Two-stage oxidation treatment system and method for treating refractory wastewater by using calcium peroxide to catalyze ozone

Abstract

The invention discloses a two-stage oxidation treatment system and method for treating refractory wastewater by using calcium peroxide to catalyze ozone, and belongs to the technical field of refractory wastewater treatment. The constructed primary O3 pretreatment and secondary catalytic ozonation enhanced degradation system can reduce the interference of small molecular organic matters on the system operation, improve the utilization rate of calcium peroxide, enable the pH value of the effluent to be close to neutral, reduce the impact load of the inlet water and improve the treatment efficiency through a reflux mode, and finally, under the condition of low-cost operation, the treatment efficiency is improved. Organic matters and total phosphorus are removed, and meanwhile, detoxification is realized, so that the effluent reaches the standard.

Description

Technical Field

[0001] The present invention belongs to the technical field of treatment of refractory wastewater, and more specifically relates to a two-stage oxidation treatment system and method for treating refractory wastewater by using calcium peroxide to catalyze ozone. Background Art

[0002] Refractory wastewater including coking wastewater and medical wastewater has the characteristics of strong toxicity, complex pollutant structure, and poor biodegradability, which makes the current conventional treatment technologies such as flocculation precipitation, activated sludge method, adsorption method, etc. have many limitations when used to treat these wastewaters. The advanced ozone oxidation technology can effectively degrade refractory pollutants because it can generate strongly oxidizing free radicals, purifying the wastewater, but there are still problems such as high power consumption and treatment cost, high requirements for influent water quality, secondary pollution and disinfection by-products. Due to these defects, the traditional ozone process is difficult to be applied to the actual wastewater treatment process with complex water quality and large pH value fluctuations. Therefore, it is of great significance to develop a method that can treat refractory wastewater including coking wastewater and medical wastewater with complex water quality and large pH value fluctuations. Summary of the Invention

[0003] The purpose of the present invention is to provide a two-stage oxidation treatment system and method for treating refractory wastewater by using calcium peroxide to catalyze ozone, so as to solve the problems existing in the above-mentioned prior art and achieve the efficient treatment of refractory wastewater with complex water quality and large pH value fluctuations.

[0004] To achieve the above purpose, the present invention provides the following solutions:

[0005] One of the technical solutions of the present invention: Provide a two-stage oxidation treatment method for refractory wastewater. After the wastewater is subjected to coagulation precipitation, it is pretreated with ozone, and then CaO2 is added to catalyze ozone for oxidation treatment.

[0006] Preferably, the indexes of the wastewater after coagulation precipitation are: for coking wastewater: TOC = 106.6 mg / L, COD = 410 mg / L, TP = 0.9 mg / L (medical wastewater does not undergo coagulation precipitation); the indexes after ozone pretreatment; the indexes after ozone pretreatment are: for coking wastewater: TOC = 98.9 mg / L, COD = 352.4 mg / L, TP = 0.9 mg / L; for medical wastewater: TOC = 33.5 mg / L, COD = 88.7 mg / L, TP = 0.15 mg / L.

[0007] Preferably, the treatment concentration of ozone in the ozone pretreatment process is 15 mg / L. In the process of adding CaO2 to catalyze ozone for oxidation treatment, the ozone concentration is 15 mg / L, and the CaO2 concentration is 0.06 - 0.15 g / L.

[0008] Preferably, the refractory wastewater is coking wastewater or medical wastewater.

[0009] Preferably, when the refractory wastewater is coking wastewater, the ozone pretreatment time is 0.5 - 1 h, and the oxidation treatment time is 4 - 6 h; when the refractory wastewater is medical wastewater, the ozone pretreatment time is 0.25 - 0.5 h, and the oxidation treatment time is 0.75 - 1.5 h.

[0010] Preferably, the organic pollutants in the refractory wastewater include nitrobenzene.

[0011] Preferably, the pH value of the refractory wastewater is 3 - 11.

[0012] The second technical solution of the present invention: provides a system for the above two - stage oxidation treatment method, including a coagulation sedimentation tank, an adjustment tank, and an oxidation degradation unit connected in sequence; the oxidation degradation unit includes a first reactor and a second reactor, the first reactor and the second reactor are connected through a one - way connection pipe, and a one - way reflux pipe is also arranged between the first reactor and the second reactor.

[0013] Preferably, in the stable operation stage of sewage treatment, the first reactor is used for the O3 pretreatment reaction, and the second reactor is used for the CaO2 - catalyzed O3 treatment reaction.

[0014] Furthermore, the first reactor and the second reactor are of cylindrical design, aerated by bottom aeration discs, and both include a lift pump, an air inlet valve, a sludge discharge port, a sampling port, a reflux valve, and an effluent valve.

[0015] The third technical solution of the present invention: provides a continuous method for treating refractory wastewater based on the system of the above two - stage oxidation treatment method, including the following steps:

[0016] The refractory wastewater undergoes coagulation sedimentation in the coagulation sedimentation tank and then is transferred to the adjustment tank;

[0017] Part of the sewage in the adjustment tank is respectively transferred to the first reactor and the second reactor for ozone pretreatment, and then CaO2 is added to the first reactor and the second reactor to catalyze ozone for oxidation treatment;

[0018] The remaining sewage in the adjustment tank is continuously transported to the first reactor for ozone pretreatment, and the sewage pretreated by ozone in the first reactor enters the second reactor through a one - way connection pipe and is oxidized by using CaO2 - catalyzed ozone to achieve continuous treatment of refractory wastewater.

