Method and system for removing heavy metals in wastewater

Abstract

The invention belongs to the technical field of wastewater treatment, and particularly relates to a method and system for removing heavy metals in wastewater, and the system comprises a collecting tank, a regulating tank, a Fenton-ultrasonic synergistic reaction tank, an addition and reduction sedimentation tank, a flocculation tank, a first sedimentation tank, a three-cavity nickel removal tank, a second sedimentation tank, a multi-parameter monitoring tank, an A / O tank, a third sedimentation tank and a clean water tank which are communicated in sequence. Discharging the adjusted wastewater containing the heavy metals into a Fenton-ultrasonic synergistic reaction tank to realize complex breaking of the complex-state heavy metals; adjusting the wastewater subjected to complex breaking treatment to be neutral, so that heavy metals are converted into hydroxide precipitates, and most of the heavy metals are removed at the stage; discharging the treated water into a flocculation tank, standing and precipitating, and enabling supernate to enter a nickel removal tank; and an organic sulfur catching agent is added into the nickel removal tank to strengthen chelation reaction, so that the nickel content is less than 0.1 ppm. According to the system, through four-stage cooperation of oxidation, precipitation, dynamic capture and intelligent feedback, the complex nickel removal problem is solved, and the comprehensive heavy metal removal rate is larger than or equal to 99.5%.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of wastewater treatment, and particularly relates to a method and system for removing heavy metals in wastewater. BACKGROUND

[0002] The existing heavy metal wastewater treatment method has problems such as incomplete removal of complex heavy metals, low reaction efficiency, large consumption of reagents, high risk of secondary pollution of sludge, etc. The simple Fenton reaction has limited efficiency in breaking the complex heavy metals, and the single-cavity reaction of the traditional nickel removal tank easily leads to uneven mixing of reagents, and the heavy metals in the sludge after dewatering are easy to leach out, which is difficult to meet the strict environmental protection requirements. Therefore, it is of great significance to develop an integrated technology with high efficiency, intelligent control, and safe disposal of sludge. SUMMARY

[0003] The technical problem to be solved by the application is to provide a method for removing heavy metals in wastewater, which can realize efficient and stable removal of heavy metals by strengthening reaction efficiency, optimizing reaction process, and intelligent control and safe disposal.

[0004] In order to achieve the above-mentioned purpose, the technical scheme adopted by the application is as follows: A method for removing heavy metals in wastewater, comprising the following steps: S1, the heavy metal wastewater is sent into a collection tank for full stirring and homogenization, and then into a pH adjusting tank for adjusting pH; S2, then sent into a Fenton-ultrasonic synergistic reaction tank, and ferrous sulfate and hydrogen peroxide are added by a reagent adding system, and the reaction is carried out under the synergistic action of stirring and ultrasonic for 1-1.5h; S3, the effluent of the Fenton-ultrasonic tank is sent into an alkali addition precipitation tank, calcium hydroxide solution is added to adjust to neutral, and hydroxide precipitate is formed; S4, the effluent of the alkali addition precipitation tank is sent into a flocculation tank, polyacrylamide solution is added, and slow stirring reaction is carried out; the effluent of the reaction is sent into a first precipitation tank for standing and precipitation; S5, the supernatant of the first precipitation tank is sent into a three-cavity nickel removal tank, and after chelation, flocculation and maturation reaction, the effluent is sent into a second precipitation tank; S6, the supernatant of the second precipitation tank is sent into a multi-parameter monitoring tank, and the effluent is fed back to the three-cavity nickel removal tank or the Fenton-ultrasonic synergistic reaction tank through online detection and feedback control; S7, the effluent meeting the standard is sent into an A / O tank to remove organic matters such as COD, and the effluent is separated from sludge in a third precipitation tank and then sent into a clear water tank for discharge; S8, the sludge in the alkali addition precipitation tank, the first precipitation tank, the second precipitation tank and the A / O tank is sent into a sludge tank for deep solidification-dewatering module treatment, the sludge cake is transported out, and the filtrate is sent back into the collection tank.

[0005] Specifically, in step S1, the heavy metals in the wastewater include at least nickel; and the pH of the wastewater in the adjusting tank is controlled at 2.5-3.5.

