Method and apparatus for treating oil-containing emulsified wastewater

Abstract

This invention provides a method and equipment for treating oily emulsified wastewater. The method includes: first, subjecting the oily emulsified wastewater to micro-aeration three-phase separation treatment, then to electrochemical treatment, and finally to biological activated carbon treatment; wherein the electrochemical treatment employs a cascade electrocoagulation device, which comprises multiple modules arranged horizontally or vertically. The equipment, used to implement the aforementioned method for treating oily emulsified wastewater, includes: a micro-aeration three-phase separator, an electrochemical device, and an activated carbon device. The method and equipment for treating oily emulsified wastewater provided by this invention, targeting the pollution characteristics of oily and polymer-containing wastewater, improves the demulsification efficiency of the wastewater by optimizing the structure of the electrochemical device, combining micro-aeration three-phase separation treatment, biological activated carbon treatment, and enhancing the level of automation. The treated wastewater can be directly discharged into a comprehensive wastewater treatment system.

Description

TECHNICAL FIELD

[0001] The present application relates to a treatment method and equipment for oil-containing emulsified wastewater, and belongs to the technical field of oil and petrochemical wastewater treatment and resource treatment. BACKGROUND

[0002] In recent years, the oil and petrochemical industry has undergone great changes in oil and gas production operation methods. The use of unconventional oil and gas hydraulic fracturing and other stimulation measures requires a large amount of water, and the pollution load of the flowback waste liquid is high, which makes oil and gas production enterprises in environmentally fragile areas and water resource scarce areas face severe challenges in ecological environment protection. Moreover, with the deep exploitation of crude oil and the widespread application of tertiary oil recovery technology, the water content and salt content of crude oil are high, and there is a large amount of mud and a large amount of emulsifiers and high molecular polymers, which seriously emulsify oil and water, and also bring many adverse effects to oil refining production and pollution prevention.

[0003] The fundamental problem of pollution prevention and control in the process of oil and gas production and processing is the destabilization and separation of oil-containing and polymer-containing waste liquid. Generally, oil-containing and polymer-containing waste liquid has small surface tension, high polymer concentration, strong stability, and high fine solid content, and presents a very stable emulsified state, so it is difficult for conventional processes to achieve efficient destabilization. In order to ensure the sustainable and green development of oil and gas production and processing industry, it is necessary to focus on breaking through the problem of efficient demulsification treatment of polymer-containing and oil-containing waste liquid, and to improve the intelligentization and standardization of the treatment process system.

[0004] At present, the commonly used method for oil-containing and polymer-containing waste liquid is chemical demulsification, which mainly changes the type and interfacial properties of oil-containing emulsion by adding reagents to achieve destabilization and oil removal, but the cost of reagent addition is high. Other treatment technologies also have their own characteristics, but there are some shortcomings in actual operation, such as complex treatment process, complex treatment equipment, low treatment efficiency for some high salinity, high chloride ion, high COD and high pollution waste liquid, etc. In recent years, with the in-depth study of electrochemical technology in the treatment of oil-containing and salt-containing wastewater, some enterprises have also begun to use electrochemical process to treat operation waste liquid and electro-deionization wastewater, especially the electro-coagulation-air flotation method, which uses the comprehensive action of electric field reverse demulsification, electrochemical flocculation demulsification and micro-air flotation auxiliary sedimentation separation to realize oil-water separation and remove most of the oil in water, including suspended oil, dispersed oil, emulsified oil and dissolved oil. The electrochemical wastewater treatment device occupies a small area, and compared with the chemical demulsification technology, it does not need to add reagents, and the power consumption cost is low. In addition, the dregs are compact and have low water content, which reduces the high cost of outsourcing treatment of oil-containing sludge.

[0005] However, with the increasing complexity of reservoir modification waste liquid and electro-deionization wastewater pollution composition, it is urgent to optimize the electrochemical process, improve the demulsification efficiency, enhance the impact resistance, and improve the intelligent control. SUMMARY

[0006] To address the aforementioned technical problems, the present invention aims to provide a method and apparatus for treating oily emulsified wastewater. The method and apparatus of the present invention exhibit high removal rates of petroleum hydrocarbons, COD, and SS from the wastewater.

[0007] To achieve the above objectives, the present invention first provides a method for treating oily emulsified wastewater, which includes the following steps:

[0008] The oily emulsified wastewater is first treated by micro-aeration three-phase separation, then the wastewater obtained after treatment is electrochemically treated, and then treated by biological activated carbon to obtain the treated wastewater.

[0009] The electrochemical treatment is carried out using a cascade electrocoagulation device; the cascade electrocoagulation device includes multiple horizontally arranged modules, and each horizontally arranged module is provided with a partition to form a series connection of baffles between the multiple modules; or the cascade electrocoagulation device includes multiple vertically arranged modules, with wastewater entering from the bottom and exiting from the top in the vertically arranged modules.

[0010] In the above method, preferably, the oil-containing emulsified wastewater contains 200–4000 mg / L of petroleum hydrocarbons, 1000–15000 mg / L of COD, 500–6000 mg / L of SS (suspended solids), and has a conductivity of 600–2000 μS / cm. The wastewater treatment method of this invention can more effectively treat Pickering emulsion systems that are difficult to treat with conventional processes, while existing treatment processes can only address oil-water emulsion systems caused by non-solid particles.

