Method for effectively recovering phosphorus from aquaculture wastewater and reducing tetracycline antibiotic residues

Abstract

The invention relates to a method for effectively recovering phosphorus from aquaculture wastewater and reducing tetracycline antibiotic residues by using seawater as a magnesium source. Firstly, through a seawater pretreatment step, seawater is filtered and purified to remove impurities, and a clean magnesium source is provided for reaction. Next, in the phosphate precipitation stage, the pretreated seawater is added into the aquaculture wastewater, the pH value is adjusted to 8.0-10.5, preferably 9.0, and the magnesium / phosphorus molar ratio is set to be 1.0-2.0, preferably 1.8, so that the phosphate and magnesium ions are promoted to generate struvite precipitates. Rich positive ions in seawater and tetracycline antibiotics are used for competitively combining phosphate ions, so that adsorption and coprecipitation of the antibiotics are effectively reduced, and the content of the antibiotics in the product is reduced. And finally, separating and purifying the precipitate to obtain the struvite with high safety. The method is simple, low in cost, good in effect and suitable for large-scale wastewater treatment, and has important environment-friendly and economic values.

Description

Technical Field

[0001] The invention relates to the technical field of wastewater treatment and resource recovery, in particular to an environmentally friendly technology for recovering phosphorus from aquaculture wastewater and reducing tetracycline antibiotic residues by using seawater as a magnesium source. Background Art

[0002] As global environmental awareness continues to increase, wastewater treatment technology is developing in the direction of resource utilization, high efficiency and environmental protection. Aquaculture wastewater is rich in nutrients such as nitrogen and phosphorus. If not properly treated, it will cause serious pollution to the environment, but these substances are also indispensable fertilizer components in agricultural production. Therefore, developing a technology that can recover these valuable resources from aquaculture wastewater has become a research focus in the field of wastewater treatment.

[0003] The struvite process, as an emerging wastewater treatment and resource recovery technology, can not only effectively reduce the phosphorus content in wastewater, but also generate slow-release fertilizers with high added value by converting phosphates in wastewater into magnesium ammonium phosphate (MAP) which is insoluble in water, with the molecular formula: (MgNH4PO4·6H2O). However, the production cost of struvite limits its large-scale application, mainly due to chemical costs, especially the cost of magnesium, which accounts for 75% of the total cost. Seawater, as a natural, abundant and economical source of magnesium, has been proven to effectively recover phosphates from wastewater to form struvite precipitation. However, the common tetracycline antibiotic residues in aquaculture wastewater, as well as the effects of other ions in seawater on struvite formation and antibiotic migration, limit the widespread application of this process. When treating aquaculture wastewater, the existing technology often finds it difficult to simultaneously achieve efficient recovery of phosphorus and effective control of antibiotic residues, which can easily affect the quality and safety of the recovered products. Summary of the invention

[0004] The purpose of the present invention is to solve the technical problems of high production cost of struvite and high antibiotic residue, and propose a method of using seawater as a magnesium source to recover phosphorus from aquaculture wastewater and reduce tetracycline antibiotic residues.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for effectively recovering phosphorus from aquaculture wastewater and reducing tetracycline antibiotic residues by using seawater as a magnesium source comprises the following steps:

[0007] S1. Seawater pretreatment: Filter and purify seawater to remove large particles of impurities and some organic matter to provide a clean magnesium source for subsequent reactions;

[0008] S2, phosphate precipitation: adding the pretreated seawater to the aquaculture wastewater, and adjusting the pH to 8.0-10.5, preferably 9.0, and adjusting the magnesium / phosphorus molar ratio to magnesium / phosphorus = 1.0-2.0, preferably 1.8, to promote the reaction of phosphate and magnesium ions to form struvite precipitation;

[0009] S3. Separation and purification of precipitate: Separate the precipitate containing struvite and further purify it. The obtained product can be vacuum dried.

[0010] In some embodiments, step S1 specifically includes: repeatedly filtering and purifying the seawater, measuring the turbidity change until large particle impurities and part of the organic matter are removed, and stopping the filtration when the turbidity reaches 1NTU or below to obtain a clean magnesium source.