[0019] The technical mechanism of the present invention is as follows:

[0020] In the process of degrading wastewater by the existing ozone and per - ozone systems, OH in the solution will be continuously consumed- This results in an affected degradation performance. The low activity of ozone under acidic conditions makes it difficult for these systems to effectively degrade pollutants. After adding CaO2 to the degradation system to replace the traditional H2O2 in the present invention, not only the degradation effect of the ozonation process on wastewater under acidic conditions is improved, but also the degradation effect of wastewater under neutral and alkaline conditions is more remarkable. The reason is that the hydrolysis of CaO2 in water can provide a large amount of OH for catalyzing O3 - and H2O2 (CaO2 + 2H2O = H2O2 + Ca 2+ + 2OH - ). CaO2 existing in the system in solid form can continuously provide OH - and H2O2, and stabilize the pH, enabling the reaction system to be stably within the pH range with the highest ozone activity for a relatively long time. Moreover, the heterogeneous process increases the direct contact with O3 and the adsorption of pollutants in actual wastewater, thereby achieving a double improvement in O3 utilization rate and wastewater treatment effect.

[0021] In the present invention, by adding CaO2, an O3 / CaO2 treatment system is constructed, and units such as O3 pretreatment and reflux are added. Pretreatment can effectively reduce the influence of wastewater components on ·OH (certain easily degradable components and long carbon chain molecules will consume ·OH with stronger oxidation ability, resulting in a decrease in the amount of ·OH used for oxidizing refractory components). Reflux can reduce the outflow of CaO2 in the second reactor, thereby fully performing pre-catalysis in the regulation tank. Moreover, the residual O3 in water can also be mixed with the influent water to achieve pre-catalysis (this method reduces the treatment time and CaO2 dosage of the system, as detailed in Example 3). This enables these wastewaters to be rapidly and effectively degraded, improves the treatment capacity of the ozonation system, can better treat real wastewaters with complex water quality, reduces power consumption and treatment costs, and has no secondary pollution problem, thus having great practical value.

[0022] The present invention discovers that for the constructed O3 pretreatment + O3 / CaO2 enhanced treatment process, regardless of the initial acidity or alkalinity of the wastewater to be degraded, the addition of CaO2 can keep ozone within a high-activity pH range, and the effluent pH value is stable at neutral during the continuous reaction process. The reason is that CaO2 has hydrolysis and slowly releases OH -This ability guarantees the occurrence of synergistic reactions in the ozonation system, broadens the applicable pH range for wastewater degradation in the ozonation system, and enables the treatment of acidic wastewater and wastewater with large pH fluctuations in industrial applications. For acidic wastewater, the ability of CaO2 to rapidly hydrolyze and release H2O2 under acidic conditions can effectively neutralize the acidity in the water, increase the influent pH value through reflux, thereby quickly raising the pH to the high-activity range of ozone, and providing a large amount of H2O2 for catalyzing O3; for wastewater with large pH variations, the ability of CaO2 to rapidly hydrolyze under acidic conditions and slowly release H2O2 and OH - under medium and alkaline conditions can stabilize the pH.

[0023] Compared with the single ozone and ozonation systems, the O3 pretreatment + O3 / CaO2 enhanced treatment process constructed in the present invention has better wastewater degradation effect, higher degradation rate and lower cost.

[0024] The present invention discloses the following technical effects:

[0025] 1. The addition of calcium peroxide can efficiently catalyze the ozone system, stabilize the system pH value, effectively improve the treatment effect of refractory wastewater, enhance the mineralization effect and simultaneously remove phosphorus in the wastewater, thus improving the effluent quality.

[0026] 2. The primary O3 pretreatment + secondary catalytic ozonation enhanced degradation system constructed in the present invention can reduce the interference of small-molecule organic matters on the system operation, improve the utilization rate of calcium peroxide, make the effluent pH value close to neutral, and reduce the influent shock load and improve the treatment efficiency through reflux. Finally, under low-cost operation, it can achieve detoxification while removing organic matters and total phosphorus, making the effluent meet the standards. Description of the Drawings

[0027] Figure 1 It is the nitrobenzene (NB) degradation effect diagram under different initial pH value conditions for Effect Examples 1 to 3. Among them, (a) corresponds to the initial pH = 3, (b) corresponds to the initial pH = 5, (c) corresponds to the initial pH = 7, (d) corresponds to the initial pH = 9, and (e) corresponds to the initial pH = 11;

[0028] Figure 2 It is the change diagram of the system pH value during the test when the initial pH values of Effect Example 3 are 3, 5, 7, and 11 respectively. Among them, (a) corresponds to the initial pH = 3, (b) corresponds to the initial pH = 5, (c) corresponds to the initial pH = 7, and (d) corresponds to the initial pH = 11;

[0029] Figure 3 It is the nitrobenzene (NB) degradation effect diagram for Effect Examples 3 to 5;

[0030] Figure 4Structural schematic diagram of the oxidation degradation unit of the present invention. Among them, 1 - first reactor, 2 - second reactor, 3 - ozone generator, 4 - connecting pipe between the first reactor and the second reactor, 5 - sampling port of the first reactor, 6 - water outlet of the second reactor, 7 - sampling port of the second reactor, 8 - reflux port of the second reactor, 9 - bottom aeration disk, 10 - tail gas treatment device, 11 - intake pipeline, 12 - sludge discharge port, 13 - lift pump;

