A method for deep removal of total nitrogen from water by autotrophic-heterotrophic sulfur-denitrification and its application

Abstract

This invention discloses a method and application for deep removal of total nitrogen from water by autotrophic-heterotrophic sulfur denitrification, relating to the field of deep ammonia removal technology in wastewater treatment; comprising the following steps: S1, adding suspended sulfur carrier to a biological contact oxidation tank; S2, adding sulfur autotrophic denitrifying bacteria to the biological contact oxidation tank, with a dosage of 2-5 kg / m³. 3 After the carrier is filled with water, it is aerated for 48-240 hours; S3, after water exchange, sulfur heterotrophic denitrifying bacteria are added to the biological contact oxidation tank at a dosage of 2-3 kg / m³. 3 Carrier, aerated for 24-48 hours; S4, add swarm-sensing factor to the biological contact oxidation tank at a dosage of 0.01-0.03 kg / m³. 3 S5. Aerate for 24 hours; S6. Introduce the wastewater to be treated for denitrification. The wastewater treatment method of the present invention can remove total nitrogen without the need for additional carbon source when the organic matter content (COD value) is low, so that the effluent meets the Class IV surface water standard.

Description

Technical Field

[0001] This invention relates to the field of deep ammonia removal technology in wastewater treatment, specifically to a method and application of deep nitrogen removal using a sulfur-containing carrier-heterotrophic sulfur microorganism-autotrophic sulfur microorganism. Background Technology

[0002] With the increasing emphasis placed on environmental protection by the state, wastewater treatment plant discharge standards are becoming increasingly stringent, among which total nitrogen is a particularly difficult indicator for wastewater treatment plants to meet. Currently, to ensure that total nitrogen standards are met, wastewater treatment plants often resort to adding additional carbon sources, such as acetic acid, sludge digestion liquid, or waste molasses, to the denitrification process. This not only increases wastewater treatment costs but, if not properly controlled, can also lead to an increase in effluent COD, which in turn negatively impacts the effluent quality.

[0003] Total nitrogen removal relies on denitrifying microorganisms, most of which are heterotrophic. Autotrophic denitrifying microorganisms also exist in nature, but most of them have harsh growth conditions and are affected by carbon sources, making them unable to compete with heterotrophic denitrifying microorganisms. They are easily replaced by heterotrophic microorganisms when applied on a large scale. Summary of the Invention

[0004] Therefore, the main objective of this invention is to provide a method for deep removal of total nitrogen from water through autotrophic-heterotrophic sulfur denitrification. This method combines heterotrophic and autotrophic sulfur denitrifying bacteria, utilizes sulfur-containing carriers and quorum sensing signal molecules to rationally regulate their ecological niche, and achieves a combined autotrophic-heterotrophic denitrification process within a single reactor, resulting in effluent total nitrogen levels that meet the Class IV surface water standard.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] A method for deep removal of total nitrogen from water by autotrophic-heterotrophic sulfur denitrification includes the following steps:

[0007] S1. Suspended sulfur carrier is added to the biological contact oxidation tank;

[0008] S2. Add sulfur-autotrophic denitrifying bacteria to the biological contact oxidation tank at a dosage of 2-5 kg / m³. 3 After the carrier is introduced into the water, it should be aerated for 48-240 hours, and the dissolved oxygen should be controlled to be no higher than 1 mg / L.

[0009] S3. After water exchange, add sulfur heterotrophic denitrifying bacteria to the biological contact oxidation tank at a dosage of 2-3 kg / m³. 3 Carrier, simmer for 24-48 hours, and control dissolved oxygen not to exceed 1 mg / L;

[0010] S4. Add quorum sensing signal molecules to the biological contact oxidation tank at a dosage of 0.01-0.03 kg / m³. 3 Expose to simmering conditions for 24 hours;

[0011] S5. Introduce the wastewater to be treated for denitrification.

[0012] Furthermore, the suspended sulfur carrier in step S1 is prepared from sulfur powder and polyurethane, and the specific surface area of ​​the suspended sulfur carrier is not less than 2000 m². 2 ·m -3 The suspended sulfur carrier is cubic or cuboid in shape, with a side length of 1.5-2.5 cm, and can remain suspended in water. The sulfur loading of the suspended sulfur carrier is 2-5 kg / m³. 3 Carrier volume.

[0013] Specifically, sulfur powder is mixed with polyurethane raw materials at a mass ratio of 1:10-20 and foamed. The prepolymer and foaming agent are mixed under stirring at 120-170 rpm. The mixture is then cured at a certain temperature (75-85℃) to form a carrier, which is then cut into specified sizes to form a suspended sulfur carrier.

[0014] Furthermore, in step S1, the amount of suspended sulfur carrier added is 30%-50% of the volume of the biological contact oxidation tank.

