Nutrient for biochemical treatment of organic wastewater and preparation method thereof

Abstract

The application discloses a nutrient agent in biochemical treatment of organic wastewater and a preparation method thereof, and relates to the technical field of wastewater treatment. The nutrient agent comprises cassava starch derivatives, and the cassava starch derivatives are esterification derivatives of cassava starch with a substitution degree of 0.18-0.19; in the esterification derivatives, the chemical structure for esterification grafting comprises carboxylic acid compounds; and the carboxylic acid compounds at least comprise mercaptobutane dicarboxylic acid. The nutrient agent is more easily absorbed by microorganisms, the removal rates of COD and ammonia nitrogen in wastewater are obviously increased when the nutrient agent is applied to a wastewater treatment process, the total amount of beneficial bacteria in active sludge can be increased, and the application range is wide.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of wastewater treatment, and particularly relates to a nutrient agent in biochemical treatment of organic wastewater and a preparation method thereof. BACKGROUND

[0002] With the development of industry, the amount of wastewater increases accordingly. In order to maintain the balance of the ecological system, the wastewater needs to be treated to meet the corresponding discharge standard before being discharged or entering the recycling equipment. The generated wastewater mainly includes landfill leachate, papermaking wastewater, printing and dyeing wastewater, coal chemical industry wastewater and food wastewater, etc. These wastewaters contain a large amount of organic matter, ammonia nitrogen, phosphorus and some pollutants. With the progress of the times, the biochemical treatment method is generally selected for wastewater treatment to remove organic matter, ammonia nitrogen and some suspended solids in the wastewater.

[0003] At present, the A2O process is mostly used in the biochemical treatment method to achieve denitrification and phosphorus removal and degradation of organic matter in water. Some anaerobic microorganisms and aerobic microorganisms in activated sludge are used to degrade COD, ammonia nitrogen and phosphorus and other pollutants in water. After the organic matter (pollutants) in the wastewater is adsorbed by the flocculation of aerobic bacteria and bacteria, under the condition that the oxygen (dissolved oxygen: DO) is dissolved in water, the bacteria will obtain the energy required for their own reproduction, thereby using the oxygen to decompose the adsorbed organic matter into water and carbon dioxide. On the other hand, through the decomposition, the energy generated is used to make the organic matter nutritionized, thereby proliferating (synthesizing) new bacterial bodies (sludge).

[0004] The microorganisms (bacteria) in the activated sludge mainly belong to the nutrient microorganisms (bacteria) which will utilize the organic carbon source (BOD) to synthesize bacterial bodies. The bacterial body synthesis is the same as the generation of protein, enzyme and nucleic acid, and nitrogen and phosphorus are indispensable nutrient sources. In addition, inorganic elements such as sulfur, calcium, magnesium, iron and aluminum are also important bacterial body constituent factors. Therefore, the bacterial body generation speed is closely related to the types and amounts of the added microbial nutrient agent, and a single nutrient agent cannot meet the needs of the growth of the bacterial flora, resulting in slow bacterial body synthesis and low treatment efficiency. SUMMARY

[0005] The present application aims to provide a nutrient agent in biochemical treatment of organic wastewater and a preparation method thereof. The nutrient agent is more easily absorbed by microorganisms, significantly enhances the removal rate of COD and ammonia nitrogen in wastewater when applied to the wastewater treatment process, and can increase the total amount of beneficial bacteria in activated sludge, and has a wide application range.

[0006] The technical scheme adopted by the present application to achieve the above-mentioned purpose is as follows:

[0007] A cassava starch derivative is a cassava starch esterification derivative with a substitution degree of 0.18-0.19.

[0008] Among the aforementioned cassava starch esterification derivatives, the chemical structures used for esterification grafting include carboxylic acid compounds; these carboxylic acid compounds include at least mercaptosuccinic acid. This invention uses mercaptosuccinic acid to esterify and derivatize cassava starch, preparing cassava starch derivatives, which are then applied to the preparation of nutrients for the biochemical treatment of organic wastewater. When added to a wastewater treatment system, they effectively enhance wastewater treatment efficiency, significantly improving the removal rates of COD and ammonia nitrogen in the wastewater; they also increase the total amount of beneficial bacteria in activated sludge, increasing sludge concentration and thus promoting wastewater treatment. This may be because the modification of cassava starch with mercaptosuccinic acid may disrupt the internal crystalline structure of the starch granules, transforming it into an amorphous structure, which is more conducive to microbial absorption and utilization, providing a better nutritional environment for the survival and proliferation of beneficial bacteria.

