CN115636507B - Constructed Wetland Slow Release Filler Based on Sulfur Autotrophic Denitrification - Google Patents

Abstract

The invention discloses an artificial wetland slow-release filler based on sulfur autotrophic denitrification, which is composed of filler particles and sodium thiosulfate slow-release particles, and the filling ratio of the filler particles to sodium thiosulfate slow-release particles is 1:0.8～ 1.2; the filler particles are composed of the following components: 30% to 50% of straw, 10% to 20% of calcium hydroxide, 20% to 40% of Portland cement, and 10% to 20% of activated carbon . The sodium thiosulfate slow-release granules are cement slow-release granules wrapped with paraffin, and the cement slow-release granules are composed of the following components: 35% to 45% of sodium thiosulfate, 15% to 25% of hard Fatty acid, 35% to 45% Portland cement. The artificial wetland slow-release filler of the present invention has the advantages of high removal efficiency, high mechanical strength, no need to add carbon source, resource saving, environmental friendliness, etc., and has good application prospects in biological denitrification, sewage treatment and the like.

Description

Constructed Wetland Slow Release Filler Based on Sulfur Autotrophic Denitrification

technical field

The invention relates to an artificial wetland slow-release filler based on sulfur autotrophic denitrification, which belongs to the technical field of water treatment.

Background technique

With the rapid development of my country's economy and the acceleration of urbanization, the discharge of domestic and industrial wastewater continues to increase, resulting in excessive nitrogen content in water bodies, resulting in eutrophication of water bodies. Eutrophication of the water body will lead to excessive growth of algae, reduce the transparency and dissolved oxygen of the water body, and even release toxic substances to damage the aquatic ecological environment. At the same time, nitrate will also be converted into nitrite, which will endanger human health and even induce cancer. Therefore, it is imminent to develop an economical, efficient, and ecologically beneficial denitrification process.

At present, the commonly used denitrification treatment methods include physical, biological and chemical methods. Physical denitrification methods include air stripping denitrification method and ion exchange method, but this method cannot fundamentally solve the problem. Chemical denitrification methods include breakpoint chlorine addition method and ammonium magnesium phosphate precipitation method, but the cost is high and a large number of by-products are generated, which is easy to cause secondary pollution. The biological method is to use the denitrification of microorganisms to convert nitrate into nitrogen. This method can completely remove nitrate in theory, and has the advantages of high removal efficiency, low operating cost and good ecological effect. Therefore, biological denitrification is the current method. The most mainstream denitrification method.

Biological denitrification can be divided into autotrophic denitrification and heterotrophic denitrification according to the different electron donors required by microorganisms. Wastewater in my country generally has the characteristics of high nitrogen and low carbon. Using autotrophic denitrification to treat wastewater does not need to add external carbon sources, which can effectively reduce treatment costs. Moreover, autotrophic bacteria have a long growth cycle and low sludge production, which can reduce Sludge treatment costs. Among them, the sulfur autotrophic denitrification denitrification method using sulfur source as the electron donor for denitrification is safer.

In biological denitrification, due to the complex operation and management of the traditional activated sludge method, high investment and high energy consumption, the constructed wetland system with simple process, large buffer capacity, low operating cost and good ecological benefits has been more and more widely used. Applications. If the artificial wetland method is combined with the sulfur autotrophic denitrification method, the advantages of both can be taken into account. There are many substances that can be used as sulfur source donors, among which sodium thiosulfate has the highest removal efficiency, but sodium thiosulfate is easily soluble in water, so preparing a kind of material that can realize sodium thiosulfate sustained release and release alkalinity Constructed wetland fillers that balance the acidity generated during the denitrification process, are porous to facilitate microbial attachment, and have a certain mechanical strength have become current research hotspots.

Contents of the invention

Aiming at the above prior art, the present invention provides a slow-release filler for artificial wetlands based on sulfur autotrophic denitrification. The artificial wetland slow-release filler of the present invention has the advantages of high removal efficiency, high mechanical strength, no need for additional carbon source, resource saving, environmental friendliness, etc., and has good application prospects in biological denitrification, sewage treatment and the like.

The present invention is achieved through the following technical solutions:

A slow-release filler for artificial wetlands based on sulfur autotrophic denitrification, composed of filler particles and sodium thiosulfate slow-release particles, the filling ratio of filler particles and sodium thiosulfate slow-release particles is 1:0.8 to 1.2, by weight ratio.

The particle diameters of the filler particles and the sodium thiosulfate slow-release particles are both 4-8 mm, preferably 6 mm.

