Biofilm carrier suitable for low-temperature sewage treatment, preparation method and application

Abstract

The invention discloses a biofilm carrier suitable for low-temperature sewage treatment and a preparation method and application thereof.The biofilm carrier takes SiC ceramic as a biofilm framework, the upper portion of the SiC ceramic is coated with a photo-thermal agent to form a photo-thermal conversion functional area, the lower portion of the SiC ceramic is a microbial adhesion functional area, and meanwhile the upper portion of the SiC ceramic is loaded with temperature response type nanocapsules; and efficient photo-thermal conversion can be carried out, functional bacteria are adsorbed and enriched, the biomass is improved, and the bacterial activity is improved in a low-temperature environment. The preparation method of the biofilm carrier is simple, and the ammonia nitrogen removal rate is high after the biofilm carrier is applied to microbial wastewater treatment.

Description

Technical Field

[0001] The present invention relates to the field of environmental pollutant treatment, and in particular to a biofilm carrier suitable for low-temperature sewage treatment, a preparation method and an application thereof. Background Art

[0002] In global water resource management, microbial water treatment technology, a key component of wastewater treatment and water purification, faces an increasingly prominent challenge in achieving efficient nitrogen removal in low-temperature environments, becoming a critical technical bottleneck in the water treatment sector. Low temperatures (typically below 15°C) significantly slow the metabolic rate of microorganisms, especially those key microorganisms in the nitrification and denitrification processes, such as nitrifying bacteria and anaerobic ammonium-oxidizing bacteria. This reduced activity directly impacts nitrogen conversion, reducing nitrogen removal efficiency.

[0003] Low temperatures not only affect the activity of free microorganisms but also the formation and stability of biofilms. Biofilms play a crucial role in water treatment. Low temperatures slow the maturation of biofilms, affecting their structure and, in turn, the attachment and growth of denitrifying microorganisms, reducing the stability and efficiency of the denitrification process. Under low temperature conditions, the operating conditions of water treatment systems (such as dissolved oxygen, pH, and nutrient ratios) are more sensitive to microbial activity. Precisely regulating these conditions to meet the needs of microorganisms in low-temperature environments is key to achieving stable denitrification, but this also increases operational complexity.

[0004] The application of biofilm technology under low temperature conditions can take advantage of the high adaptability of biofilms to environmental changes and improve denitrification efficiency and system stability by optimizing the cultivation and maintenance conditions of biofilms. However, these regulatory measures cannot change the temperature of the microenvironment, so the performance improvement of low-temperature microbial water treatment is limited. CN202310758686.X discloses a preparation method and application of a Schottky junction-doped composite polyvinylidene fluoride mixed membrane with excellent photothermal conversion capability. This method uses simple doping and phase conversion as the main means to incorporate photocatalytic materials into photothermal materials and make them into composite membrane materials for photooxidation / reduction of organic pollutants, thereby achieving the effect of photodegradation of organic dyes and antibacterial effects.

[0005] Photothermal conversion is a process that concentrates solar radiation through reflection and absorption, converting it into heat and raising the temperature. It is a low-cost, highly efficient energy conversion method. An ideal photothermal conversion microbial water treatment carrier should possess efficient and robust photothermal conversion performance. Winter sunlight intensity is weaker, so the photothermal carrier needs to have high spectral absorption across the entire solar spectrum, effectively raising the carrier's microenvironment temperature in low winter light conditions. Furthermore, because the ultraviolet region of sunlight has a strong inhibitory effect on microbial activity, the carrier requires a light-free microenvironment. Introducing light into wastewater systems can cause photosynthetic algae to proliferate. When exposed to light, photosynthetic algae produce oxygen, which significantly inhibits the activity of anaerobic bacteria. Some algae also produce algal toxins that can kill bacteria. Bacteria often possess photosensitive proteins, and the activity of some bacteria is inhibited by light. Therefore, the photothermal carrier must have functional regions that protect microorganisms sensitive to ultraviolet light or other wavelengths of sunlight under full-spectrum light. Finally, as a microbial carrier, the photothermal carrier needs to have strong microbial adhesion attraction and excellent biocompatibility, so that microorganisms can achieve efficient adsorption on the carrier surface and efficient microbial biochemical reactions in a low-temperature environment.

