Sewage treatment method for improving production efficiency of soybean whey wastewater okara

Abstract

The present application relates to sewage treatment technical field, especially improve soybean whey wastewater soybean dregs production efficiency's sewage treatment method, the present application has increased the step of microbial fermentation flocculation and dewatering reflux on the basis of traditional whey wastewater treatment process, and the parameter involved therein has been optimized, the experimental result shows that, with the method described in the present application carries out the treatment efficiency of whey wastewater treatment is high, and the processing cost is low, has good application prospect.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to a wastewater treatment method for improving the efficiency of soybean whey wastewater and soybean residue production. Background Technology

[0002] The processing of soy protein isolate and soy products generates a large amount of soy whey wastewater. Studies show that approximately 30-35 cubic meters of this wastewater are produced for every ton of soy protein isolate produced. 3 Soybean whey water. Soybean whey water is rich in organic matter, its main components being small-molecule water-soluble proteins, sucrose, and inorganic salts. It also contains small amounts of soybean oligosaccharides, amylase, cytochromes, isoflavones, soybean saponins, phytic acid, and other nutrients. The use and application areas of soy protein isolate are increasing year by year, inevitably increasing the amount of soybean whey wastewater generated. This type of whey wastewater has a low dry matter content and is difficult to utilize. Currently, our company mainly uses a combination of pretreatment and biochemical treatment for disposal. Half of the suspended solids in the whey wastewater are extracted using an air flotation + plate and frame filter press. The remaining wastewater undergoes anaerobic fermentation followed by aerobic fermentation, where the organic components are decomposed by microorganisms. After meeting discharge standards, it is discharged into the municipal sewage network.

[0003] Flocculation, as an indispensable pre-treatment unit in whey wastewater treatment, determines the operating conditions of subsequent processes and has become an important research topic in the field of environmental engineering. Particles dispersed in wastewater cannot be effectively separated due to their solidification and settling stability. To disrupt this stability, accelerate flocculation, and quickly achieve mud-water separation, additional flocculants need to be added. Commonly used flocculants are classified into inorganic flocculants, organic flocculants, and microbial flocculants. Commonly used inorganic flocculants include iron salts and aluminum salts, which are inexpensive but have drawbacks such as high requirements for the working environment (e.g., pH, temperature, etc.) and corrosive effects on equipment. Organic polymeric flocculants are not significantly dependent on the environment and can achieve good flocculation results; however, the monomers released after the decomposition of polymeric flocculants have strong neurotoxicity, and their use has been limited or banned in many countries. Microbial flocculants (MBF) are highly efficient, safe, non-toxic, biodegradable, and do not cause secondary pollution. They overcome the disadvantages of traditional flocculants, such as poor biodegradability, harm to human health, and increased environmental risks. MBF has a broader spectrum of applications in wastewater treatment and can achieve excellent results.

[0004] Microbial flocculants are a class of microbial metabolites with flocculation activity. They can coagulate and precipitate non-degradable solid suspended particles and colloidal particles in liquids. They are highly efficient, non-toxic, and do not cause secondary pollution; they are biodegradable and safe green water treatment agents. Therefore, the preparation of novel microbial flocculants to achieve efficient flocculation and sedimentation and reduce suspended particulate matter in wastewater is of significant research importance for wastewater treatment and remediation.

[0005] There is relatively little research on improving soybean residue production efficiency using microbial flocculants, and this invention will fill the gap in this technical field. Summary of the Invention

[0006] In view of this, the technical problem to be solved by the present invention is to provide a wastewater treatment method for improving the production efficiency of soybean whey wastewater and soybean residue.

[0007] This invention provides a method for treating whey wastewater, comprising the following steps:

[0008] Step 1: Mix the first whey wastewater, Kluyveromyces Marcius LBSW23-01 and corn starch and ferment to obtain fermentation flocculent liquid;

[0009] Step 2: After the second whey wastewater is treated with fermentation flocculant, it undergoes second and third flocculation and then air flotation. The supernatant obtained from air flotation is subjected to anaerobic fermentation, and the residue obtained from air flotation is dewatered.

[0010] Step 3: The dehydrated solid is filtered and dried to obtain solid residue, and the dehydrated liquid is recycled back into the fermentation flocculant for further treatment.

