CN118005237A - A method and device for treating polycyclic aromatic hydrocarbons in urban drainage overflow pollution - Google Patents

Abstract

The application relates to the technical field of urban drainage pipe network overflow sewage treatment, in particular to a method and a device for treating polycyclic aromatic hydrocarbon in urban drainage overflow pollution. The application provides a treatment method of polycyclic aromatic hydrocarbon in urban drainage overflow pollution, which comprises the following steps: s1: screening urban drainage overflow sewage to remove solid matters to obtain first treated water; s2: pre-panning the first treated water to obtain second treated water; s3: placing the second treated water in an anoxic environment and an aerobic environment for reaction to obtain third treated water; s4: reacting the third treated water with a coagulant and a flocculant, and removing the precipitate to obtain fourth treated water; s5: and (3) treating the fourth treated water by micro-nano bubbles, ozone and a catalyst to obtain water from which the polycyclic aromatic hydrocarbon is removed. The application adopts the coagulation and multistage AO pool and micro-nano bubble ozone to achieve the purpose of controlling the polycyclic aromatic hydrocarbon in the overflow pollution of the urban drainage pipe network, and the combined process has high removal efficiency and cost saving, and can be widely used.

Description

A method and device for treating polycyclic aromatic hydrocarbons in urban drainage overflow pollution

Technical Field

The present application relates to the technical field of urban drainage network overflow sewage treatment, and in particular to a method and device for treating polycyclic aromatic hydrocarbons in urban drainage overflow pollution.

Background technique

Overflow water from urban drainage networks refers to the sewage that overflows and is directly discharged through the drainage system when the water volume exceeds the drainage network's transportation capacity during the rainy season. At this time, the water contains a large amount of pollutants, mainly including organic matter, TP (total phosphorus), TN (total nitrogen), SS (suspended solids), pathogenic microorganisms, heavy metals, polycyclic aromatic hydrocarbons (PAHs), etc.

PAHs are highly carcinogenic environmental pollutants with multiple homologues, and their toxicity is often the result of the synergistic effects of multiple homologues. Among the 16 PAHs listed as priority pollutants by USEPA, 7 are recognized as highly carcinogenic, including benzo[a]anthracene, benzo[a]pyrene, benzo[b]fluoranthene, benzo[k]fluoranthene, chrysene, dibenzo[a,h]anthracene, and indeno[1,2,3-cd]pyrene.

For the terminal treatment process of overflow water from urban drainage pipe networks, a combination of rapid coagulation and sedimentation + high-efficiency fiber filter is usually used. This combined process can achieve removal rates of 80%, 50% and 80% or more for SS, COD (chemical oxygen demand) and TP, and can remove most insoluble pollutants.

In addition, the activated sludge method can also be used to reduce the pollution of overflow sewage to water bodies. For example, a sewage treatment plant in a Yangtze River protection project uses an equipment-based pure membrane MBBR system to treat overflow sewage. The system adopts two operating modes: rainy season and dry season. The average concentrations of effluent COD, ammonia nitrogen, TP, and SS are 30mg/L, 3mg/L, 0.5mg/L, and 10mg/L, respectively. It greatly reduces the entry of pollutants into natural water bodies through overflow, and controls the occurrence of black and smelly water bodies at the source.

The conventional process has limited ability to remove PAHs, and the removal efficiency is usually less than 30%. Therefore, it is necessary to develop a treatment method with higher removal efficiency for PAHs.

Summary of the invention

In view of the shortcomings of the prior art described above, the inventors of this application have found that adding an ozone micro-nano bubble treatment unit can effectively remove polycyclic aromatic hydrocarbons in overflow pollution. Ozone is a strong oxidant with a high redox potential, which can directly or indirectly react with polycyclic aromatic hydrocarbons. Micro-nano bubbles have special physical and chemical properties. Ordinary bubbles quickly rise to the water surface and burst and disappear, while micro-nano bubbles rise slowly and exist for a short time, which can effectively improve the utilization rate of ozone.

To achieve the above-mentioned purpose and other related purposes, the first aspect of the present application provides a method for treating polycyclic aromatic hydrocarbons in urban drainage overflow pollution, comprising the following steps:

S1: Screening and removing solid matter from urban drainage overflow sewage to obtain first treated water;

S2: pre-washing the first treated water to obtain second treated water;

S3: placing the second treated water in an anoxic environment and an aerobic environment to react to obtain third treated water;

S4: reacting the third treated water with a coagulant and a flocculant, and removing the precipitate to obtain a fourth treated water;

S5: treating the fourth treated water with micro-nano bubbles, ozone and a catalyst to obtain water after removing polycyclic aromatic hydrocarbons.

In any embodiment of the present application, in step S1, the solid matter includes one or more of gravel, branches, towels, and paper.

In any embodiment of the present application, in step S1, the screening is performed in the grate; preferably, the flow velocity of the urban drainage overflow sewage in the grate is 0.7-0.9 m/s; the water flow velocity in front of the grate is 0.6-0.7 m/s; and the water depth in front of the grate is 0.15-0.25 m.

In any embodiment of the present application, in step S2, the pre-elution separates the sludge and the sewage by stirring the first treated water, dissolving the polycyclic aromatic hydrocarbons in the organic matter particles into the sewage, and obtaining the second treated water.

In any embodiment of the present application, in step S2, the pre-elution time is 20 to 30 minutes.

In any embodiment of the present application, in step S3, the volume ratio of the anoxic environment to the aerobic environment is 1:1.5-2.5.

