Deep denitrification method for wastewater with high ammonia nitrogen and low carbon nitrogen ratio

Abstract

The invention discloses a high-ammonia-nitrogen low-carbon-nitrogen-ratio wastewater deep denitrification method, and belongs to the technical field of sewage treatment. According to the invention, an MABR process and an SAD process are combined, hydrophilic biological source sulfur is used as an electron donor for denitrification, a reactor is built, and a high-ammonia-nitrogen low-carbon-nitrogen-ratio wastewater deep denitrification treatment process is provided. The MABR is utilized to realize efficient conversion of ammonia nitrogen, and the characteristic of high bioavailability of biological source sulfur is utilized to enrich denitrifying functional bacteria on the outermost layer of the membrane filament, so that the efficient and stable denitrification efficiency is maintained. A new strategy is provided for a sewage treatment plant to treat high-ammonia-nitrogen low-carbon-nitrogen-ratio wastewater, and a new thought is provided for efficient and stable nitrogen removal.

Description

Technical Field

[0001] The present invention relates to a method for deep denitrification of wastewater with high ammonia nitrogen and low carbon-nitrogen ratio, belonging to the technical field of sewage treatment. Background Art

[0002] High ammonia nitrogen wastewater from industrial wastewater such as coking and synthetic ammonia, landfill leachate and urban sewage causes many harms to water bodies, such as reducing the dissolved oxygen concentration in water and accelerating water eutrophication, threatening the aquatic ecosystem. The removal of nitrogen in wastewater usually depends on the biological denitrification process. Organic carbon sources are very important for the growth process of microorganisms and will also affect the denitrification rate in the biological denitrification process. Free ammonia in high ammonia nitrogen wastewater will inhibit the activities of bacteria in aerobic and anaerobic environments, compete with organic pollutants for electron acceptors, and affect the microbial ecosystem in the wastewater treatment process. At present, wastewater basically shows the characteristics of low C / N ratio. To solve the nitrification and denitrification problems of low C / N ratio wastewater, organic matter (such as methanol and acetic acid) is usually supplemented additionally to supplement the carbon source and electron donor. However, this will increase the treatment cost and organic load of the wastewater, and there is a risk of secondary pollution caused by carbon source leakage. Therefore, the development of low-carbon / zero-carbon denitrification technology has received more and more attention.

[0003] Among different wastewater treatment technologies, membrane aerated biofilm reactor (MABR) is a powerful and prominent technology, which operates by the reverse diffusion of oxygen and pollutants into the biofilm. In MABR, the membrane is both a fixed carrier for the biofilm and a microporous aerator. The unique structure makes MABR have versatility, such as efficient removal of carbon and nitrogen, high oxygen transfer efficiency (up to 100%), high functional stability against shock loads and toxic substrates, and small floor area. MABR mainly converts ammonia nitrogen into nitrate nitrogen through the nitrification process. Limited by the low C / N ratio, the effect of further converting nitrate nitrogen is poor, and there may be nitrite nitrogen accumulation.

[0004] Sulfur autotrophic denitrification (SAD) is considered a promising method for nitrate removal. It has received more and more attention because it does not require external organic carbon sources and produces less sludge. SAD refers to the process of using low-valent reduced inorganic sulfur (such as sulfide, thiosulfate, elemental sulfur) as an electron donor and nitrate and nitrite as electron acceptors for denitrification. The most commonly used electron donor in SAD is chemical elemental sulfur, which has the advantages of low price, easy transportation and treatment, and is usually applied to sewage treatment in the form of a fixed packed bed. However, the low solubility and hydrophobicity of chemical elemental sulfur will lead to low bioavailability, and coupled with the impact of shock loads, the biofilm on sulfur particles is easy to fall off, resulting in the loss of functional flora, and ultimately it is difficult to fully exert the strength of stable denitrification and difficult to achieve complete denitrification under high nitrogen load.