[0031] Figure 5 TOC removal rates (mineralization rates) of Effect Examples 1 - 3, Examples 1 - 2, and Comparative Examples 1 - 4. Among them, (a) corresponds to Effect Examples 1 - 3, (b) corresponds to Example 1, Comparative Example 1, and Comparative Example 2, (c) corresponds to Example 2, Comparative Example 3, and Comparative Example 4;

[0032] Figure 6 Cost accounting results for treating each ton of coking wastewater by Example 1, Comparative Example 1, Comparative Example 2, and conventional Fenton method;

[0033] Figure 7 TOC and COD values of the coking wastewater after treatment in Example 3;

[0034] Figure 8 Effluent pH values of the wastewater after treatment in Examples 1 - 3 and Comparative Examples 1 - 4. Among them, (a) corresponds to Example 1, Example 3, Comparative Example 1, and Comparative Example 2, (b) corresponds to Example 2, Comparative Example 3, and Comparative Example 4;

[0035] Figure 9 Toxicity index results of Effect Example 6. Among them, (a) corresponds to the Escherichia coli culture result, (b) corresponds to the mung bean seed germination result, (c) corresponds to the zebrafish embryo development result;

[0036] Figure 10 Flow chart of the O3 - O3 / CaO2 continuous treatment method in Example 3;

[0037] Figure 11 COD and TOC removal rates of the coking wastewater and medical wastewater after O3 pretreatment in Examples 1 and 2;

[0038] Figure 12 Effluent COD and TOC values under different systems in Examples 2, 3, Comparative Example 5, and Comparative Example 6. Among them, (a) is the effluent TOC value of coking wastewater; (b) is the effluent COD value of coking wastewater, (c) is the effluent TOC value of medical wastewater, (d) is the effluent COD value of medical wastewater. Detailed implementation manners

[0039] The various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be construed as a limitation on the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0040] It should be understood that the terms used in the present invention are only for describing particular embodiments and are not intended to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0041] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0042] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific embodiments of the present invention specification, which are obvious to those skilled in the art. Other embodiments obtained from the specification of the present invention are obvious to those skilled in the art. The specification and examples of the present invention are merely exemplary.

[0043] Regarding the use of "comprising", "including", "having", "containing", etc. herein, they are all open-ended terms, meaning including but not limited to.

[0044] It should be noted that the aspects not described in detail in the present invention are all conventional operating means in the art and are not the focus of the present invention.

[0045] In the following examples, comparative examples, and effect examples of the present invention, the raw materials used are all commercially available products unless otherwise specified. The source of the commercially available products does not affect the technical effects of the present invention.

[0046] The specific steps of the conventional Fenton method involved in the present invention are as follows:

[0047] 1. Add 314.8 g of ferrous sulfate heptahydrate (34.3 g for medical wastewater) to 50 L of coking wastewater after coagulation and sedimentation;

[0048] 2. Add approximately 29 mg of H2SO4 (24 mg for medical wastewater) to the coking wastewater, and at this time, the pH of the wastewater is approximately 3;

[0049] 3. Add 229 g of 30% hydrogen peroxide (25 g for medical wastewater) to start the reaction for 2 hours

[0050] In the following embodiments of the present invention, a two-stage oxidation treatment system is used for wastewater treatment. The two-stage oxidation treatment system includes a coagulation sedimentation tank, an adjustment tank, and an oxidation degradation unit arranged in sequence; the coagulation sedimentation tank and the adjustment tank are products of the prior art and will not be elaborated here. The oxidation degradation unit is as follows Figure 4 shown, where 1 - the first reactor, 2 - the second reactor, 3 - the ozone generator, 4 - the connecting pipe between the first reactor and the second reactor, 5 - the sampling port of the first reactor, 6 - the water outlet of the second reactor, 7 - the sampling port of the second reactor, 8 - the reflux port of the second reactor, 9 - the bottom aeration disk, 10 - the tail gas treatment device, 11 - the inlet gas pipeline, 12 - the sludge discharge port, 13 - the lift pump; the first reactor is used for

[0051] Example 1

[0052] This example provides a method for treating coking wastewater by O3 - O3 / CaO2 batch process. The specific steps are as follows

[0053] 50 L of coking wastewater (the initial TOC value of the coking wastewater is 120.1 mg / L, the COD value is 468.7 mg / L, and the initial pH value is 7.9, taken from Chongqing Iron and Steel (Group) Co., Ltd. After coagulation sedimentation treatment, the TOC value is 106.6 mg / L, the COD value is 410 mg / L, and the pH value is 6.4) that has flowed through the coagulation sedimentation tank and the adjustment tank in sequence is evenly placed in two reaction vessels as shown Figure 4 shown; then, using an ozone generator as the ozone generating device and dry air as the gas source, controlling the gas flow rate to be 1000 mL / min, while introducing O3 into the reactor, the reaction starts to be timed (the treatment concentration of ozone in the reactor is 15 mg / L). After reacting for 0.5 h, CaO2 is evenly added to the two reactors (the concentration of calcium peroxide in the reactor is 0.1 g / L), and after continuing to react for 4 h, the TOC degradation rate of the coking wastewater is measured

[0054] Example 2

[0055] This example provides a method for treating medical wastewater by O3 - O3 / CaO2 batch process. The specific steps are as follows

