A bio-iron sulfide composite filler, its preparation method and application

Abstract

This invention relates to the field of wastewater treatment materials technology, and discloses a bio-iron sulfide composite packing material, its preparation method, and its application. The raw materials for preparing the bio-iron sulfide composite packing material of this invention include limestone gravel, iron hydroxyl oxide, nutrient solution I, and sulfate-reduced sludge; wherein the limestone gravel contains 70%–80% limestone by mass. This composite packing material not only has a simple preparation process, low cost, and readily available raw materials, but also allows the immobilized and adsorbed sulfate to be recycled in the secondary bio-sulfidation stage, achieving sulfur recycling and effectively avoiding secondary pollution problems caused by excessive sulfate production.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment materials technology, and in particular to a bio-iron sulfide composite packing material, its preparation method, and its application. Background Technology

[0002] With the continuous development of human industry, nitrogen and phosphorus elements in natural water bodies have suffered severe damage. Excessive nitrogen and phosphate discharges into natural water bodies have caused serious harm to ecosystems and human health. These excess nitrogen and phosphorus accumulate in water, leading to eutrophication, excessive algal growth, harming fish and other aquatic organisms, and causing serious environmental problems. Biological treatment technology is currently mainly used to remove nitrogen and phosphorus from wastewater due to its advantages of mild reaction conditions, inexpensive and readily available raw materials, significant effects, and low investment costs. However, because urban wastewater treatment often results in low carbon-to-nitrogen ratios (C / N), traditional wastewater treatment processes require the addition of additional carbon sources or the use of chemical reagents to enhance nitrogen and phosphorus removal in order to meet strict nitrogen and phosphorus discharge standards. However, these processes still suffer from problems such as high energy consumption, high costs, large land area requirements, inadequate nitrogen and phosphorus removal efficiency, and unstable effluent quality, which urgently need to be addressed.

[0003] Related studies have shown that using natural pyrite compounds for enhanced nitrogen and phosphorus removal can effectively solve the aforementioned problems. This method is based on the traditional activated sludge process, introducing nitrogen and phosphorus removal technology at the end of secondary treatment. It utilizes pyrite compounds as electron donors, achieving biological nitrogen removal without an external carbon source through a sulfur autotrophic denitrification process. Simultaneously, precipitation occurs through the interaction between iron and phosphorus, achieving chemically enhanced phosphorus removal. However, this method still faces some unresolved issues. For example, natural pyrite has low activity, and the autotrophic denitrification rate of microorganisms is very slow, typically requiring more than one day of hydraulic retention time. To improve the nitrogen removal efficiency of natural pyrite, methods such as reducing packing size and surface modification are needed, which increases the overall process cost, making it impractical for wastewater treatment projects. Furthermore, during denitrification, a large amount of reduced sulfur is oxidized to sulfate. If not removed in time, this sulfate will be directly discharged into water bodies, causing a series of environmental pollution problems such as black and odorous water bodies.

[0004] Therefore, there is an urgent need to find a wastewater treatment material that is efficient, low-energy, and does not cause secondary pollution, in order to alleviate environmental pollution pressure. Summary of the Invention

[0005] This invention aims to solve at least one of the technical problems existing in the prior art. To this end, this invention proposes a bio-sulfided iron composite filler, its preparation method, and its application. This composite filler not only has a simple preparation process, low cost, and readily available raw materials, but also allows the sulfate that has been immobilized and adsorbed to be recycled in the re-biosulfidation stage, thus realizing the recycling of sulfur and effectively avoiding the secondary pollution problem caused by excessive sulfate production.

[0006] The present invention also proposes a method for preparing the above-mentioned bio-iron sulfide composite filler.

[0007] The present invention also proposes a method for recycling the above-mentioned bio-sulfide iron composite packing.

[0008] The present invention also proposes a wastewater treatment method.

[0009] The present invention also proposes the application of the above-mentioned bio-iron sulfide composite packing material and its preparation method or recycling method in wastewater treatment.

[0010] In a first aspect, the present invention provides a bio-iron sulfide composite packing material, the raw materials for which include limestone gravel, iron hydroxyl oxide, nutrient solution I, and sulfate-reduced sludge.

