Treatment method of ammonia nitrogen and refractory copper cyanide wastewater

Abstract

The application provides a method for treating wastewater containing ammonia nitrogen and refractory copper cyanide, and belongs to the field of wastewater treatment, wherein the wastewater first enters a first-stage oxidation reactor, and the stable structure of copper cyanide complex is destroyed by adding an oxidizing agent; then, a copper removal agent and a pH adjusting agent are added in a copper removal reactor to make copper ions precipitate and separate out; then, the copper sludge is completely separated and removed through a solid-liquid separation process; the overflow liquid and the filter press liquid are combined, and then oxidized and solid-liquid separated again to completely remove residual cyanide and organic matter; finally, the purified liquid which has removed copper cyanide interference through two-stage oxidation is delivered to a biological reaction system to perform biochemical reaction, so that the effluent can reach the reuse or discharge standard. The application effectively solves the toxicity inhibition of refractory wastewater on the biochemical system, realizes step-by-step removal and resource utilization of toxic and harmful substances, ensures that the effluent can stably reach the standard for reuse or discharge, and has the advantages of efficient treatment, economic environmental protection and convenient operation.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to a method for treating wastewater containing ammonia nitrogen and difficult-to-treat copper cyanide to meet standards. Background Technology

[0002] Cyanide leaching is the mainstream wet leaching process in the gold industry due to its simplicity and high gold recovery rate. Currently, the gold industry generally adopts a process flow of "carbon leaching – desorption electrolysis – gold mud smelting". However, in actual production, due to the associated characteristics of gold, copper, and other metallic minerals, a large amount of copper-cyanide complexes are formed during cyanide leaching, and these complexes enter subsequent processing stages. In the cyanide tailings filtration and slurry treatment process, conventional cyanides (such as CN) in the circulating liquid... - This substance can be effectively removed by traditional redox methods such as hydrogen peroxide and sodium metabisulfite. However, for copper-cyanide complexes [Cu(CN)4] with relatively stable complexation constants... 3- The oxidizing power of these conventional reagents is severely insufficient, making it difficult to destroy their stable coordination structure, resulting in the continuous accumulation of copper-cyanide complexes. At the same time, during the traditional acidic cyanide destruction process, the ammonia nitrogen produced by cyanide destruction also accumulates continuously in the circulating liquid, resulting in a certain concentration of copper-cyanide complexes and copper-ammonia complexes in the entire wastewater system, affecting the treatment indicators for the harmless treatment of cyanide tailings.

[0003] Currently, the common treatment method for wastewater containing ammonia nitrogen and difficult-to-treat copper cyanide is to periodically discharge a portion of the filter press circulating liquid from the system and replenish it with fresh water. However, this method not only fails to fundamentally solve the problem but also wastes water resources and poses a risk of secondary pollution. The traditional concentrated sulfuric acid acidification method can also break the complex, but this method has low complex-breaking efficiency, especially in the presence of copper ammonia complexes, making it difficult to completely release and precipitate copper ions. In addition, strong acidic conditions can lead to the release of hydrogen cyanide gas, posing a huge safety hazard.

[0004] In view of this, it is necessary to design a method for treating wastewater containing ammonia nitrogen and difficult-to-treat copper cyanide to meet the standards, so as to solve the above problems. Summary of the Invention

[0005] In view of the technical problems existing in the background art, this application provides a method for treating wastewater containing ammonia nitrogen and difficult-to-treat copper cyanide to meet standards. By rationally designing the water treatment process, using copper removal agents and adjusting parameters, pollutants such as heavy metal ions, COD, and ammonia nitrogen in the wastewater are removed, thereby achieving environmental benefits.

[0006] This application provides a method for treating wastewater containing ammonia nitrogen and difficult-to-treat copper cyanide to meet standards, including the following steps:

[0007] S1. Input the wastewater containing ammonia nitrogen and difficult-to-treat copper cyanide into the primary oxidation reactor, add oxidant, and obtain primary oxidation turbid liquid;

[0008] S2. Input the primary oxidation turbid liquid obtained in step S1 into the copper removal reactor, add copper removal agent and pH adjuster to obtain copper removal turbid liquid;

[0009] A flocculant is added to the copper-removed turbid liquid, and after solid-liquid separation, copper-removed underflow and copper-removed overflow are obtained;

[0010] The copper-removed underflow is subjected to pressure filtration and dewatering treatment to obtain copper-removed filter residue and copper-removed filter liquid.

