AWWA WQTC52966

Pilot-scale experiments were conducted at the Fort Collins (Colorado)Water Treatment Facility to optimize a coagulation process to treat spring snowmelt runoff water that is characterized by elevated total organic carbon (TOC) concentrations, low alkalinity, and relatively low turbidity. The process consists of alkalinity and pH adjustment (using lime and carbon dioxide) prior to rapid mix, followed by the addition of alum at two locations separated by approximately 30 seconds of detention time (two-stage coagulation). The pilot experiments were conducted to refine the post-coagulation pH and alkalinity targets in order to optimize the lime and carbon dioxide doses. The pilot experiments were also designed to further evaluate two-stage coagulation, including comparisons to single-stage alum addition where the total alum doseis applied to either one backmix-type reactor or one in-line mixer. Includes 5 references, tables, figures.