MULTI-STAGE APPARATUS AND PROCESS FOR ADVANCED OXIDATION TREATMENT OF WASTEWATER

Abstract

The present disclosure discloses a multi-stage apparatus and process for advanced oxidation treatment of wastewater, and belongs to the field of wastewater treatment in environmental protection. The apparatus includes a liquid-liquid mixing unit, a preheating unit, a gas-liquid mixing unit, a parallel photocatalytic reactor group and an oxidation tower connected in sequence. According to characteristics of free radical reactions, the parallel photocatalytic reactor group and the oxidation tower in the apparatus are reasonably designed, utilization rates of the ozone and the hydrogen peroxide are increased, and the wastewater treatment cost is reduced.

Claims

1. A multi-stage apparatus for advanced oxidation treatment of wastewater, comprising a liquid-liquid mixing unit, a preheating unit, a gas-liquid mixing unit, a parallel photocatalytic reactor group and an oxidation tower connected in sequence; wherein the liquid-liquid mixing unit is used for mixing to-be-treated wastewater and hydrogen peroxide; the preheating unit is used for preheating a mixed solution of the to-be-treated wastewater and the hydrogen peroxide; the gas-liquid mixing unit is used for mixing ozone at room temperature and the preheated mixed solution of the to-be-treated wastewater and the hydrogen peroxide to form a gas-liquid mixture; and the parallel photocatalytic reactor group is internally provided with several photocatalytic reactors.

2. The multi-stage apparatus for advanced oxidation treatment of wastewater according to claim 1, wherein an effective volume of the oxidation tower is greater than a sum of effective volumes of the photocatalytic reactors in the parallel photocatalytic reactor group.

3. The multi-stage apparatus for advanced oxidation treatment of wastewater according to claim 2, wherein the effective volume of the oxidation tower is 5-50 times the sum of the effective volumes of the photocatalytic reactors in the parallel photocatalytic reactor group.

4. The multi-stage apparatus for advanced oxidation treatment of wastewater according to claim 2, wherein a height-to-diameter ratio of the photocatalytic reactor is 8-15; and/or a height-to-diameter ratio of the oxidation tower is 5-20.

5. The multi-stage apparatus for advanced oxidation treatment of wastewater according to claim 2, wherein an ultraviolet lamp is axially arranged in the photocatalytic reactor in a water flow direction.

6. The multi-stage apparatus for advanced oxidation treatment of wastewater according to claim 2, wherein a guide plate is arranged on a cylinder wall of the photocatalytic reactor.

7. The multi-stage apparatus for advanced oxidation treatment of wastewater according to claim 2, wherein a liquid-liquid static mixer is used as a liquid-liquid mixing equipment; and a gas-liquid static mixer is used as a gas-liquid mixing device.

8. A process for advanced oxidation treatment of wastewater by using a multi-stage apparatus, the multi-stage apparatus comprising a liquid-liquid mixing unit, a preheating unit, a gas-liquid mixing unit, a parallel photocatalytic reactor group and an oxidation tower connected in sequence; wherein the liquid-liquid mixing unit is used for mixing to-be-treated wastewater and hydrogen peroxide; the preheating unit is used for preheating a mixed solution of the to-be-treated wastewater and the hydrogen peroxide; the gas-liquid mixing unit is used for mixing ozone at room temperature and the preheated mixed solution of the to-be-treated wastewater and the hydrogen peroxide to form a gas-liquid mixture; the parallel photocatalytic reactor group is internally provided with several photocatalytic reactors; and the process comprising the following steps: S1: mixing to-be-treated wastewater and hydrogen peroxide; S2: preheating a mixed solution of the to-be-treated wastewater and the hydrogen peroxide; S3: mixing ozone at room temperature and the preheated mixed solution of the to-be-treated wastewater and the hydrogen peroxide to form a gas-liquid mixture; S4: making the gas-liquid mixture enter the parallel photocatalytic reactor group for a reaction for a residence time t.sub.1, wherein the residence time refers to a reaction time of a stage when a COD degradation rate k is equal to or greater than 1; and S5: making effluent in step S4 enter the oxidation tower for a residence time t.sub.2 and then discharging the effluent, wherein the residence time refers to a reaction time of a stage when the COD degradation rate k is less than 1; wherein k refers to a decrease of a mass concentration of COD in the wastewater per minute with a unit of mg/(L.Math.min).

