Preparation method of composite biological nitrogen and phosphorus removal filter material

Abstract

The invention discloses a preparation method of a composite biological nitrogen and phosphorus removal filter material, and relates to the technical field of sewage treatment. The preparation method of the composite biological nitrogen and phosphorus removal filter material comprises the following steps: loading sulfur and pyrite with oyster shells to prepare an integrated composite biological carrier with a foaming structure; sulfur loaded in the oyster shells can provide electrons for the denitrification nitrogen removal process; pyrite in the structure is rich in iron element, and can also participate in auxiliary phosphorus removal while providing nitrogen removal electrons; meanwhile, the foamed porous structure of the novel filter material is also beneficial to improving the specific surface area of a carrier, and bacteria can be efficiently and rapidly enriched; according to the present invention, the oyster shell is adopted as the carrier of the filler, the organic matter component is adopted as the slow release carbon source to provide a part of electrons so as to achieve heterotrophic denitrification, and the calcium carbonate component in the oyster shell can provide alkalinity so as to make up the insufficient alkalinity problem during the autotrophic denitrification process;

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and specifically to a preparation method of a composite biological denitrification and phosphorus removal filter material. Background Art

[0002] The filter material used in the traditional sulfur autotrophic denitrification process selects elemental sulfur particles and limestone as raw materials and mixes them in a certain volume ratio. The volume of the particles is small and not the same, the volume of the filler cannot be controlled, and the mixing method of the volume ratio cannot be used as an accurate standard for measuring the total amount of substances. Moreover, sulfur and limestone may generate dust and waste gas during production and use, causing environmental pollution. Harmful gases may be released during the mining and processing of sulfur, and limestone mining may also damage the ecological environment. In addition, the mining of both requires a large amount of energy and resources, and the supply of these raw materials may be restricted by region and mining cost, increasing the environmental pressure.

[0003] As a coastal city, Rizhao has one of the largest oyster farming bases in the country, and a large amount of oyster shell waste is generated by the oyster deep processing industry every year. At the same time, due to the developed steel industry, sulfur as a by-product is also relatively abundant. In view of the fact that the hydrogen ions generated during the sulfur autotrophic denitrification process lower the pH of the system, resulting in a slow denitrification rate, oyster shells with good buffering performance and sulfur, a by-product of the steel industry, are selected as the main raw materials, and fly ash is added as an auxiliary material, which is beneficial to buffering the pH. At the same time, due to their own characteristics, fly ash mixture and oyster shell powder buffer with the acid generated by the reaction, and quickly cool down after melting and extruding the generated gas, increasing the pores, which is beneficial to the filter material being loose and porous. Even in the case of small particle size, the specific surface area can be increased, which is beneficial to the good living environment of microorganisms. One of the filter material raw materials, pyrite, can undergo an oxidation reaction with oxygen in water, playing a role in buffering DO and accelerating the reaction rate.

[0004] In addition, the steel industry also generates a large amount of waste such as fly ash mixture and slag powder, which affects the urban development. Considering its high activity, it can be selected as the gel material and alkalinity supplement of the filter material. The present invention selects multi-source waste as the filter material raw material, and at the same time, according to different formula ratios, it can solve the problem of high sulfate yield and limited application in closed waters or downstream drinking water source areas, realize the resource utilization and high-efficiency utilization of industrial solid waste, solve the actual problems encountered in urban development, and drive the development of the entire environmental protection industry at the same time, achieving a win-win situation of economic, social and environmental benefits. After retrieval, it is found that the patent application document with the Chinese patent application number 201910326682 discloses a siderite-modified sulfur lightweight material, its preparation method and application. The preparation method is to mix siderite and sulfur and heat them to melt to obtain a molten mixture of siderite, sulfur and pyrite; use physical foaming or chemical foaming methods to foam the obtained molten mixture of siderite, sulfur and pyrite, and cool and shape it to obtain a siderite-modified sulfur lightweight material. This material has the characteristics of large specific surface area, light weight, high reaction activity, easy microbial attachment, slow-release electron donor denitrification and iron ion phosphorus removal, and can achieve more microbial attachment amount, improve the microbial utilization rate, and thus improve the removal rate of nitrogen and phosphorus pollutants. It is filled in a fixed bed to treat wastewater by filtration, inoculated with microorganisms, added with nutrient solution for cultivation, and after the microbial biofilm is completed, the reactor is started and begins to operate, mainly used for synchronous removal of nitrate nitrogen and phosphate in wastewater. However, the siderite-modified sulfur material used in this invention is relatively light in weight, the release of iron element is slow, the surface wear during backwashing is high, and the carbon source release of the system is unstable.