[0005] Biogenic sulfur is the desulfurization product of biogas slurry. Compared with chemical elemental sulfur, biogenic sulfur has higher water solubility and higher biological utilization rate. Although the purity of sulfur is lower than that of chemical elemental sulfur, the unique components such as proteins and metal ions on the surface of biogenic sulfur are more conducive to improving the denitrification rate of sulfur-oxidizing bacteria.

[0006] Therefore, replacing chemical elemental sulfur with biogenic sulfur in the SAD process can not only reduce costs but also realize the resource utilization of biogenic sulfur. Summary of the Invention

[0007] In order to address the difficulties that MABR is difficult to achieve complete conversion of nitrate nitrogen, the low biological utilization rate of chemical elemental sulfur, and the easy loss of functional bacteria, making it difficult to achieve high-load denitrification, the present invention combines the MABR process with the SAD process, uses hydrophilic biogenic sulfur as the electron donor for denitrification, constructs a reactor, and proposes a deep denitrification treatment process for high-ammonia-nitrogen and low-carbon-nitrogen-ratio wastewater. The MABR is used to achieve efficient conversion of ammonia nitrogen, and the high biological utilization rate of biogenic sulfur is utilized to enrich denitrifying functional bacteria on the outermost layer of the membrane filaments, maintaining high-efficiency and stable denitrification performance. The present invention provides a new strategy for sewage treatment plants to treat high-ammonia-nitrogen and low-carbon-nitrogen-ratio wastewater and provides new ideas for achieving high-efficiency and stable denitrification.

[0008] The first object of the present invention is to provide a method for denitrifying high-ammonia-nitrogen and low-carbon-nitrogen-ratio wastewater, which uses hollow fiber membrane filaments to sequentially enrich nitrifying bacteria and denitrifying bacteria, and treats high-ammonia-nitrogen and low-carbon-nitrogen-ratio wastewater under the condition of adding biogenic sulfur.

[0009] In one embodiment, the steps of sequentially enriching nitrifying bacteria and denitrifying bacteria in the hollow fiber membrane filaments include:

[0010] (1) Aerobic tank sludge is inoculated into the reactor, oxygen is introduced into the hollow fiber membrane filaments, the concentration of NH4 + -N is 50 - 200 mg / L, the concentration of organic carbon source is 100 - 150 mg / L, and it is operated for 40 - 45 days to obtain hollow fiber membrane filaments enriched with nitrifying bacteria;

[0011] (2) After the hollow fiber membrane filaments are enriched with nitrifying bacteria, denitrifying tank sludge is inoculated into the reactor, the concentration of biogenic sulfur is 450 - 500 mg / L, and it is operated for 10 - 20 days to obtain hollow fiber membrane filaments sequentially enriched with nitrifying bacteria and denitrifying bacteria.

[0012] In one embodiment, in the hollow fiber membrane filaments enriched with nitrifying bacteria in step (1), the abundance of nitrifying bacteria reaches 50 - 60%.

[0013] In one embodiment, the nitrifying bacteria enriched in step (1) are Nitrosomonas, Nitrosospira, and Nitrobacter.

[0014] In one embodiment, in step (1), at NH4 + -N concentrations of 50, 100, and 200 mg / L respectively, it runs for 15 days respectively.

[0015] In one embodiment, the relative abundance of denitrifying bacteria enriched in step (2) reaches 60 - 65%.

[0016] In one embodiment, the denitrifying bacteria enriched in step (2) are Ferritrophicum, norank_f__PHOS-HE36, and Thiomonas.

[0017] In one embodiment, the concentration of biogenic sulfur is 450 - 500 mg / L.

[0018] In one embodiment, the length of the hollow fiber membrane filament is 0.3 - 0.5 m.

[0019] The second object of the present invention is to provide a sewage reactor, and the sewage reactor contains hollow fiber membrane filaments that sequentially enrich nitrifying bacteria and denitrifying bacteria.

