A method for treating adipic acid wastewater with internal reflux

Abstract

The invention discloses a method for treating adipic acid wastewater with internal reflux, relates to the technical field of wastewater treatment, and particularly relates to a multi-stage wastewater treatment method. By using processes such as electrochemical treatment and internal buffering and internal reflux, the wastewater after biological denitrification can be used as internal reflux for acid-base neutralization, the pH of the wastewater can be adjusted by itself, and denitrification treatment can be further performed by reflux. The problems of excessively high acidity of the wastewater and the need for additional addition of a neutralizing substance can be solved by reflux. Repeated biological denitrification during the reflux process improves denitrification efficiency, improves treatment effect, and reduces costs. The defects of the prior art in that the adipic acid wastewater has excessively high acidity, high nitric nitrogen content, and the need for additional addition of a neutralizing substance are solved. Furthermore, iron ions participate in reactions multiple times during the electrochemical treatment and biological denitrification processes, thereby ensuring that nitrate nitrogen and other pollutants are fully removed and promoting the reduction of nitrate nitrogen.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater treatment, in particular to a multi-stage wastewater treatment method, and in particular to a method for treating adipic acid wastewater with internal reflux. Background Art

[0002] Adipic acid wastewater is a high-concentration industrial wastewater generated during the production of adipic acid. It has unique properties and composition. The wastewater contains a large amount of organic acid by-products, a high organic matter content, and a high nitrate and nitrogen content. It requires biological denitrification treatment and is difficult to treat.

[0003] Before biological denitrification treatment, alkali needs to be added to the adipic acid wastewater to make the pH value consistent with biological denitrification. However, the wastewater after biological denitrification has a high alkalinity and needs to be neutralized by adding acid. Additional neutralizing substances need to be added, which increases the treatment cost.

[0004] Therefore, it is necessary to improve the adipic acid wastewater treatment method in the prior art to solve the above problems. Summary of the Invention

[0005] The present invention overcomes the deficiencies of the prior art and provides a method for treating adipic acid wastewater with internal reflux, aiming to solve the defects of the prior art in that the adipic acid wastewater is too acidic, has a high nitric nitrogen content, and requires the additional addition of a neutralizing substance.

[0006] To achieve the above object, the technical solution adopted by the present invention is: a method for treating adipic acid wastewater with internal reflux, comprising the following steps:

[0007] S1: buffering the adipic acid wastewater, performing electrochemical treatment during the buffering process, and discharging the first treated wastewater;

[0008] S2: neutralizing the first treated wastewater in S1 with acid and alkali to obtain second treated wastewater;

[0009] S3: biologically denitrifying the second treated wastewater in S2, precipitating the wastewater after biological denitrification, and neutralizing the clear water after precipitation by internal reflux as alkaline solution to neutralize the acid and alkali with the first treated wastewater in S1;

[0010] S4: After the neutralization and internal reflux in S3 are performed several times, the precipitated clean water is subjected to buffering internal reflux in proportion and used as the inlet buffer water in S1, and the remaining clean water is used as treated wastewater.

[0011] In a preferred embodiment of the present invention, the electrochemical treatment in S1 is to use iron filings and copper mesh to perform a primary reduction reaction, and add urea to perform a secondary reduction reaction.

[0012] In a preferred embodiment of the present invention, the ratio of the amount of iron filings added to the nitrate nitrogen in the wastewater is 15-20:1, and the ratio of the amount of urea added to the nitrate nitrogen in the wastewater is 1.5-3:1.

[0013] In a preferred embodiment of the present invention, the specific steps of the preliminary reduction reaction are to adjust the pH of the wastewater to 3.0-6.0 and then use iron filings and copper mesh to perform a preliminary reduction reaction, and the secondary reduction reaction is to adjust the pH of the wastewater to 1.0-3.0 and heat the wastewater to 40-60°C before adding urea.

[0014] In a preferred embodiment of the present invention, the pH of the preliminary reduction reaction is adjusted by buffering the precipitated clean water in S4 and then refluxing it.

[0015] In a preferred embodiment of the present invention, the pH of the wastewater before biological denitrification of the second treated wastewater in S3 is 7.0-7.6.

[0016] In a preferred embodiment of the present invention, heavy metals are removed before the S3 biological denitrification, and the removed heavy metal components are copper ions and nickel ions.

[0017] In a preferred embodiment of the present invention, the removal method is to use a chelating resin for removal.

[0018] In a preferred embodiment of the present invention, in S3, the precipitate after precipitation is returned to the biological denitrification area.

[0019] In a preferred embodiment of the present invention, the number of neutralization internal refluxes in S4 is determined based on the nitric nitrogen content in the clean water after precipitation, and the nitric nitrogen content in the treated wastewater is less than 10 mg / L.