[0011] In some embodiments, the microporous filter membrane used in the filtration is a 0.22 μm, 50 mm water system membrane.

[0012] In some embodiments, the filtration is performed three times.

[0013] In some embodiments, in step S2, the reaction temperature is 25°C-30°C, the stirring speed is 200-500rpm, and the reaction time is 1-2h.

[0014] In some embodiments, in step S2, the pH is adjusted to 9.0.

[0015] In some embodiments, in step S3, the filtration uses a microporous filter membrane of 0.22 μm and a 50 mm aqueous membrane, the product is washed with deionized water three times, and vacuum dried at 35° C. for 24 hours.

[0016] In some embodiments, in step S3, the solid phase extraction method uses an Oasis HLB cartridge to concentrate the antibiotics in the sample, and the concentrate is subjected to liquid chromatography-tandem mass spectrometry (LC-MS / MS) combined with a chromatographic column for antibiotic identification and quantification. The mass spectrometry system equipped with an electrospray ionization source operates in positive mode, the desolvation temperature is 300°C, and the capillary voltage is 5.5 kV.

[0017] In some embodiments, the ammonium nitrogen (NH4 + -N) content is 200-2000mg / L, orthophosphate (PO4 3- -P) content is 50-300mg / L, soluble organic matter content is 0-120mg / L, and oxytetracycline (OTC) content is 50-1000μg / L.

[0018] In some embodiments, the pH value is adjusted using 2 mol / L NaOH and 1 mol / L HCl solution.

[0019] The beneficial effects of the present invention compared with the prior art include:

[0020] The present invention uses seawater as a magnesium source to effectively recover phosphorus from aquaculture wastewater and reduce tetracycline antibiotic residues. The method uses seawater as a magnesium source, and adjusts the molar ratio of magnesium in seawater to phosphorus in wastewater to 1.0-2.0, preferably 1.8, and utilizes cations (Na + , K + Mg 2+ , Ca 2+ ) and tetracycline antibiotics in combination with PO4 3- The competitive relationship during binding reduces the interaction between tetracycline antibiotics and PO4 3- The opportunity of combining can inhibit the adsorption of antibiotics to reduce the adsorption and co-precipitation of antibiotics, thereby reducing the amount of antibiotics in the final product and producing safer struvite. By controlling the pH value of the reaction to 8.0-10.5, the conditions of the above competitive reaction can be further optimized, the precipitation efficiency of phosphate can be improved, and the adsorption of antibiotics can be minimized.

[0021] The magnesium ion content in seawater is rich and the acquisition cost is low, which greatly reduces the production cost; it also reduces the dependence on pure magnesium sources and the use of chemical reagents, making it more environmentally friendly; by optimizing the magnesium / phosphorus molar ratio and the reaction pH value, the phosphorus recovery efficiency is improved, and at the same time, the adsorption and co-precipitation of antibiotics are effectively inhibited, and the antibiotic residues in the final product are significantly reduced. The economic benefits and safety of struvite are significantly increased, which is better than the existing struvite recovered from pure magnesium sources. The method is simple, effective, has a low production cost, and a wide range of applications.

[0022] In some embodiments, filtered and purified seawater is used as a magnesium source. The magnesium ion content in seawater is rich and the acquisition cost is low, which greatly reduces the production cost. The operation is simple, easy to implement, and suitable for large-scale application.

[0023] Other beneficial effects of the embodiments of the present invention will be further described below. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a flow chart of a method for effectively recovering phosphorus from aquaculture wastewater and reducing tetracycline antibiotic residues using seawater as a magnesium source in an embodiment of the present invention;

[0025] Figure 2a to Figure 2b is a SEM photograph of the struvite crystal recovery product in Examples 2 and 3 of the present invention;

[0026] Figure 3a to Figure 3b is the XRD spectrum of the struvite crystallization recovery product in Examples 2 and 3 of the present invention;

[0027] Figure 4a to Figure 4b is a graph showing the change of ammonium ions in Examples 2 and 3 of the present invention;

[0028] Figure 5a to Figure 5b is a graph showing changes in phosphate ions in Examples 2 and 3 of the present invention;

[0029] Figure 6 It is the ultraviolet spectrophotometric curve of oxytetracycline and calcium and magnesium ions in Example 4 of the present invention versus the control example. DETAILED DESCRIPTION

[0030] The present invention is further described below with reference to the accompanying drawings and in combination with preferred embodiments. It should be noted that the embodiments and features in the embodiments of the present application can be combined with each other without conflict.

