A biological fluidized bed coupled with ozone oxidation water purification process for micro-polluted source water

Abstract

The application provides a biological fluidized bed coupling ozone oxidation water purification system for micro-polluted water source water, which comprises a biological fluidized pool, an ozone oxidation pool and a gas driving pool; the biological fluidized pool, the ozone oxidation pool and the gas driving pool are sequentially connected; the water inlet pipe of the biological fluidized pool is arranged at the lower part below the filter plate, the water outlet pipe is arranged at the upper part, the cushion layer is arranged above the filter plate in the pool, the cushion layer is composed of multiple layers of goose pebbles, two layers of carrier fillings are arranged above the cushion layer, the lower layer is large-particle broken activated carbon, and the upper layer is biological filling. In the application, the biological fluidized pool is firstly treated, then the ozone oxidation is carried out, and then the gas driving pool is entered, and then the conventional treatment process is entered; the ozone is used for pre-sterilization after the biological treatment, bacteria are prevented from entering the subsequent section, the biological treatment coupling ozone oxidation can preferentially degrade organic matters, the particles are pretreated, the dissolved oxygen of the outlet water is reduced by the gas driving, the flocculation is promoted, the efficiency of flocculation and sedimentation is improved, and then the removal capacity of the whole process to pollutants is improved.

Description

Technical Field

[0001] This invention belongs to the field of water treatment, specifically relating to a biological fluidized bed coupled ozone oxidation water purification process for slightly polluted water sources. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Surface water is gradually becoming one of the main sources of drinking water. However, surface water in many areas is polluted to varying degrees, especially with persistently high levels of organic matter, ammonia nitrogen, and turbidity, posing a severe challenge to conventional drinking water treatment processes. Traditional water purification processes such as flocculation, sedimentation, filtration, and disinfection may have limitations when dealing with some complex pollution problems, failing to effectively remove certain stubborn pollutants. Moreover, as the degree of pollution intensifies, the treatment capacity and efficiency of conventional processes become increasingly insufficient. To overcome the shortcomings of conventional processes, ozone + activated carbon filter technology is often used for advanced drinking water treatment. Although this improves the efficiency of pollutant removal to some extent, it leads to a longer process flow, with only a slight increase in efficiency and a sharp rise in operating costs.

[0004] To fundamentally address the aforementioned problems, patent CN115353256A proposes a novel process for treating slightly polluted source water. This process employs an ozone pre-oxidation tank + biochar tank + high-speed mechanical mixing tank + flocculation sedimentation + filtration. By placing the ozone pre-oxidation tank and biochar tank before the conventional process, the traditional sequence of removing particulate matter before organic matter is changed. Instead, the process prioritizes the removal of organic matter and pre-treats the suspended particles to optimize flocculation, before coupling it with the conventional process. Compared to conventional treatment processes combined with advanced treatment processes, this method significantly improves the treatment efficiency for organic matter, turbidity, and ammonia nitrogen. However, during application, significant room for improvement has been found, particularly in terms of pollutant removal efficiency and operating cost reduction. Summary of the Invention

[0005] To further optimize the treatment process of slightly polluted water sources, reduce operating costs, improve pollutant removal efficiency and effluent quality, this invention provides a biological fluidized bed coupled ozone oxidation water purification process for slightly polluted water sources.

[0006] Ozone-biological activated carbon technology, as a very mature advanced water purification process, is widely used in existing surface water plants. However, with the release and implementation of GB5749-2022, which added several new pollutant indicators, the treatment capacity of this process is insufficient to meet the new standards. At the same time, people have higher demands for high-quality water, and water supply companies are becoming increasingly strict on operating costs. There is also a greater demand for new processes that are more energy-efficient, reduce consumption, and have higher treatment efficiency. In addition, during operation, the post-ozone activated carbon process causes the biofilm on the biological activated carbon to grow too quickly due to the high dissolved oxygen provided by ozone. Frequent backwashing leads to the shedding of the biofilm from the biochar into the clear water tank, causing biological leakage. Chlorination cannot effectively kill the biofilm, and once it enters the pipe network, it can easily lead to the spread of diseases. In this application, biological fluidized bed treatment is performed first, followed by ozone oxidation, and then the process proceeds to conventional treatment. After biological treatment, ozone plays a pre-sterilization role, preventing bacteria from entering subsequent stages. Even if a small amount of bacteria does enter subsequent stages, it can be removed by conventional processes. Moreover, the combination of biological treatment and ozone oxidation can pre-treat particulate matter, promoting flocculation and improving the efficiency of flocculation and sedimentation, thereby enhancing the overall process's ability to remove pollutants.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a biological fluidized bed coupled with ozone oxidation water purification system for slightly polluted water sources, comprising: a biological fluidized bed, an ozone oxidation bed, and an aeration bed;