[0056] 50 L of medical wastewater (with an initial TOC value of 35.2 mg / L, a COD value of 102.1 mg / L, and an initial pH value of 5.6, taken from a hospital in Chongqing and without coagulation and sedimentation treatment) that has undergone coagulation and sedimentation treatment and will flow through the coagulation sedimentation tank and the regulating tank in sequence is evenly placed in Figure 4 the two reaction vessels shown below; then, using an ozone generator as the ozone generation device and dry air as the gas source, controlling the gas flow rate at 1000 mL / min, starting the reaction timer while introducing O3 into the reactor (the treatment concentration of ozone in the reactor is 15 mg / L), after reacting for 0.25 h, adding CaO2 to the two reactors (the concentration of calcium peroxide in the reactor is 0.1 g / L), and continuing to react for 0.75 h before measuring the TOC degradation rate of the medical wastewater.

[0057] Figure 11 The COD and TOC values of the coking wastewater and medical wastewater after O3 pretreatment described in Example 1 and Example 2.

[0058] From Figure 11 it can be seen that after the wastewater is pretreated with O3, the removal rate of COD is significantly higher than that of TOC, indicating that the main function of this method is to oxidize organic matter to form intermediates rather than complete mineralization (wherein easily degradable small molecules can be mineralized). In fact, it is difficult to achieve an ideal mineralization rate with O3 alone to completely degrade organic matter because, without a catalyst, the amount of ·OH with strong oxidation ability generated by O3 is very small, and most organic matter is directly oxidized by O3. The oxidation ability of O3 is far less than that of ·OH, and it can only oxidize most refractory organic matter to intermediates. Combining theory and water quality test results, we determined that O3 pretreatment can effectively reduce the consumption of small molecule organic matter and easily degradable macromolecules by ·OH, that is, reduce their interference with the degradation of pollutants in the catalytic ozone system. The schematic equation is as follows:

[0059]

[0060] Example 3

[0061] This example provides a method for continuously treating coking wastewater using O3 - O3 / CaO2 by continuously introducing new coking wastewater on the basis of the coking wastewater treatment process of Example 1. The specific steps are as follows:

[0062] After the coking wastewater in Example 1 was treated, the ozone generator remained as it was. Through the lift pump, the coking wastewater treated by coagulation and sedimentation in the regulation tank was transported to the first reactor at a flow rate of 0.25 L / min. The flow rate of the connecting pipe between the two reactors was controlled at 0.25 L / min, the flow rate at the outlet of the second reactor was 0.15 L / min, and the flow rate of the reflux pipe was 0.1 L / min (refluxed to the regulation tank, and the mixed liquid was lifted to the first reactor by the lift pump). Commercial CaO2 was added to the second reactor at a rate of 22.5 mg / min (equivalent concentration of 0.15 g / L). After the reactor had been operating stably for 5.5 hours (i.e., after all the coking wastewater treated in Example 1 had been discharged), the feeding rate of commercial CaO2 was adjusted to 9 mg / min (equivalent concentration of 0.06 g / L). At this time, it was counted as the 0 hour. It was operated in the above manner for 12 h, and the effluent TOC and COD values were measured every hour.

[0063] Figure 7 For the TOC and COD values of the coking wastewater treated in Example 3.

[0064] From Figure 7 It can be seen that the process of continuously treating coking wastewater by O3 - O3 / CaO2 of the present invention can operate continuously and stably within 12 h. Among them, the COD value has been below 80 mg / L all the time. Under the operating conditions of continuous influent and effluent, the effluent water quality can be guaranteed to meet the standards, overcoming the problems that the previous catalytic ozone process cannot have continuous influent and effluent or the effluent water quality is unstable.

[0065] Comparative Example 1

[0066] This comparative example provides a method for treating coking wastewater by O3 batchwise alone. The specific steps are as follows:

[0067] 50 L of coking wastewater (the initial TOC value of the coking wastewater was 120.1 mg / L, the COD value was 468.7 mg / L, the initial pH value was 7.9, taken from Chongqing Iron and Steel (Group) Co., Ltd., and after coagulation and sedimentation treatment, the TOC value was 106.6 mg / L, the COD value was 410 mg / L, and the pH value was 6.4) that had flowed through the coagulation sedimentation tank and the regulation tank in sequence was evenly placed in the two reaction vessels as shown in Figure 4 shown; then, with the ozone generator as the ozone - generating device and dry air as the gas source, the gas flow rate was controlled at 1000 mL / min, and the reaction started to be timed while O3 was introduced into the reactor. After reacting for 8 h, the TOC degradation rate of the coking wastewater was measured.

[0068] Comparative Example 2

[0069] This comparative example provides a method for treating coking wastewater by O3 / H2O2 batchwise. The specific steps are as follows:

[0070] 50 L of coking wastewater that has undergone coagulation sedimentation treatment and will flow through a coagulation sedimentation tank and an adjustment tank in sequence (the initial TOC value of the coking wastewater is 120.1 mg / L, the COD value is 468.7 mg / L, the initial pH value is 7.9, taken from Chongqing Iron and Steel (Group) Co., Ltd., and after coagulation sedimentation treatment, the TOC value is 106.6 mg / L, the COD value is 410 mg / L, and the pH value is 6.4) is evenly placed in Figure 4 the two reaction vessels shown as follows; 7.09 mL of 30 wt% H2O2 solution (i.e., a concentration of 1.38 mM) is evenly added to the two reactors; then, with an ozone generator as the ozone generation device and dry air as the gas source, the gas flow rate is controlled at 1000 mL / min, and the reaction starts timing while introducing O3 into the reactor. After reacting for 6 h, the TOC degradation rate of the coking wastewater is measured.

