Integrated equipment for treating oil-containing emulsified wastewater

Abstract

The utility model relates to the technical field of environment-friendly water treatment, in particular to integrated equipment for treating oil-containing emulsified wastewater, which comprises an oil separation tank, a demulsification flocculation tank, an air floatation tank, an oxidation tank, a first sedimentation tank, an anaerobic tank, an aerobic tank, a second sedimentation tank and a sand filter which are sequentially arranged according to the flowing direction of the oil-containing wastewater. The integrated equipment for treating the oil-containing emulsified wastewater has the beneficial effects that the oil-containing emulsified wastewater is treated by adopting a combined process of a physicochemical method and a biological method. The front end adopts oil separation-demulsification-flocculation-air flotation, the middle is Fenton oxidation, and the rear end adopts anaerobic and aerobic biochemical treatment. Through on-site construction and agent debugging, the technology treats the oil-containing emulsified wastewater of which the COD (Chemical Oxygen Demand) of raw water is as high as 50,000-100,000 and the oil content is as high as 1000mg / L until the COD is less than 500mg / L and the oil content is less than 20mg / L.

Description

Technical Field

[0001] This utility model relates to the field of environmental water treatment technology, specifically to an integrated device for treating oily emulsified wastewater. Background Technology

[0002] Oily wastewater has a wide range of sources, including cleaning wastewater from the railway locomotive and shipbuilding industries, oily wastewater from the petrochemical industry, wastewater from machining, and food processing. Petroleum pollutants in oily wastewater generally exist in four states: based on droplet size, they are classified as floating oil, dispersed oil, emulsified oil, and dissolved oil. Floating and dispersed oil, due to their larger particle size, can be removed by simple physical processes to achieve oil-water separation. Emulsified oil exists in an emulsified state in water, with droplet sizes generally between 0.1-10 μm. Emulsified oil usually exists stably in water under the action of surfactants, and its removal is a key and challenging aspect of oily wastewater treatment. Dissolved oil is oil in a dissolved state, with droplet diameters generally no larger than 0.1 μm and extremely low concentrations; it is typically treated using physicochemical and biological methods.

[0003] In recent years, domestic and international research has focused on various methods for treating oily wastewater, including physical, physicochemical, chemical, and biological methods. Key technologies include gravity sedimentation, flotation, membrane separation, adsorption, acidification, electrocoagulation, flocculation, demulsification, and biological processes. However, oily wastewater is complex, containing not only petroleum pollutants but also large amounts of surfactants and hydrophilic oily organic matter. This limits the application of various treatment processes to oily wastewater. Therefore, combined treatment using multiple methods and leveraging their complementary advantages has attracted widespread attention from researchers.

[0004] Demulsification involves the physicochemical interaction of an emulsifier with the oil-water interface to reduce the interfacial tension and the strength and thickness of the oil-water interfacial film, thus destabilizing the oil-containing emulsion and achieving oil-water separation. The demulsifier's oil removal mechanism mainly includes active component displacement, wrinkling and deformation, compression of the electric double layer, collisional breaking of the interfacial film, adsorption bridging, charge neutralization, and entrapment and sweeping. Although demulsification can destabilize oil droplets in water, leading to oil-water separation, it cannot directly remove oil droplets and organic matter. Therefore, demulsification is generally used in combination with other water treatment technologies, such as demulsification-flotation, demulsification-membrane separation, and demulsification-flocculation. Painmanakul et al. used a demulsification-flotation combined method to treat oily wastewater containing large amounts of anionic surfactants. Researchers studied the relationship between oil removal rate, COD, and other indicators with demulsifier dosage, pH value, and gas flow rate. They found that at the optimal pH range of 8-10 and a demulsifier dosage of 800-1400 mg / L, both COD and oil removal rates could reach 99%. Zhang et al. combined demulsifier with reverse osmosis membrane separation technology for the treatment of oily wastewater. Under demulsification conditions of 80-90℃, a demulsifier dosage of 0.1%, and a reaction time of 30-50 min, combined with reverse osmosis membrane treatment technology, with experimental parameters of 3.6 MPa driving pressure and 1.5 m³ / h flow rate, the COD removal rate of the water sample reached 99.96%, and the oil removal rate was as high as 100%, meeting the first-class standard for integrated industrial wastewater discharge. Duan et al. synthesized a nonionic demulsifier using ethylene oxide and propylene oxide, and used it in combination with the flocculant polyethyleneimine. Under certain temperature conditions, the HLB value at the oil-demulsifier-water system interface reached 0, the oil-water interface became unstable, and the oil-water separation of the emulsion was achieved after stirring for a certain period of time.

