A method for advanced treatment of soy sauce wastewater and its sludge treatment

Abstract

The present invention relates to a method for advanced treatment of soy sauce wastewater and its sludge treatment, comprising: S1: After the soy sauce wastewater is filtered, the produced water is successively subjected to magnetic coagulation treatment and flocculation treatment, and magnetic powder is added during the magnetic coagulation treatment; S2: The produced water obtained in step S1 is subjected to sludge-water separation, and the separated produced water is input into a Fenton reactor for oxidation treatment; S3: The produced water obtained after Fenton treatment is subjected to sludge-water separation, the separated produced water meets the discharge standard and is discharged, and the separated sludge is discharged into a sludge reaction kettle; S4: Sulfuric acid and iron filings are added to the sludge reaction kettle and heated for reaction. After the reaction, the produced water is centrifugally filtered, and the filtrate is input into a reagent reaction kettle; Sulfuric acid, KClO3 and activated carbon powder are added into the reagent reaction kettle to generate polymeric ferric sulfate with adsorption performance, which can be recycled for the coagulation treatment in step S1; S5: The sludge generated in the sedimentation tank of step S2 and the sludge generated by centrifugal filtration in step S4 are mixed and then concentrated and dewatered.

Description

Technical Field

[0001] The present invention belongs to the technical field of soy sauce wastewater treatment, and particularly relates to a method for advanced treatment of soy sauce wastewater and its sludge treatment. Background Art

[0002] The process of producing soy sauce mainly includes steps such as koji making, fermentation, backwashing, and packaging, and wastewater will be generated in these steps. For example, wastewater generated during the cleaning of production sites and equipment, soaking of raw materials, waste liquid and overflow liquid from each tank, flushing of fermentation tank pools, and cleaning of packaging containers. This wastewater is characterized by high concentration, large load variation, and high chroma, and belongs to difficult-to-treat organic wastewater.

[0003] Soy sauce pigment is the most difficult part to remove in soy sauce wastewater. Soy sauce pigment mainly consists of two parts: one is the black substance formed during the soy sauce fermentation process due to the sugar-amine reaction (Maillard reaction); the other is the caramel pigment artificially added during product formulation. Both of the above substances are high-molecular compounds with complex structures, and the chromophore groups they contain are composed of 2 or more conjugated chromophores. These conjugated chromophores cause the organic molecule to produce absorption peaks in the visible light region, making the wastewater have chroma and it is very difficult to achieve the decolorization effect through conventional treatment processes.

[0004] It has been found through research that after the wastewater is treated by biochemical treatment, there is still about 1200 mg / L of COD, of which 30% is hydrophobic organic matter, which can be removed by adsorption methods such as coagulation, while about 70% of the organic matter is hydrophilic, and traditional oxidation adsorption methods are required to effectively remove it. In addition, the chroma of soy sauce wastewater is extremely high, the removal effect by direct activated carbon adsorption is poor, and it will have a destructive effect on the activated carbon, and the chroma has a tendency to deepen during the oxygenation and stripping process.

[0005] Therefore, the wastewater generated from the production of soy sauce has a high chroma and complex pollutant structures, and the advanced treatment process used has a complex process, unsatisfactory effect, and high cost, which is a technical problem faced by those skilled in the art. Summary of the Invention

[0006] In view of the above problems, the present invention provides a method for advanced treatment of soy sauce wastewater and its sludge treatment, including the following steps:

[0007] S1: After the soy sauce wastewater is filtered, it is successively subjected to magnetic coagulation treatment and flocculation treatment, and magnetic powder is added during the magnetic coagulation treatment;

[0008] S2: The produced water obtained in step S1 is input into a sedimentation tank for separation of mud and water, and the separated produced water is input into a Fenton reactor. After adjusting the pH value, ferrous sulfate and hydrogen peroxide agents are added to the Fenton reactor to oxidize, adsorb, and degrade the COD and chroma in the wastewater;

[0009] S3: The effluent obtained after Fenton treatment is input into a high-density sedimentation tank for neutralization and sludge-water separation. The separated effluent can meet the discharge standards, and the separated sludge is discharged into a sludge reaction kettle.

[0010] S4: Concentrated sulfuric acid and iron filings are added to the sludge reaction kettle and heated for reaction to produce ferrous sulfate. After the effluent is centrifugally filtered, the filtrate is input into a reagent reaction kettle.

[0011] Sulfuric acid, KClO3 and activated carbon powder are added to the reagent reaction kettle for oxidation, hydrolysis and polymerization reactions to generate polymeric ferric sulfate with adsorption performance, and the polymeric ferric sulfate is then used for the coagulation treatment in step S1.