[0006] Specifically, in step S2, the medicament adding system dynamically adds ferrous sulfate and hydrogen peroxide according to the ORP value, the adding amount is 400-500 mg / L of ferrous sulfate and 200-300 mg / L of hydrogen peroxide, so that the ORP value is controlled at 200-300 mV; at the same time, the ultrasonic device is started, and the reaction is carried out under the stirring of 200-300 W, 20-40 kHz and 30-40 revolutions / minute for 1-1.5 h, so as to strengthen the complex heavy metal complex.

[0007] Specifically, in step S3, the calcium hydroxide aqueous solution with a mass concentration of 0.05%-0.3% is added to the alkaline precipitation tank to adjust the pH to 7-8, so as to form hydroxide precipitate, and the stirring is carried out for 10-15 minutes.

[0008] Specifically, in step S4, the polyacrylamide aqueous solution with a mass concentration of 0.1%-0.2% is added to the flocculation tank, the adding amount is 5-6 ml / L, and slow stirring is carried out to promote the formation of flocs.

[0009] Specifically, in step S5, in the chelation reaction, the organic sulfur capture agent aqueous solution with a mass concentration of 4-6% is added, the adding amount of the organic sulfur capture agent is 8-10 times of the content of the heavy metal, and the stirring is carried out at 40-50 revolutions / minute for 8-10 min; In the flocculation reaction, the polyaluminum chloride aqueous solution with a mass concentration of 4-6% is added, the adding amount of the polyaluminum chloride is equal to that of the organic sulfur capture agent, and the stirring is carried out at 30-35 revolutions / minute for 5-6 min; In the maturation reaction, the polyacrylamide solution with a mass concentration of 0.1% is added at 4-5 ml / L of wastewater, and the stirring is carried out at 15-20 revolutions / minute for 3-5 min.

[0010] Specifically, in step S6, the multi-parameter monitoring tank is monitored in real time by an online nickel ion monitor and a COD detector, when the nickel concentration is 0.1-0.5 mg / L, the wastewater is returned to the three-cavity nickel removal tank, when the nickel concentration is >0.5 mg / L, the wastewater is returned to the Fenton-ultrasonic synergistic reaction tank, and the wastewater meeting the standard is introduced into the A / O system.

[0011] Specifically, in step S7, the A / O tank is stirred in the anoxic zone and aerated in the aerobic zone to control the dissolved oxygen at 2-4 mg / L, the O tank is filled with high-density polyethylene fillers, the filling rate is 20%-50%, and the sludge return ratio is 50%-100%.

[0012] Specifically, in step S8, each sludge is introduced into a sludge tank, and a nano zirconium phosphate and cement composite solidification agent is added, the adding amount is 5-8% of the dry weight of the sludge, the sludge is dewatered by a filter press to a water content of ≤60%, the sludge cake is transported and disposed, and the filtrate is returned to a collection tank.

[0013] Further, the application also claims the above-mentioned system for removing heavy metals in wastewater, comprising a collection tank, an adjusting tank, a Fenton-ultrasonic synergistic reaction tank, an alkali precipitation tank, a flocculation tank, a first precipitation tank, a three-cavity nickel removal tank, a second precipitation tank, a multi-parameter monitoring tank, an A / O tank, a third precipitation tank, and a clean water tank connected in sequence. The collection tank is provided with a stirring device. The pH self-adaptive adjusting device in the adjusting tank is linked with a metering pump through a pH sensor, and automatically adds dilute sulfuric acid to stabilize the pH at 2.5-3.5, with an adjusting response time of ≤30s. The Fenton-ultrasonic synergistic reaction tank is provided with an ultrasonic transducer, a ferrous sulfate adding device, a hydrogen peroxide adding device, and a stirring device. The medicament adding system comprises an online sensor monitoring, a PLC controller, and a metering pump group, and dynamically adjusts the adding amount of ferrous sulfate, hydrogen peroxide, alkali, and nickel removal agent according to the real-time water quality pH, ORP, and heavy metal concentration, with a control accuracy of ±2%. The three-cavity nickel removal tank comprises a chelation cavity, a flocculation cavity, and a maturation cavity connected in sequence. The multi-parameter monitoring tank is provided with an online nickel ion monitor, a COD online detector, and a pH sensor, with a detection interval of 20-30 minutes; and a staged reflux system comprises a primary reflux pipe connected to the three-cavity nickel removal tank and a secondary reflux pipe connected to the Fenton-ultrasonic tank. The deep solidification-dewatering module comprises a sludge tank, a solidifying agent adding device, and a plate-and-frame filter press.

