Method for treating organic nitrogen wastewater through ozone oxidation

Abstract

The invention relates to a method for treating organic nitrogen wastewater by ozone oxidation, which comprises the following steps: mixing organic nitrogen wastewater with a concentrated solution of ammoximation process wastewater, and adjusting the pH value of the solution to be less than 7.0 to obtain mixed wastewater; in the presence of a solid-phase catalyst, ozone is in contact with the mixed wastewater for ozone oxidation treatment; the molar ratio of the ozone to the detected substance in the mixed wastewater in terms of H2O2 is (1-5): 1, the content ratio of the detected substance in the mixed wastewater in terms of H2O2 to COD (Chemical Oxygen Demand) is (1-10): 1, the solid-phase catalyst comprises a carrier and an active component loaded on the carrier, and the active component is selected from one or more of tin, cerium, manganese, cobalt and copper. According to the method disclosed by the invention, the contents of organic nitrogen and organic carbon in the organic nitrogen wastewater can be reduced, the biodegradability is improved, and the treated wastewater has a relatively low COD (Chemical Oxygen Demand) value and a relatively high B / C value.

Description

Technical Field

[0001] The present disclosure relates to a wastewater treatment method, and in particular, to a method for treating organic nitrogen wastewater by ozone oxidation. Background Art

[0002] Organic nitrogen wastewater refers to wastewater mixed with benzene organic pollutants, such as benzene, toluene, chlorobenzene, nitrobenzene, etc., which are relatively common pollutants. Benzene pollutants are stable in nature and difficult to degrade in the environment. Conventional treatment processes such as adsorption and flocculation are difficult to effectively treat. The current treatment methods mainly include adsorption, chemical oxidation, microbial methods, etc.

[0003] The adsorption method often has the problem of adsorbent regeneration, and the adsorbent that cannot be regenerated is treated as hazardous waste, which increases the cost of wastewater treatment. Wet oxidation is the most commonly used chemical oxidation method for benzene wastewater treatment. This method has wide applicability and good treatment effect, but this method usually operates under high temperature and high pressure, with high equipment investment and complex operation. The microbial method usually needs to be used in conjunction with the advanced oxidation method. The advanced oxidation method is used to oxidize benzene substances, improve the biodegradability of the wastewater, and then use the microbial method for treatment. This method has a long treatment process and a long cycle.

[0004] On the other hand, in the production of caprolactam, the COD of wastewater produced by the ammoximation process is as high as 2000-12000 mg / L. The wastewater contains trace amounts of organic impurities such as toluene, cyclohexanone oxime, cyclohexanol, and cyclohexanone. After the wastewater is distilled and organic matter is recovered by the stripping tower, if it is directly discharged into the sewage treatment system, the refractory organic matter in it will impact the biochemical treatment device. Therefore, the wastewater at the bottom of the wastewater stripping tower needs to be pretreated before biochemical treatment to reduce the refractory organic matter in it. Studies have found that organic peroxides in ammoximation wastewater are the main reason affecting the biodegradability of wastewater. However, the properties of this type of organic peroxide in wastewater are relatively stable, and it is difficult to remove it by conventional methods of decomposing hydrogen peroxide. At present, the pretreatment of ammoximation wastewater mainly focuses on catalytic oxidation. For example, CN110540336A discloses a method for treating ammoximation wastewater and its application, which is to add a flocculant to the ammoximation wastewater, adjust the wastewater to acidity after pre-sedimentation, perform enhanced sedimentation, adjust the wastewater to alkalinity after filtration, perform catalytic oxidation reaction, and then enter biochemical treatment. This method produces a large amount of precipitation, and the sedimentation tank occupies a large area. Summary of the invention

[0005] The purpose of the present disclosure is to provide a method for treating organic nitrogen wastewater by ozone oxidation, which can reduce the organic nitrogen and organic carbon contents in the organic nitrogen wastewater, improve biodegradability, and make the treated wastewater have a lower COD value and a higher B / C value.

