Sulfur-iron coupled autotrophic denitrification filler and preparation method thereof

Abstract

The invention discloses a sulfur-iron coupled autotrophic denitrification filler and a preparation method thereof, and belongs to the technical field of sewage treatment. Titanium dioxide and hydroxyapatite are mixed to obtain a reinforcing agent, the reinforcing agent is compounded with sulfur, siderite and activated carbon, and finally the sulfur-iron coupled autotrophic denitrification filler is obtained. An SEM image shows that the sulfur-iron coupled autotrophic denitrification filler has a clearly visible porous structure and a crystal structure, the porous structure enables microorganisms to be attached to the surface of the filler more easily, and the crystal structure is siderite, so that the fluctuation of pH in the environment can be effectively reduced in the reaction process, and the adsorption capacity of the sulfur-iron coupled autotrophic denitrification filler is improved. And iron ions can be released to remove phosphate in water. By adding the reinforcing agent composed of titanium dioxide and hydroxyapatite, the removal effect of NO3-N or PO4 < 3-P > can be remarkably improved, in a 30-day reactor test, the effective nitrogen removal time is 711h, the effective nitrogen removal time is 683h, the requirements of sewage treatment are met, and the filler can be popularized as a novel filler.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and in particular to a sulfide-iron coupled autotrophic denitrification filler and a preparation method thereof. Background Art

[0002] The use of agricultural fertilizers and the discharge of domestic wastewater will produce a large amount of nitrogen and phosphorus-containing wastewater, which seriously pollutes water bodies. Nitrogen and phosphorus must be effectively controlled to prevent them from causing further harm to the environment and human health. In the treatment of nitrogen and phosphorus-containing wastewater, previous studies believed that nitrogen removal and phosphorus removal were two independent processes. With further research, it was found that the phosphorus concentration decreased under anoxic conditions. Subsequent studies showed that polyphosphate bacteria can absorb phosphorus using nitrate as an electron acceptor in anoxic environments, and this phenomenon has been confirmed successively. In the 1990s, KubaT et al. found that under anaerobic / anoxic operating conditions, a facultative anaerobic microorganism that can use nitrate or oxygen as an electron acceptor can be enriched. This microorganism absorbs trace amounts of phosphorus while denitrifying and is defined as a denitrifying polyphosphate bacteria. In the end, the two originally independent processes of denitrification and biological phosphorus removal were combined into one, which not only effectively overcame the contradictions between sludge age, carbon source, nitrification and denitrification, phosphorus release and phosphorus absorption in traditional biological denitrification and phosphorus removal processes, but also saved aeration volume and reduced the amount of residual sludge, and gradually became widely adopted.

[0003] Autotrophic denitrification is the process of denitrifying with CO3 2- , HCO 3- etc. as carbon sources, inorganic S 2- 、S2O3 2- , Fe, etc. are electron donors, and NO 3- -N, NO 2- -N is reduced to N2. Sulfur and iron sulfide can be used by autotrophic denitrifying bacteria (such as denitrifying Thiobacillus) to convert NO 3- -N is reduced to N2; at the same time, the acid produced by the denitrification process can promote the dissolution of pyrite, providing more sulfide and Fe 2+ As an electron donor. 2+ Oxidation produces Fe 3+ , can be used with PO4 3- The reaction generates a precipitate, achieving the purpose of simultaneously removing nitrogen and phosphorus. From the above reaction principle, it can be seen that in the autotrophic denitrification process, on the one hand, sulfur and iron need to be provided as autotrophic denitrification electron donors, and on the other hand, porous materials need to be provided as attachment sites for autotrophic denitrifying bacteria. On this basis, continuously obtaining sulfur-iron coupled autotrophic denitrification fillers with high reaction efficiency is the current research direction of wastewater treatment. Summary of the Invention

[0004] In view of the above-mentioned prior art, the object of the present invention is to provide a sulfide-iron coupled autotrophic denitrification filler and a preparation method thereof.

[0005] To achieve the above object, the present invention adopts the following technical solutions: In a first aspect of the present invention, a sulfur-iron coupled autotrophic denitrification filler is provided, wherein the sulfur-iron coupled autotrophic denitrification filler comprises sulfur, siderite, activated carbon and an enhancer; The reinforcing agent is at least one of titanium dioxide and hydroxyapatite.