[0011] According to a specific embodiment of the present invention, preferably, the above method further includes the following step: before the oily emulsified wastewater undergoes micro-aeration three-phase separation treatment, an organic electrolyte is added to the oily emulsified wastewater. More preferably, the organic electrolyte includes quaternary ammonium salt organic matter and / or oleate organic matter, etc., and the amount added is 10-100 mg / L based on the volume of the oily emulsified wastewater (this amount is the total amount of organic electrolyte added to the wastewater). More preferably, the amount of organic electrolyte added is 50-100 mg / L. Particularly preferably, the quaternary ammonium salt organic matter includes one or a combination of several of alkyl trimethyl quaternary ammonium salt, dimethyl diallyl ammonium chloride, methacryloyloxyethyl trimethyl ammonium chloride, and trimethylvinyl ammonium bromide, etc., and the oleate organic matter includes sodium oleate and / or potassium oleate, etc. The present invention adds organic electrolytes to oily emulsified wastewater. First, it can change the hydrophilic-lipophilic balance of the emulsion, promote the entry of organic matter into the oil phase and improve the three-phase separation efficiency. Second, it can increase the negative charge of the emulsion, which is beneficial to its migration and separation in the subsequent electric field.

[0012] In the above method, preferably, the micro-aeration three-phase separation treatment is carried out by using a micro-aeration three-phase separator, the residence time of the oil-containing emulsified wastewater in the micro-aeration three-phase separator is 10-30 min, the separated wastewater enters the cascade electrocoagulation device, and the oil-containing floating sludge separated in the micro-aeration three-phase separator is concentrated in the middle cylinder of the micro-aeration three-phase separator for 1-5 days, and then the oil-containing floating sludge is collected. After the micro-aeration three-phase separation treatment of the present application, the organic pollutants in the oil-containing floating sludge can be concentrated by 500-2000 times. The oil-containing floating sludge treated by the micro-aeration three-phase separation treatment can be collected and then treated by a coking device for resource utilization, or directly dewatered. The present application uses the micro-aeration three-phase separation treatment as a pretreatment of the oil-containing emulsified wastewater, which is placed before the electrochemical treatment, so that the large-scale materials in the wastewater can be effectively removed, and after the removal of the large-scale oil-containing materials by the micro-aeration three-phase separation, the small-scale and stable emulsified materials are treated by the electrochemical treatment.

[0013] In the above method, preferably, the residence time of the wastewater treated by the micro-aeration three-phase separation treatment in the cascade electrocoagulation device is 10-30 min.

[0014] In the above method, preferably, the cascade electrocoagulation device comprises 2-4 groups of modules arranged in a transverse direction or 2-4 groups of modules arranged in a longitudinal direction.

[0015] In the above method, preferably, when the cascade electrocoagulation device comprises 2-4 groups of modules arranged in a transverse direction, the electric field strength of each group of modules is 30-50 V / m, and the polar water ratio is 2-3 L / dm 2 .

[0016] In the above method, preferably, the polar plates of each group of modules arranged in a transverse direction in the cascade electrocoagulation device are respectively a soluble polar plate (such as an iron polar plate, an aluminum polar plate, etc.) and / or a stainless steel polar plate, the distance between each two polar plates is 2-4 cm, and the number of polar plates of each group of modules is 15-30. More preferably, the 15-30 polar plates of each group of modules are divided into several groups, each group has 3-5 polar plates, the two polar plates at the ends of each group of polar plates are connected to the power supply electrodes, the polar plates in the middle of each group of polar plates are not connected to the power supply electrodes and are used as induction electrodes, and each adjacent two groups of polar plates share the polar plates connected to the power supply electrodes. Those skilled in the art should understand that when the 15-30 polar plates of each group of modules are divided into several groups, except that the two polar plates at the ends of the module are only used as cathodes or anodes, the other polar plates connected to the power supply are used as anodes on one side and cathodes on the other side. The cascade electrocoagulation device of the present application adopts a plurality of groups of modules arranged in a transverse direction in series, which can present different induction electric field strengths by using different polar plate distances and polar plate numbers, so as to realize the synergistic effect of demulsification, flocculation and air floatation separation in the electrochemical treatment.

[0017] In the above method, preferably, each group of modules arranged horizontally in the cascade electrocoagulation device is individually controlled by its own power supply, and the total current (in A) of all horizontally arranged modules / the wastewater flow rate entering the cascade electrocoagulation device (in m³) is... 3 / h) is 6~8A / m 3 / h, more preferably 7 to 7.5 A / m 3 The invention limits the total current (in A) of each horizontally arranged group of modules to the wastewater flow rate (in m³) entering the cascade electrocoagulation device. 3 The ratio of total current to flow rate is 6-8 A / m³. 3 / h (more preferably 7 to 7.5 A / m) 3 The current (in A) of the horizontally arranged single modules in the cascade electrocoagulation device is approximately equal to the wastewater flow rate (in m³ / h) entering the single module. This allows the cascade electrocoagulation device of the present invention to more fully exert its synergistic effects of demulsification, flocculation, and air flotation separation. 3 / h) can be 2~3A / m 3 / h. The current / flow ratio of a single module is set within the above range depending on the number of modules connected in series.

[0018] In the above method, preferably, a screen can be provided between the longitudinally arranged multiple modules in the cascade electrocoagulation device. The screen acts as a support, allowing wastewater to enter from the bottom and exit from the top in the longitudinally arranged multiple modules, floating directly to the surface. The screen can maintain a channel for the wastewater to float upwards. The screen can include cement screens, concrete screens, etc.

[0019] In the above method, preferably, when the cascade electrocoagulation device includes 2 to 4 groups of modules arranged longitudinally, the electric field strength of each group of modules is 30 to 50 V / m, and the electrode-to-water ratio is 1.5 to 2.5 L / dm. 2 .