[0005] Therefore, if a more stable, efficient and wear-resistant sewage treatment composite filler or method can be developed, it will be beneficial to the development of the sewage treatment industry. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a new type of composite foamed biological filter based on foamed sulfur autotrophic filter material, strengthen various denitrification pathways of the filter material, reduce the wear caused by backwashing, improve the recovery rate of phosphate, and improve the treatment efficiency.

[0007] A technical solution proposed by the present invention to solve the above technical problem is: a preparation method of a composite biological denitrification and phosphorus removal filter material, including the following specific steps: S1. Foam the molten mixture of sulfur and pyrite to obtain a foamed blank; S2. Mix the foamed blank, oyster powder and fly ash, and continue to foam for 1 - 2 min to form a composite biological denitrification and phosphorus removal filter material.

[0008] Preferably, in the above step S1, the molten mixture of sulfur and pyrite is obtained by mixing sulfur and pyrite and heating them to melt at 120 - 160 °C.

[0009] Preferably, in the above step S1, in the molten mixture of sulfur and pyrite, the mass ratio of sulfur to pyrite is 10 - 16:1 - 3.

[0010] Preferably, in the above step S1, sodium bicarbonate is used as the foaming agent during foaming, and the mass ratio of sodium bicarbonate to the molten mixture of sulfur and pyrite is 0.02 - 0.04:10.

[0011] Preferably, in the above step S1, the density of the foamed blank is 1.4~1.6 g / cm 3 , and the porosity is 25%~32%.

[0012] Preferably, in the above steps S1 and S2, sodium bicarbonate is used as the foaming agent during foaming, and the mass ratio of sodium bicarbonate to the molten mixture of sulfur and pyrite is 0.02~0.04:10.

[0013] Preferably, in the above steps S1 and S2, the stirring speed during foaming is 40~60 rpm, and the time is 2~4 min.

[0014] Preferably, in the above step S2, the mass ratio of the foamed blank, oyster powder and fly ash is 65~85:10~30:5.

[0015] Preferably, in the above step S2, the particle size of the oyster powder is 1 mm: the particle size of the crushed oyster powder is 0.5~1 mm.

[0016] Preferably, in the above step S2, the density of the foamed blank is 1.6~2.0 g / cm 3 , and the porosity is 25%~32%.

[0017] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: The composite biological nitrogen and phosphorus removal filter material in the present invention is prepared by compounding sulfur, pyrite, oyster powder and fly ash and foaming them.

[0018] The traditional filter materials produced by sulfur and limestone / sulfur and siderite are mineral resources, with high carbon emissions during production, insufficient buffering of ph, and the phenomenon of gradually becoming acidic after running for a period of time and finally system collapse. They also have insufficient tolerance to DO and fail at 1.0 mg / L, with high sulfate yield and insufficient hardness; In the present invention, after the filter material is first foamed with sodium bicarbonate, fly ash and oyster powder are added for secondary foaming. The filter material itself is transformed into a porous structure, the specific surface area increases, which is helpful for the attachment of microorganisms and the improvement of biomass, enhancing the nitrogen removal enhancement effect of the nitrogen removal effect. Adding fly ash, which is loose and porous, small in particle size, good in adsorption activity, diverse in elemental composition, beneficial for the growth of microorganisms and buffering PH. Adding oyster powder, which is bio-friendly and buffers alkalinity. Adding the tailing pyrite powder of mineral processing to buffer DO and accelerate the reaction rate. Adding pyrite powder and oyster powder for heterotrophic and chemical oxygen consumption. The porous characteristics of the mixture of oyster powder and fly ash itself increase the porous characteristics after buffering with the acid generated by the reaction. After hot melt extrusion and rapid cooling, cracks are formed on the surface of the filter material. Through this formula ratio, chemical phosphorus and sulfur removal are carried out to obtain a composite biological nitrogen and phosphorus removal filter material with higher hardness and better wear resistance. Specific embodiments

[0019] The present invention will be specifically described below through embodiments. It is necessary to point out here that the following embodiments are only used to further illustrate the present invention and cannot be construed as limiting the protection scope of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention based on the above content of the present invention. Unless otherwise defined, all professional and scientific terms used herein have the same meaning as those familiar to those skilled in the art.

