A deep phosphorus removal process for water bodies

Abstract

This application discloses a deep phosphorus removal process for water bodies, characterized by the following operations: inoculating activated sludge containing polyphosphate-accumulating bacteria into a reactor, discharging wastewater to be treated for anaerobic treatment, obtaining anaerobic wastewater and activated sludge; controlling the oxygen content in the reactor for aerobic treatment, obtaining aerobic wastewater, which is then discharged into a sedimentation tank for sedimentation and separation, completing the wastewater phosphorus removal; by weight, the polyphosphate-accumulating bacteria comprises an activated carbon carrier and polyphosphate-accumulating bacteria and nano-iron applied to the activated carbon carrier. This application can inhibit the denitrification of polyphosphate-accumulating bacteria in the anaerobic stage and increase the PHB storage in the bacteria, thereby achieving a deeper polyphosphate-accumulating phosphorus removal effect.

Description

Technical Field

[0001] This application relates to the field of wastewater phosphorus removal, and in particular to a deep phosphorus removal process for water bodies. Background Technology

[0002] Currently, common methods for phosphorus removal from industrial wastewater mainly include chemical phosphorus removal, biological phosphorus removal, and combinations of the two. Chemical phosphorus removal often relies on the addition of chemical agents such as iron or aluminum salts to form insoluble phosphate precipitates; while biological phosphorus removal technology, especially biological phosphorus removal based on activated sludge systems, is widely used due to its environmental friendliness and cost-effectiveness.

[0003] In biological phosphorus removal technology, polyphosphate-accumulating bacteria (PABs) play a central role. Under anaerobic conditions, PPAs decompose the polyphosphates stored within their cells, releasing phosphorus into the water. This process generates energy, which is used to absorb readily biodegradable organic matter (such as low-molecular-weight fatty acids) and convert it into energy-storing substances such as poly(β-hydroxybutyrate) (PHA). Under aerobic conditions, PPAs utilize the stored PHA and other organic matter as a carbon source, generating significant energy through respiration. They then absorb phosphates from the water and convert them into polyphosphates, storing them within their cells. This mechanism not only achieves effective phosphorus removal but also promotes phosphorus recycling. Compared to chemical phosphorus removal, biological phosphorus removal processes are more economical and sustainable, reducing secondary pollution problems.

[0004] However, it is worth noting that polyphosphate-accumulating bacteria may also engage in denitrification during the anaerobic phase, in addition to releasing phosphorus, especially when nitrate nitrogen (NO3) is present in the water. - In this situation, some polyphosphate-accumulating bacteria may utilize nitrate nitrogen as an electron acceptor to convert nitrogen. While this behavior helps with denitrification, it also means that some energy and carbon sources (such as PHA) originally used for polyphosphate synthesis are used for denitrification. This process may not only reduce the total amount of phosphorus released during the anaerobic stage but also reduce the available carbon source during the aerobic stage, thus lowering the phosphorus uptake efficiency of polyphosphate-accumulating bacteria. Summary of the Invention

[0005] This application provides a deep phosphorus removal process for water bodies that can inhibit denitrification by polyphosphate-accumulating bacteria during the anaerobic stage and improve the phosphorus absorption efficiency of the bacteria.

[0006] This application provides a deep dephosphorization process, which includes the following operations:

[0007] Activated sludge containing polyphosphate-accumulating agents is inoculated into a reactor, and wastewater to be treated is discharged into it for anaerobic treatment to obtain anaerobic wastewater and activated sludge. The oxygen content in the reactor is controlled to carry out aerobic treatment to obtain aerobic wastewater, which is then discharged into a sedimentation tank for sedimentation and separation to complete the phosphorus removal from the wastewater.

[0008] By weight, the polyphosphate-producing agent comprises an activated carbon carrier and polyphosphate-producing bacteria and nano-iron applied to the activated carbon carrier.

[0009] Nano-zero valent iron can neutralize nitrate nitrogen (NO3) surrounding polyphosphate-accumulating bacteria. - ) is reduced to ammonium nitrogen (NH4) + This disrupts the conditions for denitrification, inhibits the denitrification of polyphosphate-accumulating bacteria in an anaerobic environment, thereby increasing the content of available PHB in the aerobic stage and promoting phosphorus absorption by the bacteria.

