AWWA WQTC54994

Many surface water systems experience inefficient settling in their treatment process. Activated silica used as a secondary coagulant can improve this process by creating a faster settling floc. This project tested a new generation of activated silica using CO2 as an activator. Field testing showed that activated silica improved the settled turbidity at the treatment plant and also showed that the alum level could be reduced as much as 33% while still maintaining or improving performance. This resulted in lowering the chemical treatment costs. Activated silica can provide improved settling for plants with difficult to settle floc particles, cold water, or low alkalinity. By improving settling, activated silica can help utilities meet future regulations requiring lower water turbidity. Activated silica can significantly improve coagulation and reduce the coagulant dose leading to less sludge produced and potentially reduced operating cost for water treatment plants. Includes tables, figures.