[0006] Furthermore, the mass ratio of sulfur, siderite, activated carbon and enhancer is (50-100) g: (10-40) g: (1-20) g: (1-20) g.

[0007] Furthermore, the reinforcing agents are titanium dioxide and hydroxyapatite.

[0008] Furthermore, the mass ratio of titanium dioxide to hydroxyapatite is (0.5-5) g:1 g.

[0009] The second aspect of the present invention provides a method for preparing the ferrosulphur-coupled autotrophic denitrification filler, comprising the following steps: (1) crushing, grinding and screening siderite to obtain siderite powder; (2) melting the sulfur to obtain a modified sulfur melt having amorphous characteristics; (3) Mix the siderite powder, activated carbon, and enhancer in a uniform ratio, and slowly add them to the melted modified sulfur melt while stirring to obtain a mixed liquid; (4) The obtained mixed liquid is dripped into balls to obtain sulfur-iron coupled autotrophic denitrification filler.

[0010] Furthermore, in step (1), the FeCO3 content in the siderite is ≥92%, the particles are crushed to 1-10 mm, the grinding time is 2-8 h, and the sieving mesh size is 50-200 mesh.

[0011] Furthermore, in step (2), the sulfur purity is ≥90%. During the melt treatment, the heating rate is controlled to be 2-10°C / min, and the material is heated to 140-160°C under a nitrogen protective atmosphere, and the constant temperature stirring is continued for 15-60 min to form a modified sulfur melt with amorphous characteristics.

[0012] Furthermore, in step (3), stirring is performed for 10-20 min.

[0013] Furthermore, in step (4), the mixed liquid is dripped through a dripping plate with a pore size of 1-10 mm to form balls, and the temperature of the cooling water used for dripping and forming balls is 10-20°C.

[0014] The third aspect of the present invention provides the use of the ferrosulphur-coupled autotrophic denitrification filler in the treatment of nitrogen and phosphorus-containing wastewater.

[0015] Beneficial effects of the present invention: The present invention mixes titanium dioxide and hydroxyapatite to obtain an enhancer, and then compounds it with sulfur, siderite and activated carbon to finally obtain a sulfur-iron coupled autotrophic denitrification filler. From the SEM image, it can be seen that the sulfur-iron coupled autotrophic denitrification filler has a clearly visible porous structure and crystal structure. The porous structure can make it easier for microorganisms to adhere to the filler surface. The crystal structure is siderite, which can effectively reduce the pH fluctuation in the environment during the reaction process and release iron ions to remove phosphates in the water. Adding an enhancer composed of titanium dioxide and hydroxyapatite can significantly increase NO3 — N or PO4 3— The removal effect of P is shown in the 30-day reactor test, with an effective nitrogen removal time of 711h and an effective nitrogen removal time of 683h, which meets the requirements of sewage treatment and can be promoted as a new type of filler. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is the SEM image of sulfur-iron coupled autotrophic denitrification filler. DETAILED DESCRIPTION

[0017] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present application belongs.

[0018] In order to enable those skilled in the art to more clearly understand the technical solution of the present application, the technical solution of the present application will be described in detail below with reference to specific embodiments.

[0019] All experimental materials used in the examples of the present invention, not specifically described, are conventional experimental materials in the art and are commercially available. The titanium dioxide used in the present invention has a CAS number of 1317-80-2 and a particle size of approximately 21 nm, and was purchased from Guangdong Xiaoda Chemical Co., Ltd.; the hydroxyapatite used has a particle size of 60 nm and was purchased from Xi'an Wanfang Biotechnology Co., Ltd.

[0020] Example 1 Preparation of enhancer Titanium dioxide and hydroxyapatite were uniformly mixed in a mass ratio of 1 g:1 g to obtain a reinforcing agent.

[0021] Preparation of Sulfur-Iron Coupled Autotrophic Denitrification Filler The specific steps are as follows: (1) Natural siderite (FeCO3 content ≥ 92%) was crushed to particles < 5 mm by a jaw crusher and then wet ground in a planetary ball mill. After grinding for 4 h, the powder was sieved (150 mesh) to obtain a fine powder of 24.3 ± 0.8 μm.

