Sewage denitrification system based on autotrophic microorganisms

Abstract

The invention discloses a sewage denitrification system based on autotrophic microorganisms, and relates to the technical field of biology. The sewage denitrification system comprises a wastewater supply unit, a strain supply unit and a biological membrane unit, the wastewater supply unit and the strain supply unit are respectively connected with the biological membrane unit and can respectively supply wastewater and strains to the biological membrane unit; the biological membrane unit is loaded with a filler; the filler comprises elemental sulfur and tourmaline, the strain comprises sulfur autotrophic denitrifying bacteria and tourmaline autotrophic denitrifying bacteria. According to the sewage denitrification system constructed through flora domestication and electron transfer improvement, chemical energy required by the reaction in 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] The invention relates to the field of biotechnology, in particular to a sewage denitrification system based on autotrophic microorganisms. Background Art

[0002] With the improvement of emission standards, solving the technical bottleneck of sewage treatment projects is an urgent need to curb water pollution and protect water ecology, and at the same time it poses a huge challenge to the treatment capacity of the existing denitrification process of urban sewage treatment plants. The sewage treatment industry is facing new challenges. The mainstream sewage treatment technology with high energy consumption and high "carbon footprint" is facing elimination; autotrophic denitrification is a deep denitrification treatment technology with great development potential because it does not require a carbon source. Especially when sewage treatment plants attach importance to carbon resource recovery and the carbon-nitrogen ratio in water is further reduced, autotrophic denitrification has the characteristics of high denitrification efficiency and low operating cost. Therefore, autotrophic denitrification has stronger competitiveness and application value, and can be used as a deep denitrification unit in sewage treatment plants, with great industry prospects and promotion value.

[0003] The problems of biological denitrification are mainly concentrated in the following key aspects, which have become a major obstacle to its efficient and stable operation:

[0004] (1) Generation duration

[0005] Nitrifying bacteria, especially nitrosobacteria and Nitrobacter, grow and reproduce very slowly. Compared with common heterotrophic bacteria, their generation time is much longer. For example, the generation time of nitrosobacteria may reach more than ten hours or even dozens of hours. This makes it difficult for nitrifying bacteria to quickly enrich and form a sufficient population in the microbial denitrification system to efficiently complete the conversion of ammonia nitrogen to nitrate nitrogen, which easily leads to unstable nitrification, thereby affecting the continuity and efficiency of the entire denitrification process.

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

[0007] Various types of bacteria involved in microbial denitrification, including nitrifying bacteria and denitrifying bacteria, are very sensitive to changes in environmental conditions. They have relatively strict suitable ranges for environmental factors such as temperature, pH value, and dissolved oxygen. For example, the suitable pH value for nitrifying bacteria is generally 7.5-8.5, and the activity is higher at a temperature of 20-30°C; the suitable pH value for denitrifying bacteria is generally 7-8, and the temperature is more suitable at 15-25°C. Once these environmental factors deviate from the suitable range, the activity of the microorganisms will be significantly inhibited, and may even lead to the death of the microorganisms, making the denitrification process unable to proceed normally.

[0008] In response to the common problems in the sewage denitrification industry, the present invention intends to reveal the efficient coupling deep denitrification mechanism of nitrogen pollutants in sewage in the power medium and autotrophic microbial system, and develop a sewage deep denitrification technology based on autotrophic denitrification engineering bacteria and efficient electron transfer, in order to solve the problems of high energy consumption for total nitrogen removal in existing urban sewage, the need for external carbon source, high operating costs, and low total nitrogen removal efficiency. Summary of the invention

[0009] The purpose of the present invention is to provide a sewage denitrification system based on autotrophic microorganisms to solve the problems existing in the above-mentioned prior art. The sewage denitrification system constructed by the present invention through bacterial flora domestication and improved electron transfer reduces the chemical energy required for the autotrophic denitrification process reaction, realizes efficient removal of total nitrogen, and improves the denitrification reaction efficiency under low carbon-nitrogen ratio conditions.