[0011] In step 1, the inoculum size of Kluyveromyces martensii LBSW23-01 in the whey wastewater is 1.0 × 10⁻⁶. 6 ~5.0×10 6 cfu / mL; In this invention, the *Kluyveromyces martensii* LBSW23-01 can be a solid inoculum or a liquid inoculum, and this invention does not limit this; In a specific embodiment of this invention, the *Kluyveromyces martensii* LBSW23-01 is obtained by culturing in YPD liquid medium, and after culturing in a shaking incubator at 35℃ and 150~250rpm for 24h, 1.0×10⁻⁶ cfu / mL is obtained. 8 ~5.0×10 8 A seed culture of cfu / mL was added at 1% v / v of the whey wastewater volume.

[0012] The amount of corn starch added to the whey wastewater is 0% (m / v) to 1.0% (m / v), specifically, the amount of corn starch added to the whey wastewater is 0.5% (v / v whey wastewater). In a specific embodiment of the present invention, corn starch was screened as a flocculant. The experimental results showed that diatomaceous earth had the best flocculation effect on whey water, followed by corn starch. Light calcium carbonate had no effect on whey water, but since the whey wastewater treated in this invention is used as a feed ingredient, corn starch was selected. Specifically, compared with other concentrations, when the amount of corn starch added was 0.5% (v / v whey wastewater), the number of yeast colonies increased the most, and the suspended solids in the effluent were the lowest.

[0013] Furthermore, the fermentation conditions are 37°C for 12 hours and dissolved oxygen of 1-4 mg / L, specifically, dissolved oxygen of 2 mg / L;

[0014] In this invention, the dissolved oxygen content was optimized. Experimental results showed that the number of colonies was highest when the dissolved oxygen was 4 mg / L, but the device suffered from severe foaming. Considering all factors, a dissolved oxygen of 2 mg / L was selected to reduce foaming and increase the relative number of bacteria.

[0015] The ratio of the influent flow rate of the second whey wastewater to the reflux flow rate of the dehydrated liquid is (1~3):1, specifically 2:1. In this invention, the ratio of the influent flow rate of the second whey wastewater to the reflux flow rate of the dehydrated liquid flowing back into the fermentation flocculant circulation treatment was optimized. Experimental results show that when the reflux flow rate: influent flow rate = 3:1, the yeast colony count in the fermentation tank is the highest at 23.8 million CFU / mL. However, from the perspective of economy and operational stability, the reflux flow rate: influent flow rate = 2:1 is the most suitable.

[0016] The initial ratio of the sum of the influent flow rate and the reflux flow rate to the volume of the fermentation flocculant is 2:1.

[0017] The second whey wastewater is treated with fermentation flocculant for 1 to 3 hours, specifically 2 hours. This invention optimizes the residence time (treatment time) of whey wastewater in the fermentation tank after fermentation. Experimental results show that the growth rate of flocculant bacteria is the highest after a residence time of 2 hours.

[0018] The second flocculant is PAC with a basicity of 70% to 80%; specifically, the second flocculant is drinking water grade PAC with a basicity of 75%. The present invention screened the first flocculant, and the experimental results showed that the suspended solids content and absorbance were the lowest after treatment with drinking water grade PAC with a basicity of 75%.

[0019] The PAC was purchased from Zibo Zhenghe Water Purification Agent Co., Ltd., and is a liquid. Specifically, in this invention, it is 10% PAC of drinking water grade with a basicity of 75%.

[0020] The concentration of the second flocculant is 0.04 vt‰ to 0.12 vt‰, specifically 0.1 vt‰. This invention optimizes the addition amount of the second flocculant. Experimental results show that as the addition amount of drinking water grade PAC (10%) with a basicity of 75% increases, the suspended solids gradually decrease. 1.2‰ has the best effect, but there is no significant difference from 1.0‰. Considering all factors, the addition amount of PAC is selected as 1.0‰. Since the PAC content is 10%, the addition amount of PAC is selected as 0.1 vt‰.

[0021] The second flocculation condition is to adjust the pH to 4.2-4.5 and stir for 5 minutes.

[0022] The third flocculant is a PAM anion with a molecular weight of 8 million to 16 million; specifically, a PAM anion with a molecular weight of 16 million. This invention screened the types and molecular weights of the third flocculant. Experimental results showed that PAM anions had the best flocculation effect on whey compared to others. Further screening of the molecular weight of the third flocculant on this basis showed that PAM anions with a molecular weight of 16 million had the best flocculation effect.

