Nitro wastewater treatment method and system

Abstract

The invention discloses a nitro wastewater treatment method and system. On one hand, the treatment method comprises the following steps: S1, pretreating the nitro wastewater; s2, adjusting the pH value of the pretreated nitro wastewater to a suitable range, and electrolyzing; s3, oxidizing the electrolyzed nitro wastewater to obtain pretreated wastewater; and S4, deeply purifying the pretreated wastewater to obtain treated wastewater. On the other hand, the method is implemented through a pretreatment device, an electrolysis device, an oxidation reaction device, a reverse osmosis membrane device and an ultraviolet disinfection device. According to the treatment method of the nitro wastewater, the treatment efficiency of the nitro wastewater is remarkably improved through step-by-step treatment of a plurality of steps, so that the finally treated wastewater reaches the discharge standard. The chemical oxygen demand (COD) of the nitro wastewater treated by the method does not exceed 50mg / L, the biological oxygen demand (BOD) of the nitro wastewater does not exceed 20mg / L, the suspended solid (SS) of the nitro wastewater does not exceed 12mg / L, the concentration of nitro compounds does not exceed 10mg / L, and the nitro wastewater meets the emission standard.

Description

Technical Field

[0001] The present application relates to the technical field of wastewater treatment, and in particular to a method and system for treating nitro wastewater. Background Art

[0002] With the development of industry, wastewater containing nitro compounds is increasing day by day. These wastewaters mainly come from the pharmaceutical, dye, pesticide, explosive and other industries. Nitro compounds are a kind of organic pollutants that are difficult to degrade. They are highly toxic and pose a serious threat to the environment and human health. Traditional wastewater treatment methods such as biological treatment and chemical precipitation are often difficult to effectively remove nitro compounds, and thus it is difficult to meet increasingly stringent environmental protection requirements. Therefore, it is particularly important to develop a more efficient and reliable nitro wastewater pretreatment process. Summary of the invention

[0003] In order to solve at least one of the above technical problems, the present invention provides an efficient and low-cost method for treating nitro wastewater, which achieves effective treatment of nitro wastewater through multiple steps such as pretreatment, electrolytic treatment, chemical oxidation and deep purification, ensuring that the treated wastewater meets the discharge standards.

[0004] On the one hand, the present application provides a method for treating nitro wastewater, the method comprising the following steps:

[0005] S1. Pre-treating nitro wastewater;

[0006] S2, adjusting the pH value of the nitro wastewater pretreated in step S1 to an appropriate range, and performing electrolysis;

[0007] S3, oxidizing the nitro wastewater electrolyzed in step S2 to obtain pretreated wastewater;

[0008] S4. Deeply purify the pretreated wastewater in step S3 to obtain treated wastewater.

[0009] By adopting the above technical solution, the effective treatment of nitro wastewater is achieved. This method can not only improve the treatment efficiency, but also ensure that the treated wastewater meets the discharge standards, and has important application value.

[0010] Optionally, in step S1, the pretreatment is selected from one or more of filtration, sedimentation, softening or flocculation.

[0011] By adopting the above technical solution, suspended matter, colloidal substances, etc. in wastewater can be removed, creating favorable conditions for subsequent treatment steps.

[0012] Optionally, in step S2, the pH value is adjusted to 2-5.

[0013] By adopting the above technical solutions, the efficiency of electrolysis and chemical oxidation can be improved. Acidic conditions help to generate more free radicals, thereby improving the degradation effect.

[0014] Optionally, in step S2, the electrolysis conditions include: using a high-voltage pulsed DC power supply, setting the electrolysis time to 8 to 15 minutes, the working voltage to 400 to 450 V, and the electrode material to be selected from one of platinum, titanium or graphite.

[0015] By adopting the above technical solution, an efficient degradation effect can be achieved. Electrolytic treatment can not only remove some nitro compounds, but also generate free radicals with strong oxidizing properties (such as hydroxyl radicals -OH), further improving the treatment effect. In addition, electrolytic treatment does not produce additional chemical by-products, reducing the complexity of subsequent treatment.

