A composite biofilm reaction device and method for deep treatment of petrochemical wastewater

Abstract

The application discloses a composite biofilm reaction device and method for deep treatment of petrochemical wastewater, and belongs to the field of wastewater treatment. In view of the problem that the treatment of refractory organic matters and ammonia nitrogen in petrochemical wastewater does not meet the discharge standard, the application combines the advantages of fixed bed and fluidized bed technology, and ensures that the water quality after treatment meets the discharge standard. The two kinds of fillers of the composite biofilm reaction device include filler A and filler B. The filler A is in a granular shape, is fixed in the reactor by using a special structure, avoids loss of particulate matters, provides a stable adhesion environment for microorganisms, and promotes the formation of a biofilm; the filler B is made of light material and is arranged in the reactor, the good fluidity of the filler B enlarges the effective contact area of the biofilm and enhances the transmission efficiency of oxygen and organic matters in wastewater; in addition, the device adopts a bottom aeration form, ensures efficient transmission and distribution of oxygen, and creates an environment favorable for growth and metabolism of microorganisms. The application solves the key bottleneck problem of petrochemical wastewater treatment.

Description

Technical Field

[0001] This invention designs a composite biofilm reactor that integrates the advantages of various packing materials, specifically targeting the deep treatment of characteristic pollutants in petrochemical wastewater, and belongs to the field of wastewater treatment technology. Background Technology

[0002] The presence of persistent organic matter and ammonia nitrogen in petrochemical wastewater poses a significant technological bottleneck in its treatment. Direct discharge of these pollutants would cause irreversible damage to the ecological environment. This underscores the urgent need to develop advanced treatment technologies that can effectively remove these pollutants. Biofilm processes have become a focal point in this field due to their excellent treatment capacity, high stability, low operating costs, and high space utilization. However, it is worth noting that the type of biofilm and the design of the packing material used significantly impact the wastewater treatment effect.

[0003] In the 1950s, biofilm processes initially relied primarily on the natural growth of a single type of biofilm and the degradation by microorganisms. Due to technological limitations, its effectiveness and application scope in practice were relatively limited. However, with technological advancements, researchers began to explore and introduce new materials and design strategies to optimize biofilm performance, and the technology gradually became applicable to the treatment of wastewater containing recalcitrant organic matter. In studies on single packing materials, lightweight packing materials such as polyethylene and polyvinyl chloride exhibit good flowability and oxygen transfer capabilities, but suffer from poor biofilm stability. Granular packing materials such as activated carbon and ceramsite provide a stable environment for biofilm growth, but traditional stacking methods can easily lead to problems such as limited oxygen transfer, obstructed water flow, and excessively thick biofilms. Some researchers have also fixed granular packing materials in the reactor, but the efficiency of oxygen and nutrient transfer remains an issue. In recent years, to compensate for the shortcomings of single packing materials, researchers have attempted to combine different types of packing materials to achieve a balance between treatment efficiency and biofilm stability. However, the rational configuration and optimization of different types of packing materials to achieve optimal treatment results remains a technical challenge.

[0004] This novel composite packing technology cleverly combines fixed and fluidized packing materials, maintaining the high treatment efficiency and mass transfer performance of fluidized packing while leveraging the advantages of fixed packing in biofilm stability. This idea opens up new avenues for the advanced treatment of recalcitrant organic matter and ammonia nitrogen in wastewater.

[0005] Under the current stringent environmental standards and new policies, petrochemical wastewater treatment faces higher requirements. This includes achieving the treatment of characteristic pollutants in petrochemical wastewater (COD and NH4). + The efficient removal of nitrogen (N-O) has become a top priority. With its technological and economic advantages, the composite biofilm reactor holds promise as an effective tool for solving the current problem of advanced petrochemical wastewater treatment. Summary of the Invention

