Advanced treatment technology for cadmium-containing wastewater

Abstract

The invention discloses a cadmium-containing wastewater advanced treatment technology, and relates to the technical field of wastewater treatment.The treatment technology comprises the following steps that S1, raw water pretreatment is conducted, specifically, acidic cadmium-containing wastewater is independently collected, a precipitator is added, stirring is conducted, and after aeration and standing are conducted, supernate and sediment are obtained; s2, deep treatment: carrying out advanced oxidation treatment on the pretreated wastewater to break complexation; s3, follow-up treatment: adding a special chelating agent into the wastewater subjected to advanced treatment for treatment; s4, detecting and discharging: discharging the treated wastewater into an intermediate water tank after the treated wastewater is detected to be qualified. The cadmium-containing wastewater is deeply treated by using the complex breaking agent and the heavy metal capturing agent, so that cadmium ions and other harmful substances in the wastewater can be efficiently removed, deep purification of the wastewater is realized, the effluent quality is ensured to meet the discharge standard, and the problems of low discharge standard and high treatment difficulty of the cadmium-containing wastewater are solved; the requirement of long-term operation of a sewage plant is met, and remarkable economic benefits and social benefits are brought.

Description

Technical Field

[0001] The invention relates to the technical field of wastewater treatment, and in particular to a deep treatment technology for cadmium-containing wastewater. Background Art

[0002] With the rapid development of modern industrial production, especially the rapid development of metal smelting, mining, electroplating and other industries, the discharge of cadmium-containing wastewater has increased significantly. Cadmium is a toxic and harmful heavy metal element that is extremely harmful to the human body and the environment. Therefore, the treatment of cadmium-containing wastewater has become an urgent problem to be solved. At present, the treatment methods of cadmium-containing wastewater are mainly divided into three categories: physical method, chemical method and biological method. Physical methods mainly include precipitation, filtration, adsorption, etc.; chemical methods mainly include oxidation-reduction, neutralization precipitation, complex precipitation, etc.; biological methods mainly use microorganisms or plants to absorb and transform cadmium in wastewater. However, these traditional methods have some problems in treatment effect, treatment efficiency, cost and secondary pollution. Because the enterprise has acidic cadmium plating, its complexing property is strong and the discharge concentration is very low. In order to ensure that the drainage meets the standards, a deep treatment technology for cadmium-containing wastewater is urgently needed to treat the cadmium-containing wastewater in depth.

[0003] The existing technology has the following problems:

[0004] Traditional methods are difficult to use when treating high-concentration cadmium-containing wastewater, and it is often difficult to achieve the ideal removal effect. Some methods require a long treatment time, and a large amount of energy and chemical reagents are consumed during the treatment process. The sediment and waste residue generated during the treatment process may cause secondary pollution to the environment. Summary of the invention

[0005] The present invention provides a cadmium-containing wastewater deep treatment technology to solve the problems raised in the above background technology.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0007] A cadmium-containing wastewater deep treatment technology, the treatment technology comprises the following steps:

[0008] S1. Raw water pretreatment: collect the acidic cadmium-containing wastewater separately, add a precipitant, stir it, aerate it and let it stand to obtain a supernatant and sediment;

[0009] S2, advanced treatment: subjecting the pre-treated wastewater to advanced oxidation treatment to break the complex;

[0010] S3, subsequent treatment: adding a special chelating agent to the wastewater after deep treatment for treatment;

[0011] S4. Testing and discharge: The treated wastewater is discharged into the intermediate water tank after passing the test.

[0012] Preferably, the precipitant is one or more of calcium oxide, sodium hydroxide, calcium hydroxide, sodium carbonate, and sodium bicarbonate solutions with a concentration of ≥5%.

[0013] Preferably, after adding the agent to S1, the pH value of the wastewater is adjusted to 5-9, and the aeration time is 10-20 minutes.

[0014] Preferably, S2 comprises the following steps:

[0015] Add 0.5% of complex breaking agent to the pretreated wastewater and stir it. After reacting for 30 minutes, pump it to the cadmium concentration reduction line for concentration reduction treatment, collect the ions with strong complexing ability and then re-treat them further.

