A method for ozone oxidation treatment of organic nitrogen wastewater

Abstract

The present disclosure relates to a method for treating organic nitrogen wastewater by ozone oxidation, which comprises: mixing the organic nitrogen wastewater with a concentrated solution of ammoximation process wastewater, adjusting the pH of the solution to less than 7.0 to obtain mixed wastewater; contacting ozone with the mixed wastewater in the presence of a solid-phase catalyst to perform ozone oxidation treatment; the molar ratio of ozone to detectable substance calculated as H2O2 in the mixed wastewater is (1-5):1, and the content ratio of the detectable substance calculated as H2O2 to COD in the mixed wastewater is (1-10):1; the solid-phase catalyst comprises a carrier and an active component supported on the carrier, and the active component is selected from one or more of tin, cerium, manganese, cobalt and copper. The method of the present disclosure can reduce the content of organic nitrogen and organic carbon in the organic nitrogen wastewater, improve the biodegradability, and make the treated wastewater have a lower COD value and a higher B / C value.

Description

TECHNICAL FIELD

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

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

[0003] The adsorption method often has the problem of producing adsorbent regeneration, and the non-regenerable adsorbent is treated and disposed 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 it usually operates at high temperature and high pressure, which requires high equipment investment and complex operation.

[0004] On the other hand, in caprolactam production, the wastewater produced by the ammonium oxime process has a COD as high as 2000-12000 mg / L. The wastewater contains trace amounts of organic impurities such as toluene, cyclohexanone oxime, cyclohexanol, and cyclohexanone. After distillation in a stripping tower to recover organic matter, if the wastewater 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 stripping tower needs to be pretreated to reduce the refractory organic matter before biochemical treatment. Research has found that the organic peroxide in the ammonium oxime wastewater is the main reason affecting the biodegradability of the wastewater. However, this type of organic peroxide is relatively stable in nature, and it is difficult to remove using the conventional method of decomposing hydrogen peroxide. Currently, the pretreatment of ammonium oxime wastewater mainly focuses on catalytic oxidation. For example, CN110540336A discloses a treatment method for ammonium oxime wastewater and its application, which involves adding a flocculating agent to the ammonium oxime wastewater, pre-sedimenting, adjusting the wastewater to be acidic, intensively settling, filtering, adjusting the wastewater to be alkaline, and then performing catalytic oxidation before entering the biochemical process. This method produces a large amount of sediment, and the sedimentation tank occupies a large area. SUMMARY

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

[0006] To achieve the above object, the present disclosure discloses a method for ozone oxidation treatment of organic nitrogen wastewater, which comprises: mixing organic nitrogen wastewater with concentrated solution of ammoximation process wastewater, adjusting pH of the solution to less than 7.0 to obtain mixed wastewater; contacting ozone with the mixed wastewater in the presence of a solid phase catalyst to perform ozone oxidation treatment; the molar ratio of the ozone to the detectable substance calculated as H2O2 in the mixed wastewater is (1-5):1, and the content ratio of the detectable substance calculated as H2O2 to COD in the mixed wastewater is (1-10):1; the solid phase catalyst comprises a carrier and an active component supported 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 detectable substance calculated as H2O2 in the mixed wastewater is (1.2-2):1; and the content ratio of the detectable substance calculated as H2O2 to COD in the mixed wastewater is (4-8):1.

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

[0009] Optionally, the organic nitrogen in the organic nitrogen wastewater is selected from one or more of alcohol amine, amide and aliphatic amine, and the alcohol amine is selected from N-methyl diethanolamine.

[0010] Optionally, the COD of the ammoximation industrial wastewater is 300-30000 mg / L, preferably 500-15000 mg / L; and the content of the detectable substance calculated as H2O2 is 200-30000 mg / L, preferably 500-15000 mg / L.

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

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

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

[0014] Optionally, the carrier is selected from ceramic membranes, and the active component comprises tin, cerium and manganese.

