A closed-loop processing and resource recycling process for down processing wastewater

Abstract

The application discloses a kind of eiderdown processing wastewater closed loop processing and resource recycling process, it is related to industrial wastewater treatment technical field.The process is through the synergistic effect of pretreatment unit, enhanced biochemical treatment unit, advanced treatment unit and resource recovery unit, the high concentration organic wastewater generated in eiderdown processing process is handled by classification, while recycling eiderdown fiber, grease and water resources in wastewater.The process realizes zero discharge or near zero discharge of wastewater, greatly reduces the water cost and environmental risk of eiderdown processing enterprise, solves the problems such as incomplete treatment, serious resource waste and secondary pollution in traditional process, recovers grease and eiderdown fiber in wastewater through air floatation separation device, realizes the recycling of resources, and the depth treatment unit adopts sand filter, activated carbon adsorption and ultrafiltration membrane combined process, further removes residual pollutants, to ensure that effluent quality meets the reuse standard.

Description

Technical Field

[0001] This invention relates to the field of industrial wastewater treatment technology, specifically to a closed-loop treatment and resource recovery process for down processing wastewater. Background Technology

[0002] Down processing is a traditional advantageous industry in my country, mainly involving processes such as washing, degreasing, disinfection, and drying. This process generates large amounts of high-concentration organic wastewater. This wastewater contains abundant down fibers, animal fats, proteins, detergents, disinfectants, and impurities such as silt. It is characterized by high COD concentration, high suspended solids content, high oil content, and good biodegradability, but is difficult to treat. Direct discharge without effective treatment will cause serious pollution to aquatic environments, leading to eutrophication and damaging aquatic ecosystems.

[0003] The existing technology has the following problems: 1. The quality of the treated effluent is unstable and difficult to meet the reuse standards. Most of the treated water is discharged directly, resulting in a serious waste of water resources. 2. Useful substances such as down fibers and oils in the wastewater were not effectively recovered, which not only increased the load on subsequent treatment units, but also led to resource loss and secondary pollution. Summary of the Invention

[0004] This invention provides a closed-loop treatment and resource recycling process for wastewater from down processing to solve the problems mentioned in the background art.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A closed-loop treatment and resource recovery process for down processing wastewater is provided, comprising the following steps: (1) Pretreatment: The wastewater from down processing is introduced into the grit chamber to remove large particles and long fibers, and then enters the equalization tank for water quality and quantity adjustment; (2) Primary resource recovery: The adjusted wastewater is pumped into the dissolved air flotation separation device, where the oil and some suspended down fibers in the wastewater are separated by dissolved air flotation. The recovered oil is refined and used in industrial production, and the recovered down fibers are washed, disinfected and reused. (3) Enhanced biochemical treatment: The effluent from the air flotation enters the anoxic tank for denitrification and nitrogen removal, and then enters the aerobic tank. The process of combining activated sludge and biofilm methods is used to remove organic matter and ammonia nitrogen from the wastewater. (4) Secondary resource recovery: The effluent after biochemical treatment enters the sedimentation tank for solid-liquid separation. Part of the settled sludge is returned to the anoxic tank and the aerobic tank, and the other part enters the sludge treatment system. The filtrate after sludge dewatering is returned to the equalization tank. The dewatered sludge is dried and used to make organic fertilizer. (5) Advanced treatment: The effluent from the sedimentation tank is successively passed through a sand filter, an activated carbon adsorption tank and an ultrafiltration membrane module for advanced treatment to remove residual suspended solids, organic matter and microorganisms; (6) Disinfection and reuse: The effluent after deep treatment enters the disinfection tank and is disinfected by a combination of ultraviolet light and sodium hypochlorite. Part of the disinfected effluent is reused for processes such as washing and degreasing in down processing, and the other part is used for greening the factory area, road cleaning and equipment washing, so as to realize the closed-loop reuse of wastewater.

[0006] Furthermore, the air flotation separation device adopts pressurized dissolved air flotation, with a dissolved air pressure of 0.3-0.5 MPa and a reflux ratio of 20%-30%. The air flotation tank is equipped with a scum scraper and an oil scraper, which are used to collect scum and oil respectively.