[0016] Adjust the pH of the cadmium-containing wastewater after the concentration reduction treatment to 3-4, add 0.5% of the complex breaking agent again for stirring, react for 30 minutes, pump it to the cadmium treatment line, add a heavy metal capture agent for treatment, and filter it using a filtering device to obtain a supernatant and a sediment;

[0017] If in the process experiment, the cadmium-containing wastewater has a strong complexing property after concentration reduction and the complex breaking agent cannot achieve the expected complex breaking effect, it is necessary to change the complex breaking agent in the second step to Fenton reagent for Fenton oxidation process treatment.

[0018] Preferably, the heavy metal capture agent includes inorganic salt heavy metal capture agents and organic heavy metal capture agents. The inorganic salt heavy metal capture agent includes but is not limited to sodium sulfide, polyaluminium chloride, iron salts, and phosphates. The organic heavy metal capture agent includes but is not limited to organosulfur TMT heavy metal capture agents and polyamine heavy metal capture agents.

[0019] Preferably, the Fenton reagent is ferrous sulfate and hydrogen peroxide, and in the Fenton oxidation process, ferrous sulfate is first added and then hydrogen peroxide is added. The process parameters of the Fenton oxidation process are:

[0020] The dosage of ferrous sulfate is 20 mg / L;

[0021] The dosage of hydrogen peroxide is 100 mg / L;

[0022] pH value is 3-5;

[0023] The reaction time is 20-30min.

[0024] Preferably, the special chelating agent is a composite chelating agent prepared by compounding trisodium thiocyanate and sodium dimethyldithiocarbamate, and the mass ratios of trisodium thiocyanate and sodium dimethyldithiocarbamate are 20%-65% and 35%-80% respectively.

[0025] Preferably, S3 comprises: adding a special chelating agent to the deeply treated wastewater, the mass ratio of the special chelating agent to the wastewater being 1:200-1:5000, stirring for 5-30 minutes, then adding polyalumina, the mass ratio of polyalumina to the wastewater being 1:200-1:5000, stirring again for 5-30 minutes, standing at room temperature for 0.5-12 hours, and filtering using a filter.

[0026] Due to the adoption of the above technical solution, the present invention has the following technical advances compared with the prior art:

[0027] 1. The present invention provides a cadmium-containing wastewater deep treatment technology. By using a complex-breaking agent and a heavy metal capture agent to deeply treat the cadmium-containing wastewater, the cadmium ions and other harmful substances in the wastewater can be efficiently removed, and the deep purification of the wastewater can be achieved. It ensures that the effluent water quality meets the discharge standards, solves the problems of low discharge standards and great treatment difficulty of cadmium-containing wastewater, meets the needs of long-term operation of sewage treatment plants, brings significant economic and social benefits, and has a simple process flow.

[0028] 2. The present invention provides a deep treatment technology for cadmium-containing wastewater. A special chelating agent is used to form a stable chelate with heavy metal ions in the wastewater to remove them from the wastewater. The cadmium concentration in the treated wastewater is far lower than the national emission standard, and the chelate precipitation is stable, which reduces the secondary pollution of the environment caused by cadmium precipitates. The technology is environmentally friendly, energy-efficient, has little precipitation, is non-toxic, and reduces the treatment cost.

[0029] 3. The present invention provides a deep treatment technology for cadmium-containing wastewater, which improves the treatment efficiency and reduces the treatment cost of cadmium-containing wastewater by optimizing the wastewater treatment process. In the process experiment, when the cadmium-containing wastewater after concentration reduction has strong complexing and the complex breaking agent cannot achieve the expected complex breaking effect, the complex breaking agent is replaced by Fenton reagent for Fenton oxidation process treatment, thereby ensuring that the treatment effect is stable and reliable, shortening the treatment time of the wastewater, and avoiding the consumption of a large amount of energy and chemical reagents.

[0030] 4. The present invention provides a deep treatment technology for cadmium-containing wastewater. By using a precipitant to remove part of the cadmium ions in the wastewater, and then using a deep treatment technology to deeply remove the cadmium, the amount of precipitant used can be effectively reduced, the scaling rate of the on-site process can be reduced, the descaling maintenance time can be reduced, and the production efficiency can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The present invention is a process flow chart for the deep treatment of cadmium-containing wastewater. DETAILED DESCRIPTION

[0032] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further explained below in conjunction with specific implementation methods.