[0071] Figure 6 The results of the cost accounting for treating each ton of coking wastewater by Example 1, Comparative Example 1, Comparative Example 2, and the conventional Fenton method are shown. In Figure 6 it, O3 represents Comparative Example 1, O3 / H2O2 represents Comparative Example 2, and CaO2 / O3 represents Example 1.

[0072] As Figure 6 can be seen, the cost per ton of water treatment for the O3 - O3 / CaO2 continuous process for treating coking wastewater described in the present invention is only 5.08 yuan, which is nearly 50% lower than 8.95 yuan of the ozone system in Comparative Example 1, indicating that it is a green, economical, and efficient treatment technology.

[0073] Comparative Example 3

[0074] This comparative example provides a method for treating medical wastewater by using O3 in a batch mode alone, and the specific steps are as follows:

[0075] 50 L of medical wastewater that has flowed through a coagulation sedimentation tank and an adjustment tank in sequence (the initial TOC value of the medical wastewater is 35.3 mg / L, the COD value is 102.1 mg / L, the initial pH is 5.6, taken from a certain hospital in Chongqing, and no coagulation sedimentation treatment is carried out.) is evenly placed in Figure 4 the two reaction vessels shown as follows; then, with an ozone generator as the ozone generation device and dry air as the gas source, the gas flow rate is controlled at 1000 mL / min, and the reaction starts timing while introducing O3 into the reactor. After reacting for 1 h, the TOC degradation rate of the medical wastewater is measured.

[0076] Comparative Example 4

[0077] This comparative example provides a method for treating medical wastewater by using O3 / H2O2 in a batch mode, and the specific steps are as follows:

[0078] 50 L of medical wastewater that will flow through a coagulation sedimentation tank and an adjustment tank in sequence (the initial TOC value of the medical wastewater is 18.1 mg / L, the COD value is 43.0 mg / L, the initial pH is 5.6, taken from a hospital in Chongqing, without coagulation sedimentation treatment) is evenly placed in Figure 4 the two reaction vessels shown; 7.09 mL of 30 wt% H2O2 solution (i.e., the concentration is 1.38 mM) is evenly added to the two reactors; then, using an ozone generator as the ozone generation device and dry air as the gas source, the gas flow rate is controlled at 1000 mL / min, and the reaction starts timing while introducing O3 into the reactor. After reacting for 1 h, the TOC degradation rate of the coking wastewater is measured.

[0079] Figure 8 The effluent pH values after treating the wastewater described in Examples 1 - 3 and Comparative Examples 1 - 4, where (a) corresponds to Example 1, Example 3, Comparative Example 1, and Comparative Example 2, and (b) corresponds to Example 2, Comparative Example 3, and Comparative Example 4. In Figure 8 the (a) of Figure 8 , O3 represents Comparative Example 1, H2O2 / O3 represents Comparative Example 2, CaO2 / O3 represents Example 1, and CaO2 / O3 continuous flow represents Example 3; in

[0080] the (b) of Figure 8 , O3 represents Comparative Example 3, H2O2 / O3 represents Comparative Example 4, and CaO2 / O3 represents Example 2.

[0081] Comparative Example 5

[0082] The difference from Example 2 is that CaO2 is respectively replaced with an equal amount of Fe2O3, Al2O3, Mn2O3, or MnO2, and the others are the same as Example 2.

[0083] Comparative Example 6

[0084] The difference from Example 3 is that CaO2 is respectively replaced with an equal amount of Fe2O3, Al2O3, Mn2O3, or MnO2, and the others are the same as Example 3.

[0085] The effluent COD and TOC values under different systems described in Example 2, Example 3, Comparative Example 5, and Comparative Example 6, where (a) is the effluent TOC value of the coking wastewater; (b) is the effluent COD value of the coking wastewater, (c) is the effluent TOC value of the medical wastewater, and (d) is the effluent COD value of the medical wastewater.

[0086] FromFigure 12 It can be seen that the degradation effect of the system containing CaO2 has been significantly improved compared with that of the conventional systems containing Fe2O3, Al2O3, Mn2O3, and MnO2. Nitrobenzene is chemically used as a probe for ·OH and can quantify the concentration of ·OH in the reaction. The faster nitrobenzene is degraded, the more ·OH there is in the system. Combining the degradation of nitrobenzene below, CaO2 can effectively catalyze O3 to generate a large amount of ·OH, thereby significantly improving the degradation effect.

[0087] Since the organic pollutants in coking wastewater and medical wastewater are mainly nitrobenzene, in order to ensure that the experimental results are not affected by factors such as water quality fluctuations, the degradation effects of different degradation methods on an artificially prepared pollutant solution (nitrobenzene solution) were studied to illustrate the degradation effects of different degradation methods, and Effect Examples 1 to 5 were provided. Among them, Effect Examples 1 to 3 verified the effects of the methods of degrading nitrobenzene (NB) using O3 alone, using O3 / H2O2 to degrade nitrobenzene (NB), and using O3 / CaO2 to degrade nitrobenzene (NB) on the degradation efficiency of nitrobenzene, and Effect Examples 3 to 5 verified the effect of the addition amount of commercial CaO2 on the degradation efficiency of nitrobenzene. Specifically as follows:

[0088] Effect Example 1

[0089] A method for degrading nitrobenzene (NB) using O3 alone is provided, and the steps are as follows:

[0090] Transfer 0.166 mL of liquid NB to a 1 L volumetric flask, make up the volume, and dissolve it by ultrasonic wave to obtain a NB mother liquor (200 mg / L).