[0012] S5: After the sludge generated in the sedimentation tank in step S2 is subjected to magnetic powder recovery, it is mixed with the sludge generated by centrifugal filtration in step S4, and then concentrated and dehydrated to produce a cake.

[0013] Optionally, in step S1, during magnetic coagulation treatment, magnetic powder and polymeric ferric sulfate are added. When the whole process is just started, fresh magnetic powder and polymeric ferric sulfate are used. After the process flow starts running, the magnetic powder recovered in step S5 and the polymeric ferric sulfate generated in step S4 are used.

[0014] Optionally, in step S2, the Fenton reactor is equipped with a first on-line pH meter to detect the pH value of the wastewater in real time. The addition amount of sulfuric acid is controlled by an ORP on-line monitor to adjust the pH value of the wastewater to 3.5 - 3.8.

[0015] Optionally, in step S3, the high-density sedimentation tank is equipped with a second on-line pH meter. The addition amount of liquid caustic is controlled by the ORP on-line monitor cooperating with it to neutralize the remaining sulfuric acid in the Fenton reaction and ensure that the pH value of the effluent from the high-density sedimentation tank meets the standards; the pH value in the high-density sedimentation tank is 6.5.

[0016] Optionally, in step S4, the volume ratio of the concentrated sulfuric acid added to the sludge in the sludge reaction kettle is (0.01 - 0.02):1. After adding the concentrated sulfuric acid, the sludge reaction kettle is heated to 80 - 90 °C. After reacting for 10 - 15 min, iron filings are added, and the reaction is fully stirred for 40 - 50 min. When the color changes from rust red to light green, it is regarded that all ferric ions have become ferrous sulfate and dissolved in the effluent; the molar ratio of iron filings to concentrated sulfuric acid is greater than 1:3.

[0017] The effluent is centrifugally filtered, the sludge is discharged to a sludge thickening tank, and the filtrate is input into a reagent reaction kettle.

[0018] KClO3, sulfuric acid and activated carbon powder are added to the reagent reaction kettle. The volume ratio of the activated carbon powder to the filtrate in the reagent reaction kettle is (0.07 - 0.13):1, and the reaction generates polymeric aluminum sulfate with adsorption performance.

[0019] In step S5, the sludge generated in the sedimentation tank of step S2 is subjected to magnetic powder recovery. The recovered magnetic powder is reused for coagulation treatment. The remaining sludge is then mixed with the sludge generated by centrifugal filtration in step S4, and then input into a sludge thickening tank for thickening and dewatering to produce sludge cakes.

[0020] Optionally, a magnetic powder recovery device is used for magnetic powder recovery of the sludge generated in the sedimentation tank in step S2. The magnetic powder recovery device includes a housing, a flexible mesh plate and a drainage trough inside the housing. There is a sludge inlet at the top of the housing and a first sludge outlet at the bottom. The sludge inlet is above the flexible mesh plate.

[0021] Guide rails are respectively provided on the inner walls on both sides of the housing. The two ends of the flexible mesh plate are respectively slidably connected to the guide rails on both sides, so that the flexible mesh plate moves along the guide rails. The flexible mesh plate is provided with magnetic bodies for attracting magnetic powder and flocs containing magnetic powder in the influent water.

[0022] The flexible mesh plate is horizontally laid and forms an oval shape in the vertical direction, similar to the shape of a conveyor track. The upper and lower horizontal linear parts of the flexible mesh plate are the upper flexible mesh plate and the lower flexible mesh plate respectively. The drainage trough is arranged inside the circle formed by the flexible mesh plate for receiving the sewage and sludge without magnetic powder falling from the upper flexible mesh plate and discharging them out of the housing.

[0023] Further optionally, the flexible mesh plate includes a plurality of cross beams and longitudinal beams that are crisscrossed. The cross beams are parallel to the moving direction of the upper flexible mesh plate, the longitudinal beams are perpendicular to the cross beams, and the longitudinal beams are hollow. Each longitudinal beam is provided with a movable magnetic body, and the magnetic body is parallel to the longitudinal beam.

[0024] When the magnetic body is close to the side wall of the longitudinal beam, the flexible mesh plate can adsorb magnetic powder and sludge containing magnetic powder. When the magnetic body leaves the side wall of the longitudinal beam, the flexible mesh plate releases the adsorbed magnetic powder and sludge containing magnetic powder, causing them to fall and be discharged through the magnetic powder discharge port.