[0023] The concentration of the third flocculant is 0.002 g / L to 0.08 g / L; specifically 0.001 g / L. In a specific embodiment of the present invention, the amount of the third flocculant added was optimized. Experimental results show that the optimal amount of PAM anion (1 g / L) added to 200 mL of whey water is 1.0%.

[0024] The third flocculation condition is stirring for 30 seconds;

[0025] The second whey wastewater also needs to be treated with glucose, the amount of which is 83.5 g / L to 250 g / L; specifically 125 g / L, which is related to the residence time of the whey wastewater in the fermentation tank. The optimal residence time is 2 hours, so the amount of glucose added is 125 g / L.

[0026] The rate at which the whey wastewater from the inlet tank enters the fermentation tank after fermentation is 16.7 L / h to 50 L / h; specifically 25 L / h, which is related to the residence time of the whey wastewater in the fermentation tank. The optimal residence time is 2 hours, so the rate at which the whey wastewater from the inlet tank enters the fermentation tank after fermentation is 25 L / h.

[0027] In this invention, the fermentation process of the treatment method selects Kluyveromyces martensii LBSW23-01 as the fermentation strain and supplements it with corn starch to improve the flocculation efficiency of whey wastewater. Furthermore, the first flocculant and the second flocculant were screened and optimized, and the flocculation effect was further improved based on the fermentation. The reflux and influent ratio and the residence time were also optimized to improve the treatment efficiency of whey wastewater while saving costs. Therefore, the various parameters in this application complement each other and work synergistically to improve the overall treatment efficiency of whey wastewater.

[0028] This invention adds microbial fermentation flocculation and dehydration reflux steps to the traditional whey wastewater treatment process, and optimizes the parameters involved. Experimental results show that the whey wastewater treatment method of this invention has high treatment efficiency and low treatment cost, and has good application prospects. Attached Figure Description

[0029] Figure 1 Show the original process flow;

[0030] Figure 2 Show the improved process flow;

[0031] Figure 3 Yeast colony count detection;

[0032] Figure 4 Detection of suspended solids content;

[0033] Figure 5 The effect of PAM addition on flocculation efficiency is shown. Detailed Implementation

[0034] This invention provides a wastewater treatment method for improving the efficiency of soybean whey wastewater and soybean residue production. Those skilled in the art can refer to the content of this document and appropriately modify the process parameters to achieve the desired result. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this invention. The methods and applications of this invention have been described through preferred embodiments. Those skilled in the art can obviously make modifications or appropriate alterations and combinations to the methods and applications described herein without departing from the content, spirit, and scope of this invention to implement and apply the technology of this invention.

[0035] The test materials used in this invention are all common commercially available products. The invention is further illustrated below with reference to embodiments:

[0036] Example 1: Wastewater Treatment Method to Improve the Production Efficiency of Soybean Whey Wastewater and Soybean Residue

[0037] In patent CN 2023111795730, this invention isolates a strain of Kluyveromyces marxianus LBSW23-01 from soybean whey wastewater. This yeast is characterized by high protein content, large biomass, and stable proliferation in whey wastewater. However, in field applications, it was found that this yeast has a short residence time, short survival time, and is unable to proliferate. To solve this problem and improve the treatment efficiency of soybean whey wastewater and soybean residue, this invention provides a wastewater treatment method to improve the production efficiency of soybean whey wastewater and soybean residue.

[0038] 1. Process Flow

[0039] Process flow as follows Figure 2 As shown, for Figure 1 The existing process shown is modified. The new process adds a fermentation tank between the inlet tank and the high-efficiency air flotation tank, and at the same time, the effluent from the fermentation tank and the pressurized screw press is refluxed to ensure the content of microorganisms.

[0040] The retention time in the fermentation tank is 2 hours;

[0041] The reflux is defined as the reflux rate of the fermentation tank to the influent rate = 2:1, and all the effluent from the pressurized screw is refluxed.

[0042] 2. Preparation of microbial flocculants:

[0043] A microbial flocculant was prepared from Kluyveromyces marxianus LBSW23-01, which has the preservation number CGMCC No.27921.

[0044] The fermentation medium is YPD medium.

[0045] The YPD medium formula is: 2% glucose, 1.0% yeast extract, 2.0% peptone, and the balance of distilled water, pH 6.8~7.0, sterilized at 121℃ for 20 min.