[0020] In the above method, preferably, the electrodes of each longitudinally arranged module in the cascade electrocoagulation device are soluble electrodes (e.g., iron electrodes, aluminum electrodes, etc.) and / or stainless steel electrodes, with a spacing of 1.5–4 cm between every two electrodes, and 15–30 electrodes per module. More preferably, the 15–30 electrodes of each module are divided into several groups, with 3–5 electrodes per group. The two electrodes at both ends of each group are connected to the power supply electrode, while the middle electrode serves as an induction electrode and is not connected to the power supply electrode. Furthermore, each pair of adjacent groups shares the electrode connected to the power supply electrode. Those skilled in the art should understand that when the 15–30 electrodes of each module are divided into several groups, except for the two electrodes at both ends of the module which serve only as cathodes or anodes, the other electrodes connected to the power supply are all used with one side as an anode and the other side as a cathode. The cascade electrocoagulation device of the present invention can also adopt multiple sets of modules arranged longitudinally. Different induced electric field intensities can be presented through different electrode spacing and number of electrodes, so as to realize the synergistic effect of demulsification, flocculation and air flotation separation in electrochemical treatment. Furthermore, the wastewater enters from the bottom and exits from the top through the multiple sets of modules arranged longitudinally, and the air flotation effect reduces resistance and accelerates separation, resulting in higher efficiency.

[0021] In the above method, preferably, each group of modules arranged longitudinally in the cascade electrocoagulation device is individually controlled by its own power supply, and the total current (in A) of all longitudinally arranged modules / the wastewater flow rate entering the cascade electrocoagulation device (in m³) 3 / h) is 6~10A / m 3 / h, more preferably 7.5 to 8.5 A / m 3 Approximately / h. This invention limits the total current (in A) of each longitudinally arranged group of modules to the wastewater flow rate (in m³) entering the cascade electrocoagulation device. 3 The ratio of total current to flow rate is 6-10 A / m. 3 / h (more preferably 7.5 to 8.5 A / m) 3 The current (in A) of the longitudinally arranged single modules in the cascade electrocoagulation device is approximately equal to the wastewater flow rate (in m³ / h) entering the single module. This allows the cascade electrocoagulation device of the present invention to more fully exert its synergistic effect of demulsification, flocculation, and air flotation separation. 3 / h) can be 2~4A / m 3 / h. The current / flow ratio of a single module is set within the above range depending on the number of modules connected in series.

[0022] In the above method, preferably, the wastewater flow rate entering the cascade electrocoagulation device is 4-70 m³ / h. 3 / h, more preferably 10-70m 3 / h.

[0023] According to a specific embodiment of the present invention, preferably, the above method further includes the following steps: using a computer system to control and display the online flow rate, online current, and voltage of the cascade electrocoagulation device; and calculating the total current (in A) of each group of modules / the wastewater flow rate (in m³) entering the cascade electrocoagulation device. 3 The ratio of current (A) to wastewater flow rate (m³ / h) entering a single module, and the ratio of current (A) to wastewater flow rate entering a single module. 3 The ratio of / h) is used to adjust the total current and the current of each module according to the changes in the wastewater flow rate entering the cascade electrocoagulation device. This invention uses a computer system (i.e., a PLC control system) to control the cascade electrocoagulation device, which can more efficiently control the current, voltage, and wastewater flow rate of the cascade electrocoagulation device and make real-time adjustments. This has the advantages of energy saving and reduced consumption, and can ensure the long-term stable operation of the equipment.

[0024] This invention uses a cascade electrocoagulation device to electrochemically treat wastewater, which can further remove small-scale oily emulsions, particulate matter and other substances. The dissolved organic matter in the wastewater is then treated with biological activated carbon.

[0025] In the above method, preferably, the biological activated carbon treatment is carried out using a biological activated carbon reactor. The residence time of the wastewater after electrochemical treatment in the biological activated carbon reactor is 30 to 60 minutes. The wastewater after biological activated carbon treatment can be directly discharged into a conventional integrated sewage treatment system in the field.

[0026] In the above method, preferably, the oil removal rate of the wastewater treated by the oil-containing emulsified wastewater treatment method is 90%–99.7%, the COD removal rate is 85%–98%, and the SS removal rate is 85%–99%. More preferably, the oil removal rate of the wastewater treated by the oil-containing emulsified wastewater treatment method is 96%–99.7%, the COD removal rate is 90%–98%, and the SS removal rate is 95%–99%.

[0027] This invention provides a method for treating oily emulsified wastewater. First, a micro-aeration three-phase separator is used to treat the wastewater, effectively removing a significant proportion of petroleum substances and COD. Higher influent organic load and longer retention time result in higher removal rates. Furthermore, this invention adds an organic electrolyte before the micro-aeration three-phase separation treatment, which shortens the retention time and improves pollutant removal efficiency. Then, electrochemical treatment is employed, utilizing a cascade electrocoagulation device with horizontally arranged baffled series modular units or vertically arranged bottom-influent-top-effluent series modular units. This reduces the adhesion of oily scum to the electrode surface and enhances the synergistic effect of demulsification, flocculation, and flotation separation, shortening the retention time and improving demulsification and oil removal efficiency. Simultaneously, automatic control is achieved through a current-flow relationship model, ensuring good effluent quality, reducing treatment costs, significantly saving labor costs, and lowering the failure rate. While the efficiency of the dissolved electrode used in this invention is higher than that of stainless steel electrodes, its removal of dissolved organic matter is limited, and the COD in the wastewater after electrochemical treatment remains high. Therefore, the present invention also incorporates biological activated carbon treatment after electrochemical treatment, which can significantly remove COD and retain substances such as colloidal matter and particulate matter from crude oil. Wastewater treated by the biological activated carbon of the present invention can be directly discharged into the integrated sewage treatment system.