[0010] Denitrification of urban sewage is still a bottleneck problem in water treatment. In view of the problems faced by conventional autotrophic denitrification, such as slow growth of autotrophic denitrifying bacteria, poor impact resistance, low process efficiency, and difficulty in long-term maintenance, a denitrification system of "regulating communities and enhancing electron transfer" is proposed to solve this technical problem. The ability of power mediators to provide electrons to microorganisms is fully utilized to build a self-sustaining denitrification system, so that autotrophic denitrification can get rid of the problem of electron donors. By strengthening microbial electron transfer, the denitrification reaction efficiency under low carbon-nitrogen ratio conditions is improved, which provides a basis for the design, commissioning and operation of deep denitrification process for urban sewage.

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

[0012] The present invention provides a wastewater denitrification system based on autotrophic microorganisms, comprising a wastewater supply unit, a bacterial strain supply unit and a biofilm unit; the wastewater supply unit and the bacterial strain supply unit are respectively connected to the biofilm unit, and can supply wastewater and bacterial strains to the biofilm unit respectively;

[0013] The biofilm unit is loaded with fillers; the fillers include elemental sulfur and tourmaline;

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

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

[0016] Furthermore, the tourmaline autotrophic denitrifying bacteria is obtained by enrichment and domestication culture using 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 elemental sulfur to the tourmaline is (7-3):(3-7).

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

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

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

[0022] Furthermore, the application includes reducing the by-product NO2 - -N and SO4 2- The production of.

[0023] The present invention also provides a sewage denitrification method, comprising the step of using the above-mentioned sewage denitrification system to denitrify the sewage.

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

[0025] The present invention proposes a denitrification system of "regulating communities and enhancing electron transfer" to solve the technical difficulties in microbial denitrification, give full play to the ability of power mediators to provide electrons to microorganisms, construct self-sustaining denitrification sewage treatment equipment, and free the microorganisms in the autotrophic denitrification denitrification equipment from the trouble of electron donors. Compared with the conventional denitrification process, the present invention constructs a sulfur-tourmaline autotrophic denitrification system by domesticating the bacterial community and improving electron transfer, which reduces the chemical energy required for the autotrophic denitrification process reaction, achieves efficient removal of total nitrogen, and improves the denitrification reaction efficiency under low carbon-nitrogen ratio conditions. Different from the existing autotrophic denitrification reaction, the present invention, on the one hand, reduces the amount of chemical electron donors and accelerates the electron transfer process by screening and constructing power mediators; on the other hand, it screens and compound autotrophic microorganisms, strengthens their ability to obtain electrons and applies them to the operation of pilot equipment.

[0026] The invention has been verified through Chinese test that the wastewater denitrification system of the invention can obtain the highest NO3 - -N removal rate was 3.49 mg L -1 N h, the denitrification efficiency of adding tourmaline increased by 10% compared with the denitrification of sulfur autotrophic denitrification alone. The nitrate denitrification efficiency under different electron donor combination ratios was adjusted, and the average removal efficiency was relatively stable under the ratio of 7 / 3 (sulfur / tourmaline), which could reach 0.74 mg L -1 Nh.

[0027] The sewage denitrification system of the present invention is used as a sewage deep denitrification deep treatment system, which can greatly save the cost of adding carbon sources. A sewage treatment plant with a capacity of 100,000 tons / day uses the sewage denitrification system of the present invention for deep denitrification, which can save nearly 6 million yuan in carbon source (glucose) each year, and has excellent economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0029] Figure 1 Venn diagram for microbial samples;

[0030] Figure 2 This is a comparison chart of relative abundance at the phylum level;

[0031] Figure 3 The graphs are the changes of nitrogen (A), sulfate (B) concentration and pH (C) in the autotrophic denitrification process at different sulfur and tourmaline ratios;

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

[0033] Figure 5 NO3 for the pilot reactor running for 60 days - -Statistical chart of N removal rate;

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

[0035] Figure 7 This is a statistical chart of the pH changes in the pilot reactor. DETAILED DESCRIPTION

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

[0037] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0038] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0039] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

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

[0041] The mesh number of the tourmaline used in the present invention is 8000 mesh. After washing it with tap water for several times until the supernatant is clear, ultrasonic vibration is performed for 30 minutes, and then it is rinsed with deionized water for 5 times to remove the tiny particles attached to the surface. It is dried at 50°C and stored in a sealed bag for use. It mainly contains Na 3.10%, Al 36.48%, Si 40.17% and Fe 20.25%.