[0011] The limestone gravel contains 70% to 80% limestone by mass.

[0012] The composite filler according to embodiments of the present invention has at least the following beneficial effects:

[0013] (1) The bio-sulfided iron composite packing of the present invention can be used as an electron donor for sulfur autotrophic denitrification, realizing enhanced nitrogen and phosphorus removal without the need for carbon sources and chemical reagents. In the context of low C / N ratio in urban sewage today, compared with traditional biological denitrification methods, it does not require the addition of an additional organic carbon source as an electron donor, and it has its own phosphorus removal function, so there is no need to add additional chemical reagents for phosphorus removal.

[0014] (2) The bio-sulfide iron composite packing of the present invention contains gravel containing limestone, which has a good adsorption effect on sulfate under neutral conditions. The sulfate produced during the denitrification process will be fixed on the surface of the material and will not be directly discharged into the water body. This greatly avoids secondary pollution problems such as black and odorous water bodies caused by excessive sulfate discharge. The effect is significantly better than that of ordinary gravel. Moreover, the fixed sulfate can be used again in the material regeneration step after denitrification. Therefore, the composite packing of the present invention also has the excellent characteristics of being recyclable and regenerable.

[0015] (3) The raw materials of the bio-sulfided iron composite filler of the present invention are simple and readily available, with low preparation cost and good industrial application value.

[0016] In some embodiments of the present invention, the iron hydroxyoxide includes at least one of α-FeOOH, β-FeOOH, γ-FeOOH, δ-FeOOH, and amorphous FeOOH.

[0017] In some embodiments of the present invention, the nutrient salt solution I comprises 0.05–0.2 g / L yeast extract, 3.5–4.5 mL / L sodium lactate, 0.05–0.2 g / L ascorbic acid, 0.1–1.2 g / L cysteine ​​hydrochloride, 0.5–1.5 g / L NH4Cl, 0.5–1.5 g / L Na2SO4, 1.5–2.5 g / L MgSO4·7H2O, and 0.05–0.2 g / L CaCl2·2H2O.

[0018] In some embodiments of the present invention, the nutrient salt solution I comprises 0.05–0.1 g / L yeast extract, 3.5–4 mL / L sodium lactate, 0.05–0.1 g / L ascorbic acid, 0.1–1.0 g / L cysteine ​​hydrochloride, 0.5–1.0 g / L NH4Cl, 0.5–1.0 g / L Na2SO4, 1.5–2.0 g / L MgSO4·7H2O, and 0.05–0.1 g / L CaCl2·2H2O.

[0019] In some embodiments of the present invention, the final concentration of sulfate ions in the nutrient solution I is 1.2 to 1.8 g / L.

[0020] In some embodiments of the present invention, the solvent in the nutrient solution I is water, preferably deionized water.

[0021] In some embodiments of the present invention, the sulfate-reducing sludge is obtained by acclimating anaerobic sludge from a wastewater treatment plant and enriching it with sulfate-reducing bacteria.

[0022] In some embodiments of the present invention, the wastewater treatment plant is a municipal wastewater treatment plant.

[0023] In some embodiments of the present invention, the wastewater treatment plant employs the A2 / O process.

[0024] In some embodiments of the present invention, the specific preparation method of the sulfate-reducing sludge includes: placing anaerobic sludge obtained from a wastewater treatment plant in an anaerobic reactor for acclimation, enriching sulfate-reducing bacteria, and when the effluent S 2- When the concentration tends to be stable and is above 200 mg / L, let it stand and collect the precipitate.

[0025] In some embodiments of the present invention, the anaerobic reactor operates in a semi-continuous mode, the influent formula uses a special culture medium for sulfate-reducing bacteria, the hydraulic retention time is 10-12 hours, and the sludge retention time is 10-12 hours.

