A stable and efficient short-cut nitrification membrane aeration biofilm construction method

Abstract

The application discloses a kind of stable and efficient short-range nitrification membrane aeration biofilm construction method, belong to wastewater treatment technical field.The method is as follows: the ammonia nitrogen-containing wastewater is continuously introduced into the membrane aeration biofilm reactor (MABR) inoculated with nitrification sludge, and first forms nitrification biofilm.Further by adding alkali pump to the reactor intermittent injection containing sulfide lye, maintain the pH value of reactor between 8.0~8.5, sulfide ion concentration is not less than 15mg S / L.At the same time, adjust the gas supply pressure, so that the reactor dissolved oxygen is less than 0.1mg / L.Utilize sulfide ion (HS ‑ ), pH and low dissolved oxygen combination, efficiently inhibit nitrite oxidizing bacteria in biofilm, construct stable short-range nitrification membrane aeration biofilm.The biofilm can be used for low-concentration ammonia nitrogen wastewater treatment, and energy consumption is low, easy to control.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of sewage treatment, and particularly relates to a stable and efficient short-cut nitrification membrane aeration biofilm construction method. BACKGROUND

[0002] With the rapid development of China's economy, water body nitrogen pollution is becoming increasingly serious. The traditional activated sludge process has high energy and material consumption for denitrification, and new denitrification technologies need to be developed urgently. The short-cut nitrification process can greatly reduce aeration energy consumption and carbon source demand by controlling ammonia oxidation to nitrite and then converting the nitrite to nitrogen gas through denitrification or anaerobic ammonia oxidation. This process can greatly reduce aeration energy consumption and carbon source demand, and is proved to be the most promising denitrification technology. However, how to establish a stable short-cut nitrification is the difficulty and key of this technology.

[0003] A method and device for treating sewage based on short-cut nitrification are disclosed in Chinese patent application No. CN117945545A. The method uses sulfides to treat sludge in a sludge treatment reactor by presetting treatment conditions, then inputs the treated sludge and sewage into a short-cut nitrification reactor, and constructs a short-cut nitrification treatment system according to preset culture conditions and treats the sewage. This method increases the complexity of the system by treating sludge and water separately. In addition, the activated sludge system has inherent shortcomings and limitations.

[0004] Compared with the activated sludge system, the membrane aeration biofilm can efficiently utilize oxygen, and the oxygen utilization rate can reach 100%. The system further reduces aeration energy consumption through a bubbleless aeration process, and shows greater attraction in the denitrification process. However, there is an essential difference between the membrane aeration biofilm and the activated sludge system in mechanism. In the membrane aeration biofilm, the oxygen concentration presents a gradient distribution, which makes it difficult to effectively inhibit nitrite reducing bacteria, and thus makes it difficult to establish a short-cut nitrification process. In addition, the existing short-cut nitrification establishment methods are mostly aimed at high ammonia nitrogen wastewater, and the treatment effect is not good for low ammonia nitrogen wastewater. SUMMARY

[0005] In order to solve the problems in the prior art, the application provides a construction method of stable and efficient short-cut nitrification membrane aeration biofilm, which is aimed at low ammonia nitrogen wastewater, provides a stable nitrite source for the anaerobic ammonia oxidation process, and reduces the aeration energy consumption and organic carbon addition of the denitrification process, and reduces carbon emissions.

[0006] The specific technical solutions adopted by the application are as follows:

[0007] The application provides a stable and efficient short-cut nitrification membrane aeration biofilm construction method, which comprises the following steps: continuously feeding ammonia-nitrogen-containing wastewater into a membrane aeration biofilm reactor inoculated with nitrifying sludge, wherein the membrane aeration biofilm reactor is provided with a water inlet, a water outlet and an internal circulation pipeline, and a hollow fiber membrane assembly is arranged in the membrane aeration biofilm reactor; a monitoring device for detecting the dissolved oxygen and pH value in the membrane aeration biofilm reactor is arranged on the internal circulation pipeline; the hollow fiber membrane assembly is connected with a pressurized oxygen source for controlling the dissolved oxygen in the membrane aeration biofilm reactor; the monitoring device is connected with a pH control device for controlling the operation of an alkali feeding pump; and the alkali feeding pump is connected with an alkali solution tank containing sulfide-containing alkali solution, so as to feed the sulfide-containing alkali solution into the membrane aeration biofilm reactor.

