Autotrophic denitrification filler, its preparation method and application

Abstract

The application discloses a kind of autotrophic denitrification fillings and its preparation method and application, it is related to water treatment technical field.The raw material of the autotrophic denitrification filling of the application includes the following components by mass fraction: 64 parts of sulfur powder, 25 parts of oyster shell, 10 parts of iron powder and 1 part of foaming agent.The autotrophic denitrification filling of the application is used, and the sulfur / iron autotrophic denitrification bacteria on the surface of the filling take elemental sulfur and zero-valent iron as electron donor, and the oyster shell provides alkalinity and inorganic carbon source by slow-release CaCO3, which reduces NO3 ‑ -N to N2;At the same time, dissolved Fe 2+ React with PO4 3‑ In water body, form Fe3 (PO4) 2 insoluble precipitate, and realize simultaneous phosphorus removal.The autotrophic denitrification filling of the application has high hardness and compressive strength, small density, and long service life.The raw material of the autotrophic denitrification filling of the application is cheap and easy to obtain, and the preparation process is simple, and no additional carbon source is needed when used, which is suitable for efficient, low-cost, low-carbon emission treatment of low carbon-nitrogen ratio aquaculture effluent.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, and in particular to an autotrophic denitrification packing material, its preparation method, and its application. Background Technology

[0002] Aquaculture wastewater is a major source of pollution in aquaculture. The large amounts of feed input and fish excrement generated during the aquaculture process lead to the accumulation of nitrogen and phosphorus pollutants in the water. Excessive nitrogen and phosphorus can cause pH fluctuations and reduced dissolved oxygen, resulting in eutrophication and increased mortality rates in aquatic organisms. Furthermore, direct discharge without treatment can negatively impact the surrounding ecosystem and endanger human health. Therefore, aquaculture wastewater must undergo nitrogen and phosphorus removal treatment before discharge. Currently, heterotrophic denitrification is a commonly used nitrogen removal method, which requires the addition of a carbon source. However, the amount of carbon source added is difficult to control; insufficient carbon source will affect nitrogen removal efficiency, while excessive carbon source will lead to microbial population imbalance and affect phosphorus removal. In addition, the operating costs of carbon source addition and carbon emissions increase significantly.

[0003] Sulfur autotrophic denitrification (SAD) is an effective strategy for treating wastewater with a low carbon-to-nitrogen ratio (C / N). Among various reduced sulfur compounds, elemental sulfur (S) is the most effective. 0 SAD technology is advantageous due to its low cost and ease of management. However, it has two main limitations: first, it cannot remove phosphorus, limiting its application in integrated nutrient management; second, the denitrification process produces sulfate (SO42-). 2 (⁻), leading to alkalinity depletion and pH decrease. Since pH and alkalinity are key factors in maintaining the activity of denitrifying bacteria and ensuring nitrogen removal efficiency, additional alkalinity needs to be added to maintain a neutral water environment, further increasing treatment costs and operational complexity.

[0004] Based on the aforementioned shortcomings of existing technologies, developing a highly efficient self-nutritive denitrification packing material that can simultaneously remove nitrogen and phosphorus, maintain alkalinity autonomously, and requires no external carbon source has become a key direction for solving the problem of treating aquaculture wastewater with a low carbon-to-nitrogen ratio. Summary of the Invention

[0005] The purpose of this invention is to provide an autotrophic denitrification packing material, its preparation method and application, so as to solve the problems of high loss, low reaction rate and poor phosphorus removal effect of sulfur autotrophic denitrification packing materials in the prior art.

[0006] To achieve the above objectives, the present invention provides the following solution:

[0007] One of the technical solutions of the present invention is a self-trophic denitrification packing material, which, by mass, comprises the following components: 64 parts sulfur powder, 25 parts oyster shells, 10 parts iron powder, and 1 part foaming agent.