[0046] Liquid seed preparation: The activated strain was transferred to 200 mL of YPD liquid medium and cultured in a shaking incubator at 35°C at 150-250 rpm for 24 h.

[0047] After obtaining the above-mentioned liquid bacterial agent, a solid bacterial agent can also be obtained, and its preparation method is as follows:

[0048] Preparation of solid inoculum: After fermentation, 2%–4% diatomaceous earth and 1%–3% light calcium carbonate were added to the fermented liquid at a mass ratio for adsorption treatment. The fermented liquid was then centrifuged and separated to obtain solid microbial cells. After drying, microbial powder was obtained. The moisture content of the microbial powder was controlled below 10%, and the effective viable cell count was tested to be 1.0 × 10⁻⁶. 10 ~2.0×10 10 cfu / g.

[0049] The microbial agent can be a liquid or solid agent; the yeast colony count in the liquid agent is 1.0 × 10⁻⁶. 8 ~5.0×10 8 CFU / mL; the yeast colony count in the solid inoculum is 1.0 × 10⁻⁶. 10 ~2.0×10 10 cfu / g.

[0050] 3. Processing procedure

[0051] Microbial flocculant was introduced into the fermentation tank at an inoculum size of 1% v / v (colony count of 1.0 × 10⁻⁶). 6 ~5.0×10 6 Add corn starch (cfu / mL) to the fermentation tank, dissolve it completely, and ferment at 37℃ for 12 hours, during which aeration is turned on.

[0052] The amount of corn starch added is 0.5% (m / v).

[0053] The dissolved oxygen in the aeration system is controlled to be above 2 mg / L;

[0054] After fermentation, adjust the pH to 4.2-4.5 with sodium hydroxide or hydrochloric acid, then add flocculant PAC and stir for 5 minutes, followed by adding PAM and stirring for 30 seconds.

[0055] The PAC is of drinking water grade with a content of 10%, a basicity of 75%m / v, and an addition amount of 1vt‰.

[0056] The PAM is anionic PAM with a molecular weight of 16 million, prepared as a 1‰ solution, and added at a rate of 2% v / v.

[0057] 4. Soybean residue production efficiency

[0058] Table 1. Improvement in soybean residue production efficiency

[0059] The above modifications were applied to the air flotation site. The fermentation tank was filled with whey water, dissolved oxygen was controlled at 2.0 mg / L, stirring was performed at 60 rpm, corn starch was added at 0.5% m / v, and Kluyveromyces Marcius was inoculated at 1% v / v. Fermentation was carried out at room temperature for 12 hours. After fermentation, whey water was introduced and remained in the fermentation tank for 2 hours. The ratio of fermentation tank return flow rate to influent flow rate was 2:1.

[0060] After the modification, the suspended solids in the influent of the dissolved air flotation (DAF) system increased from 4200 mg / L to 10460 mg / L, while the suspended solids in the effluent decreased from 1800 mg / L to 1650 mg / L. The production efficiency improved from 57.2% to 84.22%, demonstrating significant results. One DAF tank can treat 2000 tons of wastewater per day, increasing soybean residue production by 7.6 tons and generating economic benefits of 15,300 yuan.

[0061] Example 2: Parameter optimization in a wastewater treatment method to improve the efficiency of soybean whey wastewater and soybean residue production.

[0062] 1. Determining the return flow rate

[0063] To determine the optimal influent and reflux flow rates, three gradients were designed: reflux to influent flow rates of 1:1, 2:1, and 3:1. An experiment was designed for verification. The apparatus volume was 100L, the reaction system volume was 50L, the reaction temperature was 37℃, the inoculum size was 1% v / v, and the dissolved oxygen concentration was 2.0 mg / L. After 12 hours of fermentation, influent and reflux were started at an influent flow rate of 50L / h. 250g / h of corn starch was added evenly. After 72 hours of stable operation, samples were taken to detect the bacterial count in the fermentation tank.

[0064] Table 2. Effect of reflux ratio on yeast

[0065]

[0066] As shown in Table 2, the number of bacterial colonies in the fermentation tank was 26 million CFU / mL when water was first introduced. The highest number of yeast colonies in the fermentation tank was 23.8 million CFU / mL when the reflux rate was 3:1. However, considering both economic efficiency and operational stability, a reflux rate of 2:1 was the most suitable ratio.

