A method for recycling and circulating iron resources based on a series connection type biological reduction of fenton iron mud

Abstract

The application belongs to the field of Fenton iron sludge treatment, and discloses a method for recovering and recycling iron resources based on Fenton iron sludge series biological reduction. The method comprises the following steps: mixing the acid Fenton iron sludge with concentrated high-solid-content iron sludge, nutrients and ammonia-nitrogen-containing wastewater, and under the nitrogen atmosphere, the acidophilic heterotrophic iron-reducing bacteria partially reduce the trivalent iron to divalent iron, and at the same time, the hydrated and complex trivalent iron is converted into ionic trivalent iron, so as to obtain a sludge-water mixture containing ionic Fe 2+ , Fe 3+ and NH4 + , under the nitrogen atmosphere, the iron-oxidizing ammonia bacteria utilize Fe 3+ and NH4 + to perform the autotrophic iron reduction reaction, so as to obtain a sludge-water mixture containing ionic Fe 2+ , and through solid-liquid separation, the supernatant containing ionic Fe 2+ is directly used as a catalyst of the Fenton oxidation unit. The application overcomes the problems of needing to add acid to recover divalent iron, low utilization rate of hydrated and complex trivalent iron by the iron-oxidizing ammonia bacteria, and low iron resource recovery efficiency and poor system stability.

Description

Technical Field

[0001] This invention belongs to the field of Fenton iron sludge treatment, and more specifically, relates to a method for iron resource recovery and recycling based on Fenton iron sludge series-type bioreduction. Background Technology

[0002] Fenton oxidation, as one of the advanced oxidation technologies in wastewater treatment, has shown excellent results in removing recalcitrant organic matter from water. This method utilizes Fe in an acidic solution environment with a pH of approximately 3.0. 2+ The catalytic action of H2O2 decomposes to produce hydroxyl radicals (·OH) with strong oxidizing activity, achieving deep removal of recalcitrant COD from organic wastewater. However, Fenton iron sludge, mainly composed of Fe(OH)3, is generated in large quantities with the addition of liquid alkali during the process. The environmental risks brought about by this complex heterogeneous mixture have become the main reason hindering the market application of Fenton technology. Based on the iron-rich characteristics of Fenton iron sludge, single acid dissolution, roasting-acid dissolution, and electrochemical regeneration methods can all achieve the purpose of recycling iron resources. For example, CN105836987A proposes a method for promoting the resource utilization of Fenton iron sludge using electroreduction. This method obtains a certain concentration of ferric sulfate anolyte by adding acid and diluting. After the organic matter is oxidized in the anode chamber of the diaphragm electrolytic cell, it is pumped into the cathode chamber, so that the Fe in the solution... 3+ Reduced to Fe 2+ This provides raw materials for subsequent concentration and crystallization to prepare industrial ferrous sulfate products; CN114349296A discloses a method for obtaining nitrogen-doped carbon-supported Fe single-atom catalysts using Fenton iron sludge. This method involves calcining a mixture of Fenton iron sludge powders, followed by magnetic separation. The magnetic fraction is then acid-washed and centrifuged, with the supernatant being rich in Fe. 3+ In an acidic solution, the lower layer of insoluble matter is the Fe-SAC / NC catalyst. All of the above methods involve high investment costs and are not intended to achieve the direct reuse of recovered iron resources in Fenton oxidation technology.