[0006] In order to overcome the problem of easy loss of low-temperature microorganisms and improve the low-temperature microbial water treatment performance, the inventors of the present invention utilized the technical conditions of the laboratory and obtained the present invention after a long period of research and experiments. Summary of the Invention

[0007] In view of the deficiencies in the prior art, the present invention aims to provide a biofilm carrier suitable for low-temperature sewage treatment, a preparation method and an application thereof, so as to solve the problems mentioned in the background technology.

[0008] The technical solution adopted by the present invention to achieve the above-mentioned purpose is: A low-temperature sewage treatment biofilm carrier uses SiC ceramics as the biofilm skeleton, a photothermal agent is coated on the upper part of the SiC ceramics to form a photothermal conversion functional area, and the lower part of the SiC ceramics is a microbial adhesion functional area.

[0009] Preferably, the photothermal agent consists of PDMS, polyhexane, and α-Fe2O3@PANI.

[0010] Preferably, temperature-responsive nanocapsules are also loaded on the SiC ceramic.

[0011] Preferably, the temperature-responsive nanocapsule consists of a temperature-sensitive poly (N-isopropylacrylamide) (PNIPAM) shell and a sustained-release microbial growth promoter core. When the carrier microenvironment temperature rises (>25°C), the PNIPAM shell shrinks and releases the microbial growth promoter in the core.

[0012] Preferably, the microbial growth promoter comprises one or more of cobalamin, menadione and biotin.

[0013] A method for preparing a low-temperature sewage treatment biofilm carrier specifically comprises the following steps: Step 1: Preparation of α-Fe2O3 nanoparticles: Sodium nitrate was added to the prepared FeCl3 solution, and after adjusting the pH, the solution was poured into a polytetrafluoroethylene-lined reaction vessel and reacted at 95°C for 4 hours. After cooling to room temperature, the yellow solid was collected by centrifugation and washing. Finally, the yellow solid was calcined in a furnace at 550°C for 2 hours to produce α-Fe2O3 nanoparticles. Step 2: Preparation of α-Fe2O3@PANI: Aniline and deionized water were mixed and placed in an ice-water bath. Hydrochloric acid was slowly added to adjust the pH to 0.8-1.0. The α-Fe2O3 nanoparticles obtained in Step 1 were added and ultrasonicated. Ammonium persulfate solution was slowly added to promote the polymerization of aniline. The mixture was stirred and allowed to stand at -4°C for 24 hours to achieve sufficient precipitation and polymerization. Finally, α-Fe2O3@PANI was obtained after washing with deionized water and ethanol. Step 3: Prepare a photothermal agent: PDMS is prepared by mixing a PDMS precursor and a cross-linking agent in a ratio of 10:1, and then adding the mixture to polyhexane. After thorough stirring, the α-Fe2O3@PANI prepared in step 2 is added to the mixture and stirred until uniformly mixed to obtain the photothermal agent. Step 4: Prepare a low-temperature sewage treatment biofilm carrier: coat the photothermal agent prepared in step 3 on a SiC ceramic skeleton and dry it at 70° C. for 5 hours.

[0014] Preferably, in step 1, the pH is adjusted to 1.5.

[0015] Preferably, in step 2, the molar ratio of aniline to α-Fe2O3 nanoparticles is 4:1-3.

[0016] Preferably, the mass fraction ratio of PDMS, polyhexane and α-Fe2O3@PANI in the mixed solution of step three is 10%:10%:80%.

[0017] Preferably, the porosity of the SiC ceramic in step 4 is 10 ppi.

[0018] The present invention also provides the use of the prepared low-temperature sewage treatment biofilm carrier in low-temperature microbial water treatment.

[0019] The present invention has the following beneficial effects: 1. The low-temperature sewage treatment biofilm carrier prepared by the present invention can realize the rapid start-up of the reactor in a low-temperature environment (below 15°C) and quickly attract microorganisms to form a film and attach; 2. The surface of the low-temperature sewage treatment biofilm carrier is divided into a photothermal conversion functional area and a microbial adhesion functional area, which can realize photothermal conversion and promote the attachment of microorganisms; in addition, the carrier can adsorb DNA in the environment, regulate the structure of the biofilm, and promote the maturation and mass transfer of porous biofilms. The carrier can slowly release iron ions, promote bacterial film formation through chemotaxis, and increase the abundance of functional bacteria. The carrier can also efficiently intercept water treatment functional bacteria with slow growth rates, such as anaerobic ammonia oxidizing bacteria, and ensure good effluent water quality.