[0015] Furthermore, the biological contact oxidation tank in step S1 consists of multiple square-shaped individual tanks.

[0016] Furthermore, the biological contact oxidation tank in step S1 is a baffled corridor type, with a length-to-width ratio of no more than 5:1 and a width of less than 6.0m.

[0017] Furthermore, the sulfur heterotrophic denitrifying bacteria in step S3 are selected from at least one of the genera Thaurea and the class Anaerolineae, namely Commonas Methylotenera.

[0018] Further, the sulfur autotrophic denitrifying bacteria in step S2 are selected from at least one of Thiobacillus denitrificans, Thiobacillus thiooxidans, Thiobacillus ferrooxidans, Thiobacillus novellas, Thiobacillus intermedius, and Thiobacillus perometabolis.

[0019] Furthermore, the quorum sensing signal molecule in step S4 can also be called a quorum sensing factor, selected from at least one of C14-HSL, C6-HSL, 3-oxo-C8-HSL, and 3-oxo-C14-HSL (all of which belong to homoserine lactones).

[0020] C14-HSL (acylhomoserine lactone) stimulates bacterial growth, migration, and protease activity; C6-HSL (N-hexanoyl-L-homoserine lactone) affects cell metabolism; 3-oxo-C8-HSL (N-(3-oxooctanoyl)-L-homoserine lactone) participates in quorum sensing in denitrifying bacteria; (N-(3-oxotetradecanoyl)-L-homoserine lactone) is a quorum sensing inducer involved in the mechanism regulating quorum sensing.

[0021] Furthermore, in step S5, during denitrification, the concentration of dissolved oxygen in the wastewater within the control device is maintained at 0.5-0.8 mg / L, and the wastewater retention time is 6-12 h.

[0022] The method for removing total nitrogen from water according to this invention has a denitrification loading of 1.2-2.4 kg NO3--N / (m 3 The total nitrogen removal rate can reach 50-95%; the treatment depth can reach effluent TN≤1.5mg / L. (filler .d); the total nitrogen removal rate can reach 50-95%; the treatment depth can reach effluent TN≤1.5mg / L.

[0023] This process is applicable to wastewater treatment in urban sewage treatment plants and industrial wastewater with low carbon-to-nitrogen ratios; it utilizes the combined action of autotrophic denitrifying microorganisms to remove total nitrogen from wastewater.

[0024] The main features are: (1) combining autotrophic sulfur denitrification process with heterotrophic sulfur denitrification process, realizing the conversion of total nitrogen into nitrogen gas through autotrophic nitrification process in the reactor; (2) changing the traditional heterotrophic denitrification process of sewage treatment to autotrophic-heterotrophic denitrification process, which can complete the denitrification process without external carbon source; (3) this process can be directly used for the treatment of sewage with low carbon-to-nitrogen ratio; or directly connected to the back end of the aerobic tank of urban sewage treatment plant to continue to remove total nitrogen; (4) this process is mainly composed of five parts: influent, reaction zone, effluent, aeration device, and monitoring system; (5) the main body of the reaction tank is a plug flow biological contact oxidation tank, which can be set with different numbers of square single tanks or baffled corridor type according to the situation; its length-to-width ratio is not greater than 5:1, and its width should be less than 6.0m to ensure uniform distribution of carrier; (6) the reaction tank is equipped with suspended carrier, usually polyurethane suspended carrier, with a specific surface area of ​​not less than 2000m². 2 ·m -3 The shape is cubic or cuboid with a side length of 1.5-2.5cm, ensuring that it has three environments at the same time: aerobic, anoxic, and facultative anaerobic, and can remain suspended in water; (7) The process denitrification load is 1.2-2.4kgNO3--N / (m3 (8) Oxygen is supplied to the reactor through an aeration device to control the concentration of dissolved oxygen in the wastewater within the device to be 0.5-0.8 mg / L; (9) To ensure the smooth progress of autonitrification and denitrification, autotrophic nitrifying bacteria and autotrophic denitrifying bacteria need to be added at once at the initial stage of reactor startup. The addition method is to first add autotrophic denitrifying bacteria to allow them to grow and then add heterotrophic denitrifying bacteria to achieve the purpose of growing autotrophic denitrifying bacteria inside the carrier and growing autotrophic nitrifying bacteria on the surface of the carrier. Finally, a group-sensing factor is added to control the coordinated progress of autotrophic-heterotrophic denitrification.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] (1) The wastewater treatment method of the present invention can remove total nitrogen without the need for additional carbon source addition when the organic matter content (COD value) is low, so that the effluent meets the Class IV standard of surface water.

[0027] (2) The present invention can realize the combined denitrification of heterotrophic and autotrophic microorganisms in the same reactor.