[0016] Optionally, in step S3, the oxidation conditions include: the oxidant is selected from Fenton's reagent or potassium permanganate, the oxidation temperature is 20 to 40° C., and the oxidation time is 1 to 3 hours;

[0017] If the oxidant is Fenton's reagent, the concentration of hydrogen peroxide is 300-500 mg / L, Fe 2+ The concentration is 4-6 mg / L;

[0018] If the oxidant is potassium permanganate, the concentration of the potassium permanganate is 20-30 mg / L.

[0019] By adopting the above technical solution, the residual organic matter in the wastewater can be further oxidized under acidic conditions to ensure the treatment effect. The combined use of chemical oxidation can not only further remove nitro compounds, but also treat substances that have not been completely degraded during the electrolysis process. In addition, chemical oxidation can generate more free radicals and improve treatment efficiency.

[0020] Based on the combination of electrolysis and chemical oxidation of the present invention, nitro compounds can be more thoroughly degraded. Electrolysis can decompose macromolecular nitro compounds into small molecules, while chemical oxidation can further oxidize these small molecules, thereby ensuring the treatment effect of nitro wastewater, making the wastewater meet the corresponding discharge standards, and having higher economic benefits and environmental advantages.

[0021] Optionally, the step S3 further includes: the pretreated wastewater is further treated by activated carbon adsorption.

[0022] Further preferred in this scheme is that the pore size of the activated carbon is 2 to 50 nm, the dosage is 0.1 to 1 g / L; and the adsorption time is 15 to 30 min.

[0023] By adopting the above technical solutions, organic pollutants, pigments, odors and trace heavy metals in wastewater can be removed. Activated carbon can effectively adsorb various pollutants due to its large specific surface area and developed pore structure, thereby achieving efficient pollutant removal.

[0024] Optionally, in step S4, the deep purification adopts reverse osmosis technology, and the operating pressure of the reverse osmosis is 1 to 3 MPa; the reverse osmosis membrane is a polyamide composite membrane or an aromatic polyamide composite membrane.

[0025] By adopting the above technical solution, dissolved organic matter and other residual pollutants in the wastewater can be removed, further improving the purity of the wastewater.

[0026] Optionally, the method further includes: S5, adjusting the pH value of the wastewater in S4 to neutral, and then treating it with ultraviolet light; the ultraviolet light is selected from the UVC band with a wavelength of 250 to 280 nm.

[0027] By adopting the above technical solution, pathogenic microorganisms in the wastewater can be completely killed to ensure that the wastewater meets the discharge standards.

[0028] On the other hand, the present application provides a system for implementing the above-mentioned nitro wastewater treatment method, the system comprising a pretreatment device, an electrolysis device, an oxidation reaction device, a reverse osmosis membrane device and an ultraviolet disinfection device;

[0029] Passing the nitro wastewater into the pretreatment device to remove suspended matter and particulate matter in the nitro wastewater to obtain the pretreated nitro wastewater;

[0030] The pretreated nitro wastewater is introduced into the electrolysis device to degrade part of the nitro compounds to obtain the electrolyzed nitro wastewater;

[0031] Passing the electrolyzed nitro wastewater into the oxidation reaction device to further degrade nitro compounds to obtain the pretreated wastewater;

[0032] Passing the pretreated wastewater into the reverse osmosis membrane device to remove dissolved organic matter and residual pollutants in the wastewater to obtain the treated wastewater;

[0033] The treated wastewater is passed into an ultraviolet disinfection device to remove pathogenic microorganisms in the wastewater and obtain wastewater that meets the discharge standards.

[0034] By adopting the above technical solution, it can be ensured that nitro wastewater is effectively treated and meets the discharge standards. This method not only solves the problems existing in traditional treatment methods, but also improves the treatment efficiency and effect.