[0020] Embodiment 1

[0021] In this embodiment, the preparation method of the composite biological nitrogen and phosphorus removal filter material is as follows: S1. Sulfur and pyrite are mixed in a mass ratio of 10:1 and heated and melted at 120 °C to obtain a molten mixture of sulfur and pyrite; the molten mixture of sulfur and pyrite is foamed, and sodium bicarbonate is used as the foaming agent during foaming. The mass ratio of sodium bicarbonate to the molten mixture of sulfur and pyrite is 0.02:10. The stirring speed during foaming is 40 rpm and the time is 2 min to obtain a foamed blank. The density of the foamed blank is 1.4 g / cm 3 , and the porosity is 25%; S2. The foamed blank, oyster powder and fly ash are mixed in a mass ratio of 65:30:5 and continue to foam for 1 min to form. The density of the foamed blank is 1.6 g / cm 3 , the porosity is 25%, the particle size of the oyster powder is 1 mm, and the composite biological nitrogen and phosphorus removal filter material is obtained.

[0022] Embodiment 2

[0023] In this embodiment, the preparation method of the composite biological nitrogen and phosphorus removal filter material is as follows: S1. Sulfur and pyrite are mixed in a mass ratio of 13:2 and heated and melted at 140 °C to obtain a molten mixture of sulfur and pyrite; the molten mixture of sulfur and pyrite is foamed, and sodium bicarbonate is used as the foaming agent during foaming. The mass ratio of sodium bicarbonate to the molten mixture of sulfur and pyrite is 0.03:10. The stirring speed during foaming is 40 rpm and the time is 2 min to obtain a foamed blank. The density of the foamed blank is 1.5 g / cm 3 , and the porosity is 28%; S2. The foamed blank, oyster powder and fly ash are mixed in a mass ratio of 75:20:5 and continue to foam for 1 min to form. The density of the foamed blank is 1.8 g / cm 3 , the porosity is 29%, the particle size of the oyster powder is 1 mm, and the composite biological nitrogen and phosphorus removal filter material is obtained.

[0024] Embodiment 3

[0025] In this embodiment, the preparation method of the composite biological nitrogen and phosphorus removal filter material is as follows: S1. Mix sulfur and pyrite in a mass ratio of 16:3, heat and melt them at 160 °C to obtain a molten mixture of sulfur and pyrite; foam the molten mixture of sulfur and pyrite. When foaming, use sodium bicarbonate as the foaming agent, and the mass ratio of sodium bicarbonate to the molten mixture of sulfur and pyrite is 0.04:10. The stirring speed during foaming is 40 rpm and the time is 2 min to obtain a foamed blank. The density of the foamed blank is 1.6 g / cm 3 , and the porosity is 32%; S2. Mix the foamed blank, oyster powder and fly ash in a mass ratio of 85:10:5, continue to foam for 2 min to form. The density of the foamed blank is 2.0 g / cm 3 , the porosity is 32%, and the particle size of the oyster powder is 1 mm to obtain a composite biological denitrification and phosphorus removal filter material.

[0026] Comparative Example 1 S1. Mix sulfur and ferrous carbonate in a mass ratio of 13:2, heat and melt them at 140 °C to obtain a molten mixture of sulfur and ferrous carbonate; S2. Mix the molten mixture of sulfur and ferrous carbonate and fly ash in a mass ratio of 75:5, stir evenly and crush to obtain a composite biological denitrification and phosphorus removal filter material.

[0027] Effect Example Load the preparation methods of the composite biological denitrification and phosphorus removal filter materials of the examples and comparative examples into a fixed-bed reactor, inoculate denitrifying sludge, complete film formation after culturing for 7 d, and conduct denitrification effect analysis.