[0008] The short-cut nitrification membrane aeration biofilm construction method specifically comprises the following steps:

[0009] Firstly, nitrifying biofilm is formed in the membrane aeration biofilm reactor inoculated with nitrifying sludge; then, the sulfide-containing alkali solution is intermittently injected into the membrane aeration biofilm reactor through the alkali feeding pump, so as to maintain the pH value in the membrane aeration biofilm reactor at 8.0-8.5 and the concentration of sulfhydryl ions not less than 15 mg S / L; meanwhile, the gas supply pressure is adjusted through the pressurized oxygen source, so as to make the concentration of dissolved oxygen in the membrane aeration biofilm reactor less than 0.1 mg / L; and the sulfhydryl ions, pH and low dissolved oxygen are combined to inhibit the nitrite oxidizing bacteria in the biofilm, so as to construct the stable short-cut nitrification membrane aeration biofilm.

[0010] Preferably, the pH value of the sulfide-containing alkali solution is higher than 12, wherein the alkali solution is sodium carbonate solution or sodium hydroxide solution, and the sulfide is sodium sulfide.

[0011] Further, the concentration of sodium carbonate in the sulfide-containing alkali solution is 5-15 g / L, and the concentration of sodium sulfide is 0.5-0.8 g / L.

[0012] Preferably, the hollow fiber membrane assembly is composed of dense polypropylene hollow fiber membranes, and the surface micropore diameter of the polypropylene hollow fiber membranes is 0.1-1 nm.

[0013] Preferably, the output pressure of the pressurized oxygen source is 0.05±0.01 MPa.

[0014] Preferably, the ammonia-nitrogen concentration in the ammonia-nitrogen-containing wastewater is 50-100 mg N / L.

[0015] Preferably, the concentration of sulfhydryl ions in the membrane aeration biofilm reactor is 16-25 mg S / L.

[0016] As preferred, when the monitoring device detects that the pH value in the membrane aerated biofilm reactor is lower than 8.0, the pH control device controls the alkali pump to start and input the sulfide-containing alkali liquor into the membrane aerated biofilm reactor, so as to maintain the pH value in the membrane aerated biofilm reactor within the set 8.0-8.5.

[0017] As preferred, a circulating pump is arranged on the internal circulation pipeline, and the circulating pump is used to mix the wastewater in the membrane aerated biofilm reactor.

[0018] As preferred, the membrane aerated biofilm reactor adopts the top-in and bottom-out water inlet and outlet mode.

[0019] Compared with the prior art, the present application has the following beneficial effects:

[0020] (1) The construction method provided by the present application successfully constructs the short-cut nitrification membrane aerated biofilm by intermittently adding sulfide, controlling the pH value within 8.0-8.5 and under the condition of low dissolved oxygen. The test shows that when the pH value in the reactor is controlled within 8.0-8.5 and the sulfide exists in the form of sulfide ion (HS - ), the strongest inhibition effect on nitrite oxidizing bacteria is shown. The low dissolved oxygen and the inhibition effect on nitrite oxidizing bacteria together achieve long-term inhibition of nitrite oxidizing bacteria.

[0021] (2) The construction method provided by the present application is simple and easy to implement, and is suitable for large-scale application. The biofilm constructed by the present application can be used for low-concentration ammonia-nitrogen wastewater treatment, and has lower denitrification energy consumption and a more stable and easy-to-control biofilm system. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 Fig. 1 is a schematic diagram of a short-cut nitrification membrane aerated biofilm treatment device in the present application;

[0023] Figure 2 Fig. 5 is a running effect diagram of the membrane aerated biofilm reactor in Example 1;

[0024] Figure 3 Fig. 6 is a running effect diagram of the membrane aerated biofilm reactor in Comparative Example 1;

[0025] Figure 4 Fig. 7 is a running effect diagram of the membrane aerated biofilm reactors in Comparative Example 2 and Comparative Example 3;

[0026] In the figure, 1 is a water inlet device, 2 is a hollow fiber membrane assembly, 3 is a monitoring device, 4 is an alkali liquor tank, 5 is a water outlet device, 6 is a pressurized oxygen source, 7 is a water inlet pump, 8 is a circulating pump, and 9 is an alkali pump. DETAILED DESCRIPTION

[0027] The present invention will be further described and illustrated below with reference to the accompanying drawings and specific embodiments. The technical features of each embodiment of the present invention can be combined accordingly, provided that there is no mutual conflict.