[0031] Antibiotics interfere with normal precipitation reactions and lead to a decrease in the amount of precipitate generated, resulting in a decrease in the purity of the precipitate and the enrichment of antibiotics, which poses a potential risk to the environment and human health. The struvite chemical precipitation method can achieve nitrogen and phosphorus removal in wastewater, and has the advantages of simple operation and rapid reaction. However, the cost of magnesium sources limits its large-scale application. Therefore, using an economical alternative magnesium source to produce struvite crystals, reducing the production cost of the struvite chemical precipitation method and the enrichment of antibiotics in the product has huge economic benefits and environmental value.

[0032] Seawater is a low-cost and easily accessible alternative magnesium source, with a magnesium ion content of approximately 1300 mg / L, second only to sodium ions. The abundant magnesium ions in seawater have been successfully used to recover phosphorus from urine and urban sewage, and have great potential in the large-scale treatment of phosphorus-containing wastewater. The cations rich in seawater compete with positively charged struvite crystals, which may lead to a reduction in the adsorption capacity of antibiotics. In theory, the higher the concentration of cations, the stronger the inhibitory effect on antibiotic adsorption. Therefore, the cations rich in seawater may be the key to inhibiting the content of antibiotics in the recovered products.

[0033] The embodiment of the present invention provides a method for effectively recovering phosphorus from aquaculture wastewater and reducing tetracycline antibiotic residues by using seawater as a magnesium source. The filtered and purified seawater is used as the magnesium source. The seawater is rich in magnesium ions and has a low acquisition cost, thereby greatly reducing the production cost. + , K + Mg 2+ , Ca 2+) and the positively charged struvite inhibit the adsorption of antibiotics. By adjusting the reaction conditions and optimizing the reaction environment, the crystallization of struvite is promoted, the adsorption and coprecipitation of antibiotics are reduced, thereby reducing the amount of antibiotics in the final product, removing nitrogen and phosphorus while recovering safer struvite. In particular, when the reaction pH was 9.0 and the magnesium / phosphorus molar ratio was 1.8, a phosphorus removal rate of 98.59% and a struvite purity of 97.78% were obtained, and when the oxytetracycline concentration in the reaction environment was increased to 200 μg / L, the oxytetracycline residue detected in the crystals was only 18.68 μg / g. The seawater used in the embodiment of the present invention as an alternative magnesium source for the production of struvite has better economic benefits than the existing pure magnesium source, and can produce safer struvite in the presence of a typical tetracycline antibiotic-oxytetracycline, avoiding the addition of additional chemical reagents while achieving safe product recovery, providing an economical alternative magnesium source for phosphorus-containing wastewater treatment, and providing a process flow reference for large-scale phosphorus recovery.

[0034] like Figure 1 As shown, the method provided by the embodiment of the present invention for effectively recovering phosphorus from aquaculture wastewater and reducing tetracycline antibiotic residues by using seawater as a magnesium source comprises the following steps:

[0035] Step 1: pre-treat seawater to obtain a clean magnesium source. Specifically, the steps include:

[0036] (1) Collect seawater samples.

[0037] (2) Refrigerated (2-4°C) seawater samples were filtered using a 0.22 μm, 50 mm water system membrane (Mg ions in seawater (Mg 2+ ) content is 1000-1500mg / L, calcium ion (Ca 2+ ) content is 300-500mg / L), and the filtration is repeated 3-5 times, and the turbidity change is measured until the large particles of impurities and part of the organic matter are removed. When the turbidity reaches 1NTU or below, the filtration is stopped to obtain a clean magnesium source.

[0038] (3) After the filtration is completed, the obtained seawater is stored in a refrigerator at 2-4°C for future use.

