AWWA ACE65322

This powerpoint presentation outlines optimal treatment technology and design considerations for small-scale treatment of surface water with elevated organic loading at the town of Mahone Bay. Background information presented includes: 1,000 residents; surface water source - Oakland Lake; aging existing treatment infrastructure, packaged coagulation, flocculation, filtration; and, challenging water quality, elevated disinfection byproducts (DBPs). Statistics for raw water quality are provided, along with treatment objectives that include: pathogen removal; total organic carbon (TOC), color, DBP precursor removal; and, slight metals removal. Candidate processes for TOC removal included: conventional coagulation, flocculation, sedimentation, filtration; solids contact clarifier; dissolved air flotation (DAF); and, membranes - preferred option. Pilot testing evaluated three membrane processes that included: coagulation followed by microfiltration (Coagulation/MF); ultrafiltration followed by nanofiltration (UF/NF); and, multi-media filtration followed by nanofiltration (MMF/NF). Design evaluation included: cost, capital vs operational; treated water quality, DBP formation potential; environmental impacts, residuals formation, required treatment, energy; operational complexity, mechanical vs chemical process; and, regulatory implications, redundancy, log removal credit. Cost estimates are provided along with pilot results, operational summary, residuals formation, operational complexity, membrane regulatory implications, and decision evaluation criteria.