[0011] S3. Input the copper-removed overflow and copper-removed filtrate obtained in step S2 into the secondary oxidation reactor, add oxidant, and obtain secondary oxidation turbid liquid;

[0012] A flocculant is added to the secondary oxidation turbid liquid, and after solid-liquid separation, secondary oxidation underflow and secondary oxidation overflow are obtained;

[0013] The secondary oxidation underflow is subjected to pressure filtration and dewatering treatment to obtain secondary oxidation residue and secondary oxidation filtrate.

[0014] S4. The secondary oxidation overflow and the secondary oxidation filtrate obtained in step S3 are used as purification liquids and input into the bioreactor system for biochemical reaction. The effluent is reused in the production process or discharged after meeting the standards.

[0015] As a further improvement of this application, in step S1, the oxidant is one or more of hydrogen peroxide, ozone, sodium metabisulfite, and sodium sulfite, and the dosage is the same as that of CN. f The reaction is 6 to 10 times the theoretical value.

[0016] As a further improvement of this application, in step S2, the dosage of the copper removal agent is 6 to 12 times the copper content in the wastewater, and the copper removal agent includes sodium dimethyl dithiocarbamate.

[0017] As a further improvement of this application, the copper removal agent also includes one or more of sodium ethyl xanthate, sodium polysulfide, diethylenetriamine, and sodium bicarbonate, wherein sodium dimethyl dithiocarbamate accounts for ≥80% by mass.

[0018] As a further improvement of this application, in step S2, the pH adjuster is a biological oxidation liquid, the reaction pH is controlled at 6.5~7.0, and the copper removal reaction time is 0.5~1.0h; the biological oxidation liquid is acidic wastewater with an iron ion concentration ≥10000mg / L.

[0019] As a further improvement of this application, in step S3, the oxidant is one or more of hydrogen peroxide, ozone, sodium metabisulfite, and sodium sulfite.

[0020] As a further improvement of this application, in step S3, the amount of oxidant added is the amount of CN remaining after the copper removal reaction. T The total amount removed is 2 to 5 times the theoretical value plus 0.1 to 0.2 times the amount of copper removal agent used.

[0021] As a further improvement of this application, in step S4, the bioreactor system includes a regulating system, an anoxic tank, an aerobic tank, a solid-liquid separation device, and an effluent tank.

[0022] As a further improvement of this application, the concentration of activated sludge in the anoxic tank and the aerobic tank is 3000~12000mg / L, the dissolved oxygen in the aerobic tank is 2.0~4.0mg / L, and the dissolved oxygen in the anoxic tank is <0.5mg / L.

[0023] As a further improvement of this application, the ammonia nitrogen concentration in the purified liquid is 15~800 mg / L, the copper ion concentration is <5 mg / L, and the total cyanide concentration is <10 mg / L.

[0024] The beneficial effects of this application are as follows:

[0025] This application provides a method for treating wastewater containing ammonia nitrogen and difficult-to-treat copper-cyanide to meet standards. It employs a combined process of chemical pretreatment and advanced biochemical treatment. The wastewater first enters a primary oxidation reactor, where a strong oxidant is added to disrupt the stable structure of the copper-cyanide complex. Subsequently, a copper removal agent and pH adjuster are added to a copper removal reactor to precipitate copper ions. A solid-liquid separation process then thoroughly removes copper sludge. The treated overflow and filtrate are combined and enter a secondary oxidation reactor for further oxidation and solid-liquid separation to completely remove residual cyanide and organic matter. Finally, the purified liquid, after two stages of oxidation and removal of copper-cyanide interference, is transported to a biological reaction system for biochemical reaction. Microorganisms efficiently degrade ammonia nitrogen, ultimately ensuring the effluent meets reuse or discharge standards. This application effectively solves the problem of toxicity inhibition of difficult-to-treat wastewater on the biological system, achieving stepwise removal and resource utilization of toxic and harmful substances, ensuring stable effluent compliance for reuse or discharge, and combining the advantages of high-efficiency treatment, economic and environmental protection, and convenient operation.

