A stainless steel pickling wastewater recycling treatment system and method
By combining heavy metal capture ponds, calcium carbonate industrial solid waste ponds, and crystallization fluidized bed with microbial methods to treat stainless steel pickling wastewater, the problems of poor removal efficiency and high cost of multiple pollutants in existing technologies have been solved, and efficient reuse and resource utilization of wastewater have been achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- GUANGXI ENVIRONMENTAL PROTECTION IND DEV RES INST CO LTD
- Filing Date
- 2026-01-21
- Publication Date
- 2026-05-29
AI Technical Summary
Existing technologies cannot efficiently remove multiple pollutants from stainless steel pickling wastewater, resulting in high treatment costs and large sludge production, making wastewater reuse difficult.
The method combines physicochemical and biological treatments, employing a heavy metal capture pond and a calcium carbonate industrial solid waste pond for initial removal of heavy metals and fluoride ions, a crystallization fluidized bed for deep removal of fluoride ions and heavy metals, and a microbial method for simultaneous removal of sulfates and nitrates.
It achieves simultaneous and efficient removal of multiple pollutants, reduces treatment costs and sludge production, ensures effluent quality meets reuse requirements, utilizes wastewater as a resource, and reduces water waste.
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Figure CN122102407A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of wastewater treatment technology, and in particular to a system and method for the reuse and treatment of stainless steel pickling wastewater. Background Technology
[0002] Pickling is a crucial surface treatment process in the production and processing of stainless steel, generating a large amount of stainless steel pickling wastewater. This wastewater contains various pollutants, primarily heavy metal ions such as nickel, chromium, iron, and thallium, as well as anionic pollutants such as fluorine, sulfates, and nitrates. Direct discharge of this wastewater without effective treatment will not only severely pollute water bodies, soil, and other ecological environments, but also waste water resources and valuable substances contained within them. Furthermore, the heavy metal ions in the wastewater are toxic and difficult to degrade, accumulating through the food chain and posing a significant threat to human health.
[0003] Currently, the main methods for treating stainless steel pickling wastewater include physicochemical treatment and biological treatment. Physicochemical treatment typically uses processes such as neutralization precipitation, coagulation sedimentation, and adsorption to remove heavy metals and fluoride ions from the wastewater. However, this method is less effective at removing sulfates and nitrates, and it generates a large amount of sludge, resulting in high sludge disposal costs. Furthermore, the large dosage of chemicals required contributes to the overall high treatment cost. Biological treatment primarily utilizes the metabolic activity of microorganisms to remove organic pollutants and inorganic pollutants such as nitrogen and sulfur from the wastewater. However, stainless steel pickling wastewater has strong acidity and high concentrations of heavy metals, making it highly toxic to microorganisms. Therefore, it is difficult to directly apply biological treatment methods; complex pretreatment is required, increasing the treatment process and cost. Moreover, biological treatment alone cannot effectively remove heavy metals and fluoride ions from the wastewater.
[0004] Therefore, the existing technology lacks a treatment system and method that can simultaneously and efficiently remove multiple pollutants such as nickel, chromium, iron, thallium, fluorine, sulfate, and nitrate from stainless steel pickling wastewater, while also having low treatment costs, low sludge production, and the ability to reuse the wastewater. Summary of the Invention
[0005] The purpose of this invention is to provide a stainless steel pickling wastewater reuse treatment system and method, overcoming the aforementioned deficiencies in existing stainless steel pickling wastewater treatment methods. This invention can simultaneously and efficiently remove multiple pollutants from wastewater, reducing treatment costs and sludge production, and achieving wastewater purification and reuse. It is suitable for treating stainless steel pickling wastewater containing heavy metal ions such as nickel, chromium, iron, and thallium, as well as pollutants such as fluorine, sulfate, and nitrate.
[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for reusing stainless steel pickling wastewater includes the following steps: Step 1: Preliminary removal of heavy metals and fluoride ions in heavy metal capture ponds and calcium carbonate industrial solid waste ponds; The heavy metal scavenging agent reacts with heavy metal ions such as nickel, chromium, and iron in the wastewater to form stable chelate precipitates; calcium carbonate industrial waste powder undergoes an acid-base neutralization reaction with the acid in the wastewater, raising the pH of the wastewater to meet coagulation requirements, while simultaneously dissolving calcium... 2+ With F - The reaction produces CaF2 precipitate, which is then separated from the water through coagulation and sedimentation, allowing heavy metals and F to be separated. - Completely removed from water. CO2 gas generated from calcium carbonate industrial waste powder is collected and then fed into a pressurized dissolved gas system into a crystallization fluidized bed. Step 2: Deep removal of fluoride ions and heavy metals by a crystallization fluidized bed; The presence of crystal nuclei promotes the combination of residual fluoride ions in wastewater with calcium ions generated from the dissolution of Ca(OH)2 to form calcium fluoride precipitate. Simultaneously, due to the increased pH value, trace amounts of heavy metal ions remaining in the wastewater form hydroxide precipitates, further reducing the concentration of heavy metal ions and fluoride in the wastewater. - The concentration reduces the microbial toxicity of subsequent biological treatments; Step 3: Simultaneous removal of sulfate and nitrate by microbial method.
