Preparation method of an algae-based powder carrier and its application in high-density loading of microorganisms

Abstract

The present invention discloses a method for preparing an algae-based powder carrier and its application in high-density loading of microorganisms, belonging to the field of new material research and development and preparation technology. The method for preparing the algae-based powder carrier of the present invention comprises the following steps: adding diatomaceous earth, metal salt and hydrogen peroxide solution to a solvent, stirring, hydrothermally heating, filtering, drying and roasting to obtain a preliminary matrix; adding the preliminary matrix, a cross-linking agent and an initiator to the gel solution, and obtaining the algae-based powder carrier after polymerization reaction. The algae-based powder carrier prepared by the present invention can promote the rapid growth of microorganisms, achieve high-density loading of microorganisms, and thereby make the structure of the formed activated sludge dense, enhance the sedimentation performance and impact resistance of the sludge, and significantly improve the treatment effect of sewage. The carrier effectively solves the technical problems of poor operating stability and insufficient impact resistance of existing sewage treatment plants.

Description

Technical Field

[0001] The present invention relates to the technical field of new material research and development and preparation, and in particular to a method for preparing an algae-based powder carrier and its application in high-density loading of microorganisms. Background Art

[0002] Currently, the most mature and efficient sewage treatment method is to treat domestic sewage in municipal sewage treatment plants to achieve standard discharge. The core unit of this process is the activated sludge process in secondary treatment, which can remove most pollutants. However, in response to the rapidly increasing sewage volume, the activated sludge process faces technical bottlenecks such as substandard effluent, insufficient operational stability, and poor economic efficiency. This is primarily due to the problems of conventional activated sludge, such as loose floc structure, poor settling performance, and sludge bulking.

[0003] To address these issues, attached carrier growth technology is often used to increase microbial density and adjust activated sludge structure. This technology involves adding carriers to the biochemical reaction tank, enabling the microorganisms to rapidly achieve high-density loading, thereby improving wastewater treatment performance. It is a low-cost and highly effective method for upgrading wastewater treatment plants. Currently, commonly used carriers include polyurethane and polypropylene fillers, but these materials suffer from insufficient activated sludge loading capacity, poor stability, and suboptimal wastewater treatment results. Therefore, the search for new carriers to improve wastewater treatment performance is urgent. Summary of the Invention

[0004] The present invention aims to provide a method for preparing an algae-based powder carrier and its application in high-density microbial loading to address the aforementioned problems of the prior art. To achieve this objective, the present invention provides the following solutions:

[0005] One of the technical solutions of the present invention: a method for preparing an algae-based powder carrier, comprising the following steps:

[0006] (1) Add diatomaceous earth, metal salt and hydrogen peroxide solution into a solvent, stir, hydrothermally heat, filter, dry and calcine to obtain a preliminary matrix;

[0007] (2) The gel monomer and water are stirred and mixed uniformly to obtain a gel solution; the preliminary matrix, cross-linking agent and initiator are added to the gel solution, stirred uniformly, washed with water, dried and ground after polymerization reaction to obtain the algae-based powder carrier.

[0008] Diatomaceous earth is a biogenic siliceous rock material composed of amorphous silicon dioxide diatom shells and other microbial siliceous remains. It has a large number of orderly arranged micropores and a large specific surface area, which can promote the rapid reproduction of microorganisms on its surface and more easily form high-concentration, densely structured microbial aggregates. In addition, under neutral (such as anaerobic tanks) or weakly alkaline (such as anoxic tanks, aerobic tanks) conditions, although diatomaceous earth has a strong adsorption capacity for cations such as ammonia and nitrogen, its ability to remove negatively charged pollutants on the surface is relatively limited. By introducing multivalent positive ions (Al 3+ and Fe 3+ ), which can reduce the electrostatic repulsion between microorganisms and negatively charged pollutants, enhance their contact probability, and thus promote the removal of pollutants.

[0009] Furthermore, in step (1), the ratio of the diatomaceous earth, metal salt, hydrogen peroxide solution and solvent is 300-500 mg: 100-300 mg: 2-5 mL: 100-150 mL;

[0010] The hydrothermal temperature is 120-160°C and the time is 12-15 hours;

[0011] The metal salt includes an iron salt or an aluminum salt; the iron salt includes iron nitrate, iron chloride and iron sulfate.

