Composite phosphorus removal agent and method for removing organic phosphorus from circulating water

Abstract

The application discloses a composite phosphorus removal agent and a method for removing organic phosphorus from circulating cooling water, which can effectively and economically remove the organic phosphorus in the waste water. The inorganic phosphorus and the organic phosphorus in the waste water can be effectively removed through the mutual cooperation among the substances in the phosphorus removal agent. The phosphorus removal agent has low dosage and good removal effect, and can meet the demand for removing the organic phosphorus in the waste water under alkaline conditions.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater treatment, in particular to a composite dephosphorizing agent for organic phosphorus in circulating water and a method for removing organic phosphorus. Background Art

[0002] Excessive phosphorus in water can lead to eutrophication. Phosphorus is one of the major pollutant emissions subject to strict national control. As environmental protection efforts become increasingly stringent, the government has established stricter limits on phosphorus emissions in wastewater. Effective July 1, 2017, Sinopec Corporation began enforcing the GB31570-2015 "Petroleum Refining Industry Pollutant Emission Standard" and GB31571-2015 "Petrochemical Industry Pollutant Emission Standard," raising the total phosphorus concentration in discharged wastewater from less than 1.0 mg / L to a special emission limit of less than 0.50 mg / L. Petroleum refining and deep processing inevitably generate large amounts of high-phosphorus wastewater. Circulating water, due to its high total phosphorus content and large volume, accounts for over two-thirds of the plant's total annual phosphorus emissions. Organic phosphorus contributes over 50% of this total phosphorus, making it the primary source of organic phosphorus in wastewater treatment plants.

[0003] Methods for removing organic phosphorus from circulating cooling water wastewater primarily include biological, oxidative degradation, and chemical methods. Biological removal of organic phosphorus is a relatively economical phosphorus removal technology. This method utilizes phosphate-releasing bacteria and, under appropriate conditions, can remove over 80% of organic phosphorus from wastewater. However, it is not suitable for treating wastewater with poor biodegradability. To inhibit microbial growth, circulating cooling water systems often continuously administer oxidizing and non-oxidizing biocides during operation. As a result, the BOD (biochemical oxygen demand) / COD (chemical oxygen demand) ratio of the wastewater is nearly zero, resulting in poor biodegradability and poor phosphorus removal using direct biological methods. Oxidative degradation methods utilize methods such as Fenton oxidation, photocatalytic oxidation, ozone-catalytic oxidation, iron-carbon microelectrolysis, and low-temperature plasma-catalytic oxidation to oxidatively degrade organic phosphorus, breaking down organic phosphate groups into orthophosphates and organic matter for removal. However, the volume of circulating cooling water wastewater required for treatment is large, typically reaching hundreds or even thousands of cubic meters per hour. Oxidative degradation methods are costly and energy-intensive. Chemical phosphorus removal is a method of removing phosphorus by reacting chemical substances with phosphate in wastewater to generate insoluble phosphate precipitates. However, the chemical method can only remove phosphate (orthophosphorus) in wastewater and has poor effect on organic phosphorus in wastewater. In addition, the circulating water and double-membrane backwash water contain a large amount of organic phosphorus corrosion inhibitors and scale inhibitors and high molecular scale inhibitors and dispersants, which seriously affect the precipitation effect of phosphorus removal.

[0004] On the other hand, the simultaneous industrial phosphorus and hardness removal process can minimize the company's infrastructure investment and operating costs and improve treatment efficiency. However, the alkaline environment of the hardness removal reaction will seriously affect the removal of organic phosphorus. Therefore, it is necessary to develop a technology for removing organic phosphorus that is resistant to high pH values.

[0005] CN101941770B discloses a method for removing phosphorus from phosphorus-containing wastewater, which uses bleaching powder to remove total phosphorus from the wastewater. The free chlorine released by the bleaching powder converts organic phosphorus into phosphates or phosphites. Calcium ions in the bleaching powder react with the phosphates or phosphites to produce precipitates that are removed. However, this method requires a large dosage, and the free chlorine released by the bleaching powder is limited. Under normal temperature and a given pH, the organic phosphorus cannot be completely oxidized to orthophosphorus.