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

[0016] By the technical solution, the method for ozone oxidation treatment of organic nitrogen wastewater is provided, which adopts ozone and concentrated liquid of ammoxilation industrial wastewater to oxidize and decompose organic nitrogen and organic carbon in the organic nitrogen wastewater. Specifically, in the presence of a solid-phase catalyst, the high-concentration detectable substance with H2O2 property contained in the concentrated liquid of ammoxilation industrial wastewater has a synergistic effect with ozone, on the one hand, ozone can not only oxidize and decompose long chains of organic nitrogen and organic carbon in the organic nitrogen wastewater, but also oxidize and decompose long chains of the detectable substance with H2O2 property in the concentrated liquid, so that the content of organic pollutants in the mixed wastewater is greatly reduced, and the biodegradability is improved; on the other hand, the detectable substance with H2O2 property in the concentrated liquid generates various free radicals after being excited by the solid-phase catalyst, the free radicals can destroy the structure of organic nitrogen in the organic nitrogen wastewater, convert nitrogen into ammonia nitrogen, further oxidize ammonia nitrogen into nitrogen gas, and also can degrade macromolecular organic carbon into small-molecular organic matter or directly mineralize into carbon dioxide, so that the effluent water quality of the treated wastewater has a low COD value and a high B / C value, and the wastewater can be directly discharged to a sewage treatment plant, so as 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 specific embodiments. 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 ozone oxidation treatment of organic nitrogen wastewater, the method comprising: mixing organic nitrogen wastewater with concentrated liquid of ammoxilation process wastewater, adjusting the pH of the solution to less than 7.0 to obtain mixed wastewater; in the presence of a solid-phase catalyst, contacting ozone with the mixed wastewater to perform ozone oxidation treatment; the molar ratio of the ozone to the detectable substance calculated as H2O2 in the mixed wastewater is (1-5):1, the content ratio of the detectable substance calculated as H2O2 to COD in the mixed wastewater 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. In one embodiment, the pH of the solution is adjusted to 2.0-5.0. The detectable substance calculated as H2O2 refers to an organic peroxide-like substance with H2O2 property, and the content of the detectable substance is detected by the method of GB1616-2003.

[0020] The inventors of the present disclosure found in intensive research that, in the presence of a solid-phase catalyst, ozone has a synergistic effect with the high-concentration detectable substance with H2O2 property contained in the concentrated solution of the ammoximation industrial wastewater, on the one hand, ozone can not only oxidize and degrade the long chain of organic nitrogen and organic carbon in the organic nitrogen wastewater, but also oxidize and degrade the long chain of the detectable substance with H2O2 property in the concentrated solution, so that the content of organic pollutants in the mixed wastewater is greatly reduced, and the biodegradability is improved; on the other hand, the detectable substance with H2O2 property in the concentrated solution is excited by the solid-phase catalyst to produce various 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, and also degrade macromolecular 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, and can be directly discharged to a wastewater treatment plant, achieving the purpose of treating waste with waste.

[0021] In an embodiment of the present disclosure, the molar ratio of ozone to the detectable substance in the mixed wastewater calculated as H2O2 is (1.2-2):1; the content ratio of the detectable substance in the mixed wastewater calculated as H2O2 to COD is (4-8):1. In the above-mentioned embodiment, by selecting the preferred mixed wastewater, the organic nitrogen, organic carbon in the mixed wastewater and ozone and the organic peroxide with H2O2 property are fully contacted, and the oxidation treatment effect is improved.

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

[0023] In an embodiment of the present disclosure, the organic nitrogen wastewater comprises organic nitrogen and organic carbon, the organic nitrogen is selected from one or more of alcohol amine, amide and aliphatic amine, and the alcohol amine is selected from N-methyl diethanolamine. In an 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 of the present disclosure contains a large amount of organic nitrogen and macromolecular organic carbon, the COD value is above 50 mg / L, the B / C is close to 0, has the characteristics of high toxicity and poor biodegradability, and cannot be directly discharged into a wastewater treatment system.

[0024] In one embodiment of the present disclosure, the COD of the ammox industrial wastewater is 300-30000 mg / L, preferably 500-15000 mg / L; the content of the detectable substance calculated based on H2O2 is 200-30000 mg / L, preferably 500-15000 mg / L. The ammox industrial wastewater of the present disclosure contains a large amount of organic peroxide-like substance which is toxic and harmful to microorganisms and has the property of H2O2, and the B / C is close to 0, so it cannot be directly discharged into the wastewater treatment system to avoid causing a large number of deaths of microorganisms.

