A diffuse light fogging device and method of use suitable for advanced removal of perfluorinated compounds from wastewater treatment plant effluent

Abstract

The application discloses a dispersion type light atomization device suitable for deep removal of perfluorinated compounds in tail water of a sewage plant and a use method, and the device comprises a reactor main body, an ultraviolet lamp group and an external system. The inner wall of the reactor main body is an aluminum film mirror surface with a protective layer; the top is provided with a rotary three-nozzle atomization nozzle; the top is provided with an air outlet pipe; the side of the main body is provided with an air inlet; the bottom is provided with a water tank, and the water tank is provided with a condensing system and a water outlet pipe below. The ultraviolet lamp group has two groups of upper and lower lamps, each group has three lamp tubes with a main wavelength of 185 nm and three lamp tubes with a main wavelength of 254 nm, and the lamp tubes are distributed at intervals, and an air stirrer is located on both sides of the lamp tubes; the two groups of lamp tubes are provided with a funnel-shaped reflection buffer. The external system has an atomization system and an air system. The application utilizes atomization and ultraviolet irradiation to manufacture a micro-ozone environment, so that the flow state operation is used to improve the ozone yield and the mass transfer efficiency of the ozone, the ozone manufacturing cost is reduced, the utilization rate of the ozone is improved, the removal rate of the perfluorinated compounds is enhanced, and the device has the advantages of small occupation area and convenient use.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment, and in particular to a process for the deep treatment of perfluorinated compounds in wastewater effluent from wastewater treatment plants. Background Technology

[0002] Currently, treating perfluorinated compounds in water faces multiple challenges. Traditional filtration and biological processes are largely ineffective. While highly efficient technologies exist (such as adsorption with specialized resins and advanced oxidation-reduction processes), they generally suffer from high costs, enormous energy consumption, and the generation of high-concentration concentrates or the need for complex combined systems. For numerous small industrial areas with dispersed emissions and limited financial and technological capabilities, introducing and stably operating such complex and expensive advanced treatment systems is extremely difficult, making it practically impossible to effectively block perfluorinated compound pollution.

[0003] Most industrial parks nowadays are equipped with conventional wastewater treatment processes, but the problem of perfluorinated compounds in the effluent often exceeds standards, necessitating advanced treatment. Ozone, as a common wastewater treatment method, can effectively remove perfluorinated compounds due to its strong oxidizing properties, but its widespread adoption faces the following challenges:

[0004] (1) Ozone preparation and storage are difficult and energy consumption is high. Ozone generators rely on high-voltage discharge, resulting in high equipment investment and maintenance costs; the power consumption to produce 1 kg of ozone is as high as 10-15 kWh, leading to significant operating costs. Ozone is only slightly soluble in water, requiring a high-efficiency contact reaction device, which occupies a large area. In addition, ozone is easily decomposed and cannot be stored, requiring on-site preparation. Furthermore, its use process easily generates byproducts such as bromate, and tail gas treatment also increases the complexity of the system. These factors together restrict its application, especially in small-scale water treatment.

[0005] (2) Low system mass transfer efficiency and slow processing. In water treatment oxidation processes, mass transfer efficiency is often the core limiting factor. Taking ozone as an example, its low solubility and low diffusion rate in water severely limit its effective transfer to the pollutant interface. Even if sufficient ozone is added, if the gas-liquid contact is insufficient, the mixing intensity is inadequate, or the reaction time is short, the ozone cannot fully contact and react with the target pollutant, which will directly lead to a significant decrease in oxidation efficiency.

[0006] (3) Traditional ozone oxidation methods have limited oxidizing activity and low efficiency. The core problem with traditional ozone oxidation for treating perfluorinated compounds is the insufficient direct oxidizing ability of ozone molecules. The CF bond energy of perfluorinated compounds is around 500 kJ / mol, which is difficult for ozone to attack directly. However, hydroxyl radicals, which have stronger oxidizing power, can effectively break long chains. However, as a byproduct of traditional ozone processes, hydroxyl radicals have low concentrations and short durations, resulting in low removal rates and high energy consumption for perfluorinated compounds, making it difficult to achieve efficient degradation in an engineered manner.

