Method and system for treating organic wastewater by mixed acid nitration

Abstract

The application discloses a mixed acid nitration organic wastewater treatment method and system and belongs to the technical field of organic chemical wastewater treatment. ‑ The application can effectively degrade toxic and harmful pollutants in wastewater and meets the subsequent biochemical treatment demand, and provides practical value for effective treatment of wastewater in the production process of nitryl pyrazole compounds.

Description

Technical Field

[0001] This invention relates to the field of organic chemical wastewater treatment technology, specifically to a method and system for treating mixed acid nitrification organic wastewater. Background Technology

[0002] With the rapid development of my country's industry, various chemical agents are widely used in various sectors, especially in pesticides, pharmaceuticals, textiles, papermaking, printing and dyeing, and chemicals. The production and use of explosives also generate industrial wastewater containing recalcitrant organic matter. The treatment of organic wastewater has long been a major challenge in water environmental protection and a research hotspot for scientists both domestically and internationally. Therefore, this study focuses on the wastewater generated during the synthesis of nitropyrazole, aiming to find effective treatment methods to alleviate environmental pressure.

[0003] Traditional industrial wastewater treatment methods typically employ a combination of processes including stripping, thermal decomposition, and ammonia distillation to improve the biodegradability of wastewater. However, during the treatment process, the wastewater contains a large amount of DNP (3,4-dinitropyrazole), and high-temperature heating poses certain safety hazards. Furthermore, this method requires equipment that is resistant to high temperatures and corrosion, significantly increasing treatment costs.

[0004] Studies have shown that Fenton, Fenton-like, and photo-Fenton oxidation technologies can effectively treat nitrobenzene wastewater. However, in practice, high doses of oxidants (such as hydrogen peroxide) or prolonged strong ultraviolet irradiation are required to effectively degrade nitro compounds in the water. The use of additives further increases operating costs, and common oxides (hydrogen peroxide, sodium hypochlorite, chlorine dioxide, etc.) also pose certain storage hazards. Furthermore, research indicates that Fenton-like advanced oxidation technologies produce more toxic secondary pollutants when treating nitro compounds. After wastewater oxidation treatment, biodegradability is only slightly improved, while still exhibiting considerable toxicity to microorganisms, severely increasing the burden and harm on subsequent biological treatment systems. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for treating mixed acid nitrification organic wastewater. This method utilizes acetic acid naturally present in the production process and added zero-valent iron as raw materials to generate active free radicals, achieving the oxidative degradation of recalcitrant pollutants such as nitropyrazoles and mesitylene in the strong acid wastewater. Finally, combined with biochemical treatment, the wastewater is effectively discharged in compliance with standards.

[0006] The present invention adopts the following technical solution.

[0007] The first aspect of this invention discloses a method for treating mixed acid nitrification organic wastewater, comprising the following steps:

[0008] Advanced oxidation of zero-valent iron: A set amount of zero-valent iron is added to the wastewater and mixed to carry out an oxidation reaction;

[0009] Biological treatment: The above-mentioned oxidized wastewater is subjected to pH adjustment and COD / NO3 reduction. - -N regulation is applied, and the wastewater is then introduced into aerobic and anaerobic reactors for biochemical treatment to obtain wastewater that can be discharged.

[0010] Preferably, the wastewater is wastewater containing acetic acid, sulfuric acid, nitric acid, nitropyrazole compounds and mesitylene under strong acid conditions, wherein the content of acetic acid is not less than 0.28% and the content of nitric acid is not less than 3%.

[0011] Preferably, the amount of zero-valent iron added is not less than 0.2 g / L.

[0012] Preferably, the pH adjustment is performed using any one of NaOH, Na2CO3, or NaHCO3, with a COD / NO3 ratio of [missing information]. - -N adjustment is achieved using sodium acetate or sodium nitrate.

[0013] Preferably, the pH is adjusted to neutral, and the COD / NO3... - -N is adjusted to 6-12.

[0014] Preferably, the reactor is an anaerobic-aerobic series reactor, with its water temperature controlled at 25-30℃. Nitrogen gas is introduced into the anaerobic reactor to maintain anaerobic conditions, and oxygen gas is introduced into the aerobic reactor to maintain aerobic conditions. A peristaltic pump is used to circulate the flow between the two reactors.