[0005] However, in actual applications of oily wastewater treatment, demulsification, flocculation, and their combined processes still have many shortcomings:

[0006] (1) In the process of treating high-concentration emulsified oily wastewater in water-in-oil using a combination of demulsification and flocculation, the current commercial industrial-grade demulsifiers and flocculants have limited effect on highly stable emulsified oily wastewater. Moreover, the agents have strong pH selectivity and a narrow range. Therefore, this combination method needs to be improved in terms of agents.

[0007] (2) In terms of flocculation process, existing inorganic polymer flocculants such as aluminum salt and iron salt, organic flocculants such as chitosan and sodium cellulose, as well as organic polymer flocculants such as polyacrylamide have good treatment effects on low-concentration and poorly stable oily wastewater. However, the process currently has disadvantages such as large dosage of flocculants, low removal rate, and complicated steps; and poor treatment effect on high-concentration oily emulsified wastewater.

[0008] (3) The demulsification-air flotation combined process is also a common oily wastewater treatment process. This combined process first requires the addition of a certain amount of demulsifier to demulsify the emulsified oily wastewater, and finally uses microporous aeration to carry out air flotation treatment. Finally, a scraper is used to scrape off the floating oil and other flocs. This combined method has disadvantages such as numerous equipment, high energy consumption, general treatment effect, and high application cost.

[0009] In summary, existing demulsification, flocculation, and combined processes have various drawbacks. The main reason is that current industrial-grade treatment agents (such as demulsifiers and flocculants) are not effective in treating this type of high-concentration oily emulsified wastewater, and their application costs are high and the processes are cumbersome. Utility Model Content

[0010] The technical problem to be solved by this utility model is to provide an integrated equipment for treating oily emulsified wastewater with high processing efficiency and good processing effect.

[0011] To solve the above-mentioned technical problems, the technical solution adopted by this utility model is as follows: an integrated device for treating oily emulsified wastewater is provided, including: an oil separator, a demulsification and flocculation tank, an air flotation tank, an oxidation tank, a first sedimentation tank, an anaerobic tank, an aerobic tank, a second sedimentation tank and a sand filter tank arranged in sequence according to the flow direction of the oily wastewater.

[0012] The oil separator is used to remove surface oil from oily emulsified wastewater by gravity.

[0013] The demulsifier and flocculant are provided in the demulsifier and flocculant tank;

[0014] The anaerobic tank is used to degrade high molecular weight substances and insoluble substances in wastewater into low molecular weight substances and soluble substances through anaerobic processes.

[0015] Furthermore, in the aforementioned integrated equipment for treating oily emulsified wastewater, an equalization tank is provided between the oil separator and the demulsification and flocculation tank. The equalization tank is used to cool and homogenize the oily emulsified wastewater.

[0016] Furthermore, the aforementioned integrated equipment for treating oily emulsified wastewater also includes a sludge tank, where the mixed liquid obtained from the demulsification and flocculation tank undergoes sludge-water separation in an air flotation tank, and the sludge is scraped into the sludge tank by a sludge scraper.

[0017] Furthermore, the aforementioned integrated equipment for treating oily emulsified wastewater also includes a screw pump and a plate and frame filter press. The sludge from the sludge tank is pumped to the plate and frame filter press for dewatering, and the filtrate generated during the dewatering process is returned to the equalization tank.

[0018] Furthermore, in the aforementioned integrated equipment for treating oily emulsified wastewater, the sludge from the first and second sedimentation tanks is transported to a sludge storage tank via sludge pipelines, and then pumped to a plate and frame filter press for dewatering via a screw pump. The dry sludge with a moisture content of less than 80% after dewatering by the plate and frame filter press is transported off-site for disposal, and the filtrate generated during the dewatering process is returned to the equalization tank.

[0019] Furthermore, in the aforementioned integrated equipment for treating oily emulsified wastewater, the sludge from the sand filter is transported to a sludge tank via a sludge pipeline, then pumped to a plate and frame filter press for dewatering. The dry sludge with a moisture content of less than 80% after dewatering by the plate and frame filter press is transported off-site for disposal, and the filtrate generated during the dewatering process is returned to the equalization tank.

