CN116813079A - Biological composite filler for generating polysulfide to realize deep denitrification and preparation method thereof - Google Patents

Abstract

The invention discloses a preparation method of biological composite filler for generating polysulfide to realize deep denitrification, which belongs to the technical field of sewage biological treatment. The absorption and utilization of sulfur autotrophic bacteria to elemental sulfur are mediated by extracellular substances, under the condition of elemental sulfur, the substances containing sulfhydryl structures are highly expressed and differentially expressed, and activate the elemental sulfur, so that sulfur is biologically modified to generate polysulfide which is used as a soluble intermediate for bacterial utilization. The biological composite filler prepared by the invention has the advantages that the formation of organic polysulfide is promoted by adding a small amount of cysteine, the solubility of sulfur in sewage is improved, the formation of sulfur source and EPS absorbed by sulfur oxidizing bacteria is facilitated, the domestication time of microorganisms is shortened, and the denitrification capability is improved.

Description

A biological composite filler that generates polysulfides to achieve deep denitrification and its preparation method

Technical field

The invention belongs to the field of sewage denitrification treatment, and specifically relates to a biological composite filler that generates polysulfides to achieve deep denitrification and a preparation method thereof.

Background technique

Elemental sulfur is often used in the field of sewage treatment due to its cheap, easy to obtain, non-toxic and harmless characteristics. The use of elemental sulfur as an inorganic electron donor to deeply denitrify oligotrophic nitrogen-containing wastewater, such as drinking water, groundwater and secondary effluent from urban sewage treatment plants, has been a hot research topic in recent years. Compared with the heterotrophic denitrification process that uses organic carbon sources as electron donors, the elemental sulfur autotrophic denitrification process (SADN) has the advantages of low sludge yield and low operating cost. However, the low solubility of elemental sulfur results in poor bioavailability, which limits the rate of SADN and affects the wide application of this process.

Currently, many studies are devoted to exploring how to improve the transfer rate of electrons from S ⁰ to sulfur-oxidizing denitrifying bacteria for nitrate reduction to thereby increase the SADN rate. Polysulfide (S _n ^2- ) is under neutral to alkaline conditions (Formula 1) is generated by the chemical reaction between elemental sulfur and sulfide. As a transfer carrier for soluble zero-valent sulfur in water, its bioavailability is much higher than that of S ⁰ ; Once S _n ^2- is produced, it can be quickly removed by sulfur Oxidizing denitrifying bacteria use it to achieve rapid reduction of nitrate (Equation 2). Therefore, S _n ^2- can serve as a media for electron conduction between sulfur oxidizing denitrifying bacteria and S ⁰ to speed up the electron transfer rate between the two.

However, polysulfide chemicals are extremely expensive and difficult to store for a long time, so it is not suitable to add them directly in the sewage treatment process. Using sulfides (such as sodium sulfide, sodium hydrosulfide, etc.) as precursors can promote the natural formation of _Sn ^2- , but there are safety risks in the transportation, use and storage of sulfides.

By adding an organic carbon source into the sulfur autotrophic reactor, heterotrophic sulfur reducing bacteria can convert elemental sulfur or sulfate into S _n ^2- and increase the denitrification rate. However, the difficulty with this method is that it is difficult to precisely control the amount of organic carbon. Too much organic carbon will cause heterotrophic bacteria to proliferate in large numbers, occupy the ecological niche of sulfur autotrophic bacteria, and destroy the balance of the reactor. During the proliferation of sulfur autotrophic bacteria, Organic matter will be produced more or less. A small amount of non-corresponding organic matter will not promote the reactor, but will lead to high effluent COD. In previous research and practice, trace amounts of COD can always be detected in the effluent of all sulfur autotrophic reaction tanks without external organic carbon sources. It is generally believed that they are endogenous organic substances produced by sulfur autotrophic bacteria during cell proliferation. High-quality organic carbon sources such as sodium acetate and ethanol are mainly absorbed and utilized by heterotrophic bacteria to perform heterotrophic denitrification or heterotrophic sulfur reduction activities. Only a few sulfur autotrophic bacteria can absorb and utilize such organic carbon sources.

Contents of the invention

The invention provides a biological composite filler that generates polysulfides to achieve deep denitrification and a preparation method thereof. The prepared biological composite filler can shorten the acclimation time of a sulfur autotrophic reactor, improve the bioavailability of sulfur elements, and achieve high efficiency, Deep denitrification.

