Process for integrated treatment of polluted underground water based on internal circulation ozone contact reaction tower

Abstract

The invention discloses a process for integrated treatment of polluted underground water based on an internal circulation ozone contact reaction tower. The process comprises the following steps: S1, primary treatment; s2, ozone contact reaction; to-be-treated water is introduced into the water inlet of the tower body, ozone gas is injected into the inner cylinder to promote water flow in the inner cylinder to flow to the two filling layers from bottom to top, and then the water flow circularly flows back to the inner cylinder; s3, carrying out aeration treatment; s4, precipitating and filtering; according to the process for treating the sewage by adopting the internal circulation ozone contact reaction tower, the gas-liquid mass transfer effect can be optimized, the flow state of ozone is smoother, the ozone utilization rate is increased by 25% or above, and the sewage treatment effect can be improved by setting the whole-flow process.

Description

Technical Field

[0001] The invention relates to the technical field of water treatment, and in particular to a process for treating contaminated groundwater based on an integrated internal circulation ozone contact reaction tower. Background Art

[0002] In recent years, many closed chemical companies have left behind soil and groundwater pollution problems. When treating these contaminated soils, multiphase extraction methods are used. Multiphase extraction (MPE) technology is an in-situ remediation technology with high remediation efficiency, large treatment area, and can be applied to high-concentration contaminated land. Through vacuum extraction, soil gas, groundwater and floating oil layers in underground contaminated areas are extracted to the ground for phase separation and treatment to achieve the purpose of site remediation. Multiphase extraction will obtain a large amount of multiphase extracts, which also contain low-concentration dissolved organic matter, with complex components, large concentration fluctuations, variable flow rates, and many difficult-to-degrade organic matter. They need to be treated before they can be reused or directly discharged into surface water.

[0003] In the process of water treatment of multiphase extracts, advanced oxidation processes are usually used; advanced oxidation processes can produce free radicals with strong oxidizing properties. These free radicals are non-selective to organic matter and can treat toxic and harmful wastewater. Advanced oxidation processes include Fenton process, photochemical oxidation process, electrochemical oxidation process, catalytic ozonation process, etc. Among them, catalytic ozonation process has the characteristics of high oxidation ability, short treatment time, low selectivity to organic matter, and the catalyst can form different oxidation mechanisms, has strong adaptability to wastewater, and is a potential process for treating multiphase extracts.

[0004] At present, in the catalytic ozonation process, due to the poor ozone mass transfer effect and low ozone utilization rate in the traditional packed tower, the ozone dosage in actual application is large, and the energy consumption of the ozone preparation process is high, resulting in high cost of ozonation technology. According to the results of literature calculations, the ozone transfer efficiency in the empty tower is less than 25%, which is inefficient for water treatment; the internal circulation ozone contact reaction tower is a device that uses the strong oxidizing property of ozone to treat wastewater. In the existing treatment process, the process method for water treatment using the internal circulation ozone contact reaction tower needs to be optimized to improve the effect of water treatment. Summary of the invention

[0005] In order to solve the above problems, the present invention provides a process for treating contaminated groundwater based on an integrated internal circulation ozone contact reaction tower.

[0006] A process for treating contaminated groundwater based on an internal circulation ozone contact reaction tower, wherein the internal circulation ozone contact reaction tower comprises a tower body, two filling layers arranged inside the tower body for ozone catalysis, and an inner cylinder inside the tower body for reflux; the process comprises the following steps:

[0007] S1, preliminary processing;

[0008] The contaminated groundwater is treated by an oil-water separation system to obtain oil and water to be treated, the oil is recovered, and then the obtained water to be treated is filtered, wherein the filtration adopts a filter with a pore size of 0.45 μm; then the filtered water to be treated is coagulated; the coagulation treatment is as follows: polyaluminium chloride and polyacrylamide are added to the water to be treated at a ratio of 150-250 mg: 8-15 mg: 1 L, and then stirred at a speed of 150-200 rpm for 0.5-2 min, and then stirred at a speed of 70-90 rpm for 10 min and then allowed to stand for separation to obtain the water to be treated after preliminary treatment;

[0009] S2, ozone contact reaction;

[0010] The water to be treated after preliminary treatment is 1-5m 3 / h flow rate into the water inlet of the tower body, inject ozone gas into the inner cylinder to promote the water flow in the inner cylinder to flow from bottom to top to the two filling layers, and then circulate back to the inner cylinder, the ozone dosage is 200-700 mg / L·h; the water volume of the circulating reflux is controlled to be 50-80% of the water volume of the water inlet, the reflux speed is 0.5-2m / s; the ozone contact reaction time is 20-40min;

[0011] S3, aeration treatment;

[0012] After the ozone contact reaction is completed, stop introducing ozone and perform aeration treatment. The aeration flow rate is 0.5 to 2 L / min and the aeration time is 10 to 30 min.

[0013] S4, sedimentation filtration;

[0014] The aerated water enters the sedimentation tank and is treated after 12 to 24 hours of sedimentation.

[0015] Description: The above method, by setting reasonable and scientific ozone contact parameters, increases the residence time of ozone in the filling layer, improves the ozone utilization and mass transfer efficiency, reduces the energy consumption of the reaction tower, and improves the efficiency of catalytic degradation of sewage. Through aeration treatment, ozone in the water can be removed to prevent ozone from causing new pollution to the water body.

[0016] Furthermore, in the S2 ozone contact reaction, micro-nano bubbles are used to assist ozone catalysis; the method of using micro-nano bubbles to assist ozone catalysis includes: before the ozone gas enters the internal circulation ozone contact reaction tower, the ozone gas is dispersed by a micro-nano bubble generator to generate micro-nano bubbles, and the generated micro-nano bubbles are injected into the inner cylinder; wherein the power of the micro-nano bubble generator is 50 to 200 W, the micro-nano bubble gas flow rate is 0.5 to 2 L / min, and the residence time of the ozone gas in the micro-nano bubble generator is 2 to 5 min.