[0026] In some embodiments of the present invention, the sulfate-reducing bacteria culture medium comprises 3-5 mL / L sodium lactate, 0.5-1.5 g / L NH4Cl, 0.3-0.7 g / L KH2PO4, 0.5-1.5 g / L Na2SO4, 2.0 g / L MgSO4·7H2O, 0.05-0.15 g / L CaCl2·H2O, 0.05-0.15 g / L ascorbic acid, 0.5-1.5 g / L yeast extract, and 0.3-0.7 g / L cysteine ​​hydrochloride.

[0027] A second aspect of the present invention provides a method for preparing the bio-iron sulfide composite filler described in the first aspect, comprising the following steps:

[0028] S1. Disperse the sulfate-reduced sludge in the nutrient solution I to obtain a sulfate-reduced sludge mixture;

[0029] S2. Under solvent conditions, the hydroxyl iron oxide is mixed with the limestone gravel, and then the sulfate-reduced sludge mixture is added to obtain a limestone gravel / bio-iron sulfide mixture.

[0030] S3. The limestone gravel / bio-iron sulfide mixture is cultured, and the solid phase is collected after solid-liquid separation.

[0031] According to the preparation method of the present invention, it has at least the following beneficial effects: the bio-sulfide iron composite filler of the present invention is prepared by a biochemical synthesis method of sulfur reduction, and its preparation method is simple and suitable for industrial production.

[0032] In some embodiments of the present invention, the dispersion method includes magnetic stirring.

[0033] In some embodiments of the present invention, the solvent includes deionized water.

[0034] In some embodiments of the present invention, the final concentration of ferric hydroxide in the limestone gravel / bio-iron sulfide mixture is 6-8 g / L;

[0035] And / or, the final concentration of the limestone gravel is 80–120 g / L.

[0036] In some embodiments of the present invention, the final concentration of ferric hydroxide in the limestone gravel / bio-ferric sulfide mixture is 6-7.5 g / L;

[0037] And / or, the final concentration of the limestone gravel is 80–110 g / L.

[0038] In some embodiments of the present invention, the sulfur-to-iron ratio (S / Fe) in the limestone gravel / bio-iron sulfide mixture is 1:(5-10).

[0039] When the sulfur-to-iron ratio is too low, the sulfur anions produced by the reduction of biological sulfur cannot fully react with iron to form ferric sulfide hydroxyl oxide, and some sulfur anions will form hydrogen sulfide and be lost into the air.

[0040] In some embodiments of the present invention, the mixed liquid volatile suspended solids (MLVSS) concentration of the sulfate-reduced sludge in the limestone gravel / bio-iron sulfide mixture is 3 g / L to 5 g / L.

[0041] In some embodiments of the present invention, the solid-liquid separation method includes centrifugation.

[0042] In some embodiments of the present invention, the centrifugation speed is 5000-8000 rpm, preferably 6000 rpm.

[0043] In some embodiments of the present invention, the centrifugation time is 2 to 8 minutes, preferably 5 minutes.

[0044] In some embodiments of the present invention, the culture temperature is 25–35°C.

[0045] In some embodiments of the present invention, the stirring speed during cultivation is 400 to 500 rpm.

[0046] In a third aspect, the present invention provides a method for recovering the bio-iron sulfide composite packing described in the first aspect, wherein the bio-iron sulfide composite packing after biological denitrification treatment is mixed with nutrient salt solution II, and the solid phase is collected after solid-liquid separation.

[0047] In some embodiments of the present invention, the nutrient salt solution II comprises 0.05–0.2 g / L yeast extract, 3.5–4.5 mL / L sodium lactate, 0.05–0.2 g / L ascorbic acid, 0.1–1.2 g / L cysteine ​​hydrochloride, 0.5–1.5 g / L NH4Cl, and 0.05–0.2 g / L CaCl2·2H2O.

[0048] In some embodiments of the present invention, the solvent in the nutrient solution II is water, preferably deionized water.

[0049] A fourth aspect of the present invention provides a wastewater treatment method, comprising contacting the bio-iron sulfide composite packing material described in the first aspect or the bio-iron sulfide composite packing material obtained by the recovery method described in the third aspect with wastewater.

[0050] In a fifth aspect, the present invention provides an application of the bio-iron sulfide composite packing described in the first aspect, the preparation method described in the second aspect, or the recovery method described in the third aspect in wastewater treatment.

