Method for treating high-oil-content and high-COD (Chemical Oxygen Demand) wastewater through microwave-induced catalytic oxidation

Abstract

The invention belongs to the technical field of industrial water treatment, and particularly relates to a method for treating high-oil-content and high-COD (Chemical Oxygen Demand) wastewater through microwave-induced catalytic oxidation. The method comprises the following steps: demulsifying desulfurized wastewater by using a demulsifier, removing oil by air flotation, adjusting the pH value to be alkaline, fully mixing with a reaction agent, performing microwave-induced catalytic oxidation, performing heat exchange, and performing coagulating sedimentation treatment in sequence, thereby completing the storage of produced water, the reaction agent comprises a microwave reaction carrier, a microwave reaction catalyst and a microwave reaction auxiliary catalyst. The microwave reaction carrier is charcoal powder and / or activated carbon powder; the microwave reaction catalyst is calcium aluminum silicate; the microwave reaction auxiliary catalyst is medical stone powder. Compared with the prior art, the method has the advantages that the recovery rate of the high-oil-content and high-COD wastewater can be effectively increased, the microwave utilization efficiency is high, the effluent quality is stable, the process automation degree is high, the operation is convenient, and the real zero emission of the gas field produced water can be realized.

Description

Technical Field

[0001] This invention belongs to the field of industrial water treatment technology, specifically relating to a method for microwave-induced catalytic oxidation treatment of wastewater with high oil content and high COD. Background Technology

[0002] With the large-scale development of complex mountainous high-sulfur gas fields such as the high-sulfur gas field in northeastern Sichuan, wet gas gathering and transportation technology has become the mainstream due to its economic advantages. However, the wastewater generated by the batch processing of gas field gathering and transportation pipelines has an extremely complex composition, rich in pollutants such as waste engine oil, oil-based corrosion inhibitor residues, and elemental sulfur. It exhibits the characteristics of high oil content, high COD, high viscosity, and high pollutant load, which are difficult to degrade, posing a severe challenge to the targeted nature and deep purification capabilities of the treatment process.

[0003] The current gas field's "batch treatment wastewater mixed with gas field water for treatment and then reinjected" model and "demulsification + coagulation sedimentation + filtration" process system have significant compatibility defects for this type of specific wastewater and can no longer meet production and environmental protection requirements. The mixed treatment model is inherently incompatible: the batch treatment wastewater from gathering and transmission pipelines differs greatly in quality from the gas field water. The former is mainly composed of recalcitrant oils and corrosion inhibitor residues, and its high viscosity exacerbates the separation difficulty; the latter is mainly composed of dissolved salts. When the two are mixed, they interfere with each other's treatment targets, making it difficult for existing processes to achieve targeted removal of high-oil-content and high-COD components. At the same time, mixed treatment is limited by equipment capacity, resulting in a low processing volume that cannot match the cyclical wastewater generation of batch treatment operations, easily leading to the accumulation and deterioration of high-viscosity wastewater.

[0004] Conventional processes are insufficient in their treatment efficiency: the "demulsification + coagulation sedimentation + filtration" process has limited efficiency in removing residual high-viscosity oil-based corrosion inhibitors and elemental sulfur, easily leading to clogging of the filter unit; it also cannot effectively degrade recalcitrant organic matter to reduce COD, nor can it deeply remove low-concentration sulfides, leaving the effluent still carrying a large amount of pollutants, failing to solve the core problem of "high oil content and high COD" in this type of wastewater. Furthermore, conventional processes have poor adaptability to water quality fluctuations in this type of wastewater, making it difficult to guarantee the stability of the effluent quality.

[0005] Reinjection causes serious formation damage: Due to the high oil content and high viscosity of this type of wastewater, pollutants that remain after existing treatment processes are easily deposited and adsorbed in formation pores, leading to decreased formation permeability, increased blockage, increased reinjection pressure, and a gradual decline in reinjection capacity. This not only increases operating load and energy consumption but may also affect gas field production release and even cause irreversible formation damage.

