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

Abstract

The invention discloses a preparation method of an algae-based powder carrier and application of the algae-based powder carrier in high-density loading of microorganisms, and belongs to the technical field of research, development and preparation of new materials. The preparation method of the algae-based powder carrier comprises the following steps: adding diatomite, metal salt and a hydrogen peroxide solution into a solvent, stirring, and carrying out hydrothermal treatment, suction filtration, drying and roasting to obtain a primary matrix; and adding the primary matrix, a cross-linking agent and an initiator into the gel solution, and carrying out polymerization reaction to obtain the algae-based powder carrier. The algae-based powder carrier prepared by the invention can promote rapid growth of microorganisms and realize high-density loading of the microorganisms, so that the formed activated sludge is compact in structure, the settling performance and impact resistance of the sludge are enhanced, and the sewage treatment effect is remarkably improved. The carrier effectively solves the technical problems that an existing sewage treatment plant is poor in operation stability and insufficient in impact resistance.

Description

Technical Field

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

[0002] At present, incorporating domestic sewage into urban sewage treatment plants for treatment to achieve up-to-standard discharge is the most mature and efficient sewage treatment method. Among them, the core functional unit is the activated sludge method in secondary treatment, which can remove most pollutants. However, when dealing with the rapidly increasing sewage volume, the activated sludge method faces technical bottlenecks such as unqualified effluent, insufficient operation stability, and poor economy. This is mainly due to problems such as loose floc structure, poor sedimentation performance, and sludge bulking in conventional activated sludge.

[0003] To solve the above problems, the attached carrier growth technology is usually adopted to increase the microbial density and regulate the activated sludge structure. This technology promotes the rapid high-density loading of microorganisms by adding carriers to the biochemical reaction tank, thereby improving the sewage treatment performance. It is one of the methods with relatively low cost and quick effect in the upgrading and transformation of sewage treatment plants. Currently, commonly used carriers include polyurethane and polypropylene fillers, etc., but there are problems such as insufficient activated sludge loading capacity, poor stability, and unsatisfactory sewage treatment effect. Therefore, there is an urgent need to find new carriers to improve the sewage treatment effect. Summary of the Invention

[0004] The purpose of the present invention is to provide a preparation method of an algal-based powder carrier and its application in high-density microbial loading to solve the problems existing in the above-mentioned prior art. To achieve the above purpose, the present invention provides the following solutions:

[0005] One of the technical solutions of the present invention: A preparation method of an algal-based powder carrier, comprising the following steps:

[0006] (1) Adding diatomite, metal salt, and hydrogen peroxide solution to a solvent, stirring, followed by hydrothermal treatment, suction filtration, drying, and calcination to obtain a preliminary matrix;

[0007] (2) Stirring and mixing a gel monomer and water evenly to obtain a gel solution; adding the preliminary matrix, a cross-linking agent, and an initiator to the gel solution, stirring evenly, performing a polymerization reaction, followed by washing with water, drying, and grinding to obtain the algal-based powder carrier.

[0008] Diatomaceous earth is a biosiliceous rock material composed of amorphous silica 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 is more likely to form high-concentration and structurally dense microbial aggregates. In addition, under neutral (such as anaerobic ponds) or weakly alkaline (such as anoxic ponds, aerobic ponds) conditions, although diatomaceous earth has a strong adsorption capacity for cations such as ammonia nitrogen, its ability to remove pollutants with a negatively charged surface is relatively limited. By introducing polyvalent cations (Al 3+ and Fe 3+ ) into the system, the electrostatic repulsion between microorganisms and negatively charged pollutants can be reduced, and their contact probability can be enhanced, thereby promoting the removal of pollutants.

[0009] Furthermore, in step (1), the dosage 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 temperature of the hydrothermal treatment is 120-160 °C, and the time is 12-15 h;

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

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

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

[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 interspecies electron transfer of microorganisms, improve the metabolic activity of microorganisms, and thus improve the pollutant removal ability of microorganisms; on the other hand, they can promote the secretion of extracellular secretions of microorganisms, and their combination with iron or iron ions can enhance the microbial density in the sludge, enhance the flocculation and sedimentation of the sludge, and reduce sludge bulking.