[0028] The key to short-cut nitrification lies in effectively inhibiting or eliminating nitrite-oxidizing bacteria while maintaining the activity of ammonia-oxidizing bacteria. Due to the diversity and adaptability of nitrite-oxidizing bacteria, they are difficult to stably inhibit by a single factor. Furthermore, in aerated biofilms, the connections between microorganisms are closer, and the biofilm renewal cycle is relatively longer than that of activated sludge, making the inhibition of nitrite-oxidizing bacteria even more challenging.

[0029] like Figure 1 As shown, the present invention provides a treatment device for constructing a stable and efficient short-cut nitrification membrane aerated biofilm. The treatment device includes a membrane aerated biofilm reactor (MABR), an influent device 1, a hollow fiber membrane module 2, a monitoring device 3, an alkali tank 4, an effluent device 5, a pressurized oxygen source 6, an influent pump 7, a circulation pump 8, an alkali pump 9, and a pH control device.

[0030] The treatment device provided by this invention includes an inlet, an outlet, and an internal circulation pipeline on the membrane aerated biofilm reactor. The inlet is connected to the inlet device 1 via an inlet pump 7, and the outlet is connected to the outlet device 5. A monitoring device 3 is installed on the internal circulation pipeline to detect dissolved oxygen and pH value within the membrane aerated biofilm reactor. A circulation pump 8 is also installed on the internal circulation pipeline to mix the wastewater within the membrane aerated biofilm reactor evenly.

[0031] In the treatment device provided by this invention, a hollow fiber membrane module 2 is installed inside the membrane aeration biofilm reactor. It should be noted that, as a preferred embodiment of this invention, the effective volume of the membrane aeration biofilm reactor used in this embodiment is 3L. The hollow fiber membrane module 2 used inside the membrane aeration biofilm reactor is composed of a dense polypropylene hollow fiber membrane, and the effective membrane area of ​​the hollow fiber membrane module 2 is 0.63m². 2 .

[0032] In the processing device provided by this invention, the top of the hollow fiber membrane module 2 is connected to a pressurized oxygen source 6. The pressurized oxygen source 6 can be an oxygen cylinder, used to control the dissolved oxygen concentration inside the membrane aerated biofilm reactor. The output pressure of the pressurized oxygen source is controlled to be 0.05 ± 0.01 MPa.

[0033] In the processing device provided by this invention, the monitoring device 3 is connected to the pH control device, which can control the opening or closing of the alkali pump 9. The alkali pump 9 is connected to the alkali tank 4 containing sulfide-containing alkali solution. When the pump 9 is turned on, it can transport the sulfide-containing alkali solution to the membrane aerated biofilm reactor, adjusting the pH value and the concentration of hydrogen sulfide ions in the membrane aerated biofilm reactor.

[0034] During implementation, a certain amount of nitrified sludge is first inoculated into the membrane aerated biofilm reactor (BBR), and ammonia-nitrogen-containing wastewater is continuously supplied to the BBR through the inlet, causing a preliminary nitrification biofilm to form on the surface of the hollow fiber membrane module. Subsequently, sulfide-containing alkaline solution is intermittently injected into the BBR via alkali pump 9 to maintain the pH value within the BBR between 8.0 and 8.5, and the hydrosulfide ion concentration not less than 15 mg S / L. Simultaneously, the air supply pressure is adjusted by pressurized oxygen source 6 to ensure that the dissolved oxygen concentration within the BBR is below 0.1 mg / L.