[0007] Under anaerobic conditions, sulfate-reducing bacteria utilize the organic matrix in wastewater as electron donors to reduce sulfate ions in the wastewater to H2S or S. 0 In a sulfur autotrophic denitrification tank, sulfur autotrophic denitrifying bacteria utilize H2S or S2S. 0 As an electron donor, nitrate ions (NO3) in wastewater... 3- As an electron acceptor, it undergoes sulfur autotrophic denitrification, reducing nitrate ions to nitrogen gas (N2).
[0008] Furthermore, in step one, the initial removal includes the following steps: (1) Pass the stainless steel pickling wastewater into the heavy metal capture tank, add heavy metal capture agent into the heavy metal capture tank to form a stable chelate precipitate. (2) The wastewater in the heavy metal capture tank is fed into the calcium carbonate industrial waste tank, and calcium carbonate industrial waste powder is added to the calcium carbonate industrial waste tank at the same time to make the wastewater and calcium carbonate industrial waste powder fully mixed. (3) Pass the mixed liquid in the calcium carbonate industrial waste pool into the coagulation tank, add coagulant into the coagulation tank, and the coagulant forms flocs in the wastewater. The flocs adsorb calcium fluoride precipitate, heavy metal carbonate precipitate and other small suspended solids in the water. (4) The mixed liquid in the coagulation tank is fed into the sedimentation tank for mud-water separation. The settled sludge is discharged into the physicochemical sludge treatment system through the sludge outlet of the sedimentation tank for treatment, while the supernatant of the sedimentation tank enters the subsequent treatment process.
[0009] Furthermore, in step two, depth removal includes the following steps: (1) Pass the supernatant from the sedimentation tank into the crystallization fluidized bed, and simultaneously add Ca(OH)2 into the crystallization fluidized bed through the Ca(OH)2 dosing device. Crystal nuclei are pre-added into the crystallization fluidized bed. (2) During the operation of the crystallization fluidized bed, the pressurized dissolved gas system pressurizes the collected CO2 gas and introduces it into the crystallization fluidized bed.
[0010] Furthermore, in step three, the simultaneous removal specifically includes: first, the wastewater treated by the crystallization fluidized bed is fed into the sulfate reduction tank, and then the mixed liquid in the sulfate reduction tank is fed into the sulfur autotrophic denitrification tank; during the sulfur autotrophic denitrification reaction, the pressurized dissolved gas system introduces excess CO2 gas into the sulfur autotrophic denitrification tank; part of the wastewater treated by the sulfur autotrophic denitrification tank is directly reused in stainless steel production, and part is returned to the sulfate reduction tank.
[0011] A stainless steel pickling wastewater reuse and treatment system includes a physicochemical treatment system and a biological treatment system, wherein the physicochemical treatment system and the biological treatment system are connected. The physicochemical treatment system includes a heavy metal capture system, a crystallization fluidized bed system, and a physicochemical sludge treatment system. The heavy metal capture system is connected to the crystallization fluidized bed system. The crystallization fluidized bed system is connected to both the physicochemical sludge treatment system and the biological treatment system. The physicochemical sludge treatment system is also connected to the heavy metal capture system. The biological treatment system includes a sulfate reduction system, a sulfur autotrophic denitrification system, and a biological sludge treatment system. The sulfate reduction system is connected to the crystallization fluidized bed system and the sulfur autotrophic denitrification system, respectively. The sulfur autotrophic denitrification system is connected to the biological sludge treatment system, and the biological sludge treatment system is connected to the sulfate reduction system.
[0012] Furthermore, the heavy metal capture system includes a heavy metal capture tank, a calcium carbonate industrial waste tank, a coagulation tank, and a sedimentation tank. The heavy metal capture tank is connected to the calcium carbonate industrial waste tank and the physicochemical sludge treatment system, respectively. The calcium carbonate industrial waste tank is connected to the coagulation tank and the physicochemical sludge treatment system, respectively. The coagulation tank is connected to the sedimentation tank, and the sedimentation tank is connected to the crystallization fluidized bed system and the physicochemical sludge treatment system, respectively.