[0009] Specifically, carboxylic acid compounds also include 5-sulfosalicylic acid. Similarly, further modification of cassava starch with 5-sulfosalicylic acid has a beneficial effect on the starch structure, providing microorganisms with a wider variety of nutrients. This significantly increases the total amount of beneficial bacteria in the sludge, which is more conducive to the biochemical treatment process and thus significantly enhances the wastewater treatment effect, resulting in a marked improvement in COD and ammonia nitrogen removal rates.

[0010] A nutrient agent for the biochemical treatment of organic wastewater includes the above-mentioned cassava starch derivative.

[0011] More specifically, the nutrients used for the biochemical treatment of the aforementioned organic wastewater include, by weight: 15-50 parts cassava starch derivative, 10-20 parts urea, 2-5 parts sodium carbonate, 0.5-2 parts potassium dihydrogen phosphate, 0.5-2 parts sodium hydrogen phosphate, 0.5-2 parts potassium chloride, 1-2 parts calcium chloride, 2-5 parts magnesium chloride, 1-2 parts ferrous sulfate heptahydrate, 0.5-2 parts aluminum chloride, 1-2 parts zinc sulfate, 5-10 parts beef extract, and 60-80 parts deionized water.

[0012] This invention further discloses a method for preparing the above-mentioned cassava starch derivative, comprising:

[0013] Mercaptosuccinic acid and 5-sulfosalicylic acid were dissolved in deionized water and the pH was adjusted to 2.5-3.5. Then, cassava starch was added and mixed thoroughly. The mixture was placed at room temperature for 8-10 hours, followed by drying at 45-55°C for 24 hours to dehydrate to a moisture content of 5-10%. The mixture was then pulverized and placed under vacuum at 120-130°C for 4-6 hours. After removal, the mixture was washed with distilled water, centrifuged three times, and dried under vacuum at 40-50°C for 24 hours. The pulverized mixture was then used to obtain the cassava starch derivative.

[0014] Specifically, the molar ratio of mercaptosuccinic acid to 5-sulfosalicylic acid is 1:0.6 to 0.9; the amount of mercaptosuccinic acid used is 16 to 20 wt% of the dry basis of cassava starch; and the solid-liquid ratio of mercaptosuccinic acid to deionized water is 0.2 to 0.3 g: 1 mL.

[0015] More preferably, urea is replaced by sustained-release urea.

[0016] Specifically, the slow-release urea is obtained by polymer coating urea; the polymer includes 2-methacryloxyethylphosphocholine-modified polyacrylate polymers. This invention uses 2-methacryloxyethylphosphocholine-modified polyacrylate polymers as a film material to coat urea and prepare slow-release urea, which has better slow-release performance. When used in wastewater treatment, it can further enhance the removal efficiency of wastewater treatment processes, significantly increasing the removal rates of COD and ammonia nitrogen in wastewater, while effectively prolonging the action time of nutrients and promoting the wastewater treatment process; it can also increase the total amount of beneficial bacteria in activated sludge, enhancing the wastewater treatment effect. This may be because using 2-methacryloxyethylphosphocholine-modified polyacrylate polymers introduces more active functional groups into the polymer, which may have a beneficial impact on the polymer's spatial structure, improving its pore structure and thus better regulating the slow-release effect of urea.

[0017] Specifically, the method for synthesizing the aforementioned sustained-release urea includes:

[0018] Take a toluene / tetrahydrofuran mixture, and slowly add a mixed solution of monomers (butyl methacrylate, acrylic acid, and 2-methacryloyloxyethyl phosphocholine) and half the amount of initiator azobisisobutyronitrile over 1-2 hours at a water bath temperature of 70-80℃. After reacting for 0.5-1 hour, raise the temperature to 75-85℃, add the remaining initiator, and keep it at this temperature for 1.5-2.5 hours. Then, cool it to room temperature, slowly add methanol to precipitate the polymer, extract it, and dry the resulting solid under vacuum at 55-65℃ to obtain the polymer.

