Activated carbon, due to its well-developed pore structure, large specific surface area, and excellent adsorption performance, is a widely used deep purification material in wastewater treatment. Its core function is to adsorb and remove recalcitrant organic pollutants, odors, and some trace pollutants from water. Specific functions and effects are as follows:
I. Core Function: Pollutant Adsorption
Activated carbon adsorption is based on a dual mechanism of physical adsorption (van der Waals forces) and chemical adsorption (chemical bonding), achieving targeted removal of various pollutants in wastewater:
Removal of Recalcitrant Organic Matter
For aromatic compounds, polycyclic aromatic hydrocarbons, phenols, pesticide residues, dye molecules, etc., which cannot be degraded by biochemical treatment, activated carbon can retain these molecules in its pores through the sieving effect of micropores and mesopores, significantly reducing the chemical oxygen demand (COD) and color of wastewater. It is particularly suitable for the deep treatment of industrial wastewater from printing and dyeing, chemical, and pharmaceutical industries.
Odor and Color Removal: Odors in wastewater are mostly caused by sulfides, ammonia nitrogen derivatives, and volatile organic compounds (VOCs), while color comes from dyes and humic substances. Activated carbon has strong adsorption selectivity for these substances, effectively improving the sensory indicators of effluent, for example, achieving a decolorization rate of 80%~95% for dyeing and printing wastewater.
Removal of Trace Toxic and Harmful Substances: Activated carbon adsorbs heavy metal ions (such as mercury, lead, and chromium) (through chelation of surface functional groups), disinfection byproduct precursors (such as humic acid and halogenated hydrocarbon precursors), antibiotics, endocrine disruptors, and other trace pollutants in water, reducing the biotoxicity of wastewater and ensuring effluent safety (especially suitable for reuse or discharge into sensitive water bodies).
Residual Chlorine Removal: For wastewater treatment processes using chlorine disinfection, activated carbon can reduce free chlorine and chloramines in the water to chloride ions, preventing residual chlorine from harming the microorganisms in subsequent biological systems, and simultaneously preventing chlorine from reacting with organic matter to form new disinfection byproducts.
II. Auxiliary Functions: Optimizing Wastewater Treatment System Performance
Improving Biochemical Treatment Efficiency (as a Biological Carrier)
Granular activated carbon (GAC) can serve as a carrier for biological activated carbon (BAC). Its surface can harbor a large number of microorganisms, forming a synergistic effect of "adsorption + biodegradation": the activated carbon first adsorbs organic matter, and then the microorganisms degrade the adsorbed pollutants, extending the lifespan of the activated carbon while further reducing the concentration of organic matter in the wastewater.
Improving Sludge Settling Performance
Adding powdered activated carbon (PAC) to the activated sludge process can adsorb viscous organic matter in the sludge, reducing the risk of sludge bulking, improving sludge settling speed and dewatering efficiency, and reducing sludge treatment costs.
Emergency Handling of Sudden Pollution Events
When a wastewater treatment plant encounters a sudden organic matter leak or a shock load on water quality, powdered activated carbon can be quickly added. Through efficient adsorption, it can reduce the concentration of pollutants in a short time, preventing the collapse of the biological system and serving as a "safety barrier" for emergency handling.
