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

Abstract

The invention discloses a gel carrier suitable for low-temperature sewage treatment and a preparation method and application thereof.The gel carrier is divided into an upper layer and a lower layer, the upper layer of the gel carrier is a photothermal conversion layer, the lower layer of the gel carrier is a microbial growth layer, and anaerobic ammonium oxidation flora is embedded in the lower layer of the gel carrier; the thickness ratio of the photothermal 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 heterojunctions, the microenvironment temperature is increased through the photothermal-magnetic thermal synergistic effect, the limitation of low illumination in winter is broken through, and rapid starting of the reactor can be achieved at the low temperature of 15 DEG C. The gel carrier prepared by the invention can decompose nitrogen-containing pollutants in wastewater in an anaerobic environment.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of environmental pollutant treatment, in particular to a gel carrier suitable for low-temperature sewage treatment, a preparation method and application. BACKGROUND

[0002] The massive discharge of nitrogenous wastewater not only exacerbates water eutrophication, leading to the overgrowth of harmful algae and aquatic plants, disrupting the balance of aquatic ecosystems, but also seriously affects people's living environment and health. Sewage denitrification technology, as the key to controlling nitrogen pollution, plays an irreplaceable role in maintaining ecological safety, ensuring national health and promoting the sustainable development of society and economy.

[0003] Microbial water treatment technology, as the core link of sewage treatment, faces the severe challenge of maintaining high-efficiency denitrification capacity in low-temperature environments (usually below 15°C). Under low-temperature conditions, the metabolic activity of microorganisms decreases significantly, especially for nitrifying bacteria and anaerobic ammonia-oxidizing bacteria. The weakening of these microbial activities directly affects the conversion rate of nitrogen, thereby reducing the efficiency of the entire denitrification process. Low temperature not only inhibits the activity of free microorganisms, but also threatens the formation and stability of biofilms. Biofilms are an indispensable part of water treatment processes, and low-temperature conditions delay the maturation process of biofilms, affecting their structure and interfering with the attachment and growth of denitrifying microorganisms, reducing the stability and efficiency of the denitrification process. In addition, under low-temperature conditions, the microbial population structure may change significantly, and microorganisms adapted to low-temperature environments may dominate. These microorganisms have significant differences in denitrification efficiency and stability from those at normal temperatures, which requires in-depth research and optimization of microbial populations to ensure denitrification efficiency.

[0004] CN201510985470.2 discloses a sewage treatment composite gel material embedding microorganisms and a preparation method thereof. The method uses carrageenan and polyacrylamide composite gel as embedding agent, porous starch as adsorbent as carrier, and inorganic powder as additive to embed microorganisms, which is applied to sewage treatment and can effectively adsorb and remove heavy metal ions and degrade organic matter. This method is easy to realize the separation of liquid and solid, reduces the flushing of biomass from the treatment system, and prevents the formation of air pockets inside the gel particles.

[0005] Photo-thermal conversion is a process of concentrating solar radiation energy through reflection, absorption, etc., and converting it into heat to increase temperature, which is a low-cost and efficient energy conversion method. CN202310758686.X discloses a preparation method and application of a Schottky junction doped composite polyvinyl fluoride mixed film with excellent photo-thermal conversion capability. The method uses simple doping and phase transition as the main means to incorporate photocatalytic materials into photo-thermal materials and make them into composite film materials for photo-oxidation / reduction of organic pollutants, thereby achieving the effect of photo-degradation of organic dyes and antibacterial effect.

[0006] Anaerobic ammonia oxidation process is a new type of biological nitrogen removal technology, which has the advantages of no need for aeration, low energy consumption, and less excess sludge, and is suitable for industrial wastewater and municipal wastewater treatment. However, the growth rate of anaerobic ammonia oxidation bacteria is relatively slow, and the activity is reduced under low temperature conditions, which limits its application in some environments.

[0007] In view of the above prior art and the shortcomings of anaerobic ammonia oxidation process in practice, the inventors of the present application have obtained the present application by utilizing the technical conditions of the laboratory, through long-term research and experiment. SUMMARY

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

[0009] The technical scheme adopted by the present application to achieve the above-mentioned purpose is: A low-temperature wastewater treatment gel carrier, the gel carrier is divided into upper and lower 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, wherein an anaerobic ammonia oxidation bacterial group is embedded in the lower layer of the gel carrier.