In any embodiment of the present application, in step S3, the second treated water enters the anoxic environment and the aerobic environment in batches; preferably, the second treated water is divided into 3 to 5 batches.

In any embodiment of the present application, in step S3, the reaction time of the second treated water in an anoxic environment is 3 to 5 hours, and the reaction time in an aerobic environment is 7 to 9 hours.

In any embodiment of the present application, in step S3, the second treatment water is divided into three batches, and the water intake of the first batch: the second batch: the third batch is 40%: 40%: 30%; the volume ratio of the anoxic environment and the aerobic environment in the first batch: the second batch: the third batch is 1:1:2.

In any embodiment of the present application, in step S4, the coagulant is selected from polyaluminium chloride and/or polyferric chloride; the flocculant is polyacrylamide and magnetic Fe ₃ O ₄ powder; preferably, the dosage of magnetic Fe ₃ O ₄ powder is 0.5-1 mg/L.

In any embodiment of the present application, in step S4, when the third treated water reacts with the coagulant and the flocculant, mechanical stirring is used to make the average surface water load 8 to 12 m ³ /m ² ·h.

In any embodiment of the present application, in step S4, the reaction time of the third treated water and the coagulant is 5 to 10 minutes.

In any embodiment of the present application, in step S4, the reaction time of the third treated water and the flocculant is 5 to 10 minutes.

In any embodiment of the present application, in step S4, the reaction time of removing precipitation from the third treated water is 20 to 30 minutes.

In any embodiment of the present application, in step S5, the catalyst is selected from manganese ferrite, and the dosage of the catalyst is 0.1-0.5 mg/L.

In any embodiment of the present application, in step S5, the dosage of ozone is 3-8 mg/L.

In any embodiment of the present application, in step S5, the ozone and clean water are pressurized and evacuated to obtain a gas-liquid mixture containing micro-nano bubbles; preferably, the vacuum degree of the evacuation is 0.025-0.03Mpa; the pressure of the pressurization is 0.25-0.40MPa; based on the total volume of the gas-liquid mixture, the gas content therein is 5-10%. The flow rate of the gas in the gas-liquid mixture is 7-8L/min; the flow rate of the liquid in the gas-liquid mixture is 5-6L/min; more preferably, based on the total volume of the gas, the volume of micro-nano bubbles accounts for 60-80%.

The second aspect of the present application provides a device for treating polycyclic aromatic hydrocarbons in urban drainage overflow pollution, comprising a grid, a pre-washing tank, a multi-stage AO tank, a coagulation tank, a sedimentation tank, and an ozone reaction tank connected in sequence; the ozone reaction tank is connected to an ozone generator through a microbubble generating system.

In any embodiment of the present application, the microbubble generating system comprises a connected gas-liquid circulation pump and a gas-liquid releaser, the gas-liquid releaser is connected to the ozone reaction tank; the gas-liquid circulation pump is connected to the ozone generator; preferably, the gas-liquid circulation pump is used to pressurize and evacuate the introduced gas and liquid to obtain a gas-liquid mixture containing micro-nano bubbles; more preferably, the vacuum degree of the evacuation is 0.025-0.03 MPa; the pressurized pressure is 0.25-0.40 MPa; based on the total volume of the gas-liquid mixture, the gas content therein is 5-10%; the gas flow rate in the gas-liquid mixture is 7-8 L/min; the liquid flow rate in the gas-liquid mixture is 5-6 L/min; based on the total volume of the gas, the volume proportion of micro-nano bubbles is 60-80%. In order to better degrade polycyclic aromatic hydrocarbons, nano catalyst material manganese ferrite MnFe ₂ O ₄ can also be added, and the addition amount is 0.1-0.5 mg/L. The nano catalyst material manganese ferrite MnFe ₂ O ₄ has a spinel structure, and Fe ³⁺ can better stimulate ozone to produce free radicals and degrade difficult-to-degrade organic matter. At the same time, Mn ²⁺ plays a certain catalytic role on ozone.

In any embodiment of the present application, the multi-stage AO tank includes several connected anoxic zones and aerobic zones; the anoxic zone is connected to the pre-elution tank, and the aerobic zone is connected to the coagulation tank; preferably, the volume ratio of the anoxic zone to the aerobic zone is 1:1.5~2.5.

In any embodiment of the present application, the coagulation tank includes a connected T1 rapid reaction coagulation tank and a T2 magnetic medium mixing reaction tank; the T1 rapid reaction coagulation tank is connected to the multi-stage AO tank, and the T2 magnetic medium mixing reaction tank is connected to the sedimentation tank; preferably, a coagulant is provided in the T1 rapid reaction coagulation tank; a flocculant is provided in the T2 magnetic medium mixing reaction tank; more preferably, the coagulant is selected from polyaluminum chloride and/or polyferric chloride; the flocculant is selected from polyacrylamide. In order to better adsorb and precipitate polycyclic aromatic hydrocarbons, magnetic _Fe3O4 powder can be added to the _T2 magnetic medium in an amount of 0.5 to 1 mg/L.

In any embodiment of the present application, the ozone reaction tank includes a connected reaction tank and a clean water tank, the reaction tank is connected to the sedimentation tank, and the clean water tank is connected to the microbubble generating system.

In any embodiment of the present application, the ozone reaction tank further includes an aeration disk connected to an ozone generator.

In any embodiment of the present application, the ozone generator is used to add ozone, and the dosage of the ozone is 3-8 mg/L.

The third aspect of the present application provides the use of the aforementioned treatment method or the aforementioned treatment device in purifying urban drainage overflow pollution.