[0051] In some embodiments of the present invention, the wastewater treatment includes nitrogen removal.

[0052] In some embodiments of the present invention, the denitrification includes the removal of nitrate nitrogen.

[0053] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. Attached Figure Description

[0054] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein:

[0055] Figure 1 This is a statistical chart showing the change in nitrate nitrogen concentration during the denitrification process of the present invention using bio-sulfided iron composite packing (experimental group) and ordinary gravel mixed sulfided hydroxyl iron oxide packing (control group).

[0056] Figure 2 This is a statistical chart showing the changes in sulfate ion concentration during the denitrification process of the present invention using bio-sulfided iron composite packing (experimental group) and ordinary gravel mixed sulfided hydroxyl oxide packing (control group).

[0057] Figure 3 This is a statistical chart showing the change in nitrate nitrogen concentration during the denitrification process of the regenerated bio-iron sulfide composite packing material in an embodiment of the present invention.

[0058] Figure 4 This is a statistical chart showing the change in sulfate ion concentration during the denitrification process of the regenerated bio-iron sulfide composite packing material in an embodiment of the present invention. Detailed Implementation

[0059] The following will describe the concept and technical effects of the present invention clearly and completely with reference to embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0060] The terms "preferred," "more preferably," etc., used in this invention refer to embodiments of the invention that provide certain beneficial effects under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of this invention.

[0061] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0062] In the description of this invention, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0063] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0064] Example 1: Preparation of bio-iron sulfide composite packing

[0065] This embodiment provides a method for preparing a bio-iron sulfide composite filler, which specifically includes the following contents.

[0066] 1. Preparation of sulfate-reduced sludge

[0067] The sulfate-reducing bacteria used in this example were enriched and cultured from anaerobic sludge in a municipal wastewater treatment plant in Zhongshan City, Guangdong Province (the wastewater treatment plant uses the A2 / O process). The anaerobic sludge was placed in a special medium for sulfate-reducing bacteria for acclimatization and cultivation. The medium consisted of 3.84 mL / L sodium lactate, 1.0 g / L NH4Cl, 0.5 g / L KH2PO4, 1.0 g / L Na2SO4, 2.0 g / L MgSO4·7H2O, 0.1 g / L CaCl2·H2O, 0.1 g / L ascorbic acid, 1.0 g / L yeast extract, and 0.5 g / L cysteine ​​hydrochloride. 1000 mL blue-capped bottles were used for culturing the sulfate-reducing bacteria. Deionized water was used throughout the cultivation process. The cultivation conditions included magnetic stirring at 25°C and a rotation speed of 500 rpm. Water samples from the sludge culture vessel were measured every two days, and the effluent sulfur content (S) was measured. 2- Once the concentration stabilizes and exceeds 200 mg / L, the supernatant is removed after standing to obtain sulfate-reduced sludge.

[0068] 2. Preparation of sulfide ferric hydroxide filler

[0069] The method for preparing sulfide hydroxyl iron oxide filler in this embodiment includes the following steps:

[0070] Step S1: Take a well-active sulfate-reduced sludge (MLVSS of 4 g / L), let it stand, and remove the supernatant. Disperse the sulfate-reduced sludge into nutrient solution I, which specifically contains 0.1 g / L yeast extract, 4.0 mL / L sodium lactate, 0.1 g / L ascorbic acid, 0.5 g / L cysteine ​​hydrochloride, 1.0 g / L NH4Cl, 1.0 g / L Na2SO4, 2.0 g / L MgSO4·7H2O, and 0.1 g / L CaCl2·2H2O. Control the SO42- content in nutrient solution I. 2- A sulfate-reduced sludge mixture was obtained with a concentration of 1.45 g / L, wherein the MLVSS of the mixed sulfate-reduced sludge was 4 g / L.

[0071] Step S2: Take iron hydroxyl oxide powder (final concentration 6.8 g / L) and limestone-containing gravel (final concentration 108.8 g / L, limestone mass fraction in limestone gravel is 73%) and mix them in deionized water so that the iron hydroxyl oxide powder can fully adhere to the surface of the gravel to obtain limestone gravel / iron hydroxyl oxide composite.