[0006] This invention discloses a composite biofilm reactor for the advanced treatment of petrochemical wastewater, belonging to the field of wastewater treatment technology. The composite biofilm reactor uses two types of packing materials: packing material A and packing material B. Packing material A is granular and fixed in the reactor using a specialized structure, which not only prevents particulate loss but also provides a stable attachment environment for microorganisms, promoting biofilm formation. Packing material B is made of lightweight materials and is placed in the reactor; its good fluidity expands the effective contact area of ​​the biofilm and enhances the transfer efficiency of oxygen and organic matter in the wastewater. Furthermore, this device employs bottom aeration to ensure efficient oxygen transfer and distribution, creating an environment conducive to microbial growth and metabolism, further enhancing the removal of recalcitrant organic matter and ammonia nitrogen. This method integrates the advantages of fixed-bed and fluidized-bed technologies, ensuring that the treated water quality meets stringent national discharge standards.

[0007] The objective of this invention is achieved through the following technical solution: a composite biofilm reactor for deep treatment of petrochemical wastewater, characterized in that:

[0008] The pre-film reactor (1) includes an inlet tank (1.1), a peristaltic pump (1.2), an inlet (1.3), a pH / DO meter (1.4), a stirrer (1.5), an air pump (1.6), a gas flow meter (1.7), an aeration disc (1.8), a stirring paddle (1.9), a hollow fiber membrane (1.10), a pressure gauge (1.11), an outlet pump (1.12), an inlet level controller (1.13), and an outlet level controller (1.14); the composite biofilm reactor includes an inlet tank (2.1), a peristaltic pump (2.2), an inlet (2.3), a pH / DO meter (2.4), a heating rod (2.5), an air pump (2.6), a gas flow meter (2.7), an aeration disc (2.8), an outlet (2.9), a first packing fixing plate (2.10), and a first packing fixing device. The composite biofilm reactor comprises, from bottom to top, a first packing layer A, a packing layer B, and a second packing layer A; wherein, the first packing layer A is composed of a first packing fixing plate (2.10) and a first packing fixing device (2.11), and packing A is placed in the first packing fixing device (2.11); the packing layer B is located between the first packing fixing plate (2.10) and the second packing fixing plate (2.12), and packing B is disposed in the packing layer B; the second packing layer A is composed of a second packing fixing plate (2.12) and a second packing fixing device (2.13), and packing A is placed in the second packing fixing device (2.13); the first packing fixing device (2.11) and the second packing fixing device (2.13) are hollow spherical structures with hollowed-out middle sections.

[0009] The nutrient solution in the inlet tank (1.1) enters the pre-film reactor (1) through the inlet (1.3) via the peristaltic pump (1.2), and a 40mm high packing layer A composed of packing material A is placed in the reactor for biofilm formation; the petrochemical wastewater requiring deep treatment in the inlet tank (2.1) enters the composite biofilm reactor (2) through the inlet (2.3) via the peristaltic pump (2.2), and the total height of the system composed of the first packing layer A, the packing layer B, and the second packing layer A is 100mm; the first packing fixing plate (2.10) is located at the bottom of the biofilm reactor, 40mm away from the bottom of the tank, forming a water-air buffer zone; the packing material A is placed in the reactor. The first packing fixing device (2.11) of the first packing fixing plate (2.10) forms a first packing layer A with a diameter of 40 mm; the packing layer B is located between the first packing fixing plate (2.10) and the second packing fixing plate (2.12) and is composed of packing B with a height of 60 mm; the packing A is placed in the second packing fixing device (2.13) of the second packing fixing plate (2.12) to form a second packing layer A with a diameter of 40 mm; the water flow and air flow are made to pass from bottom to top through the composite biofilm system composed of the first packing layer A, the packing layer B and the second packing layer A, and the water overflows through the outlet (2.9).