[0003] Existing technologies have attempted to combine ferric ammonium oxidation (FMO) with Fenton oxidation to achieve deep denitrification of wastewater. For example, existing technologies use a Fenton unit to treat wastewater COD, ultimately achieving denitrification through ferric ammonium oxidation and denitrification by denitrifying bacteria in an anoxic zone. Simultaneously, iron sludge generated from the Fenton treatment is introduced into the ferric ammonium oxidation unit; however, the production of ferrous iron is merely a byproduct of this existing technology. Furthermore, ferric ammonium oxidation bacteria have low utilization efficiency for hydrated and organically complexed ferric iron in the Fenton iron sludge. Additionally, although this existing technology designs for recirculating the supernatant containing ferrous iron back to the Fenton front end to recycle iron, it still suffers from low iron resource recovery efficiency and limited recycling value; the recirculated iron mainly exists in a diluted state. 2+The low concentration and poor activity of Fenton iron sludge make it difficult to directly reuse as a high-efficiency catalyst, resulting in the underutilization of its resource value. Furthermore, the existing technology places the iron-ammonia oxidation unit within the main wastewater treatment process, resulting in a large wastewater volume. Other pollutants and impurities in the influent can easily inhibit or toxicize the bacterial flora, leading to poor system resistance to shock loads. In summary, the existing technology's approach of treating wastewater as the primary focus and recovering iron resources as a secondary objective cannot fundamentally solve the disposal problems of Fenton iron sludge and achieve efficient recycling of iron resources.

[0004] Therefore, in order to solve the problems of environmental pollution and waste of iron resources caused by the formation of large amounts of iron sludge from Fenton oxidation, it is urgent to propose a new method for iron resource recovery and recycling based on the series bioreduction of Fenton iron sludge. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by proposing a method for iron resource recovery and recycling based on Fenton iron sludge series-connected biological reduction. This invention overcomes the problems of existing technologies, such as the need for acid addition to recover ferrous iron, low utilization rates of hydrated and complexed ferric iron by iron-ammonia-oxidizing bacteria, and low iron resource recovery efficiency and poor system stability resulting from directly embedding the iron-ammonia oxidation process into a comprehensive wastewater treatment system.

[0006] To achieve the above objectives, this invention provides a method for iron resource recovery and recycling based on Fenton iron sludge series-connected biological reduction, the method comprising the following steps: S1: The acidic Fenton iron sludge produced by the Fenton oxidation unit is concentrated to obtain high-solids iron sludge; the high-solids iron sludge, acidophilic heterotrophic iron-reducing bacteria nutrients, ammonia nitrogen-containing wastewater and pH adjuster are mixed to obtain a mixed system; S2: The mixed system is fed into a first bioreactor containing acidophilic heterotrophic iron-reducing bacteria and a carbon source. Under a nitrogen atmosphere, the acidophilic heterotrophic iron-reducing bacteria utilize the carbon source in a slightly acidic environment to generate electrons, partially reducing the ferric iron in the mixed system to ferrous iron. Simultaneously, in the slightly acidic environment, the acidophilic iron-reducing bacteria convert hydrated ferric iron and organic complexed ferric iron into an ionic state that is easily utilized by iron-ammonia-oxidizing bacteria. As a result, ionic Fe is obtained in the first bioreactor. 2+ Fe 3+ and NH4 + The mud-water mixture; the Fe-containing ionized Fe 2+ Fe 3+ and NH4 + The mud-water mixture is fed into a second bioreactor equipped with iron-ammonia-oxidizing bacteria. Under a nitrogen atmosphere, the iron-ammonia-oxidizing bacteria utilize the ionized Fe... 2+ Fe 3+ and NH4 +Fe in mud-water mixture 3+ and NH4 + An autotrophic iron reduction reaction is carried out to reduce ionic ferric iron to ionic ferrous iron, yielding ionic Fe in the second bioreactor. 2+ A mixture of mud and water; S3: Under a nitrogen atmosphere, the ionic Fe... 2+ The mud-water mixture was subjected to solid-liquid separation to obtain Fe containing ions. 2+ The supernatant and biological residue; the Fe-containing liquid 2+ The supernatant was used directly as a catalyst for the Fenton oxidation unit.