[0010] Preferably, the photo-thermal conversion layer is composed of FeS2 / PANI and PDMS, and the concentration of FeS2 / PANI is 10%; Preferably, the microbial growth layer comprises PVA / SA and FeS2 / PANI hydrogel, wherein the mass fraction of FeS2 / PANI hydrogel is 2.5 ‰; Preferably, the thickness ratio of the photo-thermal conversion layer to the microbial growth layer is 1-1.5:4.

[0011] A preparation method of a low-temperature wastewater treatment gel carrier, specifically comprising the following steps: Step one, synthesis of PANI: aniline was mixed with deionized water and placed in an ice water bath, slowly add hydrochloric acid to adjust pH to 0.8-1.0, slowly add ammonium persulfate solution to aniline solution, stirring and reacting, standing in the environment of-4℃ for 24h to achieve full precipitation and polymerization. Finally, washed with deionized water and ethanol.

[0012] Step two, synthesis of FeS2 / PANI: FeCl3, (NH2)2CS and ammonia were added to the PANI aqueous solution respectively, heated and reacted, continuously dialyzed in anaerobic conditions for 24h with ultrapure water, and further vacuum freeze-dried to obtain FeS2 nanoparticle modified PANI (referred to as FeS2 / PANI).

[0013] Step three, making photo-thermal conversion layer: dilute FeS2 / PANI after vacuum freeze-drying treatment in step two with PDMS, so that the concentration of FeS2 / PANI is 10%-15%, pour the mixed solution of FeS2 / PANI and PDMS into a round mold, control the thickness to be 1-1.5mm, then place the round mold in a 100℃ oven for 12-16h to solidify, and obtain the photo-thermal conversion layer.

[0014] Step four, making microbial growth layer: prepare a mixed solution of 12% (w / v) polyvinyl alcohol (PVA) and 2% (w / v) sodium alginate (SA), add 2.5‰ FeS2 / PANI obtained in step two and 0.2‰-0.6‰ magnetic nanoparticles to the mixed solution, then stir uniformly to obtain a gel mixed solution; grind the anaerobic ammonia oxidation granular sludge into flocculent biological aggregates, take 0.05g VSS / L biological aggregates and pour into the gel mixed solution, stir at a speed of 80-120r / min for 10-20min to obtain the microbial growth layer.

[0015] Step five, making low-temperature sewage treatment gel carrier: pour the microbial growth layer into the round mold of step three, so that the photo-thermal conversion layer and the microbial growth layer are tightly combined, then place in a 4% (w / v) CaCl2 solution for 12h to solidify, and obtain the low-temperature sewage treatment gel carrier.

[0016] Preferably, the concentration ratio of FeCl3 to PANI in step two 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.

[0017] Preferably, the heating temperature in step two is 160 °C, and the reaction time is 12h.

[0018] Preferably, the diameter of the flocculent biological aggregates in step four is <50μm.

[0019] Preferably, the anaerobic ammonia oxidation granular sludge in step four is from anaerobic ammonia oxidation bacteria cultured in an anaerobic fermentation tank, wherein the anaerobic ammonia oxidation bacteria account for 50%-80%.

[0020] The application also provides a low-temperature wastewater treatment gel carrier and an application thereof in low-temperature wastewater treatment. 2 The application also provides a low-temperature wastewater treatment gel carrier and an application thereof in low-temperature wastewater treatment.

[0021] Preferably, the membrane bioreactor is an anaerobic environment.

[0022] Preferably, the wastewater treatment is the decomposition of nitrogen-containing pollutants in water bodies.

[0023] Polyaniline has good light absorption capacity and light-heat conversion energy. At the same time, polyaniline has conductivity, which can help mediate bacteria to cooperate with electron transport and electron wires. FeS2 can be oxidized by oxygen to provide essential iron elements for the growth of anaerobic ammonia oxidation bacteria, and can directly promote the metabolism of nitrogen with anaerobic ammonia oxidation bacteria.

[0024] The application has the following beneficial effects: 1. PANI / FeS2 can perform efficient light-heat conversion, help to improve the microenvironment temperature of the gel, efficiently intercept water treatment functional bacteria with slow growth rate such as anaerobic ammonia oxidation bacteria, and can realize the rapid start of the reactor, and can guarantee good effluent water quality.