[0025] Further optionally, the magnetic powder recovery device further includes a plurality of rolling barrels and magnetic separation drums. The rolling barrels are arranged below the lower flexible mesh plate for rolling and crushing the sludge adsorbed on the flexible mesh plate. The magnetic separation drums are correspondingly arranged below the lower flexible mesh plate after the rolling barrels for receiving the remaining magnetic powder and a small amount of crushed sludge on the flexible mesh plate and performing magnetic separation of the magnetic powder again.

[0026] Further optionally, the magnetic separation drum includes a hollow cylinder body, a rotating shaft and a scraper. The hollow cylinder body is made of a permanent magnet material. The rotating shaft is at the center of the hollow cylinder body and is parallel to the hollow cylinder body. The rotating shaft passes through the side wall of the housing and is connected to an external driving device. The rotating shaft is connected and fixed to the inner wall of the hollow cylinder body through a plurality of support rods to drive the hollow cylinder body to rotate.

[0027] The scraper is inclined, with the top end of the scraper contacting the outer sidewall of the hollow cylinder, and the bottom end of the scraper connected to the magnetic discharge port. The magnetic discharge port is provided on the sidewall of the outer shell obliquely below the magnetic separation drum, and a magnetic powder recovery container can be arranged outside the outer shell.

[0028] Further optionally, support pieces are respectively arranged on the inner sides of both ends of the longitudinal beam. Two position gears, namely the upper and middle position gears, are arranged on the surfaces of the two support pieces facing each other. Both ends of the magnetic body are connected to the corresponding position gears of the two support pieces, so that the magnetic body always remains horizontal; by switching the position gears, the distance between the magnetic body and the inner sidewall of the longitudinal beam is changed. Description of the Drawings

[0029] Figure 1 is a schematic process flow diagram of Embodiment 1;

[0030] Figure 2 is a schematic structural diagram of the magnetic powder recovery device of Embodiment 2;

[0031] Figure 3 is Figure 2 a side view schematic diagram of;

[0032] Figure 4 is a schematic structural diagram of the flexible mesh plate;

[0033] Figure 5 is a schematic structural diagram of the longitudinal beam and the magnetic body.

[0034] In the drawings, 1 - flexible mesh plate, 2 - drainage groove, 3 - mud inlet, 4 - guide rail, 5 - magnetic body, 6 - upper layer flexible mesh plate, 7 - lower layer flexible mesh plate, 8 - cross beam, 9 - longitudinal beam, 10 - magnetic discharge port, 11 - rolling barrel, 12 - slider, 13 - support piece, 14 - upper position gear, 15 - middle position gear, 16 - limiting plate, 17 - hollow cylinder, 18 - rotating shaft, 19 - scraper, 20 - water distribution pipe. Detailed Embodiments

[0035] Embodiment 1

[0036] This embodiment provides a method for the advanced treatment of soy sauce wastewater and its sludge treatment, as Figure 1 , including the following steps:

[0037] S1: After the soy sauce wastewater undergoes filtration pretreatment, the produced water is successively subjected to magnetic coagulation treatment and flocculation treatment, and magnetic powder is added during the magnetic coagulation treatment;

[0038] S2: The produced water obtained in step S1 is input into a sedimentation tank for mud-water separation. The separated produced water is input into a Fenton reactor. After adjusting the pH value, ferrous sulfate and hydrogen peroxide agents are added to the Fenton reactor to oxidize, adsorb, and degrade the COD and color in the wastewater;

[0039] S3: The effluent obtained after Fenton treatment is input into a high-density sedimentation tank for neutralization and sludge-water separation. The separated effluent can meet the discharge standards, and the separated sludge is discharged into a sludge reaction kettle.

[0040] S4: Concentrated sulfuric acid and iron filings are added to the sludge reaction kettle, and heated for reaction to produce ferrous sulfate. After the effluent is centrifugally filtered, the filtrate is input into a chemical reaction kettle.

[0041] Sulfuric acid, KClO3 and activated carbon powder are added into the chemical reaction kettle for oxidation, hydrolysis and polymerization reactions to generate polymeric ferric sulfate with adsorption performance, and the polymeric ferric sulfate is then used for the coagulation treatment in step S1.

[0042] S5: After the sludge generated in the sedimentation tank in step S2 is subjected to magnetic powder recovery, it is mixed with the sludge generated by centrifugal filtration in step S4, and then concentrated and dehydrated to produce a mud cake.

[0043] In step S1, during magnetic coagulation treatment, magnetic powder and polymeric ferric sulfate are added. When the entire process is just started, fresh magnetic powder and polymeric ferric sulfate are used. After the process flow runs, the magnetic powder recovered in step S5 and the polymeric ferric sulfate generated in step S4 are used. Flocculation treatment uses PAM reagent. By reacting with magnetic powder, coagulant and flocculant, most of the hydrophobic pollutants and a small part of hydrophilic pollutants in the soy sauce wastewater are removed.

