A denitrification biological filter with maifanite-based sulfur-iron composite packing and its application

Abstract

This invention discloses a denitrifying biological filter based on maifanite-based sulfur-iron composite packing material and its application, belonging to the field of wastewater treatment technology. The denitrifying biological filter established by this invention comprises, from top to bottom, an influent distribution system, a filter media layer, a support layer, an air-water distribution system, and an air distribution pipe system. The composite packing material is prepared by homogeneous mixing and granulation of pyrrhotite, sulfur, and maifanite in a volume ratio of 2-6:1-3:1-3. Based on the sulfur-iron composite autotrophic denitrification process using pyrrhotite and sulfur, and using maifanite, a natural mineral, instead of traditional calcium carbonate as a novel pH adjuster, it effectively maintains the pH of the system, ensuring long-term stable operation. The denitrifying biological filter established using this composite packing material exhibits high reaction efficiency and strong nitrogen and phosphorus removal effects in wastewater treatment applications.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically relating to a denitrification biological filter based on maifanite-based sulfur-iron composite packing and its application. Background Technology

[0002] In order to meet increasingly stringent wastewater discharge standards, there is an urgent need for new technologies to remove nitrogen and phosphorus from wastewater in urban wastewater treatment plants at a deeper level.

[0003] Heterotrophic denitrification and chemical phosphorus removal are two widely used advanced treatment processes. The former requires the addition of an external carbon source, while the latter requires the addition of coagulants. Both suffer from high costs, difficulty in controlling dosage, a high risk of secondary pollution, large sludge production, and high disposal costs. However, recent studies have confirmed the significant effects of sulfur and pyrrhotite in the advanced treatment of nitrogen and phosphorus in wastewater. Furthermore, the sulfur / pyrrhotite autotrophic denitrification process offers advantages such as no need for an external carbon source, low cost, no risk of secondary pollution, and low sludge production. Therefore, the sulfur / pyrrhotite autotrophic denitrification process shows great promise for the advanced nitrogen and phosphorus removal treatment of biological effluent from municipal wastewater treatment plants.

[0004] However, while traditional sulfur / limestone autotrophic denitrification processes have strong nitrogen removal capabilities, they are ineffective at phosphorus removal, and single-origin autotrophic denitrification processes have excellent phosphorus removal capabilities but poor nitrogen removal capabilities. Therefore, using either sulfur or pyrrhotite alone for autotrophic denitrification has certain limitations. Summary of the Invention

[0005] The purpose of this invention is to provide a denitrification biological filter based on maifanite-based sulfur-iron composite packing and its application, so as to solve the problem of poor nitrogen and phosphorus removal effect of existing denitrification biological filters.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A denitrifying biological filter based on maifanite-based sulfur-iron composite filler includes, from top to bottom, an inlet water distribution system; a filter media layer; a support layer; an air-water distribution system; and an air distribution pipe system. The filter media layer (2) is filled with maifanite-based sulfur-iron composite filler, the support layer (3) is filled with pebbles, and the air-water distribution system (4) is filled with filter bricks.

[0008] Furthermore, the preparation method of the maifanite-based sulfur-iron composite filler includes the following steps:

[0009] S1. Screening: Pyrrhotite, sulfur and maifanite are ground and then sieved;

[0010] S2. Mixing: Pyrrhotite, sulfur and maifanite are homogenously mixed in a volume ratio of 2-6:1-3:1-3 to form a mixture;

[0011] S3. Granulation: The mixture is granulated to obtain maifanite-based sulfur-iron composite filler.

[0012] Furthermore, the particle size of the pyrrhotite, sulfur, and maifanite is 200-600 mesh, preferably 500 mesh for the pyrrhotite and 300 mesh for the sulfur and maifanite.

[0013] Furthermore, the maifanite-based sulfur-iron composite filler particles are spherical or ellipsoidal and have hollow pores with a particle size of 3-6 mm.

[0014] This invention also provides an application of a maifanite-based sulfur-iron composite packing denitrification biological filter as described above in the treatment of nitrogen- and phosphorus-containing wastewater, comprising the following steps:

[0015] Step 1: Arrange the air distribution pipe system, air-water distribution system, support layer, filter media layer, and water inlet distribution system in sequence from bottom to top; fill the filter media layer with the prepared maifanite-based sulfur-iron composite packing, fill the support layer with pebbles, and fill the air-water distribution system with filter bricks;

[0016] Step 2, Microbial Inoculation and Biofilm Formation: Inoculate the acclimatized activated sludge into the filter bed, add growth medium and culture until microbial inoculation and biofilm formation are completed;

[0017] Step 3, Operation of the filter: Wastewater is introduced into the filter in an upflow manner. The influent is pumped into the filter by a peristaltic pump at the bottom of the filter, and the effluent flows out from the outlet pipe at the top of the filter.