[0020] 3. The staggered honeycomb structure design of the low-temperature sewage treatment biofilm carrier enables the formation of a light-free area in the lower layer of the carrier during the light-heat conversion process, avoiding direct exposure of microorganisms to the ultraviolet region of sunlight, effectively preventing the killing effect of ultraviolet light on microorganisms, and providing a suitable growth environment for microorganisms; 4. The surface of the low-temperature sewage treatment biofilm carrier can also be loaded with pH-responsive nanocapsules to achieve intelligent regulation. The released biological factors enrich functional bacteria through chemotaxis, and at the same time activate the coenzyme synthesis and energy metabolism of microorganisms at low temperatures, forming a positive feedback loop of "photothermal warming-factor release-metabolic activation", thereby achieving dynamic enhancement of microbial activity in low-temperature environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the structure of the device; Figure 2 It is the change of ammonia nitrogen, nitrite nitrogen and nitrate nitrogen content in the reactor inlet and outlet water; Figure 3 is the change of the bacterial population in the two reactors (where R p is the bacterial community structure of the experimental group reactor with biofilm carrier, R c is the bacterial community structure of the control group reactor). DETAILED DESCRIPTION

[0022] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than for limiting the claims of the invention.

[0023] It should be noted that the activated sludge used in the present invention is not limited to its source; any water treatment microorganisms that are severely affected by low temperatures are suitable for the method of this patent. The photothermal carrier used in the present invention has been modified to have good microbial adsorption and film formation and microbial loading capacity, which facilitates the immobilization of microorganisms. Example

[0024] Step 1: Preparation of α-Fe2O3 nanoparticles: Dissolve 0.81 g of FeCl3·6H2O in 20 mL of deionized water, then add 1.70 g of NaNO3. Adjust the pH of the solution to 1.5 by dropwise addition of hydrochloric acid. Transfer the solution to a 25 mL Teflon-lined reaction vessel and react at 95°C for 4 hours. After cooling to room temperature, collect the yellow solid by centrifugation and washing. Finally, calcine the yellow solid in a furnace at 550°C for 2 hours to produce α-Fe2O3.

[0025] Step 2: Preparation of α-Fe2O3@PANI: Mix 9 mL (0.1 mol) of aniline with 200 mL of deionized water and place in an ice-water bath. Slowly add hydrochloric acid to the aniline to control the pH at 1.0. Then, add 8 g (0.05 mol) of the synthesized α-Fe2O3 nanoparticles to the above solution and sonicate. Dissolve 6.1 g of ammonium persulfate in 100 mL of deionized water. Slowly add the ammonium persulfate solution to the suspension to promote the polymerization of aniline. Store the solution at -4°C for 24 hours to allow for complete precipitation and polymerization. Finally, wash with deionized water and ethanol to obtain α-Fe2O3@PANI.

[0026] Several different α-Fe2O3@PANI composites were prepared by varying the amount of α-Fe2O3 in the reaction system (0 mol, 0.025 mmol, 0.05 mmol, 0.075 mmol), labeled as α-Fe2O3 / PANI-n (n = 0, 1, 2, 3). Through batch experiments, n = 2 was preferably selected for support preparation.

[0027] Step 3: Prepare the photothermal agent: Mix the PDMS precursor (the initial reactant in the PDMS synthesis process) and the cross-linking agent (which causes a cross-linking reaction between PDMS precursor molecules) in a ratio of 10:1 and add it to polyhexane. After thorough stirring, add α-Fe2O3@PANI to the mixture to maintain the mass fraction of PDMS at 10%, polyhexane at 10%, and α-Fe2O3@PANI at 80%.

[0028] Step 4. Preparation of low-temperature sewage treatment biofilm carrier: The above-mentioned mixed solution (mass fraction of PDMS is 10%, polyhexane is 10%, and α-Fe2O3@PANI is 80%) is coated on a SiC ceramic skeleton (porosity is 10 ppi) and dried at 70°C for 5 h to obtain the prepared low-temperature sewage treatment biofilm carrier.

[0029] Temperature-responsive nanocapsules were loaded onto a low-temperature wastewater treatment biofilm carrier. The nanocapsules consist of a temperature-sensitive poly (N-isopropylacrylamide) (PNIPAM) shell and a core containing a slow-release microbial growth promoter. When the carrier's microenvironmental temperature exceeds 25°C, the PNIPAM shell contracts and releases the microbial growth promoters contained within the core, including but not limited to cobalamin, menadione, and biotin. This enables intelligent photothermal-assisted regulation of microbial metabolic activity. The core microbial growth promoter used in this experiment was cobalamin. Example

[0030] Testing the water treatment effects of low-temperature wastewater treatment biofilm carriers The microbial water treatment device was operated using a photothermal reactor made in our laboratory. Figure 1 ), the device consists of five parts: water inlet system, aeration system, photothermal carrier system, water outlet system and water bath system.