[0020] In one embodiment, the steps of sequentially enriching nitrifying bacteria and denitrifying bacteria in the hollow fiber membrane filaments include:

[0021] (1) Aerobic tank sludge is inoculated into the reactor, oxygen is introduced into the hollow fiber membrane filaments, the NH4 + -N concentration is 50 - 200 mg / L, the organic carbon source concentration is 100 - 150 mg / L, and it runs for 40 - 45 days to obtain hollow fiber membrane filaments enriched with nitrifying bacteria;

[0022] (2) After the hollow fiber membrane filaments are enriched with nitrifying bacteria, denitrifying tank sludge is inoculated into the reactor, the biogenic sulfur concentration is 450 - 500 mg / L, and it runs for 10 - 20 days to obtain hollow fiber membrane filaments that sequentially enrich nitrifying bacteria and denitrifying bacteria.

[0023] In one embodiment, the hollow fiber membrane filaments are connected with an oxygen cylinder, a gas flow meter, and a gas pressure gauge.

[0024] In one embodiment, in the hollow fiber membrane filaments enriched with nitrifying bacteria in step (1), the abundance of nitrifying bacteria reaches 50 - 60%;

[0025] In step (1), at NH4 + -N concentrations of 50, 100, and 200 mg / L respectively, it runs for 15 days respectively.

[0026] The third object of the present invention is to provide the application of any of the above methods or any of the above sewage reactors in treating sewage.

[0027] Advantages of the present invention

[0028] (1) This process can achieve complete removal of high-concentration ammonia nitrogen in low-carbon ratio wastewater; specifically, hollow fiber membrane filaments (with an effective length of 0.3 m) enriched with nitrifying bacteria and denitrifying bacteria can treat wastewater containing 195.6 mg / L of NH4 + -N, 95.0 mg / L of COD, and 2.5 mg / L of PO4 3- -P, and all nitrogen can be removed within 11 h.

[0029] (2) Using biogenic sulfur with high bioavailability as the electron donor for autotrophic denitrification does not require additional carbon source supplementation and can effectively enrich denitrifying functional bacteria;

[0030] (3) Biogenic sulfur, as a waste in biogas desulfurization waste liquid, is recycled, realizing resource recovery and reuse while achieving efficient denitrification;

[0031] (4) Combining the MABR process with the SAD process enables efficient nitrogen removal in the same reactor. The miniaturization of the reactor greatly saves space occupancy and allows for faster and more extensive distributed deployment. Description of the drawings

[0032] Figure 1 It is a schematic diagram of the wastewater treatment system.

[0033] Figure 2 It is a graph of the nitrification rate of nitrifying bacteria after successful biofilm formation.

[0034] Figure 3 It is a graph of the denitrification rate of the reactor after enrichment of denitrifying bacteria.

[0035] Figure 4 It is the nitrogen removal effect of the hollow fiber membrane filament - nitrifying bacteria - denitrifying bacteria module. Detailed implementation manners

[0036] The following are descriptions of the preferred embodiments of the present invention. It should be understood that the embodiments are for better explaining the present invention and are not used to limit the present invention.

[0037] In this application, combining MABR with the SAD process using biogenic sulfur as the electron donor can effectively couple the nitrification and sulfur autotrophic denitrification processes. Through internal aeration of the hollow fiber membrane and addition of external ammonia nitrogen, nitrifying bacteria can be effectively enriched outside the hollow fiber membrane and inside the biofilm, realizing the conversion of ammonia nitrogen to nitrate nitrogen. The addition of biogenic sulfur can effectively provide an electron donor for sulfur autotrophic denitrifying bacteria, and the nitrate nitrogen generated during the nitrification process can be used as an electron acceptor, enabling its effective enrichment in the outer layer of the biofilm.

[0038] In this process, microorganisms attach to the surface of hollow fiber membranes to form biofilms. Due to the concentration gradients of oxygen, substrates, etc. within the biofilms, different microenvironments are formed, providing unique ecological niches for different types of microorganisms (such as nitrifying bacteria and sulfur autotrophic denitrifying bacteria). This process realizes the coupling of nitrification and sulfur autotrophic denitrification processes in a single reactor, effectively reducing construction costs and providing new ideas for the treatment of high-ammonia-nitrogen and low-carbon-nitrogen-ratio wastewater and the resource utilization of biogenic sulfur.