[0072] Step S3: Mix the above limestone gravel / ferric hydroxide composite with the above sulfate-reduced sludge mixture, and incubate at 25°C with magnetic stirring at 400-500 rpm for 48 hours. Centrifuge at 6000 rpm for 5 minutes and collect the precipitate to obtain the biological iron sulfide composite packing.

[0073] Example 2: Recycling method of bio-iron sulfide composite packing

[0074] This embodiment provides a method for regenerating the bio-iron sulfide composite packing after biological denitrification treatment as described in Example 1 above. Specifically, it includes: firstly, separating the bio-iron sulfide composite packing after biological denitrification treatment and mixing it with nutrient solution II. The specific components of nutrient solution II are: 0.1 g / L yeast extract, 3.84 mL / L sodium lactate, 0.1 g / L ascorbic acid, 0.5 g / L cysteine ​​hydrochloride, 1.0 g / L NH4Cl, and 0.1 g / L CaCl2·2H2O. This nutrient solution II does not contain SO42-. 2- The sulfur source required for the regeneration of this composite packing is SO4 adsorbed during the biological denitrification process. 2- Then, the mixture was cultured at 25–35℃ with magnetic stirring at 400–500 rpm for 48 hours, centrifuged at 6000 rpm for 5 minutes, and the precipitate was collected to obtain the regenerated biological iron sulfide composite packing.

[0075] Comparative Example 1: Preparation of ordinary gravel mixed with sulfurized hydroxyl oxide iron filler

[0076] This comparative example provides a method for preparing ordinary gravel mixed with sulfurized hydroxyl iron oxide filler. The specific preparation method is as follows:

[0077] Step S1: Take iron hydroxyl oxide powder (final concentration 6.8 g / L) and ordinary gravel (final concentration 108.8 g / L, limestone content <5%) and mix them in deionized water to make the iron hydroxyl oxide powder fully adhere to the surface of the gravel, thus obtaining ordinary gravel / iron hydroxyl oxide composite.

[0078] Step S2: Mix the above limestone gravel / ferric hydroxide composite with the sulfate-reduced sludge mixture prepared in Example 1 above, and incubate at 25°C with magnetic stirring at 400-500 rpm for 48 hours. Centrifuge at 6000 rpm for 5 minutes and take the precipitate to obtain the ordinary gravel mixed with biological iron sulfide composite packing.

[0079] Test Example 1: Denitrification and Sulfate Adsorption Efficiency of Bio-ferric Sulfide Composite Packing Material

[0080] This test example examines the denitrification and sulfate adsorption effects of the bio-iron sulfide composite packing material prepared in Example 1 and the ordinary gravel mixed iron sulfide hydroxyl oxide packing material prepared in Comparative Example 1. The specific methods are as follows:

[0081] First, experimental and control groups were set up. The experimental group was given 34 g / L of the bio-iron sulfide composite packing material synthesized in Example 1, while the control group was given 34 g / L of the ordinary gravel mixed sulfurized hydroxyl oxide packing material synthesized in Comparative Example 1. Then, the sulfur autotrophic denitrification sludge with good activity was allowed to stand and the supernatant was removed. The sulfur autotrophic denitrification sludge was mixed with nitrate nitrogen-containing wastewater (simulated wastewater) and added to the experimental and control groups respectively. The mixture was then magnetically stirred (500 rpm) at room temperature for 12 h, and the denitrification effect and sulfate adsorption effect were detected.

[0082] The sulfur-autotrophic denitrifying sludge in this test case was obtained through acclimation and cultivation from anaerobic sludge in a municipal wastewater treatment plant in Zhongshan City, Guangdong Province (the wastewater treatment plant uses the A2 / O process). The acclimation culture medium for the sulfur-autotrophic denitrifying sludge consisted of: 5.0 g / L Na2S2O3·5H2O, 2.0 g / L KH2PO4, 2.0 g / L KNO3, 1.0 g / L NaHCO3, 0.5 g / L NH4Cl, 0.5 g / L MgCl2·6H2O, and 0.01 g / L FeSO4·7H2O. 1000 mL blue-capped bottles were used for acclimation of the sulfur-autotrophic denitrifying sludge. Deionized water was used throughout the cultivation process. The cultivation conditions were 25°C with magnetic stirring at 500 rpm. Water samples were measured every two days to control NO3 levels. - The -N concentration was kept stable below 5 mg / L, and then the supernatant was removed after standing to obtain a sulfur autotrophic denitrification sludge with good activity.