[0035] In summary, the present invention includes at least one of the following beneficial technical effects:

[0036] The method for treating nitro wastewater of the present invention can significantly improve the treatment efficiency of nitro wastewater through step-by-step treatment of multiple steps, and each step has a clear goal and effect, ensuring that the wastewater after final treatment meets the discharge standard. The present invention is based on a combination of electrolysis and chemical oxidation, which can more thoroughly degrade nitro compounds. Electrolysis treatment can decompose macromolecular nitro compounds into small molecules, while chemical oxidation can further oxidize these small molecules, thereby ensuring the treatment effect of nitro wastewater, making the wastewater meet the corresponding discharge standard, and having higher economic benefits and environmental advantages.

[0037] The treatment method of nitro wastewater of the present invention first removes suspended matter and particulate matter through pretreatment, which not only reduces the pressure of subsequent treatment steps, but also avoids wear and blockage of subsequent treatment equipment, thereby extending the service life of the equipment. Secondly, electrolytic treatment can effectively degrade some nitro compounds, especially those substances that are not easily biodegradable. The active substances (such as free radicals) generated during the electrolytic process can destroy the structure of nitro compounds and convert them into a more easily handled form; the composite chemical oxidation treatment further enhances the removal effect of nitro compounds and other organic matter, and can more effectively degrade intermediate products. Furthermore, reverse osmosis technology can remove soluble organic matter and other residual pollutants in wastewater, further improving the purity of wastewater. Finally, ultraviolet disinfection can completely kill pathogenic microorganisms in wastewater, ensuring that the treated wastewater is safe and harmless.

[0038] The nitro wastewater obtained by the treatment method and system of the present invention meets the discharge standard, and its chemical oxygen demand (COD) does not exceed 50 mg / L, the biological oxygen demand (BOD) does not exceed 20 mg / L, the suspended solids (SS) does not exceed 12 mg / L, and the nitro compound concentration does not exceed 10 mg / L. DETAILED DESCRIPTION

[0039] The present application provides a method for treating nitro wastewater, the method comprising the following steps:

[0040] S1. Pre-treating nitro wastewater;

[0041] S2, adjusting the pH value of the nitro wastewater pretreated in step S1 to an appropriate range, and performing electrolysis;

[0042] S3, oxidizing the nitro wastewater electrolyzed in step S2 to obtain pretreated wastewater;

[0043] S4. Deeply purify the pretreated wastewater in step S3 to obtain treated wastewater.

[0044] The present application further optimizes the processing of step S3, including: the pre-treated wastewater is also treated by activated carbon adsorption.

[0045] Based on the above method, the inventors also provide that, S5, after adjusting the pH value of the wastewater in S4 to neutral, ultraviolet light treatment is used; the ultraviolet light uses a UVC band with a wavelength of 250 to 280 nm.

[0046] The present application also provides a system for implementing the above-mentioned nitro wastewater treatment method, characterized in that the system includes a pretreatment device, an electrolysis device, an oxidation reaction device, a reverse osmosis membrane device and an ultraviolet disinfection device;

[0047] Passing the nitro wastewater into the pretreatment device to remove suspended matter and particulate matter in the nitro wastewater to obtain the pretreated nitro wastewater;

[0048] The pretreated nitro wastewater is introduced into the electrolysis device to degrade part of the nitro compounds to obtain the electrolyzed nitro wastewater;

[0049] Passing the electrolyzed nitro wastewater into the oxidation reaction device to further degrade nitro compounds to obtain the pretreated wastewater;

[0050] Passing the pretreated wastewater into the reverse osmosis membrane device to remove dissolved organic matter and residual pollutants in the wastewater to obtain the treated wastewater;

[0051] The treated wastewater is passed into an ultraviolet disinfection device to remove pathogenic microorganisms in the wastewater and obtain wastewater that meets the discharge standards.

[0052] The inventors found in actual industrial production applications that nitro compounds in wastewater are difficult to completely degrade by conventional biological treatment methods due to their stable chemical structure. In addition, although existing chemical treatment methods such as chemical oxidation, coagulation and precipitation can remove nitro compounds to a certain extent, the treatment efficiency is low and it is difficult to meet strict emission standards. At the same time, some advanced oxidation technologies such as Fenton reagent oxidation and ozone oxidation have certain treatment effects, but due to their large dosage, the treatment cost is high and is not suitable for large-scale application. In addition, new by-products may be generated during the treatment process, which increases the difficulty of treatment.