[0018] Preferably, the inoculation and colonization time of the bacterial community is 2-8 days.

[0019] Preferably, the hydraulic retention time of the maifanite-based sulfur-iron composite packing denitrification biological filter is 0.5-3h.

[0020] The beneficial effects of this invention are:

[0021] 1. This invention establishes a maifanite-based sulfur-iron composite packing denitrification biological filter, which uses pyrrhotite (Fe...) 1-x Sulfur and maifanite (S, 0 < x < 0.125) are mixed together in a certain proportion as packing material for a denitrifying filter, constructing a sulfur-iron autotrophic denitrification system with a common electron donor. By coordinating the growth of autotrophic denitrifying bacteria using sulfur and pyrrhotite as sulfur sources, the two are coupled together. With maifanite as a pH adjuster, excellent nitrogen and phosphorus removal effects are maintained while ensuring long-term stable operation of the system. The biological filter system described in this invention requires no additional carbon source, is low in cost, and produces little sludge, making it suitable for removing nitrates and phosphates from industrial wastewater.

[0022] 2. In the composite packing provided by this invention, pyrrhotite and sulfur provide the sulfur source as electron donors, while sulfur-autotrophic denitrifying bacteria use nitrate as an electron acceptor to reduce nitrate nitrogen to nitrogen gas, achieving denitrification. The reaction formulas are Equations 1 and 2. The Fe produced during the pyrrhotite denitrification process... 2+ Fe generated after the reaction 3+ And Fe in maifanite 3+ It can react with phosphate to form a precipitate, thereby achieving phosphorus removal; the reaction formulas are Equations 3 and 4. In addition, S dissolved from pyrrhotite... 2- The positive chain reaction formed with sulfur accelerates the rate at which electrons are donated by the electron donor, and the polysulfides generated by the chain reaction are more readily utilized by microorganisms, thus increasing the denitrification rate. Simultaneously, the coupling reaction accelerates the release of iron ions from pyrrhotite, increasing the phosphorus removal rate. Maifanite serves two purposes: firstly, it neutralizes the acids produced during sulfur autotrophic denitrification; secondly, the trace elements such as Al, Fe, and Ca dissolved from it can increase microbial activity and enhance bioaggregation.

[0023] 50NO3 - +55S + 20CO2 + 38H2O + 4NH4 + →25N2↑+55SO4 2- +64H + +4C5H7O2N (Equation 1)

[0024] 0.625FeS + NO3 - +0.5H₂O→0.5N₂↑+0.625SO₄ 2- +0.625Fe 2+ +OH - (Equation 2)

[0025] 2NO3 - +10Fe 2+ +12H + →N2↑+10Fe 3+ +6H2O (Equation 3)

[0026] Fe 3+ +PO4 3- →FePO4↓ (Equation 4)

[0027] 3. The denitrifying biological filter of this invention is a sulfur-iron autotrophic denitrifying biological filter. Compared with previous heterotrophic denitrifying filters, it does not require additional carbon source addition and does not cause secondary pollution. Compared with traditional single autotrophic denitrifying filters, it has a shorter start-up time, longer service life, and lower SO4 levels. 2- It reduces yield, stabilizes pH, and has a stronger effect on nitrogen and phosphorus removal.

[0028] 4. This invention effectively improves the electron donation rate of electron donors by generating negatively valence sulfur ions from pyrrhotite and the positive chain reaction between sulfur and pyrrhotite. The two are coupled with each other, effectively increasing the electron donation rate of both pyrrhotite and sulfur.

[0029] 5. H+ produced by sulfur autotrophic denitrification + Dissolve pyrrhotite to produce HS - (Equation 5), when the HS in the solution - When the concentration and pH are suitable, water-insoluble solid elemental sulfur is rapidly converted into polysulfides. These polysulfides act as transfer carriers for soluble zero-valent sulfur, allowing the water-insoluble solid elemental sulfur to be dispersed into the aqueous phase and utilized by microorganisms, thus accelerating the utilization of elemental sulfur. Conversely, an increased rate of sulfur autotrophic denitrification will generate more H₂O. + This, in turn, promotes the dissolution of pyrrhotite, effectively increasing the rate at which pyrrhotite and sulfur, both electron donors, donate electrons. Furthermore, the generated HS... - It can also perform denitrification (Equation 6), thereby increasing the rate of sulfur-iron coupled autotrophic denitrification. The combined reaction of this system achieves the purpose of coupled acceleration, greatly improving the denitrification rate and shortening the hydraulic retention time to 0.5-3h, forming a more long-term, efficient, and stable nitrogen and phosphorus removal technology.

[0030] FeS+H + →Fe 2+ +HS - (Equation 5)

[0031] 5HS - +8NO3 - +3H + →4N2↑+5SO4 2- +4H2O (Formula 6) Attached Figure Description

[0032] The invention will now be further described with reference to the accompanying drawings.