Compared with the prior art, the beneficial effects of this application are:

The present application adopts coagulant, flocculant + multi-stage anoxic aerobic environment + micro-nano bubble ozone + catalyst to achieve the purpose of controlling polycyclic aromatic hydrocarbons in overflow pollution of urban drainage pipe network. The combined process has high removal efficiency, cost saving and can be widely used.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of the structure of the processing device of the present application.

FIG. 2 is a detailed schematic diagram of the processing device of the present application.

FIG. 3 is a diagram of a multi-stage AO pool of the treatment device of the present application.

FIG. 4 is a structural diagram of a coagulation tank and a sedimentation tank of the treatment device of the present application.

Component number description:

1 Grille

2 Pre-washing tank

3 multi-level AO pool

30 Water inlet pipe

31 Hypoxic Zone

311 Anoxic Agitator

32 Aerobic Zone

321 aeration pipe

33 water outlet pipe

4 Coagulation tank

41T1 Rapid Response Coagulation Tank

42T2 magnetic medium mixing reaction tank

5 Sedimentation Tanks

6Ozone reaction tank

61 discharge port

62 stirring device

63 Clear Water Pool

64 aeration plate

65 reaction pool

7Micro bubble generation system

71 Gas-liquid circulation pump

72 gas-liquid releaser

73 Vacuum gauge

74 Gas flow meter

75Y filter

8. Ozone Generator

Detailed ways

In order to make the invention purpose, technical scheme and beneficial effect of the present application clearer, the present application is further described below in conjunction with the examples. It should be understood that the examples are only used to explain the present application and are not used to limit the scope of the application. The test methods used in the following examples are conventional methods unless otherwise specified, and those familiar with the technology can easily understand other advantages and effects of the present application from the contents disclosed in this description.

After extensive exploration and research, the inventor of this application discovered a method and device for treating polycyclic aromatic hydrocarbons in urban drainage overflow pollution, and completed this application on this basis.

The first aspect of the present application provides a method for treating polycyclic aromatic hydrocarbons in urban drainage overflow pollution, comprising the following steps:

S1: Screening and removing solid matter from urban drainage overflow sewage to obtain first treated water;

S2: pre-washing the first treated water to obtain second treated water;

S3: placing the second treated water in an anoxic environment and an aerobic environment to react to obtain third treated water;

S4: reacting the third treated water with a coagulant and a flocculant, and removing the precipitate to obtain a fourth treated water;

S5: treating the fourth treated water with micro-nano bubbles, ozone and a catalyst to obtain water after removing polycyclic aromatic hydrocarbons.

In the treatment method provided in the present application, step S1 refers to screening the urban drainage overflow sewage to remove solid matter and obtain the first treated water. The solid matter includes one or more of gravel, branches, towels, and paper. In step S1, the screening is carried out in the grid; preferably, the flow rate of the urban drainage overflow sewage in the grid is 0.7-0.9 m/s; the water flow rate in front of the grid is 0.6-0.7 m/s; the water depth in front of the grid is 0.15-0.25 m. The purpose of step S1 is to remove solid matter, such as larger suspended matter, floating matter, and fibrous matter in sewage, to ensure the normal operation of subsequent treatment units and water pumps, thereby reducing the processing load of subsequent treatment units and avoiding blockage of sludge pipes.

In the treatment method provided in the present application, step S2 refers to pre-eluting the first treated water to obtain the second treated water. The pre-eluting separates the sludge and the sewage by stirring the first treated water, dissolving the polycyclic aromatic hydrocarbons in the organic particles into the sewage, and obtaining the second treated water. The pre-eluting time is 20 to 30 minutes. The role of the pre-eluting is to better separate the particles from the soluble organic matter. In some embodiments, the pre-eluting can be performed in the pre-eluting tank 2.

In the treatment method provided in the present application, step S3 refers to placing the second treated water in an anoxic environment and an aerobic environment for reaction to obtain the third treated water. Among them, the volume ratio of the anoxic environment and the aerobic environment is 1:1.5-2.5; specifically, it can be 1:1.5-1.7, 1:1.7-2, or 1:2-2.5, etc. In step S3, the second treated water enters the anoxic environment and the aerobic environment in batches according to a certain proportion, so that the second treated water can be fully purified. Preferably, the batches of the second treated water are 3-5 batches. In step S3, the second treated water is divided into 3 batches, and the water intake of the first batch: the second batch: the third batch is 40%:40%:30%. The volume ratio of the anoxic environment and the aerobic environment in the first batch: the second batch: the third batch is 1:1:2. In step S3, the reaction time of the second treated water in the anoxic environment is 3-5h, and the reaction time in the aerobic environment is 7-9h. In some embodiments, step S3 can be performed in a multi-stage AO tank 3. The purpose of step S3 is to further remove organic matter, TN, TP, polycyclic aromatic hydrocarbons and other substances.

In the treatment method provided by the present application, step S4 refers to reacting the third treated water with a coagulant and a flocculant, and removing the precipitate to obtain the fourth treated water. Wherein, the coagulant is selected from polyaluminium chloride (PAC) and/or polyferric chloride; the flocculant is selected from polyacrylamide (PAM) and magnetic Fe ₃ O ₄ powder. The dosage of magnetic Fe ₃ O ₄ powder is 0.5-1 mg/L; specifically, it can be 0.5-0.7 mg/L, 0.7-0.8 mg/L, or 0.8-1 mg/L, etc. The function of magnetic Fe ₃ O ₄ powder is to better adsorb and precipitate polycyclic aromatic hydrocarbons. In step S4, when the third treated water reacts with the coagulant and the flocculant, mechanical stirring and frequency conversion control are adopted to make the average surface water load 8-12 m ³ /m ² ·h. The reaction time of the third treated water with the coagulant is 5-10 min. The reaction time of the third treated water with the flocculant is 5-10 min. The reaction time of the third treated water to remove the precipitate is 20-30 min. In some embodiments, step S4 can be performed in the coagulation tank 4 and the sedimentation tank 5. In a specific embodiment of the present application, the third treated water first reacts with the coagulant PAC, and then the coagulant and the sewage mixture are quickly stirred to make them quickly mixed and uniform, and then react with the flocculant and stir at high speed, and finally remove the precipitate to obtain the fourth treated water. The purpose of step S4 is to further remove substances such as SS and TP to prevent clogging of subsequent reaction pipelines.