[0039] Step 2: pH adjustment, based on the optimal pH conditions determined experimentally. Specifically include:

[0040] The seawater in step 1 is mixed with the nitrogen-phosphorus-containing sewage to be treated, and the total volume of the mixture is 1L, wherein the nitrogen content is 810mg / L, the phosphorus content is 285mg / L, the soluble organic matter (humic acid) content is 60mg / L, and the oxytetracycline content is 200μg / L, and the pH value of the reaction solution is adjusted to optimize the reaction environment of magnesium ions and phosphate ions. The reaction pH adjustment range is 8.0-10.5, the magnesium / phosphorus molar ratio is 1.0, the reaction temperature is 25°C-30°C, the stirring speed is 200-500rpm, and the reaction time is 1-2h.

[0041] Step 3: Optimizing the magnesium / phosphorus molar ratio, determining and adjusting the molar ratio of magnesium to phosphorus in seawater. Specifically including:

[0042] The seawater in step 1 is mixed with the nitrogen and phosphorus-containing wastewater to be treated, and the total mixed volume is 1L, wherein the nitrogen content is 810mg / L, the phosphorus content is 285mg / L, the soluble organic matter (humic acid) content is 60mg / L, and the oxytetracycline content is 200μg / L. The magnesium / phosphorus molar ratio is adjusted by changing the amount of seawater, and the magnesium / phosphorus molar ratio is adjusted in the range of 1.0-2.0. The reaction pH is determined to be 9.0 according to step S2, the reaction temperature is 25°C-30°C, the stirring speed is 200-500rpm, and the reaction time is 1-2h.

[0043] By adjusting the molar ratio of magnesium in seawater to phosphorus in wastewater, the cations (Na + , K + Mg 2+ , Ca 2+ ) and tetracycline antibiotics in combination with PO4 3- The competitive relationship during binding inhibits the adsorption of antibiotics to reduce the adsorption and co-precipitation of antibiotics, thereby reducing the antibiotic content in the final product.

[0044] Step 4, phosphate precipitation, adding the pretreated seawater to the aquaculture wastewater, and promoting the reaction of phosphate with magnesium ions to generate struvite precipitation by adjusting the pH and magnesium / phosphorus molar ratio. Specifically including:

[0045] The seawater in step 1 is mixed with the nitrogen-phosphorus-containing wastewater to be treated, and the total mixed volume is 1L, wherein the nitrogen content is 810mg / L, the phosphorus content is 285mg / L, the soluble organic matter (humic acid) content is 60mg / L, the oxytetracycline content is 200μg / L, the reaction pH is determined to be 9.0 according to step S2, the magnesium / phosphorus molar ratio is determined to be 1.8 according to step S3, the reaction temperature is 25℃-30℃, the stirring speed is 200-500rpm, and the reaction time is 1-2h.

[0046] Step 5: Separation and purification of the precipitate: Separate the precipitate containing struvite by filtration, and further purify it by washing and other steps to remove the antibiotics and other impurities remaining on the surface, and vacuum dry the obtained product. Specifically including:

[0047] The microporous filter membrane used for filtration was 0.22 μm, 50 mm water system membrane, the product was washed with deionized water three times, and vacuum dried at 35° C. for 24 h.

[0048] Step 6: Product and residue analysis, using solid phase extraction and liquid chromatography-tandem mass spectrometry (LC-MS / MS) to accurately assess the content of antibiotics in the product and the product quality. Specifically include:

[0049] Oasis HLB cartridges were used to concentrate the antibiotics in the samples. The concentrate was subjected to liquid chromatography-tandem mass spectrometry (LC-MS / MS) combined with a chromatographic column for antibiotic identification and quantification. The mass spectrometer system equipped with an electrospray ionization source operated in positive mode, with a desolvation temperature of 300°C and a capillary voltage of 5.5 kV.

[0050] In some embodiments, the ammonium nitrogen (NH4 + -N) content is 200-2000mg / L, orthophosphate (PO4 3- -P) content is 50-300mg / L, soluble organic matter content is 0-120mg / L, and oxytetracycline (OTC) content is 50-1000μg / L.

[0051] In some embodiments, the magnesium ions (Mg 2+ ) content is 1000-1500mg / L, calcium ion (Ca 2 + ) content is 300-500mg / L.

[0052] In some embodiments, the pH value is adjusted using NaOH at a concentration of 2 mol / L and HCl at a concentration of 1 mol / L.

