A pyrite-based autotrophic denitrification filler, a preparation method and application thereof

Abstract

The application provides a sulfur-iron-based autotrophic denitrification filler as well as a preparation method and application thereof, and belongs to the technical field of water treatment. The sulfur-iron-based autotrophic denitrification filler provided by the application comprises a sulfur-iron-based composite carrier; the sulfur-iron-based composite carrier is composed of diatomite powder, medical stone powder, a sulfur metabolism intermediate, an oxidation-reduction mediator, sulfur powder and iron powder in a mass ratio of (20-100):(50-100):(10-20):(10-20):(100-500):(20-200). The sulfur-iron-based autotrophic denitrification filler provided by the application has a removal efficiency of NO3 ‑ N in wastewater of 98% or more and a removal efficiency of TP in wastewater of 90% or more.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of water treatment, in particular to a sulfur-iron-based autotrophic denitrification filler and a preparation method and application thereof. BACKGROUND

[0002] Agricultural fertilizer use and domestic wastewater discharge can produce a large amount of wastewater containing nitrogen and phosphorus, which seriously pollutes water bodies. It is necessary to effectively control nitrogen and phosphorus to prevent further harm to the environment and human health. The treatment method of NO3 - -N includes ion exchange method, reverse osmosis method, chemical reduction method, adsorption method and biological method. The biological denitrification process has low operation cost and does not cause secondary pollution, and is one of the most effective and feasible nitrate removal processes.

[0003] Sulfur autotrophic denitrification is under the action of Thiobacillus denitrificans, and CO3 2- , HCO3 - , etc. as carbon source, inorganic S 2- , S2O3 2- , etc. as electron donor, NO3 - -N, NO2 - -N is reduced to N2. This method often uses sulfur as electron donor, has the advantages of no need to add organic carbon source and low operation cost, and thus becomes a commonly used denitrification method in the field of wastewater treatment. However, H + is continuously produced in the process of sulfur autotrophic denitrification, which leads to low pH of effluent, and the low solubility of sulfur leads to poor electron transfer efficiency, and microorganisms are easily lost with water during operation, so it is difficult to simultaneously remove nitrogen and phosphorus, and the effluent quality is difficult to meet the wastewater discharge standard. SUMMARY

[0004] Therefore, the present application aims to provide a sulfur-iron-based autotrophic denitrification filler and a preparation method and application thereof. The sulfur-iron-based autotrophic denitrification filler provided by the present application solves the problems of low pH of effluent, low sulfur utilization rate, poor electron transfer efficiency and easy loss of denitrification bacteria in the process of sulfur autotrophic denitrification.

[0005] In order to achieve the above-mentioned purpose, the present application provides the following technical scheme: a sulfur-iron-based autotrophic denitrification filler, comprising a sulfur-iron-based composite carrier; the sulfur-iron-based composite carrier is composed of diatomite powder: rhyolite powder: sulfur metabolism intermediate: redox mediator: sulfur powder: iron powder = (20-100): (50-100): (10-20): (10-20): (100-500): (20-200) in mass ratio, preferably diatomite powder: rhyolite powder: sulfur metabolism intermediate: redox mediator: sulfur powder: iron powder = 50:80:15:15:200:100.

[0006] The added medical stone and diatomite in the invention can adsorb organic matters, heavy metals and other harmful substances in water, and the microporous structure of diatomite can adsorb microorganisms for their attachment growth, the medical stone has the effect of adjusting pH, and can increase the alkalinity of water body; the added sulfur metabolism intermediate can promote the conversion of sulfur into polysulfide and accelerate the dissolution of sulfur; and the added oxidation-reduction mediator can accelerate the electron transfer rate and enhance the microbial activity.

[0007] In the invention, the addition of appropriate amount of iron powder can improve the denitrification and phosphorus removal performance of the sulfur-iron-based autotrophic denitrification filler, but when the iron powder is excessive, it will cause the denitrification capacity of the system to decrease sharply, which may be caused by the strong reducing property of iron leading to the instability of the system. Therefore, the control of the content of iron powder is the key to the preparation of the filler, and therefore, the invention preferably has the above mass ratio range.