[0006] CN107555649B discloses a method for deep removal of organic phosphorus from wastewater. This involves adding ozone and a co-catalyst to the wastewater to initiate an oxidation reaction, using a strong oxidant to treat the wastewater containing organic phosphorus. However, this method requires harsh reaction conditions, requires a large amount of co-catalyst, and is very expensive.

[0007] CN111977772B is a kind of phosphorus remover for processing phosphating wastewater, and the main agent of its phosphorus remover is guanidine polymer hydrochloride, is a class of nitrogenous organic matter, and the phosphorus in the phosphating wastewater processed is mainly orthophosphate, that is, inorganic phosphorus.But, now on the market, there are already very mature methods and products to remove inorganic phosphorus, and organic phosphorus contains CP bond, is difficult to remove by this method.In addition, this method adds guanidine polymer hydrochloride in the treated water, can increase the content of organic nitrogen that is difficult to remove in water, in this method, the dosage of phosphorus remover is 0.65-30.8g / L, and dosage is very large, under the large environment that current national standard requires external drainage total nitrogen to be less than 30mg / L, is not suitable for industrial implementation.

[0008] In 2016, Yan Wenbao's master's thesis, "Research on the Removal of Organic Phosphorus in Circulating Water," at Shandong University, investigated the effectiveness of different agents in removing the organic phosphorus corrosion and scale inhibitors HEDP, PBTCA, and ATMP from circulating cooling water effluent. The results showed that while flocculants such as aluminum sulfate, ferric chloride, ferrous sulfate, and magnesium chloride could remove some organic phosphorus, they still failed to meet the Class I discharge standard of less than 0.5 mg / L total phosphorus in treated water. Furthermore, the dosage of these agents, as high as 2.0-6.0 g / L, was prohibitive for industrial application. Furthermore, although the pH of the wastewater was raised before treatment in this study, the addition of large amounts of strong acid and weak base salts resulted in a pH of only 6.8-7.1 after treatment. Therefore, the phosphorus removal reaction occurred under neutral conditions, which still did not meet the alkaline pH required for subsequent direct hardness removal.

[0009] Therefore, there is still no suitable method in the prior art that can effectively remove organic phosphorus in wastewater under alkaline pH conditions. Summary of the Invention

[0010] The purpose of the present invention is to overcome the defects of the prior art and provide a composite phosphorus removal agent and a method for removing organic phosphorus in circulating cooling water wastewater, which can efficiently and economically remove inorganic phosphorus and organic phosphorus in wastewater through the synergistic effect between substances in the phosphorus removal agent. The phosphorus removal agent has a low dosage and a good removal effect, meeting the demand for removing organic phosphorus in wastewater under alkaline conditions.

[0011] The purpose of the present invention is achieved by adopting the following technical solutions.

[0012] The present invention provides a composite phosphorus removal agent, characterized in that the composite phosphorus removal agent comprises an inorganic phosphorus removal agent and a phosphorus removal synergist;

[0013] The phosphorus removal synergist is selected from the compounds of the following general formula:

[0014] RO-(C2H4O) n -(C3H6O) m -R',

[0015] Wherein R is H, C6-C20 alkyl or C6-C20 alkylcarbonyl, n=0-50, m=0-50, m and n are not 0 at the same time, R' is H, OH, SO3M or C1-C6 straight chain alkyl, and M is a monovalent metal cation.

[0016] The present invention also provides a method for removing organic phosphorus in wastewater, which is characterized in that the pH of the phosphorus-containing wastewater is adjusted to 9.5-11, and the composite phosphorus removal agent of the present invention is added. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The figure shows the effect of the composite phosphorus removal agent of the present invention on removing various organic phosphorus corrosion and scale inhibitors in circulating cooling water wastewater. DETAILED DESCRIPTION

[0018] The present invention will be described in further detail below with reference to the accompanying drawings and examples, through which the features and advantages of the present invention will become more clearly understood.