[0006] Environmental and safety risks are prominent: After the upgrading of national environmental protection regulations, it is difficult for existing processes to consistently meet the standards for COD, oil content and other indicators of the effluent, and face the risk of production shutdown for rectification and penalties; at the same time, the high content of sulfides in the wastewater can easily release toxic gases, and the accumulation and leakage of high viscosity wastewater can easily cause soil and groundwater pollution. In addition, the low degree of automation of the process and the high risk of human intervention make it difficult to adapt to the green and safe development needs of gas fields.

[0007] Patent CN104291505A discloses a method for treating oily wastewater discharge using microwave-enhanced iron-carbon combined microwave catalytic oxidation, comprising the following steps: 1) pretreatment of activated carbon and iron filings using a pretreatment process; 2) treatment of the oily wastewater using microwave-enhanced iron-carbon micro-electrolysis reaction; 3) the oily wastewater after microwave-enhanced iron-carbon treatment entering a chemical separation system; 4) the wastewater after the chemical separation system entering the microwave catalytic oxidation process; 5) treatment of the effluent meeting discharge standards. This process uses microwave catalytic oxidation to treat oily wastewater at the end of the traditional "microwave-enhanced iron-carbon pretreatment + flocculation and chemical dosing" treatment method. However, in this patent, the microwave catalytic oxidation system is only used as a key process for oil removal, and COD removal mainly relies on the chemical separation system, resulting in low microwave utilization efficiency. It can only treat wastewater with a COD value of less than 2000 mg / L and an oil content of less than 200 mg / L, and cannot meet the treatment requirements for high-oil-content and high-COD wastewater.

[0008] In summary, existing technologies cannot effectively solve the problem of targeted purification of high-oil-content and high-COD wastewater generated by batch processing operations in gas field gathering and transmission pipelines. There is an urgent need to develop specialized treatment technologies that are highly targeted and have stable treatment efficiency. Summary of the Invention

[0009] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a microwave-induced catalytic oxidation method for treating wastewater with high oil content and high COD.

[0010] The objective of this invention can be achieved through the following technical solutions: A method for treating high-oil-content and high-COD wastewater by microwave-induced catalytic oxidation includes the following steps: the desulfurized wastewater is sequentially subjected to demulsification with a demulsifier, oil removal by air flotation, pH adjustment to alkaline, thorough mixing with a reaction agent, microwave-induced catalytic oxidation, heat exchange, coagulation and sedimentation treatment, and then the product water is stored. The reaction agents include a microwave reaction carrier, a microwave reaction catalyst, and a microwave reaction auxiliary catalyst.

[0011] Furthermore, the wastewater is oily, high-COD wastewater generated during the batch processing of gas field gathering and transmission pipelines.

[0012] Furthermore, the wastewater contains ≥10wt% waste engine oil, has high viscosity, ≤6mg / L sulfur content, 5~20wt% corrosion inhibitor content, ≥50000 mg / L COD value, and ≥70wt% water content.

[0013] Preferably, the wastewater contains 10-15 wt% waste engine oil and has a COD value of 50,000-80,000 mg / L.

[0014] Furthermore, the demulsifier is an anionic surfactant; The dosage of the demulsifier is 1.0~10 g / L, and the demulsification reaction time is 0.5~2.0 h.

[0015] Preferably, the demulsifier is selected from one or more of sodium dodecyl sulfonate, sodium dodecyl sulfate, and sodium dodecylbenzene sulfonate; the dosage of the demulsifier is 2.0~6.0 g / L, and the demulsification reaction time is 0.5~1.0 h.

[0016] More preferably, the demulsifier is sodium dodecylbenzenesulfonate.

[0017] Furthermore, the aforementioned air flotation oil removal is nitrogen dissolved air flotation oil removal, with the following process parameters: residence time 10~20 s, processing temperature 10~70℃, dissolved air pressure 0.3~0.4 MPa, dissolved air flow rate in the dissolved air release pipe 15~20 m / s, release flow rate at the release head 0.5~1.0 m / s, and release bubble diameter 30~50 μm.

[0018] Preferably, the processing temperature is 30~70℃.

[0019] Furthermore, the pH adjustment is achieved using Na2CO3 and / or NaOH as the adjusting agent, resulting in a wastewater pH of 9-10 after adjustment.

[0020] Preferably, the pH adjustment agent used is NaOH; the pH value of the wastewater after adjustment is 9.0~9.5.