[0010] Preferably, the nano-iron is modified nano-iron with carbon-doped titanium dioxide coated on its surface.

[0011] Firstly, carbon-doped carbon dioxide (C-TiO2) coating helps protect nano-iron and reduces its contact oxidation with dissolved oxygen and metal ions in water. Secondly, C-TiO2 has excellent photocatalytic degradation properties, converting large organic molecules adsorbed on it into small carbon sources that are easily absorbed and utilized by polyphosphate-accumulating bacteria, thus promoting PHB production and improving phosphorus uptake during the aerobic phase. Thirdly, carbon doping can form abundant Z-shaped heterojunctions within the TiO2 crystal. This structure effectively expands the response spectrum of TiO2, enhancing its photocatalytic effect under visible light.

[0012] It should be noted that the effect of the carbon-doped carbon dioxide coating layer mentioned above requires the application of ultraviolet or visible light irradiation from the outside.

[0013] Preferably, the modified nano-iron is prepared according to the following method:

[0014] Preparation of nano-iron: A soluble ferric salt solution is dissolved in an ethanol solution, and a reducing agent solution is added dropwise under nitrogen protection to reduce iron ions to iron atoms, thus obtaining a nano-iron solution;

[0015] Precursor preparation: Add dispersant solution to nano iron solution, stir evenly, add anhydrous ethanol solution of tetrabutyl titanate, and disperse evenly to obtain precursor solution;

[0016] Preparation of modified nano-iron: Under stirring conditions, a mixed solution of deionized water, anhydrous ethanol and glacial acetic acid was added dropwise to the precursor solution, and the reaction was stirred to obtain a gel; the gel was aged, dried, ground into powder and then calcined to obtain modified nano-iron;

[0017] Preferably, in the modified nano-iron preparation step, the mass ratio of deionized water, anhydrous ethanol and glacial acetic acid is (3-4):(7-9):(8-10).

[0018] Preferably, the calcination temperature is 500-600℃ and the calcination time is 2-3 hours.

[0019] Preferably, the mass ratio of the tetrabutyl titanate to the ferric salt is 4 to 6:1.

[0020] Preferably, the stirring reaction time is 3 to 5 hours.

[0021] Preferably, the trivalent iron salt is selected from at least one of ferric nitrate, ferric chloride, and ferric sulfate.

[0022] Preferably, the reducing agent is sodium borohydride and / or potassium borohydride.

[0023] Preferably, the concentration of the dispersant in the precursor solution is 2-4 wt%.

[0024] Preferably, the dispersant comprises fatty alcohol polyoxyethylene ether and carboxymethyl cellulose in a mass ratio of 1:1 to 3.

[0025] Fatty alcohol polyoxyethylene ethers can reduce the surface energy of nano-iron and improve its dispersibility. Carboxymethyl cellulose can increase the viscosity of the solution, ensuring the suspension of nano-iron; in addition, carboxymethyl cellulose can act as a carbon source, providing carbon elements for the preparation of C-TiO2 during calcination.

[0026] Preferably, the polyphosphate bacteria include at least one of Acinetobacter, Aeromonas, and Pseudomonas.

[0027] Preferably, the raw materials of the polyphosphate-accumulating agent include: 10 parts activated carbon carrier, 8-12 parts polyphosphate-accumulating bacteria, 0.8-1.5 parts nano iron, and 1-3 parts binder.

[0028] Preferably, the adhesive comprises water-soluble chitosan and polyethylene polyamine in a mass ratio of 1:0.9 to 1.2.

[0029] Preferably, the degree of deacetylation of the water-soluble chitosan is greater than 80%.

[0030] Preferably, the viscosity of the water-soluble chitosan is 100-200 mPa·s.

[0031] The polyethylene polyamine is selected from at least one of diethylenetriamine, triethylenetetramine, and tetraethylenepentamine.

[0032] The adhesive plays a crucial role in promoting the adhesion of nano-iron to the surface and micropores of the activated carbon carrier. Water-soluble chitosan acts as the primary adhesive, while polyethylene polyamine acts as a cross-linking agent. The cross-linking with water-soluble chitosan forms a network structure, which helps ensure the strong adhesion of the nano-iron and prevents it from easily peeling off in water. Furthermore, this network structure has good hydrophilicity, which enhances the wetting of water molecules with the polyphosphate-accumulating bacteria, removes dirt adhering to the surface of the polyphosphate-accumulating bacteria, and ensures its phosphorus absorption function.

