A method for removing phosphorus from acidic phosphorus-containing wastewater

Abstract

The present invention relates to a method for removing phosphorus from acidic phosphorus-containing wastewater, comprising the following steps: 1) subjecting catalyst wastewater to sludge-water separation to obtain phosphorus-containing wastewater and sludge residue; 2) adding an electrolyte salt to the phosphorus-containing wastewater and stirring to homogenize; 3) further adding an alkali to the phosphorus-containing wastewater to adjust the pH of the phosphorus-containing wastewater to 3-7, so that the wastewater becomes colloidal; and 4) subjecting the colloidal wastewater to solid-liquid separation. The present invention reduces the phosphorus content of ultra-high-concentration phosphorus-containing catalyst wastewater exceeding 10,000 mg / L to below 3 mg / L after treatment, achieving efficient phosphorus removal from ultra-high-concentration phosphorus-containing catalyst wastewater and avoiding impact on sewage treatment plants.

Description

Technical Field

[0001] The invention belongs to the technical field of wastewater treatment, and particularly relates to a method for removing phosphorus from acidic phosphorus-containing wastewater. Background Art

[0002] In recent years, with the rapid development of the catalyst production industry, compounds such as aluminosilicates have been widely used, but the wastewater produced has high turbidity and complex components. In addition, in order to adjust the acid-base activity, electronic and geometric structure of the catalyst and improve the performance of the catalyst, catalyst additives need to be added during catalyst production. Phosphorus-containing additives are one of them. However, with the addition of phosphorus additives, a large amount of high-concentration phosphorus-containing wastewater will be generated. For the main Al-containing 3+ PO4 3- Ionic catalyst wastewater contains phosphorus in the range of 10,000-15,000 mg / L, a pH of 0.5-2.0, and total dissolved solids of 30,000-50,000 mg / L. If left untreated, this wastewater will have a significant impact on subsequent sewage treatment systems. Therefore, the need for simple, rapid, low-cost, and efficient treatment of this type of phosphorus-containing wastewater has become a key concern.

[0003] At present, the main treatment technologies for phosphorus-containing wastewater at home and abroad are chemical, biological and adsorption methods. Among them, the chemical method mainly uses flocculation and precipitation to treat inorganic and high-concentration phosphorus-containing wastewater. This method has good phosphorus removal effect and stable operation; the biological method mainly uses A / O, A 2 Processes such as sintering, sintering, and sintering-branch reactors (SBRs) are used to treat low-concentration and organic phosphorus-containing wastewater. Adsorption methods primarily utilize low-cost, high-adsorption adsorbents such as fly ash and zeolite to treat low-concentration phosphorus-containing wastewater. However, some ultra-high-concentration phosphorus-containing wastewaters currently appearing in industrial production are difficult to treat through flocculation and precipitation methods to ensure that phosphorus discharge in the wastewater meets discharge standards. Combination processes, such as chemical-biological and chemical-adsorption methods, are often used. These processes are suitable for treating phosphorus-containing wastewater with concentrations less than 2000 mg / L. However, there are few reports on the treatment of ultra-high-concentration phosphorus-containing catalyst wastewater with a pH less than 2 and a phosphorus content exceeding 10,000 mg / L. Therefore, the development of an efficient wastewater phosphorus removal method is urgently needed.

[0004] CN112742345A discloses a method for removing phosphorus and nitrogen from wastewater using modified diatomaceous earth. The method involves adding diatomaceous earth to a sulfuric acid solution or a hydrochloric acid solution for a first modification step, then adding solid anhydrous magnesium sulfate and stirring to obtain a semi-muddy modified diatomaceous earth mixture. Solid sodium phosphate is then added to the resulting mixture for a second modification step. The modified diatomaceous earth is then added to the aeration tank of the biological treatment section of the wastewater treatment plant or to the effluent of the aeration process section to remove phosphorus and nitrogen from the wastewater. This invention utilizes chemical precipitation combined with biological methods to remove nitrogen and phosphorus from wastewater. However, the optimal ratio of the reagents is determined based on the total amount of ammonia nitrogen and the ratio of phosphate radicals, resulting in poor treatment results for wastewater with extremely high phosphorus content.

