm unit is an upflow bioreactor.

3. The application of a wastewater denitrification system as described in any one of claims 1-2 in wastewater denitrification.

4. The application according to claim 3, characterized in that, The application includes reducing the byproduct NO2. - -N and SO4 2- The generation of.

5. A wastewater denitrification method, characterized in that, The procedure includes the step of denitrifying wastewater using the wastewater denitrification system described in any one of claims 1-2.

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