[0007] Therefore, in view of the problems of the prior art, the present invention proposes a diffuse photo-atomization device and its usage method for the deep removal of perfluorinated compounds in wastewater effluent. The invention atomizes the effluent and mixes it thoroughly with ozone generated by ultraviolet light to efficiently remove perfluorinated compounds. The main advantages of the present invention include (1) simple and low cost of ozone generation. Ozone is generated in the reactor by irradiation with ultraviolet light of a specific wavelength. After the ozone is generated, it can come into contact with perfluorinated compounds, saving the cost of traditional ozone generation and storage. (2) improved system mass transfer efficiency and fast processing. The effluent is dispersed into water mist, and the perfluorinated compounds dissolved in it have a larger contact area with ozone. In addition, the gas in the reactor is in a flow state, which increases the probability of water mist contacting ozone. (3) multiple reactions complement each other and have high efficiency. The ozone and hydroxyl radicals generated during the reaction are both strong oxidants that can remove perfluorinated compounds. The high energy of ultraviolet light itself also has the function of photolysis of some fluoride precursors, further increasing the treatment efficiency of perfluorinated compounds in the effluent. The advantages and disadvantages of this equipment in removing perfluorinated compounds compared to traditional ozone treatment processes are shown in Table 1.

[0008] Table 1. Process Comparison

[0009] Ozone oxidation This process Advantages: 1. No chemical reagents are required, and there is no risk of secondary pollution; 2. No intermediate products are generated. Inheritance: 1. No reagents are needed; ozone is decomposed using ultraviolet light; 2. It belongs to advanced oxidation, resulting in thorough decomposition. Disadvantages: 1. Ozone preparation and storage are difficult and energy consumption is high; 2. The system has low mass transfer efficiency and slow processing; 3. Ozone oxidation has a limited variety of active molecules and low efficiency. Improvements: 1. UV-generated ozone, produced and used immediately; 2. Fluidized bed operation, high contact probability; 3. Complementary effects of UV light, ozone, and hydroxyl radical removers, resulting in improved removal efficiency. Summary of the Invention

[0010] To address the problems of existing technologies, this invention provides a diffused photo-atomization device and its application method suitable for the deep removal of perfluorinated compounds from wastewater treatment plant effluent. This device atomizes the effluent treated by traditional processes, creating a micro-ozone environment through ultraviolet irradiation. Fluidized operation enhances ozone yield and its contact efficiency with pollutants, forming a deep treatment mode through the combined action of ozone, hydroxyl radicals, and ultraviolet light. This invention is suitable for small-scale wastewater treatment plant effluent, effectively removing perfluorinated compounds from the effluent, and offers advantages such as low cost, high efficiency, and ease of application.

[0011] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0012] A diffused photo-atomization device suitable for the deep removal of perfluorinated compounds in wastewater effluent from sewage treatment plants includes a reactor body, an ultraviolet lamp assembly, and an external auxiliary system.

[0013] The reactor body is cylindrical, with a radius of 1m and a height of 4m, and its inner wall is made of a protective aluminum film mirror. The top of the reactor has a water inlet with a three-nozzle rotating atomizing nozzle; the bottom has a funnel-shaped water tank connected to an outlet pipe, and the water tank is made of alloy. A condenser is installed below the water tank. An air outlet pipe is located on the side of the top, bending upwards; air inlets are located on the sides of the main body at heights of 1.5m and 3.2m.