In the treatment method provided in the present application, step S5 refers to treating the fourth treated water with micro-nano bubbles, ozone and a catalyst to obtain water after removing polycyclic aromatic hydrocarbons. Among them, the dosage of ozone is 3-8 mg/L; specifically, it can be 3-5 mg/L, 5-7 mg/L, or 7-8 mg/L. Ozone and clean water are pressurized and vacuumed to obtain a gas-liquid mixture containing micro-nano bubbles; preferably, the vacuum degree of the vacuum pumping is 0.025-0.03Mpa; specifically, it can be 0.025-0.027Mpa, 0.027-0.0028Mpa, or 0.028-0.03Mpa. The pressure of the pressurization is 0.25-0.40MPa; specifically, it can be 0.25-0.30MPa, 0.30-0.35MPa, or 0.35-0.40MPa. Based on the total volume of the gas-liquid mixture, the gas content therein is 5-10%; specifically, it can be 5-8%, 8-9%, or 9-10%. The flow rate of the gas in the gas-liquid mixture is 7-8L/min; specifically, it can be 7-7.2L/min, 7.2-7.5L/min, or 7.5-8L/min. The flow rate of the liquid in the gas-liquid mixture is 5-6L/min; specifically, it can be 5-5.2L/min, 5.2-5.5L/min, or 5.5-6L/min. Based on the total volume of the gas, the volume proportion of micro-nano bubbles is 60-80%; specifically, it can be 60-65%, 65-70%, or 70-80%. Ozone is a strong oxidant with a high redox potential. It can directly or indirectly react with polycyclic aromatic hydrocarbons. Micro-nano bubbles have special physical and chemical properties. Ordinary bubbles quickly rise to the water surface and burst and disappear. Micro-nano bubbles rise slowly and exist for a long time, which can effectively improve the utilization rate of ozone. Therefore, micro-bubble ozone can further reduce polycyclic aromatic hydrocarbons. In some embodiments, the catalyst is selected from manganese ferrite, and the dosage of the catalyst is 0.1-0.5 mg/L; specifically, it can be 0.1-0.3 mg/L, 0.3-0.4 mg/L, or 0.4-0.5 mg/L. The catalyst manganese ferrite MnFe ₂ O ₄ , preferably nano manganese ferrite MnFe ₂ O _4, has a spinel structure, and Fe ³⁺ can better excite ozone to produce free radicals and degrade refractory organic matter. At the same time, Mn ²⁺ plays a certain catalytic role in ozone. Therefore, the micro-nano bubbles, ozone and catalyst in step S5 can work together to more comprehensively and effectively remove polycyclic aromatic hydrocarbons. In some embodiments, step S5 can be performed using an ozone reaction tank 6 , a microbubble generating system 7 and an ozone generator 8 .

The second aspect of the present application provides a device for treating polycyclic aromatic hydrocarbons in urban drainage overflow pollution, as shown in Figure 1, comprising a grid 1, a pre-elution tank 2, a multi-stage AO tank 3, a coagulation tank 4, a sedimentation tank 5, and an ozone reaction tank 6 connected in sequence; the ozone reaction tank 6 is connected to an ozone generator 8 via a microbubble generating system 7. The device of the present application has a simple structure, occupies a small area, and is conducive to industrial application.

In the treatment device provided in the present application, the grid 1 is used to remove solid matter, such as larger suspended matter, floating matter, and fibrous matter in sewage, to ensure the normal operation of subsequent treatment units and water pumps, thereby reducing the processing load of subsequent treatment units and avoiding blockage of sludge discharge pipes.

In the treatment device provided in the present application, the pre-elution tank 2 is used to dissolve the polycyclic aromatic hydrocarbons in the organic particles into the sewage, so as to better separate the particles from the soluble organic matter.

In the treatment device provided in the present application, as shown in FIG3 , the multi-stage AO pool 3 includes a plurality of connected anoxic zones 31 and aerobic zones 32; the anoxic zone 31 is connected to the pre-elution pool 2, and the aerobic zone 32 is connected to the coagulation pool 4; preferably, the volume ratio of the anoxic zone 31 and the aerobic zone 32 is 1:1.5-2.5. The multi-stage AO pool 3 adopts a multi-stage AO pool sewage treatment process with divided water inlet, and the number of reactor sections of the anoxic zone 31 and the aerobic zone 32 is generally selected from 3 to 5 levels. The amount of sewage to be treated enters each level of anoxic section according to a certain proportion, so that the sewage is purified. Preferably, the number of reactor sections of the anoxic zone 31 and the aerobic zone 32 is 3, and the water inlet of each level is 40%:40%:30% respectively.

In some embodiments, as shown in Fig. 3, an anoxic zone 31 is provided with an anoxic stirrer 311 for stirring and mixing and maintaining an anoxic environment. An aeration pipe 321 is provided at the bottom of the aerobic zone 32 for providing air.