[0053] The following is a detailed description of a method for effectively recovering phosphorus from aquaculture wastewater and reducing tetracycline antibiotic residues by using seawater as a magnesium source in conjunction with specific examples.

[0054] Example 1

[0055] A method for pretreating seawater to obtain a clean magnesium source comprises the following steps:

[0056] (1) Collect seawater samples.

[0057] (2) The seawater sample stored in a refrigerator (4°C) was filtered using a 0.22 μm, 50 mm water system membrane (Mg ions in seawater (Mg 2+ ) content is 1200mg / L, calcium ion (Ca 2+ ) content is 300 mg / L), and the filtration is repeated 3 times. The turbidity change is measured until the large particles of impurities and part of the organic matter are removed. When the turbidity reaches 1 NTU or below, the filtration is stopped to obtain a clean magnesium source.

[0058] (3) After the filtration is completed, the obtained seawater is stored in a refrigerator at 4°C for future use.

[0059] Example 2

[0060] A method for effectively recovering phosphorus from aquaculture wastewater and reducing tetracycline antibiotic residues by using seawater as a magnesium source comprises the following steps:

[0061] (1) Collect aquaculture wastewater samples, filter the aquaculture wastewater samples stored in a refrigerator (4°C) using a 0.22μm, 50mm water system membrane, and repeat the filtration three times to measure the turbidity change until large particles of impurities and some organic matter are removed. When the turbidity reaches 1NTU or below, stop filtration to obtain the aquaculture wastewater required for the reaction. After the filtration is completed, the aquaculture wastewater obtained is stored in a 4°C refrigerator for refrigeration.

[0062] (2) The seawater preserved in Example 1 was mixed with the aquaculture wastewater, and deionized water was added to ensure that the total volume of the system was 1 L, wherein the nitrogen content in the system was 810 mg / L, the phosphorus content was 285 mg / L, the soluble organic matter (humic acid) content was 60 mg / L, the oxytetracycline content was 200 μg / L, and the magnesium / phosphorus molar ratio was 1.0, and then stirred for 10 min at a temperature of 25° C. and a rotation speed of 200 rpm to ensure sufficient mixing.

[0063] (3) The reaction pH was then adjusted by adding 2 mol / L NaOH solution and 1 mol / L HCl solution. The reaction pH was selected to be 8.0, 8.5, 9.0, 9.5, 10.0 and 10.5. The reaction was carried out at a reaction temperature of 25° C. and a stirring speed of 200 rpm for 2 h.

[0064] (4) After the reaction is completed, the product is separated by sedimentation, filtered and washed, and placed in an oven at a constant temperature of 35°C for 24 hours to a constant weight, thereby obtaining six groups of struvite products at different reaction pH values.

[0065] The results of three parallel experiments were characterized and analyzed, and the average oxytetracycline content of struvite at six different reaction pH levels was 27.26 μg / g (pH=8.0), 18.89 μg / g (pH=8.5), 27.72 μg / g (pH=9.0), 72.77 μg / g (pH=9.5), 87.48 μg / g (pH=10.0) and 103.35 μg / g (pH=10.5), respectively.

[0066] Example 3

[0067] A method for effectively recovering phosphorus from aquaculture wastewater and reducing tetracycline antibiotic residues by using seawater as a magnesium source comprises the following steps:

[0068] (1) The seawater stored in Example 1 was mixed with the aquaculture wastewater in Example 2, and deionized water was added to ensure that the total volume of the system was 1 L, wherein the nitrogen content in the system was 810 mg / L, the phosphorus content was 285 mg / L, the soluble organic matter (humic acid) content was 60 mg / L, and the oxytetracycline content was 200 μg / L. The magnesium / phosphorus molar ratio was adjusted by changing the amount of seawater, and the magnesium / phosphorus molar ratio was selected to be 1.0, 1.2, 1.4, 1.6, 1.8 and 2.0, and then stirred for 10 min at a temperature of 25° C. and a rotation speed of 200 rpm to be fully mixed.