[0021] Further, the microwave reaction carrier is charcoal powder and / or activated carbon powder, with an addition amount of 1.0~10 g / L; preferably, the microwave reaction carrier is activated carbon powder, with an addition amount of 2.0~5.0 g / L; The microwave reaction catalyst is calcium aluminum silicate, with an addition amount of 1.0~10 g / L; preferably, the addition amount is 2.0~5.0 g / L.

[0022] The microwave reaction-assisted catalyst is maifanite powder, with an addition amount of 0.5~5 g / L; preferably, the addition amount is 0.6~2.0 g / L.

[0023] The reaction time between the reagent and the wastewater is 0.5 to 2.0 h.

[0024] Preferably, the reaction time between the reagent and the wastewater is 0.5 to 1.0 h.

[0025] Furthermore, the process conditions for microwave-induced catalytic oxidation are: wastewater flow rate 150~400 L / h, microwave reaction power 2~10 kW, and reaction time 1~5 min.

[0026] Preferably, the process conditions for microwave-induced catalytic oxidation are: wastewater flow rate 200~300 L / h, microwave reaction power 5~8 kW, and reaction time 2~5 min.

[0027] Furthermore, the wastewater temperature after microwave-induced catalytic oxidation treatment is 70~90℃. Before entering the heat exchange unit, it is first introduced into an intermediate water tank to reduce the temperature of the wastewater entering the heat exchange unit to 60~80℃. At the same time, it can be used to store and regulate the water volume. After being treated by the heat exchange unit, the wastewater temperature reaches 30~50℃.

[0028] Furthermore, the coagulation and sedimentation treatment is carried out in an inclined tube sedimentation tank. In the coagulation and sedimentation treatment, the coagulant used is a mixture of any one of polyaluminum ferric sulfate, aluminum chloride, and polyaluminum chloride with polyacrylamide; preferably, the coagulant is a mixture of polyaluminum chloride and polyacrylamide; the mass ratio of the two is (20~100):1, more preferably (50~100):1; the dosage of the coagulant is 1~10 mg / L, more preferably 2~6 mg / L.

[0029] After treatment using the process of this invention, the effluent indicators at each stage are as follows: After demulsification treatment, the COD value of the wastewater is 50,000~80,000 mg / L, the oil content is 5~7.5wt%, and the pH value is 5~7. After air flotation oil removal treatment, the oil content of the wastewater is 0.1~0.4wt%; After microwave-induced catalytic oxidation treatment, the oil content of the wastewater is 150~600 mg / L; After coagulation and sedimentation treatment (i.e., the final effluent), the COD value of the wastewater is 2900~5000 mg / L, the oil content is 50~150 mg / L, and the pH value is 6~9; the corresponding COD removal rate is ≥90%, and the oil removal rate is ≥99%.

[0030] Compared with the prior art, the present invention has the following beneficial effects: (1) In response to the problem of treating high oil content (oil percentage ≥10wt%), high COD (≥50000mg / L) and high viscosity wastewater generated by gas field gathering and transmission pipelines, this invention innovatively adopts a combined process of "demulsification → air flotation oil removal → microwave-induced catalytic oxidation → coagulation sedimentation". Through the synergistic cooperation of each unit, the industry pain points such as separation difficulties and low degradation efficiency caused by high oil content and high viscosity of this type of wastewater are accurately solved, realizing the efficient treatment of high-difficulty wastewater and filling the gap in existing technology.

[0031] (2) This invention optimizes and determines the optimal addition ratio of microwave reaction carrier, microwave reaction catalyst, and microwave reaction auxiliary catalyst to form a synergistic effect mechanism of "adsorption-catalytic oxidation": Charcoal powder and / or activated carbon powder, as microwave reaction carriers, can efficiently adsorb organic pollutants in wastewater, providing sufficient adsorption capacity and reaction contact sites. The dosage should be controlled at 1.0~10 g / L. Too high a dosage will lead to increased viscosity of the reaction system and reduced microwave penetration, while too low a dosage will result in insufficient effective reaction sites and a decrease in pollutant removal rate.