[0026] This application involves sequentially treating ammonia nitrogen and difficult-to-treat copper-cyanide wastewater through primary oxidation, copper removal with biological oxidation liquid and copper removal agents, secondary oxidation, and deep biological treatment. Strongly complexed copper-cyanide complexes are removed by copper removal agents and secondary oxidation, while residual ammonia nitrogen and ammonia nitrogen generated from the oxidation of cyanide in the wastewater are removed through deep biological purification. During the copper removal process, a biological oxidation liquid containing high concentrations of heavy metal ions such as iron is used as a pH adjuster to assist in the precipitation and removal of copper and ferric-cyanide complexes in the wastewater. The secondary oxidation process not only removes cyanide released during copper removal but also removes residual copper removal agents and their reaction decomposition products, eliminating their negative impact on the downstream biological treatment.

[0027] This application addresses the pollution characteristics of cyanide-containing wastewater rich in stable copper-cyanide complexes and ammonia nitrogen. It employs a highly efficient complex-breaking and copper-precipitating agent, overcoming the safety hazards of the strong acid reaction conditions associated with traditional concentrated sulfuric acid acidification for complex-breaking and copper precipitation. Combining this agent with the current technological characteristics of cyanide-containing wastewater treatment, and through the use of copper removal agents and a rationally designed water treatment process, the wastewater containing ammonia nitrogen and difficult-to-treat copper-cyanide undergoes sequential primary oxidation treatment, biological oxidation liquid-assisted copper removal agent treatment, secondary oxidation treatment, and biochemical treatment. This allows the deeply purified liquid to be reused in enterprise production or to meet the Class I standard of the "Integrated Wastewater Discharge Standard" (GB8978-1996) before being discharged, ensuring normal production operations and achieving a balance between economic and environmental benefits.

[0028] This application successfully overcomes the problem of effectively treating wastewater containing ammonia nitrogen and stable complexed copper cyanide by further controlling parameters such as the oxidant addition point, oxidant dosage, type of copper removal agent, addition point and dosage, and type and pH value of pH adjuster in the treatment process. The treatment method for ammonia nitrogen-containing and difficult-to-treat copper cyanide wastewater provided by this application is simple, safe and reliable in operation, uses common and inexpensive raw materials, can achieve deep purification of copper cyanide wastewater, reduce the impact of its reuse on production processes, and achieve compliant discharge of cyanide-containing wastewater. It has significant economic, environmental, and social benefits, and provides a new approach to the comprehensive treatment of copper cyanide wastewater.

[0029] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0030] To more clearly illustrate the technical solutions of this application, the accompanying drawings used in this application will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without any creative effort.

[0031] Figure 1 This is a flowchart illustrating the method for treating ammonia nitrogen-containing and difficult-to-treat copper-cyanide wastewater to meet standards, as provided in the embodiments of this application. Detailed Implementation

[0032] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0034] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0035] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0036] In the cyanide gold extraction process, due to the co-occurrence of gold and copper, cyanide-containing wastewater often contains copper-cyanide complexes. In the cyanide tailings filtration and slurry treatment process, the filtration circulating liquid is in a closed loop for a long time, leading to the continuous accumulation of stable copper-cyanide complexes that are difficult to treat with conventional cyanide-breaking agents, as well as ammonia nitrogen produced by cyanide decomposition, forming difficult-to-treat copper-cyanide wastewater. Traditional methods either cannot be discharged externally due to "zero discharge" requirements, or the acidification method, although capable of breaking the complexes, carries significant safety risks due to incomplete breakdown and leakage of highly toxic hydrogen cyanide gas.

[0037] To address the technical problems of low treatment efficiency, incomplete treatment, and high risk in existing methods for treating ammonia nitrogen-containing and difficult-to-treat copper cyanide wastewater, this application provides a method for treating ammonia nitrogen-containing and difficult-to-treat copper cyanide wastewater to meet discharge standards. This method combines chemical pretreatment with advanced biochemical treatment to achieve the technical effect of compliant discharge of cyanide-containing wastewater.

[0038] Please refer to Figure 1 This application provides a method for treating wastewater containing ammonia nitrogen and difficult-to-treat copper cyanide to meet standards, including the following steps:

[0039] S1. Input the wastewater containing ammonia nitrogen and difficult-to-treat copper cyanide into the primary oxidation reactor, add oxidant, and obtain primary oxidation turbid liquid;

[0040] S2. Input the primary oxidation turbid liquid obtained in step S1 into the copper removal reactor, add copper removal agent and pH adjuster to obtain copper removal turbid liquid;

[0041] A flocculant was added to the copper-removed turbid liquid, and after solid-liquid separation, copper-removed underflow and copper-removed overflow were obtained.

