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 an upcoming 40 mgd plant expansion. Microfiltration (MF), ultrafiltration (UF), and nanofiltration (NF) membranes were tested with several pretreatment processes. The selected advanced water treatment (AWT) process for the plant expansion treating secondary effluent includes: coagulant addition and clarification for phosphorus reduction; MF or UF membranes with pretreatment strainers for particle removal (including microbes); granular activated carbon (GAC) following ozone for disinfection and organic reduction; and ozone for disinfection. Includes tables, figures.