[0017] Note: The above-mentioned micro-nano bubble-assisted ozone catalysis can significantly increase the solubility and contact area of ​​ozone and improve the oxidation efficiency; by integrating micro-nano bubble technology into the treatment process of the internal circulation ozone contact reaction tower, the utilization rate of ozone and the removal efficiency of pollutants can be significantly improved, thereby improving the overall treatment effect.

[0018] Furthermore, in the preliminary treatment of S1, the oil-water separation system includes an oil-water separator, an oil collection tank and a to-be-treated water collection tank.

[0019] Furthermore, the oil-water separator is a gravity oil-water separator.

[0020] Description: The above gravity oil-water separator has the advantages of simple structure, easy maintenance, energy saving and environmental protection, and high separation efficiency.

[0021] Furthermore, during the oil-water separation process, 0.5 to 1 mmol / L of a separation aid is added, and the separation aid is methyl methacrylate.

[0022] Description: Methyl methacrylate, as an auxiliary agent for oil-water separation, can improve separation efficiency, enhance stability and environmental protection.

[0023] Furthermore, a layer of catalyst is provided on each of the two filling layers, the ratio of the spacing between the filling layers to the height of the reaction tower is 0.16-0.25, the catalyst on the lower filling layer is a spherical aluminum-based catalyst, and the catalyst on the upper filling layer is a vanadium-based catalyst, and the dosage of the spherical aluminum-based catalyst and the vanadium-based catalyst is in a ratio of 500-800g:5L to the reaction tower.

[0024] Note: The above two layers of different types of catalysts may have different active sites and catalytic mechanisms. Their combined use can produce a synergistic effect and improve the removal efficiency of pollutants. The two-layer system using spherical aluminum-based catalysts and vanadium-based catalysts can provide a more comprehensive, efficient and stable water treatment solution, especially for complex and variable polluted water quality.

[0025] Furthermore, the spherical aluminum-based catalyst uses a Co3O4 / Al2O3 catalyst, and the vanadium-based catalyst uses a V2O5 / TiO2 catalyst.

[0026] Description: Co3O4 / Al2O3 catalyst has high catalytic activity, good dispersibility, stability and selectivity; V2O5 / TiO2 catalyst has the advantages of excellent oxidation performance, low-temperature activity, good thermal stability and large specific surface area: Co3O4 / Al2O3 catalyst can improve the selectivity of pollutants in water treatment, while V2O5 / TiO2 catalyst is suitable for strong oxidizing environment. The combination of these two can have a better effect in water treatment.

[0027] Furthermore, the preparation method of the Co3O4 / Al2O3 catalyst comprises:

[0028] Firstly, the Al2O3 is pretreated by radio frequency plasma, the power of radio frequency plasma treatment is 50-200W, and the treatment time is 5-10min;

[0029] Take a CoSO4 solution with a concentration of 0.5-1 mol / L, add Al2O3 to the CoSO4 solution at a ratio of 1-2 g: 2-5 mL, and at the same time add ammonia water to adjust the pH to 7-9, the temperature is 60-80°C, the reaction time is 2-4 hours, and a precipitate is obtained;

[0030] The precipitate is dried and placed under plasma with a power of 100 to 500 W. Co(acac)2 gas with a flow rate of 10 ml / min is introduced for deposition for 5 to 20 min. The precipitate is then calcined at 300 to 500 °C for 2 to 3 h to obtain a Co3O4 / Al2O3 catalyst.

[0031] Description: The Co3O4 / Al2O3 catalyst obtained by the above method can increase the active sites on the support surface by plasma pretreatment, improve the adsorption capacity of the metal precursor, and avoid the multiple steps and possible heterogeneity in the traditional precipitation process.

[0032] Furthermore, the preparation method of the V2O5 / TiO2 catalyst comprises:

[0033] Dissolve ammonium metavanadate in deionized water at a ratio of 1 to 3 g: 100 ml to form an ammonium metavanadate solution; then add titanium dioxide to the prepared ammonium metavanadate solution at a ratio of 3 to 4 g: 100 ml, and stir at a temperature of 40 to 60° C. for 2 to 4 hours;

[0034] Then, 5-15% of ammonium tungstate by mass of ammonium metavanadate is added and mixed to obtain a mixture, which is dried completely at 70-80°C, and then calcined at 400-500°C for 2-3h to obtain a V2O5 / TiO2 catalyst.

[0035] Description: The V2O5 / TiO2 catalyst prepared by the above method has good stability and regeneration, which can extend the service life of the catalyst. The catalyst is easy to regenerate and its activity can be restored by appropriate regeneration methods after deactivation, such as thermal regeneration, chemical regeneration, etc.

[0036] The beneficial effects of the present invention are:

[0037] The method of the present invention increases the residence time of ozone in the filling layer, improves the ozone utilization and mass transfer efficiency, reduces the energy consumption of the reaction tower, and improves the efficiency of sewage catalytic degradation by setting reasonable and scientific ozone contact parameters and operation methods. Ozone in water can be removed by aeration treatment to prevent ozone from causing new pollution to the water body. At the same time, the ozone catalysis assisted by micro-nano bubbles can significantly increase the solubility and contact area of ​​ozone and improve the oxidation efficiency. By integrating the micro-nano bubble technology into the treatment process of the internal circulation ozone contact reaction tower, the utilization rate of ozone and the removal efficiency of pollutants can be significantly improved, thereby improving the overall treatment effect. In addition, the water treatment effect is further improved by the setting of the catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a graph comparing the COD and TOC treatment effects of high-concentration wastewater in an embodiment of the present invention (a: COD; b: TOC);

[0039] Figure 2 This is a comparison chart of the treatment effects of characteristic pollutants in high-concentration wastewater in the embodiments of the present invention;

[0040] Figure 3 This is a comparison chart of the treatment effects of COD and TOC on medium-concentration wastewater in the embodiments of the present invention;

[0041] Figure 4 This is a comparison chart of the treatment effects of characteristic pollutants in medium-concentration wastewater in the embodiments of the present invention;

[0042] Figure 5 This is a comparison chart of the treatment effects of low-concentration wastewater COD and TOC in the embodiments of the present invention;

[0043] Figure 6 This is a comparison diagram of the treatment effects of low-concentration wastewater characteristic pollutants in the embodiments of the present invention; DETAILED DESCRIPTION

[0044] In order to further illustrate the method adopted by the present invention and the effect achieved, the technical solution of the present invention will be clearly and completely described in combination with experiments below.