[0033] like Figure 1 As shown, a deep treatment technology for cadmium-containing wastewater includes the following steps:

[0034] S1. Raw water pretreatment: collect the acidic cadmium-containing wastewater separately, add a precipitant, stir it, aerate it and let it stand to obtain a supernatant and sediment;

[0035] S2, advanced treatment: subjecting the pre-treated wastewater to advanced oxidation treatment to break the complex;

[0036] S3, subsequent treatment: adding a special chelating agent to the wastewater after deep treatment for treatment;

[0037] S4. Testing and discharge: The treated wastewater is discharged into the intermediate water tank after passing the test.

[0038] Cadmium-containing wastewater is treated through the steps of raw water pretreatment, deep treatment, subsequent treatment, detection and discharge, which can effectively remove cadmium ions in the wastewater, realize deep purification and reuse of wastewater, and help to achieve effective treatment of cadmium-containing wastewater and sustainable development of the environment. The use of precipitants to remove some cadmium ions in the wastewater, and then using deep treatment technology to deeply remove cadmium, can effectively reduce the amount of precipitants, reduce the scaling rate of on-site processes, reduce the descaling and maintenance time, and improve production efficiency. Since the implementation of this process plan, a total of 6,720 tons of cadmium-containing wastewater have been treated, with a reagent cost of 9.35 yuan / ton and a total sewage treatment plant cost of about 50 yuan / ton, which can basically meet the long-term operation needs of the sewage treatment plant. Cadmium is a necessary electroplating process for aerospace and military enterprises, and its wastewater treatment is a problem that has plagued the development of the industry for a long time. This process solves the problem of treating cadmium-containing wastewater and has a great promoting effect on the development of the above industries, thereby bringing significant economic and social benefits.

[0039] The precipitant is one or more of calcium oxide, sodium hydroxide, calcium hydroxide, sodium carbonate and sodium bicarbonate solutions with a concentration of ≥5%.

[0040] After adding the reagent to S1, adjust the pH value of the wastewater to 5-9 and the aeration time to 10-20 minutes.

[0041] S2 includes the following steps:

[0042] Add 0.5% of complex breaking agent to the pretreated wastewater and stir it. After reacting for 30 minutes, pump it to the cadmium concentration reduction line for concentration reduction treatment. The purpose of this step is to separate the cadmium ions with weak complexing and easy to handle in the cadmium-containing wastewater, and collect the ions with strong complexing and re-process them further.

[0043] Adjust the pH of the cadmium-containing wastewater after the concentration reduction treatment to 3-4, add 0.5% of the complex breaking agent again for stirring, react for 30 minutes, pump it to the cadmium treatment line, add a heavy metal capture agent for treatment, and filter it using a filtering device to obtain a supernatant and a sediment;

[0044] If in the process experiment, the cadmium-containing wastewater has a strong complexing property after concentration reduction, and the complex breaking agent cannot achieve the expected complex breaking effect, it is necessary to change the complex breaking agent in the second step to Fenton reagent for Fenton oxidation process treatment. This can make full use of the efficient oxidation degradation ability of the Fenton oxidation process, improve the removal rate of cadmium ions, and purify water quality, which will help improve the overall efficiency of wastewater treatment, meet the requirements of environmental protection and sustainable development, optimize the wastewater treatment process, improve the treatment efficiency, and reduce the treatment cost of cadmium-containing wastewater.

[0045] Complex breakers are oxidants, and their main function is to oxidize and decompose complexes in wastewater into free metal ions, thus creating conditions for the subsequent heavy metal capture and chelation process.

[0046] Heavy metal scavengers chelate heavy metal ions through a variety of chelating groups to form stable insoluble substances and precipitate, thereby achieving the purpose of removing heavy metal ions. In addition, heavy metal scavengers can also significantly increase the precipitation speed and removal rate through flocculation and net capture under the action of macromolecules in their body structure;

[0047] By using complex breakers and heavy metal capture agents to deeply treat cadmium-containing wastewater, cadmium ions and other harmful substances in the wastewater can be efficiently removed, deep purification of the wastewater can be achieved, and the effluent quality can be ensured to meet the emission standards. This solves the problem of low emission standards and difficult treatment of cadmium-containing wastewater, meets the needs of long-term operation of sewage treatment plants, and brings significant economic and social benefits.

[0048] Heavy metal capture agents include inorganic salt heavy metal capture agents and organic heavy metal capture agents. Inorganic salt heavy metal capture agents include but are not limited to sodium sulfide, polyaluminium chloride, iron salts, and phosphates. Organic heavy metal capture agents include but are not limited to organosulfur TMT heavy metal capture agents and polyamine heavy metal capture agents.

