Method and device for treating refractory organic wastewater by multi-stage filter material enhanced ozone oxidation

Abstract

The application provides a method and device for treating refractory organic wastewater by multi-level filter material reinforced ozone oxidation. The method comprises: filling filter material into an ozone oxidation reaction tank in a multi-level or multi-layer manner; making wastewater to be treated enter from the top of the ozone oxidation reaction tank, and ozone to be introduced from the bottom of the ozone oxidation reaction tank; and after the wastewater to be treated flows through the multi-level or multi-layer filter material and simultaneously undergoes ozone oxidation reaction, the wastewater to be treated flows out from the bottom of the ozone oxidation reaction tank to obtain treated effluent. The device comprises: an ozone oxidation reaction tank, and filter material filled in the ozone oxidation reaction tank, and the filter material is filled in the ozone oxidation reaction tank in a multi-level or multi-layer manner. The method and device of the application utilize the wastewater treatment by the combination of multi-layer or multi-level filter material and ozone oxidation, the multi-layer or multi-level filter material has both filtering and catalytic performance, and has a synergistic effect with ozone to improve oxidation efficiency, reduce material addition, and reduce operation cost.

Description

Technical Field

[0001] This invention relates to the field of organic wastewater treatment technology, specifically to a method and apparatus for treating recalcitrant organic wastewater using multi-stage filter media enhanced ozone oxidation. Background Technology

[0002] Conventional wastewater treatment processes typically produce effluent containing large amounts of recalcitrant organic pollutants and fine suspended solids after physicochemical or biological treatment. To meet increasingly stringent wastewater discharge standards and reduce the environmental damage caused by recalcitrant organic pollutants, advanced oxidation technologies are needed to remove them. Ozone oxidation technology is considered a promising advanced oxidation technology due to its ease of operation and lack of secondary pollution. However, ozone molecules are selective and readily produce acidic intermediates. Acidic conditions inhibit ozone decomposition and the generation of reactive oxygen species. Furthermore, suspended solids readily consume ozone, resulting in low ozone utilization, which limits the engineering application of ozone oxidation technology. Enhancing ozone oxidation technology mainly involves improving the ozone oxidation reactor and adding ozone catalysts.

[0003] CN114538597A reports a manganese-based membrane catalytic contactor for enhancing ozone oxidation of emerging pollutants. This contactor improves ozone mass transfer efficiency and promotes ozone dissolution in water, while enhancing the catalytic activity of ozone on emerging pollutants in water, achieving deep degradation of emerging pollutants and improving their biodegradability. It can be used for wastewater treatment or advanced drinking water treatment.

[0004] CN111068737A reports a method for preparing a catalyst for enhanced ozone oxidation of oily wastewater and an internal circulation device. The catalyst is a carbonitride loaded with catalytically active components, which can promote ozone decomposition to generate hydroxyl radicals, thereby improving the efficiency of ozone treatment of organic matter and increasing ozone utilization. This internal circulation device significantly increases ozone residence time and improves reaction efficiency.

[0005] CN211999003U reports an ozone reactor in which a catalyst packing layer is provided in the reaction chamber. Ozone oxidizes the wastewater entering through the inlet and moves with the water flow to the catalyst packing layer. At this time, the catalyst on the catalyst packing layer undergoes an ozone catalytic oxidation reaction, thereby enhancing the ozone oxidation effect, improving ozone utilization efficiency, and thus improving the oxidation efficiency of wastewater.

[0006] In addition, CN102745863A reports a high-efficiency fluidized upflow multilayer composite filter biological filter coupled with ozone and a water treatment method using the biological filter. The composite filter layer is only used to adsorb and buffer nitrogen and phosphorus pollutants and support the microbial activity. The front end needs to be set with separate ozone oxidation and ozone catalytic oxidation units to improve the biochemical properties of the water. The catalytic ozone oxidation method needs to use ultraviolet light, ultrasound, metal oxide catalysts or hydrogen peroxide for synergistic effect.

[0007] Similarly, CN207276242U reports an ozone-activated carbon catalytic oxidation biofilter device. This filter requires the use of filter media suitable for biological support (such as activated carbon or ceramsite), utilizing adsorption and support to synergistically improve the performance of biological metabolism of organic pollutants. However, it does not address the development of universally applicable filter media or the performance of synergistic ozone treatment of recalcitrant organic wastewater.

[0008] The development of active ozone catalysts requires analysis of material surface properties, structural characteristics, and the composition of active components. The literature mentioned above covers the preparation of ozone catalysts and the improvement of ozone reactors, both of which can effectively improve ozone utilization. Combining ozone with biological filters can enhance nitrogen and phosphorus treatment performance, but this can only be achieved with filter media that have adsorption or support functions, and it does not address the development of universal filter media for synergistic ozone treatment of recalcitrant organic wastewater. Considering the impact of suspended solids in wastewater on ozone oxidation efficiency and the production cost limitations of ozone catalysts, finding universal materials to enhance ozone oxidation, improve ozone utilization, enhance the performance of ozone oxidation systems, improve the treatment effect of recalcitrant organic wastewater, and reduce investment and operating costs is a research direction that researchers continue to focus on.

[0009] Therefore, developing a method and apparatus for treating recalcitrant organic wastewater by ozone oxidation enhanced with multi-level filter media has become one of the urgent problems to be solved in this field. Summary of the Invention

[0010] To address the aforementioned technical problems, the present invention aims to provide a method and apparatus for treating recalcitrant organic wastewater using multi-layered filter media enhanced ozone oxidation. The method and apparatus of the present invention utilize a combination of multi-layered or multi-stage filter media and ozone oxidation for wastewater treatment. The multi-layered or multi-stage filter media possesses both filtration and catalytic properties, thereby improving oxidation efficiency, reducing material additions, and lowering operating costs.

[0011] To achieve the above objectives, the first aspect of the present invention provides a method for treating recalcitrant organic wastewater by enhanced ozone oxidation using multi-stage filter media, comprising the following steps:

[0012] (1) The filter media is filled into the ozone oxidation reaction tank in a multi-stage or multi-layer manner;

[0013] (2) The wastewater to be treated enters from the top of the ozone oxidation reaction tank, and ozone is introduced from the bottom of the ozone oxidation reaction tank. After the wastewater to be treated flows through multiple or multiple layers of filter media and undergoes ozone oxidation reaction, it flows out from the bottom of the ozone oxidation reaction tank to obtain the treated effluent.

[0014] In the above-mentioned method for treating recalcitrant organic wastewater using multi-stage filter media enhanced ozone oxidation, preferably, the filter media consists of filter media of different particle sizes obtained through crushing, washing, and sieving. This invention uses filter media of different particle sizes, packed into the ozone oxidation reaction tank in a multi-stage or multi-layer manner, which can reduce the occurrence of gas retention.