[0020] The present invention solves the defects existing in the background technology and has the following beneficial effects:

[0021] (1) The present invention provides a method for treating adipic acid wastewater with internal reflux. Through electrochemical treatment and internal buffering and internal reflux processes, the wastewater after biological denitrification can be used as internal reflux for acid-base neutralization, the pH of the wastewater can be adjusted by itself, and denitrification treatment can be further carried out by reflux. Compared with the adipic acid wastewater treatment method in the prior art, the problem of excessive acidity of the wastewater and the need for additional addition of neutralizing substances can be solved by reflux. Repeated biological denitrification in the reflux process improves the denitrification efficiency, while improving the treatment effect and reducing the cost, thereby solving the defects of the prior art in that the adipic acid wastewater has excessive acidity, high nitric nitrogen content, and the need for additional addition of neutralizing substances.

[0022] (2) In the present invention, iron filings and copper mesh form a micro-electrolysis reaction during electrochemical treatment, which promotes the reduction reaction of nitrate nitrogen in wastewater. Ammonia produced by the thermal decomposition of urea can act as a reducing agent under acidic conditions, reacting chemically with nitrate nitrogen to reduce it to a low-toxic nitride. Compared with the existing technology, the nitrate nitrogen content in the wastewater is significantly reduced, reducing the burden of subsequent biological denitrification.

[0023] (3) In the present invention, the clean water flowing back into the buffer is treated wastewater, and its pH is relatively stable and close to neutral. Returning this part of clean water to the inlet buffer area can effectively neutralize the acidity of the inlet water and reduce the acidity of the wastewater. Compared with the existing technology, the treatment products of the wastewater itself are utilized, which reduces the demand for additional neutralizing substances and reduces the treatment cost.

[0024] (4) In the present invention, wastewater reflux allows wastewater to be recycled in the system, thereby improving treatment efficiency. Through internal reflux and buffered internal reflux, wastewater is treated multiple times. Iron ions participate in the reaction multiple times during electrochemical treatment and biological denitrification. Compared with the existing technology, its utilization efficiency is improved, and it can ensure that nitrate nitrogen and other pollutants are fully removed. Iron ions continue to act as electron donors during the reflux process, promoting the reduction of nitrate nitrogen. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments described in the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive efforts.

[0026] Figure 1 It is a method step diagram of a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0027] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0028] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the scope of protection of the present invention is not limited to the specific embodiments disclosed below.

[0029] like Figure 1As shown, a method for treating adipic acid wastewater with internal reflux comprises the following steps:

[0030] S1: buffering the adipic acid wastewater, performing electrochemical treatment during the buffering process, and discharging the first treated wastewater;

[0031] S2: neutralizing the first treated wastewater in S1 with acid and alkali to obtain second treated wastewater;

[0032] S3: biologically denitrify the second treated wastewater in S2, precipitate the wastewater after biological denitrification, and neutralize the clear water after precipitation by internal reflux as alkaline solution to neutralize the acid and alkali with the first treated wastewater in S1;

[0033] S4: After the neutralization and internal reflux in S3 are performed several times, the precipitated clean water is subjected to buffering internal reflux in proportion and used as the inlet buffer water in S1, and the remaining clean water is used as treated wastewater.

[0034] A method for treating adipic acid wastewater with internal reflux can use wastewater after biological denitrification as internal reflux for acid-base neutralization through electrochemical treatment and internal buffering and internal reflux processes, can adjust the pH of the wastewater by itself, and further perform denitrification treatment through reflux. The problem of excessive acidity of the wastewater and the need for additional addition of neutralizing substances can be solved through reflux. Repeated biological denitrification during the reflux process improves denitrification efficiency, improves treatment effect and reduces cost, and solves the defects of adipic acid wastewater in the prior art, such as excessive acidity, high nitric nitrogen content and the need for additional addition of neutralizing substances.

[0035] In S1, the electrochemical treatment uses iron filings and copper mesh for a primary reduction reaction, followed by the addition of urea for a secondary reduction reaction. The iron filings and copper mesh form a micro-electrolysis reaction during the electrochemical treatment. The iron filings act as a reducing agent, and the copper mesh acts as a conductive medium, promoting the reduction of nitrate nitrogen in the wastewater. This reduces the acidity of the wastewater while adding ferrous ions. Under acidic conditions, the iron filings and copper mesh react with the nitrate nitrogen in the wastewater, reducing it to nitrogen gas and other low-toxic nitrides.

[0036] When heated under acidic conditions, urea decomposes into ammonia and carbon dioxide, further adjusting the wastewater's pH. Heating urea under acidic conditions further promotes the reduction of nitrate nitrogen. The ammonia produced by urea decomposition also serves as a substrate for subsequent biological denitrification. The combined effects of the primary and secondary reduction reactions significantly reduce the nitrate nitrogen content in the wastewater, alleviating the burden of subsequent biological denitrification.