[0035] It should be noted that sulfides in this membrane-aerated biofilm reactor are in the form of hydrogen sulfide ions (HS-H2O). - The presence of nitrite in the biofilm directly inhibits nitrite-oxidizing bacteria. Simultaneously, the low dissolved oxygen conditions (dissolved oxygen concentration below 0.1 mg / L) further limit the growth of nitrite-oxidizing bacteria, ultimately leading to the formation of a stable short-range nitrification film aerated biofilm.

[0036] It should be noted that nitrifying bacteria are widely distributed in nature, and the method described in this invention can selectively inhibit nitrite-oxidizing bacteria. Therefore, this invention does not require limitation on the species or community of bacteria. Activated sludge from wastewater treatment plants can be directly inoculated into the membrane aerated biofilm reactor as a source of nitrifying bacteria, rapidly forming a nitrifying biofilm.

[0037] It should be noted that the pH value of the sulfide-containing alkaline solution is preferably above 12, and the sulfide can be sodium sulfide, while the alkaline solution can be a sodium carbonate solution or a sodium hydroxide solution. Each addition of the sulfide-containing alkaline solution should ensure that the peak actual detected sulfide concentration in the membrane aerated biofilm reactor is not less than 15 mg S / L. The specific concentration can be adjusted and optimized based on the reactor's performance, with the final inhibition effect on nitrite-oxidizing bacteria or the cumulative efficiency of nitrite as the benchmark.

[0038] In this invention, the preferred water inlet and outlet method is bottom inlet and top outlet. The ammonia nitrogen concentration in the inlet ammonia nitrogen-containing wastewater can be 50-100 mg N / L, preferably 50 mg / L.

[0039] To further demonstrate the specific technical effects of the present invention, the treatment effects achieved by the method disclosed in the present invention are shown below based on the above-mentioned stable and efficient short-range nitrification membrane aerated biofilm treatment device.

[0040] Example 1

[0041] This embodiment provides a method for constructing a stable and efficient short-range nitrification membrane aerated biofilm using the above-mentioned treatment device, as detailed below:

[0042] (1) Prepare a simulated wastewater containing 50 mg N / L ammonia nitrogen as the influent to the membrane aerated biofilm reactor. The pH value of this simulated wastewater is between 7.0 and 7.5. Prepare a solution containing 10 g / L sodium carbonate and 0.6 g / L sodium sulfide as the sulfide-containing alkaline solution. The pH value of this sulfide-containing alkaline solution is in the range of 12 to 13.

[0043] The simulated wastewater composition also includes: 605 mg / L MgSO4·7H2O, 53 mg / L KH2PO4, 54 mg / L CaCl2, 600 mg / L NaHCO3, FeCl3·6H2O 3.03 mg / L, H3BO3 0.3 mg / L, CoCl2·6H2O 0.3 mg / L, MnCl2·4H2O 0.24 mg / L, ZnSO4·7H2O 0.24 mg / L, Na2MoO4·2H2O 0.12 mg / L, CuSO4·5H2O 0.06 mg / L, and KI 0.06 mg / L.

[0044] (2) A certain amount of nitrified sludge from the secondary sedimentation tank of a wastewater treatment plant was pre-inoculated into the membrane aerated biofilm reactor, and simulated wastewater was continuously injected into it, maintaining a hydraulic retention time of 24 hours to initially form a nitrifying biofilm. During this period, as a control group, the efficiency of the membrane aerated biofilm reactor was as follows: Figure 2 As shown in the figure, the ammonia nitrogen removal rate is above 85%, and the average effluent ammonia nitrogen concentration is 7 mg N / L. Most of the ammonia nitrogen in the influent is converted to nitrate, resulting in an average effluent nitrate concentration of 27 mg N / L. The average effluent nitrite concentration is 13 mg N / L, and the nitrite accumulation rate is only 32%.

[0045] (3) On day 12, sulfide-containing alkaline solution was intermittently injected into the membrane aerated biofilm reactor via alkali pump 9 to maintain the pH value within the reactor between 8.0 and 8.5. Simultaneously, the gas supply pressure was adjusted via pressurized oxygen source 6 to control the dissolved oxygen concentration within the reactor to below 0.1 mg / L. Each injection of sulfide-containing alkaline solution maintained the hydrosulfide ion concentration within the reactor at 16 mg / L. This combination of hydrosulfide ions, pH, and low dissolved oxygen inhibited nitrite-oxidizing bacteria in the biofilm, thus constructing a stable short-range nitrification membrane aerated biofilm.