In order to achieve the above objectives, the present invention provides the following technical solutions:

A method for preparing a biological composite filler that generates polysulfides to achieve deep denitrification, including the following steps:

S1: Mix polyvinyl acetate and glycerin to prepare mixture A;

S2: Mix and stir sulfur and calcium carbonate, add them to mixture A after mixing evenly, and perform the first mixing to prepare mixture B;

S3: Mix cysteine, trace elements and sodium alginate aqueous solution for a second time to dissolve them to prepare mixture C;

S4: Add the mixture B, mixture C and sodium dodecylbenzene sulfonate obtained in S2 into the container for the third mixing, add the foaming agent, stir and mix thoroughly to obtain the mixture, heat, melt, feed, Injection granulation to obtain the required filler.

In the above steps, the mass ratio of polyvinyl acetate and glycerol described in S1 is (15~20): (30~35);

The sulfur and calcium carbonate described in S2 are stirred until they are grayish yellow and uniform, and the sulfur and calcium carbonate are powdery; the mass ratio of the sulfur and calcium carbonate is (20~40): (15~20); the sulfur The mass ratio to mixture A is (20~40): (3~6);

The mass ratio of sulfur and cysteine is (20~40): (0.5~2); the mass fraction of the sodium alginate aqueous solution is 2~5wt%; the mass ratio of the sulfur and sodium alginate solution is (20～40): (1～3); The composition of the trace elements (based on sodium alginate solution: g L-1): disodium ethylenediaminetetraacetate (EDTA-Na)5, ferrous sulfate (FeSO ₄ )5, disodium ethylenediaminetetraacetate (EDTA-Na) 15, boric acid (H ₃ BO ₄ ) 0.0014, manganese chloride tetrahydrate (MnCl ₂ ·4H ₂ O) 0.99, copper sulfate pentahydrate (CuSO ₄ ·5H ₂ O)0.25, zinc sulfate heptahydrate (ZnSO ₄ ·7H ₂ O) 0.43, nickel chloride hexahydrate (NiCl ₂ ·6H ₂ O) 0.19, sodium selenate decahydrate (NaSeO ₄ ·10H ₂ O) 0.21, sodium molybdate dihydrate (NaMoO ₄ ·2H ₂ O) 0.22;

The second mixing method in S3 is heating and stirring, the temperature is 45~55℃, and the time is 10~20min;

The mass ratio of the sulfur and sodium dodecylbenzene sulfonate is (20-40): (4-7);

The mass ratio of the sulfur to the foaming agent is (20-40): (5-8); the foaming agent is sodium bicarbonate solution, and the mass fraction of the sodium bicarbonate solution is 0.5-2wt%;

The melt granulation described in S4 is carried out under the conditions of protective atmosphere and stirring; the temperature of the melt granulation is 240-280°C, the stirring speed is 120-150 rpm, and the specific time is based on the quality of the raw materials; Vacuum feeding can use an electric vacuum feeding machine or a pneumatic vacuum feeding machine.

The particle size of the biological composite filler prepared by the above preparation method to generate polysulfides and achieve deep denitrification is 8 to 15 mm.

Beneficial effects: The present invention provides a biological composite filler that generates polysulfides to achieve deep denitrification and a preparation method thereof. Compared with the existing technology, the present invention has the following advantages:

The biological composite filler provided by the present invention that generates polysulfides to achieve deep denitrification uses sulfur and limestone as the matrix, adds cysteine and mixes it evenly, while supplementing trace elements. After adhesion and foaming treatment, it is finally shaped to produce polysulfide. Biological composite filler that achieves deep denitrification of sulfide. As a natural anionic polysaccharide, sodium alginate is non-toxic and has good biocompatibility. It can effectively protect microorganisms from harmful environmental media and is an ideal material for fixing microbial cells. As a solid surfactant, sodium dodecylbenzene sulfonate improves the hydrophilicity of the filler surface, increases the degree of microbial enrichment, greatly improves microbial activity, and greatly increases its utilization rate of sulfur sources, carbon sources and nutrients. , can also improve the denitrification effect of microorganisms on nitrogen-containing pollutants. The absorption and utilization of elemental sulfur by sulfur autotrophic bacteria is mediated by extracellular substances. Under elemental sulfur conditions, substances containing sulfhydryl structures are highly expressed and differentially expressed. They activate elemental sulfur, biologically modify the sulfur, and generate polysulfides. As a soluble intermediate, it changes the chemical form of sulfur from hydrophobic to hydrophilic for bacterial utilization. The biological composite filler prepared by the present invention activates the elemental sulfur by adding a small amount of cysteine, thereby turning the elemental sulfur into a soluble polysulfide form and entering the cell. Once S _n ^2- is generated, it can be quickly absorbed by the sulfur Oxidative denitrifying bacteria use it to achieve rapid reduction of nitrate. A small amount of cysteine is used as a primer for sulfur autotrophic denitrifying bacteria to activate elemental sulfur and make it easier to absorb. It promotes the formation of organic polysulfides and improves the concentration of sulfur in sewage. Solubility, combined with trace elements, promotes the proliferation and growth of microorganisms, which is conducive to the absorption of sulfur sources by sulfur-oxidizing bacteria and the formation of EPS, shortens the domestication time of microorganisms, and improves denitrification capabilities. There is no need to add additional chemicals such as organic matter and sulfides, and biological treatment units Simple, low operating cost, good denitrification effect, stable system performance, and high denitrification rate.