[0033] It should be noted that selecting water-soluble chitosan with appropriate viscosity is beneficial in ensuring a balance between its binding ability and permeability, improving the adhesion rate of nano-iron, and inhibiting the denitrification of polyphosphate-accumulating bacteria.

[0034] Preferably, the polyphosphate agent is obtained by dissolving the adhesive in water, adding nano-iron, polyphosphate bacteria and activated carbon carrier, stirring evenly, letting stand, filtering out the precipitate, and drying.

[0035] In summary, this application has the following beneficial effects:

[0036] 1. This application effectively inhibits the denitrification of polyphosphate-accumulating bacteria under anaerobic conditions by co-loading polyphosphate-accumulating bacteria and nano-iron onto an activated carbon carrier, thereby reducing their antagonistic effect on the phosphorus release and polyphosphate accumulation process, improving PHB utilization, and increasing phosphorus absorption rate.

[0037] 2. This application coats carbon-doped titanium dioxide onto the surface of nano-iron, which helps to convert the large molecular organic matter attached to the surface of polyphosphate-accumulating agent into small molecular carbon sources that are easily bioavailable, thereby increasing the content of PHB produced in the anaerobic phosphorus release stage and promoting the polyphosphate-accumulating effect in the aerobic stage.

[0038] 3. Using water-soluble chitosan and polyethylene polyamine as raw materials, a hydrophilic network structure is formed on the surface of polyphosphate-producing bacteria, which not only effectively improves the stability of nano-iron adhesion, but also reduces the deposition of dirt on the surface of the bacteria, significantly improving the long-term effect of polyphosphate-producing bacteria. Detailed Implementation

[0039] Preparation Example

[0040] Preparation Example 1

[0041] Modified nano-iron was prepared according to the following steps:

[0042] Preparation of nano-iron: 2.5g of ferric nitrate solution was added to 250mL of ethanol in water (ethanol volume ratio of 80%), stirred and dissolved to obtain a reaction solution for later use; 0.45g of sodium borohydride was added to 50mL of water to prepare a reducing agent solution for later use; under nitrogen protection, the reducing agent solution was slowly added to the reaction solution, and the addition was completed in 0.5h. After stirring for 30min, nano-iron solution was obtained.

[0043] Precursor preparation: 7.5g of fatty alcohol polyoxyethylene ether and 12.5g of carboxymethyl cellulose were added to 300mL of water and stirred until homogeneous to obtain a dispersant solution for later use; 12.5g of tetrabutyl titanate was added to 50mL of anhydrous ethanol and stirred until dissolved to obtain a tetrabutyl titanate solution for later use; the above nano iron solution was added to the dispersant solution and stirred until homogeneous, and then the tetrabutyl titanate solution was added and stirred until homogeneous to obtain the precursor solution.

[0044] Preparation of modified nano-iron: Under stirring conditions, a mixed solution of 30g deionized water, 80g anhydrous ethanol and 90g glacial acetic acid was added dropwise to the above precursor solution, and the mixture was stirred for 4h to obtain a gel; the gel was aged and dried, ground into powder and then calcined at 550±10℃ to obtain modified nano-iron.

[0045] Preparation Example 2

[0046] Modified nano-iron was prepared according to the following steps:

[0047] Preparation of nano-iron: 2.5g of ferric nitrate solution was added to 250mL of ethanol in water (ethanol volume ratio of 80%), stirred and dissolved to obtain a reaction solution for later use; 0.5g of sodium borohydride was added to 50mL of water to prepare a reducing agent solution for later use; under nitrogen protection, the reducing agent solution was slowly added to the reaction solution, and the addition was completed in 0.5h. After stirring for 30min, nano-iron solution was obtained.

[0048] Precursor preparation: 5g of fatty alcohol polyoxyethylene ether and 15g of carboxymethyl cellulose were added to 300mL of water and stirred until homogeneous to obtain a dispersant solution for later use; 10.2g of tetrabutyl titanate was added to 50mL of anhydrous ethanol and stirred until dissolved to obtain a tetrabutyl titanate solution for later use; the above nano iron solution was added to the dispersant solution and stirred until homogeneous, and then the tetrabutyl titanate solution was added and stirred until homogeneous to obtain the precursor solution.