9. The process for advanced oxidation treatment of wastewater according to claim 8, wherein a preheating temperature in step S2 is 50-65° C.

10. The process for advanced oxidation treatment of wastewater according to claim 8, wherein the residence time t.sub.1 in the parallel photocatalytic reactor group in step S4 is 1-60 min, and the residence time t.sub.2 in the oxidation tower in step S5 is 20-360 min.

11. The process for advanced oxidation treatment of wastewater according to claim 9, wherein the residence time t.sub.1 in the parallel photocatalytic reactor group in step S4 is 1-60 min, and the residence time t.sub.2 in the oxidation tower in step S5 is 20-360 min.

12. A process for advanced oxidation treatment of wastewater by using a multi-stage apparatus, the multi-stage apparatus comprising a liquid-liquid mixing unit, a preheating unit, a gas-liquid mixing unit, a parallel photocatalytic reactor group and an oxidation tower connected in sequence; wherein the liquid-liquid mixing unit is used for mixing to-be-treated wastewater and hydrogen peroxide; the preheating unit is used for preheating a mixed solution of the to-be-treated wastewater and the hydrogen peroxide; the gas-liquid mixing unit is used for mixing ozone at room temperature and the preheated mixed solution of the to-be-treated wastewater and the hydrogen peroxide to form a gas-liquid mixture; the parallel photocatalytic reactor group is internally provided with several photocatalytic reactors; the effective volume of the oxidation tower is 5-50 times the sum of the effective volumes of the photocatalytic reactors in the parallel photocatalytic reactor group; and the process comprising the following steps: S1: mixing to-be-treated wastewater and hydrogen peroxide; S2: preheating a mixed solution of the to-be-treated wastewater and the hydrogen peroxide; S3: mixing ozone at room temperature and the preheated mixed solution of the to-be-treated wastewater and the hydrogen peroxide to form a gas-liquid mixture; S4: making the gas-liquid mixture enter the parallel photocatalytic reactor group for a reaction for a residence time t.sub.1, wherein the residence time refers to a reaction time of a stage when a COD degradation rate k is equal to or greater than 1; and S5: making effluent in step S4 enter the oxidation tower for a residence time t.sub.2 and then discharging the effluent, wherein the residence time refers to a reaction time of a stage when the COD degradation rate k is less than 1; wherein k refers to a decrease of a mass concentration of COD in the wastewater per minute with a unit of mg/(L.Math.min).

13. The process for advanced oxidation treatment of wastewater according to claim 12, wherein a preheating temperature in step S2 is 50-65° C.

14. The process for advanced oxidation treatment of wastewater according to claim 12, wherein the residence time t.sub.1 in the parallel photocatalytic reactor group in step S4 is 1-60 min, and the residence time t.sub.2 in the oxidation tower in step S5 is 20-360 min.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0044] FIG. 1 is a flowchart showing a process and apparatus for advanced oxidation treatment of wastewater in the present disclosure;

[0045] FIG. 2 is a schematic diagram of a photocatalytic reactor in the present disclosure;

[0046] FIG. 3 shows change curves of a COD concentration and a k value with time in a small pilot test in Example 1;

[0047] FIG. 4 shows change curves of a COD concentration and a k value with time in a small pilot test in Example 2; and

[0048] FIG. 5 shows change curves of a COD concentration and a k value with time in a small pilot test in Example 3;

[0049] where, labels in the drawings are as follows: 1. wastewater tube; 2. hydrogen peroxide tube; 3. ozone tube; 4. oxidation effluent tube; 5. exhaust tube; 6. hydrogen peroxide feeding pump; 7. wastewater feeding pump; 8. liquid-liquid mixer; 9. preheater; 10. gas-liquid mixer; 11. photocatalytic reactor; 11-1. feeding port; 11-2. discharging port; 11-3. reactor cylinder; 11-4. ultraviolet lamp; 11-5, guide plate; 11-6, electrical wiring; and 12. oxidation tower.

