A method and apparatus for treating large-scale reflux water to enhance biological nitrogen removal efficiency

Abstract

This invention discloses a method and apparatus for treating wastewater with a large reflux ratio to enhance biological nitrogen removal efficiency, belonging to the field of environmental engineering technology. Based on the SBBR process, the mixed liquor at the end of the biological treatment tank is refluxed back to the beginning of the biological treatment tank at a high reflux ratio. Biological packing material is arranged in the biological treatment tank. The SBBR reactor operates in anaerobic / aerobic mode; no reflux occurs during the anaerobic period, while reflux and aeration are performed during the aerobic period, and the DO concentration is monitored in real time. Aeration is stopped when the DO concentration rises to a preset value. After the aerobic period, reflux is stopped, and the system enters a settling and drainage period, completing one cycle. This invention can effectively increase the mass transfer force from the liquid phase to the biofilm, enhance the exchange rate of substances between the liquid phase and the biofilm, and improve biological nitrogen removal efficiency, showing promising application prospects.

Description

Technical Field

[0001] This invention belongs to the field of environmental engineering technology, specifically relating to a method and apparatus for treating large-scale reflux water to enhance biological denitrification efficiency. Background Technology

[0002] Nitrogen is one of the three major contributors to water pollution (C, N, P). Economically and effectively removing nitrogen has always been a primary objective of wastewater treatment research.

[0003] Currently, the treatment of domestic sewage from rural areas, government offices, schools, highway service areas, and tourist attractions that cannot be connected to municipal sewage networks typically employs integrated treatment equipment. The biological treatment units used in these systems often utilize biofilm or sludge membrane processes to maintain high system stability, but their effectiveness in removing total nitrogen is often unsatisfactory. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a method and apparatus for treating large-scale reflux water to enhance biological denitrification efficiency. This method effectively increases the mass transfer force from the liquid phase to the biofilm, enhances the exchange rate of substances between the liquid phase and the biofilm, and improves biological denitrification efficiency.

[0005] This invention is achieved through the following technical solution:

[0006] This invention discloses a high-return water treatment method to enhance biological denitrification efficiency, based on the SBBR process, in which the mixed liquor at the end of the biological treatment tank is returned to the beginning of the biological treatment tank at a high return ratio; and biological packing material is arranged in the biological treatment tank.

[0007] The SBBR reactor operates in anaerobic / aerobic mode. During the anaerobic period, there is no reflux, while during the aerobic period, reflux and aeration are carried out, and the DO concentration is monitored in real time. When the DO concentration rises to the preset value, aeration is stopped. After the aerobic period ends, reflux is stopped, and the reactor enters the settling and drainage period to complete one cycle of operation.

[0008] Preferably, the spacing of the biological packing material along the water flow direction is lower than the spacing perpendicular to the water flow direction.

[0009] More preferably, the biological packing material is a suspended packing material.

[0010] More preferably, the spacing of the biological packing material along the water flow direction is the diameter of the biological packing material + 50 to 80 mm, and the spacing of the biological packing material along the direction perpendicular to the water flow direction is the diameter of the biological packing material + 150 to 200 mm.

[0011] Preferably, the duration of the anaerobic period is 1 to 2 hours.

[0012] Preferably, the cross-sectional flow velocity of the reflux is 0.2 to 0.4 cm / s.

[0013] Preferably, the preset value is 3.0 mg / L.

[0014] The apparatus disclosed in this invention for implementing the above-mentioned enhanced biological denitrification efficiency large-scale reflux water treatment method includes a biological treatment tank, with an inlet pipe at the beginning and an outlet at the end. The biological treatment tank is equipped with an aeration device and a DO concentration monitoring device. The apparatus is characterized by a partition between the beginning and end of the biological treatment tank, which allows the inlet water to flow from the beginning to the end of the biological treatment tank along a U-shaped flow channel; a reflux device is provided between the beginning and end of the biological treatment tank; and a packing frame is installed inside the biological treatment tank, on which biological packing material is arranged.

[0015] Preferably, the reflux device is an air stripping device or a reflux pump.

[0016] Preferably, the outlet end is an outlet pipe or an outlet weir.

[0017] Compared with the prior art, the present invention has the following beneficial technical effects:

[0018] This invention discloses a high-recirculation wastewater treatment method for enhancing biological nitrogen removal efficiency. The method elevates the nitrified liquid from the end of the biological treatment tank to the beginning, creating a large recirculation flow. This increases the mass transfer force from the liquid phase to the biofilm, enhances the exchange rate of substances between the liquid phase and the biofilm, and improves biological nitrogen removal efficiency. Compared to traditional contact oxidation processes, this invention adds an anaerobic period without recirculation, reducing the risk of sludge bulking and providing conditions for microorganisms to store easily degradable organic matter into PHA. During the aerobic period, recirculation and aeration are performed. Under aerobic conditions, ammonia is oxidized to nitrate nitrogen, and the anoxic zone inside the biofilm converts nitrate nitrogen into nitrogen gas, thus achieving nitrogen removal. The ammonia oxidation reaction ends when the dissolved oxygen (DO) concentration reaches a preset value; at this point, aeration is stopped, and the reaction proceeds to the next stage. Experimental results show that when treating artificially prepared simulated domestic wastewater, the total inorganic nitrogen in the reactor effluent is less than 3 mg / L, indicating promising application prospects.