[0067] 2. Determining the length of stay

[0068] Based on the above-mentioned apparatus, the residence time was determined to be 1 hour, 2 hours, and 3 hours, with influent flow rates of 50 L / h, 25 L / h, and 16.7 L / h, respectively. The glucose addition was adjusted to 250 g / h, 125 g / h, and 83.5 g / h, with other parameters remaining the same. After 72 hours of stable operation, samples were taken to test the bacterial count in the fermentation tank.

[0069] Table 3. Effects of residence time on yeast

[0070]

[0071] As shown in Table 3, the number of bacterial colonies in the fermentation tank at the start of water intake was 26 million CFU / mL. The highest number of yeast colonies was 26.5 million CFU / mL at a residence time of 3 hours, followed by 22.6 million CFU / mL at a residence time of 2 hours. However, the growth rate was the highest at a residence time of 2 hours. Therefore, the optimal ratio of return flow rate to influent flow rate is 2:1.

[0072] 3. Determining the aeration rate

[0073] Based on the above-mentioned device, the aeration rate was determined. The device was first adjusted to 1 mg / L and operated stably for 3 days. Then, it was adjusted to 2 mg / L and operated stably for another 3 days. Finally, the aeration rate was adjusted to 4 mg / L and operated stably for 3 days. During this period, samples were taken to test the yeast count. Other conditions were: reaction temperature 37℃, inoculum size 1% v / v, influent flow rate 50 L / h, corn starch 250 g / h, reflux rate:influent flow rate = 2:1, and residence time 2 hours.

[0074] Table 4. Effects of dissolved oxygen on yeast

[0075]

[0076] As shown in Table 4, the highest number of bacterial colonies was observed when the dissolved oxygen was 4 mg / L. However, the device experienced severe foaming. Therefore, considering all factors, a dissolved oxygen concentration of 2 mg / L was selected.

[0077] 4. Flocculant Screening

[0078] 4.1 Screening of Flocculant Types

[0079] To study the flocculation properties of corn starch, air flotation influent was used as the research object. Four 500mL Erlenmeyer flasks were taken, and 200mL of whey water was added. 1.0g of corn starch, light calcium carbonate and diatomaceous earth were added respectively. The blank was used as a control without any reagents. The flasks were stirred with a magnetic stirrer at 500rpm for 5 minutes and allowed to settle for 10 minutes. The absorbance of the supernatant was measured at 550nm.

[0080] Table 5. Detection of corn starch flocculation properties

[0081]

[0082] As shown in Table 5, diatomaceous earth has the best flocculation effect on whey, followed by corn starch, while light calcium carbonate has no effect on whey. Since soybean residue is used as a feed ingredient, corn starch was chosen.

[0083] 4.2 Determination of Flocculant Dosage

[0084] Using air flotation influent as the research object, a concentration gradient was designed to verify the amount of corn starch added. Five 500mL Erlenmeyer flasks were used, each containing 200mL of whey water. Then, 0g, 0.2g, 0.5g, 1.0g, and 2.0g of corn starch were added, resulting in corn starch solutions with concentrations of 0%, 0.10%, 0.25%, 0.50%, and 1.0% (m / v). 2mL of the liquid bacterial agent prepared in Example 2 was added to each solution, and the solutions were incubated at 37℃ and 200rpm for 12 hours. The yeast colony count and suspended solids content were then measured. Another 50mL of the solution was placed in a centrifuge tube and centrifuged at 5000rpm for 5 minutes. The supernatant was discarded, and the precipitate was dried at 105℃ for at least 6 hours for crude protein content determination, following GB / T 6432-2018, Determination of Crude Protein Content in Feed - Kjeldahl Method. The remaining 100mL was placed in different Erlenmeyer flasks, each containing 10% PAC. Add 0.1 mL of distilled water to the blank group, place a magnetic stirrer on it, and stir at 500 rpm for 5 minutes. Add 2 mL of 1‰ PAM anion solution to each blank group, place the blank group on a magnetic stirrer, and continue stirring at 500 rpm for 30 seconds. Allow the mixture to stand for 10 minutes to settle. Take the supernatant and measure the absorbance at 550 nm and the suspended solids content. The suspended solids detection method refers to the national standard GB11901-89 Water Quality Determination of Suspended Solids Gravimetric Method.

[0085] Table 6. Effect of corn starch addition on yeast.