[0015] Preferably, the initial acclimatization agent in the anaerobic-aerobic series reactor is a compound microbial preparation B350. The compound microbial preparation and water components are added to the container to obtain an acclimatization culture medium for acclimatization to obtain a biofilm.

[0016] Preferably, the water composition includes: KNO3, CH3COONa, ferric chloride, KH2PO4, MgCl2·6H2O, CaCl2 and trace element mother liquor.

[0017] Preferably, the acclimatization culture medium has the same COD / NO3 composition as the wastewater. - -N ratio.

[0018] A second aspect of the present invention provides a mixed acid nitrification organic wastewater treatment system, which performs the aforementioned mixed acid nitrification organic wastewater treatment method, comprising: an oxidation module and a biochemical module;

[0019] The oxidation module includes a reaction vessel for adding zero-valent iron to wastewater to carry out an oxidation reaction;

[0020] The biochemical module includes an anaerobic-aerobic series reactor for biochemical treatment of wastewater, achieving compliant discharge of wastewater.

[0021] Compared with the prior art, the beneficial effects of the present invention include at least the following:

[0022] To address the safety hazards and high treatment costs associated with high-temperature heating and the poor biodegradability of recalcitrant organic compounds in traditional processes involving stripping, thermal decomposition, and ammonia distillation, this invention proposes a zero-valent iron advanced oxidation technology combined with biochemical treatment to effectively treat the highly acidic organic wastewater generated during the production of nitropyrazole compounds. Compared to traditional Fenton oxidation, this invention utilizes acetic acid, which is already present in the production process, as an oxidant, effectively achieving the high-efficiency degradation of 1-nitropyrazole, 3-nitropyrazole, 3,4-dinitropyrazole, and mesitylene, significantly reducing the toxicity of the effluent. Furthermore, the biochemical treatment process further degrades small-molecule organic pollutants in the wastewater, ensuring that the wastewater meets discharge standards. Attached Figure Description

[0023] Figure 1 The changes in pollutants in the wastewater obtained from N-nitration and C-nitration reactions are observed after adding 0.05g of zero-valent iron.

[0024] Figure 2 The changes in pollutants in the wastewater obtained from N-nitration and C-nitration reactions are observed after adding 0.1g of zero-valent iron.

[0025] Figure 3 The changes in pollutants in the wastewater obtained from N-nitration and C-nitration reactions are observed after adding 0.2g of zero-valent iron.

[0026] Figure 4 This is a schematic diagram of an anaerobic-aerobic series reactor;

[0027] Figure 5 It is a biochemical treatment of COD and NO3 - -N content changes with reaction time. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of this invention. The embodiments described in this application are merely some embodiments of this invention, and not all embodiments. Based on the spirit of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this invention.

[0029] This invention provides a method for treating mixed acid nitrification organic wastewater, comprising the following steps:

[0030] Step 1, Zero-valent iron advanced oxidation technology: Add a set amount of zero-valent iron to nitrified organic wastewater under strong acid conditions, mix thoroughly and carry out the oxidation reaction;

[0031] Advanced oxidation technology utilizes the active free radicals generated in water bodies. With their strong oxidizing properties, they can effectively oxidize organic pollutants in water bodies and improve the biodegradability of water bodies.

[0032] In step 1, the wastewater contains acetic acid, sulfuric acid, nitric acid, nitropyrazole compounds, and mesitylene, wherein the content of acetic acid is not less than 0.28%, the content of nitric acid is not less than 3%, and the amount of zero-valent iron added is set to be not less than 0.2 g / L.

[0033] Step 2, Biochemical Treatment Technology: Adjust the pH of the oxidized wastewater to neutral and regulate the COD / NO3 ratio. - -N is 6-12, with a preferred value of 10. The wastewater enters aerobic and anaerobic reactors for biochemical treatment to achieve compliant discharge.

[0034] In step 2, pH adjustment can be achieved using NaOH, Na₂CO₃, or NaHCO₃, with NaHCO₃ being the optimal choice for COD / NO₃ ratio. - -N adjustment is achieved using sodium acetate or sodium nitrate.

[0035] In step 2, an anaerobic-aerobic series reactor is used, such as... Figure 4 As shown, in the anaerobic-aerobic series reactor, the initial acclimation agent is compound microbial preparation B350 (containing 28 kinds of functional microorganisms and rich catalytic enzymes).