[0015] In the above-mentioned method for treating recalcitrant organic wastewater using multi-stage filter media enhanced ozone oxidation, preferably, the filter media comprises one or a combination of several of the following: quartz sand, gravel, volcanic rock, manganese sand, magnetite, and dolomite, and the filter media has a particle size range of d. 10 Filter media with different particle sizes ranging from 0.25mm to 8mm.

[0016] In the above-mentioned method for treating recalcitrant organic wastewater by enhanced ozone oxidation using multi-level filter media, preferably, the total height of the filter media is 1 / 2–4 / 5 of the height of the ozone oxidation reaction tank.

[0017] In some specific embodiments of the present invention, the filter media is filled into the ozone oxidation reaction tank in a three-layer primary manner, with a filling height of 1 / 2 of the height of the ozone oxidation reaction tank. The three layers of filter media from top to bottom are quartz sand, magnetite, and dolomite, respectively, with a filling volume ratio of quartz sand, magnetite, and dolomite of 1:1:1. The particle size of the quartz sand is d. 10 = 0.5-2mm (preferably, d) 10 =0.5mm), the grain size of magnetite and dolomite is d 10 = 0.8-8mm (preferably, the particle size of magnetite is d) 10 =0.8mm, the grain size of dolomite is d 10 =1.2mm).

[0018] In some specific embodiments of the present invention, the filter media is filled into the ozone oxidation reaction tank in a two-stage manner. The two-stage filter media, from top to bottom, are a first-stage filter media and a second-stage filter media. The filling height of the first-stage filter media is 1 / 3 of the height of the ozone oxidation reaction tank. The first-stage filter media includes two layers of filter media, from top to bottom, namely volcanic rock and quartz sand. The filling volume ratio of volcanic rock and quartz sand is 1:1, and the particle size of the volcanic rock is d. 10 = 0.5-4mm (preferably, d) 10 =0.8mm), the particle size of quartz sand is d 10 = 0.8-6mm (preferably, d)10 =1.2mm); The filling height of the second-stage filter media is 1 / 3 of the height of the ozone oxidation reaction tank. The second-stage filter media consists of two layers of filter media. From top to bottom, the two layers of filter media are manganese sand and dolomite, respectively. The filling volume ratio of manganese sand and dolomite is 1:1, and the particle size of manganese sand and dolomite is d. 10 =0.25-6mm (preferably, the particle size of manganese sand ore is d) 10 =0.8mm, the grain size of dolomite is d 10 =2mm).

[0019] In some specific embodiments of the present invention, the filter media is filled into the ozone oxidation reaction tank in a two-stage manner. The two-stage filter media, from top to bottom, are the first-stage filter media and the second-stage filter media. The filling height of the first-stage filter media is 1 / 3 of the height of the ozone oxidation reaction tank. The first-stage filter media includes three layers of filter media, from top to bottom: quartz sand, magnetite, and dolomite. The filling volume ratio of quartz sand, magnetite, and dolomite is 1:2:1, and the particle size of quartz sand and magnetite is d. 10 =0.5-4mm, the particle size of dolomite is d 10 =0.85-8mm (preferably, the particle size of the quartz sand is d) 10 =0.5mm, the particle size of magnetite is d 10 =0.8mm, the grain size of dolomite is d 10 =1.2mm); The filling height of the second-stage filter media is 1 / 3 of the height of the ozone oxidation reaction tank. The second-stage filter media consists of three layers: magnetite, volcanic rock, and gravel, from top to bottom. The volume ratio of magnetite, volcanic rock, and gravel is 2:2:1. The particle size of the magnetite is d 10 = 0.5-2mm (preferably, d) 10 =0.8mm), the grain size of the volcanic rock is d 10 = 0.85-4mm (preferably, d) 10 =1.2mm), the gravel particle size is d 10 = 1.2-8mm (preferably, d) 10 =2mm).

[0020] In some specific embodiments of the present invention, the filter media is filled into the ozone oxidation reaction tank in a three-stage manner. The three stages of filter media, from top to bottom, are the first stage filter media, the second stage filter media, and the third stage filter media. The filling height of the first stage filter media is 1 / 5 of the height of the ozone oxidation reaction tank. The first stage filter media includes three layers of filter media, from top to bottom: manganese sand, quartz sand, and volcanic rock. The filling volume ratio of manganese sand, quartz sand, and volcanic rock is 1:1:1. The particle size of manganese sand and quartz sand is d. 10 =0.5-4mm, the grain size of volcanic rock is d 10=0.85-6mm (preferably, the particle size of both manganese sand and quartz sand is d) 10 =0.8mm, the grain size of volcanic rock is d 10 =1.2mm); The filling height of the second-stage filter media is 1 / 5 of the height of the ozone oxidation reaction tank. The second-stage filter media consists of three layers, from top to bottom: magnetite, dolomite, and manganese sand. The filling volume ratio of magnetite, dolomite, and manganese sand is 1:1:1. The particle size of magnetite and dolomite is d 10 =0.25-4mm (preferably, all are d) 10 =2mm), the particle size of manganese sand ore is d 10 = 0.5-2mm (preferably, d) 10 =1.2mm); The filling height of the third-stage filter media is 1 / 5 of the height of the ozone oxidation reaction tank. The third-stage filter media consists of three layers, from top to bottom: manganese sand, magnetite, and gravel. The filling volume ratio of manganese sand, magnetite, and gravel is 1:1:1. The particle size of the manganese sand is d. 10 = 0.85-4mm (preferably, d) 10 =2mm), the particle size of magnetite is d 10 = 0.85-6mm (preferably, d) 10 =4.5mm), the gravel particle size is d 10 = 1.2-8mm (preferably, d) 10 =6mm).

[0021] In the above-mentioned method for treating recalcitrant organic wastewater by enhanced ozone oxidation using multi-level filter media, preferably, the ozone injection rate is 0.6-1.5 mgO3 / mgCOD, based on the COD in the wastewater to be treated.

[0022] In the above-mentioned method for treating recalcitrant organic wastewater by enhanced ozone oxidation using multi-level filter media, preferably, the hydraulic retention time of the wastewater to be treated in the ozone oxidation reaction tank is 30-90 minutes.

[0023] In the above-mentioned method for treating recalcitrant organic wastewater using multi-stage filter media enhanced ozone oxidation, preferably, the wastewater to be treated has a COD of 40-400 mg / L, a suspended solids content of 30-200 mg / L, and a pH range of 2-10. The method of this invention can effectively treat recalcitrant organic wastewater from the chemical industry, especially from the oil refining and chemical industry.

