AWWA ACE56249

Gwinnett County, Georgia conducted a membrane pilot and demonstration test program to compare with the existing "high-lime" process train for possible selection in the tertiary treatment facilities of a 40 mgd plant expansion. Microfiltration (MF), ultrafiltration (UF), and nanofiltration (NF) membranes were tested with several pretreatment processes. The selected tertiary treatment process for the plant expansion treating secondary effluent included: coagulant addition and clarification for phosphorus, solids, and organics reduction; strainers or screens (500 micron or finer) for larger-size solids reduction prior to MF/UF; MF or UF membranes for submicron particle removal (including microbes); granular activated carbon (GAC) following ozone for disinfection and organic reduction; and, final ozone for disinfection. Membrane system selection involved evaluating prequalified-MF/UF proposals considering initial and present worth costs and several specified qualitative factors, "proof testing" the selected membrane system following chemical clarification of secondary effluent, and incorporating the preselected MF or UF system into the overall tertiary treatment facility design and construction bid documents. Includes tables, figures.