[0069] (2) Then, the reaction pH was adjusted by adding 2 mol / L NaOH solution and 1 mol / L HCl solution. The reaction pH was selected as 9.0 according to Example 2. The reaction was carried out at a reaction temperature of 25° C. and a stirring speed of 200 rpm for 2 h.

[0070] (3) After the reaction is completed, the product is subjected to sedimentation separation, suction filtration and washing, and then placed in an oven at a constant temperature of 35° C. and dried for 24 h until constant weight is obtained, thereby obtaining six groups of struvite products at different magnesium / phosphorus molar ratios.

[0071] The results of three parallel experiments were characterized and analyzed, and the average oxytetracycline content of struvite at six groups of different magnesium / phosphorus molar ratios was obtained as 28.05 μg / g (magnesium / phosphorus = 1.0), 25.08 μg / g (magnesium / phosphorus = 1.2), 19.98 μg / g (magnesium / phosphorus = 1.4), 20.02 μg / g (magnesium / phosphorus = 1.6), 18.68 μg / g (magnesium / phosphorus = 1.8) and 21.17 μg / g (magnesium / phosphorus = 2.0), respectively.

[0072] Example 4

[0073] A method for effectively recovering phosphorus from aquaculture wastewater and reducing tetracycline antibiotic residues by using seawater as a magnesium source comprises the following steps:

[0074] (1) The seawater stored in Example 1 was mixed with the aquaculture wastewater in Example 2, and deionized water was added to ensure that the total volume of the system was 1 L, wherein the nitrogen content in the system was 810 mg / L, the phosphorus content was 285 mg / L, the soluble organic matter (humic acid) content was 60 mg / L, the oxytetracycline content was 200 μg / L, and the magnesium / phosphorus molar ratio was selected as 1.8 according to Example 3, and then stirred for 10 min at a temperature of 25° C. and a rotation speed of 200 rpm to be fully mixed.

[0075] (2) Then, the reaction pH was adjusted by adding 2 mol / L NaOH solution and 1 mol / L HCl solution. The reaction pH was selected as 9.0 according to Example 2. The reaction was carried out at a reaction temperature of 25° C. and a stirring speed of 200 rpm for 2 h.

[0076] (3) After the reaction is completed, the product is separated by sedimentation, filtered and washed, and placed in an oven at a constant temperature of 35° C. to dry for 24 h until constant weight is obtained, thereby obtaining a struvite product at the optimal reaction pH and magnesium / phosphorus molar ratio.

[0077] The results of three parallel experiments were characterized and analyzed, and the oxytetracycline content of struvite was obtained to be 18.68 μg / g.

[0078] Comparison Example

[0079] A method for effectively recovering phosphorus from aquaculture wastewater and reducing tetracycline antibiotic residues by using seawater as a magnesium source comprises the following steps:

[0080] (1) Preparation of the pure magnesium source used in this example: According to the magnesium ion content in seawater, MgCl2·6H2O was dissolved in ultrapure water to prepare a pure magnesium source stock solution (Mg 2+ =1200 mg / L). Store in a refrigerator (4°C) for later use.

[0081] (2) The preserved pure magnesium source was mixed with the aquaculture wastewater in Example 2, and the total volume of the system was ensured to be 1 L by adding deionized water, wherein the nitrogen content in the system was 810 mg / L, the phosphorus content was 285 mg / L, the soluble organic matter (humic acid) content was 60 mg / L, the oxytetracycline content was 200 μg / L, and the magnesium / phosphorus molar ratio was selected to be 1.8, and then stirred for 10 min at a temperature of 25°C and a rotation speed of 200 rpm to ensure sufficient mixing.

[0082] (3) Then, the reaction pH was adjusted by adding 2 mol / L NaOH solution and 1 mol / L HCl solution. The reaction pH was selected to be 9.0. The reaction was carried out at a reaction temperature of 25° C. and a stirring speed of 200 rpm for 2 h.

[0083] (4) After the reaction is completed, the product is subjected to sedimentation separation, suction filtration and washing, and then placed in an oven at a constant temperature of 35° C. to dry for 24 h until constant weight is obtained, thereby obtaining a struvite product at an optimal reaction pH and magnesium / phosphorus molar ratio.

[0084] The results of three parallel experiments were characterized and analyzed, and the oxytetracycline content of struvite was obtained to be 20.35 μg / g.

