A functional carrier filler, its preparation method and use

Abstract

The application discloses a functional carrier filler, a preparation method and application thereof. The functional carrier filler comprises a polyethylene carrier and a functional layer loaded on the surface of the polyethylene carrier; and the functional layer comprises amino graphene. The application fixes the amino graphene on the surface of the polyethylene carrier, so that the surface of the filler is rich in nitrogen functional groups capable of mediating electron transfer, the electron transfer of microorganisms is promoted, the biodegradation of antibiotics is strengthened, the specific surface area of the carrier is improved, and the biofilm is hung, the functional carrier filler is used as a suspended filler of a moving bed biofilm reactor, and is used in a post-denitrification MBBR process after sewage treatment, so that the denitrification rate is improved, the degradation of antibiotics is promoted, the use of carbon sources is reduced, and energy saving and emission reduction are facilitated.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sewage treatment, in particular to a functional carrier filler and a preparation method and application thereof. BACKGROUND

[0002] Antibiotics have ecological toxicity and the risk of producing antibiotic resistance genes, which endanger the ecological environment safety and human health in the environment. The main way to reduce antibiotic pollution is to strengthen the treatment of sewage containing antibiotics and reduce the discharge of antibiotics into natural water bodies.

[0003] At present, the common treatment methods for sewage containing antibiotics are physical method, chemical method and biochemical method. The physical method mainly uses activated carbon and other materials to adsorb antibiotics in sewage, but the adsorbent is difficult to regenerate, the antibiotics are not truly degraded, and improper disposal may cause secondary pollution. The chemical method mainly includes chlorine and ozone oxidation and other advanced oxidation methods. Chemical oxidation method can quickly degrade antibiotics, but the treatment cost is high, and toxic by-products may be produced. The biochemical method such as activated sludge method and biofilm method mainly uses microorganisms to degrade antibiotics, and the cost is relatively low, so it is widely used, but the degradation reaction rate is relatively slow, the residual rate of antibiotics in the effluent of the actual sewage plant is high, and the total nitrogen in the effluent is often over-standard.

[0004] The moving bed biofilm reactor (MBBR) is a kind of biofilm method process which uses suspended filler to provide space for microorganisms to attach and grow, so as to realize efficient treatment of sewage. The core of MBBR process is the suspended filler. The multi-layer biofilm formed on the surface of the filler is a complex and diverse micro-ecosystem, and is controlled by the material properties of the filler surface. MBBR has been used as a post-denitrification deep denitrification treatment process in domestic and foreign sewage plants, but the post-denitrification MBBR currently needs to add additional carbon source reagent to provide an electron donor for denitrification, which not only has high cost, but also increases carbon emissions. In addition, the post-denitrification MBBR currently has insufficient antibiotic removal efficiency, and cannot effectively solve the problem of antibiotic environmental pollution. SUMMARY

[0005] In view of the above problems, the present application provides a functional carrier filler and a preparation method and application thereof, which can effectively remove antibiotics in sewage in the existing MBBR denitrification process.

[0006] To achieve the above-mentioned purpose, the present application realizes the following technical scheme:

[0007] In a first aspect, the present application provides a functional carrier filler, which comprises a polyethylene carrier and a functional layer loaded on the surface of the polyethylene carrier; the composition of the functional layer comprises amino graphene.

[0008] Preferably, the preparation method of the amino graphene comprises the following steps:

[0009] The graphene oxide is fully dispersed in water to obtain a graphene oxide dispersion liquid;

[0010] The graphene oxide dispersion liquid is mixed with ammonia water, and then a hydrothermal reaction is performed to obtain amino graphene.

[0011] Preferably, the mass ratio of graphene oxide to water in the graphene oxide dispersion liquid is (0.01-1):70, the mass concentration of the ammonia water is 20-25%, and the volume ratio of the graphene oxide dispersion liquid to the ammonia water is 1:(1-4).

[0012] Preferably, the temperature of the hydrothermal reaction is 180-200 DEG C, and the time is 10-12 h.

[0013] In a second aspect, the application provides a preparation method of a functional carrier filler, comprising the following steps: mixing a polyethylene carrier and amino graphene, then heating at 135-140 DEG C, and after cooling, shaping, washing, and drying to obtain the functional carrier filler.

[0014] Preferably, the mass ratio of the polyethylene carrier to the amino graphene is (1.7-1.8):(10-15).

[0015] Preferably, the heating time is 20-40 min.

[0016] In a third aspect, the application provides a moving bed biofilm reactor comprising the functional carrier filler as described in the first aspect.

[0017] Preferably, the volume of the functional carrier filler accounts for 30-50% of the volume of the moving bed biofilm reactor.

[0018] In a fourth aspect, the application provides an application of the moving bed biofilm reactor as described in the third aspect in sewage treatment.

[0019] The application has the following beneficial effects:

[0020] The application fixes the amino graphene on the surface of the polyethylene carrier, so that the surface of the filler is rich in nitrogen functional groups that can mediate electron transfer, which can promote microbial electron transfer, strengthen antibiotic biodegradation, and improve the specific surface area of the carrier to facilitate biofilm formation.

