AWWA ACE54281

In May 2000, the Marco Island Lime Softening Water Treatment Plant (LSWTP) of Marco Island, Florida, was expandedfrom 5.0 to 6.67 million gallons per day (mgd) with the addition of a 1.67 mgd immersed membrane ultrafiltration (UF). The Marco Island LSWTP was previously limited to 5.0 mgd of production based on conventional sand filter capacity. This facility provides treatment of surface water from the Marco Lakes. Raw water from the Marco Lakes supply is pumped 9.5 miles to the Marco Island LSWTP. The raw water source contains elevated color (>40 cpu), total organic carbon (TOC) (>12 mg/L), UV-254 (0.181), hardness (>350 mg/L as CaCO3), and moderate total dissolved solids (TDS) (>900 mg/L). Implementation of a full-scale 1.67 mgd UF process downstream of the Marco Island lime softening process demonstrated an average filteredturbidity of 0.05 NTU versus an average sand filtered finished water turbidity of 0.1 NTU. Includes 9 references, tables, figure.