[0019] Add the polymer to a toluene / tetrahydrofuran mixture, stir at 70-80°C for 1-3 hours, reflux until completely dissolved, and then cool to room temperature to obtain a polymer solution. Then add urea to a coating machine at a coating temperature of 55-65°C and a rotation speed of 1200-1400 r / min. Add the polymer solution dropwise for coating for 5-15 minutes. Then cure in a vacuum drying oven at 75-85°C for 24 hours to obtain slow-release urea.

[0020] Specifically, the solid-liquid ratio of the monomer to the mixture is 0.8–1.2 g: 1 mL; the molar ratio of butyl methacrylate, acrylic acid, and 2-methacryloyloxyethyl phosphocholine is 1:0.2–0.4:0.1–0.3.

[0021] Specifically, the volume ratio of toluene to tetrahydrofuran in the mixture is 3 to 5:1.

[0022] Specifically, the amount of initiator added is 0.5 to 1.5 wt% of the total monomer.

[0023] Specifically, the concentration of the polymer solution is 0.1–0.2 g / mL; the concentration of added urea is 2–4 wt%.

[0024] The preparation method of the above-mentioned nutrient agent for biochemical treatment of organic wastewater includes:

[0025] (1) Sodium carbonate, potassium dihydrogen phosphate, sodium hydrogen phosphate, ferrous sulfate heptahydrate, potassium chloride and distilled water are mixed and stirred according to the weight ratio, and then centrifuged to obtain the supernatant.

[0026] (2) Mix the cassava starch derivative, supernatant, calcium chloride, magnesium chloride, aluminum chloride and zinc sulfate, heat to 40-60°C, and then let stand to cool to obtain a cooling liquid;

[0027] (3) Mix the coolant, urea and beef extract, stir and let stand to obtain the nutrient for the biochemical treatment of organic wastewater.

[0028] Specifically, the preparation method of the above-mentioned nutrient agent for biochemical treatment of organic wastewater includes:

[0029] (1) Mix sodium carbonate, potassium dihydrogen phosphate, sodium hydrogen phosphate, ferrous sulfate heptahydrate, potassium chloride and distilled water according to the weight ratio and stir for 30-60 minutes. The temperature is controlled at 25-40℃. Add the mixture to a centrifuge and centrifuge to obtain the supernatant.

[0030] (2) Add the cassava starch derivative, supernatant, calcium chloride, magnesium chloride, aluminum chloride and zinc sulfate into a stirred tank, control the temperature at 40-60℃, stir for 40-60 min, let stand and cool to obtain a cooling liquid;

[0031] (3) Add coolant, urea and beef extract into a stirring tank, control the temperature at 25-40℃, stir for 60-90 minutes, and let stand to obtain the nutrient agent for the biochemical treatment of organic wastewater.

[0032] Another object of the present invention is to disclose the use of the above-mentioned cassava starch derivative in the preparation of microbial nutrients.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] This invention employs mercaptosuccinic acid and / or 5-sulfosalicylic acid to esterify and derivatize cassava starch, preparing cassava starch derivatives. These derivatives are then applied to the preparation of nutrients for the biochemical treatment of organic wastewater. When added to a wastewater treatment system, they effectively enhance wastewater treatment, significantly improving the removal rates of COD and ammonia nitrogen. Furthermore, they increase the total amount of beneficial bacteria in activated sludge, increasing sludge concentration. Simultaneously, this invention uses 2-methacryloyloxyethyl phosphate-choline modified polyacrylate polymers as a film material to encapsulate urea, preparing slow-release urea with superior slow-release properties. When applied to wastewater treatment, this further enhances the removal efficiency of the wastewater treatment process, effectively prolonging the duration of the nutrient's action and promoting the wastewater treatment process. It also increases the total amount of beneficial bacteria in activated sludge, further enhancing the wastewater treatment effect.