[0013] Furthermore, a gas collection pipe is installed at the top of the calcium carbonate industrial waste pool, which is used to store calcium carbonate industrial waste powder; the sludge outlet of the sedimentation tank is connected to a physicochemical sludge treatment system for treating the physicochemical sludge generated in the sedimentation tank.
[0014] Furthermore, the crystallization fluidized bed system includes a crystallization fluidized bed and a pressurized dissolved air system. The inlet of the crystallization fluidized bed is connected to the supernatant outlet of the sedimentation tank via a pipe, and a Ca(OH)2 dosing device is installed on the connecting pipe. The crystallization fluidized bed is connected to both a physicochemical sludge treatment system and a sulfate reduction system. The air inlet of the pressurized dissolved air system is connected to a gas collection pipe at the top of the calcium carbonate industrial waste pond via a pipe, and the air outlet of the pressurized dissolved air system is connected to the crystallization fluidized bed.
[0015] Furthermore, the sulfate reduction system includes a sulfate reduction tank, the inlet of which is connected to the outlet of the crystallization fluidized bed via a pipe. The sulfate reduction tank is equipped with an anaerobic environment and sulfate-reducing bacteria.
[0016] Furthermore, the sulfur autotrophic denitrification system includes a sulfur autotrophic denitrification tank, the inlet of which is connected to the outlet of the sulfate reduction tank. The sulfur autotrophic denitrification tank is equipped with sulfur autotrophic denitrifying bacteria. The outlet of the pressurized dissolved air system is also connected to the sulfur autotrophic denitrification tank via a pipeline to introduce excess CO2 gas into the sulfur autotrophic denitrification tank. The inlet of the biological sludge treatment system is connected to the sludge outlets of the sulfate reduction tank and the sulfur autotrophic denitrification tank, respectively, to treat the biological sludge generated during the biological treatment process.
[0017] The present invention, by adopting the above-described technical solution, has the following beneficial effects: 1. This invention organically combines physical and chemical treatment with biological treatment, which can simultaneously and efficiently remove various pollutants such as nickel, chromium, iron, thallium, fluorine, sulfate, and nitrate from stainless steel pickling wastewater. The treatment effect is good, and the effluent quality can meet the requirements for reuse, realizing the resource utilization of wastewater and reducing the waste of water resources.
[0018] 2. In the physicochemical treatment process, this invention uses calcium carbonate industrial waste powder as a neutralizing agent and defluorinating agent. This not only realizes the resource utilization of industrial waste and reduces reagent costs, but also adjusts the pH value of wastewater through its reaction with the wastewater. Simultaneously, the generated CO2 gas can serve as a stirring gas source for the subsequent crystallization fluidized bed and a carbon source for the sulfur autotrophic denitrification tank, further reducing treatment costs and achieving resource recycling. This also avoids the generation of Cl... - The introduction of irrelevant anions can affect the reuse of wastewater.
[0019] 3. The addition of crystal nuclei in the crystallization fluidized bed system of this invention promotes the formation of calcium fluoride precipitate, reduces the amount of Ca(OH)2 added, and lowers the cost of reagent consumption. At the same time, the addition of Ca(OH)2 can not only deeply remove fluoride ions, but also further reduce the concentration of heavy metals, reduce the toxicity to subsequent microorganisms, and ensure the stable operation of biological treatment.
[0020] 4. In the biological treatment process, this invention utilizes the synergistic effect of sulfate-reducing bacteria and sulfur-autotrophic denitrifying bacteria to achieve simultaneous removal of sulfate and nitrate, without the need for a large amount of external organic carbon source, thus reducing operating costs. Furthermore, the biological treatment produces less sludge, reducing sludge disposal costs.
[0021] 5. The entire treatment system of the present invention has a simple process, is easy to operate, and the units work together to achieve high treatment efficiency and stable operation. It is suitable for the treatment and reuse of large-scale stainless steel pickling wastewater. Attached Figure Description
[0022] Figure 1 This is a process flow diagram of the wastewater reuse treatment of the present invention. Detailed Implementation
[0023] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and preferred embodiments. However, it should be noted that many details listed in the specification are merely to provide the reader with a thorough understanding of one or more aspects of the present invention, and these aspects of the invention can be implemented even without these specific details.