[0031] The water inlet system includes a water inlet bottle (1) and a water inlet peristaltic pump (2). The water inlet bottle (1) is sealed with a rubber stopper. Two holes are drilled in the rubber stopper using a hole punch and two glass tubes are inserted. One of the holes is connected to a 10L air bag (to prevent negative pressure from forming in the wide-mouth bottle after water inflow, which would affect the water inflow speed or cause the bottle wall to rupture). The other end of the plastic tube is connected to the water inlet peristaltic pump (2). The other end of the plastic tube is connected to the water inlet (3) of the membrane bioreactor (4). The speed of the peristaltic pump (2) can be set to an appropriate value to adapt to different hydraulic retention times.

[0032] The aeration system consists of an aeration head (7), an aeration pipe (8) and a gas flow meter (13). One end of the aeration pipe (8) is connected to the aeration head (7), and the other end is connected to the flow meter (13). The aeration head (7) is placed in the membrane bioreactor (4). During aeration, the gas flow meter (13) is connected to the aeration gas cylinder to control the aeration flow.

[0033] The membrane bioreactor (4) is cylindrical in shape. A water inlet (3) is provided at the bottom of the reactor (4). A water bath heating jacket (5) is provided on the outer layer to simulate the low temperature environment of the reactor (4). The reactor (4) utilizes magnetic stirring, which is beneficial to the transfer of the matrix inside the reactor (4) and the uniform reaction. The stirring rate is set to 100-150 rpm during operation. The biofilm carrier (9) is placed inside the reactor (4) at a height of about 1 / 2 of the reactor (4). The water outlet is connected to the outlet pipe of the reactor (4). The reactor (4) operates in a continuous water inlet and outlet mode, and the hydraulic retention time changes with the change of the performance of the reactor (4).

[0034] The water outlet system includes a water outlet peristaltic pump (15) and a water outlet bottle (16). One end of the plastic tube of the water outlet peristaltic pump (15) is connected to the water outlet pipe of the reactor, and the other end is connected to the water outlet bottle (16).

[0035] A water bath circulation system is used to simulate the ambient temperature. Constant temperature water flows through the chiller (12) and the membrane bioreactor water bath heating jacket (5) to form a closed circulation loop, and the temperature inside the reactor (4). The constant temperature cold water generated by the chiller (12) is introduced into the water bath inlet (14). The water bath inlet (14) and the water bath outlet (14) of the reactor are connected to the water bath heating jacket (5), and the water bath outlet (14) is connected to the chiller (12), and the constant temperature water flows back to the chiller (19). That is, the constant temperature cold water in the chiller (12) flows through the water bath inlet to the water bath jacket (5), and then flows from the water bath jacket (5) to the reactor water bath outlet (14) and flows back to the chiller (12), forming a circulating water bath system.

[0036] A xenon lamp (10) was used to simulate sunlight, and the sunlight intensity was set to 0.6 KW / m 2 .

[0037] The following is further explained using the anaerobic ammonium oxidation process in this reactor as an example: First, the biofilm carrier was fixed in the reactor, anaerobic ammonium oxidation sludge (anaerobic ammonium oxidation bacteria from anaerobic fermentation tanks, with an anaerobic ammonium oxidation bacteria ratio of 50%-80%) was added, and the reactor was started. The reactor was inoculated with anaerobic ammonium oxidation sludge at a concentration of 0.05 gVSS / L, and the initial HRT was set to 24 h. The anaerobic environment of the reactor inlet water was maintained by a gas mixture of N2 / CO2 (95 / 5%). The NH in the inlet and effluent water was measured every two days. 4+ -N, NO 2– -N and NO 3– The performance of the reactor was monitored by measuring the concentration of -N. The reactor was kept in an anaerobic environment, using a water bath to simulate a low temperature environment of 15°C, and the pH of the inlet water was between 7.3 and 7.8. A xenon lamp was used to simulate sunlight, and the sunlight intensity was set to 0.6 KW / m 2 After irradiation for 4 hours under these conditions, the temperature of the support rose to 30.5 degrees Celsius, and a lightless area formed under the support.