[0007] Furthermore, the anoxic tank is equipped with elastic three-dimensional packing material, with a packing material filling rate of 50%-60%, a hydraulic retention time of 6-8 hours, and a dissolved oxygen concentration controlled at 0.2-0.5 mg / L.

[0008] Furthermore, the aerobic tank adopts the aerobic section of the A / O process, and is equipped with combined biological packing material with a packing material filling rate of 40%-50%, a hydraulic retention time of 12-16 hours, a dissolved oxygen concentration controlled at 2-4 mg / L, and a sludge return ratio of 50%-100%.

[0009] Furthermore, the sand filter uses quartz sand filter media with a particle size of 0.5-1.2 mm, a filter layer thickness of 800-1200 mm, and a filtration speed of 5-8 m / h.

[0010] Furthermore, the activated carbon adsorption tank uses columnar activated carbon with an iodine value ≥800mg / g, a filter layer thickness of 1000-1500mm, and an empty bed contact time of 20-30 minutes.

[0011] Furthermore, the ultrafiltration membrane module uses a hollow fiber ultrafiltration membrane with a molecular weight cutoff of 10-50 kDa, an operating pressure of 0.1-0.3 MPa, and a membrane flux of 15-25 L / (m²). 2 ·h).

[0012] Furthermore, the disinfection pool is equipped with an ultraviolet sterilizer and a sodium hypochlorite dosing device, with an ultraviolet dose of 30-50 mJ / cm². 2 The dosage of sodium hypochlorite is 5-10 mg / L, and the contact time is 30-60 minutes.

[0013] Due to the adoption of the above technical solution, the technical progress achieved by this invention compared to the prior art is as follows: 1. This invention adopts a closed-loop treatment process, which realizes the resource reuse of wastewater from down processing, significantly reduces the amount of fresh water used, and lowers the water costs for enterprises.

[0014] 2. This invention recovers oil and down fibers from wastewater through an air flotation separation device, realizing the recycling of resources and improving the economic benefits of enterprises.

[0015] 3. This invention employs anoxic-aerobic combined process, which effectively removes organic matter and ammonia nitrogen from wastewater, improving treatment efficiency and effluent quality.

[0016] 4. The deep treatment unit of this invention adopts a combination of sand filtration, activated carbon adsorption and ultrafiltration membrane technology to further remove residual pollutants and ensure that the effluent water quality meets the reuse standard. 5. This invention uses a combined ultraviolet light and sodium hypochlorite disinfection method, which has a good sterilization effect, leaves no residue, and avoids secondary pollution; 6. The sludge of this invention is dehydrated and dried and then used to make organic fertilizer, realizing the resource utilization of sludge and solving the problem of sludge disposal. Attached Figure Description

[0017] Figure 1 This is a flowchart of the process of the present invention. Detailed Implementation

[0018] Implementation Plan like Figure 1 As shown, the closed-loop treatment and resource recycling process for down processing wastewater of the present invention mainly consists of a pretreatment unit, a primary resource recovery unit, an enhanced biochemical treatment unit, a secondary resource recovery unit, a deep treatment unit, and a disinfection and recycling unit.

[0019] The pretreatment unit includes a bar screen and an equalization tank. The bar screen contains coarse and fine screens; the coarse screen has a spacing of 10-20 mm, and the fine screen has a spacing of 3-5 mm, used to remove large particulate impurities and long fibers from the wastewater. The equalization tank is used to regulate the quality and quantity of the wastewater; it is equipped with a submersible mixer and a level controller, and the hydraulic retention time is 8-12 hours.

[0020] The primary resource recovery unit is an air flotation separation device, employing pressurized dissolved air flotation. This device consists of a dissolved air tank, a release device, an air flotation tank, a sludge scraper, an oil skimmer, and an air compressor. The pressure inside the dissolved air tank is 0.3-0.5 MPa, and the reflux ratio is 20%-30%. The air flotation tank is divided into a contact zone and a separation zone. The release device is installed in the contact zone, and the sludge scraper and oil skimmer are installed in the separation zone. The sludge scraper collects scum, and the oil skimmer collects floating oil. The recovered floating oil is further separated in an oil separator and then enters the oil refining system. After refining through processes such as heating, dehydration, decolorization, and deodorization, it is used to produce industrial lubricants, soaps, and other products. The recovered sludge mainly consists of down fibers, which, after washing, disinfection, and drying, are reused in down processing.