[0008] Preferably, the sulfur metabolism intermediate is L-cysteine or DL-cysteine.

[0009] Preferably, the oxidation-reduction mediator is fulvic acid (FA) or anthraquinone-2,6-disulfonic acid (AQDS).

[0010] Preferably, the sulfur-iron-based autotrophic denitrification filler further comprises an artificial biofilm, and the artificial biofilm coats the sulfur-iron-based composite carrier; the artificial biofilm is composed of denitrifying sulfur bacteria, iron autotrophic denitrifying bacteria and sodium alginate.

[0011] The invention attaches an artificial biofilm to the surface of the sulfur-iron-based composite carrier, which can avoid the loss of denitrifying bacteria and accelerate the denitrification rate.

[0012] Further preferably, the thickness of the artificial biofilm is 100±5um.

[0013] Further preferably, the preparation method of the denitrifying sulfur bacteria and the iron autotrophic denitrifying bacteria is as follows: the denitrifying sulfur bacteria and the iron autotrophic denitrifying bacteria are respectively inoculated into a liquid culture medium, and then placed in a shaking bed at 30℃ for one week, and when the denitrifying sulfur bacteria and the iron autotrophic denitrifying bacteria are in logarithmic growth, the bacterial suspension is collected by centrifugation.

[0014] Further preferably, the composition and content of the denitrifying sulfur bacteria liquid culture medium are as follows: 5g / L Na2S2O3·5H2O, 2g / L KNO3, 2g / L KH2PO4, 1g / L NaHCO3, 0.05g / L MgCl2·6H2O, 0.05g / L NH4Cl, and 0.001g / L FeSO4·7H2O.

[0015] The iron autotrophic denitrification bacteria liquid culture medium components and contents are: 0.216 g / L KNO3, 0.017 g / L K2HPO4, 0.024 g / L MgCl2·6H2O, 0.020 g / L CaCl2·2H2O, 0.2 g / L NaHCO3, and 0.407 g / L FeCl3·6H2O.

[0016] The application further provides a preparation method of the sulfur-iron-based autotrophic denitrification filler, comprising the following steps:

[0017] The diatomite powder, the cornelian chalcedony powder, the sulfur metabolism intermediate, the redox mediator, the sulfur powder and the iron powder are mixed according to the mass ratio, water is added, stirring is conducted, a paste is obtained, and then the paste is dried to obtain a sulfur-iron-based composite carrier;

[0018] The denitrifying sulfur bacteria suspension, the iron autotrophic denitrification bacteria suspension and the sodium alginate solution are mixed, the mixture is spin-coated on the surface of the sulfur-iron-based composite carrier, then the mixture is immersed into a calcium chloride solution to complete a cross-linking reaction, and cold storage solidification is conducted to obtain the sulfur-iron-based autotrophic denitrification filler.

[0019] Preferably, the volume ratio of the denitrifying sulfur bacteria suspension, the iron autotrophic denitrification bacteria suspension and the sodium alginate solution is (1-2):1:(2-3), and the mass fraction of sodium alginate in the sodium alginate solution is 2-5%.

[0020] Preferably, the mass fraction of the calcium chloride solution is 0.5-2%.

[0021] The sulfur-iron-based autotrophic denitrification filler prepared by the method has a particle size of 2-5 mm and a weight of about 0.1 g.

[0022] The application further provides application of the sulfur-iron-based autotrophic denitrification filler in denitrification and dephosphorization water treatment.