DETAILED DESCRIPTION

[0050] It should be noted that when one component is expressed as “being connected to” another component, the component may be directly connected to the another component, or two components may be directly integrated. At the same time, terms such as “upper”, “lower”, “left”, “right”, “middle” and other terms cited in this specification are only used for ease of description and are not intended to limit the implementable scope. Modifications or adjustments of a relative relationship shall be fall within the implementable scope of the present disclosure without substantively changing the technical content.

[0051] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by a person skilled in the art of the present disclosure.

[0052] The present disclosure is further described below in conjunction with specific embodiments.

[0053] A photocatalytic ozone and hydrogen peroxide oxidation process of wastewater is a free radical reaction process and generally includes free radical initiation, a free radical chain reaction and free radical termination. In this process, main factors affecting an oxidation effect of the wastewater include generation of free radicals, a high enough mass transfer rate in a free radical chain reaction stage and an enough residence time in a free radical termination stage to ensure that a reaction is conducted more thoroughly. A wastewater treatment equipment and a process apparatus of the present disclosure are designed based on the photocatalytic ozone and hydrogen peroxide oxidation process of the wastewater. An operating process of the wastewater treatment process and apparatus of the present disclosure is described below with reference to FIG. 1.

[0054] As shown in FIG. 1, a multi-stage apparatus for advanced oxidation treatment of wastewater in the present disclosure includes a liquid-liquid mixing unit, a preheating unit, a gas-liquid mixing unit, a parallel photocatalytic reactor group and an oxidation tower connected in sequence; the liquid-liquid mixing unit is used for mixing to-be-treated wastewater and hydrogen peroxide; the preheating unit is used for preheating a mixed solution of the to-be-treated wastewater and the hydrogen peroxide; the gas-liquid mixing unit is used for mixing ozone at room temperature and the preheated mixed solution of the to-be-treated wastewater and the hydrogen peroxide to form a gas-liquid mixture; and the parallel photocatalytic reactor group is internally provided with several photocatalytic reactors, and an ultraviolet lamp is axially arranged in the photocatalytic reactor in a water flow direction. The ultraviolet lamp is installed in a glass tube, during operation, the glass tube is polluted by pollutants in the wastewater, the photocatalytic efficiency is reduced, and the glass tube needs to be removed and cleaned regularly; the parallel photocatalytic reactor group is used for a rapid oxidation reaction to shorten a residence time of materials in a photocatalytic reaction stage; and the oxidation tower is used for prolonging a residence time of effluent in the parallel photocatalytic reactor group.

[0055] A process flow specifically includes that the wastewater passing through a wastewater tube 1 and the hydrogen peroxide passing through a hydrogen peroxide tube 2 are pumped into a liquid-liquid mixer 8 for mixing by using a wastewater feeding pump 7 and a hydrogen peroxide feeding pump 6 respectively, preheated in a preheater 9 and mixed with the ozone from an ozone tube 3 in a gas-liquid mixer 10 to complete gas-liquid mixing and then enter each photocatalytic reactor 11 in the parallel photocatalytic reactor group. As shown in FIG. 2, an ultraviolet lamp 11-4 is axially arranged in the photocatalytic reactor 11 vertically, a guide plate 11-5 is arranged in a reactor cylinder 11-3, a water flow enters the photocatalytic reactor 11 through a feeding port 11-1 for a rapid oxidation reaction, the residence time of the materials in the photocatalytic reactor 11 is short, but due to an effect of the guide plate 11-5 in the photocatalytic reactor 11, a backmixing degree of the materials in the reactor is increased, and a reaction rate in the photocatalytic reactor 11 is greatly increased. Effluent is discharged from a discharging port 11-2 and then enters an oxidation tower 12 from a lower end, the oxidation tower 12 is a plate tower and is internally provided with several layers of sieve trays, finally effluent is discharged from an oxidation effluent tube 4, and gas is discharged from an exhaust tube 5.