[0036] Take 1 mL of the above bacterial agent and acclimate it in four 250 mL shake flasks to obtain biofilm.

[0037] The water composition is as follows: KNO3, CH3COONa, ferric chloride, KH2PO4, MgCl2·6H2O, CaCl2 and trace element mother liquor.

[0038] In a preferred but non-limiting embodiment of the present invention, the water composition is specifically: KNO3 (0.72 g / L, NO3-) - -N equivalent 100mg / L), CH3COONa (0.64g / L, COD equivalent 500mg / L), 750mg / L ferric chloride, KH2PO4 (21.9mg / L, phosphorus equivalent 5mg / L), 20mg / L MgCl2·6H2O, 1mg / L CaCl2, 1ml / L trace element mother liquor.

[0039] The acclimatization culture medium composition was kept the same as that of the wastewater, with the same COD / NO3 ratio. -The -N ratio was used to select two shake flasks, keeping them in an anaerobic state while continuously aerating the other two shake flasks to maintain an aerobic state, ensuring that the microorganisms could grow uniformly on the polyurethane foam carrier (Polyurethane Foam, PUF, 1cm×1cm×1cm).

[0040] All shake flasks were incubated in a constant-temperature water bath shaker (90 rpm) at 30°C in the dark. A functionally stable biofilm was obtained when the acclimatized biofilm on the carrier was clearly visible and the water quality stabilized after a period of cultivation.

[0041] The anaerobic-aerobic series reactor consists of two 500mL containers connected in series. The water temperature is controlled at 25-30℃. Nitrogen gas is introduced into one reactor at a rate of 20mL / min to maintain anaerobic conditions, while oxygen gas is introduced into the other at a rate of 20mL / min to maintain aerobic conditions. A peristaltic pump circulates the gas between the two reactors at a flow rate of 5-20mL / min. Figure 5 As shown, after biochemical treatment in an anaerobic-aerobic series reactor, COD and NO3... - -N content decreases with increasing reaction time.

[0042] It is worth noting that the 500mL container mentioned above is only one choice of reaction vessel for experimental environments. In engineering practice, any reaction vessel with anaerobic-aerobic function used by those skilled in the art to implement this invention falls within the scope of this invention.

[0043] Example 1:

[0044] The wastewater solution obtained from the N-nitration and C-nitration reactions during the production of 3,4-dinitropyrazole (DNP) was diluted 100 times. 50 mL of the solution was then transferred to a 250 mL Erlenmeyer flask, and 0.05 g of iron filings were quickly added to each flask. The flask was then placed in a water bath at 25°C and 200 rpm and shaken for 300 minutes. The solution was then... Figure 1 As shown, the degradation rates of N-nitropyrazole (87.5%), 3-nitropyrazole (72.1%), mesitylene (35%), and DNP (85%) were subjected to biochemical treatment.

[0045] Before water treatment, the pH of the effluent is adjusted to approximately 6-7 using sodium bicarbonate solution. Sodium nitrate solution is then added to control the COD / NO3 ratio in the effluent. - -N is around 10.

[0046] The wastewater is fed into an anaerobic-aerobic reactor in series, where it continuously circulates between the two reactors.

[0047] Example 2:

[0048] The wastewater solution obtained from the N-nitration and C-nitration reactions during the production of 3,4-dinitropyrazole (DNP) was diluted 100 times. 50 mL of the solution was then transferred to a 250 mL Erlenmeyer flask, and 0.1 g of iron filings was quickly added to each flask. The flask was then placed in a water bath at 25°C and 200 rpm and shaken for 300 minutes. The solution was then... Figure 2 As shown, the degradation rates of N-nitropyrazole (97.1%), 3-nitropyrazole (93.5%), mesitylene (51%), and DNP (98.9%) were determined by biochemical treatment.

[0049] Before water treatment, the pH of the effluent is adjusted to approximately 6-7 using sodium bicarbonate solution. Sodium nitrate solution is then added to control the COD / NO3 ratio in the effluent. - -N is around 10.

[0050] The wastewater is fed into an anaerobic-aerobic reactor in series, where it continuously circulates between the two reactors.