[0023] Beneficial technical effects:

[0024] The sulfur-iron-based autotrophic denitrification filler provided by the application uses elemental sulfur and elemental iron as electron donors, iron ions and phosphate ions generate a precipitate, and the purpose of simultaneous denitrification and dephosphorization can be achieved; the cornelian chalcedony and diatomite are introduced, which can not only adjust the pH of the system, but also can adsorb a large amount of microorganisms to make the microorganisms adhere to the carrier and grow; the sulfur metabolism intermediate is added to promote the conversion of sulfur into polysulfides and improve the bioavailability of sulfur; the redox mediator is added to accelerate the electron transfer rate; in addition, the artificial biofilm is attached to the surface of the sulfur-iron-based composite carrier, which avoids the loss of denitrifying bacteria and thus accelerates the denitrification rate and improves the denitrification efficiency.

[0025] The sulfur-iron-based autotrophic denitrification filler provided by the application can remove NO3 -The removal efficiency of N is more than 98%, and the removal efficiency of TP in sewage is more than 90%. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0027] Figure 1 It is a schematic diagram of the denitrification and phosphorus removal device in the present application, wherein 1 is a water inlet tank, 2 is a water inlet pipe, 3 is a peristaltic pump, 4 is a ferrous sulfide-based autotrophic denitrification filler, 5 is an overflow weir, 6 is an exhaust hole, 7 is a water outlet, 8 is a water outlet pipe, and 9 is a water outlet tank.

[0028] Figure 2 It is a comparison diagram of the removal rate of nitrate by using the ferrous sulfide-based autotrophic denitrification filler obtained in Example 1 and a commercially available product.

[0029] Figure 3 It is a comparison diagram of the phosphorus removal effect by using the ferrous sulfide-based autotrophic denitrification filler obtained in Example 1 and a commercially available product. DETAILED DESCRIPTION

[0030] Various illustrative embodiments of the present application are described in detail below, which should not be considered as limiting the present application, but should be understood as a more detailed description of some aspects, characteristics and embodiments of the present application.

[0031] It should be understood that the terms described in the present application are only for describing the specific embodiments, and are not used to limit the present application. In addition, for the numerical range in the present application, it should be understood that each intermediate value between the upper limit and the lower limit of the range is also specifically disclosed. Each smaller range between any stated value or intermediate value in the stated range, and any other stated value or intermediate value in the stated range, is also included in the present application. The upper limit and the lower limit of these smaller ranges can be independently included or excluded from the range.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials in connection with which the documents are concerned. In the event of any conflict between the content of this specification and the documents incorporated by reference, the content of this specification will control.

[0033] Many modifications and variations to the illustrative embodiments described herein will be apparent to those of ordinary skill in the art from this specification, which is to be regarded in an illustrative manner. Other embodiments will be apparent to those of ordinary skill in the art from consideration of the specification and practice of the subject matter disclosed herein. The specification and examples are illustrative only.

[0034] As used herein, the terms "comprise", "comprising", "include", "including", "have", "having" and the like are open-ended and do not exclude additional, unrecited elements or method steps.

[0035] The present application provides a sulfur-iron-based autotrophic denitrification filler, comprising a sulfur-iron-based composite carrier and an artificial biofilm, the composite carrier is prepared from diatomite powder, medical stone powder, sulfur metabolism intermediates, redox mediators, sulfur powder and iron powder; the artificial biofilm is composed of denitrifying sulfur bacteria, iron autotrophic denitrifying bacteria and sodium alginate. The preparation method of the sulfur-iron-based autotrophic denitrification filler comprises the following specific steps:

[0036] (1) Mix diatomite powder, medical stone powder, sulfur metabolism intermediates, redox mediators, sulfur powder and iron powder according to a mass ratio of (20-100):(50-100):(10-20):(10-20):(100-500):(20-200), stir uniformly, add an appropriate amount of water, continue to stir until fully mixed, and obtain a paste, wherein the sulfur metabolism intermediates are L-cysteine or DL-cysteine, and the redox mediators are FA or AQDS;

[0037] (2) Pour the paste into a round tablet mold, naturally dry and fix and form at room temperature, naturally dry after pouring out of the mold, and obtain the sulfur-iron-based composite carrier filler;