[0012] The gel monomer includes sodium alginate or natural polysaccharide (such as chitosan).

[0013] The concentration of the hydrogen peroxide solution is 30% (meaning that in 100g of hydrogen peroxide solution, the mass of hydrogen peroxide is 30g and the mass of water is 70g).

[0014] Iron-based particles (provided by iron salts) can release iron or iron ions. On the one hand, they can provide attachment sites for microorganisms and act as electron donors to promote electron transfer between microbial species, thereby increasing microbial metabolic activity and thus improving the microbial ability to remove pollutants. On the other hand, they can promote the secretion of microbial extracellular secretions, which, combined with iron or iron ions, can enhance the microbial density in sludge, enhance sludge flocculation and sedimentation, and reduce sludge swelling.

[0015] Sodium alginate or chitosan, as the raw materials of the gel, can replace extracellular secretions to play an adhesive role in the early stage of microbial growth. It also has good biodegradability and can be decomposed into nutrients by microorganisms under certain conditions, thereby extending the survival time and life cycle of microorganisms, and further promoting microbial metabolism and the removal of pollutants.

[0016] The present invention uses an algae-based powder carrier prepared from diatomaceous earth, iron-based particles (iron salts) and gel (sodium alginate or chitosan) as a growth carrier, which can achieve high-density loading of microorganisms and cultivate high-concentration activated sludge, thereby improving sewage treatment performance and effectively solving key technical problems such as substandard effluent from existing sewage treatment plants.

[0017] Furthermore, in step (1), the stirring temperature is 20-30°C, the time is 15-60 min, and the speed is 800-1000 r / min.

[0018] Furthermore, in step (1), the calcination temperature is 300-500° C., the calcination time is 3-5 h, and the atmosphere is nitrogen.

[0019] Furthermore, in step (2), the ratio of the amount of the gel monomer, water, preliminary matrix, cross-linking agent and initiator is 1~3g:80~120mL:1~3g:10~30mg:10~30mg.

[0020] Furthermore, when preparing the gel solution, the stirring temperature is 20-30° C. and the stirring time is 30-60 min.

[0021] Furthermore, in step (2), the polymerization reaction temperature is 20-30° C., and the time is 1-3 hours; and the polymerization reaction is carried out under a nitrogen atmosphere.

[0022] Furthermore, in step (2), the cross-linking agent includes N,N-methylenebisacrylamide; and the initiator includes ammonium persulfate.

[0023] Furthermore, in step (2), the drying temperature is 60-80° C. and the drying time is 6-8 hours.

[0024] Furthermore, in step (2), the particle size of the algae-based powder carrier is 10-100 μm, the pore size is 1-100 nm, and the specific surface area is 63.60-80.34 m 2 / g.

[0025] The working principle of the present invention:

[0026] This invention leverages the properties of diatomaceous earth (high specific surface area and excellent adsorption properties) and the enhanced effects of iron-based particle modification to create a porous carrier with a regular structure and high specific surface area, further enhancing microbial attachment and growth efficiency (determined by the MLVSS / MLSS ratio). Sodium alginate or chitosan, as gel monomers, provides attachment sites during the initial growth phase and acts as a nutrient to extend the microbial survival period, promoting the formation of microbial flocs and high-density loading. Activated sludge cultured using the algae-based powder carrier prepared in this invention exhibits smaller particle size and excellent settling properties.

[0027] The second technical solution of the present invention: an algae-based powder carrier prepared by the above-mentioned preparation method.

[0028] The third technical solution of the present invention: an application of the above-mentioned algae-based powder carrier in high-density loading of microorganisms.

[0029] Technical solution four of the present invention: an application of the above-mentioned algae-based powder carrier in sewage treatment.

[0030] The present invention discloses the following technical effects:

[0031] (1) The materials used in the preparation of the algae-based powder carrier of the present invention are inexpensive and widely available, and the preparation process of the present invention is simple. The prepared algae-based powder carrier is suitable for multiple additions in small doses and has a high cost-effectiveness ratio.

[0032] (2) The diatomaceous earth, metal salt and gel monomer used in the present invention are all environmentally friendly materials and will not cause secondary pollution.