[0049] The Fenton reagent is ferrous sulfate and hydrogen peroxide. In the Fenton oxidation process, ferrous sulfate is added first and then hydrogen peroxide. The process parameters of the Fenton oxidation process are:

[0050] The dosage of ferrous sulfate is 20 mg / L;

[0051] The dosage of hydrogen peroxide is 100 mg / L;

[0052] pH value is 3-5;

[0053] The reaction time is 20-30min.

[0054] The special chelating agent is a composite chelating agent prepared by compounding trisodium thiocyanate and sodium dimethyl dithiocarbamate, wherein the mass ratios of trisodium thiocyanate and sodium dimethyl dithiocarbamate are 20%-65% and 35%-80% respectively.

[0055] S3 includes: adding a special chelating agent to the wastewater after deep treatment, the mass ratio of the special chelating agent to the wastewater is 1:200-1:5000, stirring for 5-30 minutes, then adding polyalumina, the mass ratio of polyalumina to the wastewater is 1:200-1:5000, stirring again for 5-30 minutes, standing at room temperature for 0.5-12 hours, and filtering using a filter.

[0056] By using special chelating agents to form stable chelates with heavy metal ions in wastewater, they are removed from the wastewater. The cadmium concentration in the treated wastewater is far lower than the national emission standards, and the chelate precipitation is stable, reducing the secondary pollution of the environment caused by cadmium precipitates. It is environmentally friendly, energy-efficient, less precipitated, non-toxic, and reduces treatment costs.

[0057] In summary, acidic cadmium-containing wastewater is collected separately, the pH value of the wastewater is adjusted to 5-9, a precipitant is added to stir and aerate for 10-20 minutes, and after standing, a supernatant and a sludge are obtained, 0.5% of a complexing agent is added to the pretreated wastewater for stirring, and after reacting for 30 minutes, it is pumped to the cadmium-containing concentration reduction line for concentration reduction treatment. The purpose of this step is to separate some cadmium ions with weaker complexation and easy to handle in the cadmium-containing wastewater, and the ions with stronger complexation are collected and further treated again, and the pH of the cadmium-containing wastewater after the concentration reduction treatment is adjusted back to 3-4, 0.5% of a complexing agent is added again for stirring, and after reacting for 30 minutes, it is pumped to the cadmium treatment line, and a heavy metal capture agent is added for treatment, and a filtration device is used for filtration to obtain a supernatant. Liquid and sediment. If in the process experiment, the cadmium-containing wastewater has a strong complexing property after the concentration reduction, and the complex breaking agent cannot achieve the expected complex breaking effect, it is necessary to change the complex breaking agent in the second step to Fenton reagent for Fenton oxidation process treatment, make full use of the efficient oxidation degradation ability of the Fenton oxidation process, improve the removal rate of cadmium ions, and purify the water quality, while avoiding the consumption of a large amount of energy and chemical reagents, which is helpful to improve the overall efficiency of wastewater treatment, optimize the wastewater treatment process, and reduce the treatment cost of cadmium-containing wastewater. Using complex breaking agents and heavy metal capture agents to deeply treat cadmium-containing wastewater can effectively remove cadmium ions and other harmful substances in the wastewater, achieve deep purification of the wastewater, ensure that the effluent water quality meets the discharge standards, and add special chelating agents to the deeply treated wastewater. In the water, the mass ratio of special chelating agent to wastewater is 1:200-1:5000. After stirring for 5-30 minutes, add polyalumina, the mass ratio of polyalumina to wastewater is 1:200-1:5000. After stirring for 5-30 minutes, let it stand at room temperature for 0.5-12 hours, and use a filter to filter it. The treated wastewater is discharged into the intermediate water pool after passing the test. The process is simple and solves the problem of low discharge standards and difficult treatment of cadmium-containing wastewater. Special chelating agents are used to form stable chelates with heavy metal ions in wastewater to remove them from wastewater. The cadmium concentration in the treated wastewater is much lower than the national emission standard, and the chelate precipitation is stable, which reduces the secondary pollution of cadmium precipitates to the environment. The treatment technology can shorten the treatment time of wastewater, use precipitants to remove some cadmium ions in the wastewater, and then use deep treatment technology to deeply remove cadmium, which can effectively reduce the dosage of precipitants, reduce the scaling rate of on-site processes, reduce the descaling and maintenance time, and improve production efficiency. Since the implementation of this process plan, a total of 6,720 tons of cadmium-containing wastewater have been treated, the cost of the agent is 9.35 yuan / ton, and the total cost of the sewage treatment plant is about 50 yuan / ton, which can basically meet the long-term operation needs of the sewage treatment plant. Cadmium is a necessary electroplating process for aerospace and military enterprises, and its wastewater treatment has been a problem that has plagued the development of the industry for a long time. This process solves the problem of treating cadmium-containing wastewater and has a great promoting effect on the development of the above industries, thereby bringing significant economic and social benefits.