[0085] Table 1 Phosphorus removal rate, struvite purity and oxytetracycline content of the embodiments of the present invention and the comparative examples

[0086]

[0087] The SEM photos of the struvite crystals recovered in Examples 2 and 3 of the present invention are as follows Figure 2a to Figure 2b As shown; the XRD patterns of the struvite crystallization products recovered in Examples 2 and 3 are as shown Figure 3a and 3b As shown; the ammonium ion change curve diagram in Examples 2 and 3 is as shown Figure 4a and 4b As shown; the phosphate ion change curve diagram in Examples 2 and 3 is as shown Figure 5a and 5b As shown; the UV spectrophotometric curve of oxytetracycline and calcium and magnesium ion system is as shown Figure 6 shown.

[0088] From Table 1 and Figure 2a to Figure 2b , Figure 3a to Figure 3b , Figure 4a to Figure 4b and Figure 5a to Figure 5b It can be seen that when seawater is used as a magnesium source, after adjusting the reaction pH and magnesium / phosphorus molar ratio, it has a better nitrogen and phosphorus removal effect, higher product purity, and lower oxytetracycline enrichment; in Example 2, when the reaction pH increases from 8.0 to 10.5, the phosphorus removal rate increases, but the purity of struvite increases first and then decreases, and the oxytetracycline content decreases first and then increases, that is, pH is too high and too low, which is not conducive to the recovery of struvite. The phosphorus removal rate, product purity and antibiotic enrichment are comprehensively considered, and pH = 9.0 is determined to be the optimal reaction pH. In Example 3, when the magnesium / phosphorus molar ratio increases from 1.0 to 2.0, phosphorus removal increases significantly, but the purity of struvite decreases slightly, and the oxytetracycline content decreases first and then increases. In general, the increase in magnesium / phosphorus molar ratio, that is, the increase in seawater dosage is beneficial to the production of high-quality struvite, but the increase in magnesium / phosphorus molar ratio to a certain extent will reduce the quality of struvite. Therefore, considering comprehensively, the magnesium / phosphorus molar ratio of 1.8 is determined to be the optimal magnesium / phosphorus molar ratio. Compared with the control example, although the phosphorus removal rate and struvite purity of seawater as the magnesium source are slightly insufficient compared with the pure magnesium source, the enrichment degree of oxytetracycline under the same conditions is lower, which is expected to achieve large-scale, safe and efficient production of struvite. Figure 6The ultraviolet spectrophotometric curve explains the principle of the present invention, which shows the competitive effect of cations in seawater on oxytetracycline, represented by calcium ions. When calcium ions are present, the complexation of magnesium ions and oxytetracycline in a pure magnesium source system is significantly inhibited.

[0089] The above results show that adjusting the reaction pH and magnesium / phosphorus molar ratio in the treatment of aquaculture wastewater using seawater as a magnesium source has a wide range of applications, providing a simpler and more effective treatment method for antibiotic-containing wastewater. The prepared struvite has higher safety, providing a new way for the resource utilization of struvite.

[0090] The embodiment of the present invention uses seawater as a magnesium source to effectively recover phosphorus from aquaculture wastewater and reduce tetracycline antibiotic residues. When seawater is used as a magnesium source, after adjusting the reaction pH and magnesium / phosphorus molar ratio, it has a better nitrogen and phosphorus removal effect, a higher product purity, and a lower oxytetracycline enrichment degree. Compared with the recovered product of pure magnesium source under the same conditions (20.35 μg / g), the product of Example 4 of the present invention after adjusting the reaction pH and magnesium / phosphorus molar ratio has a lower occurrence content of oxytetracycline (18.68 μg / g), and has stronger practical applicability. Figure 6 It is shown that in the traditional expensive pure magnesium source system, magnesium ions are more likely to combine with oxytetracycline, resulting in an increase in the antibiotic content in the final product, which hinders the safe use of struvite. However, economical seawater as a magnesium source will inhibit the adsorption of antibiotics due to the presence of cations (such as calcium ions) rich in it. Therefore, the method of the present invention will help promote the combination of sewage antibiotic treatment process and struvite crystallization process, save antibiotic sewage treatment costs, and promote the use of seawater as a magnesium source in sewage treatment.

