A phosphorus removal agent composition for treating phosphorus-containing wastewater and a method for applying the same

Abstract

The present application relates to the field of sewage treatment, in particular to a phosphorus removal agent composition for phosphorus-containing wastewater and an application method thereof.The phosphorus removal agent composition comprises, by mass fraction, 50-88% of inorganic metal salt, 10-45% of polymeric metal salt and 2-15% of cationic surfactant.The mass concentration ratio of the phosphorus removal agent composition to total phosphorus in the phosphorus-containing wastewater is 5-50:1.The phosphorus removal agent composition is particularly suitable for phosphorus removal treatment of circulating water blowdown wastewater, especially circulating water blowdown wastewater with more than 50% of organic phosphorus.

Description

Technical Field

[0001] The present invention relates to the field of sewage treatment, and in particular to a phosphorus removal agent composition for treating phosphorus-containing wastewater and an application method thereof. Background Art

[0002] Phosphorus is a bionutrient. If left uncontrolled, it can lead to eutrophication of water bodies and seriously impact aquatic environmental quality. Phosphorus emission standards have been gradually tightened in recent years. GB 31570-2015, "Petroleum Refining Industry Pollutant Emission Standard," and GB 31571-2015, "Petrochemical Industry Pollutant Emission Standard," have set stricter limits on total phosphorus in wastewater discharged from petrochemical enterprises.

[0003] The circulating water wastewater of petrochemical enterprises has a high phosphorus content and a large water volume. Its discharge accounts for more than 2 / 3 of the annual phosphorus discharge of the entire plant, and it is the source of phosphorus in the sewage treatment plant. Effectively removing phosphorus from circulating water wastewater can greatly reduce the pressure of phosphorus removal at the end of the sewage treatment plant. The phosphorus in circulating water wastewater includes inorganic phosphorus and organic phosphorus, and the removal methods include biochemical method and chemical precipitation method. Due to the poor biodegradability of circulating water wastewater, the direct use of biochemical phosphorus removal method is not effective. The inorganic phosphorus in circulating water wastewater can be removed by adding aluminum salts, iron salts or calcium salts to form phosphate precipitation; while the removal of organic phosphorus is more difficult, and it is often first converted into inorganic phosphorus by oxidation methods such as photocatalytic oxidation, ozone oxidation, and Fenton oxidation, and then the corresponding chemical agents are added for removal. However, the volume of circulating water wastewater is large, generally in the hundreds of m 3 / h or even thousands of m 3 / h, the oxidation method is costly and energy-intensive.

[0004] Patents CN105668749B, CN105668748B, CN105668747B, and CN105668746B disclose methods for removing phosphorus from wastewater containing 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTCA), hydroxyethylidene diphosphonic acid (HEDP), aminotrimethylene phosphonic acid (ATMP), and mixtures of these organophosphorus compounds. These methods first add solid calcium hydroxide to the wastewater to adjust the pH to 11-12, then add iron or aluminum salts. Finally, anionic polyacrylamide, a flocculant, is added for precipitation and separation. Calculations show that in these patents, the mass concentration ratio of iron or aluminum salts to phosphorus is 166-420:1, requiring excessive amounts of phosphorus removal agents. Furthermore, this method requires adjusting the pH to alkaline, further increasing treatment costs.

[0005] In the composite aspect of phosphorus removal agent, patent CN103991941B discloses a composite sewage chemical phosphorus removal agent, which is a mixed solution of ferrous sulfate-aluminum chloride-methanol-polydimethyl diallyl ammonium chloride. The polydimethyl diallyl ammonium chloride plays a role in improving the phosphorus removal effect through the bridging adsorption of organic polymer compounds, which is consistent with the action of commonly used flocculants such as polyacrylamide. Patent CN111977772B discloses a phosphorus removal agent for treating phosphating wastewater, which is composed of guanidine polymer hydrochloride, polyaluminum chloride and anionic polyacrylamide. The phosphorus in the treated phosphating wastewater is orthophosphate. SUMMARY

[0006] The purpose of the present application is to overcome the defects of poor removal effect of organic phosphorus in circulating water blowdown water and excessive dosage of phosphorus removal agent in the prior art, and to provide a phosphorus removal agent composition capable of efficiently and economically removing phosphorus-containing wastewater, especially organic phosphorus in circulating water blowdown water.