[0038] (3) Inoculate the denitrifying sulfur bacteria and the iron autotrophic denitrifying bacteria into liquid culture media respectively, place them in a 30℃ shaking table, culture for one week, and collect the bacterial suspension by centrifugation at 7000 rpm / min for 5 min when the denitrifying sulfur bacteria and the iron autotrophic denitrifying bacteria are in logarithmic growth;

[0039] The liquid culture medium of the denitrifying sulfur bacteria comprises 5g / L Na2S2O3·5H2O, 2g / L KNO3, 2g / L KH2PO4, 1g / L NaHCO3, 0.05g / L MgCl2·6H2O, 0.05g / L NH4Cl and 0.001g / L FeSO4·7H2O.

[0040] Iron autotrophic denitrifying bacteria liquid medium: 0.216 g / L KNO3, 0.017 g / L K2HPO4, 0.024 g / L MgCl2·6H2O, 0.020 g / L CaCl2·2H2O, 0.2 g / L NaHCO3, 0.407 g / L FeCl3·6H2O;

[0041] (4) The denitrifying bacteria suspension, the iron autotrophic denitrifying bacteria suspension and the 2-5wt% sodium alginate solution are completely mixed according to the volume ratio of (1-2):1:(2-3), then 0.1mL of the mixture is extracted by using a 1mL syringe and transferred to the prepared sulfur-iron-based composite carrier filler, and rotated at 350rpm / min for 9s on a rotary coater to ensure that the biofilm is uniformly distributed on the sulfur-iron-based composite carrier filler;

[0042] (5) The sulfur-iron-based composite carrier filler coated with the biofilm coating is immersed in a 0.5-2wt% CaCl2 solution for 10s to complete the cross-linking reaction, and is refrigerated and solidified for 24h to obtain the sulfur-iron-based autotrophic denitrification filler.

[0043] The municipal sewage plant secondary sedimentation tank return sludge is inoculated, simulated wastewater is introduced as influent, and the sulfur-iron-based autotrophic denitrification filler of the present application is added into the reaction column as shown in the figure to carry out the wastewater denitrification and phosphorus removal treatment. Figure 1

[0044] In order to better understand the present application, the content of the present application is further illustrated below in combination with examples, but the content of the present application is not limited to the following examples only.

[0045] The instruments and reagents used in the examples can be obtained through the market channel if no special instructions are given.

[0046] Example 1

[0047] A preparation method of a sulfur-iron-based autotrophic denitrification filler, the steps are as follows:

[0048] (1) The diatomite powder, the rhyolite powder, the DL-cysteine, the fulvic acid, the sulfur powder and the iron powder are mixed, stirred uniformly according to the mass ratio of 50:80:15:15:200:100, an appropriate amount of water is added, and the stirring is continuously carried out until the mixture is fully mixed to obtain a paste.

[0049] (2) The paste is poured into a round piece mold, naturally dried and fixed and shaped at room temperature, naturally dried after being poured out of the mold to obtain a sulfur-iron-based composite carrier filler.

[0050] ​(3) The Thiobacillus denitrificans and the iron autotrophic denitrifying bacteria were inoculated into liquid culture medium respectively, and were placed in a shaking bed at 30℃ and cultured for one week. When the Thiobacillus denitrificans and the iron autotrophic denitrifying bacteria were in logarithmic growth phase, the bacterial suspension was collected by centrifugation at 7000 rpm / min for 5 min;

[0051] The composition and content of the Thiobacillus denitrificans liquid culture medium are as follows: 5 g / L Na2S2O3·5H2O, 2 g / L KNO3, 2 g / L KH2PO4, 1 g / L NaHCO3, 0.05 g / L MgCl2·6H2O, 0.05 g / L NH4Cl, and 0.001 g / L FeSO4·7H2O.