[0044] The polymeric ferric sulfate generated in step S4 has good adsorption and coagulation effects, can quickly adsorb and degrade the organic matter that is difficult to biodegrade in the wastewater. After magnetic coagulation treatment and flocculation treatment, the wastewater COD can be reduced from 1200mg / L to about 700mg / L, reducing the pressure and cost of subsequent treatment. The polymeric ferric sulfate generated in step S4 has a certain acidity. After being washed many times, the acidity is reduced to avoid reacting with the magnetic powder in step S1.

[0045] In step S2, the Fenton reactor is equipped with a first on-line pH meter to detect the pH value of the wastewater in real time. The addition amount of sulfuric acid is controlled by an ORP on-line monitor to adjust the pH value of the wastewater to 3.5 - 3.8. In the Fenton treatment process, by reasonably adjusting the ratio of ferrous sulfate and hydrogen peroxide, the reaction generates polynuclear hydroxy complex iron and hydroxyl radicals, which can quickly degrade the COD that is difficult to biodegrade, adsorb and degrade the hydrophilic COD, and achieve the effect of decolorization.

[0046] In step S3, the high-density sedimentation tank is equipped with a second on-line pH meter, and the addition amount of liquid caustic soda is controlled by the ORP on-line monitor in cooperation with it to neutralize the remaining sulfuric acid in the Fenton reaction and ensure that the pH value of the effluent from the high-density sedimentation tank meets the standards.

[0047] The high-density sedimentation tank can be a conventional high-density sedimentation tank in the art, and the pH value in the high-density sedimentation tank is 6.5.

[0048] The produced water in step S3 meets the reclaimed intermediate water quality.

[0049] In step S4, the volume ratio of concentrated sulfuric acid added into the sludge reactor to the sludge in the sludge reactor is 0.02:1. After adding the concentrated sulfuric acid, the sludge reactor is heated to 90 °C. After reacting for 10 min, iron filings are added, and the mixture is stirred and reacted fully for 40 min. When the color changes from rust red to light green, it is regarded that all ferric ions have become ferrous sulfate and dissolved in the produced water; the molar ratio of iron filings to concentrated sulfuric acid is greater than 1:3.

[0050] The produced water is centrifugally filtered, the sludge is discharged to the sludge thickening tank, and the filtrate is input into the reagent reaction tank.

[0051] KClO3, sulfuric acid, and activated carbon powder are added into the reagent reaction tank. The volume ratio of the activated carbon powder to the filtrate in the reagent reaction tank is 0.07:1, and polyaluminum sulfate with adsorbability is generated by reaction. The dosages of KClO3 and sulfuric acid are appropriately increased compared with the dosages required by chemical reactions to ensure complete reaction.

[0052] In step S5, the sludge generated in the sedimentation tank of step S2 is subjected to magnetic powder recovery. The recovered magnetic powder is reused for coagulation treatment. The remaining sludge is mixed with the sludge generated by centrifugal filtration in step S4, and then input into the sludge thickening tank for thickening and dewatering to produce sludge cakes.

[0053] In step S5, the method for magnetic powder recovery is as follows: the sludge is input into a traditional magnetic separation device in batches, that is, the sludge is input from the inlet at the top of the device. There is only one continuously rotating magnetic drum in the device to attract magnetic powder, and the non-magnetic sludge is discharged from the outlet at the bottom of the device.

[0054] Comparative Example 1

[0055] The method for advanced treatment of soy sauce wastewater and its sludge treatment in this comparative example is the same as that in Example 1, except that step S4 is not included. The sludge separated in step S3 is not discharged into the sludge reactor, but directly input into the sludge thickening tank for thickening and dewatering to produce sludge cakes.

[0056] At present, the sludge produced by the Fenton reaction is defined as hazardous waste in most places. Its sludge is directly concentrated and dewatered to produce sludge cakes. The operating cost of the entire process in Comparative Example 1 is 3.0 yuan per ton of wastewater conventionally. However, in the present invention, through the resource treatment of the sludge produced by Fenton treatment, the sludge is no longer regarded as hazardous waste, the disposal cost of the sludge will be reduced, and polyaluminum sulfate with an adsorption effect is generated and reused for coagulation treatment. The operating cost of the entire process in Example 1 is 1.9 yuan per ton of wastewater.