[0042] Example 1

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

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

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

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

[0047] Sulfur autotrophic denitrifying bacteria and tourmaline autotrophic denitrifying bacteria were obtained by enriching and culturing the anaerobic sludge from the sewage treatment plant as follows:

[0048] The enriched microbial culture medium and the autotrophic denitrification culture medium were used to enrich and acclimate the autotrophic denitrifying bacteria in the anaerobic bottle. The enriched microbial culture medium was used, and elemental sulfur and tourmaline were used as electron donors, respectively, and inoculated into the anaerobic sludge, and anaerobic culture was carried out in a constant temperature shaker (speed 125rpm). During the enrichment culture process, the sulfur autotrophic denitrification process and the tourmaline autotrophic denitrification process were maintained at a constant temperature of 30°C, and the pH value was maintained at 7.0-7.5. Regularly monitor the NO3 in the system - -N, NO2 - -N、NH4 + -N, pH and other indicators, and timely adjust the pH value in the system, and regularly replace the culture medium with autotrophic denitrification culture medium. After 40 days of cultivation, sulfur autotrophic denitrifying bacteria culture solution and tourmaline autotrophic denitrifying bacteria culture solution were obtained respectively.

[0049] For the cultivation process of sulfur autotrophic denitrifying bacteria, whenever NO3 - When the content of -N dropped to 0 mg / L, the bacterial solution was centrifuged and transferred to a new autotrophic denitrification medium. The intervals between seven changes of the medium were 8 days, 8 days, 4 days, 2 days, 2 days, 3 days, 2 days and 3 days, indicating that the bacterial activity was gradually increasing. - The concentration of -N ranged from 0 to 35.67 mg / L, indicating that there was no accumulation of nitrite.

[0050] Similar to sulfur autotrophic denitrifying bacteria, for the culture process of tourmaline autotrophic denitrifying bacteria, whenever NO3 -When the -N content dropped to 0 mg / L, the bacterial solution was centrifuged and the strain was transferred to a new culture medium. During the 40-day culture process, the culture medium was only replaced once, which was much less frequent than the sulfur autotrophic denitrification process. Tourmaline autotrophic denitrification system NO2 - -N hardly increased, indicating that the activity of tourmaline autotrophic denitrifiers was much lower than that of sulfur autotrophic denitrifiers. After enrichment and acclimation, sulfur autotrophic denitrifiers and tourmaline autotrophic denitrifiers with higher denitrification efficiency were obtained. In short, the results showed that after enrichment and acclimation, sulfur autotrophic denitrifiers and tourmaline autotrophic denitrifiers with higher denitrification efficiency were obtained, but the denitrification efficiency of sulfur autotrophic denitrifiers was higher than that of tourmaline autotrophic denitrifiers because sulfur autotrophic denitrifiers grew faster.

[0051] 2. Microbial Community Analysis

[0052] The study used Illumina high-throughput sequencing technology to analyze the changes in autotrophic microbial diversity, sample similarity, community structure, and community system during the denitrification process under the influence of the self-generated field at the level of phylum, class, order, family, and genus, in order to deeply reveal molecular biological information such as the metabolic activity of autotrophic microorganisms. Samples were extracted from the sulfur autotrophic denitrifiers (S) and tourmaline autotrophic denitrifiers (T) obtained by enrichment culture in step 1 for high-throughput sequencing, and the Venn diagram of OTUs and the relative abundance comparison at the phylum level were obtained, as well as the sample-species relationship diagram at the class and genus levels, as shown in the figure. Figure 1-Figure 2 shown.