[0056] The mixed solution of the wastewater and the hydrogen peroxide mixed by the liquid-liquid mixer 8 enters the preheater 9 and is preheated to 50-65° C. to facilitate generation of free radicals with maximum efficiency when mixed with the ozone in the next step; and a fixed-tube-sheet heat exchanger is generally used as the preheater 9, and a heat exchange area is calculated according to actual operating conditions and is generally 1-100 m.sup.2. A discharge temperature of the mixed solution of the wastewater and the hydrogen peroxide from the preheater 9 is adjusted according to a flow rate of hot water (heat transfer oil or other heating media can also be used) of the heat exchanger.

[0057] The number and specification of the photocatalytic reactor 11 are determined according to an actual processing capacity, generally 5-60 photocatalytic reactors are appropriate, the inner diameter is generally 50-300 mm, and the height of the reactor is generally 500-2000 mm. The ultraviolet lamp 11-4 is installed in a glass tube, during actual operation, the glass tube of the ultraviolet lamp 11-4 is polluted by pollutants in the wastewater, the photocatalytic efficiency is reduced, and the glass tube needs to be removed and cleaned regularly.

[0058] Reaction effluent from a top of the photocatalytic reactor 11 is collected into a bottom of the oxidation tower 12 and flows through the oxidation tower from bottom to top for a further reaction. The residence time in the oxidation tower is generally 20-360 min, and after a reaction is completed, gas and liquid are discharged from a top of the tower and a side port in an upper part of the tower respectively.

Example 1

[0059] In this example, wastewater (mainly containing pollutants such as glyphosate and formaldehyde with an influent COD concentration of 221 mg/L) was treated.

[0060] I. Investigation of the Change of a COD Degradation Rate During Wastewater Treatment by Using a Small Pilot Test

[0061] First, the change of the COD degradation rate during a wastewater reaction was investigated by using a small pilot test; and an apparatus and method used in the small pilot test were as follows:

[0062] in the small pilot test, a multi-stage apparatus for advanced oxidation treatment of wastewater shown in FIG. 1 was not used for treatment, but a single large-volume photocatalytic reactor was used, so that the whole reaction was conducted in the same photocatalytic reactor, where a volume of the photocatalytic reactor was 15 L, a photocatalytic power was 400 W, and an added amount of the wastewater was 10 L; and

[0063] a process for treatment of wastewater by using the above device included the following steps:

[0064] 1) the to-be-treated wastewater and hydrogen peroxide were added into the photocatalytic reactor, where an added amount of the hydrogen peroxide was 20 mL (a mass concentration of the hydrogen peroxide was 30%);

[0065] 2) a mixed solution of the to-be-treated wastewater and the hydrogen peroxide was preheated to 55° C.;

[0066] 3) ozone at room temperature was introduced into the reactor, where an introduced amount of the ozone was 50 g/h; and

[0067] 4) an effluent COD concentration was monitored and reached 11.7 mg/L within 240 min, where the change of the COD concentration with a reaction time t was shown in FIG. 3.

[0068] According to results of the small pilot test of the wastewater shown in FIG. 3 and results of an oxidation experiment of the wastewater, it was shown that it took 240 minutes to reach a target COD degradation value, the COD degradation rate was very high in the first 30 minutes, a decrease, namely a k value, of the COD concentration of the wastewater per minute was not less than 1, the COD degradation rate was significantly reduced in the next 210 minutes, the k value was reduced, and the reaction was mild.

[0069] II. Treatment of the Wastewater by Using the Equipment Shown in FIG. 1

[0070] Accordingly, the multi-stage apparatus for advanced oxidation treatment of wastewater shown in FIG. 1 (a specific structure was as described above) was used for normal treatment, that is, a parallel photocatalytic reactor group and an oxidation tower 12 were combined in series, and the wastewater was subjected to a rapid reaction in the parallel photocatalytic reactor group first and then stayed in the oxidation tower 12 for a period of time for a slow reaction, where, an inner diameter of a photocatalytic reactor 11 was 200 mm, a height of the photocatalytic reactor was 1600 mm, a volume of a single photocatalytic reactor 11 was about 50 L, a total of 50 photocatalytic reactors 11 were installed in parallel, and a total effective volume of the photocatalytic reactor group was about 2.5 m.sup.3; and a diameter of the oxidation tower 12 was 1600 mm, a height of the oxidation tower was 8.2 m, a total volume of the oxidation tower 12 was 17.5 m.sup.3, and a designed processing capacity was 5 m.sup.3/h.