[0053] Based on the fact that the existing technologies are not as good as the inventors' expectations, the inventors made the present invention through further experiments and explorations. The present invention achieves effective treatment of nitro wastewater through multiple steps such as pretreatment, electrolytic treatment, chemical oxidation and deep purification, ensuring that the treated wastewater meets the discharge standards.

[0054] In order to improve the treatment efficiency and effect, the inventor first pre-treats the nitro wastewater, which can not only remove suspended matter, colloidal substances, etc. in the wastewater, create favorable conditions for subsequent treatment steps, but also avoid wear and blockage of subsequent treatment equipment, and extend the service life of the equipment. Secondly, by adjusting the pH value to a suitable range (such as acidic conditions), the efficiency of electrolysis and chemical oxidation can be improved. At the same time, the inventor adopts a combination of electrolysis and chemical oxidation to further improve the degradation efficiency, reduce the subsequent treatment compound, and improve the treatment effect. The nitro compounds are initially degraded by electrolysis, which can improve the reaction selectivity of chemical oxidation and reduce unnecessary by-product generation. In addition, electrolysis can replace the chemical agents required for some chemical oxidation, thereby reducing the treatment cost, and the two use different equipment to improve the utilization rate of the equipment. Finally, through reverse osmosis technology and ultraviolet disinfection devices, it is possible to further obtain water bodies with high purity, higher water quality, and safe and harmless.

[0055] The present application is further described below in conjunction with specific examples. The materials and equipment used in the examples are all commercially available conventional items unless otherwise specified.

[0056] Activated carbon pore size 2~50nm Shandong Huatan Environmental Protection Technology Co., Ltd.

[0057] Sand particle size 0.6~0.8mmChongqing Jinghan Environmental Protection Equipment Co., Ltd.

[0058] The following are examples of the present invention.

[0059] Example 1

[0060] Taking the nitro-containing wastewater from a production enterprise in Dongzhi Economic Development Zone, Anhui Province as an example, according to the relevant detection methods recorded in the national standard GB8978-1996 "Comprehensive Wastewater Discharge Standard" and GB4918-1985 "Spectrophotometric Standard for the Determination of Total Nitro Compounds in Industrial Wastewater", the indicators of the wastewater are: COD 1685mg / L, BOD338mg / L, SS184mg / L, nitro compound concentration 548mg / L;

[0061] The method for treating nitro-containing wastewater in this embodiment comprises the following steps:

[0062] S1. The nitro-containing wastewater was allowed to stand for 4 hours to allow the suspended matter to settle naturally, and the nitro-containing wastewater in the upper layer was taken for sand filtration. The sand filtration flow rate was set to 12 m / h and the time was 20 min to obtain the pretreated nitro-containing wastewater;

[0063] S2, adjusting the pH value of the nitro wastewater pretreated in step S1 to 2, using a high-voltage pulsed DC power supply under stirring conditions, setting the electrolysis time to 15 min, the working voltage to 400 V, the temperature to 20° C., the electrode material to platinum, the electrode spacing to 3 cm, and electrolyzing the nitro wastewater after pH adjustment;

[0064] S3, using Fenton reagent to oxidize the nitro wastewater electrolyzed in step S2, setting the oxidation temperature to 20°C and the oxidation time to 3h to obtain pretreated wastewater; wherein the concentration of hydrogen peroxide is 300mg / L, the addition amount is 16.85ml / L, and Fe 2+ The concentration is 4mg / L and the addition amount is 126ml / L;

[0065] The nitro wastewater after chemical oxidation treatment was also adsorbed by activated carbon, with the dosage set at 0.5 g / L and the adsorption time set at 30 min to obtain pretreated wastewater;

[0066] S4, setting the operating pressure to 1 MPa, selecting a polyamide composite membrane as a reverse osmosis membrane, and deeply purifying the pretreated wastewater in step S3 to obtain treated wastewater;

[0067] S5. The pH value of the wastewater in step S4 is adjusted to 7.2, and ultraviolet light C with a wavelength of 250 nm is used for light treatment to obtain treated wastewater.