[0021] The enhanced biological treatment unit includes an anoxic tank and an aerobic tank. The anoxic tank is equipped with elastic three-dimensional packing material, with a packing fill rate of 50%-60%. A submersible mixer is installed within the tank, with a hydraulic retention time of 6-8 hours and dissolved oxygen concentration controlled at 0.2-0.5 mg / L. The aerobic tank utilizes the aerobic section of the A / O process, equipped with combined biological packing material, with a packing fill rate of 40%-50%. Microporous aerators are installed at the bottom of the tank, and oxygen is supplied by a Roots blower. The hydraulic retention time is 12-16 hours, and the dissolved oxygen concentration is controlled at 2-4 mg / L. The sludge return ratio is 50%-100%. In the anoxic tank, denitrifying bacteria utilize organic matter in the influent as a carbon source to reduce nitrate nitrogen in the aerobic tank's return mixed liquor to nitrogen gas, achieving denitrification. In the aerobic tank, aerobic microorganisms decompose organic matter in the wastewater into carbon dioxide and water, while simultaneously oxidizing ammonia nitrogen to nitrate nitrogen.

[0022] The secondary resource recovery unit is a sedimentation tank, specifically a radial flow sedimentation tank, with a surface loading rate of 1.0-1.5 m³. 3 / (m 2 The hydraulic retention time is 2-3 hours. A scraper is installed in the sedimentation tank to collect the settled sludge. Part of the settled sludge is returned to the anoxic and aerobic tanks to maintain the sludge concentration, while the other part enters the sludge treatment system. The sludge treatment system includes a sludge thickening tank, a sludge dewatering machine, and a sludge drying area. After thickening in the thickening tank for 24-48 hours, the sludge enters the sludge dewatering machine for dewatering, reducing the moisture content to below 80%. After drying in the drying area, the dewatered sludge has a moisture content below 40% and is used to make organic fertilizer. The filtrate from the dewatered sludge is returned to the equalization tank for further treatment.

[0023] The advanced treatment unit includes a sand filter, an activated carbon adsorption tank, and an ultrafiltration membrane module. The sand filter uses quartz sand as filter media, with a particle size of 0.5-1.2 mm, a filter bed thickness of 800-1200 mm, and a filtration velocity of 5-8 m / h. The activated carbon adsorption tank uses columnar activated carbon with an iodine value ≥800 mg / g, a filter bed thickness of 1000-1500 mm, and an empty bed contact time of 20-30 minutes. The ultrafiltration membrane module uses hollow fiber ultrafiltration membranes with a molecular weight cutoff of 10-50 kDa, an operating pressure of 0.1-0.3 MPa, and a membrane flux of 15-25 L / (m²). 2 •h). The advanced treatment unit further removes residual suspended solids, organic matter, and microorganisms from the biological effluent, ensuring that the effluent quality meets reuse standards.

[0024] The disinfection and reuse unit is a disinfection tank that uses a combined ultraviolet (UV) and sodium hypochlorite disinfection method. The disinfection tank is equipped with a UV sterilizer and a sodium hypochlorite dosing device, with a UV dose of 30-50 mJ / cm². 2 The sodium hypochlorite dosage is 5-10 mg / L, and the contact time is 30-60 minutes. The effluent quality after disinfection meets the standards of "Water Quality for Industrial Water Reuse of Urban Wastewater" (GB / T19923-2005) and "Water Quality for Urban Miscellaneous Water Reuse of Urban Wastewater" (GB / T18920-2020). Part of the effluent is reused in the washing and degreasing processes of down processing, while the other part is used for greening the factory area, road cleaning, and equipment flushing, realizing closed-loop reuse of wastewater.

[0025] This implementation plan comprehensively and efficiently treats down processing wastewater through the synergistic effects of pretreatment, primary resource recovery, enhanced biochemical treatment, secondary resource recovery, advanced treatment, and disinfection and reuse, while simultaneously achieving the resource-based reuse of water resources, down fibers, and oils.