[0020] Furthermore, in the aforementioned integrated equipment for treating oily emulsified wastewater, the oil separator is equipped with concentrated hydrochloric acid to adjust the pH value of the oily emulsified wastewater.

[0021] Furthermore, in the aforementioned integrated equipment for treating oily emulsified wastewater, the oxidation tank is a Fenton oxidation tank.

[0022] The beneficial effects of this invention are as follows: This integrated equipment for treating oily emulsified wastewater employs a combination of physicochemical and biological methods. The front end uses oil separation, demulsification, flocculation, and air flotation; the middle stage involves Fenton oxidation; and the rear end undergoes anaerobic-aerobic biological treatment. After on-site construction and reagent adjustment, this process treats oily emulsified wastewater with a raw COD as high as 50,000-100,000 and an oil content as high as 1,000 mg / L to a COD of less than 500 mg / L and an oil content of less than 20 mg / L. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the integrated equipment for treating oily emulsified wastewater, which is a specific embodiment of this utility model.

[0024] Figure 2 The tailwater treatment flow chart of the integrated equipment for treating oily emulsified wastewater in Embodiment 1 of this utility model is shown.

[0025] Label Explanation:

[0026] 1. First sulfuric acid dosing tank; 2. Demulsifier dosing tank; 3. PAC dosing tank; 4. First PAM dosing tank; 5. Hydrogen peroxide dosing tank; 6. Ferrous sulfate dosing tank; 7. First sodium hydroxide dosing tank;

[0027] 8. Equalization tank;

[0028] 9. Grease trap; 10. Sewage lift pump;

[0029] 11. Demulsification reaction tank; 12. First flocculation reaction tank; 13. First coagulation reaction tank; 14. Air flotation pressure tank; 15. Air flotation tank;

[0030] 16. First pH adjustment tank; 17. Fenton oxidation tank; 18. pH adjustment tank; 19. Coagulation tank; 20. First sedimentation tank;

[0031] 21. Second PAM dosing tank; 22. Second sodium hydroxide dosing tank; 23. Disulfuric acid dosing tank; 24. Flocculant dosing tank;

[0032] 25. Anaerobic reactor; 26. Anoxic reactor; 27. Aerobic aeration reactor;

[0033] 28. Second pH adjustment tank; 29. ​​Second flocculation reaction tank; 30. Second coagulation reaction tank; 31. Second sedimentation tank;

[0034] 32. Sand filter tank. Detailed Implementation

[0035] To explain in detail the technical content, objectives, and effects of this utility model, the following description is provided in conjunction with the embodiments and accompanying drawings.

[0036] Example 1

[0037] Please see Figure 1 and Figure 2 This utility model provides an integrated device for treating oily emulsified wastewater. The integrated device for treating oily emulsified wastewater includes, in sequence according to the flow direction of the oily wastewater: an oil separator, a demulsification and flocculation tank, an air flotation tank, an oxidation tank, a first sedimentation tank, an anaerobic tank, an aerobic tank, a second sedimentation tank, and a sand filter.

[0038] The oil separator is used to remove surface oil from oily emulsified wastewater by gravity.

[0039] The demulsifier and flocculant are provided in the demulsifier and flocculant tank;

[0040] The anaerobic tank is used to degrade high molecular weight substances and insoluble substances in wastewater into low molecular weight substances and soluble substances through anaerobic processes.

[0041] In the aforementioned integrated equipment for treating oily emulsified wastewater, an equalization tank is provided between the oil separator and the demulsification and flocculation tank. The equalization tank is used to cool and homogenize the oily emulsified wastewater.

[0042] like Figure 1As shown, the integrated equipment for treating oily emulsified wastewater in this embodiment specifically includes the following dosing devices in sequence: a first sulfuric acid dosing tank 1; a demulsifier dosing tank 2; a PAC dosing tank 3; a first PAM dosing tank 4; a hydrogen peroxide dosing tank 5; a ferrous sulfate dosing tank 6; and a first sodium hydroxide dosing tank 7.

[0043] (1) The oily emulsified wastewater first flows into the oil separator 9 by gravity, and the pH of the wastewater is adjusted to 6-7 by acid to achieve preliminary oil-water separation. The surface oil is removed by the oil separator 9.

[0044] Wastewater flows into equalization tank 8. After being cooled, homogenized and equalized in the equalization tank, the wastewater is pumped into the demulsification-flocculation tank (i.e., the demulsification reaction tank and the first flocculation reaction tank). Demulsifier and flocculant are added respectively. The emulsion wastewater is first demulsified and flocculated in the demulsification-flocculation tank.