[0028] A second aspect of the present invention provides a treatment device for oily emulsified wastewater, which is used to implement the above-mentioned treatment method for oily emulsified wastewater, comprising: a micro-aeration three-phase separator, an electrochemical device, and an activated carbon device; the oily emulsified wastewater is transported via a pipeline connected to the inlet of the micro-aeration three-phase separator, the outlet of the micro-aeration three-phase separator is connected via a pipeline to the inlet of the electrochemical device, and the outlet of the electrochemical device is connected via a pipeline to the inlet of the activated carbon device.

[0029] The electrochemical device is a cascade electrocoagulation device; the cascade electrocoagulation device includes multiple groups of modules arranged horizontally, and each group of modules is provided with a partition to form a series connection of baffles between the multiple groups of modules; or the cascade electrocoagulation device includes multiple groups of modules arranged vertically.

[0030] In the above-mentioned equipment, preferably, the cascade electrocoagulation device includes 2 to 4 groups of modules arranged horizontally or 2 to 4 groups of modules arranged vertically.

[0031] In the aforementioned equipment, preferably, when the cascade electrocoagulation device comprises 2 to 4 groups of modules arranged horizontally, the electric field strength of each group of modules is 30 to 50 V / m, and the electrode-to-water ratio is 2 to 3 L / dm. 2 .

[0032] In the aforementioned equipment, preferably, the electrodes of each group of modules arranged horizontally in the cascade electrocoagulation device are soluble electrodes (e.g., iron electrodes, aluminum electrodes, etc.) and / or stainless steel electrodes, with a spacing of 2-4 cm between every two electrodes, and 15-30 electrodes per group. More preferably, the 15-30 electrodes of each group are divided into several subgroups, with 3-5 electrodes per subgroup. The two electrodes at both ends of each subgroup are connected to the power supply electrode, while the middle electrode serves as an induction electrode and is not connected to the power supply electrode. Furthermore, each pair of adjacent subgroups shares the electrode connected to the power supply electrode. Those skilled in the art should understand that when the 15-30 electrodes of each group are divided into several subgroups, except for the two electrodes at both ends of the module which serve only as cathodes or anodes, the other electrodes connected to the power supply are all used with one side as an anode and the other side as a cathode.

[0033] In the aforementioned equipment, preferably, each group of modules arranged horizontally in the cascade electrocoagulation device is individually controlled by its own power supply, and the total current (in A) of all horizontally arranged modules / the wastewater flow rate entering the cascade electrocoagulation device (in m³) is... 3 / h) is 6~8A / m 3 / h, more preferably 7 to 7.5 A / m 3 / h or so.

[0034] In the aforementioned equipment, preferably, the current / wastewater flow rate entering the horizontally arranged single-unit modules in the cascade electrocoagulation device is 2-3 A / m³. 3 / h.

[0035] In the above-mentioned equipment, preferably, a grid is provided between the longitudinally arranged multiple groups of modules in the stepped electrocoagulation device.

[0036] In the aforementioned equipment, preferably, when the cascade electrocoagulation device comprises 2 to 4 groups of modules arranged longitudinally, the electric field strength of each group of modules is 30 to 50 V / m, and the electrode-to-water ratio is 1.5 to 2.5 L / dm. 2 .

[0037] In the aforementioned equipment, preferably, the electrodes of each longitudinally arranged module in the cascade electrocoagulation device are soluble electrodes (e.g., iron electrodes, aluminum electrodes, etc.) and / or stainless steel electrodes, with a spacing of 2-4 cm between every two electrodes, and 15-30 electrodes per module. More preferably, the 15-30 electrodes of each module are divided into several groups, with 3-5 electrodes per group. The two electrodes at both ends of each group are connected to the power supply electrode, while the middle electrode serves as an induction electrode and is not connected to the power supply electrode. Furthermore, each pair of adjacent groups shares the electrode connected to the power supply electrode. Those skilled in the art should understand that when the 15-30 electrodes of each module are divided into several groups, except for the two electrodes at both ends of the module which serve only as cathodes or anodes, the other electrodes connected to the power supply are all used with one side as an anode and the other side as a cathode.

[0038] In the aforementioned equipment, preferably, each group of modules arranged longitudinally in the cascade electrocoagulation device is individually controlled by its own power supply, and the total current (in A) of all longitudinally arranged modules / the wastewater flow rate entering the cascade electrocoagulation device (in m³) is... 3 / h) is 6~10A / m 3 / h, more preferably 7.5 to 8.5 A / m 3 / h or so.

[0039] In the aforementioned equipment, preferably, the current / wastewater flow rate entering the single module of the longitudinally arranged single module in the cascade electrocoagulation device is 2-4 A / m³. 3 / h.

[0040] According to a specific embodiment of the present invention, preferably, the above-mentioned device further includes: a computer system for controlling and displaying the online flow rate, online current, and voltage of the cascade electrocoagulation device; and calculating the total current (in A) of each group of modules / the wastewater flow rate (in m³) entering the cascade electrocoagulation device. 3 The ratio of current (A) to wastewater flow rate (m³ / h) entering a single module, and the ratio of current (A) to wastewater flow rate entering a single module. 3 The ratio of / h) is used to adjust the total current of each module and the current of each module according to the changes in the wastewater flow rate entering the cascade electrocoagulation device.

[0041] In the above-mentioned equipment, preferably, the activated carbon device is a biological activated carbon reactor.