[0083] The simulated wastewater contained 0.3 g / L KH2PO4, 0.6 g / L KNO3, 0.15 g / L NaHCO3, 0.075 g / L NH4Cl, 0.075 g / L MgCl2·6H2O and 0.001 g / L FeSO4·7H2O.

[0084] Test results as follows Figure 1 and Figure 2 As shown, where Figure 1 This is a statistical graph showing the changes in nitrate nitrogen concentration. Figure 2 The graph shows the statistical changes in sulfate ion concentration. The results indicate that both the control and experimental groups achieved denitrification efficiencies exceeding 90%, with post-reaction nitrate and nitrogen concentrations of 6.09 mg / L and 5.18 mg / L, respectively. However, the control group was unable to retain SO42-. 2- SO4 in the effluent 2- When the concentration reached 452 mg / L, the experimental group could adsorb and retain SO4. 2- SO4 in the effluent 2- At a concentration of 60 mg / L, its sulfate adsorption efficiency was increased by 86.73% compared to the control group.

[0085] Test Example 2: Denitrification and Sulfate Adsorption Effects of Regenerated Bio-ferric Sulfide Composite Packing Material

[0086] In this test example, the regenerated biological iron sulfide composite packing material prepared in Example 2 above was applied to the biological denitrification of secondary effluent from a wastewater treatment plant. Its denitrification and sulfate adsorption effects were tested again, and the specific methods are as follows:

[0087] First, 34 g / L of the regenerated bio-iron sulfide composite packing synthesized in Example 2 was added. Then, the sulfur autotrophic denitrification sludge with good activity from Test Example 1 was allowed to stand and the supernatant was removed. The sulfur autotrophic denitrification sludge was mixed with nitrate nitrogen-containing wastewater (simulated wastewater) and added to the reactor. The mixture was then magnetically stirred (500 rpm) at room temperature for 12 h, and the denitrification effect and sulfate adsorption effect were detected.

[0088] The simulated wastewater contained 0.3 g / L KH2PO4, 0.6 g / L KNO3, 0.15 g / L NaHCO3, 0.075 g / L NH4Cl, 0.075 g / L MgCl2·6H2O and 0.001 g / L FeSO4·7H2O.

[0089] Test results as follows Figure 3 and Figure 4 As shown, where Figure 3 This is a statistical graph showing the changes in nitrate nitrogen concentration. Figure 4 The graph shows the statistical changes in sulfate ion concentration. The results indicate that the regenerated bio-iron sulfide composite packing material prepared in Example 2 can achieve a denitrification efficiency of 90.5%, with an effluent sulfate concentration of approximately 55.3 mg / L. Therefore, the bio-iron sulfide composite packing material of this invention can be recycled, effectively improving the utilization rate of the composite packing material.

[0090] In summary, this invention provides a bio-iron sulfide composite filler, its preparation method, and its application, which have the following advantages:

[0091] (1) The bio-sulfurized iron composite packing of the present invention can be used as an electron donor for sulfur autotrophic denitrification after bio-sulfurization. In the context of low C / N ratio in urban sewage, compared with traditional biological denitrification methods, it does not require the addition of an organic carbon source as an electron donor, and it has its own phosphorus removal function, so there is no need to add chemical reagents for phosphorus removal. In addition, the application of autotrophic denitrification and membrane biological treatment reduces the production of sludge, avoids the cost increase caused by the treatment and disposal of a large amount of excess sludge, and the overall process operating cost and energy consumption are low.