[0071] Wastewater treatment included the following steps:

[0072] S1: the to-be-treated wastewater and hydrogen peroxide were mixed, where a flow rate of the wastewater was 5 m.sup.3/h, and an added amount of the hydrogen peroxide was 2 kg/h (a mass concentration of the hydrogen peroxide was 30%);

[0073] S2: a mixed solution of the to-be-treated wastewater and the hydrogen peroxide was preheated to 55° C.;

[0074] S3: ozone at room temperature was mixed with the preheated mixed solution of the to-be-treated wastewater and the hydrogen peroxide to form a gas-liquid mixture, where an introduced amount of the ozone was 1200 g/h;

[0075] S4: the gas-liquid mixture entered the parallel photocatalytic reactor group for a reaction at a photocatalytic power of 30 kw for a residence time t.sub.1, where the residence time referred to a reaction time of a stage when the COD degradation rate k was equal to or greater than 1 in the small pilot test and was about 30 min; and

[0076] S5: effluent in step S4 entered the oxidation tower for a residence time t.sub.2 and then was discharged, where the residence time referred to a reaction time of a stage when the COD degradation rate k was less than 1 in the small pilot test and was about 210 min. The COD concentration of the effluent from the oxidation tower was 9.35 mg/L and reached a target value.

[0077] The above results showed that when the parallel photocatalytic reactor group and the large-volume oxidation tower in this example were connected in series and the residence time was set accordingly, the ozone efficiency (a ratio of a theoretical required amount of the ozone to an actual added amount of the ozone, where a theoretical added amount of the ozone was equal to a decrease of the COD concentration, that is, a mass concentration of ΔCOD) was 88%; and it was worth noting that in existing industrial treatment, when a conventional process of photocatalytic ozone and hydrogen peroxide oxidation was used, the ozone efficiency was generally not higher than 60% (under the condition that an added ratio of the hydrogen peroxide and the photocatalytic power were basically the same). Therefore, by using the treatment process in this example, the utilization efficiency of the ozone can be greatly improved, and power consumption of an ozone generator was reduced.

Example 2

[0078] In this example, wastewater (mainly containing pollutants such as ethers with an influent COD concentration of 86 mg/L) was treated.

[0079] I. Investigation of the Change of a COD Degradation Rate During Wastewater Treatment by Using a Small Pilot Test

[0080] First, the change of the COD degradation rate during a wastewater reaction was investigated by using a small pilot test; and an apparatus and method used in the small pilot test were as follows:

[0081] in the small pilot test, a multi-stage apparatus for advanced oxidation treatment of wastewater shown in FIG. 1 was not used for treatment, but a single large-volume photocatalytic reactor was used, so that the whole reaction was conducted in the same photocatalytic reactor, where a volume of the photocatalytic reactor was 15 L, a photocatalytic power was 400 W, and an added amount of the wastewater was 10 L; and

[0082] a process for treatment of wastewater by using the above device included the following steps:

[0083] 1) the to-be-treated wastewater and hydrogen peroxide were added into the photocatalytic reactor, where an added amount of the hydrogen peroxide was 20 mL (a mass concentration of the hydrogen peroxide was 30%);

[0084] 2) a mixed solution of the to-be-treated wastewater and the hydrogen peroxide was preheated to 50° C.;

[0085] 3) ozone at room temperature was introduced into the reactor, where an introduced amount of the ozone was 20 g/h; and

[0086] 4) an effluent COD concentration was monitored and reached 2.8 mg/L within 120 min, where the change of the COD concentration with a reaction time t was shown in FIG. 4.

[0087] According to results of the small pilot test of the wastewater shown in FIG. 4 and results of an oxidation experiment of the wastewater, it was shown that it took 120 minutes to reach a target COD degradation value, the COD degradation rate was very high in the first 15 minutes, a k value was not less than 1, the COD degradation rate was significantly reduced in the next 105 minutes, and the reaction was mild.