[0022] (2) Industrial-grade sulfur (purity ≥99.9%) was melted in an electrically heated jacketed reactor. The heating rate was controlled at 5±0.5°C / min. The material was heated to 150±2°C under a nitrogen atmosphere and stirred at this constant temperature for 30 min to form a modified sulfur melt with amorphous characteristics.

[0023] (3) Prepare the materials in a mass ratio of sulfur: siderite: activated carbon: enhancer = 70:20:5:5 (all in g). Stir the siderite, activated carbon, and enhancer evenly according to the ratio and slowly add them to the melted sulfur while stirring. After stirring for about 15 minutes, a mixed liquid is obtained.

[0024] (4) Balling: The pellets are formed by dripping through a dripping orifice plate with a hole diameter of 5 mm, and the cooling water temperature is 10-20℃.

[0025] (5) Screening: The finished product is screened with a 2 mm sieve to obtain the sulfur-iron coupled autotrophic denitrification filler.

[0026] The obtained ferrosulphur-coupled autotrophic denitrification filler was observed by electron microscope. Figure 1 As shown, it can be seen from the SEM image that the sulfide-iron coupled autotrophic denitrification filler has a clearly visible porous structure and crystal structure. The porous structure can make it easier for microorganisms to adhere to the filler surface. The crystal structure is siderite, which can not only effectively reduce the pH fluctuation in the environment during the reaction process, but also release iron ions to remove phosphate in the water.

[0027] Example 2 Preparation of enhancer Titanium dioxide and hydroxyapatite were uniformly mixed in a mass ratio of 1 g:1 g to obtain a reinforcing agent.

[0028] Preparation of Sulfur-Iron Coupled Autotrophic Denitrification Filler The specific steps are as follows: (1) Natural siderite (FeCO3 content ≥ 92%) was crushed to particles < 5 mm by a jaw crusher and then wet ground in a planetary ball mill. After grinding for 4 h, the powder was sieved (150 mesh) to obtain a fine powder of 24.3 ± 0.8 μm.

[0029] (2) Industrial-grade sulfur (purity ≥99.9%) was melted in an electrically heated jacketed reactor. The heating rate was controlled at 5±0.5°C / min. The material was heated to 150±2°C under a nitrogen atmosphere and stirred at this constant temperature for 30 min to form a modified sulfur melt with amorphous characteristics.

[0030] (3) Prepare the materials in a mass ratio of sulfur: siderite: activated carbon: enhancer = 65:20:5:10 (all in g). Stir the siderite, activated carbon, and enhancer evenly according to the ratio and slowly add them to the melted sulfur while stirring. After stirring for about 15 minutes, a mixed liquid is obtained.

[0031] (4) Balling: The pellets are formed by dripping through a dripping orifice plate with a hole diameter of 5 mm, and the cooling water temperature is 10-20℃.

[0032] (5) Screening: The finished product is screened with a 2 mm sieve to obtain the sulfur-iron coupled autotrophic denitrification filler.

[0033] Example 3 Preparation of enhancer Titanium dioxide and hydroxyapatite were uniformly mixed in a mass ratio of 1 g:1 g to obtain a reinforcing agent.

[0034] Preparation of Sulfur-Iron Coupled Autotrophic Denitrification Filler The specific steps are as follows: (1) Natural siderite (FeCO3 content ≥ 92%) was crushed to particles < 5 mm by a jaw crusher and then wet ground in a planetary ball mill. After grinding for 4 h, the powder was sieved (150 mesh) to obtain a fine powder of 24.3 ± 0.8 μm.

[0035] (2) Industrial-grade sulfur (purity ≥99.9%) was melted in an electrically heated jacketed reactor. The heating rate was controlled at 5±0.5°C / min. The material was heated to 150±2°C under a nitrogen atmosphere and stirred at this constant temperature for 30 min to form a modified sulfur melt with amorphous characteristics.

[0036] (3) Prepare the materials in a mass ratio of sulfur: siderite: activated carbon: enhancer = 70:15:5:10 (all in g). Stir the siderite, activated carbon, and enhancer evenly according to the ratio and slowly add them to the melted sulfur while stirring. After stirring for about 15 minutes, a mixed liquid is obtained.