[0042] According to a specific embodiment of the present invention, the above-mentioned equipment also includes some necessary conventional equipment such as pumps. The present invention does not impose any special limitations on this, and those skilled in the art can install booster pumps or the like on certain delivery pipelines according to actual conditions.

[0043] In summary, the method and equipment for treating oily emulsified wastewater provided by this invention, targeting the pollution characteristics of oily and polymer-containing wastewater, improves the demulsification efficiency of oily and polymer-containing wastewater by optimizing the structure of the electrochemical device, combining micro-aeration three-phase separation treatment, biological activated carbon treatment, and enhancing the level of automation. This helps to resist fluctuations and shocks in pollution load, reduce operating costs, and thus ensure the stable and efficient operation of the wastewater treatment system, supporting the pollution reduction, carbon reduction, and sustainable development of petroleum and petrochemical enterprises. Attached Figure Description

[0044] Figure 1 This is a structural diagram of the equipment for treating oily emulsified wastewater provided in Example 1;

[0045] Explanation of main component symbols: 1-Micro-aeration three-phase separator, 2-Step electrocoagulation device, 3-Biological activated carbon reactor, 4-Boost pump.

[0046] Figure 2 This is a structural diagram of the cascade electrocoagulation device provided in Example 1.

[0047] Figure 3 This graph shows the relationship between the total current of the cascade electrocoagulation device and the wastewater flow rate when the oily emulsified wastewater contains different COD contents.

[0048] Figure 4 This is a structural diagram of the cascade electrocoagulation device provided in Example 12. Detailed Implementation

[0049] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0050] Example 1

[0051] This embodiment provides a treatment device for oily emulsified wastewater, such as... Figure 1 As shown, it includes: a micro-aeration three-phase separator 1, a cascade electrocoagulation device 2, a biological activated carbon reactor 3, and a booster pump 4; the pipeline for conveying the oily emulsified wastewater is connected to the inlet of the micro-aeration three-phase separator 1 via the booster pump 4, the outlet of the micro-aeration three-phase separator 1 is connected to the inlet of the cascade electrocoagulation device 2 via a pipeline, and the outlet of the cascade electrocoagulation device 2 is connected to the inlet of the biological activated carbon reactor 3 via a pipeline.

[0052] Among them, such as Figure 2 As shown, the cascade electrocoagulation device 2 includes three groups of modules arranged horizontally, and each group of modules is provided with a partition to form a series connection of baffles between the three groups of modules;

[0053] The electric field strengths of the three modules are 40V / m, 30V / m, and 25V / m, respectively, and the electrode-to-water ratios are 2.5L / dm. 2 ;

[0054] In the cascade electrocoagulation device 2, each module has stainless steel electrodes, and the spacing between the electrodes in the three series-connected modules is 3 cm. The first module has 25 electrodes, which are divided into 6 groups of 5 electrodes each. The two electrodes at the ends of each group are connected to the power electrode, while the three middle electrodes serve as induction electrodes and are not connected to the power electrode. Each pair of adjacent groups shares the electrodes connected to the power electrode (there are 5 shared electrodes in 6 groups). The second module has 25 electrodes, which are divided into 8 groups of 4 electrodes each. The first group has 4 plates, with the two end plates connected to the power supply electrode and the two middle plates acting as induction electrodes without being connected to the power supply electrode. Each pair of adjacent groups shares the plate connected to the power supply electrode (7 shared electrodes in 8 groups). The third group has 25 plates, which are divided into 12 groups of 3 plates each. In each group, the two end plates are connected to the power supply electrode and the middle plate acts as an induction electrode without being connected to the power supply electrode. Each pair of adjacent groups shares the plate connected to the power supply electrode (11 shared electrodes in 12 groups).

[0055] Each module in the cascade electrocoagulation device 2 is controlled independently by its own power supply, and the currents of the three modules are set to 8A, 10A and 12A respectively.

[0056] The oily emulsified wastewater treatment equipment in this embodiment further includes: a computer system, which is used to control and display the online flow rate, online current, and voltage of the cascade electrocoagulation device; and to calculate the total current (in A) of each group of modules / the wastewater flow rate (in m³) entering the cascade electrocoagulation device. 3 The ratio of current (A) to wastewater flow rate (m³ / h) entering a single module, and the ratio of current (A) to wastewater flow rate entering a single module. 3 The ratio of / h) is used to adjust the total current of each module and the current of each module according to the changes in the wastewater flow rate entering the cascade electrocoagulation device.

[0057] Example 2

[0058] This embodiment provides a method for treating oily emulsified wastewater, which uses the treatment equipment for oily emulsified wastewater provided in Embodiment 1. The oily emulsified wastewater treated in this embodiment has a petroleum content of 633 mg / L, a COD content of 5392 mg / L, and a SS content of 1196 mg / L.

[0059] The processing method includes the following steps:

[0060] Before performing micro-aeration three-phase separation treatment on the oily emulsified wastewater, an organic electrolyte is added to the pipeline for transporting the oily emulsified wastewater; the organic electrolyte includes dimethyl diallyl ammonium chloride or sodium oleate, and the amount added is 100 mg / L based on the volume of the oily emulsified wastewater.

[0061] Then, the oily emulsified wastewater is pumped by a booster pump 4 into a micro-aeration three-phase separator 1 for treatment. The residence time of the oily emulsified wastewater in the micro-aeration three-phase separator 1 is 20 minutes. The separated wastewater enters the stepped electrocoagulation device 2. The separated oily scum is concentrated in the middle cylinder of the micro-aeration three-phase separator 1 for 3 days and then collected. After treatment by the micro-aeration three-phase separator 1, the COD in the oily scum is concentrated by 1000 times, reaching a proportion of 2.6%. The oily scum after treatment by the micro-aeration three-phase separator 1 can be collected and processed for resource utilization through a coking unit, or it can be directly used for sludge dewatering.