[0006] In order to achieve the above-mentioned purpose, the present disclosure discloses a method for treating organic nitrogen wastewater by ozone oxidation, the method comprising: mixing the organic nitrogen wastewater with a concentrated solution of ammoximation process wastewater, adjusting the pH of the solution to less than 7.0, and obtaining mixed wastewater; contacting the mixed wastewater with ozone in the presence of a solid-phase catalyst to perform ozone oxidation treatment; the molar ratio of the ozone to the detected object in terms of H2O2 in the mixed wastewater is (1-5):1, and the content ratio of the detected object in terms of H2O2 to COD in the mixed wastewater is (1-10):1, and the solid-phase catalyst comprises a carrier and an active component loaded on the carrier, and the active component is selected from one or more of tin, cerium, manganese, cobalt and copper.

[0007] Optionally, the molar ratio of the ozone to the detected substance in the mixed wastewater calculated as H2O2 is (1.2-2):1; the content ratio of the detected substance in the mixed wastewater calculated as H2O2 to COD is (4-8):1.

[0008] Optionally, the COD of the organic nitrogen wastewater is 50 to 2000 mg / L, preferably 100 to 1500 mg / L; the organic nitrogen content is 30 to 500 mg / L, preferably 30 to 200 mg / L.

[0009] Optionally, the organic nitrogen in the organic nitrogen wastewater is selected from one or more of alcoholamines, amides and fatty amines, and the alcoholamine is selected from N-methyldiethanolamine.

[0010] Optionally, the COD of the ammoximation industrial wastewater is 300 to 30,000 mg / L, preferably 500 to 15,000 mg / L; the content of the detected substance in terms of H2O2 is 200 to 30,000 mg / L, preferably 500 to 15,000 mg / L.

[0011] Optionally, the preparation method of the concentrated solution includes: concentrating the ammoximation process wastewater by a reduced pressure distillation method or a membrane concentration method to obtain the concentrated solution and fresh water; the temperature of the reduced pressure distillation is 50 to 100°C, preferably 60 to 90°C; the time is 0.2 to 10h, preferably 0.5 to 5h; the vacuum degree is 0.01 to 0.1KPa, preferably 0.02 to 0.08KPa.

[0012] Optionally, the volume of the concentrated liquid is 3-20%, preferably 5-15%, of the volume of the ammoximation process wastewater.

[0013] Optionally, the carrier is selected from one or more of alumina, ceramic membrane, molecular sieve and activated carbon; based on the total weight of the carrier, the content of the active component in terms of metal element is 1 to 10 weight %, preferably 2 to 4 weight %.

[0014] Optionally, the support is selected from a ceramic membrane, and the active components include tin, cerium and manganese.

[0015] Optionally, the temperature of the ozone oxidation treatment is 5 to 50° C., preferably 10 to 40° C.; the time is 30 to 180 min, preferably 40 to 100 min.

[0016] Through the above technical scheme, the present disclosure provides a method for treating organic nitrogen wastewater with ozone oxidation, which uses ozone and concentrated solution of ammonia oxime industrial wastewater to oxidatively decompose organic nitrogen and organic carbon in the organic nitrogen wastewater. Specifically, in the presence of a solid phase catalyst, ozone and the high concentration of H2O2-containing detection objects in the concentrated solution of ammonia oxime industrial wastewater have a synergistic effect. On the one hand, ozone can not only oxidize and degrade the long chains of organic nitrogen and organic carbon in the organic nitrogen wastewater, but also oxidize and degrade the detection objects with H2O2 properties in the concentrated solution. The long chain can significantly reduce the content of organic pollutants in the mixed wastewater and improve its biodegradability; on the other hand, the detected substances with H2O2 properties in the concentrate are excited by the solid phase catalyst to produce a variety of free radicals, which can destroy the organic nitrogen structure in the organic nitrogen wastewater, convert nitrogen into ammonia nitrogen, further oxidize it into nitrogen gas, and degrade large molecular organic carbon into small molecular organic matter or directly mineralize it into carbon dioxide, so that the effluent water quality of the treated wastewater has a lower COD value and a higher B / C value, which can be directly discharged to the sewage treatment plant to achieve the purpose of treating waste with waste.