[0009] The biological fluidized bed, ozone oxidation bed, and aeration bed are connected in sequence. The inlet pipe of the biological fluidized bed is located at the bottom, below the filter plate, and the outlet pipe is located at the top. A cushion layer is set above the filter plate in the bed. The cushion layer is composed of multiple layers of pebbles. Two layers of carrier packing are set on top of the cushion layer. The lower layer is large-particle crushed activated carbon, and the upper layer is biological packing.

[0010] In some embodiments, the particle size of the lower carrier packing is 1.5 to 2.5 mm, and the thickness is 30 cm to 50 cm.

[0011] In some embodiments, the upper biological packing material is coconut shell activated carbon or directional pore-controlled activated carbon.

[0012] In some embodiments, the upper biological packing material has a particle size of 0.5–1.0 mm and a thickness of 1.5–2.0 μm.

[0013] In some embodiments, the inlet pipe of the ozone oxidation tank is located at the upper part of the tank body, and the outlet pipe and return outlet pipe are located at the lower part of the tank body. A jet aerator is installed at the bottom of the tank. The ozone oxidation tank can be divided into sections and operated in series.

[0014] In some embodiments, a hydrogen peroxide dosing pipeline is provided inside the ozone oxidation tank.

[0015] In some embodiments, the ozone oxidation tank return effluent pipe is connected to a return pump and an electromagnetic flow meter via a pipeline, and the return electromagnetic flow meter operates in conjunction with the return pump.

[0016] In some embodiments, the aeration tank is provided with an inlet pipe and an outlet pipe, with the inlet pipe located at the upper part of the tank and the outlet pipe located at the lower part of the tank. An aeration pipe is provided at the bottom of the tank for aeration of the aeration tank.

[0017] A second aspect of the present invention provides a biological fluidized bed coupled with ozone oxidation water purification process for slightly polluted water sources, comprising:

[0018] The above-described system is used to treat slightly polluted water sources, which flow sequentially through a biological fluidization tank, an ozone oxidation tank, and an aeration tank.

[0019] Among them, the hydraulic retention time of the biological packing material in the biological fluidized bed is 5 to 15 minutes, and the fluidization expansion rate is 30% to 50%.

[0020] The hydraulic retention time in the ozone oxidation tank is 10–20 min, and the return flow rate is 50%–200% of the influent flow rate; the sum of the return flow rate and the influent flow rate remains constant.

[0021] The air-to-water ratio in the aeration tank is 0.5 to 1:1, and the hydraulic retention time is 10 to 20 minutes.

[0022] In some implementations, the slightly polluted source water is combined with the return water through the raw water pipeline and then enters the biological fluidized bed after passing through the pipeline mixer.

[0023] A third aspect of the invention provides the application of the system in the field of water treatment.

[0024] Beneficial effects of the present invention

[0025] (1) The biological fluidized bed is in direct contact with the slightly polluted water source and is also inoculated with the surviving microbial population in the source water, which acts as a microbial selector. Here, the microbial population is constantly undergoing processes such as adaptation, elimination, selection, and proliferation, thereby cultivating, domesticating, and inducing microbial populations that are adapted to the source water. Some of the microorganisms in the source water are also adsorbed and bound by the packing material in the fluidized bed. The nutrients in the source water are directly utilized by the microorganisms in the fluidized bed, and the biofilm formation speed of the biochemical fluidized bed is fast. At the same time, the microorganisms in the source water and the microorganisms on the packing material of the fluidized bed form a symbiotic system, which strengthens the biological action of the source water, improves the biodegradation efficiency, increases the removal rate of pollutants such as organic matter and ammonia nitrogen, and reduces the cost of pollutant removal.

[0026] (2) The biological fluidized bed is in direct contact with the slightly polluted water source. High oxygen-consuming substances in the source water, such as iron and manganese, are directly consumed by the organisms in the biological fluidized bed and become elements for biological growth. They no longer enter the subsequent process, reducing the amount of ozone added due to iron oxide and manganese in the subsequent process.