[0062] Then the wastewater obtained after being treated by the micro-aeration three-phase separator 1 is fed into the cascade electrocoagulation device 2 for electrochemical treatment. The wastewater enters from the bottom and exits from the top in all three modules of the cascade electrocoagulation device 2, and the wastewater stays in the cascade electrocoagulation device 2 for 30 minutes.

[0063] The electric field strengths of the three modules are 40V / m, 30V / m, and 25V / m, respectively, and the electrode-to-water ratios are 2.5L / dm. 2 ;

[0064] Each module in the cascade electrocoagulation device 2 is individually controlled by its own power supply. The current settings for the three modules are 8A, 10A, and 12A, respectively. The wastewater flow rate in the cascade electrocoagulation device 2 is 4m³. 3 / h, and the total current of each module (unit A) / the wastewater flow rate entering the cascade electrocoagulation device (unit m³) 3 / h) is 7.5; the current (unit A) of a single module in the cascade electrocoagulation device 2 / the wastewater flow rate entering the single module (unit m) 3 The values ​​for ( / h) are 2, 2.5, and 3 respectively;

[0065] Furthermore, a computer system is used to control and display the online flow rate, online current, and voltage of the cascade electrocoagulation device; and to calculate the total current (in A) of each module group / the wastewater flow rate (in m³) entering the cascade electrocoagulation device. 3 The ratio of current (A) to wastewater flow rate (m³ / h) entering a single module, and the ratio of current (A) to wastewater flow rate entering a single module. 3 The ratio of / h) is used to adjust the total current of each module and the current of a single module according to the changes in the wastewater flow rate entering the cascade electrocoagulation device.

[0066] At this point, the removal rate of petroleum in the wastewater is ≥91%, the removal rate of COD is over 82%, the removal rate of SS is 90%, and the total operating cost is approximately RMB 2.0 per ton of water.

[0067] The wastewater treated by the cascade electrocoagulation device 2 is then fed into the biological activated carbon reactor 3 for further treatment. The residence time of the wastewater in the biological activated carbon reactor is 60 minutes. The wastewater treated by the biological activated carbon can be directly discharged into a conventional integrated wastewater treatment system in this field.

[0068] The oil-containing emulsified wastewater treated by the method described in this embodiment has a petroleum removal rate of 99%, a COD removal rate of 90%, and a SS removal rate of 95%.

[0069] In addition, this embodiment studies the relationship between the total current of the cascade electrocoagulation device for electrochemical treatment and the wastewater flow rate.

[0070] Based on the treatment capacity (i.e., wastewater flow rate) of 5m³ 3 The experimental data were analyzed using a per-hour rate to further investigate the relationship between current (A) and flow rate (B). The experimental data revealed that when wastewater COD ≤ 5000 mg / L, the contribution rate of the cascade electrocoagulation device to COD removal was ≥ 85%; when 5000 mg / L ≤ wastewater COD ≤ 10000 mg / L, the average contribution rate was approximately 45%; and when wastewater COD ≥ 10000 mg / L, the average contribution rate was 10%.

[0071] Regression analysis of the response values ​​was performed using Design-Expert, and the fitted regression equation was as follows: COD removal contribution rate = 20.56258 + 1.59825 × current + 36.30587 × flow rate - 9.08976E-003 × wastewater COD - 0.31845 × current × flow rate + 8.81891E-005 × current × wastewater COD - 7.51835E-004 × flow rate × wastewater COD - 0.021722 × current² - 0.22615 × flow rate² + 1.14950E-007 × electro-desalination wastewater COD 2 The relationship between the total current and wastewater flow rate of the cascade electrocoagulation device under different COD content conditions was analyzed.

[0072] ① For wastewater with COD ≤ 5000 mg / L, the contribution rate of the cascade electrocoagulation device to COD removal is 85%;

[0073] 22.82=2.04A+32.55B-0.32AB-0.021722A 2 -0.23B 2

[0074] That is, when B is 10-70m 3 When / h, A = 24.1 + 6.69B

[0075] ② For wastewater COD ≤ 5000mg / L ≤ 10000mg / L, the contribution rate of the cascade electrocoagulation device to COD removal is 45%;

[0076] 45.23=2.31A+30.3B-0.32AB-0.021722A 2 -0.23B 2

[0077] That is, when B is 10-70m 3 When / h, A = 15.68 + 6.65B

[0078] ③ For wastewater with COD ≥ 10000 mg / L, the contribution rate of the cascade electrocoagulation device to COD removal is 10%;

[0079] 71.99=2.66A+27.29B-0.32AB-0.021722A 2 -0.23B 2

[0080] That is, when B is 10-70m 3 When / h, A = 4.247 + 6.62B

[0081] The relationship between the total current and wastewater flow rate of a cascade electrocoagulation device under different influent COD conditions was obtained using the assignment method, such as... Figure 3 As shown in the figure. It can be seen that when the processing capacity is expanded to 10–70 m³ / s... 3 At a rate of / h, the basic A / B ratio can be controlled to around 7 to 7.5, which enables the cascade electrocoagulation device of this invention to more fully exert its synergistic effects of demulsification, flocculation, and air flotation separation.