[0035] Therefore, the present invention provides a nutrient agent for the biochemical treatment of organic wastewater and its preparation method. This nutrient agent is more easily absorbed by microorganisms, and its application in wastewater treatment processes significantly enhances the removal rate of COD and ammonia nitrogen in wastewater. It can also increase the total amount of beneficial bacteria in activated sludge and has a wide range of applications. Attached Figure Description

[0036] Figure 1 The infrared spectral test results of the cassava starch derivative and its cassava starch in Example 1 of this invention;

[0037] Figure 2 The infrared spectral test results are for the polymers prepared in Examples 5 and 7 of this invention;

[0038] Figure 3 This is a diagram illustrating the sustained-release properties of the sustained-release urea prepared according to the present invention. Detailed Implementation

[0039] The technical solution of the present invention will be further described in detail below with reference to specific embodiments:

[0040] Example 1:

[0041] A nutrient agent for the biochemical treatment of organic wastewater comprises, by weight: 38 parts cassava starch derivative, 15 parts urea, 4 parts sodium carbonate, 1 part potassium dihydrogen phosphate, 1 part sodium ammonia dihydrogen phosphate, 1 part potassium chloride, 1.5 parts calcium chloride, 3 parts magnesium chloride, 1.5 parts ferrous sulfate heptahydrate, 1 part aluminum chloride, 1.5 parts zinc sulfate, 8 parts beef extract, and 70 parts deionized water.

[0042] Preparation of the above-mentioned nutrients for the biochemical treatment of organic wastewater:

[0043] (1) Sodium carbonate, potassium dihydrogen phosphate, sodium hydrogen phosphate, ferrous sulfate heptahydrate, potassium chloride and distilled water were mixed and stirred for 45 min according to the weight ratio, the temperature was controlled at 35℃, and then centrifuged to obtain the supernatant.

[0044] (2) Add the cassava starch derivative, supernatant, calcium chloride, magnesium chloride, aluminum chloride and zinc sulfate into a stirred tank, control the temperature at 50℃, stir for 50 min, let stand and cool to obtain a cooling liquid;

[0045] (3) Add coolant, urea and beef extract to a mixing tank, control the temperature at 35℃, stir for 75 minutes, and let stand to obtain the nutrient agent for the biochemical treatment of organic wastewater.

[0046] Preparation of cassava starch derivatives:

[0047] Mercaptosuccinic acid and 5-sulfosalicylic acid (molar ratio of 1:0.78) were dissolved in deionized water (solid-liquid ratio of mercaptosuccinic acid to deionized water was 0.25 g:1 mL), and the pH was adjusted to 3.0. Then, cassava starch (the amount of mercaptosuccinic acid used was 18 wt% of the dry basis of cassava starch) was added, and the mixture was thoroughly mixed and placed at room temperature for 9 h. Then, it was dried at 50 °C for 24 h to remove moisture to a moisture content of 8.2%. After that, it was pulverized and then heated under vacuum at 126 °C for 5 h. After that, it was taken out, washed with distilled water, centrifuged three times, dried under vacuum at 45 °C for 24 h, and pulverized to obtain a cassava starch derivative (degree of substitution of 0.188).

[0048] Example 2:

[0049] A nutrient agent for the biochemical treatment of organic wastewater comprises, by weight: 20 parts cassava starch derivative, 12 parts urea, 2 parts sodium carbonate, 2 parts potassium dihydrogen phosphate, 0.5 parts sodium hydrogen phosphate, 0.5 parts potassium chloride, 1 part calcium chloride, 3 parts magnesium chloride, 1 part ferrous sulfate heptahydrate, 0.5 parts aluminum chloride, 1 part zinc sulfate, 5 parts beef extract, and 60 parts deionized water.

[0050] The preparation of the above-mentioned nutrient agent for the biochemical treatment of organic wastewater is the same as in Example 1.

[0051] The difference between the preparation of the cassava starch derivative and Example 1 is that the molar ratio of mercaptosuccinic acid and 5-sulfosalicylic acid is 1:0.64; the amount of mercaptosuccinic acid used is 17.2 wt% of the dry basis of cassava starch; and the degree of substitution of the cassava starch derivative is 0.184.