[0028] (3) The method provided by the present invention can be directly used for the treatment of wastewater with low carbon-to-nitrogen ratio; or it can be directly connected to the downstream end of the aerobic tank of an urban wastewater treatment plant to continue the removal of total nitrogen. Attached Figure Description

[0029] Figure 1 These are naked-eye observation images and scanning electron microscope scans of the carrier provided in the embodiments of the present invention.

[0030] Figure 2 This refers to the nitrogen content of wastewater entering and exiting the biological fluidized bed reactor, which has been placed in an autotrophic denitrifying microbial culture medium, as provided in this embodiment of the invention. Detailed Implementation

[0031] Numerous specific details are set forth in the following description to provide a full understanding of the invention. However, the invention can be practiced in many other ways different from those described herein, and similar modifications can be made by those skilled in the art without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0033] Example 1: Preparation of Suspended Sulfur Support

[0034] Sulfur powder and polyurethane raw materials were mixed at a ratio of 1:15 (by mass) and foamed. The mixture was stirred at 150 rpm, and prepolymer and foaming agent were added. The mixture was cured at 80°C to form a carrier, which was then cut into cubic or cuboid suspended sulfur carriers with side lengths of 1.5-2.5 cm. The specific surface area of ​​this carrier was 2500 m². 2 ·m -3 The sulfur loading is 2.2 kg / m³. 3 (Carrier volume), and the carrier can remain suspended in water.

[0035] Electron micrographs of its surface and interior are as follows Figure 1 As shown.

[0036] Example 2: Cultivation of biological fluidized carriers

[0037] The 2x2cm suspended sulfur carrier prepared in Example 1 was placed in an autotrophic denitrifying microbial culture medium (autotrophic microbial content not less than 2x10). 10 Cultured for 4 days in a medium containing at least 2 x 10⁻⁶ cells / L of heterotrophic denitrifying microorganisms. Then cultured for another 2 days in a heterotrophic denitrifying microbial culture medium (heterotrophic denitrifying microorganism content not less than 2 x 10⁻⁶ cells / L). 10 (Number of bacteria / L) to form a stable biological biautotrophic carrier. The sulfur-autotrophic denitrifying microorganisms include one or more of the following: *Thiobacillus denitrificans*, *Thiobacillus thiooxidans*, *Thiobacillus ferrooxidans*, *Thiobacillus novellas*, *Thiobacillus intermedius*, and *Thiobacillus perometabolis*. In this embodiment, a mixture of *Thiobacillus denitrificans*, *Thiobacillus thiooxidans*, and *Thiobacillus intermedius* is specifically selected. The heterotrophic denitrifying microorganisms are one or more of the following: *Thauera*, *Comamonas Methylotenera*, and *Anaerolineae*. In this embodiment, *Thauera* and *Comamonas Methylotenera* are specifically selected.

[0038] Example 3: Application of biological fluidized carrier in wastewater treatment

[0039] In a wastewater treatment plant, wastewater enters an aerobic biological oxidation tank, where organic matter is largely removed. It then enters an autotrophic-heterotrophic sulfur-denitrification biological fluidized bed reactor, which contains 40% cultured biological fluidized carriers (obtained in Example 2). The dissolved oxygen concentration is controlled at 1.0 mg / L, and the retention time is 6 hours. Ammonia nitrogen and nitrate nitrogen levels in the influent and effluent are measured.

[0040] like Figure 2 As shown, the average influent nitrate nitrogen level in the reactor was 35 mg / L, and the average effluent nitrate nitrogen level was 1.2 mg / L, meeting the Class IV surface water standard. The reactor operated stably for one year with limited temperature influence. This indicates that the process can remove total nitrogen without the need for adding a new carbon source. The sulfur-containing suspended carrier provides favorable survival conditions for autotrophic-heterotrophic denitrifying bacteria, and quorum factors control autotrophic and heterotrophic denitrification.

[0041] Example 4: Application of deep denitrification in wastewater treatment plants

[0042] A wastewater treatment plant has biological contact oxidation tanks, which are designed with different numbers of square single tanks or baffled corridors depending on the situation. Their length-to-width ratio is no greater than 5:1. To ensure uniform distribution of the carriers, their width should be less than 6.0m. The average nitrate nitrogen in the influent of the biological contact oxidation tank is 26.7±3.7mg / L.