[0049] Preparation of modified nano-iron: Under stirring conditions, a mixed solution of 40g deionized water, 70g anhydrous ethanol and 100g glacial acetic acid was added dropwise to the above precursor solution, and the mixture was stirred for 4h to obtain a gel; the gel was aged and dried, ground into powder and then calcined at 550±10℃ to obtain modified nano-iron.

[0050] Preparation Example 3

[0051] Modified nano-iron was prepared according to the following steps:

[0052] Preparation of nano-iron: 2.5g of ferric nitrate solution was added to 250mL of ethanol in water (ethanol volume ratio of 80%), stirred and dissolved to obtain a reaction solution for later use; 0.45g of sodium borohydride was added to 50mL of water to prepare a reducing agent solution for later use; under nitrogen protection, the reducing agent solution was slowly added to the reaction solution, and the addition was completed in 0.5h. After stirring for 30min, nano-iron solution was obtained.

[0053] Precursor preparation: 9g of fatty alcohol polyoxyethylene ether and 9g of carboxymethyl cellulose were added to 300mL of water and stirred until homogeneous to obtain a dispersant solution for later use; 15g of tetrabutyl titanate was added to 50mL of anhydrous ethanol and stirred until dissolved to obtain a tetrabutyl titanate solution for later use; the above nano iron solution was added to the dispersant solution and stirred until homogeneous, and then the tetrabutyl titanate solution was added and stirred until homogeneous to obtain the precursor solution.

[0054] Preparation of modified nano-iron: Under stirring conditions, a mixed solution of 40g deionized water, 70g anhydrous ethanol and 80g glacial acetic acid was added dropwise to the above precursor solution, and the mixture was stirred for 5h to obtain a gel; the gel was aged and dried, ground into powder and then calcined at 550±10℃ to obtain modified nano-iron.

[0055] Preparation Example 4,

[0056] The modified iron nanoparticles differ from those in Preparation Example 1 in that no carbon source was added during the precursor preparation step, resulting in titanium dioxide coating on the surface of the iron nanoparticles. The specific procedures are as follows:

[0057] Precursor preparation: 20g of fatty alcohol polyoxyethylene ether was added to 300mL of water and stirred until homogeneous to obtain a dispersant solution for later use; 12.5g of tetrabutyl titanate was added to 50mL of anhydrous ethanol and stirred until dissolved to obtain a tetrabutyl titanate solution for later use; the above nano iron solution was added to the dispersant solution and stirred until homogeneous, and then the tetrabutyl titanate solution was added and stirred until homogeneous to obtain the precursor solution.

[0058] Preparation Example 5

[0059] Nano-iron was prepared as follows: 2.5 g of ferric nitrate solution was added to 250 mL of ethanol (80% ethanol by volume), and stirred to dissolve, obtaining a reaction solution for later use; 0.45 g of sodium borohydride was added to 50 mL of water to prepare a reducing agent solution for later use; under nitrogen protection, the reducing agent solution was slowly added to the reaction solution, and the addition was completed in 0.5 h. After stirring for 30 min, the precipitate was separated by centrifugation, washed with water, and dried to obtain nano-iron.

[0060] Example

[0061] The SBR reactor used in this embodiment has a diameter of 30cm, a height of 50cm, a total volume of 12L, and an effective volume of 10L. It is entirely made of plexiglass, with a cylindrical upper section and a conical bottom sludge discharge hopper. A row of sampling ports spaced 10cm apart is vertically positioned on the reactor wall. A sludge discharge pipe and a microporous aerator are located at the bottom, using forced-air aeration with a rotor flow meter to regulate the aeration rate. The reactor temperature is controlled by a temperature controller, and a temperature sensor monitors the water temperature changes online. A dissolved oxygen (DO) meter measures the dissolved oxygen content during the reaction process online.