[0007] In this invention, the acidic Fenton iron sludge (pH=3.0-4.0) produced by the front-end Fenton oxidation unit is the sole treatment target. Through a core process chain of "concentration and conditioning - segmented series bioreduction - oxygen-controlled separation", a high concentration of Fe is ultimately produced. 2+ The solution is recycled back to the Fenton oxidation unit, achieving a closed-loop cycle of the iron catalyst within the plant and source reduction of iron sludge. Specifically, through a series-connected bioreduction design, the process of reducing ferric iron (Fe3+) by acidophilic heterotrophic iron-reducing bacteria is coupled with the process of reducing ferric iron by ferroammonia-oxidizing bacteria. First, in the acidophilic heterotrophic iron-reducing unit, at a lower pH, acidophilic heterotrophic iron-reducing bacteria reduce some of the ferric iron in the iron sludge. Simultaneously, acidophilic iron-reducing bacteria convert hydrated ferric iron and organic complexed ferric iron into ionic states that are easily utilized by ferroammonia-oxidizing bacteria. Then, the mixed solution containing ferric and ferrous iron is sent to the ferroammonia-oxidizing unit, where ammonia nitrogen is used as an electron donor and ferric ions as an electron acceptor to deeply reduce the remaining ferric iron. Finally, through oxygen-controlled solid-liquid separation, a slightly acidic, high-concentration ferrous iron supernatant is obtained and directly recycled back to the Fenton oxidation unit, thereby significantly reducing the cost of adding ferrous iron in the Fenton reaction and the disposal costs of Fenton iron sludge.

[0008] In this invention, ferric iron in Fenton iron mud exists in the form of ferric hydroxide and complexed iron. Neither of these two forms is easily utilized by iron-ammonia oxidizing bacteria. The acidophilic heterotrophic iron reduction unit can convert these two forms of iron into an ionic state that is easily utilized by anaerobic iron-ammonia oxidizing bacteria. For solid ferric hydroxide: it is mainly converted and reduced to soluble Fe through direct enzymatic reduction by acidophilic heterotrophic iron-reducing bacteria, indirect chemical reduction through secretion of electron mediators, and acid dissolution. 2+ Even a small portion of Fe 3+ Not reduced to Fe 2+ It also transforms into soluble Fe through acid dissolution and changes in the ion concentration product. 3+ The ionic state is also more conducive to its utilization by the iron-ammonia oxidation reaction unit; For complexed iron: microorganisms directly take up and reduce specific iron complexes or dissociate and reduce the complexes under acidic conditions, breaking the stable structure of the iron complex and Fe. 3+ Reduced to Fe 2+ The remaining unreduced Fe 3+ It will exist in ionic form.

[0009] According to the present invention, preferably, the pH of the acidic Fenton iron sludge produced by the Fenton oxidation unit is 3.0-4.0.

[0010] According to the present invention, preferably, the solids content of the high-solids iron sludge is 5-10%.

[0011] In this invention, the purpose of the concentration process is to reduce the volumetric load on the subsequent bioreactor. The concentration process can be achieved through gravity settling or mechanical methods.

[0012] According to the present invention, preferably, the acidophilic heterotrophic iron-reducing bacteria nutrient is at least one selected from phosphate, zinc sulfate, copper sulfate, and sodium molybdate. The acidophilic heterotrophic iron-reducing bacteria nutrient can promote the growth and enrichment of functional microorganisms in the first bioreactor.

[0013] According to the present invention, preferably, the ammonia nitrogen-containing wastewater is wastewater that has undergone impurity removal pretreatment, has an ammonia nitrogen concentration of 200-250 mg / L, and a pH of 6-7; The amount of ammonia-nitrogen-containing wastewater added to the mixed system is based on Fe... 3+ NH4 + The molar ratio is set to (3-3.6):1.

[0014] According to the present invention, preferably, the pH of the mixed system is 4.5-5.5 (which is a suitable reaction condition for acidophilic heterotrophic iron-reducing bacteria).

[0015] In this invention, the high-solids iron sludge, acidophilic heterotrophic iron-reducing bacteria nutrients, and ammonia nitrogen-containing wastewater are mixed in a conditioning tank.

[0016] According to the present invention, preferably, the solid-liquid mass ratio in the mixed system is (2.5-3.5):1.