[0008] The autotrophic denitrification packing material of this invention is actually a sulfur-iron-oyster shell porous autotrophic denitrification composite packing material. Sulfur autotrophic denitrification alone cannot remove phosphorus, which limits its application in integrated nutrient management. To solve this problem, this invention combines sulfur autotrophic denitrification and iron autotrophic denitrification. On the one hand, zero-valent iron can act as a direct electron donor in iron autotrophic denitrification to remove nitrates, thereby improving the denitrification effect. On the other hand, the acid produced during sulfur autotrophic denitrification can enhance iron dissolution, not only alleviating the surface passivation problem during iron autotrophic denitrification and enhancing nitrate removal, but also releasing Fe... 2+ It can also react with PO4 in water. 3- The formation of insoluble precipitates promotes phosphorus removal. Therefore, the addition of iron powder not only improves the denitrification effect of the sulfur-autotrophic denitrification packing but also enables it to achieve good phosphorus removal while denitrifying. Furthermore, oyster shells, with their high porosity and high calcium carbonate content, are naturally suited to microbial attachment and pH adjustment requirements. Their addition promotes microbial attachment and pH adjustment, thus facilitating the denitrification reaction. Moreover, the addition of a foaming agent in the raw material system gives the packing a loose and porous structure (porosity > 40%), significantly increasing its specific surface area (specific surface area > 10 m²). 2 / g), enhancing its adsorption capacity, extending the contact time between the packing and the effluent, providing a habitat for denitrifying bacteria, and further effectively improving the denitrification effect. Specifically, when the self-trophic denitrifying packing of the present invention is used, the sulfur / iron autotrophic denitrifying bacteria on the surface of the packing use elemental sulfur and zero-valent iron as electron donors, and the oyster shell slowly releases CaCO3 to provide alkalinity and inorganic carbon source, thus reducing NO3 - -N is reduced to N2; simultaneously, the dissolved Fe 2+ With PO4 in water 3- Precipitation occurs, forming an insoluble Fe3(PO4)2 precipitate, thus achieving simultaneous phosphorus removal.

[0009] In addition, oyster shells are a major waste product of seafood processing and catering, and traditional landfilling is both land-consuming and environmentally polluting. This invention uses them to prepare autotrophic denitrification packing material, which can achieve dual sustainability of "waste resource utilization" and "optimized denitrification efficiency".

[0010] Preferably, the foaming agent comprises sodium bicarbonate.

[0011] The raw materials for the autotrophic denitrification packing include the following components: 64 parts sulfur powder, 25 parts oyster shells, 10 parts iron powder, and 1 part sodium bicarbonate. The 64 parts by weight of sulfur powder serve as the primary electron donor, and its dosage strikes a balance between ensuring the electron donor required for denitrification and maintaining the optimal reaction rate of the system, making it the core component for achieving efficient nitrogen removal. The 10 parts by weight of iron powder serve as an auxiliary electron donor, enhancing electron transfer through a micro-galvanic cell effect with sulfur and effectively precipitating sulfides to eliminate their inhibitory effect. Simultaneously, the iron powder gradually transforms into dissolved Fe during the reaction. 2+ With PO4 in water 3- Precipitation occurs, forming an insoluble Fe3(PO4)2 precipitate, achieving efficient phosphorus removal and further expanding the packing material's simultaneous nitrogen and phosphorus removal function. 25 parts by weight of oyster shells are used as a pH buffer; the dosage is such that it does not completely block the production of H2 from sulfur denitrification. + To promote Fe 2+ This process is essential for the formation of the necessary steps, while also preventing excessive decrease in environmental pH due to the accumulation of acidic substances. This prevents excessive dissolution and reaction of iron in the packing material due to prolonged exposure to a strongly acidic environment, ultimately achieving effective control over the rate of iron consumption and ensuring the preservation of Fe during the phosphorus removal process. 2+ A continuous and stable supply is ensured. One part by weight of the foaming agent is used to form an ideal porous structure inside the filler, thereby significantly increasing the specific surface area, optimizing mass transfer conditions, and promoting biofilm adhesion.

[0012] The second technical solution of the present invention: a method for preparing the above-mentioned autotrophic denitrification packing material, comprising the following steps:

[0013] The oyster shells are calcined and then crushed to obtain oyster shell powder; the sulfur powder is heated and melted to obtain molten sulfur; the oyster shell powder and the iron powder are added to the molten sulfur, stirred at low speed, and then the foaming agent is added and stirred at high speed. After cooling and crushing, the autotrophic denitrification packing is obtained.

[0014] The filler prepared by the method of this invention has a porosity >40% and a specific surface area >10 m². 2 / g, compressive strength >3 MPa, density 1.2-1.4 g / cm³ 3 .

[0015] Furthermore, the calcination temperature is 500-550 ℃, and the time is 60 min.

[0016] Optionally, the process before calcination also includes cleaning and drying the oyster shells.

[0017] Furthermore, the pulverization specifically refers to pulverizing to the point where it can pass through a 100-mesh sieve.

[0018] Furthermore, the heating and melting temperature is 158 °C.

[0019] Furthermore, the low-speed stirring is performed at a speed of 200 rpm for 20 minutes.

[0020] Furthermore, the high-speed stirring speed is 400 rpm and the time is 10 min.

[0021] Furthermore, the crushing specifically refers to crushing to a particle size of 1-2 cm.

[0022] The third technical solution of the present invention: the application of the above-mentioned self-trophic denitrification packing in the simultaneous denitrification and phosphorus removal of aquaculture wastewater.