[0062] Example 1: A deep phosphorus removal process for water bodies, the treatment steps are as follows:

[0063] Preparation of polyphosphate-accumulating bacteria: 10g of water-soluble chitosan and 10g of diethylenetriamine were dissolved in water. 12g of the modified nano-iron obtained in Preparation Example 1, 100g of polyphosphate-accumulating bacteria, and 100g of activated carbon carrier were added. The mixture was stirred for 1 hour, allowed to stand for 3 hours, filtered to remove the precipitate, and dried at room temperature to obtain the final product. The water-soluble chitosan had a degree of deacetylation of 90% and a viscosity of 100–120 mPa·s. The polyphosphate-accumulating bacteria included 60g of Acinetobacter spp. and 40g of Pseudomonas spp. The activated carbon carrier had an iodine adsorption value of 900 mg / g and a D50 particle size of 2–3 mm.

[0064] First, the SBR reactor is placed under xenon lamp irradiation. Then, activated sludge containing polyphosphate-accumulating bacteria is inoculated into the SBR reactor. The aeration device is turned off, and the wastewater to be treated (initial phosphorus content 40-50 mg / L, nitrate nitrogen content 1-2 mg / L) is introduced, with the wastewater temperature controlled at 23-26℃. The dissolved oxygen content is reduced to below 0.2 mg / L by stirring, and anaerobic treatment is carried out for 3 hours to obtain anaerobic wastewater and activated sludge. The aeration device is then turned on to maintain the dissolved oxygen content at 3±0.5 mg / L, and aerobic treatment is carried out for 5 hours to obtain aerobic wastewater, which is discharged into a sedimentation tank for sedimentation and separation. The settled sludge (containing polyphosphate-accumulating bacteria) is returned to the reactor, and the separated supernatant is discharged, completing the phosphorus removal process.

[0065] Example 2: A deep phosphorus removal process for water bodies, the treatment steps are as follows:

[0066] Preparation of polyphosphate-accumulating bacteria: 5g of water-soluble chitosan and 6g of diethylenetriamine were dissolved in water. 9.5g of modified nano-iron obtained in Preparation Example 2, 80g of polyphosphate-accumulating bacteria, and 100g of activated carbon carrier were added. The mixture was stirred for 1 hour, allowed to stand for 3 hours, filtered to remove the precipitate, and dried at room temperature to obtain the final product. The water-soluble chitosan had a degree of deacetylation of 90% and a viscosity of 100–120 mPa·s; the polyphosphate-accumulating bacteria consisted of 30g of Acinetobacter spp. and 50g of Pseudomonas spp.; the activated carbon carrier had an iodine adsorption value of 900 mg / g and a D50 particle size of 2–3 mm.

[0067] First, the SBR reactor is placed under xenon lamp irradiation. Then, activated sludge containing polyphosphate-accumulating bacteria is inoculated into the SBR reactor. The aeration device is turned off, and the wastewater to be treated (initial phosphorus content 40-50 mg / L, nitrate nitrogen content 1-2 mg / L) is introduced, with the wastewater temperature controlled at 23-26℃. The dissolved oxygen content is reduced to below 0.2 mg / L by stirring, and anaerobic treatment is carried out for 3 hours to obtain anaerobic wastewater and activated sludge. The aeration device is then turned on to maintain the dissolved oxygen content at 3±0.5 mg / L, and aerobic treatment is carried out for 5 hours to obtain aerobic wastewater, which is discharged into a sedimentation tank for sedimentation and separation. The settled sludge (containing polyphosphate-accumulating bacteria) is returned to the reactor, and the separated supernatant is discharged, completing the phosphorus removal process.

[0068] Example 3: A deep phosphorus removal process for water bodies, the treatment steps are as follows:

[0069] Preparation of polyphosphate-accumulating bacteria: 15g of water-soluble chitosan and 15g of diethylenetriamine were dissolved in water. Then, 15g of modified nano-iron obtained in Preparation Example 3, 120g of polyphosphate-accumulating bacteria, and 100g of activated carbon carrier were added. The mixture was stirred for 1.5h, allowed to stand for 4h, filtered to remove the precipitate, and dried at room temperature to obtain the final product. The water-soluble chitosan had a degree of deacetylation of 90% and a viscosity of 100–120 mPa·s; the polyphosphate-accumulating bacteria consisted of 50g of Acinetobacter spp. and 70g of Pseudomonas spp.; the activated carbon carrier had an iodine adsorption value of 900 mg / g and a D50 particle size of 2–3 mm.