[0027] (3) The effluent from the biological fluidized bed enters the ozone oxidation tank. The ozone oxidation tank further oxidizes the organic matter in the effluent that cannot be biologically oxidized, and performs ring-opening, chain breaking or mineralization on the recalcitrant organic matter, thereby improving the biodegradability of the water. Then the effluent is returned to the front-end biological fluidized bed for biological oxidation, thus realizing the combination of organic matter biochemical oxidation and advanced oxidation. At the same time, after ozone aeration, the ozone oxidation tank can provide supersaturated dissolved oxygen water. The supersaturated dissolved oxygen water is returned to the biological fluidized bed, which can improve biological activity and the rate of biological removal of pollutants, reduce the hydraulic retention time of the biological fluidized bed, and improve the removal efficiency of organic matter and ammonia nitrogen. Studies have shown that when the hydraulic retention time of supersaturated dissolved oxygen water is 15 minutes, the removal rate of organic matter can reach more than 80%, which is more than 30% higher than that of conventional dissolved oxygen, and the removal rate of ammonia nitrogen can reach more than 95%, which is more than 25% higher than that of conventional dissolved oxygen.

[0028] (4) The effluent from the biological fluidized bed enters the ozone oxidation tank, which can further oxidize the effluent from the biological fluidized bed. After adding hydrogen peroxide, it can also remove new organic pollutants. At the same time, due to the high oxidation-reduction potential of ozone, it has the effect of sterilization and disinfection, which sterilizes and disinfects the bacteria and microorganisms flowing out of the biological fluidized bed, preventing bacteria and viruses from entering the subsequent treatment unit, preventing the growth of microorganisms in the subsequent treatment unit, and improving the sedimentation effect.

[0029] (5) Ozone aeration in the ozone oxidation tank provides supersaturated dissolved oxygen water, which has a great promoting effect on the organisms in the upstream biochemical fluidized bed. However, if the supersaturated dissolved oxygen water comes out of the ozone oxidation tank and directly enters the subsequent conventional processes such as flocculation and sedimentation, studies have shown that when polyaluminum chloride coagulant is added under supersaturated dissolved oxygen conditions, polyaluminum chloride is an inorganic particle with a hydrophobic and aerophilic surface, which will induce supersaturated gas to condense into bubbles on its surface. Therefore, supersaturated dissolved oxygen will adhere to the flocs and precipitate as bubbles, providing buoyancy to the flocs and affecting the floc sedimentation effect. It may even cause them to float and form scum. Therefore, the supersaturated dissolved oxygen water from the ozone oxidation tank of this invention enters the aeration tank for aeration, which reduces the dissolved oxygen in the pretreated effluent, improves the coagulation and sedimentation performance of the subsequent conventional treatment process, improves the removal efficiency of particulate matter, and significantly improves the effluent turbidity.

[0030] (6) The source water and return water enter the biological fluidized bed through automatic control to achieve a stable total flow rate. The influent flow rate of the biological fluidized bed remains constant, and its various operating states are relatively stable, with the expansion rate remaining unchanged. The organic matter in the influent first enters the lower packing zone of the biological fluidized bed. The ozone carried in the return water is decomposed into oxygen under the action of large-particle activated carbon, preventing excessively high concentrations of ozone from entering the upper biological fluidized packing zone. Under the catalytic action of activated carbon, the organic matter in the influent is oxidized. The particulate matter in the influent passes through the pores of the lower large-particle activated carbon and enters the upper fluidized layer. The particulate matter flows out of the biological fluidized bed with the rising water flow and enters the subsequent process. The aged biofilm fragments and worn activated carbon powder that fall off from the biological fluidized bed also flow out of the biological fluidized bed with the rising water flow and enter the subsequent process. Then, they gradually enter the conventional mixing flocculation tank, providing more flocculation cores for the flocculation process and improving flocculation efficiency.

[0031] (7) The process of this invention is simple, the process flow is short, it is practical and easy to promote. Attached Figure Description

[0032] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. Exemplary embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0033] Figure 1 This is a schematic diagram of a biological fluidized bed coupled with ozone oxidation water purification process for slightly polluted water sources according to the present invention. Detailed Implementation

[0034] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0035] The present invention provides a biological fluidized bed coupled with ozone oxidation water purification process for slightly polluted water source, which mainly includes a biological fluidized bed, an ozone oxidation bed, and an aeration bed, which are connected in sequence.