[0037] The ratio of iron filings added to nitrate nitrogen in the wastewater should be 15-20:1, and the ratio of urea added to nitrate nitrogen in the wastewater should be 1.5-3:1. A 15-20:1 ratio of iron filings to nitrate nitrogen ensures sufficient iron filings participate in the reaction, effectively reducing the acidity and nitrate nitrogen content in the wastewater. A 1.5-3:1 ratio of urea to nitrate nitrogen ensures that the ammonia produced by urea decomposition can effectively neutralize the acidity in the wastewater, further reducing the nitrate nitrogen content in the wastewater.

[0038] The specific steps of the primary reduction reaction are to adjust the pH of the wastewater to 3.0-6.0 and then use iron filings and copper mesh to perform the primary reduction reaction. The secondary reduction reaction is to adjust the pH of the wastewater to 1.0-3.0 and heat the wastewater to 40-60°C before adding urea.

[0039] The pH of the preliminary reduction reaction is adjusted by refluxing the precipitated clean water in the buffer in S4. The clean water refluxing in the buffer is treated wastewater, and its pH is relatively stable and close to neutral. Returning this part of clean water to the inlet buffer area can effectively neutralize the acidity of the inlet water and reduce the acidity of the wastewater. This pH adjustment method utilizes the treatment products of the wastewater itself, reduces the demand for additional neutralizing substances, and reduces treatment costs. The clean water refluxing in the buffer acts as a buffer substance, which is used to adjust the acidity of the inlet water, and can further reduce the nitrate nitrogen content in the overall wastewater while reducing the acidity of the wastewater.

[0040] The pH of the second treated wastewater in S3 before biological denitrification is 7.0-7.6. Adjusting the wastewater pH to 7.0-7.6, close to neutral, can effectively neutralize the acidity of the wastewater. Denitrifying bacteria are most active in an environment with a pH of 7.0-7.6 and can efficiently reduce nitrate nitrogen to nitrogen gas. Iron ions can act as electron donors under conditions of pH 7.0-7.6, promoting the metabolic activity of denitrifying bacteria and accelerating the reduction of nitrate nitrogen. Iron ions are one of the trace elements required for microbial growth. Under conditions of pH 7.0-7.6, iron ions have high bioavailability, which can promote the activity of denitrifying bacteria and improve the efficiency of biological denitrification. This condition ensures the efficient implementation of the biological denitrification process and further reduces the nitrate nitrogen content in the wastewater.

[0041] Before S3 biological denitrification, heavy metals are removed. The removed heavy metal components are copper and nickel ions, and the removal method is to remove them using chelating resins. Heavy metal ions are toxic to denitrifying bacteria, inhibiting their metabolic activity and reducing the efficiency of biological denitrification. Using chelating resins to remove these heavy metal ions can significantly increase the activity of denitrifying bacteria, thereby improving the efficiency of nitrate nitrogen reduction and further reducing the nitrate nitrogen content in the wastewater. Heavy metal ions compete with iron ions for adsorption, reducing the bioavailability of iron ions. Removing these heavy metal ions with chelating resins can improve the bioavailability of iron ions, allowing them to participate more effectively in the biological denitrification process.

[0042] In S3, the settled sediment is returned to the biological denitrification area. The iron ions in the sediment can continue to participate in the nitrate nitrogen reduction reaction, further reducing the nitrate nitrogen content in the wastewater. The sediment contains unreacted organic matter and nitrogen compounds. These substances can serve as substrates for denitrifying bacteria during the recirculation process, further promoting nitrate nitrogen reduction. This method not only reduces the use of chemical reagents, but also reduces the amount of chemical sludge generated during the treatment process, reducing secondary pollution.

[0043] The number of neutralization internal recirculations in S4 is determined by the nitrate-nitrogen content in the clear water after precipitation, and the nitrate-nitrogen content in the treated wastewater is less than 10 mg / L. By dynamically adjusting the number of internal recirculations based on the nitrate-nitrogen content in the clear water after precipitation, it is ensured that the wastewater undergoes sufficient treatment to reduce the nitrate-nitrogen content to below 10 mg / L. This dynamic adjustment mechanism ensures the flexibility and efficiency of the treatment process and can adapt to wastewater of varying concentrations. During the internal recirculation process, the wastewater passes through the biological denitrification area multiple times, and each cycle further removes nitrate-nitrogen, ensuring that the nitrate-nitrogen content in the final effluent meets the standard.

[0044] After multiple treatments, the pH of the recirculated clean water remains relatively stable and near-neutral. This internal recirculation effectively neutralizes the wastewater's acidity, reducing the need for additional neutralizing agents. This neutralization process utilizes the wastewater's own treatment products, lowering treatment costs. By dynamically adjusting the number of internal recirculation cycles, the entire treatment system forms a closed loop, achieving resource recycling and optimizing the treatment process. This not only improves treatment efficiency, but also reduces costs and minimizes environmental impact.