[0037] (4) Balling: The pellets are formed by dripping through a dripping orifice plate with a hole diameter of 5 mm, and the cooling water temperature is 10-20℃.

[0038] (5) Screening: The finished product is screened with a 2 mm sieve to obtain the sulfur-iron coupled autotrophic denitrification filler.

[0039] Comparative Example 1 The difference between this comparative example 1 and embodiment 1 is that no enhancer is used in the preparation process of the ferrous sulfide coupled autotrophic denitrification filler, and the specific steps are as follows: (1) Natural siderite (FeCO3 content ≥ 92%) was crushed to particles < 5 mm by a jaw crusher and then wet ground in a planetary ball mill. After grinding for 4 h, the powder was sieved (150 mesh) to obtain a fine powder of 24.3 ± 0.8 μm.

[0040] (2) Industrial-grade sulfur (purity ≥99.9%) was melted in an electrically heated jacketed reactor. The heating rate was controlled at 5±0.5°C / min. The material was heated to 150±2°C under a nitrogen atmosphere and stirred at this constant temperature for 30 min to form a modified sulfur melt with amorphous characteristics.

[0041] (3) Prepare the material according to the mass ratio of sulfur: siderite: activated carbon = 70:20:5 (all in g). Stir the siderite and activated carbon evenly according to the ratio and slowly add them to the melted sulfur while stirring. After stirring for about 15 minutes, a mixed liquid is obtained.

[0042] (4) Balling: The pellets are formed by dripping through a dripping orifice plate with a hole diameter of 5 mm, and the cooling water temperature is 10-20℃.

[0043] (5) Screening: The finished product is screened with a 2 mm sieve to obtain the sulfur-iron coupled autotrophic denitrification filler.

[0044] Comparative Example 2 The difference between this comparative example 1 and Example 1 is that, in the preparation process of the ferrous sulfide coupled autotrophic denitrification filler, titanium dioxide is used as a reinforcing agent, and the specific steps are as follows: (1) Natural siderite (FeCO3 content ≥ 92%) was crushed to particles < 5 mm by a jaw crusher and then wet ground in a planetary ball mill. After grinding for 4 h, the powder was sieved (150 mesh) to obtain a fine powder of 24.3 ± 0.8 μm.

[0045] (2) Industrial-grade sulfur (purity ≥99.9%) was melted in an electrically heated jacketed reactor. The heating rate was controlled at 5±0.5°C / min. The material was heated to 150±2°C under a nitrogen atmosphere and stirred at this constant temperature for 30 min to form a modified sulfur melt with amorphous characteristics.

[0046] (3) Prepare the materials in a mass ratio of sulfur: siderite: activated carbon: enhancer = 70:20:5:5 (all in g). Stir the siderite, activated carbon, and enhancer evenly according to the ratio and slowly add them to the melted sulfur while stirring. After stirring for about 15 minutes, a mixed liquid is obtained.

[0047] (4) Balling: The pellets are formed by dripping through a dripping orifice plate with a hole diameter of 5 mm, and the cooling water temperature is 10-20℃.

[0048] (5) Screening: The finished product is screened with a 2 mm sieve to obtain the sulfur-iron coupled autotrophic denitrification filler.

[0049] Comparative Example 3 The difference between this comparative example 1 and Example 1 is that, in the preparation process of the ferrous sulfide coupled autotrophic denitrification filler, hydroxyapatite is used as a reinforcing agent, and the specific steps are as follows: (1) Natural siderite (FeCO3 content ≥ 92%) was crushed to particles < 5 mm by a jaw crusher and then wet ground in a planetary ball mill. After grinding for 4 h, the powder was sieved (150 mesh) to obtain a fine powder of 24.3 ± 0.8 μm.

[0050] (2) Industrial-grade sulfur (purity ≥99.9%) was melted in an electrically heated jacketed reactor. The heating rate was controlled at 5±0.5°C / min. The material was heated to 150±2°C under a nitrogen atmosphere and stirred at this constant temperature for 30 min to form a modified sulfur melt with amorphous characteristics.

