The basin screens out large debris and settles out sand and silt. This allows the impurities to begin coagulating, or forming small particles that can more easily be removed. Back to Map Flocculation - the small contaminant particles formed in the rapid mix begin to collect and form larger particles, called floc, which are heavier than water. The water is mixed slowly at different speeds to assist floc formation, and a polymer is added to strengthen the floc. Inclined plates are used to speed the settling.
Clear water is skimmed off the top of the basin.
Back to Map Solids Drawoff - after settling to the bottom of the basin, the floc is scraped into a pit and drawn off through a pipeline. The resulting material, residual solids, are spread out in a shallow pond, where they dry out for easier handling. Back to Map Filters - the clarified water flows through layers of sand and anthracite coal to remove any remaining impurities. Back to Map Clearwell - a small holding tank where the finishing process takes place, ensuring that the water is safe and healthy to drink. Chlorine is added as a disinfectant according to state and federal regulations.