[0052] Example 3:

[0053] A nutrient agent for the biochemical treatment of organic wastewater comprises, by weight: 50 parts cassava starch derivative, 20 parts urea, 4 parts sodium carbonate, 2 parts potassium dihydrogen phosphate, 0.5 parts sodium hydrogen phosphate, 2 parts potassium chloride, 2 parts calcium chloride, 5 parts magnesium chloride, 2 parts ferrous sulfate heptahydrate, 1.5 parts aluminum chloride, 1.8 parts zinc sulfate, 10 parts beef extract, and 80 parts deionized water.

[0054] The preparation of the above-mentioned nutrient agent for the biochemical treatment of organic wastewater is the same as in Example 1.

[0055] The difference between the preparation of the cassava starch derivative and Example 1 is that the molar ratio of mercaptosuccinic acid and 5-sulfosalicylic acid is 1:0.8; the amount of mercaptosuccinic acid used is 19.2 wt% of the dry basis of cassava starch; and the degree of substitution of the cassava starch derivative is 0.19.

[0056] Example 4:

[0057] The difference between the nutrient agent for the biochemical treatment of organic wastewater and Example 1 is that the cassava starch derivative is prepared in this example.

[0058] The preparation of the above-mentioned nutrient agent for the biochemical treatment of organic wastewater is the same as in Example 1.

[0059] The difference between the preparation of the cassava starch derivative and Example 1 is that 5-sulfosalicylic acid is replaced with an equimolar amount of mercaptosuccinic acid.

[0060] Example 5:

[0061] The difference between the nutrient agent for the biochemical treatment of organic wastewater and Example 1 is that it uses slow-release urea instead of urea.

[0062] The preparation of the above-mentioned nutrient agent for the biochemical treatment of organic wastewater is the same as in Example 1.

[0063] The preparation of the cassava starch derivative was the same as in Example 1.

[0064] Synthesis of sustained-release urea:

[0065] Take a toluene / tetrahydrofuran (v / v, 4:1) mixture, and slowly add a mixture of monomers (butyl methacrylate, acrylic acid, and 2-methacryloyloxyethyl phosphocholine in a molar ratio of 1:0.3:0.2; solid-liquid ratio of 1g:1mL) and half the amount of initiator azobisisobutyronitrile over 1.5 hours. After reacting for 0.5 hours, raise the temperature to 80°C, add the remaining initiator (the total amount of initiator added is 1.2wt% of the total monomers), keep warm for 2 hours, then cool to room temperature, slowly add methanol to precipitate, extract, and dry the obtained solid under vacuum at 60°C to obtain the polymer.

[0066] The polymer was added to a toluene / tetrahydrofuran (v / v, 4:1) mixture, stirred at 75°C for 2 hours, refluxed, and cooled to room temperature to obtain a polymer solution with a concentration of 0.16 g / mL. Urea (3.2 wt% of the added concentration) was then added to a BYC-300 coating machine at a coating temperature of 60°C and a rotation speed of 1250 r / min. The above polymer solution was added dropwise for coating for 10 minutes. The mixture was then cured in a vacuum drying oven at 80°C for 24 hours to obtain sustained-release urea.

[0067] Example 6:

[0068] The difference between the nutrient agent for the biochemical treatment of organic wastewater and Example 5 is that cassava starch is used instead of cassava starch derivatives.

[0069] The preparation of the above-mentioned nutrient agent for the biochemical treatment of organic wastewater is the same as in Example 5.

[0070] The synthesis of sustained-release urea was the same as in Example 5.

[0071] Example 7:

[0072] The difference between the nutrient agent for the biochemical treatment of organic wastewater and Example 6 is that the slow-release urea is prepared in this example.

[0073] The preparation of the above-mentioned nutrient agent for the biochemical treatment of organic wastewater is the same as in Example 6.

[0074] The difference between the synthesis of sustained-release urea and that in Example 6 is that butyl methacrylate is used instead of an equal molar amount of 2-methacryloyloxyethyl choline phosphate.

[0075] Example 8:

[0076] The difference between the nutrient agent for the biochemical treatment of organic wastewater and Example 1 is that cassava starch is used instead of cassava starch derivatives.

[0077] The preparation of the above-mentioned nutrient agent for the biochemical treatment of organic wastewater is the same as in Example 1.