[0014] Compared with the prior art, the application has the following beneficial effects: (1) Fenton-ultrasonic synergistic reinforcement: ultrasonic cavitation effect promotes the generation of hydroxyl radicals, the decomplexation efficiency is improved by 20-30%, the reaction time is shortened by 25-33%, and the medicament consumption is reduced; (2) Three-cavity nickel removal tank segmented reaction: precise control of chelation-flocculation-maturation is realized, the medicament utilization rate is increased by 15%, and the nickel concentration is stably reduced to below 0.1 ppm; (3) Intelligent control system: through real-time feedback of ORP, pH, and heavy metal concentration, the medicament adding amount is optimized by 10-15%, and the operation cost is reduced by 20-25%; (4) Staged reflux design: invalid reflux is avoided, the treatment efficiency is improved by 15%, and the effluent stability is ensured to meet the standard; (5) Deep solidification of sludge: the heavy metal leaching concentration is ≤0.05 mg / L, meeting the hazardous waste disposal standard, and eliminating the risk of secondary pollution (6) High integration of the overall process, the comprehensive heavy metal removal rate is ≥99.7%, the COD removal rate is ≥90%, and it is suitable for high-difficulty heavy metal wastewater treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, and the above and / or other advantages of the present invention will become more apparent.

[0016] Figure 1 This is a schematic diagram of the process of removing heavy metals from wastewater according to the present invention. DETAILED DESCRIPTION

[0017] The present invention can be better understood with reference to the following examples.

[0018] like Figure 1 As shown, the system for removing heavy metals from wastewater of the present invention includes a collection tank, a regulating tank, a Fenton-ultrasonic synergistic reaction tank, an alkali precipitation tank, a flocculation tank, a first precipitation tank, a three-chamber nickel removal tank, a second precipitation tank, a multi-parameter monitoring tank, an A / O tank, a third precipitation tank, and a clear water tank connected in sequence; A stirring device is provided in the collecting tank; The pH self-adaptive adjustment device in the regulating tank is linked to the metering pump through the pH sensor, and automatically adds dilute sulfuric acid to stably control the pH at 2.5-3.5, with an adjustment response time of ≤30s; The Fenton-ultrasound synergistic reaction tank is equipped with an ultrasonic transducer, a ferrous sulfate dosing device, a hydrogen peroxide dosing device and a stirring device; The drug dosing system includes online sensor monitoring, PLC controller and metering pump group, which dynamically adjusts the dosage of ferrous sulfate, hydrogen peroxide, alkali solution and nickel removal agent according to the real-time water quality pH, ORP and heavy metal concentration, with a control accuracy of ±2%; The three-chamber nickel removal tank comprises a chelating chamber, a flocculation chamber, and a maturation chamber which are connected in sequence; The multi-parameter monitoring pool is equipped with an online nickel ion monitor, a COD online detector and a pH sensor, with a detection interval of 20-30 minutes; the graded reflux system includes a primary reflux pipe connected to the three-chamber nickel removal pool and a secondary reflux pipe connected to the Fenton-ultrasonic pool; The deep solidification-dehydration module includes a sludge tank, a solidifying agent dosing device and a plate and frame filter press.