[0057] Example 2

[0058] The method for advanced treatment of soy sauce wastewater and its sludge treatment in this comparative example is the same as that in Example 1, except that, as Figures 2 - 5 shown, in step S2, a magnetic powder recovery device is used for magnetic powder recovery of the sludge generated in the sedimentation tank. The magnetic powder recovery device includes a housing and a flexible mesh plate 1 and a drainage tank 2 inside the housing. A sludge inlet 3 is provided at the top of the housing, and a first sludge discharge port is provided at the bottom. The sludge inlet 3 is located above the flexible mesh plate 1;

[0059] Guide rails 4 are respectively provided on the inner walls on both sides of the housing. The two ends of the flexible mesh plate 1 are respectively slidably connected to the guide rails 4 on both sides, so that the flexible mesh plate 1 moves along the guide rails 4; a magnetic body 5 is provided inside the flexible mesh plate 1 for attracting magnetic powder and flocs containing magnetic powder in the influent water;

[0060] The flexible mesh plate 1 is horizontally laid and forms an oval shape in the vertical direction, similar to the shape of a conveyor track. The upper and lower horizontal linear parts of the flexible mesh plate 1 are respectively an upper-layer flexible mesh plate 6 and a lower-layer flexible mesh plate 7; the drainage tank 2 is arranged inside the circle formed by the flexible mesh plate 1 for receiving the sewage and sludge without magnetic powder falling from the upper-layer flexible mesh plate 6 and discharging them from the housing.

[0061] The flexible mesh plate 1 includes a number of cross beams 8 and longitudinal beams 9 that intersect horizontally and vertically. The cross beams 8 are parallel to the moving direction of the upper-layer flexible mesh plate 6, the longitudinal beams 9 are perpendicular to the cross beams 8, and the longitudinal beams 9 are hollow. A movable magnetic body 5 is provided inside each longitudinal beam 9, and the magnetic body 5 is parallel to the longitudinal beam 9;

[0062] When the magnetic body 5 is close to the side wall of the longitudinal beam 9, the flexible mesh plate 1 can adsorb magnetic powder and sludge containing magnetic powder. When the magnetic body 5 leaves the side wall of the longitudinal beam 9, the flexible mesh plate 1 releases the adsorbed magnetic powder and sludge containing magnetic powder, causing them to fall and be discharged through the magnetic powder discharge port 10.

[0063] The magnetic powder recovery device further includes five rolling barrels 11 and a magnetic separation roller. The rolling barrels 11 are arranged below the lower-layer flexible mesh plate 7 for rolling and crushing the sludge adsorbed on the flexible mesh plate 1; the magnetic separation roller is correspondingly arranged below the lower-layer flexible mesh plate 7 after the rolling barrels 11 for receiving the remaining magnetic powder and a small amount of crushed sludge on the flexible mesh plate 1 and performing magnetic separation on the magnetic powder again.

[0064] The cross beam 8 is solid, which improves the overall strength of the flexible mesh plate 1 and prevents it from being damaged by the rolling barrels 11; the flexible mesh plate 1 is made of elastic rubber material and can be bent and pressed and then restored to its original shape.

[0065] Both ends of the longitudinal beam 9 are closed and are respectively provided with hard connecting heads for facilitating firm connection with the sliders 12 on the guide rails 4;

[0066] Support plates 13 are respectively provided on the inner sides of the two ends of the longitudinal beam 9, and the two support plates 13 are provided with two upper and middle position gears on the sides facing each other. The two ends of the magnetic body 5 are connected to the corresponding position gears of the two support plates 13, so that the magnetic body 5 always remains horizontal; by switching the position gears, the distance between the magnetic body 5 and the inner wall of the longitudinal beam 9 is changed.

[0067] As a specific implementation, each longitudinal beam 9 is connected to a number of cross beams 8, the cross beams 8 are solid and connected to the outside of the longitudinal beam 9, and the interior of the longitudinal beam 9 is hollow as a whole, so that the magnetic body 5 in the longitudinal beam 9 can pass through the longitudinal beam 9; the magnetic body 5 is a slender magnetic rod, which is passed through the interior of the longitudinal beam 9, and the two ends of the magnetic body 5 are connected to the position gears corresponding to the two support plates 13. Specifically, the two ends of the magnetic body 5 are fixedly connected to the upper position gears 14 of the two support plates 13. At this time, the side of the magnetic body 5 is close to the upper inner wall of the longitudinal beam 9, attracting the magnetic powder and the sludge containing the magnetic powder entering from the mud inlet 3; when the position gear is switched to the middle position gear 15, the side of the magnetic body 5 leaves the inner wall of the longitudinal beam 9, that is, it is suspended in the longitudinal beam 9, neither close to the upper inner wall nor the lower inner wall. This state causes the flexible mesh 1 to lose its magnetic attraction, and the magnetic powder and the sludge containing the magnetic powder on the flexible mesh 1 fall off. Since the interior of the longitudinal beam 9 is a closed space with no water therein, the position gear can be an existing switch shifting device that can realize the above functions.