[0045] Embodiment 1: A process for treating contaminated groundwater based on an integrated internal circulation ozone contact reaction tower, wherein the internal circulation ozone contact reaction tower comprises a tower body, two filling layers for ozone catalysis arranged inside the tower body, and an inner cylinder for reflux inside the tower body; the process comprises the following steps:

[0046] S1, preliminary processing;

[0047] The contaminated groundwater is treated by an oil-water separation system to obtain oil and water to be treated, the oil is recovered, and then the obtained water to be treated is filtered, wherein the filtration adopts a filter with a pore size of 0.45 μm; then the filtered water to be treated is coagulated; the coagulation treatment is as follows: polyaluminium chloride and polyacrylamide are added to the water to be treated at a ratio of 200 mg:10 mg:1 L, and then stirred at a speed of 160 rpm for 1 minute, and then stirred at a speed of 80 rpm for 10 minutes and then allowed to stand for separation to obtain the water to be treated after preliminary treatment;

[0048] The oil-water separation system comprises an oil-water separator, an oil collection tank and a to-be-treated water collection tank.

[0049] The oil-water separator is a gravity oil-water separator.

[0050] During the oil-water separation process, 0.8 mmol / L of a separation aid is added, wherein the separation aid is methyl methacrylate;

[0051] A layer of catalyst is provided on each of the two packing layers, the ratio of the spacing between the packing layers to the height of the reaction tower is 0.20, the catalyst on the packing layer located at the bottom is a spherical aluminum-based catalyst, the catalyst on the packing layer located at the top is a vanadium-based catalyst, and the dosage of the spherical aluminum-based catalyst and the vanadium-based catalyst to the reaction tower is 600g:5L in ratio;

[0052] The spherical aluminum-based catalyst uses a Co3O4 / Al2O3 catalyst, and the vanadium-based catalyst uses a V2O5 / TiO2 catalyst.

[0053] The preparation method of the Co3O4 / Al2O3 catalyst comprises:

[0054] Firstly, Al2O3 was pretreated by radio frequency plasma, the power of radio frequency plasma treatment was 100W, and the treatment time was 7min;

[0055] Take a 0.7 mol / L CoSO4 solution, add Al2O3 to the CoSO4 solution at a ratio of 1.5 g:4 mL, and add ammonia water to adjust the pH to 8. The temperature is 70°C and the reaction time is 3 h to obtain a precipitate.

[0056] The precipitate was dried and placed under plasma with a power of 300 W. Co(acac)2 gas with a flow rate of 10 ml / min was introduced for deposition for 10 min. The precipitate was then calcined at 400°C for 2.5 h to obtain a Co3O4 / Al2O3 catalyst.

[0057] The preparation method of the V2O5 / TiO2 catalyst comprises:

[0058] Dissolve ammonium metavanadate in deionized water at a ratio of 2 g:100 ml to form an ammonium metavanadate solution; then add titanium dioxide to the prepared ammonium metavanadate solution at a ratio of 3.2 g:100 ml, and stir at 50°C for 3 hours;

[0059] Then, ammonium tungstate accounting for 10% of the mass of ammonium metavanadate was added and mixed to obtain a mixture, and the mixture was dried at a temperature of 75° C. until complete, and then calcined at a temperature of 450° C. for 2.5 hours to obtain a V2O5 / TiO2 catalyst.

[0060] S2, ozone contact reaction;

[0061] The treated water after preliminary treatment is 3 / h flow rate is introduced into the water inlet of the tower body, ozone gas is injected into the inner cylinder to promote the water flow in the inner cylinder to flow from bottom to top to the two filling layers, and then circulate back to the inner cylinder, the ozone dosage is 500mg / L·h; the water volume of the circulating reflux is controlled to be 60% of the water volume of the water inlet, the reflux speed is 1m / s; the ozone contact reaction time is 30min;

[0062] In the above-mentioned ozone contact reaction, micro-nano bubbles are used to assist ozone catalysis; the method of using micro-nano bubbles to assist ozone catalysis comprises: before the ozone gas enters the internal circulation ozone contact reaction tower, the ozone gas is dispersed by a micro-nano bubble generator to generate micro-nano bubbles, and the generated micro-nano bubbles are injected into the inner cylinder; wherein the power of the micro-nano bubble generator is 100W, the micro-nano bubble gas flow rate is 0.8L / min, and the residence time in the micro-nano bubble generator is 3min;

[0063] S3, aeration treatment;

[0064] After the ozone contact reaction is completed, stop introducing ozone and perform aeration treatment. The aeration flow rate is 1L / min and the aeration time is 20min.

[0065] S4, sedimentation filtration;

[0066] The aerated water enters the sedimentation tank, where it is filtered after settling for 15 hours to complete the treatment.

[0067] Example 2: This example is different from Example 1 in that the processing parameters in S1 are different. During the oil-water separation process, 0.5 mmol / L of a separation aid is added, and the separation aid is methyl methacrylate. The coagulation treatment is as follows: polyaluminum chloride and polyacrylamide are added to the water to be treated in a ratio of 150 mg: 15 mg: 1L, and then stirred at a speed of 150 rpm for 2 minutes, and then stirred at a speed of 70 rpm for 10 minutes and then allowed to stand for separation to obtain the water to be treated after preliminary treatment.

[0068] Example 3: The difference between this example and Example 1 is that the processing parameters in S1 are different. During the oil-water separation process, 1 mmol / L of separation aid is added, and the separation aid is methyl methacrylate. The coagulation treatment is: polyaluminum chloride and polyacrylamide are added to the water to be treated in a ratio of 250 mg: 8 mg: 1L, and then stirred at a speed of 200 rpm for 0.5 min, and then stirred at a speed of 90 rpm for 10 min and then allowed to stand for separation to obtain the water to be treated after preliminary treatment.