[0086]

[0087] From Table 6 and Figure 3 The test results show that when 0.5% corn starch is added, the number of yeast colonies increases the most and the suspended solids in the effluent are the lowest. Corn starch has a promoting effect on flocculation, so choosing 0.5% corn starch as the most suitable addition amount is appropriate.

[0088] 5. PAC Screening

[0089] 5.1 PAC Screening

[0090] Table 7. PAC Type Filtering

[0091]

[0092] The experiment was conducted in 500mL glass beakers. The wastewater used was 200mL of whey water flotation influent. Six groups were set up: #1 (blank control), #2 (chemical PAC (10%) with a basicity of 70%), #3 (drinking water grade PAC (10%) with a basicity of 60%), #4 (drinking water grade PAC (10%) with a basicity of 70%), #5 (drinking water grade PAC (10%) with a basicity of 75%), and #6 (drinking water grade PAC (10%) with a basicity of 80%). 500mL of whey water was added to each of the six beakers. 0.5mL of the corresponding PAC was added to each of the six beakers (#2-#6). 0.5mL of distilled water was added to the blank control group. The mixture was stirred at 500rpm for 5 minutes using a magnetic stirrer. Then, 10mL of 1‰ PAM anion solution was added to each beaker, and the mixture was stirred at 500rpm using a magnetic stirrer. Continue stirring for 30 seconds, allow to settle for 10 minutes, and take the supernatant to test the absorbance at 550 nm and the suspended solids content. The suspended solids test method refers to the national standard GB11901-89 Determination of Suspended Solids in Water by Gravimetric Method.

[0093] After testing (as shown in Table 7), PAC No. 5, a drinking water grade, has the lowest basicity (75%), suspended solids content, and absorbance, and is therefore selected as the best choice.

[0094] 5.2 Determination of PAC Addition Amount

[0095] The experiment was conducted in 1000mL glass beakers. The wastewater used was whey flotation influent, and the PAC used was drinking water grade PAC with a content of 10% and a basicity of 75%. The amount of PAC added was set in 6 groups: 0 VT‰, 0.4 VT‰, 0.6 VT‰, 0.8 VT‰, 1.0 VT‰, and 1.2 VT‰. The reaction system was 500mL, placed on a magnetic stirrer, and stirred at 500rpm for 5 minutes. Then, 10mL of 1‰ PAM anion was added to each beaker, placed on a magnetic stirrer, and stirred at 500rpm for 30s. After settling for 10 minutes, the supernatant was taken and the absorbance at 550nm and the suspended solids content were measured.

[0096] Table 8. Determination of PAC Addition Amount

[0097]

[0098] From the test results table 8 and Figure 4 It can be seen that as the amount of PAC added increases, the suspended solids gradually decrease, with 1.2‰ showing the best effect, but there is no significant difference compared to 1.0‰. Considering all factors, the amount of PAC added is chosen to be 1.0‰.

[0099] 6. Optimization of PAM

[0100] 6.1 PAM Type Filtering

[0101] Select PAM anionic, PAM cationic, and nonionic PAM, accurately weigh 0.1g, place in a 100mL beaker, dissolve in water, and dilute to volume to prepare a 1.0‰ working solution. Add 200mL of whey water to each of three 500mL Erlenmeyer flasks, add 0.2mL of drinking water-grade PAC (10% content) with a basicity of 75% to each flask, place on a magnetic stirrer, and stir at 500rpm for 5 minutes. Then add 4mL each of the 1‰ PAM anionic, PAM cationic, and nonionic PAM solutions to each flask, and continue stirring at 500rpm for 30s. Allow to stand for 10 minutes to settle, and take the supernatant to measure the absorbance at 550nm and the suspended solids content.

[0102] Table 9. PAM Type Filtering

[0103]

[0104] Tests showed that PAM anions had the best flocculation effect on whey, so PAM anions were added during the air flotation process.

[0105] 6.2 Selection of PAM molecular weight

[0106] Purchase PAM reagents with specific molecular weights of 8 million, 10 million, 12 million, and 16 million. Accurately weigh 0.1 g of each reagent and place it in a 100 mL beaker. Dissolve the reagent in water and dilute to volume to prepare a 1.0‰ working solution. Add 200 mL of emulsion water to each of four 500 mL Erlenmeyer flasks. Add 0.2 mL of PAC (10% concentration) with a basicity of 75% to each flask. Place the flasks on a magnetic stirrer and stir at 500 rpm for 5 minutes. Then, add 4 mL of the 1‰ PAM anionic solution (8 million, 10 million, 12 million, and 16 million respectively). Continue stirring at 500 rpm for 30 seconds. Allow the solution to settle for 10 minutes. Take the supernatant and measure the absorbance at 550 nm and the suspended solids content.