In some embodiments, as shown in FIG3 , the multi-stage AO tank 3 further includes an inlet pipe 30 and an outlet pipe 33. The inlet pipe 30 is arranged at the bottom of the first-stage anoxic zone and is connected to the pre-elution tank 2. The outlet pipe 33 is arranged at the top of the last-stage aerobic zone 32 and is connected to the coagulation tank 4. The function of the multi-stage AO tank 3 is to further remove organic matter, TN, TP, polycyclic aromatic hydrocarbons and other substances.

In the treatment device provided by the present application, as shown in FIG4 , the coagulation tank 4 includes a connected T1 rapid reaction coagulation tank 41 and a T2 magnetic medium mixing reaction tank 42; the T1 rapid reaction coagulation tank 41 is connected to the multi-stage AO tank 3, specifically, the T1 rapid reaction coagulation tank 41 is connected to the outlet pipe 33. The T2 magnetic medium mixing reaction tank 42 is connected to the sedimentation tank 5; preferably, a coagulant is provided in the T1 rapid reaction coagulation tank 41; a flocculant is provided in the T2 magnetic medium mixing reaction tank 42; more preferably, the coagulant is selected from polyaluminum chloride and/or polyferric chloride; the flocculant is selected from polyacrylamide and magnetic Fe ₃ O ₄ powder. The dosage of magnetic Fe ₃ O ₄ powder is 0.5-1 mg/L; specifically, it can be 0.5-0.7 mg/L, 0.7-0.8 mg/L, or 0.8-1 mg/L, etc. The function of magnetic Fe ₃ O ₄ powder is to better adsorb and precipitate polycyclic aromatic hydrocarbons. Coagulants and flocculants can make particles that are difficult to settle in the water aggregate to form colloids, which then combine with impurities in the water to form larger flocs. Flocs have strong adsorption capacity and can not only adsorb suspended matter, but also some bacteria and soluble substances. Through adsorption, flocs increase in volume and sink.

In the treatment device provided by the present application, as shown in Figure 4, the sedimentation tank 5 adopts upward flow inclined plate (tube) sedimentation. The function of the coagulation tank 4 and the sedimentation tank 5 is to further remove substances such as SS and TP to prevent clogging of subsequent reaction pipelines.

In the treatment device provided by the present application, as shown in FIG2 , the ozone reaction tank 6 includes a connected reaction tank 65 and a clean water tank 63, the reaction tank 65 is connected to the sedimentation tank 5, and a stirring device 62 is provided in the reaction tank 65 for stirring and accelerating the reaction between sewage and microbubble ozone. The clean water tank 63 is connected to the gas-liquid circulation pump 71 in the microbubble generating system 7, and the clean water tank 63 includes clean water. An aeration disk 64 is provided in the reaction tank 65, which is connected to the ozone generator 8 for discharging ozone in the ozone generator 8.

In the treatment device provided by the present application, as shown in Figure 2, the microbubble generating system 7 includes a connected gas-liquid circulation pump 71 and a gas-liquid releaser 72, and the gas-liquid releaser 72 is connected to the reaction tank 65; the gas-liquid circulation pump 71 is connected to the ozone generator 8; preferably, the gas-liquid circulation pump 71 is used to pressurize and vacuum the gas introduced into the ozone generator 8 and the liquid introduced into the clean water tank 63 to obtain a gas-liquid mixture containing micro-nano bubbles, and discharge it into the reaction tank 65 through the gas-liquid releaser 72 to react with the sewage in the reaction tank 65; more preferably, the vacuum degree of the vacuum extraction is 0.025~0.03Mpa; specifically, it can be 0.025~0.027Mpa, 0.027~0.0028Mpa, or 0.028~0.03Mpa, etc. The pressurized pressure is 0.25-0.40 MPa; specifically, it can be 0.25-0.30 MPa, 0.30-0.35 MPa, or 0.35-0.40 MPa.

The stable operation mode of the gas-liquid circulation pump 71 is to first adjust the liquid flow rate introduced into the clear water tank 63, control the vacuum degree at 0.025-0.03Mpa, and then gradually adjust the gas flow rate introduced into the ozone generator 8. Under this condition, the gas-liquid circulation pump 71 can operate smoothly. If the adjustment is not made in this way, the operation of the gas-liquid circulation pump 71 is not stable, so that the content of ozone and micro-nano bubbles in the discharged gas-liquid mixture cannot meet the treatment requirements. Unless otherwise specified, the flow rate and flow rate of this application have the same meaning. Based on the total volume of the gas-liquid mixture, the gas content therein is 5-10%; specifically, it can be 5-8%, 8-9%, or 9-10%, etc. The flow rate of the gas in the gas-liquid mixture is 7-8L/min; specifically, it can be 7-7.2L/min, 7.2-7.5L/min, or 7.5-8L/min, etc. The flow rate of the liquid in the gas-liquid mixture is 5-6 L/min; specifically, it can be 5-5.2 L/min, 5.2-5.5 L/min, or 5.5-6 L/min, etc. Based on the total volume of the gas, the volume proportion of the micro-nano bubbles is 60-80%; specifically, it can be 60-65%, 65-70%, or 70-80%, etc.