[0091] The experimental group was divided into 5 groups. Each group took 30 mL of the NB mother liquor into a glass reactor, diluted it to 300 mL with ultrapure water, and stirred it with a magnetic stirrer; NaOH and HCl were used to adjust the initial pH values of the NB solutions in each experimental group to obtain NB solutions with initial pH values of 3, 5, 7, 9, and 11 respectively; before the start of each group of experiments, 1 mL of the NB solution was taken as the test sample at the zero time, and its concentration was measured using high performance liquid chromatography (HPLC).

[0092] An ozone generator was used as the ozone generation device, dry air was used as the gas source, the gas flow rate was controlled at 200 mL / min, and at this time the O3 concentration was about 15 mg / L. While introducing ozone into each experimental group, the reaction started to be timed.

[0093] Every 3 minutes, 1 mL of the reaction solution in each experimental group was taken into a test tube, and then 50 μL of sodium thiosulfate solution (0.1 g / L) was added to quench the active species in the reaction solution to terminate the reaction; the total reaction time was 18 minutes. The removal of NB was measured using high performance liquid chromatography (HPLC).

[0094] Effect Example 2

[0095] A method for degrading nitrobenzene (NB) using O3 / H2O2 is provided, and the steps are as follows:

[0096] Transfer 0.166 mL of liquid NB and make up the volume in a 1 L volumetric flask and dissolve it by ultrasonic treatment to obtain the NB stock solution.

[0097] The experimental groups are divided into 5 groups in total. Take 30 mL of the NB stock solution in each group and dilute it to 300 mL in a glass reactor and stir it with a magnetic stirrer; use NaOH and HCl to adjust the initial pH value of the NB solution in each experimental group to obtain NB solutions with initial pH values of 3, 5, 7, 9, and 11 respectively; before the start of each group of experiments, take 1 mL of the solution as the test sample at the zero time, and use high performance liquid chromatography (HPLC) to test its concentration.

[0098] Add 43 μL of 30 wt% H2O2 solution (i.e., the concentration is 1.38 mM) to each reactor and stir evenly; use an ozone generator as the ozone generation device, use dry air as the gas source, control the gas flow rate to be 200 mL / min, adjust the O3 concentration to 15 mg / L, and start timing the reaction while introducing ozone into each experimental group.

[0099] Take 1 mL of the reaction solution from each experimental group in a test tube every 3 min, and then add 50 μL of sodium thiosulfate solution (0.1 g / L) to quench the active species in the reaction solution to terminate the reaction; the total reaction time is 18 min. Use high performance liquid chromatography (HPLC) to test the removal of NB.

[0100] Effect Example 3

[0101] A method for degrading nitrobenzene (NB) using O3 / CaO2 is provided:

[0102] Transfer 0.166 mL of liquid NB and make up the volume in a 1 L volumetric flask and dissolve it by ultrasonic treatment to obtain the NB stock solution.

[0103] The experimental groups are divided into 5 groups in total. Take 30 mL of the NB stock solution in each group and dilute it to 300 mL in a glass reactor and stir it with a magnetic stirrer; use NaOH and HCl to adjust the initial pH value of the NB solution in each experimental group to obtain NB solutions with initial pH values of 3, 5, 7, 9, and 11 respectively; before the start of each group of experiments, take 1 mL of the solution as the test sample at the zero time, and use high performance liquid chromatography (HPLC) to test its concentration.

[0104] Add 30 mg (i.e., 0.1 g / L) of CaO2 to each group of reactors and stir evenly. Use an ozone generator as the ozone generation device, with dry air as the gas source, control the gas flow rate at 200 mL / min, adjust the O3 concentration to 15 mg / L, and start timing the reaction while introducing ozone into each experimental group.

[0105] Take 1 mL of the reaction solution from each experimental group into a test tube every 3 min, and then add 50 μL of sodium thiosulfate solution (0.1 g / L) to quench the active species in the reaction solution to terminate the reaction. The total reaction time is 18 min. Use high-performance liquid chromatography (HPLC) to test the removal of NB.

[0106] Figure 1 Figures for the degradation of nitrobenzene (NB) in Effect Examples 1 - 3 under different initial pH conditions, where (a) corresponds to an initial pH = 3, (b) corresponds to an initial pH = 5, (c) corresponds to an initial pH = 7, (d) corresponds to an initial pH = 9, and (e) corresponds to an initial pH = 11. In Figure 1 it, O3 represents Effect Example 1, O3 / H2O2 represents Effect Example 2, and O3 / CaO2 represents Effect Example 3.

[0107] From Figure 1 it can be seen that in the relatively wide pH range of pH = 3 - 11, the O3 / CaO2 treatment process is significantly superior to traditional ozone (Effect Example 1) and per-ozone (Effect Example 2) technologies in treating the typical pollutant NB in chemical industrial wastewater. Although the effect of Effect Example 2 has also been greatly improved in a strong alkaline environment, the effect of Effect Example 3 is still better than that of Effect Example 2. That is to say, the effect is significantly improved after replacing H2O2 with CaO2.