[0025] 2. PANI / FeS2 has a dense conductive network, which helps to mediate the communication and cooperation between bacterial flora and promotes the growth of bacterial flora. FeS2 in PANI / FeS2 can react with oxygen to help bacteria flora create an anaerobic microenvironment and help anaerobic bacteria flora grow.

[0026] 3. Magnetic nanoparticles (such as Fe3O4) realize three innovative functions by using its magnetic response characteristics: first, dynamic regulation of biofilm distribution, under the guidance of the magnetic field gradient, the gel can autonomously migrate to the low biomass area to maintain the uniformity of the membrane thickness; second, magnetic-heat synergistic efficiency, light-heat conversion and magnetic particle alternating magnetic field heat production are superimposed, which makes the microenvironment temperature increase by 5-8℃ and breaks through the illumination limit; third, anti-algal pollution, periodic magnetic field interferes with the phototaxis and photosynthesis of algae, inhibits its adhesion, and the treatment group reduces by more than 70% compared with the control group. The material interface heterojunction promotes the separation of photo-generated carriers, and the surface modification optimizes the biocompatibility, finally forms an intelligent response type light-heat carrier, which significantly improves the low-temperature denitrification efficiency and system stability. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is a light-heat functional reactor operation microbial water treatment device; Figure 2 is the reactor influent and effluent ammonia nitrogen, nitrite nitrogen, nitrate nitrogen content change graph (wherein Figure R g is the reactor influent and effluent ammonia nitrogen, nitrite nitrogen, nitrate nitrogen content change graph in the experimental group; Figure R c is the reactor influent and effluent ammonia nitrogen, nitrite nitrogen, nitrate nitrogen content change graph in the control group); Figure 3 is the reactor bacterial flora change of the experimental group and the control group (wherein Figure R g is the experimental group reactor bacterial flora structure with gel carrier, R c is the control group reactor bacterial flora structure). DETAILED DESCRIPTION

[0028] In order to further understand the present application, the preferred embodiments of the present application are described below in conjunction with examples, but it should be understood that these descriptions are only for further illustrating the features and advantages of the present application, and are not limitations to the claims of the present application.

[0029] All raw materials of the present application have no particular restrictions on their sources, and can be purchased on the market or prepared according to conventional methods well known to those skilled in the art. EXAMPLE

[0030] Preparation of low-temperature sewage treatment gel carrier: Step one, synthesis of PANI: 9 mL of 0.1 mol / L aniline was mixed with 200 ml of deionized water and placed in an ice water bath, and hydrochloric acid was slowly added to adjust the pH to 1.0. 6.1 grams of ammonium persulfate was dissolved in 100 mL of deionized water, and the ammonium persulfate solution was slowly added to the aniline solution to promote the polymerization process of aniline. The solution was stored at -4℃ and left to stand for 24h to achieve full precipitation and polymerization. Finally, deionized water and ethanol were used for washing.

[0031] Step two, 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 water were added to 10 mL of 0.135 g / mL PANI aqueous solution. Subsequently, the mixed solution was heated to 160 °C for 12 h to form FeS2 nanoparticle modified PANI (abbreviated as FeS2 / PANI). Under anaerobic conditions, FeS2 / PANI was vacuum freeze-dried after continuous dialysis in ultrapure water for 2 days.

[0032] Step three, making the photo-thermal conversion layer: dilute FeS2 / PANI after vacuum freeze-drying in step two with PDMS to make the concentration of FeS2 / PANI 10%-15%, pour the mixed solution of FeS2 / PANI and PDMS into a round mold, control the thickness to be 1mm, then put the round mold in a 100℃ oven to solidify for 12h, and get the photo-thermal conversion layer.

[0033] Step four, making the microbial growth layer: prepare a mixed solution of 12% (w / v) polyvinyl alcohol (PVA) and 2% (w / v) sodium alginate (SA), add 2.5‰ of FeS2 / PANI obtained in step two to the mixed solution and mix evenly, then add 0.5‰ of magnetic nanoparticles, and stir evenly to get a gel mixed solution; grind the anaerobic ammonia oxidation granular sludge into flocculent biological aggregates, take 0.05g VSS / L biological aggregates, pour into the gel mixed solution, and stir at a speed of 80r / min for 15min to get the microbial growth layer.