[0032] By leveraging the interaction between microwaves and charcoal powder and / or activated carbon powder, and taking advantage of the rapid heating properties of charcoal powder and / or activated carbon powder under microwave irradiation, a localized high-temperature reaction environment is created within the system. Simultaneously, charcoal powder and / or activated carbon powder possess both strong reducing ability and catalytic activity, enabling them to efficiently decompose organic pollutants adsorbed within their pores or coexisting in the system.

[0033] Calcium aluminum silicate, as a microwave reaction catalyst, can form a high-temperature hot spot under microwave action, which can undergo a highly efficient catalytic oxidation reaction with the organic matter adsorbed on the microwave reaction carrier; if the amount of calcium aluminum silicate is too small, the high-temperature hot spot will be insufficient, and the degradation efficiency will be reduced.

[0034] Calcium aluminum silicate can be used alone or in combination with maifan stone powder (microwave reaction auxiliary catalyst) to further reduce microwave loss and improve microwave absorption capacity and reaction rate. This invention determines the optimal addition ratio of microwave reaction carrier, catalyst and auxiliary catalyst to generate a significant synergistic effect among the components, thereby achieving a synergistic enhancement of adsorption performance and catalytic oxidation efficiency, greatly improving the degradation rate of organic pollutants, and ensuring stable and reliable wastewater treatment results.

[0035] (3) The present invention has outstanding treatment efficiency. The final effluent COD value is reduced to 2900~5000 mg / L, the oil content is reduced to 50~150 mg / L, and the pH value is stable at 6~9. The COD removal rate is ≥90%, the oil removal rate is ≥99%, and all indicators meet the requirements for subsequent reuse. The treatment process is unaffected by fluctuations in ambient temperature and raw water pollutant concentration. Furthermore, the process flow is short, and the physicochemical reactions of pollutant degradation are rapid. It can be flexibly started and stopped according to actual production needs, which greatly improves the process adaptability and operational stability, and avoids the shortcomings of existing technologies whose treatment effects are easily affected by external factors.

[0036] (4) This invention can significantly improve the reuse rate of gas field wastewater. The treated effluent can be returned to the integrated pool of the sewage treatment plant as the influent source for the low-temperature distillation station and the resource-based water treatment station, thus realizing the resource utilization of wastewater and achieving the environmental protection goals of water conservation and emission reduction. Reducing the amount of wastewater reinjected from gas fields not only lowers the investment in the construction and operation of reinjection wells, but also avoids the potential impact of reinjection on the underground ecological environment, ultimately achieving true zero discharge of produced water from gas fields, which aligns with the development trend of green energy.

[0037] (5) The microwave-induced catalytic oxidation technology used in this invention utilizes microwave radiation (frequency 300MHz~300GHz) to achieve efficient degradation of pollutants through a dual mechanism of dielectric heating and non-thermal effects. The thermal effect and induced catalytic oxidation of microwaves not only significantly accelerate the chemical reaction rate and shorten the processing time, but also feature no pollution, simple equipment structure, small footprint, and high microwave utilization efficiency. Furthermore, the entire process is highly automated and easy to operate, requiring no complex manual intervention, effectively reducing maintenance costs.

[0038] This invention provides a practical technical solution and guidance for the industrial application of microwave technology in the treatment of complex industrial wastewater by optimizing process parameters and using self-developed special reagents. It has broad promotion value and good application prospects. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the process flow of a microwave-induced catalytic oxidation method for treating high-oil-content and high-COD wastewater according to Embodiment 1 of the present invention; Among them, 1-raw water, 2-demulsification tank, 3-dosing system, 4-air flotation device, 5-pH adjustment tank, 6-reaction tank, 7-microwave reactor, 8-plate heat exchanger, 9-inclined tube sedimentation tank, 10-effluent; Figure 2 The images shown are before and after the wastewater from the gas field gathering and transmission pipeline in Embodiment 1 of the present invention. (a) shows the appearance of the wastewater before treatment, and (b) shows the appearance of the wastewater after treatment. Detailed Implementation

[0040] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0041] Unless otherwise specified, all raw materials and equipment used in this invention are commercially available products.