[0033] (3) The algae-based powder carrier prepared by the present invention can load microorganisms at a high density, so that the formed activated sludge has a dense structure, excellent sedimentation performance, and good impact resistance, which significantly improves the sewage treatment effect and effectively solves the technical problems of poor operating stability and insufficient impact resistance of existing sewage treatment plants.

[0034] (4) The algae-based powder carrier prepared by the present invention is suitable for influent with a low C / N ratio (COD / TN < 4), has strong tolerance to changes in water quality, and has a wide range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0036] Figure 1This is a transmission electron micrograph of the diatomaceous earth support prepared in Comparative Example 1;

[0037] Figure 2 This is a transmission electron micrograph of the algae-based powder carrier prepared in Example 1;

[0038] Figure 3 The nitrogen adsorption-desorption isotherm of the diatomaceous earth carrier prepared in Comparative Example 1;

[0039] Figure 4 This is the nitrogen adsorption-desorption isotherm of the algae-based powder carrier prepared in Example 1;

[0040] Figure 5 This is the pore size distribution diagram of the diatomaceous earth carrier prepared in Comparative Example 1;

[0041] Figure 6 This is the pore size distribution diagram of the algae-based powder carrier prepared in Example 1;

[0042] Figure 7 This is the change diagram of volatile suspended solids concentration (MLVSS) in the mixed liquor of activated sludge;

[0043] Figure 8 This is a graph showing the change in the concentration of suspended solids (MLSS) in the mixed liquor of activated sludge;

[0044] Figure 9 This is the change diagram of organic matter content (MLVSS / MLSS) of activated sludge;

[0045] Figure 10 is the particle size change diagram of activated sludge;

[0046] Figure 11 This is the change diagram of the sludge settling ratio (SV30) of activated sludge. DETAILED DESCRIPTION

[0047] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0048] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any intermediate value within a stated value or stated range and any other stated value or intermediate value within the stated range is also encompassed by the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0049] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0050] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be exemplary only.

[0051] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0052] The composition determination results of the diatomaceous earth used in the specific embodiment of the present invention are shown in Table 1.

[0053] Table 1 Composition of diatomaceous earth

[0054] element <![CDATA[SiO2]]> <![CDATA[Al2O3]]> <![CDATA[Fe2O3]]> MgO CaO LOI <![CDATA[Specific surface area (m 2 / g)]]> Content (wt%) 48.65 19.64 2.94 0.40 2.53 25.84 4.398

[0055] LOI: Loss on Ignition.

[0056] Example 1

[0057] A method for preparing an algae-based powder carrier:

[0058] (1) Take 400 mg of diatomaceous earth and 200 mg of ferric nitrate, dissolve them in 100 mL of anhydrous ethanol, and use an ultrasonic cleaner to ultrasonicate for 15 minutes to form a uniform mixed solution. Add 3 mL of 30% hydrogen peroxide solution dropwise to the mixed solution and stir vigorously for 60 minutes (stirring speed is 800 r / min, temperature is 25°C). Then transfer the obtained mixed solution to a hydrothermal kettle for hydrothermal reaction (temperature is 160°C, time is 12 hours). After the hydrothermal kettle is cooled naturally, take out the mixed solution, filter it, and dry it (80°C in an oven for 4 hours) to form an intermediate. Then place the intermediate in an atmosphere furnace (control the calcination atmosphere to be nitrogen atmosphere) and calcine at 400°C for 3 hours to obtain a preliminary matrix.

[0059] (2) Dissolve 1g of sodium alginate in 80mL of deionized water and stir at 25°C for 30min to form a gel solution. Mix the gel solution with 1g of the preliminary matrix, stir thoroughly, add 10mg of N,N-methylenebisacrylamide and 10mg of ammonium persulfate, stir again, and place in a nitrogen environment at 25°C for 2h to allow the polymerization reaction to form an algae-based carrier. Soak the algae-based carrier in deionized water for 5d, changing the water every 8h to wash away the unreacted monomers. Then place it in an oven and dry it at 80°C for 8h to constant weight. Use a grinder to crush it to obtain a particle size range of 10~100μm, a pore size of 1~100nm, and a specific surface area of ​​73.62m 2 / g of algae-based powder carrier.