[0045] Specifically, in the above process, the oily emulsified wastewater flows through the following channels in sequence:

[0046] Regulating tank 8;

[0047] 9. Grease trap; 10. Sewage lift pump;

[0048] Demulsification reaction tank 11; First flocculation reaction tank 12; First coagulation reaction tank 13;

[0049] (2) The above-obtained mixture enters the flotation tank 15 (equipped with a flotation pressure tank 14) for mud-water separation. The sludge in the water floats to the top through the action of micro bubbles and is scraped into the sludge storage tank by a sludge scraper. The clear liquid at the bottom flows into the Fenton oxidation tank 17, where the dissolved COD is decomposed under oxidation.

[0050] Oily emulsified wastewater flows sequentially through: flotation tank 15; first pH adjustment tank 16 (acid addition); Fenton oxidation tank 17; pH adjustment tank 18 (alkali addition); coagulation tank 19; first sedimentation tank 20.

[0051] (3) The wastewater after oxidation and decomposition also produces sludge. The mixed liquid flows into the first sedimentation tank 20 (marked as sedimentation tank in the flow chart) for sludge-water separation, and the lower sludge is discharged into the sludge tank. After oxidation and decomposition, the wastewater still has a high COD and cannot meet the discharge standards, so further biochemical treatment is required. Therefore, the supernatant of the first sedimentation tank 20 is pumped into the anaerobic tank.

[0052] like Figure 1 As shown, the integrated equipment for treating oily emulsified wastewater in this embodiment further includes the following additives in sequence: 21, second PAM dosing tank 21; 22, second sodium hydroxide dosing tank 22; disulfide dosing tank 23; 24, flocculant dosing tank 24;

[0053] (4) The anaerobic tank adopts forced stirring. In the anaerobic tank, some high molecular weight substances and insoluble substances in the wastewater are degraded into small molecular weight substances and soluble substances through anaerobic processes, improving biodegradability and BOD / COD value, which not only creates conditions for subsequent aerobic biochemical treatment, but also reduces the biodegradation pressure of the subsequent aerobic stage. After treatment in the anaerobic tank, the wastewater flows into the aerobic tank.

[0054] The aerobic tank employs a composite process of activated sludge and combined packing material, enabling the separation of sludge from different functional microorganisms within the same reactor. The aerobic tank is filled with combined packing material with a large specific surface area, immobilizing the microorganisms within it. Under the action of these microorganisms, organic matter in the wastewater is degraded.

[0055] The effluent mixture from the aerobic tank undergoes sludge-water separation in the second sedimentation tank 31 (marked as the secondary sedimentation tank in the flow chart). Part of the bottom sludge is returned to the aerobic tank, while the excess is discharged to the anaerobic tank. The remaining sludge is discharged into the sludge tank; the effluent from the second sedimentation tank 31 is discharged into the equalization and conditioning tank.

[0056] After being pumped from the equalization tank into the intermediate tank, the wastewater is further purified by removing turbidity and some COD, making it clear. Finally, it is filtered through a sand filter to meet discharge standards.

[0057] Specifically, in the above process, the oily emulsified wastewater flows through the following channels in sequence:

[0058] 25 Anaerobic reactor; 26 Anoxic tank; 27 Aerobic aeration tank;

[0059] Second pH adjustment tank 28; second flocculation reaction tank 29; second coagulation reaction tank 30; second sedimentation tank 31; sand filter tank 32.

[0060] (5) such as Figure 2 As shown, the sludge treatment process flow is as follows: Sludge from the flotation tank, first sedimentation tank, second sedimentation tank, anaerobic tank, aerobic tank, and sand filtration is transported via sludge pipeline to a sludge storage tank. It is then pumped by a screw pump to a plate and frame filter press for dewatering. The dewatered sludge, with a moisture content of approximately 80% or less, is transported off-site for disposal. The filtrate generated during dewatering is returned to the equalization tank.

[0061] Furthermore, this application also provides preferred demulsifiers and flocculants:

[0062] 1) This application screens conventional demulsifiers and combines them with flocculants. Through screening, a highly efficient oil-removing demulsifier—the cationic demulsifier hexadecyltrimethylammonium chloride—was selected. Experiments using this demulsifier, through adsorption displacement and charge neutralization, demulsify the emulsion, causing emulsion instability and small oil droplet aggregation, which is beneficial for subsequent flocculation and sedimentation. Experimental results show that the demulsification effect is optimal when the dosage of hexadecyltrimethylammonium chloride as a demulsifier is 200 mg / L.