[0042] The copper-removed underflow is subjected to pressure filtration and dewatering treatment to obtain copper-removed filter residue and copper-removed filter liquid;

[0043] S3. Input the copper-removed overflow and copper-removed filtrate obtained in step S2 into the secondary oxidation reactor, add oxidant, and obtain secondary oxidation turbid liquid;

[0044] A flocculant was added to the turbid secondary oxidation liquid, and after solid-liquid separation, the secondary oxidation underflow and secondary oxidation overflow liquid were obtained.

[0045] The secondary oxidation underflow was subjected to pressure filtration and dewatering treatment to obtain secondary oxidation slag and secondary oxidation filtrate;

[0046] S4. The secondary oxidation overflow and secondary oxidation filtrate obtained in step S3 are used as purification liquids and fed into the bioreactor system for biochemical reaction. The effluent is reused in the production process or discharged after meeting the standards.

[0047] In the technical solution of this application embodiment, addressing the two core challenges of difficult-to-treat copper-cyanide wastewater and high-concentration ammonia nitrogen, this application utilizes the powerful means of chemical oxidation to first disrupt the stable structure of the copper-cyanide complex, converting cyanide and heavy metal copper into low-toxicity or non-toxic forms and separating them, thereby removing substances that have a highly toxic inhibitory effect on subsequent microorganisms. The pretreated purified liquid is then introduced into a biological reaction system, utilizing the metabolic activities of microorganisms to efficiently degrade the remaining ammonia nitrogen and a small amount of residual pollutants, ultimately achieving stable compliance with wastewater standards and reuse. Specifically, the concentration of copper in the ammonia nitrogen-containing and difficult-to-treat copper-cyanide wastewater is not less than 30 mg / L, the concentration of cyanide is not less than 100 mg / L, the concentration of ammonia nitrogen is not less than 15 mg / L, the pH value is alkaline, and the wastewater contains relatively stable copper-cyanide complexes ([Cu(CN)4)4) that are difficult to treat with conventional oxidants. 3− ).

[0048] Furthermore, in some embodiments, in step S1, the oxidant is one or more of hydrogen peroxide, ozone, sodium metabisulfite, and sodium sulfite, and the dosage is the same as that of CN. f (Free cyanide) 6 to 10 times the theoretical value of the reaction.

[0049] In the technical solution of this application embodiment, the oxidant can oxidize cyanide into less toxic cyanate, or further oxidize it into carbon dioxide and nitrogen. The dosage ensures the thoroughness of the oxidation reaction, avoiding cyanide residue due to insufficient oxidant, while also avoiding resource waste or secondary pollution caused by excessive use of oxidant. The type of oxidant (cyanide removal agent) used determines whether pH adjuster, air, or oxygen needs to be added for auxiliary reaction. pH adjusters can be sulfuric acid, acidic wastewater (such as biological oxidation liquid, acidic smelting wastewater with low concentrations of heavy metals, etc.), lime, sodium hydroxide, carbide slag, etc. The reaction time is controlled at 1-2 hours. Specific control parameters can be determined experimentally, but it is necessary to treat all easily treatable cyanide, i.e., until the cyanide removal rate remains essentially unchanged by increasing the dosage of the cyanide removal agent.

[0050] Furthermore, in some embodiments, in step S2, the amount of copper removal agent added is 6 to 12 times the copper content in the wastewater, and the copper removal agent includes sodium dimethyl dithiocarbamate.

[0051] In the technical solution of this application embodiment, the dosage needs to take into account the existing form of copper in the wastewater (such as free state, complexed state) and the influence of other interfering ions. A dosage of 6 to 12 times the amount of the reagent ensures sufficient reaction and avoids copper residue due to insufficient reagent.

[0052] Furthermore, in some embodiments, the copper-containing agent also includes one or more of sodium ethyl xanthate, sodium polysulfide, diethylenetriamine, and sodium bicarbonate, wherein sodium dimethyl dithiocarbamate accounts for ≥80% by mass.