[0051] (3) Prepare the materials in a mass ratio of sulfur: siderite: activated carbon: enhancer = 70:20:5:5 (all in g). Stir the siderite, activated carbon, and enhancer evenly according to the ratio and slowly add them to the melted sulfur while stirring. After stirring for about 15 minutes, a mixed liquid is obtained.

[0052] (4) Balling: The pellets are formed by dripping through a dripping orifice plate with a hole diameter of 5 mm, and the cooling water temperature is 10-20℃.

[0053] (5) Screening: The finished product is screened with a 2 mm sieve to obtain the sulfur-iron coupled autotrophic denitrification filler.

[0054] Test example Small-scale dephosphorization and nitrogen removal effect test The dephosphorization and nitrogen removal effects of the ferrous sulfur-coupled autotrophic denitrification fillers prepared in Example 1 and Comparative Examples 1 to 3 were tested as follows: (1) Preparation of synthetic wastewater. Synthetic wastewater was prepared based on the concentration of the main pollutants in the secondary effluent. The composition was as follows: KNO3 0.404 g / L, KH2PO4 0.0272 g / L, NaHCO3 0.8 g / L, MgCl2·6H2O 0.1 g / L, and NH4Cl 0.1 g / L. The concentrations of nitrate and phosphate were 56 mg / L and 6.2 mg / L, respectively.

[0055] (2) Activated sludge acclimation. The activated sludge in this experiment was obtained from the anaerobic tank of the sewage treatment plant. 100 ml of activated sludge and 900 ml of liquid matrix were added to a 1 L anaerobic bottle for acclimation. The main components of the liquid matrix are as follows: Na2S2O3·5H2O (5 g / L), KNO3 (2 g / L), KH2PO4 (2 g / L), NaHCO3 (1 g / L), NH4Cl (0.5 g / L), MgCl2·6H2O (0.5 g / L), FeSO4·7H2O (0.02 g / L). After a 7-day acclimation period, the culture medium was replaced and the above steps were repeated; the nitrate nitrogen removal rate was continuously monitored during three cycles (7 days each) to ensure that the acclimation was complete.

[0056] (3) Inoculation. Add the activated sludge suspension (50 ml), sulfide-iron coupled autotrophic denitrification filler (50 g), and synthetic sewage (900 ml) to a 1000 ml conical flask. Purge the conical flask with nitrogen for 5 minutes to provide an anaerobic environment for the denitrifying microorganisms.

[0057] (4) Place the conical flask in a constant temperature shaker at 30°C and 60 rpm. Samples are taken regularly for analysis at a sampling interval of 1 h. 5 mL of the sample is drawn using a disposable syringe. After passing the sample through a 0.45 μm filter, the nitrate nitrogen and phosphate contents are rapidly determined, and the nitrogen and phosphorus removal rates are calculated.

[0058] NO3 — N or PO4 3— The time required for the P removal rate to reach 90% was recorded as the effective removal time. The shorter the time, the higher the removal efficiency, reflecting that under the current experimental conditions, the effect of sulfur-iron coupled autotrophic denitrification filler was better.

[0059] The results are shown in Table 1: Table 1: Effective removal time of nitrate nitrogen and phosphate As shown in Table 2, compared with Comparative Examples 1-3, Examples 1-3 have better effects, indicating that when preparing the sulfur-iron coupled autotrophic denitrification filler, adding a reinforcing agent composed of titanium dioxide and hydroxyapatite can significantly increase the NO3 — N or PO4 3—Among them, Example 1 has the best effect, with an effective nitrogen removal time of 54 hours and an effective nitrogen removal time of 76 hours.