[0063] 2) Through screening and compounding of flocculants, this application obtained an inorganic polymeric flocculant that exhibits excellent flocculation and sedimentation effects on water samples containing demulsified emulsions. When polyaluminum chloride is used as a flocculant at a dosage of 1000 mg / L, the flocculant utilizes charge neutralization, adsorption bridging, and netting / sweeping mechanisms to flocculate and settle pollutants such as oil droplets, surfactants, and metal fragments from the emulsion, demonstrating excellent treatment performance.

[0064] Furthermore, the reaction pH and reaction time of the demulsification-flocculation process were investigated. It was found that the reaction pH was between 6 and 7 and the reaction time was 60 min, which had the best effect on the treatment of wastewater containing emulsions, with COD removal rate of over 95% and oil removal rate of over 97%.

[0065] In summary, this application, through research on oily wastewater treatment methods, decided to adopt a combined physicochemical and biological process to treat this type of wastewater. The front end employs oil separation, demulsification, flocculation, and air flotation; the middle stage involves Fenton oxidation; and the rear end undergoes anaerobic-aerobic biological treatment. After on-site construction and reagent adjustment, this process effectively treated oily emulsified wastewater with a raw COD as high as 50,000-100,000 and an oil content as high as 1,000 mg / L to a COD of less than 500 mg / L and an oil content of less than 20 mg / L.

[0066] The above description is merely an embodiment of this utility model and does not limit the patent scope of this utility model. Any equivalent modifications made based on the content of this utility model specification and drawings, or direct or indirect applications in related technical fields, are similarly included within the patent protection scope of this utility model.

Claims

1. An integrated device for treating oily emulsified wastewater, characterized in that, The system includes, in sequence according to the flow direction of the oily wastewater: oil separator, demulsification and flocculation tank, dissolved air flotation tank, oxidation tank, first sedimentation tank, anaerobic tank, aerobic tank, second sedimentation tank, and sand filter. The oil separator is used to remove surface oil from oily emulsified wastewater by gravity. The demulsifier and flocculant are provided in the demulsifier and flocculant tank; The anaerobic tank is used to degrade high molecular weight substances and insoluble substances in wastewater into low molecular weight substances and soluble substances through anaerobic processes.

2. The integrated equipment for treating oily emulsified wastewater according to claim 1, characterized in that, An equalization tank is also provided between the oil separator and the demulsification and flocculation tank. The equalization tank is used to cool and homogenize the oil-containing emulsified wastewater.

3. The integrated equipment for treating oily emulsified wastewater according to claim 2, characterized in that, It also includes a sludge tank, where the mixed liquor obtained from the demulsification and flocculation tank is separated into mud and water in an air flotation tank, and the sludge is scraped into the sludge tank by a sludge scraper.

4. The integrated equipment for treating oily emulsified wastewater according to claim 3, characterized in that, It also includes a screw pump and a plate and frame filter press. The sludge in the sludge tank is pumped to the plate and frame filter press for dewatering. The filtrate generated during the dewatering process is returned to the equalization tank.

5. The integrated equipment for treating oily emulsified wastewater according to claim 4, characterized in that, The sludge from the first and second sedimentation tanks is transported to the sludge tank for storage via sludge pipelines. It is then pumped to a plate and frame filter press for dewatering. The dry sludge with a moisture content of less than 80% after dewatering by the plate and frame filter press is transported off-site for disposal. The filtrate generated during the dewatering process is returned to the equalization tank.

6. The integrated equipment for treating oily emulsified wastewater according to claim 4, characterized in that, The sludge from the sand filter is transported to the sludge tank via a sludge pipeline and then pumped to a plate and frame filter press for dewatering. The dry sludge with a moisture content of less than 80% after dewatering is transported off-site for disposal, and the filtrate generated during the dewatering process is returned to the equalization tank.

7. The integrated equipment for treating oily emulsified wastewater according to claim 1, characterized in that, The oil separator is equipped with concentrated hydrochloric acid to adjust the pH value of the oily emulsified wastewater.

8. The integrated equipment for treating oily emulsified wastewater according to claim 1, characterized in that, The oxidation tank is a Fenton oxidation tank.

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