[0088] II. Treatment of the Wastewater by Using the Equipment Shown in FIG. 1

[0089] Accordingly, the multi-stage apparatus for advanced oxidation treatment of wastewater shown in FIG. 1 (a specific structure was as described above) was used for normal treatment, that is, a parallel photocatalytic reactor group and an oxidation tower 12 were combined in series, and the wastewater was subjected to a rapid reaction in the parallel photocatalytic reactor group first and then stayed in the oxidation tower 12 for a period of time for a slow reaction, where, an inner diameter of a photocatalytic reactor 11 was 150 mm, a height of the photocatalytic reactor was 1400 mm, a volume of a single photocatalytic reactor 11 was about 25 L, a total of 30 photocatalytic reactors 11 were installed in parallel, and a total effective volume of the photocatalytic reactor group was about 0.75 m.sup.3; and a diameter of the oxidation tower 12 was 1000 mm, a height of the oxidation tower was 6.4 m, a total volume of the oxidation tower 12 was 5.25 m.sup.3, and a designed processing capacity was 3 m.sup.3/h.

[0090] Wastewater treatment included the following steps:

[0091] S1: the to-be-treated wastewater and hydrogen peroxide were mixed, where a flow rate of the wastewater was 3 m.sup.3/h, and an added amount of the hydrogen peroxide was 1 kg/h (a mass concentration of the hydrogen peroxide was 30%);

[0092] S2: a mixed solution of the to-be-treated wastewater and the hydrogen peroxide was preheated to 50° C.;

[0093] S3: ozone at room temperature was mixed with the preheated mixed solution of the to-be-treated wastewater and the hydrogen peroxide to form a gas-liquid mixture, where an introduced amount of the ozone was 300 g/h;

[0094] S4: the gas-liquid mixture entered the parallel photocatalytic reactor group for a reaction at a photocatalytic power of 22 kw for a residence time t.sub.1, where the residence time referred to a reaction time of a stage when the COD degradation rate k was equal to or greater than 1 in the small pilot test and was about 15 min; and

[0095] S5: effluent in step S4 entered the oxidation tower for a residence time t.sub.2 and then was discharged, where the residence time referred to a reaction time of a stage when the COD degradation rate k was less than 1 in the small pilot test and was about 105 min. The COD concentration of the effluent from the oxidation tower was 2.1 mg/L and reached a target value.

[0096] The above results showed that when the parallel photocatalytic reactor group and the large-volume oxidation tower in this example were connected in series and the residence time was set accordingly, the ozone efficiency (a ratio of a theoretical required amount of the ozone to an actual added amount of the ozone) was 86%; when a conventional process of photocatalytic ozone and hydrogen peroxide oxidation was used, the ozone efficiency was generally not higher than 60% (under the condition that an added ratio of the hydrogen peroxide and the photocatalytic power were basically the same); and similarly, by using the treatment process in this example, the utilization efficiency of the ozone can be greatly improved, and power consumption of an ozone generator was reduced.

Example 3

[0097] In this example, wastewater (mainly containing pollutants such as phenoxycarboxylic acids with an influent COD concentration of 221 mg/L) was treated.

[0098] I. Investigation of the Change of a COD Degradation Rate During Wastewater Treatment by Using a Small Pilot Test

[0099] First, the change of the COD degradation rate during a wastewater reaction was investigated by using a small pilot test; and an apparatus and method used in the small pilot test were as follows:

[0100] in the small pilot test, a multi-stage apparatus for advanced oxidation treatment of wastewater shown in FIG. 1 was not used for treatment, but a single large-volume photocatalytic reactor was used, so that the whole reaction was conducted in the same photocatalytic reactor, where a volume of the photocatalytic reactor was 15 L, a photocatalytic power was 400 W, and an added amount of the wastewater was 10 L; and

[0101] a process for treatment of wastewater by using the above device included the following steps:

[0102] 1) the to-be-treated wastewater and hydrogen peroxide were added into the photocatalytic reactor, where an added amount of the hydrogen peroxide was 20 mL (a mass concentration of the hydrogen peroxide was 30%);

[0103] 2) a mixed solution of the to-be-treated wastewater and the hydrogen peroxide was preheated to 62° C.;

[0104] 3) ozone at room temperature was introduced into the reactor, where an introduced amount of the ozone was 50 g/h; and

[0105] 4) an effluent COD concentration was monitored and reached 10.35 mg/L within 180 min, where the change of the COD concentration with a reaction time t was shown in FIG. 5.