[0053] The two autotrophic denitrifying microorganisms had a total of 67 OTUs based on operational taxonomic units, and the number of unshared OTUs was not much different, indicating that the microbial diversity and structure of the two were similar. The relative abundance of bacterial communities in the phylum was evaluated. Proteobacteria and Bacteroidetes were dominant phyla, accounting for more than 75% of the total microbial sequences of the two samples. Among them, Proteobacteria was the most common denitrifying group in the denitrification bioreactor. It accounted for 96.7% and 81.4% in tourmaline autotrophic denitrifiers and sulfur autotrophic denitrifiers, respectively. Bacteroidetes exist in the anaerobic denitrification process, mainly used to degrade high-molecular compounds in the nitrate reduction process. It accounted for 1.5% and 17.7% in tourmaline autotrophic denitrifiers and sulfur autotrophic denitrifiers, respectively.

[0054] At the class level, the relative abundance of Betaproteobacteria, the most dominant in tourmaline autotrophic denitrifiers and sulfur autotrophic denitrifiers, was roughly equal, accounting for 42.4% and 41.8%, respectively. The results showed that both systems were enriched with Betaproteobacteria with good nitrate removal ability. In tourmaline autotrophic denitrifiers and sulfur autotrophic denitrifiers, Alphaproteobacteria accounted for 22.8% and 29.3%, respectively, which are speculated to be Thiobacillus that use sulfur metabolism to survive.

[0055] At the genus level, Thiobacillus is considered to be the main autotrophic denitrifier, which is related to the oxidation of inorganic sulfur and the promotion of nitrate reduction. It accounts for 1.5% and 19.1% in tourmaline autotrophic denitrifiers and sulfur autotrophic denitrifiers, respectively, which also verifies that the rate of denitrification by sulfur autotrophic denitrification is higher than that of tourmaline autotrophic denitrification. Paracoccus accounts for 69.7% and 14.7% in T and S, respectively, and is a typical denitrifying bacteria that can use nitrate as an electron acceptor and reduce it to nitrogen gas, thereby participating in the denitrification process.

[0056] Example 2

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

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

[0059] 1 g of a powder mixture containing elemental sulfur (S) and tourmaline (T) in different mass ratios (S:T ratios of 10:0, 7:3, 5:5, 3:7 and 0:10) was mixed with 50 mL of inoculum and 200 mL of synthetic wastewater in a 250 mL anaerobic bottle (before filling, the bottle was flushed with nitrogen for 20 minutes to remove oxygen interference), sealed, and placed in a constant temperature shaking incubator for mixing and accelerated culture under the following conditions (temperature = 30 ° C; speed = 130 rpm). About 6 mL of the mixed solution was sampled from the bottle every 6 hours. The water samples were tested for pH, NO3 - -N, NO2 - -N、SO4 2-All batch experiments were repeated and the mean and standard deviation of the data were reported. Figure 3 shown.

[0060] Depend on Figure 3 As shown in Figure A, when the total oxidized nitrogen (TON) is reduced to zero, the reaction time for complete denitrification is 138h, 102h, 120h, 126h, and 150h at S:T10:0, 7:3, 5:5, 3:7, and 0:10 ratios, respectively. The average N removal rate of SAD (representing S:T of 10:0, i.e., sulfur autotrophic denitrification system) (0.219mg / (L·h)) is higher than that of TAD (representing S:T of 0:10, i.e., tourmaline autotrophic denitrification system) (0.201mg / (L·h)). With the change of S:T, the order of average N removal rate is S:T 7:3>S:T 5:5>S:T 3:7>S:T 10:0>S:T0:10. When S:T was 7:3, the average N removal efficiency of STAD (standing for sulfur-tourmaline autotrophic denitrification system) (0.290 mg / (L·h)) was higher.

[0061] In batch experiments, 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, Figure 3 As shown in B, SO4 2- The generated concentrations were 165.80, 145.11, 141.38, 136.16 and 14.72 mg / L, showing a downward trend. 2- The order of content 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 2- The formation of SO4 2- Risk of exceeding emission standards.

[0062] Depend on Figure 3 As shown in C, in the STAD system, the same amount of NO3 is reduced - -N, the more tourmaline is used, the more H it produces + This is because tourmaline has the ability to adjust the pH balance, that is, to make the system more alkaline, so the pH value 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 summary, the optimal addition mass ratio of sulfur to tourmaline was finally determined to be 7:3.