[0019] The specific removal methods are as follows: S1. Send the heavy metal wastewater into the collection tank for thorough mixing and homogenization, and then send it into the regulating tank for pH adjustment; S2, then sent to the Fenton-ultrasound synergistic reaction tank, added ferrous sulfate and hydrogen peroxide through the reagent dosing system, and reacted for 1-1.5 hours under the synergistic action of stirring and ultrasound; S3, the effluent from the Fenton-ultrasonic pool enters the alkali precipitation tank, where calcium hydroxide solution is added to adjust it to neutrality to form hydroxide precipitation; S4, the water from the alkaline precipitation tank enters the flocculation tank, polyacrylamide solution is added, and slow stirring reaction is carried out; the reaction water enters the first precipitation tank for standing and precipitation; S5, the supernatant of the first precipitation tank enters the three-cavity nickel removal tank, and after chelation, flocculation and maturation reaction, it enters the second precipitation tank; S6, the supernatant of the second precipitation tank enters the multi-parameter monitoring tank, and through online detection feedback control, it is classified and refluxed to the three-cavity nickel removal tank or the Fenton-ultrasonic synergistic reaction tank; S7, the standard wastewater enters the A / O tank to remove COD and other organic matters, the effluent is separated from the sludge in the third precipitation tank and then enters the clear water tank for discharge; S8, the sludge in the alkaline precipitation tank, the first precipitation tank, the second precipitation tank and the A / O tank is sent to the sludge tank for deep solidification-dewatering module treatment, the mud cake is transported out, and the filtrate is sent back to the collection tank.

[0020] In some embodiments, in step S1, the heavy metals in the wastewater at least include nickel; the pH of the wastewater in the conditioning tank is stably controlled at 2.5-3.5.

[0021] In some embodiments, in step S2, the reagent adding system dynamically adds ferrous sulfate and hydrogen peroxide according to the ORP value, the adding amount is 400-500 mg / L of ferrous sulfate and 200-300 mg / L of hydrogen peroxide, so that the ORP value is controlled at 200-300 mV; at the same time, the ultrasonic device is started, and the reaction is carried out under the stirring of 200-300 W, 20-40 kHz and 30-40 revolutions / minute for 1-1.5 h to strengthen the complexation of heavy metals.

[0022] In some embodiments, in step S3, calcium hydroxide solution with a mass concentration of 0.3% is added to the alkaline precipitation tank to adjust the pH to 7-8, the adding amount is 10-20 ml / L, and hydroxide precipitate is formed, and stirring is carried out for 10-15 minutes.

[0023] In some embodiments, in step S4, polyacrylamide solution with a mass concentration of 0.1% is added to the flocculation tank, and the adding amount is 5-6 ml / L, slow stirring is carried out to promote the formation of flocs.

[0024] In some embodiments, in step S5, during the chelation reaction, organic sulfur-based capture agent solution with a mass concentration of 5% is added, the adding amount of the organic sulfur-based capture agent is 8-10 times the content of heavy metals, and stirring is carried out at 40-50 revolutions / minute for 8-10 minutes; During the flocculation reaction, polyaluminum chloride solution with a mass concentration of 5% is added, the adding amount of the polyaluminum chloride is equal to that of the organic sulfur-based capture agent, and stirring is carried out at 30-35 revolutions / minute for 5-6 minutes; During the maturation reaction, 0.1% polyacrylamide solution is added at 4-5 ml / L of the wastewater, and the reaction is stirred at 15-20 revolutions per minute for 3-5 minutes.

[0025] In some embodiments, in step S6, the multi-parameter monitoring tank is monitored in real time by an online nickel ion monitor and a COD detector, and when the nickel concentration is 0.1-0.5 mg / L, the wastewater is returned to the three-cavity nickel removal tank, and when the nickel concentration is greater than 0.5 mg / L, the wastewater is returned to the Fenton-ultrasonic synergistic reaction tank, and the wastewater meeting the standard is introduced into the A / O system.

[0026] In some embodiments, in step S7, the A / O tank is stirred in the anoxic zone and aerated in the aerobic zone to control the dissolved oxygen at 2-4 mg / L, the O tank is filled with high-density polyethylene fillers, the filling rate is 20%-50%, and the sludge return ratio is 50%-100%.

[0027] In some embodiments, in step S8, each sludge enters a sludge tank, and a nanoscale zirconium phosphate and cement composite solidification agent is added, the addition amount is 5-8% of the dry weight of the sludge, and the sludge is dewatered by a filter press to a water content of ≤60%, the sludge cake is transported for disposal, and the filtrate is returned to a collection tank.