[0021] The functional carrier filler provided by the application can be used as the suspended filler of the moving bed biofilm reactor (MBBR) for post-denitrification MBBR process after sewage treatment, which can improve the denitrification rate, promote antibiotic degradation, reduce the use of carbon source, and is conducive to energy saving and emission reduction. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings of the embodiments will be briefly introduced below.

[0023] Figure 1 The scanning electron microscope image of the functional carrier filler prepared for the embodiment 1 of the present application;

[0024] Figure 2 The actual object image of the functional carrier filler prepared for the embodiment 1 of the present application;

[0025] Figure 3 The degradation curve diagram of metronidazole for the functional carrier filler prepared for the embodiment 1 of the present application and the traditional high-density polyethylene filler. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative efforts belong to the protection scope of the present application.

[0027] For antibiotics in sewage, the physical method and chemical oxidation method for removing antibiotics have high cost, and have problems such as possible generation of toxic by-products, secondary pollution, and the like, so that the practical application is difficult. The treatment capacity of the traditional biochemical method for treating antibiotics is limited, and extra carbon source needs to be added for deep denitrification. There are still a large amount of refractory organic pollutants (such as antibiotics) in the secondary treatment effluent of the actual sewage plant, which can theoretically be used as an electron donor to provide electrons for denitrification, and the difficulty lies in that the energy barrier of the electron transfer process is high, and the microbial reaction is slow.

[0028] In view of the above problems, the present application provides a new type of suspended filler of surface-fixed amino graphene, and applies it to a moving bed biofilm reactor (MBBR) as a post-denitrification deep treatment process after sewage treatment, so as to realize the enhanced removal of antibiotics and denitrification. The main principle is to use the nitrogen-doped functional groups on the surface of the amino graphene material, such as amino, pyridine, pyrrole-type nitrogen, and the like, to mediate the extracellular electron transfer process of the microorganisms in the biofilm, and then to couple the enhanced antibiotic degradation and post-denitrification, so as to remove the antibiotics in the sewage while further reducing the COD and total nitrogen in the effluent. In addition, the specific surface area and roughness of the filler are increased by fixing the amino graphene, which is more conducive to the attachment and growth of the microbial biofilm, and the biofilm is more easily formed. By culturing, domesticating, screening and enriching the microbial communities capable of degrading and difficultly biodegrading COD on the surface of the filler under the operation conditions of the post-denitrification of sewage, the residual organic pollutants difficultly biodegradable in the secondary effluent of the sewage plant can be effectively used as the denitrification electron donor, so as to realize the reduction of the consumption of carbon source chemicals, and achieve the purpose of energy saving and emission reduction.

[0029] In order to further illustrate the present application, a functional carrier filler and a preparation method and application thereof provided by the present application are described in detail below in combination with examples, but it should not be understood as limiting the protection scope of the present application.

[0030] Example 1

[0031] Preparation of amino graphene material: industrial-grade graphene oxide (50 ~ 100 μm) was used as raw material, and graphene oxide and pure water were mixed in a mass ratio of 1:70, and then ultrasonic treatment was carried out for 2 hours to make the graphene oxide completely dispersed in water. Stirring was maintained during the ultrasonic treatment to prevent wall hanging and precipitation. The completely dispersed graphene oxide dispersion was added to the hydrothermal reaction kettle with ammonia water (25wt%) in a volume ratio of 1:4, and reacted at 200℃ for 12h. After cooling to room temperature, the supernatant was removed. The obtained solid material was washed with 0.1M hydrochloric acid solution, pure water and ethanol for 5 times alternately to remove the residual ammonia thereon. After washing, the solid material was vacuum dried to remove water, and then ground to obtain the amino graphene material.

[0032] Elemental analysis was carried out on the graphene oxide and amino graphene by using the elemental analyzer produced by Elementar Analysis System Company, Germany, as shown in Table 1. The elemental analysis showed that the N content of the amino graphene (AG) was higher than that of the graphene oxide (GO), indicating that the graphene oxide was successfully amino-functionalized.

[0033] Table 1

[0034]

[0035] Preparation of functional carrier filler: the functional carrier filler was prepared in the independently developed "a device for preparing high-density polyethylene filler fixed with functional particles" (patent number: CN219988151U). Specifically, the high-density polyethylene K1 filler and the amino graphene were mixed and loaded into the loading part in a mass ratio of 1.7:10, and then the device was placed in the heating part, so that the temperature of the heating chamber where the device was located was maintained at 135-140℃, and heated for 30min. At this time, the high-density polyethylene was uniformly rotated and softened by heating, and the amino graphene was adhered to the surface of the high-density polyethylene filler. After heating, the device was completely cooled, and then the filler was shaped, washed and dried to obtain the functional carrier filler.

[0036] The surface of the filler was observed by scanning electron microscope as shown in Figure 1 , it can be seen that the amino graphene is loaded on the surface of the polyethylene. The actual product of the prepared filler is shown in Figure 2 .