[0039] Raw materials used in the examples:

[0040] The hollow fiber membrane filaments were purchased from Mitsubishi Chemical Corporation of Japan, with a pore size of 0.1 - 0.15 μm, an outer diameter of 280 μm, and a model of MHF-200TL;

[0041] The aerobic sludge was taken from the aerobic tank of a sewage treatment plant in Wuxi;

[0042] The denitrifying sludge was taken from the sulfur autotrophic denitrifying filter of a sewage treatment plant in Wuxi;

[0043] The biogenic sulfur was taken from a biogas desulfurization plant in Wuxi.

[0044] Example 1: A method for deep nitrogen removal of high-ammonia-nitrogen and low-carbon-nitrogen-ratio wastewater

[0045] 1. Construct a hollow fiber membrane filament - nitrifying bacteria - denitrifying bacteria assembly

[0046] To construct a hollow fiber membrane filament - nitrifying bacteria - denitrifying bacteria assembly, the steps are as follows:

[0047] (1) Domestication and enrichment of nitrifying bacteria

[0048] At low ammonia-nitrogen concentrations, the initial enrichment of nitrifying bacteria is achieved through aeration. To ensure that the enriched nitrifying bacteria can effectively cope with the impact of high ammonia-nitrogen, the ammonia-nitrogen concentration is gradually increased to achieve further enrichment of nitrifying bacteria.

[0049] In a reactor (5L), 2L of aerobic sludge with an aerobic sludge concentration of 4.5 g / L from the aerobic tank was inoculated. The process of enriching nitrifying bacteria was divided into three stages according to different influent ammonia-nitrogen concentrations. The influent NH4 +The -N concentrations were 50, 100, and 200 mg / L respectively, and the system was operated at room temperature for 15 days under different influent ammonia nitrogen concentrations; in each influent, KH2PO4 (1 mg P / L) was used as the phosphorus source, sodium acetate was used as the organic carbon source (100 mg COD / L), and NaHCO3 (125 mg / L) was added to control the pH (7 - 7.5); the oxygen cylinder was kept open, and a hollow fiber membrane (0.3 m) was used to efficiently transfer oxygen to keep the dissolved oxygen concentration at 3 - 5 mg / L, which was beneficial to the enrichment of nitrifying bacteria; the enrichment process lasted for 45 days to make the relative abundance of nitrifying bacteria reach 60% (specifically Nitrosomonas, Nitrosospira, and Nitrobacter).

[0050] After the enrichment process of nitrifying bacteria, there was obvious microbial adhesion on the hollow fiber membrane, which would not fall off under ultrasonic conditions, and the nitrification rate could reach 19.5 mg NH4 + -N / L·h (such as Figure 2 ), showing good denitrification efficiency, indicating that the hollow fiber membrane was successfully biofilm - formed.

[0051] (2) Enrichment of denitrifying bacteria

[0052] After the nitrifying bacteria were successfully biofilm - formed, 2 L of denitrifying sludge with a concentration of 4.4 g / L from the denitrification tank was inoculated into the reactor. Biogenic sulfur was used as the electron donor for autotrophic denitrification, and the nitrate nitrogen produced during the nitrification process was used as the electron acceptor to enrich denitrifying bacteria. Biogenic sulfur was added every 5 h to make the concentration reach 450 mg / L to ensure sufficient electron donors; this domestication process lasted for 20 days. The enrichment of denitrifying bacteria was judged by measuring the denitrification rate (the relative abundances of Ferritrophicum, norank_f__PHOS - HE36, and Thiomonas were as high as 65%), and the denitrification rate could reach 17.5 mg NO3 - -N / L·h (such as Figure 3 ), indicating the successful enrichment of denitrifying bacteria, and a hollow fiber membrane filament - nitrifying bacteria - denitrifying bacteria assembly was constructed.