[0052] The composition and content of the Thiobacillus denitrificans liquid culture medium are as follows: 5 g / L Na2S2O3·5H2O, 2 g / L KNO3, 2 g / L KH2PO4, 1 g / L NaHCO3, 0.05 g / L MgCl2·6H2O, 0.05 g / L NH4Cl, and 0.001 g / L FeSO4·7H2O.

[0053] (4) The Thiobacillus denitrificans suspension and the iron autotrophic denitrifying bacteria suspension were completely mixed with 2wt% sodium alginate solution at a volume ratio of 2:1:3. Then, 0.1 mL of the mixture was extracted with a 1 mL syringe and transferred to the prepared sulfur-iron-based composite carrier filler, and was rotated at 350 rpm / min for 9 s on a rotary coater to ensure that the biofilm was uniformly distributed on the sulfur-iron-based composite carrier filler.

[0054] (5) The sulfur-iron-based composite carrier filler coated with the biofilm coating layer was immersed in a 0.5wt% CaCl2 solution for 10 s to complete the cross-linking reaction, and was refrigerated and solidified for 24 h to obtain the sulfur-iron-based autotrophic denitrification filler.

[0055] The secondary sedimentation tank backflow sludge of a municipal sewage treatment plant was inoculated, and simulated wastewater was introduced as influent, and the filler of the present embodiment was added to the reaction column as shown in Figure 1 The denitrification effect of the filler of the present embodiment was compared with that of four fillers widely used on the market (filler 1 mainly contains sulfur; filler 2 mainly contains sulfur and pyrite; filler 3 contains effective iron powder; and filler 4 mainly contains siderite; and a blank control, i.e., no filler, was also performed). A multi-channel peristaltic pump was used to control the uniform flow rate of the influent of each reaction column, and the influent flow rate was adjusted in time according to the effluent quality. The treatment effect is shown in Figure 2 and Figure 3 It can be seen that the filler in Example 1 has better denitrification performance and phosphorus removal effect.

[0056] Example 2

[0057] The same as example 1, except that the mass ratio of diatomite powder, tripolite powder, DL-cysteine, fulvic acid, sulfur powder and iron powder is 50:80:15:15:100:60.

[0058] Example 3

[0059] The same as example 1, except that the mass ratio of diatomite powder, tripolite powder, DL-cysteine, fulvic acid, sulfur powder and iron powder is 100:100:20:20:300:100.

[0060] Example 4

[0061] The same as example 1, except that the mass fraction of sodium alginate solution is 5%.

[0062] Example 5

[0063] The same as example 1, except that the volume ratio of Thiobacillus denitrificans suspension, iron autotrophic denitrifying bacteria suspension and sodium alginate solution is 1:1:2.

[0064] Example 6

[0065] The same as example 1, except that the mass fraction of CaCl2 solution is 2%.

[0066] Comparative example 1

[0067] The same as example 1, except that no iron powder is added in step (1).

[0068] Comparative example 2

[0069] The same as example 1, except that the amount of iron powder added in step (1) is 10 times that of example 1.

[0070] Comparative example 3

[0071] The same as example 1, except that no tripolite is added in step (1).

[0072] Comparative example 4

[0073] The same as example 1, except that no sulfur metabolism intermediate and redox mediator is added in step (1).

[0074] The sulfur-iron-based autotrophic denitrification fillers prepared by examples 1-6 and comparative examples 1-4 are used for denitrification and phosphorus removal water treatment, and the experimental data of denitrification performance are shown in table 1.

[0075] Table 1

[0076]

[0077]

[0078] As can be seen from Table 1, adding an appropriate amount of iron powder can improve the denitrification and phosphorus removal performance, and excessive iron powder will cause the denitrification capacity of the system to decrease sharply, which may be due to the strong reducing property of iron leading to system instability, and therefore controlling the content of iron powder is the key to preparing the filler. Example 3 shows that the nitrogen removal rate of the system without adding medical stone decreases, which may be due to the accumulation of H2S caused by the sulfur autotrophic denitrification process. Example 4 shows that the nitrogen and phosphorus removal rates of the system decrease without adding the sulfur metabolism intermediates and redox mediators, which may be due to the fact that sulfur is not easy to be converted into polysulfides, which is difficult to be utilized by microorganisms, and the slow electron transfer rate leads to the decrease of the denitrification and phosphorus removal rate of the system. +