[0042] Example 1 A method for treating high-oil-content and high-COD wastewater using microwave-induced catalytic oxidation, the process flow is as follows: Figure 1 As shown, the specific steps are as follows: Demulsification treatment: Desulfurized raw water 1 is transported to demulsification tank 2. Sodium dodecylbenzenesulfonate is added to demulsification tank 2 through dosing system 3 as a demulsifier. The dosage of demulsifier is 4 g / L (based on wastewater volume). The stirring speed is controlled at 400 rpm and stirring is continued for 30 min to complete the demulsification reaction.

[0043] Air flotation treatment: The demulsified wastewater is connected to nitrogen dissolved air flotation device 4. The operating parameters of the device are set as follows: flotation residence time 10 s, treatment temperature 30℃, dissolved air pressure 0.3 MPa, dissolved air flow rate in the dissolved air release pipe 16 m / s, release flow rate in the release head 0.5 m / s, and average bubble release diameter 41 μm. The floating oil and some suspended impurities in the wastewater are removed by air flotation.

[0044] pH Adjustment and Reagent Mixing: The wastewater after flotation treatment enters the pH adjustment tank 5, where 30% liquid alkali is added via the dosing system 3 to adjust the pH value to 9-9.2. The wastewater is then transferred to the reaction tank 6, where three reaction agents are added sequentially via the dosing system 3: activated carbon powder, calcium aluminum silicate, and maifanite powder. The dosage of activated carbon powder is 3 g / L (based on wastewater volume), calcium aluminum silicate is 3 g / L (based on wastewater volume), and maifanite powder is 0.8 g / L (based on wastewater volume). Extensive experimental research by the inventors has confirmed that the order of agent addition has little impact on the treatment effect, while the uniformity of agent mixing is a key factor affecting the efficiency of microwave catalytic oxidation. Therefore, the stirring speed is controlled at 600 rpm, and stirring is continued for 30 minutes to ensure thorough mixing of the agents and wastewater.

[0045] Microwave catalytic oxidation treatment: The above-mentioned uniformly mixed wastewater is fed into microwave reactor 7 at a flow rate of 250 L / h. The microwave output power of microwave reactor 7 is adjusted to 5 kW, and the reaction time is controlled to 3 min to complete the microwave-induced catalytic oxidation reaction.

[0046] Cooling and coagulation sedimentation: The effluent from microwave reactor 7 first enters the intermediate tank for buffering, and then is cooled to 30~50℃ by plate heat exchanger 8 (i.e., heat exchange unit), and then transported to inclined tube sedimentation tank 9 for coagulation sedimentation treatment; a coagulant is added to the inclined tube sedimentation tank 9 at a ratio of 3 mg / L (based on wastewater volume). The coagulant is a composite coagulant formed by mixing polyaluminum chloride and polyacrylamide at a mass ratio of 80:1. The residence time of wastewater in the inclined tube sedimentation tank 9 is controlled to be 30 min to achieve solid-liquid separation.

[0047] Permeate storage: 10g of the effluent after coagulation and sedimentation is stored in the permeate tank. See Table 1 for details of raw water and effluent parameters at each stage. Table 1 Raw water and effluent indicators at each stage Example 2 A method for treating high-oil-content and high-COD wastewater using microwave-induced catalytic oxidation, the process flow is as follows: Figure 1 As shown, the specific steps are as follows: Demulsification treatment: Desulfurized raw water 1 is transported to demulsification tank 2. Sodium dodecylbenzenesulfonate is added to demulsification tank 2 through dosing system 3 as a demulsifier. The dosage of demulsifier is 5 g / L (based on wastewater volume). The stirring speed is controlled at 400 rpm and stirring is continued for 45 min to complete the demulsification reaction.

[0048] Air flotation treatment: The demulsified wastewater is connected to nitrogen dissolved air flotation device 4. The operating parameters of the device are set as follows: flotation residence time 15 s, treatment temperature 50℃, dissolved air pressure 0.35 MPa, dissolved air flow rate in the dissolved air release pipe 16 m / s, release flow rate in the release head 0.6 m / s, and average bubble diameter 35 μm. The floating oil and some suspended impurities in the wastewater are removed by air flotation.