[0010] A method for using a novel composite biofilm reactor for deep treatment of petrochemical wastewater, characterized by comprising the following steps:

[0011] (1) Pre-film formation in the reactor: New, unformed packing material A is placed in the pre-film reactor (1), and activated sludge is added to the reactor. The activated sludge used for inoculation is return sludge from the secondary sedimentation tank of the wastewater treatment plant. After inoculation, the suspended sludge concentration in the reactor is 2000-2500 mg / L. The nutrient solution in the influent tank (1.1) is introduced into the pre-film reactor (1) through the inlet (1.3) via the peristaltic pump (1.2). The reactor operates in an intermittent mode, consisting of five stages: influent, reaction, sedimentation, effluent, and idle. Each cycle lasts 6 hours, with four cycles per day. The influent cycle is 15 minutes, the reaction cycle is 240 minutes, the sedimentation cycle is 30 minutes, the effluent cycle is 15 minutes, and the idle cycle is 60 minutes. During the reaction stage, an air pump (1.6), a gas flow meter (1.7), and an aeration disc (1.8) are used to aerate the bottom of the pre-film reactor (1) to maintain dissolved oxygen at 2-3 mg / L. When the biomass increases to more than 0.1 mg SS / g and the biofilm on the packing surface is more than 500 μm thick, the reactor enters a stable operating state. The reactor is considered to have successfully formed a biofilm after operating stably for more than 10 days.

[0012] (2) Inoculation of packing material and start-up of composite biofilm reactor: Take out packing material A from the pre-film reactor (1) and sieve it multiple times through a 30-mesh sieve to ensure complete separation of packing material A from activated sludge. Place the sieved packing material A into the first packing layer A and the second packing layer A respectively, and inoculate the new un-filmed packing material B into packing layer B; add NH4 in the influent tank (2.1) + Petrochemical wastewater with N=30-40 mg / L and COD=100-200 mg / L requiring deep treatment enters the composite biofilm reactor (2) from the bottom through the inlet (2.3) using a peristaltic pump (2.2). Continuous aeration is performed at the bottom of the composite biofilm reactor (2) using an air pump (2.6), a gas flow meter (2.7), and an aeration disc (2.8) to maintain dissolved oxygen at 2-3 mg / L. The composite biofilm reactor (2) operates at a hydraulic retention time of 18.5 h and a temperature of 25-30 °C. When the effluent NH4... + The composite biofilm reactor is considered to have been successfully started up if -N < 8 mg / L, COD removal rate ≥ 50%, biomass increases to 0.3 mg SS / g or more, and the biofilm thickness on the packing surface is ≥ 1000 μm.

[0013] (3) Stable operation of the system: The composite biofilm reactor (2) operates at a hydraulic retention time of 18.5h, an air-to-water ratio of 20:1, and a temperature of 25-30℃. The air pump (2.6), gas flow meter (2.7), and aeration disc (2.8) are used to continuously aerate the bottom of the composite biofilm reactor (2) to maintain dissolved oxygen at 2-3mg / L. The outlet (2.9) is an overflow outlet. The reactor mainly relies on the synergistic effect of microorganisms on the packing material, including anaerobic bacteria, hypoxic bacteria, and aerobic bacteria.

[0014] (4) Replacement of packing material: After long-term use, the composite biofilm reactor (2) will experience a decline in packing material performance, such as wear, deformation, aging, corrosion, etc., and the effluent indicators will show NH4 for more than 10 days. + When -N > 15 mg / L and COD removal rate ≤ 30%, both types of packing materials need to be replaced. If packing material A exhibits the above phenomenon, it can be removed from the first packing fixing device (2.11) and the second packing fixing device (2.13), and a portion of the old packing material A can be gradually replaced by regeneration or supplementing with new packing material. If packing material B exhibits the above phenomenon, it can be removed from packing layer B, and the old packing material B can be replaced by supplementing with new packing material.

[0015] Based on the type of biofilm and the design of the packing material used, a composite packing technology is employed to combine fixed packing material A and fluidized packing material B. Packing material A is granular and fixed to the upper and lower parts of the reactor using a dedicated structure; packing material B is made of lightweight material and is positioned in the middle of the reactor. The total filling rate is 50% of the reaction tank volume. Significant differences exist in the geometric characteristics and pore structure of the two carriers.