[0068] The shape of the guide rail 4 is the same as the shape formed by the flexible mesh plate 1, which is also an oblong shape; arc-shaped limit plates 16 protruding outward are respectively provided at the arc-shaped positions on both sides of the flexible mesh plate 1, so that when the flexible mesh plate 1 moves to the limit plate 16, an arc-shaped turning is formed;

[0069] A plurality of sliders 12 are provided on the inner side of each guide rail 4. The two sliders 12 corresponding to the two guide rails 4 are respectively connected to the two ends of the same longitudinal beam 9, and are used to drive the flexible mesh plate 1 to move along the oblong guide rail 4;

[0070] The driving device of each guide rail 4 is arranged at a corresponding position outside the shell, passes through the side wall of the shell to connect and control the slider 12, and then drives the flexible mesh plate 1 to move along the oblong shape.

[0071] The drainage trough 2 is arranged between the upper flexible mesh plate 6 and the lower flexible mesh plate 7, and is used to receive the sewage and sludge without magnetic powder falling from the upper flexible mesh plate 6; the length of the drainage trough 2 is not less than the length of the upper flexible mesh plate 6, and the drainage trough 2 extends to the side wall of the outer shell in the direction of the longitudinal beam 9, and a second mud discharge port is opened on the side wall, so that the material in the drainage trough 2 is discharged from the outer shell and then input into the sludge concentration tank.

[0072] The rolling barrels 11 are arranged on the upstream side in the rotation direction of the lower flexible mesh plate 7. Five rolling barrels 11 are arranged side by side in sequence along the rotation direction of the lower flexible mesh plate 7 and are located below the lower flexible mesh plate 7. The upper surface of the rolling barrel 11 is in pressing contact with the lower surface of the lower flexible mesh plate 7;

[0073] The lower edge of the limiting plate 16 close to the rolling barrel 11 extends horizontally to the position of the last rolling barrel 11, and cooperates with the rolling barrel 11 to crush the sludge on the flexible mesh plate 1, maintaining the straight state of the lower flexible mesh plate 7. The rolling barrel 11 is a cylindrical barrel, and its rotating shaft is connected to the motor outside the housing.

[0074] The magnetic separation drum includes a hollow cylinder 17, a rotating shaft 18 and a scraping plate 19. The hollow cylinder 17 is made of a permanent magnet material. The rotating shaft 18 is at the center of the hollow cylinder 17 and is parallel to the hollow cylinder 17. The rotating shaft 18 passes through the side wall of the housing and is connected to an external driving device. The rotating shaft 18 is connected and fixed to the inner wall of the hollow cylinder 17 through three support rods to drive the hollow cylinder 17 to rotate;

[0075] The scraping plate 19 is inclined. The top end of the scraping plate 19 contacts the outer side wall of the hollow cylinder 17. The bottom end of the scraping plate 19 is connected to a magnetic discharge port 10. The magnetic discharge port 10 is arranged on the side wall of the housing obliquely below the magnetic separation drum. A magnetic powder recovery container can be arranged outside the housing.

[0076] The mud inlet 3 is connected to a water distribution pipe 20. The water distribution pipe 20 is arranged above the upper flexible mesh plate 6, so that the muddy water input from the mud inlet 3 is evenly distributed and falls on the upper flexible mesh plate 6. The water distribution pipe 20 can be a conventional water distribution pipe 20.

[0077] The magnetic body 5 in the longitudinal beam 9 of the upper flexible mesh plate 6 moved to below the water distribution pipe 20 is switched to the upper position gear 14. The magnetic body 5 is closely attached to the upper inner side wall of the longitudinal beam 9. The upper surface of the upper flexible mesh plate 6 exerts a magnetic attraction effect. At the same time, the flexible mesh plate 1 moves clockwise along the guide rail 4. The sludge and sewage without magnetic powder pass through the filtration of the upper flexible mesh plate 6 and fall into the sludge discharge groove and are discharged to the sludge thickening tank;

[0078] When the flexible mesh plate 1 moves to the limiting plate 16 on the right side, it is bent into an arc shape. After passing through the arc section, the upper surface of the upper flexible mesh plate 6 becomes the lower surface of the lower flexible mesh plate 7, and the lower surface is in direct contact with the rolling barrel 11. The rolling barrel 11 and the extending part of the limiting plate 16 on the right side in the horizontal direction cooperate to crush the sludge on the flexible mesh plate 1. The non-magnetic sludge will fall off and be discharged to the sludge thickening tank through the first sludge discharge port;