[0082] Comparative Example 1, Example 3, Example 4, Example 5

[0083] Comparative Examples 1, 3, 4, and 5 each provide a method for treating oily emulsified wastewater. These methods treat oily emulsified wastewater with a petroleum content of 4000 mg / L, a COD content of 15000 mg / L, and a SS content of 2500 mg / L. These methods are essentially the same as the treatment method in Example 2. The differences lie in whether or not an organic electrolyte is added, the amount of organic electrolyte added, the type of electrodes used in the cascade electrocoagulation device 2, the average electric field strength (i.e., the average electric field strength of the three modules), and the treatment time. The specific parameters for these differences, as well as the petroleum content, COD content, and SS content of the treated wastewater, are shown in Table 1.

[0084] Table 1

[0085]

[0086]

[0087] Comparative Example 2, Example 6, Example 7, Example 8

[0088] Comparative Examples 2, 6, 7, and 8 each provide a method for treating oily emulsified wastewater. These methods treat oily emulsified wastewater with a petroleum content of 1000 mg / L, a COD content of 5000 mg / L, and a SS content of 900 mg / L. These methods are essentially the same as the treatment method in Example 2. The differences lie in whether or not an organic electrolyte is added, the amount of organic electrolyte added, the type of electrodes used in the cascade electrocoagulation device 2, the electric field strength, and the treatment time. The specific parameters for these differences, as well as the petroleum content, COD content, and SS content of the treated wastewater, are shown in Table 2.

[0089] Table 2

[0090]

[0091] Comparative Example 3, Example 9, Example 10, Example 11

[0092] Comparative Examples 3, 9, 10, and 11 each provide a method for treating oily emulsified wastewater. These methods treat oily emulsified wastewater with a petroleum content of 200 mg / L, a COD content of 1500 mg / L, and a SS content of 300 mg / L. These methods are essentially the same as the treatment method in Example 2. The differences lie in whether or not an organic electrolyte is added, the amount of organic electrolyte added, the type of electrodes used in the cascade electrocoagulation device 2, the electric field strength, and the treatment time. The specific parameters for these differences, as well as the petroleum content, COD content, and SS content of the treated wastewater, are shown in Table 3.

[0093] Table 3

[0094]

[0095] Example 12

[0096] This embodiment provides a treatment device for oily emulsified wastewater, which differs from the cascade electrocoagulation device in the device of Embodiment 1, but is otherwise the same. The structural diagram of the cascade electrocoagulation device in this embodiment is shown below. Figure 4 As shown.

[0097] The cascade electrocoagulation device includes three sets of modules arranged longitudinally, with a grid between the three sets of modules;

[0098] The electric field strengths of the three modules are 50V / m, 45V / m, and 40V / m, respectively, and the electrode-to-water ratios are 1.8L / dm. 2 ;

[0099] Each module in the cascade electrocoagulation device has 25 electrodes, and the distance between the electrodes in all three modules is 3 cm. The first module has 25 electrodes, which are divided into 6 groups of 5 electrodes each. The two electrodes at the ends of each group are connected to the power electrode, while the three middle electrodes serve as induction electrodes and are not connected to the power electrode. Each pair of adjacent groups shares the electrodes connected to the power electrode (there are 5 shared electrodes in 6 groups). The second module has 25 electrodes, which are divided into 8 groups of 4 electrodes each. The first group of electrodes consists of two electrodes at each end connected to the power supply electrode, and two electrodes in the middle serving as induction electrodes that are not connected to the power supply electrode. Each pair of adjacent groups shares the electrode connected to the power supply electrode (there are 7 shared electrodes in 8 groups). The third group of modules consists of 25 electrodes, which are divided into 12 groups of 3 electrodes each. In each group of 3 electrodes, the two electrodes at each end are connected to the power supply electrode, and one electrode in the middle serves as an induction electrode that is not connected to the power supply electrode. Each pair of adjacent groups shares the electrode connected to the power supply electrode (there are 11 shared electrodes in 12 groups).

[0100] Each module in the cascade electrocoagulation device is controlled independently by its own power supply, and the current settings for the three modules are 9.5A, 11A, and 13A, respectively.

[0101] This embodiment also provides a method for treating oily emulsified wastewater, which uses the oily emulsified wastewater treatment equipment provided in this embodiment. The oily emulsified wastewater treated in this embodiment has a petroleum content of 633 mg / L, a COD content of 5392 mg / L, and a SS content of 1196 mg / L.

[0102] The treatment method includes steps that are basically the same as in Example 2, except that: the wastewater enters from the bottom and exits from the top in three longitudinally arranged modules of the cascade electrocoagulation device; each module in the cascade electrocoagulation device is individually controlled by its own power supply; the current settings for the three modules are 9.5A, 11A, and 13A, respectively; and the wastewater flow rate in the cascade electrocoagulation device is 4m³. 3 / h, and the total current of each module (unit A) / the wastewater flow rate entering the cascade electrocoagulation device (unit m³) 3 / h) is 8.375A / m 3 / h; Current (in A) of a single module in the cascade electrocoagulation device / Wastewater flow rate entering the single module (in m³ / h) 3 / h) are 2.375A / m 3 / h, 2.75A / m 3 / h and 3.25A / m 3 / h. At this time, the removal rate of petroleum in the wastewater is ≥91.5%, the removal rate of COD is over 83%, the removal rate of SS is 92%, and the total operating cost is about 2.3 yuan / ton of water.

[0103] The wastewater, after being treated by the cascade electrocoagulation device, is then treated in a biological activated carbon reactor. The residence time of the wastewater in the biological activated carbon reactor is 60 minutes. The wastewater treated by the biological activated carbon can be directly discharged into a conventional integrated wastewater treatment system in this field.