[0060] Decontamination of fillers in reactors The sulfide-iron coupled autotrophic denitrification filler prepared in Example 1 and Comparative Examples 1-3 is placed in a column reactor. The column reactor is made of polymethyl methacrylate. The reactor consists of five units, each unit has a cross-sectional diameter of 10 cm and a height of 20 cm. There are five units in total, with a total height of 100 cm and an effective volume of 6.5 L. The bottom water inlet area is filled with round materials, such as small pebbles, to optimize fluid mechanics. The filler area is designed to be detachable, and the units are connected with threads to ensure air tightness. Synthetic wastewater is introduced from the water tank from bottom to top through a peristaltic pump. The synthetic wastewater includes 23 mg / L NO3 - -N, 1.5mg / LPO4 3- -P. The HRT was controlled by adjusting the speed of the peristaltic pump. During the entire experimental operation, the reactor was kept in a dark environment to prevent potential interference from photosensitive microorganisms during the experiment. At the beginning of the operation, the HRT of the reactor was set to 12h. After the microbial acclimation was completed, the HRT was set to 3h. After fifteen days of operation, backwashing was performed, including 3 minutes of air washing and 5 minutes of combined air and reflux liquid washing. The air washing flow rate was 1.0L / min, while the reflux liquid washing flow rate was 0.5L / min. The HRT after backwashing was set to 3h. Sampling was taken regularly for analysis, the nitrate nitrogen and phosphate content of the samples were measured, and the nitrogen removal rate and phosphorus removal rate were calculated. The effective removal time within the 30 days of the experiment was statistically analyzed.

[0061] The results are shown in Table 2: Table 2: Effective removal time As shown in Table 2, compared with Comparative Examples 1-3, Example 1 has a better effect, indicating that when preparing the sulfur-iron coupled autotrophic denitrification filler, adding a reinforcing agent composed of titanium dioxide and hydroxyapatite can significantly increase the NO3 — N or PO4 3— Among them, Example 1 has the best effect, with an effective nitrogen removal time of 711 hours and an effective nitrogen removal time of 683 hours.

[0062] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A ferrous sulfide coupled autotrophic denitrification filler, characterized in that: The sulfur-iron coupled autotrophic denitrification filler comprises sulfur, siderite, activated carbon and an enhancer; The reinforcing agent is at least one of titanium dioxide and hydroxyapatite.

2. The ferrosulphur-coupled autotrophic denitrification filler according to claim 1, characterized in that: The mass ratio of sulfur, siderite, activated carbon and enhancer is (50-100) g: (10-40) g: (1-20) g: (1-20) g.

3. The ferrosulphur-coupled autotrophic denitrification filler according to claim 1, characterized in that: The reinforcing agents are titanium dioxide and hydroxyapatite.

4. The ferrosulphur-coupled autotrophic denitrification filler according to claim 3, characterized in that: The mass ratio of titanium dioxide to hydroxyapatite is (0.5-5) g:1 g.

5. The method for preparing the ferrosulfur coupled autotrophic denitrification filler according to any one of claims 1 to 4, characterized in that: The steps include: (1) crushing, grinding and screening siderite to obtain siderite powder; (2) melting the sulfur to obtain a modified sulfur melt having amorphous characteristics; (3) Mix the siderite powder, activated carbon, and enhancer in a uniform ratio, and slowly add them to the melted modified sulfur melt while stirring to obtain a mixed liquid; (4) The obtained mixed liquid is dripped into balls to obtain sulfur-iron coupled autotrophic denitrification filler.

6. The method for preparing the ferrosulfur coupled autotrophic denitrification filler according to claim 5, characterized in that: In step (1), the FeCO3 content in the siderite is ≥92%, the particles are crushed to 1-10 mm, the grinding time is 2-8 h, and the sieving mesh size is 50-200 mesh.

7. The method for preparing the ferrous sulfur coupled autotrophic denitrification filler according to claim 5, characterized in that: In step (2), the sulfur purity is ≥90%. During the melt treatment, the heating rate is controlled to be 2-10 °C / min, the material is heated to 140-160 °C under a nitrogen protective atmosphere, and the constant temperature stirring is continued for 15-60 min to form a modified sulfur melt with amorphous characteristics.

8. The method for preparing the ferrosulfur coupled autotrophic denitrification filler according to claim 5, characterized in that: In step (3), stir for 10-20 min.

9. The method for preparing the ferrosulfur coupled autotrophic denitrification filler according to claim 5, characterized in that: In step (4), the mixed liquid is dripped through a dripping plate with a pore size of 1-10 mm to form balls, and the temperature of the cooling water used for dripping and forming balls is 10-20°C.

10. Use of the ferrosulfur coupled autotrophic denitrification filler according to any one of claims 1 to 4 in the treatment of nitrogen and phosphorus-containing wastewater.

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