[0016] Packing material A is located in the first packing fixing device (2.11) and the second packing fixing device (2.13), preventing packing material loss. Packing material A can be composed of granular packing materials such as activated carbon and ceramsite, with a particle size of 1-2 mm. This granular packing material provides a stable environment for biofilm growth.

[0017] Packing material B is located within packing layer B. Packing material B is mainly made of lightweight fillers such as polyethylene and polystyrene, exhibiting high fluidity and a honeycomb structure. This lightweight packing material possesses excellent fluidity and oxygen transfer capabilities.

[0018] This invention has the following advantages:

[0019] 1) This invention integrates the features of fixed bed and fluidized bed technologies. By rationally configuring and optimizing different types of packing materials, the reactor can simultaneously achieve high treatment efficiency and a stable biofilm.

[0020] 2) This invention adopts bottom aeration to ensure efficient oxygen transfer and distribution, creating an environment conducive to microbial growth and metabolism, and further enhancing the removal efficiency of recalcitrant organic matter and ammonia nitrogen.

[0021] 3) This invention employs a novel composite biofilm reactor for the deep treatment of petrochemical wastewater, effectively eliminating the presence of characteristic pollutants (COD and NH4) in the wastewater. + The efficient removal of nitrogen (N) meets the requirements for upgrading emissions standards, making it an economical and environmentally friendly treatment device. Attached Figure Description

[0022] Figure 1 Yes: Schematic diagram of the structure of pre-film reactor and composite biofilm reactor.

[0023] Figure 1In the diagram: 1.1 – Inlet water tank; 1 – Pre-film reactor; 1.2 – Peristaltic pump; 1.3 – Inlet; 1.4 – pH / DO meter; 1.5 – Agitator; 1.6 – Air pump; 1.7 – Gas flow meter; 1.8 – Aeration disc; 1.9 – Agitator; 1.10 – Hollow fiber membrane; 1.11 – Pressure gauge; 1.12 – Outlet pump; 1.13 – Inlet water level controller; 1.14 – Outlet water level controller ; 2.1 - Inlet water tank; 2 - Composite biofilm reactor; 2.2 - Peristaltic pump; 2.3 - Inlet; 2.4 - pH / DO meter; 2.5 - Heating rod; 2.6 - Air pump; 2.7 - Gas flow meter; 2.8 - Aeration disc; 2.9 - Outlet; 2.10 - First packing fixing plate; 2.11 - First packing fixing device; 2.12 - Second packing fixing plate; 2.13 - Second packing fixing device.

[0024] Figure 2 These are: a structural diagram of packing A located in the first packing fixing device (2.11) and the second packing fixing device (2.13), and a structural diagram of packing B.

[0025] Figure 2 In the middle: 2.11 - First packing fixing device, 2.13 - Second packing fixing device. Detailed Implementation

[0026] The implementation scheme of the present invention is described below with reference to the accompanying drawings and detailed examples:

[0027] exist Figure 1The illustrated embodiment shows a schematic cross-sectional view of a composite biofilm reactor for the deep treatment of petrochemical wastewater according to the present invention. The apparatus includes a pre-coated membrane reactor (1) and a composite biofilm reactor (2). The pre-film reactor (1) includes an inlet tank (1.1), a peristaltic pump (1.2), an inlet (1.3), a pH / DO meter (1.4), a stirrer (1.5), an air pump (1.6), a gas flow meter (1.7), an aeration disc (1.8), a stirring paddle (1.9), a hollow fiber membrane (1.10), a pressure gauge (1.11), an outlet pump (1.12), an inlet level controller (1.13), and an outlet level controller (1.14); the composite biofilm reactor includes an inlet tank (2.1), a peristaltic pump (2.2), an inlet (2.3), a pH / DO meter (2.4), a heating rod (2.5), an air pump (2.6), a gas flow meter (2.7), an aeration disc (2.8), an outlet (2.9), a first packing fixing plate (2.10), and a first packing fixing device. The composite biofilm reactor comprises, from bottom to top, a first packing layer A, a packing layer B, and a second packing layer A; wherein, the first packing layer A is composed of a first packing fixing plate (2.10) and a first packing fixing device (2.11), and packing A is placed in the first packing fixing device (2.11); the packing layer B is located between the first packing fixing plate (2.10) and the second packing fixing plate (2.12), and packing B is disposed in the packing layer B; the second packing layer A is composed of a second packing fixing plate (2.12) and a second packing fixing device (2.13), and packing A is placed in the second packing fixing device (2.13); the first packing fixing device (2.11) and the second packing fixing device (2.13) are hollow spherical structures with hollowed-out middle sections.