[0045] Internal recirculation causes wastewater to pass through the biological denitrification zone multiple times. Iron ions, acting as electron donors, promote the metabolic activity of denitrifying bacteria and accelerate the reduction of nitrate nitrogen. This synergistic effect significantly improves the efficiency of nitrate nitrogen removal. Internal recirculation and the reuse of iron ions form a closed-loop system, achieving resource recycling. Iron ions not only participate in the reduction of nitrate nitrogen but also serve as a trace element required for microbial growth, promoting microbial activity and further improving treatment efficiency. The iron hydroxide precipitate generated by iron ions can adhere to the surface of the biofilm or activated sludge, enhancing sludge settling and preventing sludge bulking. The alkaline solution in the internal recirculation neutralizes the acidic wastewater in the S1 stage, while the hydrolysis reaction of iron ions forms a weak buffer system that mitigates drastic pH fluctuations, maintaining a stable acidic environment in the S1 stage and neutral biological denitrification conditions in the S3 stage.

[0046] Example 1

[0047] This embodiment provides a method for treating adipic acid wastewater with internal reflux, and the specific steps are as follows:

[0048] S1: performing inlet buffering on adipic acid wastewater and performing electrochemical treatment during the inlet buffering process. The electrochemical treatment includes performing a primary reduction reaction using iron filings and a copper mesh, and adding urea for a secondary reduction reaction. The ratio of the amount of iron filings added to the mass of nitrate nitrogen in the wastewater is 12.5:1, and the ratio of the amount of urea added to the mass of nitrate nitrogen in the wastewater is 2:1. The specific steps include adjusting the pH of the wastewater to 3.0, performing a primary reduction reaction using iron filings and a copper mesh, and performing a secondary reduction reaction by adjusting the pH of the wastewater to 3.0 and heating the wastewater to 50° C., and then adding urea, and discharging the first treated wastewater.

[0049] S2: neutralizing the first treated wastewater in S1 with acid and alkali to obtain second treated wastewater;

[0050] S3: biologically denitrifying the second treated wastewater in S2, removing heavy metals before biological denitrification, and removing heavy metal components such as copper ions and nickel ions by using a chelating resin. The pH of the wastewater before biological denitrification is 7.0. The wastewater after biological denitrification is precipitated, and the precipitate is returned to the biological denitrification area. The clear water after precipitation is neutralized and refluxed as an alkali solution to perform acid-base neutralization with the first treated wastewater in S1;

[0051] S4: After the neutralization internal reflux in S3 is performed several times, the precipitated clean water is subjected to buffer internal reflux in proportion and used as the inlet buffer water in S1. The pH of the preliminary reduction reaction is adjusted by the buffer internal reflux of the precipitated clean water in S4. The remaining clean water is used as the treated wastewater. The number of neutralization internal refluxes is determined according to the nitric nitrogen content in the precipitated clean water. The nitric nitrogen content in the treated wastewater is <10 mg / L.

[0052] Example 2

[0053] This embodiment provides a method for treating adipic acid wastewater with internal reflux, and the specific steps are as follows:

[0054] S1: performing inlet buffering on adipic acid wastewater and performing electrochemical treatment during the inlet buffering process. The electrochemical treatment includes performing a primary reduction reaction using iron filings and a copper mesh, and adding urea for a secondary reduction reaction. The ratio of the amount of iron filings added to the mass of nitrate nitrogen in the wastewater is 15:1, and the ratio of the amount of urea added to the mass of nitrate nitrogen in the wastewater is 2:1. The specific steps include adjusting the pH of the wastewater to 3.0, then performing a primary reduction reaction using iron filings and a copper mesh, and performing a secondary reduction reaction by adjusting the pH of the wastewater to 3.0 and heating the wastewater to 50° C., and then adding urea, and discharging the first treated wastewater.

[0055] S2: neutralizing the first treated wastewater in S1 with acid and alkali to obtain second treated wastewater;

[0056] S3: biologically denitrifying the second treated wastewater in S2, removing heavy metals before biological denitrification, and removing heavy metal components such as copper ions and nickel ions by using a chelating resin. The pH of the wastewater before biological denitrification is 7.0. The wastewater after biological denitrification is precipitated, and the precipitate is returned to the biological denitrification area. The clear water after precipitation is neutralized and refluxed as an alkali solution to perform acid-base neutralization with the first treated wastewater in S1;

[0057] S4: After the neutralization internal reflux in S3 is performed several times, the precipitated clean water is subjected to buffer internal reflux in proportion and used as the inlet buffer water in S1. The pH of the preliminary reduction reaction is adjusted by the buffer internal reflux of the precipitated clean water in S4. The remaining clean water is used as the treated wastewater. The number of neutralization internal refluxes is determined according to the nitric nitrogen content in the precipitated clean water. The nitric nitrogen content in the treated wastewater is <10 mg / L.