[0038] In order to investigate the effect of the biofilm carrier on the reactor performance in the present invention, taking the anaerobic ammonium oxidation process as an example, two reactors were started and operated in parallel, one of which was the anaerobic ammonium oxidation reactor R with the biofilm carrier added as mentioned above. P , another reactor R c Unmodified conventional SiC ceramic carriers were added. During reactor operation, the carriers used in this study achieved functional zoning on the porous ceramics, with the upper layer achieving photothermal conversion, while the lower layer enabled microbial attachment and increased functional bacterial abundance. Furthermore, a small amount of algae in the upper layer provided terminal treatment for the entire reactor's wastewater.

[0039] The changes in the contents of ammonia nitrogen, nitrite nitrogen and nitrate nitrogen in the inlet and outlet water of the two reactors were measured. Figure 2 It can be seen that R p and R c After 100 days of operation, all were successfully started, including R P The reactor starts up faster, R P The denitrification performance of the reactor is R c 4 times of the reactor; the bacterial flora changes in the reactor are as follows Figure 3 As shown in Figure 2, the abundance of anaerobic ammonium oxidizing bacteria increased by 21%, and R P The biomass of the reactor was compared with that of R c The reactor was improved by 2.2 times. This shows that the biofilm carrier prepared in this study can achieve rapid startup of the reactor in a low-temperature environment, and the carrier can perform efficient photothermal conversion, while also absorbing and enriching functional bacteria and increasing biomass.

Claims

1. A low-temperature sewage treatment biofilm carrier, characterized in that: The biofilm carrier uses SiC ceramics as the biofilm skeleton, and a photothermal agent is coated on the upper part of the SiC ceramics to form a photothermal conversion functional area, and the lower part of the SiC ceramics is the microbial adhesion functional area.

2. The low-temperature sewage treatment biofilm carrier according to claim 1, characterized in that The photothermal agent consists of PDMS, polyhexane and α-Fe2O3@PANI.

3. The low-temperature sewage treatment biofilm carrier according to claim 1, characterized in that Temperature-responsive nanocapsules are also loaded on the upper portion of the SiC ceramic.

4. The low-temperature sewage treatment biofilm carrier according to claim 3, characterized in that The temperature-responsive nanocapsule consists of a poly (N-isopropylacrylamide) shell and a microbial growth promoter core.

5. The low-temperature sewage treatment biofilm carrier according to claim 4, characterized in that The microbial growth promoter includes one or more of cobalamin, menadione and biotin.

6. A method for preparing a low-temperature sewage treatment biofilm carrier, characterized in that: The following steps are involved: S101, adding sodium nitrate to the prepared FeCl3 solution, adjusting the pH, and then pouring the solution into a polytetrafluoroethylene-lined reaction vessel, reacting at 95°C for 4 hours, cooling to room temperature, collecting a yellow solid by centrifugation and washing, and finally calcining the yellow solid in a furnace at 550°C for 2 hours to produce α-Fe2O3 nanoparticles; S102, mixing aniline and deionized water and placing the mixture in an ice-water bath, slowly adding hydrochloric acid to adjust the pH to 0.8-1.0, adding the α-Fe2O3 nanoparticles prepared in step S101 and then ultrasonically treating, slowly adding ammonium persulfate solution, reacting while stirring, standing at -4°C for 24 hours, and then washing with deionized water and ethanol to prepare α-Fe2O3@PANI; S103, mixing a PDMS precursor and a cross-linking agent in a ratio of 10:1 to prepare PDMS, and adding the mixture to polyhexane. After sufficient stirring, the α-Fe2O3@PANI prepared in step S102 is added to the mixture and continued to stir evenly to obtain a photothermal agent; S104, coating the photothermal agent prepared in step S103 on the SiC ceramic skeleton, and drying at 70° C. for 5 h to obtain a low-temperature sewage treatment biofilm carrier.

7. The method for preparing a low-temperature sewage treatment biofilm carrier according to claim 6, characterized in that: In step S101, the pH is adjusted to 1.

5.

8. The method for preparing a low-temperature sewage treatment biofilm carrier according to claim 6, characterized in that: In step S102, the molar ratio of aniline to α-Fe2O3 nanoparticles is 4:1-3.

9. The method for preparing a low-temperature sewage treatment biofilm carrier according to claim 6, characterized in that: The mass fraction ratio of PDMS, polyhexane and α-Fe2O3@PANI in the mixed solution of step S103 is 10%:10%:80%.

10. Use of the low-temperature sewage treatment biofilm carrier according to any one of claims 1 to 5 in low-temperature microbial water treatment.

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