A method for inhibiting phosphate fouling and clogging of anaerobic ammonia oxidation granular sludge

Abstract

This invention discloses a method for inhibiting phosphate scaling and clogging in granular anaerobic ammonia oxidation (ANAO) sludge using magnetic biochar. By slowly releasing an iron source and utilizing the porous carrier properties of MBC, the direct precipitation of iron ions with phosphate in solution is reduced, maintaining unobstructed mass transfer channels within the granular sludge and improving denitrification performance. This invention uses MBC as the iron source carrier, which is added to the system during the operation of the ANAO reactor. The iron species in the MBC are supported on a carbon-based framework in the form of magnetite nanocrystals, enabling a slow-release supply of iron. Simultaneously, the porous structure and surface functional groups of MBC promote microbial attachment and enhance electron transfer processes. Through these effects, phosphate scaling is inhibited, and the unobstructed mass transfer channels within the granular sludge are maintained, thereby improving the system's denitrification performance. This method is simple to operate and suitable for the stable operation of ANAO systems in high-phosphate wastewater treatment processes.

Description

Technical Field

[0001] This invention relates to a method for inhibiting mass transfer blockage caused by phosphate scaling in anaerobic ammonia oxidation granular sludge under high phosphate wastewater conditions by adding magnetic biochar (MBC) to regulate the occurrence and release pathway of iron. This method belongs to the field of wastewater biological denitrification technology. Background Technology

[0002] Anaerobic ammonia oxidation (Anammox) technology, due to its low consumption and high efficiency, shows significant promise for the treatment of high ammonia nitrogen wastewater. Granular sludge morphology is key to the efficient retention of ammonia by anaerobic ammonia oxidizing bacteria (AnAOB). Iron plays a central role in the Anammox metabolic network: Fe 2+ As the central coordinating ion of the porphyrin ring, Fe participates in the synthesis and conformational maintenance of cytochrome c, forming the structural basis of the electron transport chain; simultaneously, Fe... 2+ As an essential cofactor for hydrazine synthase (HZS) and hydrazine dehydrogenase (HDH), it directly determines the synthesis and conversion efficiency of hydrazine intermediates. Furthermore, Fe... 2+ By compressing the cell surface electric double layer and stimulating the secretion of hydrophobic proteins in EPS, granular sludge formation is promoted.

[0003] However, when treating high-phosphorus wastewater (such as wastewater from the papermaking and slaughtering industries), the system often contains a large amount of PO4. 3- Ions. They readily react with PO4 when a free iron source is added. 3- Insoluble phosphates (such as ferric phosphate or iron phosphate) precipitate, causing them to deposit on the surface or within the pores of anaerobic granular sludge, forming a passivation layer and clogging mass transfer channels. When the sludge particle density is too high, it accumulates at the bottom of the reactor, affecting the fluidization characteristics of the sludge bed, reducing microbial activity, and ultimately leading to reactor failure.

[0004] Biochar is a carbon material with a high specific surface area and abundant surface functional groups, exhibiting excellent adsorption performance and electron transfer capabilities for pollutants in water. MBC prepared by loading Fe3O4 nanoparticles onto biochar retains the carrier properties of biochar while also possessing good electrical conductivity, thereby promoting electron transfer and sludge granulation during anaerobic processes.

[0005] Therefore, there is an urgent need for a method that can both provide a slow-release iron source and inhibit the deposition of phosphate on the surface and inside of granular sludge. Summary of the Invention

[0006] The technical problem to be solved by this invention is that the direct addition of free iron sources to high-phosphate wastewater can easily cause iron and phosphorus precipitation and blockage, affecting the stable operation of the anaerobic ammonia oxidation system.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0008] A method for inhibiting phosphate scaling and clogging of anaerobic ammonia oxidation granular sludge: During the operation of the anaerobic ammonia oxidation reactor for wastewater treatment, magnetic biochar is added to the reaction system; through the dispersion of the magnetic biochar in the reaction system, iron is released into the microenvironment of the granular sludge in a slow-release manner, thereby reducing the probability of iron ions reacting with phosphate in the bulk liquid phase; at the same time, phosphate deposition on the surface and in the internal pores of the granular sludge is inhibited, thereby slowing down or avoiding mass transfer clogging of the granular sludge.