[0107] Table 10. PAM molecular weight screening

[0108]

[0109] Tests showed that PAM with a molecular weight of 16 million had the best flocculation effect.

[0110] 6.3 Determination of PAM Addition Amount

[0111] Accurately weigh 0.1 g of PAM anion (16 million), place it in a 100 mL beaker, dissolve it in water, and dilute to a final volume to prepare a 1.0‰ working solution. Take eight 500 mL Erlenmeyer flasks, add 200 mL of whey water to each flask, and add 0.2 mL of PAC (10% concentration) with a basicity of 75% to each flask. Place the flasks on a magnetic stirrer and stir at 500 rpm for 5 minutes. Then, add 0 mL, 0.4 mL (500-fold dilution), 1.0 mL (200-fold dilution), 4.0 mL (50-fold dilution), 8.0 mL (25-fold dilution), 12 mL (16-17-fold dilution), and 16 mL (12.5-fold dilution) of the 1‰ PAM anion solution in sequence. Place the flasks on a magnetic stirrer and continue stirring at 500 rpm for 30 seconds. Allow the solution to settle for 10 minutes, and then measure the absorbance of the supernatant at 550 nm.

[0112] The absorbance of the supernatant of the test sample and the supernatant of the blank control solution were measured at 550 nm using a UV spectrophotometer. The flocculation rate was calculated using the following formula:

[0113] Flocculation rate (%) = (BA) / B × 100 In the above formula,

[0114] A - Measure the absorbance of the sample supernatant;

[0115] B - Absorbance of the supernatant of the blank solution.

[0116] Table 11. Determination of PAM Addition Amount

[0117]

[0118] From Table 11 and Figure 5 It can be seen that the optimal addition amount of PAM anions is 1.0%.

[0119] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for treating whey wastewater, characterized in that, Includes the following steps: Step 1: Mix the first whey wastewater, Kluyveromyces Marcius LBSW23-01 and corn starch and ferment to obtain fermentation flocculent liquid; Step 2: After the second whey wastewater is treated with fermentation flocculant, it undergoes second and third flocculation and then air flotation. The supernatant obtained from air flotation is subjected to anaerobic fermentation, and the residue obtained from air flotation is dewatered. Step 3: The dehydrated solid is filtered and dried to obtain solid residue, and the dehydrated liquid is recycled back into the fermentation flocculant for further treatment. In step 1, the inoculum size of Kluyveromyces martensii LBSW23-01 in the whey wastewater is 1.0 × 10⁻⁶. 6 ~5.0×10 6 cfu / mL; The amount of corn starch added to the whey wastewater is 1 g / L to 10 g / L.

2. The processing method according to claim 1, characterized in that, The fermentation conditions were 37°C for 12 hours and dissolved oxygen of 1-4 mg / L.

3. The processing method according to claim 1, characterized in that, The ratio of the influent flow rate of the second whey wastewater to the reflux flow rate of the dehydrated liquid is (1~3):

1.

4. The processing method according to claim 3, characterized in that, The initial ratio of the sum of the influent flow rate and the reflux flow rate to the volume of the fermentation flocculant is 2:

1.

5. The processing method according to claim 1, characterized in that, The second whey wastewater is treated with fermentation flocculant for 1 to 3 hours.

6. The processing method according to claim 1, characterized in that, The second flocculant is PAC with a basicity of 70% to 80%; The concentration of the flocculant used in the second flocculation is 0.04vt‰~0.12vt‰.

7. The processing method according to claim 1, characterized in that, The flocculant of the third flocculation has a molecular weight of 8 million to 16 million PAM anions. The concentration of the flocculant used in the third flocculation is 0.002 g / L to 0.08 g / L.

8. The processing method according to claim 1, characterized in that, The second whey wastewater also needs to be treated with glucose, and the amount of glucose added is 83.5 g / L to 250 g / L.

9. The processing method according to claim 1, characterized in that, The influent flow rate of the second whey wastewater is 16.7 L / h to 50 L / h.

10. The application of the treatment method according to any one of claims 1 to 9 in wastewater treatment.

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