[0033] Figure 1 This is a schematic diagram of the structure of the denitrification biological filter with maifanite-based sulfur-iron composite packing in Embodiment 1 of the present invention;

[0034] Figure 2 This refers to the nitrogen and phosphorus concentrations in the influent and effluent of the denitrification biological filter in Example 4 of this invention after 100 days of operation.

[0035] Figure 3 This refers to the nitrogen and phosphorus concentrations in the influent and effluent of the denitrification biological filter in Example 5 of this invention after 80 days of operation.

[0036] Figure 4The nitrogen and phosphorus concentrations in the influent and effluent of the denitrification biological filter in Example 6 of this invention after 180 days of operation.

[0037] In the diagram: 1. Water inlet and distribution system; 2. Filter media layer; 3. Support layer; 4. Air-water distribution system; 5. Air distribution pipe system. Detailed Implementation

[0038] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0039] Example 1

[0040] A maifanite-based sulfur-iron composite packing denitrification biological filter, arranged from bottom to top as follows: air distribution pipe system 5, air-water distribution system 4, support layer 3, filter media layer 2, and inlet water distribution system 1; its structural schematic diagram is shown below. Figure 1 As shown; the prepared maifanite-based sulfur-iron composite filler is used to fill the filter media layer, pebbles are used to fill the support layer, and filter bricks are used to fill the air-water distribution system;

[0041] The preparation method of the maifanite-based sulfur-iron composite filler includes the following steps:

[0042] S1. Screening: Pyrrhic iron, sulfur and maifanite are ground and then screened. The particle size of pyrrhic iron is 500 mesh, and the particle size of sulfur and maifanite is 300 mesh.

[0043] S2. Mixing: Pyrrhotite, sulfur and maifanite are homogenously mixed in a volume ratio of 6:1:1 to form a mixture;

[0044] S3. Granulation: The mixture is granulated to obtain spherical or ellipsoidal granular maifanite-based sulfur-iron composite filler with a hollow pore structure, with a particle size of 3-6 mm.

[0045] Example 2

[0046] A denitrification biological filter with maifanite-based sulfur-iron composite packing is arranged in the same way as in Example 1, except that:

[0047] The preparation method of maifanite-based sulfur-iron composite filler includes the following steps:

[0048] S1. Screening: Pyrrhic iron, sulfur and maifanite are ground and then screened. The particle size of pyrrhic iron is 500 mesh, and the particle size of sulfur and maifanite is 300 mesh.

[0049] S2. Mixing: Pyrrhotite, sulfur and maifanite are homogenously mixed in a volume ratio of 2:3:1 to form a mixture;

[0050] S3. Granulation: The mixture is granulated to obtain spherical or ellipsoidal granular maifanite-based sulfur-iron composite filler with a hollow pore structure, with a particle size of 3-6 mm.

[0051] Example 3

[0052] A denitrification biological filter with maifanite-based sulfur-iron composite packing is arranged in the same way as in Example 1, except that:

[0053] The preparation method of maifanite-based sulfur-iron composite filler includes the following steps:

[0054] S1. Screening: Pyrrhic iron, sulfur and maifanite are ground and then screened. The particle size of pyrrhic iron is 500 mesh, and the particle size of sulfur and maifanite is 300 mesh.

[0055] S2. Mixing: Mix pyrrhotite, sulfur and maifanite in a volume ratio of 2:1:2 to form a mixture;

[0056] S3. Granulation: The mixture is granulated to obtain spherical or ellipsoidal granular maifanite-based sulfur-iron composite filler with a hollow pore structure, with a particle size of 3-6 mm.

[0057] Example 4

[0058] The application of a maifanite-based sulfur-iron composite packing denitrification biological filter in the treatment of nitrogen- and phosphorus-containing wastewater includes the following steps:

[0059] Step 1: Use the maifanite-based sulfur-iron composite packing denitrification biological filter as described in Example 1;

[0060] Step 2, Microbial inoculation and biofilm formation: The acclimated activated sludge is inoculated into the denitrification biological filter and cultured with growth medium. The microbial inoculation and biofilm formation time is 6 days.

[0061] Step 3, Filter Operation: Wastewater is introduced into the filter using an upflow method. The influent is pumped into the filter by a peristaltic pump at the bottom, and the effluent flows out from the outlet pipe at the top. The hydraulic retention time is 3 hours, and the operating time is 100 days. The average influent nitrate nitrogen concentration is 5.63 mg / L, and the average effluent nitrate nitrogen concentration is 0.31 mg / L. The average influent phosphate phosphorus concentration is 0.64 mg / L, and the average effluent phosphate phosphorus concentration is 0.09 mg / L. Specific influent and effluent nitrogen and phosphorus concentrations are as follows... Figure 2 As shown.