[0024] According to a specific embodiment of the present invention, preferably, the method for treating recalcitrant organic wastewater by enhanced ozone oxidation using multi-level filter media further includes step (3): using the treated effluent flowing from the bottom of the ozone oxidation reaction tank as backwashing liquid to backwash the filter media, thereby improving the service life of the filter media. More preferably, the backwashing cycle is 20-30 days, that is, backwashing is performed once every 20-30 days. More specifically, the backwashing liquid enters from the bottom of the ozone oxidation reaction tank, backwashes the filter media, and then exits from the top of the ozone oxidation reaction tank.

[0025] In the above-described method for treating recalcitrant organic wastewater using multi-stage filter media enhanced ozone oxidation, preferably, the treated effluent has a COD of 20-100 mg / L, a suspended solids content of 2-10 mg / L, and a pH range of 6-8. According to a specific embodiment of the present invention, the above-described method for treating recalcitrant organic wastewater using multi-stage filter media enhanced ozone oxidation achieves a COD removal rate of over 69% and a suspended solids removal rate of over 83% in the wastewater.

[0026] This invention discloses a method for treating recalcitrant organic wastewater using multi-stage filter media enhanced ozone oxidation. The method employs filter media of different particle sizes, packed into an ozone oxidation reaction tank in multiple stages or layers, reducing gas retention. The wastewater enters the reaction tank from the top, and as it flows through the multi-stage filter media, it traps suspended solids, reducing ozone consumption and improving oxidation efficiency. Simultaneously, ozone is introduced from the bottom of the tank, using the multi-stage filter media as a catalyst to catalyze the ozone oxidation reaction, promoting ozone decomposition to generate non-selective reactive oxygen species, degrading or mineralizing recalcitrant organic pollutants in the wastewater, and enhancing oxidation capacity and efficiency. Furthermore, the treated effluent can be periodically used as backwashing liquid to backwash the filter media, extending its lifespan. Additionally, this method buffers the pH of the ozone oxidation reaction system to neutral or slightly alkaline, facilitating ozone decomposition and enhancing its efficiency.

[0027] A second aspect of the present invention provides an apparatus for treating recalcitrant organic wastewater by enhanced ozone oxidation with multi-level filter media. The apparatus is used to implement the above-mentioned method for treating recalcitrant organic wastewater by enhanced ozone oxidation with multi-level filter media. The apparatus includes: an ozone oxidation reaction tank, and filter media filled in the ozone oxidation reaction tank, wherein the filter media is filled in the ozone oxidation reaction tank in a multi-level or multi-layer manner.

[0028] In the above-mentioned multi-level filter media enhanced ozone oxidation treatment device for recalcitrant organic wastewater, preferably, the filter media is filter media of different particle sizes that have been crushed, washed and screened.

[0029] In the aforementioned multi-stage filter media enhanced ozone oxidation treatment device for recalcitrant organic wastewater, preferably, the filter media comprises one or a combination of several selected from quartz sand, gravel, volcanic rock, manganese sand, magnetite, and dolomite, and the filter media has a particle size range of d. 10 Filter media with different particle sizes ranging from 0.25mm to 8mm.

[0030] In the above-mentioned multi-level filter media enhanced ozone oxidation treatment device for recalcitrant organic wastewater, preferably, the total filling height of the filter media is 1 / 2–4 / 5 of the height of the ozone oxidation reaction tank.

[0031] In the aforementioned multi-layer filter media enhanced ozone oxidation treatment device for recalcitrant organic wastewater, preferably, the filter media is filled into the ozone oxidation reaction tank in a three-layer, one-stage manner, with a filling height of 1 / 2 of the ozone oxidation reaction tank height. The three layers of filter media, from top to bottom, are quartz sand, magnetite, and dolomite, with a filling volume ratio of quartz sand, magnetite, and dolomite of 1:1:1. The particle size of the quartz sand is d. 10 = 0.5-2mm (preferably, d) 10 =0.5mm), the grain size of magnetite and dolomite is d 10 = 0.8-8mm (preferably, the particle size of magnetite is d) 10 =0.8mm, the grain size of dolomite is d 10 =1.2mm).

[0032] In the aforementioned multi-stage filter media enhanced ozone oxidation treatment device for recalcitrant organic wastewater, preferably, the filter media is filled into the ozone oxidation reaction tank in a two-stage manner. The two-stage filter media, from top to bottom, are the first-stage filter media and the second-stage filter media. The filling height of the first-stage filter media is 1 / 3 of the height of the ozone oxidation reaction tank. The first-stage filter media includes two layers of filter media, from top to bottom, namely volcanic rock and quartz sand. The filling volume ratio of volcanic rock and quartz sand is 1:1, and the particle size of the volcanic rock is d. 10 = 0.5-4mm (preferably, d) 10 =0.8mm), the particle size of quartz sand is d 10 = 0.8-6mm (preferably, d) 10 =1.2mm); The filling height of the second-stage filter media is 1 / 3 of the height of the ozone oxidation reaction tank. The second-stage filter media consists of two layers of filter media. From top to bottom, the two layers of filter media are manganese sand and dolomite, respectively. The filling volume ratio of manganese sand and dolomite is 1:1, and the particle size of manganese sand and dolomite is d. 10 =0.25-6mm (preferably, the particle size of manganese sand ore is d) 10 =0.8mm, the grain size of dolomite is d 10 =2mm).

[0033] In the aforementioned multi-stage filter media enhanced ozone oxidation treatment device for recalcitrant organic wastewater, preferably, the filter media are filled into the ozone oxidation reaction tank in a two-stage manner. The two-stage filter media, from top to bottom, are the first-stage filter media and the second-stage filter media. The filling height of the first-stage filter media is 1 / 3 of the height of the ozone oxidation reaction tank. The first-stage filter media includes three layers of filter media, from top to bottom: quartz sand, magnetite, and dolomite. The filling volume ratio of quartz sand, magnetite, and dolomite is 1:2:1, and the particle size of quartz sand and magnetite is d. 10 =0.5-4mm, the particle size of dolomite is d 10 =0.85-8mm (preferably, the particle size of the quartz sand is d) 10 =0.5mm, the particle size of magnetite is d 10 =0.8mm, the grain size of dolomite is d 10 =1.2mm); The filling height of the second-stage filter media is 1 / 3 of the height of the ozone oxidation reaction tank. The second-stage filter media consists of three layers: magnetite, volcanic rock, and gravel, from top to bottom. The volume ratio of magnetite, volcanic rock, and gravel is 2:2:1. The particle size of the magnetite is d 10 = 0.5-2mm (preferably, d) 10 =0.8mm), the grain size of the volcanic rock is d 10 = 0.85-4mm (preferably, d) 10 =1.2mm), the gravel particle size is d 10 = 1.2-8mm (preferably, d) 10 =2mm).