[0017] Other features and advantages of the present disclosure will be described in detail in the following detailed description. DETAILED DESCRIPTION

[0018] The specific embodiments of the present disclosure are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present disclosure, and are not used to limit the present disclosure.

[0019] The first aspect of the present disclosure provides a method for treating organic nitrogen wastewater by ozone oxidation, the method comprising: mixing the organic nitrogen wastewater with a concentrated solution of ammoximation process wastewater, adjusting the solution pH to less than 7.0, and obtaining mixed wastewater; contacting the mixed wastewater with ozone in the presence of a solid phase catalyst to perform ozone oxidation treatment; the molar ratio of the ozone to the detected object in terms of H2O2 in the mixed wastewater is (1-5):1, the content ratio of the detected object in terms of H2O2 to COD in the mixed wastewater is (1-10):1, and the solid phase catalyst comprises a carrier and an active component loaded on the carrier, the active component being selected from one or more of tin, cerium, manganese, cobalt and copper. In one embodiment, the solution pH is adjusted to 2.0-5.0. The detected object in terms of H2O2 refers to an organic peroxide-like substance having the properties of H2O2, and the content of the detected object is detected by the method of GB1616-2003.

[0020] The inventors of the present disclosure have found in in-depth research that in the presence of a solid-phase catalyst, ozone and the high-concentration detection objects with H2O2 properties contained in the concentrated solution of ammonia oxime industrial wastewater have a synergistic effect. On the one hand, ozone can not only oxidize and degrade the long chains of organic nitrogen and organic carbon in the organic nitrogen wastewater, but also oxidize and degrade the long chains of the detection objects with H2O2 properties in the concentrated solution, so that the content of organic pollutants in the mixed wastewater is greatly reduced, and its biodegradability is improved; on the other hand, the detection objects with H2O2 properties in the concentrated solution are excited by the solid-phase catalyst to produce a variety of free radicals, which can further destroy the structure of organic nitrogen in the organic nitrogen wastewater, convert nitrogen into ammonia nitrogen, further oxidize it into nitrogen gas, and degrade large-molecule organic carbon into small-molecule organic matter or directly mineralize it into carbon dioxide, so that the effluent water quality of the treated wastewater has a lower COD value and a higher B / C value, and can be directly discharged to a sewage treatment plant to achieve the purpose of treating waste with waste.

[0021] In one embodiment of the present disclosure, the molar ratio of the ozone to the detected object in the mixed wastewater in terms of H2O2 is (1.2-2):1; the content ratio of the detected object in terms of H2O2 to COD in the mixed wastewater is (4-8):1. In the above embodiment, by selecting the preferred mixed wastewater, it is beneficial for the organic nitrogen and organic carbon in the mixed wastewater to fully contact with the ozone and the quasi-organic peroxide having the properties of H2O2, thereby improving the oxidation treatment effect.

[0022] In one embodiment of the present disclosure, the COD of the organic nitrogen wastewater is 50 to 2000 mg / L, preferably 100 to 1500 mg / L; the organic nitrogen content is 30 to 500 mg / L, preferably 30 to 200 mg / L.

[0023] In one embodiment of the present disclosure, the organic nitrogen wastewater includes organic nitrogen and organic carbon, the organic nitrogen is selected from one or more of alcohol amines, amides and fatty amines, and the alcohol amine is selected from N-methyldiethanolamine. In one embodiment, the organic nitrogen wastewater is selected from one or more of dye wastewater, petrochemical wastewater, coal chemical wastewater and pesticide wastewater. The organic nitrogen wastewater disclosed in the present disclosure contains a large amount of organic nitrogen and macromolecular organic carbon, with a COD value of more than 50 mg / L and a B / C value close to 0. It has the characteristics of high toxicity and poor biodegradability and cannot be directly discharged into the wastewater treatment system.