[0026] The present invention will be further described in detail below with reference to embodiments: Example 1 A down processing enterprise generates 1000m³ of wastewater per day. 3 The wastewater has the following characteristics: CODcr = 1500-2000 mg / L, BOD5 = 600-800 mg / L, SS = 800-1200 mg / L, ammonia nitrogen = 30-50 mg / L, and oil content = 100-150 mg / L. The process of this invention is used for treatment, and the specific steps are as follows: (1) Pretreatment: Wastewater first enters the grit chamber, where large particles and long fibers are removed by coarse and fine grit chambers, and then enters the equalization tank to adjust the water quality and quantity. The hydraulic retention time is 10 hours.

[0027] (2) Primary Resource Recovery: The adjusted wastewater is pumped into the dissolved air flotation (DAF) separator at a dissolved air pressure of 0.4 MPa and a reflux ratio of 25%. The scum and oil scrapers in the DAF tank collect scum and oil, respectively. Approximately 120 kg of grease and 80 kg of down fibers are recovered daily. The recovered grease is refined and used to produce industrial lubricating oil, while the recovered down fibers are cleaned, disinfected, and dried before being reused in production.

[0028] (3) Enhanced biological treatment: The effluent from the air flotation enters the anoxic tank, with a hydraulic retention time of 7 hours and a dissolved oxygen concentration controlled at 0.3 mg / L. Then it enters the aerobic tank, with a hydraulic retention time of 14 hours and a dissolved oxygen concentration controlled at 3 mg / L. The sludge return ratio is 75%.

[0029] (4) Secondary resource recovery: The effluent after biochemical treatment enters the sedimentation tank with a surface loading of 1.2 m³. 3 / (m 2 The hydraulic retention time is 2.5 hours. Part of the settled sludge is returned to the anoxic and aerobic tanks, while the other part enters the sludge treatment system. Approximately 5 tons of dewatered sludge are produced daily, which is dried and used to make organic fertilizer.

[0030] (5) Advanced Treatment: The effluent from the sedimentation tank sequentially passes through a sand filter, an activated carbon adsorption tank, and an ultrafiltration membrane module. The sand filter uses 0.8 mm filter media with a filter bed thickness of 1000 mm and a filtration velocity of 6 m / h. The activated carbon adsorption tank uses columnar activated carbon with an iodine value of 900 mg / g, a filter bed thickness of 1200 mm, and an empty bed contact time of 25 minutes. The ultrafiltration membrane module uses a hollow fiber ultrafiltration membrane with a molecular weight cutoff of 30 kDa, an operating pressure of 0.2 MPa, and a membrane flux of 20 L / (m³). 2 ·h).

[0031] (6) Disinfection and reuse: The effluent after deep treatment enters the disinfection tank, with an ultraviolet radiation dose of 40 mJ / cm². 2 The sodium hypochlorite dosage was 7 mg / L, and the contact time was 45 minutes.

[0032] The treated effluent quality is as follows: CODcr ≤ 30 mg / L, BOD5 ≤ 10 mg / L, SS ≤ 5 mg / L, ammonia nitrogen ≤ 5 mg / L, and oil ≤ 1 mg / L, meeting the standards of "Water Quality Standard for Industrial Water Reuse of Urban Wastewater" (GB / T19923-2005) and "Water Quality Standard for Urban Miscellaneous Water Reuse of Urban Wastewater" (GB / T18920-2020). The daily reuse volume is approximately 950 m³. 3 The reuse rate has reached over 95%.

[0033] This embodiment demonstrates that the process of the present invention can effectively treat wastewater from down processing, achieving closed-loop reuse of wastewater and comprehensive utilization of resources. Example 2 A large down processing enterprise generates 3000m³ of wastewater per day. 3 The wastewater has the following characteristics: CODcr = 1800-2500 mg / L, BOD5 = 700-1000 mg / L, SS = 1000-1500 mg / L, ammonia nitrogen = 40-60 mg / L, and oil content = 120-200 mg / L. The process of this invention is used for treatment, and the specific steps are as follows: (1) Pretreatment: Wastewater first enters the grit chamber, where large particles and long fibers are removed by coarse and fine screens. Then it enters the equalization tank to adjust the water quality and quantity. The hydraulic retention time is 12 hours. The equalization tank is equipped with a submersible mixer and a level controller to ensure uniform water quality.