[0019] The word "exemplary" is used exclusively herein to mean "serving as an example, example, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. Although various aspects of the embodiments are shown in the drawings, the drawings are not necessarily drawn to scale unless otherwise indicated.

[0020] In addition, the technical features involved in different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0021] The inventors discovered during their research that, compared to neutral conditions, alkaline pH conditions shift the reaction equilibrium between the prior art phosphorus removal agents and organic phosphorus to the left, hindering the reaction between the two agents and significantly reducing the effectiveness of organic phosphorus removal. Furthermore, carbonate ions added to wastewater for hardness removal can interfere with the reaction between the phosphorus removal agent and organic phosphorus. Furthermore, the scale inhibitors and dispersants contained in circulating cooling water wastewater also have a significant negative impact on phosphorus removal. To achieve the same phosphorus removal effect, higher concentrations of the phosphorus removal agent must be added to wastewater containing the scale inhibitors and dispersants, which is clearly not conducive to industrial application.

[0022] Based on the findings of the inventors, the present invention provides a composite phosphorus removal agent, comprising an inorganic phosphorus removal agent and a phosphorus removal synergist.

[0023] In the present invention, the phosphorus removal synergist is selected from the compounds of the following general formula:

[0024] RO-(C2H4O) n -(C3H6O) m -R'

[0025] Wherein R is H, C6-C20 alkyl or C6-C20 alkylcarbonyl, preferably H or C8-C16 straight-chain alkyl, n=0-50, preferably n=5-22, m=0-50, preferably m=5-20, m and n are not 0 at the same time, R' is H, OH, SO3M or C1-C6 straight-chain alkyl, and M is a monovalent metal cation.

[0026] The present invention also provides a method for removing organic phosphorus in wastewater, which is characterized in that the pH of the phosphorus-containing wastewater is adjusted to 9.5-11, and the composite phosphorus removal agent of the present invention is added.

[0027] The composite phosphorus removal agent of the present invention can form complex precipitation with phosphonate or phosphine carboxylate in the organic phosphorus compound molecules in waste water under alkaline conditions.

[0028] According to an embodiment of the present invention, the inorganic phosphorus removal agent undergoes a hydrolysis reaction in the wastewater and reacts with organic phosphorus, chelates with phosphonate or phosphine carboxylate, etc., so that the organic phosphorus forms a colloid or precipitate, and can destabilize the formed colloid and allow the suspended precipitate to settle rapidly. The inorganic phosphorus removal agent can be selected from one or both of an inorganic small molecule phosphorus removal agent and an inorganic polymer phosphorus removal agent. The inorganic small molecule phosphorus removal agent and the inorganic polymer phosphorus removal agent are compounded, and the synergistic effect of the inorganic small molecule phosphorus removal agent and the inorganic polymer phosphorus removal agent can be brought into play, with better effect. In an embodiment of the present invention, the mass ratio of the inorganic small molecule phosphorus removal agent and the inorganic polymer phosphorus removal agent is 1: (0.25-1.5), preferably 1: (0.3-0.8). The inorganic small molecule phosphorus removal agent is preferably selected from one or more of aluminum sulfate, potassium aluminum sulfate, aluminum chloride, ferric sulfate, ferric chloride, aluminum ferric chloride, and aluminum ferric sulfate. The inorganic polymer phosphorus removal agent is preferably selected from one or more of polyaluminum sulfate, polyaluminum chloride, polyferric chloride sulfate, polyaluminum silicate sulfate, polyferric sulfate, polyferric trichloride, and polyaluminum chloride.