[0070] First, the SBR reactor is placed under xenon lamp irradiation. Then, activated sludge containing polyphosphate-accumulating bacteria is inoculated into the SBR reactor. The aeration device is turned off, and the wastewater to be treated (initial phosphorus content 40-50 mg / L, nitrate nitrogen content 1-2 mg / L) is introduced, with the wastewater temperature controlled at 23-26℃. The dissolved oxygen content is reduced to below 0.2 mg / L by stirring, and anaerobic treatment is carried out for 3 hours to obtain anaerobic wastewater and activated sludge. The aeration device is then turned on to maintain the dissolved oxygen content at 3±0.5 mg / L, and aerobic treatment is carried out for 5 hours to obtain aerobic wastewater, which is discharged into a sedimentation tank for sedimentation and separation. The settled sludge (containing polyphosphate-accumulating bacteria) is returned to the reactor, and the separated supernatant is discharged, completing the phosphorus removal process.

[0071] Example 4, a deep phosphorus removal process for water bodies, differs from Example 1 in that, in the preparation of polyphosphate-accumulating bacteria, an equal amount of modified nano-iron obtained in Example 4 is used instead of the modified nano-iron obtained in Example 1.

[0072] Example 5, a deep phosphorus removal process for water, differs from Example 1 in that, in the preparation of polyphosphate-accumulating bacteria, an equal amount of nano-iron obtained in Example 5 is used to replace the modified nano-iron obtained in Example 1.

[0073] Example 6, a deep phosphorus removal process for water bodies, differs from Example 1 in that, in the preparation of polyphosphate-accumulating bacteria, an equal amount of water-soluble chitosan is used instead of diethylenetriamine.

[0074] Example 7, a deep phosphorus removal process for water bodies, differs from Example 1 in that, in the preparation of polyphosphate-accumulating bacteria, an equal amount of sodium alginate (viscosity 130-150 mPa·s) is used to replace water-soluble chitosan.

[0075] Comparative Example

[0076] Comparative Example 1, a deep phosphorus removal process for water bodies, differs from Example 5 in that nano-iron is not added during the preparation of polyphosphate-accumulating bacteria.

[0077] Performance testing

[0078] Experiment 1: Phosphorus Removal Rate Test of Polyphosphate-Acting Agent

[0079] (1) Samples were taken from the supernatant obtained from each example and comparative example, and the remaining phosphorus content was determined by ammonium molybdate spectrophotometry. The phosphorus removal rate was calculated and denoted as P1.

[0080] (2) In accordance with the ultraviolet spectrophotometry method specified in HJ / T 346-2007, determine the content of nitrate nitrogen in the supernatant of the solution and calculate the nitrate nitrogen reduction rate.

[0081] Experiment 2: Stability Test of Polyphosphate Polymer

[0082] The sludge (containing polyphosphate-accumulating agents) from the sedimentation tank is returned to the reactor for phosphorus removal from the circulating wastewater using the same process. The phosphorus content of the supernatant after the 3rd and 5th cycles is determined using ammonium molybdate spectrophotometry, and the phosphorus removal rates are calculated and denoted as P3 and P5, respectively. A higher phosphorus removal rate indicates better stability and durability of the polyphosphate-accumulating agents.

[0083] Table 1. Test Results

[0084]

[0085] Analysis of experimental results:

[0086] (1) As can be seen from Examples 1-7 and Comparative Example 1, and Table 1, the addition of nano-iron to polyphosphate-accumulating bacteria can improve its phosphorus and nitrate removal efficiency in wastewater. This may be because nano-iron can reduce nitrate nitrogen in wastewater, inhibiting polyphosphate-accumulating bacteria from using nitrate nitrogen for denitrification. This increases phosphorus release and the production of PHB within the bacteria, while reducing the consumption of PHB stored in the bacteria by denitrification. This effectively enhances the polyphosphate accumulation of the bacteria during the aerobic stage, thereby increasing the phosphorus removal rate.

[0087] It should be noted that the rate of nitrate nitrogen consumption due to denitrification by polyphosphate-accumulating bacteria is lower than that due to the reduction effect of nano-iron.