Description of the drawings

Figure 1 is a diagram showing the water output effect of the reactor in Embodiment 1 of the present invention;

Figure 2 is a diagram of the water output effect of the reactor in Embodiment 2 of the present invention;

Figure 3 is a diagram showing the water output effect of the reactor in Embodiment 3 of the present invention.

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments:

A method for preparing a biological composite filler that generates polysulfides to achieve deep denitrification, including the following steps:

Mix polyvinyl acetate and glycerol to prepare mixture A; the mass ratio of polyvinyl acetate and glycerol is preferably (15-20): (30-35), more preferably 20:30;

Mix and stir sulfur and calcium carbonate, add them to mixture A after even distribution, and perform the first mixing to prepare mixture B. The sulfur and calcium carbonate are in powder form, and the mass ratio of the sulfur and calcium carbonate is (20 to 40 ): (15~20), more preferably 30:20; the mass ratio of the sulfur to mixture A is (20~40): (3~6), more preferably 30:5, the sulfur can be used as sulfur The source is utilized by sulfur autotrophic denitrifying bacteria to form sulfur autotrophic denitrification; the calcium carbonate is a buffer to resist the influence of adverse external pH. Mixture A serves as a binder between sulfur and calcium carbonate, which can provide toughness, strength and strength to the filler. Plasticity; the first mixing method is preferably stirring, the stirring speed is preferably 10000~20000rpm, more preferably 15000rpm, and the time is preferably 0.5~1h, more preferably 0.75h;

Mix cysteine, trace elements and sodium alginate aqueous solution for a second time to dissolve them to prepare mixture C; the mass fraction of the sodium alginate aqueous solution is preferably 2 to 5wt%, more preferably 4wt%, which can be Make a homemade solution or purchase a product. The mass ratio of sulfur to cysteine is preferably (20-40): (0.5-2), more preferably 30:1. The mass ratio of sulfur to sodium alginate solution is (20～40): (1～3), more preferably 30:2; both cysteine and trace elements are added to the sodium alginate solution, and there is no order of mixing. The second mixing method is heating Stirring, the rotating speed of the stirring is preferably 200-600rpm, more preferably 300rpm, the time is preferably 20-50min, more preferably 40min, the temperature is preferably 45-55°C, more preferably 50°C;

Add mixture B, mixture C and sodium dodecyl benzene sulfonate into the container for the third mixing, add a foaming agent, stir thoroughly and mix evenly to obtain a mixture, conduct heating and melting, vacuum feeding, and injection granulation to obtain Required filler; the second mixing is preferably after the initial mixing of Mixture B and Mixture C, and then mixing the obtained initial mixture with sodium dodecylbenzene sulfonate. The method of initial mixing is preferably stirring, and the The stirring speed is preferably 8000 to 15000 rpm, more preferably 12000 rpm, and the stirring time is preferably 40 to 60 min, more preferably 50 min. The remixing method is preferably the same as the initial mixing, and will not be described again. In the present invention, the mass ratio of the sulfur and sodium dodecylbenzene sulfonate is (20-40): (4-7), and the mass ratio of the sulfur and the foaming agent is preferably (20-40) (5~8), more preferably 30:6~7; the foaming agent is sodium bicarbonate solution, the mass fraction is preferably 0.5~2wt%, more preferably 1~2wt%, the foaming agent is added when Evenly put in during the third mixing; the melting and granulating is carried out under the conditions of protective atmosphere and stirring. The temperature of the melting and granulating is preferably 240-280°C, more preferably 270°C, and the stirring speed is 120-150rpm. . The present invention has no special limitations on the specific operation steps of the granulation, as long as granular materials with a particle size of 8 to 15 mm can be obtained; in the embodiment of the present invention, the equipment used for the granulation is preferably a granulator, specifically a granulator. The composite material obtained after heat treatment is transported to the granulation machine for granulation. In the present invention, it is preferred to granulate the biocomposite filler so that the biocomposite filler has greater mechanical strength, smaller particle size, and larger specific surface area.