[0078] Experimental Example 1:

[0079] Infrared characterization

[0080] The tests were conducted using a Fourier transform infrared spectroscopy (FTIR) instrument. The sample was mixed with potassium bromide at a 1:100 ratio, ground, and pressed into a pellet. The wavelength range was 4000–500 cm⁻¹. -1 .

[0081] The cassava starch derivative prepared in Example 1 and cassava starch were subjected to the above tests, and the results are as follows: Figure 1As shown in the figure. Analysis of the figure reveals that, compared to the infrared test results of cassava starch, the infrared spectrum of the cassava starch derivative prepared in Example 1 shows a higher concentration at 2600 cm⁻¹. -1 A characteristic absorption peak for thiol groups appears nearby, at 1720 cm⁻¹. -1 Characteristic absorption peaks of C=O bonds appear nearby, 1650–1500 cm⁻¹ -1 The characteristic absorption peak of the benzene ring skeleton appears within the range, at 1185 cm⁻¹. -1 534cm -1 The presence of characteristic absorption peaks of sulfonic acid groups nearby indicates that the cassava starch derivative in Example 1 was successfully prepared.

[0082] The polymers prepared in Examples 5 and 7 were subjected to the above tests, and the results are as follows: Figure 2 As shown in the figure. Analysis of the figure reveals that, compared to the infrared test results of the polymer prepared in Example 7, the infrared spectrum of the polymer prepared in Example 5 shows a higher value at 1283 cm⁻¹. -1 1048cm -1 The characteristic absorption peak of the phosphate group is located near 1248 cm⁻¹. -1 The presence of a characteristic absorption peak of CN bonds nearby indicates that the polymer in Example 5 was successfully prepared.

[0083] Experimental Example 2:

[0084] An Exploration of the Application of Nutrients in the Biochemical Treatment of Organic Wastewater

[0085] Using a wastewater treatment plant as a test site, the plant has a daily treatment capacity of approximately 400 tons. The specific treatment process is a combination of physicochemical treatment, aerobic biological treatment, multi-stage biological treatment, and membrane biological treatment. The influent COD value is 2500 mg / L, and the average influent ammonia nitrogen value is 60 mg / L. For two consecutive weeks, 12 ppm / m³ of ammonia nitrogen was added to the aerobic tank. 3 The nutrient solution was used to measure the COD and ammonia nitrogen levels in the effluent and calculate its removal rate.

[0086] The nutrients prepared in Examples 1-8 for the biochemical treatment of organic wastewater were subjected to the above tests, and the results are shown in Table 1:

[0087] Table 1. Test results of effluent water quality indicators

[0088] Sample COD removal rate (%) Ammonia nitrogen removal rate (%) Example 1 93.1 96.5 Example 2 92.9 96.0 Example 3 93.5 96.3 Example 4 90.7 95.1 Example 5 96.8 98.7 Example 6 92.6 96.4 Example 7 90.2 95.2 Example 8 88.4 94.0

[0089] Analysis of the data in Table 1 shows that adding the nutrient agent for the biochemical treatment of organic wastewater prepared in Example 1 to the aerobic tank significantly improved the COD and ammonia nitrogen removal rates in the effluent compared to Example 8, and also compared to Example 4. Example 4 showed better results than Example 8, indicating that modifying cassava starch with mercaptosuccinic acid and / or 5-sulfosalicylic acid to prepare cassava starch derivatives, and applying them to the preparation of nutrient agents for the biochemical treatment of organic wastewater, can effectively enhance the wastewater treatment effect, significantly improving both COD and ammonia nitrogen removal rates. Example 5 showed better results than Example 1, and Example 6 showed better results than Examples 7 and 8, indicating that modifying acrylate polymers with 2-methacryloyloxyethyl phosphocholine and preparing slow-release urea by coating urea, when used as a nutrient component in wastewater treatment, can further enhance the removal capacity of the wastewater treatment process, further improving the removal effect of COD and ammonia nitrogen in the wastewater.

[0090] The total amount of beneficial bacteria and the sludge concentration in the aerobic tank were measured simultaneously, and the results are shown in Table 2.