[0024] like Figure 1 As shown, a method for reusing and treating stainless steel pickling wastewater includes the following steps: 1. Preliminary removal of heavy metals and fluoride ions from industrial solid waste containing heavy metal scavenging agents and calcium carbonate. Stainless steel pickling wastewater is fed into a heavy metal capture tank. Heavy metal precipitating agent is added to the tank. The heavy metal precipitating agent reacts with heavy metal ions such as nickel, chromium, and iron in the wastewater to form stable chelate precipitates, thus achieving the initial capture of heavy metal ions. Subsequently, the wastewater, after preliminary heavy metal removal, was fed into a calcium carbonate industrial waste pond. Simultaneously, calcium carbonate industrial waste powder was added to the pond to ensure thorough mixing. The calcium carbonate in the powder dissolved completely in the acidic wastewater. The resulting calcium ions combined with fluoride ions in the wastewater to form calcium fluoride precipitate. Some carbonate ions combined with incompletely removed heavy metal ions to form heavy metal carbonate precipitates, while other carbonate ions combined with H+ ions in the wastewater... +The reaction produces CO2 gas, which is collected through a gas collection pipe at the top of the calcium carbonate industrial waste pond and then introduced into a pressurized dissolved gas system; as calcium carbonate continuously consumes H+ from the wastewater... + The pH value of the wastewater gradually increases; Next, the mixed liquid in the calcium carbonate industrial waste pond is passed into the coagulation tank, and a coagulant is added to the coagulation tank. The coagulant forms flocs in the wastewater, and the flocs adsorb calcium fluoride precipitate, heavy metal carbonate precipitate and other small suspended solids in the water. Finally, the mixed liquor in the coagulation tank is fed into the sedimentation tank for sludge-water separation. The settled sludge (physicochemical sludge) is discharged into the physicochemical sludge treatment system through the sludge outlet of the sedimentation tank for treatment, while the supernatant from the sedimentation tank enters the subsequent treatment process.
[0025] 2. Deep removal of fluoride ions and heavy metals by crystallization fluidized bed The supernatant from the sedimentation tank is fed into a crystallization fluidized bed, and Ca(OH)2 is simultaneously added to the fluidized bed via a Ca(OH)2 dosing device. Pre-added crystal nuclei promote the combination of residual fluoride ions in the wastewater with calcium ions produced by the dissolution of Ca(OH)2, forming calcium fluoride precipitate, further reducing the concentration of fluoride ions in the wastewater and simultaneously reducing the amount of Ca(OH)2 required. Furthermore, the addition of Ca(OH)2 further increases the pH of the wastewater, causing residual trace heavy metal ions to form heavy metal hydroxide precipitates, further reducing the concentration of heavy metal ions in the wastewater and mitigating the toxicity of heavy metals to microorganisms during subsequent biological treatment. During the operation of the crystallization fluidized bed, the pressurized dissolved gas system pressurizes the collected CO2 gas and introduces it into the crystallization fluidized bed. The pressurized CO2 gas forms microbubbles in the crystallization fluidized bed, which on the one hand plays a stirring role, allowing the wastewater, Ca(OH)2, crystal nuclei and precipitates to come into full contact, thereby improving the reaction efficiency; on the other hand, it can promote the growth and formation of calcium fluoride crystals, which facilitates subsequent precipitation and separation. The precipitates generated in the crystallization fluidized bed enter the subsequent separation unit (such as the sedimentation zone) together with the wastewater for separation. The separated precipitates can be recycled as crystal nuclei or discharged into the physicochemical sludge treatment system, while the treated wastewater enters the biological treatment system.
[0026] 3. Simultaneous removal of sulfate and nitrate by microbial method Wastewater treated by the crystallization fluidized bed is fed into a sulfate reduction tank, which is an anaerobic environment containing sulfate-reducing bacteria. Under anaerobic conditions, the sulfate-reducing bacteria utilize the organic matrix in the wastewater as electron donors to reduce sulfate ions in the wastewater to H₂S or S₂S. 0 ; Subsequently, the mixed liquor from the sulfate reduction tank is passed into the sulfur autotrophic denitrification tank, where sulfur autotrophic denitrifying bacteria are added to produce H2S or S2S. 0 As an electron donor, nitrate ions (NO3) in wastewater... 3- As an electron acceptor, sulfur autotrophic denitrification occurs, reducing nitrate ions to nitrogen (N2), which is then discharged through the exhaust port at the top of the sulfur autotrophic denitrification tank. During the sulfur autotrophic denitrification process, the pressurized dissolved gas system introduces excess CO2 gas (the portion exceeding the requirements of the crystallization fluidized bed) into the sulfur autotrophic denitrification tank. The CO2 gas serves as the carbon source for sulfur autotrophic denitrifying bacteria, meeting the needs of microbial growth and metabolism, and improving the efficiency of the sulfur autotrophic denitrification reaction.