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

[0016] The present invention uses an algal-based powder carrier prepared from diatomaceous earth, iron-based particles (iron salts), and a 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 the sewage treatment performance and effectively solving key technical problems such as non-compliance of the effluent from existing sewage treatment plants.

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

[0018] Further, in step (1), the temperature of the roasting is 300~500°C, the time is 3~5 h, and the atmosphere is a nitrogen atmosphere.

[0019] Further, in step (2), the dosage 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.

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

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

[0022] Further, in step (2), the crosslinking agent includes N,N-methylenebisacrylamide; the initiator includes ammonium persulfate.

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

[0024] Further, in step (2), the particle size of the algal-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] Based on the characteristics of diatomaceous earth (high specific surface area and good adsorption performance) and the enhancement effect of iron-based particle modification, the present invention forms a porous carrier with regular structure and high specific surface area, further improving the attachment ability and growth efficiency of microorganisms (which can be determined by the MLVSS / MLSS ratio). Sodium alginate or chitosan is used as a gel monomer to provide attachment sites in the initial stage of microbial growth and can act as nutrients to extend the survival cycle of microorganisms, promoting the formation and high-density loading of microbial flocs. The activated sludge cultured with the algal-based powder carrier prepared by the present invention shows a smaller particle size and excellent sedimentation performance.

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

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

[0029] The fourth technical solution of the present invention: An application of the above algal-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 algal-based powder carrier of the present invention are inexpensive and widely available, and the preparation process of the present invention is simple. The prepared algal-based powder carrier is suitable for small-dose and multiple dosing, with a high cost-benefit ratio.

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

[0033] (3) The algal-based powder carrier prepared by the present invention can load microorganisms at high density, making the formed activated sludge have a dense structure, excellent sedimentation performance and good shock resistance, significantly improving the sewage treatment effect, and effectively solving the technical problems of poor operation stability and insufficient shock resistance of existing sewage treatment plants.

[0034] (4) The algal-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 water quality changes, and has a wide range of applications. Description of the Drawings

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0036] Figure 1Transmission electron micrograph of the diatomite support prepared in Comparative Example 1;

[0037] Figure 2 Transmission electron micrograph of the algal-based powder support prepared in Example 1;

[0038] Figure 3 Nitrogen adsorption-desorption isotherm of the diatomite support prepared in Comparative Example 1;

[0039] Figure 4 Nitrogen adsorption-desorption isotherm of the algal-based powder support prepared in Example 1;

[0040] Figure 5 Pore size distribution diagram of the diatomite support prepared in Comparative Example 1;

[0041] Figure 6 Pore size distribution diagram of the algal-based powder support prepared in Example 1;

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

[0043] Figure 8 Graph of the change in the concentration of suspended solids (MLSS) in the mixed liquor of activated sludge;

[0044] Figure 9 Graph of the change in the organic matter content (MLVSS / MLSS) of activated sludge;

[0045] Figure 10 Graph of the change in the particle size of activated sludge;

[0046] Figure 11 Graph of the change in the sludge volume index (SV30) of activated sludge. Detailed Description of the Invention

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

[0048] It should be understood that the terms used in the present invention are only for describing specific embodiments and are not intended to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0049] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Although this invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of this invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the said documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0050] Without departing from the scope or spirit of this invention, various modifications and variations can be made to the specific embodiments of the specification of this invention, which are obvious to those skilled in the art. Other embodiments obtained from the specification of this invention are obvious to those skilled in the art. The specification and examples of this invention are merely exemplary.

[0051] Regarding the use of "comprising", "including", "having", "containing", etc. herein, they are all open-ended terms, meaning including but not limited to.

[0052] The results of the component determination of the diatomaceous earth used in the specific embodiments of this invention are shown in Table 1.

[0053] Table 1 Components of Diatomaceous Earth

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

[0055] L.O.I: Loss on Ignition.