[0053] In the technical solution of this application embodiment, sodium dimethyl dithiocarbamate is used as the main active ingredient. Its high proportion ensures the full reaction between the reagent and copper ions, while assisting other reagents to achieve synergistic effects, thereby achieving efficient and stable removal of copper ions from difficult-to-treat copper cyanide wastewater.

[0054] Furthermore, in some embodiments, in step S2, the pH adjuster is a biological oxidation liquid, the reaction pH is controlled at 6.5~7.0, and the copper removal reaction time is 0.5~1.0h; the biological oxidation liquid is acidic wastewater with an iron ion concentration ≥10000mg / L.

[0055] In the technical solution of this application embodiment, the biological oxidation liquid is an acidic wastewater with an iron ion concentration ≥10000mg / L, and its acidity mainly comes from free H+. + In the copper removal reaction, this liquid acts as a natural pH buffer, neutralizing alkaline conditions and stabilizing the reaction environment. Iron ions in the biological oxidation liquid readily form ferric hydroxide (Fe(OH)3) colloids under alkaline conditions. These colloids have a large specific surface area, allowing them to adsorb copper ions or their complexes from the water, forming co-precipitates and improving the copper removal rate. A reaction time of 0.5–1.0 h helps achieve precipitation equilibrium; extending the reaction time may lead to excessive flocculation of the colloids, making sedimentation difficult. Using iron-containing acidic wastewater (such as mining wastewater or metallurgical wastewater) as a pH adjuster reduces the cost of chemical agents (such as sulfuric acid) and enables wastewater recycling. Compared to traditional strong acid and strong base adjusters, the neutralization products of the biological oxidation liquid (such as Fe(OH)3) are easier to dehydrate, reducing the difficulty of sludge disposal. Specifically, the flocculant added to the copper-removing turbid liquid is a non-ionic flocculant, preferably non-ionic polyacrylamide (NPAM).

[0056] Furthermore, in some embodiments, in step S3, the oxidant is one or more of hydrogen peroxide, ozone, sodium metabisulfite, and sodium sulfite. The amount of oxidant added is the amount of CN remaining after the copper removal reaction. T The sum of 2 to 5 times the theoretical value of (total cyanide) removal and 0.1 to 0.2 times the amount of copper removal agent used.

[0057] In the technical solution of this application embodiment, the oxidant is used to remove residual cyanide and residual copper removal agents and decomposition products of copper removal agents. Its core objective is to break the chemical bonds of cyanide and convert it into low-toxicity or non-toxic substances (such as CO2, N2, cyanate (CNO)). - After copper removal reactions, the wastewater may contain residual free cyanide or copper-cyanide complexes (such as [Cu(CN)4]). 3-The latter is more difficult to decompose, requiring a higher oxidant concentration and a coverage area of ​​2-5 times to cope with water quality fluctuations (such as changes in cyanide concentration) and oxidation efficiency losses (such as the effects of temperature and pH). Copper removal agents may contain thio groups (-CS), which compete with the oxidant for reaction, consuming some of the oxidant. The residual thio groups can be converted into sulfates under oxidation conditions, avoiding sulfur pollution in subsequent treatment. The oxidation reaction usually requires a pH of 9-11 (such as ozone oxidation) or acidity (such as sodium metabisulfite), which needs to be coordinated with the pH adjustment in step S2. The reaction time needs to be 0.5-2 hours to ensure complete decomposition of cyanide, which can be controlled by monitoring the cyanide concentration endpoint. Specifically, the flocculant added to the secondary oxidation turbid liquid is a non-ionic flocculant, preferably non-ionic polyacrylamide (NPAM).

[0058] Furthermore, in some embodiments, in step S4, the bioreactor system includes a regulating system, an anoxic tank, an aerobic tank, a solid-liquid separation device, and an effluent tank. The activated sludge concentration in the anoxic and aerobic tanks is 3000~12000 mg / L, the dissolved oxygen in the aerobic tank is 2.0~4.0 mg / L, and the dissolved oxygen in the anoxic tank is <0.5 mg / L.