[0019] Furthermore, the spacing of the biological packing material along the water flow direction is lower than that perpendicular to the water flow direction, which can minimize the water pressure difference while achieving the required flow velocity.

[0020] Furthermore, the duration of the anaerobic period is 1 to 2 hours. This anaerobic stage can reduce the risk of sludge bulking and facilitate the storage of external carbon sources as internal carbon sources by microorganisms, which is beneficial for simultaneous nitrification and denitrification under large recirculation during the aerobic period.

[0021] The large-scale reflux water treatment device for enhancing biological denitrification efficiency disclosed in this invention has a reasonable structural design, can be based on existing SBBR reactors without requiring excessive modifications, and has good compatibility with existing equipment. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the overall structure of the device of the present invention;

[0023] Figure 2 This is an overall structural diagram of the device according to an embodiment of the present invention;

[0024] Figure 3 The figure shows the experimental results of the example.

[0025] In the diagram: 1 is the biological treatment tank, 2 is the baffle plate, 3 is the packing frame, 4 is the inlet pipe, 5 is the outlet, and 6 is the reflux device. Detailed Implementation

[0026] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. These descriptions are intended to explain the invention and not to limit it.

[0027] The present invention provides a high-return water treatment method for enhancing biological denitrification efficiency, which is based on the SBBR (Sequencing Batch Biofilm Reactor) process. The mixed liquor at the end of the biological treatment tank 1 is returned to the beginning of the biological treatment tank 1 at a high return ratio; biological packing material is arranged in the biological treatment tank 1.

[0028] The SBBR reactor operates in anaerobic / aerobic mode. During the anaerobic period, there is no reflux, while during the aerobic period, reflux and aeration are carried out, and the DO concentration is monitored in real time. When the DO (dissolved oxygen) concentration rises to the preset value, aeration is stopped. After the aerobic period ends, reflux is stopped, and the reactor enters the settling and drainage period to complete one cycle of operation.

[0029] In a preferred embodiment of the invention, the spacing of the biological packing material along the water flow direction is lower than the spacing perpendicular to the water flow direction. The biological packing material is preferably a suspended packing material, such as soft packing material, semi-soft packing material, or combined packing material. Specifically, the spacing of the biological packing material along the water flow direction is the diameter of the biological packing material + 50 to 80 mm, and the spacing of the biological packing material perpendicular to the water flow direction is the diameter of the biological packing material + 150 to 200 mm.

[0030] In a preferred embodiment of the present invention, the duration of the anaerobic period is 1 to 2 hours.

[0031] In a preferred embodiment of the present invention, the cross-sectional flow velocity of the recirculation is 0.2 to 0.4 cm / s.

[0032] In a preferred embodiment of the present invention, the preset value is 3.0 mg / L.

[0033] like Figure 1 This document describes a specific apparatus for implementing the above-mentioned method for enhancing biological nitrogen removal efficiency in large-scale reflux water treatment. This apparatus serves as an example to illustrate the method for enhancing biological nitrogen removal efficiency in large-scale reflux water treatment of the present invention, and does not constitute a limitation of the present invention.

[0034] The device includes a biological tank 1, with an inlet pipe 4 at the beginning and an outlet pipe 5 at the end. The biological tank 1 is equipped with an aeration device and a DO concentration monitoring device. The device is characterized in that a partition 2 is provided between the beginning and end of the biological tank 1, which allows the inlet water to flow from the beginning of the biological tank 1 along a U-shaped flow channel to the end of the biological tank 1; a reflux device 6 is provided between the beginning and end of the biological tank 1; and a packing frame 3 is provided inside the biological tank 1, on which biological packing materials are arranged.

[0035] In a preferred embodiment of the present invention, the reflux device 6 is an air stripping device or a reflux pump.

[0036] The outlet end 5 is either an outlet pipe or an outlet weir, depending on the specific type of reactor.

[0037] The invention will be further explained and illustrated below with a specific example:

[0038] The device structure and main dimensions of this embodiment are as follows: Figure 2 As shown, the reflux device 6 in this embodiment is an air stripping device, which is connected to an air pipe. The experiment was conducted using artificially prepared simulated domestic sewage, and the operation process is as follows:

[0039] (1) A baffle 2 is installed in the middle of the biological tank 1 to make the reactor structure conducive to the return of the end mixture to the beginning. A stripping device is set at the end of the biological tank 1 to return the nitrified liquid to the beginning of the biological tank 1 in a large reflux manner.