[0036] The biological fluidized bed is equipped with an inlet pipe and an outlet pipe. The inlet pipe is located at the bottom, below the filter plate. Slightly polluted source water is introduced into the biological fluidized bed after merging with the return water pipe through the raw water pipe and passing through a pipe mixer. Electromagnetic flow meters are installed on both the raw water pipe and the return water pipe. The outlet pipe is located at the top. A cushion layer composed of multiple layers of pebbles is placed above the filter plate in the bed, with the particle size decreasing from bottom to top. Above the cushion layer are two layers of carrier packing. The lower layer is large-particle crushed activated carbon with a particle size of 1.5–2.5 mm and a thickness of 30–50 cm. The upper layer is biological packing, preferably coconut shell activated carbon or directional controlled-pore activated carbon with a particle size of 0.5–1.0 mm and a thickness of 1.5–2.0 m. The hydraulic retention time of the biological packing in the biological fluidized bed is 5–15 min, and the fluidization expansion rate is 30%–50%.

[0037] The ozone oxidation tank is equipped with an inlet pipe, an outlet pipe, and a return outlet pipe. The inlet pipe is located at the top of the tank, while the outlet and return outlet pipes are located at the bottom. A jet aerator is installed at the bottom of the tank for ozone aeration. The ozone oxidation tank can be divided into compartments and operated in series. A hydrogen peroxide dosing pipeline is installed within the ozone oxidation tank, and the hydraulic retention time of the ozone oxidation tank is 10–20 minutes.

[0038] The ozone oxidation tank's return water outlet pipe is connected to a return pump and an electromagnetic flow meter via a pipeline. The return electromagnetic flow meter operates in conjunction with the return pump. The return pump frequency is controlled by signals from the return electromagnetic flow meter and the raw water electromagnetic flow meter to control the return flow rate, keeping the sum of the return water volume and the raw water volume stable. The return flow rate is 50% to 200% of the influent volume.

[0039] The aeration tank is equipped with an inlet pipe and an outlet pipe. The inlet pipe is located at the upper part of the tank, and the outlet pipe is located at the lower part of the tank. An aeration pipe is installed at the bottom of the tank for aeration. The air-to-water ratio of the aeration tank is 0.5 to 1:1, and the hydraulic retention time is 10 to 20 minutes.

[0040] The present invention will be further described in detail below with reference to specific embodiments. It should be noted that the specific embodiments are explanations of the present invention and not limitations thereof.

[0041] Example 1

[0042] A biological fluidized bed coupled with ozone oxidation water purification process for slightly polluted water sources mainly includes a biological fluidized bed, an ozone oxidation bed, and an aeration bed, which are connected in sequence.

[0043] The biological fluidized bed is equipped with an inlet pipe and an outlet pipe. The inlet pipe is located at the bottom, below the filter plate. Slightly polluted source water is introduced into the biological fluidized bed after merging with the return water pipe through the raw water pipe and passing through a pipe mixer. Electromagnetic flow meters are installed on both the raw water pipe and the return water pipe. The outlet pipe is located at the top. Above the filter plate in the bed, a cushion layer consisting of three layers of pebbles with decreasing particle size from bottom to top is placed. Above the cushion layer are two layers of carrier packing: the lower layer is an ozone catalyst with a particle size of 1.5–2.5 mm and a thickness of 50 cm; the upper layer is biological packing material, using coconut shell activated carbon with a particle size of 0.5–1.0 mm and a thickness of 1.5 m. The hydraulic retention time of the biological packing material in the biological fluidized bed is 15 minutes, and the fluidization expansion rate is 30%.

[0044] The ozone oxidation tank is equipped with an inlet pipe, an outlet pipe, and a return outlet pipe. The inlet pipe is located at the top of the tank, while the outlet and return outlet pipes are located at the bottom. A jet aerator is installed at the bottom of the tank for ozone aeration. The ozone oxidation tank is divided into three compartments connected in series. A hydrogen peroxide dosing pipeline is installed within the ozone oxidation tank, and the hydraulic retention time is 20 minutes.