[0014] There are two sets of UV lamps. Each set has six UV lamps, two air stirrers, and one reflector. The UV lamps are 1m long, arranged in a ring, with three main wavelengths of 185nm and three main wavelengths of 254nm, spaced apart, and their on / off state controlled by a circuit. The air stirrers are fixed to the inner wall of the reactor at the same height as the bottom of each set of lamps, tilted upwards at a 60° angle to the inner wall. The first set is located in the upper half of the reactor, and the second set is in the lower half, separated by a reflector. The reflector is funnel-shaped, with the funnel wall made of aluminum film mirror coated with a protective layer, and the narrow opening having a mesh-like perforated structure; the reflector of the first set is located below its lamps, with the wide opening facing upwards; the reflector of the second set is located above its lamps, with the wide opening facing downwards.

[0015] The external systems include an atomization system and an air system. The atomization system consists of a booster pump and an atomizing compressor; water pipes connect sequentially to the tailwater storage tank, booster pump, atomizing compressor, and atomizing nozzles on the reactor body. The air system dries and filters the air before introducing it into the reactor through the air inlet.

[0016] This invention has the following advantages:

[0017] 1. Reduce ozone preparation and storage costs. This system eliminates the need for expensive traditional ozone-generating equipment such as high-voltage electricity, saving both money and space. Furthermore, ozone, being an unstable gas, requires specialized equipment for storage and transfer, often resulting in losses. In this system, water mist is directly mixed with the generated ozone, improving ozone utilization and avoiding storage costs.

[0018] 2. Enhanced ozone mass transfer efficiency. In this equipment, perfluorinated compounds are dissolved in water mist and move in a fluidized state with the water mist. The water mist acts as a carrier, allowing the perfluorinated compounds to fully contact ultraviolet light and ozone. In the water mist state, the surface area is greatly increased, increasing the contact probability and improving the mass transfer efficiency.

[0019] 3. Improve the removal rate of perfluorinated compounds. Ozone, as a strong oxidant, can remove some perfluorinated compounds. Furthermore, under ultraviolet light, ozone can generate hydroxyl radicals, which have stronger oxidizing properties, can break chemical bonds, decompose perfluorinated compounds, and achieve more thorough removal. In addition, ultraviolet light also has a photolytic effect on the precursors of fluorides.

[0020] 4. No risk of secondary pollution. The treatment process does not require the addition of additional chemical agents; ultraviolet light with a wavelength of 254nm will decompose ozone, and the remaining ozone is in trace amounts, which easily combines with other reducing substances or decomposes naturally, so there is almost no leakage.

[0021] 5. Easy to apply. The equipment is easy to disassemble, transport, and assemble. In addition to perfluorinated compounds, it can treat most common pollutants and can be flexibly used for temporary wastewater treatment projects or emergency treatment in industrial parks. The overall size of the device is small, making it suitable for upgrading and retrofitting wastewater treatment plants. Attached Figure Description

[0022] Figure 1 A front cross-sectional view of the present invention is shown.

[0023] Figure 2 A top-view cross-sectional view showing the distribution of the ultraviolet lamp arrays.

[0024] Figure 3 The diagram shows a top view of the reflective buffer and a schematic diagram of its reflective action.

[0025] Figure 4 The data graphs for ozone production and removal in Example 1 are shown.

[0026] Figure 5 The image shows a comparison between the wastewater treatment process of this equipment and that of traditional methods.

[0027] Among them are:

[0028] 1. Booster pump; 2. Atomizing compressor; 3. Rotary three-nozzle nozzle; 4. Ultraviolet lamp; 5. Air mixer; 6. Reflector damper; 7. Air inlet; 8. Air outlet; 9. Air system; 10. Condensation system. Detailed Implementation

[0029] The invention will now be explained in detail with reference to the illustrations and specific implementation schemes.

[0030] The reactor mechanism in this invention is as follows:

[0031] Step 1: Wastewater effluent from the wastewater treatment plant is stored in a storage tank and pumped to an atomizing compressor. Under pressure and the combined action of the nozzles, it is atomized into a water mist and sprayed into the reactor. The air system is then activated, and purified air enters the reactor through the air inlet.