[0027] Wastewater treated in the sulfur autotrophic denitrification tank is partially reused in stainless steel production, and partially recycled to the sulfate reduction tank to further remove sulfate generated in the sulfur autotrophic denitrification tank, ensuring that the sulfate concentration in the effluent meets reuse requirements. Biological sludge generated during the operation of the sulfate reduction tank and the sulfur autotrophic denitrification tank is discharged into a biological sludge treatment system through their respective sludge outlets for further treatment.
[0028] A stainless steel pickling wastewater reuse and treatment system includes a physicochemical treatment system and a biological treatment system, wherein the physicochemical treatment system is connected to the biological treatment system. The physicochemical treatment system includes a heavy metal capture system, a crystallization fluidized bed system, and a physicochemical sludge treatment system. The heavy metal capture system is connected to the crystallization fluidized bed system, which is connected to both the physicochemical sludge treatment system and the biological treatment system. The physicochemical sludge treatment system is also connected to the heavy metal capture system. The biological treatment system includes a sulfate reduction system, a sulfur autotrophic denitrification system, and a biological sludge treatment system. The sulfate reduction system is connected to both the crystallization fluidized bed system and the sulfur autotrophic denitrification system, which is connected to the biological sludge treatment system. The biological sludge treatment system is also connected to the sulfate reduction system.
[0029] In an embodiment of the present invention, the heavy metal capture system includes a heavy metal capture tank, a calcium carbonate industrial waste tank, a coagulation tank, and a sedimentation tank. The heavy metal capture tank is connected to the calcium carbonate industrial waste tank and the physicochemical sludge treatment system, respectively. The calcium carbonate industrial waste tank is connected to the coagulation tank and the physicochemical sludge treatment system, respectively. The coagulation tank is connected to the sedimentation tank, and the sedimentation tank is connected to the crystallization fluidized bed system and the physicochemical sludge treatment system, respectively.
[0030] In an embodiment of the present invention, a gas collection pipe is provided at the top of the calcium carbonate industrial waste pool, and the calcium carbonate industrial waste pool is used to store calcium carbonate industrial waste powder; the sludge outlet of the sedimentation tank is connected to a physicochemical sludge treatment system for treating the physicochemical sludge generated in the sedimentation tank.
[0031] In an embodiment of the present invention, the crystallization fluidized bed system includes a crystallization fluidized bed and a pressurized dissolved air system. The inlet of the crystallization fluidized bed is connected to the supernatant outlet of the sedimentation tank via a pipe, and a Ca(OH)2 dosing device is installed on the connecting pipe. The crystallization fluidized bed is connected to a physicochemical sludge treatment system and a sulfate reduction system, respectively. The air inlet of the pressurized dissolved air system is connected to a gas collection pipe at the top of the calcium carbonate industrial waste pond via a pipe, and the air outlet of the pressurized dissolved air system is connected to the crystallization fluidized bed.
[0032] In an embodiment of the present invention, the sulfate reduction system includes a sulfate reduction tank, the inlet of which is connected to the outlet of a crystallization fluidized bed via a pipe, the sulfate reduction tank is provided with an anaerobic environment, and sulfate-reducing bacteria are provided in the sulfate reduction tank.
[0033] In an embodiment of the present invention, the sulfur autotrophic denitrification system includes a sulfur autotrophic denitrification tank, the inlet of which is connected to the outlet of a sulfate reduction tank, sulfur autotrophic denitrification bacteria are provided in the sulfur autotrophic denitrification tank, the outlet of the pressurized dissolved air system is also connected to the sulfur autotrophic denitrification tank through a pipeline for introducing excess CO2 gas into the sulfur autotrophic denitrification tank, and the inlet of the biological sludge treatment system is connected to the sludge outlets of the sulfate reduction tank and the sulfur autotrophic denitrification tank respectively for treating the biological sludge generated during the biological treatment process.