[0068] The treated wastewater was tested and its indicators were COD 48mg / L, BOD 16mg / L, SS 5mg / L, and nitro compound concentration 7mg / L, which met the relevant emission standards.

[0069] Example 2

[0070] The nitro-containing wastewater treatment object is the same as that in Example 1. The nitro-containing wastewater treatment method of this embodiment comprises the following steps:

[0071] S1. The nitro-containing wastewater was allowed to stand for 4 hours to allow the suspended matter to settle naturally, and the nitro-containing wastewater in the upper layer was taken for sand filtration. The sand filtration flow rate was set to 12 m / h and the time was 20 min to obtain the pretreated nitro-containing wastewater;

[0072] S2, adjusting the pH value of the nitro wastewater after pretreatment in step S1 to 3, using a high-voltage pulsed DC power supply under stirring conditions, setting the electrolysis time to 12 min, the working voltage to 420 V, the temperature to 30 ° C, the electrode material to graphite, the electrode spacing to 3 cm, and electrolyzing the nitro wastewater after pH adjustment;

[0073] S3, using Fenton reagent to oxidize the nitro wastewater electrolyzed in step S2, setting the oxidation temperature to 30°C and the oxidation time to 2h to obtain pretreated wastewater; wherein the concentration of hydrogen peroxide is 400mg / L, the addition amount is 12.64ml / L, and Fe 2+ The concentration is 5mg / L and the amount added is 101ml / L;

[0074] The nitro wastewater after chemical oxidation treatment was also adsorbed by activated carbon, with the dosage set at 0.8 g / L and the adsorption time set at 25 min to obtain pretreated wastewater;

[0075] S4, setting the operating pressure to 2 MPa, selecting a polyamide composite membrane as a reverse osmosis membrane, deeply purifying the pretreated wastewater in step S3 to obtain treated wastewater;

[0076] S5. The pH value of the wastewater in step S4 is adjusted to 7.2, and ultraviolet light C with a wavelength of 260 nm is used for light treatment to obtain treated wastewater.

[0077] The treated wastewater was tested and its indicators were COD 45mg / L, BOD 16mg / L, SS 5mg / L, and nitro compound concentration 5mg / L, which met the relevant emission standards.

[0078] Example 3

[0079] The nitro-containing wastewater treatment object is the same as that in Example 1. The nitro-containing wastewater treatment method of this embodiment comprises the following steps:

[0080] S1, leaving the nitro-containing wastewater to stand for 4 hours to allow the suspended matter to settle naturally, thereby obtaining pretreated nitro-containing wastewater;

[0081] S2, adjusting the pH value of the nitro wastewater after pretreatment in step S1 to 4, using a high-voltage pulsed DC power supply under stirring conditions, setting the electrolysis time to 8 min, the working voltage to 450 V, the temperature to 40° C., the electrode material to platinum, the electrode spacing to 3 cm, and electrolyzing the nitro wastewater after pH adjustment;

[0082] S3, using potassium permanganate with a concentration of 20 mg / L and a volume of 16.85 mg / L to oxidize the nitro wastewater electrolyzed in step S2, setting the oxidation temperature to 40° C. and the oxidation time to 1 hour to obtain pretreated wastewater;

[0083] The nitro wastewater after chemical oxidation treatment was also adsorbed by activated carbon, with the dosage set at 1 g / L and the adsorption time set at 15 min to obtain pretreated wastewater;

[0084] S4, setting the operating pressure to 3 MPa, selecting an aromatic polyamide composite membrane as a reverse osmosis membrane, and deeply purifying the pretreated wastewater in step S3 to obtain treated wastewater;

[0085] S5. The pH value of the wastewater in step S4 is adjusted to 7.2, and ultraviolet light C with a wavelength of 280 nm is used for light treatment to obtain treated wastewater.