[0007] The present application also provides a method for using the phosphorus removal agent composition.

[0008] The present application provides a phosphorus removal agent composition for treating phosphorus-containing wastewater, which comprises, by mass fraction: inorganic metal salt 50-88%, polymeric metal salt 10-45%, and quaternary ammonium salt cationic surfactant 2-15%.

[0009] Preferably, the phosphorus removal agent composition of the present application comprises, by mass fraction: inorganic metal salt 60-82%, polymeric metal salt 12-35%, and cationic surfactant 5-12%.

[0010] Preferably, the inorganic metal salt is a trivalent iron salt and an aluminum salt, such as ferric chloride, aluminum chloride, ferric sulfate, aluminum sulfate, etc.

[0011] Preferably, the polymeric metal salt is a polymer of a trivalent iron salt and an aluminum salt, preferably polymeric ferric chloride, polymeric aluminum chloride, polymeric aluminum sulfate, polymeric ferric sulfate, etc.

[0012] Wherein, the quaternary ammonium salt cationic surfactant is selected from a single-chain quaternary ammonium salt cationic surfactant and a double-chain quaternary ammonium salt cationic surfactant, more preferably a double-chain quaternary ammonium salt cationic surfactant. The single-chain quaternary ammonium salt cationic surfactant is preferably at least one of C10-C18 alkyl trimethyl ammonium halide and C10-C18 alkyl imidazole halide, such as tetradecyl trimethyl ammonium bromide or ammonium chloride, hexadecyl trimethyl ammonium bromide or ammonium chloride, octadecyl trimethyl ammonium bromide or ammonium chloride, 1-methyl-3-dodecyl imidazole bromide or chloride; the double-chain quaternary ammonium salt cationic surfactant is preferably at least one of di-C8-C14 alkyl dimethyl ammonium halide, such as didecyl dimethyl ammonium bromide or ammonium chloride, didoctadecyl dimethyl ammonium chloride or ammonium bromide, etc.

[0013] The application method of the phosphorus removal agent composition provided by the present invention comprises: adjusting the pH of phosphorus-containing wastewater to 6-10, adding the phosphorus removal agent composition of the present invention, stirring, and precipitating.

[0014] Preferably, the pH of the phosphorus-containing wastewater is adjusted to 6-8. Typical circulating water systems operate under natural pH conditions or with acidification, with the pH controlled between 6.8 and 9.5. Since the phosphorus removal agent composition dissolves in water and its aqueous solution has a pH <7, it can lower the pH of the treated wastewater, essentially eliminating the need for additional acid or alkali to adjust the wastewater.

[0015] When the phosphorus removal agent composition of the present invention is used to treat phosphorus-containing wastewater, the mass concentration ratio of the phosphorus removal agent composition to the total phosphorus in the phosphorus-containing wastewater is 5 to 50:1, preferably 10 to 40:1.

[0016] The total phosphorus mass concentration in the phosphorus-containing wastewater is 0.5 to 5 mg / L. In particular, since the phosphorus removal agent composition performs significantly better than other phosphorus removal agents in treating wastewater with a high proportion of organic phosphorus, the proportion of organic phosphorus contained in the phosphorus-containing wastewater can be greater than 50%, for example, it can be 50% to 100%, preferably 50% to 90%.