[0023] Furthermore, the aquaculture wastewater is a low carbon-to-nitrogen ratio aquaculture wastewater.

[0024] The present invention discloses the following technical effects:

[0025] The self-trophic denitrification packing of the present invention has high hardness and compressive strength, low density, and long service life.

[0026] The self-trophic denitrification packing material system of the present invention incorporates a foaming agent. The addition of the foaming agent gives the packing a loose and porous structure, significantly increases its specific surface area, enhances its adsorption capacity, prolongs the contact time between the packing and the effluent, and provides a habitat for denitrifying bacteria.

[0027] The self-trophic denitrification packing material of this invention can effectively remove nitrogen from aquaculture effluent. Its core denitrification principle is to use autotrophic bacteria attached to the surface, with elemental sulfur and elemental iron as electron donors and energy sources, and inorganic carbon provided by oyster shells as carbon source for growth, converting sulfur and iron into sulfate ions and iron ions; using these electrons and energy, nitrate nitrogen is gradually converted into nitrogen gas.

[0028] The self-trophic denitrification packing material of this invention also has excellent phosphorus removal effect. Its core principle for phosphorus removal is to utilize the H2 produced during the sulfur denitrification process. + This causes the pH to drop, and the low pH environment promotes the conversion of iron in the packing material to Fe. 2+ The dissolved Fe 2+ With PO4 in water 3- Precipitation occurs, forming an insoluble precipitate of Fe3(PO4)2, thereby achieving the effect of phosphorus removal.

[0029] Experiments show that when the HRT of aquaculture effluent is 4 h, the total nitrogen can be reduced from 26.80 mg / L to 6.07 mg / L, and the total phosphorus can be reduced from 5.49 mg / L to 0.28 mg / L. The nitrogen removal rate is >77%, the phosphorus removal rate is >94%, and the pH of the effluent is stable at 7.29±0.23.

[0030] The self-trophic denitrification packing material of this invention is made from inexpensive and readily available raw materials, has a simple preparation process, and does not require an external carbon source during use. It is suitable for efficient, low-cost, and low-carbon emission treatment of aquaculture wastewater with a low carbon-to-nitrogen ratio. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a schematic diagram of the treatment device used in the performance test of aquaculture wastewater treatment in this invention. Detailed Implementation

[0033] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0034] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0035] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0036] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0037] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0038] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0039] In the following embodiments and comparative examples of the present invention, room temperature refers specifically to 20-30 °C.

[0040] Unless otherwise specified, all raw materials used in the following embodiments and comparative examples of this invention are commercially available products.

[0041] Example 1

[0042] A self-nutritive denitrification packing material, by mass parts, comprises: 64 parts sulfur powder, 25 parts oyster shells, 10 parts iron powder, and 1 part sodium bicarbonate foaming agent.

[0043] The preparation steps of the above-mentioned autotrophic denitrification packing are as follows:

[0044] (1) Clean the oyster shells and dry them at 105 °C for 12 h to obtain clean oyster shell raw materials.

[0045] (2) Preheat the muffle furnace to 200 °C, put the oyster shells cleaned and dried in step (1) into the muffle furnace, heat to 500 °C and maintain for 60 min (i.e. calcined at 500 °C for 60 min), and then cool to room temperature.

[0046] (3) Crush the oyster shells obtained in step (2) and pass them through a 100-mesh sieve to obtain oyster shell powder.

[0047] (4) After heating the sulfur powder to 158 °C to melt it, add the oyster shell powder and iron powder obtained in step (3) to the molten sulfur. Stir at 200 rpm for 20 min, then add the foaming agent sodium bicarbonate. Stir at 400 rpm for 10 min, then cool to room temperature. Finally, crush the particles to a particle size of 1-2 cm to obtain granular autotrophic denitrification packing.

[0048] Comparative Example 1

[0049] A self-trophic denitrification packing material, by mass parts, comprises: 74 parts sulfur powder, 25 parts oyster shells and 1 part sodium bicarbonate foaming agent.

[0050] The preparation steps of the above-mentioned autotrophic denitrification packing are as follows:

[0051] (1) Clean the oyster shells and dry them at 105 °C for 12 h to obtain clean oyster shell raw materials.

[0052] (2) Preheat the muffle furnace to 200 °C, put the oyster shells cleaned and dried in step (1) into the muffle furnace, heat to 500 °C and maintain for 60 min (i.e. calcined at 500 °C for 60 min), and then cool to room temperature.

[0053] (3) Crush the oyster shells obtained in step (2) and pass them through a 100-mesh sieve to obtain oyster shell powder.

[0054] (4) After heating the sulfur powder to 158 °C to melt it, add the oyster shell powder obtained in step (3) to the molten sulfur, stir at 200 rpm for 20 min, add the foaming agent sodium bicarbonate, stir at 400 rpm for 10 min, cool to room temperature, and then crush to a particle size of 1-2 cm to obtain granular autotrophic denitrification packing.