[0058] Example 3

[0059] This embodiment provides a method for treating adipic acid wastewater with internal reflux, and the specific steps are as follows:

[0060] S1: performing inlet buffering on adipic acid wastewater and performing electrochemical treatment during the inlet buffering process. The electrochemical treatment includes performing a primary reduction reaction using iron filings and a copper mesh, and adding urea for a secondary reduction reaction. The ratio of the amount of iron filings added to the mass of nitrate nitrogen in the wastewater is 17.5:1, and the ratio of the amount of urea added to the mass of nitrate nitrogen in the wastewater is 2:1. The specific steps include adjusting the pH of the wastewater to 3.0, performing a primary reduction reaction using iron filings and a copper mesh, and performing a secondary reduction reaction by adjusting the pH of the wastewater to 3.0 and heating the wastewater to 50° C., and then adding urea, and discharging the first treated wastewater.

[0061] S2: neutralizing the first treated wastewater in S1 with acid and alkali to obtain second treated wastewater;

[0062] S3: biologically denitrifying the second treated wastewater in S2, removing heavy metals before biological denitrification, and removing heavy metal components such as copper ions and nickel ions by using a chelating resin. The pH of the wastewater before biological denitrification is 7.0. The wastewater after biological denitrification is precipitated, and the precipitate is returned to the biological denitrification area. The clear water after precipitation is neutralized and refluxed as an alkali solution to perform acid-base neutralization with the first treated wastewater in S1;

[0063] S4: After the neutralization internal reflux in S3 is performed several times, the precipitated clean water is subjected to buffer internal reflux in proportion and used as the inlet buffer water in S1. The pH of the preliminary reduction reaction is adjusted by the buffer internal reflux of the precipitated clean water in S4. The remaining clean water is used as the treated wastewater. The number of neutralization internal refluxes is determined according to the nitric nitrogen content in the precipitated clean water. The nitric nitrogen content in the treated wastewater is <10 mg / L.

[0064] Example 4

[0065] This embodiment provides a method for treating adipic acid wastewater with internal reflux, and the specific steps are as follows:

[0066] S1: performing inlet buffering on adipic acid wastewater and performing electrochemical treatment during the inlet buffering process. The electrochemical treatment includes performing a primary reduction reaction using iron filings and a copper mesh, and adding urea for a secondary reduction reaction. The ratio of the amount of iron filings added to the mass of nitrate nitrogen in the wastewater is 20:1, and the ratio of the amount of urea added to the mass of nitrate nitrogen in the wastewater is 2:1. The specific steps include adjusting the pH of the wastewater to 3.0, then performing a primary reduction reaction using iron filings and a copper mesh, and performing a secondary reduction reaction by adjusting the pH of the wastewater to 3.0 and heating the wastewater to 50° C., and then adding urea, and discharging the first treated wastewater.

[0067] S2: neutralizing the first treated wastewater in S1 with acid and alkali to obtain second treated wastewater;

[0068] S3: biologically denitrifying the second treated wastewater in S2, removing heavy metals before biological denitrification, and removing heavy metal components such as copper ions and nickel ions by using a chelating resin. The pH of the wastewater before biological denitrification is 7.0. The wastewater after biological denitrification is precipitated, and the precipitate is returned to the biological denitrification area. The clear water after precipitation is neutralized and refluxed as an alkali solution to perform acid-base neutralization with the first treated wastewater in S1;

[0069] S4: After the neutralization internal reflux in S3 is performed several times, the precipitated clean water is subjected to buffer internal reflux in proportion and used as the inlet buffer water in S1. The pH of the preliminary reduction reaction is adjusted by the buffer internal reflux of the precipitated clean water in S4. The remaining clean water is used as the treated wastewater. The number of neutralization internal refluxes is determined according to the nitric nitrogen content in the precipitated clean water. The nitric nitrogen content in the treated wastewater is <10 mg / L.

[0070] Example 5

[0071] This embodiment provides a method for treating adipic acid wastewater with internal reflux, and the specific steps are as follows:

[0072] S1: performing inlet buffering on adipic acid wastewater and performing electrochemical treatment during the inlet buffering process. The electrochemical treatment includes performing a primary reduction reaction using iron filings and a copper mesh, and adding urea for a secondary reduction reaction. The ratio of the amount of iron filings added to the mass of nitrate nitrogen in the wastewater is 22.5:1, and the ratio of the amount of urea added to the mass of nitrate nitrogen in the wastewater is 2:1. The specific steps include adjusting the pH of the wastewater to 3.0, then performing a primary reduction reaction using iron filings and a copper mesh, and performing a secondary reduction reaction by adjusting the pH of the wastewater to 3.0 and heating the wastewater to 50° C., and then adding urea, and discharging the first treated wastewater.