The filler particles are composed of the following components: 30% to 50% of straw, 10% to 20% of calcium hydroxide, 20% to 40% of Portland cement, 10% to 20% of activated carbon, according to Percentage by weight.

The sodium thiosulfate slow-release granules are cement slow-release granules wrapped with paraffin, and the cement slow-release granules are composed of the following components: 35% to 45% of sodium thiosulfate, 15% to 25% of hard Fatty acid, 35% to 45% Portland cement, calculated by weight percentage; paraffin accounts for 15% to 25% of the weight of cement slow-release particles, and the thickness of the wrapped paraffin layer is 0.8 to 1.2 mm.

Further, the filler particles are prepared by the following method: mixing straw powder, calcium hydroxide, cement, activated carbon and water, the ratio of material to water is 1:0.8-1.2, stirring evenly (20-40 minutes), to obtain Mixed slurry; pour the mixed slurry into a spherical mold and dry to obtain filler particles. Cover the filler particles with a layer of burlap, and use a watering can to keep the burlap moist for a week to improve the mechanical strength of the filler. The straw powder is prepared by the following method: crush the straw (using a crusher), and sieve with a sieve of 80-120 meshes to obtain the straw powder.

Further, the straw is selected from wheat straw, corn straw, sorghum straw, rice straw and the like.

Further, the sodium thiosulfate slow-release granules are prepared by the following method:

(1) Mix stearic acid with absolute ethanol, heat in a water bath to 70-80°C, stir until the stearic acid is completely melted, add sodium thiosulfate, stir well to make it evenly dispersed, and naturally cool to 30-80°C while stirring. 35°C, wait until the solids are completely precipitated; dry the precipitated solids (absolute ethanol is completely volatilized), sieve with a sieve of 80-120 meshes, and obtain sustained-release capsules;

The weight ratio of stearic acid, absolute ethanol and sodium thiosulfate is 1:1:(2-3);

(2) Mix slow-release capsules, cement and appropriate amount of water (material-to-water ratio 1:0.8-1.2) to obtain a mixed slurry; pour the mixed slurry into a spherical mold and dry to obtain cement sustained-release granules;

(3) Heat the solid paraffin in a water bath to 65-75°C. After the paraffin is completely melted, soak the cement slow-release granules in the paraffin for 5-10 seconds, take it out, and cool it to room temperature to obtain a thiosulfate coated with a layer of paraffin. Sodium sulfate sustained release granules.

The artificial wetland slow-release filler based on sulfur autotrophic denitrification is used as filler in biological denitrification and sewage treatment.

The artificial wetland slow-release filler based on sulfur autotrophic denitrification of the present invention is composed of filler particles and sodium thiosulfate slow-release particles. When the filler particles are used alone, the bacterial growth rate is slow due to the lack of sulfur source; when the sodium thiosulfate slow-release particles are used alone, the surface of the slow-release particles is smooth, which is not conducive to microbial attachment. Therefore, when the two particles are used alone, the denitrification effect is poor. When the two fillers are used together in a certain ratio (controlling the ratio of sodium thiosulfate and hydrated lime), the hydrated lime in the filler particles can perfectly neutralize the alkali produced by microorganisms due to the degradation of the sulfur source in the sodium thiosulfate slow-release granules To maintain the neutral environment required for microbial growth; the two complement each other and cooperate with each other.

The artificial wetland slow-release filler based on sulfur autotrophic denitrification of the present invention has the following beneficial effects:

(1) The present invention uses sodium thiosulfate as the sulfur source material, and its treatment efficiency is higher than that of the current mainstream artificial wetland fillers that use sulfur as the sulfur source.

(2) In the present invention, activated carbon is added to the raw materials of the artificial wetland filler, and the activated carbon can absorb nitrate in water, increase the hydraulic retention time, and improve the treatment effect.

(3) The present invention uses hydrated lime as the alkalinity-providing substance and Portland cement as the binder. After the two are mixed, the mechanical strength is higher. At the same time, Portland cement also has weak alkalinity, which can neutralize part of the sulfur acid produced by denitrification. And calcium ions can also combine with phosphate in water to form insoluble substances, so that the filler has the function of phosphorus removal.

(4) No sintering, low carbon and environmental protection.

(5) In the present invention, straw is added to the raw materials of artificial wetland filler, which not only makes the filler more porous, increases the bio-adhesion area, but also releases carbon sources, improves the efficiency of sulfur autotrophic heterotrophic denitrification, and increases the New ways to utilize straw.