[0025] In one embodiment of the present disclosure, the preparation method of the concentrated solution comprises: concentrating the ammox process wastewater by using a vacuum distillation method or a membrane concentration method to obtain the concentrated solution and fresh water; the temperature of the vacuum distillation is 50-100°C, preferably 60-90°C; the time is 0.2-10 h, preferably 0.5-5 h; and the vacuum degree is 0.01-0.1 KPa, preferably 0.02-0.08 KPa. In the above embodiment, by selecting the concentration method, the detectable substance with the property of H2O2 in the ammox industrial wastewater is concentrated in the concentrated solution, the B / C value of the fresh water after concentration treatment is improved, and the fresh water can be directly discharged into the existing wastewater treatment plant of the enterprise.

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

[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; the content of the active component calculated based on the total weight of the carrier is 1-10 wt%, preferably 2-4 wt%; in one preferred embodiment, the carrier is selected from ceramic membrane, and the active component comprises tin, cerium and manganese. In the above embodiment, by selecting the solid-phase catalyst with the preferred content, the solid-phase catalyst can be uniformly contacted with the mixed wastewater, and the catalytic effect is improved.

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

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

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

[0031] Example 1

[0032] (1) The COD of ammonia oximation industrial wastewater of a petrochemical plant is 3970 mg / L, the mass concentration of detectable substance calculated by H2O2 is 6120 mg / L, and B / C is 0.01; the ammonia oximation industrial wastewater is concentrated by the method of reduced pressure distillation, the temperature of reduced pressure distillation is 80°C, the time is 2 h, the vacuum degree is 0.08 KPa, 10% of the volume of the ammonia oximation process wastewater is concentrated liquid, and 90% of the volume of the ammonia oximation process wastewater is fresh water;

[0033] (2) The concentrated liquid obtained in step (1) is mixed with organic nitrogen wastewater, the organic nitrogen wastewater is wastewater containing N-methyldiethanolamine (MDEA, i.e., organic nitrogen) discharged by a natural gas plant, the influent water quality is that the COD is 344 mg / L, the content of MDEA is 170 mg / L, and B / C is 0.01; the pH of the solution is adjusted to 4.0 to obtain mixed wastewater, and the content ratio of detectable substance calculated by H2O2 to COD in the mixed wastewater is 5:1;

[0034] (3) The mixed wastewater is introduced into an ozone reactor filled with a ceramic membrane loaded with tin, cerium and manganese, and ozone is introduced to perform ozone oxidation treatment on the mixed wastewater, wherein the molar ratio of introduced ozone to detectable substance calculated by H2O2 in the mixed wastewater is 1.3:1, the ozone oxidation treatment is performed at 30°C for 50 min, the total content of tin, cerium and manganese is 2.9% by weight based on the total weight of the ceramic membrane, and the effluent water quality of the treated wastewater is detected, 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 content ratio of detectable substance calculated by 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 introduced ozone to detectable substance calculated by H2O2 in the mixed wastewater 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 ozone to the detectable substance in the mixed wastewater calculated by H2O2 is 5:1, and the effluent 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 tin-cerium-manganese loaded ceramic membrane is replaced by cerium-manganese loaded γ-Al2O3, and the effluent quality of the treated wastewater is shown in Table 1.

[0043] Example 6

[0044] The same as example 1, the only difference is that in step (2), the organic nitrogen wastewater is acrylonitrile-containing wastewater discharged by a chemical plant, the influent quality of which is: COD is 1053 mg / L, the content of acrylonitrile is 193 mg / L, and B / C is 0.23; the content ratio of the detectable substance to COD in the mixed wastewater calculated by H2O2 is 5:1.

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

[0046] Comparative Example 1

[0047] The same as example 1, the only difference is that step (1) is not performed, and the concentrated solution of ammoximation process wastewater is not added to the organic nitrogen wastewater in step (2), and 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, and the amount of air introduced is 1.2 times the amount of oxidizing agent required for the COD value in the mixed wastewater, and the effluent 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, and the concentrated solution in step (2) is replaced by the same amount of 27% mass fraction hydrogen peroxide, and the effluent 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 quality of the treated wastewater is shown in Table 1.

[0054] COD removal rate % = 100% x (COD content of influent water quality of organic nitrogen wastewater - COD content of effluent water quality of wastewater after treatment) / COD content of influent water quality of organic nitrogen wastewater;

[0055] Organic nitrogen removal rate % = 100% x (organic nitrogen content of influent water quality of organic nitrogen wastewater - organic nitrogen content of effluent water quality of wastewater after treatment) / organic nitrogen content of influent water quality of organic nitrogen wastewater.