[0073] S2: neutralizing the first treated wastewater in S1 with acid and alkali to obtain second treated wastewater;

[0074] S3: biologically denitrifying the second treated wastewater in S2, removing heavy metals before biological denitrification, and removing heavy metal components such as copper ions and nickel ions by using a chelating resin. The pH of the wastewater before biological denitrification is 7.0. The wastewater after biological denitrification is precipitated, and the precipitate is returned to the biological denitrification area. The clear water after precipitation is neutralized and refluxed as an alkali solution to perform acid-base neutralization with the first treated wastewater in S1;

[0075] S4: After the neutralization internal reflux in S3 is performed several times, the precipitated clean water is subjected to buffer internal reflux in proportion and used as the inlet buffer water in S1. The pH of the preliminary reduction reaction is adjusted by the buffer internal reflux of the precipitated clean water in S4. The remaining clean water is used as the treated wastewater. The number of neutralization internal refluxes is determined according to the nitric nitrogen content in the precipitated clean water. The nitric nitrogen content in the treated wastewater is <10 mg / L.

[0076] Example 6

[0077] This embodiment provides a method for treating adipic acid wastewater with internal reflux, and the specific steps are as follows:

[0078] S1: performing inlet buffering on adipic acid wastewater and performing electrochemical treatment during the inlet buffering process. The electrochemical treatment includes performing a primary reduction reaction using iron filings and a copper mesh, and adding urea for a secondary reduction reaction. The ratio of the amount of iron filings added to the mass of nitrate nitrogen in the wastewater is 17.5:1, and the ratio of the amount of urea added to the mass of nitrate nitrogen in the wastewater is 2:1. The specific steps include adjusting the pH of the wastewater to 3.0, performing a primary reduction reaction using iron filings and a copper mesh, and performing a secondary reduction reaction by adjusting the pH of the wastewater to 3.0 and heating the wastewater to 50° C., and then adding urea, and discharging the first treated wastewater.

[0079] S2: neutralizing the first treated wastewater in S1 with acid and alkali to obtain second treated wastewater;

[0080] S3: biologically denitrifying the second treated wastewater in S2, removing heavy metals before biological denitrification, and removing heavy metal components such as copper ions and nickel ions by using a chelating resin. The pH of the wastewater before biological denitrification is 6.7. The wastewater after biological denitrification is precipitated, and the precipitate is returned to the biological denitrification area. The clear water after precipitation is neutralized and refluxed as an alkali solution to perform acid-base neutralization with the first treated wastewater in S1;

[0081] S4: After the neutralization internal reflux in S3 is performed several times, the precipitated clean water is subjected to buffer internal reflux in proportion and used as the inlet buffer water in S1. The pH of the preliminary reduction reaction is adjusted by the buffer internal reflux of the precipitated clean water in S4. The remaining clean water is used as the treated wastewater. The number of neutralization internal refluxes is determined according to the nitric nitrogen content in the precipitated clean water. The nitric nitrogen content in the treated wastewater is <10 mg / L.

[0082] Example 7

[0083] This embodiment provides a method for treating adipic acid wastewater with internal reflux, and the specific steps are as follows:

[0084] S1: performing inlet buffering on adipic acid wastewater and performing electrochemical treatment during the inlet buffering process. The electrochemical treatment includes performing a primary reduction reaction using iron filings and a copper mesh, and adding urea for a secondary reduction reaction. The ratio of the amount of iron filings added to the mass of nitrate nitrogen in the wastewater is 17.5:1, and the ratio of the amount of urea added to the mass of nitrate nitrogen in the wastewater is 2:1. The specific steps include adjusting the pH of the wastewater to 3.0, performing a primary reduction reaction using iron filings and a copper mesh, and performing a secondary reduction reaction by adjusting the pH of the wastewater to 3.0 and heating the wastewater to 50° C., and then adding urea, and discharging the first treated wastewater.

[0085] S2: neutralizing the first treated wastewater in S1 with acid and alkali to obtain second treated wastewater;

[0086] S3: biologically denitrifying the second treated wastewater in S2. Before biological denitrification, heavy metals are removed. The removed heavy metal components are copper ions and nickel ions. The removal method is to use a chelating resin for removal. The pH of the wastewater before biological denitrification is 7.3. The wastewater after biological denitrification is precipitated. The precipitate after precipitation is returned to the biological denitrification area. The clear water after precipitation is neutralized and refluxed as an alkali solution to perform acid-base neutralization with the first treated wastewater in S1.

[0087] S4: After the neutralization internal reflux in S3 is performed several times, the precipitated clean water is subjected to buffer internal reflux in proportion and used as the inlet buffer water in S1. The pH of the preliminary reduction reaction is adjusted by the buffer internal reflux of the precipitated clean water in S4. The remaining clean water is used as the treated wastewater. The number of neutralization internal refluxes is determined according to the nitric nitrogen content in the precipitated clean water. The nitric nitrogen content in the treated wastewater is <10 mg / L.

[0088] Example 8

[0089] This embodiment provides a method for treating adipic acid wastewater with internal reflux, and the specific steps are as follows:

[0090] S1: performing inlet buffering on adipic acid wastewater and performing electrochemical treatment during the inlet buffering process. The electrochemical treatment includes performing a primary reduction reaction using iron filings and a copper mesh, and adding urea for a secondary reduction reaction. The ratio of the amount of iron filings added to the mass of nitrate nitrogen in the wastewater is 17.5:1, and the ratio of the amount of urea added to the mass of nitrate nitrogen in the wastewater is 2:1. The specific steps include adjusting the pH of the wastewater to 3.0, performing a primary reduction reaction using iron filings and a copper mesh, and performing a secondary reduction reaction by adjusting the pH of the wastewater to 3.0 and heating the wastewater to 50° C., and then adding urea, and discharging the first treated wastewater.