[0017] The present invention provides a dephosphorization agent composition for removing organic phosphorus in phosphorus-containing wastewater, which has low dosage and good treatment effect. The inventors found in their research that inorganic metal salts, such as trivalent iron salts and aluminum salts, can form chelates with organic phosphorus; the adsorption effect of polymetallic salts on flocs and their own bridging effect during the hydrolysis process can promote the detachment of the chelate from water, and the inorganic metal salts and polymetallic salts can play a better synergistic role under a certain ratio; the inventors further found that the addition of a small amount of ionic surfactants, particularly quaternary ammonium salt-type cationic surfactants, can effectively improve the effect of removing organic phosphorus. Quaternary ammonium salt-type cationic surfactants can not only adsorb organic phosphorus anions through the cations they carry, but more importantly, the long chains they carry can be inserted into the micelles of the flocs, increasing the hydrophobicity of the micelles, thereby promoting the destabilization of the flocs and the collision and aggregation between the flocs through van der Waals interactions. DETAILED DESCRIPTION

[0018] In the following examples, the mass concentrations of total phosphorus and orthophosphorus (measured as P) were determined using the ammonium molybdate spectrophotometric method specified in GB / T 6913-2008. The mass concentration of organic phosphorus (measured as P) is the total phosphorus concentration minus the orthophosphorus concentration.

[0019] Example 1

[0020] Phosphorus-containing wastewater A comes from the wastewater discharged from a refinery's circulating water system: its circulating water system adds various agents such as orthophosphorus and organophosphorus scale inhibitor HPAA; the total phosphorus mass concentration of the wastewater discharged from this system is 2.2 mg / L (measured as P, the same below), of which the mass concentration of organophosphorus is 1.86 mg / L.

[0021] The composition of the components in the phosphorus removal agent composition 1 is (by mass): 65% of ferric chloride, 28% of polyaluminium chloride, and 7% of didodecyldimethylammonium chloride.

[0022] Phosphorus-containing wastewater A was fed into a phosphorus removal unit and phosphorus removal agent composition 1 (dosage concentration: 60 mg / L) was added. The pH after addition of the phosphorus removal agent composition was 7.9. The mixture was stirred for 10 minutes. After settling for 30 minutes, the supernatant was collected and measured for total phosphorus and organic phosphorus. The phosphorus removal results are shown in Table 1.

[0023] Comparative Example 1

[0024] Phosphorus removal agent D1 is 70% ferric chloride and 30% polyaluminium chloride.

[0025] The experimental method is the same as that of Example 2, except that the phosphorus removal agent D1 (dosage concentration is 60 mg / L) is added. The phosphorus removal results are shown in Table 1.

[0026] Comparative Example 2

[0027] Phosphorus removal agent D2 is polyaluminium chloride.

[0028] The experimental method is the same as that of Example 2, except that the phosphorus removal agent D2 (dosage concentration is 60 mg / L) is added. The phosphorus removal results are shown in Table 1.

[0029] Example 2

[0030] The composition of the components in the phosphorus removal agent composition 2 is: 65% of ferric chloride, 28% of polyaluminium chloride, and 7% of tetradecyltrimethylammonium chloride.

[0031] The experimental method is the same as that of Example 1, except that the phosphorus removal agent composition 2 (dosage concentration is 60 mg / L) is added. The phosphorus removal results are shown in Table 1.

[0032] Example 3

[0033] Phosphorus-containing wastewater B comes from the wastewater discharged from a refinery's circulating water system: its circulating water system adds various agents such as the organic phosphorus scale inhibitor PBTCA; the total phosphorus mass concentration of the wastewater discharged from this system is 3 mg / L (measured in P, the same below), of which the mass concentration of organic phosphorus is 3 mg / L.

[0034] The composition of the components in the phosphorus removal agent composition 3 is: 80% of ferric chloride, 15% of polyaluminium chloride, and 5% of didodecyldimethylammonium chloride.

[0035] Phosphorus-containing wastewater B was fed into a phosphorus removal unit and phosphorus removal agent composition 3 (dosage concentration: 120 mg / L) was added. The pH after addition of the phosphorus removal agent composition was 7.5. The mixture was stirred for 10 minutes. After settling for 30 minutes, the supernatant was collected and the total phosphorus content in the water was determined. The phosphorus removal results are shown in Table 1.

[0036] Comparative Example 3

[0037] The composition of the components in the phosphorus removal agent composition D3 is: 20% of ferric chloride, 73% of polyaluminium chloride, and 7% of tetradecyltrimethylammonium chloride.