[0032] In step 1, the central shaft of the atomizing nozzle rotates under the action of the motor, evenly dispersing water droplets in all directions. Due to the bend in the outlet pipe, the water mist condenses on the inner wall of the orifice and falls back into the reactor. The air intake rate V is calculated by the following formula:

[0033]

[0034]

[0035] In the formula, 'a' represents the ozone dosage, kg / m³. 3 S represents the theoretically required amount of ozone, kg / m³ 3This value is greatly affected by water quality and can be measured by sampling. The value is generally between 0.05 and 0.5 kg / m³. 3 K represents the ozone contact efficiency, %, ranging from 70% to 80%; V represents the air intake rate, kg / h; Q represents the influent flow rate, m³ / h. 3 / h; n represents the ozone production rate in the air, %, ranging from 1.5 to 2.5; 1.06 is the safety factor.

[0036] Step 2: Start the air mixer to mix the water mist and gas. Turn on different wavelengths of UV lamps at intervals; the on-time ratio of the 185nm and 254nm UV lamps is calculated. The UV light is reflected from the reflective buffer to all corners of the reactor. Under UV irradiation, ozone and hydroxyl radicals are generated, which come into contact with the water mist and remove perfluorinated compounds.

[0037] In step 2, at an ultraviolet wavelength of 185 nm, oxygen in the air gains photon energy and is converted into ozone, which removes perfluorinated compounds. The formula for generating ozone is shown below.

[0038] 3O2 + hν → 2O3

[0039] When the ultraviolet light wavelength shifts to 254 nm, ozone decomposes at this wavelength, generating more potent hydroxyl radicals. These radicals can break the CF bonds in perfluorinated compounds, causing chain scission and defluorination reactions, thus removing perfluorinated compounds more efficiently. Furthermore, this ozone decomposition prevents ozone from dispersing into the outside air and causing secondary pollution. Simultaneously, this wavelength of ultraviolet light can directly photodegrade some fluoride precursors, such as fluoroacetic acid and monofluoroethane. The formula for generating hydroxyl radicals is shown below.

[0040] O3 + H2O + hν → ·OH

[0041] The 185nm and 254nm UV lamps have a power of 44W. To ensure complete removal of pollutants and minimize ozone residue, their on-time ratio is calculated using the following formula, with the total on-time per cycle controlled within 5 minutes:

[0042]

[0043] In the formula, This indicates the ratio of the on-time of 185nm and 254nm ultraviolet lamps; This represents the safety factor, with a value ranging from 3 to 5. This represents the ratio of the rate at which 185nm and 254nm ultraviolet lamps generate and decompose ozone at the same power, with a value ranging from 20 to 50.

[0044] Step 3: After the first set of ultraviolet treatments, the water mist passes through a reflective buffer under gravity and enters the second set of ultraviolet lamps. The reaction here is the same as in the first set, which enhances the treatment of the effluent. Because a condensation device is installed under the bottom water tank, the water mist quickly condenses here, collects, and is discharged into the outlet pipe.

[0045] Example 1: Ozone Test

[0046] To ensure the normal operation of the equipment, its ozone production performance was tested by introducing pure water at a flow rate of 100 m³ / h. 3 / d, air inlet flow rate 50kg / h. Turn on the 185nm UV lamp for continuous irradiation, open the air inlet to extract gas for testing, and measure the ozone content. Repeat this experimental process. To test the equipment's ozone decomposition performance, the 185nm and 254nm UV lamps were turned on for 60s and 90s per cycle, respectively. Gas was extracted from the outlet during equipment operation for testing, and the test results are as follows. Figure 4 As shown.

[0047] The results show that the equipment produces stable ozone, and the concentration meets the treatment requirements. During the complete operating cycle, there is almost no ozone leakage.

[0048] Example 2: Treatment of perfluorinated compounds in high-concentration industrial wastewater

[0049] The main industry in this industrial park is chemical manufacturing. The wastewater source is perfluorinated compound washing wastewater. This wastewater was used as a test sample and introduced into the equipment at an influent flow rate of 100 m³ / h. 3 / d. The concentration of perfluorinated compounds is approximately 90 mg / L.