[0029] The inventors unexpectedly discovered during experiments that the phosphorus removal synergist molecules have excellent electrolyte resistance and antistatic properties during the phosphorus removal reaction and subsequent precipitation process, and have synergistic synergy with the main phosphorus removal agent. The hydrophilic oxygen-containing groups contained in the molecules are irregularly bent and stretched in the sewage, and the lone pair electrons on the large number of oxygen atoms make the system charge density large and widely distributed. Adding a small amount to water can reduce the electrostatic repulsion between particles / interfaces during the phosphorus removal process in the wastewater. On the other hand, the hydrophobic groups in the phosphorus removal synergist molecules can also promote particle aggregation and accelerate solution destabilization, greatly improving the pH resistance of the phosphorus removal agent, significantly improving the removal effect of organic phosphorus in circulating cooling water wastewater under high pH conditions, and at the same time greatly reducing the dosage of the agent.

[0030] According to an embodiment of the present invention, the composite phosphorus removal agent of the present invention can effectively remove organic phosphorus in wastewater, and the amount used in the wastewater is such that the mass concentration ratio of the total phosphorus in the phosphorus-containing wastewater to the composite phosphorus removal agent is between 1:(5-50).

[0031] According to an embodiment of the present invention, the consumption of the phosphorus removal synergist is that the mass ratio of inorganic phosphorus removal agent and phosphorus removal synergist is 1:(0.02-0.20), preferably 1:(0.04-0.10). The phosphorus removal synergist can be selected from but not limited to one or more of C6-C20 fatty alcohol polyoxyethylene ether, C6-C20 fatty alcohol polyoxypropylene ether, C6-C20 alkylphenol polyoxyethylene ether, C6-C20 alkylphenol polyoxypropylene ether, C6-C20 fatty alcohol polyoxyethylene ether sulfonate, C6-C20 alkylphenol polyoxyethylene ether sulfonate, polyethylene glycols, and polypropylene glycols. Adopting two or more phosphorus removal synergists to be composite, effect is better, has the organophosphorus that is more conducive to removing in waste water, and reduces the consumption of medicament.

[0032] According to an embodiment of the present invention, the composite phosphorus removal agent also includes an organic polymer flocculant. The organic polymer flocculant can strengthen flocculation and precipitation, promote the formation of flocs, and destabilize suspended sediments and colloids. The organic polymer flocculant adsorbs suspended particles and colloids in the wastewater, so that the polymer chains are entangled and cross-linked to form bridges, thereby increasing the size and coarsening of the flocculation structure, and finally forming a precipitate for removal. According to an embodiment of the present invention, the organic polymer flocculant can be a natural and synthetic organic polymer flocculant conventional in the art. Preferably, the organic polymer flocculant is a polyacrylamide flocculant, which can include at least one selected from anionic polyacrylamide, cationic polyacrylamide and non-ionic polyacrylamide. The number average molecular weight of the polymer flocculant is generally 6 million to 50 million, preferably 8 million to 40 million. According to an embodiment of the present invention, only a small amount of organic polymer flocculant needs to be added to exert its effect, the flocculation speed is fast, and it is less affected by coexisting salts, sewage pH value and temperature. Compounding an inorganic phosphorus removal agent with an organic polymer flocculant can leverage the rapid gel breaking properties of the inorganic phosphorus removal agent and the adsorption and bridging capabilities of the organic polymer flocculant, achieving a synergistic effect. In an embodiment of the present invention, the mass ratio of the inorganic phosphorus removal agent to the organic polymer flocculant is 1:(0.005-0.05), preferably 1:(0.015-0.02).

[0033] According to an embodiment of the present invention, a composite phosphorus removal agent of the present invention is provided for use in wastewater containing organic phosphorus to remove organic phosphorus. In particular, the composite phosphorus removal agent of the present invention is particularly suitable for removing organic phosphorus from wastewater under alkaline conditions.