[0005] CN111995104A discloses a process for removing phosphorus and fluoride from industrial wastewater. The process involves adjusting the pH of the wastewater to 2-3, gradually adding calcium hydroxide and stirring until the pH reaches 10-11, adding a flocculant and centrifuging, filtering to obtain a first filtrate, measuring the calcium ion content of the first filtrate, adding a slightly excessive amount of sodium carbonate and stirring, then centrifuging and filtering to obtain a second filtrate, adding sulfuric acid to adjust the pH to 6-8, and filtering after standing for 1 hour. This invention uses a chemical precipitation method to remove phosphorus and fluoride from industrial wastewater, but this method is difficult to apply to phosphorus removal in strongly acidic, high-phosphorus catalyst wastewater.

[0006] CN111547939A discloses a phosphorus removal process for high-concentration COD wastewater. The process involves discharging the wastewater into a primary treatment tank, where insoluble particulate matter, suspended solids, and floating matter are physically removed, discharging liquid 1. Liquid 1 undergoes anaerobic treatment to degrade macromolecular substances into small molecules, discharging liquid 2. Liquid 2 then enters an electrochemical water treatment device, where, after electrochemical treatment, low-phosphorus wastewater is discharged. The process then proceeds to a secondary sedimentation tank and a deammonification process. This invention utilizes anaerobic treatment to reduce the COD content of the wastewater, electrochemical phosphorus removal, and a deammonification membrane for ammonia removal. While effective at removing high-concentration COD, it is less effective at removing phosphorus.

[0007] CN112678990A discloses a method for treating phosphate-containing wastewater and its application. The method involves adding acid to adjust the pH of the wastewater to 3-6, adding magnesium salt and ammonium salt, and stirring to obtain a reaction solution. Alkaline solution is then added to adjust the pH of the reaction to 7-8, precipitating magnesium ammonium phosphate solids. Solid-liquid separation is then performed to reduce the total phosphorus in the wastewater. This invention significantly removes total phosphorus from wastewater, but is not suitable for phosphorus removal from strongly acidic, high-phosphorus catalyst wastewater.

[0008] In view of the limitations of the above existing technologies, how to remove phosphorus from strongly acidic high-phosphorus catalyst wastewater is an urgent problem to be solved. Summary of the Invention

[0009] The object of the present invention is to provide a method for removing phosphorus from acidic phosphorus-containing wastewater to solve the defect in the prior art that the treatment effect of high-phosphorus-containing and strongly acidic wastewater is not ideal.

[0010] To achieve the above object, the present invention provides a method for removing phosphorus from acidic phosphorus-containing wastewater, comprising the following steps:

[0011] 1) Separating the catalyst wastewater into mud and water to obtain phosphorus-containing waste liquid and mud residue;

[0012] 2) adding electrolyte salts to the phosphorus-containing waste liquid and stirring to homogenize;

[0013] 3) Continue to add alkali to the phosphorus-containing waste liquid to adjust the pH of the phosphorus-containing waste liquid to 3-7, and the waste liquid is in a sol state;

[0014] 4) Separate the waste liquid into solid and liquid form.

[0015] In the method for removing phosphorus from acidic phosphorus-containing wastewater of the present invention, the mud-water separation method in step 1) is natural sedimentation, and the natural sedimentation time is 6 to 30 hours, preferably 15 to 24 hours.

[0016] The phosphorus removal method for acidic phosphorus-containing wastewater of the present invention, wherein the pH of the phosphorus-containing wastewater obtained after mud-water separation in step 1) is less than or equal to 2, and the phosphorus content is greater than or equal to 10,000 mg / L.

[0017] In the method for removing phosphorus from acidic phosphorus-containing wastewater of the present invention, the electrolyte salts in step 2) are inorganic salts and organic salts.

[0018] In the method for removing phosphorus from acidic phosphorus-containing wastewater of the present invention, the electrolyte salt in step 2) is one or more of NaCl, ZnCl2, MgCl2, KCl, NaCH3COOH and NH4CH3COOH.