[0060] Comparative Example 1

[0061] Preparation of diatomaceous earth carrier:

[0062] 400 mg of diatomaceous earth was dissolved in 100 mL of anhydrous ethanol and ultrasonically cleaned for 15 minutes to form a homogeneous mixed solution. 3 mL of 30% hydrogen peroxide solution was added dropwise to the mixed solution, and the mixture was stirred vigorously for 60 minutes (at 800 rpm and 25°C). The resulting mixed solution was then transferred to a hydrothermal autoclave for a hydrothermal reaction (160°C for 12 hours). After the autoclave cooled naturally, the mixed solution was removed, filtered, and dried (at 80°C in an oven for 4 hours) to form an intermediate. The intermediate was then calcined at 400°C for 3 hours in an atmosphere furnace (controlled calcination atmosphere with nitrogen) to obtain a preliminary matrix. The matrix was then pulverized using a grinder to produce particles with a size range of 10–100 μm, a pore size of 1–100 nm, and a specific surface area of ​​31.18 m 2 / g of diatomaceous earth carrier.

[0063] Effect Example 1

[0064] The transmission electron microscope image of the diatomite carrier prepared in Comparative Example 1 is shown in FIG. Figure 1 ; Transmission electron microscopy of the algae-based powder carrier prepared in Example 1 is shown in Figure 2 .

[0065] from Figure 2 It can be seen that the algae-based powder carrier has a significant porous structure, which can provide excellent sites for the attachment and growth of microorganisms.

[0066] The nitrogen adsorption-desorption isotherms and pore size distribution of the diatomite carrier prepared in Comparative Example 1 and the algae-based powder carrier prepared in Example 1 were tested by surface area and porosity analyzer. Figure 3-Figure 6 , Figure 3 is the nitrogen adsorption-desorption isotherm of diatomite support, Figure 4is the nitrogen adsorption-desorption isotherm of the algae-based powder carrier. Figure 5 is the pore size distribution diagram of diatomaceous earth carrier, Figure 6 This is the pore size distribution diagram of the algae-based powder carrier.

[0067] from Figure 3-Figure 6 It can be seen that the algae-based powder carrier has a higher specific surface area and a larger adsorption capacity.

[0068] Example 2

[0069] High-density loading of microorganisms on algae-based powder carriers:

[0070] The algae-based powder carrier prepared in Example 1 was put into A 2 Microbial loading was performed in a small pilot device (96 L), and the concentration of algae-based powder carrier was always maintained at 20 mg / L. 2 The domestic sewage in O was taken from a sewage treatment plant in Tianjin. The influent water quality was chemical oxygen demand (COD) 191 mg / L, total nitrogen (TN) 50 mg / L, total phosphorus (TP) 5 mg / L, C / N 3.82, A 2 The inlet flow rate of O was set at 1.25L / h. The activated sludge was taken from the secondary sedimentation tank of the same sewage treatment plant. 5L of mud-water mixture was taken and allowed to settle for 6h. The supernatant was skimmed off and added to A 2 O reactor. The initial activated sludge MLVSS was 2118 mg / L, MLSS was 4323 mg / L (i.e., sludge concentration), and the sludge particle size was 64.47 μm. Days 0 to 2 were the sludge stabilization period, and no algae-based powder carrier was added. Algae-based powder carrier was added starting on day 3 and continued for 30 days. MLVSS was measured every 5 days ( Figure 7 ) and MLSS ( Figure 8 ), calculate MLVSS / MLSS ( Figure 9 ), determine the activated sludge particle size ( Figure 10 ) and SV30 ( Figure 11 ).

[0071] from Figures 7 to 11 As can be seen from the data, the organic matter content of the activated sludge continued to increase. Around day 20, the MLVSS / MLSS ratio reached 0.75, indicating an increase in the microbial load on the carrier. Simultaneously, the floc size of the activated sludge increased (from 64.47 μm to 86.69 μm), demonstrating significant sludge granulation. The SV30 value decreased from 35% and stabilized at 25%, demonstrating the high microbial load on the algae-based powder carrier and indicating improved sludge settling performance.

[0072] Comparative Example 2

[0073] Same as Example 1, except that diatomaceous earth is replaced with basalt of equal mass, and its composition information is shown in the table.

[0074] Table 2 Composition of basalt

[0075] element C O Na Al Si K Ca Fe <![CDATA[Specific surface area (m 2 / g)]]> Content (wt%) 8.66 50.79 4.92 10.67 20.67 0.38 3.55 0.36 1.467

[0076] Comparative Example 3

[0077] Same as Example 1, except that sodium alginate was replaced with polyurethane powder (Mw: 10000) of equal mass.