[0091] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art of the present invention, several equivalent substitutions or obvious variations can be made without departing from the concept of the present invention, and the performance or use is the same, which should be regarded as belonging to the protection scope of the present invention.

Claims

1. A method for effectively recovering phosphorus from aquaculture wastewater and reducing tetracycline antibiotic residues by using seawater as a magnesium source, It is characterized in that The steps include: S1. Seawater pretreatment: Filter and purify seawater to remove large particle impurities and some organic matter to provide a clean magnesium source for subsequent reactions; S2, phosphate precipitation: adding the pretreated seawater to the aquaculture wastewater, and adjusting the pH to 8.0-10.5, preferably 9.0, and adjusting the magnesium / phosphorus molar ratio to magnesium / phosphorus = 1.0-2.0, preferably 1.8, to promote the reaction of phosphate and magnesium ions to form struvite precipitation; S3. Separation and purification of precipitate: Separate the precipitate containing struvite and further purify it.

2. The method for effectively recovering phosphorus from aquaculture wastewater and reducing tetracycline antibiotic residues by using seawater as a magnesium source as claimed in claim 1, It is characterized in that Step S1 specifically includes: repeatedly filtering and purifying the seawater, measuring the turbidity change until large particle impurities and part of organic matter are removed, and stopping the filtration when the turbidity reaches 1NTU or below to obtain a clean magnesium source.

3. The method for effectively recovering phosphorus from aquaculture wastewater and reducing tetracycline antibiotic residues by using seawater as a magnesium source as claimed in claim 2, It is characterized in that The microporous filter membrane used in the filtration is a 0.22 μm, 50 mm water system membrane.

4. The method for effectively recovering phosphorus from aquaculture wastewater and reducing tetracycline antibiotic residues by using seawater as a magnesium source as claimed in claim 2, It is characterized in that The filtration times are 3 times.

5. The method for effectively recovering phosphorus from aquaculture wastewater and reducing tetracycline antibiotic residues by using seawater as a magnesium source as claimed in claim 1, It is characterized in that In step S2, the reaction temperature is 25°C-30°C, the stirring speed is 200-500rpm, and the reaction time is 1-2h.

6. The method for effectively recovering phosphorus from aquaculture wastewater and reducing tetracycline antibiotic residues by using seawater as a magnesium source as claimed in claim 1, It is characterized in that In step S2, the pH is adjusted to 9.

0.

7. The method for effectively recovering phosphorus from aquaculture wastewater and reducing tetracycline antibiotic residues by using seawater as a magnesium source as claimed in claim 1, It is characterized in that In step S3, the filtration is performed using a 0.22 μm microporous membrane and a 50 mm water membrane, the product is washed with deionized water for 3 times, and then vacuum dried at 35° C. for 24 h.

8. The method for effectively recovering phosphorus from aquaculture wastewater and reducing tetracycline antibiotic residues by using seawater as a magnesium source as claimed in claim 1, It is characterized in that In step S3, the solid phase extraction method uses an Oasis HLB cartridge to concentrate the antibiotics in the sample, and the concentrate is subjected to liquid chromatography-tandem mass spectrometry (LC-MS / MS) combined with a chromatographic column for antibiotic identification and quantification. The mass spectrometry system equipped with an electrospray ionization source operates in positive mode, the desolvation temperature is 300°C, and the capillary voltage is 5.5 kV.

9. The method for effectively recovering phosphorus from aquaculture wastewater and reducing tetracycline antibiotic residues by using seawater as a magnesium source as claimed in claim 1, It is characterized in that The ammonium nitrogen (NH 4 + -N) content is 200-2000mg / L, orthophosphate (PO 4 3- -P) content is 50-300mg / L, soluble organic matter content is 0-120mg / L, and oxytetracycline (OTC) content is 50-1000μg / L.

10. The method for effectively recovering phosphorus from aquaculture wastewater and reducing tetracycline antibiotic residues by using seawater as a magnesium source as claimed in claim 1, It is characterized in that The pH value was adjusted using 2 mol / L NaOH and 1 mol / L HCl solution.

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