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

Abstract

The application discloses a gel carrier suitable for low-temperature sewage treatment, a preparation method and application, and the gel carrier is divided into two layers, the upper layer of the gel carrier is a light-heat conversion layer, and the lower layer of the gel carrier is a microbial growth layer, anaerobic ammonia oxidation bacteria are embedded in the lower layer of the gel carrier, the thickness ratio of the light-heat conversion layer to the microbial growth layer is controlled to be 1-1.5:4, magnetic nanoparticles are added in the gel preparation process to form a heterojunction, the microenvironment temperature is improved through a light-heat-magnetic heat synergistic effect, the low-light limitation in winter is broken, and the reactor can be rapidly started under a low-temperature condition of 15 DEG C. The prepared gel carrier can decompose nitrogen-containing pollutants in wastewater in an anaerobic environment.

Description

Technical Field

[0001] This invention relates to the field of environmental pollutant treatment, specifically to a gel carrier suitable for low-temperature wastewater treatment, its preparation method, and its application. Background Technology

[0002] The large-scale discharge of nitrogen wastewater not only exacerbates eutrophication, leading to the overgrowth of harmful algae and aquatic plants and disrupting the balance of aquatic ecosystems, but also seriously affects people's living environment and health. Wastewater denitrification technology, as a key to controlling nitrogen pollution, plays an irreplaceable role in maintaining ecological security, protecting public health, and promoting sustainable socio-economic development.

[0003] Microbial water treatment technology, as a core component of wastewater treatment, faces the severe challenge of maintaining high-efficiency nitrogen removal capacity in low-temperature environments (typically below 15°C). Under low-temperature conditions, the metabolic activity of microorganisms decreases significantly, especially for nitrifying bacteria and anaerobic ammonia-oxidizing bacteria. This reduced activity directly affects the nitrogen conversion rate, thus lowering the efficiency of the entire nitrogen removal process. Low temperatures not only inhibit the activity of free-floating microorganisms but also threaten the formation and stability of biofilms. Biofilms are an indispensable component in water treatment; low temperatures delay the biofilm maturation process, affecting their structure and thus interfering with the attachment and growth of nitrogen-removing microorganisms, reducing the stability and efficiency of the nitrogen removal process. Furthermore, under low-temperature conditions, the microbial community structure may change significantly, with microorganisms adapted to low-temperature environments potentially becoming dominant. The nitrogen removal efficiency and stability of these microorganisms differ significantly from those at room temperature, necessitating in-depth research and optimization of microbial communities to ensure nitrogen removal efficiency.

[0004] CN201510985470.2 discloses a wastewater treatment composite gel material for encapsulating microorganisms and its preparation method. The method uses carrageenan and polyacrylamide composite gel as encapsulating agents and porous starch as adsorbents as carriers, and inorganic powders as additives to encapsulate microorganisms. When applied to wastewater treatment, it can effectively adsorb and remove heavy metal ions and degrade organic matter. Although this method can easily achieve the separation of liquid and solid, reduce the erosion of biomass from the treatment system, and prevent the formation of air pockets inside the gel particles.

[0005] Photothermal conversion is a process that concentrates solar radiation energy through reflection, absorption, and other means, converting it into heat to raise the temperature. It is a low-cost and efficient energy conversion method. CN202310758686.X discloses a method for preparing and applying a Schottky junction-doped composite polyvinylidene fluoride hybrid film with excellent photothermal conversion capabilities. This method mainly uses simple doping and phase conversion to incorporate photocatalytic materials into photothermal materials and make them into composite film materials for the photo-oxidation / reduction of organic pollutants, thereby achieving the effects of photodegradation of organic dyes and antibacterial properties.

[0006] Anaerobic ammonia oxidation is a novel biological nitrogen removal technology with advantages such as no need for aeration, low energy consumption, and minimal sludge residue, making it suitable for industrial wastewater and municipal sewage treatment. However, the growth rate of anaerobic ammonia oxidizing bacteria is relatively slow, and their activity decreases under low-temperature conditions, which limits its application in certain environments.

[0007] In view of the shortcomings of the existing technology and anaerobic ammonia oxidation process in practice, the inventors of this invention obtained this invention through long-term research and experimentation using the technical conditions of this laboratory. Summary of the Invention

[0008] In view of the shortcomings of the prior art, the present invention aims to provide a gel carrier, preparation method and application suitable for low temperature wastewater treatment, so as to solve the problems mentioned in the background art.