[0086] The treated wastewater was tested and its indicators were COD 40mg / L, BOD 14mg / L, SS 9mg / L, and nitro compound concentration 10mg / L, which met the relevant emission standards.

[0087] Comparative Example 1

[0088] The difference from Example 1 is that in step S2, the pH value is adjusted to 6-7.

[0089] The treated wastewater was tested and its indicators were COD 98mg / L, BOD 82mg / L, SS 9mg / L, and nitro compound concentration 328mg / L.

[0090] Comparative Example 2

[0091] The difference from Example 2 is that in step S2, the electrolysis time is 20 min and the working voltage is 500 V.

[0092] The treated wastewater was tested and its indicators were COD 48mg / L, BOD 20mg / L, SS 9mg / L, and nitro compound concentration 10mg / L.

[0093] Comparative Example 3

[0094] The difference from Example 3 is that in step S3, the oxidation temperature is 50° C. and the oxidation time is 2 h.

[0095] The treated wastewater was tested and its indicators were COD 36mg / L, BOD 14mg / L, SS 10mg / L, and nitro compound concentration 8mg / L.

[0096] Combining Comparative Example 1 with Example 1, the concentrations of COD, BOD, and nitro compounds increased when the pH environment of the wastewater was changed before formal treatment, which shows that the acidic conditions of the present invention are more conducive to subsequent electrolysis and chemical oxidation treatment. This may be because: under neutral pH conditions, the efficiency of electrolysis and chemical oxidation will decrease, thereby affecting the removal rate of COD; and neutral conditions are conducive to the growth and metabolic activities of microorganisms, so the biological oxygen demand is relatively higher than that of Example 1; similarly, nitro compounds are more chemically stable under neutral conditions and are not prone to chemical reactions. The main removal method depends on filtration and adsorption steps, so the wastewater still contains a high content of nitro compounds.

[0097] Combining Comparative Examples 2 and 3 with Examples 2 and 3, the indicators of the treated wastewater in Comparative Examples 2 and 3 are similar to those in Examples 2 and 3, which shows that, on the basis of the present application, further increasing the electrolysis time and the operating voltage, or the oxidation temperature and time, has little effect on the indicators in the treated wastewater, but the whole treatment process increases the energy consumption, increases the treatment cost, and leads to low economic benefits. Therefore, controlling the relevant operating conditions of various aspects in the treatment steps within the scope of the present invention can not only efficiently and high-quality complete the treatment of nitro-containing wastewater, but also significantly reduce the cost as a whole, with certain economic benefits.

[0098] In addition, the inventor takes the above embodiment as an example and makes some adjustments to the processing process to obtain the following comparative example:

[0099] Comparative Example 4

[0100] The difference from Example 1 is that step S1 is missing, and the other steps remain unchanged.

[0101] Comparative Example 5

[0102] The difference from Example 1 is that electrolysis is not performed in step S2, and the other steps remain unchanged.

[0103] Comparative Example 6

[0104] The difference from Example 2 is that the oxidation treatment in step S3 is missing, and the other steps remain unchanged.

[0105] Comparative Example 7

[0106] The difference from Example 2 is that in step S3, activated carbon adsorption is not performed on the pretreated wastewater, and the other steps remain unchanged.

[0107] Comparative Example 8

[0108] The difference from Example 3 is that step S5 is missing, and the other steps remain unchanged.

[0109] The relevant performance indicators of the wastewater after treatment in Comparative Examples 4 to 8 are shown in Table 1.

[0110] Table 1 Related indicators of wastewater after treatment in comparative examples 4 to 8

[0111]

[0112]

[0113] By comparing the above embodiments and comparative examples, combined with the index test in Table 1, we can obtain:

[0114] (1) Combining Comparative Example 4 with Example 1, if the suspended matter and large particles are not treated, the subsequent treatment of the nitro-containing wastewater will be seriously affected, resulting in poor overall treatment effect. This is because: the suspended matter and large particles may contain organic components, which will significantly increase the various indicators of the wastewater. In addition, the suspended matter and large particles will increase the burden of the subsequent treatment steps, and increase the blockage and / or wear of the equipment, thereby increasing the treatment cost. Therefore, step S1 is crucial in the treatment method of the present invention.