[0079] The above only describes the preferred embodiments of the present application, and it should be noted that for those skilled in the art, some improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements should also be considered as the protection scope of the present application.​

Claims

1. A sulfur-iron-based autotrophic denitrification packing material, characterized in that, The product contains a sulfur-iron-based composite carrier; the sulfur-iron-based composite carrier is composed of diatomaceous earth powder: maifanite powder: sulfur metabolism intermediate: redox mediator: sulfur powder: iron powder in a mass ratio of (20-100): (50-100): (10-20): (10-20): (100-500): (20-200); The sulfur metabolism intermediate is L-cysteine ​​or DL-cysteine. The redox mediator is fulvic acid or anthraquinone-2,6-disulfonic acid; It also includes an artificial biofilm, which coats the sulfur-iron-based composite carrier; the artificial biofilm is composed of denitrifying sulfur bacteria, iron-autotrophic denitrifying bacteria and sodium alginate.

2. The sulfur-iron-based autotrophic denitrification packing material according to claim 1, characterized in that, The thickness of the artificial biomembrane is 100±5 μm.

3. The sulfur-iron-based autotrophic denitrification packing material according to claim 1, characterized in that, The preparation method of the denitrifying sulfur bacteria and ferroautotrophic denitrifying bacteria is as follows: the denitrifying sulfur bacteria and ferroautotrophic denitrifying bacteria are inoculated into liquid culture medium respectively, and then placed in a shaker at 30°C for one week. When the denitrifying sulfur bacteria and ferroautotrophic denitrifying bacteria show logarithmic growth, the bacterial suspension is collected by centrifugation.

4. The sulfur-iron-based autotrophic denitrification packing material according to claim 3, characterized in that, The composition and content of the liquid culture medium for *Thiobacillus denitrifyingus* are as follows: 5 g / L Na₂S₂O₃·5H₂O, 2 g / L KNO₃, 2 g / L KH₂PO₄, 1 g / L NaHCO₃, 0.05 g / L MgCl₂·6H₂O, 0.05 g / L NH₄Cl, 0.001 g / L FeSO₄·7H₂O; The composition and content of the iron-autotrophic denitrifying bacteria liquid culture medium are as follows: 0.216 g / L KNO3, 0.017 g / L K2HPO4, 0.024 g / L MgCl2·6H2O, 0.020 g / L CaCl2·2H2O, 0.2 g / L NaHCO3, and 0.407 g / L FeCl3·6H2O.

5. The method for preparing the sulfur-iron-based autotrophic denitrification packing material according to any one of claims 1-4, characterized in that, Includes the following steps: Diatomaceous earth powder, maifanite powder, sulfur metabolism intermediate, redox mediator, sulfur powder, and iron powder are mixed in a certain mass ratio, water is added, and the mixture is stirred to obtain a paste. The paste is then dried to obtain a sulfur-iron-based composite carrier. Suspension of denitrifying thiobacillus, suspension of iron-autotrophic denitrifying bacteria, and sodium alginate solution were mixed. The mixture was then spin-coated onto the surface of the sulfur-iron-based composite carrier and immersed in CaCl2 solution to complete the cross-linking reaction. After cold curing, sulfur-iron-based autotrophic denitrification filler was obtained.

6. The preparation method according to claim 5, characterized in that, The volume ratio of the denitrifying thiobacillus suspension, the iron-autotrophic denitrifying bacteria suspension, and the sodium alginate solution is (1-2):1:(2-3); the mass fraction of sodium alginate in the sodium alginate solution is 2-5%.

7. The application of the sulfur-iron-based autotrophic denitrification packing material according to any one of claims 1-4 in denitrification and phosphorus removal water treatment.

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