[0055] Comparative Example 2

[0056] An autotrophic denitrification packing material, by mass parts, comprises: 65 parts sulfur powder, 25 parts oyster shells, and 10 parts iron powder.

[0057] The preparation steps of the above-mentioned autotrophic denitrification packing are as follows:

[0058] (1) Clean the oyster shells and dry them at 105 °C for 12 h to obtain clean oyster shell raw materials.

[0059] (2) Preheat the muffle furnace to 200 °C, put the oyster shells cleaned and dried in step (1) into the muffle furnace, heat to 500 °C and maintain for 60 min (i.e. calcined at 500 °C for 60 min), and then cool to room temperature.

[0060] (3) Crush the oyster shells obtained in step (2) and pass them through a 100-mesh sieve to obtain oyster shell powder.

[0061] (4) After heating the sulfur powder to 158 °C to melt it, add the oyster shell powder and iron powder obtained in step (3) to the molten sulfur, stir at 200 rpm for 20 min, cool to room temperature, and then crush to a particle size of 1-2 cm to obtain granular autotrophic denitrification packing.

[0062] Test Example 1

[0063] Physical performance testing:

[0064] The porosity, specific surface area, compressive strength and density of the autotrophic denitrification packings prepared in each embodiment and comparative example were tested, and the results are shown in Table 1 (expressed as mean ± standard deviation).

[0065] Table 1 Physical performance test results

[0066]

[0067] Test Example 2

[0068] Aquaculture wastewater treatment performance test:

[0069] A wastewater treatment experiment was conducted using wastewater from a California bass farm in a pond (influent total nitrogen content 24.41±1.82 mg / L, total phosphorus content 5.23±0.36 mg / L, COD 26.5±6.5 mg / L, C / N ratio 1.09±0.35, pH 7.42±0.24). The hydraulic retention times (HRTs) were 2 h, 3 h, 4 h, 5 h, and 6 h. The treatment apparatus was as follows: Figure 1 As shown, the working volume of the reactor was 2.49 L, and the effective volume was 0.98 L. Before the experiment, aquaculture wastewater was introduced for a 14-day pre-culture. The aquaculture wastewater to be treated was pumped into the reactor from the bottom of the device using a peristaltic pump. After being treated by the autotrophic denitrification packing material in the reactor (the autotrophic denitrification packing material prepared in each example and comparative example was used as the experimental packing material, and an equal volume of volcanic rock with a particle size of 1-2 cm was used as the control group), the wastewater flowed out. The test results are shown in Table 2 (the total nitrogen and total phosphorus contents of the influent under different hydraulic retention times in Table 2 are inconsistent because aquaculture wastewater from the same pond at different time periods was used).

[0070] Table 2

[0071]

[0072] As can be seen from the comparison of Example 1, Comparative Examples 1-2 and the control group in Table 2, the autotrophic denitrification packing of the present invention can effectively remove total nitrogen and total phosphorus from aquaculture effluent.

[0073] In addition to nitrogen and phosphorus removal rates, the average pH value of the effluent from each group was also tested, as shown in Table 3.

[0074] Table 3

[0075]

[0076] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. An autotrophic denitrification packing material, characterized in that, The raw materials include the following components in mass fraction: 64 parts of sulfur powder, 25 parts of oyster shell, 10 parts of iron powder and 1 part of foaming agent; The foaming agent includes sodium bicarbonate; The preparation steps of the autotrophic denitrification filler include: The oyster shell is calcined and crushed to obtain oyster shell powder; the sulfur powder is heated and melted to obtain molten sulfur; the oyster shell powder and the iron powder are added into the molten sulfur, and then the foaming agent is added and stirred at a low speed, and then stirred at a high speed, and then cooled and crushed to obtain the autotrophic denitrification filler; The calcination temperature is 500-550 ℃, and the time is 60 min.

2. The autotrophic denitrification packing material of claim 1, wherein, The crushing is specifically crushing to pass through a 100-mesh screen.

3. The autotrophic denitrification packing material of claim 1, wherein The temperature of the heating and melting is 158 ℃.

4. The autotrophic denitrification packing material of claim 1, wherein, The stirring speed at the low speed is 200 rpm, and the time is 20 min; And / or, the stirring speed at the high speed is 400 rpm, and the time is 10 min.

5. The autotrophic denitrification packing material of claim 1, wherein The crushing is specifically crushing to have a particle size of 1-2 cm.

6. Application of the autotrophic denitrification filler according to any one of claims 1-5 in synchronous nitrogen and phosphorus removal in aquaculture tail water.

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