[0009] Preferably, the magnetic biochar contains iron oxides supported on a carbon-based material.

[0010] More preferably, the iron oxide is magnetite, i.e., Fe3O4.

[0011] Furthermore, the Fe3O4 particle size is 20-100 nm. Fe3O4 nanocrystals possess stable chemical properties and can continuously release Fe. 2+ Nanoscale Fe3O4 nanocrystals facilitate surface adsorption and dispersion, thereby enhancing the sustained-release effect.

[0012] Preferably, the magnetic biochar has a porous structure, which is beneficial for enhancing microbial attachment and accelerating the granulation of anaerobic ammonia oxidation sludge.

[0013] Preferably, the dosage of the magnetic biochar is 0.05~3.0 g / L. A significant scale inhibition effect can be observed within this dosage range.

[0014] Preferably, the magnetic biochar is added during the start-up phase of the anaerobic ammonia oxidation reactor to promote the formation of granular sludge. Adding magnetic biochar can act as a sludge nucleation carrier, increasing sludge particle size and activity.

[0015] Preferably, after granular sludge becomes scaled and clogged, the granular sludge is pretreated before magnetic biochar is added to restore its mass transfer performance.

[0016] Preferably, the pretreatment is physical crushing.

[0017] Preferably, the PO4 in the wastewater 3- The concentration is 5~20 mg / L.

[0018] This invention provides a method for inhibiting phosphate scaling and clogging in anaerobic ammonia oxidation granular sludge using magnetic biochar. By slowly releasing an iron source and utilizing the porous carrier characteristics of MBC, the direct precipitation of iron ions with phosphate in the solution is reduced, the mass transfer channels inside the granular sludge remain unobstructed, and the denitrification performance is improved.

[0019] Compared with the prior art, the present invention has the following beneficial effects: 1. Inhibits phosphate scaling in wastewater: By using MBC slow-release iron source, Fe can be significantly reduced. 2+ With PO4 3- The direct precipitation reaction inhibits the deposition of phosphates on the surface and in the pores of granular sludge.

[0020] 2. Maintain unobstructed mass transfer channels in granular sludge: The iron source released by MBC mainly acts on the microenvironment of granular sludge, reducing the amount of sediment in the main liquid, which can keep the internal channels of granular sludge unobstructed, improve the fluidity of the sludge bed and the amount of microorganisms in the reactor.

[0021] 3. Improve system denitrification efficiency: Since mass transfer and sludge activity are guaranteed, the method of this invention can improve the removal efficiency of ammonia nitrogen and total nitrogen in the system, while avoiding system collapse caused by blockage.

[0022] 4. Excellent carrier function for microorganisms: MBC has a porous carbon-based structure and surface functional groups, which can promote the attachment of anaerobic ammonia-oxidizing bacteria and enhance the electron transfer of microorganisms; MBC can enhance the granulation and stability of sludge and provide a secondary habitat for granular sludge.

[0023] 5. Simple operation: The method of this invention does not require complicated equipment. It only requires adding MBC to the reactor regularly in proportion to inhibit scale formation. It is suitable for the dosing process of conventional anaerobic ammonia oxidation reactors in sewage treatment plants. Detailed Implementation

[0024] To make the present invention more apparent and understandable, preferred embodiments are described in detail below.