[0079] After the lower flexible mesh plate 7 passes through the rolling barrel 11, it moves above the magnetic separation drum. The magnetic body 5 in the longitudinal beam 9 is switched to the middle position gear 15, and it can be separated from the lower surface of the lower flexible mesh plate 7. The lower surface loses the magnetic attraction effect. The remaining magnetic powder and a small amount of sludge naturally fall onto the hollow cylinder 17, adsorb magnetic powder again, the non-magnetic sludge falls to the bottom of the housing and is discharged. The magnetic powder adsorbed by the hollow cylinder 17 is scraped off by the scraper 19 and then slides along the scraper 19 to the magnetic discharge port 10 for discharge.

[0080] In the magnetic powder recovery device provided by the present invention, there are two-stage magnetic attraction processes. First, through the magnetic attraction and filtration of the flexible mesh plate 1, the sludge containing magnetic powder is initially attracted for the first magnetic sludge separation; then after crushing, the magnetic powder inside the sludge can be fully exposed. The magnetic sludge falling from the flexible mesh frame that has lost its magnetism falls onto the magnetic separation drum for the second magnetic sludge separation. The magnetic powder scraped off by the scraper 19 has a higher purity, improving the magnetic powder recovery effect; the crushed sludge separated from the magnetic powder falls into the bottom of the housing and is discharged.

[0081] The magnetic powder recovery rates of Example 1 and Example 2 are 65% and 82% respectively. It can be seen that using the above magnetic powder recovery device can significantly improve the magnetic powder recovery rate. Magnetic powder recovery rate = mass of recovered magnetic powder × 100% / total mass of added magnetic powder.

Claims

1. A method for advanced treatment of soy sauce wastewater and its sludge treatment, characterized in that, It includes the following steps: S1: After the soy sauce wastewater is filtered, the produced water is successively subjected to magnetic coagulation treatment and flocculation treatment. During the magnetic coagulation treatment, magnetic powder is added. S2: The produced water obtained in step S1 is input into a sedimentation tank for sludge-water separation. The separated produced water is input into a Fenton reactor. After adjusting the pH value, ferrous sulfate and hydrogen peroxide agents are added to the Fenton reactor to oxidize, adsorb, and degrade the COD and chromaticity in the wastewater. S3: The produced water obtained after Fenton treatment is input into a high-density sedimentation tank for neutralization and sludge-water separation. The separated produced water can meet the discharge standards, and the separated sludge is discharged into a sludge reaction kettle. S4: Concentrated sulfuric acid and iron filings are added to the sludge reaction kettle, and heated for reaction to produce ferrous sulfate. After the produced water is centrifugally filtered, the filtrate is input into a reagent reaction kettle. Sulfuric acid, KClO3, and activated carbon powder are added into the reagent reaction kettle for oxidation, hydrolysis, and polymerization reactions to generate polymeric ferric sulfate with adsorption performance, and the polymeric ferric sulfate is then used for the coagulation treatment in step S1. S5: After the sludge produced in the sedimentation tank in step S2 is subjected to magnetic powder recovery, it is mixed with the sludge produced by centrifugal filtration in step S4, and then concentrated and dehydrated to produce a mud cake. In step S1, during the magnetic coagulation treatment, magnetic powder and polymeric ferric sulfate are added. When the entire process is just started, fresh magnetic powder and polymeric ferric sulfate are used. After the process flow starts running, the magnetic powder recovered in step S5 and the polymeric ferric sulfate produced in step S4 are used.

2. The method for deep treatment of soy sauce wastewater and its sludge treatment according to claim 1, characterized in that, In step S2, the Fenton reactor is equipped with a first on-line pH meter to real-time detect the pH value of the wastewater, and the addition amount of sulfuric acid is controlled by an ORP on-line monitor to adjust the pH value of the wastewater to 3.5 - 3.

8.

3. The method for deep treatment of soy sauce wastewater and its sludge treatment according to claim 1, characterized in that In step S3, the high-density sedimentation tank is equipped with a second on-line pH meter, and the addition amount of liquid caustic is controlled by the ORP on-line monitor cooperating with it to neutralize the remaining sulfuric acid in the Fenton reaction and ensure that the pH value of the produced water in the high-density sedimentation tank meets the standards; the pH value in the high-density sedimentation tank is 6.

5.