[0108] Figure 2 Figure for the change of the system pH value during the test when the initial pH values of Effect Example 3 are 3, 5, 7, and 11 respectively, where (a) corresponds to an initial pH = 3, (b) corresponds to an initial pH = 5, (c) corresponds to an initial pH = 7, and (d) corresponds to an initial pH = 11.

[0109] From Figure 2 it can be seen that in a weak acid or strong alkaline environment, CaO2 can stabilize the pH within the range where O3 has the highest activity (pH > 10). Even under strong acid conditions, the system can still maintain a weakly alkaline environment, enhancing the treatment effect.

[0110] Figure 5 Figures for the TOC removal rate (mineralization rate) of Effect Examples 1 - 3, Examples 1 - 2, and Comparative Examples 1 - 4, where (a) corresponds to Effect Examples 1 - 3, (b) corresponds to Example 1, Comparative Example 1, and Comparative Example 2, and (c) corresponds to Example 2, Comparative Example 3, and Comparative Example 4. In Figure 5In (a) thereof, O3 represents Effect Example 1, O3 / H2O2 represents Effect Example 2, and O3 / CaO2 represents Effect Example 3; in Figure 5 In (b) thereof, O3 represents Comparative Example 1, O3 / H2O2 represents Comparative Example 2, and O3 / CaO2 represents Example 1; in Figure 5 In (c) thereof, O3 represents Comparative Example 3, O3 / H2O2 represents Comparative Example 4, and O3 / CaO2 represents Example 2.

[0111] It can be seen from Figure 5 that regardless of which kind of wastewater (coking wastewater, medical wastewater) is degraded, the mineralization rate of the O3-O3 / CaO2 treatment process described in the present invention is significantly higher than that of the traditional ozone and per-ozone systems, proving that the process described in the present invention has a more thorough pollutant removal effect and better effluent water quality.

[0112] Effect Example 4

[0113] The difference from Effect Example 3 is that the dosage of CaO2 is adjusted to 18 mg (i.e., 0.06 g / L), and the others are the same as Effect Example 3.

[0114] Effect Example 5

[0115] The difference from Effect Example 3 is that the dosage of CaO2 is adjusted to 45 mg (i.e., 0.15 g / L), and the others are the same as Effect Example 3.

[0116] Figure 3 It is the nitrobenzene (NB) degradation effect diagram of Effect Examples 3 to 5.

[0117] It can be seen from Figure 3 that under the CaO2 dosage of 0.06 - 0.15 g / L, there is no significant difference in treating the single pollutant NB, and an ideal treatment efficiency can also be achieved under the operation conditions of low dosage.

[0118] In order to verify the toxicity of the wastewater treated in Examples 1 - 2, Comparative Examples 1 - 4, and Effect Examples 1 - 3, the wastewater treated in Examples 1 - 2, Comparative Examples 1 - 4, and Effect Examples 1 - 3 was respectively subjected to Escherichia coli culture, mung bean seed germination, and zebrafish embryo culture to verify the toxicity of the wastewater treated by each of the methods, and the specific situation is shown in Effect Example 6.

[0119] Effect Example 6

[0120] Evaluate the toxicity of the wastewater treated in Examples 1 - 2, Comparative Examples 1 - 4, and Effect Examples 1 - 3:

[0121] Escherichia coli culture: Pipette 100 mL of Escherichia coli strain solution and place it in a sterilized liquid medium (10 g of peptone, 5 g of yeast extract, 10 g of NaCl, made up to 1 L, sterilized at 121 °C for 20 min in a high-pressure steam sterilizer). After culturing in a constant-temperature shaker at 37 °C for 48 h, pipette 13 aliquots of 1 mL each of the Escherichia coli-containing culture solution, and add 4 mL of the wastewater treated in Examples 1-2, Comparative Examples 1-4, and Effect Examples 1-3 thereto (among which, four control groups are also set up, namely adding 4 mL of ultrapure water, adding 4 mL of NB solution, adding 4 mL of the untreated coking wastewater described in Example 1, and adding 4 mL of the untreated medical wastewater described in Example 2), and continue to culture in a constant-temperature shaker at 37 °C for 12 h. Under a sterile environment, dilute the culture solutions of each group by 10 6 times, then take 0.2 mL of the diluted culture solution and evenly spread it on an agar medium with the same composition and concentration as the liquid medium (15.2 g / L of agar). After culturing in a constant-temperature incubator at 37 °C for 12 h, taking the culture result with ultrapure water as the benchmark, statistically normalize the number of colonies in each group.

[0122] Mung bean seed germination: Add 10 mL of the wastewater treated in Examples 1-2, Comparative Examples 1-4, and Effect Examples 1-3 to a culture dish (among which, four control groups are also set up, namely adding 10 mL of ultrapure water, adding 10 mL of NB solution, adding 10 mL of the untreated coking wastewater described in Example 1, and adding 10 mL of the untreated medical wastewater described in Example 2). Put 20 mung bean seeds that have been soaked in water for one day in advance into each culture dish. Cover the lid, and open it after the seeds germinate. After 10 days, statistically calculate the germination rate and stem length of each group.