[0038] The experimental method is the same as that of Example 1, except that the phosphorus removal agent composition D3 (dosage concentration is 60 mg / L) is added. The phosphorus removal results are shown in Table 1.

[0039] Example 4

[0040] The composition of the components in the phosphorus removal agent composition 4 is: 78% of ferric chloride, 20% of polyaluminium chloride, and 2% of didecyldimethylammonium bromide.

[0041] The experimental method is the same as that of Example 1, except that the phosphorus removal agent composition 4 (dosage concentration is 60 mg / L) is added. The phosphorus removal results are shown in Table 1.

[0042] Example 5

[0043] The composition of the components in the phosphorus removal composition 5 is: 63% of ferric chloride, 27% of polyaluminium chloride, and 10% of 1-methyl-3-dodecyl imidazole bromide.

[0044] The experimental method is the same as that of Example 3, except that the phosphorus removal agent composition 5 (dosage concentration is 100 mg / L) is added. The phosphorus removal results are shown in Table 1.

[0045] Table 1 Phosphorus removal results

[0046]

[0047]

[0048] From the comparison between Example 1 and Example 2, it can be seen that the synergistic effect of the double-chain cationic surfactant is better than that of the single-chain cationic surfactant; from Example 1 and Comparative Examples 1 and 2, it can be seen that the addition of quaternary ammonium salt cationic surfactants can promote the removal of phosphorus; from the comparison between Example 1 and Comparative Example 3, it can be seen that inorganic metal salts and polymeric metal salts can only exert better synergistic effects at a certain ratio.

Claims

1. A method for using a phosphorus removal agent composition to remove organic phosphorus in phosphorus-containing wastewater, the phosphorus removal agent composition comprising, by weight: 50% to 88% of an inorganic metal salt, 10% to 45% of a polymeric metal salt, and 2% to 15% of a quaternary ammonium salt cationic surfactant. The inorganic metal salt is selected from trivalent iron salts and aluminum salts, the polymeric metal salt is selected from polymers of trivalent iron salts and aluminum salts, and the quaternary ammonium salt cationic surfactant is selected from tetradecyltrimethylammonium bromide or ammonium chloride, hexadecyltrimethylammonium bromide or ammonium chloride, octadecyltrimethylammonium bromide or ammonium chloride, 1-methyl-3-dodecylimidazolium bromide or chloride, 1-methyl-3-dodecylimidazolium bromide or chloride, didecyldimethylammonium bromide or ammonium chloride, didodecyldimethylammonium chloride or ammonium bromide. The quaternary ammonium salt cationic surfactant absorbs organic phosphorus anions through its own cations, and its long chains are inserted into the micelles of the flocs, thereby increasing the hydrophobicity of the micelles, thereby promoting the destabilization of the flocs and the collision and aggregation between the flocs through van der Waals interactions.

2. The method according to claim 1, wherein Calculated by mass, it includes: 60% to 82% of inorganic metal salt, 12% to 35% of polymeric metal salt, and 5% to 12% of cationic surfactant.

3. The method according to claim 1, wherein The inorganic metal salt is selected from one or more of ferric chloride, aluminum chloride, ferric sulfate and aluminum sulfate.

4. The method according to claim 1, wherein The polymeric metal salt is selected from one or more of polyferric chloride, polyaluminum chloride, polyaluminum sulfate and polyferric sulfate.

5. The method according to claim 1, comprising: The pH of the phosphorus-containing wastewater is adjusted to 6-10, and the phosphorus removal agent composition is added, stirred, and precipitated.

6. The method according to claim 1, wherein The mass concentration ratio of the phosphorus removal agent composition to the total phosphorus in the phosphorus-containing wastewater is 5-50:

1.

7. The method according to claim 1, wherein The mass concentration ratio of the phosphorus removal agent composition to the total phosphorus in the phosphorus-containing wastewater is 10-40:

1.

8. The method according to claim 1, wherein The total phosphorus mass concentration in the phosphorus-containing wastewater is 0.5~5 mg / L.

9. The method according to claim 1, wherein The proportion of organic phosphorus contained in the phosphorus-containing wastewater is 50% to 100%.

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