4. The method for deep treatment of soy sauce wastewater and its sludge treatment according to claim 1, characterized in that, In step S4, the volume ratio of the concentrated sulfuric acid added into the sludge reaction kettle to the sludge in the sludge reaction kettle is (0.01 - 0.02):

1. After adding the concentrated sulfuric acid, the sludge reaction kettle is heated to 80 - 90 °C, and after reacting for 10 - 15 min, iron filings are added, and fully stirred and reacted for 40 - 50 min. The molar ratio of iron filings to concentrated sulfuric acid is greater than 1:

3. The produced water of the sludge reaction kettle is centrifugally filtered, and the filtered sludge is discharged to a sludge thickening tank, and the filtrate is input into a reagent reaction kettle. The volume ratio of the activated carbon powder added into the reagent reaction kettle to the filtrate in the reagent reaction kettle is (0.07 - 0.13):

1.

5. The method for deeply treating soy sauce wastewater and sludge treatment according to claim 1, characterized in that, In step S2, the magnetic powder recovery of the sludge produced in the sedimentation tank is carried out by a magnetic powder recovery device. The magnetic powder recovery device includes a housing and a flexible mesh plate and a drainage groove inside the housing. The top of the housing is provided with a sludge inlet, and the bottom is provided with a first sludge discharge port. The sludge inlet is above the flexible mesh plate. Guide rails are respectively arranged on the inner walls on both sides of the housing. The two ends of the flexible mesh plate are respectively slidably connected to the guide rails on both sides, so that the flexible mesh plate moves along the guide rails; a magnetic body is arranged inside the flexible mesh plate to attract the magnetic powder and the floc containing magnetic powder in the influent water. The flexible mesh plate is horizontally laid and forms an oval shape in the vertical direction. The upper and lower horizontal linear parts of the flexible mesh plate are the upper flexible mesh plate and the lower flexible mesh plate respectively. The drainage groove is arranged inside the circle formed by the flexible mesh plate, and is used to receive the sewage and non-magnetic sludge falling from the upper flexible mesh plate, and discharge them out of the housing.

6. The method for advanced treatment of soy sauce wastewater and its sludge treatment according to claim 5, characterized in that, The flexible mesh plate includes a number of cross beams and longitudinal beams that intersect horizontally and vertically. The cross beams are parallel to the moving direction of the upper flexible mesh plate, the longitudinal beams are perpendicular to the cross beams, and the longitudinal beams are hollow. A movable magnetic body is arranged in each longitudinal beam, and the magnetic body is parallel to the longitudinal beam. When the magnetic body is close to the side wall of the longitudinal beam, the flexible mesh plate can adsorb magnetic powder and sludge containing magnetic powder. When the magnetic body leaves the side wall of the longitudinal beam, the flexible mesh plate releases the adsorbed magnetic powder and sludge containing magnetic powder, making them fall and be discharged through the magnetic powder discharge port.

7. The method for deep treatment of soy sauce wastewater and its sludge treatment according to claim 6, characterized in that, The magnetic powder recovery device further includes a number of rolling barrels and magnetic separation drums. The rolling barrels are arranged below the lower flexible mesh plate and are used to roll and crush the sludge adsorbed on the flexible mesh plate. The magnetic separation drum is correspondingly arranged below the lower flexible mesh plate after the rolling barrel, and is used to receive the remaining magnetic powder and a small amount of crushed sludge on the flexible mesh plate, and perform magnetic separation on the magnetic powder again.

8. The method for deeply treating soy sauce wastewater and its sludge treatment according to claim 7, characterized in that The magnetic separation drum includes a hollow cylinder body, a rotating shaft and a scraper. The hollow cylinder body is made of a permanent magnet material. The rotating shaft is at the center of the hollow cylinder body and is parallel to the hollow cylinder body. The rotating shaft passes through the side wall of the housing and is connected to an external driving device. The rotating shaft is connected to the inner wall of the hollow cylinder body through a number of support rods to drive the hollow cylinder body to rotate. The scraper is inclined. The top end of the scraper contacts the outer side wall of the hollow cylinder body, and the bottom end of the scraper is connected to the magnetic powder discharge port. The magnetic powder discharge port is arranged on the side wall of the housing obliquely below the magnetic separation drum, and a magnetic powder recovery container can be arranged outside the housing.

9. The method for deep treatment of soy sauce wastewater and its sludge treatment according to claim 6, characterized in that, Supporting pieces are respectively arranged on the inner sides of both ends of the longitudinal beam. Two positions, upper and middle, are arranged on the surfaces of the two supporting pieces facing each other. Both ends of the magnetic body are connected to the corresponding position gears of the two supporting pieces, so that the magnetic body always remains horizontal. By switching the position gears, the distance between the magnetic body and the inner side wall of the longitudinal beam is changed.

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