[0034] In the aforementioned multi-stage filter media enhanced ozone oxidation treatment device for recalcitrant organic wastewater, preferably, the filter media is filled into the ozone oxidation reaction tank in a three-stage manner. The three stages of filter media, from top to bottom, are the first stage, the second stage, and the third stage. The filling height of the first stage filter media is 1 / 5 of the height of the ozone oxidation reaction tank. The first stage filter media comprises three layers: manganese sand, quartz sand, and volcanic rock, from top to bottom. The volume ratio of manganese sand, quartz sand, and volcanic rock is 1:1:1. The particle size of the manganese sand and quartz sand is d. 10 =0.5-4mm, the grain size of volcanic rock is d 10 =0.85-6mm (preferably, the particle size of both manganese sand and quartz sand is d) 10 =0.8mm, the grain size of volcanic rock is d 10=1.2mm); The filling height of the second-stage filter media is 1 / 5 of the height of the ozone oxidation reaction tank. The second-stage filter media consists of three layers, from top to bottom: magnetite, dolomite, and manganese sand. The filling volume ratio of magnetite, dolomite, and manganese sand is 1:1:1. The particle size of magnetite and dolomite is d 10 =0.25-4mm (preferably, all are d) 10 =2mm), the particle size of manganese sand ore is d 10 = 0.5-2mm (preferably, d) 10 =1.2mm); The filling height of the third-stage filter media is 1 / 5 of the height of the ozone oxidation reaction tank. The third-stage filter media consists of three layers, from top to bottom: manganese sand, magnetite, and gravel. The filling volume ratio of manganese sand, magnetite, and gravel is 1:1:1. The particle size of the manganese sand is d. 10 = 0.85-4mm (preferably, d) 10 =2mm), the particle size of magnetite is d 10 = 0.85-6mm (preferably, d) 10 =4.5mm), the gravel particle size is d 10 = 1.2-8mm (preferably, d) 10 =6mm).

[0035] In the above-mentioned multi-level filter media enhanced ozone oxidation treatment device for recalcitrant organic wastewater, preferably, the top of the ozone oxidation reaction tank is provided with a wastewater inlet and an overflow outlet, and the bottom is provided with an ozone inlet and a treated effluent outlet.

[0036] In the above-mentioned multi-level filter media enhanced ozone oxidation treatment device for recalcitrant organic wastewater, preferably, the bottom of the ozone oxidation reaction tank is provided with a backwash liquid inlet and the top is provided with a backwash drain outlet.

[0037] In the above-mentioned multi-level filter media enhanced ozone oxidation treatment device for recalcitrant organic wastewater, preferably, a water distributor is provided inside the ozone oxidation reaction tank, the water distributor is located above the filter media and is connected to the wastewater inlet to be treated.

[0038] In the aforementioned multi-stage filter media enhanced ozone oxidation treatment device for recalcitrant organic wastewater, preferably, a support layer is provided inside the ozone oxidation reaction tank, with the support layer located below each stage of filter media. The material and particle size of the support layer can be conventionally selected by those skilled in the art.

[0039] In the above-mentioned multi-level filter media enhanced ozone oxidation treatment device for recalcitrant organic wastewater, preferably, the ozone oxidation reaction tank is provided with an aeration disc, which is located below the support layer and communicates with the ozone inlet.

[0040] The technical solution of this invention integrates the filtration unit and the ozone oxidation unit into one unit, reducing construction costs and floor space. Solid suspended matter, due to its surface electrical properties and the presence of organic matter such as microorganisms, easily adsorbs and consumes ozone. However, the unique multi-layer or multi-stage filter media of this invention can trap solid suspended matter, reducing ozone consumption and improving ozone utilization. Simultaneously, the multi-layer or multi-stage filter media of this invention acts as an ozone catalyst, catalyzing the decomposition of ozone to produce non-selective active oxygen species, thus improving oxidation efficiency and enhancing the treatment depth of recalcitrant organic wastewater. Furthermore, the method of this invention can buffer the pH of the ozone oxidation reaction system to neutral or weakly alkaline, which facilitates ozone decomposition and enhances ozone decomposition efficiency. Moreover, the multi-layer or multi-stage filter media of this invention, acting as an ozone catalyst, can be regenerated through backwashing.

[0041] In summary, the method and apparatus of the present invention utilize a combination of multi-layer or multi-stage filter media and ozone oxidation for wastewater treatment. The multi-layer or multi-stage filter media has both filtration and catalytic properties, and works synergistically with ozone to improve oxidation efficiency, reduce material addition, and lower operating costs. Attached Figure Description

[0042] Figure 1 A process flow diagram of a method for treating recalcitrant organic wastewater using multi-level filter media enhanced ozone oxidation, provided for specific embodiments of the present invention.

[0043] Figure 2 A schematic diagram of the structure of a multi-level filter media enhanced ozone oxidation device for treating recalcitrant organic wastewater, provided for a specific embodiment of the present invention.

[0044] Explanation of icon numbers:

[0045] 1-Ozone oxidation reaction tank; 2-Filter media; 3-Wastewater inlet to be treated; 4-Overflow outlet; 5-Ozone inlet; 6-Treatment effluent outlet; 7-Backwash liquid inlet; 8-Backwash outlet; 9-Water distributor; 10-Support layer; 11-Aeration disc. Detailed Implementation

[0046] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0047] According to specific embodiments of the present invention, such as Figure 1 As shown, the present invention provides a method for treating recalcitrant organic wastewater by enhanced ozone oxidation using multi-stage filter media, comprising the following steps:

[0048] (1) The filter media is filled into the ozone oxidation reaction tank in a multi-stage or multi-layer manner; the filter media is filter media of different particle sizes after crushing, washing and screening, and the filter media includes one or a combination of several of the following: quartz sand, gravel, volcanic rock, manganese sand, magnetite and dolomite, and the filter media has a particle size range of d. 10 Filter media with different particle sizes ranging from 0.25mm to 8mm; the total filling height of the filter media is 1 / 2 to 4 / 5 of the height of the ozone oxidation reaction tank;

[0049] (2) The wastewater to be treated is pumped into the ozone oxidation reaction tank from the top, and ozone is introduced into the ozone oxidation reaction tank from the bottom. After the wastewater to be treated flows through multiple stages or multiple layers of filter media and undergoes ozone oxidation reaction, it is pumped out from the bottom of the ozone oxidation reaction tank to obtain the treated effluent. Based on the COD in the wastewater to be treated, the ozone introduction rate is 0.6-1.5 mgO3 / mgCOD. The hydraulic retention time of the wastewater to be treated in the ozone oxidation reaction tank is 30-90 min.