[0069] Example 4: This example is different from Example 1 in that the preparation component parameters of the Co3O4 / Al2O3 catalyst are different. A CoSO4 solution with a concentration of 0.5 mol / L is taken, and Al2O3 is added to the CoSO4 solution at a ratio of 1 g:2 mL, and ammonia water is added dropwise to adjust the pH to 9.

[0070] Example 5: This example is different from Example 1 in that the preparation component parameters of the Co3O4 / Al2O3 catalyst are different. A CoSO4 solution with a concentration of 1 mol / L is taken, and Al2O3 is added to the CoSO4 solution in a ratio of 2g:5mL, and ammonia water is added dropwise to adjust the pH to 7.

[0071] Example 6: This example is different from Example 1 in that the parameters of the preparation method of the Co3O4 / Al2O3 catalyst are different. First, Al2O3 is pretreated with radio frequency plasma. The power of the radio frequency plasma treatment is 50 W and the treatment time is 10 min.

[0072] Take a CoSO4 solution with a concentration of , add Al2O3 to the CoSO4 solution, and at the same time drop ammonia water, the temperature is 60℃, the reaction time is 2h, and a precipitate is obtained;

[0073] The precipitate was dried and placed under plasma with a power of 100 W. Co(acac)2 gas with a flow rate of 10 ml / min was introduced for deposition for 5 min. The precipitate was then calcined at 300°C for 2 h to obtain a Co3O4 / Al2O3 catalyst.

[0074] Example 7: This example is different from Example 1 in that the parameters of the preparation method of the Co3O4 / Al2O3 catalyst are different. First, Al2O3 is pretreated with radio frequency plasma. The power of the radio frequency plasma treatment is 200 W and the treatment time is 5 min.

[0075] Take a CoSO4 solution with a concentration of , add Al2O3 to the CoSO4 solution, and at the same time drop ammonia water, the temperature is 80℃, the reaction time is 4h, and a precipitate is obtained;

[0076] The precipitate is dried and placed under plasma with a power of 100 to 500 W. Co(acac)2 gas with a flow rate of 10 ml / min is introduced for deposition for 20 min. The precipitate is then calcined at 500°C for 3 h to obtain a Co3O4 / Al2O3 catalyst.

[0077] Example 8: The difference between this example and Example 1 is that the preparation component parameters of the V2O5 / TiO2 catalyst are different. Ammonium metavanadate is dissolved in deionized water at a ratio of 3g:100ml to form an ammonium metavanadate solution; titanium dioxide is added to the prepared ammonium metavanadate solution at a ratio of 4g:100ml; and then ammonium tungstate accounting for 5% of the mass of the ammonium metavanadate is added and mixed.

[0078] Example 9: The difference between this example and Example 1 is that the preparation component parameters of the V2O5 / TiO2 catalyst are different. Ammonium metavanadate is dissolved in deionized water at a ratio of 1g:100ml to form an ammonium metavanadate solution; titanium dioxide is added to the prepared ammonium metavanadate solution at a ratio of 3g:100ml; and then ammonium tungstate accounting for 15% of the mass of the ammonium metavanadate is added and mixed.

[0079] Example 10: The difference between this example and Example 1 is that the parameters of the preparation method of the V2O5 / TiO2 catalyst are different. Ammonium metavanadate is dissolved in deionized water to form an ammonium metavanadate solution; titanium dioxide is added to the prepared ammonium metavanadate solution and stirred at 60°C for 2 hours; then ammonium tungstate is added and mixed to obtain a mixture, and the mixture is dried to completion at 70°C, and then calcined at 400°C for 2 hours to obtain a V2O5 / TiO2 catalyst.

[0080] Example 11: The difference between this example and Example 1 is that the parameters of the preparation method of the V2O5 / TiO2 catalyst are different. Ammonium metavanadate is dissolved in deionized water to form an ammonium metavanadate solution; titanium dioxide is added to the prepared ammonium metavanadate solution and stirred at 40°C for 4 hours; then ammonium tungstate is added and mixed to obtain a mixture, and the mixture is dried to completion at 80°C, and then calcined at 500°C for 3 hours to obtain a V2O5 / TiO2 catalyst.

[0081] Example 12: This example is different from Example 1 in that the flow rate of the water to be treated in S2 is different. The water to be treated is 3 / h is introduced into the water inlet of the tower body, and the amount of circulating reflux water is 80% of the amount of water at the water inlet.

[0082] Example 13: This example is different from Example 1 in that the flow rate of the water to be treated in S2 is different. The water to be treated is 3 / h is introduced into the water inlet of the tower body, and the amount of circulating reflux water is 50% of the amount of water at the water inlet.

[0083] Example 14: This example is different from Example 1 in that the ozone dosage in S2 is different, and the ozone dosage is 200 mg / L·h.

[0084] Example 15: This example is different from Example 1 in that the ozone dosage in S2 is different, and the ozone dosage is 700 mg / L·h.

[0085] Example 16: This example is different from Example 1 in that the reflux velocity in S2 is 0.5-2 m / s; and the ozone contact reaction time is 20 min.

[0086] Example 17: This example is different from Example 1 in that the reflux velocity in S2 is 0.5-2 m / s; and the ozone contact reaction time is 40 min.

[0087] Example 18: This example is different from Example 1 in that the power of the micro-nano bubble generator is 50 W, the micro-nano bubble gas flow rate is 2 L / min, and the residence time is 2 min.

[0088] Example 19: This example is different from Example 1 in that the power of the micro-nano bubble generator is 200 W, the micro-nano bubble gas flow rate is 0.5 L / min, and the residence time is 5 min.

[0089] Example 20: This example is different from Example 1 in that the flow rate of aeration treatment in S3 is 0.5 L / min, and the aeration treatment time is 10 min; and filtration is performed after sedimentation for 12 h in S4.

[0090] Example 21: This example is different from Example 1 in that the flow rate of aeration treatment in S3 is 2 L / min, and the aeration treatment time is 30 min; and the sedimentation in S4 is filtered after 24 h.