[0024] In one embodiment of the present disclosure, the COD of the ammoximation industrial wastewater is 300-30000 mg / L, preferably 500-15000 mg / L; the content of the detected object in terms of H2O2 is 200-30000 mg / L, preferably 500-15000 mg / L. The ammoximation industrial wastewater of the present disclosure contains a large amount of organic peroxide-like substances with the properties of H2O2, which are toxic and harmful to microorganisms, and the B / C is close to 0. It cannot be directly discharged into the wastewater treatment system to avoid causing a large number of microbial deaths.

[0025] In one embodiment of the present disclosure, the preparation method of the concentrated solution includes: using a vacuum distillation method or a membrane concentration method to concentrate the ammoximation process wastewater to obtain the concentrated solution and fresh water; the vacuum distillation temperature is 50-100°C, preferably 60-90°C; the time is 0.2-10h, preferably 0.5-5h; the vacuum degree is 0.01-0.1KPa, preferably 0.02-0.08KPa. In the above embodiment, the selected concentration method is conducive to concentrating the detected substances with H2O2 properties in the ammoximation industrial wastewater in the concentrated solution, improving the B / C value of the fresh water after concentration treatment, so that it can directly enter the existing sewage treatment plant of the enterprise for treatment.

[0026] In one embodiment of the present disclosure, the volume of the concentrated solution is 3-20%, preferably 5-15%, of the volume of the ammoximation process wastewater.

[0027] In one embodiment of the present disclosure, the carrier is selected from one or more of alumina, ceramic membrane, molecular sieve and activated carbon; based on the total weight of the carrier, the content of the active component in terms of metal element is 1 to 10% by weight, preferably 2 to 4% by weight; in a preferred embodiment, the carrier is selected from a ceramic membrane, and the active component includes tin, cerium and manganese. In the above embodiment, the preferred content of the solid phase catalyst is selected to facilitate uniform contact between the solid phase catalyst and the mixed wastewater, thereby improving its catalytic effect.

[0028] In one embodiment of the present disclosure, the ozone oxidation treatment is carried out at room temperature and pressure, for example, the temperature is 5 to 50° C., preferably 10 to 40° C.; the pressure is 0.1 MPa, and the time is 30 to 180 min, preferably 40 to 100 min.

[0029] The present disclosure is further described in detail by examples. The ceramic membrane and alumina used in the examples can be obtained through commercial channels. The ceramic membrane was purchased from Zhangjiagang Huayuan Environmental Technology Co., Ltd., and the alumina was purchased from Sasol.

[0030] The determination method of BOD is the five-day biochemical method (HJ 505-2009), the determination method of COD is the potassium dichromate method (GB11914-89), and B / C is the ratio of BOD to COD. The content of active components loaded on the carrier is tested by XRF analyzer, and the instrument model is Rigaku 3271E.

[0031] Example 1

[0032] (1) The COD of the ammoximation wastewater of a petrochemical plant was 3970 mg / L, the mass concentration of the detected substance in terms of H2O2 was 6120 mg / L, and the B / C ratio was 0.01. The ammoximation wastewater was concentrated by vacuum distillation at a temperature of 80°C, a time of 2 h, and a vacuum degree of 0.08 KPa to obtain a concentrated solution with a volume of 10% of the volume of the ammoximation wastewater and a fresh water with a volume of 90% of the volume of the ammoximation wastewater.

[0033] (2) Mixing the concentrated liquid obtained in step (1) with organic nitrogen wastewater, wherein the organic nitrogen wastewater is wastewater discharged from a natural gas plant containing N-methyldiethanolamine (MDEA, i.e., organic nitrogen), and the inlet water quality is: COD is 344 mg / L, MDEA content is 170 mg / L, and B / C is 0.01. Adjusting the solution pH to 4.0, a mixed wastewater is obtained, wherein the ratio of the detected substance in terms of H2O2 to COD in the mixed wastewater is 5:1;

[0034] (3) The mixed wastewater was passed into an ozone reactor filled with a ceramic membrane loaded with tin, cerium and manganese, and ozone was introduced to perform ozone oxidation treatment on the mixed wastewater, wherein the molar ratio of the ozone introduced to the detected substance in terms of H2O2 in the mixed wastewater was 1.3:1, and the ozone oxidation treatment was performed at 30°C for 50 min. Based on the total weight of the ceramic membrane, the total content of tin, cerium and manganese in terms of metal elements was 2.9% by weight. The effluent water quality of the treated wastewater was tested, and the results are shown in Table 1.