[0034] Step five, making the low-temperature sewage treatment gel carrier: pour the microbial growth layer into the round mold of step three, so that the photo-thermal conversion layer and the microbial growth layer are tightly combined, then put it in a 4% (w / v) CaCl2 solution to solidify for 12h, and get the low-temperature sewage treatment gel carrier. Example

[0035] Test the water treatment effect of the low-temperature sewage treatment gel carrier Use the self-made photo-thermal function reactor in the laboratory to run the microbial water treatment device (4) Figure 1 , which is composed of a water inlet system, an aeration system, a photo-thermal carrier system, a water outlet system, and a water bath system.

[0036] 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 plug, and two holes are drilled on the plug with a hole puncher, and two glass tubes are inserted into the holes, one of which is connected to a 10L air bag (to prevent negative pressure in the wide-mouth bottle after water is poured in, affecting the water inlet speed or causing the bottle wall to break), and the other is connected to the plastic tube of the water inlet peristaltic pump (2), and the other end of the plastic tube is connected to the water inlet (3) of the water treatment reactor (4). The speed of the peristaltic pump (2) can be set to an appropriate value to adapt to different hydraulic retention times.

[0037] The aeration system is composed of an aeration head (7), an aeration pipe (8), and a gas flow meter (13), the aeration pipe (8) is connected to the aeration head (7) at one end and to the flow meter (13) at the other end, the aeration head (7) is placed in the reactor (4), and when aeration is performed, the gas flow meter (13) is connected to the gas cylinder for aeration to control the aeration flow.

[0038] The water treatment reactor (4) is cylindrical in shape, and the reactor (4) is provided with a water inlet (3) at the bottom and a water bath heating jacket (5) outside, which simulates the low-temperature environment of the reactor (4). The low-temperature sewage treatment gel carrier (6) is placed inside the reactor (4) with a filling ratio of 50%, and the water outlet is connected to the water outlet pipe of the reactor (4). The reactor (4) is operated in a continuous water inlet and continuous water outlet mode, and the hydraulic retention time changes with the performance of the reactor (4).

[0039] The water outlet system includes a water outlet peristaltic pump (14) and a water outlet bottle (15). One end of the plastic tube of the water outlet peristaltic pump (14) is connected to the water outlet pipe of the reactor, and the other end is connected to the water outlet bottle (15).

[0040] The water bath circulation system is used to simulate the ambient temperature. The constant temperature water flows through the water bath heating jacket (5) and the membrane bioreactor water bath heating jacket (5) to form a closed circulation loop. The constant temperature water produced by the water chiller (12) is introduced into the water bath inlet (14) of the reactor. 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 water chiller (12). The constant temperature water is re-circulated to the water chiller (19). That is, the constant temperature water in the water 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 water bath outlet (14) of the reactor and back to the water chiller (12) to form a circulating water bath system.

[0041] The xenon lamp (10) is used to simulate sunlight irradiation, and the sunlight intensity is set to 0.6 KW / m 2 (simulating weak sunlight in winter).

[0042] The water treatment effect of the low-temperature sewage treatment gel carrier is tested by using the above device, and the steps are as follows: First, set the initial hydraulic retention time to 24h, control the temperature of the water treatment reactor below 15℃, and keep the pH value of the influent between 7.3 and 7.8. The concentration of ammonia nitrogen and nitrite nitrogen in the influent is 30 mg / L, the anaerobic environment of the reactor influent is maintained by using N2 / CO2 (95 / 5%) gas mixture, and the sunlight intensity is set to 0.6 KW / m 2 .

[0043] Second, the performance of the reactor is monitored by measuring the concentrations of NH4 + -N, NO2 – -N and NO3 – -N in the influent and effluent every two days.

[0044] At the same time, two reactors are started and operated in parallel, one is the above-mentioned anaerobic ammonia oxidation reactor Rg , another reactor R c Add unmodified traditional polyvinyl alcohol / sodium alginate gel embedded anaerobic ammonia oxidation bacteria.

[0045] The changes of ammonia nitrogen, nitrite nitrogen and nitrate nitrogen content in the reactor water in and out are shown in Figure 2 , from which it can be seen that R g and R c are successfully started after 70 cycles, in which R g reactor starts faster, and the denitrification performance of R g reactor is 4 times that of R c reactor; the change of microbial community in the reactor is shown in Figure 3 , in which the abundance of anaerobic ammonia oxidation bacteria is increased by 16%, and the biomass of R g reactor is increased by 1.8 times compared with R c reactor. This shows that the low-temperature sewage treatment gel carrier prepared in this study can realize the rapid start of the reactor in a low-temperature environment, and accelerate the growth rate of microorganisms. The gel is internally provided with a light-heat zone and a microbial growth functional zone, which can realize efficient light-heat conversion and accelerate the growth of anaerobic ammonia oxidation bacteria, and the composite gel can consume oxygen, thereby promoting the growth of anaerobic bacteria.