[0091] S2: neutralizing the first treated wastewater in S1 with acid and alkali to obtain second treated wastewater;

[0092] S3: biologically denitrifying the second treated wastewater in S2, removing heavy metals before biological denitrification, and removing heavy metal components such as copper ions and nickel ions by using a chelating resin for removal. The pH of the wastewater before biological denitrification is 7.6, and the wastewater after biological denitrification is precipitated. The precipitate is returned to the biological denitrification area, and the clear water after precipitation is neutralized and refluxed as an alkali solution to perform acid-base neutralization with the first treated wastewater in S1;

[0093] S4: After the neutralization internal reflux in S3 is performed several times, the precipitated clean water is subjected to buffer internal reflux in proportion and used as the inlet buffer water in S1. The pH of the preliminary reduction reaction is adjusted by the buffer internal reflux of the precipitated clean water in S4. The remaining clean water is used as the treated wastewater. The number of neutralization internal refluxes is determined according to the nitric nitrogen content in the precipitated clean water. The nitric nitrogen content in the treated wastewater is <10 mg / L.

[0094] Embodiment 9

[0095] This embodiment provides a method for treating adipic acid wastewater with internal reflux, and the specific steps are as follows:

[0096] S1: performing inlet buffering on adipic acid wastewater and performing electrochemical treatment during the inlet buffering process. The electrochemical treatment includes performing a primary reduction reaction using iron filings and a copper mesh, and adding urea for a secondary reduction reaction. The ratio of the amount of iron filings added to the mass of nitrate nitrogen in the wastewater is 17.5:1, and the ratio of the amount of urea added to the mass of nitrate nitrogen in the wastewater is 2:1. The specific steps include adjusting the pH of the wastewater to 3.0, performing a primary reduction reaction using iron filings and a copper mesh, and performing a secondary reduction reaction by adjusting the pH of the wastewater to 3.0 and heating the wastewater to 50° C., and then adding urea, and discharging the first treated wastewater.

[0097] S2: neutralizing the first treated wastewater in S1 with acid and alkali to obtain second treated wastewater;

[0098] S3: biologically denitrifying the second treated wastewater in S2. Before biological denitrification, heavy metals are removed. The removed heavy metal components are copper ions and nickel ions. The removal method is to use a chelating resin for removal. The pH of the wastewater before biological denitrification is 7.9. The wastewater after biological denitrification is precipitated. The precipitate after precipitation is returned to the biological denitrification area. The clear water after precipitation is neutralized and refluxed as an alkali solution to perform acid-base neutralization with the first treated wastewater in S1.

[0099] S4: After the neutralization internal reflux in S3 is performed several times, the precipitated clean water is subjected to buffer internal reflux in proportion and used as the inlet buffer water in S1. The pH of the preliminary reduction reaction is adjusted by the buffer internal reflux of the precipitated clean water in S4. The remaining clean water is used as the treated wastewater. The number of neutralization internal refluxes is determined according to the nitric nitrogen content in the precipitated clean water. The nitric nitrogen content in the treated wastewater is <10 mg / L.

[0100] Comparative Example 1

[0101] This comparative example 1 provides a method for treating adipic acid wastewater, and the specific steps are as follows:

[0102] S1: adding sodium hydroxide to the adipic acid wastewater to make the pH of the adipic acid wastewater 7.3;

[0103] S2: biologically denitrifying the adipic acid wastewater after adjusting the pH, precipitating the wastewater after biological denitrification, and using the clear water after precipitation as the treated wastewater.

[0104] The wastewater before and after biological denitrification in Examples 1 to 9 and Comparative Example 1 was taken, and the nitrate nitrogen content in the wastewater was tested respectively to obtain the nitrate nitrogen content of the wastewater before denitrification and the nitrate nitrogen removal rate. The nitrate nitrogen content in the wastewater was determined according to GB / T 7480-1987, and the nitrate nitrogen removal rate was the rate of change of the nitrate nitrogen content before and after denitrification. The specific data are shown in Table 1.

[0105] Table 1 Nitrate nitrogen content and nitrate nitrogen removal rate of wastewater before denitrification in Examples 1 to 9 and Comparative Example 1

[0106]

[0107] It can be seen from Table 1 that the nitrate nitrogen content of the wastewater before denitrification in Examples 1 to 9 is less than the nitrate nitrogen content of the wastewater before denitrification in Comparative Example 1, and the nitrate nitrogen removal rates of Examples 1 to 9 are greater than the nitrate nitrogen removal rate of Comparative Example 1. This application has superiority.