[0050] (3) The treated effluent pumped from the bottom of the ozone oxidation reaction tank is used as backwashing liquid to backwash the filter media regularly, thereby improving the service life of the filter media; the backwashing cycle is 20-30 days; the backwashing liquid enters from the bottom of the ozone oxidation reaction tank, backwashes the filter media, and then exits from the top of the ozone oxidation reaction tank.

[0051] The wastewater to be treated has a COD of 40-400 mg / L, a suspended solids content of 30-200 mg / L, and a pH range of 2-10. More specifically, the wastewater to be treated can be effluent from physicochemical and / or biological treatment in the art. The treated effluent has a COD of 20-100 mg / L, a suspended solids content of 2-10 mg / L, and a pH range of 6-8.

[0052] According to specific embodiments of the present invention, the present invention also provides an apparatus for treating recalcitrant organic wastewater using multi-stage filter media enhanced ozone oxidation. The apparatus is used to implement the aforementioned method for treating recalcitrant organic wastewater using multi-stage filter media enhanced ozone oxidation. Figure 2As shown, the device includes: an ozone oxidation reaction tank 1, and filter media 2 filled in the ozone oxidation reaction tank 1, wherein the filter media 2 is filled in the ozone oxidation reaction tank 1 in a multi-stage or multi-layer manner, and the total filling height of the multi-stage or multi-layer filter media 2 is 1 / 2–4 / 5 of the height of the ozone oxidation reaction tank 1; the top of the ozone oxidation reaction tank 1 is provided with a wastewater inlet 3 and an overflow outlet 4, and the bottom is provided with an ozone inlet 5 and a treated effluent outlet 6; the ozone oxidation reaction tank 1… The bottom is provided with a backwash liquid inlet 7, and the top is provided with a backwash drain outlet 8; the ozone oxidation reaction tank 1 is provided with a water distributor 9, which is located above the filter media 2 and is connected to the wastewater inlet 3 to be treated; the ozone oxidation reaction tank 1 is provided with a support layer 10, which is provided below each stage of filter media 2; the ozone oxidation reaction tank 1 is provided with an aeration disc 11, which is located below the support layer 10 and is connected to the ozone inlet 5.

[0053] Example 1

[0054] This embodiment provides a method for treating recalcitrant organic wastewater using multi-level filter media enhanced ozone oxidation.

[0055] The wastewater treated by this method is as follows: COD = 118 mg / L, suspended solids content 72 mg / L, pH = 6.2 of the effluent from the biochemical unit of a certain refining and chemical wastewater treatment plant.

[0056] The method includes the following steps:

[0057] (1) The filter media is filled into the ozone oxidation reaction tank in a three-layer primary manner. The filling height is 1 / 2 of the height of the ozone oxidation reaction tank. The three layers of filter media from top to bottom are quartz sand, magnetite, and dolomite, respectively. The filling volume ratio of quartz sand, magnetite, and dolomite is 1:1:1. The particle size of quartz sand is d. 10 =0.5mm, the particle size of magnetite is d 10 =0.8mm, the grain size of dolomite is d 10 =1.2mm;

[0058] (2) The wastewater to be treated is pumped into the ozone oxidation reaction tank from the top with an influent flow rate of 20L / h. Ozone is introduced from the bottom of the ozone oxidation reaction tank. Based on the amount of wastewater to be treated, the ozone introduction rate is 90mg (i.e., 0.76mgO3 / mgCOD). After the wastewater to be treated flows through the first-stage three-layer filter media and undergoes ozone oxidation reaction, it is pumped out from the bottom of the ozone oxidation reaction tank to obtain the treated effluent. The hydraulic retention time of the wastewater to be treated in the ozone oxidation reaction tank is 1.5h.

[0059] (3) The treated effluent pumped from the bottom of the ozone oxidation reaction tank is used as backwashing liquid to backwash the filter media regularly, thereby improving the service life of the filter media; the backwashing cycle is 20-30 days; the backwashing liquid enters from the bottom of the ozone oxidation reaction tank, backwashes the filter media, and then exits from the top of the ozone oxidation reaction tank.

[0060] The treated effluent was sampled and tested. The results were as follows: COD of the treated effluent was 23.2 mg / L, with a removal rate of 80.3%; the suspended solids content of the treated effluent was 9.4 mg / L, with a removal rate of 86.9%; and the pH of the treated effluent was 7.6.

[0061] Comparative Example 1

[0062] This comparative example provides a method for treating recalcitrant organic wastewater using ozone oxidation. This method replaces the filter media in Example 1 with a commercial ozone catalyst (i.e., metal-supported Al2O3 microspheres), while keeping other conditions unchanged, to obtain treated effluent.

[0063] The treated effluent was sampled and tested. The results were as follows: COD of the treated effluent was 64.5 mg / L, with a removal rate of 45.3%; the suspended solids content of the treated effluent was 39 mg / L, with a removal rate of 45.8%; and the pH of the treated effluent was 5.8.

[0064] Comparative Example 2

[0065] This comparative example provides a method for treating recalcitrant organic wastewater using multi-stage filter media enhanced ozone oxidation. This method uses ceramsite, natural zeolite, and gravel as filter media to replace the filter media in Example 1. The ceramsite, natural zeolite, and gravel are packed into the ozone oxidation reaction tank in a three-layer, one-stage manner, with a packing height of 1 / 2 of the tank's height. The three layers of filter media, from top to bottom, are ceramsite, natural zeolite, and gravel, with a packing volume ratio of 1:1:1. The particle size of the ceramsite is d. 10 =1.2mm, the particle size of natural zeolite is d 10 =2mm, the gravel particle size is d 10 =4.5mm; other conditions remain unchanged, and the treated effluent is obtained.

[0066] The treated effluent was sampled and tested. The results were as follows: COD of the treated effluent was 47.1 mg / L, with a removal rate of 60.1%; the suspended solids content of the treated effluent was 15.2 mg / L, with a removal rate of 78.9%; and the pH of the treated effluent was 7.6.

[0067] Example 2

[0068] This embodiment provides a method for treating recalcitrant organic wastewater using multi-level filter media enhanced ozone oxidation.

[0069] The wastewater treated by this method is as follows: COD = 74.5 mg / L, suspended solids content 56 mg / L, pH = 5.8 of the effluent from the biochemical unit of a certain refining and chemical wastewater treatment plant.