[0028] Specific application effects: Taking chemical nickel water in a certain place as an example, the chemical nickel water is washed from the sewage pipeline into a collection tank for preliminary mixing, the pH is adjusted to 3.0 in the adjusting tank, ferrous sulfate 450 mg / L and hydrogen peroxide 250 mg / L are added into the Fenton-ultrasonic tank, a 300W, 30kHz ultrasonic is started, and the stirring reaction is carried out for 1.2h; the pH is adjusted to 7.5 by adding alkali to form a hydroxide precipitate, and 0.1% PAM is added into the flocculation tank; the supernatant is introduced into the three-cavity nickel removal tank, 5% organic sulfur capture agent (10 times the nickel content) is added into the chelation cavity, an equal amount of 5% PAC is added into the flocculation cavity, and 0.1% PAM is added into the maturation cavity; the wastewater meeting the standard of the monitoring tank is introduced into the A / O system, and 5% composite solidification agent is added into the sludge to dewater to a water content of 55%. The running results show that the comprehensive removal rate of heavy metals is 99.8%, the nickel concentration is stably below 0.08 ppm, and the running cost is reduced by 22%.

[0029] The application provides a method and system for removing heavy metals from wastewater, and there are many methods and approaches for realizing the technical scheme, and the preferred embodiments of the application are described above, and it should be pointed out that ordinary technical personnel in the technical field can make some improvements and refinements without departing from the principles of the application, and these improvements and refinements should also be regarded as the protection scope of the application. The components not explicitly described in the embodiments can be realized by using the existing technology.

Claims

1. A method for removing heavy metals from wastewater, characterized in that: The steps include: S1. Send the heavy metal wastewater into the collection tank for thorough mixing and homogenization, and then send it into the regulating tank for pH adjustment; S2, then sent to the Fenton-ultrasound synergistic reaction tank, added ferrous sulfate and hydrogen peroxide through the reagent dosing system, and reacted for 1-1.5 hours under the synergistic action of stirring and ultrasound; S3, the effluent from the Fenton-ultrasonic pool enters the alkali precipitation tank, where calcium hydroxide solution is added to adjust it to neutrality to form hydroxide precipitation; S4, the effluent from the alkali sedimentation tank enters the flocculation tank, where polyacrylamide solution is added and slowly stirred for reaction; the effluent from the reaction enters the first sedimentation tank for static precipitation; S5. The supernatant from the first sedimentation tank enters the three-chamber nickel removal tank, and then enters the second sedimentation tank after undergoing chelation, flocculation, and aging reactions in sequence; S6. The supernatant of the second sedimentation tank enters the multi-parameter monitoring tank and is graded and refluxed to the three-chamber nickel removal tank or the Fenton-ultrasonic synergistic reaction tank through online detection feedback control; S7, the wastewater that meets the standards enters the A / O tank to remove COD and other organic matter, and the effluent is separated by mud and water in the third sedimentation tank and then enters the clear water tank for discharge; S8. The sludge in the alkali sedimentation tank, the first sedimentation tank, the second sedimentation tank, and the A / O tank is sent to the sludge tank deep solidification-dehydration module for treatment, the mud cake is transported out, and the filtrate is sent back to the collection tank.

2. The method for removing heavy metals from wastewater according to claim 1, wherein In step S1, the heavy metals in the wastewater include at least nickel; and the pH of the wastewater in the regulating tank is stably controlled at 2.5-3.

5.

3. The method for removing heavy metals from wastewater according to claim 1, wherein In step S2, the drug dosing system dynamically adds ferrous sulfate and hydrogen peroxide according to the ORP value, with the dosage being 400-500 mg / L ferrous sulfate and 200-300 mg / L hydrogen peroxide, so that the ORP value is controlled at 200-300 mV; at the same time, the ultrasonic device is turned on, and the reaction is carried out for 1-1.5 hours under stirring at 200-300 W, 20-40 kHz, and 30-40 rpm to enhance the decomposition of complexed heavy metals.