[0019] In the method for removing phosphorus from acidic phosphorus-containing wastewater of the present invention, the amount of electrolyte salt added in step 2) is 1 to 10 g / L, preferably 3 to 7 g / L.

[0020] In the method for removing phosphorus from acidic phosphorus-containing wastewater of the present invention, the alkali in step 3) is one or more of an inorganic alkali and an organic alkali.

[0021] In the method for removing phosphorus from acidic phosphorus-containing wastewater of the present invention, the alkali in step 3) is a solid alkali or an alkali solution.

[0022] Beneficial effects of the present invention:

[0023] The method of the present invention solves the problem of self-polymerization of strongly acidic high phosphorus catalyst wastewater during the process of adding alkali to adjust the pH value, and uses strong electrolyte salts to reduce the self-polymerization of strongly acidic high phosphorus catalyst wastewater during the process of adding alkali to adjust the pH value. 3+ and PO4 3- Catalyst wastewater, under strong acidic conditions Al 3+ and PO4 3- It exists in the form of ions, but when adding alkali to adjust the pH value, on the one hand, Al 3+ and PO4 3- The reaction generates AlPO4 precipitate; on the other hand, Al 3+ It will quickly hydrolyze to form a charged mononuclear complex Al(OH) 2+ 、Al(OH)2 +and AlO2 - etc., the mononuclear complex will further condense through collision to form a series of polynuclear complexes Al n (OH) m (3n-m)+ (n>1, m≤3n), these aluminum multinuclear complexes often have high positive charge and specific surface area, which can quickly absorb negatively charged impurities in water, promote the rapid destabilization, coagulation and precipitation of colloids and suspended matter, so the water body undergoes a strong self-polymerization reaction, and it is difficult to cross the self-polymerization section of pH 2 to 3. This technology uses the salt effect to prevent colloid contact and reduce the chance of collision and sedimentation by adding strong electrolyte salts. 2+ 、Al(OH)2 + and AlO2 - etc. exist in the form of monomers, thereby preventing the rapid self-aggregation of the colloid, so that the pH of the strongly acidic and high-concentration phosphorus-containing wastewater can be smoothly adjusted, and by adjusting the pH value and solid-liquid separation, the phosphorus in the wastewater can be removed in the form of sludge.

[0024] The present invention reduces the phosphorus content of ultra-high-concentration phosphorus-containing catalyst wastewater exceeding 10,000 mg / L to below 3 mg / L after treatment, thereby achieving efficient phosphorus removal in ultra-high-phosphorus-containing catalyst wastewater and avoiding impact on sewage treatment plants. DETAILED DESCRIPTION

[0025] The present invention is described in detail below by way of examples. It is necessary to point out that the following examples are only used to further illustrate the present invention and are not to be construed as limiting the scope of protection of the present invention. Those skilled in the art may make some non-essential improvements and adjustments to the present invention based on the above disclosure.

[0026] A method for removing phosphorus from acidic phosphorus-containing wastewater comprises the following steps:

[0027] 1) Separating the catalyst wastewater into mud and water to obtain phosphorus-containing waste liquid and mud residue;

[0028] 2) adding electrolyte salts to the phosphorus-containing waste liquid and stirring to homogenize;

[0029] 3) Continue to add alkali to the phosphorus-containing waste liquid to adjust the pH of the phosphorus-containing waste liquid to 3-7, and the waste liquid is in a sol state;

[0030] 4) Separate the waste liquid into solid and liquid form.

[0031] Wherein, in step 1), the mud-water separation method is natural sedimentation, and the natural sedimentation time is 6 to 30 hours, preferably 15 to 24 hours.

[0032] The pH of the phosphorus-containing waste liquid obtained after mud-water separation in step 1) is less than or equal to 2, and the phosphorus content is greater than or equal to 10,000 mg / L.

[0033] The electrolyte salt in step 2) is a strong electrolyte, which may be an inorganic salt and / or an organic salt. The electrolyte may be added all at once or in batches.

[0034] Wherein, the electrolyte salt in step 2) is one or more of NaCl, ZnCl2, MgCl2, KCl, NaCH3COOH and NH4CH3COOH.