[0056] Example 1

[0057] A preparation method of an algal-based powder carrier:

[0058] (1) Take 400 mg of diatomaceous earth and 200 mg of ferric nitrate, dissolve them in 100 mL of absolute ethanol, and ultrasonicate for 15 min using an ultrasonic cleaner to form a uniform mixed solution. Gradually add 3 mL of a 30% hydrogen peroxide solution dropwise to the mixed solution, and stir vigorously for 60 min (stirring speed is 800 r / min, temperature is 25 °C). Then transfer the obtained mixed solution to a hydrothermal autoclave for hydrothermal reaction (temperature is 160 °C, time is 12 h). After the hydrothermal autoclave cools naturally, take out the mixed solution, perform suction filtration and drying (in an oven at 80 °C for 4 h) to form an intermediate. Subsequently, place the intermediate in an atmosphere furnace (control the calcination atmosphere as a nitrogen atmosphere) and calcine at 400 °C for 3 h to obtain a preliminary matrix.

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

[0060] Comparative Example 1

[0061] Preparation of diatomite carrier:

[0062] Take 400 mg of diatomite and dissolve it in 100 mL of absolute ethanol. Use an ultrasonic cleaner to ultrasonicate for 15 min to form a homogeneous mixed solution. Gradually add 3 mL of 30% hydrogen peroxide solution to the mixed solution and stir vigorously for 60 min (stirring speed is 800 r / min, temperature is 25 °C). Then transfer the obtained mixed solution to a hydrothermal reactor for hydrothermal reaction (temperature is 160 °C, time is 12 h). After the hydrothermal reactor cools naturally, take out the mixed solution, perform suction filtration and drying (80 °C in an oven for 4 h) to form an intermediate. Then place the intermediate in an atmosphere furnace (control the calcination atmosphere as a nitrogen atmosphere) and calcine at 400 °C for 3 h to obtain a preliminary matrix. Use a grinder to crush it to obtain a diatomite carrier with a particle size range of 10 - 100 μm, a pore size of 1 - 100 nm, and a specific surface area of 31.18 m 2 / g.

[0063] Effect Example 1

[0064] The transmission electron micrograph of the diatomite carrier prepared in Comparative Example 1 is shown in Figure 1 ; the transmission electron micrograph of the algal-based powder carrier prepared in Example 1 is shown in Figure 2 .

[0065] It can be seen from Figure 2 that the algal-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 isotherm and pore size distribution of the diatomite carrier prepared in Comparative Example 1 and the algal-based powder carrier prepared in Example 1 were tested by a specific surface area and porosity analyzer, and the results are shown in Figures 3 - 6 , Figure 3 is the nitrogen adsorption - desorption isotherm of the diatomite carrier, Figure 4The nitrogen adsorption - desorption isotherm of the algal - based powder carrier Figure 5 The pore size distribution diagram of the diatomite carrier Figure 6 The pore size distribution diagram of the algal - based powder carrier

[0067] From Figures 3 - 6 it can be seen that the algal - based powder carrier has a higher specific surface area and a larger adsorption capacity.

[0068] Example 2

[0069] High - density loading of microorganisms on the algal - based powder carrier:

[0070] Put the algal - based powder carrier prepared in Example 1 into the A 2 O pilot - scale device (96L) for microorganism loading, and the concentration of the algal - based powder carrier is always maintained at 20mg / L. The domestic sewage in A 2 O is taken from a sewage treatment plant in Tianjin. The influent water quality is chemical oxygen demand (COD) 191mg / L, total nitrogen (TN) 50mg / L, total phosphorus (TP) 5mg / L, C / N 3.82. The influent flow rate of A 2 O is set at 1.25L / h. The activated sludge is taken from the secondary sedimentation tank of the same sewage treatment plant. Take 5L of the mixed sludge and water, precipitate for 6h, skim off the supernatant, and add it to the A 2 O reactor. The initial MLVSS of the activated sludge is 2118 mg / L, MLSS is 4323mg / L (i.e., sludge concentration), and the sludge particle size is 64.47μm. From 0 to 2d is the sludge stabilization period, and no algal - based powder carrier is added. The algal - based powder carrier is added starting from the 3rd day and continuously cultured for 30d. Measure MLVSS ( Figure 7 ) and MLSS ( Figure 8 ) every 5d, calculate MLVSS / MLSS ( Figure 9 ), measure the activated sludge particle size ( Figure 10 ) and SV30 ( Figure 11 ).

[0071] From Figures 7 - 11 it can be seen that the organic matter content of the activated sludge continuously increases. Around 20d, the MLVSS / MLSS ratio can reach 0.75, indicating an increase in the amount of microorganisms loaded on the carrier. At the same time, the floc particle size of the activated sludge increases (from 64.47μm to 86.69μm), indicating obvious sludge granulation effect. SV30 decreases from 35% and stabilizes at 25%, proving the high - density loading of microorganisms on the algal - based powder carrier and indicating better sludge sedimentation performance.