4. The method for removing heavy metals from wastewater according to claim 1, wherein In step S3, a calcium hydroxide aqueous solution with a mass concentration of 0.05% to 0.3% is added to the alkali precipitation tank to adjust the pH to 7-8 to form a hydroxide precipitate, and the mixture is stirred for 10-15 minutes.

5. The method for removing heavy metals from wastewater according to claim 1, wherein In step S4, a polyacrylamide aqueous solution with a mass concentration of 0.1% to 0.2% is added to the flocculation tank in an amount of 5 to 6 ml / L, and slow stirring is performed to promote floc formation.

6. The method for removing heavy metals from wastewater according to claim 1, characterized in that In step S5, during the chelation reaction, an organic sulfur scavenger aqueous solution with a mass concentration of 4-6% is added, and the amount of the organic sulfur scavenger added is 8-10 times the heavy metal content, and the reaction is stirred at 40-50 rpm for 8-10 minutes; During the flocculation reaction, add a 4-6% polyaluminium chloride solution, the amount of polyaluminium chloride added is equal to the amount of the organic sulfur scavenger, and stir at 30-35 rpm for 5-6 minutes; During the aging reaction, add 0.1% polyacrylamide solution to 4-5 ml / L of wastewater, and stir at 15-20 rpm for 3-5 minutes.

7. The method for removing heavy metals from wastewater according to claim 1, wherein: In step S6, the multi-parameter monitoring pool is monitored in real time by an online nickel ion monitor and a COD detector. When the nickel concentration is 0.1-0.5 mg / L, it is returned to the three-chamber nickel removal pool. When it is greater than 0.5 mg / L, it is returned to the Fenton-ultrasonic synergistic reaction pool. The qualified wastewater enters the A / O system.

8. The method for removing heavy metals from wastewater according to claim 1, wherein: In step S7, the anoxic zone of the A / O tank is stirred and the aerobic zone is aerated to control the dissolved oxygen to 2-4 mg / L, the O tank is filled with high-density polyethylene filler, the filling rate is 20%-50%, and the sludge return ratio is 50%-100%.

9. The method for removing heavy metals from wastewater according to claim 1, wherein: In step S8, each sludge enters the sludge pool, and nano-scale zirconium phosphate and cement composite curing agent are added in an amount of 5-8% of the dry weight of the sludge. The sludge is dehydrated by a filter press to a moisture content of ≤60%. The mud cake is transported out for disposal, and the filtrate is returned to the collection pool.

10. A system for implementing the method according to any one of claims 1 to 9, characterized in that: It includes a collection tank, a regulating tank, a Fenton-ultrasonic synergistic reaction tank, an alkali-adding sedimentation tank, a flocculation tank, a first sedimentation tank, a three-chamber nickel removal tank, a second sedimentation tank, a multi-parameter monitoring tank, an A / O tank, a third sedimentation tank, and a clear water tank, which are connected in sequence; A stirring device is provided in the collecting tank; The pH self-adaptive adjustment device in the regulating tank is linked to the metering pump through the pH sensor, and automatically adds dilute sulfuric acid to stably control the pH at 2.5-3.5, with an adjustment response time of ≤30s; The Fenton-ultrasound synergistic reaction tank is equipped with an ultrasonic transducer, a ferrous sulfate dosing device, a hydrogen peroxide dosing device and a stirring device; The drug dosing system includes online sensor monitoring, PLC controller and metering pump group, which dynamically adjusts the dosage of ferrous sulfate, hydrogen peroxide, alkali solution and nickel removal agent according to the real-time water quality pH, ORP and heavy metal concentration, with a control accuracy of ±2%; The three-chamber nickel removal tank comprises a chelating chamber, a flocculation chamber, and a maturation chamber which are connected in sequence; The multi-parameter monitoring pool is equipped with an online nickel ion monitor, a COD online detector and a pH sensor, with a detection interval of 20-30 minutes; the graded reflux system includes a primary reflux pipe connected to the three-chamber nickel removal pool and a secondary reflux pipe connected to the Fenton-ultrasonic pool; The deep solidification-dehydration module includes a sludge tank, a solidifying agent dosing device and a plate and frame filter press.

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