[0034] Example 1 The pickling wastewater generated by a stainless steel manufacturing company has the following main pollutant concentrations: nickel ions 5.2 mg / L, chromium ions 3.8 mg / L, iron ions 20.5 mg / L, fluoride ions 85 mg / L, sulfate ions 2500 mg / L, nitrate ions 320 mg / L, and a pH value of 1.5. The wastewater is treated using the treatment system and method of this invention, with the specific steps as follows: Preliminary removal of heavy metals and fluoride ions from industrial solid waste containing calcium carbonate using metal scavenging agents: The above-mentioned pickling wastewater was introduced into a heavy metal scavenging tank at a flow rate of 10 m³ / h. A heavy metal scavenging agent with a mass concentration of 10% was added to the heavy metal scavenging tank at a dosage of 0.5 L / m³ of wastewater, and the mixture was stirred and reacted for 30 min. Subsequently, the wastewater enters the calcium carbonate industrial waste pool, and calcium carbonate industrial waste powder with a particle size of 100-200 mesh is added to the pool at a dosage of 200g / m³ of wastewater. The mixture is stirred and reacted for 60 minutes. During this process, the CO2 gas generated is collected through the top gas collection pipe and then introduced into the pressurized dissolved gas system. After the reaction, the pH value of the wastewater rises to 4.5. Next, the wastewater enters the coagulation tank, and 5% polyaluminum chloride coagulant is added to the coagulation tank at a dosage of 1.0 L / m³ of wastewater. The mixture is stirred and reacted for 15 min. Then, 0.1% polyacrylamide coagulant is added at a dosage of 0.2 L / m³ of wastewater, and the mixture is stirred and reacted for 5 min. Finally, the wastewater enters a sedimentation tank for sludge-water separation, with a sedimentation time of 2 hours. The supernatant from the sedimentation tank is then sent for further treatment, while the physicochemical sludge is discharged into the physicochemical sludge treatment system. Testing revealed the following concentrations of pollutants in the supernatant: nickel ions 0.3 mg / L, chromium ions 0.2 mg / L, iron ions 1.5 mg / L, fluoride ions 25 mg / L, sulfate ions 2480 mg / L, and nitrate ions 315 mg / L.
[0035] Deep removal of fluoride ions and heavy metals by a crystallization fluidized bed: The supernatant from the sedimentation tank enters the crystallization fluidized bed, where crystal nuclei with a particle size of 50-100 μm are pre-added at a rate of 50 g / m³ of wastewater. A 20% Ca(OH)₂ solution is added to the crystallization fluidized bed via a Ca(OH)₂ dosing device at a rate of 0.8 L / m³ of wastewater. The operating temperature of the crystallization fluidized bed is controlled at 25℃, and the hydraulic retention time is 40 min. Simultaneously, a pressurized dissolved gas system pressurizes collected CO₂ gas to 0.3 MPa and introduces it into the crystallization fluidized bed at a flow rate of 0.5 m³ / h. The wastewater treated by the crystallization fluidized bed is then separated by sedimentation and enters the biological treatment system. The concentrations of pollutants in the wastewater at this time were as follows: nickel ions 0.05 mg / L, chromium ions 0.03 mg / L, iron ions 0.2 mg / L, fluoride ions 3.2 mg / L, sulfate ions 2470 mg / L, nitrate ions 310 mg / L, and the pH value was 7.5.
[0036] Simultaneous removal of sulfate and nitrate by microbial method: Wastewater from the crystallization fluidized bed treatment enters the sulfate reduction tank, where it is inoculated with anaerobic bacteria (sulfate-reducing bacteria concentration of 10). 8 (CFU / mL), control the dissolved oxygen concentration in the tank to ≤0.2mg / L, temperature 30℃, hydraulic retention time 8h; Subsequently, the wastewater enters a sulfur autotrophic denitrification tank, which is inoculated with sulfur autotrophic denitrifying bacteria (concentration of 10). 7 (CFU / mL), control temperature 28℃, hydraulic retention time 6h, and at the same time, the excess CO2 gas in the pressurized dissolved air system is introduced into the sulfur autotrophic denitrification tank at a flow rate of 0.3m³ / h. The wastewater treated by the sulfur autotrophic denitrification tank was tested, and the concentrations of various pollutants were as follows: nickel ions not detected, chromium ions not detected, iron ions not detected, fluoride ions 1.0 mg / L, sulfate ions 350 mg / L, nitrate ions 5 mg / L, and pH value 7.57. The effluent quality meets the reuse requirements of the pickling process rinsing water of the enterprise and can be directly reused; the biological sludge is discharged into the biological sludge treatment system for treatment.