[0072] Comparative Example 2

[0073] Same as Example 1, the only difference is that the diatomite is replaced with an equal mass of basalt, 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 an equal mass of polyurethane powder (Mw: 10000).

[0078] Effect Example 2

[0079] Test the sewage treatment performance of the algal-based powder carriers and the highly loaded microorganisms prepared in Example 1 and Comparative Examples 1-3. The specific method is as follows:

[0080] Put the carriers prepared in Example 1 or Comparative Examples 1-3 into an A 2 / O pilot-scale device (96 L) for microorganism loading, and the concentration of the algal-based powder carrier was always maintained at 20 mg / L. The domestic sewage in the A 2 / O was taken from a sewage treatment plant in Tianjin, and 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. The A 2 / O influent flow rate was set at 1.25 L / h. The activated sludge was taken from the secondary sedimentation tank of the same sewage treatment plant. 5 L of the mud-water mixture was taken, sedimented for 6 h, the supernatant was removed, and it was added to the A 2 / O reactor. From 0 to 2 days was the sludge stabilization period, and no carrier was added. On the 3rd day, the carrier was added and continuously cultured for 30 days. The average value of the pollutant removal rate was measured. The formula for calculating the pollutant removal rate: removal rate (%) = (influent value - effluent value) / influent value × 100%; The COD and TP values were measured by the potassium dichromate method (GB11914-89), and the TN value was measured by the alkaline potassium persulfate digestion ultraviolet spectrophotometry (HJ636-2012). The measurement results are shown in Table 3.

[0081] Table 3 Average value of the removal rate of each pollutant in 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] According to the test results in Table 3, it can be seen that the algal-based powder carriers prepared with diatomite and sodium alginate can enhance the high-density loading of microorganisms and strengthen the removal of pollutants in sewage by microorganisms. The removal rates of COD, TN, and TP can reach as high as 97.5%, 77.5%, and 88.5%. The carriers prepared with basalt and polyurethane powder in Comparative Example 2 and Comparative Example 3 have a worse pollutant removal effect than the algal-based powder carriers.

[0084] The embodiments described above are only descriptions of the preferred embodiments of the present invention and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A preparation method of an algal-based powder carrier, characterized in that, It includes the following steps: Add diatomite, metal salt and hydrogen peroxide solution into a solvent, stir, and then carry out hydrothermal treatment, suction filtration, drying and calcination to obtain a preliminary matrix; Add the preliminary matrix, crosslinking agent and initiator into the gel solution, and obtain the algal-based powder carrier after polymerization reaction.

2. The preparation method according to claim 1, characterized in that, The dosage ratio of the diatomite, metal salt, hydrogen peroxide solution and solvent is 300-500 mg: 100-300 mg: 2-5 mL: 100-150 mL; the concentration of the hydrogen peroxide solution is 30%; And / or, the temperature of the hydrothermal treatment is 120-160 °C, and the time is 12-15 h; And / or, the metal salt includes iron salt or aluminum salt; And / or, the gel monomer in the gel solution includes sodium alginate or natural polysaccharide.

3. The preparation method according to claim 1, characterized in that, The temperature of the calcination is 300-500 °C, the time is 3-5 h, and the atmosphere is nitrogen atmosphere.

4. The preparation method according to claim 1, wherein, The gel solution is prepared from a gel monomer and water; The dosage 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.

5. The preparation method according to claim 1, characterized in that, The temperature of the polymerization reaction is 20-30 °C, and the time is 1-3 h; the polymerization reaction is carried out under a nitrogen atmosphere.

6. The preparation method according to claim 1, wherein The crosslinking agent includes N,N-methylenebisacrylamide; the initiator includes ammonium persulfate.

7. The preparation method according to claim 1, characterized in that The particle size of the algal-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.

8. An algal-based powder carrier prepared by the preparation method according to any one of claims 1 to 7.

9. An application of the algal-based powder carrier according to claim 8 in high-density loading of microorganisms.

10. An application of the algal-based powder carrier according to claim 8 in sewage treatment.

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