[0035] Example 2

[0036] The same as Example 1, the only difference is that in step (2), the ratio of the content of the detected substance in terms of H2O2 to COD in the mixed wastewater is 2:1, and the effluent water quality of the treated wastewater is shown in Table 1.

[0037] Example 3

[0038] The same as Example 1, the only difference is that in step (3), the molar ratio of the ozone introduced to the detected substance in the mixed wastewater in terms of H2O2 is 1.5:1, and the effluent water quality of the treated wastewater is shown in Table 1.

[0039] Example 4

[0040] The same as Example 1, the only difference is that in step (3), the molar ratio of the ozone introduced to the detected substance in the mixed wastewater in terms of H2O2 is 5:1, and the effluent water quality of the treated wastewater is shown in Table 1.

[0041] Example 5

[0042] The same as Example 1, the only difference is that in step (3), the ceramic membrane loaded with tin, cerium and manganese is replaced with γ-Al2O3 loaded with cerium and manganese. The effluent water quality of the treated wastewater is shown in Table 1.

[0043] Example 6

[0044] The method is the same as Example 1, except that: in step (2), the organic nitrogen wastewater is wastewater containing acrylonitrile discharged from a chemical plant, and the inlet water quality is: COD is 1053 mg / L, acrylonitrile content is 193 mg / L, and B / C is 0.23; the ratio of the content of the detected substance in terms of H2O2 to COD in the mixed wastewater is 5:1;

[0045] In step (3), the solid phase catalyst is alumina loaded with cerium and manganese, and the total content of cerium and manganese in terms of metal elements is 3.8% by weight based on the total weight of the alumina. The effluent quality of the treated wastewater is shown in Table 1.

[0046] Comparative Example 1

[0047] The method is the same as Example 1, except that step (1) is not performed, and the concentrated solution of ammonia oximation process wastewater is not added to the organic nitrogen wastewater in step (2). The effluent quality of the treated wastewater is shown in Table 1.

[0048] Comparative Example 2

[0049] The same as Example 1, the only difference is that step (3) is not performed, and air is introduced into the mixed wastewater obtained in step (2) for oxidation treatment. The amount of air introduced is 1.2 times the amount of oxidant required for the COD value in the mixed wastewater. The effluent water quality of the treated wastewater is shown in Table 1.

[0050] Comparative Example 3

[0051] The same as Example 1, the only difference is that: step (1) is not performed, the concentrated solution in step (2) is replaced by the same amount of hydrogen peroxide with a mass fraction of 27%, and the effluent water quality of the treated wastewater is shown in Table 1.

[0052] Comparative Example 4

[0053] The same as Example 1, the only difference is that in step (2), the pH of the mixed wastewater is adjusted to 8.5, and the effluent water quality of the treated wastewater is shown in Table 1.

[0054] Wherein, COD removal rate % = 100% × (COD content of organic nitrogen wastewater influent quality - COD content of treated wastewater effluent quality) / COD content of organic nitrogen wastewater influent quality;

[0055] Organic nitrogen removal rate % = 100% × (organic nitrogen content of organic nitrogen wastewater inlet water quality - organic nitrogen content of treated wastewater effluent water quality) / organic nitrogen content of organic nitrogen wastewater inlet water quality.

[0056] Table 1

[0057]

[0058] *In the table, "organic nitrogen" refers to acrylonitrile for Example 6 and to MDEA for the other examples and comparative examples.