In the treatment device provided in the present application, the ozone generator 8 is used to add ozone, and the dosage of the ozone is 3 to 8 mg/L; specifically, it can be 3 to 5 mg/L, 5 to 7 mg/L, or 7 to 8 mg/L, etc. Ozone can undergo an oxidation reaction with polycyclic aromatic hydrocarbons, and the micro-nano bubbles rise slowly and exist for a long time, which can effectively improve the utilization rate of ozone. When the micro-bubble generating system 7 works stably, the micro-nano bubbles in the reaction tank 65 shrink by themselves, the volume becomes smaller, and the rising speed becomes slower, so the ozone solubility can be improved, thereby reducing the ozone loss rate. At this time, the ozone dosage can be gradually reduced to 3 to 4 mg/L. Therefore, the present application adopts a specific treatment method, which can not only use micro-nano bubble ozone to further reduce polycyclic aromatic hydrocarbons, but also use the volume change of micro-nano bubbles to reduce the amount of ozone, so as to meet the requirements of removing polycyclic aromatic hydrocarbons.

In some embodiments, the reaction pool 65 also includes a catalyst manganese ferrite, and the amount of the catalyst added is 0.1-0.5 mg/L; specifically, it can be 0.1-0.3 mg/L, 0.3-0.4 mg/L, or 0.4-0.5 mg/L. Manganese ferrite MnFe ₂ O ₄ is preferably nano manganese ferrite MnFe ₂ O ₄ , which has a spinel structure, and Fe ³⁺ can better excite ozone to produce free radicals and degrade refractory organic matter. At the same time, Mn ²⁺ plays a certain catalytic role on ozone. Therefore, micro-nano bubbles, ozone and catalysts can work together to more comprehensively and effectively remove polycyclic aromatic hydrocarbons.

In the treatment device provided in the present application, the gas-liquid circulation pump 71 utilizes the clean water in the clean water tank 63 to fully mix with the ozone in the ozone generator 8 and pressurizes and evacuates to produce microbubble ozone water, and the microbubble ozone water flows back to the ozone reaction tank 6, continuously providing microbubble ozone water to the ozone reaction tank 6, where the microbubble ozone water fully reacts with polycyclic aromatic hydrocarbons.

In the treatment device provided by the present application, as shown in FIG2 , a Y-type filter 75, a vacuum meter 73 and a gas flow meter 74 connected in sequence are also provided between the gas-liquid circulation pump 71 and the clean water tank 63. Among them, the Y-type filter 75 is used to remove impurities to protect the normal use of valves and equipment. The vacuum meter 73 is used to detect the vacuum degree in the gas-liquid circulation pump 71, and the gas flow meter is used to detect the flow rate of ozone delivered by the ozone generator 8. Ozone in the ozone reaction tank 6 undergoes an oxidation reaction with polycyclic aromatic hydrocarbons, and micro-nano bubbles effectively improve the utilization rate of ozone, and micro-bubble ozone can further reduce polycyclic aromatic hydrocarbons.

In the treatment device provided in the present application, as shown in FIG. 2 , a discharge port 61 is also provided at the bottom of the ozone reaction tank 6 for discharging the treated sewage. The sewage treated by the treatment device of the present application can effectively control polycyclic aromatic hydrocarbons.

The third aspect of the present application provides the use of the aforementioned treatment method or the aforementioned treatment device in purifying urban drainage overflow pollution. The present application can achieve efficient removal of polycyclic aromatic hydrocarbons in urban overflow pollution.

The present application is further described below by way of examples, but the scope of the present application is not limited thereby.

Example 1

Taking the urban overflow sewage with a treatment scale of 100m ³ /d as an example, the following method is adopted and the treatment is carried out in the treatment device shown in Figures 1 to 4:

S1: Screening the overflow sewage from urban drainage in the grid 1 to obtain the first treated water;

S2: pre-washing the first treated water in the pre-washing tank 2 to obtain second treated water;

S3: placing the second treated water in the multi-stage AO tank 3 for reaction to obtain third treated water;

S4: treating the third treated water in the coagulation tank 4 and the sedimentation tank 5 to obtain fourth treated water;

S5: The fourth treated water is treated in the ozone reaction tank 6 with micro-nano bubbles, ozone and catalyst manganese ferrite to obtain water after the polycyclic aromatic hydrocarbons are removed.

Among them, the parameters of the grid 1 are: width B = 0.8m, channel depth 2m, grid spacing b = 20mm, and the power of the water pump in the grid N = 1.1kW.

The multi-stage AO pool 3 has a total of 6 partitions, and the expenditures of each partition are L×B×H=1.1m×2.5m×2m (anoxic zone 31), L×B×H=1.4m×2.5m×2m (aerobic zone 32), L×B×H=1.1m×2.5m×2m (anoxic zone 31), L×B×H=1.4m×2.5m×2m (aerobic zone 32), L×B×H=1.1m×2.5m×2m (anoxic zone 31), and L×B×H=3.9m×2.5m×2m (aerobic zone 32).

The single tank size of the pre-elution tank 2 is L×B×H=1m×1m×2m.

In the coagulation tank 4: the single tank size of the T1 rapid reaction coagulation tank 41 is L×B×H=0.5m×0.5m×2m, and the single tank size of the T2 magnetic medium mixed reaction tank 42 is L×B×H=0.5m×0.5m×2m. The T1 rapid reaction coagulation tank 41 contains coagulants, which are polyaluminum chloride and polyferric chloride, and the T2 magnetic medium mixed reaction tank 42 contains flocculants, which are polyacrylamide and magnetic Fe ₃ O ₄ powder, and the dosage of the magnetic Fe ₃ O ₄ powder is 0.5 mg/L.

The single tank size of the sedimentation tank 5 is L×B×H=1m×1m×2m.