[0035] Wherein, the amount of electrolyte salt added in step 2) is 1 to 10 g / L, preferably 3 to 7 g / L.

[0036] Wherein, the base in step 3) is one or more of an inorganic base and an organic base.

[0037] Wherein, the base in step 3) is a solid base or an alkaline solution.

[0038] In step 3), the pH of the phosphorus-containing wastewater after alkali adjustment is 3-7. When strong electrolyte salts are added to the phosphorus-containing wastewater, a portion of PO4 3- It exists as AlPO4 precipitation, and part of it exists as PO4 3- In the form of most Al 3+ Al(OH) 2+ 、Al(OH)2 + and AlO2 - As the pH value increases to 3, the mononuclear complex will further condense through collision and transform into amorphous Al(OH)3 with high positive charge and specific surface area, which can quickly adsorb PO4 with negative charge in water. 3- ; However, when the pH is greater than 7, Al(OH)3 gradually dissolves and releases part of the adsorbed PO4 3- , which leads to an increase in total phosphorus in water, so the present invention controls the pH range to 3-7.

[0039] The solid-liquid separation in step 4) can be performed by filtration or centrifugation.

[0040] Evaluation and analysis method: The analysis of total phosphorus was carried out in accordance with GB 11893-89 (ammonium molybdate spectrophotometry).

[0041] Example 1

[0042] A catalyst wastewater treatment project was conducted, with a pH of 0.66 and a total phosphorus content of 14,800 mg / L. The wastewater was allowed to settle naturally for 24 hours to separate the supernatant and sludge. The supernatant was then treated for phosphorus removal, and the settled sludge was discharged. NaCl was added to the supernatant at a dosage of 5 g / L and stirred until completely dissolved. NaOH was then added while stirring to adjust the pH to 5.0, resulting in a white colloidal sol. Solid-liquid separation was performed by filtration, and the phosphorus content of the filtrate was determined. The total phosphorus content of the resulting filtrate was 1.85 mg / L.

[0043] Example 2

[0044] A catalyst wastewater treatment project was conducted, resulting in a pH of 1.08 and a total phosphorus content of 11,535 mg / L. The wastewater was allowed to settle naturally for 15 hours to separate the supernatant and sludge. The supernatant was then treated for phosphorus removal, and the settled sludge was discharged. ZnCl2 was added to the supernatant at a dosage of 2 g / L and stirred until completely dissolved. N-methyldiethanolamine was then added while stirring to adjust the pH to 7.0, resulting in a white colloidal sol. Solid-liquid separation was performed by filtration, and the phosphorus content of the filtrate was determined. The total phosphorus content of the resulting filtrate was 2.27 mg / L.

[0045] Example 3

[0046] A catalyst wastewater treatment project was conducted, resulting in a pH of 1.56 and a total phosphorus content of 13,925 mg / L. The wastewater was allowed to settle naturally for 30 hours to separate the supernatant and sludge. The supernatant was then treated for phosphorus removal, and the settled sludge was discharged. MgCl2 was added to the supernatant at a dosage of 10 g / L and stirred until completely dissolved. KOH was then added with stirring to adjust the pH to 6.0, resulting in a white colloidal sol. Solid-liquid separation was performed by filtration, and the phosphorus content of the filtrate was determined. The total phosphorus content of the resulting filtrate was 1.46 mg / L.

[0047] Example 4

[0048] A catalyst wastewater treatment project was conducted, resulting in a pH of 0.74 and a total phosphorus content of 13249 mg / L. The wastewater was allowed to settle naturally for 20 hours to separate the supernatant and sludge. The supernatant was then treated for phosphorus removal, and the settled sludge was discharged. NaCH3COOH was added to the supernatant at a dosage of 1 g / L and stirred until completely dissolved. KOH was then added while stirring to adjust the pH to 3.0, resulting in a white colloidal sol. Solid-liquid separation was performed by filtration, and the phosphorus content of the filtrate was determined. The total phosphorus content of the resulting filtrate was 2.82 mg / L.