[0049] pH Adjustment and Reagent Mixing: The wastewater after flotation treatment enters the pH adjustment tank 5. 30% liquid alkali is added to the tank via the dosing system 3 to adjust the pH value of the wastewater to 9.2-9.5. The wastewater is then transferred to the reaction tank 6, where three reaction reagents are added sequentially via the dosing system 3: activated carbon powder, calcium aluminum silicate, and maifanite powder. The dosage of activated carbon powder is 5 g / L (based on wastewater volume), calcium aluminum silicate is 3 g / L (based on wastewater volume), and maifanite powder is 1.0 g / L (based on wastewater volume). The stirring speed is controlled at 600 rpm, and stirring is continued for 50 minutes to ensure thorough mixing of the reagents and wastewater.

[0050] Microwave catalytic oxidation treatment: The above-mentioned uniformly mixed wastewater is fed into microwave reactor 7 at a flow rate of 400 L / h. The microwave output power of microwave reactor 7 is adjusted to 6 kW, and the reaction time is controlled to 2 min to complete the microwave-induced catalytic oxidation reaction.

[0051] Cooling and coagulation sedimentation: The effluent from microwave reactor 7 first enters the intermediate tank for buffering, and then is cooled to 30~50℃ by plate heat exchanger 8, and then transported to inclined tube sedimentation tank 9 for coagulation sedimentation treatment; a coagulant is added to the inclined tube sedimentation tank 9 at a ratio of 4 mg / L (based on wastewater volume). The coagulant is a composite coagulant formed by mixing polyaluminum chloride and polyacrylamide at a mass ratio of 60:1. The residence time of wastewater in the inclined tube sedimentation tank 9 is controlled to be 30 min to achieve solid-liquid separation.

[0052] Permeate storage: 10g of the effluent after coagulation and sedimentation is stored in the permeate tank. See Table 2 for details of raw water and effluent parameters at each stage. Table 2 Raw water and effluent indicators at each stage Example 3 A method for treating high-oil-content and high-COD wastewater using microwave-induced catalytic oxidation, the process flow is as follows: Figure 1 As shown, the specific steps are as follows: Demulsification treatment: Desulfurized raw water 1 is transported to demulsification tank 2. Sodium dodecylbenzenesulfonate is added to demulsification tank 2 through dosing system 3 as a demulsifier. The dosage of demulsifier is 2 g / L (based on wastewater volume). The stirring speed is controlled at 400 rpm and stirring is continued for 60 min to complete the demulsification reaction.

[0053] Air flotation treatment: The demulsified wastewater is connected to nitrogen dissolved air flotation device 4. The operating parameters of the device are set as follows: flotation residence time 20 s, treatment temperature 60℃, dissolved air pressure 0.4 MPa, dissolved air flow rate in the dissolved air release pipe 20 m / s, release flow rate in the release head 1.0 m / s, and average bubble diameter of 32 μm. The floating oil and some suspended impurities in the wastewater are removed by air flotation.

[0054] pH Adjustment and Reagent Mixing: The wastewater after flotation treatment enters the pH adjustment tank 5. 30% liquid alkali is added to the tank via the dosing system 3 to adjust the pH value of the wastewater to 9.2-9.5. The wastewater is then transferred to the reaction tank 6, where three reaction agents are added sequentially via the dosing system 3: activated carbon powder, calcium aluminum silicate, and maifanite powder. The dosage of activated carbon powder is 2 g / L (based on wastewater volume), calcium aluminum silicate is 5 g / L (based on wastewater volume), and maifanite powder is 2 g / L (based on wastewater volume). The stirring speed is 600 rpm, and stirring is continued for 60 minutes to ensure thorough mixing of the agents and wastewater.

[0055] Microwave catalytic oxidation treatment: The above-mentioned uniformly mixed wastewater is fed into microwave reactor 7 at a flow rate of 200 L / h. The microwave output power of microwave reactor 7 is adjusted to 8 kW, and the reaction time is controlled to 4 min to complete the microwave-induced catalytic oxidation reaction.

[0056] Cooling and coagulation sedimentation: The effluent from microwave reactor 7 first enters the intermediate tank for buffering, and then is cooled to 30~50℃ by plate heat exchanger 8 (i.e., heat exchange unit), and then transported to inclined tube sedimentation tank 9 for coagulation sedimentation treatment; a coagulant is added to the inclined tube sedimentation tank 9 at a ratio of 6 mg / L (based on wastewater volume). The coagulant is a composite coagulant formed by mixing polyaluminum chloride and polyacrylamide at a mass ratio of 100:1. The residence time of wastewater in the inclined tube sedimentation tank 9 is controlled to be 30 min to achieve solid-liquid separation.