[0091] Table 2. Sludge Concentration Test Results

[0092]

[0093]

[0094] Analysis of the data in Table 2 shows that adding the nutrient agent for the biochemical treatment of organic wastewater prepared in Example 1 to the aerobic tank resulted in significantly higher total beneficial bacteria and sludge concentration than in Example 8, and was also better than in Example 4. The effect of Example 4 was better than that of Example 8, indicating that modifying cassava starch with mercaptosuccinic acid and / or 5-sulfosalicylic acid to prepare cassava starch derivatives, and applying them to the preparation of nutrient agents for the biochemical treatment of organic wastewater, can effectively increase the total amount of beneficial bacteria in the sludge, increase the concentration of activated sludge, and thus significantly enhance the wastewater treatment effect. The effect of Example 5 was better than that of Example 1, and the effect of Example 6 was better than that of Examples 7 and 8, indicating that modifying acrylate polymers with 2-methacryloyloxyethyl phosphocholine and preparing slow-release urea by coating urea, and applying it as a nutrient component in wastewater treatment, can further increase the total amount of beneficial bacteria in the sludge, increase the sludge concentration, and enhance the removal capacity of the wastewater treatment process.

[0095] Experimental Example 3:

[0096] Study on the sustained-release effect of sustained-release urea samples

[0097] Take 5g of the sample to be tested, add 200g of soil and mix well. Then put it into a PVC pipe with a diameter of 5cm and a length of 60cm, and place a thin gauze at the bottom for filtration. Rinse with 250mL of distilled water at room temperature periodically, then collect the filtrate, measure the absorbance at 440nm using ultraviolet-visible spectroscopy, and calculate the nitrogen content released based on the absorbance of the solution.

[0098] The sustained-release urea prepared in Examples 5 and 7 were subjected to the above tests, and the results are as follows: Figure 3 As shown in the figure, the slow-release urea prepared in Example 5 has a lower slow-release rate than that prepared in Example 7, but a higher cumulative release rate. This indicates that the use of 2-methacryloyloxyethyl phosphocholine to modify acrylate polymers and coat urea to prepare slow-release urea results in a higher coating amount and a better ability to slow down the urea release rate, prolonging the duration of nutrient action and thus more effectively improving wastewater treatment.

[0099] The conventional techniques described in the above embodiments are existing technologies known to those skilled in the art, and therefore will not be described in detail here.

[0100] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A nutrient agent for the biochemical treatment of organic wastewater, characterized in that: Its components include, by weight, 15-50 parts of cassava starch derivative, 10-20 parts of urea, 2-5 parts of sodium carbonate, 0.5-2 parts of potassium dihydrogen phosphate, 0.5-2 parts of sodium hydrogen phosphate, 0.5-2 parts of potassium chloride, 1-2 parts of calcium chloride, 2-5 parts of magnesium chloride, 1-2 parts of ferrous sulfate heptahydrate, 0.5-2 parts of aluminum chloride, 1-2 parts of zinc sulfate, 5-10 parts of beef extract, and 60-80 parts of deionized water; the cassava starch derivative is a cassava starch esterification derivative with a degree of substitution of 0.18-0.19; the chemical structure used for esterification grafting of the cassava starch esterification derivative includes carboxylic acid compounds; the carboxylic acid compounds include mercaptosuccinic acid and 5-sulfosalicylic acid; the urea is replaced by slow-release urea; the slow-release urea is obtained by polymer coating urea; the polymer includes 2-methacryloyloxyethyl phosphate choline modified polyacrylate polymer.

2. The method for preparing the nutrient agent for biochemical treatment of organic wastewater according to claim 1, comprising: (1) Sodium carbonate, potassium dihydrogen phosphate, sodium hydrogen phosphate, ferrous sulfate heptahydrate, potassium chloride and distilled water are mixed and stirred according to the weight ratio, and centrifuged to obtain the supernatant; (2) Mix the cassava starch derivative, supernatant, calcium chloride, magnesium chloride, aluminum chloride and zinc sulfate, heat to 40~60℃, and then let stand to cool to obtain a cooling liquid; (3) Mix the coolant, urea and beef extract, stir and let stand to obtain the nutrient for the biochemical treatment of organic wastewater.

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