[0009] The technical solution adopted by the present invention to achieve the above objectives is as follows:

[0010] A low-temperature wastewater treatment gel carrier is provided, which consists of two layers: an upper layer is a photothermal conversion layer, and a lower layer is a microbial growth layer, wherein anaerobic ammonia-oxidizing bacteria are embedded in the lower layer.

[0011] Preferably, the photothermal conversion layer is composed of FeS2 / PANI and PDMS, and the concentration of FeS2 / PANI is 10%.

[0012] Preferably, the microbial growth layer comprises PVA / SA and FeS2 / PANI hydrogel, wherein the mass fraction of FeS2 / PANI hydrogel is 2.5‰;

[0013] Preferably, the thickness ratio of the photothermal conversion layer to the microbial growth layer is 1-1.5:4.

[0014] A method for preparing a low-temperature wastewater treatment gel carrier specifically includes the following steps:

[0015] Step 1: Synthesis of PANI: Aniline and deionized water are mixed and placed in an ice-water bath. Hydrochloric acid is slowly added to adjust the pH to 0.8-1.0. Ammonium persulfate solution is slowly added to the aniline solution while stirring. The mixture is allowed to stand at -4°C for 24 hours to achieve complete precipitation and polymerization. Finally, the mixture is washed with deionized water and ethanol.

[0016] Step 2: Synthesis of FeS2 / PANI: FeCl3, (NH2)2CS and ammonia water were added to the PANI aqueous solution, heated and reacted, and after 24 hours of continuous dialyzing with ultrapure water under anaerobic conditions, the PANI modified with FeS2 nanoparticles (abbreviated as FeS2 / PANI) was obtained by further vacuum freeze drying.

[0017] Step 3: Fabrication of the photothermal conversion layer: Dilute the FeS2 / PANI treated by vacuum freeze-drying in Step 2 with PDMS to make the concentration of FeS2 / PANI 10%-15%. Pour the mixture of FeS2 / PANI and PDMS into a circular mold, control its thickness to be 1-1.5 mm, and then place the circular mold in a 100℃ oven for curing for 12-16 h to obtain the photothermal conversion layer.

[0018] Step 4: Preparation of the microbial growth layer: Prepare a mixture of 12% (w / v) polyvinyl alcohol (PVA) and 2% (w / v) sodium alginate (SA). Add 2.5‰ of FeS2 / PANI obtained in Step 2 and 0.2‰-0.6‰ of magnetic nanoparticles to the mixture, and then stir evenly to obtain a gel mixture solution. Grind the anaerobic ammonia oxidation granular sludge thoroughly into flocculent bioaggregates. Take 0.05g of VSS / L bioaggregates and pour them into the gel mixture solution. Stir at 80-120r / min for 10-20min to obtain the microbial growth layer.

[0019] Step 5: Prepare the low-temperature wastewater treatment gel carrier: Pour the microbial growth layer into the circular mold from Step 3 to ensure that the photothermal conversion layer and the microbial growth layer are tightly bonded. Then, place it in a 4% (w / v) CaCl2 solution to cure for 12 hours to obtain the low-temperature wastewater treatment gel carrier.

[0020] Preferably, in step two, the concentration ratio of FeCl3 to PANI is 1:1 and the volume ratio is 1:2; the concentration ratio of (NH2)2CS to PANI is 38:135 and the volume ratio is 1:2.

[0021] Preferably, the heating temperature in step two is 160 °C and the reaction time is 12 h.

[0022] Preferably, the diameter of the flocculent bio-aggregates in step four is <50 μm.

[0023] Preferably, the anaerobic ammonia oxidation granular sludge in step four comes from anaerobic ammonia oxidizing bacteria cultured in an anaerobic fermenter, wherein the proportion of anaerobic ammonia oxidizing bacteria is 50%-80%.

[0024] This invention also provides an application of a low-temperature wastewater treatment gel carrier in low-temperature wastewater treatment, specifically comprising: adding the low-temperature wastewater treatment gel carrier into a membrane bioreactor, and placing the membrane bioreactor in a 0.6 kW / m² environment. 2 It is used for wastewater treatment under light intensity.

[0025] Preferably, the membrane bioreactor is an anaerobic environment.

[0026] Preferably, the wastewater treatment involves decomposing nitrogen-containing pollutants in the water body.

[0027] Polyaniline possesses excellent light absorption and photothermal energy conversion capabilities. Simultaneously, polyaniline exhibits electrical conductivity, which can aid in mediating electron transport and electron-wire interactions within bacteria. FeS2 can be oxidized by oxygen, providing essential iron for the growth of anaerobic ammonia-oxidizing bacteria, and can also directly synergistically promote nitrogen metabolism with these bacteria.