[0050] The intake rate V is calculated using the following formula:

[0051]

[0052]

[0053] In the formula, 'a' represents the ozone dosage, kg / m³. 3 S represents the theoretically required amount of ozone, kg / m³ 3 The sample measured 0.32 kg / m³. 3 K represents the ozone contact efficiency, %, with a value of 75; V represents the air intake rate, kg / h; Q represents the influent flow rate, with a value of 100m³. 3 / d; n represents the ozone production rate in the air, %, with a value of 2.5; 1.06 is the safety factor.

[0054] The calculated air intake flow rate of this equipment is 75.4 kg / h.

[0055]

[0056] In the formula, This indicates the ratio of the on-time of 185nm and 254nm ultraviolet lamps; This represents the safety factor, with a value of 4. This represents the ratio of the rate at which 185nm and 254nm ultraviolet lamps produce and decompose ozone at the same power, with a value of 20.

[0057] The UV lamp on-off interval ratio is 0.64, with the 185nm on-off duration being 64s and the 254nm on-off duration being 100s per cycle.

[0058] After starting the equipment and completing the reaction, the effluent was tested. The effluent quality after treatment is shown in Table 2. The results show that this equipment achieves a removal rate of up to 96% for perfluorinated compounds and has the advantages of a short start-up cycle and stable effluent quality, making it suitable for advanced wastewater treatment in industrial parks.

[0059] Table 2. Perfluorinated Compound Effluent Status

[0060] Time / d 1 2 3 4 5 6 7 Influent water quality (mg / L) 90.5 91.2 90.4 88.5 89.4 89.9 90.1 Effluent water quality (mg / L) 5.6 4.1 3.1 3.2 3.0 3.5 3.3 Removal rate (%) 93.8 95.5 96.6 96.5 96.6 96.1 96.3

[0061] Example 3: Treatment of perfluorinated compounds in municipal wastewater effluent

[0062] To determine the removal efficiency of the equipment for trace perfluorinated compounds in the effluent, a portion of the effluent was introduced from the wastewater treatment plant. The influent concentration was measured at 294 ng / L, and the influent flow rate was also 100 m³ / L. 3 / d.

[0063] The intake rate V is calculated using the following formula:

[0064]

[0065]

[0066] In the formula, 'a' represents the ozone dosage, kg / m³. 3 S represents the theoretically required amount of ozone, kg / m³ 3 The value is 0.05 kg / m 3 K represents the ozone contact efficiency, %, with a value of 75; V represents the air intake rate, kg / h; Q represents the influent flow rate, with a value of 100m³. 3 / d; n represents the ozone production rate in the air, %, with a value of 1.5; 1.06 is the safety factor.

[0067] The calculated air intake flow rate of this equipment is 19.6 kg / h.

[0068]

[0069] In the formula, This indicates the ratio of the on-time of 185nm and 254nm ultraviolet lamps; This represents the safety factor, with a value of 4. This represents the ratio of the rate at which 185nm and 254nm ultraviolet lamps produce and decompose ozone at the same power, with a value of 20.

[0070] The UV lamp on-off interval ratio is 0.65, with the 185nm on-off time being 65s and the 254nm on-off time being 100s per cycle.

[0071] During equipment operation, effluent is collected to detect perfluorinated compound concentrations. Additionally, while this equipment is being tested, the same effluent is passed through a conventional ozone process; changes in effluent quality are observed to influence, for example... Figure 5 As shown in the figure. Tests have shown that this equipment achieves a removal rate of approximately 85% for perfluorinated compounds, significantly higher than the 74% achieved by traditional processes.

[0072] The overall parameters of the reactor are shown in Table 3 below.

[0073] Table 3 Reactor Operating Parameters

[0074] project parameter Dimensions (m) r=1,h=4 <![CDATA[Volume (m 3 )]]> 12.6 Hydraulic residence time (h) 3 <![CDATA[Inlet flow rate (m 3 / d)]]> 100 Power consumption (kW) 2.6 Operating cost (yuan / day) 46.8 Construction cost (ten thousand yuan) 12.7

[0075] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various equivalent transformations can be made to the technical solutions of the present invention, and these equivalent transformations all fall within the protection scope of the present invention.