[0053] 2. Establish a wastewater treatment system

[0054] Use the hollow fiber membrane filament - nitrifying bacteria - denitrifying bacteria assembly constructed in 1 to establish a wastewater treatment system.

[0055] The entire wastewater treatment system is as shown in Figure 1 and includes: a reactor (2), an influent tank (4), a hollow fiber membrane module (1), an oxygen cylinder (6), a gas flowmeter (7), a gas pressure gauge (8), a biogenic sulfur supplement tank (5), a stirrer (9), and a water pump (3);

[0056] Among them, the wastewater treatment system operates in a continuous flow manner. The working volume of the reactor is 5L. The influent is pumped into the reactor through the valve opening at the lower left of the reactor by a feed pump and discharged from the upper right. The hollow fiber membrane module (0.3m) in the reactor is connected to an oxygen cylinder. The dissolved oxygen concentration is controlled at 2-4mg / L through a gas flow meter, and the concentration of biogenic sulfur is 96.6g / L. Sufficient oxygen supply is maintained during the operation process.

[0057] 3. Detect the denitrification effect of the wastewater treatment system

[0058] Use the wastewater treatment system built in 2 to detect the denitrification effect of high ammonia nitrogen and low carbon nitrogen ratio wastewater. The steps are as follows:

[0059] Utilize actual wastewater to detect the denitrification effect of the hollow fiber membrane filament-nitrifying bacteria-denitrifying bacteria module. When the influent contains 195.6mg / L of NH4 + -N, 95.0mg / L of COD, and 2.5mg / L of PO4 3- -P, when the reactor starts to operate, supplement biogenic sulfur to make the concentration reach 450mg / L. After the reactor operates for 5h, supplement it again to make the concentration reach 450mg / L of biogenic sulfur. All nitrogen can be removed after the reactor operates for 11h, and almost no NH4 remains in the effluent + -N, NO3 - -N and COD. The denitrification effect of the influent and effluent is as Figure 4 shown.

[0060] Comparative Example 1: Only use MABR for denitrification

[0061] On the basis of Example 1, only nitrifying bacteria are enriched on the hollow fiber membrane filaments in 1, and denitrifying functional bacteria are not enriched. The remaining steps are the same as those in Example 1.

[0062] Comparative Example 2: Use chemical sulfur source

[0063] On the basis of Example 1, use a chemical sulfur source to replace the biogenic sulfur in Example 1, and the steps are the same as those in Example 1.

[0064] Comparative Example 3: Enrich nitrifying bacteria and denitrifying bacteria separately

[0065] Use membrane filaments to enrich nitrifying bacteria and denitrifying bacteria respectively. The steps are as follows:

[0066] According to the method in Example 1, enrich nitrifying bacteria and denitrifying bacteria on the hollow fiber membrane filaments respectively (the total amount of hollow fiber membrane filaments used is the same as that in Example 1). The steps for enriching nitrifying bacteria are the same as those in Example 1; for enriching denitrifying bacteria, NO3 needs to be supplemented in the influent - -N, NO3 --N concentrations were 50, 100, and 200 mg / L respectively. According to the different NO3 - -N concentrations, it was carried out in three stages (15 days for each stage, a total of 45 days). No oxygen was provided during this process. After microorganisms adhered to the membrane filaments, the hollow fiber membrane module was taken out and merged with the hollow fiber membrane module enriched with nitrifying bacteria.

[0067] Comparative Example 4: Using hollow fiber membrane filaments to enrich denitrifying bacteria first and then nitrifying bacteria

[0068] Based on Example 1, using hollow fiber membrane filaments to enrich denitrifying bacteria first and then nitrifying bacteria. When treating sewage, oxygen was introduced into the reaction tank from another pipeline (aeration head), and the oxygen concentration was 2 - 4 mg / L. The remaining steps were the same as those in Example 1.