[0025] Example 1: Validation of the effect of MBC as a sludge granulation carrier Magnetite biochar (MBC) can be prepared using biomass such as straw, sawdust, and sludge as carbon sources, following conventional biochar preparation processes (e.g., pyrolysis at 400–600℃). The biochar is then co-precipitated or impregnated with FeCl3 solution before calcination, resulting in the loading of magnetite nanoparticles (Fe3O4) onto the carbon matrix. For example, biochar and FeCl3 are mixed at a mass ratio of 1:8, co-precipitated under alkaline conditions, and calcined to obtain Fe3O4-containing magnetic biochar (MBC). The MBC is a black powder with a porous structure. For example, in this embodiment, the MBC used has an Fe content of approximately 10% and a particle size of approximately 50 nm.

[0026] Two parallel SBR reactors were set up and inoculated with flocculent Anammox sludge (MLVSS ≈ 2.5 g / L, particle size < 0.1 mm). The control group received no additives, while the experimental group received 1.0 g / L LMBC. Operating conditions: 35℃, pH 7.2, influent NH4+. + -N 90mg / L, NO2 --N 120mg / L. The treatment lasted 50 days, and the results are shown in Table 1.

[0027] Table 1. Effects of MBC on the Granulation Process of Anaerobic Ammonium Oxidation Sludge

[0028] Example 2: Verification of MBC's Anti-scaling Effect under High Phosphorus Conditions Two groups of sludge that had formed stable particles were taken: one group originated from free Fe 2+ The system, a group derived from the MBC system, was placed in separate reactors, with 10 mg / L PO4 introduced into the influent for each reactor. 3- The experiment was run for 50 days, and the results are shown in Table 2.

[0029] Table 2 Comparison of particle mass transfer and mineral deposition in different iron source systems under high phosphorus conditions

[0030] Example 3: Verification of the enhanced denitrification effect of MBC Take the free Fe that has been severely blocked 2+ The granular sludge (η=0.35) in the system was crushed, washed, and divided into two portions. The control group received continuous addition of 15 mg / L free Fe. 2+ The experimental group was given 1.5 g / L LMBC. The treatment lasted for 40 days, and the results are shown in Table 3.

[0031] Table 3. Comparison of denitrification performance of clogged sludge after different remediation strategies

[0032] The above embodiments demonstrate that the method of the present invention effectively solves the problem of phosphate scaling and clogging in anaerobic ammonia oxidation granular sludge in high-phosphorus wastewater by leveraging the triple synergistic technology advantages of MBC, and has significant engineering application value.

Claims

1. A method for inhibiting phosphate scaling and clogging in anaerobic ammonia oxidation granular sludge, characterized in that, During the operation of the anaerobic ammonia oxidation reactor for wastewater treatment, magnetic biochar is added to the reaction system. Through the dispersion of the magnetic biochar in the reaction system, iron is released into the microenvironment of the granular sludge in a slow-release manner, thereby reducing the probability of iron ions reacting with phosphates in the main liquid phase. At the same time, it inhibits the deposition of phosphates on the surface and in the internal pores of the granular sludge, thereby slowing down or avoiding mass transfer blockage of the granular sludge.

2. The method as described in claim 1, characterized in that, The magnetic biochar contains iron oxides supported on a carbon-based material.

3. The method as described in claim 2, characterized in that, The iron oxide mentioned is magnetite, namely Fe3O4.

4. The method as described in claim 3, characterized in that, The particle size of the Fe3O4 is 20~100nm.

5. The method as described in claim 1, characterized in that, The magnetic biochar has a porous structure, which is beneficial for enhancing microbial attachment and accelerating the granulation of anaerobic ammonia oxidation sludge.

6. The method as described in claim 1, characterized in that, The dosage of the magnetic biochar is 0.05~3.0 g / L.

7. The method as described in claim 1, characterized in that, The magnetic biochar is added during the start-up phase of the anaerobic ammonia oxidation reactor to promote the formation of granular sludge.

8. The method as described in claim 1, characterized in that, After granular sludge becomes scaled and clogged, it is pretreated before magnetic biochar is added to restore its mass transfer performance.

9. The method as described in claim 1, characterized in that, The pretreatment is physical crushing.

10. The method according to any one of claims 1-9, characterized in that, The wastewater contains PO4 3- The concentration is 5~20 mg / L.

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