[0040] (2) Biological packing material is arranged on the packing frame 3 in the biological tank 1, with a high density along the water flow direction and a spacing of 60 mm, and a low density perpendicular to the water flow direction and a spacing of 180 mm, so as to minimize the water pressure difference while achieving the required flow velocity; Figure 2 The black circle in the image exemplifies a portion of the biological packing material on the packing holder 3;

[0041] (3) The SBBR (Sequencing Batch Biofilm Reactor) process is adopted, and the reactor is operated in anaerobic / aerobic mode;

[0042] (4) After the reactor completes the water intake, it enters the anaerobic period, which lasts for 1-2 hours. During the anaerobic period, the reflux is not turned on.

[0043] (5) After the anaerobic period, the reactor enters the aerobic period. During the aerobic period, the aeration device and the reflux device are turned on. The reflux flow rate is determined according to the cross-sectional velocity of the reflux liquid, and the cross-sectional velocity is controlled at 0.2-0.4 cm / s.

[0044] (6) Aeration is stopped when the DO concentration in the liquid phase rises to 3.0 mg / L by online detection;

[0045] (7) After the aerobic period ends, the backflow is stopped and the system enters the settling and drainage period to complete one cycle of operation.

[0046] The reflux ratio is 3000% in Stage I, 300-3000% in Stage II, and 3000% in Stage III. NH4 + -N and TIN removal effects are as follows Figure 3 As shown in the figure, the first stage is the reactor start-up (first 29 days) and the stable operation stage (30-40 days) under a large reflux ratio. The second stage is the operation stage with a reduced reflux ratio, which is reduced to 300-1000%. In this stage, the denitrification efficiency is slightly lower than that of the stable operation period in the first stage. The third stage is when the reflux ratio is increased to the design value of 3000%, and the effluent denitrification efficiency is increased again to over 98%.

[0047] It should be noted that the present invention is not limited to the above embodiments, and any obvious improvements or modifications made by those skilled in the art to the above embodiments will not exceed the scope of the concept of the present invention and the protection scope of the appended claims.

Claims

1. A method for treating large-scale reflux water to enhance biological nitrogen removal efficiency, based on the SBBR process, characterized in that, The mixed liquid at the end of the biological treatment tank (1) is returned to the beginning of the biological treatment tank (1) at a large reflux ratio; Biological packing material is arranged in the biological tank (1); The SBBR reactor operates in anaerobic / aerobic mode. During the anaerobic period, there is no backflow, while during the aerobic period, backflow and aeration are performed, and the DO concentration is monitored in real time. When the DO concentration rises to a preset value, aeration is stopped. After the aerobic period ends, backflow is stopped, and the reactor enters a settling and drainage period to complete one cycle of operation. The spacing of the biological packing material along the water flow direction is lower than the spacing perpendicular to the water flow direction. The biological packing material is a suspended packing material. The spacing of the biological packing material along the water flow direction is the diameter of the biological packing material + 50~80mm; the spacing of the biological packing material perpendicular to the water flow direction is the diameter of the biological packing material + 150~200mm.

2. The method for treating large-scale reflux water to enhance biological denitrification efficiency according to claim 1, characterized in that, The anaerobic period lasts for 1 to 2 hours.

3. The method for treating large-scale reflux water to enhance biological denitrification efficiency according to claim 1, characterized in that, The cross-sectional velocity of the reflux is 0.2~0.4 cm / s.

4. The method for treating large-scale reflux water to enhance biological denitrification efficiency according to claim 1, characterized in that, The preset value is 3.0 mg / L.

5. A large-scale reflux water treatment device for enhancing biological denitrification efficiency in the large-scale reflux water treatment method for enhancing biological denitrification efficiency according to any one of claims 1 to 4, comprising a biological treatment tank (1), an inlet pipe (4) at the head end of the biological treatment tank (1), an outlet end (5) at the tail end of the biological treatment tank (1), and an aeration device and a DO concentration monitoring device provided inside the biological treatment tank (1), characterized in that, A baffle (2) is provided between the first end and the last end of the biochemical tank (1). The baffle (2) allows the influent to flow from the first end of the biochemical tank (1) along the U-shaped flow channel to the last end of the biochemical tank (1). A reflux device (6) is provided between the first end and the last end of the biochemical tank (1). A packing frame (3) is provided inside the biochemical tank (1), and biological packing is arranged on the packing frame (3).

6. The large-scale reflux water treatment device for enhancing biological denitrification efficiency according to claim 5, characterized in that, The reflux device (6) is an air stripping device or a reflux pump.

7. The large-scale reflux water treatment device for enhancing biological denitrification efficiency according to claim 5, characterized in that, The outlet end (5) is a water outlet pipe or a water outlet weir.

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