[0017] According to the present invention, preferably, the reaction temperature in the first bioreactor and the second bioreactor is independently 25-35°C. The first and second bioreactors are equipped with stirring equipment and heating equipment.

[0018] According to the present invention, preferably, the reaction time in the first bioreactor is 2-3 days; and the reaction time in the second bioreactor is 1-2 days.

[0019] According to the present invention, preferably, the nitrogen atmosphere ensures that the first bioreactor, the second bioreactor, and the equipment for solid-liquid separation (the equipment for solid-liquid separation needs to be well-sealed to ensure the presence of ionized Fe) 2+ The redox potential of the mud-water mixture is below -100mV to prevent ionic Fe. 2+ The dissolved oxygen concentration in each of the oxidized cells was independently <0.2 mg / L.

[0020] According to the present invention, preferably, the carbon source is sodium acetate and / or glucose.

[0021] According to the present invention, preferably, the amount of carbon source added in the first bioreactor is based on the COD:Fe ratio. 3+ The molar ratio is set to (0.8-1.2):1.

[0022] According to the present invention, preferably, the pH of the slightly acidic environment is 4.5-5.5. The slightly acidic environment is constructed from a mixed system.

[0023] According to the present invention, preferably, the ionic Fe... 2+ Fe 3+ and NH4 + The carbon source in the mud-water mixture is ≤0.5mg / L.

[0024] According to the present invention, preferably, the ionic Fe... 2+ The pH of the supernatant is 5.0-5.5, and the ionic state of Fe is... 2+ The concentration of Fe is ≥2000 mg / L, which meets the conditions for direct use as a catalyst in the Fenton oxidation unit, and the Fe-containing ionized Fe... 2+ The supernatant is acidic, which reduces the amount of acid required in the Fenton reaction. No acid or alkali needs to be added during the entire reaction process, reducing operating costs.

[0025] In this invention, the biological sludge separated from the solid-liquid mixture in step S3 mainly consists of inert impurities that have not been completely dissolved, microbial cells, and a small amount of iron minerals, which can be disposed of as general solid waste.

[0026] The beneficial effects of the technical solution of this invention are as follows: This invention provides a new resource recovery approach that primarily treats Fenton iron sludge and co-treats wastewater. This invention overcomes the problems in existing technologies, such as the need for acid addition to recover ferrous iron, low utilization rates of hydrated and complexed ferric iron by iron-ammonia-oxidizing bacteria, and low iron resource recovery efficiency and poor system stability caused by directly embedding the iron-ammonia oxidation process into a comprehensive wastewater treatment system. Specifically: 1. Due to the limited water intake strategy of this invention, that is, the amount of water used for high solid content Fenton iron sludge and ammonia nitrogen wastewater is small, thus ensuring the recovery of high concentration of divalent iron ions.