[0091] Example 22: This example is different from Example 1 in that the ratio of the spacing between the filling layers to the height of the reaction tower is 0.16, the catalyst on the lower filling layer is a spherical aluminum-based catalyst, the catalyst on the upper filling layer is a vanadium-based catalyst, and the ratio of the amount of the aluminum-based catalyst to the vanadium-based catalyst added to the reaction tower is 500g:5L.

[0092] Example 23: This example is different from Example 1 in that the ratio of the spacing between the filling layers to the height of the reaction tower is 0.25, the catalyst on the lower filling layer is a spherical aluminum-based catalyst, and the catalyst on the upper filling layer is a vanadium-based catalyst, and the ratio of the amount of the aluminum-based catalyst to the vanadium-based catalyst added to the reaction tower is 800g:5L.

[0093] Experimental Example: The description of this experimental example is based on the scheme described in Example 1, and is intended to illustrate the practical application effect of the present invention.

[0094] Experimental example:

[0095] 1. The optimized internal circulation ozone contact reaction tower and the traditional ozone reaction tower were used to treat the same wastewater. According to the method of Example 1, the aeration flow rate was 900 mL / min and the concentration of 45 g / m was introduced into the reactor. 3 O3, intermittent treatment for 60 minutes, then continuous treatment for 120 minutes, ozone dosage 600mg / L·h. And the treatment effect with and without catalyst was investigated respectively, the catalyst dosage was 800g, and the volume of the reaction tower was 4.7L;

[0096] The experimental water is a wastewater from a pesticide factory with multiple extraction solutions. The COD of the high-concentration wastewater is 2000 mg / L. The removal effects of COD, TOC and characteristic pollutants are compared. Figure 1 shown.

[0097] Depend on Figure 1 As we know, for high-concentration wastewater, when the tower is empty or a catalyst is added, the removal efficiency of COD and TOC of the internal circulation ozone reactor is significantly improved compared with the ordinary ozone reactor after 60 minutes of treatment, and the removal rate of characteristic pollutants is also significantly improved. In the following two HRT continuous treatment processes, the treatment efficiency of the internal circulation ozone reactor has a slight decrease, but the improvement in ozone treatment efficiency compared with the ordinary ozone reactor is still obvious.

[0098] In the case of an empty tower, the treatment lasted for 60 minutes, the ozone dosage was 600 mg / (L·h), and the COD degradation of ICR wastewater was 440 mg / L, which was 57.14% higher than that of OR, and the TOC degradation was 59.4 mg / L, which was 65% higher than that of OR. After 2 HRT continuous flow treatments, the COD degradation of ICR was 430 mg / L and the TOC degradation was 58.6 mg / L every 60 minutes, respectively. The treatment effect of ICR was still significantly improved compared with OR. The COD removal effect of ICR reached 0.72 mg COD for 1 mg ozone, and OR removed 0.48 mg COD, with a significant improvement effect.

[0099] When the catalyst is added, the treatment time is 60 minutes, the ozone dosage is 600 mg / (L·h), and the COD degradation of ICR wastewater is 532 mg / L, which is 60.98% higher than that of OR, and the TOC degradation is 66.6 mg / L, which is 66.7% higher than that of OR. After 2 HRT continuous flow treatments, the COD degradation of ICR is 520 mg / L and the TOC degradation is 58.1 mg / L every 60 minutes, respectively. The treatment effect of ICR is still significantly improved compared with OR. The COD removal effect of ICR is 0.87 mg COD for 1 mg ozone, and OR removes 0.51 mg COD, which is a significant improvement.

[0100] Adding catalysts further increases the pollutant removal rate of ICR compared to OR, because the internal circulation function in ICR allows the catalyst to contact ozone more fully and increases the pores of the catalyst. In addition, the continuous type decreases the pollutant treatment rate of ICR compared to the intermittent type, because the continuous operation increases the turbulence of the water flow inside the OR and improves the treatment effect.

[0101] The degradation of some characteristic pollutants (dichloromethane, chloroform, benzene, chlorobenzene, toluene) in the multiphase extract during the catalytic ozonation process was analyzed. The experimental results are as follows: Figure 2 shown.

[0102] (a: ozone dosage 600 mg / (L·h) without catalyst; b: ozone dosage 600 mg / (L·h) with catalyst)

[0103] In the ICR system, after 2 HRT continuous treatment with ozone dosage of 600 mg / (L·h), without adding catalyst, the removal rates of chlorobenzene, dichloromethane, benzene, toluene and chloroform were 93.7%, 94.3%, 84.6%, 84.6% and 83.2%, respectively, which were 17.1%, 19.7%, 19%, 19.4% and 15.3% higher than OR. With the addition of catalyst, the removal rates of chlorobenzene, dichloromethane, benzene, toluene and chloroform were 93.6%, 96.6%, 94.3%, 85.1% and 87%, respectively, which were 14.4%, 19.7%, 16%, 16.1% and 18.7% higher than OR. Under continuous operation, the removal rate of ICR characteristic pollutants is significantly higher than the COD removal rate, because ozone converts difficult-to-degrade pollutants into easily degradable substances by destroying the structure. In addition, the improvement in the removal rate of characteristic pollutants by ICR is lower than that by OR. On the one hand, this is because the reflux condition of the internal circulation system is affected under continuous flow operation. On the other hand, the continuous operation increases the water flow disturbance in OR, resulting in a good turbulent state in the reaction tower.

[0104] Although neither dichloromethane nor chloroform reached the Class III groundwater standard after 120 minutes of continuous flow treatment, the degradation rate of dichloromethane and chloroform in the ordinary ozone reaction tower and the internal circulation ozone reaction tower was very fast compared with the internal circulation ozone reaction tower. In the actual process, it only needs to appropriately extend the reaction time to achieve the effect of complete degradation. The initial concentration of benzene was 222 mg / L. After 120 minutes of continuous flow treatment in the internal circulation ozone reaction tower system, the concentration was reduced to 12 mg / L. The Class III groundwater standard can be reached by increasing the time. The initial concentration of chlorobenzene was about 157 mg / L. After 120 minutes of continuous flow treatment in the ordinary ozone reaction tower and the internal circulation ozone reaction tower, the concentrations were 31 mg / L and 9.9 mg / L, respectively, reaching the Class II groundwater standard. The initial concentration of toluene was about 74.68 mg / L. After 120 minutes of continuous flow treatment in the ordinary ozone reaction tower and the internal circulation ozone reaction tower, the concentrations were 16.7 mg / L and 11.1 mg / L, respectively, reaching the Class II groundwater standard. In the removal of characteristic pollutants, the oxidation efficiency of the internal circulation ozone reaction tower system is much higher than that of the ordinary ozone reaction tower system.