[0059] In the technical solution of this application embodiment, the regulating system is used for homogenization and quantity, buffering water quality and quantity fluctuations, and ensuring the stability of subsequent biological treatment. The retention time is 2-6 hours, and sedimentation is prevented by stirring or aeration. The anoxic tank is used for denitrification, utilizing denitrifying bacteria in activated sludge to reduce nitrates to nitrogen gas and remove ammonia nitrogen produced by cyanide oxidation. Dissolved oxygen (DO) is controlled to be <0.5 mg / L by stirring to avoid oxygen inhibiting denitrifying enzyme activity. The pH of the aerobic tank is 6.5-8.5, and nitrifying bacteria in the aerobic tank oxidize NH3-N to NO2. - Nitrifying bacteria further oxidize it into NO3. -Aerobic bacteria decompose residual COD and cyanate hydrolysis products. Dissolved oxygen (DO) is controlled at 2.0–4.0 mg / L using aeration to ensure nitrifying bacteria dominance and prevent sludge bulking. A solid-liquid separation device separates activated sludge from purified water. The sludge is returned to the anoxic / aerobic tank to maintain a high sludge concentration, with the return flow rate controlled at 30–200%. Water meeting standards is temporarily stored in the effluent tank, and discharged after monitoring pH, COD, ammonia nitrogen, and other indicators. Increased activated sludge concentration improves volumetric loading, reduces the reactor volume, and enhances shock resistance. Specifically, an external carbon source is used to control the activated sludge F / M (organic loading rate) to a range of 0.1–0.3 kg BOD / (kg MLVSS·d); phosphorus is added to control the N / P ratio at 5:1. Activated sludge is rich in Thiobacillus, Nitrospira, norank Saccharimonadale, Denitrosoma, and Thaurea.

[0060] Furthermore, in some embodiments, the concentration of ammonia nitrogen in the purified solution is 15~800 mg / L, the concentration of copper ions is <5 mg / L, and the concentration of total cyanide is <10 mg / L.

[0061] In the technical solution of this application embodiment, the ammonia nitrogen range indicates that the system can handle high-load wastewater. By adjusting the sludge concentration and retention time to adapt to changes, the low limits of copper and cyanide avoid biotoxicity and ensure system stability.

[0062] The following are some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0063] Example 1

[0064] This embodiment provides a method for treating wastewater containing ammonia nitrogen and difficult-to-treat copper cyanide to meet standards. The method targets easily releasing cyanide, copper cyanide complexes, heavy metals such as copper, and ammonia nitrogen in the wastewater (material composition detailed in Table 1). Figure 1 As shown, it includes the following steps:

[0065] S1. Input the wastewater containing ammonia nitrogen and difficult-to-treat copper cyanide into the primary oxidation reactor (cyanide removal reactor). Based on the content of easily released cyanide in the wastewater, add 10 mL / L (CN) hydrogen peroxide. fThe reaction was carried out at 6.57 times the theoretical value. During the reaction, the pH value was controlled to be ≥6.5 using 10% sodium hydroxide solution. The stirring time was 1.5 h. After increasing the amount of hydrogen peroxide, the cyanide content in the wastewater no longer decreased, and a turbid liquid of primary oxidation was obtained.

[0066] S2. The primary oxidation turbid liquid obtained in step S1 is fed into the copper removal reactor. The pH value is controlled at around 6.5 using a biological oxidation liquid (approximately 1 mL / L). At the same time, 2.5 g / L of copper removal agent (8.01 times the copper content) is added for copper removal treatment. The reaction is stirred for 30 min to obtain a copper-removed turbid liquid. The copper removal agent is composed of sodium dimethyl dithiocarbamate, sodium ethyl xanthate, diethylenetriamine, and sodium bicarbonate in a molar ratio of 8:0.5:1:1. The composition of the biological oxidation liquid is shown in Table 2.

[0067] Nonionic polyacrylamide was added to the copper removal turbidity solution, and after solid-liquid separation by a thickener, copper removal underflow and copper removal overflow were obtained.

[0068] The copper-removed underflow is subjected to pressure filtration and dewatering treatment to obtain copper-removed filter residue and copper-removed filter liquid;

[0069] S3. Input the copper-removed overflow and copper-removed filtrate obtained in step S2 into the secondary oxidation reactor, and add 1.65 mL / L (CN) hydrogen peroxide. T The solution was subjected to a secondary oxidation treatment (3.14 times the theoretical reaction value + 0.15 times the copper removal agent dosage) to obtain a secondary oxidized turbid liquid.