[0028] The nutrient solution in the inlet tank (1.1) enters the pre-film reactor (1) through the inlet (1.3) via the peristaltic pump (1.2), and a 40mm high packing layer A composed of packing material A is placed in the reactor for biofilm formation; the petrochemical wastewater requiring deep treatment in the inlet tank (2.1) enters the composite biofilm reactor (2) through the inlet (2.3) via the peristaltic pump (2.2), and the total height of the system composed of the first packing layer A, the packing layer B, and the second packing layer A is 100mm; the first packing fixing plate (2.10) is located at the bottom of the biofilm reactor, 40mm away from the bottom of the tank, forming a water-air buffer zone; the packing material A is placed in the reactor. The first packing fixing device (2.11) of the first packing fixing plate (2.10) forms a first packing layer A with a diameter of 40 mm; the packing layer B is located between the first packing fixing plate (2.10) and the second packing fixing plate (2.12) and is composed of packing B with a height of 60 mm; the packing A is placed in the second packing fixing device (2.13) of the second packing fixing plate (2.12) to form a second packing layer A with a diameter of 40 mm; the water flow and air flow are made to pass from bottom to top through the composite biofilm system composed of the first packing layer A, the packing layer B and the second packing layer A, and the water overflows through the outlet (2.9).

[0029] Test system such as Figure 1 As shown, the pre-film reactor (1) has a total volume of 4L, an effective volume of 2.5L, a filling ratio of 30%, and a drainage ratio of 50%. The nutrient solution containing m(C):m(N):m(P) = 100:5:1 in the inlet tank (1.1) enters the pre-film reactor (1) through the inlet (1.3) via a peristaltic pump (1.2), and the effluent is discharged through a hollow fiber membrane (1.10) and an outlet pump (1.12). The composite biofilm reactor (2) has a total volume of 4.5L and an effective volume of 3L. The inlet tank (2.1) contains NH4+. + Petrochemical wastewater with N = 30-40 mg / L and COD = 100-200 mg / L requiring deep treatment enters the biofilm reactor (2) from the bottom through the inlet (2.3) via a peristaltic pump (2.2), and overflows through the outlet (2.9).

[0030] During the experiment, the pre-film reactor used wastewater with a certain amount of nutrient solution. The specific water quality was as follows: MgSO4·7H2O = 40 mg / L, MnSO4·7H2O = 1.2 mg / L, KH2PO4 = 5 mg / L, FeSO4 = 0.6 mg / L, CaCl2 = 1.2 mg / L, NH4HCO3 = 23.4 mg / L, glucose = 73 mg / L. The composite biofilm reactor used simulated secondary biochemical effluent from a petrochemical plant. The specific water quality was as follows: COD concentration 100-200 mg / L, NH4...+ -N concentration is 30-40 mg / L, SS < 200 mg / L.

[0031] The specific operation steps are as follows:

[0032] (1) Pre-film formation in the reactor:

[0033] New, un-film-attached packing material A is placed in the pre-film reactor (1), and activated sludge is added to the reactor. The inoculated activated sludge is return sludge from the secondary sedimentation tank of the wastewater treatment plant, and the suspended sludge concentration in the reactor after inoculation is 2000-2500 mg / L. Nutrient solution with m(C):m(N):m(P) = 100:5:1 in the influent tank (1.1) is introduced into the pre-film reactor (1) through the inlet (1.3) via a peristaltic pump (1.2). The system operates in an intermittent mode, consisting of five stages: influent, reaction, sedimentation, effluent, and idle. Each cycle lasts 6 hours, with four cycles per day. The influent cycle is 15 minutes, the reaction cycle is 240 minutes, the sedimentation cycle is 30 minutes, the effluent cycle is 15 minutes, and the idle cycle is 60 minutes. During the reaction stage, an air pump (1.6), a gas flow meter (1.7), and an aeration disc (1.8) are used to aerate the bottom of the pre-film reactor (1) to maintain dissolved oxygen at 2-3 mg / L. A pressure gauge (1.11) monitors the effluent pressure to characterize the clogging of the hollow fiber membrane. When the negative pressure is greater than 10 MPa, for example, when the pressure gauge shows a negative pressure of 15 MPa, it indicates that the hollow fiber membrane is clogged and needs to be cleaned and replaced. When membrane clogging is not addressed in time, the liquid level rises to the effective volume of the pre-film reactor (1), and the influent level controller starts working, immediately stopping the peristaltic pump (1.2) to prevent overflow of the sludge and packing mixture and loss of sludge and packing. When the level controller reaches the effective volume of the pre-film reactor (1), the effluent level gauge (1.11) starts working, immediately starting the effluent pump (1.12) to discharge the water in the reactor through the hollow fiber membrane (1.10) and the effluent pump (1.12). Biomass and biofilm thickness are measured. When the biomass increases to above 0.1 mg SS / g and the biofilm thickness on the packing surface is above 500 μm, the reactor enters a stable operating state. Stable operation for more than 10 days is considered a successful biofilm formation in the reactor.

[0034] (2) Inoculation of packing material and start-up of the composite biofilm reactor:

[0035] Take out the packing material A from the pre-film reactor (1) and sieve it multiple times through a 30-mesh sieve to ensure complete separation of packing material A from activated sludge. Place the sieved packing material A into the first packing layer A and the second packing layer A respectively, and inoculate the new un-filmed packing material B into packing layer B; add NH4 from the influent tank (2.1) +Petrochemical wastewater with N=30-40 mg / L and COD=100-200 mg / L requiring deep treatment enters the composite biofilm reactor (2) from the bottom through the inlet (2.3) using a peristaltic pump (2.2). Continuous aeration is performed at the bottom of the composite biofilm reactor (2) using an air pump (2.6), a gas flow meter (2.7), and an aeration disc (2.8) to maintain dissolved oxygen at 2-3 mg / L. The composite biofilm reactor (2) operates at a hydraulic retention time of 18.5 h and a temperature of 25-30 °C. The COD removal rate and effluent NH4+ are calculated. + -N concentration indicators and biomass and biofilm thickness indicators were measured. When NH4+ effluent... + The composite biofilm reactor is considered to have been successfully started up if -N < 8 mg / L, COD removal rate ≥ 50%, biomass increases to 0.3 mg SS / g or more, and the biofilm thickness on the packing surface is ≥ 1000 μm.

[0036] (3) Stable operation of the system:

[0037] The composite biofilm reactor (2) was operated at a hydraulic retention time of 18.5 h, an air-to-water ratio of 20:1, and a temperature of 25-30 °C. Continuous aeration was carried out at the bottom of the composite biofilm reactor (2) using an air pump (2.6), a gas flow meter (2.7), and an aeration disc (2.8) to maintain dissolved oxygen at 2-3 mg / L. The optimal air-to-water ratio (10:1, 20:1, and 30:1) of the composite biofilm reactor (2) was determined by adjusting the gas flow rate of the gas flow meter (2.7) and the inlet flow rate of the peristaltic pump (2.2). The optimal gas and liquid flow rates were selected as the optimal reaction parameters (20:1), and the COD removal rate and effluent NH4 were calculated. + -N concentration index. The outlet (2.9) of this composite biofilm reactor (2) is an overflow outlet; the composite biofilm reactor (2) mainly achieves the removal of ammonia nitrogen and the conversion of organic matter through the synergistic effect of microorganisms on the packing material, including anaerobic bacteria, hypoxic bacteria and aerobic bacteria. Packing material A is conducive to the formation and long-term stability of biofilm, and packing material B has good fluidity and oxygen transfer capacity; in addition, the bottom aeration form is adopted to ensure efficient oxygen transfer and distribution, create an environment conducive to the growth and metabolism of microorganisms, and further enhance the removal efficiency of recalcitrant organic matter and ammonia nitrogen.