[0105] Through the treatment results of high-concentration wastewater under the above-mentioned continuous working conditions, it can be found that the use and setting of the reaction tower in the method of this embodiment (i.e., the design of the ozone oxidation catalysis method) and the selection of the catalyst have better effects than those in the prior art. Therefore, it can be seen that the process method in the embodiment of the present invention is more preferred (the same is true for the treatment results of the following two and three for different polluted wastewaters).

[0106] 2. Comparative study on the treatment effect of medium-concentration wastewater under continuous conditions

[0107] The optimized internal circulation ozone contact reactor and the ordinary ozone reactor were used to treat the same wastewater. The aeration flow rate was 600 mL / min and the concentration of 45 g / m 3 O3, intermittent treatment for 60 minutes, then continuous treatment for 120 minutes, ozone dosage 400mg / (L·h). The treatment effects of adding catalyst and not adding catalyst were investigated respectively. The dosage of catalyst was 800g. The experimental water was a number of extract wastewater from a pesticide factory. The COD of the medium concentration wastewater was 500mg / L. The removal effects of COD, TOC and characteristic pollutants were compared. Figure 3 shown.

[0108] Depend on Figure 3 As far as we know, for medium-concentration wastewater, when the tower is empty or a catalyst is added, the removal efficiency of COD and TOC of the internal circulation ozone reactor is significantly improved compared with the ordinary ozone reactor after 60 minutes of treatment, and the removal rate of characteristic pollutants is also significantly improved. In the following two HRT continuous treatment processes, the treatment efficiency of the internal circulation ozone reactor has a slight decrease, but the improvement in treatment efficiency compared with the ordinary ozone reactor is still obvious.

[0109] After 60 minutes of treatment, the ozone dosage was 400 mg / (L·h), and the ICR treated the wastewater. In the case of an empty tower, the COD removal rate was 39.51%, which was 9.97% higher than that of OR, and the TOC degradation was 39.84%, which was 10.59% higher than that of OR. After 2 HRT continuous treatments, the COD removal rate of ICR was 38.68% and the TOC degradation was 39.60% every 60 minutes. With the addition of catalyst, the COD removal rate was 42.62%, which was 11.82% higher than that of OR, and the TOC degradation was 40.71%, which was 11.14% higher than that of OR. After 2 HRT continuous treatments, the COD removal rate of ICR was 41.77% and the TOC degradation was 40.55% every 60 minutes. The treatment effect of ICR was still significantly improved compared with OR. Due to the decrease in the initial concentration of pollutants, the increase in the removal rate of pollutants by ICR compared with OR decreased, which was because the concentration of pollutants limited the reaction intensity.

[0110] The degradation of some characteristic pollutants (dichloromethane, chloroform, benzene, chlorobenzene, toluene) in the multiphase extract during the catalytic ozonation process was analyzed. The experimental results are as follows: Figure 4 shown.

[0111] (a: ozone dosage 400 mg / (L·h) without catalyst; b: ozone dosage 400 mg / (L·h) with catalyst)

[0112] In the ICR system, after 2 HRT continuous treatment with ozone dosage of 400 mg / (L·h), without adding catalyst, the removal rates of chlorobenzene, dichloromethane, benzene, toluene and chloroform were 97.7%, 98.9%, 98.2%, 98.4% and 99%, respectively, which were 3.6%, 1.4%, 2.2%, 3.3% and 3.1% higher than OR. With the addition of catalyst, the removal rates of chlorobenzene, dichloromethane, benzene, toluene and chloroform were 98%, 98.9%, 98.4%, 98.8% and 99.1%, respectively, which were 3.2%, 0.8%, 2.1%, 3.1% and 2.5% higher than OR. Due to the low initial concentration, the removal rates of characteristic pollutants in continuous operation of ICR and OR reached more than 95%.

[0113] After 120 minutes of continuous flow treatment in the ordinary ozone reaction tower and the internal circulation ozone reaction tower, chloroform reached the groundwater Class II and Class I standards respectively. The initial concentration of dichloromethane was 920 mg / L. After 120 minutes of continuous flow treatment in the internal circulation ozone reaction tower system, the concentration was reduced to 2.05 mg / L, reaching the groundwater Class II standard. The initial concentration of benzene was 222 mg / L. After 120 minutes of continuous flow treatment in the internal circulation ozone reaction tower system, the concentration was reduced to 0.37 mg / L, reaching the groundwater Class I standard. The initial concentration of chlorobenzene was about 157 mg / L. After 120 minutes of continuous flow treatment in the ordinary ozone reaction tower and the internal circulation ozone reaction tower, the concentrations were 0.446 mg / L and 0.566 mg / L, reaching the groundwater Class I and Class II standards respectively. The initial concentration of toluene was about 74.68 mg / L. After 120 minutes of continuous flow treatment in the ordinary ozone reaction tower and the internal circulation ozone reaction tower, the concentrations were 0.14 mg / L and 0.11 mg / L, respectively, reaching the Class I groundwater standard. In the removal of characteristic pollutants, the oxidation efficiency of the internal circulation ozone reaction tower system is higher than that of the ordinary ozone reaction tower system.