[0064] Example 3

[0065] The sulfur-tourmaline autotrophic denitrification system constructed in this embodiment includes a wastewater supply unit, a strain supply unit and a biofilm unit. The wastewater supply unit and the strain supply unit are respectively connected to the biofilm unit, and wastewater and strains can be supplied to the biofilm unit. The biofilm unit adopts a sulfur-tourmaline autotrophic denitrification reactor, which is an upflow bioreactor. The reactor is made of steel and has a columnar structure. The filter tank has a diameter of 600mm, a height of 2500mm, a filter layer height of 1000mm, a water outlet height of 2331.5mm, and an effective volume of 659L. Sulfur particles and tourmaline polyurethane (i.e., tourmaline powder is loaded with a polyurethane carrier) are filled, and the two are alternately placed in the reactor, wherein the filling mass ratio of sulfur to tourmaline is 7:3, and subsequently 200L of sulfur autotrophic denitrifying bacteria liquid and 300L of tourmaline autotrophic denitrifying bacteria liquid are added (the two bacterial liquids are obtained by diluting the two culture liquids obtained by enrichment and acclimation culture in Example 2 by 10 times, and the OD is measured. 600 0.071 and 0.068 respectively).

[0066] According to the four time-series cycle of water inlet-circulation biofilm cultivation-close the circulation pump-stationary reaction-water inlet (water outlet), the daily water change volume is 200L at the beginning, and the nitrate values ​​of the inlet and outlet water are tested daily. Based on the nitrate nitrogen removal rate of more than 50%, the water change volume is gradually increased. When the daily water change volume reaches more than 500L, biofilm formation can be considered complete. On the 26th day, the daily water change volume reaches more than 500L and the nitrate nitrogen removal rate reaches 100% (more than 50%), and biofilm formation is completed.

[0067] Under the condition of 18h residence time, the reactor performed well and the removal efficiency of nitrate nitrogen was stable at 94.04±2.33%. The concentration of ammonia nitrogen in the inlet and outlet water was stable between 0.7 and 0.9mg / L. The stable concentration of ammonia nitrogen indicated that the microbial activity remained at a stable level. Low concentrations of nitrite nitrogen (0.01-0.02mg / L) were detected in the outlet water, indicating that there was almost no NO2 - -N accumulation, nitrogen is quickly reduced to nitrogen gas. The average COD concentration of the effluent is 23.81 mg / L, and the average COD concentration of the inlet is 20.80 mg / L. The COD concentration has decreased slightly, indicating that the process may have consumed some organic matter. - -N removal is accompanied by SO4 2- Theoretically, 283.79 mg / L of sulfate ions should be generated, but only 225.21 mg / L was generated. It can be seen that the addition of tourmaline will reduce SO4 2- The production of.

[0068] The reactor was operated for 120 days and divided into two stages according to the hydraulic retention time (HRT). The HRT of the first and second stages were 16 and 12 hours, respectively. The water temperature varied between 21.1 and 24.1°C during operation, and the average temperatures of the first and second stages were 23.53±1.53 and 23.05±0.49°C, respectively. During the 120-day operation, the average NO3 - -N and its removal rate were 18.25±2.36mg / L, 4.94±2.68mg / L and 72.74±16.00%, respectively. It is worth noting that at each HRT, when the reactor is running stably, the nitrate removal rate can reach more than 80%, which means that the denitrification effect is stable. - The removal efficiency of -N was 82.83±12.67% in the first stage of the experiment. Reducing HRT is one of the ways to treat more wastewater in the same time, but this will affect the denitrification efficiency. The present invention gradually shortens the residence time to find a compromise condition so that the denitrification performance of the reactor remains excellent. After 27 days of operation, the HRT of SLADB was adjusted from 16 hours to 12 hours. The results show that the average NO3 - The -N removal rate dropped to 72.7 ± 7.58%, which indicates that the efficiency and speed of autotrophic denitrification may be affected and decreased at this stage, but the nitrogen removal efficiency is still excellent.

[0069] The pilot reactor was operated for 60 days at HRT 16 and 12 h for NO3 - -N concentration and NO3 - -N removal rate see Figure 4-Figure 5 .