[0051] Example 3:

[0052] The wastewater solutions obtained from the N-nitration and C-nitration reactions during the production of 3,4-dinitropyrazole (DNP) were diluted 100 times. 50 mL of the solution was then transferred to a 250 mL Erlenmeyer flask, and 0.2 g of iron filings were quickly added to each flask. The flasks were then placed in a water bath at 25°C and 200 rpm and shaken for 300 minutes. The mixture was then allowed to settle. Figure 3 As shown, the degradation rates of N-nitropyrazole (99.1%), 3-nitropyrazole (99.5%), mesitylene (74%), and DNP (99%) were determined by biochemical treatment.

[0053] Before water treatment, the pH of the effluent is adjusted to approximately 6-7 using sodium bicarbonate solution. Sodium nitrate solution is then added to control the COD / NO3 ratio in the effluent. - -N is around 10.

[0054] The wastewater is fed into an anaerobic-aerobic reactor in series, where it continuously circulates between the two reactors.

[0055] Compared with the prior art, the beneficial effects of the present invention include at least the following:

[0056] To address the safety hazards and high treatment costs associated with high-temperature heating and the poor biodegradability of recalcitrant organic compounds in traditional processes involving stripping, thermal decomposition, and ammonia distillation, this invention proposes a zero-valent iron advanced oxidation technology combined with biochemical treatment to effectively treat the highly acidic organic wastewater generated during the production of nitropyrazole compounds. Compared to traditional Fenton oxidation, this invention utilizes acetic acid, which is already present in the production process, as an oxidant, effectively achieving the high-efficiency degradation of 1-nitropyrazole, 3-nitropyrazole, 3,4-dinitropyrazole, and mesitylene, significantly reducing the toxicity of the effluent. Furthermore, the biochemical treatment process further degrades small-molecule organic pollutants in the wastewater, ensuring that the wastewater meets discharge standards.

[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. A mixed acid nitration organic wastewater treatment method, characterized in that it comprises the following steps: Zero-valent iron advanced oxidation: a certain amount of zero-valent iron is added to the wastewater, and mixed to carry out oxidation reaction; The wastewater is wastewater containing acetic acid, sulfuric acid, nitric acid, nitro-pyrazole compounds and mesitylene under strong acid conditions, wherein the content of acetic acid is not less than 0.28%, and the content of nitric acid is not less than 3%; the zero-valent iron dosage is not less than 0.2 g / L; the oxidation degradation of the wastewater is realized by using acetic acid and zero-valent iron as raw materials to produce active free radicals; 2. The mixed acid nitration organic wastewater treatment method according to claim 1, characterized in that: Biochemical treatment: The above oxidized wastewater is subjected to pH adjustment and COD / NO3 - -N regulation, and enters the aerobic and anaerobic reactors for biochemical treatment to obtain dischargeable wastewater.

3. The mixed acid nitration organic wastewater treatment method according to claim 2, characterized in that: The pH adjustment employs any one among NaOH, Na2CO3 or NaHCO3, COD / NO3 - - N adjustment employs sodium acetate or sodium nitrate.

4. The mixed acid nitration organic wastewater treatment method according to claim 1, characterized in that: The pH is adjusted to neutral, the COD / NO3 - - N regulation is 6-12. The reactor is an anaerobic-aerobic series reactor, and the water temperature is controlled at 25-30℃; nitrogen is introduced into the anaerobic reactor to maintain anaerobic conditions, and oxygen is introduced into the aerobic reactor to maintain aerobic conditions; a peristaltic pump is used to circulate the flow in the two reactors.

5. The mixed acid nitration organic wastewater treatment method according to claim 4, characterized in that: The initial domesticated bacterial agent in the anaerobic-aerobic series reactor is a composite microbial preparation B350; the composite microbial preparation and water ingredients are added to a container to obtain a domesticated culture medium for domesticating to obtain a biofilm.

6. The mixed acid nitration organic wastewater treatment method according to claim 5, characterized in that: The water ingredients include KNO3, CH3COONa, ferric chloride, KH2PO4, MgCl2·6H2O, CaCl2 and trace element mother liquor.

7. The mixed acid nitration organic wastewater treatment method according to claim 5, characterized in that: ​ The acclimation medium composition remains the same COD / NO3 - - N ratio.

Images