[0027] 2. This invention, through a series-connected biological reduction design combined with a limited influent strategy, technically couples the acidophilic heterotrophic iron reduction unit with the iron-ammonia oxidation unit, successfully transforming Fenton iron sludge from waste to be disposed of into a high-value reusable resource. This directly reduces the reagent dosage costs in the Fenton oxidation reaction system and avoids soil pollution and resource waste caused by the discharge of large amounts of iron sludge. Specifically: (1) This invention utilizes two types of biological reduction (acidophilic heterotrophic iron-reducing bacteria and iron-ammonia-oxidizing bacteria) to enhance the iron reduction effect and increase the reduction rate of ferrous iron; (2) The present invention utilizes acidophilic heterotrophic iron-reducing bacteria to reduce iron, which can make full use of carbon source and reduce the additional COD brought to Fenton unit when ferrous iron is recycled. The iron ammonia oxidizing bacteria of the present invention use ammonia nitrogen in wastewater as substrate. The iron ammonia oxidizing unit does not require carbon source. Therefore, while ensuring a high iron reduction rate, the iron ammonia oxidizing unit also reduces the overall carbon source usage of the present invention and reduces operating costs. (3) The present invention utilizes acidophilic heterotrophic iron-reducing bacteria to reduce iron. In an acidic environment, some ferric iron is reduced to ferrous iron, while hydrated ferric iron and ferric iron complexed with organic matter are converted into ionic state that is easily utilized by iron ammonia-oxidizing bacteria, thus creating favorable conditions for improving the efficiency of iron ammonia oxidation reaction. (4) The low pH environment design of this invention ensures that the acidophilic heterotrophic iron reduction unit and the iron ammonia oxidation unit are always in a slightly acidic environment. On the one hand, this is conducive to the entry of ferrous iron into the solution in ionic form, reducing the amount of acid added later to dissolve ferrous ions; on the other hand, the acidic environment can avoid the growth of methanogenic bacteria, denitrifying bacteria and other microorganisms that are not conducive to iron reduction, thus reducing the occurrence of side reactions. (5) By using a limited water intake strategy (i.e., low water consumption for Fenton sludge with high solids content and ammonia nitrogen wastewater), the concentration of ferrous ions in the recovery solution can be effectively increased, reducing the disadvantage of increased water consumption in the Fenton unit due to the reuse of ferrous ions in the Fenton unit.

[0028] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0029] The above and other objects, features and advantages of the present invention will become more apparent from the more detailed description of exemplary embodiments of the invention in conjunction with the accompanying drawings.

[0030] Figure 1 The diagram shows a flow chart of an iron resource recovery and recycling method based on Fenton iron sludge series bioreduction provided in Embodiment 1 of the present invention. Detailed Implementation

[0031] Preferred embodiments of the invention will now be described in more detail. While preferred embodiments of the invention are described below, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0032] In the following embodiments: The acidophilic heterotrophic iron-reducing bacteria used are at the genus level. Acidiphilium The domestication method for acidophilic heterotrophic iron-reducing bacteria is to collect biological samples in the field and gradually reduce the pH, increase the concentration of ferric iron and the amount of carbon source under anaerobic conditions to obtain acidophilic heterotrophic iron-reducing bacteria. The iron-oxidizing bacteria used are classified at the genus level as follows: Acidimicrobiaceae The acclimatization method for iron-oxidizing bacteria involves using activated sludge from a municipal wastewater treatment plant as the initial seed sludge, and gradually increasing NH4 under anaerobic conditions. + Iron-oxidizing bacteria were obtained by domestication and cultivation using a method involving the addition of ferric iron at different concentrations.

[0033] Example 1

[0034] This embodiment provides a method for iron resource recovery and recycling based on Fenton iron sludge series-connected bioreduction, such as... Figure 1 As shown.

[0035] A wastewater treatment plant in an industrial park uses Fenton advanced oxidation to treat recalcitrant chemical wastewater, producing an acidic Fenton iron sludge mixture with a pH of approximately 3.2 daily. The solids content of this acidic Fenton iron sludge mixture is approximately 2%, and the total iron concentration (as expressed in Fe) is... 3+ The concentration (calculated) is 3000-3500 mg / L; The method includes the following steps: S1: The above-mentioned acidic Fenton iron sludge mixture is concentrated (by gravity settling in a thickening tank) to obtain high-solids iron sludge (10% solids content); 15m of the high-solids iron sludge is then... 3 Acidophilic heterotrophic iron-reducing bacteria nutrients, potassium dihydrogen phosphate, ammonia nitrogen-containing wastewater, and pH adjuster are mixed and stirred in a conditioning tank to obtain a mixed system (pH stabilized at 5.0). in: The ammonia-nitrogen-containing wastewater is taken from an industrial park, pretreated for impurity removal, with an ammonia nitrogen concentration of 200-250 mg / L and a pH of 6.5; the amount of ammonia-nitrogen-containing wastewater added to the mixed system is based on Fe 3+ NH4 + The molar ratio is set at 3:1 (considering a 1.1 times guarantee factor). The amount of potassium dihydrogen phosphate added to the mixed system is set according to a P:Fe molar ratio of 0.03:1.