[0070] The method includes the following steps:

[0071] (1) The filter media is filled into the ozone oxidation reaction tank in a two-stage manner. The two-stage filter media, from top to bottom, are the first-stage filter media and the second-stage filter media. The filling height of the first-stage filter media is 1 / 3 of the height of the ozone oxidation reaction tank. The first-stage filter media consists of three layers of filter media, from top to bottom: quartz sand, magnetite, and dolomite. The filling volume ratio of quartz sand, magnetite, and dolomite is 1:2:1. The particle size of the quartz sand is d. 10 =0.5mm, the particle size of magnetite is d 10 =0.8mm, the grain size of dolomite is d 10 =1.2mm; The filling height of the second-stage filter media is 1 / 3 of the height of the ozone oxidation reaction tank. The second-stage filter media consists of three layers: magnetite, volcanic rock, and gravel, from top to bottom. The volume ratio of magnetite, volcanic rock, and gravel is 2:2:1. The particle size of the magnetite is d. 10 =0.8mm, the grain size of volcanic rock is d 10 =1.2mm, the gravel particle size is d 10 =2mm;

[0072] (2) The wastewater to be treated is pumped into the ozone oxidation reaction tank from the top with an influent flow rate of 50 L / h. Ozone is introduced from the bottom of the ozone oxidation reaction tank. Based on the amount of wastewater to be treated, the ozone introduction rate is 50 mg (i.e., 0.67 mg O3 / mg COD). After the wastewater to be treated flows through the secondary filter media and undergoes ozone oxidation reaction, it is pumped out from the bottom of the ozone oxidation reaction tank to obtain the treated effluent. The hydraulic retention time of the wastewater to be treated in the ozone oxidation reaction tank is 0.6 h.

[0073] (3) The treated effluent pumped from the bottom of the ozone oxidation reaction tank is used as backwashing liquid to backwash the filter media regularly, thereby improving the service life of the filter media; the backwashing cycle is 20-30 days; the backwashing liquid enters from the bottom of the ozone oxidation reaction tank, backwashes the filter media, and then exits from the top of the ozone oxidation reaction tank.

[0074] The treated effluent was sampled and tested. The results were as follows: COD of the treated effluent was 20.4 mg / L, with a removal rate of 72.4%; the suspended solids content of the treated effluent was 7.2 mg / L, with a removal rate of 87.1%; and the pH of the treated effluent was 7.2.

[0075] Comparative Example 3

[0076] This comparative example provides a method for treating recalcitrant organic wastewater using ozone oxidation. This method replaces the filter media in Example 2 with a commercial ozone catalyst (i.e., metal-supported granular activated carbon), while keeping other conditions unchanged, to obtain treated effluent.

[0077] The treated effluent was sampled and tested. The results were as follows: COD of the treated effluent was 38.1 mg / L, with a removal rate of 48.8%; the suspended solids content of the treated effluent was 23 mg / L, with a removal rate of 58.9%; and the pH of the treated effluent was 5.4.

[0078] Comparative Example 4

[0079] This comparative example provides a method for treating recalcitrant organic wastewater using multi-stage filter media enhanced ozone oxidation. This method uses granular activated carbon, ceramsite, and pebbles as filter media to replace the filter media in Example 2. The filter media are filled into the ozone oxidation reaction tank in a two-stage manner. The two-stage filter media, from top to bottom, are the first-stage filter media and the second-stage filter media. The filling height of both the first-stage and second-stage filter media is 1 / 3 of the height of the ozone oxidation reaction tank. Both the first-stage and second-stage filter media consist of three layers of filter media, from top to bottom: granular activated carbon, ceramsite, and pebbles. The filling volume ratio of granular activated carbon, ceramsite, and pebbles is 1:1:1. The particle size of the granular activated carbon is d. 10 =0.85mm, the particle size of the ceramsite is d 10 =1.2mm, the particle size of the pebble is d 10 =4.4mm; other conditions remain unchanged, and the treated effluent is obtained.

[0080] The treated effluent was sampled and tested. The results were as follows: COD of the treated effluent was 44.7 mg / L, with a removal rate of 40%; the suspended solids content of the treated effluent was 14.2 mg / L, with a removal rate of 74.6%; and the pH of the treated effluent was 6.4.

[0081] Example 3

[0082] This embodiment provides a method for treating recalcitrant organic wastewater using multi-level filter media enhanced ozone oxidation.

[0083] The wastewater treated by this method is: coagulated effluent from a certain refining and chemical desalination plant with COD = 316 mg / L, suspended solids content of 36 mg / L, and pH = 4.3.

[0084] The method includes the following steps:

[0085] (1) The filter media is filled into the ozone oxidation reaction tank in a three-stage manner. The three-stage filter media are, from top to bottom, the first stage filter media, the second stage filter media, and the third stage filter media. The filling height of the first stage filter media is 1 / 5 of the height of the ozone oxidation reaction tank. The first stage filter media consists of three layers of filter media, from top to bottom, manganese sand, quartz sand, and volcanic rock. The filling volume ratio of manganese sand, quartz sand, and volcanic rock is 1:1:1. The particle size of manganese sand and quartz sand is d. 10 =0.8mm, the grain size of volcanic rock is d 10 =1.2mm; The filling height of the second-stage filter media is 1 / 5 of the height of the ozone oxidation reaction tank. The second-stage filter media consists of three layers, from top to bottom: magnetite, dolomite, and manganese sand. The filling volume ratio of magnetite, dolomite, and manganese sand is 1:1:1. The particle size of magnetite and dolomite is d. 10 =2mm, the particle size of manganese sand ore is d 10 =1.2mm; The filling height of the third-stage filter media is 1 / 5 of the height of the ozone oxidation reaction tank. The third-stage filter media consists of three layers, from top to bottom: manganese sand, magnetite, and gravel. The filling volume ratio of manganese sand, magnetite, and gravel is 1:1:1. The particle size of the manganese sand is d. 10 =2mm, the particle size of magnetite is d 10 = 4.5mm, the gravel particle size is d 10 =6mm;

[0086] (2) The wastewater to be treated is pumped into the ozone oxidation reaction tank from the top with an influent flow rate of 15L / h. Ozone is introduced from the bottom of the ozone oxidation reaction tank. Based on the amount of wastewater to be treated, the ozone introduction rate is 200mg (i.e., 0.63mgO3 / mgCOD). The wastewater to be treated flows through the secondary filter media and undergoes ozone oxidation reaction. Then, it is pumped out from the bottom of the ozone oxidation reaction tank to obtain the treated effluent. The hydraulic retention time of the wastewater to be treated in the ozone oxidation reaction tank is 0.5h.

[0087] (3) The treated effluent pumped from the bottom of the ozone oxidation reaction tank is used as backwashing liquid to backwash the filter media regularly, thereby improving the service life of the filter media; the backwashing cycle is 20-30 days; the backwashing liquid enters from the bottom of the ozone oxidation reaction tank, backwashes the filter media, and then exits from the top of the ozone oxidation reaction tank.