[0034] According to an embodiment of the present invention, a method for removing organic phosphorus from wastewater is provided, wherein the pH of the phosphorus-containing wastewater is adjusted to 9.5-11, and the composite phosphorus removal agent of the present invention is added. Specifically, the pH of the phosphorus-containing wastewater is adjusted to 9.5-11, and the composite phosphorus removal agent of the present invention is added, wherein the mass concentration ratio of the phosphorus removal agent to the total phosphorus in the phosphorus-containing wastewater is (5-50):1, and the mixture is stirred to allow a phosphorus removal reaction to occur. After further flocculation and sedimentation, the phosphorus-containing sludge is discharged into a sludge thickening tank.

[0035] The composite phosphorus removal agent of the present invention can efficiently and economically remove organic phosphorus from wastewater containing organic phosphorus, such as circulating cooling water blowdown. The composite phosphorus removal agent of the present invention effectively removes both inorganic and organic phosphorus from wastewater through the synergistic interaction between the substances in the agent, achieving high removal efficiency while requiring a low dosage of the agent. In particular, the composite phosphorus removal agent of the present invention can remove organic phosphorus from wastewater under alkaline conditions.

[0036] Example 1

[0037] The organophosphorus corrosion and scale inhibitors listed in Table 1 were added to the circulating cooling water of a petrochemical enterprise to make the organophosphorus content in the wastewater reach 4.0 mg / L (measured in P, the same below). Composite phosphorus removal agent stock solutions were prepared and added to the wastewater at amounts of 60 mg / L, 80 mg / L, 100 mg / L and 120 mg / L, respectively. After addition, the concentrations of the components of the composite phosphorus removal agent in the wastewater are as follows.

[0038] 60mg / L: aluminum ferric sulfate 34mg / L, polysilicon aluminum sulfate 20mg / L, polypropylene glycol 400 3.9mg / L, polyoxyethylene ether sulfonate 2.1mg / L;

[0039] 80mg / L: aluminum ferric sulfate 43mg / L, polysilicon aluminum sulfate 29mg / L, polypropylene glycol 400 5.2mg / L, polyoxyethylene ether sulfonate 2.8mg / L;

[0040] 100mg / L: aluminum ferric sulfate 60mg / L, polysilicon aluminum sulfate 30mg / L, polypropylene glycol 400 6.5mg / L, polyoxyethylene ether sulfonate 3.5mg / L;

[0041] 120mg / L: aluminum ferric sulfate 78mg / L, polysilicate aluminum sulfate 30mg / L, polypropylene glycol 400 7.8mg / L, polyoxyethylene ether sulfonate 4.2mg / L.

[0042] Adjust the reaction pH to 9.8-10.0, react for 10 minutes, and settle for 30 minutes before taking the supernatant to determine the total phosphorus (organic phosphorus) in the water. The phosphorus removal effects of different concentrations of phosphorus removal agents are as follows: Figure 1 shown.

[0043] Table 1 Organophosphorus corrosion and scale inhibitors added in Example 1 and their corresponding abbreviations

[0044]

[0045] Depend on Figure 1 It can be seen from the phosphorus removal effect that the composite phosphorus removal agent of the present invention can achieve a good removal effect on various organic phosphorus in wastewater even under alkaline conditions, achieving a special emission limit of total phosphorus mass concentration less than 0.50 mg / L, and the amount of phosphorus removal agent added is small, which is conducive to large-scale industrial application.

[0046] Example 2

[0047] The total phosphorus concentration in the circulating water of a petrochemical enterprise was 3.8 mg / L, of which 77% was organic phosphorus. A composite phosphorus removal agent with the following composition was added to the wastewater (the concentration refers to the concentration of each component in the wastewater after the composite phosphorus removal agent is added): 60 mg / L of ferric sulfate, 20 mg / L of polyferric chloride, 10.5 mg / L of polyoxyethylene polyoxypropylene copolymer (Pluronic P123), and 5.5 mg / L of fatty alcohol polyoxyethylene ether-15. The mixture was stirred evenly, the pH value was adjusted to 10.4-10.7, the reaction was carried out for 10 minutes, and the supernatant was taken for determination after flocculation and sedimentation for 30 minutes. The remaining organic phosphorus in the wastewater was 0.24 mg / L.