[0056] Table 1

[0057]

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

[0059] From the results of Table 1 above, it can be seen that, compared with Comparative Examples 1-4, Examples 1-6 use ozone and concentrated liquid of ammoximation industrial wastewater to oxidize organic nitrogen wastewater, which can effectively degrade organic nitrogen and macromolecular organic carbon in the organic nitrogen wastewater, improve biodegradability, and achieve the purpose of waste treatment with waste. The wastewater after treatment in Comparative Examples 1-4 has poor effluent water quality because they do not use the technical solutions of the present disclosure.

[0060] The above describes preferred embodiments of the present disclosure, but the present disclosure is not limited to the specific details in the above-described embodiments. Within the technical concept of the present disclosure, various simple modifications can be made to the technical solutions of the present disclosure, and these simple modifications all belong to the protection scope of the present disclosure.

[0061] In addition, it should be noted that each specific technical feature described in the above-described specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the present disclosure will not further describe various possible combinations.

[0062] In addition, various different embodiments of the present disclosure can also be combined in any appropriate manner, as long as they do not deviate from the idea of the present disclosure, and they should also be considered as disclosed by the present disclosure.

Claims

1. A method for treating organic nitrogen wastewater by ozone oxidation, characterized in that, The method includes: mixing organic nitrogen wastewater with a concentrated solution of ammonia oxime process wastewater, adjusting the pH of the solution to below 5.0 to obtain mixed wastewater; and contacting ozone with the mixed wastewater in the presence of a solid-phase catalyst to perform ozone oxidation treatment; wherein the organic nitrogen in the organic nitrogen wastewater is selected from one or more of alcohol amines, amides, and fatty amines. The molar ratio of ozone to the detected H2O2 in the mixed wastewater is (1~5):1, and the content ratio of the detected H2O2 to COD in the mixed wastewater is (1~10):

1. The solid catalyst includes a support and an active component supported on the support, 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 ozone to the H2O2 detected in the mixed wastewater is (1.2~2):1; the content ratio of the H2O2 detected in the mixed wastewater to COD is (4~8):

1.

3. The method according to claim 1, characterized in that, The organic nitrogen wastewater has a COD of 50~2000 mg / L and an organic nitrogen content of 30~500 mg / L.

4. The method according to claim 3, characterized in that, The organic nitrogen wastewater has a COD of 100~1500 mg / L and an organic nitrogen content of 30~200 mg / L.

5. The method according to claim 1, characterized in that, The alcoholamine is selected from N-methyldiethanolamine.

6. The method according to claim 1, characterized in that, The COD of the ammonia oxime process wastewater is 300~30000 mg / L, and the content of the detected substances, calculated as H2O2, is 200~30000 mg / L.

7. The method according to claim 6, characterized in that, The COD of the ammonia oxime industrial wastewater is 500~15000 mg / L, and the content of the detected substances, calculated as H2O2, is 500~15000 mg / L.

8. The method according to claim 1, characterized in that, The method for preparing the concentrate includes: concentrating the wastewater from the ammonia oxime process using a vacuum distillation method or a membrane concentration method to obtain the concentrate and fresh water; the vacuum distillation temperature is 50~100℃, the time is 0.2~10h, and the vacuum degree is 0.01~0.1KPa.

9. The method according to claim 8, characterized in that, The vacuum distillation is carried out at a temperature of 60~90℃ for 0.5~5h and a vacuum degree of 0.02~0.08KPa.

10. The method according to claim 8, characterized in that, The volume of the concentrate is 3 to 20% of the volume of the ammonia oxime process wastewater.

11. The method according to claim 10, characterized in that, The volume of the concentrate is 5-15% of the volume of the ammonia oxime process wastewater.

12. 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; the content of the active component, calculated as metal element, is 1 to 10% by weight, based on the total weight of the carrier.

13. The method according to claim 12, characterized in that, Based on the total weight of the carrier, the content of the active component, calculated as metal element, is 2-4% by weight.

14. The method according to claim 12, characterized in that, The carrier is selected from ceramic membranes, and the active components include tin, cerium, and manganese.

15. The method according to claim 1, characterized in that, The ozone oxidation treatment is carried out at a temperature of 5~50℃ for a time of 30~180min.

16. The method according to claim 15, characterized in that, The ozone oxidation treatment is carried out at a temperature of 10~40℃ for a time of 40~100min.

Images