Claims

1. A diffused photo-atomization device suitable for deep removal of perfluorinated compounds from wastewater treatment plant effluent, characterized in that: It includes the reactor body, ultraviolet lamp assembly, and external auxiliary systems.

2. The reactor body according to claim 1, characterized in that: The reactor body is cylindrical with an inner wall made of a protective aluminum film mirror. There is a water inlet at the top, which is connected to a rotary three-nozzle nozzle. There is an air outlet pipe on the side of the top, which bends upward. There is an air inlet on the side of the main body. A funnel-shaped water tank is installed at the bottom, and a condensation system is installed under the water tank. The bottom of the water tank is connected to the water outlet pipe.

3. The ultraviolet lamp assembly according to claim 1, characterized in that: There are two sets of UV lamps. Each set has six UV lamps, two air stirrers, and one reflector. The UV lamps are arranged in a ring, with three having a dominant wavelength of 185nm and the other three having a dominant wavelength of 254nm, spaced apart. The air stirrers are fixed to the inner wall of the reactor and tilted upwards. The first set of lamps is located in the upper half of the reactor, and the second set is in the lower half, separated by a reflector. The reflector is funnel-shaped, with the funnel wall made of a protective aluminum film mirror and a mesh-like perforated structure at the narrow opening. The reflector for the first set is located below its lamps, with the wide opening facing upwards; the reflector for the second set is located above its lamps, with the wide opening facing downwards.

4. The external system according to claim 1, characterized in that: It includes an atomization system and an air system. The atomization system includes a booster pump and an atomizing compressor; water pipes connect sequentially to the tailwater storage tank, the booster pump, the atomizing compressor, and the atomizing nozzles on the reactor body. The air system dries and filters the air and connects to the air inlet on the reactor body.

5. The method of using the diffusion-type photo-atomization device for deep removal of perfluorinated compounds in wastewater effluent according to any one of claims 1 to 4, characterized in that, The specific steps include the following: Step 1: Wastewater effluent from the wastewater treatment plant is stored in a storage tank and pumped to an atomizing compressor. Under pressure and the combined action of the nozzles, it is atomized into a water mist and sprayed into the reactor. The air system is then activated, and purified air enters the reactor through the air inlet. The air intake rate V is calculated using the following formula: In the formula, 'a' represents the ozone dosage, kg / m³. 3 S represents the theoretically required amount of ozone, kg / m³ 3 This value is greatly affected by water quality and can be measured by sampling. The value is generally between 0.05 and 0.5 kg / m³. 3 K represents the ozone contact efficiency, %, ranging from 70% to 80%; V represents the air intake rate, kg / h; Q represents the influent flow rate, m³ / h. 3 / h; n represents the ozone production rate in the air, %, ranging from 1.5 to 2.5; 1.06 is the safety factor. Step 2: Start the air mixer to mix the water mist and gas. Turn on different wavelength UV lamps at intervals; the UV light is reflected from the reflective buffer to all corners of the reactor. The 185nm and 254nm UV lamps have a power of 44W, and their on-time ratio is calculated using the following formula. The total on-time per cycle is controlled within 5 minutes: In the formula, This indicates the ratio of the on-time of 185nm and 254nm ultraviolet lamps; This represents the safety factor, with a value ranging from 3 to 5. This represents the ratio of the rate at which 185nm and 254nm ultraviolet lamps generate and decompose ozone at the same power, with a value ranging from 20 to 50. Step 3: After the first set of ultraviolet treatments, the water mist passes through a reflective buffer under gravity and enters the second set of ultraviolet lamps. The reaction that occurs here is the same as in the first set, which enhances the treatment of the effluent. The water droplets that have completed the entire process collect and are discharged through the outlet pipe.

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