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

[0071] Sulfur autotrophic denitrification process, each removal of 1mg / L NO3 - -N produces 5.7mg / L SO4 2- When sulfur autotrophic denitrification system is used to treat NO3 - When the N concentration in wastewater is lower than 48 mg / L, the NO3 - -N concentrations are within the safety limits set by the EPA. However, when deep treatment of nitrates in wastewater treatment plants is performed, it is still necessary to evaluate the SO4 2- concentration.

[0072] SO4 in the tail water of the present invention 2-The concentration range of SO4 2- The actual effluent concentration fluctuates closely around the theoretical effluent concentration and is generally lower than 250 mg / L ( Figure 6 In the sulfur-tourmaline autotrophic denitrification system, tourmaline acts as a pH buffer and potential substrate for autotrophic denitrification, which can maintain acid-base balance and support microbial growth. During the operation of the reactor, due to the buffering effect of tourmaline, the pH dropped slightly, and the effluent pH remained neutral. The average pH values ​​of the inlet and outlet water were 7.90±0.27 and 7.54±0.19, respectively ( Figure 7 ). The stability of the pH environment in this system is conducive to the accumulation of biomass and the denitrification rate.

[0073] Based on the above test results, in the sulfur-tourmaline autotrophic denitrification, the highest NO3 - -N removal rate was 3.49 mg·L -1 N h, mainly contributed by tourmaline and elemental sulfur as electron donors. The results showed that the denitrification efficiency of autotrophic denitrification with tourmaline was increased by 10% compared with that of sulfur alone. The nitrate denitrification efficiency under different electron donor combination ratios was adjusted, and the average removal efficiency was relatively stable under the ratio of 7 / 3 (sulfur / tourmaline), which could reach 0.74 mg·L -1 Nh.

[0074] The sulfur-tourmaline pilot reactor was successfully started and the denitrification efficiency was improved. Each HRT (16h and 12h) reactor operated stably, and the nitrate removal rate could reach more than 80%, achieving a stable denitrification effect. At the same time, the addition of tourmaline reduced NO2 - -N and SO4 2- The amount of by-product accumulation is controlled, and the pH in the environment is regulated to stabilize the normal operation of the reaction. The effluent standard reaches the Class A standard (i.e., total nitrogen emission is less than 10 mg / L).

[0075] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A sewage denitrification system based on autotrophic microorganisms, characterized in that: It includes a wastewater supply unit, a bacterial strain supply unit and a biofilm unit; the wastewater supply unit and the bacterial strain supply unit are respectively connected to the biofilm unit, and can supply wastewater and bacterial strains to the biofilm unit respectively; The biofilm unit is loaded with fillers; the fillers include elemental sulfur and tourmaline; The bacterial species include sulfur autotrophic denitrifying bacteria and tourmaline autotrophic denitrifying bacteria.

2. The sewage denitrification system according to claim 1, characterized in that: The sulfur autotrophic denitrifying bacteria are obtained by enrichment and domestication culture using elemental sulfur as an electron donor.

3. The sewage denitrification system according to claim 1, characterized in that: The tourmaline autotrophic denitrifying bacteria are obtained by enrichment and domestication culture using tourmaline as an electron donor.

4. The sewage denitrification system according to claim 1, characterized in that: The elemental sulfur and the tourmaline are alternately loaded in the biofilm unit.

5. The sewage denitrification system according to claim 1, characterized in that: The mass ratio of the sulfur element to the tourmaline is (7-3):(3-7).

6. The sewage denitrification system according to claim 5, characterized in that: The mass ratio of the elemental sulfur to the tourmaline is 7:

3.

7. The sewage denitrification system according to claim 1, characterized in that: The biofilm unit adopts an upflow bioreactor.

8. Use of the sewage denitrification system as described in any one of claims 1 to 7 in sewage denitrification.

9. The use according to claim 8, characterized in that: The application includes reducing the by-product NO2 - -N and SO4 2- The production of.

10. A method for denitrification of sewage, characterized in that: The method comprises the step of denitrifying the sewage by using the sewage denitrification system described in any one of claims 1 to 7.

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