[0045] The ozone oxidation tank's return water outlet pipe is connected to a return pump and an electromagnetic flow meter via a pipeline. The return electromagnetic flow meter operates in conjunction with the return pump. The return pump frequency is controlled by signals from the return electromagnetic flow meter and the raw water electromagnetic flow meter to control the return flow rate, keeping the sum of the return water volume and the raw water volume stable. The return flow rate is 50% to 200% of the influent volume.

[0046] The aeration tank is equipped with an inlet pipe and an outlet pipe. The inlet pipe is located at the upper part of the tank, and the outlet pipe is located at the lower part of the tank. An aeration pipe is installed at the bottom of the tank for aeration. The air-to-water ratio of the aeration tank is 0.5 to 1:1, and the hydraulic retention time is 10 to 20 minutes.

[0047] Application Example 1

[0048] The process described in Example 1 was used to treat a slightly polluted water source (TOC: 5.82 mg / L, ammonia nitrogen: 1.09 mg / L, particle count: 7368 CNT / ml, turbidity: 9.34 NTU). The effluent entered a high-speed mechanical mixing + flocculation sedimentation + filtration process. The ozone dosage in the ozone oxidation tank was 5 mg / L. The test results showed that the average TOC of the effluent was 0.71 mg / L, the average ammonia nitrogen was 0.05 mg / L, the average particle count was 86 CNT / ml, the average turbidity was 0.038 NTU, and the average total bacterial count was 92 CFU / ml. The effluent quality met and exceeded the "Standards for Drinking Water Quality (GB5749-2022)".

[0049] Application Example 2

[0050] The process described in Example 1 was used to treat a slightly polluted water source (TOC: 5.82 mg / L, ammonia nitrogen: 1.09 mg / L, particle count: 7368 CNT / ml, turbidity: 9.34 NTU). The effluent entered a high-speed mechanical mixing + flocculation sedimentation + filtration process. The ozone dosage in the ozone oxidation tank was 5 mg / L, and the hydrogen peroxide dosage was 2.5 mg / L. The effluent showed an average TOC of 0.54 mg / L, an average ammonia nitrogen of 0.04 mg / L, an average particle count of 84 CNT / ml, an average turbidity of 0.035 NTU, and an average total bacterial count of 86 CFU / ml. The effluent quality met and exceeded the "Standards for Drinking Water Quality (GB5749-2022)".

[0051] Comparative Example 1

[0052] A slightly polluted source water (TOC: 5.82 mg / L, ammonia nitrogen: 1.09 mg / L, particle count: 7368 CNT / ml, turbidity: 9.34 NTU) was treated using an ozone pre-oxidation tank + biochar tank + high-speed mechanical mixing tank + flocculation sedimentation + filtration process. The ozone dosage in the ozone oxidation tank was 5 mg / L, and other process operating parameters were kept the same as in Application Example 1. The average TOC of the effluent was 1.02 mg / L, the average ammonia nitrogen was 0.11 mg / L, the average particle count was 128 CNT / ml, the average turbidity was 0.074 NTU, and the average total bacterial count was 276 CFU / ml.

[0053] Comparative Example 2

[0054] The difference from Application Example 1 is that a "biological fluidized bed" was used instead of a "biological fluidized bed + ozone oxidation bed + aeration bed" to treat a slightly polluted water source (TOC: 5.82 mg / L, ammonia nitrogen 1.09 mg / L, particle count 7368 CNT / ml, turbidity 9.34 NTU). The effluent entered a high-speed mechanical mixing + flocculation sedimentation + filtration process. After testing, the average TOC of the effluent was 1.32 mg / L, the average ammonia nitrogen was 0.22 mg / L, the average particle count was 147 CNT / ml, the average turbidity was 0.089 NTU, and the average total bacterial count was 346 CFU / ml.

[0055] Comparative Example 3

[0056] The difference from Application Example 1 is that a "biological fluidized bed + ozone oxidation bed" was used instead of a "biological fluidized bed + ozone oxidation bed + aeration bed" to treat a slightly polluted water source (TOC: 5.82 mg / L, ammonia nitrogen 1.09 mg / L, particle count 7368 CNT / ml, turbidity 9.34 NTU). The effluent entered a high-speed mechanical mixing + flocculation sedimentation + filtration process. After testing, the average TOC of the effluent was 0.74 mg / L, the average ammonia nitrogen was 0.06 mg / L, the average particle count was 138 CNT / ml, the average turbidity was 0.085 NTU, and the average total bacterial count was 234 CFU / ml.