[0088] The treated effluent was sampled and tested. The results were as follows: COD of the treated effluent was 97.3 mg / L, with a removal rate of 69.2%; the suspended solids content of the treated effluent was 6 mg / L, with a removal rate of 83.3%; and the pH of the treated effluent was 6.8.

[0089] Comparative Example 5

[0090] This comparative example provides a method for treating recalcitrant organic wastewater using ozone oxidation. This method involves removing the filter media from Example 3 and then treating the wastewater solely with ozone oxidation, keeping other conditions unchanged, to obtain treated effluent.

[0091] The treated effluent was sampled and tested. The results were as follows: COD of the treated effluent was 266.7 mg / L, with a removal rate of 15.6%; the suspended solids content of the treated effluent was 32 mg / L, with a removal rate of 11.1%; and the pH of the treated effluent was 4.1.

[0092] Comparative Example 6

[0093] This comparative example provides a method for treating recalcitrant organic wastewater using multi-stage filter media enhanced ozone oxidation. This method uses granular activated carbon, ceramsite, and natural zeolite as filter media to replace the filter media in Example 3. The filter media are filled into the ozone oxidation reaction tank in a three-stage manner. The three stages of filter media, from top to bottom, are the first stage, the second stage, and the third stage. The filling height of the first, second, and third stages of filter media is 1 / 5 of the height of the ozone oxidation reaction tank. Each of the first, second, and third stages of filter media consists of three layers: granular activated carbon, ceramsite, and natural zeolite, from top to bottom. The volume ratio of granular activated carbon, ceramsite, and natural zeolite is 1:1:1. The particle size of the granular activated carbon is d. 10 =0.45mm, the particle size of the ceramsite is d 10 =0.85mm, the particle size of natural zeolite is d 10 =1.2mm; other conditions remain unchanged, and the treated effluent is obtained.

[0094] The treated effluent was sampled and tested. The results were as follows: COD of the treated effluent was 164.7 mg / L, with a removal rate of 47.8%; the suspended solids content of the treated effluent was 9.2 mg / L, with a removal rate of 74.4%; and the pH of the treated effluent was 5.6.

Claims

1. A method for treating recalcitrant organic wastewater using multi-stage filter media enhanced ozone oxidation, comprising the following steps: (1) The filter media is filled into the ozone oxidation reaction tank in a multi-stage or multi-layer manner; (2) The wastewater to be treated enters from the top of the ozone oxidation reaction tank, and ozone is introduced from the bottom of the ozone oxidation reaction tank. After the wastewater to be treated flows through multiple stages or multiple layers of filter media and undergoes catalytic ozone oxidation reaction, it flows out from the bottom of the ozone oxidation reaction tank to obtain the treated effluent. The filter media is filled into the ozone oxidation reaction tank in a three-layer primary configuration, with a filling height of 1 / 2 of the tank's height. The three layers of filter media, from top to bottom, consist of quartz sand, magnetite, and dolomite, with a volume ratio of 1:1:

1. The particle size of the quartz sand is d. 10 =0.5-2 mm, the grain size of magnetite and dolomite is d 10 =0.8-8 mm; Alternatively, the filter media may be filled into the ozone oxidation reaction tank in a two-stage manner. The two-stage filter media, from top to bottom, consist of a first-stage filter media and a second-stage filter media. The filling height of the first-stage filter media is 1 / 3 of the height of the ozone oxidation reaction tank. The first-stage filter media comprises two layers of filter media, from top to bottom: volcanic rock and quartz sand. The filling volume ratio of volcanic rock to quartz sand is 1:1, and the particle size of the volcanic rock is d. 10 =0.5-4 mm, the particle size of quartz sand is d 10 =0.8-6 mm; The filling height of the second-stage filter media is 1 / 3 of the height of the ozone oxidation reaction tank. The second-stage filter media consists of two layers: manganese sand and dolomite from top to bottom, with a volume ratio of 1:

1. The particle size of the manganese sand and dolomite is d. 10 =0.25-6 mm; Alternatively, the filter media may be filled into the ozone oxidation reaction tank in a two-stage manner. The two-stage filter media, from top to bottom, consist of a first-stage filter media and a second-stage filter media. The filling height of the first-stage filter media is 1 / 3 of the height of the ozone oxidation reaction tank. The first-stage filter media comprises three layers of filter media, from top to bottom: quartz sand, magnetite, and dolomite. The filling volume ratio of quartz sand, magnetite, and dolomite is 1:2:1, and the particle size of quartz sand and magnetite is d. 10 =0.5-4 mm, the grain size of dolomite is d 10 =0.85-8 mm; The filling height of the second-stage filter media is 1 / 3 of the height of the ozone oxidation reaction tank. The second-stage filter media consists of three layers: magnetite, volcanic rock, and gravel, from top to bottom. The volume ratio of magnetite, volcanic rock, and gravel is 2:2:

1. The particle size of the magnetite is d. 10 =0.5-2 mm, the grain size of volcanic rock is d 10 =0.85-4 mm, the gravel particle size is d 10 =1.2-8 mm; Alternatively, the filter media may be filled into the ozone oxidation reaction tank in a three-stage manner, with the three stages being, from top to bottom, the first stage, the second stage, and the third stage. The filling height of the first stage filter media is 1 / 5 of the height of the ozone oxidation reaction tank. The first stage filter media consists of three layers: manganese sand, quartz sand, and volcanic rock, from top to bottom. The filling volume ratio of manganese sand, quartz sand, and volcanic rock is 1:1:1, and the particle size of the manganese sand and quartz sand is d. 10 =0.5-4 mm, the grain size of volcanic rock is d 10 =0.85-6 mm; The filling height of the second-stage filter media is 1 / 5 of the height of the ozone oxidation reaction tank. The second-stage filter media consists of three layers, from top to bottom: magnetite, dolomite, and manganese sand. The filling volume ratio of magnetite, dolomite, and manganese sand is 1:1:

1. The particle size of magnetite and dolomite is d. 10 =0.25-4 mm, the particle size of manganese sand ore is d 10 =0.5-2mm; The filling height of the third-stage filter media is 1 / 5 of the height of the ozone oxidation reaction tank. The third-stage filter media consists of three layers, from top to bottom: manganese sand, magnetite, and gravel. The filling volume ratio of manganese sand, magnetite, and gravel is 1:1:

1. The particle size of the manganese sand is d. 10 =0.85-4 mm, the grain size of magnetite is d 10 =0.85-6 mm, the gravel particle size is d 10 =1.2-8 mm.