[0115] (2) Combining Comparative Example 5 with Example 1, Comparative Example 6 and Example 2, it can be seen that the treatment effect of treating nitro-containing wastewater by only electrolysis or only chemical oxidation is far inferior to the effect of using the two in combination. Therefore, the inventors believe that the treatment method of combining electrolysis with chemical oxidation can significantly reduce the values ​​of various indicators in nitro-containing wastewater, thereby improving the treatment effect and efficiency of the entire process, thereby ensuring that nitro wastewater meets the corresponding discharge standards, and has higher economic benefits and environmental advantages.

[0116] (3) Combining Comparative Example 7 and Example 2, although most of the organic matter has been oxidized and decomposed after electrolysis and chemical oxidation treatment, there may still be some small molecular organic matter or intermediate products that are difficult to oxidize. After treatment with activated carbon, due to its strong adsorption capacity, these residual organic matter can be adsorbed, further reducing various indicators in the wastewater, improving the water quality of the wastewater, and further improving the treatment efficiency and effect of nitro-containing wastewater. Therefore, the present invention combines electrolysis, chemical oxidation treatment and activated carbon adsorption to achieve better treatment efficiency and effect, and has certain economic benefits.

[0117] (4) In combination with Comparative Example 8 and Example 3, if ultraviolet light disinfection is performed, it will have a certain impact on the COD and BOD values ​​in the wastewater. The main function of ultraviolet disinfection is to inactivate microorganisms (such as bacteria, viruses, etc.) in the wastewater. If ultraviolet disinfection is not performed, the microorganisms in the wastewater may not be effectively inactivated, increasing the potential risks to the environment and human health after discharge. In addition, the inventors also found that ultraviolet disinfection itself does not directly target the oxidation of organic matter, but it can assist the chemical oxidation process to further reduce the COD and BOD values ​​of the water body.

[0118] Based on the processing method of Example 3, the inventors designed a system for implementing the method, and obtained Example 4, which specifically includes:

[0119] S1. Pass the nitro-containing wastewater into a pretreatment device and let it stand for 4 hours to allow the suspended matter to settle naturally to obtain pretreated nitro-containing wastewater;

[0120] S2. In the pretreatment device, the pH value of the nitro wastewater pretreated in step S1 is adjusted to 4, and the nitro wastewater is introduced into the electrolysis device. The stirrer in the electrolysis device is turned on, and a high-voltage pulsed DC power supply is used. The electrolysis time is set to 8 min, the working voltage is 450 V, the temperature is 40° C., the electrode material is platinum, and the electrode spacing is 3 cm. The nitro wastewater after pH adjustment is electrolyzed;

[0121] S3. The nitro wastewater obtained by electrolysis in step S2 is further introduced into an oxidation reaction device, and oxidized by potassium permanganate with a concentration of 20 mg / L and a volume of 16.85 mg / L, and the oxidation temperature is set to 40° C. and the oxidation time is 1 h to obtain pretreated wastewater;

[0122] The nitro wastewater after chemical oxidation treatment was also adsorbed by activated carbon, with the dosage set at 1 g / L and the adsorption time set at 15 min to obtain pretreated wastewater;

[0123] S4, passing the pretreated wastewater of step S3 into a reverse osmosis device, setting the operating pressure to 3MPa, selecting an aromatic polyamide composite membrane as the reverse osmosis membrane, and deeply purifying to obtain treated wastewater;

[0124] S5. Pass the wastewater from step S4 into an ultraviolet disinfection device, adjust the pH value to 7.2, and use ultraviolet light C with a wavelength of 280nm for light treatment to obtain treated wastewater, which is discharged normally.

