23-14: Coagulant/Polymer 101: Fundamentals of Sedimentation and Dewatering

Despite the wide-spread use of polymers in water and wastewater treatment and their associated high recurring expense, understanding exactly how to optimize the polymer use in water and wastewater treatment is not well understood. This discussion will review the basics of polymer chemistry, goals of activation, the development of optimized polymer mixing equipment and case studies. Proper way of handling and storage of dry or emulsion polymer is reviewed as well as the shelf-life of neat polymer and diluted polymer solution. The use of solution viscosity will be discussed as a reliable measure of the efficiency of polymer solution. Due to its unique property of polymers, polymer activation/mixing requires well established scientific understanding. The benefits of utilizing two-stage mixing are demonstrated by theoretical consideration and lab test data. Sufficient residence time in an emulsion polymer system is also found to improve the efficiency of the polymer solution. Benefits of two-stage mixing and adequate residence time are clearly illustrated with pilot trials at two municipal water and wastewater treatment plants.