[0036] S2: The mixture is fed into a bioreactor containing acclimated acidophilic heterotrophic iron-reducing bacteria and sodium acetate (the amount of sodium acetate added in the first bioreactor is based on COD:Fe). 3+ In a first bioreactor (with a molar ratio of 1:1), under conditions of 28-30°C and a nitrogen atmosphere, the acidophilic heterotrophic iron-reducing bacteria utilize the carbon source to generate electrons through metabolism, partially reducing the ferric iron in the mixed system to ferrous iron. Simultaneously, they convert hydrated and complexed ferric iron into ionic ferric iron. After this stage lasts for 48 hours, ferric iron containing ionic Fe is obtained in the first bioreactor. 2+ Fe 3+ and NH4 + The mud-water mixture (with a residual carbon source of 0.1 mg / L). The ion-containing Fe 2+ Fe 3+ and NH4 + The mud-water mixture is fed into a second bioreactor equipped with iron-ammonia-oxidizing bacteria. Under conditions of 28-30°C and a nitrogen atmosphere, the iron-ammonia-oxidizing bacteria utilize the ionic Fe... 2+ Fe 3+ and NH4 + Fe in mud-water mixture 3+ and NH4 + An autotrophic iron reduction reaction was carried out to reduce ionic ferric iron to ionic ferrous iron. After this stage lasted for 24 hours, ionic Fe was obtained in the second bioreactor. 2+ A mixture of mud and water; in: Both the first and second bioreactors are operating in sequencing batch reactor (SBR) mode. The effective volume of the first bioreactor is 20 m³. 3 All are equipped with stirrers, online pH and ORP monitoring probes, temperature control and nitrogen coverage systems; During the iron reduction reaction, the pH of the system in the first bioreactor slowly and naturally rises from 5.0 to 5.3. The iron reduction reaction reduces 50% of the Fe in the mixed system of step S1. 3+ It was restored.

[0037] S3: Remove all ionized Fe from the second bioreactor. 2+ The mud-water mixture was transferred through a closed pipeline to a closed centrifuge protected by nitrogen for solid-liquid separation, yielding Fe containing ions. 2+ The supernatant (containing Fe ions) 2 +The ionic Fe in the supernatant 2+ The concentration of [unspecified substance] is ≥2000 mg / L, ammonia nitrogen concentration is less than 5 mg / L, COD is less than 50 mg / L) and biological residues; the [unspecified substance] containing ionic Fe [unspecified substance]... 2+ The supernatant is directly pumped into the ferrous sulfate storage tank of the Fenton oxidation unit in the industrial park's wastewater treatment plant and reused as a high-quality catalyst.

[0038] In this embodiment, the nitrogen atmosphere ensures that the dissolved oxygen concentration in the first bioreactor, the second bioreactor, and the equipment performing the solid-liquid separation is independently <0.1 mg / L (strictly hypoxic conditions).

[0039] Through the treatment described in this embodiment, the resource recovery rate of total iron in Fenton iron sludge can reach 85%. The recycled Fe-containing ions... 2+ The supernatant can replace more than 50% of the fresh ferrous sulfate reagent consumed by the plant, while also synergistically removing ammonia nitrogen from the added wastewater. The entire resource recovery process forms a closed loop of iron catalyst within the plant.