[0057] Permeate storage: 10g of the effluent after coagulation and sedimentation enters the permeate tank for storage. See Table 3 for details of raw water and effluent parameters at each stage. Table 3 Raw water and effluent indicators at each stage The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for treating high-oil-content and high-COD wastewater by microwave-induced catalytic oxidation, characterized in that, The process includes the following steps: the desulfurized wastewater is sequentially treated with a demulsifier, air flotation for oil removal, pH adjustment to alkaline, thorough mixing with the reaction agent, microwave-induced catalytic oxidation, heat exchange, and coagulation sedimentation before the product water is stored. The reaction agents include a microwave reaction carrier, a microwave reaction catalyst, and a microwave reaction auxiliary catalyst.

2. The method for treating high-oil-content and high-COD wastewater by microwave-induced catalytic oxidation according to claim 1, characterized in that, The wastewater in question is oily, high-COD wastewater generated during the batch processing of gas field gathering and transmission pipelines.

3. The method for treating high-oil-content and high-COD wastewater by microwave-induced catalytic oxidation according to claim 2, characterized in that, The wastewater contains 10-15 wt% waste engine oil, 5-20 wt% corrosion inhibitor, COD ≥ 50,000 mg / L, and water content ≥ 70 wt%.

4. The method for treating high-oil-content and high-COD wastewater by microwave-induced catalytic oxidation according to claim 1, characterized in that, The demulsifier is an anionic surfactant; the dosage of the demulsifier is 1.0~10 g / L, and the demulsification reaction time is 0.5~2.0 h.

5. The method for microwave-induced catalytic oxidation treatment of high-oil-content and high-COD wastewater according to claim 1, characterized in that, The aforementioned air flotation oil removal is nitrogen dissolved air flotation oil removal, with the following process parameters: residence time 10~20s, treatment temperature 10~70℃, dissolved air pressure 0.3~0.4MPa, dissolved air flow rate in the dissolved air release pipe 15~20m / s, release flow rate at the release head 0.5~1.0m / s, and release bubble diameter 30~50μm.

6. The method for microwave-induced catalytic oxidation treatment of high-oil-content and high-COD wastewater according to claim 1, characterized in that, The pH adjustment uses Na2CO3 and / or NaOH as the adjusting agent, and the pH value of the wastewater after adjustment is 9~10.

7. The method for microwave-induced catalytic oxidation treatment of high-oil-content and high-COD wastewater according to claim 1, characterized in that, The microwave reaction carrier is charcoal powder and / or activated carbon powder, with an addition amount of 1.0~10g / L; The microwave reaction catalyst is calcium aluminum silicate, with a dosage of 1.0~10 g / L; The microwave reaction-assisted catalyst is maifanite powder, with an addition amount of 0.5~5 g / L; The reaction time between the reagent and the wastewater is 0.5~2.0h.

8. The method for treating high-oil-content and high-COD wastewater by microwave-induced catalytic oxidation according to claim 1, characterized in that, The process conditions for microwave-induced catalytic oxidation are: wastewater flow rate 150~400L / h, microwave reaction power 2~10kW, and reaction time 1~5min.

9. The method for treating high-oil-content and high-COD wastewater by microwave-induced catalytic oxidation according to claim 1, characterized in that, The wastewater temperature after microwave-induced catalytic oxidation treatment is 70~90℃. Before entering the heat exchange unit, it is first introduced into an intermediate water tank to reduce the temperature of the wastewater entering the heat exchange unit to 60~80℃. After treatment by the heat exchange unit, the wastewater temperature reaches 30~50℃.

10. The method for treating high-oil-content and high-COD wastewater by microwave-induced catalytic oxidation according to claim 1, characterized in that, In the coagulation and sedimentation treatment, the coagulant used is a mixture of any one of polyaluminum ferric sulfate, aluminum chloride, and polyaluminum chloride with polyacrylamide; the mass ratio of the two is (20~100):1; the dosage of the coagulant is 1~10 mg / L.

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