[0114] 3. Comparative study on the treatment effect of low-concentration wastewater under continuous conditions

[0115] The optimized internal circulation ozone contact reactor and the ordinary ozone reactor were used to treat the same wastewater. The aeration flow rate was 600 mL / min and the concentration of 45 g / m 3O3, intermittent treatment for 60 minutes, then continuous treatment for 120 minutes, ozone dosage 400mg / (L·h). The treatment effects of adding catalyst and not adding catalyst were investigated respectively. The dosage of catalyst was 800g. The experimental water was a number of extract wastewater from a pesticide factory. The COD of high-concentration wastewater was 200mg / L. The removal effects of COD, TOC and characteristic pollutants were compared. Figure 5 shown.

[0116] Depend on Figure 5 As far as we know, for low-concentration wastewater, when the tower is empty or a catalyst is added, the removal efficiency of COD and TOC of the internal circulation ozone reactor is significantly improved compared with the ordinary ozone reactor after 60 minutes of treatment, and the removal rate of characteristic pollutants is also significantly improved. In the following two HRT continuous flow treatment processes, the treatment efficiency of the internal circulation ozone reactor decreased slightly, but the improvement in treatment efficiency compared with the ordinary ozone reactor was still obvious.

[0117] After 60 minutes of treatment, the ozone dosage was 400 mg / (L·h), and the ICR treated the wastewater. In the case of an empty tower, the COD removal rate was 49.59%, which was 17.69% higher than that of OR. The TOC degradation was 45.67%, which was 17.07% higher than that of OR. After 2 HRT continuous flow treatments, the COD removal rate of ICR was 47.96% and the TOC degradation was 46.11% every 60 minutes. With the addition of catalyst, the COD removal rate was 24.02% higher than that of OR, and the TOC degradation was 56.13%, which was 16.46% higher than that of OR. After 2 HRT continuous flow treatments, the COD removal rate of ICR was 60.74% and the TOC degradation was 54.89% every 60 minutes. The treatment effect of ICR was still significantly improved compared with OR. Under continuous conditions, since the catalyst and ozone in ICR are in more complete contact, the COD removal rate is improved more significantly.

[0118] The degradation of some characteristic pollutants (dichloromethane, chloroform, benzene, chlorobenzene, toluene) in the multiphase extract during the catalytic ozonation process was analyzed. The experimental results are as follows: Figure 6 shown.

[0119] (a: ozone dosage 400 mg / (L·h) without catalyst; b: ozone dosage 400 mg / (L·h) with catalyst)

[0120] In the ICR system, after 2 HRT continuous treatment with ozone dosage of 600 mg / (L·h), without adding catalyst, the removal rates of chlorobenzene, dichloromethane, benzene, toluene and chloroform were 99.8%, 99.8%, 99.4%, 99.6% and 99.8% respectively, which were 1.6%, 0.6%, 0.4%, 0.5% and 0.7% higher than OR. With the addition of catalyst, the removal rates of chlorobenzene, dichloromethane, benzene, toluene and chloroform were 99.4%, 99.8%, 99.8%, 99.5% and 99.6% respectively, which were 0.9%, 0.7%, 0.5%, 0.4% and 0.5% higher than OR. The removal rates of characteristic pollutants by ICR and OR were both above 98%.

[0121] The initial concentration of chlorobenzene was 15.2 mg / L. After 30 minutes of reaction in the internal circulation ozone reaction tower system, the concentration decreased to 0.112 mg / L, reaching the Class I standard for groundwater. The initial concentration of dichloromethane was 368 mg / L. After 30 minutes of reaction in the internal circulation ozone reaction tower system, the concentration decreased to 0.66 mg / L, reaching the Class I standard for groundwater. The initial concentration of benzene was 21.6 mg / L. After 30 minutes of reaction in the internal circulation ozone reaction tower system, the concentration decreased to 0.128 mg / L, reaching the Class I standard for groundwater. The initial concentration of chloroform was around 248.8 mg / L. After 30 minutes of reaction in the ordinary ozone reaction tower and the internal circulation ozone reaction tower, the concentrations were 1.4 mg / L and 0.516 mg / L, respectively, reaching the Class II standard for groundwater. The initial concentration of toluene was about 7.2 mg / L. After 30 minutes of reaction in the ordinary ozone reaction tower and the internal circulation ozone reaction tower, the concentrations were 0.072 mg / L and 0.04 mg / L, respectively, reaching the Class I groundwater standard. In the removal of characteristic pollutants, the oxidation efficiency of the internal circulation ozone reaction tower system is higher than that of the ordinary ozone reaction tower system.

[0122] 4. Comparative study on the treatment effects of low-concentration wastewater using different treatment methods

[0123] Comparative Example 1: The difference from Example 1 is that the microporous diffuser used in the traditional process is directly used for operation without the treatment of micro-nano bubble-assisted ozone catalysis.

[0124] Comparative Example 2: The difference from Example 1 is that no separation aid is added to carry out the separation process.

[0125] Comparative Example 3: The difference from Example 1 is that the catalysts in the two filling layers are the same, both using V2O5 / TiO2 catalysts.

[0126] Comparative Example 4: The difference from Example 1 is that the catalysts of the two filling layers are both commercially available Co3O4 / Al2O3 catalysts and V2O5 / TiO2 catalysts.

[0127] Comparisons of Example 1 to Comparative Examples 1 to 4 are shown in Table 1.

[0128] Table 1 Experimental results of different treatment methods for low-concentration wastewater treatment effects

[0129]

[0130]

[0131] As can be seen from Table 1, by comparing Example 1 with Comparative Example 1, it can be seen that the method in Example 1 is more preferred, which may be because the solubility and contact area of ​​ozone are significantly increased and the oxidation efficiency is improved through the treatment of micro-nano bubbles assisted ozone catalysis in Example 1; by integrating micro-nano bubble technology into the treatment process of the internal circulation ozone contact reaction tower, the utilization rate of ozone and the removal efficiency of pollutants can be significantly improved, thereby improving the overall treatment effect.

[0132] By comparing Example 1 with Comparative Example 2, it can be seen that the method of adding a separation aid in Example 1 is more preferred. The reason is that after adding the separation aid, the oil and water in the sewage are separated more thoroughly, and the pollutant content in the water to be treated is easier to remove, which can avoid the problem that the pollutants in Comparative Example 2 exist in the form of tiny oil droplets, resulting in poor water treatment effect;

[0133] By comparing Example 1, Comparative Example 3 and Comparative Example 4, it can be found that the catalyst design method in Example 1 is more preferred. This method enables the two catalysts to have a certain synergistic effect in addition to playing their respective functions, and can further improve the catalytic effect to improve the water treatment effect.