[0070] Nonionic polyacrylamide was added to the secondary oxidation turbid liquid, and after solid-liquid separation by a thickener, the secondary oxidation underflow and secondary oxidation overflow were obtained.

[0071] The secondary oxidation underflow was subjected to pressure filtration and dewatering treatment to obtain secondary oxidation filter residue and secondary oxidation filtrate;

[0072] S4. The secondary oxidation overflow and secondary oxidation filtrate obtained in step S3 are used as purified liquids and input into the biological reaction system for biochemical reaction. Through the equalization tank, anoxic tank, aerobic tank, and solid-liquid separation device, the N / P ratio is controlled at 5:1; the DO in the anoxic tank is controlled below 0.5 mg / L, and the DO concentration in the aerobic tank is controlled at 2.0~4.0 mg / L by aeration; the pH in the aerobic tank is 7.5~8.5; the return flow rate of activated sludge is controlled at 100~200%, and the concentration of activated sludge in the anoxic tank and aerobic tank is controlled at 3000~6000 mg / L. After the reaction is complete, a deeply purified liquid is obtained, which is reused in the production process or discharged after meeting the standards.

[0073] The relevant technical specifications of this embodiment are shown in the table below.

[0074] Table 1. Content of various substances in wastewater containing ammonia nitrogen and difficult-to-treat copper cyanide.

[0075]

[0076] Table 2. Content of main substances in biological oxidation liquid

[0077]

[0078] Table 3 Technical indicators of each section of this process

[0079]

[0080] Table 4 Removal rates of various pollutants

[0081]

[0082] Comparative Examples 1-10

[0083] Comparative Examples 1-10 provide methods for treating ammonia nitrogen-containing and difficult-to-treat copper-cyanide wastewater to meet standards. Compared with Example 1, the only differences are the amount of hydrogen peroxide added in step S1, the amount of copper removal agent added in step S2, the type of pH adjuster in step S2, and the amount of hydrogen peroxide used in step S3, as shown in Table 5.

[0084] Table 5 Process parameters for Comparative Examples 1-10

[0085]

[0086] After treating the ammonia nitrogen-containing and difficult-to-treat copper cyanide wastewater according to the methods provided in Comparative Examples 1-10 above, the effluent was tested, and the relevant technical indicators are shown in Table 6.

[0087] Table 6 Results of the comparative experiment

[0088]

[0089]

[0090] As shown in Table 6, insufficient or no copper removal agent, or poor pH control, will result in the inability to remove complexed copper and cyanide, leading to high copper and cyanide concentrations in the deep purification influent, biological inactivation, ineffective ammonia nitrogen removal, and excessive levels of cyanide, copper, and ammonia nitrogen in the effluent. Excessive copper removal agent will result in a large amount of residual agent and its decomposition products after treatment, affecting the biological activity of the deep purification process and causing ammonia nitrogen levels in the effluent to fail to meet standards. Adding copper removal agents directly without cyanide pretreatment or with insufficient dosage of primary cyanide pretreatment will also lead to incomplete copper removal, low cyanide removal rate, high cyanide and copper concentrations in the deep purification influent, biological inactivation, and ineffective ammonia nitrogen removal. The effluent showed substandard levels of cyanide, copper, and ammonia nitrogen. Using concentrated sulfuric acid instead of biological oxidation liquid to adjust the pH meant that trace amounts of ferricyanide in the wastewater could not be completely removed. The copper removal reaction resulted in very little precipitation; without co-precipitation with other metals like iron, the copper-containing precipitate was difficult to separate from the water, failing to achieve the desired copper removal effect and impacting downstream biological ammonia nitrogen removal. Insufficient dosage of the secondary oxidant led to incomplete cyanide removal, residual copper removal agents and decomposition products, affecting microbial activity and causing ammonia nitrogen levels to exceed standards. Excessive dosage of the secondary oxidant resulted in residual oxidant having a disinfecting effect on microorganisms, reducing microbial populations and causing ammonia nitrogen levels to exceed standards. Therefore, the primary oxidation reaction, copper removal reaction, and secondary oxidation reaction all require strict control of agent dosing points, dosages, pH levels, and other control conditions according to the treatment process requirements to achieve the final treatment objective.