The vacuum degree at the inlet of the gas-liquid circulation pump 71 is 0.025MPa, the outlet pressure is 0.25-0.40MPa, the gas flow rate is 7-8L/min, the water flow rate is 5.0L/min at this time, the total volume of the microbubble ozone water is used as the benchmark, and the gas content therein is 10%. In this adjustment process, the stable operation mode is to first adjust the water flow rate introduced into the clear water tank 63, control the vacuum degree, and then gradually adjust the flow rate of the gas introduced into the ozone generator 8. Under this condition, the device can run smoothly, and a large number of micro-nano bubbles are generated in the reactor. The ozone dosage is 5mg/L. When the microbubble generating system 7 works stably, the bubbles shrink by themselves, the bubble volume becomes smaller, and the rising speed becomes slower. Therefore, the ozone solubility can be improved, thereby reducing the ozone loss rate. At this time, the ozone dosage can be gradually reduced to 3-4mg/L. In order to better degrade polycyclic aromatic hydrocarbons, nano catalyst material _{manganese ferrite MnFe2O4 is} added to the ozone reaction tank 6, and the dosage is 0.2mg/L. The nano catalyst material _manganese ferrite _MnFe2O4 has a spinel structure, and Fe3 ⁺ can better stimulate ozone to produce free radicals and degrade difficult-to-degrade organic matter. At the same time, Mn2 ⁺ plays a certain catalytic role on ozone. When the initial polycyclic aromatic hydrocarbon concentration in the urban overflow sewage is 10ug/L, the effluent concentration after treatment by the device is 2-3ug/L, and the treatment efficiency is (influent concentration-effluent concentration)/influent concentration = 70-80%.

Comparative Example 1

Taking the urban overflow sewage with a treatment scale of ^100m3 /d as an example, the following method is used for treatment:

S1: Screening the overflow sewage from urban drainage in the grid 1 to obtain the first treated water;

S2: pre-washing the first treated water in the pre-washing tank 2 to obtain second treated water;

S3: treating the second treated water in the coagulation tank 4 and the sedimentation tank 5 to obtain third treated water;

S4: The third treated water is treated with micro-nano bubbles and ozone in the ozone reaction tank 6 to obtain water after the polycyclic aromatic hydrocarbons are removed.

Among them, the parameters of the grid 1 are: width B = 0.8m, channel depth 2m, grid spacing b = 20mm, and the power of the water pump in the grid N = 1.1kW.

The single tank size of the pre-elution tank 2 is L×B×H=1m×1m×2m.

In the coagulation tank 4: the single tank size of the T1 rapid reaction coagulation tank 41 is L×B×H=0.5m×0.5m×2m, and the single tank size of the T2 magnetic medium mixed reaction tank 42 is L×B×H=0.5m×0.5m×2m. The T1 rapid reaction coagulation tank 41 contains coagulants, which are polyaluminum chloride and polyferric chloride, and the T2 magnetic medium mixed reaction tank 42 contains flocculants, which are polyacrylamide and magnetic Fe ₃ O ₄ powder, and the dosage of the magnetic Fe ₃ O ₄ powder is 0.5 mg/L.

The single tank size of the sedimentation tank 5 is L×B×H=1m×1m×2m.

The vacuum degree of the gas-liquid circulation pump 71 inlet is 0.025MPa, the outlet pressure is 0.25-0.40MPa, the gas flow rate is 7-8L/min, the water flow rate is 5.0L/min, the total volume of the microbubble ozone water is used as the benchmark, and the gas content is 10%. Under this condition, the device runs smoothly, a large number of micro-nano bubbles are generated in the reactor, the ozone dosage is 5mg/L, when the initial polycyclic aromatic hydrocarbons concentration in the urban overflow sewage is 10ug/L, the effluent concentration after treatment by this device is 4-5ug/L, and the treatment efficiency is (influent concentration-effluent concentration)/influent concentration = 50-60%

Comparative Example 1 lacks multi-stage AO treatment and catalyst manganese ferrite, and it can be seen that the PAH treatment efficiency is lower than that of Example 1.

In summary, the present application adopts coagulant, flocculant + multi-stage anoxic aerobic environment + micro-nano bubble ozone + catalyst to achieve the purpose of controlling polycyclic aromatic hydrocarbons in overflow pollution of urban drainage network and meet the requirements of removing polycyclic aromatic hydrocarbons. The overall combined process of the present application has high removal efficiency and cost saving and can be widely used.

The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present application. Anyone familiar with the technology may modify or change the above embodiments without violating the spirit and scope of the present application. Therefore, all equivalent modifications or changes made by a person of ordinary skill in the art without departing from the spirit and technical ideas disclosed by the present invention shall still be covered by the claims of the present application.

Claims (10)

1. A treatment method of polycyclic aromatic hydrocarbon in urban drainage overflow pollution comprises the following steps:

s1: screening urban drainage overflow sewage to remove solid matters to obtain first treated water;

S2: pre-panning the first treated water to obtain second treated water;

S3: placing the second treated water in an anoxic environment and an aerobic environment for reaction to obtain third treated water;

S4: reacting the third treated water with a coagulant and a flocculant, and removing the precipitate to obtain fourth treated water;

s5: and (3) treating the fourth treated water by micro-nano bubbles, ozone and a catalyst to obtain water from which the polycyclic aromatic hydrocarbon is removed.

2. The process according to claim 1, wherein in step S1, the solid matter comprises one or more of crushed stone, branches, towels, paper;

And/or, in step S1, the screening is performed in a grid; the flow rate of the urban drainage overflow sewage passing through the grid is 0.7-0.9 m/s; the water flow speed in front of the grille is 0.6-0.7 m/s; the depth of water in front of the grille is 0.15-0.25 m.