[0038] Experimental results show that after the system is running stably, the biofilm reactor can achieve a COD removal rate of 80% and an NH4 removal rate of 98%. + -N removal rate, with high efficiency in removing refractory organic matter and ammonia nitrogen from petrochemical wastewater.

[0039] (4) Packing material replacement:

[0040] The composite biofilm reactor (2) will experience a decline in packing performance after long-term use, such as wear, deformation, aging, and corrosion, and the effluent indicators will show NH4 for more than 10 days. + When -N > 15 mg / L and COD removal rate ≤ 30%, both types of packing materials need to be replaced. If packing material A exhibits the above phenomenon, it can be removed from the first packing fixing device (2.11) and the second packing fixing device (2.13), and a portion of the old packing material A can be gradually replaced by regeneration or supplementing with new packing material. If packing material B exhibits the above phenomenon, it can be removed from packing layer B, and the old packing material B can be replaced by supplementing with new packing material.

[0041] The above are specific implementation examples of the present invention, which are intended to help those skilled in the art to better understand and apply the present invention. However, the implementation of the present invention is not limited to these examples. Therefore, any simple improvements made to the present invention by those skilled in the art are within the scope of protection of the present invention.

Claims

1. A combined biofilm process for advanced treatment of petrochemical wastewater, the process using a device comprising: Pre-hanging film reactor (1), composite bio-membrane reactor (2); Wherein, the pre-hanging film reactor (1) includes water tank (1.1), peristaltic pump (1.2), water inlet (1.3), pH / DO tester (1.4), stirrer (1.5), air pump (1.6), gas flow meter (1.7), aeration disc (1.8), stirring paddle (1.9), hollow fiber membrane (1.10), pressure gauge (1.11), water pump (1.12), water level controller (1.13), water level controller (1.14); the composite bio-membrane reactor includes water tank (2.1), peristaltic pump (2.2), water inlet (2.3), pH / DO tester (2.4), heating rod (2.5), air pump (2.6), gas flow meter (2.7), aeration disc (2.8), water outlet (2.9), first filler fixing plate (2.10), first filler fixing device (2.11), second filler fixing plate (2.12), second filler fixing device (2.13); the composite bio-membrane reactor includes first filler layer A, filler layer B, second filler layer A from bottom to top; wherein, the first filler layer A is composed of the first filler fixing plate (2.10) and the first filler fixing device (2.11), and the filler A is arranged in the first filler fixing device (2.11); the filler layer B is located between the first filler fixing plate (2.10) and the second filler fixing plate (2.12), and the filler B is arranged in the filler layer B; the second filler layer A is composed of the second filler fixing plate (2.12) and the second filler fixing device (2.13), and the filler A is arranged in the second filler fixing device (2.13); the first filler fixing device (2.11) and the second filler fixing device (2.13) are hollow spherical structures with hollow in the middle; The nutrient solution in the water inlet tank (1.1) enters the pre-membrane reactor (1) from the water inlet (1.3) through the peristaltic pump (1.2), and the filler A is placed in the reactor to form a filler layer A with a height of 40 mm for membrane formation; the petrochemical wastewater in the water inlet tank (2.1) that needs to be deeply treated enters the composite bio-membrane reactor (2) from the water inlet (2.3) through the peristaltic pump (2.2), and the system composed of the first filler layer A, the filler layer B and the second filler layer A has a total height of 100 mm; the first filler fixing plate (2.10) is located at the lower part of the bio-membrane reactor, and the distance from the first filler fixing plate (2.10) to the bottom of the pool body is 40 mm, forming a water and gas buffer zone; the filler A is placed in the first filler fixing device (2.11) of the first filler fixing plate (2.10) to form the first filler layer A with a diameter of 40 mm; the filler layer