[0078] Effect Example 2

[0079] The wastewater treatment performance of the algae-based powder carriers and high-density loaded microorganisms prepared in Example 1 and Comparative Examples 1-3 was tested. The specific method is as follows:

[0080] The carrier prepared in Example 1 or Comparative Examples 1 to 3 was placed in A 2 Microbial loading was performed in a small pilot device (96 L), and the concentration of algae-based powder carrier was always maintained at 20 mg / L. 2 The domestic sewage in O was taken from a sewage treatment plant in Tianjin. The influent water quality was chemical oxygen demand (COD) 191 mg / L, total nitrogen (TN) 50 mg / L, total phosphorus (TP) 5 mg / L, C / N 3.82, A 2 The inlet flow rate of O was set at 1.25L / h. The activated sludge was taken from the secondary sedimentation tank of the same sewage treatment plant. 5L of mud-water mixture was taken and allowed to settle for 6h. The supernatant was skimmed off and added to A 2 O reactor. Days 0 to 2 were the sludge stabilization period, with no carrier added. Carriers were added starting on day 3 and continued for 30 days. The average pollutant removal rate was determined using the formula: removal rate (%) = (influent value - effluent value) / influent value × 100%. COD and TP values ​​were determined using the potassium dichromate method (GB11914-89), and TN value was determined using alkaline potassium persulfate digestion and UV spectrophotometry (HJ636-2012). The results are shown in Table 3.

[0081] Table 3 Average removal rates of various pollutants over 30 days

[0082] COD removal rate (%) TN removal rate (%) TP removal rate (%) Example 1 97.5 77.5 88.5 Comparative Example 1 94.2 68.6 81.7 Comparative Example 2 92.1 65.4 65.1 Comparative Example 3 93.4 68.1 82.1

[0083] The test results in Table 3 show that the algae-based powder carrier prepared using diatomaceous earth and sodium alginate can enhance high-density microbial loading and strengthen microbial removal of pollutants in wastewater, with COD, TN, and TP removal rates reaching 97.5%, 77.5%, and 88.5%, respectively. Comparative Examples 2 and 3, which used carriers made from basalt and polyurethane powder as raw materials, were less effective at removing pollutants than the algae-based powder carrier.

[0084] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for preparing an algae-based powder carrier, characterized in that: The following steps are involved: Adding diatomaceous earth, metal salt and hydrogen peroxide solution into a solvent, stirring, hydrothermal treatment, suction filtration, drying and calcination to obtain a preliminary matrix; Adding the preliminary matrix, cross-linking agent and initiator into the gel solution, and performing polymerization reaction to obtain the algae-based powder carrier; The usage ratio of the diatomaceous earth, metal salt, hydrogen peroxide solution and solvent is 300-500 mg: 100-300 mg: 2-5 mL: 100-150 mL; the mass concentration of the hydrogen peroxide solution is 30%; The hydrothermal temperature is 120-160°C and the time is 12-15 hours; The metal salt includes an iron salt or an aluminum salt; the iron salt includes iron nitrate, iron chloride and iron sulfate; The gel monomer in the gel solution includes sodium alginate; The calcination temperature is 300-500°C, the time is 3-5 hours, and the atmosphere is nitrogen; The gel solution is prepared from gel monomer and water; The ratio of the gel monomer, water, preliminary matrix, crosslinking agent and initiator is 1-3 g: 80-120 mL: 1-3 g: 10-30 mg: 10-30 mg; The polymerization reaction is carried out at a temperature of 20-30° C. and for a time of 1-3 hours under a nitrogen atmosphere. The cross-linking agent includes N,N-methylenebisacrylamide; the initiator includes ammonium persulfate.

2. The preparation method according to claim 1, characterized in that The algae-based powder carrier has a particle size of 10-100 μm, a pore size of 1-100 nm, and a specific surface area of ​​63.60-80.34 m 2 / g.

3. An algae-based powder carrier prepared by the preparation method according to any one of claims 1 to 2.

4. Use of the algae-based powder carrier according to claim 3 in high-density loading of microorganisms.

5. Use of the algae-based powder carrier according to claim 3 in sewage treatment.

Images