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In the process of modern industrial and urban development, wastewater treatment has become a top priority for environmental protection. Among them, chemical oxygen demand (COD) is one of the important indicators to measure the degree of organic pollution in water bodies. High COD values mean that there are a large number of organic pollutants in the water body, which not only threatens the ecological environment, but also has potential harm to human health. Therefore, how to effectively reduce the COD value in wastewater has always been an important research topic in the field of water treatment. Shufang Activated Carbon will share my experience and experience of successfully reducing the COD value in wastewater using coal powder activated carbon.
Activated carbon is a specially treated carbon material with a developed pore structure and a huge specific surface area. The specific surface area of each gram of activated carbon can reach 500 to 1500 square meters. The adsorption function of activated carbon mainly relies on its physical and chemical adsorption capacity, and achieves the purpose of purifying water quality by adsorbing organic pollutants in wastewater.
Physical adsorption: The microporous structure of activated carbon can effectively capture and store organic molecules. This adsorption force mainly depends on the van der Waals force, which is a weak and extensive intermolecular force.
Chemical adsorption: The functional groups on the surface of activated carbon react chemically with pollutants to form chemical bonds. This adsorption force is strong and can firmly fix pollutant molecules.
In addition, activated carbon also has a good detoxification function, adsorbing poisons through its huge surface area, thereby preventing the spread and absorption of poisons.
Activated carbon is usually divided into powdered carbon and granular carbon. Powdered carbon is mainly used for wastewater treatment, using the suspended contact adsorption method; while granular carbon is often used for filtration-adsorption method.
Powdered activated carbon: commonly used in wastewater treatment, powdered activated carbon is suspended in wastewater for adsorption reaction. This method is suitable for treating wastewater with high COD values, because the micropores of powdered activated carbon can quickly adsorb organic pollutants and fully contact with wastewater.
Granular activated carbon: mainly used in the deep treatment stage, purifying wastewater through the dual effects of filtration and adsorption. Granular activated carbon is suitable for treating wastewater after preliminary treatment, and further removing residual organic pollutants and heavy metals.
Activated carbon has the following significant advantages in wastewater treatment:
High-efficiency adsorption capacity: Activated carbon has a strong adsorption capacity for organic matter, color, odor, etc. in wastewater, especially for organic pollutants such as benzene compounds and phenol compounds that are difficult to remove by biological and chemical methods.
Strong adaptability: Activated carbon has strong adaptability to changes in water quality, water temperature and water volume, and can maintain stable treatment effects under different conditions.
Small footprint: The activated carbon treatment device has a compact structure, small footprint, and is easy to install and operate.
Recycling: Saturated activated carbon can be reused through regeneration treatment, reducing the risk of secondary pollution.
Removal of heavy metals: Activated carbon also has a good adsorption effect on heavy metals such as mercury, lead, iron, nickel, etc. in wastewater, and is suitable for the treatment of electroplating wastewater and smelting wastewater.
The application of activated carbon in wastewater treatment is mainly achieved through the following steps:
Dosing and mixing: The pre-weighed powdered activated carbon is evenly added to the wastewater, and it is fully dispersed by mechanical stirring or gas stirring to ensure that the activated carbon is fully in contact with the pollutants.
Contact reaction: In the reaction tank, the wastewater is fully in contact with the powdered activated carbon, and the reaction time is usually 30 minutes to 1 hour. At this stage, the adsorption effect is optimized by adjusting the stirring intensity and reaction time.
Solid-liquid separation: After the reaction, the wastewater enters the solid-liquid separation unit, and the activated carbon adsorbed with pollutants is separated from the wastewater by sedimentation, filtration or centrifugal separation.
Post-treatment: The separated clean water may need further treatment, such as sand filtration, ultraviolet disinfection, etc., to ensure that the effluent quality meets the discharge standards.
Coal-based powdered activated carbon treatment of COD in wastewater mainly depends on its adsorption capacity. In actual operation, I used the following steps to successfully reduce the COD value in wastewater to below 200:
Pretreatment: Coarsely filter the wastewater to remove large suspended solids and adjust the pH value to 6-8 to optimize the adsorption effect of activated carbon.
Activated carbon addition: According to the optimal dosage determined by the experiment, powdered activated carbon is added to the wastewater and evenly dispersed by stirring. In my case, after multiple adjustments, the final dosage was 400-600ppm.
Reaction time: Keep the contact time in the reaction tank for 30 minutes to 1 hour to ensure sufficient adsorption.
Solid-liquid separation: With the assistance of efficient precipitants, the activated carbon adsorbed with pollutants is separated from the wastewater.
Post-treatment: Further treat the clean water to ensure that it meets the emission standards.
Through the above method, I successfully reduced the COD value in the wastewater from 600 mg/L to below 200 mg/L. At the same time, the chromaticity, turbidity and other indicators in the wastewater have also been significantly improved.
Advantages and disadvantages of powdered activated carbon treatment
Although powdered activated carbon has a significant effect in reducing COD values, there are also some issues that need attention.
Advantages:
Efficient adsorption: It can quickly adsorb organic pollutants in wastewater and improve treatment efficiency.
Strong adaptability: It has a good removal effect on different types of organic pollutants.
Easy operation: The process is simple and easy to control and implement.
Disadvantages:
High cost: The cost of using powdered activated carbon is relatively high, especially when treating large-scale high-COD wastewater.
Secondary pollution risk: Incomplete solid-liquid separation may lead to residual powdered activated carbon, causing secondary pollution.
Disposal difficulty: Used activated carbon contains a large amount of pollutants and needs to be properly disposed of to avoid environmental pollution.
Future Prospects and Suggestions
In order to further improve the application effect of powdered activated carbon in wastewater treatment, research and optimization can be carried out from the following aspects:
Develop new activated carbon materials: improve production processes and material formulas, and develop more efficient activated carbon products.
Optimize process flow: Combine advanced technologies such as membrane separation and biological treatment to optimize the dosing process of powdered activated carbon.
Reduce the cost of use: Reduce the cost of powdered activated carbon through large-scale production and process improvement.
Strengthen waste management: Develop a complete waste activated carbon disposal plan to ensure environmentally friendly and safe recycling and reuse.
In short, powdered activated carbon, as an efficient water treatment material, has shown great potential and advantages in reducing COD values. Through reasonable selection, optimized process design and scientific management, efficient COD removal effects can be achieved, water quality can be improved, and positive contributions can be made to environmental protection and sustainable use of water resources. I hope that the sharing of this article can provide useful references for peers and jointly promote the development and application of water treatment technology.