[0125] In summary, the treatment method of nitro wastewater of the present invention can significantly improve the treatment efficiency of nitro wastewater through step-by-step treatment of multiple steps, and each step has a clear goal and effect, ensuring that the wastewater after final treatment meets the discharge standard. The present invention is based on a combination of electrolysis and chemical oxidation, which can more thoroughly degrade nitro compounds. Electrolysis can decompose macromolecular nitro compounds into small molecules, while chemical oxidation can further oxidize these small molecules, thereby ensuring the treatment effect of nitro wastewater, so that the wastewater meets the corresponding discharge standard, and has higher economic benefits and environmental advantages.

[0126] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for treating nitro wastewater, characterized in that: The method comprises the following steps: S1. Pre-treating nitro wastewater; S2, adjusting the pH value of the nitro wastewater pretreated in step S1 to an appropriate range, and performing electrolysis; S3, oxidizing the nitro wastewater electrolyzed in step S2 to obtain pretreated wastewater; S4. Deeply purify the pretreated wastewater in step S3 to obtain treated wastewater.

2. The method for treating nitro wastewater according to claim 1, characterized in that: In step S1, the pretreatment is selected from one or more of filtration, sedimentation, softening or flocculation.

3. The method for treating nitro wastewater according to claim 1, characterized in that: In step S2, the pH value is adjusted to 2-5.

4. The method for treating nitro wastewater according to claim 1, characterized in that: In step S2, the electrolysis conditions include: using a high-voltage pulsed DC power supply, setting the electrolysis time to 8 to 15 minutes, the working voltage to 400 to 450 V, and the electrode material to be selected from one of platinum, titanium or graphite.

5. The method for treating nitro wastewater according to claim 1, characterized in that: In step S3, the oxidation conditions include: the oxidant is selected from Fenton's reagent or potassium permanganate, the oxidation temperature is 20 to 40° C., and the oxidation time is 1 to 3 hours; If the oxidant is Fenton's reagent, the concentration of hydrogen peroxide is 300-500 mg / L, Fe 2+ The concentration is 4-6 mg / L; If the oxidant is potassium permanganate, the concentration of the potassium permanganate is 20-30 mg / L.

6. The method for treating nitro wastewater according to claim 1, characterized in that: The step S3 further includes: the pretreated wastewater is further treated by activated carbon adsorption.

7. The method for treating nitro wastewater according to claim 6, characterized in that: The pore size of the activated carbon is 2-50 nm, the dosage is 0.1-1 g / L; the adsorption time is 15-30 min.

8. The method for treating nitro wastewater according to claim 1, characterized in that: In step S4, the deep purification adopts reverse osmosis technology, and the operating pressure of the reverse osmosis is 1-3 MPa; the reverse osmosis membrane is a polyamide composite membrane or an aromatic polyamide composite membrane.

9. The method for treating nitro wastewater according to claim 1, characterized in that: The method further comprises: S5, adjusting the pH value of the wastewater in S4 to neutral, and then treating it with ultraviolet light; the ultraviolet light is selected from the UVC band with a wavelength of 250 to 280 nm.

10. A system for implementing the nitro wastewater treatment method according to any one of claims 1 to 9, characterized in that: The system includes a pretreatment device, an electrolysis device, an oxidation reaction device, a reverse osmosis membrane device and an ultraviolet disinfection device; Passing the nitro wastewater into the pretreatment device to remove suspended matter and particulate matter in the nitro wastewater to obtain the pretreated nitro wastewater; The pretreated nitro wastewater is introduced into the electrolysis device to degrade part of the nitro compounds to obtain the electrolyzed nitro wastewater; Passing the electrolyzed nitro wastewater into the oxidation reaction device to further degrade nitro compounds to obtain the pretreated wastewater; Passing the pretreated wastewater into the reverse osmosis membrane device to remove dissolved organic matter and residual pollutants in the wastewater to obtain the treated wastewater; The treated wastewater is passed into an ultraviolet disinfection device to remove pathogenic microorganisms in the wastewater and obtain wastewater that meets the discharge standards.

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