[0088] (2) Combining Examples 1 and 4-5 with Table 1, it can be seen that coating the surface of nano-iron with titanium dioxide or carbon-doped titanium dioxide is beneficial to improving the phosphorus removal rate. The reason may be that titanium dioxide or carbon-doped titanium dioxide has photocatalytic degradation effect, which can degrade macromolecular organic matter in wastewater and convert it into small molecule carbon sources that are easily absorbed and utilized by bacteria, promote the generation and accumulation of PHB, and help increase the polyphosphate accumulation in the aerobic stage.

[0089] (3) Combining Examples 1 and 6-7 with Table 1, it can be seen that using diethylenetriamine and water-soluble chitosan as binders is beneficial to improving the stability of phosphorus absorption by polyphosphate-accumulating agents and maintaining a higher phosphorus removal rate during long-term operation. This may be because diethylenetriamine and water-soluble chitosan, while improving the adhesion of nano-iron and polyphosphate-accumulating bacteria, can form a stable hydrophilic network structure, which helps reduce the accumulation and clogging of surface dirt, ensuring the stable performance of polyphosphate-accumulating agents during long-term operation.

[0090] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A deep phosphorus removal process for water bodies, characterized in that, This includes the following operations: Activated sludge containing polyphosphate-accumulating agents is inoculated into a reactor, and wastewater to be treated is discharged into it for anaerobic treatment to obtain anaerobic wastewater and activated sludge. The oxygen content in the reactor is controlled to carry out aerobic treatment to obtain aerobic wastewater, which is then discharged into a sedimentation tank for sedimentation and separation to complete the phosphorus removal from the wastewater. By weight, the polyphosphate-accumulating agent comprises an activated carbon carrier, polyphosphate-accumulating bacteria applied to the activated carbon carrier, and modified iron nanoparticles coated with carbon-doped titanium dioxide. The modified iron nanoparticles are prepared according to the following method: Preparation of nano-iron: A soluble ferric salt solution is dissolved in an ethanol solution, and a reducing agent solution is added dropwise under nitrogen protection to reduce iron ions to iron atoms, thus obtaining a nano-iron solution; Precursor preparation: Add dispersant solution to nano iron solution, stir evenly, add anhydrous ethanol solution of tetrabutyl titanate, and disperse evenly to obtain precursor solution; Preparation of modified nano-iron: Under stirring conditions, a mixed solution of deionized water, anhydrous ethanol and glacial acetic acid was added dropwise to the precursor solution, and the reaction was stirred to obtain a gel; the gel was aged, dried, ground into powder and then calcined to obtain modified nano-iron; In the modified nano-iron preparation step, the mass ratio of deionized water, anhydrous ethanol and glacial acetic acid is (3-4):(7-9):(8-10); The calcination temperature is 500–600℃, and the calcination time is 2–3 hours.

2. The process according to claim 1, characterized in that, The dispersant comprises fatty alcohol polyoxyethylene ether and carboxymethyl cellulose in a mass ratio of 1:1 to 3.

3. The process according to claim 1, characterized in that, The polyphosphate-accumulating bacteria include at least one of Acinetobacter, Aeromonas, and Pseudomonas.

4. The process according to claim 1, characterized in that, The raw materials of the polyphosphate-accumulating agent include: 10 parts activated carbon carrier, 8-12 parts polyphosphate-accumulating bacteria, 0.8-1.5 parts nano iron, and 1-3 parts binder.

5. The process according to claim 4, characterized in that, The adhesive comprises water-soluble chitosan and polyethylene polyamine in a mass ratio of 1:0.9 to 1.2, wherein the degree of deacetylation of the water-soluble chitosan is greater than 80%.

6. The process according to claim 5, characterized in that, The viscosity of the water-soluble chitosan is 100–200 mPa·s.

7. The process according to claim 5, characterized in that, The polyethylene polyamine is selected from at least one of diethylenetriamine, triethylenetetramine, and tetraethylenepentamine.

8. The process according to any one of claims 4 to 7, characterized in that, The polyphosphate-producing agent is obtained by dissolving the adhesive in water, adding nano-iron, polyphosphate bacteria and activated carbon carrier, stirring evenly, letting stand, filtering out the precipitate, and drying.

Images