[0062] Example 5

[0063] The application of a maifanite-based sulfur-iron composite packing denitrification biological filter in the treatment of nitrogen- and phosphorus-containing wastewater includes the following steps:

[0064] Step 1: Use the maifanite-based sulfur-iron composite packing denitrification biological filter as described in Example 2;

[0065] Step 2, Microbial inoculation and biofilm formation: Inoculate the acclimatized activated sludge into the denitrification biological filter and add growth medium for culture. The microbial inoculation and biofilm formation time is 5 days.

[0066] Step 3, Filter Operation: Wastewater is introduced into the filter using an upflow method. The influent is pumped into the filter by a peristaltic pump at the bottom, and the effluent flows out from the outlet pipe at the top. The hydraulic retention time is 0.5 hours, and the operating time is 80 days. The average influent nitrate nitrogen concentration is 8.74 mg / L, and the average effluent nitrate nitrogen concentration is 0.06 mg / L. The average influent phosphate phosphorus concentration is 2.81 mg / L, and the average effluent phosphate phosphorus concentration is 1.45 mg / L. Specific influent and effluent nitrogen and phosphorus concentrations are as follows... Figure 3 As shown.

[0067] Example 6

[0068] The application of a maifanite-based sulfur-iron composite packing denitrification biological filter in the treatment of nitrogen- and phosphorus-containing wastewater includes the following steps:

[0069] Step 1: Use the maifanite-based sulfur-iron composite packing denitrification biological filter as described in Example 3;

[0070] Step 2, Microbial inoculation and biofilm formation: The acclimated activated sludge is inoculated into the denitrification biological filter and cultured with growth medium. The microbial inoculation and biofilm formation time is 8 days.

[0071] Step 3, Filter Operation: Wastewater is introduced into the filter using an upflow method. The influent is pumped into the filter by a peristaltic pump at the bottom, and the effluent flows out from the outlet pipe at the top. The hydraulic retention time is 1 hour, and the operating time is 180 days. The average influent nitrate nitrogen concentration is 16.20 mg / L, and the average effluent nitrate nitrogen concentration is 2.21 mg / L. The average influent phosphate phosphorus concentration is 8.11 mg / L, and the average effluent phosphate phosphorus concentration is 0.38 mg / L. Specific influent and effluent nitrogen and phosphorus concentrations are as follows... Figure 4 As shown.

[0072] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0073] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A denitrification biological filter with maifanite-based sulfur-iron composite packing, characterized in that, It includes, from top to bottom, a water inlet and distribution system (1), a filter media layer (2), a support layer (3), an air-water distribution system (4), and an air distribution pipe system (5); the filter media layer (2) is filled with maifanite-based sulfur-iron composite filler, the support layer (3) is filled with pebbles, and the air-water distribution system (4) is filled with filter bricks; The specific preparation method of the maifanite-based sulfur-iron composite filler is as follows: S1. The pyrrhotite, sulfur and maifanite were ground and sieved respectively, and the particle size was 200-600 mesh. S2. Mix pyrrhotite, sulfur and maifanite in a volume ratio of 2-6:1-3:1-3 to form a mixture; S3. Granulate the mixture to obtain maifanite-based sulfur-iron composite filler.

2. The denitrification biological filter based on maifanite-based sulfur-iron composite packing material according to claim 1, characterized in that, The maifanite-based sulfur-iron composite filler is spherical or ellipsoidal in shape and has hollow pores with a particle size of 3-6 mm.

3. A method for treating nitrogen- and phosphorus-containing wastewater using a maifanite-based sulfur-iron composite packing denitrification biological filter according to any one of claims 1-2, characterized in that, Includes the following steps: Step 1: Arrange the air distribution pipe system (5), air-water distribution system (4), support layer (3), filter media layer (2), and water inlet distribution system (1) in the following order from bottom to top; fill the filter media layer with the prepared maifanite-based sulfur-iron composite filler, fill the support layer with pebbles, and fill the air-water distribution system with filter bricks; Step 2: Inoculate the acclimatized activated sludge into the biological filter, add growth medium and culture until the bacterial colony inoculation and biofilm formation are completed. Step 3: Introduce wastewater into the filter in an upflow manner. The influent is pumped in by a peristaltic pump at the bottom of the filter, and the effluent flows out from the outlet pipe at the top of the filter.

4. The method for treating nitrogen and phosphorus-containing wastewater using a maifanite-based sulfur-iron composite packing denitrification biological filter according to claim 3, characterized in that, The inoculation and colonization time of the bacterial flora is 2-8 days.

5. The method for treating nitrogen- and phosphorus-containing wastewater using a maifanite-based sulfur-iron composite packing denitrification biological filter according to claim 3, characterized in that, The hydraulic retention time of the denitrification biological filter with maifanite-based sulfur-iron composite packing is 0.5-3 hours.

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