[0046] like Figure 2 As shown, after 12 days, the average nitrite concentration in the effluent increased to 31 mg N / L, the nitrate concentration in the effluent decreased to 7 mg N / L, and the nitrite accumulation rate increased to over 80%.

[0047] The abundance of nitrifying bacteria was measured in two phases (before and after day 12), revealing that the relative abundance of the main nitrite-oxidizing bacterium, Nitrospira, decreased from 7% to below 1%. This indicates that nitrite-oxidizing bacteria were successfully inhibited using the above method, and a short-range nitrification membrane aerated biofilm was successfully constructed.

[0048] Comparative Example 1

[0049] The reaction apparatus, operating method, and operating conditions used in this comparative example are the same as in Example 1, except that only an alkaline solution containing 10 g / L sodium carbonate is introduced starting from day 20, and a sulfide-containing alkaline solution containing 10 g / L sodium carbonate and 0.6 g / L sodium sulfide solution is introduced starting from day 30.

[0050] like Figure 3 As shown, the results indicate that, under the same conditions of pH, dissolved oxygen, and other parameters, the short-cut nitrification efficiency of the membrane aerated biofilm reactor gradually decreased, with the effluent nitrate concentration gradually increasing to 28 mg N / L on day 29, while the nitrite accumulation rate decreased to 37%. This demonstrates that simply controlling the pH to 8.0–8.5 and the dissolved oxygen concentration below 0.1 mg / L is insufficient to achieve stable short-cut nitrification membrane aerated biofilm. Adding 0.6 g / L sodium sulfide to the alkaline solution on day 30 significantly reduced the effluent nitrate concentration to approximately 10 mg N / L, while simultaneously increasing the nitrite accumulation rate to over 65% and maintaining stability. Therefore, sulfide addition is essential for achieving stable short-cut nitrification membrane aerated biofilm.

[0051] Comparative Example 2

[0052] The reaction apparatus, operating method, and operating conditions used in this comparative example are the same as in Example 1. The difference lies in the use of a pH control device to control the pH value in the membrane aerated biofilm reactor within the ranges of 6.0–6.5, 7.5–8.0, or 8.0–8.5, respectively, while a sulfide-containing alkaline solution is continuously added through the inlet. The results are as follows: Figure 4 As shown.

[0053] Comparative Example 3

[0054] The reaction apparatus, operating method, and operating conditions used in this comparative example are the same as in Example 1, except that the pH value in the membrane aerated biofilm reactor is controlled at 6.0–6.5 using a pH control device, and sulfide-containing alkaline solution is added intermittently via an alkali addition pump. The results are as follows: Figure 4 As shown.

[0055] like Figure 4As shown, it was found that regardless of whether the pH was acidic and sulfide was added intermittently (Comparative Example 3), or under different pH conditions and sulfide was added continuously (Comparative Example 2), stable nitrite accumulation could not be achieved, and the effluent was mostly nitrate. Intermittent sulfide addition can instantaneously generate high concentrations of hydrosulfide (HS-H2O). - Sulfide ions have a significant inhibitory effect on nitrite-oxidizing bacteria. However, when sulfides are added continuously, low concentrations fail to produce an inhibitory effect, while high concentrations induce the proliferation and growth of sulfur-oxidizing bacteria, resulting in the loss of the inhibitory effect.

[0056] Therefore, a stable short-range nitrification membrane aeration biofilm construction can only be achieved by controlling the pH value between 8.0 and 8.5, supplying sulfides intermittently through alkaline solution, and maintaining a dissolved oxygen concentration below 0.1 mg / L.

[0057] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the invention. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the invention. Therefore, all technical solutions obtained through equivalent substitution or transformation fall within the protection scope of the present invention.