Example 1

Prepare Mixture A with a mass ratio of polyvinyl acetate and glycerin of 20:30, then weigh 35 parts of sulfur, 15 parts of calcium carbonate and 5 parts of Mixture A in terms of mass parts, and stir for 1 hour at a rotation speed of 15,000 rpm. Mix until mixture B is obtained; weigh 2 parts of cysteine and 3 parts of sodium alginate solution in terms of mass parts, add cysteine and trace elements to the 4wt% sodium alginate solution, and rotate at 300 rpm. Heat and stir for 50 minutes at a temperature of 45 to 55°C to prepare mixture C; weigh 7 parts of sodium dodecylbenzene sulfonate in terms of mass parts, and add dodecylbenzene after initial mixing of mixture B and mixture C. Stir the sodium sulfonate for 50 minutes at a rotation speed of 12,000 rpm. Weigh 5 parts of 1wt% sodium bicarbonate solution in terms of mass parts and add them evenly during the stirring process to obtain the filler raw materials; transport the raw materials to the injection molding machine through a vacuum feeder in a protective atmosphere and stirring conditions, maintaining 240 to 280°C for filler production, and obtaining the biocomposite filler after cooling.

Example 2

Prepare Mixture A with a mass ratio of polyvinyl acetate and glycerin of 20:30, then weigh 30 parts of sulfur, 20 parts of calcium carbonate and 5 parts of Mixture A in terms of mass parts, and stir for 0.75h at a rotation speed of 15000 rpm. , until mixture B is obtained; weigh 1 part of cysteine and 2 parts of sodium alginate solution in terms of mass parts, add cysteine and trace elements into the 4wt% sodium alginate solution, and rotate at 300 rpm , heat and stir for 40 minutes at a temperature of 45 to 55°C to prepare mixture C; weigh 5 parts of sodium dodecylbenzene sulfonate in terms of mass parts, and add dodecyl benzene after initial mixing of mixture B and mixture C. Stir sodium benzenesulfonate for 50 minutes at a rotation speed of 12,000 rpm. Weigh 3 parts of 2wt% sodium bicarbonate solution in terms of mass parts and add them evenly during the stirring process to obtain filler raw materials; transport the raw materials to the injection molding machine through a vacuum feeder In the machine, the process is carried out under the conditions of protective atmosphere and stirring, and the filler is produced at a temperature of 240 to 280°C. After cooling, the biocomposite filler is obtained.

Example 3

Prepare Mixture A with a mass ratio of polyvinyl acetate and glycerin of 20:30, then weigh 25 parts of sulfur, 25 parts of calcium carbonate and 3 parts of Mixture A in terms of mass parts and stir for 0.5h at a rotation speed of 15000 rpm. , until mixture B is obtained; weigh 0.5 parts of cysteine and 1 part of sodium alginate solution in terms of mass parts, add cysteine and trace elements into the 4wt% sodium alginate solution, and rotate at 300 rpm , heat and stir for 45 minutes at a temperature of 45 to 55°C to prepare mixture C; weigh 4 parts of sodium dodecylbenzene sulfonate in terms of mass parts, and add dodecyl benzene sulfonate after initial mixing of mixture B and mixture C. Stir sodium benzenesulfonate for 50 minutes at a rotation speed of 12,000 rpm. Weigh 5 parts of 0.5wt% sodium bicarbonate solution in terms of mass parts and add them evenly during the stirring process to obtain the filler raw materials; transport the raw materials to In the injection molding machine, the process is carried out under the conditions of protective atmosphere and stirring, and the filler is produced at a temperature of 240 to 280°C. After cooling, the biocomposite filler is obtained.

