Polyacrylamide (PAM) achieves efficient purification in sewage treatment mainly through the physical and chemical effects of its polymer chains. Its core functions include flocculation and sedimentation, sludge dehydration and pollutant removal. The specific functions are as follows:
1. Flocculation and sedimentation enhancement
Bridging adsorption and charge neutralization: The long molecular chain of PAM adsorbs suspended particles in sewage (such as colloids, organic matter, heavy metals, etc.), forming a "bridging effect" to condense tiny particles into large flocs, accelerating sedimentation or floating separation. Anionic PAM (APAM) is suitable for inorganic suspended matter with positive charge (such as mining wastewater and metallurgical wastewater), while cationic PAM (CPAM) is more effective for negatively charged organic pollutants (such as urban sewage and food wastewater).
Netting effect: PAM molecular chains form dense flocs by wrapping pollutants, improving the efficiency of solid-liquid separation and significantly reducing turbidity and COD (chemical oxygen demand).
2. Sludge dewatering and reduction
Improve dewatering efficiency: In the sludge treatment process, cationic PAM reduces the hydrophilicity of sludge by charge neutralization, enhances its aggregation, makes it easier to dehydrate sludge through belt filter presses, centrifuges and other equipment, and reduces sludge volume and treatment costs.
Avoid secondary pollution: The addition of PAM can solidify organic matter in sludge and reduce the risk of secondary pollution.
3. Industry-specific applications
Industrial wastewater: For example, coal washing wastewater needs to use anionic PAM to remove suspended particles; paper-making wastewater needs to combine inorganic flocculants and anionic PAM to treat fiber impurities.
Domestic sewage: PAM is used to quickly settle organic matter and ammonia nitrogen to increase the capacity of the treatment plant.
Special fields: Electronic electroplating wastewater needs to adjust the pH and use PAM to precipitate heavy metals (such as Cr(OH)₃).