[0028] The present invention has the following beneficial effects:

[0029] 1. PANI / FeS2 can perform efficient photothermal conversion, which helps to increase the microenvironment temperature of the gel and efficiently retain slow-growing water treatment functional bacteria such as anaerobic ammonia oxidizing bacteria, enabling rapid reactor start-up while ensuring good effluent quality.

[0030] 2. PANI / FeS2 possesses a dense conductive network, which helps mediate communication and cooperation among bacterial communities, promoting their growth. The FeS2 in PANI / FeS2 can react with oxygen, helping the bacterial community create an anaerobic microenvironment and supporting its growth.

[0031] 3. Magnetic nanoparticles (such as Fe3O4) utilize their magnetic response properties to achieve three innovative functions: First, they dynamically regulate biofilm distribution; guided by a magnetic field gradient, the gel can autonomously migrate to low biomass regions, maintaining uniform film thickness. Second, they achieve synergistic magnetothermal efficiency enhancement; the superposition of photothermal conversion and heat generation from the alternating magnetic field of the magnetic particles raises the microenvironment temperature by 5-8℃, overcoming light limitations. Third, they resist algal contamination; the periodic magnetic field interferes with algal phototaxis and photosynthesis, inhibiting algal attachment, reducing algal contamination by more than 70% compared to the control group. The heterojunction at the material interface promotes photogenerated carrier separation, and surface modification optimizes biocompatibility, ultimately forming a smart responsive photothermal carrier that significantly improves low-temperature denitrification efficiency and system stability. Attached Figure Description

[0032] Figure 1It is a photothermal functional reactor operating a microbial water treatment device;

[0033] Figure 2 This is a graph showing the changes in ammonia nitrogen, nitrite nitrogen, and nitrate nitrogen content in the reactor influent and effluent (where Figure R is a graph showing the changes in ammonia nitrogen, nitrite nitrogen, and nitrate nitrogen content in the reactor influent and effluent). g This is a schematic diagram showing the changes in ammonia nitrogen, nitrite nitrogen, and nitrate nitrogen content in the influent and effluent of the reactor with a gel carrier in the experimental group; Figure R c (This is a schematic diagram showing the changes in ammonia nitrogen, nitrite nitrogen, and nitrate nitrogen content in the influent and effluent of the control group).

[0034] Figure 3 The changes in reactor microbiota in the experimental and control groups (Figure R) g The experimental group reactor microbial community structure was set up with a gel carrier. c This is the microbial community structure of the control group reactor. Detailed Implementation

[0035] 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, and not for limiting the scope of the claims.

[0036] There are no particular restrictions on the source of any raw materials used in this invention; they can be purchased from the market or prepared using conventional methods known to those skilled in the art.

[0037] Example 1

[0038] Preparation of low-temperature wastewater treatment gel carrier:

[0039] Step 1: Synthesis of PANI: Mix 9 mL of 0.1 mol / L aniline with 200 mL of deionized water and place in an ice-water bath. Slowly add hydrochloric acid to adjust the pH to 1.0. Dissolve 6.1 g of ammonium persulfate in 100 mL of deionized water. Slowly add the ammonium persulfate solution to the aniline solution to promote the polymerization process of aniline. Store the solution at -4℃ and let it stand for 24 h to allow for complete precipitation and polymerization. Finally, wash with deionized water and ethanol.

[0040] Step 2: Synthesis of FeS2 / PANI: 5 mL of 0.135 g / mL FeCl3, 5 mL of 0.038 g / mL (NH2)2CS, and 30 µL of 28% ammonia solution were added to 10 mL of 0.135 g / mL PANI aqueous solution. The mixture was then heated to 160 °C for 12 h to form FeS2 nanoparticle-modified PANI (referred to as FeS2 / PANI). Under anaerobic conditions, FeS2 / PANI was subjected to continuous dialyzing with ultrapure water for 2 days followed by vacuum freeze-drying.

[0041] Step 3: Fabrication of the photothermal conversion layer: Dilute the FeS2 / PANI treated by vacuum freeze-drying in Step 2 with PDMS to make the concentration of FeS2 / PANI 10%-15%. Pour the mixture of FeS2 / PANI and PDMS into a circular mold, control its thickness to 1mm, and then place the circular mold in a 100℃ oven for curing for 12h to obtain the photothermal conversion layer.

[0042] Step 4: Preparation of the microbial growth layer: Prepare a mixture of 12% (w / v) polyvinyl alcohol (PVA) and 2% (w / v) sodium alginate (SA). Add 2.5‰ of FeS2 / PANI obtained in Step 2 to the mixture and mix thoroughly. Then add 0.5‰ of magnetic nanoparticles and stir until homogeneous to obtain a gel mixture solution. Grind the anaerobic ammonia oxidation granular sludge thoroughly into flocculent bioaggregates. Take 0.05g of VSS / L bioaggregates and pour them into the gel mixture solution. Stir at 80r / min for 15min to obtain the microbial growth layer.