The biological composite filler particles prepared in Examples 1 to 3 are respectively filled into fixed-bed biological column reactors, inoculated and enriched with nitrate-dependent sulfur autotrophic denitrifying bacteria and anaerobic sludge, and film-forming is carried out; After the membrane is completed, a peristaltic pump is used to introduce simulated nitrogen-containing wastewater into the reactor. The simulated nitrogen-containing wastewater is prepared from sodium nitrate and tap water. The nitrate nitrogen concentration in the simulated nitrogen-containing wastewater is 40 mg/L; the reactor It is divided into stage I (0-30d), stage II (30-60d) and stage III (60-90d) to run for a period of time respectively. The hydraulic retention time of each stage is 9h, 6h and 3h respectively, and the water discharge situation is observed. Among them, the reactor corresponding to the biocomposite filler particles prepared in Example 1 is marked as reactor E1, the reactor corresponding to the biocomposite filler particles prepared in Example 2 is marked as reactor E2, and the reactor corresponding to the biocomposite filler particles prepared in Example 3 is marked as reactor E2. The reactor is designated as reactor E3, and the results are shown in Figures 1 to 3 respectively. It can be seen from Figures 1 to 3 that the water output effect of reactor E2 is relatively excellent. The average nitrate nitrogen removal rate in stage III reaches 91.7%, while the removal rates of other reactors are basically around 88%, which proves that the nitrate nitrogen removal rate provided by the present invention Biocomposite filler particles can achieve excellent denitrification effects in sewage treatment and have high practical utilization value.

The above are only preferred embodiments of the present invention, which will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that for those of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present invention, which all fall within the protection of the present invention.

Claims (10)

1. The preparation method of the biological composite filler for generating polysulfide to realize deep denitrification is characterized by comprising the following steps of:

s1: mixing polyvinyl acetate with glycerol to obtain a mixture A;

s2: mixing and stirring sulfur and calcium carbonate, adding the mixture into the mixture A after uniformly mixing, and carrying out first mixing to obtain a mixture B;

s3: mixing cysteine, microelements and sodium alginate water solution for the second time, and dissolving to obtain a mixture C;

s4: adding the mixture B, the mixture C and sodium dodecyl benzene sulfonate into a container for third mixing, adding a foaming agent, fully stirring and uniformly mixing to obtain a mixture, and carrying out heating melting, feeding, injection molding and granulating to obtain the required filler.

2. The preparation method of the biological composite filler for generating polysulfide to realize deep denitrification according to claim 1, wherein the mass ratio of polyvinyl acetate to glycerol in S1 is (15-20): (30-35).

3. The preparation method of the biological composite filler for generating polysulfide to realize deep denitrification according to claim 1, wherein the mass ratio of sulfur to calcium carbonate is (20-40): (15-20); the mass ratio of the sulfur to the mixture A is (20-40): (3-6).

4. The method for preparing the biological composite filler for generating polysulfide to realize deep denitrification according to claim 1 or 3, wherein the mass ratio of sulfur to cysteine in S3 is (20-40): (0.5-2); the mass ratio of the sulfur to the sodium alginate solution is (20-40): (1-3).

5. The preparation method of the biological composite filler for generating polysulfide to realize deep denitrification, which is characterized by comprising the following steps of 2-5wt% of sodium alginate aqueous solution.

6. The method for preparing the biological composite filler for generating polysulfide to realize deep denitrification according to claim 4, wherein the second mixing mode in S3 is heating and stirring, the temperature is 45-55 ℃, and the time is 10-20 min.

7. The method for preparing the biological composite filler for generating polysulfide to realize deep denitrification according to claim 1 or 3, wherein the mass ratio of sulfur to sodium dodecyl benzene sulfonate in S4 is (20-40): (4-7); the mass ratio of the sulfur to the foaming agent is (20-40): (5-8).

8. The preparation method of the biological composite filler for generating polysulfide to realize deep denitrification according to claim 7, wherein the foaming agent is sodium bicarbonate solution, and the mass fraction of the sodium bicarbonate solution is 0.5-2wt%.

9. The method for producing a biological composite filler for deep denitrification by polysulfide formation according to claim 1, wherein the melt granulation in S4 is performed under a protective atmosphere and under stirring; the temperature is 240-280 ℃, and the stirring speed is 120-150 rpm.

10. The biological composite filler for generating polysulfide to realize deep denitrification, which is prepared by the method of any one of claims 1 to 9, is characterized in that the particle size of the filler is 8 to 15mm; the cysteine in the filler can change elemental sulfur into soluble polysulfide, and the polysulfide is utilized by sulfur oxidation denitrifying bacteria after being produced, so that nitrate reduction is realized.