[0059] From the results in Table 1 above, it can be seen that compared with Comparative Examples 1 to 4, when Examples 1 to 6 use concentrated solutions of ozone and ammoximized industrial wastewater to oxidize organic nitrogen wastewater, they can effectively degrade organic nitrogen and macromolecular organic carbon in organic nitrogen wastewater, improve biodegradability, and achieve the purpose of treating waste with waste. However, Comparative Examples 1 to 4 do not use the technical solution disclosed in the present invention, and the effluent water quality of the treated wastewater is poor.

[0060] The preferred embodiments of the present disclosure are described in detail above; however, the present disclosure is not limited to the specific details in the above embodiments. Within the technical concept of the present disclosure, a variety of simple modifications can be made to the technical solution of the present disclosure, and these simple modifications all fall within the protection scope of the present disclosure.

[0061] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present disclosure will not further describe various possible combinations.

[0062] In addition, various embodiments of the present disclosure may be arbitrarily combined, and as long as they do not violate the concept of the present disclosure, they should also be regarded as the contents disclosed by the present disclosure.

Claims

1. A method for treating organic nitrogen wastewater by ozone oxidation, characterized in that: The method comprises: mixing organic nitrogen wastewater with concentrated solution of ammonia oximation process wastewater, adjusting the pH of the solution to less than 7.0, to obtain mixed wastewater; contacting the mixed wastewater with ozone in the presence of a solid phase catalyst to perform ozone oxidation treatment; The molar ratio of the ozone to the detected object in the mixed wastewater calculated as H2O2 is (1-5):1, the content ratio of the detected object in the mixed wastewater calculated as H2O2 to COD is (1-10):1, and the solid phase catalyst includes a carrier and an active component loaded on the carrier, and the active component is selected from one or more of tin, cerium, manganese, cobalt and copper.

2. The method according to claim 1, characterized in that The molar ratio of the ozone to the detected substance in the mixed wastewater calculated as H2O2 is (1.2-2):1; the content ratio of the detected substance in the mixed wastewater calculated as H2O2 to COD is (4-8):

1.

3. The method according to claim 1, characterized in that The COD of the organic nitrogen wastewater is 50 to 2000 mg / L, preferably 100 to 1500 mg / L; the organic nitrogen content is 30 to 500 mg / L, preferably 30 to 200 mg / L.

4. The method according to claim 1, characterized in that The organic nitrogen in the organic nitrogen wastewater is selected from one or more of alcoholamines, amides and fatty amines, and the alcoholamine is selected from N-methyldiethanolamine.

5. The method according to claim 1, characterized in that: The COD of the ammoximation industrial wastewater is 300 to 30,000 mg / L, preferably 500 to 15,000 mg / L; the content of the detected substance in terms of H2O2 is 200 to 30,000 mg / L, preferably 500 to 15,000 mg / L.

6. The method according to claim 1, characterized in that The preparation method of the concentrated solution comprises: concentrating the ammoximation process wastewater by a reduced pressure distillation method or a membrane concentration method to obtain the concentrated solution and fresh water; the temperature of the reduced pressure distillation is 50 to 100° C., preferably 60 to 90° C.; the time is 0.2 to 10 hours, preferably 0.5 to 5 hours; the vacuum degree is 0.01 to 0.1 KPa, preferably 0.02 to 0.08 KPa.

7. The method according to claim 6, characterized in that The volume of the concentrated liquid is 3-20%, preferably 5-15%, of the volume of the ammoximation process wastewater.

8. The method according to claim 1, characterized in that The carrier is selected from one or more of alumina, ceramic membrane, molecular sieve and activated carbon; based on the total weight of the carrier, the content of the active component in terms of metal element is 1 to 10 weight %, preferably 2 to 4 weight %.

9. The method according to claim 8, characterized in that The carrier is selected from ceramic membranes, and the active components include tin, cerium and manganese.

10. The method according to claim 1, characterized in that The temperature of the ozone oxidation treatment is 5 to 50° C., preferably 10 to 40° C.; the time is 30 to 180 minutes, preferably 40 to 100 minutes.

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