Claims

1. A process for treating contaminated groundwater based on an internal circulation ozone contact reaction tower, characterized in that: The internal circulation ozone contact reaction tower comprises a tower body, two filling layers arranged inside the tower body for ozone catalysis, and an inner cylinder inside the tower body for reflux; and comprises the following steps: S1, preliminary processing; The contaminated groundwater is treated by an oil-water separation system to obtain oil and water to be treated, the oil is recovered, and then the obtained water to be treated is filtered, wherein the filtration adopts a filter with a pore size of 0.45 μm; then the filtered water to be treated is coagulated; the coagulation treatment is as follows: polyaluminium chloride and polyacrylamide are added to the water to be treated at a ratio of 150-250 mg: 8-15 mg: 1 L, and then stirred at a speed of 150-200 rpm for 0.5-2 min, and then stirred at a speed of 70-90 rpm for 10 min and then allowed to stand for separation to obtain the water to be treated after preliminary treatment; S2, ozone contact reaction; The water to be treated after preliminary treatment is 1-5m 3 / h flow rate into the water inlet of the tower body, inject ozone gas into the inner cylinder to promote the water flow in the inner cylinder to flow from bottom to top to the two filling layers, and then circulate back to the inner cylinder, the ozone dosage is 200-700 mg / L·h; the water volume of the circulating reflux is controlled to be 50-80% of the water volume of the water inlet, the reflux speed is 0.5-2m / s; the ozone contact reaction time is 20-40min; S3, aeration treatment; After the ozone contact reaction is completed, stop introducing ozone and perform aeration treatment. The aeration flow rate is 0.5 to 2 L / min and the aeration time is 10 to 30 min. S4, sedimentation filtration; The aerated water enters the sedimentation tank and is treated after 12 to 24 hours of sedimentation.

2. A process for treating contaminated groundwater based on an internal circulation ozone contact reaction tower integrated with the invention as claimed in claim 1, characterized in that: In the S2 ozone contact reaction, micro-nano bubbles are used to assist ozone catalysis; the method of using micro-nano bubbles to assist ozone catalysis includes: before the ozone gas enters the internal circulation ozone contact reaction tower, the ozone gas is dispersed by a micro-nano bubble generator to generate micro-nano bubbles, and the generated micro-nano bubbles are injected into the inner cylinder; wherein the power of the micro-nano bubble generator is 50 to 200 W, the micro-nano bubble gas flow rate is 0.5 to 2 L / min, and the residence time of the ozone gas in the micro-nano bubble generator is 2 to 5 min.

3. A process for treating contaminated groundwater based on an internal circulation ozone contact reaction tower integrated with the invention as claimed in claim 1, characterized in that: In S1 preliminary treatment, the oil-water separation system includes an oil-water separator, an oil collection tank and a to-be-treated water collection tank.

4. A process for treating contaminated groundwater based on an internal circulation ozone contact reaction tower integrated with the method of claim 3, characterized in that: The oil-water separator is a gravity oil-water separator.

5. A process for treating contaminated groundwater based on an internal circulation ozone contact reaction tower integrated with the method of claim 3, characterized in that: During the oil-water separation process, 0.5-1 mmol / L of a separation aid is added, and the separation aid is methyl methacrylate.

6. A process for treating contaminated groundwater based on an internal circulation ozone contact reaction tower integrated with the invention as claimed in claim 1, characterized in that: A layer of catalyst is provided on each of the two filling layers, and the ratio of the spacing between the filling layers to the height of the reaction tower is 0.16-0.

25. The catalyst on the lower filling layer is a spherical aluminum-based catalyst, and the catalyst on the upper filling layer is a vanadium-based catalyst. The dosage of the spherical aluminum-based catalyst and the vanadium-based catalyst is in a ratio of 500-800g:5L to the reaction tower.

7. A process for treating contaminated groundwater based on an internal circulation ozone contact reaction tower integrated with the method of claim 6, characterized in that: The spherical aluminum-based catalyst uses a Co3O4 / Al2O3 catalyst, and the vanadium-based catalyst uses a V2O5 / TiO2 catalyst.

8. A process for treating contaminated groundwater based on an internal circulation ozone contact reaction tower integrated with the method of claim 7, characterized in that: The preparation method of the Co3O4 / Al2O3 catalyst comprises: Firstly, the Al2O3 is pretreated by radio frequency plasma, the power of radio frequency plasma treatment is 50-200W, and the treatment time is 5-10min; Take a CoSO4 solution with a concentration of 0.5-1 mol / L, add Al2O3 to the CoSO4 solution at a ratio of 1-2 g: 2-5 mL, and at the same time add ammonia water to adjust the pH to 7-9, the temperature is 60-80°C, the reaction time is 2-4 hours, and a precipitate is obtained; The precipitate is dried and placed under plasma, and Co(acac)2 gas with a flow rate of 10 ml / min is introduced for deposition for 5 to 20 minutes, and then calcined at 300 to 500°C for 2 to 3 hours to obtain a Co3O4 / Al2O3 catalyst.

9. A process for treating contaminated groundwater based on an internal circulation ozone contact reaction tower integrated with the invention as claimed in claim 7, characterized in that: The preparation method of the V2O5 / TiO2 catalyst comprises: Dissolve ammonium metavanadate in deionized water at a ratio of 1 to 3 g: 100 ml to form an ammonium metavanadate solution; then add titanium dioxide to the prepared ammonium metavanadate solution at a ratio of 3 to 4 g: 100 ml, and stir at a temperature of 40 to 60° C. for 2 to 4 hours; Then, 5-15% of ammonium tungstate by mass of ammonium metavanadate is added and mixed to obtain a mixture, which is dried completely at 70-80°C, and then calcined at 400-500°C for 2-3h to obtain a V2O5 / TiO2 catalyst.

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