[0037] Example 2

[0038] The functional carrier packing material prepared in Example 1 was added to a moving bed biofilm reactor (MBBR) for biofilm formation. The volume of the functional carrier packing material accounted for 30% of the volume of the MBBR. Activated sludge from the anoxic section of a wastewater treatment plant was used as inoculum. During the MBBR biofilm formation start-up phase, the inoculum sludge concentration was maintained at approximately 300 mg / L for one week. After one week, significant biofilm attachment was observed, demonstrating a certain capacity for COD degradation and denitrification. During the biofilm formation phase, the MBBR was not aerated, dissolved oxygen was controlled at 0-0.5 mg / L, and thorough stirring ensured sufficient contact between the packing material and the inoculum sludge. The nitrate nitrogen concentration in the sludge was maintained above 15 mgN / L, and an additional carbon source was added to control COD above 150 mg / L (approximately one-third of which was a biodegradable carbon source).

[0039] After the biofilm formation stage, the MBBR was adjusted to a continuous flow state with a hydraulic retention time of 4 hours and dissolved oxygen controlled at 0-0.5 mg / L. To screen for bacteria that could utilize recalcitrant COD for post-denitrification, the amount of additional carbon source added was gradually reduced until COD was below 100 mg / L, and the influent nitrate nitrogen concentration was 15 mgN / L and COD concentration was below 100 mg / L (within the range of secondary effluent from the wastewater treatment plant). After one month, the reactor entered the stable operation stage. When the reactor entered the stable operation stage, tests showed that the MBBR biofilm biomass reached over 0.5 g / L, and the nitrate nitrogen removal rate was close to 100%. Under these conditions, the stable operation of the post-denitrification MBBR could be maintained while ensuring effective removal and biodegradation of antibiotics. Furthermore, the amino-graphene on the packing surface was not completely covered by the biofilm, thus continuously promoting denitrification and antibiotic removal in subsequent processes.

[0040] After 60 days of stable operation of the MBBR reactor, the biofilm biomass stabilized at around 0.7 g / L, the nitrate nitrogen removal rate was about 95%, and the COD removal rate was about 70%.

[0041] Application examples

[0042] The biofilm-coated packing material from Example 2, the uncoated functional carrier packing material from Example 1, and the conventional high-density polyethylene packing material without amino-graphene loading (after biofilm formation) were used in MBBR reactors. Metronidazole was used as the test antibiotic in simulated wastewater, with an initial metronidazole concentration of 400 μg / L and initial COD and NO3-N concentrations of 150 mg / L and 15 mgN / L, respectively. The results showed that the biofilm-coated functional packing material of this invention achieved a COD removal rate of up to 80% and a NO3-N removal rate of up to 100% within 12 hours in the MBBR. The antibiotic test results are as follows... Figure 3 As shown. From Figure 3(a) It can be seen that the functional packing MBBR after biofilm formation can achieve a drug degradation rate of 100% for metronidazole after 48 hours, while the degradation rate of metronidazole in the traditional high-density polyethylene packing MBBR reactor is only 75%. Figure 3 (b) shows the adsorption curve of metronidazole on a functional carrier packing material without a membrane attachment. Generally, carbon-based materials usually have adsorption properties for antibiotics, while from... Figure 3 (b) It can be seen that the functional carrier filler of the present invention has no adsorption effect on nitroimidazole antibiotics, which further proves that the immobilization of aminographene can promote biofilm formation, thereby accelerating the biodegradation of nitroimidazole antibiotics.

[0043] It should be noted that all the above embodiments belong to the same inventive concept, and the descriptions of each embodiment have different focuses. Where the description in a particular embodiment is not detailed, please refer to the description in other embodiments.

[0044] The embodiments described above are merely illustrative of implementation methods of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. The application of a functional carrier packing material in wastewater treatment, used in a moving bed biofilm reactor to enhance antibiotic biodegradation, characterized in that, The functional carrier filler includes a polyethylene carrier and a functional layer loaded on the surface of the polyethylene carrier; the functional layer comprises amino-graphene, and the preparation method of the amino-graphene includes the following steps: Graphene oxide was completely dispersed in water to obtain a graphene oxide dispersion. The graphene oxide dispersion was mixed with ammonia water and then subjected to a hydrothermal reaction to obtain aminographene.

2. The application according to claim 1, characterized in that, The mass ratio of graphene oxide to water in the graphene oxide dispersion is (0.01~1):70, the mass concentration of ammonia water is 20~25%, and the volume ratio of graphene oxide dispersion to ammonia water is 1:(1~4).

3. The application according to claim 1, characterized in that, The hydrothermal reaction is carried out at a temperature of 180-200℃ for 10-12 hours.

4. The application according to claim 1, characterized in that, The preparation method of the functional carrier filler includes the following steps: The polyethylene carrier and amino graphene are mixed, then heated at 135-140°C, cooled, shaped, washed, and dried to obtain the functional carrier filler.

5. The application according to claim 4, characterized in that, The mass ratio of the polyethylene carrier to the amino graphene is (1.7~1.8):(10~15).

6. The application according to claim 4, characterized in that, The heating time is 20-40 minutes.

7. The application according to claim 1, characterized in that, The volume of the functional carrier packing accounts for 30% to 50% of the volume of the moving bed biofilm reactor.

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