[0091] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A method for treating wastewater containing ammonia nitrogen and difficult-to-treat copper cyanide to meet standards, characterized in that, Includes the following steps: S1. Input the wastewater containing ammonia nitrogen and difficult-to-treat copper cyanide into the primary oxidation reactor, add oxidant, and obtain primary oxidation turbid liquid; S2. Input the primary oxidation turbid liquid obtained in step S1 into the copper removal reactor, add copper removal agent and pH adjuster to obtain copper removal turbid liquid; the pH adjuster is a biological oxidation liquid, and the reaction pH is controlled at 6.5~7.0, the biological oxidation liquid is acidic wastewater with iron ion concentration ≥10000mg / L; A flocculant is added to the copper-removed turbid liquid, and after solid-liquid separation, copper-removed underflow and copper-removed overflow are obtained; The copper-removed underflow is subjected to pressure filtration and dewatering treatment to obtain copper-removed filter residue and copper-removed filter liquid. S3. Input the copper-removed overflow and copper-removed filtrate obtained in step S2 into the secondary oxidation reactor, add oxidant, and obtain secondary oxidation turbid liquid; A flocculant is added to the secondary oxidation turbid liquid, and after solid-liquid separation, secondary oxidation underflow and secondary oxidation overflow are obtained; The secondary oxidation underflow is subjected to pressure filtration and dewatering treatment to obtain secondary oxidation residue and secondary oxidation filtrate. S4. The secondary oxidation overflow and the secondary oxidation filtrate obtained in step S3 are used as purification liquids and input into the bioreactor system for biochemical reaction. The effluent is reused in the production process or discharged after meeting the standards.

2. The method for treating ammonia nitrogen-containing and difficult-to-treat copper-cyanide wastewater to meet standards according to claim 1, characterized in that, In step S1, the oxidant is one or more of hydrogen peroxide, ozone, sodium metabisulfite, and sodium sulfite, and the dosage is the same as that of CN. f The reaction is 6 to 10 times the theoretical value.

3. The method for treating ammonia nitrogen-containing and difficult-to-treat copper-cyanide wastewater to meet standards according to claim 1, characterized in that, In step S2, the dosage of the copper removal agent is 6 to 12 times the copper content in the wastewater, and the copper removal agent includes sodium dimethyl dithiocarbamate.

4. The method for treating ammonia nitrogen-containing and difficult-to-treat copper-cyanide wastewater to meet standards according to claim 3, characterized in that, The copper removal agent also includes one or more of sodium ethyl xanthate, sodium polysulfide, diethylenetriamine, and sodium bicarbonate, wherein sodium dimethyl dithiocarbamate accounts for ≥80% by mass.

5. The method for treating ammonia nitrogen-containing and difficult-to-treat copper-cyanide wastewater to meet standards according to claim 1, characterized in that, In step S2, the copper removal reaction time is 0.5~1.0 h.

6. The method for treating ammonia nitrogen-containing and difficult-to-treat copper-cyanide wastewater to meet standards according to claim 1, characterized in that, In step S3, the oxidant is one or more of hydrogen peroxide, ozone, sodium metabisulfite, and sodium sulfite.

7. The method for treating ammonia nitrogen-containing and difficult-to-treat copper cyanide wastewater to meet standards according to claim 6, characterized in that, In step S3, the amount of oxidant added is the amount of CN remaining after the copper removal reaction. T The total amount removed is 2 to 5 times the theoretical value plus 0.1 to 0.2 times the amount of copper removal agent used.

8. The method for treating ammonia nitrogen-containing and difficult-to-treat copper-cyanide wastewater to meet standards according to claim 1, characterized in that, In step S4, the bioreactor system includes a regulating system, an anoxic tank, an aerobic tank, a solid-liquid separation device, and an effluent tank.

9. The method for treating ammonia nitrogen-containing and difficult-to-treat copper-cyanide wastewater to meet standards according to claim 8, characterized in that, The concentration of activated sludge in the anoxic tank and the aerobic tank is 3000~12000 mg / L, the dissolved oxygen in the aerobic tank is 2.0~4.0 mg / L, and the dissolved oxygen in the anoxic tank is <0.5 mg / L.

10. The method for treating ammonia nitrogen-containing and difficult-to-treat copper-cyanide wastewater to meet standards according to claim 9, characterized in that, The ammonia nitrogen concentration in the purified solution is 15~800 mg / L, the copper ion concentration is <5 mg / L, and the total cyanide concentration is <10 mg / L.

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