[0028] After the reactor is started, it runs for 30 d, is backwashed once every 5 d, the backwashing time is 20 min, and the backwashing intensity is 8 L / (s·m 2 ). The main components of the artificial simulated wastewater in the reactor are: nitrate-nitrogen 15 mg / L, phosphate-phosphorus content 8 mg / L, the reactor temperature is 20 °C, and the hydraulic retention time is 1 h.

[0029] For the preparation methods of the composite biological denitrification and phosphorus removal filter materials prepared in the examples and comparative examples, the experimental results are as follows:

[0030] The effluent analysis of the reactor is shown in Table 1. It can be found from the comparison of the experimental data that the preparation methods of the composite biological denitrification and phosphorus removal filter materials prepared in Examples 1-3 still have a stable and efficient denitrification effect after running for 30 d and being washed 6 times after the reactor is started; In the present invention, after the filter material is foamed with sodium bicarbonate, fly ash and oyster powder are added for secondary foaming. The filter material itself is transformed into a porous structure, and the specific surface area increases, which helps the attachment of microorganisms and the improvement of biomass, strengthening the denitrification enhancement effect of the denitrification effect. Fly ash is added, which is loose and porous, has a small particle size, good adsorption activity, diverse elemental compositions, is beneficial to the growth of microorganisms, and buffers the pH. Oyster powder is added, which is bio-friendly and buffers the alkalinity. Tailings pyrite powder from ore dressing is added to buffer the DO and accelerate the reaction rate. The addition of pyrite powder and oyster powder enables heterotrophic and chemical oxygen consumption. The porous characteristics of the mixture of oyster powder and fly ash itself are increased after buffering with the acid generated by the reaction. After hot melt extrusion and rapid cooling, cracks are formed on the surface of the filter material. Through this formulation ratio, chemical phosphorus and sulfur removal are carried out to obtain a composite biological denitrification and phosphorus removal filter material with higher hardness and better wear resistance.

[0031] Obviously, the above embodiments are merely examples for clearly illustrating the embodiments of the present invention, rather than limitations on the embodiments of the present invention. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all the embodiments here. And these obvious changes or modifications derived from the spirit of the present invention are still within the protection scope of the present invention.

Claims

1. A method for preparing a composite biological denitrification and phosphorus removal filter material, characterized in that: The specific steps include: S1. The molten mixture of sulfur and pyrite is foamed to obtain a foamed blank; S2. Mix the foaming blank, oyster powder and fly ash, and continue foaming for 1 to 2 minutes to form a composite biological denitrification and phosphorus removal filter material.

2. The method for preparing a composite biological denitrification and dephosphorization filter material according to claim 1, characterized in that: In the above step S1., the molten mixture of sulfur and pyrite is prepared by mixing sulfur and pyrite and then heating and melting them at 120-160°C.

3. The method for preparing a composite biological denitrification and phosphorus removal filter material according to claim 1, characterized in that: In the above step S1., in the molten mixture of sulfur and pyrite, the mass ratio of sulfur to pyrite is 10-16:1-3.

4. The method for preparing a composite biological denitrification and phosphorus removal filter material according to claim 1, characterized in that: In the above step S1., the density of the foamed blank is 1.4-1.6 g / cm 3 , the porosity is 25%~32%.

5. The method for preparing a composite biological denitrification and phosphorus removal filter material according to claim 1, characterized in that: In the above steps S1 and S2, sodium bicarbonate is used as a foaming agent during foaming, and the mass ratio of sodium bicarbonate to the molten mixture of sulfur and pyrite is 0.02-0.04:

10.

6. The method for preparing a composite biological denitrification and phosphorus removal filter material according to claim 1, characterized in that: In the above steps S1 and S2, the stirring speed during foaming is 40-60 rpm and the time is 2-4 min.

7. The method for preparing a composite biological denitrification and dephosphorization filter material according to claim 1, characterized in that: In the above step S2., the mass ratio of the foaming blank, oyster powder and fly ash is 65~85:10~30:

5.

8. The method for preparing a composite biological denitrification and phosphorus removal filter material according to claim 1, characterized in that: In the above step S2., the particle size of the oyster powder is 1 mm.

9. The method for preparing a composite biological denitrification and phosphorus removal filter material according to claim 1, characterized in that: In the above step S2., the density of the foamed blank is 1.6-2.0 g / cm 3 , the porosity is 25%~32%.

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