B is located between the first filler fixing plate (2.10) and the second filler fixing plate (2.12) and is composed of the filler B with a height of 60 mm; the filler A is placed in the second filler fixing device (2.13) of the second filler fixing plate (2.12) to form the second filler layer A with a diameter of 40 mm; the water flow and the gas flow pass through the composite bio-membrane system composed of the first filler layer A, the filler layer B and the second filler layer A from bottom to top in the form of bottom aeration, and the effluent overflows from the water outlet (2.9); It is characterized by comprising the following steps: (1) Pre-membrane reactor: new fillers A without membrane formation are placed in the pre-membrane reactor (1), and activated sludge is added in the reactor; the inoculated activity is the backflow sludge of the secondary sedimentation tank of a wastewater treatment plant, and the suspended sludge concentration of the reactor after inoculation is 2000-2500 mg / L; the nutrient solution in the water inlet tank (1.1) enters the pre-membrane reactor (1) from the water inlet (1.3) through the peristaltic pump (1.2); intermittent mode is adopted to operate according to the five stages of water inlet-reaction-settling- effluent-idling, 6 h as a cycle, 4 cycles a day, wherein the water inlet is 15 min, the reaction is 240 min, the settling is 30 min, the effluent is 15 min, and the idling is 60 min; in the reaction stage, the air pump (1.6), the gas flow meter (1.7) and the aeration disc (1.8) are used to aerate at the bottom of the pre-membrane reactor (1) to maintain the dissolved oxygen at 2-3 mg / L; when the biomass increases to 0.1 mg SS / g or more, and the bio-membrane attached to the surface of the filler is thicker than 500 μm, the reactor enters a stable operation state, and the reactor is considered to be successfully membrane-formed when the state is stably operated for more than 10 days; (2) Inoculation of the filler and start-up of the composite biofilm reactor: the filler A in the pre-film reactor (1) was removed, placed in a 30 mesh screen and sieved several times to ensure that the filler A was completely separated from the activated sludge; the sieved filler A was placed in the first filler layer A and the second filler layer A, respectively, and the new un-filmed filler B was placed in the filler layer B for inoculation; NH4 + The petrochemical wastewater with NH4 + -N < 8 mg / L, COD removal rate ≥ 50%, biomass increased to 0.3 mg SS / g or more and the thickness of the biofilm attached to the surface of the filler was 1000 μm or more, and the stable operation for 15 days or more was considered as the successful start-up of the composite biofilm reactor. (3) Stable operation of the system: the composite bio-membrane reactor (2) is operated under the conditions of a hydraulic retention time of 18.5 h, a gas-water ratio of 20:1 and a temperature of 25-30 ℃; the air pump (2.6), the gas flow meter (2.7) and the aeration disc (2.8) are used to continuously aerate at the bottom of the composite bio-membrane reactor (2) to maintain the dissolved oxygen at 2-3 mg / L, and the effluent overflows from the water outlet (2.9); (4) The update of the filler: the composite bio-membrane reactor (2) will appear the performance decline of the filler after long-term use, and the effluent indicators appear NH4 + -N>15 mg / L, and the COD removal rate is ≤30 %, the two fillers inside need to be updated; if the filler A appears the above phenomena, the filler A can be taken out from the first filler fixing device (2.11) and the second filler fixing device (2.13), and the method of regenerating or supplementing new fillers is used to gradually replace a part of the old filler A; if the filler B appears the above phenomena, the filler B can be taken out from the filler layer B, and the method of supplementing new fillers is used to replace the old filler B.

2. The method according to claim 1, filler A is located in the first filler fixing device (2.11) and the second filler fixing device (2.13), filler A is granular activated carbon or ceramic particles; the particle size is 1-2 mm; filler B is located in the filler layer B; filler B is polyethylene or polystyrene.

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