[0069] Comparative Example 5: Changing the concentration of nitrifying bacteria (enrichment time)

[0070] Based on Example 1, the enrichment time of nitrifying bacteria was shortened (i.e., nitrifying bacteria were only enriched when the nitrate nitrogen concentration was 50 mg / L, with a duration of 15 days). The remaining steps were the same as those in Example 1.

[0071] Comparative Example 6: Not adding sodium acetate

[0072] Based on Example 1, sodium acetate was not added. The remaining steps were the same as those in Example 1.

[0073] Detect the sewage treatment effects of Comparative Examples 1 - 6, and the results are shown in Table 1. Table 1 Sewage treatment results

[0074]

[0075] Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Anyone familiar with this technology can make various modifications and decorations without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be defined by the claims.

Claims

1. A method for nitrogen removal from wastewater with high ammonia nitrogen and low carbon-nitrogen ratio, characterized in that, Use hollow fiber membrane filaments to enrich nitrifying bacteria and denitrifying bacteria in sequence, and treat wastewater with high ammonia nitrogen and low carbon-nitrogen ratio under the condition of adding biogenic sulfur.

2. The method according to claim 1, wherein The steps of enriching nitrifying bacteria and denitrifying bacteria with hollow fiber membrane filaments in sequence include: (1) Inoculate the aerobic pond sludge in the reactor, and introduce oxygen into the hollow fiber membrane filaments. The concentration of NH4 + -N is 50 - 200 mg / L, the concentration of sodium acetate is 100 - 150 mg / L, and operate for 40 - 45 days to obtain hollow fiber membrane filaments enriched with nitrifying bacteria; (2) After the hollow fiber membrane filaments enrich nitrifying bacteria, the reactor is inoculated with denitrification tank sludge, the concentration of biogenic sulfur is 450 - 500 mg / L, and it runs for 10 - 20 days to obtain hollow fiber membrane filaments that have enriched nitrifying bacteria and denitrifying bacteria in sequence.

3. The method according to claim 2, wherein In the hollow fiber membrane filaments for enriching nitrifying bacteria in step (1), the abundance of nitrifying bacteria reaches 50 - 60%.

4. The method according to claim 2, wherein In step (1), at NH4 + -N concentrations of 50, 100, and 200 mg / L respectively, it was run for 15 days each.

5. The method according to claim 1, characterized in that, The concentration of biogenic sulfur is 450 - 500 mg / L.

6. A sewage reactor, characterized in that, The sewage reactor contains hollow fiber membrane filaments that have enriched nitrifying bacteria and denitrifying bacteria in sequence.

7. The sewage reactor according to claim 6, wherein, The steps of enriching nitrifying bacteria and denitrifying bacteria with hollow fiber membrane filaments in sequence include: (1) Inoculate aerobic pond sludge in the reactor, introduce oxygen into the hollow fiber membrane filaments, with the NH4 + -N concentration being 50 - 200 mg / L, the organic carbon source concentration being 100 - 150 mg / L, and operate for 40 - 45 days to obtain hollow fiber membrane filaments enriched with nitrifying bacteria; (2) After the hollow fiber membrane filaments enrich nitrifying bacteria, the reactor is inoculated with denitrification tank sludge, the concentration of biogenic sulfur is 450 - 500 mg / L, and it runs for 10 - 20 days to obtain hollow fiber membrane filaments that have enriched nitrifying bacteria and denitrifying bacteria in sequence.

8. The sewage reactor according to claim 6, characterized in that, The hollow fiber membrane filaments are connected with an oxygen cylinder, a gas flow meter, and a gas pressure gauge.

9. The sewage reactor according to claim 6, characterized in that, In the hollow fiber membrane filaments for enriching nitrifying bacteria in step (1), the abundance of nitrifying bacteria reaches 50 - 60%; In step (1), at NH4 + -N concentrations of 50, 100, and 200 mg / L respectively, the operation was carried out for 15 days each.

10. The application of the method according to any one of claims 1 - 5 or the sewage reactor according to any one of claims 6 - 9 in treating sewage.

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