[0034] (2) Primary resource recovery: The regulated wastewater is pumped into two sets of parallel air flotation separators, each with a processing capacity of 1500 m³ / h. 3 / d. The dissolved air pressure is 0.45MPa, and the reflux ratio is 30%. Scum and oil are collected by a skimmer and a scraper in the flotation tank, respectively. Approximately 450kg of oil and 250kg of down fiber are recovered daily. The recovered oil is refined and used to produce biodiesel, while the recovered down fiber is cleaned, disinfected, and dried before being reused in production.

[0035] (3) Enhanced biological treatment: The effluent from the air flotation enters two sets of parallel anoxic-aerobic systems. The hydraulic retention time of each anoxic tank is 8 hours, and the dissolved oxygen concentration is controlled at 0.4 mg / L. The hydraulic retention time of each aerobic tank is 16 hours, the dissolved oxygen concentration is controlled at 3.5 mg / L, and the sludge return ratio is 100%.

[0036] (4) Secondary resource recovery: The effluent after biochemical treatment enters two sets of parallel radial flow sedimentation tanks with a surface loading of 1.3 m³. 3 / (m 2 The hydraulic retention time is 3 hours. Part of the settled sludge is returned to the anoxic and aerobic tanks, while the other part enters the sludge treatment system. Approximately 15 tons of dewatered sludge are produced daily, which is dried and used to make organic fertilizer.

[0037] (5) Advanced Treatment: The effluent from the sedimentation tank sequentially passes through a sand filter, an activated carbon adsorption tank, and an ultrafiltration membrane module. The sand filter uses 1.0 mm filter media with a filter bed thickness of 1200 mm and a filtration velocity of 7 m / h. The activated carbon adsorption tank uses columnar activated carbon with an iodine value of 1000 mg / g, a filter bed thickness of 1500 mm, and an empty bed contact time of 30 minutes. The ultrafiltration membrane module uses a hollow fiber ultrafiltration membrane with a molecular weight cutoff of 20 kDa, an operating pressure of 0.25 MPa, and a membrane flux of 22 L / (m³). 2 ·h).

[0038] (6) Disinfection and reuse: The effluent after deep treatment enters the disinfection tank, with an ultraviolet radiation dose of 50 mJ / cm². 2 The sodium hypochlorite dosage was 8 mg / L, and the contact time was 60 minutes.

[0039] The treated effluent quality is as follows: CODcr ≤ 25 mg / L, BOD5 ≤ 8 mg / L, SS ≤ 3 mg / L, ammonia nitrogen ≤ 3 mg / L, and oil ≤ 0.5 mg / L, which is superior to the standards of "Water Quality Standard for Industrial Water Reuse of Urban Wastewater" (GB / T19923-2005) and "Water Quality Standard for Urban Miscellaneous Water Reuse of Urban Wastewater" (GB / T18920-2020). The daily reuse volume is approximately 2850 m³. 3 The reuse rate has reached over 95%.

[0040] This embodiment further verifies the effectiveness and reliability of the process of the present invention in treating high-concentration, high-volume wastewater from down processing. The present invention has been described in detail above. However, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, any modifications or improvements that do not depart from the spirit of the present invention are within the scope of protection of the present invention.