Claims

1. A low-temperature wastewater treatment gel carrier, characterized in that, The gel carrier consists of two layers: the upper layer is a photothermal conversion layer, and the lower layer is a microbial growth layer, in which anaerobic ammonia-oxidizing bacteria are embedded.

2. The low-temperature wastewater treatment gel carrier according to claim 1, characterized in that, The photothermal conversion layer is composed of FeS2 / PANI and PDMS, with the concentration of FeS2 / PANI being 10%.

3. The low-temperature wastewater treatment gel carrier according to claim 1, characterized in that, The microbial growth layer comprises PVA / SA and FeS2 / PANI hydrogels.

4. The low-temperature wastewater treatment gel carrier according to claim 1, characterized in that, The thickness ratio of the photothermal conversion layer to the microbial growth layer is 1-1.5:

4.

5. The low-temperature wastewater treatment gel carrier according to claim 3, characterized in that, The FeS2 / PANI hydrogel has a mass fraction of 2.5‰.

6. A method for preparing a low-temperature wastewater treatment gel carrier, characterized in that, Includes the following steps: S101. Mix aniline with deionized water and place in an ice-water bath. Slowly add hydrochloric acid to adjust the pH to 0.8-1.

0. Slowly add ammonium persulfate solution to the aniline solution while stirring and reacting. Let stand at -4℃ for 24 hours to achieve full precipitation and polymerization. Finally, wash with deionized water and ethanol to obtain PANI. S102. FeCl3, (NH2)2CS and ammonia water were added to PANI aqueous solution, heated to 160 °C for 12 h, and then subjected to anaerobic conditions for 24 h of continuous dialyzing with ultrapure water. After further vacuum freeze drying, FeS2 / PANI was obtained. S103. Mix PDMS with FeS2 / PANI obtained in step S102, stir evenly, pour into a circular mold, control its thickness to be 1-1.5 mm, and then place the circular mold in a 100℃ oven to cure for 12-16 h to obtain the photothermal conversion layer. S104. Prepare a mixture of 12% w / v polyvinyl alcohol and 2% w / v sodium alginate. Add 2.5‰ FeS2 / PANI and 0.2‰-0.6‰ magnetic nanoparticles to the mixture and stir until homogeneous to obtain a gel mixture solution. Grind the anaerobic ammonia oxidation granular sludge thoroughly into flocculent bioaggregates. Take 0.05g VSS / L bioaggregates and pour them into the gel mixture solution. Stir at 80-120r / min for 10-20min to obtain a microbial growth layer. S105. Pour the microbial growth layer into the circular mold from step S103, and then place it in a 4% w / v CaCl2 solution to solidify for 12 hours to obtain a low-temperature wastewater treatment gel carrier.

7. The method for preparing a low-temperature wastewater treatment gel carrier according to claim 6, characterized in that, In step S102, 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.

8. The method for preparing a low-temperature wastewater treatment gel carrier according to claim 6, characterized in that, The concentration of FeS2 / PANI in step S103 is 10%-15%.

9. The method for preparing a low-temperature wastewater treatment gel carrier according to claim 6, characterized in that, The diameter of the flocculent biological aggregates in step S104 is <50μm, and the anaerobic ammonia oxidation granular sludge comes from anaerobic ammonia oxidizing bacteria cultured in an anaerobic fermenter, wherein the proportion of anaerobic ammonia oxidizing bacteria is 50%-80%.

10. The application of the low-temperature wastewater treatment gel carrier as described in any one of claims 1-5 in low-temperature wastewater treatment, specifically comprising: A low-temperature wastewater treatment gel carrier was added to a membrane bioreactor, which was then placed in a 0.6 kW / m² environment. 2 It is used for wastewater treatment under high light intensity.

11. The application of the low-temperature wastewater treatment gel carrier according to claim 10 in low-temperature wastewater treatment, characterized in that, The membrane bioreactor is an anaerobic environment, and the wastewater treatment is to decompose nitrogen-containing pollutants in the water.

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