[0057] Comparative Example 4

[0058] The difference from Application Example 2 is that the ozone dosage in the ozone oxidation tank was 0 mg / L, while the hydrogen peroxide dosage was the same as in Application Example 2. Testing showed that the average TOC in the effluent was 0.76 mg / L, the average ammonia nitrogen was 0.12 mg / L, the average particle count was 156 CNT / ml, the average turbidity was 0.093 NTU, and the average total bacterial count was 147 CFU / ml.

[0059] The effluent sampling and testing results of Example 1, Application Example 1, and Comparative Example 1 show that, compared with the traditional ozone-biological activated carbon (O3-BAC) technology, the pretreatment process provided by this invention significantly improves the removal of TOC under the same ozone dosage, and also improves the removal rates of ammonia nitrogen, particulate matter, total bacteria count, etc. to varying degrees.

[0060] The effluent sampling and testing results of Example 1, Application Example 1, and Comparative Examples 2 and 3 show that, compared with the treatment of "biological fluidized bed" and "biological fluidized bed + ozone oxidation bed", the treatment process provided by this invention has a higher TOC removal rate and a higher removal rate of ammonia nitrogen, particulate matter, total bacteria count, etc., under the same ozone dosage.

[0061] The effluent sampling and testing results from Examples 1, 1 and 2, and Comparative Example 4 show that the combination of ozone treatment and hydrogen peroxide treatment alone can significantly improve the TOC removal rate.

[0062] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A biological fluidized bed coupled ozone oxidation water purification process for slightly polluted water sources, characterized in that, include: A biological fluidized bed coupled with ozone oxidation water purification system is used to treat slightly polluted water sources. The biological fluidized bed coupled with ozone oxidation water purification system includes a biological fluidized bed, an ozone oxidation bed, an aeration bed, and a flocculation sedimentation bed. The biological fluidized bed, ozone oxidation bed, aeration bed, and flocculation sedimentation bed are connected in sequence. The biological fluidized bed is equipped with a filter plate. The inlet pipe of the biological fluidized bed is located at the bottom of the bed and below the filter plate, and the outlet pipe is located at the top of the bed. A cushion layer is set above the filter plate in the bed. The cushion layer is composed of multiple layers of pebbles. Two layers of carrier packing are set on top of the cushion layer. The lower layer is large-particle crushed activated carbon, and the upper layer is biological packing. The upper biological packing is coconut shell activated carbon or directional controlled pore activated carbon. The inlet pipe of the ozone oxidation tank is located at the top of the tank, while the outlet pipe and return outlet pipe are located at the bottom of the tank. A jet aerator is installed at the bottom of the tank. The ozone oxidation tank is divided into compartments, with each compartment connected in series. A hydrogen peroxide dosing pipe is installed inside the ozone oxidation tank. The return outlet pipe of the ozone oxidation tank is connected to a return pump and an electromagnetic flow meter via a return pipe, and the electromagnetic flow meter and the return pump operate in conjunction. The slightly polluted source water merges with the return pipe through the raw water pipe and then enters the biological fluidized bed after passing through a pipe mixer. The aeration tank is equipped with an inlet pipe and an outlet pipe. The inlet pipe is located at the upper part of the tank body, and the outlet pipe is located at the lower part of the tank body. An aeration pipe is installed at the bottom of the tank body for aeration of the aeration tank to reduce dissolved oxygen. Slightly polluted source water flows sequentially through a biological fluidized bed, an ozone oxidation bed, an aeration bed, and a flocculation sedimentation bed. The hydraulic retention time in the biological fluidized bed is 5-15 minutes, and the fluidization expansion rate is 30%-50%. The hydraulic retention time in the ozone oxidation bed is 10-20 minutes, and the return flow rate is 50%-200% of the influent. The air-to-water ratio in the aeration bed is 0.5-1:1, and the hydraulic retention time is 10-20 minutes.

2. The biological fluidized bed coupled ozone oxidation water purification process for slightly polluted water sources as described in claim 1, characterized in that, The particle size of the lower carrier packing is 1.5~2.5mm, and the thickness is 30cm~50cm.

3. The biological fluidized bed coupled ozone oxidation water purification process for slightly polluted water sources as described in claim 1, characterized in that, The upper biological packing material has a particle size of 0.5~1.0 mm and a thickness of 1.5~2.0 m.

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