[0043] During the initial startup of the reactor, autotrophic denitrifying bacteria, heterotrophic denitrifying bacteria, and quorum factors need to be added all at once. First, 40% of the carrier (obtained in Example 1) is added, followed by the addition of autotrophic denitrifying bacteria. In this example, a mixture of *Thiobacillus denitrifyingus*, *Thiobacillus thiooxidans*, and *Thiobacillus ferrooxidans* is specifically selected, with a dosage of 4 kg / m³. 3 The carrier was aerated for 144 hours after water intake (dissolved oxygen controlled not to exceed 1 mg / L) to allow it to stabilize and grow. After water change, heterotrophic nitrifying bacteria were added again. In this example, methyltrophic tufted bacteria and anaerobic tufted bacteria were specifically selected, at a dosage of 2.5 kg / m³. 3 The carrier was aerated for 36 hours (dissolved oxygen was controlled to not exceed 1 mg / L). Finally, group sensitivity factors C14-HSL and 3-oxo-C8-HSL were added, with a total dosage of 0.02 g / kg / m³. 3 After 24 hours of aeration, it operates normally. Oxygen is supplied to the reactor through an aeration device to control the dissolved oxygen concentration in the wastewater within the device between 0.5-0.8 mg / L, with a retention time of 8 hours.

[0044] The denitrification load for this process is 2.1 kg NO3-N / (m³). 3 The total nitrogen removal rate reaches 95%, and the treatment depth can reach effluent TN≤1.5mg / L. (filler .d);

[0045] Comparative Example 1

[0046] The difference between this embodiment and embodiment 4 is that the loaded body is a Pall ring packing.

[0047] In this embodiment, the total nitrogen removal rate is only 75%.

[0048] Comparative Example 2

[0049] The difference between this embodiment and embodiment 4 is that:

[0050] Without the addition of autotrophic sulfur-denitrifying bacteria, heterotrophic sulfur-denitrifying bacteria, and swarm sensitivity factors, the reactor was started up by natural biofilm formation. As a result, the operation stability of this embodiment was poor, and the total nitrogen removal rate was only 42%.

[0051] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0052] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for deep removal of total nitrogen from water via autotrophic-heterotrophic sulfur-denitrification, characterized in that, Includes the following steps: S1. Suspended sulfur carrier is added to the biological contact oxidation tank; S2. Add sulfur-autotrophic denitrifying bacteria to the biological contact oxidation tank at a dosage of 2-5 kg / m³. 3 After the carrier is introduced into the water, it should be aerated for 48-240 hours, and the dissolved oxygen should be controlled to be no higher than 1 mg / L. S3. After water exchange, add sulfur heterotrophic denitrifying bacteria to the biological contact oxidation tank at a dosage of 2-3 kg / m³. 3 Carrier, simmer for 24-48 hours, and control dissolved oxygen not to exceed 1 mg / L; S4. Add quorum sensing signal molecules to the biological contact oxidation tank at a dosage of 0.01-0.03 kg / m³. 3 Expose to simmering conditions for 24 hours; S5. Introduce the wastewater to be treated for denitrification. During denitrification, control the concentration of dissolved oxygen in the wastewater within the device to be 0.5-0.8 mg / L, and the wastewater retention time to be 6-12 h. The suspended sulfur carrier in step S1 is prepared from sulfur powder and polyurethane, and the specific surface area of ​​the suspended sulfur carrier is not less than 2000 m². 2 ·m -3 The suspended sulfur carrier is cubic or cuboid in shape, with a side length of 1.5-2.5 cm, and can remain suspended in water. The sulfur loading of the suspended sulfur carrier is 2-5 kg / m³. 3 Carrier volume; In this process, sulfur powder is mixed with polyurethane raw materials at a mass ratio of 1:10-20 and foamed. The prepolymer and foaming agent are mixed under stirring at 120-170 rpm. The mixture is then cured at 75-85℃ to form a carrier, which is then cut into specified sizes to form a suspended sulfur carrier. In step S1, the amount of suspended sulfur carrier added is 30%-50% of the volume of the biological contact oxidation tank.

2. The method according to claim 1, characterized in that, The biological contact oxidation tank in step S1 consists of multiple square-shaped individual tanks.

3. The method according to claim 1, characterized in that, The biological contact oxidation tank in step S1 is a baffled corridor type, with a length-to-width ratio of no more than 5:1 and a width of less than 6.0m.

4. The method according to claim 1, characterized in that, The sulfur heterotrophic denitrifying bacteria in step S3 are selected from at least one of the genus *Tauridella*, *Methyltrophic Trichophyton*, and *Anaerobes*.

5. The method according to claim 1, characterized in that, The sulfur-autotrophic denitrifying bacteria in step S2 are selected from at least one of the following: denitrifying thiobacillus, thiooxidizing thiobacillus, ferrooxidizing thiobacillus, novel thiobacillus, intermediate thiobacillus, and metabolically incomplete thiobacillus.

6. The method according to claim 1, characterized in that, The community sensing signal molecule in step S4 is selected from at least one of C14-HSL, C6-HSL, 3-oxo-C8-HSL, and 3-oxo-C14-HSL.

7. The application of the method according to any one of claims 1 to 6 in the removal of total nitrogen at the downstream end of the aerobic tank of a wastewater with a low carbon-to-nitrogen ratio or a municipal wastewater treatment plant.

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