[0037] Example 2 The wastewater quality of a stainless steel pickling wastewater is shown in the table below. After a series of treatment measures, including preliminary removal of heavy metals and fluoride ions using heavy metal capture agents and calcium carbonate industrial solid waste, deep removal of fluoride ions and heavy metals via a crystallizing fluidized bed, and simultaneous removal of sulfates and nitrates by microbial methods, the effluent meets the requirements for production reuse. The specific treatment process is as follows: Preliminary removal of heavy metals and fluoride ions by heavy metal scavenging agent and calcium carbonate industrial solid waste: The above-mentioned pickling wastewater was introduced into the heavy metal scavenging tank at a flow rate of 5 m³ / h. A heavy metal scavenging agent with a mass concentration of 10% was added to the heavy metal scavenging tank at a dosage of 0.6 L / m³ of wastewater, and the mixture was stirred and reacted for 30 min. Subsequently, the wastewater enters the calcium carbonate industrial waste pool, and calcium carbonate industrial waste powder with a particle size of 100-200 mesh is added to the pool at a dosage of 220g / m³ of wastewater. The mixture is stirred and reacted for 60 minutes. During this process, the CO2 gas generated is collected through the top gas collection pipe and then introduced into the pressurized dissolved gas system. After the reaction, the pH value of the wastewater rises to 4.5. Next, the wastewater enters the coagulation tank, and 5% polyaluminum chloride coagulant is added to the coagulation tank at a dosage of 1.0 L / m³ of wastewater. The mixture is stirred and reacted for 15 min. Then, 0.1% polyacrylamide coagulant is added at a dosage of 0.2 L / m³ of wastewater, and the mixture is stirred and reacted for 5 min. Finally, the wastewater enters the sedimentation tank for sludge-water separation. The sedimentation time is 2 hours. The supernatant from the sedimentation tank enters the subsequent treatment, while the physicochemical sludge is discharged into the physicochemical sludge treatment system.
[0038] Deep removal of fluoride ions and heavy metals by a crystallization fluidized bed: The supernatant from the sedimentation tank enters the crystallization fluidized bed, where crystal nuclei with a particle size of 50-100 μm are pre-added at a rate of 50 g / m³ of wastewater. A 20% Ca(OH)₂ solution is added to the crystallization fluidized bed via a Ca(OH)₂ dosing device at a rate of 0.8 L / m³ of wastewater. The operating temperature of the crystallization fluidized bed is controlled at 25℃, and the hydraulic retention time is 40 min. Simultaneously, a pressurized dissolved gas system pressurizes collected CO₂ gas to 0.3 MPa and introduces it into the crystallization fluidized bed at a flow rate of 0.5 m³ / h. The wastewater treated by the crystallization fluidized bed is then separated by sedimentation and enters the biological treatment system.
[0039] Simultaneous removal of sulfate and nitrate by microbial method: Wastewater from the crystallization fluidized bed treatment enters the sulfate reduction tank, where it is inoculated with anaerobic bacteria (sulfate-reducing bacteria concentration of 10). 8 (CFU / mL), control the dissolved oxygen concentration in the tank to ≤0.2mg / L, temperature 30℃, hydraulic retention time 8h; Subsequently, the wastewater enters a sulfur autotrophic denitrification tank, which is inoculated with sulfur autotrophic denitrifying bacteria (concentration of 10). 7 (CFU / mL), control temperature 28℃, hydraulic retention time 6h, and at the same time, the excess CO2 gas in the pressurized dissolved air system is introduced into the sulfur autotrophic denitrification tank at a flow rate of 0.3m³ / h. The effluent from the sulfur autotrophic denitrification tank meets the reuse requirements of the pickling process water for the company and can be directly reused; the biological sludge is discharged into the biological sludge treatment system for treatment.
[0040] Conclusion: The final effluent quality fully meets the requirements for reuse of rinsing water in the stainless steel pickling process.
[0041] As can be seen from the above embodiments, the treatment system and method of the present invention can effectively remove various pollutants from stainless steel pickling wastewater, realize the reuse of wastewater, and have low treatment costs, stable operation, and good economic and environmental benefits.
[0042] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A method for reusing and treating stainless steel pickling wastewater, characterized in that: Includes the following steps: Step 1: Preliminary removal of heavy metals and fluoride ions in heavy metal capture ponds and calcium carbonate industrial solid waste ponds; Step 2: Deep removal of fluoride ions and heavy metals by a crystallization fluidized bed; Step 3: Simultaneous removal of sulfate and nitrate by microbial method.
2. The method for recycling stainless steel pickling wastewater according to claim 1, characterized in that: In step one, the initial removal includes the following steps: (1) Pass the stainless steel pickling wastewater into the heavy metal capture tank, add heavy metal capture agent into the heavy metal capture tank to form a stable chelate precipitate. (2) The wastewater in the heavy metal capture tank is fed into the calcium carbonate industrial waste tank, and calcium carbonate industrial waste powder is added to the calcium carbonate industrial waste tank at the same time to make the wastewater and calcium carbonate industrial waste powder fully mixed. (3) Pass the mixed liquid in the calcium carbonate industrial waste pool into the coagulation tank, add coagulant into the coagulation tank, and the coagulant forms flocs in the wastewater. The flocs adsorb calcium fluoride precipitate, heavy metal carbonate precipitate and other small suspended solids in the water. (4) The mixed liquid in the coagulation tank is fed into the sedimentation tank for mud-water separation. The settled sludge is discharged into the physicochemical sludge treatment system through the sludge outlet of the sedimentation tank for treatment, while the supernatant of the sedimentation tank enters the subsequent treatment process.