[0048] Example 3

[0049] The total phosphorus concentration in the circulating cooling water of a refinery is 4.5 mg / L, of which 65% is organic phosphorus. A composite phosphorus removal agent with the following composition is added to the wastewater (the concentration is the concentration of each component in the wastewater after the addition of the composite phosphorus removal agent): 80 mg / L of ferric sulfate, 30 mg / L of polyferric chloride, 2.5 mg / L of nonylphenol polyoxyethylene ether, and 5.0 mg / L of polyethylene glycol 2000. The mixture is stirred evenly, the pH value is adjusted to 10.4-10.7, the reaction is carried out for 10 minutes, and the supernatant is taken for determination after sedimentation for 30 minutes. The remaining organic phosphorus in the water is 0.39 mg / L.

[0050] Example 4

[0051] The circulating water wastewater was treated under the same conditions as in Example 3, except that 2.0 mg / L of cationic polyacrylamide with a molecular weight of 15 million was additionally added. After settling for 30 minutes, the supernatant was taken for determination, and the residual organic phosphorus in the water was 0.29 mg / L.

[0052] Example 5

[0053] The wastewater from the ethylene circulating cooling water of a certain petrochemical enterprise contained 4.5 mg / L of total phosphorus, including 3.6 mg / L of organic phosphorus. A composite phosphorus removal agent with the following composition was added to the wastewater (the concentration refers to the concentration of each component in the wastewater after the composite phosphorus removal agent is added): 90 mg / L of aluminum sulfate, 30 mg / L of polyaluminum chloride, 5.0 mg / L of fatty alcohol polyoxyethylene ether-20, 95.0 mg / L of polyoxyethylene laurate, and 1.0 mg / L of cationic polyacrylamide with a molecular weight of 20 million. The mixture was stirred evenly, the pH value was adjusted to 10.0-10.5, the reaction was carried out for 10 minutes, and the supernatant was taken for determination after sedimentation for 30 minutes. The remaining organic phosphorus in the water was 0.37 mg / L.

[0054] Comparative Example 1

[0055] Aluminum sulfate was added to the wastewater of Example 4 until its concentration in the wastewater was 90 mg / L, and the mixture was stirred evenly. The pH value was adjusted to 10.0-10.5, and the mixture was reacted for 10 minutes. After settling for 30 minutes, the supernatant was taken for determination, and the residual organic phosphorus in the water was 3.0 mg / L.

[0056] Comparative Example 2

[0057] Polyaluminum chloride was added to the wastewater of Example 4 until its concentration in the wastewater was 90 mg / L, and the mixture was stirred evenly. The pH value was adjusted to 10.0-10.5, and the mixture was reacted for 10 minutes. After settling for 30 minutes, the supernatant was taken for determination, and the residual organic phosphorus in the water was 3.1 mg / L.

[0058] Comparative Example 3

[0059] To the wastewater of Example 4, a phosphorus removal agent of the following composition was added (the concentration is the concentration of each component in the wastewater after the phosphorus removal agent was added): 90 mg / L of aluminum sulfate and 30 mg / L of polyaluminum chloride. The mixture was stirred evenly, the pH value was adjusted to 10.0-10.5, the reaction was carried out for 10 minutes, and the supernatant was taken for determination after settling for 30 minutes. The residual organic phosphorus in the water was 2.8 mg / L.

[0060] The present invention has been described above with reference to preferred embodiments, but these embodiments are merely exemplary and serve only as an illustration. On this basis, various replacements and improvements can be made to the present application, all of which fall within the scope of protection of the present application.