3. The treatment method according to claim 1, wherein in step S2, the pre-panning separates sludge and sewage by stirring the first treated water, and dissolves polycyclic aromatic hydrocarbon in the organic matter particles into the sewage to obtain second treated water;

And/or, in the step S2, the pre-panning time is 20-30 min.

4. The method according to claim 1, wherein in step S3, the volume ratio of the anoxic environment to the aerobic environment is 1:1.5 to 2.5;

and/or, in step S3, the second treated water is fed into an anoxic environment and an aerobic environment in batches; the batches of the second treatment water are 3-5 batches;

And/or in the step S3, the reaction time of the second treated water in the anoxic environment is 3-5 h, and the reaction time in the aerobic environment is 7-9 h.

5. The method according to claim 4, wherein in step S3, the second water 3 lot is processed, and the 1 st lot: batch 2: the water inflow of batch 3 was 40%:40%:30%; batch 1: batch 2: the volume ratio of the anoxic environment to the aerobic environment in the 3 rd batch is 1:1:2.

6. The process according to claim 1, wherein in step S4, the coagulant is selected from polyaluminium chloride and/or polyaluminium chloride; the flocculant is polyacrylamide and magnetic Fe ₃O₄ powder; preferably, the adding amount of the magnetic Fe ₃O₄ powder is 0.5-1 mg/L;

And/or, in the step S4, when the third treated water reacts with the coagulant and the flocculant, mechanical stirring is adopted, so that the average surface water load is 8-12 m ³/m² & h;

And/or in the step S4, the reaction time of the third treated water and the coagulant is 5-10 min;

And/or in the step S4, the reaction time of the third treated water and the flocculating agent is 5-10 min;

And/or in the step S4, the reaction time for removing the sediment of the third treatment water is 20-30 min.

7. The method according to claim 1, wherein in step S5, the catalyst is selected from manganese ferrite, and the catalyst is added in an amount of 0.1 to 0.5mg/L;

And/or the ozone adding amount is 3-8 mg/L;

and/or, in the step S5, pressurizing and vacuumizing the ozone and the clean water to obtain a gas-liquid mixture containing micro-nano bubbles; preferably, the vacuum degree of the vacuumizing is 0.025-0.03 Mpa; the pressurizing pressure is 0.25-0.40 MPa; taking the total volume of the gas-liquid mixture as a reference, wherein the gas content is 5-10%; the flow rate of the gas in the gas-liquid mixture is 7-8L/min; the flow rate of the liquid in the gas-liquid mixture is 5-6L/min; more preferably, the micro-nano bubbles occupy 60 to 80% by volume based on the total volume of the gas.

8. A treatment device for polycyclic aromatic hydrocarbon in urban drainage overflow pollution comprises a grid (1), a pre-elutriation tank (2), a multistage AO tank (3), a coagulation tank (4), a sedimentation tank (5) and an ozone reaction tank (6) which are connected in sequence; the ozone reaction tank (6) is connected with an ozone generator (8) through a micro-bubble generation system (7).

9. The treatment device according to claim 8, wherein the microbubble generation system (7) comprises a gas-liquid circulation pump (71) and a gas-liquid releaser (72) connected, the gas-liquid releaser (72) being connected to the ozone reaction tank (6); the gas-liquid circulating pump (71) is connected with the ozone generator (8); preferably, the gas-liquid circulating pump (71) is used for pressurizing and vacuumizing the introduced gas and liquid to obtain a gas-liquid mixture containing micro-nano bubbles; more preferably, the vacuum degree of the vacuuming is 0.025-0.03 Mpa; the pressurizing pressure is 0.25-0.40 MPa; taking the total volume of the gas-liquid mixture as a reference, wherein the gas content is 5-10%; the flow rate of the gas in the gas-liquid mixture is 7-8L/min; the flow rate of the liquid in the gas-liquid mixture is 5-6L/min; taking the total volume of the gas as a reference, the volume ratio of micro-nano bubbles is 60-80%;

And/or, the multistage AO pool (3) comprises a plurality of connected anoxic zones (31) and aerobic zones (32); the anoxic zone (31) is connected with the pre-elutriation tank (2), and the aerobic zone (32) is connected with the coagulation tank (4); preferably, the volume ratio of the anoxic zone (31) to the aerobic zone (32) is 1:1.5 to 2.5;

And/or the coagulation tank (4) comprises a T1 rapid reaction coagulation tank (41) and a T2 magnetic medium mixing reaction tank (42) which are connected; the T1 rapid reaction coagulation tank (41) is connected with the multistage AO tank (3), and the T2 magnetic medium mixing reaction tank (42) is connected with the sedimentation tank (5); preferably, a coagulant is arranged in the T1 rapid reaction coagulation tank (41); a flocculating agent is arranged in the T2 magnetic medium mixing reaction tank (42); more preferably, the coagulant is selected from polyaluminium chloride; the flocculant is selected from polyacrylamide;

and/or the ozone reaction tank (6) comprises a reaction tank (65) and a clean water tank (63) which are connected, and the reaction tank (65) is connected with the sedimentation tank (5); the clean water tank (63) is connected with the micro-bubble generation system (7);

and/or the ozone reaction tank (6) also comprises an aeration disc (64) which is connected with an ozone generator (8);

and/or the ozone generator (8) is used for adding ozone, and the adding amount of the ozone is 3-8 mg/L.

10. Use of a treatment process according to any one of claims 1 to 7 or a treatment apparatus according to any one of claims 8 to 9 for purifying urban drainage overflow pollution.