Claims

1. A stable and efficient short-cut nitrification membrane aerated biofilm construction method, characterized in that ammonia nitrogen-containing wastewater is continuously fed into a membrane aerated biofilm reactor inoculated with nitrifying sludge, wherein... The membrane aerated biofilm reactor is provided with a water inlet, a water outlet and an internal circulation pipeline, and a hollow fiber membrane assembly (2) is arranged inside the membrane aerated biofilm reactor; a monitoring device (3) for detecting the dissolved oxygen and pH value in the membrane aerated biofilm reactor is arranged on the internal circulation pipeline; the hollow fiber membrane assembly (2) is connected with a pressurized oxygen source (6) for controlling the dissolved oxygen in the membrane aerated biofilm reactor; the monitoring device (3) is connected with a pH control device for controlling the operation of an alkali feeding pump (9); the alkali feeding pump (9) is connected with an alkali solution tank (4) containing sulfide-containing alkali solution, and the sulfide-containing alkali solution is delivered into the membrane aerated biofilm reactor; The construction method of the short-cut nitrification membrane aerated biofilm is as follows: First, a nitrifying biofilm is formed in the membrane aerated biofilm reactor inoculated with nitrifying sludge; then, the sulfide-containing alkali solution is intermittently injected into the membrane aerated biofilm reactor through the alkali feeding pump (9) to maintain the pH value in the membrane aerated biofilm reactor at 8.0-8.5 and the concentration of sulfide ions at not less than 15 mg S / L; at the same time, the gas supply pressure is adjusted through the pressurized oxygen source (6) to make the dissolved oxygen concentration in the membrane aerated biofilm reactor less than 0.1 mg / L; the combination of sulfide ions, pH and low dissolved oxygen is used to inhibit the nitrite oxidizing bacteria in the biofilm, and a stable short-cut nitrification membrane aerated biofilm is constructed.

2. The stable high-efficiency short-cut nitrification membrane aeration biofilm construction method according to claim 1, characterized in that, The pH value of the sulfide-containing alkali solution is higher than 12, and the alkali solution is sodium carbonate solution or sodium hydroxide solution, and the sulfide is sodium sulfide.

3. The stable high-efficiency short-cut nitrification membrane aeration biofilm construction method according to claim 2, characterized in that, The concentration of sodium carbonate in the sulfide-containing alkali solution is 5-15 g / L, and the concentration of sodium sulfide is 0.5-0.8 g / L.

4. The stable high-efficiency short-cut nitrification membrane aeration biofilm construction method according to claim 1, characterized in that, The hollow fiber membrane assembly (2) is composed of dense polypropylene hollow fiber membranes, and the surface micropore diameter of the polypropylene hollow fiber membranes is 0.1-1 nm.

5. The stable high-efficiency short-cut nitrification membrane aeration biofilm construction method according to claim 1, characterized in that, The output pressure of the pressurized oxygen source (6) is 0.05±0.01 MPa.

6. The stable high-efficiency short-cut nitrification membrane aeration biofilm construction method according to claim 1, characterized in that, The ammonia nitrogen concentration of the ammonia nitrogen-containing wastewater is 50-100 mg N / L.

7. The stable high-efficiency short-cut nitrification membrane aeration biofilm construction method according to claim 1, characterized in that, The concentration of sulfide ions in the membrane aerated biofilm reactor is 16-25 mg S / L.

8. The stable high-efficiency short-cut nitrification membrane aeration biofilm construction method according to claim 1, characterized in that, When the monitoring device (3) detects that the pH value in the membrane aerated biofilm reactor is lower than 8.0, the pH control device controls the alkali feeding pump (9) to start, and the sulfide-containing alkali solution is input into the membrane aerated biofilm reactor to maintain the pH value in the membrane aerated biofilm reactor at the set value of 8.0-8.

5.

9. The stable high-efficiency short-cut nitrification membrane aeration biofilm construction method according to claim 1, characterized in that, A circulating pump (8) is arranged on the internal circulation pipeline, and the circulating pump (8) is used to mix the wastewater in the membrane aerated biofilm reactor.

10. The stable high-efficiency short-cut nitrification membrane aeration biofilm construction method according to claim 1, characterized in that, The membrane aerated biofilm reactor adopts a top-in and bottom-out water inlet and outlet mode.

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