[0108] In Examples 1 to 5, as the ratio of the amount of iron filings added to the mass of nitrate nitrogen in the wastewater increases, the nitrate nitrogen content of the wastewater first decreases and then increases before denitrification, and the nitrate nitrogen removal first increases and then decreases. This is because iron filings, as a reducing agent, can effectively reduce the nitrate nitrogen content in the wastewater within a certain range, and the synergistic effect of urea further promotes the reduction of nitrate nitrogen. Excessive iron filings will combine with ferric hydroxide to form a wrapping effect of the precipitate, hindering the reaction. At the same time, the iron ions in the precipitate cannot effectively participate in subsequent reactions, resulting in a decrease in the removal efficiency of nitrate nitrogen. This phenomenon reflects the dynamic balance between chemical reduction and biological treatment. The increase in the amount of iron filings added optimizes the treatment effect within a certain range, but excessive addition destroys this balance, ultimately leading to a decrease in denitrification effect. The preferred embodiment is Example 3.

[0109] In Examples 3 and 6 to 9, as the pH of the wastewater gradually increased before biological denitrification of the second treated wastewater, the nitrate-nitrogen content in the wastewater before denitrification first decreased and then increased, while nitrate-nitrogen removal first increased and then decreased. This is because denitrifying bacteria are most active in a near-neutral environment and can efficiently reduce nitrate-nitrogen to nitrogen gas. As the pH value increases, the activity of denitrifying bacteria gradually increases, and the nitrate-nitrogen removal rate increases accordingly. However, when the pH value exceeds 7.6, the excessively alkaline environment inhibits the metabolic activity of denitrifying bacteria, resulting in a decrease in nitrate-nitrogen removal rate. Furthermore, while iron ions are highly soluble at low pH values, as the pH value increases, they form precipitates, reducing their bioavailability and affecting the efficiency of nitrate-nitrogen reduction. Ammonia produced by urea decomposition can promote nitrate-nitrogen removal within a certain range, but excessive ammonia is toxic to denitrifying bacteria, inhibiting their activity. The reuse efficiency of iron ions in the precipitate also decreases with increasing pH. These factors work together to cause nitrate-nitrogen content to first decrease and then increase, and removal to first increase and then decrease, as the pH value increases. The preferred embodiment is embodiment seven.

[0110] The above description is based on the ideal embodiment of the present invention. Based on the above description, relevant personnel can make various changes and modifications without departing from the technical scope of this invention. The technical scope of this invention is not limited to the content of the specification and must be determined according to the scope of the claims.

Claims

1. A method for treating adipic acid wastewater with internal reflux, characterized in that: The following steps are involved: S1: buffering the adipic acid wastewater, and performing electrochemical treatment during the buffering process to discharge first treated wastewater; the electrochemical treatment comprises performing a primary reduction reaction using iron filings and a copper mesh, and adding urea for a secondary reduction reaction, wherein the mass ratio of the iron filings added to the nitrate nitrogen in the wastewater is 15-20:1, and the mass ratio of the urea added to the nitrate nitrogen in the wastewater is 1.5-3:1; S2: neutralizing the first treated wastewater in S1 with acid and alkali to obtain second treated wastewater; S3: biologically denitrifying the second treated wastewater in S2, wherein the pH of the wastewater before biological denitrification is 7.0-7.3, precipitating the wastewater after biological denitrification, neutralizing the precipitated clean water with internal reflux, and using it as an alkaline solution to neutralize the acid and alkali with the first treated wastewater in S1, and returning the precipitate to the biological denitrification area; S4: After the neutralization and internal reflux in S3 are performed several times, the clear water after precipitation is subjected to buffering internal reflux in proportion and used as the inlet buffer water in S1, and the remaining clear water is used as treated wastewater.

2. The method for treating adipic acid wastewater with internal reflux according to claim 1, wherein: The specific steps of the primary reduction reaction are to adjust the pH of the wastewater to 3.0-6.0 and then use iron filings and copper mesh to perform a primary reduction reaction. The secondary reduction reaction is to adjust the pH of the wastewater to 1.0-3.0 and heat the wastewater to 40-60° C. before adding urea.

3. The method for treating adipic acid wastewater with internal reflux according to claim 2, wherein: The pH of the preliminary reduction reaction is adjusted by refluxing the buffered clean water after precipitation in S4.

4. The method for treating adipic acid wastewater with internal reflux according to claim 1, wherein: The heavy metals are removed before the S3 biological denitrification, and the removed heavy metal components are copper ions and nickel ions.

5. The method for treating adipic acid wastewater with internal reflux according to claim 4, wherein: The removal uses a chelating resin.

6. The method for treating adipic acid wastewater with internal reflux according to claim 1, wherein: The number of neutralization internal refluxes in S4 is determined according to the nitrate nitrogen content in the clear water after precipitation, and the nitrate nitrogen content in the treated wastewater is less than 10 mg / L.

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