[0049] Comparative Example 1

[0050] A catalyst wastewater treatment project was conducted, with a pH of 0.66 and a total phosphorus content of 14,800 mg / L. The wastewater was allowed to settle naturally for 24 hours to separate the supernatant and sludge. The supernatant was then treated for phosphorus removal, and the settled sludge was discharged. NaCl was added to the supernatant at a dosage of 5 g / L and stirred until completely dissolved. NaOH was then added while stirring to adjust the pH to 2.5, resulting in a white colloidal sol. Solid-liquid separation was performed by filtration, and the phosphorus content of the filtrate was determined. The total phosphorus content of the resulting filtrate was 1,383 mg / L.

[0051] Comparative Example 2

[0052] A catalyst wastewater treatment project was conducted, with a pH of 0.66 and a total phosphorus content of 14,800 mg / L. The wastewater was allowed to settle naturally for 24 hours to separate the supernatant and sludge. The supernatant was then treated for phosphorus removal, and the settled sludge was discharged. NaCl was added to the supernatant at a dosage of 5 g / L and stirred until completely dissolved. NaOH was then added while stirring to adjust the pH to 8, resulting in a white, colloidal wastewater. Solid-liquid separation was performed by filtration, and the phosphorus content of the filtrate was determined. The total phosphorus content of the resulting filtrate was 451 mg / L.

[0053] Comparative Example 3

[0054] A catalyst wastewater treatment project was conducted, with a pH of 0.66 and a total phosphorus content of 14,800 mg / L. The wastewater was allowed to settle naturally for 24 hours to separate the supernatant and sludge. The supernatant was then treated for phosphorus removal, and the settled sludge was discharged. NaOH was added to the supernatant to adjust the pH while stirring, but the pH could only be adjusted to 1.9. Adding additional NaOH resulted in a large amount of precipitation, making stirring impossible. Solid-liquid separation was performed by filtration, and the phosphorus content in the filtrate was determined. The total phosphorus content in the resulting filtrate was 6,727 mg / L.

[0055] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art may make various corresponding changes and modifications based on the present invention, but these corresponding changes and modifications should all fall within the scope of protection of the claims of the present invention.

Claims

1. A method for removing phosphorus from acidic phosphorus-containing wastewater, characterized in that: The steps include: 1) Containing Al 3+ and PO4 3- The catalyst wastewater is subjected to mud-water separation to obtain phosphorus-containing waste liquid and sludge, wherein the pH of the phosphorus-containing waste liquid is less than or equal to 2, and the phosphorus content is greater than or equal to 10,000 mg / L; 2) Add electrolyte salts to the phosphorus-containing waste liquid and stir to homogenize; the electrolyte salts are one or more of NaCl, ZnCl2, MgCl2, KCl, NaCH3COOH and NH4CH3COOH; the amount of electrolyte salt added is 1-10g / L; 3) Continue to add alkali to the phosphorus-containing waste liquid to adjust the pH of the phosphorus-containing waste liquid to 3-7. The waste liquid is in a sol state. The electrolyte salts added in step 2) can use the salt effect to prevent colloid contact, reduce the chance of collision sedimentation, and make Al(OH) 2+ 、Al(OH)2 + and AlO2 - Existing in monomeric form, thus preventing the colloid from self-aggregating rapidly; 4) Separate the sol-like waste liquid into solid-liquid separation.

2. The method for removing phosphorus from acidic phosphorus-containing wastewater according to claim 1, wherein: In step 1), the mud and water separation method is natural sedimentation, and the natural sedimentation time is 6 to 30 hours.

3. The method for removing phosphorus from acidic phosphorus-containing wastewater according to claim 2, wherein: The natural sedimentation time is 15~24h.

4. The method for removing phosphorus from acidic phosphorus-containing wastewater according to claim 1, wherein: In step 2), the amount of electrolyte salt added is 3-7 g / L.

5. The method for removing phosphorus from acidic phosphorus-containing wastewater according to claim 1, wherein: The base in step 3) is one or more of an inorganic base and an organic base.

6. The method for removing phosphorus from acidic phosphorus-containing wastewater according to claim 1, characterized in that: In step 3), the base is a solid base or a base solution.