2. The method for treating recalcitrant organic wastewater by enhanced ozone oxidation using multi-stage filter media according to claim 1, wherein, The filter media consists of filter media of different particle sizes that have been crushed, washed, and sieved.

3. The method for treating recalcitrant organic wastewater by enhanced ozone oxidation using multi-stage filter media according to claim 1, wherein, Based on the COD in the wastewater to be treated, the ozone injection rate is 0.6-1.5 mgO3 / mgCOD.

4. The method for treating recalcitrant organic wastewater by enhanced ozone oxidation using multi-stage filter media according to claim 1, wherein, The hydraulic retention time of the wastewater to be treated in the ozone oxidation reactor is 30-90 min.

5. The method for treating recalcitrant organic wastewater by enhanced ozone oxidation using multi-stage filter media according to claim 1, wherein, The wastewater to be treated has a COD of 40-400 mg / L, a suspended solids content of 30-200 mg / L, and a pH range of 2-10.

6. The method for treating recalcitrant organic wastewater by enhanced ozone oxidation using multi-stage filter media according to claim 1, wherein, The method for treating recalcitrant organic wastewater with enhanced ozone oxidation using multi-level filter media further includes step (3): using the treated effluent flowing out from the bottom of the ozone oxidation reaction tank as backwashing liquid to backwash the filter media, thereby improving the service life of the filter media; the backwashing cycle is 20-30 days.

7. The method for treating recalcitrant organic wastewater by enhanced ozone oxidation using multi-stage filter media according to claim 1, wherein, The treated effluent has a COD of 20-100 mg / L, a suspended solids content of 2-10 mg / L, and a pH range of 6-8.

8. An apparatus for treating recalcitrant organic wastewater using multi-stage filter media enhanced ozone oxidation, the apparatus being used to implement the method for treating recalcitrant organic wastewater using multi-stage filter media enhanced ozone oxidation as described in any one of claims 1-7, the apparatus comprising: An ozone oxidation reaction tank, and filter media filled in the ozone oxidation reaction tank, wherein the filter media is filled in the ozone oxidation reaction tank in a multi-stage or multi-layer manner; The filter media is filled into the ozone oxidation reaction tank in a three-layer, single-stage manner, with a filling height of 1 / 2 of the tank's height. The three layers of filter media, from top to bottom, consist of quartz sand, magnetite, and dolomite, with a volume ratio of 1:1:

1. The particle size of the quartz sand is d. 10 =0.5-2 mm, the grain size of magnetite and dolomite is d 10 =0.8-8 mm; Alternatively, the filter media may be filled into the ozone oxidation reaction tank in a two-stage manner, with the two-stage filter media consisting of a first-stage filter media and a second-stage filter media from top to bottom; the filling height of the first-stage filter media is 1 / 3 of the height of the ozone oxidation reaction tank, and the first-stage filter media consists of two layers of filter media, with the two layers from top to bottom being volcanic rock and quartz sand, respectively, in a 1:1 volume ratio, and the particle size of the volcanic rock being d. 10 =0.5-4 mm, the particle size of quartz sand is d 10 =0.8-6 mm; The filling height of the second-stage filter media is 1 / 3 of the height of the ozone oxidation reaction tank. The second-stage filter media consists of two layers: manganese sand and dolomite from top to bottom, with a volume ratio of 1:

1. The particle size of the manganese sand and dolomite is d. 10 =0.25-6 mm; Alternatively, the filter media may be filled into the ozone oxidation reaction tank in a two-stage manner, with the two-stage filter media consisting of a first-stage filter media and a second-stage filter media from top to bottom. The filling height of the first-stage filter media is 1 / 3 of the height of the ozone oxidation reaction tank. The first-stage filter media consists of three layers of filter media, namely, quartz sand, magnetite, and dolomite, from top to bottom. The filling volume ratio of quartz sand, magnetite, and dolomite is 1:2:1, and the particle size of quartz sand and magnetite is d. 10 =0.5-4 mm, the grain size of dolomite is d 10 =0.85-8 mm; The filling height of the second-stage filter media is 1 / 3 of the height of the ozone oxidation reaction tank. The second-stage filter media consists of three layers: magnetite, volcanic rock, and gravel, from top to bottom. The volume ratio of magnetite, volcanic rock, and gravel is 2:2:

1. The particle size of the magnetite is d. 10 =0.5-2 mm, the grain size of volcanic rock is d 10 =0.85-4 mm, the gravel particle size is d 10 =1.2-8 mm; Alternatively, the filter media may be filled into the ozone oxidation reaction tank in a three-stage manner, with the three stages being, from top to bottom, the first stage, the second stage, and the third stage. The filling height of the first stage filter media is 1 / 5 of the height of the ozone oxidation reaction tank. The first stage filter media consists of three layers: manganese sand, quartz sand, and volcanic rock, from top to bottom. The filling volume ratio of manganese sand, quartz sand, and volcanic rock is 1:1:1, and the particle size of the manganese sand and quartz sand is d. 10 =0.5-4 mm, the grain size of volcanic rock is d 10 =0.85-6 mm; The filling height of the second-stage filter media is 1 / 5 of the height of the ozone oxidation reaction tank. The second-stage filter media consists of three layers, from top to bottom: magnetite, dolomite, and manganese sand. The filling volume ratio of magnetite, dolomite, and manganese sand is 1:1:

1. The particle size of magnetite and dolomite is d. 10 =0.25-4 mm, the particle size of manganese sand ore is d 10 =0.5-2 mm; The filling height of the third-stage filter media is 1 / 5 of the height of the ozone oxidation reaction tank. The third-stage filter media consists of three layers, from top to bottom: manganese sand, magnetite, and gravel. The filling volume ratio of manganese sand, magnetite, and gravel is 1:1:

1. The particle size of the manganese sand is d. 10 =0.85-4 mm, the grain size of magnetite is d 10 =0.85-6 mm, the gravel particle size is d 10 =1.2-8mm.

9. The apparatus for treating recalcitrant organic wastewater by multi-stage filter media enhanced ozone oxidation according to claim 8, wherein, The filter media consists of filter media of different particle sizes that have been crushed, washed, and sieved.

10. The apparatus for treating recalcitrant organic wastewater by multi-stage filter media enhanced ozone oxidation according to claim 8, wherein, The top of the ozone oxidation reaction tank is equipped with a wastewater inlet and an overflow outlet, while the bottom is equipped with an ozone inlet and a treated effluent outlet.

11. The apparatus for treating recalcitrant organic wastewater by enhanced ozone oxidation using multi-stage filter media according to claim 8, wherein, The ozone oxidation reaction tank is equipped with a backwash liquid inlet at the bottom and a backwash drain outlet at the top.

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