Claims

1. A closed-loop treatment and resource recovery process for down processing wastewater, characterized in that, Includes the following steps: (1) Pretreatment: The wastewater from down processing is introduced into the grit chamber to remove large particles and long fibers, and then enters the equalization tank for water quality and quantity adjustment; (2) Primary resource recovery: The adjusted wastewater is pumped into the dissolved air flotation separation device, where the oil and some suspended down fibers in the wastewater are separated by dissolved air flotation. The recovered oil is refined and used in industrial production, and the recovered down fibers are washed, disinfected and reused. (3) Enhanced biochemical treatment: The effluent from the air flotation enters the anoxic tank for denitrification and nitrogen removal, and then enters the aerobic tank. The process of combining activated sludge and biofilm methods is used to remove organic matter and ammonia nitrogen from the wastewater. (4) Secondary resource recovery: The effluent after biochemical treatment enters the sedimentation tank for solid-liquid separation. Part of the settled sludge is returned to the anoxic tank and the aerobic tank, and the other part enters the sludge treatment system. The filtrate after sludge dewatering is returned to the equalization tank. The dewatered sludge is dried and used to make organic fertilizer. (5) Advanced treatment: The effluent from the sedimentation tank is successively passed through a sand filter, an activated carbon adsorption tank and an ultrafiltration membrane module for advanced treatment to remove residual suspended solids, organic matter and microorganisms; (6) Disinfection and reuse: The effluent after deep treatment enters the disinfection tank and is disinfected by a combination of ultraviolet light and sodium hypochlorite. Part of the disinfected effluent is reused for processes such as washing and degreasing in down processing, and the other part is used for greening the factory area, road cleaning and equipment washing, so as to realize the closed-loop reuse of wastewater.

2. The closed-loop treatment and resource recovery process for down processing wastewater according to claim 1, characterized in that, The air flotation separation device adopts pressurized dissolved air flotation, with a dissolved air pressure of 0.3-0.5MPa and a reflux ratio of 20%-30%. The air flotation tank is equipped with a scum scraper and an oil scraper, which are used to collect scum and oil respectively.

3. The closed-loop treatment and resource recovery process for down processing wastewater according to claim 1, characterized in that, The anoxic tank is equipped with elastic three-dimensional packing material with a packing rate of 50%-60%, a hydraulic retention time of 6-8 hours, and a dissolved oxygen concentration controlled at 0.2-0.5 mg / L.

4. The closed-loop treatment and resource recycling process for down processing wastewater according to claim 1, characterized in that, The aerobic tank adopts the aerobic section of the A / O process. The tank is equipped with combined biological packing material with a packing material filling rate of 40%-50%, a hydraulic retention time of 12-16 hours, a dissolved oxygen concentration controlled at 2-4 mg / L, and a sludge return ratio of 50%-100%.

5. The closed-loop treatment and resource recovery process for down processing wastewater according to claim 1, characterized in that, The sand filter uses quartz sand filter media with a particle size of 0.5-1.2 mm, a filter layer thickness of 800-1200 mm, and a filtration speed of 5-8 m / h.

6. The closed-loop treatment and resource recovery process for down processing wastewater according to claim 1, characterized in that, The activated carbon adsorption tank uses columnar activated carbon with an iodine value ≥800mg / g, a filter layer thickness of 1000-1500mm, and an empty bed contact time of 20-30 minutes.

7. The closed-loop treatment and resource recovery process for down processing wastewater according to claim 1, characterized in that, The ultrafiltration membrane module uses a hollow fiber ultrafiltration membrane with a molecular weight cutoff of 10-50 kDa, an operating pressure of 0.1-0.3 MPa, and a membrane flux of 15-25 L / (m²). 2 ·h).

8. The closed-loop treatment and resource recovery process for down processing wastewater according to claim 1, characterized in that, The disinfection tank is equipped with an ultraviolet sterilizer and a sodium hypochlorite dosing device, with an ultraviolet dose of 30-50 mJ / cm². 2 The dosage of sodium hypochlorite is 5-10 mg / L, and the contact time is 30-60 minutes.

9. The closed-loop treatment and resource recovery process for down processing wastewater according to claim 1, characterized in that, The sludge treatment system includes a sludge thickening tank, a sludge dewatering machine, and a sludge drying field. After the sludge is thickened in the thickening tank for 24-48 hours, it enters the sludge dewatering machine for dewatering. The moisture content of the dewatered sludge is reduced to below 80%, and after drying in the drying field, the moisture content is reduced to below 40%.

10. A type of recycled down, obtained by treating down processing wastewater using a closed-loop treatment and resource recovery process as described in any one of claims 1-9, characterized in that, The recycled down is obtained by washing, disinfecting and drying down fibers recovered from wastewater through an air flotation separator. Its cleanliness and hygiene indicators meet the requirements of down processing and production.

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