[0123] Zebrafish embryo culture: Add 1 mL of the wastewater treated in Examples 1-2, Comparative Examples 1-4, and Effect Examples 1-3 to 1 mL of zebrafish living water (among which, four control groups are also set up, namely adding 1 mL of ultrapure water, adding 1 mL of NB solution, adding 1 mL of the untreated coking wastewater described in Example 1, and adding 1 mL of the untreated medical wastewater described in Example 2). Place it in a special medium and put one zebrafish egg. Do five parallel fish eggs for each group. After culturing for 120 h, statistically calculate the mortality rate, malformation rate, and normal survival rate.

[0124] Figure 9 Are the toxicity index results of Effect Example 6, where (a) corresponds to the Escherichia coli culture result, (b) corresponds to the mung bean seed germination result, and (c) corresponds to the zebrafish embryo development result. In Figure 9Among them, 1: ultrapure water, 2: NB solution, 3: NB treated with O3 (Effect Example 1), 4: NB treated with O3 / H2O2 (Effect Example 2), 5: NB treated with O3-O3 / CaO2 (Effect Example 3), 6: coking wastewater (untreated coking wastewater described in Example 1), 7: coking wastewater treated with O3 (Comparative Example 1), 8: coking wastewater treated with O3 / H2O2 (Comparative Example 2), 9: coking wastewater treated with O3-O3 / CaO2 (Example 1), 10: medical wastewater (untreated medical wastewater described in Example 2), 11: medical wastewater treated with O3 (Comparative Example 3), 12: medical wastewater treated with O3 / H2O2 (Comparative Example 4), 13: medical wastewater treated with O3-O3 / CaO2 (Example 2).

[0125] It can be seen from Figure 9 that under different wastewater qualities, the treatment method of O3-O3 / CaO2 described in the present invention can effectively complete the detoxification reaction. Therefore, the process proposed by the present invention is a new green, economical and efficient water treatment technology.

[0126] In this specification, each embodiment is described in a progressive manner. The key point of each embodiment is to illustrate the differences from other embodiments. The same or similar parts among the embodiments can be referred to each other.

[0127] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A two-stage oxidation treatment method for refractory wastewater, characterized in that: The wastewater is pretreated with ozone after coagulation and sedimentation, and then CaO2 is added to catalyze ozone for oxidation treatment.

2. The two-stage oxidation treatment method according to claim 1, characterized in that: The indicators of the wastewater are: coking wastewater: TOC=120.1mg / L, COD=468.7mg / L, TP=1.1mg / L; medical wastewater: TOC=35.2mg / L, COD=102.1mg / L, TP=0.15mg / L; the indicators after coagulation and sedimentation are: coking wastewater: TOC=106.6mg / L, COD=410mg / L, TP=0.9mg / L; the indicators after ozone pretreatment are: coking wastewater: TOC=98.9mg / L, COD=352.4mg / L, TP=0.9mg / L; medical wastewater: TOC=33.5mg / L, COD=88.7mg / L, TP=0.15mg / L.

3. The two-stage oxidation treatment method according to claim 1, characterized in that: The ozone treatment concentration during the ozone pretreatment process is 15 mg / L. During the ozone oxidation treatment process using CaO2 as catalyst, the ozone concentration is 15 mg / L and the CaO2 concentration is 0.06-0.15 g / L.

4. The two-stage oxidation treatment method according to claim 1, characterized in that: The difficult-to-degrade wastewater is coking wastewater or medical wastewater.

5. The two-stage oxidation treatment method according to claim 4, characterized in that: When the difficult-to-degrade wastewater is coking wastewater, the ozone pretreatment time is 0.5 to 1 hour, and the oxidation treatment time is 4 to 6 hours; when the difficult-to-degrade wastewater is medical wastewater, the ozone pretreatment time is 0.25 to 0.5 hours, and the oxidation treatment time is 0.75 to 1.5 hours.

6. The two-stage oxidation treatment method according to claim 1, characterized in that: The organic pollutants in the refractory wastewater include nitrobenzene.

7. The two-stage oxidation treatment method according to claim 1, characterized in that: The pH value of the difficult-to-degrade wastewater is 3-11.

8. A system for the two-stage oxidation treatment method according to any one of claims 1 to 7, characterized in that: It comprises a coagulation sedimentation tank, a regulating tank and an oxidative degradation unit connected in sequence; the oxidative degradation unit comprises a first reactor and a second reactor, the first reactor and the second reactor are connected through a one-way connecting pipe, and a one-way reflux pipe is also arranged between the first reactor and the second reactor.

9. The system of the two-stage oxidation treatment method according to claim 8, characterized in that: During the stable operation stage of sewage treatment, the first reactor is used for O3 pretreatment reaction, and the second reactor is used for CaO2-catalyzed O3 treatment reaction.

10. A method for continuously treating refractory wastewater based on the two-stage oxidation treatment method according to claim 8 or 9, characterized in that: The following steps are involved: The refractory wastewater is transferred to the regulating tank after coagulation and sedimentation in the coagulation and sedimentation tank; Transferring part of the sewage in the regulating tank to the first reactor and the second reactor for ozone pretreatment, and then adding CaO2 catalytic ozone to the first reactor and the second reactor for oxidation treatment; The remaining sewage in the equalization tank is continuously transported to the first reactor for ozone pretreatment. The sewage pretreated by ozone in the first reactor enters the second reactor through a one-way connecting pipe and is oxidized using CaO2 catalytic ozone to achieve continuous treatment of difficult-to-degrade wastewater.

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