[0104] The oil-containing emulsified wastewater treated by the method described in this embodiment has a petroleum removal rate of 99%, a COD removal rate of 92%, and a SS removal rate of 95%.

Claims

1. A method for treating oily emulsified wastewater, comprising the following steps: The oily emulsified wastewater is first treated by micro-aeration three-phase separation, then the wastewater obtained after treatment is electrochemically treated, and then treated by biological activated carbon to obtain the treated wastewater. Before the oily emulsified wastewater undergoes micro-aeration three-phase separation treatment, an organic electrolyte is added to the oily emulsified wastewater; the organic electrolyte is an oleate-based organic compound, and its addition amount is 10~100 mg / L based on the volume of the oily emulsified wastewater. The electrochemical treatment employs a cascade electrocoagulation device; the cascade electrocoagulation device comprises multiple horizontally arranged modules, with partitions between each horizontally arranged module to form a series connection of baffles; or the cascade electrocoagulation device comprises multiple vertically arranged modules, with wastewater entering from the bottom and exiting from the top in the vertically arranged modules; each horizontally arranged module in the cascade electrocoagulation device is individually controlled by its own power supply, and the total current of all horizontally arranged modules / wastewater flow rate entering the cascade electrocoagulation device is 7~7.5A / m³. 3 / h, the current of the horizontally arranged single module in the cascade electrocoagulation device / the wastewater flow rate entering the single module is 2~3A / m 3 / h; Each group of modules arranged longitudinally in the cascade electrocoagulation device is individually controlled by its own power supply, and the total current of all the longitudinally arranged modules / the wastewater flow rate entering the cascade electrocoagulation device is 7.5~8.5A / m. 3 / h, the current of the longitudinally arranged single module in the cascade electrocoagulation device / the wastewater flow rate entering the single module is 2~4A / m 3 / h; A computer system is used to control and display the online flow rate, online current, and voltage of the cascade electrocoagulation device; and to calculate the ratio of the total current of each group of modules to the wastewater flow rate entering the cascade electrocoagulation device, as well as the ratio of the current of a single group of modules to the wastewater flow rate entering that single group of modules, so as to adjust the total current of each group of modules and the current of a single group of modules according to the changes in the wastewater flow rate entering the cascade electrocoagulation device.

2. The method for treating oily emulsified wastewater according to claim 1, wherein, The oily emulsified wastewater contains petroleum hydrocarbons at a concentration of 200-4000 mg / L, COD at a concentration of 1000-15000 mg / L, SS at a concentration of 500-6000 mg / L, and electrical conductivity at a concentration of 600-2000 μS / cm.

3. The method for treating oily emulsified wastewater according to claim 1, wherein, The amount of organic electrolyte added is 50~100 mg / L.

4. The method for treating oily emulsified wastewater according to claim 1, wherein, The micro-aeration three-phase separation treatment is carried out using a micro-aeration three-phase separator. The residence time of the oily emulsified wastewater in the micro-aeration three-phase separator is 10-30 minutes. The separated wastewater enters the stepped electrocoagulation device. The separated oily scum is concentrated in the middle cylinder of the micro-aeration three-phase separator for 1-5 days and then collected.

5. The method for treating oily emulsified wastewater according to claim 4, wherein, After the aforementioned micro-aeration three-phase separation treatment, the organic pollutants in the oily scum are concentrated to 500-2000 times.

6. The method for treating oily emulsified wastewater according to claim 1, wherein, The wastewater after micro-aeration three-phase separation treatment stays in the cascade electrocoagulation device for 10~30 minutes.

7. The method for treating oily emulsified wastewater according to claim 1, wherein, The cascade electrocoagulation device includes 2 to 4 groups of modules arranged horizontally or 2 to 4 groups of modules arranged vertically.

8. The method for treating oily emulsified wastewater according to claim 7, wherein, When the cascade electrocoagulation device comprises 2 to 4 groups of modules arranged horizontally, the electric field strength of each group of modules is 30 to 50 V / m, and the electrode-to-water ratio is 2 to 3 L / dm. 2 .

9. The method for treating oily emulsified wastewater according to claim 1, wherein, In the stepped electrocoagulation device, the electrodes of each group of modules arranged horizontally are soluble electrodes and / or stainless steel electrodes, with a spacing of 2-4 cm between every two electrodes, and the number of electrodes in each group of modules is 15-30.

10. The method for treating oily emulsified wastewater according to claim 7, wherein, When the cascade electrocoagulation device comprises 2 to 4 groups of modules arranged longitudinally, the electric field strength of each group of modules is 30 to 50 V / m, and the electrode-to-water ratio is 1.5 to 2.5 L / dm. 2 .

11. The method for treating oily emulsified wastewater according to claim 1, wherein, In the cascade electrocoagulation device, the electrodes of each group of modules arranged longitudinally are soluble electrodes and / or stainless steel electrodes, with a spacing of 1.5 to 4 cm between every two electrodes, and the number of electrodes in each group of modules is 15 to 30.

12. The method for treating oily emulsified wastewater according to claim 1, wherein, The biological activated carbon treatment is carried out using a biological activated carbon reactor. The wastewater that has undergone electrochemical treatment has a residence time of 30 to 60 minutes in the biological activated carbon reactor. The wastewater after biological activated carbon treatment is then discharged into a conventional integrated sewage treatment system.

13. The method for treating oily emulsified wastewater according to claim 1, wherein, The oil-containing emulsified wastewater treated by the aforementioned method has a petroleum removal rate of 90-99.7%, a COD removal rate of 85-98%, and a SS removal rate of 85-99%.

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