[0058] The above generally describes the present invention in detail, but it is obvious to a person skilled in the art that some modifications or improvements can be made to the present invention. Therefore, modifications or improvements that do not depart from the spirit of the present invention are within the scope of protection of the present invention.

Claims

1. A cadmium-containing wastewater deep treatment technology, characterized in that: The processing technique includes the following steps: S1. Raw water pretreatment: collect the acidic cadmium-containing wastewater separately, add a precipitant, stir it, aerate it and let it stand to obtain a supernatant and sediment; S2, advanced treatment: subjecting the pre-treated wastewater to advanced oxidation treatment to break the complex; S3, subsequent treatment: adding a special chelating agent to the wastewater after deep treatment for treatment; S4. Testing and discharge: The treated wastewater is discharged into the intermediate water tank after passing the test.

2. A cadmium-containing wastewater deep treatment technology according to claim 1, characterized in that: The precipitant is one or more of calcium oxide, sodium hydroxide, calcium hydroxide, sodium carbonate and sodium bicarbonate solutions with a concentration of ≥5%.

3. A cadmium-containing wastewater deep treatment technology according to claim 1, characterized in that: After adding the reagent to S1, the pH value of the wastewater is adjusted to 5-9, and the aeration time is 10-20 minutes.

4. A cadmium-containing wastewater deep treatment technology according to claim 1, characterized in that: The S2 comprises the following steps: Add 0.5% of complex breaking agent to the pretreated wastewater and stir it. After reacting for 30 minutes, pump it to the cadmium concentration reduction line for concentration reduction treatment, collect the ions with strong complexing ability and then re-treat them further. Adjust the pH of the cadmium-containing wastewater after the concentration reduction treatment to 3-4, add 0.5% of the complex breaking agent again for stirring, react for 30 minutes, pump it to the cadmium treatment line, add a heavy metal capture agent for treatment, and filter it using a filtering device to obtain a supernatant and a sediment; If in the process experiment, the cadmium-containing wastewater has a strong complexing property after concentration reduction and the complex breaking agent cannot achieve the expected complex breaking effect, it is necessary to change the complex breaking agent in the second step to Fenton reagent for Fenton oxidation process treatment.

5. The cadmium-containing wastewater deep treatment technology according to claim 1 is characterized in that: Heavy metal capture agents include inorganic salt heavy metal capture agents and organic heavy metal capture agents. The inorganic salt heavy metal capture agents include but are not limited to sodium sulfide, polyaluminium chloride, iron salts, and phosphates. The organic heavy metal capture agents include but are not limited to organosulfur TMT heavy metal capture agents and polyamine heavy metal capture agents.

6. A cadmium-containing wastewater deep treatment technology according to claim 1, characterized in that: The Fenton reagent is ferrous sulfate and hydrogen peroxide. In the Fenton oxidation process, ferrous sulfate is first added and then hydrogen peroxide. The process parameters of the Fenton oxidation process are: The dosage of ferrous sulfate is 20 mg / L; The dosage of hydrogen peroxide is 100 mg / L; pH value is 3-5; The reaction time is 20-30min.

7. A cadmium-containing wastewater deep treatment technology according to claim 1, characterized in that: The special chelating agent is a composite chelating agent prepared by compounding trisodium thiocyanate and sodium dimethyl dithiocarbamate, and the mass ratios of trisodium thiocyanate and sodium dimethyl dithiocarbamate are 20%-65% and 35%-80% respectively.

8. A cadmium-containing wastewater deep treatment technology according to claim 7, characterized in that: The S3 comprises: adding a special chelating agent to the wastewater after deep treatment, the mass ratio of the special chelating agent to the wastewater is 1:200-1:5000, stirring for 5-30 minutes, then adding polyalumina, the mass ratio of polyalumina to the wastewater is 1:200-1:5000, stirring again for 5-30 minutes, standing at room temperature for 0.5-12 hours, and filtering using a filter.

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