3. The method for reusing and treating stainless steel pickling wastewater according to claim 1, characterized in that: In step two, depth removal includes the following steps: (1) Pass the supernatant from the sedimentation tank into the crystallization fluidized bed, and simultaneously add Ca(OH)2 into the crystallization fluidized bed through the Ca(OH)2 dosing device. Crystal nuclei are pre-added into the crystallization fluidized bed. (2) During the operation of the crystallization fluidized bed, the pressurized dissolved gas system pressurizes the collected CO2 gas and introduces it into the crystallization fluidized bed.
4. The method for reusing and treating stainless steel pickling wastewater according to claim 1, characterized in that: In step three, the simultaneous removal specifically includes: first, the wastewater treated by the crystallization fluidized bed is fed into the sulfate reduction tank, and then the mixed liquid in the sulfate reduction tank is fed into the sulfur autotrophic denitrification tank; during the sulfur autotrophic denitrification reaction, the pressurized dissolved gas system introduces excess CO2 gas into the sulfur autotrophic denitrification tank; part of the wastewater treated by the sulfur autotrophic denitrification tank is directly reused in stainless steel production, and part is returned to the sulfate reduction tank.
5. A stainless steel pickling wastewater reuse and treatment system, characterized in that: It includes a physicochemical treatment system and a biological treatment system, wherein the physicochemical treatment system and the biological treatment system are connected; The physicochemical treatment system includes a heavy metal capture system, a crystallization fluidized bed system, and a physicochemical sludge treatment system. The heavy metal capture system is connected to the crystallization fluidized bed system. The crystallization fluidized bed system is connected to both the physicochemical sludge treatment system and the biological treatment system. The physicochemical sludge treatment system is also connected to the heavy metal capture system. The biological treatment system includes a sulfate reduction system, a sulfur autotrophic denitrification system, and a biological sludge treatment system. The sulfate reduction system is connected to the crystallization fluidized bed system and the sulfur autotrophic denitrification system, respectively. The sulfur autotrophic denitrification system is connected to the biological sludge treatment system, and the biological sludge treatment system is connected to the sulfate reduction system.
6. The stainless steel pickling wastewater reuse treatment system according to claim 5, characterized in that: The heavy metal capture system includes a heavy metal capture tank, a calcium carbonate industrial waste tank, a coagulation tank, and a sedimentation tank. The heavy metal capture tank is connected to the calcium carbonate industrial waste tank and the physicochemical sludge treatment system, respectively. The calcium carbonate industrial waste tank is connected to the coagulation tank and the physicochemical sludge treatment system, respectively. The coagulation tank is connected to the sedimentation tank, and the sedimentation tank is connected to the crystallization fluidized bed system and the physicochemical sludge treatment system, respectively.
7. A stainless steel pickling wastewater reuse and treatment system according to claim 5, characterized in that: A gas collection pipe is installed at the top of the calcium carbonate industrial waste pool; the sludge outlet of the sedimentation tank is connected to the physicochemical sludge treatment system.
8. A stainless steel pickling wastewater reuse and treatment system according to claim 5, characterized in that: The crystallization fluidized bed system includes a crystallization fluidized bed and a pressurized dissolved air system. The inlet of the crystallization fluidized bed is connected to the supernatant outlet of the sedimentation tank via a pipe, and a Ca(OH)2 dosing device is installed on the connecting pipe. The crystallization fluidized bed is connected to both a physicochemical sludge treatment system and a sulfate reduction system. The air inlet of the pressurized dissolved air system is connected to a gas collection pipe at the top of the calcium carbonate industrial waste pond via a pipe, and the air outlet of the pressurized dissolved air system is connected to the crystallization fluidized bed.
9. A stainless steel pickling wastewater reuse and treatment system according to claim 8, characterized in that: The sulfate reduction system includes a sulfate reduction tank, the inlet of which is connected to the outlet of the crystallization fluidized bed via a pipe. The sulfate reduction tank is equipped with an anaerobic environment and sulfate-reducing bacteria.
10. A stainless steel pickling wastewater reuse and treatment system according to claim 9, characterized in that: The sulfur autotrophic denitrification system includes a sulfur autotrophic denitrification tank, the inlet of which is connected to the outlet of a sulfate reduction tank. The sulfur autotrophic denitrification tank is equipped with sulfur autotrophic denitrifying bacteria. The outlet of the pressurized dissolved air system is also connected to the sulfur autotrophic denitrification tank via a pipeline. The inlet of the biological sludge treatment system is connected to the sludge outlets of the sulfate reduction tank and the sulfur autotrophic denitrification tank, respectively.