[0043] Step 5: Fabrication of the low-temperature wastewater treatment gel carrier. Pour the microbial growth layer into the circular mold from Step 3, ensuring a tight bond between the photothermal conversion layer and the microbial growth layer. Then, place it in a 4% (w / v) CaCl2 solution to cure for 12 hours, thus obtaining the low-temperature wastewater treatment gel carrier.

[0044] Example 2

[0045] Testing the water treatment effect of low-temperature wastewater treatment gel carrier

[0046] The microbial water treatment device was operated using a self-made photothermal reactor from our laboratory. Figure 1 The device consists of five parts: an inlet system, an aeration system, a photothermal carrier system, an outlet system, and a water bath system.

[0047] The water inlet system includes an inlet bottle (1) and an inlet peristaltic pump (2). The inlet bottle (1) is sealed with a rubber stopper. Two holes need to be drilled in the rubber stopper, and two glass tubes are inserted into it. One of the tubes is connected to a 10L air bag (to prevent negative pressure from being generated inside the wide-mouth bottle after water is introduced, which would affect the water inlet speed or cause the bottle wall to break). The other tube is connected to a plastic tube of the inlet peristaltic pump (2). The other end of the plastic tube is connected to the inlet (3) of the water treatment reactor (4). The rotation speed of the inlet peristaltic pump (2) can be set to an appropriate value to accommodate different hydraulic residence times.

[0048] 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 gas flow meter (13). The aeration head (7) is placed inside the water treatment reactor (4). During aeration, the gas flow meter (13) is connected to the aeration gas cylinder to control the aeration flow rate.

[0049] The water treatment reactor (4) is cylindrical in shape. It has an inlet (3) at the bottom and a water bath heating jacket (5) on the outer layer to simulate the low-temperature environment of the reactor. A low-temperature wastewater treatment gel carrier (6) is placed inside the reactor (4) with a filling ratio of 50%, and its outlet is connected to the reactor's outlet pipe. The reactor (4) operates with continuous inlet and outlet, and the hydraulic retention time changes with the reactor's performance.

[0050] The water outlet system includes a peristaltic pump (14) and an outlet bottle (15). One end of the plastic tube of the peristaltic pump (14) is connected to the outlet pipe of the reactor, and the other end is connected to the outlet bottle (15).

[0051] A water bath circulation system is used to simulate ambient temperature. Constant-temperature water flows through a chiller and the water bath heating jacket (5) of the membrane bioreactor, forming a closed loop. The constant-temperature chilled water generated by the chiller is introduced into the water bath inlet. The reactor's water bath inlet and outlet are connected to the water bath heating jacket (5), and the water bath outlet is connected to the chiller, allowing the constant-temperature water to flow back into the chiller. In other words, the constant-temperature chilled water in the chiller flows through the water bath inlet to the water bath heating jacket (5), then from the water bath heating jacket (5) to the reactor's water bath outlet and back into the chiller, forming a circulating water bath system.

[0052] A xenon lamp (10) was used to simulate sunlight, with the sunlight intensity set to 0.6 KW / m². 2 (Simulating weak sunlight in winter).

[0053] The steps for testing the water treatment effect of the low-temperature wastewater treatment gel carrier using the above-mentioned device are as follows:

[0054] First, the initial hydraulic retention time was set to 24 hours, the temperature of the water treatment reactor was controlled below 15℃, and the influent pH was maintained between 7.3 and 7.8. The concentrations of ammonia nitrogen and nitrite nitrogen in the influent were 30 mg / L. An anaerobic environment was maintained in the reactor influent using a N2 / CO2 (95 / 5%) gas mixture. Xenon lamps were used to simulate sunlight irradiation, with the sunlight intensity set at 0.6 KW / m². 2 .

[0055] Second, by measuring NH4 in the influent and effluent every two days. + -N, NO2– -N and NO3 – The concentration of -N was monitored to assess reactor performance.

[0056] Two reactors were started and operated in parallel, one of which was the aforementioned anaerobic ammonia oxidation reactor R with added gel carrier. g Another reactor R c Anaerobic ammonia-oxidizing bacteria were added and embedded in unmodified conventional polyvinyl alcohol / sodium alginate gel.