Description of drawings

Figure 1: Photograph of filler particles.

Figure 2: Photograph of sodium thiosulfate extended-release granules.

Figure 3: Comparison chart of sustained-release performance of sustained-release granules prepared by different sustained-release processes.

Figure 4: Schematic diagram of the removal rate of nitrate nitrogen in continuous experiments.

Detailed ways

The present invention will be further described below in conjunction with embodiment. However, the scope of the present invention is not limited to the following examples. Those skilled in the art can understand that various changes and modifications can be made to the present invention without departing from the spirit and scope of the present invention.

The instruments, reagents, and materials involved in the following examples, unless otherwise specified, are conventional instruments, reagents, and materials in the prior art, and can be obtained through formal commercial channels. The experimental methods and detection methods involved in the following examples, unless otherwise specified, are conventional experimental methods and detection methods in the prior art.

The cement used in the present invention is Portland cement of po42.5 purchased from Shanshui Group. The activated carbon used in the present invention is purchased from Kangde brand powdered activated carbon. The straw used in the present invention is wheat straw.

Example 1 Constructed Wetland Slow Release Filler Based on Sulfur Autotrophic Denitrification

It is composed of filler particles and sodium thiosulfate slow-release particles, and the filling ratio of the two is 1:1, by weight. The particle diameters of the filler particles and the sodium thiosulfate slow-release particles are both 6mm.

The preparation method is as follows:

(1) Preparation of filler particles:

(1) Put the straw in the crusher and run it for 5 minutes, then use a 100-mesh screen to screen out the straw powder and set aside;

(2) Mix 40 g of straw powder, 15 g of slaked lime, 30 g of cement, 15 g of activated carbon and 100 ml of water, and stir for 30 minutes to obtain a mixed slurry; pour the mixed slurry into a spherical mold (6 mm in diameter), and dry to obtain filler particles. Cover the filler particles with a layer of burlap and keep the burlap moist with a watering can for a week. The photo of the obtained filler particles is shown in Figure 1. After testing, the specific surface area is 0.0048㎡/g, the porosity is 47%, the particle size is 6mm, the density is 0.78g/cm³, and the bulk density is 0.368g/cm³.

(2) Preparation of sodium thiosulfate sustained-release granules:

(1) Put 20 g of stearic acid into a beaker, add 20 ml of absolute ethanol, heat it in a constant temperature water bath to 75°C, stir until the stearic acid is completely melted, add 40 g of sodium thiosulfate, and stir fully to make it Disperse evenly, cool naturally to 30°C while stirring, and wait until the solids are completely precipitated; put the precipitated solids into an oven for drying (40°C), and sieve through a 100-mesh sieve to obtain sustained-release capsules;

(2) Mix 60 g of sustained-release capsules, 40 g of cement and 100 ml of water, and stir evenly to obtain a mixed slurry; pour the mixed slurry into a spherical mold (6 mm in diameter), and dry to obtain cement sustained-release granules;

(3) Heat 20 g of solid paraffin in a constant-temperature water bath to 70°C. After the paraffin is completely melted, soak the cement slow-release granules in the paraffin for 8 seconds, take it out, and cool it to room temperature to obtain a layer coated on the surface. Sodium thiosulfate slow-release granules of paraffin (the thickness of the paraffin layer is about 1.0mm) (by calculation, the weight of the wrapped paraffin is 18% of the cement slow-release granules, 20 g of paraffin is used here, in order to make the paraffin after melting can be Completely wrap the cement slow-release particles), the photo is shown in Figure 2.

Control 1: Sustained-release granules prepared from paraffin plus cement (referred to as paraffin plus cement), the preparation method is the same as above (2), the difference is that step (1) is not performed, and sodium thiosulfate is used in step (2) to replace the slow-release capsule.

Control 2: slow-release granules prepared by adding stearic acid and cement (referred to as stearic acid plus cement), the preparation method is the same as above (2), the difference is that step (3) is not carried out, and the cement slow-release obtained in step (2) The pellets are the final product.

Take two sodium thiosulfate sustained-release granules prepared above and soak them in 250 ml of water. The sustained-release rate is shown in Table 1. At the same time, the slow-release granules prepared by adding paraffin wax and cement, and the slow-release granules prepared by adding stearic acid and cement were used as controls, and the results are shown in Figure 3. As can be seen from Table 1 and Figure 3, the sodium thiosulfate sustained-release granules of the present invention have a good sustained-release effect; when no paraffin or stearic acid is added, the sustained-release effect is significantly different.