[0040] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A method for iron resource recovery and recycling based on Fenton iron sludge series bioreduction, characterized in that, The method includes the following steps: S1: The acidic Fenton iron sludge produced by the Fenton oxidation unit is concentrated to obtain high-solids iron sludge; the high-solids iron sludge, acidophilic heterotrophic iron-reducing bacteria nutrients, ammonia nitrogen-containing wastewater and pH adjuster are mixed to obtain a mixed system; The ammonia nitrogen-containing wastewater is wastewater that has undergone impurity removal pretreatment, with an ammonia nitrogen concentration of 200-250 mg / L and a pH of 6-7; The amount of ammonia-nitrogen-containing wastewater added to the mixed system is based on Fe... 3+ NH4 + The molar ratio is set to (3-3.6):1; The pH of the mixture is 4.5-5.5; The solid-liquid mass ratio in the mixture is (2.5-3.5):1; S2: The mixed system is fed into a first bioreactor containing acidophilic heterotrophic iron-reducing bacteria and a carbon source. Under a nitrogen atmosphere, the acidophilic heterotrophic iron-reducing bacteria utilize the carbon source in a slightly acidic environment to generate electrons, partially reducing the ferric iron in the mixed system to ferrous iron. Simultaneously, in the slightly acidic environment, the acidophilic heterotrophic iron-reducing bacteria convert hydrated ferric iron and organic complexed ferric iron into an ionic state that is easily utilized by iron-ammonia-oxidizing bacteria. As a result, ionic Fe is obtained in the first bioreactor. 2+ Fe 3+ and NH4 + The mud-water mixture; the Fe-containing ionized Fe 2+ Fe 3+ and NH4 + The mud-water mixture is fed into a second bioreactor equipped with iron-ammonia-oxidizing bacteria. Under a nitrogen atmosphere, the iron-ammonia-oxidizing bacteria utilize the ionized Fe... 2+ Fe 3+ and NH4 + Fe in mud-water mixture 3+ and NH4 + An autotrophic iron reduction reaction is carried out to reduce ionic ferric iron to ionic ferrous iron, yielding ionic Fe in the second bioreactor. 2+ A mixture of mud and water; S3: Under a nitrogen atmosphere, the ion-containing Fe... 2+ The mud-water mixture was subjected to solid-liquid separation to obtain Fe containing ions. 2+ The supernatant and biological residue; the Fe-containing liquid 2+ The supernatant was used directly as a catalyst for the Fenton oxidation unit.

2. The iron resource recovery and recycling method based on Fenton iron sludge series bioreduction according to claim 1, wherein, The acidic Fenton iron sludge produced by the Fenton oxidation unit has a pH of 3.0-4.0; The solids content of the high-solids iron sludge is 5-10%.

3. The iron resource recovery and recycling method based on Fenton iron sludge series bioreduction according to claim 1, wherein, The nutrients for the acidophilic heterotrophic iron-reducing bacteria are at least one of phosphate, zinc sulfate, copper sulfate, and sodium molybdate.

4. The iron resource recovery and recycling method based on Fenton iron sludge series bioreduction according to claim 1, wherein, The reaction temperatures in the first and second bioreactors are each independently 25-35℃; The reaction time in the first bioreactor is 2-3 days; the reaction time in the second bioreactor is 1-2 days. The nitrogen atmosphere ensures that the dissolved oxygen concentration in the first bioreactor, the second bioreactor, and the equipment performing the solid-liquid separation is independently <0.2 mg / L.

5. The iron resource recovery and recycling method based on Fenton iron sludge series bioreduction according to claim 1, wherein, The carbon source is sodium acetate and / or glucose; The carbon source is added in the first bioreactor at a rate based on COD:Fe 3+ The molar ratio is set to (0.8-1.2):

1.

6. The iron resource recovery and recycling method based on Fenton iron sludge series bioreduction according to claim 1, wherein, The pH of the acidic environment is 4.5-5.

5.

7. The iron resource recovery and recycling method based on Fenton iron sludge series bioreduction according to claim 1, wherein, The Fe containing ions 2+ Fe 3+ and NH4 + The carbon source in the mud-water mixture is ≤0.5mg / L.

8. The iron resource recovery and recycling method based on Fenton iron sludge series bioreduction according to claim 1, wherein, The Fe containing ions 2+ The pH of the supernatant is 5.0-5.5, and the ionic state of Fe is... 2+ The concentration is ≥2000mg / L.

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