[0057] Changes in ammonia nitrogen, nitrite nitrogen, and nitrate nitrogen content in the reactor influent and effluent are as follows: Figure 2 As shown in the figure, R can be seen from the graph. g and R c All systems successfully started after 70 cycles, with R... g The reactor starts up faster, R g The denitrification performance of the reactor is R c Four times that of the reactor; changes in the microbial community in the reactor as follows Figure 3 As shown, the abundance of anaerobic ammonia oxidizing bacteria increased by 16%, R g The biomass of the reactor compared to R c The reactor performance improved by 1.8 times. This indicates that the low-temperature wastewater treatment gel carrier prepared in this study can achieve rapid reactor start-up and accelerate microbial growth in a low-temperature environment. The gel contains a photothermal zone and a microbial growth functional zone, which can achieve efficient photothermal conversion and accelerate the growth of anaerobic ammonia-oxidizing bacteria. Furthermore, the composite gel can consume oxygen, thereby promoting the growth of anaerobic bacteria.

Claims

1. A low temperature sewage treatment gel carrier, characterized in that, The gel carrier is divided into two layers, the upper layer of the gel carrier is a photo-thermal conversion layer, and the lower layer of the gel carrier is a microbial growth layer, and the anaerobic ammonia oxidation bacteria are embedded in the lower layer of the gel carrier; The photo-thermal conversion layer is composed of FeS2 / PANI and PDMS, and the concentration of FeS2 / PANI is 10%; The microbial growth layer comprises PVA / SA, FeS2 / PANI hydrogel and magnetic nanoparticles. The thickness ratio of the photo-thermal conversion layer to the microbial growth layer is 1-1.5:

4. The SA is sodium alginate.

2. The low temperature sewage treatment gel carrier of claim 1, wherein, The mass fraction of FeS2 / PANI hydrogel in the microbial growth layer is 2.5 ‰.

3. A method of preparing a low temperature sewage treatment gel carrier as claimed in claim 1, characterised by, Comprising the following steps: S101, mixing aniline with deionized water and placing it in an ice water bath, slowly adding hydrochloric acid to adjust the pH to 0.8-1.0, slowly adding ammonium persulfate solution to the aniline solution, stirring while reacting, and standing in an environment of-4℃ for 24h to achieve complete precipitation and polymerization, and finally, washing with deionized water and ethanol to obtain PANI; S102, adding FeCl3, (NH2)2CS and ammonia water to the PANI aqueous solution respectively, heating at 160℃ for 12h, continuously dialyzing in ultrapure water for 24h under anaerobic conditions, and further vacuum freeze-drying to obtain FeS2 / PANI; S103, mixing PDMS with FeS2 / PANI obtained in step S102, stirring uniformly, and then pouring into a round mold, controlling the thickness to be 1-1.5mm, and then placing the round mold in a 100℃ oven for solidification for 12-16h to obtain the photo-thermal conversion layer; S104, preparing a mixed solution of 12% w / v polyvinyl alcohol and 2% w / v sodium alginate, adding 2.5 ‰ of FeS2 / PANI and 0.2 ‰-0.6 ‰ of magnetic nanoparticles to the mixed solution, then stirring uniformly to obtain a gel mixed solution, grinding the anaerobic ammonia oxidation granular sludge into flocculent biological aggregates, taking 0.05g VSS / L biological aggregates and pouring into the gel mixed solution, stirring at a speed of 80-120r / min for 10-20min to obtain the microbial growth layer; S105, pouring the microbial growth layer into the round mold in step S103, and then placing it in a 4% w / v CaCl2 solution for solidification for 12h to obtain the low-temperature sewage treatment gel carrier.

4. The method of claim 3, wherein the low temperature sewage treatment gel carrier is prepared by the steps of: The concentration ratio of FeCl3 to PANI in step S102 is 1:1, and the volume ratio is 1:2; the concentration ratio of (NH2)2CS to PANI is 38:135, and the volume ratio is 1:

2.

5. The method of claim 3, wherein the low temperature sewage treatment gel carrier is prepared by the steps of: The diameter of the flocculent biological aggregates in step S104 is <50μm, and the anaerobic ammonia oxidation granular sludge is from anaerobic ammonia oxidation bacteria cultured in an anaerobic fermentation tank, wherein the proportion of anaerobic ammonia oxidation bacteria is 50%-80%.

6. Use of the low temperature wastewater treatment gel carrier of claim 1 in low temperature wastewater treatment, specifically comprising: A low temperature wastewater treatment gel carrier is introduced into a membrane bioreactor, which is an anaerobic environment, and the membrane bioreactor is placed under a light intensity of 0.6 kW / m 2 to decompose nitrogen-containing pollutants in wastewater.

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