[0106] According to results of the small pilot test of the wastewater shown in FIG. 5 and results of an oxidation experiment of the wastewater, it was shown that it took 180 minutes to reach a target COD degradation value, the COD degradation rate was very high in the first 20 minutes, a k value was not less than 1, the COD degradation rate was significantly reduced in the next 160 minutes, and the reaction was mild.

[0107] II. Treatment of the Wastewater by Using the Equipment Shown in FIG. 1

[0108] Accordingly, the multi-stage apparatus for advanced oxidation treatment of wastewater shown in FIG. 1 (a specific structure was as described above) was used for normal treatment, that is, a parallel photocatalytic reactor group and an oxidation tower 12 were combined in series, and the wastewater was subjected to a rapid reaction in the parallel photocatalytic reactor group first and then stayed in the oxidation tower 12 for a period of time for a slow reaction, where, an inner diameter of a photocatalytic reactor 11 was 80 mm, a height of the photocatalytic reactor was 1100 mm, a volume of a single photocatalytic reactor 11 was about 5.6 L, a total of 60 photocatalytic reactors 11 were installed in parallel, and a total effective volume of the photocatalytic reactor group was about 0.33 m.sup.3; and a diameter of the oxidation tower 12 was 750 mm, a height of the oxidation tower was 5.8 m, a total volume of the oxidation tower 12 was 2.67 m.sup.3, and a designed processing capacity was 1 m.sup.3/h.

[0109] Wastewater treatment included the following steps:

[0110] S1: the to-be-treated wastewater and hydrogen peroxide were mixed, where a flow rate of the wastewater was 1 m.sup.3/h, and an added amount of the hydrogen peroxide was 0.5 kg/h (a mass concentration of the hydrogen peroxide was 30%);

[0111] S2: a mixed solution of the to-be-treated wastewater and the hydrogen peroxide was preheated to 62° C.;

[0112] S3: ozone at room temperature was mixed with the preheated mixed solution of the to-be-treated wastewater and the hydrogen peroxide to form a gas-liquid mixture, where an introduced amount of the ozone was 250 g/h;

[0113] S4: the gas-liquid mixture entered the parallel photocatalytic reactor group for a reaction at a photocatalytic power of 15 kw for a residence time t.sub.1, where the residence time referred to a reaction time of a stage when the COD degradation rate k was equal to or greater than 1 in the small pilot test and was about 20 min; and

[0114] S5: effluent in step S4 entered the oxidation tower for a residence time t.sub.2 and then was discharged, where the residence time referred to a reaction time of a stage when the COD degradation rate k was less than 1 in the small pilot test and was about 160 min. The COD concentration of the effluent from the oxidation tower was 10.2 mg/L and reached a target value.

[0115] The above results showed that when the parallel photocatalytic reactor group and the large-volume oxidation tower in this example were connected in series and the residence time was set accordingly, the ozone efficiency (a ratio of a theoretical required amount of the ozone to an actual added amount of the ozone) was 88.4%; as described above, in existing industrial treatment, when a conventional process of photocatalytic ozone and hydrogen peroxide oxidation was used, the ozone efficiency was generally not higher than 60% (under the condition that an added ratio of the hydrogen peroxide and the photocatalytic power were basically the same); and similarly, by using the treatment process in this example, the utilization efficiency of the ozone can be greatly improved, and power consumption of an ozone generator was reduced.

[0116] The above content is a schematic description of the present disclosure and embodiments thereof. The description is not restrictive. What is shown in the accompanying drawings is only one of the embodiments of the present disclosure, and the actual structure is not limited thereto. Therefore, similar structures and embodiments designed by a person of ordinary skill in the art as inspired by the disclosure herein without departing from the spirit of the present disclosure and without creative efforts shall fall within the protection scope of the present disclosure.