[0092] (2) Due to the solid form, low specific surface area, and crystal structure of natural pyrite, its denitrification efficiency can only be maintained at 10-70 g N / (m 3.d), the denitrification efficiency is low, which greatly limits its application in large-scale wastewater treatment facilities. In contrast, this invention uses a biochemical synthesis method based on sulfur reduction to prepare a composite packing material with a high specific surface area (approximately 58.4 m²). 2 The composite filler ( / g) not only effectively increases the biochemical reaction rate of sulfur autotrophic denitrification, but also solves the problems of low activity and excessively long hydraulic retention time required by natural pyrite, thereby improving wastewater treatment efficiency. The composite filler of this invention does not require strong acids or alkalis or high-temperature and high-pressure operating environments during preparation; it is simple, safe, environmentally friendly, reliable, and low-cost.

[0093] (3) In the present invention, the bio-iron sulfide composite packing uses gravel containing limestone as a matrix to load hydroxyl iron oxide powder. Since limestone has a good adsorption effect on sulfate under neutral conditions, the sulfate produced in the denitrification process will be fixed on the surface of the material and will not be directly discharged into the water body. This greatly avoids secondary pollution problems such as black and odorous water bodies caused by excessive sulfate discharge. Moreover, the fixed sulfate can be used again in the material regeneration step after denitrification. The material has the excellent characteristics of being recyclable and regenerable.

[0094] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

Claims

1. A biogenic iron sulfide composite filler, characterized in that, The preparation raw materials include limestone sand, hydroxyl iron oxide, nutrient salt solution I and sulfate reducing sludge; The limestone in the limestone sand has a mass percentage of 70-80%; the sulfate reducing sludge is obtained by domesticating anaerobic sludge in a sewage treatment plant to enrich sulfate reducing bacteria; and the sulfate ion in the nutrient salt solution I has a final concentration of 1.2-1.8 g / L.

2. The biogenic iron sulfide composite filler according to claim 1, characterized in that, The nutrient salt solution I includes 0.05-0.2 g / L yeast extract, 3.5-4.5 mL / L sodium lactate, 0.05-0.2 g / L ascorbic acid, 0.1-1.2 g / L cysteine hydrochloride, 0.5-1.5 g / L NH4Cl, 0.5-1.5 g / L Na2SO4, 1.5-2.5 g / L MgSO4·7H2O and 0.05-0.2 g / L CaCl2·2H2O.

3. A process for the preparation of the bio-iron sulphide composite filler as claimed in claim 1 or 2, characterized in that, The method comprises the following steps: S1, dispersing the sulfate reducing sludge in the nutrient salt solution I to obtain a sulfate reducing sludge mixture; S2, mixing the hydroxyl iron oxide with the limestone sand under solvent conditions, and then adding the sulfate reducing sludge mixture to obtain a limestone sand / biological iron sulfide mixture; S3, culturing the limestone sand / biological iron sulfide mixture, and collecting the solid phase after solid-liquid separation.

4. The production method according to claim 3, characterized by, The final concentration of the hydroxyl iron oxide in the limestone sand / biological iron sulfide mixture is 6-8 g / L; The final concentration of the limestone sand is 80-120 g / L.

5. A method for recovering the bio-iron sulfide composite filler as claimed in claim 1 or 2, characterized in that, The biological iron sulfide composite filler after biological denitrification treatment is mixed with a nutrient salt solution II, and the solid phase is collected after solid-liquid separation.

6. The recycling method according to claim 5, characterized in that, The nutrient salt solution II includes 0.05-0.2 g / L yeast extract, 3.5-4.5 mL / L sodium lactate, 0.05-0.2 g / L ascorbic acid, 0.1-1.2 g / L cysteine hydrochloride, 0.5-1.5 g / L NH4Cl and 0.05-0.2 g / L CaCl2·2H2O.

7. A method of sewage treatment, characterised in that, The biological iron sulfide composite filler as claimed in any one of claims 1-2 or obtained by the recovery method as claimed in any one of claims 5-6 is contacted with sewage.

8. Use of the biological iron sulfide composite filler as claimed in any one of claims 1-2 or obtained by the preparation method as claimed in any one of claims 3-4 or the recovery method as claimed in claims 5-6 in sewage treatment.

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