Table 1

The filler particles and sodium thiosulfate slow-release particles prepared above were filled in an upflow anaerobic sludge reactor (the filling weight ratio of the two was 1:1), and the water was fed stably and continuously through a peristaltic pump. The HRT was At 9.6 hours, the concentration of nitrate nitrogen in the influent was 130mg/L. The removal efficiency of nitrate nitrogen is shown in Table 2 and Figure 4. It can be seen from Table 2 and Figure 4 that the artificial wetland slow-release filler based on sulfur autotrophic denitrification of the present invention has a good denitrification effect.

Table 2

The above examples are provided to those skilled in the art to fully disclose and describe how to make and use the claimed embodiments and not to limit the scope of the disclosure herein. Modifications obvious to those skilled in the art are intended to be within the scope of the appended claims.

Claims (7)

1. An artificial wetland slow release filler based on sulfur autotrophic denitrification is characterized in that: the composite material consists of filler particles and sodium thiosulfate slow-release particles, wherein the filling ratio of the filler particles to the sodium thiosulfate slow-release particles is 1:0.8-1.2, and the weight ratio is calculated;

the particle size of the filler particles and the sodium thiosulfate slow-release particles is 4-8 mm;

the filler particles are composed of the following components: 30-50% of straw, 10-20% of calcium hydroxide, 20-40% of Portland cement and 10-20% of activated carbon in percentage by weight;

the sodium thiosulfate slow-release particles are cement slow-release particles coated with paraffin, and the cement slow-release particles are composed of the following components: 35-45% of sodium thiosulfate, 15-25% of stearic acid and 35-45% of Portland cement according to weight percentage; the paraffin accounts for 15-25% of the weight of the cement slow-release particles, and the thickness of the wrapped paraffin layer is 0.8-1.2 mm;

the sodium thiosulfate slow-release particles are prepared by the following method:

(1) Mixing stearic acid and absolute ethyl alcohol, heating water to 70-80 ℃, stirring until the stearic acid is completely melted, adding sodium thiosulfate, fully stirring to uniformly disperse the sodium thiosulfate, and naturally cooling to 30-35 ℃ during stirring until the solid is completely separated out; drying the precipitated solid to obtain a slow-release capsule; the weight ratio of the stearic acid, the absolute ethyl alcohol and the sodium thiosulfate is 1:1: (2-3);

(2) Mixing the slow-release capsule, cement and a proper amount of water to obtain mixed slurry; pouring the mixed slurry into a spherical mold, and drying to obtain cement slow-release particles;

(3) Heating the solid paraffin to 65-75 ℃, soaking the cement slow-release particles in the paraffin after the paraffin is completely melted for 5-10 seconds, taking out, and cooling to room temperature to obtain sodium thiosulfate slow-release particles coated with a layer of paraffin;

the straw is selected from wheat straw, corn straw, sorghum straw and rice straw.

2. The slow release filler for constructed wetlands based on sulfur autotrophic denitrification according to claim 1, wherein the filler particles are composed of: 40% of straw, 15% of calcium hydroxide, 30% of silicate cement and 15% of activated carbon.

3. The constructed wetland slow release filler based on sulfur autotrophic denitrification as claimed in claim 1, wherein the constructed wetland slow release filler is characterized in that: the cement slow-release particles are composed of the following components: 40% of sodium thiosulfate, 20% of stearic acid and 40% of Portland cement; the thickness of the wrapped paraffin layer is 1.0mm.

4. The slow release filler for constructed wetlands based on sulfur autotrophic denitrification according to claim 1, wherein the filler particles are prepared by the following method: mixing straw, calcium hydroxide, cement, active carbon and water in the material-water ratio of 1:0.8-1.2, and stirring uniformly to obtain mixed slurry; pouring the mixed slurry into a spherical mold, and drying to obtain filler particles.

5. The constructed wetland slow release filler based on sulfur autotrophic denitrification as claimed in claim 4, wherein the constructed wetland slow release filler is characterized in that: covering a layer of linen on the filler particles, and keeping the linen moist by using a watering can for a week.

6. The constructed wetland slow release filler based on sulfur autotrophic denitrification as claimed in claim 1, wherein the constructed wetland slow release filler is characterized in that: the filling ratio of the filler particles to the sodium thiosulfate slow-release particles is 1:1; the particle diameters of the filler particles and the sodium thiosulfate slow-release particles are 6mm.

7. The use of the constructed wetland slow release filler based on sulfur autotrophic denitrification as defined in any one of claims 1 to 6 in biological denitrification and sewage treatment.