Claims

1. A composite phosphorus removal agent, characterized in that: The composite phosphorus removal agent includes an inorganic phosphorus removal agent and a phosphorus removal synergist; The phosphorus removal synergist is selected from the compounds of the following general formula: R-O-(C2H4O) n -(C3H6O) m -R’, wherein R is H, C6-C20 alkyl or C6-C20 alkylcarbonyl, n=0-50, m=0-50, m and n are not 0 at the same time, R' is H, OH, SO3M or C1-C6 straight-chain alkyl, and M is a monovalent metal cation; The phosphorus removal synergist comprises one or two selected from C6-C20 fatty alcohol polyoxyethylene ethers, C6-C20 fatty alcohol polyoxypropylene ethers, C6-C20 alkylphenol polyoxyethylene ethers, C6-C20 alkylphenol polyoxypropylene ethers, C6-C20 fatty alcohol polyoxyethylene ether sulfonates, C6-C20 alkylphenol polyoxyethylene ether sulfonates, polyethylene glycols, and polypropylene glycols; The inorganic phosphorus removal agent includes an inorganic small molecule phosphorus removal agent and an inorganic high molecular phosphorus removal agent; The inorganic small molecule phosphorus removal agent includes one or more selected from aluminum sulfate, potassium aluminum sulfate, aluminum chloride, ferric sulfate, ferric chloride, aluminum ferric chloride, and aluminum ferric sulfate; The inorganic polymer dephosphorizing agent includes one or more selected from the group consisting of polyaluminum sulfate, polyaluminum chloride, polyferric sulfate chloride, polyaluminum silicate sulfate, polyferric sulfate, polyferric trichloride, and polyaluminum chloride.

2. The composite phosphorus removal agent according to claim 1, wherein The mass ratio of the inorganic phosphorus removal agent to the phosphorus removal synergist is 1:(0.02-0.20).

3. The composite phosphorus removal agent according to claim 2, characterized in that The mass ratio of the inorganic phosphorus removal agent to the phosphorus removal synergist is 1:(0.04-0.10).

4. The composite phosphorus removal agent according to any one of claims 1 to 3, characterized in that R is a C8-C16 straight chain alkyl group.

5. The composite phosphorus removal agent according to claim 1, characterized in that n=5-22。 6. The composite phosphorus removal agent according to claim 1, characterized in that m=5-20。 7. The composite phosphorus removal agent according to claim 1, characterized in that The mass ratio of the inorganic small molecule phosphorus remover to the inorganic high molecular weight phosphorus remover is 1:(0.25-1.5).

8. The composite phosphorus removal agent according to claim 7, characterized in that The mass ratio of the inorganic small molecule phosphorus remover to the inorganic high molecular weight phosphorus remover is 1:(0.3-0.8).

9. The composite phosphorus removal agent according to claim 1, characterized in that The composite phosphorus removal agent also includes an organic polymer flocculant.

10. The composite phosphorus removal agent according to claim 9, characterized in that: The mass ratio of the inorganic phosphorus removal agent to the organic polymer flocculant is 1:(0.005-0.05).

11. The composite phosphorus removal agent according to claim 10, characterized in that: The mass ratio of the inorganic phosphorus removal agent to the organic polymer flocculant is 1:(0.015-0.02).

12. The composite phosphorus removal agent according to claim 9, characterized in that: The organic polymer flocculant includes at least one selected from anionic polyacrylamide, cationic polyacrylamide and nonionic polyacrylamide, and the number average molecular weight of the polymer flocculant is 6 million to 50 million.

13. The composite phosphorus removal agent according to claim 12, characterized in that: The number average molecular weight of the polymer flocculant is 8 million to 40 million.

14. Use of the composite phosphorus removal agent according to any one of claims 1 to 13 in wastewater containing organic phosphorus.

15. A method for removing organic phosphorus from wastewater, characterized in that: The pH of the phosphorus-containing wastewater is adjusted to 9.5-11, and the composite phosphorus removal agent according to any one of claims 1-13 is added.

16. The method according to claim 15, wherein The mass concentration ratio of the total phosphorus in the phosphorus-containing wastewater to the composite phosphorus removal agent is 1:(5-50).

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